Pardaxin increases solute permeability of gills and rectal gland in the dogfish shark (Squalus acanthias).

The action of the ichthyotoxic secretion of the Red Sea flatfish Pardachirus marmoratus and its derived toxin, pardaxin, was examined in the dogfish shark (Squalus acanthias). Pardaxin was more toxic when administered to the bathing medium than when injected into a dorsal artery and it transiently diminished the spiracular rate and caused a severe struggling response in the adult shark only when administered to the head region of the shark. Pardaxin caused a transient leakage to urea and sodium between the shark and the seawater.

Structure of tight junctions during Cl secretion in the perfused rectal gland of the dogfish shark.

In epithelia that secrete sodium chloride, high-conductance tight junctions between cells have been proposed as the primary pathway for transepithelial sodium flux. We examined the properties of tight junctions in the perfused rectal gland of the dogfish shark during basal secretion and following adenosine 3',5'-cyclic monophosphate stimulation of sodium chloride secretion. Freeze-fracture electron microscopy revealed extensive interdigitation of adjacent cells with an associated amplification in the length of tight junctions per area of luminal surface, averaging 102 +/- 4.

Effects of hemodialysis and saline loading on body fluid compartments, plasma renin activity and blood pressure in patients on chronic hemodialysis.

The influence of one hemodialysis session and of subsequent loading by 1.5-2 liters N saline on blood pressure, PRA and body fluid compartments was assessed in seven patients with chronic renal failure on maintenance hemodialysis. Dialysis caused only slight decreases in plasma volume, ECV and in TEBS.

Hypomagnesemia following the diuresis of post-renal obstruction and renal transplant.

Three unusual cases are described which demonstrated hypomagnesemia and symptoms resembling magnesium deficiency syndrome. The hypomagnesemia was most likely secondary to urinary losses from diuresis following release of post-renal obstruction and renal homotransplantation. Heretofore, this association has not been described.

Pathogenic role of cyclic AMP in the impairment of urinary concentrating ability in acute hypercalcemia.

A possible association between the impairment of urinary concentrating ability and an impairment of the vasopressin-dependent cyclic AMP system in hypercalcemia was investigated in rat kidneys both in vivo and in vitro. The increases of urinary osmolality and negative free water clearance and the increase of urinary cyclic AMP excretion by vasopressin injection were significantly less in the hypercalcemic rats than in the control rats. The increase of cyclic AMP concentration by vasopressin in renal medullary tissue was significantly less in the slices obtained from the hypercalcem'c rats than in those obtained from the control rats.

Effects of catecholamines and their interaction with other hormones on cyclic 3',5'-adenosine monophosphate of the kidney.

Catecholamines have several physiological effects on the kidney. These include: (a) stimulation of renin synthesis in the cortex: (b) antidiuresis by beta adrenergic agents; and (c) diuresis by alpha adrenergic stimulation. The role of cyclic 3',5'-adenosine monophosphate (cyclic AMP) in the renal actions of catecholamines was evaluated by measuring the effects of several adrenergic agents on cyclic AMP concentration in the dog kidney.

Dissociation of bradycardia and arterial constriction during diving in the seal Phoca vitulina.

Bradycardia associated with diving in the harbor seal has been dissociated from the arterial constrictor response by intracardiac pacing. Development of arterial constriction does not depend upon the development of bradycardia. During pacing, arterial constriction continues in the absence of bradycardia.

The determination of total body exchangeable O2 stores.

A method is described for the measurement of total body exchangeable oxygen stores (TBO(2)). It is based on the dilution of the stable oxygen isotope, (18)O(2), by the body exchangeable oxygen stores under circumstances in which (18)O(2) steady-state equilibrium was evaluated simultaneously for both arterial and venous blood compartments. After evaluation of several simplifying assumptions, TBO(2) values in dog, normal man, and anemic patients were measured.