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Biomedical subjects

R Ber

Publications and source records attributed to R Ber.

58 records · Page 4Linked to original sources
PubMed1978

Proof of in vivo fusion of murine tumor cells with host cells by universal fusers.

Two mouse cell lines (A9HT CI.3C and 501-1), each carrying both a recessive and a dominant mutation (and therefore designated "universal fusers"), were utilized for selection of in vivo hybrids from tumors produced intraperitoneally and subcutaneously in appropriated hosts. The double selective medium eliminated both parental (tumor and host) cells but allowed the survival and proliferation of the fused product. This proved that hybridization between tumor and host cells occurred in vivo.

Animals↗
PubMed1969

Cell cycle events in the hydrocortisone regulation of alkaline phosphatase in HeLa S3 cells.

The increase in alkaline phosphatase in asynchronous cultures of HeLa S(3) cells grown in medium supplemented with hydrocortisone is characterized by a lag period of 10-12 hr. Present studies utilizing synchronous cell populations indicate: (a) a minimum of 8-10 hr of incubation with hydrocortisone is necessary for maximum induction of alkaline phosphatase; (b) the increase in enzyme activity produced by hydrocortisone is initiated exclusively in the synthetic phase of the cell cycle; (c) alkaline phosphatase activity does not vary appreciably over a normal control cell cycle. Radioactive hydrocortisone is rapidly distributed into HeLa cells irrespective of their position in the cell cycle, indicating that inductive effects are not governed by selective permeability during the cell cycle. Hydrocortisone-1,2-[(3)H] diffuses back from the cell into the medium when the cells are incubated in fresh medium containing no hydrocortisone, and the alkaline phosphatase induction, under these conditions, is completely reversible.

Alkaline Phosphatase↗
PubMedDate not supplied

Effects of transforming growth factor-beta on normal clonal bone cell populations.

Although transforming growth factor-beta (TGF-beta) has been implicated in the local regulation of bone growth and remodelling, its specific effects on different subpopulations of bone cells have not been elucidated. Cells derived from bone are known to be heterogeneous and include both cells of different lineages and osteoblastic populations with different levels of expression of osteoblast-associated properties. Consequently, we have isolated clonal populations of bone cells to examine more precisely the effects of TGF-beta on individual subpopulations. Several clonal populations were isolated by limiting dilution from cells derived from 21-day-old fetal rat calvaria. Two of these clones, RCA 11 and RCB 2, were used here. While the two clones responded similarly to parathyroid hormone (PTH) and isoproterenol (ISP) with increases in intracellular cAMP, prostaglandin E2 (PGE2) elicited a 10-fold higher response in RCB 2 cells compared with RCA 11. RCB 2 cells expressed a 10-fold higher alkaline phosphatase activity compared with RCA 11. Both clones synthesized a variety of bone matrix associated proteins, but only RCA 11 synthesized SPP-1 (osteopontin) constitutively. TGF-beta stimulated growth of RCB 2 cells after 24 and 48 h of treatment, but had no effect on growth of RCA 11. TGF-beta supported anchorage-independent growth of RCB 2 cells, but not that of RCA 11. A 24-h exposure to TGF-beta decreased cAMP responsiveness to PTH and ISP slightly in both clones, but had no effect on PGE2 responses. Significant reductions in alkaline phosphatase activity were seen in both clones after 24- and 48-h treatments with TGF-beta.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗