Heart rate and cardiac function curves. Their dependence on the age of the myocardium and the compliance of the ejection circuit.

Isolated, perfused hearts from 16 rats aged from 13 to 17 months were studied to examine the effects of age and of the compliance of the ejection circuit on heart rate and cardiac function curves. Heart rate was found to diminish both with age and with decreasing compliance of the ejection circuit. Cardiac function curves were also substantially modified by these two factors. It was found that old hearts adapted better to a reduced circuit compliance. This suggests that, in the intact animal, changes in the mechanical properties of the heart muscle may be an adjustment to the reduction in arterial compliance which accompanies ageing.     

Hairless mice as models for chloracne: a study of cutaneous changes induced by topical application of established chloracnegens

Two types of hairless mice, one from the inbred strains, $\text{HRS}\text{J}$, and the other from the outbred stock, Skh:HR-1, were used to study the feasibility of inducing experimental chloracne with various well-established chloracnegens. Animals were treated topically for periods ranging from 2 to 10 weeks, and the cutaneous changes were monitored. Most chloracnegens induced a distinct pattern of cutaneous pathology, but this pattern did not include hyperkeratinization of the sebaceous follicles, which is considered the pathognomonic lesion in human chloracne. Rather, the changes induced by chloracnegens such as Halowax 1014, N-wax-34, Phenclor 54, and 2,3,4,8-tetrachlorodibenzo-p-dioxin were: epidermal hyperkeratosis and hyperplasia, loss of sebaceous glands, keratinization of intradermal pilar cysts, and, often, diffuse lymphohistiocytic infiltration of the dermis. Only one chloracnegen, 3,4,3′,4′-tetrachlorobiphenyl, induced a true chloracne-like syndrome, and only in one of the strains of mice (Skh:HR-1). This syndrome involved massive hyperkeratosis of the sebaceous follicles and hyperkeratinization of intradermal pilar cysts. In many instances, these cysts spontaneously ruptured into the dermis and induced the development of pimple-like foci of inflammatory cell accumulation in the skin. All animals developing these cutaneous changes also underwent a generalized metabolic disturbance resulting in gross weight gain, primarily due to large intraabdominal fat deposits.     

Transient engraftment of T cell-depleted allogeneic bone marrow in mice improves survival rate following lethal irradiation

C3H/HeJ mice were exposed to 8 or 9 Gy total body irradiation prior to transplantation of 1-15 x 10(6) H-2 incompatible T cell-depleted bone marrow cells from C57BL/6 donors. Survival was greatly enhanced compared to irradiated controls, even at the lowest cell doses. Analysis of spleen cells 1-7 weeks post-transplant revealed that recipients of the lowest doses of T cell-depleted bone marrow had only transient engraftment of donor type cells, and that long-term recovery was autologous. This transient engraftment had a marked beneficial effect both on reconstitution of hematopoiesis and on survival.     

Angiographic findings in relation to clinical course and results of computed tomography in cerebrovascular disease

Clinical course, results of angiography and computerized tomography (CT) were compared in 204 patients with focal cerebral ischemias. The extent and the importance of the radiological results depend on the localization of the affected area, whereby essential differences exist between extra- and intracranial arteries as well as between the vertebrobasilar and the carotid arterial flow region. As to the carotid arterial system there appear to be significant correlations between the size of the infarction on the CT and the extent of the vessel stenosis on angiography. Furthermore the likelihood of deficit recovery is inversely proportional to the degree of pathology seen in both radiologic examinations. It is discussed whether these correlations, obtained from the examination of a great number of patients, can help to evaluate the significance of equivocal angiographic findings in individual cases.