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Biomedical subjects

R Rick

Publications and source records attributed to R Rick.

At least 55 records · Page 3Linked to original sources
PubMed1981

Intracellular electrolyte composition following renal ischemia.

The technique of electron microprobe analysis was used to determine the intracellular electrolyte concentrations in proximal or distal tubular cells of the rat kidney during ischemia. When the exposed kidney was maintained in air during ischemia, the composition of the surface cells differed little from control, and the electrolyte disturbances were confined to the deeper lying cells. When maintained in nitrogen, all cells underwent changes in cellular electrolyte concentrations that were uniform, indicating that the surface cells can preserve their composition during ischemia by utilizing oxygen from the air. In the proximal tubular cells, after 20 or 60 min of ischemia in nitrogen, sodium increased from 20 to 93 or 112, chloride rose from 21 to 53 or 66, potassium fell from 141 to 65 or 42, phosphate decreased from 145 to 110 or 95 mmoles.kg-1 of wet wt, and the dry wt dropped from 22.6 to 20.3 or 17.5% of wet wt, respectively. In the distal tubular cells, 20 min of ischemia in nitrogen produced little effect on cellular composition, but after 60 min, sodium increased from 11 to 77, chloride rose from 15 to 48, potassium fell from 134 to 89, phosphate decreased from 168 to 145 mmoles.kg-1 of wet wt, and the dry wt dropped from 20.8 to 18.4% of wet wt. The disturbances in sodium and potassium are caused primarily by an inhibition of the sodium/potassium pump, whereas the changes in chloride, phosphate, and dry weight content result mainly from an influx of extracellular fluid. When blood flow was reintroducing, the electrolyte disturbances were rapidly reversed in all cells, restoration being virtually complete within 60 min, but returned in some proximal cells by 18 hr of reperfusion. Thus, the disturbance in electrolyte composition increases with the duration of ischemia, is less pronounced in the distal than proximal cells and, although initially completely reversible when blood flow is restored, reappeared in the proximal cells 1 days after the initial injury.

Animals↗
PubMed1980

The osmotic behaviour of toad skin epithelium (Bufo viridis). an electron microprobe analysis.

The effect of saline adaptation on the intracellular Na, K, Cl, P concentrations and dry weight content of the toad skin epithelium (Bufo viridis) was studied using the technique of electron microprobe analysis. The measurements were performed on isolated abdominal skins either directly after dissection or after additional incubation in Ussing-type chambers. Adaptations of the toads to increasing NaCl concentrations for 7 days resulted in increased blood plasma osmolarity and a parallel increase in the cellular electrolyte, P and dry weight concentrations of the epithelium, the K increase representing the most significant fraction of the intracellular osmolarity increase. No evidence was obtained to show that the nucleus and cytoplasm reacted differently from each other and all living epithelial cell types basically showed the same response. Incubation of the isolated skins under control conditions showed a drastic inhibition of the transepithelial Na transport after adaptation to high salinities. In spite of the large variations in the transport rate almost identical intracellular electrolyte concentrations were observed. In tap water adapted toads the average cellular concentrations were 8.8 mmole/kg wet weight for Na, 109.6 for K, 41.5 for Cl, and 135.3 for P, respectively. Incubation of the skin with Ringer's solution of different osmolarities demonstrated that the epithelial cells are in osmotic equilibrium with the inner bathing solution. The results are consistent with the view that the osmotic adaptation is mainly accomplished by the movement of water.

Animals↗
PubMed1980

Electron microprobe analysis of intracellular elements in the rat kidney.

The concentrations of intracellular elements were determined by electron microprobe analysis in the nucleus and cytoplasm of freeze-dried cryosections of superficial proximal and distal tubules of the rat kidney. For the nucleus of the proximal tubular cell, the concentrations of sodium and chloride were 20 and 23 mmoles/kg of wet wt, and those of potassium and phosphorus were 144 and 150 mmoles/kg wet wt. For the nucleus of the distal tubular cell, the concentrations of sodium and chloride were significanlty lower (11 and 13 mmoles/kg wet wt), that of potassium was unchanged (143 mmoles), and that of phosphorus was significantly higher (175 mmoles). Towards the basolateral infoldings of the proximal and distal tubules and the brush border of the proximal tubules, the concentrations of sodium and chloride were higher and those of potassium and phosphorus were lower than those obtained in the nucleus, indicating the presence of extracellular compartments in these regions. Measurements performed in the centrally located cytoplasm of proximal and distal tubular cells, close to the nucleus, showed sodium and potassium concentrations to the indistinguishable from those in the nucleus, whereas chloride and phosphorus concentrations were considerably higher. These data demonstrate differences in the intracellular concentrations of phosphorus, sodium, and chloride between proximal and distal tubular cells. In neither the proximal nor the distal tubular cells, however, could a concentration difference for sodium and potassium between nucleus and cytoplasm be determined.

Animals↗
PubMed1979

Intracellular elemental concentrations in renal tubular cells. An electron microprobe analysis.

In order to be able to examine the processes involved in transepithelial transport in tissues, which are not composed of a single cell type, methods are required, which permit analysis at a cellular level. The technique of electron microprobe analysis permits the intracellular concentrations of many elements to be determined simultaneously in various portions of the cell. The application of this method to renal cortical tissue has shown that the best estimates of the cytoplasmic concentrations are to be obtained in regions close to the nucleus, farthest from the basolateral infoldings and microvilli, which separate the intracellular environment from the extracellular space. The nuclear concentrations of Na and K do not differ from those in the surrounding cytoplasm, although those of P and Cl are somewhat higher in cytoplasm. The intracellular element concentrations in the different cell types vary somewhat, proximal tubular cells contain higher concentrations of Na and Cl and lower ones of P than distal tubular cells. Following ischaemia, a manoeuvre know to result in a disturbance of intracellular electrolytes, Na was observed to rise and K to fall only in the non-surface cells of kidneys exposed to the air, but in all cells, if the kidneys were kept air-free in an atmosphere of N2. The proximal and distal tubular cells showed a variable resistance to ischaemia, the distal tubular cells being much more resistant. Despite the severity of the electrolyte disturbance following ischaemia, the intracellular composition was completely restored one hour after re-introducing renal blood flow.

Animals↗
PubMed1979

Intracellular electrolyte concentrations in epithelial tissue during various functional states.

The scanning electron microscope together with an energy dispersive system was used to quantify intracellular elemental concentrations of transporting epithelial cells under a variety of experimental conditions. In the frog skin, the Na transport pool is comprised of the intracellular compartments of all vital cells in the different cell layers, except the mitochondria rich cells. The Na content of this transport pool exchanges easily with the epithelial (outer) bathing solution. Vasopressin increases the Na permeability of the corial cell barrier. Proximal and distal tubular cells of the rat kidney show differences in the pattern of intracellular element concentrations. The distal tubular cell is more resistant to 20 min of ischemia than the proximal cell. The changes in intracellular electrolyte concentrations following 60 min of ischemia are reversible after reperfusing the kidney with blood for 60 min. In the cells of the frog skin and rat kidney, Na and K were equally distributed between the cytoplasm and the nucleus. Differences exist for P, Cl and dry weight.

Amiloride↗
PubMed1978

Electron microprobe analysis of frog skin epithelium: evidence for a syncytial sodium transport compartment.

For elucidation of the functional organization of frog skin epithelium with regard to transepithelial Na transport, electrolyte concentrations in individual epithelial cells were determined by electron microprobe analysis. The measurements were performed on 1-micron thick freeze-dried cryosections by an energy-dispersive X-ray detecting system. Quantification of the electrolyte concentrations was achieved by comparing the X-ray intensities obtained in the cells with those of an internal albumin standard. The granular, spiny, and germinal cells, which constitute the various layers of the epithelium, showed an identical behavior of their Na and K concentrations under all experimental conditions. In the control, both sides of the skin bathed in frog Ringer's solution, the mean cellular concentrations (in mmole/kg wet wt) were 9 for Na and 118 for K. Almost no change in the cellular Na occurred when the inside bathing solution was replaced by a Na-free isotonic Ringer's solution, whereas replacing the outside solution by distilled water resulted in a decrease of Na to almost zero in all layers. Inhibition of the transepithelial Na transport by ouabain (10(-4) M) produced in increase in Na to 109 and a decrease in K to 16. The effect of ouabain on the cellular Na and K concentrations was completely cancelled when the Na influx from the outside was prevented, either by removing Na or adding amiloride (10(-4) M). When, after the action of ouabain, Na was removed from the outside bathing solution, the Na and K concentration in all layers returned to control values. The latter effect could be abolished by amiloride. The other cell types of the epithelium showed under some experimental conditions a different behavior. In the cornified cells and the light cells, which occurred occasionally in the stratum granulosum, the electrolyte concentrations approximated those of the outer bathing medium under all experimental conditions. In the mitochondria-rich cells, the Na influx after ouabain could not be prevented by adding amiloride. In the gland cells, only a small change in the Na and K concentrations could be detected after ouabain. The results of the present study are consistent with a two-barrier concept of transepithelial Na transport. The Na transport compartment comprises all living epithelial layers. Therefore, with the exception of some epithelial cell types, the from skin epithelium can be regarded as a functional syncytium for Na.

Animals↗
PubMed1978

Electron microprobe analysis of the different epithelial cells of toad urinary bladder. Electrolyte concentrations at different functional states of transepithelial sodium transport.

The electrolyte composition of toad urinary bladder epithelial cells has been measured using the technique of electron microprobe analysis. Portions of hemibladders, which had been mounted in chambers and bathed with a variety of media, were layered with albumin solution on their mucosal surfaces and immediately shock-frozen in liquid propane at -180 degrees C. From the frozen material 1--2 micrometer thick cryosections were cut and promptly freeze-dried for 12 hr at-80 degrees C and 10(-6) Torr. Electron microprobe analysis using a scanning electron microscope, an energy dispersive X-ray detector, and a computer programme, to distinguish between characteristic and uncharacteristic radiations, allowed quantification of cellular ionic concentrations per kg tissue wet wt by comparison of the intensities of the emitted radiations from the cells and from the albumin layer. Granular, mitochondrial-rich, and basal cells, and the basal portions of goblet cells, showed a similar composition, being high in K (about 110 mM/kg wet wt) and low in Na (about 13 mM/kg wet wt). The apical portions of goblet cells were higher in Ca and S and lower in P and K, presumably reflecting the composition of the mucus within them. With Na-Ringer's as the mucosal medium, cells gained Na and lost K, when their serosal surfaces were exposed to ouabain, 10(-2) M. Replacement of mucosal Na by choline virtually prevented these ouabain-induced changes. Cellular ion contents were unchanged when Na in the serosal medium was replaced by choline. No differences in Na and K concentrations were detected between nuclei and cytoplasm. These results provide independent support for the hypothesis the the cellular Na transport pool in toad bladder epithelial cells derives exclusively from the mucosal medium and that no important recycling of Na occurs from the serosal medium to the cells.

Animals↗
PubMed1977

Determination of electrolytes in small biological fluid samples using energy dispersive x-ray microanalysis.

A technique is reported for the application of the energy dispersive X-ray microanalysis for the simultaneous determination of electrolytes in picoliter samples of biological fluids. The preparation is characterized by the use of thin films as a specimen support. Using this arrangement, the X-rays generated in the support are kept to a minimum. At an acceleration voltage of 25 kV the specimen preparation can be regarded as 'thin', i.e. the intensity of an emitted characteristic radiation is almost uninfluenced by the gross element composition, and, therefore, is only dependent upon the content of elements. Quantification was achieved by comparing the intensities of the characteristic radiations with that of a standard. Electrolyte concentrations of 1 mM can be detected with an accuracy of 0.1 mM SD.

Animals↗
PubMed1976

Elemental distribution of Na, P, Cl and K in different structures of myelinated nerve of Rana esculenta.

Measurements of the distribution of Na, P, Cl and K were performed in different structures of the myelinated nerve. Whereas the axon shows a typical intracellular distribution pattern for Na, Cl and K, the interstitial space and the myelin sheath show a typical extracellular pattern. These measurements have demonstrated that Na is present in the myelin sheath close to the node of Ranvier.

Animals↗
PubMed1975

Influx and efflux of sodium at the outer surface of frog skin.

The unidirectional Na influx j12, and Na efflux, j12, at the epithelial surface of the frog skin were determined under various experimental conditions. The j21 was taken as the difference between j12 and the simultaneously measured shortcircuit current (SCC). Errors in j12 determination originating from various transport rates within the skin were kept to a minimum using a normalization procedure. Under control conditions, j12 (1.20 muEquiv/cm-2. hr) was found to be only slightly larger than the SCC (1.10 MUEquiv/cm-2. hr). After inhibition of the transepithelial Na transport by amiloride, ouabain, low temperature and low Na concentration, the reduction of j12 and SCC was almost identical, indicating that the entrance of Na into the epithelium is rate limiting for the transepithelial transport. Compared to the control, j21 remained unchanged after amiloride and ouabain, but was insignificantly reduced at low temperature and significantly reduced at low Na concentration. These data are consistent with the assumption that the Na efflux follows mainly an extracellular pathway.

Amiloride↗