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Biomedical subjects

W G Walker

Publications and source records attributed to W G Walker.

At least 37 records · Page 2Linked to original sources
PubMed1985

Transient idiopathic hyperammonaemia in adults.

Transient severe hyperammonaemia developed in the absence of serious liver dysfunction in three patients being treated for acute leukaemia. The onset of the biochemical disturbance was abrupt and led rapidly to acute encephalopathy, fatal in two cases. In the third patient, prompt initiation of aggressive haemodialysis and intravenous sodium benzoate and sodium phenylacetate infusion successfully controlled plasma ammonium levels until they spontaneously resolved. The cause of the disorder remains to be determined, but urinary nitrogen partition studies suggest temporary impairment of ureagenesis in a catabolic setting as a major pathophysiological feature of this disorder. The absence of liver disease, the normal mitochondrial ultrastructure seen in two cases, and the plasma aminoacid profiles observed serve to distinguish this disorder from others such as Reye's syndrome.

Acute Disease↗
PubMed1984

A corpus callosal deficit in sequential analysis by schizophrenics.

This preliminary study evaluated interhemispheric (i.e., corpus callosal) information processing by chronic schizophrenic and normal subjects. In right-handed normals the left hemisphere has been reported to be superior in temporal sequential analysis. Consequently temporal information presented to the right hemisphere requires time to cross to the left hemisphere for analysis. Measurement of hemispheric laterality and corpus callosal transfer time were evaluated by a two-pulse temporal discrimination task. Two dot stimuli were presented with decreasing temporal separation during bilateral and unilateral conditions. Subjects were required to judge perceived simultaneity and nonsimultaneity of dot onset. The results indicate that left hemisphere function in chronic schizophrenic and normal controls is superior to the right hemisphere in temporal analysis. Corpus callosal transfer time was significantly slower for chronic schizophrenics than for normal controls.

Adult↗
PubMed1983

Treatment of acute sickle cell crises with a vasopressin analogue.

Eight patients with sickle cell anemia were treated for acute painful crises with DDAVP and intravenous fluids; five were treated with placebo and the same regimen of fluid administration. Although hyponatremia was produced in both treatment groups, duration of hospitalization did not differ between them, nor did it differ from concurrent hospitalization of other patients who received conventional treatment. Safe induction of hyponatremia required intensive laboratory surveillance, and serum sodium could be lowered without use of DDAVP. These data suggest that a controlled trial hyponatremia for acute sickle cell crises should not be performed.

Acute Disease↗
PubMed1983

Hormonal responses to acute volume changes in anephric subjects.

The response of plasma aldosterone and cortisol concentrations to acute volume depletion was studied in 18 chronically anephric subjects and four recently nephrectomized subjects. Volume-depleting hemodialysis and hemodialysis without volume depletion produced insignificant changes in plasma aldosterone concentrations in chronically anephric subjects. Failure of volume depletion to increase plasma aldosterone concentrations in these subjects could not be attributed to reductions in plasma potassium concentrations and was in marked contrast to the effect on plasma cortisol concentrations, which increased significantly during volume depletion. Changes in plasma cortisol concentrations exhibited a negative correlation with changes in diastolic blood pressure (r = -0.712, P less than 0.001) and were shown to correspond to similar changes in plasma ACTH concentrations. Comparable increases in plasma cortisol and ACTH concentrations were also demonstrated in the studies on recently nephrectomized subjects, who, in contrast to chronically anephric subjects, exhibited increases in plasma aldosterone concentrations which were concordant with the changes in plasma cortisol and ACTH concentrations. These findings suggest that plasma aldosterone concentrations are regulated by a volume-sensitive mechanism in recently nephrectomized subjects but not in chronically anephric subjects. We interpret these data as evidence of aldosterone responsiveness to ACTH that persists for a limited time only after removal of the stimulus provided by the renin-angiotensin system. Volume-related changes in plasma cortisol and ACTH concentrations occur in the absence of stimulation by a functioning renin-angiotensin system.

Adolescent↗
PubMed1982

Prevention of phosphate-induced progression of uremia in rats by 3-phosphocitric acid.

Male Sprague-Dawley rats were rendered uremic by surgical removal of 70% of functioning renal mass. This produced a rapid threefold rise in serum creatinine to 0.87 +/- 0.067 (SEM) mg/dl at 2 weeks postoperatively which declined subsequently to a value of 0.64 +/- 0.06 (SEM) and remained stable thereafter for an additional 4 weeks in animals maintained on a diet with normal phosphate content. Increase of dietary phosphate content to 2.2% at 2 weeks after surgery produced a significant and progressive increase in serum creatinine to values fourfold higher than the mean values in comparable partially nephrectomized control animals maintained on a diet with normal phosphate content (P less than 0.001). This deterioration in renal function was associated with extensive nephrocalcinosis, tubular dilatation, cellular necrosis, and marked interstitial inflammation. 3-phosphocitric acid, a compound which has been shown to prevent calcium phosphate crystal growth as well as to prevent in vivo nephrocalcinosis, was very effective in preventing this phosphate-induced deterioration of renal function and in preventing any significant increase in renal calcium content in animals fed a high phosphate diet. This compound was also effective in preventing the renal histologic changes associated with phosphate-induced uremia.

Animals↗
PubMed1981

Renal venous renin sampling. Prospective study of technique and methods.

During a three-year period, 107 patients undergoing renal arteriography were studied to evaluate the influence of renin sampling techniques and contrast material administration on renal venous renin activity. Plasma renin activity was nearly equal in three extrarenal sampling sites (antecubital vein, aorta, and lower inferior vena cava). Values for renal vein renin activity obtained with a single catheter (nonsimultaneous sampling) did not differ significantly from those obtained with two catheters (simultaneous sampling). Similarly, contrast material had no significant effect on renal vein renin activity levels. Thus, in hypertensive patients, sampling for renal venous renin activity can be performed accurately with a single venous catheter after renovascular disease has been demonstrated by arteriography.

Blood Specimen Collection↗
PubMed1981

Hepatitis B infection in patients with end stage renal disease: some characteristics and consequences.

Susceptibility to hepatitis B infection appears to be in part genetically determined. The HLA specificity Bw35 is commonly associated with a higher frequency of both transient and persistent hepatitis B surface antigen in the serum. Persistent hepatitis B surface antigenemia occurring in patients with end stage renal disease while on dialysis is associated with a poor prognosis and markedly decreased survival regardless of whether the individual is treated subsequently by chronic dialysis or by transplantation. We conclude that persistent hepatitis B surface antigenemia is not a contraindication to transplantation since outcome is not improved by management on hemodialysis.

Hepatitis B Surface Antigens↗
PubMed1981

Failure of desmopressin to lower serum sodium or prevent crisis in patients with sickle cell anemia.

An analogue of arginine vasopressin (desmopressin, DDAVP) was evaluated for production chronic hyponatremia and prevention of sickle cell crisis. With sodium restriction (100 meq Na + / day) and water loading ( greater than 3 liters/day), persistent hyponatremia could not be achieved, nor could crises be prevented or aborted. Patients would not comply with a regimen of lower salt and higher fluid intake. More rigorous treatment might be practical during acute sickle cell crises, and a regimen similar to that used here might be more effective in children, whose renal concentrating mechanisms are still intact.

Adult↗
PubMed1981

Renovascular hypertension: results of medical and surgical therapy.

Results of medical and surgical treatment of renovascular hypertension were compared retrospectively in 28 patients. Renal function remained normal throughout the study in all patients. After six months of follow-up, systolic and diastolic blood pressures were significantly lower in the 15 patients treated surgically than in the 13 patients treated medically. At 12 months however, a significant difference could be demonstrated only for systolic blood pressure and at 24 and 36 months, no difference in systolic or diastolic pressure could be demonstrated between the two groups. This failure to find a significant difference between surgical and medical therapy resulted from return of hypertension among the patients in the surgical group with arteriosclerotic renovascular hypertension; 6 of 7 patients with fibromuscular dysplasia as the etiology of the renovascular hypertension were cured by surgery and none of these relapsed during follow-up. All patients with arteriosclerotic renovascular disease who were operated upon required medication for the control of their blood pressure within 12 months after operation. The findings in this retrospective study emphasize the importance of prolonged follow-up when assessing the value of different therapies in renovascular hypertension and provide evidence indicating that medical management is acceptable and appropriate, particularly for high risk patients. The results also force recognition of the need for a randomized prospective trial of medical and surgical therapy in arteriosclerotic renovascular hypertension.

Evaluation Studies as Topic↗
PubMed1979

Hepatitis B surface antigenemia in renal transplant recipients. Increased mortality risk.

To determine effects of circulating hepatitis B surface antigen (HBsAg) on patient survival following renal transplantation, we studied 168 recipients of cadaveric grafts in whom HBsAg status was defined at transplantation by comparison of survivorships determined by actuarial life-table methods. Survival in HBsAg-positive recipients, as compared with those who were HBsAg-negative at the time of transplantation, was markedly diminished. Although graft survival appeared to be favored in the HBsAg-positive group in the early posttransplant period, the apparent protective effect was lost at nine months after grafting and thereafter, due to increased mortality in the HBsAg-positive recipients. Deaths in the antigenemic subjects were principally due to infections other than hepatitis and to cardiovascular events. We conclude that preexisting HBs antigenemia forebodes an ominous outcome for immunosuppressed renal transplant recipients, although hepatic disorders do not account for most deaths.

Cadaver↗
PubMed1979

Hypertension following renal transplantation. Causative factors and therapeutic implications.

During a five-year period, we studied 21 of 319 renal transplant recipients who were admitted for evaluation of refractory hypertension. For comparison we examined 93 consecutive patients in the renal transplant clinic. Hypertension, which was noted in 47% of the outpatients, occurred with greater frequency following renal transplantation from cadaveric donors and was associated with a decline in renal function. The 21 inpatients had higher blood pressures and were studied at an earlier stage than their outpatient counterparts. Fourteen of the inpatients had underlying stenosis of their transplant artery nd revascularization of the transplanted kidney was possible in the majority of these patients. Stenosis of the transplant artery was suggested by the occurrence of severe hypertension during the first year following transplantation, a bruit in the transplant region, and increased levels of peripheral plasma renin activity.

Adult↗
PubMed1979

Plasma levels and hepatic extraction of renin and aldosterone in alcoholic liver disease.

Arterial plasma levels and hepatic extraction of renin and aldosterone (ALDO) were measured in 24 patients with alcoholic liver disease and in 14 normal subjects being evaluated as prospective kidney donors. Patients with liver disease had higher plasma concentrations and lower fractional hepatic extractions of both renin and ALDO than the normal subjects. The quantity of renin extracted by the liver was highly correlated with plasma renin in both normal subjects and patients. Plasma ALDO concentration was positively correlated with plasma renin (p less than 0.001) but not with serum sodium, potassium or albumin concentration, inferior vena cava pressure, corrected hepatic venous wedge pressure, plasma volume or sulfobromophthalein storage or transport. Sixteen patients were restudied after one month. Six had received 40 mg/day of prednisolone, and the remaining 10 had received a placebo. Neither group had a change in plasma volume, corrected hepatic venous wedge pressure, plasma concentration or hepatic extraction of renin or ALDO. Serum albumin concentration increased and inferior vena cava pressure decreased with prednisolone therapy. These studies document high plasma levels and impaired hepatic extraction of renin and ALDO in patients with liver disease that are not corrected by short-term prednisolone therapy.

Adult↗