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J Orloff

Publications and source records attributed to J Orloff.

8 recordsLinked to original sources
PubMed1979

Microsurgical techniques in organ physiology and transplantation studies.

Experimental models for studies of physiology and pathology of different organs should be technically simple and reproducible, especially when large numbers of animals are required. Also uniform, often genetically identical, populations of animals are necessary to obtain reliable data. To meet these requirements studies should be performed on small animals. Modern microsurgical techniques help in solving these problems. The basic principles of microsurgical techniques and the microsurgical physiological and transplantation models have been described. Standardizing of techniques and models will allow better comparison of data from different centers.

Animals↗
PubMed1978

Role of prostaglandin E (PGE) in the modulation of the action of vasopressin on water flow in the urinary bladder of the toad and mammalian kidney.

PGE1 and PGE2 are known to interfere with the water permeability effect of vasopressin in toad bladder and kidney. It has been proposed that endogenous prostaglandin E (PGE), synthesized within cells of vasopressin-sensitive tissues, serves to modulate the permeability changes elicited by the neurohypophyseal hormone. Direct evidence in support of this hypothesis is as follows: vasopressin increases the biosynthesis of PGE2 in renal interstitial cells and in isolated toad bladder. In the latter, inhibition of vasopressin-induced synthesis of PGE by a variety of inhibitors results in a greater water permeability response to vasopressin. It appears that vasopressin has two effects in toad bladder and kidney: (i) it activates adenylate cyclase thereby increasing the concentration of adenosine 3',5' monophosphate (cyclic AMP), the nucleotide responsible for the resultant increase in water permeability; and (ii) it activates a phospholipase that serves to release arachidonic acid, the precursor of PGE2 from intracellular pools. The PGE derived from the arachidonic acid diminishes adenylate-cyclase activity, in consequence of which the response of the enzyme to vasopressin is modulated.

Adenylyl Cyclases↗
PubMed1976

Effect of parathyroid hormone and cyclic AMP on protein phosphorylation in rabbit kidney cortex.

Suspensions of renal cortical tubules were incubated with 33Pi and exposed to parathyroid hormone (40 mlg/ml) or 1 mM dibutyryl cyclic AMP. In other experiments homogenates of renal cortex were assayed for protein kinase and phosphoprotein phosphatase activity using [gamma-32P]ATP with or without 5 mM cyclic AMP. Proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and phosphorylation of proteins measured by liquid scintillation counting of gel slices. The pattern of protein phosphorylation was similar in control tissue from both tubule suspensions and homogenates. In intact tubules, parathyroid hormone stimulated the phosphorylation of four proteins with molecular weights of approx. 150 000, 125 000, 100 000 and 50 000 by 28%, 24%, 13%, and 20%, respectively. Results with dibutyryl cyclic AMP were comparable but more variable. Stimulation of phosphorylation by cyclic AMP in homogenates was more generalized with the major effect on a 50 000 dalton protein (50% stimulation). No effect of cyclic AMP on dephosphorylation of proteins was observed. The results are interpreted as indicating that increased phosphorylation of cell proteins is part of the cyclic AMP-mediated response of the renal cortex to parathyroid hormone.

Animals↗
PubMed1976

Effect of norepinephrine and hypertonicity on K influx and cyclic AMP in duck erythrocytes.

Cyclic adenosine 3',5'-monophosphate (cAMP) accumulation and cation transport were measured in duck erythrocytes after stimulation by norepinephrine (NE) or shrinkage induced by exposure to hypertonic media (S). Previously both NE and S were shown to initiate a similar transport process in this cell. NE elicited a rapid rise in cellular cAMP and 42K influx. Both effects were eliminated by propranolol. At concentrations of NE below 3 X 10(-8) M (the concentration at which 42K influx saturates), there was good correlation between the magnitude of the permeability change and the increment in cAMP. In contrast, medium hypertonicity, at a level which stimulated K influx to the same extent as a near-maximal norepinephrine response, did not alter cAMP content. The data are discussed in terms of a model in which S and NE activate a final common transport pathway by different mechanisms, which in the case of S does not involve cAMP.

Animals↗
PubMed1975

Lack of relationship of potential difference to fluid absorption in the proximal renal tubule.

Fluid absorption by isolated perfused rabbit proximal convoluted tubules is accompanied by an electrical potential difference (PD), negative in the lumen, when the tubule is bathed by rabbit serum and perfused with an ultrafitrate of that serum. In contrast the PD is positive when the perfusate composition approximates that of fluid in the late proximal tubule in vivo, which lacks glucose, amino acids and bicarbonate. The principal purpose of the present studies was to investigate the characteristics of fluid absorption under these conditions. Proximal convoluted tubules were dissected from rabbit kidneys and perfused in vitro. When the PD was positive, the mean net fluid absorption was 81 nl mm minus 1 min minus 1. The positive PD is caused by a chloride concentration difference across the tubule epithelium (higher in the lumen than in the bath). Elimination of the chloride concentration difference by replacing the bicarbonate in the bath as well as in the perfusate with chloride caused the PD to fall to zero without a significant change in the rate of fluid absorption. Therefore, neither the positive PD nor the chloride concentration difference is significantly related to the fluid absorption. Ouabain inhibited fluid absorption under all of the above conditions, making it likely that the fluid absorption is due to active sodium transport. Although the results are consistent with the generally accepted view that active sodium transport is a major driving force for fluid absorption, the mechanism of anion (chloride) transport is uncertain owing to the lack of correlation between fluid absorption and the transepithelial PD.

Absorption↗
PubMed1975

Release of cyclic AMP by toad urinary bladder.

Cyclic AMP accumulates in the Ringer solution bathing the toad urinary bladder in vitro. At least 4 times more cyclic AMP is released into the solution bathing the serosal surface than into the solution bathing the mucosal surface. Most of the cyclic AMP originates in the epithelial cells rather than the stroma. Vasopressin increased the content of cyclic AMP in the epithelial cells and increases the amount of cyclic AMP in the Ringer solution. Since there is not an increase in medium cyclic AMP when cell cyclic AMP levels are increased by theophylline, it is suggested that theophylline may reduce the permeability of the cell membrane to cyclic AMP. Finally, it is demonstrated that 10 mM NaF increase the amount of cyclic AMP in the epithelial cells and in the solution bathing the bladder, but block the effect of vasopressin on water permeability, presumably at a step subsequent to the formation of cyclic AMP.

Animals↗