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Biomedical subjects

S Tripathi

Publications and source records attributed to S Tripathi.

50 records · Page 3Linked to original sources
PubMed1987

Ultrastructural changes in isolated perfused proximal tubules during osmotic water flow.

Steady-state effects of osmotic gradients on extracellular spaces and cell volumes were studied by ultrastructural morphometry in isolated perfused Ambystoma proximal tubules. Solute clamping, high-resolution pressure and flow control of lumen and bath solutions were all ascertained before and during fixation. Isosmotic removal of organic substrates in the lumen reversibly abolished transport, as confirmed by transepithelial potential decrease from -4.7 +/- 0.5 to -0.5 +/- 0.2 mV (n = 8) but had no effect on ultrastructural parameters. The walls of the extracellular spaces are therefore not deformed by spontaneous solute-coupled water transport. A hyperosmolar lumen generated a streaming potential of -1.56 +/- 0.15 mV (n = 8), reduced cell volume to 65%, reduced lateral intercellular space (LIS) volume to 20%, and LIS volume density to 29% of control without significant effects on the volume of the basal extracellular labyrinth (BEL). A hyperosmolar bath generated a streaming potential of +1.96 +/- 0.30 mV (n = 7), reduced cell volume to 68%, and increased LIS volume density to 236% of control. BEL volume was 55% larger during lumen-to-bath flow than during bath-to-lumen flow. Because cell volume reduction is very similar for both directions of osmotic water flow, the oppositely directed volume changes in the extracellular spaces are secondary to transepithelial water flow. The greater change in volume of LIS compared with BEL indicates that the outermost parts of the LIS are more resistive to transepithelial water flow than the slitlike communications of the BEL with the peritubular space.

Ambystoma↗
PubMed1986

The roles of paracellular and transcellular pathways and submucosal space in isotonic water absorption by rabbit ileum.

Water movements have been studied in sheets of isolated rabbit ileum using a method which measures net volume flows across the mucosal and serosal surfaces of the tissue continuously with high resolution. At 35 degrees C, with the tissues incubated in isotonic Ringer solution containing D-glucose (25 mM) on both sides, there is a steady net inflow of fluid at the rate of 24 +/- 2 microliter cm-2 h-1 across the mucosal surface (Jm) and an outflow of 8 +/- 1 microliter cm-2 h-1 across the serosal surface (Js) (n = 16). The stable transepithelial p.d. across these tissues is 2.7 +/- 0.2 mV, serosa positive. Jm can be reversibly inhibited by anoxia. Ouabain (0.1 mM) added to the serosal solution inhibits inflow across the mucosal and serosal surfaces by 75% (n = 7) within 30 min. If phlorizin (0.1 mM) is added to the mucosal Ringer solution containing glucose (20 mM) within 30 min of the commencement of in vitro absorption, Jm is reduced from 37 +/- 3 to 28 +/- 2 microliter cm-2 h-1 (n = 3). Dilution of the mucosal Ringer solution by 50 mosmol kg-1 (with the serosal solution kept isosmolar) results in a rapid transient increase in mucosal inflow. An increase of 50 mosmol kg-1 in the mucosal Ringer solution with NaCl, sucrose or mannitol causes a transient reversal of mucosal flow, followed by a return of inflow at a reduced level. Rabbit ileum can transport water against gradients of approximately 75 mosmol kg-1 of sucrose, NaCl, or mannitol. Addition of polyethylene glycol (mol. wt. 20000; 3 mosmol kg-1) causes a sustained reversal of mucosal inflow; inflow can be restored only by removing polyethylene glycol from the mucosal Ringer solution. The tissue can absorb water against an osmotic gradient of 200 mM-glycerol. The above data have been incorporated into a new model to explain isotonic flow of fluid by this epithelium. The main features are that the hydraulic conductivity (Lp) of the mucosal boundary of the lateral intercellular space is approximately 1 X 10(-8) cm s-1 cmH2O-1. This Lp is too low to sustain isotonicity of the flow emerging from the lateral intercellular space at the observed rates. Hypertonic fluid emerging from the lateral intercellular space is diluted by transcellular water flow generated by the hypertonicity of the submucosa and back-diffusion of solute via mucosal shunt channels.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Passive water flows driven across the isolated rabbit ileum by osmotic, hydrostatic and electrical gradients.

Water flows generated by osmotic and hydrostatic pressure and electrical currents were measured in sheets of isolated rabbit ileum at 20 degrees C. Flows across the mucosal and serosal surfaces were monitored continuously by simultaneous measurement of tissue volume change (with an optical lever) and net water flows across one surface of the tissue (with a capacitance transducer). Osmotic gradients were imposed across the mucosal and serosal surfaces of the tissue separately, using probe molecules of various sizes from ethanediol (68 Da) to dextrans (161 000 Da). Flows across each surface were elicited with very short delay. The magnitudes of the flows were proportional to the osmotic gradient and related to the size of the probe molecule. Osmotic flow across the mucosal surface was associated with streaming potentials which were due to electro-osmotic water flow. The mucosal surface is a heteroporous barrier with narrow (0.7 nm radius, Lp (hydraulic conductivity) = (7.6 +/- 1.6) X 10(-9) cm s-1 cmH2O-1) cation-selective channels in parallel with wide neutral pores (ca. 6.5 nm radius, Lp = (2.3 +/- 0.2) X 10(-7) cm s-1 cmH2O-1) which admit large pressure-driven backflows from the submucosa to the lumen. There is additional evidence for a further set of narrow electroneutral pores less than 0.4 nm radius with Lp less than 7 X 10(-9) cm s-1 cmH2O-1. The serosal surface has neutral pores of uniform radius (ca. 6.5 nm), Lp = (7.6 +/- 1.6) X 10(-8) cm s-1 cmH2O-1. Hypertonic serosal solutions (100 mM-sucrose) cause osmotic transfer of fluid from isotonic mucosal solutions into the submucosa, expand it, and elevate the tissue pressure to 19.6 +/- 3.2 cmH2O (n = 4). Conversely, hypertonic mucosal solutions (100 mM-sucrose) draw fluid out of the submucosa in the presence of isotonic serosal solutions, collapse the submucosa, and lower the tissue pressure to -87.7 +/- 4.6 cmH2O (n = 5). Water flows coupled to cation movement could be generated across the mucosal surface in both directions by brief direct current pulses. The short latency of onset and cessation of flow (less than 2 s), absence of polarization potentials, and high electro-osmotic coefficients (range 50-520 mol water F-1), together with the presence of streaming potentials during osmotically generated water flows indicate electro-osmotic water flow through hydrated channels in the tight junctions and/or lateral intercellular spaces.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1985

Submicron tip breakage and silanization control improve ion-selective microelectrodes.

Probable causes of failure of otherwise well-constructed liquid ion-exchanger (LIE) micro-electrodes of average tip size less than 0.15 micron were examined. The problem could be attributed to two major variables, both localized at the tip: partial tip occlusion during fabrication prevents the generation of an electromotive force (small or absent slope and/or selectivity, high resistance); or poor hydrophobicity of the tip permits water to displace the resin from the tip (small or absent slope and/or selectivity and low electrode resistance). Controlled dry tip breakage on paper coated with glassine to final tip sizes well below 0.5 micron (confirmed by scanning electron microscopy) improves the yield of usable electrodes severalfold. Adequate silanization of the tip and consequent retention of resin at the tip can be predicted from the contact angles observed at the glass-LIE-backfilling solution interface. Satisfactory silanization can be achieved despite high ambient humidity. No evidence of shunting of Na+-LIE microelectrodes by the glass wall was seen. In the isolated perfused proximal tubule of Ambystoma tigrinum, the mean intracellular Na+ activity recorded by broken-tip electrodes (13.7 +/- 1.9 meq, n = 4) was similar to that recorded by intact electrodes (15.5 +/- 1.1 meq, n = 31).

Adsorption↗
PubMed1985

The syndrome of inappropriate secretion of antidiuretic hormone in the pharyngeal flap operation.

A prospective study was undertaken to determine whether there was a relationship between the pharyngeal flap operation and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). From August 1982 to November 1983, 25 patients underwent pharyngeal flap procedures. They were compared to a control group made up of five patients who underwent major cleft lip revisions. Twelve of the twenty-five patients (48%) who underwent pharyngeal flap procedures had inappropriately elevated serum ADH levels, low serum osmolality, and hyponatremia in the postoperative period. There was a statistically significant (p less than 0.001) drop in the serum sodium levels in the pharyngeal flap group from the preoperative to postoperative period. There was neither a statistically significant change in the serum sodium levels nor inappropriate elevation of ADH levels in the control group. Two patients who underwent pharyngeal flap procedures developed SIADH. To our knowledge this complication has not been reported in association with the pharyngeal flap operation. No specific causes were found that would explain why SIADH developed.

Adolescent↗
PubMed1980

In vitro primate gastric mucosa: electrical characteristics.

Ion transport by the resting, isolated, rhesus gastric mucosa was assessed under conditions of minimal diffusion limitation to oxygen by 1) the substitution of Na+ and Cl- of the bathing solutions with less permeant ions, 2) the drugs amiloride and ouabain, and 3) estimation of net fluxes of 22Na by methods designed to circumvent the problem of poorly matched tissues. The mucosae developed potential differences of 51.3 +/ 3.5 mV, serosal side positive and had conductances of 5.56 +/- 0.30 mS x cm-2. The permeabilities of the tissues to D-mannitol were between 7.80 x 10(-7) and 3.15 x 10(-7) cm x s-1. The relatively high conductance of this epithelium in the absence of significant edge damage and a low (32%) paracellular conductance stems mainly from a passive permeability to Cl-; active absorption of Na+ and active secretion of Cl- contribute equally to the short-circuit current. The mucosal entry step for Na+ is amiloride sensitive, whereas the serosal exit step can be inhibited by ouabain. The entry step for Cl- at the serosal membrane is possibly sodium dependent.

Amiloride↗
PubMed1978

Monoamine oxidase inhibitory and anticonvulsant properties of some newer thiosemicarbazones.

Eight 4-aryl-1-(2,3,4-trihydroxy acetophenone)-3-thiosemicarbazones were synthesised and evaluated for their ability to inhibit rat brain monoamine oxidase (MAO). All compounds exhibited concentration dependent inhibition of enzyme. The degree of enzyme inhibition was also evaluated on the basis of their I50 and I50/(S) values. Preincubation of these compounds with the enzyme system for varying lengths of time prior to the addition of substrate in no way altered their degree of inhibition. Kinetic study carried out with 4-(2-methoxyphenyl)-1-(2,3,4-trihydroxyacetophenone)-3-thiosemicarbazone revealed a competitive nature of inhibition. Anticonvulsant activity exhibited by these thiosemicarbazones (100mg/kg, i.p.) against pentylene-tetrazol-induced seizures ranged between 10-60%. Low toxicity possessed by these compounds was reflected by their approximate LD50 values ranging from 750 mg/kg to greater than 1000 mg/kg.

Acetophenones↗
PubMedDate not supplied

Syntheses of Curcumin Bioconjugates and Study of Their Antibacterial Activities against beta-Lactamase-Producing Microorganisms.

In the present study curcumin bioconjugates, viz. di-O-glycinoylcurcumin (I), di-O-glycinoyl-C(4)-glycylcurcumin (II), 5'-deoxy-5'-curcuminylthymidine (5'-cur-T) (IV), and 2'-deoxy-2'-curcuminyluridine (2'-cur-U) (V) have been synthesized and characterized by elemental analysis and (1)H NMR. The turmeric peptide (Tp) was isolated from the aqueous turmeric extract of the turmeric rhizome. The antibacterial activity of these four bioconjugates and also of the turmeric peptide and sodium salt of curcumin (III) have been tested particularly for beta-lactamase-producing microorganisms.

Bacteria↗
PubMedDate not supplied

Anticonvulsant and monoamine oxidase inhibitory activity of substituted oxadiazol-thiones.

Several 1,3,4-oxadiazol-thiones were synthesised and characterized by their melting points elemental analysis and I.R. spectra. All the oxadiazol-thiones possessed anticonvulsant activity which was reflected by protection upto 80% against pentylenetetrazole induced seizures and 40% protection against maximal electroshock induced seizures. Substantiations at position-3 of oxadiazol-thiones have shown marked effect on MAO inhibitory activity. No definite correlation between monoamine oxidase inhibitory and anticonvulsant activity could be established. It was observed that by the substitution of one, two and three methyl groups in the phenyl ring of 2-arylamino methyl side chain anticonvulsant activity against both maximal electroshock induced convulsions and pentylenetetrazol induced convulsions decreases i.e. the order of activity was found to be unsubstituted greater than monomethyl greater than dimethyl greater than trimethyl.

Animals↗
PubMedDate not supplied

The 1995 Lindberg Award. Nonthermally mediated muscle injury and necrosis in electrical trauma.

Joule heating has long been considered the principal component of tissue damage in electrical injury. Recent studies suggest electroporation, a nonthermally mediated mechanism of cell membrane damage, is also a factor. We investigated whether electroporation-mediated muscle necrosis can occur in vivo without significant Joule heating. Pulsed electric fields approximately 150 V/cm were produced in the hind limbs of anesthetized rats. In shocked limbs core muscle temperature rose less than 1.8 degrees C, yet significant damage occurred as determined by technetium-99m pyrophosphate uptake, elevated serum creatine phosphokinase, and prominent hypercontraction band degeneration of myofibers on histopathologic examination. This study is significant because it directly addresses whether nonthermal mechanisms of cell damage can cause tissue necrosis. These results indicate that electroporation effects can mediate skeletal muscle necrosis without visible thermal changes. Thus the phenomenon of "progressive recognition" may be characteristically largely explained by the occurrence of nonthermally mediated tissue damage.

Animals↗