ABSTRACT. Mental retardation and dementia characteristic of Down's syndrome (DS) have a complex pathogenesis. Golgi and immunohistochemical studies were done on DS patients and controls from foetuses and elderly adults. Golgi studies on the cerebral cortex revealed that the postsynaptic spines on the basal dendrites increase from neonate to 15 years of age and gradually decrease after 20 years in controls, but poorly increase in children and rapidly decrease in adults with DS. This deficient synaptogenesis and dendritic atrophy may be related to mental retardation. On the other hand, immunohistochem‐istry on proteins, whose genes are located on chromosome 21, revealed that c‐temiinal protein of beta‐amyloid appears in neurons of DS, S‐100‐positive glia increases in the hippocampus of neonates and adults, and membrane protein OK‐2 is expressed earlier and is more widespread in the DS brains. The overexpression and early appearance of gene products in DS brains may be related to the pathogenesis of or predisposition to mental disorders or to dendritic hypogenesis.
AY-9944 (trans-1,4-bis(2-chlorobenzylaminoethyl)cyclohexane dihydrochloride), a cationic amphiphilic drug, caused a rapid, irreversible and dose-dependent reduction of acid sphingomyelinase activity in normal human fibroblasts without changing the activities of other lysosomal hydrolases tested. Examinations of activities against synthetic substrates and of the pH-dependency of sphingomyelinase in the drug-treated cells also suggested that the reduction of activity was specific to acid sphingomyelinase. Such a specific reduction was also found with 12 other cationic amphiphilic drugs, most of which have been shown to be inducers of experimental phospholipidosis in animals and/or cultured cells. These results strongly suggest that acid sphingomyelinase is involved in the process of drug-induced lipidosis. The reduction of acid sphingomyelinase seemed not to be due to direct inhibition by these drugs, a specific loss of the enzyme into the culture medium, the presence of inhibitor in the drug-treated cells, or impaired synthesis of the enzyme. There was no indication that changes in the catalytic properties of the enzyme, or changes in the requirement of detergents for its activity occurred in the cell. These results suggest that AY-9944 and other cationic amphiphilic drugs may cause the reduction of acid sphingomyelinase activity by inducing an increased rate of degradation of the enzyme or by causing an irreversible inactivation via some undetected factor.
Three children with Leber's congenital amaurosis, agenesis of the cerebellar vermis, and infantile polycystic kidneys are described. The common clinical findings of three unrelated patients (two boys and one girl) included severe visual impairment from early infancy, profound psychomotor retardation, hypotonia, nystagmus, characteristic facial appearance with blepharoptosis, and progressive chronic renal insufficiency. The two boys died of uremia at ages 13 and 12 years. The common pathological findings in these two patients consisted of minor disproportions of cerebral lobes, almost total aplasia of the cerebellar vermis, micropolygyria of the dentate nuclei, malformations of the brain stem (including pachygyria of the inferior olivary nuclei and partial absence and anomalous position of the pyramidal tracts), and infantile polycystic kidneys; there was fatty liver in one case and hepatic fibrosis in the other. The clinicopathological findings of our two patients were entirely compatible with those of patients previously reported by Arima and other Japanese authors. Therefore, these patients seem to comprise a distinct clinicopathological entity, cerebro-oculo-hepato-renal syndrome (Arima's syndrome), different from other syndromes with retinal, cerebellar, and renal abnormalities.
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