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Biomedical subjects

D Bellamy

Publications and source records attributed to D Bellamy.

At least 55 records · Page 3Linked to original sources
PubMed1978

Influence of lodgement site on the proliferation of metastases of Walker 256 carcinoma in the rat.

The growth of s.c. Walker 256 carcinoma was found to be independent of secondary growths induced by i.v. injection. Tumour cells injected i.v. lodged mainly in the lungs, with small clusters of cells in the lymph nodes. The rate of cellular proliferation of these secondary growths of Walker carcinoma was significantly higher than that observed in the s.c. tumour. In addition, host lung tissue was found to inhibit the development of metastases, and it is postulated that the host tissue may produce a diffusible inhibitor and that differences in the effectiveness of these humoral factors may account, in part, for locational differences in tumour growth patterns.

Animals↗
PubMed1977

Density-dependent cell division after cortisol treatment of rat thymus in relation to age involution.

Cellular proliferation, in relation to cell density was investigated in the thymus of control and cortisol treated animals at 6 and 18 weeks of age. It was found that there was very little difference in the response of the two age groups to cortisol treatment. Cell density and cellular proliferation were markedly reduced 2 days after cortisol administration. From 4 days there was a rapid increase in cellular proliferation to triple the control rate. The mitotic index remained above normal until 12days then decreased to control values at 14 days. During this time the cell density of the thymus was being progressively restored. At all stages of regeneration, the mitotic index at first increased to a maximum at the mean cell density then decreased at the highest cell concentrations. A model system is discussed to account for this density dependent control of cellular proliferation in the thymus.

Aging↗
PubMed1977

A quantitative histological assessment of cellular death, in relation to mitosis, in rat thymus during growth and age involution.

The rates of cellular proliferation and cellular death were investigated in the rat thymus during growth and involution. It was found that the percentage of dead cells gradually increased with age, whilst the rate of cell proliferation declined, indicating that a substantial proportion of lymphocytes that divide in the thymus also die there. It was also found that there exists a density-dependent distribution pattern of mitotic and dead cells and that this distribution pattern changed with age. It is suggested that this mechanism of density-dependent control of the thymus may be an important factor in the age involution of the thymus.

Aging↗
PubMed1977

Spontaneous thymoma in an inbred strain of rat.

Thymomas that appear with high frequency in inbred WAB rats living into old age were examined. The spontaneous thymomas described were discrete, encapsulated bodies composed of lymphocytes and epithelial cells, with a predominance of lymphocytes. The rat neoplasms resembled the human thymomas, and their rate of incidence in older animals may suggest their use as models for the human condition.

Animals↗
PubMed1976

Factors controlling growth and age involution of the rat thymus.

Thymic development and somatic growth were investigated in three strains of rat. The well established influence of sex and age on somatic growth was confirmed. It was also found that the rate of thymic growth was not influenced by the sex of the animal until four weeks of age, but thereafter, the thymus grew faster in males compared with females of the same strain. Gonadectomy had a marked effect on the thymus, resulting in a higher rate of growth than in normal animals; but a slower initial rate of involution. The maximum thymus weights attained in gonadectomized animals were found to be independent of the age at which the animals were gonadectomized or of the sex of the animal. Gonadectomy did not influence the point at which involution began. Thymic mitotic indices of gonadectomized animals were found to be higher than those of normal animals. The influence of sex hormones on somatic growth and the development of the thymus is discussed, and it is concluded that cell loss is the regulator of thumus growth and involution.

Age Factors↗
PubMed1976

Effect of a lathyrogen (aminoacetonitrile hydrochloride) on aortic physiosclerosis and skeletal mineralization in growing rats of different age.

In one experiment, four groups of six-week-old-male PVG rats were, respectively, given tap water ('control group'), 0.00125M, 0.0025M, and 0.005M lathyrogen (aminoacetonitrile hydrochloride: AAN) solutions ad libitum for a period of 20 weeks. In a second experiment, 12-week-old male rats were similarly treated. It was found that the younger rats were far more susceptible to lathyrogenic influences than the older rats. For example, the rate of aortic physiosclerosis was significantly retarded in the six-week-old rats at dosages of 0.00125M and 0.0025M (the six-week-old rats exposed to 0.005M AAN were eliminated from the experiment before its completion), whilst physiosclerosis was unaffected even in those 12-week-old rats exposed to 0.005M AAN. The degree of mineralization of the femur (as reflected by its ash, Ca, Mg, Na, and K content) was retarded in approximately dose-dependent fashion in the rats of both ages, the effect being somewhat more pronounced in the younger animals. These results were discussed in the context of the known effects of lathyrogenic compounds on the biochemical maturation of connective tissue components, and also in the context of previous attempts to modify the lifespan of laboratory animals by lathyrogen administration.

Acetonitriles↗
PubMed1976

Electrocardiographic studies during hypotensive anaesthesia using sodium nitroprusside.

Multiple lead electrocardiographic recordings from 20 patients were studied before, during and after a period of induced hypotension with sodium nitroprusside. Although small changes in ST segment and T wave were observed in 9 patients, none of these persisted into the postoperative period. Other significant changes were confined to a temporary disturbances of cardiac rhythm in 2 patients, both of whom spontaneously reverted to sinus rhythm during the anaesthetic. Our findings indicate that there are no permanent ischaemic myocardial changes associated with induced hypotension using sodium nitroprusside.

Adolescent↗
PubMed1975

On the role of the reticular-epithelial complex in transplantation of the thymus.

Transplantation of the neonatal thymus, into young, adult hosts, resulted in massive cell death of graft cortical lymphoid tissue with apparent selective survival of the reticular-epithelial cells. The central area of the graft was progressively cleared of cell debris and the characteristic thymic architecture restored within fourteen days of grafting. Evidence obtained from the regeneration of different-sized transplants suggested that the size and shape attained by the regenerated graft was closely related to the size and shape of the donor tissue. When donor rat thymuses were transplanted in Millipore chambers, the lymphocyte population did not reappear and after seven days only reticular-epithelial cells remained, retaining their normal appearance. However, when these thymic remnants were removed from the chambers and transplanted into secondary hosts, the thymus regenerated normally, suggesting that the lymphocytes in the regenerated gland were derived from the host. Thymic remnants after cortisol treatment of donors also formed distinct organs after grafting despite the fact that they contained few donor lymphocytes. From the differential effects of cortisol on host and transplanted thymus and the different growth characteristics of transplants it appears that transplants differ in their growth/involution control system from the host thymus.

Animals↗
PubMed1975

Influence of age and sex on the calcification of rat aorta in relation to bone mineralization.

Thoracic aortas of pvg rats accumulated Ca (analysed by flame spectrophotometry) throughout mature life, with females having slightly higher levels than males at each age interval studied. Femur Ca concentration was similarly elevated in female rats, and was maintained fairly constant in both sexes after 19 weeks of age. Femur Mg and K levels showed an over-all decrease with age; whilst the Na concentration fell up to 19 weeks, and then decreased steadily. It was concluded that a simple shift of Ca from the ageing skeleton into soft tissues cannot adequately account for aortic physiosclerosis.

Age Factors↗
PubMed1975

Age changes in some inorganic constituents of bone and aorta: a comparative study in wild-trapped and laboratory mice (Mus).

Age changes in tibia Ca, Mg, Na and K concentrations in wild populations of house mice trapped on the islands of Skokholm and May were compared with the changes monitored in a laboratory-bred strain of Skokholm mice, and in Tuck albino mice. Strain differences were recorded in the temporal changes of Ca, Mg and Na--the wild-trapped Skokholm population having a particularly characteristic alteration in tibial chemistry. Strain differences in bone-electrolytes were attributed predominantly to fundamental genetic differences between populations. Tibia Na and K levels were far more variable than the Ca and Mg levels in all four strains. Electrolyte variability was greater in the wild populations than in laboratory populations. Some thoracic aortas taken from female mice trapped on Skokholm were highly calcified, due possibly to gross arteriosclerosis produced by the endocrine events of reproduction. Elevated calcium levels were not detected in male aortas taken from the wild; neither were the aortas of male and female laboratory-bred Skokholm mice subject to gross calcification.

Aging↗
PubMed1975

Hypothalamo-pituitary-adrenal function in intrinsic non-atopic asthma.

Sixteen patients with intrinsic non-atopic asthma with persistent wheezing who had never been treated with corticosteroids showed normal adrenocortical responses to prolonged stimulation with Tetracosactin Depot. In a subgroup of six patients the hypothalamo-pituitary-adrenal (HPA) response to a standard insulin stress test was normal. It is concluded that impaired responsiveness of the HPA axis is unlikely to be a common factor in initiating or maintaining airways obstruction in patients with intrinsic asthma.

Adrenal Glands↗
PubMed1975

A case of primary alveolar hypoventilation associated with mild proximal myopathy.

A 34-year-old man presented with clinical features of primary alveolar hypoventilation, but was found additionally to have an adult onset myopathy caused by acid maltase deficiency. This was not severe, as judged clinically, and was initially overlooked. His vital capacity and sprint maximal ventilatory volume were only slightly reduced, and the ventilatory response to CO2 was virtually absent. There was, however, a mild impairment in the ability to decrease Pco2 to normal by voluntary hyperventilation. The relation of myopathy and alveolar hypoventilation is discussed, and it is proposed that the primary muscle disease predisposed the patient to the development of the ventilatory abnormality.

Adult↗