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  • 1
    ISSN: 1432-1106
    Keywords: Precentral motor cortex ; Unit recording ; Isometric precision grip ; Force and rate of force change ; Microstimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The activity of single neurons within the hand area of the precentral motor cortex of primates was recorded during the performance of a maintained precision grip between the thumb and forefinger. The finger opposition forces were exerted against a strain gauge which allowed force changes to be studied under near isometric conditions. Task performance required the generation of a force ramp (the dynamic phase) and thereafter the maintenance of a stable force for one second (the static phase). Intracortical stimulation through the recording electrode was used to verify that the recordings were made from the appropriate somatotopographic area of the motor cortex. From a total of 221 recorded neurons, 76 were found to be either activated or deactivated during performance of the task. Among the 51 activated neurons, most discharged at higher frequencies during the dynamic phase, than during the static phase. The discharge of some of these neurons could be related to both force (F) and rate of force change (df/dt) whereas certain others could only be correlated with df/dt. The change in discharge frequency for these neurons generally occurred prior to the onset of EMG activity. Eight neurons were more active during maintained force than during the force ramp. The discharge frequency could not be correlated with df/dt and only one showed a significant positive relation to force. The change in discharge frequency for these neurons either coincided or occurred after the onset of EMG activity.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1463
    Keywords: Pinealocytes ; mole ; sexual cycle ; ultrastructure ; paracrystalline structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Resume L'évolution quantitative de quelques paramètres ultrastructuraux (structures paracristallines, appareils de Golgi, grains de sécrétion) des pinéalocytes de la taupe, a été suivie pendant les différentes phases du cycle sexuel. Cette étude a permis de montrer une augmentation du nombre des structures paracristallines et des appareils de Golgi pendant la phase de pleine activité sexuelle chez les mâles et pendant l'œstrus, la gestation et la lactation chez les femelles. De plus, l'apparition d'un phénomène de vacuolisation des pinéalocytes a été observée pendant le proestrus. Ces résultats semblent démontrer d'étroites relations entre l'activité endocrine de l'axe adénohypophyse-gonades et l'accroissement des synthèses des pinéalocytes. Aucune évolution du nombre de grains de sécrétion n'a été observée pendant les différentes phases du cycle sexuel.
    Notes: Summary Changes of some ultrastructural parameters (paracrystalline structures, Golgi apparatus, secretory granules) in mole pinealocytes were quantitatively studied during the various phases of the sexual cycle. An increase in quantity of paracrystalline structures and of the Golgi apparatuses was demonstrated during the period of high sexual activity in male pinealocytes and during oestrus, gestation and lactation in female pinealocytes. Moreover, the appearance of vacuoles in female pinealocytes was observed during pro-oestrus. These results seem to demonstrate close relationship between the endocrine activity of the hypophyseo-gonadal axis and the synthesis of some compounds by the pinealocytes. No increase in the quantity of secretory granules was observed during the various phases of the sexual cycle studied.
    Type of Medium: Electronic Resource
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