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Biomedical subjects

L Martis

Publications and source records attributed to L Martis.

At least 19 recordsLinked to original sources
PubMed2001

Hyaluronan modifies inflammatory response and peritoneal permeability during peritonitis in rats.

The effect of high-molecular-weight hyaluronan (HA) on peritoneal and systemic inflammation and peritoneal permeability to water and solutes was studied during endotoxin-induced peritonitis in rats. Acute peritonitis was induced by adding lipopolysaccharide (LPS) to the dialysis fluid (Dianeal 3.86; Baxter Healthcare, Ireland, Castlebar). HA was added to the dialysis solution in a concentration of 10 mg/dL. During 4- and 8-hour dwells of the dialysis fluid, we studied the intensity of peritoneal (dialysate) and systemic (blood) inflammation (dialysate cell count and differential, cytokine and HA levels), as well as the transperitoneal transport of solutes and water. In rats, the addition of LPS to the dialysis fluid induced changes in inflammatory reaction and transperitoneal transport similar to those seen in continuous ambulatory peritoneal dialysis patients with peritonitis. During peritonitis, the addition of HA to the dialysis fluid reduced the loss of ultrafiltration, which resulted in a greater peritoneal creatinine clearance during the 8 hours of dwell (29.9 +/- 6.7 mL/8 h in the HA-LPS group versus 19.7 +/- 7.8 mL/8 h in the LPS group; P < 0.05). Dialysate interferon-gamma (INF-gamma) levels during peritonitis were greater in HA-treated animals (536.8 +/- 296.6 pg/mL in the HA-LPS group versus 169.8 +/- 137.8 pg/mL in the LPS group; P < 0.05). Dialysate elastase activity increased during peritonitis (44.4 +/- 9.3 versus 14.2 +/- 4.1 U/mL in peritonitis-free rats); during peritonitis, the increase in dialysate elastase activity was less pronounced in the rats that had HA in the dialysate (27.3 +/- 4.1 U/mL versus the LPS group; P: < 0.01). We conclude that HA added to the dialysis fluid reduces loss of ultrafiltration during peritonitis in rats. In the presence of HA dialysate, INF-gamma levels during peritonitis increased, whereas elastase activity decreased; these changes might improve the peritoneal immune reaction during peritonitis and at the same time prevent peritoneal membrane injury.

Acute Disease↗
PubMed2000

Dialysis solution containing hyaluronan: effect on peritoneal permeability and inflammation in rats.

BACKGROUND: Hyaluronan (HA), a high molecular weight mucopolysaccharide found in interstitial tissues and fluid, is lost from the peritoneal cavity during peritoneal dialysis. In order to determine the role of HA in peritoneal function, we investigated the effects of exogenous HA on peritoneal permeability, markers of intraperitoneal inflammation, and peritoneal morphology in rats exposed to peritoneal dialysis solution for four weeks. METHODS: Wistar rats were infused intraperitoneally, twice daily, with conventional, hypertonic dialysis solution (Dianeal 3.86%; control) or Dianeal solution containing 10 mg/dL of high molecular weight HA. Peritoneal permeabilities and clearances of solutes and protein were determined using a modified peritoneal permeability test (peritoneal equilibration test) at the beginning and the end of the treatment. Peritoneal volume and ultrafiltration were determined using a macromolecular marker and by gravimetric methods. Peritoneal inflammation was determined by cell counts and differential and by the measurement of cytokine concentrations in the dialysate effluent. Peritoneal thickness and HA content were determined in liver and mesentery biopsies taken at the end of the experiment. RESULTS: After four weeks of exposure to the dialysis solution, transperitoneal protein equilibration was significantly lower in HA-treated rats compared with rats treated with Dianeal alone (46% lower for albumin, P < 0.003; 33% lower for total protein, P < 0.001). The total drained volume after a four hour dwell was 29% higher in the HA group compared with the control (P < 0.001), yielding a positive net ultrafiltration in the HA group versus a negative net ultrafiltration in controls. Peritoneal clearances of urea and creatinine tended to be elevated in HA-treated rats, while clearances of total protein and albumin tended to be lower. Dialysate effluent from rats exposed to HA contained a lower percentage of neutrophils (8.8 +/- 22.8 +/- 9.5%, P < 0.01) and lower levels of the cytokines, tumor necrosis factor-alpha (11.2 +/- 14.7 vs. 42.3 +/- 35.3 pg/mL, P < 0.05) and monocyte chemoattractant protein-1 MCP-1 (72.0 +/- 86.5 vs. 402.4 +/- 258.3 pg/mL, P < 0.02), compared with rats treated with Dianeal alone. The thickness of the peritoneal interstitium showed a similar increase in both groups, but mesenteric tissue from the HA group contained more HA (48%, P < 0.01) than tissue from control animals. CONCLUSIONS: The addition of HA to peritoneal dialysis solution decreases protein permeability, increases ultrafiltration, and decreases cytokine levels and the proportion of peritoneal neutrophils in dialysate from rats exposed to hypertonic dialysis solution. These results suggest that exogenous HA may help to protect the peritoneal membrane during exposure to dialysis solutions. These benefits, if sustained in the clinical setting, could lead to improvements in the therapy of peritoneal dialysis.

Animals↗
PubMed1999

New solutions for peritoneal dialysis in adult and pediatric patients.

The standard PD solutions used today contain physiological electrolyte profiles similar to that of interstitial fluids and are supplemented with glucose as the osmotic agent. Improvements in solution composition during the last 20 years have been largely restricted to minor changes in buffer and electrolyte levels. Newer PD solutions, on the other hand, are designed to manage comorbidities associated with patients on maintenance dialysis, to tailor the ultrafiltration profile based upon dwell time, and to better preserve peritoneal membrane function and host defenses. The evidence to date indicates that, in malnourished PD patients (children and adults), IP amino acids improve protein nutritional status, particularly if low protein intakes are a cause of the malnutrition. The availability of glucose polymers allows the clinician to complement standard glucose-based formulations with one that can provide improved ultrafiltration in both CAPD and APD patients for long dwells, and in patients experiencing ultrafiltration loss owing to a large effective peritoneal surface area. Owing to the reduced calorie and carbohydrate load, glucose polymers may also offer long-term metabolic advantages. Although the control of acid-base balance can be well managed in the vast majority of patients with a 35-40 mmol/L lactate solution, the development and clinical evaluation of bicarbonate-based solutions is underway as a result of concern over the potentially bioincompatible nature of acidic lactate formulations. To date, in vitro, ex vivo, and limited clinical studies show that such formulations, and in particular bicarbonate/lactate combinations are efficacious and well tolerated, and show improved peritoneal cell function versus conventional solutions. In conclusion, ongoing research and development has produced a new generation of PD solutions that, to various degrees, meet different criteria established for an ideal PD solution for chronic adult and pediatric patients on PD. These criteria include good clearance and ultrafiltration, supply of nutrition, iso-osmolality, physiologic pH, bicarbonate buffer, and minimal absorption of the osmotic agent. Several of the new solutions have already demonstrated clinical utility in controlled clinical trials and are commercially available in Europe. Wider clinical use will further add to our understanding of the impact of these formulations on patient outcomes.

Adult↗
PubMed1998

Treatment of malnutrition with 1.1% amino acid peritoneal dialysis solution: results of a multicenter outpatient study.

A peritoneal dialysis (PD) solution containing 1.1% amino acids as the osmotic agent was evaluated in a 3-month randomized, prospective, open-label study in malnourished PD patients. Patients in the treatment group (DAA) received one or two exchanges daily with the amino acid solution, depending on tolerance, in place of glucose solutions. Controls (DD) received their usual therapy with glucose dialysate. Fifty-four DAA and 51 DD patients completed the study. In DAA, but not in DD patients, there was a significant increase at month 3 in serum insulin-like growth factor-1 (IGF-1) levels and significant decreases in serum potassium (all 3 months) and inorganic phosphorus levels (months 1 and 3), indicating a general anabolic response. Prealbumin and transferrin levels were significantly increased in DAA but not in DD patients at month 1, but the groups did not differ at months 2 and 3. In patients with baseline albumin levels less than 3.5 g/dL (bromcresol green [BCG] method), DAA patients showed increases in albumin, transferrin (months 1 and 2), and prealbumin levels (all 3 months) relative to baseline values, whereas these serum protein levels were unchanged in DD patients, although the changes from baseline did not differ between groups. In this subgroup, midarm muscle circumference (MAMC) did not change in DD or DAA patients. In patients with baseline albumin levels of 3.5 g/dL or greater, DD patients had decreases in albumin and total protein levels at all 3 months and in prealbumin levels at months 1 and 2, relative to baseline. In DAA patients, there were fewer changes in serum proteins. MAMC increased significantly from baseline in DAA but not in DD patients, although changes from baseline did not differ between DAA and DD groups. DAA patients showed no changes in peritoneal membrane transport characteristics. The results indicate that treatment with one or two exchanges daily of this amino acid-based PD solution is safe and provides nutritional benefit for malnourished PD patients.

Amino Acids↗
PubMed1998

Peritoneal dialysis solutions for the 21st century.

Existing peritoneal dialysis (PD) solutions were formulated for the maintenance of fluid and electrolyte balance, correction of metabolic acidosis, and the removal of metabolic waste products. Solutions currently in development are designed to improve biocompatibility by neutralizing pH and reducing glucose degradation products. PD solutions developed for the 21st century will address major clinical needs related to the maintenance of adequate nutrition, improvement of cardiovascular comorbidity, preservation of peritoneal membrane function, and adequacy of dialysis. Nutrineal is the first example of a PD solution to address such a clinical need. Another example is a low sodium solution to improve sodium balance thereby reducing the incidence of hypertension and the need for antihypertensive medication. New solutions under investigation will employ additives to protect the peritoneal membrane during peritonitis and chronic PD and to optimize PD therapy via improvements in ultrafiltration and solute clearances. Examples include the use of antioxidants to reduce oxidative damage during peritonitis and the use of glycosaminoglycans or other additives to enhance ultrafiltration. Future concepts include remodeling of the peritoneum, for example, the use of mesothelial gene therapy to introduce metabolic and anabolic machinery to remove or perpetually recycle metabolic wastes. The 21st century promises to be an exciting and fruitful time for the investigation and development of new products for the improvement of PD therapy.

Cardiovascular Diseases↗
PubMed1998

Elevation of whole-blood glutathione in peritoneal dialysis patients by L-2-oxothiazolidine-4-carboxylate, a cysteine prodrug (Procysteine).

Glutathione is a major cellular antioxidant that protects protein thiols and inhibits cellular damage due to oxygen free radicals. It has been reported previously that patients undergoing dialysis have low levels of blood glutathione, which may lead to increased susceptibility to oxidant stress. L-2-oxothiazolidine-4-carboxylic acid (OTZ) is a cysteine prodrug that raises cellular glutathione levels by increasing delivery of cysteine, the rate-limiting substrate for glutathione synthesis. This study investigates the effect of OTZ on blood glutathione in a blinded, placebo-controlled study of patients with chronic renal failure treated by peritoneal dialysis. Twenty patients were randomly selected to receive OTZ (0.5 g three times a day orally with meals) or placebo for 14 d. Patients visited the clinic for predose blood collection and safety evaluation at baseline (days 3, 7, and 14 and again at 14 d from the last dose [follow-up]). Glutathione concentrations were determined in whole blood by HPLC. OTZ resulted in a significant rise in whole-blood glutathione at days 7 (594 +/- 129 mumol/L) and 14 (620 +/- 108 mumol/L) compared with baseline (544 +/- 139 mumol/L) (P < 0.01 and P < 0.05, respectively). Glutathione was also significantly increased at days 7 and 14 when normalized by hematocrit (Hct) or hemoglobin to correct for anemic status (e.g., 20.7 +/- 5.7 mumol/L per % Hct [day 7] and 20.9 +/- 4.0 mumol/L per % Hct [day 14] versus 18.0 +/- 4.2 mumol/L per % Hct [baseline]; P < 0.05). Glutathione levels did not change in the placebo group at any patient visit, and levels in the OTZ-treated group returned to baseline at follow-up. There were no serious adverse events attributable to OTZ, and the drug appeared to be well tolerated by patients with renal failure treated by continuous ambulatory peritoneal dialysis. Our results show that OTZ increases blood glutathione levels, which may improve antioxidant status in dialysis patients.

Administration, Oral↗
PubMed1998

New developments in peritoneal dialysis solutions.

Existing peritoneal dialysis (PD) solutions were formulated mainly for the maintenance of fluid and electrolyte balance, correction of metabolic acidosis, and the removal of metabolic waste products. New solutions in development, and recently approved in some countries, are designed to improve ultrafiltration during long dwells (polyglucose or icodextrin solutions), to treat malnutrition (amino-acids solutions), and to improve peritoneal biocompatibility (bicarbonate-buffered solutions). Other new solutions under investigation are designed to address unmet clinical needs, including cardiovascular disease and sodium balance, through the use of a low-sodium PD solution; long-term peritoneal viability, through improvements in sterilization processes and the use of nonglucose osmotic agents; and PD adequacy, through the use of solution additives (such as glycosaminoglycans) and tailored PD prescriptions using APD. Future concepts for PD include remodeling of the peritoneum, perhaps using mesothelial gene therapy to introduce metabolic and anabolic machinery to remove or perpetually recycle metabolic wastes.

Amino Acids↗
PubMed1998

Maltose and isomaltose in uremic plasma following icodextrin administration.

The presence of mixed disaccharides (maltose and isomaltose) in plasma from uremic patients has been previously investigated using gel-permeation chromatography. However, this method is unable to separate maltose (linked alpha-1-4) from isomaltose (linked alpha-1-6). We describe an alternative method using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD) for the direct determination of maltose and isomaltose in uremic plasma. We measured maltose and isomaltose using HPAE-PAD in 6 normal subjects and in 15 uremic patients before and after once-daily icodextrin administration for at least 4 weeks. Both maltose and isomaltose were below limits of detection (< 1.0 mg/L) in plasma from normal controls. Patients with end-stage renal disease treated by continuous ambulatory peritoneal dialysis had elevated levels of isomaltose (23.6 +/- 8.3 mg/L) but low levels of maltose (< 3.0 mg/L). Treatment with icodextrin resulted in elevated plasma levels of maltose (range: 500-1600 mg/L), while levels of isomaltose declined to 9.8 +/- 5.2 mg/L (P < 0.0001 vs. baseline levels). We conclude that isomaltose (not maltose) is the primary disaccharide isomer that is elevated in the plasma of uremic patients, whereas maltose is the primary disaccharide isomer that is elevated following icodextrin administration. Furthermore, icodextrin administration results in an apparent reduction of isomaltose. Additional investigation will be required to address the mechanism for the reduction of isomaltose in patients treated by icodextrin.

Chromatography, High Pressure Liquid↗
PubMed1997

In vitro simulation of the effect of peritoneal dialysis solution on mesothelial cells.

All previous in vitro biocompatibility tests of peritoneal dialysis fluids have shown that these have inhibitory effects on the function of peritoneal mesothelium. This report presents results from in vitro experiments performed to study the effect of dialysis fluids (Dianeal 1.36 and Dianeal 3.86; Baxter, Round Lake, IL) on the function of mesothelial cells under conditions that simulate the in vivo state of these solutions in the peritoneal cavity. Thus, cells were initially exposed only to the unused fluids that were thereafter gradually diluted (over 4 hours) with pooled effluent dialysate from continuous ambulatory peritoneal dialysis patients. During the following 20 hours, cells were incubated in a mixture of unused fluid (10% vol/vol) and dialysate effluent (90% vol/vol). The mesothelial cells exposed to dialysis fluids under such conditions became activated cells compared with exposed to dialysate effluent (control) alone. Thus, synthesis by mesothelial cells of all tested substances was enhanced during exposure of the mesothelium to the dialysis fluids: interleukin-6: Dianeal 1.36, +257%; Dianeal 3.86, +181% (both P < 0.05); hyaluronic acid: Dianeal 1.36, +72%; Dianeal 3.86, +63% (both P < 0.05); tissue plasminogen activator: Dianeal 3.86, +33% (P < 0.05); and plasminogen activator/inhibitor-1: Dianeal 1.36, +28%; Dianeal 3.86, +38% (both P < 0.05). Our results show that the peritoneal mesothelium becomes activated when it is exposed to acidic, hyperosmotic dialysis fluids diluted with the dialysate effluent, in a manner that imitates the in vivo changes in these solutions during their intraperitoneal dwell.

Cells, Cultured↗
PubMed1997

Impact of terminal heat sterilization on the quality of peritoneal dialysis solutions.

In order to meet the sterility requirements imposed by the various regulatory bodies around the world, peritoneal dialysis solutions are terminally heat-sterilized at an acid pH. There is growing concern that both acid pH and the glucose degradation products formed during terminal heat sterilization adversely affect the quality of the therapy provided to the end-stage renal failure patient on peritoneal dialysis. Acid pH and glucose degradation products are thought to contribute to impaired host defense and hence to increased risk of infection, loss of ultrafiltration, and peritoneal fibrosis. On the other hand, peritoneal dialysis solutions prepared by aseptic processing are devoid of in vitro cytotoxicity and hence are considered more biocompatible than heat-sterilized solutions. With new technologies permitting aseptic processing to achieve sterility assurance levels approaching solutions manufactured by terminal heat sterilization, it is possible to produce solutions that are more biocompatible than heat-sterilized products without increasing the risk of microbial contamination.

Abdominal Pain↗
PubMed1997

Alterations of intraperitoneal inflammation by the addition of L-2-oxothiazolidine-carboxylate.

The authors studied the effect of L-2-oxothiazolidine-carboxylate (OTZ), a substrate for intracellular glutathione synthesis, in an in vivo model of lipopolysaccharide (LPS)-induced peritonitis in rats. The addition of LPS to dialysis fluid increased the white blood cell (WBC) count and the nitrite (index of NO synthesis) level in the dialysate. The simultaneous addition of OTZ to the dialysis fluid prevented an increase of WBCs but not of nitrites in the dialysate. Intraperitoneal inflammation was accompanied by a decrease in net transperitoneal ultrafiltration, an increase in the absorption of glucose, and a loss of protein into the dialysate. OTZ partially reversed the effect of peritonitis on net ultrafiltration. Peritoneal leukocytes from rats exposed to LPS showed a reduced concentration of glutathione, an effect that was reversed in the presence of OTZ. These results show that the supplementation of dialysis fluid with OTZ modified the peritoneal reaction to acute inflammation.

Albumins↗
PubMed1996

L-2-Oxothiazolidine-4-carboxylate and N-acetylcysteine as precursors of intracellular glutathione in human peritoneal mesothelial cells.

L-2-Oxothiazolidine-4-carboxylate and N-acetylcysteine as substrates for intracellular glutathione in human peritoneal mesothelial cells were tested. Both substances at concentrations of 0.01 mM and higher augmented the level of glutathione in mesothelial cells. L-2-Oxothiazolidine-4-carboxylate had a milder but more stable effect than N-acetylcysteine. Cells with increased concentrations of the intracellular glutathione were more resistant to injury by free radicals. When used at higher concentrations (> 1 mM), both substances became cytostatic to mesothelial cells as evidenced by growth inhibition.

Acetylcysteine↗
PubMed1996

Intracellular glutathione in human peritoneal mesothelial cells exposed in vitro to dialysis fluid.

Effect of peritoneal dialysis fluids on glutathione (GSH/GSSG) level in human peritoneal mesothelial cells was tested in in vitro experiments. To mimic in vivo conditions, cells were initially exposed to dialysis fluids (Dianeal 1.36%, Dianeal 2.27%, Dianeal 3.86%) that subsequently were diluted with dialysate effluent at time intervals. GSH/GSSG concentration in cells initially decreased but returned to normal values thereafter. This decrease in the intracellular concentration of glutathione was less when pH of the tested dialysis fluid was adjusted to 7.3. In further experiments with mesothelial cells exposed to Earle's salts solution supplemented with glucose and/or lactate, we have shown that in the presence of low pH, lactate is the main factor causing depletion of intracellular glutathione. When added to the dialysis solution at a concentration of 0.1 mM, L-2-oxothiazolidine-4-carboxylate, a precursor of glutathione, not only prevents the initial decrease in glutathione concentration but also augments the final intracellular level of this thiol.

Analysis of Variance↗
PubMed1996

In vitro detection of hydrogen peroxide in mesothelial cells.

Hydrogen peroxide can be indirectly detected in mesothelial cells by measuring the rate of inhibition of the intracellular catalase activity by 3-amino-1, 2,3-triazole (AT). AT binds and inhibits catalase only in the presence of hydrogen peroxide, and the effect is proportional to the amount of hydrogen peroxide. The effect of AT on catalase activity is prevented in the presence of ethanol. In mesothelial cells in vitro exposed to dialysis fluids (Dianeal 1.36%, 2.27%, and 3.86%) no significantly increased generation of hydrogen peroxide was detected. However, interleukin-1 (IL-1) (10 ng/mL) enhances, within two hours (+40%, p < 0.05), intracellular production of hydrogen peroxide. The presented method of detection of intracellular hydrogen peroxide may be helpful in studies of the pathomechanisms causing mesothelial damage in conditions of peritoneal dialysis.

Amitrole↗
PubMed1996

Effect of vitamin E on peroxidation and permeability of the peritoneum.

Because of the evidence that peritoneal macrophages are activated during peritoneal dialysis, we hypothesised that the injury of the peritoneum is, at least in part, dependent on the intraperitoneal generation of free radicals. The aim of the study was to evaluate the effect of vitamin E on the peroxidation and permeability of the peritoneum during chronic peritoneal dialysis in rats. Supplementation of the intraperitoneally infused saline with vitamin E decreased the peroxidation of peritoneum estimated as the malondialdehyde (MDA) level in rats' omentum. However the permeability of the peritoneum to glucose and protein in vitamin E treated rats was increased. In in vitro study we have found that vitamin E is cytotoxic to human mesothelial cells (HMC) as measured by inhibition of their proliferation and this effect was irreversible. We conclude that vitamin E, despite its antioxidant effect, causes the changes of the peritoneum permeability which could decrease the effectiveness of peritoneal dialysis.

Animals↗
PubMed1995

Changes in biocompatibility of dialysis fluid during its dwell in the peritoneal cavity.

OBJECTIVE: To evaluate the changes in biocompatibility of peritoneal dialysis solutions during intraperitoneal dwell. DESIGN: We studied the effect of the drained dialysates at time 0 and after 30, 60, 120, 240, and 360 minutes of intraperitoneal dwell on the growth of peritoneal mesothelial cells and fibroblasts and the synthesis of proteins by these cells. On one day the patients were dialyzed with glucose-based Dianeal and on alternate days with an amino acid-containing solution based on Travasol. PATIENTS: Dialysates were collected from 4 patients during continuous ambulatory peritoneal dialysis (CAPD) training. RESULTS: Unused dialysis solutions containing glucose or amino acids inhibit growth of mesothelial cells and fibroblasts. Dialysates obtained after 30 or 60 minutes of intraperitoneal dwell support the growth of these cells in a way similar to 10% fetal calf serum, but dialysates drained after a longer dwell of 120-360 minutes had a stronger effect on growth of these cells than did serum. All glucose-based dialysates stimulate the synthesis of collagen in mesothelial cells, whereas they reduce the synthesis of non-collagen proteins. All glucose-based dialysates reduce the synthesis of collagen and non-collagen proteins in fibroblasts compared with the production of these proteins in the presence of serum. CONCLUSION: Changes in the properties of the dialysis solutions during their intraperitoneal dwells do not seem to increase their biocompatibility. Indeed, excessive mitogenic effect and the stimulation of collagen synthesis of the dialysates may induce pathological changes in the peritoneum.

Biocompatible Materials↗