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The role of the foetal adrenal cortex in the initiation of parturition in the sheep is well established; however the evidence for a similar role by the human foetal adrenal is circumstantial and based upon the association of prolonged gestation with foetal adrenal hypoplasia (Anderson, Laurence & Turnbull, 1969; Roberts & Cawdery, 1970) and of premature delivery with foetal adrenal hyperplasia (Anderson, Laurence, Davies, Campbell & Turnbull, 1971). There is no information concerning changes in levels of corticosteroids in the human foetus in late pregnancy and the present study was undertaken in order to examine the relationship of umbilical cord arterial and venous plasma concentrations of corticosteroids at the time of delivery to gestational age of the foetus and type of labour.
Matched samples of umbilical cord arterial and venous blood were collected during December 1971 — January 1972. Plasma levels of corticosteroids were determined by a competitive protein-binding technique (Murphy,
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SUMMARY
Pituitaries from Japanese quail were superfused continuously for up to 12 h and the luteinizing hormone (LH) in the superfusate was measured by radioimmunoassay. After an initial period the release rate remained low and relatively constant. The introduction of hypothalamic extracts prepared from quail substantially increased immunoreactive LH release. The responses were dose-dependent. Cortical extracts caused a minor but significant response. Dopamine was inactive in the system. The technique is attractive because it allows for repetitive stimulation of the same pituitary glands with treatments being administered every 30–45 min.
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ABSTRACT
The present study was undertaken to determine the involvement of the two established vasopressin receptor subtypes (V1 and V2) in arginine vasopressin (AVP)-induced natriuresis and also to determine whether changes in mean arterial pressure (MAP) and/or the renally active hormones atrial natriuretic peptide (ANP), angiotensin II (AII) and aldosterone are a prerequisite for the expression of AVP-induced natriuresis.
In Sprague–Dawley rats which were anaesthetized with Inactin (5-ethyl-5-(1′-methylpropyl)-2-thiobarbiturate) and infused with 0·077 mol NaCl/l, infusion of 63 fmol AVP/min was found to be natriuretic whereas an approximately equipotent dose of the specific V2 agonist [deamino-cis1, d-Arg8]-vasopressin (dDAVP) did not induce natriuresis. The specific V1 antagonist [β-mercapto-β,β-cyclopenta-methylene-propionyl1, O-Me-Tyr2, Arg8]-vasopressin when administered prior to infusion of 63 fmol AVP/min did not inhibit AVP-induced natriuresis. AVP-induced natriuresis was not accompanied by changes in MAP or in the plasma concentrations of the renally active hormones ANP, AII or aldosterone.
These results suggest that neither the V1 nor the V2 receptor subtypes are involved in AVP-induced natriuresis. In addition, it was found that changes in MAP, plasma ANP, All or aldosterone concentrations were not a prerequisite for AVP-induced natriuresis.
Journal of Endocrinology (1993) 136, 283–288
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Search for other papers by P. A. Sinnett-Smith in
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ABSTRACT
The effects of exogenous GH on growth and body composition were investigated in lines of mice selected for high or low body weight (P-lines) or high or low body fat (F-lines). Mice from all lines were given daily injections of recombinant bovine GH or a placebo for 21 days from 4 weeks old. They were killed and various organ weights measured. There was no consistent effect of GH on organ weights. In all lines of mice the rate of weight gain and final weight increased in response to GH. In both lines selected for body fat, GH treatment decreased fat content. The low body weight mice also became less fat, but in the high body weight mice GH treatment increased fat percentage. The results indicate that the differences in growth rate and body composition observed in these lines are not due to differences in responsiveness to GH.
Journal of Endocrinology (1991) 131, 19–24
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Search for other papers by MARGARET SMITH in
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Departments of Biochemistry and *Obstetrics and Gynaecology, University of Western Australia, Nedlands, Australia
(Received 25 April 1977)
The hormonal signal for lactogenesis in a number of different species is considered to be a precipitous fall in the concentration of progesterone in the blood during late pregnancy (see Hartmann, Trevethan & Shelton, 1973). In women, the major fall in the level of blood progesterone just after delivery (Yannone, McCurdy & Goldfien, 1968) precedes lactogenesis by 2-3 days (Reynolds, 1972). However, the effects of this fall may be modified to some extent by progesterone, which accumulates in the milk (Heap, Gwyn, Laing & Walters, 1973). Progesterone could be the 'lipid-soluble substance' in the mammary secretion which Linzell & Peaker (1974) suggested might control the final stage of lactogenesis. The purpose of the present investigation was to compare changes in the concentrations of progesterone, lactose and α-lactalbumin in the mammary secretion of women
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Search for other papers by I. D. SMITH in
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SUMMARY
Marked rises in both unconjugated and sulphoconjugated oestrone, oestradiol-17β and oestriol were observed in human foetal plasma between mid-gestation and term. Significant arterio-venous differences for the individual oestrogens in the unconjugated form were found in the umbilical cord plasma. No consistent arterio-venous differences were found for the oestrogen sulphates. This indicates that all three oestrogens are secreted from the placenta into the foetal circulation in the unconjugated form. Mean unconjugated oestrogen (oestrone + oestradiol-17β + oestriol) levels rose from 22·7 ng/ml at 17–20 weeks of gestation to 108·9 ng/ml at term in umbilical venous plasma and from 4·3 ng/ml to 23·3 ng/ml in umbilical arterial plasma. This represents a secretion rate of approximately 30 mg oestrogen/day into the umbilical vein at term. Mean oestrogen sulphate levels rose from 128 ng/ml to 313 ng/ml in the cord plasma during the same period. Of the three oestrogens measured, oestriol was quantitatively the major oestrogen in foetal plasma. It consistently represented about 78% of the unconjugated fraction and 95% of the sulphate fraction at all stages of gestation.
The method of delivery did not have a significant effect on the oestrogen levels in uncomplicated pregnancies. Similar oestrogen levels were found in foetal heart blood after either hysterotomy or spontaneous abortion at 16–20 weeks of gestation, and no significant differences were found for oestrogen levels in cord plasma after elective Caesarean section at 38–39 weeks when compared with oestrogen levels after normal delivery at term.
A significant rise in foetal unconjugated oestrogens at a time when foetal corticosteroids are increasing may be of physiological importance for foetal maturation in women.
Search for other papers by P. W. NATHANIELSZ in
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Prostaglandin F2α (PGF2α) has been shown to possess luteolytic properties in several species including the rabbit (Duncan & Pharriss, 1970; O'Grady, Kohorn, Glass, Caldwell, Brock & Speroff, 1972). Surgical removal of the corpus luteum leads to parturition in the rabbit. Thus, PGF2α should initiate parturition in this species. In primates, controversy has arisen over the ability of PGF2α to produce luteolysis (Kirton, Pharriss & Forbes, 1970). Since prostaglandins are very rapidly cleared by the pulmonary circulation, observed discrepancies may be due to the actual route of administration and dosage used.
Experiments have been carried out to measure the effect of PGF2α in producing parturition in the pregnant rabbit. PGF2α was infused continuously into rabbits with an indwelling aortic catheter (Nathanielsz & Abel, 1972). Infusions were started on day 21 and continued until delivery. PGF2α was infused at dose rates varying from 1·125 ng/h
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SUMMARY
A Pettenkofer and sulphuric acid chromogen, excreted as a glucuronide and found in the fractions of urine that also contain hydroxylated Δ5-3β-hydroxysteroids and pregnanediol, was identified as p-menth-1-ene-8,9-diol (uroterpenol). Pettenkofer chromogenicity in a compound of this nature has not previously been reported. The recovery of uroterpenol in urine after ingestion of limonene showed that it was a metabolic product of this unhydroxylated monoterpene. Although experiments on its excretion by normal subjects indicated that it was largely, if not entirely, of dietary origin, there was evidence that its rate of excretion in women was influenced by endocrine factors. Hormonal effects on the formation and/or excretion of glucuronides in general are suggested. Care is needed to ensure that dietary constituents and their metabolites, which are excreted as glucuronides and exhibit colour reactions commonly used in the estimation of urinary steroids, are not confused with hormonal metabolites.
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Isolated porcine thyroid cells were surface-labelled with 125I using the lactoperoxidase technique. Samples of the cells were then cultured and harvested at various intervals for up to 7 days. The labelled proteins remaining on the cells or shed into the culture medium were analysed by electrophoresis on polyacrylamide gels run in sodium dodecyl sulphate. These studies indicated that the several different surface proteins of the thyroid cells were lost from the cell surface at similar rates (half-time of approximately 28 h) as the result, at least in part, of a process which depended on active cell metabolism. In addition, the gel profiles obtained from analysis of both medium and membrane-bound labelled proteins were similar and this suggested that peptide cleavage was not involved in the shedding of the majority of these proteins.