Search Results

You are looking at 31 - 40 of 619 items for :

  • Refine by access: All content x
Clear All
G. Robinson
Search for other papers by G. Robinson in
Google Scholar
PubMed
Close
and
J. J. Evans
Search for other papers by J. J. Evans in
Google Scholar
PubMed
Close

ABSTRACT

We previously demonstrated that oxytocin stimulates LH release from rat pituitary cells in vitro and advances follicular development and ovulation in mice in vivo. This study reports an investigation of rat LH levels following in-vivo administration of oxytocin. Injection of oxytocin (10 mIU/g, i.p.) to rats at 07.00, 08.00 and 09.00 h of pro-oestrus or at 09.00, 10.00 and 11.00 h of pro-oestrus advanced the onset of the LH surge (P<0.005) and attainment of peak concentrations of LH (P<0.02) in peripheral blood. On the other hand, the descending phase of the LH surge and the surge amplitude were not altered by oxytocin. Treatment at 05.00, 06.00 and 07.00 h of pro-oestrus or at 11.00, 12.00 and 13.00 h of pro-oestrus had no effect on the LH profile. A higher oxytocin dose (20 mIU/g) inhibited LH release when treatment was begun at 05.00, 07.00 or 09.00 h of pro-oestrus. A lower dose (5 mIU/g) was ineffective in altering LH concentrations. In addition, injections of oxytocin (10 mIU/g) at oestrus, metoestrus or dioestrus had no effect on the release of LH. Thus the efficacy of oxytocin in altering concentrations of LH was dose dependent and also critically affected by the day of the oestrous cycle and the time of pro-oestrus. Removal of endogenous oxytocin activity by the use of an oxytocin receptor antagonist abolished the pro-oestrous LH surge, indicating that oxytocin is a vital physiological component of the LH-releasing mechanism in rats. The study provides unequivocal evidence that oxytocin induces LH release in vivo, but the manifestation of oxytocin activity is dependent upon conditions of exposure.

Journal of Endocrinology (1990) 125, 425–432

Restricted access
I. plevrakis
Search for other papers by I. plevrakis in
Google Scholar
PubMed
Close
,
C. Clamagirand
Search for other papers by C. Clamagirand in
Google Scholar
PubMed
Close
, and
G. Pontonnier
Search for other papers by G. Pontonnier in
Google Scholar
PubMed
Close

ABSTRACT

Human granulosa cells were collected from preovulatory follicles during follicular puncture for in-vitro fertilization. They were cultured in serum-free medium supplemented with ascorbic acid. Using a combination of high-performance liquid chromatography and radioimmunoassay, the oxytocin material present in the cell extracts and secreted into the medium was identified. When cells were deprived of ascorbate, intermediary forms resulting of the post-translational processing of pro-oxytocin/neurophysin were detected. These data demonstrate that oxytocin biosynthesis occurs in human granulosa cells.

Restricted access
E Houdeau Laboratoire de Physiologie et Physiopathologie, UMR-CNRS 7079, Paris cedex 05, France
Unité de Neuro-Gastroentérologie et Nutrition, INRA, 31931 Toulouse cedex 9, France

Search for other papers by E Houdeau in
Google Scholar
PubMed
Close
,
A Lévy Laboratoire de Physiologie et Physiopathologie, UMR-CNRS 7079, Paris cedex 05, France
Unité de Neuro-Gastroentérologie et Nutrition, INRA, 31931 Toulouse cedex 9, France

Search for other papers by A Lévy in
Google Scholar
PubMed
Close
, and
S Mhaouty-Kodja Laboratoire de Physiologie et Physiopathologie, UMR-CNRS 7079, Paris cedex 05, France
Unité de Neuro-Gastroentérologie et Nutrition, INRA, 31931 Toulouse cedex 9, France

Search for other papers by S Mhaouty-Kodja in
Google Scholar
PubMed
Close

role in the regulation of uterine contractility. Indeed, contractant factors like oxytocin (OT), prostaglandins or norepinephrine utilize PLC-coupled receptors (OT receptors (OTR), prostaglandin F2α receptors (FP) and α1-adrenergic receptors (AR

Free access
T. Higuchi
Search for other papers by T. Higuchi in
Google Scholar
PubMed
Close
,
K. Honda
Search for other papers by K. Honda in
Google Scholar
PubMed
Close
,
T. Fukuoka
Search for other papers by T. Fukuoka in
Google Scholar
PubMed
Close
,
H. Negoro
Search for other papers by H. Negoro in
Google Scholar
PubMed
Close
, and
K. Wakabayashi
Search for other papers by K. Wakabayashi in
Google Scholar
PubMed
Close

ABSTRACT

A highly sensitive and specific radioimmunoassay (RIA) for oxytocin was developed and used to measure oxytocin concentrations during both suckling and parturition in individual rats. In urethane-anaesthetized rats, the suckling stimuli, provided by ten pups, induced intermittent increases in intramammary pressure of about 10 mmHg. This was associated with a significant (P < 0·01) increase in serum oxytocin levels from 19·5 ± 4·5 (s.e.m., n = 9) to 49·1 ± 7·4 pmol/l (n = 9) in the samples taken within 30 s from the time of the peak in the pressure. These rises in serum oxytocin returned rapidly to the basal levels as expected from the short half-life (1·46 min) of oxytocin in general circulation.

On day 22 or 23 of gestation, serum oxytocin levels remained stable until 0–0·5 h before the first fetus was expelled. They then increased significantly (P < 0·01) from 27·6± 4·6 pmol/l (n = 19) in samples taken 0–0·5 h before to 45·1 ± 5·6 pmol/l in samples taken after the expulsion of the first fetus and gradually increased until the last fetus was expelled. Serum oxytocin concentrations then declined but remained higher than those observed before the first fetus had been born until at least 1–1·5 h after the expulsion of the last fetus. Thus, this oxytocin RIA revealed increased concentrations of the hormone in blood during both suckling and parturition in the rat.

J. Endocr. (1985) 105, 339–346

Restricted access
P. Melin
Search for other papers by P. Melin in
Google Scholar
PubMed
Close
,
J. Trojnar
Search for other papers by J. Trojnar in
Google Scholar
PubMed
Close
,
B. Johansson
Search for other papers by B. Johansson in
Google Scholar
PubMed
Close
,
H. Vilhardt
Search for other papers by H. Vilhardt in
Google Scholar
PubMed
Close
, and
M. Åkerlund
Search for other papers by M. Åkerlund in
Google Scholar
PubMed
Close

ABSTRACT

With the aim of developing inhibitors of vasopressin-and oxytocin-induced uterine activity, 17 analogues of 1-deamino-oxytocin were synthesized by the solid-phase method. Modifications were made at positions 2, O-methyltyrosine (Tyr(OMe)) and O-ethyltyrosine (Tyr(OEt)),d-Tyr,d-Tyr(OEt),d-Trp; 4, Val,Thr and 8, Orn,Cit,Arg,d-Arg.

The analogues were tested for antiuterotonic activity in vitro and in vivo in the rat and in vitro on myometrial strips from non-pregnant women and pregnant women at term. Their selectivity was also investigated in blood pressure and antidiuretic bioassays in rats. Results were compared with those from an original antiuterotonic analogue 1-deamino-2-Tyr(OEt)-oxytocin (d(OEt)-oxytocin). In the rat in vitro and in vivo all analogues possessed higher antiuterotonic activity than d(OEt)-oxytocin. The negative logarithm of the molar concentration of the antagonist which reduced the effect of a dose of agonist to that of half the dose (pA2) was between 7·6 and 8·9 for all the new inhibitors compared with 7·2 for d(OEt)-oxytocin. The highest pA2 value was found for 1-deamino-2-Tyr(OMe)-8-Orn-oxytocin (8·9 ± 0·2, s.e.m.) and 1-deamino-2-Tyr(OEt)-4-Thr-8-Orn-oxytocin (8·9 ± 0·6). In myometrium from non-pregnant women the most potent peptide was 1-deamino-2-d-Tyr(OEt)-4-Th r-8-Orn-oxytocin (17·2 ± 2·0 times more potent that d(OEt)-oxytocin). In myometrium from pregnant women the inhibitory effects of the majority of the analogues were less pronounced. In the rat in vivo the most potent analogue 1-deamino-2-d-Trp-4-Val-8-Orn-oxytocin was 19·9 ± 2·5 times more active than d(OEt)-oxytocin. Exchanging l-tyrosine for the d form generally increased inhibitory activity as well as specificity of the analogues. Alkylation of the d-tyrosine residue did not appear to be necessary for inhibition. Substitution with d-tryptophan at position 2 gave analogues with high inhibitory potency in the rat in vitro and in vivo, but which exhibited weak effects in women in vitro. There was no correlation between the inhibitory effects on myometrium from non-pregnant and pregnant women nor between rat and human data. The high antiuterotonic activity of 1-deamino-2-d-Tyr(OEt)-4-Val-8-Orn-oxytocin and 1-deamino-2-d-Tyr(OEt)-4-Thr-8-Orn-oxytocin combined with low blood pressure and antidiuretic effects make these two analogues interesting for clinical studies.

J. Endocr. (1986) 111, 125–131

Restricted access
M. D. Stoneham
Search for other papers by M. D. Stoneham in
Google Scholar
PubMed
Close
,
B. J. Everitt
Search for other papers by B. J. Everitt in
Google Scholar
PubMed
Close
,
S. Hansen
Search for other papers by S. Hansen in
Google Scholar
PubMed
Close
,
S. L. Lightman
Search for other papers by S. L. Lightman in
Google Scholar
PubMed
Close
, and
K. Todd
Search for other papers by K. Todd in
Google Scholar
PubMed
Close

ABSTRACT

In male New Zealand white rabbits, it was shown that oxytocin but not vasopressin concentrations in plasma were markedly raised after ejaculation. In male Wistar rats, oxytocin infused into the internal carotid artery reduced the number of intromissions made before ejaculation but had no other significant effect. Infusion of oxytocin into the third ventricle increased the latencies to the first mount and intromission and lengthened post-ejaculatory refractory periods. It is suggested that oxytocin released into the periphery during coitus, while not essentially involved in ejaculation, may exert effects on the genital periphery. Behavioural effects of centrally administered oxytocin suggest that it may play a role in the neural mechanisms underlying post-ejaculatory refractoriness.

J. Endocr. (1985) 107, 97–106

Restricted access
B. A. EDWARDS
Search for other papers by B. A. EDWARDS in
Google Scholar
PubMed
Close

Radioactivity accumulates in the posterior pituitary after intravenous injections of [3H]oxytocin (Aroskar, Chan, Stouffer, Schneider, Murti & du Vigneaud, 1964) or tritiated lysine vasopressin ([3H]LVP) (Willumsen & Bie, 1969). These results allow for the possibility that the neurohypophysial hormones may be taken up by the pituitary after the release of endogenous, or the administration of exogenous, oxytocin and vasopressin. The experiments in vitro of Pliška, Thorn & Vilhardt (1971) and Edwards (1971) showed that uptake of radioactivity occurred after incubation of neural lobes with labelled vasopressin but that much of the activity was not associated with hormone. The present communication describes a study on the uptake of [3H]oxytocin by neural lobes of rats incubated in vitro.

Halved neural lobes were incubated in a bicarbonate buffer (McIlwain & Rodnight, 1962) containing [3H]oxytocin (prepared in the Departement de Biologie, Commissariat à l'Energie Atomique, France) and non-radioactive purified oxytocin

Restricted access
T. CHARD
Search for other papers by T. CHARD in
Google Scholar
PubMed
Close

The first radioimmunoassay was described by Yalow & Berson in 1960, since when the technique has been widely used in physiological and patho-physiological studies of the protein hormones. The success in this field has led to a number of attempts to develop similar assays for the small peptide hormones (molecular weight less than 3000). However, these compounds present certain difficulties which have considerably retarded progress. The purpose of the present review is to discuss the problems of the radioimmunoassay of the neurohypophysial peptides, with particular reference to oxytocin and vasopressin.

The problems of the radioimmunoassay of small peptide hormones

There are two major problems. (1) Being of low molecular weight (about 1000) they are poor immunogens. As a result, the preparation of high-affinity antisera is considerably more exacting than in the case of larger molecules. (2) Their levels in the circulation are, in molar terms, considerably lower than those of

Restricted access
Yoko Fujiwara Department of Pharmacology, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo 157-8535, Japan
Department of Genomic Drug Discovery Science, Graduate School of Pharmaceutical Sciences, Kyoto University Faculty of Pharmaceutical Sciences, Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan

Search for other papers by Yoko Fujiwara in
Google Scholar
PubMed
Close
,
Masami Hiroyama Department of Pharmacology, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo 157-8535, Japan
Department of Genomic Drug Discovery Science, Graduate School of Pharmaceutical Sciences, Kyoto University Faculty of Pharmaceutical Sciences, Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan

Search for other papers by Masami Hiroyama in
Google Scholar
PubMed
Close
,
Atsushi Sanbe Department of Pharmacology, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo 157-8535, Japan
Department of Genomic Drug Discovery Science, Graduate School of Pharmaceutical Sciences, Kyoto University Faculty of Pharmaceutical Sciences, Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan

Search for other papers by Atsushi Sanbe in
Google Scholar
PubMed
Close
,
Junji Yamauchi Department of Pharmacology, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo 157-8535, Japan
Department of Genomic Drug Discovery Science, Graduate School of Pharmaceutical Sciences, Kyoto University Faculty of Pharmaceutical Sciences, Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan

Search for other papers by Junji Yamauchi in
Google Scholar
PubMed
Close
,
Gozoh Tsujimoto Department of Pharmacology, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo 157-8535, Japan
Department of Genomic Drug Discovery Science, Graduate School of Pharmaceutical Sciences, Kyoto University Faculty of Pharmaceutical Sciences, Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan

Search for other papers by Gozoh Tsujimoto in
Google Scholar
PubMed
Close
, and
Akito Tanoue Department of Pharmacology, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo 157-8535, Japan
Department of Genomic Drug Discovery Science, Graduate School of Pharmaceutical Sciences, Kyoto University Faculty of Pharmaceutical Sciences, Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan

Search for other papers by Akito Tanoue in
Google Scholar
PubMed
Close

Introduction Arginine-vasopressin (AVP) and oxytocin (OT) are neurohypophysial hormones synthesized in the paraventricular nucleus and supraoptic nucleus of the hypothalamus. AVP acts in many organs and plays a variety of

Free access
Akiko Katoh Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan
Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by Akiko Katoh in
Google Scholar
PubMed
Close
,
Hiroaki Fujihara Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by Hiroaki Fujihara in
Google Scholar
PubMed
Close
,
Toyoaki Ohbuchi Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan
Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by Toyoaki Ohbuchi in
Google Scholar
PubMed
Close
,
Tatsushi Onaka Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by Tatsushi Onaka in
Google Scholar
PubMed
Close
,
W Scott Young III Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by W Scott Young III in
Google Scholar
PubMed
Close
,
Govindan Dayanithi Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by Govindan Dayanithi in
Google Scholar
PubMed
Close
,
Yuka Yamasaki Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by Yuka Yamasaki in
Google Scholar
PubMed
Close
,
Mitsuhiro Kawata Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by Mitsuhiro Kawata in
Google Scholar
PubMed
Close
,
Hitoshi Suzuki Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by Hitoshi Suzuki in
Google Scholar
PubMed
Close
,
Hiroki Otsubo Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by Hiroki Otsubo in
Google Scholar
PubMed
Close
,
Hideaki Suzuki Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by Hideaki Suzuki in
Google Scholar
PubMed
Close
,
David Murphy Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by David Murphy in
Google Scholar
PubMed
Close
, and
Yoichi Ueta Departments of, Physiology, Otorhynolaryngology, Department of Physiology, Section on Neural Gene Expression, Department of Cellular Neurophysiology, Department of Anatomy and Neurobiology, Molecular Neuroendocrinology Research Group, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan

Search for other papers by Yoichi Ueta in
Google Scholar
PubMed
Close

Introduction The neurohypophyseal hormones arginine vasopressin (AVP) and oxytocin (OXT) are mainly synthesised in discrete groups of magnocellular neurosecretory cells (MNCs) that are located in the hypothalamus. The gene expression, synthesis and

Free access