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A Taranta

Publications and source records attributed to A Taranta.

72 records · Page 4Linked to original sources
PubMed1969

Dissociation of hemolytic and lymphocyte-transforming activities of streptolysin S preparations.

The ability of streptolysin S preparations to induce high percentages of transformation in human peripheral blood lymphocytes was confirmed in a series of apparently healthy donors. Transforming activity was not demonstrated in the two media used for streptolysin S production, nor in control preparations in which a strain each of Streptococcus viridans, Staphylococcus aureus (nonhemolytic), and Diplococcus pneumoniae was substituted for the beta hemolytic streptococcal strain used for streptolysin S production. The relation of the hemolytic activity to the lymphocyte transforming activity of streptolysin S preparations was studied by means of inactivation and fractionation experiments. Heating produced a loss in both activities, but more in the hemolytic than in the transforming activity. The transformation obtained with a heated preparation had a high degree of correlation with that obtained with the unheated preparation in a series of normal subjects and patients with various rheumatic diseases, whose lymphocytes were often less responsive to stimulation with streptolysin S preparations (both heated and unheated) than the lymphocytes of the normal subjects studied. Treatment of streptolysin S preparations with chymotrypsin, vegetable lecithin, or trypan blue (the latter in minute amounts) resulted in preparations with no detectable hemolytic activity but with undiminished lymphocyte transforming activity. Chromatographic fractionations on DEAE-Sephadex columns yielded fractions endowed with transforming but not with hemolytic activity, and other fractions endowed with hemolytic but not with transforming activity. The recovery of the hemolytic activity was not complete and quantitation of the recovery of the transforming activity was not attempted. These experiments indicate that the hemolytic and transforming activities of streptolysin S preparations are independent of each other, and specifically that they are the attributes of two different streptococcal products, one of which is streptolysin S. The other is a nonhemolytic streptococcal product present in streptolysin S preparations but previously unrecognized. Some implications of these findings are discussed.

Blood Donors↗
PubMedDate not supplied

A novel calcium sensor stimulating inositol phosphate formation and [Ca2+]i signaling expressed by GCT23 osteoclast-like cells.

Osteoclast activity is inhibited by elevated [Ca2+]o; however, the underlying molecular mechanism is unknown. We used the human osteoclast-like cells GCT23 to elucidate their cation-sensing properties. Cells responded to elevated [Ca2+]o with rapid concentration-dependent [Ca2+]i transients (EC50 = 7.8 mm, time to peak 44 +/- 4 sec) that were due to release from intracellular stores, followed by Ca2+ influx across the plasma membrane. Ca2+ store depletion by thapsigargin, endothelin-1, or bradykinin activated calcium entry pathways. Cells responded similarly to Ni2+ and Cd2+ with albeit slower kinetics (EC50 <10 microm and <100 microm, times to peak 140 +/- 25 sec and 150 +/- 24 sec, respectively). The three cations stimulated inositol phosphate production (two-fold, p <.02) similar to bradykinin (2.5-fold, p <. 002), which activates a phospholipase C (PLC)-coupled receptor in GCT23 cells. The cells did not respond to 0.1-1 mM Gd3+ or neomycin B, indicating that the parathyroid calcium receptor (PCaR) is not functionally expressed. In confirmation, PCaR could not be detected by reverse transcriptase polymerase chain reaction in GCT23 cells and in mouse osteoclasts, and the calcimimetic compound NPS R-568 failed to produce the left shift of the concentration-response curve characteristic for PCaR. Our data demonstrate for the first time that cation sensing by osteoclast-like GCT23 cells is mediated by a PLC-coupled receptor that is not identical to PCaR.

Animals↗