Biomedical subjects

D Benayahu

Publications and source records attributed to D Benayahu.

43 records · Page 3Linked to original sources

PubMed1993

Osteoblasts release a soluble factor that modulates immunoglobulin secretion by mature B cells.

An osteogenic member, MBA-15 cell line, from marrow stroma compartment, was examined for its ability to regulate mature lymphoma B cell line functions. The effect of MBA-15 cell secreting factor/s on cell proliferation, immunoglobulin secretion and isotype switch of 29M4.1 IgM+ mature B cell line was examined. The factor causes temporal arrest in cell proliferation, augments immunoglobulin secretion and has no effect on isotype switching. The results revealed a direct effect of the MBA-15 factors on the B cell functions. Factors secreted by other osteoblastic cells (ROS 17/2.8 and MC-3T3-E1) possess the same biological activities. In contrast, factors secreted by an endothelial adipocyte stromal cell line 14F1.1 lack these properties.

Analysis of Variance↗

PubMed1993

Marrow stroma-derived osteogenic clonal cell lines: putative stages in osteoblastic differentiation.

This report documents characterization of five osteogenic cell subpopulations of bone marrow stroma. The clonally derived cell lines were isolated from the parental line MBA-15 known to express osteoblastic-associated features in vitro and to form bone in vivo. The latter, presumably "arrested" at a particular stage along the osteogenic lineage, are useful models to study the processes involved in the differentiation of bone forming cells. The clones differ in their morphology, proliferation rate, quantities and distribution of extracellular matrix proteins, levels of alkaline phosphatase activity and activation of adenylate cyclase by parathyroid hormone and/or prostaglandin E. These properties have been retained during prolonged growth and subculturing through many passages. MBA-15.4 is a presumptive preosteoblast with a fibroblast-like appearance; it proliferates rapidly, synthesizes equal amounts of collagen and noncollagenous proteins, and produces constitutively low levels of alkaline phosphatase. This clone has PGE2-stimulated adenylate cyclase activity and a very low constitutive response to PTH. On the other hand, MBA-15.6 has a large polygonal morphology with limited proliferative potential, synthesizes twice as much noncollagenous proteins as collagen, has high alkaline phosphatase activity, and responds strongly to PTH. The characteristics of the other clones place them between these two categories. The effects of 10(-7) M dexamethasone or 10(-12)-10(-8) M 1,25 dihydroxyvitamin D3 on growth and differentiation further strengthen the variance between these clones. The different in vitro characteristics of the various clones were directly reflected in their bone formation ability in vivo. When transplanted under the renal capsule, MBA-15.33 formed a thick fibrous tissue, MBA-15.4 formed small foci of bone, and MBA-15.6 formed massive woven bone at the same period of time.

Adenylyl Cyclases↗

PubMed1992

Hemopoietic functions of marrow-derived osteogenic cells.

Osteoblasts, members of the marrow stromal cellular network, may play an active role in the hemopoietic microenvironment as well as in bone remodeling. In this study, we examined the extent to which marrow-derived osteogenic cells (MBA-15) possess various stromal functions. This marrow stromal-derived cell line was shown by us to exhibit osteoblastic characteristics in culture and to form bone in vivo. These cells are shown here to constitutively produce and secrete cytokines identified as M-CSF, GM-CSF, and IL-6. MBA-15 cells modulate growth of normal and malignant myeloid and lymphoid cells as well as leukemia cell lines in vitro. Cell-cell interactions were studied in co-cultures with adherent MBA-15 cells and the target hemopoietic cells. Growth inhibition effects, observed under various experimental conditions, can be attributed to the presence of different soluble and membrane-bound inhibitory activities produced by MBA-15 cells. Thus, MBA-15 cells spontaneously produce both stimulators and inhibitors that can affect myeloid and lymphoid cell growth. Marrow osteogenic cells may therefore participate in the stromal regulation of hemopoiesis.

Alkaline Phosphatase↗

PubMed1991

Subpopulations of marrow stromal cells share a variety of osteoblastic markers.

A series of stromal cell lines derived from mouse bone marrow, representing subpopulations of putative stromal cell types, were examined for the expression of osteoblastic properties. The effects of dexamethasone and specific inhibitors on alkaline phosphatase activity, cAMP response to bone-seeking hormones, and the ability to mineralize extracellular matrix in vitro as well as collagen typing were used as osteoblastic markers. We found that all stromal cell types examined possess some osteoblastic features but differ in the degree of expression. The data provide support to the hypothesis of a common stem cell for marrow stromal cells.

Alkaline Phosphatase↗

PubMed1990

Neutral endopeptidase (EC 3.4.24.11) is highly expressed on osteoblastic cells and other marrow stromal cell types.

A series of cultured mouse marrow stromal cell lines of different phenotype characteristics were examined for their neutral endopeptidase (NEP) activity using the highly selective chromophoric substrate of enzyme, 3-carboxypropanoyl-alanyl-alanyl-leucine 4-nitroanilide. All the cell lines tested contained appreciable amounts of NEP activity, but the cells expressing an osteoblastic phenotype, MBA-15, showed the high levels. Other non-stromal osteoblastic cell lines, MC-3T3-E1, ROS 17/2.8 cells derived from mouse long bone explants, were also rich in NEP. A four-fold stimulation of NEP activity was observed when certain MBA-15 clones were cultured in the presence of 1 alpha,25-dihydroxyvitamin D3. Since NEP is an effective cell-surface endopeptidase, it may play a role in the dynamics of bone formation, via interaction with biologically active polypeptides.

Amino Acid Sequence↗

PubMed1989

Bone marrow-derived stromal cell line expressing osteoblastic phenotype in vitro and osteogenic capacity in vivo.

Marrow stroma has been shown to have osteogenic potential. Here we report the characterization of a unique stromal cell line derived from mouse bone marrow (MBA-15), which expresses osteoblastic phenotype in vitro and forms bone in vivo. More than 70% of cells in culture were histochemically positive for alkaline phosphatase. The enzyme levels were enhanced threefold when cultures were treated with dexamethasone. Gel electrophoresis of [3H]-proline-labeled cultures showed that MBA-15 cells produced only type I collagen. These cells were responsive to PTH, as indicated by a 50-fold increase in intracellular cAMP. Prostaglandin E2, but not calcitonin, stimulated cAMP up to 70-fold. When cultures were grown to confluence and fed daily with ascorbic acid and beta-glycerophosphate, the cells formed a Von Kossa positive, thick extracellular matrix, shown to contain hydroxyapatite crystals. MBA-15 cells produced mineralized bone when implanted in diffusion chambers. These results indicate that the MBA-15 cell line possesses osteoblastic features in vitro and osteogenic capacity in vivo.

Alkaline Phosphatase↗

PubMed1983

Comparative study of protamine chloride and sulphate in relation to the heparin rebound phenomenon.

The heparin rebound phenomenon is observed when protamine sulphate, but not protamine chloride, is employed for the neutralization of heparin. On investigating the stability of several protamine compounds towards the protaminolytic activity of human plasma, we found that while protamine chloride was stable, both the sulphate and the phosphate were degradeable. The free base showed intermediary stability which persisted upon its conversion to either chloride or sulphate. Likewise, conversion of the sulphate into the chloride by means of an ion exchange column, did not alter its sensitivity. Apparently, the stability of protamine derivatives is not influenced by the specific anion bound to them but is rather acquired in the course of the manufacturing procedures involved in their preparation.

Blood Coagulation↗