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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A microcellular dispersion procedure for the rat neurohypophysis was developed, comprising tissue softening and dissociation using a special sieving sytringe. In preparatory studies the influence of mesh width, and treatment with trypsin, pronase or collagenase-hyaluronidase was investigated using light and electron microscopy, as well as with microchemistry by means of protein and lactate dehydrogenase activity determinations. Trypsinization gave the best results. In the final adopted procedure, 3 incubated neurohypophyses were sequentially sieved through a 200- and a 50-mum mesh. The resulting 50-mul dispersion was found to contain numerous ultrastructurally well-preserved pinched-off axonal endings (neurosecretosomes), and pituicytes often revealing processes. On the basis of DNA and oxytocin assays 11% of the pituicytes and 28% of the axonal cytoplasm were recovered. Oxytocin immunofluorescence microscopy showed hormone within the neurosecretosomes, but often also in the cytoplasm of pituicytes. Microdensity gradient centrifugation was performed on neurohypophyseal disperions, in order to obtain fractions enriched for neurosecretosomes and pituicytes. Fractions were characterized by means of phase contrast, oxytocin immunofluorescence and electron microscopy, as well as by oxytocin and DNA assays as respective markers. With a 10:14:22% (w/v) Ficoll gradient, fractions were obtained for which the relative purification was by a factor of 4 on the basis of DNA/oxytocin ratios.
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PMID:Enzymic preparation of neurosecretosome- and pituicyte-enriched fractions from the rat neurohypophysis. 18 63

Vasopressin is shown to be a potent mitogen for Swiss 3T3 cells. The hormone (1--10 ng/ml) causes a striking shift of the dose--response curve for the effect of serum on thymidine incorporation by cultures of 3T3 cells arrested in the G1/G0 phase of the cell cycle. In the absence of added serum, the effect of vasopressin on DNA synthesis is greatly potentiated by insulin, epidermal growth factor, and a factor isolated from medium conditioned by simian virus 40-infected baby hamster kidney cells. The mitogenic effect of vasopressin is dependent on time and hormone concentration. In the presence of insulin, the half-maximal effect elicited by the peptide is obtained at 0.6 ng/ml. [Arg]Vasopressin and [Lys]vasopressin are equally potent. The vasopressins are 10(3)-fold more potent than oxytocin. In the presence of a low (2.5%) concentration of serum, vasopressins stimulate cell proliferation.
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PMID:Vasopressin stimulation of mouse 3T3 cell growth. 31 1

In non-covalently bound complexes of serveral serine proteases and of ribounclease with DNA the enzymes were protected against the effects of ionizing radiation. No scavenging by the nucleic acids was observed. Similarly, complexing trypsin with silica protected the enzyme from radiolytic destruction. Irradiation of solutions of serine proteases required about twice the D37 dose to produce about 10% polymerization: significantly lower relative doses were effective in causing polymerization in both lima bean protease inhibitor and in the octapeptidal hormone oxytocin. Several sulfhydryl enzymes which have been examined were very efficiently inactivated by ionizing radiation. There was, at the same time, apparent formation of novel intra-molecular -S-S- bonds.
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PMID:Cross linking in the radiolysis of some enzymes and related proteins. 92 May 9

Retinoic acid receptors are ligand-dependent transcription factors that stimulate gene transcription from promoters containing retinoic acid or thyroid hormone response elements. We describe a high-affinity binding site from the rat oxytocin promoter that mediates negative transcriptional regulation by the retinoic acid receptor. To examine whether strong, constitutive transactivation domains would be capable of stimulating gene transcription when bound to this DNA binding site that normally mediates transcriptional repression, we fused the transactivation domain of the herpes simplex viral protein VP16 to the amino terminus of the retinoic acid receptor and tested the activity of the chimeric protein on the negative retinoic acid response element. This chimeric retinoic acid receptor acted as a strong, constitutive transactivator when bound to promoters containing palindromic thyroid hormone/retinoic acid response elements but surprisingly it still repressed gene transcription when bound to promoters containing the oxytocin-negative retinoic acid response element. These results suggest that a negative DNA binding site itself can inhibit the function of even potent constitutive transactivation domains, and provide evidence that tethering of a constitutive transactivation domain to DNA is insufficient to activate gene transcription.
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PMID:A negative retinoic acid response element in the rat oxytocin promoter restricts transcriptional stimulation by heterologous transactivation domains. 131 Oct 87

Just before the onset of labour, uterine myometrium becomes extremely sensitive to oxytocin, for which it is a primary target tissue, because of a dramatic increase in the number of oxytocin receptors. We report here the structure and expression of the human oxytocin receptor complementary DNA isolated by expression cloning. The encoded receptor is a 388-amino-acid polypeptide with 7 transmembrane domains typical of G protein-coupled receptors. The oxytocin receptor, expressed in Xenopus oocytes, specifically responds to oxytocin and induces an inward membrane current. Messenger RNAs for the receptor are of two sizes, 3.6 kilobases in breast, and 4.4 kilobases in ovary, uterine endometrium and myometrium. The mRNA level in the myometrium is very high at term. We conclude that the increase in receptor number in the myometrium at labour is, at least in part, due to the increase in mRNA.
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PMID:Structure and expression of a human oxytocin receptor. 131 46

Specific receptors for oxytocin (OT) on intact luteal cells are demonstrated. Cultured cells from bovine corpora lutea (CL) at different stages (Days 3-5, 8-12, and 15-18 of the estrous cycle) were examined for OT receptors by a radioreceptor assay using the 125I-labeled OT antagonist [d(CH2)5,Tyr(Me)2,Thr4,Tyr-NH2(9)] -vasotocin. Binding specificity was demonstrated in displacement studies with various related peptides. Scatchard analysis revealed the presence of a binding site with an association constant of Ka = 2.6 x 10(9) M-1 and a capacity of 5.9 fmol/micrograms DNA. Additionally, in 50% of the experiments (n = 6) two different binding sites were observed. The Ka of the high-affinity site was 2.6 x 10(10) M-1; its capacity was 0.73 fmol/micrograms DNA. The low-affinity site had an apparent Ka of 4.9 x 10(8) M-1 and a capacity of 8.8 fmol/micrograms DNA. Observation of one versus two binding sites related neither to the assay conditions nor to the state of the individual CL used for the cell culture and therefore appeared to reflect individual variation within the OT receptor population. Significant binding of OT was observed at all luteal stages. OT binding was maximal at the mid-luteal stage (Days 8-12). We conclude that a direct action of OT on the bovine CL is mediated by the OT receptor, supporting the hypothesis that luteal OT plays an important physiological role in the regulation of progesterone release and/or other luteal functions in a paracrine or autocrine fashion.
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PMID:Evidence for oxytocin receptors in cultured bovine luteal cells. 132 97

Molecular cloning of the vasotocin gene of a cyclostome, the Pacific hagfish Eptatretus stouti, reveals, in contrast to other known members of the vertebrate vasopressin/oxytocin hormone gene family, an unusual exon-intron organization. Although the location of three exons and two introns is conserved, an additional intron is present 5' of the coding region of the hagfish gene. The third intron, which is greater than 14 kilobase pairs in size, contains on the opposite DNA strand to that encoding vasotocin an open reading frame exhibiting striking similarity to the putative transposase of Tc1-like nonretroviral mobile genetic DNA elements, so far reported only from nematodes and Drosophila. The hagfish element, called Tes1, is flanked by inverted terminal repeats representing an example of the existence of a typical inverted terminal-repeat transposon within vertebrates. The presence of Tc1-like elements in nematodes, Drosophila, and cyclostomes indicates that these genetic elements have a much broader phylogenetic distribution than hitherto expected.
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PMID:Presence of a member of the Tc1-like transposon family from nematodes and Drosophila within the vasotocin gene of a primitive vertebrate, the Pacific hagfish Eptatretus stouti. 137 21

In order to clarify the biological activities of (-)-oxetanocin G, and (-)-oxetanocin A and its carbocyclic analogue, (-)-carboxetanocin G, the inhibitory effects of triphosphate derivatives of these compounds (OXT-GTP, OXT-ATP, and C-OXT-GTP) on eukaryotic and viral DNA polymerases were examined. DNA polymerase alpha purified from calf thymus was weakly inhibited by OXT-GTP and OXT-ATP but strongly by C-OXT-GTP, the Ki value being 0.22 microM. On the other hand, rat DNA polymerase beta was not affected by these analogues. DNA polymerase gamma purified from bovine testes was very weakly inhibited by OXT-GTP and OXT-ATP, but not by C-OXT-GTP. DNA polymerase from herpes simplex virus type-II (HSV-II) was strongly inhibited by all three analogues, the Ki values ranging from 0.5 to 1.0 microM. Human immunodeficiency virus-encoded reverse transcriptase (HIV RT) was also strongly inhibited by these three analogues, the Ki value of C-OXT-GTP being slightly smaller than that of OXT-GTP or OXT-ATP. Analysis of products synthesized on singly primed M13 single-stranded DNA by DNA polymerase alpha, HSV-II DNA polymerase or HIV RT in the presence of the analogues revealed that OXT-GTP and C-OXT-GTP were incorporated into DNA and caused chain termination mainly at sites one or two nucleotides beyond the cytosine bases on the template.
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PMID:Inhibitory effects of triphosphate derivatives of oxetanocin G and related compounds on eukaryotic and viral DNA polymerases and human immunodeficiency virus reverse transcriptase. 138 92

Competition with specific oligonucleotides in DNA-binding experiments, polyacrylamide gel electrophoresis, and recognition by specific antibodies have identified the ubiquitous transcription factor COUP as one of the nuclear proteins binding to the promoter region of the bovine oxytocin gene in endogenously expressing bovine granulosa cells. PCR cloning of partial cDNA sequences for bovine COUP-TF I and II and development of RNase protection assays demonstrated the up-regulation of COUP-TF in bovine granulosa cells and corpus luteum under conditions where the oxytocin gene is switched off. These experimental results from in vitro and in vivo studies point to the direct involvement of COUP-TF in oxytocin gene down-regulation during luteinization of bovine granulosa cells.
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PMID:The COUP transcription factor (COUP-TF) is directly involved in the regulation of oxytocin gene expression in luteinizing bovine granulosa cells. 144 99

The ruminant conceptus secretes proteins during early pregnancy which maintain the corpus luteum. These trophoblast proteins are related to the alpha II-interferons and prevent luteolysis indirectly by disrupting the secretion of endometrial prostaglandin. Although trophoblast interferons appear to be largely confined to the uterine lumen, it remains possible that they also act peripherally. This report describes in vitro studies which suggest that interferon may influence hormone secretion by the ovary directly. The study employed i) a well defined serum-free culture model in which bovine granulosa cells secrete the luteal hormones progesterone and oxytocin, and ii) serum-free and serum-supplemented cultures of cells from early CL. Dose-response experiments were performed using bovine recombinant alpha-interferon (brIFN). Progesterone and oxytocin secretions were measured over 4-5 days of culture and DNA content was also determined. Low concentrations of brIFN (10(-15) mol/l to 10(-11) mol/l) stimulated progesterone secretion by granulosa cells by up to three fold, without significantly affecting oxytocin concentrations or culture DNA content. Concentrations of 10(-10) mol/l to 10(-1) mol/l suppressed progesterone secretion in a log dose-related manner (r = 0.97) with evidence of toxicity (lower oxytocin concentrations and significantly reduced DNA compared with controls). Progesterone secretion by luteal cells in serum-free culture was stimulated in the presence of 10(-15) mol/l brIFN, whilst high concentrations again caused inhibition. The data show that ovarian cells can respond directly to low concentrations of interferon-like proteins.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Direct stimulation of bovine ovarian progesterone secretion by low concentrations of alpha-interferon. 147 25


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