Wide-pulse-high-frequency neuromuscular stimulation of triceps surae induces greater muscle fatigue compared with conventional stimulation.

We compared the extent and origin of muscle fatigue induced by short-pulse-low-frequency [conventional (CONV)] and wide-pulse-high-frequency (WPHF) neuromuscular electrical stimulation. We expected CONV contractions to mainly originate from depolarization of axonal terminal branches (spatially determined muscle fiber recruitment) and WPHF contractions to be partly produced via a central pathway (motor unit recruitment according to size principle). Greater neuromuscular fatigue was, therefore, expected following CONV compared with WPHF. Fourteen healthy subjects underwent 20 WPHF (1 ms-100 Hz) and CONV (50 μs-25 Hz) evoked isometric triceps surae contractions (work/rest periods 20:40 s) at an initial target of 10% of maximal voluntary contraction (MVC) force. Force-time integral of the 20 evoked contractions (FTI) was used as main index of muscle fatigue; MVC force loss was also quantified. Central and peripheral fatigue were assessed by voluntary activation level and paired stimulation amplitudes, respectively. FTI in WPHF was significantly lower than in CONV (21,717 ± 11,541 vs. 37,958 ± 9,898 N·s P<0,001). The reductions in MVC force (WPHF: -7.0 ± 2.7%; CONV: -6.2 ± 2.5%; P < 0.01) and paired stimulation amplitude (WPHF: -8.0 ± 4.0%; CONV: -7.4 ± 6.1%; P < 0.001) were similar between conditions, whereas no change was observed for voluntary activation level (P > 0.05). Overall, our results showed a different motor unit recruitment pattern between the two neuromuscular electrical stimulation modalities with a lower FTI indicating greater muscle fatigue for WPHF, possibly limiting the presumed benefits for rehabilitation programs.

Pulse wave analysis of aortic pressure: diastole should also be considered.

BACKGROUND: : The systolic augmentation index (sAix), calculated from the central aortic pulse wave (reconstructed from the noninvasive recording of the radial pulse with applanation tonometry), is widely used as a simple index of central arterial stiffness, but has the disadvantage of also being influenced by the timing of the reflected with respect to the forward pressure wave, as shown by its inverse dependence on heart rate (HR). During diastole, the central aortic pulse also contains reflected waves, but their relationship to arterial stiffness and HR has not been studied. METHODS: : In 48 men and 45 women, all healthy, with ages ranging from 19 to 70 years, we measured pulse wave velocity (PWV, patients supine), a standard evaluator of arterial stiffness, and carried out radial applanation tonometry (patients sitting and supine). The impact of reflected waves on the diastolic part of the aortic pressure waveform was quantified in the form of a diastolic augmentation index (dAix). RESULTS: : Across ages, sexes, and body position, there was an inverse relationship between the sAix and the dAix. When PWV and HR were added as covariates to a prediction model including age, sex and body position as main factors, the sAix was directly related to PWV (P < 0.0001) and inversely to HR (P < 0.0001). With the same analysis, the dAix was inversely related to PWV (P < 0.0001) and independent of HR (P = 0.52). CONCLUSION: : The dAix has the same degree of linkage to arterial stiffness as the more conventional sAix, while being immune to the confounding effect of HR. The quantification of diastolic aortic pressure augmentation by reflected waves could be a useful adjunct to pulse wave analysis.

Acute effects of transmyocardial laser revascularization on left-ventricular function: an haemodynamic and echocardiographic study.

While the lesions produced by transmyocardial laser revascularisation (TMLR) induce scar formation, it is important to determine whether this procedure can be deleterious for the left-ventricular function, which is already impaired by the underlying ischaemic process in some patients. Ten channels were drilled in the left lateral wall of the hearts of ten pigs (mean weight, 61 +/- 8.2kg) with a Holmium:YAG laser. Haemodynamic measurements and echocardiographic assessment of left-ventricular function were performed before the TMLR procedure, 5 and 30 min after, and lastly after 5 min of pacing at a rate increased by 30% of the baseline value. Echocardiographic assessment was in the short axis at the level of the laser channels, and included left-ventricular ejection fraction and segmental wall motility of the lasered area (scale 0-3:0 = normal 1 = hypokinesia, 2 = akinesia, 3 = dyskinesia). Values at 5 and 30 min were compared with baseline values; the difference was considered significant if p < 0.05. Haemodynamical values were stable throughout all the procedures. The ejection fraction showed a slight but significant decrease 5 min after the creation of the channels (60.4 +/- 6.8% vs 54 +/- 7.6%, p=0.02) and recovered at 30min. The segmental motility score of the involved areas increased to 1 after 5 min in five animals, and came back to 0 at 30 min except in one animal. Even with pacing no segmental dysfunction occurred. The reversibility of the segmental hypokinesia induced by TMLR, as well as the absence of pace-induced dysfunction 30 min after the procedure strongly suggest the inocuity of TMLR in this experimental set-up.

Profound impact of uncomplicated pregnancy on diastolic, but not systolic pulse contour of aortic pressure

RESUME: L'objectif de cette étude était de déterminer l'impact de la grossesse non compliquée sur l'onde de pouls de la pression aortique centrale. Méthode 66 femmes au total avec une grossesse simple ont été réparties en trois groupes selon le stade de leur gestation: premier trimestre (T1, n=22), deuxième trimestre (T2, n=20) et troisième trimestre (T3, n=24). Le groupe contrôle (C, n=21) était constitué de femmes non enceintes, en bonne santé habituelle, prenant une contraception oestroprogestative. La tonométrie d'aplanation a été utilisée pour l'acquisition des ondes de pouls centrale un appareil disponible dans le commerce (SphygmoCor) permet l'enregistrement de l'onde de pouls périphérique avec un tonomètre d'aplanation de l'artère radiale au niveau du poignet, puis effectue sa transformation en sa forme centrale, grâce à une analyse de Fourrier et une fonction de transfert. L'influence des ondes réfléchies sur l'onde de pouls a été déterminée non seulement pendant la systole (augmentation systolique), comme on procède habituellement dans l'analyse de l'onde de pouls, mais aussi pendant la diastole (augmentation diastolique). Résultats Au cours de la grossesse, les pressions centrales systolique et diastolique sont restées inchangées et comparables aux valeurs mesurées chez les femmes qui ne sont pas enceintes. Dans le groupe contrôle, l'augmentation systolique s'élevait à 8.1±7.5% de la pression de pouls ; il n'y avait pas de différence statistiquement significative avec les valeurs obtenues chez les femmes enceintes, et ce, à n'importe quel stade de la grossesse (T1 : 4.6±11.4%, T2: 5.0±9.3%, T3 : 4.7±8.1%). Par contre, l'amplitude de l'augmentation diastolique diminuait avec la progression de la grossesse (C 6.5±2.4%, T1 : 5.2±3.1%, T2 : 3.8±2.6%; P=0.002 versus C; T3 : 2.3±2.0%; P<0.0001 versus C et P=0.004 versus T 1). Conclusion La grossesse ne modifie pas la forme de l'onde de pouls systolique centrale, ce qui implique de la part du système cardiovasculaire une adaptation fine à la demande croissante de flux sanguin, et ce, à tous les stades de la grossesse. Par contre, l'amplitude de l'onde de réflexion atteignant l'aorte pendant la diastole diminue progressivement au cours de la grossesse. Perspectives De récentes études montrent qu'une valeur anormalement haute de l'augmentation systolique de la pression centrale, comme on peut la déterminer avec la tonométrie d'aplanation, pourrait être un indice de trouble hypertensif de la grossesse débutant. Cette technique simple pourrait être d'autant plus facile à mettre en oeuvre si les valeurs normales pour l'augmentation systolique étaient indépendantes du stade de la grossesse, comme le suggèrent nos résultats, du moins pour les mesures prises en position assise.

Heterogeneous 40Ar* distributions in naturally deformed muscovite: in situ UV-laser ablation evidence for micro structurally controlled intragrain diffusion

Micas are commonly used in Ar-40/Ar-39 thermochronological studies of variably deformed rocks yet the physical basis by which deformation may affect radiogenic argon retention in mica is poorly constrained. This study examines the relationship between deformation and deformation-induced microstructures on radiogenic argon retention in muscovite, A combination of furnace step-heating and high-spatial resolution in situ UV-laser ablation Ar-40/Ar-39 analyses are reported for deformed muscovites sampled from a granitic pegmatite vein within the Siviez-Mischabel Nappe, western Swiss Alps (Penninic domain, Brianconnais unit). The pegmatite forms part of the Variscan (similar to 350 Ma) Alpine basement and exhibits a prominent Alpine S-C fabric including numerous mica `fish' that developed under greenschist facies metamorphic conditions, during the dominant Tertiary Alpine tectonic phase of nappe emplacement. Furnace step-heating of milligram quantities of separated muscovite grains yields an Ar-40/Ar-39 age spectrum with two distinct staircase segments but without any statistical plateau, consistent with a previous study from the same area. A single (3 X 5 mm) muscovite porphyroclast (fish) was investigated by in situ UV-laser ablation. A histogram plot of 170 individual Ar-40/Ar-39 UV-laser ablation ages exhibit a range from 115 to 387 Ma with modes at approximately 340 and 260 Ma. A variogram statistical treatment of the (40)Ad/Ar-39 results reveals ages correlated with two directions; a highly correlated direction at 310 degrees and a lesser correlation at 0 degrees relative to the sense of shearing. Using the highly correlated direction a statistically generated (Kriging method) age contour map of the Ar-40/Ar-39 data reveals a series of elongated contours subparallel to the C-surfaces which where formed during Tertiary nappe emplacement. Similar data distributions and slightly younger apparent ages are recognized in a smaller mica fish. The observed intragrain age variations are interpreted to reflect the partial loss of radiogenic argon during Alpine (similar to 35 Ma) greenschist facies metamorphism. One-dirnensional diffusion modelling results are consistent with the idea that the zones of youngest apparent age represent incipient shear band development within the mica porphyroclasts, thus providing a network of fast diffusion pathways. During Alpine greenschist facies metamorphism the incipient shear bands enhanced the intragrain loss of radiogenic argon. The structurally controlled intragrain age variations observed in this investigation imply that deformation has a direct control on the effective length scale for argon diffusion, which is consistent with the heterogeneous nature of deformation. (C) 2001 Elsevier Science B.V. All rights reserved.

An intense form of homeostatic proliferation of naive CD8+ cells driven by IL-2.

In conditions of T lymphopenia, interleukin (IL) 7 levels rise and, via T cell receptor for antigen-self-major histocompatibility complex (MHC) interaction, induce residual naive T cells to proliferate. This pattern of lymphopenia-induced "homeostatic" proliferation is typically quite slow and causes a gradual increase in total T cell numbers and differentiation into cells with features of memory cells. In contrast, we describe a novel form of homeostatic proliferation that occurs when naive T cells encounter raised levels of IL-2 and IL-15 in vivo. In this situation, CD8(+) T cells undergo massive expansion and rapid differentiation into effector cells, thus closely resembling the T cell response to foreign antigens. However, the responses induced by IL-2/IL-15 are not seen in MHC-deficient hosts, implying that the responses are driven by self-ligands. Hence, homeostatic proliferation of naive T cells can be either slow or fast, with the quality of the response to self being dictated by the particular cytokine (IL-7 vs. IL-2/IL-15) concerned. The relevance of the data to the gradual transition of naive T cells into memory-phenotype (MP) cells with age is discussed.

Détermination de la séquence chronologique entre les impressions électrophotographiques (imprimantes laser et photocopieurs) et les traits de stylos à bille, sans croisement

Ce travail décrit une méthode optique pour établir l'ordre chronologique de la séquence entre les impressions électrophotographiques (imprimantes laser et photocopieurs) et les signatures apposées au stylo à bille, sans croisement. Les auteurs ont utilisé un microscope optique avec des grossissements allant de 100 à 500 fois qui permettent de distinguer l'apparence des microparticules de toner selon qu'elles se situent au-dessus ou au-dessous de l'encre de stylo à billes. Les tests à l'aveugle ont montré un taux de réussite de 100 % permettant ainsi de valider les résultats proposés par Aginsky (2002).

Are there vascular density gradients along myocardial laser channels?

BACKGROUND: Clinical studies suggest that transmyocardial laser revascularization may improve regional blood flow of the subendocardial layer. The vascular growth pattern of laser channels was analyzed. METHODS: Twenty pigs were randomized to undergo ligation of left marginal arteries (n = 5), to undergo transmyocardial laser revascularization of the left lateral wall (n = 5), to undergo both procedures (n = 5) or to a control group (n = 5). All the animals were sacrificed after 1 month. Computed morphometric analysis of vascular density of the involved area was expressed as number of vascular structures per square millimeter (+/-1 standard deviation). RESULTS: The vascular density of the scar tissue of the laser channel was significantly increased in comparison with myocardial infarction alone: 49.6+/-12.8/mm2 versus 25.5+/-8.6/mm2 (p < 0.0001). The vascular densities of subendocardial and subepicardial channel areas were similar: 52.9+/-16.8/mm2 versus 46.3+/-13.6/mm2 (p = 0.41). The area immediately adjacent to the channels showed a vascular density similar to that of normal tissue: 6.02+/-1.7/mm2 versus 5.2+/-1.9/mm2 (p = 0.08). In the infarction + transmyocardial laser revascularization group, the channels were indistinguishable from infarction scar. CONCLUSIONS: Scars of transmyocardial laser revascularization channels exhibit an increased vascular density in comparison with scar tissue of myocardial infarction, which does not extend into their immediate vicinity. There was no vascular density gradient along the longitudinal axis of the channels.

Krypton laser photocoagulation induces retinal vascular remodeling rather than choroidal neovascularization.

The purpose of this study is to analyze the retina and choroid response following krypton laser photocoagulation. Ninety-two C57BL6/Sev129 and 32 C57BL/6J, 5-6-week-old mice received one single krypton (630 nm) laser lesion: 50 microm, 0.05 s, 400 mW. On the following day, every day thereafter for 1 week and every 2-3 days for the following 3 weeks, serial sections throughout the lesion were systematically collected and studied. Immunohistology using specific markers or antibodies for glial fibrillary acidic protein (GFAP) (astrocytes, glia and Muller's cells), von Willebrand (vW) (vascular endothelial cells), TUNEL (cells undergoing caspase dependent apoptosis), PCNA (proliferating cell nuclear antigen) p36, CD4 and F4/80 (infiltrating inflammatory and T cells), DAPI (cell nuclei) and routine histology were carried out. Laser confocal microscopy was also performed on flat mounts. Temporal and spatial observations of the created photocoagulation lesions demonstrate that, after a few hours, activated glial cells within the retinal path of the laser beam express GFAP. After 48 h, GFAP-positive staining was also detected within the choroid lesion center. "Movement" of this GFAP-positive expression towards the lasered choroid was preceded by a well-demarcated and localized apoptosis of the retina outer nuclear layer cells within the laser beam path. Later, death of retinal outer nuclear cells and layer thinning at this site was followed by evagination of the inner nuclear retinal layer. Funneling of the entire inner nuclear and the thinned outer nuclear layers into the choroid lesion center was accompanied by "dragging" of the retinal capillaries. Thus, from days 10 to 14 after krypton laser photocoagulation onward, well-formed blood capillaries (of retinal origin) were observed within the lesion. Only a few of the vW-positive capillary endothelial cells stained also for PCNA p36. In the choroid, dilatation of the vascular bed occurred at the vicinity of the photocoagulation site and around it. Confocal microscopy demonstrates that the vessels throughout the path lesion are located within the neuroretina while in the choroid (after separation of the neural retina) only GFAP-positive but no lectin-positive cells can be seen. The involvement of infiltrating inflammatory cells in these remodeling and healing processes remained minimal throughout the study period. During the 4 weeks following krypton laser photocoagulation in the mouse eye, processes of wound healing and remodeling appear to be driven by cells (and vessels) originating from the retina.

Statistical discrimination of black gel pen inks analysed by laser desorption/ionization mass spectrometry

Pearson correlation coefficients were applied for the objective comparison of 30 black gel pen inks analysed by laser desorption ionization mass spectrometry (LDI-MS). The mass spectra were obtained for ink lines directly on paper using positive and negative ion modes at several laser intensities. This methodology has the advantage of taking into account the reproducibility of the results as well as the variability between spectra of different pens. A differentiation threshold could thus be selected in order to avoid the risk of false differentiation. Combining results from positive and negative mode yielded a discriminating power up to 85%, which was better than the one obtained previously with other optical comparison methodologies. The technique also allowed discriminating between pens from the same brand.

L'application de la spectroscopie Raman en criminalistique pour l'analyse du colorant des fibres textiles en acrylique, coton et laine

RESUME La méthode de la spectroscopie Raman est une technique d'analyse chimique basée sur l'exploitation du phénomène de diffusion de la lumière (light scattering). Ce phénomène fut observé pour la première fois en 1928 par Raman et Krishnan. Ces observations permirent à Raman d'obtenir le Prix Nobel en physique en 1930. L'application de la spectroscopie Raman a été entreprise pour l'analyse du colorant de fibres textiles en acrylique, en coton et en laine de couleurs bleue, rouge et noire. Nous avons ainsi pu confirmer que la technique est adaptée pour l'analyse in situ de traces de taille microscopique. De plus, elle peut être qualifiée de rapide, non destructive et ne nécessite aucune préparation particulière des échantillons. Cependant, le phénomène de la fluorescence s'est révélé être l'inconvénient le plus important. Lors de l'analyse des fibres, différentes conditions analytiques ont été testées et il est apparu qu'elles dépendaient surtout du laser choisi. Son potentiel pour la détection et l'identification des colorants imprégnés dans les fibres a été confirmé dans cette étude. Une banque de données spectrale comprenant soixante colorants de référence a été réalisée dans le but d'identifier le colorant principal imprégné dans les fibres collectées. De plus, l'analyse de différents blocs de couleur, caractérisés par des échantillons d'origine inconnue demandés à diverses personnes, a permis de diviser ces derniers en plusieurs groupes et d'évaluer la rareté des configurations des spectres Raman obtenus. La capacité de la technique Raman à différencier ces échantillons a été évaluée et comparée à celle des méthodes conventionnelles pour l'analyse des fibres textiles, à savoir la micro spectrophotométrie UV-Vis (MSP) et la chromatographie sur couche mince (CCM). La technique Raman s'est révélée être moins discriminatoire que la MSP pour tous les blocs de couleurs considérés. C'est pourquoi dans le cadre d'une séquence analytique nous recommandons l'utilisation du Raman après celle de la méthode d'analyse de la couleur, à partir d'un nombre de sources lasers le plus élevé possible. Finalement, la possibilité de disposer d'instruments équipés avec plusieurs longueurs d'onde d'excitation, outre leur pouvoir de réduire la fluorescence, permet l'exploitation d'un plus grand nombre d'échantillons. ABSTRACT Raman spectroscopy allows for the measurement of the inelastic scattering of light due to the vibrational modes of a molecule when irradiated by an intense monochromatic source such as a laser. Such a phenomenon was observed for the first time by Raman and Krishnan in 1928. For this observation, Raman was awarded with the Nobel Prize in Physics in 1930. The application of Raman spectroscopy has been undertaken for the dye analysis of textile fibers. Blue, black and red acrylics, cottons and wools were examined. The Raman technique presents advantages such as non-destructive nature, fast analysis time, and the possibility of performing microscopic in situ analyses. However, the problem of fluorescence was often encountered. Several aspects were investigated according to the best analytical conditions for every type/color fiber combination. The potential of the technique for the detection and identification of dyes was confirmed. A spectral database of 60 reference dyes was built to detect the main dyes used for the coloration of fiber samples. Particular attention was placed on the discriminating power of the technique. Based on the results from the Raman analysis for the different blocs of color submitted to analyses, it was possible to obtain different classes of fibers according to the general shape of spectra. The ability of Raman spectroscopy to differentiate samples was compared to the one of the conventional techniques used for the analysis of textile fibers, like UV-Vis Microspectrophotometry (UV-Vis MSP) and thin layer chromatography (TLC). The Raman technique resulted to be less discriminative than MSP for every bloc of color considered in this study. Thus, it is recommended to use Raman spectroscopy after MSP and light microscopy to be considered for an analytical sequence. It was shown that using several laser wavelengths allowed for the reduction of fluorescence and for the exploitation of a higher number of samples.

Wechsel von einem mechanischen Mikrokeratom auf einen Femtosekunden-Laser zur Korrektur von Astigmatismus mittels LASIK: klinische Ergebnisse einer retrospektiven, konsekutiven Vergleichsstudie Moving from a Mechanical Microkeratome to a Femtosecond Laser for LASIK to Correct Astigmatic Patients: Clinical Outcomes of a Retrospective, Consecutive, Comparative Study.

Background: To evaluate outcomes after optimized laser in situ keratomileusis (LASIK) for astigmatism correction with flap created by a mechanical microkeratome or a femtosecond laser. Patients and Methods: In this retrospective study, a total of 102 eyes of 71 consecutive patients were enrolled undergoing optimized LASIK treatments using the Allegretto laser system (WaveLight Laser Technologie AG, Erlangen, Germany). A mechanical microkeratome for flap creation was used (One Use, Moria®) in 46 eyes (31 patients, spherical equivalent [SE] -4.44 D ± 2.4) and a femtosecond laser was used (LDV, Ziemer®) in 56 eyes (40 patients, spherical equivalent [SE] -3.07 D ± 3.3). The two groups were matched for inclusion criteria and were operated under similar conditions by the same surgeon. Results: Overall, the preoperative spherical equivalent was -9.5 diopters (D) to +3.37 D; the preoperative manifest astigmatism was between -1.5 D and -3.5 D. At 6 months postoperatively, the mean postoperative uncorrected distance visual acuity (UDVA) was 0.93 ± 0.17 (range 0.4 to 1.2) in the Moria group and 1.0 ± 0.21 (range 0.6 to 1.6) in the Femto group, which was statistically significant (p = 0.003). Comparing the cylinder power there was a statistical difference between the two groups (p = 0.0015). Conclusions: This study shows that the method of flap creation has a significant impact on postoperative astigmatism with a significantly better postoperative UDVA in the Femto group. These findings suggest that the femtosecond laser provides a better platform for LASIK treatment of astigmatism than the commonly used microkeratome.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry, a revolution in clinical microbial identification.

Until recently, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) techniques for the identification of microorganisms remained confined to research laboratories. In the last 2 years, the availability of relatively simple to use MALDI-TOF MS devices, which can be utilized in clinical microbiology laboratories, has changed the laboratory workflows for the identification of pathogens. Recently, the first prospective studies regarding the performance in routine bacterial identification showed that MALDI-TOF MS is a fast, reliable and cost-effective technique that has the potential to replace and/or complement conventional phenotypic identification for most bacterial strains isolated in clinical microbiology laboratories. For routine bacterial isolates, correct identification by MALDI-TOF MS at the species level was obtained in 84.1-93.6% of instances. In one of these studies, a protein extraction step clearly improved the overall valid identification yield, from 70.3% to 93.2%. This review focuses on the current state of use of MALDI-TOF MS for the identification of routine bacterial isolates and on the main difficulties that may lead to erroneous or doubtful identifications.