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Biomedical subjects

T H Thomas

Publications and source records attributed to T H Thomas.

100 records · Page 6Linked to original sources
PubMed1976

The specificity of antisera for the radioimmunoassay of arginine-vasopressin in human plasma and urine during water loading and dehydration.

1. Rabbit antisera against arginine-vasopressin (AVP) were evaluated for sensitivity and specificity in a radioimmunoassay based on the extraction of AVP from plasma and urine on to Florisil. 2. Comparison of the immunoreactivity of AVP with analogues showed that one antiserum (R2) reacted principally with the hexapeptide ring and another (R4) bound to the tripeptide tail and was reactive with some reduction and hydrolytic products of the native peptide. 3. The minimum amount of AVP measurable in the radioimmunoassay was 1 pg. The extraction of AVP from plasma and urine gave a recovery of 93 per cent (sd 5 per cent). A plasma sample repeatedly assayed with R2 gave a value of 1.4 ng/1 (sd 0.2, n=12). 4. The antiserum specific for the hexapeptide ring (R2) showed that in normal subjects AVP concentration ranged from 3.2 +/- 2.52 ng/1 after dehydration to 0.16 +/- 0.1 ng/1 after water loading.

Animals↗
PubMed1975

A simple, inexpensive, high pressure liquid chromatographic method for separating cytokinins in plant extracts.

Separation of a mixture of the main cytokinins occurring naturally in plant tissues was achieved by high pressure liquid chromatography using insoluble polyvinylpyrrolidone as the solid support. The separation of each cytokinin was first assessed over a range of salt and l-butanol concentrations and pH using a mixture of borate buffer and l-butanol as the mobile phase to determine the conditions necessary for optimum resolution. A discrete separation of zeatin, N-6-(Delta-2-isopentenyl)adenine, their related ribonucleosides, and kinetin was achieved using a simple isocratic elution with 0.025 m borate buffer at pH 6.8 and 4% (v/v) l-butanol. A number of cytokinin-active compounds were detected in cabbage extracts by the Amaranthus betacyanin bioassay using this separation technique.

Journal Article↗
PubMedDate not supplied

Increased proximal tubular sodium reabsorption in hypertensive patients with type 2 diabetes.

Hyperinsulinaemia and sodium retention have been studied in 22 Type 2 diabetic patients (10 normotensive, 12 hypertensive) and 10 normal control subjects matched for age, sex, and body mass index. Exchangeable sodium was similar in the three groups. Plasma renin activity and plasma angiotensin II were lower in both groups of diabetic patients than in the normal control subjects (p less than 0.01). Plasma atrial natriuretic peptide was increased in the hypertensive patients (7.3 +/- 1.1 vs normotensive 4.7 +/- 1.1 pmol l-1 and control 4.0 +/- 0.2 pmol l-1, p less than 0.01). Fractional lithium clearance, a measure of sodium clearance from the proximal tubule, was decreased (18.5 +/- 1.4, p less than 0.01) and fractional excretion of sodium in the distal tubule was increased (6.66 +/- 0.66, p less than 0.01) in untreated hypertensive diabetic patients compared with both normotensive diabetic patients (25.3 +/- 1.6 and 3.96 +/- 0.52 respectively) and normal control subjects (25.2 +/- 2.9 and 3.31 +/- 0.38, respectively). Fasting serum insulin was higher in hypertensive than in normotensive diabetic patients (18.5 +/- 3.0 vs 10.7 +/- 1.1 mU l-1, p less than 0.01) and higher in both groups than in normal control subjects (5.6 +/- 0.1 mU l-1, both p less than 0.01). Creatinine clearance was higher in both groups of diabetic patients than in normal control subjects (p less than 0.05). Thus there appears to be increased proximal renal tubular sodium reabsorption in these hypertensive Type 2 diabetic patients, matched by a reduction in distal sodium reabsorption so that net sodium excretion was maintained. This was associated with fasting hyperinsulinaemia.

Aldosterone↗