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Biomedical subjects

J E Alexander

Publications and source records attributed to J E Alexander.

At least 73 records · Page 4Linked to original sources
PubMed1979

Hemodynamic effects of xylazine in the calf.

The hemodynamic effects of sedative level doses of xylazine in five chronically instrumented calves were studied. These effects included immediate and prolonged reductions in heart rate, cardiac output, arterial blood pressure, and left ventricular dp/dt max. Stroke volume showed an initial decrease in value with a return in 15 minutes to base-line values. Total peripheral resistance, end-diastolic left ventricular pressure, end-diastolic left ventricular volume, and left ventricular residual fraction were increased after drug administration. The results indicate that a depressed myocardium results from xylazine administration. With one exception (the absence of a hypertensive response), these effects largely parallel, both quantitatively and qualitatively, those seen with this drug in other species. Sedation by xylazine is produced in cattle at doses which are small compared to those which is required for sedation in other species. These same small doses in cattle also cause hemodynamic changes.

Animals↗
PubMed1975

Effect of starvation on renal metabolism in the rat.

The effects of starvation on the acid-base status of the rat and on the glucoeogenic and ammoniagenic capacity of rat renal-cortical slices were examined. Starvation for 48 or 72 hr did not affect acid-base status, and urinary ammonia production did not change. Kidney cortical slices from starved as compared to fed rats showed increased gluconeogenic capacity when incubated with the substrated pyruvate, succinate, fumarate, malate, 2-oxyoglutarate, glutamine and glutamate. Renal cortical tissue from starved rats also had increased activity of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase. Renal cortical slices from starved rats did not differ from those from fed rats in the ability to produce ammonia from glutamine or glutamate, nor was there any difference inhe activity of glutaminase between these groups. These results show that renal gluconeogenic capacity is increased in starved rats in the absence of systemic acidosis, and starvation does not lead to an increase in urinary ammonia excretion or renal ammoniagenic capacity.

Acid-Base Equilibrium↗
PubMedDate not supplied

Hemispheric differences for P300 amplitude from an auditory oddball task.

The P3(00) event-related potential (ERP) was elicited in 80 normal, right-handed male subjects using a simple auditory stimulus discrimination task, with electroencephalographic (EEG) activity recorded at 19 electrodes. P300 amplitude was larger over the right compared to left hemisphere electrode sites primarily at anterior-medial locations (F3/4, C3/4) for both target and standard stimuli. The N100, P200, and N200 components also demonstrated several similar, albeit less robust, hemispheric asymmetries. No hemispheric effects for P300 latency were observed, with few consistent latency findings for any of the other components obtained. The results suggest that the discrimination process underlying P300 generation may originate with right frontal activation.

Acoustic Stimulation↗
PubMedDate not supplied

Developmentally advanced EEG alpha power in gifted male and female adolescents.

An electroencephalographic (EEG) study of gifted and average ability male and female adolescents, as well as college students of both sexes, was conducted to investigate further the relative contributions the left and right cerebral hemispheres during an eyes open (baseline) task in all groups. A total of 90 subjects had baseline EEG recorded in three groups with equal numbers of males and females: 30 gifted adolescents, 30 average ability adolescents, and 30 college-age subjects. Overall alpha power (8-12 Hz resting potential) was significantly greater in average ability subjects compared to both college-age subjects. Moreover, there were no significant differences in overall alpha power between college-age and gifted adolescent subjects. However, college-age and gifted adolescent subjects had different RH/LH patterns of activation such that at temporal and parietal locations college-age and gifted adolescent subjects had greater LH alpha power levels whereas gifted adolescents had greater RH alpha power. These findings suggest that gifted adolescents may have a developmentally enhanced state of brain activity, one that more closely resembles that of college-age adults to whom they also resemble in terms of cognitive development.

Adolescent↗