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Biomedical subjects

V Simon

Publications and source records attributed to V Simon.

At least 19 recordsLinked to original sources

Biogenic volatile organic compounds (BVOCs) emissions from Abies alba in a French forest.

Air quality studies need to be based on accurate and reliable data, particularly in the field of the emissions. Biogenic emissions from forests, crops, and grasslands are now considered as major compounds in photochemical processes. Unfortunately, depending on the type of vegetation, these emissions are not so often reliably defined. As an example, although the silver fir (Abies alba) is a very widespread conifer tree in the French and European areas, its standard emission rate is not available in the literature. This study investigates the isoprene and monoterpenes emission from A. alba in France measured during the fieldwork organised in the Fossé Rhénan, from May to June 2003. A dynamic cuvette method was used. Limonene was the predominant monoterpene emitted, followed by camphene, alpha-pinene and eucalyptol. No isoprene emission was detected. The four monoterpenes measured showed different behaviours according to micrometeorological conditions. In fact, emissions of limonene, alpha-pinene and camphene were temperature-dependant while eucalyptol emissions were temperature and light dependant. Biogenic volatile organic compounds emissions were modeled using information gathered during the field study. Emissions of the three monoterpenes previously quoted were achieved using the monoterpenes algorithm developed by Tingey et al. (1980) [Tingey D, Manning M, Grothaus L, Burns W. Influence of light and temperature on monoterpene emission rates from slash pine. Plant Physiol 1980;65: 797-801.] and the isoprene algorithm [Guenther, A., Monson, R., Fall, R., 1991. Isoprene and monoterpene emission rate variability: observations with eucalyptus and emission rate algorithm development. J Geophys Res 26A: 10799-10808.]; [Guenther, A., Zimmerman, P., Harley, P., Monson, R., Fall, R., 1993. Isoprene and monoterpene emission rate variability: model evaluation and sensitivity analysis. J Geophys Res 98D: 12609-12617.]) was used for the eucalyptol emission. With these methods, simulation results and observations agreed fairly well. The standard emission rate (303 K) and beta-coefficient averaged for limonene, camphene and alpha-pinene were respectively of 0.63 microg gdw-1 h-1 and 0.06 K-1. For eucalyptol, the standard emission rate (T=303 K and PAR=1000 micromol m-2 s-1) was 0.26 microg gdw-1 h-1. This classified A. alba as a weak monoterpenes emitter.

Abies↗

Titanium--hydroxyapatite porous structures for endosseous applications.

Materials for uncemented endosseous implants have to assure an as short as possible osseointegration time. Thus, a material with both surface bioactivity and a porous outer structure can become a preferred choice for this type of applications. This paper presents a class of titanium-base PM composites, reinforced with particulate hydroxyapatite. Raw materials were titanium powder, obtained through hydriding--milling--dehydriding, with the grain size of 63-100 microm, and sol-gel hydroxyapatite (HA) powder, produced by the reaction between Ca(NO3)2 x 4H2O and (NH4)2HPO4. Blends with 5 to 50% HA were prepared and pressed in a rigid die, producing single composition or gradual composition samples. The applied pressure was of 400, 500 or 600 MPa. Sintering was performed in vacuum, at 1160 ( composite function)C. All samples, although well sintered, displayed swelling during sintering, due to diffusion into the matrix. The increase in volume is more severe for higher amounts of HA in the green compacts and for higher applied compaction pressure. Compacts with a gradual increase of the HA content are recommended from the functional and mechanical point of view, but the increase should be slow, not to produce interlayer cracks. The outer surface shows interconnected pores, suitable for the ingrowth of vital new bone.

Bone and Bones↗

Two functionally distinct pools of Src kinases for PDGF receptor signalling.

The cytoplasmic tyrosine kinases of the Src family (SFK) play important roles in cell responses induced by growth factors, including cell growth, survival and migration. Here, we review how SFK participate in PDGF (platelet-derived growth factor) receptor signalling leading to DNA synthesis and actin assembly. Furthermore, evidence for a spatial compartmentalization of SFK signalling is also discussed.

Actins↗

The impact of reduction in the benzene limit value in gasoline on airborne benzene, toluene and xylenes levels.

Background benzene, toluene, xylenes (BTX) average concentrations have been measured over the urban agglomeration of Toulouse, France, during both springtime and summer periods of 1999 and 2001. The benzene average amount over the two Toulouse campaigns in 1999 is equal to 2.2 microg/m(3), very close to the French air quality standard and well under the average value of 5 microg/m(3) recommended by European Economic Community countries, recognising that those regulations are given for a whole year. BTX pollution over Toulouse has, in particular, been produced by motor vehicle exhaust gases. For the study conducted during the same periods of 2001, benzene concentrations were within the French quality value in the whole area. This is because the benzene limit value contained in gasoline went from 5% to 1% since 2000 January 1. It will be important to measure benzene over annual periods in order to know its exact values over such a period and to observe its potential seasonal variations.

Journal Article↗

Predictors of treatment failure during highly active antiretroviral therapy (racing trial).

PURPOSE: To determine factors associated with virological failure during long-term treatment with the triple combination of saquinavir soft gel capsule, zalcitabine and zidovudine. METHOD: Open-label, prospective, multicentre study undertaken in private practices and the outpatient department of the Auguste-Viktoria-Hospital. A total of 95 patients with plasma HIV RNA > 5000 copies/ml who had received no more than 6 months pre-treatment with NRTIs and no prior PI therapy received saquinavir soft gel, zalcitabine and zidovudine for 52 weeks, before being randomly assigned to either remain on therapy or switch to nelfinavir, lamivudine and zidovudine for further 52 weeks. RESULTS: Combination therapy with saquinavir, zalcitabine and zidovudine was found to be effective and well tolerated, with virological response to therapy maintained for up to 2 years. In patients responding to therapy, switching to a novel triple regimen did not result in a virological or immunological worsening, but it did not confer an additional clinical benefit. Factors predictive of early treatment failure (virological failure within 16 weeks of treatment initiation) included high viral load and presence of RT mutations at baseline (OR: 0.30, 95% CI 0.11 0.83 and OR 0.13, 95% CI 0.03 0.52, respectively), with baseline viral load and the development of genotypic mutations on therapy being predictive of late treatment failure (16 52 weeks; OR: 0.15, 95% 0.05 0.46 and OR: 0.26, 95% CI < 0.001 1.16, respectively). Plasma saquinavir concentration < 50 mg/ml at 4 weeks was also found to be an independent risk factor for both early and late treatment failure (OR: 1.80, 95% CI 1.23 2.64 and OR: 1.16, 95% CI 0.84 1.60, respectively). CONCLUSIONS: While antiretroviral drug resistance appears to be a principal cause of treatment failure, other factors such as inadequate drug plasma concentrations also play a role.

Adult↗

Volatile organic compounds cytotoxicity and expression of HSP72, HSP90 and GRP78 stress proteins in cultured human cells.

The aim of this study was to determine whether overexpression of stress proteins (SPs) could be a sensitive biomarker for cell injury due to exposure to low doses of volatile organic compounds (VOCs) such as benzene, ethylbenzene, toluene, xylene, and chlorinated derivatives (ClB). Sublethal and cytotoxic threshold concentrations of the VOCs were determined by studying the growth rate of normal (fibroblasts) or tumor-derived human cell lines (A549, HepG2) exposed for 4 days to VOCs. Changes in SP expression as a function of concentrations were investigated by Western blotting.VOC toxicity was found to be correlated with their degree of chlorination and their hydrophobicity. Cytotoxic threshold concentrations (no-observed effect concentration, NOEC) were found to be similar for the three cell lines. It was observed that using a mixture of VOCs, each of them at concentration below the NOEC, resulted in an actual toxicity to the cells. This finding reveals a synergistic effect and should be taken into account when assessing threshold risk and exposure limit values in the worker's environment when several pollutants may be present. HSP72 and HSP90 expression levels were not affected whereas GRP78 expression was increased by all the VOCs. Taking into account the specific molecular function of GRP78, it suggests that VOC exposure results in misfolded or underglycosylated protein accumulation in the endoplasmic reticulum. GRP78 overexpression was closely related to the magnitude of growth inhibition due to increasing concentrations of each VOC. The overexpression was found to be significant for concentrations 5 to 30 times higher than NOEC, indicating that, under our experimental conditions, GRP78 expression cannot be considered as a sensitive biomarker of exposure to environmental VOCs.

Benzene↗

Development of hydrogel implants for urinary incontinence treatment.

Hydrogel implants for urinary incontinence treatment based on HEMA supplemented with 10% methacrylic acid have been developed. The swelling properties of implants were tested in vitro and in vivo after implantation to laboratory mice. Biocompatibility has been determined by incubation of implants in tissue culture, by histological examination of adjacent tissues after subcutaneous application of implants to laboratory mouse in a long-term experiment, and by flow cytometry examination of blood cells. The swelling of hydrogel implants was completed in 6-24 h. There was no effect on in vitro growth of cells incubated with implants. In mice, implants were well tolerated without any sign of inflammatory reaction. The material allows an elastic compression of urethra compensating a damaged sphincter after trans-urethral sub-mucosal implantation of hydrogel cylinders.

Animals↗

[Treatment of urinary stress incontinence in women with a periurethral implant].

OBJECTIVE: The aim of this article is the comprehensive information about different bulking substances and their use for the treatment of genuine stress urinary incontinence in women. DESIGN: The review summarizes various materials used for this purpose, methods of their application, possible complications and results of clinical studies of implants. SETTING: Department of Obstetrics and Gynaecology of Charles University and Faculty Hospital Bulovka takes part in the development of the new metacrylate of Czech origin. SUBJECT AND METHOD: Current scientific literature as listed in the article. CONCLUSION: Implants seem to be a useful alternative method in the treatment of the genuine stress incontinence in women.

Adipose Tissue↗

[Hydrogen expandable implants in the treatment of stress incontinence in women--a pilot study].

OBJECTIVE: The aim of the study was to evaluate the use of new-type implants for the treatment of female urinary stress incontinence. The patients with intrinsic sphincter deficiency were also included, the other were after previous surgery for GSI. DESIGN: Original article. SETTING: Departments of Obstetrics and Gynaecology, Faculty Hospital Na Bulovce and General Faculty Hospital, 1. Faculty of Medicine, Charles University, Prague, Institute of Macromolecular Chemistry, Czech Academy of Science, Prague. METHODS: We operated 9 patients, two of them with type III (McGuire) urinary stress incontinence the rest after operations for GSI in general anesthesia. Six to nine hydrogel swelling implants were introduced into the submucosa of proximal urethra under the transrectal ultrasound guidance. We evaluated the effect 6 to 9 months after the operation. RESULTS: Two patient were dry (negative stress-test and pad-weight test), one patient had substantial improvement, 4 had mild improvement and 2 did not notice any change. We found de novo urge symptoms in four patients, two of them were of the motor type. CONCLUSION: The new type of implants reached the success rate of other currently used materials. The improvement of stress incontinence was on the cost of de novo urge symptoms in some patients. The urgency was successfully managed with spasmolytic drugs.

Female↗

Contribution of the bacterial endosymbiont to the biosynthesis of pyrimidine nucleotides in the deep-sea tube worm Riftia pachyptila.

The deep-sea tube worm Riftia pachyptila (Vestimentifera) from hydrothermal vents lives in an intimate symbiosis with a sulfur-oxidizing bacterium. That involves specific interactions and obligatory metabolic exchanges between the two organisms. In this work, we analyzed the contribution of the two partners to the biosynthesis of pyrimidine nucleotides through both the "de novo" and "salvage" pathways. The first three enzymes of the de novo pathway, carbamyl-phosphate synthetase, aspartate transcarbamylase, and dihydroorotase, were present only in the trophosome, the symbiont-containing tissue. The study of these enzymes in terms of their catalytic and regulatory properties in both the trophosome and the isolated symbiotic bacteria provided a clear indication of the microbial origin of these enzymes. In contrast, the succeeding enzymes of this de novo pathway, dihydroorotate dehydrogenase and orotate phosphoribosyltransferase, were present in all body parts of the worm. This finding indicates that the animal is fully dependent on the symbiont for the de novo biosynthesis of pyrimidines. In addition, it suggests that the synthesis of pyrimidines in other tissues is possible from the intermediary metabolites provided by the trophosomal tissue and from nucleic acid degradation products since the enzymes of the salvage pathway appear to be present in all tissues of the worm. Analysis of these salvage pathway enzymes in the trophosome strongly suggested that these enzymes belong to the worm. In accordance with this conclusion, none of these enzyme activities was found in the isolated bacteria. The enzymes involved in the production of the precursors of carbamyl phosphate and nitrogen assimilation, glutamine synthetase and nitrate reductase, were also investigated, and it appears that these two enzymes are present in the bacteria.

Animals↗

The effect of conjugated linoleic acid on platelet function, platelet fatty acid composition, and blood coagulation in humans.

Despite extensive research on conjugated linoleic acid (CLA) showing multiple beneficial effects in animal models, little is known about the role of dietary CLA in human health. To investigate if the beneficial effects of CLA seen in animal models are relevant to humans, we conducted a study with 17 healthy female volunteers who lived in the Metabolic Research Unit of the Western Human Nutrition Research Center for 93 d. This paper reports only the results from this study that are related to the effects of CLA supplementation on blood coagulation, platelet function, and platelet fatty acid composition. Throughout the study, the subjects were fed a low-fat diet (30 en% fat, 19 en% protein, and 51 en% carbohydrate) consisting of natural foods with the recommended dietary allowances for all known nutrients. After a 30-d stabilization period, subjects were randomly assigned to either an intervention group (n = 10) whose diet was supplemented with 3.9 g/d of CLA or a control group (n = 7) who received an equivalent amount of sunflower oil consisting of 72.6% linoleic acid with no detectable CLA. Platelet aggregation was measured in platelet-rich plasma using adenosine diphosphate, collagen, and arachidonic acid agonists. No statistical difference was detected between the amount of agonist required to produce 50% aggregation of platelet-rich plasma before and after the subjects consumed the CLA, with the exception of a decrease in response to collagen. This decrease was found in both control and intervention groups with no significant difference between the groups, suggesting that both linoleic acid (sunflower oil) and CLA might have similar effects on platelet function. The prothrombin time, activated partial thromboplastin time, and the antithrombin III levels in the subjects were determined. Again, there was no statistically significant difference in these three parameters when pre- and post-CLA consumption values were compared. The in vivo bleeding times were also unaffected by CLA supplementation (10.4 + 2.8 min pre- and 10.2 + 1.6 min postconsumption). Platelet fatty acid composition was not markedly influenced by the consumption of dietary CLA, although there was a small increase in the amount of the 9 cis,11 trans-18:2 isomer normally present in platelets after feeding CLA for 63 days. In addition, small amounts of the 8 trans,10 cis-18:2 and the 10 trans,12 cis-18:2 isomers were detected in the platelets along with traces of some of the other isomers. Thus, when compared to sunflower oil, the blood-clotting parameters and in vitro platelet aggregation showed that adding 3.9 g/d of dietary CLA to a typical Western diet for 63 d produces no observable physiological change in blood coagulation and platelet function in healthy adult females. Short-term consumption of CLA does not seem to exhibit antithrombotic properties in humans.

Adult↗

The effect of conjugated linoleic acid on plasma lipoproteins and tissue fatty acid composition in humans.

Conjugated linoleic acid (CLA) has been suggested by some animal studies to possess antiatherogenic properties. To determine, in humans, the effect of dietary CLA on blood lipids, lipoproteins, and tissue fatty acid composition, we conducted a 93-d study with 17 healthy female volunteers at the Metabolic Research Unit of the Western Human Nutrition Research Center. Throughout the study, subjects were fed a low-fat diet [30 energy percent (en%) fat, 19 en% protein, and 51 en% carbohydrate] that consisted of natural foods with the recommended dietary allowances for all known nutrients. After a 30-d stabilization period, subjects were randomly assigned to either an intervention group (n = 10) supplemented daily with capsules containing 3.9 g of CLA or a control group (n = 7) that received an equivalent amount of sunflower oil. The CLA capsules (CLA 65%) contained four major cis/trans geometric isomers (11.4% 9 cis-,11 trans-18:2; 10.8% 8 trans-,10 cis-18:2; 15.3% 11 cis-,13 trans-18:2; and 14.7% 10 trans-,12 cis-18:2) and their corresponding cis/cis (6.74% total) and trans/trans (5.99% total) varieties in smaller amounts. Fasting blood was drawn on study days 30 (end of the stabilization period), 60 (midpoint of the intervention period), and 93 (end of the intervention period). Adipose tissue samples were taken on days 30 and 93. CLA supplementation for 63 d did not change the levels of plasma cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, and triglycerides. The weight percentage of CLA in plasma increased from 0.28 +/- 0.06 to 1.09 +/- 0.31 (n = 10, P < 0.05) after the supplementation. The 9 cis-,11 trans-isomer was the most prominent variety followed by the 11 cis-,13 trans- and 10 trans-,12 cis-isomers in lesser amounts. CLA in adipose tissue was not influenced by the supplementation (0.79 +/- 0.18 to 0.83 +/- 0.19 wt%) (n = 10) and the 9 cis-,11 trans-variety was the only isomer present. Thus, contrary to findings from some animal studies, CLA does not seem to offer health benefits, in the short term, regarding the prevention of atherosclerosis in humans. CLA supplementation for 2 mon did not alter the blood cholesterol or lipoprotein levels of healthy, normolipidemic subjects. The supplementation did increase CLA in the plasma but only 4.23% of the ingested CLA was present in the plasma at any given time. No adverse effect of CLA supplementation was detected in this study.

Adipose Tissue↗

Decade-long experience with surgical therapy of myasthenia gravis: early complications of 324 transsternal thymectomies.

BACKGROUND: We studied the incidences and evaluated the management of early postoperative complications after thymectomy for myasthenia gravis. METHODS: During the period between 1987 and 1996, 324 thymectomies were performed through median sternotomy access under general anesthesia. Postoperative management was administered according to a standardized protocol of anticholinesterase medication, which was withdrawn for the 48 hours of obligatory postoperative mechanical ventilation. The mean age of patients was 34 years (range, 8 to 71 years). RESULTS: One hundred forty-nine patients made an uneventful recovery; 104 patients had only minor complications, whereas 71 patients had major complications. The mortality rate was 0.6% (2 patients). The major surgical complications were recorded as sternal bleeding (1 patient) and sternal disruption (1 patient). The major general complications were recorded as tracheal stenosis (1 patient), pneumonia (3 patients), heart failure (1 patient), gastric hemorrhage (1 patient), and respiratory insufficiency (71 patients). Forty-six reintubations were performed on 40 patients and 19 tracheostomies (6%) were performed postoperatively. CONCLUSIONS: The excessive incidence of respiratory insufficiency and airway-associated morbidity was potentially related, at least partially, to prolonged mechanical ventilation and withdrawal of anticholinesterase medication. Earlier weaning of patients with revision of 48-hour withdrawal of anticholinesterase medication is necessary.

Adolescent↗

Microarray analysis of diurnal and circadian-regulated genes in Arabidopsis.

Plants respond to day/night cycling in a number of physiological ways. At the mRNA level, the expression of some genes changes during the 24-hr period. To identify novel genes regulated in this way, we used microarrays containing 11,521 Arabidopsis expressed sequence tags, representing an estimated 7800 unique genes, to determine gene expression levels at 6-hr intervals throughout the day. Eleven percent of the genes, encompassing genes expressed at both high and low levels, showed a diurnal expression pattern. Approximately 2% cycled with a circadian rhythm. By clustering microarray data from 47 additional nonrelated experiments, we identified groups of genes regulated only by the circadian clock. These groups contained the already characterized clock-associated genes LHY, CCA1, and GI, suggesting that other key circadian clock genes might be found within these clusters.

Arabidopsis↗

Concomitant increase of G protein-coupled receptor kinase activity and uncoupling of beta-adrenergic receptors in rat myometrium at parturition.

The myometrial beta-adrenergic receptor (beta-AR)-adenylyl cyclase pathway is markedly desensitized at the end of pregnancy in the rat. We have investigated whether changes in the amount and/or the activity of G protein-coupled receptor kinase (GRK) occurred at the same period of pregnancy. Using Northern and Western blotting, we have identified GRK2, GRK5, GRK6, and a small amount of GRK3 in late pregnant rat myometrium. GRK activity, as measured by in vitro phosphorylation of rhodopsin, was detected in both cytosolic and plasma membrane fractions. Interestingly, in the 6-10 h preceding parturition, there was a substantial increase (+190%) of myometrial membrane-associated GRK activity. This was associated with an increase in membrane GRK2 immunoreactivity. Such alterations occurred concomitantly with uncoupling of beta-AR, as assessed by quantification of high-affinity binding receptors. These data suggest that GRK activity increase may be one of the mechanisms underlying alterations in the coupling between beta-AR and adenylyl cyclase and may thus contribute to the initiation of myometrial contractions at term.

Animals↗

[Surgical treatment of recurrent urethral strictures in males after unsuccessful operations].

BACKGROUND: Subvesical obstructions of any origin represent a frequent and serious disorder occurring predominantly in males. Often it brings incontinence and/or erectility dysfunction, infection of urinary tract. Relapses of the acute pyelonephritis can turn into chronic tubulointersticial one and terminate in the renal insufficiency. To treat strictures, dilation, intermittent catheterization and recently stent introduction were used. Most suitable appears a stent from composite polymers. The aim of our work was to test properties of stents developed in the Institute of Macromolecular Chemistry ASCR. METHODS AND RESULTS: Stents from composite polymers, which are non-toxic, not-irritable can swell in body fluids and have mechanical properties similar to that of silicone rubber. Properties of the material are functionally graded and the casting or repoussé from the material can subsequently change its shape. Ten patients (males, aged 25 to 78 years) with long urethral strictures in its bulbocavernous part (50%) were treated with this method. Strictures were caused by pelvical fractures (4 times), prostate hypertrophy surgery (4 times), prolonged catheterizations (2 times). All patients were followed for 16 to 26 month and had no severities. CONCLUSION: Our results indicate that stent from composite polymers and silicone may have long-acting effects without irritation or crust formation and beneficially effected healing of the spongio-fibrous process.

Adult↗

HIV-related nontuberculous mycobacterial infection: incidence, survival analysis and associated risk factors.

To evaluate the incidence and survival time for AIDS-patients affected by different stages of nontuberculous mycobacterial (NTM) infection we performed a retrospective study. Data of 1540 hospitalised AIDS-patients was analyzed with respect to survival time and incidence rates. The overall incidence rate of NTM following AIDS was 16.6/100 person-years (PY), with an increase from 12.1/100PY (1987-1990) to 18.9/100PY (1991-1994). Antiretroviral therapy (ART) and toxoplasmosis prophylaxis reduced the risk of NTM disease whereas CD4 cells <40/ microl at time of the first AIDS defining illness led to a 2.5 fold higher risk. Pneumocystis carinii pneumonia (PCP), wasting syndrome and PCP prophylaxis increased the risk of progression from colonization to dissemination. Cryptococcus neoformans infection, wasting syndrome, PCP prophylaxis and CD4 cells <40/ microl were linked to immediate NTM dissemination. Though the incidence of NTM dissemination increased by the factor 1.56 in 1991-1994, survival did not differ between patients with and without NTM infection.

AIDS-Related Opportunistic Infections↗