Intracerebroventricular injection of TNF-alpha promotes sleep and is recovered in cervical lymph. (25/5528)

Recent studies have shown that the central nervous system (CNS) communicates with the periphery by the drainage of cerebrospinal fluid and brain interstitial fluid into blood and lymph. We hypothesized that tumor necrosis factor (TNF)-alpha would not only influence the CNS by promoting sleep but also would be directly transmitted into the peripheral immune system. Five hundred nanograms of 125I-labeled TNF-alpha were injected into the lateral ventricles of the brain of six sheep and sampled in venous blood and cervical and prescapular lymph every 30 min for 6 h. 125I-TNF-alpha was measured in lymph nodes and control fat, skin, and muscle tissues 6 h postinjection. 125I-TNF-alpha was detected in the cervical lymphatics within the first 30 min and peaked within 2-3 h. 125I-TNF-alpha counts were elevated in the nodes of the head and neck region. Polysomnographic recordings of four animals showed that TNF-alpha induced a significant increase in slow-wave sleep at postinjection hours 4 and 5. CNS TNF-alpha and its direct drainage into the lymphatic system may influence both the sleeping/waking brain and peripheral immune functions.  (+info)

Frequency and causes of discrepancy between Kt/V and creatinine clearance. (26/5528)

This study examines the frequency of discrepancy between Kt/V urea and creatinine clearance (Ccr) measurements in patients on peritoneal dialysis (PD) and the reasons for this discrepancy. DESIGN: Nonrandomized, retrospective data analysis. SETTING: Single PD unit of a university teaching hospital. PATIENTS: All adult patients receiving PD at our center from January 1995 to December 1996. METHODS: Actual (a) and desired (d) body weight (BW) were used to calculate urea volume of distribution (V) and body surface area (BSA). Patients were divided into four groups based upon their total small solute clearances (Kt/V and Ccr, normalized by actual weight) and three additional groups based upon actual/desired (a/d) body weight ratio. An additional analysis was performed for the subset of anuric patients. Data collected for all patients included the following: total Kt, total Ccr, 4-hour dialysate/ plasma (D/P) creatinine, serum albumin concentration, duration of PD, actual body weight, age, and height. RESULTS: Twenty-three percent of the clearance measurements in our study were discrepant, defined as having values for either Kt/V or Ccr (but not both) above the accepted targets of Kt/V > or = 2.0/wk and Ccr > or = 60 L/wk/ 1.73 m2. Patients with both values above target are more likely to have higher residual renal function. Patients who are significantly less than BWd and patients on PD for a longer time are more likely to have adequate Kt/V but not Ccr. Furthermore, patients who are less than 90% or greater than 110% of BWd have markedly different values for Kt/V and Ccr when BWa versus BWd values are used. CONCLUSIONS: Kt/V and Ccr values are frequently discrepant; a number of factors affect these two measurements to varying degrees, including weight, degree of residual renal function, and duration of PD.  (+info)

The standard peritoneal permeability analysis in the rabbit: a longitudinal model for peritoneal dialysis. (27/5528)

OBJECTIVE: The development of an experimental peritoneal dialysis (PD) model in rabbits to investigate peritoneal transport characteristics during a longitudinal follow-up and to assess normal values of these peritoneal transport parameters. DESIGN: Peritoneal transport parameters were determined in conscious, unrestrained rabbits by standard peritoneal permeability analysis adjusted for rabbits (SPAR). In this test a 1-hour dwell with 3.86% glucose dialysate is used. Dextran 70 (1g/L) was added to the dialysate to allow calculation of fluid kinetics. Dialysate samples were taken before, 10, and 40 minutes after instillation and at the end of the dwell. Blood was drawn at the end of the dwell. EXPERIMENTAL ANIMALS: Eighteen female New Zealand White rabbits (2565 g) were included for catheter implantation. SPARs were performed in 15 animals; the other 3 were excluded due to complications. MAIN OUTCOME: The mass transfer area coefficients (MTACs) of the low molecular weight solutes urea (MTAC(urea)) and creatinine (MTACcr) were calculated. The clearances of albumin (CIalb) and IgG (CI(IgG)), glucose absorption, and fluid transport were computed. Coefficients of intraindividual variation (Vc) were calculated for these parameters. RESULTS: The main complications were catheter obstruction and/or dislocation. Five rabbits underwent uncomplicated PD during a 4-week period. Fifteen SPARs in 15 stable rabbits were performed and analyzed to obtain normal values. Means and standard deviations of the transport parameters were as follows: MTAC(urea) 2.24+/-0.57 mL/min, MTACcr 1.61+/-0.30 mU/min, CI(alb) 52.9+/-17.2 microL/min, CI(IgG) 44.5+/-22.9 UL/min. The transcapillary ultrafiltration rate was 0.66+/-0.13 mL/min and the lymphatic absorption rate 0.47+/-0.26 mL/min. The parameters of solute transport were upscaled to those in humans using two different methods. MTACs of low molecular weight solutes in rabbits and patients were of the same order of magnitude, but the clearance of albumin was approximately four times higher in rabbits than in patients, and that of IgG eight times. In all rabbits sieving of sodium was observed. The dialysate/plasma (D/P) of sodium decreased to a minimum at 40 min (p<0.003 vs the initial value), followed by a rise to 60 min. The minimal value was 0.884+/-0.002. The coefficients of variation calculated on 7 rabbits that underwent two or more SPARs were similar to those assessed from the patient data. This indicates stability of the model and reproducibility of the SPAR. CONCLUSION: The conscious rabbit model for PD can be used for repeated studies on peritoneal transport.  (+info)

A comparative study of the rifampicin binding and elution characteristics for collagen- and albumin-sealed vascular grafts. (28/5528)

OBJECTIVES: To assess the rifampicin binding and elution characteristics for three protein-sealed vascular grafts. DESIGN: In vitro study. MATERIALS: Cardial and Hemashield collagen-sealed and the DeBakey/Vasculour albumin-sealed vascular grafts. METHODS: The grafts were soaked in a 60,000 mg/l solution of rifampicin at 37 degrees C for 15 min. Bound drug was eluted from the grafts at 37 degrees C and at timed intervals the concentrations of rifampicin remaining in the grafts were determined. RESULTS: Although all three grafts contained high concentrations of rifampicin immediately after soaking these rapidly fell on washing and only a small fraction of the adsorbed rifampicin was tightly bound to the grafts. Rifampicin loading of this tightly bound fraction was similar for the two collagen-sealed grafts (1.7-2.0 mg/kg) but higher for the albumin-sealed graft (16.0 mg/kg). Elution of the tightly bound fraction appeared to follow first-order kinetics with elimination half-lives of 89-141 h. The concentrations of rifampicin remaining in the grafts after eight days were above those needed to inhibit sensitive staphylococci and were 0.7 mg/kg (collagen-sealed grafts) to 3.7 mg/kg (albumin-sealed graft). CONCLUSIONS: There is broad equivalence between the rifampicin binding and elution for the two collagen-sealed grafts, but there appears to be slightly higher binding for the albumin-sealed graft.  (+info)

Structural characterization, stability and fatty acid-binding properties of two French genetic variants of human serum albumin. (29/5528)

Four bisalbuminemic, unrelated persons were found in Bretagne, France, and their variant and normal albumins were isolated by DEAE ion exchange chromatography, reduced, carboxymethylated and treated with CNBr. Comparative two-dimensional electrophoresis of the CNBr digests showed that three of the variants were modified in fragment CB4, whereas the fourth had an abnormal fragment CB1. These fragments were isolated, digested with trypsin and mapped by reverse-phase HPLC. Sequencing of altered tryptic peptides showed that the three variants modified in CB4 were caused by the same, previously unreported, amino acid substitution: Asp314-->Val (albumin Brest). The fourth, however, was a proalbumin variant with the change Arg-2-->Cys (albumin Ildut). Both amino acid substitutions can be explained by point mutations in the structural gene: GAT-->GTT (albumin Brest) and CGT-->TGT (albumin Ildut). The proalbumin Ildut is very unstable and already in vivo it is to a large extent cleaved posttranslationally to Arg-Albumin and normal albumin. Furthermore, we observed that during a lengthy isolation procedure the remaining proalbumin was changed to Arg-Albumin or proalbumin lacking Arg-6. In addition, part of normal albumin had lost Asp1. Gas chromatographic investigations using isolated proteins indicated that albumin Brest has improved in vivo fatty acid-binding properties, whereas the structural modification(s) of albumin Ildut does not affect fatty acid binding.  (+info)

Active suppression in orally tolerized rats coincides with in situ transforming growth factor-beta (TGF-beta) expression in the draining lymph nodes. (30/5528)

Adult rats were fed pellets containing ovalbumin (OvA) during 4 weeks, and were 2 weeks thereafter immunized subcutaneously with a mixture of OvA and human serum albumin (HSA) in Freund's complete adjuvant (day 0). As a result of the immunization, the draining lymph nodes of the nontolerized (control) rats were heavily enlarged from day 10 to day 18; however, this size increase was absent in the OvA-fed rats. This manifestation of active suppression in the tolerized rats was preceded by the appearance of scattered CD4+ TGF-beta-expressing T cells in the T cell area of their lymph nodes (days 5-8); correspondingly, the levels of TGF-beta mRNA in the nodes were elevated in the tolerant rats compared with the control rats. The anti-OvA antibody levels in sera from the rats revealed that there was an initial B cell priming in the OvA-fed group, with levels higher than in the control group during the first week. Thereafter, suppression governed the response, and from day 10 onwards the anti-OvA levels were considerably lower than in the controls. When other groups of animals were pretreated with neutralizing anti-TGF-beta antibodies 1 day before the immunization, the anti-OvA response of the OvA-fed rats was restored to the levels of the control group, demonstrating the importance of TGF-beta in the maintenance of suppression. In conclusion, we demonstrate that TGF-beta-producing cells appear in the draining lymph nodes shortly after immunization in rats made orally tolerant using a relatively high-dose feeding regime; these cells are probably responsible for the down-regulation of the immune response observed in the OvA-fed rats.  (+info)

Phase I trial of methotrexate-albumin in a weekly intravenous bolus regimen in cancer patients. Phase I Study Group of the Association for Medical Oncology of the German Cancer Society. (31/5528)

Methotrexate-albumin conjugate (MTX-HSA) is a novel human albumin-based prodrug conjugate of methotrexate (MTX). A low MTX loading rate provided optimal tumor targeting and therapeutic efficacy during preclinical testing. The objectives of this first Phase I study of MTX-HSA were to determine dose-limiting toxicity (DLT) and maximum tolerated dose (MTD) in a weekly regimen. Seventeen cancer patients who were no longer amenable to standard treatment were enrolled and were evaluable for DLT. Up to eight injections were performed in weekly intervals. Dose escalation was as follows: 20, 40, 50, and then 60 mg/m2 MTX-HSA (based on the amount of MTX bound to albumin). Additional MTX-HSA courses were feasible in case of tumor response. DLT (mainly stomatitis, Common Toxicity Criteria grade 3) occurred, beginning at the 50 mg/m2 dose level after repeated administrations; in one case, thrombocytopenia was dose-limiting. Two events of DLT occurred at the 60 mg/m2 dose level within the first two administrations. Mild anemia, transaminitis, and one case of skin toxicity were found. No significant leukopenia, nausea, renal toxicity, or other toxicities were observed. MTX-HSA was well tolerated. Drug accumulation occurred on the weekly schedule. The half-life of the drug was estimated to be up to 3 weeks. Tumor responses were seen in three patients: (a) a partial response was seen in one patient with renal cell carcinoma (response duration, 30 months, ongoing); (b) a minor response was seen in one patient with pleural mesothelioma (response duration, 31 months, ongoing); and (c) a minor response was seen in one patient with renal cell carcinoma (response duration, 14 months until progression). Poststudy treatment was administered at 2-4-week intervals. No signs of toxicity or drug accumulation were seen. Altered pharmacological properties of MTX-HSA such as plasma half-life, tumor targeting, or intracellular metabolism might have contributed to these responses. The MTD for weekly administration was 4 x 50 mg/m2 MTX-HSA during short-term treatment. A regimen with MTX-HSA injections of 50 mg/m2 every 2 weeks was recommended for a further clinical Phase I study.  (+info)

Midazolam metabolism by modified Caco-2 monolayers: effects of extracellular protein binding. (32/5528)

It has been suggested that the binding of a drug to plasma proteins will influence the intestinal extraction efficiency when drug is delivered to the mucosal epithelium via either the gut lumen or vasculature. We evaluated this hypothesis using cytochrome P-450 (CYP)3A4-expressing Caco-2 monolayers as a model for the intestinal epithelial barrier and midazolam as a CYP3A-specific enzyme probe. The rate of 1'-hydroxylation was measured following apical or basolateral midazolam administration to monolayers incubated in the presence or absence of 4 g/dl of human serum albumin (HSA) in the basolateral compartment medium. The midazolam-free fraction in culture medium containing HSA was 3.3%. Inclusion of HSA in the basolateral medium decreased peak intracellular midazolam accumulation after an apical midazolam dose (3 microM) by 35% and reduced the 1'-hydroxymidazolam formation rate by approximately 20%. Because of the accelerated diffusion of midazolam through the cell monolayer and into the basolateral compartment, there was a 61% reduction in the first-pass metabolic extraction ratio: 13.3 +/- 0. 12% for control versus 5.2 +/- 1% with HSA. Compared with control, addition of HSA resulted in a 91% decrease in the peak intracellular midazolam level and a 86% decrease in the rate of 1'-hydroxylation after the administration of midazolam into basolateral medium. These findings suggest that, in vivo, binding of a drug to plasma proteins will impact both first-pass and systemic intestinal midazolam extraction efficiency. Furthermore, the effect will be more pronounced for a drug that is delivered to mucosal enterocytes by way of arterial blood, compared with oral drug delivery.  (+info)