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Pluripotent hemopoietic stem cells (P-HSCs) were thought to be c-kit ؉ , but recent reports indicate that they are c-kit low . In the present report, we provide evidence using Ly5 congenic mice that P-HSCs are c-kit

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A small number of B cells are found in the thymus of normal mice. A population of B lymphocytes could be enriched to greater than 90% purity by isolating a low-density fraction on Percoll density gradients and then depleting T cells with a mixture of anti-Thy-1, CD4, and CD8 mAbs and complement. Enrichment was monitored by surface Ig staining and by functional studies (responsiveness to LPS, and to anti-mu plus IL-4). When the phenotype of these B cells was studied by flow cytometry, 60-80% had the phenotype Ly-1+ (CD5), Ia+, B220low (CD45R), and Mac-1+ (CD 11b). In contrast, splenic B cells lacked CD5 and CD11b and expressed higher levels of B220 and Ia antigens. These results indicate that most thymic B cells have the phenotype of the Ly-1 B cell subset, which was identified previously as a trace subpopulation in some peripheral tissues and is thought to play a role in autoantibody formation.

We discuss the new challenges and directions facing the use of big data and artificial intelligence (AI) in education research, policy-making, and industry. In recent years, applications of big data and AI in education have made significant headways. This highlights a novel trend in leading-edge educational research. The convenience and embeddedness of data collection within educational technologies, paired with computational techniques have made the analyses of big data a reality. We are moving beyond proof-of-concept demonstrations and applications of techniques, and are beginning to see substantial adoption in many areas of education. The key research trends in the domains of big data and AI are associated with assessment, individualized learning, and precision education. Model-driven data analytics approaches will grow quickly to guide the development, interpretation, and validation of the algorithms. However, conclusions from educational analytics should, of course, be applied with caution. At the education policy level, the government should be devoted to supporting lifelong learning, offering teacher education programs, and protecting personal data. With regard to the education industry, reciprocal and mutually beneficial relationships should be developed in order to enhance academia-industry collaboration. Furthermore, it is important to make sure that technologies are guided by relevant theoretical frameworks and are empirically tested. Lastly, in this paper we advocate an in-depth dialog between supporters of "cold" technology and "warm" humanity so that it can lead to greater understanding among teachers and students about how technology, and specifically, the big data explosion and AI revolution can bring new opportunities (and challenges) that can be best leveraged for pedagogical practices and learning.

Thrombopoietin (TPO) plays a critical role not only in proliferation and differentiation of megakaryocytes but also in erythroid differentiation. We have investigated whether the different pathway of mitogen-activated protein kinase (MAPK) after TPO stimulation may discriminate megakaryocyte and erythroid differentiation. In this study, we have used human CD34+ hematopoietic progenitor cells (HPCs) from cord blood (CB) in serum-free liquid culture supplemented with TPO, to compare the respective effects of specific inhibitors of MAPK kinase (MEK) (PD98059) and p38 MAP kinase (p38) (SB203580) on megakaryocyte and erythroid development. PD98059, but not SB203580, significantly suppressed TPO-induced megakaryocyte differentiation when examined by the expression of CD41 and polyploidy assay. In the presence of SB203580, CD34+/CD36+ erythroid progenitors clearly decreased, whereas they increased when cultured with PD98059. These results indicate that activation of extracellular-signal-regulated kinase (ERK) is required for TPO-induced megakaryocyte differentiation and that p38 is required for TPO-induced erythroid differentiation.

Summary. Thrombocytopenia is typically observed in patients undergoing cord blood transplantation. We hypothesized that delayed recovery of the platelet count might be caused by defects in the megakaryocytic differentiation pathway of cord blood progenitors. To test this hypothesis, we compared the features of in vitro megakaryocytopoiesis between cord blood progenitors and those in bone marrow cells after isolation of CD34 cells as progenitors. The proliferative responses of the progenitors in cord blood are higher than those in bone marrow cells in the presence of interleukin (IL)-3, stem cell factor (SCF) and thrombopoietin (TPO). However, the ability to generate mature megakaryocytes was higher in bone marrow progenitors than in cord blood in the same in vitro culture system, when examined by the expression of CD41, polyploidy and proplatelet formation. Furthermore, an earlier induction of c-mpl protein, a receptor for TPO, was observed in the progenitors from bone marrow than in those from cord blood in the presence of SCF and IL-3. Therefore, the ability to generate mature megakaryocytes in bone marrow progenitors is superior to that in cord blood, and the delayed engraftment of platelets after cord blood transplantation might be attributed to the features of cord blood megakaryocyte progenitors.

In the present study we have characterized natural suppressor (NS) cells, which nonspeciflically suppress mitogen responses and mixed-lymphocyte reaction. The strongest NS activity was found in a fraction of relatively low-density cells (1.