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Biomedical subjects

D Fiorentino

Publications and source records attributed to D Fiorentino.

At least 19 recordsLinked to original sources
PubMed1996

The mechanism of action of cyclosporin A and FK506.

The immunosuppressants cyclosporin A (CsA), FK506, and rapamycin suppress the immune response by inhibiting evolutionary conserved signal transduction pathways. CsA, FK506, and rapamycin bind to their intracellular receptors, immunophilins, creating composite surfaces that block the activity of specific targets. For CsA/cyclophilin and FK506/FKBP the target is calcineurin. Because of the large surface area of interaction of the drug-immunophilin complex with calcineurin, FK506 and CsA have a specificity for their biologic targets that is equivalent to growth factor-receptor interactions. To date, all the therapeutic as well as toxic effects of these drugs have been shown to be due to inhibition of calcineurin. Inhibition of the action of calcineurin results in a complete block in the translocation of the cytosolic component of the nuclear factor of activated T cells (NF-AT), resulting in a failure to activate the genes regulated by the NF-AT transcription factor. These genes include those required for B-cell help such as interleukin (IL-4) and CD40 ligand as well as those necessary for T-cell proliferation such as IL-2. The purpose of this article is to illustrate the means by which these drugs produce immunosuppression.

Animals↗
PubMed1995

Chromatography in DNA radiolabeling: hands-off automation using a robotic workstation.

The experiments described in the present paper were performed in order to determine whether the Biomek-1000 (Beckman Instruments, Fullerton, CA, USA) automated laboratory workstation can be used in a fully automated DNA labeling method followed by automated gravity-driven size exclusion purification of molecular probes. To this aim, we performed random oligodeoxyribonucleotide priming of a HIV-1 LTR probe that was used for molecular hybridization to Southern blotted polymerase chain reaction products. The results obtained demonstrate that the automatically labeled probe can be efficiently purified by automated and gravity-driven Sephadex G-50 chromatography, without any major changes in hybridization property. This robotic methodology can be used in several procedures employing radioisotope labeling.

Base Sequence↗
PubMed1994

Immunophilins interact with calcineurin in the absence of exogenous immunosuppressive ligands.

The peptidyl-prolyl isomerases FKBP12 and cyclophilin A (immunophilins) form complexes with the immunosuppressants FK506 and cyclosporin A that inhibit the phosphatase calcineurin. With the yeast two hybrid system, we detect complexes between FKBP12 and the calcineurin A catalytic subunit in both the presence and absence of FK506. Mutations in FKBP12 surface residues or the absence of the calcineurin B regulatory subunit perturb the FK506-dependent, but not the ligand-independent, FKBP12-calcineurin complex. By affinity chromatography, both FKBP12 and cyclophilin A bind calcineurin A in the absence of ligand, and FK506 and cyclosporin A respectively potentiate these interactions. Both in vivo and in vitro, the peptidyl-prolyl isomerase active sites are dispensable for ligand-independent immunophilin-calcineurin complexes. Lastly, by genetic analyses we demonstrate that FKBP12 modulates calcineurin functions in vivo. These findings reveal that immunophilins interact with calcineurin in the absence of exogenous ligands and suggest that immunosuppressants may take advantage of the inherent ability of immunophilins to interact with calcineurin.

Amino Acid Isomerases↗
PubMed1994

A chromatographic procedure for fully automated isolation of DNA from human whole blood.

Isolation of DNA from peripheral blood constitutes a fundamental step in the molecular diagnosis of genetic disorders, analysis of mutations of oncogenes and detection of nucleic-acid sequences of pathogenic organisms in clinical samples. We investigated whether dextran sedimentation of blood followed by the chromatographic isolation of DNA could be applied to the Biomek-1000 automated laboratory workstation in order to develop a fully automated method of DNA isolation from whole blood. Under our experimental conditions, the Biomek-1000 could perform fully automated DNA isolation from seven human whole blood samples in less than 1.5 h. Our data indicate that the DNA isolated from human blood in this way is suitable for polymerase chain reaction.

Autoanalysis↗
PubMed1994

Capillary electrophoresis: detection of hybridization between synthetic oligonucleotides and HIV-1 genomic DNA amplified by polymerase-chain reaction.

The polymerase chain reaction (PCR) is one of the most efficient techniques for measuring the viral load of HIV-infected samples. Determination of the specificity of PCR products is usually based on Southern blotting and hybridization of the amplified DNA to radioactive oligonucleotide probes specific for sequences comprised between the PCR primers. The recent introduction of capillary electrophoresis (CE) for identification of HIV-1 and HTLV-I PCR products appears interesting in light of its reproducibility, sensitivity and because it is fast and suitable for detection of DNA/DNA and DNA/RNA hybrids. We demonstrate that specific hybridization of a HIV-1 oligonucleotide probe to single-stranded DNA obtained by unbalanced PCR is detectable by capillary electrophoresis. This enabled us the application of a one-step, non-radioactive protocol to demonstrate the specificity of amplification of HIV-1 genomic sequences by PCR. This procedure is simple, reproducible and is suggested as an integral part of automated diagnostic systems based on the use of laboratory work stations for DNA isolation, preparation of PCR reactions and analysis of PCR products.

Base Sequence↗
PubMed1993

Use of an automated laboratory workstation for isolation of genomic DNA suitable for PCR and allele-specific hybridization.

In this paper we describe the isolation of genomic DNA by using anion exchange chromatography performed on a Biomek 1000 Automated Laboratory Workstation. This procedure allows the automated isolation of DNA suitable for most molecular analyses employed in diagnosis of genetic pathologies and infectious diseases. The genomic DNA isolated by using the Biomek 1000 was indeed found to be suitable for polymerase chain reaction and allele-specific hybridization.

Alleles↗
PubMed1991

Production of IL-10 by CD4+ T lymphocytes correlates with down-regulation of Th1 cytokine synthesis in helminth infection.

After the onset of parasite egg deposition, mice infected with the helminth Schistosoma mansoni mount strong Th2 cytokine responses in the absence of significant Th1 cytokine synthesis. To examine the basis of this immunoregulatory state, spleen or lymph node cells from schistosome-infected mice were stimulated with parasite-specific Ag and the supernatants tested for their capacity to suppress IFN-gamma synthesis by a Th1 cell line. Strong inhibition was observed that was neutralized by a mAb against IL-10, a cytokine previously shown to down-regulate Th1 cytokine synthesis. By means of ELISA measurements the production of IL-10 in schistosome infection was confirmed and shown to depend on CD4+ T cells. IL-10 synthesis stimulated by either mitogen or Ag was observed only at those stages of infection when Th2 response induction and Th1 cytokine down-regulation also occurred and was not detected in mice vaccinated with attenuated parasites. Moreover, the addition of the neutralizing anti-IL-10 mAb to Ag-stimulated spleen cell cultures from infected mice caused a dramatic augmentation in IFN-gamma synthesis. These findings suggest that IL-10 is responsible for the down-regulation of Th1 responses observed in schistosome infections, a phenomenon that may enable the parasite to escape potentially harmful cell-mediated responses.

Animals↗
PubMed1989

Inhibitors and inactivators of beta-lactamase from Mycobacterium fortuitum.

The inhibiting or inactivating effects of some beta-lactam antibiotics on beta-lactamase from Mycobacterium fortuitum were studied. Among all substrates tested, clavulanic acid and sulbactam were the strongest competitive inhibitors of the enzyme although the latter was slightly hydrolyzed. Imipenem and cefoxitin scarcely inhibited the beta-lactamase yet expressed good activity against the microorganism in vitro, suggesting that the effectiveness of these drugs on M. fortuitum might be due to high permeation through the cell wall. All the isoxazolylpenicillins tested and methicillin inactivated the enzyme of M. fortuitum by a first rapid phase of acylation followed by a steady-state process of enzyme reactivation (deacylation). Clavulanic acid and sulbactam showed Ki values for the enzyme inactivation closely corresponding to hematic concentrations achievable in vivo during antibiotic treatment.

Anti-Bacterial Agents↗
PubMed1989

Beta-lactamase production and biological characteristics in nitrosoguanidine induced Mycobacterium fortuitum mutants.

In order to elucidate the role of beta-lactamase in the resistance of M. fortuitum to beta-lactams, M. fortuitum ATCC 19542 and three mutants, strains D 316, D 319 and D 170 obtained from it by nitrosoguanidine treatment, were studied. Furthermore the kinetics of the beta-lactamase production during the bacterial growth and many biochemical and enzymatic characteristics of parent and mutant strains were investigated. Amoxicillin MICs well correlated with the beta-lactamase production in the high producer strains D 316 and D 319; on the contrary in strain D 170 a high MIC was joined with a moderate production of the enzyme showing that not only beta-lactamase but also other mechanisms can be effective in the resistance of M. fortuitum to beta-lactams. Clavulanic acid, an inhibitor of beta-lactamase, reduced MICs to amoxicillin in high and in low producer strains. The production of extracellular beta-lactamase occurred in a M. fortuitum mutant strain mainly during the stationary phase, indicating that a cell wall damage or initial autolysis could be responsible for the release of enzyme. Enzymatic and biochemical characteristics were not affected by nitrosoguanidine treatment except for nitrate test which showed only a weak positivity in high producer strains.

Anti-Bacterial Agents↗
PubMed1987

Flunarizine and migraine in childhood. An evaluation of endocrine function.

Flunarizine was tested for prophylactic efficacy and for side effects in 10- to 13-year-old patients with severe migraine (greater than 2 attacks per month). The 13 preadolescents received a single 5-mg dose at night for 2 months. The attack frequency decreased significantly, and the effect was maintained over time. The endocrine status, investigated before and after treatment, showed no significant interference with pituitary, beta-pancreatic, or gonadal function.

Adolescent↗