Biomedical subjects

R S Carson

Publications and source records attributed to R S Carson.

29 records · Page 2Linked to original sources

PubMed1986

Effect of long-term infusion of ovine corticotrophin-releasing factor in the immature ovine fetus.

Synthetic ovine corticotrophin-releasing factor (oCRF) was infused continuously into the jugular veins of six ovine fetuses for 5-11 days. Two fetuses receiving 0.1 and 1.0 microgram oCRF/h from gestational days 134 and 135 respectively, lambed prematurely on days 141 and 140 respectively. Three out of four fetuses receiving oCRF at 2.4 micrograms/h, from 125 days of gestation, delivered spontaneously at 131, 131 and 136 days, whilst one died in utero at 132 days. Two fetuses receiving vehicle only or oCRF intra-amniotically, were born at 148 and 145 days respectively, whilst six fetuses chronically cannulated but not infused were born at 149.8 +/- 2.1 (S.D.) days. In ewes lambing at term, maternal plasma progesterone concentrations were 41.4 +/- 11.4 (S.E.M.; n = 5), 28.8 +/- 7.8 (n = 6), 17.1 +/- 4.8 (n = 5) and 7.9 +/- 1.1 (n = 4) nmol/l on 3, 2, 1 and 0 days respectively before the lambs were born. No such decrease in maternal plasma progesterone concentrations was seen in the oCRF-infused fetuses. Fetal plasma concentrations of immunoreactive ACTH were maintained above normal in oCRF-infused fetuses, but some desensitization to bolus oCRF injections occurred in these fetuses. Four of the five fetuses born prematurely were sufficiently mature to survive, being able to stand, breathe and suckle. It is concluded that continuous oCRF infusions into immature fetuses can accelerate maturation of a number of organs and systems culminating in the premature delivery of viable lambs.

Adrenocorticotropic Hormone↗

PubMed1985

Distribution of specific androgen binding sites within the ovine ovarian follicle.

Two specific androgen binding sites were characterized in the ovine follicle with [3H]DHT, [3H]T and [3H]R-1881 as ligands, different incubation times and a charcoal separation step: the first, with characteristics very similar to testicular ABP in terms of its capacity, affinity, association and dissociation rates and specificity for natural and synthetic androgens, was found in serum, follicular fluid and the 27000 X g particulate and cytosol fractions of granulosa cells; the second, classic androgen receptors, were found in the cytosol with high affinity and low capacity for the synthetic androgen R-1881 and a very slow steroid-protein rate of dissociation. Saturation analysis on purified nuclei showed only the presence of the androgen receptor binding R-1881 with capacity similar to cytosol receptor. Isolated follicles showed a direct correlation between the total concentrations of androgen ([3H]-[3H]R-1881) binding sites and the follicular diameter. The complex actions which androgens exert on granulosa cell function may be mediated by interactions in vivo between these extra- and intracellular specific androgen binding proteins.

Animals↗

PubMed1984

Identification at the onset of luteolysis of follicles capable of ovulation in the ewe.

Follicles of various sizes at the surface of the ovary were ablated by electrocautery at the time of cloprostenol-induced luteolysis in ewes and the interval from cloprostenol treatment to the onset of the LH surge determined as an index of the time from luteolysis to ovulation. When follicles 2-4 mm or greater than 4 mm diameter remained in the ovaries, the interval from cloprostenol treatment to the onset of the LH surge was similar to that in sham-operated (control) ewes (55-60 h), whereas when the only follicles remaining were less than 2 mm, the interval was extended by 24 h (P less than 0.05). This study demonstrates that follicles capable of ovulating can be selected from those greater than or equal to 2 mm diameter at luteolysis, emphasizing the flexibility of the sheep ovary in its final selection of the ovulatory follicle.

Animals↗

PubMed1984

Relationships between aromatase activity, follicular fluid oestradiol-17 beta and testosterone concentrations, and diameter and atresia of individual ovine follicles.

Aromatase activity was measured in granulosa cells using a 1-h in-vitro assay. This activity correlated with the concentration of oestradiol-17 beta and the ratio of oestradiol-17 beta to testosterone in follicular fluid of individual follicles ranging from 1.5 to 7.0 mm diameter. These data show an 8-10-fold difference in aromatase activity between small and large follicles and that aromatase activity per cell increased in small non-atretic follicles (less than 3.5 mm) whereas it remained relatively constant in large nonatretic follicles (greater than or equal to 3.5 mm). Aromatase activity was much lower in follicles at more advanced stages of atresia. Atresia was assessed using the morphological and the morphometric methods (% of maximum number of granulosa cells/follicle). Although the morphological method of assessment was preferable to the morphometric method, it did not differentiate a decrease in aromatase activity as a very early event in the atretic process. We believe this is due to the inability of these methods to detect follicles in the initial stages of atresia.

Animals↗

PubMed1982

Successful fertilisation of human oocytes in vitro: concentration of estradiol-17 beta, progesterone and androstenedione in the antral fluid of donor follicles.

Oocytes and matched samples of follicular fluid were obtained from 156 pre-ovulatory follicles in 125 women 26--36 h after either administration of hCG or the onset of an endogenous LR surge. Concentrations of estradiol-17 beta (E2), progesterone (P) and androstenedione (A4) in the fluid of individual donor follicles were measured and related to the success of fertilisation of oocytes in vitro and the incidence of pregnancies after embryo transfer. Oocytes which gave rise to successful pregnancies were obtained from follicles which contained greater concentrations of E2 and a higher ratio of E2:P than did oocytes from which pregnancy did not result. These data provide direct evidence in support of the hypothesis that estrogenic follicles are the sole source of ova which undergo fertilisation and subsequently give rise to pregnancy in women.

Androstenedione↗

PubMed1981