Showing papers by "University of Münster published in 1995"

Increased Cortical Representation of the Fingers of the Left Hand in String Players

Abstract: Magnetic source imaging revealed that the cortical representation of the digits of the left hand of string players was larger than that in controls. The effect was smallest for the left thumb, and no such differences were observed for the representations of the right hand digits. The amount of cortical reorganization in the representation of the fingering digits was correlated with the age at which the person had begun to play. These results suggest that the representation of different parts of the body in the primary somatosensory cortex of humans depends on use and changes to conform to the current needs and experiences of the individual.

Phantom-limb pain as a perceptual correlate of cortical reorganization following arm amputation

Abstract: Although phantom-limb pain is a frequent consequence of the amputation of an extremity, little is known about its origin. On the basis of the demonstration of substantial plasticity of the somatosensory cortex after amputation or somatosensory deafferentation in adult monkeys, it has been suggested that cortical reorganization could account for some non-painful phantom-limb phenomena in amputees and that cortical reorganization has an adaptive (that is, pain-preventing) function. Theoretical and empirical work on chronic back pain has revealed a positive relationship between the amount of cortical alteration and the magnitude of pain, so we predicted that cortical reorganization and phantom-limb pain should be positively related. Using non-invasive neuromagnetic imaging techniques to determine cortical reorganization in humans, we report a very strong direct relationship (r = 0.93) between the amount of cortical reorganization and the magnitude of phantom limb pain (but not non-painful phantom phenomena) experienced after arm amputation. These data indicate that phantom-limb pain is related to, and may be a consequence of, plastic changes in primary somatosensory cortex.

Diversity of bacterial polyhydroxyalkanoic acids

Abstract: An overview is provided on the diversity of biosynthetic polyhydroxyalkanoic acids, and all hitherto known constituents of these microbial storage compounds are listed. The occurrence of 91 different hydroxyalkanoic acids reflects the low substrate specificity of polyhydroxyalkanoic acid synthases which are the key enzymes of polyhydroxyalkanoic acid biosynthesis. In addition, the importance of bacterial anabolism and catabolism, which provide the coenzyme A thioesters of the respective hydroxyalkanoic acids as substrates to these PHA synthases, is emphasized.

Crystal structure of a purple acid phosphatase containing a dinuclear Fe(III)-Zn(II) active site.

Abstract: Kidney bean purple acid phosphatase (KBPAP) is an Fe(III)-Zn(II) metalloenzyme resembling the mammalian Fe(III)-Fe(II) purple acid phosphatases. The structure of the homodimeric 111-kilodalton KBPAP was determined at a resolution of 2.9 angstroms. The enzyme contains two domains in each subunit. The active site is located in the carboxyl-terminal domain at the carboxy end of two sandwiched beta alpha beta alpha beta motifs. The two metal ions are 3.1 angstroms apart and bridged monodentately by Asp164. The iron is further coordinated by Tyr167, His325, and Asp135, and the zinc by His286, His323, and Asn201. The active-site structure is consistent with previous proposals regarding the mechanism of phosphate ester hydrolysis involving nucleophilic attack on the phosphate group by an Fe(III)-coordinated hydroxide ion.

Pulmonary aspergillosis: early diagnosis improves survival.

Abstract: Bronchoscopy obtaining bronchoalveolar lavage (BAL) fluid and bronchial secretions (BS) and/or high-resolution computed tomography (CT) of the lungs were performed in 33 patients with pulmonary aspergillosis from 1987 to 1992 The sensitivity of BAL fluid or BS for detecting histologically proven fungal disease was 33 and 50%, respectively, whereas positive serologies were only documented in 8% of the cases CT scans contributed to the early diagnosis of opportunistic fungal pneumonia: characteristic CT signs were found in 16 of 19 episodes The more frequent use of bronchoscopy and CT scans between 1990 and 1992 compared to 1987-1989 for the differential diagnosis of new pulmonary infiltrates resulted in earlier appropriate treatment The average introduction of intravenous (iv) antifungal therapy after the onset of pneumonia was shifted from 12 to 7 days (p < 005) The timely implementation of iv antimycotic therapy had a significant impact on survival Initiation of antifungal treatment later than 10 days after the onset of pneumonia resulted in a mortality of 90%, as opposed to 41% with an earlier start of antimycotics (p < 001) The earlier use of appropriate antifungal therapy in the second treatment period improved survival from 33 to 50% (NS) Bronchoscopy and high-resolution CT scans are mutually complementary diagnostic tools and should be performed as early as possible in the course of pneumonia for patients at high risk for aspergillosis

Fossil arbuscular mycorrhizae from the Early Devonian

Abstract: The 400 million-year-old Rhynie chert has provided a wealth of information not only of early land plants, but also of the fungi that inhabited this paleoecosystem. In this paper we report t...

Scalp topography and analysis of intracranial sources of face-evoked potentials

Abstract: Several reports have described that a positive vertex peak of an evoked potential varied in amplitude and latency specifically when images of faces were the eliciting stimulus. The scalp topography and the possible underlying dipole sources of this peak are the subject of this report. We presented black-and-white photographs of human faces, flowers and leaves to 16 healthy subjects and recorded the evoked brain potentials from 31 scalp electrodes. We found the previously described higher amplitude of the positive vertex peak when faces were the crucial stimulus, but the latency of this peak was the same (180 ms) for all three categories of stimulus. At the posterior temporal electrodes, the face waveforms showed a negative peak at 175 ms, which was only rudimentary in the waveforms elicited by the other stimuli. Since in most previous reports a mastoid reference was used, it is most likely that the previously described latency shift of the positive vertex peak associated with face stimuli was due to the interaction with this posterior temporal peak. The dipole analysis of the possible generators of the recorded potentials suggested the sequential activation of occipital, lateral temporal and mesio-temporal brain structures during the perception of a human face.

Sex determination in dioecious plants Melandrium album and M. rubrum using high-resolution flow cytometry

Abstract: High-resolution flow cytometry was used to analyze nuclear DNA content in dioecious plants Melandrium album and M. rubrum. Very low coefficients of variation (0.53-0.70%) of G0/1 peaks were obtained after the analysis of nuclei isolated by chopping leaf tissues. In both species, females have lower DNA content than males due to sex chromosome heteromorphism. This made it possible to discriminate peaks belonging to female and male nuclei on the same histogram and permitted unambiguous sex identification in both species. The results indicated the possibility of diagnosing sex also in other heterogametic dioecious plants. The assay described here might be interesting in any area where rapid sex identification is required at an early stage of plant development.

Considerations on the structure and biochemistry of bacterial polyhydroxyalkanoic acid inclusions

Abstract: Some mathematical calculations were done that provided information about the structure and biochemistry of polyhydroxyalkanoic acid (PHA) granules and about the amounts of the different constituents that contribute to the PHA granules. The data obtained from these calculations are compared with data from the literature, which show that PHA granules consist not only of the polyester but also of phospholipids and proteins. The latter are referred to as granule-associated proteins, and they are always located at the surface of the PHA granules. A concept is proposed that distinguishes four classes of structurally and functionally different granule-associated proteins: (i) class I comprises the PHA synthases, which catalyze the formation of ester linkages between the constituents; (ii) class II comprises the PHA depolymerases, which are responsible for the intracellular degradation of PHA, (iii) class III comprises a new type of protein, which is referred to as phasins and which has most probably a function analogous to that of oleosins in oilseed plants, and (iv) class IV comprises all other proteins, which have been found to be associated with the granules but do not belong to classes I-III. Particular emphasis is placed on the phasins, which constitute a significant fraction of the total cellular protein. Phasins are assumed to form a close protein layer at the surface of the granules, providing the interface between the hydrophilic cytoplasm and the much more hydrophobic core of the PHA inclusion.

Dimer reconstruction of diamond, Si, and Ge (001) surfaces.

Abstract: Ab initio calculations of structural and electronic properties of the C(001)-(2 \ifmmode\times\else\texttimes\fi{} 1) diamond surface are reported and discussed in direct comparison with Si(001) and Ge(001). Our results strongly favor a symmetric dimer reconstruction of C(001)-(2 \ifmmode\times\else\texttimes\fi{} 1) as opposed to an asymmetric dimer reconstruction of Si and Ge (001). The physical origin and quantitative nature of the dimer reconstructions are investigated systematically, and it is shown by analyzing chemical trends why Si(001) is the most subtle case for an unequivocal surface structure determination.

Properties of intrinsic point defects in silicon determined by zinc diffusion experiments under nonequilibrium conditions.

Abstract: The present paper deals with self- and foreign-atom diffusion processes in Si. We focus on the foreign-atom Zn whose diffusion behavior is shown to be influenced by intrinsic point defects like Si self-interstitials (I) and vacancies (V). Diffusion experiments with Zn in dislocation-free Si were carried out between 1208 and 870 \ifmmode^\circ\else\textdegree\fi{}C applying a special method to perform isothermal diffusion anneals as short as a few seconds. Concentration-depth profiles measured with the help of spreading-resistance analysis are completely described by simultaneous diffusion via the kickout and dissociative mechanism. The evolution of Zn diffusion with time is characterized by short-, intermediate-, and long-time diffusion regimes. Profiles belonging to the long-time regime are suitable to extract transport capacities of intrinsic defects given by the product of thermal equilibrium concentration and diffusion coefficient. Zn profiles after intermediate diffusion times are shown to be sensitive to the prevailing thermal equilibrium concentration of Si self-interstitials. Results are presented for the thermal equilibrium concentrations of self-interstitials and vacancies as well as their transport properties. From the temperature dependence of these quantities the formation and migration enthalpy of I and V are obtained. These data are compared to previous experimental results as well as theoretical calculations.

Update on treatment of varicocele: counselling as effective as occlusion of the vena spermatica.

Abstract: This prospective randomized study was performed in order to investigate the effects of interventive treatment or counselling on pregnancy rates in infertile couples in whose male partners a varicocele was diagnosed. The present report extends a previous study using the same design. A total of 125 couples were included in the current study while the previous report comprised 95 couples. Couples fulfilling the inclusion criteria were allocated randomly either to interventive treatment (surgical ligation or angiographic embolization of the spermatic vein) (n = 62) or to counselling as the sole treatment (n = 63). Couples were followed over the subsequent 12 months and seen at 3-monthly intervals. At the end of the 12 month period pregnancy rates, as the main outcome measure, were 29% in the group given interventive treatment and 25.4% in the counselled group and were not significantly different. The only significant difference found, regardless of treatment modality, was the wives' age at admittance: the 34 wives achieving a pregnancy were 28.8 +/- 0.6 years (mean +/- SE) old while the 91 non-pregnant wives were 31.2 +/- 0.3 years old (P < 0.05). The study suggests that regular counselling of the infertile couples is as effective as interventive treatment of varicoceles in achieving pregnancies.

Association of variables of coagulation, fibrinolysis and acute-phase with atherosclerosis in coronary and peripheral arteries and those arteries supplying the brain.

Abstract: We investigated the vessel status of coronary and peripheral arteries and those arteries supplying the brain in 929 consecutive male patients admitted to a coronary rehabilitation unit. The severity of coronary atherosclerosis was scored using coronary angiography. Changes in extracranial brain vessels and manifest cerebrovascular disease (CVD) were determined by B-mode ultrasound and Doppler examination. Peripheral arterial disease (PAD) was diagnosed using base-line and stress oscillography. We assessed variables of coagulation, fibrinolysis, and the acute phase response. There was a significant increase in plasma fibrinogen, plasminogen, d-dimer and C-reactive protein (CRP) with increasing severity of coronary heart disease. Compared to men with unaffected arteries, men with 3 diseased coronary arteries had 58% greater d-dimer concentrations. Patients with CVD and PAD, respectively, also had significantly higher fibrinogen, d-dimer and CRP concentrations. We did not find an association between plasminogen activator inhibitor activity and the severity of coronary atherosclerosis. In conclusion, plasma fibrinogen, d-dimer and CRP concentrations were significantly related to atherosclerosis in the coronary, peripheral and extracranial brain arteries.

Identification of male germ cells undergoing apoptosis in adult rats.

Abstract: The possible role of apoptosis in spontaneous or induced germ cell death was investigated by treating adult male rats with either a GnRH antagonist (112.5 micrograms kg-1 day-1 for 14 days) or methoxyacetic acid (650 micrograms kg-1; single dose) or sham-treated with either of the vehicles (n = 3 per group). The antagonist virtually abolished gonadotrophin secretion, while methoxyacetic acid reduced serum testosterone concentrations and slightly increased those of FSH (neither significantly). Bands of low molecular mass characteristic of apoptotically degraded DNA were detected by electrophoresis in both treatment groups but not in the controls. Sectioned, Carnoy-fixed testes were screened for degenerating cells with periodic acid-Schiff's base and haemalaun or examined for apoptotic cells using a modified in situ end-labelling procedure. Periodic acid-Schiff's-stained dying cells were found in low numbers in control animals with a distribution and frequency that matched that of apoptotic cells. Degenerating germ cells identified by histology were present at certain stages of spermatogenesis after 2 weeks of antagonist treatment. A comparison of their distribution with that of end-labelled cells identified the cell death as apoptotic. Methoxyacetic acid caused a massive depletion of spermatocytes at stages IX-II, which was also found to be apoptotic. It is concluded that spontaneous germ cell death in adult rats is apoptotic and that both gonadotrophin ablation and administration of methoxyacetic acid can cause apoptosis in the germ cells of adult male rats, but via different routes.

A point mutation in the tyrosine hydroxylase gene associated with Segawa's syndrome.

Abstract: We have examined the molecular basis of Segawa's syndrome in six families with seven affected children. In one family two siblings with this disease carried a point mutation in exon 11 of the tyrosine hydroxylase gene, resulting in an amino acid exchange of Gln381 to Lys381. These results suggest that a change in tyrosine hydroxylase causes this form of Segawa's syndrome.

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) of membrane proteins and non-covalent complexes

Abstract: Matrix-assisted laser desorption/ionization (MALDI) mass spectra and methods to improve their quality are reported for three hydrophobic, membrane-bound proteins: porin from Escherichia coli, bacteriorhodopsin from Halobacterium salinarium and cholesterolesterase from Pseudomonas fluorescens. Several commonly used UV and IR matrices have been tested. In addition, the susceptibility of MALDI mass spectrometry to various neutral and ionic detergents, known usually to degrade the quality of MALDI mass spectra, has been tested systematically. For porin, consisting of three identical non-covalently bound subunits, a new sample preparation is reported, resulting in the desorption of the intact quaternary protein structure. This leads to a better understanding of the way a given analyte is embedded into the host matrix crystals.

Efficient scheme for GW quasiparticle band-structure calculations with applications to bulk Si and to the Si(001)-(2×1) surface

Abstract: We report an efficient scheme for evaluating the quasiparticle corrections to local-density-approximation (LDA) band structures within the GW approximation. In this scheme, the GW self-energy corrections are evaluated in a sufficiently flexible Gaussian orbital basis set instead of using plane-wave Fourier representations of the relevant two-point functions. It turns out that this set has to include orbitals up to f-type symmetry, when in the LDA calculations Gaussian orbitals up to d-type symmetry are needed for convergence. For bulk Si, both schemes yield virtually identical quasiparticle band structures and the demand on computer time is roughly the same. For the Si(001)-(2\ifmmode\times\else\texttimes\fi{}1) surface, the GW Gaussian orbital scheme is a factor of 5 faster. In our calculations for Si(001)-(2\ifmmode\times\else\texttimes\fi{}1) the dynamic dielectric matrix is obtained by applying a plasmon-pole approximation. The static dielectric matrix of the Si(001) surface is fully calculated within the random phase approximation (RPA). In addition, we have performed quasiparticle surface band-structure calculations employing two model dielectric matrices. Our respective results are compared with those obtained employing the full RPA dielectric matrix as well as with results of previous calculations by other authors which were based on model dielectric matrices.

Evoked and induced gamma-band activity of the human cortex.

Abstract: The evoked gamma-band activity is an event related rhythmic response which persists within the first 100 ms after the stimulus onset. It shows spectral peaks between 30 and 40 Hz in the auditory, between 45 and 55 Hz in the somatosensory and between 100 and 110 Hz in the visual system. After separation of the wide-band activity in slow and gamma-band activity, a moving single equivalent current dipole model accounts for each activity almost completely. The induced gamma-band activity is not phase-locked to the stimulus or it is strongly gittering and thus it cannot be extracted in time domain. In this case we are using signal analysis methods in frequency domain. The evaluation of the induced brain gamma-band activity around 30 Hz shows differences to word and nonword stimuli. It was supposed that the induced gamma-band activity represents the synchronized activity of Hebbian cell assemblies correlated to words.

Hyperhomocysteinemia and the risk for vascular disease in hemodialysis patients.

Abstract: The objective of this study was to examine if hyperhomocysteinemia is associated with occlusive vascular disease in hemodialysis patients. The study design included risk factor analysis and determination of serum homocysteine in hemodialysis patients. Fifty chronic uremic patients on regular hemodialysis treatment were studied. Twenty-four patients had coronary, cerebral, or peripheral signs of occlusive vascular disease. Cerebral vascular disease was diagnosed by computed tomography, arterial angiography, or Doppler sonography of the carotid and vertebral arteries. Coronary vascular disease was diagnosed by documented history of myocardial infarction or by coronary angiography. The diagnosis of peripheral vascular disease was established by angiography of the lower limb arteries. In all control patients, Doppler sonography of the carotid, vertebral, and lower limb arteries and thallium-201 exercise imaging were without pathologic results. Measurements included blood pressure, body mass index, smoking behavior, serum homocysteine (measured by gas chromatography/mass spectrometry), serum total, low-density lipoprotein, and high-density lipoprotein cholesterol, lipoprotein (a), triglycerides, and plasma fibrinogen. In a stepwise multiple logistic regression analysis, high serum homocysteine was significantly associated with occlusive arterial disease (R = 0.23; P = 0.031). Furthermore, hypertension (R = 0.18; P = 0.058), but not serum total, low-density lipoprotein, and high-density lipoprotein cholesterol, lipoprotein (a), triglycerides, diabetes mellitus, body mass index, plasma fibrinogen, and smoking behavior, was significantly associated with atherosclerosis. Our results support the hypothesis that hyperhomocysteinemia is an independent risk factor for vascular disease in hemodialysis patients.