Exposure of cultured MRC5 human fibroblasts or NCTC 2544 human keratinocytes to mild doses of ultraviolet A (UVA: 320-400 nm) radiations markedly decreased the actin reactivity with fluorescein-labeled phalloidin. This indicates a change in the degree of polymerization of actin and thus in the organization of actin filaments. Such a phenomenon might be involved in the previously reported UVA-induced inhibition of specific and nonspecific endocytotic processes.
Cholesterol synthesis, esterification and efflux were investigated in cultured fibroblasts from patients with Niemann-Pick disease type C. Sterol synthesis from sodium acetate was markedly increased in the two Niemann-Pick disease type C strains as compared to controls, either in the presence or absence of exogenous cholesterol supply by low-density lipoproteins. By contrast, cholesterol esterification was about 2-3-fold reduced when measured by oleic acid incorporation into cholesteryl esters and 10-15-fold reduced when measured with labelled free cholesterol as precursor, although acylcoenzyme-A:cholesterol acyltransferase activity was normal when studied in vitro on cell homogenates. Chase experiments with 14C-cholesterol demonstrated that the rate of cholesterol efflux was decreased by about 3-4-fold in fibroblasts from patients with Niemann-Pick disease type C. These results provide further evidence for alterations of sterol metabolism in Niemann-Pick disease type C and support the hypothesis of a trapping of exogenous cholesterol, which cannot enter the regulatory intracellular pools.
This is a report on a stored lipid atypical ultrastructural pattern in skin samples of Fabry's disease expressed exclusively in the endothelium. The pattern consisted of intersecting short crescentic tightly packed membranes with a periodicity identical to that in classical ultrastructural variants. At low magnification the lysosomal aggregates of the material resembled "sunbursts" or aggregates of densely packed squirming villus-like structures. According to results of ultrastructural, lipid, and lectin histochemical analyses including analysis of the patients' blood groups, it could be concluded that it is just a variant physical state of the otherwise typical Fabry lipid. Its origin could be attributed to impeded formation (or maintenance) of larger lipid lamellae. It was found in great amounts in skin capillaries in 2 cases, and rarely in 5 additional cases. Knowledge of this atypical ultrastructural pattern is of practical significance because it could, if prevalent, cause diagnostic problems.
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