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1.
Mitochondrial DNA variation was examined in one of the southem most populations of domestic reindeer, inhabiting Tyva Republic (Tuva). In Tuvinian population sequence polymorphism of the mitochondrial DNA D-loop region was demonstrated. In a sample of 29 individuals 7 mitotypes were distinguished, pointing to the preservation of rather high level of genetic diversity in this population. 相似文献
2.
N Iu Belenkov E B Korolev M O Gromyko 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1985,35(4):674-677
Reactivity of neurones in orbitofrontal cortex of the cat to the action of light or sound was studied in consecutive stages of alimentary behaviour conditioned by the smell and then the sight of food. Changes were found of the character of neuronal reactions to the light and sound stimuli at the change of smell to the sight of food. A conclusion is drown, that polysensory properties of the neurones of the orbitofrontal cortex provide integral organization of brain sensory function at separate stages of alimentary behaviour. 相似文献
3.
A S Taisova N P Korolev N S Griaznova E Ia Zinchenko Z I Lesovaia 《Antibiotiki i khimioterapii͡a》1989,34(7):496-504
Interaction between penicillins and model membrane systems, flat black bilayer lipid membranes (BLM) composed of vegetable or bacterial phospholipids was studied with an account of the complicated structure of bacterial cell membranes and possible presence in them of "pure" bilayer lipid areas. By their effect on electroconductivity of the BLM the antibiotics could be divided into three groups: those having no effect on the BLM electroconductivity at the maximum concentrations i.e. benzylpenicillin, carbenicillin, piperacillin (at pH 6.0 and 7.0) and ampicillin (at pH 6.0), those insignificantly changing electroconductivity of the BLM i.e. carfecillin and azlocillin and those having a significant effect on the BLM electroconductivity i.e. ampicillin N-acyl derivatives and 6-APA. The effect of ampicillin on the BLM conductivity markedly depended on the electrolite pH. The penicillins bound to the bilayer and induced changes in the transmembrane potential (evident from the changes in the second harmonic of the capacitive current) and the BLM elasticity-capacitance parameters (evident from the changes in the ratio of the amplitudes of the first and third harmonics). It was shown that all the penicillins penetrated through the BLM composed of either vegetable or bacterial phospholipids. The capacity for the transmembrane transfer without changing of the bilayer conductivity must be connected with the fact that the penetrating antibiotics did not induce any changes in the BLM structure. The effect on the conductivity probably depended in its turn on the form of the molecule and the ratio of the hydrophilic and hydrophobic parts in it. 相似文献
4.
The thermotropic properties of multilamellar liposomes from egg yolk lecithin, hydrogenized egg yolk lecithin and several mixtures of these two lipids were studied with the application of excimer--forming optical probe pyrene and microcalorimetry. It was discovered that when the proportion of the egg yolk lecithin in the lipid mixture was raised the temperature of the main phase transition reduced. For all this, independent of the lipid mixture composition when the temperature was raised, apparently, polarity of pyrene microenvironment in the liposomes bilayers decreased. On the basis of the analysis of solidus and liquidus curves obtained from calorimetric studies of the lipid mixtures and bend points of Arrhenius anamorphose obtained during the pyrene excimer formation measurements some conclusions were made about the role of unmodified and hydrogenized egg yolk lecithin cluster formation in the determination of thermotropic properties of the liposomes from the above two lipids mixtures. High temperature phase transition discovered for the egg yolk lecithin while measuring the pyrene excimer formation is proposed to be closely connected with temperature-dependent changes in the organization of phospholipid heads on the interphase bilayer/H2O solution. 相似文献
5.
The work was concerned with studying the effect of gramicidin S derivatives with modified free amino groups of ornithine residues on bacterial cells and protoplasts. The substitution of the amino groups with neutral or carboxyl-containing groups eliminated or sharply decreased the antibacterial activity of gramicidin S, its binding to the cells, and the ability to change the permeability of the cytoplasmic membranes of the intact cells. However, the neutral derivatives and the derivative with acidic properties showed a considerable lytic activity when they were incubated with the protoplasts of Micrococcus lysodeikticus, Bacillus megaterium and Bacillus subtilis. Hence, these compounds preserved a certain membranotropic level. Those gramicidin S derivatives with modified ornithine amino groups which possessed basic properties were similar to gramicidin S in the antibiotic activity, the modified permeability of the membranes, the ability to bind with the cells, and the lytic action on the protoplasts. 相似文献
6.
Thermal denaturation of Na- and Li-DNA from chicken erythrocytes was studied by means of scanning microcalorimetry in salt-free solutions at DNA concentrations (Cp) from 4.5 · 10?2 to 1 · 10?3 moles of nucleotides/liter (M). Linear dependencies of DNA melting temperature (Tm) vs lgCp were obtained: ((1)) ((2)) for Na- and Li-DNA, respectively. Microcalorimetry data were compared with the results of spectrophotometric studies at 260 nm of DNA thermal denaturation in Me-DNA + MeCl solutions at Cp ? (6–8) · 10?5 M and Cs = 0–40 mM (Me is Na or Li, Cs is salt concentration). It was found that Eqs. (1) and (2) are valid in DNA salt-free solutions over the Cp range 6 · 10?5?4.5 · 10?2M. Protonation of DNA bases due to the absorption of CO2 from air in Na-DNA + NaCl solutions affects DNA melting parameters at Cs < 4 mM. Linear dependence of Tm on lga+ is found in Na-DNA + NaCl at Cs > 0.4 mMin the absence of contact of solutions with CO2 from air (a+ is cation activity). A dependence of [dTm/dlga+] on Li+ activity was observed in Li-DNA + LiCl solutions at Cs < 10 mM: [dTm/dlga+] increases from 17°–18° at Cs > 10 mM to 28°–30° at Cs ? 0.2–0.4 mM. Spectrophotometric measurements at 282 nm show that this effect was caused by protonation of bases in fragments of denatured DNA in neutral solutions. The Poisson–Boltzmann (PB) equation was solved for salt-free DNA at the melting point. The linear dependence of Tm vs lgCp was interpreted in terms of Manning's condensation theory. PB and Manning's theories fit the experimental data if charge density parameter (ξ) of denatured DNA is in the range 1.8–2.1 (assuming for native DNA ξ = 4.2). Specificity of Li ions in interactions with DNA is discussed. © 1994 John Wiley & Sons, Inc. 相似文献
7.
The nearest 5' context of 2559 human stop codons was analysed in comparison with the same context of stop-like codons (UGG, UGC, UGU, CGA for UGA; CAA, UAU, UAC for UAA; and UGG, UAU, UAC, CAG for UAG). The non-random distribution of some nucleotides upstream of the stop codons was observed. For instance, uridine is over-represented in position -3 upstream of UAG. Several codons were shown to be over-represented immediately upstream of the stop codons: UUU(Phe), AGC(Ser), and the Lys and Ala codon families before UGA; AAG(Lys), GCG(Ala), and the Ser and Leu codon families before UAA; and UCA(Ser), AUG(Met), and the Phe codon family before UAG. In contrast, the Thr and Gly codon families were under-represented before UGA, while ACC(Thr) and the Gly codon family were under-represented before UAG and UAA respectively. In an earlier study, uridine was shown to be over-represented in position -3 before UGA in Escherichia coli [Arkov,A.L., Korolev,S.V. and Kisselev,L.L. (1993) Nucleic Acids Res., 21,2891-2897]. In that study, the codons for Lys, Phe and Ser were shown to be over-represented immediately upstream of E. coli stop codons. Consequently, E. coli and human termination codons have similar 5' contexts. The present study suggests that the 5' context of stop codons may modulate the efficiency of peptide chain termination and (or) stop codon readthrough in higher eukaryotes, and that the mechanisms of such a modulation in prokaryotes and higher eukaryotes may be very similar. 相似文献
8.
V G Korolev 《Radiobiologiia》1984,24(6):728-738
Because of a great variety and different reparability of radiation-induced DNA lesions it is difficult to evaluate the radiobiological significance of certain individual alterations. It is suggested that the radionuclides incorporated into DNA can be used to imitate different types of radiation damages to DNA. Both qualitative and quantitative aspects of the problem are discussed. 相似文献
9.
Sporulation and antibiotic production, as well as the effect of exogenic antibacterial substances on bacterial sporogenesis were studied in various strains of Bac. pumilus and Bac. pumilus and Bac. subtilis. The bacteria were grown on a solid sporulation medium with and without the antibiotics. After 5-day incubation the presence of refractyl spores was determined with a phase-contrast method. It was found that in the strains of Bac. pumilus producing antibacterial substances the sporulation was normal. The loss of the capacity for synthesizing such substances resulted in asporegenicity or oligosporogenicity. This allowed a conclusion on existence of phenomenological connection between sporulation and antibiotic production. The study of the antibiotic effect on bacterial sporogenesis showed negative results which are discussed in the paper along two directions: (1) the antibiotics did not probably participate in regulation of the bacteria cell differentiation, (2) the antibiotics regulated the bacterial sporogenesis though their effect was not as yet detected because of methodical difficulties. Therefore, the problem of the antibiotic participation in regulation of sporulation in Bac. pumilus and Bac. subtilis remains open. 相似文献
10.
Xrs2, a DNA Repair Gene of Saccharomyces Cerevisiae, Is Needed for Meiotic Recombination 总被引:7,自引:0,他引:7 下载免费PDF全文
The XRS2 gene of Saccharomyces cerevisiae has been previously identified as a DNA repair gene. In this communication, we show that XRS2 also encodes an essential meiotic function. Spore inviability of xrs2 strains is rescued by a spo13 mutation, but meiotic recombination (both gene conversion and crossing over) is highly depressed in spo13 xrs2 diploids. The xrs2 mutation suppresses spore inviability of a spo13 rad52 strain suggesting that XRS2 acts prior to RAD52 in the meiotic recombination pathway. In agreement with the genetic data, meiosis-specific double-strand breaks at the ARG4 meiotic recombination hotspot are not detected in xrs2 strains. Despite its effects on meiotic recombination, the xrs2 mutation does not prevent mitotic recombination events, including homologous integration of linear DNA, mating-type switching and radiation-induced gene conversion. Moreover, xrs2 strains display a mitotic hyper-rec phenotype. Haploid xrs2 cells fail to carry out G2-repair of gamma-induced lesions, whereas xrs2 diploids are able to perform some diploid-specific repair of these lesions. Meiotic and mitotic phenotypes of xrs2 cells are very similar to those of rad50 cells suggesting that XRS2 is involved in homologous recombination in a way analogous to that of RAD50. 相似文献