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Biomedical subjects

J W Wells

Publications and source records attributed to J W Wells.

At least 73 records · Page 4Linked to original sources
PubMed1980

Competitive binding studies with multiple sites. Effects arising from depletion of the free radioligand.

Apparently anomalous behaviour arises if a radiolabelled drug and a non-radioactive drug compete for binding to a membrane-bound receptor when (a) there is severe depletion of the radiolabelled drug and (b) the non-radioactive drug binds to a heterogeneous population of binding sites. In extreme cases, binding of the non-radioactive drug to the sites of high affinity can be obscured completely. This phenomenon is illustrated by the binding of carbachol to muscarinic receptors, estimated by inhibition of a radiolabelled antagonist.

Animals↗
PubMed1980

Cellular changes in the granulosa layer of the maturing ovarian follicle of the domestic fowl.

1. The relationships between length, width and height of the maturing ovarian follicle of the domestic fowl (Gallus domesticus) are shown. 2. During the rapid-growth phase (yolk deposition) of the oocyte, i.e. an increase in size from about 9 mm diameter to 35 mm diameter, there is about a 15-fold increase in its surface area. During this time the number of granulosa cells adjacent to the oocyte increases by about 5-fold. 3. The granulosa cells become flatter during the growth period of the follicle, consequently increasing their surface area adjacent to the oocyte by about 3-fold. 4. Together the change in shape of the granulosa cells and the increase in their number account for the increase in area of the granulosa layer during follicular growth. 5. Measurement of the DNA content of the granulosa layer indicated a progressive decrease in the cellular content of DNA as the follicle matures.

Animals↗
PubMed1980

Effect of ovine LH on the progesterone content of the granulosa cells in preovulatory follicles of the domestic fowl (Gallus Domesticus).

Laying hens were injected i.v. with a single dose of ovine LH (100 microgram) 6-8 hr after a known ovulation, i.e. when plasma LH concentrations are low. Groups of 4 birds were killed at 15 min intervals up to 1 h after injection and the complete granulosa was obtained from 4 or 5 of the largest preovulatory follicles of each bird for progesterone measurement by g.l.c. Compared with the saline-injected controls which had negligible levels of progesterone, granulosa progesterone increased in all the LH-treated birds. The maximum response (mean progesterone content 1966 ng/follicle) occurred 45 min after injection but there was a significant decline by 60 min. It is concluded that the granulosa cells provide most of the preovulatory plasma progesterone increase.

Animals↗
PubMed1980

Effect of luteinizing hormone on progesterone secretion in vitro by the granulosa cells of the domestic fowl (Gallus domesticus).

During short periods of incubation (3 h) the secretion of progesterone by granulosa cells from the largest preovulatory follicle of the fowl was higher (160 pmol/micrograms DNA) with ovine LH in the medium than without it (60 pmol/micrograms DNA). Granulosa cells from follicles collected 24 and 48 h before their expected ovulation secreted progesterone at similar rates to cells from the largest follicle which was likely to ovulate within 5 h. The identity of progesterone was confirmed by physicochemical methods. After granulosa cells had been incubated with LH in Medium 199 for 24 h, the concentration of progesterone in the medium was 1.65 mumol/l whereas oestrone and oestradiol were present at concentrations of 254 and 199 pmol/l respectively. The results indicate that the larger yellow yolk-filled follicles of the ovarian hierarchy in the domestic fowl contribute to the preovulatory surge of progesterone which has been observed in the peripheral blood.

Animals↗
PubMed1979

Activity of ovarian delta 5-3 beta-hydroxysteroid dehydrogenase in the domestic fowl (Gallus domesticus) with respect to age.

The distribution of delta 5-3 beta-hydroxysteroid dehydrogenase was examined in the ovaries of hens aged 8--30 weeks. At all ages the interstitial cells (both thecal and stromal) gave a positive formazan reaction, but a positive reaction was not obtained in the granulosa cells of follicles less than 5 mm diameter in mature or immature birds. Since activity was restricted to follicles of larger size than this, it is concluded that steroidogenesis occurs in the granulosa cells for only the last 7--8 days of their life in the preovulatory follicle.

3-Hydroxysteroid Dehydrogenases↗
PubMed1978

Role of the granulosa cells of the postovulatory follicle of the domestic fowl in oviposition.

Surgical removal of the granulosa cells, leaving the remainder of the postovulatory follicle (POF) intact (including the thecal interstitial cells), resulted in delays of oviposition of about 19 h; similar delays were obtained when the granulosa was left in situ but was damaged by the insertion of a silicone disc into the POF. The insertion of wax balls resulted in delays of 3-4 h but the granulosa appeared to be normal. It is concluded that the integrity of the granulosa is important for normal oviposition.

Animals↗
PubMed1978

Steroid hormones in the postovulatory follicle of the domestic fowl (Gallus domesticus).

Progesterone, androstenedione, testosterone, oestrone and oestradiol were measured in the postovulatory follicle (POF) at various times up to 52 h after ovulation. The 3-fold decrease in progesterone, the major constituent, which occurred over the first 15--20 h resembled the changes previously described for the enzyme, 3beta-hydroxy-steroid dehydrogenase. At 1 h before ovulation the granulosa cells of the anteovulatory follicle (AOF) contained 50 times more progesterone than the POF granulosa fraction collected 2--3 h later. The thecal portion of the AOF had progesterone concentrations 5 times those of the POF theca, but the latter contained higher concentrations of androstenedione and oestrone.

Animals↗
PubMed1977

Activity of 3beta-hydroxyteroid dehydrogenase in the postovulatory follicle of the domestic fowl (Gallus domesticus).

The activity of delta5-3beta-hydroxysteroid dehydrogenase (3beta-HSD) in the postovulatory follicle (POF) of the domestic hen was studied; it declined rapidly during the first 15 h after ovulation and then fell gradually until 52 h when there was no detectable activity. Comparison of 3beta-HSD and glucose 6-phosphate dehydrogenase activities in the theca and granulosa cells indicated that the changes in enzymatic activity can be attributed to the thecal component; the enzyme activity in granulosa cells was stable up to 35 h after ovulation. The results appear consistent with the hypothesis that the POF is a source of steroid hormones.

Animals↗