Biomedical subjects

S Fischer

Publications and source records attributed to S Fischer.

At least 145 records · Page 8Linked to original sources

PubMed1999

A complete BAC-based physical map of the Arabidopsis thaliana genome.

Arabidopsis thaliana is a small flowering plant that serves as the major model system in plant molecular genetics. The efforts of many scientists have produced genetic maps that provide extensive coverage of the genome (http://genome-www. stanford.edu/Arabidopsis/maps.html). Recently, detailed YAC, BAC, P1 and cosmid-based physical maps (that is, representations of genomic regions as sets of overlapping clones of corresponding libraries) have been established that extend over wide genomic areas ranging from several hundreds of kilobases to entire chromosomes. These maps provide an entry to gain deeper insight into the A. thaliana genome structure. A. thaliana has been chosen as the subject of the first large-scale project intended to determine the full genome sequence of a plant. This sequencing project, together with the increasing interest in map-based gene cloning, has highlighted the requirement for a complete and accurate physical map of this plant species. To supply the scientific community with a high-quality resource, we present here a complete physical map of A. thaliana using essentially the IGF BAC library. The map consists of 27 contigs that cover the entire genome, except for the presumptive centromeric regions, nucleolar organization regions (NOR) and telomeric areas. This is the first reported map of a complex organism based entirely on BAC clones and it represents the most homogeneous and complete physical map established to date for any plant genome. Furthermore, the analysis performed here serves as a model for an efficient physical mapping procedure using BAC clones that can be applied to other complex genomes.

Arabidopsis↗

PubMed1999

bioWidgets: data interaction components for genomics.

MOTIVATION: The presentation of genomics data in a perspicuous visual format is critical for its rapid interpretation and validation. Relatively few public database developers have the resources to implement sophisticated front-end user interfaces themselves. Accordingly, these developers would benefit from a reusable toolkit of user interface and data visualization components. RESULTS: We have designed the bioWidget toolkit as a set of JavaBean components. It includes a wide array of user interface components and defines an architecture for assembling applications. The toolkit is founded on established software engineering design patterns and principles, including componentry, Model-View-Controller, factored models and schema neutrality. As a proof of concept, we have used the bioWidget toolkit to create three extendible applications: AnnotView, BlastView and AlignView.

Amino Acid Sequence↗

PubMed1999

hSiah2 is a new Vav binding protein which inhibits Vav-mediated signaling pathways.

The hematopoietic proto-oncogene vav has been characterized as a Rac1-GDP/GTP exchanger protein which regulates cytoskeletal reorganization as well as signaling pathways leading to the activation of stress-activated protein kinases (SAPK/JNKs). Furthermore, vav overexpression enhances basal and T-cell receptor (TCR)-mediated stimulation of the nuclear factor of activated T cells (NFAT). We report here the interaction between Vav and hSiah2, a mammalian homolog of Drosophila Seven in absentia (Sina) that has been implicated in R7 photoreceptor cell formation during Drosophila eye development via the proteasome degradation pathway. Vav and hSiah2 interact in vitro and in vivo and colocalize in the cytoplasm of hematopoietic cells. The Src homology domain of Vav and the C-terminal region of hSiah2 are required for this interaction. We provide evidence for a negative regulation by hSiah2 of Vav-induced basal and TCR-mediated NFAT-dependent transcription. Overexpression of hSiah2 also inhibits the onco-Vav-induced JNK activation. Although the Vav-interacting domain is located in the C-terminal portion of hSiah2, the N-terminal region of hSiah2 is necessary for the inhibitory role that seems to be independent of the proteasome degradation.

Animals↗

PubMed1999

Hypoxia induces permeability in brain microvessel endothelial cells via VEGF and NO.

In this study, an in vitro model of the blood-brain barrier, consisting of porcine brain-derived microvascular endothelial cells (BMEC), was used to evaluate the mechanism of hypoxia-induced hyperpermeability. We show that hypoxia-induced permeability in BMEC was completely abolished by a neutralizing antibody to vascular endothelial growth factor (VEGF). In contrast, under normoxic conditions, addition of VEGF up to 100 ng/ml did not alter monolayer barrier function. Treatment with either hypoxia or VEGF under normoxic conditions induced a twofold increase in VEGF binding sites and VEGF receptor 1 (Flt-1) mRNA expression in BMEC. Hypoxia-induced permeability also was prevented by the nitric oxide (NO) synthase inhibitor NG-monomethyl-L-arginine, suggesting that NO is involved in hypoxia-induced permeability changes, which was confirmed by measurements of the cGMP level. During normoxia, treatment with VEGF (5 ng/ml) increased permeability as well as cGMP content in the presence of several antioxidants. These results suggest that hypoxia-induced permeability in vitro is mediated by the VEGF/VEGF receptor system in an autocrine manner and is essentially dependent on reducing conditions stabilizing the second messenger NO as the mediator of changes in barrier function of BMEC.

Animals↗

PubMed1999

Microvascular endothelial cells remodel cultured adult cardiomyocytes and increase their survival.

We investigated the paracrine effect of cardiac microvascular endothelial cells (MVEC) on cultured adult rat cardiomyocytes (ARC). ARC were exposed for 8 days to serum-free medium (CM) conditioned by MVEC. Controls were grown in FCS or FCS-free medium. Protein synthesis of CM-stimulated ARC increased twofold versus 5% FCS-stimulated cells until day 8. Seventy-nine percent of CM-treated myocytes survived, whereas only twenty-four percent of FCS-free ARC retained viability. The phenotype of myocytes exposed to CM was different from control. Analysis by confocal laser microscopy of CM-stimulated myocytes showed actin staining throughout the whole cell body up to the peripheral extensions, with concomitant appearance of myomesin in a cross-striated pattern. The reexpression of fetal alpha-smooth muscle actin determined immunohistochemically and by Western blot increased from day 6 in CM-treated cells, whereas ARC grown in up to 20% serum were negative. These effects could not be mimicked by any of the other cardioactive substances tested here, indicating a novel trophic factor in CM.

Actins↗

PubMed1999

[Calcium supplementation and bone absorptiometry in girls].

BACKGROUND: The achievement of a peak bone mass is an important factor in the prevention of osteoporotic fractures. In normal children, the amount of calcium intake could affect bone mineral increment. AIM: To assess the effect of a daily 500 mg calcium supplement on bone mineral density, in a group of healthy Chilean girls. PATIENTS AND METHODS: Fifty healthy girls were studied and 25 were randomly assigned to receive a 500 mg calcium supplement during 10 months. Bone mineral density of the distal and ultradistal region of the forearm was measured in all girls by single X ray absorptiometry (Osteometer DTX-100) at the beginning and end of the study. Bone mineral density was expressed as Z values. RESULTS: Significant increments in bone mineral density at the distal radioulnar region were obtained in the supplemented girls. No significant changes in bone density were observed in control girls. CONCLUSIONS: A daily 500 mg calcium supplement for 10 months increased bone mineral density in healthy girls.

Absorptiometry, Photon↗

PubMed1999

Oligoclonal immunoglobulin heavy-chain and T-cell receptor delta rearrangements persist in a recurrent acute lymphoblastic leukemia with one immunoglobulin kappa rearrangement as a clonal marker.

Acute lymphoblastic leukemias (ALLs) represent the clonal expansion of a lymphoid precursor cell. Therefore, all cells of an ALL should have identical antigen receptor gene rearrangements. In a patient with diploid ALL of the B-cell precursor immunophenotype, seven different clonal rearrangements of the immunoglobulin heavy-chain genes (IgH) were identified, implying the presence of oligoclonal populations. All of these rearrangements were only detectable after a modification of the polymerase chain reaction for the complementarity determining region of the IgH genes using V(H) gene framework 3 and (H) consensus primers. Sequence analysis showed that these rearrangements were completely unrelated to each other. Only two of these rearrangements were detectable by Southern blot analysis. Quantification and single-cell analysis confirmed the high frequency of these latter two rearrangements, as well as their presence in the same clonal population. The other rearrangements characterized less than 5% of the leukemic population. In addition, two T-cell receptor Vdelta2-Ddelta3 (TCRdelta) rearrangements were identified, both at a similar frequency. However, they were derived from different cells. An Igkappa rearrangement represented the only clonal marker in this leukemia. All of the Ig and TCRdelta rearrangements, with the exception of one IgH rearrangement, remained stable throughout the course of the disease. The persistence of such a great number of distinct IgH rearrangements at different quantities within the leukemic population and of the two biclonal TCRdelta rearrangements is compatible with the presence of a clonal disease that is defined by the Igkappa rearrangement.

Adolescent↗

PubMed1998

Barbiturates decrease the expression of vascular endothelial growth factor in hypoxic cultures of porcine brain derived microvascular endothelial cells.

Vascular endothelial growth factor (VEGF) is known to be produced in higher amounts during hypoxia by a variety of cell types and has been shown to increase the permeability of brain derived microvascular endothelial cells (BMEC) during hypoxia by an autocrine mechanism. Because the barbiturates, methohexital (MH) and thiopental (TP), induced a dose-dependent reduction in hypoxia-induced permeability changes of BMEC, the effect of both barbiturates on the VEGF expression during hypoxia was investigated. Both barbiturates decreased the hypoxia-induced expression of VEGF in BMEC in a concentration-dependent manner. This effect is partly caused by the impairment of the hypoxia-induced VEGF mRNA stabilization. VEGF-induced permeability changes during normoxia were unaffected by the barbiturates suggesting that MH and TP are directly reducing hypoxia-induced VEGF synthesis. In conclusion, the inhibiting effect of these barbiturates on the hypoxia-induced VEGF expression results in the decreased permeability of the BMEC monolayer during hypoxia, which may contribute to the described neuroprotective action of barbiturates by reduction of brain edema formation.

Adenosine↗

PubMed1998

Grb2 and its apoptotic isoform Grb3-3 associate with heterogeneous nuclear ribonucleoprotein C, and these interactions are modulated by poly(U) RNA.

Grb2 is an adaptor molecule comprising one Src homology (SH) 2 and two SH3 domains. This protein has a natural isoform named Grb3-3 with a deletion within the SH2 domain. Numerous evidence points to a functional connection between SH2- and SH3-containing proteins and molecules implicated in RNA biogenesis. In this context, we have examined the binding of Grb2 and Grb3-3 to heterogeneous nuclear ribonucleoprotein (hnRNP) C. By the use of an in vivo genetic approach and through in vitro experiments, we furnish evidence that both Grb2 and Grb3-3 interact with hnRNP C proteins. Subcellular fractionation studies clearly show that Grb2 is partially localized in the nucleus. In addition, coimmunoprecipitation experiments demonstrate that Grb2.hnRNP C complexes exist in intact hematopoietic cells. The carboxyl-terminal SH3 domains of Grb2 and Grb3-3 are primarily responsible for the association with hnRNP C. However, although the proline-rich motif of hnRNP C is involved in the interaction with Grb2, it is not in the binding to Grb3-3. Furthermore, poly(U) RNA inhibits the association of Grb2 with hnRNP C, whereas it enhances the interaction between Grb3-3 and hnRNP C. These findings suggest that the Grb2/Grb3-3-hnRNP C interactions might fulfill different biological functions.

3T3 Cells↗

PubMed1998

Vav binding to heterogeneous nuclear ribonucleoprotein (hnRNP) C. Evidence for Vav-hnRNP interactions in an RNA-dependent manner.

The vav proto-oncogene is exclusively expressed in hematopoietic cells and encodes a 95-kDa protein that contains multiple structural domains. Vav is involved in the expansion of T and B cells, in antigen-mediated proliferative responses, and in the induction of intrathymic T cell maturation. It becomes rapidly and transiently tyrosine-phosphorylated upon triggering of a large number of surface receptors and catalyzes GDP/GTP exchange on Rac-1. We now provide evidence for the specific interaction of Vav with heterogeneous nuclear ribonucleoprotein (hnRNP) C. Vav and hnRNP C interact both in vivo and in vitro mediated through the carboxyl Src homology 3 domain of Vav and the proline-rich motif located in the nuclear retention sequence of hnRNP C. More importantly, Vav-hnRNP C complexes are present in living hematopoietic cells and both proteins localize in the nuclei, mainly on perichromatic fibrils but also on clusters of interchromatin granules. The Vav-hnRNP C interaction is regulated by poly(U) RNA, although a basal association is still detected in the absence of RNA. Furthermore, RNA homopolymers differentially alter the binding affinity of Vav to hnRNP C and hnRNP K. We propose that Vav-hnRNP interactions may be established in an RNA-dependent manner.

Cell Line↗

PubMed1998

Construction and characterization of the IGF Arabidopsis BAC library.

A bacterial artificial chromosome (BAC) library has been established for Arabidopsis thaliana (ecotype Col-0) covering about seven haploid nuclear genome equivalents. This library, called the Institut für Genbiologische Forschung (IGF) BAC library, consists of 10,752 recombinant clones carrying inserts (generated by partial EcoRI digestion) of an average size of about 100 kb in a modified BAC vector, pBeloBAC-Kan. Hybridization with organellar DNA and nuclear repetitive DNA elements revealed the presence of 1.1% clones with mitochondrial DNA, 0.2% clones with plastid DNA, 3.2% clones with the 180 bp paracentromeric repeat, 1.6% clones with 5S rDNA, and 10.8% clones with the 18S-25S rDNA repeat. With its extensive genome coverage, its rather uniformly sized inserts (80 kb < 85% < 120 kb) and low contamination with organellar DNA, this library provides an excellent resource for A. thaliana genomic mapping, map-based gene cloning, and genome sequencing.

Arabidopsis↗

PubMed1998

European study on dose-response relationship of acarbose as a first-line drug in non-insulin-dependent diabetes mellitus: efficacy and safety of low and high doses.

The aim of this double-blind, placebo-controlled, multinational, five-arm study was to investigate the dose-response relationship of acarbose as a first-line drug in the treatment of type 2 diabetes (non-insulin dependent) over a range of minimal and maximal doses according to the European recommendations. The study included 495 patients from 7 countries who were insufficiently controlled with diet alone (glycosylated haemoglobin HbA1C 6.5%-9%). Acarbose, 25, 50, 100 or 200 mg t.i.d., or placebo t.i.d. was given for 24 weeks. Even a low dosage of 25 mg t.i.d. acarbose reduced fasting and postprandial blood glucose levels (1 h postprandial -11.6%; 2 h postprandial -11.3%). Acarbose in a dosage of 200 mg t.i.d. had the greatest effect on these parameters. In the placebo group the mean 2 h postprandial area under the curve (AUC) value for blood glucose was 22.6 mmol/l after 24 weeks' therapy. The mean 2 h postprandial AUC values in the patients given acarbose at doses of 25, 50, 100 and 200 mg t.i.d. were found to be 21.2, 19.6, 20.3 and 18.5 mmol/l, respectively. The corresponding HbA1C values for the placebo and acarbose groups were 7.83%, 7.37%, 7.08%, 6.98% and 6.79%. Interestingly, there was a plateau of blood glucose level at a dosage of 50-100 mg t.i.d. The frequency of flatulence decreased with the duration of drug therapy, but we could not find a linear relationship between doses of acarbose and the gastrointestinal side effects. Less than 3% of patients stopped tablet intake due to adverse events.

Acarbose↗

PubMed1998

In situ localization of a high molecular weight cross-reactive allergen in pollen and plant-derived food by immunogold electron microscopy.

BACKGROUND: A high molecular weight (60 kd) allergen has been recently identified as a cross-reactive moiety in pollen and plant-derived food. While the cross-reactive allergen has been characterized by immunochemical techniques, little is known concerning its biologic properties. OBJECTIVE: In this investigation we studied the in situ localization of the 60 kd cross-reactive allergen in tree, grass, and weed pollen, as well as in plant-derived food (apple and celery). METHODS: A monoclonal antibody (3A4) that was raised against the major mugwort pollen allergen, Art v 1, was used to demonstrate the presence of related allergens in nitrocellulose-blotted pollen and plant-food extracts. The tissue localization of the cross-reactive allergen was investigated by immunogold electron microscopy. RESULTS: Monoclonal antibody 3A4 recognized IgE epitopes of the 60 kd mugwort allergen and cross-reacted with moieties of comparable molecular weights in birch and timothy grass pollen, as well as in apple and celery extracts. In pollen and plant-derived food the allergen could be localized intracellularly in ribosome-rich areas in the mitochondria and the nucleus. No labeling was observed in the pollen or cell walls or in organelles that are engaged in storage (e.g., starch granules and lipid particles). CONCLUSION: Tree, grass, and weed pollen, as well as plant-derived foods, contain a high molecular weight Art v 1-cross-reactive allergen that maps to similar cell compartments.

Allergens↗

PubMed1998

Multiplex PCR for TCR delta rearrangements: a rapid and specific approach for the detection and identification of immature and mature rearrangements in ALL.

The preferential occurrence of immature T-cell receptor (TCR) delta rearrangements (i.e. incomplete Ddelta2-Ddelta3 and Vdelta2-Ddelta3) in B-cell precursor acute lymphoblastic leukaemia (BCP ALL) and of predominantly mature rearrangements (incomplete Ddelta2-Jdelta1, complete Vdelta1, Vdelta2, Vdelta3 to Jdelta1) in T-lineage ALL prompted us to establish two separate multiplex PCR systems for the identification of clonal TCRdelta rearrangements. PCR products of the expected size for the specific rearrangements were detectable from a dilution of 100-1000 clonal cells in 150000 polyclonal cells. Both multiplex PCR systems were used to analyse samples from 86 childhood BCPALLs and 30 T-lineage ALLs. The results of the multiplex PCRs were controlled by standard PCR analyses for the individual rearrangements and Southern blots, which were identical. Only immature TCRdelta rearrangements were detected in BCP ALL (59%), whereas no rearrangement was found in the remaining BCP leukaemias, thus confirming the exclusive presence of immature TCRdelta rearrangements in B-lineage cells. 50% of the T-lineage ALLs contained mature rearrangements, but no immature rearrangements were found. These two multiplex PCR techniques appear to be reliable and fast aids in the analysis of clonal TCRdelta rearrangements in ALL.

Blotting, Southern↗

PubMed1998

Use of the IGF BAC library for physical mapping of the Arabidopsis thaliana genome.

In order to generate a physical map of the Arabidopsis thaliana genome based on bacterial artificial chromosome clones (BACs), an iterative high throughput hybridisation strategy was applied and its efficiency was evaluated. Thus, probes generated from both ends of 500 BAC clones selected from the Arabidopsis-IGF-BAC library were hybridised to the entire library gridded on high density filters. The 1000 hybridisation reactions identified 4496 clones (41.8% of the complete library, or 50.3% if organellar, centromeric, and ribosomal DNA carrying clones are excluded) which were assembled into a minimum of 220 contigs. These results demonstrate the viability of the applied 'double-end clone-limited/sampling without replacement' hybridisation strategy for the generation of a high resolution physical map, and provide a highly useful resource for map-based gene cloning approaches and further genome analysis.

Arabidopsis↗

PubMed1998

Exclusion of lumbar arteries by aortic endovascular grafts: can angiography demonstrate sealing characteristics?

BACKGROUND: This study evaluates sealing characteristics of two designs of endovascular grafts by angiographic demonstration of exclusion of porcine lumbar arteries. METHODS: 6 endovascular grafts (3 self-expandable with integrated polyurethane wall versus 3 nitinol structures covered with polyester fabric) were implanted in 6 porcine aortae. Perfusion of lumbar arteries was assessed by angiography after implantation and by angiography and dissection at graft explantation after 4 +/- 2 months. Tissue healing was evaluated by light and scanning electron microscopy. RESULTS: Immediate exclusion of the lumbar arteries was achieved in 14/31 vessels (12 by polyurethane grafts and 2 by polyester grafts, p < 0.001). Follow-up angiography and dissection at explantation revealed perfusion of 30/31 lumbar arteries with a collateral network in most cases. Another reason for reperfusion of initially excluded branches was distention of the polyurethane grafts with resulting shortening allowing reperfusion of 8 of the 31 originally covered branches. Histological examination revealed a complete neointimal lining and a tight contact between endovascular grafts and aorta. CONCLUSIONS: The immediate angiographic demonstration of exclusion of lumbar arteries predicts sealing characteristics of endovascular grafts. Later angiographic reappearance is due to development of a collateral network and possible shortening of self-expandable devices.

Animals↗

PubMed1998

Unacceptable results of the Mayo procedure for repair of abdominal incisional hernias.

OBJECTIVE: To evaluate the current practice of incisional hernia repair in Germany and analysis of the results of the Mayo duplication technique done in our hospital over a 10-year period. DESIGN: Nationwide survey, retrospective analysis. SETTING: University department, Germany. SUBJECTS: Survey of most surgical departments and of 114 patients with 135 incisional hernias in our unit. INTERVENTION: Mayo duplication repair incisional hernias. MAIN OUTCOME MEASURES: Common practice, recurrence rates, quality of life. RESULTS: The Mayo overlap is the preferred technique in most surgical departments. The estimated failure rates (12% or less) in general practice are grossly underestimated. In our hospital the recurrence rate after Mayo duplication repair was 61/114 (54%) during a follow up time of 5.7 years with a follow-up-rate of 84%. Univariate and multivariate analyses failed to identify any predisposing factors. All patients with incisional hernias had limitations their physical function. CONCLUSIONS: The widely used Mayo procedure leads to unacceptable results for repair of incisional hernias and other techniques should be evaluated and used more often. Repair of an incisional hernia does not improve overall quality of life.

Female↗

PubMed1998

Role of Akt and c-Jun N-terminal kinase 2 in apoptosis induced by interleukin-4 deprivation.

We have shown previously that interleukin-4 (IL-4) protects TS1alphabeta cells from apoptosis, but very little is known about the mechanism by which IL-4 exerts this effect. We found that Akt activity, which is dependent on phosphatidylinositol 3 kinase, is reduced in IL-4-deprived TS1alphabeta cells. Overexpression of wild-type Akt or a constitutively active Akt mutant protects cells from IL-4 deprivation-induced apoptosis. Readdition of IL-4 before the commitment point is able to restore Akt activity. We also show expression and c-Jun N-terminal kinase 2 activation after IL-4 deprivation. Overexpression of the constitutively activated Akt mutant in IL-4-deprived cells correlates with inhibition of c-Jun N-terminal kinase 2 activity. Finally, TS1alphabeta survival is independent of Bcl-2, Bcl-x, or Bax.

Animals↗