An ultrastructural study of murine splenic lipofuscinosis

Involvement of the tyrosinase gene in the deposition of cardiac lipofuscin in mice. Association with aortic fatty streak development

Lipofuscin pigment, a terminal oxidation product, accumulates within cells during the normal aging process and under certain pathological conditions. We have analyzed a genetic cross between two inbred mouse strains, BALB/cJ and a subline of C57BL/6J, which differ in lipofuscin deposition. A comparison of the segregation pattern of cardiac lipofuscin with the albino locus (c) on mouse chromosome 7 revealed complete concordance. Analysis of spontaneous mutants of the tyrosinase gene, encoded by the albino locus, confirmed that the tyrosinase gene itself controls lipofuscin formation. Genetic analysis of other strains indicated that one or more additional genes cab contribute to the inheritance of lipofuscin. We also present evidence for an association between cardiac lipofuscin deposition and aortic fatty streak development in the mouse.

Phagocytosis and lipofuscin accumulation in lymph node macrophages

Lipofuscin is considered to be undigestible material present in secondary lysosomes. During histological and electron microscopical studies lipofuscin was observed in macrophages in popliteal lymph nodes in 3-6 month-old-male Wistar rats after occlusion of the afferent lymph flow to the lymph node. No pathological alterations were found in the lymph node after the operation. However, the number of macrophages was severely reduced. Simultaneously the number of secondary lysosomes increased in the remaining macrophages reaching a plateau 4 weeks after operation. At this time three quarters of the residual bodies already contained lipofuscin granules. In the following weeks almost all macrophages showed lipofuscin in increasing amounts. Macrophages in normal contralateral lymph nodes of the same rats rarely contained lipofuscin. The increased phagocytosis of the remaining macrophages thus preceded the appearance of lipofuscin. We suggest that lipofuscin results from an inadequate intralysosomal digestion.

Lipofuscin accumulation in the human spleen with an unusual distribution. A case report

Lipofuscin granules were found in an unusual distribution in an atrophic human spleen. The pigment was confined to the sinus littoral cells and was absent from the splenic histiocytes. The lipofuscin differed from the ceroid-type of lipofuscin found in the various conditions associated with the 'syndrome of the sea-blue histiocyte' in its distribution, ultrastructure and its association with splenic atrophy rather than splenomegaly.

Genetic basis of susceptibility to splenic lipofuscinosis in mice

Spleens with black pigment in them were found in 4–57% of mice from 17 stocks, all sublines of C57BL or with significant C57BL ancestry. Splenic lipofuscinosis was absent from 16 stocks, including three C57BL/6By × BALB/cBy recombinant - inbred lines. Progeny testing showed all C57BL/6J mice to be equally likely to develop black spleens. The penetrance of lipofuscinosis differed between sublines but not between the sexes or between laboratories. Susceptibility to lipofuscinosis showed dominant, autosomal, inheritance in F1 hybrids. Observations on backcrosses and on recombinant inbred lines and their intercrosses indicated the existence of two genetic factors. Splenic lipofuscinosis was prevented either by a deficiency of melanin or by homozygosity for a non-C57BL allele close to thec-pregion of chromosome 7. The presence of a C57BL allele at a locus on another chromosome is necessary for lipofuscinosis to occur.

Copper accumulation in primary biliary cirrhosis. An electron and X-ray microanalytical study

Ultrastructural and X-Ray microanalytical aspects of primary biliary cirrhosis were analysed and compared to those of normal liver. Electron microscopic studies showed a significant increase of dense lipofuscin-like granules in PBC compared to the hepatocytes of normal liver (665%). These granules (0.3-2.7 micrometers in diameter) were formed by the association of primary lysosomes and lipid droplets. X-Ray microanalysis of these structures showed the presence of Calcium, Phosphorus, Potassium, Chlorine, Sulphur, Aluminium and Copper. The coexistence of Sulphur with other mineral elements suggests the occurrence of metalloproteins binding these elements. These findings provide evidence that intralysosomal sequestration of mineral elements, especially copper protects the hepatocytes from cytotoxic effects.