Kiyoshi Takami

A meiotic DNA polymerase from Coprinus cinereus: further purification and characterization

A meiotic DNA polymerase that is present at a high level of activity in meiotic cells of a basidiomycete, Coprinus cinereus, was purified to near homogeneity using synthetic RNA homopolymer [poly(C)] cellulose column chromatography. This report presents the first extensive purification and characterization of any eukaryotic DNA polymerase having a role in meiosis. This enzyme is a single polypeptide with a molecular mass of 65,000. Activity in this enzyme requires magnesium ions and occurs at an optimal pH of 7.5. It is strongly inhibited by dideoxythymidine triphosphate but is relatively insensitive to aphidicolin and N-ethylmaleimide and can use poly(C)/oligo(dG)12–18 as a template-primer. Polymerase activity can be found only in cells at meiotic prophase, even though the enzyme has been identified in somatic cells in an inactive state using immunoblot analysis. Its distinctive distribution makes possible a genetic and biochemical analysis of functional role of a meiotic DNA polymerase in meiotic recombination, repair and synthesis.

Connection Between Built Environment and Travel Behavior: Propensity Score Approach Under a Continuous Treatment Regime

In recent years, the compact city concept has become a paradigm of sustainable urban development under the premise that mixed-use, high-density cities can significantly reduce automobile dependency and promote the use of alternative modes. This claim, however, hinges on the existence of a true causal mechanism between the built environment and travel behavior. This study tackled the causality problem by using a propensity score approach but differed from previous studies in that this study relaxed the binary treatment assumption (i.e., urban versus suburban) and assumed a continuous treatment of urbanization level, estimated as a latent variable. Methodologically, the propensity score stratification method used was successful in mitigating residential self-selection bias on estimates of the effect of the built environment on nonwork trip frequency and traveled distance. Overestimation ranges for the direct regression estimates against the estimates stratified on the propensity score ranged from 6% to 36%. Findings suggested the existence of a causal mode substitution mechanism from car to nonmotorized modes given positive increases in the latent score of urbanization level.

Sustainable Regeneration of a Car-dependent City: The Case of Toyama toward a Compact City

Toyama Prefecture is one of three prefectures that comprise the Hokuriku Region at the Sea of Japan side of central Japan. Toyama City is its prefectural capital, and the second-largest city in Hokuriku after Kanazawa City (Fig. 10-1). About 420,000 people live in the city after the merger of seven municipalities in 2005, and the population of its metropolitan area is about 540,000.

A Study on Variation in Residents' Car Use by Location of Housing Development

To examine the likely relationship between proximity to the railway station and less car use, this paper compares the average amount of car-based travel of residents in three housing complexes. As a result, it is shown that the average car mileage of residents nearer to the station is not necessarily less than those who live far from it. Another result is that residents in the housing complex nearer to the major focus of “kiss & ride” or shopping activity use car less in such purposes. So, car use can be reduced by locating them proximately.