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Biomedical subjects

R D Phillips

Publications and source records attributed to R D Phillips.

At least 55 records · Page 3Linked to original sources
PubMed1983

Perinatal exposure to 60-Hz electric fields: effects on the development of the visual-evoked response in rats.

Two independent series of experiments were performed on 114 male Sprague-Dawley-derived, albino rat pups, which represented 61 litters in experimental series I and 53 litters in experimental series II. Animals were exposed for 20 h/day from conception to testing (postnatal days 11-20) to a vertical, 65-kV/m, 60-Hz electric field or sham-exposed. Recordings of the visual-evoked response (VER) were obtained using a small silver ball electrode placed epidurally over the visual cortex. Visual stimuli consisted of 10-microseconds light flashes delivered at 0.2 Hz. Computer-averaged VERs were obtained and power spectral analyses (fast Fourier transform) were performed on the tapered (split cosine-bell window), averaged VERs. The expected age-related changes were clearly evident; however, a detailed analysis of VER component latencies, peak-to-peak amplitude, and power spectra failed to reveal any consistent, statistically significant effect of exposure to 60-Hz electric fields.

Animals↗
PubMed1983

Hematologic and immunologic effects of pulsed microwaves in mice.

Mice were exposed in the far field in an anechoic chamber to 2,880-MHz pulsed microwaves 3 to 7.5 h daily, 5 days/week for 60 to 360 h. Three experiments were performed at average power densities of 5 mW/cm2 and six at 10 mW/cm2, corresponding to averaged specific absorption rates (SARs) of 2.25 and 4.50 mW/g, respectively. Each experiment consisted of eight mice, with a concurrently sham-exposed group of eight. In two of three studies at 5 mW/cm2, there was a significant increase in bone marrow cellularity in the microwave-exposed groups compared to the sham-exposed groups. Significant differences were occasionally seen in erythrocyte, leukocyte, and platelet values from microwave-exposed groups, but were not consistently observed. In one of six groups exposed at 10 mW/cm2, mean bone marrow cellularity was reduced significantly in the microwave-exposed mice; in another group, the lymphocyte count was increased. In only one exposure (10 mW/cm2 for 360 h) was any significant effect noted on serum proteins: a reduction to 5.1 +/- 0.3 g/dl in the exposed versus 5.6 +/- 0.4 g/dl in the sham-exposed mice. This was due to a decrease in alpha and beta globulins, with no effect on albumin or gamma globulin concentrations. No effect on bone marrow granulocyte/macrophage colony-forming units (CFU) was revealed following exposure of mice to pulsed microwaves at 5 mW/cm2. In one of four exposures at 10 mW/cm2, there was a significant increase in CFU-agar colonies. No significant effects of exposures at 10 mW/cm2 were observed on in vivo and in vitro assays of cell-mediated immune functions. No exposure-related histopathologic lesions were found from examination of several tissues and organs. Results of these series of exposures of mice at SARs of 2.25 and 4.50 mW/g indicated no consistent effects on the hematologic, immunologic, or histopathologic variables examined.

Animals↗
PubMed1982

Effects of 60 Hz-electric fields on specific humoral and cellular components of the immune system.

We evaluated humoral and cellular functions of the immune system of Swiss-Webster mice exposed to 60-Hz electric fields at 100 kV/m. No significant differences were observed in primary antibody response to keyhole limpet hemocyanin (precipitating antibody levels) between exposed (30 to 60 days) and control mice, nor were there significant changes in mitogen-stimulation response of spleen cells from mice similarly exposed for 90 or 150 days when compared to sham-exposed animals.

Animals↗
PubMed1982

A behavioral response of swine to a 60-Hz electric field.

It has been shown that rats, given the choice, will spend more time out of a 60-Hz electric field than in it at field strengths greater than or equal to 75 kV/m. This paper describes research to examine the relevance of these data to a different species, the pig. Miniature pigs that had been exposed to a 60-Hz electric field at 30 kV/m for 20 h/day, 7 days/week for as long as 6 months, were tested for their preference for the presence or absence of the field during a 23.5-h period. Similar to earlier results with rats, miniature pigs spent more time out of the electric field than in it during the sleeping period.

Animals↗
PubMed1982

Modification of the saturation kinetics model to produce a more versatile protein quality assay.

The saturation kinetics (SK) model relates response to nutrient (protein) intake in higher organisms by the equations: r = (bK1 + Rmax In)(K1 + In); where r is response and I is intake. Experimental data are fitted to this equation by interactive computer programs in which the intercept, b; a nutrition constant K1; an asymptotic response value Rmax; and an apparent kinetic order, n, are calculated. This model, unlike linear methods (PER, NPU) closely fits experimental data and predicts protein quality over a wide range of intake values. However, the SK model fails to converge to realistic values of Rmax and K1 unless protein of a sufficient quality or concentration or both, to produce a distinct plateau is fed. Also, the model may fail to distinguish statistically between the qualities of proteins which are easily differentiated by linear methods. These problems are ameliorated by assigning predetermined values to b and Rmax. When b was fixed as the mean response (body nitrogen) of rats fed protein-free diet, and Rmax was assigned a value related to the maximum response of rats fed an excess of high quality protein (casein), reasonable and statistically different values of K1 and n were predicted for casein, peanut protein and wheat gluten.

Animals↗
PubMed1982

In vitro assay for predicting protein efficiency ratio as measured by rat bioassay: collaborative study.

Seven laboratories collaborated in testing the calculated protein efficiency ratio (C-PER and DC-PER). The collaborative study required each laboratory to analyze 6 foods and a control protein (ANRC casein) for in vitro apparent protein digestibility, amino acid composition, and PER via rat bioassay. The 6 foods or food ingredients tested were nonfat dry milk, cooked chicken muscle, protein-fortified dry breakfast cereal, textured soy protein, oat-based dry breakfast cereal, and durum wheat flour. Data obtained from the study were analyzed statistically for the intralaboratory variation for each method of analysis (i.e., amino acid analysis, PER, etc.). The ability of the C-PER to rapidly predict rat PER was also measured. The C-PER and DC-PER methods were adopted official first action.

Amino Acids↗
PubMed1981

Endocrinological effects of strong 60-Hz electric fields on rats.

Adult male rats were exposed or sham-exposed to 60-Hz electric fields without spark discharges, ozone, or significant levels of other secondary variables. No effects were observed on body weights or plasma hormone levels after 30 days of exposure at an effective field strength of 68 kV/m. After 120 days of exposure (effective field strength = 64 kV/m, effects were inconsistent, with significant reductions in body weight and plasma levels of follicle-stimulating hormone and corticosterone occurring in one replicate experiment but not in the other. Plasma testosterone levels were significantly reduced after 120 days of exposure in one experiment, with a similar but not statistically significant reduction in a replicate experiment. Weanling rats, exposed or sham-exposed in electric fields with an effective field strength of 80 kV/m from 20 to 56 days of age, exhibited identical or closely similar growth trends in body and organ weights. Hormone levels in exposed and sham-exposed groups were also similar. However, there was an apparent phase shift between the two groups in the cyclic variations of concentrations of hormones at different stages of development, particularly with respect to follicle-stimulating hormone and corticosterone. We concluded that 60-Hz electric fields may bring about subtle changes in the endocrine system of rats, and that these changes may be related to alterations in episodic rhythms.

Animals↗
PubMed1981

Chronic exposure to 60-Hz electric fields: effects on pineal function in the rat.

As a component of studies to search for effects of 60-Hz electric field exposure on mammalian endocrine function, concentrations of melatonin, 5-methoxytryptophol, and serotonin-N-acetyl transferase activity were measured in the pineal glands of rats exposed or sham-exposed at 65 kV/m for 30 days. In two replicate experiments there were statistically significant differences between exposed and control rats in that the normal nocturnal increase in pineal melatonin content was depressed in the exposed animals. Concentrations of 5-methoxytryptophol were increased in the pineal glands of the exposed groups when compared to sham-exposed controls. An alteration was also observed in serotonin-N-acetyl transferase activity, with lower levels measured in pineal glands from exposed animals.

Animals↗
PubMed1981

Growth and metabolism of rodents exposed to 60-Hz electric fields.

There have been a number of reports in the literature concerning growth-related changes in various animal species exposed to high-strength electric fields. Many of the laboratories reporting such effects have not documented and controlled for the secondary factors that are associated with generating high-strength electric fields (ie, corona, ozone, harmonic distortion, cage vibration, spark discharge). We have designed an exposure system in which we eliminated or minimized these secondary factors, therefore enabling us to examine only the effects of electric fields per se. Sprague-Dawley rats and Swiss-Webster mice were exposed to 60-Hz electric fields at kV/m for up to four months. In 17 individual experiments, we found a greater number of experiments in which the exposed rats had lower body weights than controls. This trend was not evident in data obtained from 14 individual mouse experiments. In more exhaustive growth studies, we found no significant differences in body weights, organ weights, or O2 consumption between exposed and sham-exposed controls. Our failure to detect any major changes in growth was probably the result of eliminating or minimizing the secondary factors associated with electric field exposure.

Animals↗
PubMed1981

Linear and nonlinear models for measuring protein nutritional quality.

Several widely used linear methods for assessing protein nutritional quality were compared to a nonlinear model. Male, weanling Sprague-Dawley rats were fed diets containing 2--31% casein, peanut and wheat gluten protein for 4 weeks. One control group received a protein-free diet and another was killed at the start of the experiment. Nitrogen intake and animal response in terms of body weight and nitrogen were measured for each rat. PER, NPR, NPU, linear regression (LR) slopes and saturated kinetics (SK) parameters were calculated from the data. The linear models provide a single estimate of protein quality, while the SK model can estimate quality at any point along the intake-response curve. At maintenance (delta Body Weight or delta Body Nitrogen = 0) the SK model ranked peanut and gluten protein higher relative to casein than the linear methods, while at higher protein intakes the SK model gave lower relative rankings to those proteins. The SK model closely fit the experimental data over the entire intake-response range but did not converge to a meaningful solution when an insufficient quality of quantity of protein was included in the diet. Unlike the linear models, the SK model failed to distinguish statistically between the quality of proteins in several cases.

Animals↗
PubMed1980

High-performance liquid chromatographic analysis of the mycotoxin citrinin and its application to biological fluids.

Citrinin is a toxic metabolite produced by several species of Penicillium and Aspergillus. Citrinin is nephrotoxic and has been implicated in disease outbreaks in animals and humans. Citrinin was resolved in a sharp peak by reversed-phase high-performance liquid chromatography on a small-article (10 micrometers) column by elution in 4.25 min with a phosphoric acid (0.25 N)-acetonitrile-2-propanol solvent (55:35:10). Detection was by ultraviolet absorbance at 340 nm. The relationship between peak height and area and quantity injected was linear over a range of 2--50 ng at 340 nm and 5--200 ng at 365 nm. Retention time and peak area were highly reproducible. As little as 2--5 ng citrinin was detectable. Complete recovery of citrinin from plasma samples containing known quantities of [14C]citrinin was obtained over a range of 5--40 micrograms/ml by treatment of the plasma with 1 N hydrochloric acid followed by extraction with ethyl acetate. The method provides for the direct analysis of citrinin in urine and bile without prior extraction.

Animals↗
PubMed1980

Cardiovascular response of rats exposed to 60-Hz electric fields.

Recently, it has been reported that exposure to high-strength electric fields can influence electrocardiogram (ECG) patterns, heart rates, and blood pressures in various species of animals. Our studies were designed to evaluate these reported effects and to help clarify some of the disagreement present in the literature. Various cardiovascular variables were measured in Sprague-Dawley rats exposed or sham-exposed to 60-Hz electric fields at 80 or 100 kV/m for periods up to four months. No significant differences in heart rates, ECG patterns, blood pressures, or vascular reactivity were observed between exposed and sham-exposed rats after 8 hours, 40 hours, 1 month, or 4 months of exposure. Blood pressure and heart rate measurements, made during exposure to a 100-kV/m electric field for one hour, revealed no significant differences between exposed and sham-exposed groups. In addition, physiologic reserve capacity, measured in rats subjected to low temperature after exposure to 100 kV/m for one month, showed that electric-field exposure had no significant effect on physiological response to cold stress. Our studies cannot be directly compared to the work of other investigators because of differences in animal species and electric-field characteristics. However, our failure to detect any cardiovascular changes may have been the result of 1) eliminating secondary field effects such as shocks, audible noise, corona, and ozone; 2) minimizing steady-state micro-currents between the mouth of the animal and watering devices; and 3) minimizing electric-field-induced vibration of the electrodes and animal cages.

Animals↗
PubMed1980

Comparison of the coupling of grounded humans, swine and rats to vertical, 60-Hz electric fields.

Published and new data for grounded humans, swine, and rats exposed to vertical, 60-Hz electric fields are used to determine field strengths at the surfaces of the bodies and average components of induced-current density along the axes of the bodies. At the tops of the bodies, surface electric fields are increased (enhanced) over the unperturbed field strength present before the subjects entered the field by factors of 17, 7, and 4 for humans, swine, and rats, respectively. For an unperturbed field strength of 10 kV/m, average induced axial current densities in the neck, chest, abdomen, and feet are: 550, 190 250, and 200 nA/cm2, respectively, for humans; 40, 13, 20, and 1100 nA/cm2, respectively, for swine; and 28, 16, 2, and 1400 nA/cm2, respectively, for rats. These data are used to show that the actual electric fields experienced by animals depend strongly on the shape of the body and its orientation relative to the electric field and ground plane. This fact must be taken into account if biological data obtained with laboratory animals are to be used for the assessment of possible hazards to humans exposed to 60-Hz electric fields.

Animals↗
PubMed1980

Chronic exposure to a 60-Hz electric field: effects on synaptic transmission and peripheral nerve function in the rat.

Several reports have suggested that the nervous system can be affected by exposure to electric fields and that these effects may have detrimental health consequences for the exposed organism. The purpose of this study was to investigate the effects of chronic (30-day) exposure of rats to a 60Hz, 100-kV/m electric field on synaptic transmission and peripheral-nerve function. One hundred forty-four rats, housed in individual polycarbonate cages were exposed to uniform, vertical, 60-Hz electric fields in a system free of corona discharge and ozone formation and in which the animals did not receive spark discharges or other shocks during exposure. Following 30 days of exposure to the electric field, superior cervical sympathetic ganglia, vagus and sciatic nerves were removed from rats anesthetized with urethan, placed in a temperature-controlled chamber, and superfused with a modified mammalian Ringer's solution equilibrated with 95% O2 and 5% CO2. Several measures and tests were used to characterize synaptic transmission and peripheral-nerve function. These included amplitude, area, and configuration of the postsynaptic or whole-nerve compound-action potential; conduction velocity; accommodation; refractory period; strength-duration curves; conditioning-test (C-T) response, frequency response; post-tetanic response; and high-frequency-induced fatigue. The results of a series of neurophysiologic tests and measurements indicate that only synaptic transmission is significantly and consistently affected by chronic (30-day) exposure to a 60-Hz, 100-kV/m electric field. Specifically, and increase in synaptic excitability was detected in replicated measurements of the C-T response ratio. In addition, there are trends in other data that can be interpreted to suggest a generalized increase in neuronal excitability in exposed animals.

Action Potentials↗
PubMed1980

Effects of 60-Hz electric fields on avoidance behavior and activity of rats.

In repeated short-term tests (four sessions, each of 45-minute duration), and one longer test (a 23.5-hour session), behavior of rats was evaluated in a long, narrow shuttlebox. One side of the box was exposed to an electric field at various strengths, while a visually identical opposite side was shielded from exposure. In the short-term tests, rats generally remained shielded from electric fields of 90 kV/m and greater during the first session, and maintained this response in subsequent sessions. In the longer test, this same preference response was demonstrated at field strengths of 75 kV/m and greater; however, at 25 and 50 kV/m, rats exhibited a statistically significant preference for the exposed region of the shuttlebox, but only during the light portion of a 12-hour light: 12-hour dark cycle. Exposed animals made more traverses than sham-exposed controls between the two ends of the shuttlebox during the first hour of the test. The experimental data support the hypothesis that the observed behavioral effects are the result of direct interaction of the electric field with the animal, and not the result of secondary factors such as electric shocks, corona discharge, audible noise, ozone, or vibration of the experimental apparatus.

Animals↗