Interactions of the inhibitory component of troponin, F-actin, and tropomyosin

The interaction of the inhibitory component (TN I) of troponin and F-actin in the presence and absence of tropomyosin was studied by a number of physico-chemical techniques: i.e., gel filtration, ultracentrifugation, flow birefringence, viscosity and dynamic viscoelasticity measurements, and electron microscopy. The results indicated that TN I and F-actin interact with each other more strongly in the presence of tropomyosin than in its absence. The physiological implication of this finding is discussed.

Pseudocyst of the pericardium developing during maintenance hemodialysis. Report of two cases

Two cases of pericardial pseudocyst which developed in the course of maintenance hemodialysis are reported. Both patients were usually free of complaints, although there was evidence of the previous pericarditis with recent accumulation of pericardial effusion. As a possible mechanism leading to pericardial pseudocyst formation, distension of a weak area of the thickened pericardium due to an increase in intrapericardial pressure was assumed. Therefore, pericardial pseudocyst is one of the likely complications of patients on maintenance hemodialysis.

Renal tubular acidosis, presenting as a syndrome resembling Bartter's syndrome, in a patient with arachnodactyly

A 23-year-old man with Marfan's syndrome (forme fruste) and renal tubular acidosis presented a syndrome closely resembling that reported by Bartter et al. (1962), i.c., a markedly increased plasma renin activity (PRA), hypokalaemia with normal blood pressure, decreased response of blood pressure to angiotensin II infusion and hyperaldosteronism. Hyperplasia of the juxtaglomerular apparatus was seen on renal biopsy. The studies on renal tubular function demonstrated that the patient had a unique feature corresponding to a proximal type of renal tubular acidosis (RTA).

During the period of sodium restriction the patient showed an abrupt decrease in sodium excretion to near or below intake levels with a tendency to potassium conservation but PRA remained unchanged. Sodiumloading did not suppress the increased level of PRA and albumin infusion showed only a little suppression of PRA. On the other hand, the oral administration of furosemide induced a significant increase in PRA. Replacement therapy with potassium induced a marked elevation of the urinary aldosterone level with a concomitant decrease in PRA when the serum potassium rose, but the PRA still remained above a level 10 times as high as the normal value.

These findings suggested that the mechanism of renin secretion in this patient was reset at a high level. A hypothetical role of PRA in the reset mechanism of renin secretion and pathophysiology of this patient are discussed. The relationship between RTA and Marfan's syndrome remains obscure.