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Biomedical subjects

J C Rodger

Publications and source records attributed to J C Rodger.

18 recordsLinked 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↗
PubMed1978

Differential transport of spermatozoa into the two sides of the genital tract of a monovular marsupial, the tammar wallaby (Macropus eugenii).

Ovulation in the tammar wallaby alternates between the ovaries. The genital duct of each side enters the median vaginal culs-de-sac separately. Post-partum oestrus occurred 0.4 days after birth and ovulation 1 day later. After a single copulation spermatozoa were found in both cervical canals at 0.5 h and extended to the oviduct on the non-parturient side only by 8 h. Very few spermatozoa were found in sections of the post-partum uterus or its associated oviduct at any time. Spermatozoa were recovered by flushing from both sides but the numbers were 2-20 times greater in the non-parturient than in the post-partum side: the greatest difference occurred in the cervical canals 2-5 h after copulation. In females which had undergone a previous infertile cycle, spermatozoa were abundant in both cervices and both uteri. It is concluded that the differential distribution of spermatozoa in post-partum animals was (1) due to failure of transport in the recently pregnant side of the tract, rather than attraction of spermatozoa to the ovulation side, and (2) established at the cervix which, on the ovulation side, provides a reservoir of spermatozoa for 24 h after copulation.

Animals↗
PubMed1977

Down's syndrome: an atheroma-free model?

Postmortem examination of five institutionalised patients with Down's syndrome (DS) aged 40-66 years showed a complete absence of atheroma, while a similar number of mental defectives with DS were found to have mild or severe atheroma. Previous investigation of risk factors for atheroma in 70 patients with DS and 70 age-and sex-matched mental defectives living in the same institution showed significantly lower systolic and diastolic blood pressures in the DS group, with the exception of systolic pressure in men under 40. Fasting serum cholesterol and triglyceride concentrations were similar in the two groups, but triglyceride concentrations were significantly lower than in normal people without a history of vascular disease. These unexplained observations may be relevant in further studies of the pathogenesis of atheroma.

Adult↗
PubMed1977

Thyroid function in adults with Down's syndrome.

The thyroid status of 82 institutionalized adults with Down's syndrome has been assessed. Compared to age and sex matched control subjects, these patients had significantly lower mean total serum thyroxine (T4) and triiodothyronine (T3) concentrations (T4; 69.1+/-22.2 nmol/1; (mean+/-SD) vs. 100.1+/-19.1, P less than 0.001; T13; 1.61+/-0.47 nmol/1 vs. 1.76+/-0.34, P less than 0.025), lower free thyroxine index (FTI), (FTI; 66.1+/-22.4 vs. 95.1+/-20.2, P less than 0.001), and higher basal serum thyrotrophin (TSH) concentrations (TSH; 7.6+/-10.7 mU/1 vs. 3.8+/-1.5, P less than 0.001). These changes were not related to age or sex. Abnormalities in one or more test of thyroid function were demonstrated in at least 38 (46%) of the 82 patients. Two main patterns of abnormality were defined: 1) subnormal T4, FTI and elevated basal TSH levels (primary hypothyroidism) in 13 (16%). All seven of the 13 patients in whom TRH tests were performed showed the expected exaggerated TSH response, and seven out of the 13 patients (54%) had positive thyroid antibodies, 2) Subnormal T4, subnormal or low normal FTI, and basal TSH levels within the normal range in 18 (22%). The mean basal TSH concentration was, however, significantly higher than in patients with normal T4 and FTI levels, suggesting a minor degree of thyroid failure. Only two of the 18 patients (11%) had positive thyroid antibodies. Of the 17 patients in the group tested, 13 showed a normal TSH response to TRH, three an exagerrated response (all females), and one had an impaired response. Other patterns of abnormal thyroid function were observed occasionally: one female patient had biochemical T3 toxicosis; another had the biochemical pattern of subclinical hypothyroidism, four patients with normal basal T4, FTI and TSH levels showed an exaggerated TSH response to TRH and one patient had an impaired response. These data indicate that htyroid dysfunction, in particular hypothyroidism, is common in adults with Down's syndrome, though specific tests are usually required to make the diagnosis. The general reduction in thyroid function in Down's syndrome may be due to impaired development of the thyroid gland. However, frank chemical hypothyroidism may occur only when thyroiditis is superimposed on preexisting diminished thyroid reserve.

Adult↗
PubMed1976

Motion of mitral apparatus in hypertrophic cardiomyopathy with obstruction.

Motion of the mitral apparatus in hypertrophic cardiomyopathy with obstruction was investigated by conventional single dimensional and multidimensional echocardiography. In systole, anterosuperior displacement of the posterior papillary muscle, failure of mitral valve closure, and anterior motion of both mitral leaflets were shown. The anterior leaflet was seen to impinge on the posterior papillary muscle but not on the interventricular septum in systole. The abnormality of the single dimensional mitral echogram, previously ascribed to systolic anterior motion of the mitral anterior leaflet, was found to be a complex of echoes from the chordae tendineae, the papillary muscle, and, furthest from the septum, the mitral anterior leaflet. It is concluded that systolic anterior motion of the mitral anterior leaflet is of smaller amplitude than others have suggested, and that obstruction to left ventricular outflow in hypertrophic cardiomyopathy is produced by systolic contact between the mitral anterior cusp and the posterior papillary muscle. The theory is put forward that displacement of the posterior papillary muscle above and in front of the mitral leaflets produces chordal slackening, and that it is displacement of the chordae tendineae by the blood flowing to the aortic root during left ventricular ejection, which is responsible for systolic anterior motion of the mitral leaflets.

Adolescent↗
PubMed1975

Measurement of diastolic closure rate of normal mitral valve.

Published values for the diastolic closure rate of the normalmitral vary and reflect diffference in methods of recording and measurement. From strip chart records it was concluded that the form of the recorded mitral diastolic closure slope can vary, that reproducible measurements of the closure rate can be made from echograms in which diastolic closure approximates closely to a monophasic form, that the amplitude of these echograms is maximal, and that their closure movements remain essentially monophasic at chart speeds up to 100 mm/s. Measuring only complexes with essentially monophasic closure movements, the within and between-subjected variation of the normal mitral diastolic closure rate was investigated. The ranges obtained from multiple measurements in a single subject and from a group of 45 normal subjects were comparable but the distribution of the results differed. It was concluded that there was a real between-subject variation in the normal mitral diastolic closure rate and that the diastolic closure rate in a single subject should be determined by measurement of a series of complexes. The accuracy of measurement of the diastolic closure rate of the normal mitral valve has been improved by using strip chart records and by measuring only echograms in which diastolic closure approximates closely to a monophasic form.

Adolescent↗
PubMed1975

Electroejaculation of Australian marsupials and analyses of the sugars in the seminal plasma from three macropod species.

Electroejaculation of a variety of Australian marsupials was attempted in this study. The animals used were conscious, sedated, anaesthetized or recently shot. Electroejaculation proved to be a satisfactory means of obtaining seminal plasma but not spermatozoa. The largest volumes of seminal plasma were collected from animals shortly after death. Anaesthetized animals also provided useful volumes of seminal plasma but only insignificant amounts were obtained from conscious and sedated animals. Quantitative analyses of N-acetylglucosamine, glucose and anthronereactive material were made of deproteinized, deionized, water extracts of seminal plasma from electroejaculates obtained from wallabies and kangaroos shortly after death. The major seminal sugar of the three macropod species was N-acetylglucosamine and glucose was also present in quite large concentrations. These observations show that the pattern of sugars in the prostate gland of marsupials is reflected in the semen.

Anesthesia, General↗
PubMed1975

Free N-acetylaminosugar in the seminal plasma of eutherian mammals.

The seminal plasma of seven eutherian species, including man, was examined for the presence of free N-acetylaminosugar. Only man had appreciable levels of N-acetylaminosugar in the semen (37-1 mg/100 ml), but in all cases this free N-acetylaminosugar was probably the result of breakdown of polysaccharides by semen glycosidases. High levels of free N-acetylaminosugar thus appear to be peculiar to marsupials.

Acetylglucosamine↗