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Biomedical subjects

P M Summers

Publications and source records attributed to P M Summers.

At least 19 recordsLinked to original sources
PubMed1989

Changing responsiveness of luteal cells of the marmoset monkey (Callithrix jacchus) to luteotrophic and luteolytic agents during normal and conception cycles.

Dispersed marmoset luteal cells were incubated for 2 h and progesterone production measured after exposure to hCG, cloprostenol, dibutyryl cAMP, PGF-2 alpha, PGF-2, adrenaline or melatonin. The cells were studied on Days 6, 14 and 20 after ovulation in conception and non-conception cycles. Luteal cells from Day 14 non-pregnant marmosets were compared with human luteal cells taken in the mid-luteal phase. All the treatments stimulated progesterone production including cloprostenol, which is luteolytic when administered to the marmoset in vivo, but the degree of response varied with the stage of the cycle or pregnancy and between marmoset and human luteal cells. In the marmoset, overall analysis of the effect of the treatments showed that, on Day 6 after ovulation, there was no significant effect of any of the treatments in cells from pregnant or non-pregnant animals. In contrast, luteal cells from non-pregnant animals on Day 14 showed a significant response to the treatments (F (8,41) = 2.79, P less than 0.0145) whereas cells from pregnant Day-14 animals were responsive; in cells from pregnant animals, the control production of progesterone was high and already equivalent to the levels stimulated by the treatments. By Day 20, cells from pregnant animals produced lower control concentrations of progesterone than did those on Day 14 and there was a significant overall effect of the treatments (F (8,33) = 3.78, P less than 0.003). These results show that the marmoset CL gains responsiveness to treatment between Days 6 and 14 after ovulation in the non-pregnant cycle. In pregnancy, on Day 14, 2 days after attachment of the embryo, the high control concentrations of progesterone and absence of response to treatment suggest that an embryo message may have affected the CL, providing an endogenous stimulus.

Animals↗
PubMed1988

Births following the transfer of cultured embryos obtained by in vitro and in vivo fertilization in the marmoset monkey (Callithrix jacchus).

The aim of this study was to determine whether marmoset monkeys are a suitable primate model for in vitro fertilization (IVF), embryo culture, and transplantation studies. A prostaglandin analogue given in early pregnancy and human chorionic gonadotropin given near the end of the ensuing follicular phase were used for controlling the reproductive cycle, timing oocyte collection, and synchronizing the cycles of oocyte donors and embryo recipients. Five embryos obtained by IVF were transferred at early stages to the uterus of three recipients, and two gave birth to live infants. Some of the embryos were cultured to advanced blastocyst stages. In vivo fertilized oocytes were also cultured and transferred to two recipients, and one gave birth. We concluded that the marmoset is one of the best primates for such investigations.

Animals↗
PubMed1988

Normal in-vivo development of marmoset monkey embryos after trophectoderm biopsy.

A procedure was developed to remove trophectoderm cells from day-8 blastocysts of the marmoset monkey. Using micromanipulative techniques, a tear was made in the zona pellucida opposite the inner cell mass which facilitated the controlled herniation of trophectoderm cells as the blastocysts developed in vitro. After 24 h (day-9 blastocysts) and 48 h (day-10 blastocysts) of culture approximately 20% and approximately 50% respectively of the blastocyst had herniated. The herniated trophectoderm was cut off by freehand and the biopsied blastocysts transferred to recipients. Normal offspring were born but pregnancies could be established from day-10 blastocysts only if the recipients were treated with human chorionic gonadotrophin during early pregnancy. One pregnancy was established after the transfer of three frozen biopsied day-10 blastocysts. Biopsies of 30-50 cells from day-10 blastocysts could be readily grown in vitro as trophoblast vesicles to in excess of 1000 cells but biopsies of less than 20 cells from day-9 blastocysts formed a monolayer of binucleated and multinucleated cells with limited cell replication. Assuming human trophectoderm cells have a similar capacity to the marmoset to grow in vitro, the application of this technique to human blastocysts would provide sufficient cells on which the preimplantation diagnosis of a genetic disorder could be made.

Animals↗
PubMed1988

Embryonic signals during the peri-implantation period in primates.

During the peri-implantation period of pregnancy in primates, chorionic gonadotrophin (CG) is the first clear signal of the embryo's presence and viability. In the marmoset (Callithrix jacchus) implantation begins on Day 11-12 after ovulation and CG is secreted by the embryo from this time. The inner cell mass is necessary for the normal secretion of CG by the trophoblast. Implantation can be disrupted both in vivo and in vitro by antisera to the hCG-beta subunit. The secretion of a platelet activating factor by the preimplantation embryo has yet to be confirmed, as has the physiological function of this and other preimplantation signals. Local sampling by perfusion of the corpus luteum allows a direct measurement of the interactions between luteotrophins and luteolysins, as well as a method of screening potential new agents for regulating the function of the corpus luteum.

Animals↗
PubMed1988

Quality management: program design. An interdisciplinary approach.

Concepts of quality management related to program design and implementation are relatively new to the health care field. The process used to satisfy the requirements of program evaluation, business planning, and clinical care quality assurance within the framework of quality management is discussed. Using an interdisciplinary approach, the authors trace the development of a specific rehabilitation program. Such programs can allow the health care provider to be more fruitfully involved in a health care service design beneficial to the patients served.

Hospital Bed Capacity, 300 to 499↗
PubMed1987

Controlled ovulation in the marmoset monkey (Callithrix jacchus) with human chorionic gonadotropin following prostaglandin-induced luteal regression.

Controlled induction of ovulation in the marmoset monkey was attempted with a single injection of human chorionic gonadotropin (hCG; 50 IU) given on day 7 after prostaglandin-induced luteal regression. Animals given hCG (n = 12) ovulated within a 2-day period (days 9 and 10 after prostaglandin) compared with a 4-day period (days 9 to 12) in the control group (n = 12). The mean interval to ovulation was similar in both groups. There was no difference in the timing of the preovulatory estradiol (E2) peak between groups, although E2 levels on the day of hCG injection were lower than in controls on the day of the onset of the luteinizing hormone surge. All animals given hCG ovulated and 11 of 12 became pregnant. Ten of 11 embryos recovered surgically from six of these animals were normal blastocysts; 5 of the remaining 6 animals carried pregnancies to term. The results are of practical importance for experiments involving follicular and oocyte maturation and the collection and transfer of embryos.

Animals↗
PubMed1987

The effects of cryopreservation and transfer on embryonic development in the common marmoset monkey, Callithrix jacchus.

Embryos were collected at the 4-10-cell stage from the oviducts (Day 4; Day 1 = ovulation) or as morulae (Day 7) from the uterus of marmosets and frozen in 1.5 M-DMSO (Days 4 and 7) or 1.0 M-glycerol (Day 4 only), using a slow freezing and thawing technique. Of 22 Day-4 embryos frozen in DMSO, 18 were recovered and 16 of these were transferred to 10 synchronized recipients; 7 recipients became pregnant compared with all 7 control recipients receiving 10 unfrozen embryos. Fifteen frozen-thawed morulae were transferred to 9 Day-6 recipients; the pregnancy rate (55.6%) was lower than for control embryos (85.7%). Embryos frozen in glycerol suffered severe osmotic stress during glycerol addition and removal. Of 8 recipients, 3 (37.5%) became pregnant but only one fetus was carried to term. These results on embryo collection, freezing and transfer in the marmoset have important implications for developing improved methods for freezing human embryos and the breeding of endangered primates.

Animals↗
PubMed1987

Successful transfer of the embryos of Przewalski's horses (Equus przewalskii) and Grant's zebra (E. burchelli) to domestic mares (E. caballus).

Blastocysts were collected non-surgically from 2 Przewalski's horse and 2 Grant's zebra mares and transferred extra-specifically to domestic horse and donkey recipients. Nine Przewalski's horse embryos were transferred surgically, and 2 non-surgically, to domestic Welsh-type pony mares. After surgical transfer, 7 (77.8%) pregnancies were established and 4 foals were born. Twelve Grant's zebra embryos were transferred surgically to 5 pony and 7 domestic donkey recipients respectively and 1 non-surgically to a donkey; 3 (60%) zebra-in-horse pregnancies were established and 2 went to term. Only 2 (28.6%) zebra-in-donkey pregnancies were established but neither went to term, although one zebra foal was aborted alive at Day 292 but failed to survive. No pregnancies resulted from the non-surgical transfers. Measurement of chorionic gonadotrophin concentrations and parental-specific lymphocytotoxic antibodies in the serum of the recipient animals indicated a pronounced maternal immunological response to the extra-specific embryo, but this could not be correlated with success or failure of pregnancy. The results indicate that extra-specific embryo transfer may be a useful aid to breeding exotic equids in captivity.

Animals↗
PubMed1987

Partial purification and characterization of chorionic gonadotrophin in plasma and in culture medium of trophoblast cells from the marmoset monkey (Callithrix jacchus).

A biologically active gonadotrophin has been purified from the media of long-term cultures of trophoblast cells of the common marmoset monkey by a combination of precipitation and chromatography. Marmoset chorionic gonadotrophin (CG) is a glycoprotein which binds Concanavalin A and wheat germ agglutinin. The protein purified from culture media exists as several isoelectric species with pI in the range pH 3.5-4.5. On gel filtration it eluted with an apparent molecular weight of 68-72,000 but on PAGE migrated as if it was 58-65,000. A glycoprotein with similar characteristics has been recovered from plasma samples of pregnant marmosets. Biological activity of partly purified CG from media, as determined by a mouse testicular cell bioassay, was 1-3 i.u./mg protein.

Animals↗
PubMed1987

Failure of the prostaglandin F2 alpha analogue, cloprostenol, to induce functional luteolysis in the olive baboon (Papio cynocephalus anubis).

The prostaglandin F2 alpha analogue, cloprostenol, which is an effective luteolytic agent in the common marmoset, was administered intramuscularly to olive baboons to determine if it possessed luteolytic properties in this species. The results showed that functional luteolysis was not induced when cloprostenol was administered during the mid- to late luteal phase or during early pregnancy.

Animals↗
PubMed1985

Long-term acceptance of full thickness body skin grafts between Bos taurus-Bos indicus chimeric twins.

Body skin was grafted between Bos taurus-Bos indicus haemopoietic chimeric calves produced by embryo transfer. Grafts of body skin from Bos taurus animals to their Bos indicus chimeric co-twins survived for more than 2 and 1/2 years as assessed by the growth of hair from the grafts. There was no evidence of survival of the reciprocal grafts. It is suggested that depilation, dehydration and desquamation are not suitable criteria for assessment of skin grafts in cattle.

Animals↗
PubMed1985

Cloprostenol-induced luteolysis in the marmoset monkey (Callithrix jacchus).

A single intramuscular injection of 0.5 micrograms cloprostenol was not luteolytic on Day 6 or 7 of the ovarian cycle (N = 3), but was luteolytic in some animals (3/5) on Day 8 and 9 and luteolytic in all 23 animals treated between Days 10 and 17 of the ovarian cycle, and in 7 animals treated between Days 19 and 43 of pregnancy. Luteal function was monitored by measurement of progesterone in peripheral blood using a simple and rapid non-extraction assay. There was a dramatic fall in peripheral blood progesterone to less than 10 ng/ml within 24 h of cloprostenol injection; progesterone remained at this low level until the day after post-treatment ovulation. The interval from cloprostenol injection to ovulation in animals treated between Days 8 and 17 was 10.7 +/- 0.3 days. A similar interval was found in pregnant animals. Embryos recovered from the uterus after cloprostenol treatment were morphologically normal (23/24).

Animals↗
PubMed1984

Interspecific chimerism--the characterization and immunological responsiveness of Bos taurus-Bos indicus haemopoietic chimeras produced by embryo transfer.

Bos taurus-Bos indicus twin calves were produced by embryo transfer and their degree of haemopoietic chimerism and immune responsiveness examined. All 10 pairs of Friesian-Brahman twins were chimeric compared with only 6 out of 12 pairs of Jersey-Brahman twins. In the Friesian-Brahman twins, Friesian lymphocytes predominated in all calves while in the Jersey-Brahman twins there was no uniform dominance of one cell type over another. All calves that had chimeric lymphocyte populations were also erythrocyte chimeras, although in two pairs of twins the genotype of the erythrocytes was different from the genotype of the lymphocytes. The lymphocytes of all chimeric calves failed to respond in mixed lymphocyte culture (MLC) tests to the lymphocytes of their co-twins but gave vigorous responses to cells from other calves. Primary and secondary immune responses to keyhole limpet haemocyanin (KLH) antigen were studied in the efferent prefemoral lymph in normal Jersey, Friesian and Brahman calves, in 1 set of Jersey-Brahman twins and in 5 sets of Friesian-Brahman twins. The immune responses of chimeric twins with genetically identical lymphocyte populations were quite dissimilar and were characteristic of the somatic genotype of the calf and not of the genotype of the lymphocyte population. The chimeric status of the cell population in the lymph did not change significantly during the response. These results suggest that either the genetic capacity of a population of lymphocytes to recognize and respond to antigens can be modified during ontogeny in an alien genetic environment or that a crucial determinant of the final outcome of an immune response is not the immunocompetent cell itself but the physiological and anatomical environment in which it exists.

Animals↗
PubMed1981

Clinical survey of tumours and tumour-like lesions in horses in south east Queensland.

The results of a retrospective survey of tumours and tumour-like lesions encountered in horses in a veterinary practice in south east Queensland between 1956 and 1978 are presented. Forty-two per cent of the lesions were examined histologically. The most commonly occurring neoplasms were the equine sarcoid, papilloma and squamous cell carcinoma of the eye and external genitalia. Neurofibroma was an important problem in the eyelid region. Intra-abdominal tumours were rarely encountered in this series.

Animals↗
PubMed1979

Ossifying ameloblastoma in a horse.

The features of an ossifying ameloblastoma in a 5-year-old gelding are described. The tumour developed in the angle of the right mandible and microscopically consisted of multiple follicles and islands of epithelial tissue adjacent to which were trabeculae of bone, osteoid and compact collagenous tissue.

Animals↗