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51.
52.
The south American rodent Graomys griseoflavus exhibits a remarkable chromosome polymorphism as a consequence of four Robertsonian fusions. Focusing on the genetic analysis of the taxon, genome organization of all karyomorphs was studied at chromosome and molecular organization level. Cytogenetic (G, NOR and Re banding) and molecular (satellite and mitochondrial DNAs) events accompanying chromosome divergence allowed tracing a phylogenetic relationship among all karyomorphs. Available data led to propose that chromosome evolution of G. griseoflavus occurred in a non-random sequence of centric fusions, supporting the hypothesis of single origin for Robertsonian karyomorphs. 相似文献
53.
A novel mechanism of repression of the vascular endothelial growth factor promoter,by single strand DNA binding cold shock domain (Y-box) proteins in normoxic fibroblasts 总被引:4,自引:0,他引:4
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Coles LS Diamond P Lambrusco L Hunter J Burrows J Vadas MA Goodall GJ 《Nucleic acids research》2002,30(22):4845-4854
54.
The gene for neurofibromatosis type 1 (NF1), mapping to 17q11.2, has one of the highest observed mutation rates, partially because of its large size and gene conversion primed by NF1 pseudogenes. We have previously shown by means of high resolution fluorescence in situ hybridization (FISH) that a number of the loci flanking the NF1 gene are duplicated, in agreement with the reported presence of NF1 repetitive sequences (REPs). We report a direct tandem duplication of the NF1 gene identified in 17q11.2 by high-resolution FISH. FISH on stretched chromosomes with locus-specific probes revealed the duplication of the NF1 gene from the promoter to 3'UTR, but with at least the absence of exon 22. Fiber FISH with P1 artificial and bacterial artifical chromosomes, including the NF1 5'UTR and 3'UTR and flanking regions, visualized the direct tandem duplication with a similar, but not identical, genomic organization of the NF1 duplicon copies. Duplication was probably present in the human-chimpanzee-gorilla common ancestor, as demonstrated here by the finding of the duplicated NF1 gene at orthologous chromosome loci. The NF1 intrachromosomal duplication may contribute to the high whole-gene mutation rate by gene conversion, although the functional activity of the NF1 copy remains to be investigated. Detection of the NF1 duplicon by high-resolution FISH may pave the way to filling the gaps in the human genomic sequence of the pericentromeric 17q11.2 region. 相似文献
55.
The crystals of the soil-isolated Bacillus thuringiensis (Bt) strain A4 consist of two polypeptides with molecular mass of 140 kDa and 32 kDa that exhibit insecticidal activity against
adult flies of Bactrocera oleae (Diptera). Plasmid curing applied to this strain resulted in the isolation of several subclones exhibiting alterations in
their crystal polypeptides as well as two acrystalliferous subclones. The crystals of subclone 1.1 lacked the 32-kDa polypeptide
and consisted uniquely of a 140-kDa polypeptide antigenically related to the parental 140-kDa crystal polypeptide. Additionally,
the crystals of this subclone exhibited insecticidal activity against B. oleae equivalent to that of the parental strain. Therefore, the 32-kDa crystal polypeptide is dispensable for insecticidal activity,
which appears to be dependent on the presence of the 140-kDa crystal polypeptide.
Received: 5 April 2000 / Accepted 2 May 2000 相似文献
56.
Although it is known that drug addicts are a high-risk group for disruption of many homeostatic processes, little is know
about changes in serum trace elements concentrations after taking the psychoactive substances. The aim of the study was to
check the influence of the taking homemade heroin on serum level of copper. Blood samples were taken from 30 opiate addicts,
and copper concentrations were measured by the means of atomic absorption spectrophotometry. The result of the study show
that in the examined group, copper serum concentrations (1.35 mg/L) upon admission to the clinic were higher than in the control
group (1.11 mg/L) but decreased during hospitalization (1.18 mg/L). There was no correlation between duration of stay at the
hospital and changes in serum copper concentration. 相似文献
57.
Blanca Lidia Arroyo-Flores Carlos Calvo-Méndez Arturo Flores-Carreón Everardo López-Romero 《Antonie van Leeuwenhoek》1998,73(4):289-297
Incubation of a mixed membrane fraction isolated from C. albicans yeast cells with Nonidet P-40 at a detergent/protein ratio as low of 0.025 (0.016–0.019%, w/v) yielded a soluble fraction that catalyzed the transfer of mannose from GDP-[14C] Man into dolichol phosphate mannose and from this intermediate into mannoproteins. Over 95% of the sugar in mannoproteins was O-linked as judged from its release after -elimination. Mannose was identified as the sole product after this treatment. Transfer activity did not depend on exogenous lipid acceptor indicating that the latter was solubilized along with the mannosyl transferases. Synthesis of mannolipid and mannoproteins occurred at optima temperatures of 20 °C and 37 °C, respectively, and at a pH in the range of 7.5-9.5. Mannosyl transfer into the mannolipid was stimulated by Mg2+and inhibited by Ca2+and Mn2+whereas mannoprotein labeling was stimulated by Mn2+and to a lower extent by Mg2+. When measured as a function of substrate concentration, the synthesis of the mannolipid was a nearly linear function of GDP-Man concentration in the range of 5 to 32 M whereas protein mannosylation exhibited hyperbolic kinetics with saturation reached at about 10 M. The solubilized preparation was able to utilize an exogenous source of mannolipid as sugar donor for protein mannosylation. Dinucleotides and, to a higher extent trinucleotides, inhibited mannosyl transfer into the mannolipid and hence into mannoproteins. 相似文献
58.
A new species ofSorghastrum,S. pohlianum, from Mexico is described and illustrated. A numerical analysis comparing the new species to the closest species (S. nutans andS. nudipes) was undertaken. The first three principal components explain 84% of the variation of the taxa involved. In addition there is morphological evidence to distinguish the new species from its closest relatives. It differs fromS. nutans by showing smaller inflorescences, having sterile lemmas and anthers, and having somewhat smaller but wider blades and different flowering periods. In addition, it is distinguished fromS. nudipes due to the presence of auricles > 1 mm long and inflorescence branches bearing spikelets along their entire length. 相似文献
59.
60.
Diane F. Matesic Joseph A. Erwin Edna S. Kaneshiro 《The Journal of eukaryotic microbiology》1998,45(1):156-163
ABSTRACT Paramecium tetraurelia contains high concentrations of ethanolamine sphingolipids, especially in its ciliary membrane. Three ethanolamine sphingophospholipids with different long chain bases (dihydrosphingosine, sphingosine and phytosphingosine), and their phosphonyl analogs, were previously identified and characterized. In the present study, radiolabeling experiments on lag- and log-phase cells were performed to investigate the extent of sphingolipid biosynthetic capacities of the ciliate. Long chain bases of sphingolipids are formed by an initial condensation reaction of serine with a fatty-coenzyme A. Thus, radiolabeled palmitic acid, stearic acid and serine were used as precursor compounds in these experiments. The results indicated that (1) sphingolipid precursors were incorporated into every major lipid fraction. (2) ethanolamine sphingophosphonolipids accumulated faster than the ethanolamine sphingophospholipids, (3) in contrast to these sphingolipids, the glycerolipid, phosphatidyethanolamine. accumulated faster than its phosphono analog, and (4) palmitic acid, but not stearic acid, was incorporated into the long chain bases of ethanolamine sphingophospho- and sphingophosphonolipids. consistent with an earlier report demonstrating that these lipids contain only C,g long chain bases. Since P. tetraurelia takes up serine and other water-soluble substrates very slowly, and catabolizes fatty acids rapidly, label is randomized in intact cells. Thus, cell-free protocols provide useful experimental systems for studies of sphingolipid biosynthesis than do intact organisms, when the uptake of precursor substrates are slow. 相似文献