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At least 19 recordsLinked to original sources

PubMed1990

Water movements after an intraruminal water load in pregnant and lactating Sardi sheep.

The effects of an intraruminal load of 3 litres of water on body water movements was compared in Sardi sheep during the last month of pregnancy, lactation and a non-pregnant, non-lactating control period. Before the water load, rumen fluid volume, estimated by polyethylene glycol was similar in pregnant, compared to control, animals and 27% higher in lactating sheep. After the water load, rumen volume returned to pre-hydration level in 1 h during pregnancy, after 3 h during lactation and in the control period. Rumen osmolality decreased by 40% and remained at this low level for 3 h after the water load in all physiological periods. When the water load was tritiated water (TOH), the rate of TOH transfer into plasma was faster during the last month of pregnancy than during the control period. Plasma osmolality and proteins decreased in response to the water load. No differences in these responses were observed between pregnancy, lactation and the control period. Water diuresis began in the first 30 min following the water load in pregnant ewes and in the second 30 min in lactating and control ewes. The diuresis was also more pronounced in pregnant, than in non-pregnant, states. These results indicate that water is more rapidly absorbed from the gastrointestinal tract in pregnant, rather than in non-pregnant, sheep. This may partly explain the increased water turnover seen during pregnancy.

Animals↗

PubMed1985

A steady-state filtration model for transluminal water movement in small and large blood vessels.

It is now generally accepted that the intercellular cleft between adjacent endothelial cells is the primary pathway for the transluminal movement of water and small ions in the vasculature. A steady-state theoretical model has been developed to show quantitatively how the geometry of the intercellular cleft between adjacent endothelial cells is related to both the water movement and pressure distribution in the subendothelial space and to examine how the existence of a subendothelial interaction layer affects the hydraulic resistance of the media of vessels of varying wall thickness. The velocity and pressure fields in the media are described using porous matrix theory based on Darcy's law and a lubrication-type analysis is used to describe the flow in a variable geometry intercellular cleft. These two equations are solved simultaneously to determine the unknown pressure distribution beneath the endothelium and the flow in the arterial media. Application of this model shows that, when the tight junction in the cleft is 26 A or less, more than half of the total hydraulic resistance of the wall occurs across the endothelial cell monolayer, for a vessel whose wall thickness is less than 0.02 cm. This finding is in good agreement with the experimental findings of Vargas, et al. (1978) for rabbit aorta. Contrary to previous belief, the model shows that the filtration resistance of an arterial wall with intact endothelium does not scale linearly with wall thickness due to the highly nonlinear resistance of the endothelial interaction layer.

Animals↗

PubMed1985

Use of a chemical tracer to evaluate water movement through two automatic watering rack manifolds during flushing.

A sodium fluorescein solution was introduced into an upfeed serpentine and a horizontal automatic watering rack manifold. Water samples were collected from nine drinking valves on each manifold prior to and after flushing at 12 pounds per square inch water pressure for 15 seconds, one minute, and five minutes. The water samples were assayed for fluorescein and it was found that the chemical was effectively removed by flushing from the upfeed serpentine manifold, while significant levels of fluorescein remained in the horizontal manifold even after five minutes flushing.

Animals↗

PubMed1987

Ion transport and water movement.

Secretion of water and electrolytes in salivary glands occurs by a dual process involving the formation of a plasma-like, isotonic primary secretion in salivary acini and its subsequent modification in salivary ducts by the removal and addition of specific ions. The mechanisms underlying the formation of primary acinar secretion have been investigated with a number of experimental approaches such as electrophysiology, the measurement of ion transport in gland fragments and dispersed acinar cells, and the evaluation of the ionic requirements for secretion in isolated, perfused gland preparations. The accumulated evidence suggests that salivary secretion is formed by a complex interaction between passive and active ion movements across acinar cell membranes, resulting in the trans-acinar movement of Cl- and Na+ and, by the osmotic gradient which develops, of water. A major consequence of stimulation is the release of K+ through Ca++- and voltage-sensitive channels and its subsequent recycling back into the cells by ouabain- and furosemide-sensitive transport systems. This results in NaCl uptake across the basolateral cell membrane and the subsequent efflux of Cl through luminal membrane channels, which also appear to be sensitive to cellular Ca++. The rates of these various ion movements appear to be, therefore, closely linked and interdependent. Ductal modification of the primary secretion has been studied in microperfused duct preparations. The evidence likewise indicates that it involves interactions between complex conductance pathways in the luminal cell membrane and a Na, K pump present in the basolateral cell membrane and that it is under autonomic and hormonal control. Activation of ductal transport mechanisms results in NaCl reabsorption and KHCO3 secretion. Final saliva thus differs from primary secretion in electrolyte composition and, because water permeability is low in the duct epithelium, becomes hypotonic. Alterations in fluid and electrolyte secretion such as those observed in disease can result, therefore, from disturbances in one or more of these complex transport processes in acinar or duct cells.

Animals↗

PubMed1991

Water movement in the rabbit eye.

The intraocular distribution of topically applied D2O was quantified using deuterium nuclear magnetic resonance (NMR) spectroscopy. D2O appeared in all tissues with the highest concentration in the aqueous humor (1.2 M); however, it rapidly dissipated from the eye. Surface coil NMR spectroscopy on D2O-treated eyes in vivo showed that the flow pattern was best described by a single exponential decay plus a constant. This suggests that the D2O flow consisted of a flow component representing vascular circulation (with a flow rate constant of 0.101 min-1), and a reservoir-like component. Topical D2O in conjunction with the surface-coil NMR technique can be used to examine the movement of water in the anterior segment of the living eye.

Animals↗

PubMed1992

Visualization of water movement in the living rabbit eye.

Water enriched with the stable isotope 17O (H2(17)O) shortens the transverse relaxation time (T2) of protons in water and can therefore be used as the contrast agent for proton magnetic resonance (MR) imaging. This agent can be given topically or intravenously to demonstrate water movement in the eye. Topical H2(17)O (0.05-0.1 ml/eye, 10% enrichment) entered the anterior chamber within 5 min and dissipated from the chamber in a single-exponential fashion (flow-rate constant k = 0.1 min-1), principally due to an exchange with the iridic circulation. No H2(17)O was detected in the vitreous. Intravenous administration of H2(17)O (1 ml/kg, 10% enrichment) resulted in rapid entry (less than 20 min) of the agent into the aqueous chamber. Again, no H2(17)O was detected in the vitreous. The lens region, on the other hand, showed an increase in image intensity with time that reached a plateau after 40 min. Although these findings are preliminary, acetazolamide (20 mg/kg injected intravenously) appeared to affect iridic circulation, possibly through vasoconstriction. Potential application of this H2(17)O-enhanced MR imaging technique is discussed.

Administration, Topical↗

PubMed1991

Peripheral and central nervous responses evoked by small water movements in a cephalopod.

Potentials were recorded from the epidermal head lines and from the CNS of young cuttlefish, Sepia officinalis, in response to weak water movements. 1. Within the test range 0.5-400 Hz a sinusoidal water movement elicits up to 4 components of response if the electrode is placed on a headline: (i) a positive phasic ON response; (ii) a tonic frequency-following microphonic response; (iii) a slow negative OFF response; and (iv) compound nerve impulses. 2. The amplitude of both the ON wave and the microphonic potential depends on stimulus frequency, stimulus amplitude and stimulus rise time. Frequencies around 100 Hz and short rise times are most effective in eliciting strong potentials. The minimal threshold was 0.06 microns peak-to-peak water displacement at 100 Hz (18.8 microns/s as velocity). 3. Change of direction of tangential sphere movement (parallel vs. across the head lines) has only a small effect on the microphonic and the summed nerve potentials. 4. Frequency and/or amplitude modulations of a carrier stimulus elicit responses at the onset and offset of the modulation and marked changes in the tonic microphonic response. 5. Evoked potentials can be recorded from the brain while stimulating the epidermal lines with weak water movements. The brain potentials differ in several aspects from the potentials of the head lines and show little or no onset or offset wave at the transitions of a frequency and amplitude modulation.

Animals↗

PubMed1978

PGE-release, blood flow and transmucosal water movement after mechanical stimulation of the rat jejunal mucosa.

1. The influence of weak mechanical stimulation of the jejunal mucosa in vivo on PGE-release, on intestinal blood flow and transmucosal water movement was studied in rats. 2. Mechanical stimulation of the mucosa increased PGE-release into the venous outflow and into the gut lumen. This increase is followed by an increase in intestinal blood flow and transmucosal movement of tritiated water in both directions. 3. Pretreatment of the rat with indomethacin reduced the effect of mechanical stimulation on PGE-release. Indomethacin further reduced the increase in blood flow and in secretion of tritiated water. Absorption of tritiated water was not changed in these experiments. 4. Pretreatment of the rat with atropine (1 mg/kg, i.p.) or perfusion of the gut with methysergide (10 microgram/ml) did not influence the increase in intestinal blood flow after mechanical stimulation. 5. It is suggested that enhanced intestinal blood flow and transmucosal movement of tritiated water after mechanical stimulation are mainly provoked by a preceding release of PGE. 6. It is further supposed that such a mechanism may be physiologically involved in regulation of intestinal blood flow and transmucosal water movement during food intake.

Animals↗

PubMed1989

The effect of varnishes and other surface treatments on water movement across the glass ionomer cement surface. II.

The aesthetic restorative glass ionomer cements undergo a rather prolonged setting reaction during which time they are susceptible to water uptake and water loss. If they can be maintained in isolation long enough in the oral cavity then the clinical result will be superior. A further series of surface treatments has been tested and it has been shown that immediate covering of the immature glass ionomer cement surface with light-activated bonding resin is the most effective method of limiting water movement across the surface. This restriction of water movement is not effective for all light-activated bonding resins suggesting that there may be a physico-chemical interaction occurring on the glass ionomer cement surface with certain of the resins.

Composite Resins↗

PubMed1975

Effect of secretin on intestinal monosaccharide absorption and new water movement in the rat.

Repeated intravenous injections of 2.0 clinical units (CU) secretin per kg body weight showed no effect on jejunal glucose absorption and net water movement in perfusion studies in vivo. The in vitro uptake of galactose and 3-O-methylglucose was not altered by a secretin load given 12 min before sacrifice. The values for Km and Vmax were identical after secretin and in a control group. The conflicting results of different authors concerning the effect of secretin on net water movement and solute absorption may be due to differences in experimental techniques, different, mostly pharmacological doses of the hormone, and a diverse response of heterogeneous species.

Animals↗

PubMed1977

The function of prostaglandins in transmucosal water movement and blood flow in the rat jejunum.

1. Jejunal loops of anaesthetized rats were perfused with isotonic buffer containing PGE1, PGF2alpha or indomethacin. Intestinal blood flow, absorption and secretion of tritiated water were measured. 2. PGE1 at the low concentration of 0.1 microgram ml-1 did not influence intestinal blood flow but increased secretion and decreased absorption of tritiated water. In higher concentrations (0.5 and 6.5 microgram ml-1), blood flow, secretion and absorption were enhanced. 3. PGF2alpha, even in the high concentration of 50 microgram ml-1, did not influence intestinal blood flow but enhanced secretion and decreased absorption of tritiated water. 4. Indomethacin (1 microgram ml-1) decreased intestinal blood flow and secretion but enhanced absorption of tritiated water. 5. The effects of indomethacin on blood flow can be prevented and those on secretion can be even reversed by an additional infusion of PGE1 (0.5 microgram ml-1). 6. PGs appear to play a physiological role in the regulation of intestinal blood flow and transmucosal water movement, since inhibition of endogenous PG synthesis by indomethacin results in effects opposite to those of intraluminally applied PGE1. The results obtained with the low concentration of PGE1 (0.1 microgram ml-1) and with PGF2alpha (50 microgram ml-1) strongly indicate that intestinal water movement can be changed independently of intestinal blood flow.

Animals↗

PubMed1976

Model of solute and water movement in the kidney.

Finite difference equations describing salt and water movement in a model of the mammalian kidney have been solved numerically by an extension of the Newton-Raphson method used for the medullary counterflow system. The method permits both steady-state and transient solutions. It has been possible to simulate behavior of the whole kidney as a function of hydrostatic pressures in renal artery, vein, and pelvis; protein and other solute concentrations in arterial blood; and phenomenological equations describing transport of solute and water across nephron and capillary walls. With the model it has been possible to compute concentrations, flows, and hydrostatic pressures in the various nephron segments and in cortical and medullary capillaries and interstitium. In a general way, calculations on the model have met intuitive expectations. In addition, they have reemphasized the critical dependence of renal function on the hydraulic and solute permeabilities of glomerular, postglomerular, and medullary capillaries. These studies provide additional support for our thesis that the functional unit of the kidney is not the single nephron, but a nephrovascular unit consisting of a group of nephrons and their tightly coupled vasculature.

Blood Pressure↗

PubMed1976

Regional ileitis (Crohn's disease). II. Electrolyte and water movement in the ileum during perfusion with bile acids.

Electrolyte and water movement was studied by steady state perfusion technique in the ileum of 11 patients with regional ileitis (Crohn's disease). Six patients who at the time of investigation had diarrhoea showed a constant secretion of salts and fluid during perfusion with control perfusate. Per 24 hours, the ileal effluents to colon would exceed the normal amount by 1-2 litres. In the 5 patients without diarrhoea the absorption patterns were normal. Electrolytes and water moved in parallel. Dihydroxy bile acids enhanced secretion or decreased absorption respectively, in the two groups of patients. It is concluded that functional disturbances of salt and water absorption in the inflamed ileum may be of significant physiological importance in the pathogenesis of diarrhoea observed in patients with regional ileitis.

Adult↗

PubMed1989

Water movement: does thermodynamic interpretation distort reality?

In a recent theoretical analysis of water flow, Finkelstein (Water Movement Through Lipid Bilayers, Pores, and Plasma Membranes: Theory and Reality, 1987) has attacked the contributions of irreversible thermodynamics, stating that "the thermodynamic treatment of uphill water flow completely distorts reality." Instead he presents a mechanistic formulation. For a porous membrane, water flow is attributed to convection generated by a favorable hydrostatic pressure gradient within pores, even when in the presence of permeant solutes water moves against its chemical potential gradient; water flow may "drag", solute, to an extent determined by the solute partition coefficient, but the possibility that solute flow may drag water is excluded. We argue that this formulation violates the second law of thermodynamics. Water cannot move against its chemical potential gradient because of the influence of only part of the chemical potential gradient. Furthermore, the proposed mechanism requires that at one of the membrane-solution interfaces water must move against both its concentration gradient and the hydrostatic pressure gradient. Also considered by Finkelstein is the nature of the reflection coefficient sigma, a kinetic variable, which he concludes can be evaluated (in a porous membrane) by measurement of the (equilibrium) solute partition coefficient. We claim that in general it is not possible to evaluate a kinetic variable from measurements of equilibrium parameters alone. A valid kinetic analysis must incorporate the contribution of all coupled flows.

Body Water↗

PubMed1977

Ouabain-insensitive salt and water movements in duck red cells. II. Norepinephrine stimulation of sodium plus potassium cotransport.

Catecholamines induce net salt and water movements in duck red cells incubated in isotonic solutions. The rate of this response is approximately three times greater than a comparable effect observed in 400 mosmol hypertonic solutions in the absence of hormone (W.F. Schmidt and T. J. McManus. 1977 a.J. Gen. Physiol. 70:59-79. Otherwise, these two systems share a great many similarities. In both cases, net water and salt movements have a marked dependence on external cation concentrations, are sensitive to furosemide and insensitive to ouabain, and allow the substitution of rubidium for external potassium. In the presence of ouabain, but the absence of external potassium (or rubidium), a furosemide-sensitive net extrusion of sodium against a large electrochemical gradient can be demonstrated. When norepinephrine-treated cells are incubated with ouabain and sufficient external sodium, the furosemide-sensitive, unidirectional influxes of both sodium and rubidium are half- maximally saturated at similar rubidium concentrations; with saturating external rubidium, the same fluxes are half-maximal at comparable levels of external sodium. In the absence of sodium, a catecholamine-stimulated, furosemide-sensitive influx of rubidium persists. In the absence of rubidium, a similar but smaller component of sodium influx can be seen. We interpret these results in terms of a cotransport model for sodium plus potassium which is activated by hypertonicity or norepinephrine. When either ion is absent from the incubation medium, the system promotes an exchange-diffusion type of movement of the co-ion into the cells. In the absence of external potassium, net movement of potassium out of the cell leads to a coupled extrusion of sodium against its electrochemical gradient.

Animals↗

PubMed1991

Transepithelial water movement in response to carbamazepine, chlorpropamide and demeclocycline in toad urinary bladder.

1. Osmotic water movement across toad isolated hemibladders was measured by a gravimetric method. 2. The influence of carbamazepine, chlorpropamide and demeclocycline on the antidiuretic hormone (ADH)-induced water flow rate was examined. 3. No antidiuretic activity due to carbamazepine alone was observed but a slight inhibition due to ADH-induced water flow was observed in the presence of carbamazepine over a selected dose-range. This was unexpected and is inconsistent with data from in vivo studies in man. 4. Chlorpropamide potentiated ADH-induced water flow, in keeping with the hypothesis that chlorpropamide sensitizes the renal tubules to ADH-induced water flow. 5. Demeclocycline inhibited ADH-induced water flow. The mechanism of action remains unclear.

Animals↗

PubMed1985

Carrier-mediated KCl accumulation accompanied by water movements is involved in the control of physiological K+ levels by astrocytes.

Potassium accumulation and water transport into mouse astrocytes in primary cultures were investigated when external potassium was increased from 3 to 12 mM. The intracellular potassium content increased by 63% within 50 s of such a change. The increase consisted of a ouabain- and furosemide-sensitive component, both contributing in about the same amounts. Experiments with altered ion composition revealed that the furosemide-sensitive component consisted of a KCl accumulation. Water moved into the astrocytes without delay after such an external K+ increase and increased the cell water by 27%. This water increase was abolished in solutions with reduced Cl- and during application of furosemide. Thus, these results on a KCl uptake accompanied by water movements into astrocytes suggest a potential mechanism by which glial cells in situ can regulate external K+ levels.

Animals↗

PubMed1979

An analysis of water movement between myocardial tissue and capillary blood during reactive hyperemia.

The colloid osmotic pressure (COP) of blood from the great cardiac vein was continuously measured by means of a membrane colloid osmometer during the reactive hyperemia following temporary occlusion of the anterior descending branch of the left coronary artery in anesthetized open-chest dogs. The COP increased sharply after releasing the occlusion, then decreased below the preocclusion level before gradually returning to it. These findings indicate that a measurable amount of water moved from the capillary blood into the myocardial tissues and then flowed back slowly into the capillary blood. To analyse the factors affecting this water movement, a method is proposed in which the Starling mechanism is combined with the interstitial volume elasticity and a steady-state solution of a Navier-Stokes equation. The pressure observed with a catheter wedged into a branch of the great cardiac vein was used as a measure of capillary perfusion pressure. During the coronary arterial occlusion, the filtration constant increased while the volume elasticity of the myocardial interstitial spaces decreased rapidly. The filtration constant and volume elasticity of the interstitial space under normal conditions were approximately estimated to be 2.4 X 10(-11) cm/(sec.dyn.cm-2) and 1.1 X 10(7) dyn.cm-2, respectively.

Animals↗