Relative osmotic effects of raffinose, KCl, and NaCl across basolateral cell membrane

1990 ◽  
Vol 259 (4) ◽  
pp. F594-F597 ◽  
Author(s):  
L. W. Welling ◽  
D. J. Welling ◽  
T. Ochs
Keyword(s):  
Reflection Coefficient ◽  
Cell Membrane ◽  
Proximal Tubule ◽  
The Other ◽  
Hypertonic Medium ◽  
Arithmetic Average ◽  
Basolateral Cell Membrane ◽  
Osmotic Effects

Lumen-collapsed segments of rabbit S2 proximal tubule were bathed in isotonic medium and then exposed acutely to a medium made hypertonic by the addition of raffinose, NaCl, KCl, Na gluconate, K gluconate, or choline Cl. The result was a rapid efflux of water and a shrinking of the tubule, which could be measured by video techniques within the first 0.1 s. After reequilibration in isotonic medium, each tubule was then exposed to a second hypertonic medium to provide a direct comparison between two different solutes, either NaCl vs. KCl or raffinose vs. any one of the other solutes. Because raffinose is impermeant across the basolateral cell membrane, the ratio of its effect to that of another solute is a measure of the reflection coefficient (sigma) of that other solute. The following results were obtained: sigma KCl = 0.70 +/- 0.02, sigma K gluconate = 0.97 +/- 0.07, sigma Na gluconate = 0.84 +/- 0.06, and sigma choline Cl = 0.75 +/- 0.06. We previously have reported sigma NaCl = 0.56 +/- 0.07. If sigma of each salt is considered to be the arithmetic average of its component parts, and if gluconate and choline are considered to be impermeant, we also obtain sigma Na+ = 0.68, sigma K+ = 0.94, and sigma Cl- = 0.50.

Na+ electrochemical gradient and Na+-Ca2+ exchange in rat proximal tubule

1989 ◽  
Vol 257 (4) ◽  
pp. F531-F538
Author(s):  
J. H. Dominguez ◽  
J. K. Rothrock ◽  
W. L. Macias ◽  
J. Price
Keyword(s):  
Cell Membrane ◽  
Proximal Tubule ◽  
Thermodynamic Analysis ◽  
Cytosolic Calcium ◽  
Proximal Tubules ◽  
The Other ◽  
Electrochemical Gradient ◽  
Basolateral Cell Membrane ◽  
45Ca Efflux ◽  
Rat Proximal Tubule

he basolateral cell membrane of the rat proximal tubule contains a Na+-Ca2+ exchanger that may participate in the regulation of cytosolic calcium (Cai) and Ca2+ transport. In this work, the activity and orientation of the Na+-Ca2+ exchanger was studied in rat proximal tubules. The experiments were based on the thermodynamic notion that the exchanger is driven by the prevalence of either of two electrochemical gradients, that for Na+ (delta mu Na+) or for Ca2+ (delta mu Ca2+). Reductions in delta mu Na+, achieved by lowering extracellular Na+ (Nao) from 150 to 15 mM, increased Cai, decreased 45Ca efflux, and increased 45Ca influx. These changes occurred concurrently. When delta mu Na+ was reduced by increasing intracellular Na+ (Nai) with 10(-3) M oubain, Cai also increased. The effect of ouabain was probably dependent on Nai accumulation because the surge in Cai was prevented by exposure of the tubules to 5 mM Nao before ouabain exposure. On the other hand, when delta mu Na+ was lowered mM Nao and then by reducing Nao to 15 mM, Cai rose in two additive stages. We conclude from these data that in the rat proximal tubule the basal state of the Na+-Ca2+ exchanger is in forward mode, Nao-Cai. Moreover, the function of the Na+-Ca2+ exchanger is in accord with predictions derived from a thermodynamic analysis of its function.

Isolated perfused salamander proximal tubule: methods, electrophysiology, and transport

1981 ◽  
Vol 241 (1) ◽  
pp. F39-F52 ◽  
Author(s):  
H. Sackin ◽  
E. L. Boulpaep
Keyword(s):  
Cell Membrane ◽  
Proximal Tubule ◽  
Fluid Transport ◽  
Transference Number ◽  
Detailed Comparison ◽  
Proximal Tubules ◽  
Potential Difference ◽  
Ambystoma Tigrinum ◽  
Basolateral Cell Membrane

Techniques are presented for the isolation and perfusion of renal proximal tubules from the neotenic salamander Ambystoma tigrinum. Methods are described for a determination of normal values for fluid transport and electrophysiological parameters. Stable cellular microelectrode recordings are reported that constitute the first intracellular measurements in an isolated perfused tubule preparation. With identical solutions in lumen and bath, fluid reabsorption averaged 0.28 nl.min-1.mm-1, transepithelial potential difference averaged -4.5 mV, transepithelial resistance was 52.1 omega.cm2, and the transepithelial chloride-to-sodium transference number ratio was 3.4. The basolateral cell membrane potential difference averaged -59.6 mV, and the ratio of apical-to-basolateral cell membrane resistance was between 3.9 and 5. Viability of the isolated perfused salamander proximal tubule preparation is demonstrated by a detailed comparison of the present data with results of in vivo micropuncture experiments on both Necturus and intact Ambystoma kidneys. In addition to being an advantageous preparation for long-term intracellular recordings, the Ambystoma kidney is unique in that proximal tubules can be studied both in isolation and by conventional micropuncture.

Micropuncture study of ammonia excretion in the rat

1963 ◽  
Vol 205 (1) ◽  
pp. 127-132 ◽  
Author(s):  
Sheldon Glabman ◽  
R. M. Klose ◽  
Gerhard Giebisch
Keyword(s):  
Proximal Tubule ◽  
Ammonium Chloride ◽  
Ammonia Excretion ◽  
The Other ◽  
Water Reabsorption ◽  
Micropuncture Study

Ammonia has been determined in blood and in samples of tubular fluid obtained by micropuncture at various sites along the nephron from two groups of rats, one untreated and the other pretreated with ammonium chloride. Ammonia has been found in tubular fluid from all segments of the nephron, the concentrations being generally higher in those animals which were pretreated with ammonium chloride. In addition, there is a tendency for the concentration of ammonia to increase as the site of micropuncture progresses along the nephron. In the proximal tubule, concentrations of ammonia have been found which are greater than can be accounted for solely by the extraction of water in this segment. This is taken to indicate tubular addition of ammonia at this site. Since the increments of ammonia along the nephron generally exceed that which could be due to water reabsorption, it is concluded that all parts of the nephron contribute to urinary ammonia excretion.

scholarly journals The Relationships between Cholesterol and Suicide: An Update

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Domenico De Berardis ◽  
Stefano Marini ◽  
Monica Piersanti ◽  
Marilde Cavuto ◽  
Giampaolo Perna ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Cell Membrane ◽  
The Other ◽  
Core Component ◽  
Cell Membrane Stability ◽  
Cholesterol Levels ◽  
The Central Nervous System ◽  
Larger Sample

Cholesterol is a core component of the central nervous system, essential for the cell membrane stability and the correct functioning of neurotransmission. It has been observed that cholesterol may be somewhat associated with suicidal behaviours. Therefore, the aim of this paper was to elucidate current facts and views about the role of cholesterol levels in mood disorders. The majority of the studies reviewed in the present paper suggest an interesting relationship between cholesterol (especially lower levels) and suicidality. On the other hand, particularly during the last years, relationships between serum cholesterol and suicidality were doubted on the basis of some recent studies that have not found any correlation. However, the debate on relationships between cholesterol and suicide is open and longitudinal studies on a larger sample of patients are needed to further clarify this important issue.

Rotary movements and fluid membranes in termite flagellates

1976 ◽  
Vol 20 (3) ◽  
pp. 619-638
Author(s):  
S.L. Tamm ◽  
S. Tamm
Keyword(s):  
Plasma Membrane ◽  
Comparative Analysis ◽  
Cell Membrane ◽  
Shear Zone ◽  
Surrounding Medium ◽  
The Other ◽  
Visual Evidence ◽  
Fluid Membranes ◽  
Internal Motor ◽  
Rotary Motor

We previously described a remarkable type of cell motility that provided direct, visual evidence for the fluid nature of cell membranes. The movement involved continual, unidirectional rotation of one part of a protozoan, including the plasma membrane and cytoplasmic organelles, in relation to a neighbouring part. The cell membrane in the ‘shear zone’ appeared continuous with that of the rest of the cell. The rotary motor consisted, at least in part, of a non-contractile, microtubular axostyle which extended centrally through the cell. The protozoan was a devescovinid flagellate found in the hindgut of a Florida termite. In this paper, we have confirmed earlier reports of this type of motility in other kinds of devescovinids from Australian termites. By demonstrating continuity of the plasma membrane in the shear zone of the Australian devescovinids as well, we have obtained additional examples that provide direct, visual evidence for fluid membranes. A comparative analysis of rotational motility in various devescovinids revealed 2 different kinds of rotary mechanisms. Hyperdevescovina probably have an internal motor, in which one part of the cell exerts forces against another part, as in the Florida termite devescovinid. Devescovina species, on the other hand, have an external motor, in which flagellar and/or papillar movements exert forces against the surrounding medium. The structure of the axostyle in different devescovinids was compared, and its role in rotational motility discussed with respect to the behavioural data.

Ketoconazole - an antifungal drug for oral use

1981 ◽  
Vol 19 (23) ◽  
pp. 91-92
Keyword(s):  
Antifungal Activity ◽  
Cell Membrane ◽  
Oral Administration ◽  
Antifungal Agent ◽  
Systemic Effect ◽  
Antifungal Drug ◽  
The Other ◽  
Membrane Synthesis ◽  
Fungal Cell

Ketoconazole (Nizoral - Janssen) is a new antifungal agent. Like the other imidazoles with antifungal activity such as miconazole,1 clotrimazole2 and econazole,3 it acts by inhibiting fungal cell-membrane synthesis.4 It is well absorbed and exerts a systemic effect; it is thus suitable for oral administration.

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