Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 55
Filtrar
Más filtros

Bases de datos
País/Región como asunto
Tipo del documento
Intervalo de año de publicación
1.
Minerva Chir ; 67(5): 421-8, 2012 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-23232480

RESUMEN

AIM: Ischemic gastritis is poorly known by physicians and is often fatal if not correctly diagnosed. Here, we report on the clinical, endoscopic and imaging features and treatment outcomes for five ischemic gastritis patients. METHODS: This was a retrospective, single-centre study of patients treated for ischemic gastritis between January 2009 and April 2012. All patients underwent transluminal angioplasty or open revascularization surgery. RESULTS: Five patients (4 men, 1 female) were included in the present study. The condition was diagnosed in two cases of peritonitis with gastric or duodenal perforation, two cases of acute epigastric pain and one case of gastric bleeding, profuse vomiting and hypovolemic shock. Three of the five patients had endoscopically proven gastric ulcerations or necrosis. A computed tomography scan contributed to the diagnosis in all cases. The symptoms resolved in all cases after gastric revascularization via an aortohepatic bypass (N.=1), a renohepatic bypass (N.=1), a retrograde iliosuperior mesenteric bypass (N.=2) with associated celiac artery angioplasty (N.=1) and celiac and superior mesenteric artery angioplasty (N.=1). During follow-up, three patients died of starvation due to short bowel syndrome (N.=1) or metastatic lung cancer (N.=2). CONCLUSION: Ischemic gastritis is a component of celiac territory ischemia syndrome and is closely associated with chronic or acute mesenteric ischemia. Computed tomography always informs the diagnosis. The rapid healing observed here after revascularization confirmed the ischemic nature of the condition and the inappropriateness of gastric resection in this context.


Asunto(s)
Gastritis/etiología , Isquemia/etiología , Estómago/irrigación sanguínea , Arteria Celíaca , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Síndrome
2.
Epidemiol Psychiatr Sci ; 28(6): 598-602, 2019 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-30977461

RESUMEN

To experience sexual violence and abuse is to experience silence. This commentary explores some of the ways in which psychiatry reinforces the silencing of sexual violence survivors. We argue that current psychiatric responses to sexual violence typically constitute iatrogenic harm including through: a failure to provide services that meet survivors' needs, a failure to believe or validate disclosures; experiences of medicalisation and diagnoses which can delegitimise people's own knowledge and meaning; 'power over' relational approaches which can prevent compassionate responses and result in staff having to develop their own coping strategies; and poorly addressed and reported experiences of sexual violence within psychiatric settings. We argue that these multiple forms of silencing have arisen in part because of biomedical dominance, a lack of support and training in sexual violence for staff, inconsistent access to structured, reflective supervision, and the difficulties of facing the horror of sexual violence and abuse. We then describe community-based and grassroots responses, and consider the potential of trauma-informed approaches. Whilst this paper has a UK focus, some aspects will resonate globally, particularly given that Western psychiatry is increasingly being exported around the globe.


Asunto(s)
Servicios de Salud Mental , Violación/psicología , Delitos Sexuales/psicología , Investigación sobre Servicios de Salud , Humanos
3.
J Inherit Metab Dis ; 31 Suppl 2: S223-5, 2008 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-18500574

RESUMEN

Neurological crises do not occur in patients with tyrosinaemia type I treated with NTBC. We report an 8 month-old boy with severe neurological crisis after interruption of NTBC treatment including progressive ascending polyneuropathy and diaphragmatic paralysis, arterial hypertension, respiratory distress requiring mechanical ventilation who later also developed impaired liver function and tubulopathy. After re-introduction of NTBC the patient slowly regained normal neurological functions and recovered completely.


Asunto(s)
Ciclohexanonas/administración & dosificación , Inhibidores Enzimáticos/administración & dosificación , Nitrobenzoatos/administración & dosificación , Polineuropatías/etiología , Parálisis Respiratoria/etiología , Tirosinemias/tratamiento farmacológico , Esquema de Medicación , Humanos , Hipertensión/etiología , Lactante , Masculino , Cumplimiento de la Medicación , Polineuropatías/fisiopatología , Polineuropatías/terapia , Respiración Artificial , Insuficiencia Respiratoria/etiología , Parálisis Respiratoria/fisiopatología , Parálisis Respiratoria/terapia , Tirosinemias/complicaciones , Tirosinemias/diagnóstico
4.
Leukemia ; 21(1): 121-8, 2007 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-17039236

RESUMEN

Recently, we and others described a new chromosomal rearrangement, that is, inv(7)(p15q34) and t(7;7)(p15;q34) involving the T-cell receptor beta (TCRbeta) (7q34) and the HOXA gene locus (7p15) in 5% of T-cell acute lymphoblastic leukemia (T-ALL) patients leading to transcriptional activation of especially HOXA10. To further address the clinical, immunophenotypical and molecular genetic findings of this chromosomal aberration, we studied 330 additional T-ALLs. This revealed TCRbeta-HOXA rearrangements in five additional patients, which brings the total to 14 cases in 424 patients (3.3%). Real-time quantitative PCR analysis for HOXA10 gene expression was performed in 170 T-ALL patients and detected HOXA10 overexpression in 25.2% of cases including all the cases with a TCRbeta-HOXA rearrangement (8.2%). In contrast, expression of the short HOXA10 transcript, HOXA10b, was almost exclusively found in the TCRbeta-HOXA rearranged cases, suggesting a specific role for the HOXA10b short transcript in TCRbeta-HOXA-mediated oncogenesis. Other molecular and/or cytogenetic aberrations frequently found in subtypes of T-ALL (SIL-TAL1, CALM-AF10, HOX11, HOX11L2) were not detected in the TCRbeta-HOXA rearranged cases except for deletion 9p21 and NOTCH1 activating mutations, which were present in 64 and 67%, respectively. In conclusion, this study defines TCRbeta-HOXA rearranged T-ALLs as a distinct cytogenetic subgroup by clinical, immunophenotypical and molecular genetic characteristics.


Asunto(s)
Proteínas de Homeodominio/genética , Leucemia-Linfoma de Células T del Adulto/genética , Receptores de Antígenos de Linfocitos T alfa-beta/genética , Adolescente , Adulto , Niño , Deleción Cromosómica , Inversión Cromosómica , Femenino , Reordenamiento Génico de Linfocito T , Proteínas Homeobox A10 , Humanos , Inmunofenotipificación , Leucemia-Linfoma de Células T del Adulto/patología , Leucemia-Linfoma de Células T del Adulto/fisiopatología , Masculino , Persona de Mediana Edad , Receptor Notch1/genética , Activación Transcripcional , Translocación Genética
5.
Nutr Neurosci ; 11(5): 207-12, 2008 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-18782480

RESUMEN

We compared the maturation of the monosynaptic stretch reflex in control rats and in rats submitted to neonatal malnutrition. Electrical stimulations of the sciatic nerve were applied in wakeful rats of different ages (21-90 days) to record, by surface electrodes, the maximal direct motor response (M(max)) or the maximal Hoffmann reflex (H(max)). Percussion on the Achilles tendon induced the T-reflex. Animals submitted to neonatal malnutrition showed significant reductions in H-reflex latency and in velocity index of nervous conduction. The H- or T-reflex amplitudes were lower for malnourished rats of 21 days but the difference was significant only for the T(max)/M(max) ratios. The reflexes evoked at older ages did not present differences between control and malnourished rats. In conclusion, rats submitted to neonatal malnutrition present long-term alteration in reflex latency and nervous conduction velocity. Neonatal malnutrition also alters the reflex excitability at weaning but, since the rat were submitted to a normal diet after weaning, a normal reflex excitability was rapidly recovered which indicates a remarkable plasticity of the reflex pathway.


Asunto(s)
Animales Recién Nacidos , Desnutrición/complicaciones , Reflejo Monosináptico/fisiología , Reflejo de Estiramiento/fisiología , Envejecimiento , Animales , Estimulación Eléctrica , Femenino , Lactancia , Masculino , Desnutrición/dietoterapia , Desnutrición/fisiopatología , Embarazo , Ratas , Ratas Wistar
6.
Leukemia ; 20(4): 696-706, 2006 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-16467868

RESUMEN

The NUP98 gene is fused with 19 different partner genes in various human hematopoietic malignancies. In order to gain additional clinico-hematological data and to identify new partners of NUP98, the Groupe Francophone de Cytogénétique Hématologique (GFCH) collected cases of hematological malignancies where a 11p15 rearrangement was detected. Fluorescence in situ hybridization (FISH) analysis showed that 35% of these patients (23/66) carried a rearrangement of the NUP98 locus. Genes of the HOXA cluster and the nuclear-receptor set domain (NSD) genes were frequently fused to NUP98, mainly in de novo myeloid malignancies whereas the DDX10 and TOP1 genes were equally rearranged in de novo and in therapy-related myeloid proliferations. Involvement of ADD3 and C6ORF80 genes were detected, respectively, in myeloid disorders and in T-cell acute lymphoblastic leukemia (T-ALL), whereas the RAP1GDS1 gene was fused to NUP98 in T-ALL. Three new chromosomal breakpoints: 3q22.1, 7p15 (in a localization distinct from the HOXA locus) and Xq28 were detected in rearrangements with the NUP98 gene locus. The present study as well as a review of the 73 cases previously reported in the literature allowed us to delineate some chromosomal, clinical and molecular features of patients carrying a NUP98 gene rearrangements.


Asunto(s)
Neoplasias Hematológicas/genética , Proteínas de Complejo Poro Nuclear/genética , Translocación Genética/genética , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Niño , Preescolar , Análisis Citogenético , Femenino , Francia , Proteínas de Homeodominio/genética , Humanos , Hibridación Fluorescente in Situ , Lactante , Masculino , Persona de Mediana Edad , Receptores Citoplasmáticos y Nucleares/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Sensibilidad y Especificidad , Sociedades Médicas
7.
Ann Biol Clin (Paris) ; 65(5): 569-73, 2007.
Artículo en Francés | MEDLINE | ID: mdl-17913678

RESUMEN

We report a new case of transient myeloproliferative disorder (TMD) in a non Down syndrome neonate. The cytogenetic and molecular studies within from the blood blast cells identified a trisomy 21 and a partial deletion in exon 2 of the transcription factor GATA1. Spontaneous regression of the TMD was achieved at the age of 1 month as the clonal and molecular abnormalities. A survey by periodic cytological examinations of peripheral blood cells and GATA1 mutation analysis was instituted since three years and has not detected up to date acute leukaemia.


Asunto(s)
Enfermedades del Prematuro/diagnóstico , Recien Nacido Prematuro , Trastornos Mieloproliferativos/diagnóstico , Enfermedades en Gemelos , Síndrome de Down/genética , Exones/genética , Estudios de Seguimiento , Factor de Transcripción GATA1/genética , Eliminación de Gen , Humanos , Recién Nacido , Masculino , Mutación/genética , Remisión Espontánea , Gemelos Dicigóticos
8.
Leukemia ; 7(4): 509-15, 1993 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-8464228

RESUMEN

Cytogenetic follow-up studies such as those reported after allogeneic bone marrow transplantation are not available in patients submitted to an autologous bone marrow transplantation (ABMT). Of 114 patients with acute leukemia (69 acute myelocytic AML, 43 acute lymphocytic ALL, 2 undifferentiated) who underwent an ABMT in our institution in the period from February 1983 to December 1989, 66 had evaluable cytogenetic data post-transplant. They all received a pretransplant regimen consisting of cyclophosphamide (CY) and total body irradiation (TBI) followed by reinfusion of marrow purged with mafosfamide. Twenty patients showed chromosomal damage at some time; of these, six relapsed early post-ABMT, one died while in persisting remission at 81 months post-ABMT from overwhelming pneumococcal sepsis related to a previous splenectomy, and 13 are still alive and well at 13 to 88 months post-transplant. The bone marrow cytogenetic abnormalities were complex: they included various numbers of clonal aberrations or variations or combination of those; they affected all but the Y chromosome, with a predominance however for chromosomes 1, 3, 6, and 7; they were often transitory and in some instances became modified with time. None of these chromosomal abnormalities was connected with the initial leukemia, even in the 6 patients who relapsed early. In the other 14 patients, these abnormalities have so far had no detectable unfavourable implication. The origin of these abnormalities is unknown: both the pretransplant regimen (CY and/or TBI) and/or marrow purging with mafosfamide can be incriminated. Additional studies in patients autografted with pretransplant regimen not containing TBI and/or with unpurged marrow are necessary to discriminate between these two possibilities.


Asunto(s)
Antineoplásicos , Purgación de la Médula Ósea , Aberraciones Cromosómicas , Ciclofosfamida/análogos & derivados , Leucemia/genética , Femenino , Humanos , Leucemia/cirugía , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/cirugía , Masculino , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/cirugía , Factores de Tiempo , Trasplante Autólogo , Resultado del Tratamiento
9.
Leukemia ; 17(9): 1851-7, 2003 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-12970786

RESUMEN

To accurately estimate the incidence of HOX11L2 expression, and determine the associated cytogenetic features, in T-cell acute lymphoblastic leukemia (T-ALL), the Groupe Français de Cytogénétique Hématologique (GFCH) carried out a retrospective study of both childhood and adult patients. In total, 364 patients were included (211 children

Asunto(s)
Cromosomas Humanos Par 14/genética , Cromosomas Humanos Par 5/genética , Proteínas de Homeodominio/genética , Leucemia-Linfoma de Células T del Adulto/genética , Proteínas Oncogénicas/genética , Translocación Genética , Adolescente , Adulto , Niño , Preescolar , Aberraciones Cromosómicas , Células Clonales , Femenino , Humanos , Inmunofenotipificación , Hibridación Fluorescente in Situ , Cariotipificación , Masculino , Ploidias , Proteínas Proto-Oncogénicas , Estudios Retrospectivos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Tasa de Supervivencia
10.
J Electromyogr Kinesiol ; 15(3): 310-5, 2005 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-15763678

RESUMEN

Surface electromyograms (EMG) of back muscles are often corrupted by electrocardiogram (ECG) signals. This noise in the EMG signals does not allow to appreciate correctly the spectral content of the EMG signals and to follow its evolution during, for example, a fatigue process. Several methods have been proposed to reject the ECG noise from EMG recordings, but seldom taking into account the eventual changes in ECG characteristics during the experiment. In this paper we propose an adaptive filtering algorithm specifically developed for the rejection of the electrocardiogram corrupting surface electromyograms (SEMG). The first step of the study was to choose the ECG electrode position in order to record the ECG with a shape similar to that found in the noised SEMGs. Then, the efficiency of different algorithms were tested on 28 erector spinae SEMG recordings. The best algorithm belongs to the fast recursive least square family (FRLS). More precisely, the best results were obtained with the simplified formulation of a FRLS algorithm. As an application of the adaptive filtering, the paper compares the evolutions of spectral parameters of noised or denoised (after adaptive filtering) surface EMGs recorded on erector spinae muscles during a trunk extension. The fatigue test was analyzed on 16 EMG recordings. After adaptive filtering, mean initial values of energy and of mean power frequency (MPF) were significantly lower and higher respectively. The differences corresponded to the removal of the ECG components. Furthermore, classical fatigue criteria (increase in energy and decrease in MPF values over time during the fatigue test) were better observed on the denoised EMGs. The mean values of the slopes of the energy-time and MPF-time linear relationships differed significantly when established before and after adaptive filtering. These results account for the efficacy of the adaptive filtering method proposed here to denoise electrophysiological signals.


Asunto(s)
Electrocardiografía , Electromiografía , Procesamiento de Señales Asistido por Computador , Algoritmos , Artefactos , Dorso , Humanos , Movimiento , Contracción Muscular/fisiología , Fatiga Muscular/fisiología , Músculo Esquelético/fisiología , Factores de Tiempo
11.
Exp Hematol ; 27(12): 1822-30, 1999 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-10641600

RESUMEN

Several prospective randomized trials in acute myelocytic leukemia (AML) documented a lower relapse rate with autologous bone marrow transplantation (ABMT) than with conventional chemotherapy. However, they also identified some transplant difficulties, such as failure to collect sufficient numbers of stem cells, slow kinetics of engraftment, and a high transplant-related mortality that diminished or negated positive impact on overall survival. Data for ABMT are inconclusive in acute lymphocytic leukemia (ALL) in adults. We retrospectively analyzed patients with acute leukemia autografted with marrow purged with mafosfamide after January 1983 in our institution. The population comprised 229 consecutive patients; 165 with AML [123 in first remission (CR1), 32 in second remission (CR2)]; 61 with ALL (46 in CR1, 4 in CR2); and 3 with undifferentiated acute leukemia. All patients were autografted with marrow purged with mafosfamide. Mafosfamide was given at a constant dose of 50 microg/mL in 103 and adjusted individually to produce a CFU-GM LD 95 (5% residual CFU-GM post purging) in 126. The outcome was analyzed for correlation with patient characteristics, the disease including cytogenetics, and the graft itself. Prognostic factors identified by multivariate analysis were used to derive a prognostic classification. Patients receiving higher doses of marrow submitted to purging (>5.46 x 10(4) CFU-GM/kg) experienced a lower treatment-related mortality (RR = 0.11, p = 0.005) and a higher leukemia-free (RR = 0.5, p = 0.005) and overall survival (RR = 0.4, p = 0.001). Patients receiving <0.004% CFU-GM of marrow actually infused post purging had a lower relapse rate (RR = 0.51, p = 0.003). Modeling of prognostic groups identified good-, intermediate-, and poor-risk categories. Patients receiving a stem cell dose evaluated before purging of >5.46 x 10(4) CFU-GM/kg and doses actually infused post purging of < or =0.02 x 10(4)/kg had a treatment-related mortality of only 2+/-2%, a leukemia-free survival of 70%, and an overall survival of 77+/-7% at 10 years. In this study of autotransplantation for acute leukemia using mafosfamide-purged marrow, the stem cell dose used for purging and the intensity of purging were the most important factors predicting outcome.


Asunto(s)
Antineoplásicos/farmacología , Purgación de la Médula Ósea , Trasplante de Médula Ósea , Ciclofosfamida/análogos & derivados , Leucemia Mieloide Aguda/terapia , Adolescente , Adulto , Anciano , Antineoplásicos/uso terapéutico , Recuento de Células , Niño , Ciclofosfamida/farmacología , Ciclofosfamida/uso terapéutico , Femenino , Supervivencia de Injerto , Humanos , Leucemia Mieloide Aguda/fisiopatología , Masculino , Persona de Mediana Edad , Ensayos Clínicos Controlados Aleatorios como Asunto , Estudios Retrospectivos , Trasplante Homólogo , Resultado del Tratamiento
12.
Sleep ; 10(4): 297-305, 1987 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-3659728

RESUMEN

To investigate the prevalence of excessive daytime somnolence and contributing factors, 58,162 draftees between 17 and 22 years of age, registered in two selection centers of the French army, were screened by means of a 17-item questionnaire. In response, 8,201 subjects (14.1%) reported occasional daytime sleep episodes, 2,210 (3.8%) one or two daily episodes, and 640 (1.1%) more than two daily episodes. Of the total sample, five percent or 2,933 considered these sleep episodes to affect their lives. Different possible factors of daytime sleep episodes were investigated, including hours of nocturnal sleep, sleep-wake schedule, sleep difficulties, use of hypnotics, snoring, and occurrence of cataplexy. A strong association was found between these factors and excessive daytime somnolence. A stepwise multivariate analysis was performed on five of these factors: hours of nocturnal sleep, sleep-wake schedule, sleep difficulties, use of hypnotics, and snoring. All five factors were shown to be independently related to excessive daytime somnolence and were ranked in the following descending order: use of hypnotics, sleep difficulties, irregular sleep-wake schedule, snoring, and hours of sleep.


Asunto(s)
Ritmo Circadiano , Fases del Sueño/fisiología , Trastornos del Sueño-Vigilia/etiología , Adolescente , Adulto , Catalepsia/complicaciones , Humanos , Hipnóticos y Sedantes/farmacología , Masculino , Fases del Sueño/efectos de los fármacos , Ronquido/complicaciones , Encuestas y Cuestionarios , Factores de Tiempo
13.
J Appl Physiol (1985) ; 90(1): 179-88, 2001 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-11133909

RESUMEN

The effects of long-term spaceflight (90-180 days) on the contractile and elastic characteristics of the human plantarflexor muscles were studied in 14 cosmonauts before and 2-3 days after landing. Despite countermeasures practiced aboard, spaceflight was found to induce a decrease in maximal isometric torque (17%), whereas an index of maximal shortening velocity was found to increase (31%). In addition, maximal muscle activation evaluated during isokinetic tests decreased by 39%. Changes in musculotendinous stiffness and whole joint stiffness were characterized by means of quick-release movements and sinusoidal perturbations. Musculotendinous stiffness was found to be increased by 25%. Whole joint stiffness decreased under passive conditions (21%), whereas whole joint stiffness under active conditions remained unchanged after spaceflight (-1%). This invariance suggests an adaptive mechanism to counterbalance the decrease in stiffness of passive structures by an increased active stiffness. Changes in neural drive could participate in this equilibrium.


Asunto(s)
Músculo Esquelético/fisiología , Vuelo Espacial , Astronautas , Fenómenos Biomecánicos , Elasticidad , Humanos , Contracción Isométrica/fisiología , Articulaciones/fisiología , Masculino , Contracción Muscular/fisiología , Tendones/fisiología
14.
J Neurosci Methods ; 51(1): 71-6, 1994 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-8189751

RESUMEN

Electrical stimulations of the sciatic nerve were applied in rats awake to seek motor direct (M) or reflex (H) responses as in humans. Achilles tendon percussions were also applied to induce T reflexes. The responses were obtained, 3 times, in each leg of 12 rats and identified as M, H, T responses considering their latencies. The experiments also indicated a lateralization of the reflex activities since 70% of the rats presented significant higher reflexes in 1 leg. Mean reflex values were calculated taking into account this lateralization. Thus T and H reflex changes in the rat could provide an index of neuromuscular plasticity.


Asunto(s)
Tendón Calcáneo/fisiología , Reflejo H/fisiología , Neurología/métodos , Reflejo/fisiología , Animales , Estimulación Eléctrica , Lateralidad Funcional , Miembro Posterior , Humanos , Estimulación Física , Ratas , Ratas Sprague-Dawley , Tiempo de Reacción , Nervio Ciático/fisiología
15.
Cancer Genet Cytogenet ; 110(1): 54-6, 1999 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-10198623

RESUMEN

Two cases of papillary renal cell carcinoma (RCC) with a karyotype 46,X,t(X;1)(p11.2;q21) in two female patients aged 9 and 29 years are reported. These observations, and the review of the 17 reported cases with a translocation at band Xp11 confirm that this abnormality delineates a clinicopathological entity within the classical papillary RCC, characterized by the early age of occurrence and, probably, distinct histological features. Including these two new female cases, the sex ratio in cases with t(X;1) appears similar to that observed in the other papillary RCC.


Asunto(s)
Carcinoma Papilar/genética , Carcinoma de Células Renales/genética , Cromosomas Humanos Par 1 , Neoplasias Renales/genética , Translocación Genética , Cromosoma X , Niño , Femenino , Humanos
16.
Chronobiol Int ; 21(4-5): 631-43, 2004 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-15470959

RESUMEN

Variations in force and electromyographic (EMG) activities of skeletal muscles with the time-of-day have been previously described, but not for a postural muscle, submitted to daily postural and locomotor tasks. In this article, mechanical performances, EMGs, and the ratio between these parameters, i.e., the neuromuscular efficiency (NME), were measured on the triceps surae (TS) of eight subjects, two times each day, at 6:00 and 18:00 h. NME was evaluated under different experimental conditions (electrically induced contractions, reflex contractions, maximal and submaximal voluntary isometric contractions, and during a natural movement, a drop jump) to determine whether mechanisms, peripheral or central in origin, were responsible for the eventual changes in NME with time-of-day. To calculate NME in induced conditions (NMEind), a supramaximal electrical stimulus was applied to the tibial nerve, and the maximal M wave of TS (TS Mmax) and the amplitude of the twitch tension (PtMmax) in response to this electrical stimulation were quantified. TS Mmax was significantly lower in the evening (mean gain value -10.7 +/- 5.5%, p < 0.05), whereas PtMmax was not significantly modified. NMEind (PtMmax/TS Mmax) was significantly higher in the evening (mean gain of 17.6 +/- 5.8%, p < 0.05), and this increase was necessarily peripheral in origin. Secondly, maximal tendon taps were applied to the Achilles tendon in order to quantify at the two times-of-day the reflexes in response to a mechanical stimulus. The maximal reflex, TS Tmax/Mmax (%), the peak amplitude of the twitch tension associated to this tendon jerk (PtTmax), and the corresponding NME (NMEreflex = PtTmax/TS Tmax/Mmax) were not affected by time-of-day, indicating that reflex excitability did not present daytime variations when tested under these conditions. Voluntary isometric contractions were required under maximal (MVC) and submaximal (25% MVC) conditions, and the corresponding torques and TS EMG were measured. MVC was higher in the evening (mean gain: 8.6 +/- 2.7%, p < 0.05) and TS EMGmax (normalized with regard to TS Mmax) also increased in the evening but not significantly; thus, NMEMvc was not modified. At 25% of MVC, TS EMG was significantly higher in the evening (mean gain of 23 +/- 13.9%, p <0.05) and a trend for a lower NME25%MVC in the evening was observed, a result probably representative of a higher muscle fatigue state in the evening. Finally, to test the muscle capacities during a natural task, a NME index was calculated during a drop jump (DJ). The NMEDJ was defined as the ratio between jump height and mean amplitude of TS EMG (% of TS Mmax) between the drop and the jump. Both jump height and NMEDJ were significantly higher in the evening (mean gains of 10.9 +/- 4.5% and 15.7 +/- 7.4%, respectively, p <0.05). In conclusion, daytime changes in the efficiency of postural muscles seem to depend on both peripheral and central mechanisms. According to the experimental conditions, NME of the postural muscle could increase, remain constant, or even decrease in the evening, and this result may reflect reverse effects of better contractile capacities and higher fatigue state.


Asunto(s)
Ritmo Circadiano/fisiología , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Adolescente , Adulto , Estimulación Eléctrica , Electromiografía , Humanos , Contracción Isométrica/fisiología , Masculino , Unión Neuromuscular/fisiología , Reflejo/fisiología
17.
J Electromyogr Kinesiol ; 4(2): 95-103, 1994.
Artículo en Inglés | MEDLINE | ID: mdl-20870550

RESUMEN

Neuronal connections between the peroneus longus and the soleus, ago-antagonist bifunctional muscles, were investigated by reflex analysis. The peroneus longus H-reflex, obtained by stimulating the common peroneal nerve, was conditioned by a posterior tibial nerve stimulation. This conditioning stimulus induced an early inhibition of the peroneus longus H-reflex and the degree of inhibition increased with the conditioning stimulus intensity. The soleus H-reflex, solicited by stimulating the posterior tibial nerve, was conditioned by passive adduction movements. These movements were passive quick-release movements achieved by a specific device containing an electromagnet and stiff springs. The passive adduction movement induced both a myotatic reflex in the stretched muscles and an early inhibition of the test soleus H-reflex. This inhibition is most likely due to the activation of the primary spindle afferents of the stretched muscles. Thus we propose an antagonist neuronal scheme between peroneus longus and soleus muscles in spite of their agonism in plantarflexion.

18.
J Electromyogr Kinesiol ; 10(4): 217-24, 2000 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-10969194

RESUMEN

Surface electromyograms (EMGs) were analysed on the short and long head of the biceps brachii (BBSH and BBLH) during single (F and S) or dual (F+S) flexion and supination tasks. It was confirmed, by the analysis of EMG root-mean-square (RMS) values, that the highest activations of BBSH and BBLH were obtained during a maximal dual task. This study was essentially concerned with the analysis of power spectra data obtained during progressive or ramp contractions (RCs). The shape of the power spectra established during the first second of the RCs differs between F, S and F+S tasks. Differences in mean power frequency (MPF) calculated during RCs would be representative of a recruitment of motor units (MUs) that is, at least partly, task-dependent. In order to compare MPF values calculated from RCs performed under different mechanical conditions (F, S and F+S), MPF-RMS(PSD) relationships have been established (RMS(PSD) being defined as the power spectrum density RMS). Both BBSH and BBLH exhibited initial MPF values higher in supination RC than in flexion RC. Because of plateau values reached at the same level of muscle activation whatever the task performed, the slope of the MPF-RMS(PSD) relationship was lower in S than in F. These results are in favour of MU recruitment that is, at least partly, different in F and in S conditions. Dual submaximal tasks seem to mix the activation of the F and S subpopulations of MUs as revealed by the spectral parameters obtained during F+S ramp contractions. This study could find some implication in the field of muscle rehabilitation or reinforcement.


Asunto(s)
Brazo/fisiología , Electromiografía , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Potenciales de Acción/fisiología , Adulto , Prueba de Esfuerzo , Femenino , Humanos , Masculino , Valores de Referencia
19.
J Electromyogr Kinesiol ; 6(1): 3-11, 1996 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-20719658

RESUMEN

Electromyograms (EMG) of the long head (LH) and the short head (SH) of the biceps brachii were recorded during linearly increasing isometric elbow torques. These ramp contractions concerned flexion or supination of the elbow performed separately (flexion or supination single tasks) and simultaneously (flexion/supination dual tasks). EMG-torque relationships and EMG-EMG relationships were established. The EMG-torque relationships of the SH and LH show a more increased activity in supination than in flexion single task. The highest levels of LH and SH activations were found in the dual tasks. For the majority of subjects, the maximal flexion and supination torques reached in dual tasks were identical to those developed in single tasks. In the single tasks, the LH-SH relative contributions varied from one subject to another as attested by the EMG LH-EMG SH relationships, whereas in dual tasks, the EMG LH-EMG SH relationship was close to the identity line for all subjects, indicating a higher and homogeneous activation of both heads of the biceps. It is concluded that dual tasks are indicated in order to spread the motor unit (MU) recruitment or to activate fully a bifunctional muscle.

20.
Electromyogr Clin Neurophysiol ; 32(7-8): 331-9, 1992.
Artículo en Inglés | MEDLINE | ID: mdl-1526213

RESUMEN

The disynaptic Ia-alpha inhibition between the tibialis anterior and the soleus muscles is now well known. This neuronal organization has been established thanks to the analysis of the Hoffmann reflex (H reflex) changes following an electrical stimulation of the antagonist muscle nerve. In some cases, anatomical constraints impede the use of this classical technique for assessing a reciprocal Ia inhibition between muscles. Furthermore, an electrical stimulus solicits the primary spindle afferents in conditions which are very different from their natural stimulus: the muscle stretch. Thus we have undertaken to analyse the changes of a soleus H reflex following a rapid stretch of the ankle dorsiflexors and therefore of their prime-mover: the tibialis anterior. The mechanical perturbations were imposed with a strong initial acceleration and a limited angular displacement thanks to an original device including electromagnet and spring. This technique, derivated from the quick release technique, was applied on relaxed muscles to avoid a co-contraction phenomenon. 45 to 50 ms after the initiation of the mechanical perturbation an early reflex response was observed on the stretched tibialis anterior. The area of this first reflex response was related to the initial acceleration of the passive dorsiflexion. Several arguments are presented in favour of the myotatic origin of this reflex component. The passive dorsiflexion used as a conditioning stimulus led to a strong and longlasting inhibition of the test soleus H reflex. The early inhibition of the soleus H reflex was observed only about 18 ms after the conditioning stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)


Asunto(s)
Reflejo H/fisiología , Músculos/fisiología , Adulto , Estimulación Eléctrica , Electromiografía , Humanos , Movimiento/fisiología
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA