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Motional Stark effect polarimetry is a key diagnostic for plasma fusion research since its usage on PBX-M. The MSE diagnostic measures the radial magnetic pitch angle profile in a plasma from a neutral beam by observation of Stark split D-alpha emission from atoms excited by collision with ions and electrons in the plasma. The pitch angle measurement is used with equilibrium reconstruction codes to determine the q-profile for studies of plasma stability, confinement, and transport. Historically, the algorithm was used in a post-processing fashion. The goal of our work was to apply this method in real time and pass the results to the plasma control system computer for real-time equilibrium reconstruction and control.
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Spin polarization in chiral molecules is a magnetic molecular response associated with electron transport and enantioselective bond polarization that occurs even in the absence of an external magnetic field. An unexpected finding by Santos and co-workers reported enantiospecific NMR responses in solid-state cross-polarization (CP) experiments, suggesting a possible additional contribution to the indirect nuclear spin-spin coupling in chiral molecules induced by bond polarization in the presence of spin-orbit coupling. Herein we provide a theoretical treatment for this phenomenon, presenting an effective spin-Hamiltonian for helical molecules like DNA and density functional theory (DFT) results on amino acids that confirm the dependence of J-couplings on the choice of enantiomer. The connection between nuclear spin dynamics and chirality could offer insights for molecular sensing and quantum information sciences. These results establish NMR as a potential tool for chiral discrimination without external agents.
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An overview of the plans for the motional Stark effect (MSE) diagnostic installation on the International Thermonuclear Experimental Reactor (ITER) is presented. The MSE diagnostic uniquely provides spatially localized magnetic field measurements inside the plasma. These are used to constrain equilibrium reconstructions to determine q(r), the safety factor as a function of minor radius. Meeting the system requirements to deliver q-profiles and related quantities with the specified radial resolution of 20 points over the minor radius, 10 ms time resolution, and better than 10% accuracy is challenging. MSE systems observe the D/H-α emission near 656.3 nm from neutral beams. As the beam atoms traverse the magnetic field, Bâ, at high velocity, vâ, they experience a Lorentz electric field, vâ×Bâ, which causes the spectral emission to be split and polarized due to the Stark effect. Traditional MSE-LP (line polarization) measurements determine the direction of the magnetic field in the observation volume using polarimetric analysis of the detected light. The harsh conditions of ITER are expected to deposit thin films of contaminants on the first mirror, which would alter the polarization state of reflected light significantly. On ITER, the combination of high magnetic field strength and high energy beams makes the Stark spectrum resolution suitable for the determination of the magnetic field magnitude from the line shift, so this approach has been selected. Every aspect of the measurement system must be planned for the burning plasma environment and carefully analyzed ahead of time. Current status and plans for the system are presented.
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As a part of ITER beam aided diagnostics, the design of Motional Stark Effect (MSE) diagnostic observing the emission from the Balmer-α line is underway. The physics of Stark splitting shows that the Stark manifold is polarization dependent, and the energy splitting results in a line shift proportional to the electric field. Due to the challenges of maintaining the calibration of the plasma facing mirrors in ITER, the conventional MSE polarimetry measurement technique is replaced with a spectral approach that is deemed more favorable in the ITER environment. The MSE line shift (LS) diagnostic is designed to quantify the Lorentz electric field magnitude by measuring the Stark manifold using visible spectroscopy. In the presence of large magnetic fields and high energy heating beams of 1 MeV, the expected Stark splitting is much larger than in typical devices. The MSE-LS design has unique challenges requiring careful consideration and modeling of its viewing geometry and photon budget. The MSE-LS approach on ITER is promising but has stringent demands on the allowable errors for the statistical and systematic fitting uncertainties. In this study, a full system model and numerical simulations of data for each sightline are completed. For a range of optical transmission fractions, photon noise analysis is conducted to determine the statistical uncertainties. This provides guidance on the spectrometer throughput, dispersion at the detector, optics, and other design choices. A conceptual design of a high throughput spectrometer with a volume phase transmission grating is presented.
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BACKGROUND: Ankle sprains are common musculoskeletal injuries in which the ligaments of the ankle partially or completely tear due to sudden stretching. OBJECTIVES: To critically appraise, evaluate and establish the best available evidence to determine the effectiveness of proprioceptive and neuromuscular training (PNT) compared to bracing in reducing the recurrence rate of ankle sprains in athletes. METHODOLOGY: The following seven databases were searched in June 2017: PubMed, Cochrane Library, PEDro, ScienceDirect, Scopus, SPORTDiscus, EBSCO Host: CINAHL. The main search terms used were "ankle sprains", "proprioceptive training", "neuromuscular training" and "bracing". The quality of the trials were critically appraised according to the PEDro scale. The RevMan 5© software was used to pool results. RESULTS: Three studies met the inclusion criteria and the quality according to the PEDro scale ranged from 4/10-7/10. The pooled data showed no difference between PNT and bracing in reducing the recurrence rate of ankle sprains in athletes at 12 months after initiation of the study. CONCLUSION: This systematic review of the overall effect suggested that current evidence (Level II) does not favour the use of PNT over bracing in reducing the recurrence rate of ankle sprains. Physiotherapists are advised to use either PNT or bracing according to the patients preference and their own expertise.
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Traumatismos del Tobillo/prevención & control , Traumatismos en Atletas/prevención & control , Tirantes , Modalidades de Fisioterapia , Propiocepción , Esguinces y Distensiones/prevención & control , Humanos , RecurrenciaRESUMEN
The objective of this study was to identify and analyze the geographic distribution of dentists, in the global context, through available scientific evidence, highlighting the following aspects: 1) the determinants of the geographic distribution of dentists, 2) corrective intervention implemented, and 3) their monitoring and evaluation. A scoping review of the published and gray literature was carried out in scientific databases and in relevant websites. We used an adaptation of a World Health Organization framework to study the distribution of human resources in health to analyze selected publications. After applying the eligibility criteria, 53 publications were included in the review; 10 related to the determinants of geographical distribution, 5 to interventions implemented, and 38 to the monitoring and evaluation process. More studies are needed to identify local determinants of the geographical distribution of dentists and to define adapted intervention strategies to make it more equitable. Knowledge Transfer Statement: The geographic inequality of dentists is a problem for health systems because it has a direct impact on access to services and the oral health conditions of a population. Our study was based on a theoretical conceptual framework formulated in 3 components: 1) determinants of the geographical distribution, 2) strategies implemented to correct the problem, and 3) monitoring and evaluation. It can assist in designing oral health policy and guide decisions by policy makers.
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Odontólogos , Política de Salud , Fuerza Laboral en Salud , Humanos , Salud Bucal , Factores Socioeconómicos , Organización Mundial de la SaludRESUMEN
Many plasma diagnostics contain complementary information. For example, the double-foil soft x-ray system (SXR) and the Thomson Scattering diagnostic (TS) on the Madison Symmetric Torus both measure electron temperature. The complementary information from these diagnostics can be combined using a systematic method based on integrated data analysis techniques, leading to more accurate and sensitive results. An integrated data analysis tool based on Bayesian probability theory was able to estimate electron temperatures that are consistent with both the SXR and TS diagnostics and more precise than either. A Markov Chain Monte Carlo analysis to increase the flexibility of the tool was implemented and benchmarked against a grid search method.
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Introducción Las enfermedades oncohematológicas son una causa importante de mortalidad en Argentina, y el trasplante de células progenitoras hematopoyéticas (TCPH) es el tratamiento de elección en muchos de los casos. Existen pocos datos sobre la incidencia y la relevancia clínica de la infección por rinovirus (RV) en TCPH, una población en la que otros virus respiratorios causan alta tasa de infección del tracto respiratorio inferior y mortalidad. OBJETIVOS Estimar la incidencia de infección del tracto respiratorio superior (ITRS) e inferior (ITRI) por RV en pacientes con TCPH. Describir sus características clínicas, factores de riesgo y evolución. MÉTODOS Se realizó un estudio de cohorte prospectivo. RESULTADOS Se incluyó a 26 pacientes 24 (92,3%) con TCPH autólogo y 2 (7,7%) con TCPH alogénico. Quedaron excluidos del estudio 2 pacientes por presentar hisopado nasofaríngeo basal con PCR positiva para RV, mientras que 6 (23,1%) presentaron síntomas de ITRS sin diagnóstico virológico y 1 presentó ITRI con diagnóstico de neumonía por virus parainfluenza en el lavado broncoalveolar. En el seguimiento de los pacientes hasta el día 100 no se documentaron infecciones por RV. Discusión A diferencia de otros estudios, no se pudo evidenciar la presencia de RV como patógeno de las infecciones del tracto respiratorio en la población descripta. Este hallazgo podría estar determinado por el bajo número de pacientes incluidos. Sin embargo, el hecho de no haber detectado RV en la población estudiada constituye un dato epidemiológico de relevancia, principalmente porque empieza a responder al interrogante de la incidencia de RV en Argentina y sirve como punto de partida para continuar con el estudio, ampliando el tiempo y número de pacientes, de cara a los objetivos secundarios propuestos inicialmente.
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Neumonía Viral , Infecciones del Sistema Respiratorio , Rhinovirus , Trasplante de Células Madre HematopoyéticasRESUMEN
INTRODUCCIÓN La diarrea es una de las complicaciones más frecuentes del trasplante renal, con consecuencias potencialmente graves. OBJETIVOS Describir las características epidemiológicas y los hallazgos microbiológicos en pacientes internados con trasplante renal o renopáncreas y diarrea aguda y persistente en un hospital universitario de la ciudad de Buenos Aires. MÉTODOS Se realizó un estudio de corte transversal, con análisis descriptivo de 52 pacientes. RESULTADOS La mediana de edad de los pacientes fue de 47 años. El 80,8% habían recibido un trasplante renal; el resto, renopáncreas. El 71,2% se encontraban en el período post-trasplante tardío. La diarrea fue el motivo de ingreso en el 64,7% de los casos. El 50% de los pacientes no tuvo un diagnóstico etiológico de diarrea; un 36% tuvo diarrea con causa microbiológica específica: 6% enfermedad por citomegalovirus (CMV), 12% atribuida a CMV, 10% rotavirus y 8% Clostridium difficile; el resto (14%), diarrea atribuida a fármacos: mofetil micofenolato (MMF) y sirolimus. De los pacientes con diarrea con causa microbiológica específica, el 44% había recibido inmunosupresores a altas dosis recientemente, a diferencia de los otros grupos (p=0,048). Todos los pacientes con diarrea atribuida a fármacos recibían como parte del tratamiento inmunosupresor al ingreso MMF (p=0,039). Cabe resaltar la ausencia de parásitos como agentes etiológicos de diarrea. La mediana de duración de internación fue de 6 días, y un 14,6% persistió con diarrea al quinto día de internación. Todos los pacientes tuvieron resolución de la diarrea al alta, y un tercio persistió con insuficiencia renal. DISCUSIÓN La información derivada es casi exclusiva del medio estudiado y sirve como punto de partida para la realización de nuevas investigaciones, dirigidas a mejorar los métodos diagnósticos y terapéuticos en pacientes trasplantados renales con diarrea aguda y persistente.
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Trasplante de Riñón , Citomegalovirus , Diarrea , Ácido MicofenólicoRESUMEN
The quality of plasma produced in a magnetic confinement fusion device is influenced to a large extent by the neutral gas surrounding the plasma. The plasma is fueled by the ionization of neutrals, and charge exchange interactions between edge neutrals and plasma ions are a sink of energy and momentum. Here we describe a diagnostic capable of measuring the spatial distribution of neutral gas in a magnetically confined fusion plasma. A high intensity (5 MW/cm(2)), narrow bandwidth (0.1 cm(-1)) laser is injected into a hydrogen plasma to excite the Lyman ß transition via the simultaneous absorption of two 205 nm photons. The absorption rate, determined by measurement of subsequent Balmer α emission, is proportional to the number of particles with a given velocity. Calibration is performed in situ by filling the chamber to a known pressure of neutral krypton and exciting a transition close in wavelength to that used in hydrogen. We present details of the calibration procedure, including a technique for identifying saturation broadening, measurements of the neutral density profile in a hydrogen helicon plasma, and discuss the application of the diagnostic to plasmas in the DIII-D tokamak.
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Objectives: Check the progress of hospitalization and death of the patients that use clopidogrel associated with omeprazole and the patients that do not. Methods A retrospective cohort was conducted between January 2007 and November 2009 to evaluate patients that were using clopidogrel in association or not with omeprazole. Results The study included 2823 patients. Of these patients, 36% were female and 64% were male, the mean age was 63 years. Regarding the association of drugs for gastric protection, omeprazole was prescribed to 45%, ranitidine for 9%, while 46% of patients were not receiving gastroprotective medication. As for the analysis by groups, 35.5% of the omeprazole group was hospitalized after starting treatment with clopidogrel, compared with 25.7% in the group without omeprazole. In evaluating the deaths among patients using clopidogrel in the study period, we found the occurrence of 36 deaths, 22 in the omeprazole group and 14 in the other group. Conclusions In our study, we did not evaluate the clinical status of the patients and the rates of reinfarction. And, as our study data showed, there are not any statistically differences between the groups that used clopidogrel associated with omeprazole, with ranitidine or that did not use any gastroprotective medication (AU)
Objetivos: Comprobar el incremento en la tasa de hospitalización y fallecimiento de los pacientes que reciben clopidogrel asociado con omeprazol y los pacientes que no lo reciben. Métodos: Entre enero de 2007 y noviembre de 2009 se realizó un estudio de cohorte retrospectivo para evaluar a los pacientes que recibían clopidogrel, independientemente de si estaba asociado o no a omeprazol. Resultados: El estudio incluyó a 2823 pacientes, de los cuales, 36% eran mujeres y 64% eran hombres, con una media de edad de 63 años. En cuanto a la asociación de medicamentos gastroprotectores, al 45% se le había recetado omeprazol y al 9% ranitidina, mientras que al46% de los pacientes no se le administraba este tipo de medicación. Si evaluamos el uso de los medicamentos por grupos, observamos que el 35,5% del grupo del omeprazol se encontraba hospitalizado tras comenzar el tratamiento con clopidogrel, al igual que el 25,7% del grupo al que no se le administraba omeprazol. Al evaluar los fallecimientos entre pacientes que recibían clopidogrel durante el periodo de estudio, observamos que se produjeron 36 fallecimientos,22 en el grupo del omeprazol y 14 en el grupo que no tomaba omeprazol. Conclusiones: En nuestro estudio no evaluamos el estado clínico de los pacientes ni las tasas de reinfarto. Como demuestran nuestros datos, no existen diferencias estadísticas entre los grupos que recibían clopidogrel asociado con omeprazol, ranitidina o que no recibían ningún tipo de medicamento gastroprotector (AU)
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Humanos , Omeprazol/uso terapéutico , Sustancias Protectoras/uso terapéutico , Inhibidores de Agregación Plaquetaria/uso terapéutico , Antiulcerosos/uso terapéutico , Inhibidores de la Bomba de Protones/uso terapéutico , Utilización de Medicamentos/estadística & datos numéricos , Ranitidina/uso terapéutico , Estudios RetrospectivosRESUMEN
Polystyrene-b-polymethylmethacrylate (PS-b-PMMA) was selected as the host for 4-(4-nitrophenylazo)aniline (Disperse Orange 3, DO3) based on a previous study of DO3/PMMA and DO3/PS binary blends. Selective location of DO3 into the PMMA block of the copolymer was expected during self-assembly of the block copolymer since a preferential interaction of DO3 with PMMA has been demonstrated. However, surface segregation of DO3 was found during the thermal annealing used to nanostructure the copolymer. To avoid this, a thermoplastic polymer (Azo-TP) was synthesized from the bulk reaction of DO3 and diglycidyl ether of bisphenol A (DGEBA). The choice of DGEBA as a co-reactant was an attempt to encourage the selective location of azo groups in the PMMA phase of PS-b-PMMA. An inspection of solutions of Azo-TP in PS and PMMA, corroborates the preferential affinity of Azo-TP for PMMA. The Azo-TP could be satisfactorily dissolved in PS-b-PMMA. We have investigated the growth and decay processes of the optically induced birefringence in films of PS-b-PMMA containing 12 wt% Azo-TP. The resulting materials showed a good photoinduced time response, high maximum birefringence and an elevated fraction of remnant anisotropy.
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OBJECTIVES: Check the progress of hospitalization and death of the patients that use clopidogrel associated with omeprazole and the patients that do not. METHODS: A retrospective cohort was conducted between January 2007 and November 2009 to evaluate patients that were using clopidogrel in association or not with omeprazole. RESULTS: The study included 2823 patients. Of these patients, 36% were female and 64% were male, the mean age was 63 years. Regarding the association of drugs for gastric protection, omeprazole was prescribed to 45%, ranitidine for 9%, while 46% of patients were not receiving gastroprotective medication. As for the analysis by groups, 35.5% of the omeprazole group was hospitalized after starting treatment with clopidogrel, compared with 25.7% in the group without omeprazole. In evaluating the deaths among patients using clopidogrel in the study period, we found the occurrence of 36 deaths, 22 in the omeprazole group and 14 in the other group. CONCLUSIONS: In our study, we did not evaluate the clinical status of the patients and the rates of reinfarction. And, as our study data showed, there are not any statistically differences between the groups that used clopidogrel associated with omeprazole, with ranitidine or that did not use any gastroprotective medication.
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Antiulcerosos/administración & dosificación , Omeprazol/administración & dosificación , Inhibidores de Agregación Plaquetaria/administración & dosificación , Ticlopidina/análogos & derivados , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Antiulcerosos/efectos adversos , Antiulcerosos/uso terapéutico , Niño , Clopidogrel , Estudios de Cohortes , Femenino , Mortalidad Hospitalaria , Hospitalización , Humanos , Masculino , Persona de Mediana Edad , Omeprazol/efectos adversos , Omeprazol/uso terapéutico , Inhibidores de Agregación Plaquetaria/efectos adversos , Inhibidores de Agregación Plaquetaria/uso terapéutico , Ranitidina/administración & dosificación , Ranitidina/uso terapéutico , Estudios Retrospectivos , Ticlopidina/administración & dosificación , Ticlopidina/efectos adversos , Ticlopidina/uso terapéutico , Adulto JovenRESUMEN
Muscle cellularity was studied in Pagellus bogaraveo juveniles fed on diets with different protein contents. Measured in transversal body sections, at both post-opercular and post-anal locations, the morphometric variables estimated were: total muscle area (A), total number of fibres (N), number of fibres per unit area of muscle (N (A)) and cross-sectional fibre area (a) of the two main muscle fibre types. At the end of the experiment fish fed on diets having more than 40% of protein displayed significantly higher body weight. Fish fed on protein-rich diets exhibited greater a and N. For fish fed on 30 and 50% protein diets the morphometric parameters measured grew linearly with the fish weight. High-protein diets favoured muscle hyperplasia. When comparing rostral and caudal locations, a greater N and a smaller a of posterior red fibres were the consistent differences found-a fact, to our knowledge, so far unreported for fish.
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Fenómenos Fisiológicos Nutricionales de los Animales , Proteínas en la Dieta/administración & dosificación , Desarrollo de Músculos , Fibras Musculares Esqueléticas/efectos de los fármacos , Perciformes/anatomía & histología , Perciformes/crecimiento & desarrollo , Animales , Tamaño Corporal , Fibras Musculares de Contracción Rápida/citología , Fibras Musculares de Contracción Rápida/efectos de los fármacos , Fibras Musculares Esqueléticas/citología , Fibras Musculares de Contracción Lenta/citología , Fibras Musculares de Contracción Lenta/efectos de los fármacosRESUMEN
To understand better the growth mechanisms in the economically important fish Pagellus bogaraveo, in terms of muscle fibre hyperplasia v. hypertrophy, the lateral muscle of this fish was studied morphometrically from hatching to juvenile comparing rostral and caudal locations. Fish were sampled at 0, 5, 23, 40, 70, 100, 140 and 180 days. Fibre types were first identified by succinate dehydrogenase (SDH) and immunostaining with a polyclonal antibody against fish slow myosin (4-96). Morphometric variables were then measured in transverse body sections, at both post-opercular and post-anal locations, to estimate the following variables: total muscle area [A (muscle)], total fibre number [N (fibres)], fibre number per unit area of muscle [N(A)(fibres, muscle)] and cross-sectional fibre area [a (fibres)] of the two main muscle fibre types (white and red). Overall, growth throughout the various stages resulted from increases both in the number and in the size of muscle fibres, paralleled by an expansion of the [A (muscle)]. Nonetheless, that increase was not significant between 0-5 days on one hand and 100-140 days, on the other hand. On the contrary, the [N(A)(fibres, muscle)] declined as the body length increased. Analysis of the muscle growth kinetics suggested that, within the important time frame studied, hyperplasia gave the main relative contribution to the increase of white muscle [A (white muscle)], whereas red muscle [A (red muscle)] mainly grew by hypertrophy, with both phenomena occurring at a faster pace posteriorly in the body. Finally, when comparing rostral and caudal locations, a greater [N (fibres)] and [A (muscle)] of the posterior white and red fibres were the consistent features. It was also observed that the proportion of the cross-sectional area of the myotomal muscle comprised of white muscle was greater in the anterior part of the fish.
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Desarrollo de Músculos , Fibras Musculares Esqueléticas/fisiología , Dorada/crecimiento & desarrollo , Animales , Hiperplasia , Hipertrofia , Fibras Musculares Esqueléticas/patologíaRESUMEN
A study was undertaken to determine the resources available in Italian hospitals for the control of nosocomial infections and the factors favouring a successful approach. During January-May 2000 a questionnaire about infection control was sent to the hospital health director of all Italian National Health System hospitals treating acute patients and with more than 3500 admissions in 1999. An active programme was defined as a hospital infection control committee (HICC) meeting at least four times in 1999, the presence of a doctor with infection control responsibilities, a nurse employed in infection control and at least one surveillance activity and one infection control guideline issued or updated in the past two years. There was a response rate of 87.5% (463/529). Almost fifteen percent (69/463) of hospitals had an active programme for Infection Control and 76.2% (353/463) had a HICC. Seventy-one percent (330/463) of the hospitals had a hospital infection control physician and 53% (250/463) had infection control nurses. Fifty-two percent (242/463) reported at least one surveillance activity and 70.8% (328/463) had issued or updated at least one guidance document in the last two years. The presence of regional policies [odds ratio (OR) 8.7], operative groups (OR 4.2), at least one full-time nurse (OR 4.6) and a hospital annual plan which specified infection control (OR 2.1) were statistically associated with an active programme in the multivariate analysis.
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Infección Hospitalaria/prevención & control , Control de Infecciones/organización & administración , Política Organizacional , Capacidad de Camas en Hospitales , Humanos , Profesionales para Control de Infecciones/provisión & distribución , Italia , Modelos Logísticos , Análisis Multivariante , Vigilancia de la PoblaciónRESUMEN
Generation of spontaneous rhythmic activity is a distinct feature of developing spinal networks. We report that rat embryo organotypic spinal cultures contain the basic circuits responsible for pattern generation. In this preparation rhythmic activity can be recorded from ventral interneurons and is developmentally regulated. When chronically grown in the presence of an AMPA/kainate receptor blocker, this circuit expresses long-term plasticity consisting largely of increased frequency of fast synaptic activity and reduction in slow GABAergic events. We examined whether, once this form of homeostatic plasticity is established, the network could still exhibit rhythmicity with properties similar to controls. Control or chronically treated ventral interneurons spontaneously generated (with similar probability) irregular, network-driven bursts over a background of ongoing synaptic activity. In control cultures increasing network excitability by strychnine plus bicuculline, or by raising [K(+)](o), induced rapid-onset, regular rhythmic bursts. In treated cultures the same pharmacological block of Cl(-)-mediated transmission or high-K(+) application also induced regular patterned activity, although significantly faster and, in the case of high K(+), characterized by slow onset due to postsynaptic current summation. Enhancing GABAergic transmission by pentobarbital surprisingly accelerated the high-K(+) rhythm of control cells (though depressing background activity), whereas it slowed it down in chronically treated cells. This contrasting effect of pentobarbital suggests that, to preserve bursting ability, chronic slices developed a distinct GABAergic inhibitory control on over-expressed bursting circuits. Conversely, in control slices GABAergic transmission depressed spontaneous activity but it facilitated bursting frequency. Thus, even after homeostatic rearrangement, developing mammalian spinal networks still generate rhythmic activity.
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Homeostasis/efectos de los fármacos , Plasticidad Neuronal/fisiología , Receptores AMPA/antagonistas & inhibidores , Receptores de Ácido Kaínico/antagonistas & inhibidores , Médula Espinal/fisiología , 6-Ciano 7-nitroquinoxalina 2,3-diona/farmacología , Animales , Canales de Cloruro/efectos de los fármacos , Canales de Cloruro/fisiología , Electrofisiología , Antagonistas de Aminoácidos Excitadores/farmacología , Femenino , Moduladores del GABA/farmacología , Glicinérgicos/farmacología , Inmunohistoquímica , Plasticidad Neuronal/efectos de los fármacos , Técnicas de Cultivo de Órganos , Técnicas de Placa-Clamp , Pentobarbital/farmacología , Potasio/metabolismo , Embarazo , Ratas , Receptores de GABA-A/efectos de los fármacos , Médula Espinal/efectos de los fármacos , Estricnina/farmacología , Ácido gamma-Aminobutírico/metabolismoRESUMEN
OBJECTIVES: Spastic patients were studied to understand whether stance unsteadiness is associated with changes in the control of voluntary force, muscle tone, or reflex excitability, rather than to abnormal posture connected to the motor deficit itself. METHODS: Twenty four normal subjects, 12 patients affected by amyotrophic lateral sclerosis (ALS), seven by spastic paraparesis, and 14 by hemiparesis were studied. All patients featured various degrees of spasticity and paresis but were free from clinically evident sensory deficits. Body sway during quiet upright stance was assessed through a stabilometric platform under both eyes open (EO) and eyes closed (EC) conditions. The sudden rotation of a supporting platform, in a toe up and toe down direction respectively, evoked short (SLR) and medium latency (MLR) reflex responses to stretch of the soleus or the tibialis anterior (TA) muscle. RESULTS: No relation was found between clinical findings (tone, muscle strength, tendon reflexes, plantar response, and duration of disease) and body sway. On average, all patient groups exhibited a forward shift of the centre of foot pressure (CFP) with respect to normal subjects; in addition, paraparetic and to a much larger extent hemiparetic patients showed a lateral shift of CFP. Body sway area was significantly increased only in the hemiparetic patients. No relation was found between position of the CFP and sway within any patient group. Soleus SLR was increased in all patients with respect to normal subjects. TA SLR was often seen in both patients with ALS and paraparetic patients, but only rarely in normal subjects and hemiparetic patients. However, no relation was found between amplitude of soleus or TA SLRs and stabilometric variables. The frequency and size of soleus MLR and TA MLR were decreased in all patients. These responses were decreased in size and not modulated by background EMG in the affected leg of hemiparetic patients, suggesting a disturbed control of spinal reflexes fed by spindle group II afferent fibres. CONCLUSIONS: It is proposed that body posture, paresis, or monosynaptic reflex hyperexcitability do not affect the control of equilibrium during quiet upright stance. In hemiparetic patients, the decreased amplitude of MLRs might be the main cause of the large postural instability. The results are congruent with the hypothesis of a role for group II afferent input in the reflex control of equilibrium.
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Espasticidad Muscular/fisiopatología , Paresia/fisiopatología , Postura/fisiología , Reflejo/fisiología , Adulto , Anciano , Análisis de Varianza , Electromiografía , Pie/fisiopatología , Humanos , Persona de Mediana Edad , Tiempo de Reacción/fisiologíaRESUMEN
1. The well-developed cytoarchitecture of rat organotypic spinal cord culture makes it a suitable model to explore how persistent suppression of certain synaptic inputs might be compensated by increased synaptic efficacy (homeostatic plasticity). 2. Spontaneous or electrically evoked synaptic transmission of patch-clamped ventral horn interneurons was studied in control solution after blocking, for the second week in culture, AMPA/kainate receptors with CNQX or glycine and GABAA receptors with strychnine and bicuculline, or indiscriminately removing inputs with tetrodotoxin (TTX). 3. In untreated cells, spontaneous postsynaptic currents (PSCs) had fast (tau < 5 ms) or slow (tau > 10 ms) decay. A similar separation was observed when recording miniature currents (mPSCs). Slow decay PSCs were suppressed by strychnine plus bicuculline while fast decay events were eliminated by CNQX. 4. After chronic CNQX treatment the frequency of spontaneous, fast PSCs (of larger amplitude) or mPSCs was almost doubled with respect to control. These events were blocked by acutely applied CNQX, which unmasked slow PSCs. 5. After chronic TTX treatment neither the frequency nor the amplitude of spontaneous events was changed. 6. After chronic strychnine and bicuculline treatment the frequency and amplitude of all PSCs was decreased in most cells. mPSCs were also decreased in frequency. Spontaneous or electrically evoked currents acquired a larger component mediated by NMDA receptor activity. 7. The developing spinal network thus operated distinct homeostatic processes which led to strong enhancement in glutamatergic transmission after CNQX block or to broad downregulation of synaptic activity following chronic exposure to strychnine and bicuculline.