Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.5 (RNase)
 17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

After homogenization of intestinal mucosa from vitamin D-replete chicks and high speed centrifugation, the major proportion of the vitamin D-induced calcium-binding protein is present in the supernatant fraction. However, the centrifugate, after repeated washing, contains significant amounts of bound calcium-binding protein that can be solubilized by Triton X-100. The bound calcium-binding protein is identical to soluble calcium-binding protein by the criteria of immunological identity, electrophoretic mobility, and molecular size, as determined by gel filtration chromatography. The bound calcium-binding protein is only partially released by sonication, osmotic shock or by ribonuclease treatment. Bound and soluble calcium-binding protein are not present in rachitic chick intestine. The addition of calcium-binding protein to rachitic mucosa prior to homogenization does not yield a Triton X-100 solubilizable form, indicating that bound calcium-binding protein in vitamin D-replete intestine is not due to adsorption or vesicular entrapment of soluble calcium-binding protein. The overall evidence suggests that part of the intestinal calcium-binding protein is membrane-bound.
 ...
PMID:Evidence for a membrane-bound fraction of chick intestinal calcium-binding protein. 63 6

In the vitamin D-depleted rat, all nucleated tissues examined (brain, lung, heart, pancreas, liver, cartilage, muscle, bone, kidney, and intestine) contained a soluble substance which bound 25-hydroxy[3H]cholecalciferol in vitro specifically and sedimented at 6.3 S in linear sucrose gradients. The serum-steroid complex sedimented a 4.1 S, and erythrocyte lysates were apparently devoid of specific binding activity. The ability of these cytosols to specifically bind the steroid was destroyed by treatment with trypsin, but not by RNase, DNase, or 1 mM p-hydroxymercuribenzoate. The sedimentation pattern was not altered in sucrose gradients containing 0.5 M KCl or following cytosol preparation and ultracentrifugation in gradients containing 0.012 M dithiothreitol. The apparent avidity for 25-hydroxycholecalciferol (KA similar to 2 times 10- M) was slightly higher in muscle and kidney cytosols than in serum, but serum contained a large number of specific binding sites. The presence of widespread, high affinity binding proteins for 25-hydroxycholecalciferol raises the possibility that tissues other than the intestine, bone, and kidney may respond directly to vitamin D metabolites.
 ...
PMID:Widespread, specific binding of 25-hydroxycholecalciferol in rat tissues. 114 Dec 9

Several studies have shown that the 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) receptor protein levels increase in response to 1,25-(OH)2D3. We have studied the mechanism of this regulation in both mouse fibroblasts and rat intestinal epithelial cells. Cell extracts and total RNA were prepared at varying times after addition of 1,25-(OH)2D3. The 1,25-(OH)2D3 receptor protein levels, measured using an immunoradiometric assay, rose significantly 2-3 h posttreatment and had risen 3-fold at 8 h. Concurrently, the 1,25-(OH)2D3 receptor mRNA content, measured using a ribonuclease protection assay, was not altered by 1,25-(OH)2D3 during this time. In cycloheximide-blocked cells, the administration of 1,25-(OH)2D3 markedly reduced the degradation rate of previously formed receptor. The 1,25-(OH)2D3 receptor protein half-life was determined as 4 h in the absence of 1,25-(OH)2D3 and increased to at least 8 h in the presence of 1,25-(OH)2D3. We also measured the 1,25-(OH)2D3 receptor mRNA levels in the duodena and kidney of vitamin D-deficient rats after a single 150-pmol injection of 1,25-(OH)2D3. Again, we found that 1,25-(OH)2D3 receptor mRNA levels were not changed in these tissues after 1,25-(OH)2D3 treatment. Therefore, the elevation of the 1,25-(OH)2D3 receptor protein following 1,25-(OH)2D3 administration is apparently the result of increased receptor protein lifetime and not increased transcription.
 ...
PMID:Up-regulation of the vitamin D receptor in response to 1,25-dihydroxyvitamin D3 results from ligand-induced stabilization. 132 92

Murine complement protein H is encoded by a 100-kb gene on chromosome 1. A 3.2-kb fragment of the 5' flanking region of the H gene was sequenced, and two transcription start sites for this gene were identified by RNase protection and S1 nuclease analyses, each of which had upstream TATA and CAAT boxes. This region shares sequence homology with known regulatory elements, including the SV40 enhancer consensus, the Sp1 binding site, and two glucocorticoid-responsive core elements (GRE). Tissue and cell-line specificity has been examined by Northern analysis, and the 4.4-kb full-length H messenger RNA was identified in liver, kidney, spleen, thymus, liver cell line 1469, and L cells. IFN-gamma did not induce H mRNA expression in the macrophage cell line P388D.1 but had a positive effect on both the mRNA and protein levels of H in L cells. PMA, LPS, and vitamin D did not increase H mRNA levels in L cells. Pursuant to the discovery of two GRE in the 5' regulatory region of the H gene, we examined the effects of glucocorticoids on H mRNA expression. Dexamethasone (10(-7) M) was found to increase markedly the levels of H mRNA and protein after 24 h of incubation, and the effect on the mRNA was detectable by 30 min. The fact that H is a down-regulator of complement activation is consistent with the known immunosuppressive role of glucocorticoids. To our knowledge, this is the first time that dexamethasone has been shown to increase the levels of a complement protein.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Analysis of complement factor H mRNA expression: dexamethasone and IFN-gamma increase the level of H in L cells. 253 12

Undegraded polyribosome preparations may be obtained from chick intestinal mucosa if ribonuclease activity is strictly controlled. This is best achieved by homogenization of the mucosa directly in rat liver cell-sap. 2. The extent of amino acid incorporation by chick intestinal polyribosomes is greatly influenced by the source of the cell-sap. Sephadex-treated intestinal cell-sap caused impaired incorporation and release of completed polypeptide chains, whereas Sephadex-treated rat liver cell-sap promoted the polymerization of up to 90 amino acids per ribosome. Under optimum conditions 30-35% of the nascent polypeptide chains are completed and released. 3. The preparation of an antiserum against the calcium-binding protein formed in response to vitamin D is described. It is shown that the antiserum is highly specific for calcium-binding protein. 4. This antiserum was used to investigate the ability of chick intestinal polyribosomes to synthesize calciumbinding protein. Only polyribosomes from chicks receiving vitamin D have the ability to synthesize calcium-binding protein. Moreover, the product formed in vitro has the same electrophoretic mobility as calcium-binding protein synthesized in vivo. 5. It is concluded that one of the main functions of vitamin D in the small intestine is to induce the synthesis de novo of calcium-binding protein.
 ...
PMID:The response of the small intestine to vitamin D. Isolation and properties of chick intestinal polyribosomes. 445 90

Osteoclast-activating factor (OAF) is a soluble mediator found in supernates of human peripheral leukocytes which have been cultured with antigens or phytomitogens. OAF is a potent stimulator of osteoclastic resorption of fetal bone in organ culture. The present studies were designed to characterize OAF chemically. Bone resorbing activity from supernates of leukocytes cultured without added plasma was not lost on dialysis using a membrane with a molecular weight cutoff of 3,500, but was lost when heated to 60 degrees C for 30 min. The activity was lost after treatment with trypsin or pronase but not after treatment with ribonuclease or neuraminidase. Papain, which inactivated parathyroid hormone at a concentration of 25 mug/ml, did not inactivate OAF at 250 mug/ml. OAF did not react with an antibody to bovine parathyroid hormone which cross-reacts with human parathyroid hormone. OAF was also distinguished from active metabolites of vitamin D and from prostaglandin by extraction procedures and immunoassay for prostaglandin E(2). When the medium from activated leukocytes cultured with autologous plasma was fractionated by gel filtration on Sephadex, bone resorbing activity eluated both with plasma proteins and in lower molecular weight fractions. However, when medium from leukocytes cultured without added plasma was chromatographed, all the OAF activity was eluted in a sharp low molecular weight peak located between chymotrypsinogen (25,000 molecular weight) and ribonuclease A (13,700 molecular weight). This peak contained about 4% of the total protein originally present in the supernate. Its activity was destroyed by overnight incubation at 37 degrees C at pH 6 or 8, but not at pH 7.2. After incubation at 4 degrees C, the activity was lost at pH 3 or 10, but not at pH 4-9. The active fraction from Sephadex G-100 was therefore chromatographed at pH 7.2 on DEAE cellulose and carboxymethyl cellulose. The active material was not adsorbed; however, about sevenfold further purification was achieved by removal of contaminants. The material obtained after sequential Sephadex, DEAE and, carboxymethyl cellulose chromatography stimulated resorption of fetal rat bone in culture at concentrations of 0.75-3 mug protein/ml, indicating that this preparation of OAF was nearly as potent as bovine parathyroid hormone in this system.
 ...
PMID:Partial purification of osteoclast-activating factor from phytohemagglutinin-stimulated human leukocytes. 482 37

Methods were devised for the assay of tRNA methylases of rat bone. The activities of bone tRNA methylases are similar to those from other mammalian tissues. However, unlike reports on liver methylases, no inhibitors were found in the supernatant fraction from pH5 precipitate of bone extracts. The effects of vitamins A and D on the methylation of tRNA by cell-free extracts of rat bone were studied. Deficiency of either vitamin resulted in a decrease in the rate and extent of tRNA methylation, whereas the administration of vitamin A to hypovitaminotic-A rats and vitamin D to hypovitaminotic-D rats increased the rate and extent of tRNA methylation. These effects appear to be apart from changes in ribonuclease activity or in concentrations of calcium or magnesium. No evidence of inhibitors of tRNA methylases was found in bone extracts from vitamin-deficient rats nor of activators in bone extracts from deficient rats given vitamin A or D. The pattern of tRNA methylation under conditions of vitamin A or D deficiency was not changed, suggesting a generalized cellular deficiency. It was of significance to find that the specificity for methylation of specific bases in tRNA was different after the administration of vitamin A as contrasted with the effects of vitamin D. The possible significance of tRNA methylation to the biochemical action of the vitamins on bone is discussed.
 ...
PMID:Transfer ribonucleic acid methylases of bone. Studies on vitamin A and D deficiency. 507 19

The vitamin D hormone, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], was shown to increase intestinal plasma membrane calcium pump (PMCA) gene expression. The present study was done to determine whether gene transcription is involved in this process. Nuclei were isolated from duodena of vitamin-D-deficient chicks given 1,25(OH)2D3 intracardially at various times before experiment. The abundance of PMCA RNA in the nuclear and total cellular fractions, measured by a ribonuclease protection assay, was significantly increased above control values at 1.5 hr. and maximized at 3 hr. post-dose. As shown, cross-contamination of nuclear PMCA RNA by cytosolic RNA cannot account for these results. These studies are the first to show that 1,25(OH)2D3 regulates expression of a plasma membrane calcium pump gene by increasing the rate of transcription.
 ...
PMID:Vitamin-D-dependent transcriptional regulation of the intestinal plasma membrane calcium pump. 754 21

The aim of the present work was to characterize at the molecular level the mechanism of PTH resistance in a rat model of secondary hyperparathyroidism resulting from vitamin D deprivation. PTH/PTH-related protein (PTHrp) receptor messenger RNA (mRNA) expression, assayed by ribonuclease protection analysis, was studied in the kidney, femoral epi/metaphysis, and diaphysis. In addition, in the kidney, PTH/PTHrp receptor mRNA expression was correlated to receptor function by measuring adenyl cyclase activity in crude renal membranes after stimulation by PTH (10(-10) - 10(-6) M), forskolin (0.1 and 0.2 mM), NaF (5 and 10 mM), and isoproterenol (1 and 10 microM). Four groups of rats were studied to investigate the effects of calcium, PTH, and/or vitamin D status. The first group received a control diet (D+D+). The second group received a diet deficient in vitamin D until death (D-D-). In the two other groups that also received a vitamin D-deficient diet, the hypocalcemia and the hyperparathyroidism were later corrected, by either vitamin D supplementation (D-D+) or lactose and high calcium diet (D-Ca+), 1 week before death. The results revealed a 2-fold decrease in the PTH-induced adenyl cyclase activity of the renal membranes in the D-D- rats compared to those in the three other groups. There was no significant difference in the four groups in adenyl cyclase activity stimulated by forskolin, NaF, and isoproterenol. The decrease in PTH-induced adenyl cyclase activity was associated with an approximately 2-fold increase in PTH/PTHrp receptor mRNA expression in the kidneys of the D-D- rats compared to controls. Normalization of PTH/PTHrp receptor mRNA expression was observed after vitamin D supplementation (D-D+ rats), but not after correction of the hypocalcemia and secondary hyperparathyroidism by oral lactose and calcium supplementation. In the epi/metaphysis, an approximately 2-fold increase in PTH/PTHrp receptor mRNA was also observed in the D-D- rats compared to the controls; this increase was partially corrected upon normalization of the calcemia and PTH levels with either vitamin D (D-D+ group) or lactose/calcium (D-Ca+ group). In the diaphysis, no change in the expression of PTH/PTHrp receptor mRNA was observed in any group.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Parathyroid hormone (PTH)/PTH-related protein receptor messenger ribonucleic acid expression and PTH response in a rat model of secondary hyperparathyroidism associated with vitamin D deficiency. 764 81

Retinoids are metabolites of vitamin A that can regulate gene expression in a range of embryonic and adult cell types. They do this by binding to nuclear receptors belonging to the steroid/thyroid hormone receptor superfamily of ligand-activated transcription factors. Vertebrates possess two classes of nuclear retinoid-receptor genes, each with three members. These are the RAR-alpha, RAR-beta and RAR-gamma genes and the RXR-alpha, RXR-beta and RXR-gamma genes. In this paper we show by cDNA cloning and ribonuclease protection that the chicken RXR-gamma gene gives rise to two mRNA species (RXR-gamma 1 and RXR-gamma 2) that differ at their 5' ends. The two mRNAs have different tissue distributions in the 10-day-old chick embryo. RXR-gamma 2 mRNA was present in the eye and dorsal root ganglia but was undetectable in the liver. In contrast, RXR-gamma 1 mRNA was present in liver, was undetectable in dorsal root ganglia and was just detectable in the eye, where it was much less abundant than RXR-gamma 2 mRNA. The predicted protein products of the RXR-gamma 1 and RXR-gamma 2 mRNAs differ at their N-termini, in a region thought to modulate transcriptional transactivation by the receptor. These results show that at least one of the retinoid-X-receptor (RXR) genes gives rise to more than one protein product, a principle previously established for the retinoic acid-receptor (RAR) genes. The existence of multiple RXR protein isoforms would increase the range of heterodimers formed between RXRs and other nuclear receptors, including RARs and the receptors for thyroid hormone, vitamin D and peroxisome proliferators. This could increase the diversity of transcriptional responses mediated by these molecules.
 ...
PMID:The chicken retinoid-X-receptor-gamma gene gives rise to two distinct species of mRNA with different patterns of expression. 803 82


1 2 Next >>