Effect of chemical sympathectomy on renal hydroelectrolytic handling in dogs with chronic caval constriction

The effect of renal selective chemical sympathectomy by intrarenal infusion of 6-hydroxydopamine (6-OHDA, 5 mg/kg body weight) on the renal excretion of water and electrolytes was studied in 7 dogs in whom a syndrome of sodium and water retention and ascites formation was induced by partial constriction of thoracic inferior vena cava. Propranolol (1 mg) and phentolamine (3 mg) were also injected to obviate acute systemic hemodynamic changes. Sympathectomy was performed once in 4 dogs and three times in 3 dogs. Sympathectomy induced an abrupt and transient increase in urinary flow (from 170 +/- 30 to 890 +/- 60 ml/24 h) and sodium excretion (from 4.5 +/- 1.5 to 178 +/- 21 mEq/24 h). This was accompanied by an important fall in plasma renin activity (from 2.2 +/- 0.2 to 0.5 +/- 0.1 ng angiotensin I/ml/h) and aldosterone, and disappearance of ascites. It is concluded that chemical sympathectomy, by increasing renal sodium and water excretion, mobilizes the ascites induced by chronic caval constriction, a fact that highlights the role of the renal sympathetic system in the pathogenesis of sodium and water retention by the kidney.     

Trypanosoma cruzi: distribution of fluorescently labeled tubulin and actin in epimastigotes

Cytoskeletal components were visualized in epimastigote forms of Trypanosoma cruzi by double immunofluorescence microscopy using monospecific antibodies against tubulin and against actin. Intense staining of the flagellum and the edges of the cell body was observed when the cells were stained with anti-tubulin, reflecting the presence of the basal bodies, the flagellar axoneme and the subpellicular microtubules. A less intense staining was seen in the cell body of epimastigotes stained with anti-actin. However, an intense staining was observed with this antibody in the flagellum, in a pattern similar to that observed with anti-tubulin. It is suggested that the paraxial structure, which is formed by a complex array of 6-nm-thick microfilaments is composed, at least in part, of actin.     

Glucose transport in Entamoeba histolytica

That the uptake of glucose by the parasitic amoeba Entamoeba histolytica occurs by an equilibrative transport system is supported by the following observations. 1. The rate of glucose uptake is several orders of magnitude greater than the uptake by pinocytosis. 2. The uptake of glucose exhibits saturation kinetics, with K(m)=1.6mm and V(max.) ranging from 2 to 5mumol/min per ml of cells at 37 degrees C. 3. The glucose analogues 2-deoxyglucose, 3-O-methylglucose and d-xylose are transported by the glucose system although with much less affinity. Competitive inhibition was observed between pairs of substrates, with K(i) values for any sugar closely coincident with the corresponding K(m). 4. d-Xylose, a sugar not metabolized by the cells, equilibrated with 80% of the amoebal cell water. 5. Cells equilibrated with xylose exhibited countertransport of this sugar against its concentration gradient when another substrate was added to the medium. 6. Blocking of glycolysis by iodoacetate or F(-) has no immediate effect on transport. The presence of a glucose-transport system in E. histolytica contrasts with the situation found in the non-parasitic amoeba, where pinocytosis seems to be the only mechanism of solute uptake.