A REGIONAL STUDY OF SOME OSMOTIC, IONIC AND AGE FACTORS AFFECTING THE STABILITY OF CEREBRAL LYSOSOMES 1

An examination was made of the effect of changes in the osmolarity and the ionic composition of the homogenizing medium on the partition of lysosomal arylsulphatase and N -acetylglucosaminidase of cerebral cortex, hypothalamus and thalamus of the rat. Sulphatase appeared to be more sensitive to hypotonicity than glucosaminidase, since a higher proportion of the sulphatase was released from the lysosomes into the soluble fraction of the cells from all three neuroanatomical areas examined. In the presence of 250 mM-sucrose, supplementation with 10 mM-Mg led to clumping of the lysosomes and their translocation into the heavy-particulate fraction; no such effect of 10 mM-Mg was noted in the absence of 250 mM-sucrose. The intracellular distribution of bound N -acetylneuraminic acid (bound-NANA) was also examined. The shifts observed in its intracellular localization as a result of changes in the ionic composition of the homogenizing medium rule out bound-NANA as a structural component of the membrane of the cortical lysosome. However regional differences in the response of bound-NANA to ionic factors were observed. Lysosomes from cerebral cortex of adult and 12-day-old rats were also compared. Differences in the pattern of distribution of lysosomes in linear sucrose gradients and in response to ionic factors were uncovered. The results support the previously enunciated concept (Sellinger and Hiatt, 1968) of a regional microheterogeneity of lysosomes and add a new, age-related dimension to it.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65807/1/j.1471-4159.1969.tb05969.x.pd

Cerebral lysosomes. VI. The in vivo uptake of Triton-WR-1339 by the lysosomes of the immature cerebral cortex and cerebellum

The detergent Triton-WR-1339 was injected intrathecally into immature rats and its uptake by the lysosomes of the cerebral cortex and the cerebellum was demonstrated. Uptake was assessed in vitro by examining the shift of the lysosomes centrifugal fractions sedimenting at lower speeds than those commonly yielding these granules from control brains. This shift was maximal after 3 daily injections of Triton when arylsulfatase and , the two lysosomal hydrolases studied, exhibited peaks of relative specific activity (RSA) in fractions known to contain myelin fragments and nerve endings rather than in the heavier fraction known to concentrate lysosomes. A significant proportion of the cortical and cerebellar lysosomes failed to take up the detergent even after 3 days of continued administration.The apparent irreversibility of the uptake process was suggested by the finding that the RSA values for the two hydrolases were still highest in the myelin and light nerve ending fractions 4 days after the administration of Triton-WR-1339 had been discontinued. Sedimentation in linear density gradients of sucrose readily separated the populations of Triton-filled and Triton-devoid lysosomes.The results demonstrate the ability of cerebral lysosomes to perform a functional task characteristic of their extracerebral counterparts. It has not been established whether the uptake of Triton-WR-1339 was selective into the lysosomes of neuronal or glial cells or wether it proceeded uniformly into both cell types.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33687/1/0000199.pd

The action of trypsin and neuraminidase on the synaptic membranes of brain cortex

The population of intracellular membranes of rat cerebral cortex which exhibited the highest relative specific concentration of bound N-acetylneuraminic acid (NANA) and the highest relative specific activity of acetylcholinesterase (EC 3.1.1.7) (synaptic membranes) was incubated with bacterial neuraminidase and with trypsin under a number of experimental conditions. The electrokinetic profile displayed by the membrane preparation upon zonal density gradient electrophoresis changed as a result of the removal of bound NANA by neuraminidase, while its acetylcholinesterase activity remained unaffected; conversely, the action of trypsin led to the inactivation of acetylcholinesterase before any significant alterations of the electrophoretic mobility of the membranes became apparent. Prolonged incubation alone or in the presence of either neuraminidase or trypsin, resulted in the loss of membrane electrophoretic homogeneity, a circumstance which, most likely, reflects a disaggregation of the structural matrix of the membrane.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33001/1/0000385.pd