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At least 703 records · Page 39Linked to original sources
PubMed1994

Incidence of Norwalk virus infections during a prospective epidemiological study of drinking water-related gastrointestinal illness.

To determine the seroprevalence of Norwalk virus and whether Norwalk virus contributed to an observed increase in illness in tap water drinkers participating in a prospective epidemiological study, sera collected during the study were examined for changes in Norwalk virus antibody titer, using a specific enzyme immunoassay. Antibodies to Norwalk virus were measured in sera collected in March, June and September 1988 and in June 1989, and antibodies were found in 79% of the individuals. Seroprevalence increased with age, being 55% (ages 9-19), 79% (20-39), 87% (40-49), 84% (50-59), and 100% (60 and older). Norwalk infections occurred in 33% of the individuals during the course of the study. The highest rate of infection (expressed as a monthly rate) was observed during the summer of 1988. These results confirm that a large number of infections owing to Norwalk viruses occur throughout the year. A previous seroconversion or a high serum titer were not always protective. Finally, there was no detectable difference in infection rate between consumers of tap water and consumers of water treated by reverse-osmosis units, suggesting that Norwalk virus infections were not responsible for the excess of gastrointestinal illness observed in tap water drinkers during this epidemiological study.

Adolescent↗
PubMed1997

AQUAPORINS AND WATER PERMEABILITY OF PLANT MEMBRANES.

The mechanisms of plant membrane water permeability have remained elusive until the recent discovery in both vacuolar and plasma membranes of a class of water channel proteins named aquaporins. Similar to their animal counterparts, plant aquaporins have six membrane-spanning domains and belong to the MIP superfamily of transmembrane channel proteins. Their very high efficiency and selectivity in transporting water molecules have been mostly characterized using heterologous expression in Xenopus oocytes. However, techniques set up to measure the osmotic water permeability of plant membranes such as transcellular osmosis, pressure probe measurements, or stopped-flow spectrophotometry are now being used to analyze the function of plant aquaporins in their native membranes. Multiple mechanisms, at the transcriptional and posttranslational levels, control the expression and activity of the numerous aquaporin isoforms found in plants. These studies suggest a general role for aquaporins in regulating transmembrane water transport during the growth, development, and stress responses of plants. Future research will investigate the integrated function of aquaporins in long-distance water transport and cellular osmoregulation.

Journal Article↗
PubMed1995

A simple student laboratory on osmotic flow, osmotic pressure, and the reflection coefficient.

Osmosis is usually taught from the point of view of the osmotic pressure developed when solutions of different concentrations of solute are separated by an ideal semipermeable membrane. The osmotic pressure is defined at equilibrium when there is no net flow, and it takes some time to reach this equilibrium. Although the osmotic pressure is certainly important, teaching only this point of view implicitly diminishes the importance of osmotic flow, which begins almost instantaneously across a membrane. A device was constructed with which students could measure the flow across a model membrane (dialysis tubing) as a function of concentration for solutes of different sizes. The device produced flows that were linearly proportional to the concentration, providing a confirmation of van't Hoff's law. Separate student groups repeated these experiments using both different solutes and different dialysis membranes. The combined results of four student groups showed that the flow across these nonideal membranes depends on the solute and membrane as well as the concentration of solute. Given a value for area times filtration coefficient (A x Lp) for the membranes (determined beforehand by their instructor), the students could calculate the reflection coefficient (sigma) for three solutes and two membranes. The results showed that large solutes had large sigma and that less porous membranes had larger sigma. A concurrent demonstration using this device and membranes showed that the osmotic flow can generate large pressures. These experiments and demonstration provide a balanced view of osmotic flow and pressure.

Dialysis↗
PubMed2001

Pulmonary and renal pressure-flow relationships: what should be taught?

This article is from a symposium presented at the annual meeting of the Human Anatomy and Physiology Society (HAPS) on June 11, 2000. The presentation was funded under the auspices of a National Science Foundation Course, Curriculum, and Laboratory Improvement Program entitled "Development of Active Learning Materials for Physiology and Functional Anatomy: A Cooperative HAPS-APS Initiative." This symposium was part of the first module to be developed on "gradients and conductances: what flows where and why?" This presentation was designed to model the usefulness of the general model of gradients and conductances in the physiology and pathophysiology of the respiratory and renal systems. Thirteen different examples of pressure-flow-resistance and concentration-flux relationships are introduced; several ideas for active-learning activities and simple figures appropriate for undergraduate physiology classes are included. The symposium assumes that undergraduate students have already learned about diffusion, osmosis, and the basic principles of cardiovascular physiology. The presentation was designed to follow a symposium entitled: "Cardiovascular pressure-flow relationships: what should be taught?"

Cardiovascular Physiological Phenomena↗
PubMed2005

Fluid secretion and the Na+-K+-2Cl- cotransporter in mouse exorbital lacrimal gland.

We have previously suggested that fluid flow in the mouse exorbital lacrimal gland is driven by the opening of apical Cl- and K+ channels. These ions move into the lumen of the gland and water follows by osmosis. In many tissues, the Na+-K+-2Cl- cotransporter (NKCC1) replaces the Cl- and K+ ions that move into the lumen. We hypothesize that mouse exorbital lacrimal glands would have NKCC1 co-transporters and that they would be important in fluid transport by this gland. We used immunocytochemistry to localize NKCC1-like immunoreactivity to the membranes of the acinar cells as well as to the basolateral membranes of the duct cells. We developed a method to measure tear flow and its composition from mouse glands in situ. Stimulation with the acetylcholine agonist carbachol produced a peak flow followed by a plateau. Ion concentration measurements of this stimulated fluid showed it was high in K+ and Cl-. Treatment of the gland with furosemide, a blocker of the NKCC1 cotransporter, reduced the plateau phase of fluid flow by approximately 30%. Isolated cells exposed to a hypertonic shock shrank by approximately 20% and then showed a regulatory volume increase (RVI). Both the RVI and swelling were blocked by treatment with furosemide. Cells isolated from these glands shrink by approximately 10% in the presence of carbachol. Blocking NKCC1 with furosemide reduced the amount of shrinkage by approximately 50%. These data suggest that NKCC1 plays an important role in fluid secretion by the exorbital gland of mice.

Animals↗
PubMed1996

In vivo inhibition of transcellular water channels (aquaporin-1) during acute peritoneal dialysis in rats.

During peritoneal dialysis (PD), a major portion of the osmotically induced water transport to the peritoneum can be predicted to occur through endothelial water-selective channels. Aquaporin-1 (AQP-1) has recently been recognized as the molecular correlate to such channels. Aquaporins can be inhibited by mercurials. In the present study, HgCl2 was applied locally to the peritoneal cavity in rats after short-term tissue fixation, used to protect the tissues from HgCl2 damage. Dianeal (3.86%) was employed as dialysis fluid, 125I-albumin as an intraperitoneal volume marker, and 51Cr-EDTA (constantly infused intravenously) to assess peritoneal small-solute permeability characteristics. Immunocytochemistry and immunoelectron microscopy revealed abundant AQP-1 labeling in capillary endothelium in peritoneal tissues, representing sites for HgCl2 inhibition of water transport. HgCl2 treatment reduced water flow and inhibited the sieving of Na+ without causing any untoward changes in microvascular permeability, compared with that of fixed control rats, in which the peritoneal cavity was exposed to tissue fixation alone. In fixed control rats, the mean intraperitoneal volume (IPV) increased from 20.5 +/- 0.15 to 25.0 +/- 0.52 ml in 60 min, whereas in the HgCl2-treated rats, the increment was only from 20.7 +/- 0.23 to 23.5 +/- 0.4 ml. In fixed control rats, the dialysate Na+ fell from 135.3 +/- 0.97 to 131.3 +/- 1.72 mM, whereas in the HgCl2-treated rats the dialysate Na+ concentration remained unchanged between 0 and 40 min, further supporting that water channels had been blocked. Computer simulations of peritoneal transport were compatible with a 66% inhibition of water flow through aquaporins. The observed HgCl2 inhibition of transcellular water channels strongly indicates a critical role of aquaporins in PD and provides evidence that water channels are crucial in transendothelial water transport when driven by crystalloid osmosis.

Animals↗
PubMed2005

The transport barrier in intraperitoneal therapy.

The peritoneal cavity is important in clinical medicine because of its use as a portal of entry for drugs utilized in regional chemotherapy and as a means of dialysis for anephric patients. The barrier between the therapeutic solution in the cavity and the plasma does not correspond to the classic semipermeable membrane but instead is a complex structure of cells, extracellular matrix, and blood microvessels in the surrounding tissue. New research on the nature of the capillary barrier and on the orderly array of extracellular matrix molecules has provided insights into the physiological basis of osmosis and the alterations in transport that result from infusion of large volumes of fluid. The anatomic peritoneum is highly permeable to water, small solutes, and proteins and therefore is not a physical barrier. However, the cells of the mesothelium play an essential role in the immune response in the cavity and produce cytokines and chemokines in response to contact with noncompatible solutions. The process of inflammation, which depends on the interaction of mesothelial, interstitial, and endothelial cells, ultimately leads to angiogenesis and fibrosis and the functional alteration of the barrier. New animal models, such as the transgenic mouse, will accelerate the discovery of methods to preserve the functional peritoneal barrier.

Animals↗
PubMed1983

Cell osmotic water permeability of isolated rabbit proximal convoluted tubules.

Cell osmotic water permeability, Pcos, of the peritubular aspect of the proximal convoluted tubule (PCT) was measured from the time course of cell volume changes subsequent to the sudden imposition of an osmotic gradient, delta Cio, across the cell membrane of PCT that had been dissected and mounted in a chamber. The possibilities of artifact were minimized. The bath was vigorously stirred, the solutions could be 95% changed within 0.1 s, and small osmotic gradients (10-20 mosM) were used. Thus, the osmotically induced water flow was a linear function of delta Cio and the effect of the 70-microns-thick unstirred layers was negligible. In addition, data were extrapolated to delta Cio = 0. Pcos for PCT was 41.6 (+/- 3.5) X 10(-4) cm3 X s-1 X osM-1 per cm2 of peritubular basal area. The standing gradient osmotic theory for transcellular osmosis is incompatible with this value. Published values for Pcos of PST are 25.1 X 10(-4), and for the transepithelial permeability Peos values are 64 X 10(-4) for PCT and 94 X 10(-4) for PST, in the same units. These results indicate that there is room for paracellular water flow in both nephron segments and that the magnitude of the transcellular and paracellular water flows may vary from one segment of the proximal tubule to another.

Animals↗
PubMed1978

Colloid osmotic pressure changes of dog's blood exposed to different mixtures of CO2 and air.

Hansen's membrane manometer method for measuring plasma colloid osmotic pressure was used to obtain the osmolality changes of dogs breathing different levels of CO2. Osmotic pressure was converted to osmolality by calibration of the manometer with saline and plasma, using freezing point depression osmometry. The addition of 10 vol% of CO2 to tonometered blood caused about a 2.0 mosmol/kg H2O increase of osmolality, or 1.2% increase of red blood cell volume. The swelling of the red blood cells was probably due to osmosis caused by Cl- exchanged for the HCO3- which was produced rapidly by carbonic anhydrase present in the red blood cells. The change in colloid osmotic pressure accompanying a change in co2 tension was measured on blood obtained from dogs breathing different CO2 mixtures. It was approximately 0.14 mosmol/kg H2O per Torr Pco2. The corresponding change in red cell volume could not be calculated from this because water can exchange between the plasma and tissues.

Animals↗
PubMed1999

Trace elements in end-stage renal disease. 2. Clinical implication of trace elements.

For human beings trace elements are essential nutrients with a gamut of functions. They are for instance indispensable components of many enzymes, so they have some regulatory functions and they may affect immune reactions and free radical generation. Abnormalities of trace elements are primarily the result of uremia, and they may be further modified and sometimes greatly exacerbated by the dialysis procedure. The role of trace elements in hemodialysis (HD) patients has not yet been fully characterized. To prevent some complications in chronic HD patients, it is very important to regulate the levels of trace elements by adequate water treatment. Reverse osmosis is able to prevent the accumulation of the majority of trace elements in the patients. Zinc supplementation may be recommended for patients with proven zinc deficiency, but for all chronic renal failure patients it is questionable. Selenium deficiency is to be suspected in dialyzed patients and selenium supplementation may be beneficial (increasing glutathione peroxidase activity, cardioprotective effect, immunostimulatory properties) for chronic renal failure patients. Supplementation with a trace element may be indicated when its depletion was unequivocally documented and when there is evidence of the positive effects of this element on the quality of life of the dialyzed patients.

Chemistry Techniques, Analytical↗
PubMed2005

Water treatment for hemodialysis: a 2005 update.

Water for dialysis represents an additive risk factors to the chronic inflammatory state documented in patients on ESRD. The possibility of sustaining proinflammatory cytokines through microbial derived products, coming from dialysate or infused solutions, is enhanced by biofilm presence on piping and on water treatment system or monitor components. Spread use of reverse osmosis, loop distribution system and pre-treatment components tailored to local raw water characteristics have greatly contributed to a general improvement in final water quality. Notwithstanding these contributions literature still reports fatal accidents or significant percentage of dialysis units not complying to the water quality standards. Technological improvement lowers chemical contamination but microbial quality relays more on quality assurance programs than on technology. Optimal water quality represents part of the anti-inflammatory strategies we need to assure to our dialysis patients to improve outcome.

Humans↗
PubMed2006

Peritoneal transport with icodextrin solution.

Icodextrin is the only large molecular weight osmotic agent available in peritoneal dialysis solutions. Icodextrin (compared to glucose) has a prolonged positive ultrafiltration because of the slow absortion of icodextrin due to its large molecular weight. As icodextrin induces transcapillary ultrafiltration by a mechanism resembling 'colloid' osmosis (with the ultrafiltration occurring mainly through the small pores) almost no sieving of solutes is observed with icodextrin-based solution resulting in increased convective transport and clearance of small solutes. In general, the transport characteristics of the peritoneal membrane are similar with glucose- and icodextrin-based solution, but results from the EAPOS study suggests that use of icodextrin-based solution may be associated with less changes in peritoneal transport with time.

Biological Transport↗
PubMed1980

Disturbances of trace element concentrations in plasma of patients with chronic renal failure.

Plasma concentrations of 6 essential trace elements were measured in undialyzed and hemodialyzed patients with chronic renal failure (CRF) and in healthy volunteers by tube-excited X-ray fluorescence analysis and atomic absorption analysis. The influences of hemodialysis on plasma concentrations of Al, Zn, Cu and Br were also studied. High plasma concentrations of Al and Cu and low concentrations of plasma Zn were found in nondialyzed patients with CRF. Plasma concentrations of Al and Cu increased and Zn and Br decreased in the hemodialyzed patients with CRF. An elevated concentration of plasma Al may be primarily caused by permeation from dialysate across the dialyzer membrane. The use of water produced by reverse osmosis will prevent the elevation of plasma Al concentration in patients with CRF.

Adult↗
PubMed1985

Aluminium-induced anaemia in haemodialysis patients.

It appears well established that a microcytic, hypochromic anaemia is present in patients receiving regular haemodialysis treatment, who also suffer from chronic aluminium intoxication. This characteristic anaemia is slightly improved following deionization or reverse-osmosis treatment of dialysate water. Iron deficiency has been tentatively excluded as a cause of this anaemia by measurement of serum ferritin levels. The exact mechanisms involved in the pathogenesis of this anaemia are still to be fully elucidated but a disturbance in haem synthesis and porphyrin metabolism seems probable, and secondary effects of PTH in the bone marrow may be involved. Evidence has accumulated that aluminium is the most likely ion responsible for this anaemia but other ions, trace metals in excess or deficiency and potentially toxic substances cannot be excluded yet.

Aluminum↗
PubMed1986

Bone aluminum deposition in maintenance dialysis patients treated with aluminium-free dialysate: role of aluminium hydroxide consumption.

Postmortem iliac crest biopsies were performed on 16 uremic patients. 3 had been treated conservatively while 13 had been entered into a maintenance dialysis program. The dialysate was treated by reverse osmosis for more than 10 years, and the aluminium concentration was consistently below the detection limit of 0.15 mol/l. 14 patients had been treated with aluminium hydroxide. Bone histomorphometry, aluminium labelling intensity, osteoid surface aluminium labelling extent (Al/OBI) and bone aluminium concentration were measured. 14 patients had significant bone aluminium deposition, including 2 who were not on dialysis of whom 1 had not received aluminium hydroxide. Bone aluminium concentration and labelling intensity were correlated to total aluminium hydroxide consumption (p less than 0.001, p less than 0.05) and present dose (p less than 0.01, p less than 0.01), while Al/OBI was not. The two patients with the highest aluminium concentrations had symptomatic osteomalacia, but 4 patients with significantly raised concentrations and mineralisation front labelling had secondary hyperparathyroidism. It is concluded that bone aluminium deposition occurs despite the use of aluminium-free dialysate and is associated with total and present aluminium hydroxide consumption; heavy aluminium deposition is associated with severe and symptomatic osteomalacia, but can also be observed in the presence of predominant hyperparathyroidism; aluminium deposition can occur in the absence of treatment with dialysis or aluminium hydroxide; bone aluminium concentration and labelling intensity are a better measure of bone deposition than Al/OBI.

Adolescent↗
PubMed1989

Accumulation of aluminium in patients with acute renal failure.

Serum aluminium was monitored in 19 patients admitted with acute oligo-anuric renal failure. The maximum serum aluminium obtained during the course of treatment was greater (p less than 0.05) in 4 patients treated by haemodialysis alone, mean +/- sem 3.78 +/- 0.71 mumol/l than in 4 patients treated only by haemofiltration, 0.60 +/- 0.22 greater (p less than 0.05) during treatment with haemodialysis, 2.7 +/- 0.62 mumol/l than during treatment with haemofiltration, 1.36 +/- 0.15 mumol/l. There was a significant positive correlation between the maximum serum aluminium during treatment with haemodialysis and the number of hours of haemodialysis given (r = 0.76, p less than 0.001). There was no significant increase in serum aluminium due to the administration of human albumin solutions. The aluminium content of dialysate water represents a major source of aluminium in patients with acute renal failure; prevention by reverse-osmosis water purification is recommended.

Acute Kidney Injury↗
PubMed1997

Detection of peptidoglycan and endotoxin in dialysate, using silkworm larvae plasma and limulus amebocyte lysate methods.

Silkworm larvae plasma (SLP) reagent is activated by peptidoglycan (PG), a fragment of both the gram-positive and gram-negative bacterial cell wall, as well as beta-glucan (BG), a component of fungi. It is possible to measure contamination of gram-positive bacteria quantitatively by combining the conventional limulus amebocyte lysate (LAL) and PG measurement methods. Therefore, a more highly accurate analysis of dialysate can be made using both SLP and LAL methods to detect endotoxin (ET) and/or PG contamination. We studied the effects of contaminated dialysate on human peripheral blood mononuclear cells (PBMC) by producing various cytokines in vitro. Muramyl dipeptide (MDP) was used as the biologically active minimum constituent of PG. A total of 54 dialysate samples were obtained under sterile conditions from 4 sites: (1) reverse osmosis water unit; (2) proportioning unit; (3) multiple dialysate preparation console, and (4) personal dialysate preparation console, at 9 dialysis facilities. To detect bacterial contamination, the samples were measured with LAL(C), LAL(G) and SLP methods. PBMC were collected from 10 healthy controls and from 10 hemodialysis patients and cultured for 24 h with ET, MDP, ET + MDP and contaminated dialysate. IL-1 receptor antagonist (IL-1Ra), IL-1 beta and TNF-alpha in the culture medium supernatants were measured using the ELISA method. PG was not detected in dialysate from sites 1 or 2. However, dialysate from the inlet of the dialyzer at the bedside monitor of the central supply and personal console showed 4.1 +/- 6.1 ng/ml for site 3 (in 7 of 18 samples) and 3.3 +/- 4.6 ng/ml for site 4 (in 3 of 18 samples). Contamination by PG alone and complex contamination by PG and ET were also detected. Furthermore, IL-1Ra, IL-1 beta and TNF-alpha production by PBMC increased in accordance with the concentrations of MDP. Cytokine production was enhanced 5-10 times more where MDP and ET coexisted than where either MDP or ET existed alone, showing the synergic effects of MDP and ET. Based on these results, there is a high possibility that PG may also be a pyrogen in the dialysate prior to this study. ET had been considered the only pyrogen in dialysate. Therefore, it is essential to recognize the existence of both ET and PG in investigating dialysate contamination.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1996

Investigation of skin-derived lymph: an approach to get insight into the skin immune system.

The skin acts as a mechanical, physicochemical and immunological control and defense system, and its lymphatic vessels play a role in the regulation of cell hydration and osmosis, as well as in immunological responses. Skin-derived signals, produced in response to various agents acting on the skin, arrive with the afferent lymph at the regional lymph nodes. These signals reflect the immunological processes in the skin and may also determine the reactions in the lymph node. By analyzing afferent lymph derived from specific skin lesions it should therefore be possible to get insight into local pathomechanisms as well as the signal transmission in skin disorders. In this report, we present methodological aspects of such skin-derived lymph studies and review the results obtained from studies of sodium-lauryl-sulfate-induced irritative contact dermatitis in humans.

Cytokines↗