Biomedical subjects

J Kayser

Publications and source records attributed to J Kayser.

At least 19 recordsLinked to original sources

PubMed2001

Event-related potentials in schizophrenia during tonal and phonetic oddball tasks: relations to diagnostic subtype, symptom features and verbal memory.

BACKGROUND: This study compares event-related potentials for paranoid patients (n = 13) versus matched undifferentiated patients and unmedicated patients (n = 14) versus matched healthy adults. METHODS: Event-related potentials of right-handed patients and control subjects were recorded from 30 electrodes during oddball tasks using consonant-vowel syllables or complex tones. Patients were also assessed using the Positive and Negative Syndrome Scale, the Thought Disorder Index, and the Wechsler Memory Scale. RESULTS: Paranoid patients did not differ from undifferentiated patients in N1 or P3 amplitude but showed larger N2 at frontocentral sites to phonetic stimuli, as well as larger N2 over left than right hemisphere. Unmedicated patients showed reduced N2, but not N1 or P3, compared to control subjects. CONCLUSIONS: The N2 findings are consistent with neuropsychological evidence of greater verbal abilities and left hemisphere dominance in paranoid than nonparanoid schizophrenia. The findings also confirm the relationship of P3 to total Brief Psychiatric Rating Scale score, negative symptoms, and verbal associative memory.

Adult↗

PubMed2001

Event-related brain potentials (ERPs) in schizophrenia for tonal and phonetic oddball tasks.

BACKGROUND: Prior studies using simple target detection ("oddball") tasks with pure tones have reported asymmetric reduction of the P3 event-related potential (ERP). This study investigated the time course and topography of ERPs recorded during both tonal and phonetic oddball tasks. METHODS: Event-related potentials of 66 patients (14 unmedicated) diagnosed with schizophrenia (n = 46) or schizoaffective disorder (n = 20) and 32 healthy adults were recorded from 30 scalp electrodes during two oddball tasks using consonant-vowel syllables or complex tones. Overlapping ERP components were identified and measured by covariance-based principal components analysis. RESULTS: Schizophrenic patients showed marked, task-independent reductions of early negative potentials (N1, N2) but not reduced P3 amplitude or abnormal P3 asymmetry. Task-related hemispheric asymmetries of the N2/P3 complex were similar in healthy adults and schizophrenic patients. Poorer task performance in patients was related to ERP amplitudes, but could not account for reductions of early negativities. CONCLUSIONS: The findings suggest that both patients and control subjects activated lateralized cortical networks required for pitch (right frontotemporal) and phoneme (left parietotemporal) discrimination. Task-independent reductions of negativities between 80 and 280 msec after stimulus onset suggest a deficit of automatic stimulus classification in schizophrenia, which may be partly compensated by later effortful processing.

Adult↗

PubMed2001

A convenient method for detecting electrolyte bridges in multichannel electroencephalogram and event-related potential recordings.

Dense electrode arrays offer numerous advantages over single channel electroencephalogram/event-related potential (EEG/ERP) recordings, but also exaggerate the influence of common error sources arising from the preparation of scalp placements. Even with conventional low density recordings (e.g. 30-channel Electro-Cap), over-application of electrode gel may result in electrolyte leakage and create low impedance bridges, particularly at vertically-aligned sites (e.g. inferior-lateral). The ensuing electrical short produces an artificial similarity of ERPs at neighboring sites that distorts the ERP topography. This artifact is not immediately apparent in group averages, and may even go undetected after visual inspection of the individual ERP waveforms. Besides adding noise variance to the topography, this error source also has the capacity to introduce systematic, localized artifacts (e.g. add or remove evidence of lateralized activity). Electrolyte bridges causing these artifacts can be easily detected by a simple variant of the Hjorth algorithm (intrinsic Hjorth), in which spatial interelectrode distances are replaced by an electrical analog of distance (i.e. the variances of the difference waveforms for all pairwise combinations of electrodes). When a low impedance bridge exists, the Hjorth algorithm identifies all affected sites as flat lines that are readily distinguishable from Hjorth waveforms at unbridged electrodes.

Algorithms↗

PubMed2000

The Tübingen balloon. A new method for adjusting the tension of the fundic wrap during laparoscopic Nissen fundoplication.

An adequate fundic wrap is fundamental to the success of conventional and laparoscopic Nissen fundoplications. Nevertheless, up to now there has been no standardized method for the surgeon to determine intraoperatively the width and tension of the fundic wrap according to objective criteria. With the support of Rüsch (Kernen, Germany), we developed a measurement balloon for use in laparoscopic Nissen fundoplication. The balloon allows the surgeon to define the width of the wrap and predetermine its length, as well as to measure its tension. Depending on the measured balloon pressure, the surgeon can perform fundic sutures more or less tightly. On the basis of 41 fundoplication model tests, we found that a fundic wrap typically described as "loose and floppy" produced a balloon pressure of 50-60 mmHg. In 10 laparoscopic Nissen fundoplications on domestic pigs, we were able to adjust the fundic wrap intraoperatively to a balloon pressure in this range (mean; 53.5; SD; 2.25). After the optimal intraoperative balloon pressure in humans has been investigated in a prospective study that is in progress, the Tübingen balloon is expected to serve as an instrument for quality assurance in reflux surgery.

Animals↗

PubMed2000

Event-related potentials (ERPs) to hemifield presentations of emotional stimuli: differences between depressed patients and healthy adults in P3 amplitude and asymmetry.

Depression may involve dysfunction of right parietotemporal cortex, a region activated during perception of affective stimuli. To further test this hypothesis, event-related brain potentials (ERPs) were measured in a paradigm previously shown to produce ERP asymmetries to affective stimuli over parietal sites in healthy adults. Pictures of patients with dermatological diseases showing disordered or healed facial areas before (negative) or after (neutral) surgical treatment were briefly exposed for 250 ms to either the left or right hemifield. ERPs of 30 unmedicated, unipolar depressed patients and 16 healthy adults, all right-handed, were recorded from 30 electrodes. A principal components analysis extracted factors which closely corresponded to distinctive ERP components previously reported for this task (N1, N2, early P3, late P3, slow wave). Significant effects of emotional content, i.e. enhanced amplitudes to negative than neutral stimuli, were found for early and late P3. Control subjects showed significant hemispheric asymmetries of emotional processing for late P3 (peak latency 460 ms), with the largest emotional content effects over the right parietal region. In striking contrast to control subjects, depressed patients did not show an increase in late P3 for negative compared to neutral stimuli over either hemisphere and had smaller late P3 amplitude than control subjects. Patients did, however, show larger early P3 (peak latency 330 ms) to negative than neutral stimuli. Results suggest intact early discrimination but abnormal late appraisal of affective content in depression, which may arise from selective inhibition of right parietal regions integral for perceiving and evaluating emotional stimuli.

Adult↗

PubMed2000

Is resting anterior EEG alpha asymmetry a trait marker for depression? Findings for healthy adults and clinically depressed patients.

Several lines of evidence suggest that asymmetric anterior brain activation is related to affective style, linking left hemisphere activation to positive affect and right hemisphere activation to negative affect. However, previous reports of left frontal hypoactivation in depressed patients were not confirmed in recent studies. This study evaluated additional characteristics of resting EEG alpha (8-13 Hz) asymmetry in 15 clinically depressed patients and 22 healthy adults by recording EEG activity on two separate occasions, 2-4 weeks apart. Across both sessions, group differences in anterior EEG asymmetry were compatible with the original hypothesis. However, groups differed in temporal stability of anterior EEG asymmetry, which was retest reliable in controls but not depressed patients. In contrast, temporal stability of posterior EEG asymmetry was acceptable in both groups. Increased variability of anterior EEG asymmetry may be a characteristic feature for depression, and, if so, this would challenge the notion that anterior EEG alpha asymmetry is a trait marker for depression.

Adult↗

PubMed1999

Left temporal lobe dysfunction in schizophrenia: event-related potential and behavioral evidence from phonetic and tonal dichotic listening tasks.

BACKGROUND: Asymmetric reduction of the P3 event-related potential (ERP) has provided evidence of left temporal lobe dysfunction in schizophrenia. Prior studies have been limited by reliance on simple target detection (oddball) tasks with pure tones. This study investigated the time course and topography of ERPs to binaural syllables or complex tones in dichotic listening tasks. METHODS: Event-related potentials of 26 patients meeting criteria for schizophrenia (n = 19) or schizoaffective disorder (n = 7) and 26 healthy controls were recorded from 30 scalp electrodes during 2 dichotic tasks in which different syllables or complex tones were simultaneously presented to each ear. A principal components analysis was used to derive factor scores corresponding to overlapping components in ERP waveforms--N1, N2, P3, and a late-positive potential. RESULTS: Healthy controls showed a right ear advantage for perceiving dichotic syllables, which was associated with greater N2 amplitude at left than right temporoparietal sites. Patients with schizophrenia did not show either this perceptual or N2 asymmetry. Patients also had smaller late-positive potential amplitude when compared with controls for both syllables and complex tones, with greatest decrement over left temporal sites. CONCLUSIONS: A right ear advantage in healthy adults for perceiving consonant-vowels was associated with a left-lateralized ERP component peaking at 200 milliseconds after syllable onset (N2). Patients with schizophrenia failed to show either of these task-dependent asymmetries, which may indicate a dysfunction of left temporal regions involved in phonetic classification. A task-independent asymmetric reduction of a later positive potential in patients with schizophrenia resembled left temporal P3 reductions reported for auditory oddball tasks.

Acoustic Stimulation↗

PubMed1999

Brain event-related potentials (ERPs) in schizophrenia during a word recognition memory task.

Impairments of recognition memory for words and attenuation of the ERP 'old-new' effect have been found in patients with left medial temporal lobe damage. If left temporal lobe dysfunction in schizophrenia involves medial structures (e.g. hippocampus), then schizophrenic patients might show similar abnormalities of verbal recognition memory. This study recorded ERPs from 30 electrode sites while subjects were engaged in a continuous word recognition memory task. Results are reported for 24 patients having a diagnosis of schizophrenia (n = 16) or schizoaffective disorder (n = 8) and 19 age-matched healthy controls. Both patients and controls showed the expected 'old-new' effect, with greater late positivity to correctly recognized old words at posterior sites, and there was also no significant difference between groups in P3 amplitude. However, accuracy of word recognition memory was poorer in patients than controls, and patients showed markedly smaller N2 amplitude. Reduced amplitudes of N2 and N2-P3 were associated with poorer performance, with highest correlations over the left inferior parietal (N2) and left medial parietal (N2-P3) region. Moreover, patients failed to show significantly greater left than right hemisphere amplitude of N2-P3 at posterior sites, which was seen for healthy controls. These findings suggest that impaired word recognition in schizophrenia may arise from a left lateralized deficit at an early stage of processing, beginning at 200-300 ms after word onset.

Adult↗

PubMed1999

The SPI-3 pathogenicity island of Salmonella enterica.

Pathogenicity islands are chromosomal clusters of pathogen-specific virulence genes often found at tRNA loci. We have determined the molecular genetic structure of SPI-3, a 17-kb pathogenicity island located at the selC tRNA locus of Salmonella enterica serovar Typhimurium. The G+C content of SPI-3 (47.5%) differs from that of the Salmonella genome (52%), consistent with the notion that these sequences have been horizontally acquired. SPI-3 harbors 10 open reading frames organized in six transcriptional units, which include the previously described mgtCB operon encoding the macrophage survival protein MgtC and the Mg2+ transporter MgtB. Among the newly identified open reading frames, one exhibits sequence similarity to the ToxR regulatory protein of Vibrio cholerae and one is similar to the AIDA-I adhesin of enteropathogenic Escherichia coli. The distribution of SPI-3 sequences varies among the salmonellae: the right end of the island, which harbors the virulence gene mgtC, is present in all eight subspecies of Salmonella; however, a four-gene cluster at the center of SPI-3 is found in only some of the subspecies and is bracketed by remnants of insertion sequences, suggesting a multistep process in the evolution of SPI-3 sequences.

Adenosine Triphosphatases↗

PubMed1998

Dissociation of brain ERP topographies for tonal and phonetic oddball tasks.

ERP topographies for 30 scalp electrodes were examined in 26 healthy right-handed volunteers during oddball tasks (20% targets) using binaurally presented consonant-vowel syllables or complex tones. Response hand was counterbalanced across participants. Both window averages and a principal components analysis (PCA) with Varimax rotation revealed task-related (tonal/phonetic) hemispheric asymmetries for N2, early P3, and particularly for N2-P3 amplitude. In the tonal task, N2 was maximal over right lateral-temporal regions, and early P3 over right medial-parietal regions. For the phonetic task, N2 was maximal over the left lateral-parietal regions, and late P3/N3 over left medial-parietal regions. A response-related frontal negativity (N3) interacted with task-related asymmetries in an unbalanced fashion. The distinct, asymmetric N2 and P3 topographies for tonal and phonetic tasks presumably reflect differential involvement of cortical structures in pitch (right frontotemporal) and phoneme (left parietotemporal) discrimination.

Acoustic Stimulation↗

PubMed1998

Response- and stimulus-related ERP asymmetries in a tonal oddball task: a Laplacian analysis.

Previous studies have found greater P3 amplitude over right than left hemisphere sites in a tonal oddball task with a reaction time (RT) response. This asymmetry had a central topography, and interacted with response hand. Identification of the processes underlying these asymmetries requires the use of additional methods for separating response- and stimulus-related contributions. We applied local Hjorth and spherical spline algorithms to compute surface Laplacian topographies of ERP data recorded from 30 scalp electrodes in a pooled sample of 46 right-handed healthy adults. For both methods, the current sources underlying the late positive complex were largest at medial parietal regions, but were asymmetric at central and frontocentral sites. Although a frontocentral sink contralateral to the response hand contributed to the asymmetry of the classic P3 peak, the source asymmetry was most robust after the sink had resolved. The late source was largest at electrode C4 for right hand responses, and was further enhanced in subjects showing a dichotic left ear advantage, but was unrelated to response speed. We conclude that the right hemisphere source reflects an interaction of response-related asymmetries with right hemisphere processes responsible for pitch discrimination.

Acoustic Stimulation↗

PubMed1998

The time course of visuospatial processing deficits in schizophrenia: an event-related brain potential study.

Event-related brain potentials (ERPs) were recorded during a dot enumeration task so as to investigate electrophysiologic correlates of early visuospatial processing in schizophrenia. Twenty-eight patients having a diagnosis of schizophrenia (n = 19) or schizoaffective disorder (n = 9) and 28 controls were tested. Patients showed poorer dot enumeration than did controls and also had markedly reduced early negative ERPs, which began about 150 ms after stimulus onset at the peak of the N1 potential and reached its maximum about 275 ms at the N2 peak. The N1 reduction in patients was greatest over left parietal sites for stimuli in the right visual field. The marked N1 and N2 reductions in patients are supportive of models postulating deficits in early visuospatial attention and allocation of conceptual resources in schizophrenia.

Adult↗

PubMed1997

Event-related potential (ERP) asymmetries to emotional stimuli in a visual half-field paradigm.

To investigate the hypothesis of a right hemispheric superiority in negative emotional processing, event-related potentials (ERPs) were recorded from 17 sites (Fz, Cz, Pz, F3/4, F7/8, C3/4, T7/8, P3/4, P7/8, O1/2) in a visual half-field paradigm. While maintaining fixation, right-handed women viewed pictures of patients with dermatological diseases before (negative) and after (neutral) cosmetic surgery. A principal components analysis with Varimax rotation performed on ERPs revealed factors identified as N1, N2, early P3, late P3, and slow wave. Repeated measures analyses of variance performed on factor scores revealed a significant effect of emotional content for all factors except for N1. However, asymmetries in emotional processing were restricted to N2 and early P3, with maximal effects over the right parietal region. N2-P3 amplitude was augmented for negative and reduced for neutral stimuli over right hemisphere regions. Visual field presentation interacted with these asymmetries in enhancing amplitudes contralaterally for early but ipsilaterally for late ERP components. Overall, findings for N2 and P3 support theories of an asymmetry in emotional processing.

Adult↗

PubMed1997

Regulation of polymyxin resistance and adaptation to low-Mg2+ environments.

The PmrA-PmrB two-component system of Salmonella typhimurium controls resistance to the peptide antibiotic polymyxin B and to several antimicrobial proteins from human neutrophils. Amino acid substitutions in the regulatory protein PmrA conferring resistance to polymyxin lower the overall negative charge of the lipopolysaccharide (LPS), which results in decreased bacterial binding to cationic polypeptides and increased bacterial survival within human neutrophils. We have now identified three PmrA-activated loci that are required for polymyxin resistance. These loci were previously shown to be necessary for growth on low-Mg2+ solid media, indicating that LPS modifications that mediate polymyxin resistance are responsible for the adaptation to Mg2+-limited environments. Conditions that promote transcription of PmrA-activated genes--growth in mildly acidic pH and micromolar Mg2+ concentrations--increased survival in the presence of polymyxin over 16,000-fold in a wild-type organism but not in a mutant lacking pmrA. Our experiments suggest that low pH and low Mg2+ concentrations may induce expression of PmrA-activated genes within phagocytic cells and promote bacterial resistance to host antimicrobial proteins. We propose that the LPS is a Mg2+ reservoir and that the PmrA-controlled LPS modifications neutralize surface negative charges when Mg2+ is transported into the cytoplasm during growth in Mg2+-limited environments.

Alleles↗

PubMed1996

[Technique and indications for sphincter-saving transanal resection in rectal carcinoma].

Using a transanal procedure, two different operative techniques are possible: the TEM technique (Transanal Endoscopic Microsurgery), which is more and more accepted in the world as method of choice for the local resection of adenomas and carcinomas pT1 "low risk" in the rectum and the lower sigma. The technically difficult procedure requires much experience. It should therefore only be practiced in centers to reach an acceptable number of clinical cases. In the lower third of the rectum, especially in locations close to the dentate line, the conventional transanal resection of tumours is also an adequate procedure.

Anal Canal↗

PubMed1995

Endoscopic Approach.

The increasing use of the laparoscopic approach in colorectal surgery depends not only on the indications but also on technological development. Better visualization of the operative field is available using a three-chip camera or three-dimensional system. Alternative port positionings together with curved instruments increase the degree of freedom during operation. Complex laparoscopic procedures need highly specific instruments. We have developed atraumatic bowel graspers, different types of retractors, and innovative combination instruments. OREST II, a new multipurpose system that assists the organization of laparascopic surgery is described.

Journal Article↗

PubMed1982

Clinical value of empirical amphotericin B in patients with acute myelogenous leukemia.

From August 1977 to October 1978, 23 patients with acute myelogenous leukemia (AML) received induction therapy at Vanderbilt University Hospital. Six patients died of documented fungal infection, predominantly aspergillus pneumonia; the complete remission rate was only 40%. Based on this experience we began using amphotericin B empirically in any AML patient remaining febrile or having recurrent fever after a week of broad spectrum antibiotics. Of 22 patients treated from October 1978 to August 1980, none died of fungal infection during induction therapy; the remission rate increased significantly to 77%. Chemotherapy and supportive care were otherwise unchanged during this period. While the first group was older, the improvement in remission rate was also seen in patients younger than 60 years of age. Since fungal infection may be difficult to document, this study suggests that empirical amphotericin B is reasonable therapy in leukemic patients remaining febrile or having a recurrent fever following a week of broad spectrum antibiotics, if the institution has a high incidence of fungal infections.

Adult↗

PubMed1982

Electrocardiographic changes in acute pancreatitis.

Electrograms recorded during 50 episodes of acute pancreatitis were analyzed and compared to those recorded during an asymptomatic period. Ten episodes of acute pancreatitis occurred in eight patients with normal ECGs during an asymptomatic period. Nonspecific ST-T changes were recorded in only two of them (one with mild hypokalemia). ECGs recorded during 40 episodes of acute pancreatitis in 24 patients who had ECG abnormalities during an asymptomatic period revealed no significant changes during 33 of the episodes. The seven episodes associated with significant ECG changes occurred in patients with previous ECG abnormalities. Review of the literature and of our cases strongly suggests that significant ECG alterations during acute pancreatitis usually occur in patients with previous cardiac abnormalities.

Acute Disease↗