Photoinduced group transfer radical addition of carbamotelluroates to acetylenes.

[reaction: see text] Te-Phenyl carbamotelluroates 1 add to acetylenes under irradiation of visible light to yield beta-telluroacrylamides 2 regioselectively. This reaction would be initiated by homolytic cleavage of the carbamoyl carbon-tellurium bond, producing carbamoyl and PhTe radicals. The addition reaction proceeds via a radical chain mechanism comprising two processes: (i) addition of carbamoyl radicals at the terminal carbon of the triple bond, giving vinylic radicals, and (ii) S(H)2 reaction on the Te atom caused by the attack of the vinyl radicals to 1.

Mineralized nodule formation by cultures of human dental pulp-derived fibroblasts.

Pulp fibroblasts were isolated from human deciduous and supernumerary teeth and cultured in vitro. With continued culture in normal tissue-culture medium, six pulp fibroblast strains formed cell nodules after 10-15 days. By electron microscopy the nodules had matrix vesicles, and needle-shaped crystals associated with a dense network of collagen fibrils. The crystalline material exhibited a pattern consistent with hydroxyapatite when nodules were examined by X-ray diffractometry. Furthermore, the cells showed high levels of alkaline phosphatase activity, which could be increased more than seven-fold by the addition of 1,25(OH)2D3 (5 x 10(-9)-5 x 10(-8) M). In addition to the production of type I collagen, these cells also synthesized fibronectin and osteonectin. The formation of mineralized tissue nodules by pulp cells in vitro provides a useful system for study of the pathological calcification of pulp tissues.

Histologic evaluation of tissue response to sintered lanthanum-containing hydroxyapatites subcutaneously implanted in rats.

Hydroxyapatite, lanthanum-containing hydroxyapatite, and lanthanum- and zirconium-containing hydroxyapatite discs were implanted subcutaneously in the backs of rats. The implanted discs and surrounding tissues were removed at 5 and 12 hours, and 1, 3, 7, 14, 30 and 60 days after implantation, and fixed in paraformaldehyde. Tissue samples were dehydrated and embedded in paraffin. Paraffin sections were cut and stained with hematoxylin and eosin, van Gieson's, and Masson's trichrome. The early tissue reaction was exudative due to fibrin deposition and infiltration by polymorphonuclear leukocytes and macrophages. The later reaction was characterized by the formation of fibrous tissue without inflammatory cell infiltration. The tissue reaction to all three types of material was identical by two months after implantation.