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Biomedical subjects

J C Rodger

Publications and source records attributed to J C Rodger.

At least 55 records · Page 3Linked to original sources
PubMed1992

Gonadotrophin-induced oestrus and ovulation in the polyovulatory marsupial Sminthopsis crassicaudata.

Sminthopsis crassicaudata is a small (approximately 16 g) polyovulatory dasyurid marsupial which has the potential to become an important model species. This study examined the use of exogenous hormone treatment to manipulate the breeding of S. crassicaudata and as a means to obtain timed developmental stages for further study. Two thirds (21/32) of the females treated with 1.0 or 5.0 I.U. of pregnant mare serum gonadotrophin (PMSG) had ovulated when the contents of their reproductive tracts were examined 5 or 6 days later. Only one of eight females treated with 0.2 I.U. PMSG had ovulated in the same period. Although a similar proportion of animals treated with 1.0 I.U. and 5.0 I.U. ovulated, the ovulation rate was significantly lower when the higher dose was administered (mean of 10.5 ovulations per female v. 3.8 ovulations per female). In addition, the ovaries of 6/8 of the animals treated with 5.0 I.U. PMSG had luteinized follicles with degenerating oocytes, evidence of over-stimulation. Follicular luteinization also occurred in 4/8 animals treated with 1 I.U. PMSG. Oocyte maturation and ovulation occurred following PMSG stimulation without injection of synthetic gonadotrophin releasing hormone (GnRH). Treatment with a 10-micrograms dose of GnRH following PMSG seemed to have no effect on the outcome. Of the females that had ovulated by Day 6, three quarters had mated and some had fertilized eggs and two-cell embryos in the oviducts and uteri. In a further series of experiments the subsequent development of embryos conceived after PMSG treatment was assessed. Two thirds of treated females mated within 7 days of treatment and 60% of these matings yielded embryos when examined 11 days after PMSG. However, full-term development was only achieved in one animal. Gonadotrophin treatment of S. crassicaudata thus may have application as a means to obtain mature or maturing oocytes, cleavage stage embryos and blastocysts, but at this stage it appears not to offer promise as a method to achieve full-term development.

Animal Husbandry↗
PubMed1992

Evidence that cortical granule formation is a periovulatory event in marsupials.

Formation of cortical granules was examined in superovulated oocytes from three marsupial species, brushtail possums (Trichosurus vulpecula) tammar wallabies (Macropus eugeniii) and grey short-tailed opossums (Monodelphis domestica) and in oocytes obtained during natural cycles in Macropus eugenii. Superovulation was induced by pregnant mares' serum gonadotrophin/gonadotrophin-releasing hormone (PMSG/GnRH) protocols and natural ovulation by removal of pouch young. Oocytes were collected after ovariectomy or by laparoscopically guided follicle aspiration into Hanks balanced salt solution (HBSS) supplemented with either 2.5% fetal calf serum (FCS) or 2.5% bovine serum albumin (BSA). Ovulated oocytes were collected by removing and flushing the oviducts with HBSS and fixed immediately for electron microscopy. There were no differences in the morphology or timing of formation of cortical granules between superovulated and naturally cycling animals. Cortical granules were absent from germinal vesicle (GV) stage follicular oocytes before the luteinizing hormone (LH) surge in all species. Dark cortical granules, similar in appearance to those seen in the oocytes of eutherian mammals, were found just beneath the plasma membrane (9 per 100 microns of plasma membrane) of preovulatory oocytes at germinal vesicle, metaphase 1 or anaphase 1 stages. In addition, they contained a number of less electron-dense cortical granules (12 per 100 microns plasma membrane). The cortical cytoplasm of preovulatory oocytes was rich in Golgi complexes actively involved in vesicle formation. Large numbers of dark cortical granules (90 per 100 microns plasma membrane) were found only in ovulated oocytes. A small number of cortical granules of lighter electron density were also present in ovulated oocytes. This suggests that the marsupial oocyte is following a very different timetable for cortical granule formation and accumulation from eutherian mammals and that oocytes of marsupials may not achieve cytoplasmic maturity until after ovulation. The significance of these events for fertilization and development remains to be established.

Animals↗
PubMed1992

Unexpected oocyte growth after follicular antrum formation in four marsupial species.

During examination of maturing preovulatory marsupial oocytes we noted that oocyte diameters were invariably about 50% greater than the figures reported in earlier histological studies. As all previous investigations were limited to small follicles (at most 25% the size of the ovulating follicle), the present study was initiated to examine oocyte growth during the whole period of follicular development. Oocyte and follicle diameters were measured for three Australian (Trichosurus vulpecula, Macropus eugenii and Bettongia penicillata--fresh nonfixed material) and one American marsupial species (Monodelphis domestica--histological sections) in which multiple follicle development had been induced by exogenous gonadotrophin treatment. In all species oocytes were obtained from follicles ranging from pre-antral to immediately pre-ovulatory (maximum follicle sizes obtained were: T. vulpecula, 4.5 mm; M. eugenii, 4.3 mm; B. penicillata, 2.5 mm; M. domestica, 0.7 mm). In two of the species (T. vulpecula and B. penicillata) ovulated oocytes were also examined. In T. vulpecula and M. eugenii oocytes were found to achieve much greater diameters than previously reported from histological studies of small follicles (< 0.8 mm) and similar patterns of growth were found in the other two species. In the four species oocytes reached diameters about two to three times that found for eutherian mammals. It was concluded that the marsupial oocyte continued to grow after formation of the follicular antrum and that, although the rate of oocyte growth slowed in larger follicles, it continued into the period immediately before ovulation. In B. penicillata the largest oocytes were obtained after ovulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

A simple glycerol-based freezing protocol for the semen of a marsupial Trichosurus vulpecula, the common brushtail possum.

Frozen storage of semen and embryos is now a well established part of the breeding of many eutherian mammals but it has not been applied to marsupials. This paper reports the first successful technique for the frozen preservation of marsupial spermatozoa. Semen was collected by electroejaculation under anaesthesia from a pool of five brushtail possums. The ejaculated semen was diluted 1:1 with Krebs Henseleit Ringer, centrifuged at 800 g for 5 min, resuspended in the test cryoprotectant media at 1, 2 and 5 x 10(6) spermatozoa mL-1 and 7, 10.5, 14 and 17.5% glycerol and then drawn up into 0.25 mL plastic straws. The spermatozoa were rapidly frozen in the vapour phase, 6 cm above liquid nitrogen, for 30 min before the straws were plunged into the liquid. Sperm motility was assessed blind for coded straws by phase-contrast microscopy on a warmed stage (35 degrees C), before freezing and after rapid thawing in a water bath at 37 degrees C (10 s). The highest recovery of both percentage motility (around 50-60%) and progressive motility (around 0.5-1 unit lower than prefreeze) occurred when spermatozoa were frozen and thawed in the presence of 17.5% glycerol. Recovery of motility was greater at the higher sperm concentrations (2 and 5 x 10(6) mL-1). There was no evidence of acrosomal damage or loss after freezing and thawing in high concentrations of glycerol. The only defect detected in spermatozoa subjected to the protocol was a variable tendency to bending of the neck region. This ranged from heads inclined at a slight angle to the tail through to complete flexure.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrosome↗
PubMed1991

Floppy mitral valves in elderly patients: clinical features and associated echocardiographic findings.

The clinical features and echocardiographic findings of a series of elderly patients with floppy mitral valves are presented. Palpitation was a common presenting complaint and 50% of patients had significant arrhythmias documented. Chest-wall deformity or Marfanoid habitus were common clinical findings. Seventy-nine per cent of patients had associated myxomatous degeneration of the aortic valve. The high incidence of arrhythmias in the series gives cause for concern since all required anti-arrhythmic therapy. The identification of these patients is therefore of practical importance.

Aged↗
PubMed1991

Stability of the acrosome of the brush-tailed possum (Trichosurus vulpecula) and tammar wallaby (Macropus eugenii) in vitro and after exposure to conditions and agents known to cause capacitation or acrosome reaction of eutherian spermatozoa.

Ejaculated spermatozoa from brush-tailed possums and tammar wallabies were washed by a 'swim up' procedure into Hanks Balanced Salt Solution (HBSS), and then exposed to test solutions. Spermatozoa were incubated at 33 degrees C, or room temperature when long-term sperm survival (greater than 10 h) was required. Exposure of spermatozoa to calcium ionophore A23187, cyclic nucleotides, phosphoinositide pathway intermediates, lysophospholipids, trypsin or 'capacitating' high ionic-strength medium (380 mosmol) followed by 3% bovine serum albumin for periods up to 24 h did not induce acrosomal loss. However, there were major changes within the acrosome: large numbers of empty membrane-bound vesicles were formed, the electron density of the acrosomal matrix decreased and the acrosome swelled slightly. The origin of the vesicles is unclear but the acrosomal membranes and the plasma membrane remained intact.

Acrosome↗
PubMed1988

A PMSG/GnRH method for the superovulation of the monovulatory brush-tailed possum (Trichosurus vulpecula).

Optimal ovarian stimulation with minimal degenerative changes was achieved in brush-tailed possums 3 days after a subcutaneous injection of 10 i.u. PMSG. This treatment alone did not result in ovulation and only rarely in oocyte maturation. Ovulation of 8-24 mature oocytes occurred when on the 3rd day after 10 i.u. PMSG the female received 3 intramuscular injections of 50 micrograms synthetic gonadotrophin-releasing hormone (GnRH) 90 min apart. Superovulation was achieved in immature, cycling, pregnant and lactating females, but not in animals in the preovulatory phase of a natural oestrous cycle.

Animals↗
PubMed1987

Myocardial scintigraphy with I-123 heptadecanoic acid as a test for coronary heart disease.

We have evaluated 123I-heptadecanoic acid for myocardial scintigraphy in the diagnosis of coronary heart disease by comparing the results obtained with it in subject groups with high and low probabilities of disease. We conclude that although some patients in the former group can be identified, the test is neither sufficiently sensitive nor specific for routine clinical use.

Adult↗
PubMed1987

Class I major histocompatibility complex antigen expression on early murine trophoblast and its induction by lymphokines in vitro.

The expression of paternal class I and class II major histocompatibility complex (MHC) antigens in cultures of murine ectoplacental cone trophoblast was examined using immunogold labelled antibodies and electron microscopy. Class I MHC antigens could be induced on ectoplacental cone derived trophoblast following exposure to concanavalin A stimulated T cell supernatants. Class I MHC antigens were not detected in untreated trophoblast cultures. Class II MHC antigens were never detected on trophoblast whether treated or untreated. This is the first report of the experimental induction of Class I MHC antigens on a population of normally MHC-negative trophoblast cells.

Animals↗
PubMed1987

Class I major histocompatibility complex antigen expression on early murine trophoblast and its induction by lymphokines in vitro. II. The role of gamma interferon in the responses of primary and secondary giant cells.

The induction of paternal Class I and II MHC antigens by crude lymphokine preparations or purified recombinant gamma interferon was investigated on (C57BL/6J X CBA/H)F1 primary and secondary trophoblast giant cell outgrowths from 3.5-day post-coital (pc) blastocyst and 7.5-day pc ectoplacental cone preparations, respectively, using sensitive immunogold labelling techniques and electron microscopy. Class I MHC (but not Class II) antigens could readily be induced on secondary trophoblast giant cells, by incubation in vitro with gamma interferon for 40 h. However, repeated attempts to induce detectable MHC antigens on primary trophoblast giant cells failed. Mock-treated (C57BL/6J X CBA/H)F1 secondary trophoblast giant cell control preparations failed to express detectable MHC antigens. These findings suggest that, at the time of implantation, there is a time window during which MHC antigens are neither expressed constitutively nor are inducible by soluble factors which normally modulate cell surface MHC antigen concentration.

Animals↗
PubMed1987

Pre-treatment with beta blockers and the frequency of hypokalaemia in patients with acute chest pain.

Plasma potassium concentration was measured at admission in 1234 patients who presented with acute chest pain. One hundred and ninety five patients were on beta blockers before admission. The potassium concentrations of patients admitted early (within four hours of onset of symptoms) were compared with those admitted later (4-18 hours after onset of symptoms). There was a transient fall in plasma potassium concentrations in patients not pre-treated with beta blockers. This was not seen in patients who had been on beta blockers before admission. Non-selective beta blockers were more effective than cardioselective agents in maintaining concentrations of plasma potassium. These findings suggest a mechanism for the beneficial effects of beta blockers on morbidity and mortality in acute myocardial infarction.

Adrenergic beta-Antagonists↗
PubMed1987

Anisoylated plasminogen streptokinase activator complex versus placebo. A preliminary multicentre study of safety and early mortality in acute myocardial infarction.

90 patients were enrolled into this preliminary multicentre study of the efficacy and safety of 30 units intravenous anisoylated plasminogen streptokinase activator complex (APSAC) compared with placebo in patients with acute myocardial infarction. 45 patients received APSAC and 45 placebo; the groups were similar for age, weight and site of infarction. There were significantly more women treated with APSAC (p less than 0.02). The mean time to treatment was 3.3 hours after symptoms of myocardial infarction for APSAC and 3 hours for placebo. The 30-day mortality was 7 patients in the placebo group and 1 in the APSAC group (p = 0.058). Adverse events were generally minor and were of similar overall frequency in both groups. There were more haemorrhagic events with APSAC, from which all patients recovered, and more cardiovascular events with placebo including 2 deaths from cardiogenic shock. APSAC showed a trend towards a reduction in 30-day mortality. Experience from this study has led to the initiation of the APSAC in myocardial infarction multicentre mortality study (AIMS).

Anistreplase↗
PubMed1985

Active anti-paternal immunization does not affect the success of marsupial pregnancy.

Active anti-paternal immunization does not compromise pregnancy in eutherian mammals. However, in an earlier study in a marsupial, grafting with paternal skin appeared to have resulted in transient infertility. In the present study, by critically monitoring the breeding efficiency of tammar wallabies sensitized against their mate's transplantation antigens, we aimed to resolve the question of immunologically mediated infertility in marsupials. Eight experimental females received two full-thickness skin grafts from their prospective mate and eight controls grafts of their own skin. The experimental group were monitored for 30 reproductive cycles and produced 24 pouch young (PY), whereas the control animals produced 28 young from 33 cycles. Five of the 11 apparently non-fertile cycles were judged to be normal pregnancies where the young had failed to reach the pouch (cycle length less than 28 days; rapid plasma progesterone decline coincident with oestrus). True infertility was thus limited and, although occurring mainly in the male-skin grafted group (5 cycles), this was not significantly different (chi 2, P greater than 0.5) from the controls (1 cycle) and represented the effect of one very poor breeder. We conclude that allogeneic pregnancy in marsupials is not compromised by active anti-paternal immunization. Infertility observed here, and in the earlier study, reflected disturbance of breeding owing to handling of the animals or the poor reproductive efficiency of individual animals in small experimental groups.

Animals↗
PubMed1985

Lack of a requirement for a maternal humoral immune response to establish or maintain successful allogeneic pregnancy.

In general, breeding pairs are not major histocompatibility complex (MHC)-compatible, and therefore the fetoplacental unit can be considered as a natural allograft. In many mammals pregnancy leads to the production of nonlytic antibodies of antipaternal MHC specificity. It has been suggested that these protect the semiallogeneic fetus from rejection by acting as blocking or enhancing factors--or, alternatively, that they are part of a humoral response involved in the establishment of normal pregnancy. These hypotheses were tested in allomated mice made B cell deficient by continuous treatment with alpha IgM mu antiserum. The status of the maternal immune system was assessed by in vivo antibody production, in vitro mitogen responses, and allograft rejection. By these criteria B cell function could not be demonstrated in alpha IgM mu treated female mice, but T cell responses were unaffected. Allogeneic pregnancy, however, was not compromised by this humoral immune system dysfunction--litter size and neonatal survival being the same in the alpha IgM mu and control serum-treated groups. These results indicate that a maternal humoral immune response is not essential for the establishment of pregnancy or the survival of the semiallogeneic fetus.

Agammaglobulinemia↗