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Biomedical subjects

T Shirahama

Publications and source records attributed to T Shirahama.

At least 109 records · Page 6Linked to original sources
PubMed1974

Blockage of amyloid induction by colchicine in an animal model.

Colchicine was found to have a strong inhibitory effect on amyloid induction in an animal model. When CBA/J mice were treated with colchicine concurrently with the amyloid induction regimen, the incidence of amyloidosis was, depending upon the dosage of colchicine, significantly decreased (0.005-0.010 mg colchicine per day) or completely blocked (more than 0.015 mg colchicine per day). The colchicine treatment was effective not only when colchicine was given for the entire course of the amyloid induction regimen but also when it was given only in the late pre-amyloid or the amyloid phase of the regimen or to the recipients after the transfer of amyloid. The data suggest the colchicine is effective in blocking amyloidogenesis at its final stage(s), while it may not affect significantly amyloid already deposited in the tissue.

Amyloid↗
PubMed1974

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.

Acid Phosphatase↗
PubMed1973

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.

Acid Phosphatase↗
PubMed1970

Incorporation of [14C] glucosamine and [14C] leucine into mouse kidney beta-glucuronidase induced by gonadotrophin.

Male BALB/C mice were injected intraperitoneally with 2.5 i.u. of gonadotrophin. After the injection, increase of beta-glucuronidase activity was first observed in the microsomal fraction. By 36h 45-50% of the total homogenate activity was found in the microsomal fraction compared with 20-25% in the control microsomal fraction. From 36 to 80h not only microsomal beta-glucuronidase but also lysosomal beta-glucuronidase increased progressively. After 69h stimulation with 2.5 i.u. of gonadotrophin, d-[1-(14)C]glucosamine or l-[U-(14)C]leucine was injected intraperitoneally. After a further 3h the kidneys were homogenized and five particulate fractions were prepared by differential centrifugation. The beta-glucuronidase in the microsomal and lysosomal fractions was released respectively by ultrasonication and by freezing and thawing treatment. The enzyme was purified by organic-solvent precipitation and by sucrose-density-gradient centrifugation. The results demonstrated the incorporation of these two labels into the mouse renal beta-glucuronidase. The microsomal beta-glucuronidase was much more radioactive than the lysosomal enzyme and approx. 80% of the newly synthesized enzyme appeared in microsomes and approx. 20% of that was found in lysosomes at this period. These results suggest that the mouse renal beta-glucuronidase is a glycoprotein and that the newly synthesized enzyme is transported from endoplasmic reticulum to lysosomes.

Animals↗
PubMed1968

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.

Animals↗
PubMed1967

High-resolution electron microscopic analysis of the amyloid fibril.

The ultrastructural organization of the fibrous component of amyloid has been analyzed by means of high resolution electron microscopy of negatively stained isolated amyloid fibrils and of positively stained amyloid fibrils in thin tissue sections. It was found that a number of subunits could be resolved according to their dimensions. The following structural organization is proposed. The amyloid fibril, the fibrous component of amyloid as seen in electron microscopy of thin tissue sections, consists of a number of filaments aggregated side-by-side. These amyloid filaments are approximately 75-80 A in diameter and consist of five (or less likely six) subunits (amyloid protofibrils) which are arranged parallel to each other, longitudinal or slightly oblique to the long axis of the filament. The filament has often seemed to disperse into several longitudinal rows. The amyloid protofibril is about 25-35 A wide and appears to consist of two or three subunit strands helically arranged with a 35-50-A repeat (or, less likely, is composed of globular subunits aggregated end-to-end). These amyloid subprotofibrillar strands measure approximately 10-15 A in diameter.

Amyloidosis↗