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A Viola

Publications and source records attributed to A Viola.

At least 37 records · Page 2Linked to original sources
PubMed1997

Quantitative contribution of CD4 and CD8 to T cell antigen receptor serial triggering.

CD4 and CD8 are thought to function as coreceptors by binding to the cognate major histocompatibility complex (MHC) molecules recognized by the T cell antigen receptor (TCR) and initiating the signal transduction cascade. We report that during T cell-antigen-presenting cell interaction, triggered TCRs and coreceptors are downregulated and degraded with identical kinetics. This coordinated disappearance takes place whenever the TCR is triggered, even when the coreceptor does not engage the cognate MHC molecule and is the consequence of binding of the coreceptor-associated Lck to ZAP-70. The interaction of coreceptor and cognate MHC molecules is dispensable when T cells are stimulated by optimal ligands, but becomes crucial when suboptimal ligands are used. In the latter case the coreceptor increases the efficiency of TCR triggering without changing the activation threshold or the quality of the T cell response.

CD4 Antigens↗
PubMed1997

A T cell receptor (TCR) antagonist competitively inhibits serial TCR triggering by low-affinity ligands, but does not affect triggering by high-affinity anti-CD3 antibodies.

It has been demonstrated that modified peptides which fail to induce detectable T cell responses can act as T cell receptor (TCR) antagonists when presented together with agonist by the same antigen-presenting cell (APC). We report that a TCR antagonist competitively inhibits TCR triggering induced by low-affinity ligands such as agonistic peptides or bacterial superantigens. However, the same antagonist cannot inhibit TCR triggering and T cell activation induced by high-affinity anti-CD3 antibodies that engage most TCR at once. These results indicate that TCR antagonists inhibit T cell responses by interfering with the ongoing process of serial triggering, rather than by delivering an inhibitory signal to T cells.

Antibodies, Monoclonal↗
PubMed1997

Phototoxicity of some novel porphyrin hybrids against the human leukemic cell line TF-1.

Photodynamic induced cytotoxicity by porphyrin-DNA cross linker/intercalator hybrid diads and triads has been studied on the human leukemic cell line TF-1. Cells were incubated for 1 to 4 h with these new photosensitizers and irradiated with white light. Cell survival was assessed by the propidium iodide staining, using flow cytometry analysis. A comparison of the dark and light cell survival factor values suggests that irradiation has a significant effect on the toxicity at low concentrations for the porphyrin-chlorambucil diad and to a lesser extent at high concentrations for the porphyrin-acridone diad, the porphyrin-acridine diad and the porphyrin-cholic acid-chlorambucil triad. While the intrinsic antileukemic (via DNA cross-linking) activity of the chlorambucil moiety and the structural details may be responsible for the photoenhancement of the toxicity, the presence of acridine or acridone which are avid intercalators of DNA, is responsible for a similar effect seen for diads.

Acridines↗
PubMed1997

Compound heterozygosity for Hb Lepore-Boston and Hb Neapolis (Dhonburi) [beta 126(H4)Val-->Gly] in a patient from Naples, Italy.

The simultaneous presence of two hemoglobin variants has been detected in a 14-month-old patient affected by thalassemia intermedia. The two variants were characterized by a combination of allele-specific amplification methods and mass spectrometric procedures carried out on isolated globins. These were identified as Hb Lepore-Boston and Hb Neapolis (also known as Hb Dhonburi) or beta 126 (H4)Val-->Gly. Hb Lepore-Boston is the most common hybrid variant detected in Campania and several cases of Hb Neapolis which causes a mild hypochromic microcytic anemia have been identified in this region in the last few years. This is the first report of a double heterozygosity involving Hb Lepore-Boston and Hb Neapolis.

Follow-Up Studies↗
PubMed1997

[Dynamic phototherapy: study of anti-tumour potentialities of bis (tri n-hexylsiloxy) silicon phthalocyanine on malignant achromic M6 melanocytes. EPR study of phototoxic mechanism].

Photodynamic therapy of cancerous cells is a technique relying upon the irradiation of tumorous cells after selective incorporation of a photosensitizer. The bis (tri n-hexylsiloxy) silicon phthalocyanine is a second generation photosensitizer. Anti-cancerous potentialities of this molecule have been evaluated against the melanotic M6 cell line. Results have evidenced a high phototoxicity at low concentration and no dark toxicity under the same conditions. EPR studies on the photochemical pathways involved in phototoxicity processes have been realised in solvent and model membranes (liposomes). Results provide evidences for the production of singlet oxygen (1O2) as well as superoxide (02(o)-) and hydroxyl radicals (0OH).

Antineoplastic Agents↗
PubMed1996

T cell activation determined by T cell receptor number and tunable thresholds.

The requirements for T cell activation have been reported to vary widely depending on the state of the T cell, the type of antigen-presenting cell, and the nature of the T cell receptor (TCR) ligand. A unitary requirement for T cell responses was revealed by measurement of the number of triggered TCRs. Irrespective of the nature of the triggering ligand, T cells "counted" the number of triggered TCRs and responded when a threshold of approximately 8000 TCRs was reached. The capacity to reach the activation threshold was severely compromised by a reduction in the number of TCRs. Costimulatory signals lowered the activation threshold to approximately 1500 TCRs, thus making T cells more sensitive to antigenic stimulation.

Antibodies↗
PubMed1996

Electron paramagnetic resonance evidence of the generation of superoxide (O2.-) and hydroxyl (.OH) radicals by irradiation of a new photodynamic therapy photosensitizer, Victoria Blue BO.

Electron paramagnetic resonance (EPR) experiments were performed on Victoria Blue BO, a cationic dye whose photocytotoxicity has been studied against the human leukaemic cell lines K-562 and TF-1. EPR experiments with 2,2,6,6-tetramethyl-4-piperidone and spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide showed that, on illumination in aerated aqueous solution or DL-alpha-dipalmitoylphosphatidylcholine liposomes, photoexcited Victoria Blue BO is unable to generate 1O2, whereas O2.- and .OH are trapped by 5,5-dimethyl-1-pyrroline-N-oxide in the presence or absence of electron donors. The O2.- formed probably leads to the .OH radical, with an efficiency which is increased by electron donors such as FE2+.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1996

Genomic localization of the human gene encoding Dr1, a negative modulator of transcription of class II and class III genes.

Dr1 is a nuclear protein of 19 kDa that exists in the nucleoplasm as a homotetramer. By binding to TBP (the DNA-binding subunit of TFIID, and also a subunit of SL1 and TFIIIB), the protein blocks class II and class III preinitiation complex assembly, thus repressing the activity of the corresponding promoters. Since transcription of class I genes is unaffected by Dr1. it has been proposed that the protein may coordinate the expression of class I, class II and class III genes. By somatic cell genetics and fluorescence in situ hybridization, we have localized the gene (DR1), present in the genome of higher eukaryotes as a single copy, to human chromosome region 1p21-->p13. The nucleotide sequence conservation of the coding segment of the gene, as determined by Noah's ark blot analysis, and its ubiquitous transcription suggest that Dr1 has an important biological role, which could be related to the negative control of cell proliferation.

Animals↗
PubMed1993

DNA polymorphisms associated with Hb D-Los Angeles [beta 121(GH4)Glu-->Gln] in southern Italy.

We detected Hb D-Los Angeles [beta 121(GH4)Glu-->Gln], the most common hemoglobin variant after Hb S and Hb Lepore-Boston, in six unrelated families in Southern Italy. Ten patients were studied; eight patients were heterozygotes and two were compound heterozygotes for the hemoglobin variant and the beta-thalassemia codon 39 (C-->T) nonsense mutation. The beta-globin gene sequence was characterized by polymerase chain reaction direct sequencing; restriction fragment length polymorphisms were defined by Southern blot analysis. The gene variant, due to the GAA-->CAA substitution at codon 121, was found in association with the 5' subhaplotype [+ - - - -] and the beta-globin gene framework 1; in addition, it was found to be associated with the absence of Ava II/phi beta and Xmn I/5'G gamma, and with the presence of Hpa I/3' beta. This restriction fragment length polymorphism haplotype is common in the Mediterranean area as well as in other populations. The findings are equally compatible with an independent origin in the Mediterranean area or with origin in Asia and subsequent spread to Italy.

Base Sequence↗
PubMed1993

Hb O-Arab [beta 121(GH4)Glu-->Lys]: association with DNA polymorphisms of African ancestry in two Mediterranean families.

Hb O-Arab [beta 121(GH4)Glu-->Lys] was detected in two Mediterranean families, one from Southern Italy and the other from Albania. The GAA-->AAA mutation at codon 121 was characterized by DNA sequencing. The mutant genes were associated with the same beta-globin gene framework variant and with the rare Hpa I/3' beta polymorphic restriction site generating a 7.0 kb fragment. However, at 5' the gene of the Italian family was associated with the restriction fragment length polymorphism subhaplotype [+ - - - +] and the Taq I/3'G gamma polymorphic site, while that of the Albanian family was associated with subhaplotype [- - - - +] but not with the Taq I/3'G gamma site. The particular features of these polymorphisms support the hypothesis of an African origin for the Hb O-Arab gene and a subsequent recombination event leading to the haplotype found in the Italian family.

Adolescent↗
PubMed1991

Hemoglobin Neapolis, beta 126(H4)Val----Gly: a novel beta-chain variant associated with a mild beta-thalassemia phenotype and displaying anomalous stability features.

A novel beta-chain, beta 126(H4)Val----Gly, electrophoretically silent, was detected by reverse-phase high performance liquid chromatography in three unrelated families from Naples (Southern Italy) and accounted for about 30% of the total beta-chains. The amino acid substitution was detected by HPLC fingerprint. The eight heterozygous patients showed hematologic and biosynthetic alterations of mild beta-thalassemia type. The hemoglobin variant showed abnormal stability features. It was unstable in the heat stability and isopropanol precipitation tests, but did not cause a hemolytic syndrome in vivo and was stable in a time-course experiment of biosynthesis in vitro. DNA polymerase chain reaction direct sequencing of the mutated gene from 135 nt upstream of the cap site to 106 nt downstream of the polyadenylation site showed only the beta 126 GTG----GGG mutation, which was confirmed in the other patients by allele-specific oligonucleotide hybridization. The mutation was found to be associated with a type II beta-globin framework and restriction fragment length polymorphism haplotype V. The novel variant was named hemoglobin Neapolis.

Base Sequence↗
PubMed1991

(Alpha)alpha 5.3: a novel alpha(+)-thalassemia deletion with the breakpoints in the alpha 2-globin gene and in close proximity to an Alu family repeat between the psi alpha 2- and psi alpha 1-globin genes.

A novel 5.3-kb deletion of the alpha-globin gene cluster was observed in a family from Naples, Southern Italy. It removes the 5' end of the alpha 2-globin gene, causing an alpha (+)-thalassemia defect. Because of the presence of the residual 3' end of the alpha 2-globin gene, we indicated this new haplotype with the symbol (alpha)alpha 5.3. The 5' breakpoint, the first to be reported in the intergene region of the psi alpha 2- and psi alpha 1-globin genes, is located 822 bp upstream of the cap site of the psi alpha 1-gene and about 150 bp upstream of a 300-nt Alu family member. The 3' breakpoint is located in the IVS-1 nt 58 of the alpha 2-globin gene. The 5.3-kb deleted fragment shows particular characteristics: it contains four Alu sequences having long regions 80% complementary and the 5'-GGCC-3' short repeat at both ends. The sequences spanning across the breakpoints on the same strand and containing this repeat on their 3' and 5' ends, respectively, are 17 of 25 base complementary. These particular features led us to assume the formation of a multistem-loop due to the intrastrand interaction between the complementary regions as intermediate to the deletion. The unusual localization of the 5' breakpoint suggests that even the intergene region of the psi alpha 2- and psi alpha 1-globin genes may function as a deletion target.

Base Sequence↗
PubMed1988

Entrapment of the medial meniscus in a fracture of the tibial eminence.

Fracture of the intercondylar eminence of the tibia is unusual in adults. Long-term morbidity is uncommon. This is a case in which the anterior horn of the medial meniscus became entrapped in the fracture site after non-operative treatment of a completely displaced fracture, causing persistent medial knee pain. Arthroscopic release of the entrapped meniscus provided excellent relief of symptoms.

Adult↗
PubMed1982

[Not Available].

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History, Modern 1601-↗
PubMed1982

[Soft tissue sarcoma: histologic factors of prognosis].

With the intention of evaluating the prognostic value of 4 histopathological factors (cellularity polymorphism, mitotic index and necrosis), 80 cases of soft tissue sarcomas treated between 1960 and 1979 at the Oncology Institute of Montevideo, Uruguay were reviewed. There was a high correlation between the 4 variables. Their results provided similar models for actuarial survival rates and coefficients of regression. Nevertheless, when the factors were combined according to a linear regression model, cellularity lost almost all of its prognostic value, while necrosis and mitosis increased the prognostic influence of the equation. The percentage of variance explained by the combination of these factors was only 27 per cent. It is supposed that a substantial part of residual variance is due to factors which have not been included in the model, that is, the size of tumor, the depth of the lesion and its location. It is also conceivable that the intermediate number of cases and, more important, the heterogeneous distribution of histopathological types and primary sites might modify these results. Multiple prognostic evaluations are recommended for each histopathological type and for each different site.

Adolescent↗
PubMed1977

Dependence of cytoplasmic on mitochondrial protein synthesis in K. lactis CBS 2360. II. Genetic studies.

A few eryR mutants independently isolated from K. lactis CBS 2360 display a conditional lethal phenotype at the temperature of 36 degrees C. In addition to drug resistance, also conditional lethality shows a non-Mendelian pattern of inheritance and is affected by exposure of the cells to Ethidium Bromide, indicating that in this yeast mitochondrial DNA controls cell viability. The results obtained from biochemical analysis suggest that the cellular functions in which are involved the gene products of the mitochondrial mutants analized are cytoplasmic protein and RNA syntheses.

Cytoplasm↗