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J Sodek

Publications and source records attributed to J Sodek.

168 records · Page 10Linked to original sources
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The distribution of soluble, mineral-bound, and matrix-bound proteins in osteoporotic and normal bones.

Very little is known about the composition of noncollagenous protein (NCP) in osteoporotic bone. We have obtained osteoporotic (OP) cancellous bone samples from 2-4 cm below the surface of human femoral heads and compared the protein profiles to age-matched (old controls, OC), as well as young autopsy controls (YC). The proteins were analyzed using a serial extraction method which liberates proteins from distinct pools; first, proteins were extracted in 4.0 M GuHCl (G1), followed by the extraction of mineral-bound protein with 0.5 M EDTA (E), and finally the protein previously masked by the mineral was released by a second 4.0 M GuHCl extraction (G2). The tissue residue was digested with bacterial collagenase liberating proteins bound to the collagenous matrix. Uniform bone preparations of finely ground bone powder were used for our study. The protein content of the four groups was determined together with the protein distribution using amino acid analysis and gel-electrophoresis. Our data indicate that the noncollagenous protein content is considerably reduced in osteoporotic bone when compared with age-matched or young controls, whereas the collagen content is unaffected. When bone proteins were investigated using gel-electrophoresis we found a similar distribution of proteins in the G1 and E fractions of all three groups, but the osteoporotic bone samples, using densitometric analysis of the gels, showed quantitative differences in a number of the proteins. The greatest differences were observed in the G2 extract, where the NCP of osteoporotic bone was limited to a few low-molecular-weight bands when compared with the OCs or YCs.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
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↗
PubMedDate not supplied

Synthesis of TGF-beta 1 by vascular endothelial cells is correlated with cell spreading.

Cultured vascular endothelial cells (ECs) secrete transforming growth factor beta (TGF-beta) which stimulates intimal smooth muscle cells to synthesize increased amounts of lipoprotein-binding proteoglycans. We report here that the amount of TGF-beta 1 synthesized by ECs is correlated with EC density and cell spreading. ECs cultured at low density synthesized and secreted 2- to 3-fold more TGF-beta, measured by the Mink lung cell assay, than intermediate and high density cultures, and this increase in secreted protein was matched by a corresponding increase in mRNA for TGF-beta 1 measured by Northern hybridization using a [32P]-labeled cDNA probe for TGF-beta 1. TGF-beta 1 mRNA was detected in individual cells by in situ hybridization with the cDNA probe labeled with [35S] and with a [35S]-labeled 30-mer antisense oligonucleotide. In situ mRNA levels did not relate to cell density per se but to cell area. The larger the area of substratum covered, the more mRNA per cell, irrespective of cell density. For cell areas in the range 500-1,200 microns 2, a doubling of cell area resulted in an approximately 3-fold increase in mRNA. Cells cultured at low density had a larger mean cell area than cells cultured at higher densities, and this increased area was sufficient to account for the increased TGF-beta 1 mRNA levels found for the low density cultures by Northern hybridization. Despite variations in cell area, cell volumes did not change significantly with cell density.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗