Specifics about office spirometry.
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Costs and Cost Analysis↗
Biomedical subjects
N S Davis
Publications and source records attributed to N S Davis.
Resistivity of spores to ultraviolet and gamma radiation while exposed to ultrahigh vacuum or at atmospheric pressure.
Viability studies were conducted on microbial spores subjected to ultrahigh vacuum (UHV) in the 10(-9) to 10(-10) torr range. After 5 to 7 days in vacuum, they were exposed to ultraviolet (UV) or to gamma radiation either while still under vacuum or in the presence of dried air. Among the four test organisms subjected to UHV and ultraviolet radiation, Aspergillus niger was the most resistant; Bacillus megaterium, B. subtilis var. niger, and B. stearothermophilus were about equally less resistant. All four spores were more sensitive to ultraviolet radiation when UHV-dried than when desiccant-dried. Of the four test organisms subjected to UHV and gamma radiation, B. megaterium proved to be the most resistant; A. niger was the least resistant; and the remaining two organisms were of intermediate resistivity. All four organisms were less radiation resistant when UHV-dried than when irradiated in their normally hydrated state, and all showed an increased radiosensitivity after vacuum drying when oxygen was present. In addition, spores of B. subtilis var. niger and A. niger were less radiosensitive when UHV-dried and irradiated in vacuum than when "wet" and irradiated in air, whereas the reverse relationship was observed for the remaining two organisms. Based on the fact that microbial contaminants can be readily shielded from UV light by soils, metal particles, etc., and considering that the levels of ionizing radiations reported to be present in interstellar space are generally lower than those used in these experiments, the decrease in radioresistivity imparted by UHV drying is not of a sufficient magnitude to sterilize dependably portions of a spacecraft while on a mission.
Aspergillus↗
Exposure of microorganisms to simulated extraterrestrial space ecology.
Spores of five test organisms, Bacillus subtilis var. niger, Bacillus megaterium, Bacillus stearothermophilus, Clostridium sporogenes and Aspergillus niger and soils were exposed, while under ultra high vacuum to temperatures of from -190 degrees C to +170 degrees C for 45 days. Up to a temperature of 25 degrees C no loss in viability of the test spores were noted when compared to original populations maintained at room temperature at atmospheric pressure over a desiccant. At elevated temperatures differences in resistivity occurred so that at 88 degrees C only B. subtilis var. niger and A. niger survived in appreciable numbers. At 107 degrees C only A. niger spores survived, but none were recoverable after exposure to 120 degrees C. In comparison B. subtilis var. niger survived at atmospheric pressure and 90 degrees C for 5 days while none of the other spores were viable after 48 hours. Four groups of organisms in soil, mesophilic aerobes and anaerobes, molds and actinomycetes were similarly tested in the vacuum chamber. From one soil sample only actinomycetes survived 120 degrees C, whereas one other soil sample yielded viable bacteria after exposure to 170 degrees C. The resistance of the isolates to high temperatures in the absence of soil is being evaluated. Several organisms have been found to resists 120 degrees C in ultra-high vacuum for 4-5 days, and experiments at higher temperatures are in progress. When irradiated with gamma rays from a cobalt-60 source, there was a difference between vacuum dried test spores irradiated while still under vacuum to those exposed to air immediately before irradiation. A reduction of from one-third to one-ninth of the viability of spores irradiated in vacuum occurred with vacuum-treated spores irradiated in air.
Aspergillus niger↗
Effect of catheter composition on sperm quality.
Bladder catheterization for collection of retrograde ejaculates is commonly practiced, although previous studies have shown that materials used in the manufacture of the catheters may be toxic to sperm. Potential toxicity is particularly relevant to electroejaculation, as sperm from anejaculatory individuals undergoing this procedure characteristically exhibit poor motility and viability. To determine the effect of short-term exposure to various catheter materials on sperm quality, donor semen was diluted with BWW medium and aliquots incubated for 1 and 5 minutes with segments of four different catheters. The catheters were composed of latex, silicone rubber, polytetrafluoroethylene (Teflon), and radio-opaque Teflon, respectively. Following incubation, eosin-nigrosin staining for viability was performed and sperm motility assessed using computer-assisted sperm analysis (Cellsoft, Cryo Resources, Ltd). In the second phase of the study, donor semen was incubated with catheter segments coated with 0.3 ml of a water-soluble, nontoxic lubricant (Cellulosagel, Lederle) to evaluate whether the combination adversely affects sperm. Percent motility and viability for the semen specimens incubated with the four catheters alone did not differ significantly from control values either at 1 or at 5 minutes (P = 0.3, motility; P = 0.6, viability). The addition of lubricant did not change the catheter data significantly, indicating the absence of independent or synergistic toxicity (P = 0.5, motility; P = 0.4, viability). This study provides substantial evidence that brief exposure to conventional catheters, with or without a nontoxic lubricant, does not adversely affect sperm motility or viability.(ABSTRACT TRUNCATED AT 250 WORDS)
Catheters, Indwelling↗