Circadian rhythms of serum renin activity and serum corticosterone, prolactin, and aldosterone concentrations in the male rat on normal and low-sodium diets

To investigate the control of aldosterone secretion, non-stress levels of serum aldosterone, corticosterone, and prolactin, and renin activity were determined at 4-h intervals during 24-h light-dark cycles in adult male rats on regular and low-sodium diets. Circadian rhythms of plasma aldosterone, prolactin, and corticosterone concentrations and of serum renin activity were demonstrated during a regular sodium diet. When the rats were on a low-sodium diet, a circadian rhythm of serum corticosterone and aldosterone concentration was observed, but there was no circadian variation in serum renin activity or in serum prolactin concentration. Serum aldosterone concentration correlated with serum corticosterone concentration (r = 0.48) and serum renin activity (r = 0.36) during a low-sodium diet. Serum prolactin concentration did not correlate with serum aldosterone concentration or serum osmolality. These data are compatible with a role for renin and ACTH, but not for prolactin, in the modulation of aldosterone secretion in the rat.     

Anisocytosis and the C-1000 Channelyzer in macrocytic anaemia

Red cell anisocytosis as assessed using the Coulter Channelyzer C-1000 showed an increase with progressive anaemia in 25 patients with macrocytosis due to B12 and/or folate deficiency. In deficiency of a single factor, the degree of anisocytosis increased with progressive anaemia. In five cases with B12 and folate deficiency combined, anisocytosis was markedly increased out of proportion to the degree of anaemia present. Iron stores were also reduced in four of these cases. It is suggested that objective measurement of anisocytosis is of early diagnostic value in the assessment of multiple haematinic factor deficiency, for example, in macrocytic anaemia associated with malabsorption states and unexpected multiple deficiency states.     

Thiamine triphosphate levels and histopathology. Correlation in Leigh disease

Thiamine and thiamine triphosphate (TTP) values were assayed in various brain regions in 11 controls and 13 patients with subacute necrotizing encephalomyelopathy (SNE, Leigh disease). The TTP values of normal brain were 5% of the total thiamine value. The relative TTP (or % TTP) level was consistently low in the pons, midbrain, and cerebellum of all the SNE brains. Twenty-five percent of the SNE brains had normal TTP levels in the frontal region. The TTP values correlated with the degrees of pathologic involvement in all sampled regions of the brain except the cerebellum. The concentration of thiamine in the mammillary bodies exceeded its concentration elsewhere in both control and SNE brains. The finding of low TTP levels in morphologically abnormal regions supports the hypothesis that TTP deficiency is etiologically related to SNE.     

Systemic methotrexate toxicity. A pharmacological study of its occurrence after intrathecal administration in a patient with renal failure

Methotrexate pharmacokinetic studies, performed on a patient with renal impairment who had toxic effects following 20 mg/sq m of intrathecally administered methotrexate, demonstrated prolonged serum concentrations of the drug, which accounted for the condition. After the return of normal renal function, pharmacokinetic studies were repeated following the same dose and route of administration of methotrexate. On this occasion there was a rapid clearance of serum methotrexate below toxic levels.     

Increasing polyunsaturation of milk fats by feeding formaldehyde protected sunflower-soybean supplement

A practical means of protecting fats of a feed concentrate containing high polyunsaturated fatty acids is described. A ground mixture of 30% soybeans and 70% sunflower seeds was treated with 1% formaldehyde to protect the unsaturated lipids from microbial hydrogenation in the rumen. This was fed as a supplement to two Holstein cows in amounts that were doubled weekly. These ranged from 524 to 8384 g/day and provided successively increasing intakes of 100, 200, 400, 800, and 1600 g of linoleic acid daily. Percent milk fat increased by more than one, and linoleic acid (C18:2) of milk fat increased from 2.5 to 20% with compensatory declines in myristic (C14:0) and palmitic (C16:0) acids. Cholesterol and vitamin E of plasma both doubled at the highest supplementation. Milk yield, solids-not-fat, protein and milk cholesterol were unaltered. Fat in feces doubled from about 3 to 6%. Daily linoleic acid content of feces increased from 25 g to 120 g, indicating a dietary loss of 7 to 10% of this polyunsaturated acid. These cheaper feed ingredients elevated the polyunsaturated fats in milk as effectively as the expensive purified casein and safflower oil supplements in previous experiments.     

Betadrenoceptors in urinary bladder

When rat peroneal nerves were fixed under 5 different fixation schedules with various osmolalities (310, 410 and 900 milliosmoles), the frequency of abnormality of mitochondria in the axoplasm was lowest in myelinated fibers fixed with 6% glutaraldehyde in 0.1 M cacodylate buffer (900 milliosmoles). The relationship of axonal area to number of myelin lamellae was significantly different between high-osmolality fixation and low-osmolality fixation. Assuming that the number of myelin lamellae remains the same with fixation, there was a significant shrinkage in the axonal area of fibers with high-osmolality fixation. The amount of shrinkage was less in larger fibers than in smaller fibers fixed at high osmolality.     

Fungal products. Part XVII. Microbiological hydroxylation of gibberellin A9 and its methyl ester

Angiotensin II (A II) and analogues were tested for their ability to restore electrical and mechanical activity to cardiac muscle preparations in which the fast Na+ channels had been inactivated by partial depolarization (22-27 mM K+) or by tetrodotoxin (TTX). The partially depolarized or TTX-blocked preparations were chosen because under these conditions electrical and mechanical responses are primarily Ca2+ -dependent. In depolarized rabbit right atria, A II restored spontaneous mechanical and electrical activity (measured by both intracellular and extracellular recording techniques). The frequency of action potential discharge was concentration-dependent; the threshold concentration of A II was 10(-10) M, the ED50 was 8 X 10(-9) M, and the maximum effect was observed at 5 X 10(-8) M. In contrast, depolarized guinea pig atria were insensitive to A II, Sar1-angiotensin II, and des-Asp1-angiotensin II, even at concentrations as high as 10(-5) M. Rabbit papillary muscle (TTX-blocked), embryonic (18-day) chick heart (partially depolarized) and chick heart reaggregates (TTX-blocked) responded similarly to rabbit atria in that A II (9.6 X 10(-7) M) restored both electrical and mechanical activity. We found that in these preparations the action of A II was unaffected by propranolol (5.0 X 10(-6) M to 5.0 X 10(-5) M) but was blocked by Mn2+ (10(-3) M), D-600 (1 X 10(-7) g/ml) and the specific A II antagonists Sar1-Ala8-angiotensin II (P-113) (5.0 X 10(-5) M) and Sar1-Ile8-angiotensin II (5.28 X 10(-5) M). We conclude that the positive inotropic effect of A II on the myocardium is due to its ability to increase transmembrane ion movements in or through the cell membrane. The ability of Mn2+ and D-600 to block this effect suggests that this ion movement is via the so-called "slow channels."     

An electrophoretic analysis of RNA synthesis in normal and lobeless Ilyanassa embryo

A primary infection with schistosoma mansoni, of 5 or more weeks duration, stimulated a high level of resistance to a challenge infection in the WO outbred strain of golden hamster. In sharp contrast, the LGN strain showed no statistically significant immunity to reinfection in most experiments and where detected the level of resistance was only about half that observed in the WO strain. Immunity to reinfection was assayed with the lung recovery method which assesses resistance a few days after challenge and with the conventional perfusion assay which measures immunity 6 weeks after challenge. Wide differences in the immune response to S. mansoni in different strains of the same host species have not been reported previously.     

Regulation of nitrogen catabolic enzymes in chick liver -- effects of amino acids

It is well-known that in the chick, dietary protein increases the levels of several hepatic enzymes that are involved in nitrogen metabolism and excretion. However, the biochemical mechanism of this response is essentially unknown. The experiments presented in this paper show that the chick is responding to alpha-amino nitrogen and not to any specific amino acid. Furthermore, it is shown that this system responds to endogenous sources of nitrogen as well as dietary protein and that the xanthine dehydrogenase response involves regulation of enzyme synthesis without changing the rate of degradation.