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Biomedical subjects

R M Bailey

Publications and source records attributed to R M Bailey.

At least 19 recordsLinked to original sources
PubMed2007

Late Pleistocene human skull from Hofmeyr, South Africa, and modern human origins.

The lack of Late Pleistocene human fossils from sub-Saharan Africa has limited paleontological testing of competing models of recent human evolution. We have dated a skull from Hofmeyr, South Africa, to 36.2 +/- 3.3 thousand years ago through a combination of optically stimulated luminescence and uranium-series dating methods. The skull is morphologically modern overall but displays some archaic features. Its strongest morphometric affinities are with Upper Paleolithic (UP) Eurasians rather than recent, geographically proximate people. The Hofmeyr cranium is consistent with the hypothesis that UP Eurasians descended from a population that emigrated from sub-Saharan Africa in the Late Pleistocene.

Africa South of the Sahara↗
PubMed1986

Polycarbonate-polyether (PC-PE) flat sheet membrane: manufacture, structure and performance.

Polycarbonate-polyether (PC-PE) polymer, prepared by solution or interfacial polymerization, was used to produce a dry PC-PE diffusion membrane by means of the phase inversion technique. The mechanical stabilities and diffusive permeabilities of chloride, phosphate and vitamin B12 were determined for this membrane. Additionally, close control over manufacturing parameters allowed the study of the effects of varied membrane thickness (at constant ultrafiltration rate) and varied ultrafiltration rate (at constant membrane thickness) on solute diffusive permeabilities. Both increased ultrafiltration rate and decreased thickness resulted in an increase in solute diffusive permeabilities.

Humans↗
PubMed1984

Respiratory responses of humans exposed to an aerosol-gas pollutant mixture: multivariate contrast of a complex atmosphere to clean air and sodium chloride aerosol controls.

Data from a group of 20 subjects with normal baseline pulmonary function, who were exposed for 2 h to a test atmosphere containing a complex mixture of pollutants, have been contrasted with data from two other groups exposed to presumably non-toxic control atmospheres. Group 1 was exposed to clean air, group 2 was exposed to clean air containing sodium chloride aerosol at 270 micrograms m-3, and group 3 was exposed to the complex atmosphere containing sodium chloride (332 micrograms m-3) and zinc ammonium sulfate (23 micrograms m-3) aerosols plus nitrogen dioxide (0.5 ppm) and sulfur dioxide (0.5 ppm). These atmospheres (ranked according to the presumed relative toxicities of the components; clean air = 0, sodium chloride = 1, complex mixture = 2) were contrasted using multiple regression and partial correlation analyses. The effects of exposure to the complex gas-aerosol mixture on forced expiratory performance were not significantly different from those observed in subjects exposed to clean air or to sodium chloride aerosol.

Adolescent↗
PubMed1984

Time course of exercise-induced bronchoconstriction in asthmatics exposed to sulfur dioxide.

Young adult asthmatic volunteers (N = 17) were exposed to 0.75 ppm sulfur dioxide (SO2) for 3-hr periods, exercising vigorously for the first 10 min and resting thereafter. Specific airway resistance (SRaw) and symptoms were recorded preexposure, immediately postexercise, and after 1, 2, and 3 hr of exposure. Symptoms and SRaw were significantly increased after exercise, relative to preexposure measurements. Group mean SRaw and symptom increases were no longer significant at 1 hr. In a few individuals, effects may have persisted for 2 hr or more. On separate occasions, comparable exposures were conducted, and forced expiratory spirometry was performed preexposure and postexercise, in addition to the other tests. Inclusion of spirometry did not significantly affect the other results. Spirometry and SRaw showed nearly equal significance in changes postexercise. Thus, in general, asthmatics' bronchoconstriction induced by exercise in SO2 seems to reverse quickly with rest, even if SO2 exposure continues. Spirometry may be useful for studying pollution-induced bronchoconstriction when SRaw measurements are impractical.

Adult↗
PubMed1984

Comparative effects of sulfur dioxide exposures at 5 degrees C and 22 degrees C in exercising asthmatics.

Either airway cooling or sulfur dioxide (SO2) can induce bronchoconstriction in many asthmatics. Whether these two stresses act synergistically is a question with important public health implications. Eight young adult asthmatic volunteers were exposed to SO2 at 0.0, 0.2, 0.4, and 0.6 ppm, during 5 min heavy exercise at 5 degrees C, both with high (approximately 85%) and with low (approximately 50%) relative humidity. Physiologic response increased with increasing SO2 concentration but did not vary significantly with humidity. Symptom response was marginally greater at low than at high humidity. Twenty-four asthmatics were exposed similarly to clean air and to 0.6 ppm SO2, at 5 degrees C and also at 22 degrees C, always at high relative humidity. For this group, physiologic and clinical responses to SO2 (in excess of responses to clean air) were highly significant, regardless of temperature. The mean excess responses at 5 degrees compared with those at 22 degrees C were not statistically significant in clean air or SO2. Thus, moderate cold stress exacerbated the untoward response to SO2 only slightly and inconsistently in these asthmatic subjects.

Adolescent↗
PubMed1981

Exposures of human volunteers to a controlled atmospheric mixture of ozone, sulfur dioxide and sulfuric acid.

Nineteen human volunteers with normal pulmonary function and no history of asthma were exposed on two separate days to clean air and to an atmospheric mixture containing ozone (O3), 0.37 ppm, sulfur dioxide (SO2), 0.37 ppm, and sulfuric acid aerosol (B2SO4), 100 micrograms/m3. Subjects were exposed under carefully controlled conditions for two hours. During this period, the subjects alternately exercised for 15 minutes, at a level calculated to double minute ventilation, and rested for 15 minutes. The experimental goal was to determine whether the presence of the copollutants, H2SO4 and SO2, would significantly enhance the irritant potential of ozone, or cause decrements in pulmonary function on the order of 10 - 20 percent. Statistical analysis of the group averaged data suggested that the mixture may have been slightly more irritating to the subjects than was O3 alone. A large percentage of the subjects exhibited small decrements in pulmonary function. The group averaged FEV1.0 (forced expiratory volume in one second) on the exposure day was depressed 3.7 percent from the control value. One might expect O3 alone to depress FEV1.0 by about 2.8 percent under similar exposure conditions.

Adult↗
PubMed1981

Human exposure to ferric sulfate aerosol: effects on pulmonary function and respiratory symptoms.

Twenty normal and 18 asthmatic human volunteers were exposed to ferric sulfate aerosol at a nominal concentration of 75 microgram/m3 (equivalent to 20 microgram iron/m3). The concentration and particle size distribution (2 micron mass median aerodynamic diameter; geometric standard deviation of 3) were selected to simulate worst case ambient conditions. Ferric sulfate was chosen for study because it is toxic, it is a respiratory system irritant, and increased use of coal and high sulfur fuel oils will lead to increased concentrations of iron and sulfate in ambient air. A double-blind protocol was followed in which each subject was exposed on two days, separated by about a three week period. The subjects were exposed to clean air (sham) on one day and to ferric sulfate aerosol on the other (exposure); the order of exposure was selected randomly. Neither the subjects nor the staff performing the clinical testing were informed as to the nature of the atmosphere on any given day. Pulmonary function tests were performed immediately before (pre) and after (post) each 2 hr sham or exposure period; this protocol included intermittent exercise. Pre- and post-exposure symptom score interviews were also administered. On the average, the two groups of subjects did not exhibit significant pre- to post-changes in total respiratory system resistance, forced expiratory flow/volume performance, and single breath nitrogen washout parameters. None of the subjects reported more than slight changes in symptoms during exposure. Five individuals showed small but significant decremental trends in pulmonary function; however, nine subjects tended to improve after exposure.

Adolescent↗
PubMed1979

Controlled exposures of human volunteers to sulfate aerosols. Health effects and aerosol characterization.

Our laboratory has undertaken the study of possible acute adverse health effects of sulfate aerosols through controlled exposures of volunteer human subjects. Both healthy and asthmatic adult men were exposed for 2-hour periods (with intermittent exercise) to ammonium sulfate, ammonium bisulfate, and sulfuric acid of particle size distributions and concentrations intended to simulate "worst case" exposures during Los Angeles smog episodes. Lung function tests were performed by the subjects on entering and before exiting from a carefully controlled environmental chamber. Subject symptoms were evluated in a standardized manner. Aerosol concentrations and size distributions were determined by an on-line computer/aerometric monitoring system; gravimetric and chemical analyses were performed on impactor and total filter samples after test exposures. We found little or no evidence of adverse health effects from 2-hour multiple-day exposures to any of the compounds at "worst case" ambient concentrations.

Aerosols↗
PubMed1977

From professional monopoly to corporate oligopoly:the clinical laboratory industry in transition.

Until the mid-1960s the nonhospital clinical laboratory industry was dominated by pathologists. The ethics of medical professionalism protected the pathologists' market from price competition and from any serious threat from new entrants into the market. Immune from the competitive pressures of the marketplace, pathologists exerted monopoly control in local markets. That power was eroded by laboratories operated by technologists and bioanalysts and was finally overcome by the entry of large corporations into the industry. The market power of the largest corporate laboratories is now growing to a point where competition may again be thwarted. The professional ethics of pathologists allowed high prices, but there was little push toward higher volume. The commercial ethics of the corporate entrants brought lower prices but resulted in strong pressure for greater test quantities. In either case, the power wielded by the dominant producer would seem to go against the consumer's interests.

Automation↗