Search PubMed⌕ Search

Biomedical subjects

G J Marcus

Publications and source records attributed to G J Marcus.

At least 37 records · Page 2Linked to original sources
PubMed1983

Seasonal effects of PMSG and number of inseminations on fertility of progestogen-treated sheep.

The influence of pregnant mares' serum gonadotropin (PMSG) on reproductive performance of sheep bred by artificial insemination (AI) was studied in the anestrous and estrous seasons. Ewes were treated with progestogen-impregnated intravaginal sponges in June and October. One-half of the ewes in each trial received PMSG at sponge removal and were inseminated 55 h after sponge removal. One-half of the ewes in each treatment group were reinseminated 5 h later. Conception rates in June and October were 82 and 87% with PMSG and 18 and 48% without PMSG, respectively. The corresponding lambing rates were 60 and 74% with PMSG and 10 and 26% without PMSG. Litter size was unaffected by season or PMSG use. Embryonic mortality estimated over both trials was 22% after the first 2 wk of pregnancy with PMSG, but was 44% when PMSG treatment was omitted. Two inseminations were not superior to one. These data indicate that irrespective of season or double insemination, PMSG improves reproductive performance of ewes bred by AI at progestogen-synchronized estrus.

Animals↗
PubMed1982

Influence of sperm number and seminal plasma on fertility of progestagen-treated sheep in confinement.

Progestagen-impregnated vaginal sponges + PMSG were used to synchronize oestrus in crossbred adult ewes which were inseminated 56 h after sponge removal with 0.5 ml diluted semen containing 400, 200, 100, 50 or 25 x 10(6) spermatozoa per insemination. The diluent was skim milk-citrate or pooled seminal plasma. There was no difference in reproductive performance due to the insemination medium. Fertility (no. of ewes lambing) after insemination of 400 or 200 x 10(6) spermatozoa was 68% and was similar to that observed after natural service at progestagen-induced oestrus. When less than or equal to 100 x 10(6) spermatozoa were inseminated, fertility fell markedly and the number of lambs per ewe inseminated decreased. A decrease in litter size also occurred. The data indicate that insemination of 200 x 10(6) spermatozoa, i.e. less than 10% of the number in a single ram ejaculate, allows normal conception rates in progestagen-treated ewes.

Animals↗
PubMed1980

Influence of estradiol-17 beta on fertility in confined sheep inseminated with frozen semen.

Impaired sperm transport is believed to be a major cause of reduced fertiity in ewes inseminated with frozen semen. Because of suggestions that estradiol improves sperm transport, estradiol-17 beta was given to mature ewes at progestagen-induced estrus to test effects on fertility after artificial insemination with frozen semen. Conception rates, based on progesterone determinations made 18 days after insemination, were 43% for ewes injected with 50 microgram estradiol-17 beta and inseminated with frozen semsn, 52% for ewes inseminated with frozen semen but given no estradiol and 86% for ewes inseminated with fresh semen. Lambing rates were 6, 35 and 69%, respectively. The markedly greater difference between conception rates and lambing rates for the estradiol-treated ewes suggests that estradiol caused a substantial increase in the early embryonic mortality associated with the use of frozen semen.

Animals↗
PubMed1979

Cholesterol biosynthesis and progesterone production by chorionic cells of the early sheep conceptus in vitro.

Dissociated trophoblast cells from the chorion of the 21-day sheep conceptus were shown to produce progesterone in vitro. Evidence that this represented synthesis de novo was provided by the prolonged production of progesterone in the absence of added precursor steroids. Radioactive cholesterol was isolated after incubation of dispersed chorionic cells with acetate-1-14C.

Acetates↗
PubMed1979

Metabolism of progesterone by chorionic cells of the early sheep conceptus in vitro.

Progesterone-4-14C was extensively metabolized during incubation with dispersed trophoblast prepared from chorionic membranes of the 21-day sheep conceptus. Of the metabolites formed, 17, 20 alpha-dihydroxypregn-4-en-3-one, 20 alpha-hydroxypregn-4-en-3-one, 20 beta-hydroxypregn-4-en-3-one, 5 alpha-pregnane-3 alpha, 17,20 alpha-triol, 5 beta-pregnane-3 alpha, 17,20 alpha-triol, 5 beta-pregnane-3 alpha,20 alpha-diol, 3 beta-hydroxy-5 alpha-pregnan-20-one, 3 alpha-hydroxy-5 beta-pregnan-20-one, 20 beta-hydroxy-5 beta-pregnan-3-one, 5 alpha-pregnane-3,20-dione and 5 beta-pregnane-3,20-dione were identified. These findings indicate that the sheep conceptus acquires extensive steroid metabolizing capability very early in pregnancy.

Animals↗
PubMed1975

Influence of prostaglandin F autoantibodies on the estrous cycle of the guinea pig.

Adult female guinea pigs were actively immunized with prostaglandin F-2alpha conjugated to bovine serum albumin (BSA). Control animals, immunized against BSA continued to cycle normally, while the animals immunized against prostaglandin F-2alpha stopped cycling after one to three normal cycles. Laparotomy at 30 days after the last estrus revealed no recently formed corpora lutea. During the remaining 70 days of observation the antibody titer increased to 1:700, accompanied by increasing total serum estrogens (136 pg/ml at day 100) and a slow decline in circulating progesterone levels (0.6 ng/ml at day 100). The ovaries at day 100 contained degenerated corpora lutea and luteinized follicles. The suppression of the estrous cycle in the present experiments was interpreted as resulting from prolongation of luteal function as well as from inhibition of ovulation.

Animals↗