Although cells of the osteoblast lineage express functional ERs, direct effects of estrogen on bone formation remain obscure. In the present study, we have investigated estrogen effects on osteoblastic and adipocytic differentiation from a mouse bone marrow stromal cell line, ST-2, which had been manipulated to overexpress either human ER alpha (ST2ER alpha) or ER beta (ST2ER beta). Treatment with bone morphogenetic protein-2 increased alkaline phosphatase activity as well as the number of Oil Red O-positive adipocytes, indicating that bone morphogenetic protein-2 stimulated both osteoblastic and adipocytic differentiation from these bipotential cells. In both ST2ER alpha and ST2ER beta cells, cotreatment with E2 caused enhancement of alkaline phosphatase activity and suppression of lipid accumulation. These effects were completely reversed by an ER antagonist, ICI182780. Therefore, the estrogen regulation occurred in an ER-specific manner but without ER subtype specificity. Moreover, dose response curves of the opposing effects of estrogen on osteoblastogenesis and adipogenesis formed an apparent mirror image, consistent with a reciprocal regulation of differentiation into the two cell lineages. These results demonstrate that estrogen directly modulates differentiation of bipotential stromal cells into the osteoblast and adipocyte lineages, causing a lineage shift toward the osteoblast. Such effects would lead to direct stimulation of bone formation and thereby contribute to the protective effects of estrogen on bone.

Immunohistochemical localization of collagen types I, II, and X, aggrecan, versican, dentin matrix protein (DMP)-1, martix extracellular phosphoprotein (MEPE) were performed for Meckel’s cartilage, cranial base cartilage, and mandibular condylar cartilage in human midterm fetuses; staining patterns within the condylar cartilage were compared to those within other cartilaginous structures. Mandibular condylar cartilage contained aggrecan; it also had more type I collagen and a thicker hypertrophic cell layer than the other two types of cartilage; these three characteristics are similar to those of the secondary cartilage of rodents. MEPE immunoreactivity was first evident in the cartilage matrix of all types of cartilage in the human fetuses and in Meckel’s cartilage of mice and rats. MEPE immunoreactivity was enhanced in the deep layer of the hypertrophic cell layer and in the cartilaginous core of the bone trabeculae in the primary spongiosa. These results indicated that MEPE is a component of cartilage matrix and may be involved in cartilage mineralization. DMP-1 immunoreactivity first became evident in human bone lacunae walls and canaliculi; this pattern of expression was comparable to the pattern seen in rodents. In addition, chondroid bone was evident in the mandibular (glenoid) fossa of the temporal bone, and it had aggrecan, collagen types I and X, MEPE, and DMP-1 immunoreactivity; these findings indicated that chondroid bone in this region has phenotypic expression indicative of both hypertrophic chondrocytes and osteocytes.

Demonstration of putative Co-binding domains in dentin matrix of rat incisors ajrer dnily injections of 1-hydroxyethy/idene-1, 1-bisphosphonate ( HEBP). Eur J Oral Sci 1998; 106 (supp/1 ): 274-281. Eur J Oral Sci, 1998 In order to clarify the initial process of dentin mineralization, the inhibitory effect of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) on dentin mineralization was investigated. Rats (I 00 g) were subcutaneously injected with HEBP (8 mg P/ kg) for 7 or 14 d , and the incisors were processed for Ca histochemistry and/or electron microscopy. HEBP-treated incisors demonstrated ladder-like alternate rows of mineralized and non-mineralized dentin at the apical end . GBHA revealed moderate Ca reactions in the nonmineralized circumpulpal dentin matrix where electron microscopy revealed rich distribution of fine mesh-like electron-dense material. Non-mineralized mantle dentin matrix was negative for Ca but contained numerous matrix vesicles ( MVs) filled with crystalline and/or amorphous mineral deposits. Mineralization of circumpulpal dentin occurred independently of MV-rich mantle dentin layer in affected specimens. Our data provide histochemical evidence of possible Ca-binding property of the circumpulpal dentin matrix and its absence in the mantle dentin where MY-mediated mineralization occurs. In the mantle dentin, HEBP does not interfere with crystal growth in MVs but inhibits its outgrowth after membrane rupture. It is proposed that circumpulpal dentin matrix has a potential to mineralize independently of MY-mediated mineralization of mantle dentin, a lthough MVs determine the initial site and timing of dentin mineralization.

Immunohistochemical localization of versican and tenascin-C were performed; the periosteum of ossifying mandible and the perichondrium of Meckel's cartilage, of vertebral cartilage, and of mandibular condylar cartilage were examined in midterm human fetuses. Versican immunoreactivity was restricted and evident only in perichondrium of Meckel's cartilage and vertebral cartilage; conversely, tenascin-C immunoreactivity was only evident in periosteum. Therefore, versican and tenascin-C can be used as molecular markers for human fetal perichondrium and fetal periosteum, respectively. Meckel's cartilage underwent endochondral ossification when it was incorporated into the ossifying mandible at the deciduous lateral incisor region. Versican immunoreactivity in the perichondrium gradually became weak toward the anterior primary bone marrow. Tenascin-C immunoreactivity in the primary bone marrow was also weak, but tenascin-C positive areas did not overlap with versicanpositive areas; therefore, degradation of the perichondrium probably progressed slowly. Meanwhile, versican-positive perichondrium and tenascin-C-positive periosteum around the bone collar in vertebral cartilage were clearly discriminated. Therefore, the degradation of Meckel's cartilage perichondrium during endochondral ossification occurred at a different rate than did degradation of vertebral cartilage perichondrium. Additionally, the perichondrium of mandibular condylar cartilage showed tenascin-C immunoreactivity, but not versican immunoreactivity. That perichondrium of mandibular condylar cartilage has immunoreactivity

The extrinsic muscles are subdivided into small groups of fibers depending on their spatial interrelationships, suggesting that they contain many functional units. Some units act separately, and others cooperate across the traditional boundaries of the muscles.

We have recently identified a diabetic patient with marked fasting hyperinsulinemia. Family study revealed that the abnormality was an autosomal dominant trait. High-performance liquid chromatography (HPLC) profile of the patient's serum insulin showed that she had an abnormal insulin in addition to a normal insulin. We have purified her insulin(s) from the specimen of her pancreas, which was biopsied during an operation of cholelithiasis. Insulin was also immunologically purified from the serum of her portal vein. The reverse-phase HPLC analysis revealed that the ratios of normal to abnormal insulin in the pancreas, portal vein, and peripheral vein were 5:4, 4:5, and 1:7, respectively. Radioreceptor assay for insulin using guinea pig kidney membrane revealed that the binding activities of the normal component insulin, the abnormal component insulin and her pancreatic insulin containing, both components were 100, 5, and 50% of standard human insulin, respectively. The biological activities of the normal components the abnormal component and her pancreatic insulin to stimulate glucose oxidation in rat adipocytes were found to be 100, 8, and 60% of standard human insulin, respectively. Analysis of amino acid sequences of the abnormal insulin purified from her pancreas strongly suggested the substitution of leucine for valine at the third position of the A chain, A3 (Val --Leu).

No abstract

No abstract