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Biomedical subjects

A Fischer

Publications and source records attributed to A Fischer.

At least 253 records · Page 14Linked to original sources
PubMed1999

Methods to assess free radicals and oxidative stress in biological systems.

Oxidative stress results from a disruption of the prooxidant/antioxidant cellular balance and monitoring free radical status becomes an interesting challenge in animal and human nutrition. In the present work, merits and limitations of different analytical techniques (HPLC, GC-MS, fluorometric and colourometric assays, ELISA, gel electrophoresis) for the measurement of radical mediated alterations in the cellular integrity of lipids (malondialdehyde, hydrocarbon gases, F2-isoprostanes) proteins (protein carbonyls, 3-nitrotyrosine) and DNA (8-hydroxy-2'-deoxyguanosine) are discussed. Besides these indirect methods, owing to the fact that free radicals are paramagnetic, electron paramagnetic resonance spectroscopy combined with spin trapping has become a valuable tool to directly assess and to better understand the mechanisms of free radical reactions. With this approach a radical that is too short-lived to be detected, adds to a spin-trapping agent to form a relatively long-lived radical adduct. Information obtained from the hyperfine splitting of the spin-trapped adduct can provide identification and quantification of the originally generated free radicals.

Animals↗
PubMed1999

Linkage of familial hemophagocytic lymphohistiocytosis to 10q21-22 and evidence for heterogeneity.

Familial hemophagocytic lymphohistiocytosis (FHL) is an autosomal recessive disorder characterized by the early onset of overwhelming activation of T lymphocytes and macrophages, invariably leading to death, in the absence of allogeneic bone marrow transplantation. Using genomewide genetic linkage analysis, we analyzed a group of 17 families with FHL and mapped a locus for FHL to the proximal region of the long arm of chromosome 10. Ten families showed no recombination with three tightly linked markers, D10S1650 (LOD score [Z]=6.99), D10S556 (Z=5.40), and D10S206 (Z=3.24), with a maximum multipoint LOD score of 11.22 at the D10S1650 locus. Haplotype analysis of these 10 families allowed us to establish D10S206 and D10S1665 as the telomeric and the centromeric flanking markers, respectively. Heterogeneity analysis and haplotype inspection of the remaining families confirmed that in seven families FHL was not linked to the 10q21-22 region, thus providing evidence for genetic heterogeneity of this condition.

Adult↗
PubMed1999

Does 29-mer RNA hairpin of the HIV-1 TAR RNA sequence bind magnesium? 19F-NMR and modelling studies.

5-Fluorouridine residues have been introduced into functionally important bulge and loop regions of 29-mer HIV-1 TAR RNA hairpins I and II to study Mg2+ and Ca2+ binding using 19F-NMR spectroscopy. There was no substantial binding detected up to 20-molar excess in case of both cations, whereas association of argininamide, used as a reference ligand, could be detected at less than 1-molar excess. The deltadelta 19F value of 1.93 ppm observed for (F)U23 upon argininamide binding is in agreement with former NMR studies of TAR RNA/argininamide complex. However, obtained results do not confirm U38 x A27 x U23 base-triple formation. The unmodified HIV-1 TAR RNA hairpin resulted from 600 ps in aqua molecular dynamics simulation was subjected to a molecular mechanics modelling of Mg+ binding.

Base Sequence↗
PubMed1999

Cellular sources of enhanced brain-derived neurotrophic factor production in a mouse model of allergic inflammation.

The aim of this study was to investigate production and cellular sources of brain-derived neurotrophic factor (BDNF) production in allergic asthma. For this purpose a mouse model of chronic and severe ovalbumin (OVA)-induced airway inflammation was developed. Allergen-exposed mice developed elevated immunoglobulin E titers; airway inflammation with influx of lymphocytes, monocytes, and eosinophils; and airway hyperresponsiveness. In addition to an influx of inflammatory cells, interleukin (IL)-4 and IL-5 production were enhanced, macrophages showed morphologic signs of activation, and airway epithelium was thickened and displayed a goblet-cell hyperplasia with a marked mucus production. BDNF was detected using in situ hybridization and enzyme-linked immunosorbent assay. Constitutive expression of BDNF messenger RNA (mRNA) was observed in the respiratory epithelium of sensitized and nonsensitized mouse lungs. In addition, BDNF mRNA was detected in airway inflammatory infiltrations and bronchoalveolar lavage fluid (BALF) cells of OVA-sensitized and aerosol-challenged mice. Highest BDNF protein levels were detected in BALF after long-term allergen aerosol exposure. Analysis of BDNF production by isolated lymphocyte subsets revealed T but not B cells as a cellular source of BDNF. In addition, activated alveolar macrophages were identified as BDNF-positive cells. These data indicate that in allergic airway inflammation BDNF production is upregulated and immune cells serve as a source of BDNF.

Allergens↗
PubMed1999

Genetic basis of hemophagocytic lymphohistiocytosis syndrome (Review).

The group of immune disorders which leads to the occurrence of hemophagocytic lymphohistiocytosis (HLH) syndrome presents a strange paradox in that patients with these conditions associate a dramatic immune response to infection with the failure to establish an effective immune response. During the last few years, significant progress was made in the characterization and the understanding of the molecular basis involved in these inherited immune disorders. The hemophagocytic lymphohistiocytosis syndrome which characterized the evolution of the Chediak-Higashi syndrome and the Griscelli disease results from defects affecting intracellular trafficking. A defective SH2 protein interacting with T lymphocyte intracellular signaling pathways is the cause of the X-linked lymphoproliferative disease, whereas at least three distinct genetic defects can lead to the familial hemophagocytic lymphohistiocytosis. The molecular characterization of these latter defects is in progress. This review summarizes the recent advances as well as their implications in the diagnosis and the understanding of the physiopathology of these disorders.

Animals↗
PubMed1999

Reversal of increased diastolic stiffness in mitral stenosis after successful balloon valvuloplasty.

BACKGROUND AND AIM OF THE STUDY: Abnormal passive elastic properties have been reported in patients with severe mitral stenosis and have been attributed to either: (i) chamber atrophy due to unloading; (ii) myocardial fibrosis; (iii) right and left ventricular (LV) interaction; or (iv) internal restrictions due to the rigid mitral valve apparatus. The study aim was to evaluate the effect of percutaneous mitral balloon valvuloplasty (PMV) on passive elastic properties in 19 patients with severe mitral stenosis. Ten patients with normal coronary arteries and LV function served as controls. METHODS: LV high-fidelity pressure measurements and simultaneous biplane LV angiograms were obtained before and after PMV (n = 11). The constant of chamber stiffness (b; ml(-1)) was calculated from the diastolic pressure-volume relationship and the constant of myocardial stiffness (beta) from the diastolic stress-strain relationship. The time constant of relaxation (T; ms) was calculated from the LV pressure decay during isovolumic relaxation. Regional ejection fraction (radial axis system) was determined in six regions of the right anterior oblique (RAO) and left anterior oblique (LAO) angiographic projections. RESULTS: Mitral valve area was increased from 1.0 to 2.2 cm2 after PMV, whereas diastolic pressure gradient was reduced from 14 to 4 mmHg. Global LV ejection fraction (EF) was slightly reduced (57% versus 63%; p<0.05) before valvuloplasty and normalized thereafter. Regional EF increased significantly (p<0.05) in the posterolateral region of the LAO projection after intervention. Myocardial stiffness was increased before, and decreased significantly after balloon valvuloplasty (from 16 to 11; p<0.05). The rate of relaxation and chamber stiffness remained unchanged. CONCLUSIONS: Myocardial stiffness is increased in patients with mitral stenosis, but normalized after successful PMV. The improvement in passive elastic properties after valvuloplasty can be explained by the mobilization of the subvalvular apparatus with an improvement in regional LV function.

Adult↗
PubMed1999

Gastric hemorrhage in dogs given high doses of methylprednisolone sodium succinate.

OBJECTIVE: To determine whether healthy dogs given high doses of methylprednisolone sodium succinate (MPSS) develop gastrointestinal tract ulcers and hemorrhage. ANIMALS: 19 healthy male hound-type dogs. PROCEDURE: Dogs were assigned randomly to intravenously receive high doses of MPSS (30 mg/kg of body weight, initially, then 15 mg/kg 2 and 6 hours later, and, subsequently, every 6 hours for a total of 48 hours; n = 10) or an equal volume of saline (0.9% NaCl) solution (9). Gastroduodenoscopy was performed before and after treatment. Endoscopic evidence of gross hemorrhage in the cardia, fundus, antrum, and duodenum of each dog was graded from none (0) to severe (3), and a total stomach score was calculated as the sum of the regional gastric scores. Number of ulcers were recorded. The pH of gastric fluid and evidence of occult gastric and fecal blood were measured. Food retention was recorded. RESULTS: Gastric hemorrhage was evident in all dogs after MPSS administration and was severe in 9 of 10 dogs but not visible in any dog after saline treatment. Occult gastric blood was detected more commonly (9/10 vs 2/9), median gastric acidity was greater (pH 1 vs pH 3), and food was retained more commonly (7/10 vs 1/9) in the stomach of MPSS-treated dogs. CONCLUSIONS AND CLINICAL RELEVANCE: High doses of MPSS cause gastric hemorrhage in dogs. All dogs treated with high doses of MPSS should be treated with mucosal protectants or antacids to prevent gastric hemorrhage.

Animals↗
PubMed1999

Efficacy of misoprostol in prevention of gastric hemorrhage in dogs treated with high doses of methylprednisolone sodium succinate.

OBJECTIVE: To determine whether administration of misoprostol prevents gastric hemorrhage in healthy dogs treated with high doses of methylprednisolone sodium succinate (MPSS). ANIMALS: 18 healthy hound-type dogs of both sexes. PROCEDURE: All dogs were given high doses of MPSS (30 mg/kg of body weight, initially, then 15 mg/kg 2 and 6 hours later, and, subsequently, q 6 h for a total of 48 hours) IV. Dogs were assigned randomly to receive concurrent treatment with misoprostol (4 to 6 microg/kg, PO, q 8 h; n = 9) or an empty gelatin capsule (9). Gastroduodenoscopy was performed before and after treatment. Hemorrhage was graded from none (0) to severe (3) for each cardia, fundus, antrum, and duodenum. A total stomach score was calculated as the sum of the regional stomach scores. Food retention was recorded, and pH of gastric fluid was determined. Gastric and fecal occult blood was measured. RESULTS: Gastric hemorrhage was evident in all dogs after MPSS administration, and its severity was similar in both groups. Median total stomach score was 6 for misoprostol-treated dogs and 5.5 for dogs given the gelatin capsule. Difference in gastric acidity, frequency of food retention, and incidence of occult blood in gastric fluid and feces was not apparent between the 2 groups. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of misoprostol (4 to 6 microg/kg, PO, q 8 h) does not prevent gastric hemorrhage caused by high doses of MPSS. Alternative prophylactic treatment should be considered.

Animals↗
PubMed1998

Inherited interleukin 12 deficiency in a child with bacille Calmette-Guérin and Salmonella enteritidis disseminated infection.

Interferon-gamma receptor ligand-binding chain (IFN-gammaR1) or signaling chain (IFN-gammaR2) deficiency, like interleukin 12 receptor beta1 chain (IL-12Rbeta1) deficiency, predispose to severe infections due to poorly virulent mycobacteria and salmonella. A child with bacille Calmette-Guérin and Salmonella enteritidis infection was investigated. Mutations in the genes for IFN-gammaR1, IFN-gammaR2, IL-12Rbeta1, and other molecules implicated in IL-12- or IFN-gamma-mediated immunity were sought. A large homozygous deletion within the IL-12 p40 subunit gene was found, precluding expression of functional IL-12 p70 cytokine by activated dendritic cells and phagocytes. As a result, IFN-gamma production by lymphocytes was markedly impaired. This is the first discovered human disease resulting from a cytokine gene defect. It suggests that IL-12 is essential to and appears specific for protective immunity to intracellular bacteria such as mycobacteria and salmonella.

BCG Vaccine↗
PubMed1998

gammac gene transfer in the presence of stem cell factor, FLT-3L, interleukin-7 (IL-7), IL-1, and IL-15 cytokines restores T-cell differentiation from gammac(-) X-linked severe combined immunodeficiency hematopoietic progenitor cells in murine fetal thymic organ cultures.

X-linked severe combined immunodeficiency (SCID-Xl) is a rare human inherited disorder in which early T and natural killer (NK) lymphocyte development is blocked. The genetic disorder results from mutations in the common gammac chain that participates in several cytokine receptors including the interleukin-2 (IL-2), IL-4, IL-7, IL-9, and IL-15 receptors. We have shown in a previous report that gammac gene transfer into SCID-Xl bone marrow (BM) cells restores efficient NK cell differentiation. In this study, we have focused on the introduction of the gammac gene into SCID-Xl hematopoietic stem cells with the goal of obtaining differentiation into mature T cells. For this purpose, we used the in vitro hybrid fetal thymic organ culture (FTOC) system in which a combination of cytokines consisting of stem cell factor (SCF), Flt-3L, IL-7, IL-1, and IL-15 is added concomitantly. In this culture system, CD34(+) marrow cells from two SCID-Xl patients were able to mature into double positive CD4(+) CD8(+) cells and to a lesser degree into CD4(+) TCRbeta+ single positive cells after retroviral-mediated gammac gene transfer. In addition, examination of the output cell population at the TCR DJbeta1 locus exhibited multiple rearrangements. These results indicate that restoration of the gammac/JAK/STAT signaling pathway during the early developmental stages of thymocytes can correct the T-cell differentiation block in SCID-Xl hematopoietic progenitor cells and therefore establishes a basis for further clinical gammac gene transfer studies.

Animals↗
PubMed1998

Anti-B-cell monoclonal antibody treatment of severe posttransplant B-lymphoproliferative disorder: prognostic factors and long-term outcome.

B-lymphoproliferative disorder (BLPD) is a rare but severe complication of organ and bone marrow transplantation (BMT). Profound cytotoxic T-cell deficiency is thought to allow the outgrowth of Epstein-Barr virus-transformed B cells. When possible, reduction of immunosuppressive treatment or surgery for localized disease may cure BLPD. Therapeutic approaches using chemotherapy or antiviral drugs have limited effects on survival. Adoptive immunotherapy with donor T-cell infusions has given promising results in BMT recipients. We previously reported that administration of two monoclonal anti-B-cell antibodies (anti-CD21 and anti-CD24) could contribute to the control of oligoclonal BLPD. Here we report the long-term results of treatment with these monoclonal anti-B-cell antibodies for cases of severe BLPD. In an open multicenter trial, 58 patients in whom aggressive B-cell lymphoproliferative disorder developed after BMT (n = 27) or organ (n = 31) transplantation received 0.2 mg/kg/d of specific anti-CD21 and anti-CD24 murine monoclonal antibodies (MoAbs) for 10 days. The treatment was well tolerated. Thirty-six of the 59 episodes of BLPD in the 58 patients presented complete remission (61%). The relapse rate was low (3 of 36, 8%). Multivariate analysis identified the following risk factors for partial or no response to anti-B-cell MoAb therapy: multivisceral disease (P </= .005), central nervous system involvement (P </= .05), and late onset of BLPD (P </= .005). The overall long-term survival was 46% (median follow-up, 61 months); it was lower among BMT patients (35%) than organ transplant patients (55%). None of the patients who had received BMT for hematological malignancy survived for 1 year. Eight of these 11 patients presented monoclonal BLPD. Tumor burden was the only other variable that contributed significantly to poor survival. Thus, as assessed from this long-term study, the use of anti-B-cell MoAbs therefore appears to be a safe and relatively effective therapy for severe posttransplant BLPD.

Adolescent↗
PubMed1998

Defect in IgV gene somatic hypermutation in common variable immuno-deficiency syndrome.

Common Variable Immuno-Deficiency (CVID) is the most common symptomatic primary antibody-deficiency syndrome, but the basic immunologic defects underlying this syndrome are not well defined. We report here that among eight patients studied (six CVID and two hypogammaglobulinemic patients with recurrent infections), there is in two CVID patients a dramatic reduction in Ig V gene somatic hypermutation with 40-75% of IgG transcripts totally devoid of mutations in the circulating memory B cell compartment. Functional assays of the T cell compartment point to an intrinsic B cell defect in the process of antibody affinity maturation in these two cases.

Adult↗
PubMed1998

Conditional lineage ablation to model human diseases.

Cell loss contributes to the pathogenesis of many inherited and acquired human diseases. We have developed a system to conditionally ablate cells of any lineage and developmental stage in the mouse by regulated expression of the diphtheria toxin A (DTA) gene by using tetracycline-responsive promoters. As an example of this approach, we targeted expression of DTA to the hearts of adult mice to model structural abnormalities commonly observed in human cardiomyopathies. Induction of DTA expression resulted in cell loss, fibrosis, and chamber dilatation. As in many human cardiomyopathies, transgenic mice developed spontaneous arrhythmias in vivo, and programmed electrical stimulation of isolated-perfused transgenic hearts demonstrated a strikingly high incidence of spontaneous and inducible ventricular tachycardia. Affected mice showed marked perturbations of cardiac gap junction channel expression and localization, including a subset with disorganized epicardial activation patterns as revealed by optical action potential mapping. These studies provide important insights into mechanisms of arrhythmogenesis and suggest that conditional lineage ablation may have wide applicability for studies of disease pathogenesis.

Action Potentials↗
PubMed1998

Sam68 association with p120GAP in CD4+ T cells is dependent on CD4 molecule expression.

p120 GTPase-activating protein (p120GAP) is a major negative regulator of p21ras activity in several cell types including T cells. Catalytic activity of this enzyme is regulated in part by its interaction with several associated tyrosine-phosphorylated proteins. Sam68 was initially described as associated with p120GAP. It has been further established that Sam68 is a substrate of src kinases in mitosis and that it is not associated with p120GAP in transformed fibroblasts. We describe herein that Sam68 associates with p120GAP and PLC gamma 1 in human mature T cells and in a T cell line expressing the CD4 molecule HUT78 CD4+. This association is present in nonactivated cells and increases after anti-CD3 activation. It is dependent on CD4 expression and, in part, on the association of CD4 with p56lck, as shown by the strongly decreased association of Sam68 with p120GAP in the CD4- mutants, HUT78 CD4-, and by the reduced association of Sam68 with both p120GAP and p56lck in the HUT78 T cell line expressing a CD4 mutant unable to interact with p56lck, HUT78 C420/22. We propose that recruitment of Sam68, via CD4/p56lck, to the inner face of the plasma membrane may permit, via its docking properties, the correct association of key signaling molecules including PLC gamma 1 and p120GAP. This formation of transduction modules will enable the activation of different signaling cascades including the p21ras pathway and an array of downstream events, ultimately leading to T cell activation.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Enhancement of monocyte procoagulant activity by adhesion on vascular smooth muscle cells and intercellular adhesion molecule-1-transfected Chinese hamster ovary cells.

BACKGROUND: Plaque erosion is a frequent finding in sudden death due to coronary thrombosis. The present study sought to investigate whether monocyte adhesion to human aortic vascular smooth muscle cells (VSMCs) induces procoagulant activity (PCA) and whether this could be mediated by intercellular adhesion molecule-1 (ICAM-1). METHODS AND RESULTS: We incubated mononuclear cells (MNCs) with VSMCs and ICAM-1-transfected Chinese hamster ovary (CHO) cells, investigated monocyte tissue factor (TF) mRNA expression by Northern blot analysis and TF protein expression by ELISA, and measured PCA. Incubation of MNCs with VSMCs for 6 hours increased PCA from 0.7+/-0.1 to 166.0+/-37.9 mU/105 cells (P=0.007), which could be inhibited in a dose-dependent manner by the addition of blocking anti-ICAM-1 monoclonal antibodies. Prestimulation of VSMCs with interleukin-1beta enhanced surface ICAM-1 expression significantly but did not induce PCA in VSMCs. Incubation of MNCs with prestimulated VSMCs led to a further increase in PCA to 239.9+/-27.9 mU/10(5) cells (P=0.02 compared with incubation with unstimulated VSMCs). Incubation of MNCs with VSMCs enhanced TF mRNA after 2 hours and significantly increased TF protein content after 6 hours. Incubation of purified monocytes with ICAM-1-transfected CHO cells increased PCA from 1.2+/-0.2 to 81.9+/-3.3 mU/10(5) cells (P<0.001 compared with incubation with untransfected CHO cells) after 6 hours. This effect could be inhibited significantly by the addition of blocking anti-CD18, anti-CD11b, or anti-CD11c monoclonal antibodies. Similar results were obtained for MNCs. CONCLUSIONS: Monocyte adhesion to VSMCs induces TF mRNA and protein expression and monocyte PCA, which is regulated by beta2-integrin-mediated monocyte adhesion to ICAM-1 on VSMCs.

Animals↗
PubMed1998

A human severe combined immunodeficiency (SCID) condition with increased sensitivity to ionizing radiations and impaired V(D)J rearrangements defines a new DNA recombination/repair deficiency.

The products of recombination activating gene (RAG)1 and RAG2 initiate the lymphoid-specific phase of the V(D)J recombination by creating a DNA double-strand break (dsb), leaving hairpin-sealed coding ends. The next step uses the general DNA repair machinery of the cells to resolve this dsb. Several genes involved in both V(D)J recombination and DNA repair have been identified through the analysis of in vitro mutants (Chinese hamster ovary cells) and in vivo situations of murine and equine severe combined immunodeficiency (scid). These studies lead to the description of the Ku-DNA-dependent protein kinase complex and the XRCC4 factor. A human SCID condition is characterized by an absence of B and T lymphocytes. One subset of these patients also demonstrates an increased sensitivity to the ionizing radiation of their fibroblasts and bone marrow precursor cells. This phenotype is accompanied by a profound defect in V(D)J recombination with a lack of coding joint formation, whereas signal joints are normal. Functional and genetic analyses distinguish these patients from the other recombination/repair mutants, and thus define a new group of mutants whose affected gene(s) is involved in sensitivity to ionizing radiation and V(D)J recombination.

Animals↗
PubMed1998

Highly restricted human T cell repertoire in peripheral blood and tissue-infiltrating lymphocytes in Omenn's syndrome.

Omenn's syndrome is an inherited human combined immunodeficiency condition characterized by the presence of a large population of activated and tissue-infiltrating T cells. Analysis of the TCRB repertoire revealed a highly restricted TCRBV usage in three patients. More strikingly, T cell clones from the three patients expressed TCRB chains with VDJ junction similarities, suggesting a common antigenic specificity. Analysis of the TCRA repertoire in one patient also revealed a restricted TCRAV usage. Finally, analysis of the TCRBV repertoire of tissue-infiltrating T cells in one patient suggested nonrandom tissue migration. These results suggest that the oligoclonal expansion of T cells observed in Omenn's syndrome could be the consequence of autoimmune proliferation generated by a profound defect in lymphocyte development.

Humans↗