Estrogen Attenuates the Pressor Response Mediated by the Group III Mechanoreflex

PURPOSE: We investigated the effects of group III mechanoreceptors to cardiovascular responses in both pre-menopausal woman and post-menopausal woman during passive ankle dorsiflexion (PAD). METHODS: Twenty healthy volunteers (10 post-menopausal women and 10 pre-menopausal women) were recruited for this study. Stroke volume (SV), heart rate (HR), cardiac output (CO), and total vascular conductances (TVC) were measured continuously throughout the experiment. To stimulate the group III mechanoreceptors, PAD was performed for one minute. RESULTS: The results showed that mean arterial pressure (MAP) mediated by the mechanoreflex activation was significantly increased in both groups. However, this pressor response was significantly higher in post-menopausal women. This reflex significantly increased both SV and CO in pre-menopausal women, while there were no differences in post-menopausal women. There was no difference in HR in either group. The mechanoreflex significantly decreased TVC in post-menopausal woman, while there was no difference in pre-menopausal woman. CONCLUSION: The results indicate that the excessive pressor response mediated by the mechanoreflex occurs due to overactivity of group III mechanorecptors and the mechanism is produced mainly via peripheral vasoconstriction in post-menopausal women.

Passive stiffness of rat skeletal muscle undernourished during fetal development

OBJECTIVES: The aim of the study was to investigate the effect of fetal undernutrition on the passive mechanical properties of skeletal muscle of weaned and young adult rats. INTRODUCTION: A poor nutrition supply during fetal development affects physiological functions of the fetus. From a mechanical point of view, skeletal muscle can be also characterized by its resistance to passive stretch. METHODS: Male Wistar rats were divided into two groups according to their mother's diet during pregnancy: a control group (mothers fed a 17 percent protein diet) and an isocaloric low-protein group (mothers fed a 7.8 percent protein diet). At birth, all mothers received a standardized meal ad libitum. At the age of 25 and 90 days, the soleus muscle and extensor digitorum longus (EDL) muscles were removed in order to test the passive mechanical properties. A first mechanical test consisted of an incremental stepwise extension test using fast velocity stretching (500 mm/s) enabling us to measure, for each extension stepwise, the dynamic stress (σd) and the steady stress (σs). A second test consisted of a slow velocity stretch in order to calculate normalized stiffness and tangent modulus from the stress-strain relationship. RESULTS: The results for the mechanical properties showed an important increase in passive stiffness in both the soleus and EDL muscles in weaned rat. In contrast, no modification was observed in young adult rats. CONCLUSIONS: The increase in passive stiffness in skeletal muscle of weaned rat submitted to intrauterine undernutrition it is most likely due to changes in muscle passive stiffness.

pattern of modulation of short latency reflex linking the pretibial muscles to the knee extensors during gait in human

To find out pattern of modulation of heteronymous reflex linking the pretibial muscles to quadriceps motoneurones in normal subjects during treadmill walking. A non-randomized quasi-experimental study was performed in ten cases in Shahid Beheshti University [MC] Tehran, Iran, from September 2006 to August 2007. The reflex was elicited by applying stimuli of three time's motor threshold in tibialis anterior to common peroneal nerve at several instants of gait cycle. Surface EMGs from tibialis anterior, vastus medialis and rectus femoris of the right leg was used to measure the intensity of the muscular activity and the magnitude of the reflex. The data were analysed by Pearson test for the strength of their correlation. The reflex showed a significant correlation with the intensity of contraction in quadriceps especially during the early stance phase. The correlation was poor during transition period from stance to swing where rectus femoris showed a small peak of activity. The peak of activity in tibialis anterior was on average 69 +/- 21 ms preceded that of quadriceps. This precedence of activity in tibialis anterior and the strong presence of the reflex during the early stance phase may indicate a positive feed-forward effect from ankle flexor afferents to quadriceps

Eliciting knee jerk--a new method of reinforcement.

This study was designed to detect the sensitivity of different methods of eliciting knee jerks and to compare the conventional methods with the newly purposed maneuver. Knee jerk (a deep tendon reflex) was elicited in 123 apparently normal population (77 males and 46 females) with three different methods (1) without applying reinforcement, (2) applying Jendrassik maneuver (strong voluntary contraction of upper limbs) and (3) using the new method of reinforcement--that is by dorsiflexion of ankle joint of the same foot voluntarily as strong as possible on which the jerk would be elicitated. The sensitivity of the method without reinforcement was found to be is 87.8%; that with Jendrassik maneuver was 93.5%, whereas the sensitivity of newly proposed maneuver was 99.2%. Results of the present study have served to demonstrate that elicitation of knee jerk with newly proposed reinforcement maneuver is the best among all three methods.

Fundamentos biológicos de la elongación según tiempo de estiramiento y actividad contráctil / Biological background of stretching according to time and lengthening contractile activity

Se analizaron los fundamentos biológicos de las técnicas de elongación muscular, en relación con dos variables: tiempo de mantención y presencia de actividad contráctil antes o durante la aplicación del estiramiento. Se busca así hacer un análisis comparativo de los principios de dos métodos: el Stretching Global Activo, y el contraer-relajar, una modalidad basada en la Facilitación Neuromuscular Propioceptiva. Se producen dos respuestas, conceptualmente distintas: a)la disminución de la tensión que genera el músculo en reposo, y b) la elongación muscular propiamente tal. La primera, conocida como relajación de fuerza es una adaptación a corto plazo, atribuído a la conducta viscoelástica del Tejido Conectivo Intramuscular, y se evidencia por una disminución del torque pasivo de aprox. un 30 por ciento. La segunda respuesta corresponde a una adaptación a largo plazo, por aumento real de la longitud del vientre muscular, e implica una adición de sarcómeros en serie. Los estiramientos breves, con o sin contracción previa del músculo, producen relajación de fuerza, cuyo efecto no excede los 60'; a largo plazo, producen aumento de rango de movimiento, pero sin modificar la pendiente de la curva torque / rango, de lo que se deduce que, más que una elongación real, existe sólo una mayor tolerancia al estiramiento , Según evidencia en modelo animal, la verdadera elongación se lograría sólo con tiempos prolongados de estiramiento, o con una sumación de una gran cantidad de estiramientos breves. La contracción isométrica durante el estiramiento amplificaría la adición de sarcómeros en serie. Se concluye que los fundamentos del Stretching Global Activo están más respaldados por la evidencia que los de la elongación realizada con principios de Facilitación Neuromuscular, aunque ambos son útiles dependiendo del propósito.

Plasticidad muscular y técnicas de elongación: I parte: bases biológicas del acortamiento / Muscle plasticity and stretching techniques. Part I: biological basis of shortening

En esta serie de dos partes, se revisan y relacionan los aspectos: biomecánicos, neurofisiológicos, morfohistológicos y bioquímicos implicados tanto en el acortamiento como en la elongación muscular. El propósito es determinar y fundamentar, basado en la mejor evidencia disponible, algunos de los parámetros más eficientes para ser aplicados en las Técnicas de Elongación. Para ello se usa como punto de referencia dos métodos: a) el basado en principios de Facilitación Neuromuscular Propioceptiva y b) el Stretching Global Activo, los que difieren en muchas variables. El análisis comparativo se centra en dos: a) el tiempo de mantención del estiramiento y b) la actividad contráctil del músculo a estirar, antes o durante el mismo; las conclusiones se presentarán en la II parte. Esta I parte de enfoca en el fenómeno del acortamiento muscular propiamente tal, concluyéndose que, desde el punto de vista Biomecánico, existen diferencias conceptuales entre cambios a corto plazo (el aumento de la rigidez pasiva) y a largo plazo (disminución de la longitud propiamente tal), que se explican por un comportamiento histológico diferente: lo primero se relaciona con la proliferación de Tejido Conectivo Intramuscular, específicamente perimisio; mientras que lo segundo se debe a una disminución del número de sarcómeros en serie. Esta pérdida de sarcómeros es una expresión de la capacidad plástica del músculo esquelético, para buscar la longitud óptima de cada sarcómero. Se cita además la nueva Hipótesis sobre la propiedad contráctil del perimisio, y su posible rol en el acortamiento.

The effect of elbow position on biceps tendon reflex.

BACKGROUND: Testing of tendon (T) reflex is the basic method used in the diagnostic procedure of clinical neurology. Measurement of T reflexes precisely can be a valuable adjunct to clinical examination. Quantification of T reflexes may provide more accurate results. AIMS: To analyze the effect of elbow position on biceps T reflex. SETTINGS AND DESIGN: A self-controlled clinical trial of biceps T reflex testing at the Electrophysiology Unit of the Department of Physical Medicine and Rehabilitation. METHODS AND MATERIALS: Biceps T reflex was obtained utilizing a hand-held electronic reflex hammer in 50 extremities of 25 healthy volunteers and the effect of elbow position (at 90 degrees , 120 degrees and 150 degrees ) on reflex response was evaluated. STATISTICAL ANALYSIS: Repeated-measures analysis of variance by the General Linear Model and Pearson correlation test procedures. RESULTS: Onset latency was significantly shorter at 120 degrees of elbow position. The maximum amplitude value of biceps T reflex was obtained at 90 degrees of elbow position. Onset latency of the reflex correlated significantly with the height and arm length but not with age. CONCLUSIONS: The electrophysiological measurement of T reflexes is an easy and useful method in the quantification of reflexes, supplying more objective data. However, when performing T reflex studies, the position of the extremity should be taken into consideration to achieve more reliable results.

Early onset cerebellar ataxia with retained tendon reflexes (EOCA) and olivopontocerebellar atrophy (OPCA): a computed tomographic study.

Computed tomographic (CT) studies in olivopontocerebellar atrophies (OPCA) and 'early onset cerebellar ataxia with retained tendon reflexes (EOCA)' are few and vary widely in methodology and criteria for cerebellar and brainstem atrophy. In this prospective study, CT scan observations on 26 patients (EOCA-11, OPCA-15) were compared with 31 controls using qualitative and quantitative assessment of cisterns, ventricles and atrophy of brain. Vermian and/or cerebellar hemispheric (predominantly anterior) atrophy was present in 80.8% and both were equally common. Cerebral cortical atrophy (26.9%) and leukoariosis (15.4%) were less frequently seen. Statistically significant atrophy of pons, brachium pontis, cerebellum and midbrain was noted in patient group. No significant differences were observed between EOCA and OPCA groups. Evidence of atrophy did not correlate with either the duration of illness or the severity of cerebellar ataxia in both the groups. The severity of brainstem atrophy in 14 patients with and 12 patients without abnormal brainstem auditory evoked response did not differ significantly. This study highlights the methodology of CT evaluation for brainstem and cerebellar atrophy, draws attention to cerebral atrophy and emphasizes the lack of significant differences in CT morphology between OPCA and EOCA patients.

Dolores musculoesquéleticos del crecimiento y desarrollo en niños / Growing pains in children

Se tomó una muestra significativa de 100 pacientes de la consulta externa del Servicio de Ortopedia del Hospital Tacuba, ISSSTE, del mes de julio al mes de octubre de 1998 con un rango de edad entre 3 y 12 años. El objetivo era descubrir la existencia del dolor en miembros inferiores, relacionados con el crecimiento y desarrollo, sin patología agregada suponiendo que se debe a un edema subclínico secundario a fatiga por ejercicio físico y demostrar su mejoría rehabilitación específica. Se tomaron estudios radiológicos (AP pelvis, AP y LAT e rodillas, tobillos, dorsoplantar, oblicua y lateral de ambos pies) del segmento afectado, se realizaron exámenes de laboratorio (biometría hemática, velocidad de sedimentación globular, factor reumatoide, proteína C reactiva, exudado faríngeo) y examen físico para descartar datos de otra patología. Posteriormente se entregó un instructivo de ejercicios de estiramiento y adiestramiento a los padres, para la realización de los mismos a los niños con algún problema ortopédico sencillo tal como pie plano, pie cavo, genu valgo o varo fisiológicos y defectos de la marcha, o clínicamente sanos. Se dió seguimiento para valoración de la mejoría. Se encontró que de los 100 pacientes estudiados 60 por ciento presentaban alteraciones ortopédicas. El 47 por ciento requirieron ortosis (zapatos ortopédico, plantillas, separador para Hallux, etc.); 40 por ciento se encontraban clínicamante sanos. Después de los ejercicios de estiramiento se encontró desaparición de los dolores en un 76 por ciento de los pacientes y disminución en la intensidad y frecuencia en el 24 por ciento restante

Early onset cerebellar ataxia with retained tendon reflexes: a clinical, electrophysiological and computed tomographic study.

Fourteen patients of Early Onset Cerebellar Ataxia with retained tendon reflexes (EOCA) were prospectively evaluated clinically, electorphysiologically and with CT scan. Their age and duration of symptoms were 18.6 +/- 8.3 years and 7.8 +/- 5.1 years respectively. High consanguinity (91.7%) and positive family history (76.9%) suggested autosomal recessive inheritance. Apart from cerebellar signs and brisk knee jerks in all, other important findings were abnormal ocular movements (mostly impaired saccades) in 92.8%, Babinski's sign (78.6%), brisk ankle jerks (64.3%), spasticity in lower limbs (50%) and impairment of proprioceptive sensations (50%). Neuropsychological tests, done in 12 patients, were abnormal in all. Abnormalities of electroneuromyographic studies were universal, motor conduction parameters (85.7%) being more affected than sensory (78.6%). One or more modalities of evoked potentials were abnormal in 71.4%, that of brainstem auditory evoked response being most frequent (50%), followed by posterior tibial somatosensory evoked potential (SSEP) (46.1%) and median SSEP and visual evoked potential (30.8% each). CT scan (n = 12) showed atrophy of brainstem (91.7%), cerebellar hemisphere and/or vermis (83.3%) and cerebral cortex (33.3%). There was no correlation between the duration of disease and degree of disability or abnormalities of nerve conduction and CT parameters. The rationality of the diagnosis of this recently recognised entity of 'EOCA' in Indian context is discussed.

Ankle reflex photomotogram in thyroid dysfunctions.

The tap to half relaxation time of tendon achilles reflex was measured in thirty control subjects, forty-five thyrotoxic and sixty hypothyroid patients. The half relaxation time in the control males and females was 279.33 +/- 76.39 msec and 320.00 +/- 52.37 msec. respectively. In thyrotoxic males and females the half relaxation time was 256.67 +/- 31.62 msec (P less than 0.01) and 252.50 +/- 47.68 msec (P less than 0.01) respectively. Amongst the hypothyroid male and female patients the half relaxation time was 405.0 +/- 35.56 msec (P less than 0.01) and 422.5 +/- 115.36 (P less than 0.01) respectively. As all these values were statistically significant, we consider the photomotographic measurement of ankle reflex as an important aid to the diagnosis of thyroid hormone imbalances.