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Biomedical subjects

R J Mapletoft

Publications and source records attributed to R J Mapletoft.

At least 73 records · Page 4Linked to original sources
PubMed1989

Immunological approaches to contraception in dogs.

The demand for safe, effective and cost-efficient means of pet population control has generated interest in the development of alternatives to surgical gonadectomy. The purpose of this review is to discuss the potential of immunological approaches to fertility control and to outline recent developments that may aid their design. Among the most promising candidates for immunoneutralization is gonadotrophin releasing hormone (GnRH). We have developed a reliable and reproducible GnRH-protein conjugate antigen and demonstrated that immunologically induced infertility is possible in dogs.

Adjuvants, Immunologic↗
PubMed1988

A synthetic luteinizing hormone releasing hormone vaccine. I. Conjugation and specificity trials in BALB/c mice.

The immunobiology of luteinizing hormone releasing hormone (LHRH) was explored, to provide a conceptual and practical basis for the use of LHRH in immunocastration. Cysteine substituted analogues of LHRH were synthesized including Cys1-LHRH (C1-LHRH), Cys6-LHRH (C6-LHRH) and Cys10-LHRH (C10-LHRH). These were reacted to carrier molecules using the heterobifunctional cross-linking reagent m-maleimidobenzoylsulfosuccinimide ester (SMBS), producing peptide-carrier conjugates of known peptide content and conjugation orientation. This reaction regime was found to be rapid, efficient and allowed for easy control of peptide to carrier ratios. Conjugates were used in active immunization trials in BALB/c mice to characterize the murine immune response against LHRH. BALB/c mice were shown to have the capacity to recognise all three cysteine substituted LHRH analogues and to produce antibodies cross-reactive with native LHRH. The specificity of LHRH antisera generated was found to be dependent on the site of conjugation of the peptide to carrier molecule. C1-LHRH generated carboxy terminal directed antibodies, C10-LHRH generated amino terminal directed antibodies, while C6-LHRH could generate amino terminal directed or carboxy terminal directed antibodies, or both within a given animal. No intrinsically immunodominant epitopes were seen within the LHRH molecule.

Animals↗
PubMed1988

A synthetic luteinizing hormone releasing hormone vaccine II. Temporal aspects of titer development and formulation trials in BALB/c mice.

Cysteine substituted analogues of luteinizing hormone releasing hormone (LHRH) were coupled to carrier molecules, and the resulting conjugates used to characterize the immune response to native LHRH generated in BALB/c mice and to formulate vaccines in an effort to maximize titer development. In an active immunization trial designed to characterize temporal aspects of anti-LHRH titer development, titers could be detected 1 week after initial immunization. No differences were observed in response between male and female mice. Booster immunizations could enhance the titers against LHRH. The titers developed against the carrier molecule were uniformly higher than the corresponding anti-LHRH titers throughout the course of the trial. In separate trials, vaccines were formulated and tested in BALB/c mice for titer development against LHRH. Adjuvants, carrier molecules, dosage and peptide to carrier ratio were considered. Dosages of 50 micrograms conjugate per immunization per mouse, at conjugation ratios of 3-12 peptides per 10(5) Da carrier molecule, were found to produce immune responses. Adjuvants including Havlogen and dimethyldioctadecylammonium bromide (DDA), and carrier molecules including keyhole limpet hemocyanin (KLH), porcine thyroglobulin (TGB) and equine gamma globulin (EGG) were all found to be effective.

Adjuvants, Immunologic↗
PubMed1987

Superovulation in the cow using estradiol 17beta or GnRH in conjunction with FSH-P.

A study was designed to evaluate the superovulatory response in the cow when either estradiol 17beta or gonadotrophin releasing hormone (GnRH) was used in a superovulatory regimen with follicle stimulating hormone (FSH-P). Fifty-four cyclic crossbred females were superovulated in replicates between Days 8 and 12 of their cycle. All animals were treated with 28 mg of FSH-P in twice-daily decreasing doses, each receiving 500 mug cloprostenol (PGF) 48 h after initiation of treatment. Group 1 served as FSH-P controls, Group 2 received FSH-P and 400 mug of estradiol 17beta 36 h after PGF, and Group 3 received FSH-P and 250 mug GnRH 48 h after PGF. Inseminations with one vial of frozen semen were done at 12, 24 and 36 h after the onset of estrus. Ova/embryos were collected nonsurgically at Day 7 postestrus. Numbers of corpora lutea (CL) were recorded after palpation per rectum and the recovered ova and embryos were evaluated. All females were bled for endocrine examination. There were no differences in ovarian response among these treatments. Mean total ova/embryos collected in Group 3 was significantly higher than in Groups 1 or 2 (P < 0.05); however, no significant difference existed between groups in the mean numbers of fertilized or transferable embryos. Similarly, no significant differences existed between groups for recovery rate, fertilization rate, or percentage of transferable embryos. Serum estradiol levels were significantly higher at the expected end of ovulation in Group 2, and this tended to be associated with higher fertilization and transferable embryo rates. Furthermore, a significant positive correlation was found to exist between CL numbers and each of the ova/embryo parameters and the estradiol levels at estrus.

Journal Article↗
PubMed1987

Scrotal circumference of two-year-old bulls of several beef breeds.

Scrotal circumference (SC) was measured on 7,918 2-yr-old Angus, Charolais, horned and polled Herefords, Limousin, Shorthorn, and Simmental bulls presented to culling committees at six show/sales between 1977 and 1983. Only SC data from bulls within the age range of 24 +/- 4 mo were used. Scrotal circumference data were corrected across breeds for the effects of location-year and sire and were adjusted to a common bull age of 730 d. The adjusted mean SC (+/- SE) for 2-yr-old beef bulls was Simmental, 38.8 +/- 0.10 cm (n = 540); Aberdeen Angus, 37.2 +/- 0.09 cm (n = 629); Charolais, 36.3 +/- 0.09 cm (n = 499); horned Hereford, 36.1 +/- 0.03 cm (n = 3,769); polled Hereford, 35.6 +/- 0.04 cm (n = 2,170); Shorthorn, 34.9 +/- 0.11 cm (n = 231); and Limousin, 32.2 +/- 0.18 cm (n = 80). The authors' recommendations of minimum acceptable SC for 2-yr-old beef bulls are Simmental, 36.0 cm; Angus and Charolais, 35.0 cm; horned and polled Herefords and Shorthorn, 34.0 cm; and Limousin, 33.0 cm.

Journal Article↗
PubMed1986

Superovulatory and endocrine responses in heifers treated with FSH-P at different stages of the estrous cycle.

Forty-two Holstein heifers were superovulated with FSH-P (total dose, 30 mg) and cloprostenol. Treatment was initiated on Day 3 (Group D3, n = 11), Day 6 (Group D6, n = 11), Day 9 (Group D9, n = 10) or Day 12 (Group D12, n = 10) of the estrous cycle. Heifers were bled daily for serum progesterone and estradiol-17beta determinations and every 6 h for a 48-h duration at the expected time of estrus for luteinizing hormone (LH) assay. Ova and embryos were flushed from the reproductive tracts and the number of corpora lutea (CL) were recorded after slaughter on Day 7 post-estrus. Mean (+/- SEM) numbers of observed CL were higher (P < 0.05) in Group D9 (33.3 +/- 4.8) than in Group D3 (15.3 +/- 3.8), with Group D6 (17.0 +/- 2.9) and Group D12 (23.9 +/- 7.3) being intermediate. Similarly, mean (+/- SEM) numbers of fertilized embryos were highest (P < 0.05) in Group D9 (13.3 +/- 2.2). There was also a nonsignificant trend for the number of transferable embryos to be greatest in Group D9. Neither serum progesterone concentrations 3 d after the LH peak nor peak serum estradiol 17beta concentrations differed among groups, but both were significantly correlated with numbers of observed CL and total ova and embryos.

Journal Article↗
PubMed1986

Factors affecting survival of deep frozen bovine embryos in vitro: The effect of freezing container and method of removing cryoprotectant.

The effect of freezing container and method of glycerol removal on in vitro survival of frozen-thawed Day 7 bovine embryos was investigated. Two hundred and fifteen embryos were frozen in ampules or straws, in either vertical or horizontal position and at a cooling rate of 0.3 degrees C/minute from -7 degrees C to -35 degrees C, before being plunged into liquid nitrogen. Samples were thawed in a water bath at +35 degrees C and glycerol was removed by either step-wise dilution (increments 0.25 M) or by exposure to 1.0 M sucrose for 10 minutes. A total of 197 embryos was recovered post-thaw (91%) with an overall survival after 1, 3, 6 and 24 hours in culture of 87, 81, 71, and 23%, respectively. Embryonic quality and percent survival, as assessed morphologically, did not change significantly between 1 and 3 hours but decreased significantly between 6 and 24 hours in culture (p < 0.05). Survival at 24 hours was significantly higher after removal of the cryoprotectant with sucrose when compared to the step-wise glycerol dilution (p < 0.05). Overall, embryonic survival in straws equaled that in ampules; freezing orientation of straws did not affect results. Further, glycerol removal with sucrose tended to yield survival superior to that provided by a step-wise dilution technique.

Journal Article↗
PubMed1985

Monoclonal antibodies against LHRH: development and immunoactivity in vivo and in vitro.

Mouse myeloma NS1-Ag4 cells were fused with spleen cells from a BALB/c mouse previously immunized with luteinizing hormone releasing hormone (LHRH) conjugated to serum bovine albumin (BSA). Fused cells were grown in HAT restrictive medium which was screened for LHRH binding ability via a primary binding assay employing [125I]LHRH and cold ethanol precipitation. One clone (hy-USASK/DSIL-LHRH-A1) was selected for further study. Cell culture fluid and ascites fluid bound 30% of [125I]LHRH at 1:4000 and 1:400,000 dilution respectively. A competitive inhibition assay using ascites fluid at 1:2,000,000 dilution and LHRH standards at 0.125-32.0 ng/ml was established. Initial studies using rabbit anti-mouse allotype sera in a horseradish peroxidase (HRP)-ELISA system indicate the antibody is IgG1. A dose of 0.5 ml ascites fluid containing LHRH antibody given intravenously (i.v.) on day 9 of gestation was effective in terminating pregnancy in rats. A 1 cm progesterone implant made of elastomer polymer and placed interperitoneally blocked this effect. Ascites fluid (4.5 ml) containing LHRH antibody, when infused i.v. into mature spayed female dogs induced a precipitous decline in mean luteinizing hormone (LH) levels and reduced LH pulsatility over 4 days. It was concluded that the mouse monoclonal antibody is specific for LHRH, and can interrupt reproductive events in vivo.

Abortion, Induced↗
PubMed1981

Influence of GnRH infusion on endocrine parameters and duration of postpartum anestrus in beef cows.

The effect of an intravenous infusion of gonadotrophin releasing hormone (GnRH) on the duration of postpartum anestrus in suckled beef cows was studied. Twenty-eight, mature, suckled beef cows were assigned in equal numbers to one of four treatment groups which were based on infusion with saline or GnRH (15ug/hour for 12 hours) and stage postpartum (pp) (20 or 35 days). Serum LH and progesterone were determined by radioimmunoassay for the period which began 5 days pre-infusion and ended at 55 days postpartum (ie: 35 or 20 days post-infusion). Serum LH remained below 5ng/ml during infusion in all control cows. Peak serum LH values, times of LH peaks, and duration of LH responses (means +/- SE) during infusion were 49 +/- 12 ng/ml, 162 +/- 42 minutes and 7.8 +/- 1.3 hours for the 20 day group and 44 +/- ng/ml, 144 +/- 6 minutes, and 8.2 +/- 1.1 hours for the 35 day group respectively. Serum progesterone levels indicated that the proportion of cows showing the onset of estrous cycles within 10 days of infusion was greater in the 20 day pp GnRH group (4/7) than the 20 day pp saline group (0/7) (p < .05) but was not significantly different between the 35 day pp GnRH (4/7) and 35 day pp saline (2/6) groups. The incidence of estrus was not affected by GnRH treatment and was 37% in all cows prior to 55 days pp. It was concluded that infusions of GnRH for 12 hours at a rate of 15 ug/hour could induce estrous cycles in suckled beef cows treated at 20 days postpartum.

Journal Article↗
PubMed1981

Induction of abortion in feedlot heifers with a combination of cloprostenol and dexamethasone.

A field trial was conducted to assess the efficacy of a combined prostaglandin F(2)alpha analogue (cloprostenol) and dexamethasone treatment as an abortifacient in feedlot heifers. Heifers were grouped according to stage of gestation as follows: Group I, one to four months, n = 37: group II, four to six months, n = 40: group III, six to eight months, n = 40: group IV, one to eight months, n = 29. Heifers in groups I, II and III received a simultaneous intramuscular injection of 500 mug cloprostenol and 25 mg dexamethasone at the time of rectal palpation for pregnancy diagnosis. Heifers in group IV were subjected to rectal palpation for pregnancy diagnosis but received no treatments. Heifers were observed daily for two weeks for abortion and rectal palpations were done 50 days after treatment to determine reproductive status. HEIFERS ABORTING AFTER TREATMENT WERE AS FOLLOWS: Group I, 37/37; group II, 37/40, group III, 37/40; group IV, 0/29. In each of groups II and III there was one pregnancy and two cases of fetal mummification. The numbers of abortions in groups I, II and III were significantly different from that in group IV (P</=0.01). Weight gains were satisfactory and there was no illness associated with treatment. Results indicate that a combination of prostaglandin F(2)alpha analogue and dexamethasone will induce abortion at all stages of pregnancy in feedlot heifers.

Abortion, Induced↗
PubMed1981

Termination of pregnancy with cloprostenol and dexamethasone in intact or ovariectomized cows.

Termination of pregnancy in cows was investigated using sham-operated (SH) or ovariectomized (OV) cows treated with either a saline vehicle (V), cloprostenol (PG), dexamethasone (DEX) or dexamethasone and cloprostenol (DEX+PG). Surgery was done at 210 days of pregnancy and treatment was administered 72 hours later. Days (mean+/-S.E.) from treatment to termination of pregnancy for the treatment groups were: sham-operated +vehicle (SH+V): 61.5+/-11.3; ovariectomized+vehicle (OV+V): 53.4+/-15.7; sham-operated+cloprostenol (SH+PG): 61.8+/-1.7; ovariectomized+cloprostenol (OV+PG): 54.5+/-13.1; shamoperated+dexamethasone (SH+DEX): 74.8+/-4.8; ovariectomized+dexamethasone (OV+DEX): 2.8+/-0.4; shamoperated+dexamethasone+cloprostenol (SH+DEX+PG) 26.0+/-23.0; ovariectomized+dexamethasone+cloprostenol (OV+DEX+PG): 7.2+/-4.9. Pregnancies in the OV+DEX and OV+DEX+PG groups were terminated significantly earlier than in all other groups (P<0.05) except the SH+DEX+PG group. These findings suggest that dexamethasone will terminate pregnancy in cows near seven months of gestation after the ovarian source of progesterone has been removed by either an injection of prostaglandin or by ovariectomy.

Abortion, Induced↗
PubMed1975

Functional anatomy of the testicular vascular pedicle in the rhesus monkey: evidence for a local testosterone concentrating mechanism (38513).

The detailed anatomy of arteries and veins in the testicular pedicle of the rhesus monkey, with special emphasis on an area of extensive surface contact between these vessels in the spermatic cord, is described. The mean plasma testosterone concentration in blood from the testicular artery was significantly greater than the mean for samples collected simultaneously from the contralateral femoral artery in 11 monkeys. These observations are interpreted as supportive of the hypothesis that a hormone concentrating mechanism involving the local transfer of testoterone between the vessels of the pampiniform plexus and the spermatic artery exists in the male-rhesus monkey.

Animals↗