Epidemiologic studies suggest that the consumption of cruciferous vegetables is associated with a reduced risk for several types of cancer including cancer of colon. Experimental studies indicate that dithiolthiones, naturally occurring substances in cruciferous vegetables, possess anticarcinogenic properties. 5-(2-Pyrazinyl)-4-methyl-1,2-dithiol-3-thione (oltipraz), a substituted dithiolthione, has been tested for its chemopreventive activity. We studied the effect of dietary oltipraz on liver and colonic mucosal enzymes and DNA adducts to evaluate the modulating role of this agent during the early period of azoxymethane (AOM)-induced carcinogenesis. At 6 weeks of age, groups of animals were fed the AIN-76A diet containing 0 and 300 ppm oltipraz. At 8 weeks of age, all of the animals except vehicle-treated animals were administered a subcutaneous injection of AOM (15 mg/kg body wt/week for 2 weeks). Animals intended for vehicle treatment were administered normal saline subcutaneously. Fifteen hours after the second AOM injection, six animals each from control oltipraz diet groups were sacrificed and liver and colonic mucosa from each animal were used for DNA adduct analysis. Animals intended for liver and colonic mucosal glutathione S-transferase, tyrosine specific protein kinase (TPK), and ornithine decarboxylase (ODC) enzyme assays were killed 5 days after the second AOM or saline injection. The results of this study indicated that dietary oltipraz significantly increased liver (P less than 0.001) and colonic mucosal (P greater than 0.05) weights, but had no effect on body weights (P greater than 0.05). In saline-treated animals, feeding of oltipraz significantly increased the cytosolic glutathione S-transferase (P less than 0.001) and ODC (P less than 0.05) activities in the liver and colon when compared with those fed the control diet. Although our unpublished results indicate an inhibitory role of oltipraz when fed during the initiation and postinitiation phases of intestinal carcinogenesis, the increased ODC activity may indicate a possible role of oltipraz in colon tumor promotion. Additional studies are indicated to test the antitumor properties of oltipraz administered during the postinitiation phases. AOM treatment significantly increased the TPK (P less than 0.0001) and ODC (P less than 0.01) activities in the liver and colon of animals fed the control diet. Dietary oltipraz significantly suppressed the AOM-induced TPK (P less than 0.001) activities in liver and colon and ODC (P less than 0.01) activity of colon. Analysis of nucleic acid bases, O6-methylguanine, and 7-methylguanine revealed that dietary oltipraz significantly (P less than 0.05) inhibited the AOM-induced adduct species. These results suggest that dietary oltipraz enhances the colonic and liver glutathione S-transferase activity and reduced the formation of DNA adducts. In addition, dietary oltipraz modulates liver and colonic ODC and TPK activities that have been shown to play a role in tumor promotion. 相似文献
The effect of dimethoate on gingival and uteral collagen crosslinking was studied in normal and high protein diets fed female albino rats. The gingival and uteral samples were collected from all the groups of rats and percent reversibility of neutral salt soluble collagen gel and the solubility of insoluble collagen in KCNS or urea were determined. The analysis of gingival and uteral samples showed alpha 1 and alpha 2 sub units of neutral salt soluble collagen appreciably increased beta chains and aldehyde content significantly decreased in dimethoate treated animals compared to controls. The results indicate that due to the effect of dimethoate, the crosslinking and maturation of collagen are impaired. 相似文献
The impact of atrazine, a triazine herbicide, on the lipid metabolism of fish, Sarotherodon mossambica was studied. Significant changes were reported in the lipid profiles of liver and muscle as a function of exposure period. 相似文献
Changes in oxidative metabolism of hepatopancreas and muscle tissues of penaeid prawn, Metapenaeus monoceros was studied, following its exposure to selected organophosphorous insecticides phosphamidon, dichlorovos and methylparathion. The OPI are found to inhibit the activity levels of acetylcholinesterase, succinate dehydrogenase, isocitrate dehydrogenase, pyruvate dehydrogenase, lactate dehydrogenase and cytochrome-c-oxidase and cause accumulation of acetylcholine in the hepatopancreas and muscle tissues. These changes in the activity levels of selected oxidative enzymes during insecticide exposure in these tissues of prawn indicates the shift in the metabolic emphasis from aerobic to anaerobic conditions and is interpreted as a functional adaptation to insecticide induced metabolic stress. These observed changes at cellular level pave way for successful survival of prawns in insecticide polluted environ. 相似文献
1. 1.|Changes in tissue metabolite concentrations and enzyme activities in the pedipalpal (PM) and heart (HM) muscles of the tropical scorpion Heterometrus fulvipes show that the metabolism in PM and HM is fundamentally reorganized following low (18°C) and high (38°C) temperature acclimation.
2. 2.|Changes in metabolite concentrations show that metabolite biosynthesis showed increases after cold acclimation but decreases after warm acclimation.
3. 3.|Similarly, changes in enzyme activities show a preponderance of glycolysis and HMP shunt activity after cold acclimation, while after warm acclimation glycogenolysis, oxidative metabolism and gluconeogenesis predominated.
4. 4.|Higher metabolite concentrations and enzyme activities both before and after thermal acclimation in HM reflect its greater compensatory abilities.
Previous studies have reported a high incidence of hemoglobin E (HbE) in Northeast Indian populations. In the present study 10 endogamous populations of Assam belonging to two racial groups, Caucasoid and Mongoloid, were examined. The frequency of HbE gene (Hb beta E) in the Caucasoid caste populations is around 0.1, whereas the gene is highly prevalent in the Mongoloid populations, frequencies ranging between 0.2 and 0.6. Predominance of Hb beta E in the Tibeto-Burman speakers is contrary to observations made in Southeast Asia, where an association between Austro-Asiatic speakers and high prevalence of HbE exist. The highest occurrence of the gene in this area, which is on the far end of the proposed centre of distribution in Northern Kampuchea and Northeast Thailand, is also a deviation from the expected pattern of gene distribution. It is speculated that Hb beta E in the Tibeto-Burman populations of Assam arose by an independent mutation which contributed to the high frequencies of Hb beta E in the Northeast Indian populations. 相似文献
Water hyacinth [Eichhornia crassipes (Mart) Solms] productivity and detritus accumulation were evaluated in eutrophic lake water with and without added nutrients
(fertilized and control reservoirs, respectively). Seasonal changes in plant productivity and detritus accumulation were determined
at monthly intervals for one year.
Significant differences were observed in plant productivity between seasons and nutrient additions. Seasonal plant productivity
ranged from 1.9 to 23.1 mg (dry wt) ha−1 for the fertilized reservoir and −0.2 to 10.2 mg ha−1 for the control reservoir. Detritus accumulation was not significantly different between seasons or nutrient additions. Seasonal
N assimilation by plants ranged from 34 to 242 kg N ha−1 for plants in the fertilized reservoir and < 0 to 104 kg N ha−1 for plants in the control reservoir. Annual net N recovered in detritus represented 21 and 28% of the total N removed by
plants in the fertilized and control reservoirs, respectively. Net N loading to the reservoirs from detritus was 92 to 148
kg N ha−1 yr−1. 相似文献
External invertase is the product of the SUC2 gene of Saccharomyces cerevisiae. The deduced sequence of this enzyme (Taussig, R., and Carlson, M. (1983) Nucleic Acid Res. 11, 1943-1954) reveals it to contain 14 potential N-linked glycosylation sites, or sequons, although only 9-10 appear to be glycosylated (Trimble, R. B., and Maley, F. (1977) J. Biol. Chem. 252, 4409-4412). To determine the location of the glycosylated sequons, external invertase was deglycosylated with endo-beta-acetylglucosaminidase H and its component peptides analyzed by both fast atom bombardment mass spectrometry (FABMS) and classical peptide isolation procedures. By use of the former technique most of the glucosamine-containing sequons could be located and by the latter sufficient amounts of small glucosamine-containing peptides were isolated to enable their quantitation. From the combined FABMS and glucosamine analyses, it was established that eight of the sequons in a subunit of invertase are either completely or almost completely glycosylated, while five others are glycosylated to the extent of about 50% or less. In the case of two overlapping sequons (4 and 5), which include Asn92-Asn93-Thr-Ser, only the first Asn was glycosylated. Thus, all but one of the sequons of external invertase are glycosylated to some extent, giving an appearance of only 9-10 N-linked oligosaccharides/subunit. The sequence identity of both external and internal invertase was verified by FABMS and by peptide sequence analysis. In only one site was an amino acid found to differ from that deduced from the DNA sequence of the SUC2 gene. This occurred at position 390 where a proline was found in place of alanine, which could result from a single base change in the triplet specifying the latter amino acid. 相似文献