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Biomedical subjects

M Jena

Publications and source records attributed to M Jena.

9 recordsLinked to original sources
PubMed1999

Vasoconstrictors and nitrovasodilators reciprocally regulate the Na+-K+-2Cl- cotransporter in rat aorta.

Little is known about the function and regulation of the Na+-K+-2Cl- cotransporter NKCC1 in vascular smooth muscle. The activity of NKCC1 was measured as the bumetanide-sensitive efflux of 86Rb+ from intact smooth muscle of the rat aorta. Hypertonic shrinkage (440 mosmol/kgH2O) rapidly doubled cotransporter activity, consistent with its volume-regulatory function. NKCC1 was also acutely activated by the vasoconstrictors ANG II (52%), phenylephrine (50%), endothelin (53%), and 30 mM KCl (54%). Both nitric oxide and nitroprusside inhibited basal NKCC1 activity (39 and 34%, respectively), and nitroprusside completely reversed the stimulation by phenylephrine. The phosphorylation of NKCC1 was increased by hypertonic shrinkage, phenylephrine, and KCl and was reduced by nitroprusside. The inhibition of NKCC1 significantly reduced the contraction of rat aorta induced by phenylephrine (63% at 10 nM, 26% at 30 nM) but not by KCl. We conclude that the Na+-K+-2Cl- cotransporter in vascular smooth muscle is reciprocally regulated by vasoconstrictors and nitrovasodilators and contributes to smooth muscle contraction, indicating that alterations in NKCC1 could influence vascular smooth muscle tone in vivo.

Angiotensin II↗
PubMed1997

A volume-sensitive, IP3-insensitive Ca2+ store in vascular endothelial cells.

The mechanism by which cell swelling and other physical forces increase the intracellular Ca2+ concentration ([Ca2+]i) is poorly defined. In vascular endothelial cells, the increase in [Ca2+]i after hypotonic swelling was independent of external Ca2+ and membrane potential, was not blocked by La3+ or Gd3+, and was prevented by thapsigargin, indicative of intracellular release. This release also occurred after depletion of agonist-sensitive Ca2+ stores. In cells in which the plasma membrane was permeabilized with saponin, hypotonic medium stimulated release of 45Ca2+ from a thapsigargin-sensitive site. Isosmotic substitutions with sucrose or urea revealed that this release was due specifically to swelling and not to changes in osmolarity or ion concentrations. This volume-sensitive release was inhibited by high concentrations of La3+ and Gd3+ in a time-dependent manner, suggesting inhibition from within the storage compartment. Release was not inhibited by ruthenium red or by prior stimulation with inositol 1,4,5-trisphosphate (IP3), indicating that the volume-sensitive storage site is distinct from mitochondria and from stores sensitive to ryanodine or IP3. The results suggest the presence of a novel, stretch-activated Ca2+ store in endothelial cells that could contribute to their mechanosensitivity.

Adenosine Triphosphate↗
PubMed1997

Granulomatous interstitial nephritis and uveitis presenting as salt-losing nephropathy.

Salt-wasting nephropathy is a rare syndrome in which renal insufficiency is associated with extracellular volume depletion from marked natriuresis in the absence of adrenal insufficiency or diuretics. We report the clinical course of a 23-year-old woman with renal insufficiency, in association with orthostatic hypotension and salt wasting. A combination of daily infusion of saline, a high-salt diet and oral fludrocortisone did not compensate for her salt loses. Renal biopsy showed noncaseating granulomas and marked interstitial inflammation. Renal function and salt loss improved with prednisone therapy and 6 months after withdrawal of steroids, her renal function remains stable.

Adult↗
PubMed1996

Rapidly reversible acute renal failure from ureteral obstruction in pregnancy.

We report a case of acute renal failure due to bilateral ureteral obstruction that rapidly resolved after delivery. Acute renal failure secondary to bilateral ureteral obstruction is rare; to our knowledge, only 18 cases have been reported in the English literature. Review of these cases reveals that twin pregnancies, polyhydramnios, and obstruction of the solitary kidney seem to increase the risk of obstructive renal failure. Measures including induced delivery, amniocentesis, and insertion of ureteral stents or nephrostomy tubes undertaken to relieve the ureteral obstruction usually lead to rapid improvement in urine flow and renal function. Acute renal failure secondary to bilateral ureteral obstruction is a rare but reversible complication of pregnancy.

Acute Kidney Injury↗
PubMed1979

On the mechanism of film neoplastogenesis.

Since the inception of experimental cancer research, all theories concerning the mechanism of transformation of normal cells into neoplastic cells were constructed on the basis of the postulate that interaction of an agent and cell constituents is a condition indispensable for the occurrence of the neoplastic transformation. In the course of the past three decades, however, all attempts to uncover agents responsible for the transformations induced by chemically inert films implanted in living tissues or for the "spontaneous" transformations in vitro in cell cultures devoid of added neoplastogens, yielded consistently negative results. In regard to the neoplastogenic effect of imbedded inert films, the present article takes into consideration that films implanted in living tissues hinder the circulation of interstitial fluid in their vicinity and as a result elicit anoxia and protracted low pH gradients in the environment of the cells adjacent to the films. The effects of such protracted low pH on the metabolic activities of the surviving cells are examined and a working hypothesis is offered concerning the role of protracted environmental low pH in the mechanism of film neoplastogenesis.

Amino Acids↗
PubMedDate not supplied

On the definition, cause and nomenclature of cancer.

Definitions and terms currently employed in the nomenclature of cancer are examined and found inadequate or misleading. It is suggested that the two entirely different processes involved in cancer, namely, neoplastic transformation and neoplastic disease, be clearly distinguished and rigorously defined. It is also suggested that proper terms and expressions to describe these processes be adopted and clearly defined.

Animals↗