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61.
The regulatory mechanism for the hormonal control of prolactin (PRL) and growth hormone (GH) gene expression in rat pituitary gland during gestation and lactation is verified in this study. The level of PRL-specific mRNA (mRNAPRL) sequences in the pituitary gland is elevated in the later part of gestation and more prominently so in lactation. In contrast the expression of GH gene is inhibited in the same tissue during gestation and lactation resulting in the dramatic decrease in the level of GH-specific mRNA (mRNAGH) sequences. We now demonstrate the influence of a tissue-specific altered DNA methylation pattern on the temporal modulation of expression of PRL and GH genes in the pituitary gland during alternate physiological states. An altered methylation pattern of specific "-C-" residues only in the coding region of PRL and GH gene can be detected concurrently with the altered level of expression of these genes in the pituitary gland during gestation and lactation. These results also demonstrate the dynamic state of methylation of specific -C- residues during the transition of these two genes from one state of expression to another in the same tissue. A correlation between site-specific DNA methylation and tissue-specific expression of PRL and GH gene in pituitary gland is reported. Thus a role of DNA methylation in the hormonal control of PRL and GH gene expression in physiological states such as pregnancy and lactation is proposed. 相似文献
62.
C B Siegall T T Hla A Kumar 《Biochemical and biophysical research communications》1988,154(3):1010-1017
Functional reconstitution of U1 small nuclear ribonucleoprotein particle (U1 snRNP) was performed using in vitro transcribed U1 snRNA. Hela cell nuclear extract was depleted of its constituent snRNPs by centrifugation at 100,000 X g. The supernatant was devoid of snRNAs and lacked cleavage activity in splicing reactions using in vitro transcribed beta-globin pre-mRNA as substrate. The resulting pellet which contained the snRNAs, retained 5' splice site cleavage activity in a similar splicing reaction. Supplementation of the inactive supernatant fraction with in vitro transcribed U1 snRNA, partially restored 5' splice site cleavage activity thereby demonstrating the specific requirement of U1 snRNP in the initial stage of pre-mRNA splicing. 相似文献
63.
The high molecular weight aminoacyl-tRNA synthetase complex (the 24S complex) was isolated from rat liver by ultracentrifugation. The lysyl-tRNA synthetase (E.C. 6.1.1.6) was selectively dissociated by hydrophobic interaction chromatography on 1,6 diaminohexyl agarose followed by hydroxylapatite chromatography and DEAE chromatography. The lysyl-tRNA synthetase dissociated from the 24S synthetase complex was purified approximately to 2700 fold with 14% yield. 相似文献
64.
The most abundant anhydrase isoenzyme from the erythrocyte of Indian buffalo has been purified using affinity gel and DEAE-cellulose ion-exchange columns and single crystals suitable for X-ray diffraction studies have been obtained. The unit cell dimensions are a = 46.8 A, b = 104.5 A, c = 60.4 A, beta = 91.2 degrees and the space group is P2(1), with two molecules per asymmetric unit. 相似文献
65.
Malathi Chari K. Gupta T. G. Prasad K. S. Krishna Sastry M. Udaya Kumar 《Plant and Soil》1986,91(1):109-114
Summary The effect of calcium in the water relations and tolerance to moisture deficits was tested in groundnut and cowpea. In both species, enrichment of tissue with calcium resulted in maintenance of a higher water status under stress associated with low proline accumulation. The extent of membrane damage (as reflected by the absorbance at 273 nm) was lesser in leaves of plants fed with higher levels of Ca++ when subjected to simulated stress. The rate of water loss from the leaves of Ca++-enriched plants was also lower. The possible role of Ca++ in inducing membrane stability and maintenance of higher water status is discussed. 相似文献
66.
R A Fisher R Kumar D J Hanahan M S Olson 《The Journal of biological chemistry》1986,261(19):8817-8823
The beta-adrenergic agonist isoproterenol inhibited the glycogenolytic response of platelet-activating factor (AGEPC, 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine) in perfused livers derived from fed rats. AGEPC-stimulated hepatic vasoconstriction, measured by increases in portal vein pressure, also was inhibited by prior isoproterenol infusion. Isoproterenol-mediated inhibition of these hepatic responses to AGEPC was not apparent when isoproterenol (10 microM) was coinfused with the beta-receptor antagonist propranolol (75 microM) or when isoproterenol was replaced with the alpha-adrenergic agonist phenylephrine (10 microM). alpha-Agonist-induced glycogenolysis and vasoconstriction in the perfused liver was unaffected by isoproterenol infusion. Glucagon (2.3 nM) had no effect on the glycogenolytic or vasoconstrictive responses of the liver to AGEPC despite the fact that glucagon increased hepatic cAMP levels to a far greater extent than isoproterenol. Additionally, inhibition of the hepatic responses to AGEPC by isoproterenol occurred in perfused livers from mature rats (i.e. greater than 300 g) in which liver parenchymal cells lack functional beta-adrenergic receptors. The data presented in this study illustrate a specific inhibition of AGEPC-induced hepatic glycogenolysis and vasoconstriction by beta-adrenergic stimulation of the perfused liver. This inhibition appears to be mediated by interaction of isoproterenol with nonparenchymal cells within the liver. These findings are consistent with the concept that AGEPC stimulates hepatic glycogenolysis by an indirect mechanism involving hepatic vasoconstriction. 相似文献
67.
68.
Effect of spermidine on the conformation of bacteriophage MS2 RNA. Electron microscopy and computer modeling 总被引:2,自引:0,他引:2
The structure of single-stranded RNA from the bacteriophage MS2 has been examined by electron microscopy in the presence of the polyamine spermidine. The molecules are found in two alternate conformations. The first of these can be characterized as a cruciform structure composed of three large loops approximately 500 to 700 nucleotides in size. The interior of the molecule has extensive base-paired regions which connect distant regions of the molecule; the farthest being 2500 nucleotides apart. In the second conformation, the molecules appear rod-like. Two of the large loops disappear, and these regions form, instead, extensive long-range helices. Computer modeling has been employed to explore the base-pairing potential of the sequence of bacteriophage MS2 RNA. Double-stranded regions identified by electron microscopy are shown to occur in local G + C-rich stretches of the RNA. Detailed models have been calculated for two regions of long-range contact. One of these includes the ribosome-binding site for the viral coat protein gene. The results are discussed in the context of the known role of RNA structure in the regulation of viral gene expression. 相似文献
69.
70.
J M Londowski L K Revelle S B Kost R A Corradino R Kumar 《Journal of steroid biochemistry》1985,23(1):81-85
We synthesized 3 beta-thiovitamin D3 from 7-dehydrocholesterol and tested its biological activity and protein binding properties. The thiovitamin was found to be a weak vitamin D agonist at high doses in vivo. It was poorly bound by both vitamin D-binding protein as well as by the intestinal cytosol receptor for 1,25-dihydroxyvitamin D. It did not increase the synthesis of calcium binding protein in the chick embryonic duodenum and did not block the activity of 1,25-dihydroxyvitamin D3 in this system. We conclude that 3 beta-thiovitamin D3 is a weak vitamin D agonist in vivo with no agonist activity or antagonist activity to 1,25-dihydroxyvitamin D3 in the chick embryonic duodenum. 相似文献