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Cancer cells undergo metabolic rewiring to support rapid proliferation and survival in challenging environments. Glutamine is a preferred resource for cancer metabolism, as it provides both carbon and nitrogen for cellular biogenesis. Recent studies suggest the potential anticancer activity of amino acid analogs. Some of these analogs disrupt cellular nucleotide synthesis, thereby inhibiting the formation of DNA and RNA in cancer cells. In the present study, we investigated the anticancer properties of Acivicin and Azaserine in the breast cancer MCF-7 cell line, comparing their effects to those on the non-tumorigenic MCF-10 epithelial cell line in vitro. Interestingly, at lower concentrations, both Acivicin and Azaserine showed potent inhibition of MCF-7 cell proliferation, as assessed by the MTT assay, without detectable toxicity to normal cells. In contrast, Sorafenib (Nexavar), a commonly used drug for solid tumors, showed harmful effects on normal cells, as indicated by increased lactate dehydrogenase (LDH) production in treated cells. Furthermore, unlike Sorafenib, treatment with Acivicin and Azaserine significantly affected apoptotic signaling in treated cells, indicating the role of both amino acid analogs in activating programmed cell death (PCD), as assessed by the Annexin-V assay, DAPI staining, and the relative expression of tumor suppressor genes PTEN and P53. ELISA analysis of MCF-7 cells revealed that both Acivicin and Azaserine treatments promoted the production of anti-inflammatory cytokines, including IL-4 and IL-10, while significantly reducing the production of tumor necrosis factor alpha (TNF-α). Mechanistically, both Acivicin and Azaserine treatment led to a significant reduction in the expression of glutamine synthetase (GS) at both the RNA and protein levels, resulting in a decrease in intracellular glutamine concentrations over time. Additionally, both treatments showed comparable effects on Raf-1 gene expression and protein phosphorylation when compared with Sorafenib, a Raf-1 inhibitor. Moreover, docking studies confirmed the strong binding affinity between Acivicin, Azaserine, and glutamine synthetase, as evidenced by their docking scores and binding interactions with the enzyme crystal. Collectively, these findings provide evidence for the anticancer activity of the two amino acid analogs Acivicin and Azaserine as antagonists of glutamine synthetase, offering novel insights into potential therapeutic strategies for breast cancer. [ABSTRACT FROM AUTHOR]

Resveratrol, which is thought to have a preventive effect on the formation of different types of cancer, is abundant in grapes and other foods. Resveratrol has been shown to have anti‐cancer effects by in vitro andin vivo studies, however this is the first time its effect on atypical acinar cell foci (AACF), known as precursor forms of pancreatic carcinoma, has been experimentally investigated. Male Sprague Dawley rats, each consisting of 5 experimental groups (Cont, AzCont, AzRes10, AzRes15, and AzRes20), 10 of which were 14 days old, were used in the study. In the azaserine groups (AzCont, AzRes10, AzRes15, and AzRes20), it was investigated how the development of Atypical Cell Foci (AACF) resulting from intraperitoneal injection (i.p.) of azaserine (30 mg/kg bw) in 14‐day‐old rats was affected by dietary restoration. Male rats in the resveratrol group (AzRes10, AzRes15, and AzRes20) were fed diets containing 10%, 15%, or 20% mmol resveratrol for an 8‐month experimental period 1 week after the last azaserine injection. Pancreas preparations prepared from histological sections were examined for AACF burden and analyzed via a video image analyzer. One‐way analysis of variance (ANOVA) non‐parametric statistical analyses were performed to test whether there was a difference between the averages of the experimental and control groups. The AACF load in the azaserine group (AzCont) compared to the control group (Cont) was found to be statistically significant in all categories (p < 0.05). The calculated estimated mean AACF volume (mm3) values and the AACF ratio as a percentage of the calculated organ volume were statistically significantly lower in all resveratrol groups (AzRes10, AzRes15, and AzRes20) compared to the azaserine control group (AzCont). The calculated estimated mean AACF volume (mm3) values and the AACF ratio as a percentage of the calculated organ volume were statistically significantly lower in all resveratrol groups (AzRes10, AzRes15, and AzRes20) compared to the azaserine control group (AzCont) (p < 0.05). In addition, the calculated estimated mean AACF diameter (mm) in the AzRes10 and AzRes15 groups, in the AzRes15 group the calculated estimated mean AACF number in the whole organ and the calculated average AACF number per unit area were found to be statistically significant compared to the azaserine control group (AzCont) (p < 0.05). According to the results of our study, it has been shown that atypical acinar cell foci (AACF) formed in the exocrine pancreas of rats with azaserine can be reduced by a diet containing resveratrol. It was determined that the tumor burden decreased statistically significantly (p ≤ 0.05) in resveratrol‐treated rats. Accordingly, it is thought that the inhibitory effects of resveratrol may contribute to studies that reduce the occurrence of pancreatic cancer. [ABSTRACT FROM AUTHOR]

Azaserine is a bacterial metabolite containing a biologically unusual and synthetically enabling α-diazoester functional group. Herein, we report the discovery of the azaserine (aza) biosynthetic gene cluster from Glycomyces harbinensis. Discovery of related gene clusters reveals previously unappreciated azaserine producers, and heterologous expression of the aza gene cluster confirms its role in azaserine assembly. Notably, this gene cluster encodes homologues of hydrazonoacetic acid (HYAA)-producing enzymes, implicating HYAA in α-diazoester biosynthesis. Isotope feeding and biochemical experiments support this hypothesis. These discoveries indicate that a 2-electron oxidation of a hydrazonoacetyl intermediate is required for α-diazoester formation, constituting a distinct logic for diazo biosynthesis. Uncovering this biological route for α-diazoester synthesis now enables the production of a highly versatile carbene precursor in cells, facilitating approaches for engineering complete carbene-mediated biosynthetic transformations in vivo.

Biosynthesis is an environmentally benign and renewable approach that can be used to produce a broad range of natural and, in some cases, new-to-nature products. However, biology lacks many of the reactions that are available to synthetic chemists, resulting in a narrower scope of accessible products when using biosynthesis rather than synthetic chemistry. A prime example of such chemistry is carbene-transfer reactions1. Although it was recently shown that carbene-transfer reactions can be performed in a cell and used for biosynthesis2,3, carbene donors and unnatural cofactors needed to be added exogenously and transported into cells to effect the desired reactions, precluding cost-effective scale-up of the biosynthesis process with these reactions. Here we report the access to a diazo ester carbene precursor by cellular metabolism and a microbial platform for introducing unnatural carbene-transfer reactions into biosynthesis. The α-diazoester azaserine was produced by expressing a biosynthetic gene cluster in Streptomyces albus. The intracellularly produced azaserine was used as a carbene donor to cyclopropanate another intracellularly produced molecule-styrene. The reaction was catalysed by engineered P450 mutants containing a native cofactor with excellent diastereoselectivity and a moderate yield. Our study establishes a scalable, microbial platform for conducting intracellular abiological carbene-transfer reactions to functionalize a range of natural and new-to-nature products and expands the scope of organic products that can be produced by cellular metabolism.

Azaserine (o-diazoacetyl-L-serine) is an antimetabolite obtained from streptomycetes cultures and is used experimentally to produce atypical acinar cell focus (AACF) in rat exocrine pancreas. Propolis is a resinous hive product with antioxidant, anticarcinogenic, antimicrobial and anti-inflammatory effects that bees collect from the plants around them. In this study, we aimed performed to investigate the effect of ethanol extract of propolis (EEP) on serum biochemical changes in azaserin induced pancreatic cancer in Wistar rats. For this purpose, male Wistar albino rats were randomly divided into 4 groups, 10 in each group. AzCt and AzProp group 2-week-old male rats were given azaserine (30 mg/kg bw) intraperitoneally (ip). Propolis (EEP) (oral 80 mg/lt) was added to the drinking water of Prop and AzProp group rats. For the first time in this study, the effects of propolis on rats with neoplastic structures formed by azaserine were investigated in terms of biochemical parameters (AST, ALP, ALT, BILD, BILT, CHOL, LDH, TRIG, UREA, TAS, TOS and OSI). According to this; AzProp group values were compared to AzCt group, respectively, AST, UREA, TOS and OSI, there is a statistically significant difference in terms of values. As a result, it was seen that the oxidative stress caused by azaserine-induced neoplastic structures decreased with the use of propolis and that propolis had a positive effect on the measured biochemical parameters. [ABSTRACT FROM AUTHOR]

In higher plants ammonium (NH 4 +) assimilation occurs mainly through the glutamine synthetase/glutamate synthase (GS/GOGAT) pathway. Nevertheless, when plants are exposed to stress conditions, such as excess of ammonium, the contribution of alternative routes of ammonium assimilation such as glutamate dehydrogenase (GDH) and asparagine synthetase (AS) activities might serve as detoxification mechanisms. In this work, the in vivo functions of these pathways were studied after supplying an excess of ammonium to tomato (Solanum lycopersicum L. cv. Agora Hybrid F1) roots previously adapted to grow under either nitrate or ammonium nutrition. The short-term incorporation of labelled ammonium (15NH 4 +) into the main amino acids was determined by GC–MS in the presence or absence of methionine sulphoximine (MSX) and azaserine (AZA), inhibitors of GS and GOGAT activities, respectively. Tomato roots were able to respond rapidly to excess ammonium by enhancing ammonium assimilation regardless of the previous nutritional regime to which the plant was adapted to grow. The assimilation of 15NH 4 + could take place through pathways other than GS/GOGAT, since the inhibition of GS and GOGAT did not completely impede the incorporation of the labelled nitrogen into major amino acids. The in vivo formation of Asn by AS was shown to be exclusively Gln-dependent since the root was unable to incorporate 15NH 4 + directly into Asn. On the other hand, an in vivo aminating capacity was revealed for GDH, since newly labelled Glu synthesis occurred even when GS and/or GOGAT activities were inhibited. The aminating GDH activity in tomato roots responded to an excess ammonium supply independently of the previous nutritional regime to which the plant had been subjected. [ABSTRACT FROM AUTHOR]

Trypanosoma cruzi is the aetiologic agent of Chagas disease, which affects people in the Americas and worldwide. The parasite has a complex life cycle that alternates among mammalian hosts and insect vectors. During its life cycle, T. cruzi passes through different environments and faces nutrient shortages. It has been established that amino acids, such as proline, histidine, alanine, and glutamate, are crucial to T. cruzi survival. Recently, we described that T. cruzi can biosynthesize glutamine from glutamate and/or obtain it from the extracellular environment, and the role of glutamine in energetic metabolism and metacyclogenesis was demonstrated. In this study, we analysed the effect of glutamine analogues on the parasite life cycle. Here, we show that glutamine analogues impair cell proliferation, the developmental cycle during the infection of mammalian host cells and metacyclogenesis. Taken together, these results show that glutamine is an important metabolite for T. cruzi survival and suggest that glutamine analogues can be used as scaffolds for the development of new trypanocidal drugs. These data also reinforce the supposition that glutamine metabolism is an unexplored possible therapeutic target.

Organisms are subjected to a variety of stress and physiological impact in the event of drug administration. Drug extrusion plays a critical role in the survival of organisms. The present study elucidate the role of glutamate transporter, EAAT2 in survival of model organism silkworm injected with azaserine, a glutamine analogue and offer a possible explanation for a contrasting observation of greater survival at higher dosage and lesser survival in lower dosage. Our results have shown a dosage dependent inhibition of gamma glutamyl transferase (GGT) activity, differential expression of EAAT2 transporter along with concomitant changes in residual concentration of azaserine, glutamate and cysteine that undermine cysteine transport. The current results also suggest that survival is dependent on EAAT2 transporter in cysteine-glutamate/azaserine transport and rejuvenation of ATP formation as observed in higher but not in lower dosage received worms.

Aim: The present study was performed to investigate the effect of Phyllanthus amarus extracts on serum biochemical changes in azaserine induced pancreatic cancer in Wistar rats. Materials and Methods: Pancreatic cancer was developed in Wistar rats by intraperitoneal administration of azaserine (cancer inducer) for 21 days at the concentration of 5 mg/kg body weight. Aqueous and alcoholic extracts were given to rats of different groups as per protocol. Results: The results data revealed that oral administration of P. amarus extracts had a significant change in pancreatic amylase, lipase, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase activity. Conclusion: We concluded that extract of P. amarus possessed chemoprotective activity against azaserine induced pancreatic cancer in Wistar rats.

Pancreatic cancer is a malignant neoplasm originating from transformed cells arising in tissues forming the pancreas. The most common type of pancreatic cancer is adeno-carcinoma. The present experiment was carried out to study histopathological changes occur in pancreas in different groups of azaserine induced pancreatic cancer in Wistar rats with and without the treatment of aqueous and alcoholic extract of Phyllanthus amarus at different doses. Histopathological examination of pancreas of untreated group of rats showed hyperplasia of pancreatic duct, necrosis, fatty changes, haemorrhages between pancreatic cells. The rats treated with Phyllanthus amarus extracts showed no pathological lesions.

Aim: The effect of acetylsalicylic acid (ASA) on thiol levels was studied in a rat model of azaserine carcinogenesis.Materials and Methods: ASA and azaserine were applied to the animals to research changes in cellular sulfhydryl (-SH) content and variations in free and protein-bound molecules containing the -SH group. Such effects in rats injected with azaserine were investigated at low (200 ppm) and high (400 ppm) concentrations of ASA over a relatively short (6 months) and a relatively long (12 months) period.Results: Changes in the hepatic, pancreatic, and renal -SH contents were also determined.Conclusion: Compared to the other tissues studied, the liver contained the highest levels of both free and protein-bound -SH. [ABSTRACT FROM AUTHOR]

Azaserine ( 1 ) is a natural product and nonproteinogenic amino acid containing a diazo group. Here we report the biosynthetic gene cluster for 1 from Glycomyces harbinensis . We then use isotopic feeding, gene deletion, and biochemical experiments to support a pathway whereby hydrazinoacetic acid ( 2 ) and a peptidyl carrier protein-loaded serine ( 3 ) are intermediates on route to the final natural product 1 .

Hydatid cyst is a zoonotic infestation caused by Echinococcus granulosus, and it is known that some parasites found in humans cause cancer in humans or some may have a protective effect against cancer. Cancer is one of the most serious health problems of today and it has been shown in some studies that parasites such as Echinococcus granulosus can have an inhibitory effect. The aim of this study was determined as whether Echinococcus granulosus has an inhibitory effect on exocrine pancreatic cancer with the help of the azaserine-rat model used in different cancer studies.  Material and Methods: During experimental process a total of 45 male Wistar rats used, 14-day-old male Wistar rats were divided into groups according to the experimental protocol, administered azaserine injection protocol or kept as a control group without azaserine injection. Animals are grouped as Group 1, Control Group (group not treated with Azaserine and not injected with protoscolex.) (E-A-) (n=7); Group 2, Group injected with (IP) Azaserine only (30mg/kg) (E-A+)  (n=8);Group 3, Group injected (IP) with protoscolex suspension of 1 cc only (E+A-) (n=15);Group 4, Group injected both Azaserine (IP) and protoscolex suspension (IP) (E+A+) (n=15). Atypical Acinar Cell Foci (AACF) load in the exocrine pancreas of each rat was measured quantitatively with the help of a video image analyzer and the AACF load was calculated with the help of a mathematical model. Results: Findings showed that the Atypical Acinar Cell Foci (AACF) burden was statistically significantly lower in the Azaserine+ protoscolex (Azaserine-injected-protoscolex-implanted) rat group compared to the other groups, suggesting that Echinococcosis in the azaserine-rat model could inhibit the development of precursor foci of neoplastic changes in the exocrine pancreas. Conclusion: The most significant aspect of our study is that it contributes new insights into the controversy that Echinococcosis suppresses pancreatic cancer.

The present study was undertaken to investigate the effect of Emilia sonchifolia on azaserine (O-diazoacetyl-L-serine)-induced pancreatic dysplasia in Wistar albino rats. Methods Administration of azaserine [30 mg/kg body weight intraperitoneal (i.p.) weekly for 1 month] to male Wistar albino rats resulted in pancreatic dysplasia, which was evident from the histopathological studies. Results A significant decrease of pancreatic and hepatic enzymatic antioxidants like superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST), and non-enzymatic antioxidants like vitamin C, glutathione (GSH) content, and a significant increase in pancreatic serum amylase and lipase, and hepatic marker enzymes aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) were found. Treatment of rats with the n-hexane extract of Emilia sonchifolia for 16 weeks resulted in a concomitant reduction in pancreatic and hepatic damage. Conclusion The results suggest that Emilia sonchifolia can be used as a therapeutic agent against precancerous lesions which could prevent pancreatic dysplasia. [ABSTRACT FROM AUTHOR]

Objectives. Through the hexosamine biosynthetic pathway (HBP) proteins are modified by O-linked-β-N-acetylglucosamine (O-GlcNAc), which acts as a stress sensor. Augmentation of O-GlcNAc confers cardioprotection against ischemia- reperfusion injury, but its role in ischemic preconditioning (IPC) is unknown. Azaserine and alloxan are unspecific blockers of the HBP and have been used to block the cardioprotective effects of O-GlcNAc. We hypothesized that IPC reduces infarct size and increases O-GlcNAc levels in hearts subjected to ischemia-reperfusion injury, and that these effects could be blocked by azaserine and alloxan. Design. Isolated rat hearts subjected to 40 min global ischemia and 120 min reperfusion were randomized to control, IPC, IPC + azaserine or alloxan, or control + azaserine or alloxan. The effects on infarct size, hemodynamic recovery, myocardial O-GlcNAc levels, and HBP enzyme activities were determined. Results. IPC reduced infarct size, increased O-GlcNAc levels, O-GlcNAc-transferase levels, and O-GlcNAc-transferase activity. Azaserine and alloxan did not block the effect of IPC on O-GlcNAc levels and O-GlcNAc-transferase activity. Conclusions. IPC increased O-GlcNAc levels though increased O-GlcNAc-transferase expression and activity. Azaserine and alloxan failed to block these effects presumably due to poor specificity and sensitivity of the blockers, and IPC-mediated cardioprotection may therefore still be dependent on O-GlcNAc. [ABSTRACT FROM AUTHOR]

Using 0.1 mol% to 1 mol% potassium carbonate in an acetonitrile-deuterium oxide mixture acts as a 'privileged' reaction system, which at ambient temperature affords, via a one-pot-onecycle procedure, a-D-diazoacetates, a-D-diazoacetamides, or a-Ddiazoketones from the corresponding nondeuterated form. The protocol is inexpensive, employs readily available materials, does not require harsh reaction conditions, requires two hours for completion, and affords the desired products in good yields and with excellent levels of deuterium incorporation. Exemplifying our protocol the first isotope labelled synthesis of N-Boc-a-D-azaserine with =95% D-incorporation is reported. [ABSTRACT FROM AUTHOR]

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 10 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)). Our results indicate 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. [ABSTRACT FROM AUTHOR]

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)). Our results indicate 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. [ABSTRACT FROM AUTHOR]

PURPOSE: The objective of the present study was to investigate the effects of azaserine on cysteine influx and efflux in erythrocytes. Azaserine is a potent carcinogen and induces tumors especially in the pancreas. Azaserine structurally resembles glutamine and thus interferes with a variety biological processes including enzymatic activities and transmembrane transport of solutes. Glutamine and cysteine have been shown to share similar transport mechanisms. In this respect azaserine, structurally resembling glutamine, may effect the cysteine transport across the cell membrane or conversely cysteine availability may effect the uptake or release of azaserine. METHODS: In the present study, erythrocytes were treated with different concentrations of azaserine and cysteine and then cysteine influx and efflux processes in erythrocytes were measured through detection of nonprotein, soluble free-SH levels. The effect of glutamine on cysteine transport was also measured in a similar way. RESULTS: Our results indicate that azaserine has an effect on bi-directional transport of cysteine through the erythrocyte membranes. An induction of cysteine influx was observed in the presence of 2 mM of azaserine (2.4 ± 0.07 μmol/ml erythrocyte) compared to the absence of azaserine (1.9 ± 0.14 μmol/ml erythrocyte). However, the effect of azaserine on cysteine efflux from erythrocytes was more pronounced and started at 0.5 mM of azaserine and then increased in a concentration dependent manner. In the presence of 2 mM of azaserine, the cysteine efflux reached to 0.71± 0.05 μmol/ml erythrocyte and in the absence of azaserine the efflux reached to 0.51± 0.01 μmol/ml erythrocyte. Glutamine at 2 mM concentration also significantly increased the cysteine efflux from erythrocytes. CONCLUSION: Our results suggest that carcinogenic compound azaserine affects the flux of cysteine through erythrocyte membranes. This result suggest that azaserine may enter the erythrocytes by an azaserine/cysteine exchange mechanism. Glutamine which shares structural similarity with azaserine did not show any effect on cysteine influx. We suggest that in addition to its effect on induction of DNA damage and enzymatic activities, the described effects of azaserine in this study may contribute to its carcinogenity. Azaserine may limit the cysteine availability as it gains entry into the cells in exchange with cysteine. This process may represent a mechanism by which azaserine is accumulated in tissues in which it leads to carcinogenesis. [ABSTRACT FROM AUTHOR]

The present study was conducted to study the serum biochemical changes inazaserine induced pancreatic cancer in wistar rats. Aqueous and alcoholic extract of plant Phyllanthus amarus was administered orally once in a day for 21 days in experimentally induced pancreatic cancerrats. Azaserine was given as a cancer inducerintaperitonially at the dose rate of 5 mg/kg body weight once in a week for 3 weeks. Azaserine is widely used in the field of experimental pancreatic- carcinogenesis. GGT, LDH, total bilirubin, uric acid, total protein and glucose changes were recorded during the experiment. Data revealed that P. amarus extracts possess significant activity against pancreatic damage. [ABSTRACT FROM AUTHOR]

Abstract: In vivo 15N nuclear magnetic resonance (NMR) as well as 15N solid-state magic angle spinning (MAS) NMR spectroscopy were used to investigate nitrogen metabolism in cultured white spruce (Picea glauca) buds. Long-term as well as short-term experiments were carried out involving the use of inhibitors of the nitrogen pathways such as methionine sulfoximine (MSO), azaserine (AZA) and aminooxyacetate (AOA). Both in vivo and solid-state NMR showed that when MSO blocked glutamine synthetase (GS) no NH4 + is incorporated. When glutamate synthase (GOGAT) is blocked by AZA there is some incorporation into glutamine (Gln), but very little into α-amino groups (glutamate, Glu). The transamination inhibitor AOA does not affect the metabolism of 15NH4 + into Gln and Glu, but blocks the production of arginine (Arg), as would be expected. Proline (Pro) and γ-aminobutyric acid (GABA), which are produced directly from Glu without a transamination step, were not affected. The solid-state NMR experiments showed that protein synthesis occurred. Collectively, our results show that NH4 + can only be assimilated through the GS/GOGAT pathway in P. glauca buds. [Copyright &y& Elsevier]

The growth of Escherichia coli is inhibited by an antibiotic compound, azaserine (O-diazoacetyl-l-serine). Previous studies revealed the biochemical properties of azaserine, which involves inhibition of various enzymatic reactions as well as introduction of DNA breakage. However, genetically, nothing has been elucidated except that all the azaserine-resistant strains isolated so far carry lesions in the aroP gene as a primary determinant. Here, we demonstrate that, in addition to AroP, the LIV-I/LS system, an ATP-binding cassette type transporter, is involved in azaserine sensitivity of E. coli, by genetic analysis and transport studies, in which Ki value for azaserine was determined to be ∼10-3 M. [Copyright &y& Elsevier]

The progression of azaserine-induced rat pancreatic adenocarcinoma (AC) was characterised using quantitative and semiquantitative immunohistochemistry for proliferating cell nuclear antigen (PCNA), basement membrane laminin (BML) and trypsinogen (TG). Samples were taken 5–20 months after initiation. High PCNA-labelling indices (PCNA LIs) were measured 5 months after the induction of atypical acinar cell nodules (AACNs), which decreased later and stagnated until a further decline in the month 10 adenomas. Then a second premalignant proliferative wave was observed (month 13) within the adenoma stage. Later, in month 20 differentiated ACs PCNA LIs fell to the host tissue level but were found highest in the month 20 anaplastic ACs indicating a switch to malignant proliferation. Month 20 invasive ACs showed a number of separate proliferative foci. In early AACNs, BML decreased and remained low till the local maximum in the month 13 adenoma. Invasive ACs did not express BML. Month 5 AACN and differentiated AC were TG deficient but anaplastic AC regained its TG expression. However invasive AC was again TG negative. These results are discussed in combination with our previous data on progressional changes of autophagic capacity and microvessel densities. [ABSTRACT FROM AUTHOR]

The hexosamine biosynthesis pathway plays a role in the modification of cellular proteins via the provision of substrate for addition of O-linked N-acetylglucosamine (GlcNAc). The relative importance of the GlcNAc modification of proteins to insulin secretion from pancreatic β-cells has not been investigated and so remains unclear. In the present study, we show that inhibition of the hexosamine biosynthesis pathway decreases insulin secretion from mouse islets in response to a number of secretagogues, including glucose. This impairment in β-cell function could not be attributed to reduced islet insulin content, altered ATP levels, or cell death and was restored with the addition of N-acetylglucosamine, a substrate that enters the pathway below the point of inhibition. Western blot analysis revealed that decreased islet protein glycosylation paralleled the decrease in insulin secretion following inhibition of the pathway. In conclusion, the data suggest a role for the hexosamine biosynthesis pathway in regulating the secretion of insulin by altering protein glycosylation. This finding may have implications for the development of type 2 diabetes, as chronic increase in flux through the hexosamine biosynthesis pathway may lead to the deterioration of β-cell function via abnormal protein glycosylation. [Copyright &y& Elsevier]

A combination of inhibitor and N studies were used to investigate the photorespiratory nitrogen cycle in maize, a C plant. Inhibitors used included isonicotinyl hydrazide which blocks the conversion of glycine to serine, methionine sulfoximine an inhibitor of GS and azaserine an inhibitor of GOGAT. Results from levels of ammonia and amino acids and the distribution of N into NH, serine, glutamine and glutamate indicated that the photorespiratory N-cycle occurs in this C plant, but the rate of flux through this pathway is low as compared with that in C plants. [ABSTRACT FROM AUTHOR]

The effect of caerulein on pancreatic ATPase-positive lesions and ATPase-deficient lesions induced by azaserine was investigated in Wistar rats. Rats were given 2 μg/kg body weight of caerulein every other day for 65 wk, and from experimental week 3, were given weekly injections of 10 mg/kg body weight of azaserine for 25 wk. Carcinogen-induced pancreatic lesions were examined by histochemical techniques, and were classified as ATPase-positive and ATPase-deficient. Quantitative histological analysis showed that prolonged administration of caerulein resulted in a significant increase in the number and size of ATPase-positive lesions, but did not influence the number or size of ATPase-deficient lesions. This finding indicates that caerulein enhances pancreatic carcinogenesis. [ABSTRACT FROM AUTHOR]

The incidence of spontaneous and induced neoplasms of the exocrine pancreas in rats is higher in males than in females. Castration, ovariectomy, and hormone replacement with estradiol and testosterone have been shown to influence the growth of carcinogen-induced preneoplastic foci in the azaserine-rat model of pancreatic carcinogenesis. Similar hormonal treatments have also influenced the growth of an azaserine-induced poorly differentiated acinar cell carcinoma that can be transplanted syngeneically in Lewis rats. The effect on growth of preneoplastic lesions and carcinomas is similar. The preneoplastic lesions and transplanted tumors grow faster in intact male rats than in castrated rats, and the growth of the lesions and tumors is inhibited by estrogen treatment. It appears that testosterone supports the growth of preneoplastic foci and carcinomas, whereas estrogen inhibits such growth. The mechanism is unknown and may be direct, or an indirect effect may be mediated through a peptide hormone. Tamoxifen treatment did not significantly influence the growth of the transplanted carcinomas in the rat model. [ABSTRACT FROM AUTHOR]

In vivo inhibition of glutamine synthetase (GS) by l-methionine sulfoximine induces sporulation in a protease deficient mutant of Bacillus polymyxa. This induction of sporulation is accompanied by derepression of EDTA insensitive proteases(s) which seems to be specific for differentiation. Some amino acid analogues derepress proteolytic activity without inducing sporulation, but these proteases are sensitive to metal chelators like those in the vegetative cells. When the proteolytic activity is restored, the mutant cells, which are smaller than the parental strain, regain their normal size. [ABSTRACT FROM AUTHOR]