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Biomedical subjects

T Morgan

Publications and source records attributed to T Morgan.

At least 181 records · Page 10Linked to original sources
PubMed1976

The effect of lithium on the permeability response induced in the collecting duct by antidiuretic hormone.

The diffusional and osmotic water permeability of collecting ducts in isolated papillae of rats' kidneys were measured in papillae taken from normal and lithium pretreated rats. The diffusional water permeability of collecting ducts in papillae from normal rats in the absence of ADH was 4.1 +/- 0.2 (S.E.M.) (n = 18) muM s-1 increasing to 7.2 +/- 0.6 mum s-1 with ADH. Values obtained with lithium (10 mM) in the medium, perfusate or both and in papillae taken from lithium pretreated rats did not differ significantly from the above. The cyclic AMP content of the papillae taken from normal rats was 83 +/- 6 pm mg protein in the absence of ADH and increased to 196 +/- 12 (n = 13) with 500 mu units ml-1 ADH. Lithium 10 mM in the medium did not alter this response. Papillae from lithium pretreated rats had a similar basal level of cyclic AMP but the increment in a lithium (10 mM) medium after ADH was significantly less. These results indicate that the impaired water handling of lithium treated rats is probably not due to a failure of the membrane to increase its permeability to water after ADH. Though lithium does alter the production of cyclic AMP this is not believed to be important regarding any alteration in water permeability. We believe it is probable that lithium interferes with sodium chloride transport at some more proximal nephron segment thereby producing the syndrome of polyuria.

Animals↗
PubMed1976

Renal physiology.

The kidney is composed of one million nephrons that function as a series of integrated units. The excretion of a wide range of natural and artificial compounds results from unselective filtration and specific reclamation of wanted substances. Active transport of weak acids and weak bases supplements this mechanism. In addition to its excretory function, the kidney has important endocrine and metabolic functions and influences the function and metabolism of most body systems. An understanding of renal function affords an explanation for many of the phenomena observed in renal disease.

Absorption↗
PubMed1976

The effect on blood pressure of beta-adrenoceptor blocking drugs administered once daily and their duration of action when therapy is ceased.

The control of blood pressure achieved was similar whether pindolol or propranolol was given once or three times daily. When the drugs were ceased the antihypertensive effect lasted for longer than 24 h. There was no rebound hypertension. The full effect of the drug on blood pressure was seen within 24 h of its recommencement. Changes in blood pressure, pulse rate, and plasma renin activity occurred but these were not considered to be causally related. The response of plasma renin activity to posture was ablated when the patients were receiving beta-adrenoceptor blocking drugs.

Adult↗
PubMed1975

Renin secretion at the individual nephron level.

Blood was collected from the descending aorta, from a renal efferent arteriole and from the renal vein of a rat. The renin concentrations of the blood samples were measured. The renal vein renin concentration was 673 +/- 81 (SE) ng ml-1h-1 which was significantly higher than the concentration in the aorta of 456 +/- 50 (SE) ng ml-1h-1. The concentration of renin in the renal efferent arteriole was significantly lower than that in the aorta. These observations imply that net renin secretion is a combination of two processes; removal between artery and efferent arteriole and entry between efferent arteriole and renal vein. It appears that renin is released into the interstitium and enters the circulation at the capillary level rather than being released into the afferent or efferent arterioles. This mode of secretion supports the suggestion that the renin angiotensin system may primarily work intra-renally rather than through the systemic circulation.

Animals↗
PubMed1975

Sodium restriction and thiazide diuretics in the treatment of hypertension.

In a group of hypertensive patients it has been shown that moderate sodium chloride restriction has a hypotensive effect that is similar to that produced by thiazide diuretics. Blood pressure changed in relation to body weight in individual patients, and appeared to correlate with their sodium balance. The more a patient was depleted of sodium, the lower was the blood pressure. The serum potassium level fell with the use of thiazide diuretics, but in this group of patients there was little change in total body potassium content. The fall in serum potassium level appeared to relate to a shift into the cells due to the accompanying alkalosis. Potassium supplementation appeared to have had little effect and was unnecessary for most patients who were given diuretics for hypertension. Amiloride corrected the alkalosis and restored the serum potassium level to normal.

Amiloride↗
PubMed1975

Renin measurement in blood collected from the efferent arteriole of the kidney of the rat.

Plasma renin could be detected in 16 nl of rat plasma by incubating at 50 degrees C, pH 6.2 with 20 mul of a rat renin substrate. In 60 nl samples it could be estimated and differences in concentration of 20% could be detected. Plasma renin concentration was measured in blood from the superficial efferent arterioles of a rat's kidney. The concentration of renin in different efferent arterioles of the same rat were similar. The renin concentration of efferent arteriolar blood was 361 plus or (-1)89 (S.D.) ng Al ml minus 1 (blood) hour (-1) which was not different from the renin concentration of simultaneously taken femoral artery blood (340 +/- 217). Plasma concentration can be measured in efferent arteriolar blood and will allow the control of renin secretion to be studied.

Angiotensin II↗
PubMed1975

Changes in plasma renin activity and blood pressure after acute and chronic administration of beta-adrenergic receptor-blocking drugs.

1. Prindolol and propranolol chronically cause a fall in mean blood pressure and mean plasma renin activity, but no correlation was observed between the two variables. 2. The response of blood pressure to prindolol and propranolol was not predicted by the basal plasma renin activity. 3. Propranolol administered acutely caused the plasma renin activity to fall with no acute change in blood pressure, whereas prindolol caused the blood pressure to fall with no change in plasma renin activity. 4. The effects of beta-adrenergic-blocking drugs on plasma renin activity and blood pressure can be dissociated and it is unlikely that their hypotensive action is mediated through the renin-angiotensin system. 5. Basal plasma renin activity does not identify the patients who will respond to beta-adrenergic-blocking drugs.

Adult↗
PubMed1975

Effects of pattern of ventilation on pulmonary metabolism and mechanics.

Effects of three patterns of mechanical ventilation on pulmonary mechanics, lung phospholipid and surface activity were studied in the normal closed-chest dog. The patterns were continuous mechanical ventilation with: 1) tidal volume (VT)=15 ml/kg; 2) VT=15 ml/kg with 10 cm H2O positive end-expiratory pressure (PEEP); 3) VT=50 ml/kg. THE DOGS IN EACH GROUP WERE VENTILATED FOR 24 HOURS, WITH CAREFUL ATTENTION PAID TO MAINTENANCE OF NORMAL BLOOD GASES, FLUID BALANCE, AND CARDIAC OUTPUT. The animals were sacrificed and the lungs studied to determine pressure-volume curves, dry lung weight/wet lung weight ratios, phospholpid contents and surface activities. The results were compared with control values in acutely sacrificed unventilated dogs. No significant change from controls was found with any pattern of ventilation employed with the exception of the tendency for lungs ventilated with PEEP to retain fluid (decreased dry lung weight/wet lung weight ratio).

Animals↗