Chlorine resistance of poliovirus isolants recovered from drinking water

Poliovirus 1 isolants were recovered from finished drinking water produced by a modern, well-operated water treatment plant. These waters contained free chlorine residuals in excess of 1 mg/liter. The chlorine inactivation of purified high-titer preparations of two such isolants was compared with the inactivation behavior of two stock strains of poliovirus 1, LSc and Mahoney. The surviving fraction of virus derived from the two natural isolants was shown to be orders of magnitude greater than that of the standard strains. These results raise the question whether indirect drinking water standards based on free chlorine residuals are adequate public health measures, or whether direct standards based on virus determinations might be necessary.     

PCO(2) threshold for CNS oxygen toxicity in rats in the low range of hyperbaric PO(2).

Central nervous system (CNS) oxygen toxicity, as manifested by the first electrical discharge (FED) in the electroencephalogram, can occur as convulsions and loss of consciousness. CO(2) potentiates this risk by vasodilation and pH reduction. We suggest that CO(2) can produce CNS oxygen toxicity at a PO(2) that does not on its own ultimately cause FED. We searched for the CO(2) threshold that will result in the appearance of FED at a PO(2) between 507 and 253 kPa. Rats were exposed to a PO(2) and an inspired PCO(2) in 1-kPa steps to define the threshold for FED. The results confirmed our assumption that each rat has its own PCO(2) threshold, any PCO(2) above which will cause FED but below which no FED will occur. As PO(2) decreased from 507 to 456, 405, and 355 kPa, the percentage of rats that exhibited FED without the addition of CO(2) (F(0)) dropped from 91 to 62, to 8 and 0%, respectively. The percentage of rats (F) having FED as a function of PCO(2) was sigmoid in shape and displaced toward high PCO(2) with the reduction in PO(2). The following formula is suggested to express risk as a function of PCO(2) and PO(2) [abstract: see text] where P(50) is the PCO(2)for the half response and N is power. A small increase in PCO(2) at a PO(2) that does not cause CNS oxygen toxicity may shift an entire population into the risk zone. Closed-circuit divers who are CO(2)retainers or divers who have elevated inspired CO(2)are at increased risk of CNS oxygen toxicity.     

Erythrocyte membrane Ca2+ ATPase: reactivities of human A, AS, and S erythrocytes with steroid hormones

In a preliminary study we reported a significant enhancement of Ca2+ ATPase activity in sickle cell membranes in the presence of progesterone and testosterone. In this work the reactivity of various classes of steroid hormones with the membranes of hemoglobin variants was investigated. A consistent universal stimulation of Ca2+ ATPase activity in sickle cell membranes by the different classes of steroid hormones does not appear to correlate with any major structural differences of the hormones or the presence of reactive functional groups. The universal interaction of the hormones with sickle cell membranes probably enhances Ca2+ efflux through the Ca2+ ATPase without directly affecting the characteristics of the pump.     

Effects of industrial respirators on breathing pattern at different work levels

The effects of a filtering device and an air-line apparatus on breathing pattern were studied in healthy men with different physical characteristics and work capacity. The subjects comprised nine construction workers aged 35-44, and nine firemen aged 21-35. The construction workers' mean maximal oxygen consumption (VO2max) was 34.5 ml min-1 kg-1, the firemen's 66.9 ml min-1 kg-1. Breathing pattern was analyzed for its components, inspiratory time, expiratory time, breathing frequency, tidal volume, and pulmonary ventilation at rest, during two submaximal treadmill walks when the subjects' absolute work load was equal, and during recovery. Neither the filtering device nor the air-line apparatus had a significant effect on breathing pattern when compared with the control values measured twice with a low-resistance breathing valve. A significantly longer expiratory time, lower breathing frequency, and smaller pulmonary ventilation were found for the firemen with the breathing valve and the industrial respirators. The breathing pattern of the construction workers and the firemen differed, but the alterations were not induced by the use of the filtering device or the air-line apparatus when studied at aerobic work levels up to 60% VO2max.     

Animal housing influences the response of bone to spaceflight in juvenile rats.

The rat has been used extensively as an animal model to study the effects of spaceflight on bone metabolism. The results of these studies have been inconsistent. On some missions, bone formation at the periosteal bone surface of weight-bearing bones is impaired and on others it is not, suggesting that experimental conditions may be an important determinant of bone responsiveness to spaceflight. To determine whether animal housing can affect the response of bone to spaceflight, we studied young growing (juvenile) rats group housed in the animal enclosure module and singly housed in the research animal holding facility under otherwise identical flight conditions (Spacelab Life Science 1). Spaceflight reduced periosteal bone formation by 30% (P < 0.001) and bone mass by 7% in single-housed animals but had little or no effect on formation (-6%) or mass (-3%) in group-housed animals. Group housing reduced the response of bone to spaceflight by as much as 80%. The data suggest that housing can dramatically affect the skeletal response of juvenile rats to spaceflight. These observations explain many of the discrepancies in previous flight studies and emphasize the need to study more closely the effects of housing (physical-social interaction) on the response of bone to the weightlessness of spaceflight.     

Metabolism of palmitate in cultured rat Sertoli cells

Isolated rat Sertoli cells were incubated in the presence of [1-14C]palmitate at a cell concentration of 1.54 +/- 0.31 mg protein/flask (n = 7). The oxidation of palmitate was concentration dependent and maximal oxidation was obtained at 0.35 mM-palmitate. At a saturating concentration of palmitate the oxidation was linear for at least 6 h. About 65% of the total amount of palmitate oxidized during 5 h at 0.52 mM-palmitate (109 +/- 44 nmol/flask, n = 5) was recovered as CO2 and the rest as acid-soluble compounds. Almost all radioactive acid-soluble compounds which were secreted by the Sertoli cells were shown to be 3-hydroxybutyrate and acetoacetate. The palmitate recovery in cellular lipids and triacylglycerols was 9.4 +/- 5.1 nmol/flask (n = 5) and 3.5 +/- 2.8 nmol/flask (n = 5) respectively. Addition of glucose had no significant effect on palmitate oxidation but caused a 9-fold increase in esterification of palmitate into triacylglycerols. We conclude that cultured rat Sertoli cells can oxidize palmitate to CO2 and ketone bodies and that fatty acids appear to be a major energy substrate for these cells.