Showing papers on "Animal mortality published in 1972"

Radiation Dose, Dose Rate, and Quality in Suppression of the Humoral Immune Response

Abstract: Radiation-induced immunosuppression was studied with special emphasis on the factors of dose rate and quality of the radiation. Fission neutrons, x-rays, and 60 Co γ-rays at dose rates ranging from 2.8 to 95 rads/min were tested for their biologic effect. Data reported earlier from our laboratory were supplemented as necessary to allow intercomparisons to be made. The biologic systems in the mouse included: a) animal mortality, b) immune response capability of the irradiated animal, and c) antibody formation by irradiated spleen cells cultured in unresponsive hosts. The following empiric relationships were established: a) the three biologic responses were each related to the radiation dose by a probit-type analysis, b) the magnitude of the dose-rate effect was an exponential function of the linear energy transfer (LET), and c) the inverse cube root dose-rate relationship reported earlier was confirmed. Immunosuppression of the whole animal was related to mortality, but not in a simple manner: as the LET of the radiation used declined, the level of immunosuppression at the LD 50 increased, indicating that mortality is not necessarily a measure of the level of immune activity. We present an empiric expression relating the radiation dose rate and quality (LET) to the expected biologic effect, anticipating the possible application of these data to clinical situations.

Pathophysiology of Acute Myocardial Infarction in Conscious Dogs

Abstract: Experimental models of acute myocardial infarction (1–5) have usually involved anesthesia in the open- and closed-chest dog, and had several limitations, including: (1) hemodynamics could be monitored continuously only for a limited time, under anesthesia and usually thoracotomy; (2) animal mortality was very high and early; and (3) ventricular arrhythmias occurred early with potassium egress from the damaged myocardium. To avoid these limitations, several investigators devised models of acute myocardial infarction in un- anesthetized animals (6–8). In the model devised by Khouri et al (6), coronary insufficiency was induced by gradually reducing circumflex coronary flow to zero over several days. However, the gradual reduction in flow permitted the coronary vascular bed, including collaterals, and the myocardium to make compensatory changes, so that when occlusion was complete, minimal infarction frequently results (6, 9). Hood, et al (7) used a similar unanesthetized dog model and gradually occluded the anterior descending coronary artery. Since their study produced a higher frequency of large infarcts, the rate of occlusion was probably faster. Another disadvantage of this preparation was the lack of coronary blood flow monitoring, so that the precise onset of occlusion was not known.

The relative potencies of heat-killed and acetone-killed vaccines against Salmonella typhimurium in mice

Abstract: Mice were immunized against Salmonella typhimurium with graded doses of heat-killed (HK) and acetone-killed (AK) vaccines and then challenged by the oral or intraperitoneal routes with two doses of S. typhimurium. HK and AK vaccines gave good protection against an intraperitoneal challenge, but failed to protect against an oral challenge which is presumably the natural mode of infection. HK vaccine was as potent as AK vaccine in reducing the mortality rate among mice challenged by the intraperitoneal route but, unlike HK vaccine, AK vaccine was also able to reduce the infectivity rate. With a small intraperitoneal challenge dose it was observed that a gradual increase in vaccine dose is associated with a corresponding fall in mortality rate, but with a larger challenge dose an increase in vaccine dose was associated with a corresponding increase in mortality rates. It was concluded that the protective potency of this type of vaccine may partly depend upon the total amount of antigen in the animal, i.e. including both the vaccine and the challenge organisms, at a critical time after challenge.