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Biomedical subjects

D K Gray

Publications and source records attributed to D K Gray.

9 recordsLinked to original sources
PubMed1984

Sampling problems and nonparametric solutions in clinical neuropsychological research.

Research data in clinical neuropsychology frequently do not conform to the requirements for parametric statistical analysis. In some of these cases, data analysis by parametric techniques does not identify existing differences. The usefulness of nonparametric statistical tools in evaluating irregular data sets is demonstrated in three cases examples. Methodological considerations arising from these examples are discussed.

Brain Damage, Chronic↗
PubMed1984

Nutritional status and lymphocyte function in maintenance hemodialysis patients.

Nutritional status and lymphocyte transformation were examined in 30 clinically stable men who underwent maintenance hemodialysis for 1 to 141 months. The men displayed decreased relative body weight, triceps and subscapular skinfold thickness, midarm circumference, midarm muscle circumference, serum total protein, albumin, transferrin, IgG, IgA, IgM, and C3 concentrations. There were many abnormalities in the plasma amino acid pattern. Lymphocyte transformation stimulated by phytohemagglutin or pokeweed mitogen was reduced. Many nutritional parameters correlated with each other and with the rate of lymphocyte transformation. There was a tendency (p = 0.06) for higher mortality in the malnourished patients during a mean follow-up period of 43.3 months. These findings suggest that clinically stable men undergoing maintenance hemodialysis are typically malnourished. Poor nutritional status may be a cause of impaired lymphocyte function. Malnutrition or wasting may indicate that the patient is at risk for a higher mortality rate.

Adult↗
PubMed1984

Renal effects of volume expansion in the renal-denervated nonhuman primate.

Experiments were performed to determine the role of renal nerves in mediating the renal excretory effects of volume expansion in the nonhuman primate. Male Macaca fascicularis monkeys underwent chronic bilateral renal denervation or sham surgery. After a 1- to 2-wk recovery period, each animal was anesthetized with pentobarbital sodium and volume expanded 20% of estimated blood volume. Two types of volume expansion were used, a hemodilutional expansion using 6% dextran in isotonic saline and an isohemic expansion using each monkey's own blood that had previously been withdrawn in exchange for dextran. Renal denervation did not attenuate the excretory responses to volume expansion in that similar increases in urine flow, sodium excretion, filtered load of sodium excreted, osmolar and free water clearances occurred in both the renal-denervated and sham-operated groups. The onset of the responses was not delayed by renal denervation. Furthermore, the results were the same with both volume expansions. These results suggest that, in the monkey, decreases in renal nerve activity that occur with volume expansion are not necessary for eliciting the excretory responses to this hypervolemic stimulus or that other factors compensate if the kidneys are chronically denervated. In addition, the failure of renal denervation to attenuate the excretory effects of a cell-free volume expansion is not related to any dilutional characteristics of the expansion.

Animals↗
PubMed1984

Head-up tilt in the nonhuman primate. Effects of renal denervation.

Experiments were performed to determine the role of the renal nerves in mediating the antinatriuresis of head-up tilt in the nonhuman primate. Male Macaca fascicularis monkeys underwent chronic bilateral renal denervation or sham surgery and were allowed a 1- to 2-week recovery period. After that time, each animal was anesthetized with sodium pentobarbital and subjected to 40 min of 35 degrees head-up tilt. Renal perfusion pressure was maintained constant throughout the experiment. Tilt caused significant decreases in urine flow, sodium excretion and osmolar clearance and increases in urine osmolality in both groups. Creatinine and para-aminohippurate clearances decreased in the sham-operated animals but were unchanged in the denervated animals. Although the pattern of the renal excretory responses showed some group differences in that a significant antidiuresis and antinatriuresis occurred after 10 min of tilt in the sham-operated group but not until 20 min in the denervated group, the magnitudes of these excretory responses were similar in both groups throughout the entire tilt procedure. These results suggest that, in this species, the renal nerves are not necessary for eliciting the overall antinatriuretic response to orthostasis but may have some minor involvement in the onset of the response.

Animals↗
PubMed1982

Biphasic effects of ethanol on open-field activity: sensitivity and tolerance in C57BL/6N and DBA/2N mice.

Male C57BL/6N (C57) and DBA/2N (DBA) inbred mice were found to differ in open-field behavior after an acute ip injection of ethanol and in the development of tolerance to repeated injections. DBA mice showed only increased activity for 28 min after ethanol doses up to 2.67% g/kg when compared with saline-injected controls. Under the same conditions, C57 mice showed dose-related increases in activity during the first 4 min, followed by dose-related decreases in activity. The effects endured for at least 60 min after injection in both strains. In a third experiment, mice were injected daily with saline or 2.0 g/kg ethanol and tested on Days 1, 5, 9, and 13 for open-field activity. On the 17th day, all mice were tested after an ethanol injection. Neither strain showed tolerance to the activity-stimulating effect of ethanol. Some evidence for tolerance to the effect of ethanol to reduce activity in C57 mice was found. In a fourth experiment, twice-daily injections of ethanol for 10 days produced marked tolerance to the depressant effect of an injection on the 11th day in C57 mice, compared with those in a control group given ethanol for the first time on the 11th day. No tolerance to the stimulant effect of ethanol was seen in C57s. DBA mice were injected twice daily for 19 days but did not display tolerance when tested on Day 10 or on Day 20, Indeed, DBA mice chronically treated with ethanol exhibited more marked stimulation of activity after ethanol than mice treated chronically with saline. Differences in blood ethanol concentrations between the strains could not account for any of the observed differences. Implications for the genetic control of responses to ethanol are discussed.

Animals↗
PubMed1981

In vitro determinants of plasma renin activity in serially-studied inbred dogs with neonatally induced coarctation hypertension: renin reactivity, renin substrate, and renin concentration.

Increased renin activity of plasma, suggesting an excess of circulating accelerators and/or deficit of inhibitors of the renin reaction, has been reported in a number of hypertensive states; however, its contribution to genesis and/or maintenance of hypertension is unknown. To longitudinally assess the evolution of plasma renin reactivity in relation to blood pressure in neonatally-induced coarctation hypertension, we have made serial observations in 6 coarcted dogs and in 7 littermate controls over 1-12 months post-aortic-banding during varied steady-state sodium intake. Measurements of renin activity (defined as the increment of angiotensin I-generation rate following addition of exogenous renin to plasma), renin substrate concentration (RS), and plasma renin activity (PRA), together with calculation of plasma renin concentration (PRC) (as PRC = PRA divided by renin reactivity) provided estimates of the three major determinants of PRA. RS values were adjusted for variability due to assay-control and to age via covariate analysis. Results indicate no difference in adjusted RS between coarcted and control dogs, thus obviating the influence of RS differences on renin reactivity results. Renin reactivity and PRC in coarcted dogs were also comparable to control values. Furthermore, responses of RS, renin reactivity and PRC to dietary sodium manipulation were similar in coarcted and control animals. We conclude that circulating modifiers of the renin reaction play no role in the genesis or in the first-year maintenance of neonatally-induced coarctation hypertension.

Animals↗
PubMed1976

Corticotropin releasing factor (CRF) activity in rat plasma.

The ACTH-releasing activity of hypothalamic extract and rat plasma was examined with the dispersed rat pituitary cell technique of Swallow and Sayer (8). Although both plasma and serum caused ACTH release which was dose-related, stress did not enhance the ACTH releasing activity. Furthermore, separation studies of plasma using ultrafiltration and gel separation suggest that the CRF activity in plasma is associated with molecules of a molecular weight greater than 15,000.

Animals↗