Browsing by Author "RUIZ, G"

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    AGE-RELATED RESPONSES OF SKELETAL-MUSCLE AFTER ECTOPIC INNERVATION, WITH PARTICULAR REFERENCE TO 16S ACETYLCHOLINESTERASE, IN ADULT-RATS
    (1984) MALDONADO, M; RAMIREZ, BU; RUIZ, G; YAMUY, J; INESTROSA, NC
    The formation of ectopic junctions between the foreign fibular nerve and the soleus muscle of young (35-day-old) and mature (200-day-old) adult rats was induced by severing the normal nerve 4 wk after implanting the foreign nerve. The various molecular forms of acetylcholinesterase (AChE) were studied both at the implanted region and at the original denervated endplates. The velocity of contraction was also studied. In young rats the 16S form was first detected in the ectopic junctions around day 5 after reinnervation; this form rapidly increased during the following weeks, reaching a plateau by day 20. By contrast, in mature rats the appearance of the 16S AChE was dramatically delayed; in fact, it could not be observed before day 80 after reinnervation. (The 16S AChE form appeared at day 20 after reinnervation in the original denervated endplates of young rats; however, at the same time, no effect was observed in mature animals.) The original, slow muscle fibers of the soleus became faster upon reinnervation; this change also occurred much earlier in younger than in mature rats. A loss of plasticity in the skeletal muscle of mature rats is indicated. Caution is suggested in the use of the ectopic innervation model to study development in mature adult rats.
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    EFFECT OF PHENYTOIN ON CYTOSKELETAL PROTEIN-PHOSPHORYLATION AND NEURONAL STRUCTURE IN THE RAT SENSORY CORTEX
    (1987) RUIZ, G; FLORES, OG; GONZALEZPLAZA, R; INESTROSA, NC
    Phenytoin (PH) is commonly used as an anticonvulsant drug, and it causes several collateral effects including morphological changes in brain cortex neurons and teratogenic lesions in infants of epileptic mothers. Several lines of evidence indicate that PH may exert its action through the modification of phosphorylation patterns of neuronal polypeptides. We have studied the effects of PH on the phosphorylation of cytoskeletal proteins, because this could be related to the structural modifications induced by PH administration. The dendritic pattern of deep layers of the somatosensory cortex is clearly modified by PH but not the cell number, indicating that the drug disturbs the architecture of the neurons examined. In fact, the pattern of phosphorylation in cytoskeletal extracts of brains of 30-day-old rats is changed by PH. In vitro labeling experiments show decrease in the [32P] level of a 43-kDa polypeptide, whereas 38- and 120-kDa polypeptides show increases in their [32P] contents. The 43-kDa polypeptide has been identified as actin by in vitro experiments using a novel approach to determine cytoskeletal polypeptide behavior. We conclude that PH affects the posttranslational phosphorylation of actin and other related cytoskeletal proteins and in this manner may alter the normal morphological layout of dendritic patterns in the somatosensory cortex.
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    MEMBRANE-BOUND FORM OF ACETYLCHOLINESTERASE ACTIVATED DURING POSTNATAL-DEVELOPMENT OF THE RAT SOMATOSENSORY CORTEX
    (1985) INESTROSA, NC; RUIZ, G
    We are interested in the expression of synapse-specific macromolecules and its correlation with the appearance of neuronal types and synaptogenesis during development of the mammalian brain. We report here studies showing that the appearance of acetylcholinesterase (AChE) at layer IV of the rat somatosensory cortex is correlated with the expression of a membrane-bound AChE. Both its electrophoretic mobility and its sedimentation coefficient remain unaltered during maturation; however, its kinetics parameters, the heat and fixative sensitivities and the substrate inhibition changed through development. Our results suggest that an adult form of membrane-bound AChE is expressed postnatally.