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Biomedical subjects

J Orloff

Publications and source records attributed to J Orloff.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1972

The effect of aldosterone on the accumulation of adenosine 3':5'-cyclic monophosphate in toad bladder epithelial cells in response to vasopressin and theophylline.

Vasopressin and theophylline both increase the content of adenosine 3':5'-cyclic monophosphate (cAMP) in epithelial cells of the urinary bladder of toads (Bufo marinus). Incubation of the tissue with 0.2 muM aldosterone markedly increases this response to the two agents; incubation for a similar time without steroid reduces the response. The permeability responses (sodium transport and water flow) of the intact tissue to vasopressin, theophylline, and exogenous cAMP are also considerably greater in bladders incubated with aldosterone than without. The results are interpreted as indicating that the foregoing permissive effects of aldosterone on the permeability responses to vasopressin and theophylline are mediated by a steroid-dependent increase in the accumulation of cAMP in the pertinent epithelial cells, probably as a consequence of a diminution in the rate of degradation of the intracellular nucleotide.

Aldosterone↗
PubMed1971

The effect of norepinephrine and dibutyryl cyclic adenosine monophosphate on cation transport in duck erythrocytes.

Freshly prepared duck erythrocytes, incubated either in plasma or an isotonic synthetic medium containing norepinephrine ([K] of both media approximately 2.5 mM), maintain water and electrolyte composition in the steady state (upper steady state) for at least 90 min. If incubated in the synthetic medium without norepinephrine or in plasma to which a beta-adrenergic blocking agent (propranolol) is added, the cells lose both water and electrolyte (predominantly KCl) until a new steady state is reached (lower steady state). Reaccumulation of water and electrolyte from isotonic solutions toward the upper steady-state levels requires the addition of norepinephrine and KCl. Reaccumulation is maximal when the concentration of K and norepinephrine in the medium is 15 mM and 10(-7)M, respectively. Dibutyryl cyclic-AMP (10(-2)M) mimics norepinephrine in lower steady-state cells. Although an analogous effect in upper steady-state cells was not established with certainty, it is proposed that the catecholamine-induced net changes in water and electrolyte movement in duck erythrocytes are a consequence of stimulation of the activity of a membrane-bound adenyl cyclase system.

Adenine Nucleotides↗
PubMed1971

Kidney.

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Acidosis↗
PubMed1971

Characteristics of NaCl and water transport in the renal proximal tubule.

Renal proximal tubular transport of salt and water has been examined using isolated perfused rabbit tubules. In this method direct measurements can be made under controlled conditions not readily achieved in vivo. The results are in general agreement with previous micropuncture studies in other species, supporting the validity of both sets of measurements. In the present studies, absorption of sodium salts and water occurred without change in the concentration of Na in the lumen except when a poorly reabsorbed solute (raffinose) was present, in which case, mean concentration of Na in the lumen reached a steady-state value 33-35 mEq liter(-1) less than in the bath. The tubule is very permeable to sodium salts (sodium permeability = 9.3 x 10(-5) cm sec(-1), sigma(NaCl) = 0.68-(0.71) and to water (hydraulic conductivity [L(p)] = 2.9 to 6.3 x 10(-5) cm sec(-1) atm(-1)). Net reabsorptive flux of Na was only 20% of the unidirectional Na flux. The steady-state concentration difference for Na in the presence of raffinose and sigma(NaCl) in the present studies was the same as previously found by micropuncture in the rat. On the other hand Na permeability, net Na transport rate, and L(p) were all from one-half to one-third as great in the isolated rabbit tubule as in the rat in vivo. Apparently, although the transport mechanisms appear to be basically the same in the two species, there are fewer transport units and passive permeability paths per unit length in the rabbit tubule than in the rat.

Animals↗