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11.
Graphodatsky AS Sablina OV Meyer MN Malikov VG Isakova EA Trifonov VA Polyakov AV Lushnikova TP Vorobieva NV Serdyukova NA Perelman PL Borodin PM Benda P Frynta D Leikepová L Munclinger P Piálek J Sádlová J Zima J 《Cytogenetics and cell genetics》2000,88(3-4):296-304
Karyotypes of Calomyscus from different regions of Turkmenistan, Iran, and Azerbaijan were studied using chromosome banding (G- and C-banding) and analyses of meiosis in laboratory hybrids. Extensive variation in the diploid number and the number of autosomal arms (FNa) was revealed (2n = 30, FNa = 44; 2n = 32, FNa = 42; 2n = 44, FNa = 46; 2n = 44, FNa = 58; 2n = 37, FNa = 44; 2n = 50, FNa = 50; 2n = 52, FNa = 56). Centric and tandem fusions and heterochromatin changes were identified as the major modes of karyotype evolution in this group. Natural hybrids between individuals with different karyotypes were recorded, and regular chromosome pairing in meiosis was observed in laboratory hybrids. Fluorescence in situ hybridization with a 353-bp BspRI complex tandem repeat indicated that chromosomal repatterning occurred recently within the genus. There is no unequivocal evidence suggesting the role of chromosomal change in the speciation of the populations of Calomyscus examined. 相似文献
12.
The surface area of very low density lipoproteins (VLDL) from the serum of 15 healthy donors and the surface area of artificial lipid particles have been estimated. The artificial particles were prepared as a mixture of egg phosphatidylcholine and triolein. Two fluorescent probes - energy donor and acceptor - were placed on the surface, and Forster's nonradiative energy transfer was measured; the transfer efficiency is a function of surface area. The fluorescent probe K-68 (4-[5-(phenyloxazolyl-2)-1-pentadecyl)pyridinium) was used as a donor, and DSP-12 (dimethylamino)styryl-N-dodecylpyridinium) was used as an acceptor. The specific surface area of the artificial lipid particles was estimated to be 0.585 +/- 0.015 nm2 per phosphatidylcholine molecule, which is 15% less than in lipid bilayers. The specific area of VLDL particles was 259 +/- 65 m2 per g of total VLDL. This value is close to the specific area of low density lipoproteins (LDL), and corresponds to the area of a spherical particle 10-12 nm in radius. However, VLDL are assumed to be much larger particles as compared with LDL. Therefore, the new data of the VLDL surface area raise a problem of revision of the existing VLDL models. 相似文献
13.
Effects of medium viscosity on kinetic parameters of poly(U) hydrolysis catalyzed by RNase from Bac. intermedius 7P (binase) were studied in solutions of sucrose (4-50 wt. %) and glycerol (35-62 wt. %) in Tris--sodium acetate buffer (pH 7.5) at 25 degreesC. The rate constant of reaction kcat was practically unchanged over a wide range of viscosities (1-15 cP for sucrose and 2.5-3 cP for glycerol). In glycerol solutions, kcat slightly increased with viscosity increase from 4 to 10 cP. Addition of NaCl to the buffer medium resulted in an inhibitory effect of Na+ on kcat, prevented by 50% sucrose or 60% glycerol. It is concluded that binase-catalyzed poly(U) cleavage occurs through a "tense"-substrate mechanism, similarly to reactions catalyzed by alpha-chymotrypsin, trypsin, and laccase. 相似文献
14.
Interest in the use of low-copy nuclear genes for phylogenetic analyses of
plants has grown rapidly, because highly repetitive genes such as those
commonly used are limited in number. Furthermore, because low- copy genes
are subject to different evolutionary processes than are plastid genes or
highly repetitive nuclear markers, they provide a valuable source of
independent phylogenetic evidence. The gene for granule-bound starch
synthase (GBSSI or waxy) exists in a single copy in nearly all plants
examined so far. Our study of GBSSI had three parts: (1) Amino acid
sequences were compared across a broad taxonomic range, including grasses,
four dicotyledons, and the microbial homologs of GBSSI. Inferred structural
information was used to aid in the alignment of these very divergent
sequences. The informed alignments highlight amino acids that are conserved
across all sequences, and demonstrate that structural motifs can be highly
conserved in spite of marked divergence in amino acid sequence. (2)
Maximum-likelihood (ML) analyses were used to examine exon sequence
evolution throughout grasses. Differences in probabilities among
substitution types and marked among-site rate variation contributed to the
observed pattern of variation. Of the parameters examined in our set of
likelihood models, the inclusion of among-site rate variation following a
gamma distribution caused the greatest improvement in likelihood score. (3)
We performed cladistic parsimony analyses of GBSSI sequences throughout
grasses, within tribes, and within genera to examine the phylogenetic
utility of the gene. Introns provide useful information among very closely
related species, but quickly become difficult to align among more divergent
taxa. Exons are variable enough to provide extensive resolution within the
family, but with low bootstrap support. The combined results of amino acid
sequence comparisons, maximum-likelihood analyses, and phylogenetic studies
underscore factors that might affect phylogenetic reconstruction. In this
case, accommodation of the variable rate of evolution among sites might be
the first step in maximizing the phylogenetic utility of GBSSI.
相似文献
15.
16.
Preparations of low-density lipoproteins from healthy donor blood contain lipoprotein particles with different capacity for aggregation: upon stirring, some particles form aggregates significantly more quick than others. After stirring, lipoprotein particles are separated by ultracentrifugation into two fractions: a fraction of large aggregates and a fraction of small particles without intermediate forms. It is known that lipoprotein aggregates can accelerate intracellular accumulation of lipids. Therefore, it is supposed that particles of high aggregation ability are more atherogenic. 相似文献
17.
A cytogenetic examination of spreaded cells of diapausing and early activated blastocysts obtained from 7 female western spotted skunks was performed. Mitosis was not observed in 1626 cells obtained from 9 diapausing blastocysts; however, 12 (1.5%) figures of diploid mitosis were seen in 851 cells from 5 early activated embryos. Diameter of the cell nuclei varied from 4 to 29 microm during diapause, and from 5 to 40 microm in activated blastocyst, and the heterogeneity in nuclear size was significantly different between diapausing and activated embryos (P<0.01). About 80% of nuclei from diapausing blastocysts measured 9 to 16 microm, whereas a similar percentage of nuclei from activated blastocysts ranged from 15 to 27 microm. Many enlarged nuclei exhibited morphological features characteristic of mammalian polytene (i.e. endopolyploid with polytenic organization of chromosomes) trophoblast cells. The number of silver stained nucleoli in all the nuclei did not exceed 2, which corresponds to the number of nucleolus organizers in the diploid karyotype in this species of skunk and suggests the polytene organization of chromosomes in enlarged nuclei. About 10% of large interphase nuclei were observed to undergo amitosis, i.e. direct division by constriction. The resulting nuclear fragments in diapausing blastocysts usually had normal morphology and active nucleoli. In activated embryos, nearly 15% of amitotically divided nuclei appeared to be dividing into fragments of unequal size, one of which had normal cell nuclear morphology and extremely large silver positive nucleoli, and the other fragment exhibited signs of cell death. We interpret these data as indicating that 1) amitotic division of trophoblast endopolyploid cell nuclei in the skunk blastocysts may generate new trophoblast cells which contribute to increased cell number during both diapause and activation stages, and 2) activation of blastocysts after diapause is related to the production of trophoblast cells with enhanced synthetic capabilities. 相似文献
18.
TI Pollin T Isakova KA Jablonski PI de Bakker A Taylor J McAteer Q Pan ES Horton LM Delahanty D Altshuler AR Shuldiner RB Goldberg JC Florez PW Franks;Diabetes Prevention Program Research Group 《PLoS genetics》2012,8(8):e1002895
Weight-loss interventions generally improve lipid profiles and reduce cardiovascular disease risk, but effects are variable and may depend on genetic factors. We performed a genetic association analysis of data from 2,993 participants in the Diabetes Prevention Program to test the hypotheses that a genetic risk score (GRS) based on deleterious alleles at 32 lipid-associated single-nucleotide polymorphisms modifies the effects of lifestyle and/or metformin interventions on lipid levels and nuclear magnetic resonance (NMR) lipoprotein subfraction size and number. Twenty-three loci previously associated with fasting LDL-C, HDL-C, or triglycerides replicated (P = 0.04–1×10−17). Except for total HDL particles (r = −0.03, P = 0.26), all components of the lipid profile correlated with the GRS (partial |r| = 0.07–0.17, P = 5×10−5–1×10−19). The GRS was associated with higher baseline-adjusted 1-year LDL cholesterol levels (β = +0.87, SEE±0.22 mg/dl/allele, P = 8×10−5, P
interaction = 0.02) in the lifestyle intervention group, but not in the placebo (β = +0.20, SEE±0.22 mg/dl/allele, P = 0.35) or metformin (β = −0.03, SEE±0.22 mg/dl/allele, P = 0.90; P
interaction = 0.64) groups. Similarly, a higher GRS predicted a greater number of baseline-adjusted small LDL particles at 1 year in the lifestyle intervention arm (β = +0.30, SEE±0.012 ln nmol/L/allele, P = 0.01, P
interaction = 0.01) but not in the placebo (β = −0.002, SEE±0.008 ln nmol/L/allele, P = 0.74) or metformin (β = +0.013, SEE±0.008 nmol/L/allele, P = 0.12; P
interaction = 0.24) groups. Our findings suggest that a high genetic burden confers an adverse lipid profile and predicts attenuated response in LDL-C levels and small LDL particle number to dietary and physical activity interventions aimed at weight loss. 相似文献
19.
20.
E S Kan A V Chervonski? V R Isakova B D Brondz Z K Blandova 《Biulleten' eksperimental'no? biologii i meditsiny》1986,102(8):203-205
The differences in the generation of specific suppressor T cells (SSTC) against H-2Kb wild type were investigated in H-2Kbm1, H-2Kbm3 and H-2Kbm4 mutants. Anti-Kb SSTC were produced only by bm3 mutant and F1(BALB/c X bm3) hybrid. T-cell nature of SSTC of bm3 mutant was confirmed by anti-Thy 1.2 monoclonal antibodies described in the same study. 相似文献