Search PubMed⌕ Search

Biomedical subjects

D T Baird

Publications and source records attributed to D T Baird.

At least 325 records · Page 18Linked to original sources
PubMed1976

Endocrine changes associated with luteal regression in the ewe; the secretion of ovarian oestradiol, progesterone and androstenedione and uterine prostaglandin F2alpha throughout the oestrous cycle.

The concentrations of oestradiol, androstenedione, progesterone and prostaglandin F2alpha (PGF2alpha) were measured in utero-ovarian autotransplants. The secretion of oestradiol was closely correlated with that of androstenedione (r = 0-67, P less than 0-001) indicating a common origin from the Graafian follicle. The concentration of these two steroids fluctuated at random throughout the luteal phase with the maximum secretion occurring about 2 days before the onset of oestrus. Functional regression of the corpus luteum, as indicated by a fall in the secretion of progesterone, began on day 12 or day 13, i.e. about 4 days before the onset of oestrus. In five of the six cycles the first significant rise in the secretion of PGF2alpha occurred on days 12-14 at the time of decline of progesterone secretion, although the release of PGF2alpha was maximal on the day before the onset of oestrus. There was very little release of PGF2alpha from the uterus before day 12. The temporal relationship of these events suggests that the uterus will only release PGF2alpha after it has been primed for 7-10 days with progesterone. The initiation of luteal regression is independent of secretion of oestradiol by the pre-ovulatory follicle which may, however, stimulate the further release of PGF2alpha responsible for irreversible structural luteolysis on the day of pro-oestrus.

Androstenedione↗
PubMed1976

Changes in the secretion of ovarian steroid and pituitary luteinizing hormone in the peri-ovulatory period in the ewe: the effect of progesterone.

The secretion rates of oestradiol, androstenedione and progesterone and the peripheral plasma concentration of LH were measured in 12 ewes with ovarian autotransplants before and after luteal regression induced by a single intramuscular injection of a synthetic prostaglandin (PG) analogue, 16-aryloxyprostaglandin F 2alpha (I.C.I. 80996). Luteal regression was followed by a fourfold rise in the basal concentration of LH and increased secretion of oestradiol. In five out of six ewes there was a discharge of LH with the peak occurring 36--78 h after the injection of the PG analogue. The secretion of oestradiol declined from 3-68 +/- 1-08 to 0-33 +/- 0-6 (S.E.M.) ng/min in the 24 h following the LH peak (P less than 0-001). In the remaining six ewes in which progesterone was implanted subcutaneously 24 h after the injection of PG analogue, follicular development was suppressed as indicated by the low secretion of oestradiol and androstenedione. The basal concentration of LH fell to values similar to those observed during the luteal phase after the implant of progesterone. The secretion of androstenedione followed a similar pattern to that of oestradiol in those ewes which showed presumptive evidence of ovulation. These results suggest that progesterone reinforces the negative feedback effects of oestrogen in the ewe.

Androstenedione↗
PubMed1976

Concentration of oestrogens and androgens in human ovarian venous plasma and follicular fluid throughout the menstrual cycle.

The concentrations of androstenedione, testosterone, oestrone and oestradiol-17beta were measured in peripheral and ovarian venous blood and follicular fluid of women at various stages of the menstrual cycle. The concentration of oestradiol was similar in small follicles (diameter less than 8 mm) at all stages of the menstrual cycle and in large follicles (diameter greater than or equal to 8 mm) except during the mid- and late follicular phase when the concentration reached a peak (approximately 1500 ng/ml). The concentration of androstenedione was lowest in large preovulatory follicles at midcycle at a time when the secretion into the ovarian vein was markedly increased. The concentration of testosterone in large follicles (greater than or equal to 8 mm) was unchanged during the follicular phase whereas in small follicles there was a peak at mid-cycle. The rise in the concentration of testosterone and androstenedione at mid-cycle in peripheral plasma may be due to increased secretion by the preovulatory follicle into the ovarian vein. It is suggested that the relatively low concentration of androstenedione in follicular fluid of the preovulatory follicle arises from increased aromatization by granulosa cells in the course of oestrogen synthesis.

Adult↗
PubMed1975

Ovulation.

Explore the source record for details and available documents.

Female↗
PubMed1975

Concentration of oestrone and oestradiol in follicular fluid and ovarian venous blood of women.

The concentrations of oestrone and oestradiol as measured by a double isotope derivative method in fluid from Graafian follicles at different phases of the menstrual cycle were compared to the corresponding concentrations in ovarian and peripheral venous plasma collected simultaneously. In follicular fluid the concentration of oestradiol was much greater than that of oestrone. The concentrations of oestrogens were similar in fluid collected from small follicles at all phases of the cycle. The concentration of oestradiol in large follicles (greater than 1 cm diameter) was much higher in the mid-late follicular phase of the cycle (mean = 5390 plus or minus 1330 nmol/l) than in large or small follicles at other phases of the cycle. In the mid-late follicular phase of the cycle large follicles were invariably associated with high concentrations of oestradiol in venous plasma draining the corresponding ovary (mean 49 plus or minus 12 nmol/l). The mean ratio of oestradiol/oestrone in fluid from large follicles in which the concentration of oestradiol was greater than 1400 nmol/l (18.0 plus or minus 1.0, n = 10) was significantly higher than the ratio in corresponding samples of ovarian venous plasma (10.7 plus or minus 1.4, n = 11). These findings suggest that when the concentration of oestradiol in a Graafian follicle exceeds 3500 nmol/l it is likely to be functionally active.

Body Fluids↗
PubMed1975

Relationship between the secretion of the corpus luteum and the length of the follicular phase of the ovarian cycle.

The variation in the length of the follicular phase in many mammals may be related to the cellular origin of oestradiol secreted during the luteal phase. In all species the time taken for a small developing follicle (4-5 layers of granulosa cells) to mature to a preovulatory follicle may be the same as that which has been found experimentally in the mouse (10-17 days). In animals such as the sheep, in which there is no source of oestradiol other than the Graafian follicle, follicular development proceeds unimpaired throughout the luteal phase, and the 'follicular phse' which involves only the final stages of maturation of the Graafian follicle is relatively short. In primates, however, in which there is an extrafollicular source of oestrogen from the CL, the secretion of gonadotrophins is suppressed during each luteal phase to a level too low to initiate and maintain follicular development. At the end of each luteal phase and the beginning of the subsequent follicular phase, therefore, it is necessary to initiate the growth of a new crop of small follicles. The time taken for these follicles to develop inot preovulatory follicles determines the length of the follicular phase.

Animals↗