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Biomedical subjects

D Lehmann

Publications and source records attributed to D Lehmann.

At least 19 recordsLinked to original sources
PubMed2006

Stapled transanal rectal resection under laparoscopic surveillance for rectocele and concomitant enterocele.

PURPOSE: Stapled transanal rectal resection recently became a recommended surgical procedure for obstructed defecation syndrome. One problem when using a transanal stapling device for rectal surgery is the potential threat to structures located in front of the anterior rectal wall. We decided to perform a combined procedure of transanal rectal resection with a simultaneous laparoscopy for patients with obstructed defecation syndrome and an enterocele. METHODS: Between November 2002 and May 2005 a total of 41 patients were treated surgically for obstructed defecation syndrome. Four patients with concomitant enterocele underwent stapled transanal rectal resection under laparoscopic surveillance. Before surgery all patients underwent preoperative assessment, including clinical examination, colonoscopy, conventional video defecography, dynamic magnetic resonance imaging defecography, gynecology examinations, and psychologic evaluation. RESULTS: The mean operative time was 50 (+/-16.5) minutes for the conventional stapled transanal rectal resection and 67 (+/-14.1) minutes for combined laparoscopy and stapled transanal rectal resection (P < 0.01). Three major complications were observed: two had bleeding in the staple line (one from each group) and one had a late abscess in the staple line. CONCLUSIONS: The combination of the stapled transanal rectal resection procedure and laparoscopy provides the opportunity to perform transanal rectal resection without the threat of intra-abdominal lesions caused by enterocele.

Digestive System Surgical Procedures↗
PubMed2005

Rate of progression of cognitive decline in Alzheimer's disease: effect of butyrylcholinesterase K gene variation.

OBJECTIVE: To determine whether individuals with Alzheimer's disease (AD) and the K variant allele of butyrylcholinesterase have a slower rate of cognitive decline than those without the K variant allele of butyrylcholinesterase. METHOD: The cognitive status of 339 community based subjects with AD was assessed with the Mini Mental State Examination at baseline and yearly over a three year follow up period. The rates of cognitive decline of subjects with and without the K variant allele were compared. RESULT: Presence of the K allele was associated with a slower average rate of cognitive decline in subjects with severe AD. CONCLUSIONS: This finding is consistent with the suggestion that the K variant of butyrylcholinesterase has an important role in disease progression in AD, and this may have implications for treatment.

Aged↗
PubMed2004

Characterization of BoHV-1 gE envelope glycoprotein mimotopes obtained by phage display.

A phage-displayed peptide library was screened using four mAbs directed against bovine herpesvirus 1 (BoHV-1) gE glycoprotein to identify peptides mimicking this glycoprotein. The selected mimotopes allowed us to characterize the epitopes corresponding to the mAbs as continuous and proteinic and to consider using these peptides in further studies. One epitope has been clearly located at the C-terminus of the protein (amino-acids 561-569). The three other mAbs enabled us to stress the immunogenic relevance of the proline-rich motifs of gE. Selected peptides showed no clear sequence identity with gE, but there is a clear link between gE proline-rich regions and the amino-acid composition of the mimotopes. The proline-rich motifs of gE are potentially located in flanking regions involved in the gE/gl glycoprotein complex formation. N-terminal fusion to pill or pVIII filamentous phage protein, C-terminal fusion to the T7 phage capsid protein, biotinylated synthetic peptides and insertion between the non-cleaved CX leader sequence and the C-terminal part of Caulobacter crescentus RsaA protein have been tested in order to increase the valency of a model peptide. We have diverted the C. crescentus expression system and proven its usefulness using the RsaA protein as a scaffold displaying the peptides of interest. Comparison between these different display systems in an indirect ELISA, indicates that the C. crescentus expression and the T7 phage display systems have some major advantages.

Amino Acid Sequence↗
PubMed2004

Subsecond changes of global brain state in illusory multistable motion perception.

This study explored transient changes in EEG microstates and spatial Omega complexity associated with changes in multistable perception. 21-channel EEG was recorded from 13 healthy subjects viewing an alternating dot pattern that induced illusory motion with ambiguous direction. Baseline epochs with stable motion direction were compared to epochs immediately preceding stimuli that were perceived with changed motion direction ('reference stimuli'). About 750 ms before reference stimuli, Omega complexity decreased as compared to baseline, and two of four classes of EEG microstates changed their probability of occurrence. About 300 ms before reference stimuli, Omega complexity increased and the previous deviations of EEG microstates were reversed. Given earlier results on Omega complexity and microstates, these sub-second EEG changes might parallel longer-lasting fluctuations in vigilance. Assumedly, the discontinuities of illusory motion thus occur during sub-second dips in arousal, and the following reconstruction of the illusion coincides with a state of relative over-arousal.

Adult↗
PubMed2004

Transgenic Russian wildrye (Psathyrostachys juncea) plants obtained by biolistic transformation of embryogenic suspension cells.

Russian wildrye (Psathyrostachys juncea (Fisch.) Nevski) is a cool-season forage species well adapted to semi-arid climates. We are interested in developing biotechnological methods to improve this monocot forage species. Single genotype-derived embryogenic suspension cultures were established from the Russian wildrye cultivar Bozoisky-Select, and were used as target cells for biolistic transformation. A chimeric hygromycin phosphotransferase gene (hph) was used as the selectable marker, and a chimeric beta-glucuronidase (gusA) gene was co-transformed with hph. Resistant calli were obtained from 29% of the bombarded dishes after selection with 200 mg/l hygromycin. Plants were regenerated from 45% of the hygromycin resistant calli. Thirty-six transgenic Russian wildrye plants were recovered after microprojectile bombardment of suspension cells and subsequent hygromycin selection. The transgenic nature of the regenerated plants was demonstrated by Southern hybridization analysis using undigested and digested genomic DNA samples. When a second gene (gusA) was co-transformed with hph, a reasonably high co-transformation frequency of 78% was observed. Transgenic expression of gusA was confirmed by GUS staining of shoot and leaf tissues. Fertile transgenic plants were obtained after two winters of vernalization under field conditions. This is the first report on the generation of transgenic plants in Russian wildrye.

Base Sequence↗
PubMed2004

Brain areas and time course of emotional processing.

The aims of the present study were to identify brain regions involved in emotional processing as well as to follow the time sequence of these processes in the millisecond-range resolution using low resolution brain electromagnetic tomography (LORETA). Different emotional (happy, sad, angry, fearful, and disgust) and neutral faces were presented to 17 healthy, right-handed volunteers on a computer screen while 25-channel EEG data were recorded. Subjects were instructed to generate the same emotion as shown in the presented faces. Event-related potentials (ERPs) were computed for each emotion and neutral condition, and analyzed as sequences of potential distribution maps. Paired topographic analysis of variance tests of the ERP maps identified time segments of significant differences between responses to emotional and neutral faces. For these significant segments, statistical analyses of functional LORETA images were performed to identify active brain regions for the different emotions. Significant differences occurred in different time segments within the first 500 ms after stimulus onset. Each emotional condition showed specific activation patterns in different brain regions, changing over time. In the majority of significant time segments, activation was highest in the right frontal areas. Strongest activation was found in the happy, sad, and disgust conditions in extended fronto-temporal areas. Happy, sad, and disgust conditions also produced earlier and more widely distributed differences than anger and fear. Our findings are in good agreement with other brain-imaging studies (PET/fMRI). But unlike other imaging techniques, LORETA allows to follow the time sequence in the millisecond-range resolution.

Adult↗
PubMed2004

Outcomes of myringoplasty in Australian Aboriginal children and factors associated with success: a prospective case series.

The objective of this study was to assess the outcomes of myringoplasties in Aboriginal children and to identify factors associated with a successful outcome with the use of prospective case series from primary health care clinics and hospitals in four rural and remote regions of Western Australia. All 58 Aboriginal children, aged 5-15 years, who underwent 78 myringoplasties between 1 January 2000 and 30 June 2001 were included in the study. Complete postoperative (post-op) follow-up was achieved following 78% of myringoplasties. The main outcome measures were (a) success, i.e. an intact tympanic membrane and normal hearing six or more months post-op in the operated ear, (b) closure of the perforation, (c) Post-op hearing improvement. Forty-nine per cent of myringoplasties were successful, 72% resulted in closure or reduction in the size of the perforation and 51% resulted in hearing improvement. After controlling for age, sex, clustering and number of previous myringoplasties, no association was observed between success or hearing improvement and perforation size, or the presence of serous aural discharge at the time of surgery. Myringoplasty resulted in hearing improvement and/or perforation closure in a significant proportion of children. Thus, primary school-aged Aboriginal children in whom conservative management of chronic suppurative otitis media has been unsuccessful should have access to myringoplasty because of the positive impact on their socialization, language and learning that results from improved hearing.

Acoustic Impedance Tests↗
PubMed2004

Fluctuations of source locations of EEG activity during transition from alertness to sleep in Alzheimer's disease and vascular dementia.

Vascular dementia (VaD) differs from Alzheimer's disease (AD) in larger fluctuations of cognitive impairment, hypothetically because of deteriorated vigilance control. Vigilance levels are reflected by locations of EEG sources. Transition from alertness to sleep might be particularly sensitive to degradations of vigilance control. Twelve AD and 12 VaD patients (medication free, mean age 75.6 and 77.6 years, respectively, difference = n.s.), and 12 healthy elderly subjects (mean age 70.6 years), who served as controls, were studied (each group comprised 2 males and 10 females). A twenty-one-channel EEG was recorded from full alertness to the onset of sleep stage 2. Dipole source modeling, based on Fast Fourier Transform dipole approximation, yielded 3D source localizations in 7 EEG frequency bands. For each brain axis, means of source location differences between successive 20-second periods were calculated (fluctuation magnitude). EEG band-wise MANCOVAs (3 brain axes, 3 subject groups, covariate: age) showed differences in fluctuation magnitude between groups in the 10.5- to 12-Hz alpha(2) frequency band (p=0.0066). Post hoc ANCOVAs for the axes (3 subject groups, covariate: age) were significant on the superior-inferior axis: VaD patients had higher fluctuations than AD patients and controls, without significant difference between the latter two. Thus, larger source fluctuations in VaD might reflect the patients' decreased vigilance control, accounting for their increased fluctuations of cognitive impairment.

Aged↗
PubMed2003

Field performance of transgenic tall fescue (Festuca arundinacea Schreb.) plants and their progenies.

Tall fescue (Festuca arundinacea Schreb.) is a hexaploid, outcrossing grass species widely used for forage and turf purposes. Transgenic tall fescue plants were generated by biolistic transformation of embryogenic cell suspension cultures that were derived from single genotypes of widely used cultivar Kentucky-31. Primary transgenics from two genotypes, their corresponding regenerants from the same genotypes and control seed-derived plants were transferred to the field and evaluated for 2 years. Progenies of these three classes of plants were obtained and evaluated together with seed-derived plants in a second field experiment. The agronomic characteristics evaluated were: heading date, anthesis date, height, growth habit, number of reproductive tillers, seed yield and biomass. The agronomic performance of the primary transgenics and regenerants was generally inferior to that of the seed-derived plants, with primary transgenics having fewer tillers and a lower seed yield. However, no major differences between the progenies of transgenics and the progenies of seed-derived plants were found for the agronomic traits evaluated. Primary transgenics and regenerants from the same genotype were more uniform than plants from seeds. Progenies of transgenics performed similarly to progenies of the regenerants. The addition of a selectable marker gene in the plant genome seems to have had little effect on the agronomic performance of the regenerated plants. No indication of weediness of the transgenic tall fescue plants was observed. Our results indicate that outcrossing grass plants generated through transgenic approaches can be incorporated into forage breeding programs.

Biolistics↗
PubMed2003

Chronic schizophrenics with positive symptomatology have shortened EEG microstate durations.

OBJECTIVE: In young, first-episode, never-treated schizophrenics compared with controls, (a) generally shorter durations of EEG microstates were reported (Koukkou et al., Brain Topogr 6 (1994) 251; Kinoshita et al., Psychiatry Res Neuroimaging 83 (1998) 58), and (b) specifically, shorter duration of a particular class of microstates (Koenig et al., Eur Arch Psychiatry Clin Neurosci 249 (1999) 205). We now examined whether older, chronic schizophrenic patients with positive symptomatology also show these characteristics. METHODS: Multichannel resting EEG (62.2 s/subject) from two subject groups, 14 patients (36.1+/-10.2 years old) and 13 controls (35.1+/-8.2 years old), all males, was analyzed into microstates using a global approach for microstate analysis that clustered the microstates into 4 classes (Koenig et al., 1999). RESULTS: (a) Hypothesis testing of general microstate shortening supported a trend (P=0.064). (b) Two-way repeated measure ANOVA (two subject groupsx4 microstate classes) showed a significant group effect for microstate duration. Posthoc tests revealed that a microstate class with brain electric field orientation from left central to right central-posterior had significantly shorter microstates in patients than controls (68.5 vs. 76.1 ms, P=0.034). CONCLUSIONS: The results were in line with the results from young, never-treated, productive patients, thus suggesting that in schizophrenic information processing, one class of mental operations might intermittently cause deviant mental constructs because of premature termination of processing.

Adult↗
PubMed2003

Therapeutic drug monitoring of clozapine and relapse--a retrospective study of routine clinical data.

OBJECTIVE: Therapeutic drug monitoring (TDM) of the atypical antipsychotic drug clozapine is recommended. Clinical studies have indicated a therapeutic window for clozapine serum levels in schizophrenic and schizo-affective patients during acute treatment, i.e. for patients who do not respond to treatment with typical antipsychotics. However, despite the frequent use of clozapine also in maintenance treatment, very few data are available showing the relationship between serum levels of clozapine and the prevention of relapse. Thus, the primary objective of the study was to investigate the relationship between serum levels ofclozapine and relapse during maintenance treatment. METHODS: A retrospective study of routine TDM-data was conducted. Samples obtained on an acute treatment ward from patients with < 4 days hospitalization (recent admissions) were regarded as samples associated with relapse. Samples which can be attributed to an intoxication were identified as described in the TDM-form. The serum level of clozapine, as well as age, gender, smoking habits, concurrent drugs, psychiatric diagnosis and dose of clozapine were evaluated. Data analysis was performed on individual samples and, alternatively, on multiple samples from a single patient which are summarized according to a typical clinical situation. RESULTS: 404 serum levels were measured in 86 patients. After exclusion of patients receiving acute treatment, 65 relevant clinical situations were identified in 50 patients: 12 relapses, 8 intoxications (a total of 20 situations with poor outcome) and 45 situations involving patients with good maintenance outcome. Samples involving relapse had serum levels of 198 +/- 211 ng/ml (10-624), intoxications had serum levels of 1,969 +/- 705 ng/ml (900-2,900) and those with good outcome had serum levels of 384 +/- 255 ng/ml (56-1,028) (mean +/- SD (range)). By means of sensitivity of receiver operating characteristic curves (ROC) a lower limit of the therapeutic window can be estimated at about 50-250 ng/ml and an upper limit at about 745-1,050 ng/ml. The frequencies of good and poor outcome were significantly different within and outside these ranges, e.g. chi2 = 11.8 and p < 0.001 for 250 to 745 ng/ml. Comparison of only good outcome and relapse provided a significant difference in the serum level of clozapine (Student's t-test p = 0.024). However, 67% of relapses were predicted in a model of logistic regression only if the variables serum level and concurrent treatment with other psychotropic drugs were included simultaneously as independent variables. Neither variable was able to predict relapse if used as a single variable in separate models. Finally, it was found that serum levels of clozapine were increased in women, in aged patients and in nonsmokers. CONCLUSIONS: It is tentatively concluded that serum levels of clozapine < 50 ng/ml are related to relapse irrespective of concurrent psychotropic drugs. In cases where there are no concurrent psychotropic drugs, serum levels of clozapine < 250 ng/ml are associated with relapse. The risk of relapse is low for serum levels of clozapine > 250 ng/ml irrespective of concurrent psychotropic drugs. The risk of intoxication is increased with serum levels > 750 ng/ml. The TDM of clozapine is recommended during maintenance treatment.

Adult↗
PubMed2002

Improvement of serological discrimination between herpesvirus-infected animals and animals vaccinated with marker vaccines.

Control/eradication plans of bovine herpesvirus 1 (BHV1) and suid herpesvirus 1 (SHV1) infections involve vaccination with inactivated or attenuated gE-deleted marker vaccines and associated companion serological tests to discriminate naturally infected from vaccinated animals. Blocking or competitive enzyme-linked immunosorbent assays (ELISAs) have been designed for the detection of specific antibodies against BHV1 or SHV1 gE glycoprotein. The antigen source usually consists of a crude viral preparation in which gE is associated with other envelope glycoproteins. Such assays suffer from a lack of specificity which is not due to serological cross-reactions with other pathogens. Interestingly, false-positive results occur with sera collected from multivaccinated cattle or pigs. After multivaccination with a marker vaccine, the binding of the conjugated monoclonal antibody used as a tracer, could be hampered by antibodies directed against the other viral glycoproteins. In order to validate the steric hindrance hypothesis, a simple preadsorption of such samples was carried out with a preparation of antigen devoid of gE, prior to the blocking ELISA itself. The decrease in antibody concentrations against the major glycoproteins, clearly leads to a better discrimination between positive and negative samples; that is between infected and multivaccinated animals, without significant loss of sensitivity. This experiment confirms the steric hindrance hypothesis, therefore serum preadsorption could be an easy way to improve the specificity of currently available diagnostic tests.

Animals↗
PubMed2002

Spatial organization of EEG activity from alertness to sleep stage 2 in old and younger subjects.

In order to elucidate brain mechanisms that contribute to the increased tendency for vigilance dysregulation in the elderly, we examined the spatial organization of brain electric activity [electroencephalogram (EEG)] during decreasing vigilance from alertness to onset of sleep stage 2, comparing 7 old and 10 younger, healthy subjects (60-79 and 18-41 years old, respectively). Two features were analyzed: (1) change of location of the brain electric source gravity centers of the EEG frequency bands, and (2) magnitude of fluctuation of these locations over time. Multichannel EEG was analyzed into source gravity center localizations for seven EEG frequency bands, using fast Fourier transform (FFT) Dipole Approximation (first principal component-single source modeling in the frequency domain). Multivariate analysis of covariance (MANCOVA) showed: source localizations were more anterior in old than younger subjects for beta-1 and more superior for all three beta bands; from alertness to sleep, delta and theta EEG sources (inhibitory activity) changed to more posterior and superior areas, and alpha-1 and -2 (routine activity) and beta-1 and -2 sources (excitatory activity) towards anterior and superior areas. Fluctuations of the source locations of delta and beta-2 were larger on the superior--inferior axis, and of beta-2 smaller on the left-right axis in the old than younger subjects. The results suggest functional specifications (inhibitory, routine, excitatory) of cortical positron emission tomography (PET) changes reported in sleep. In sum, aging exhibits changes in spatial organization of EEG-generating neuronal assemblies; during the transition wakefulness-to-sleep, aging affects the spatial-temporal dynamics of this organization. The latter is suggested to contribute to the increased risk for consciousness disturbances in the elderly.

Adolescent↗
PubMed2002

Functional imaging with low-resolution brain electromagnetic tomography (LORETA): a review.

This paper reviews several recent publications that have successfully used the functional brain imaging method known as LORETA. Emphasis is placed on the electrophysiological and neuroanatomical basis of the method, on the localization properties of the method, and on the validation of the method in real experimental human data. Papers that criticize LORETA are briefly discussed. LORETA publications in the 1994-1997 period based localization inference on images of raw electric neuronal activity. In 1998, a series of papers appeared that based localization inference on the statistical parametric mapping methodology applied to high-time resolution LORETA images. Starting in 1999, quantitative neuroanatomy was added to the methodology, based on the digitized Talairach atlas provided by the Brain Imaging Centre, Montreal Neurological Institute. The combination of these methodological developments has placed LORETA at a level that compares favorably to the more classical functional imaging methods, such as PET and fMRI.

Brain↗
PubMed2001

Brain sources of EEG gamma frequency during volitionally meditation-induced, altered states of consciousness, and experience of the self.

Multichannel EEG of an advanced meditator was recorded during four different, repeated meditations. Locations of intracerebral source gravity centers as well as Low Resolution Electromagnetic Tomography (LORETA) functional images of the EEG 'gamma' (35-44 Hz) frequency band activity differed significantly between meditations. Thus, during volitionally self-initiated, altered states of consciousness that were associated with different subjective meditation states, different brain neuronal populations were active. The brain areas predominantly involved during the self-induced meditation states aiming at visualization (right posterior) and verbalization (left central) agreed with known brain functional neuroanatomy. The brain areas involved in the self-induced, meditational dissolution and reconstitution of the experience of the self (right fronto-temporal) are discussed in the context of neural substrates implicated in normal self-representation and reality testing, as well as in depersonalization disorders and detachment from self after brain lesions.

Brain Mapping↗
PubMed2001

Decreased functional connectivity of EEG theta-frequency activity in first-episode, neuroleptic-naïve patients with schizophrenia: preliminary results.

We explored and refined the hypothesis that during a first episode of acute schizophrenia a disorganization of brain functioning is present. A novel EEG measure was introduced, Global Field Synchronization (GFS), that estimates functional connectivity of brain processes in different EEG frequency bands. The measure was applied to EEG's from 11 never-treated, first-episode, young patients with an acute, positive, schizophrenic symptomatology and from 19 controls, residing in Bern, Switzerland. In comparison to age- and sex- matched controls, patients had significantly decreased GFS in the theta EEG frequency band, indicating a loosened functional connectivity of processes in this frequency. The result was confirmed in an independent, comparable patient group from Osaka, Japan (9 patients and 9 controls), thus making a total of 20 analyzed patients. Previous EEG research in healthy, awake subjects indicated a positive correlation of theta activity with memory functions. Thus, our result suggests a loss of mutual interdependence of memory functions in patients with acute schizophrenia, which agrees well with previous reports of working memory dysfunction in schizophrenia.

Acute Disease↗
PubMed2001

Localization of MDMA-induced brain activity in healthy volunteers using low resolution brain electromagnetic tomography (LORETA).

3,4-Methylenedioxymethamphetamine (MDMA; 'Ecstasy') is a psychostimulant drug producing heightened mood and facilitated social communication. In animal studies, MDMA effects are primarily mediated by serotonin (5-HT), but also by dopamine (DA) and possibly noradrenaline (NA). In humans, however, the neurochemical and neurophysiological basis of acute MDMA effects remains unknown. The distribution of active neuronal populations after administration of a single dose of MDMA (1.7 mg/kg) or placebo was studied in 16 healthy, MDMA-naïve volunteers. Thirty-one-channel scalp EEGs during resting with open and closed eyes was analyzed in the different EEG frequency bands. Scalp maps of power showed significant, global differences between MDMA and placebo in both eye conditions and all frequency bands. Low resolution brain electromagnetic tomography (LORETA) was used to compute 3D, functional images of electric neuronal activity from the scalp EEG data. MDMA produced a widespread decrease of slow and medium frequency activity and an increase of fast frequency activity in the anterior temporal and posterior orbital cortex, concomitant with a marked enhancement of mood, emotional arousal and increased extraversion. This activation of frontotemporal areas indicates that the observed enhancement of mood and possibly the increased extroversion rely on modulation of limbic orbitofrontal and anterotemporal structures known to be involved in emotional processes. Comparison of the MDMA-specific EEG pattern with that of various 5-HT, DA, and NA agonists indicates that serotonin, noradrenaline, and, to a lesser degree, dopamine, contribute to the effects of MDMA on EEG, and possibly also on mood and behavior.

Action Potentials↗