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1.
Milena Riesová-Kučerová 《Biologia Plantarum》1969,11(5):338-346
The dependence of the frequency of recessive lethal (two groups), chlorophyll and morphological mutations on the mutagen concentration was determined in M2 after subjection to N-nitroso-N-methylurea applied to seeds ofArabidopsis in three concentrations (0·05, 0·10 and 0·20mm). The observed frequencies were compared with the theoretically expected ones for the linear and for two exponential types of dependence, by using the t-test, according to the formulas m=k. C, m=k. C3/2, m=k. C2. No satisfactory agreement with any expected type of dependence was found when directly observed frequencies were used. Since a considerable deficit of mutation frequency was observed in high concentrations, the correction of frequency values was done with respect to the probability of occurence of double mutations. After such a correction, a clear exponential relation was found in both types of lethals and a linear one in chlorophyll and morphological mutations. The probable occurence of multiple mutations should be, therefore, taken into account if the dependence of mutation frequency on the concentration of mutagen is discussed. 相似文献
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It has been widely reported that polyunsaturated fatty acids-rich diets (PUFA n-6) cause immunodeficiency. In this study, fresh weight, DNA and lipid content and rate of lipogenesis from 3H2O of thymus, spleen, mesenteric lymph nodes and liver were assessed in rats fed polyunsaturated (UC) or saturated (SC) fatty acids-rich chows. The results obtained indicate that both types of fatty acids caused similar increment of lipid content in the immune tissues. The rate of lipogenesis was decreased only in the thymus of (UC) rats and liver of both experimental groups as compared to control rats. The results of fresh weight and DNA content was decreased only by (UC) diet. 相似文献
4.
Fabrizio Villani Milena Galimberti Elena Monti Francesco Piccinini Enrica Lanza Annalinda Rozza Luigia Favalli Paola Poggi Franco Zunino 《Free radical research》1990,11(1):145-151
The effects of two sulfhydryl compounds, glutathione (GSH) and N-acetylcysteine (NAC), on the cardiotoxicity of doxorubicin (DXR) were tested on in vitro and in vivo models. DXR was administered to rats as 4 weekly i.v. doses of 3mg/kg. GSH (1.5 mmoles/kg), given i.v. 10 min before and 1 hr after DXR, was found to prevent the development of the delayed cardiotoxic effects of DXR, as assessed by electrocardiographic and mechanical parameters, as well as by histological examination of left ventricular preparations. In contrast, equimolar oral doses of NAC (1 hr before and 2hrs after DXR) were found to be ineffective. Both GSH and NAC prevented the negative inotropic effect produced by DXR on isolated rat atria. A good correlation exists between the cardioprotective effects of the two agents and their ability to enhance the non-protein sulfhydryl group content of the myocardium. Differences observed in vivo between GSH and NAC might be accounted for by pharmacokinetic factors. 相似文献
5.
E. S. Dias E. F. Araújo W. V. Guimarães R. M. C. Muchovej 《World journal of microbiology & biotechnology》1996,12(6):625-628
Experiments were performed with the mycorrhizal fungus Suillus granulatus to define the parameters for production and regeneration of protoplasts. Protoplasts were released at frequencies between 1 and 3×107/ml from mycelium 3 to 7 days old. The best osmotic stabilizer for protoplast release was MgSO4 (0.7 m). To optimize protoplast release and regeneration an enzyme (Novozym 234) concentration 1.7 mg/ml was chosen, with a digestion time of 1 to 2 h. Regenerated colonies formed mycorrhizae within 60 days after inoculation in Pinus caribaea var. hondurensis seedlings. 相似文献
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Milena Sedliaková Viera Slezáriková Jela Brozmanová František Mašek Viktória Bayerová 《Mutation research》1980,71(1):15-23
3 wild-type strains of E. coli, namely K12 AB2497, B/r WP2 and 15 555-7v proficient in excision and post-replication repair, differ markedly in their UV resistance. To elucidate this difference, the influence was investigated of induction by application of inducing fluence (IF) before lethal fluence (LF) on repair processes after LF. In cells distinguished by low UV resistance (E. coli 15 555-7; E. coli B/r WP2), dimer excision was less complete in cultures irradiated with IF + LF than in cultures irradiated with LF only. The highly resistant E. coli K12 AB2497 performed complete excision both after IF + LF or after LF alone. All 3 types of cell survived better after IF + LF than after LF only. Because, in most strains so far investigated, the application of IF reduced dimer excision and increased survival, dimer excision per se does not appear important for survival.We conclude that the rate and completeness of dimer excision can serve as a measure of efficiency of the excision system whose action is necessary for repair of another lesion. Cells of all investigated strains could not resume DNA replication and died progressively when irradiated with LF and post-incubated with chloramphenicol (LF CAP+). Thus, it appears that inducible proteins are necessary for repair in all wild-type E. coli cells give with potentially lethal doses of UV irradiation. 相似文献
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Romeu Cardoso Guimarães 《Origins of life and evolution of the biosphere》2011,41(4):357-371
An investigation of the biosynthesis pathways producing glycine and serine was necessary to clarify an apparent inconsistency
between the self-referential model (SRM) for the formation of the genetic code and the model of coevolution of encodings and
of amino acid biosynthesis routes. According to the SRM proposal, glycine was the first amino acid encoded, followed by serine.
The coevolution model does not state precisely which the first encodings were, only presenting a list of about ten early assignments
including the derivation of glycine from serine—this being derived from the glycolysis intermediate glycerate, which reverses
the order proposed by the self-referential model. Our search identified the glycine-serine pathway of syntheses based on one-carbon
sources, involving activities of the glycine decarboxylase complex and its associated serine hydroxymethyltransferase, which
is consistent with the order proposed by the self-referential model and supports its rationale for the origin of the genetic
code: protein synthesis was developed inside an early metabolic system, serving the function of a sink of amino acids; the
first peptides were glycine-rich and fit for the function of building the early ribonucleoproteins; glycine consumption in
proteins drove the fixation of the glycine-serine pathway. 相似文献