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Biomedical subjects

R H Douglas

Publications and source records attributed to R H Douglas.

At least 73 records · Page 4Linked to original sources
PubMed1982

A biological embryo-reduction mechanism for the elimination of excess embryos in mares.

Only one embryo was found in each of 15 pregnant mares in which multiple, synchronous (0 or 1 day apart) ovulations were induced with a pituitary extract. In the brood-farm mares, fewer (P<.05) twin pregnancies were associated with synchronous, double ovulations (0 39 ), than with asynchronous, double ovulations (9 57 ). Higher (P<.05) pregnancy rates (number of mares pregnant, regardless of number of embryos) were obtained in pituitary extract-treated mares with multiple, synchronous ovulations (15 18 ) than in treated mares with single ovulations (6 14 ). Similarily, pregnancy rates were higher (P<.01) in brood-farm mares with double, synchronous ovulations (39 47 ) than in brood-farm mares with single ovulations (1320 2426 ). Our interpretation is that ova produced by synchronous, double ovulations are viable and fertilizable (indicated by higher pregnancy rates), but that one of the resulting embryos is eliminated (indicated by the absence of twins).

Journal Article↗
PubMed1982

Effect of increased photoperiod on hormone concentrations in thoroughbred stallions.

Stallions on two Central Kentucky farms (9/farm) were studied during the 1980 breeding season. On one farm stallions were exposed to an increased photoperiod (16 h light/day) from 1 December 1979; on the second farm the stallions were maintained in an ambient photoperiod. On the basis of matings per conception (total mating/mares in foal) stallions on each farm were assigned to a high fertility (1 . 9-2 . 4 matings per conception, N = 4) or low fertility (2 . 6-5 . 6 matings per conception, N = 5) group. Exposure of stallions to increased photoperiod significantly increased serum concentrations of dehydroepiandrosterone (DHA), androstenedione, testosterone and oestrone by the start of the breeding season (16 February) while concentrations of oestradiol-17 beta and total oestrogens were similar in the two groups. LH was the only hormone significantly affected by the fertility of stallions, with LH concentrations consistently higher in the 'increased light-high fertility' stallions compared to the low basal concentration observed in the other 3 groups during the early breeding season (16 Feb.-31 March). FSH concentrations were not significantly affected by photoperiod or fertility, but appeared to be consistently higher in the 'increased light-high fertility' stallions than in the 'increased light-low fertility' stallions. The 'increased light-high fertility' stallions were mated to more mares than were stallions in the other 3 groups and differences in LH and FSH concentrations may therefore have been confounded with frequency of mating. Seasonal conception rates were unaffected by increased photoperiod.

Androgens↗
PubMed1982

Some aspects of equine embryo transfer.

The number of successful embryo recoveries was 56.0% in experimental mares with no history of breeding problems but in barren mares only 34.3% of embryo recovery attempts were successful. When a recovery attempt was successful, the incidence of twin embryos was 10.7% in experimental mares and 16.7% in barren mares. Maintenance of embryos in vitro for greater than 6 h before non-surgical transfer significantly reduced pregnancy rates compared to maintenance for less than 3 h. The pregnancy rate in recipients at 100 days after ovulation was lower (P less than 0.05) than those at 24 and 30 days after ovulation.

Aging↗
PubMed1982

Electron microscopy of the ventricular lining associated with the hypothalamus and median eminence of prepubertal female horses.

Scanning electron microscopy showed that cells in the infundibular recess of prepubertal female horses were devoid of cilia and sparsely covered with stubby microvilli and small blebs, whereas superior ventricular areas were covered with cilia. Ciliated ependymal cells in supraoptic-suprachiasmatic areas were associated with extensive blebbing, and folded tissue adjacent to the inferior borders of the mamillary body displayed distinct bands of cilia regularly interrupted by areas of sparsely ciliated cells which appeared to be undergoing ciliogenesis. Arcuate ependymal areas had well developed basal tanycyte processes separated by large intercellular spaces. Basal tanycyte processes usually terminated as encapsulating processes around supendymal nerve endings or fibre bundles. The end feet of tanycyte processes encapsulating nerve terminations contained granules and vesicles similar to those found in the neurone, suggesting leaching of neuropeptides from this area of the hypothalamus into CSF. Secretion of substances into CSF was also suggested by scanning electron microscopy observations of blebbing on the apical surfaces of cells. Undeveloped apical microvilli suggest that transport of substances from the CSF to central endocrine tissues and vasculature is probably minimal in prepubertal female horses. However, the ultrastructural observations do suggest that substances may be transferred from the hypothalamic nuclei into the CSF.

Aging↗
PubMed1981

Plasma oxytocin concentrations in cyclic mares and sexually aroused stallions.

An experiment was conducted to measure plasma oxytocin concentrations at 4 different stages of the estrous cycle in 11 pony mares. Plasma oxytocin concentrations (muU/ml +/- SE) were found to be higher (P<.01) on day 2 of estrous (39.8 +/- 12.5) and day 5 post-ovulation (33.1 +/- 12.0) than on day 10 (2.3 +/- 1.6) and day 15 post-ovulation (6.8 +/- 4.1). A second experiment was conducted to measure jugular plasma oxytocin concentrations before and after sexual arousal in six pony stallions. Oxytocin concentrations (muU/ml +/- SE) were higher (P<0.06) after sexual arousal (50.5 +/- 8.9) than before sexual arousal (23.8 +/- 2.9). These data suggest plasma oxytocin concentrations may be associated with ovarian function in mares and with sexual behavior in stallions.

Journal Article↗
PubMed1981

Control of ovulation in cycling mares with ovarian steroids and prostaglandin.

A combined progesterone-estradiol-17beta treatment was given in two experiments conducted to examine its effectiveness in controlling ovulation time in cycling mares. In the first experiment, the combined steroid (150 mg progesterone, 10 mg estradiol-17beta daily for 10 days) alone or combined with prostaglandin on the first and last days of steroid treatment resulted in ovulation in 15 of 16 mares 9-13 days after last injection, 13 of them on days 10-12. A CL present prior to treatment in one mare that received no prostaglandin persisted through and for 14 days after treatment. In the second experiment the combined steroid treatment started on the first or second day of estrus blocked ovulation in only 5 of 13 mares. Thus prostaglandin is necessary at least at the end of treatment. In both experiments a total of 20 mares with no luteal function at the end of steroid treatment ovulated on days 9-13 after last injection, 18 of these on days 10-12. These results indicate that the combined steroid-prostaglandin treatment can result in ovulations in a very restricted interval with apparently a normal distribution.

Journal Article↗
PubMed1980

Characterization of multiple immunoglobulin mu-chains synthesized by two clones of a B cell lymphoma.

We have identified 3 species of mu-chain synthesized by mouse WEHI 279 lymphoma cells that differ in cellular location, size and charge--mui (internal), mum (membrane), and mus (secreted). Lactoperoxidase and galactose oxidase labeling experiments localize the mum chain to the plasma membrane and the mui chain to the cytoplasm. Pulse-chase experiments demonstrate that the mui pool contains precursors to both mum and mus chains. Comparative peptide mapping studies and cell labeling in the presence of tunicamycin suggest that the mum chain is 2000 daltons larger than the mus chains and that the difference is due to polypeptide alterations rather than carbohydrate differences. The WEHI 279 lymphoma has differentiated while in culture to a more advanced stage in the pathway of B cell differentiation.

Animals↗
PubMed1980

Estrus, ovulation, and serum hormones in mares given prostaglandin F2 alpha, estradiol, and gonadotropin-releasing hormone.

A gonadotropin-releasing hormone (GnRH) was injected in mares given prostaglandin F2 alpha (PGF2 alpha) to induce luteolysis in an attempt to sunchronize ovulation. Pretreatment with estradiol-17 beta (E2-17 beta) was used to determine whether or not estradiol would enhance the release of luteinizing hormone (LH) after treatment with GnRH. Twelve mares were used in a balanced Latin square crossover design. Mares were injected with PGF2 alpha, treatment A; PGF2 alpha mgnRH, treatment B; or PGF2 alpha me2-17 beta mgnRH, treatment C. The interval +/- SEM from PGF2 alpha injection to estrus was 3.3 +/- 0.2, 3.2 +/- 0.3, and 2.3 +/- 0.1 days for treatments A, B, and C, respectively. The mean interval in days from injection to first ovulation averaged 1 day less (P less than 0.10) for treatments B (6.7 +/- 0.6) and C (6.2 +/- 0.3) than for treatment A (7.6 +/- 0.7). The furation of estrus and the interval from ovulation to end of estrus were similar among the three treatment groups. Mares treated with GnRH (treatments B and C) had a significant (P less than 0.01) two- to threefold increase in LH concentrations when compared with controls. Pretreatment with estradiol-17 beta did not appear to enhance LH release after GnRH was given, and the time of ovulation was not significantly changed by GnRH treatment.

Animals↗
PubMed1979

Prolonged interovulatory interval after oestradiol treatment in mares.

This study was designed to test if oestradiol treatment would prevent or delay luteolysis in mares. Mares (5/group) received 0, 0.1, 1.0 or 10.0 mg oestradiol-17 beta daily from the day of ovulation until the next ovulation or for a maximum of 32 days. This treatment did not prevent luteolysis which occurred 15.8, 16.8, 15.8 and 17.3 days after the previous ovulation for the mares treated with 0, 0.1, 1.0 and 10.0 mg oestradiol respectively. Although oestradiol treatment failed to alter oestrous behaviour after luteolysis, daily treatment with 10.0 mg oestradiol prevented follicular growth and inhibited ovulation.

Animals↗
PubMed1979

The critical period for the maternal recognition of pregnancy in pony mares.

Two experiments were performed to deterine the critical time at which the equine blastocyst must be present within the uterus of the mare to prevent regression of the corpus luteum, and thus establish the critical time for the maternal recognition of pregnancy. A non-surgical blastocyst collection technique was developed to study this relationship between the blastocyst and the maternal ovary. Results from these experiments demonstrated that the cyclic life-span of the corpus luteum is not affected by the presence of the blastocyst within the mare's uterus until after Day 14 after ovulation. Luteal function was prolonged when blastocysts were removed on Day 15 or later. The critical period for the maternal recognition of pregnancy in the Pony mare appears to be confined to the period between Days 14 and 16 after ovulation.

Animals↗
PubMed1978

Evidence that two forms of bovine erythrocyte cytochrome b5 are identical to segments of microsomal cytochrome b5.

Homogeneous preparations of two forms of soluble cytochrome b5 have been obtained from bovine erythrocytes by successive chromatography on DEAE-cellulose, Bio-Gel P-60, and DEAE-Sephadex. Although the two forms could be separated on disc gel electrophoresis, they appeared to have similar molecular weights of approximately 12,000 and identical visible absorbance spectra. The tryptic hemepeptides derived from the two forms of bovine erythrocyte cytochrome b5 are electrophoretically indistinguishable from each other and from the tryptic core hemepeptide derived from liver microsomal cytochrome b5. The bovine erythrocyte tryptic hemepeptide was purified to homogeneity; its amino acid composition was shown to be identical to that of tryptic hemepeptide from liver microsomal cytochrome b5. The amino acid compositions of the two isolatable forms of erythrocyte cytochrome b5 correspond well to the compositions of the 97- and 95-residue segments of native liver microsomal cytochrome b5 that begin at the NH2 terminus. These results agree with the hypothesis that soluble erythrocyte cytochrome b5 is derived from microsomal protein by proteolysis during erythroid maturation.

Amino Acids↗
PubMed1976

Effects of repeated daily injections of prostaglandin F2alpha on ovaries in mares.

In experiment 1, seven groups of pony mares (2 or 3/group) were given either no injections (controls), or 5 (5X) or 10 (10X) daily subcutaneous (SC) injections of 1.25 mg PGF2alpha beginning on days 1, 7 or 13 post-ovulation. Compared to controls (24.5 days), the interovulatory interval was longer (P less than ..05) for day 7, 10X (33.5 days) and day 13, 10X mares (49.0 days) but was not different for the remaining groups. In experiment 2, nine groups of pony mares (4/group) were given either no injections (controls) or 1 (1X) or 10 (10X) daily SC injections of 1.25 mg PGF2alpha beginning on day 2 of estrus or on days 1, 7 or 13 post-ovulation. Compared to controls (25.0 days), the interovulatory interval was longer (P less than .05) for day 13 post-ovulation, 10X mares (40.0 days) and shorter (P less than .05) for day 1 post-ovulation, 10X mares (14.5 days). The interovulatory interval for the remaining groups was no different (P less than .05) from that for controls. In day 13 post-ovulation, 10X mares, the longer interovulatory interval did not appear to be related to a depression in either peripheral LH concentration (no effect of treatment on LH) or can follicular development (no effect of treatment on diameter of largest follicle). This suggests that circulating levels of gonadotropins were adequate for ovarian follicular development and ovulation and the effect of repeated dialy injections of PGF2alpha in preventing ovulation was likely exerted at the ovarian level directly on the follicle.

Animals↗
PubMed1976

Concentration of prostaglandins F in uterine venous plasma of anesthetized mares during the estrous cycle and early pregnancy.

Prostaglandins F were quantitated by radioimmunoassay in uterine venous plasma of anesthetized mares on day 7 of estrus, days 2, 6, 10, 14 or 18 of diestrus and days 10, 14 or 18 of pregnancy. The PGF concentration was greater (P less than .01) at day 14 of diestrus than at all other days studied. The concentrations at days 10 and 18 of diestrus and at days 10, 14 and 18 of pregnancy were greater (P less than .05) than at day 7 of estrus and days 2 and 6 of diestrus. PGF concentrations at days 10 and 14 were greater (P less than .01) for diestrous than for pregnant mares.

Animals↗