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Biomedical subjects

W K Stewart

Publications and source records attributed to W K Stewart.

At least 73 records · Page 4Linked to original sources
PubMed1984

Bone marrow iron and plasma ferritin in dialysed patients given intravenous iron-dextran.

Bone marrow biopsies have been taken in 28 patients on or approaching maintenance haemodialysis before and after treatment with monthly intravenous iron-dextran (Imferon). Stainable marrow iron was compared with blood Hb, plasma ferritin, erythrocyte protoporphyrin and MCH levels at the time of biopsy, and with previous or subsequent responses to iron in terms of blood Hb and MCH. There was a positive correlation between bone marrow iron and plasma ferritin levels both before and after iron therapy. All the patients with excess marrow iron had high plasma ferritin. However, six patients with low or normal marrow iron also had high plasma ferritin, two of these before iron therapy was given. Seven of the eight patients with no detectable marrow iron had low plasma ferritin. Three of the 28 patients failed to respond to iron with an increased blood Hb. MCH increased in all patients studied during iron therapy. All but one of the patients with high plasma ferritin prior to iron therapy responded well to iron. Although a good correlation between plasma ferritin and marrow iron can be shown in dialysed patients given intravenous iron-dextran, a high plasma ferritin level in an individual patient should not by itself preclude iron therapy.

Bone Marrow↗
PubMed1982

Plasma retinol and retinol binding protein concentrations in patients on maintenance haemodialysis with and without vitamin A supplements.

Plasma retinol and retinol-binding protein (RBP) concentrations have been estimated in patients on maintenance haemodialysis over a 4-year period. For the first 2 years multivitamin supplements containing vitamin A were taken, and for the second 2 years no vitamin A supplements were given. Mean plasma retinol concentrations decreased significantly but only from 3.8 times normal to 3.1 times normal after vitamin A supplements stopped. There was no significant change in th high plasma RBP levels. Ultracentrifugation of plasma at a salt density of 1.21 showed that nearly all the retinol was associated with RBP in the high density protein fraction, as it is with normal subjects. Column chromatography confirmed that there was no increase in plasma retinyl esters in the renal failure patients, as is found in hypervitaminosis A due to drug overdosage. The high plasma retinol and RBP levels remained remarkably stable in individual patients throughout the 4-year study. The increase in plasma RBP was possibly related to residual urine output. The results are compatible with a feedback mechanism whereby the extent of the increase in plasma RBP as renal failure develops controls the consequent high plasma level of retinol.

Anuria↗
PubMed1982

Improved phosphate clearances with polycarbonate membranes.

Clearance studies of urea, creatinine and inorganic phosphate have been carried out using polycarbonate dialysers on 20 occasions in two patients undergoing routine maintenance haemodialysis. Clearances were calculated using plasma concentrations and both measured blood flow and calculated plasma flow. Urea and creatinine clearances were comparable to those obtained with cellulose-based dialysers, but phosphate clearances were relatively increased, averaging over 70% of urea clearances. All clearances were reduced as TMP values increased, a feature at variance with the usual situation with cellulose membranes. Polycarbonate dialysers have the advantage of higher relative phosphate clearances in addition to the other advantages claimed for them.

Cellulose↗
PubMed1982

Mitogen-stimulated lymphocyte growth and chronic uraemia.

Lymphocytes were isolated from venous blood by the Böyum method from 36 patients with chronic renal failure: the preparations were more frequently and more heavily contaminated with non-lymphoid cells than the equivalent preparations from normal controls. Volume spectroscopy measurements showed that, in the samples without gross contamination, lymphocytes from uraemic subjects react to mitogen stimulation with normal pre-S-phase cell-cycle kinetics. In other experiments, plasma from uraemic patients was shown to be more potent than serum in inhibiting the growth of mitogen-stimulated lymphocytes from normal subjects, both in the first G1-phase and in replicative growth. Thus humoral suppression appears to be more important than a cellular defect in explaining the depressed responses of uraemic blood to mitogen stimulation.

Cell Cycle↗
PubMed1980

Bone marrow cellularity and iron stores in chronic renal failure.

Bone marrow biopsies of 15 patients with chronic renal failure (CRF) were compared with those of a control group matched for age and sex. Using a point-counting method for assessing cellularity, there was no significant difference in marrow cellularity between the CRF patients and the control group. There was a significant difference in the myeloid-erythroid ratio (p < 0.05) between the control group and the CRF patients, the latter group having a lower ratio. A point-counting method was used for the assessment of iron stores. Of 8 CRF patients who had not been given intravenous iron, oral iron or blood transfusion, 2 had greater iron stores than the control group.

Adult↗
PubMed1977

Urinary mercury excretion and proteinuria in pathology laboratory staff.

The use of mercuric chloride as an histological fixative was associated with high environmental atmospheric concentrations of mercury vapour (up to 0-5 nmol/l) as well as mercury compounds (total Hg to 1-0 nmol/l). Technicians exposed to this environment showed increased urinary mercury (median value 265 nmol/24h) and protein outputs (median value 117 mg protein/24h). Routine control measures, ventilation and careful handling of mercuric chloride solutions, reduced the level of atmospheric mercury vapour levels to within acceptable limits (threshold limit values 0-01 mg/m3 (0-05 nmol/l) alkul compounds and 0-05 mg/m3 (0-25 nmol/l) for all forms except alkyl). This reduction was associated with the disappearance of trace proteinuria from the technicians' urine. Contamination of histology laboratories by mercuric chloride should be minimised.

Adolescent↗
PubMed1976

Effect of carbohydrate intake on the urinary excretion of magnesium, calcium and sodium in fasting obese patients.

The urinary excretion of magnesium, calcium and sodium has been measured in 19 obese patients undergoing 12 days on complete fast (days 1-12) followed by 6 days of carbohydrate supplementation (days 13-18), while receiving no mineral supplements or either calcium, magnesium or sodium supplements. Magnesium and calcium followed different excretion patterns during the 12 days fast. The oral administration of 107 g carbohydrate daily during days 13-19 resulted in a marked decrease in the urinary excretion of magnesium, calcium and sodium by the non-, calcium- and sodium-supplemented patients, but there was no carbohydrate-induced reduction in magnesium excretion in the magnesium-supplemented patients. The kidney appears capable of selectively influencing calcium and sodium reabsorption, without magnesium excretion being affected. It is suggested that involvement in increased renal gluconeongenesis during fasting renders the renal tubule incapable of maximally conserving both divalent and monovalent ions. The increased tubular reabsorption of urinary constituents induced by carbohydrate administration probably stems from the concomitant reduction in gluconeogenesis.

Adult↗