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101.
We measured single strand breaks (SSB) in pancreas DNA produced by N-nitrosobis(2-oxopropyl)amine (BOP) in hamsters fed purified diets containing added sodium selenite (Se) at 0.0, 0.1 and 5.0 ppm. There were fewer SSB in those given the 5.0 ppm Se diet throughout the experiment. One hour after dosing with BOP (20 mg/kg), there were 2.26 ± 0.47, 2.83 ± 0.43 and 1.74 ± 0.43 SSB per 108 daltons (mean ± S.E.M.) respectively in the three groups. The SSB were repaired faster in the 5.0 ppm Se-fed group. The approximate half-lives of the SSB were 33, 30 and 8 days, respectively. In the hamsters fed 5.0 ppm Se there was a small, statistically significant increase in pancreatic DNA synthesis. Autoradiographic analysis indicated that this was repair synthesis. In a second experiment, hamsters were fed one of the three diets prior to and for 2 days after administration of a single dose of BOP (20 mg/kg). They were then fed the 5.0 ppm Se diet for 5 days. The number of SSB was compared with those in hamsters fed their original diet for 7 days after BOP dosing. There was a statistically significant difference in the number of SSB in the hamsters fed 0.1 ppm Se before and for 2 days after BOP. In these hamsters there were 1.21 ± 0.24 SSB per 108 daltons compared with 3.19 ± 0.4 (mean ± S.E.M.). These results suggest high levels of dietary Se stimulate the repair of carcinogen-induced DNA damage. 相似文献
102.
M.P. Merville J. Piette J. Decuyper C.M. Calberg-Bacq A. Van De Vorst 《Chemico-biological interactions》1983,44(3):275-287
Irradiation in the presence of O2, with near-UV light of five promazine (PZ) derivatives added to erythrocyte ghost membranes, causes covalent cross-linking between proteins as revealed by a progressive decrease in the amounts of proteins separable by electrophoresis after denaturation. The induction of cross-links in the two spectrin subunits is a single-hit process as a function of the irradiation time; relatively the rate constants (in min?1) of the photoreactions were 0.060 with chlorpromazine (CPZ), 0.039 with methoxypromazine (MTPZ), 0.031 with PZ, 0.029 with triflupromazine (TFPZ) and 0.006 with acepromazine (ACPZ).A main photochemical intermediate implicated in the spectrin aggregation seems to be the cation radical of the PZ derivatives. Indeed, (i) the chemically generated cation radicals can induce the reaction in the dark; (ii) the photoaggregation is regularly reduced upon addition of increasing concentrations of NaN3; (iii) NaN3 similarly affects the amount of cross-links induced by the isolated cation radicals. Hydroxyl radicals are also involved in the photocross-linking when the reaction is initiated only by MTPZ and not by the other sensitizers.In the absence of oxygen during irradiation, PZ, MTPZ and ACPZ completely loose their cross-linking activities whereas CPZ and TFPZ remain as efficient as in the presence of oxygen. 相似文献
103.
The irreversible binding of [2,3-14C]acrylonitrile (VCN) to proteins, RNA and DNA of various tissues of male Sprague-Dawley rats after a single oral dose of 46.5 mg/kg (0.5 LD50) has been studied. Proteins were isolated by chloroform-isoamyl alcohol-phenol extraction. RNA and DNA were separated by hydroxyapatite chromatography. Binding of VCN to proteins was extensive and was time dependent. Radioactivity in nucleic acids was registered in the liver and the target organs, stomach and brain. DNA alkylation, which increased by time, was significantly higher in the target organs, brain and stomach (119 and 81 pmol/mg, respectively, at 24 h) than that in the liver. The covalent binding indices for the liver, stomach and brain at 24 h after dosing were, 5.9, 51.9 and 65.3, respectively. These results suggest that VCN is able to act as a multipotent carcinogen by alkylation of DNA in the extrahepatic target tissues, stomach and brain. 相似文献
104.
Sodium dodecyl sulfate electrophoresis of rockfish hemolysate was carried out to investigate problems in the systematics of the genus Sebastes. Results generally revealed species-specific electropherograms that were generally intra-specifically invariant. Experimental findings supported the distinction of S. chrysomelas and S. carnatus as valid species which hitherto had not been accomplished on a morphometric or meristic basis. Moreover, common protein subunits occurred within all specimens studied, and additional interspecific differences suggested several biochemical subgroupings (caurinus, nebulosus; paucispinis, goodei; carnatus, chrysomelas, atrovirens, melanops, mystinus and serranoides). These proposed subgroupings generally differed from previous classifications based on morphometric and meristic data. Some of these differences may ultimately be attributed to pressure adaptive differences in the hemoglobin molecule. 相似文献
105.
The incorporation of labelled amino acids into proteins was measured in vivo in the kidney of control rats and rats that received puromycin aminonucleoside. There was an increase in the synthesis of kidney proteins after the aminonucleoside that was similar to the increased synthesis previously observed in cell-free and slice preparations. The increased synthesis in vivo and in vitro especially involved proteins of the prealbumin fraction of average molecular weights of approx. 50 000, 35 000, 25000, 18 000, and 10 000. The largest of these proteins was identified as kidney ribonuclease inhibitor and additional evidence was obtained for the increased synthesis of the kidney inhibitor after aminonucleoside. 相似文献
106.
Jeffrey R. Bloomquist David M. Soderlund Douglas C. Knipple 《Archives of insect biochemistry and physiology》1989,10(4):293-302
Resistance to pyrethroid insecticides and dichlorodiphenyltrichloroethane (DDT) was investigated in the napts (no action potential, temperature sensitive) mutant of Drosophila melanogaster. In surface contact bioassays, the napts strain showed threefold resistance to deltamethrin at the LC50 level when compared to susceptible Canton-S flies. Cross-resistance was also observed to DDT and the pyrethroids NRDC 157 [3-phenoxybenzyl [1R,cis]-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate], fenfluthrin, and MTI-800 [1-(3-phenoxy-4-fluorophenyl)-4-(4-ethoxyphenyl)-4-methylpentane]. The onset of intoxication by pyrethroids in napts flies was markedly delayed, a finding that is consistent with the existence of a resistance mechanism involving reduced neuronal sensitivity. Resistance at the level of the nerve was confirmed by electrophysiological recordings of spontaneous and evoked activity in the dorsolongitudinal flight muscles of poisoned flies. Preparations from napts insects treated with fenfluthrin displayed longer latencies to the appearance of spontaneous activity and also an absence or reduction in burst discharges compared to equivalent preparations from susceptible individuals. These results are discussed in light of competing hypotheses concerning the mechanism underlying knockdown resistance and reduced nerve sensitivity in insects. 相似文献
107.
Summary Two different3H-saxitoxin-binding proteins, with distinct biochemical and functional properties, were isolated from rat brain using a combination of anion exchange and lectin affinity chromatography as well as high resolution size exclusion and anion exchange HPLC. The alpha subunits of the binding proteins had different apparent molecular weights on SDS-PAGE (Type A: 235,000; Type B: 260,000). When reconstituted into planar lipid bilayers, the two saxitoxin-binding proteins formed sodium channels with different apparent single-channel conductances in the presence of batrachotoxin (Type A: 22 pS; Type B: 12 pS) and veratridine (Type A: 9 pS; Type B: 5 pS). The subtypes were further distinguished by scorpion (Leiurus quinquestriatus) venom which had different effects on single-channel conductance and gating of veratridine-activated Type A and Type B channels. Scorpion venom caused a 19% increase in single-channel conductance of Type A channels and a 35-mV hyperpolarizing shift in activation. Scropion venom double the single-channel conductance of Type B channels and shifted activation by at least 85 mV. 相似文献
108.
Robert Nielsen 《The Journal of membrane biology》1990,113(1):31-38
Summary Prostaglandins are known to stimulate the active transepithelial Na+ uptake and the active secretion of Cl– from the glands of isolated frog skin. In the present work the effect of prostaglandin E2 (PGE2) on the glandular Na+ conductance was examined. In order to avoid interference from the Na+ uptake and the glandular Cl– secretion the experiments were carried out on skins where the Cl– secretion was inhibited (the skins were bathed in Cl– Ringer's solution in the presence of furosemide, or in NO
3
–
Ringer's solution), and the active Na+ uptake was blocked by the addition of amiloride. Transepithelial current, water flow and ion fluxes were measured. A negative current was passed across the skins (the skins were clamped at –100 mV, basolateral solution was taken as reference). When PGE2, was added to the skins under these experimental conditions, the current became more negative; this was mainly due to an increase in the Na+ efflux. Together with the increase in Na+ efflux a significant increase of the water secretion was observed. The water secretion was coupled to the efflux of Na+, and when one Na+ was pulled from the basolateral to the apical solution via this pathway 230 molecules of water follwed. From the data presented it is suggested that this pathway for Na+ is confined to the exocrine glands. 相似文献
109.
本实验用生物测定法观察了模拟海拔5000m高度连续缺氧20d对大鼠肺动脉内皮依赖性和非内皮依赖性舒张反应的影响。结果显示慢性缺氧明显抑制了肺内和肺外动脉对乙酰胆碱、ATP、硝普钠和异丙肾上腺素舒张反应的敏感性和反应性。在浓度为10~(-6)mol/L时,缺氧组大鼠肺内动脉对乙酰胆碱、硝普钠和异丙肾上腺素的舒张反应分别只有对照组大鼠的61.3%、75.9%和61.7%,对浓度为1.8×10~(-5)mol/L的ATP的舒张反应只有对照组大鼠的64.9%。研究表明,ATP和乙酰胆碱主要是通过内皮舒张因子使肺动脉产生内皮依赖性舒张反应,硝普钠和异丙肾上腺素分别通过直接激活血管平滑肌细胞鸟苷酸环化酶和β受体使血管产生非内皮依赖性舒张反应。缺氧同时抑制了肺动脉内皮依赖性和非内皮依赖性舒张反应,提示慢性缺氧可能抑制了正常肺内舒血管活性物质的生理作用。 相似文献
110.
The effects of nitrogen starvation in the presence or absence of sodium in the culture medium were monitored in batch cultures of the marine diatom Phaeodactylum tricornutum Bohlin. During nitrogen starvation in the presence of sodium, cell nitrogen and chlorophyll a decreased, mainly as a consequence of continued cell division. These decreases were accompanied by decreases in the rates of photosynthesis and respiration. There was no change in either cell volume or carbohydrate, but both carbon and lipid increased. During nitrogen starvation in the absence of sodium, cell division ceased. Cell nitrogen and chlorophyll a remained constant, and respiration did not decrease, but the changes in the photosynthetic rate and the lipid content per cell were similar to cultures that were nitrogen-starved in the presence of sodium. The carbon-to-nitrogen ratio increased in both cultures. Nitrogen, in the form of nitrate, and sodium were resupplied to cultures that had been preconditioned in nitrogen- and sodium-deficient medium for 5 d. Control cultures to which neither nitrate or sodium were added remained in a static state with respect to cell number, volume, and carbohydrate but showed slight increases in lipid. Cells in cultures to which 10 mM nitrate alone was added showed a similar response to cultures where no additions were made. Cells in cultures to which 50 mM sodium alone was added divided for 2 d, with concomitant small decreases in all measured constituents. Cell division resumed in cultures to which both sodium and nitrate were added. The lipid content fell dramatically in these cells and was correlated to metabolic oxidation via measured increases in the activity of the glyoxylate cycle enzyme, isocitrate lyase. We conclude that lipids are stored as a function of decreased growth rate and are metabolized to a small extent when cell division resumes. However, much higher rates of metabolism occur if cell division resumes in the presence of a nitrogen source. 相似文献