Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The plasma concentrations of the gastrointestinal regulatory peptides vasoactive intestinal polypeptide (VIP), insulin, secretin, somatostatin, motilin, pancreatic polypeptide (PP) and gastric inhibitory polypeptide (GIP), as well as blood glucose, were measured in eight healthy women before, during and after oxytocin infusion in post-term pregnancies. Plasma VIP increased significantly (P less than 0.01) during oxytocin infusion. Plasma secretin showed a significant (P less than 0.05) decrease during oxytocin infusion. Plasma somatostatin remained unchanged during oxytocin infusion, but thereafter a significant (P less than 0.05) increase occurred. Both plasma motilin and plasma PP showed a non-significant increase during oxytocin infusion with sustained levels thereafter. No changes were found for plasma insulin, GIP and blood glucose.
 ...
PMID:Gastrointestinal regulatory peptides during oxytocin infusion in post-term pregnancies. 290 9

We studied five cases of central nervous system neuronal tumor, one gangliocytoma and four gangliogliomas, both ultrastructurally and immunohistochemically, using antibodies to neuroendocrine markers including tyrosine hydroxylase (TH), serotonin (5HT), somatostatin (SOM), met-enkephalin (MEK), leu-enkephalin (LEK), substance P (SP), gastrin, vasopressin, oxytocin, vasoactive intestinal polypeptide, adrenocorticotropic hormone and calcitonin. In all cases, the presence of dense-core vesicles (60-250 nm) in the neuronal elements was the characteristic ultrastructural finding. Synapses were observed in two cases. Immunohistochemically, variable numbers of neuronal cells showed positive staining for SOM in five cases, TH, MEK and LEK in three cases, and 5HT and SP in one case each. The others were negative. Positive immunoreactivity for multiple markers was shown in all cases. SOM, TH, 5HT and SP were present in the small- to medium-sized cells, while MEK and LEK were almost exclusively confined to the large cells. Our study clearly indicated that these tumors contained neuronal cells which were not homogeneous with regard to neuroendocrine markers.
 ...
PMID:Neuroendocrine markers in central nervous system neuronal tumors (gangliocytoma and ganglioglioma). 292 88

In addition to corticotropin-releasing factor (CRF) and structurally related peptides, arginine vasopressin (AVP), oxytocin, angiotensin II, vasoactive intestinal polypeptide, peptide histidine isoleucinamide, epinephrine (E), and norepinephrine induce secretion of adrenocorticotropin (ACTH) from corticotropic cells in vitro. The apparent affinity and intrinsic ACTH-releasing activity of these substances are lower than those of CRF. These substances can also act synergistically with CRF. In this paper the role of catecholamines and AVP in the control of ACTH release is discussed. Infusion i.v. of E increases plasma ACTH and corticosterone to levels that are normally found during stress. E-induced stimulation of pituitary-adrenal activity is mediated by beta adrenoceptors and involves release of CRF, because it can be prevented by beta-adrenoceptor blockers and by destruction of CRF neurons (hypothalamic lesions), blockade of CRF release (chlorpromazine, morphine, and Nembutal), or administration of CRF antiserum. Although stress can cause a vast increase in plasma E, circulating E is not essential for the acute stress-induced release of ACTH because blockade of beta (or alpha) adrenoceptors, administration of chlorisondamine, or extirpation of the adrenal medulla and sympathectomy do not prevent the pituitary-adrenal response to stress. In contrast, circulating E plays a major role in the release of intermediate-lobe peptides during emotional stress. Studies of the role of AVP in pituitary-adrenal control by the use of pressor receptor (V1) antagonists are not valuable because of the ineffectiveness of such antagonists in blocking AVP-induced release of ACTH from corticotropic cells in vitro. Treatment of rats with an antiserum to AVP reduces the ACTH response to stress. We conclude that AVP has an important role in stress-induced activation of the pituitary-adrenal system, possibly by potentiating the effects of CRF.
 ...
PMID:Role of epinephrine and vasopressin in the control of the pituitary-adrenal response to stress. 298 37

The hypothalamic paraventricular nucleus (PVN) has been implicated in a remarkable number of functions including control of pituitary-adrenocortical activity in response to stress, body fluid homeostasis, milk ejection reflex, prolactin secretion, thyroid hormone secretion, analgesia, food intake, gastrointestinal functions, cardiovascular functions, and control of pineal melatonin synthesis. Paraventricular neurons produce hormones of key importance in neuroendocrine regulation such as vasopressin (VP), oxytocin (OX), 41-residue corticotropin releasing factor (CRF), thyrotropin releasing hormone (TRH), somatostatin (SOM) and the putative prolactin releasing factor vasoactive intestinal polypeptide (VIP). Three recent advances pertinent to the organization of the PVN include: (1) the evidence that the structure of the PVN is compartmental in nature, topographically segregated cellular units seem to carry out different functions; (2) the discovery that paraventricular neurons are capable of expressing a multitude of neuromediators simultaneously, thus cellular units can be best specified by a certain combination of neuromediators; (3) evidence that the composition of the neuromediator "cocktail" in individual neurons is variable and depends on the physiological status of the animal. Hence, the PVN may be best considered as a dynamic mosaic of chemically specified subgroups of neurons. The flexibility of neurotransmitter status in paraventricular neurons may play a central role of a functional plasticity of fixed anatomical circuits.
 ...
PMID:Dynamism of chemoarchitecture in the hypothalamic paraventricular nucleus. 304 19

We previously reported that the rat posterior pituitary contains a potent PRL-releasing factor (PRF) which is distinct from oxytocin (OT), TRH, and angiotensin II (AII). The objectives of this study were 1) to examine whether posterior pituitary extracts stimulate PRL release in the presence of dopamine (DA), 2) to determine the chemical nature of PRF, and 3) to estimate its mol wt. Perifused anterior pituitary cells were used to assess PRF activity. Posterior pituitaries and medial basal hypothalamus (MBH) fragments were extracted with perchloric acid and lyophilized. Subsequent to various treatments, samples were reconstituted in the perifusion medium and introduced to the cells in short pulses. Fractions were collected and analyzed for hormone content by RIA. During a constant infusion of DA (50 nM), PRL secretion was inhibited by 75%, yet the posterior pituitary extract retained its ability to rapidly stimulate PRL release. Studies using proteolytic enzymes showed that posterior pituitary PRF was resistant to inactivation by trypsin, whereas the PRF activity of AII was abolished. Both chymotrypsin and proline-specific endopeptidase significantly reduced the PRF activity in the posterior pituitary. The PRL-releasing activity of TRH was not affected by chymotrypsin. Immunoreactive vasoactive intestinal polypeptide was undetectable in posterior pituitary extracts. Oxidation of posterior pituitary extracts with performic acid caused only a modest reduction of their PRF activity, while the ability of OT to stimulate PRL release as well as immunoreactive OT was abolished. Studies using ultrafiltration membranes showed that the PRF activity in the posterior pituitary was less than 5,000 mol wt. Furthermore, posterior pituitary PRF partitioned in nearly equal amounts across 1K membranes, as did AII and OT. In contrast, about 80% of the PRF activity in the MBH and all of the synthetic TRH passed through the 1K membranes. We conclude that 1) posterior pituitary PRF can stimulate PRL secretion from perifused anterior pituitary cells in the presence of physiological concentrations of DA; 2) PRF is a small peptide(s) of less than 5,000, and perhaps closer to 1,000, mol wt; 3) PRF is resistant to inactivation by trypsin and to oxidation by performic acid, but is hydrolyzed by both chymotrypsin and proline-specific endopeptidase; and 4) these data further distinguish posterior pituitary PRF from known PRL secretagogues.
 ...
PMID:Characterization of prolactin-releasing factor in the rat posterior pituitary. 313 Nov 18

The observation that suckling evokes a modest rise in serum TSH when compared with that of prolactin is inconsistent with the hypothesis that TRH serves as a hypophysiotropic mediator of this response. In the present study we attempted to provide an explanation for this discrepancy by determining whether any of a growing number of putative prolactin releasing factors could alter pituitary responsiveness to TRH. Anterior pituitaries from lactating (day 14) rats were monodispersed with trypsin, cultured for 2 days, and then incubated in the presence of medium alone or medium containing TRH, dopamine, or a combination of these secretagogues. Companion sets of cultures were incubated concurrently with either beta-endorphin, neurotensin, oxytocin, serotonin, vasoactive intestinal polypeptide, or lysine vasopressin. As expected, TRH stimulated and dopamine suppressed prolactin release. None of the substances tested except oxytocin had a significant effect on pituitary cell responsiveness to TRH or dopamine. Oxytocin had no effect on prolactin secretion when tested alone or in combination with TRH and dopamine. TRH alone stimulated TSH release by these cultures, while oxytocin and dopamine were ineffective by themselves. However, TSH secretion by cultures treated simultaneously with TRH and oxytocin could be suppressed to approximately half of that released by cells incubated with TRH alone. These results demonstrate that oxytocin attenuates TRH-induced TSH release by a direct action on pituitary cells without affecting the prolactin response. This selectivity of responsiveness imparted by oxytocin might contribute to the blunted release of TSH after suckling.
 ...
PMID:Oxytocin attenuates TRH-induced TSH release from rat pituitary cells. 315 75

A 'big' frog (Rana esculenta) neurophysin, encompassing sequences homologous to mammalian MSEL-neurophysin and copeptin, has been passed through a trypsin-Sepharose column in order to compare its conformation with that of the two-domain intermediate precursor isolated from guinea pig. Whereas the polypeptide possesses 8 arginine residues, only two cleavages were observed located in a putative inter-domain sequence (at Arg-94 and Arg-114). Because free vasotocin has been isolated from the frog, it is assumed that pro-vasotocin has a three-domain conformation similar to that of pro-vasopressin but processing in amphibians involves only one step rather than two steps as in mammals.
 ...
PMID:An amphibian two-domain 'big' neurophysin: conformational homology with the mammalian MSEL-neurophysin/copeptin intermediate precursor shown by trypsin-sepharose proteolysis. 325 54

Particulate fractions of human small intestinal mucosa contain an enzyme capable of hydrolyzing N-benzoyl-L-tyrosyl-p-aminobenzoic acid (PABA-peptide), a substrate used for clinical purposes to assess exocrine function of the pancreas (PABA test, pancreas function test). In this paper we describe the purification of PABA-peptide hydrolase (PPH) by immunoaffinity chromatography using a monoclonal antibody (Mab), HBB 3/716/36, bound to protein A-Sepharose, and the characterization of the purified enzyme. The final preparation of the enzyme was in the immobilized form, i.e., bound to Mab-protein A-Sepharose, and showed a 765-fold enrichment over the mucosal homogenate. The enrichment factor in purified microvillus membranes was comparable to that of sucrase-isomaltase, a microvillar marker enzyme. This, together with immunoelectron microscopy using protein A-gold, indicated that PPH is located in the apical membrane of intestinal epithelial cells. The enzyme was found to be present throughout the small intestine with the activity in distal ileum being 4.5-fold higher than that in the proximal duodenum. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the immunoaffinity-purified PPH under reducing conditions revealed a polypeptide band with a relative molecular weight (Mr) of 100,000; under nonreducing conditions a major band with Mr 200,000 was observed. This indicates that PPH consists of two subunits with Mr 100,000 each, which are held together by one or more disulfide bonds. Two-dimensional polyacrylamide gel electrophoresis of the enzyme showed marked microheterogeneity, with pI's ranging from 6.0 to 6.85, probably due to glycosylation. The Km for PABA-peptide was 16.7 mM, and the pH optimum was 7.5-8.0 PPH activity was not inhibited by phenylmethylsulfonyl fluoride; pepstatin, leupeptin, amastatin, bestatin, puromycin, iodoacetate, or phosphoramidon. Activity was affected by captopril and Zinkov inhibitor, and in particular by thiol and chelating reagents. Chelator-inhibited PPH could be reactivated by bivalent metal ions, Zn2+ being the most effective. The enzyme catalyzed the hydrolysis of peptides including insulin B-chain, angiotensins I and II, bradykinin and bradykinin derivatives, oxytocin, and substance P, in each case yielding reproducible peptide fragments. On the basis of amino acid analysis of the products it could be concluded that peptides are hydrolyzed preferentially after an aromatic residue.
 ...
PMID:N-benzoyl-L-tyrosyl-p-aminobenzoic acid hydrolase: a metalloendopeptidase of the human intestinal microvillus membrane which degrades biologically active peptides. 326 61

We examined the extent to which rates of enzymatic conversion of the oxytocin biosynthetic precursor to mature peptide are modulated by intramolecular and intermolecular assembly of precursor and polypeptide intermediates. The biosynthesized precursor contains hormone and neurophysin sequences linked by a Gly-Lys-Arg sequence and undergoes enzymatic processing reactions which include endoproteolytic cleavage at the Lys-Arg dibasic sequence, carboxypeptidase B-like exoproteolytic cleavage, and enzymatic amidation. We evaluated the effect of neurophysin on such processing reactions using semisynthetic precursors of oxytocin/bovine neurophysin I and synthetic oxytocinyl precursor intermediates as substrates. Neurophysin I at high concentration (0.7 mM) reduced the rates of carboxy-peptidase B-like conversion of oxytocinyl-Gly-Lys-Arg to oxytocinyl-Gly and the enzymatic amidation of oxytocinyl-Gly to mature (C-terminal amidated) oxytocin. The dependence of rate suppression on the concentrations of peptide substrate and neurophysin I suggested that suppression is due to intermolecular formation of hormone-neurophysin complexes which are aggregated at least to dimers. An analogous intramolecular neurophysin effect was found for endoproteolytic processing of semisynthetic precursors. Endoproteinase Lys-C cleaved the Lys11-Arg12 peptide bond in a native-like semisynthetic precursor at a significantly slower rate than it did an assembly-deficient precursor analogue. The difference in semisynthetic precursor endoproteolysis rates is most substantial at the high concentrations at which the native-like precursor would form dimers but the assembly-deficient analogue would not. The native-like semisynthetic precursor was more stable than the assembly-deficient precursor analogue to tryptic digestion. The concentration-dependent effects of neurophysin, both intramolecularly as a precursor domain and intermolecularly as an interacting protein, are likely to occur in the secretory granules in which the biosynthetic precursors are packaged. The molecular organization of both hormone/neurophysin precursors and the noncovalently complexed hormone-neurophysin intermediates can be expected to play a role in modulating enzymatic processing reactions that lead to mature neurohypophysial hormones.
 ...
PMID:Effect of neurophysin on enzymatic maturation of oxytocin from its precursor. 327 58

Recent reports indicate that oxytocin exerts direct effects on the release of insulin and glucagon from the endocrine pancreas of the rat. The purpose of this study was to determine whether oxytocin-like immunoreactivity is present in the anglerfish islet, and if it is associated with subsets of hormone-producing cells. Antisera against oxytocin, insulin, glucagon, somatostatin, neuropeptide Y, and the 200-kd neurofilament polypeptide were applied to serial 5 micrometers sections of pancreatic islets. The antiserum to the 200-kd neurofilament polypeptide labeled nerve bundles and axons, some of which were also stained with the oxytocin antiserum. Oxytocin immunoreactivity was observed in large nerves that branched into varicose fibers. These fibers were consistently associated only with clusters of insulin-producing cells. Successive application of oxytocin and insulin antisera to the same section provided additional verification of this relationship. Oxytocin-labeled nerves were not associated with cells immunoreactive to glucagon, somatostatin, or neuropeptide Y (anglerfish peptide Yg). The results demonstrate that oxytocin or an oxytocin-like peptide is located in fibers that surround only insulin-producing cells in the anglerfish islet. Although the functional significance of this observation remains to be determined, the results imply that oxytocin, or an oxytocin-like peptide, may affect the synthesis or release of insulin from anglerfish islets.
 ...
PMID:Oxytocin-like immunoreactive nerves are associated with insulin-containing cells in pancreatic islets of anglerfish (Lophius americanus). 330 46


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>