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Biomedical subjects

M A Meloni

Publications and source records attributed to M A Meloni.

32 records · Page 2Linked to original sources
PubMed1996

Movements and interactions of leukocytes in microgravity.

The mitogenic activation of human lymphocytes resuspended in vitro is dramatically reduced in microgravity. As cell-cell contacts are one of the elements essential for activation, the behaviour of human leukocytes (mainly lymphocytes and monocytes as accessory cells) in the presence of the mitogen concanavalin A was studied in the centrifuge microscope NIZEMI at 0 x g. Aggregates (formed by intercellular bindings of membrane glycoproteins via the tetravalent alpha-glucoside ligand concanavalin A) were found at 0 x g as well as at 1 x g already 12 h after the addition of the mitogen. In general, the aggregates observed at 0 x g after an incubation time of 46 and 78 h were smaller than the corresponding aggregates in the ground control. The findings are of primary importance since they confirm the indirect evidence we had from earlier Spacelab experiments and demonstrate that cell-cell contacts are occurring also in microgravity. In addition, single cells in 0 x g show a significant higher locomotion velocity than the cells at 1 x g. The fact that the locomotion capability is not decreased during the 78-h incubation with concanavalin A provides further evidence that the cells are not proceeding through the cell cycle.

Biotechnology↗
PubMed1996

Activation signals of T lymphocytes in microgravity.

Human peripheral blood lymphocytes and monocytes were activated with concanavalin A with or without exogenous recombinant interleukin 1 (IL-1) alone or IL-1 + interleukin 2 (IL-2) under microgravity conditions to test the hypothesis that lack of production of IL-1 by monocytes is the cause of the near total loss of activation observed earlier on several Spacelab flights. The 60 min failure of the on-board 1 x g reference centrifuge at the time of the addition of the activator renders the in-flight data at 1 x g unreliable. However, the data from a previous experiment on SLS-1 show that there is no difference between the results from the in-flight 1 x g centrifuge and 1 x g on ground. The comparison between the data of the cultures at 0 x g in space and of the synchronous control at 1 x g on ground show that exogenous IL-1 and IL-2 do not prevent the loss of activity (measured as the mitotic index) at 0 x g; production of interferon-gamma, however, is partially restored. In contrast to a previous experiment in space, the production of IL-1 is not inhibited.

Biotechnology↗
PubMed1991

[Cell adhesion in neoplastic cells and syngeneic fibroblasts of the rat: effect of progesterone and estradiol].

Recent advances in the study on the importance of steroid receptors in the treatment of hormone-responsive tumors established the relationship between plasma membrane and the first steps of the cellular response to the endocrine stimulus. We have therefore found interesting to study the influence of estrogen and progesterone on cell adhesion of neoplastic (SGS/3A) and normal syngeneic (FG) cells. We demonstrated the presence of a nuclear estrogenic and a cytosolic progestin receptor in the SGS/3A cells. In syngeneic fibroblasts both receptors are absent. Cell adhesion kinetics obtained determining the percent of single labeled cells with 3H-leucine adhering to confluent monolayer (cell-cell adhesion) showed that the physiological concentrations of estradiol and progesterone induce an inhibition of cell-substratum adhesion (25-30%) in neoplastic cells, but do not influence cell-cell adhesion. In FG cells the two hormones cause an increase of cell-substratum adhesion (35-40%), but do not influence cell-cell adhesion. Results suggest that FG cells, although lacking cytoplasmic or nuclear receptors for estradiol and progesterone, probably have other steroid-receptive molecules involved in adhesive processes on their cell-surface.

Animals↗
PubMed1990

[Effect of dimethyladipimidate and dimethylsuberimidate on cell-cell adhesion in rat fibroblasts].

In a study performed to identify the molecular mechanisms which regulate cell to cell adhesion and contact inhibition in neoplastic and syngeneic normal cells of the rat we have observed that the adhesive capacity depends on the reagents used, either EDTA or trypsin, to release the cells from monolayer. Taking profit of this last property and of the possibility of blocking free -NH2 groups on membrane proteins with specific cross-linking reagents "in vitro", we have studied in this work the behaviour of the proteins of the cell coat involved in cell to cell adhesion of rat fibroblasts FG/2. The cross-linking reagents used were dimethyladipimidate (DMA) and dimethylsuberimidate (DMS). The cells were exposed to the reagents at 0 degrees C for 30'. Cell to cell adhesion was measured by determining the percentage of single cells labeled with 3H-leucine, adhering to a confluent monolayer at different incubation times. The inhibitory effect on cell to cell adhesion brought about by cross-linking reagents indicates that a) EDTA-released cells are more sensitive to both imides than those released with trypsin, b) DMA is more effective on trypsin-released cells and c) DMS is more effective on EDTA-released cells. Therefore, we conclude that the inhibition of adhesion by reaction with the two cross-linking reagents is more likely due to a stiffening of the molecules of the cell coat involved in the adhesion, rather than to the modification of -NH2 residues which should specifically participate to adhesive process.

Animals↗
PubMed1989

[Cell adhesion in rat fibroblasts: effect of tumor promoters].

In a study performed on transformed (SGS/3A) and normal syngeneic rat cells (FG/2) to identify the molecular mechanisms which regulate cell adhesion and contact inhibition in cell transformation, we investigated the effects of tumor promoters on cell to cell adhesion of rat fibroblasts. As tumor promoters we used 12-tetradecanoyl-phorbole-13-acetate (TPA) and the melittin, a polypeptide from bee venom, both substances capable of stimulating the neoplastic transformation. The intercellular adhesion assay consists in determining the percent of single cells labeled with 3H-L-leucine adhering to a confluent monolayer of unlabeled cells at different incubation times. The increase of cell-cell adhesion caused by TPA and melittin confirms what we have constantly observed in other experiments, i.e. that neoplastic cells SGS/3A always have a higher intercellular adhesion capacity than corresponding normal syngenic cells FG/2. Since one of the effects of the tumor promoters is also induction of a reversible alteration of the cytoskeleton, it is likely that their action on intercellular adhesion is regulated by a mechanism analogous to that proposed for explaining the increased intercellular adhesion observed after treatment with antimicrotubular compounds.

Animals↗
PubMed1985

Characterization of tumor cell lines from a spontaneous rat sarcoma expressing an endogenous retrovirus.

We have characterized various biologic, immunologic and growth properties of several cell lines established from a spontaneous rat sarcoma that was discovered more than 60 yr ago. The tumors consisted of mixed cell types with no detectable host cellular immune response. Cultures derived from single-cell clones of the parental cell line were non-invasive but highly tumorigenic even in adult rats. The cultured cells spontaneously released replication-competent endogenous rat type C virus which did not carry a transforming gene in its genome. Since normal cells from the same rat strain did not produce a retrovirus, it is possible that production of the endogenous retrovirus may have triggered specific cellular changes necessary for the oncogene expression and development of this tumor.

Animals↗
PubMed1983

[Electron microscopic features of neoplastic cells (SGS-3A) cultivated in agar].

The agar suspension culture method was applied to enrich for neoplastic cells in cultures of a cellular strain (SGS-3) derived from Sarcoma Galliera. This method suppresses the growth of normal cells without impairing colony formation by neoplastic cells. The analysis by electron microscopy of colonies of SGS-3A cells cultured in agar medium shows that cytoplasmatic bridges are present in the regions of cell-cell contact.

Agar↗
PubMed1981

[Effect of iodoacetamide on cell-cell adhesion of fibroblasts in the rat].

The -SH groups of rat fibroblasts of cell-coat were blocked with Iodacetamide. This substance interferes negatively on the homologous intercellular adhesion of the tested cells, with a proportional effect related to the concentration used. The meaning of -SH groups on the cell-cell interactions is discussed.

Animals↗
PubMed1980

[Distribution of the O-groups of E. coli strains isolated from urinary infections in Sardinia].

We refer to the results of the serological identification of E.Coli strains from urinary tract infections and from faeces of healthy subjects in Sardinia. The serological groups more frequently found in urinary tract infections (06, 018, 075) of our geographical region one similar to those of other authors. The fact that some of the 0-groups (02, 018, 075, 04) which occurred more frequently in urinary tract infections are also the most prevalent among faecal strains, supports the theory of prevalence; the presence of 0-groups (06, 01, 011, 09) in urinary infections alone does not leave out a specific disposition towards growth in the urinary tract of the same strains.

Escherichia coli↗