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991.
N I Kalabukhov V A Serdiuk N V She?kina 《Zhurnal evoliutsionno? biokhimii i fiziologii》1976,12(6):532-538
In several geographic populations of the Arctic ground squirrel C. parryi, studies have been made on changes in oxygen consumption during decrease of the ambient temperature from 25 to 3-4 degrees, thermal preference, hemoglobin content of the blood and composition of the adipose tissue (both brown and white, subcutaneous and visceral). Significant shifts of these indices were found. In animals from various parts of the species area, different sensitivity to cooling was found, as indicated by determinations of oxygen consumption at different temperatures and the prefered temperature: different hemoglobin content of the blood was also found together with differences in the level of two unsaturated fatty acids - the oleic and linoleic ones. Comparison of these data with similar results obtained on various populations of the Siberian ground squirrel C. undulatus revealed obvious differences between these close species with respect to the indices studied. 相似文献
992.
Methods for site-directed multiple modification of DNA have been developed and used for modification of either one or two strands of plasmid DNA. Plasmid DNAs modified in the region of the tet gene were transformed into Escherichia coli cells and Tet colonies were screened. It was shown that multiple lesions in one DNA strand performed using either N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or sodium bisulfite were effectively repaired in the cell by error-free mechanism. In contrast, modification of two DNA strands led to induction of mutations. The efficiency of mutagenesis in the case of modification of a local region of one DNA strand with sodium bisulfite and modification of the other strand with MNNG was 1.1-7.9%. Mutations were analysed by restriction mapping and sequencing. All of them were G----A transitions. 相似文献
993.
Cloning of genes for bacterial glycosyltransferases. I. Selection of hybrid plasmids carrying genes for two glucosyltransferases. 总被引:6,自引:0,他引:6
A method of identifying plasmids containing genes responsible for synthesis of nucleotide sugar:lipopolysaccharide glycosyltransferases is described. Hybrid ColE1 plasmids containing random fragments of the chromosome of Escherichia coli K12 were introduced into an indicator strain of Salmonella typhimurium which lacks UDP-glucose:lipopolysaccharide glucosyltransferase I due to an rfaG mutation. Plasmids capable of correcting the transferase defect were identified by their ability to convert the bacteriophage sensitivity pattern of the recipient strain from Ffm-sensitive to Ffm-resistant. Analysis of the lipopolysaccharide of the S. typhimurium/ColE1 hybrid strains and assay of cell extracts defined the new enzyme activities. Two plasmids were identified which carried the rfaG+ gene; one of these plasmids also contained genetic information for a second glucosyltransferase, the E. coli glucosyltransferase II, which normally is not present in S. typhimurium. 相似文献
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The effect of primycin, a guanidine-type antibiotic was studied on the electric properties and 42K+ uptake of the frog sartorius and semitendinosus muscle. Both in normal and choline chloride Ringer solution, primycin evoked a concentration and time dependent depolarization of the surface membrane of the muscle. This depolarization was significantly increased by Na ions. Primycin treatment was shown to evoke a dose-dependent decrease of the depolarization induced by 20 mM K+-Ringer. When the muscles were incubated in a Ringer solution containing choline chloride, during an incubation period of 30 min the uptake of 42K+ was decreased to 12% upon the exposure to 5 x 10(-6) mol primycin as compared to the control value. As the primycin-induced depolarization increased, the shape and amplitude of the action potentials elicited by square-wave electric impulses were altered and decreased, respectively. In sodium isaethionate Ringer 1--2 x 10(-6) M primycin induced a slow depolarization resulting in firing potentials. The results suggest that primycin depolarizes the surface membrane exclusively through the blockade of the resting K+ channels, the other phenomena being the results of this depolarizing effect. 相似文献
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A V Paniutich B I Rubika?te N N Vo?tenok E A Shidlovskaia S L Grokhovski? A L Zhuze O O Favorova 《Bioorganicheskaia khimiia》1989,15(8):1060-1069
The importance of protein phosphorylation at tyrosyl hydroxy groups in the control of cell proliferation has recently been established. For identification of tyrosine-phosphorylated proteins, monoclonal antibodies (Mabs) against artificial immunogens containing O-phosphotyrosine (pTyr) or tripeptide pTyr-Gly-Gly as haptens were generated; the haptens were coupled to carrier proteins (bovine serum albumin, human immunoglobulin, keyhole limpet hemocyanin). After immunization of mice with pTyr coupled to keyhole limpet hemocyanin, Mabs were generated which were highly specific for pTyr and did not cross-react with O-phosphoserine, O-phosphothreonine, tyrosine or nucleoside-5'-monophosphates. The Mabs specifically react with tyrosinephosphorylated proteins in the Rous sarcoma virus-transformed rat XC-cell. 相似文献