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At least 145 records · Page 8Linked to original sources
PubMed1977

Effects of Abscisic Acid and of Hydrostatic Pressure Gradient on Water Movement through Excised Sunflower Roots.

The effect of abscisic acid on the exudation rate from decapitated roots of sunflower plants (Helianthus annuus L.) was investigated in the presence and absence of an imposed hydrostatic pressure gradient. The magnitude of the abscisic acid effect was constant even when suctions up to 60 cm Hg were applied to the cut stumps.When roots were bathed in a THO-labeled nutrient solution, the course of the appearance of radioactivity in the exudate, expressed as a function of exudate volume, was not affected by abscisic acid treatment but was strongly speeded up by applying suction.The implications of those findings with regard to the water pathway through the root and the location of the abscisic acid effect are discussed.

Journal Article↗
PubMed1977

Selective compartmentation of the hydration products of carbon dioxide in liposomes, and its role in regulating water movement.

Using liposomes, some possible consequences of auxin-stimulated proton secretion in plant tissues are modelled. Liposomes, made specifically permeable to protons and potassium ions, but containing at least one impermeant, swell at a rate which is proportional to the availability and hydration rate of carbon dioxide; the gas functions as a source of proton and dehydrated anion and this enables a net transfer of KHCO3 to take place.

Carbon Dioxide↗
PubMed1979

Water movement across split frog skin.

A net inward fluid reabsorption (salt-linked flow) has been observed in isolated skin epithelium (split skin) with the same magnitude as in whole skin when identical NaCl Ringer solutions were used to bathe both sides. Split skins also respond to a hyperosmotic sucrose solution bathing the outer (epithelial) surface by generating an outward osmotic flow. A non-linear relationship between osmotic flow and the osmotic gradient has been found in split skin similar to that found in whole skin.

Animals↗
PubMed1987

Net sodium and water movements in the newborn rabbit collecting tubule: lack of modifications by indomethacin.

In contrast to adult tubules, a bath-to-lumen sodium gradient was followed by net sodium entry in the lumen of in vitro isolated perfused newborn (3-5 days) rabbit collecting tubules. In addition, transepithelial voltage and electrical resistance were lower in newborn tubules. The sodium flux into the lumen was unaffected by indomethacin. These observations suggest that the newborn collecting tubule may be unable to maintain an adequate sodium gradient for the optimal function of the urinary concentrating mechanism, and that endogenous prostaglandins are not involved in this defect.

Animals↗
PubMed1985

Control of transcapillary water movement by vasoactive agents.

Experiments were performed to demonstrate that papaverine can increase capillary filtration coefficient, CFC, and to investigate whether this increase could be reversed by isoproterenol, norepinephrine and plasma. The study used the isolated cat hindlimb, perfused at constant flow with a recirculated blood-albumin solution. It was observed that papaverine increased CFC in a dose-dependent manner, and that this effect could be reversed by isoproterenol and norepinephrine. Norepinephrine reduced CFC even in the presence of phentolamine. Plasma, previously shown to reduce CFC when papaverine was present, was shown to have no such effect when papaverine was absent. It is argued that the CFC changes are best explained by changes in the hydraulic conductivity of the exchange vessels, rather than through changes in the perfused surface area, and that the CFC changes are similar to the permeability changes caused by inflammatory mediators and catecholamines observed by others.

Animals↗
PubMedDate not supplied

Kinetics of osmotic water movement from rabbit patellar tendon and medial collateral ligament fibroblasts.

The present study is part of a program to optimize the cryopreservation ligament and tendon allografts for the biological remodeling that occurs following transplantation. The osmotic behavior of fibroblasts from the medial collateral ligament (MCL) and the patellar tendon (PT) of new zealand white rabbits was measured to obtain the hydraulic conductivity (and its temperature dependence) as well as the osmotically inactive volume. MCL fibroblasts were found to have an isotonic cell volume of 3800 (m(3), an osmotically inactive volume of 1300 (microm(3), and a hydraulic conductivity of 0.56 (microm/min/atm at 20 degrees C with an activation energy of 10.9 kcal/mol. PT fibroblasts were found to have an isotonic cell volume of 6300 (microm(3), an osmotically inactive volume of 2000 (microm(3), and a hydraulic conductivity of 0.71 (m/min/atm at 20 degrees C with an activation energy of 10.1 kcal/mol.

Animals↗
PubMed1962

Studies on the movement of water through the isolated toad bladder and its modification by vasopressin.

Measurements of diffusion permeability and of net transfer of water have been made across the isolated urinary bladder of the toad, Bufo marinus, and the effects thereon of mammalian neurohypophyseal hormone have been examined. In the absence of a transmembrane osmotic gradient, vasopressin increases the unidirectional flux of water from a mean of 340 to a mean of 570 microl per cm(2) per hour but the net water movement remains essentially zero. In the presence of an osmotic gradient but without hormone net transfer of water remains very small. On addition of hormone large net fluxes of water occur; the magnitude of which is linearly proportional to the osmotic gradient. The action of the hormone on movement of water is not dependent on the presence of sodium or on active transport of sodium. Comparison of the net transport of water and of unidirectional diffusion permeability of the membrane to water indicates that non-diffusional transport must predominate as the means by which net movement occurs in the presence of an osmotic gradient. An action of the hormone on the mucosal surface of the bladder wall is demonstrated. The effects of the hormone on water movement are most simply explained as an action to increase the permeability and porosity of the mucosal surface of the membrane.

Animals↗
PubMed1977

Intestinal perfusion studies in tropical sprue. 2. Movement of water and electrolytes.

Jejunal absorption of sodium and water has been investigated in 10 normal Indians and 11 patients with chronic tropical sprue. Normal saline and solutions containing amino acids and dipeptides were studied. In both groups little absorption of sodium and water from normal saline was seen. Mean water and sodium absorption from the free amino acid or dipeptide solutions showed no significant difference between the groups and was similar to absorption from normal saline. These results differ from data obtained in normal English subjects where at these concentrations significant stimulation of sodium and water absorption was seen. In a proportion of subjects in both groups net secretion was observed. However, no correlation was seen between mucosal histology or luminal bacteriology and sodium or water movement. These findings in patients with chronic tropical sprue are similar to findings in normal Indians and suggest that jejunal handling of sodium and water is abnormal when compared with normal English subjects, but that the mucosa is not in a secretory phase as seen in certain other diarrhoeal states or in the acute early phase of sprue.

Amino Acids↗
PubMed1993

Contraction-induced movements of water in single fibres of frog skeletal muscle.

Although X-ray diffraction measurements imply almost constant filament separation during isometric contraction, such constancy does not hold at the level of the isolated cell; cell cross-section increases substantially during isometric contraction. This expansion could arise from accumulation of water drawn from other fibre regions, or from water drawn into the cell from outside. To distinguish between these hypotheses, we froze single fibres of frog skeletal muscle that were jacketed by a thin layer of water. Frozen fibres were freeze-substituted, sectioned transversely, and examined in the electron microscope. In fibres frozen during contraction, we found large amounts of water just beneath the sarcolemma, less in deeper regions, and almost none in the fibre core. Such gradients were absent or diminished in fibres frozen in the relaxed state. The water was not confined to the myofibril space alone; we found large water spaces between myofibrils, particularly near mitochondria. Accumulation of water between myofibrils and around mitochondria implies that the driving force for water movement probably lies outside the filament lattice, and may therefore be osmotic. The fact that the distribution was nonuniform-highest near the sarcolemma and lowest in the core--implies that the water was likely drawn from the thin jacket surrounding the cell. Thus, the contractile cycle appears to be associated with water entry into and exit from the cell.

Animals↗
PubMed1984

Discordant effects of glucocorticoids on active and passive transport of calcium in the rat duodenum.

The effect of glucocorticoids on duodenal active and passive calcium transport was studied by the in situ intestinal loop technique, using 2.0 mM and 50 mM concentrations of calcium. The administration of prednisolone resulted in a significant increase of fluid and sodium absorption. The final luminal calcium concentration was increased in the prednisolone-treated group. Under conditions where active transport predominates (2 mM), glucocorticoids decreased lumen-to-plasma and increased plasma-to-lumen calcium flux, resulting in a decrease of net calcium absorption. Under conditions where passive transport predominates (50 mM), glucocorticoids did not decrease calcium absorption in the duodenum. These data suggest that under conditions where passive transport predominates, glucocorticoids indirectly enhance calcium absorption by an effect on water movement. Water movement enhances calcium absorption by concentrating unabsorbed calcium within the intestinal lumen. The increase in passive diffusion of calcium in the duodenum compensates for the inhibition of the active transport of calcium by glucocorticoids.

Animals↗
PubMed1990

Pharmacologic modification of transperitoneal movement of water.

Investigations concerning the influence of pharmacologic agents on transperitoneal water movement are predominantly undertaken in the hope that their results can help in a restoration of net ultrafiltration (UF) volume toward normal in cases with declining UF during long-term dialysis treatment. Net UF volume represents the difference between net transcapillary UF and lymphatic absorption. The choice of a pharmacological agent for enhancing UF depends on the mechanisms responsible for net UF loss, which include: (a) early dissipation of the transperitoneal osmotic gradient; (b) decrease in the peritoneal surface area; (c) lymphomonokine overproduction; (d) enhanced lymphatic absorption; (e) high residual volumes left in the peritoneal cavity; or (f) a combination of these factors. Leakage of dialysate to the abdominal wall sometimes occurring in peritoneally dialysed patients (1), according to a definition of net UF volume, cannot be regarded as a true UF loss.

Humans↗
PubMed2003

Water flow patterns in subsurface flow constructed wetlands designed for on-site domestic wastewater treatment.

Bypass flow in subsurface flow constructed wetlands, which may be related to several wetland characteristics, reduces detention time and may result in inadequately treated wastewater. Subsurface flow constructed wetlands, 2.3 m wide by 4.8 m long and containing a gravel matrix, were used to investigate the impact of wetland depth, inlet pipe location, loading volume, and plants on water flow. Flow patterns were determined using blue dye or bromide as tracers. The blue dye adsorbed to the gravel and was not an effective tracer for following water movement. Water dispersed as it flowed through the wetland, and approximately two pore volumes of added water were required to displace approximately 99% of the bromide tracer added as a pulse. In 17 and 25 cm deep wetlands, water flow was uniform with depth, and inlet depth had little influence on water flow patterns. Water flow in a 40 cm deep wetland was not uniform with depth for either inlet pipe placement. The presence of plants caused preferential water flow around root masses, thereby, limiting their potential to interface with wastewater. Water mixing by dispersion from the surface to deeper depths may enhance aeration. Bromide was first detected in effluent after only 0.5 pore volumes of tap water had been added. This indicates that detention time for some wastewater would be less than expected, since plug flow is usually assumed in subsurface flow constructed wetlands. This occurrence should be considered for time-dependent treatments, such as fecal coliform and biological oxygen demand reduction.

Adsorption↗