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N Colvin

Publications and source records attributed to N Colvin.

4 recordsLinked to original sources
PubMed1987

A rapid, sensitive and reliable assay for inhibin bioactivity.

A rapid 2-day quantitative assay for inhibin bioactivity based on FSH secretion from pituitary cells of immature female rats is described. The bioassay exhibited steeper slopes, improved precision and greater (fourfold) sensitivity compared with a previously established pituitary FSH cell content assay. Whole pituitary glands were used for the preparation of pituitary cells and the method for cell dispersion required a single enzymatic treatment with trypsin. Cells (180,000 viable cells per well) were dispensed into culture media containing inhibin and incubated for 48 h. Media were removed and assayed for FSH by radioimmunoassay. Using a ram rete testis fluid preparation as standard the inhibin dose-response curves of 25 consecutive experiments showed indices of precision of -0.08(mean)[range -0.04 to -0.17] and Finney's G values of 0.017[0.003-0.06]. The mean ED40 was 0.17 units of inhibin activity per well with interassay variation of 16.2% at this point of the dose-response curve. The assay had a practical capacity of 400 wells, permitting the measurement of dose-response curves of at least 40 unknowns with three dose points and triplicate wells per dose. The assay is specific for inhibin-containing preparations from several animal species. Overall, the assay is simple, precise, and sensitive, indicative of its applicability to the measurement of inhibin samples with low inhibin bioactivity and to the screening of large numbers of fractions during inhibin purification.

Animals↗
PubMed1983

Prostaglandin F and 13,14-dihydro-15-keto prostaglandin F in the endometrium and uterine flushings of sheep before implantation.

The concentrations of prostaglandin F (PGF) and its major metabolite, 13,14-dihydro-15-keto prostaglandin F-2 alpha (PGFM), were measured in caruncular and intercaruncular endometrium of pregnant and non-pregnant ewes on Days 9, 11, 13 and 15 after mating (Day 0) and related to the content of PGF and PGFM in the uterine flushings. The tissue concentrations of PGF and PGFM increased with time after mating particularly on Days 13 and 15 and to a greater extent in pregnancy. However, the ratio of PGF to PGFM remained constant at 0.7, except on Day 15 in non-pregnant endometrium when it fell to 0.3 (P less than 0.05), suggesting that synthesis rather than metabolism was limiting tissue concentrations of PGs. The changes in tissue concentrations of PGF and PGFM were reflected in the contents of PGF and PGFM in the uterine flushings of non-pregnant, but not pregnant ewes. Pregnant ewes had relatively more PGF and less PGFM than did non-pregnant ewes on Day 15. Moreover, there was always 5-10-fold less PGFM than PGF in the uterine flushings. It is concluded that the increase in PG in the uterine lumen in pregnancy has its origin in the blastocyst, and that pregnancy may be associated with an increase in the synthesis and retention of PGs in the endometrium, rather than a redistribution towards the uterine lumen away from the uterine venous drainage.

Animals↗
PubMed1982

Oestrogen receptors and protein synthesis in caruncular and intercaruncular endometrium of sheep before implantation.

The rate of protein synthesis was higher in caruncular (P less than 0.05) and intercaruncular endometrium (P less than 0.01) of pregnant compared to non-pregnant ewes on Day 11 (Day 0 = day of oestrus), but not on Days 9, 13 and 15. Cytosolic oestrogen receptor concentrations (nmol/mg protein) were lower in caruncular endometrium of pregnant ewes than in non-pregnant ewes on Days 9 (P less than 0.02), 13 (P less than 0.05) and 15 (P less than 0.001) but not on Day 11. In intercaruncular endometrium, the receptor values were lower on Day 15 (P less than 0.02) of pregnancy compared to non-pregnancy, but not on the other days. The dissociation constant (0.75-2.55 x 10(-10) M) of oestradiol-17 beta for cytosolic receptors was similar in both tissues, regardless of pregnancy status or day of sampling. The rate of protein synthesis was generally higher in intercaruncular endometrium whereas cytosol receptor concentrations were higher in caruncular endometrium. When the blastocyst was confined to one uterine horn on Day 2 in another group of ewes, there was a decrease in nuclear (P less than 0.05), cytosolic (P less than 0.05) and total (P less than 0.05) oestrogen receptors only in caruncular endometrium in the pregnant horn on Day 15. There were no difference in the proportions of receptors localized in nuclear fractions or in the rate of protein synthesis in either endometrial tissue from the pregnant or the non-pregnant horn. We conclude that the ovine blastocyst is capable of influencing oestrogen receptors levels in caruncular and intercaruncular endometrium by a local action as early as Day 9, well before endocrine recognition of pregnancy on Day 12 and attachment on Day 15.

Animals↗