Effect of x-irradiation on cell kinetics of esophageal membrane cells in mice

International Nuclear Information System (INIS)

Ando, Koichi; Tsunemoto, Hiroshi; Urano, Muneyasu; Koike, Sachiko

1977-01-01

Effect of x-irradiation on the cell kinetics of esophageal membrane cells was studied in C3Hf/He male mice. Experimental methods include; counting the number of basal and superficial cells, and pulse or continuous labelling by tritiated thymidine. Esophageal area was irradiated with 1000 rad of 200 kVp x-rays and cell kinetics were studied on the 5th post-irradiation day. Autoradiography revealed the shortening of the cell cycle time, specifically in G- and G- phases. Numbers of basal cells and of superficial cells were found to increase for 5 days after irradiation. Continuous labelling experiments using infusion technique demonstrated than growth fraction of irradiated basal cells was 1.0 as well as that of non-irradiated cells. It was of interest that the migration time, i.e., the time required for labelled cells to migrate from basal cell layer to superficial cell layer, was shortened approximately 1/3 of that of non-irradiated control after irradiation. Diurnal variation was observed not only in normal basal cells but also in irradiated ones, and the rate of increase of labelling index after continuous labelling was independent of the time when the labelling was started. (auth.)

Effect of x irradiation on cell kinetics of esophageal membrane cells in mice

Energy Technology Data Exchange (ETDEWEB)

Ando, K; Tsunemoto, H; Urano, M; Koike, S [National Inst. of Radiological Sciences, Chiba (Japan)

1977-05-01

Effect of x irradiation on the cell kinetics of esophageal membrane cells was studied in C3Hf/He male mice. Experimental methods include; counting the number of basal and superficial cells, and pulse or continuous labelling by tritiated thymidine. Esophageal area was irradiated with 1000 rad of 200 kVp x rays and cell kinetics were studied on the 5th post-irradiation day. Autoradiography revealed the shortening of the cell cycle time, specifically in G- and G- phases. Numbers of basal cells and of superficial cells were found to increase for 5 days after irradiation. Continuous labelling experiments using infusion technique demonstrated than growth fraction of irradiated basal cells was 1.0 as well as that of non-irradiated cells. It was of interest that the migration time, i.e., the time required for labelled cells to migrate from basal cell layer to superficial cell layer, was shortened approximately 1/3 of that of non-irradiated control after irradiation. Diurnal variation was observed not only in normal basal cells but also in irradiated ones, and the rate of increase of labelling index after continuous labelling was independent of the time when the labelling was started.

Differences in kinetic variables between injured and noninjured novice runners : A prospective cohort study

NARCIS (Netherlands)

Bredeweg, Steef W.; Kluitenberg, Bas; Bessem, Bram; Buist, Ida

Objectives: This prospective study examined differences in kinetic variables between injured and noninjured novice female and male runners and their potential contribution to RRIs. Design: A prospective cohort study. Methods: At baseline vertical ground reaction forces were assessed with an

[Synergistic effect of cell kinetics-directed chemo-endocrine therapy on experimental mammary tumors].

Science.gov (United States)

Ueki, H

1987-11-01

We tried to demonstrate that the cell kinetics-directed chemoendocrine therapy is more effective on hormone dependent breast cancer than empirical combination of the endocrine therapy and chemotherapy. Cell kinetics of each tumor was measured by flow cytometric analysis. Estrogen dependent human breast cancer cell line MCF-7 was used in vitro. In vivo, androgen dependent SC-115 carcinoma was transplanted to DDS mice. In vitro, tamoxifen was administered as the endocrine therapy. In vivo, we carried out testectomy on DDS mice. Effect of the endocrine therapy on the cell kinetics of the tumor was thought to be G1-S depression. High density 5FU was administered as the chemotherapeutic agents, whose content was 1 microgram/ml in vitro and 40 mg/kg in vivo. 5FU brought temporary decrease of cells in S phase. Only anteceding 5FU administration had synergistic effect in combination of 5FU and the endocrine therapy. 5FU was convinced to act more effectively on cells in S phase, so it was shown that cell kinetics-directed schedule was superior to the empirical treatment schedule in chemoendocrine therapy.

Influence of flotation cell volume and solids mass on kinetics of sulfide ore flotation

Directory of Open Access Journals (Sweden)

Plawski Michal

2016-01-01

Full Text Available The paper presents studies on the influence of flotation cell capacity and mass of solids in the suspension on the flotation kinetics of sulfide copper ore. A sample of copper ore that was collected from the Polkowice Mine of KGHM Polska Miedz S.A. in Poland was used in the experiments. It was determined that neither the volume of flotation cell nor the mass of solids had influence on the type of kinetics equation of flotation. Copper-bearing minerals floated according to the second-order equation, while the remaining components according to the first-order equation. The kinetic rate constants and maximum recovery of the studied components decreased with increasing solids mass in the flotation cell, regardless of the capacity of the cell. The best results were obtained for tests using a 1.0 dm3 cell, while the less favorable kinetics results were observed in the test with the smallest cell of 0.75 dm3 volume. The obtained results can be helpful in choosing the most appropriate methodology of upgrading the sulfide copper ore from Poland in order to obtain the best kinetics results.

Effect of body mass and midsole hardness on kinetic and perceptual variables during basketball landing manoeuvres.

Science.gov (United States)

Nin, Darren Z; Lam, Wing K; Kong, Pui W

2016-01-01

This study investigated the effects of body mass and shoe midsole hardness on kinetic and perceptual variables during the performance of three basketball movements: (1) the first and landing steps of layup, (2) shot-blocking landing and (3) drop landing. Thirty male basketball players, assigned into "heavy" (n = 15, mass 82.7 ± 4.3 kg) or "light" (n = 15, mass 63.1 ± 2.8 kg) groups, performed five trials of each movement in three identical shoes of varying midsole hardness (soft, medium, hard). Vertical ground reaction force (VGRF) during landing was sampled using multiple wooden-top force plates. Perceptual responses on five variables (forefoot cushioning, rearfoot cushioning, forefoot stability, rearfoot stability and overall comfort) were rated after each movement condition using a 150-mm Visual Analogue Scale (VAS). A mixed factorial analysis of variance (ANOVA) (Body Mass × Shoe) was applied to all kinetic and perceptual variables. During the first step of the layup, the loading rate associated with rearfoot contact was 40.7% higher in the "heavy" than "light" groups (P = .014) and 12.4% higher in hard compared with soft shoes (P = .011). Forefoot peak VGRF in a soft shoe was higher (P = .011) than in a hard shoe during shot-block landing. Both "heavy" and "light" groups preferred softer to harder shoes. Overall, body mass had little effect on kinetic or perceptual variables.

Tumor cell proliferation kinetics and tumor growth rate

Energy Technology Data Exchange (ETDEWEB)

Tubiana, M

1989-01-01

The present knowledge on the growth rate and the proliferation kinetics of human tumor is based on the measurement of the tumor doubling times (DT) in several hundred patients and on the determination of the proportion of proliferating cells with radioactive thymidine or by flow cytometry in large numbers of patients. The results show that the DT of human tumor varies widely, from less than one week to over one year with a median value of approximately 2 months. The DTs are significantly correlated with the histological type. They depend upon (1) the duration of the cell cycle whose mean duration is 2 days with small variations from tumor to tumor, (2) the proportion of proliferating cells and consequently the cell birth rate which varies widely among tumors and which is significantly correlated to the DT, (3) the cell loss factors which also vary widely and which are the greatest when proliferation is most intensive. These studies have several clinical implications: (a) they have further increased our understanding of the natural history of human tumor, (b) they have therapeutic implications since tumor responsiveness and curability by radiation and drugs are strongly influenced by the cell kinetic parameters of the tumor, (c) the proportion of proliferating cells is of great prognostic value in several types of human cancers. The investigation of the molecular defects, which are correlated with the perturbation of control of cell proliferation, should lead to significant fundamental and therapeutic advances. (orig.).

Visualizing the effect of tumor microenvironments on radiation-induced cell kinetics in multicellular spheroids consisting of HeLa cells

International Nuclear Information System (INIS)

Kaida, Atsushi; Miura, Masahiko

2013-01-01

Highlights: •We visualized radiation-induced cell kinetics in spheroids. •HeLa-Fucci cells were used for detection of cell-cycle changes. •Radiation-induced G2 arrest was prolonged in the spheroid. •The inner and outer cell fractions behaved differently. -- Abstract: In this study, we visualized the effect of tumor microenvironments on radiation-induced tumor cell kinetics. For this purpose, we utilized a multicellular spheroid model, with a diameter of ∼500 μm, consisting of HeLa cells expressing the fluorescent ubiquitination-based cell-cycle indicator (Fucci). In live spheroids, a confocal laser scanning microscope allowed us to clearly monitor cell kinetics at depths of up to 60 μm. Surprisingly, a remarkable prolongation of G2 arrest was observed in the outer region of the spheroid relative to monolayer-cultured cells. Scale, an aqueous reagent that renders tissues optically transparent, allowed visualization deeper inside spheroids. About 16 h after irradiation, a red fluorescent cell fraction, presumably a quiescent G0 cell fraction, became distinct from the outer fraction consisting of proliferating cells, most of which exhibited green fluorescence indicative of G2 arrest. Thereafter, the red cell fraction began to emit green fluorescence and remained in prolonged G2 arrest. Thus, for the first time, we visualized the prolongation of radiation-induced G2 arrest in spheroids and the differences in cell kinetics between the outer and inner fractions

Solid KHT tumor dispersal for flow cytometric cell kinetic analysis

International Nuclear Information System (INIS)

Pallavicini, M.G.; Folstad, L.J.; Dunbar, C.

1981-01-01

A bacterial neutral protease was used to disperse KHT solid tumors into single cell suspensions suitable for routine cell kinetic analysis by flow cytometry and for clonogenic cell survival. Neutral protease disaggregation under conditions which would be suitable for routine tumor dispersal was compared with a trypsin/DNase procedure. Cell yield, clonogenic cell survival, DNA distributions of untreated and drug-perturbed tumors, rates of radioactive precursor incorporation during the cell cycle, and preferential cell cycle phase-specific cell loss were investigated. Tumors dispersed with neutral protease yielded approximately four times more cells than those dispersed with trypsin/DNase and approximately a 1.5-fold higher plating efficiency in a semisolid agar system. Quantitative analysis of DNA distributions obtained from untreated and cytosine-arabinoside-perturbed tumors produced similar results with both dispersal procedures. The rates of incorporation of tritiated thymidine during the cell cycle were also similar with neutral protease and trypsin/DNase dispersal. Preferential phase-specific cell loss was not obseved with either technique. We find that neutral protease provides good single cell suspensions of the KHT tumor for cell survival measurements and for cell kinetic analysis of drug-induced perturbations by flow cytometry. In addition, the high cell yields facilitate electronic cell sorting where large numbers of cells are often required

Kinetics of particle ensembles with variable charges

International Nuclear Information System (INIS)

Ivlev, A. V.; Zhdanov, S.; Klumov, B.; Morfill, G.; Tsytovich, V. N.; Angelis, U. de

2005-01-01

One of the remarkable features distinguishing complex (dusty) plasmas from usual plasmas is that charges on the grains are not constant, but fluctuate in time around some equilibrium value which, in then, is some function of spatial coordinates. Generally, ensembles of particles with variable charges are non-Hamiltonian systems where the mutual collisions do not conserve energy. Therefore, the use of thermodynamic potentials to describe such systems is not really valid. An appropriate way to investigate their evolution is to employ the kinetic approach. We studied (both analytical and numerically) two cases: (a) inhomogeneous charge-it depends on the particle coordinate but does not change in time, and (b)fluctuating charge-it changes in time around the equilibrium value, which is constant in space. For both cases we used the Fokker-Planck approach to derive the collision integral which describes the momentum and energy transfer in mutual particle collisions as well as in the collisions with neutrals. We obtained that the mean particle energy grows in time when the neutral friction is below a certain threshold (as shown in Fig. 1). In case (a) the energy changes as ∞(t c r-t)''2, in case (b) it scales as ∞(t c r-t)''-1, exhibiting the explosion-like growth with t c r a critical time scale. The obtained solutions can be of significant importance for laboratory dusty plasmas as well as for space plasma environments, where inhomogeneous charge distributions are often present. For instance, the instability can cause dust heating in low-pressure complex plasma experiments, it can be responsible for the melting of plasma crystals, it might operate in protoplanetary disks and effect the kinetics of the planet formation, etc. (Author)

Effect of elevated temperatures on cell cycle kinetics of rat gliosarcoma cells

International Nuclear Information System (INIS)

Ross-Riveros, P.

1978-07-01

9L rat gliosarcoma cells were examined in vitro for survival response to hyperthermic temperatures ranging from 39.0 0 to 45.0 0 C for graded exposure times. At 43.0 0 C, the split exposure response was also studied. Changes in cell cycle kinetics resulting from hyperthermia were compared for isosurvival levels achieved by appropriate exposure time to either 42.5 0 C or 43.0 0 C. After heat treatment, cells were held at 37.0 0 C for varying recovery periods. Cells were then either prepared for flow microfluorometry (FMF), or exposed to tritiated thymidine ( 3 HTdR) for autoradiography. The survival studies indicated that the rate of change in cell killing for each increasing degree centigrade was greater for temperatures below 43.0 0 C than for temperatures above 43.0 0 C. The shoulder width of the survival curves was maximal at 42.5 0 C. The shoulder width represents an important parameter since it describes a threshold time after which significant cell killing occurs. Thus both 43.0 0 C, the temperature at which mortality kinetics changed, and 42.5 0 C, the temperature at which the shoulder width was maximum, represent critical temperatures for the 9L cells. When 9L cells were given an initial conditioning exposure to 43.0 0 C, then returned to 37 0 C for 3 hrs, followed by graded exposure intervals at 43.0 0 , the resulting survival curve indicated that cells required longer times for equal cell killing than for the single exposure condition, suggesting that the cells possess a capability to adapt to the higher temperature

Viral kinetics of Enterovirus 71 in human abdomyosarcoma cells

Science.gov (United States)

Lu, Jing; He, Ya-Qing; Yi, Li-Na; Zan, Hong; Kung, Hsiang-Fu; He, Ming-Liang

2011-01-01

AIM: To characterise the viral kinetics of enterovirus 71 (EV71). METHODS: In this study, human rhabdomyosarcoma (RD) cells were infected with EV71 at different multiplicity of infection (MOI). After infection, the cytopathic effect (CPE) was monitored and recorded using a phase contrast microscope associated with a CCD camera at different time points post viral infection (0, 6, 12, 24 h post infection). Cell growth and viability were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in both EV71 infected and mock infected cells at each time point. EV71 replication kinetics in RD cells was determined by measuring the total intracellular viral RNA with real-time reverse-transcription polymerase chain reaction (qRT-PCR). Also, the intracellular and extracellular virion RNA was isolated and quantified at different time points to analyze the viral package and secretion. The expression of viral protein was determined by analyze the levels of viral structure protein VP1 with Western blotting. RESULTS: EV71 infection induced a significant CPE as early as 6 h post infection (p.i.) in both RD cells infected with high ratio of virus (MOI 10) and low ratio of virus (MOI 1). In EV71 infected cells, the cell growth was inhibited and the number of viable cells was rapidly decreased in the later phase of infection. EV71 virions were uncoated immediately after entry. The intracellular viral RNA began to increase at as early as 3 h p.i. and the exponential increase was found between 3 h to 6 h p.i. in both infected groups. For viral structure protein synthesis, results from western-blot showed that intracellular viral protein VP1 could not be detected until 6 h p.i. in the cells infected at either MOI 1 or MOI 10; and reached the peak at 9 h p.i. in the cells infected with EV71 at both MOI 1 and MOI 10. Simultaneously, the viral package and secretion were also actively processed as the virus underwent rapid replication. The viral package kinetics

Survival and kinetics of Chinese hamster ovary cell subpopulations induced by Adriamycin and radiation

International Nuclear Information System (INIS)

Schneiderman, M.H.

1979-01-01

Mitotic selection of Chinese hamster ovary (CHO) cells, at 10 min intervals after the initiation of Adriamycin and/or x-ray treatment was used to measure the kinetics and survival of cells which progressed without delay, the ''refractory'' cells, the cells that reached mitosis only after recovery from the treatment-induced delay, the ''recovered'' cells, and the survival of the cells remaining attached to the flask 5 h after treatment. The cell kinetics were determined from the rate at which cells entered mitosis, and the reproductive integrity from the survival of the selected refractory, recovered and remaining (unselected) cells

Integrated stoichiometric, thermodynamic and kinetic modelling of steady state metabolism.

Science.gov (United States)

Fleming, R M T; Thiele, I; Provan, G; Nasheuer, H P

2010-06-07

The quantitative analysis of biochemical reactions and metabolites is at frontier of biological sciences. The recent availability of high-throughput technology data sets in biology has paved the way for new modelling approaches at various levels of complexity including the metabolome of a cell or an organism. Understanding the metabolism of a single cell and multi-cell organism will provide the knowledge for the rational design of growth conditions to produce commercially valuable reagents in biotechnology. Here, we demonstrate how equations representing steady state mass conservation, energy conservation, the second law of thermodynamics, and reversible enzyme kinetics can be formulated as a single system of linear equalities and inequalities, in addition to linear equalities on exponential variables. Even though the feasible set is non-convex, the reformulation is exact and amenable to large-scale numerical analysis, a prerequisite for computationally feasible genome scale modelling. Integrating flux, concentration and kinetic variables in a unified constraint-based formulation is aimed at increasing the quantitative predictive capacity of flux balance analysis. Incorporation of experimental and theoretical bounds on thermodynamic and kinetic variables ensures that the predicted steady state fluxes are both thermodynamically and biochemically feasible. The resulting in silico predictions are tested against fluxomic data for central metabolism in Escherichia coli and compare favourably with in silico prediction by flux balance analysis. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Cell kinetic parameters of a solid mammary adenocarcinoma

International Nuclear Information System (INIS)

Porschen, R.; Feinendegen, L.E.

1978-01-01

Several cell kinetic parameters of the mammary adenocarcinoma EO 771 were evaluated by means of tumor volume measurements and of 125 I-UdR. The in-situ measured activity loss rate is disturbed by a slow elimination of labelled necrotic cells and by reutilization of 125 I-UdR. The restrictions of the I-UdR method are mentioned and the measured activity loss rates are compared with calculated volume loss rates. (orig./MG) [de

The Particle-in-Cell and Kinetic Simulation Software Center

Science.gov (United States)

Mori, W. B.; Decyk, V. K.; Tableman, A.; Fonseca, R. A.; Tsung, F. S.; Hu, Q.; Winjum, B. J.; An, W.; Dalichaouch, T. N.; Davidson, A.; Hildebrand, L.; Joglekar, A.; May, J.; Miller, K.; Touati, M.; Xu, X. L.

2017-10-01

The UCLA Particle-in-Cell and Kinetic Simulation Software Center (PICKSC) aims to support an international community of PIC and plasma kinetic software developers, users, and educators; to increase the use of this software for accelerating the rate of scientific discovery; and to be a repository of knowledge and history for PIC. We discuss progress towards making available and documenting illustrative open-source software programs and distinct production programs; developing and comparing different PIC algorithms; coordinating the development of resources for the educational use of kinetic software; and the outcomes of our first sponsored OSIRIS users workshop. We also welcome input and discussion from anyone interested in using or developing kinetic software, in obtaining access to our codes, in collaborating, in sharing their own software, or in commenting on how PICKSC can better serve the DPP community. Supported by NSF under Grant ACI-1339893 and by the UCLA Institute for Digital Research and Education.

Cesium removal and kinetics equilibrium: Precipitation kinetics

International Nuclear Information System (INIS)

Barnes, M.J.

1999-01-01

This task consisted of both non-radioactive and radioactive (tracer) tests examining the influence of potentially significant variables on cesium tetraphenylborate precipitation kinetics. The work investigated the time required to reach cesium decontamination and the conditions that affect the cesium precipitation kinetics

A study on the potential of cell kinetically directed fractionation schemes in radiotherapy

International Nuclear Information System (INIS)

Oostrum, I.E.A. van.

1990-01-01

In this thesis, the phenomenon of radiation-induced synchronization of cells into the radiosensitive G 2 phase of the cell cycle and the exploitation of this phenomenon to enhance the efficacy of frationated radiotherapy was investigated. A nude mouse model was used to investigate the cell kinetics of 6 human xenotransplanted tumours before and after irradiation. In the second part of the investigation it was tested whether split dose irradiation intervals, based on cell kinetic data of the tumours (i.e. timing of maximal accumulation of cells in G 2 ) would result in an enhanced response compared with those at non optimal intervals (author), 297 refs.; 35 figs.; 25 tabs

Analysis of cell kinetics after gamma ray irradiation using anti-BrdU monoclonal antibody

International Nuclear Information System (INIS)

Akagi, Kiyoshi; Tanaka, Yoshimasa

1989-01-01

The cell cycle was analyzed using anti-BrdU monoclonal antibody, and changes in cell kinetics after gamma ray irradiation as evaluated by this BrdU-PI double staining were compared with those evaluated by the DNA histogram method based on PI staining. The effect of irradiation on the cell kinetics has been studied according primarily to the number of G2 blocked cells. By the present BrdU method, rapid transition of the G1-S phase was observed within 2 hours of irradiation, and then G1 block was observed. Cells in the S phase progressed to the G2 + M cells returned to the G1 phase after 18 or more hours. These initial G1 blocked cells induced by irradiation were confirmed for the fist time by the present BrdU-PI double staining. By the conventional method based on the DNA histogram, accurate determination of S cell fraction was difficult due to overlapping of the DNA contents of G1 cells and early S cells and those of late S cells and G2 cells. On the other hand, BrdU-PI double staining allowed direct differentiation of G1, S, and G2 + M cells, especially between G1-S and S-G2 + M cells. The analysis of cell kinetics using BrdU is advantageous over the conventional autoradiographic methods in that it allowed more rapid assay with very high sensitivity. In addition, BrdU is alrady used clinically as an enhancement agent in radiation therapy for cancer. The present method is considered to be indispensable for evaluation of the percentage of S cells in the tumor tissue and analysis of cell kinetics after irradiation and chemotherapy against cancer. (author)

Determinants of cell-to-cell variability in protein kinase signaling.

Science.gov (United States)

Jeschke, Matthias; Baumgärtner, Stephan; Legewie, Stefan

2013-01-01

Cells reliably sense environmental changes despite internal and external fluctuations, but the mechanisms underlying robustness remain unclear. We analyzed how fluctuations in signaling protein concentrations give rise to cell-to-cell variability in protein kinase signaling using analytical theory and numerical simulations. We characterized the dose-response behavior of signaling cascades by calculating the stimulus level at which a pathway responds ('pathway sensitivity') and the maximal activation level upon strong stimulation. Minimal kinase cascades with gradual dose-response behavior show strong variability, because the pathway sensitivity and the maximal activation level cannot be simultaneously invariant. Negative feedback regulation resolves this trade-off and coordinately reduces fluctuations in the pathway sensitivity and maximal activation. Feedbacks acting at different levels in the cascade control different aspects of the dose-response curve, thereby synergistically reducing the variability. We also investigated more complex, ultrasensitive signaling cascades capable of switch-like decision making, and found that these can be inherently robust to protein concentration fluctuations. We describe how the cell-to-cell variability of ultrasensitive signaling systems can be actively regulated, e.g., by altering the expression of phosphatase(s) or by feedback/feedforward loops. Our calculations reveal that slow transcriptional negative feedback loops allow for variability suppression while maintaining switch-like decision making. Taken together, we describe design principles of signaling cascades that promote robustness. Our results may explain why certain signaling cascades like the yeast pheromone pathway show switch-like decision making with little cell-to-cell variability.

The epidermal cell kinetic response to ultraviolet B irradiation combines regenerative proliferation and carcinogen associated cell cycle delay

Energy Technology Data Exchange (ETDEWEB)

Olsen, W.M.; Kirkhus, B. (Oslo Univ. (Norway))

1989-09-01

The cell cycle traverse of epidermal basal cells 24 h after in vivo exposure of ultraviolet B (UVB) irradiation was studied by immunochemical staining of incorporated bromodeoxyuridine (BrdU) and bivariate BrdU/DNA flow cytometric analysis. The results were compared with the cell kinetic patterns following topical application of the skin carcinogen methylnitrosourea (MNU) as well as the skin irritant cantharidin. The cell cycle traverse in hairless mouse epidermis 24 h after in vivo exposure to UVB seemed to be a combination of the cell kinetic effects following chemical skin carcinogens and skin irritants. UVB irradiation induced both a delay in transit time through S phase, probably due to DNA damage and subsequent repair, as well as a reduction in the total cell cycle time consistent with rapid regenerative proliferation. (author).

Sinusoidal voltage protocols for rapid characterisation of ion channel kinetics.

Science.gov (United States)

Beattie, Kylie A; Hill, Adam P; Bardenet, Rémi; Cui, Yi; Vandenberg, Jamie I; Gavaghan, David J; de Boer, Teun P; Mirams, Gary R

2018-03-24

Ion current kinetics are commonly represented by current-voltage relationships, time constant-voltage relationships and subsequently mathematical models fitted to these. These experiments take substantial time, which means they are rarely performed in the same cell. Rather than traditional square-wave voltage clamps, we fitted a model to the current evoked by a novel sum-of-sinusoids voltage clamp that was only 8 s long. Short protocols that can be performed multiple times within a single cell will offer many new opportunities to measure how ion current kinetics are affected by changing conditions. The new model predicts the current under traditional square-wave protocols well, with better predictions of underlying currents than literature models. The current under a novel physiologically relevant series of action potential clamps is predicted extremely well. The short sinusoidal protocols allow a model to be fully fitted to individual cells, allowing us to examine cell-cell variability in current kinetics for the first time. Understanding the roles of ion currents is crucial to predict the action of pharmaceuticals and mutations in different scenarios, and thereby to guide clinical interventions in the heart, brain and other electrophysiological systems. Our ability to predict how ion currents contribute to cellular electrophysiology is in turn critically dependent on our characterisation of ion channel kinetics - the voltage-dependent rates of transition between open, closed and inactivated channel states. We present a new method for rapidly exploring and characterising ion channel kinetics, applying it to the hERG potassium channel as an example, with the aim of generating a quantitatively predictive representation of the ion current. We fitted a mathematical model to currents evoked by a novel 8 second sinusoidal voltage clamp in CHO cells overexpressing hERG1a. The model was then used to predict over 5 minutes of recordings in the same cell in response to

Comparison of micronucleus frequencies and proliferation kinetics in three X-irradiated cell lines

International Nuclear Information System (INIS)

Kaffenberger, W.; Becker, K.; Beuningen, D. van

1990-01-01

The kinetics of the occurrence of micronuclei was correlated with the survival of three mammalian cell lines of human, monkey, and mouse origin after irradiation with 240 kV X-rays. Particular attention was paid to the evaluation of the individual proliferation kinetics of the cell lines as well as to the characterization of micronuclei subpopulation with respect to size and possible biological importance using DNA and BUdR labelling techniques, fluorescence microscopy, and image analysis. The results demonstrate very characteristic size distributions of micronuclei for the three cell lines independent of radiation dose and time after irradiation. A close correlation between cell death and the occurrence of micronuclei (expressed as a calculated 'MN index') after irradiation could be established only when the kinetics of progression of cells through the cell cycle (e.g. the doubling time) and the biological characteristics of micronuclei (e.g. BUdR positivity, the micronucleus frequencies, and the number of micronuclei per main nucleus) were taken into account. Therefore, the micronucleus assay might not be useful as a quantitative perdictive assay in vivo but may allow qualitative estimations of radiation damage only because the necessary proliferation parameters of the cells might not be possible to establish in vivo. (orig.) [de

Determinants of cell-to-cell variability in protein kinase signaling.

Directory of Open Access Journals (Sweden)

Matthias Jeschke

Full Text Available Cells reliably sense environmental changes despite internal and external fluctuations, but the mechanisms underlying robustness remain unclear. We analyzed how fluctuations in signaling protein concentrations give rise to cell-to-cell variability in protein kinase signaling using analytical theory and numerical simulations. We characterized the dose-response behavior of signaling cascades by calculating the stimulus level at which a pathway responds ('pathway sensitivity' and the maximal activation level upon strong stimulation. Minimal kinase cascades with gradual dose-response behavior show strong variability, because the pathway sensitivity and the maximal activation level cannot be simultaneously invariant. Negative feedback regulation resolves this trade-off and coordinately reduces fluctuations in the pathway sensitivity and maximal activation. Feedbacks acting at different levels in the cascade control different aspects of the dose-response curve, thereby synergistically reducing the variability. We also investigated more complex, ultrasensitive signaling cascades capable of switch-like decision making, and found that these can be inherently robust to protein concentration fluctuations. We describe how the cell-to-cell variability of ultrasensitive signaling systems can be actively regulated, e.g., by altering the expression of phosphatase(s or by feedback/feedforward loops. Our calculations reveal that slow transcriptional negative feedback loops allow for variability suppression while maintaining switch-like decision making. Taken together, we describe design principles of signaling cascades that promote robustness. Our results may explain why certain signaling cascades like the yeast pheromone pathway show switch-like decision making with little cell-to-cell variability.

Kinetics of thymine dimer excision in ultraviolet-irradiated human cells

International Nuclear Information System (INIS)

Ehmann, U.K.; Cook, K.H.; Friedberg, E.C.

1978-01-01

We have investigated the kinetics of the loss of thymine dimers from the acid-insoluble fraction of several ultraviolet (uv)-irradiated cultured human cell lines. Our results show that uv fluences between 10 and 40 J/m 2 produce an average of 21 to 85 x 10 5 thymine dimers per cell and an eventual maximal loss per cell of 12 to 20 x 10 5 thymine dimers. The time for half-maximal loss of dimers ranged from 12 to 22 h after uv irradiation. In contrast, the time for half-maximal repair synthesis of DNA measured by autoradiography was 4.5 h. This figure agrees well with reported half-maximal repair synthesis times, which range from 0.5 to 3.6 h based on our analysis. The discrepancy in the kinetics of the loss of thymine dimers from DNA and repair synthesis is discussed in terms of possible molecular mechanisms of thymine dimer excision in vivo and in terms of possible experimental artifacts

Cell cycle analyses with a pulse cytophotometer: the effect of chemical and physical noxae on the kinetics of the proliferation of tumor cells

International Nuclear Information System (INIS)

Goehde, W.

The following studies were conducted on Ehrlich ascites tumor cells using the pulse cytophotometer: rate of DNA synthesis during the S phase; the effect of cytostatic drugs, endoxan, bleomycin, and other antibiotics on cell kinetics; and effects of x radiation and 1 to 6 MeV neutrons on cell kinetics

Cell kinetic and radiosensitivity of PHA stimulated goat lymphocytes

International Nuclear Information System (INIS)

Debuyst, B.; Rosenthal, M.; Leonard, A.

1982-01-01

The harlequin-staining method has been used to study the cell kinetic of goat peripheral blood lymphocytes stimulated by phytohemagglutinin and to assess their radiosensitivity. At 48 h, the standardized culture time employed for human lymphocytes, 71% of the goat lymphocytes are in first mitosis, 23% are in second mitosis and 5% in third. Irradiation with 200 rads X-rays induces an average of 24,5 dicentric chromosomes per hundred cells in first mitosis [fr

An Evaluation of Kinetic Parameters of Cadmium and Copper Biosorption by Immobilized Cells

Directory of Open Access Journals (Sweden)

Nelly Georgieva

2007-10-01

Full Text Available Bioremediation is the use of living organisms to reduce or eliminate environmental hazards resulting from the accumulation of toxic chemicals and other hazardous wastes. This technology is based on the utilization of microorganisms to transform organic and inorganic compounds. The filamentous yeast Trichosporon cutaneum strain R57, immobilized and free cells was cultivated as batch culture on a liquid medium in the presence of various concentrations of cadmium and copper ions. The simultaneous uptake and accumulation of Cd2+ and Cu2+ ions by Tr. cutaneum cells depending on the initial concentration of Cd2+ and Cu2+ in the medium were studied. The potential use of the free and immobilized cells of Trichosporon cutaneum to remove cadmium and copper ions, from aqueous solutions was evaluated. Two important physicochemical aspects for the evaluation of the sorption process as a unit operation are the equilibrium of sorption and the kinetics. The Cd2+ and Cu2+ ions biosorption capacities of all tested adsorbent were presented as a function of the initial concentration of metal ions within the aqueous biosorption medium. The individual, as well as bicomponent sorption kinetics of copper and cadmium ions by immobilised cells of Trichosporon cutaneum R57 is presented. A second order kinetic model obtains kinetic parameters for the copper and cadmium ions.

Personalized Whole-Cell Kinetic Models of Metabolism for Discovery in Genomics and Pharmacodynamics

DEFF Research Database (Denmark)

Bordbar, Aarash; McCloskey, Douglas; Zielinski, Daniel C

2015-01-01

Understanding individual variation is fundamental to personalized medicine. Yet interpreting complex phenotype data, such as multi-compartment metabolomic profiles, in the context of genotype data for an individual is complicated by interactions within and between cells and remains an unresolved...... challenge. Here, we constructed multi-omic, data-driven, personalized whole-cell kinetic models of erythrocyte metabolism for 24 healthy individuals based on fasting-state plasma and erythrocyte metabolomics and whole-genome genotyping. We show that personalized kinetic rate constants, rather than...

Cell kinetics of hypoxic cells in a murine tumour in vivo: flow cytometric determination of the radiation-induced blockage of cell cycle progression

International Nuclear Information System (INIS)

Rutgers, D.H.; Niessen, D.P.P.; Linden, P.M. van der

1987-01-01

Cells from the small cell population of viable cells in the large necrotic centre of murine M8013 tumours were investigated with respect to their cell kinetics. Flow cytometry (FCM) of this part of subcutaneously transplanted tumours revealed the presence of tumour cells with G1,S and G2 + M phase DNA-contents. These severely hypoxic cells could have stopped cell cycle progression due to the nutritional deprivation, irrespective of their position within the cell cycle. Labelling methods, used to disclose the cell kinetics of this cell population, are hampered by the absence of a transport system in these large necrotic areas. Therefore FCM was used to monitor radiation induced changes in the cell cycle distribution. From this investigation it was concluded that hypoxic cells in the necrotic centre of the M8013 tumour progress through the cell cycle. As well as a cell population with a cell cycle time (Tsub(c)) of approximately 84 hr, a subpopulation with a Tsub(c) of approximately 21 hr occurred. (author)

Effect of knee and trunk angle on kinetic variables during the isometric midthigh pull: test-retest reliability.

Science.gov (United States)

Comfort, Paul; Jones, Paul A; McMahon, John J; Newton, Robert

2015-01-01

The isometric midthigh pull (IMTP) has been used to monitor changes in force, maximum rate of force development (mRFD), and impulse, with performance in this task being associated with performance in athletic tasks. Numerous postures have been adopted in the literature, which may affect the kinetic variables during the task; therefore, the aim of this investigation was to determine whether different knee-joint angles (120°, 130°, 140°, and 150°) and hip-joint angles (125° and 145°), including the subjects preferred posture, affect force, mRFD, and impulse during the IMTP. Intraclass correlation coefficients demonstrated high within-session reliability (r ≥ .870, P kinetic variables determined in all postures, excluding impulse measures during the 130° knee-flexion, 125° hip-flexion posture, which showed a low to moderate reliability (r = .666-.739, P .819, P kinetic variables. There were no significant differences in peak force (P > .05, Cohen d = 0.037, power = .408), mRFD (P > .05, Cohen d = 0.037, power = .409), or impulse at 100 ms (P > .05, Cohen d = 0.056, power = .609), 200 ms (P > .05, Cohen d = 0.057, power = .624), or 300 ms (P > .05, Cohen d = 0.061, power = .656) across postures. Smallest detectable differences demonstrated that changes in performance of >1.3% in peak isometric force, >10.3% in mRFD, >5.3% in impulse at 100 ms, >4.4% in impulse at 200 ms, and >7.1% in impulse at 300 ms should be considered meaningful, irrespective of posture.

Cell kinetics of gastrointestinal tumors after different nutritional regimens. A preliminary report

International Nuclear Information System (INIS)

Franchi, F.; Rossi-Fanelli, F.; Seminara, P.; Cascino, A.; Barone, C.; Scucchi, L.

1991-01-01

Forty-four cases of different untreated gastrointestinal tumors were studied with regard to cell kinetic activity. As a pilot experiment, the authors also determined the 3H-TdR Labeling Index (LI) in 28 patients in basal conditions and after 15 days of nutritional manipulation with prevalently lipid-based or glucose-based feeding to ascertain whether selective nutritional regimens could affect tumor proliferation. Preliminary results from this study indicate that a kinetic perturbation is induced in tumor cells by nutritional manipulation. Lipid-based feeding seems to produce effects similar to those of chemical or physical anticancer agents, thus suggesting a possible supporting role of nutritional manipulation in cancer treatment strategy

Prospects in the Study of Stem-Cell Kinetics

Energy Technology Data Exchange (ETDEWEB)

Till, J. E. [Department of Medical Biophysics, University of Toronto (Canada); Ontario Cancer Instute, Toronto, ON (Canada)

1968-08-15

The recent rapid progress in the field of stem-cell kinetics has been due in large part to the development of reliable in-vivo assays for the functions of haemopoietic stem cells. As a direct result of the availability of these assays, several novel and interesting phenomena have been described. What is now needed is not so much further search for new phenomena as an understanding of the phenomena that have already been uncovered. It is postulated that new approaches will be required for the analysis of these phenomena, and that future progress in the field will be strongly dependent on the development of methods suitable for the detailed study of the growth and differentiation of populations of haemopoietic cells in culture systems. (author)

Measuring kinetic drivers of pneumolysin pore structure.

Science.gov (United States)

Gilbert, Robert J C; Sonnen, Andreas F-P

2016-05-01

Most membrane attack complex-perforin/cholesterol-dependent cytolysin (MACPF/CDC) proteins are thought to form pores in target membranes by assembling into pre-pore oligomers before undergoing a pre-pore to pore transition. Assembly during pore formation is into both full rings of subunits and incomplete rings (arcs). The balance between arcs and full rings is determined by a mechanism dependent on protein concentration in which arc pores arise due to kinetic trapping of the pre-pore forms by the depletion of free protein subunits during oligomerization. Here we describe the use of a kinetic assay to study pore formation in red blood cells by the MACPF/CDC pneumolysin from Streptococcus pneumoniae. We show that cell lysis displays two kinds of dependence on protein concentration. At lower concentrations, it is dependent on the pre-pore to pore transition of arc oligomers, which we show to be a cooperative process. At higher concentrations, it is dependent on the amount of pneumolysin bound to the membrane and reflects the affinity of the protein for its receptor, cholesterol. A lag occurs before cell lysis begins; this is dependent on oligomerization of pneumolysin. Kinetic dissection of cell lysis by pneumolysin demonstrates the capacity of MACPF/CDCs to generate pore-forming oligomeric structures of variable size with, most likely, different functional roles in biology.

Second Law Analysis for a Variable Viscosity Reactive Couette Flow under Arrhenius Kinetics

Directory of Open Access Journals (Sweden)

N. S. Kobo

2010-01-01

Full Text Available This study investigates the inherent irreversibility associated with the Couette flow of a reacting variable viscosity combustible material under Arrhenius kinetics. The nonlinear equations of momentum and energy governing the flow system are solved both analytically using a perturbation method and numerically using the standard Newton Raphson shooting method along with a fourth-order Runge Kutta integration algorithm to obtain the velocity and temperature distributions which essentially expedite to obtain expressions for volumetric entropy generation numbers, irreversibility distribution ratio, and the Bejan number in the flow field.

Radiosensitivity and cell kinetics of the human solid cancer transplanted to nude mouse

International Nuclear Information System (INIS)

Ikeuchi, Shunji

1983-01-01

This study was undertaken to analyse the relationship between radiosensitivity and cell kinetics of human solid cancer in experimental nude mouse system. Four strains of tumors used for the experiment were poorly differentiated squamous cell carcinoma of the lung (Lu-9), oat cell carcinoma of the lung (Lu-24), well differentiated squamous cell carcinoma of the tongue (To-1) and moderately differentiated squamous cell carcinoma of the esophagus (Es-4) which were serially transplantable to BALB/c nude mice. Radiosensitivity was evaluated by tumor growth in terms of inhibition rate, histological change and host reaction after irradiation. Cell kinetics were studied by autoradiography with pulse administration of 3 H-thymidine to mice. Although Lu-24 was most radiosensitive, followed by To-1, Es-4 and Lu-9 in the order of sensitivity, it was suggested that they might be more radioresistant in nude mice without T-cell function than in human. Regarding squamous cell carcinomas, well differentiated type was more radiosensitive than poorly differentiated one. All of these tumors in nude mouse revealed distinct percent labeled mitosis curves with two clear peaks which were quite different from those in human body. Lu-24 showed a characteristic pattern with a long time lag before visible growth, short G 1 , and low growth fraction, compared to other three tumors. Three strains of squamous cell carcinoma demonstrated similar cell kinetic factors which were almost the same as those in human body reported previously. The differences in volume doubling time of tumor, growth fraction and cell loss factor were partially related to those of radiosensitivities among tumors except for Lu-24. The theoretical volume doubling time was proved to be most reliable for estimation of effectiveness of irradiation, but the labeling index was not a valuable indicator for it. (author)

Enrichment of tumor cells for cell kinetic analysis in human tumor biopsies using cytokeratin gating

International Nuclear Information System (INIS)

Haustermans, K.; Hofland, I.; Ramaekers, M.; Ivanyi, D.; Balm, A.J.M.; Geboes, K.; Lerut, T.; Schueren, E. van der; Begg, A.C.

1996-01-01

Purpose: To determine the feasibility of using cytokeratin antibodies to distinguish normal and malignant cells in human tumors using flow cytometry. The goal was ultimately to increase the accuracy of cell kinetic measurements on human tumor biopsies. Material and methods: A panel of four antibodies was screened on a series of 48 tumors from two centres; 22 head and neck tumors (Amsterdam) and 26 esophagus carcinomas (Leuven). First, screening was carried out by immunohistochemistry on frozen sections to test intensity of staining and the fraction of cytokeratin-positive tumor cells. The antibody showing the most positive staining was then used for flow cytometry on the same tumor. Results: The two broadest spectrum antibodies (AE1/AE3, E3/C4) showed overall the best results with immunohistochemical staining, being positive in over 95% of tumors. Good cell suspensions for DNA flow cytometry could be made from frozen material by a mechanical method, whereas enzymatic methods with trypsin or collagenase were judged failures in almost all cases. >From fresh material, both collagenase and trypsin produced good suspensions for flow cytometry, although the fraction of tumor cells, judged by proportion aneuploid cells, was markedly higher for trypsin. Using the best cytokeratin antibody for each tumor, two parameter flow cytometry was done (cytokeratin versus DNA content). Enrichment of tumor cells was then tested by measuring the fraction of aneuploid cells (the presumed malignant population) of cytokeratin-positive cells versus all cells. An enrichment factor ranging between 0 (no enrichment) and 1 (perfect enrichment, tumor cells only) was then calculated. The average enrichment was 0.60 for head and neck tumors and 0.59 for esophagus tumors. Conclusions: We conclude that this method can substantially enrich the proportion of tumor cells in biopsies from carcinomas. Application of this method could significantly enhance accuracy of tumor cell kinetic measurements

Dynamic Modeling of Cell-Free Biochemical Networks Using Effective Kinetic Models

Science.gov (United States)

2015-03-03

based whole-cell models of E. coli [6]. Conversely , highly abstracted kinetic frameworks, such as the cybernetic framework, represented a paradigm shift...metabolic objective function has been the optimization of biomass formation [18], although other metabolic objectives have also been estimated [19...experimental data. Toward these questions, we explored five hypothetical cell-free networks. Each network shared the same enzymatic connectivity, but

In vivo cell kinetics in breast carcinogenesis

International Nuclear Information System (INIS)

Bai, Maria; Agnantis, Niki J; Kamina, Sevasti; Demou, Asimina; Zagorianakou, Panayiota; Katsaraki, Aphroditi; Kanavaros, Panayiotis

2001-01-01

Disruption of the balance between apoptosis and proliferation is considered to be an important factor in the development and progression of tumours. In the present study we determined the in vivo cell kinetics along the spectrum of apparently normal epithelium, hyperplasia, preinvasive lesions and invasive carcinoma, in breast tissues affected by fibrocystic changes in which preinvasive and/or invasive lesions developed, as a model of breast carcinogenesis. A total of 32 areas of apparently normal epithelium and 135 ductal proliferative and neoplastic lesions were studied. More than one epithelial lesion per case were analyzed. The apoptotic index (AI) and the proliferative index (PI) were expressed as the percentage of TdT-mediated dUTP-nick end-labelling (TUNEL) and Ki-67-positive cells, respectively. The PI/AI (P/A index) was calculated for each case. The AIs and PIs were significantly higher in hyperplasia than in apparently normal epithelium (P = 0.04 and P = 0.0005, respectively), in atypical hyperplasia than in hyperplasia (P = 0.01 and P = 0.04, respectively) and in invasive carcinoma than in in situ carcinoma (P < 0.001 and P < 0.001, respectively). The two indices were similar in atypical hyperplasia and in in situ carcinoma. The P/A index increased significantly from normal epithelium to hyperplasia (P = 0.01) and from preinvasive lesions to invasive carcinoma (P = 0.04) whereas it was decreased (non-significantly) from hyperplasia to preinvasive lesions. A strong positive correlation between the AIs and the PIs was found (r = 0.83, P < 0.001). These findings suggest accelerating cell turnover along the continuum of breast carcinogenesis. Atypical hyperplasias and in situ carcinomas might be kinetically similar lesions. In the transition from normal epithelium to hyperplasia and from preinvasive lesions to invasive carcinoma the net growth of epithelial cells results from a growth imbalance in favour of proliferation. In the transition from hyperplasia

MarCell trademark software for modeling bone marrow radiation cell kinetics

International Nuclear Information System (INIS)

Hasan, J.S.; Jones, T.D.; Morris, M.D.

1997-01-01

Differential equations were used to model cellular injury, repair, and compensatory proliferation in the irradiated bone marrow. Recently, that model was implemented as MarCell trademark, a user-friendly MS-DOS computer program that allows users from a variety of technical disciplines to evaluate complex radiation exposure. The software allows menu selections for different sources of ionizing radiation. Choices for cell lineages include progenitor, stroma, and malignant, and the available species include mouse, rat, dog, sheep, swine, burro, and man. An attractive feature is that any protracted irradiation can be compared with an equivalent prompt dose (EPD) in terms of cell kinetics for either the source used or for a reference such as 250 kVp x rays or 60 Co. EPD is used to mean a dose rate for which no meaningful biological recovery occurs during the period of irradiation. For human as species, output from MarCell trademark includes: risk of 30-day mortality; risk of whole-body cancer and leukemia based either on radiation-induced cytopenia or compensatory cell proliferation; cell survival and repopulation plots as functions of time or dose; and 4-week recovery following treatment. copyright 1997 American Association of Physicists in Medicine

Using a split luciferase assay (SLA) to measure the kinetics of cell-cell fusion mediated by herpes simplex virus glycoproteins.

Science.gov (United States)

Saw, Wan Ting; Matsuda, Zene; Eisenberg, Roselyn J; Cohen, Gary H; Atanasiu, Doina

2015-11-15

Herpes simplex virus (HSV) entry and cell-cell fusion require the envelope proteins gD, gH/gL and gB. We propose that receptor-activated conformational changes to gD activate gH/gL, which then triggers gB (the fusogen) into an active form. To study this dynamic process, we have adapted a dual split protein assay originally developed to study the kinetics of human immunodeficiency virus (HIV) mediated fusion. This assay uses a chimera of split forms of renilla luciferase (RL) and green fluorescent protein (GFP). Effector cells are co-transfected with the glycoproteins and one of the split reporters. Receptor-bearing target cells are transfected with the second reporter. Co-culture results in fusion and restoration of RL, which can convert a membrane permeable substrate into a luminescent product, thereby enabling one to monitor initiation and extent of fusion in live cells in real time. Restoration of GFP can also be studied by fluorescence microscopy. Two sets of split reporters have been developed: the original one allows one to measure fusion kinetics over hours whereas the more recent version was designed to enhance the sensitivity of RL activity allowing one to monitor both initiation and rates of fusion in minutes. Here, we provide a detailed, step-by-step protocol for the optimization of the assay (which we call the SLA for split luciferase assay) using the HSV system. We also show several examples of the power of this assay to examine both the initiation and kinetics of cell-cell fusion by wild type forms of gD, gB, gH/gL of both serotypes of HSV as well as the effect of mutations and antibodies that alter the kinetics of fusion. The SLA can be applied to other viral systems that carry out membrane fusion. Copyright © 2015 Elsevier Inc. All rights reserved.

Aging increases cell-to-cell transcriptional variability upon immune stimulation.

Science.gov (United States)

Martinez-Jimenez, Celia Pilar; Eling, Nils; Chen, Hung-Chang; Vallejos, Catalina A; Kolodziejczyk, Aleksandra A; Connor, Frances; Stojic, Lovorka; Rayner, Timothy F; Stubbington, Michael J T; Teichmann, Sarah A; de la Roche, Maike; Marioni, John C; Odom, Duncan T

2017-03-31

Aging is characterized by progressive loss of physiological and cellular functions, but the molecular basis of this decline remains unclear. We explored how aging affects transcriptional dynamics using single-cell RNA sequencing of unstimulated and stimulated naïve and effector memory CD4 + T cells from young and old mice from two divergent species. In young animals, immunological activation drives a conserved transcriptomic switch, resulting in tightly controlled gene expression characterized by a strong up-regulation of a core activation program, coupled with a decrease in cell-to-cell variability. Aging perturbed the activation of this core program and increased expression heterogeneity across populations of cells in both species. These discoveries suggest that increased cell-to-cell transcriptional variability will be a hallmark feature of aging across most, if not all, mammalian tissues. Copyright © 2017, American Association for the Advancement of Science.

Energy Transfer Kinetics in Photosynthesis as an Inspiration for Improving Organic Solar Cells.

Science.gov (United States)

Nganou, Collins; Lackner, Gerhard; Teschome, Bezu; Deen, M Jamal; Adir, Noam; Pouhe, David; Lupascu, Doru C; Mkandawire, Martin

2017-06-07

Clues to designing highly efficient organic solar cells may lie in understanding the architecture of light-harvesting systems and exciton energy transfer (EET) processes in very efficient photosynthetic organisms. Here, we compare the kinetics of excitation energy tunnelling from the intact phycobilisome (PBS) light-harvesting antenna system to the reaction center in photosystem II in intact cells of the cyanobacterium Acaryochloris marina with the charge transfer after conversion of photons into photocurrent in vertically aligned carbon nanotube (va-CNT) organic solar cells with poly(3-hexyl)thiophene (P3HT) as the pigment. We find that the kinetics in electron hole creation following excitation at 600 nm in both PBS and va-CNT solar cells to be 450 and 500 fs, respectively. The EET process has a 3 and 14 ps pathway in the PBS, while in va-CNT solar cell devices, the charge trapping in the CNT takes 11 and 258 ps. We show that the main hindrance to efficiency of va-CNT organic solar cells is the slow migration of the charges after exciton formation.

Spatiotemporal Variability of Turbulence Kinetic Energy Budgets in the Convective Boundary Layer over Both Simple and Complex Terrain

Energy Technology Data Exchange (ETDEWEB)

Rai, Raj K. [Pacific Northwest National Laboratory, Richland, Washington; Berg, Larry K. [Pacific Northwest National Laboratory, Richland, Washington; Pekour, Mikhail [Pacific Northwest National Laboratory, Richland, Washington; Shaw, William J. [Pacific Northwest National Laboratory, Richland, Washington; Kosovic, Branko [National Center for Atmospheric Research, Boulder, Colorado; Mirocha, Jeffrey D. [Lawrence Livermore National Laboratory, Livermore, California; Ennis, Brandon L. [Sandia National Laboratories, Albuquerque, New Mexico

2017-12-01

The assumption of sub-grid scale (SGS) horizontal homogeneity within a model grid cell, which forms the basis of SGS turbulence closures used by mesoscale models, becomes increasingly tenuous as grid spacing is reduced to a few kilometers or less, such as in many emerging high-resolution applications. Herein, we use the turbulence kinetic energy (TKE) budget equation to study the spatio-temporal variability in two types of terrain—complex (Columbia Basin Wind Energy Study [CBWES] site, north-eastern Oregon) and flat (ScaledWind Farm Technologies [SWiFT] site, west Texas) using the Weather Research and Forecasting (WRF) model. In each case six-nested domains (three domains each for mesoscale and large-eddy simulation [LES]) are used to downscale the horizontal grid spacing from 10 km to 10 m using the WRF model framework. The model output was used to calculate the values of the TKE budget terms in vertical and horizontal planes as well as the averages of grid cells contained in the four quadrants (a quarter area) of the LES domain. The budget terms calculated along the planes and the mean profile of budget terms show larger spatial variability at CBWES site than at the SWiFT site. The contribution of the horizontal derivative of the shear production term to the total production shear was found to be 45% and 15% of the total shear, at the CBWES and SWiFT sites, respectively, indicating that the horizontal derivatives applied in the budget equation should not be ignored in mesoscale model parameterizations, especially for cases with complex terrain with <10 km scale.

Modulating cell-to-cell variability and sensitivity to death ligands by co-drugging

International Nuclear Information System (INIS)

Flusberg, Deborah A; Sorger, Peter K

2013-01-01

TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) holds promise as an anti-cancer therapeutic but efficiently induces apoptosis in only a subset of tumor cell lines. Moreover, even in clonal populations of responsive lines, only a fraction of cells dies in response to TRAIL and individual cells exhibit cell-to-cell variability in the timing of cell death. Fractional killing in these cell populations appears to arise not from genetic differences among cells but rather from differences in gene expression states, fluctuations in protein levels and the extent to which TRAIL-induced death or survival pathways become activated. In this study, we ask how cell-to-cell variability manifests in cell types with different sensitivities to TRAIL, as well as how it changes when cells are exposed to combinations of drugs. We show that individual cells that survive treatment with TRAIL can regenerate the sensitivity and death-time distribution of the parental population, demonstrating that fractional killing is a stable property of cell populations. We also show that cell-to-cell variability in the timing and probability of apoptosis in response to treatment can be tuned using combinations of drugs that together increase apoptotic sensitivity compared to treatment with one drug alone. In the case of TRAIL, modulation of cell-to-cell variability by co-drugging appears to involve a reduction in the threshold for mitochondrial outer membrane permeabilization. (paper)

Radiation Induced G2 Chromatic Break and Repairs Kinetics in Human Lymphoblastoid Cells

International Nuclear Information System (INIS)

Seong, Jin Sil

1993-01-01

In understanding radiosensitivity a new concept of inherent radiosensitivity based on individuality and heterogeneity within a population has recently beer explored. There has been some discussion of possible mechanism underlying differences in radiosensitivity between cells. Ataxia telangiectasia(AT), a rare autosomal recessive genetic disorder, is characterized by hypersensitivity to lonizing radiation and other DNA damaging agents at the cellular level. There have been a lot of efforts to describe the cause of this hypersensitivity to radiation. At the cellular level, chromosome repair kinetics study would be an appropriate approach. The purpose of this study was to better understand radiosensitivity in an approach to investigate kinetics of induction and repair of G2 chromatic breaks using normal, AT heterozygous(ATH), and AT homozygous lymphoblastoid cell lines. In an attempt to estimate initial damage, 9-β-D-arabinosyl-2-fluoroadenine, an inhibitor of DNA synthesis and repair, was used in this study. It was found from this study that radiation induces higher chromatid breaks in AT than in normal and ATH cells. There was no significant differences of initial chromatid breaks between normal and ATH cells. Repair kinetics was the same for all. So the higher level of breaks in AT G2 cells is thought to be a reflection of the increased initial damage. The amount of initial damage correlated well with survival fraction at 2 Gy of cell survival curve following radiation. Therefore, the difference of radiosensitivity in terms of G2 chromosomal sensitivity is thought to result from the difference of initial damage

Cell kinetics, DNA integrity, differentiation, and lipid fingerprinting analysis of rabbit adipose-derived stem cells.

Science.gov (United States)

Barretto, Letícia Siqueira de Sá; Lessio, Camila; Sawaki e Nakamura, Ahy Natally; Lo Turco, Edson Guimarães; da Silva, Camila Gonzaga; Zambon, João Paulo; Gozzo, Fábio César; Pilau, Eduardo Jorge; de Almeida, Fernando Gonçalves

2014-10-01

Human adipose tissue has been described as a potential alternative reservoir for stem cells. Although studies have been performed in rabbits using autologous adipose-derived stem cells (ADSC), these cells have not been well characterized. The primary objectives of this study were to demonstrate the presence of adipose-derived stem cells isolated from rabbit inguinal fat pads and to characterize them through osteogenic and adipogenic in vitro differentiation and lipid fingerprinting analysis. The secondary objective was to evaluate cell behavior through growth kinetics, cell viability, and DNA integrity. Rabbit ADSCs were isolated to determine the in vitro growth kinetics and cell viability. DNA integrity was assessed by an alkaline Comet assay in passages 0 and 5. The osteogenic differentiation was evaluated by Von Kossa, and Alizarin Red S staining and adipogenic differentiation were assessed by Oil Red O staining. Lipid fingerprinting analyses of control, adipogenic, and osteogenic differentiated cells were performed by MALDI-TOF/MS. We demonstrate that rabbit ADSC have a constant growth rate at the early passages, with increased DNA fragmentation at or after passage 5. Rabbit ADSC viability was similar in passages 2 and 5 (90.7% and 86.6%, respectively), but there was a tendency to decreased cellular growth rate after passage 3. The ADSC were characterized by the expression of surface markers such as CD29 (67.4%) and CD44 (89.4%), using CD 45 (0.77%) as a negative control. ADSC from rabbits were successfully isolated form the inguinal region. These cells were capable to differentiate into osteogenic and adipogenic tissue when they were placed in inductive media. After each passage, there was a trend towards decreased cell growth. On the other hand, DNA fragmentation increased at each passage. ADSC had a different lipid profile when placed in control, adipogenic, or osteogenic media.

Growth and production kinetics of human x mouse and mouse hybridoma cells at reduced temperature and serum content.

Science.gov (United States)

Borth, N; Heider, R; Assadian, A; Katinger, H

1992-09-01

The growth and production kinetics of a mouse hybridoma cell line and a human-mouse heterohybridoma were analyzed under conditions of reduced temperature and serum content. The mouse hybridoma P24 had a constant cell specific production rate and RNA content, while the heterohybridoma 3D6-LC4 showed growth associated production kinetics and an increased RNA content at higher growth rates. This behaviour of 3D6-LC4 cells can be explained by the unusual cell cycle kinetics of this line, which can be arrested in any phase under growth limiting conditions, so that a low growth rate does not result in a greater portion of high producing G1-phase cells. Substrate limitation changes the cell cycle distribution of this cell line to a greater extent than low temperature or serum content, which indicates that this stress factor exerts a greater physiological control than assumed.

A novel microculture kinetic assay (MiCK assay) for malignant cell growth and chemosensitivity.

Science.gov (United States)

Kravtsov, V D

1994-01-01

The THERMOmax microplate reader was adapted for monitoring the growth kinetics of human leukaemic OCI/AML-2 and mouse tumour J-774.1 cell lines in continuous culture. Fluid evaporation from wells, CO2 escape and contamination were prevented by hermetic sealing of the microcultures in wells of a 96-well microplate, thus enabling the cells to grow exponentially for 72 h under the conditions of the incubated microplate reader. For both OCI/AML-2 cells, which grow in suspension, and adherent J-774.1 cells, a linear correlation was demonstrated between the number of unstained cells seeded in a given microplate well and the optical density (OD) of that well. Therefore, the OD/time curve of the culture could be deemed to be its growth curve. By the use of the linear fit equation, the actual number of the cells in the wells was computable at any time point of the assay. In the chemosensitivity test, an inhibitory effect of ARA-C on the growth of the cells could be estimated by viewing of the growth curves plotted on the screen. The maximum kinetic rates (Vmax) of the curves in the control and the ARA-C-treated wells were compared, yielding a growth inhibition index (GII). Comparison of results of the kinetic chemosensitivity assay with those of a [3H]thymidine incorporation assay revealed that the novel assay is suitable for precise quantitation of the cell chemosensitivity, is more informative and has the added technical advantage of performance without recourse to radioactive or chemically hazardous substances.

Mechanisms and kinetics models for ultrasonic waste activated sludge disintegration.

Science.gov (United States)

Wang, Fen; Wang, Yong; Ji, Min

2005-08-31

Ultrasonic energy can be applied as pre-treatment to disintegrate sludge flocs and disrupt bacterial cells' walls, and the hydrolysis can be improved, so that the rate of sludge digestion and methane production is improved. In this paper, by adding NaHCO3 to mask the oxidizing effect of OH, the mechanisms of disintegration are investigated. In addition, kinetics models for ultrasonic sludge disintegration are established by applying multi-variable linear regression method. It has been found that hydro-mechanical shear forces predominantly responsible for the disintegration, and the contribution of oxidizing effect of OH increases with the amount of the ultrasonic density and ultrasonic intensity. It has also been inferred from the kinetics model which dependent variable is SCOD+ that both sludge pH and sludge concentration significantly affect the disintegration.

Kinetics of saccharose fermentation by Kombucha

Directory of Open Access Journals (Sweden)

Lončar Eva S.

2014-01-01

Full Text Available Kinetics of saccharose fermentation by Kombucha is not yet well defined due to lack of knowledge of reaction mechanisms taking place during this process. In this research kinetics of saccharose fermentation by Kombucha was analysed using the suggested empirical model. The data were obtained on 1.5 g L-1 of black tea, with 66.47 g L-1 of saccharose and using 10% (v/v or 15% (v/v of Kombucha. Total number of viable cells was as follows: approximately 5x105 of yeast cells per mL of the inoculum and approximately 2x106 of bacteria cells per mL of the inoculum. The samples were analysed after 0, 3, 4, 5, 6, 7 and 10 days. Their pH values and contents of saccharose, glucose, fructose, total acids and ethanol were determined. A saccharose concentration model was defined as sigmoidal function at 22oC and 30oC, and with 10% (v/v and 15% (v/v of inoculum quantity. Determination coefficients of the functions were very high (R2>0.99. Reaction rates were calculated as first derivatives of Boltzmann’s functions. No simple correlation between rate of reaction and independent variables (temperature and inoculum concentration was found. Analysis of empirical model indicated that saccharose fermentation by Kombucha occurred according to very complex kinetics. [Projekat Ministarstva nauke Republike Srbije, br. III 46009

Modeling bubble dynamics and radical kinetics in ultrasound induced microalgal cell disruption.

Science.gov (United States)

Wang, Meng; Yuan, Wenqiao

2016-01-01

Microalgal cell disruption induced by acoustic cavitation was simulated through solving the bubble dynamics in an acoustical field and their radial kinetics (chemical kinetics of radical species) occurring in the bubble during its oscillation, as well as calculating the bubble wall pressure at the collapse point. Modeling results indicated that increasing ultrasonic intensity led to a substantial increase in the number of bubbles formed during acoustic cavitation, however, the pressure generated when the bubbles collapsed decreased. Therefore, cumulative collapse pressure (CCP) of bubbles was used to quantify acoustic disruption of a freshwater alga, Scenedesmus dimorphus, and a marine alga, Nannochloropsis oculata and compare with experimental results. The strong correlations between CCP and the intracellular lipid fluorescence density, chlorophyll-a fluorescence density, and cell particle/debris concentration were found, which suggests that the developed models could accurately predict acoustic cell disruption, and can be utilized in the scale up and optimization of the process. Copyright © 2015 Elsevier B.V. All rights reserved.

Preliminary model and validation of molten carbonate fuel cell kinetics under sulphur poisoning

Science.gov (United States)

Audasso, E.; Nam, S.; Arato, E.; Bosio, B.

2017-06-01

MCFC represents an effective technology to deal with CO2 capture and relative applications. If used for these purposes, due to the working conditions and the possible feeding, MCFC must cope with a different number of poisoning gases such as sulphur compounds. In literature, different works deal with the development of kinetic models to describe MCFC performance to help both industrial applications and laboratory simulations. However, in literature attempts to realize a proper model able to consider the effects of poisoning compounds are scarce. The first aim of the present work is to provide a semi-empirical kinetic formulation capable to take into account the effects that sulphur compounds (in particular SO2) have on the MCFC performance. The second aim is to provide a practical example of how to effectively include the poisoning effects in kinetic models to simulate fuel cells performances. To test the reliability of the proposed approach, the obtained formulation is implemented in the kinetic core of the SIMFC (SIMulation of Fuel Cells) code, an MCFC 3D model realized by the Process Engineering Research Team (PERT) of the University of Genova. Validation is performed through data collected at the Korea Institute of Science and Technology in Seoul.

Kinetics of apoptotic markers in exogeneously induced apoptosis of EL4 cells.

Science.gov (United States)

Jessel, Robert; Haertel, Steffen; Socaciu, Carmen; Tykhonova, Svetlana; Diehl, Horst A

2002-01-01

We investigated the time-dependence of apoptotic events in EL4 cells by monitoring plasma membrane changes in correlation to DNA fragmentation and cell shrinkage. We applied three apoptosis inducers (staurosporine, tubericidine and X-rays) and we looked at various markers to follow the early-to-late apoptotic events: phospholipid translocation (identified through annexin V-fluorescein assay and propidium iodide), lipid package (via merocyanine assay), membrane fluidity and anisotropy (via fluorescent measurements), DNA fragmentation by the fluorescence-labeling test and cell size measurements. The different apoptotic inducers caused different reactions of the cells: staurosporine induced apoptosis most rapidly in a high number of cells, tubercidine triggered apoptosis only in the S phase cells, while X-rays caused a G2/M arrest and subsequently apoptosis. Loss of lipid asymmetry is promptly detectable after one hour of incubation time. The phosphatidylserine translocation, decrease of lipid package and anisotropy, and the increase of membrane fluidity appeared to be based on the same process of lipid asymmetry loss. Therefore, the DNA fragmentation and the cell shrinkage appear to be parallel and independent processes running on different time scales but which are kinetically inter-related. The results indicate different signal steps to apoptosis dependent on inducer characteristics but the kinetics of "early-to-late" apoptosis appears to be a fixed program.

Robustness of MEK-ERK Dynamics and Origins of Cell-to-Cell Variability in MAPK Signaling

Directory of Open Access Journals (Sweden)

Sarah Filippi

2016-06-01

Full Text Available Cellular signaling processes can exhibit pronounced cell-to-cell variability in genetically identical cells. This affects how individual cells respond differentially to the same environmental stimulus. However, the origins of cell-to-cell variability in cellular signaling systems remain poorly understood. Here, we measure the dynamics of phosphorylated MEK and ERK across cell populations and quantify the levels of population heterogeneity over time using high-throughput image cytometry. We use a statistical modeling framework to show that extrinsic noise, particularly that from upstream MEK, is the dominant factor causing cell-to-cell variability in ERK phosphorylation, rather than stochasticity in the phosphorylation/dephosphorylation of ERK. We furthermore show that without extrinsic noise in the core module, variable (including noisy signals would be faithfully reproduced downstream, but the within-module extrinsic variability distorts these signals and leads to a drastic reduction in the mutual information between incoming signal and ERK activity.

Quantitative carbon-14 autoradiography at the cellular level: principles and application for cell kinetic studies

International Nuclear Information System (INIS)

Doermer, P.

1981-01-01

Amounts of radio-labelled substances as low as 10 -18 moles incorporated into individual cells can be measured by utilizing techniques of quantitative autoradiography. The principles and application of quantitative carbon-14 autoradiography are reviewed. Silver grain densities can be counted by automated microphotometry allowing on-line data processing by an interfaced computer. Rate measurements of 14 C-thymidine incorporation into individual cells yield values of the DNA synthesis rate and the DNA synthesis time of a cell compartment can be derived. This is an essential time parameter for the evaluation of kinetic events in proliferating cell populations. This method is applicable to human cells without radiation hazard to man and provides an optimal source of detailed information on the kinetics of normal and diseased human haematopoiesis. Examples of application consist of thalassaemia, malaria infection, iron deficiency anaemia and acute myelogenous leukaemia. (author)

Cell respiration under hypoxia: facts and artefacts in mitochondrial oxygen kinetics.

Science.gov (United States)

Scandurra, Francesca M; Gnaiger, Erich

2010-01-01

When oxygen supply to tissues is limiting, mitochondrial respiration and ATP production are compromised. To assess the bioenergetic consequences under normoxia and hypoxia, quantitative evaluation of mitochondrial oxygen kinetics is required. Using high-resolution respirometry, the "apparent K (m)" for oxygen or p (50) of respiration in 32D cells was determined at 0.05 +/- 0.01 kPa (0.4 mmHg, 0.5 microM, 0.25% air saturation). Close agreement with p (50) of isolated mitochondria indicates that intracellular gradients are small in small cells at routine activity. At intracellular p (O2) respiration is limited by >2% with a p (50) of 0.05 kPa. Over-estimation of p (50) at 0.4 kPa (3 mmHg) would imply significant (>17%) oxygen limitation of respiration under intracellular normoxia. Based on a critical review, we conclude that p (50) ranges from 0.01 to 0.10 kPa in mitochondria and small cells in the absence of inhibitors of cytochrome c oxidase, whereas experimental artefacts explain the controversial >200-fold range of p (50) in the literature on mitochondrial oxygen kinetics.

Elementary kinetic modelling applied to solid oxide fuel cell pattern anodes and a direct flame fuel cell system

Energy Technology Data Exchange (ETDEWEB)

Vogler, Marcel

2009-05-27

In the course of this thesis a model for the prediction of polarisation characteristics of solid oxide fuel cells (SOFC) was developed. The model is based on an elementary kinetic description of electrochemical reactions and the fundamental conservation principles of mass and energy. The model allows to predict the current-voltage relation of an SOFC and offers ideal possibilities for model validation. The aim of this thesis is the identification of rate-limiting processes and the determination of the elementary pathway during charge transfer. The numerical simulation of experiments with model anodes allowed to identify a hydrogen transfer to be the most probable charge-transfer reaction and revealed the influence of diffusive transport. Applying the hydrogen oxidation kinetics to the direct flame fuel cell system (DFFC) showed that electrochemical oxidation of CO is possible based on the same mechanism. Based on the quantification of loss processes in the DFFC system, improvements on cell design, predicting 80% increase of efficiency, were proposed. (orig.)

Phase transformation kinetics of Voronoi cells in space tessellation governed by the Kolmogorov–Johnson–Mehl–Avrami model

Energy Technology Data Exchange (ETDEWEB)

Tomellini, Massimo, E-mail: tomellini@uniroma2.it

2017-03-26

On the basis of the Kolmogorov–Johnson–Mehl–Avrami (KJMA) method for space tessellation the kinetics of Voronoi cell filling, by central grain growth, has been studied as a function of the cell size. This is done by solving an integral equation for which a class of solutions is obtained in closed form, where the cell-size probability density is the Gamma distribution function. The computation gives the time evolution of the mean grain size, as a function of cell volume, which is further employed for describing the grain-size probability density function. The present approach is applied to determine, analytically, the exact grain-size distribution function in 1D and the size distributions in 2D and 3D through approximation. - Highlights: • The kinetics of cell filling is determined for Poisson–Voronoi tessellation in dD. • The kinetics is obtained in closed form by solving an integral equation. • Connection between the evolution of the mean grain and the size distribution is studied. • The exact grain-size distribution function is determined, analytically, in 1D.

Physiological role of Kv1.3 channel in T lymphocyte cell investigated quantitatively by kinetic modeling.

Directory of Open Access Journals (Sweden)

Panpan Hou

Full Text Available Kv1.3 channel is a delayed rectifier channel abundant in human T lymphocytes. Chronic inflammatory and autoimmune disorders lead to the over-expression of Kv1.3 in T cells. To quantitatively study the regulatory mechanism and physiological function of Kv1.3 in T cells, it is necessary to have a precise kinetic model of Kv1.3. In this study, we firstly established a kinetic model capable to precisely replicate all the kinetic features for Kv1.3 channels, and then constructed a T-cell model composed of ion channels including Ca2+-release activated calcium (CRAC channel, intermediate K+ (IK channel, TASK channel and Kv1.3 channel for quantitatively simulating the changes in membrane potentials and local Ca2+ signaling messengers during activation of T cells. Based on the experimental data from current-clamp recordings, we successfully demonstrated that Kv1.3 dominated the membrane potential of T cells to manipulate the Ca2+ influx via CRAC channel. Our results revealed that the deficient expression of Kv1.3 channel would cause the less Ca2+ signal, leading to the less efficiency in secretion. This was the first successful attempt to simulate membrane potential in non-excitable cells, which laid a solid basis for quantitatively studying the regulatory mechanism and physiological role of channels in non-excitable cells.

Electrochemical reduction of CO₂ and H₂O into fuels: Cell types and kinetic barriers

DEFF Research Database (Denmark)

Mogensen, Mogens Bjerg

2013-01-01

of production rate/cost. Production rate is determined mainly by electrode kinetics. Therefore, parallel to improving the electrodes of these electrolyser cells, other cell types, which have faster electrode kinetics, can electrolyse CO2 and have potential lower investment costs, are being researched...

Kinetic parameters evaluation of PWRs using static cell and core calculation codes

International Nuclear Information System (INIS)

Jahanbin, Ali; Malmir, Hessam

2012-01-01

Highlights: ► In this study, we have calculated effective delayed neutron fraction and prompt neutron lifetime in PWRs. ► New software has been developed to link the WIMS, BORGES and CITATION codes in Visual C computer programming language. ► This software is used for calculation of the kinetic parameters in a typical VVER-1000 and NOK Beznau reactor. ► The ratios ((β eff ) i )/((β eff ) core ) , which are the important input data for the reactivity accident analysis, are also calculated. - Abstract: In this paper, evaluation of the kinetic parameters (effective delayed neutron fraction and prompt neutron lifetime) in PWRs, using static cell and core calculation codes, is reported. A new software has been developed to link the WIMS, BORGES and CITATION codes in Visual C computer programming language. Using the WIMS cell calculation code, multigroup microscopic cross-sections and number densities of different materials can be generated in a binary file. By the use of BORGES code, these binary-form cross-sections and number densities are converted to a format readable by the CITATION core calculation code, by which the kinetic parameters can be finally obtained. This software is used for calculation of the kinetic parameters in a typical VVER-1000 and NOK Beznau reactor. The ratios ((β eff ) i )/((β eff ) core ) , which are the important input data for the reactivity accident analysis, are also calculated. Benchmarking of the results against the final safety analysis report (FSAR) of the aforementioned reactors shows very good agreements with these published documents.

Contributions of cell growth and biochemical reactions to nongenetic variability of cells.

NARCIS (Netherlands)

Schwabe, A.; Bruggeman, F.J.

2014-01-01

Cell-to-cell variability in the molecular composition of isogenic, steady-state growing cells arises spontaneously from the inherent stochasticity of intracellular biochemical reactions and cell growth. Here, we present a general decomposition of the total variance in the copy number per cell of a

Carbonate-mediated Fe(II) oxidation in the air-cathode fuel cell: a kinetic model in terms of Fe(II) speciation.

Science.gov (United States)

Song, Wei; Zhai, Lin-Feng; Cui, Yu-Zhi; Sun, Min; Jiang, Yuan

2013-06-06

Due to the high redox activity of Fe(II) and its abundance in natural waters, the electro-oxidation of Fe(II) can be found in many air-cathode fuel cell systems, such as acid mine drainage fuel cells and sediment microbial fuel cells. To deeply understand these iron-related systems, it is essential to elucidate the kinetics and mechanisms involved in the electro-oxidation of Fe(II). This work aims to develop a kinetic model that adequately describes the electro-oxidation process of Fe(II) in air-cathode fuel cells. The speciation of Fe(II) is incorporated into the model, and contributions of individual Fe(II) species to the overall Fe(II) oxidation rate are quantitatively evaluated. The results show that the kinetic model can accurately predict the electro-oxidation rate of Fe(II) in air-cathode fuel cells. FeCO3, Fe(OH)2, and Fe(CO3)2(2-) are the most important species determining the electro-oxidation kinetics of Fe(II). The Fe(II) oxidation rate is primarily controlled by the oxidation of FeCO3 species at low pH, whereas at high pH Fe(OH)2 and Fe(CO3)2(2-) are the dominant species. Solution pH, carbonate concentration, and solution salinity are able to influence the electro-oxidation kinetics of Fe(II) through changing both distribution and kinetic activity of Fe(II) species.

Kinetics of cell lysis for Microcystis aeruginosa and Nitzschia palea in the exposure to β-cyclocitral

International Nuclear Information System (INIS)

Chang, De-Wei; Hsieh, Meng-Ling; Chen, Yan-Min; Lin, Tsair-Fuh; Chang, Jo-Shu

2011-01-01

The effect of an algal metabolite, β-cyclocitral, on the cell integrity of two cyanobacteria and one diatom was investigated. The cyanobacteria, Microcystis aeruginosa PCC 7005 and PCC 7820, and the diatom, Nitzschia palea, were exposed to various concentrations of β-cyclocitral. Scanning electron microscope (SEM) results indicate that the cells of tested species were greatly altered after being exposed to β-cyclocitral. A flow cytometer coupled with the SYTOX stain and chlorophyll-a auto-fluorescence was used to quantify the effect of β-cyclocitral on cell integrity for the tested cyanobacteria and diatom. Kinetic experiments show that about 5-10 mg L -1 of β-cyclocitral for the two M. aeruginosa strains and a much lower concentration, 0.1-0.5 mg L -1 , for N. palea were needed to cause 15-20% of cells to rupture. When the β-cyclocitral concentration was increased to 200-1000 mg L -1 for M. aeruginosa and 5-10 mg L -1 for N. palea, almost all the cells ruptured between 8 and 24 h. A first-order kinetic model is able to describe the data of cell integrity over time. The extracted rate constant values well correlate with the applied β-cyclocitral dosages. The obtained kinetic parameters may be used to estimate β-cyclocitral dosage and contact time required for the control of cyanobacteria and diatoms in water bodies.

Cell and tissue kinetics of the subependymal layer in mouse brain following heavy charged particle irradiation

International Nuclear Information System (INIS)

Manley, N.B.

1988-01-01

The following studies investigate the cellular response and cell population kinetics of the subependymal layer in the mouse brain exposed to heavy charged particle irradiation. Partial brain irradiation with helium and neon ions was confined to one cortex of the brain. Both the irradiated and the unirradiated contralateral cortex showed similar disturbances of the cell and tissue kinetics in the subependymal layers. The irradiated hemisphere exhibited histological damage, whereas the unirradiated side appeared normal histologically. The decrease in the values of the labeling indices 1 week after charged particle irradiation was dose- and ion-dependent. Mitotic indices 1 week after 10 and 25 Gy helium and after 10 Gy neon were the same as those seen in the control mice. Analysis of cell kinetics 1 week after 10 Gy helium and 10 Gy neon irradiation suggests the presence of a progenitor subpopulation that is proliferating with a shorter cell cycle. Comparison of the responses to the different charged particle beams indicates that neon ions are more effective in producing direct cellular damage than the helium ions, but the surviving proliferating cells several divisions later continue to maintain active cell renewal. Based on the 1 week post-irradiation H 3 -TdR labeling indices, a rough estimate of the RBE for neon ions is at least 2.5 when compared to helium ions

Variability and Order in Cytoskeletal Dynamics of Motile Amoeboid Cells

Science.gov (United States)

Hsu, Hsin-Fang; Bodenschatz, Eberhard; Westendorf, Christian; Gholami, Azam; Pumir, Alain; Tarantola, Marco; Beta, Carsten

2017-10-01

The chemotactic motion of eukaryotic cells such as leukocytes or metastatic cancer cells relies on membrane protrusions driven by the polymerization and depolymerization of actin. Here we show that the response of the actin system to a receptor stimulus is subject to a threshold value that varies strongly from cell to cell. Above the threshold, we observe pronounced cell-to-cell variability in the response amplitude. The polymerization time, however, is almost constant over the entire range of response amplitudes, while the depolymerization time increases with increasing amplitude. We show that cell-to-cell variability in the response amplitude correlates with the amount of Arp2 /3 , a protein that enhances actin polymerization. A time-delayed feedback model for the cortical actin concentration is consistent with all our observations and confirms the role of Arp2 /3 in the observed cell-to-cell variability. Taken together, our observations highlight robust regulation of the actin response that enables a reliable timing of cell movement.

Kinetic analysis of dihydroxyacetone production from crude glycerol by immobilized cells of Gluconobacter oxydans MTCC 904.

Science.gov (United States)

Dikshit, Pritam Kumar; Moholkar, Vijayanand S

2016-09-01

The present study has investigated kinetic features of bioconversion of biodiesel-derived crude glycerol to dihydroxyacetone with immobilized Gluconobacter oxydans cells using modified Haldane substrate-inhibition model. The results have been compared against free cells and pure glycerol. Relative variations in the kinetic parameters KS, KI, Vmax, n and X reveal that immobilized G. oxydans cells (on PU foam substrate) with crude glycerol as substrate give higher order of inhibition (n) and lower maximum reaction velocities (Vmax). These results are essentially implications of substrate transport restrictions across immobilization matrix, which causes retention of substrate in the matrix and reduction in fractional available substrate (X) for the cells. This causes reduction in both KS (substrate concentration at Vmax/2) and KI (inhibition constant) as compared to free cells. For immobilized cells, substrate concentration (Smax) corresponding to Vmax is practically same for both pure and crude glycerol as substrate. Copyright © 2016 Elsevier Ltd. All rights reserved.

Quantitative carbon-14 autoradiography at the cellular level: principles and application for cell kinetic studies. [Review

Energy Technology Data Exchange (ETDEWEB)

Doermer, P [Gesellschaft fuer Strahlen- und Umweltforschung m.b.H., Muenchen (Germany, F.R.). Inst. fuer Haematologie

1981-03-01

Amounts of radio-labelled substances as low as 10/sup -18/ moles incorporated into individual cells can be measured by utilizing techniques of quantitative autoradiography. The principles and application of quantitative carbon-14 autoradiography are reviewed. Silver grain densities can be counted by automated microphotometry allowing on-line data processing by an interfaced computer. Rate measurements of /sup 14/C-thymidine incorporation into individual cells yield values of the DNA synthesis rate and the DNA synthesis time of a cell compartment can be derived. This is an essential time parameter for the evaluation of kinetic events in proliferating cell populations. This method is applicable to human cells without radiation hazard to man and provides an optimal source of detailed information on the kinetics of normal and diseased human haematopoiesis. Examples of application consist of thalassaemia, malaria infection, iron deficiency anaemia and acute myelogenous leukaemia.

Ion-neutral gas reactions in a collision/reaction cell in inductively coupled plasma mass spectrometry: Correlation of ion signal decrease to kinetic rate constants

Energy Technology Data Exchange (ETDEWEB)

Gray, Patrick J. [Trace Element Research Laboratory, School of Earth Sciences, The Ohio State University, 125 S. Oval Mall, Columbus, OH 43210 (United States); Department of Chemistry, The Ohio State University, 120 18th Avenue, Columbus, OH 43210 (United States); Olesik, John W., E-mail: olesik.2@osu.edu [Trace Element Research Laboratory, School of Earth Sciences, The Ohio State University, 125 S. Oval Mall, Columbus, OH 43210 (United States)

2015-03-01

Reaction gas flow rate dependent Ar{sub 2}{sup +} and Ar{sup +} signals are correlated to fundamental kinetic rate coefficients. A simple calculation, assuming that gas exits the reaction cell due only to effusion, is described to estimate the gas pressure in the reaction cell. The value of the product of the kinetic rate constant and the ion residence time in the reaction cell can be determined from experimental measurement of the decrease in an ion signal as a function of reaction gas flow rate. New kinetic rate constants are determined for the reaction of CH{sub 3}F with Ar{sup +} and Ar{sub 2}{sup +}. - Highlights: • How to determine pressure and the product of the kinetic rate constant times the ion residence time in reaction cell • Relate measured ICP-DRC-MS signals versus gas flow rate to kinetic rate constants measured previously using SIFT-MS • Describe how to determine previously unmeasured kinetic rate constants using ICP-DRC-MS.

Effects of hyperthermia on growth kinetics of Chinese hamster ovarian carcinoma cells

International Nuclear Information System (INIS)

Leeper, D.B.; Bobyock, S.B.

1987-01-01

The effects of hyperthermia on growth rate, cell volume, and density at plateau phase were studied in OvCa cells in monolayer culture in McCoy's 5a + 10% FCS. At 37 0 C, T/sub G/=9.3 hr, cell density at plateau was 32 x 10/sup 4//cm/sup 2/, and mean cell volume decreased from 1200 μ/sup 3/ at the onset of exponential growth to 850 μ/sup 3/ in plateau phase. Cells were acutely heated for 60' at 43 0 ,30' at 44 0 , or 15' at 45 0 (S.F.=20%) and incubated at 37 0 ; or were chronically heated for up to 80 hr at 39-42 0 . Acute heating at 43-45 0 delayed cell division for appx 13 hr after which growth resumed with a T/sub G/=18 hr. Incubation at 39-40 0 had no effect on T/sub G/, but temperatures of 40.5-42 0 increased T/sub G/ at ΔH=176 kcal/mole. Increasing incubation temperature decreased cell density at plateau phase and altered cell volume kinetics. Cell density in plateau phase was 20 x 10/sup 4//cm/sup 2/ at 39 0 , 13 x 10/sup 4//cm/sup 2/ at 40 0 , 5x10/sup 4//cm/sup 2/ at 41 0 . Growth was greatly reduced at 42 0 (T/sub G/=55 hr) and doubling did not occur before onset of cell lysis. The decrease in cell volume with growth of the culture was unaffected at 39 0 . However, at temperatures ≥40 0 cell volume transiently increase, and the rate of decrease in volume that normally occurred with growth at 37-39 0 was less such that at 41 0 there was no decrease in volume at all before cells entered plateau phase. The authors' hypothesis is that the effects of heat on growth kinetics are related to alterations in rates of protein synthesis. This is currently being tested

Distinguishing between stochasticity and determinism: Examples from cell cycle duration variability.

Science.gov (United States)

Pearl Mizrahi, Sivan; Sandler, Oded; Lande-Diner, Laura; Balaban, Nathalie Q; Simon, Itamar

2016-01-01

We describe a recent approach for distinguishing between stochastic and deterministic sources of variability, focusing on the mammalian cell cycle. Variability between cells is often attributed to stochastic noise, although it may be generated by deterministic components. Interestingly, lineage information can be used to distinguish between variability and determinism. Analysis of correlations within a lineage of the mammalian cell cycle duration revealed its deterministic nature. Here, we discuss the sources of such variability and the possibility that the underlying deterministic process is due to the circadian clock. Finally, we discuss the "kicked cell cycle" model and its implication on the study of the cell cycle in healthy and cancerous tissues. © 2015 WILEY Periodicals, Inc.

Statolith sedimentation kinetics and force transduction to the cortical endoplasmic reticulum in gravity-sensing Arabidopsis columella cells.

Science.gov (United States)

Leitz, Guenther; Kang, Byung-Ho; Schoenwaelder, Monica E A; Staehelin, L Andrew

2009-03-01

The starch statolith hypothesis of gravity sensing in plants postulates that the sedimentation of statoliths in specialized statocytes (columella cells) provides the means for converting the gravitational potential energy into a biochemical signal. We have analyzed the sedimentation kinetics of statoliths in the central S2 columella cells of Arabidopsis thaliana. The statoliths can form compact aggregates with gap sizes between statoliths approaching sedimentation phase, the statoliths tend to move at a distance to the cortical endoplasmic reticulum (ER) boundary and interact only transiently with the ER. Statoliths moved by laser tweezers against the ER boundary experience an elastic lift force upon release from the optical trap. High-resolution electron tomography analysis of statolith-to-ER contact sites indicate that the weight of statoliths is sufficient to locally deform the ER membranes that can potentially activate mechanosensitive ion channels. We suggest that in root columella cells, the transduction of the kinetic energy of sedimenting statoliths into a biochemical signal involves a combination of statolith-driven motion of the cytosol, statolith-induced deformation of the ER membranes, and a rapid release of kinetic energy from the ER during reorientation to activate mechanosensitive sites within the central columella cells.

Culture of normal human blood cells in a diffusion chamber system II. Lymphocyte and plasma cell kinetics

International Nuclear Information System (INIS)

Chikkappa, G.; Carsten, A.L.; Chanana, A.D.; Cronkite, E.P.

1979-01-01

Normal human blood leukocytes were cultured in Millipore diffusion chambers implanted into the peritoneal cavities of irradiated mice. The evaluation of survival and proliferation kinetics of cells in lymphyocytic series suggested that the lymphoid cells are formed from transition of small and/or large lymphocytes, and the lymphoblasts from the lymphoid cells. There was also evidence indicating that some of the cells in these two compartments are formed by proliferation. The evaluation of plasmacytic series suggested that the plasma cells are formed from plasmacytoid-lymphocytes by transition, and the latter from the transition of lymphocytes. In addition, relatively a small fraction of cells in these two compartments are formed by proliferation. mature plasma cells do not and immature plasma cells do proliferate. Estimation of magnitude of plasma cells formed in the cultures at day 18 indicated that at least one plasma cell is formed for every 6 normal human blood lymphocytes introduced into the culture

Analysis of individual cells identifies cell-to-cell variability following induction of cellular senescence.

Science.gov (United States)

Wiley, Christopher D; Flynn, James M; Morrissey, Christapher; Lebofsky, Ronald; Shuga, Joe; Dong, Xiao; Unger, Marc A; Vijg, Jan; Melov, Simon; Campisi, Judith

2017-10-01

Senescent cells play important roles in both physiological and pathological processes, including cancer and aging. In all cases, however, senescent cells comprise only a small fraction of tissues. Senescent phenotypes have been studied largely in relatively homogeneous populations of cultured cells. In vivo, senescent cells are generally identified by a small number of markers, but whether and how these markers vary among individual cells is unknown. We therefore utilized a combination of single-cell isolation and a nanofluidic PCR platform to determine the contributions of individual cells to the overall gene expression profile of senescent human fibroblast populations. Individual senescent cells were surprisingly heterogeneous in their gene expression signatures. This cell-to-cell variability resulted in a loss of correlation among the expression of several senescence-associated genes. Many genes encoding senescence-associated secretory phenotype (SASP) factors, a major contributor to the effects of senescent cells in vivo, showed marked variability with a subset of highly induced genes accounting for the increases observed at the population level. Inflammatory genes in clustered genomic loci showed a greater correlation with senescence compared to nonclustered loci, suggesting that these genes are coregulated by genomic location. Together, these data offer new insights into how genes are regulated in senescent cells and suggest that single markers are inadequate to identify senescent cells in vivo. © 2017 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

Programmed Cell-to-Cell Variability in Ras Activity Triggers Emergent Behaviors during Mammary Epithelial Morphogenesis

Directory of Open Access Journals (Sweden)

Jennifer S. Liu

2012-11-01

Full Text Available Variability in signaling pathway activation between neighboring epithelial cells can arise from local differences in the microenvironment, noisy gene expression, or acquired genetic changes. To investigate the consequences of this cell-to-cell variability in signaling pathway activation on coordinated multicellular processes such as morphogenesis, we use DNA-programmed assembly to construct three-dimensional MCF10A microtissues that are mosaic for low-level expression of activated H-Ras. We find two emergent behaviors in mosaic microtissues: cells with activated H-Ras are basally extruded or lead motile multicellular protrusions that direct the collective motility of their wild-type neighbors. Remarkably, these behaviors are not observed in homogeneous microtissues in which all cells express the activated Ras protein, indicating that heterogeneity in Ras activity, rather than the total amount of Ras activity, is critical for these processes. Our results directly demonstrate that cell-to-cell variability in pathway activation within local populations of epithelial cells can drive emergent behaviors during epithelial morphogenesis.

KINEMATIC AND KINETIC VARIABLES DIFFER BETWEEN KETTLEBELL SWING STYLES.

Science.gov (United States)

Bullock, Garrett S; Schmitt, Abigail C; Shutt, Jason M; Cook, Gray; Butler, Robert J

2017-06-01

Kettlebell (KB) and indian club swings (ICS) are used diversely for developing strength and power. It has been proposed that multiple swing techniques can be used interchangeably to elicit similar adaptations within performance training. Hypothesis/Purpose: It was hypothesized that there will be not be a difference in peak joint angles between types of swings. Furthermore, given the nature of the overhead kettlebell swing (OKS), it was hypothesized that the OKS will be associated with a greater cycle time and a greater vertical impulse compared to shoulder height swing (SKS) and ICS. The purpose of this study was to analyze the kinematics and kinetics of the SKS, OKS, and ICS. Cross-sectional cohort. Fifteen healthy subjects underwent 3D biomechanical analysis for assessment of kinematic and kinetic data. Subjects performed two trials of ten repetitions at full effort for each swing in a randomized order using either a standard set of 0.45 kg indian clubs or sex specific KB loads (Female = 12kg, Male = 20kg). Lower extremity sagittal plane kinematics and kinetics were analyzed for peak values during the down and up portions of the swing patterns. Statistical analyses were carried out utilizing one-way ANOVAs ( p power training. 2.

Antiretroviral Tissue Kinetics: In Vivo Imaging Using Positron Emission Tomography▿

OpenAIRE

Di Mascio, Michele; Srinivasula, Sharat; Bhattacharjee, Abesh; Cheng, Lily; Martiniova, Lucia; Herscovitch, Peter; Lertora, Juan; Kiesewetter, Dale

2009-01-01

Our current knowledge on the antiviral efficacy, dosing, and toxicity of available highly active antiretroviral therapy regimens is mostly derived from plasma or blood kinetics of anti-human immunodeficiency virus (anti-HIV) drugs. However, the blood comprises only 2% of the total target cells in the body. Tissue drug levels may differ substantially from corresponding plasma levels, and drug distribution processes may be characterized by high intertissue variability, leading to suboptimal tar...

Binding kinetics of magnetic nanoparticles on latex beads and yeast cells studied by magnetorelaxometry

International Nuclear Information System (INIS)

Eberbeck, Dietmar; Bergemann, Christian; Hartwig, Stefan; Steinhoff, Uwe; Trahms, Lutz

2005-01-01

The ion exchange mediated binding of magnetic nanoparticles (MNP) to modified latex spheres and yeast cells was quantified using magnetorelaxometry. By fitting subsequently recorded relaxation curves, the kinetics of the binding reactions was extracted. The signal of MNP with weak ion exchanger groups bound to latex and yeast cells scales linearly with the concentration of latex beads or yeast cells whereas that of MNP with strong ion exchanger groups is proportional to the square root of concentration. The binding of the latter leads to a much stronger aggregation of yeast cells than the former MNP

Proliferation kinetics and survival of mammal cells after treatment with radiation of various ionization densities and with hyperthermia

International Nuclear Information System (INIS)

Schlag, H.

1977-01-01

Survival and proliferation kinetics of chinese hamster cells after Co-γ-, π - -meson irradiation, hyperthermia (40 - 43 0 C), and a combination of Co-γ irradiation and hyperthermia were studied in this paper. After γ-irradiation, exponential-phase and stationary-phase cells showed equal survival rates for equal doses. Cytofluorometric analysis showed that there was a dose-dependent delay in the synthesis phase with subsequent cell blocking in the G 2 +M phase. After irradiation with π - mesons, there is a dose-dependent accumulation in the G 2 +M phase, with a RBE of 2.2. The different response of S-phase cells to radiations of different LET may be explained with the inactivation kinetics typical of each type of radiation. The effectiveness of hyperthermal treatment depends on the stage of growth of the cells. A temperature of 40 0 C does not induce cell killing, not even after prolonged exposure. After 7 hours' exposure to 41 0 C, on the other hand, 80% of the cells are killed after blocking in G 2 +M. Exposure to 42 0 C for 1-2 h induces a synchronisation effect which is induced by a block in S and G 2 +M. After exposure to 42 0 C for 4 h, however, the cells blocked in S are killed in this phase. Combination of Co-γ radiation leads to increased cells killing and also to sensitization, especially of cells in the exponential growth stage. The proliferation kinetics effects of this combined treatment are the same as after pion irradiation. (orig.) [de

Kinetic modeling of cell metabolism for microbial production.

Science.gov (United States)

Costa, Rafael S; Hartmann, Andras; Vinga, Susana

2016-02-10

Kinetic models of cellular metabolism are important tools for the rational design of metabolic engineering strategies and to explain properties of complex biological systems. The recent developments in high-throughput experimental data are leading to new computational approaches for building kinetic models of metabolism. Herein, we briefly survey the available databases, standards and software tools that can be applied for kinetic models of metabolism. In addition, we give an overview about recently developed ordinary differential equations (ODE)-based kinetic models of metabolism and some of the main applications of such models are illustrated in guiding metabolic engineering design. Finally, we review the kinetic modeling approaches of large-scale networks that are emerging, discussing their main advantages, challenges and limitations. Copyright © 2015 Elsevier B.V. All rights reserved.

DEFLUORIDATION OF DRINKING WATER BY ELECTROCOAGULATION/ELECTROFLOTATION - KINETIC STUDY

Directory of Open Access Journals (Sweden)

Bennajah Mounir

2010-06-01

Full Text Available A variable order kinetic (VOK model derived from the langmuir-freundlish equation was applied to determine the kinetics of fluoride removal reaction by electrocoagulation (EC. Synthetic solutions were employed to elucidate the effects of the initial fluoride concentration, the applied current and the initial acidity on the simulation results of the model. The proposed model successfully describes the fluoride removal in Airlift reactor in comparison with the experimental results. In this study two EC cells with the same capacity (V = 20 L were used to carry out fluoride removal with aluminum electrodes, the first is a stirred tank reactor (STR the second is an airlift reactor (ALR. The comparison of energy consumption demonstrates that the (ALR is advantageous for carrying out the defluoridation removal process.

Fulfillment of the kinetic Bohm criterion in a quasineutral particle-in-cell model

International Nuclear Information System (INIS)

Ahedo, Eduardo; Santos, Robert; Parra, Felix I.

2010-01-01

Quasineutral particle-in-cell models of ions must fulfill the kinetic Bohm criterion, in its inequality form, at the domain boundary in order to match correctly with solutions of the Debye sheaths tied to the walls. The simple, fluid form of the Bohm criterion is shown to be a bad approximation of the exact, kinetic form when the ion velocity distribution function has a significant dispersion and involves different charge numbers. The fulfillment of the Bohm criterion is measured by a weighting algorithm at the boundary, but linear weighting algorithms have difficulties to reproduce the nonlinear behavior around the sheath edge. A surface weighting algorithm with an extended temporal weighting is proposed and shown to behave better than the standard volumetric weighting. Still, this must be supplemented by a forcing algorithm of the kinetic Bohm criterion. This postulates a small potential fall in a supplementary, thin, transition layer. The electron-wall interaction is shown to be of little relevance in the fulfillment of the Bohm criterion.

Origins and implications of pluripotent stem cell variability and heterogeneity

Science.gov (United States)

Cahan, Patrick; Daley, George Q.

2014-01-01

Pluripotent stem cells constitute a platform to model disease and developmental processes and can potentially be used in regenerative medicine. However, not all pluripotent cell lines are equal in their capacity to differentiate into desired cell types in vitro. Genetic and epigenetic variations contribute to functional variability between cell lines and heterogeneity within clones. These genetic and epigenetic variations could ‘lock’ the pluripotency network resulting in residual pluripotent cells or alter the signalling response of developmental pathways leading to lineage bias. The molecular contributors to functional variability and heterogeneity in both embryonic stem (ES) cells and induced pluripotent stem (iPS) cells are only beginning to emerge, yet they are crucial to the future of the stem cell field. PMID:23673969

ASPEN: A fully kinetic, reduced-description particle-in-cell model for simulating parametric instabilities

International Nuclear Information System (INIS)

Vu, H.X.; Bezzerides, B.; DuBois, D.F.

1999-01-01

A fully kinetic, reduced-description particle-in-cell (RPIC) model is presented in which deviations from quasineutrality, electron and ion kinetic effects, and nonlinear interactions between low-frequency and high-frequency parametric instabilities are modeled correctly. The model is based on a reduced description where the electromagnetic field is represented by three separate temporal envelopes in order to model parametric instabilities with low-frequency and high-frequency daughter waves. Because temporal envelope approximations are invoked, the simulation can be performed on the electron time scale instead of the time scale of the light waves. The electrons and ions are represented by discrete finite-size particles, permitting electron and ion kinetic effects to be modeled properly. The Poisson equation is utilized to ensure that space-charge effects are included. The RPIC model is fully three dimensional and has been implemented in two dimensions on the Accelerated Strategic Computing Initiative (ASCI) parallel computer at Los Alamos National Laboratory, and the resulting simulation code has been named ASPEN. The authors believe this code is the first particle-in-cell code capable of simulating the interaction between low-frequency and high-frequency parametric instabilities in multiple dimensions. Test simulations of stimulated Raman scattering, stimulated Brillouin scattering, and Langmuir decay instability are presented

Effect on growth and cell cycle kinetics of estradiol and tamoxifen on MCF-7 human breast cancer cells grown in vitro and in nude mice

DEFF Research Database (Denmark)

Brünner, N; Bronzert, D; Vindeløv, L L

1989-01-01

The effects of estradiol and tamoxifen (TAM) on the estrogen-dependent human breast cancer cell line MCF-7 grown in vitro and in nude mice were compared. The effect on growth was determined by cell number in vitro and by tumor growth curves in nude mice. The effects on the cell cycle kinetics were...... determined by repeated flow cytometric DNA analyses in vitro and in vivo and by the technique of labeled mitosis in nude mouse-grown tumors. Under in vitro conditions, estradiol induced a pronounced increase in S-phase fraction and cell number. TAM inhibited growth of MCF-7 cells with a concomitant increase...... in the G1 phase from 60% to 75%. In nude mice, MCF-7 only formed tumors in estradiol-supplemented mice. No differences were observed in growth and cell kinetics between 0.1 and 1.0 mg of estradiol. Daily i.p. injections of TAM resulted in tumor growth inhibition with shrinkage of tumors. The flow...

Cell kinetics during regeneration in the sponge Halisarca caerulea: how local is the response to tissue damage?

NARCIS (Netherlands)

Alexander, B.E.; Achlatis, M.; Osinga, R.; van der Geest, H.G.; Cleutjens, J.P.M.; Schutte, B.; de Goeij, J.M.

2015-01-01

Sponges have a remarkable capacity to rapidly regenerate in response to wound infliction. In addition, sponges rapidly renew their filter systems (choanocytes) to maintain a healthy population of cells. This study describes the cell kinetics of choanocytes in the encrusting reef sponge Halisarca

Kinetic Studies on State of the Art Solid Oxide Cells – A Comparison between Hydrogen/Steam and Reformate Fuels

DEFF Research Database (Denmark)

Njodzefon, Jean-Claude; Graves, Christopher R.; Mogensen, Mogens Bjerg

2015-01-01

Electrochemical reaction kinetics at the electrodes of Solid Oxide Cells (SOCs) were investigated at 700 °C for two cells with different fuel electrode microstructures as well as on a third cell with a reduced active electrode area. Three fuel mixtures were investigated – hydrogen/steam and refor......Electrochemical reaction kinetics at the electrodes of Solid Oxide Cells (SOCs) were investigated at 700 °C for two cells with different fuel electrode microstructures as well as on a third cell with a reduced active electrode area. Three fuel mixtures were investigated – hydrogen....../steam fuel split into two processes with opposing temperature behavior in the reformate fuels. An 87.5% reduction in active electrode area diminishes the gas conversion impedance in the hydrogen/steam fuel at high fuel flow rates. In both reformates, the second and third lowest frequency processes merged...

[Lectin-binding patterns and cell kinetics of head and neck squamous cell carcinomas].

Science.gov (United States)

Gotoh, T

1991-01-01

In order to elucidate the cell characteristics of head and neck squamous cell carcinomas, the cell kinetics and lectin binding patterns were compared with the histological classification and staging of the tumors, using surgically resected materials (maxillary sinus 10, oral cavity 21, pharynx 8, larynx 11). Eight biotinylated lectins (WGA, 1-PHA, ConA, UEA1, RCA1, SBA, DBA, PNA) were applied to the paraffin-embedded sections, and were visualized histochemically by the streptavidin-alkaline phosphatase method. The DNA contents of the isolated carcinoma cells obtained from the adjacent thick sections were evaluated using an epi-illumination cytofluorometer after propidium iodide staining. On lectin histochemistry, the binding pattern of WGA lectin was similar between carcinoma tissues and normal tissues, but the binding was more intense in well differentiated than less differentiated carcinomas. Lymph node metastasis was found to be related to the presence of cells with poor WGA-binding. In the binding patterns of the other lectins, RCA1, SBA and ConA were related to the differentiation of carcinomas, but they were not related to the TNM-classification. DNA cytofluorometry exhibited marked polyploidization, which progressed with the advancement of the clinical and pathological staging of carcinomas. However, the DNA ploidy pattern was not associated with the cell characteristics such as the degree of histological differentiation and the lectin-binding pattern, except that the appearance of aneuploidy had some relationship with the binding-patterns of UEA1 and 1-PHA.

Effect of hypoxia on thallium kinetics in cultured chick myocardial cells

International Nuclear Information System (INIS)

Friedman, B.J.; Beihn, R.; Friedman, J.P.

1987-01-01

To assess the effect of hypoxia on cellular thallium-201 ( 201 Tl) uptake and washout independent of coronary flow, we studied thallium kinetics during normoxia and hypoxia in cultured chick ventricular cells. Monolayers of contracting ventricular cells grown on coverslips were placed in a chamber and perfused to asymptote with media containing 201 Tl. Perfusates were equilibrated with 5% CO 2 -95% air or 5% CO 2 -95% nitrogen for normoxia and hypoxia, respectively. Washout thallium kinetics were then observed during perfusion with unlabeled media. Twenty paired experiments were performed, randomly alternating the sequence of normoxia and hypoxia. Pharmacokinetics for thallium were determined by computer using standard formulae. Thallium uptake and washout were best described by assuming that intracellular thallium was contained within a single compartment. Cellular thallium uptake, as well as transfer rate constants for thallium uptake and for thallium washout during normoxia and hypoxia, were compared using paired t-tests. During normoxia and hypoxia, respectively, thallium uptake was 22 +/- 7% and 19 +/- 7% of asymptote (p less than 0.01); the compartmental rate constant for uptake by the cell was 0.16 +/- 0.07 min-1 and 0.15 +/- 0.06 min-1 (N.S.); and the transfer rate constant for washout from the cell was 0.26 +/- 0.06 min-1 and 0.23 +/- 0.05 min-1 (p less than 0.01). We conclude that there was a small (14%) decrease in thallium uptake during hypoxia. The rate of thallium uptake and washout was slightly less during hypoxia, although only the rate of washout was significantly less. These data show that cellular accumulation of thallium and the rate of washout of thallium were minimally decreased by hypoxia independent of blood flow

Delayed Activation Kinetics of Th2- and Th17 Cells Compared to Th1 Cells.

Science.gov (United States)

Duechting, Andrea; Przybyla, Anna; Kuerten, Stefanie; Lehmann, Paul V

2017-09-12

During immune responses, different classes of T cells arise: Th1, Th2, and Th17. Mobilizing the right class plays a critical role in successful host defense and therefore defining the ratios of Th1/Th2/Th17 cells within the antigen-specific T cell repertoire is critical for immune monitoring purposes. Antigen-specific Th1, Th2, and Th17 cells can be detected by challenging peripheral blood mononuclear cells (PBMC) with antigen, and establishing the numbers of T cells producing the respective lead cytokine, IFN-γ and IL-2 for Th1 cells, IL-4 and IL-5 for Th2, and IL-17 for Th-17 cells, respectively. Traditionally, these cytokines are measured within 6 h in flow cytometry. We show here that 6 h of stimulation is sufficient to detect peptide-induced production of IFN-γ, but 24 h are required to reveal the full frequency of protein antigen-specific Th1 cells. Also the detection of IL-2 producing Th1 cells requires 24 h stimulation cultures. Measurements of IL-4 producing Th2 cells requires 48-h cultures and 96 h are required for frequency measurements of IL-5 and IL-17 secreting T cells. Therefore, accounting for the differential secretion kinetics of these cytokines is critical for the accurate determination of the frequencies and ratios of antigen-specific Th1, Th2, and Th17 cells.

Kinetic of magnetic nanoparticles uptake evaluated by morphometry of mice peritoneal cells

International Nuclear Information System (INIS)

Silva, L.P.; Kuckelhaus, S.; Guedes, M.H.A.; Lacava, Z.G.M.; Tedesco, A.C.; Morais, P.C.; Azevedo, R.B.

2005-01-01

The development of magnetic fluids (MFs) has led to a wide range of new biomedical applications. Nevertheless, few studies have examined the kinetics of the magnetic nanoparticles (MNPs) internalization by phagocytes. In this study, we present morphometry as a method to quantify the cell surface covered by MNPs. The maximum cell surface covered by MNPs aggregates was 32.5% (8.5 min), 18.3% (24.1 min), and 18.0% (20.2 min) in DMSA, citric acid and dextran-coated MNPs, respectively. We concluded that the phagocytosis process of MNPs is strongly dependent upon the coating species

Bone cell kinetics in the metaphysis of the growing long bone of the rat

International Nuclear Information System (INIS)

Kimmel, D.B.; Jee, W.S.

1976-01-01

The growing long bone metaphysis of rats was studied in a cell kinetic and morphometric analysis using tritiated thymidine as a tracer of cells. The results showed striking differences in the distribution and movements of osteoprogenitor and osteoblasts as compared to the osteoclasts. The results also showed a deficiency in cell production in the proliferating bone cells in the metaphysis. A new model of bone cell origin, proliferation, and movements in the metaphysis is proposed; osteoblasts and osteoprogenitor cells, the bone surface cells endemic to the metaphysis, are a continuum in adding bone forming cells and forming new bone on the calcified cartilage cores of the metaphysis. The osteoclasts, on the other hand, arise from mononuclear blood cells brought to the metaphysis through metaphyseal blood vessel spaces near the growth cartilage-metaphyseal junction

Kinetic Risk Factors of Running-Related Injuries in Female Recreational Runners.

Science.gov (United States)

Napier, Christopher; MacLean, Christopher L; Maurer, Jessica; Taunton, Jack E; Hunt, Michael A

2018-05-30

Our objective was to prospectively investigate the association of kinetic variables with running-related injury (RRI) risk. Seventy-four healthy female recreational runners ran on an instrumented treadmill while 3D kinetic and kinematic data were collected. Kinetic outcomes were vertical impact transient, average vertical loading rate, instantaneous vertical loading rate, active peak, vertical impulse, and peak braking force (PBF). Participants followed a 15-week half-marathon training program. Exposure time (hours of running) was calculated from start of program until onset of injury, loss to follow-up, or end of program. After converting kinetic variables from continuous to ordinal variables based on tertiles, Cox proportional hazard models with competing risks were fit for each variable independently, before analysis in a forward stepwise multivariable model. Sixty-five participants were included in the final analysis, with a 33.8% injury rate. PBF was the only kinetic variable that was a significant predictor of RRI. Runners in the highest tertile (PBF recreational runners and should be considered as a target for gait retraining interventions. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Hydrocarbon fermentation: kinetics of microbial cell growth

Energy Technology Data Exchange (ETDEWEB)

Goma, G [Institut National des Sciences Appliquees, Toulouse; Ribot, D

1978-11-01

Modeling of microbial growth using nonmiscible substrate is studied when kinetics of substrate dissolution is rate limiting. When the substrate concentration is low, the growth rate is described by an analytical relation that can be identified as a Contois relationship. If the substrate concentration is greater than a critical value S/sub crit/, the potentially useful hydrocarbon S* concentration is described by S* = S/sub crit//(1 + S/sub crit//S). A relationship was found between S/sub crit/ and the biomass concentration X. When X increased, S/sub crit/ decreased. The cell growth rate is related to a relation ..mu.. = ..mu../sub m/(A(X/S/sub crit/)(1 + S/sub crit//S) + 1)/sup -1/. This model describes the evolution of the growth rate when exponential or linear growth occurs, which is related to physico-chemical properties and hydrodynamic fermentation conditions. Experimental data to support the model are presented.

Kinetics of Cu (II) separation by ion flotation techniques, in cells with flexible spargers

International Nuclear Information System (INIS)

Reyes, M.; Tavera, F. J.; Escudero, R.; Patino, F.; Salinas, E.; Rivera, I.

2010-01-01

This research studies and experimentally determines the kinetic parameters and effect of modifying the hydrodynamics and chemical conditions of the air-liquid dispersions during the Cu (II) extraction by ion flotation techniques in cells with porous spargers. Results show that the elimination of Cu (II) from solution can be carried out by ion flotation in one stage, obtaining efficiencies of 68% and 56% for the flat and cylindrical sparger respectively with a xanthate concentration of 0,02 g/l. In multistage systems five cells, recoveries over 92 % were achieved for both sparger geometries. The behavior of the flotation apparent kinetic constant is linear to the parameters that characterize dispersion (Jg, eg y Db), until a point is achieved where the process instability makes the system inoperable. The results show that removing base metal ions by ion flotation is strongly affected by the following factors: collector concentration [C], Jg, eg, Db, Jl and Sb. (Author) 20 refs

CELL POPULATION KINETICS OF EXCISED ROOTS OF PISUM SATIVUM

Science.gov (United States)

Van't Hof, Jack

1965-01-01

The cell population kinetics of excised, cultured pea roots was studied with the use of tritiated thymidine and colchicine to determine (1) the influence of excision, (2) the influence of sucrose concentration, (3) the average mitotic cycle duration, and (4) the duration of mitosis and the G 1, S, and G 2 periods of interphase.1 The results indicate that the process of excision causes a drop in the frequency of mitotic figures when performed either at the beginning of the culture period or after 100 hours in culture. This initial decrease in frequency of cell division is independent of sucrose concentration, but the subsequent rise in frequency of division, after 12 hours in culture, is dependent upon sucrose concentration. Two per cent sucrose maintains the shortest mitotic cycle duration. The use of colchicine indicated an average cycle duration of 20 hours, whereas the use of tritiated thymidine produced an average cycle duration of 17 hours. PMID:5857253

Kinetics of chromatid aberrations in G2 ataxia-telangiectasia cells exposed to X-rays and ara A

International Nuclear Information System (INIS)

Mozdarani, Hossein; Bryant, P.E.

1989-01-01

The cytogenetic effects of X-rays alone or in combination with 9-β-D-arabinofuranosyladenine (ara A) were studied in an immortalized fibroblastic line of ataxia-telangiectasia (A-T) cells. It is postulated that the kinetics of disappearance (rejoining) of chromatid deletions with postirradiation incubation time reflects the underlying repair of dsb, and is inhibited by ara A. The rejoining kinetics for deletions in A-T was similar to that found in a previous study of normal human fibroblasts (Mozdarani and Bryant 1987). The number of deletions in X-irradiated A-T cells at 1.5 h before fixation was found to be higher by a factor of approximately 2 than that found previously in normals, indicating that in A-T a higher rate of conversion of dsb into chromatid deletions occurs. The frequency of exchanges induced in G2 A-T cells was similarly enhanced but, unlike the situation in normal cells, ara A was found to cause only a slight increase in this frequency. (author)

Kinetics of antigen specific and non-specific polyclonal B-cell responses during lethal Plasmodium yoelii malaria

Directory of Open Access Journals (Sweden)

Laurence Rolland

1992-06-01

Full Text Available In order to study the kinetics and composition of the polyclonal B-cell activation associated to malaria infection, antigen-specific and non-specific B-cell responses were evaluated in the spleens of mice infected with Plasmodium yoelii 17 XL or injected with lysed erythrocytes or plasma from P. yoelii infected mice or with P. falciparum culture supernatants. Spleen/body weigth ratio, numbers of nucleated spleen cells and Immunoglobulin-containing and Immunoglobulin-secreting cells increased progressively during the course of infection,in parallel to the parasitemia. A different pattern of kinetics was observed when anti-sheep red blood cell and anti-trinitrophenylated-sheep red blood cell plaque forming cells response were studied: maximum values were observed at early stages of infection, whereas the number of total Immunoglobulin-containing and Immunoglobulin-secreting cells were not yet altered. Conversely, at the end of infection, when these latter values reached their maximum, the anti-sheep red blood cell and anti-trinitrophenylated-sheep red blood cell specific responses were normal or even infranormal. In mice injected with Plasmodium-derived material, a higher increase in antigen-specific PFC was observed, as compared to the increase of Immunoglobulin-containing and Immunoglobulin-secreting cell numbers. This suggested a "preferential" (antigen-plus mitogen-induced stimulation of antigen-specific cells rather than a generalized non-specific (mitogen-induced triggering of B-lymphocytes. On the basis of these and previous results, it is suggested that polyclonal B-cell activation that takes place during the course of infection appears as a result of successive waves of antigen-specific B-cell activation.

Light-Mediated Kinetic Control Reveals the Temporal Effect of the Raf/MEK/ERK Pathway in PC12 Cell Neurite Outgrowth

Science.gov (United States)

Zhang, Kai; Duan, Liting; Ong, Qunxiang; Lin, Ziliang; Varman, Pooja Mahendra; Sung, Kijung; Cui, Bianxiao

2014-01-01

It has been proposed that differential activation kinetics allows cells to use a common set of signaling pathways to specify distinct cellular outcomes. For example, nerve growth factor (NGF) and epidermal growth factor (EGF) induce different activation kinetics of the Raf/MEK/ERK signaling pathway and result in differentiation and proliferation, respectively. However, a direct and quantitative linkage between the temporal profile of Raf/MEK/ERK activation and the cellular outputs has not been established due to a lack of means to precisely perturb its signaling kinetics. Here, we construct a light-gated protein-protein interaction system to regulate the activation pattern of the Raf/MEK/ERK signaling pathway. Light-induced activation of the Raf/MEK/ERK cascade leads to significant neurite outgrowth in rat PC12 pheochromocytoma cell lines in the absence of growth factors. Compared with NGF stimulation, light stimulation induces longer but fewer neurites. Intermittent on/off illumination reveals that cells achieve maximum neurite outgrowth if the off-time duration per cycle is shorter than 45 min. Overall, light-mediated kinetic control enables precise dissection of the temporal dimension within the intracellular signal transduction network. PMID:24667437

A compendium of temperature responses of Rubisco kinetic traits: variability among and within photosynthetic groups and impacts on photosynthesis modeling

Science.gov (United States)

Galmés, Jeroni; Hermida-Carrera, Carmen; Laanisto, Lauri; Niinemets, Ülo

2016-01-01

The present study provides a synthesis of the in vitro and in vivo temperature responses of Rubisco Michaelis–Menten constants for CO2 (Kc) and O2 (Ko), specificity factor (Sc,o) and maximum carboxylase turnover rate (kcatc) for 49 species from all the main photosynthetic kingdoms of life. Novel correction routines were developed for in vitro data to remove the effects of study-to-study differences in Rubisco assays. The compilation revealed differences in the energy of activation (∆Ha) of Rubisco kinetics between higher plants and other photosynthetic groups, although photosynthetic bacteria and algae were under-represented and very few species have been investigated so far. Within plants, the variation in Rubisco temperature responses was related to species’ climate and photosynthetic mechanism, with differences in ∆Ha for kcatc among C3 plants from cool and warm environments, and in ∆Ha for kcatc and Kc among C3 and C4 plants. A negative correlation was observed among ∆Ha for Sc/o and species’ growth temperature for all data pooled, supporting the convergent adjustment of the temperature sensitivity of Rubisco kinetics to species’ thermal history. Simulations of the influence of varying temperature dependences of Rubisco kinetics on Rubisco-limited photosynthesis suggested improved photosynthetic performance of C3 plants from cool habitats at lower temperatures, and C3 plants from warm habitats at higher temperatures, especially at higher CO2 concentration. Thus, variation in Rubisco kinetics for different groups of photosynthetic organisms might need consideration to improve prediction of photosynthesis in future climates. Comparisons between in vitro and in vivo data revealed common trends, but also highlighted a large variability among both types of Rubisco kinetics currently used to simulate photosynthesis, emphasizing the need for more experimental work to fill in the gaps in Rubisco datasets and improve scaling from enzyme kinetics to

Measuring cell cycle progression kinetics with metabolic labeling and flow cytometry.

Science.gov (United States)

Fleisig, Helen; Wong, Judy

2012-05-22

Precise control of the initiation and subsequent progression through the various phases of the cell cycle are of paramount importance in proliferating cells. Cell cycle division is an integral part of growth and reproduction and deregulation of key cell cycle components have been implicated in the precipitating events of carcinogenesis. Molecular agents in anti-cancer therapies frequently target biological pathways responsible for the regulation and coordination of cell cycle division. Although cell cycle kinetics tend to vary according to cell type, the distribution of cells amongst the four stages of the cell cycle is rather consistent within a particular cell line due to the consistent pattern of mitogen and growth factor expression. Genotoxic events and other cellular stressors can result in a temporary block of cell cycle progression, resulting in arrest or a temporary pause in a particular cell cycle phase to allow for instigation of the appropriate response mechanism. The ability to experimentally observe the behavior of a cell population with reference to their cell cycle progression stage is an important advance in cell biology. Common procedures such as mitotic shake off, differential centrifugation or flow cytometry-based sorting are used to isolate cells at specific stages of the cell cycle. These fractionated, cell cycle phase-enriched populations are then subjected to experimental treatments. Yield, purity and viability of the separated fractions can often be compromised using these physical separation methods. As well, the time lapse between separation of the cell populations and the start of experimental treatment, whereby the fractionated cells can progress from the selected cell cycle stage, can pose significant challenges in the successful implementation and interpretation of these experiments. Other approaches to study cell cycle stages include the use of chemicals to synchronize cells. Treatment of cells with chemical inhibitors of key

Statolith Sedimentation Kinetics and Force Transduction to the Cortical Endoplasmic Reticulum in Gravity-Sensing Arabidopsis Columella Cells[W][OA

Science.gov (United States)

Leitz, Guenther; Kang, Byung-Ho; Schoenwaelder, Monica E.A.; Staehelin, L. Andrew

2009-01-01

The starch statolith hypothesis of gravity sensing in plants postulates that the sedimentation of statoliths in specialized statocytes (columella cells) provides the means for converting the gravitational potential energy into a biochemical signal. We have analyzed the sedimentation kinetics of statoliths in the central S2 columella cells of Arabidopsis thaliana. The statoliths can form compact aggregates with gap sizes between statoliths approaching sedimentation phase, the statoliths tend to move at a distance to the cortical endoplasmic reticulum (ER) boundary and interact only transiently with the ER. Statoliths moved by laser tweezers against the ER boundary experience an elastic lift force upon release from the optical trap. High-resolution electron tomography analysis of statolith-to-ER contact sites indicate that the weight of statoliths is sufficient to locally deform the ER membranes that can potentially activate mechanosensitive ion channels. We suggest that in root columella cells, the transduction of the kinetic energy of sedimenting statoliths into a biochemical signal involves a combination of statolith-driven motion of the cytosol, statolith-induced deformation of the ER membranes, and a rapid release of kinetic energy from the ER during reorientation to activate mechanosensitive sites within the central columella cells. PMID:19276442

Lymphoid cell kinetics under continuous low dose-rate gamma irradiation: A comparison study

Science.gov (United States)

Foster, B. R.

1975-01-01

A comparison study was conducted of the effects of continuous low dose-rate gamma irradiation on cell population kinetics of lymphoid tissue (white pulp) of the mouse spleen with findings as they relate to the mouse thymus. Experimental techniques employed included autoradiography and specific labeling with tritiated thymidine (TdR-(h-3)). The problem studied involved the mechanism of cell proliferation of lymphoid tissue of the mouse spleen and thymus under the stress of continuous irradiation at a dose rate of 10 roentgens (R) per day for 105 days (15 weeks). The aim was to determine whether or not a steady state or near-steady state of cell population could be established for this period of time, and what compensatory mechanisms of cell population were involved.

Mitochondria and the non-genetic origins of cell-to-cell variability: More is different.

Science.gov (United States)

Guantes, Raúl; Díaz-Colunga, Juan; Iborra, Francisco J

2016-01-01

Gene expression activity is heterogeneous in a population of isogenic cells. Identifying the molecular basis of this variability will improve our understanding of phenomena like tumor resistance to drugs, virus infection, or cell fate choice. The complexity of the molecular steps and machines involved in transcription and translation could introduce sources of randomness at many levels, but a common constraint to most of these processes is its energy dependence. In eukaryotic cells, most of this energy is provided by mitochondria. A clonal population of cells may show a large variability in the number and functionality of mitochondria. Here, we discuss how differences in the mitochondrial content of each cell contribute to heterogeneity in gene products. Changes in the amount of mitochondria can also entail drastic alterations of a cell's gene expression program, which ultimately leads to phenotypic diversity. Also watch the Video Abstract. © 2015 WILEY Periodicals, Inc.

State and Kinetic Parameters Estimation of Bio-Ethanol Production with Immobilized Cells

OpenAIRE

Mihaylova, Iva; Popova, Silviya; Kostov, Georgi; Ignatova, Maya; Lubenova, Velislava; Naydenova, Vessela; Pircheva, Desislava; Angelov, Mihail

2013-01-01

In this paper, state and kinetic parameters estimation based on extended Kalman filter (EKF) is proposed. Experimental data from alcoholic fermentation process with immobilized cells is used. The measurements of glucose and ethanol concentration are used as on-line measurements for observers design and biomass concentration is used for results verification. Biomass, substrate and product concentrations inside immobilized compounds are estimated using the proposed algorithm. Monitoring of the ...

Acquisition of data from on-line laser turbidimeter and calculation of some kinetic variables in computer-coupled automated fed-batch culture

International Nuclear Information System (INIS)

Kadotani, Y.; Miyamoto, K.; Mishima, N.; Kominami, M.; Yamane, T.

1995-01-01

Output signals of a commercially available on-line laser turbidimeter exhibit fluctuations due to air and/or CO 2 bubbles. A simple data processing algorithm and a personal computer software have been developed to smooth the noisy turbidity data acquired, and to utilize them for the on-line calculations of some kinetic variables involved in batch and fed-batch cultures of uniformly dispersed microorganisms. With this software, about 10 3 instantaneous turbidity data acquired over 55 s are averaged and convert it to dry cell concentration, X, every minute. Also, volume of the culture broth, V, is estimated from the averaged output data of weight loss of feed solution reservoir, W, using an electronic balance on which the reservoir is placed. Then, the computer software is used to perform linear regression analyses over the past 30 min of the total biomass, VX, the natural logarithm of the total biomass, ln(VX), and the weight loss, W, in order to calculate volumetric growth rate, d(VX)/dt, specific growth rate, μ [ = dln(VX)/dt] and the rate of W, dW/dt, every minute in a fed-batch culture. The software used to perform the first-order regression analyses of VX, ln(VX) and W was applied to batch or fed-batch cultures of Escherichia coli on minimum synthetic or natural complex media. Sample determination coefficients of the three different variables (VX, ln(VX) and W) were close to unity, indicating that the calculations are accurate. Furthermore, growth yield, Y x/s , and specific substrate consumption rate, q sc , were approximately estimated from the data, dW/dt and in a ‘balanced’ fed-batch culture of E. coli on the minimum synthetic medium where the computer-aided substrate-feeding system automatically matches well with the cell growth. (author)

Mechanism of seasonal eddy kinetic energy variability in the eastern equatorial Pacific Ocean

Science.gov (United States)

Wang, Minyang; Du, Yan; Qiu, Bo; Cheng, Xuhua; Luo, Yiyong; Chen, Xiao; Feng, Ming

2017-04-01

Enhanced mesoscale eddy activities or tropical instability waves (TIWs) exist along the northern front of the cold tongue in the eastern equatorial Pacific Ocean. In this study, we investigate seasonal variability of eddy kinetic energy (EKE) over this region and its associated dynamic mechanism using a global, eddy-resolving ocean general circulation model (OGCM) simulation, the equatorial mooring data, and satellite altimeter observations. The seasonal-varying enhanced EKE signals are found to expand westward from 100°W in June to 180°W in December between 0°N and 6°N. This westward expansion in EKE is closely connected to the barotropically-baroclinically unstable zonal flows that are in thermal-wind balance with the seasonal-varying thermocline trough along 4°N. By adopting an 1½-layer reduced-gravity model, we confirm that the seasonal perturbation of the thermocline trough is dominated by the anticyclonic wind stress curl forcing, which develops due to southerly winds along 4°N from June to December.

On an analytical formulation for the mono-energetic neutron space-kinetic equation in full cylinder symmetry

International Nuclear Information System (INIS)

Oliveira, F.R.; Bodmann, B.E.J.; Vilhena, M.T.; Carvalho, F.

2017-01-01

Highlights: • The present work presents an exact solution to neutron spatial kinetic equation. • It is an exact solution in a heterogeneous cylinder with temporal dependence. • The solution was constructed through the separation of variables method. - Abstract: In the present work we discuss a system of partial differential equations that model neutron space-kinetics in cylindrical geometry and are defined by two sectionally homogeneous cylinder cells, mono-energetic neutrons and one group of delayed neutron precursors. The solution is determined using the technique of variable separation. The associated complete spectra with respect to each variable separation are analysed and truncated such as to allow a parameterized global solution. For the obtained solution we present some numerical results for the scalar neutron flux and its time dependence and projection on the cylinder axis z and the radial and cylinder axis projection. As a case study we consider an insertion of an absorbing medium in the upper cylinder cell. Continuity of the scalar flux at the interface between the two cylinder elements and conserved current density is explained and related to scale invariance of the partial differential equation system together with the initial and boundary conditions. Some numerical results for the scalar angular neutron flux and associated current densities are shown.

Cell kinetics of Ehrlich ascites carcinoma transplanted in mice with different degrees of tumor resistance

International Nuclear Information System (INIS)

Brandt, K.L.B.

1974-01-01

Cell proliferation kinetics of Ehrlich ascites carcinoma grown in two strains of mice with different degrees of resistance to this tumor were examined. In the first portion of the study, growth of Ehrlich ascites carcinoma in nonresistant Swiss (Iowa) and slightly resistant CF1 mice was examined by measuring animal weight gain and host survival time after intraperitoneal injection of tumor cells. Since it appeared that CF1 mice were inherently more resistant than Swiss mice to the Ehrlich carcinoma, the second part of this investigation involved attempts to immunize CF1 mice against the tumor. Subcutaneous injections of Ehrlich cells previously exposed in vitro to 5000 R of 250 kVp x rays were utilized. One immunizing inoculation of lethally irradiated tumor cells afforded protection against an intraperitoneal challenge of 40 thousand Ehrlich cells. By varying the number and timing of immunizing inoculations it was possible to induce different degrees of tumor resistance in these mice. The most effective immunizing procedure utilized multiple inoculations of lethally irradiated tumor cells (LITC), followed by challenges with viable tumor cells (less than 1 million) which were rejected. These mice could then resist challenge inocula of 4 million viable tumor cells. In a few animals the immunizing procedures were ineffective; these animals, when challenged, developed even larger tumors than control mice. Tumor cell proliferation kinetics in these animals as well as in mice that were rejecting the tumor were examined in the third phase of the project. A shortening of the cell cycle was observed in almost all LITC-treated mice, whether tumor growth was eventually inhibited or stimulated. Decreased duration of the DNA-synthesis phase (S) of the tumor cell cycle was also a consistent finding. The role of the immune response in stimulating mitosis as well as in killing foreign cells was discussed. (U.S.)

Kinetics of oxidation of H2 and reduction of H2O in Ni-YSZ based solid oxide cells

DEFF Research Database (Denmark)

Ebbesen, Sune Dalgaard; Mogensen, Mogens Bjerg

2012-01-01

Reduction of H2O and oxidation of H2 was studied in a Ni-YSZ electrode supported Solid Oxide Cells produced at DTU Energy conversion (former Risø DTU). Polarisation (i-V) and electrochemical impedance spectroscopic characterisation show that the kinetics for reduction of H 2O is slower compared...... to oxidation of H2. The kinetic differences cannot be explained by the reaction mechanisms which are similar in the two cases but are rather an effect of the thermodynamics. The preliminary analysis performed in this study show that the slow kinetic for reduction is partly related to the endothermic nature...... of the reaction, cooling the active electrode, thereby leading to slower kinetics at low current densities. Likewise, the increased kinetic for oxidation was found to be related to the exothermic nature of the reaction, heating the active electrode, and thereby leading to faster kinetics. At higher current...

Electrochemical Quantification of Extracellular Local H2O2 Kinetics Originating from Single Cells.

Science.gov (United States)

Bozem, Monika; Knapp, Phillip; Mirčeski, Valentin; Slowik, Ewa J; Bogeski, Ivan; Kappl, Reinhard; Heinemann, Christian; Hoth, Markus

2017-05-15

H 2 O 2 is produced by all eukaryotic cells under physiological and pathological conditions. Due to its enormous relevance for cell signaling at low concentrations and antipathogenic function at high concentrations, precise quantification of extracellular local H 2 O 2 concentrations ([H 2 O 2 ]) originating from single cells is required. Using a scanning electrochemical microscope and bare platinum disk ultramicroelectrodes, we established sensitive long-term measurements of extracellular [H 2 O 2 ] kinetics originating from single primary human monocytes (MCs) ex vivo. For the electrochemical techniques square wave voltammetry, cyclic and linear scan voltammetry, and chronoamperometry, detection limits for [H 2 O 2 ] were determined to be 5, 50, and 500 nM, respectively. Following phorbol ester stimulation, local [H 2 O 2 ] 5-8 μm above a single MC increased by 3.4 nM/s within the first 10 min before reaching a plateau. After extracellular addition of H 2 O 2 to an unstimulated MC, the local [H 2 O 2 ] decreased on average by 4.2 nM/s due to degradation processes of the cell. Using the scanning mode of the setup, we found that H 2 O 2 is evenly distributed around the producing cell and can still be detected up to 30 μm away from the cell. The electrochemical single-cell measurements were validated in MC populations using electron spin resonance spectroscopy and the Amplex ® UltraRed assay. Innovation and Conclusion: We demonstrate a highly sensitive, spatially, and temporally resolved electrochemical approach to monitor dynamics of production and degradation processes for H 2 O 2 separately. Local extracellular [H 2 O 2 ] kinetics originating from single cells is quantified in real time. Antioxid. Redox Signal. 00, 000-000.

Effects of growth rate, cell size, motion, and elemental stoichiometry on nutrient transport kinetics.

Science.gov (United States)

Flynn, Kevin J; Skibinski, David O F; Lindemann, Christian

2018-04-01

Nutrient acquisition is a critical determinant for the competitive advantage for auto- and osmohetero- trophs alike. Nutrient limited growth is commonly described on a whole cell basis through reference to a maximum growth rate (Gmax) and a half-saturation constant (KG). This empirical application of a Michaelis-Menten like description ignores the multiple underlying feedbacks between physiology contributing to growth, cell size, elemental stoichiometry and cell motion. Here we explore these relationships with reference to the kinetics of the nutrient transporter protein, the transporter rate density at the cell surface (TRD; potential transport rate per unit plasma-membrane area), and diffusion gradients. While the half saturation value for the limiting nutrient increases rapidly with cell size, significant mitigation is afforded by cell motion (swimming or sedimentation), and by decreasing the cellular carbon density. There is thus potential for high vacuolation and high sedimentation rates in diatoms to significantly decrease KG and increase species competitive advantage. Our results also suggest that Gmax for larger non-diatom protists may be constrained by rates of nutrient transport. For a given carbon density, cell size and TRD, the value of Gmax/KG remains constant. This implies that species or strains with a lower Gmax might coincidentally have a competitive advantage under nutrient limited conditions as they also express lower values of KG. The ability of cells to modulate the TRD according to their nutritional status, and hence change the instantaneous maximum transport rate, has a very marked effect upon transport and growth kinetics. Analyses and dynamic models that do not consider such modulation will inevitably fail to properly reflect competitive advantage in nutrient acquisition. This has important implications for the accurate representation and predictive capabilities of model applications, in particular in a changing environment.

Association of footprint measurements with plantar kinetics: a linear regression model.

Science.gov (United States)

Fascione, Jeanna M; Crews, Ryan T; Wrobel, James S

2014-03-01

The use of foot measurements to classify morphology and interpret foot function remains one of the focal concepts of lower-extremity biomechanics. However, only 27% to 55% of midfoot variance in foot pressures has been determined in the most comprehensive models. We investigated whether dynamic walking footprint measurements are associated with inter-individual foot loading variability. Thirty individuals (15 men and 15 women; mean ± SD age, 27.17 ± 2.21 years) walked at a self-selected speed over an electronic pedography platform using the midgait technique. Kinetic variables (contact time, peak pressure, pressure-time integral, and force-time integral) were collected for six masked regions. Footprints were digitized for area and linear boundaries using digital photo planimetry software. Six footprint measurements were determined: contact area, footprint index, arch index, truncated arch index, Chippaux-Smirak index, and Staheli index. Linear regression analysis with a Bonferroni adjustment was performed to determine the association between the footprint measurements and each of the kinetic variables. The findings demonstrate that a relationship exists between increased midfoot contact and increased kinetic values in respective locations. Many of these variables produced large effect sizes while describing 38% to 71% of the common variance of select plantar kinetic variables in the medial midfoot region. In addition, larger footprints were associated with larger kinetic values at the medial heel region and both masked forefoot regions. Dynamic footprint measurements are associated with dynamic plantar loading kinetics, with emphasis on the midfoot region.

The merits of cell kinetic parameters for the assessment of intrinsic cellular radiosensitivity to photon and high linear energy transfer neutron irradiation

International Nuclear Information System (INIS)

Theron, Therina; Slabbert, Jacobus; Serafin, Antonio; Boehm, Lothar

1997-01-01

Purpose: Differences in tumor response and intrinsic cellular radiosensitivity make the selection of patients for specific radiation modalities very difficult. The reasons for these differences are still unclear, but are thought to be due to genomic and cellular characteristics. Because radiosensitivities vary between cell cycle stages and because S phase cells are very radioresistant, cell cycle kinetic parameters could be a candidate for predicting intrinsic radiosensitivity. Methods and Materials: A panel of 15 tumor cell lines was analyzed for S phase content and potential doubling times (T pot ), and the influence of these parameters on the intrinsic radiosensitivity to 60 Coγ- and p(66)/Be neutron irradiation was assessed. Results: S phase content and T pot show a statistically significant correlation with the mean inactivation dose for photons. The correlation between cell kinetic parameters and the mean inactivation dose for neutrons showed the same trend as photon sensitivity but this was not found to be statistically significant. Conclusions: S phase content and T pot were identified as suitable criteria for predicting photon sensitivity. It is suggested that cell kinetic parameters could play a role in identifying neutron sensitive tumors if both tumor and normal cells are analyzed

Time-dependent cell disintegration kinetics in lung tumors after irradiation

International Nuclear Information System (INIS)

Chvetsov, Alexei V; Palta, Jatinder J; Nagata, Yasushi

2008-01-01

We study the time-dependent disintegration kinetics of tumor cells that did not survive radiotherapy treatment. To evaluate the cell disintegration rate after irradiation, we studied the volume changes of solitary lung tumors after stereotactic radiotherapy. The analysis is performed using two approximations: (1) tumor volume is a linear function of the total cell number in the tumor and (2) the cell disintegration rate is governed by the exponential decay with constant risk, which is defined by the initial cell number and a half-life T 1/2 . The half-life T 1/2 is determined using the least-squares fit to the clinical data on lung tumor size variation with time after stereotactic radiotherapy. We show that the tumor volume variation after stereotactic radiotherapy of solitary lung tumors can be approximated by an exponential function. A small constant component in the volume variation does not change with time; however, this component may be the residual irregular density due to radiation fibrosis and was, therefore, subtracted from the total volume variation in our computations. Using computerized fitting of the exponent function to the clinical data for selected patients, we have determined that the average half-life T 1/2 of cell disintegration is 28.2 days for squamous cell carcinoma and 72.4 days for adenocarcinoma. This model is needed for simulating the tumor volume variation during radiotherapy, which may be important for time-dependent treatment planning of proton therapy that is sensitive to density variations

A Nonlinear Mixed Effects Approach for Modeling the Cell-To-Cell Variability of Mig1 Dynamics in Yeast.

Directory of Open Access Journals (Sweden)

Joachim Almquist

Full Text Available The last decade has seen a rapid development of experimental techniques that allow data collection from individual cells. These techniques have enabled the discovery and characterization of variability within a population of genetically identical cells. Nonlinear mixed effects (NLME modeling is an established framework for studying variability between individuals in a population, frequently used in pharmacokinetics and pharmacodynamics, but its potential for studies of cell-to-cell variability in molecular cell biology is yet to be exploited. Here we take advantage of this novel application of NLME modeling to study cell-to-cell variability in the dynamic behavior of the yeast transcription repressor Mig1. In particular, we investigate a recently discovered phenomenon where Mig1 during a short and transient period exits the nucleus when cells experience a shift from high to intermediate levels of extracellular glucose. A phenomenological model based on ordinary differential equations describing the transient dynamics of nuclear Mig1 is introduced, and according to the NLME methodology the parameters of this model are in turn modeled by a multivariate probability distribution. Using time-lapse microscopy data from nearly 200 cells, we estimate this parameter distribution according to the approach of maximizing the population likelihood. Based on the estimated distribution, parameter values for individual cells are furthermore characterized and the resulting Mig1 dynamics are compared to the single cell times-series data. The proposed NLME framework is also compared to the intuitive but limited standard two-stage (STS approach. We demonstrate that the latter may overestimate variabilities by up to almost five fold. Finally, Monte Carlo simulations of the inferred population model are used to predict the distribution of key characteristics of the Mig1 transient response. We find that with decreasing levels of post-shift glucose, the transient

Granulocyte kinetics

International Nuclear Information System (INIS)

Peters, A.M.; Lavender, J.P.; Saverymuttu, S.H.

1985-01-01

By using density gradient materials enriched with autologous plasma, the authors have been able to isolate granulocutes from other cellular elements and label them with In-111 without separation from a plasma environment. The kinetic behavior of these cells suggests that phenomena attributed to granulocyte activation are greatly reduced by this labeling. Here, they review their study of granulocyte kinetics in health and disease in hope of quantifying sites of margination and identifying principal sites of destruction. The three principle headings of the paper are distribution, life-span, and destruction

In vitro studies of ante-mortem proliferation kinetics

International Nuclear Information System (INIS)

McBride, W.H.; Withers, H.R.

1986-01-01

Using K562 human erythroblastoid cells, it was concluded that dose fractionation has no discrepant effect on the ante-mortem proliferation kinetics of doomed cells as opposed to clonogenic cell survival and that effects on ante-mortem proliferation kinetics cannot be solely responsible for the differences in fractionation response between early and late responding tissues. (UK)

FUSION OF SENDAI VIRUS WITH HUMAN HL-60 AND CEM CELLS - DIFFERENT KINETICS OF FUSION FOR 2 ISOLATES

NARCIS (Netherlands)

DELIMA, MCP; NIR, S; FLASHER, D; KLAPPE, K; HOEKSTRA, D; DUZGUNES, N

1991-01-01

The kinetics of fusion of Sendai virus (Z strain) with the human promyelocytic leukemia cell line HL-60, and the human T lymphocytic leukemia cell line CEM was investigated. Fusion was monitored by fluorescence dequenching of octadecylrhodamine (R-18) incorporated in the viral membrane. For one

Proteomic analyses for profiling regulated proteins/enzymes by Fucus vesiculosus fucoidan in B16 melanoma cells: A combination of enzyme kinetics functional study.

Science.gov (United States)

Wang, Zhi-Jiang; Zheng, Li; Yang, Jun-Mo; Kang, Yani; Park, Yong-Doo

2018-06-01

Fucoidans are complex sulfated polysaccharides that have a wide range of biological activities. Previously, we reported the various effects of Fucus vesiculosus fucoidan on tyrosinase and B16 melanoma cells. In this study, to identify fucoidan-targeted proteins in B16 melanoma cells, we performed a proteomics study and integrated enzyme kinetics. We detected 19 candidate proteins dysregulated by fucoidan treatment. Among the probed proteins, the enzyme kinetics of two candidate enzymes, namely lactate dehydrogenase (LDH) as an upregulated protein and superoxide dismutase (SOD) as a downregulated enzyme, were determined. The enzyme kinetics results showed that Fucus vesiculosus fucoidan significantly inhibited LDH catalytic function while it did not affect SOD activity even at a high dose, while only slightly decreased activity (up to 10%) at a low dose. Based on our previous and present observations, fucoidan could inhibit B16 melanoma cells growth via regulating proteins/enzymes expression levels such as LDH and SOD known as cell survival biomarkers. Interestingly, both expression level and enzyme catalytic activity of LDH were regulated by fucoidan, which could directly induce the apoptotic effect on B16 melanoma cells along with SOD downregulation. This study highlights how combining proteomics with enzyme kinetics can yield valuable insights into fucoidan targets. Copyright © 2018 Elsevier B.V. All rights reserved.

Kinetics of cadmium accumulation and its effects on microtubule integrity and cell viability in the seagrass Cymodocea nodosa

Energy Technology Data Exchange (ETDEWEB)

Malea, Paraskevi, E-mail: malea@bio.auth.gr [Department of Botany, School of Biology, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki (Greece); Adamakis, Ioannis-Dimosthenis S. [Department of Botany, School of Biology, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki (Greece); Kevrekidis, Theodoros [Laboratory of Environmental Research and Education, Democritus University of Thrace, Nea Hili, GR-68100 Alexandroupolis (Greece)

2013-11-15

Highlights: •Cd effect on microtubules and viability of seagrass leaf cells was assessed. •The Michaelis–Menten equation satisfactorily dercribed the kinetics of Cd uptake. •Cd depolymerized MTs after 3–9 d of exposure, cell death occurred at later time. •Toxicity appeared to depend on Cd uptake rate rather than on tissue Cd content. •MTs can be used as biomarker of Cd stress and uptake rate for predicting effects. -- Abstract: The kinetics of cadmium accumulation and its effects on microtubule cytoskeleton and cell viability in leaf blades of the seagrass Cymodocea nodosa were investigated under laboratory conditions in exposure concentrations ranging from 0.5 to 40 mg L{sup −1}. An initial rapid accumulation of cadmium was followed by a steady state. The Michaelis–Menten model adequately described metal accumulation; equilibrium concentration and uptake velocity tended to increase, whereas bioconcentration factor at equilibrium to decrease, as the exposure concentration increased. Cadmium depolymerized microtubules after 3–9 d of exposure, depending on trace metal concentration, indicating that microtubules could be used as an early biomarker of cadmium stress; cell death, occurring at later time than microtubule disturbance, was also observed. Microtubule depolymerization expressed as percentage of reduction of fluorescence intensity and cell mortality expressed as percentage of live cells increased with time. The lowest experimental tissue concentration associated with the onset of microtubule depolymerization and cell death (98.5–128.9 μg g{sup −1} dry wt, 0.5 mg L{sup −1} treatment, 7th and 9th d) was within the wide range of reported cadmium concentrations in leaves of seagrass species from various geographical areas. This lowest tissue concentration was exceeded up to the 3rd d at higher exposure concentrations, but toxic effects were generally detected at later time. The time periods required for the onset of depolymerization and

Similar kinetics of chromatid aberrations in X-irradiated xrs 5 and wild-type Chinese hamster ovary cells

International Nuclear Information System (INIS)

MacLeod, R.A.F.; Bryant, P.E.

1990-01-01

We have studied the kinetics of chromatid aberrations in cells of the Chinese hamster ovary (CHO-K1) derived, X-ray sensitive cell line xrs 5 irradiated in the G 2 phase at 37 0 C, as well as during a cell cycle extended by transient hypothermia at 33 0 C. While a given X-ray dose was estimated to produce about 4 times as many chromatid break and twice the frequency of exchanges in xrs 5 cells as in the parent line, there was no difference between the lines in the rates of disappearance of chromatid breaks during G 2 at either temperature; and similar patterns of chromatid exchange kinetics were observed in the two lines. Both the frequencies and distributions of chromatid breaks at different times after irradiation are consistent with the view that the disappearance of these during incubation represents a repair process. These results imply that the G 2 chromosomal radiosensitivity of the xrs 5 mutant resides at the level of initial chromatid damage. (author)

Single cell Hi-C reveals cell-to-cell variability in chromosome structure

Science.gov (United States)

Schoenfelder, Stefan; Yaffe, Eitan; Dean, Wendy; Laue, Ernest D.; Tanay, Amos; Fraser, Peter

2013-01-01

Large-scale chromosome structure and spatial nuclear arrangement have been linked to control of gene expression and DNA replication and repair. Genomic techniques based on chromosome conformation capture assess contacts for millions of loci simultaneously, but do so by averaging chromosome conformations from millions of nuclei. Here we introduce single cell Hi-C, combined with genome-wide statistical analysis and structural modeling of single copy X chromosomes, to show that individual chromosomes maintain domain organisation at the megabase scale, but show variable cell-to-cell chromosome territory structures at larger scales. Despite this structural stochasticity, localisation of active gene domains to boundaries of territories is a hallmark of chromosomal conformation. Single cell Hi-C data bridge current gaps between genomics and microscopy studies of chromosomes, demonstrating how modular organisation underlies dynamic chromosome structure, and how this structure is probabilistically linked with genome activity patterns. PMID:24067610

Integrated Analysis of Contractile Kinetics, Force Generation, and Electrical Activity in Single Human Stem Cell-Derived Cardiomyocytes

Directory of Open Access Journals (Sweden)

Jan David Kijlstra

2015-12-01

Full Text Available The quantitative analysis of cardiomyocyte function is essential for stem cell-based approaches for the in vitro study of human cardiac physiology and pathophysiology. We present a method to comprehensively assess the function of single human pluripotent stem cell-derived cardiomyocyte (hPSC-CMs through simultaneous quantitative analysis of contraction kinetics, force generation, and electrical activity. We demonstrate that statistical analysis of movies of contracting hPSC-CMs can be used to quantify changes in cellular morphology over time and compute contractile kinetics. Using a biomechanical model that incorporates substrate stiffness, we calculate cardiomyocyte force generation at single-cell resolution and validate this approach with conventional traction force microscopy. The addition of fluorescent calcium indicators or membrane potential dyes allows the simultaneous analysis of contractility and calcium handling or action potential morphology. Accordingly, our approach has the potential for broad application in the study of cardiac disease, drug discovery, and cardiotoxicity screening.

Solutions for the Cell Cycle in Cell Lines Derived from Human Tumors

Directory of Open Access Journals (Sweden)

B. Zubik-Kowal

2006-01-01

Full Text Available The goal of the paper is to compute efficiently solutions for model equations that have the potential to describe the growth of human tumor cells and their responses to radiotherapy or chemotherapy. The mathematical model involves four unknown functions of two independent variables: the time variable t and dimensionless relative DNA content x. The unknown functions can be thought of as the number density of cells and are solutions of a system of four partial differential equations. We construct solutions of the system, which allow us to observe the number density of cells for different t and x values. We present results of our experiments which simulate population kinetics of human cancer cells in vitro. Our results show a correspondence between predicted and experimental data.

Monitoring the initiation and kinetics of human dendritic cell-induced polarization of autologous naive CD4+ T cells.

Directory of Open Access Journals (Sweden)

Tammy Oth

Full Text Available A crucial step in generating de novo immune responses is the polarization of naive cognate CD4+ T cells by pathogen-triggered dendritic cells (DC. In the human setting, standardized DC-dependent systems are lacking to study molecular events during the initiation of a naive CD4+ T cell response. We developed a TCR-restricted assay to compare different pathogen-triggered human DC for their capacities to instruct functional differentiation of autologous, naive CD4+ T cells. We demonstrated that this methodology can be applied to compare differently matured DC in terms of kinetics, direction, and magnitude of the naive CD4+ T cell response. Furthermore, we showed the applicability of this assay to study the T cell polarizing capacity of low-frequency blood-derived DC populations directly isolated ex vivo. This methodology for addressing APC-dependent instruction of naive CD4+ T cells in a human autologous setting will provide researchers with a valuable tool to gain more insight into molecular mechanisms occurring in the early phase of T cell polarization. In addition, it may also allow the study of pharmacological agents on DC-dependent T cell polarization in the human system.

Kinetics of C3H 10T1/2 mouse cells

International Nuclear Information System (INIS)

Metting, N.F.; Mortenson, E.; Braby, L.A.; Nelson, J.M.

1987-01-01

The 10T1/2 cell line has been brought to PNL because of its usefulness as an in vitro biological system for transformation assay, and because a fast repair process in response to irradiation has been observed in these cells. Before using the cells in radiobiological studies, it was important to observe the growth kinetics of our cultures and verify their similarity to those reported by other laboratories in which they are used, so that our subsequent measurements could be compared with and added to the body of scientific work already compiled. To become familiar with the cell morphology and cloning characteristics, we conducted an experiment in which a number of flasks were seeded with about 350 cells each. Each day, starting with the second day after plating, a flask was stained and the number of clones plus the number of cells in each clone were counted. There are several types of cell morphologies within the population. Flow cytometry (FCM) studies were used to assess cell cycle characteristics, Again, a number of flasks were seeded, but this time with a large number of exponentially growing cells. Measurements indicated that the cultures were probably more or less synchronized at their initiation by plating efficiency effects, that they maintained a loose synchrony by phases through about the eighth day and that before at least the eleventh day they began to pile up in G1 phase

Time-dependent cell disintegration kinetics in lung tumors after irradiation

Energy Technology Data Exchange (ETDEWEB)

Chvetsov, Alexei V; Palta, Jatinder J [Department of Radiation Oncology, University of Florida, Gainesville, FL (United States); Nagata, Yasushi [Department of Therapeutic Radiology and Oncology, Kyoto University, Kyoto (Japan)], E-mail: chvetsov@ufl.edu

2008-05-07

We study the time-dependent disintegration kinetics of tumor cells that did not survive radiotherapy treatment. To evaluate the cell disintegration rate after irradiation, we studied the volume changes of solitary lung tumors after stereotactic radiotherapy. The analysis is performed using two approximations: (1) tumor volume is a linear function of the total cell number in the tumor and (2) the cell disintegration rate is governed by the exponential decay with constant risk, which is defined by the initial cell number and a half-life T{sub 1/2}. The half-life T{sub 1/2} is determined using the least-squares fit to the clinical data on lung tumor size variation with time after stereotactic radiotherapy. We show that the tumor volume variation after stereotactic radiotherapy of solitary lung tumors can be approximated by an exponential function. A small constant component in the volume variation does not change with time; however, this component may be the residual irregular density due to radiation fibrosis and was, therefore, subtracted from the total volume variation in our computations. Using computerized fitting of the exponent function to the clinical data for selected patients, we have determined that the average half-life T{sub 1/2} of cell disintegration is 28.2 days for squamous cell carcinoma and 72.4 days for adenocarcinoma. This model is needed for simulating the tumor volume variation during radiotherapy, which may be important for time-dependent treatment planning of proton therapy that is sensitive to density variations.

Interphase death of dividing cells. Kinetics of death of cultured Chinese hamster fibroblasts after irradiation with various doses

International Nuclear Information System (INIS)

Kublik, L.N.; Veksler, A.M.; Ehjdus, L.Kh.

1989-01-01

In studying the kinetics of interphase death (ID) of cultured Chinese hamster cells after irradiation with doses of 100 to 800 Gy the authors showed an increase in the ID rate with increasing radiation dose; the presence of serum in the medium both during and after irradiation prevents the cell death

Metabolic and Kinetic analyses of influenza production in perfusion HEK293 cell culture

Directory of Open Access Journals (Sweden)

Lohr Verena

2011-09-01

Full Text Available Abstract Background Cell culture-based production of influenza vaccine remains an attractive alternative to egg-based production. Short response time and high production yields are the key success factors for the broader adoption of cell culture technology for industrial manufacturing of pandemic and seasonal influenza vaccines. Recently, HEK293SF cells have been successfully used to produce influenza viruses, achieving hemagglutinin (HA and infectious viral particle (IVP titers in the highest ranges reported to date. In the same study, it was suggested that beyond 4 × 106 cells/mL, viral production was limited by a lack of nutrients or an accumulation of toxic products. Results To further improve viral titers at high cell densities, perfusion culture mode was evaluated. Productivities of both perfusion and batch culture modes were compared at an infection cell density of 6 × 106 cells/mL. The metabolism, including glycolysis, glutaminolysis and amino acids utilization as well as physiological indicators such as viability and apoptosis were extensively documented for the two modes of culture before and after viral infection to identify potential metabolic limitations. A 3 L bioreactor with a perfusion rate of 0.5 vol/day allowed us to reach maximal titers of 3.3 × 1011 IVP/mL and 4.0 logHA units/mL, corresponding to a total production of 1.0 × 1015 IVP and 7.8 logHA units after 3 days post-infection. Overall, perfusion mode titers were higher by almost one order of magnitude over the batch culture mode of production. This improvement was associated with an activation of the cell metabolism as seen by a 1.5-fold and 4-fold higher consumption rates of glucose and glutamine respectively. A shift in the viral production kinetics was also observed leading to an accumulation of more viable cells with a higher specific production and causing an increase in the total volumetric production of infectious influenza particles. Conclusions These results

Kinetics of heat damage autologous red blood cells. Mechanism of clearance from blood

Energy Technology Data Exchange (ETDEWEB)

Peters, A.M.; Ryan, P.F.J.; Klonizakis, I.; Elkon, K.B.; Lewis, S.M.; Hughes, G.R.V.; Lavender, J.P. (Hammersmith Hospital, London (UK))

1982-01-01

The kinetics of radiolabelled heat damage red cell (HDRBC) distribution have been studied in humans using a gamma camera, and compared with the kinetics of other blood cells. Liver uptake of /sup 111/In labelled HDRBC was completed within about 10 min of injection; splenic uptake was biphasic with a half time of about 5 min over the first 20 min in following injection, and a later half time much longer than this. Activity initially present in the lung fields cleared within 24 h. The rate constant of liver uptake of sup(99m)Tc labelled HDRBC and of /sup 111/In labelled platelets were very similar; the rate constants of splenic uptake of these 2 particles were also very similar up to about 20 min following injection when the splenic platelet levels became constant and the HDRBC level continued to slowly rise. Splenic uptake and blood clearance of red cells coated with IgG (IgG-RBC), in contrast to HDRBC, were monoexponential. It was concluded that: (1) the blood clearance of HDRBC was due to pooling within, and to irreversible extraction by, the spleen; (2) liver uptake of HDRBC, which was irreversible, was completed within 10 min of injection; (3) IgG-RBC clearance was due to irreversible extraction by the spleen; (4) HDRBC uptake in the lung was unrelated to reticuloendothelial function, and represented prolonged transit through the lung microvasculature.

Species Entropies in the Kinetic Range of Collisionless Plasma Turbulence: Particle-in-cell Simulations

Science.gov (United States)

Gary, S. Peter; Zhao, Yinjian; Hughes, R. Scott; Wang, Joseph; Parashar, Tulasi N.

2018-06-01

Three-dimensional particle-in-cell simulations of the forward cascade of decaying turbulence in the relatively short-wavelength kinetic range have been carried out as initial-value problems on collisionless, homogeneous, magnetized electron-ion plasma models. The simulations have addressed both whistler turbulence at β i = β e = 0.25 and kinetic Alfvén turbulence at β i = β e = 0.50, computing the species energy dissipation rates as well as the increase of the Boltzmann entropies for both ions and electrons as functions of the initial dimensionless fluctuating magnetic field energy density ε o in the range 0 ≤ ε o ≤ 0.50. This study shows that electron and ion entropies display similar rates of increase and that all four entropy rates increase approximately as ε o , consistent with the assumption that the quasilinear premise is valid for the initial conditions assumed for these simulations. The simulations further predict that the time rates of ion entropy increase should be substantially greater for kinetic Alfvén turbulence than for whistler turbulence.

Kinetics of potassium, rubidium and cesium in rat

International Nuclear Information System (INIS)

Natsuhori, Masahiro; Kosaka, Shigetoshi; Nishikawa, Miki; Okida, Masato; Ito, Nobuhiko

1998-01-01

Apparent incorporation rates of K and Rb into red blood cells were investigated in rats in consideration of passive diffusion to clarify in vivo kinetics of alkali metals. First, the incorporation rates of K and Rb into blood cells were determined by incubating blood samples from SD rat with 42 K and 86 Rb-buffers. And parameters involving in these incorporations such as Vmax (maximum rate of active transport), {S} (substrate concentration), Km (Michaelis constant), n (cooperativity of active transport), etc. were evaluated based on the time-course changes in K and Rb incorporation. Then, K and Rb were given to SD rats and the respective levels in plasma, red blood cells and urine were determined. The parameters were evaluated based on the time course changes in these levels by using compartment model. Similarly, the kinetics of Cs were investigated in rats. The absorption, distribution and disappearance of alkali metals were investigated in vivo to compare in vivo kinetics among the metals. By applying the kinetic parameters analyzed, Cs kinetics, in vivo could be estimated and Cs intake was able to be also estimated by determining the Cs levels of blood cells, urine and plasma. (M.N.)

A discontinuous Galerkin method on kinetic flocking models

OpenAIRE

Tan, Changhui

2014-01-01

We study kinetic representations of flocking models. They arise from agent-based models for self-organized dynamics, such as Cucker-Smale and Motsch-Tadmor models. We prove flocking behavior for the kinetic descriptions of flocking systems, which indicates a concentration in velocity variable in infinite time. We propose a discontinuous Galerkin method to treat the asymptotic $\\delta$-singularity, and construct high order positive preserving scheme to solve kinetic flocking systems.

Kinetics of EGFR expression during fractionated irradiation varies between different human squamous cell carcinoma lines in nude mice

International Nuclear Information System (INIS)

Eicheler, Wolfgang; Krause, Mechthild; Hessel, Franziska; Zips, Daniel; Baumann, Michael

2005-01-01

Background and purpose: Preclinical and clinical data indicate that high pretherapeutic EGFR expression is associated with poor local tumour control, possibly caused by a high repopulation rate of clonogenic cells during radiotherapy in these tumours. Previous data reported from our laboratory showed a correlation between EGFR expression and acceleration of repopulation in poorly differentiated FaDu human squamous cell carcinoma (SCC) during fractionated irradiation. To test whether this is a general phenomenon, two further SCC were investigated in the present study. Patients and methods: GL and UT-SCC-14, two moderately well differentiated and keratinising hSCC, were grown as xenografts in nude mice. Functional data on the repopulation kinetics during fractionated irradiation for these tumour models have been previously determined. The expression of EGFR during fractionation was analysed by immunohistochemistry. Endpoints were the membrane-staining score and the proportion of EGFR-positive cells (EGFR labelling index). Results: Different kinetics of EGFR expression during fractionated RT were found. In UT-SCC-14, EGFR staining score and labelling index increased significantly during radiotherapy. In GL SCC, the EGFR expression was unchanged. Both tumours are characterized by a small but significant repopulation rate during radiotherapy. Conclusions: The expression of EGFR may change significantly during fractionated irradiation. No clear correlation between EGFR expression and the repopulation kinetics of clonogenic tumour cells during fractionated irradiation was found. The changes in EGFR expression during irradiation warrant further investigation on their prognostic implications and on their importance for therapeutic interventions

Variability and reproducibility of rubidium-82 kinetic parameters in the myocardium of the anesthetized canine

International Nuclear Information System (INIS)

Coxson, P.G.; Brennan, K.M.; Huesman, R.H.

1995-01-01

Kinetic analysis of 82 Rb (I) dynamic PET data produces quantitative measures which could be used to evaluate ischemic heart disease. These measures have the potential to generate objective comparisons of different patients or the same patient at different times. To achieve this potential, it is essential to determine the variability and reproducibility of the kinetic parameters. A total of 48 I dynamic PET datasets were acquired from two pure bred beagles. Each animal underwent eight I PET studies with essentially the same protocol for three successive weeks. Data were acquired with the Donner 600-Crystal Positron Tomograph (PET600). In each week, single-slice dynamic I PET datasets were collected with the animal at rest at three different gantry positions separated by 5 mm. Additional dataset were collected after dipyridamole infusion and after administration of aminophylline to induce a return to rest. A two-compartment kinetic model with correction for myocardial vasculature and spillover from the left ventricular blood pool was used to analyze the dynamic datasets. Model parameters for uptake (k 1 ), washout (k 2 ) and vascular fraction (f v ) were estimated in 11-14 myocardial regions of interest (ROIs) using a weighted least-squares criterion. Statistical fluctuation due to the PET acquisition process was minimized by using a relatively high I dose (about 30 mCi) to take advantage of the high count rate capacity of the PET600. The variation in mean k 1 , where the mean is taken over the myocardial ROIs was 10%-20% (Dog 1) and 15%-50% (Dog 2) among the rest studies conducted on the same data. Similar variation was evident in comparing studies in the same animal for different weeks. Spatial and temporal variation in estimates of the uptake rate (k 1 ) of I in the resting myocardium of the anesthetized canine are small in relation to the functional increase in k 1 , following dipyridamole stress. 17 refs., 14 figs

Kinetics of plasma membrane electron transport in a pulmonary endothelial cell-column.

Science.gov (United States)

Olson, L E; Merker, M P; Bongard, R D; Brantmeier, B M; Audi, S H; Linehan, J H; Dawson, C A

1998-01-01

Thiazine dyes such as toluidine blue O (TBO) are reduced at the luminal endothelial surface. The purpose of this study was to determine the rate of this reaction in endothelial cells in culture. A multiple indicator dilution method was used to measure the reaction kinetics during transient passage of a TBO-containing bolus through a chromatographic column filled with bovine pulmonary arterial endothelial cells grown on microcarrier beads (cell-column). A bolus containing TBO and an inert extracellular reference indicator (FITC-Dextran) was injected upstream of the cell-column, and the indicator concentrations were measured downstream using on-line photodetection. The effects of column flow rate, PO2, and TBO concentration were studied. The fraction of TBO reduced upon passage through the cell-column decreased with increasing flow indicating that the reaction rate rather than TBO delivery controlled TBO reduction. The fraction of TBO reduced did not change with PO2 or dose in the ranges studied. TBO reduction was about 10 times that for steady state TBO sequestration by these cells which, along with the lack of a PO2 effect indicates that the rapid rate of reduction is not the rate-limiting step in steady state sequestration.

RON kinase isoforms demonstrate variable cell motility in normal cells.

Science.gov (United States)

Greenbaum, Alissa; Rajput, Ashwani; Wan, Guanghua

2016-09-01

Aberrant RON (Recepteur d'Origine Nantais) tyrosine kinase activation causes the epithelial cell to evade normal growth pathways, resulting in unregulated cell proliferation, increased cell motility and decreased apoptosis. Wildtype (wt) RON has been shown to play a role in metastasis of epithelial malignancies. It presents an important potential therapeutic target for colorectal, breast, gastric and pancreatic cancer. Little is known about functional differences amongst RON isoforms RON155, RON160 and RON165. The purpose of this study was to determine the effect of various RON kinase isoforms on cell motility. Cell lines with stable expression of wtRON were generated by inserting the coding region of RON in pTagRFP (tagged red fluorescence protein plasmid). The expression constructs of RON variants (RON155, RON160 and RON165) were generated by creating a mutagenesis-based wtRON-pTag RFP plasmid and stably transfected into HEK 293 cells. The wound closure scratch assay was used to investigate the effect on cell migratory capacity of wild type RON and its variants. RON transfected cells demonstrated increased cell motility compared to HEK293 control cells. RON165 cell motility was significantly increased compared to RON160 (mean percentage of wound covered 37.37% vs. 32.40%; p = 0.03). RON tyrosine kinase isoforms have variable cell motility. This may reflect a difference in the behavior of malignant epithelial cells and their capacity for metastasis.

Kinetic Modeling of Corn Fermentation with S. cerevisiae Using a Variable Temperature Strategy

Directory of Open Access Journals (Sweden)

Augusto C. M. Souza

2018-04-01

Full Text Available While fermentation is usually done at a fixed temperature, in this study, the effect of having a controlled variable temperature was analyzed. A nonlinear system was used to model batch ethanol fermentation, using corn as substrate and the yeast Saccharomyces cerevisiae, at five different fixed and controlled variable temperatures. The lower temperatures presented higher ethanol yields but took a longer time to reach equilibrium. Higher temperatures had higher initial growth rates, but the decay of yeast cells was faster compared to the lower temperatures. However, in a controlled variable temperature model, the temperature decreased with time with the initial value of 40 ∘ C. When analyzing a time window of 60 h, the ethanol production increased 20% compared to the batch with the highest temperature; however, the yield was still 12% lower compared to the 20 ∘ C batch. When the 24 h’ simulation was analyzed, the controlled model had a higher ethanol concentration compared to both fixed temperature batches.

Kinetic Modeling of Corn Fermentation with S. cerevisiae Using a Variable Temperature Strategy.

Science.gov (United States)

Souza, Augusto C M; Mousaviraad, Mohammad; Mapoka, Kenneth O M; Rosentrater, Kurt A

2018-04-24

While fermentation is usually done at a fixed temperature, in this study, the effect of having a controlled variable temperature was analyzed. A nonlinear system was used to model batch ethanol fermentation, using corn as substrate and the yeast Saccharomyces cerevisiae , at five different fixed and controlled variable temperatures. The lower temperatures presented higher ethanol yields but took a longer time to reach equilibrium. Higher temperatures had higher initial growth rates, but the decay of yeast cells was faster compared to the lower temperatures. However, in a controlled variable temperature model, the temperature decreased with time with the initial value of 40 ∘ C. When analyzing a time window of 60 h, the ethanol production increased 20% compared to the batch with the highest temperature; however, the yield was still 12% lower compared to the 20 ∘ C batch. When the 24 h’ simulation was analyzed, the controlled model had a higher ethanol concentration compared to both fixed temperature batches.

Flow cytometric kinetic assay of the activity of Na+/H+ antiporter in mammalian cells.

Science.gov (United States)

Dolz, María; O'Connor, José-Enrique; Lequerica, Juan L

2004-10-01

The Na(+)/H(+) exchanger (NHE) of mammalian cells is an integral membrane protein that extrudes H(+) ion in exchange for extracellular Na(+) and plays a crucial role in the regulation of intracellular pH (pHi). Thus, when pHi is lowered, NHE extrudes protons at a rate depending of pHi that can be expressed as pH units/s. To abolish the activity of other cellular pH-restoring systems, cells were incubated in bicarbonate-free Dulbecco's modified Eagle's medium buffered with HEPES. Flow cytometry was used to determine pHi with 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester or 5-(and-6)-carboxy SNARF-1 acetoxymethyl ester acetate, and the appropriate fluorescence ratios were measured. The calibration of fluorescence ratios versus pHi was established by using ionophore nigericin. The activity of NHE was calculated by a kinetic flow cytometric assay as the slope at time 0 of the best-fit curve of pHi recovery versus time after intracellular acidification with a pulse of exogenous sodium propionate. The kinetic method allowed determination of the pHi-dependent activity of NHE in cell lines and primary cell cultures. NHE activity values were demonstrated to be up to 0.016 pH units/s within the pHi range of 7.3 to 6.3. The inhibition of NHE activity by the specific inhibitor ethyl isopropyl amiloride was easily detected by this method. The assay conditions can be used to relate variations in pHi with the activity of NHE and provide a standardized method to compare between different cells, inhibitors, models of ischemia by acidification, and other relevant experimental or clinical situations.

Long-term changes in cell population kinetics of skin tissue after local beta-irradiation

Energy Technology Data Exchange (ETDEWEB)

Yamaguchi, T [National Inst. of Radiological Sciences, Chiba (Japan)

1975-06-01

Using /sup 3/H-thymidine autoradiography, long-term alterations in cell kinetics were studied in guinea pig skin after ..beta..irradiation with 3000 rads. After complete depopulation, epidermal basal cells at the radiation margin became proliferative 10 days postirradiation and spread over the depopulated area. When epithelization (20 days) was complete the cell cycle time of the basal cells reverted to normal, but the differentiation rate was much slower than that in unirradiated skin. This appeared to be a cause of the persistent (acanthotic) hyperplasia. Similar but slower changes were found in dermal tissue. Reparative proliferation of fibroblasts and capillary endothelial cells began at 20 and 30 days, respectively. Active fibroblastic proliferation was found as late as 110 days. This, along with the abortive nature of the reparative angiogenesis, seemed to be a cause of the later fibrosis (150 to 400 days).

Radiation-induced changes in cell proliferation kinetics in uterine cervix cancer

Energy Technology Data Exchange (ETDEWEB)

Siracka, E; Siracky, J; Pappova, N [Slovenska Akademia Vied, Bratislava (Czechoslovakia). Cancer Research Inst.; Schreiner, P [Komenskeho Univ., Bratislava (Czechoslovakia). Chair of Oncology and Radiology

1979-06-01

In vitro double labeling autoradiography for measuring the labeling index, duration of S phase and potential doubling time has been used to assess the effect of a single and fractionated test dose of irradiation in uterine cervix cancer applied in 21 patients. Tumor-labeling index fell significantly in those tumors which had a high labeling index before irradiation, and these cases were found later to exhibit a good radiation response. Duration of S phase which ranged between 9 and 27 hours prior to irradiation was increased. Differences between the potential doubling time and the actual doubling time suggest a massive cell loss in tumors which were, for the most part, of exophytic type. Fractionated irradiation provides more reliable informations than a single dose and is useful for investigation of dynamic changes in the kinetics of an asynchronous cell population.

Dependence of cancer cell adhesion kinetics on integrin ligand surface density measured by a high-throughput label-free resonant waveguide grating biosensor.

Science.gov (United States)

Orgovan, Norbert; Peter, Beatrix; Bősze, Szilvia; Ramsden, Jeremy J; Szabó, Bálint; Horvath, Robert

2014-02-07

A novel high-throughput label-free resonant waveguide grating (RWG) imager biosensor, the Epic® BenchTop (BT), was utilized to determine the dependence of cell spreading kinetics on the average surface density (v(RGD)) of integrin ligand RGD-motifs. v(RGD) was tuned over four orders of magnitude by co-adsorbing the biologically inactive PLL-g-PEG and the RGD-functionalized PLL-g-PEG-RGD synthetic copolymers from their mixed solutions onto the sensor surface. Using highly adherent human cervical tumor (HeLa) cells as a model system, cell adhesion kinetic data of unprecedented quality were obtained. Spreading kinetics were fitted with the logistic equation to obtain the spreading rate constant (r) and the maximum biosensor response (Δλmax), which is assumed to be directly proportional to the maximum spread contact area (Amax). r was found to be independent of the surface density of integrin ligands. In contrast, Δλmax increased with increasing RGD surface density until saturation at high densities. Interpreting the latter behavior with a simple kinetic mass action model, a 2D dissociation constant of 1753 ± 243 μm(-2) (corresponding to a 3D dissociation constant of ~30 μM) was obtained for the binding between RGD-specific integrins embedded in the cell membrane and PLL-g-PEG-RGD. All of these results were obtained completely noninvasively without using any labels.

Disposable micro-fluidic biosensor array for online parallelized cell adhesion kinetics analysis on quartz crystal resonators

DEFF Research Database (Denmark)

Cama, G.; Jacobs, T.; Dimaki, Maria

2010-01-01

among all the sensors of the array. As well, dedicated sensor interface electronics were developed and optimized for fast spectra acquisition of all 16 QCRs with a miniaturized impedance analyzer. This allowed performing cell cultivation experiments for the observation of fast cellular reaction kinetics...

Effects of Iron-Oxide Nanoparticle Surface Chemistry on Uptake Kinetics and Cytotoxicity in CHO-K1 Cells

Directory of Open Access Journals (Sweden)

Camille C. Hanot

2015-12-01

Full Text Available Superparamagnetic iron-oxide nanoparticles (SPIONs show great promise for multiple applications in biomedicine. While a number of studies have examined their safety profile, the toxicity of these particles on reproductive organs remains uncertain. The goal of this study was to evaluate the cytotoxicity of starch-coated, aminated, and PEGylated SPIONs on a cell line derived from Chinese Hamster ovaries (CHO-K1 cells. We evaluated the effect of particle diameter (50 and 100 nm and polyethylene glycol (PEG chain length (2k, 5k and 20k Da on the cytotoxicity of SPIONs by investigating cell viability using the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT and sulforhodamine B (SRB assays. The kinetics and extent of SPION uptake by CHO-K1 cells was also studied, as well as the resulting generation of intracellular reactive oxygen species (ROS. Cell toxicity profiles of SPIONs correlated strongly with their cellular uptake kinetics, which was strongly dependent on surface properties of the particles. PEGylation caused a decrease in both uptake and cytotoxicity compared to aminated SPIONs. Interestingly, 2k Da PEG-modifed SPIONs displayed the lowest cellular uptake and cytotoxicity among all studied particles. These results emphasize the importance of surface coatings when engineering nanoparticles for biomedical applications.

Biological-clinical study of radiosensitivity and chemosensitivity of squamous cell carcinoma of the mouth. Growth and regression rates, dynamic histology, and cell kinetics

International Nuclear Information System (INIS)

Friedman, M.; Nervi, C.

1974-01-01

Effects of combined methotrexate and radiotherapy were studied in 22 patients with advanced squamous cell cancer of the upper air passages. Studies included clinical growth rate of tumor volume prior to treatment, cell kinetics before treatment, electron microscope studies of serial biopsies, response of tumor to methotrexate and radiation, and time and rate of recurrences. Case histories are described for four different types of tumors and results are discussed. (U.S.)

Oxygen reduction kinetics on graphite cathodes in sediment microbial fuel cells.

Science.gov (United States)

Renslow, Ryan; Donovan, Conrad; Shim, Matthew; Babauta, Jerome; Nannapaneni, Srilekha; Schenk, James; Beyenal, Haluk

2011-12-28

Sediment microbial fuel cells (SMFCs) have been used as renewable power sources for sensors in fresh and ocean waters. Organic compounds at the anode drive anodic reactions, while oxygen drives cathodic reactions. An understanding of oxygen reduction kinetics and the factors that determine graphite cathode performance is needed to predict cathodic current and potential losses, and eventually to estimate the power production of SMFCs. Our goals were to (1) experimentally quantify the dependence of oxygen reduction kinetics on temperature, electrode potential, and dissolved oxygen concentration for the graphite cathodes of SMFCs and (2) develop a mechanistic model. To accomplish this, we monitored current on polarized cathodes in river and ocean SMFCs. We found that (1) after oxygen reduction is initiated, the current density is linearly dependent on polarization potential for both SMFC types; (2) current density magnitude increases linearly with temperature in river SMFCs but remains constant with temperature in ocean SMFCs; (3) the standard heterogeneous rate constant controls the current density temperature dependence; (4) river and ocean SMFC graphite cathodes have large potential losses, estimated by the model to be 470 mV and 614 mV, respectively; and (5) the electrochemical potential available at the cathode is the primary factor controlling reduction kinetic rates. The mechanistic model based on thermodynamic and electrochemical principles successfully fit and predicted the data. The data, experimental system, and model can be used in future studies to guide SMFC design and deployment, assess SMFC current production, test cathode material performance, and predict cathode contamination.

Uptake kinetics and nanotoxicity of silica nanoparticles are cell type dependent.

Science.gov (United States)

Blechinger, Julia; Bauer, Alexander T; Torrano, Adriano A; Gorzelanny, Christian; Bräuchle, Christoph; Schneider, Stefan W

2013-12-09

In this study, it is shown that the cytotoxic response of cells as well as the uptake kinetics of nanoparticles (NPs) is cell type dependent. We use silica NPs with a diameter of 310 nm labeled with perylene dye and 304 nm unlabeled particles to evaluate cell type-dependent uptake and cytotoxicity on human vascular endothelial cells (HUVEC) and cancer cells derived from the cervix carcinoma (HeLa). Besides their size, the particles are characterized concerning homogeneity of the labeling and their zeta potential. The cellular uptake of the labeled NPs is quantified by imaging the cells via confocal microscopy in a time-dependent manner, with subsequent image analysis via a custom-made and freely available digital method, Particle_in_Cell-3D. We find that within the first 4 h of interaction, the uptake of silica NPs into the cytoplasm is up to 10 times more efficient in HUVEC than in HeLa cells. Interestingly, after 10 or 24 h of interaction, the number of intracellular particles for HeLa cells by far surpasses the one for HUVEC. Inhibitor studies show that these endothelial cells internalize 310 nm SiO₂ NPs via the clathrin-dependent pathway. Remarkably, the differences in the amount of taken up NPs are not directly reflected by the metabolic activity and membrane integrity of the individual cell types. Interaction with NPs leads to a concentration-dependent decrease in mitochondrial activity and an increase in membrane leakage for HUVEC, whereas HeLa cells show only a reduced mitochondrial activity and no membrane leakage. In addition, silica NPs lead to HUVEC cell death while HeLa cells survive. These findings indicate that HUVEC are more sensitive than HeLa cells upon silica NP exposure. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Does the preference of peripheral versus central venous access in peripheral blood stem cell collection/yield change stem cell kinetics in autologous stem cell transplantation?

Science.gov (United States)

Dogu, Mehmet Hilmi; Kaya, Ali Hakan; Berber, Ilhami; Sari, İsmail; Tekgündüz, Emre; Erkurt, Mehmet Ali; Iskender, Dicle; Kayıkçı, Ömur; Kuku, Irfan; Kaya, Emin; Keskin, Ali; Altuntaş, Fevzi

2016-02-01

Central venous access is often used during apheresis procedure in stem cell collection. The aim of the present study was to evaluate whether central or peripheral venous access has an effect on stem cell yield and the kinetics of the procedure and the product in patients undergoing ASCT after high dose therapy. A total of 327 patients were retrospectively reviewed. The use of peripheral venous access for stem cell yield was significantly more frequent in males compared to females (p = 0.005). Total volume of the product was significantly lower in central venous access group (p = 0.046). As being a less invasive procedure, peripheral venous access can be used for stem cell yield in eligible selected patients. Copyright © 2016 Elsevier Ltd. All rights reserved.

Epithelial cell kinetics in mouse and rat skin irradiated with electrons

International Nuclear Information System (INIS)

McMaster-Schuyler, L.

1984-02-01

Experiments were performed to examine the kinetic responses of mouse and rat epidermal cells in vivo after single doses of ionizing radiation including responses of hair follicles at times after irradiation. The labeling indices in both species were reduced to 30 to 50% of control values immediately following irradiation at all the doses. In the rat, the labeling indices recovered and overshot control values within the first three days after 300 to 1200 rads. The mouse labeling indices continued to be suppressed for up to 10 days after 300 to 2400 rads. This indicated that rat G 1 phase epidermal cells recovered three times faster than those of the mouse with respect to the ability to maintain or increase control level cell proliferation after irradiation. After 1800 and 2400 rads, doses which produce skin ulceration, both species showed a reduction in their labeling indices for up to 7 days, indicating that a dose-dependent mechanism of recovery may be operable in the rat. 99 refs., 15 figs., 6 tabs

Kinetics of red blood cell rouleaux formation studied by light scattering.

Science.gov (United States)

Szolna-Chodór, Alicja; Bosek, Maciej; Grzegorzewski, Bronislaw

2015-02-01

Red blood cell (RBC) rouleaux formation was experimentally studied using a light scattering technique. The suspensions of RBCs were obtained from the blood of healthy donors. Hematocrit of the samples was adjusted ranging from 1% to 4%. Measurements of the intensity of the coherent component of light scattered by the suspensions were performed and the scattering coefficient of the suspensions was determined. The number of RBCs per rouleaux was obtained using anomalous diffraction theory. The technique was used to show the effect of time, hematocrit, and sample thickness on the process. The number of cells per rouleaux first increases linearly, reaches a critical value at ∼3 cells per rouleaux, and then a further increase in the rouleaux size is observed. The kinetic constant of the rouleaux growth in the linear region is found to be independent of hematocrit. The aggregation rate increases as the sample thickness increases. The time at which the critical region appears strongly decreases as the hematocrit of the suspension increases. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)

Production kinetics of zirconium tetrachloride

International Nuclear Information System (INIS)

Sudjoko, D.; Masduki, B.; Sunardjo; Sulistyo, B.

1996-01-01

This research was intended to study the kinetics of zirconium tetrachloride production. The process was carried out in semi continuous reactor, equipped with heater, temperature controller, sublimator and scrubber. The variables investigated were time, temperature and the pellet forming pressure. Within the range of variables studied, the expression of the process in the chemical reaction controller region and diffusion controller region were both presented. (author)

Variable elimination in chemical reaction networks with mass-action kinetics

DEFF Research Database (Denmark)

Feliu, Elisenda; Wiuf, C.

2012-01-01

We consider chemical reaction networks taken with mass-action kinetics. The steady states of such a system are solutions to a system of polynomial equations. Even for small systems the task of finding the solutions is daunting. We develop an algebraic framework and procedure for linear elimination...

Kinetics and hybrid kinetic-fluid models for nonequilibrium gas and plasmas

International Nuclear Information System (INIS)

Crouseilles, N.

2004-12-01

For a few decades, the application of the physics of plasmas has appeared in different fields like laser-matter interaction, astrophysics or thermonuclear fusion. In this thesis, we are interested in the modeling and the numerical study of nonequilibrium gas and plasmas. To describe such systems, two ways are usually used: the fluid description and the kinetic description. When we study a nonequilibrium system, fluid models are not sufficient and a kinetic description have to be used. However, solving a kinetic model requires the discretization of a large number of variables, which is quite expensive from a numerical point of view. The aim of this work is to propose a hybrid kinetic-fluid model thanks to a domain decomposition method in the velocity space. The derivation of the hybrid model is done in two different contexts: the rarefied gas context and the more complicated plasmas context. The derivation partly relies on Levermore's entropy minimization approach. The so-obtained model is then discretized and validated on various numerical test cases. In a second stage, a numerical study of a fully kinetic model is presented. A collisional plasma constituted of electrons and ions is considered through the Vlasov-Poisson-Fokker-Planck-Landau equation. Then, a numerical scheme which preserves total mass and total energy is presented. This discretization permits in particular a numerical study of the Landau damping. (author)

Osteoclast cell-surface specializations and nuclear kinetics during egg-laying in Japanese quail

International Nuclear Information System (INIS)

Miller, S.C.

1981-01-01

Medullary bone deposits serve as a reservoir of labile calcium for egg-shell calcification in birds. Quantitative transmission-electron-microscope methods and light-microscope autoradiographic cell-population-kinetic analyses were used to determine changes in cell-surface specializations and population dynamics of medullary bone osteoclasts during egg-laying in Japanese quail. Prior to egg-shell formation, from 0 to about 8 hours after the previous oviposition, very few osteoclast profiles had ruffled borders. The appearance of ruffled borders coincided with the beginning of egg-shell calcification, about 9-10 hours after the previous oviposition. During egg-shell calcification, about 10-21 hours after the previous oviposition, most osteoclast profiles had ruffled borders. Ruffled borders disappeared at the completion of egg-shell calcification and commencement of egg-shell pigmentation. Thus, functional activities of medullary bone osteoclasts appear to be closely synchronized with egg-shell calcification during egg-laying. From 1 to 48 hours after a single injection of 3H-thymidine (3H-TdR), very few labeled osteoclast nuclei were seen during egg-laying. Following multiple injections of 3H-TdR, the percentage of labeled nuclei reached a peak at about 170 hours after the first injection. At this peak-labeling time, relatively few of the osteoclast profiles that had labeled nuclei had two or more; although the average number of nuclei per osteoclast profile was about 3.6. These kinetic data suggest that the medullary bone osteoclast population has a prolonged rate of turnover compared to rapid changes in cell activities associated with each 24-hour egg-laying cycle; and collectively they would suggest that rapid changes in osteoclast functions occur independently of changes in cell-population dynamics

Effects of x-irradiation on cell kinetics of oral epithelium in mice

International Nuclear Information System (INIS)

Jinnouchi, Kenichi

1982-01-01

The acute radiation effects on the tongue and lip mucosa epithelium were cytokinetically investigated after the local irradiation at the head part of C 3 Hf/He mice with single dose of 516 mC/kg(2000R) of X rays. The microautoradiographic study was performed for these two kinds of oral epithelium at various times after the pulse-labeling with 3 H-thymidine, which followed immediately after the irradiation. The cell kinetics of irradiated as well as unirradiated basal cells were investigated by observing the changes in frequencies of the labeled cells and the labeled mitoses in the epithelium along the time course after irradiation. The results of the analysis of the percent frequencies of mitotic cells as a function of time after the labeling and the irradiation showed that the movement of the labeled cells were blocked at G 2 phase for about 6 hr and that the cell cycle time after the 1st post irradiation mitoses became shorter than that of the unirradiated cells. However, no change was found in the migration rate of the tongue epithelium, i.e., the time required for labeled cells to migrate from basal cell layer to prickle-granular cell layer. On the other hand, only 25% of labeled cells in the lip mucosa epithelium migrated into prickle-granular cell layer until 40 hr after irradiation, and it was hardly observed that the labeled cells moved into mitotic phase. These results suggest that basal cell of the lip mucosa is more radiosensitive than that of the tongue epithelium. (author)

Adaptation of endothelial cells to physiologically-modeled, variable shear stress.

Directory of Open Access Journals (Sweden)

Joseph S Uzarski

Full Text Available Endothelial cell (EC function is mediated by variable hemodynamic shear stress patterns at the vascular wall, where complex shear stress profiles directly correlate with blood flow conditions that vary temporally based on metabolic demand. The interactions of these more complex and variable shear fields with EC have not been represented in hemodynamic flow models. We hypothesized that EC exposed to pulsatile shear stress that changes in magnitude and duration, modeled directly from real-time physiological variations in heart rate, would elicit phenotypic changes as relevant to their critical roles in thrombosis, hemostasis, and inflammation. Here we designed a physiological flow (PF model based on short-term temporal changes in blood flow observed in vivo and compared it to static culture and steady flow (SF at a fixed pulse frequency of 1.3 Hz. Results show significant changes in gene regulation as a function of temporally variable flow, indicating a reduced wound phenotype more representative of quiescence. EC cultured under PF exhibited significantly higher endothelial nitric oxide synthase (eNOS activity (PF: 176.0±11.9 nmol/10(5 EC; SF: 115.0±12.5 nmol/10(5 EC, p = 0.002 and lower TNF-a-induced HL-60 leukocyte adhesion (PF: 37±6 HL-60 cells/mm(2; SF: 111±18 HL-60/mm(2, p = 0.003 than cells cultured under SF which is consistent with a more quiescent anti-inflammatory and anti-thrombotic phenotype. In vitro models have become increasingly adept at mimicking natural physiology and in doing so have clarified the importance of both chemical and physical cues that drive cell function. These data illustrate that the variability in metabolic demand and subsequent changes in perfusion resulting in constantly variable shear stress plays a key role in EC function that has not previously been described.

Origins and implications of pluripotent stem cell variability and heterogeneity

OpenAIRE

Cahan, Patrick; Daley, George Q.

2013-01-01

Pluripotent stem cells constitute a platform to model disease and developmental processes and can potentially be used in regenerative medicine. However, not all pluripotent cell lines are equal in their capacity to differentiate into desired cell types in vitro. Genetic and epigenetic variations contribute to functional variability between cell lines and heterogeneity within clones. These genetic and epigenetic variations could ‘lock’ the pluripotency network resulting in residual pluripotent...

Stochastic chemical kinetics theory and (mostly) systems biological applications

CERN Document Server

Érdi, Péter; Lente, Gabor

2014-01-01

This volume reviews the theory and simulation methods of stochastic kinetics by integrating historical and recent perspectives, presents applications, mostly in the context of systems biology and also in combustion theory. In recent years, due to the development in experimental techniques, such as optical imaging, single cell analysis, and fluorescence spectroscopy, biochemical kinetic data inside single living cells have increasingly been available. The emergence of systems biology brought renaissance in the application of stochastic kinetic methods.

Kinetic structures of quasi-perpendicular shocks in global particle-in-cell simulations

International Nuclear Information System (INIS)

Peng, Ivy Bo; Markidis, Stefano; Laure, Erwin; Johlander, Andreas; Vaivads, Andris; Khotyaintsev, Yuri; Henri, Pierre; Lapenta, Giovanni

2015-01-01

We carried out global Particle-in-Cell simulations of the interaction between the solar wind and a magnetosphere to study the kinetic collisionless physics in super-critical quasi-perpendicular shocks. After an initial simulation transient, a collisionless bow shock forms as a result of the interaction of the solar wind and a planet magnetic dipole. The shock ramp has a thickness of approximately one ion skin depth and is followed by a trailing wave train in the shock downstream. At the downstream edge of the bow shock, whistler waves propagate along the magnetic field lines and the presence of electron cyclotron waves has been identified. A small part of the solar wind ion population is specularly reflected by the shock while a larger part is deflected and heated by the shock. Solar wind ions and electrons are heated in the perpendicular directions. Ions are accelerated in the perpendicular direction in the trailing wave train region. This work is an initial effort to study the electron and ion kinetic effects developed near the bow shock in a realistic magnetic field configuration

Kinetics of transmembrane transport of small molecules into electropermeabilized cells.

Science.gov (United States)

Pucihar, Gorazd; Kotnik, Tadej; Miklavcic, Damijan; Teissié, Justin

2008-09-15

The transport of propidium iodide into electropermeabilized Chinese hamster ovary cells was monitored with a photomultiplier tube during and after the electric pulse. The influence of pulse amplitude and duration on the transport kinetics was investigated with time resolutions from 200 ns to 4 ms in intervals from 400 micros to 8 s. The transport became detectable as early as 60 micros after the start of the pulse, continued for tens of seconds after the pulse, and was faster and larger for higher pulse amplitudes and/or longer pulse durations. With fixed pulse parameters, transport into confluent monolayers of cells was slower than transport into suspended cells. Different time courses of fluorescence increase were observed during and at various times after the pulse, reflecting different transport mechanisms and ongoing membrane resealing. The data were compared to theoretical predictions of the Nernst-Planck equation. After a delay of 60 micros, the time course of fluorescence during the pulse was approximately linear, supporting a mainly electrophoretic solution of the Nernst-Planck equation. The time course after the pulse agreed with diffusional solution of the Nernst-Planck equation if the membrane resealing was assumed to consist of three distinct components, with time constants in the range of tens of microseconds, hundreds of microseconds, and tens of seconds, respectively.

On direct internal methane steam reforming kinetics in operating solid oxide fuel cells with nickel-ceria anodes

Science.gov (United States)

Thallam Thattai, A.; van Biert, L.; Aravind, P. V.

2017-12-01

Major operating challenges remain to safely operate methane fuelled solid oxide fuel cells due to undesirable temperature gradients across the porous anode and carbon deposition. This article presents an experimental study on methane steam reforming (MSR) global kinetics for single operating SOFCs with Ni-GDC (gadolinium doped ceria) anodes for low steam to carbon (S/C) ratios and moderate current densities. The study points out the hitherto insufficient research on MSR global and intrinsic kinetics for operating SOFCs with complete Ni-ceria anodes. Further, it emphasizes the need to develop readily applicable global kinetic models as a subsequent step from previously reported state-of-art and complex intrinsic models. Two rate expressions of the Power law (PL) and Langmuir-Hinshelwood (LH) type have been compared and based on the analysis, limitations of using previously proposed rate expressions for Ni catalytic beds to study MSR kinetics for complete cermet anodes have been identified. Firstly, it has been shown that methane reforming on metallic (Ni) current collectors may not be always negligible, contrary to literature reports. Both PL and LH kinetic models predict significantly different local MSR reaction rate and species partial pressure distributions along the normalized reactor length, indicating a strong need for further experimental verifications.

Plasma and memory B-cell kinetics in infants following a primary schedule of CRM 197-conjugated serogroup C meningococcal polysaccharide vaccine.

Science.gov (United States)

Kelly, Dominic F; Snape, Matthew D; Perrett, Kirsten P; Clutterbuck, Elizabeth A; Lewis, Susan; Blanchard Rohner, Geraldine; Jones, Meryl; Yu, Ly-Mee; Pollard, Andrew J

2009-05-01

The induction of persistent protective levels of pathogen-specific antibody is an important goal of immunization against childhood infections. However, antibody persistence is poor after immunization in infancy versus later in life. Serogroup C meningococci (MenC) are an important cause of bacteraemia and meningitis in children. The use of protein-polysaccharide conjugate vaccines against MenC has been associated with a significant decline in the incidence of invasive disease. However, vaccine effectiveness is negligible by more than 1 year after a three-dose priming series in infancy and corresponds to a rapid decline in antibody following an initial immune response. The cellular mechanisms underlying the generation of persistent antibody in this age group are unclear. An essential prelude to larger studies of peripheral blood B cells is an understanding of B-cell kinetics following immunization. We measured MenC- and diphtheria-specific plasma and memory B-cell kinetics in infants receiving a CRM(197) (cross-reactive material; mutant diphtheria toxoid)-conjugated MenC vaccine at 2, 3 and 4 months of age. Plasma cell responses were more delayed after the first dose when compared with the rapid appearance of plasma cells after the third dose. Memory B cells were detectable at all time-points following the third dose as opposed to the low frequency seen following a first dose. This study provides data on B-cell kinetics following a primary schedule of immunization in young infants upon which to base further studies of the underlying cellular mechanism of humoral immunity.

Kinetics of human T-cell expression of LFA-1, IL-2 receptor, and ICAM-1 following antigenic stimulation in vitro

DEFF Research Database (Denmark)

Hviid, L; Felsing, A; Theander, T G

1993-01-01

-specific stimulation is available. In the present study we have examined phenotypic T-cell changes after in vitro stimulation by the antigens purified derivative of tuberculin (PPD) and tetanus toxoid (TT). We show that the well-established differences in kinetics of mitogen- and antigen-induced T-cell proliferation...... of all 3 surface antigens showed similar kinetics, and correlated with the magnitude of the lymphoproliferative response. By day 8 (PHA-stimulation) or day 12 (PPD or TT stimulation), the lymphoproliferative response was essentially completed, the expression of CD11a and CD54 had approached...

Coupling Chemical Kinetics and Flashes in Reactive, Thermal and Compositional Reservoir Simulation

DEFF Research Database (Denmark)

Kristensen, Morten Rode; Gerritsen, Margot G.; Thomsen, Per Grove

2007-01-01

of convergence and error test failures by more than 50% compared to direct integration without the new algorithm. To facilitate the algorithmic development we construct a virtual kinetic cell model. We use implicit one-step ESDIRK (Explicit Singly Diagonal Implicit Runge-Kutta) methods for integration......Phase changes are known to cause convergence problems for integration of stiff kinetics in thermal and compositional reservoir simulations. We propose an algorithm for detection and location of phase changes based on discrete event system theory. The algorithm provides a robust way for handling...... the switching of variables and equations required when the number of phases changes. We extend the method to handle full phase equilibrium described by an equation of state. Experiments show that the new algorithm improves the robustness of the integration process near phase boundaries by lowering the number...

Kinetics of Uranium(VI) Desorption from Contaminated Sediments: Effect of Geochemical Conditions and Model Evaluation

International Nuclear Information System (INIS)

Liu, Chongxuan; Shi, Zhenqing; Zachara, John M.

2009-01-01

Stirred-flow cell experiments were performed to investigate the kinetics of uranyl (U(VI)) desorption from a contaminated sediment collected from the Hanford 300 Area at the US Department of Energy (DOE) Hanford Site, Washington. Three influent solutions of variable pH, Ca and carbonate concentrations that affected U(VI) aqueous and surface speciation were used under dynamic flow conditions to evaluate the effect of geochemical conditions on the rate of U(VI) desorption. The measured rate of U(VI) desorption varied with solution chemical composition that evolved as a result of thermodynamic and kinetic interactions between the influent solutions and sediment. The solution chemical composition that led to a lower equilibrium U(VI) sorption to the solid phase yielded a faster desorption rate. The experimental results were used to evaluate a multi-rate, surface complexation model (SCM) that has been proposed to describe U(VI) desorption kinetics in the Hanford sediment that contained complex sorbed U(VI) species in mass transfer limited domains. The model was modified and supplemented by including multi-rate, ion exchange reactions to describe the geochemical interactions between the solutions and sediment. With the same set of model parameters, the modified model reasonably well described the evolution of major ions and the rates of U(VI) desorption under variable geochemical and flow conditions, implying that the multi-rate SCM is an effective way to describe U(VI) desorption kinetics in subsurface sediments

Predicting storage-dependent damage to red blood cells using nitrite oxidation kinetics, peroxiredoxin-2 oxidation, and hemoglobin and free heme measurements.

Science.gov (United States)

Oh, Joo-Yeun; Stapley, Ryan; Harper, Victoria; Marques, Marisa B; Patel, Rakesh P

2015-12-01

Storage-dependent damage to red blood cells (RBCs) varies significantly. Identifying RBC units that will undergo higher levels of hemolysis during storage may allow for more efficient inventory management decision-making. Oxidative-stress mediates storage-dependent damage to RBCs and will depend on the oxidant:antioxidant balance. We reasoned that this balance or redox tone will serve as a determinant of how a given RBC unit stores and that its assessment in "young" RBCs will predict storage-dependent hemolysis. RBCs were sampled from bags and segments stored for 7 to 42 days. Redox tone was assessed by nitrite oxidation kinetics and peroxiredoxin-2 (Prx-2) oxidation. In parallel, hemolysis was assessed by measuring cell-free hemoglobin (Hb) and free heme (hemin). Correlation analyses were performed to determine if Day 7 measurements predicted either the level of hemolysis at Day 35 or the increase in hemolysis during storage. Higher Day 7 Prx-2 oxidation was associated with higher Day 35 Prx-2 oxidation, suggesting that early assessment of this variable may identify RBCs that will incur the most oxidative damage during storage. RBCs that oxidized nitrite faster on Day 7 were associated with the greatest levels of storage-dependent hemolysis and increases in Prx-2 oxidation. An inverse relationship between storage-dependent changes in oxyhemoglobin and free heme was observed underscoring an unappreciated reciprocity between these molecular species. Moreover, free heme was higher in the bag compared to paired segments, with opposite trends observed for free Hb. Measurement of Prx-2 oxidation and nitrite oxidation kinetics early during RBC storage may predict storage-dependent damage to RBC including hemolysis-dependent formation of free Hb and heme. © 2015 AABB.

A study of charge transfer kinetics in dye-sensitized surface conductivity solar cells

Energy Technology Data Exchange (ETDEWEB)

Friedrich, Dennis

2011-05-15

The efficiency of the quasi-solid-state dye-sensitized solar cell developed by Junghaenel and Tributsch, the so-called Nano Surface Conductivity Solar Cell (NSCSC), was improved from 2% to 3.5% introducing a compact TiO{sub 2} underlayer, modifying the surface of the mesoporous TiO{sub 2} electrode, optimizing the deposition process of the electrolyte film, and replacing the platinum counter electrode by a carbon layer. Space-resolved photocurrent images revealed the importance of a homogeneous distribution of the electrolyte film. An uneven dispersion led to localized areas of high and low photocurrents, whereas the latter were attributed to an insufficient concentration of the redox couple. Impedance spectroscopy was performed on cells containing different concentrations of the redox couple. By modeling the spectra using an equivalent circuit with a transmission line of resistive and capacitive elements, the characteristic parameters of electron transport in the TiO{sub 2}, such as diffusion length and electron lifetime were obtained. The measurements indicated that the transport of the positive charge to the counter electrode is the main process limiting the efficiency of the cells. Excess charge carrier decay in functioning devices was analyzed by contactless transient photoconductance measurements in the microwave frequency range (TRMC). The lifetime of the photogenerated charge carriers was observed to decrease with increasing applied potential, reaching its maximum close to the opencircuit potential of the cell, where the photocurrent density was minimal, i.e. the potential dependent decay observed was limited by the injection of electrons into the front contact. The functioning of this NSCSC indicated that the transport of the positive charge occurs by solid-state diffusion at the surface of the TiO{sub 2} particles. TRMC measurements on subset devices in the form of sensitized TiO{sub 2} layers revealed charge carrier kinetics strongly dependent on the

Developmental block and programmed cell death in Bos indicus embryos: effects of protein supplementation source and developmental kinetics.

Directory of Open Access Journals (Sweden)

Sheila Merlo Garcia

Full Text Available The aims of this study were to determine if the protein source of the medium influences zebu embryo development and if developmental kinetics, developmental block and programmed cell death are related. The culture medium was supplemented with either fetal calf serum or bovine serum albumin. The embryos were classified as Fast (n = 1,235 or Slow (n = 485 based on the time required to reach the fourth cell cycle (48 h and 90 h post insemination - hpi -, respectively. The Slow group was further separated into two groups: those presenting exactly 4 cells at 48 hpi (Slow/4 cells and those that reached the fourth cell cycle at 90 hpi (Slow. Blastocyst quality, DNA fragmentation, mitochondrial membrane potential and signs of apoptosis or necrosis were evaluated. The Slow group had higher incidence of developmental block than the Fast group. The embryos supplemented with fetal calf serum had lower quality. DNA fragmentation and mitochondrial membrane potential were absent in embryos at 48 hpi but present at 90 hpi. Early signs of apoptosis were more frequent in the Slow and Slow/4 cell groups than in the Fast group. We concluded that fetal calf serum reduces blastocyst development and quality, but the mechanism appears to be independent of DNA fragmentation. The apoptotic cells detected at 48 hpi reveal a possible mechanism of programmed cell death activation prior to genome activation. The apoptotic cells observed in the slow-developing embryos suggested a relationship between programmed cell death and embryonic developmental kinetics in zebu in vitro-produced embryos.

Sub-minute kinetics of human red cell fumarase: 1 H spin-echo NMR spectroscopy and 13 C rapid-dissolution dynamic nuclear polarization.

Science.gov (United States)

Shishmarev, Dmitry; Wright, Alan J; Rodrigues, Tiago B; Pileio, Giuseppe; Stevanato, Gabriele; Brindle, Kevin M; Kuchel, Philip W

2018-03-01

Fumarate is an important probe of metabolism in hyperpolarized magnetic resonance imaging and spectroscopy. It is used to detect the release of fumarase in cancer tissues, which is associated with necrosis and drug treatment. Nevertheless, there are limited reports describing the detailed kinetic studies of this enzyme in various cells and tissues. Thus, we aimed to evaluate the sub-minute kinetics of human red blood cell fumarase using nuclear magnetic resonance (NMR) spectroscopy, and to provide a quantitative description of the enzyme that is relevant to the use of fumarate as a probe of cell rupture. The fumarase reaction was studied using time courses of 1 H spin-echo and 13 C-NMR spectra. 1 H-NMR experiments showed that the fumarase reaction in hemolysates is sufficiently rapid to make its kinetics amenable to study in a period of approximately 3 min, a timescale characteristic of hyperpolarized 13 C-NMR spectroscopy. The rapid-dissolution dynamic nuclear polarization (RD-DNP) technique was used to hyperpolarize [1,4- 13 C]fumarate, which was injected into concentrated hemolysates. The kinetic data were analyzed using recently developed FmR α analysis and modeling of the enzymatic reaction using Michaelis-Menten equations. In RD-DNP experiments, the decline in the 13 C-NMR signal from fumarate, and the concurrent rise and fall of that from malate, were captured with high spectral resolution and signal-to-noise ratio, which allowed the robust quantification of fumarase kinetics. The kinetic parameters obtained indicate the potential contribution of hemolysis to the overall rate of the fumarase reaction when 13 C-NMR RD-DNP is used to detect necrosis in animal models of implanted tumors. The analytical procedures developed will be applicable to studies of other rapid enzymatic reactions using conventional and hyperpolarized substrate NMR spectroscopy. Copyright © 2018 John Wiley & Sons, Ltd.

Kinetic models of cell growth, substrate utilization and bio ...

African Journals Online (AJOL)

Bio-decolorization kinetic studies of distillery effluent in a batch culture were conducted using Aspergillus fumigatus. A simple model was proposed using the Logistic Equation for the growth, Leudeking-Piret kinetics for bio-decolorization, and also for substrate utilization. The proposed models appeared to provide a suitable ...

Correlated receptor transport processes buffer single-cell heterogeneity.

Directory of Open Access Journals (Sweden)

Stefan M Kallenberger

2017-09-01

Full Text Available Cells typically vary in their response to extracellular ligands. Receptor transport processes modulate ligand-receptor induced signal transduction and impact the variability in cellular responses. Here, we quantitatively characterized cellular variability in erythropoietin receptor (EpoR trafficking at the single-cell level based on live-cell imaging and mathematical modeling. Using ensembles of single-cell mathematical models reduced parameter uncertainties and showed that rapid EpoR turnover, transport of internalized EpoR back to the plasma membrane, and degradation of Epo-EpoR complexes were essential for receptor trafficking. EpoR trafficking dynamics in adherent H838 lung cancer cells closely resembled the dynamics previously characterized by mathematical modeling in suspension cells, indicating that dynamic properties of the EpoR system are widely conserved. Receptor transport processes differed by one order of magnitude between individual cells. However, the concentration of activated Epo-EpoR complexes was less variable due to the correlated kinetics of opposing transport processes acting as a buffering system.

Electrocatalysis and kinetics of the direct alcohol fuel cells. DEMS and ac voltammetry studies

Energy Technology Data Exchange (ETDEWEB)

Othman Mostafa, Ehab Mostafa

2013-01-11

For the direct methanol fuel cell (DMFC) operating at low temperature, the main problem that arises at the anode is its poisoning (deactivation) due to the accumulation of the fuel adsorption product (CO{sub ad}) which can only be oxidized at high potentials (> 0.7 V). For low temperature direct ethanol fuel cells (DEFCs), the main problem that arises at the anode, beside its poisoning by ethanol adsorption products (CO{sub ad} and CH{sub x,ad}), is the incomplete ethanol oxidation due to the difficulty of (C-C) bond breaking. In the previous types of fuel cells, a sluggish oxygen reduction reaction (ORR) kinetics was observed at the cathode which results in a large voltage drop. Such behavior is due to strong inhibition of the cathodic ORR, resulting in high overpotentials and therefore, significant deterioration in the energy conversion efficiency of the cell. The slow kinetic behavior stems from the difficulty of (O=O) bond breaking. In order to model the conditions of continuous oxidation/reduction in a fuel cell, the continuous mass transfer to the electrode surface is necessary. Therefore, mass spectrometry and AC voltammetry measurements presented here were done using the thin layer flow through cell. This thesis aims at a determination of the rate constant of single reaction steps during the oxidation of CO, methanol and ethanol at different platinum surfaces. Towards that aim, I investigated the electrocatalytic oxidation and adsorption rate of methanol (chapter 3) and the electrocatalytic oxidation of ethanol (chapter 4) at different Pt surfaces, using DEMS. In chapter 5, the potential dependence of the bulk and adsorbed methanol oxidation reaction rate (presented by the apparent transfer coefficient, {alpha}') and the corresponding Tafel slope of the reaction have been determined under convection conditions using a potential modulation ac voltammetry technique. Finally, as an application of the method presented in chapter 5, my work in chapter 6

Kinetics of the cells of the hematopoietic system in the course of postradiation regeneration. [Mice

Energy Technology Data Exchange (ETDEWEB)

Kondratenko, N F

1975-01-01

Twenty-four hours after sublethal whole-body irradiation (200 rad) of mice, only 4 percent of the stem cells were viable and continued to differentiate. Exponential growth of these cells started a day later and by week 2 the number was completely restored and stabilized. The kinetics of committed precursors of granulocytes and macrophages was different. Some 20 percent of these cells were viable 24 hours after irradiation and the granulocytes in particular continued to differentiate into mature cellular elements. The total number remained at the minimal level for a week, after which the logarithmic phase began, with complete recovery achieved toward the end of week 2 after irradiation. Thus, the restoration of hematopoiesis in sublethally irradiated mice is due primarily to the exponential growth of surviving stem cells in bone marrow.

On-rate based optimization of structure-kinetic relationship--surfing the kinetic map.

Science.gov (United States)

Schoop, Andreas; Dey, Fabian

2015-10-01

In the lead discovery process residence time has become an important parameter for the identification and characterization of the most efficacious compounds in vivo. To enable the success of compound optimization by medicinal chemistry toward a desired residence time the understanding of structure-kinetic relationship (SKR) is essential. This article reviews various approaches to monitor SKR and suggests using the on-rate as the key monitoring parameter. The literature is reviewed and examples of compound series with low variability as well as with significant changes in on-rates are highlighted. Furthermore, findings of kinetic on-rate changes are presented and potential underlying rationales are discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

Kinetics of Ca2+- and ATP-dependent, voltage-controlled anion conductance in the plasma membrane of mesophyll cells of Pisum sativum

NARCIS (Netherlands)

Elzenga, J.T.M.; van Volkenburgh, E.

Whole-cell patch-clamp techniques were used to measure anion currents through the plasma membrane of protoplasts of mesophyll cells of expanding pea (Pisum sativum L.) leaves. Voltage-induced changes of the currents could be modelled with single exponential activation and deactivation kinetics. The

Kinetics and comparison of δ-aminolevulinic-acid-induced endogenous protoporphyrin-IX in single cell by steady state and multiphoton fluorescence imaging

Science.gov (United States)

Ganesan, Singaravelu; Elangovan, Masilamani; Periasamy, Ammasi

2001-04-01

Photodynamic Therapy has emerged as a new modality in the treatment of various nonmalignant and malignant diseases. It involves the systemic administration of tumor specific photo-sensitizers with the subsequent application of visible light. This combination causes the generation of cytotoxic species, which damage sensitive targets, producing cell injury and tumor destruction. Although, photofrin is the only photosensitizer currently approved for PDT and tumor detection, its concomitant cutaneous photosensitization poses a significant problem. Hence, δ-aminoleuvulinic acid (δ-ALA) a precursor for the endogenous production of Protoporphyrin IX, through heme biosynthesis pathway, has gained significant importance in the Photodynamic Therapy. Though δ-ALA is present naturally in the cells, exogenous δ-ALA helps to synthesis more of PpIX in the tumor cells, as the fast growing tumor cells take up the administered δ-ALA more than the normal cells. Based on these facts, many invasive studies have been reported on the kinetics of δ-ALA at cellular level by chemical extraction of PpIX from the cells. In the present study we have studied the kinetics of δ-ALA induced PpIX fluorescence from Hela cells by perchloric/Methanol extraction method. However, the amount of PpIX synthesized in the cells at different point of incubation time by noninvasive methods has not been reported. Hence we have also used a noninvasive technique of measuring the kinetics δ-ALA induced PPIX fluorescence from Hela, an epithelial cell derived from human cervical cancer by both single photon (steady state) and multi photon excitation. From the studies it is observed that the δ-ALA induced PpIX is more at 2 hours incubation time for 2 mM of δ-ALA concentration. Further, it is observed that with steady state fluorescence imaging method, the excitation light itself cause the Photodynamic damage, due to the prolonged exposure of the cells than in multi photon excitation, leading to the rounding

Determination of DNA-synthetizing lymphatic cells as a kinetic and prognostic factor in non-Hodgkin lymphoma

International Nuclear Information System (INIS)

Heiss, F.

1982-01-01

A differentiated clinical and pathoanatomical classification of non-Hodgkin lymphomas is presented. On this basis, diagnostic, prognostic and pathophysiological information on the main types of lymphoma can be obtained from the measurement of the rosette-forming cell fraction (T-cell fraction) and from the autoradiographic determination of the proliferating cell fraction. This approach under the aspect of proliferation kinetics was employed in 9 patients with chronic B-lymphadenosis, 3 patients with chronic T-lymphadenosis, 14 patients with immunocytoma, 15 patients with different types of non-Hodgkin lymphoma, and 3 patients with angioimmunoblastic lymphadenopathy, both for primary diagnosis and in follow-up examinations. (orig./MG) [de

Performance of 12Ah aerospace nickel-cadmium cells of design variable groups

Science.gov (United States)

Vasanth, K. L.

1985-01-01

The design variable program of NASA is a systematic approach to evaluate the performance of 12Ah aerospace nickel-cadmium cells of 9 important cell designs. These cells were life cycled in a Low-Earth Orbit (LEO) regime for 3 to 4 years. Representative cells taken from the design variable groups after different cycling periods have been examined. The results show that: (1) positive swelling and carbonate content in the electrolyte increases as a function of the number of cycles, (2) electrolyte distribution follows the order NEG greater than POS greater than SEP, 3) control and no PQ groups outperformed the rest of the groups and (4) the polypropylene group shows very heavy cadmium migration and poor performance.

Intestinal and peritoneal mast cells differ in kinetics of quantal release

Energy Technology Data Exchange (ETDEWEB)

Balseiro-Gomez, Santiago, E-mail: sanbalgom@alum.us.es; Ramirez-Ponce, M. Pilar, E-mail: pponce@us.es; Acosta, Jorge, E-mail: jorgealo@us.es; Ales, Eva, E-mail: eales@us.es; Flores, Juan A., E-mail: jaflores@us.es

2016-01-15

5-hydroxytriptamine (5-HT, serotonin) storage and release in mast cell (MC) secretory granules (SG) are dependent on serglycin proteoglycans (PG). This notion is based on the studies of MC of the connective tissue subtype that predominantly contain PG of the heparin type, whereas intestinal mucosal MC, which contain predominantly chondroitin sulfate, have been poorly explored. In the present study, we addressed the possibility that PG contents may differently affect the storage and release of preformed mediators in these two MC subclasses and explain in part their different functional properties. Rat peritoneal (PMC) and intestinal mast cells (IMC) were isolated and purified using a percoll gradient, and the efflux of 5-HT from each SG was measured by amperometric detection. IMC exhibited a ∼34% reduction in the release of 5-HT compared with PMC because of a lower number of exocytotic events, rather than a lower secretion per single exocytotic event. Amperometric spikes from IMC exhibited a slower decay phase and increased half-width but a similar ascending phase and foot parameters, indicating that the fusion pore kinetics are comparable in both MC subclasses. We conclude that both PG subtypes are equally efficient systems, directly involved in serotonin accumulation, and play a crucial role in regulating the kinetics of exocytosis from SG, providing specific secretory properties for the two cellular subtypes. - Highlights: • We improved a method for isolating and purifying IMC. • There was a reduction in total serotonin release in IMC with respect to PMC. • This decrease was not due to less secretion per quantum but a lower number of exocytotic events. • There was also a deceleration of exocytosis in IMC with respect to PMC.

Kinetic Study of COS with Tertiary Alkanolamine Solutions. 2. Modeling and Experiments in a Stirred Cell Reactor

NARCIS (Netherlands)

Littel, Rob J.; Versteeg, Geert F.; Swaaij, Wim P.M. van

1992-01-01

Absorption experiments of COS into aqueous solutions of MDEA and DEMEA at 303 K have been carried out in a stirred cell reactor. An absorption model, based on Higbie’s penetration theory, has been developed and applied to interpret the absorption experiments, using the kinetic data obtained in part

Kinetics of the membrane current mediated by serotonin 5-HT3 receptors in cultured mouse neuroblastoma cells.

NARCIS (Netherlands)

Neijt, H.C.; Plomp, J.J.; Vijverberg, H.P.M.

1989-01-01

1. Ionic currents mediated by serotonin 5-HT3 receptors were studied in the mouse neuroblastoma cell line N1E-115, using suction pipettes for intracellular perfusion and voltage clamp recording. The dependence of the kinetics of the membrane current on serotonin concentration was investigated. 2. At

[Prostate cancer. Part 1: Review of cell kinetics over the years 1966-2015 and future perspectives of the new grading of the International Society of Urological Pathology (ISUP)].

Science.gov (United States)

Helpap, B; Bubendorf, L

2016-02-01

Using tritium-labeled thymidine histoautoradiography, the AgNOR staining technique and Ki67-MIB-1 immunohistochemistry to study cell kinetics, prostate cancer can be subdivided into slowly, moderately and rapidly proliferating tumors. These are important supplementary methods and prerequisites for a grading as low, intermediate and high-grade in addition to classical histology and cytology. Cytometry of DNA can confirm the cell kinetics of prostate cancer by detection of a predominance of diploid or aneuploid cell nuclei but should only be evaluated together with histological investigations. All histology-based analyses of cell kinetics encompass the classical highly and poorly differentiated glandular and cribriform patterns as well as solid undifferentiated structures and the various subcategories. The malignancy grading of prostate cancer can result from the summation of histological grading and cell kinetic analyses, as long as the named investigations are included. The future perspectives of individualized therapy options, including active surveillance in early low-grade and also for high-grade prostate cancer and new antihormonal treatment in advanced disease, may increasingly rely on tissue biomarkers and advanced technologies for whole genome analysis including next generation sequencing.

Experimental studies on the mechanism of leukemogenesis following the hemopoietic stem cell kinetics

Energy Technology Data Exchange (ETDEWEB)

Bessho, Masami; Hirashima, Kunitake (National Inst. of Radiological Sciences, Chiba (Japan))

1982-12-01

The mechanism of radiation-induced myeloid leukemogenesis was studied experimentally following the hemopoietic stem cell kinetics. Pluripotent stem cells (CFU-S) regarded as target cells to Friend virus (FV) were highly susceptible to leukemic cell transformation by FV during the regeneration period after irradiation. Experimental studies using RFM mice revealed that (1) the period of leukemic transformation closely corresponded to the prolonged suppressive period of CFU-C after irradiation, when significantly increased fraction of CFU-C is in S-phase, (2) the leukemic cell transformation after irradiation occurred earlier and more frequently than the overt leukemia, (3) some unknown host factors except cellular immunity played an important role in the establishment of overt leukemia, (4) lipopolysaccharide administrated after irradiation increased the incidence of myeloid leukemia whereas urethane decreased it. Another experimental systems using C3H/He mice bearing CSF-producing tumor revealed that the incidence of myeloid leukemia after a low-dose irradiation increased when CFU-S and CFU-C were proliferating and differentiating actively by the stimulus of CSF produced by the tumor. The mechanism of this phenomenon can be regarded as the activation of leukemia virus in irradiated bodies.

CRYSTALLIZATION KINETICS OF AMMONIUM PERCHLORATE IN AN AGITATED VESSEL

Directory of Open Access Journals (Sweden)

Nahidh Kaseer

2013-05-01

Full Text Available 31Overall crystal growth kinetics for ammonium perchlorate in laboratory scale batch  agitated vessel crystallizer have been determined from batch experiments performed in an integral mode. The effects of temperature between 30-60ºC, seed size 0.07, 0.120 and 0.275 mm and stirrer speed 160, 340, and 480 rpm, on the kinetics of crystal growth were investigated. Two different methods, viz. polynomial fitting and initial derivative were used to predict the kinetics expression. In general both methods gave comparable results for growth kinetics estimation. The order of growth process is not more than two. The activation energy for crystal growth of ammonium perchlorate was determined and found  to be equal to 5.8 kJ/ mole.            Finally, the influence of the affecting parameters on the crystal growth rate gives general expression that had an obvious dependence of the growth rate on each variables of concern (temperature, seed size, and stirrer speed .The general overall growth rate expression had shown that super saturation is the most significant variable. While the positive dependence of the stirrer speed demonstrates the importance of the diffusional step in the growth rate model. Moreover, the positive dependence of the seed size demonstrate the importance of the surface integration  step in the growth rate model. All the studied variables tend to suggest that the growth rate characteristics  of ammonium perchlorate from aqueous solution commenced in a batch crystallizer are diffusion kinetic controlled process.

Electrochemical cell and electrode designs for high-temperature/high-pressure kinetic measurements

International Nuclear Information System (INIS)

Nagy, Z.; Yonco, R.M.

1987-05-01

Many corrosion processes of interest to the nuclear power industry occur in high-temperature/high-pressure aqueous systems. The investigation of the kinetics of the appropriate electrode reactions is a serious experimental challenge, partially because of the high temperatures and pressures and partially because many of these reactions are very rapid, requiring fast relaxation measurements. An electrochemical measuring system is described which is suitable for measurements of the kinetics of fast electrode reactions at temperatures extending to at least 300 0 C and pressures to at least 10 MPa (100 atmospheres). The system includes solution preparation and handling equipment, the electrochemical cell, and several electrode designs. One of the new designs is a coaxial working electrode-counter electrode assembly; this electrode can be used with very fast-rising pulses, and it provides a well defined, repeatedly-polishable working surface. Low-impedance reference electrodes are also described, based on electrode concepts responding to the pH or the redox potential of the test solution. Additionally, a novel, long-life primary reference electrode design is reported, based on a modification of the external, pressure-balanced Ag/AgCl reference electrode

Electrochemical cell and electrode designs for high-temperature/high-pressure kinetic measurements

International Nuclear Information System (INIS)

Nagy, Z.; Yonco, R.M.

1988-01-01

Many corrosion processes of interest to the nuclear power industry occur in high-temperature/high-pressure aqueous systems. The investigation of the kinetics of the appropriate electrode reactions is a serious experimental challenge, partially because of the high temperatures and pressures and partially because many of these reactions are very rapid, requiring fast relaxation measurements. An electrochemical measuring system is described which is suitable for measurements of the kinetics of fast electrode reactions at temperatures extending to at least 300 0 C and pressures to at least 10 MPa (100 atmospheres). The system includes solution preparation and handling equipment, the electrochemical cell, and several electrode designs. One of the new designs is a coaxial working electrode-counter electrode assembly; this electrode can be used with very fast-rising pulses, and it provides a well defined, repeatedly-polishable working surface. Low-impedance reference electrodes are also described, based on electrode concepts responding to the pH or the redox potential of the test solution. Additionally, a novel, long-life primary reference electrode design is reported, based on a modification of the external, pressure-balanced Ag/AgCl reference electrode

Cell to Cell Variability of Radiation-Induced Foci: Relation between Observed Damage and Energy Deposition.

Science.gov (United States)

Gruel, Gaëtan; Villagrasa, Carmen; Voisin, Pascale; Clairand, Isabelle; Benderitter, Marc; Bottollier-Depois, Jean-François; Barquinero, Joan Francesc

2016-01-01

Most studies that aim to understand the interactions between different types of photon radiation and cellular DNA assume homogeneous cell irradiation, with all cells receiving the same amount of energy. The level of DNA damage is therefore generally determined by averaging it over the entire population of exposed cells. However, evaluating the molecular consequences of a stochastic phenomenon such as energy deposition of ionizing radiation by measuring only an average effect may not be sufficient for understanding some aspects of the cellular response to this radiation. The variance among the cells associated with this average effect may also be important for the behaviour of irradiated tissue. In this study, we accurately estimated the distribution of the number of radiation-induced γH2AX foci (RIF) per cell nucleus in a large population of endothelial cells exposed to 3 macroscopic doses of gamma rays from 60Co. The number of RIF varied significantly and reproducibly from cell to cell, with its relative standard deviation ranging from 36% to 18% depending on the macroscopic dose delivered. Interestingly, this relative cell-to-cell variability increased as the dose decreased, contrary to the mean RIF count per cell. This result shows that the dose effect, in terms of the number of DNA lesions indicated by RIF is not as simple as a purely proportional relation in which relative SD is constant with dose. To analyse the origins of this observed variability, we calculated the spread of the specific energy distribution for the different target volumes and subvolumes in which RIF can be generated. Variances, standard deviations and relative standard deviations all changed similarly from dose to dose for biological and calculated microdosimetric values. This similarity is an important argument that supports the hypothesis of the conservation of the association between the number of RIF per nucleus and the specific energy per DNA molecule. This comparison allowed us to

Cell to Cell Variability of Radiation-Induced Foci: Relation between Observed Damage and Energy Deposition.

Directory of Open Access Journals (Sweden)

Gaëtan Gruel

Full Text Available Most studies that aim to understand the interactions between different types of photon radiation and cellular DNA assume homogeneous cell irradiation, with all cells receiving the same amount of energy. The level of DNA damage is therefore generally determined by averaging it over the entire population of exposed cells. However, evaluating the molecular consequences of a stochastic phenomenon such as energy deposition of ionizing radiation by measuring only an average effect may not be sufficient for understanding some aspects of the cellular response to this radiation. The variance among the cells associated with this average effect may also be important for the behaviour of irradiated tissue. In this study, we accurately estimated the distribution of the number of radiation-induced γH2AX foci (RIF per cell nucleus in a large population of endothelial cells exposed to 3 macroscopic doses of gamma rays from 60Co. The number of RIF varied significantly and reproducibly from cell to cell, with its relative standard deviation ranging from 36% to 18% depending on the macroscopic dose delivered. Interestingly, this relative cell-to-cell variability increased as the dose decreased, contrary to the mean RIF count per cell. This result shows that the dose effect, in terms of the number of DNA lesions indicated by RIF is not as simple as a purely proportional relation in which relative SD is constant with dose. To analyse the origins of this observed variability, we calculated the spread of the specific energy distribution for the different target volumes and subvolumes in which RIF can be generated. Variances, standard deviations and relative standard deviations all changed similarly from dose to dose for biological and calculated microdosimetric values. This similarity is an important argument that supports the hypothesis of the conservation of the association between the number of RIF per nucleus and the specific energy per DNA molecule. This

Variable-angle total internal reflection fluorescence microscopy of intact cells of Arabidopsis thaliana

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Kim Myung K

2011-09-01

Full Text Available Abstract Background Total internal reflection fluorescence microscopy (TIRFM is a powerful tool for observing fluorescently labeled molecules on the plasma membrane surface of animal cells. However, the utility of TIRFM in plant cell studies has been limited by the fact that plants have cell walls, thick peripheral layers surrounding the plasma membrane. Recently, a new technique known as variable-angle epifluorescence microscopy (VAEM was developed to circumvent this problem. However, the lack of a detailed analysis of the optical principles underlying VAEM has limited its applications in plant-cell biology. Results Here, we present theoretical and experimental evidence supporting the use of variable-angle TIRFM in observations of intact plant cells. We show that when total internal reflection occurs at the cell wall/cytosol interface with an appropriate angle of incidence, an evanescent wave field of constant depth is produced inside the cytosol. Results of experimental TIRFM observations of the dynamic behaviors of phototropin 1 (a membrane receptor protein and clathrin light chain (a vesicle coat protein support our theoretical analysis. Conclusions These findings demonstrate that variable-angle TIRFM is appropriate for quantitative live imaging of cells in intact tissues of Arabidopsis thaliana.

Effect of hypothermia on cell kinetics and response to hyperthermia and x rays

International Nuclear Information System (INIS)

van Rijn, J.; van den Berg, J.; Kipp, J.B.A.; Schamhart, D.H.J.; van Wijk, R.

1985-01-01

Hyperthermia is a potent radio enhancer. Studies using hypothermia in combination with irradiation have given confusing results due to lack of uniformity in experimental design. This report shows that hypothermia might have potential significance in the treatment of malignant cells with both thermo- and radiotherapy. Reuber H35 hepatoma cells, clone KRC-7 were used to study the effect of hypothermia on cell kinetics and subsequent response to hyperthermia and/or X rays. Cells were incubated at 8.5 0 C or between 25 and 37 0 C for 24 hr prior to hyperthermia or irradiation. Hypothermia caused sensitization to both hyperthermia and X rays. In contrast to the effect of hypothermia on either hyperthermia or X rays alone, thermal radiosensitization was decreased in hypothermically pretreated cells (24 hr at 25 0 C) compared to control cells (37 0 C). The expression of thermotolerance and the rate of development at 37 0 C after an initial heating at 42.5 0 C were not influenced after preincubation at 25 0 C for 24 hr. The expression of thermotolerance for heat or heat plus X rays during incubation at 41 0 C occurred in a significantly smaller number of cells after 24 hr preincubation at 25 0 C. The enhanced thermo- and radiosensitivity in hypothermically treated cells disappeared in approximately 6 hr after return to 37 0 C

Inactivation kinetics of various chemical disinfectants on Aeromonas hydrophila planktonic cells and biofilms.

Science.gov (United States)

Jahid, Iqbal Kabir; Ha, Sang-Do

2014-05-01

The present article focuses on the inactivation kinetics of various disinfectants including ethanol, sodium hypochlorite, hydrogen peroxide, peracetic acid, and benzalkonium chloride against Aeromonas hydrophila biofilms and planktonic cells. Efficacy was determined by viable plate count and compared using a modified Weibull model. The removal of the biofilms matrix was determined by the crystal violet assay and was confirmed by field-emission scanning electron microscope. The results revealed that all the experimental data and calculated Weibull α (scale) and β (shape) parameters had a good fit, as the R(2) values were between 0.88 and 0.99. Biofilms are more resistant to disinfectants than planktonic cells. Ethanol (70%) was the most effective in killing cells in the biofilms and significantly reduced (preduction as well as the effectiveness of chemical disinfectants on biofilms. The study showed that the Weibull model could successfully be used on food and food contact surfaces to determine the exact contact time for killing biofilms-forming foodborne pathogens.

SOS reaction kinetics of bacterial cells induced by ultraviolet radiation and α particles

International Nuclear Information System (INIS)

Bonev, M.; Kolev, S.

2000-01-01

It is the purpose of the work to apply the SOS lux test for detecting α particles, as well as to study the SOS system kinetics. Two strains with plasmid pPLS-1 are used: wild type C600 lux and its isogen lysogen with α prophage one. Irradiation is done on dacron nuclear filters. The source of α particles is Am 241 with power 5 Gy/min, and the ultraviolet source - a lamp emitting rays with wave length 254 nm. The light yield is measured by installations made up of scintilometer VA-S-968, High-voltage electric power, and one channel analyzer Strahlugsmessgerat 20046. The SOS lux text is based on the recombinant plasmid pPLS-1 which is a derivative of pBR322 where the lux gene is set under the control of an SOS promoter. E coly recA + strains containing the construction produce considerable amount of photons in the visible zone following treatment with agents damaging the DNA of cells. The kinetic curves of SOS response are obtained after irradiation with α particles and UV rays. DNA damaging agents cause an increase in the initial SOS response rate in the range od smaller doses, and a decrease reaching to block of the one in the high doses range. The light yield of lysogenic cells is lower. As compared to nonelysogene ones. DNA damage caused by α particles are more difficult to repair as compared to pyrimidine dimers. (author)

On-line study of growth kinetics of single hyphae of Aspergillus oryzae in a flow-through cell

DEFF Research Database (Denmark)

Christiansen, Torben; Spohr, Anders Bendsen; Nielsen, Jens Bredal

1999-01-01

Using image analysis the growth kinetics of the single hyphae of the filamentous fungus Aspergillus oryzae has been determined on-line in a flow-through cell at different glucose concentrations in the range from 26 mg L-1 to 20 g L-1. The tip extension rate of the individual hyphae can be described...... with saturation type kinetics with respect to the length of the hyphae. The maximum tip extension rate is constant for all hyphae measured at the same glucose concentration, whereas the saturation constant for the hyphae varies significantly between the hyphae even within the same hyphal element. When apical...... branching occurs, it is observed that the tip extension rate decreases temporarily. The number of branches formed on a hypha is proportional to the length of the hypha that exceeds a certain minimum length required to support the growth of a new branch. The observed kinetics has been used to simulate...

Nuclear reprogramming: kinetics of cell cycle and metabolic progression as determinants of success.

Directory of Open Access Journals (Sweden)

Sebastian Thomas Balbach

Full Text Available Establishment of totipotency after somatic cell nuclear transfer (NT requires not only reprogramming of gene expression, but also conversion of the cell cycle from quiescence to the precisely timed sequence of embryonic cleavage. Inadequate adaptation of the somatic nucleus to the embryonic cell cycle regime may lay the foundation for NT embryo failure and their reported lower cell counts. We combined bright field and fluorescence imaging of histone H(2b-GFP expressing mouse embryos, to record cell divisions up to the blastocyst stage. This allowed us to quantitatively analyze cleavage kinetics of cloned embryos and revealed an extended and inconstant duration of the second and third cell cycles compared to fertilized controls generated by intracytoplasmic sperm injection (ICSI. Compared to fertilized embryos, slow and fast cleaving NT embryos presented similar rates of errors in M phase, but were considerably less tolerant to mitotic errors and underwent cleavage arrest. Although NT embryos vary substantially in their speed of cell cycle progression, transcriptome analysis did not detect systematic differences between fast and slow NT embryos. Profiling of amino acid turnover during pre-implantation development revealed that NT embryos consume lower amounts of amino acids, in particular arginine, than fertilized embryos until morula stage. An increased arginine supplementation enhanced development to blastocyst and increased embryo cell numbers. We conclude that a cell cycle delay, which is independent of pluripotency marker reactivation, and metabolic restraints reduce cell counts of NT embryos and impede their development.

Decohesion Kinetics in Polymer Organic Solar Cells

KAUST Repository

Bruner, Christopher; Novoa, Fernando; Dupont, Stephanie; Dauskardt, Reinhold

2014-01-01

© 2014 American Chemical Society. We investigate the role of molecular weight (MW) of the photoactive polymer poly(3-hexylthiophene) (P3HT) on the temperature-dependent decohesion kinetics of bulk heterojunction (BHJ) organic solar cells (OSCs). The MW of P3HT has been directly correlated to its carrier field effect mobilities and the ambient temperature also affects OSC in-service performance and P3HT arrangement within the BHJ layer. Under inert conditions, time-dependent decohesion readily occurs within the BHJ layer at loads well below its fracture resistance. We observe that by increasing the MW of P3HT, greater resistance to decohesion is achieved. However, failure consistently occurs within the BHJ layer representing the weakest layer within the device stack. Additionally, it was found that at temperatures below the glass transition temperature (∼41-45 °C), decohesion was characterized by brittle failure via molecular bond rupture. Above the glass transition temperature, decohesion growth occurred by a viscoelastic process in the BHJ layer, leading to a significant degree of viscoelastic deformation. We develop a viscoelastic model based on molecular relaxation to describe the resulting behavior. The study has implications for OSC long-term reliability and device performance, which are important for OSC production and implementation.

Decohesion Kinetics in Polymer Organic Solar Cells

KAUST Repository

Bruner, Christopher

2014-12-10

© 2014 American Chemical Society. We investigate the role of molecular weight (MW) of the photoactive polymer poly(3-hexylthiophene) (P3HT) on the temperature-dependent decohesion kinetics of bulk heterojunction (BHJ) organic solar cells (OSCs). The MW of P3HT has been directly correlated to its carrier field effect mobilities and the ambient temperature also affects OSC in-service performance and P3HT arrangement within the BHJ layer. Under inert conditions, time-dependent decohesion readily occurs within the BHJ layer at loads well below its fracture resistance. We observe that by increasing the MW of P3HT, greater resistance to decohesion is achieved. However, failure consistently occurs within the BHJ layer representing the weakest layer within the device stack. Additionally, it was found that at temperatures below the glass transition temperature (∼41-45 °C), decohesion was characterized by brittle failure via molecular bond rupture. Above the glass transition temperature, decohesion growth occurred by a viscoelastic process in the BHJ layer, leading to a significant degree of viscoelastic deformation. We develop a viscoelastic model based on molecular relaxation to describe the resulting behavior. The study has implications for OSC long-term reliability and device performance, which are important for OSC production and implementation.

Decohesion kinetics in polymer organic solar cells.

Science.gov (United States)

Bruner, Christopher; Novoa, Fernando; Dupont, Stephanie; Dauskardt, Reinhold

2014-12-10

We investigate the role of molecular weight (MW) of the photoactive polymer poly(3-hexylthiophene) (P3HT) on the temperature-dependent decohesion kinetics of bulk heterojunction (BHJ) organic solar cells (OSCs). The MW of P3HT has been directly correlated to its carrier field effect mobilities and the ambient temperature also affects OSC in-service performance and P3HT arrangement within the BHJ layer. Under inert conditions, time-dependent decohesion readily occurs within the BHJ layer at loads well below its fracture resistance. We observe that by increasing the MW of P3HT, greater resistance to decohesion is achieved. However, failure consistently occurs within the BHJ layer representing the weakest layer within the device stack. Additionally, it was found that at temperatures below the glass transition temperature (∼41-45 °C), decohesion was characterized by brittle failure via molecular bond rupture. Above the glass transition temperature, decohesion growth occurred by a viscoelastic process in the BHJ layer, leading to a significant degree of viscoelastic deformation. We develop a viscoelastic model based on molecular relaxation to describe the resulting behavior. The study has implications for OSC long-term reliability and device performance, which are important for OSC production and implementation.

Live cell imaging reveals marked variability in myoblast proliferation and fate

Science.gov (United States)

2013-01-01

Background During the process of muscle regeneration, activated stem cells termed satellite cells proliferate, and then differentiate to form new myofibers that restore the injured area. Yet not all satellite cells contribute to muscle repair. Some continue to proliferate, others die, and others become quiescent and are available for regeneration following subsequent injury. The mechanisms that regulate the adoption of different cell fates in a muscle cell precursor population remain unclear. Methods We have used live cell imaging and lineage tracing to study cell fate in the C2 myoblast line. Results Analyzing the behavior of individual myoblasts revealed marked variability in both cell cycle duration and viability, but similarities between cells derived from the same parental lineage. As a consequence, lineage sizes and outcomes differed dramatically, and individual lineages made uneven contributions toward the terminally differentiated population. Thus, the cohort of myoblasts undergoing differentiation at the end of an experiment differed dramatically from the lineages present at the beginning. Treatment with IGF-I increased myoblast number by maintaining viability and by stimulating a fraction of cells to complete one additional cell cycle in differentiation medium, and as a consequence reduced the variability of the terminal population compared with controls. Conclusion Our results reveal that heterogeneity of responses to external cues is an intrinsic property of cultured myoblasts that may be explained in part by parental lineage, and demonstrate the power of live cell imaging for understanding how muscle differentiation is regulated. PMID:23638706

Annealing Kinetic Model Using Fast and Slow Metastable Defects for Hydrogenated-Amorphous-Silicon-Based Solar Cells

Directory of Open Access Journals (Sweden)

Seung Yeop Myong

2007-01-01

Full Text Available The two-component kinetic model employing “fast” and “slow” metastable defects for the annealing behaviors in pin-type hydrogenated-amorphous-silicon- (a-Si:H- based solar cells is simulated using a normalized fill factor. Reported annealing data on pin-type a-Si:H-based solar cells are revisited and fitted using the model to confirm its validity. It is verified that the two-component model is suitable for fitting the various experimental phenomena. In addition, the activation energy for annealing of the solar cells depends on the definition of the recovery time. From the thermally activated and high electric field annealing behaviors, the plausible microscopic mechanism on the defect removal process is discussed.

Release kinetics and cell viability of ibuprofen nanocrystals produced by melt-emulsification.

Science.gov (United States)

Fernandes, A R; Dias-Ferreira, J; Cabral, C; Garcia, M L; Souto, E B

2018-06-01

The clinical use of poorly water-soluble drugs has become a big challenge in pharmaceutical development due to the compromised bioavailability of the drugs in vivo. Nanocrystals have been proposed as a formulation strategy to improve the dissolution properties of these drugs. The benefits of using nanocrystals in drug delivery, when compared to other nanoparticles, are related to their production facilities, simple structure, and suitability for a variety of administration routes. High pressure homogenization (HPH) is the most promising production process, which can be employed at low or high temperatures. Ibuprofen nanocrystals with a mean size below 175 nm, and polydispersity below 0.18, have been produced by melt-emulsification, followed by HPH. Two nanocrystal formulations, differing on the surfactant composition, have been produced, their in vitro ibuprofen release tested in Franz diffusion cells and adjusted to several kinetic models (zero order, first order, Higuchi, Hixson-Crowell, Korsmeyer-Peppas, Baker-Lonsdale and Weibull model). Cell viability was assessed at 3, 6 and 24 h of incubation on human epithelial colorectal cells (Caco-2) by AlamarBlue ® colorimetric assay. For both formulations, Caco-2 cells viability was dependent on the drug concentration and time of exposure. Copyright © 2018 Elsevier B.V. All rights reserved.

Kinetic analysis of in vitro production of wild-type Spodoptera frugiperda nucleopolyhedrovirus

Directory of Open Access Journals (Sweden)

Andréa Farias de Almeida

2010-04-01

Full Text Available In this study, the kinetic behavior of Sf9 and Sf21 cells used in the production of a baculovirus biopesticide to control the pest of corn Spodoptera frugiperda was analyzed. Kinetic variables such as maximum specific growth rate, cell productivity, mean rate of infection, as well as the mean rate of occlusion body production were determined during the infection of these cell-lines with the extracellular virus of the S. frugiperda nucleopolyhedrovirus (SfMNPV. The Sf9 cell-line resulted in better viral production results (5.0 x 10(8 OB/mL than the Sf21 cell-line (2.5 x 10(8 OB/mL.Neste trabalho, analisou-se o comportamento cinético das células Sf9 e Sf21 utilizadas na produção de biopesticida para o controle de Spodoptera frugiperda. Variáveis cinéticas, como velocidade específica máxima de crescimento, produtividade em células, velocidade média de infecção e a velocidade média de produção de OB foram determinadas durante a infecção destas linhagens com o vírus extracelular do nucleopoliedrovirus de S. frugiperda. A linhagem Sf9 resultou em melhores resultados de produção do baculovírus (5 x 10(8 OB/mL, quando comparada à linhagem Sf21 (2,5 x 10(8 OB/mL e outras linhagens da literatura.

Simulating kinetic parameters in transporter mediated permeability across Caco-2 cells. A case study on estrange-3-sulphate

DEFF Research Database (Denmark)

Rolsted, Kamilla; Rapin, Nicolas; Steffansen, Bente

2011-01-01

Substances that compete for the same saturable intestinal transporters may when dosed together lead to altered permeability and hence influence bioavailability. The aim was to simulate kinetic parameters, i.e. K(m) and J(max), for transporter mediated E(1)S permeability across Caco-2 cells...

Growth Kinetics, Characterization, and Plasticity of Human Menstrual Blood Stem Cells

Directory of Open Access Journals (Sweden)

Davood Mehrabani

2016-03-01

Full Text Available One of the readily available sources of mesenchymal stem cells (MSCs is menstrual blood-derived stem cells (Men-SCs, which exhibit characteristics similar to other types of MSCs. This study was performed to determine the growth kinetics, plasticity, and characterization of Men-SCs in women. During spring 2014 in the southern Iranian city of Shiraz, menstrual blood (5 mL was obtained from 10 women on their third day of menstruation in 2 age groups of 30 to 40 and 40 to 50 years old. Ficoll was used to separate the mononuclear cell fraction. After the Men-SCs were cultured, they were subcultured up to passage 4. Growth behavior and population doubling time were evaluated by seeding 5×104 cells into 12- and 24-well culture plates, and the colonies were enumerated. The expression of CD44, CD90, and CD34 was evaluated. The osteogenic potential was assessed by alizarin red staining. The Men-SCs were shown to be plastic adherent and spindle-shaped. Regarding the growth curves in the 12- and 24-well culture plates, it was demonstrated that in the women aged between 30 and 40 years, population doubling time was 55.5 and 62 hours, respectively, while these values in the women aged between 40 and 50 years were 70.4 and 72.4 hours, correspondingly. Positive expression of CD44 and CD90 and negative expression of CD34 were noted. In the osteogenic differentiation medium, the cells differentiated toward osteoblasts. As human Men-SCs are easily collectable without any invasive procedure and are a safe and rapid source of MSCs, they can be a good candidate for stem cell banking and cell transplantation in women.

Systems, methods and computer-readable media to model kinetic performance of rechargeable electrochemical devices

Science.gov (United States)

Gering, Kevin L.

2013-01-01

A system includes an electrochemical cell, monitoring hardware, and a computing system. The monitoring hardware samples performance characteristics of the electrochemical cell. The computing system determines cell information from the performance characteristics. The computing system also analyzes the cell information of the electrochemical cell with a Butler-Volmer (BV) expression modified to determine exchange current density of the electrochemical cell by including kinetic performance information related to pulse-time dependence, electrode surface availability, or a combination thereof. A set of sigmoid-based expressions may be included with the modified-BV expression to determine kinetic performance as a function of pulse time. The determined exchange current density may be used with the modified-BV expression, with or without the sigmoid expressions, to analyze other characteristics of the electrochemical cell. Model parameters can be defined in terms of cell aging, making the overall kinetics model amenable to predictive estimates of cell kinetic performance along the aging timeline.

Mesenchymal stem cells from sternum: the type of heart disease, ischemic or valvular, does not influence the cell culture establishment and growth kinetics.

Science.gov (United States)

Dias, Lucinara Dadda; Casali, Karina Rabello; Ghem, Carine; da Silva, Melissa Kristocheck; Sausen, Grasiele; Palma, Patrícia Bonini; Covas, Dimas Tadeu; Kalil, Renato A K; Schaan, Beatriz D; Nardi, Nance Beyer; Markoski, Melissa Medeiros

2017-07-25

In an attempt to increase the therapeutic potential for myocardial regeneration, there is a quest for new cell sources and types for cell therapy protocols. The pathophysiology of heart diseases may affect cellular characteristics and therapeutic results. To study the proliferative and differentiation potential of mesenchymal stem cells (MSC), isolated from bone marrow (BM) of sternum, we made a comparative analysis between samples of patients with ischemic (IHD) or non-ischemic valvular (VHD) heart diseases. We included patients with IHD (n = 42) or VHD (n = 20), with average age of 60 years and no differences in cardiovascular risk factors. BM samples were collected (16.4 ± 6 mL) and submitted to centrifugation with Ficoll-Paque, yielding 4.5 ± 1.5 × 10 7  cells/mL. Morphology, immunophenotype and differentiation ability had proven that the cultivated sternal BM cells had MSC features. The colony forming unit-fibroblast (CFU-F) frequency was similar between groups (p = 0.510), but VHD samples showed positive correlation to plated cells vs. CFU-F number (r = 0.499, p = 0.049). The MSC culture was established in 29% of collected samples, achieved passage 9, without significant difference in expansion kinetics between groups (p > 0.05). Dyslipidemia and the use of statins was associated with culture establishment for IHD patients (p = 0.049 and p = 0.006, respectively). Together, these results show that the sternum bone can be used as a source for MSC isolation, and that ischemic or valvular diseases do not influence the cellular yield, culture establishment or in vitro growth kinetics.

MOS current gain cells with electronically variable gain and constant bandwidth

NARCIS (Netherlands)

Klumperink, Eric A.M.; Seevinck, Evert

1989-01-01

Two MOS current gain cells are proposed that provide linear amplification of currents supplied by several linear MOS V-I converters. The gain is electronically variable by a voltage or a current and can be made insensitive to temperature and IC processing. The gain cells have a constant

Heterogeneity of osteosarcoma cell lines led to variable responses in reprogramming.

Science.gov (United States)

Choong, Pei Feng; Teh, Hui Xin; Teoh, Hoon Koon; Ong, Han Kiat; Choo, Kong Bung; Sugii, Shigeki; Cheong, Soon Keng; Kamarul, Tunku

2014-01-01

Four osteosarcoma cell lines, Saos-2, MG-63, G-292 and U-2 OS, were reprogrammed to pluripotent state using Yamanaka factors retroviral transduction method. Embryonic stem cell (ESC)-like clusters started to appear between 15 to 20 days post transduction. Morphology of the colonies resembled that of ESC colonies with defined border and tightly-packed cells. The reprogrammed sarcomas expressed alkaline phosphatase and pluripotency markers, OCT4, SSEA4, TRA-1-60 and TRA-1-81, as in ESC up to Passage 15. All reprogrammed sarcomas could form embryoid body-like spheres when cultured in suspension in a low attachment dish for up to 10 days. Further testing on the directed differentiation capacity of the reprogrammed sarcomas showed all four reprogrammed sarcoma lines could differentiate into adipocytes while reprogrammed Saos-2-REP, MG-63-REP and G-292-REP could differentiate into osteocytes. Among the 4 osteosarcoma cell lines, U-2 OS reported the highest transduction efficiency but recorded the lowest reprogramming stability under long term culture. Thus, there may be intrinsic differences governing the variable responses of osteosarcoma cell lines towards reprogramming and long term culture effect of the reprogrammed cells. This is a first report to associate intrinsic factors in different osteosarcoma cell lines with variable reprogramming responses and effects on the reprogrammed cells after prolonged culture.

Heterogeneity of Osteosarcoma Cell Lines Led to Variable Responses in Reprogramming

Science.gov (United States)

Choong, Pei Feng; Teh, Hui Xin; Teoh, Hoon Koon; Ong, Han Kiat; Choo, Kong Bung; Sugii, Shigeki; Cheong, Soon Keng; Kamarul, Tunku

2014-01-01

Four osteosarcoma cell lines, Saos-2, MG-63, G-292 and U-2 OS, were reprogrammed to pluripotent state using Yamanaka factors retroviral transduction method. Embryonic stem cell (ESC)-like clusters started to appear between 15 to 20 days post transduction. Morphology of the colonies resembled that of ESC colonies with defined border and tightly-packed cells. The reprogrammed sarcomas expressed alkaline phosphatase and pluripotency markers, OCT4, SSEA4, TRA-1-60 and TRA-1-81, as in ESC up to Passage 15. All reprogrammed sarcomas could form embryoid body-like spheres when cultured in suspension in a low attachment dish for up to 10 days. Further testing on the directed differentiation capacity of the reprogrammed sarcomas showed all four reprogrammed sarcoma lines could differentiate into adipocytes while reprogrammed Saos-2-REP, MG-63-REP and G-292-REP could differentiate into osteocytes. Among the 4 osteosarcoma cell lines, U-2 OS reported the highest transduction efficiency but recorded the lowest reprogramming stability under long term culture. Thus, there may be intrinsic differences governing the variable responses of osteosarcoma cell lines towards reprogramming and long term culture effect of the reprogrammed cells. This is a first report to associate intrinsic factors in different osteosarcoma cell lines with variable reprogramming responses and effects on the reprogrammed cells after prolonged culture. PMID:25170299

The recruitability and cell-cycle state of intestinal stem cells

International Nuclear Information System (INIS)

Potten, C.S.; Chadwick, C.; Ijiri, K.; Tsubouchi, S.; Hanson, W.R.

1984-01-01

Evidence is presented which suggests that the crypts of the small intestine contain at least two discrete but interdependent classes of stem cells, some with discrete cell kinetic properties and some with discrete radiation responses or radiosensitivities. Very low doses of X rays or gamma rays, or neutrons, kill a few cells in the stem cell regions of the crypt in a sensitive dose-dependent manner. Similar doses generate several different cell kinetic responses within either the clonogenic fraction or the cells at the stem cell position within the crypt. The cell kinetic responses range from apparent recruitment of G0 clonogenic cells into cycle, to a marked shortening of the average cell cycle of the cells at the stem cell position. It is suggested that the cell kinetic changes may be the consequence of the cell destruction

Kinetic Studies on Ni-YSZ Composite Electrodes

DEFF Research Database (Denmark)

Njodzefon, Jean-Claude; Sudireddy, Bhaskar Reddy; Hjelm, Johan

2015-01-01

AC and DC techniques were applied to investigate the electrochemical reaction kinetics of porous composite Ni/8-mol% yttria-stabilized zirconia (Ni/8YSZ) solid oxide cell (SOC) electrodes using a novel pseudo-3-electrode cell geometry. From OCV impedance spectra an activation energy Ea of 1.13 e......V, prefactor yan of 3.7·105·T, hydrogen and steam partial pressure dependencies a and b respectively of -0.07 and 0.22 were determined. DC current density vs. overpotential curves compared with those predicted using the determined kinetic parameters. Apparent Butler-Volmer charge transfer coefficients α were...... branch and the need for different α values for each branch suggests that a simple BV model of the measured electrode kinetics is insufficient and/or different reaction mechanisms might be occurring in anodic vs cathodic polarization....

Revealing chemical processes and kinetics of drug action within single living cells via plasmonic Raman probes.

Science.gov (United States)

Li, Shan-Shan; Guan, Qi-Yuan; Meng, Gang; Chang, Xiao-Feng; Wei, Ji-Wu; Wang, Peng; Kang, Bin; Xu, Jing-Juan; Chen, Hong-Yuan

2017-05-23

Better understanding the drug action within cells may extend our knowledge on drug action mechanisms and promote new drugs discovery. Herein, we studied the processes of drug induced chemical changes on proteins and nucleic acids in human breast adenocarcinoma (MCF-7) cells via time-resolved plasmonic-enhanced Raman spectroscopy (PERS) in combination with principal component analysis (PCA). Using three popular chemotherapy drugs (fluorouracil, cisplatin and camptothecin) as models, chemical changes during drug action process were clearly discriminated. Reaction kinetics related to protein denaturation, conformational modification, DNA damage and their associated biomolecular events were calculated. Through rate constants and reaction delay times, the different action modes of these drugs could be distinguished. These results may provide vital insights into understanding the chemical reactions associated with drug-cell interactions.

The kinetics of fossil resin extraction from a flotation concentrate

Energy Technology Data Exchange (ETDEWEB)

Li, L.; Yu, Q.; Miller, J.D. [Univ. of Utah, Salt Lake City, UT (United States)

1995-11-01

The kinetics of fossil resin extraction from a flotation concentrate by heptane were investigated as a function of process variables using monosize particles. Experimental results provide for a better understanding of the refining process and the basis for subsequent design and construction of a continuous resin refining circuit. Based on the effect of process variables (particle size, stirring speed, and temperature) the resin extraction rate appears to be controlled by surface solvation phenomena. The initial extraction rate was found to be inversely proportional to the initial particle size and a kinetic model is being developed to describe the experimental results.

Body mass index and other anthropometric variables in children with sickle cell anaemia.

Science.gov (United States)

Odetunde, Odutola Israel; Chinawa, Josephat Maduabuchi; Achigbu, Kingsley Ihedioha; Achigbu, Eberechukwu O

2016-01-01

The objectives of this study were to determine the anthropometric variables of children with sickle cell anaemia and comparing it with those with normal haemoglobin genotype. A cross sectional study of anthropometric measurements was conducted over a period of six months. Children with sickle cell anaemia in steady state aged between 6-20 years were recruited. Nutritional assessment was done using anthropometrical variables. Data were analyzed using the Statistical Package for Social Sciences program (SPSS), version 20. The sickle cell patients comprised of 20 males and 20 females. There were an equal number of controls with an equal male to female ratio of 1:1. Forty eight percent (19) of the children with sickle cell anemia were underweight (sickle cell anemia were low when compared with children with normal Haemoglobin genotype.

Kinetic Analysis of Horizontal Plyometric Exercise Intensity.

Science.gov (United States)

Kossow, Andrew J; Ebben, William P

2018-05-01

Kossow, AJ, DeChiara, TG, Neahous, SM, and Ebben, WP. Kinetic analysis of horizontal plyometric exercise intensity. J Strength Cond Res 32(5): 1222-1229, 2018-Plyometric exercises are frequently performed as part of a strength and conditioning program. Most studies assessed the kinetics of plyometric exercises primarily performed in the vertical plane. The purpose of this study was to evaluate the multiplanar kinetic characteristics of a variety of plyometric exercises, which have a significant horizontal component. This study also sought to assess sex differences in the intensity progression of these exercises. Ten men and 10 women served as subjects. The subjects performed a variety of plyometric exercises including the double-leg hop, standing long jump, single-leg standing long jump, bounding, skipping, power skipping, cone hops, and 45.72-cm hurdle hops. Subjects also performed the countermovement jump for comparison. All plyometric exercises were evaluated using a force platform. Dependent variables included the landing rate of force development and landing ground reaction forces for each exercise in the vertical, frontal, and sagittal planes. A 2-way mixed analysis of variance with repeated-measures for plyometric exercise type demonstrated main effects for exercise type for all dependent variables (p ≤ 0.001). There was no significant interaction between plyometric exercise type and sex for any of the variable assessed. Bonferroni-adjusted pairwise comparisons identified a number of differences between the plyometric exercises for the dependent variables assessed (p ≤ 0.05). These findings should be used to guide practitioners in the progression of plyometric exercise intensity, and thus program design, for those who require significant horizontal power in their sport.

Cellular Kinetics of Perivascular MSC Precursors

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William C. W. Chen

2013-01-01

Full Text Available Mesenchymal stem/stromal cells (MSCs and MSC-like multipotent stem/progenitor cells have been widely investigated for regenerative medicine and deemed promising in clinical applications. In order to further improve MSC-based stem cell therapeutics, it is important to understand the cellular kinetics and functional roles of MSCs in the dynamic regenerative processes. However, due to the heterogeneous nature of typical MSC cultures, their native identity and anatomical localization in the body have remained unclear, making it difficult to decipher the existence of distinct cell subsets within the MSC entity. Recent studies have shown that several blood-vessel-derived precursor cell populations, purified by flow cytometry from multiple human organs, give rise to bona fide MSCs, suggesting that the vasculature serves as a systemic reservoir of MSC-like stem/progenitor cells. Using individually purified MSC-like precursor cell subsets, we and other researchers have been able to investigate the differential phenotypes and regenerative capacities of these contributing cellular constituents in the MSC pool. In this review, we will discuss the identification and characterization of perivascular MSC precursors, including pericytes and adventitial cells, and focus on their cellular kinetics: cell adhesion, migration, engraftment, homing, and intercellular cross-talk during tissue repair and regeneration.

Campylobacter jejuni induces diverse kinetics and profiles of cytokine genes in INT-407 cells

International Nuclear Information System (INIS)

Al-Amri, Ahlam I.; Bakhiet, Moiz O.; Botta, Giuseppe A.; Tabbara, Khaled S.; Ismaeel, Abdelrahman Y.; Al-Mahmeed, Ali E.; Bin Danya, Khalid M.

2008-01-01

Objective was to examine the kinetic ability of embryonic human epithelial INT-407 cells to express messenger ribonucleic acid (mRNA) for various cytokines and chemokines in response to Campylobacter jejuni (C. jejuni) stimulation. In an experimental single-blind study, cultured embryonic human epithelial INT-407 cells were treated with different concentrations of viable C. jejuni, its sonicated and filtered supernatant. A modified non-radioactive in situ hybridization using probe cocktails was used to measure mRNA levels for the pro-inflammatory cytokines interleukin (IL)-1beta, IL-6, interferon-gamma, tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1 and IL-8 and the anti-inflammatory cytokines, IL-4 and IL-10. The study was carried out from September 2005 to March 2007 at the Department of Microbiology, Immunology and Infectious Diseases, College of Medicine and Medical Sciences, Arabian Gulf University, Bahrain. Viable C. jejuni sonicated bacteria and filtered supernatant induced high mRNA expression for the pro-inflammatory cytokines IL-1 beta, IL-6, IFN-gama, TNF-alpha, TGF-beta and IL-8 which peaked at the 12 hours post stimulation. Anti-inflammatory cytokine IL-4 and IL-10 mNRA expression were induced maximally at 3 hours post stimulation mainly by sonicated bacteria and filtrated supernatant, however, not with living bacteria and filtrated supernatant, however, not with living bacteria. Untreated embryonic human epithelial INT-407 cells expressed low amount of mNRA for the various cytokines and chemokines at all time points. For each cytokine, 4 samples were used per time hour. This study demonstrated that embryonic human epithelial INT-407 cells in response to viable C. jejuni or its cytotxins can alter cytokine and chemokine mNRA expression patterns and kinetics suggesting a potential role for these mediators in the immunopathogenesis of the infection caused by this pathogen, which might be relevant for future immunotherapeutic

Conformational kinetics of aliphatic tails

Science.gov (United States)

Ferrarini, Alberta; Moro, Giorgio; Nordio, Pier Luigi

The master equation describing the random walk between sites identified with the stable conformers of a chain molecule, represents the extension to the time domain of the Rotational Isomeric State model. The asymptotic analysis of the multidimensional diffusion equation in the continuous torsional variables subjected to the configurational potential, provides a rigorous justification for the discrete models, and it supplies, without resorting to phenomenological parameters, molecular definitions of the kinetic rates for the conformational transitions occurring at each segment of the chain. The coupling between the torsional variables is fully taken into account, giving rise to cooperative effects. A complete calculation of the specific correlation functions which describe the time evolution of the angular functions probed by N.M.R. and dielectric relaxation measurements, has been performed for alkyl chains attached to a massive core. The resulting behaviour has been compared with the decay of trans and gauche populations of specific bonds, expressed in terms of suitable correlation functions whose time integrals lead quite naturally to the definition of effective kinetic constants for the conformational transitions.

Biodegradation kinetics for pesticide exposure assessment.

Science.gov (United States)

Wolt, J D; Nelson, H P; Cleveland, C B; van Wesenbeeck, I J

2001-01-01

Understanding pesticide risks requires characterizing pesticide exposure within the environment in a manner that can be broadly generalized across widely varied conditions of use. The coupled processes of sorption and soil degradation are especially important for understanding the potential environmental exposure of pesticides. The data obtained from degradation studies are inherently variable and, when limited in extent, lend uncertainty to exposure characterization and risk assessment. Pesticide decline in soils reflects dynamically coupled processes of sorption and degradation that add complexity to the treatment of soil biodegradation data from a kinetic perspective. Additional complexity arises from study design limitations that may not fully account for the decline in microbial activity of test systems, or that may be inadequate for considerations of all potential dissipation routes for a given pesticide. Accordingly, kinetic treatment of data must accommodate a variety of differing approaches starting with very simple assumptions as to reaction dynamics and extending to more involved treatments if warranted by the available experimental data. Selection of the appropriate kinetic model to describe pesticide degradation should rely on statistical evaluation of the data fit to ensure that the models used are not overparameterized. Recognizing the effects of experimental conditions and methods for kinetic treatment of degradation data is critical for making appropriate comparisons among pesticide biodegradation data sets. Assessment of variability in soil half-life among soils is uncertain because for many pesticides the data on soil degradation rate are limited to one or two soils. Reasonable upper-bound estimates of soil half-life are necessary in risk assessment so that estimated environmental concentrations can be developed from exposure models. Thus, an understanding of the variable and uncertain distribution of soil half-lives in the environment is

Mechanisms and kinetic profiles of superoxide-stimulated nitrosative processes in cells using a diaminofluorescein probe.

Science.gov (United States)

Damasceno, Fernando Cruvinel; Facci, Rômulo Rodrigues; da Silva, Thalita Marques; Toledo, José Carlos

2014-12-01

In this study, we examined the mechanisms and kinetic profiles of intracellular nitrosative processes using diaminofluorescein (DAF-2) as a target in RAW 264.7 cells. The intracellular formation of the fluorescent, nitrosated product diaminofluorescein triazol (DAFT) from both endogenous and exogenous nitric oxide (NO) was prevented by deoxygenation and by cell membrane-permeable superoxide (O2(-)) scavengers but not by extracellular bovine Cu,Zn-SOD. In addition, the DAFT formation rate decreased in the presence of cell membrane-permeable Mn porphyrins that are known to scavenge peroxynitrite (ONOO(-)) but was enhanced by HCO3(-)/CO2. Together, these results indicate that nitrosative processes in RAW 264.7 cells depend on endogenous intracellular O2(-) and are stimulated by ONOO(-)/CO2-derived radical oxidants. The N2O3 scavenger sodium azide (NaN3) only partially attenuated the DAFT formation rate and only with high NO (>120 nM), suggesting that DAFT formation occurs by nitrosation (azide-susceptible DAFT formation) and predominantly by oxidative nitrosylation (azide-resistant DAFT formation). Interestingly, the DAFT formation rate increased linearly with NO concentrations of up to 120-140 nM but thereafter underwent a sharp transition and became insensitive to NO. This behavior indicates the sudden exhaustion of an endogenous cell substrate that reacts rapidly with NO and induces nitrosative processes, consistent with the involvement of intracellular O2(-). On the other hand, intracellular DAFT formation stimulated by a fixed flux of xanthine oxidase-derived extracellular O2(-) that also occurs by nitrosation and oxidative nitrosylation increased, peaked, and then decreased with increasing NO, as previously observed. Thus, our findings complementarily show that intra- and extracellular O2(-)-dependent nitrosative processes occurring by the same chemical mechanisms do not necessarily depend on NO concentration and exhibit different unusual kinetic profiles with

Kinetics of T cell-activation molecules in response to Mycobacterium tuberculosis antigens

Directory of Open Access Journals (Sweden)

Antas Paulo RZ

2002-01-01

Full Text Available The phenotypic features acquired subsequent to antigen-specific stimulation in vitro were evaluated by means of the kinetic expressions of CD69 and CD25 activation molecules on T lymphocytes and assayed by flow cytometry in response to PPD, Ag85B, and ferritin in PPD-positive healthy control individuals. In response to PHA, CD69 staining on both CD4+ and CD8+ T cells became initially marked after 4 h, peaked at 24 h, and quickly decreased after 120 h. For CD25, a latter expression was detected around 8 h, having increased after 96 h. As expected, the response rate to the mycobacterial antigens was much lower than that to the mitogen. Positive staining was high after 96 h for CD25 and after 24 h for CD69. CD69 expression was significantly enhanced (p < 0.05 on CD8+ as compared to CD4+ T cells. High levels were also found between 96-120 h. Regarding Ag85B, CD25+ cells were mostly CD4+ instead of CD8+ T cells. Moreover, in response to ferritin, a lower CD25 expression was noted. The present data will allow further characterization of the immune response to new mycobacterial-specific antigens and their evaluation for possible inclusion in developing new diagnostic techniques for tuberculosis as well in a new vaccine to prevent the disease.

Real-time relationship between PKA biochemical signal network dynamics and increased action potential firing rate in heart pacemaker cells: Kinetics of PKA activation in heart pacemaker cells.

Science.gov (United States)

Yaniv, Yael; Ganesan, Ambhighainath; Yang, Dongmei; Ziman, Bruce D; Lyashkov, Alexey E; Levchenko, Andre; Zhang, Jin; Lakatta, Edward G

2015-09-01

cAMP-PKA protein kinase is a key nodal signaling pathway that regulates a wide range of heart pacemaker cell functions. These functions are predicted to be involved in regulation of spontaneous action potential (AP) generation of these cells. Here we investigate if the kinetics and stoichiometry of increase in PKA activity match the increase in AP firing rate in response to β-adrenergic receptor (β-AR) stimulation or phosphodiesterase (PDE) inhibition, that alters the AP firing rate of heart sinoatrial pacemaker cells. In cultured adult rabbit pacemaker cells infected with an adenovirus expressing the FRET sensor AKAR3, the EC50 in response to graded increases in the intensity of β-AR stimulation (by Isoproterenol) the magnitude of the increases in PKA activity and the spontaneous AP firing rate were similar (0.4±0.1nM vs. 0.6±0.15nM, respectively). Moreover, the kinetics (t1/2) of the increases in PKA activity and spontaneous AP firing rate in response to β-AR stimulation or PDE inhibition were tightly linked. We characterized the system rate-limiting biochemical reactions by integrating these experimentally derived data into a mechanistic-computational model. Model simulations predicted that phospholamban phosphorylation is a potent target of the increase in PKA activity that links to increase in spontaneous AP firing rate. In summary, the kinetics and stoichiometry of increases in PKA activity in response to a physiological (β-AR stimulation) or pharmacological (PDE inhibitor) stimuli match those of changes in the AP firing rate. Thus Ca(2+)-cAMP/PKA-dependent phosphorylation limits the rate and magnitude of increase in spontaneous AP firing rate. Copyright © 2015 Elsevier Ltd. All rights reserved.

Investigation of Halohydrins Degradation by Whole Cells and Cell-free Extract of Pseudomonas putida DSM 437: A Kinetic Approach

Directory of Open Access Journals (Sweden)

A. Konti

2017-10-01

Full Text Available The biodegradation of two halohydrins (1,3-dichloro-2-propanol and 3-chloro-1,2-propanediol by P. putida DSM 437 was investigated. Intact cells of previously acclimatized P. putida DSM 437 as well as cell-free extracts were used in order to study the degradation kinetics. When whole cells were used, a maximum biodegradation rate of 3-CPD (vmax = 1.28.10–5 mmol mg–1 DCW h–1 was determined, which was more than 4 times higher than that of 1,3-DCP. However, the affinity towards both halohydrins (Km was practically the same. When using cell-free extract, the apparent vmax and Km values for 1,3-DCP were estimated at 9.61.10–6 mmol mg–1 protein h–1 and 8.00 mM, respectively, while for 3-CPD the corresponding values were 2.42.10–5 mmol mg–1 protein h–1 and 9.07 mM. GC-MS analysis of cell-free extracts samples spiked with 1,3-DCP revealed the presence of 3-CPD and glycerol, intermediates of 1,3-DCP degradation pathway. 3-CPD degradation was strongly inhibited by the presence of epichlorohydrin and to a lesser extent by glycidol, intermediates of dehalogenation pathway.

Internalization kinetics and cytoplasmic localization of functionalized diatomite nanoparticles in cancer cells by Raman imaging.

Science.gov (United States)

Managò, Stefano; Migliaccio, Nunzia; Terracciano, Monica; Napolitano, Michela; Martucci, Nicola M; De Stefano, Luca; Rendina, Ivo; De Luca, Anna Chiara; Lamberti, Annalisa; Rea, Ilaria

2018-04-01

Porous biosilica nanoparticles obtained from diatomites (DNPs) have been recently demonstrated to be non-toxic nanovectors of therapeutic agents in cancer cells. In this work, the internalization kinetics and intracellular spatial distribution of functionalized DNPs incubated with human lung epidermoid carcinoma cell line (H1355) up to 72 hours are investigated by Raman imaging. The label-free Raman results are compared with confocal fluorescence microscopy and photoluminescence (PL) data. Raman bands specifically assigned to DNPs and cellular components provide evidence that the nanovectors are internalized and co-localize with lipid environments. A considerable DNPs uptake in cells is observed within 6 hours, with equilibrium being achieved after 18 hours. The obtained data show the presence of DNPs up to 72 hours, without damage to cell viability or morphology. The PL measurements performed on DNPs not penetrating the cells at different incubation times are strongly correlated with the results obtained by Raman imaging and confocal microscopy analyses. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Genesis and kinetics of peritoneal macrophages

International Nuclear Information System (INIS)

Wacker, H.H.

1982-01-01

The author intended to develop an experimental model for investigations of the proliferation kinetics of tissue macrophages, using the example of peritoneal macrophages. To get a suitable cell population, a blood cell population was labelled with 3 H-thymidine and transferred in a parabiotic test. (orig./MG) [de

Kinetics of Bio-Reactions

DEFF Research Database (Denmark)

Villadsen, John

2015-01-01

his chapter predicts the specific rates of reaction by means of a mathematical expression, the kinetics of the reaction. This expression can be derived through a mechanistic interpretation of an enzymatically catalyzed reaction, but it is essentially of empirical nature for cell reactions. The mo...

A novel study of the kinetics of external hierarchical nanostructures in methanol fuel cell

International Nuclear Information System (INIS)

Al-Halhouli, M; Yurchenko, O; Urban, G; Kieninger, J

2015-01-01

For the purpose of a direct methanol fuel cell (DMFC), this research investigates the kinetics of methanol oxidation in a porous layer consisting of external hierarchical nanostructures through 2D COMSOL simulation. Three different lengths of nanowires (L) were considered in simulations. The investigation showed that specific activity was reversely proportional to nanowires length and roughness factor (Rf). However, the current density increased by increasing Rf. Although the current density in case of L = 200 nm and 500 nm was identical with respect to Rf, there was a slight deviation when L = 1000 nm due to the changing from kinetic to diffusion controlled regime, which was identified by investigation of Thiele modulus. The catalytic efficiency for L = 1000 nm dropped to 50% at Rf = 140, whereas the high efficiency with no mass-transport limitation was achieved by shorter nanowires. Therefore, increasing Rf within the simulation range resulted in increasing the total catalytic activity but simultaneously decreasing the specific activity because of the decrease in pore accessibility and catalytic efficiency of nanostructures. (paper)

Parameters and kinetics of olive mill wastewater dephenolization by immobilized Rhodotorula glutinis cells.

Science.gov (United States)

Bozkoyunlu, Gaye; Takaç, Serpil

2014-01-01

Olive mill wastewater (OMW) with total phenol (TP) concentration range of 300-1200 mg/L was treated with alginate-immobilized Rhodotorula glutinis cells in batch system. The effects of pellet properties (diameter, alginate concentration and cell loading (CL)) and operational parameters (initial TP concentration, agitation rate and reusability of pellets) on dephenolization of OMW were studied. Up to 87% dephenolization was obtained after 120 h biodegradations. The utilization number of pellets increased with the addition of calcium ions into the biodegradation medium. The overall effectiveness factors calculated for different conditions showed that diffusional limitations arising from pellet size and pellet composition could be neglected. Mass transfer limitations appeared to be more effective at high substrate concentrations and low agitation rates. The parameters of logistic model for growth kinetics of R. glutinis in OMW were estimated at different initial phenol concentrations of OMW by curve-fitting of experimental data with the model.

Radiobiology of Cell Renewal Systems

Energy Technology Data Exchange (ETDEWEB)

Patt, H. M. [Laboratory of Radiobiology, University of California Medical Center, San Francisco, CA (United States)

1968-08-15

In recent years, considerable attention has been given to quantitative aspects of radiation effects on cell renewal systems. The behaviour of stem-type cells has been a focal point of interest, and it has been assumed by many that the fraction of surviving stem cells is the principal determinant of the probability of survival of the irradiated system or organism. The apparent close similarity in dose requirements for impairment of reproductive capacity, and the similarity in early repair and in stage sensitivity in vitro and in vivo.clearly indicate that purely cellular phenomena are reflected in the organized population. It does not necessarily follow, however, that there is a straightforward relationship between radiation effects on stem cells and the response of systems or organisms. Indeed, this is not so. It is abundantly clear that differential radiosensitivity is anchored in a number of variables that are associated with the organizational framework of the system and its environment. Many, but not all, effects can be understood in terms of the normal kinetics of the developmental pathway. Yet, deviations from normal kinetics that are minor in the steady state can have profound significance in the perturbed state. To understand the radiobiology of cell renewal systems and to place the many possible variables in reasonable perspective, we need to know a good deal more about the interplay of the component parts than we do at present. When we view the totality of an organized cell population, it seems necessary to postulate mechanisms external to any given cell in the regulation of the balanced sequence of proliferation and differentiation. At present, we have only a vague idea about this. Most attention has been directed to the proliferative process and it is encouraging to note the growing interest in the more developmental facets of cell renewal. (author)

Fast kinetics of the oxygen effe4ct for DNA double-strand breakage and cell killing in irradiated yeast

Energy Technology Data Exchange (ETDEWEB)

Frankenberg, D; Frankenberg-Schwager, M; Harbich, R [Gesellschaft fuer Strahlen- und Umweltforschung mbH, Frankfurt/Main (Germany, F.R.). Inst. fuer Biophysikalische Strahlenforschung; Michael, B D [Mount Vernon Hospital, Northwood (UK). Gray Lab.

1990-03-01

The most important result of dsb kinetic data presented here is that lifetimes of the oxygen-dependent precursors are dose-dependent. This seems mainly to be caused by increased depletion of GSH at high doses. Therefore, shorter lifetimes of the oxygen-dependent precursors of dsb as measured by the inactivation of rad54-3 cells at 36{sup 0}C (t{sub 1/2}=0.25ms), or of stationary haploid GSH{sup +} cells (t{sub 1/2}=0.37 ms) are considered to be more relevant values, especially at low doses than those obtained by direct measurements (t{sub 1/2}=2.18 ms). Rejoining of dsb complicates the kinetics of the oxygen effect as measured at the survival level at the permissive temperature for dsb rejoining. When rejoining of dsb is allowed, besides the fast component a slow component becomes detectable. It is speculated that dsb having such long-living precursors are less readily susceptible for enzymatic rejoining, or are even irreparable. (author).

Fundamentals of 3-D Neutron Kinetics and Current Status

International Nuclear Information System (INIS)

Aragones, J.M.

2008-01-01

This lecture includes the following topics: 1) A summary of the cell and lattice calculations used to generate the neutron reaction data for neutron kinetics, including the spectral and burnup calculations of LWR cells and fuel assembly lattices, and the main nodal kinetics parameters: mean neutron generation time and delayed neutron fraction; 2) the features of the advanced nodal methods for 3-D LWR core physics, including the treatment of partially inserted control rods, fuel assembly grids, fuel burnup and xenon and samarium transients, and excore detector responses, that are essential for core surveillance, axial offset control and operating transient analysis; 3) the advanced nodal methods for 3-D LWR core neutron kinetics (best estimate safety analysis, real-time simulation); and 4) example applications to 3-D neutron kinetics problems in transient analysis of PWR cores, including model, benchmark and operational transients without, or with simple, thermal-hydraulics feedback.

Involvement of Igf1r in Bronchiolar Epithelial Regeneration: Role during Repair Kinetics after Selective Club Cell Ablation.

Directory of Open Access Journals (Sweden)

Icíar P López

Full Text Available Regeneration of lung epithelium is vital for maintaining airway function and integrity. An imbalance between epithelial damage and repair is at the basis of numerous chronic lung diseases such as asthma, COPD, pulmonary fibrosis and lung cancer. IGF (Insulin-like Growth Factors signaling has been associated with most of these respiratory pathologies, although their mechanisms of action in this tissue remain poorly understood. Expression profiles analyses of IGF system genes performed in mouse lung support their functional implication in pulmonary ontogeny. Immuno-localization revealed high expression levels of Igf1r (Insulin-like Growth Factor 1 Receptor in lung epithelial cells, alveolar macrophages and smooth muscle. To further understand the role of Igf1r in pulmonary homeostasis, two distinct lung epithelial-specific Igf1r mutant mice were generated and studied. The lack of Igf1r disturbed airway epithelial differentiation in adult mice, and revealed enhanced proliferation and altered morphology in distal airway club cells. During recovery after naphthalene-induced club cell injury, the kinetics of terminal bronchiolar epithelium regeneration was hindered in Igf1r mutants, revealing increased proliferation and delayed differentiation of club and ciliated cells. Amid airway restoration, lungs of Igf1r deficient mice showed increased levels of Igf1, Insr, Igfbp3 and epithelial precursor markers, reduced amounts of Scgb1a1 protein, and alterations in IGF signaling mediators. These results support the role of Igf1r in controlling the kinetics of cell proliferation and differentiation during pulmonary airway epithelial regeneration after injury.

Modification of structural chromosome mutations by zinc ions at wavelike kinetics of radiation mutagenesis in Crepis Capillaris seed cells

International Nuclear Information System (INIS)

Mustafaev, Kh. B.; Pomanov, V.P.

1979-01-01

The resting seeds Cr. capillaris have been irradiated by gamma rays in the 4 kR dose. Immediately after irradiation and within different terms of storage the seeds have been grown in the 3.5x10 -5 M solution ZnCl 2 and in the distilled water. Chromosome structural mutations in the K-mitosis of the first cell cycle have been studied. The frequency modification of chromosomal rearrangement by zinc ions at the waveline kinetics of the radiation mutagenesis is revealed as follows: zinc ions increase the mutation frequency at the points of waveline kinetics maximum and exert no influence at minimum points

Investigation of resistance switching in SiO x RRAM cells using a 3D multi-scale kinetic Monte Carlo simulator

Science.gov (United States)

Sadi, Toufik; Mehonic, Adnan; Montesi, Luca; Buckwell, Mark; Kenyon, Anthony; Asenov, Asen

2018-02-01

We employ an advanced three-dimensional (3D) electro-thermal simulator to explore the physics and potential of oxide-based resistive random-access memory (RRAM) cells. The physical simulation model has been developed recently, and couples a kinetic Monte Carlo study of electron and ionic transport to the self-heating phenomenon while accounting carefully for the physics of vacancy generation and recombination, and trapping mechanisms. The simulation framework successfully captures resistance switching, including the electroforming, set and reset processes, by modeling the dynamics of conductive filaments in the 3D space. This work focuses on the promising yet less studied RRAM structures based on silicon-rich silica (SiO x ) RRAMs. We explain the intrinsic nature of resistance switching of the SiO x layer, analyze the effect of self-heating on device performance, highlight the role of the initial vacancy distributions acting as precursors for switching, and also stress the importance of using 3D physics-based models to capture accurately the switching processes. The simulation work is backed by experimental studies. The simulator is useful for improving our understanding of the little-known physics of SiO x resistive memory devices, as well as other oxide-based RRAM systems (e.g. transition metal oxide RRAMs), offering design and optimization capabilities with regard to the reliability and variability of memory cells.

Investigation of resistance switching in SiO x RRAM cells using a 3D multi-scale kinetic Monte Carlo simulator.

Science.gov (United States)

Sadi, Toufik; Mehonic, Adnan; Montesi, Luca; Buckwell, Mark; Kenyon, Anthony; Asenov, Asen

2018-02-28

We employ an advanced three-dimensional (3D) electro-thermal simulator to explore the physics and potential of oxide-based resistive random-access memory (RRAM) cells. The physical simulation model has been developed recently, and couples a kinetic Monte Carlo study of electron and ionic transport to the self-heating phenomenon while accounting carefully for the physics of vacancy generation and recombination, and trapping mechanisms. The simulation framework successfully captures resistance switching, including the electroforming, set and reset processes, by modeling the dynamics of conductive filaments in the 3D space. This work focuses on the promising yet less studied RRAM structures based on silicon-rich silica (SiO x ) RRAMs. We explain the intrinsic nature of resistance switching of the SiO x layer, analyze the effect of self-heating on device performance, highlight the role of the initial vacancy distributions acting as precursors for switching, and also stress the importance of using 3D physics-based models to capture accurately the switching processes. The simulation work is backed by experimental studies. The simulator is useful for improving our understanding of the little-known physics of SiO x resistive memory devices, as well as other oxide-based RRAM systems (e.g. transition metal oxide RRAMs), offering design and optimization capabilities with regard to the reliability and variability of memory cells.

A critical look at the kinetic models of thermoluminescence-II. Non-first order kinetics

International Nuclear Information System (INIS)

Sunta, C M; Ayta, W E F; Chubaci, J F D; Watanabe, S

2005-01-01

Non-first order (FO) kinetics models are of three types; second order (SO), general order (GO) and mixed order (MO). It is shown that all three of these have constraints in their energy level schemes and their applicable parameter values. In nature such restrictions are not expected to exist. The thermoluminescence (TL) glow peaks produced by these models shift their position and change their shape as the trap occupancies change. Such characteristics are very unlike those found in samples of real materials. In these models, in general, retrapping predominates over recombination. It is shown that the quasi-equilibrium (QE) assumption implied in the derivation of the TL equation of these models is quite valid, thus disproving earlier workers' conclusion that QE cannot be held under retrapping dominant conditions. However notwithstanding their validity, they suffer from the shortcomings as stated above and have certain lacunae. For example, the kinetic order (KO) parameter and the pre-exponential factor which are assumed to be the constant parameters of the GO kinetics expression turn out to be variables when this expression is applied to plausible physical models. Further, in glow peak characterization using the GO expression, the quality of fit is found to deteriorate when the best fitted value of KO parameter is different from 1 and 2. This means that the found value of the basic parameter, namely the activation energy, becomes subject to error. In the MO kinetics model, the value of the KO parameter α would change with dose, and thus in this model also, as in the GO model, no single value of KO can be assigned to a given glow peak. The paper discusses TL of real materials having characteristics typically like those of FO kinetics. Theoretically too, a plausible physical model of TL emission produces glow peaks which have characteristics of FO kinetics under a wide variety of parametric combinations. In the background of the above findings, it is suggested that

Kinetics of rebounding of lymphoid and myeloid cells in mouse peripheral blood, spleen and bone marrow after treatment with cyclophosphamide

OpenAIRE

Salem, Mohamed L.; Al-Khami, Amir A.; El-Nagaar, Sabry A.; Zidan, Abdel-Aziz A.; Al-Sharkawi, Ismail M.; Díaz-Montero, C. Marcela; Cole, David J.

2012-01-01

Recently, we showed that post cyclophosphamide (CTX) microenvironment benefits the function of transferred T cells. Analysis of the kinetics of cellular recovery after CTX treatment showed that a single 4 mg/mouse CTX treatment decreased the absolute number of leukocytes in the peripheral blood (PBL) at days 3-15, and in the spleen and bone marrow (BM) at days 3-6. The absolute numbers of CD11c+CD11b− and CD11c+CD11b+ dendritic cells (DCs), CD11b+ and Ly6G+ myeloid cells, T and B cells, CD4+C...

Kinetics of the maintenance of the epidermis

Science.gov (United States)

Zhdanov, Vladimir P.; Cho, Nam-Joon

2013-08-01

The epidermis is the outermost layer of skin. It is comprised of keratin-containing cells called keratinocytes. Functionally, the epidermis serves as a physical barrier that can prevent infection and regulate body hydration. Maintenance and repair of the epidermis are important for human health. Mechanistically, these processes occur primarily via proliferation and differentiation of stem cells located in the basal monolayer. These processes are believed to depend on cell-cell communication and spatial constraints but existing kinetic models focus mainly on proliferation and differentiation. To address this issue, we present a mean-field kinetic model that takes these additional factors into account and describes the epidermis at a biosystem level. The corresponding equations operate with the populations of stem cells and differentiated cells in the basal layer. The keratinocytes located above the basal layer are treated at a more coarse-grained level by considering the thickness of the epidermis. The model clarifies the likely role of various negative feedbacks that may control the epidermis and, accordingly, provides insight into the cellular mechanisms underlying complex biological phenomena such as wound healing.

Statistical validity of using ratio variables in human kinetics research.

Science.gov (United States)

Liu, Yuanlong; Schutz, Robert W

2003-09-01

The purposes of this study were to investigate the validity of the simple ratio and three alternative deflation models and examine how the variation of the numerator and denominator variables affects the reliability of a ratio variable. A simple ratio and three alternative deflation models were fitted to four empirical data sets, and common criteria were applied to determine the best model for deflation. Intraclass correlation was used to examine the component effect on the reliability of a ratio variable. The results indicate that the validity, of a deflation model depends on the statistical characteristics of the particular component variables used, and an optimal deflation model for all ratio variables may not exist. Therefore, it is recommended that different models be fitted to each empirical data set to determine the best deflation model. It was found that the reliability of a simple ratio is affected by the coefficients of variation and the within- and between-trial correlations between the numerator and denominator variables. It was recommended that researchers should compute the reliability of the derived ratio scores and not assume that strong reliabilities in the numerator and denominator measures automatically lead to high reliability in the ratio measures.

Smoothing Control of Wind Farm Output by Using Kinetic Energy of Variable Speed Wind Power Generators

Science.gov (United States)

Sato, Daiki; Saitoh, Hiroumi

This paper proposes a new control method for reducing fluctuation of power system frequency through smoothing active power output of wind farm. The proposal is based on the modulation of rotaional kinetic energy of variable speed wind power generators through power converters between permanent magnet synchronous generators (PMSG) and transmission lines. In this paper, the proposed control is called Fluctuation Absorption by Flywheel Characteristics control (FAFC). The FAFC can be easily implemented by adding wind farm output signal to Maximum Power Point Tracking control signal through a feedback control loop. In order to verify the effectiveness of the FAFC control, a simulation study was carried out. In the study, it was assumed that the wind farm consisting of PMSG type wind power generator and induction machine type wind power generaotors is connected with a power sysem. The results of the study show that the FAFC control is a useful method for reducing the impacts of wind farm output fluctuation on system frequency without additional devices such as secondary battery.

Reporting of sex as a variable in cardiovascular studies using cultured cells

Directory of Open Access Journals (Sweden)

Taylor K

2011-11-01

Full Text Available Abstract Background Chromosomal complement, including that provided by the sex chromosomes, influences expression of proteins and molecular signaling in every cell. However, less than 50% of the scientific studies published in 2009 using experimental animals reported sex as a biological variable. Because every cell has a sex, we conducted a literature review to determine the extent to which sex is reported as a variable in cardiovascular studies on cultured cells. Methods Articles from 10 cardiovascular journals with high impact factors (Circulation, J Am Coll Cardiol, Eur Heart J, Circ Res, Arterioscler Thromb Vasc Biol, Cardiovasc Res, J Mol Cell Cardiol, Am J Physiol Heart Circ Physiol, J Heart Lung Transplant and J Cardiovasc Pharmacol and published in 2010 were searched using terms 'cultured' and 'cells' in any order to determine if the sex of those cells was reported. Studies using established cell lines were excluded. Results Using two separate search strategies, we found that only 25 of 90 articles (28% and 20 of 101 articles (19.8% reported the sex of cells. Of those reporting the sex of cells, most (68.9%; n = 31 used only male cells and none used exclusively female cells. In studies reporting the sex of cells of cardiovascular origin, 40% used vascular smooth-muscle cells, and 30% used stem/progenitor cells. In studies using cells of human origin, 35% did not report the sex of those cells. None of the studies using neonatal cardiac myocytes reported the sex of those cells. Conclusions The complement of sex chromosomes in cells studied in culture has the potential to affect expression of proteins and 'mechanistic' signaling pathways. Therefore, consistent with scientific excellence, editorial policies should require reporting sex of cells used in in vitro experiments.

The regrowth kinetic of the surviving population is independent of acute and chronic responses to temozolomide in glioblastoma cell lines

International Nuclear Information System (INIS)

Silva, Andrew Oliveira; Dalsin, Eloisa; Onzi, Giovana Ravizzoni; Filippi-Chiela, Eduardo Cremonese; Lenz, Guido

2016-01-01

Chemotherapy acts on cancer cells by producing multiple effects on a cell population including cell cycle arrest, necrosis, apoptosis and senescence. However, often a subpopulation of cells survives and the behavior of this subpopulation, which is responsible for cancer recurrence, remains obscure. Here we investigated the in vitro short- and long-term responses of six glioblastoma cell lines to clinically relevant doses of temozolomide for 5 days followed by 23 days of recovery, mimicking the standard schedule used in glioblastoma patient for this drug. These cells presented different profiles of sensitivity to temozolomide with varying levels of cell cycle arrest, autophagy and senescence, followed by a regrowth of the surviving cells. The initial reduction in cell number and the subsequent regrowth was analyzed with four new parameters applied to Cumulative Population Doubling (CPD) curves that describe the overall sensitivity of the population and the characteristic of the regrowth: the relative end point CPD (RendCPD); the relative Area Under Curve (rAUC); the Relative Time to Cross a Threshold (RTCT); and the Relative Proliferation Rate (RPR). Surprisingly, the kinetics of regrowth were not predicted by the mechanisms activated after treatment nor by the acute or overall sensitivity. With this study we added new parameters that describe key responses of glioblastoma cell populations to temozolomide treatment. These parameters can also be applied to other cell types and treatments and will help to understand the behavior of the surviving cancer cells after treatment and shed light on studies of cancer resistance and recurrence. - Highlights: • Little is known about the behavior of the glioma cells surviving to TMZ. • The short- and long-term response of six glioma cells lines to TMZ varies considerably. • These glioma cells lines recovered proliferation after therapeutic levels of TMZ. • The growth velocity of the surviving cells was different from the

The regrowth kinetic of the surviving population is independent of acute and chronic responses to temozolomide in glioblastoma cell lines

Energy Technology Data Exchange (ETDEWEB)

Silva, Andrew Oliveira, E-mail: andrewbiomed@gmail.com [Department of Biophysics, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil); Dalsin, Eloisa, E-mail: dalsineloisa@gmail.com [Department of Biophysics, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil); Onzi, Giovana Ravizzoni, E-mail: gioonzi@gmail.com [Department of Biophysics, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil); Center of Biotechnology, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil); Filippi-Chiela, Eduardo Cremonese, E-mail: eduardochiela@gmail.com [Department of Biophysics, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil); Lenz, Guido, E-mail: lenz@ufrgs.br [Department of Biophysics, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil); Center of Biotechnology, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil)

2016-11-01

Chemotherapy acts on cancer cells by producing multiple effects on a cell population including cell cycle arrest, necrosis, apoptosis and senescence. However, often a subpopulation of cells survives and the behavior of this subpopulation, which is responsible for cancer recurrence, remains obscure. Here we investigated the in vitro short- and long-term responses of six glioblastoma cell lines to clinically relevant doses of temozolomide for 5 days followed by 23 days of recovery, mimicking the standard schedule used in glioblastoma patient for this drug. These cells presented different profiles of sensitivity to temozolomide with varying levels of cell cycle arrest, autophagy and senescence, followed by a regrowth of the surviving cells. The initial reduction in cell number and the subsequent regrowth was analyzed with four new parameters applied to Cumulative Population Doubling (CPD) curves that describe the overall sensitivity of the population and the characteristic of the regrowth: the relative end point CPD (RendCPD); the relative Area Under Curve (rAUC); the Relative Time to Cross a Threshold (RTCT); and the Relative Proliferation Rate (RPR). Surprisingly, the kinetics of regrowth were not predicted by the mechanisms activated after treatment nor by the acute or overall sensitivity. With this study we added new parameters that describe key responses of glioblastoma cell populations to temozolomide treatment. These parameters can also be applied to other cell types and treatments and will help to understand the behavior of the surviving cancer cells after treatment and shed light on studies of cancer resistance and recurrence. - Highlights: • Little is known about the behavior of the glioma cells surviving to TMZ. • The short- and long-term response of six glioma cells lines to TMZ varies considerably. • These glioma cells lines recovered proliferation after therapeutic levels of TMZ. • The growth velocity of the surviving cells was different from the

Kinetics of circulating endothelial progenitor cells in patients undergoing carotid artery surgery

Directory of Open Access Journals (Sweden)

Kalender G

2016-12-01

Full Text Available G Kalender,1 A Kornberger,2 M Lisy,1 Andres Beiras-Fernandez,2 UA Stock2 1Deparment of General, Thoracic and Vascular Surgery, Hoechst Hospital, 2Department of Thoracic and Cardiovascular Surgery, University Hospital Frankfurt, Frankfurt am Main, Germany Aim: Endothelial progenitor cells (EPCs are primitive cells found in the bone marrow and peripheral blood (PB. In particular, the potential of EPCs to differentiate into mature endothelial cells remains of high interest for clinical applications such as bio-functionalized patches for autologous seeding after implantation. The objective of this study was to determine EPCs’ kinetics in patients undergoing carotid artery thromboendarterectomy (CTEA and patch angioplasty. Methods: Twenty CTEA patients were included (15 male, mean age 76 years. PB samples were taken at 1 day preoperatively, and at 1, 3, and 5 days postoperatively. Flow cytometric analysis was performed for CD34, CD133, KDR, and CD45. Expression of KDR, SDF-1α, and G-CSF was analyzed by means of enzyme-linked immunosorbent assay. Results: Fluorescence-activated cell sorting analysis revealed 0.031%±0.016% (% of PB mononuclear cells KDR+ cells and 0.052%±0.022% CD45-/CD34+/CD133+ cells, preoperatively. A 33% decrease of CD45–/CD34+/CD133+ cells was observed at day 1 after surgery. However, a relative number (compared to initial preoperative values of CD45-/CD34+/CD133+ cells was found on day 3 (82% and on day 5 (94% postoperatively. More profound upregulated levels of CD45–CD34+/CD133+ cells were observed for diabetic (+47% compared to nondiabetic and male (+38% compared to female patients. No significant postoperative time-dependent differences were found in numbers of KDR+ cells and the concentrations of the cytokines KDR and G-CSF. However, the SDF-1α levels decreased significantly on day 1 postoperatively but returned to preoperative levels by day 3. Conclusion: CTEA results in short-term downregulation of circulating

Effect of chamber characteristics, loading and analysis time on motility and kinetic variables analysed with the CASA-mot system in goat sperm.

Science.gov (United States)

Del Gallego, R; Sadeghi, S; Blasco, E; Soler, C; Yániz, J L; Silvestre, M A

2017-02-01

Several factors unrelated to the semen samples could be influencing in the sperm motility analysis. The aim of the present research was to study the effect of four chambers with different characteristics, namely; slide-coverslip, Spermtrack, ISAS D4C10, and ISAS D4C20 on the sperm motility. The filling procedure (drop or capillarity) and analysis time (0, 120 and 240s), depth of chamber (10 or 20μm) and field on motility variables were analysed by use of the CASA-mot system in goat sperm. Use of the drop-filling chambers resulted in greater values than capillarity-filling chambers for all sperm motility and kinetic variables, except for LIN (64.5% compared with 56.3% of motility for drop- and capillarity-filling chambers respectively, PCASA-mot system with a drop-loaded chamber within 2min after filling the chamber. Copyright © 2016 Elsevier B.V. All rights reserved.

A Cs-137 afterloading device. Preliminary results of cell kinetic effects of low dose-rate irradiation in an experimental tumour

International Nuclear Information System (INIS)

Rutgers, D.H.

1988-01-01

A Cs-137 afterloading technique is described which can be used in experimental tumours. Preliminary results, obtained with the human cervical carcinoma ME-180 xenografted to nude athymic mice, demonstrated that 20 Gy of low dose-rate irradiation induced an important redistribution of cells over cell cycle. The proportion of cells in G2-phase increased from 14.4% to 44.2% at 140 hours after irradiation. This method allows an accurate calculation of the dose-rate distribution in the tumour. Investigations of the cell kinetic effects of low dose-rate irradiation, at different dose-rates and different total doses, are therefore facilitated by the technique. (orig.) [de

[Upper extremity kinetics and energy expenditure during walker-assisted gait in children with cerebral palsy].

Science.gov (United States)

Konop, Katherine A; Strifling, Kelly M B; Wang, Mei; Cao, Kevin; Eastwood, Daniel; Jackson, Scott; Ackman, Jeffrey; Altiok, Haluk; Schwab, Jeffrey; Harris, Gerald F

2009-01-01

We evaluated the relationships between upper extremity (UE) kinetics and the energy expenditure index during anterior and posterior walker-assisted gait in children with spastic diplegic cerebral palsy (CP). Ten children (3 boys, 7 girls; mean age 12.1 years; range 8 to 18 years) with spastic diplegic CP, who ambulated with a walker underwent gait analyses that included UE kinematics and kinetics. Upper extremity kinetics were obtained using instrumented walker handles. Energy expenditure index was obtained using the heart rate method (EEIHR) by subtracting resting heart rate from walking heart rate, and dividing by the walking speed. Correlations were sought between the kinetic variables and the EEIHR and temporal and stride parameters. In general, anterior walker use was associated with a higher EEIHR. Several kinetic variables correlated well with temporal and stride parameters, as well as the EEIHR. All of the significant correlations (r>0.80; pwalker use and involved joint reaction forces (JRF) rather than moments. Some variables showed multiple strong correlations during anterior walker use, including the medial JRF in the wrist, the posterior JRF in the elbow, and the inferior and superior JRFs in the shoulder. The observed correlations may indicate a relationship between the force used to advance the body forward within the walker frame and an increased EEIHR. More work is needed to refine the correlations, and to explore relationships with other variables, including the joint kinematics.

Coupling Chemical Kinetics and Flashes in Reactive, Thermal and Compositional Reservoir Simulation

DEFF Research Database (Denmark)

Kristensen, Morten Rode; Gerritsen, Margot G.; Thomsen, Per Grove

2007-01-01

of convergence and error test failures by more than 50% compared to direct integration without the new algorithm. To facilitate the algorithmic development we construct a virtual kinetic cell model. We use implicit one-step ESDIRK (Explicit Singly Diagonal Implicit Runge-Kutta) methods for integration...... of the kinetics. The kinetic cell model serves both as a tool for the development and testing of tailored solvers as well as a testbed for studying the interactions between chemical kinetics and phase behavior. A comparison between a Kvalue correlation based approach and a more rigorous equation of state based......Phase changes are known to cause convergence problems for integration of stiff kinetics in thermal and compositional reservoir simulations. We propose an algorithm for detection and location of phase changes based on discrete event system theory. The algorithm provides a robust way for handling...

Fundamental studies of leukemic cell labeling with 111 In-oxine and their applications to cell kinetics in patients with acute leukemia

International Nuclear Information System (INIS)

Takagi, Yuhkoh; Matsuda, Shin; Uchida, Tatsumi; Kariyone, Shigeo

1984-01-01

Fundamental studies of leukemic cell labeling with 111 In-oxine and their applications to leukemic cell kinetics in five patients with acute myeloblastic leukemia (AML) were examined. Labeling efficiency of leukemic cells was 80.3 +- 3.6% for more than 1 x 10 8 cells at room temperature for 20 minutes of incubation followed by two times washes. Cell viability determined by means of trypanblue exclusion test was 95.3 +- 2.6%. In vitro elution rate of 111 In from the labeled cells during 12 hours was 10.0 +- 1.2%. The disappearance curves of labeled leukemic cells in AMLs followed a single exponential fashion, and the half time of disappearance (T 1/2) ranged from 9.6 to 31.8 hours. Total blood leukemic cell pool (TBLCP) calculated with the dilution principles of radioisotopes correlated significantly with the leukemic cell counts (LC) in the peripheral blood (Y = 0.32 + 1.94X, r = 0.99). In the studies of organ distribution which were observed and analized with gamma camera and computer, labeled leukemic cells passed through lungs within 15 minutes. Radioactivity in the spleen increased rapidly for 30 - 60 minutes, then reached a plateau. Hepatic radioactivity showed a temporary decrease during 10 - 60 minutes following the moderate accumulation in initial 10 minutes. In two cases, bone marrow was visualized 24 hours after the injection. Radioactivity of the leukemic cells isolated from the bone marrow at 22 hours after the injection in one case was one third of the radioactivity in leukemic cells obtained from the peripheral blood at the same time. (author)

Double labeling autoradiography. Cell kinetic studies with 3H- and 14C-thymidine

International Nuclear Information System (INIS)

Schultze, B.

1981-01-01

Examples of the multiple applicability of the double labeling method with 3 H- and 14 C-TdR are demonstrated. Double labeling with 3 H- and 14 C-TdR makes it possible to determine the cycle and its phases with high precision by modifying the usual percent labeled mitoses method with a single injection of 3 H-TdR. In addition, data is provided on the variances of the transit times through the cycle phases. For example, in the case of the jejunal crypt cells of the mouse, the transit times through successive cycle phases are uncorrelated. In the case of glial cells the double labeling method provides cell kinetic parameters despite the paucity of proliferating glial cells. In the adult untreated animal, glial cell mitoses are so rare that the percent labeled mitoses method can not be utilized. However, the S-phase duration can be measured by double labeling and the cycle time can be determined by the so-called method of labeled S phases. With the latter method the passage through the S phase of the 3 H-TdR-labeled S phase cells can be registered by injecting 14 C-TdR at different time intervals following 3 H-TdR application. In this way an S-phase duration of about 10 hr and a cycle time of about 20 hr was found for glial cells in the adult untreated mouse. An exchange of glial cells between the growth fraction and the nongrowth fraction has also been shown by double labeling. A quite different application of the double labeling method with 3H- and 14 C-TdR is the in vivo study of the cell cycle phase-specific effect of drugs used in chemotherapy of tumors. The effect of vincristine on these cells has been studied. Vincristine affects cells in S and G2 in such a manner that they are arrested during the next metaphase and subsequently become necrotic. It has no effect on G1 cells

Variability in cell response of Cronobacter sakazakii after mild-heat treatments and its impact on food safety

Directory of Open Access Journals (Sweden)

Julio eParra-Flores

2016-04-01

Full Text Available Cronobacter spp. have been responsible for severe infections in infants associated with consumption of powdered infant formula (PIF and follow-up formulae (FUF. Despite several risk assessments described in published studies, few approaches have considered the tremendous variability in cell response that small micropopulations or single cells can have in infant formula during storage, preparation or post process/preparation before the feeding of infants. Stochastic approaches can better describe microbial single cell response than deterministic models as we prove in this study. A large variability of lag phase was observed in single cell and micropopulations of ≤50 cells. This variability increased as the heat shock increased and growth temperature decreased. Obviously, variability of growth of individual Cronobacter sakazakii cell is affected by inoculum size, growth temperature and the probability of cells able to grow at the conditions imposed by the experimental conditions should be taken into account, especially when errors in bottle-preparation practices, such as improper holding temperatures or manipulation, may lead to growth of the pathogen to a critical cell level. The mean probability of illness from initial inoculum size of 1 cell were below 0.2 in all the cases and for inoculum size of 50 cells the mean probability of illness were, in most of the cases, was above 0.7.

Kinetics of particle deposition at heterogeneous surfaces

Science.gov (United States)

Stojiljković, D. Lj.; Vrhovac, S. B.

2017-12-01

The random sequential adsorption (RSA) approach is used to analyze adsorption of spherical particles of fixed diameter d0 on nonuniform surfaces covered by square cells arranged in a square lattice pattern. To characterize such pattern two dimensionless parameters are used: the cell size α and the cell-cell separation β, measured in terms of the particle diameter d0. Adsorption is assumed to occur if the particle (projected) center lies within a cell area. We focus on the kinetics of deposition process in the case when no more than a single disk can be placed onto any square cell (α deposition process is not consistent with the power law behavior. However, if the geometry of the pattern approaches towards ;noninteracting conditions; (β > 1), when adsorption on each cell can be decoupled, approach of the coverage fraction θ(t) to θJ becomes closer to the exponential law. Consequently, changing the pattern parameters in the present model allows to interpolate the deposition kinetics between the continuum limit and the lattice-like behavior. Structural properties of the jammed-state coverings are studied in terms of the radial distribution function g(r) and spatial distribution of particles inside the cell. Various, non-trivial spatial distributions are observed depending on the geometry of the pattern.

Examining the sources of variability in cell culture media used for biopharmaceutical production.

Science.gov (United States)

McGillicuddy, Nicola; Floris, Patrick; Albrecht, Simone; Bones, Jonathan

2018-01-01

Raw materials, in particular cell culture media, represent a significant source of variability to biopharmaceutical manufacturing processes that can detrimentally affect cellular growth, viability and specific productivity or alter the quality profile of the expressed therapeutic protein. The continual expansion of the biopharmaceutical industry is creating an increasing demand on the production and supply chain consistency for cell culture media, especially as companies embrace intensive continuous processing. Here, we provide a historical perspective regarding the transition from serum containing to serum-free media, the development of chemically-defined cell culture media for biopharmaceutical production using industrial scale bioprocesses and review production mechanisms for liquid and powder culture media. An overview and critique of analytical approaches used for the characterisation of cell culture media and the identification of root causes of variability are also provided, including in-depth liquid phase separations, mass spectrometry and spectroscopic methods.

Enhancing charge transfer kinetics by nanoscale catalytic cermet interlayer.

Science.gov (United States)

An, Jihwan; Kim, Young-Beom; Gür, Turgut M; Prinz, Fritz B

2012-12-01

Enhancing the density of catalytic sites is crucial for improving the performance of energy conversion devices. This work demonstrates the kinetic role of 2 nm thin YSZ/Pt cermet layers on enhancing the oxygen reduction kinetics for low temperature solid oxide fuel cells. Cermet layers were deposited between the porous Pt cathode and the dense YSZ electrolyte wafer using atomic layer deposition (ALD). Not only the catalytic role of the cermet layer itself but the mixing effect in the cermet was explored. For cells with unmixed and fully mixed cermet interlayers, the maximum power density was enhanced by a factor of 1.5 and 1.8 at 400 °C, and by 2.3 and 2.7 at 450 °C, respectively, when compared to control cells with no cermet interlayer. The observed enhancement in cell performance is believed to be due to the increased triple phase boundary (TPB) density in the cermet interlayer. We also believe that the sustained kinetics for the fully mixed cermet layer sample stems from better thermal stability of Pt islands separated by the ALD YSZ matrix, which helped to maintain the high-density TPBs even at elevated temperature.

Influence of Body Composition on Gait Kinetics throughout Pregnancy and Postpartum Period

Science.gov (United States)

Branco, Marco; Santos-Rocha, Rita; Vieira, Filomena; Silva, Maria-Raquel; Aguiar, Liliana; Veloso, António P.

2016-01-01

Pregnancy leads to several changes in body composition and morphology of women. It is not clear whether the biomechanical changes occurring in this period are due exclusively to body composition and size or to other physiological factors. The purpose was to quantify the morphology and body composition of women throughout pregnancy and in the postpartum period and identify the contribution of these parameters on the lower limb joints kinetic during gait. Eleven women were assessed longitudinally, regarding anthropometric, body composition, and kinetic parameters of gait. Body composition and body dimensions showed a significant increase during pregnancy and a decrease in the postpartum period. In the postpartum period, body composition was similar to the 1st trimester, except for triceps skinfold, total calf area, and body mass index, with higher results than at the beginning of pregnancy. Regression models were developed to predict women's internal loading through anthropometric variables. Four models include variables associated with the amount of fat; four models include variables related to overall body weight; three models include fat-free mass; one model includes the shape of the trunk as a predictor variable. Changes in maternal body composition and morphology largely determine kinetic dynamics of the joints in pregnant women. PMID:27073713

The gait standard deviation, a single measure of kinematic variability.

Science.gov (United States)

Sangeux, Morgan; Passmore, Elyse; Graham, H Kerr; Tirosh, Oren

2016-05-01

Measurement of gait kinematic variability provides relevant clinical information in certain conditions affecting the neuromotor control of movement. In this article, we present a measure of overall gait kinematic variability, GaitSD, based on combination of waveforms' standard deviation. The waveform standard deviation is the common numerator in established indices of variability such as Kadaba's coefficient of multiple correlation or Winter's waveform coefficient of variation. Gait data were collected on typically developing children aged 6-17 years. Large number of strides was captured for each child, average 45 (SD: 11) for kinematics and 19 (SD: 5) for kinetics. We used a bootstrap procedure to determine the precision of GaitSD as a function of the number of strides processed. We compared the within-subject, stride-to-stride, variability with the, between-subject, variability of the normative pattern. Finally, we investigated the correlation between age and gait kinematic, kinetic and spatio-temporal variability. In typically developing children, the relative precision of GaitSD was 10% as soon as 6 strides were captured. As a comparison, spatio-temporal parameters required 30 strides to reach the same relative precision. The ratio stride-to-stride divided by normative pattern variability was smaller in kinematic variables (the smallest for pelvic tilt, 28%) than in kinetic and spatio-temporal variables (the largest for normalised stride length, 95%). GaitSD had a strong, negative correlation with age. We show that gait consistency may stabilise only at, or after, skeletal maturity. Copyright © 2016 Elsevier B.V. All rights reserved.

Gyrocenter-gauge kinetic theory

International Nuclear Information System (INIS)

Qin, H.; Tang, W.M.; Lee, W.W.

2000-01-01

Gyrocenter-gauge kinetic theory is developed as an extension of the existing gyrokinetic theories. In essence, the formalism introduced here is a kinetic description of magnetized plasmas in the gyrocenter coordinates which is fully equivalent to the Vlasov-Maxwell system in the particle coordinates. In particular, provided the gyroradius is smaller than the scale-length of the magnetic field, it can treat high frequency range as well as the usual low frequency range normally associated with gyrokinetic approaches. A significant advantage of this formalism is that it enables the direct particle-in-cell simulations of compressional Alfven waves for MHD applications and of RF waves relevant to plasma heating in space and laboratory plasmas. The gyrocenter-gauge kinetic susceptibility for arbitrary wavelength and arbitrary frequency electromagnetic perturbations in a homogeneous magnetized plasma is shown to recover exactly the classical result obtained by integrating the Vlasov-Maxwell system in the particle coordinates. This demonstrates that all the waves supported by the Vlasov-Maxwell system can be studied using the gyrocenter-gauge kinetic model in the gyrocenter coordinates. This theoretical approach is so named to distinguish it from the existing gyrokinetic theory, which has been successfully developed and applied to many important low-frequency and long parallel wavelength problems, where the conventional meaning of gyrokinetic has been standardized. Besides the usual gyrokinetic distribution function, the gyrocenter-gauge kinetic theory emphasizes as well the gyrocenter-gauge distribution function, which sometimes contains all the physics of the problems being studied, and whose importance has not been realized previously. The gyrocenter-gauge distribution function enters Maxwell's equations through the pull-back transformation of the gyrocenter transformation, which depends on the perturbed fields. The efficacy of the gyrocenter-gauge kinetic approach is

Mechanistic and kinetic aspects of microbial inactivation in food irradiation processes

International Nuclear Information System (INIS)

Tukenmez, I.

2004-01-01

Full text: A proper reaction mechanism was searched by analyzing the inactivation processes of microorganisms during food irradiation by ionizing radiation. By employing transition-state theory, it was assumed that the overall inactivation process involves a reversible sub-lethal stress and repair reactions to form reversibly injured cell or sensitized cell, which then undergoes irreversible injury leading to dead cell. A shoulder in low dose range in survival kinetics was associated with the repair process. Depending on the postulated mechanism, kinetic model equations were derived. The kinetics of cell inactivation by irradiation was expressed as depending on irradiation dose. By using experimental data in the developed model the inactivation parameters including threshold dose, radiation yield, decimal reduction dose and minimum sterilization dose were evaluated and microbial inactivation by irradiation was simulated by using the numerical values of the parameters. Developed model and model parameters may be used for the process control and the assessment of product quality in radiation preservation of food

Semi-local machine-learned kinetic energy density functional with third-order gradients of electron density

Science.gov (United States)

Seino, Junji; Kageyama, Ryo; Fujinami, Mikito; Ikabata, Yasuhiro; Nakai, Hiromi

2018-06-01

A semi-local kinetic energy density functional (KEDF) was constructed based on machine learning (ML). The present scheme adopts electron densities and their gradients up to third-order as the explanatory variables for ML and the Kohn-Sham (KS) kinetic energy density as the response variable in atoms and molecules. Numerical assessments of the present scheme were performed in atomic and molecular systems, including first- and second-period elements. The results of 37 conventional KEDFs with explicit formulae were also compared with those of the ML KEDF with an implicit formula. The inclusion of the higher order gradients reduces the deviation of the total kinetic energies from the KS calculations in a stepwise manner. Furthermore, our scheme with the third-order gradient resulted in the closest kinetic energies to the KS calculations out of the presented functionals.

Read margin analysis of crossbar arrays using the cell-variability-aware simulation method

Science.gov (United States)

Sun, Wookyung; Choi, Sujin; Shin, Hyungsoon

2018-02-01

This paper proposes a new concept of read margin analysis of crossbar arrays using cell-variability-aware simulation. The size of the crossbar array should be considered to predict the read margin characteristic of the crossbar array because the read margin depends on the number of word lines and bit lines. However, an excessively high-CPU time is required to simulate large arrays using a commercial circuit simulator. A variability-aware MATLAB simulator that considers independent variability sources is developed to analyze the characteristics of the read margin according to the array size. The developed MATLAB simulator provides an effective method for reducing the simulation time while maintaining the accuracy of the read margin estimation in the crossbar array. The simulation is also highly efficient in analyzing the characteristic of the crossbar memory array considering the statistical variations in the cell characteristics.

Antibody Fc engineering improves frequency and promotes kinetic boosting of serial killing mediated by NK cells

Science.gov (United States)

Romain, Gabrielle; Senyukov, Vladimir; Rey-Villamizar, Nicolas; Merouane, Amine; Kelton, William; Liadi, Ivan; Mahendra, Ankit; Charab, Wissam; Georgiou, George; Roysam, Badrinath; Lee, Dean A.

2014-01-01

The efficacy of most therapeutic monoclonal antibodies (mAbs) targeting tumor antigens results primarily from their ability to elicit potent cytotoxicity through effector-mediated functions. We have engineered the fragment crystallizable (Fc) region of the immunoglobulin G (IgG) mAb, HuM195, targeting the leukemic antigen CD33, by introducing the triple mutation Ser293Asp/Ala330Leu/Ile332Glu (DLE), and developed Time-lapse Imaging Microscopy in Nanowell Grids to analyze antibody-dependent cell-mediated cytotoxicity kinetics of thousands of individual natural killer (NK) cells and mAb-coated target cells. We demonstrate that the DLE-HuM195 antibody increases both the quality and the quantity of NK cell-mediated antibody-dependent cytotoxicity by endowing more NK cells to participate in cytotoxicity via accrued CD16-mediated signaling and by increasing serial killing of target cells. NK cells encountering targets coated with DLE-HuM195 induce rapid target cell apoptosis by promoting simultaneous conjugates to multiple target cells and induce apoptosis in twice the number of target cells within the same period as the wild-type mAb. Enhanced target killing was also associated with increased frequency of NK cells undergoing apoptosis, but this effect was donor-dependent. Antibody-based therapies targeting tumor antigens will benefit from a better understanding of cell-mediated tumor elimination, and our work opens further opportunities for the therapeutic targeting of CD33 in the treatment of acute myeloid leukemia. PMID:25232058

Reactor kinetics revisited: a coefficient based model (CBM)

International Nuclear Information System (INIS)

Ratemi, W.M.

2011-01-01

In this paper, a nuclear reactor kinetics model based on Guelph expansion coefficients calculation ( Coefficients Based Model, CBM), for n groups of delayed neutrons is developed. The accompanying characteristic equation is a polynomial form of the Inhour equation with the same coefficients of the CBM- kinetics model. Those coefficients depend on Universal abc- values which are dependent on the type of the fuel fueling a nuclear reactor. Furthermore, such coefficients are linearly dependent on the inserted reactivity. In this paper, the Universal abc- values have been presented symbolically, for the first time, as well as with their numerical values for U-235 fueled reactors for one, two, three, and six groups of delayed neutrons. Simulation studies for constant and variable reactivity insertions are made for the CBM kinetics model, and a comparison of results, with numerical solutions of classical kinetics models for one, two, three, and six groups of delayed neutrons are presented. The results show good agreements, especially for single step insertion of reactivity, with the advantage of the CBM- solution of not encountering the stiffness problem accompanying the numerical solutions of the classical kinetics model. (author)

Sensitivity analysis of intracellular signaling pathway kinetics predicts targets for stem cell fate control.

Directory of Open Access Journals (Sweden)

Alborz Mahdavi

2007-07-01

Full Text Available Directing stem cell fate requires knowledge of how signaling networks integrate temporally and spatially segregated stimuli. We developed and validated a computational model of signal transducer and activator of transcription-3 (Stat3 pathway kinetics, a signaling network involved in embryonic stem cell (ESC self-renewal. Our analysis identified novel pathway responses; for example, overexpression of the receptor glycoprotein-130 results in reduced pathway activation and increased ESC differentiation. We used a systematic in silico screen to identify novel targets and protein interactions involved in Stat3 activation. Our analysis demonstrates that signaling activation and desensitization (the inability to respond to ligand restimulation is regulated by balancing the activation state of a distributed set of parameters including nuclear export of Stat3, nuclear phosphatase activity, inhibition by suppressor of cytokine signaling, and receptor trafficking. This knowledge was used to devise a temporally modulated ligand delivery strategy that maximizes signaling activation and leads to enhanced ESC self-renewal.

Transient competitive complexation in biological kinetic isotope fractionation explains nonsteady isotopic effects: Theory and application to denitrification in soils

Science.gov (United States)

Maggi, Federico; Riley, William J.

2009-12-01

The theoretical formulation of biological kinetic isotope fractionation often assumes first-order or Michaelis-Menten kinetics, the latter solved under the quasi-steady state assumption. Both formulations lead to a constant isotope fractionation factor, therefore they may return incorrect estimations of isotopic effects and misleading interpretations of isotopic signatures when fractionation is not a steady process. We have analyzed the isotopic signature of denitrification in biogeochemical soil systems by Menyailo and Hungate (2006) in which high and variable 15N-N2O enrichment during N2O production and inverse isotope fractionation during N2O consumption could not be explained with first-order kinetics and the Rayleigh equation, or with Michaelis-Menten kinetics. When Michaelis-Menten kinetics were coupled to Monod kinetics to describe biomass and enzyme dynamics, and the quasi-steady state assumption was relaxed, transient Michaelis-Menten-Monod kinetics accurately reproduced the observed concentrations, and variable and inverse isotope fractionations. These results imply a substantial revision in modeling isotopic effects, suggesting that steady state kinetics such as first-order, Rayleigh, and classic Michaelis-Menten kinetics should be superseded by transient kinetics in conjunction with biomass and enzyme dynamics.

Kinetics and dynamics of cyclosporine A in three hepatic cell culture systems

NARCIS (Netherlands)

Bellwon, P; Truisi, G L; Bois, Frederic Y; Wilmes, A; Schmidt, T.; Savary, C C; Parmentier, C.C.; Hewitt, P.G.; Schmal, O; Josse, R.; Richert, L.; Guillouzo, A; Mueller, S O; Jennings, P; Testai, E; Dekant, W.

2015-01-01

In vitro experiments have a high potential to improve current chemical safety assessment and reduce the number of animals used. However, most studies conduct hazard assessment alone, largely ignoring exposure and kinetic parameters. Therefore, in this study the kinetics of cyclosporine A (CsA) and

Kinetic and mass transfer studies on the isomerization of cellulose hydrolyzate using immobilized Streptomyces cells

Energy Technology Data Exchange (ETDEWEB)

Ghose, T K; Chand, S

1978-01-01

Streptomyces cells possessing glucose isomerase activity, heat-treated and confined within polyester sacs have been used in batch/continuous isomerization of enzymatically hydrolyzed microcrystalline cellulose. Conversion data at different concentrations of substrate closely follow the reactor performance equation based on the reaction kinetics. The effect of external film and pore diffusional resistances were experimentally found to be negligible. The dispersion effects in the packed bed column have been evaluated by pulse input tracer analysis. Continuous operation of the column to isomerize cellulose hydrolyzate (2.0 M glucose) showed an exponential deactivation of enzyme activity with a half-life of 447 h.

From in vitro to in vivo: Integration of the virtual cell based assay with physiologically based kinetic modelling.

Science.gov (United States)

Paini, Alicia; Sala Benito, Jose Vicente; Bessems, Jos; Worth, Andrew P

2017-12-01

Physiologically based kinetic (PBK) models and the virtual cell based assay can be linked to form so called physiologically based dynamic (PBD) models. This study illustrates the development and application of a PBK model for prediction of estragole-induced DNA adduct formation and hepatotoxicity in humans. To address the hepatotoxicity, HepaRG cells were used as a surrogate for liver cells, with cell viability being used as the in vitro toxicological endpoint. Information on DNA adduct formation was taken from the literature. Since estragole induced cell damage is not directly caused by the parent compound, but by a reactive metabolite, information on the metabolic pathway was incorporated into the model. In addition, a user-friendly tool was developed by implementing the PBK/D model into a KNIME workflow. This workflow can be used to perform in vitro to in vivo extrapolation and forward as backward dosimetry in support of chemical risk assessment. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Kinetic quantification of plyometric exercise intensity.

Science.gov (United States)

Ebben, William P; Fauth, McKenzie L; Garceau, Luke R; Petushek, Erich J

2011-12-01

Ebben, WP, Fauth, ML, Garceau, LR, and Petushek, EJ. Kinetic quantification of plyometric exercise intensity. J Strength Cond Res 25(12): 3288-3298, 2011-Quantification of plyometric exercise intensity is necessary to understand the characteristics of these exercises and the proper progression of this mode of exercise. The purpose of this study was to assess the kinetic characteristics of a variety of plyometric exercises. This study also sought to assess gender differences in these variables. Twenty-six men and 23 women with previous experience in performing plyometric training served as subjects. The subjects performed a variety of plyometric exercises including line hops, 15.24-cm cone hops, squat jumps, tuck jumps, countermovement jumps (CMJs), loaded CMJs equal to 30% of 1 repetition maximum squat, depth jumps normalized to the subject's jump height (JH), and single leg jumps. All plyometric exercises were assessed with a force platform. Outcome variables associated with the takeoff, airborne, and landing phase of each plyometric exercise were evaluated. These variables included the peak vertical ground reaction force (GRF) during takeoff, the time to takeoff, flight time, JH, peak power, landing rate of force development, and peak vertical GRF during landing. A 2-way mixed analysis of variance with repeated measures for plyometric exercise type demonstrated main effects for exercise type and all outcome variables (p ≤ 0.05) and for the interaction between gender and peak vertical GRF during takeoff (p ≤ 0.05). Bonferroni-adjusted pairwise comparisons identified a number of differences between the plyometric exercises for the outcome variables assessed (p ≤ 0.05). These findings can be used to guide the progression of plyometric training by incorporating exercises of increasing intensity over the course of a program.

Interplay of bistable kinetics of gene expression during cellular growth

International Nuclear Information System (INIS)

Zhdanov, Vladimir P

2009-01-01

In cells, the bistable kinetics of gene expression can be observed on the level of (i) one gene with positive feedback between protein and mRNA production, (ii) two genes with negative mutual feedback between protein and mRNA production, or (iii) in more complex cases. We analyse the interplay of two genes of type (ii) governed by a gene of type (i) during cellular growth. In particular, using kinetic Monte Carlo simulations, we show that in the case where gene 1, operating in the bistable regime, regulates mutually inhibiting genes 2 and 3, also operating in the bistable regime, the latter genes may eventually be trapped either to the state with high transcriptional activity of gene 2 and low activity of gene 3 or to the state with high transcriptional activity of gene 3 and low activity of gene 2. The probability to get to one of these states depends on the values of the model parameters. If genes 2 and 3 are kinetically equivalent, the probability is equal to 0.5. Thus, our model illustrates how different intracellular states can be chosen at random with predetermined probabilities. This type of kinetics of gene expression may be behind complex processes occurring in cells, e.g., behind the choice of the fate by stem cells

A kinetic approach to some quasi-linear laws of macroeconomics

Science.gov (United States)

Gligor, M.; Ignat, M.

2002-11-01

Some previous works have presented the data on wealth and income distributions in developed countries and have found that the great majority of population is described by an exponential distribution, which results in idea that the kinetic approach could be adequate to describe this empirical evidence. The aim of our paper is to extend this framework by developing a systematic kinetic approach of the socio-economic systems and to explain how linear laws, modelling correlations between macroeconomic variables, may arise in this context. Firstly we construct the Boltzmann kinetic equation for an idealised system composed by many individuals (workers, officers, business men, etc.), each of them getting a certain income and spending money for their needs. To each individual a certain time variable amount of money is associated this meaning him/her phase space coordinate. In this way the exponential distribution of money in a closed economy is explicitly found. The extension of this result, including states near the equilibrium, give us the possibility to take into account the regular increase of the total amount of money, according to the modern economic theories. The Kubo-Green-Onsager linear response theory leads us to a set of linear equations between some macroeconomic variables. Finally, the validity of such laws is discussed in relation with the time reversal symmetry and is tested empirically using some macroeconomic time series.

Murine scid cells complement ataxia-telangiectasia cells and show a normal port-irradiation response of DNA synthesis

International Nuclear Information System (INIS)

Komatsu, K.; Yoshida, M.; Okumura, Y.

1993-01-01

The murine severe combined immunodeficient mutation (scid) is characterized by a lack of both B and T cells, due to a deficit in lymphoid variable-(diversity)-joining (V(D)J) rearrangement. Scid cells are highly sensitive to both radiation-induced killing and chromosomal aberrations. Significantly reduced D 0 and n values were demonstrated in scid cells and were similar to ataxia-telangiectasia (AT) cells (a unique human disease conferring whole body radiosensitivity). However, the kinetics of DNA synthesis after irradiation were different between the two cell types. In contrast with the radioresistant DNA synthesis of AT cells, DNA synthesis of scid cells was markedly inhibited after irradiation. The existence of different mutations was also supported by evidence of complementation in somatic cell hybrids between scid cells and AT cells. Results indicate that the radiobiological character of scid is similar to AT but is presumably caused by different mechanisms. (author)

Effect of various 3H-thymidine concentrations on the kinetics of chinese hamster cell division

International Nuclear Information System (INIS)

Yuzhakov, V.V.; Lychev, V.A.

1985-01-01

A study of the asynchronous culture of Chinese hamster fibroblasts by autoradiography has shown that the pulse (15 min) incorporation of 3 H-thymidine in nuclear DNA influences the kinetics of labelled cell proliferation. The results obtained suggest that one of the early biological effects of the pulse incorporation of 3 H-thymidine is a delay in the occurrence of the first mitosis. With the concentration of 3 H-thymidine 37 kBq/ml the slowing down of the movement of labelled cells in the cycle is detected by a shift and overlapping of waves of labelled and unlabelled mitotic cells. In an increase of the concentration up to 370-925 kBq/ml the pattern of the curves of labelled mitotic cells is distorted. These distortions are well interpreted by the nature of change of the index of labelled and unlabelled mitotic cells. After an increase in 3 H-thymidine concentration from 37 up to 370-925 kBq/ml the mitotic activity of cells labelled at the end of S-phase decreases from 1 to o0.6-0.1% respectively. With the concentration of 925 kBq/ml for these cells incorporating 3 H-thymidine at the end of S-phase, a delay of the entry into mitosis reaches 6-8 h. Autoradiography data with assessment of granule density suggest that mitotic activity and the period of delay in the occurrence of mitosis depend on the dose of irradiation with intranuclear tritium

Studies on the effects of ionizing radiation and chemotherapeutic agents on hematopoiesis according to the stem-cell kinetics

International Nuclear Information System (INIS)

Hirashima, Kunitake

1975-01-01

The fundamental problem of the effects of ionizing radiation and antineoplastic drugs on hematopoiesis can be explained by the kinetic study on the hematopoietic stem-cell population. Quantitative comparison of a single x-irradiation and a single administration of several antineoplastic drugs on the stem-cell population was performed by the splenic colony-forming method. The repopulation pattern of stem-cells in mice after a single 150 rad irradiation was compared with that after the administration of corresponding dose of cyclophosphamide. It was demonstrated that the additional administration of cyclophosphamide immediately after the x-irradiation significantly accelerated repopulation of the stem-cell compartment. The mechanism of repopulation of the stem-cell compartment after partial irradiation was also studied according to the immigration theory of stem-cells. An in vitro colony-forming technique for the human bone marrow cells was introduced and compared with other assay methods for stem-cells. From the hematological observations of accidentally irradiated patients, it was determined that the thromboelastogram values were regarded as one of the most useful indicators for detecting the earliest recovery sign of the hematopoietic stem-cells. (Evans, J.)

Isolation and functional aspects of free luteal cells

International Nuclear Information System (INIS)

Luborsky, J.L.; Berhrman, H.R.

1985-01-01

Methods of luteal cell isolation employ enzymatic treatment of luteal tissue with collagenase and deoxyribonuclease. Additional enzymes such as hyaluronidase or Pronase are also used in some instances. Isolated luteal cells retain the morphological characteristics of steroid secreting cells after isolation. They contain mitochondria, variable amounts of lipid droplets, and an extensive smooth endoplasmic reticulum. Isolated luteal cells have been used in numerous studies to examine the regulation of steriodogenesis by luteinizing hormone (LH). LH receptor binding studies were employed to quantitate specific properties of hormone-receptor interaction in relation to cellular function. Binding of [ 125 I]LH to bovine luteal cells and membranes was compared and it was concluded that the enzymatic treatment used to isolate cells did not change the LH receptor binding kinetics

Priming Adipose-Derived Mesenchymal Stem Cells with Hyaluronan Alters Growth Kinetics and Increases Attachment to Articular Cartilage

Directory of Open Access Journals (Sweden)

Peter Succar

2016-01-01

Full Text Available Background. Biological therapeutics such as adipose-derived mesenchymal stem cell (MSC therapy are gaining acceptance for knee-osteoarthritis (OA treatment. Reports of OA-patients show reductions in cartilage defects and regeneration of hyaline-like-cartilage with MSC-therapy. Suspending MSCs in hyaluronan commonly occurs in animals and humans, usually without supporting data. Objective. To elucidate the effects of different concentrations of hyaluronan on MSC growth kinetics. Methods. Using a range of hyaluronan concentrations, we measured MSC adherence and proliferation on culture plastic surfaces and a novel cartilage-adhesion assay. We employed time-course and dispersion imaging to assess MSC binding to cartilage. Cytokine profiling was also conducted on the MSC-secretome. Results. Hyaluronan had dose-dependent effects on growth kinetics of MSCs at concentrations of entanglement point (1 mg/mL. At higher concentrations, viscosity effects outweighed benefits of additional hyaluronan. The cartilage-adhesion assay highlighted for the first time that hyaluronan-primed MSCs increased cell attachment to cartilage whilst the presence of hyaluronan did not. Our time-course suggested patients undergoing MSC-therapy for OA could benefit from joint-immobilisation for up to 8 hours. Hyaluronan also greatly affected dispersion of MSCs on cartilage. Conclusion. Our results should be considered in future trials with MSC-therapy using hyaluronan as a vehicle, for the treatment of OA.

The Kinetics and the Permeation Properties of Piezo Channels.

Science.gov (United States)

Gnanasambandam, R; Gottlieb, P A; Sachs, F

2017-01-01

Piezo channels are eukaryotic, cation-selective mechanosensitive channels (MSCs), which show rapid activation and voltage-dependent inactivation. The kinetics of these channels are largely consistent across multiple cell types and different stimulation paradigms with some minor variability. No accessory subunits that associate with Piezo channels have been reported. They are homotrimers and each ∼300kD monomer has an N-terminal propeller blade-like mechanosensing module, which can confer mechanosensing capabilities on ASIC-1 (the trimeric non-MSC, acid-sensing ion channel-1) and a C-terminal pore module, which influences conductance, selectivity, and channel inactivation. Repeated stimulation can cause domain fracture and diffusion of these channels leading to synchronous loss of inactivation. The reconstituted channels spontaneously open only in asymmetric bilayers but lack inactivation. Mutations that cause hereditary xerocytosis alter PIEZO1 kinetics. The kinetics of the wild-type PIEZO1 and alterations thereof in mutants (M2225R, R2456K, and DhPIEZO1) are summarized in the form of a quantitative model and hosted online. The pore is permeable to alkali ions although Li + permeates poorly. Divalent cations, notably Ca 2+ , traverse the channel and inhibit the flux of monovalents. The large monovalent organic cations such as tetramethyl ammonium and tetraethyl ammonium can traverse the channel, but slowly, suggesting a pore diameter of ∼8Å, and the estimated in-plane area change upon opening is around 6-20nm 2 . Ruthenium red can enter the channel only from the extracellular side and seems to bind in a pocket close to residue 2496. Copyright © 2017 Elsevier Inc. All rights reserved.

Kinetic energy management in road traffic injury prevention: a call for action

Directory of Open Access Journals (Sweden)

Davoud Khorasani-Zavareh

2015-01-01

Full Text Available Abstract: By virtue of their variability, mass and speed have important roles in transferring energies during a crash incidence (kinetic energy. The sum of kinetic energy is important in determining an injury severity and that is equal to one half of the vehicle mass multiplied by the square of the vehicle speed. To meet the Vision Zero policy (a traffic safety policy prevention activities should be focused on vehicle speed management. Understanding the role of kinetic energy will help to develop measures to reduce the generation, distribution, and effects of this energy during a road traffic crash. Road traffic injury preventive activities necessitate Kinetic energy management to improve road user safety.

Kinetics of bacterial fluorescence staining with 3,3'-diethylthiacyanine.

Science.gov (United States)

Thomas, Marlon S; Nuñez, Vicente; Upadhyayula, Srigokul; Zielins, Elizabeth R; Bao, Duoduo; Vasquez, Jacob M; Bahmani, Baharak; Vullev, Valentine I

2010-06-15

For more than a century, colorimetric and fluorescence staining have been the foundation of a broad range of key bioanalytical techniques. The dynamics of such staining processes, however, still remains largely unexplored. We investigated the kinetics of fluorescence staining of two gram-negative and two gram-positive species with 3,3'-diethylthiacyanine (THIA) iodide. An increase in the THIA fluorescence quantum yield, induced by the bacterial dye uptake, was the principal reason for the observed emission enhancement. The fluorescence quantum yield of THIA depended on the media viscosity and not on the media polarity, which suggested that the microenvironment of the dye molecules taken up by the cells was restrictive. The kinetics of fluorescence staining did not manifest a statistically significant dependence neither on the dye concentration, nor on the cell count. In the presence of surfactant additives, however, the fluorescence-enhancement kinetic patterns manifested species specificity with statistically significant discernibility.

125IdUrd-induced chromosome fragments, assayed by premature chromosome condensation, and DNA double-strand breaks have similar repair kinetics in G1-phase CHO-cells

International Nuclear Information System (INIS)

Iliakis, George; Pantelias, G.E.; Okayasu, Ryuichi; Seaner, Robert

1987-01-01

The effect of 125 I-decay on cell lethality, and induction of chromosome and DNA damage, was studied in synchronous non-cycling, G 1 -phase CHO-cells. Neutral filter elution was used to assay repair of DNA double-strand breaks (dsbs), and premature chromosome condensation was used to assay repair of chromosome fragments and induction of ring chromosomes. The results indicate very little repair at the cell survival level (repair of PLD). At the DNA level an efficient repair of DNA dsbs was observed, with kinetics similar to those observed after exposure to X-rays. At the chromosome level a fast repair of prematurely condensed chromosome fragments was observed, with a concomitant increase in the number of ring chromosomes induced. The repair kinetics of chromosome fragments and DNA dsbs were very similar, suggesting that DNA dsbs may underlie chromosome fragmentation. (author)

Reproductive death and population kinetics in survival fractions of in vitro hamster cells during 48 hours after X-irradiation with doses up to 800 Rds. Pt. 2

International Nuclear Information System (INIS)

Hagemann, G.

1976-01-01

By means of a quantitative analysis, the time dependency of the number of dead cells and the resulting statement of cell numbers are compared with colony survival curves and with the distribution of colony sizes. The obtained periodical variation of reproductively killed cells is analyzed through population kinetics and is reduced to the number of those among the irradiated cells which show radiation-induced lethal reproductive damage. Therefrom, together with both sorts of interphase-dead cells, the dose dependency of the three lethal fractions results, taking into consideration the quantitative cellular statement. The formation of maxima of reproductively killed cells at the intervals of generation time until F 3 -generation is explained by an autosynchronization of partly lethally injured cell populations. From colony size distributions a linear dose dependency of the mean colony size group can be derived; this is discussed in connection with DNA double strand breaks regarded as a possible cause of reproductive lethal damages. The data obtained concerning the development of a cell population with radiation damages are evaluated by the construction of phylogenetic schedules for every 300 rd and 500 rd. By this means, the underlying population kinetics is being revised quantitatively. (orig.) [de

Kinetics of tracheid development explain conifer tree-ring structure.

Science.gov (United States)

Cuny, Henri E; Rathgeber, Cyrille B K; Frank, David; Fonti, Patrick; Fournier, Meriem

2014-09-01

Conifer tree rings are generally composed of large, thin-walled cells of light earlywood followed by narrow, thick-walled cells of dense latewood. Yet, how wood formation processes and the associated kinetics create this typical pattern remains poorly understood. We monitored tree-ring formation weekly over 3 yr in 45 trees of three conifer species in France. Data were used to model cell development kinetics, and to attribute the relative importance of the duration and rate of cell enlargement and cell wall deposition on tree-ring structure. Cell enlargement duration contributed to 75% of changes in cell diameter along the tree rings. Remarkably, the amount of wall material per cell was quite constant along the rings. Consequently, and in contrast with widespread belief, changes in cell wall thickness were not principally attributed to the duration and rate of wall deposition (33%), but rather to the changes in cell size (67%). Cell enlargement duration, as the main driver of cell size and wall thickness, contributed to 56% of wood density variation along the rings. This mechanistic framework now forms the basis for unraveling how environmental stresses trigger deviations (e.g. false rings) from the normal tree-ring structure. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Trapped particle stability for the kinetic stabilizer

Science.gov (United States)

Berk, H. L.; Pratt, J.

2011-08-01

A kinetically stabilized axially symmetric tandem mirror (KSTM) uses the momentum flux of low-energy, unconfined particles that sample only the outer end-regions of the mirror plugs, where large favourable field-line curvature exists. The window of operation is determined for achieving magnetohydrodynamic (MHD) stability with tolerable energy drain from the kinetic stabilizer. Then MHD stable systems are analysed for stability of the trapped particle mode. This mode is characterized by the detachment of the central-cell plasma from the kinetic-stabilizer region without inducing field-line bending. Stability of the trapped particle mode is sensitive to the electron connection between the stabilizer and the end plug. It is found that the stability condition for the trapped particle mode is more constraining than the stability condition for the MHD mode, and it is challenging to satisfy the required power constraint. Furthermore, a severe power drain may arise from the necessary connection of low-energy electrons in the kinetic stabilizer to the central region.

Anomalous electron transport in Hall-effect thrusters: Comparison between quasi-linear kinetic theory and particle-in-cell simulations

Science.gov (United States)

Lafleur, T.; Martorelli, R.; Chabert, P.; Bourdon, A.

2018-06-01

Kinetic drift instabilities have been implicated as a possible mechanism leading to anomalous electron cross-field transport in E × B discharges, such as Hall-effect thrusters. Such instabilities, which are driven by the large disparity in electron and ion drift velocities, present a significant challenge to modelling efforts without resorting to time-consuming particle-in-cell (PIC) simulations. Here, we test aspects of quasi-linear kinetic theory with 2D PIC simulations with the aim of developing a self-consistent treatment of these instabilities. The specific quantities of interest are the instability growth rate (which determines the spatial and temporal evolution of the instability amplitude), and the instability-enhanced electron-ion friction force (which leads to "anomalous" electron transport). By using the self-consistently obtained electron distribution functions from the PIC simulations (which are in general non-Maxwellian), we find that the predictions of the quasi-linear kinetic theory are in good agreement with the simulation results. By contrast, the use of Maxwellian distributions leads to a growth rate and electron-ion friction force that is around 2-4 times higher, and consequently significantly overestimates the electron transport. A possible method for self-consistently modelling the distribution functions without requiring PIC simulations is discussed.

Non-kinetic capabilities: complementing the kinetic prevalence to targeting

OpenAIRE

Ducheine, P.

2014-01-01

Targeting is used in military doctrine to describe a military operational way, using (military) means to influence a target (or addressee) in order to achieve designated political and/or military goals. The four factors italicized are used to analyse non-kinetic targeting, complementing our knowledge and understanding of the kinetic prevalence. Paradoxically, non-kinetic targeting is not recognized as a separate concept: kinetic and non-kinetic are intertwined facets of targeting. Kinetic tar...

Fundamental studies of leukemic cell labeling with /sup 111/In-oxine and their applications to cell kinetics in patients with acute leukemia

Energy Technology Data Exchange (ETDEWEB)

Takagi, Yuhkoh; Matsuda, Shin; Uchida, Tatsumi; Kariyone, Shigeo [Fukushima Medical Coll. (Japan)

1984-04-01

Fundamental studies of leukemic cell labeling with /sup 111/In-oxine and their applications to leukemic cell kinetics in five patients with acute myeloblastic leukemia (AML) were examined. Labeling efficiency of leukemic cells was 80.3 +- 3.6% for more than 1 x 10/sup 8/ cells at room temperature for 20 minutes of incubation followed by two times washes. Cell viability determined by means of trypanblue exclusion test was 95.3 +- 2.6%. In vitro elution rate of /sup 111/In from the labeled cells during 12 hours was 10.0 +- 1.2%. The disappearance curves of labeled leukemic cells in AMLs followed a single exponential fashion, and the half time of disappearance (T 1/2) ranged from 9.6 to 31.8 hours. Total blood leukemic cell pool (TBLCP) calculated with the dilution principles of radioisotopes correlated significantly with the leukemic cell counts (LC) in the peripheral blood (Y = 0.32 + 1.94X, r = 0.99). In the studies of organ distribution which were observed and analyzed with gamma camera and computer, labeled leukemic cells passed through lungs within 15 minutes. Radioactivity in the spleen increased rapidly for 30 - 60 minutes, then reached a plateau. Hepatic radioactivity showed a temporary decrease during 10 - 60 minutes following the moderate accumulation in initial 10 minutes. In two cases, bone marrow was visualized 24 hours after the injection. Radioactivity of the leukemic cells isolated from the bone marrow at 22 hours after the injection in one case was one third of the radioactivity in leukemic cells obtained from the peripheral blood at the same time.

Accounting for inherent variability of growth in microbial risk assessment.

Science.gov (United States)

Marks, H M; Coleman, M E

2005-04-15

Risk assessments of pathogens need to account for the growth of small number of cells under varying conditions. In order to determine the possible risks that occur when there are small numbers of cells, stochastic models of growth are needed that would capture the distribution of the number of cells over replicate trials of the same scenario or environmental conditions. This paper provides a simple stochastic growth model, accounting only for inherent cell-growth variability, assuming constant growth kinetic parameters, for an initial, small, numbers of cells assumed to be transforming from a stationary to an exponential phase. Two, basic, microbial sets of assumptions are considered: serial, where it is assume that cells transform through a lag phase before entering the exponential phase of growth; and parallel, where it is assumed that lag and exponential phases develop in parallel. The model is based on, first determining the distribution of the time when growth commences, and then modelling the conditional distribution of the number of cells. For the latter distribution, it is found that a Weibull distribution provides a simple approximation to the conditional distribution of the relative growth, so that the model developed in this paper can be easily implemented in risk assessments using commercial software packages.

Kinetics of carboplatin-DNA binding in genomic DNA and bladder cancer cells as determined by accelerator mass spectrometry

International Nuclear Information System (INIS)

Hah, S S; Stivers, K M; Vere White, R; Henderson, P T

2005-01-01

Cisplatin and carboplatin are platinum-based drugs that are widely used in cancer chemotherapy. The cytotoxicity of these drugs is mediated by platinum-DNA monoadducts and intra- and interstrand diadducts, which are formed following uptake of the drug into the nucleus of cells. The pharmacodynamics of carboplatin display fewer side effects than for cisplatin, albeit with less potency, which may be due to differences in rates of DNA adduct formation. We report the use of accelerator mass spectrometry (AMS), a sensitive detection method often used for radiocarbon quantitation, to measure both the kinetics of [ 14 C]carboplatin-DNA adduct formation with genomic DNA and drug uptake and DNA binding in T24 human bladder cancer cells. Only carboplatin-DNA monoadducts contain radiocarbon in the platinated DNA, which allowed for calculation of kinetic rates and concentrations within the system. The percent of radiocarbon bound to salmon sperm DNA in the form of monoadducts was measured by AMS over 24 h. Knowledge of both the starting concentration of the parent carboplatin and the concentration of radiocarbon in the DNA at a variety of time points allowed calculation of the rates of Pt-DNA monoadduct formation and conversion to toxic cross-links. Importantly, the rate of carboplatin-DNA monoadduct formation was approximately 100-fold slower than that reported for the more potent cisplatin analogue, which may explain the lower toxicity of carboplatin. T24 human bladder cancer cells were incubated with a subpharmacological dose of [ 14 C]carboplatin, and the rate of accumulation of radiocarbon in the cells and nuclear DNA was measured by AMS. The lowest concentration of radiocarbon measured was approximately 1 amol/10 (micro)g of DNA. This sensitivity may allow the method to be used for clinical applications

Kinetics of carboplatin-DNA binding in genomic DNA and bladder cancer cells as determined by accelerator mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Hah, S S; Stivers, K M; Vere White, R; Henderson, P T

2005-12-29

Cisplatin and carboplatin are platinum-based drugs that are widely used in cancer chemotherapy. The cytotoxicity of these drugs is mediated by platinum-DNA monoadducts and intra- and interstrand diadducts, which are formed following uptake of the drug into the nucleus of cells. The pharmacodynamics of carboplatin display fewer side effects than for cisplatin, albeit with less potency, which may be due to differences in rates of DNA adduct formation. We report the use of accelerator mass spectrometry (AMS), a sensitive detection method often used for radiocarbon quantitation, to measure both the kinetics of [{sup 14}C]carboplatin-DNA adduct formation with genomic DNA and drug uptake and DNA binding in T24 human bladder cancer cells. Only carboplatin-DNA monoadducts contain radiocarbon in the platinated DNA, which allowed for calculation of kinetic rates and concentrations within the system. The percent of radiocarbon bound to salmon sperm DNA in the form of monoadducts was measured by AMS over 24 h. Knowledge of both the starting concentration of the parent carboplatin and the concentration of radiocarbon in the DNA at a variety of time points allowed calculation of the rates of Pt-DNA monoadduct formation and conversion to toxic cross-links. Importantly, the rate of carboplatin-DNA monoadduct formation was approximately 100-fold slower than that reported for the more potent cisplatin analogue, which may explain the lower toxicity of carboplatin. T24 human bladder cancer cells were incubated with a subpharmacological dose of [{sup 14}C]carboplatin, and the rate of accumulation of radiocarbon in the cells and nuclear DNA was measured by AMS. The lowest concentration of radiocarbon measured was approximately 1 amol/10 {micro}g of DNA. This sensitivity may allow the method to be used for clinical applications.

Rate kernel theory for pseudo-first-order kinetics of diffusion-influenced reactions and application to fluorescence quenching kinetics.

Science.gov (United States)

Yang, Mino

2007-06-07

Theoretical foundation of rate kernel equation approaches for diffusion-influenced chemical reactions is presented and applied to explain the kinetics of fluorescence quenching reactions. A many-body master equation is constructed by introducing stochastic terms, which characterize the rates of chemical reactions, into the many-body Smoluchowski equation. A Langevin-type of memory equation for the density fields of reactants evolving under the influence of time-independent perturbation is derived. This equation should be useful in predicting the time evolution of reactant concentrations approaching the steady state attained by the perturbation as well as the steady-state concentrations. The dynamics of fluctuation occurring in equilibrium state can be predicted by the memory equation by turning the perturbation off and consequently may be useful in obtaining the linear response to a time-dependent perturbation. It is found that unimolecular decay processes including the time-independent perturbation can be incorporated into bimolecular reaction kinetics as a Laplace transform variable. As a result, a theory for bimolecular reactions along with the unimolecular process turned off is sufficient to predict overall reaction kinetics including the effects of unimolecular reactions and perturbation. As the present formulation is applied to steady-state kinetics of fluorescence quenching reactions, the exact relation between fluorophore concentrations and the intensity of excitation light is derived.

Process Analytical Technology for Advanced Process Control in Biologics Manufacturing with the Aid of Macroscopic Kinetic Modeling

Directory of Open Access Journals (Sweden)

Martin Kornecki

2018-03-01

Full Text Available Productivity improvements of mammalian cell culture in the production of recombinant proteins have been made by optimizing cell lines, media, and process operation. This led to enhanced titers and process robustness without increasing the cost of the upstream processing (USP; however, a downstream bottleneck remains. In terms of process control improvement, the process analytical technology (PAT initiative, initiated by the American Food and Drug Administration (FDA, aims to measure, analyze, monitor, and ultimately control all important attributes of a bioprocess. Especially, spectroscopic methods such as Raman or near-infrared spectroscopy enable one to meet these analytical requirements, preferably in-situ. In combination with chemometric techniques like partial least square (PLS or principal component analysis (PCA, it is possible to generate soft sensors, which estimate process variables based on process and measurement models for the enhanced control of bioprocesses. Macroscopic kinetic models can be used to simulate cell metabolism. These models are able to enhance the process understanding by predicting the dynamic of cells during cultivation. In this article, in-situ turbidity (transmission, 880 nm and ex-situ Raman spectroscopy (785 nm measurements are combined with an offline macroscopic Monod kinetic model in order to predict substrate concentrations. Experimental data of Chinese hamster ovary cultivations in bioreactors show a sufficiently linear correlation (R2 ≥ 0.97 between turbidity and total cell concentration. PLS regression of Raman spectra generates a prediction model, which was validated via offline viable cell concentration measurement (RMSE ≤ 13.82, R2 ≥ 0.92. Based on these measurements, the macroscopic Monod model can be used to determine different process attributes, e.g., glucose concentration. In consequence, it is possible to approximately calculate (R2 ≥ 0.96 glucose concentration based on online cell

Process Analytical Technology for Advanced Process Control in Biologics Manufacturing with the Aid of Macroscopic Kinetic Modeling.

Science.gov (United States)

Kornecki, Martin; Strube, Jochen

2018-03-16

Productivity improvements of mammalian cell culture in the production of recombinant proteins have been made by optimizing cell lines, media, and process operation. This led to enhanced titers and process robustness without increasing the cost of the upstream processing (USP); however, a downstream bottleneck remains. In terms of process control improvement, the process analytical technology (PAT) initiative, initiated by the American Food and Drug Administration (FDA), aims to measure, analyze, monitor, and ultimately control all important attributes of a bioprocess. Especially, spectroscopic methods such as Raman or near-infrared spectroscopy enable one to meet these analytical requirements, preferably in-situ. In combination with chemometric techniques like partial least square (PLS) or principal component analysis (PCA), it is possible to generate soft sensors, which estimate process variables based on process and measurement models for the enhanced control of bioprocesses. Macroscopic kinetic models can be used to simulate cell metabolism. These models are able to enhance the process understanding by predicting the dynamic of cells during cultivation. In this article, in-situ turbidity (transmission, 880 nm) and ex-situ Raman spectroscopy (785 nm) measurements are combined with an offline macroscopic Monod kinetic model in order to predict substrate concentrations. Experimental data of Chinese hamster ovary cultivations in bioreactors show a sufficiently linear correlation (R² ≥ 0.97) between turbidity and total cell concentration. PLS regression of Raman spectra generates a prediction model, which was validated via offline viable cell concentration measurement (RMSE ≤ 13.82, R² ≥ 0.92). Based on these measurements, the macroscopic Monod model can be used to determine different process attributes, e.g., glucose concentration. In consequence, it is possible to approximately calculate (R² ≥ 0.96) glucose concentration based on online cell

The merits of DNA content and cell kinetic parameters for the assessment of intrinsic cellular radiosensitivity to photon and high-LET neutron irradiation

International Nuclear Information System (INIS)

Theron, C.S.; Serafin, A.; Bohm, L.; Slabbert, J.P.

1997-01-01

Differences of the intrinsic cellular radiosensitivity between tumours make the selection of patients for specific radiation schedules very difficult. The reasons for these variations are still unclear, but are thought to be due to genomic and cellular characteristics. Radiosensitivities vary between cell cycle stages, with S-phase cells being most radioresistant and G2/M phase cells most radiosensitive. It is also well established that most tumour cells have an abnormal ploidy. DNA content and cellular proliferation kinetics therefore could influence the intrinsic radiosensitivity. This prompted us to assess the merits of these parameters as predictors of radiation response. (authors)

Simplified methodology for control cell constant calculations of the reactor cores for the space kinetics

International Nuclear Information System (INIS)

Santos, Rubens Souza dos; Martinez, Aquilino Senra; Alvim, Antonio Carlos Marques

2002-01-01

In this work is presented a methodology which focuses the distribution of neutron absorber rods in nuclear reactor power plants, for utilizing in space kinetic calculations, principally in the cluster ejection transients of control rods. A numerical model for macroscopic constant calculations based on the knowledge of the neutron flux without the control rods is proposed, as alternative to the analytical models, based on the hypothesis of the null current on the cell super boundaries. The proposed model in this work has itself showed adequate to deal with problems with strong space dependence, once that the model showed consistence in the global average built in the analytical model. (author)

Radiation-induced changes in glomerular and tubular cell kinetics and morphology following irradiation of a single kidney in the pig

International Nuclear Information System (INIS)

Robbins, Mike E. C.; Bonsib, Stephen M.; Ikeda, Andrea; Soranson, Julie A.; Wilson, George D.; Rezvani, Mohi; Golding, Stephen J.; Whitehouse, Elizabeth; Hopewell, John W.

1995-01-01

Purpose: Radiation-induced changes in glomerular and tubular cell kinetics and morphology following irradiation of a single pig kidney were assessed. Methods and Materials: The right kidney of 13 adult female Large White pigs was irradiated with a single dose of 9.8 Gy γ rays. Animals were serially killed between 2 and 24 weeks postirradiation (PI); 1 h prior to postmortem each pig received 500 mg bromodeoxyuridine (BrdUrd). At postmortem, both kidneys were removed and tissue taken to prepare cell suspensions. The labeling index (LI) of these suspensions was measured using flow cytometry; in vivo BrdUrd incorporation in glomerular and tubular cells was determined immunohistochemically. The kidneys were also assessed histologically. Results: Irradiation of the right kidney alone resulted in a significant increase in renal cell LI in both the irradiated and the contralateral unirradiated kidney within 2 weeks of irradiation; peak values of 1.57 ± 0.32% and 1.04 ± 0.13%, respectively, were seen 4 weeks PI, significantly greater p < 0.001) than the preirradiation value of 0.18 ± 0.01%. The LI values then declined with time, but remained greater than those seen prior to irradiation. A similar pattern of response was determined from counts of labeled glomerular and tubular cells identified immunohistochemically. The increase in labeled glomerular cells was seen 2 weeks PI, whereas that for the tubular cells did not occur until 4 weeks PI. The irradiated kidney exhibited diffuse, progressive glomerular alterations. In contrast, tubular damage was focal; the irradiated kidney also exhibited a prominent vasculopathy, involving arteriolar and peripheral interlobular artery thickening. The contralateral unirradiated kidney appeared unchanged. Conclusion: These findings confirm the hypothesis that the morphologic and kinetic responses observed after irradiation of a single kidney are similar to those observed after irradiation of both kidneys. Renal irradiation results in

Cell-Free Protein Synthesis Enhancement from Real-Time NMR Metabolite Kinetics: Redirecting Energy Fluxes in Hybrid RRL Systems.

Science.gov (United States)

Panthu, Baptiste; Ohlmann, Théophile; Perrier, Johan; Schlattner, Uwe; Jalinot, Pierre; Elena-Herrmann, Bénédicte; Rautureau, Gilles J P

2018-01-19

A counterintuitive cell-free protein synthesis (CFPS) strategy, based on reducing the ribosomal fraction in rabbit reticulocyte lysate (RRL), triggers the development of hybrid systems composed of RRL ribosome-free supernatant complemented with ribosomes from different mammalian cell-types. Hybrid RRL systems maintain translational properties of the original ribosome cell types, and deliver protein expression levels similar to RRL. Here, we show that persistent ribosome-associated metabolic activity consuming ATP is a major obstacle for maximal protein yield. We provide a detailed picture of hybrid CFPS systems energetic metabolism based on real-time nuclear magnetic resonance (NMR) investigation of metabolites kinetics. We demonstrate that protein synthesis capacity has an upper limit at native ribosome concentration and that lower amounts of the ribosomal fraction optimize energy fluxes toward protein translation, consequently increasing CFPS yield. These results provide a rationalized strategy for further mammalian CFPS developments and reveal the potential of real-time NMR metabolism phenotyping for optimization of cell-free protein expression systems.

Multi-region and single-cell sequencing reveal variable genomic heterogeneity in rectal cancer.

Science.gov (United States)

Liu, Mingshan; Liu, Yang; Di, Jiabo; Su, Zhe; Yang, Hong; Jiang, Beihai; Wang, Zaozao; Zhuang, Meng; Bai, Fan; Su, Xiangqian

2017-11-23

Colorectal cancer is a heterogeneous group of malignancies with complex molecular subtypes. While colon cancer has been widely investigated, studies on rectal cancer are very limited. Here, we performed multi-region whole-exome sequencing and single-cell whole-genome sequencing to examine the genomic intratumor heterogeneity (ITH) of rectal tumors. We sequenced nine tumor regions and 88 single cells from two rectal cancer patients with tumors of the same molecular classification and characterized their mutation profiles and somatic copy number alterations (SCNAs) at the multi-region and the single-cell levels. A variable extent of genomic heterogeneity was observed between the two patients, and the degree of ITH increased when analyzed on the single-cell level. We found that major SCNAs were early events in cancer development and inherited steadily. Single-cell sequencing revealed mutations and SCNAs which were hidden in bulk sequencing. In summary, we studied the ITH of rectal cancer at regional and single-cell resolution and demonstrated that variable heterogeneity existed in two patients. The mutational scenarios and SCNA profiles of two patients with treatment naïve from the same molecular subtype are quite different. Our results suggest each tumor possesses its own architecture, which may result in different diagnosis, prognosis, and drug responses. Remarkable ITH exists in the two patients we have studied, providing a preliminary impression of ITH in rectal cancer.

Using Equation-Free Computation to Accelerate Network-Free Stochastic Simulation of Chemical Kinetics.

Science.gov (United States)

Lin, Yen Ting; Chylek, Lily A; Lemons, Nathan W; Hlavacek, William S

2018-06-21

The chemical kinetics of many complex systems can be concisely represented by reaction rules, which can be used to generate reaction events via a kinetic Monte Carlo method that has been termed network-free simulation. Here, we demonstrate accelerated network-free simulation through a novel approach to equation-free computation. In this process, variables are introduced that approximately capture system state. Derivatives of these variables are estimated using short bursts of exact stochastic simulation and finite differencing. The variables are then projected forward in time via a numerical integration scheme, after which a new exact stochastic simulation is initialized and the whole process repeats. The projection step increases efficiency by bypassing the firing of numerous individual reaction events. As we show, the projected variables may be defined as populations of building blocks of chemical species. The maximal number of connected molecules included in these building blocks determines the degree of approximation. Equation-free acceleration of network-free simulation is found to be both accurate and efficient.

Modelling of elementary kinetics of H2 and CO oxidation on ceria pattern cells

International Nuclear Information System (INIS)

Patel, HC; Tabish, AN; Aravind, PV

2015-01-01

Elementary kinetic mechanisms of fuel oxidation on ceria have not been dealt with in detail in literature. An elementary kinetic model is developed considering charge transfer and adsorption steps for electrochemical H 2 and CO oxidation on ceria. The reaction chemistry is solved by fitting previously obtained impedance spectra for H 2 and CO oxidation on ceria. The rate determining step is found to be the charge transfer rather than the adsorption for both H 2 and CO. A method is presented to extend the kinetics obtained from pattern anodes to macroscopic simulations in which the activation overvoltage can be calculated on the basis of elementary kinetics.

Possibilities and limitations of the kinetic plot method in supercritical fluid chromatography.

Science.gov (United States)

De Pauw, Ruben; Desmet, Gert; Broeckhoven, Ken

2013-08-30

Although supercritical fluid chromatography (SFC) is becoming a technique of increasing importance in the field of analytical chromatography, methods to compare the performance of SFC-columns and separations in an unbiased way are not fully developed. The present study uses mathematical models to investigate the possibilities and limitations of the kinetic plot method in SFC as this easily allows to investigate a wide range of operating pressures, retention and mobile phase conditions. The variable column length (L) kinetic plot method was further investigated in this work. Since the pressure history is identical for each measurement, this method gives the true kinetic performance limit in SFC. The deviations of the traditional way of measuring the performance as a function of flow rate (fixed back pressure and column length) and the isopycnic method with respect to this variable column length method were investigated under a wide range of operational conditions. It is found that using the variable L method, extrapolations towards other pressure drops are not valid in SFC (deviation of ∼15% for extrapolation from 50 to 200bar pressure drop). The isopycnic method provides the best prediction but its use is limited when operating closer towards critical point conditions. When an organic modifier is used, the predictions are improved for both methods with respect to the variable L method (e.g. deviations decreases from 20% to 2% when 20mol% of methanol is added). Copyright © 2013 Elsevier B.V. All rights reserved.

Self-discharge rate of lithium thionyl-chloride cells

Energy Technology Data Exchange (ETDEWEB)

Cieslak, W.R.

1993-12-31

Our low-rate lithium/thionyl-chloride ``D`` cell is required to provide power continuously for up to 10 years. The cell was designed at Sandia National Laboratories and manufactured at Eagle-Picher Industries, Joplin, Missouri. We have conducted accelerated aging studies at elevated temperatures to predict long-term performance of cells fabricated in 1992. Cells using 1.0M LiAlCl{sub 4} electrolyte follow Arrhenius kinetics with an activation energy of 14.6 Kcal/mol. This results in an annual capacity loss to self-discharge of 0.13 Ah at 25 C. Cells using a 1.0M LiAlCl{sub 4}{sm_bullet}SO{sub 2} electrolyte do not follow Arrhenius behavior. The performance of aged cells from an earlier fabrication lot is variable.

Oxygen Reduction Kinetics of La2-xSrxNiO 4+delta Electrodes for Solid Oxide Fuel Cells

Science.gov (United States)

Guan, Bo

In the development of intermediate temperature solid oxide fuel cell (IT-SOFC), mixed ionic-electronic conductors (MIEC) have drawn big interests due to their both ionic and electronic species transport which can enlarge the 3-dimension of the cathode network. This thesis presents an investigation of MIEC of Ruddlesden-popper (RP) phases like K2NiF4 type La2NiO4+delta (LNO)-based oxides which have interesting transport, catalytic properties and suitable thermal expansion coefficients. The motivation of this present work is to further understand the fundamental of the effect of Sr doing on the oxygen reduction reaction (ORR) kinetics of LNO cathode. Porous symmetrical cells of La2-xSrxNiO4+delta (0≤x≤0.4) were fabricated and characterized by electrochemical impedance spectroscopy (EIS) in different PO2 from temperature range of 600˜800°C. The spectra were analyzed based on the impedance model introduced by Adler et al. The rate determining steps (RDS) for ORR were proposed and the responsible reasons were discussed. The overall polarization resistances of doped samples increase with Sr level. Surface oxygen exchange and bulk ionic diffusion co-control the ORR kinetics. With high Sr content (x=0.3, 0.4), oxygen ion transfer resistance between nickelate/electrolyte is observed. However for porous symmetrical cells it is hard to associate the resistance from EIS directly to each ORR elementary processes because of the difficulty in describing the microstructure of the porous electrode. The dense electrode configuration was adopted in this thesis. By using the dense electrode, the surface area, the thickness of electrode, the interface between electrode and electrolyte and lastly the 3PB are theoretically well-defined. Through this method, there is a good chance to distinguish the contribution of surface exchange from other processes. Dense and thin electrode layers in thickness of ˜40 mum are fabricated by using a novel spray modified pressing method. Negligible

Evidence for Dynamic Chemical Kinetics at Individual Molecular Ruthenium Catalysts.

Science.gov (United States)

Easter, Quinn T; Blum, Suzanne A

2018-02-05

Catalytic cycles are typically depicted as possessing time-invariant steps with fixed rates. Yet the true behavior of individual catalysts with respect to time is unknown, hidden by the ensemble averaging inherent to bulk measurements. Evidence is presented for variable chemical kinetics at individual catalysts, with a focus on ring-opening metathesis polymerization catalyzed by the second-generation Grubbs' ruthenium catalyst. Fluorescence microscopy is used to probe the chemical kinetics of the reaction because the technique possesses sufficient sensitivity for the detection of single chemical reactions. Insertion reactions in submicron regions likely occur at groups of many (not single) catalysts, yet not so many that their unique kinetic behavior is ensemble averaged. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kinetics of ethanol production by immobilized Kluyveromyces marxianus cells at varying sugar concentrations of Jerusalem artichoke juice

Energy Technology Data Exchange (ETDEWEB)

Bajpai, P.; Margaritis, A.

1987-08-01

Kinetics of ethanol fermentation at varying sugar concentrations of Jerusalem artichoke tuber extract has been studied using Kluyveromyces marxianus cells immobilized in calcium alginate gel beads. A maximum ethanol concentration of 111 g/l was achieved at an initial sugar concentration of 260 g/l in 20 hours, when the immobilized cell concentration in the calcium alginate beads was 53.3 g dry wt./l bead volume. Ethanol yield remained almost unaffected by initial sugar concentration up to 250 g/l and was found to be about 88% of the theoretical. Maximum rate of ethanol production decreased from 22.5 g ethanol/l/h to 10.5 g ethanol/l/h while the maximum rate of total sugars utilization decreased from 74.9 g sugars/l/h to 28.5 g sugars/l/h as the initial substrate concentration was increased from 100 to 300 g/l. The concentration of free cells in the fermentation broth was low.

Linking genes to microbial growth kinetics: an integrated biochemical systems engineering approach

NARCIS (Netherlands)

Koutinas, M.; Kiparissides, A.; Silva-Rocha, R.; Lam, M.C.; Martins Dos Santos, V.A.P.; Lorenzo, de V.; Pistikopoulos, E.N.; Mantalaris, A.

2011-01-01

The majority of models describing the kinetic properties of a microorganism for a given substrate are unstructured and empirical. They are formulated in this manner so that the complex mechanism of cell growth is simplified. Herein, a novel approach for modelling microbial growth kinetics is

Electrophysiological approach to determine kinetic parameters of sucrose uptake by single sieve elements or phloem parenchyma cells in intact Vicia faba plants.

Science.gov (United States)

Hafke, Jens B; Höll, Sabina-Roxana; Kühn, Christina; van Bel, Aart J E

2013-01-01

Apart from cut aphid stylets in combination with electrophysiology, no attempts have been made thus far to measure in vivo sucrose-uptake properties of sieve elements. We investigated the kinetics of sucrose uptake by single sieve elements and phloem parenchyma cells in Vicia faba plants. To this end, microelectrodes were inserted into free-lying phloem cells in the main vein of the youngest fully-expanded leaf, half-way along the stem, in the transition zone between the autotrophic and heterotrophic part of the stem, and in the root axis. A top-to-bottom membrane potential gradient of sieve elements was observed along the stem (-130 mV to -110 mV), while the membrane potential of the phloem parenchyma cells was stable (approx. -100 mV). In roots, the membrane potential of sieve elements dropped abruptly to -55 mV. Bathing solutions having various sucrose concentrations were administered and sucrose/H(+)-induced depolarizations were recorded. Data analysis by non-linear least-square data fittings as well as by linear Eadie-Hofstee (EH) -transformations pointed at biphasic Michaelis-Menten kinetics (2 MM, EH: K m1 1.2-1.8 mM, K m2 6.6-9.0 mM) of sucrose uptake by sieve elements. However, Akaike's Information Criterion (AIC) favored single MM kinetics. Using single MM as the best-fitting model, K m values for sucrose uptake by sieve elements decreased along the plant axis from 1 to 7 mM. For phloem parenchyma cells, higher K m values (EH: K m1 10 mM, K m2 70 mM) as compared to sieve elements were found. In preliminary patch-clamp experiments with sieve-element protoplasts, small sucrose-coupled proton currents (-0.1 to -0.3 pA/pF) were detected in the whole-cell mode. In conclusion (a) K m values for sucrose uptake measured by electrophysiology are similar to those obtained with heterologous systems, (b) electrophysiology provides a useful tool for in situ determination of K m values, (c) As yet, it remains unclear if one or two uptake systems are involved in sucrose

Liquid holding recovery kinetics in yeast cells with regard to radiation quality

International Nuclear Information System (INIS)

Kim, Jin Kyu; Lee, Byoung Hun; Petin, Vladislav G.

2004-01-01

It is widely accepted that the RBE of ionizing radiation with a high linear energy transfer (LET) is dependent both on the increased probability of primary damage production (physical events) and the reduced ability of a cell for post-irradiation recovery (biological events). A relatively unexpected role of the specific repair pathways in the RBE of high-LET radiation was demonstrated for bacterial, yeast and mammalian cells. It seems to exist a common agreement that high-LET radiations produce more portion of damage that are considered to be irreversible compared with low-LET radiation such as photons. Cellular recovery and repair of radiation-induced DNA double-strand breaks (DSB) could be also dependent upon radiation quality. Studies concerning the rate of the recovery and repair from radiation damage produced with low- and high-LET radiations in cells of various origins on the survival and macromolecular level have also revealed that in general at a high ionization density, these processes may be reduced or even absent. When irradiated yeast cells are held in a liquid non-nutrient media at 30 .deg. C before planting on to a growth medium, their survival increases. This phenomena is known as liquid holding recovery (LHR). A quantitative approach describing the LHR kinetics of the yeast cells was described, which enables the estimation of the probability of the recovery per unit time and the fraction of the irreversible damage. The main goals of this study were (i) to answer the question whether or not high-LET radiation affects the recovery process itself or if it only produces a higher level of severe irreversible damage that cannot be repaired at all; (ii) to elucidate the role of irreversible damage and the probability of recovery in some rad mutants of the yeast Saccharomyces cerevisiae. In this study, the liquid-holing recovery will serve as an indicator of the cellular repair activity

Dysregulation of Innate Lymphoid Cells in Common Variable Immunodeficiency.

Science.gov (United States)

Maglione, Paul J; Cols, Montserrat; Cunningham-Rundles, Charlotte

2017-10-05

Common variable immunodeficiency (CVID) is the most prevalent symptomatic primary immune deficiency. With widespread use of immunoglobulin replacement therapy, non-infectious complications, such as autoimmunity, chronic intestinal inflammation, and lung disease, have replaced infections as the major cause of morbidity and mortality in this immune deficiency. The pathogenic mechanisms that underlie the development of these complications in CVID are not known; however, there have been numerous associated laboratory findings. Among the most intriguing of these associations is elevation of interferon signature genes in CVID patients with inflammatory/autoimmune complications, as a similar gene expression profile is found in systemic lupus erythematosus and other chronic inflammatory diseases. Linked with this heightened interferon signature in CVID is an expansion of circulating IFN-γ-producing innate lymphoid cells. Innate lymphoid cells are key regulators of both protective and pathogenic immune responses that have been extensively studied in recent years. Further exploration of innate lymphoid cell biology in CVID may uncover key mechanisms underlying the development of inflammatory complications in these patients and may inspire much needed novel therapeutic approaches.

Drift-free kinetic equations for turbulent dispersion

Science.gov (United States)

Bragg, A.; Swailes, D. C.; Skartlien, R.

2012-11-01

The dispersion of passive scalars and inertial particles in a turbulent flow can be described in terms of probability density functions (PDFs) defining the statistical distribution of relevant scalar or particle variables. The construction of transport equations governing the evolution of such PDFs has been the subject of numerous studies, and various authors have presented formulations for this type of equation, usually referred to as a kinetic equation. In the literature it is often stated, and widely assumed, that these PDF kinetic equation formulations are equivalent. In this paper it is shown that this is not the case, and the significance of differences among the various forms is considered. In particular, consideration is given to which form of equation is most appropriate for modeling dispersion in inhomogeneous turbulence and most consistent with the underlying particle equation of motion. In this regard the PDF equations for inertial particles are considered in the limit of zero particle Stokes number and assessed against the fully mixed (zero-drift) condition for fluid points. A long-standing question regarding the validity of kinetic equations in the fluid-point limit is answered; it is demonstrated formally that one version of the kinetic equation (derived using the Furutsu-Novikov method) provides a model that satisfies this zero-drift condition exactly in both homogeneous and inhomogeneous systems. In contrast, other forms of the kinetic equation do not satisfy this limit or apply only in a limited regime.

Chemical kinetic functional sensitivity analysis: Elementary sensitivities

International Nuclear Information System (INIS)

Demiralp, M.; Rabitz, H.

1981-01-01

Sensitivity analysis is considered for kinetics problems defined in the space--time domain. This extends an earlier temporal Green's function method to handle calculations of elementary functional sensitivities deltau/sub i//deltaα/sub j/ where u/sub i/ is the ith species concentration and α/sub j/ is the jth system parameter. The system parameters include rate constants, diffusion coefficients, initial conditions, boundary conditions, or any other well-defined variables in the kinetic equations. These parameters are generally considered to be functions of position and/or time. Derivation of the governing equations for the sensitivities and the Green's funciton are presented. The physical interpretation of the Green's function and sensitivities is given along with a discussion of the relation of this work to earlier research

Kinetic theory of two-temperature polyatomic plasmas

Science.gov (United States)

Orlac'h, Jean-Maxime; Giovangigli, Vincent; Novikova, Tatiana; Roca i Cabarrocas, Pere

2018-03-01

We investigate the kinetic theory of two-temperature plasmas for reactive polyatomic gas mixtures. The Knudsen number is taken proportional to the square root of the mass ratio between electrons and heavy-species, and thermal non-equilibrium between electrons and heavy species is allowed. The kinetic non-equilibrium framework also requires a weak coupling between electrons and internal energy modes of heavy species. The zeroth-order and first-order fluid equations are derived by using a generalized Chapman-Enskog method. Expressions for transport fluxes are obtained in terms of macroscopic variable gradients and the corresponding transport coefficients are expressed as bracket products of species perturbed distribution functions. The theory derived in this paper provides a consistent fluid model for non-thermal multicomponent plasmas.

Association between morphometric variables and nocturnal desaturation in sickle-cell anemia.

Science.gov (United States)

Salles, Cristina; Bispo, Marcelo; Trindade-Ramos, Regina Terse

2014-01-01

to evaluate associations between morphometric variables, cervical circumference (CC), and abdominal circumference (AC) with the presence of nocturnal desaturation in children and adolescents with sickle-cell anemia. all patients were submitted to baseline polysomnography, oral cavity measurements (maxillary intermolar distance, mandibular intermolar distance, and overjet), and CC and AC measurements. a total of 85 patients were evaluated. A positive correlation was observed between the height/age Z-score and CC measurement (r = 0.233, p = 0.031). The presence of nocturnal desaturation was associated with CC (59.2± 9.3 vs. 67.5 ± 10.7, p = 0.006) and AC measurements (27.0 ± 2.0 vs. 29.0± 2.1, p = 0.028). There was a negative correlation between desaturation and maxillary intermolar distance (r = -0.365, p = 0.001) and mandibular intermolar distance (r = -0.233, p = 0.037). the morphometric variables of CC and AC may contribute to raise suspicion of nocturnal desaturation in children and adolescents with sickle-cell anemia. Copyright © 2014 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.

Association between morphometric variables and nocturnal desaturation in sickle-cell anemia

Directory of Open Access Journals (Sweden)

Cristina Salles

2014-07-01

Full Text Available OBJECTIVE: to evaluate associations between morphometric variables, cervical circumference (CC, and abdominal circumference (AC with the presence of nocturnal desaturation in children and adolescents with sickle-cell anemia. METHODS: all patients were submitted to baseline polysomnography, oral cavity measurements (maxillary intermolar distance, mandibular intermolar distance, and overjet, and CC and AC measurements. RESULTS: a total of 85 patients were evaluated. A positive correlation was observed between the height/age Z-score and CC measurement (r = 0.233, p = 0.031. The presence of nocturnal desaturation was associated with CC (59.2± 9.3 vs. 67.5 ± 10.7, p = 0.006 and AC measurements (27.0 ± 2.0 vs. 29.0± 2.1, p = 0.028. There was a negative correlation between desaturation and maxillary intermolar distance (r = -0.365, p = 0.001 and mandibular intermolar distance (r = -0.233, p = 0.037. CONCLUSIONS: the morphometric variables of CC and AC may contribute to raise suspicion of nocturnal desaturation in children and adolescents with sickle-cell anemia.

Growth kinetics and in vivo radiosensitivity in nude mice of two subpopulations derived from a single human small cell carcinoma of the lung

DEFF Research Database (Denmark)

Spang-Thomsen, M; Clerici, M; Engelholm, S A

1986-01-01

, and by the cell cycle distribution changes monitored by FCM. The results showed that the tumors differed in the in vivo radiosensitivity despite similarities in the growth kinetics. The results support the concept that difference in sensitivity among tumor subpopulations is an important reason for therapeutic...

Kinetic and dynamic probability-density-function descriptions of disperse turbulent two-phase flows

Science.gov (United States)

Minier, Jean-Pierre; Profeta, Christophe

2015-11-01

This article analyzes the status of two classical one-particle probability density function (PDF) descriptions of the dynamics of discrete particles dispersed in turbulent flows. The first PDF formulation considers only the process made up by particle position and velocity Zp=(xp,Up) and is represented by its PDF p (t ;yp,Vp) which is the solution of a kinetic PDF equation obtained through a flux closure based on the Furutsu-Novikov theorem. The second PDF formulation includes fluid variables into the particle state vector, for example, the fluid velocity seen by particles Zp=(xp,Up,Us) , and, consequently, handles an extended PDF p (t ;yp,Vp,Vs) which is the solution of a dynamic PDF equation. For high-Reynolds-number fluid flows, a typical formulation of the latter category relies on a Langevin model for the trajectories of the fluid seen or, conversely, on a Fokker-Planck equation for the extended PDF. In the present work, a new derivation of the kinetic PDF equation is worked out and new physical expressions of the dispersion tensors entering the kinetic PDF equation are obtained by starting from the extended PDF and integrating over the fluid seen. This demonstrates that, under the same assumption of a Gaussian colored noise and irrespective of the specific stochastic model chosen for the fluid seen, the kinetic PDF description is the marginal of a dynamic PDF one. However, a detailed analysis reveals that kinetic PDF models of particle dynamics in turbulent flows described by statistical correlations constitute incomplete stand-alone PDF descriptions and, moreover, that present kinetic-PDF equations are mathematically ill posed. This is shown to be the consequence of the non-Markovian characteristic of the stochastic process retained to describe the system and the use of an external colored noise. Furthermore, developments bring out that well-posed PDF descriptions are essentially due to a proper choice of the variables selected to describe physical systems

Atomistic mechanisms of ReRAM cell operation and reliability

Science.gov (United States)

Pandey, Sumeet C.

2018-01-01

We present results from first-principles-based modeling that captures functionally important physical phenomena critical to cell materials selection, operation, and reliability for resistance-switching memory technologies. An atomic-scale description of retention, the low- and high-resistance states (RS), and the sources of intrinsic cell-level variability in ReRAM is discussed. Through the results obtained from density functional theory, non-equilibrium Green’s function, molecular dynamics, and kinetic Monte Carlo simulations; the role of variable-charge vacancy defects and metal impurities in determining the RS, the LRS-stability, and electron-conduction in such RS is reported. Although, the statistical electrical characteristics of the oxygen-vacancy (Ox-ReRAM) and conductive-bridging RAM (M-ReRAM) are notably different, the underlying similar electrochemical phenomena describing retention and formation/dissolution of RS are being discussed.

A multiplexed method for kinetic measurements of apoptosis and proliferation using live-content imaging.

Science.gov (United States)

Artymovich, Katherine; Appledorn, Daniel M

2015-01-01

In vitro cell proliferation and apoptosis assays are widely used to study cancer cell biology. Commonly used methodologies are however performed at a single, user-defined endpoint. We describe a kinetic multiplex assay incorporating the CellPlayer(TM) NucLight Red reagent to measure proliferation and the CellPlayer(TM) Caspase-3/7 reagent to measure apoptosis using the two-color, live-content imaging platform, IncuCyte(TM) ZOOM. High-definition phase-contrast images provide an additional qualitative validation of cell death based on morphological characteristics. The kinetic data generated using this strategy can be used to derive informed pharmacology measurements to screen potential cancer therapeutics.

Glutathione reductase: solvent equilibrium and kinetic isotope effects

International Nuclear Information System (INIS)

Wong, K.K.; Vanoni, M.A.; Blanchard, J.S.

1988-01-01

Glutathione reductase catalyzes the NADPH-dependent reduction of oxidized glutathione (GSSG). The kinetic mechanism is ping-pong, and we have investigated the rate-limiting nature of proton-transfer steps in the reactions catalyzed by the spinach, yeast, and human erythrocyte glutathione reductases using a combination of alternate substrate and solvent kinetic isotope effects. With NADPH or GSSG as the variable substrate, at a fixed, saturating concentration of the other substrate, solvent kinetic isotope effects were observed on V but not V/K. Plots of Vm vs mole fraction of D 2 O (proton inventories) were linear in both cases for the yeast, spinach, and human erythrocyte enzymes. When solvent kinetic isotope effect studies were performed with DTNB instead of GSSG as an alternate substrate, a solvent kinetic isotope effect of 1.0 was observed. Solvent kinetic isotope effect measurements were also performed on the asymmetric disulfides GSSNB and GSSNP by using human erythrocyte glutathione reductase. The Km values for GSSNB and GSSNP were 70 microM and 13 microM, respectively, and V values were 62 and 57% of the one calculated for GSSG, respectively. Both of these substrates yield solvent kinetic isotope effects greater than 1.0 on both V and V/K and linear proton inventories, indicating that a single proton-transfer step is still rate limiting. These data are discussed in relationship to the chemical mechanism of GSSG reduction and the identity of the proton-transfer step whose rate is sensitive to solvent isotopic composition. Finally, the solvent equilibrium isotope effect measured with yeast glutathione reductase is 4.98, which allows us to calculate a fractionation factor for the thiol moiety of GSH of 0.456

Enterovirus strain and type-specific differences in growth kinetics and virus-induced cell destruction in human pancreatic duct epithelial HPDE cells.

Science.gov (United States)

Smura, Teemu; Natri, Olli; Ylipaasto, Petri; Hellman, Marika; Al-Hello, Haider; Piemonti, Lorenzo; Roivainen, Merja

2015-12-02

Enterovirus infections have been suspected to be involved in the development of type 1 diabetes. However, the pathogenetic mechanism of enterovirus-induced type 1 diabetes is not known. Pancreatic ductal cells are closely associated with pancreatic islets. Therefore, enterovirus infections in ductal cells may also affect beta-cells and be involved in the induction of type 1 diabetes. The aim of this study was to assess the ability of different enterovirus strains to infect, replicate and produce cytopathic effect in human pancreatic ductal cells. Furthermore, the viral factors that affect these capabilities were studied. The pancreatic ductal cells were highly susceptible to enterovirus infections. Both viral growth and cytolysis were detected for several enterovirus serotypes. However, the viral growth and capability to induce cytopathic effect (cpe) did not correlate completely. Some of the virus strains replicated in ductal cells without apparent cpe. Furthermore, there were strain-specific differences in the growth kinetics and the ability to cause cpe within some serotypes. Viral adaptation experiments were carried out to study the potential genetic determinants behind these phenotypic differences. The blind-passage of non-lytic CV-B6-Schmitt strain in HPDE-cells resulted in lytic phenotype and increased progeny production. This was associated with the substitution of a single amino acid (K257E) in the virus capsid protein VP1 and the viral ability to use decay accelerating factor (DAF) as a receptor. This study demonstrates considerable plasticity in the cell tropism, receptor usage and cytolytic properties of enteroviruses and underlines the strong effect of single or few amino acid substitutions in cell tropism and lytic capabilities of a given enterovirus. Since ductal cells are anatomically close to pancreatic islets, the capability of enteroviruses to infect and destroy pancreatic ductal cells may also implicate in respect to enterovirus induced type 1

Kinetic study of ozonation of molasses fermentation wastewater

International Nuclear Information System (INIS)

Coca, M.; Pena, M.; Gonzalez, G.

2007-01-01

A kinetic study of molasses wastewater ozonation was carried out in a stirred tank reactor to obtain the rate constants for the decolorization reaction and the regime through which ozone is absorbed. First, fundamental mass transfer parameters such as ozone solubility, volumetric mass transfer coefficients and ozone decomposition kinetics were determined from semi-batch experiments in organic-free solutions with an ionic composition similar that of industrial wastewater. The influence of operating variables such as the stirring rate and gas flow rate on the kinetic and mass transfer parameters was also studied. The application of film theory allows to establish that the reactions between ozone and colored compounds in wastewater take place in the fast and pseudo-first-order regime, within the liquid film. The decolorization rate constants were evaluated at pH 8.7 and 25 deg. C, varying from 0.6 x 10 7 to 3.8 x 10 7 L mol -1 s -1 , depending on the stirring rate and the inlet gas flow

Kinematic and kinetic analysis of overhand, sidearm and underhand lacrosse shot techniques.

Science.gov (United States)

Macaulay, Charles A J; Katz, Larry; Stergiou, Pro; Stefanyshyn, Darren; Tomaghelli, Luciano

2017-12-01

Lacrosse requires the coordinated performance of many complex skills. One of these skills is shooting on the opponents' net using one of three techniques: overhand, sidearm or underhand. The purpose of this study was to (i) determine which technique generated the highest ball velocity and greatest shot accuracy and (ii) identify kinematic and kinetic variables that contribute to a high velocity and high accuracy shot. Twelve elite male lacrosse players participated in this study. Kinematic data were sampled at 250 Hz, while two-dimensional force plates collected ground reaction force data (1000 Hz). Statistical analysis showed significantly greater ball velocity for the sidearm technique than overhand (P  0.05). Kinematic and kinetic variables were not significantly correlated to shot accuracy or velocity across all shot types; however, when analysed independently, the lead foot horizontal impulse showed a negative correlation with underhand ball velocity (P = 0.042). This study identifies the technique with the highest ball velocity, defines kinematic and kinetic predictors related to ball velocity and provides information to coaches and athletes concerned with improving lacrosse shot performance.

Atomic kinetics of a neon photoionized plasma experiment at Z

Science.gov (United States)

Mayes, Daniel C.; Mancini, Roberto; Bailey, James E.; Loisel, Guillaume; Rochau, Gregory; ZAPP Collaboration

2018-06-01

We discuss an experimental effort to study the atomic kinetics in astrophysically relevant photoionized plasmas via K-shell line absorption spectroscopy. The experiment employs the intense x-ray flux emitted at the collapse of a Z-pinch to heat and backlight a photoionized plasma contained within a cm-scale gas cell placed at a variable distance from the Z-pinch and filled with neon gas pressures in the range from 3.5 to 30 Torr. The experimental platform affords an order of magnitude range in the ionization parameter characterizing the photoionized plasma at the peak of the x-ray drive from about 5 to 80 erg*cm/s. Thus, the experiment allows for the study of trends in ionization distribution as a function of the ionization parameter. An x-ray crystal spectrometer capable of time-integrated and/or time-gated configurations is used to collect absorption spectra. The spectra show line absorption by several ionization stages of neon, including Be-, Li-, He-, and H-like ions. Analysis of these spectra yields ion areal densities and charge state distributions, which can be compared with simulation results from atomic kinetics codes. In addition, the electron temperature is extracted from level population ratios of nearby energy levels in Li- and Be-like ions, which can be used to test heating models of photoionized plasmas.

In vivo cell kinetic measurements in a randomized trial of continuous hyperfractionated accelerated radiotherapy with or without mitomycin C in head-and-neck cancer

International Nuclear Information System (INIS)

Dobrowsky, Werner; Dobrowsky, Eva; Wilson, George D.

2003-01-01

Purpose: Tumor cell repopulation is still considered to be a major cause of failure in radiotherapy. In this study, we investigated the influence of cell kinetic parameters on the outcome of patients treated in a randomized trial of accelerated fractionation, with or without mitomycin C, vs. conventional fractionation. Methods and Materials: Sixty-two patients were studied using administration of bromodeoxyuridine (BrdUrd), and cell kinetic parameters were measured using flow cytometry. The patients were treated with either 70 Gy for 7 weeks or 55.3 Gy for 17 continuous days (V-CHART) with or without 20 mg/m 2 mitomycin C on day 5. Results: The potential doubling time (Tpot) and labeling index (LI) failed to provide any prognostic information with regard to local control or survival. However, the duration of the S phase (Ts) revealed patients whose tumors had a long Ts had significantly worse local control (p = 0.028) and survival (p = 0.034) irrespective of treatment. A similar trend was evident within the different treatment arms particularly associated with overall survival. Conclusions: The Ts values of head-and-neck squamous cell cancers provided prognostic information that predicted clinical outcome irrespective of treatment schedule in this study. This neglected parameter of the Tpot method might provide information related to redistribution of cells during fractionated radiotherapy

Single cell adhesion strength assessed with variable-angle total internal reflection fluorescence microscopy

Directory of Open Access Journals (Sweden)

Marcelina Cardoso Dos Santos

2017-06-01

Full Text Available We propose a new strategy to evaluate adhesion strength at the single cell level. This approach involves variable-angle total internal reflection fluorescence microscopy to monitor in real time the topography of cell membranes, i.e. a map of the membrane/substrate separation distance. According to the Boltzmann distribution, both potential energy profile and dissociation energy related to the interactions between the cell membrane and the substrate were determined from the membrane topography. We have highlighted on glass substrates coated with poly-L-lysine and fibronectin, that the dissociation energy is a reliable parameter to quantify the adhesion strength of MDA-MB-231 motile cells.

Kinetics and mechanisms of thiol-disulfide exchange covering direct substitution and thiol oxidation-mediated pathways.

Science.gov (United States)

Nagy, Péter

2013-05-01

Disulfides are important building blocks in the secondary and tertiary structures of proteins, serving as inter- and intra-subunit cross links. Disulfides are also the major products of thiol oxidation, a process that has primary roles in defense mechanisms against oxidative stress and in redox regulation of cell signaling. Although disulfides are relatively stable, their reduction, isomerisation, and interconversion as well as their production reactions are catalyzed by delicate enzyme machineries, providing a dynamic system in biology. Redox homeostasis, a thermodynamic parameter that determines which reactions can occur in cellular compartments, is also balanced by the thiol-disulfide pool. However, it is the kinetic properties of the reactions that best represent cell dynamics, because the partitioning of the possible reactions depends on kinetic parameters. This review is focused on the kinetics and mechanisms of thiol-disulfide substitution and redox reactions. It summarizes the challenges and advances that are associated with kinetic investigations in small molecular and enzymatic systems from a rigorous chemical perspective using biological examples. The most important parameters that influence reaction rates are discussed in detail. Kinetic studies of proteins are more challenging than small molecules, and quite often investigators are forced to sacrifice the rigor of the experimental approach to obtain the important kinetic and mechanistic information. However, recent technological advances allow a more comprehensive analysis of enzymatic systems via using the systematic kinetics apparatus that was developed for small molecule reactions, which is expected to provide further insight into the cell's machinery.

Hepatitis C treatment response kinetics and impact of baseline predictors

DEFF Research Database (Denmark)

Lindh, M; Arnholm, B; Eilard, A

2011-01-01

Summary. The optimal duration of treatment for hepatitis C virus (HCV) infections is highly variable but critical for achieving cure (sustained virological response, SVR). We prospectively investigated the impact of age, fibrosis, baseline viraemia and genotype on the early viral kinetics...... above 400 000 IU/mL were strongly associated with slower second phase declines of HCV RNA. Genotype 2/3 infections responded more rapidly than genotype 1, reaching week 4 negativity (RVR) in 59%vs 22%. We conclude that baseline response predictors such as age, fibrosis and viral load were well reflected...... by the early viral kinetics as assessed by repeated HCV RNA quantifications. The kinetic patterns and the high relapse rate in genotype 2/3 patients without RVR suggest that this group might benefit from treatment durations longer than 24 weeks....

Mathematical modeling provides kinetic details of the human immune response to vaccination

Directory of Open Access Journals (Sweden)

Dustin eLe

2015-01-01

Full Text Available With major advances in experimental techniques to track antigen-specific immune responses many basic questions on the kinetics of virus-specific immunity in humans remain unanswered. To gain insights into kinetics of T and B cell responses in human volunteers we combine mathematical models and experimental data from recent studies employing vaccines against yellow fever and smallpox. Yellow fever virus-specific CD8 T cell population expanded slowly with the average doubling time of 2 days peaking 2.5 weeks post immunization. Interestingly, we found that the peak of the yellow fever-specific CD8 T cell response is determined by the rate of T cell proliferation and not by the precursor frequency of antigen-specific cells as has been suggested in several studies in mice. We also found that while the frequency of virus-specific T cells increases slowly, the slow increase can still accurately explain clearance of yellow fever virus in the blood. Our additional mathematical model describes well the kinetics of virus-specific antibody-secreting cell and antibody response to vaccinia virus in vaccinated individuals suggesting that most of antibodies in 3 months post immunization are derived from the population of circulating antibody-secreting cells. Taken together, our analysis provides novel insights into mechanisms by which live vaccines induce immunity to viral infections and highlight challenges of applying methods of mathematical modeling to the current, state-of-the-art yet limited immunological data.

Mathematical modeling provides kinetic details of the human immune response to vaccination.

Science.gov (United States)

Le, Dustin; Miller, Joseph D; Ganusov, Vitaly V

2014-01-01

With major advances in experimental techniques to track antigen-specific immune responses many basic questions on the kinetics of virus-specific immunity in humans remain unanswered. To gain insights into kinetics of T and B cell responses in human volunteers we combined mathematical models and experimental data from recent studies employing vaccines against yellow fever and smallpox. Yellow fever virus-specific CD8 T cell population expanded slowly with the average doubling time of 2 days peaking 2.5 weeks post immunization. Interestingly, we found that the peak of the yellow fever-specific CD8 T cell response was determined by the rate of T cell proliferation and not by the precursor frequency of antigen-specific cells as has been suggested in several studies in mice. We also found that while the frequency of virus-specific T cells increased slowly, the slow increase could still accurately explain clearance of yellow fever virus in the blood. Our additional mathematical model described well the kinetics of virus-specific antibody-secreting cell and antibody response to vaccinia virus in vaccinated individuals suggesting that most of antibodies in 3 months post immunization were derived from the population of circulating antibody-secreting cells. Taken together, our analysis provided novel insights into mechanisms by which live vaccines induce immunity to viral infections and highlighted challenges of applying methods of mathematical modeling to the current, state-of-the-art yet limited immunological data.

Systematic microcarrier screening and agitated culture conditions improves human mesenchymal stem cell yield in bioreactors

Science.gov (United States)

Rafiq, Qasim A.; Coopman, Karen; Nienow, Alvin W.

2016-01-01

Abstract Production of human mesenchymal stem cells for allogeneic cell therapies requires scalable, cost‐effective manufacturing processes. Microcarriers enable the culture of anchorage‐dependent cells in stirred‐tank bioreactors. However, no robust, transferable methodology for microcarrier selection exists, with studies providing little or no reason explaining why a microcarrier was employed. We systematically evaluated 13 microcarriers for human bone marrow‐derived MSC (hBM‐MSCs) expansion from three donors to establish a reproducible and transferable methodology for microcarrier selection. Monolayer studies demonstrated input cell line variability with respect to growth kinetics and metabolite flux. HBM‐MSC1 underwent more cumulative population doublings over three passages in comparison to hBM‐MSC2 and hBM‐MSC3. In 100 mL spinner flasks, agitated conditions were significantly better than static conditions, irrespective of donor, and relative microcarrier performance was identical where the same microcarriers outperformed others with respect to growth kinetics and metabolite flux. Relative growth kinetics between donor cells on the microcarriers were the same as the monolayer study. Plastic microcarriers were selected as the optimal microcarrier for hBM‐MSC expansion. HBM‐MSCs were successfully harvested and characterised, demonstrating hBM‐MSC immunophenotype and differentiation capacity. This approach provides a systematic method for microcarrier selection, and the findings identify potentially significant bioprocessing implications for microcarrier‐based allogeneic cell therapy manufacture. PMID:26632496

Technical specifications of variable speed motors for negative pressure control in hot cell area

Energy Technology Data Exchange (ETDEWEB)

Kim, Seon Duk; Bang, H. S.; Cho, W. K

2002-01-01

Hot cells are the facilities for handling the high radioactive materials and various R and D activities are performed using hot cells. Therefore the control of air flow in hot cell area is very important technology and it is started with the variable speed motor(VSM) controlling the air handling system in that area. This report describes various technical aspects of VS motors and will be useful for understanding the practical technologies of VS motors and also for optimization of the negative pressure controls in hot cell area.

Cellular radiation effects and hyperthermia cell cycle kinetics of radiation sensitive mutants of saccharomyces cerevisiae after x-irradiation and hyperthermia

International Nuclear Information System (INIS)

Fingerhut, R.; Kiefer, J.; Otto, F.

1983-01-01

Radiosensitive mutants rad2, rad9, and rad51 of Saccharomyces cerevisiae were X-irradiated with 120 Gy or 60 Gy, heated at 50 0 C for 30 min or treated with a combination of both and incubated in nutrient medium at 30 0 C. Cell number, percentage of budding cells, and cell cycle progression were determined in 45-min intervals. Cell cycle kinetics were investigated by flow cytofluorometry. Hyperthermia leads mainly to a lengthening of G1, whereas X-rays arrest cells of the rad2 and rad9 mutant in G2 and the rad51 - mutant additionaly in a state with DNA contents above G2. Cell division dealy is influenced by oxygen in all strains but to a lesser extent in the rad2 mutant. The effect of the combined treatment appears to be merely additive in the rad2 and rad9 mutant while the rad51 mutant is sensitized to X-irradiation by hyperthermia. No selective action of hyperthermia on hypoxic cells was found. (orig.)

Glutamic Acid Signal Synchronizes Protein Synthesis Kinetics in Hepatocytes from Old Rats for the Following Several Days. Cell Metabolism Memory.

Science.gov (United States)

Brodsky, V Y; Malchenko, L A; Lazarev, D S; Butorina, N N; Dubovaya, T K; Zvezdina, N D

2018-03-01

The kinetics of protein synthesis was investigated in primary cultures of hepatocytes from old rats in serum-free medium. The rats were fed mixed fodder supplemented with glutamic acid and then transferred to a regular mixed fodder. The amplitude of protein synthesis rhythm in hepatocytes isolated from these rats increased on average 2-fold in comparison with the rats not receiving glutamic acid supplement. Based on this indicator reflecting the degree of cell-cell interactions, the cells from old rats were not different from those of young rats. The effect was preserved for 3-4 days. These results are discussed in connection with our previous data on preservation of the effect of single administration of gangliosides, noradrenaline, serotonin, and other synchronizers on various cell populations. In contrast to the other investigated factors, glutamic acid is capable of penetrating the blood-brain barrier, which makes its effect possible not only in the case of hepatocytes and other non-brain cells, but also in neurons.

Electrochemical kinetic and mass transfer model for direct ethanol alkaline fuel cell (DEAFC)

Science.gov (United States)

Abdullah, S.; Kamarudin, S. K.; Hasran, U. A.; Masdar, M. S.; Daud, W. R. W.

2016-07-01

A mathematical model is developed for a liquid-feed DEAFC incorporating an alkaline anion-exchange membrane. The one-dimensional mass transport of chemical species is modelled using isothermal, single-phase and steady-state assumptions. The anode and cathode electrochemical reactions use the Tafel kinetics approach, with two limiting cases, for the reaction order. The model fully accounts for the mixed potential effects of ethanol oxidation at the cathode due to ethanol crossover via an alkaline anion-exchange membrane. In contrast to a polymer electrolyte membrane model, the current model considers the flux of ethanol at the membrane as the difference between diffusive and electroosmotic effects. The model is used to investigate the effects of the ethanol and alkali inlet feed concentrations at the anode. The model predicts that the cell performance is almost identical for different ethanol concentrations at a low current density. Moreover, the model results show that feeding the DEAFC with 5 M NaOH and 3 M ethanol at specific operating conditions yields a better performance at a higher current density. Furthermore, the model indicates that crossover effects on the DEAFC performance are significant. The cell performance decrease from its theoretical value when a parasitic current is enabled in the model.

Probing Temperature-Dependent Recombination Kinetics in Polymer:Fullerene Solar Cells by Electric Noise Spectroscopy

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Giovanni Landi

2017-09-01

Full Text Available The influence of solvent additives on the temperature behavior of both charge carrier transport and recombination kinetics in bulk heterojunction solar cells has been investigated by electric noise spectroscopy. The observed differences in charge carrier lifetime and mobility are attributed to a different film ordering and donor-acceptor phase segregation in the blend. The measured temperature dependence indicates that bimolecular recombination is the dominant loss mechanism in the active layer, affecting the device performance. Blend devices prepared with a high-boiling-point solvent additive show a decreased recombination rate at the donor-acceptor interface as compared to the ones prepared with the reference solvent. A clear correlation between the device performance and the morphological properties is discussed in terms of the temperature dependence of the mobility-lifetime product.

CD117 immunoexpression in canine mast cell tumours: correlations with pathological variables and proliferation markers

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Pires Maria A

2007-08-01

Full Text Available Abstract Background Cutaneous mast cell tumours are one of the most common neoplasms in dogs and show a highly variable biologic behaviour. Several prognosis tools have been proposed for canine mast cell tumours, including histological grading and cell proliferation markers. CD117 is a receptor tyrosine kinase thought to play a key role in human and canine mast cell neoplasms. Normal (membrane-associated and aberrant (cytoplasmic, focal or diffuse CD117 immunoexpression patterns have been identified in canine mast cell tumours. Cytoplasmic CD117 expression has been found to correlate with higher histological grade and with a worsened post-surgical prognosis. This study addresses the role of CD117 in canine mast cell tumours by studying the correlations between CD117 immunoexpression patterns, two proliferation markers (Ki67 and AgNORs histological grade, and several other pathological variables. Results Highly significant (p Conclusion These findings highlight the key role of CD117 in the biopathology of canine MCTs and confirm the relationship between aberrant CD117 expression and increased cell proliferation and higher histological grade. Further studies are needed to unravel the cellular mechanisms underlying focal and diffuse cytoplasmic CD117 staining patterns, and their respective biopathologic relevance.

A Microdosimetric-Kinetic Model of Cell Killing by Irradiation from Permanently Incorporated Radionuclides.

Science.gov (United States)

Hawkins, Roland B

2018-01-01

An expression for the surviving fraction of a replicating population of cells exposed to permanently incorporated radionuclide is derived from the microdosimetric-kinetic model. It includes dependency on total implant dose, linear energy transfer (LET), decay rate of the radionuclide, the repair rate of potentially lethal lesions in DNA and the volume doubling time of the target population. This is used to obtain an expression for the biologically effective dose ( BED α / β ) based on the minimum survival achieved by the implant that is equivalent to, and can be compared and combined with, the BED α / β calculated for a fractionated course of radiation treatment. Approximate relationships are presented that are useful in the calculation of BED α / β for alpha- or beta-emitting radionuclides with half-life significantly greater than, or nearly equal to, the approximately 1-h repair half-life of radiation-induced potentially lethal lesions.

Bumetanide kinetics in renal failure

International Nuclear Information System (INIS)

Pentikaeinen, P.J.P.; Pasternack, A.; Lampainen, E.; Neuvonen, P.J.; Penttilae, A.

1985-01-01

To study the effects of renal failure on bumetanide kinetics, the authors administered single intravenous doses of 1.0 mg/3.08 microCi 14 C-bumetanide to six healthy subjects and 22 patients with variable degrees of renal failure. The kinetics of 14 C-bumetanide and total 14 C were adequately described by a two-compartment open model in the control subjects and in the patients. The volume of the central compartment and the distribution t1/2 were of the same order in both groups, whereas the mean (+/- SE) volume at steady state was larger (22.1 +/- 1.6 and 16.9 +/- 1.0 L) and the elimination t1/2 was longer (1.9 +/- 0.2 and 1.4 +/- 0.1 hours) in patients with renal failure than in healthy controls. Bumetanide renal clearance was lower (10 +/- 3 and 90 +/- 13 ml/min) in patients than in subjects and correlated with creatinine clearance (r = 0.784) and log serum creatinine level (r = -0.843), whereas nonrenal clearance was significantly higher in the patients (153 +/- 14 and 99 +/- 6 ml/min). Bumetanide total plasma clearance did not significantly change. The non-protein-bound, free fraction of bumetanide was higher in patients and correlated with plasma albumin levels (r = -0.777). The kinetics of total 14 C showed similar but greater changes than those of 14C-bumetanide. Thus the most important changes in bumetanide kinetics in patients with renal failure are low renal clearance and a high free fraction, with a consequent increase in nonrenal clearance, volume of distribution, and elimination t1/2

Sex-Based Differences in Knee Kinetics With Anterior Cruciate Ligament Strain on Cadaveric Impact Simulations

Science.gov (United States)

Schilaty, Nathan D.; Bates, Nathaniel A.; Nagelli, Christopher; Krych, Aaron J.; Hewett, Timothy E.

2018-01-01

Background: Females are at an increased risk of sustaining noncontact knee ligament injuries as compared with their male counterparts. The kinetics that load the anterior cruciate ligament (ACL) are still under dispute in the literature. Purpose/Hypothesis: The purpose of this study was to determine whether there are differences in knee kinetics between the sexes that lead to greater ACL strain in females when similar external loads are applied during a simulated drop vertical jump landing task. It was hypothesized that female limbs would demonstrate significant differences in knee abduction moment that predispose females to ACL injury when compared with males. Study Design: Controlled laboratory study. Methods: Motion analysis data of 67 athletes who performed a drop vertical jump were collected. The kinematic and kinetic data were used to categorize tertiles of relative risk, and these values were input into a cadaveric impact simulator to assess ligamentous loads during the simulated landing task. Uni- and multiaxial load cells and differential variable reluctance transducer strain sensors were utilized to collect kinetic data and maximum ACL strain for analysis. Conditions of external loads applied to the cadaveric limbs were systematically varied and randomized. Data were analyzed with 2-way repeated-measures analysis of variance and the Fisher exact test. Results: Five kinetic parameters were evaluated. Of the 5 kinetic variables, only knee abduction moment (KAM) demonstrated significant differences in females as compared with males (F 1,136 = 4.398, P = .038). When normalized to height and weight, this difference between males and females increased in significance (F 1,136 = 7.155, P = .008). Compared with males, females exhibited a 10.3-N·m increased knee abduction torque at 66 milliseconds postimpact and a 22.3-N·m increased abduction torque at 100 milliseconds postimpact. For loading condition, the condition of “maximum ACL strain” demonstrated a

The effect of the physical properties of the substrate on the kinetics of cell adhesion and crawling studied by an axisymmetric diffusion-energy balance coupled model.

Science.gov (United States)

Samadi-Dooki, Aref; Shodja, Hossein M; Malekmotiei, Leila

2015-05-14

In this paper an analytical approach to study the effect of the substrate physical properties on the kinetics of adhesion and motility behavior of cells is presented. Cell adhesion is mediated by the binding of cell wall receptors and substrate's complementary ligands, and tight adhesion is accomplished by the recruitment of the cell wall binders to the adhesion zone. The binders' movement is modeled as their axisymmetric diffusion in the fluid-like cell membrane. In order to preserve the thermodynamic consistency, the energy balance for the cell-substrate interaction is imposed on the diffusion equation. Solving the axisymmetric diffusion-energy balance coupled equations, it turns out that the physical properties of the substrate (substrate's ligand spacing and stiffness) have considerable effects on the cell adhesion and motility kinetics. For a rigid substrate with uniform distribution of immobile ligands, the maximum ligand spacing which does not interrupt adhesion growth is found to be about 57 nm. It is also found that as a consequence of the reduction in the energy dissipation in the isolated adhesion system, cell adhesion is facilitated by increasing substrate's stiffness. Moreover, the directional movement of cells on a substrate with gradients in mechanical compliance is explored with an extension of the adhesion formulation. It is shown that cells tend to move from soft to stiff regions of the substrate, but their movement is decelerated as the stiffness of the substrate increases. These findings based on the proposed theoretical model are in excellent agreement with the previous experimental observations.

Tracking of cell nuclei for assessment of in vitro uptake kinetics in ultrasound-mediated drug delivery using fibered confocal fluorescence microscopy.

Science.gov (United States)

Derieppe, Marc; de Senneville, Baudouin Denis; Kuijf, Hugo; Moonen, Chrit; Bos, Clemens

2014-10-01

Previously, we demonstrated the feasibility to monitor ultrasound-mediated uptake of a cell-impermeable model drug in real time with fibered confocal fluorescence microscopy. Here, we present a complete post-processing methodology, which corrects for cell displacements, to improve the accuracy of pharmacokinetic parameter estimation. Nucleus detection was performed based on the radial symmetry transform algorithm. Cell tracking used an iterative closest point approach. Pharmacokinetic parameters were calculated by fitting a two-compartment model to the time-intensity curves of individual cells. Cells were tracked successfully, improving time-intensity curve accuracy and pharmacokinetic parameter estimation. With tracking, 93 % of the 370 nuclei showed a fluorescence signal variation that was well-described by a two-compartment model. In addition, parameter distributions were narrower, thus increasing precision. Dedicated image analysis was implemented and enabled studying ultrasound-mediated model drug uptake kinetics in hundreds of cells per experiment, using fiber-based confocal fluorescence microscopy.

A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions

International Nuclear Information System (INIS)

Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C.; Brooks, Scott C; Pace, Molly; Kim, Young Jin; Jardine, Philip M.; Watson, David B.

2007-01-01

This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M. partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M. species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing NE equilibrium reactions and a set of reactive transport equations of M-NE kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions

A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions.

Science.gov (United States)

Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C; Brooks, Scott C; Pace, Molly N; Kim, Young-Jin; Jardine, Philip M; Watson, David B

2007-06-16

This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing N(E) equilibrium reactions and a set of reactive transport equations of M-N(E) kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions.

Using ground reaction force to predict knee kinetic asymmetry following anterior cruciate ligament reconstruction.

Science.gov (United States)

Dai, B; Butler, R J; Garrett, W E; Queen, R M

2014-12-01

Asymmetries in sagittal plane knee kinetics have been identified as a risk factor for anterior cruciate ligament (ACL) re-injury. Clinical tools are needed to identify the asymmetries. This study examined the relationships between knee kinetic asymmetries and ground reaction force (GRF) asymmetries during athletic tasks in adolescent patients following ACL reconstruction (ACL-R). Kinematic and GRF data were collected during a stop-jump task and a side-cutting task for 23 patients. Asymmetry indices between the surgical and non-surgical limbs were calculated for GRF and knee kinetic variables. For the stop-jump task, knee kinetics asymmetry indices were correlated with all GRF asymmetry indices (P kinetic asymmetry indices were correlated with the peak propulsion vertical GRF and vertical GRF impulse asymmetry indices (P kinetic asymmetries and therefore may assist in optimizing rehabilitation outcomes and minimizing re-injury rates. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Kinetic Typography

DEFF Research Database (Denmark)

van Leeuwen, Theo; Djonov, Emilia

2014-01-01

After discussing broad cultural drivers behind the development of kinetic typography, the chapter outlines an approach to analysing kinetic typography which is based on Halliday's theory of transitivity, as applied by Kress and Van Leeuwen to visual images.......After discussing broad cultural drivers behind the development of kinetic typography, the chapter outlines an approach to analysing kinetic typography which is based on Halliday's theory of transitivity, as applied by Kress and Van Leeuwen to visual images....

1D to 3D diffusion-reaction kinetics of defects in crystals

DEFF Research Database (Denmark)

Trinkaus, H.; Heinisch, H.L.; Barashev, A.V.

2002-01-01

Microstructural features evolving in crystalline solids from diffusion-reaction kinetics of mobile components depend crucially on the dimension of the underlying diffusion process which is commonly assumed to be three-dimensional (3D). In metals, irradiation-induced displacement cascades produce...... clusters of self-interstitials performing 1D diffusion. Changes between equivalent 1D diffusion paths and transversal diffusion result in diffusion-reaction kinetics between one and three dimensions. An analytical approach suggests a single-variable function (master curve) interpolating between the 1D...

Photocatalytic degradation kinetics and mechanism of antivirus drug-lamivudine in TiO{sub 2} dispersion

Energy Technology Data Exchange (ETDEWEB)

An, Taicheng, E-mail: antc99@gig.ac.cn [State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); An, Jibin [State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); College of Petrochemical Technology, Lanzhou University of Technology, Lanzhou 730050 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Yang, Hai [State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Li, Guiying [State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Feng, Huixia [College of Petrochemical Technology, Lanzhou University of Technology, Lanzhou 730050 (China); Nie, Xiangping [Institute of Hydrobiology, Jinan University, Guangzhou 510632 (China)

2011-12-15

Highlights: Black-Right-Pointing-Pointer Photocatalytic degradation kinetics of antivirus drug lamivudine. Black-Right-Pointing-Pointer The degradation kinetics was optimized by the single-variable-at-a-time. Black-Right-Pointing-Pointer The degradation kinetics was optimized by central composite design. Black-Right-Pointing-Pointer The contribution of reactive species was investigated with addition of scavengers. Black-Right-Pointing-Pointer Six intermediates were identified and a degradation mechanism was proposed. - Abstract: Photocatalytic degradation kinetics of antivirus drug-lamivudine in aqueous TiO{sub 2} dispersions was systematically optimized by both single-variable-at-a-time and central composite design based on the response surface methodology. Three variables, TiO{sub 2} content, initial pH and lamivudine concentration, were selected to determine the dependence of degradation efficiencies of lamivudine on independent variables. Response surface methodology modeling results indicated that degradation efficiencies of lamivudine were highly affected by TiO{sub 2} content and initial lamivudine concentration. The highest degradation efficiency was achieved at suitable amount of TiO{sub 2} and with maintaining initial lamivudine concentration to a minimum. In addition, the contribution experiments of various primary reactive species produced during the photocatalysis were investigated with the addition of different scavengers and found that hydroxyl radicals was the major reactive species involved in lamivudine degradation in aqueous TiO{sub 2}. Six degradation intermediates were identified using HPLC/MS/MS, and photocatalytic degradation mechanism of lamivudine was proposed by utilizing collective information from both experimental results of HPLC/MS/MS, ion chromatography as well as total organic carbon and theoretical data of frontier electron densities and point charges.

Cell kinetic changes in the follicular epithelium of pig skin after irradiation with single and fractionated doses of X rays

International Nuclear Information System (INIS)

Morris, G.M.; Hopewell, J.W.

1989-01-01

Changes in cell kinetics of the follicular epithelium of the pig were studied after x-irradiation with single and fractionated doses (30 fractions/39 days) and compared with previous epidermal data. In the follicular epithelium there was an initial degenerative phase, when the rate of cell depletion was independent of radiation dose and mode of administration. Repopulation was seen between the 14th and 18th days after single doses (15 or 20 Gy) and by the 28th day after the start of irradiation with fractionated doses (52.3-80.0 Gy). The degree of cell depletion and subsequent rate of repopulation were independent of dose. The regenerative phase was characterized by an increased cell proliferation. Islands of cells with appearance similar to cells in the normal follicular epithelium, were seen 18 days after a single dose of 20 Gy and 42 days after the start of fractionated irradiation. Compared with the epidermis, the follicular epithelium exhibited considerably less evidence of damage after both single and fractionated doses. There was a lower incidence of degenerate cells and reduced levels of cell depletion in the follicular epithelium. (author)

Spray Drying Processing: granules production and drying kinetics of droplets

International Nuclear Information System (INIS)

Mondragon, R.; Julia, J. E.; Barba, A.; Jarque, J. C.

2013-01-01

Spray drying is a unit operation very common in many industrial processes. For each particular application, the resulting granulated material must possess determined properties that depend on the conditions in which the spray drying processing has been carried out, and whose dependence must be known in order to optimize the quality of the material obtained. The large number of variables that influence on the processes of matter and energy transfer and on the formation of granular material has required a detailed analysis of the drying process. Over the years there have been many studies on the spray drying processing of all kind of materials and the influence of process variables on the drying kinetics of the granulated material properties obtained. This article lists the most important works published for both the spray drying processing and the drying of individual droplets, as well as studies aimed at modeling the drying kinetics of drops. (Author)

Kinetic Uptake Studies of Powdered Materials in Solution

Directory of Open Access Journals (Sweden)

Mohamed H. Mohamed

2015-06-01

Full Text Available Challenges exist for the study of time dependent sorption processes for heterogeneous systems, especially in the case of dispersed nanomaterials in solvents or solutions because they are not well suited to conventional batch kinetic experiments. In this study, a comparison of batch versus a one-pot setup in two variable configurations was evaluated for the study of uptake kinetics in heterogeneous (solid/solution systems: (i conventional batch method; (ii one-pot system with dispersed adsorbent in solution with a semi-permeable barrier (filter paper or dialysis tubing for in situ sampling; and (iii one-pot system with an adsorbent confined in a semi-permeable barrier (dialysis tubing or filter paper barrier with ex situ sampling. The sorbent systems evaluated herein include several cyclodextrin-based polyurethane materials with two types of phenolic dyes: p-nitrophenol and phenolphthalein. The one-pot kinetics method with in situ (Method ii or ex situ (Method iii sampling described herein offers significant advantages for the study of heterogeneous sorption kinetics of highly dispersed sorbent materials with particles sizes across a range of dimensions from the micron to nanometer scale. The method described herein will contribute positively to the development of advanced studies for heterogeneous sorption processes where an assessment of the relative uptake properties is required at different experimental conditions. The results of this study will be advantageous for the study of nanomaterials with significant benefits over batch kinetic studies for a wide range of heterogeneous sorption processes.

Sorption kinetics of diuron on volcanic ash derived soils.

Science.gov (United States)

Cáceres-Jensen, Lizethly; Rodríguez-Becerra, Jorge; Parra-Rivero, Joselyn; Escudey, Mauricio; Barrientos, Lorena; Castro-Castillo, Vicente

2013-10-15

Diuron sorption kinetic was studied in Andisols, Inceptisol and Ultisols soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Two types of kinetic models were used to fit the experimental dates: those that allow to establish principal kinetic parameters and modeling of sorption process (pseudo-first-order, pseudo-second-order), and some ones frequently used to describe solute transport mechanisms of organic compounds on different sorbents intended for remediation purposes (Elovich equation, intraparticle diffusion, Boyd, and two-site nonequilibrium models). The best fit was obtained with the pseudo-second-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the behavior of Diuron in each soil, in Andisols were observed the highest values for both parameters. The application of the models to describe solute transport mechanisms allowed establishing that in all soils the mass transfer controls the sorption kinetic across the boundary layer and intraparticle diffusion into macropores and micropores. The slowest sorption rate was observed on Ultisols, behavior which must be taken into account when the leaching potential of Diuron is considered. Copyright © 2013 Elsevier B.V. All rights reserved.

Differential equation methods for simulation of GFP kinetics in non-steady state experiments.

Science.gov (United States)

Phair, Robert D

2018-03-15

Genetically encoded fluorescent proteins, combined with fluorescence microscopy, are widely used in cell biology to collect kinetic data on intracellular trafficking. Methods for extraction of quantitative information from these data are based on the mathematics of diffusion and tracer kinetics. Current methods, although useful and powerful, depend on the assumption that the cellular system being studied is in a steady state, that is, the assumption that all the molecular concentrations and fluxes are constant for the duration of the experiment. Here, we derive new tracer kinetic analytical methods for non-steady state biological systems by constructing mechanistic nonlinear differential equation models of the underlying cell biological processes and linking them to a separate set of differential equations governing the kinetics of the fluorescent tracer. Linking the two sets of equations is based on a new application of the fundamental tracer principle of indistinguishability and, unlike current methods, supports correct dependence of tracer kinetics on cellular dynamics. This approach thus provides a general mathematical framework for applications of GFP fluorescence microscopy (including photobleaching [FRAP, FLIP] and photoactivation to frequently encountered experimental protocols involving physiological or pharmacological perturbations (e.g., growth factors, neurotransmitters, acute knockouts, inhibitors, hormones, cytokines, and metabolites) that initiate mechanistically informative intracellular transients. When a new steady state is achieved, these methods automatically reduce to classical steady state tracer kinetic analysis. © 2018 Phair. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Unstirred Water Layers and the Kinetics of Organic Cation Transport

Science.gov (United States)

Shibayama, Takahiro; Morales, Mark; Zhang, Xiaohong; Martinez, Lucy; Berteloot, Alfred; Secomb, Timothy W.; Wright, Stephen H.

2015-01-01

Purpose Unstirred water layers (UWLs) present an unavoidable complication in the measurement of transport kinetics in cultured cells and the high rates of transport achieved by overexpressing heterologous transporters exacerbate the UWL effect. This study examined the correlation between measured Jmax and Kt values and the effect of manipulating UWL thickness or transport Jmax on the accuracy of experimentally determined kinetics of the multidrug transporters, OCT2 and MATE1. Methods Transport of TEA and MPP was measured in CHO cells that stably expressed human OCT2 or MATE1. UWL thickness was manipulated by vigorous reciprocal shaking. Several methods were used to manipulate maximal transport rates. Results Vigorous stirring stimulated uptake of OCT2-mediated transport by decreasing apparent Kt (Ktapp) values. Systematic reduction in transport rates was correlated with reduction in Ktapp values. The slope of these relationships indicated a 1500 µm UWL in multiwell plates. Reducing the influence of UWLs (by decreasing either their thickness or the Jmax of substrate transport) reduced Ktapp by 2-fold to >10-fold. Conclusions Failure to take into account the presence of UWLs in experiments using cultured cells to measure transport kinetics can result in significant underestimates of the affinity of multidrug transporters for substrates. PMID:25791216

Variability of OH rotational temperatures on time scales from hours to 15 years by kinetic temperature variations, emission layer changes, and non-LTE effects

Science.gov (United States)

Noll, Stefan

2016-07-01

Rotational temperatures derived from hydroxyl (OH) line emission are frequently used to study atmospheric temperatures at altitudes of about 87 km. While the measurement only requires intensities of a few bright lines of an OH band, the interpretation can be complicated. Ground-based temperatures are averages for the entire, typically 8 km wide emission layer. Variations in the rotational temperature are then caused by changes of the kinetic temperature and the OH emission profile. The latter can also be accompanied by differences in the layer-averaged efficiency of the thermalisation of the OH rotational level populations. Since this especially depends on the frequency of collisions with O_2, which is low at high altitudes, the non-local thermodynamic equilibrium (non-LTE) contribution to the measured temperatures can be significant and variable. In order to understand the impact of the different sources of OH rotational temperature variations from time scales of hours to a solar cycle, we have studied spectra from the astronomical echelle spectrographs X-shooter and UVES located at Cerro Paranal in Chile. While the X-shooter data spanning 3.5 years allowed us to measure temperatures for 25 OH and two O_2 bands, the UVES spectra cover no more than 10 OH bands simultaneously but a period of about 15 years. These data have been complemented by kinetic temperature and OH and O_2 emission profiles from the multi-channel radiometer SABER on the TIMED satellite. Taking the O_2 and SABER kinetic temperatures as reference and considering the different band-dependent emission profiles, we could evaluate the contribution of non-LTE effects to the measured OH rotational temperatures depending on line set, band, and time. Non-LTE contributions are significant for most bands and can exceed 10 K. The amplitudes of their average nocturnal and seasonal variation are of the order of 1 to 2 K.

Tissue kinetics, ion transport, and recruitment of mitochondria-rich cells in the skin of the toad (Bufo bufo) in response to exposure to distilled water

DEFF Research Database (Denmark)

Budtz, Poul Egede; Christoffersen, Betina C.; Johansen, Jesper S.

1995-01-01

Mitochondria-rich cells (MRC) of the amphibian epidermis are responsible for active chloride uptake at low external salinity, and new MRCs are recruited in response to exposure to distilled (deionized) water. The time-course of this recruitment, the tissue kinetics and ion transport have been...

Predicting rainfall erosivity by momentum and kinetic energy in Mediterranean environment

Science.gov (United States)

Carollo, Francesco G.; Ferro, Vito; Serio, Maria A.

2018-05-01

Rainfall erosivity is an index that describes the power of rainfall to cause soil erosion and it is used around the world for assessing and predicting soil loss on agricultural lands. Erosivity can be represented in terms of both rainfall momentum and kinetic energy, both calculated per unit time and area. Contrasting results on the representativeness of these two variables are available: some authors stated that momentum and kinetic energy are practically interchangeable in soil loss estimation while other found that kinetic energy is the most suitable expression of rainfall erosivity. The direct and continuous measurements of momentum and kinetic energy by a disdrometer allow also to establish a relationship with rainfall intensity at the study site. At first in this paper a comparison between the momentum-rainfall intensity relationships measured at Palermo and El Teularet by an optical disdrometer is presented. For a fixed rainfall intensity the measurements showed that the rainfall momentum values measured at the two experimental sites are not coincident. However both datasets presented a threshold value of rainfall intensity over which the rainfall momentum assumes a quasi-constant value. Then the reliability of a theoretically deduced relationship, linking momentum, rainfall intensity and median volume diameter, is positively verified using measured raindrop size distributions. An analysis to assess which variable, momentum or kinetic energy per unit area and time, is the best predictor of erosivity in Italy and Spain was also carried out. This investigation highlighted that the rainfall kinetic energy per unit area and time can be substituted by rainfall momentum as index for estimating the rainfall erosivity, and this result does not depend on the site where precipitation occurs. Finally, rainfall intensity measurements and soil loss data collected from the bare plots equipped at Sparacia experimental area were used to verify the reliability of some

Estrone-1-sulphate (E1S) has impact on the kinetics parameters of transporter mediated taurine and glutamate influx in Caco-2 cells

DEFF Research Database (Denmark)

Steffansen, Bente; El-Sayed, F

Previously, we have suggested estrone-1-sulfate (E1S) to be intercalated into the phospholipid membrane 1,2-dipalmitoyl-sn-glycero-3-phospho-choline (DPPC). The overall hypothesis of the present study was that E1S intercalation in the cell membrane of Caco-2 cells may changes the functionality...... of membrane transporters. The aim was therefore to investigate if addition of E1S to the growth medium of Caco-2 cells before but not during the influx study, change the kinetic parameters of transporter-mediated influx of taurine and glutamate by respective TAUT and EAAT transporters. The results show that 4...

An Integrated Workflow To Assess Technical and Biological Variability of Cell Population Frequencies in Human Peripheral Blood by Flow Cytometry.

Science.gov (United States)

Burel, Julie G; Qian, Yu; Lindestam Arlehamn, Cecilia; Weiskopf, Daniela; Zapardiel-Gonzalo, Jose; Taplitz, Randy; Gilman, Robert H; Saito, Mayuko; de Silva, Aruna D; Vijayanand, Pandurangan; Scheuermann, Richard H; Sette, Alessandro; Peters, Bjoern

2017-02-15

In the context of large-scale human system immunology studies, controlling for technical and biological variability is crucial to ensure that experimental data support research conclusions. In this study, we report on a universal workflow to evaluate both technical and biological variation in multiparameter flow cytometry, applied to the development of a 10-color panel to identify all major cell populations and T cell subsets in cryopreserved PBMC. Replicate runs from a control donation and comparison of different gating strategies assessed the technical variability associated with each cell population and permitted the calculation of a quality control score. Applying our panel to a large collection of PBMC samples, we found that most cell populations showed low intraindividual variability over time. In contrast, certain subpopulations such as CD56 T cells and Temra CD4 T cells were associated with high interindividual variability. Age but not gender had a significant effect on the frequency of several populations, with a drastic decrease in naive T cells observed in older donors. Ethnicity also influenced a significant proportion of immune cell population frequencies, emphasizing the need to account for these covariates in immune profiling studies. We also exemplify the usefulness of our workflow by identifying a novel cell-subset signature of latent tuberculosis infection. Thus, our study provides a universal workflow to establish and evaluate any flow cytometry panel in systems immunology studies. Copyright © 2017 by The American Association of Immunologists, Inc.

Kinetic modeling and exploratory numerical simulation of chloroplastic starch degradation

Directory of Open Access Journals (Sweden)

Nag Ambarish

2011-06-01

Full Text Available Abstract Background Higher plants and algae are able to fix atmospheric carbon dioxide through photosynthesis and store this fixed carbon in large quantities as starch, which can be hydrolyzed into sugars serving as feedstock for fermentation to biofuels and precursors. Rational engineering of carbon flow in plant cells requires a greater understanding of how starch breakdown fluxes respond to variations in enzyme concentrations, kinetic parameters, and metabolite concentrations. We have therefore developed and simulated a detailed kinetic ordinary differential equation model of the degradation pathways for starch synthesized in plants and green algae, which to our knowledge is the most complete such model reported to date. Results Simulation with 9 internal metabolites and 8 external metabolites, the concentrations of the latter fixed at reasonable biochemical values, leads to a single reference solution showing β-amylase activity to be the rate-limiting step in carbon flow from starch degradation. Additionally, the response coefficients for stromal glucose to the glucose transporter kcat and KM are substantial, whereas those for cytosolic glucose are not, consistent with a kinetic bottleneck due to transport. Response coefficient norms show stromal maltopentaose and cytosolic glucosylated arabinogalactan to be the most and least globally sensitive metabolites, respectively, and β-amylase kcat and KM for starch to be the kinetic parameters with the largest aggregate effect on metabolite concentrations as a whole. The latter kinetic parameters, together with those for glucose transport, have the greatest effect on stromal glucose, which is a precursor for biofuel synthetic pathways. Exploration of the steady-state solution space with respect to concentrations of 6 external metabolites and 8 dynamic metabolite concentrations show that stromal metabolism is strongly coupled to starch levels, and that transport between compartments serves to

Kinetics of phototoxicity of Fischer's medium for L5178Y leukemic cells

International Nuclear Information System (INIS)

Griffin, F.M.; Ashland, G.; Capizzi, R.L.

1981-01-01

The uncontrolled exposure of Fischer's medium to cool white fluorescent (CWF) light or other sources emitting near-ultraviolet or visible light absorbance by riboflavin is a crucial random variable in experiments which utilize L5178Y cells and this medium. The radiation effects of CWF light result in the rapid development of toxic photoproducts in the medium which are cytostatic at lower doses of radiation and cytotoxic at higher doses. After a 24-hr suspension in medium irradiated for 3 or 48 hr, the cloning efficiencies of cells subsequently plated in light-protected medium were 87 and 3%, respectively. The corresponding near-ultraviolet doses for these periods of exposure to CWF light were 0.22 x 10(4) for a 3-hr exposure and 3.47 x 10(4) J/sq m for a 48-hr exposure. Cells incubated in lightly irradiated medium resumed growth at nearly normal rates following a 24- to 48-hr period in which no increase in cell numbers occurred. Exposure of medium containing riboflavin, but not tryptophan or tyrosine, to CWF light also produces toxic medium. Tryptophan enhances riboflavin-induced phototoxicity, whereas tyrosine diminishes this effect. As photosusceptibility of this system is very high, Fischer's medium must be fully protected from all sources of light absorbable by riboflavin

Cell-cell transmission of VSV-G pseudotyped lentivector particles.

Directory of Open Access Journals (Sweden)

Amy M Skinner

Full Text Available Many replicating viruses, including HIV-1 and HTLV-1, are efficiently transmitted from the cell surface of actively infected cells upon contact with bystander cells. In a previous study, we reported the prolonged cell surface retention of VSV-G replication-deficient pseudotyped lentivector prior to endocytic entry. However, the competing kinetics of cell surface versus dissociation, neutralization or direct transfer to other cells have received comparatively little attention. Here we demonstrate that the relative efficiency of cell-cell surface transmission can outpace "cell-free" transduction at limiting vector input. This coincides with the prolonged half-life of cell bound vector but occurs, unlike HTLV-1, without evidence for particle aggregation. These studies suggest that cell-surface attachment stabilizes particles and alters neutralization kinetics. Our experiments provide novel insight into the underexplored cell-cell transmission of pseudotyped particles.

A Kinetic Model Describing Injury-Burden in Team Sports.

Science.gov (United States)

Fuller, Colin W

2017-12-01

Injuries in team sports are normally characterised by the incidence, severity, and location and type of injuries sustained: these measures, however, do not provide an insight into the variable injury-burden experienced during a season. Injury burden varies according to the team's match and training loads, the rate at which injuries are sustained and the time taken for these injuries to resolve. At the present time, this time-based variation of injury burden has not been modelled. To develop a kinetic model describing the time-based injury burden experienced by teams in elite team sports and to demonstrate the model's utility. Rates of injury were quantified using a large eight-season database of rugby injuries (5253) and exposure (60,085 player-match-hours) in English professional rugby. Rates of recovery from injury were quantified using time-to-recovery analysis of the injuries. The kinetic model proposed for predicting a team's time-based injury burden is based on a composite rate equation developed from the incidence of injury, a first-order rate of recovery from injury and the team's playing load. The utility of the model was demonstrated by examining common scenarios encountered in elite rugby. The kinetic model developed describes and predicts the variable injury-burden arising from match play during a season of rugby union based on the incidence of match injuries, the rate of recovery from injury and the playing load. The model is equally applicable to other team sports and other scenarios.

Kinetics of Surfactant Desorption at an Air–Solution Interface

KAUST Repository

Morgan, C. E.; Breward, C. J. W.; Griffiths, I. M.; Howell, P. D.; Penfold, J.; Thomas, R. K.; Tucker, I.; Petkov, J. T.; Webster, J. R. P.

2012-01-01

The kinetics of re-equilibration of the anionic surfactant sodium dodecylbenzene sulfonate at the air-solution interface have been studied using neutron reflectivity. The experimental arrangement incorporates a novel flow cell in which the subphase

Removal of mercury(II) from aqueous media using eucalyptus bark: Kinetic and equilibrium studies

International Nuclear Information System (INIS)

Ghodbane, Ilhem; Hamdaoui, Oualid

2008-01-01

In this study, eucalyptus camaldulensis bark, a forest solid waste, is proposed as a novel material for the removal of mercury(II) from aqueous phase. The operating variables studied were sorbent dosage, ionic strength, stirring speed, temperature, solution pH, contact time, and initial metal concentration. Sorption experiments indicated that the sorption capacity was dependent on operating variables and the process was strongly pH-dependent. Kinetic measurements showed that the process was uniform and rapid. In order to investigate the mechanism of sorption, kinetic data were modeled using the pseudo-first-order and pseudo-second-order kinetic equations, and intraparticle diffusion model. Among the kinetic models studied, the pseudo-second-order equation was the best applicable model to describe the sorption process. Equilibrium isotherm data were analyzed using the Langmuir and the Freundlich isotherms. The Langmuir model yields a much better fit than the Freundlich model. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy, and entropy of sorption. The maximum sorption capacity was 33.11 mg g -1 at 20 deg. C and the negative value of free energy change indicated the spontaneous nature of sorption. These results demonstrate that eucalyptus bark is very effective in the removal of Hg(II) from aqueous solutions

Bubble extinction in Hele-Shaw flow with surface tension and kinetic undercooling regularization

International Nuclear Information System (INIS)

Dallaston, Michael C; McCue, Scott W

2013-01-01

We perform an analytic and numerical study of an inviscid contracting bubble in a two-dimensional Hele-Shaw cell, where the effects of both surface tension and kinetic undercooling on the moving bubble boundary are not neglected. In contrast to expanding bubbles, in which both boundary effects regularize the ill-posedness arising from the viscous (Saffman–Taylor) instability, we show that in contracting bubbles the two boundary effects are in competition, with surface tension stabilizing the boundary, and kinetic undercooling destabilizing it. This competition leads to interesting bifurcation behaviour in the asymptotic shape of the bubble in the limit it approaches extinction. In this limit, the boundary may tend to become either circular, or approach a line or ‘slit’ of zero thickness, depending on the initial condition and the value of a nondimensional surface tension parameter. We show that over a critical range of surface tension values, both these asymptotic shapes are stable. In this regime there exists a third, unstable branch of limiting self-similar bubble shapes, with an asymptotic aspect ratio (dependent on the surface tension) between zero and one. We support our asymptotic analysis with a numerical scheme that utilizes the applicability of complex variable theory to Hele-Shaw flow. (paper)

Evaluation of tools for highly variable gene discovery from single-cell RNA-seq data.

Science.gov (United States)

Yip, Shun H; Sham, Pak Chung; Wang, Junwen

2018-02-21

Traditional RNA sequencing (RNA-seq) allows the detection of gene expression variations between two or more cell populations through differentially expressed gene (DEG) analysis. However, genes that contribute to cell-to-cell differences are not discoverable with RNA-seq because RNA-seq samples are obtained from a mixture of cells. Single-cell RNA-seq (scRNA-seq) allows the detection of gene expression in each cell. With scRNA-seq, highly variable gene (HVG) discovery allows the detection of genes that contribute strongly to cell-to-cell variation within a homogeneous cell population, such as a population of embryonic stem cells. This analysis is implemented in many software packages. In this study, we compare seven HVG methods from six software packages, including BASiCS, Brennecke, scLVM, scran, scVEGs and Seurat. Our results demonstrate that reproducibility in HVG analysis requires a larger sample size than DEG analysis. Discrepancies between methods and potential issues in these tools are discussed and recommendations are made.

Kinetics and Mechanisms of Thiol–Disulfide Exchange Covering Direct Substitution and Thiol Oxidation-Mediated Pathways

Science.gov (United States)

2013-01-01

Abstract Significance: Disulfides are important building blocks in the secondary and tertiary structures of proteins, serving as inter- and intra-subunit cross links. Disulfides are also the major products of thiol oxidation, a process that has primary roles in defense mechanisms against oxidative stress and in redox regulation of cell signaling. Although disulfides are relatively stable, their reduction, isomerisation, and interconversion as well as their production reactions are catalyzed by delicate enzyme machineries, providing a dynamic system in biology. Redox homeostasis, a thermodynamic parameter that determines which reactions can occur in cellular compartments, is also balanced by the thiol–disulfide pool. However, it is the kinetic properties of the reactions that best represent cell dynamics, because the partitioning of the possible reactions depends on kinetic parameters. Critical Issues: This review is focused on the kinetics and mechanisms of thiol–disulfide substitution and redox reactions. It summarizes the challenges and advances that are associated with kinetic investigations in small molecular and enzymatic systems from a rigorous chemical perspective using biological examples. The most important parameters that influence reaction rates are discussed in detail. Recent Advances and Future Directions: Kinetic studies of proteins are more challenging than small molecules, and quite often investigators are forced to sacrifice the rigor of the experimental approach to obtain the important kinetic and mechanistic information. However, recent technological advances allow a more comprehensive analysis of enzymatic systems via using the systematic kinetics apparatus that was developed for small molecule reactions, which is expected to provide further insight into the cell's machinery. Antioxid. Redox Signal. 18, 1623–1641. PMID:23075118

Kinetic energy of throughfall in a highly diverse forest ecosystem in the humid subtropics

Science.gov (United States)

Geißler, Christian; Kühn, Peter; Scholten, Thomas

2010-05-01

conditions. Most of the energy is supposed to be absorbed by shrubs, herbs and the litter layer. For some species in the shrub and herb layer throughfall drops are crucial for seed dispersal (Nakanishi 2002). A higher kinetic energy of throughfall should be advantageous for seed dispersal and probably support biodiversity. Further, it is shown that the variability of kinetic energy in forests varies among the age of the forest stand which can be related to the forest structure. In our case there is a high variability in young forests (left out) and gaps in the tree layer. Old forests (> 80 years) also have a high variability in kinetic energy. There, external influences like snow and wind break result in a fragmentary tree layer which allows less erosive rainfall to reach the forest floor. Medium aged forests are more homogenous regarding canopy closure or tree heights. Generally, the variability of kinetic energy in forests is increasing with the amount of rainfall. Moreover, it is shown that the kinetic energy of throughfall is species specific. For the investigated tree species the values range between 24.41 J m-2 mm-1 (Daphniphyllum oldhamii) and 33.24 J m-2 mm-1 (Schima superba) while the concurrent rainfall in the open field has an average kinetic energy of 6.75 J m-2 mm-1. Leaf size and canopy architecture are supposed to be two of the controlling variables for specific species. These results give implications for afforestation measures and are important input variables for modeling of erosion processes. Chapman, G., 1948. Size of raindrops and their striking force at the soil surface in a Red Pine plantation. Transactions - American Geophysical Union, 29: 664-670. Ellison, W.D., 1947. Soil Erosion Studies - Part II. Agricultural Engineering, 28: 197-201. Geißler, C., Kühn, P., Böhnke, M., Bruelheide, H., Shi, X., Scholten, T., under review: Measuring splash erosion potential under vegetation using sand-filled splash cups. Hall, R.L., Calder, I.R., 1993. Drop size

A genetically optimized kinetic model for ethanol electro-oxidation on Pt-based binary catalysts used in direct ethanol fuel cells

Science.gov (United States)

Sánchez-Monreal, Juan; García-Salaberri, Pablo A.; Vera, Marcos

2017-09-01

A one-dimensional model is proposed for the anode of a liquid-feed direct ethanol fuel cell. The complex kinetics of the ethanol electro-oxidation reaction is described using a multi-step reaction mechanism that considers free and adsorbed intermediate species on Pt-based binary catalysts. The adsorbed species are modeled using coverage factors to account for the blockage of the active reaction sites on the catalyst surface. The reaction rates are described by Butler-Volmer equations that are coupled to a one-dimensional mass transport model, which incorporates the effect of ethanol and acetaldehyde crossover. The proposed kinetic model circumvents the acetaldehyde bottleneck effect observed in previous studies by incorporating CH3CHOHads among the adsorbed intermediates. A multi-objetive genetic algorithm is used to determine the reaction constants using anode polarization and product selectivity data obtained from the literature. By adjusting the reaction constants using the methodology developed here, different catalyst layers could be modeled and their selectivities could be successfully reproduced.

Synergistic kinetic inhibition of natural gas hydrate formation

DEFF Research Database (Denmark)

Daraboina, Nagu; Malmos, Christine; von Solms, Nicolas

2013-01-01

Rocking cells were used to investigate the natural gas hydrate formation and decomposition in the presence of kinetic inhibitor, Luvicap. In addition, the influence of poly ethylene oxide (PEO) and NaCl on the performance of Luvicap was investigated using temperature ramping and isothermal...

Non-isothermal kinetics model to predict accurate phase transformation and hardness of 22MnB5 boron steel

Energy Technology Data Exchange (ETDEWEB)

Bok, H.-H.; Kim, S.N.; Suh, D.W. [Graduate Institute of Ferrous Technology, POSTECH, San 31, Hyoja-dong, Nam-gu, Pohang, Gyeongsangbuk-do (Korea, Republic of); Barlat, F., E-mail: f.barlat@postech.ac.kr [Graduate Institute of Ferrous Technology, POSTECH, San 31, Hyoja-dong, Nam-gu, Pohang, Gyeongsangbuk-do (Korea, Republic of); Lee, M.-G., E-mail: myounglee@korea.ac.kr [Department of Materials Science and Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul (Korea, Republic of)

2015-02-25

A non-isothermal phase transformation kinetics model obtained by modifying the well-known JMAK approach is proposed for application to a low carbon boron steel (22MnB5) sheet. In the modified kinetics model, the parameters are functions of both temperature and cooling rate, and can be identified by a numerical optimization method. Moreover, in this approach the transformation start and finish temperatures are variable instead of the constants that depend on chemical composition. These variable reference temperatures are determined from the measured CCT diagram using dilatation experiments. The kinetics model developed in this work captures the complex transformation behavior of the boron steel sheet sample accurately. In particular, the predicted hardness and phase fractions in the specimens subjected to a wide range of cooling rates were validated by experiments.

Histological and autoradiographic studies on the kinetics of bronchial epithelium cells of fetal rat lungs

International Nuclear Information System (INIS)

Aue, L.; Schneider, K.

1978-01-01

The kinetics of bronchial epithelium cells was investigated in 14- to 20-days old rats of an inbred strain (Wistar-WU, Mueller/Haan). In agreement with the data of the relevant literature, light microscopy revealed a successive evolution of the bronchial tree which consists of a glandular, a canalicular, and an alveolar part. Prophases, metaphases and reconstruction phases are relatively long mitotic phases, while anaphases and telophases are relatively short ones. Combined nuclear volumetry and autoradiography showed that the G-1 phase nuclei are smaller than the 3 H-labelled nuclei at the onset of the S phase and these, in turn, are smaller than the nuclei at the end of the S phase with double 14 C- or 3 H-label or with 'strong' 3H label. (orig./MG) [de

The formation of double-strand breaks at multiply damaged sites is driven by the kinetics of excision/incision at base damage in eukaryotic cells

International Nuclear Information System (INIS)

Kozmin, S.G.; Sedletska, Y.; Reynaud-Angelin, A.; Sage, E.; Kozmin, S.G.; Sedletska, Y.; Reynaud-Angelin, A.; Sage, E.; Gasparutto, D.

2009-01-01

It has been stipulated that repair of clustered DNA lesions may be compromised, possibly leading to the formation of double-strand breaks (DSB) and, thus, to deleterious events. Using a variety of model multiply damaged sites (MDS), we investigated parameters that govern the formation of DSB during the processing of MDS. Duplexes carrying MDS were inserted into replicative or integrative vectors, and used to transform yeast Saccharomyces cerevisiae. Formation of DSB was assessed by a relevant plasmid survival assay. Kinetics of excision/incision and DSB formation at MDS was explored using yeast cell extracts. We show that MDS composed of two uracils or abasic sites, were rapidly incised and readily converted into DSB in yeast cells. In marked contrast, none of the MDS carrying opposed oG and hU separated by 38 bp gave rise to DSB, despite the fact that some of them contained preexisting single-strand break (a 1-nt gap). Interestingly, the absence of DSB formation in this case correlated with slow excision/incision rates of lesions. We propose that the kinetics of the initial repair steps at MDS is a major parameter that direct towards the conversion of MDS into DSB. Data provides clues to the biological consequences of MDS in eukaryotic cells. (authors)

Influence of oxalic acid on the dissolution kinetics of manganese oxide

Science.gov (United States)

Godunov, E. B.; Artamonova, I. V.; Gorichev, I. G.; Lainer, Yu. A.

2012-11-01

The kinetics and electrochemical processes of the dissolution of manganese oxides with various oxidation states in sulfuric acid solutions containing oxalate ion additives is studied under variable conditions (concentration, pH, temperature). The parameters favoring a higher degree of the dissolution of manganese oxides in acidic media are determined. The optimal conditions are found for the dissolution of manganese oxides in acidic media in the presence of oxalate ions. The mechanism proposed for the dissolution of manganese oxides in sulfuric acid solutions containing oxalic acid is based on the results of kinetic and electrochemical studies. The steps of the dissolution mechanism are discussed.

Seasonal variability in the vertical current structure and kinetic energy in the Central Indian Ocean Basin

Digital Repository Service at National Institute of Oceanography (India)

Murty, V.S.N.; Savin, M.; RameshBabu, V.; Suryanarayana, A.

apart, indicates the existence of anticyclonic gyral circulation. The depth variation of kinetic energy (KE) emphasises the bottom intensification of currents with minimum KE at deeper depths followed by relatively higher KE at abyssal depths...

The combined effect of thermodynamic promoters tetrahydrofuran and cyclopentane on the kinetics of flue gas hydrate formation

DEFF Research Database (Denmark)

Daraboina, Nagu; von Solms, Nicolas

2015-01-01

) hydrate formation using a rocking cell apparatus. Hydrate formation and decomposition kinetics were investigated by constant cooling (hydrate nucleation temperature) and isothermal (hydrate nucleation time) methods. Improved (synergistic) hydrate formation kinetics (hydrate nucleation and growth) were...... of these two promoters is favorable both thermodynamically and kinetically for hydrate formation from flue gas....

An algorithm for the design and tuning of RF accelerating structures with variable cell lengths

Science.gov (United States)

Lal, Shankar; Pant, K. K.

2018-05-01

An algorithm is proposed for the design of a π mode standing wave buncher structure with variable cell lengths. It employs a two-parameter, multi-step approach for the design of the structure with desired resonant frequency and field flatness. The algorithm, along with analytical scaling laws for the design of the RF power coupling slot, makes it possible to accurately design the structure employing a freely available electromagnetic code like SUPERFISH. To compensate for machining errors, a tuning method has been devised to achieve desired RF parameters for the structure, which has been qualified by the successful tuning of a 7-cell buncher to π mode frequency of 2856 MHz with field flatness algorithm and tuning method have demonstrated the feasibility of developing an S-band accelerating structure for desired RF parameters with a relatively relaxed machining tolerance of ∼ 25 μm. This paper discusses the algorithm for the design and tuning of an RF accelerating structure with variable cell lengths.

Perturbative method for the derivation of quantum kinetic theory based on closed-time-path formalism

International Nuclear Information System (INIS)

Koide, Jun

2002-01-01

Within the closed-time-path formalism, a perturbative method is presented, which reduces the microscopic field theory to the quantum kinetic theory. In order to make this reduction, the expectation value of a physical quantity must be calculated under the condition that the Wigner distribution function is fixed, because it is the independent dynamical variable in the quantum kinetic theory. It is shown that when a nonequilibrium Green function in the form of the generalized Kadanoff-Baym ansatz is utilized, this condition appears as a cancellation of a certain part of contributions in the diagrammatic expression of the expectation value. Together with the quantum kinetic equation, which can be derived in the closed-time-path formalism, this method provides a basis for the kinetic-theoretical description

Relations between the kinetic equation and the Langevin models in two-phase flow modelling

International Nuclear Information System (INIS)

Minier, J.P.; Pozorski, J.

1997-05-01

The purpose of this paper is to discuss PDF and stochastic models which are used in two-phase flow modelling. The aim of the present analysis is essentially to try to determine relations and consistency between different models. It is first recalled that different approaches actually correspond to PDF models written either in terms of the process trajectories or in terms of the PDF itself. The main difference lies in the choice of the independent variables which are retained. Two particular models are studied, the Kinetic Equation and the Langevin Equation model. The latter uses a Langevin equation to model the fluid velocities seen along particle trajectories. The Langevin model is more general since it contains an additional variable. It is shown that, in certain cases, this variable can be summed up exactly to retrieve the Kinetic Equation model as a marginal PDF. A joint fluid and solid particle PDF which includes the characteristics of both phases is proposed at the end of the paper. (author)

Cell proliferation and thymocyte subset reconstitution in sublethally irradiated mice: Compared kinetics of endogenous and intrathymically transferred progenitors

International Nuclear Information System (INIS)

Penit, C.; Ezine, S.

1989-01-01

After sublethal (6 Gy) whole-body irradiation, the C57BL/Ba (Thy-1.1) murine thymus regenerated in two waves, on days 3-10 and 25-32, separated by a severe relapse. The second phase of depletion-reconstitution reproduced the first one, in a less synchronous manner. The depletion affected all cell subsets, but CD4+ CD8- cells decreased later than immature cells. Cell proliferation, measured by BrdUrd incorporation, started on day 3 after irradiation and concerned CD4- CD8-, CD4- CD8+, and CD4+ CD8+ cells, sequentially. CD4+ CD8- cells never represented a significant percentage of cycling cells. When irradiation was immediately followed by an intrathymic injection of 10(5) C57BL/Ka (Thy-1.2) bone marrow cells, the relapse in thymus reconstitution was no longer observed. Detected with anti-Thy-1.2 antibodies, donor cells started cycling on day 14 and showed only one wave of proliferation. In these chimeras, recipient thymocytes behave exactly like thymocytes of solely irradiated mice. Intrathymically transferred CD4- CD8- thymocytes 10(5) showed the same proliferation kinetics as endogenous cells, with a peak in number on day 10 but completely disappeared from the thymus on days 14-21. These data reflect maturational differences between intrathymic and bone marrow precursor cells and suggest different radiosensitivities not linked to proliferative status. The resting state of the thymus immigrants was shown by the absence of Thy-1 acquisition by bone marrow cells continuously labeled for 10 days with BrdUrd in vivo before intrathymic transfer. When such labeled bone marrow cells were injected in the thymus, only the minor BrdUrd- subset gave rise to Thy-1+ cells

Study of growth kinetic and modeling of ethanol production by ...