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21.
22.
23.
Nucleotide variation at the hypervariable esterase 6 isozyme locus of Drosophila simulans 总被引:2,自引:0,他引:2
Esterase 6 (Est-6/EST6) is polymorphic in both Drosophila melanogaster and
D. simulans for two common allozyme forms, as well as for several other
less common variants. Parallel latitudinal clines in the frequencies of the
common EST6-F and EST6-S allozymes in these species have previously been
interpreted in terms of a shared amino acid polymorphism that distinguishes
the two variants and is subject to selection. Here we compare the sequences
of four D. simulans Est-6 isolates and show that overall estimates of
nucleotide heterozygosity in both coding and 5' flanking regions are more
than threefold higher than those obtained previously for this gene in D.
melanogaster. Nevertheless, the ratio of replacement to exon silent-site
polymorphism in D. simulans is less than the ratio of replacement to silent
divergence between D. simulans and D. melanogaster, which could be the
result of increased efficiency of selection against replacement
polymorphisms in D. simulans or to divergent selection between the two
species. We also find that the amino acid polymorphisms separating EST6- F
and EST6-S in D. simulans are not the same as those that separate these
allozymes in D. melanogaster, implying that the shared clines do not
reflect shared molecular targets for selection. All comparisons within and
between the two species reveal a remarkable paucity of variation in a
stretch of nearly 400 bp immediately 5' of the gene, indicative of strong
selective constraint to retain essential aspects of Est-6 promoter
function.
相似文献
24.
Rats treated with varying amounts of 19-hydroxy-10(S),19-dihydrovitamin D3 prior to administration of physiologic doses of vitamin D3 exhibit normal intestinal calcium transport but are unable to mobilize bone calcium. In contrast, 19-hydroxy-10(R),19-dihydrovitamin D3 had no inhibitory activity. Circulating serum levels of 25-hydroxy[3H]vitamin D3 and 1 alpha, 25-dihydroxy[3H]vitamin D3 are markedly suppressed but not totally eliminated in animals predosed with 19-hydroxy-10(S),19-dihydrovitamin D3 before [3H]vitamin D3. Hepatic 25-hydroxy[3H]vitamin D3 levels were approximately equal in both 19-hydroxy-10(S),19-dihydroviotamin D3 treated and untreated rats. However, the rate of conversion of [3H]vitamin D3 to 25-hydroxyvitamin D3 in vivo is greatly reduced in the treated rats. The inhibitory vitamin analogue was also show to block hepatic microsomal 25-hydroxylation in vitro. These results indicate that 19-hydroxy-10(S),19-dihydrovitamin D3 is a specific inhibitor for a hepatic microsomal vitamin D3-25-hydroxylase system. 相似文献
25.
W. E. Stumpf M. Sar F. A. Reid S. Huang R. Narbaitz H. F. DeLuca 《Cell and tissue research》1981,221(2):333-338
Summary After injection of radiolabeled 1,25 (OH)2 vitamin D3, nuclear concentration of radioactivity is observed in parenchymal cells of the parathyroid gland in pregnant, adult male, and 10-day male neonatal rats. In competition studies with unlabeled 1,25 (OH)2 vitamin D3, but not with 25 (OH) vitamin D3, nuclear uptake is prevented. Experiments with 3H 25 (OH) vitamin D3, in contrast to 3H 1,25 (OH)2 vitamin D3, do not show nuclear concentration in cells of the parathyroid. The results of the autoradiographic studies suggest the presence of receptors for a direct effect of 1,25 (OH)2 vitamin D3 on the parathyroid gland for modulation of parathyroid hormone secretion. 相似文献
26.
Sample preparation and high-pressure liquid-chromatography separation methods useful for the study of retinoic acid metabolism are reported. The sample preparation procedure does not cause significant degradation of retinoic acid, and the gradient high-pressure liquid-chromatography separation method gives excellent separation of the major metabolites of retinoic acid. These methods were used to examine the metabolites of retinoic acid in blood, trachea and lung, testes, kidneys and small intestine of vitamin A-deficient rats dosed subcutaneously with 2 micrograms of [11,12-3H] retinoic acid. At 6h after dosing, a total of eight metabolites of retinoic acid produced in vivo were found in the tissues examined. Of these, four were found in most of the epithelial tissues examined, and therefore may be of interest as possible active metabolites in the epithelial functions of vitamin A. 相似文献
27.
Characteristics of a new bacteriophage, Psp231a, infecting Pseudomonas phaseolicola HB10Y.
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Bacteriophage Psp231a infects Pseudomonas phaseolicola, strain HB10Y, which is the host cell for the enveloped bacteriophage phi 6. This paper describes the biophysical characteristics of Psp231a and the physical properties of its nucleic acid. In electron micrographs the virion appears as an icosahedral structure, approximately 55 nm in diameter, with a short tail. The virion density is 1.48 g/cm3 in CsCl, and the sedimentation coefficient is approximately 407S. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed the presence of 12 polypeptides ranging in molecular weight from 5,000 to 117,000. The nucleic acid of Psp231a is linear, double-stranded DNA of molecular weight 28 X 10(6). Its density in CsCl is 1.716 g/cm3, and its sedimentation coefficient in 3 M CsCl is 20.0S, corresponding to an S020,W of 34S. 相似文献
28.
Isolation and identification of 23,25-dihydroxyvitamin D3, an in vivo metabolite of vitamin D3 总被引:3,自引:0,他引:3
Vitamin D supplemented rats produce a metabolite of 25-hydroxy[3 alpha-3H]vitamin D3 that is easily separated from known metabolites by using high-performance liquid chromatography. The production of this metabolite in vivo as well as 1,25-dihydroxyvitamin D3, 24(R),25-dihydroxyvitamin D3, and 25-hydroxyvitamin D3 26,23-lactone is largely if not totally eliminated by nephrectomy. Kidney homogenates from vitamin D supplemented chickens incubated with 25-hydroxyvitamin D3 produce significant quantities of the new, unknown metabolite. This metabolite was isolated in pure form from such incubation mixtures by using both straight-phase and reversed-phase high-performance liquid chromatography. This metabolite has been positively identified as 23,25-dihydroxyvitamin D3 by ultraviolet absorption spectrophotometry, mass spectrometry, and derivatization. This structure was confirmed by chemical synthesis of both C-23 stereoisomers. Although the natural product exactly comigrates with one of the synthetic isomers, the exact stereochemistry of the natural product remains unknown. It is possible that this new metabolite is an intermediate in the biosynthesis of 25-hydroxyvitamin D3 26,23-lactone. 相似文献
29.
A fluorinated vitamin D3 analog with biopotency greater than 1 alpha, 25-dihydroxy vitamin D3 总被引:2,自引:0,他引:2
R A Corradino H F DeLuca Y Tanaka N Ikekawa Y Kobayashi 《Biochemical and biophysical research communications》1980,96(4):1800-1803
Vitamin D metabolites and analogs induce synthesis of a specific calcium-binding protein in embryonic chick duodenum maintained in organ culture. Using calcium-binding protein biosynthesis as a specific and sensitive biochemical indicator of intrinsic biopotency, 24,24-difluoro-1α,25-dihydroxy vitamin D3 was found to be approximately four times more potent on a molar basis than the most active, naturally occurring metabolite, 1α,25-dihydroxy vitamin D3. 相似文献
30.
D DeLuca T E Mandel G A Luckenbach M M Kennedy 《Journal of immunology (Baltimore, Md. : 1950)》1980,124(4):1821-1829