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L cells (mouse fibroblasts), uninfected and infected with Chlamydia psittaci (meningopneumonitis strain), were labeled with (14)C-amino acids, and their membranous organelles were separated by isopycnic equilibrium centrifugation of whole cell homogenates on discontinuous sucrose density gradients. Incorporation of labeled amino acids into host and parasitic proteins was differentiated on the basis of susceptibility to cycloheximide. Twenty hours after infection with C. psittaci, incorporation of newly synthesized proteins into the internal membranes of L cells was almost completely inhibited, and internal membranes made prior to infection were altered or destroyed. The unit membrane that at all times surrounds the cytoplasmic vacuole containing the multiplying chlamydiae was made by the host from membranes or membrane precursors present before infection. No proteins synthesized by C. psittaci became associated with host cell membranes. Destruction or modification of the internal membranes of the host cell may be an integral part of the chlamydial developmental cycle.

Blood pressure control was examined in 75 patients with end-stage renal failure treated by regular twice-weekly haemodialysis. Dietary sodium was restricted and extracellular fluid was removed by ultrafiltration until blood pressure was normal or signs of salt depletion were observed. Failure of these measures constituted an indication for nephrectomy. Of the 75 patients, 18 were never hypertensive, 46 had hypertension which could be corrected by salt and water depletion, and 11 had persistent hypertension which could not be controlled in this way. Nine of these 11 patients underwent bilateral nephrectomy; in each of the seven in whom the post operative result could be evaluated the blood pressure returned rapidly to normal.Plasma renin activity, measured in 34 subjects, was raised above normal in six out of nine patients whose blood pressure could not be controlled by salt and water depletion and in one of the 11 patients whose blood pressure could be so controlled, but was within the normal range in all nine normotensive patients. The mean level of plasma renin activity in the first group was significantly higher than that of each of the other two groups.There was a significant correlation between hypertension during dialysis and after transplantation, suggesting that, in addition to renin, there is a non-renal factor which predisposes certain patients to hypertension in the presence of salt and water excess.