Imaging cell interactions with native and crosslinked polyelectrolyte multilayers.

The adhesion of primary chondrocytes to polyelectrolyte multilayer films, made of poly(l-lysine) (PLL) and hyaluronan (HA), was investigated for native and crosslinked films, either ending by PLL or HA. Crosslinking the film was achieved by means of a water-soluble carbodiimide in combination with N-hydroxysulfosuccinimide. The adhesion of macrophages and primary chondrocytes was investigated by microscopical techniques (optical, confocal, and atomic), providing useful information on the cell/film interface.

Evolution of liver antioxidant status and iron implication during the development of deoxycorticosterone-saline hypertension in rats.

Hypertension is known to be associated with an oxidative stress resulting from an imbalance of antioxidant defense mechanisms in various tissues. The purpose of this study was to investigate the relationship between the increase of arterial blood pressure, measured during the gradual development of experimental hypertension in deoxycorticosterone (DOCA)-salt-treated rats, and an early imbalance of liver antioxidant status. The levels of liver oxidant/antioxidant markers and iron were studied during the induction of hypertension in 3-, 6-, and 8-wk DOCA-salt-treated Sprague-Dawley rats.

Characterization of exopolysaccharides produced by cyanobacteria isolated from Polynesian microbial mats.

Six cyanobacterial isolates recovered from Polynesian microbial mats, called "kopara," were cultured using laboratory-closed photobioreactors and were shown to produce exopolymers as released and capsular exopolysaccharides (EPS). These polymers have been chemically characterized using colorimetric and elemental assays, infrared spectrometry, and gas chromatography. Both capsular and released EPS consisted of 7 to 10 different monosaccharides with neutral sugars predominating.

Experimental models of acute and chronic liver failure in nude mice to study hepatocyte transplantation.

Although hepatocyte transplantation is a promising therapy for acute liver failure in human, there is still a lack of animal models suffering from hepatic injury in which the benefits of hepatocyte transplantation could be evaluated solely, without the bias caused by immunosuppression. As a consequence, the aim of the study was first to develop reproducible models of partial hepatectomy and of thioacetamide (TA)- or Jo2-induced acute liver failure in nude mice. Chronic liver disease was also investigated by repeated injections of sublethal doses of thioacetamide.

Fourth meeting of the European Network of Research Tissue Banks - future strategy to increase collaborations in the supply of human tissue for biomedical research.

This report records the Fourth meeting of the European Network of Research Tissue Bank (Brussels, 18th March 2004) which was attended by Mel Read MEP. The existing membership of this informal group represents European Human Research Tissue Bankers, biomedical researchers seeking access to human tissue and allied groups including animal welfare representatives. This Fourth meeting provided a forum to update members on individual activity in this area.

Association mechanism between a series of rodenticide and humic acid: a frontal analysis to support the biological data.

The binding constants (K) of a series of anticoagulant rodenticides with the main soil organic component, humic acid (HA), were determined using frontal analysis approach. The order of the binding constants was identical as the one obtained in a previous paper [J. Chromatogr.

Comparison of clearance predictions using primary cultures and suspensions of human hepatocytes.

Various incubation conditions of human hepatocytes were compared for their accuracy in predicting the in vivo hepatic clearance (CL(H)) of model compounds. The test compounds were the highly cleared, low protein bound naloxone (in vivo CL(H) = 25 ml min(-1) kg(-1); free fraction = 0.6), the medium clearance, highly protein bound midazolam (CL(H) = 12 ml min(-1) kg(-1); free fraction = 0.

Degradability of polysaccharides multilayer films in the oral environment: an in vitro and in vivo study.

Biomedical devices and modified biomaterial surfaces constitute an expanding research domain in the dental field. However, such oral applications have to face a very particular environment containing specific physiological conditions and specific enzymes. To evaluate their suitability in the development of novel oral applications, the degradability of polyelectrolyte multilayer films made of the natural polysaccharides chitosan and hyaluronan (CHI/HA) was investigated in vitro and in vivo in a rat mouth model.

Layer by layer buildup of polysaccharide films: physical chemistry and cellular adhesion aspects.

The formation ofpolysaccharide films based on the alternate deposition of chitosan (CHI) and hyaluronan (HA) was investigated by several techniques. The multilayer buildup takes place in two stages: during the first stage, the surface is covered by isolated islets that grow and coalesce as the construction goes on. After several deposition steps, a continuous film is formed and the second stage of the buildup process takes place.

Polyelectrolyte multilayers functionalized by a synthetic analogue of an anti-inflammatory peptide, alpha-MSH, for coating a tracheal prosthesis.

Polyelectrolyte multilayer films made of poly (L-lysine) (PLL) and poly (L-glutamic acid) (PGA) have been functionalized by covalent binding of a synthetic analogue of the anti-inflammatory peptide, alpha-melanocyte-stimulating hormone (alpha-MSH) to PGA to create biologically active coatings for tracheal prostheses. The morphology and in vivo stability of the films were investigated by atomic force microscopy and confocal laser scanning microscopy, respectively. For the in vivo evaluation, 87 rats were implanted and examined for a period superior to 3 months.

Synthesis of 4-hydroxycoumarin and 2,4-quinolinediol derivatives and evaluation of their effects on the viability of HepG2 cells and human hepatocytes culture.

We report here the synthesis of aromatic coumarins and aromatic alpha-quinolones which were evaluated in vitro for their protective potentialities against tert-butyl hydroperoxide (t-BHP)-induced oxidative damage on human liver cell death, i.e., human hepatoma HepG2 cell line and human hepatocytes in primary culture.

Impact of serum on clearance predictions obtained from suspensions and primary cultures of rat hepatocytes.

The objective of the present study was to compare two configurations of the hepatocyte model namely suspensions (SH) and conventional primary cultures (CPC) for their ability to predict the hepatic clearance in vivo in the rat and, to investigate the impact of serum on the prediction accuracy. The metabolic competences of several cytochrome P450 isoenzymes were investigated both in CPC and SH in the presence or absence of serum. Under the same conditions, the in vitro intrinsic clearance of six test compounds metabolised by a variety of phase I and phase II enzymes (antipyrine, RO-X, mibefradil, midazolam, naloxone and oxazepam) were derived from Vmax/Km scaled up to the corresponding in vivo hepatic metabolic clearance.

[Inpatient treatment costs of skin diseases. Diagnosis-based cost calculation in a university dermatology clinic].

Background And Objective: With the advent of the DRG system, German hospitals are being forced to improve cost transparency and to uncover inefficient structures.

Methods: Diagnosis-based costs were calculated in the Department of Dermatology in the University Hospital of Freiburg for ten samples, each containing 20 cases. By using in-patient files, cost and productivity information for the fiscal year 2000 was attributed to each single case in a bottom-up-approach.

A novel exopolymer-producing bacterium, Paracoccus zeaxanthinifaciens subsp. payriae, isolated from a "kopara" mat located in Rangiroa, an atoll of French Polynesia.

An aerobic, mesophilic and heterotrophic marine bacterium designated RA19, able to produce two different exocellular polymers and zeaxanthin, was isolated from a French polynesian bacterial mat (localy named "kopara") situated in the atoll of Rangiroa. This microorganism, on the basis of its phenotypical features and the genotypic investigations, can be clearly assigned to the Parococcus zeaxanthinifaciens species and the name Parococcus zeaxanthinifaciens subsp. payriae is proposed.

Isolation and culture of primary human hepatocytes.

As our knowledge of the species differences in drug metabolism and drug-induced hepatotoxicity has expanded significantly, the need for human-relevant in vitro hepatic model systems has become more apparent than ever before. Human hepatocytes have become the "gold standard" for evaluating hepatic metabolism and toxicity of drugs and other xenobiotics in vitro. In addition, they are becoming utilized more extensively for many kinds of biomedical research, including a variety of biological, pharmacological, and toxicological studies.

Elasticity of native and cross-linked polyelectrolyte multilayer films.

Mechanical properties of polyelectrolyte multilayer films were studied by nanoindentation using the atomic force microscope (AFM). Force-distance measurements using colloidal probe tips were systematically obtained for supported films of poly(L-lysine) and hyaluronan that are suited to bio-application. Both native and covalently cross-linked films were studied as a function of increasing layer number, which increases film thickness.

Tissue collection, transport and isolation procedures required to optimize human hepatocyte isolation from waste liver surgical resections. A multilaboratory study.

Background: The European Center for Validation of Alternative Methods (ECVAM) has funded a prevalidation study in three laboratories (France, USA and UK) on the use of human hepatocyte cultures to predict cytochrome P-450 induction.

Aims And Methods: As first stage of this prevalidation study, the purpose of the present work was to set criteria for optimization and harmonization of hepatocyte isolation from human tissue among laboratories to establish a routine procedure. This was achieved by combining and/or comparing the data generated by the two independent European laboratories (France and UK).

The establishment of a network of European human research tissue banks.

This is a report of a workshop held on the establishment of human research tissue banking which was held in Levi, Finland 21-24 March 2002. There were 21 participants from 7 European countries. This meeting was attended by representatives from academia, research tissue banks and from the Biotech and Pharmaceutical Industries.

Influence of pre-, intra- and post-operative parameters of donor liver on the outcome of isolated human hepatocytes.

The aim of the present study was to analyse, retrospectively on a large panel of patients (149), the influence of the donor liver characteristics on the outcome of human hepatocyte isolation obtained from resected liver biopsies from surgical waste after hepatectomy. Among the pre-operative parameters, the type of disease, age and sex of the patient, previous chemotherapy, alcohol or tobacco consumption did not affect the yield, viability, attachment rate and function of the isolated human hepatocytes. Pre-operative biological and anatomopathological data indicated that, while mild steatosis (10% steatotic hepatocytes) tended to decrease hepatocyte yield.

Qualitative and quantitative assessment of drug-drug interaction potential in man, based on Ki, IC50 and inhibitor concentration.

Strategies used to screen new drug entities as potential inhibitors of CYP450 enzymes are now widely used to select candidates in the drug discovery process. However, the information obtained based on IC50 values are usually more of qualitative nature. The aim of this study was to find out whether a more quantitative assessment of interaction potential could be achieved on the basis of the ratio I/Ki (I corresponds to inhibitor concentration).

Improvement of stability and cell adhesion properties of polyelectrolyte multilayer films by chemical cross-linking.

Poly(L-lysine)/hyaluronan (PLL/HA) films were chemically cross-linked with a water soluble carbodiimide (EDC) in combination with a N-hydroxysulfo-succinimide (NHS) to induce amide formation. Fourier transform infrared spectroscopy confirms the conversion of carboxylate and ammonium groups into amide bonds. Quartz crystal microbalance-dissipation reveals that the cross linking reaction is accompanied by a change in the viscoelastic properties of the films leading to more rigid films.

How could aortic arginase activity enhancement be involved in DOCA-salt hypertension?

This study was to examine whether the increase in aortic arginase activity observed in DOCA-salt hypertensive rats is involved in the mechanism of physiological hypertension by participating to vessel hypertrophy and/or to the impairment of endothelium-dependent relaxation to acethylcholine. We measured polyamine content and relaxation-response to acethylcholine in aortic rings isolated from control and DOCA-salt treated Sprague-Dawley rats after in vitro modification of arginase activity. Polyamine content was significantly increased in aorta from DOCA-salt hypertensive rats compared with controls.

Opposite effect of methionine-supplemented diet, a model of hyperhomocysteinemia, on plasma and liver antioxidant status in normotensive and spontaneously hypertensive rats.

Hyperhomocysteinemia is often associated with an increase in blood pressure. However our previous study has shown that methionine supplementation induced an increase in blood pressure in Wistar-Kyoto (WKY) rats and a decrease in blood pressure in spontaneously hypertensive rats (SHR) with significant differences in plasma homocysteine (Hcy) metabolites levels. Previously liver antioxidant status has been shown to be decreased in SHR compared to WKY rats.

Antioxidant status in the liver of hypertensive and metallothionein-deficient mice.

Because oxidative stress is involved in arterial hypertension, impairment of hepatic antioxidant defences could develop in the course of this disease. Metallothionein (MT), an antioxidant protein, is present in high rates in the liver. The aim of this study was to investigate the effect of a mineralocorticoid-salt treatment on blood pressure, hepatic antioxidant enzyme activities, and cardiac MT levels in transgenic MT null mice compared with control mice to further clarify the role of MT during the experimental development of arterial hypertension.

3-D surface charges modulate protrusive and contractile contacts of chondrosarcoma cells.

Up to now, most of the studies addressing the critical roles played by protrusive and contractile cell-matrix contacts in cell adhesion, guidance, migration, matrix assembly, and activation of signaling molecules have been performed on two-dimensional surfaces. Here, we analysed the organization of chondrosarcoma cell contacts in a new three-dimensional environment made of titanium beads. Surface charges were modified by deposition of polyelectrolyte multilayer films built up by alternated polycations poly-(L-lysine) or poly(allylamine hydrochloride) and polyanions poly-(L-glutamic acid) or poly(sodium 4-styrenesulfonate).