Tomomichi Takagi

Differential Effects of Methylmercuric Chloride and Mercuric Chloride on the Histochemistry of Rat Thyroid Peroxidase and the Thyroid Peroxidase Activity of Isolated Pig Thyroid Cells

This study was designed to characterize the interaction of CH3HgCl or HgCl2 with thyroid peroxidase (TPO). Two types of experiments were performed. First, the thyroids from rats that were given 5.6 mg/kg/day of either CH3HgCl or HgCl2 for 2 weeks by intubation were subjected to histochemical treatment and then to electron microscopy. TPO activities in all cell compartments were inhibited by HgCl2 but not by CH3HgCl. Morphological observation showed that taller epithelia were induced by HgCl2, whereas flattened epithelia forming large follicles were induced by CH3HgCl. The serum thyrotropin level was substantially lowered by CH3HgCl but was unchanged by HgCl2. Second, the guaiacol oxidation by TPO in isolated and ruptured pig thyroid cells was spectrophotometrically monitored in the presence of either CH3HgCl or HgCl2. The TPO was not inhibited by CH3HgCl but was inhibited by HgCl2. These results indicated that CH3HgCl induced a hypothyroid state without affecting TPO, whereas HgCl2 inhibited TPO and induced a hypertropic state owing to compensation for loss of enzyme activity, and that the lack of inhibitory activity of CH3HgCl was not due to the inability to penetrate the cells. Therefore, there appeared to be a differential interaction of organic and inorganic forms of mercurials with the thyroid.

Muscle tissue reactions to implantation of bone matrix gelatin

Histologic changes of muscle tissue in the early stage of heterotopic osteogenesis induced by syngeneic insoluble bone matrix gelatin (BMG) with bone morphogenetic protein in rats was observed by light and electron microscopy. BMG induced cartilage in muscle tissue by Day 7 after its implantation, woven bone by Day 10, and lamellar bone with bone marrow by Day 14. The new findings in this work include (1) the disappearance of the basement membrane of muscle fibers; (2) the activation of the satellite cells of muscle fibers; (3) the appearance of fibroblastlike cells that closely resembled activated satellite cells among the degenerated muscle fibers or on the surface of the BMG; and (4) the change of fibroblastlike cells to chondroblasts or osteoblasts. These findings suggest that intramuscular implantation of BMG caused the conspicuous disappearance of the basement membrane of the muscle fiber and may play a part in osteogenesis induced by BMG.

Comparative Immunobiology of the Palatine Tonsil

Most structural and functional differences in organs of the mammalian immune system are probably adaptive modifications to a variety of environments and modes of life. Fioretti (1961) reported that the tonsils are composed of lymphoid nodules, paranodular areas, capsules of connective tissues, epithelial crypts and lymphoid cells invading the epithelium (1). But the structures of the tonsils differ in different mammals. So, in the present study, we compared the tonsillar tissues of various mammals to determine their fundamental structures.

Effect of Bupivacaine on Muscle Tissues and New Bone Formation Induced by Demineralized Bone Matrix Gelatin

Heterotopic bone formation induced by demineralized bone matrix gelatin (BMG) in bupivacaine-HCl-treated skeletal muscle was examined histologically. BMG was obtained by dehydrating diaphyseal shafts of femora and tibiae of male, 4-week-old Sprague-Dawley (SD) rats, cutting it into chips, and demineralizing and extracting the chips with various solutions. The BMG was implanted into the rectus abdominis muscle of male, 5-week-old SD rats, bupivacaine-HCl was injected at the same site, and the resulting plaques of tissues were examined histologically on days 5, 10, 15 and 20 after BMG implantation. Heterotopic bone formation occurred in all animals. The bupivacaine-treated group had more degenerated and injured muscle fibers, and more osteocytes than the control group. Electron microscopy showed that the basement membrane of muscle fibers was discontinuous and that many mononucleated cells resembling activated satellite cells were present on day 5. Many fibroblasts, undifferentiated mesenchymal cells and myogenic cells were seen in the area around the BMG. In new bones there were few osteocytes on day 10, but their numbers were increased on days 15 and 20 after implantation, especially in the bupivacaine-treated group. The population of osteocytes that increased rapidly may have included mononucleated cells similar to activated satellite cells.

Architecture of Implanted Bone Matrix Gelatin Influences Heterotopic Calcification and New Bone Formation

Abstract Heterotopic bone formation in skeletal muscle induced by compacted demineralized bone matrix gelatin (BMG) was studied histologically and biochemically. BMG was obtained by dehydrating diaphyseal shafts of femora and tibiae of 4-week-old male Sprague-Dawley rats, cutting the bone into chips, and demineralizing and extracting the chips with various solutions. The BMG was treated with 4 M guanidine-HCl, and compacted BMG was prepared by centrifugation. The compacted BMG was implanted into the rectus abdominis muscle of 5-week-old male Sprague-Dawley rats. The resulting specimens were examined histologically, and their alkaline phosphatase activity and the calcium content of the tissues were measured 3, 5, 7, 10, and 15 days after implantation. The BMG (separated BMG) with 75- to 500-μm particle sizes were implanted into control rats. The results showed that calcification, alkaline phosphatase activity, and bone formation were suppressed by implantation of the compacted BMG and that scarcely any vascularization occurred. Calcification, vascularization, and alkaline phosphatase activity were related and were indispensable for bone formation. In the control group, bone formation was observed at sites of high activity of alkaline phosphatase and well-developed vascularization. These results suggested that compacting of BMG suppressed vascularization, decreased calcification, and consequently reduced the induction of bone formation.

Appearance of Adipose Cells in Connective Tissue at the Implantation Site of Bone Matrix Gelatin and Bupivacaine Injection

Two types of adipose cells were found in the connective tissue on day 7 after bone matrix gelatin (BMG) implantation and an injection of bupivacaine: mature adipose cells with a large lipid droplet (2-140 microns) and immature adipose cells with many small lipid droplets (0.1-2 microns). On day 10 after BMG implantation, typical adipose tissue was observed near the implant. The immature adipose cells had small, spherical mitochondria, glycogen granules and cytoplasmic microvesicles, and they might differentiate from undifferentiated mesenchymal cells in the connective tissue or the peripheral cells around the vessels as a white adipose tissue. These findings suggest that the differentiation of adipose cells in the connective tissue near heterotopic bone formation might be induced not only by mechanical and/or bupivacaine injury, but also by some factor or factors of the BMG.