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Biomedical subjects

T Morgan

Publications and source records attributed to T Morgan.

At least 163 records · Page 9Linked to original sources
PubMed1980

Active and inactive renin in individual juxtaglomerular apparatuses.

1. Renin was measured in individual juxtaglomerular apparatuses before and after acidification in vitro. 2. Active renin increased with delivery of extra sodium by microperfusion to the macula densa and this increase was similar to that achieved with acidification. 3. In rats pretreated with an inhibitor of protein synthesis active renin increased when extra sodium was delivered to the macula densa. 4. Salt intake changed the amount of renin present in the juxtaglomerular apparatus. In rats on a high salt intake the total renin was low and was all in an active form.

Animals↗
PubMed1979

Treatment of mild hypertension in elderly males.

1. Males, born between 1900 and 1925, with mild hypertension have been treated for periods varying from 300 to 2000 days. 2. The life and death status of all patients (except two) was known on 1st November 1978. 3. A group of patients with mild hypertension receiving treatment based on a thiazide diuretic had a greater mortality than the other drug-treated group. 4. The increased mortality was caused by an increased number of myocardial infarcts. 5. Elderly male patients with mild hypertension probably have preexisting vascular disease and therapy should not automatically be started. If therapy is started, beta-adrenoreceptor-blocking drugs may be a preferred therapy.

Adrenergic beta-Antagonists↗
PubMed1979

The evidence that salt is an important aetiological agent, if not the cause, of hypertension.

1. Salt intake and the incidence of hypertension correlate between populations. 2. Salt intake within a population may correlate with the incidence of hypertension. 3. Disorders that lead to retention of salt cause hypertension. 4. Modest salt restriction reduces blood pressure in many patients. 5. Reducing salt balance and preventing the compensatory rise in angiotensin II controls blood pressure in most patients. 6. Salt is the probable cause of the epidemic of hypertension in the Western world; this could be prevented by salt restriction.

Aldosterone↗
PubMed1979

Improved laboratory efficiency and diagnostic accuracy with new double-lumen-protected swab for for endometrial specimens.

Intrauterine specimens were obtained from 22 patients with endometritis and 24 control patients following cesarean section by using both a new protected swab and a standard anaerobic swab. The protected swab improved the value of the direct smear and Gram stain, resulted in fewer false-positive cultures, better defined endometrial flora in patients with endometritis, and permitted major savings in laboratory personnel time and materials.

Bacteria↗
PubMed1978

The effect of labetalol in the treatment of severe drug-resistant hypertension.

Twenty-two hypertensive patients from a large clinic, who were resistant to conventional therapy, were entered into this study. Most patients previously had received beta-blocking drugs, thiazide diuretics, alpha-methyl-dopa, or vasodilator drugs (hydrallazine or prazosin) which failed to control their blood pressure. The therapy with vasodilator drugs was discontinued, and the therapy with labetalol (a drug with both alpha-blocking and beta-blocking effect) was commenced. Subsequently, as the blood pressure came under control, other drugs that the patients were taking were also withdrawn. In 13 of the 22 patients, labetalol enabled the blood pressure to be controlled at acceptable levels. In six patients, the response was not considered to be sufficient to justify continuation of labetalol therapy. In three patients, the drug was withdrawn because of postural hypotension in one patient, intractable diarrhoea in another, and an allergic-type skin rash in the third. In certain patients, postural changes in blood pressure were observed, but this rarely produced symptoms. It is suggested that, if blood pressure control is not achieved with a thiazide diuretic and a beta-blocking drug, then labetalol should be introduced and the beta-blocking drug should be withdrawn.

Aged↗
PubMed1978

A study of the interaction of catecholamines and antidiuretic hormone on water permeability and the cyclic AMP system in isolated papillae of the rat.

The diffusional water permeability of collecting ducts in vitro and the cyclic A.M.P. content of isolated papillae were measured after exposure to different concentrations of antidiuretic hormone, isoproterenol and noradrenalin. Antidiuretic hormone 25 mu units/ml. caused a 25% increase in diffusional water permeability. This response was not affected by isoproterenol (10(-6) M) or noradrenalin (2 x 10(-6) M). Antidiuretic hormone 100 mu unit ml-1 caused a 50% increase in diffusional water permeability which likewise was not altered by isoproterenol or noradrenalin. Isoproterenol (10(-6) M) and noradrenalin (2 x 10(-6) M) had no significant effect on basal levels of diffusional water permeability. Isoproterenol had no significant effect on the tissue concentration of cyclic A.M.P. concentration induced by antidiuretic hormone. Noradrenalin (2 x 10(-6) and 10(-4)) had no significant effect on basal cyclic A.M.P. concentration. However, noradrenalin inhibited the stimulation of cyclic A.M.P. induced by antidiuretic hormone. This effect was inhibited by phentolamine. This study suggests that catecholamines do not alter water handling by a direct action on the water permeability of the kidney but probably exert their action through an effect of A.D.H. release.

Animals↗
PubMed1978

Hypertension treated by salt restriction.

31 patients with a diastolic blood-pressure between 95 and 109 mm Hg have been treated for two years with a regimen involving a moderate restriction of salt in the diet. The results are compared with those in a control group and in a drug-treated group. Salt restriction has reduced the diastolic blood-pressure by 7.3+/-1.6 mm Hg, a result similar to that in patients treated with antihypertensive drugs. In the untreated group the diastolic blood-pressure rose by 1.8+/-1.1 mm Hg. Most patients did not achieve the desired amount of salt restriction and a stricter adherence to the diet might have caused further falls in blood-pressure. Excessive salt intake is probably a major cause of the epidemic of hypertension in "civilised" countries and a reduction in salt intake may help to control the epidemic. In persons with a diastolic blood-pressure between 90 and 105 mm Hg salt restriction should be tried before drugs.

Blood Pressure↗
PubMed1978

Treatment of mild hypertension.

1. A total of 206 patients, elderly males with hypertension (diastolic blood pressure 95--110 mmHg) were followed for periods varying from 1 to 5 years, 107 patients with diastolic blood pressure less than 95 mmHg were followed over the same period, and 101 patients with diastolic blood pressure greater than or equal to 110 mmHg were also followed. 2. The mortality of each group and the effect of therapy for hypertension on mortality has been compared. 3. The incidence of myocardial infarct in the group treated with thiazide diuretics is greater than in the other groups. 4. It would appear unlikely that therapy will improve the prognosis in elderly people with mild hypertension.

Benzothiadiazines↗
PubMed1977

A simplified approach to the treatment of hypertension.

A new beta-adrenoreceptor blocking drug (timolol) was used in two clinical studies. In the first double blind study administration of hydrochlorothiazide and timolol reduced the mean (formula: see text) blood pressure by 23 mm Hg, compared with a fall of nine mm Hg with administration of hydrochlorothiazide and a placebo. Plasma potassium (K+) levels fell with the administration of hydrochlorothiazide alone, but rose back to control values when patients were given timolol. In the second study (patient blind), Moduretic (hydrochlorothiazide, 50 mg and amiloride, 5 mg) and timolol were given once daily. The mean blood pressure fell by 20 +/- 2 mm Hg allowing hypertension to be controlled by this once-daily regimen; the control persisted throughout the day. Plasma potassium (K+) levels fell slightly after treatment with Moduretic, but the fall was not as great as with hydrochlorothiazide. Of the 65 patients who entered these studies, 35 had not been previously treated and had diastolic blood pressure between 105 mm Hg and 130 mm Hg. In 18 patients the diastolic blood pressure was reduced below 95 mm Hg after treatment with a diuretic alone, in 15 patients treatment with a diuretic and timolol (5 mg to 20 mg) reduced the diastolic blood pressure below 95 mm Hg. In two patients, the diastolic blood pressure was between 95 mm Hg and 100 mm Hg. The response achieved with a relatively simple therapeutic regimen that can be administered once daily suggests that the therapy of most hypertensive patients could be supervised by paramedical personnel.

Adult↗
PubMed1977

Factors controlling the release of renin. A micropuncture study in the cat.

Blood was collected by micropuncture from the efferent arteriole and superficial venules of the cat's kidney. Blood samples were also collected from the femoral artery and the renal vein. The blood renin concentrations (ng A1 m1-1 2h-1) in a basal state were 37.2 +/- 3.5 (S.E.M.) (n equal to 60) (artery), 32.5 +/- 5.2 [7] (efferent arteriole), 53.5 +/- 4(116) (superficial venule), 54.2+/- 5.4 (43) (renal vein). The corresponding values after haemorrhase were 389 +/- 98 (21), 345 +/- 115 (6), 963 +/- 208 (37), 907 +/- 290 (17), ng A1 m1-1 2h-1. The efferent arteriolar renin did not differ from that in the artery but the concentrations in superficial venular blood and renal vein were higher than arterial concentration. Thus renin entered the circulation between the efferent arteriole and the superficial venule. The blood renin concentration of different superficial venules at a steady arterial renin concentration varied markedly. Into certain venules there appeared to be little or no renin secretion, into others a marked renin secretion, suggesting a heterogeneity of renin secretion by the different nephrons. When the flow of tubular fluid to the macula densa of a group of nephrons was blocked, the renin concentration fell and was significantly less than the renin concentration in venules draining non blocked nephrons and less than in the renal vein. These results suggest that the juxtaglomerular apparatus of the nephrons do not release renin in a synchronous fashion. The release appears to be episodic and is inhibited when flow to the macula densa is ceased. This implies that a high sodium concentration at the macula densa stimulates renin release.

Animals↗
PubMed1977

A role of frusemide in resistant hypertension.

Five patients who were resistant to their antihypertensive drug therapy were admitted to hospital. Four had marked falls in blood pressure and an associated loss of weight. This fall in blood pressure was able to be repeated outside hospital by adding frusemide to their other drug therapy. Certain hypertensive patients become resistant to their antihypertensive therapy, owing to the accumulation of sodium. Thiazides may not have sufficient natriuretic properties to correct this accumulation. In these circumstances, frusemide may allow the hypertension to be controlled.

Adult↗
PubMed1977

Cinoxacin concentrations in plasma, urine and prostatic tissue after oral administration to man.

Cinoxacin, a synthetic antibacterial compound, was given orally in a dose of 500 mg to 8 patients undergoing transurethral prostatectomy. The drug was well absorbed and the peak plasma level (mean 13.9 mcg/ml) occurred 1 or 2 hours after administration. Concentrations of cinoxacin in the urine reached a peak (mean 236.5 mcg/ml) 4 to 6 hours after dosing, and remained higher than the mean MIC for most common urinary pathogens for 12 hours after administration. The concentration of cinoxacin in prostatic tissue 2.5-4 hours after administration varied between 0.6 and 6.3 mcg/g. The individual variations were unrelated to the concurrent plasma level and appeared to be influenced more by inter-subject variation than by the physicochemical properties of the drug. In 1 patient the cinoxacin level was estimated in renal tissue (70.1 mcg/g), in muscle (12.6 mcg/g), and in perirenal fat (4.7 mcg/g).

Aged↗
PubMed1977

Effect of NaCl on composition and volume of cells of the rat papilla.

The composition and volume of the cells of an isolated rat papilla were measured in media in which NaCl was varied from 150 to 600 mM; KCl, from 2 to 20 mM; or which contained mannitol, 300 mM. Change in NaCl from 150 to 600 mM reduced cell volume by 25%, increased cell Na+ content by 250% but had no significant effect on cell potassium concentration or content. Increases in K+ concentration in the media did not affect cell water or cell sodium, but the cell potassium rose by an amount approximately 3 times the increase in the medium concentration. Mannitol reduced cell volume; the cell content of sodium and potassium did not alter, but the concentration of Na+ and K+ altered reciprocally with the change in cell volume. Similar changes were observed with liver slices. This study indicated that papillary cells maintain osmotic equilibrium by the accumulation of sodium. This accumulation may influence the metabolic activity of the medullary and papillary cells.

Animals↗
PubMed1976

Optimal dose of a thiazide diuretic.

In essential hypertension, 25 mg and 100 mg of chlorthalidone per day reduced blood pressure to a similar extent. The larger amount (100 mg per day of chlorthalidone) caused a greater reduction in extracellular volume and a larger rise in plasma renin activity and serum uric acid levels. Hypokalaemia was common with 100 mg per day of chlorthalidone, but was rarely seen in patients who took 25 mg per day, and neither dose caused total body potassium depletion. In the management of hypertension, 25 mg of chlorthalidone is the preferred dose as it produces most of the antihypertensive effects with only minor biochemical changes.

Chlorthalidone↗
PubMed1976

A study in vitro of the concentrating defect associated with hypokalaemia and hypercalcaemia.

The diffusional water permeabilities of collecting ducts in the presence and absence of antidiuretic hormone have been measured in isolated papillae from normal, hypokalaemic and hypercalcaemic rats. In a similar in vitro situation the effect of antidiuretic hormone on the papillary content of cyclic AMP has been measured. The diffusional water permeability of collecting ducts in the absence of antidiuretic hormone did not differ significantly in papillae taken from the different groups of rats. The diffusional water permeability in the presence of ADH was 7.4 +/- 0.2 (S.E.M.) mum s-1 in collecting ducts taken from normal rats. In collecting ducts taken from hypokalaemic or hypercalcaemic rats the corresponding values were 5.9 +/- 0.3 and 5.8 +/- 0.5 mum s-1 respectively. This significant decrease (P less than 0.01) in the response to antidiuretic hormone would shift the point at which distal tubule fluid first attains isotonicity with the interstitium. If this shifts from cortex to medulla a greater amount of water enters the interstitium of the medulla and produces an impairment of maximal urinary concentrating ability and this defect could explain most of the observed results in hypokalaemic and hypercalcaemic. Cyclic AMP content of the tissue after the addition of ADH was reduced in papillae taken from hypokalaemic rats. This reduced activation of adenyl cyclase could be the mechanism responsible for the impaired response in water permeability but it is also possible that there is interference, with the chain of reactions mediating permeability changes, at a separate site.

Animals↗