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Biomedical subjects

C Rey

Publications and source records attributed to C Rey.

At least 91 records · Page 5Linked to original sources
PubMed1999

Heterogeneous crystallization of dicalcium phosphate dihydrate on titanium surfaces.

The kinetics of nucleation and crystal growth of dicalcium phosphate dihydrate (DCPD, CaHPO4.2H2O) on titanium powders with different grain sizes have been investigated using the constant composition crystal growth method at 37 degrees C and pH = 5.50. Nucleation is independent of titanium powder size while crystal growth rate is strongly size-dependent. A minimum relative supersaturation ratio, sigma(min), required in the system for a detectable crystal growth rate to occur, taking into account the presence of the foreign substrate in the system, was determined. Based on the kinetic data and on the various characterizations by X-ray photoelectron spectroscopy and by scanning electron microscopy, we propose a crystal growth kinetic equation as a function of two parameters: the size of the substrate and the excess of supersaturation (sigma-sigma(min)) which is squared, indicating a spiral growth mechanism.

Journal Article↗
PubMed1999

In vitro crystallization of octacalcium phosphate on type I collagen: influence of serum albumin.

The heterogeneous crystallization of octacalcium phosphate (OCP, Ca8H2(PO4)6.5H2O) on demineralized Type I collagen has been studied from metastable supersaturated solutions, at 37degreesC and pH=6.50, using the constant composition crystal growth technique. The induction period, before OCP crystal growth, varied markedly with the degree of supersaturation of the solution. The data obtained allowed us to determine the apparent order for the precipitation and the growth mechanism of OCP on Type I collagen. Infrared spectroscopy analyses indicated the progressive mineralization of collagen and observations by scanning electron microscopy confirmed the development of OCP crystals on the collagen surface. The influence of bovine serum albumin on both the kinetics of OCP nucleation and growth has also been investigated. Because this protein was adsorbed on calcium phosphate nuclei, it exhibited two distinct effects as a function of its concentration in solution. We proposed a mechanism explaining the interaction between albumin and calcium phosphate nuclei or crystals and its incidence on the OCP crystallization kinetics. Observations by scanning electron microscopy revealed a modification of the size and the appearance of crystals grown on collagen due to the adsorption of albumin on the crystal surface.

Journal Article↗
PubMed1999

Direct cytotoxicity of hypoxia-reoxygenation towards sinusoidal endothelial cells in the rat.

AIMS/BACKGROUND: Sinusoidal endothelial cells are the primary target of ischemia-reperfusion injury following liver preservation. The present study was undertaken to examine the susceptibility of sinusoidal endothelial cells to hypoxia-reoxygenation and the potential role of oxygen free radicals in the induction of cell injury. METHODS: Sinusoidal endothelial cells were isolated from rat liver. After 2 3 days of primary culture, the cells were exposed to hypoxia (N2/CO2 95/5) for 120 min and reoxygenation (O2/CO2 95/5) for 90 min. Control cells were exposed to hypoxia alone, to 95% O2 alone or were maintained under normoxic conditions. Human umbilical vein endothelial cells were used as a model of vascular endothelial cells and submitted to the same protocol. Cell viability and lipid peroxidation were assessed by LDH leakage and malondialdehyde production, respectively. In order to test the potential role of xanthine oxidase and mitochondrial dysfunction in cell injury, the cells were treated with allopurinol and potassium cyanide (KCN) respectively. RESULTS: The different gaseous treatments did not affect LDH leakage in human umbilical vein endothelial cells. In sinusoidal endothelial cells, the sequential hypoxia-reoxygenation caused a significant increase in LDH release, malondialdehyde production and xanthine oxidase activity while hypoxia alone had no effect except on xanthine oxidase activity. Allopurinol inhibited xanthine oxidase without preventing cell injury or lipid peroxidation in this latter cell type. CONCLUSIONS: The results suggest that sinusoidal endothelial cells, as opposed to vascular endothelial cells, are susceptible to a direct cytotoxic effect of hypoxia-reoxygenation. This effect occurs in combination with an increase in xanthine oxidase activity and lipid peroxidation, although cell injury is mediated at least in part by mechanisms independent of xanthine oxidase such as mitochondrial dysfunction.

Animals↗
PubMed1999

[Percutaneous closure of ostium secundum atrial septal defects using the Amplatz device. Preliminary study on 29 patients].

The aim of the study was to assess the results of percutaneous closure of ostium secundum atrial septal defects (ASD) by the Amplatz device and to compare them with those obtained by other methods. Over a one year period, closure of ASD was performed in 28 patients aged 7 to 66 years (mean of 32 years) with exclusive left-to-right shunts. The selection of patients was made by transthoracic echocardiography. Cardiac catheterisation was performed to measure the stretched diameter of the defect. After patient or parental consent, the procedure was performed under general anaesthesia. The implantation was performed under transoesophageal echocardiographic control. The diameter of the Amplatz device corresponded to the stretched diameter of the ASD. The patients were discharged from hospital 48 hours later under platelet anti-aggregant therapy for 6 months. Clinical, electrocardiographic, radiological and echocardiographic examinations were performed at 1 month, 3 months and 1 year after implantation. The stretched diameter was 12-27 mm (mean 22 mm). The device was withdrawn in one case because of a double ASD and, in another patient, failure was due to embolisation of the obturator to the pulmonary artery before its implantation. The closure was complete in 21 of the 26 cases immediately after the procedure; at one month, two residual shunts were observed but they had disappeared at 3 months and at 1 year. Out of 46 ASD closed by the Sidéris button prosthesis, occlusion was total in 29 cases and partial in 17 cases. The authors conclude that the Amplatz device is an effective prosthesis for closure of ostium secundum ASD. With strict selection procedures, the results are excellent.

Adolescent↗
PubMed1999

[Hemangioma and superficial arteriovenous malformations].

Haemangiomas are different from true superficial vascular malformations. The haemangiomas, mainly affecting the newborn and small babies, will, after a phase of progression, sometimes regress completely. Therapeutic abstention is the rule except in high risk angiomas when steroid therapy may be effective. Visceral involvement poses problems. Superficial vascular malformations, on the other hand, arise at all ages and may affect any blood vessel. Each type has a specific clinical presentation, complementary investigations and appropriate treatment. Some are slowly progressive, for example capillary, venous and lymphatic malformations. Others are haemodynamically active, such as the arteriovenous malformations. Capillary malformations are flat angiomas with aesthetic consequences, apart from the Sturge-Weber-Krabbe syndrome. Cold, blue venous malformations confirmed by ultrasonography and magnetic resonance imaging, when necessary, require treatment adapted to their site and size: compression, embolisation, surgery or abstention. Lymphatic malformations may be cystic or tissular: the cystic lymphangioma, a soft swelling of often healthy skin, with compartments separated by septa on ultrasound scan, is usually treated by ethibloc embolisation. Arteriovenous malformations, warm and pulsatile, demonstrated at arteriography, may progress rapidly and treatment by surgery or embolisation, when necessary, has to be complete. Finally, there are complex vascular malformations which pose very difficult problems of management.

Age Factors↗
PubMed1999

[Mapping and radiofrequency ablation in different forms of right peri-atriotomy flutter].

Peri-atriotomy flutter is a possible complication of surgical atriotomy. This tachycardia in an indication for radiofrequency ablation. The aim of this study was to determine the mechanism of the flutter, evaluate the possibility of mapping and the role of radiofrequency ablation in its treatment. Eleven patients with a mean age of 45 years (26-70) were referred for ablation of atrial flutter observed on average 15 years after surgical atriotomy. In 7 patients (Group I), the ECG appearances before the procedure were that of a rare flutter. Endocavitary mapping showed a circuit limited to the free wall of the right atrium with a posterior caudo-cranial and an anterior cranio-caudal front. A series of radiofrequency applications joining the atriotomy scar to the inferior vena cava interrupted the flutter in all patients and created a bidirectional block around the atriotomy. In 4 patient (Group II), the ECG appearances were that of a common flutter. A series of radiofrequency ablations in the cavo-tricuspid isthmus led to sudden change in polarity of the F wave in all patients. Repeat mapping then showed a peri-atriotomy circuit identical to that described in Group I. The whole was interpreted as a figure-of-eight circuit. The primary success rate was 100%. There were no complications but the early recurrence rate remained high. This preliminary experience confirms the value of radiofrequency ablation in the treatment of peri-atriotomy flutter and shows ECG polymorphism related to a figure-of-eight reentry circuit.

Adult↗
PubMed1999

Multiple aneurysmal dysplasia of pulmonary valvular sinuses with congenital focal aplasia of the annulus.

We report the case of a 22-year-old woman in whom a focal aplasia of the pulmonary valve annulus associated with a multiple aneurysmal compensatory dysplasia was found. This patient had been followed since the age of seven years for a congenital asymmetric hypertrophic cardiomyopathy. Cardiac Doppler analysis showed significant pulmonary valvular insufficiency. The patient underwent heart transplant surgery because of total and refractory cardiac insufficiency. Pathological examination of the explanted heart (at the European Homograft Bank) enabled us to describe this valvular malformation. To date, this anomaly has not been described in the literature. Whether it is a malformation discovered fortuitously, or whether it is responsible in part for some of the signs associated with congenital hypertrophic cardiomyopathy is unclear. However, its role might be disclosed by a rigorous investigation of the patient's family.

Adult↗
PubMed1999

Presence of genotypic resistance in nucleoside analogue-treated HIV-1-infected patients with undetectable viral load.

Patients harbouring drug-resistance viruses usually suffer a rise in serum viraemia after a variable period of time. We have investigated the relationship between the appearance of resistant genotypes and the viral load of each patient after treatment. Our objective was to assess the association between human immunodeficiency virus (HIV) RNA plasma levels and the number of drug resistance-associated point mutations after treatment. A total of 150 patients from three reference centres in Spain (Madrid, Barcelona and Seville) from a previous study (Erase Study) were included. Patients had at that time undergone antiretroviral treatment with nucleoside analogues for at least 1 year (zidovudine/didanosine; zidovudine/zalcitabine; zidovudine/zalcitabine/lamivudine; zidovudine/didanosine/lamivudine). In this study, plasma viraemia in these patients was quantified and a line probe assay was used to determine the genotype of the virus. Viral load was significantly higher in patients harbouring virus with more than three mutations than in those individuals who harboured wild-type strains (P < 0.05). Surprisingly, when patients with viral load < 500 copies/ml (13/150) were analysed, only two carried wild-type strains, whereas three had virus with more than three point mutations. The viral load of six samples was assayed using an ultrasensitive test (detection limit < 20 copies/ml). Of the three samples where viral load was < 20 copies/ml, one patient harboured wild-type virus, whereas two carried mutant virus strains. These results suggest that even in patients with undetectable viral loads by conventional methods, viral replication may continue and mutations develop. Therefore, standard values of plasma viraemia for measuring the effectiveness of the treatment should be reconsidered when patients are on antiviral regimens of just two or three nucleoside analogues.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Results of transvenous buttoned device occlusion of patent ductus arteriosus in adults. International Buttoned Device Trial Group.

Examination of the immediate and follow-up results of transvenous buttoned device occlusion of patent ductus arteriosus suggests that the method is feasible, safe, and effective irrespective of the size and shape of the ductus. Although residual shunts are present, they tend to disappear during follow-up, and complete occlusion at the time of implantation may be achieved by incorporation of a folding plug over the button loop of the device.

Adolescent↗
PubMed1998

Basic fibroblast growth factor adsorption and release properties of calcium phosphate.

Basic fibroblast growth factor (bFGF) is well known as a potent angiogenic factor playing a crucial role in wound-healing processes. Apatitic substrates such as hydroxyapatite and carbonated apatite (CA) could be potential carriers of growth factors because of their physicochemical similarities to bone mineral. These materials have been compared for their bFGF adsorption and release properties. The adsorption of the growth factor was higher on carbonated apatite than on hydroxyapatite, probably owing to environments with labile nonapatitic CO3(2-) and HPO4(2-) groups, along with a higher specific surface area which gives the CA a higher surface reactivity. These environments can be exchanged very rapidly, leading to the release of bFGF. The controlled release of adsorbed growth factor from carbonated apatite could provide means of improving bone healing in the future.

Adsorption↗
PubMed1998

Tumor necrosis factor beta and soluble APO-1/Fas independently predict progression to AIDS in HIV-seropositive patients.

The relationship between serum concentration of different components of the nerve growth factor/tumor necrosis factor (TNF) receptor family, including soluble APO-1/Fas (sAPO-1/Fas) and progression of HIV infection, was analyzed in a case-control study of individuals selected from a cohort of HIV-seropositive patients who were progressing or not progressing to AIDS while being treated with nucleoside analogs. HIV-seronegative healthy controls were also analyzed. The results showed that, despite close matching for immunologic (CD4 cell count, beta2-microglobulin concentration) and virologic (p24 antigen, detection of HIV syncytium-inducing phenotype, plasma HIV viremia) parameters, the baseline serum concentrations of TNF-beta and sAPO-1/Fas were statistically different between progressing and nonprogressing patients. In addition, serum concentrations of TNF-beta and sAPO-1/Fas showed the strongest independent predictive power for progression to AIDS in a multivariate conditional logistic regression model. Because TNF-beta and Fas were suggested to be mediators of antigen-induced cell death (AICD) in HIV infection and sAPO-1/Fas was hypothesized to protect lymphocyte against AICD, these data suggest an important pathogenetic role for AICD in the progression of HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Short-term evolution of HIV-1 viraemia and CD4+ cell counts in patients who have a primary mutation to zidovudine.

OBJECTIVE: To investigate the different responses to antiretroviral treatment including zidovudine, of patients harbouring HIV with primary resistance to zidovudine, serum viral load, and CD4+ cell counts, for 24 weeks in a group of antiretroviral-naive patients with the codon 215 mutation of the HIV pol gene and in a control group at the start of treatment. DESIGN: A case-control retrospective study (1989-1996). METHOD: Nineteen out of 210 patients previously studied harboured the codon 215 mutation, had a self-reported compliance with treatment, a minimum follow-up of 24 weeks, and were treated with zidovudine alone or in combination with other nucleoside analogues. These patients were matched with 19 patients with wild-type strains at entry by initial CD4+ cell counts, clinical status, and antiretroviral treatment. RESULTS: During the first 12 weeks, CD4+ cell counts increased (76+/-26 and 64+/-26 x 10(6)/l in wild-type and mutant virus-infected groups, respectively), decreasing slightly until week 24, although no significant differences were found between the two groups studied. Serum viral load decreased in both groups (change in serum viral load of 0.80+/-0.11 log10 and 0.87+/-0.26 log10 copies/ml, wild-type and mutant virus-infected, respectively), although no significant differences were found between groups. CONCLUSION: No significant differences were found between patients with the primary mutation to zidovudine and control patients harbouring wild-type virus in terms of short-term response measured by serum viral load and CD4+ cell counts.

Adult↗
PubMed1998

Resorbable calcium phosphate bone substitute.

The in vitro and in vivo properties of a novel, fully resorbable, apatitic calcium phosphate bone substitute (ABS) are described. The ABS was prepared from calcium phosphate precursors that were hydrated to form an injectable paste that hardens endothermically at 37 degrees C to form a poorly crystalline apatitic calcium phosphate (PCA). The PCA reaction product is stable in vivo as determined by FTIR and XRD analysis of rabbit intramuscular implants of ABS retrieved 4, 7, and 14 days postimplantation. Bone formation and resorption characteristics of the ABS material were characterized in a canine femoral slot defect model. Femoral slot defects in dogs were filled with either autologous bone implants or the ABS material. Sections of femoral bone defect site from animals sacrificed at 3, 4, 12, 26, and 52 weeks demonstrated that new bone formation proceeded similarly in both autograft and ABS filled slots. Defects receiving either material were filled with trabecular bone in the first 3 to 4 weeks after implantation; lamellar or cortical bone formation was well established by week 12. New bone formation in ABS filled defects followed a time course comparable to autologous bone graft filled defects. Histomorphometric evaluation of ABS resorption and new bone formation indicated that the ABS material was greater than 99% resorbed within 26 weeks; residual ABS occupied 0.36+/-0.36% (SEM, n = 4) of the original defect area at 26 weeks. Quantitatively and qualitatively, the autograft and ABS were associated with similar new bone growth and defect filling characteristics.

Animals↗
PubMed1998

Cellular localization of endothelin-1 and increased production in liver injury in the rat: potential for autocrine and paracrine effects on stellate cells.

Endothelin (ET) peptides have been implicated in the pathogenesis of several biological processes within the liver. ET levels are elevated in the circulation of patients with cirrhosis, and recent data suggest that ET may be overproduced in the liver itself in this condition. The aims of the current study were to elucidate the cellular source and expression of endothelin-1 (ET-1) in normal and injured liver, and to investigate its biological effects on stellate cells, the primary target of ETs in the liver. In normal hepatic cells, preproET-1 messenger RNA (mRNA) was detected in only nonparenchymal cells, predominantly in sinusoidal endothelial cells. After biliary fibrosis and early cirrhosis induced by bile duct ligation, preproET-1 mRNA and immunoreactive ET levels increased with progressive injury in whole liver extracts, as well as in isolated stellate and endothelial cell fractions. Eight days after bile duct ligation, the relative increase in preproET-1 mRNA was 1.6- and 7.6-fold above normal in sinusoidal endothelial and stellate cells, respectively. Additionally, immunoreactive ET peptide levels increased by 60% +/- 27% over basal values in sinusoidal endothelial cells and 98% +/- 40% in stellate cells. Cultured stellate cells responded dramatically to exogenous ET-1 by the spreading and up-regulation of smooth muscle alpha actin expression. Furthermore, in early culture before cellular activation, ET-1 (10 nmol/L) caused over a twofold increase in [3H]thymidine incorporation, while activated cells (i.e., those cultured for >1 week) exposed to ET-1 exhibited up to a fivefold decrease in [3H]thymidine incorporation. The data indicate that not only is ET-1 overproduced by both sinusoidal endothelial and stellate cells during liver injury, but that it also has potent effects on features of stellate cell activation. We conclude that autocrine and paracrine production of ET-1 is prominent and is likely to be important in the pathogenesis of hepatic diseases.

Actins↗