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Biomedical subjects

A M Mastro

Publications and source records attributed to A M Mastro.

At least 91 records · Page 5Linked to original sources
PubMed1983

A comparison of the mitogenic effects of a phorbol ester on lymphocytes from bovine spleen, lymph node and peripheral blood.

A comparison of the mitogenic effects of a phorbol ester on lymphocytes from bovine spleen, lymph node and peripheral blood. Bovine lymphocytes from three tissues, lymph node, spleen and peripheral blood were compared for their mitogenic responses to 12-O-tetraecanoylphorbol-13-acetate (TPA), a phorbol ester tumor promoter. TPA alone was found to be either not mitogenic or caused only a weak response when compared with the mitogenic lectin phytohemagglutinin (PHA). Of the three lymphocyte preparations, blood cells showed the greatest proliferative response to TPA. However, all three, lymph node, blood and spleen cells, showed a co-mitogenic response to TPA. That is, TPA synergistically enhanced DNA synthesis in cells stimulated with a suboptimal concentration of PHA.

Animals↗
PubMed1983

The effect of removal of adherent cells in lectin and allogeneic cell stimulation of bovine lymphocytes.

Macrophages have been shown to play an important role in lymphocyte activation in many species but not unequivocally for bovine. In this study we have shown that when sufficient care is taken to remove macrophages by adherence or by anti-macrophage serum and complement, bovine lymphocytes respond poorly to lectins or to allogenic cells in mixed lymphocyte culture. Addition of macrophages to approximately the same level as found in the unseparated cells restores the proliferative responses. The degree of response shown by the macrophage depleted cultures depends on the lectin concentration. Stimulation with lower doses of lectin is more sensitive to macrophage concentration. The mixed lymphocyte response and the response to Concanavalin A (ConA) are more sensitive to macrophages than is the response to phytohemagglutinin (PHA).

Animals↗
PubMed1983

System for enumerating and separating bovine lymphocytes, using coordinated En and Ea markers: evaluation of lymph node lymphocytes.

A procedure was developed for enumeration and separation of bovine lymph node T-lymphocyte subpopulations. An evaluation was made of T-lymphocyte rosetting with sheep erythrocytes treated with aminoethylisothiouronium bromide and neuraminidase (Ea and En) in RPMI and L-15 media. The effect of holding the lymphocytes in culture over a period of 7 days on the En and Ea markers was established. The optimal period of incubation at 0 C for isolation of the rosetting populations with respect to initial rosette formation, enrichment of the rosetting population in the recovered cells, viability after incubation, and recovery of the cells after the separation was determined. An estimate of the overlap of the Ea and En populations also was made from the separation data. We found that approximately 32% of the lymph node lymphocytes marked with En and Ea rosettes, 11% with only En, and 27% with only Ea.

Animals↗
PubMed1982

The effects of retinoic acid and a tumor promoter, 12-O-tetradecanoylphorbol-13-acetate, on lymphocyte proliferation.

The tumor promotor, 12-O-tetradecanoylphorbol-13-acetate (TPA) inhibits DNA synthesis in allogenic, mixed cultures of bovine lymphocytes. Retinoic acid, an antagonist of TPA in in vivo skin promotion, was tested for its ability to counteract the effect of TPA on lymphocyte proliferation. Retinoic acid or related compounds, retinol or retinol acetate, did not reverse or prevent the inhibitory effect of TPA. Instead retinoic acid also inhibited DNA synthesis in mixed lymphocyte cultures. On the average, about 8 microM retinoic acid inhibited the mixed lymphocyte response by 50%. The mitogenic response of lymphocytes to phytohemagglutinin (PHA) was also inhibited by retinoic acid. The degree of inhibition depended both on the concentration of PHA and of retinoic acid. Therefore, in regard to bovine lymphocytes, retinoic acid depresses DNA synthesis in both allogenic and lectin stimulated responses. Such suppression should be taken into account in the use of retinoic acid in chemotherapy.

Animals↗
PubMed1982

Effect of macrophages on phorbol ester-stimulated comitogenesis in bovine lymphocytes.

12-O-Tetradecanoylphorbol-13-acetate (TPA) added together with mitogenic lectins to bovine lymph node lymphocytes causes a synergistic increase in DNA synthesis. This comitogen effect is due to an increase in cell proliferation. To determine the role of macrophages in comitogenesis, lymphocyte preparations were depleted of macrophages by sequential adherence to glass, plastic, and nylon wool. Phagocytic cells were removed by incubation with carbonyl iron and a magnet. After macrophage depletion, the lymphocyte response to lectins decreased, indicating the accessory function of macrophages in mitogenesis. The addition of TPA or macrophages to the depleted cultures restored its response to that of the unfractionated cells. TPA was still comitogenic with lectin in lymphocyte preparations from which all residual macrophages were removed by antimacrophage serum and complement. Therefore, the comitogenic effect of TPA is independent of macrophages in these cultures.

Animals↗
PubMed1980

Suppression of lectin-stimulated DNA synthesis in bovine lymphocytes by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate.

12-O-Tetradecanoylphorbol-13-acetate (TPA) modulates DNA synthesis in bovine lymph node lymphocytes in culture. Whether TPA enhances or depresses DNA synthesis depends on when the TPA is added with regard to time of mitogenic stimulation. We have previously reported that TPA acts as a comitogen when added with the lectins phytohemagglutinin or concanavalin A, but it inhibits DNA synthesis in these cells in mixed lymphocyte culture. We report in this study that pretreatment of bovine lymph node lymphocytes with TPA depressed their proliferative response to phytohemagglutinin, concanavalin A, or pokeweek mitogen. The extent of inhibition varied somewhat with each animal and particular lectin. The effect was reversible. Inhibition was not due to a shift in the kinetics of the response or to a change in the dose response. TPA may act directly by changing the lymphocyte surface properties and/or indirectly through a cell population or product to suppress the proliferative response. One cell product, plasminogen activator, was identified in culture medium, although we have no evidence at this time that it is responsible for the inhibitory effect of TPA.

Animals↗
PubMed1979

Interaction of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate with cells in mixed-lymphocyte culture.

12-O-Tetradecanoylphorbol-13-acetate (TPA) inhibits DNA synthesis in bovine lymph node lymphocytes in mixed-lymphocyte cultures. Using a radioautographic study, we determined that TPA also blocked morphological changes in these cultures. Pretreatment of cultures of isologous lymphocytes with 10(-7) M TPA for three days prior to mixing was sufficient to block their subsequent response in mixed culture. Thus, TPA did not need to be present during the initial cell-to-cell interactions of the mixed lymphocyte response. The inhibition was not due to the death of the responding cell population because the effect was reversible. In one-way mixed-lymphocyte cultures, TPA pretreatment of either responding or stimulating cells could block DNA synthesis. The responding cells were more sensitive to TPA than were the stimulating cells. The inhibitory effect of the stimulators increased with an increase in the stimulating-to-responding cell ratio. In one-way cultures, it was also seen that lymphocytes from different animals varied both in their sensitivity to TPA and in their response to TPA-treated cells from other animals. The data taken together are consistent with the idea that TPA acts by changing cell surface recognition structures and/or indirectly, through activation of a subpopulation of cells to block the proliferative response. TPA may prove to be a valuable tool in studying cell-cell interactions and lymphocyte differentiation in vitro.

Animals↗
PubMed1978

Inhibition of the mixed lymphocyte proliferative response by phorbol esters.

The phorbol diester, 12-O-tetradecanoyl-phorbol-13-acetate, a potent cocarcinogen in mice, blocks the induction of DNA synthesis in lymphocytes undergoing the mixed lymphocyte response. At 10(-7) M diester, the induced DNA synthesis is inhibited almost completely (99%). This action of the diester affects some early step in the response which is necessary for the triggering of cell replication; on-going DNA replication is not significantly affected. Phorbol 12,13-diacetate, a less potent analogue in tumor promotion in vivo, is also a less potent inhibitor of the mixed lymphocyte response (75% inhibition at 10(-6) M). Phorbol, the parent alcohol, is not effective in either system. The use of phorbol diesters in the molecular dissection of mixed lymphocyte responses is discussed.

Animals↗
PubMed1976

Endgoenous protein kinase in outer plasma membrane of cultured 3T3 cells. Nature of the membrane-bound substrate and effect of cell density, serum addition, and oncogenic transformation.

Endogenous protein kinase activity was detected in the outer plasma membrane of 373 and SV40 transformed 3T3 cells. When intact cells were incubated with [gamma-32P]ATP, there was a transfer of [32P]phosphate into an acid-insoluble product. The reaction was: (a) linear as a function of time (up to 30 min), (b) proportional to the number of cells present and (c) dependent on temperature and Mg2+ concentration. The acid-insoluble product was susceptible to pronase but not RNase or DNase. More specifically, phosphomonoester bonds to serine and threonine were identified. There was less than 3% hydrolysis of the [gamma-32P]ATP during the reaction; moreover, free [32P]phosphate failed to substitute for the ATP. The reaction product was located on the cell surface, as evidenced by the fact that it could be removed by mild trypsin treatment of intact 3T3 cells. Further evidence for the surface location of the kinase was shown by its activity in phosphorlating exogenous substrate, histone, and phosvitin. The level of phosphorylation increased by 2- to 4-fold prior to the start of S phase when quiescent 3T3 cells were stimulated to reinitiate growth by the addition of serum. The SV40 3T3 cells had from 5- to 10-fold more activity per cell than the quiescent 3T3 cells. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and radioautography show at least 25 phosphorylated proteins; the surface label pattern of 3T3 cells differs from that of SV40-transformed 3T3 cells.

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