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Biomedical subjects

L Hurwitz

Publications and source records attributed to L Hurwitz.

At least 37 records · Page 2Linked to original sources
PubMed1975

Effects of temperature and inorganic ions on calcium accumulation in microsomes from intestinal smooth muscle.

Energy dependent calcium binding in microsomal vesicles from the longitudinal smooth muscle of the guinea pig intestine was investigated at two different temperatures (30 degrees C and 10 degrees C) and in the absence and presence of CdCl2, BaCl2 and MnCl2. The investigation was carried out to determine whether the effects of temperature and the effects of the divalent ions on microsomal calcium binding could be correlated with the effects of these interventions on the mechanical activity of the intact longitudinal fibers. A reduction in temperature from 30 degrees C to 10 degrees C inhibited both the uptake of calcium into the microsomes and the rate of release of calcium ions from the microsomes to the external medium. This exchange in temperature also slowed the rate of relaxation of the intact longitudinal muscle after it had been induced to contract with acetylcholine and subsequently allowed to relax by removing calcium ions from the bathing medium and adding 1 X 10(-3) M EGTA. The presence of CdCl2, like the reduction in temperature, decreased the uptake of calcium into the microsomal vesicles. However, the release of calcium from the microsomes was accelerated. BaCl2, produced the same effects as did CdCl2 on the uptake of calcium into microsomes but to a lesser extent. It had very little effect on the release of calcium ions from the microsomes. MnCl2 had no significant effects on either the uptake or release of calcium ions in the microsomal preparation. Both CdCl2 and MnCl2 exerted an inhibitory action on acetylcholine-induced contractile responses of the intact longitudinal fibers; whereas BaCl2 served to initiate a contractile response in the smooth muscle fibers. Thus, it would appear that the effects of a temperature change on microsomal calcium binding and on mechanical activity in intact fibers can be correlated; but the effects of CdCl2, BaCl2 and MnCl2 on these two cellular processes do not follow any consistent pattern.

Animals↗
PubMed1975

Electron microscopic localization of calcium in vascular smooth muscle.

Potassium pyroantimonate has been employed in this study to localize calcium in the vascular smooth muscle of the thoracic aorta of the rabbit. The pyroantimonate ion precipitates sodium, magnesium and calcium. Incubation of theisolated thoracic aorta in a high potassium bathing medium which does not contain sodium, magnesium or calcium depletes the tissue of sodium. Addition of 10.8 mM CaC12 to the incubation medium results in well-localized depositions of reaction product, presumably that of calcium pyroantimonate, in mitochondria, sarcoplasmic reticulum, and at the plasma membrane. Some or all of these organelles may, therefore, play a vital role in the contraction-relaxation cycle of vascular smooth muscle.

Animals↗
PubMed1975

New thoughts concerning xanthogranulomatous pyelonephritis (X-P).

A clinical and roentgenographic analysis of 13 patients with pathologically proved xanthogranulomatous pyelonephritis (X-P) has demonstrated that many previously accepted truisms associated with this disease may not be valid. As a result of this study it is suggested that X-P: 1. Does have a prominant female distribution. 2. May arise relatively acutely. 3. Can be associated with a well-functioning kidney. 4. May destroy the kidney and collecting system. 5. Does not demonstrate neovascularity. 6. Can be distinguished angiographically from hypernephroma. 7. May be associated with diabetes. Other important facts were again observed: 1. X-P is still often associated with staghorn calculi and urinary tract obstruction. 2. Proteus mirabilis is the main offending organism.

Adenocarcinoma↗
PubMed1973

Localization of calcium pump activity in smooth muscle.

A microsomal fraction isolated from longitudinal smooth muscle of guinea pig ileum actively sequesters calcium ion in the presence of magnesium and adenosine triphosphate in a fashion previously described for microsomes of the rabbit aorta. This activity in guinea pig ileum appears to be associated primarily with the plasma membrane as is found in the red cell. By contrast the uptake of calcium in aortic smooth muscle appears to be associated to an appreciable extent with intracellular membranes, possibly analogous to the sarcoplasmic reticulum of skeletal muscle.

Adenosine Triphosphatases↗
PubMed1972

A calcium pump in vascular smooth muscle.

A microsomal cell fraction derived from the intimal-medial layer of rabbit aorta takes up calcium in the presence of magnesium and adenosine triphosphate. The rate of uptake of calcium is slower than that observed in skeletal muscle microsomes. Uptake of calcium by mitochondria from the aorta is even more limited and, unlike microsomal uptake, is inhibited by azide.

Adenosine Triphosphate↗
PubMed1967

Acetylcholine and calcium on membrane permeability and contraction of intestinal smooth muscle.

Acetylcholine elicited a sustained contraction and an increase in potassium efflux in longitudinal muscle isolated from the guinea pig ileum. Stepwise increases in the calcium concentration of the bathing medium, from 0.06 to 36 mM generally reduced the increase in potassium efflux, but had a complex effect on the mechanical response. Contractions produced by high levels of acetylcholine became progressively larger or remained at a high magnitude as the calcium concentration was increased. Contractions produced by low levels of acetylcholine also improved initially, but were depressed again by the highest concentration of calcium introduced. Ethanol, in the appropriate concentration, inhibited completely the acetylcholine-induced contraction without reducing the increase in potassium efflux. Calcium reversed this effect. Both extracellular calcium and ethanol depressed the large, transient increase in muscle tone developed by fibers that were preincubated in a high calcium medium and then exposed to a calcium-free medium. These findings suggested that extracellular calcium ions react with two different sites in the membrane, a stabilizing site and a storage site. A muscle contraction is activated by calcium ions which diffuse from the storage site to the myoplasm. Calcium ions reacting with the stabilizing site impede this diffusion process. Part of the stimulatory effect of acetylcholine is derived from its capacity to counteract the action of calcium at the stabilizing site.

Acetylcholine↗