Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neoplastic cells were isolated from 2 sibling Great Dane/Labrador Retriever mixed-breed dogs in which telangiectatic type osteosarcomas arose concurrently. Cells from various sites in the same osteosarcoma appeared similar in culture, but there were differences between the 2 osteosarcomas in growth characteristics and appearance of cells. Cells from 1 osteosarcoma had a small, but significant (P less than 0.05), cyclic adenosine monophosphate response to parathyroid hormone stimulation, indicating a low order of osteoblastic differentiation. Cells from the other osteosarcoma had no response to parathyroid hormone stimulation. Cells from both osteosarcomas and a concentrated cell-free filtrate from the osteosarcoma with osteoblastic differentiation were injected into nude mice, but osteosarcomas were not induced. Results of ultrastructural examination of osteosarcoma samples for viral particles were negative and supernatant fluids from cultured cells were considered negative for viral reverse transcriptase activity.
 ...
PMID:Characterization of osteosarcoma cells from two sibling large-breed dogs. 261 26

To study the structure and function of the gene for parathyroid hormone, we obtained recombinant plasmids containing bovine parathyroid hormone cDNA. The nucleotide sequence at the 5' terminus (relative to the sense strand) of the cDNA insert in a recombinant plasmid, pPTHi4, was different from that previously reported for the bovine parathyroid hormone cDNA insert of another recombinant plasmid, pPTHm1 [Kronenberg, H. M., McDevitt, B. F., Majzoub, J. A., Nathans, J., Sharp, P. A., Potts, J. T., Jr. & Rich, A. (1979) Proc. Natl. Acad. Sci. USA 76, 4981-4985]. The first 50 nucleotides of the pPTHm1 insert were an inverted complement of nucleotides 2-51 of the pPTHi4 insert. the cDNA insert of another plasmid, pPTHi8, contained a sequence identical to nucleotides 2-51 of the pPTHi4 insert but also contained an additional 42 bases at the 5' terminus. The first 41 bases of the pPTHi8 insert were an inverted repeat of an internal sequence of the pPTHi4 insert corresponding to nucleotides 184-224. Restriction endonuclease analysis of pPTHi8 indicated that the internal sequence corresponding to this region was retained. The nucleotide sequence of a restriction fragment hybridized to parathyroid hormone mRNA and extended toward the 5' terminus of the mRNA with reverse transcriptase confirmed that the sequence at the 5' terminus of the pPTHi4 insert was an accurate copy of the parathyroid hormone mRNA sequence. These data suggest that two types of sequence rearrangements may occur at the 5' terminus, as occurred in pPTHm1, and (ii) an inverted repeat of an internal sequence, as occurred in pPTHi8.
 ...
PMID:Introduction by molecular cloning of artifactual inverted sequences at the 5' terminus of the sense strand of bovine parathyroid hormone cDNA. 617 60

The sequence of bovine parathyroid hormone mRNA has been determined by sequence analysis of near full-length cloned DNA complementary to the mRNA. Restriction fragments hybridized to the mRNA and extended toward the 5' terminus with reverse transcriptase were analyzed to derive the sequence not present in cDNA. The reverse transcripts were heterogeneous in length with three major stopping points within 8 nucleotides of each other and a minor stop about 30 bases further toward the 5' terminus of the mRNA. The sequence of the gene corresponding to the minor reverse transcript begins with the sequence 5' XXXATATATAAAA which contains the consensus sequence for a TATA box, a putative eukaryotic promoter sequence. Assuming that the major reverse transcriptase stop nearest the 5' terminus of the mRNA, which is 24 bases downstream from the TATA box, represents the beginning of bovine PTH mRNA, the mRNA contains 672 nucleotides, 100 in the 5' noncoding region, 348 in the coding region and 224 in the 3' noncoding region. Bovine PTH mRNA contains 38% G and C bases. The 3' noncoding region is particularly rich in A and U bases with the last 100 nucleotides of the molecules containing 46% U and 32% A. As with other mRNAs, the sequences CG and UAG occur much less than expected. The 5' noncoding region does not contain an AUG before the initiator codon and contains two potential regions that could base-pair with sequences near the 3' terminus of 18S ribosomal RNA. The sequence AAUAAA is present 14 nucleotides from the polyadenylic acid at the 3' terminus. Bovine PTH mRNA exhibits extensive homology with human PTH mRNA.
 ...
PMID:Nucleotide sequence of bovine parathyroid hormone messenger RNA. 618 74

DNA complementary (cDNA) to a partially purified preparation of bovine parathyroid hormone mRNA was synthesized using avian myeloblastosis viral reverse transcriptase. The PTH cDNA contained about 750 bases and was greater than 95% sensitive to digestion by S1 nuclease. Analysis of the mRNA preparation by excess RNA hybridization to the PTH cDNA revealed one rapidly hybridizing component consisting of 50% of the PTH cDNA. Sequential incubation of the PTH mRNA with reverse transcriptase and E. coli DNA polymerase I produced near full length double-stranded PTH cDNA. Of the 22 restriction endonucleases tested, double-stranded PTH cDNA could be cleaved with Alu I, Mbo II, Sau 3A, Sst I, and Taq I. The restriction fragments corresponding to the 5' terminus of the sense strand were identified for the last three enzymes by comparing the size of fragments obtained from PTH cDNA before and after cleavage of the hairpin loop connecting the two strands by S1 nuclease. The restriction map of the cDNA was used to detect clones of bacteria containing recombinant plasmids with near full length PTH cDNA inserts.
 ...
PMID:Synthesis, restriction analysis, and molecular cloning of near full length DNA complementary to bovine parathyroid hormone mRNA. 625 49

Osteoblasts express calcium channels that are thought to be involved in the transduction of extracellular signals regulating bone metabolism. The molecular identity of the pore-forming subunit (alpha 1) of L-type calcium channel(s) was determined in rat osteosarcoma UMR-106 cells, which express an osteoblast phenotype. A homology-based reverse transcriptase-polymerase chain reaction cloning strategy was employed that used primers spanning the fourth domain. Three types of cDNAs were isolated, corresponding to the alpha 1S (skeletal), alpha 1C (cardiac), and alpha 1D (neuroendocrine) isoforms. In the transmembrane segment IVS3 and the extracellular loop formed by the IVS3-S4 linker, a single pattern of mRNA splicing was found that occurs in all three types of calcium channel transcripts. Northern blot analysis revealed an 8.6-kb mRNA that hybridized to the alpha 1C probe and 4.8- and 11.7-kb mRNAs that hybridized to the alpha 1S and alpha 1D probes. Antisense oligonucleotides directed to the calcium channel alpha 1D transcript, but not those directed to alpha 1S or alpha 1C transcripts, inhibited the rise of intracellular calcium induced by parathyroid hormone. However, alpha 1D antisense oligonucleotides had no effect on the accumulation of cAMP induced by parathyroid hormone. When L-type calcium channels were activated with Bay K 8644, antisense oligonucleotides to each of the three isoforms partially inhibited the rise of intracellular calcium. The present results provide evidence for the expression of three distinct calcium channel alpha 1-subunit isoforms in an osteoblast-like cell line. We conclude that the alpha 1D isoform is selectively activated by parathyroid hormone.
 ...
PMID:Multiple calcium channel transcripts in rat osteosarcoma cells: selective activation of alpha 1D isoform by parathyroid hormone. 747 9

Parathyroid hormone-related protein (PTHrP) is synthesized by a variety of tumors and is thought to be the main cause of the clinical syndrome of humoral hypercalcemia of malignancy (HHM). In addition to its parathyroid hormone (PTH)-like actions, novel actions of PTHrP on placental calcium transport and inhibition of in vitro osteoclast activity have been demonstrated. The fact that osteoblasts act as mediators of osteoclastic bone resorption prompted us to investigate whether nontranformed, osteoblastlike cells produce PTHrP. PTHrP has been detected in developing human fetal bones and in rat long bones in culture. For this study, osteogenic cells, CRP 5/4 and CRP 10/30, were employed. Both cell types represent clonal bone cell populations established from 1-day-old rats. While CRP 10/30 cells express the osteoblastic phenotype, CRP 5/4 cells resemble cells with preosteoblastic properties. With a radioimmunoassay (RIA), utilizing antiserum directed against the amino-terminal PTHrP(1-40), it was found that both cell types synthesize PTHrP constitutively. CRP 10/30 cells produce about twice as much as CRP 5/4 cells. Transforming growth factor-beta (TGF-beta 1) was shown to increase the synthesis of PTHrP in CRP 5/4 cells by about 2.5-fold, while in CRP 10/30 cells it caused an approximate 50% reduction of PTHrP. Employing the reverse transcriptase polymerase chain reaction (RT-PCR) technique it was found that both bone cell types express mRNA for PTHrP and that the modulation of the PTHrP mRNA levels by TGF-beta 1 in CRP 5/4, and to a lesser degree in CRP 10/30 cells, was reflected in a change in the level of PTHrP protein in the culture medium.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Evidence for the synthesis of parathyroid hormone-related protein (PTHrP) by nontransformed clonal rat osteoblastic cells in vitro. 778 37

8701-BC is a recently characterized cell line isolated from a primary ductal infiltrating carcinoma of the breast (d.i.c.), showing some pleomorphism in cell microanatomy at an ultrastructural level. We have obtained different sublines of 8701-BC cells by cloning in soft agar at different concentrations (0.3% and 0.6%), and we have characterized the cloned lines by some morphological and growth parameters. 8701-BC cells and clones have been submitted to analysis by reverse transcriptase-linked polymerase chain reaction to detect mRNAs of various cytokines (transforming growth factor-beta s, tumour necrosis factors, interleukin 1s, interleukin 6, parathyroid hormone-related peptide, gamma interferon) and of urokinase, which are bioactive molecules commonly involved in cell-cell and cell-stroma interactions at primary and/or secondary sites of invasion. The aims of the present investigation were to determine: (a) if the corresponding genes are active in 8701-BC cell line and (b) if the sublines tested exhibit transcriptional heterogeneity. The results obtained show that 8701-BC cells express transcripts of transforming growth factor-beta s, urokinase and parathyroid hormone-related peptide (PTHrP), the latter product being responsible for the cancer-associated humoral hypercalcemic syndrome. Moreover, while the first two mRNAs are detectable in all the sublines tested, PTHrP is expressed almost uniquely by the clones isolated in 0.6% agar which exhibit a peculiar morphological appearance, a higher growth rate and a more active invasive behaviour in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Transforming growth factor-beta 1, beta 2, and beta 3, urokinase and parathyroid hormone-related peptide expression in 8701-BC breast cancer cells and clones. 829 80

Using a strategy based on homology to the bovine parathyroid Ca(2+)-sensing receptor previously identified by us (5), we have recently isolated an extracellular, G protein-coupled Ca2+/ polyvalent cation-sensing receptor, RaKCaR (22), from rat kidney. The localization and physiological role(s) of this receptor in the kidney are not well understood. In the present study, we assessed the distribution of mRNAs for RaKCaR and the parathyroid hormone/parathyroid hormone-related protein (PTH/PTHrP) receptor along the rat nephron by in situ hybridization and reverse transcriptase-polymerase chain reaction of microdissected nephron segments. Our results show that transcripts for both receptors coexpress at glomeruli, proximal convoluted tubule, proximal straight tubule, cortical thick ascending limb, distal convoluted tubule, and cortical collecting duct. In addition, RaKCaR (but not PTH/PTHrP receptor) transcripts were found in the medullary thick ascending limb and outer medullary and inner medullary collecting ducts. These findings raise the possibility of roles for RaKCaR not only in the regulation of divalent mineral reabsorption but also in water reabsorption and urinary concentration. Taken together, our results provide new insights in understanding the effects of hypercalcemia on hormone-stimulated salt and water transport.
 ...
PMID:Localization of the extracellular Ca(2+)-sensing receptor and PTH/PTHrP receptor in rat kidney. 889 27

Production of a member of transforming growth factor-beta (TGF-beta) superfamily, activin A, was examined in the bone tissue by using reverse transcriptase polymerase reaction. As a result, specific bands were detected showing the presence of activin A mRNA in the bone tissues. In order to localize the production site of activin A in the bone tissues, we tried to immunolocalize activin A in fetal mouse calvaria cultured in a medium containing fetal calf serum, 1 alpha-25(OH)2 vitamin D2 and parathyroid hormone. In these cultured calvaria, bone tissues including bone-resorbing osteoclasts in vitro were observed. Positive staining demonstrating the presence of activin A resided inside of the multinucleated cells in the bone resorbing lacunae, suggesting the production of activin A in osteoclasts. Activin A was also localized immunohistochemically in the osteoclast-like multinucleated cells developed in vitro. These results suggest that osteoclast produce activin in the bone tissues and that activin may play some roles by autocrine and/or paracrine manner in bone metabolisms.
 ...
PMID:Immunohistochemical detection of activin A in osteoclasts. 896 19

Cancers from patients with tumor-induced hypercalcemia usually produce a circulating factor that mimics the parathyroid hormone activity, termed parathyroid hormone-related protein. Incidence of tumor-induced hypercalcemia appears to be high in patients with squamous cell carcinoma of the esophagus, and the presence of parathyroid hormone-related protein have been shown in some primary esophageal cancers. In the present study, we have investigated the presence of parathyroid hormone-related protein in a patient with metastasized squamous cell carcinoma of the esophagus complicated with tumor-induced hypercalcemia. Protein was searched by immunohistochemistry, and messenger RNA was investigated by reverse transcriptase-polymerase chain reaction and S1 nuclease assay. Both messenger RNA and protein were detected in hepatic metastases, whereas normal esophageal mucosa and primary cancer did not express detectable protein or messenger RNA using the S1 nuclease assay. Reverse transcriptase-polymerase chain reaction was positive in all these tissues, including normal esophageal mucosa. In conclusion, the present case suggests that tumor-induced hypercalcemia due to esophageal squamous cell carcinoma may be caused by parathyroid hormone-related protein mostly released by liver metastases.
 ...
PMID:Parathyroid hormone-related protein in an esophageal squamous cell carcinoma with tumor-induced hypercalcemia. 904 Feb 21


1 2 3 Next >>