Biology subjects

Ohara, M.

Publications and source records attributed to Ohara, M..

3 recordsLinked to original sources

bioRxiv2021

Potential effects of life history on demographic genetic structure in stage-structured plant populations

O_LIPredicting temporal dynamics of genetic diversity is important for assessing long-term population persistence. In stage-structured populations, especially in perennial plant species, genetic diversity is often compared among life history stages, such as seedlings, juveniles, and flowerings, using neutral genetic markers. Because individuals in mature stages will die and be replaced by those in more immature stages over the course of time, the comparison among stages (sometimes referred to as demographic genetic structure) has been regarded as a proxy of potential genetic changes that accompany the turnover of constituent individuals. However, because demographic genetic structure had not been theoretically examined, the basic property and the validity of demographic genetic structure remained unclear. C_LIO_LIWe developed a matrix model which was made up of difference equations of expected heterozygosity, a common proxy of genetic diversity, of each life history stage at a neutral locus in stage-structured plant populations. Based on the model, we formulated demographic genetic structure as well as the annual change rate of expected heterozygosity (denoted as{eta} ). We obtained theoretical expectation of demographic genetic structure and{eta} from our model and compared them with computational results of stochastic simulation for randomly generated 3,000 life histories for model validation. We then examined the relationships of demographic genetic structure with effective population size Ne, which is the determinants of diversity loss per generation time, as well as with{eta} . C_LIO_LITheoretical expectations on{eta} and demographic genetic structure fitted well to the results of stochastic simulation, supporting the validity of our model. Demographic genetic structure varied independently of Ne and{eta} , while having a strong correlation with stable stage distribution: expected heterozygosity was lower in stages with fewer individuals. C_LIO_LIOur results indicate that demographic genetic structure strongly reflects stable stage distribution, rather than temporal genetic dynamics, and that inferring future genetic diversity solely from demographic genetic structure would be misleading. Instead of demographic genetic structure, the newly-defined statistics{eta} will be an useful tool to predict genetic diversity at the same time scale as population dynamics, facilitating evaluation on population viability from a genetic point of view. C_LI

genetics↗

bioRxiv2021

Visualization of ecological successions in lakes subdivided by volcanic eruption at Akan Caldera, Hokkaido, Japan

It is not feasible to continuously observe ecological succession in lakes because of the long time-scales generally involved. Thus, the process has been inductively deduced by comparing many lakes with different succession states, or indirectly simulated by tracking studies of smaller water bodies, experiments using microcosms or mesocosms, and reconstruction of lake history by sediment analysis. However, the reality of succession processes in large lakes with slow succession is not well understood, and new approaches are needed. Theoretically, in a group of large and small lakes of similar ages and with similar initial and watershed environments, the rate of nutrient accumulation in each lake depends on the ratio of watershed area to lake size, and the lakes are predicted to evolve to different trophic levels over time. Here, we tested this hypothesis on the 10 lakes of varying sizes in Akan Caldera, Japan, which were formed thousands of years ago by fragmentation due to volcanic eruptions within the caldera. Topographic and water quality studies showed that the ratio of accumulated watershed area to lake size (area and volume), expressed logarithmically, had a positive linear regression with the total phosphorus concentration, an indicator of trophic level. The trophic levels of the lakes were diverse, including oligotrophic, mesotrophic, and eutrophic types in the traditional "lake type" classification based on total phosphorus and chlorophyll-a concentrations. Furthermore, 21 species of aquatic macrophytes were observed by a diving survey, and the plant species composition was classified into five groups corresponding to the trophic status of the lakes, indicating a conventional "hydrarch succession". The diversity of water quality and aquatic vegetation in a group of lakes with similar origins paves the way for new comparative studies of lakes, including large lakes.

ecology↗

bioRxiv2021

Effect of luminal surface structure of decellularized aorta on thrombus formation and cell behavior

As the number of cardiovascular diseases increases, artificial heart valves and blood vessels have been developed. Although cardiovascular application using decellularized tissue have been studied, the mechanism of their functionality is still unknown. To find the important factor for preparing decellularized cardiovascular prothesis which shows good in vivo performance, the effect of luminal surface structure of decellularized aorta on thrombus formation and cell behavior was investigated. Various luminal surface structures of decellularized aorta were prepared by heating, drying and peeling. The luminal surface structure and collagen denaturation was evaluated by immunohistological staining, collagen hybridizing peptide (CHP) staining and scanning electron microscopy (SEM) analysis. To evaluate the effect of luminal surface structure of decellularized aorta on thrombus formation and cell behavior, blood clotting test and recellularization of endothelial cells and smooth muscular cells were performed. The results of blood clotting test showed that the closer the luminal surface structure is to native aorta, the higher the anti-coagulant property. From the result of cell seeding-test, it was suggested that vascular cells recognize the luminal surface structure and regulate adhesion, proliferation and functional expression. These results will provide important factor for preparing decellularized cardiovascular prothesis and lead to future development on decellularized cardiovascular applications.

bioengineering↗