Biomedical subjects

H J Lubansky

Publications and source records attributed to H J Lubansky.

6 recordsLinked to original sources

PubMed1989

Turtle urinary bladder epithelial cell line.

1. We compared enzymatic and functional properties of a turtle bladder cell line to those of turtle bladder epithelial cells. Like the original epithelium, the cell line displays carbonic anhydrase activity and acetazolamide inhibits O2 consumption in isolated cells and acidification by cells grown in monolayers. 2. Staining with acridine orange revealed the presence of cytoplasmic orange red vesicles which could be dissipated by NH4Cl or protonophores indicating that these vesicles represent areas of low pH. 3. Addition of ATP to cells permeabilized by digitonin led to reappearance of the red granules suggesting that acidification of the vesicles is mediated by H+-ATPase.

Animals↗

PubMed1987

Relationship of K and ammonia transport by the turtle bladder.

The relationship between K and ammonia transport was investigated in the turtle bladder. At serosal pH 6.4, ammonia transport is preferentially from serosa to mucosa and is, at least in part, mediated by NH4+ transport. Since K and NH4+ share similar features such as permeability and stimulation of Na-K-ATPase, we studied the interaction of transport of these ions by the turtle bladder. Removal of K from the mucosal solution inhibited partially ammonia transport from serosa to mucosa and the inhibition was reversible by restoration of K. In contrast, removal of serosal K failed to inhibit ammonia transport. Since NH4+ can replace K in the activation of Na-K-ATPase in turtle bladder plasma membrane fraction with similar K, we examined the effect of ouabain on ammonia transport. Ouabain added to the serosal solution failed to inhibit ammonia transport thus, suggesting that the Na-K-ATPase is not required for ammonia entry into the cell. Methylammonium (a competitive inhibitor of NH4+ transport in other systems) decreased both ammonia transport and the observed increase in short circuit current elicited by NH4Cl addition to the serosal solution. This finding suggests that NH4+ and methylammonium are transported through a common pathway in the serosal side. Since the permeability of the serosal side to K and NH4+ is similar, we evaluated the effect of serosal depolarization and the effect of barium, an inhibitor of K channels, on ammonia transport. Serosal depolarization inhibited ammonia transport but barium did not affect ammonia flux.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗

PubMed1986

Plasma membrane proton ATPase from human kidney.

Distal urinary acidification is thought to be mediated by a proton ATPase (H+-ATPase). We isolated a plasma membrane fraction from human kidney cortex and medulla which contained H+-ATPase activity. In both the cortex and medulla the plasma membrane fraction was enriched in alkaline phosphatase, maltase, Na+,K+-ATPase and devoid of mitochondrial and lysosomal contamination. In the presence of oligomycin (to inhibit mitochondrial ATPase) in the presence of ouabain (to inhibit Na+,K+-ATPase) and in the absence of Ca (to inhibit Ca2+-ATPase) this plasma membrane fraction showed ATPase activity which was sensitive to dicyclohexylcarbodiimide and N-ethylmaleimide. This ATPase activity was also inhibited by vanadate, 4,4'-diisothiocyano-2,2'-disulfonic stilbene and ZnSO4. In the presence of ATP, but not GTP or UTP, the plasma membrane fraction of both cortex and medulla was capable of quenching of acridine orange fluorescence, which could be dissipated by nigericin indicating acidification of the interior of the vesicles. The acidification was not affected by presence of oligomycin or ouabain indicating that it was not due to mitochondrial ATPase or Na+,K+-ATPase, respectively. Dicyclohexylcarbodiimide and N-ethylmaleimide completely abolished the acidification by this plasma membrane fraction. In the presence of valinomycin and an outward-directed K gradient, there was increased quenching of acridine orange, indicating that the H+-ATPase is electrogenic. Acidification was not altered by replacement of Na by K, but was critically dependent on the presence of chloride. In summary, the plasma membrane fraction of the human kidney cortex and medulla contains a H+-ATPase, which is similar to the H+-ATPase described in other species, and we postulate that this H+-ATPase may be involved in urinary acidification.

Adenosine Triphosphate↗

PubMed1985

Plasma membrane proton-ATPase of a turtle bladder epithelial cell line.

Urinary acidification by the turtle bladder is mediated by a proton ATPase located in the apical membrane. The present study describes a proton ATPase in the plasma membrane of a cell line of turtle bladder epithelial cells. In the presence of ouabain to inhibit Na+,K+-ATPase and in the absence of Ca2+ to inhibit Ca2+-ATPase, we measured ATPase activity of the plasma membranes of the cultured cells. This ATPase was resistant to oligomycin but sensitive to dicyclohexylcarbodiimide, N-ethylmaleimide, and vanadate. In the presence of ATP, the ATPase was capable of acidification as assessed by quenching of acridine orange. Acidification could not be elicited by other nucleotides (GTP, UTP). Acidification was inhibited by dicyclohexylcarbodiimide, N-ethylmaleimide, and vanadate but was not affected by replacement of Na+ by K+. The acidification response was dependent on the presence of chloride, abolished in the presence of gluconate, and inhibited partially by nitrate. Experiments utilizing the voltage-sensitive dye 3,3'-dipropylthiodicarbocyanine iodide showed that the proton ATPase was electrogenic and capable of responding to a favorable electric gradient. In summary, the turtle bladder epithelial cell line has a plasma membrane proton ATPase which is similar to the proton ATPase of turtle bladder epithelium and thus should allow purification and characterization of this enzyme.

Acridine Orange↗

PubMedDate not supplied

Mechanical induction of osteogenesis: the importance of pin rigidity.

Eight dogs, divided into two groups of four by varying pin rigidity, underwent 15% left tibial lengthening by the Ilizarov method. In group I, "tensioned" 1.6-mm wires maintained a rigidity approaching that of 4.0-mm pins. In group II, the wires, maintained at half the tension, averaged 45% of the rigidity measured in group I. All dogs in group I filled the experimental gap with de novo osteogenesis, whereas all of the dogs in group II prematurely bridged the gap, arresting the process of osteogenesis. From these experimental results, clinical trials have been started using commercially available external fixation devices utilizing pins with equivalent rigidity.

Adolescent↗

PubMedDate not supplied

Mechanical induction of Osteogenesis. Preliminary studies.

The animal model developed in the Soviet Union by Ilizarov has been reliably reproduced by us for the mechanical induction of osteogenesis using slow distraction. Our preliminary studies in six adult dogs indicate that this osteogenesis originates from well-structured intramembranous ossification, with rapid maturation to lamellar bone, indistinguishable from surrounding host bone. Mineralization increases steadily, reaching critical levels for radiographic visualization between Days 21 and 28. In this model, the osteogenic area then exceeds normal bone density temporarily but returns to normal density within three months. Distraction for 28 consecutive days (at 0.25 millimeters every six hours using rigid transfixion wires, as Ilizarov describes) reliably lengthened the tibiae by 12 percent, increasing mass by 27 percent, and volume by 26 percent with only a one percent change in overall density. The process required four months to add 24 millimeters of mature, lamellar bone capable of full weight-bearing by the dogs. This rate of osteogenesis, estimated at 202 microns per day, is four times faster than a human's fastest growth plate (child's distal femur at 50 microns per day). Calcium/collagen ratios did not differ significantly from normal bone controls.

Animals↗