Histochemical identification of sulfated and non-sulfated mucopolysaccharides in regenerating forelimbs of adult urodeles.
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The influence of the nervous and endocrine systems upon successive stages of limb regeneration suggest possible neuroendocrine interaction(s). Intraperitoneal injections of various agents had no effects upon blastema formation. Chlorpromazine, administered alone or with hormones, retarded morphogenesis. Prolactin, dibutyryl cAMP (db-cAMP), theophylline, and acetylcholine accelerated morphogenesis. 5'-AMP had no effect. Only db-cAMP countered the chlorpromazine-induced retardation of morphogenesis. These results suggest that neuroendocrine influences, possibly cAMP-mediated, direct, in part, the morphogenesis of the regeneration blastema.
Monkeys with unilateral dorsal rhizotomy C2-T3 used their denervated limbs to retrieve unseen food pellets when movements of the intact contralateral limb were rendered ineffective by enclosure of the hand within a container. Even after protracted use in this condition, however, the deafferented limb ceased to be used in the test situation when the intact arm was released. These findings cast doubt on interpretations of lack of use of a unilaterally dorsal rhizotomized limb as being due to cross-spinal inhibition or to learned disuse.
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In the rat cervical spinal cord the corticospinal projection on motoneurons either direct or indirect (via interneurons) comes about postnatally making it accessible for experimental research. Therefore, the postnatal developmental changes of motoneurons and in particular their dendritic fields were examined. Motoneurons innervating the two antagonistic muscles in the distal forepaw, the m. flexor digitorum profundus and the m. extensor digitorum communis, were retrogradely labelled by intramuscular injections of cholera toxin subunit B conjugated with horseradish peroxidase in rats of various postnatal ages. Following a 48-72 hour survival period the motoneurons and their dendritic fields were studied in the seventh and eighth cervical spinal cord segments. Both the number and the position of motoneurons were found to remain constant throughout postnatal development. Extensor motoneurons were positioned dorsolaterally in the ventral horn at the border of grey and white matter, flexor motoneurons were in general medial to extensor motoneurons. The results on the dendritic field demonstrate firstly, that during postnatal development the extension of the dendrites of both flexor and extensor motoneurons changes from spreading out in all directions at postnatal day 2 to spreading in only a few, specific directions from postnatal day 21 onwards, with the restriction that both motoneuron pools follow a different time scale to achieve this. Secondly, both pools have a temporal dendritic component extending into the white matter of the lateral funiculus.(ABSTRACT TRUNCATED AT 250 WORDS)
A fifth limb, quite independent of the others, was found in a pup born in our colony of Wistar rats. The malformation is described.
The neuronal activity in the motor cortex of the rhesus monkey was investigated in three different tasks performed with finger, wrist, and arm movements. A total of 125 neuronal activities were analysed. They were classified into five groups in terms of muscular contractions provoked by intracortical stimulation; neurons related to contractions of finger, wrist, elbow, shoulder, or trunk muscles. The neuronal activities in three tasks performed with finger, wrist, or arm movements were investigated for each group. Most of the neurons related to the contractions of elbow, shoulder, or trunk muscles were associated solely with arm movement. Smaller numbers of neuronal activities changed their firing frequencies in association with two or three tasks. Neurons related to the contractions of finger and wrist muscles showed various firing patterns in the three tasks; some responded to a single task with wrist or arm movement, while others changed their activities in association with more than one task. The presence of multi-task related neurons is discussed with respect to the multisegmental termination of corticospinal axons in the spinal cord.
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