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PubMed1984

Effects of tonicity on tension and intracellular sodium and calcium activities in sheep heart.

We have measured the effects of changing tonicity of the bathing solution on intracellular sodium and calcium activities and tension of sheep cardiac Purkinje strands and ventricular muscle. For Purkinje strands in solutions of normal tonicity, resting membrane potential was -77.4 +/- 0.4 mV (mean +/- SE), sodium activity was 7.9 +/- 0.4 mM, and calcium activity was 98 +/- 9 nM. For ventricular muscle in solutions of normal tonicity, resting membrane potential was -86.4 +/- 1.2 mV, sodium activity was 6.9 +/- 0.5 mM, and calcium activity was 70 +/- 4 nM. Reduction of tonicity to 75% of normal in both tissues produced depolarization of a few millivolts, and sodium activity fell almost to the level predicted for simple osmotic dilution. In Purkinje strands, calcium activity fell much more than that predicted for simple osmotic dilution. Twitch contraction was reduced in the hypotonic solution. Increase of tonicity to 150% and 200% caused the resting membrane potential to become more negative. In both tissues, sodium activity increased somewhat less than predicted from simple water movement, and calcium activity increased proportionately much more than sodium activity. The much larger change of calcium activity in both hypo- and hypertonic solutions could be explained by water movement plus the effect of sodium-calcium exchange. In hypertonic solutions, tonic tension was increased, along with the rise in calcium activity; however, the twitch tension was reduced. This reduction of twitch tension may be due to a direct effect of hypertonicity on cross-bridge behavior, as has been reported for skeletal muscle.

Animals↗
PubMedDate not supplied

Visualizing bromide and iodide water tracer in soil profiles by spray methods.

In this study we developed and tested a spray method to visualize bromide water tracer in soil profiles. The method is based on the transformation reaction of a white precipitate into a colored one (Prussian blue) in the presence of Br-. After application of water containing bromide (0.2-0.4% wt.), a soil profile is dug out from the irrigated area and sprayed with a Br- indication suspension containing ferric ion and silver ferrocyanide precipitate. About two hours later, the pattern of irrigation water movement in the soil profile appears due to the formation of Prussian blue complex. We describe the method and demonstrate its use in a field experiment to visualize water flow paths. Since this method might be subject to possible interference from Cl-, a newly designed method with iodide ion as a water tracer and its indication solution containing soluble starch and ferric ion is also presented and recommended for use in soils with high chloride background.

Bromides↗
PubMed2004

Bronchiolar expression of aquaporin-3 (AQP3) in rat lung and its dynamics in pulmonary oedema.

Aquaporins (AQPs) are water channel proteins that permit osmotically driven water movement. To determine their dynamics in pulmonary oedema, we examined the expression of mRNA and protein for AQP1, AQP3, AQP4, and AQP5 in the lungs of normal and thiourea-treated rats. In the thiourea group, lung water content increased significantly (vs. controls) with the peak at around 4 h. Semi-quantitative RT-PCR showed that AQP3 mRNA in the thiourea group rose significantly, peaking at around 4-8 h. The expression of AQP1, AQP4, AQP5, ENaC and CFTR mRNA each decreased significantly some time after the peak in lung water content. Immunoblot analysis showed that glycosylated AQP3 protein was increased 4-10 h after treatment. Expression of the other AQP proteins was not significantly altered, except for that of AQP4. Immunohistochemical examination revealed that AQP1 was expressed in endothelia, AQP3 in the basal cells of the large airways and in cuboidal cells in the bronchioles, AQP4 in the basolateral membrane of airway cells and AQP5 in type-I pneumocytes. Our results suggest that AQP3 is expressed not only in large airways, but also in bronchioles, and is related to water movement in pulmonary oedema.

Animals↗
PubMedDate not supplied

Site characterization in densely fractured dolomite: comparison of methods.

One of the challenges in characterizing fractured-rock aquifers is determining whether the equivalent porous medium approximation is valid at the problem scale. Detailed hydrogeologic characterization completed at a small study site in a densely fractured dolomite has yielded an extensive data set that was used to evaluate the utility of the continuum and discrete-fracture approaches to aquifer characterization. There are two near-vertical sets of fractures at the site; near-horizontal bedding-plane partings constitute a third fracture set. Eighteen boreholes, including five coreholes, were drilled to a depth of approximately 10.6 m. Borehole geophysical logs revealed several laterally extensive horizontal fractures and dissolution zones. Flowmeter and short-interval packer testing identified which of these features were hydraulically important. A monitoring system, consisting of short-interval piezometers and multilevel samplers, was designed to monitor four horizontal fractures and two dissolution zones. The resulting network consisted of >70 sampling points and allowed detailed monitoring of head distributions in three dimensions. Comparison of distributions of hydraulic head and hydraulic conductivity determined by these two approaches suggests that even in a densely fractured-carbonate aquifer, a characterization approach using traditional long-interval monitoring wells is inadequate to characterize ground water movement for the purposes of regulatory monitoring or site remediation. In addition, traditional multiwell pumping tests yield an average or bulk hydraulic conductivity that is not adequate for predicting rapid ground water travel times through the fracture network, and the pumping test response does not appear to be an adequate tool for assessing whether the porous medium approximation is valid.

Calcium Carbonate↗
PubMed1979

Temperature dependence of ADH-induced water flow and intramembranous particle aggregates in toad bladder.

Antidiuretic hormone (ADH)-induced luminal intramembranous particle aggregates and hormonally stimulated water flow in toad urinary bladder are reduced simultaneously with a reduction in temperature. When water movement is factored by the aggregation response, the apparent activation energy for this process decreases from 12.1 +/- 1.6 to 3.0 +/- 2.3 kilocalories per mole. The data are consistent with the view that the particle aggregates contain sites for transmembrane water movement and that these sites behave as pores.

Animals↗
PubMed2002

Aquaporin water channels and brain edema.

Brain edema accounts for much of the morbidity and mortality associated with common neurological conditions such as head trauma, brain tumors, stroke and liver failure. Treatment options are limited to osmotic agents such as mannitol, surgical decompression, and other maneuvers, none of which correct the molecular-level mechanisms responsible for brain swelling. Recent data suggest that aquaporin (AQP) water-transporting proteins may provide a key route for water movement in the brain. AQP1 is expressed in choroid plexus and probably facilitates cerebrospinal fluid secretion. AQP4 is expressed in astrocyte foot processes near capillaries and in ependymal cells lining the ventricles -- key sites for water movement between the cellular, vascular, and ventricular compartments. AQP4 expression is markedly altered in experimental models of brain injury and swelling, and transgenic mice lacking AQP4 are partially protected from brain swelling in response to acute hyponatremia and ischemic stroke. Aquaporins and regulators of brain aquaporin expression are thus potential targets for discovery of compounds for treatment of brain swelling.

Animals↗
PubMed2001

Morphological models of radiate accretive growth and the influence of hydrodynamics.

In many marine sessile organisms (for example sponges and stony corals) the skeleton is formed by an accretive growth process, where layers of material are secreted on top of each other in a surface normal deposition process. In many of these organisms the growth process exhibits a strong morphological plasticity due to differences in exposure to water movement. In general, many of these organisms tend to form thin-branching growth forms under sheltered conditions, while the growth form gradually transforms into a more compact shape when the exposure of water movement increases. In this paper, we investigate this phenomenon by combining a three-dimensional simulation model of radiate accretive growth driven by the local availability of simulated food particles and a model, based on the lattice Boltzmann method, for simulating food particle distributions caused by a combination of flow and diffusion. In the simulations two different models of a suspension feeder with accretive growth were compared. In the first model, the deposition process is exclusively driven by the local availability of food particles, in the second model the deposition process was determined by the combination of local amount of contact to the environment and availability of food particles. In the simulations it was found that hydrodynamics has a strong impact on the overall morphologies which develop in the accretive growth process. In the model exclusively driven by the local availability of food particles, column-shaped objects emerged under diffusion conditions, while more spherical and lobed object were found for the flow-dominated case. In the simulations, the Péclet number was varied independently from the Reynolds number, which was kept at a relatively low constant value. In a range of increasing Péclet numbers, indicating an increasing influence of hydrodynamics, the simulated morphologies gradually transformed from thin-branching ones into more spherical and compact morphologies in the model where deposition was controlled by the local availability of food particles and the local amount of contact with the environment.

Animal Nutritional Physiological Phenomena↗
PubMed1994

Osmolality alters tracheal blood flow and tracer uptake in anesthetized sheep.

Changes in the osmolality of airway surface liquid cause bronchoconstriction, mucus secretion, and ion transport, but little is known about the effects on the permeability of the trachea to drugs applied to the tracheal lumen. Using the anesthetized sheep, we have investigated the effects of hyperosmolar (725 +/- 11 mosmol/kg) and hyposmolar (128 +/- 5 mosmol/kg) Krebs-Henseleit (KH) solution in the tracheal lumen (mean volume 13.6 ml) on the uptake of technetium-99m-labeled diethylenetriamine pentaacetic acid (99mTc-DTPA), a low-molecular-mass hydrophilic tracer that is thought to cross the epithelium via paracellular pathways, and on blood flow. All changes in osmolality were made by altering the NaCl content. We perfused a tracheal artery and collected tracheal venous blood. Hyperosmolar KH increased water movement into the lumen (+2.0 ml) and solute flux out of the lumen. It increased arterial (+24.5%) and venous (+20.6%) flows and decreased 99mTc-DTPA concentration (-26.3%) and output (-12.0%) in venous blood. Hyposmolar KH caused water movement out of the lumen (-0.9 ml) and solute flux into the lumen. It had no effect on arterial (+0.6%) and venous (+5.5%) flows and greatly increased the concentration (+345%) and output (+375%) of 99mTc-DTPA in venous blood. The baseline permeability coefficient for 99mTc-DTPA (-9.1 x 10(-7) cm/s) was not affected by hyperosmolar KH (-8.7 x 10(-7) cm/s) but was increased by hyposmolar KH (-21.4 x 10(-7) cm/s). These results confirm that hyperosmolar liquid in the lumen increases blood flow and indicate that tracer uptake is affected by the bulk flow of water across the airway wall.

Administration, Inhalation↗
PubMed2005

Detecting axon damage in spinal cord from a mouse model of multiple sclerosis.

In the current study, the feasibility and reproducibility of in vivo diffusion tensor imaging (DTI) of the spinal cord in normal mice are illustrated followed by its application to mice with experimental allergic encephalomyelitis (EAE) to detect and differentiate axon and myelin damage. Axial diffusivity, describing water movement along the axonal fiber tract, in all regions of spinal cord white matter from EAE-affected C57BL/6 mice was significantly decreased compared to normal mice, whereas there was no statistically significant change in radial diffusivity, describing water movement across the fiber tract. Furthermore, a direct comparison between DTI and histology from a single mouse demonstrated a decrease in axial diffusivity that was supported by widespread staining of antibody against beta-amyloid precursor protein. Regionally elevated radial diffusivity corresponded with locally diminished Luxol fast blue staining in the same tissue from the EAE mouse cord. Our findings suggest that axonal damage is more widespread than myelin damage in the spinal cord white matter of mice with EAE and that in vivo DTI may provide a sensitive and specific measure of white matter injury.

Animals↗
PubMed2000

Maturational changes in rabbit renal basolateral membrane vesicle osmotic water permeability.

We have recently demonstrated that while the osmotic water permeability (Pf) of neonatal proximal tubules is higher than that of adult tubules, the Pf of brushborder membrane vesicles from neonatal rabbits is lower than that of adults. The present study examined developmental changes in the water transport characteristics of proximal tubule basolateral membranes by determining aquaporin 1 (AQP1) protein abundance and the Pf in neonatal (10-14 days old) and adult rabbit renal basolateral membrane vesicles (BLMV). At 25 degrees C the Pf of neonatal BLMV was significantly lower than the adult BLMV at osmotic gradients ranging from 40 to 160 mOsm/kg water. The activation energies for osmotic water movement were identical in the neonatal and adult BLMV (8.65 +/- 0.47 vs. 8.86 +/- 1.35 kcal x deg(-1) x mol(-1). Reflection coefficients for sodium chloride and sodium bicarbonate were identical in both the neonatal and adult BLMV and were not different from one. Mercury chloride (0.5 mM) reduced osmotic water movement by 31.3 +/- 5.5% in the adult BLMV, but by only 4.0 +/- 4.0% in neonatal vesicles (P < 0.01). Adult BLMV AQP1 abundance was higher than that in the neonate. These data demonstrate that neonatal BLMV have a lower Pf and AQP1 protein abundance than adults and that a significantly greater fraction of water traverses the basolateral membrane lipid bilayer and not water channels in neonates compared to adults. The lower Pf of the neonatal BLMV indicates that the basolateral membrane is not responsible for the higher transepithelial Pf in the neonatal proximal tubule.

Aging↗
PubMed1981

Osmotic permeability of Novikoff hepatoma cells.

The osmotic permeability coefficient (Pf) for water movement across Novikoff hepatoma cells was found to be 82 +/- 3 (S.E.) x 10(-5) cm . s-1 at 20 degrees C. The corresponding diffusional permeability coefficient for 3HHO (Pd) was 97 +/- 10 (S.E.) . 10(-5) cm . s-1, therefore the ratio Pf/Pd is close to unity. The apparent activation energy for water filtration was 10.4 +/- 0.4 (S.E.) kcal . mol-1. This value is significantly greater than the activation energy for the self diffusion of water. The product of the hydraulic permeability coefficient and the viscosity coefficient for water was temperature-dependent. However, the product of the hydraulic permeability coefficient and the viscosity coefficient for membrane lipid did not vary with temperature. These data are interpreted as evidence for water movement across a lipid membrane barrier rather than through aqueous channels.

Animals↗
PubMed1985

Glutaraldehyde fixation preserves the permeability properties of the ADH-induced water channels.

Unidirectional and net water movements were determined, in frog urinary bladders, before and after glutaraldehyde fixation. Experiments were performed in three experimental conditions: in nonstimulated preparations, after the action of antidiuretic hormone (ADH) and in nonstimulated preparations to which amphotericin B was incorporated from the luminal bath. As previously observed for net water fluxes, the increase in the unidirectional water movement induced by ADH was well preserved by glutaraldehyde fixation. After correction for the effects of unstirred layers and nonosmotic pathways, the observed correlation between the ADH-induced increases in the osmotic (Pf) and diffusional (Pd) permeability coefficients was not modified by the fixative action (before glutaraldehyde: slope 11.19, r: 0.87 +/- 0.07; n = 12; after glutaraldehyde: slope 10.67, r: 0.86 +/- 0.04, n = 39). In the case of amphotericin B, delta Pf/delta Pd = 3.08 (r: 0.83 +/- 0.08), a value similar to that observed in lipid bilayers or in nonfixed toad urinary bladders. It is concluded that: The experimental approach previously employed to study water channels in artificial lipid membranes and in amphibian urinary bladders, can be applied to the glutaraldehyde-fixed frog urinary bladder. Glutaraldehyde fixation does not modify the permeability properties of the ADH-induced water channels. Any contribution of exo-endocytic processes or cell regulatory mechanisms to the observed permeability parameters can probably be excluded. Glutaraldehyde-fixed preparations are a good model to characterize these water pathways.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1974

Structure and function in urinary bladder of foetal sheep.

1. The structure and function of the epithelial lining of the urinary bladder of sheep foetuses was investigated by electron microscopic studies made in conjunction with a series of experiments in which the permeability of the bladder to sodium and water was measured in vitro. Measurements were made at gestational ages ranging from 50 to 141 days (term = 147 days) Osmolarity and electrolyte concentrations of urine found in the foetal bladder were also measured.2. The development of tight junctions between the bladder epithelial cells was investigated by incubating the tissue with solutions containing 1 mM-LaCl(3) on the mucosal surface. No penetration of the junctions by lanthanum was observed in foetuses of 90 days or older. In younger bladders, the epithelial layer was stripped by treatment with lanthanum, but tight junctions appeared to be fully developed in early bladders incubated without lanthanum.3. The surface structure of the luminal (mucosal) plasmalemma was fully developed at 50 days.4. Unidirectional fluxes of labelled sodium and water were measured with identical solutions bathing the two surfaces of the bladder wall. No net water movement occurred; the mean ratio of efflux to influx in nine bladders was 1.002 +/- 0.039 (S.E. of mean). Under these conditions, the flux ratio for sodium was 1.735 +/- 0.143 (S.E. of mean) in twelve bladders.5. Antidiuretic hormone (ADH) had no effect on net water movement but reduced the net efflux of sodium so that the flux ratio became 1.285 +/- 0.255 (S.E. of mean) n = 8. ADH also had a striking effect on the structure of the epithelium, causing marked swelling of the intercellular spaces. The tight junctions remained an effective barrier to lanthanum penetration under these conditions; lanthanum was not observed in the enlarged spaces.

Animals↗
PubMed1989

Loss of ultrafiltration in continuous ambulatory peritoneal dialysis (CAPD).

Fifteen patients on long-term continuous ambulatory peritoneal dialysis (CAPD) were assessed with respect to net ultrafiltration capacity. Eight patients were defined as having good and seven as having poor ultrafiltration on the basis of net ultrafiltrate obtained/mmol glucose infused. Subsequently, dialysate was sampled at times 0, 1, 15, 30, 60, 90, 120, 180, and 240 min. No difference in residual volume was observed between the groups. A significantly greater decrease in dialysate sodium during the initial dialysis period in those patients with good as compared to those with poor ultrafiltration occurred, reflecting a greater transcapillary movement of electrolyte poor ultrafiltrate. In those with good ultrafiltration, glucose transfer was normal in five and rapid in three, suggesting the latter had low rates of lymphatic reabsorption. Five of seven patients with poor ultrafiltration had no fall in dialysate sodium in association with a high rate of glucose transfer, suggesting a low rate of transcapillary water movement and normal to high lymphatic absorption. Two patients with low ultrafiltration had an initial fall in dialysate sodium with a normal glucose transfer and thus net ultrafiltration is low due to elevated lymphatic reabsorption. We thus propose that the relative contribution of transcapillary water movement and lymphatic reabsorption can be determined by assessing net ultrafiltration and dialysate sodium concentration in conjunction with solute transfer.

Biological Transport↗
PubMed1986

Inhibition of the antidiuretic hormone hydroosmotic response by phospholipids and phospholipid metabolites.

Phospholipid metabolities and phospholipids containing arachidonic acid (AA) inhibited the antidiuretic hormone (ADH)-induced increase in transepithelial water flow in the toad urinary bladder, but had no effect on basal water flow when added to the serosal bathing solution. Other fatty acid-substituted phospholipid metabolites had no effect on osmotic water movement in the presence or absence of ADH. Indomethacin attenuated the inhibitory effects of the AA containing phospholipid metabolities (PMAA), suggesting that the PMAA response required AA release and prostaglandin (PG) formation. PMAA increased PGE formation as measured by radioimmunoassay. PG have been reported to inhibit ADH-stimulated water flow by inhibiting adenylcyclase. PGE2 (10(-8) M) had no effect on cyclic AMP-stimulated water flow, whereas exogenous AA and PMAA attenuated the hydroosmotic response to added cyclic AMP. Indomethacin only partially reversed the inhibition by AA of the cyclic AMP-associated water movement, suggesting that the inhibition by AA and PMAA may involve other metabolites of AA than PG. PG and the AA cascade have been implicated as cellular modulators of the ADH hydroosmotic response. The present results offer additional support to the theory that this system may regulate the intracellular events that are transduced following receptor activation by ADH.

Animals↗
PubMed2003

[Osmotic cerebral oedema: the role of plasma osmolarity and blood brain barrier].

There are five types of oedema: vasogenic, cytotoxic, interstitial, hyperemic and osmotic. The differences lie on the type and localization of the oedema, the state of the blood-brain barrier (BBB) and the pathological context. Under physiological conditions, the osmolarity of extra cellular fluids (ECFs) is equal on both sides of the BBB. However, the pathophysiological variations of circulating osmolarity (including acute hyponatremia and hypernatremia) do not affect, at the same time, the osmolarity of cerebral ECFs. This situation generates an osmotic gradient on either side of the BBB. The latter, if intact, behaves like a semi-permeable membrane allowing water transport according to the osmotic laws. Depending on its direction, water movement could induce cerebral liquid inflation (i.e. osmotic oedema) or cerebral dehydration. In case of osmotic insult, cerebral cell modify their active osmotic molecular contents in order to limit volume variation. There are two types of osmoactive molecules, organic (i.e. ideogenic osmoles: amino acids, polyols and trimethylamines) and non organic (i.e. electrolytes). In the event of plasma hypotonicity, cerebral cells expel active osmotic molecules to reduce the osmotic gradient and water movement thereby reducing edema. The opposite reaction is observed in the case of hypertonic insult. This cerebral osmoregulation becomes more effective, the slower the osmotic disorder. It explains, for example, why patients with chronic and severe hyponatremia could be asymptomatic. Severe osmotic oedema is observed mainly in water intoxication, acute hyponatremia or too rapid reduction of hyperosmolarity. However, osmotic oedema is not limited to extreme clinical circumstances. Hyponatremia, even modest, could modify cerebral blood volume and impair osmoregulation. Generally these minor modifications do not affect normal brain tissue. In the presence of cerebral lesion, osmoregulation operates only in areas of preserved BBB. The pathological zones are therefore exposed to osmotic oedema (even in cases of moderate hyponatremia) with deterioration of both clinical status and intracranial pressure. This authentic phenomenon could be insidious and difficult to differentiate from osmotic central oedema. Hyponatremia constitutes an authentic secondary cerebral insult of systemic origin, an entity clearly identified by experimental studies to justify the choice between crystalloids and colloids in neuroanaesthesia and neurointensive care. These studies have revealed an increase in water content in normal brain tissues after administration of hypotonic solutions. The increase in plasma osmolarity as a treatment modality using mannitol or hypertonic saline is based on the same concepts. The most remote indication is the occurrence of a reactive mydriasis in the context of trauma for example. More recently, therapeutic hypernatremia has been proposed to control intracranial hypertension.

Blood-Brain Barrier↗
PubMed1990

Water and ion handling in the rat cecum.

The minute-by-minute net water movement (Jw) in the rat cecum was correlated with the transepithelial potential difference (PD), short-circuit current (Isc), and the unidirectional Na+, Cl-, and Rb+ fluxes, with the following results. 1) Jw was a linear function of the applied hydrostatic or osmotic transepithelial gradients (hydrostatic permeability coefficiency = 0.164 +/- 0.018 cm/s, n = 13; osmotic permeability coefficient = 0.0014 +/- 0.0002 cm/s, n = 6). 2) A fraction of this absorptive Jw (0.17 +/- 0.03 microliter.min-1.cm-2, n = 13) was independent of the presence of any osmotic, hydrostatic, or chemical gradient. 3) This fraction was Na+ dependent, associated with an amiloride-insensitive PD and net Na+ (2.37 +/- 0.68 mu eq.h-1.cm-2, n = 6) and Cl- influxes (3.45 +/- 1.46 mu eq.h-1.cm-2, n = 6), measured under short-circuit conditions. No net Rb+ movement was detected. 4) The absorptive Jw increased when HCO3- was replaced by tris(hydroxymethyl)aminomethane (Tris+) buffer or Cl- by SO4(2-). A good agreement between the observed and the expected Jw (assuming isosmotic reabsorption) was observed in the absence of HCO3-. 5) The presence of an osmotic but not a hydrostatic transepithelial gradient generated a transepithelial PD. These results show that water movement across the rat cecum in vitro is the result of a combination of hydrostatic-, osmotic-, and transport-associated transfers. Concerning this last driving force, the observed results indicate that the transport-related Jw results from the addition of an absorptive Jw, coupled to a nonelectrogenic NaCl entry, plus a secretory Jw probably coupled to HCO3- secretion.

Animals↗