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Biomedical subjects

G Bauer

Publications and source records attributed to G Bauer.

At least 73 records · Page 4Linked to original sources
PubMed2001

Central and ambivalent role of hydrogen peroxide during intercellular induction of apoptosis.

TGF-beta pretreated non-transformed fibroblasts induce apoptosis selectively in transformed fibroblasts. This novel potential control step of oncogenesis has been termed intercellular induction of apoptosis. Intercellular signalling depends on target cell-derived extracellular superoxide anions that drive the efficiency of two signalling pathways. These are based on the formation of peroxynitrite through nitric oxide/superoxide anion interaction and on the generation of hypochlorous acid, followed by interaction of hypochlorous acid with superoxide anions, leading to the generation of hydroxyl radicals. This report demonstrates that exogenous hydrogen peroxide causes an overall inhibition of intercellular induction of apoptosis through blunting of the nitric oxide/peroxynitrite signalling pathway. When the HOCl/hydroxyl radical signalling pathway is studied separately (in the presence of an inhibitor of nitric oxide synthesis), exogenous hydrogen peroxide causes an enhancement of apoptosis induction. Based on the dual and adverse effects of hydrogen peroxide on intercellular induction of apoptosis, its steady state concentration seems to be one of the critical parameters that determine efficiency of apoptosis induction in transformed cells.

Apoptosis↗
PubMed2001

Selective apoptosis induction in transformed fibroblasts by B cell lines: involvement of reactive oxygen and nitrogen species.

B cell lines induce apoptosis selectively in transformed fibroblasts. Apoptosis induction is independent of direct cell contact. It seems to be based on superoxide anion production by transformed cells, subsequent spontaneous dismutation to hydrogen peroxide and utilization of the hydrogen peroxide by a peroxidase released by effector cells. The peroxidase then generates hypochlorous acid which may interact with target cell derived superoxide anions, yielding apoptosis-inducing hydroxyl radicals. In parallel, NO released by effector cells may interact with target cell derived superoxide anions and generate the apoptosis inducer peroxynitrite. Therefore, in parallel to their specific functions in humoral immunity, B cells seem to have the potential to contribute to those signalling pathways directed against transformed cells that have been recently shown to be established by TGF-beta treated fibroblasts. This intercellular signalling system seems to represent an evolutionary ancient system for the control of cells that potentially endanger the survival of multicellular organisms.

Acetylcysteine↗
PubMed2001

Chronic epilepsy with complex partial seizures is not always medically intractable--a long-term observational study.

OBJECTIVE: To study the prognosis of patients with complex partial seizures (CPS) with or without simple partial (SPS) and secondarily generalized tonic-clonic seizures (GTCS) and to analyze the factors related to the degree of medical responsiveness. MATERIAL AND METHODS: A total of 266 adult patients with CPS were included in a hospital based observational survey with a follow-up of 2 to 25 years. Clinical characteristics, seizure frequency, electroencephalography (EEG), cerebral computed tomography (CCT) and magnetic resonance imaging (MRI) findings were analyzed. Patients were categorized according to their degree of medical responsiveness into one of three groups: seizure free, improved control (>50% seizure reduction) and poor control. RESULTS: Mean age at follow-up was 44.7 years (SD 14.7, range 19-93). Mean age at seizure onset was 18.1 years (SD 14.7, median 15, range 1-79). Complete seizure control was achieved in 40%, improved seizure control in 36% and poor seizure control in 24%. Patients entered remission after a mean period of 15.7 years (SD 12.6, median 13, range 1-54) of active epilepsy. A third of all seizure-free patients were still in remission 6.1 years (SD 5.3, median 3.5, range 1-18) after discontinuation of antiepileptic drugs (AED). Patients with poor seizure control had a significantly younger age at onset (P<0.01), a higher initial seizure frequency (more than 3 per month) (P<0.01), abnormal neurological examination (P<0.01), and were more often mentally handicapped (P<0.01). Multiple logistic regression analysis revealed a high initial seizure frequency, mental handicap and an abnormal neurological examination as independent risk factors for poor seizure control. A positive family history, a history of febrile convulsions and/or psychosis, an abnormal EEG or MRI was not predictive of poor outcome. CONCLUSIONS: Not all patients with CPS were medically intractable. Seizure remission can be achieved after a long time of active epilepsy. Poor seizure control was associated with a high initial seizure frequency, mental handicap and abnormal neurological examination.

Adult↗
PubMed2001

Simplicity through complexity: immunoblot with recombinant antigens as the new gold standard in Epstein-Barr virus serology.

Immunofluorescence tests have been the gold standard in Epstein-Barr virus (EBV) serology during the past decades. Despite their high quality they cannot resolve significant problems with i) anticellular reactivity of some sera, ii) missing anti-EBNA-1 response in 5% of healthy individuals, and iii) loss of anti-EBNA-1 during immunosuppression. Immunoblots with recombinant EBV antigens (either in the Blot or the Line assay version) allow unequivocal serological diagnosis also in those cases that are problematic for immunofluorescence testing, 1) since due to the use of purified recombinant antigens, anticellular reactivities are no problem, and 2) since a combination of two late markers is tested (p72 and p18). Positive p18-IgG thereby defines those cases of past infections in which p72-IgG (anti-EBNA-1) is missing or has been lost. In nearly all cases, a single IgG test is sufficient for a definitive serological diagnosis. Whenever required, the immunoblot technique allows precise quantitation and avidity determination. The immunoblot with recombinant antigens represents the most sensitive, unequivocal and simple test system available at present, with the highest complexity of information obtained. Therefore, the immunoblot with recombinant antigens should be regarded as the new gold standard in EBV serology.

Antibodies, Viral↗
PubMed2000

Target cell-derived superoxide anions cause efficiency and selectivity of intercellular induction of apoptosis.

Transformed fibroblasts are specifically eliminated by their nontransformed neighbors through intercellular induction of apoptosis. This process depends on the number of nontransformed effector cells and on the local density of transformed target cells. Intercellular signalling is inhibited by SOD (a scavenger of superoxide anions), taurine (a scavenger of HOCl), 4-aminobenzoyl hydrazide (a mechanism-based inhibitor of peroxidase), DMSO (a hydroxyl radical scavenger), and two inhibitors of NO synthase. Therefore, selective apoptosis induction seems to be based on superoxide anion production by transformed cells, their spontaneous dismutation to hydrogen peroxide, and HOCl generation by a novel effector cell-derived peroxidase. HOCl then interacts with target cell-derived superoxide anions to yield hydroxyl radicals. Due to the short diffusion pathway of superoxide anions, hydroxyl radical generation is confined to the intimate vicinity of transformed cells. In parallel, NO derived from effector cells interacts with superoxide anions of target cells to yield the apoptosis inducer peroxynitrite. Reconstitution experiments using transformed or nontransformed cells in conjunction with myeloperoxidase, HOCl, or an NO donor demonstrated that superoxide anions generated extracellularly by transformed cells participate in intercellular signalling and at the same time determine transformed cells as selective targets for intercellular induction of apoptosis.

Animals↗
PubMed2000

Measurement of J/psi and psi(2S) polarization in pp collisions at sqrt[s] = 1.8 TeV.

We have measured the polarization of J/psi and psi(2S) mesons produced in pp collisions at sqrt[s] = 1.8 TeV, using data collected at the Collider Detector at Fermilab during 1992-1995. The polarization of promptly produced J/psi [psi(2S)] mesons is isolated from those produced in B-hadron decay, and measured over the kinematic range 4 [5.5]<P(T)<20 GeV/c and |y|<0.6. For P(T) greater than or approximately equal 12 GeV/c we do not observe significant polarization in the prompt component.

Journal Article↗
PubMed2000

Nanometer-scale resolution of strain and interdiffusion in self-assembled InAs/GaAs quantum dots

Tomographic nanometer-scale images of self-assembled InAs/GaAs quantum dots have been obtained from surface-sensitive x-ray diffraction. Based on the three-dimensional intensity mapping of selected regions in reciprocal space, the method yields the shape of the dots along with the lattice parameter distribution and the vertical interdiffusion profile on a subnanometer scale. The material composition is found to vary continuously from GaAs at the base of the dot to InAs at the top.

Journal Article↗
PubMed2000

Ictal urinary urge indicates seizure onset in the nondominant temporal lobe.

The authors describe six patients with medically refractory temporal lobe epilepsy whose seizures were characterized by an aura of ictal urinary urge. All seizures originated in the nondominant temporal lobe as evidenced from interictal spikes, ictal EEG, and MRI. Ictal SPECT, which was obtained in two patients, showed a hyperperfusion of the insular cortex, indicating a critical role of the insula for the generation of this symptom. Ictal urinary urge represents a new lateralizing sign indicating a seizure onset in the nondominant temporal lobe.

Adolescent↗
PubMed2000

Search for scalar top and scalar bottom quarks in pp collisions at square root s=1.8 TeV.

We have searched for direct pair production of scalar top and scalar bottom quarks in 88 pb-1 of pp collisions at sqrt[s]=1.8 TeV with the CDF detector. We looked for events with a pair of heavy flavor jets and missing energy, consistent with scalar top (bottom) quark decays to a charm (bottom) quark and a neutralino. The numbers of events that pass our selections show no significant deviation from standard model expectations. We compare our results to the next-to-leading order scalar quark production cross sections to exclude regions in scalar quark-neutralino mass parameter space.

Journal Article↗
PubMed2000

Search for a W' boson via the decay mode W'-->munumu in 1.8 TeV pp collisions.

We report the results of a search for a W' boson produced in pp collisions at a center-of-mass energy of 1.8 TeV using a 107 pb-1 data sample recorded by the Collider Detector at Fermilab. We consider the decay channel W'-->&munumu and search for anomalous production of high transverse mass munumu lepton pairs. We observe no excess of events above background and set limits on the rate of W' boson production and decay relative to standard model W boson production and decay using a fit of the transverse mass distribution observed. If we assume standard model strength couplings of the W' boson to quark and lepton pairs, we exclude a W' boson with invariant mass less than 660 GeV/c2 at 95% confidence level.

Journal Article↗
PubMed2000

Tuning of vertical and lateral correlations in self-organized PbSe/Pb1-xEuxTe quantum dot superlattices

The tuning of lateral and vertical correlations in self-organized PbSe/Pb 1-xEu xTe quantum dot superlattices by changes in the spacer thicknesses is demonstrated and shown to be due to finite size effects in the dot-dot interactions. As a consequence, different dot arrangements such as vertically aligned dot columns or fcc stacking are obtained for a single material system without changes in growth conditions. The different dot superstructures are shown to exhibit a different scaling behavior of the lateral versus vertical dot separation, as well as a different evolution of dot sizes and shapes.

Journal Article↗
PubMed2000

[Fatal methadone poisoning of a child].

The substance methadone is used for substitution therapy since the 1960s in the U.S. Mainly because of the endemic spread of HIV-1 infections among intravenous drug abusers methadone was made legally available through medical prescription in Austria in 1987. Legal authorities today also allow the patient to take home the necessary daily consumption for weekends or public holidays. The drug is distributed as a watery solution in tiny bottles, which are fitted with an ordinary screw cap. This kind of distribution may, however, have fatal consequences. This is demonstrated in the following case of accidental poisoning of an infant: A two-year-old girl whose parents were both participating in the substitution scheme was found dead in her bed in Vienna in 1997. Forensic autopsy revealed a methadone concentration in the liver tissue of 640 ng/g. The criminal investigation determined that the girl had opened a bottle of methadone solution and subsequently had taken the drug. Considering the circumstances of this accident, from the medical point of view safety devices for the screw caps of the methadone bottles should be required by law, in order to avoid future accidental poisoning.

Accidents, Home↗
PubMed2000

Suicide of a body packer.

The smuggling of illicit drugs by means of body packing has become a common problem at European airports. Europe is considered to be the fastest growing market for cocaine worldwide, and the air route is the most frequently used method of trafficking cocaine. Smuggling illicit drugs by use of body packing is considered to be a high toxicological hazard because of the risk of leakage or a package bursting. We report about the first case of suicide of a body packer by re-ingesting the content of excreted cocaine packages. The consequence of this case is that the death scene investigation and autopsy assessments in case of a body packer's death should always consider the possibility of re-ingested packages. Detention personnel should be instructed by forensic and criminalistic experts to take preventive measures.

Adult↗
PubMed2000

Intrakines--evidence for a trans-cellular mechanism of action.

Human CXCR4 is the receptor for the CXC chemokine SDF-1alpha and also acts as a coreceptor for T lymphotropic HIV-1 strains. Blocking the surface expression of this receptor via an intrakine approach has recently been shown to efficiently prevent HIV-1 infection of T cells. The CXC-chemokine gene is fused to an endoplasmic reticulum retention signal (KDEL) that retains the newly synthesized chemokine and its receptor within the cell, where both are subsequently degraded. We constructed MoMuLV-based vectors containing the SDF-KDEL construct driven by the "MND" long terminal repeat, using eGFP as a marker gene (MND-SDF-KDEL-IRES-eGFP) and a control vector (MND-X-IRES-eGFP). CEM human T lymphoblastic leukemia cells were transduced with the intrakine vector or the control vector. We detected a marked downregulation of CXCR4 expression in the cells transduced with the intrakine vectors as opposed to the cells transduced with the control vector. However, the eGFP-negative fraction of the cells transduced with the intrakine vector displayed the same CXCR4 downregulation as the eGFP-positive fraction, suggesting an effect in trans. The possibility of this being due to eGFP being silenced while SDF-KDEL was still expressed was excluded by Southern and Northern blot analyses. Upon cultivating the control cells with supernatant of the cells transduced with the intrakine vector, we observed a downregulation of CXCR4 expression on the control cells. Experiments using rhSDF-1alpha showed downregulation by the supernatant to be comparable to that achieved by the exogenous addition of 30 ng/ml SDF-1alpha. To assess the bioactivity of the secreted substance in the supernatant, a chemotaxis assay was performed. The transmigration observed was, once again, within the range of that achieved by the addition of 30 ng/ml SDF-1alpha. We conclude that the intrakine SDF-KDEL, apart from acting within the cell, is also in part secreted and causes the downregulation of the receptor by acting like a secreted chemokine.

Blotting, Northern↗
PubMed2000

Diet in residents of East and West Germany in 1991-1992 as ascertained by a retrospective food frequency questionnaire.

In this study, we compared dietary habits of residents in East (N = 76) and West Germany (N = 266) using results obtained in 1992-1993 from a retrospective semi-quantitative food frequency questionnaire referring to 1991-1992. Nutrient intakes were calculated based on the German Federal Food Code. Univariate and multivariate logistic regression was used to determine whether dietary intakes varied according to residence in East and West Germany. At the food level, East German subjects reported a higher consumption of bread, spreadable fat, and sausage, whereas West German participants reported a higher intake of fruit, vegetables, and pasta and rice. At the macronutrient level, energy intake did not differ significantly between groups, nor did the percent contribution of protein, carbohydrate, fat, and alcohol to total energy intake. East German participants had a lower total water and fibre intake, the latter significant only after adjustment for confounders. At the micro-nutrient level, East German participants had a higher intake of cobalamin, retinol and retinol-equivalents (but not of beta-carotene). There were no differences in the intake of vitamins C, D, and E between groups. Less salt and more potassium, calcium, magnesium and zinc were consumed by West than by East German subjects. Overall, both groups showed disadvantageous dietary patterns. The results are discussed in the context of an overview of other dietary surveys performed in the two parts of Germany before and after reunification. In general our results are consistent with other observations showing that dietary habits in East Germany rapidly approached those in West Germany after reunification, although some residual differences seemed to persist.

Adult↗
PubMed2000

Regulation of proliferation and apoptosis in sporadic and hereditary medullary thyroid carcinomas and their putative precursor lesions.

C-cell hyperplasia (CCH) and medullary thyroid carcinoma (MTC) in patients affected by germline mutations of the RET oncogene represent an exceptional opportunity to study the regulation of proliferation and apoptosis during tumour initiation and progression. In 56 specimens [CCH, n=1; MTC with CCH, n=26; MTC, n=20; lymph-node metastasis (LNM), n=9] from 46 patients [multiple endocrine neoplasia type 2a (MEN2a), n=24; MEN2b, n=2; familiar MTC (FMTC), n=4; sporadic MTC, n-16] and 3 cases of non-neoplastic CCH, proliferation activity (MIB1), the rate of apoptosis [dUTP nick end labelling (TUNEL)] and expression of p53, bcl-2, bcl-x and bax were investigated and compared with clinical data. In MEN-associated CCH and small MTC, bcl-2 was strongly expressed, bcl-x was moderately expressed and bax was only weakly expressed. Advanced tumours and LNM did show a more heterogeneous bcl-2 staining accompanied by an increased bax expression and accelerated proliferation. The rate of apoptosis was extremely low in all investigated tumours. P53 was detectable in three patients with rapidly growing and extensively metastasising MTC. No somatic p53 mutations were found. Hereditary MTC with germline RET mutations at codon 918 (MEN2b) and codon 634 revealed a bias towards a higher proliferation activity at a younger age and are more frequently accompanied by LNM. CCH and MTC are characterised with a preponderance of bcl-2 as a factor blocking the programmed cell death. While MTC, in general, is a slowly growing tumour, a minority of tumours do progress rapidly with high proliferation. The factors leading to an accelerated tumour progression do not seem to take their effect via the regulation of apoptosis. Certain alterations of RET are supposed to have a direct or indirect implication on proliferation and, because of this, an effect on the clinical course.

Adolescent↗
PubMed2000

Metastability of Si1-yCy epilayers under 2 MeV alpha-particle irradiation

In this work we present some recent results concerning the alpha-particles irradiation of Si1-yCy alloy epitaxially grown on silicon. The study of the damage process is interesting because of the extensive use of backscattering technique as a tool of characterisation of this kind of materials and because of the possibility of adding information about the transformations that this metastable material undergoes. We point out that the irradiation damage process causes a change in the material structure different from that due to the thermal treatments. The irradiation damage occurs at a rate much higher than in Si, however it involves only a silicon atom fraction that appears to be proportional to the substitutional carbon content.

Journal Article↗