scholarly journals Electrical Potential Difference Measurements in Perfused Single Proximal Tubules of Necturus Kidney

1961 ◽  
Vol 44 (4) ◽  
pp. 679-687 ◽  
Author(s):  
Guillermo Whittembury ◽  
Erich E. Windhager
Keyword(s):  
Electrical Potential ◽  
Proximal Tubules ◽  
The Other ◽  
Potential Difference ◽  
Stopped Flow ◽  
Electrical Potential Difference ◽  
Necturus Maculosus ◽  
Other Hand ◽  
Glomerular Filtrate

Transtubular and peritubular face electrical potential differences (P.D.) of the proximal tubules of the kidney of the amphibian Necturus maculosus have been measured in situ. These measurements have been carried out both under normal conditions, when the tubular fluid originates in the glomerular filtrate, and under conditions when the composition of the tubular fluid has been altered using the stopped flow microperfusion technique. Under normal conditions the transtubular potential difference is 20 mv. (lumen-negative) and the P.D. across the peritubular face is 74 mv. (cell-negative). The P.D. across the luminal face is thus 54 mv. (cell-negative). This electrical asymmetry is not influenced by replacing the normal tubular fluid by NaCl, NaCl + mannitol, or by alteration in the intraluminal pH from 7 to 4. On the other hand, replacement of Na by K or choline and the addition of small amounts of DNP to the perfusate diminish this asymmetry.

Site of potential difference measurements in single renal proximal tubules of Necturus

1963 ◽  
Vol 204 (3) ◽  
pp. 401-404 ◽  
Author(s):  
Guillermo Whittembury
Keyword(s):  
Interstitial Fluid ◽  
Electrical Potential ◽  
Proximal Tubules ◽  
Potential Difference ◽  
Renal Proximal Tubules ◽  
Histological Sections ◽  
Necturus Maculosus ◽  
Tubular Lumen ◽  
Tip Position

The electrical potential differences from cells and lumina of the proximal tubules of the kidney of Necturus maculosus were measured with micropipette-electrodes, in vivo, and the site of measurement was permanently marked by deposition of carmine in the tissue by iontophoresis from the tip, during recording of each potential difference. The carmine deposits were subsequently localized using serial histological sections. Two negative electrical potential steps were measured, with reference to the interstitial fluid, and the tip position unequivocally marked. a) The potential difference across the peritubular face of the cell, with the microelectrode tip in the cell, averaged –70 mv (cell negative); b) the transtubular potential difference with the tip in the tubular lumen, averaged –21 mv (lumen negative).

Bicarbonate reabsorption and electrophysiology of proximal tubules in uninephrectomized rats

1991 ◽  
Vol 81 (2) ◽  
pp. 141-146 ◽  
Author(s):  
Dirce M. Zanetta Limongi ◽  
Antonio Carlos Cassola ◽  
Viktoria Woronik ◽  
Gerhard Malnic
Keyword(s):  
Basolateral Membrane ◽  
Electrical Potential ◽  
Ringer Solution ◽  
Proximal Tubules ◽  
Potential Difference ◽  
Protonmotive Force ◽  
Electrical Potential Difference ◽  
Analogue Model ◽  
Significant Difference ◽  
Membrane Electrical Potential

1. The kinetics of acidification of luminal fluid in hypertrophied proximal tubules after unilateral nephrectomy was studied by stationary microperfusion and continuous measurement of luminal pH with antimony microelectrodes. 2. Trans-epithelial and basolateral membrane electrical potential differences were measured in order to detect modifications in electrogenic transport mechanisms under these conditions. 3. The values of stationary pH and HCO−3 concentration were significantly lower, the mean acidification half-time was not different and net reabsorptive HCO−3 fluxes in proximal tubules were significantly increased in uninephrectomized rats. According to an electrical analogue model, these results suggest (a) a reduction in the internal series resistance of the H+ pump, caused perhaps by an increased density of pump sites, and (b) an increase in the protonmotive force of the pump. 4. The trans-epithelial electrical potential difference measured in free flow conditions was significantly more lumen-positive in uninephrectomized rats. The trans-epithelial electrical potential difference measured during intraluminal perfusion with Ringer solution containing 30 mmol/l HCO−3 was significantly more negative in all groups studied. In uninephrectomized rats treated with acetazolamide, the trans-epithelial electrical potential difference was more lumen-negative than that in untreated uninephrectomized rats. These results are compatible with a steeper transepithelial Cl− gradient as well as with electrogenic, active H+ secretion. 5. There was no significant difference in the basolateral electrical potential difference between control and uninephrectomized rats. 6. In conclusion, our data show an increase in the transport rates of HCO−3 in the proximal tubule of uninephrectomized rats, which may be due to an increase in the density of transporters in the brush-border membrane, and an increased ability of the transport mechanism to create H+ gradients.

Did Ground Cover Change Over Geologic Time?

2000 ◽  
Vol 6 ◽  
pp. 171-182 ◽  
Author(s):  
Ben A. LePage ◽  
Hermann W. Pfefferkorn
Keyword(s):  
Fossil Record ◽  
Ground Cover ◽  
The Other ◽  
Detailed Account ◽  
Geologic Time ◽  
The Past ◽  
Other Hand ◽  
Plant Fossil

When one hears the term “ground cover,” one immediately thinks of “grasses.” This perception is so deep-seated that paleobotanists even have been overheard to proclaim that “there was no ground cover before grasses.” Today grasses are so predominant in many environments that this perception is perpetuated easily. On the other hand, it is difficult to imagine the absence or lack of ground cover prior to the mid-Tertiary. We tested the hypothesis that different forms of ground cover existed in the past against examples from the Recent and the fossil record (Table 1). The Recent data were obtained from a large number of sources including those in the ecological, horticultural, and microbiological literature. Other data were derived from our knowledge of Precambrian life, sedimentology and paleosols, and the plant fossil record, especially in situ floras and fossil “monocultures.” Some of the data are original observations, but many others are from the literature. A detailed account of these results will be presented elsewhere (Pfefferkorn and LePage, in preparation).

Single Proximal Tubules of the Necturus Kidney. II. Effect of 2,4-Dinitrophenol and Ouabain on Water Reabsorption

1958 ◽  
Vol 195 (3) ◽  
pp. 570-574 ◽  
Author(s):  
Hans J. Schatzmann ◽  
Erich E. Windhager ◽  
A. K. Solomon
Keyword(s):  
Proximal Tubule ◽  
Intravenous Administration ◽  
Proximal Tubules ◽  
Stopped Flow ◽  
Water Reabsorption ◽  
Necturus Maculosus ◽  
Flow Perfusion ◽  
Experimental Findings ◽  
Active Reabsorption ◽  
Normal Controls

The effect of ouabain and 2,4-dinitrophenol on water reabsorption from the proximal tubule of the kidney of Necturus maculosus has been studied using the collection and stopped flow perfusion techniques previously described. The intravenous administration of ouabain in collection experiments results in a decrease in water reabsorption from 32.7% (normal controls) to 15.4%. In stopped flow perfusion experiments on control animals, water reabsorption after 20 minutes is 27.2%. When 2,4-dinitrophenol or ouabain is added to the perfusion fluids, values of 10.2% and 9.8%, respectively, are observed. The experimental findings demonstrate that water reabsorption in the proximal tubule is inhibited by these agents. The results are in agreement with the hypothesis of active reabsorption of sodium from the proximal tubule of the kidney of Necturus.

Blood Gas Analysis

2011 ◽  
Author(s):  
Patrick Magee ◽  
Mark Tooley
Keyword(s):  
Electrical Potential ◽  
Physical Principle ◽  
Gas Analysis ◽  
The Other ◽  
Potential Difference ◽  
Ion Concentration ◽  
Blood Gas ◽  
Glass Membrane ◽  
Current Flows ◽  
Ph Electrode

A blood gas machine has electrodes to measure pH, pCO2 and pO2 and often measures Hb and some biochemistry as well [King et al. 2000]. Derived values from such a device include O2 saturation, O2 content, bicarbonate, base excess and total CO2. This is the Clarke electrode described in the previous section on gas analysers and is suitable for both respiratory and blood O2 analysis. A pH unit has been defined in Chapter 1 as. In words, this can be described as ‘the negative logarithm, to base ten, of the hydrogen ion concentration’. The physical principle on which the pH electrode is based depends on the fact that when a membrane separates two solutions of different [H+], a potential difference exists across the membrane. In a pH electrode, such a membrane is usually made of glass and the development of a potential difference between the two solutions is thought to be due to the migration of H+ into the glass matrix. If one solution consists of a standard [H+], the pH of the other solution can be estimated by measurement of the potential difference between them. The glass membrane used is selectively permeable to H+. No current flows in this device, which does not wear out, in contrast to the Clark electrode, in which current does flow and that does need periodic replacement. The pH measurement system is shown diagrammatically in Figure 17.1. It consists of two half cells. In one half it has an Ag/AgCl electrode and in the other a Hg/HgCl2 (calomel) electrode. Each electrode maintains a fixed electrical potential. The Ag/AgCl electrode is surrounded by a buffer solution of known pH, surrounded by the pH sensitive glass. Outside the glass membrane is the test solution, usually blood, whose pH is to be measured. It is the potential difference across the glass, between these two solutions, which is variable. The blood or other solution is separated from the calomel electrode by a porous plug and a potassium chloride salt bridge to minimise KCl diffusion. The potential difference across the system is about 60 mV per unit of pH change at 37◦C.

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