Densification and depression in glass transition temperature in polystyrene thin films.

Ellipsometry and X-ray reflectivity were used to characterize the mass density and the glass transition temperature of supported polystyrene (PS) thin films as a function of their thickness. By measuring the critical wave vector (qc) on the plateau of total external reflection, we evidence that PS films get denser in a confined state when the film thickness is below 50 nm. Refractive indices (n) and electron density profiles measurements confirm this statement. The density of a 6 nm (0.4 gyration radius, Rg) thick film is 30% greater than that of a 150 nm (10Rg) film. A depression of 25 °C in glass transition temperature (Tg) was revealed as the film thickness is reduced. In the context of the free volume theory, this result seems to be in apparent contradiction with the fact that thinner films are denser. However, as the thermal expansion of thinner films is found to be greater than the one of thicker films, the increase in free volume is larger for thin films when temperature is raised. Therefore, the free volume reaches a critical value at a lower Tg for thinner films. This critical value corresponds to the onset of large cooperative movements of polymer chains. The link between the densification of ultrathin films and the drop in their Tg is thus reconciled. We finally show that at their respective Tg(h) all films exhibit a critical mass density of about 1.05 g/cm(3) whatever their thickness. The thickness dependent thermal expansion related to the free volume is consequently a key factor to understand the drop in the Tg of ultrathin films.

Statistical analysis of mounded surfaces: application to the evolution of ultrathin gold film morphology with deposition temperature.

Extracting characteristic dimensions from mounded surfaces such as grain size or intergrain lengths is usually made by statistical analysis. Different statistical functions are used in the literature to extract characteristic lengths. The main issue is that depending on the choice of the statistical function the results can be very different. In this paper, we demonstrate using a series of model mounded surfaces for which characteristic dimensions are known, that a method (namely, interfacial differential function, IDF) is the most effective method to determine the different characteristic lengths. The influence on the statistical treatment of the variation of the different characteristic lengths is then studied and confirms the ability of the IDF analysis. The IDF method was used to analyze the evolution of ultrathin gold film morphology as function of deposition temperature. This approach allows us to demonstrate that the roughness increase with deposition temperature is mainly due to a grain height increase and not to a grain coarsening phenomena as it was claimed before.

Tuning the architecture of cellulose nanocrystal-poly(allylamine hydrochloride) multilayered thin films: influence of dipping parameters.

Multilayered thin films consisting of alternating cationic polyelectrolyte, poly(allylamine hydrochloride) (PAH), and anionic cellulose nanocrystals (CNs) were constructed using the dipping procedure by screening different experimental parameters: the drying step between each layer adsorption, the dipping time, the ionic strength of the PAH solution, and the concentration of CNs dispersion. We showed that the drying process and the ionic strength of PAH solution were crucial parameters for the successful construction of 8-bilayer films. Film thickness is mainly influenced by dipping time and CN concentration when using the dipping procedure without drying. Two architectures of adsorbed CN layers-a single or a double layer of CNs-were revealed on the basis of the thickness increment per bilayer, depending on experimental conditions. The layer adsorption process was investigated in real-time using quartz crystal microbalance with dissipation (QCM-D) experiments in an aqueous environment or by incorporating a drying step. On the basis of in situ construction of PAH-CN films in wet media, QCM-D data were indicative of highly hydrated films for which the progressive layer stacking is disturbed or prevented. QCM-D monitoring of CNs and PAH layer adsorption was monitored by incorporating a drying process. The impact of experimental parameters on PAH-CN multilayered construction and on CN layer configuration is discussed. This study offers new opportunities for tailoring the architecture of CN-based multilayer films.

Relative age is associated with sport dropout: evidence from youth categories of French basketball.

The aim of the current research was to investigate the relative age effect (RAE) as a factor of basketball dropout. In order to do so, we examined the distribution of birth dates of young male (n=44,498) and female (n=30,147) French basketball players who have dropped out this sport during or at the end of the 2005-2006 season. χ(2) analyses showed an underrepresentation of dropouts among male players born early in the competition year and an overrepresentation among those born late in the "9-10 years old,""11-12 years old," and "13-14 years old" categories and in the first year of the "15-17 years old" category. Concerning girls, this asymmetry was observed across the same age categories. For both boys and girls, there was no biased distribution in the "7-8 years old" category. Findings of the present study confirm that the RAE should be taken into consideration in studies about sport dropout as a variable that may influence this phenomenon significantly.

Relative age effect in female sport: a diachronic examination of soccer players.

The relative age effect (RAE) is a biased distribution of elite athletes' birthdates, with an overrepresentation of those born at the beginning of the competitive year and an underrepresentation of those born at the end. Despite an abundant literature, the impact of sex on this phenomenon remains neglected by most researchers. This study investigated the whole sample of female soccer players affiliated to the French Soccer Federation for the 2006-2007 season (n=57 892). It first aimed at testing the presence of RAE depending on age. Next, we looked at the birthdates of dropout players during the next season (n=15 285), to test whether relative age accounts for dropout from the activity. The analyses revealed significant differences between the expected and the observed distributions for all age categories. Furthermore, a significantly biased distribution of dropout players' birthdates was found for the <10, <14, and <17 categories. On the whole, dropout players are underrepresented in Q1 and Q2, but overrepresented in Q3 and Q4. This study completes the literature on RAE among females, but the inconsistency of the results calls for more research on this population.

The relative age effect in young French basketball players: a study on the whole population.

The aim of this study is to test the presence of the relative age effect (RAE) and to examine height in an overall population of the young French basketball players from 7 to 18 years old, male (n=151 259) and female (n=107 101). For the boys as for the girls, the results show a statistically significant RAE in all age categories. The effect seems more pronounced during puberty. As far as the height is concerned, players born during quarters 1 and 2 are always significantly taller than those born during quarter 4, apart from the 17-year-old female players. These results require a new look at the methodology in the statistical calculation and the interpretation of RAE. A study wanting to give a precise measurement of this effect will have to take as the expected theoretical distribution the whole population of licensed players in the corresponding years, rather than one on the global population of the country. This will avoid the hasty conclusion that an asymmetric distribution of dates of birth of professional players would be due to RAE, whereas in reality it would be representative of one existing in the population of licensed players.

Experimental evidence of the electrostatic contribution to the bending rigidity of charged membranes.

We address the issue of the origin of the bending rigidity of a charged membrane formed from amphiphilic molecules. Electrostatic effects are investigated by direct measurement of the force necessary to deform a catanionic membrane as function of the ionic strength of the medium by means of an atomic force microscope (AFM). Using continuum mechanical modeling of membrane deformation, we derive the bending rigidity of the catanionic membranes and monitor for the first time its decrease in response to increasing salt concentration.

Direct method to study membrane rigidity of small vesicles based on atomic force microscope force spectroscopy.

Mechanical properties of lipidic membranes such as their bending rigidity are governing liposome morphology and play an important role in processes like membrane fusion and adhesion. Force versus deformation measurements are the most direct means to determine this, but so far experimental data is scarce and mainly stems from techniques that are limited to giant vesicles. We present atomic force microscope force spectroscopy as a method allowing force-deformation measurements of submicron vesicles. Bending rigidities of small unilamellar dipalmitoylphosphatidylcholine (DPPC) liposomes (R<200 nm) can be derived from the force-deformation data using analytical models based on shell theory and are in good agreement with independent measurements.

Interleukin-1beta (IL-1beta) induces a crosstalk between cAMP and ceramide signaling pathways in thyroid epithelial cells.

Interleukin-1 beta (IL-1beta) is an important regulator of the thyroid cell function. This cytokine has been largely described to trigger an important biological signaling cascade: the sphingomyelin/ceramide pathway. In this report, we show that IL-1beta induces the transient activation of a neutral sphingomyelinase in porcine thyroid cells. Moreover, IL-1beta and ceramides are demonstrated to inhibit the TSH-induced cAMP production via the implication of alphaGi subunit of the adenylyl cyclase system. This crosstalk between cAMP and ceramide pathways constitutes a preponderant process in the TSH-controlled differentiation state of thyrocytes. All these results argue for the involvement of ceramides and IL-1beta in the thyroid function regulation, leading to a cell dedifferentiated state.

[Unusual presentation of infantile myofibromatosis with an ulcered plaque]. / Présentation inhabituelle d'une myofibromatose cutanée infantile en plaque unique ulcérée.

INTRODUCTION: Infantile myofibromatosis is a rare fibrovascular-like, isolated or multicentric tumor, occasionally of the bone or an organ and appearing before the age of 2. We report a case of infantile myofibromatosis in a child in an atypical form with a single, ulcerated plaque and having developed after the onset of clusters of papular nodules. OBSERVATION: An infant was seen in consultation because of asymptomatic papules that had developed on the back. The histological examination of a partial biopsy revealed a histiocytofibromatus aspect and led to the diagnosis of clusters of multiple histiocytofibromatous. One year later, the papular nodules had converged, forming a large plaque with ulcerated center. The progressive extension and the absence of healing prompted surgical exeresis and the final diagnosis of myofibromatosis. DISCUSSION: Diagnosis of infantile myofibromatosis is difficult histologically and clinically and relies on a clear anatomoclinical confrontation. The clinical aspects are varied. To our knowledge, myofibromatosis with a single ulcerated plaque has never been reported in the literature before.

Thrombospondin 1: a multifunctional protein implicated in the regulation of tumor growth.

Thrombospondins belong to a family of extracellular matrix (ECM) proteins widely found from embryonic to adult tissues. The modular structure of thrombospondins contains a series of peptide sequences implicated in a multiplicity of biological functions. Extracellular matrix undergoes important alterations under proteolysis that occurs in pathological processes like tumorigenesis. An elevated secretion of thrombospondin 1 (TSP1) is often observed in tumors and is sometimes considered as a predictive factor. However, the role of TSP1 in cancer progression remains controversial and must be carefully apprehended. The regulation of cell adhesion, proliferation, apoptosis by TSP1 is examined in the present review and it is clear from the literature and from our investigations that TSP1 presents both stimulatory and inhibitory effects. The exposition of cryptic sites upon conformational changes can partially explain this contradiction. More interestingly, the analysis of TSP1-directed intracellular signaling pathways activated through specific receptors or supramolecular receptors docking systems may be useful to discriminate the precise function of TSP1 in tumor progression. The central role played by TSP1 in the control of matrix-degrading enzyme activation and catabolism reveals attractive tracks of research and highlights the involvement of the lipoprotein receptor-related protein (LRP) receptor in these events. Therefore, TSP1-derived peptides constitute a source of potentially active matrikins which could provide essential tools in cancer therapy.

TGFbeta1 effects on functional activity of porcine thyroid cells cultured in suspension.

Thyrotropin (TSH) and transforming growth factor beta 1 (TGFbeta1) have major roles in the regulation of folliculogenesis and differentiation in thyroid cells. Isolated porcine thyroid cells cultured in the presence of TSH on a plastic surface recover a follicular architecture and exhibit normal functional properties. The addition of TGFbeta1 to the culture medium induces important morphological changes and extracellular matrix remodelling. Similarly, thyroid cells lose their ability to organify iodine and their responsiveness to adenylate cyclase. The aim of this study was to analyse the influence of TGFbeta1 on the functional activity of thyrocytes in suspension culture, independent of follicle disruption. In this system, we demonstrate that TGFbeta1 inhibits expression of thyroperoxidase, NADPH oxidase activity, iodine uptake and, consequently, iodine organification. Moreover, TGFbeta1 decreases basal and TSH-stimulated cAMP production and TSH receptor expression. Taken together, these data converge to demonstrate an essential role of TGFbeta1 in the regulation of the thyroid cell function.

Local variations of pulmonary arterial wedge pressure and wedge angiograms in patients with chronic lung disease.

This study was undertaken in 23 patients with chronic lung disease to determine whether local wedge pressure variability is related to the state of the local perfusion as observed in distal wedge angiograms. We also compared the variability of the pressures obtained after distal (mechanical) and proximal (balloon inflation) wedging of a catheter in three to six different sites in each patient. When the wedge pressure measurements were repeated in the same site (n = 7), the mean of the absolute differences was below 1 mm Hg. In individual patients, the maximal pressure difference between sites ranged from 0 to 6 mm Hg for Ppw and from 1 to 12 mm Hg for Pdw. The range in Pdw increased from normal to abnormal angiograms. These results suggest that when Pdw is high in one region, it may correspond to local perfusion abnormalities. When the wedge pressure is measured repeatedly or under different conditions, it should be determined after wedging the catheter in the same location for all of the periods of observation.

Reliability of six pulse oximeters in chronic obstructive pulmonary disease.

Six pulse oximeters with finger probes were studied in three groups of 17 hypoxemic patients with COPD aged 50 to 75 years. Transcutaneous arterial oxygen saturation (SpO2) was measured with the Nellcor N101 (oximeter 1a), the Ohmeda Biox III (oximeter lb), the Nellcor N200 (oximeter 2a), the Critikon Oxyshuttle (oximeter 2b), the Radiometer Oxi100 (oximeter 3a), and the Ohmeda Biox 3700 (oximeter 3b). The SpO2 was compared with SaO2 measured in simultaneously withdrawn samples of arterial blood (Radiometer OSM2) at three 20-minute steady-state levels of FIO2 ranging from 0.21 to 0.40 (SaO2, 62 to 100 percent). The bias (mean SpO2-SaO2 difference) and the error in precision (SD of the differences) were both below 4 percent for instruments 1a and 1b and remained below 1.2 and 3 percent, respectively, for the others. A good agreement between SpO2 and SaO2, as reflected by the Bartko intraclass correlation coefficient, was observed in instruments 2a, 3a, and 3b. The individual relationships between SpO2-SaO2 differences and SaO2 appeared to be linear and parallel. With four instruments (1a, 1b, 2a, and 2b), the mean slope of this relationship was negative, showing a systematic instrumental error: the lower the SaO2, the larger the overestimation of SaO2. The scattering of the data (precision) principally reflects a subject source of error. In most instruments a technical adjustment could greatly improve instrumental errors and accuracy. The correction of the errors due to between-subject variation would require a system of calibration adjustable by the users to each individual.

Hemodynamic effects of intravenous diltiazem in hypoxic pulmonary hypertension.

The short-term effects of intravenously administered diltiazem on pulmonary and systemic hemodynamics were evaluated in patients with hypoxic pulmonary hypertension. Twelve patients were randomly assigned to two groups in a double-blind fashion. One group (eight patients) received diltiazem, and the other group (four patients) received a placebo. Three increasing doses of diltiazem (0.2, 0.3, and 0.4 mg/kg of body weight) were injected into each patient, followed each time by an infusion (2 micrograms/kg/min, 3 micrograms/kg/min, and 4 micrograms/kg/min). The effects of the drug were also compared with those of oxygen, and the combined effect of high oxygen and diltiazem was tested. The mean plasma concentrations of diltiazem were, successively, 64 +/- 4, 158 +/- 19, and 267 +/- 40 ng/ml with the three increasing doses. There was no significant effect of diltiazem on the pulmonary vascular resistance even when given with oxygen. Diltiazem was well tolerated even at high doses. The arterial oxygen pressure, systemic oxygen supply, and oxygen consumption were unchanged. We conclude that diltiazem does not seem to decrease acutely hypoxic pulmonary vasoconstriction in patients with chronic hypoxia; however, diltiazem may be given safely to these patients for other indications, such as angina pectoris.

Computed tomography in the etiologic assessment of idiopathic spontaneous pneumothorax.

In an attempt to elucidate the origin of the so-called idiopathic spontaneous pneumothorax (ISP), clinical examination, pulmonary function tests, and computed tomography (CT) with visual quantification and density analysis were performed in 20 young patients two months after an ISP episode. Twenty controls were recruited for CT. The chest roentgenograms were normal in the two groups. The results indicated the presence of various types of emphysematous lesions (EL) in the ISP group located predominantly in the apical fields with subpleural location in 16 patients. Interestingly, diffuse but moderate centrilobular emphysema was noted in 12 of 20 patients. The EL visual quantification was always less than 5 percent of the CT slices' total areas. The lung mean density shifted significantly toward the air density in the patient group (patients: -743 +/- 57.5 HU vs controls -713 +/- 59.5 HU, p less than 0.01). These findings suggest that CT may be useful for early assessment of EL in patients with ISP.

Effect of acute hypercapnia on alpha atrial natriuretic peptide, renin, angiotensin II, aldosterone, and vasopressin plasma levels in patients with COPD.

Disturbances in hormonal systems involved in sodium and water homeostasis are common during respiratory insufficiency. To investigate the role of hypercapnia, we designed a study to examine the hormonal response to acute hypercapnia induced at constant cardiac filling pressures and without hypoxemia. Seven sedated patients with COPD receiving mechanical ventilation were studied during five successive periods. Hemodynamics, arterial blood gases, and plasma hormone levels (atrial natriuretic peptide, renin, angiotensin II, aldosterone, vasopressin) were measured three times during 60 min of acute hypercapnia (52 +/- 5 mm Hg) and at control periods, before (36 +/- 4 mm Hg) and after (42 +/- 3 mm Hg) acute hypercapnia. During acute hypercapnia, mean pulmonary arterial pressure and cardiac output were increased without variation of other measured cardiorespiratory data and hormonal levels when compared with control values. After acute hypercapnia, cardiorespiratory variables returned to control values without variations of hormonal levels. Our results show that moderate acute hypercapnia does not significantly influence the hormonal levels when cardiac filling pressures and sympathetic tone remain stable. We suggest that changes in those plasma hormones involved in salt and water homeostasis during acute hypercapnia are secondary to hemodynamic changes induced by acute respiratory failure and not to acute hypercapnia per se.

Theophylline disposition in patients with COLD with and without hypoxemia.

This study aimed to assess the effect of hypoxemia on theophylline disposition. Ten patients with a mean (+/- SEM) of 58 +/- 3 years with COLD (PaO2 55 +/- 1 mm Hg, PaCO2 46 +/- 2 mm Hg, and pH of 7.39 +/- 0.01) were hospitalized to have oxygen therapy. Before starting O2, they received intravenously, 4 mg/kg of theophylline over a 20-minute period; blood samples and urine were collected for six hours. The results suggested that hypoxia does not influence the disposition of theophylline or its metabolites.

Involvement of the ceramide signaling pathway in modulating the differentiated state of porcine thyroid cells.

Neutral sphingomyelinase (Smase) is a cell membrane-associated phospholipase that hydrolyzes sphingomyelin to phosphocholine and ceramide, a lipid second messenger involved in cell differentiation and/or apoptosis. We first evidenced that porcine cultured thyroid cells could express neutral Smase activity even if thyrotropin (TStH), an essential hormone in thyroid cell differentiation, was found to induce a 1.7-fold decrease in Smase activity. Triggering the ceramide pathway by exogenous addition of neutral bacterial Smase (0.1 U/mL for 48 h), which transiently increased ceramide level by fourfold, drastically modified thyroid cell morphology. The follicle-like structures generated by TSH were disrupted, and the Smase-induced cell spreading was accompanied by a parallel loss of cell ability to iodinate proteins as well as a decrease of the adenylate cyclase system response. These inhibitory effects have been reproduced using short-chain exogenous ceramide analogs (C2-ceramides). Overall these data showed that ceramides emerged as potential mediators of dedifferentiation in thyroid cells.

[Methotrexate pneumonitis arising during the treatment of non-Hodgkin's lymphomas with the m-BACOD protocol]. / Pneumopathies du méthotrexate survenant dans le cadre du traitement des lymphomes non hodgkiniens par le protocole m-BACOD.

We retrospectively studied 32 patients treated with the m-BACOD regimen in a single institution between January 1988 and December 1991. After four to seven courses, four patients presented severe acute pneumonitis (PaO2 < 55 mmHg in room air), with diffuse bilateral interstitial syndrome. Broncho-alveolar lavage displayed increased lymphocyte count (> 45%) with inversion of CD4/CD8 in two cases and no evidence of parasitic, bacterial or viral infection. All patients received methyl-prednisolone (0.5 to 1 mg/kg/d x 1 week) with both complete clinical and radiological recovery within a week. The m-BACOD regimen was continued without bleomycine for four patients and without bleomycine plus methotrexate for two patients, until the completion of eight courses, without recurrence of pneumonitis. Drug-exclusion decisions were made empirically because the exact nature of the pneumonitis was not recognized at the time of diagnostic. Because of the regular administration in the m-BACOD regimen, methotrexate leads to an increased risk of pneumonitis. We concluded that the use of the m-BACOD regimen should henceforth be discontinued.