Chloride secretion drives urine formation in leech nephridia.

1997 ◽  
Vol 200 (16) ◽  
pp. 2217-2227 ◽  
Author(s):  
I Zerbst-Boroffka ◽  
B Bazin ◽  
A Wenning
Keyword(s):  
Fluid Secretion ◽  
Chloride Secretion ◽  
Central Canal ◽  
Transport Mechanisms ◽  
Basolateral Side ◽  
Urine Formation ◽  
K Transport ◽  
Cl Conductance ◽  
Stimulation Of

The transport mechanisms underlying urine formation in leech nephridia were investigated in situ and in isolated preparations using pharmacological, electrophysiological and micropuncture techniques. Canalicular cells, which secrete the primary urine, function as a Cl(-)-secreting epithelium. An apical Cl- conductance contributes to the lumen-negative potential which drives transcellular K+ transport and paracellular Na+ transport. On the basolateral side, a ouabain-sensitive Na+/K(+)-ATPase contributes substantially to the cellular and transcellular potential and provides the Na+ gradient necessary for a bumetanide-sensitive Na+/K+/2Cl- cotransport. Final urine is formed by subsequent reabsorption of ions along the central canal, where KCl and NaCl are reabsorbed in different portions. The postprandial diuresis is not a consequence of the changes in blood osmolality or ion concentrations. Similar changes in the ionic environment do not promote diuresis in isolated nephridia. Apparently, the composition and volume of the primary urine cannot be separately controlled. Any increase in fluid secretion by leech canalicular cells involves upregulation of the paracellular pathway and stimulation of Cl- entry, which thereby changes the normally K(+)-enriched primary urine to the Na(+)-enriched primary urine characteristic of leeches in diuresis.

Physical Properties of Isolated Perfused Renal Tubular Basement Membranes

1971 ◽  
Vol 29 ◽  
pp. 390-391
Author(s):  
Jared Grantham ◽  
Larry Welling
Keyword(s):  
Basement Membrane ◽  
Basement Membranes ◽  
Transport Mechanisms ◽  
Permeability Characteristics ◽  
Peritubular Capillaries ◽  
Strategic Location ◽  
Tubular Lumen ◽  
Glomerular Filtrate ◽  
Urine Formation ◽  
Renal Tubular

In the course of urine formation in mammalian kidneys over 90% of the glomerular filtrate moves from the tubular lumen into the peritubular capillaries by both active and passive transport mechanisms. In all of the morphologically distinct segments of the renal tubule, e.g. proximal tubule, loop of Henle and distal nephron, the tubular absorbate passes through a basement membrane which rests against the basilar surface of the epithelial cells. The basement membrane is in a strategic location to affect the geometry of the tubules and to influence the movement of tubular absorbate into the renal interstitium. In the present studies we have determined directly some of the mechanical and permeability characteristics of tubular basement membranes.

Dependence of ion fluxes on fluid transport by rat proximal tubule

1986 ◽  
Vol 250 (4) ◽  
pp. F680-F689 ◽  
Author(s):  
K. Bomsztyk ◽  
F. S. Wright
Keyword(s):  
Proximal Tubule ◽  
Fluid Transport ◽  
Rat Kidney ◽  
Water Flux ◽  
Fluid Secretion ◽  
Proximal Convoluted Tubule ◽  
Ion Fluxes ◽  
Fluid Absorption ◽  
Fluid Flux ◽  
K Transport

The effects of changes in transepithelial water flux (Jv) on sodium, chloride, calcium, and potassium transport by the proximal convoluted tubule were examined by applying a microperfusion technique to surface segments in kidneys of anesthetized rats. Perfusion solutions were prepared with ion concentrations similar to those in fluid normally present in the later parts of the proximal tubule. Osmolality of the perfusate was adjusted with mannitol. With no mannitol in the perfusates, net fluid absorption was observed. Addition of increasing amounts of mannitol first reduced Jv to zero and then reversed net fluid flux. At the maximal rates of fluid absorption, net absorption of Na, Cl, Ca, and K was observed. When Jv was reduced to zero, Na, Cl, and Ca absorption were reduced and K entered the lumen. Na, Cl, and Ca secretion occurred in association with the highest rates of net fluid secretion. The lumen-positive transepithelial potential progressively increased as the net fluid flux was reduced to zero and then reversed. The results demonstrate that changes in net water flux can affect Na, Cl, Ca, and K transport by the proximal convoluted tubule of the rat kidney. These changes in net ion fluxes are not entirely accounted for by changes in bulk-phase transepithelial electrochemical gradients.

scholarly journals Rotavirus Infection Is Not Associated with Small Intestinal Fluid Secretion in the Adult Mouse

2006 ◽  
Vol 80 (22) ◽  
pp. 11355-11361 ◽  
Author(s):  
Shirin Kordasti ◽  
Claudia Istrate ◽  
Mahanez Banasaz ◽  
Martin Rottenberg ◽  
Henrik Sjövall ◽  
...  
Keyword(s):  
Fluid Secretion ◽  
Chloride Secretion ◽  
Potential Difference ◽  
Pathophysiological Mechanism ◽  
Rotavirus Infection ◽  
In Vivo Experiments ◽  
Adult Mice ◽  
Small Intestines

ABSTRACT In contrast to humans, adult but not infant small animals are resistant to rotavirus diarrhea. The pathophysiological mechanism behind this age-restricted diarrhea is currently unresolved, and this question was investigated by studying the secretory state of the small intestines of adult mice infected with rotavirus. Immunohistochemistry and histological examinations revealed that rotavirus (strain EDIM) infects all parts of the small intestines of adult mice, with significant numbers of infected cells in the ilea at 2 and 4 days postinfection. Furthermore, quantitative PCR revealed that 100-fold more viral RNA was produced in the ilea than in the jejuna or duodena of adult mice. In vitro perfusion experiments of the small intestine did not reveal any significant changes in net fluid secretion among mice infected for 3 days or 4 days or in those that were noninfected (37 ± 9 μl · h−1 · cm−1, 22 ± 13 μl · h−1 · cm−1, and 33 ± 6 μl · h−1 · cm−1, respectively) or in transmucosal potential difference (4.0 ± 0.3 mV versus 3.9 ± 0.4 mV), a marker for active chloride secretion, between control and rotavirus-infected mice. In vivo experiments also did not show any differences in potential difference between uninfected and infected small intestines. Furthermore, no significant differences in weight between infected and uninfected small intestines were found, nor were any differences in fecal output observed between infected and control mice. Altogether, these data suggest that rotavirus infection is not sufficient to stimulate chloride and water secretion from the small intestines of adult mice.

Visualization of the Coalescence of Bismuth Nanoparticles

2014 ◽  
Vol 20 (2) ◽  
pp. 416-424 ◽  
Author(s):  
Kai-Yang Niu ◽  
Hong-Gang Liao ◽  
Haimei Zheng
Keyword(s):  
Precursor Solution ◽  
Growth Trajectories ◽  
Transport Mechanisms ◽  
Bismuth Nanoparticles ◽  
Transmission Electron ◽  
Liquid Cell ◽  
Significant Pathway ◽  
Mass Transport Mechanisms ◽  
Bi Nanoparticles

AbstractCoalescence is a significant pathway for the growth of nanostructures. Here we studied the coalescence of Bi nanoparticles in situ by liquid cell transmission electron microscopy (TEM). The growth of Bi nanoparticles was initiated from a bismuth neodecanoate precursor solution by electron beam irradiation inside a liquid cell under the TEM. A significant number of coalescence events occurred from the as-grown Bi nanodots. Both symmetric coalescence of two equal-sized nanoparticles and asymmetric coalescence of two or more unequal-sized nanoparticles were analyzed along their growth trajectories. Our observation suggests that two mass transport mechanisms, i.e., surface diffusion and grain boundary diffusion, are responsible for the shape evolution of nanoparticles after a coalescence event.

scholarly journals STUDIES ON THE EFFECT OF CERTAIN TOXIC SUBSTANCES IN BACTERIAL CULTURES ON THE MOVEMENT OF THE INTESTINES

1926 ◽  
Vol 43 (6) ◽  
pp. 785-795 ◽  
Author(s):  
E. E. Ecker ◽  
A. Rademaekers
Keyword(s):  
Intravenous Injection ◽  
Toxic Substances ◽  
Propulsive Efficiency ◽  
Spasmodic Contraction ◽  
Strong Stimulation ◽  
Small Intestines ◽  
Slight Rise ◽  
Longitudinal Muscles ◽  
Stimulation Of

Following intravenous injection, filtrates of young cultures of B. paratyphosus B often produce marked diarrhea in rabbits. A study was made of the effect of these toxic filtrates on the motility of the small intestines of the rabbit. The observations were made on a segment of the small intestines in situ, and in the living animal. It was found that an immediate slight rise of tone of the longitudinal muscles occurred following intravenous injection of sterile broth. The same rise was noted after the injection of the toxic filtrate; but with these it was followed later (10 minutes elapsing at least) by a very strong but gradual rise of the diastolic and systolic tone, i.e., by spasmodic contraction of the intestinal muscle, which persisted at times for as long as 2 hours. In order to record simultaneously the effect on the longitudinal and circular muscles, and the propulsive efficiency of the segment the Sollmann and Rademaekers modification of Baur's technique was employed. This arrangement showed that the stimulation of the longitudinal muscles is accompanied by a similarly strong stimulation of the circular muscles, by peristalsis, and therefore by a greatly increased propulsion of intestinal contents which was sufficient to overcome the inhibition that usually occurs after preparation of the animal. With this arrangement an instance of peristaltic spasm was also noted. Broth alone failed to produce the phenomenon. Isotonic magnesium chloride or sulfate added to the bath relaxed the muscles again. Animals under deep urethane anesthesia did not show the diarrhea occurring in the intact controls, but sometimes exhibited it after the effect of the anesthetic had disappeared. So far no effects have been observed on the isolated strip (Magnus method), and further studies are being made to localize the effect, to neutralize it with a specific antiserum, and to observe the effect of filtrates of other members of the bacterial group including the dysentery bacilli.

Active NaCl absorption across split lamellae of posterior gills of the chinese crab Eriocheir sinensis: stimulation by eyestalk extract

2000 ◽  
Vol 203 (8) ◽  
pp. 1373-1381 ◽  
Author(s):  
H. Onken ◽  
A. Schobel ◽  
J. Kraft ◽  
M. Putzenlechner
Keyword(s):  
Electromotive Force ◽  
Single Channel ◽  
Short Circuit ◽  
Noise Analysis ◽  
Eriocheir Sinensis ◽  
Dialysis Tubing ◽  
Channel Current ◽  
Dose Dependent ◽  
Cl Conductance ◽  
Stimulation Of

Split lamellae of the posterior gills of freshwater-adapted Chinese crabs (Eriocheir sinensis) were mounted in a modified Ussing-type chamber, and active and electrogenic absorption of Na(+) and Cl(−) were measured as positive (I(Na)) or negative (I(Cl)) short-circuit currents. Haemolymph-side addition of eyestalk extract stimulated I(Cl) by increasing both the transcellular Cl(−) conductance and the electromotive force for Cl(−) absorption. The effect was dose-dependent. Boiling the eyestalk extract did not change its effectiveness. The stimulating factor passed through dialysis tubing, indicating that it has a molecular mass of less than 2 kDa. R(p)cAMPS, a blocker of protein kinase A, reduced the stimulated I(Cl). Eyestalk extract stimulated I(Na) by increasing the transcellular Na(+) conductance at constant electromotive force. Amiloride-induced current-noise analysis revealed that stimulation of I(Na) was accompanied by an increase in the apparent number of open apical Na(+) channels at a slightly reduced single-channel current. In addition to the electrophysiological experiments, whole gills were perfused in the presence and in the absence of putative transport stimulators, and the specific activities of the V-ATPase and the Na(+)/K(+)-ATPase were measured. Eyestalk extract, theophylline or dibutyryl-cyclic AMP stimulated the activity of the V-ATPase, whereas the activity of the Na(+)/K(+)-ATPase was unaffected. The simultaneous presence of R(p)cAMPS prevented the stimulation of V-ATPase by eyestalk extract or theophylline.

Membrane dynamics in insect malpighian tubules

1989 ◽  
Vol 257 (5) ◽  
pp. R967-R972
Author(s):  
T. J. Bradley
Keyword(s):  
Ion Transport ◽  
Driving Force ◽  
Fluid Secretion ◽  
Membrane Dynamics ◽  
Malpighian Tubules ◽  
Membrane Insertion ◽  
Cation Pump ◽  
Active Ion Transport ◽  
Urine Formation ◽  
Apical Membranes

Urine formation in insects occurs in the Malpighian tubules by means of active ion transport and osmotically coupled water flow. The rates of urine formation can vary with time and can be modulated by diuretic hormones, developmental events, and intracellular parasitism. This paper reviews a number of recent studies in which it has been demonstrated that variations in transport rate are associated with substantial changes in tubule ultrastructure in the form of membrane insertion into and deletion from the apical microvilli. The principal driving force for fluid movement in Malpighian tubules is thought to be a common cation pump located in the apical membranes. It is proposed that modulation of the apical microvillar membrane may reflect regulation by the cells of the number of common cation pump units involved in fluid secretion.

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