Long-term enhancement of pulmonary gas exchange after high-altitude residence during maturation.

In a previous study, our laboratory showed that young dogs born at sea level (SL) and raised from 2.5 mo of age to beyond somatic maturity at a high altitude (HA) of 3,100 m show enhanced resting lung function (Johnson RL Jr, Cassidy SS, Grover RF, Schutte JE, and Epstein RH. J Appl Physiol 59: 1773-1782, 1985). To examine whether HA-induced adaptation improves pulmonary gas exchange during exercise and whether adaptation is reversible when animals return to SL before somatic maturity, we raised 2.5-mo-old foxhounds at HA (3,800 m) for 5 mo (to age 7.5 mo) before returning them to SL. Lung function was measured under anesthesia 1 mo and 2 yr after return to SL and during exercise approximately 1 yr after return. In animals exposed to HA relative to simultaneous litter-matched SL controls, resting circulating blood and erythrocyte volumes, lung volumes, septal volume estimated by a rebreathing technique, and lung tissue volume estimated by high-resolution computed tomography scan were persistently higher. Lung diffusing capacity, membrane diffusing capacity, and pulmonary capillary blood volume estimated at a given cardiac output were significantly higher in animals exposed to HA, whereas maximal oxygen uptake and hematocrit were similar between groups. We conclude that relatively short exposure to HA during somatic maturation improves long-term lung function into adulthood.     

FETAL DEVELOPMENT: THE EFFECTS OF MATURATION ON IN VITRO PROTEIN SYNTHESIS BY MOUSE BRAIN TISSUE

—The elucidation of the translational regulatory events which function during the critical fetal and neonatal period is an important prerequisite to our understanding of normal, as well as abnormal, brain growth and differentiation. Brain cell suspensions and cell-free homogenates were employed to study the protein synthetic activity during the maturation of fetal- neural tissue. The results clearly demonstrated that while neural tissue from 1-day postnatal mice was 10 times more active in protein synthesis than brain tissue from adult mice, the former was many fold less active in translational events than fetal neural tissue from 13-day post-zygotic mice. Fetal polypeptide synthetic activity was found to decrease from the 13th day to the 19th day post-zygotic. This decrement in the translational activity was not due to amino acid availability or pools, or to differences, quantitatively or qualitatively, in polysome concentrations. The enhanced rate of protein synthetic activity measured with neural tissue from 13-day post-zygotic mice was shown to be due to an increase in rate of protein synthesis and not to an enhanced rate of protein degradation.     

A portable,adjustable finger printing stand

A lightweight finger printing stand is described which can be adjusted to the proper printing height. Based upon experience printing over 1,100 subjects, 12 advantages of using the stand are suggested.     

Optimal administration of dual screening tests for detecting a characteristic with special reference to low prevalence diseases.

We consider the problem of deciding optimally whether a characteristic exists based on one or two screening tests. We discuss the relative merits of giving either one or two tests, including the order in which they might be given, as well as their costs. Operating in the Bayesian mode, we derive posterior distributions for the accuracies of the tests and the prevalence of the characteristic. Applications to detecting rare conditions, such as the AIDS virus, are discussed.     

In vitro senescence of human keratinocyte cultures

Human keratinocytes have been serially cultivated in low (0.015 mM) and high (1.8 mM) calcium containing medium. The calcium concentration of the growth medium significantly influenced the cell growth period in vitro. Cells grown in low calcium medium underwent 35-40 population doublings over 16-17 passages, while cells grown in high calcium medium ceased to proliferate after 20 population doublings over 7 passages. Changing the keratinocytes from one in vitro environment to the other drastically altered the lifespan in culture of populations derived from the same primary tissue. The degree of DNA methylation of human keratinocytes was shown to decrease with age in both high and low calcium culture conditions but does not appear to be associated with differentiation.     

Heat-induced temperature sensitivity of outgrowing Bacillus cereus spores

Inactivation of Bacillus cereus spores during cooling (10 degrees C/h) from 90 degrees C occurred in two phases. One phase occurred during cooling from 90 to 80 degrees C; the second occurred during cooling from 46 to 38 degrees C. In contrast, no inactivation occurred when spores were cooled from a maximum temperature of 80 degrees C. Inactivation of spores at a constant temperature of 45 degrees C was induced by initial heat treatments from 80 to 90 degrees C. The higher temperatures accelerated the rate of inactivation. Germination of spores was required for 45 degrees C inactivation to occur; however, faster germination was not the cause of accelerated inactivation of spores receiving higher initial heat treatments. Repair of possible injury was not observed in Trypticase soy broth (BBL Microbiology Systems), peptone, beef extract, starch, or L-alanine at 30 or 35 degrees C. Microscopic evaluation of spores outgrowing at 45 degrees C revealed that when inactivation occurred, outgrowth halted at the swelling stage. Inhibition of protein synthesis by chloramphenicol at the optimum temperature also stopped outgrowth at swelling; thus protein synthesis may play a role in the 45 degree C inactivation mechanism.