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Biomedical subjects

D E Anderson

Publications and source records attributed to D E Anderson.

At least 253 records · Page 14Linked to original sources
PubMedDate not supplied

Extinction instead of incubation following classical aversive conditioning in dogs.

Two dogs received a single paired classical conditioning trial, with tone CS and 12 mA shock US. Both dogs then showed a conditioned blood pressure increase in response to the nonreinforced CS, which extinguished with additional nonreinforced presentations. The CR showed spontaneous recovery four days later, but reextinguished with additional nonreinforced presentations. The results were interpreted as not supporting Eysenck's theory of "incubation" following one-trial aversive conditioning.

Acoustic Stimulation↗
PubMedDate not supplied

High calcium intake does not prevent stress-salt hypertension in dogs.

Avoidance conditioning sessions and isotonic saline (1.3 L/day) were administered to dogs for 12 days under conditions of a low (0.1%) or high (1.5%) calcium diet. Twenty-four-hour mean arterial pressure increased comparably during the stress-salt conditioning periods on both the low (systolic: +16 +/- 5 mm Hg; diastolic: +6 +/- 2 mm Hg) and high (systolic: +17 +/- 4 mm Hg; diastolic: +11 +/- 4 mm Hg) calcium diets. Urine volume, sodium excretion, and serum calcium levels on the high calcium diet were not significantly different from those on the low calcium diet. In a second experiment, calcium was infused continuously for six days into the arterial circulation of normotensive or stress-salt hypertensive dogs at a rate of 0.12-0.23 mEq/min. Although serum calcium levels increased by up to 50% under these conditions, there were no significant effects on 24-hour levels of arterial pressure. In contrast to the protective effect of augmented potassium intake, these findings indicate that calcium intake does not influence the development of stress-salt hypertension in dogs.

Animals↗
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Cardiovascular responses to avoidance conditioning in the dog: effects of alpha adrenergic blockade.

Laboratory dogs were trained to press a response panel to postpone shocks during daily one-hour avoidance conditioning periods. Each dog was also confined in the experimental environment for 5 hours prior to the avoidance periods. Blood pressure and heart rate were monitored continuously during these experiments from chronically indwelling arterial catheters. Extended training resulted in the emergence of a cardiovascular response pattern during the pre-avoidance interval characterized by gradual increases in blood pressure together with decreases in heart rate. Elevations in both blood pressure and heart rate were sustained during the avoidance periods. During sessions in which alpha adrenergic activity was suppressed by phenoxybenzamine, absolute levels of blood pressure were found to be lower than during control (non-drug) sessions, but a progressive rise in blood pressure continued to be observed during pre-avoidance. These results suggest that sustained cardiovascular responses during avoidance periods are associated with activation of the sympathetic nervous system, but that the gradual rise in blood pressure during pre-avoidance is due to other factors.

Animals↗
PubMedDate not supplied

Total peripheral resistance changes in dogs during aversive classical conditioning.

The arterial pressure, heart rate, stroke volume, cardiac output and total peripheral resistance of laboratory dogs were monitored continuously before and during a 30 min period in which aversive classical conditioning procedures were applied. The experimental stimulation generated inhibition of behavioral activity ("freezing") together with sustained increases in arterial pressure averaging 30%, and increases in heart rate anc cardiac output of 60-70%. The calculated total peripheral resistance decreased by an average of 20%. The behavioral and cardiovascular responses were sustained during the aversive conditioning period. The results suggest that significant peripheral vasodilation occurred under these conditions which was probably not due to metabolic byproducts of behavioral activity, but probably reflected sympathetic cholinergic effects upon blood vessels in the skeletal muscles. These data document the significance of the skeletal muscle circulation in the total peripheral resistance to blood flow in unanesthetized animals.

Animals↗
PubMedDate not supplied

Time-series analysis of long-term cardiovascular response.

The purpose of this study was to illustrate the use of time-series analysis with long-term cardiovascular responding. Analyses of two successive 1000-minute mean blood pressure and heart-rate series in five chronically instrumented dogs showed that the autocorrelation function of the original series appeared highly nonstationary and that differenciation of the data produced a simple autocorrelation pattern which could be successfully modeled with stepwise autoregression. Evidence for reliable individual differences as well as change over sessions is presented and discussed.

Animals↗
PubMedDate not supplied

Preavoidance hypercapnia and decreased hematocrit in micropigs.

Previous studies found that regular confinement of dogs in an experimental environment preceding onset of an avoidance task was associated with increases in blood pressure and decreases in heart rate and respiration rate that were not prevented by adrenergic antagonists. The present study investigated a) whether divergent changes in blood pressure and heart rate also occur in micropigs preceding onset of an avoidance task, and b) the nature of changes in blood gases, plasma pH, plasma bicarbonate, hematocrit, and plasma electrolytes observed under these conditions. Blood pressure increased and heart rate decreased during 2-h preavoidance periods, whereas both blood pressure and heart rate were elevated during 20-min avoidance periods. During preavoidance periods, pO2, plasma pH, and plasma potassium pCO2 were decreased below home kennel levels during early preavoidance, whereas pCO2 and plasma bicarbonate were persistently increased and hematocrit was persistently decreased for the duration of the preavoidance periods. Each of these changes was reversed during the avoidance sessions. These findings suggest that behaviorally induced hypercapnia might participate in blood pressure regulation via increased renal sodium/hydrogen exchange and renal sodium retention.

Animals↗
PubMedDate not supplied

Synovial fluid analysis in cattle: a review of 130 cases.

OBJECTIVE: To compare synovial fluid characteristics of cattle with infectious and noninfectious arthritis. STUDY DESIGN: Retrospective cohort study. ANIMAL OR SAMPLE POPULATION: 130 cattle. METHODS: Synovial fluid was analyzed for total nucleated cell count (NCC), absolute number and percentages of polymorphonuclear (PMN) and mononuclear cells, total protein (TP) concentration, and specific gravity. Cattle were categorized as having infectious or noninfectious arthritis based on physical and lameness examinations, joint radiographs, and microbial culture results. Kruskal-Wallis 1-way analysis of variance was used to compare synovial fluid analysis data from different categories. Selection of cut-off values for the calculation of likelihood ratios, sensitivity, specificity, and positive and negative predictive values was based on examination of the distribution of the data using histograms. RESULTS: Cattle with infectious arthritis had significantly higher numbers of total NNC, PMN cells, TP concentration, and specific gravity (P = .0001) and a significantly higher percentage of PMN cells compared with cattle with noninfectious arthritis (P = .0001). The percentage of mononuclear cells was significantly higher in cattle with noninfectious arthritis (P = .0001). CONCLUSIONS: Synovial fluid analysis is useful for differentiation of infectious and noninfectious causes of joint disease in cattle. CLINICAL RELEVANCE: Cattle with a synovial fluid total NCC > 25,000 cells/microL, a PMN cell count > 20,000 cells/microL or more than 80% PMN cells, and TP > 4.5 g/dL should be considered to have infectious arthritis.

Animals↗
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Genetic study of eye cancer in cattle.

Heritabilities, phenotypic, and genetic correlations of lid and corneoscleral pigment and eye lesions associated with "cancer eye" were investigated in 2,831 Herefords from 34 herds in 21 states and one Canadian province. The results indicated that lid and corneoscleral pigment were heritable and genetically correlated. Corneoscleral pigment had a direct protective effect on lesions developing at the corneoscleral junction. Corneoscleral pigment and lesion development were apparently not genetically related, and lesion development was not heritable. These findings lead to the general conclusion that the genetic effect on pigment determines to a large extent the degree to which the eye is susceptible to some carcinogenic agent. The ultraviolet light component of sunlight is the most plausible carcinogenic agent that affects the eye. A genetic-environmental interaction is indicated, whereby an increasing amount of pigment lessens both susceptibility and the probability of lesion development, but whether lesions develop in the absence of pigment depends to a large extent on the amount of ultraviolet light to which the eye is exposed. The findings further indicate that the disease is controllable by selective breeding for increased amounts of lid pigment, which should lead to a correlated increase in lid and corneoscleral pigment and a decrease in lesions.

Aging↗
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Evaluation of a computerized review of patient physical symptoms.

This paper presents an evaluation of a medical history, data collection technique which appears to have sufficient economic justification and medical impact to consider for use in private practice and medically underserved settings. The method, which collects physical symptoms organized by bodily systems, has been tested in various medical settings, and has been implemented on a low-cost microcomputer system. The results are presented in terms of health benefit, economic impact, and medical impact, using effectiveness, feasibility, credibility, and economics as evaluation criteria.

Consumer Behavior↗
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Cardiovascular responses to avoidance conditioning in the dog: effects of beta adrenergic blockade.

Five laboratory dogs were trained to press a response panel to postpone shocks during 1-hr free-operant avoidance conditioning sessions. In addition, each dog was confined in the experimental environment for 1 hr immediately prior to each avoidance session. During these 2-hr sessions, blood pressure and heart rate were monitored continuously from indwelling catheters. After repeated exposure to the schedule, the onset of the avoidance contingency elicited acute increases in systolic and diastolic pressure and heart rate, which were maintained throughout the session. During the preavoidance interval, systolic and diastolic pressure increased gradually while heart rate decreased. Blockade of beta adrenergic receptor activity in these behaviorally-trained dogs by infusions of propranolol was associated with a significant attenuation of the tachycardia normally maintained during avoidance. Beta blockade did not prevent the rise in blood pressure or fall in heart rate during preavoidance. The results are consistent with the view that the cardiovascular pattern sustained during avoidance is mediated by activation of the sympathetic nervous system, but that the progressive change in cardiovascular activity during preavoidance intervals is mediated by other than sympathetic influences.

Animals↗
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Behavioral stress potentiates the blood pressure effects of a high sodium intake.

The present study examined the blood pressure effects of a high sodium intake administered during two levels of behavioral stress. In this double-blind study, 32 medical students were randomly assigned to receive either sodium chloride (high sodium) or placebo tablets (usual sodium). Resting blood pressure and body weight were recorded across a 14-day period preceding examinations (high stress) and during the summer when academic demands were reduced (low stress). The high sodium intake during the high stress period was associated with greater elevations in resting systolic blood pressure and mean arterial pressure than either the usual sodium intake during the high stress period or the high sodium intake during a low stress period. These findings suggest that behaviorally induced neuroendocrine responses can potentiate a blood pressure response to a high sodium intake.

Adult↗
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Inhibited breathing decreases renal sodium excretion.

This study tested the hypothesis that breathing at the upper end of the normal range of end tidal CO2 decreases renal sodium excretion. Normotensive human subjects learned to self-regulate end tidal CO2 using a respiratory gas monitor and feedback procedure. Urine flow rates were increased by a standardized water drinking regimen. Urinary volume and sodium and potassium excretion were decreased during 30 minutes of inhibited (i.e. high normal end tidal CO2) breathing, compared with levels preceding and after task performance. Blood pressure, but not heart rate, increased during task performance. Plasma volume increase under these conditions is indicated by the observation that urinary excretion of an endogenous digoxin-like factor was increased. The physiological mechanism by which inhibited breathing elicits renal sodium retention remains to be determined. This breathing pattern could mediate the role of behavioral stress in some forms of hypertension.

Adult↗