Two Hemocyte Lineages Exist in Silkworm Larval Hematopoietic Organ

BACKGROUND: Insects have multiple hemocyte morphotypes with different functions as do vertebrates, however, their hematopoietic lineages are largely unexplored with the exception of Drosophila melanogaster. METHODOLOGY/PRINCIPAL FINDINGS: To study the hematopoietic lineage of the silkworm, Bombyx mori, we investigated in vivo and in vitro differentiation of hemocyte precursors in the hematopoietic organ (HPO) into the four mature hemocyte subsets, namely, plasmatocytes, granulocytes, oenocytoids, and spherulocytes. Five days after implantation of enzymatically-dispersed HPO cells from a GFP-expressing transgenic line into the hemocoel of normal larvae, differentiation into plasmatocytes, granulocytes and oenocytoids, but not spherulocytes, was observed. When the HPO cells were cultured in vitro, plasmatocytes appeared rapidly, and oenocytoids possessing prophenol oxidase activity appeared several days later. HPO cells were also able to differentiate into a small number of granulocytes, but not into spherulocytes. When functionally mature plasmatocytes were cultured in vitro, oenocytoids were observed 10 days later. These results suggest that the hemocyte precursors in HPO first differentiate into plasmatocytes, which further change into oenocytoids. CONCLUSIONS/SIGNIFICANCE: From these results, we propose that B. mori hemocytes can be divided into two major lineages, a granulocyte lineage and a plasmatocyte-oenocytoid lineage. The origins of the spherulocytes could not be determined in this study. We construct a model for the hematopoietic lineages at the larval stage of B. mori

Flange Wrinkling in Flexible Roll Forming Process

AbstractFlexible roll forming is an advanced sheet metal forming process for producing variable cross section profiles. Flange wrinkling at the transition zone where the cross section changes is a major defect in the flexible roll forming process. In this paper, the flange wrinkling at the transition zone is studied using finite element analysis. The results showed that the strip deformation at the transition zone can be considered as a combination of two strip deformations observed in the conventional roll forming process and the flanging process. According to finite element analysis results, when the flange wrinkling occurs, compressive longitudinal strain is smaller than the necessary compressive longitudinal strain calculated by mathematical modeling to obtain the intended profile geometry in the compression zone. Therefore, comparison of compressive longitudinal strain obtained from the finite element analysis and the necessary compressive longitudinal strain is a good criterion to predict the flange wrinkling occurrence. A flexible roll forming setup was developed. Longitudinal strain history is obtained from the finite element simulation and is compared with the experimental data from the flexible roll forming setup. Results show a good agreement and confirm the finite element analysis