Human osteoblasts support hematopoietic cell development in vitro.

Background/aim: Although osteoblasts are thought to be the major component of the hematopoietic stem cell niche in the bone marrow microenvironment, the role of osteoblasts in hematopoiesis is still unclear. The ability of human osteoblasts to support early hematopoiesis was investigated.

Methods And Results: Human CD34+ bone marrow cells cultured on human osteoblasts were capable of surviving without addition of cytokines and differentiated into myeloid cells with slight proliferation.

Interleukin-7 contributes to human pro-B-cell development in a mouse stromal cell-dependent culture system.

Objective: The role of interleukin (IL)-7 in human B lymphopoiesis is still controversial. We used an in vitro culture system to verify involvement of IL-7 in development of human pro-B cells from hematopoietic stem cells.

Materials And Methods: Human CD34(+) bone marrow cells were cultured for 4 weeks on MS-5 mouse stromal cells to induce pro-B cells.

Characterization of monocyte-macrophage-lineage cells induced from CD34+ bone marrow cells in vitro.

We characterized the expression of cell surface antigens and cytokine-secreting ability of monocyte-macrophage-lineage cells induced in vitro from CD34+ bone marrow cells. After cultivation for 3 weeks, we observed 2 distinct cell fractions: a floating small, round cell fraction and an adherent large, protruding cell fraction. Both cell fractions expressed myelocyte-monocyte-lineage antigens, but mature-macrophage markers such as CD206 were expressed only by the adherent cells.

Involvement of insulin-like growth factor-I and insulin-like growth factor binding proteins in pro-B-cell development.

Objective: Insulin-like growth factor (IGF)-binding proteins (IGFBPs) are a family of proteins thought to modulate IGF function. By employing an in vitro culture system of human hematopoietic stem cells cocultured with murine bone marrow stromal cells, we examined the effects of IGF-I and IGFBPs on early B-cell development.

Materials And Methods: Human CD34(+) bone marrow cells were cocultured with murine stromal MS-5 cells for 4 weeks, and pro-B-cell number was analyzed by flow cytometry.

Laminin binding protein, 34/67 laminin receptor, carries stage-specific embryonic antigen-4 epitope defined by monoclonal antibody Raft.2.

We previously produced monoclonal antibodies against the detergent-insoluble microdomain, i.e., the raft microdomain, of the human renal cancer cell line ACHN.

Dietary bioflavonoids induce apoptosis in human leukemia cells.

Dietary bioflavonoids are secondary metabolites of plants that are known to have a variety of bio-effects, including anti-cancer activity. In this study, we examined the effects of flavonoids on the growth of human leukemia cells and found that certain flavonoids induce apoptosis in a variety of human leukemia cells. The apoptosis induced by bioflavonoids was dose-dependent and was accompanied by a disruption of the mitochondrial transmembrane potential and the activation of caspase.

Development of novel monoclonal antibody 4G8 against swine leukocyte antigen class I alpha chain.

A mouse monoclonal antibody (MAb) was generated against swine leukocyte antigen (SLA) class I alpha chain. A newly developed series of MAb clones that react with pan leukocytes were selected and tested by immuno-histochemistry using SLA class I alpha chain expressing Cos-7 cells. Among them, MAb 4G8 was characterized by the following features: (1) 4G8 reacted with Cos-7 cells transfected with SLA class I alpha chain from the d haplotype, (2) 4G8 recognized epitopes that were different from those of commercially available anti-SLA class I MAbs 74-11-10 and PT85A, and (3) 4G8 could be used to immunostain frozen sections of thymus, spleen, lymph node, kidney, and liver tissues with good results.

Shiga toxin binding to globotriaosyl ceramide induces intracellular signals that mediate cytoskeleton remodeling in human renal carcinoma-derived cells.

Shiga toxin is a bacterial toxin consisting of A and B subunits. Generally, the essential cytotoxicity of the toxin is thought to be mediated by the A subunit, which possesses RNA cleavage activity and thus induces protein synthesis inhibition. We previously reported, however, that the binding of the Shiga toxin 1-B subunit to globotriaosyl ceramide, a functional receptor for Shiga toxin, induces intracellular signals in a manner that is dependent on glycolipid-enriched membrane domains, or lipid rafts.

Characterization of a shiga-toxin 1-resistant stock of vero cells.

Shiga toxins (Stxs, also referred to as verotoxins) were first described as a novel cytotoxic activity against Vero cells. In this study, we report the characterization of an Stx1-resistant (R-) stock of Vero cells. (1) When the susceptibility of R-Vero cells to Stx1 cytotoxicity was compared to that of Stx1-sensitive (S-) Vero cells by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay, cell viability after 48-hr exposure to 10 pg/ml of Stx1 was greater than 80% and less than 15%, respectively.

Diagnostic importance of CD179a/b as markers of precursor B-cell lymphoblastic lymphoma.

Surrogate light chains consisting of VpreB (CD179a) and lambda5 (CD179b) are expressed in precursor B cells lacking a complete form of immunoglobulin and are thought to act as substitutes for conventional light chains. Upon differentiation to immature and mature B cells, CD179a/b disappear and are replaced with conventional light chains. Thus, these molecules may be useful as essential markers of precursor B cells.

Raft.1, a monoclonal antibody raised against the raft microdomain, recognizes G-protein beta1 and 2, which assemble near nucleus after shiga toxin binding to human renal cell line.

Raft microdomains are glycolipid-enriched microdomain scaffolding molecules involved in signal transduction. The binding of Shiga toxin to globotriaosyl ceramide in raft microdomains of the human renal tubular cell line ACHN causes temporal activation of Src-kinase Yes. To study the downstream signaling mechanism proceeding to the activation of Yes, we raised monoclonal antibodies (MAbs) against raft microdomains.

Rum1, an inhibitor of cyclin-dependent kinase in fission yeast, is negatively regulated by mitogen-activated protein kinase-mediated phosphorylation at Ser and Thr residues.

The p25(rum1) is an inhibitor of Cdc2 kinase expressed in fission yeast and plays an important role in cell-cycle control. As its amino-acid sequence suggests that p25(rum1) has putative phosphorylation sites for mitogen-activated protein kinase (MAPK), we investigated the ability of MAPK to phosphorylate p25(rum1). Direct in vitro kinase assay using GST-fusion proteins of wild-type as well as various mutants of p25(rum1) demonstrated that MAPK phosphorylates the N-terminal portion of p25(rum1) and residues Thr13 and Ser19 are major phosphorylation sites for MAPK.