1 The potency of single doses of the aldosterone antagonist SC8109 relative to spironolactone in reversing the urinary electrolyte effects of fludrocortisone was examined in a double-blind, balanced, crossover study in six healthy volunteers. 2 For the urinary ratio log10 10 Na/K, the relative potency of SC8109: spironolactone on a weight basis was 0.08:1 (95% confidence limits 0.04-0.13:1). 3 The potency of SC8109 relative to spironolactone for natriuresis and antikaliuresis was 0.10:1 and 0.05:1, respectively. 4 The results show excellent agreement with clinical experience where SC8109 was considered to have one tenth the potency of spironolactone. We suggest that the human bioassay employed in this study provides quantitative information which should be predictive of the therapeutic potency of aldosterone antagonists.

A sampling apparatus suitable for studying fluctuations in populations of the poultry red mite, Dermanyssus gallinae (Deg.), under field conditions is described. Four small infested poultry houses were sampled regularly for four years. In three of these years the highest population of the mite was recorded during August, and was followed by a fairly rapid fall in numbers during the autumn. Very few mites were found during the winter months. Attempts were made to increase winter populations by raising the temperature and humidity to August levels and also by increasing the amount of illumination during the winter months, but were unsuccessful.

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The activity of two aldosterone antagonists in reversing the urinary electrolyte changes induced by the mineralocorticoid fludrocortisone was examined in healthy subjects. Between 2-10 h after treatment there were dose-related increases in sodium excretion and the urine log 10 Na/K ratio, but no significant changes in urine volume, potassium concentration, or potassium excretion. Between 12-16 h after treatment there were dose-related increases in urine sodium excretion and the log 10 Na/K ratio. Unexpectedly, there were significant dose-related increases in potassium excretion despite significant dose-related reductions in urinary potassium concentration. The paradoxical increases in potassium excretion were attributed to dose-related increases in urine volume in the same period. These observations may explain the increased potassium excretion occasionally observed during clinical use of aldosterone antagonists and suggest that potassium excretion in man is influenced by the urine flow rate.

SUMMARY Sheep have been dipped in various concentrations of aldrin and dieldrin and the rate of loss of insecticide on the wool has been determined using a biological assay method. In one experiment with aldrin, the biological assay method was confirmed by chemical analysis. Depletion is rapid immediately following dipping for a period of 2–4 weeks, after this it is much slower. It has been shown that when dipping is carried out at the normal time, i.e. May to June, the chemical persists for a period of 3–4 months. When sheep are dipped in late July and August, however, the period of protection is much greater. The distribution of insecticide over the fleece has been examined; the area with least pick‐up of insecticide is in the tail region where the wool is coarse. Weather and rate of wool growth could not be correlated with rate of insecticide loss.