ABSTRACT. Spatial expression of messenger ribonucleic acid (mRNA) for osteoblastic marker in drill hole defect healing of adult male rats was analyzed by in situ hybridization. The defect was filled with hematoma 3 days after surgery, expressing Type I collagen mRNA. Hematoma was replaced with fibrous tissue on day 7, and then with new trabecular bone on day 10, originated from the intra-medullary space, respectively. mRNA for Type I collagen, parathyroid hormone 1 receptor (PTH1R), and alkaline phosphatase (ALP) were expressed in the same cell population of fibrous tissue adjacent to newly-formed trabecular bone, and in osteoblasts lining the newlyformed trabecular bone. Hematopoietic marrow with osteoclasts subsequently invaded the region, also from the intra-medullary space, replacing all the new trabecular bone by day 21, except for a thin sub-periosteal layer. mRNA for Type I collagen, PTH1R and ALP was expressed on the periosteal surface of thin layer. Although cartilage formation was not histologically visible, mRNA for Type II collagen was weakly detected in the majority of osteoblasts lining the newly-formed trabecular bone. KEY WORDS: bone defect healing, bone formation, bone resorption, in situ hybridization, osteoblast.

Photoconductivity of ZnO single crystals grown by a hydrothermal method for ultraviolet light was measured. The ZnO single crystals have photo response in a range of wavelengths shorter than 380 nm. Ofaces of ZnO single crystals of the c-plane showed higher photocurrents and wider spectral response than did Zn-faces. It is thought that band bending at the surface regions of ZnO crystals is large at the O-face but small at the Zn-face, because the surface state density for electron capture at the O-face was higher than that of the Zn-face and, therefore, carriers generated at the surface region by UV light were effectively separated at the O-face region before their recombination. The difference between photoresponces of the O-face and the Zn-face is also useful for determining the polarity of a ZnO crystal.

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