PubMed Health⌕ Search

Biomedical subjects

F S Nashat

Publications and source records attributed to F S Nashat.

25 records · Page 2Linked to original sources
PubMed1969

The effect of acute changes in haematocrit in the anaesthetized dog on the volume and character of the urine.

1. Acute changes in haematocrit were produced by exchange transfusion of dextran-in-saline or packed red cells.2. There were no significant changes in glomerular filtration rate, blood pressure, central venous pressure, heart rate, respiratory rate, blood volume or extracellular fluid volume following the exchange transfusions.3. Urine volume increased after haemodilution but decreased after haemoconcentration.4. The diuresis after haemodilution occurred despite an infusion of ADH or alcohol. Thus it could not be attributed to a change in circulating ADH level.5. There were two types of diuresis. The ;water diuretic' response was characterized by an increase in free water clearance with a reduction in urinary sodium concentration; the ;sodium diuretic' response by an increase in urinary sodium concentration but no change, or a fall, in free water clearance.6. The results were related to changes in medullary osmotic gradient found by other workers to occur when medullary blood flow rate is altered.

Anesthesia, Intravenous↗
PubMed1967

The effects of changes in haematocrit on renal function.

1. Acute changes in total body haematocrit were produced in anaesthetized dogs by the rapid infusion of packed red cells, dextran solution or hypertonic mannitol. A reduction of haematocrit resulted in a decrease in filtration fraction, and a rise of haematocrit in an increase in filtration fraction. A direct relationship between water reabsorption (relative to filtered load) and packed cell volume (P.C.V.) was also observed.2. It is suggested that the changes in filtration fraction accompanying changes in haematocrit are mediated largely by a passive alteration of efferent arteriolar resistance resulting from modifications of blood viscosity.

Journal Article↗
PubMed1966

The use of labelled vitamin B12 in the measurement of glomerular filtration rate.

1. Two preparations of radioactive vitamin B(12) labelled respectively with (57)Co and (58)Co have been employed in the estimation of the glomerular filtration rate (G.F.R.) in dogs. The intravenous injection of these preparations at an interval of 20 min resulted in a changing ratio of their activities in plasma and urine and so permitted a relation in time to be established between the urine and the plasma from which it was filtered.2. When urine and plasma were sampled at short intervals an effective renal delay or transit time could be derived from their isotope ratio curves and used as a correction in the clearance equation. This allowed serial clearances of either isotope to be calculated despite a falling plasma concentration.3. This method was applied to the study of the G.F.R. in fourteen dogs using short urine collections of 2 or 4 min for periods up to 80 min. The results under stable conditions and with deliberately induced changes in the G.F.R. are illustrated and discussed.4. Application of the technique in four patients undergoing differential renal function studies gave results comparable with those in the experimental work.5. The plasma binding of administered vitamin B(12) in serial blood samples in dogs and man was investigated.

Animals↗
PubMed1966

Concealed glomerular filtration.

1. An increase in apparent renal clearances is frequently observed on restoring urine flow after a period of anuria or on increasing it after oliguria. An analysis of such 'peaks' in clearance has been made in experiments on anaesthetized dogs, using two preparations of labelled vitamin B12 and urine collections of 1-2 min. [57Co]B12 was infused throughout the experiments, while [58Co]B12 was given as a single injection during periods of anuria or oliguria induced by noradrenaline infusion, haemorrhage or aortic obstruction. 2. The apparent high clearance in the first minute or two of restored or increased flow is an artifact explained by inclusion in the peak of material filtered earlier, but not excreted. By means of the integrated plasma concentration ratio of the two B12 isotopes during the period of low or absent flow, the excess B12 in the peak may be reapportioned between the period before the 58Co was injected and the period after it. 3. The findings indicate that filtration may temporarily continue during anuria, but this is concealed as a result of failure of onward flow of filtrate. In oliguria a similar concealment of filtration may result from the cessation of onward flow in some nephrons.

Animals↗