Some in vivo effects of pi mesons in mice.

The effect of 70 MeV pi mesons was studied to determine the effectivness of such beams aginst normal tissues in vivo. The end points included thymic weight loss, oocyte and bone marrow CFU-S survival and the induction of macroscopid lens opacities. The results indicate that pi mesons are not signifacantly more effective for these end-points than more conventional radiation sources such as 60Co gama rays, 220 kVp X rays, and 14 MeV X rays and electrons. Nor was there any detectable difference in RBE between the peak and plateau regions of the pi meson beam. The significance of these findings is discussed in relation of the the published pi meson RBE values of between 1 therefore 4 and 5 therefore 0.

Prospective life-science payloads.

A viable spacelab programme is based on the thesis that biomedical specialists require a quantifiable, and possibly mechanistic, understanding of the significant changes observed in crew, in and after manned space flights. Only then can prophylaxis or atraumatic reversal be achieved (with potentially an added use to ameliorate qualitatively similar disease aspects on Earth). This approach could justify national funding to promote lead-up ground-based research as well as research and development for special equipment, of which the "spin-off" into clinical practice could well precede its first use in Spacelab. The requirement for "applied expediency" arises from the watershed met early in the evolution of a life-sciences programme. Initially, the facility of space flight provoked numerous valid experiments designed to test for, or quantitate, gravity-dependent mechanisms and their interaction with other agents, radiation, vibration, or absence of triggers for rhythmic patterns. In parallel, measurable parameters of man's function in space were being monitored, primarily to promote survival by remedial action when available. Monitoring data were then developed to find a critical mechanism feasible to testing. Often the rationale for such tests and experiments was that "man was there" and could, moreover, attend to several biological experiments in space! The watershed appeared when man in a Spacelab was shown as a hazard to the instrumentation, cleanliness, accuracy, thermal control, weight limits, etc. essential to the other disciplines. Other than the life sciences only the technological requirements of materials processing required a manned spacelab! So, life scientists have needed to rethink their payloads, and their constrictions, to plan for compatible load sharing. A composite of proposed biomedical projects related to apparently unanswered etiology of observed changes in returning astronauts will be used to illustrate the evolution of and possible answers to sample problems. The principles outlined, their moderation by expediency (with the untouched upon need for the enthusiastic involvement of biomedical potential in space projects) should remain our guidelines. This is in spite of the expected obsolescence of these specific projects within the next decade.

Studies on the humoral regulation of granulopoiesis in leukaemic RFM mice.

Intraperitoneal diffusion chambers have been used to investigate changes in humoral factors during the development of myeloid leukaemia in mice. Normal mouse bone marrow cells form colonies of granulocytes and macrophages when cultured in semi-solid agar medium within intraperitoneal diffusion chambers. The use of mice bearing transplanted myeloid leukaemia as Agar Diffusion Chamber (ADC) hosts enhances colony formation from normal marrow. The humoral basis for this stimulation has been shown by the colony stimulating activity of the fluid entering the diffusion chambers when assayed against normal mouse bone marrow cells in agar culture in vitro. The stimulus to colony growth in ADCs and the in vitro colony stimulating activity depend on the phase in the development of the leukaemia investigated, and the stimulation was abolished by splenectomy. There was no apparent relationship between the growth of the leukaemic cell population in vivo and the level of the stimulating factor detected in leukaemic mice.