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Thomas Berger

Publications and source records attributed to Thomas Berger.

At least 19 recordsLinked to original sources
PubMed2005

Charge trapping and photoadsorption of O2 on dehydroxylated TiO2 nanocrystals--an electron paramagnetic resonance study.

The interaction of photogenerated charges with molecular oxygen was investigated on TiO2 nanocrystals by means of paramagnetic resonance (EPR) spectroscopy. Compared to photoactivation experiments in vacuum at P < 10(-6) mbar and T = 140 K, the presence of O2 enhances the concentration of persistently trapped electron and hole centres--by a factor of ten--due to the formation of adsorbed O2- species. The photoadsorption of oxygen was also tracked quantitatively by pressure measurements, and the number of trapped charges, hole centres and O2- was found to correspond to ten electron-hole pairs per TiO2 nanocrystal. Conversely, in experiments at P < 10(-6) mbar with one trapped electron-hole pair per particle, charge separation is not persistent and completely reversible with respect to temperature. Heating to 298 K causes the total annihilation of photogenerated and trapped charges.

Journal Article↗
PubMed2005

Chemistry at corners and edges: generation and adsorption of H atoms on the surface of MgO nanocubes.

We used UV light to generate site-selective O- hole centers at three-coordinated corner oxygen sites on MgO nanocubes. These highly reactive O- radicals split H2 homolytically and, in the course of this reaction, become hydroxylated and produce hydrogen atoms. The hydrogen atoms adsorb predominantly at cube edges and dissociate into surface-trapped electrons and protons. We propose that the experimentally observed (H+)(e-) centers are formed adjacent to the hydroxyl groups generated in the homolytic splitting process and can be defined as (H+)3C...(e-)(H+)NC centers where 3C and NC refer to the coordination numbers of the corresponding hydroxylated oxygen sites. Our ab initio embedded cluster calculations reveal that the electronic properties of (H+)3C...(e-)(H+)4C centers situated along MgO nanocube edges are consistent with both the electron-paramagnetic-resonance signal parameters and the reported optical-absorption properties. The transformation of corner O- centers into the (H+)3C...(e-)(H+)NC-type centers prevents their recombination with electronic surface centers and, hence, significantly alters the electronic structure of MgO nanocubes by introducing shallow electron traps.

Journal Article↗
PubMed2005

Daytime sleepiness is not increased in mild to moderate multiple sclerosis: a pupillographic study.

BACKGROUND: Daytime sleepiness has been described in multiple sclerosis (MS); a combination of MS and narcolepsy has also been observed in a few case reports. In this study, we investigated daytime sleepiness in a general sample of MS patients compared to healthy controls with the pupillographic sleepiness test (PST) and the Epworth and Stanford sleepiness scales (ESS, SSS). METHODS: A PST was performed in consecutive MS patients and controls. Additionally, a questionnaire including the ESS and the SSS was applied. RESULTS: Sixty-one MS patients (29 men and 32 women, age 34.5+/-8.3 years, mean disease duration 7.4+/-6.6 years, expanded disability status scale (EDSS) 1.7+/-1.2 (mean +/- sd)) and 42 age-matched controls (13 men and 29 women, age 36.9+/-12.9 years) participated in this study. In the MS group, the pupillary unrest index (PUI) was 5.0+/-2.0, the ESS 7.4+/-3.5 and the SSS 2.4+/-1.2, whereas in the control group, the PUI was 4.7+/-1.8, the ESS 8.4+/-4.0 and the SSS 2.4+/-1.2 (mean +/- sd). These differences were not significant. No correlation was found between PUI and the ESS or the SSS. Furthermore, no correlation was found between EDSS and sleepiness measured by PUI, ESS and SSS. CONCLUSION: In a general sample of MS patients with mild to moderate disease, there was no evidence for overall increased daytime sleepiness compared to healthy controls.

Adult↗
PubMed2005

The effect of nabilone on neuropsychological functions related to driving ability: an extended case series.

The primary goal of this prospective extended case series was to obtain the first data about the potential influence of nabilone intake on driving ability related neuropsychological functions. Six patients were investigated within a placebo controlled, double-blind crossover study of this synthetic cannabinoid (2 mg/day) in patients with multiple sclerosis and spasticity associated pain. Five neuropsychological functions (reaction time, working memory, divided attention, psychomotor speed and mental flexibility) were assessed. No indication was found of a deterioration of any of the five investigated neuropsychological functions during the 4-week treatment period with nabilone.

Adult↗
PubMed2005

Multiple disseminated large-cell acanthomas of the skin associated with human papillomavirus type 6.

Cutaneous acanthomas encompass many clinically distinct types. We describe a patient with multiple nodules on the skin of the upper limbs which were histologically diagnosed as large-cell acanthomas. Further analysis revealed, surprisingly, the presence of human papillomavirus (HPV) type 6 within these lesions. HPV type 6 should therefore be considered an important cofactor in the pathogenesis of large-cell acanthomas.

Acanthoma↗
PubMed2005

Plasma levels of soluble adhesion molecules sPECAM-1, sP-selectin and sE-selectin are associated with relapsing-remitting disease course of multiple sclerosis.

Adhesion molecule mediated leukocyte migration into the central nervous system is considered to be a critical step in the pathogenesis of multiple sclerosis (MS). We measured plasma levels of the soluble adhesion molecules sPECAM-1, sP-selectin and sE-selectin in 166 MS patients and in 36 healthy blood donors with ELISA. sPECAM-1, sP-selectin and sE-selectin plasma concentrations showed a significant increase in the relapsing-remitting disease course of MS and were elevated during relapse. These findings indicate that sPECAM-1, sP-selectin and sE-selectin might be implemented as paraclinical markers of disease activity in MS with restriction to the clinical course of the disease.

Adult↗
PubMed2005

Effects of cardiac resynchronization therapy on ventricular repolarization in patients with congestive heart failure.

INTRODUCTION: Biventricular pacing has been shown to improve the clinical status of patients with congestive heart failure, but little is known about its influence on ventricular repolarization. The aim of our study was to evaluate the effect of biventricular pacing on ECG markers of ventricular repolarization in patients with congestive heart failure. METHODS AND RESULTS: Twenty-five patients with congestive heart failure, sinus rhythm (SR), and complete LBBB (6 females; age 61 +/- 8 years; NYHA class II-III; echocardiographic ejection fraction 21 +/- 5%; QRS > or = 130 ms) underwent permanent biventricular DDDR pacemaker implantation. A high-resolution 65-lead body-surface ECG recording was performed at baseline and during right-, left-, and biventricular pacing, and the total 65-lead root mean square curve of the QRST complex and the interlead QT dispersion were assessed. The QRS duration was increased during right (RV)- and left ventricular (LV) pacing (127 +/- 26% and 117 +/- 40%; P < 0.05), as compared to SR (100%) and biventricular pacing (93 +/- 16%; ns). The QTc interval was increased during RV and LV pacing (112 +/- 12% and 114 +/- 14%; P < 0.05) as compared to SR (100%) or biventricular pacing (99 +/- 12%). There was no effect on JT interval during all pacing modes. The T(peak-end) interval was increased during right (120 +/- 34%; P < 0.01) and LV pacing (113 +/- 29%; P < 0.05) but decreased during biventricular pacing (81 +/- 19%; P < 0.01). A similar effect was found for the T(peak-end) integral and the T(peak) amplitude. QT dispersion was increased during right ventricular (129 +/- 16 ms; P < 0.05) and decreased during biventricular pacing (90 +/- 12 ms; P < 0.01), as compared to SR (114 +/- 22 ms). CONCLUSIONS: Using a high-resolution surface ECG, biventricular pacing resulted in a significant reduction of ECG markers of ventricular dispersion of repolarization.

Aged↗
PubMed2005

Homogeneous distribution of large-conductance calcium-dependent potassium channels on soma and apical dendrite of rat neocortical layer 5 pyramidal neurons.

Voltage-gated conductances on dendrites of layer 5 pyramidal neurons participate in synaptic integration and output generation. We investigated the properties and the distribution of large-conductance calcium-activated potassium channels (BK channels) in this cell type using excised patches in acute slice preparations of rat somatosensory cortex. BK channels were characterized by their large conductance and sensitivity to the specific blockers paxilline and iberiotoxin. BK channels showed a pronounced calcium-dependence with a maximal opening probability of 0.69 at 10 microm and 0.42 at 3 microm free calcium. Their opening probability and transition time constants between open and closed states are voltage-dependent. At depolarized potentials, BK channel gating is described by two open and one closed states. Depolarization increases the opening probability due to a prolongation of the open time constant and a shortening of the closed time constant. Calcium-dependence and biophysical properties of somatic and dendritic BK channels were identical. The presence of BK channels on the apical dendrite of layer 5 pyramidal neurons was shown by immunofluorescence. Patch-clamp recordings revealed a homogeneous density of BK channels on the soma and along the apical dendrite up to 850 microm with a mean density of 1.9 channels per microm(2). BK channels are expressed either isolated or in clusters containing up to four channels. This study shows the presence of BK channels on dendrites. Their activation might modulate the shape of sodium and calcium action potentials, their propagation along the dendrite, and thereby the electrotonic distance between the somatic and dendritic action potential initiation zones.

Animals↗
PubMed2004

Spectroscopic properties of trapped electrons on the surface of MgO nanoparticles.

To characterise electron-trapping sites on the surface of MgO nanoparticles, surface colour centres were generated using UV light in conjunction with selected hydrogen-based electron sources. Four different colour-centre species, including the characteristic (e-)(H+) or F(S)+(H) centre, were identified due to the distinct shape of the respective electron paramagnetic resonance (EPR) signals. The analysis of the EPR saturation behaviour down to microwave powers of 5 x 10(-3) mW reveals an enhanced spin-relaxation probability of the (e-)(H+) centre compared to all other F(S)+ centres that do not exhibit significant magnetic interactions with hydroxylic protons. Beside the dipolar magnetic interaction in the (e-)(H+) centre observed by EPR, the electronic interaction between the unpaired electron and the proton of a closely spaced OH group produces a redshift of the OH stretching band by about 70 to 170 cm(-1), as observed by infrared spectroscopy. EPR and IR spectroscopic data obtained after the selective address of individual reaction channels for surface colour-centre formation point to the fact that (e-)(H+) centres are formed by trapping electrons from H atoms. Consequently, the underlying surface defect does not belong to the sites of the MgO surface, which chemisorb hydrogen via a heterolytic splitting process.

Electron Spin Resonance Spectroscopy↗
PubMed2004

Synthesis of analogue structures of the p-quinone methide moiety of kendomycin.

[reaction: see text] The synthesis of two model p-quinone methide ring systems of the antibiotic and antiosteoporotic compound kendomycin is reported. Two approaches were examined in detail, and the two-step (i) demethylation and (ii) DMDO oxidation were found to be reliable and generally applicable. Additionally, it was found that oxidation of a benzofuran by NaIO(4) on silica produced a long-lived semiquinone radical.

Catalysis↗
PubMed2004

Sternal osteomyelitis complicating percutaneous coronary artery stenting.

Hematogenous sternal osteomyelitis is a rare infection that has been associated with i.v drug abuse and blunt thoracic trauma, but iatrogenic infections have also been described following resuscitation and in conjunction with hemodialysis catheters. Staphylococcus aureus is the most common causative organism. Stenting is the preferred treatment for isolated stenosis of the coronary artery and is associated with a low complication rate and high patency rate. Such intravascular procedures are rarely complicated by infections. A 72-year-old man developed hematogenous sternal osteomyelitis following coronary artery stenting. Radiological diagnosis was made using CT scan and MRI, and blood cultures and aspiration fluid from the infected soft tissue were positive for S. aureus. Initial therapy consisted of i.v. second-generation cephalosporin followed by oral cephalexin and later linezolid. Prolonged antibiotic therapy without surgical intervention was successful in controlling this rare complication. The patient was well at the one-year follow up, with patent stent and no signs for recurrent osteomyelitis. Although transcutaneous stenting is a widely accepted strategy for treating stenosed arteries, this case highlights the possibility of hazardous infectious complications associated with such procedures.

Aged↗
PubMed2004

Immunoglobulin-like transcripts ILT2, ILT3 and ILT7 are expressed by human dendritic cells and down-regulated following activation.

Immunoglobulin-like transcripts (ILT) represent novel immunoglobulin superfamily receptors that are expressed in myeloid, lymphoid and dendritic cells (DC). Here, we studied by gene expression profiling with DNA microarrays ILT expression in different DC subsets, including plasmacytoid DC (PDC), monocyte-derived DC (Mo-DC) and DC obtained by in vitro differentiation from CD34(+) progenitor cells, and DC activated in the presence of different activating agents. ILT2 and ILT3 were expressed in PDC, Mo-DC and DC obtained from CD34(+) cells. ILT7 mRNA was present in PDC, but absent in Mo-DC and DC obtained from CD34(+) cells, indicating that ILT7 mRNA expression seems to be a marker for PDC. CpG-DNA and inflammatory stimuli, such as TNF alpha, prostaglandin E2 (PGE2) and soluble CD40 ligand (sCD40L), and different combinations thereof are frequently employed for DC activation. Here, we demonstrate that ILT2 and ILT3 expression is down-regulated following DC activation by CpG-DNA and inflammatory stimuli at both mRNA and protein levels. Thus, activation of human DC with such stimuli involves down-regulation of inhibitory ILT2 and ILT3 receptors, and this could represent a novel mechanism contributing to DC activation.

Antigens, CD↗
PubMed2004

Computer-based technological applications in psychotherapy training.

Despite obvious and documented advantages of technological applications in education, psychotherapy training based on information technology is either still rare or limited to technical innovations such as videotape recordings. This article outlines opportunities new computer-based learning technology create for psychotherapy training. First, approaches that include computer-mediated communication between trainees and teachers/supervisors are presented. Then, computer-based learning technology for self-study purposes is discussed in the context of educational approaches to learning. Computer-based tools that have been developed and evaluated in the context of psychotherapy training are described. Evaluations of the tools are discussed.

Computer-Assisted Instruction↗
PubMed2004

HMG-CoA reductase inhibitors suppress maturation of human dendritic cells: new implications for atherosclerosis.

The beneficial effects of statins in atherosclerosis have been partly attributed to their immunomodulating functions. Dendritic cells (DC), which are "professional" antigen-presenting cells, were recently detected in atherosclerotic plaques. It is assumed that DC play a critical role in the immunological processes related to atherosclerosis. Thus, we investigated the effects of statins on maturation and antigen-presenting function of DC. Human monocyte-derived DC were incubated with simvastatin or atorvastatin (1-10microM) for different periods (1-48h), and were subsequently stimulated with a cytokine cocktail (1.25ng/ml TNF-alpha, 1ng/ml Il-1beta, and 0.5microg/ml prostaglandin E(2)) to induce maturation. In contrast to untreated DC, statin-preincubated DC exhibited an immature phenotype and a significantly lower expression of the maturation-associated markers CD83, CD40, CD86, HLA-DR, and CCR7. The inhibitory statin effect was completely reversed by mevalonate or geranylgeranyl pyrophosphate. In addition, preincubation with statins significantly reduced the ability of cytokine-stimulated DC to induce T cell proliferation. In the present study, we have shown that statins inhibit the maturation and antigen-presenting function of human myeloid dendritic cells, thus maybe contributing to their beneficial effects in atherosclerosis. Therefore, the use of statins as immunomodulators might also provide a new therapeutic approach to other immunological disorders.

Adjuvants, Immunologic↗
PubMed2004

Recovery from and consequences of severe iatrogenic lymphopenia (induced to treat autoimmune diseases).

To ascertain the consequences of severe leukopenia and the tempo of recovery, we studied the immunity of 56 adult patients treated for multiple sclerosis or systemic sclerosis with autologous CD34 cell transplantation using extremely lymphoablative conditioning. NK cell, monocyte, and neutrophil counts recovered to normal by 1 month; dendritic cell and B cell counts by 6 months; and T cell counts by 2 years posttransplant, although CD4 T cell counts remained borderline low. Initial peripheral expansion was robust for CD8 T cells but only moderate for CD4 T cells. Subsequent thymopoiesis was slow, especially in older patients. Importantly, levels of antibodies, including autoantibodies, did not drop substantially. Infections were frequent during the first 6 months, when all immune cells were deficient, and surprisingly rare (0.21 per patient year) at 7-24 months posttransplant, when only T cells (particularly CD4 T cells) were deficient. In conclusion, peripheral expansion of CD8 but not CD4 T cells is highly efficient. Prolonged CD4 lymphopenia is associated with relatively few infections, possibly due to antibodies produced by persisting pretransplant plasma cells.

Adult↗
PubMed2004

[Coherence in case conceptualizations--concept and evaluation of a computer supported training program].

In several domains of professional expertise it has been found that experts' action is based on a deep understanding of the problems they act on, and also the outcome of psychotherapies depends on the quality of the view which therapists develop of their patients. Unfortunately there are signs that the quality of case conceptualizations is suboptimal in many instances, even after special (traditional) training. This was reason for developing an innovative program for the training of partial abilities required to develop differentiated case conceptualizations. In the program specifically the graphical representation of the relations a therapist sees is supported by a computer program. The program gives fast feedback on several formal aspects of the case conceptualization, among others its coherence, and supports its further elaboration. An evaluation of the program in a controlled trial with a total of 34 participating therapists showed a good acceptance and significant effects in several criteria for the quality of the representation of the analyzed cases.

Computer-Assisted Instruction↗