Biomedical subjects

D A Redmer

Publications and source records attributed to D A Redmer.

82 records · Page 5Linked to original sources

PubMed1986

Ovarian compensatory hypertrophy following unilateral ovariectomy in the suckled sow.

The effects of unilateral ovariectomy on ovarian compensatory hypertrophy (OCH), endocrine profiles and the pituitary response to gonadotropin releasing hormone (GnRH) were studied in 46 multiparous suckled sows. On d 20 of lactation (d 0 of experiment), sows were subjected to sham ovariectomy (Sham; n = 23) or unilateral ovariectomy (ULO; n = 23). On d 1 (n = 16), 2 (n = 15) or 8 (n = 15) following initial surgery the remaining ovaries in both Sham and ULO sows were removed. Immediately following removal of the remaining ovaries, GnRH (10 micrograms) was administered to each sow. Peripheral blood samples were taken every 10 min for 80 min beginning 20 min prior to GnRH administration. No difference in ovarian weight was observed between ULO and Sham sows until d 8, when ovarian weight was greater (P less than .05) for the remaining ovary from ULO sows (3.96 +/- .21 vs 5.91 +/- .39 g). Ovarian follicular fluid weights from ULO sows were greater (P less than .05) than Sham sows on both d 2 and 8. On d 1, plasma concentrations of follicle stimulating hormone (FSH) were greater (P less than .05) in ULO sows than in Sham sows (2.9 +/- .2 vs 2.1 +/- .1 ng/ml). Plasma FSH concentrations, however, did not differ between Sham and ULO sows on either d 2 or 8. Ovarian venous concentrations of estradiol-17 beta were also greater (P less than .05) in ULO sows compared with Sham sows on d 2 but not d 8.

Animals↗

PubMed1985

Effect of follicular fluid treatment on follicle-stimulating hormone, luteinizing hormone and compensatory ovarian hypertrophy in prepuberal gilts.

Prepuberal 130-day-old gilts were treated with 10 ml of charcoal-stripped porcine serum (PS), whole porcine follicular fluid (WpFF) or charcoal-stripped pFF (CpFF) twice daily beginning the day before and continuing 8 days after unilateral ovariectomy (ULO). Follicle-stimulating hormone (FSH) declined for the first 14 h after ULO in WpFF and CpFF gilts and then by 24 h returned to values observed at or before ULO, whereas FSH was increased nearly twofold at 14 h in PS gilts. At 8 days after ULO the remaining ovaries from PS-treated gilts were heavier than ovaries from follicular fluid-treated gilts. In a second experiment, ovariectomized 130-day-old gilts were assigned to either a group infused with PS, a group infused with 5 ml CpFF, or a group infused with 10 ml Cpff at 18 and 2 h before a gonadotropin-releasing hormone (GnRH) challenge. Porcine follicular fluid had no effect on luteinizing hormone (LH) response to GnRH, depressed the FSH response to a 10-micrograms challenge of GnRH, but had no effect on FSH response to a 50-micrograms challenge of GnRH. In a third study, gilts were subjected to sham ovariectomy (Sham) or ULO at 130 days of age. GnRH (10 micrograms) was given on Days 1, 2 or 8 after surgery. The response to GnRH in ULO versus Sham gilts did not differ for FSH or LH on any day.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Metabolic clearance and production rates of oestradiol and progesterone during pubertal and postpubertal development in gilts.

The crossbred gilts studied were aged 80 days (prepubertal), 180 days (prepubertal or postpubertal) and 260 days (postpubertal or pregnant). Estimates of metabolic clearance rate (MCR) of oestradiol and progesterone were consistently less (21 and 27%) in plasma than in blood, and these differences were not influenced by age of gilt. The MCR (1/day per kg body weight) for oestradiol and progesterone in plasma was greater (P less than 0.05) for 80-day-old prepubertal gilts than for older gilts. The MCR values of oestradiol and progesterone were similar in 180-day-old and 260-day-old gilts independent of reproductive state. Production rate (PR) of oestradiol and progesterone increased with age (80-180 days), and age and reproductive state differences were much more pronounced for PR of progesterone than of oestradiol. These results support the hypothesis that a reduction in the MCR and an increase in PR of oestradiol and progesterone in the gilt are associated with the process of pubertal development, and changes in gonadal steroid concentrations appear not to alter the MCR of oestradiol and progesterone.

Age Factors↗

PubMed1985

Evidence for a non-steroidal angiotropic factor from the primate corpus luteum: stimulation of endothelial cell migration in vitro.

After luteal cells from 7 midluteal phase cynomolgus monkeys were cultured for 72 h, luteal conditioned media were found to contain angiotropic activity that stimulated endothelial cell migration in vitro, using a 48-microwell chemotaxis assembly. The number of endothelial cells that migrated through 8 micron-pore polycarbonate membranes in 2 h was three-fold greater (P less than 0.01) with luteal cell-conditioned vs identical unconditioned media. Pre-treatment of luteal cultures with hCG, FSH, or testosterone did not enhance production of the endothelial cell migration stimulating activity (P greater than 0.25). Luteal angiotropic activity was both chemotactic and chemokinetic. Angiotropic activity was retained in steroid-depleted fractions after reversed-phase chromatography. These results demonstrate that monkey luteal cells secrete a non-steroidal factor(s) which directly stimulate(s) migration of endothelial cells in vitro. A luteal angiotropic factor may be an important intraovarian regulator of the formation and lifespan of the primate corpus luteum during the ovarian cycle.

Angiogenesis Inducing Agents↗

PubMed1985

Maturation of ovarian follicles in the prepubertal gilt.

The processes of follicle development and puberty are closely related, and both are associated with maturation of the hypothalamic-pituitary-ovarian axis. Prenatal development of the ovary is independent of gonadotrophic stimulation. Beyond 60 days of age (postnatally), tertiary follicles develop and gonadotrophins begin to influence ovarian follicular development. Negative feedback regulation of pituitary gonadotrophins by ovarian secretions develops between 60 and 100 days of age. In the prepubertal gilt, no consistent changes in peripheral FSH, oestrogen or progesterone concentrations have been identified which are associated with recruitment of the first set of preovulatory follicles. Whether LH secretion increases before this recruitment remains equivocal. Few details are available on how gonadotrophic hormones stimulate ovarian function in the prepubertal gilt. On the basis of a follicular maturation model that has been described for the rat, the actions of FSH, LH and oestrogens on follicular cell receptors and the regulation of aromatase activity seem paramount. Aromatization of androgens to oestrogens has been proposed as a central regulator for follicular maturation. In the prepubertal gilt, a selective increase in peripheral FSH concentration occurs on Day 1 after unilateral ovariectomy, followed by significant increases in ovarian venous concentrations of oestradiol and inhibin on Days 2 and 4 and compensatory growth as measured by follicular fluid volume on Days 2, 4 and 8. Administration of pig follicular fluid to the prepubertal gilt during and after unilateral ovariectomy suppresses compensatory ovarian hypertrophy by mechanisms yet to be determined. In pigs a number of intraovarian factors have been identified, but there is little information on how these factors regulate follicular recruitment and growth. The factor(s) that prevents ovarian follicles in the prepubertal gilt from progressing to ovulation after acquiring the ability to ovulate in response to exogenous gonadotrophins remains unknown.

Animals↗

PubMed1984

Effect of unilateral ovariectomy on compensatory ovarian hypertrophy, peripheral concentrations of follicle-stimulating hormone and luteinizing hormone, and ovarian venous concentrations of estradiol-17 beta in prepuberal gilts.

A study was designed to characterize the compensatory ovarian response to unilateral ovariectomy (ULO) in prepuberal gilts and to investigate further the mechanisms involved in compensatory ovarian hypertrophy (COH). Forty-eight crossbred gilts were sham ovariectomized (Sham) or unilaterally ovariectomized at 130 days of age (Day 0). Remaining ovaries in ULO gilts were removed and Sham gilts were bilaterally ovariectomized 2, 4 or 8 days later. A peripheral blood sample was taken before surgery and ovarian venous blood samples were taken before removal of each ovary. Serum estradiol-17 beta (E2) concentrations were determined. Mean wet and dry ovarian weights per ovary on Day 2 for ULO and Sham gilts were 3.4 versus 2.8 and 0.26 versus 0.24 g, respectively. Those weights on Days 4 and 8 were greater (P less than 0.01) for ULO than Sham gilts. Follicular fluid weight per ovary was greater (P less than 0.05) for ULO than Sham gilts on Days 2, 4 and 8. Ovarian venous E2 concentrations were greater (P less than 0.01) for ULO than for Sham gilts on Days 2 and 4 but were similar on Day 8. In a second experiment, 42 prepuberal gilts 130 days of-age were subjected to Sham (n = 18), ULO (n = 18) or bilateral ovariectomy (BLO; n = 6) to evaluate follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secretion immediately after surgical treatment. Release of FSH within the first 24 h was greater for BLO than ULO and for ULO than Sham gilts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Estradiol and testosterone metabolic clearance and production rates during puberal development in boars.

Changes in metabolic clearance rate (MCR) and production rate (PR) of estradiol-17 beta (E2) and testosterone (T) were evaluated in crossbred boars averaging 35 +/- 1, 91 +/- 3, 118 +/- 4 and 177 +/- 6 kg at 80, 160, 260 and 560 days of age, respectively. A comparison of E2 and T MCR determined in blood or plasma was made in castrate and intact boars at 180 days of age. In the two experiments, estimates of MCR of E2 and T were consistently greater (22.0 and 23.8%) in blood than in plasma. These differences were not influenced by age of boar or castration. The MCR (l X day X kg BW) for E2 and T in plasma was greater (P less than 0.05) for 80-day-old prepuberal boars than the three groups of older boars. Production rates of E2 and T were lower in boars at 80 days of age than in older boars. Thus, a reduction in the MCR and an increase in PR of E2 and T in the boar are involved in the increased concentrations of circulating steroids associated with puberal development. Difference in MCR, determined in blood and plasma for both E2 and T, suggests that the contribution of the cellular component of blood to MCR studies in pigs should not be ignored.

Aging↗

PubMed1981

Estrus and ovulation in gilts fed a synthetic progestogen.

A synthetic progestogen, allyl trenbolone (AT), was fed to sexually mature gilts to determine the effective doses for the control of estrus and ovulation. Gilts were assigned to a control group and 5 treatment groups receiving 10.0, 12.5, 15.0, 17.5 or 20.0 mg of AT mixed in .45 kg of feed/head/day for 18 consecutive days. Ovarian morphology was determined by laparotomy following estrus or at 10 days post-treatment. AT suppressed estrus in all gilts during treatment. Estrus was effectively synchronized in treated gilts. The average interval from withdrawal of progestogen treatment to estrus was 4.5 days for 48 of 50 treated gilts that were in estrus within 10 days after treatment. The average ovulation rate in treated gilts was similar to control gilts. No detrimental side effects, due to treatment, were observed with the possible exception of a slight increase in the incidence of cystic follicles.

Journal Article↗

PubMed1981

Ovarian activity and hormonal patterns in gilts fed allyl trenbolone.

A study was conducted to establish the profile of reproductive hormones and the degree of ovarian activity in gilts fed either 2.5 or 15.0 mg of allyl trenbolone (AT) daily. Progesterone levels following regression of corpora lutea remained low (less than 1 ng/Ml) during progestin treatment. In gilts given 2.5 mg AT, plasma estradiol (E2) levels fluctuated between 7 and 13 pg/ml during treatment and began to decrease by day 2 after withdrawal of AT. Gilts given 15 mg of AT had lower (P less than .01) plasma concentrations of E2 (2.5 pg/ml) during treatment; concentrations began to increase the day after withdrawal of AT, reaching a maximum of 13.1 pg/Ml in 3.5 to 4.0 days. Luteinizing hormone (LH) levels were low (less than 1.5 ng/ml) during AT treatment. Daily feeding of AT prevented estrus in all gilts. A preovulatory surge of LH (4 ng/ml) was observed on the first day of the first post-treatment estrus. Gilts given 2.5 mg of AT daily had more (P less than .01) follicles of ovulatory size during treatment and a higher frequency of cystic follicles after withdrawal than gilts given 15 mg of AT daily. Estrus was effectively synchronized in gilts given 15 mg of AT daily, whereas the feeding of 2.5 mg AT daily resulted in an increased incidence of anestrus.

Animals↗

PubMedDate not supplied

Initial characterization of endothelial mitogens produced by bovine corpora lutea from the estrous cycle.

To further characterize mitogenic factor(s) present in luteal extracts or luteal explant conditioned media (LCM), bovine corpora lutea (CL) were homogenized or incubated in explant culture, respectively. After evaluation of luteal extracts and LCM by using an endothelial cell proliferation bioassay, mitogenic activity was characterized by immunoneutralization with antibodies against heparin-binding (fibroblast) growth factor (HBGF) 1 or 2. LCM also were subjected to ultrafiltration, as well as anion-exchange, cation-exchange, and heparin-affinity chromatography. The presence of HBGF-2 in LCM also was evaluated by using a dot immunoblot assay. Extracts of luteal tissues and LCM stimulated (P < 0.05) proliferation of endothelial cells in a dose-dependent manner. Mitogenic activity of luteal extracts and LCM was decreased (P < 0.05) by treatment with specific antibodies against HBGF-2 or HBGF-1. LCM also contained immunoreactive HBGF-2. The mitogenic activity bound to anion exchangers, phenyl-Sepharose, and heparin-agarose, but not to cation exchangers, indicating that endothelial mitogenic activity is anionic at neutral pH, has some hydrophobic characteristics, and belongs to the HBGF family of proteins. Following ultrafiltration, endothelial mitogenic activity was retained by membranes having a 30,000 or 100,000 molecular weight cutoff. In addition, LCM was resolved into four peaks of heparin-binding endothelial mitogenic activity, each with a different affinity for heparin. These data demonstrate that bovine CL contain and produce endothelial mitogens of large molecular size, which may be important regulators of luteal function. These endothelial mitogens are heparin-binding and anionic at neutral pH.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗