Showing papers on "Water flow published in 1972"

The subtidal pump: a mechanism of interstitial water exchange by wave action

Abstract: Sandy subtidal sediments are part of the earth's largest filter system. Water flow through bottom sediments is driven by wave action on the sea surface. The mechanisms involved are described, including a theoretical deduction and field measurements. As an example, the total water exchange through part of the West Atlantic shelf is computed and the influence of the phenomenon is discussed from a biological point of view and with regard to its importance for the world's oceans.

Physical properties of isolated perfused renal tubules and tubular basement membranes.

Abstract: To study the physical properties of renal tubular basement membranes directly, the epithelial layer of single isolated perfused rabbit proximal convoluted, proximal straight, and cortical collecting tubules was removed with sodium desoxycholate. Tubular segments were perfused using micropipets. The distal end of each segment was occluded in order to simplify the measurement of transmembrane water flow. The relation between outer tubular diameter and applied transmural pressure was identical in intact tubules and their respective isolated tubular basement membranes indicating that the basement membrane determines tubular distensibility. Young's modulus for basement membranes from all tubular segments corresponded to that of tendon collagen. Membrane hydraulic conductivity was measured in two ways: (a) from the rate of transmural flow in response to an applied difference in hydrostatic pressure and, (b) from the rate of transmural flow in response to a difference in colloid osmotic pressure. The hydraulic conductivity of tubular basement membranes was 300-800 times greater than that of the intact epithelial layer. Basement membrane hydraulic conductance was similar to that of peritubular and glomerular capillaries in vivo. The hydrostatic conductance of tubular basement membranes exceeded the osmotic conductance by 3-10-fold owing largely to the fact that the membranes were moderately permeable to the osmotic solute (albumin). In view of these findings we suggest that oncotic and hydrostatic pressure may play an important role in the movement of tubular absorbate from the epithelial compartment into the renal interstitium.

Lithium-induced nephrogenic diabetes insipidus: in vivo and in vitro studies.

Abstract: The physiological basis for the polyuria and polydipsia occurring in some manic-depressive patients treated with lithium salts was studied in vivo and in vitro. Three lithium-treated polyuric patients, in whom other causes of a concentrating defect were excluded, had abnormal urinary concentrating abilities after a standard water depreviation test. Two of these patients failed to respond to exogenous vasopressin (ADH) and one had a subnormal response. The abilities of these patients to excrete solute-free water (C(H2O)) was comparable to normal subjects during steady-state water diuresis, suggesting no gross abnormalities in sodium transport. However, each of these patients demonstrated abnormally low capacities to reabsorb solute-free water (T(C) (H2O)) under hydropenic conditions after administration of hypertonic saline and vasopressin. These in vivo findings demonstrate at least a nephrogenic basis for the diabetes insipidus syndrome manifested by these three patients. The defect in water transport was further characterized in toad urinary bladders in vitro. Short-circuit current (I) and water flow (W) were studied under basal, ADH-stimulated, and cyclic adenosine 3',5'-monophosphate (c-AMP)-stimulated conditions. Increasing mucosal [Li(+)] progressively inhibited basal I, and both I and W induced by ADH. Significant inhibition of basal and ADH-induced I was observed at mucosal [Li(+)] < 1.1 mEq/liter, and of ADH-induced W at mucosal [Li(+)] = 11 mEq/liter. On the other hand, at these lithium concentrations, neither c-AMP-stimulated W nor I was inhibited. Increasing serosal [Li(+)] produced significant inhibition of basal I only at [Li(+)] at least 50-fold greater than at the mucosal (urinary) surface. These in vitro studies confirm that mucosal lithium inhibits the action of ADH, but not c-AMP. Hence, lithium appears to be a significant inhibitor of ADH-stimulated water flow, probably acts from the urinary surface, and appears to exert its effect at a site biochemically proximal to c-AMP action.

The role of the lateral intercellular spaces and solute polarization effects in the passive flow of water across the rabbit gallbladder.

Abstract: Osmotic water flows were measured acrossin vitro preparations of the rabbit gallbladder by a gravimetric technique. The bladders exhibited asymmetrical osmotic behavior, in which theL p (hydraulic conductivity) for water flow from mucosa to serosa was up to four times greater than theL p for water flow in the opposite direction. This result is similar to the effects of osmotic gradients on ion and nonelectrolyte permeability reported in the first paper. As in the case of solute permeability, these changes inL p are accounted for by changes in the dimensions of the lateral intercellular spaces of the epithelium. These spaces are thus a final common pathway for the movement of both solutes and water across the epithelium. We also observed osmotic flow transients in which the initialL p was about an order of magnitude greater than the steady stateL p . These transients are largely explained by solute polarization in the unstirred layers adjacent to the epithelial membranes. A comparison between streaming potentials and water flows showed that streaming potentials are directly proportional to the rate of flow only over a limited range. These observations are readily explained on the basis of structural changes and solute polarization effects. Finally, the routes of water flow across epithelia are discussed in the light of our observations.

The Action of Abscisic Acid on Ion Uptake and Water Flow in Plant Roots

Abstract: Abscisic acid was shown to inhibit transport of potassium and chloride from the cut ends of excised barley and maize roots. Transport to the shoot of intact barley seedlings was also inhibited. Total uptake into the excised root of barley did not appear to be affected by abscisic acid. There was an increase in tracer accumulated in the root accompanying the reduction in transport from the cut end. Concentrations of abscisic acid above 10-6M produced the maximum effect.

Endogenous prostaglandins and osmotic water flow in the toad bladder

Abstract: FLORES, AURA G. A., AND GEOFFREY Mr. G. SHARP. Endogenous prostaglandins and osmotic waterflow in the toad bladder. Am. J. Physiol. 223 (6) : 1392-1397. 1972.-Prostaglandins, at low concentrations, inhibit the osmotic water-flow response to antidiuretic hormone (ADH) and to theophylline in toad bladder. They have no effect upon the response to dibutyryl cyclic AMP. Thus the prustaglandins inhibit adenyl cyclase in this tissue and decrease the stimulation of adenyl cyclase by ADH. It is not known, however, whether endogenous prostaglandins have any physiological role in reducing basal adenyl cyclase activity and hormone responses. As indomethacin inhibits prostaglandin synthetase and thus blocks prostaglandin synthesis and release, it has been used to assess the physiological role of prostaglandins. Indomethacin enhanced the osmotic water-flow response to submaximal concentrations of antidiurelic hcrmone and to dibutyryl cyclic AMP. The effect on the latter was ascribed to the inhibitory effect of indomethacin on phosphodiesterase. On a molar basis, indomethacin was estimated to be more than lo-fold more effective than theophylline in its ability to inhibit phosphodiesterase. Thus potentiation cf the response to ADH by indomethacin, even at low concentrations, is not by itself an indication that endogenous release of prostaglandins exerts a continual restraining influence on adenyl cyclase. However, it was found that indomethacin potentiated the response to high concentrations of theophylline (which alone inhibit phosphodiesterase activity). This effect is ascribed to the lifting of prostaglandin inhibition of adenyl cyclase and indicates that endogenous prostaglandins could have a regulatory role to play in the normal cell function.

Hydrodynamic patterns in lotic intertidal sands and their bioclimatological implications

Abstract: Water movement is probably the most important factor influencing life in the interstices of sandy beaches. In order to better understand this ecosystem, e.g. the distribution and migration of interstitial fauna and overall energy transfer, measurements of water flow through high energy beaches were made on the Atlantic coast of the USA. Special hot thermistor-probes and associated electronic circuits were built, capable of measuring water-flow velocity down to less than 10 μm/sec. These were buried in the sand at various depths and locations in the intertidal zone and the flow velocity recorded continuously for one or more tidal cycles. In addition, an orientation sensor was constructed and used together with the flow probe so that a picture of the flow patterns in the intertidal zone of a beach and their changes during a tidal pattern could be developed and defined quantitatively.

Flow visualization of the near-wall region in a drag-reducing channel flow

Abstract: Study to determine whether the addition of drag-reducing macromolecules alters the structure of the viscous sublayer and thereby modifies the production of kinetic energy in turbulent wall flows. This was accomplished by visualizing the near-wall region of a fully developed two-dimensional channel flow. Motion pictures were taken of dye injected into the near-wall region. Both water and a dilute drag-reducing polyethylene oxide--FRA solution were used as working fluids. The data show that the time between bursts for an individual streak in a drag-reducing flow has the value for a water flow at the reduced wall shear. Evidence strongly suggests that the dilute polymer solution decreases the production of turbulent kinetic energy by inhibiting the formation of low-speed streaks.

Water Movement in Undisturbed Swelling Clay Soil

Abstract: Hydraulic conductivities of Houston Black clay were measured in two field basins, in 73-cm and 21-cm diameter undisturbed cores, and in small cores prepared from sieved soil. Conductivities averaged about 2.5 cm/day for the field basins, about 0.3 cm/day for the undisturbed cores, and 0.1 cm/day for the disturbed soil cores. After steady-state flow through the larger, undisturbed cores was obtained, water tagged with fluorescein was used to displace water in the cores until tagged water first appeared in the effluent. Examination of cross sections of the cores at different depths showed distinctive isolated areas where tagged water was present in the soil pores. The results imply that most water contained within structural units was inactive in the flow process compared to water flow around the units. The core walls apparently cut off some large pores associated with the soil structure, causing the decreased conductivities. Therefore, only field-determined hydraulic conductivities are appropriate for use when predicting water flow in natural profiles of a swelling clay soil.

Aspects of branchial irrigation in the lobster Homarus americanus. I. Functional analysis of scaphognathite beat, water pressures and currents.

Abstract: 1. The movements of the scaphognathites of the lobster, Homarus americanus , and the resulting thrust, were resolved in two dimensions accompanied by attack angle changes. Correlation of these scaphognathite and related body movements with branchial hydrostatic pressures during forward and reversed pumping were effected by simultaneously recording on video tape. 2. Forward pumping maintains a negative pressure within the branchial chambers of 2·5-10 mm H2O superimposed on a maintained negative pressure relative to the outside of 0-5 mm H2O. The scaphognathite, by assuming a negative attack angle to the water during the upstroke of the beat, produces the positive pressure of reversals. 3. Contraction of the epimeral attractor muscle appears to contribute to the reestablishment of branchial negativity following each reversal. This muscle inserts on the epimera and by contraction enlarges the branchial chamber. 4. The role of reversals is discussed and it is concluded that their primary function is to clean foreign material from the border of hairs which filter incurrent water. Reversed beating may be a general response to all unusual stimuli to the respiratory system. 5. The pattern of water flow into and through the gill chambers was determined. The relative volume of water entering each incurrent aperture between the legs was calculated and indicated that approximately equal volumes of water entered each aperture. It is concluded that forward pumping adequately irrigates all gill surfaces.

Effects of Inflow Condition on Hydraulic Jump

Abstract: The particular aspect of the jump phenomenon considered in the paper concerns the condition of inflow, i.e., the state of flow development of the supercritical stream. Based on an unconventional concept of longitudinal extent, the hydraulic jump in a horizontal, smooth-walled channel of rectangular cross section is studied both analytically and experimentally. It is shown that jumps with developed inflow are longer, lower and subject to higher and more uniformly distributed skin friction than jumps with undeveloped inflow. The latter have shear distributions which reveal a tendency toward separation with increasing Froude number. The trend is verified by the observed behavior of jumps with undeveloped inflow at Froude number as large as 30. Semi-empirical, closed-form relationships between sequent depth ratio and Froude numbers are derived and checked against experimental evidence.

Patterns of Water Movement in Trees and Shrubs

Abstract: Paths of water flow in trees and shrubs of different sizes and chorotypes were investigated with injected dyes. Aged shrubs possessed a sectorial ascent. Young specimens of these species showed a sectorial turning into a ring ascent. Differences in pattern of water flow were observed among various tree species. Species with large and tall crowns showed either a spiral pattern or a sectorial straight pattern turning into a ring pattern of ascent. Other species exhibited a sectorial straight pattern. Since independence of branches or trunk segments is characteristic of shrubs, it is suggested that woody species exhibiting a sectorial pattern of water movement should be considered as chamaephytes. See full-text article at JSTOR

Radial Propagation of Water Potential in Stems1

Abstract: Contraction and expansion of a cotton (Gossypium hirsutum L.) stem in response to a diurnal cycle of leaf water potential is described mathematically using a passive diffusion analysis. The domain of the problem is the stem phloem and associated tissues that are bounded on the outside by impervious bark and on the inside by the xylem that is assigned measured values of leaf water potential. Semiquantitative predictions are derived from numerical solutions of the linear radial diffusion equation, which yield phloem water potential as a function of space and time. Computations relating stem diameter, leaf water potential, and water flow between xylem and phloem fit experimental data. An apparent hysteresis in the stem diameter-leaf water potential relationship is partly explained in terms of the physics of the diffusion process in the stem. This study offers possibilities for relating internal plant water status to measurable external quantities such as stem diameter and for developing a nondestructive technique for the determination of plant xylem water potential.

Some Aspects of Gas Exchange in Tuna

Abstract: 1. Some aspects of gas exchange in restrained skipjack tuna were analysed. 2. The average rate at which water flowed over the gills was 2.81/min. kg. 3. The concentration of oxygen in water entering and leaving the gills was measured and used to calculate oxygen uptake (692 mg/h.kg) and utilization (0.71). 4. The drop in hydrostatic pressure as water flowed over the gills was 1.9 cm water and agrees favourably with theoretical predictions. 5. The partial pressure of oxygen was measured in blood afferent and efferent to the gills and used to calculate effectiveness of oxygen removal from the water (90%) and the transfer factor for oxygen (0.12 ml/min.kg.mmHg). 6. The average utilization measured in free-swimming tuna was 0.56. 7. The extraordinary ability of tuna to efficiently extract oxygen from the water at high gill water flow rates is discussed.

The effect of antidiuretic hormone on solute flows in mammalian collecting tubules

Abstract: These experiments were intended to evaluate the antidiuretic hormone (ADH)-dependent reflection coefficients of urea, sucrose, and NaCl in cortical and outer medullary collecting tubules isolated from mammalian kidney. In one group of experiments, the ADH-dependent osmotic water flows, when the perfusing solutions contained hypotonic NaCl solutions, were indistinguishable from control observations when either urea or sucrose replaced, in part, NaCl in isotonic bathing solutions (cortical collecting tubules). Similarly, both in cortical and outer medullary collecting tubules exposed to ADH, there was zero net osmotic volume flow when a portion of the NaCl in the bathing and/or perfusing solutions was replaced by either sucrose or urea, so long as the perfusing and bathing solutions were isosmolal. Taken together, these observations suggest that the ADH-dependent reflection coefficients of NaCl, urea, and sucrose, in these tubules, were identical. Since the effective hydrodynamic radii of urea and sucrose are, respectively, 1.8 and 5.2 A, it is likely that sigma(i), for urea, sucrose, and NaCl, was unity. In support of this, the diffusion permeability coefficient (P(Di) cm sec(-1)) of urea was indistinguishable from zero. Since the limiting sites for urea penetration were the luminal interfaces of the tubules, these data are consistent with the view that ADH increases diffusional water flow across such interfaces.

On mathematical simulation of a pelagic ecosystem in tropical waters of the ocean

Abstract: Consideration is given to a finite-difference model of functioning of a pelagic community inhabiting the upper 0 to 200 m layer of the tropical waters of the ocean. The model was developed on the basis of original data, obtained mainly on the 44th cruise of the R.V. “Vityaz” in the western Equatorial Pacific Ocean. Changes in the system are studied in time (up to 100 days, with 1 day intervals) and in depth (from surface to 200 m depth, with 10 m intervals). The state of the system in the upwelling zone, assumed to be characterized by a homogeneous vertical distribution of all its elements, is regarded as initial. The system then develops with time while it moves with the water flow. The model was realized on a BESM-3M computor. The computations yielded a pattern of changes in time of the biomass of the elements (expressed in calories), and a pattern of their vertical distribution at different instants. The vertical distribution pattern of the major elements of the model shows a rather close correlation with their observed distribution in the ocean at the corresponding instant.

The Effect of Aldosterone on the Accumulation of Adenosine 3′:5′-Cyclic Monophosphate in Toad Bladder Epithelial Cells in Response to Vasopressin and Theophylline

Abstract: Vasopressin and theophylline both increase the content of adenosine 3′:5′-cyclic monophosphate (cAMP) in epithelial cells of the urinary bladder of toads (Bufo marinus). Incubation of the tissue with 0.2 μM aldosterone markedly increases this response to the two agents; incubation for a similar time without steroid reduces the response. The permeability responses (sodium transport and water flow) of the intact tissue to vasopressin, theophylline, and exogenous cAMP are also considerably greater in bladders incubated with aldosterone than without. The results are interpreted as indicating that the foregoing permissive effects of aldosterone on the permeability responses to vasopressin and theophylline are mediated by a steroid-dependent increase in the accumulation of cAMP in the pertinent epithelial cells, probably as a consequence of a diminution in the rate of degradation of the intracellular nucleotide.

Osmotic Regulation of Toad Bladder Responsiveness to Neurohypophyseal Hormones

Abstract: The effect of dilution of the interstitial fluids on the responsiveness of the toad urinary bladder to antidiuretic hormones has been examined in vivo and in vitro. Toads were given periodic injections with vasopressin while in water so that their plasma osmolality fell below 190 mosmoles/kg H2O. The hydraulic conductivity of bladders which had been removed from the animal and fixed with 1% glutaraldehyde was 10-fold less in overhydrated toads than in normally hydrated controls. A similar inhibitory phenomenon was observed in in vitro studies, when the tonicity of Ringer's fluid in which the bladders were suspended was lowered from its isotonic value. Mannitol, but not urea, could be effectively substituted for one-half of the NaCl content of Ringer's fluid. In other experiments it has been shown that the responsiveness of the bladder to vasotocin is depressed during bulk water movement across the tissue. This "flux inhibition" was found to depend upon the velocity and the duration of water flow from mucosa to the serosa. It is suggested that the responsiveness of the toad bladder to antidiuretic hormones diminishes as the effective osmotic pressure of the interstitial fluids declines.

Studies of the mode of action of the sulfonylureas and phenylacetamides in enhancing the effect of vasopressin.

Abstract: Chlorpropamide and acetaminophen are effective antidiuretic agents in diabetes insipidus. They appear to act by sensitizing the kidney to the low levels of vasopressin that may continue to circulate in many patients with this disease. To determine the mechanism of action of these agents, a series of studies of their effects on water flow was carried out in the isolated urinary bladder of the toad. The patterns of action of chlorpropamide and the phenylacetamides (phenacetin, acetaminophen and structurally related compounds) were compared to that of theophylline, a potent phosphodiesterase inhibitor. Theophylline enhanced the effect of low and saturating concentrations of vasopressin, enhanced the effect of cyclic AMP, had no effect on the inhibitory action of prostaglandin E1 (PGE1) and (at 3 × 10−3m) greatly increased water flow in the absence of vasopressin. Chlorpropamide differed from theophylline in all major respects, enhancing only low concentrations of vasopressin, inhibiting the effect of cyclic ...

The Movement of Water Across Vasopressin-Sensitive Epithelia

Abstract: Publisher Summary This chapter presents the evidence for the pore enlargement hypothesis and reviews the recent studies that provide a basis for an alternative view of water movement across vasopressin-sensitive epithelia and cell membranes in general. It was proposed that vasopressin enlarges pores in the membrane—permitting an increase of Poiseuille flow—with only a small accompanying increase in the diffusion rate of labeled water. Extraneous layers of a vasopressin-sensitive epithelium—the urinary bladder of the toad—retard the diffusion rate of tritiated water to a significant extent. When this retarding effect is taken into account, a number of conclusions can be drawn about the effects of vasopressin on the structure of the luminal membrane of the epithelial cell. First, the diffusion rate of water increases dramatically following vasopressin, possibly enough to account fully for the increase in water flow. Second, the activation energy for diffusion remains high following hormone treatment. This indicates that water is moving through the membrane in a highly bonded state and that there may be no change in the physical properties of the aqueous pathway. Finally, it cannot be said with certainty whether the membrane sites are channels or simply points in the membrane through which individual water molecules can move.

The Mid-Atlantic Ridge Near 45 °N. XVIII. Heat Flow Measurements

Abstract: Eighteen heat flow measurements on the Mid-Atlantic Ridge, in the detailed study area between 45 and 46 °N, have a pattern of low values up to 20 km from the median valley, high heat flow 30 to 40 km away, low values again 50 to 100 km away, finally increasing to normal heat flow at great distances. The smoothed heat flow profile is everywhere lower than that predicted by theoretical cooling plate models.It is concluded that convective water flow in the fractured, porous crustal rocks of the ridge is responsible for the low heat flow near the crest. Higher values (at 30 to 40 km from the crest) occur when the sediment cover is sufficient to cut off communication between the crust and seawater. The low heat flow zone at 50 to 100 km from the crest can be explained by heat required to warm the convectively cooled crust when the rocks are sealed and circulation stops, and by the heat absorbed in lower crustal metamorphic reactions.

Water power apparatus

Abstract: The apparatus described utilizes a raceway in which is disposed an inlet gate for concentrating and increasing the velocity of the water flowing through the raceway and also for directing the water to one side of the raceway for engagement with the paddles of a horizontally disposed water wheel. The inlet gate has a side wall which diverges against the direction of water flow. This side wall, which concentrates the water flowing into the raceway, is pivoted so that it can swing back to a neutral position to permit water flowing out of the raceway to exit freely. A second gate is disposed at the opposite end of the raceway to perform a similar function when the water is flowing in the opposite direction through the raceway.

Method and apparatus for treating dishwasher discharge

Abstract: In a dishwasher of the type in which racks of dishes are carried through a series of washing and rinsing stations, the hot, moisture laden air emitted by the dishwasher is directed over a series of cooling coils to both cool the air and remove by condensation a substantial portion of the moisture. The cooled, dried air is then exhausted to ambience. Relatively cool tap water is utilized in the cooling coils with the water passing from the coils to the first stage of the dishwasher for use in washing dishes. A valve regulates water flow to the cooling coils and is controlled by the same switch which actuates the final rinse stage of the dishwasher so that additional cooling capacity is gained during the final rinse stage. An adjustable opening is also provided for admitting ambient air into the apparatus for mixture with the air from the cooling section to prevent a build-up of condensate in the sections of the apparatus downstream of the cooling section.

Influence of intracellular and extracellular tonicities on water permeability in Characean cells

Abstract: The effect of the concentration of the central vacuolar sap on water permeability previously demonstrated onNitella internode (Tazawa and Kamiya 1966), has been further studied. By using a technique of vacuole perfusion the ionic concentration of the cell sap has been modified independently of its tonicity. Transcellular water permeability has been measured by means of a double-chamber osmometer. When the tonicities of artificial saps were adjusted to that of the natural cell sap, wide variations in the concentration of K+, Na+, or Ca++ in the vacuole did not bring about any change in the magnitude of water permeability. On the other hand, water permeability was strongly influenced by varying the tonicity of the vacuolar medium by addition of mannitol. It increased when the tonicity was lowered from the normal level, while it decreased when tonicity was heightened. Water permeability was also decreased by increase in the tonicity of the external medium. Analysis of the results showed that the specific resistance to water flow across the plasmalemma and the tonoplast in series (the reciprocal of the water permeability k′p) was related to the osmotic pressures of the intracellular (π i) and the extracellular (π 0) medium by the empirical formula, l/k′p=0.088 + 0.015 π. + 0.0074π 0. Thus, intra- and extracellular tonicities influence the water permeability of theNitella internode independently of each other. The decrease in water permeability by increase in tonicity of the intra- or extracellular medium may be explained in terms of the effect of these tonicities on hydration of the cell membranes. The water permeability ofLamprothamnium, a brackish water Characeae was only one fourth that ofNitella, a fresh water Characeae. The lower permeability inLamprothamnium may be accounted for in terms of the high tonicities of its cell sap and external medium.

Distribution of Oxygen Tension in the Blood and Water Along the Secondary Lamella of the Icefish Gill

Abstract: 1. Measurements of the gill area of two specimens of Chaenocephalus aceratus indicate that the resistance to water flow and overall exchange area are even less than had been supposed from work with other icefish. 2. Measurements of the oxygen tensions in the water and in blood entering and leaving the gills are used to determine the expected distribution of O 2 tensions along a typical secondary lamella profile. The advantage of counter-current over co-current flow is clearly indicated by such analyses. 3. The absence of complications due to the O 2 dissociation curve of the blood facilitates an extension of the analysis to different theoretical secondary lamellar profiles. It is shown that profiles similar to those usually found in fish gills are more efficient in maintaining O 2 transfer. 4. Although the percentage utilization of O 2 in the water passing through the gills is relatively low, the effectiveness of oxygenating the blood is very high in the icefish gill.