Search Results

You are looking at 1 - 10 of 13 items for

  • Author: N. Brown x
  • Refine by Access: All content x
Clear All Modify Search
Free access

Carol G. Brown and N. L. Poyser

Summary. Prostaglandin (PG) and thromboxane (TX) synthesizing capacities of the rat ovary were measured at 4-h intervals during the 4-day oestrous cycle of the rat. Production of PGE-2, PGF-2α, 6-oxo-PGF-1α and TXB-2 increased 5-fold, 1·6-fold, 1 ·7-fold and 1 ·7-fold, respectively, between 18:00 h on the day of pro-oestrus and 02:00 h at oestrus. This preferential stimulation of ovarian PGE-2 production, after the ovulatory surge of LH before ovulation, provides further evidence for the involvement of ovarian PGE-2 in ovulation in the rat. These increases in ovarian PG production were not due to differences in arachidonic acid availability, PG metabolism, or the interconversion of PGE-2 and PGF-2α. In addition, the greater stimulation of PGE-2 synthesis was not due to an increase in PGH-2 to PGE-2 synthetase activity. It is concluded that the ovulatory LH surge late in the afternoon of pro-oestrus in the rat causes an increase in ovarian cyclo-oxygenase (PGH-2 synthetase) activity with the majority of the PGH-2 synthesized being directed into the PGE-2-forming pathway.

Free access

Carol G. Brown and N. L. Poyser

Summary. Prostaglandin (PG) and thromboxane (TX) synthesis by uterine homogenates was measured at 4-h intervals during the 4-day oestrous cycle of rats. Production was in the order of 6-oxo-PGF-1α (which reflects PGI-2 synthesis) > PGF-2α > TXB-2 (which reflects TXA-2 synthesis) [ill] PGE-2. Peak production occurred at 02:00 h on the day of oestrus, after which production gradually decreased, with some fluctuation on the day of metoestrus, to reach a minimum between 22:00 and 06:00 h on the days of dioestrus and oestrus, respectively. Separation of the uterine tissues showed that, on a unit weight basis, the endometrium had a much higher PG and TX synthesizing ability than did the myometrium, although this was compensated for on a total weight basis by the much greater mass of myometrium. Endometrial PG and TX production was in the order of PGF-2α > TXB-2 [ill] 6-oxo-PGD-1α ≡ PGE-2, with PGF-2α and TXB-2 productions showing the greatest increases between 10:00 and 02:00 h on the days of pro-oestrus and oestrus, respectively. Myometrial PG and TX production was in the order of 6-oxo-PGF-1α > PGF-2α > PGE-2 ≡ TXB-2, with 6-oxo-PGF-1α and PGF-2α productions showing small increases between 10:00 and 02:00 h on the days of pro-oestrus and oestrus, respectively. Myometrial PGE-2 production decreased between these two times. Progesterone and oestradiol treatment significantly (P < 0·05) increased PGF-2α and TXB-2 synthesis, but not 6-oxo-PGF-1α and PGE-2 synthesis, by uterine homogenates from long-term ovariectomized rats but not from acutely ovariectomized rats. Since the uterine tissue concentrations of PGF-2α, TXB-2 and 6-oxo-PGF-1α, but not of PGE-2, were significantly (P < 0·05) higher at 02:00 h on the day of oestrus than at 10:00 h on the day of pro-oestrus, increased uterine PG and TX production may be involved in increasing sperm transport through the uterus at the time of ovulation (i.e. around 02:00 h on the day of oestrus) by stimulating uterine motility.

Free access

R. G. Gosden, N. Brown, and Kay Grant

Summary. In a histological survey of 19 mammalian species, Call–Exner bodies of conventional size and appearance were found in only 5, namely, human, rhesus monkey, rabbit, guinea-pig and sheep. Rabbit ovaries were used for characterizing these bodies using quantitative histochemistry, lectin binding and electron microscopy. Call–Exner bodies were topographically distinct lacunae of the extracellular space probably containing hyaluronic acid with proteoglycan complexes. The staining characteristics of the antrum and Call–Exner bodies were generally similar. However, in contrast to the antrum, the smaller lacunae contained suspended filaments with a distinctive peripheral membrane upon which a rosette of granulosa cells was resting. The membrane and narrow intercellular clefts probably prevent much exchange of large glycosaminoglycan complexes with the antrum. The origin and significance of Call–Exner bodies require further study, but it is clear that they are associated with secretion rather than with necrosis as sometimes suggested.

Keywords: Call–Exner bodies; glycosaminoglycans; Graafian follicle; granulosa cell; lectin; rabbit

Free access

C. R. Brown, N. Clarke, M. Aiken, and B. D. Bavister

Summary. Hamster zonae pellucidae were obtained from follicular oocytes, superovulated eggs, and eggs fertilized in vivo or in vitro. Zonae were labelled with N-succinimidyl-3(4-hydroxy,5-[125I]iodophenyl)propionate, and compared on single-and two-dimensional SDS-PAGE. Single-dimensional electrophoresis showed considerable differences between zona categories in the amount of label that they incorporated; follicular zonae incorporated the least label and zonae from eggs fertilized in vivo the most. On two-dimensional electrophoresis, polypeptides from 3 of the 4 zona categories migrated into 4 major groups: two of these groups each with M r 150 000–250 000 were within the M r range of ZP1, and two others, at M r 90 000 and 55 000, appeared to be analogous to ZP2 and ZP3, respectively. The fourth zona category (zonae from eggs fertilized in vivo) showed a changed polypeptide profile as well as incorporating the most label; one of the polypeptides, M r 150 000–250 000, was undetectable, but a train of M r 70 000–90 000 polypeptides and a discrete polypeptide at M r 20 000 were new. Since this changed profile did not occur in zonae from superovulated eggs, or in zonae from eggs fertilized in vitro, a synergism between oviducal factors and factors from the spermatozoon or egg, or both, towards the zona in vivo is indicated.

Keywords: fertilization; zona pellucida; electrophoresis; hamster

Free access

Carol Brown, R. G. Gosden, and N. L. Poyser

Summary. Prostaglandin (PG) production by the uterus of ovariectomized virgin rats, with and without replacement steroid therapy, was compared in animals aged 4–5 and 13–14 months. The synthesizing capacities of the uterus for PGE-2, PGF-2α. 6-keto-PGF-1α and thromboxane (TX) B-2 (expressed as the amounts synthesized per mg protein by the homogenized tissue during a 90-min incubation) were significantly lower in the ageing uteri than in young uteri. The PG and TX synthesizing capacities of the young uteri, but not of the ageing uteri, were stimulated by sequential treatment with oestradiol and progesterone implants. Tissue concentrations in and release from the uteri of PGE-2, but not of PGF-2α, were significantly lower in ageing rats than in younger rats, and occurred irrespective of the hormonal status. Treatment with steroids did not stimulate the tissue concentrations in or release from the uterus of PGE-2 or PGF-2α in young or ageing rats. Since PGs, particularly PGE-2, produced by the rat uterus have been implicated as mediators of the implantation process, reduced production of PGE-2 by the ageing uterus may explain the lower implantation rate and the consequent reduction in fertility of ageing rats.

Free access

R. G. Gosden, D. W. Richardson, N. Brown, and D. W. Davidson

Summary. The gametogenic potential of young male CBA/Ca mice aged 4–5 months was compared with that of animals 20–23 months of age which had recently ceased to sire offspring. The older mice had substantially lower circulating levels of testosterone and smaller testes. Testicular and epididymal spermatozoa were reduced in number, had more abnormal forms and fewer were progressively motile. Ageing seminiferous tubules varied in their degree of functional atrophy from complete depletion of germ cells to maintenance of sperm production. They were enclosed by a thickened basal lamina and more collagenous connective tissue and occasionally allowed the penetration of lanthanum between Sertoli cells into the ad-luminal compartment. There was no evidence of autosensitization to sperm antigens.

Free access

R. G. Gosden, R. H. F. Hunter, Evelyn Telfer, C. Torrance, and N. Brown

In common with all other cells, the oocyte and granulosa cells are bathed in extracellular fluid. It has, however, become conventional to reserve the term ‘follicular fluid’ for that fraction of the extracellular fluid that accumulates in the antrum of larger follicles. This pool of fluid is of considerable biological significance since its composition indicates the environment in which the oocyte and granulosa cells are growing and maturing. Furthermore, it buffers the internal environment of the follicle against the influence of external conditions presented by the blood stream.

The chemical composition of follicular fluid has been studied extensively and found to consist of substances derived from blood as well as from local secretion and metabolism. Particular attention has been paid to the proteins and hormonal steroids. Rather than attempt a comprehensive review, this paper will focus on general physical characteristics of the fluid and the physiological factors that influence its formation. These properties determine the rate at which extracellular fluid is accumulating and, hence, the size and morphogenesis of the Graafian follicle. It is important to reveal the mechanism and dynamics of follicular fluid formation if the composition of the fluid is to be fully understood.

Free access

B. W. Brown, Y. Cognie, P. Chemineau, N. Poulin, and O. A. Salama

Summary. The microsphere technique was used to obtain estimates of ovarian capillary blood flow near ovulation, in 8 seasonally anoestrous ewes, which were induced to ovulate by GnRH therapy. Plasma progesterone concentrations were monitored in jugular blood sampled between Days 4 and 7 after the onset of the preovulatory LH surge. The ewes were then slaughtered. Three of the ewes were treated with a single injection of 20 mg progesterone before GnRH therapy. In these ewes and 1 other, plasma progesterone values increased after ovulation and reached 1·0 ng/ml on Day 7 following the preovulatory LH surge (normal, functional CL), whilst in the other 4 ewes progesterone concentrations increased initially then declined to 0·5 ng/ml by Day 7 (abnormal CL).

In the ewes exhibiting normal luteal function, the mean ovarian capillary blood flow was significantly greater (P < 0·01) than that for ewes having abnormal luteal function. Irrespective of the type of CL produced, capillary blood flow was significantly greater (P < 0·05) in ovulatory ovaries than in non-ovulatory ovaries.

These findings indicate that the rate of capillary blood flow in ovaries near ovulation may be a critical factor in normal development and maturation of preovulatory follicles and function of subsequently formed CL.

Keywords: blood flow; anoestrus; sheep; gonadotrophins; ovary

Free access

J. L. Brown, D. E. Wildt, N. Wielebnowski, K. L. Goodrowe, L. H. Graham, S. Wells, and J. G. Howard

Faecal oestradiol and progestogen metabolite excretion was monitored in adult, female cheetahs (Acinonyx jubatus) (n = 26) for 1–24 months. Increased faecal oestradiol excretion was associated with mating or equine chorionic gonadotrophin (eCG) administration for artificial insemination, whereas increased progestogen metabolites were observed during natural and human chorionic gonadotrophin (hCG)-induced pregnant and nonpregnant luteal phases. On the basis of oestradiol excretory patterns, duration of the oestrous cycle (mean ± sem) was 13.6 ± 1.2 days with high oestradiol concentrations lasting for 4.1 ± 0.8 days. In non-gonadotrophin-treated cheetahs, 75% showed evidence of oestrous cyclicity; however, none evaluated for 1 year or longer were continuously cyclic. Rather, cyclicity was interrupted by periods of anoestrus, often exceeding several months in duration. These inactive ovarian periods were unrelated to season and were not synchronous among females. Mean duration of gestation (breeding to parturition) was 94.2 ± 0.5 days, whereas duration of faecal progestogen metabolite excretion during the nonpregnant luteal phase was 51.2 ± 3.5 days. On the basis of progestogen metabolite evaluations, spontaneous ovulation (non-mating induced) occurred only once in two females (2 of 184 oestrous cycles; 1.1%). Peak eCG-stimulated, preovulatory oestradiol concentrations were similar to those associated with natural oestrus, whereas progestogen metabolite profiles after hCG resembled those during pregnant and nonpregnant luteal phases after natural mating. In summary, results confirm that the cheetah is polyoestrus and ovulation is almost always induced. However, new evidence suggests that many females inexplicably experience periods of anoestrus unrelated to season, while 25% of the cheetahs examined expressed no ovarian activity during the study period.

Free access

P J Williams, N Marten, V Wilson, J C Litten-Brown, A M Corson, L Clarke, M E Symonds, and A Mostyn

Epidemiological studies suggest that low-birth weight infants show poor neonatal growth and increased susceptibility to metabolic syndrome, in particular, obesity and diabetes. Adipose tissue development is regulated by many genes, including members of the peroxisome proliferator-activated receptor (PPAR) and the fatty acid-binding protein (FABP) families. The aim of this study was to determine the influence of birth weight on key adipose and skeletal muscle tissue regulating genes. Piglets from 11 litters were ranked according to birth weight and 3 from each litter assigned to small, normal, or large-birth weight groups. Tissue samples were collected on day 7 or 14. Plasma metabolite concentrations and the expression of PPARG2, PPARA, FABP3, and FABP4 genes were determined in subcutaneous adipose tissue and skeletal muscle. Adipocyte number and area were determined histologically. Expression of FABP3 and 4 was significantly reduced in small and large, compared with normal, piglets in adipose tissue on day 7 and in skeletal muscle on day 14. On day 7, PPARA and PPARG2 were significantly reduced in adipose tissue from small and large piglets. Adipose tissue from small piglets contained more adipocytes than normal or large piglets. Birth weight had no effect on adipose tissue and skeletal muscle lipid content. Low-birth weight is associated with tissue-specific and time-dependent effects on lipid-regulating genes as well as morphological changes in adipose tissue. It remains to be seen whether these developmental changes alter an individual's susceptibility to metabolic syndrome.