Full Text Available Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 Pancreatic cancer is a major cause of morbidity and mortality in developed and developing countries. We studied the chemopreventive effect of Phyllanthus amarus on tissue lipid peroxidation and antioxidant status, which is used as biomarkers in azaserine induced pancreatic carcinogenesis in wistar rats. Male albino rats were randomized into 8 groups of animals each. Rats in group 1 received 1.0 ml of 0.5% carboxyl methyl cellulose (CMC everyday via intragastric intubation and served as an untreated control. Groups 2- 4 rats received Phyllanthus amarus via intragastric intubation (p.o at a daily dose of (100, 150, 200 mg/kg body weight. The rats in groups 5-8 received azaserine (5 mg/kg body weight injection once in a week intraperitonially (i.p for 3 weeks. In addition, groups 6 - 8 received Phyllanthus amarus as in groups 2-4 respectively and continued till the end of the experimental period. The animals were sacrificed at the end of 3 weeks. In the presence of azaserine, relative to the results for the control rats, there were increased levels of lipid peroxidation, as denoted by thiobarbituric acid reactive substances and decreased activities of the enzymatic antioxidants (superoxide dismutase (SOD, catalase (CAT, glutathione peroxidase (GPx, reduced glutathione (GSH. In Our study show that intragastric administration of Phyllanthus amarus inhibits pancreatic carcinogenesis, not only by modulating lipid peroxidation and antioxidant status, but also by preventing azaserine induced histopathological changes. Our results thus indicate that Phyllanthus amarus may act as a chemopreventive agent for pancreatic carcinogenesis.
Appel, M J; Meijers, M.; Van Garderen-Hoetmer, A.; Lamers, C B; Rovati, L. C.; Sprij-Mooij, D.; Jansen, J B; Woutersen, R.A.
The role of cholecystokinin in dietary fat-promoted pancreatic carcinogenesis was investigated in azaserine-treated rats, using lorglumide, a highly specific cholecystokinin-receptor antagonist. The animals were killed 8 months after the start of treatment. Cholecystokinin, but not dietary unsaturated fat, increased pancreatic weight. Rats treated with cholecystokinin developed more acidophilic atypical acinar cell nodules, adenomas and adenocarcinomas than control animals. Rats maintained on...
Appel, M.J.; Woutersen, R.A.
The present study was performed to investigate the influence of fish oil on the genotoxic effects of azaserine, using the formation of micronucleated erythrocytes as a measure for the degree of initiating potency and the number and size of putative preneoplastic pancreatic atypical acinar cell foci
Mérida, A; Candau, P.; Florencio, F.J.
Glutamine synthetase activity from Synechocystis sp. strain PCC 6803 is regulated as a function of the nitrogen source available in the medium. Addition of 0.25 mM NH4Cl to nitrate-grown cells promotes a clear short-term inactivation of glutamine synthetase, whose enzyme activity decreases to 5 to 10% of the initial value in 25 min. The intracellular levels of glutamine, determined under various conditions, taken together with the results obtained with azaserine (an inhibitor of transamidases...
Kangni Chen; Jing Zhang; (O)mür Yilmaz Tastan; Zillah Anne Deussen; Mayte Yu-Yin Siswick; Ji-Long Liu
CTP synthase is compartmentalized within a subcellular structure,termed the cytoophidium,in a range of organisms including bacteria,yeast,fruit fly and rat.Here we show that CTP synthase is also compartmentalized into cytoophidia in human cells.Surprisingly,the occurrence of cyloophidia in human cells increases upon treatment with a glutamine analog 6-diazo-5-oxo-L-norleucine (DON),an inhibitor of glutaminedependent enzymes including CTP synthase.Experiments in flies confirmned that DON globally promotes cytoophidium assembly.Clonal analysis via CTP synthase RNA interference in somatic cells indicates that CTP synthase expression level is critical for the formation of cytoophidia.Moreover,DON facilitates cytoophidium assembly even when CTP synthase level is low.A second glutamine analog azaserine also promotes cytoophidum formation.Our data demonstrate that glutamine analogs serve as useful tools in the study of cytoophidia.
Leary, R.; Larsen, D.; Watanabe, H.; Shaw, E.
The diazomethyl ketones of z-Phe and z-Phe-Phe inactivate papain by a stoichiometric reaction at the active-center thiol. Since the reagents are stable in mercaptoethanol, their reaction with papain is judged to be the result of complex formation characteristic of affinity-labeling reagents. The diazomethyl ketones react by a mechanism different from that of chloromethyl ketones, since the pH dependence of their inactivation of papain is different, the rate increasing with decreasing pH. This relationship has been observed in other cases, such as the reaction of azaserine with glutamine amidotransferases (Buchanan, J. M. (1973), Adv. Enzmol. Relat. Areas Mol. Biol. 39, 91), and is interpreted as an indication of reaction with a thiol group in its protonated form.
Dowell, K E; Armstrong, D M; Aust, J B; Cruz, A B
Several Phase II chemotherapy protocols were evaluated in patients with advanced malignancies; 158 were evaluable head and neck cases. The protocols were as follows: five-drug combination (COMFP), four-drug (COMF), (CCNU, Adriamycin, DTIC, and cytosine arabinoside. Insufficient numbers and data were received to adequately evaluate Yoshi 864, 5 Azacytidine, porfiromycin, BCNU, and Azaserine. Significant responses to therapy were noted in the four and five-drug combinations in which 30-44% of the patients had 50% or greater regression, with an average duration of 2.2 months. Adriamycin and CCNU demonstrated lesser antitumor effects, while DTIC and cytosine arabinoside did not demonstrate significant antitumor activity in the head and neck areas. Usual toxicity consisted largely of nausea and vomiting, leukopenia, and thrombocytopenia. Alopecia was not pronouced in Adriamycin-treated patients. It appears that combination chemotherapy had a higher response rate compared to single agents used in the different cooperative protocols. PMID:1116105
Woutersen, R A; van Garderen-Hoetmer, A; Lamers, C B; Scherer, E
In the past 40 years the incidence of pancreatic cancer in many Western countries had increased. Since no single factor responsible for the development of pancreatic cancer has been identified, it is believed that non-genotoxic factors may play an important role in the pathogenesis of this highly fatal form of cancer. Focal abnormalities of acinar cells, referred to as atypical acinar cell foci or nodules, occur spontaneously in rats and some other species. Their incidence increases with age from zero at birth to about 75% in 2-year-old rats. These spontaneous lesions have a phenotype that cannot be distinguished from the putative, atypical preneoplastic, acinar cell foci induced in rat pancreas by the carcinogen azaserine. Unsaturated fat (corn oil) has been found to increase the incidence of atypical acinar cell nodules and adenomas in the pancreas of non-carcinogen-treated rats without influencing the weight of the pancreas. Furthermore, unsaturated fat has a specific promoting effect on the growth potential of atypical acinar cell foci and nodules induced in rat pancreas by azaserine, resulting in an increase in the number and size of these lesions. Rats fed raw soya flour or trypsin inhibitors develop an enlarged pancreas as a result of hypertrophy and hyperplasia. They also develop acidophilic atypical acinar cell foci and nodules, adenomas and adenocarcinomas after being fed full-fat raw soya flour for 2 years. It may be concluded from the observations in rat pancreas that non-genotoxic compounds or conditions that enhance pancreatic growth may be classified as non-genotoxic pancreatic tumour promoters. The observations with corn oil, however, indicate that there may be non-genotoxic compounds that specifically enhance growth of spontaneous initiated atypical acinar cell foci without causing hyperplasia of the pancreas. The possible mechanisms whereby unsaturated fat and trypsin inhibitors exert their effects on exocrine pancreatic carcinogenesis are
Steckel, J; Roberts, J; Philips, F S; Chou, T C
Kinetic parameters, substrate specificity and exclusivity of ligands at binding sites of L-glutaminase-L-asparaginase purified from Acinetobacter glutaminasificans were studied in order to gain knowledge about the dual activities of this enzyme and its inhibition by structural analogs. Both L-glutamine and L-asparagine, which showed similar Km (4 approximately 7 X 10(-5) M) and Vmax (molecular activity 1.0 min-1) values, were competitive with each other for the substrate binding site. The products, L-glutamic acid and L-aspartic acid, showed competitive inhibition with respect to either L-glutamine or L-asparagine as substrates. Multiple inhibition of the glutaminase activity by L-glutamic acid and L-aspartic acid indicated that these ligands are mutually exclusive at the product-releasing site. The initial rates of both of the enzyme's activities were competitively inhibited by the following inhibitors (in rates of both of the enzyme's activities were competitively inhibited by the following inhibitors (in decreasing order of activity): 6-diazo-5-oxo-L-norleucine (DON), L-methionine sulfoximine, azaserine, and Acivicin. DON and azaserine inhibited both the asparaginase and glutaminase activities in a time-dependent and irreversible manner. The kinetic data suggest an ordered mechanism with glutamine or asparagine as the first substrate and glutamic acid or aspartic acid, respectively, as the last product. These results also suggest that a single mechanism and a single set of binding sites are responsible for catalyzing both of the enzyme's activities. The data also showed that succinylated enzyme, which has a 10-fold increase of plasma half-life in animals and humans and, thus, has benefit as a cancer chemotherapeutic agent, retained its catalytic activity and maintained Km and Vmax values similar to the native enzyme.
李彩凤; 徐影; 郭剑; 陈明; 桑丽敏; 刘磊; 王玉波; 马凤鸣
GS/GOGAT循环是甜菜氮素同化主要途径。甜菜幼苗在氮素诱导下，通过使用不同浓度重氮乙酰丝氨酸处理，并在处理后2、6、9、12和24 h分别取样，利用qRT-PCR技术检测幼苗GS1、GS2及GOGAT的mRNA表达水平，同时测定GOGAT和GS酶活性，分析GOGAT与GS协同变化作用。结果表明，重氮乙酰丝氨酸处理后，GOGAT酶活性在6 h时开始被抑制。GS活性在9 h时开始被抑制；GOGAT的mRNA表达量于6 h时开始下调， GS1的mRNA表达量在2 h时开始下调，而GS2的mRNA表达量于9 h时开始下调，甜菜叶片NH4+的同化以GS2/GOGAT为主。%GS/GOGAT cycle is the main assimilation ways in sugar beet. This study is based on nitrogen induction of sugar beet seedings. We processed sugar beet seedings with ranges of azaserine concentrations at different time, and quantified the GS1, GS2 and GOGAT mRNA expression level using qRT-PCR method. Simultaneously GOGAT and GS enzyme activity was also determined, further to elaborate the synegy changes of two enzymes. The results showed that after azaserine treatment of sugar beet leaves, GOGAT activity began to be inhibited at 6 h, GS activity began to be inhibited at 9 h. In addition, GOGAT mRNA expression level started to decrease at 6 h, GS1 mRNA expression level began to drop at 2 h, and GS2 mRNA expression levels started to decrease at 9 h, indicated GS2/GOGAT cycle was the main synergy way in sugar beet seedlings.
María Agustina Domínguez-Martín
Full Text Available The enzyme isocitrate dehydrogenase (ICDH; EC 188.8.131.52 catalyzes the oxidative decarboxylation of isocitrate, to produce 2-oxoglutarate. The incompleteness of the tricarboxylic acids cycle in marine cyanobacteria confers a special importance to isocitrate dehydrogenase in the C/N balance, since 2-oxoglutarate can only be metabolized through the glutamine synthetase/glutamate synthase pathway. The physiological regulation of isocitrate dehydrogenase was studied in cultures of Prochlorococcus sp. strain PCC 9511, by measuring enzyme activity and concentration using the NADPH production assay and Western blotting, respectively. The enzyme activity showed little changes under nitrogen or phosphorus starvation, or upon addition of the inhibitors DCMU, DBMIB and MSX. Azaserine, an inhibitor of glutamate synthase, induced clear increases in the isocitrate dehydrogenase activity and icd gene expression after 24 h, and also in the 2-oxoglutarate concentration. Iron starvation had the most significant effect, inducing a complete loss of isocitrate dehydrogenase activity, possibly mediated by a process of oxidative inactivation, while its concentration was unaffected. Our results suggest that isocitrate dehydrogenase responds to changes in the intracellular concentration of 2-oxoglutarate and to the redox status of the cells in Prochlorococcus.
The rate of NH4+ assimilation by N-limited Selenastrum minutum (Naeg.) Collins cells in the dark was set as an independent variable and the relationship between NH4+ assimilation rate and in vivo activity of phosphoenolpyruvate carboxylase (PEPC) was determined. In vivo activity of PEPC was measured by following the incorporation of H14CO3- into acid stable products. A linear relationship of 0.3 moles C fixed via PEPC per mole N assimilated was observed. This value agrees extremely well with the PEPC requirement for the synthesis of the amino acids found in total cellular protein. Determinations of metabolite levels in vivo at different rates of N assimilation indicated that the known metabolite effectors of S. minutum PEPC in vitro (KA Schuller, WC Plaxton, DH Turpin,  Plant Physiol 93: 1303-1311) are important regulators of this enzyme during N assimilation. As PEPC activity increased in response to increasing rates of N assimilation, there was a corresponding decline in the level of PEPC inhibitors (2-oxoglutarate, malate), an increase in the level of PEPC activators (glutamine, dihydroxyacetone phosphate), and an increase in the Gln/Glu ratio. Treatment of N-limited cells with azaserine caused an increase in the Gln/Glu ratio resulting in increased PEPC activity in the absence of N assimilation. We suggest glutamate and glutamine play a key role in regulating the anaplerotic function of PEPC in this C3 organism