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Biomedical subjects

D E House

Publications and source records attributed to D E House.

At least 55 records · Page 3Linked to original sources
PubMed1988

Effect of ambient levels of power-line-frequency electric fields on a developing vertebrate.

Fertilized eggs of Gallus domesticus were exposed continuously during their 21-day incubation period to either 50- or 60-Hz sinusoidal electric fields at an average intensity of 10 Vrms/m. The exposure apparatus was housed in an environmental room maintained at 37 degrees C and 55-60% relative humidity (RH). Within 1.5 days after hatching, the chickens were removed from the apparatus and tested. The test consisted of examining the effect of 50- or 60-Hz electromagnetic fields at 15.9 Vrms/m and 73 nTrms (in a local geomagnetic field of 38 microT, 85 degrees N) on efflux of calcium ions from the chicken brain. For eggs exposed to 60-Hz electric fields during incubation, the chicken brains demonstrated a significant response to 50-Hz fields but not to 60-Hz fields, in agreement with the results from commercially incubated eggs [Blackman et al., 1985a]. In contrast, the brains from chicks exposed during incubation to 50-Hz fields were not affected by either 50- or 60-Hz fields. These results demonstrate that exposure of a developing organism to ambient power-line-frequency electric fields at levels typically found inside buildings can alter the response of brain tissue to field-induced calcium-ion efflux. The physiological significance of this finding has yet to be established.

Animals↗
PubMed1988

Influence of electromagnetic fields on the efflux of calcium ions from brain tissue in vitro: a three-model analysis consistent with the frequency response up to 510 Hz.

The frequency dependence of electromagnetic field-induced calcium-ion efflux from chicken brain tissues has been examined at 15-Hz intervals over the range 1-510 Hz. The electric field component was 15 Vrms/m and the magnetic component varied between 59 and 69 nTrms. No patterns of response as a function of frequency could be readily discerned when the differences in mean efflux values between exposed and sham samples were compared. However, the calculated P-value, a function that combines at each frequency the difference between the means of the exposed and sham groups with the variance of each group, does provide a basis for hypothesizing the existence of three frequency-dependent patterns in the data. One pattern includes all the highly significant (P less than .01) responses which occur between 15 and 315 Hz, at 30-Hz intervals; two independent trials at 165 Hz, giving nonsignificant responses (P greater than .5), break this pattern into two groups of five frequencies each, which is contrary to the expected result for a simple Lorentz-force interaction. However, another pattern of significant results at 60, 90, and 180 Hz, but not at 300 Hz, is consistent with a Lorentz-force model. A third pattern, composed of only one significant response at 405 Hz, is very close to the resonance predicted on a linear extrapolation from high-frequency data for 13carbon atoms. This hypothetical ordering of the frequency-response profile provides the basis for future experimental designs to test each possible interaction model and for their connection to the calcium-ion efflux endpoint.

Animals↗
PubMed1988

Extrathoracic and intrathoracic removal of O3 in tidal-breathing humans.

We measured the efficiency of O3 removal from inspired air by the extrathoracic and intrathoracic airways in 18 healthy, nonsmoking, young male volunteers. Removal efficiencies were measured as a function of O3 concentration (0.1, 0.2, and 0.4 ppm), mode of breathing (nose only, mouth only, and oronasal), and respiration frequency (12 and 24 breaths/min). Subjects were placed in a controlled environmental chamber into which O3 was introduced. A small polyethylene tube was then inserted into the nose of each subject, with the tip positioned in the posterior pharynx. Samples of air were collected from the posterior pharynx through the tube and into a rapidly responding O3 analyzer yielding inspiratory and expiratory O3 concentrations in the posterior pharynx. The O3 removal efficiency of the extrathoracic airways was computed with the use of the inspiratory concentration and the chamber concentration, and intrathoracic removal efficiency was computed with the use of the inspiratory and expiratory concentrations. The mean extrathoracic removal efficiency for all measurements was 39.6 +/- 0.7% (SE), and the mean intrathoracic removal efficiency was 91.0 +/- 0.5%. Significantly less O3 was removed both extrathoracically and intrathoracically when subjects breathed at 24 breaths/min compared with 12 breaths/min (P less than 0.001). O3 concentration had no effect on extrathoracic removal efficiency, but there was a significantly greater intrathoracic removal efficiency at 0.4 ppm than at 0.1 ppm (P less than 0.05). Mode of breathing significantly affected extrathoracic removal efficiency, with less O3 removed during nasal breathing than during either mouth breathing or oronasal breathing (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Evaluating the toxicity of urban patterns of oxidant gases. II. Effects in mice from chronic exposure to nitrogen dioxide.

The study reported herein evaluates the influence of a chronic exposure to an urban pattern of NO2 (continuous baseline exposure of 0.2 ppm, on which were superimposed two 1-h spikes of 0.8 ppm NO2, 5 d/wk) as compared to the baseline exposure to determine the contribution of the spikes to toxicity. Mice were exposed for up to 52 wk with interim examinations. Multivariate analysis of variance revealed a statistically significant treatment effect on infectivity (p = 0.05) and pulmonary function (p = 0.03) parameters. Infectivity mortality of mice in the spiked exposure regimen was significantly greater than that in either the NO2-background-exposed mice or in control mice. Four of the pulmonary function variables exhibited the greatest differences among the treatment groups: end expiratory volume, vital capacity, respiratory-system compliance, and multiple-breath nitrogen washout. Results from the pulmonary-function analyses indicate that the spiked exposures to 0.8 ppm NO2 may have induced a subtle lesion. The chronic study results indicate that the presence of spikes of NO2 is contributing significantly to effects on antibacterial lung defenses and pulmonary function of mice.

Administration, Inhalation↗
PubMed1987

Influence of exposure patterns of nitrogen dioxide and modifications by ozone on susceptibility to bacterial infectious disease in mice.

The nitrogen dioxide (NO2) diurnal cycle found in urban communities usually consists of a low basal concentration upon which are superimposed higher concentration peaks or spikes of short duration. Various components of this environmental exposure mode were examined to assess effects of urban exposure profiles on susceptibility to infectious pulmonary disease. Mice were exposed to NO2 peaks of 4.5 ppm for 1, 3.5, or 7 h, challenged with Streptococcus sp. either immediately or 18 h postexposure, and then observed for mortality. When the streptococcal challenges were immediately after NO2 exposure, the mortality rate was directly related to the length of peak exposure, whether or not a basal exposure was used, and all peak lengths significantly increased mortality. When the challenge was delayed for 18 h after the peak exposure, spiked exposures of 3.5 and 7 h increased mortality to the same degree. If a 1-h peak exposure to 4.5 ppm was superimposed twice daily upon a continuous basal NO2 concentration of 1.5 ppm, there was a suggestive trend toward increased mortality near the end of the second week of exposure when challenge occurred immediately after the morning spike. Studies were also conducted to examine interactions with ozone (O3) and NO2, since urban air typically contains both of these oxidants. Using various combinations of basal and spiked exposure levels of NO2 and O3, synergistic results were obtained for streptococcal-induced mortality.

Air Pollutants↗
PubMed1986

A nonparametric version of Williams' test for a randomized block design.

A large-sample nonparametric version of Williams' test for comparing increasing doses of a substance with a zero-dose control response is given for observations from a randomized block experimental design. The method is based on Friedman-type ranks. Williams' test and the nonparametric equivalent for a one-way design are briefly described. The validity of the new method is shown and a numerical example is given.

Animals↗
PubMed1985

Effects of ELF (1-120 Hz) and modulated (50 Hz) RF fields on the efflux of calcium ions from brain tissue in vitro.

We have previously shown that 16-Hz, sinusoidal electromagnetic fields can cause enhanced efflux of calcium ions from chick brain tissue, in vitro, in two intensity regions centered on 6 and 40 Vp-p/m. Alternatively, 1-Hz and 30-Hz fields at 40 Vp-p/m did not cause enhanced efflux. We now demonstrate that although there is no enhanced efflux associated with a 42-Hz field at 30, 40, 50, or 60 Vp-p/m, a 45-Hz field causes enhanced efflux in an intensity range around 40 Vp-p/m that is essentially identical to the response observed for 16-Hz fields. Fields at 50 Hz induce enhanced efflux in a narrower intensity region between 45 and 50 Vp-p/m, while radiofrequency carrier waves, amplitude modulated at 50 Hz, also display enhanced efflux over a narrow power density range. Electromagnetic fields at 60 Hz cause enhanced efflux only at 35 and 40 Vp-p/m, intensities slightly lower than those that are effective at 50 Hz. Finally, exposures over a series of frequencies at 42.5 Vp-p/m reveal two frequency regions that elicit enhanced efflux--one centered on 15 Hz, the other extending from 45 to 105 Hz.

Animals↗
PubMed1985

A role for the magnetic field in the radiation-induced efflux of calcium ions from brain tissue in vitro.

Two independent laboratories have demonstrated that electromagnetic radiation at specific frequencies can cause a change in the efflux of calcium ions from brain tissue in vitro. In a local geomagnetic field (LGF) at a density of 38 microTesla (microT), 15- and 45-Hz electromagnetic signals (40 Vp-p/m in air) have been shown to induce a change in the efflux of calcium ions from the exposed tissues, whereas 1- and 30-Hz signals do not. We now show that the effective 15-Hz signal can be rendered ineffective when the LGF is reduced to 19 microT with Helmholtz coils. In addition, the ineffective 30-Hz signal becomes effective when the LGF is changed to +/- 25.3 microT or to +/- 76 microT. These results demonstrate that the net intensity of the LGF is an important variable. The results appear to describe a resonance-like relationship in which the frequency of the electromagnetic field that can induce a change in efflux is proportional to a product of LGF density and an index, 2n + 1, where n = 0,1. These phenomenological findings may provide a basis for evaluating the apparent lack of reproducibility of biological effects caused by low-intensity extremely-low-frequency (ELF) electromagnetic signals. In future investigations of this phenomenon, the LGF vector should be explicitly described. If the underlying mechanism involves a general property of tissue, then research conducted in the ambient electromagnetic environment (50/60 Hz) may be subjected to unnoticed and uncontrolled influences, depending on the density of the LGF.

Animals↗
PubMed1985

Role of the parasympathetic nervous system in acute lung response to ozone.

We conducted an ozone (O3) exposure study using atropine, a muscarinic receptor blocker, to determine the role of the parasympathetic nervous system in the acute response to O3. Eight normal subjects with predetermined O3 responsiveness were randomly assigned an order for four experimental exposures. For each exposure a subject inhaled either buffered saline or atropine aerosol followed by exposure either to clean air or 0.4 ppm O3. Measurements of lung mechanics, ventilatory response to exercise, and symptoms were obtained before and after exposure. O3 exposure alone resulted in significant changes in specific airway resistance, forced vital capacity (FVC), forced expiratory flow rates, tidal volume (VT), and respiratory rate (f). Atropine pretreatment prevented the significant increase in airway resistance with O3 exposure and partially blocked the decrease in forced expiratory flow rates but did not prevent a significant fall in FVC, changes in f and VT, or the frequency of reported respiratory symptoms after O3. These results suggest that the increase in pulmonary resistance during O3 exposure is mediated by a parasympathetic mechanism and that changes in other measured variables are mediated, at least partially, by mechanisms not dependent on muscarinic cholinergic receptors of the parasympathetic nervous system.

Adolescent↗
PubMed1985

Reproducibility of individual responses to ozone exposure.

Because large intersubject differences in the magnitudes of response to a single ozone (O3) exposure have been observed, we undertook to determine if this variability were due to differences in intrinsic responsiveness to O3 or to other factors. Thirty-two subjects were exposed to 1 of 5 O3 concentrations (0.12, 0.18, 0.24, 0.30, or 0.40 ppm), and each underwent one or more repeat exposures separated by from 3 wk to 14 months. Magnitudes of change for pulmonary function variables, respiratory rate and tidal volume, and for reported symptoms were compared for the repeated exposures. Changes induced in forced expiratory spirometric measurements were highly reproducible for as long as 10 months and for all tested O3 concentrations of 0.18 ppm or greater. This high degree of reproducibility indicates that the magnitude of response to a single exposure is a precise estimate of that subject's intrinsic O3 responsiveness. We conclude that the previously observed intersubject variability in magnitude of O3-induced effects is the result of large differences in intrinsic responsiveness to O3.

Adolescent↗
PubMed1983

Effects of 0.1 ppm nitrogen dioxide on airways of normal and asthmatic subjects.

It has been reported (J. Clin. Invest. 57: 301-307, 1976) that inhalation of nitrogen dioxide (NO2) will enhance the bronchial reactivity of asthmatics. This study was designed to evaluate the respiratory effect of a 1-h exposure of normal subjects and of atopic asthmatics to 0.1 parts per million (ppm) NO2. Fifteen normal and 15 asthmatic subjects were exposed to air and to NO2 in a randomized double-blind crossover design. Exposure to either atmosphere was bracketed by bronchial inhalation challenge using aerosolized metacholine chloride solutions. Plethysmographic measurements of specific airway resistance (sRaw) and the forced random noise impedance spectrum (5-30 Hz) were obtained immediately after each methacholine dose. Following acute exposure to NO2, there was a slight but not significant increase in mean base-line sRaw in both normals and asthmatics. The overall base-line resistive properties of the respiratory system determined by forced random noise excitation were not significantly affected by NO2 inhalation either. Finally, there was no change in bronchial response to methacholine challenge in either group. These findings indicate that 0.1 ppm NO2 exposure for 1 h without exercise had no demonstrable airways effects in either young atopic asthmatics with mild disease or young normal subjects.

Adolescent↗
PubMed1983

Pulmonary effects of ozone exposure during exercise: dose-response characteristics.

Because minimal data are available regarding the pulmonary effects of ozone (O3) at levels less than 0.27 ppm, six groups of healthy young males were exposed for 2.5 h to one of the following O3 concentrations: 0.0, 0.12, 0.18, 0.24, 0.30, or 0.40 ppm. Fifteen-minute periods of rest and exercise (65 l/min minute ventilation) were alternated during the first 2 h of exposure. Coughing was observed at all levels of O3 exposure. Small changes in forced-expiratory spirometric variables [forced vital capacity (FVC), forced expiratory volume in 1 s, and mean expiratory flow rate between 25 and 75% FVC] were observed at 0.12 and 0.18 ppm O3, and larger changes were found at O3 levels greater than or equal to 0.24 ppm. Changes in tidal volume and respiratory frequency during exercise, specific airway resistance, the presence of pain on deep inspiration, and shortness of breath occurred at O3 levels greater than or equal to 0.24 ppm. In conclusion, pulmonary effects of O3 were observed at levels much lower than that for which these effects have been previously described. Stimulation of airway receptors is probably the mechanism responsible for the majority of observed changes; however, the existence of a second mechanism of action is postulated.

Adolescent↗
PubMed1980

Induction of calcium-ion efflux from brain tissue by radiofrequency radiation: effect of sample number and modulation frequency on the power-density window.

Changes have been found in calcium-ion binding to brain tissue exposed in vitro to a specific power density (0.83 mW/cm2) of 147-MHz radiation, amplitude modulated by a 16-Hz sine wave. This report replicates and extends this previous work. To define more precisely the range of effective power densities, two different numbers of samples were treated in a Crawford cell. In one series, four brain tissues were exposed at a time; in the other series, four brain tissues plus six dummy loads were exposed together. While the four-sample configuration produced a narrow power-density window, the ten pseudosample configuration resulted in a broader power-density window. The reason for the sample-number dependence is unresolved, but may be due to interactions between samples and field distortions caused by the close spacing. The ten pseudosample configuration was used to test for the presence and rage of a power-density window at a sinusoidal modulation frequency of 9 Hz. The response curve at 9 Hz was essentially identical to the results for 16-Hz sinewave modulation.

Animals↗
PubMed1980

Calcium-ion efflux from brain tissue: power-density versus internal field-intensity dependencies at 50-MHz RF radiation.

In previous experiments changes were found in calcium-ion efflux from chick-brain tissue that had been exposed in vitro to 147-MHz radiation across a specific range of power densities when the field was amplitude modulated at 16 Hz. In the present study, 50-MHz radiation, similarly modulated as a sinusoid, was found to produce changes in calcium-ion efflux from chick brains exposed in vitro in a Crawford cell. Exposure conditions were optimized to broaden any power-density window and to enhance the opportunity to detect changes in the calcium-ion efflux. The results of a power-density series demonstrated two effective ranges: One spanning a range from 1.44 to 1.67 mW/cm2, and the other including 3.64 mW/cm2, which were bracketed by no-effect results at 0.72, 2.17, and 4.32 mW/cm2. peaks of positive findings are associated with near-identical rates of energy absorption: 1.4 microW/g at 147 MHz, and 1.3 microW/g at 50 MHz, which indicates that the enhanced-efflux phenomenon is more dependent on the intensity of fields in the brain than on the power density of incident radiation. In addition, the phenomenon appears to occur at multiples of some, as yet unknown, rate of radiofrequency (RF) energy absorption. Because of the extremely small increments of temperature associated with positive findings (less than 4 X 10(-4) degrees C), and the existence of more than one productive absorption rate, a solely thermal explanation appears extremely unlikely.

Animals↗
PubMed1977

Cytogenetic effects of inhaled ozone in man.

Peripheral blood samples were collected from 30 normal male volunteers before and at intervals after inhaling 0.4 ppm ozone for 4 h. Data from 4 of the subjects were excluded from the analysis because of missing data points. The blood samples were cultured for 48 h, slides made and stained with a uniform Giemsa stain, and 100 metaphase spreads per subject per treatment scored for chromosome aberrations. Cells with suspected aberrations were photographed, destained, restained with a banding procedure and rephotographed to identify the specific chromosomes and regions involved. Pre-exposure, immediate post-exposure, 3 days post-exposure, 2 weeks post-exposure and 4 weeks post-exposure means for the percentage of cells with 46 chromosomes were 93.0, 93.6, 91.7, 94.5 and 94.2, respectively; in the same order, the mean number of cells with chromatid and/or chromosome breaks per order, the mean number of cells with chromatid and/or chromosome breaks per 100 cells was 0.96, 0.85, 1.00, 0.88 and 0.81 respectively, and for chromatid and/or chromosome gaps per 100 cells: 1.35, 0.96, 1.35, 0.81 and 0.77, respectively. The means for each of these parameters as well as the mean frequencies of complex aberrations are not statistically significantly different between blood sampling times. The distribution of aberrations by chromosome and light and dark bands is not significantly influenced by ozone exposure. These data indicate no apparent detectable human cytogenetic effect due to exposure to ozone under the conditions of this experiment.

Adult↗
PubMedDate not supplied

Neurobehavioral Evaluation System (NES): comparative performance of 2nd-, 4th-, and 8th-grade Czech children.

The Neurobehavioral Evaluation System was designed for field studies of workers, but many NES tests can be performed satisfactorily by children as young as 7 or 8 years old and a few tests, such as simple reaction time, can be performed by preschool children. However, little comparative data from children of different ages or grade levels are available. Studies of school children in the Czech Republic indicate that 2nd-grade children could perform the following NES tests satisfactorily: Finger Tapping, Visual Digit Span. Continuous Performance, Symbol-Digit Substitution, Pattern Comparison, and simpler conditions of Switching Attention. Comparative scores of boys and girls from the 2nd, 4th, and 8th grades and power analyses to estimate appropriate sample size were presented. Performance varied systematically with grade level and gender. Larger samples were needed with younger children to achieve comparable levels of statistical power. Gender comparisons indicated that boys responded faster, but made more errors than girls.

Adolescent↗