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THE EARLY POST‐NATAL DEVELOPMENT OF THE NEURONAL LYSOSOME 1
Author(s) -
IdoyagaVargas V.,
Santiago Josephine C.,
Petiet Patricia D.,
Sellinger O. Z.
Publication year - 1972
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1972.tb01312.x
Subject(s) - differential centrifugation , lysosome , mitochondrion , microsome , cerebral cortex , centrifugation , biochemistry , biology , hydrolysis , enzyme , specific activity , neuron , oxidoreductase , microbiology and biotechnology , endocrinology , neuroscience
— The hydrolysis of p ‐nitrophenyl‐2‐acetamido‐2‐deoxy‐β‐ d ‐gluco‐(I) and β‐ d ‐galacto‐pyranoside (II) and of p ‐nitrophenyl‐α‐ d ‐mannopyranoside (III) by neuronal cell bodies and glial cells isolated from the cerebral cortex of 18‐day‐old or adult rats was found to be equally efficient, with relative ratios of hydrolysis for I, II and III of approximately 10:1:0.5 in both cell types and at both ages. Homogenates of the neuronal cell bodies obtained from cerebral cortices of 3‐, 8‐, 12‐, 18‐ and 32‐day‐old rats were subjected to differential centrifugation and the subcellular localization of N ‐acetyl‐β‐ d ‐glucosaminidase (EC 3.2.1.30) hydrolysing (I)] was compared to that of the mitochondrial marker, succinate‐INT‐ oxidoreductase (EC 1.3.99.1). A fraction in which N ‐acetyl‐β‐ d ‐glucosaminidase exhibited maximal specific activity could be isolated at all ages, an observation indicating that the potential for active hydrolytic performance is incorporated into the neuronal lysosome very early post‐natally. The specific activities of N ‐acetyl‐β‐ d ‐glucosaminidase and succinate‐ INT‐oxidoreductase reached their respective maxima at widely different times postnatally: at 10–12 days for the mitochondrial enzyme and at about 18 days for the glycosidase, a difference suggesting that in the cortical neuron lysosomes and mitochondria develop out of step. The mitochondrial, lysosomal and microsomal fractions obtained by differential centrifugation were subjected to equilibrium density centrifugation and the presence of two populations of N ‐acetyl‐β‐ d ‐glucosaminidase‐bearing particles was demonstrated. Although their presence was readily apparent in the neurons from 8‐ and 12‐day old brains, it was difficult to discern their presence in the neurons from the 3‐ and the 18‐day‐old brains. In 8‐day‐old brains gradient fractions obtained from neurons containing N ‐acetyl‐β‐ d ‐glucosaminidase of a specific activity up to 8‐fold higher than that of the enzyme in the original neuronal homogenate were examined by electron microscopy and the concentration of numerous lysosomes and derivative bodies in these fractions was verified. Our present study demonstrates the capability of the immature and developing neuron to tightly couple the pace of its degradative processes to that of its highly efficient and highly selective synthetic activities.