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Biomedical subjects

P Wagner

Publications and source records attributed to P Wagner.

At least 19 recordsLinked to original sources
PubMed1999

[Ultrasound biomicroscopy in iris lesions].

INTRODUCTION: It is difficult to classify lesions of the iris, especially when they are posterior or in the iridociliary angle of the eye. METHOD: We used an ultrasound biomicroscope (Humphrey, Zeiss, Oberkochen, Germany) with a high-frequency sound head (30 and 50 Hz). This study included all patients with unspecified iris processes who were examined at the University Eye Clinic and Hospital of Ulm between September 1996 and February 1997. Fifteen patients, aged between 9 to 82 years (average age = 48.9 years), were prospectively evaluated. RESULTS: A cyst of the iris or ciliary body causing a tumor of the iris was found in six cases (40%). Seven patients (47%) showed a solid tumor of the iris and two patients (13%) a solid tumor of the ciliary body. CONCLUSION: The ultrasound biomicroscope can be used to assess lesions of the iris caused by a cyst or a solid tumor. The increasing size and depth expansion of a solid tumor may be helpful for differentiating between a malignant or benign process. Up to now it has not been possible to use the ultrasonic reflectivity of the tumor to decide if it is malignant.

Adolescent↗
PubMed1998

[Quality aspects in internal medicine--from anamnesis to meta-analysis].

Quality aspects get more important in internal medicine due to novel technical developments and economic constraints. In spite of an extensive research activity in clinical medicine some research aspects of quality control are new. Among these are investigations about symptoms and complaints as well as risk factors. Too much evidence might also blur the view when the necessary data might already be available from existing studies but conclusions have not been drawn to improve quality of patient care. An instrument to this end is metaanalysis compounding the results of single studies to a more meaningful result. Thus further unnecessary trials can be avoided. Finally quality control is characterized by readiness to self-criticism. Its aim is to avoid mistakes and intends to optimize medical actions whenever possible.

Diagnosis↗
PubMed1998

Regulation of CAK kinase activity by p53.

The growth suppressor p53 is an important key element which controls cell cycle progression in response to cellular stress like DNA damage. Its ability to act as transcriptional activator or repressor links transcription and cell cycle control. Several target genes selectively transactivated by p53 are implicated in growth control, apoptosis and DNA repair. Here we report the interaction of p53 with another important dual player of cell cycle control and transcription, the protein kinase complex CDK7/cyclin H/Mat1 (CDK activating kinase, CAK kinase). This is implicated in the activating phosphorylation of CDK2/cyclin A kinase required to allow cells to proceed through the G1/S transition, and on the other hand, as a component of the basal transcription factor TFIIH found to be necessary for CTD phosphorylation of RNA polymerase II in order to allow elongation of transcription. Based on previous binding studies of p53 with other C-terminal interaction partners of p53 we demonstrate a direct physical interaction of p53 with cyclin H in vitro and in vivo. As a consequence of this interaction we tested the influence of p53 on the kinase activity of CAK kinase for CTD and CDK2 phosphorylation. The addition of wild type p53 to the kinase reactions resulted in a significant downregulation of CDK2 phosphorylation and CTD phosphorylation by the CDK activating kinase. On the other hand addition of a mutant p53His175 failed to downregulate CDK2 and CTD phosphorylation by the CDK activating kinase. In an attempt to support our findings in vivo we measured CAK kinase activity in p21-/- and p53-/- mice embryonal fibroblasts under conditions when p53 gets activated by irradiation. In the case of p21-/- cells this led to a significant reduction of CTD phosphorylation activity of the CDK activating kinase by irradiation of the cells. On the other hand in p53 cells no downregulation of CTD phosphorylation activity of CAK kinase was observed indicating that this kind of negative regulation of CAK kinase activity is exclusively due to a functional p53. These findings imply a direct involvement of p53 in triggering growth arrest by its interaction with the CDK activating kinase complex without the need of cyclin-dependent kinase inhibitors (CKIs) and potentially suggest a new mechanism for p53-dependent apoptosis.

Animals↗
PubMed1998

Light-harvesting complex II in monocomponent and mixed lipid-protein monolayers.

Monomolecular layers at the air-water interface were formed directly with isolated largest light-harvesting pigment-protein complex of Photosystem II (LHC II) or out of egg yolk lecithin (EYL) liposomes containing incorporated LHC II. Pure protein monolayers showed a mean area of 1400 A2 per molecule at the air-water interface. Monolayers were deposited onto glass slides by means of Langmuir-Blodgett (LB) technique. Chlorophyll fluorescence of LHC II-LB and EYL-LHC II-LB films proved energetic coupling of chlorophyll a and b, thus indicating native conformation of LHC II within the monolayers. Scanning force microscopy (SFM) revealed ring-like structures formed in monocomponent protein layers as well as in mixed protein-lipid films. These results suggest that a structural arrangement of LHC II is favoured in a lipid environment but that the protein has itself a strong tendency for structural complex rearrangement in our system.

Chlorophyll↗
PubMed1998

Immobilization strategies for biological scanning probe microscopy.

Biological atomic force microscopy (AFM) is now established as a method for studying the structure and function of biomolecular objects at the solid-liquid interface. Major progress in this field is linked to new developments in instrumentation, a better understanding of tip-sample interactions, and improved sample preparation techniques. In this review, the most common strategies for biomolecular immobilization with respect to biological AFM applications are summarized.

Microscopy, Atomic Force↗
PubMed1998

Herpes simplex virus proteins are damaged following photodynamic inactivation with phthalocyanines.

The photodynamic inactivation of herpes simplex virus type 1 (HSV-1) by two phthalocyanines (Pcs), the cationic dye HOSi-PcOSi(CH3)2(CH2)3N+(CH3)3I-(Pc5) and the amphiphilic dye aluminum dibenzodisulfophthalocyanine hydroxide (AlN2SB2POH), has been compared with that by the anionic dye, Merocyanine 540 (Mc540). Both Pc derivatives demonstrate a remarkable virucidal activity upon light activation even 3 h after the onset of HSV-1 adsorption, while Mc540 is effective for only 30 min after adsorption. Since fusion and virus penetration are promoted by membrane glycoproteins, we have studied the damage to viral proteins following photodynamic treatment (PDT) of HSV-1 and its relation to inactivation. The effect of AlN2SB2POH PDT is assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Major changes are found in the protein profile of PDT-treated HSV-1. A reduced ability of specific antibodies to react with HSV-1 major envelope proteins is detected by employing the Western blot assay. In particular, we demonstrate the related changes of glycoprotein D (gD), a structural protein of the HSV envelope. Since the envelope proteins participate in viral entry into the host cell, these alterations to viral envelope proteins may impair their ability to participate in early events of viral entry, leading to reduced infectivity of HSV-1. In contrast, no significant changes in the proteins' electrophoretic mobility could be seen after PDT with Mc540 or with Pc5. When HSV-1 purified proteins are subjected to combined electrophoretic and electro osmotic forces on cellulose acetate, there is a shift in their cathode mobility, which may indicate changes in the protein mass and protein net charges following AlN2SB2POH photosensitization. There are only minor changes in the virus proteins, assayed as above, when HSV-1 is treated with Pc5.

Animals↗
PubMed1998

An analysis of the brain's transfer properties in schizophrenia: amplitude frequency characteristics and evoked potentials during sleep.

BACKGROUND: Classical analysis of spontaneous sleep electroencephalogram (EEG) in schizophrenia commonly reveals alterations of sleep continuity, number of awakenings, slow-wave sleep (SWS), and REM sleep compared to healthy controls; however, conventional analysis cannot help understand dynamic differences of the sleep EEG during different sleep stages. METHODS: We measured late components of auditory evoked potentials (AEPs) and visual evoked potentials (VEPs) during different sleep stages of 11 schizophrenic inpatients and in a sex- and age-matched control group from scalp positions FZ, CZ, and PZ. According to linear system theory, we then computed the amplitude-frequency characteristic (AFC) from averaged AEPs and VEPs in different sleep stages. These AFCs describe the input-output relation of the system under study, leading to a characterization of the transfer properties of the schizophrenic brain during sleep. RESULTS: Significant differences could be found for the transfer properties during stage II and SWS between schizophrenics and controls. During REM a marked enhancement of theta resonance was seen in schizophrenics. CONCLUSIONS: The results of the present study point to highly different central nervous system transfer properties in schizophrenics and controls. Compared to previous investigations in depression, the results provide additional information for distinguishing schizophrenia and depression in EEG studies.

Adult↗
PubMed1998

Fine mapping and regulation of the association of p53 with p34cdc2.

In vivo p53 is multiply phosphorylated by different protein kinases suggesting a central role for phosphorylation in modulating p53 function. In addition, p53 was found to be associated with two protein kinases, p34cdc2 and protein kinase CK2. Here we report the precise mapping of the interaction sites of p53-p34cdc2 complexes. The p34cdc2 binding site on human p53 maps to one distinct C-terminal site LQIRGRERFE (aa 330-339) close to the corresponding phosphorylation site at serine 315. In order to test whether phosphorylation of p53 might influence the binding of p53 to p34cdc2 phosphorylation mutants of the C-terminus of p53, which mimick permanent phosphorylation, were tested on their ability to bind to p34cdc2 in vitro. Substitution of serine 315 (the p34cdc2 phosphorylation site) with aspartic acid had only little effect on complex formation whereas an exchange of serine 392 (the protein kinase CK2 phosphorylation site) to aspartic acid resulted in a significant reduced relative binding affinity of p53 to p34cdc2. The same result was obtained when the C-terminus of p53 was phosphorylated by purified protein kinase CK2 prior to examination of complex formation. In addition, the specificity of the complex formation has been checked by competition experiments with full length p53 proteins and the influence of cyclin B on complex formation was examined.

Amino Acid Sequence↗
PubMed1998

[Adjuvant whole body acupuncture in depression. A placebo-controlled study with standardized mianserin therapy].

In order to examine the efficacy of whole body acupuncture additionally applied to drug treatment in depression, a single-blind placebo-controlled study with 70 inpatients administered to three different treatment groups has been carried out. All patients were pharmacologically treated with the tetracyclic antidepressant mianserin. The verum group (n = 22) received acupuncture at specific points considered to be effective in the treatment of depression. The placebo group (n = 24) was treated with acupuncture at non-specific locations and the control group (n = 24) received only pharmacological treatment. Acupuncture was applied three times a week over a period of four weeks. Psychopathology was rated by judges blind to verum/placebo conditions twice a week over eight weeks with the CGI, GAS, BRMS and BfS rating scales. Additionally applied acupuncture improved the course of depression more than pharmacological treatment with mianserin did by itself. However, we could not detect any differences between placebo and verum acupuncture.

Acupuncture Therapy↗
PubMed1998

The role of biomineralization in microbiologically influenced corrosion.

Synthetic iron oxides (goethite, alpha-FeO.OH; hematite, Fe2O3; and ferrihydrite, Fe(OH)3) were used as model compounds to simulate the mineralogy of surface films on carbon steel. Dissolution of these oxides exposed to pure cultures of the metal-reducing bacterium, Shewanella putrefaciens, was followed by direct atomic absorption spectroscopy measurement of ferrous iron coupled with microscopic analyses using confocal laser scanning and environmental scanning electron microscopies. During an 8-day exposure the organism colonized mineral surfaces and reduced solid ferric oxides to soluble ferrous ions. Elemental composition, as monitored by energy dispersive x-ray spectroscopy, indicated mineral replacement reactions with both ferrihydrite and goethite as iron reduction occurred. When carbon steel electrodes were exposed to S. putrefaciens, microbiologically influenced corrosion was demonstrated electrochemically and microscopically.

Biodegradation, Environmental↗
PubMed1998

Effects of pulsed high-frequency electromagnetic fields on the neuroendocrine system.

The influence of pulsed high-frequency electromagnetic fields emitted from a circularly polarized antenna on the neuroendocrine system in healthy humans was investigated (900 MHz electromagnetic field, pulsed with 217 Hz, average power density 0.02 mW/cm2). Nocturnal hormone profiles of growth hormone (GH), cortisol, luteinizing hormone (LH) and melatonin were determined under polysomnographic control. An alteration in the hypothalamo-pituitary-adrenal axis activity was found with a slight, transient elevation in the cortisol serum level immediately after onset of field exposure which persisted for 1 h. For GH, LH and melatonin, no significant effects were found under exposure to the field compared to the placebo condition, regarding both total hormone production during the entire night and dynamic characteristics of the secretion pattern. Also the evaluation of the sleep EEG data revealed no significant alterations under field exposure, although there was a trend to an REM suppressive effect. The results indicate that weak high-frequency electromagnetic fields have no effects on nocturnal hormone secretion except for a slight elevation in cortisol production which is transient, pointing to an adaptation of the organism to the stimulus.

Adolescent↗
PubMed1998

Human sleep under the influence of pulsed radiofrequency electromagnetic fields: a polysomnographic study using standardized conditions.

To investigate the influence of radiofrequency electromagnetic fields (EMFs) of cellular phone GSM signals on human sleep electroencephalographic (EEG) pattern, all-night polysomnographies of 24 healthy male subjects were recorded, both with and without exposure to a circular polarized EMF (900 MHz, pulsed with a frequency of 217 Hz, pulse width 577 micros, power flux density 0.2 W/m2. Suppression of rapid eye movement (REM) sleep as well as a sleep-inducing effect under field exposure did not reach statistical significance, so that previous results indicating alterations of these sleep parameters could not be replicated. Spectral power analysis also did not reveal any alterations of the EEG rhythms during EMF exposure. The failure to confirm our previous results might be due to dose-dependent effects of the EMF on the human sleep profile.

Adolescent↗
PubMed1997

Caloric restriction attenuates dityrosine cross-linking of cardiac and skeletal muscle proteins in aging mice.

Oxidative damage, particularly to proteins, has been widely postulated to be a major causative factor in the loss of functional capacity during senescence. The nature of the various mechanisms that may contribute to protein oxidation is only partially understood. In this study, concentrations of two markers for oxidative damage, o,o'-dityrosine and o-tyrosine, were determined using stable isotope dilution gas chromatography-mass spectrometry in four tissues of the mouse, namely heart, skeletal muscle, brain, and liver, during youth (4 months old), adulthood (14 months old), and old (30 months old) age. A comparison was made between mice that had access to unlimited calories with those that were restricted to 60% of the caloric intake of the ad libitum regimen. Caloric restriction of this magnitude extends the average and maximum life span of mice by approximately 40%. In vitro studies demonstrated that o,o'-dityrosine was generated selectively in proteins exposed to tyrosyl radical. o-Tyrosine increased in proteins oxidized with hydroxyl radical, which also resulted in a variable increase in o,o'-dityrosine. In mice fed ad libitum, levels of o,o'-dityrosine increased with age in cardiac and skeletal muscle but not in liver or brain. In contrast, o-tyrosine levels did not rise with age in any of the tissues examined. These results suggest that tyrosyl radical-induced protein oxidation increases selectively with age in skeletal muscle and heart. Caloric restriction prevented the increase in o,o'-dityrosine levels in cardiac and skeletal muscle but did not influence o-tyrosine levels in any of the four tissues. This selective increase in o,o'-dityrosine levels and its prevention by a life-prolonging caloric restriction regimen raise the possibility that oxidation of muscle proteins by tyrosyl radical contributes to the deterioration of cardiac and skeletal muscle function with advancing age.

Aging↗
PubMed1997

Interaction of p53 with the human Rad51 protein.

p53 is thought to function in the maintenance of genomic stability by modulating transcription and interacting with cellular proteins to influence the cell cycle, DNA repair and apoptosis. p53 mutations occur in >50% of human cancers, and cells which lack wild type p53 accumulate karyotypic abnormalities such as amplifications, deletions, inversions and translocations. We propose that p53 hinders these promiscuous recombinational events by interacting with cellular recombination and repair machinery. We recently reported that p53 can directly bind in vivo to human Rad51 (hRad51) protein and in vitro to its bacterial homologue RecA. We used GST-fusion and his-tagged protein systems to further investigate the physical interaction between p53 and hRad51, homologue of the yeast Rad51 protein that is involved in recombination and DNA double strand repair. The hRad51 binds to wild-type p53 and to a lesser extent, point mutants 135Y, 249S and 273H. This binding is not mediated by a DNA or RNA intermediate. Mapping studies using a panel of p53 deletion mutants indicate that hRad51 could bind to two regions of p53; one between amino acids 94 and 160 and a second between 264 and 315. Addition of anti-p53 antibody PAb421 (epitope 372-381 amino acids) inhibited the interaction with hRad51. In contrast, p53 interacts with the region between aa 125 and 220 of hRad51, which is highly conserved among Rad51 related proteins from bacteria to human. In Escherichia coli ecA protein, this region is required for homo-oligomerization, suggesting that p53 might disrupt the interaction between RecA and Rad51 subunits, thus inhibiting biochemical functions of Rad51 like proteins. These data are consistent with the hypothesis that p53 interaction with hRAD51 may influence DNA recombination and repair and that additional modifications of p53 by mutation and protein binding may affect this interaction.

Binding Sites↗
PubMed1997

Reversible, site-specific immobilization of polyarginine-tagged fusion proteins on mica surfaces.

A large variety of genes is expressed as fusion proteins for the purpose of characterization and purification in molecular biology. We have used this strategy to append polyarginine peptides in order to achieve specific binding of the Arg-tag to atomically flat, negatively charged mica surfaces. We show that the model protein, hexaarginine-tagged green fluorescent protein (GFP), binds to mica via its Arg-tag based on ion exchange of naturally occurring potassium cations. Only non-specific binding was observed with the control protein that is free of the Arg-tag. This novel technology will be widely applicable to orient functional proteins on flat surfaces.

Adsorption↗
PubMed1997

Phosphorylation mutants of p53 show differential complex formation with putative dehydrogenase Tms1 of fission yeast.

The yeast tms1 gene was originally identified as a multi-copy suppressor of a lethal growth arrest caused by expression of a tumour mutant cDNA of p53 in fission yeast. The tms1 gene product (Tms1) was found to form stable complexes with p53 in yeast and in vitro; using purified recombinant proteins, the interaction was mapped to the C-terminal region of p53. This part is known to be modified by several protein kinases resulting in a transition of p53 from a latent to an activated state capable of transactivating various cellular genes involved in growth suppression or apoptosis. Since there is evidence for an evolutionary conservation of a Tms1-related protein in mammals, the effect of the phosphorylation status of the C-terminus of p53 on Tms1/p53 complex formation in vitro has been investigated. Whereas mutants changing the cdc2 phosphorylation site at position 315 of human p53 had only little effect on Tms1/p53 complex formation, we found that mutants involving the protein kinase CK2 site at position 392 showed a significantly decreased relative affinity for the Tms1 protein. The same result was obtained by using a C-terminal fragment of p53 which was phosphorylated by purified protein kinase CK2, suggesting that the complex formation of p53 with cellular C-terminal binding proteins like Tms1 impairs regulation by phosphorylation.

Binding Sites↗