Ultrastructural evidence for leakage of lysosomal contents after phagocytosis of monosodium urate crystals. A mechanism of gouty inflammation

To obtain direct evidence for the mechanism involved in gouty inflammation, human leukocytes were incubated with synthetic monosodium urate microcrystals. To trace the phago(lyso)somal contents, colloidal carbon, ferritin, Thorotrast(R) or horseradish peroxidase was added to the incubation medium, or acid phosphatase activity was localized cytochemically. The interaction was analyzed in time sequence by electron microscopy. By 5 minutes' incubation, urate crystals and tracers had appeared in the single membrane-bounded vacuoles of leukocytes. After 30 minutes' incubation, the vacuoles containing the urate crystals and the tracers were found in more than 50% of the leukocyte population. The phago(lyso)somal membrane was occasionally discontinuous, and the tracers were found in the free cytoplasm near the membrane opening as well. After 60 minutes' or more incubation, the phago(lyso)somal changes and the cytoplasmic localization of the tracers were common, and many cells showed signs of degeneration. Urate crystals mixed in cell debris were often found to be ingested by other leukocytes. These results have been interpreted as follows. Monosodium urate crystals are avidly phagocytized. The urate crystal-containing phagosomes eventually become phagolysosomes. The phagolysosomal membrane is damaged and the contents leak out into the cytoplasm. The leakage of the hydrolases initiates the host cell injury. The urate crystals released by cell disruption are again phagocytized by other cells and the series of events are repeated.

Isolation and identification by sequence analysis of experimentally induced guinea pig amyloid fibrils

Amyloidosis was produced experimentally in guinea pigs by multiple casein injections. Amyloid fibrils were isolated and fractionated and a protein obtained that had an amino acid composition comparable with A protein, a unique nonimmunoglobulin constituent of secondary amyloid deposits. N-terminal sequence analysis demonstrated a sequence homologous with that of A proteins from human and monkey preparations but preceded by a 5-residue peptide which had an N-terminal histidine. A definite species specificity in A protein from human and guinea pig was identified on immunologic analysis.

An analysis of the close relationship of lysosomes to early deposits of amyloid. Ultrastructural evidence in experimental mouse amyloidosis

On the basis of recent morpholgic and biochemical studies which suggested the possible involvement of reticuloendothelial (RE) cells and proteolytic enzymes in amyloidogenesis, the present study was undertaken to examine the ultrastructural interrelationship between lysosomes and amyloid fibrils at the sites of very early amyloid deposition. In the spleen, liver and kidney of the experimental mouse model, foci of amyloid deposits were closely associated with the RE cells. The lysosomal enzyme activity, as marked by cytochemical demonstration of acid glycerophosphatase activity, was localized in the primary type lysosomes (as defined by their electron microscopic appearance), in the Golgi complexes, in the small cytoplasmic vesicles and occasionally widespread in the cytoplasm. They showed an intimate relationship to the amyloid fibrils. The findings were interpreted as favoring the hypothesis that the hydrolases play a role in amyloid fibril formation. The enzyme activity was also demonstrated in the secondary type lysosomes which occasionally contained amyloid fibrils that appeared to be phagocytized.

Animal model for human disease: spontaneous and induced amyloidosis

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Amyloid-inducing factor and immunological unresponsiveness

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Cellular immunity in casein-induced amyloidosis

Guinea-pigs receiving multiple subcutaneous injections of casein at first developed a cellular immune response to casein but this rapidly waned when the animals became amyloidotic. By contrast, cellular immune responsiveness to non-specific antigens at first appeared to be diminished but later returned to normal under the same conditions. These results suggest that tolerance to a specific immunogen may play an important role in the pathogenesis of casein-induced amyloidosis.

Immunogenicity of amyloid

Human amyloid appears to contain two immunogenic components, the P (plasma) component and the F (fibril) component. Antisera to P component react with both autologous and homologous antigens by immunodiffusion and fluorescent antibody techniques; antisera to F component react with autologous antigens by immunodiffusion and fluorescent antibody techniques, but react with homologous antigens only by the fluorescent antibody method. Antisera to both P component and F component fail to react with non-amyloid human tissues as well as amyloid deposits in guinea-pig tissues. These results point to heterogeneity in the antigenic determinants of human amyloid and possibly greater inter-species heterogeneity of amyloid.

Lysosomal breakdown of amyloid fibrils by macrophages

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Mobilization of fatty acids in genetically obese rats

The mobilization of fatty acids has been studied in genetically obese rats of the Zucker strain and in control obese animals with bilateral destructive lesions in the hypothalamus. The body weight and size of adipose cells did not differ significantly between the genetically obese rats and the obese controls. Weight loss in control and genetically obese rats was identical during a 1 month fast. The release of glycerol and the rise in free fatty acids in adipose tissue incubated in vitro were similar in tissue from genetic and hypothalamic obese rats. Epinephrine, theophylline, and dibutyryl cyclic adenosine monophosphate all augmented lipolysis, and the effects were usually greater in the tissues from genetically obese rats.

Combined cytochemical and electron microscopic demonstration of beta-glucuronidase activity in rat liver with the use of a simultaneous coupling azo dye technique

Rat liver was fixed in formal-cacodylate-sucrose and frozen sections were incubated in a simultaneous-coupling medium containing naphthol AS-BI glucuronide as substrate and hexazonium pararosanilin as the diazo reagent. By light microscopy, the sections demonstrated beta-glucuronidase activity as red discrete granules in the pericanalicular cytoplasm and as a generalized cytoplasmic stain in the parenchymal cells. Brief treatment of sections in cold ethanol prior to incubation markedly enhanced the staining for the enzyme and made it possible to demonstrate sufficient amounts of the reaction product in sections embedded in epoxy resin following dehydration and propylene oxide treatment. Electron microscopy revealed that the reaction product was moderately electron opaque and deposited in greater amounts in the vacuolated dense bodies and occasionally in the dense bodies which did not show obvious vacuoles. In each dense body, the deposits occurred preferentially at the edge as well as in the area surrounding the vacuoles in the matrix. Control sections incubated in the presence of glucosaccharo-1:4-lactone were devoid of the reaction product. No deposits of the reaction product were found in the nucleus, mitochondria, or microbodies. The limitations of the present cytochemical technique for use in electron microscopy are briefly discussed.