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Biomedical subjects

R G Allen

Publications and source records attributed to R G Allen.

At least 109 records · Page 6Linked to original sources
PubMed1984

Effects of diethyldithiocarbamate on life span, metabolic rate, superoxide dismutase, catalase, inorganic peroxides and glutathione in the adult male housefly, Musca domestica.

The effect of inactivation of superoxide dismutase, by diethyldithiocarbamate, on life span, metabolic rate, superoxide dismutase activity, catalase activity, inorganic peroxide concentration and glutathione levels in adult male houseflies was determined. The general objective was to examine the role of free radical defenses in the aging process. Houseflies were administered 0. 1 and 10 mM diethyldithiocarbamate in their drinking water. Administration of diethyldithiocarbamate caused an extension in the average life spans of the populations while the metabolic rates were depressed. Superoxide dismutase activity was significantly reduced. Inorganic peroxide concentration and catalase activity declined in rough correspondence to the decrease in the metabolic rate. The levels of reduced glutathione were significantly elevated whereas oxidized glutathione concentrations remained relatively unaffected. The results are interpreted to indicate that a decrease in superoxide dismutase activity in the housefly, by diethyldithiocarbamate administration, is compensated by an elevation in reduced glutathione levels and reduction of oxygen consumption, suggesting the existence of alternative free radical defenses in vivo.

Animals↗
PubMed1984

Effect of age on oxygen consumption, superoxide dismutase, catalase, glutathione, inorganic peroxides and chloroform-soluble antioxidants in the adult male housefly, Musca domestica.

The objective of this study was to determine whether aging in the housefly is associated with a general decline in the efficiency of the mechanisms protective against the intermediates of oxygen metabolism. The rate of oxygen consumption, activities of superoxide dismutase (total and cyanide-insensitive) and catalase, and levels of inorganic peroxides, glutathione (GSH and GSSG) and chloroform-soluble antioxidants were measured in adult male houseflies at different ages. Rate of oxygen consumption declined in flies approaching the average life span of the population. Activity of total and cyanide-insensitive superoxide dismutase decreased during the last trimester of life. Catalase activity steadily declined with age while the concentration of inorganic peroxides gradually increased during the later two-thirds of the average life span. Levels of total glutathione and GSH decreased during later half of life whereas the relative concentration of GSSG increased during this period. The concentration of chloroform-soluble antioxidants sharply declined during the first half of life. These results are interpreted to suggest that the enzymatic and non-enzymatic defenses against oxygen free radicals and hydroperoxides tend to deteriorate with age in the adult housefly.

Aging↗
PubMed1984

Effect of physical activity on superoxide dismutase, catalase, inorganic peroxides and glutathione in the adult male housefly, Musca domestica.

Average and maximum life spans of the adult male housefly are considerably prolonged by the elimination of flying activity. The objective of this study was to elucidate further the biochemical basis of this phenomenon. Activities of the enzymes superoxide dismutase and catalase, and the concentrations of inorganic peroxides and glutathione were compared between houseflies kept under conditions of relatively high and low levels of physical activity at different ages. The activities of superoxide dismutase and catalase were not appreciably affected by the level of physical activity whereas the concentrations of inorganic peroxides and glutathione were higher in flies undergoing relatively high level of physical activity. These results are interpreted to support the concept that by-products of oxygen metabolism may play a causal role in the aging process.

Aging↗
PubMed1984

Steady-state visual evoked responses in anesthetized monkeys.

Steady-state stimuli are repeated continuously at a frequency that evokes averaged EEG waveforms with components at a frequency which is the same or some multiple of the stimulus rate. A variety of stimulus parameters are readily manipulated and controlled. We wished to assess the suitability of this approach for animal experimentation, and chose to evaluate steady-state visual evoked potential (VEP) responses to counterphased checkerboard stimuli in anesthetized adult male Rhesus monkeys. Large VEPs were reliably produced over the range of 3-6 Hz reversal rate; at 10 Hz, the VEP spectral power was clearly diminished in all monkeys. At each given reversal rate, monkeys differed substantially in variability and amount (up to 3-fold) of spectral power. These large inter-subject differences paralleled what we have seen in similar studies of unanesthetized humans. All monkeys developed large VEPs at the midline, but the topographic distribution of maximum VEP was not uniform; in 3 monkeys the power was much greater over one hemisphere than the other. Fatigue or habituation was not evident; in each monkey, there were usually no significant differences in VEP power over the 3 consecutive 30 sec segments of a given stimulation. We conclude that the anesthetized monkey can be a suitable model for study of steady-state phenomena, as long as the proper stimulus parameters are employed and as long as the level of variance is taken into account.

Anesthesia, General↗
PubMed1984

Effect of diamide administration on longevity, oxygen consumption, superoxide dismutase, catalase, inorganic peroxides and glutathione in the adult housefly, Musca domestica.

The role of glutathione as an antioxidant was examined in the adult housefly by the administration of diamide, an oxidant of glutathione. Although diamide effectively oxidized glutathione, it also stimulated the synthesis of glutathione. Diamide induced a decrease in the rate of oxygen consumption and in the activity of superoxide dismutase. Diamide increased catalase activity and the concentration of inorganic peroxides at early ages. The results suggest that oxidation of glutathione induces counterbalancing adaptive changes in the housefly.

Animals↗
PubMed1984

Effects of paraquat administration on longevity, oxygen consumption, lipid peroxidation, superoxide dismutase, catalase, glutathione reductase, inorganic peroxides and glutathione in the adult housefly.

The effects of oxidative stress in the adult male housefly were examined by the administration of 1 mM paraquat. Houseflies exhibit NADH and NADPH-diaphorase activity. Paraquat caused a significant decrease in life span, metabolic rate and the concentration of thiobarbituric acid-reactants. Concentrations of reduced glutathione and inorganic peroxides were increased by paraquat. Paraquat stimulated the activity of catalase but did not affect activities of superoxide dismutase and glutathione reductase. The levels of oxidized glutathione and the rate of fluorescent age pigment accumulation were unaffected by paraquat. Results indicate that paraquat toxicity does not result from lipid peroxidation.

Animals↗
PubMed1984

Factors contributing to amplitude variability of the steady-state visual evoked response.

Ten steady-state visual evoked responses (VER's) were recorded from each of 47 normal, adult subjects. For each subject, the mean and SD for the 10 VER amplitudes were calculated and used to determine amplitude variability. Although some subjects produced extremely reliable VER's, data from the majority showed a considerable degree of variability. A number of factors including trend (the tendency of the VER amplitudes to increase or decrease with repeated measurements), noise, attention, binocularity, accommodation, eye movements, artifacts, and electrode placement were evaluated to determine their relative contributions to this variability. Noise and trend factors produced a large proportion of the variability (75%) whereas the other factors were found to be relatively insignificant.

Accommodation, Ocular↗
PubMed1983

Effect of catalase inactivation on levels of inorganic peroxides, superoxide dismutase, glutathione, oxygen consumption and life span in adult houseflies (Musca domestica).

The effects of total inhibition of catalase, induced by 3-amino-1,2,4-triazole, on the adult housefly (Musca domestica) were examined. The lack of catalase activity had no effect on the longevity of the houseflies. Inorganic-peroxide concentration was elevated at younger ages, but declined in older flies. The rate of oxygen consumption by the flies was greatly decreased and the levels of oxidized as well as reduced glutathione were augmented. Superoxide dismutase activity showed a slight increase. This study suggests that loss of catalase activity does not affect survival of houseflies due to adaptive responses.

Amitrole↗
PubMed1983

Contrast effects of the three primary colors on human visual evoked potentials.

In this study we evaluated in humans the question of whether contrast effects with patterned color stimuli varied in the same way as is known to occur with black-and-white stimuli. Using a counterphasing checkerboard pattern, we evaluated the steady-state visual evoked potential (VEP) in 10 subjects for the response to different contrast levels in each of the 3 primary colors. Overall mean luminance of each color was photometrically equated and kept constant during all trials. The VEP was computer-averaged for 90 consecutive 1 sec epochs of stimulation, and the power at the appropriate frequency was calculated. For each color, the contrast-response curves revealed small power values at low contrast (0.1) and larger power at the 3 high-contrast settings (0.3-0.5). Power varied markedly by color and by subject. The shape of the curves, depending on color and subject, often indicated a saturation of response. A given subject commonly had a physiologically 'preferred' color in that the power with that color was consistently larger. Most subjects had definite subjective color 'preferences,' believing that they perceived the contrast better for one or two colors. However, these impressions were often not validated by the VEP responses to the various colors. These results indicate that white-light VEP responses may not necessarily reflect the response characteristics of specific colors, nor do they necessarily reflect the large inter- and intra-subject differences in color responses noted in this study.

Adult↗
PubMed1983

Clinical outcome as assessed by anthropometric parameters, albumin, and cellular immune function in high-risk infants receiving parenteral nutrition.

Twelve infants with underlying gastrointestinal tract disorders receiving 16 courses of total parenteral nutrition were retrospectively studied. Stratification according to calorie intake provided the best means for discriminating among different outcomes. Infants receiving greater than 110 calories/kg/d experienced significantly greater increases in weight, mid-arm muscle circumference, and triceps and subscapular skinfold thicknesses than did infants receiving less than 110 calories/kg/d. Catch-up growth was only seen in infants with intakes of greater than 110 calories/kg/d. In nine of these 12 infants, in vitro cellular immune parameters were assayed. Infants in both the high- and low-calorie groups experienced similar increases in transformational responses to pokeweed mitogen (PWM) and phytohemagglutinin (PHA) and in the percentage of peripheral blood T lymphocytes. No increase in serum albumin was seen regardless of calorie intake.

Anthropometry↗
PubMed1983

Amplitude variability of the steady-state visual evoked response (VER).

The reliability of steady-state visual evoked responses (VER's) was determined for nine normal subjects using Fourier analyses with 1.0 and 0.25 Hz bin resolutions. No correlations were found between VER amplitudes and subjects' reports of attention, accommodation, fixation, or perceived organization of the stimulus. Across subjects, there was also no sustained amplitude modulation of the VER by any frequency (including alpha), and frequency drift of the VER did not contribute significantly to its amplitude variability. Modeling, using mixed sine waves to simulate different signal/noise (S/N) ratios, established that a significant portion of VER amplitude variability can be accounted for by noise which occurs at the same frequency as the VER and which is not removed by ensemble averaging.

Adult↗
PubMed1983

Potassium-modulated secretion of immunoreactive melanocyte-stimulating hormone and endorphin from mouse neuro-intermediate lobes: evidence for stimulus-secretion uncoupling and rate sensitivity.

UNLABELLED: A multi-chamber perifusion system, capable of detecting transient secretory events, was used to define the roles of stepwise changes and gradients of K+ concentration in modulation of alpha-MSH and endorphin secretion. Fifteen dispersed mouse neuro-intermediate lobes per chamber were perifused with Dulbecco's Modified Eagle Medium at 0.5 ml/min. One-min fractions were collected. Ten min of 67 mM K+ elicited an immediate, very brief 4-fold increase in secretion of both hormones. Surprisingly, the return to normal K+ elicited a similar increase in secretion. Ten min K+-free medium produced an immediate decrease in secretion. Exposure to a 10-min 0-67 mM K+ gradient did not produce an increase in secretion; however, the stepwise return to normal K+, identical to that in the first experiment, elicited an immediate, brief increase in secretion. CONCLUSIONS: 1) The rapid decline in secretory activity during 67 mM K+ cannot be explained either by "down regulation" of receptors, since this secretagogue is not receptor-mediated, or by depletion of labile hormone, since a second secretory episode occurred immediately following termination of high K+. This suggests that some other cellular mechanism "uncouples" stimulus-secretory mechanisms. 2) Although depolarization with high K+ and hyperpolarization with K+-free medium were associated with increases and decreases, respectively, in secretion, it appears that it is the rate of ion flux rather than polarization which is responsible for stimulus-secretion coupling.

Animals↗
PubMed1983

Modified Shumacker repair of transposition of the great arteries. Surgical and angiocardiographic considerations.

Sixteen patients with transposition of the great arteries, 8 days to 2 1/2 years of age, underwent intra-atrial transposition of venous return by the modified Shumacker technique. A bipedicle flap of right atrial wall was used to direct vena caval return to the mitral valve, and a hinged viable flap of pericardium was used to form the lateral wall of the pulmonary venous pathway. Thirteen patients survived operation and are well to date. Two of the three nonsurvivors were less than 1 month of age at operation, and the third had an associated inlet ventricular septal defect and a straddling tricuspid valve. Early postoperative chest radiographs were compared with preoperative films in each patient. Postoperative findings included minor right pleural effusion in four, minor pneumothorax in two, and paralyzed right hemidiaphragm in one. Two patients required a permanent pacemaker because of the development of sick sinus syndrome 2 and 4 years postoperatively. Each preoperative angiocardiogram was reviewed and compared with postoperative studies in nine patients. The latter demonstrated absence of caval gradients in each, trivial baffle leaks in four, a moderate baffle leak in one, small residual ventricular septal defects in two, and mild tricuspid regurgitation in two patients.

Angiocardiography↗
PubMed1982

Differences among humans in steady-state evoked potentials: evaluation of alpha activity, attentiveness and cognitive awareness of perceptual effectiveness.

We examined some of the variables that were possible sources of the wide variability among and within human subjects in their steady-state visual evoked potentials (VEP) in response to continuously counter-phased visual stimuli (vertical bars). We found that within a given subject the magnitude of VEP was reasonably consistent during replicate trials under comparable conditions. However, across subjects there were enormous differences (as much as 17-fold) in the VEP magnitude (i.e. in the spectral power developed at the stimulus reversal frequency). These differences could not be explained by differences among subjects in arousal (alpha activity before or during stimulation), attentiveness (as indicated by reaction times to random cueing), or by a person's subjective impression of his responsiveness to stimulation.

Adult↗
PubMed1982

Life-lengthening effects of gamma-radiation on the adult housefly, Musca domestica.

Effects of gamma-irradiation on the life span of the adult housefly (Musca domestica) were examined in order to elucidate the relationship between metabolic rate, irradiation and longevity. Adult houseflies of both sexes, exposed to 0, 20, 40 and 66 kR of gamma-radiation, were housed under conditions of relatively high or low physical activity. The mean longevity of high activity males exposed to 20 and 40 kR exhibited a significant increase, whereas the average life span of all female populations, low activity males, and high activity males exposed to 66 kR was significantly decreased following irradiation. Radiation exposure caused a reduction in the rate of oxygen consumption in both sexes as well as a decrease in the incidence of wing loss in the male flies. Analysis of the results suggests that radiation-induced life-lengthening in the housefly is a consequence of reduced metabolic activity.

Animals↗