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Biomedical subjects

T G Baker

Publications and source records attributed to T G Baker.

At least 37 records · Page 2Linked to original sources
PubMed1982

Morphology, histology and steroid hormones of the gonads in intersex pigs.

Studies of 3 genetically female, intersex pigs revealed that only one showed oestrous cycles and lordosis, the other 2 exhibited various components of male sexual behaviour. Each uterus was a patent bicornuate structure, but 5 of the oviducts were incompletely formed. Two of the animals had bilateral ovotestes, whilst the third had a functional ovary on the right and an ovotestis on the left. The small ovarian portion of each ovotestis contained Graafian follicles which did not respond to a systemic injection of PMSG. The major portion of each ovotestis consisted of extensive interstitial tissue and seminiferous tubules devoid of germ cells. A structure closely resembling an epididymis adjoined the ovotestes. Concentrations of oestradiol and progesterone in plasma corresponded with those expected in the follicular phase of an oestrous cycle, but concentrations of testosterone represented approximately one-tenth of the values found in mature boars.

Animals↗
PubMed1982

The ultrastructure of rat thyroid glands under experimental conditions in organ culture.

A technique has been described which permits the maintenance for up to 6 days in organ culture of explanted thyroid glands. This provided a suitable model for an electron microscope study to be carried out on glands under experimental conditions. The appearance of the control gland was consistent with stimulation by TSH. The formation of 'intracytoplasmic' follicles was caused by injection of TSH into the culture. Parafollicular (light) cells were described for the first time in organ cultured thyroid glands.

Animals↗
PubMed1981

Oocyte depletion in XO mice and their XX sibs from 12 to 200 days post partum.

The total number of oocytes (healthy and atretic) in XO and XX mice at ages ranging from 12 to 200 days after birth was determined using a quantitative histological technique. For each oocyte the stage of the enveloping follicle was recorded. The results demonstrated that throughout the period studied XO mice had approximately half the number of oocytes found in XX mice. No increase in the incidence of atresia was detected in XO ovaries. In XO mice at 12 days of age the establishment of the population of growing follicles was clearly retarded.

Aging↗
PubMed1981

Effect of hCG, cAMP and FSH on steroidogenesis by human corpora lutea in vitro.

Human corpora lutea of various ages were minced and incubated in the presence of hCG (10 i.u./ml), cAMP (10 mM) or FSH (20 mu/ml) and production of progesterone and oestradiol was measured. Cyclic AMP and hCG stimulated progesterone and oestradiol production during at least the mid- and late luteal phases, but FSH stimulated only oestradiol production during the early and mid-luteal phases and had no effect on progesterone production. This demonstrates that progesterone and oestradiol synthesis by the human corpus luteum can be independently controlled.

Chorionic Gonadotropin↗
PubMed1980

Development of the gonad in normal and anencephalic human fetuses.

The development of the germinal and somatic cells in the gonads of normal and anencephalic fetuses was investigated. Interstitial cells were reduced in number in both sexes and in males the population of gonocytes in profiles of seminiferous tubules was reduced when Leydig cells were seeminaly absent. Ovarian differentiation up to about 34 weeks after conception was apparently normal, although precise counts of the numbers of germ cells were not carried out. Nevertheless, oogonia increased in number by mitotic divisions, oocytes progressed through meiotic prophase to the diplotene stage, and primordial follicles formed normally. By contrast, 'growing' and small antral follicles, which are a constant feature of control ovaries, were not observed in the anencephalic specimens.

Anencephaly↗
PubMed1980

The number of oocytes and the rate of atresia in unilaterally ovariectomized mice up to 8 months after surgery.

Random bred Schofield albino mice were unilaterally ovariectomized or sham-operated at 6 weeks of age and were killed 4, 8, 16 or 32 weeks later. Ovarian weights were recorded before quantitative histological analysis of the total number of oocytes per ovary, the number of follicles per size class, and the proportion of oocytes undergoing atresia. Ovarian weights were consistently higher in the unilaterally ovariectomized mice than in coeval controls and by the 8th week after surgery the weight of the remaining ovary approached the combined weights of the two ovaries in controls. On a per ovary basis, follicular 'pool' size was reduced and the number of growing follicles increased after unilateral ovariectomy, these changes occurring within the first 4 weeks after surgery. Thereafter, oocyte depletion occurred at the control rates. There was no change in the rate of atresia after surgery.

Animals↗
PubMed1979

Coronary haemodynamics and myocardial metabolism during cardiopulmonary bypass.

An experimental animal preparation is described which has allowed us to determine coronary haemodynamics and the overall myocardial metabolic rate of the disease-free, beating, normothermic heart during total cardiopulmonary bypass. We have confirmed that under these conditions the required coronary blood flow is about 50ml/min/100g myocardium, which can be achieved at a low perfusion pressure (60 mm Hg or 8 kPa), and that overall myocardial metabolism is represented by an oxygen utilization of just over 2 ml/min/100g. We have also defined the associated dynamic parameters which characterize oxygen transport in the coronary circulation during bypass. By controlling coronary perfusion, analogous in a clinical setting to selective coronary perfusion, we have demonstrated a simple linear correlation between perfusion pressure and coronary flow, indicating a "fixed" coronary vascular resistance. Under these conditions the myocardial oxygen uptake rises towards a maximum of 4ml/min/100g with the expected associated changes in the parameters characterizing oxygen transport in the coronary circulation. These trends are postulated as being a reflection of alterations in regional myocardial perfusion. By extrapolating to the clinical situation, these data have appeared to give valid information concerning the adequacy of coronary perfusion.

Animals↗
PubMed1979

Reproductive capacity of rhesus monkeys following bilateral ovarian x-irradiation.

The effect of ovarian X-irradiation of the rhesus monkey upon menstrual cycle length, duration of menstrual bleeding, excretion of gonadotrophin in the urine, concentration of gonadotrophin in the pituitary gland, ovarian histology, and breeding performance was investigated. Doses below 4000 R had no significant effect upon the above criteria. By contrast, doses of 4000 to 7000 R rapidly induced amenorrhoea in most animals, but unexpectedly these animals did not excrete greater than normal amounts of gonadotrophin. The pituitary content of gonadotrophin in cyclic and non-cyclic animals was not significantly different. Some births occurred in the animals which had been X-irradiated.

Animals↗
PubMed1979

Fine structure of gonadotrophs and prolactin producing cells in the rat pars distalis in organ culture.

A technique is described which permits the maintenance for up to 8 days in organ culture of explanted rat pituitary glands. Electron microscope studies showed that the cultured glands (whether treated with gonadotrophin-releasing hormone (GnRH) or not) were almost identical to controls in appearance, although the stellate (follicular) cells seemingly were eliminated in vitro. Gonadotrophs and prolactin-secreting cells in male and female pituitary glands were similar in appearance both in vivo and in vitro to comparable cells described by other authors. There was some evidence for an increase in the secretory activity of these cell types (particularly gonadotrophs) when the explants were treated with GnRH. The present technique thus provides a suitable and valid 'model' with which to study the effects of GnRH and steroid hormones on the release and synthesis of FSH and LH in vitro.

Animals↗
PubMed1978

Oestradiol production by human graafian follicles cultured in vitro.

Intact human Graafian follicles recovered during the preovulatory phase of the menstrual cycle and cultured in vitro, gave a mean oestradiol production of 33 ng/hour over periods of 4 to 92 hours. Treatment of follicles with human pituitary gonadotrophin or human chorionic gonadotrophin resulted in an increased production of oestradiol.

Adult↗
PubMed1978

Hormone production by the intact human corpus luteum in vitro.

Human CL removed during the menstrual cycle were cultured for up to 5 days. Production of progesterone, measured by radioimmunoassay of the culture fluid, continued throughout each experiment. Addition of hCG to the culture medium stimulated progesterone production in a biphasic manner.

Chorionic Gonadotropin↗
PubMed1978

Changes in the ovaries of rats after immunization against luteinizing hormone releasing hormone.

Rats were immunized against luteinizing hormone releasing hormone (LH-RH) and ovulation and follicular development were studied 12, 24 and 48 weeks later. The abolition of regular cyclic patterns of vaginal smears and the absence of luteal tissue in all but one of 32 rats showed that the immunization was effective in blocking ovulation. Follicular growth varied between rats and appeared to be dependent on whether the inhibition of LH-RH had been sufficient to affect the secretion of basal levels of gonadotrophins. Low levels of gonadotrophins were associated with poor follicular development, uterine atrophy and leucocytic vaginal smears, whereas levels of gonadotrophins similar to those in the dioestrous controls led to adequate follicular growth in the absence of ovulation, the production of cystic follicles, uterine stimulation and persistent vaginal oestrus. A group of rats was ovariectomized 12 weeks after immunization against LH-RH; animals with low antibody titres and large follicles responded with increases in the levels of LH and FSH in the blood, whereas in those with high antibody titres and little follicular development the concentrations of gonadotrophins remained low. The reproductive capacity of rats immunized against LH-RH was tested by caging them with normal male rats from 3 weeks after immunization. Although mating occurred in three rats during the first month, no offspring were produced. No matings occurred in the remaining 41 weeks.

Animals↗