Decalcified and nondecalcified sections of fetal bovine tibia were stained immunohistochemically with a monoclonal antibody against dentin phosphophoryn. In the epiphyseal portion of the long bone, osteoblasts, osteocytes and the bone matrix were stained, but chondrocytes and the cartilage matrix were not. Similar staining was observed in the epiphyseal and diaphyseal portions of bones. These findings suggest that a protein(s) with the same epitope as phosphophoryn may be synthesized and secreted by osteoblasts at the beginning of ossification and may be involved in mineralization of bone tissue. On Western blots of proteins extracted from fetal bovine bone, the antibody reacted with two bands of molecular weights of about 71,000 and 63,000. These proteins and antibody(s) to the proteins may be useful for detection of the phenotype of osteogenesis.
Morphologic changes following the development of lower incisal tooth germs of rat fetus
The fine structure of the osteodentin in fetal rat incisors was observed by transmission el -歯 基 礎 誌34:49-80, 1992.
(Communicated by Motoo KIMUnA, M. J. A., May 12, 1987) Recently, many types of transposons such as the P element, copia, FB element and so on, have been detected in natural populations of Drosophila melanogaster and the relationships between these elements and mutations induced by mutagens should be clarified. Greenberg and Crow (1960) partitioned the induced homozygous loads as well as genetic loads in natural populations into lethal (L) and detrimental (D) loads. When viability mutation was induced by radiation, the values of D/L ratio were variable from line to line. In some lines the ratios were 0.1-0.3, but in the other lines the D/L ratios were larger than 0.5. It is imaginable that this variation is due to whether or not the strains used had special transposons or movable genetic elements. Keeping this in mind, we tested the effects of radiation-induced and chemical-induced viability mutations. Another aim of the present experiment was to test whether or not urethane gas induces viability mutations. The results are as follows :Materials and method. Two strains of the wild-type of D. melanogaster were employed : Oregon R and Samarkand. Before exposing the flies to r-rays and urethane gas (ethyl carbamate), the second chromosomes of both strains were made isogenic by using the In(2LR)SM1,Cy/In(2LR)bwvl stock. This stock is abbreviated Cy/Pm. Experiment 1. In this experiment, many males of both isogenic second chromosome strains (+/+) were exposed to 0, 1.5, 3.0 and 4.5 kR of r-rays. After that, the males were crossed with Cy/Pm virgin females in a mass in each dose. In the next generation, Cy/+ or Pm/+ males were individually crossed with 5 Cy/Pm virgin females. In the next generation, Cy/+ virgin females and males were collected and 5-pair matings were conducted. In the offspring, phenotypically Cy (genotype is Cy/+) and wild-type flies (+/+) segregated at the expected ratio of 2: 1 (Cy/Cy is lethal). The viability of +/+ flies (v) was expressed as v=2a/ (b+1), where a and b were the number of wild-type and phenotypically Cy flies, respectively. All crosses were made in 2.5X 10 cm vials.Experiment 2. Urethane gas treatment was conducted as follows : At first saturated urethane gas was prepared. Urethane powder, 1.5 g, covered with absorbent cotton was put into the bottom of a vial (2.5 cmx 10 cm) and kept for 24 hr at 25°C. Then, Oregon R males were put into this vial. After 2 hr, anesthetized males were laid on paper inserted partially into the culture medium and kept for 22 hr at 18°C. Urethane gas exposures of 4 hr and 6 hr were conducted by repeating the above process two or three times. These exposures were scheduled so that the last intervals of the 2 hr, 4 hr, and 6 hr treatments were synchronized with each other. After the completion of the treatment, an
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