A useful and easy to develop combined stress test for myocardial perfusion imaging: Regadenoson and isometric exercise, preliminary results.

BACKGROUND: Regadenoson, a selective A2a receptor agonist, is a vasodilator increasingly used in myocardial perfusion imaging. Adjunction of isometric exercise is a simple method that could improve side effect profile while providing better image quality. METHODS: Patients undergoing SPECT MPI were prospectively enrolled in handgrip-Regadenoson (HG-Reg test, N = 20) and Regadenoson (Reg) stress test (N = 40). Investigator blinded to stress test analyzed clinical data and images. RESULTS: Heart rate (HR) increase was statistically higher in the HG-Reg group (27 vs 22 bpm, P = .019). Decrease in SBP was less frequent in the HG-Reg group than in the Reg group (55% vs 85.5%, P = .005), there were less drops >10 mmHg (45% vs 77.7%, P = .012). During stress testing, fewer subjects reported at least one side effect in the HG-Reg compared to Reg group (70% vs 92.5%, P = .021). Images were more often classified as good in the HG-Reg group (75% vs 52.5% in the Reg group, P = .25). CONCLUSIONS: Adjunction of handgrip exercise to Regadenoson administration is a well-tolerated and easy method, without loss of time. Furthermore, image quality seems to be better.

Comparison of the Antimicrobial Properties of Silver Impregnated Vascular Grafts with and without Triclosan.

OBJECTIVES: The aim was to compare the antimicrobial efficacy of the silver impregnated collagen coated polyester vascular graft (IGS) with an identical graft combining silver and triclosan (IGSy). METHODS: This was an in vitro study. A non-antimicrobial collagen polyester vascular graft served as control (IG). The IG, IGS, and IGSy grafts were contaminated separately with inoculates of each of the following micro-organisms: Staphylococcus epidermidis (SE), methicillin resistant Staphylococcus aureus (MRSA), and Escherichia coli producing extended spectrum beta-lactamase (ESBL-EC) or Candida albicans (CA). MRSA, ESBL-EC, and CA were obtained from retrieved infected grafts. The in vitro antimicrobial efficacies of the contaminated grafts were evaluated by time to kill assays over a 24 hour period in accordance with CLSI Guideline M26-A. All assays were repeated six times. Bacterial survival numbers were obtained at 1, 4, 8, and 24 hours using a standard plate count procedure. Bactericidal activity was defined as a 3 log10 reduction factor (logRF). To calculate the overall difference in the mean log10 CFU/mL within 24 hours, a one way ANOVA with a Bonferroni correction was calculated separately for each graft. RESULTS: The IG graft showed an increase in the number of viable organisms for the four strains tested. IGSy offered better antimicrobial properties than IGS for both ESBL-EC and MRSA, since only the IGSy graft achieved > 3 logRF and fulfilled the standard criteria for bactericidal activity at 24 hours with 3.78 and 4.08 logRF, respectively. For samples inoculated with SE and CA, both antimicrobial grafts achieved 24 hour bactericidal activity with > 3 logRF. However, for CA the one-way ANOVA analysis demonstrated that the IGSy graft performed differently in terms of speed of antimicrobial action, appearing more active as early as 4 hours following inoculation (p = .007). CONCLUSION: In the in vitro conditions, the Synergy vascular graft combining silver with triclosan demonstrated better short-term antimicrobial activity than the silver graft for all micro-organisms tested.

Carbon nanotubes have a deleterious effect on the nose: the first in vitro data.

BACKGROUND: The information currently available concerning carbon nanotubes toxicity is disturbing and conflicting. Moreover, little is known about their effect on the nasal cavities, which are the first target for nanoparticles. MATERIAL AND METHOD: We investigated the cytotoxicity (50 to 0.5 microg/mL) of double-walled carbon nanotube with two independent tests (MTT, Wst-1) on normal human nasal epithelial cells after 12-day exposure (control untreated nasal cells and A549). Nasal cell differentiation function, oxidative stress, the morphological features of cells in contact with DWCNTs and the localizations of the latter were also investigated. RESULTS: Exposure revealed a dose-dependent decrease in cell metabolic activity and cell growth. In nearly all conditions, normal human nasal epithelial cells were more sensitive than malignant ones. Even with both tests, the cytotoxic threshold dose could not be accurately determined because of dye adsorption by DWCNTs. Nasal cells showed stronger cytokeratin 7 and persistent UEA-I immunostaining. Cytokeratin 19 production was increased at 25 microg/mL and mucus production was stimulated from 0.5 microg/mL. A significant increase in Reactive Oxygen Species was observed from 25 microg/mL. The cell plasma membrane showed several holes and DWCNTs were present in the cytoplasm. CONCLUSION: DWCNTs seem to have a deleterious effect on nasal cells after 12-day exposure.

Comparison of perfused volume segmentation between cone-beam CT and 99mTc-MAA SPECT/CT for treatment dosimetry before selective internal radiation therapy using 90Y-glass microspheres.

PURPOSE: To compare the reliability and accuracy of the pre-treatment dosimetry predictions using cone-beam computed tomography (CBCT) versus 99mTc-labeled macroaggregated albumin (MAA) SPECT/CT for perfused volume segmentation in patients with hepatocellular carcinoma treated by selective internal radiation therapy (SIRT) using 90Y-glass microspheres. MATERIALS AND METHODS: Fifteen patients (8 men, 7 women) with a mean age of 68.3±10.5 (SD) years (range: 47-82 years) who underwent a total of 17 SIRT procedures using 90Y-glass microspheres for unresectable hepatocellular carcinoma were retrospectively included. Pre-treatment dosimetry data were calculated from 99mTc-MAA SPECT/CT using either CBCT or 99mTc-MAA SPECT/CT to segment the perfused volumes. Post-treatment dosimetry data were calculated using 90Y imaging (SPECT/CT or PET/CT). The whole liver, non-tumoral liver, and tumor volumes were segmented on CT or MRI data. The mean absorbed doses of the tumor (DT), non-tumoral liver, perfused liver (DPL) and perfused non-tumoral liver were calculated. Intra- and interobserver reliabilities were investigated by calculating Lin's concordant correlation coefficients (ρc values). The differences (biases) between pre- and post-treatment dosimetry data were assessed using the modified Bland-Altman method (for non-normally distributed variables), and systematic bias was evaluated using Passing-Bablok regression. RESULTS: The intra- and interobserver reliabilities were good-to-excellent (ρc: 0.80-0.99) for all measures using both methods. Compared with 90Y imaging, the median differences were 5.8Gy (IQR: -12.7; 16.1) and 5.6Gy (IQR: -13.6; 10.2) for DPL-CBCT and DPL-99mTc-MAA SPECT/CT, respectively. The median differences were 1.6Gy (IQR: -29; 7.53) and 9.8Gy (IQR: -28.4; 19.9) for DT-CBCT and DT-99mTc-MAA SPECT/CT respectively. Passing-Bablok regression analysis showed that both CBCT and 99mTc-MAA SPECT/CT had proportional biases and thus tendencies to overestimate DT and DPL at higher post-treatment doses. CONCLUSION: CBCT may be a reliable segmentation method, but it does not significantly increase the accuracy of dose prediction compared with that of 99mTc-MAA SPECT/CT. At higher doses both methods tend to overestimate the doses to tumors and perfused livers.

Salvage treatment for venous aneurysm complicating vascular access arteriovenous fistula: use of an exoprosthesis to reinforce the vein after aneurysmorrhaphy.

OBJECTIVES: We report a new salvage technique for treating venous aneurysms (VAs) complicating vascular access arteriovenous fistula (AVF) using externally reinforced venous aneurysmorrhaphy. DESIGN: A retrospective study over a 20-month period from a single centre. PATIENTS: Patients presenting to the vascular surgery department, Bordeaux University Hospital for revision of a vascular access AVF were included. METHODS: Reinforced venous aneurysmorrhaphy consisted in removal of redundant vessel wall followed by reinforcement using an external prosthetic graft. Patency, diameter and flow were assessed by duplex ultrasound at 1, 6 and 12 months after salvage. RESULTS: Thirty-eight eligible patients were identified. Five were excluded because VA was associated with central vein stenosis; the remaining 33 underwent salvage. Indications were rapidly expanding or painful VA in seven cases; VA with frequent bleeding or damaged overlying skin in eight; VA in close relation to a stenosis in two; and VA associated with high-flow rate in 16. Cannulation was attempted after 30 days. Mean follow-up time was 12 S.D. 5 months (range: 4-22). Two repaired AVFs failed. Primary 1-year patency was 93%. No aneurysm or infection occurred. Reduction of high flow was successful in 12 of 16 patients. The remaining four required re-operation. CONCLUSIONS: Reinforced venous aneurysmorrhaphy is effective in controlling venous dilation and achieving patency. Reduction of high-flow rates was not always achieved. Further study is needed to evaluate long-term efficacy of this treatment.

[Erythropoietin: indications and measurement]. / Erythropoïétine : Quand la prescrire ? Pourquoi et comment la doser ?

Erythropoietin (EPO) is the principal haematopoietic growth factor of the red blood cell line. Its major role is to stimulate the red blood cell production. EPO synthesis by peritubular cells in the kidney is regulated by oxygen concentration and must lead adaptation of the organism to face many different physiological situations. An imbalance can lead either to anaemia or polycythemia. Synthetic EPO, so-called recombinant, has definitively changed the treatment in the anaemia of chronic renal failure and regularly find new indications, legal (anaemia of cancer, anaemia of chronic inflammatory syndromes, myelodysplastic syndromes, neurology, cardiology...) or illegal (doping substance in sport). This article reviews the physiology, the role and the indications of EPO in clinical routine practice and define why and how EPO should be measured. We also focus on the analytical requirements for serum EPO concentration determination, especially in the differential diagnosis of polycythemias (secondary polycythemia/Polycythemia Vera).

Thyroid and gastric autoimmune diseases.

OBJECTIVES: Autoimmune thyroid disease (AITD) is frequently accompanied by other organ-specific diseases. We investigated the frequency of the association AITD-Biermer's disease (BD) in patients with AITD by investigating the prevalence of intrinsic factor antibodies (IF-Ab). DESIGN AND METHODS: Sera from 113 patients with AITD (hypo- or hyperthyroidism) were screened for the presence of type I IF-Ab with a competitive automated immunoassay based. Matched sera from 113 patients with dysthyroidism (not AITD) were tested. RESULTS: Four IF-Ab positive patients suffered from AITD. BD was known for two of them and strongly suspected in the two others. All patients with no AITD tested IF-Ab negative. B12 levels were often low whatever the etiology. CONCLUSION: The prevalence of IF-AbI is higher (3.5%) in patients with AITD. Prospective studies should investigate whether correcting thyroid dysfunction improves vitamin B12 levels, and establish whether routine screening for gastric autoimmunity is clinically useful or purely academic.

Self-crosslinked fibrous collagen/chitosan blends: Processing, properties evaluation and monitoring of degradation by bi-fluorescence imaging.

Porous collagen/chitosan scaffolds with different Collagen:Chitosan (Coll:Ch) ratios were prepared by freeze-drying followed by self-crosslinking via dehydrothermal treatment (DHT) and characterized as biomaterials for tissue engineering. Cy7 and Cy5.5 fluorochromes were covalently grafted to collagen and chitosan, respectively. Thus, it was possible, using optical fluorescence imaging of the two fluorochromes, to simultaneously track their in vivo biodegradation, in a blend scaffold form. The fluorescence signal evolution, due to the bioresorption, corroborated with histological analysis. In vitro cytocompatibility of Coll:Ch blend scaffolds were evaluated with standardized tests. In addition, the scaffolds showed a highly interconnected porous structure. Extent of crosslinking was analyzed by convergent analysis using thermogravimetry, Fourier Transform Infrared Spectroscopy and PBS uptake. The variations observed with these techniques indicate strong interactions between collagen and chitosan (covalent and hydrogen bonds) promoted by the DHT. The mechanical properties were characterized to elucidate the impact of the different processing steps in the sample preparation (DHT, neutralization and sterilization by ß-irradiation) and showed a robust processing scheme with low impact of Coll:Ch composition ratio.

Interaction between human umbilical vein endothelial cells and human osteoprogenitors triggers pleiotropic effect that may support osteoblastic function.

Osteogenesis occurs in striking interaction with angiogenesis. There is growing evidence that endothelial cells are involved in the modulation of osteoblast differentiation. We hypothesized that primary human umbilical vein endothelial cells (HUVEC) should be able to modulate primary human osteoprogenitors (HOP) function in an in vitro co-culture model. In a previous study we demonstrated that a 3 day to 3 week co-culture stimulates HOP differentiation markers such as Alkaline Phosphatase (ALP) activity and mineralization. In the present study we addressed the effects induced by the co-culture on HOP within the first 48 hours. As a prerequisite, we validated a method based on immuno-magnetic beads to separate HOP from HUVEC after co-culture. Reverse transcription-real time quantitative PCR studies demonstrated up-regulation of the ALP expression in the co-cultured HOP, confirming previous results. Surprisingly, down-regulation of runx2 and osteocalcin was also shown. Western blot analysis revealed co-culture induced down-regulation of Connexin43 expression in both cell types. Connexin43 function may be altered in co-cultured HOP as well. Stimulation of the cAMP pathway was able to counterbalance the effect of the co-culture on the ALP activity, but was not able to rescue runx2 mRNA level. Co-culture effect on HOP transcriptome was analyzed with GEArray cDNA microarray showing endothelial cells may also modulate HOP extracellular matrix production. In accordance with previous work, we propose endothelial cells may support initial osteoblastic proliferation but do not alter the ability of the osteoblasts to produce extracellular mineralizing matrix.

Effect of laser modified surface microtopochemistry on endothelial cell growth.

The introduction of microelectronics technology in the area of biological sciences has brought forth previously unforeseeable applications such as DNA or protein biochips, miniaturized, multiparametric biosensors for high performance multianalyte assays, DNA sequencing, biocomputers, and substrates for controlled cell growth (i.e. tissue engineering). We developed and investigated a new method using "cold" excimer laser beam technology combined with microlithographical techniques to create surfaces with well defined 3D microdomains in order to delineate critical microscopic surface features governing cell-material interactions. Microfabricated surfaces with microgrooves 30-3 microm deep, 10 - 1 microm wide spaced 30 microm apart were obtained with micron resolution, by "microsculpturing" polymer model surfaces using a computer controlled laser KrF excimer beam coupled with a microlithographic projection technique. The laser beam after exiting a mask was focused onto the polymer target surface via an optical setup allowing for a 10-fold reduction of the mask pattern. Various 3D micropatterned features were obtained at the micron level. Reproducible submicron features could also be obtained using this method. Subsequently, model human umbilical endothelial cells (HUVEC) were cultured on the laser microfabricated surfaces in order to study the effects of specific microscopic surface features on cell deposition and orientation. Cell deposition patterns were found to be microstructure dependant, and showed cell orientation dependency for features in the cell range dimension, a behaviour significantly different from that of a previously studied cell model (osteoprogenitor cell). This model may be a promising in so far as it is very rapid (a time frame less than a second per square centimeter of micropatterned surface) and provides further insights into the effects of surface microtopography on cell response with possible applications in the field of biosensors, biomedical and/or pharmaceutical engineering sciences.

[About a case of congenital hypothyroidism]. / A propos d'un cas d'hypothyroïdie congénitale.

A boy presented at birth dyspnea, jaundice, meteorism and hypospadias; biochemical testing revealed hyponatremia. He benefited on day 4 of neonatal screening for hypothyroidism and congenital adrenal hyperplasia (CAH) and assays showed high concentrations of 17-OHP and TSH. Because of clinical features and hyponatremia, the diagnosis of CAH was plausible. A serum control (17-OHP and TSH) carried out on day 8 showed a normal concentration of 17-OHP and a persistently elevated concentration of TSH confirmed by a second assay a few days later. A 131I scan of neck revealed an ectopic lingual thyroid. The considerable progression of false positive screening tests for CAH is mainly due to the increasing number of premature babies. We show by a retrospective analysis (7 yrs), that children with hypothyroidism also present frequently higher concentrations of 17-OHP than normal children. However, whatever the aetiology (apart from CAH), the concentrations of 17-OHP rapidly normalise.

Chitosan-based hydrogels for developing a small-diameter vascular graft: in vitro and in vivo evaluation.

AIMS: Vascular grafts made of synthetic polymers perform poorly in small-diameter applications (cardiac and peripheral bypass). Chitosan is a biocompatible natural polymer that can provide a novel biological scaffold for tissue engineering development. The goal of this study was to demonstrate the biocompatibility of a novel chitosan preparation in vitro and in vivo, and to assess its potential as a scaffold for vascular applications. METHODS AND RESULTS: A series of experiments of increasing complexity, ranging from in vitro biocompatibility and hemocompatibility tests to in vivo studies in small and large animals (rats and sheep), was performed to provide a comprehensive analysis of chitosan hydrogels' biological properties. In vitro studies established that: (i) chitosan supported human endothelial progenitor cells adhesion, proliferation and resistance to physiological shear stress; (ii) chitosan did not activate platelets, the complement system, or the intrinsic coagulation pathway. In vivo results showed: (iii) no resorption of chitosan and no chronic inflammation at 60 days in a rat heterotopic implantation model (magnetic resonance imaging and histology); (iv) no flow obstruction (Doppler ultrasound) and no thrombus formation (histology and scanning electron microscopy) at 2 h after a carotid arteriotomy repair with chitosan patches in sheep. Finally, two chitosan tubes were implanted as carotid interposition grafts for 3 days in sheep showing that chitosan was strong enough to be sutured, to withstand arterial pressure, and no flow obstruction was observed through this short period. CONCLUSION: Chitosan-based hydrogels displayed promising in vitro biocompatibility and hemocompatibility properties as well as in vivo short-term performance.

Functionalization of biomaterials and cell to cell communication.

In the field of osseous substitution, the possibilities being offered to the surgeons prove sometimes difficult to apply in particular in the case of great losses of osseous substance. For these reasons, it is necessary to develop innovative techniques to satisfy the request increasing for substitutes and to see appearing on the market solutions combining availability, perenniality and biosecurity of the implants. The implantation of stem cells in a biomaterial opens a way of development of therapeutic substitute. Moreover, in order to optimize the rehabitation of the biomaterials by the cells and the host tissues, the second approach consists in modifying the surface of materials by the coating or the grafting of adhesive factors in order to stimulate their colonization. At least, one cannot consider a tissue mechanism of repair without a better knowledge of the respective role of the various cell populations implied in the rebuilding of this tissue and their cell to cell communication processes.

In vitro endothelialized ePTFE prostheses: clinical update 20 years after the first realization.

The replacement of arteries with synthetic vascular prostheses often leads to failure when small-diameter or low-flow locations are concerned, due in part to the thrombogenicity of the graft surface. In order to improve long-term patency of these grafts, the concept of endothelial cell seeding has been suggested, the composite structure resulting from the combination of biologically active cells to prosthetic materials thus creating more biocompatible vascular substitutes. To achieve endothelialization of synthetic grafts, previous efforts aimed at "one-stage" procedure in the 1980's seemed clinically feasible but results of reported clinical trials were controversial and mostly disappointing. An alternative method is an in vitro complete and preformed endothelial lining at the time of implantation: the "two-stage" procedure which implies harvest and culture of autologous endothelial cells. Up to date, the latter approach demonstrated its superiority in terms of significantly increased patency of the grafts that underwent endothelialization several years earlier.

[Thyroglobulin mRNA detection in the follow-up of thyroid carcinomas]. / Détection des ARNm circulants de la thyroglobuline et surveillance des cancers thyroïdiens: revue de la littérature.

The follow-up of differentiated carcinomas is based on the detection of thyroglobulin (Tg) in the serum. Tg assays are immunoassays that may be hampered by autoantibodies directed against Tg. To avoid this problem some authors advocated the use of mRNA extraction and RT-PCR amplification. Quantitative methods have been developed to achieve a good analytical sensitivity. These techniques may then be alternative to the Tg assay when anti-Tg antibodies are present in the serum should it be proven they display pronostic values reliable enough for clinical diagnosis use.

Nasal irrigation: From empiricism to evidence-based medicine. A review.

Nasal irrigation plays a non-negligible role in the treatment of numerous sinonasal pathologies and postoperative care. There is, however, a wide variety of protocols. The present review of the evidence-based literature sought objective arguments for optimization and efficacy. It emerged that large-volume low-pressure nasal douche optimizes the distribution and cleansing power of the irrigation solution in the nasal cavity. Ionic composition and pH also influence mucociliary clearance and epithelium trophicity. Seawater is less rich in sodium ions and richer in bicarbonates, potassium, calcium and magnesium than is isotonic normal saline, while alkaline pH and elevated calcium concentration optimized ciliary motility in vitro. Bicarbonates reduce secretion viscosity. Potassium and magnesium promote healing and limit local inflammation. These results show that the efficacy of nasal irrigation is multifactorial. Large-volume low-pressure nasal irrigation using undiluted seawater seems, in the present state of knowledge, to be the most effective protocol.

A novel potential application for 99mTc-HMPAO: endothelial cell labeling for in vitro investigation of cell-biomaterial interactions.

UNLABELLED: Good adherence of endothelial cells (ECs) seeded on vascular prostheses and cell retention under flow conditions are important factors to consider in the use of functionalized prostheses in vascular surgery. Because 111In-oxine radiolabeling presents disadvantages, we wondered whether, because of its well-known physical properties, 99mTc-hexamethyl propyleneamine oxime (HMPAO or exametazime) could be used. METHODS: The cytotoxicity of unlabeled HMPAO and 99mTc-HMPAO at increasing concentrations and activities was tested on monolayers of the EC line EA-hy-926. The influence of temperature and time on tracer incorporation into cells was also tested. The optimal labeling conditions were applied to evaluate the retention of ECs seeded on polyester grafts under flow conditions by gamma camera detection. RESULTS: The activity of 10 MBq/10(6) cells corresponding to 4.5 microg/10(6) cells of unlabeled HMPAO, applied for 3 h at 37 degrees C (cellular uptake = 18%), was the best compromise between the maintenance of cell viability and metabolic activity and efficient detection by the gamma camera. Spontaneous leakage was observed and analyzed by high-performance liquid chromatography. A cell loss of 13% after 180-min exposure to shear stress was obtained. CONCLUSION: Our data thus indicate the feasibility of using such a radiolabeling technique to investigate EC-biomaterial interactions.

Functional upregulation of granulocytes labeled with technetium-99m-HMPAO and indium-111-oxinate.

UNLABELLED: Indium-111-oxinate-labeled granulocytes have been used in vivo for several years for the detection of abscesses. Technetium-99-m-hexamethylpropyleneamine oxime (99mTc-HMPAO) labeling has more recently been described. METHODS: The influence of radiolabeling by both radiotracers on adhesion glycoprotein CD11b quantification was studied in quiescent and formyl-methionylleucylphenylalanine (fMLP)-activated neutrophils (PMN). Adhesion was assessed on human umbilical endothelial cells (HUVEC) as well as the repercussion of the granulocyte labeling on HUVEC viability (neutral red) and metabolic activity (MTT). Chemotaxis of PMN was evaluated by measuring migration under agarose with fMLP as chemoattractant. We also measured phagocytosis and the production of hydrogen peroxide induced by staphylococcus aureus. RESULTS: Whereas whole functional integrity is maintained after labeling, most of the functions (CD11b expression, adhesion, HUVEC metabolic activity) are up-regulated while chemotaxis is decreased in the presence of both radiotracers. Indium-111-oxinate induces larger alterations than 99mTc-HMPAO. CONCLUSION: These data were obtained in normal volunteers. In patients, alterations due to the in vitro labeling procedure, in addition to potential functional alterations caused by the underlying pathology, should be taken into account during image interpretation.

Evaluation of an in vitro endothelialized vascular graft under pulsatile shear stress with a novel radiolabeling procedure.

OBJECTIVE: To improve the hemocompatibility of vascular grafts, endothelial cell (EC) seeding of biomaterials prior to implantation is critical. The current in vitro study was designed to investigate such a feasibility on a collagen-coated heparin-bonded graft and to evaluate cell detachment upon pulsatile shear stress. MATERIALS AND METHODS: Endothelial cells (EA-hy-926) were seeded onto grafts. The endothelialization of the grafts was evaluated by the [3H]-thymidine incorporation, scanning electron microscopy (SEM) and histological examinations. After in situ EC radiolabeling with a novel 99mTc technique, the prostheses were exposed to pulsatile shear stress (0.27 N/m2), mimicking the shear rate occurring in a superficial femoral artery, for 3 h in a flow circuit and EC loss quantified by gamma camera detection. RESULTS: Complete EC coverage was achieved after 5 days. Three hours of artificial perfusion resulted in a low EC loss (12.9+/-0.8%, n = 7). SEM shows EC withstanding shear stress in valleys of prosthesis circumvolutions. CONCLUSIONS: These satisfactory results could be explained by the high affinity of EC for heparinized surfaces in addition to cell surface receptors involved in adhesion to collagen.

Biocompatibility of carbon-carbon materials: blood tolerability.

Carbon-carbon composites are well known in the field of aerospace technology. Such composites have been proposed to be used as biomaterials, particularly in contact with blood. To evaluate their haemocompatibility, samples were tested in vivo and in vitro, using radiotracers. In vivo study showed the accumulation of platelets on the exposed surface material with any surface morphology, whereas platelet concentration in blood remained constant. In vitro study allowed us to distinguish, among entrapped platelets, active adhering platelets from those mechanically retained and it appeared that the bulk structure of materials influenced the adhesion mechanism of platelets.