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Biomedical subjects

T Morgan

Publications and source records attributed to T Morgan.

At least 109 records · Page 6Linked to original sources
PubMed1988

Interaction of slow-channel calcium blocking drugs with sodium restriction, diuretics and angiotensin converting enzyme inhibitors.

The interactions of nifedipine with sodium restriction, diuretics and enalapril were studied using a 2 x 2 factorial design. Nifedipine lowered blood pressure to a greater extent than sodium restriction or hydrochlorothiazide. With both of these therapies there was a negative interactive term, which indicated that their combination had no greater effect than the use of nifedipine alone. Enalapril and nifedipine lowered blood pressure by 10 +/- 2/8 +/- 1 and 11 +/- 3/8 +/- 1 mmHg, respectively. The combination lowered blood pressure by 32 +/- 3/24 +/- 2 mmHg. The reasons for these negative and positive interactions are not clear, but may relate to interactions that regulate the availability of calcium for initiation of contraction in smooth muscle cells of the arterioles.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1988

Effect of atrial peptide on collecting duct function.

1. The effects of synthetic rat atrial natriuretic peptides (ANP) on diffusional 22Na+, 36Cl- and tritiated water (THO) permeability of in vitro microperfused rat papillary collecting ducts and the effect in vivo of ANP on stop-flow sodium concentrations in the terminal segment of rabbit nephrons were studied. 2. The addition of 4 x 10(-8) or 4 x 10(-7) mol/l ANP to the medium or perfusion solution did not alter diffusional 22Na+ or 36Cl- permeability of microperfused rat papillary collecting ducts. 3. The basal diffusional THO permeability of papillary collecting ducts was not altered when 4 x 10(-7) mol/l ANP was present in the medium and did not inhibit the increment in diffusional THO permeability induced by vasopressin or reduce the permeability to water in a duct previously stimulated by vasopressin. 4. The administration of ANP (2 micrograms/kg bodyweight) to rabbits in water diuresis did not alter systemic blood pressure but induced a marked natriuresis and increases in urine flow and potassium excretion. This natriuresis was not associated with alterations in stop-flow sodium reabsorptive capacity or sodium permeability of the collecting tubules and ducts. 5. Previously reported in vivo clearance data suggest that ANP causes, at least in part, a natriuresis by altering sodium transport in the medullary collecting ducts. In this study, however, a direct effect could not be demonstrated and it is possible that the medulla needs to be functioning in its normal environment for such effects to be demonstrated.

Animals↗
PubMed1988

Effect of pH on vasopressin-induced water permeability in collecting ducts of isolated rat papillae.

1. The effects of basolateral and luminal pH on diffusional water permeability of microperfused collecting ducts of isolated rat papillae were examined in the presence and absence of vasopressin at two concentrations. 2. In the absence of vasopressin, collecting duct diffusional water permeabilities did not differ when the pH of the luminal fluid was varied. Similarly, in the absence of vasopressin, collecting duct diffusional water permeabilities did not differ when the bath pH was varied. 3. In the presence of 50 microU/ml vasopressin, increases in diffusional water permeability of collecting ducts perfused with solutions at pH 5.0, 7.4 or 9.0 did not differ significantly. Similarly, increases in diffusional water permeability induced by 200 microU/ml vasopressin were not different when collecting ducts were perfused with solutions at pH 5.0, 7.4 or 9.0. 4. The presence of vasopressin (50 microU/ml) in the bathing medium at pH 6.4, 7.4 and 8.4 induced increments in diffusional water permeability of 0.40 +/- 0.21 (n = 14, P greater than 0.05), 1.56 +/- 0.27 (n = 27, P less than 0.001) and 1.67 +/- 0.24 (n = 12, P less than 0.001) microns/s, respectively. The increment in water permeability at pH 6.4 was significantly less than that at pH 7.4 (P less than 0.001). 5. The presence of vasopressin (200 microU/ml) in the bathing medium at pH 6.4, 7.4 and 8.4 induced increments in diffusional water permeability of 2.16 +/- 0.54 (n = 9, P less than 0.01), 2.55 +/- 0.51 (n = 17, P less than 0.001) and 0.98 +/- 0.34 (n = 11, P less than 0.05) microns/s respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Interaction in hypertensive man between sodium intake, converting enzyme inhibitor (enalapril), plasma renin and blood pressure control.

Sixteen patients with hypertension entered a study in which the effects of enalapril were compared with sodium restriction, with the two in combination and with placebo using a balanced randomized double-crossover design. Each patient had four treatment phases of two weeks, duration which comprised a 2 x 2 factorial design as well as an initial period on sodium restriction and enalapril placebo. All patients received a reduced sodium diet and sodium intake was altered by slow Na tablets. Increasing sodium intake raised blood pressure similarly whether patients were receiving enalapril or its placebo. Enalapril lowered blood pressure to a similar extent in patients on either a low and high sodium intake. The combination of a low sodium intake and enalapril was additive and there was no interactive effect between the two therapies whether assessed by a linear or a logarithmic method. Plasma renin was increased by enalapril and lowered by increased sodium intake. These effects were additive and there was no interactive effect. Neither the initial plasma renin nor the rise in renin predicted which patients would respond to enalapril. Enalapril was an effective antihypertensive agent and its blood pressure-lowering effect and that of sodium restriction were additive.

Aged↗
PubMed1987

Significance of isolated antibody to hepatitis B core antigen determined by immune response to hepatitis B vaccination.

The immune response to hepatitis B vaccine was studied in 14 individuals with isolated, high-titer antibody to hepatitis B core antigen (anti-HBc) and examined as an indicator of this serologic pattern's significance. Four subjects demonstrated a low-titer antibody to hepatitis B surface antigen (anti-HBs) on repeated testing, and three in this subgroup had anamnestic responses (anti-HBs, 82 to 140 ratio units) after vaccination. Compared with 22 seronegative controls, the remaining ten had significantly higher anti-HBs response rates (78% vs 22%, P = .003) and median anti-HBs titers (4 vs 0 ratio units, P = .008) two weeks after vaccination. One of ten subjects had an anamnestic response, while another exhibited no response. The general pattern of anti-HBs responsiveness observed in those subjects with isolated, high-titer anti-HBc was intermediate between seronegative and anti-HBs-positive groups and may indicate a state of waning immunity after natural infection. Hepatitis B vaccination with follow-up anti-HBs testing should be done for those patients with isolated, high-titer anti-HBc to help exclude chronic infection and boost protective immunity.

Adult↗
PubMed1987

Reversal of benign intracranial hypertension by surgically induced weight loss.

Weight loss is recommended in the treatment of benign intracranial hypertension (BIH) but is difficult to achieve because of the administration of steroids. A 24-year-old morbidly obese woman with BIH presented with headache, a cerebrospinal fluid pressure of 300 mm H2O, enlargement of the blind spot in the right eye, and bilateral papilledema. Treatment with steroids for one year produced an increase in weight with worsening symptoms and visual findings. Gastric exclusion surgery produced a 37-kg weight loss in six months that was associated with cessation of symptoms, reduction in cerebrospinal fluid pressure to 170 mm H2O, marked improvement in visual fields, and resolution of papilledema. This raises the possibility that gastric exclusion surgery may be an effective means to achieve weight loss and ultimately a remission in obese patients with BIH.

Adult↗
PubMed1987

Immediate effects of furosemide on renal hemodynamics in chronic liver disease with ascites.

Furosemide occasionally causes azotemia in patients with ascites, independently of induced volume depletion. To define this effect, we measured renal clearances in patients with chronic liver disease and ascites and in nonascitic controls. Furosemide (80 mg i.v.) transiently increased p-aminohippurate clearance in controls (from 693 +/- 67 to 928 +/- 93 ml/min) and in 11 patients with ascites (from 418 +/- 81 to 526 +/- 80 ml/min). In contrast, in 13 patients with ascites, p-aminohippurate clearance fell by 34% (from 545 +/- 51 to 360 +/- 24 ml/min) within 20 min and by 41% within 60 min, and inulin clearance fell by 19% at 20 min and by 30% at 60 min. The renal effects lasted approximately 4 h. The renal response could not be predicted by renin activity, urinary prostaglandin excretion, urinary sodium, or clinical characteristics. In all 14 patients who received oral furosemide, p-aminohippurate clearance fell within 90 min (by 24%) and remained suppressed for at least 4 h. These immediate effects of furosemide on renal perfusion may contribute to azotemia in some patients with ascites.

Ascites↗
PubMed1987

The effect of perindopril on blood pressure in humans on different sodium intakes.

Perindopril is a new inhibitor of converting enzyme activity with a prolonged half-life. Thirty-two patients with essential hypertension and a diastolic blood pressure greater than 95 mm Hg were stratified into two groups according to their 24 h urine sodium excretion. They were randomized in a double-blind fashion to placebo or perindopril and a dose titration made in steps of 2, 4, 6, and 8 mg given once daily at weekly intervals. The goal diastolic blood pressure was 90 mm Hg. Goal blood pressure was achieved in 11 of 16 patients on perindopril and 3 of 6 patients on placebo. Perindopril caused a fall in BP of 22/11 (supine) and 27/14 (erect) mm Hg while the placebo group had falls of 3/2 (supine) and 3/0 (erect) mm Hg. Most of the blood pressure fall occurred in the first week of therapy with 2 mg/day. Side effects were few and occurred mainly in the placebo phase. There was no alteration in urine protein, white cell count, plasma urea, or creatinine. The fall in blood pressure achieved at the end of the titration or with 2 mg did not differ between the two groups. There was no correlation between blood pressure response and 24 h urine sodium or plasma renin activity. These results indicate that perindopril is an effective antihypertensive drug that appears to work equally well in patients on high or low sodium intake.

Aged↗
PubMed1987

Effect of atrial natriuretic peptide on collecting duct function evaluated by stop-flow in rabbits.

1. The effect of a low dose of a synthetic atrial natriuretic peptide (ANP), rat atriopeptin II (23 amino acids), on stop-flow sodium concentrations was examined in rabbits in water diuresis. 2. Atrial natriuretic peptide (2 micrograms/kg body weight) was injected intravenously as a bolus either before or after the commencement of stop-flow. 3. Atrial natriuretic peptide induced a significant natriuresis within 2 min of injection. This natriuresis was associated with smaller increases in urine volume and potassium excretion. Atrial natriuretic peptide did not alter blood pressure. 4. Atrial natriuretic peptide did not significantly alter stop-flow sodium concentrations. 5. These findings indicate that ANP does not directly alter sodium transport across medullary collecting ducts. 6. It is proposed that ANP acts via a mediator to alter sodium movement across terminal segments of the nephron.

Animals↗
PubMed1987

The effect of DOCA and 9 alpha-fludrocortisone on renal renin content and production.

1. DOCA and 9 alpha-fludrocortisone were given to rats. 2. Plasma renin fell rapidly with both treatments. 3. Renal renin fell slowly to a low level. 4. Renal renin fell to a lower level with DOCA than with 9 alpha-fludrocortisone. 5. When DOCA and 9 alpha-fludrocortisone were stopped plasma renin levels rose rapidly and the renal renin levels increased. 6. The data suggest that synthesis is altered rapidly but it takes a prolonged time for the kidney to become depleted of renin due to the high tissue stores and the associated inhibition of release.

17-Hydroxycorticosteroids↗
PubMed1987

Sodium restriction can delay the return of hypertension in patients previously well-controlled on drug therapy.

Sodium restriction can reduce blood pressure in hypertensive patients. The present study indicates that if hypertension is well controlled then the reemergence of hypertension can be decreased by the use of a reduced sodium intake. The present paper demonstrates that in such patients on a normal salt diet, 90% become hypertensive within 6 months while only 40% of people on a reduced sodium diet become hypertensive. It is proposed that a high sodium intake activates a number of amplifiers that causes a shift of the dose-response curve to sodium to the left and if not prevented or interrupted leads to the development of hypertension.

Aged↗
PubMed1987

Comparative studies of reduced sodium and high potassium diet in hypertension.

A decrease in sodium intake or an increase in potassium intake reduces blood pressure (BP) in people with essential hypertension. Additional potassium prevents, in sodium-sensitive people and rats, the rise in BP caused by extra sodium chloride. In people with a diastolic BP between 90 and 100 mm Hg, dietary reduction of sodium to 80 mmol/day and dietary increase of potassium to 90 mmol/day caused a fall in BP of 5.1/4.2 and 3.6/3.1 mm Hg, respectively, greater than was observed in the control group. There was a negative interaction between the two diets when used together with a BP change of 4.0/3.6 mm Hg. The fall in BP with sodium restriction was not reversed by the addition of sodium chloride and a similar fall in BP was not achieved with potassium chloride. It is possible that the response is due to some other factor. A strong correlation existed between the change in urine Na:K and the fall in BP. This study indicates that a reduced sodium or an increased potassium diet will reduce BP and should be considered for the initial management of essential hypertension.

Blood Pressure↗
PubMed1987

Effect of carvedilol and metoprolol on blood pressure, blood flow, and vascular resistance.

Carvedilol and metoprolol were given for 4 weeks in a double-blind study to patients with essential hypertension. The effects on blood pressure were measured and hemodynamic alterations were assessed by forearm venous plethysmography before and after chronic administration, and 2 h after an acute dose before and during chronic therapy. Carvedilol (50 mg/day) reduced supine and erect blood pressure, and pulse rate similar to the reduction with metoprolol (100 mg b.i.d.). There was a tendency for forearm blood flow to rise and for forearm resistance to fall with both drugs. When administered acutely, there was no fall in pulse rate with carvedilol compared to the fall with metoprolol when on placebo or active therapy. The blood pressure fall with acute administration was similar with both drugs when not on treatment, but when on chronic therapy, there was no fall with metoprolol but a marked fall with carvedilol. In this circumstance, vascular resistance rose with metoprolol but not with carvedilol. No effect of either drug on a modified cold presser test was observed. Both drugs were well tolerated and there were no significant side effects except for an excessive fall in blood pressure in one patient on carvedilol. Plasma renin activity (PRA) fell with both drugs and there was a tendency for both plasma potassium and plasma uric acid to rise. Carvedilol was well tolerated and reduced blood pressure successfully.

Adrenergic beta-Antagonists↗