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Biomedical subjects

F Sinigaglia

Publications and source records attributed to F Sinigaglia.

At least 145 records · Page 8Linked to original sources
PubMed1985

Human T lymphocyte clones specific for malaria (Plasmodium falciparum) antigens.

Peripheral blood mononuclear cells (PBM) from a patient who had lived in a malarial-endemic area were cultured in the presence of malarial antigens (a lysate of Plasmodium-infected erythrocytes). Responding cells were grown in IL-2-containing medium and then cloned, and subsequently subcloned, in the presence of phytohemagglutinin and allogeneic irradiated PBM. Ten clones were specific for malarial antigens. They proliferated in response to P. falciparum extract, but not to a lysate of uninfected erythrocytes. The response was HLA-restricted. All the clones tested responded to lysates of cells infected with parasites of either African or Asian origin. Six clones had the T4+/T8- phenotype and four the T4-/T8+ phenotype. Two of the T4+ clones recognised a parasite antigen of apparent mol. wt. approximately 50 000. All of the clones tested produced gamma-interferon following antigen stimulation.

Animals↗
PubMed1985

Mechanisms of thrombin-induced modifications of human platelet cytoskeleton.

Thrombin treated with phenylmethanesulphonyl fluoride, like active enzyme, promotes modifications to human platelet cytoskeleton. The removal of active thrombin by hirudin partially reverses this process. Chymotrypsin-treated platelets do not modify their cytoskeleton after thrombin stimulus, but are still able to increase their adhesiveness to collagen. It is concluded that thrombin influences the cytoskeleton and adhesion by non-enzymic mechanisms which may be mediated by different modulators.

Blood Platelets↗
PubMed1985

A sensitive and quantitative microassay for the detection of mycoplasma contamination: inhibition of IL-2 dependent cell line proliferation.

A simple, rapid and sensitive microassay for mycoplasma detection in cell culture is reported. The assay is based on the fact that culture supernatants from contaminated cells inhibit [3H]thymidine incorporation by an IL-2 dependent mouse cytotoxic T cell line (CTLL). The mechanism of inhibition is related to the production by several mycoplasma strains of a pyrimidine-specific nucleoside phosphorylase which can degrade the radiolabelled thymidine used for the measurement of DNA synthesis. These strains were the commonest contaminants in cultures of 24 cell lines from 5 different sources. To establish the sensitivity of the test to detect mycoplasmas we have also used the inhibition assay to monitor the clearance of mycoplasma from 2 contaminated cell lines.

Cell Division↗
PubMed1985

Inhibition of [3H]thymidine incorporation by Mycoplasma arginini-infected cells due to enzymatic cleavage of the nucleoside.

Culture supernatants contaminated by Mycoplasma arginini inhibit the incorporation of [3H]thymidine ([3H]dThd) by cytotoxic T lymphocyte cell lines. This study presents evidence that the inhibition of uptake of the nucleoside is due to the rapid cleavage of the exogenous [3H]dThd into thymine. Uridine and cytidine as well as dThd are degraded by the mycoplasma-contaminated supernatants, while no cleavage was observed with uninfected supernatants. Cells contaminated by mycoplasma apparently release a pyrimidine-specific nucleosidase, possibly a dThd phosphorylase, which is responsible for the inhibition.

Cell Line↗
PubMed1985

Rearrangement and expression of the antigen receptor alpha, beta and gamma genes in suppressor antigen-specific T cell lines.

The rearrangement and transcription of the antigen receptor alpha, beta and gamma genes were investigated in murine antigen-specific suppressor T cell lines, to establish whether the suppressor T cell subset expresses the same antigen receptor transcripts previously found in helper and cytotoxic T lymphocytes. The genomic organization of the alpha, beta and gamma chain loci was investigated using probes representative of the entire gene or fragments from variable, joining and constant regions. The present results show that in functional suppressor T cells the three antigen receptor genes are all rearranged. The beta gene is expressed in all the tested cell lines, while the expression of the alpha and gamma genes is variable. In one cell line (LH8) alpha and gamma genes are not efficiently transcribed; in the other cell line (LA41) the gamma mRNA is found in amounts similar to beta mRNA, whereas the alpha gene is expressed at low levels. These data suggest that in suppressor T cells no direct correlation exists between the expression of alpha, beta and gamma antigen receptor genes and the effector function.

Animals↗
PubMed1985

Thrombin increases the adhesion of washed human platelets to collagen.

Thrombin stimulates the adhesion of washed human platelets to fibrillar collagen. This phenomenon occurs also when platelets, before thrombin stimulation, are resuspended in the presence of prostaglandin E1 to minimize the release reaction. Enzymatic activity of thrombin is not necessary for the enhancement of platelet adhesiveness, since phenylmethylsulphonylfluoride inhibited thrombin is effective in this respect. Detachment of thrombin from thrombin treated platelets by the use of hirudin restores normal platelet adhesiveness to collagen.

Chromatography, Affinity↗
PubMed1985

Isolation and characterization of Ni-specific T cell clones from patients with Ni-contact dermatitis.

Ni-specific T lymphocyte clones (TLC) were isolated from two patients with Ni-contact dermatitis. All of the isolated TLC required both histocompatible antigen-presenting cells (APC) and Ni for induction of proliferation. By using a panel of HLA-typed Epstein Barr virus-transformed B cells (EBV-B cells) as APC and monoclonal anti-DR antibody, the clones were shown to recognize Ni in the context of HLA class II determinants. All of the clones that were isolated are OKT3+, OKT4+, OKT8-. In the presence of Ni, they polyclonally activate autologous B cells, and in the presence of Ni and autologous EBV-B cells, they produce IL 2 and very high levels of IFN-gamma. The Ni-specific clones should be helpful in the identification of the Ni-induced antigen which is recognized by T cells.

Antigen-Presenting Cells↗
PubMed1984

Acetylcholine receptor-specific suppressive T-cell factor from a retrovirally transformed T-cell line.

In both experimental and human myasthenia gravis an impairment in the immune regulation leads to an increased synthesis of antibodies against the nicotinic acetylcholine receptor (AcChoR). The present work reports the establishment of an AcChoR-specific suppressive T-cell line obtained by viral transformation of AcChoR-enriched murine T lymphocytes. Enriched T cells from Torpedo AcChoR-primed mice, prestimulated in vitro with antigen, were infected with radiation leukemia viruses and injected intravenously in congeneic recipient mice. Six months later lymphomas were observed in 20% of the injected mice and two of them, of donor origin, were established as permanent continuous cell lines in vitro. One of these lines, named LA41, expresses Thy-1.2, Lyt-2, and I-Jb surface markers. Culture supernatants of LA41 cells suppress the antigen-specific in vitro proliferation of Torpedo AcChoR-primed lymphocytes. This suppression is antigen-specific since the response induced by fetal calf AcChoR and by other antigens is not affected by addition of LA41 culture supernatant in the proliferative assay. LA41 culture supernatant injected in vivo at the time of antigen-priming suppresses also significantly the production of anti-AcChoR antibodies but not the synthesis of antibodies against other antigens--i.e., fetal calf AcChoR or alpha-bungarotoxin. These data show that LA41 cells constitutively produce Torpedo AcChoR-specific suppressor factor.

Animals↗
PubMed1984

The role of plasma fibronectin in platelet adhesion to collagen.

Human washed platelets were eluted from columns of Sepharose 4B linked to different preparations of collagen in order to evaluate cell adhesion. Collagen preparations characterized by low and high affinity toward platelets were identified. In our experiments, fibronectin purified from human plasma modified platelet adhesiveness, though not dramatically. When washed platelets, resuspended in a buffer containing fibronectin, were filtered on a low-affinity collagen-Sepharose, a significant increase in their adhesion occurred. A similar modification could be observed when platelets were allowed to adhere to the same collagen-Sepharose preconditioned with fibronectin. The effect of fibronectin was otherwise negligible when the high-affinity collagen was used for the experiments.

Chromatography, Affinity↗
PubMed1983

A non-toxic preparation of muscle acetylcholine receptor for lymphocyte proliferation studies.

An in vitro assay which measures the proliferation response of primed murine lymph node cells of fetal calf acetylcholine receptor (AchR) is described. The character of the AChR preparation is critical. The use of reagents such as proteases, metabolic inhibitors and detergents may markedly reduce the mitotic activity of cultured lymphocytes. Among protease inhibitors phenyl methyl sulfonyl fluoride (PMFS) had no effect on phytohemagglutinin (PHA) induced stimulation while iodoacetamide (IAA) at a concentration of 0.01% significantly decreased PHA activation of lymphocytes. EDTA was inhibitory at a concentration of 2 x 10(-4) M. The effect of different non-ionic detergents in the PHA responsiveness was also evaluated. Tween 20 and Tween 80 were the least toxic. These findings for AChR may be relevant to preparation of other integral membrane proteins for assay of cellular immunity.

Animals↗
PubMed1982

Anomalous erythrocytes produced by rabbits with liver damage.

Rabbit "stress macroreticulocytes" complete their membrane sialic acid content after a short "homing" in the liver. Since also normal rabbit reticulocytes are characterized by a low membrane sialic acid, the role of the liver in the maturation of these cells was investigated. For this purpose red cell modifications consequent to a severe liver steatosis, induced in rabbits by a diet lacking choline, were investigated. Animals with liver damage showed severe anemia and red cell membranes were demonstrated to have a low sialic acid content. Moreover rabbits with severe fatty liver, unlike normal animals, were not able to restore the viability of desialylated normal young erythrocytes. On the basis of these and others evidences we suggest that rabbit liver plays an important role in physiological maturation of reticulocytes.

Animals↗
PubMed1981

Enzyme studies with human and hen autopsy tissue suggest omethoate does not cause delayed neuropathy in man.

Levels of acetylcholinesterase and neurotoxic esterase were measured in brain autopsy material. In tissue from a fatal human poisoning and from hens given 4-8 x unprotected LD50 AChE was highly inhibited and neurotoxic esterase uninhibited. The findings correlate with the inhibitory power of omethoate against these enzymes in vitro. It is concluded that omethoate has negligible potential to cause delayed neuropathy and a published report of human neuropathy due to omethoate is criticised.

Acetylcholinesterase↗
PubMed1981

Ageing of rabbit red cells in vitro: membrane modifications and their possible role in red cell survival in vivo.

In vitro incubation induces, in rabbit red cell membranes, significant modifications consisting mainly in a decrease of sialic acid and galactose. In vivo the life span of incubated erythrocytes seems to be correlated to the degree of surface alterations and ATP depletion: larger surface modifications and energy charge reduction induce shorter survival time. It can therefore be postulated that incubation of red cell in vitro can cause an ageing process similar to that occurring physiologically in vivo.

Adenosine Triphosphate↗
PubMed1981

Reversible and irreversible structural modifications of erythrocyte membrane.

Membrane glycoprotein structure regulates the fate in the circulation of mammalian erythrocytes: the mechanism of this phenomenon was observed in rabbit and human red cells by in vivo and in vitro experiments. Glycoprotein remodeling can occur as a reversible desialylation process, produced by different events, or as an irreversible process consisting in a loss of sialoglycopeptides. The effect of these two phenomena on the viability of the red cell in the circulation was the subject of our investigation.

Amino Acids↗
PubMed1978

Behaviour of young and old desialylated rabbit erythrocytes in vivo.

Young and old rabbit erythrocytes, separated by density gradient centrifugation, were desialylated by neuraminidase treatment and reinjected into the animal after 51Cr labelling. Both red cell populations are quickly removed from the circulation and trapped by the liver; then a large percentage of the young cells reappear in the peripheral blood and behaves like untreated erythrocytes; old cells, on the contrary, do not return to the blood stream and are probably lysed in the liver. These results suggest that a sialic acid repair can occur on the membrane of young erythrocytes and confirm that the loss of this molecule is not by itself sufficient to determine the death of the cell.

Animals↗
PubMed1977

Self-digestion of human erythrocyte membranes. Role of adenosine triphosphate and glutathione.

Intact human erythrocytes incubated at 37 degrees C, pH7.4, release a sialoglycopeptide similar in its chemical composition, immunological and aggregation properties to the glycopeptide released by isolated 'ghost' membranes. The presence of ATP or reduced glutathione at physiological concentrations in the incubation medium of 'ghost' membranes inhibits this self-digestion process.

Adenosine Triphosphate↗