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Biomedical subjects

T J Müller

Publications and source records attributed to T J Müller.

15 recordsLinked to original sources
PubMed2007

[Possible genetic link between Darier's disease and depression. Review of the literature and case history].

Darier's disease is a rare, inherited autosomal dominant skin disorder caused by a mutation in the sarcoendoplasmatic reticulum calcium transporter (SERCA)-2-gene. In a number of pedigrees, Darier's disease closely relates with affective disorder. The most likely hypothesis for this is a susceptibility gene for affective disorder near the SERCA-2-gene. A 6.5-megabase region could be identified as a susceptibility locus. This region constitutes a susceptability locus also in affective disorder without Darier's disease. The underlying gene has not yet been identified.

Adult↗
PubMed2006

Comparison of spatial and temporal pattern for fMRI obtained with BOLD and arterial spin labeling.

Functional magnetic resonance imaging (fMRI) is presently either performed using blood oxygenation level-dependent (BOLD) contrast or using cerebral blood flow (CBF), measured with arterial spin labeling (ASL) technique. The present fMRI study aimed to provide practical hints to favour one method over the other. It involved three different acquisition methods during visual checkerboard stimulation on nine healthy subjects: 1) CBF contrast obtained from ASL, 2) BOLD contrast extracted from ASL and 3) BOLD contrast from Echo planar imaging. Previous findings were replicated; i) no differences between the three measurements were found in the location of the activated region; ii) differences were found in the temporal characteristics of the signals and iii) BOLD has significantly higher sensitivity than ASL perfusion. ASL fMRI was favoured when the investigation demands for perfusion and task related signal changes. BOLD fMRI is more suitable in conjunction with fast event related design.

Arteries↗
PubMed2001

A novel one-pot pyrrole synthesis via a coupling-isomerization-Stetter-Paal-Knorr sequence.

[reaction: see text]. 1,2,3,5-tetrasubstituted pyrroles can be synthesized in good yields in a one-pot, three-step, four-component process by a coupling-isomerization-Stetter reaction-Paal-Knorr sequence of an electron-poor (hetero)aryl halide, a terminal propargyl alcohol, an aldehyde, and a primary amine. The structures of the 1,4-diketone 4f and the pyrrole 6b were additionally supported by X-ray structure analyses.

Combinatorial Chemistry Techniques↗
PubMed2001

Electrophysiological signs of reduced prefrontal response control in schizophrenic patients.

The prefrontal cortex is considered as a brain region important in the etiopathogenesis of schizophrenic disorders. Based on converging results from different research areas, the prefrontal cortex is regarded as the anatomical and functional representation of response control under physiological conditions. In previous studies, a robust electrophysiological marker for the investigation of response control in healthy control subjects was validated. This parameter was termed NoGo anteriorisation and consists of a more anterior peak of the event-related potentials during the inhibition of a prepared motor response (NoGo condition within the Continuous Performance Test) than during its execution (Go condition). The present study investigated these brain electrical correlates of response control in 19 schizophrenic patients and 19 age- and sex-matched healthy subjects. Compared to control subjects, the event-related potentials in schizophrenic patients were located more anterior in the Go condition and, as a trend, more posterior in the NoGo condition. The NoGo anteriorisation was strongly reduced in the schizophrenic group. On a qualitative level, the NoGo anteriorisation was present in all control subjects, but not in eight of the 19 patients. The results were interpreted as an indication of a disturbed prefrontal response control in schizophrenic patients. Further studies will clarify whether this method may be useful as a global test of hypofrontality in different groups of chronic schizophrenias, or as a quantifiable measure of an affected response control system, especially in catatonic subgroups.

Adult↗
PubMed2001

Diastereoselective propargylations with planar chiral chromiumcarbonyl arene complex substituted propargyl cations.

The ionization of planar chiral ortho-substituted (arene)Cr(CO)(3)-substituted alpha-propargylic acetates 3 with Lewis acids results in the formation of stable (arene)Cr(CO)(3)-substituted alpha-propargyl cations 4. Subsequent additions of sulfur, nitrogen, oxygen, and pi-carbon nucleophiles to these organometallic electrophiles give rise to the regio- and highly diastereoselective formation of propargyl derivatives 5 in good yields (44-90%; dr = 70:30 to >99:1). The relative stereochemistry of the propargyl acetates 3 and the trapping products 5 was established by several crystal structure analyses, indicating that the cationic propargylations occurred under retention of configuration at the propargylic center. Most important for the diastereoselectivity of the nucleophilic trapping reaction is the configurational stability of the diastereotopic cation 4 as reflected by substituent effects. In situ ionizations according to an S(N)1-mechanism not only result in a considerable loss but also in an inversion of diastereoselectivity.

Journal Article↗
PubMed2001

Cognitive response control in writer's cramp.

Disturbances of the motor and sensory system as well as an alteration of the preparation of movements have been reported to play a role in the pathogenesis of dystonias. However, it is unclear whether higher aspects of cortical - like cognitive - functions are also involved. Recently, the NoGo-anteriorization (NGA) elicited with a visual continuous performance test (CPT) during recording of a 21-channel electroencephalogram has been proposed as an electrophysiological standard-index for cognitive response control. The NGA consists of a more anterior location of the positive area of the brain electrical field associated with the inhibition (NoGo-condition) compared with that of the execution (Go-condition) of a prepared motor response in the CPT. This response control paradigm was applied in 16 patients with writer's cramp (WC) and 14 age matched healthy controls. Topographical analysis of the associated event-related potentials revealed a significant (P < 0.05) NGA effect for both patients and controls. Moreover, patients with WC showed a significantly higher global field power value (P < 0.05) in the Go-condition and a significantly higher difference-amplitude (P < 0.05) in the NoGo-condition. A source location analysis with the low resolution electromagnetic tomography (LORETA) method demonstrated a hypoactivity for the Go-condition in the parietal cortex of the right hemisphere and a hyperactivity in the NoGo-condition in the left parietal cortex in patients with WC compared with healthy controls. These results indicate an altered response control in patients with WC in widespread cortical brain areas and therefore support the hypothesis that the pathogenesis of WC is not restricted to a pure sensory-motor dysfunction.

Adult↗
PubMed2001

The neurophysiological meaning of auditory P300 in subtypes of schizophrenia.

Event-related potentials are a powerful tool to investigate the real-time course of brain electrical mass activation during cognitive processing. In several psychiatric disorders, differences compared to healthy subjects have been reliably described. The specificity and the pathophysiological meaning of the findings were unclear in most studies, however. This review summarizes methodological aspects and findings, in healthy subjects and psychiatric patients, of investigations based on the auditory oddball paradigm, which evokes the P300 component of event-related potentials. Recent convergent results from P300 and brain imaging studies allowed the interpretation of P300 findings in psychotic disorders in terms of different specific and meaningful neurophysiological disturbances. Namely, core schizophrenia is characterized by a left-temporal dysfunction associated with deficits in verbal processing. Acute remitting schizophrenia-like psychoses (cycloid psychosis, ICD-10 F23), on the other hand, show normal hemispheric balance but consistent signs of cerebral hyperarousal. Recent studies further indicate that the drive for action of manic patients does not rely on over-excitation but rather on frontal disinhibition. The findings may help to further advance the understandings and sub-grouping of functional psychoses based on pathophysiological mechanisms.

Arousal↗
PubMed2000

Synthesis of functionalized ethynylphenothiazine fluorophores.

Alkynylated and butadiynyl-bridged phenothiazines with variable functionalization can be synthesized in good yields by cross-coupling and condensation approaches. In addition, the structure of the diethynylated phenothiazine (7a) has been corroborated by an X-ray structure analysis. These oligofunctional heterocycles are fluorescent with modest quantum yields (Phi(f) = 20-35%) and represent suitable building blocks for novel photoexcitable molecular wires.

Crystallography, X-Ray↗
PubMed2000

The dendritic architecture of prefrontal pyramidal neurons in schizophrenic patients.

Despite a considerable number of investigations revealing the prefrontal cortex (PFC) to be a major site of pathological changes in schizophrenia, the neuronal basis of these alterations is still unknown. We used a 3-D image analysis technique to investigate the dendritic arborization of Golgi-impregnated prefrontal pyramidal neurons in schizophrenic patients and controls. While the apical dendrites were found to be unchanged in schizophrenics, the basilar dendritic systems were markedly reduced in the patient group. A segment analysis showed that the observed alterations were mainly confined to distal dendritic segments. The dendritic changes are likely to be associated with specific dysfunctions of prefrontal circuitry and point to the pathogenetical relevance of pre- and perinatal disturbances of PFC maturation in schizophrenic patients.

Adult↗
PubMed1999

EEG signs of vigilance fluctuations preceding perceptual flips in multistable illusionary motion.

This EEG study was performed to clarify the time course of brain electrical events and possible vigilance changes associated with perceptual flips during multistable perception. 13 healthy subjects (28.5 3.8 years) were recorded with a 21-channel digital EEG during a stroboscopic alternative motion paradigm implying illusionary motion with ambiguous direction. Perceptual flips were preceded by a significant decrease of EEG frequencies, and followed by a significant frequency increase with a trend to overshoot. EEG slowing is a reliable sign of vigilance decrease and can be related to thalamic deactivation. This is consistent with a recent fMRI study, which showed thalamic deactivation associated with perceptual flips. The study added important chronological information about this phenomenon and allows the conclusion that reduced vigilance facilitates perceptual discontinuities during multistable perception.

Adult↗
PubMed1998

Prefrontal hypooxygenation during language processing assessed with near-infrared spectroscopy.

Near-infrared spectroscopy (NIRS) is a noninvasive optical method which allows in vivo measurements of relative concentrations of oxygenated (O2Hb) and desoxygenated hemoglobin (HHb). It has been successfully applied to assess the blood oxygenation changes during cerebral ischemia in man. An interesting application of NIRS is the investigation of regional cerebral blood oxygenation during physiological brain functions. In the present study, left and right anterior prefrontal brain areas of 10 healthy subjects were investigated with 2-channel NIRS during language processing (reading aloud). Nonverbal visual perception (picture observation) was performed as a control condition. Compared to the respective baseline conditions, a significant HHb increase and an O2Hb decrease as a trend were found during language processing but not during the nonverbal perceptual task, and no hemispheric differences were found. The metabolic activation patterns differed significantly between the tasks indicating the changes due to the language-related efforts but not to visual perception. Based on previous findings of metabolic brain imaging studies the results are best explained as a complementary phenomenon consisting in relative anterior prefrontal hypoperfusion due to a blood volume redistribution which favors language-related temporal areas.

Adult↗
PubMed1997

A comparison of qEEG and HMPAO-SPECT in relation to the clinical severity of Alzheimer's disease.

Electroencephalographical studies have disclosed correlations between topographical features of Fast Fourier Transformation maps and the severity of Alzheimer's disease (DAT). The object of the present study was to explore the relations of HMPAO-SPECT and quantitative EEG (qEEG) with the severity of dementia. Twenty-three patients were included in the study. Spectral and topographical EEG parameters were compared with global and regional cerebral blood flow, and with psychometric measures of clinical severity. None of the regions of interest of the SPECT scans were significantly correlated with clinical severity. Low values in delta- and theta bands, however, were related to high scores on the Mini-Mental-State examination (P < 0.01), whereas the Syndrome-Kurz test correlated inversely with the power values in the alpha and beta band. The global decrease in cerebral blood flow (CBF) was associated with a shift on the topographical alpha-centroids in the posterior direction (P < 0.01). In previous studies correlations between CBF and clinical severity were weak, indicating a high interindividual variance, or interactions with concomitant vascular lesions. Whereas SPECT is a well-established tool for the diagnosis of dementia, the present study indicates qEEG as a potential marker for the staging of the cognitive decline in DAT.

Aged↗
PubMed1997

Correlations of topographical EEG features with clinical severity in mild and moderate dementia of Alzheimer type.

Quantitative electroencephalography (qEEG) and the Folstein Mini Mental State examination (MMSE) were obtained from 31 patients affected by probable dementia of Alzheimer's type (DAT). qEEG data were examined both by spectral analysis (Fast Fourier Transformation) and by single frequency band topographical centroid, and compared with those of 24 healthy subjects of the same age group. DAT patients were found to have higher absolute power in the slow (delta and theta) frequency bands. Quantitative topographical assessment showed significantly more anteriorly located centers of gravity for the alpha and beta activity. Only alpha anteriorization was correlated with the degree of cognitive impairment as measured by the global deterioration scale and MMSE. It is concluded that quantitative topographical assessment was successful for the statistical handling of the EEG power maps, and to identify a potential parameter for the functional staging of the disease.

Aged↗