Biomedical subjects

K Maurer

Publications and source records attributed to K Maurer.

At least 91 records · Page 5Linked to original sources

PubMed1993

Equivalent dipoles of FFT data visualize drug interaction at benzodiazepine receptors.

The aim of the present investigation was to study if the benzodiazepine receptor antagonist flumazenil could reverse the effects on the brain electrical activity induced by the benzodiazepine receptor agonist midazolam. The method of FFT approximation was used for this purpose. It allows the calculation of center of gravity equivalent dipoles of spectral EEG data. The results are reference independent and allow therefore a more unambiguous interpretation compared to conventional FFT data reports. Twelve subjects were investigated before and after 0.1 mg/kg and 0.2 mg/kg midazolam respectively, directly and 4 h after administration of 1 mg flumazenil. Our results imply that the application of flumazenil after midazolam sedation leads to an almost complete restoration of the brain electrical activity. However, especially in the beta frequencies above 20 Hz differences in depth of equivalent dipoles were found directly after flumazenil application as well as 4 h later. This could suggest that neuronal generators in different brain structures were responsible for the electrical activity after flumazenil administration compared to before.

Adult↗

PubMed1993

Brain electrical activity in depression described by equivalent dipoles.

The majority of neurophysiological investigations of waking EEG in depression have been relatively disappointing. Since the topographic distribution of brain electrical activity over the scalp in the frequency domain (FFT-power) varies considerably when choosing another site for the reference, it is not surprising that various investigators reported contradictory results. The aim of the present study was to investigate differences in brain electrical activity in a sample of depressed patients as compared to healthy subjects using a newly developed method called FFT approximation. As the major finding healthy subjects and depressed patients demonstrated significantly divergent patterns of localization between frequency bands in the anterior-posterior direction. The investigation suggests that a non-invasive neurophysiological methods gives results which are comparable to those obtained by other functional and structural imaging methods in depressive illness.

Adolescent↗

PubMed1993

Age-related changes of spontaneous EEG described by equivalent dipoles.

One of the most commonly used methods for quantification of an EEG is Fast Fourier Transformation (FFT), which suffers from some serious disadvantages, for example: FFT-power data are highly dependent on the choice of reference and thus the topographical distribution of FFT-power data varies according to the used reference. Novel methods which partly resolve this problem have been developed. These methods provide unambiguous data in the frequency domain with regard to reference. In comparison to conventional FFT-power data this approach allows to a higher degree to draw topographical valid conclusions regarding brain function. The aim of the present study on brain electrical activity, using the method of FFT approximation, was to investigate age-related alterations of brain function in carefully screened healthy subjects. The major finding was that, except for a more superficially located beta-activity of higher strength with increasing, age no age-related changes in electrical brain activity were observed.

Adult↗

PubMed1993

Evidence for a gender bias in epidemiological studies of schizophrenia.

A higher lifetime morbidity risk for schizophrenia in males has been observed by several investigators. Studies controlled for errors in patient selection and other sources of artefacts, however, find an equal risk in both sexes. In order to detect the causes for the underrepresentation of women in many studies, sample composition of multicentre WHO studies was analysed. Severity of symptoms was not found to be responsible for imbalances in the male/female ratios, but cultural influences and design characteristics were: due to the scarcity of psychiatric facilities, women are less likely to receive adequate treatment in most of the developing countries investigated, since they are kept longer at home and seen by traditional healers in some cultures. Also, studies with an upper age limit of 44 years (according to DSM-III) exclude a greater proportion of female than male schizophrenic patients, and there is some evidence that schizophrenia is more often underdiagnosed in women than in men at least in some countries. Implications for future research on gender differences in schizophrenia are discussed.

Adult↗

PubMed1993

Dementia of the Alzheimer type: effects on the spontaneous EEG described by dipole sources.

The present study on brain electrical activity in healthy subjects (n = 35) and patients suffering from dementia of the Alzheimer type (DAT; n = 35) used Fast Fourier Transformation-dipole approximation to quantify differences between the two groups. DAT patients showed a shift of alpha and beta activity toward frontal brain regions. The amount of this shift correlated with the degree of dementia. The relative distribution of magnitude of activity between the frequency bands differed between DAT patients and control subjects. DAT patients had higher magnitudes in the slow frequency range, correlating with the severity of dementia, and lower ones in the alpha and beta range compared with findings in age-matched control subjects.

Aged↗

PubMed1993

Generating and testing a causal explanation of the gender difference in age at first onset of schizophrenia.

Motivated by the lack of knowledge of the pathophysiological processes underlying the manifestation of symptoms in schizophrenia, we have worked out a systematic search strategy. Since epidemiological distribution patterns consistently deviating from expected values provide valuable indications of causal relationships, we chose the higher age of females at first admission for schizophrenia, first reported by Kraepelin and since then confirmed in over 50 studies, as the basis for our study. This unexplained epidemiological finding was replicated on Danish and Mannheim case-register data by systematically controlling for selection and diagnostic artefacts and by testing alternative explanations at the individual stage of the study. To check whether the difference in age at first admission was determined by a difference in age at onset, a representative sample of 267 first-admitted patients with non-affective functional psychosis was examined by using an interview for the retrospective assessment of the onset of schizophrenia (IRAOS) designed for this purpose. Any of the definitions of first-ever onset applied--first sign of mental disorder, first psychotic symptom, first acute episode--led to a significant age difference of 3.2 to 4.1 years between the sexes. The distribution of onsets across the life cycle showed a later increase and a second, lower peak between the ages of 45 and 54 years among females compared with males. The lifetime risk for schizophrenia was equal for males and females. After testing the plausibility of psychosocial versus biological explanations we hypothesized that due to the effect of oestrogens the vulnerability threshold for schizophrenia is elevated in females until the menopause. Animal experiments and post mortem analyses showed that chronic oestrogen applications significantly shortened dopamine-induced behaviour and reduced D2 receptor sensitivity in the brain. The applicability of this pathophysiological mechanism to human schizophrenia was tested on acutely schizophrenic females with normal menstrual cycles. A significant negative correlation was found between measures of symptomatology and plasma oestrogen levels. The manifestation of symptoms in schizophrenia appears to be influenced by a sufficiently sensitive D2 receptor system in the brain, blocked by neuroleptics and modulated by oestrogens.

Age Factors↗

PubMed1993

Differences in P300 amplitudes and topography between cycloid psychosis and schizophrenia in Leonhard's classification.

In a polydiagnostic approach, we investigated the parameters of auditory P300 in a group of 18 remitted schizophrenics and in 18 age- and sex-matched controls. All patients fulfilled the criteria of schizophrenic disorder according to DSM-III-R. Applying Leonhard's classification, patients were to be subdivided into 7 cycloid psychosis and 11 Leonhard's schizophrenics. Patients with cycloid psychosis fulfilled the operational criteria of Brockington et al. We found significantly lower P300 amplitudes in the group of Leonhard's schizophrenics than in controls and in cycloid psychosis, whereas no difference could be shown between patients with cycloid psychosis and controls. Both the maxima and the minima of the P300 field map were dislocated significantly to the right in the group of Leonhard's schizophrenics but not in cycloid psychosis.

Adult↗

PubMed1993

Amplitudes of auditory P300 in remitted and residual schizophrenics: correlations with clinical features.

The parameters of auditory P300 were studied with reference-independent methods in a group of 18 remitted and residual schizophrenics, and in 18 age- and sex-matched controls. In the schizophrenic group, significant inverse correlations were found between P300 amplitudes and level of psychopathology assessed with the Scale for Assessment of Negative Symptoms and with the Brief Psychiatric Rating Scale. Clinical variables regarding social functioning and adaptation, assessed with the Schedule for Affective Disorders and Schizophrenia, and with axis V of DSM-III-R, correlated significantly with low amplitudes. The scalp locations of the maxima and minima of the P300 potentials had the tendency to be dislocated to the right in schizophrenics compared with controls. The results indicate low P300 amplitudes to be associated with pervasive cognitive impairment. Future studies will determine whether low P300 amplitudes have prognostic validity for course and outcome of schizophrenic disorders.

Acoustic Stimulation↗

PubMed1993

Segmentation of the spontaneous EEG in dementia of the Alzheimer type.

Studies on EEG data in dementia of the Alzheimer type have mainly investigated parameters in the frequency domain. However, the EEG also reflects the momentary functional state of the brain. The EEG can be partitioned into segments of spatially stationary map landscapes as characterized by the locations of potential maxima and minima, to study the time domain of the EEG. We calculated the segment structure of 19-channel EEG recordings (1-30 Hz) from 10 patients with dementia of the Alzheimer type and 10 sex-matched geriatric controls. The EEG maps corresponding to global field power peaks were used for analysis. The locations of the potential maximum and minimum of the maps were determined over the course of 20 s and used for segmentation. The segments of EEG activity were significantly fewer (p < 0.05) and the segments lasted longer (p < 0.05) in patients compared to controls. This effect could be observed over the whole period of recording and thus was not caused by only a few long segments. The data may be linked to morphological and biochemical findings of neuronal loss and loss of synapses in dementia of the Alzheimer type.

Aged↗

PubMed1993

The influence of age and sex on the onset and early course of schizophrenia.

A new standardised interview for the retrospective assessment of onset and early course of schizophrenia (IRAOS) was used to study the influence of age and sex on time of onset and psychopathology before first admission in 267 schizophrenic patients admitted for the first time. Mean age at onset, according to various operationalised definitions, differed by three to four years between the sexes. The age distribution at the earliest sign of mental disorder showed an early and steep increase until the age of 25 in males, and a delayed and smaller increase in females, with a second peak in women aged 45-79. Schizophrenia began with negative symptoms in 70% of cases, appearing two to six years before admission, and all positive symptoms appearing up to two years before. Both positive and negative symptoms accumulated exponentially. The early course of the disease was similar across age groups, except there was a longer period of negative symptoms before first admission in late-onset schizophrenia in women. The few significant age differences in symptoms were presumably due to general age-dependent reaction patterns like anxiety and depression or the cognitive development of personality, as indicated by an increase in fully elaborated positive symptoms, especially systematised paranoid delusions, with age.

Adolescent↗

PubMed1993

[A chapter in systematic schizophrenia research--the search for causal explanations for sex differences in age of onset].

With the aim of detecting causal processes contributing to the onset of schizophrenic symptoms a systematic search strategy was worked out. One of the few epidemiological findings on schizophrenia consistently diverging from expected values, the sex difference in age at first admission, was taken as a basis and replicated on data from the Danish and the Mannheim case registers by controlling for selection and diagnostic artefacts. Danish psychiatrists turned out to have underdiagnosed schizophrenia to a considerable extent at least in 1976, the year from which the analysed case-register data dated. After the exclusion of alternative explanations, the time when symptoms appeared for the first time and the first acute episode occurred was determined for a representative sample of 267 first-admitted cases with a diagnosis of non-affective functional disorder by using the IRAOS interview designed for this purpose. At any of the definitions of first onset applied the mean age of females was significantly higher than that of males, the difference ranging from 3.2 to 4.1 years. The distribution of onsets across the female life cycle showed a clearly delayed increase at young age and a second, lower peak of onsets at the age of 45-54, whereas the cumulative incidence up to the age of 60 years was equal for males and females. On assessing the plausibility of psychosocial versus biological explanations it was hypothesized that due to the effect of estrogens the vulnerability threshold for schizophrenia is raised in females until the menopause. Animal experiments and postmortem analysis showed that chronic estrogen applications significantly shortened dopamine-induced behaviour and reduced D2 receptor sensitivity in the brain. The applicability of this pathophysiological mechanism on human schizophrenia was tested on acutely schizophrenic females with normal menstrual cycles. A significant negative correlation was found between measures of symptomatology and plasma estrogen levels. Apparently, the manifestation of schizophrenic symptoms is influenced by a sufficiently sensitive D2 receptor system in the brain, blocked by neuroleptics and modulated by estrogens.

Adolescent↗

PubMed1993

[Progressive paralysis: prognostic indications by modern imaging procedures. A case report].

The case of a patient with early diagnosed neurosyphilis (general paresis) is presented. Modern neuroimaging techniques such as single photon emission computed tomography (SPECT) may give clues to the treatment outcome as early as 1 month after antibiotic treatment. Improvement of cognitive functions was accompanied by normalization of the initially altered P300-topography.

Brain Mapping↗

PubMed1992

Kluyveromyces contains a functional ABF1-homologue.

ABF1 is a multifunctional protein present in Saccharomyces cerevisiae, involved in transcription-activation and -repression as well as in DNA-replication. Several lines of evidence indicate the occurrence in the related species Kluyveromyces lactis of a protein having similar properties to those of ABF1 in S. cerevisiae. In order to identify conserved functional domains in ABF1, we have cloned and sequenced the gene encoding the ABF1-homologue from K. lactis. KIABF1 is much smaller than ScABF1 (54.6 vs. 81.7 kD). It exhibits extensive homology with its S. cerevisiae counterpart in the N-terminal region. The C-terminal domain however, is divergent, with the striking exception of a stretch of 20 amino acids, which is virtually identical in the two proteins. KIABF1 can substitute ABF1 in S. cerevisiae, emphasizing the conservation of the multiple functions of this protein.

Amino Acid Sequence↗

PubMed1992

Gender differences in schizophrenia in three cultures. Results of the WHO collaborative study on psychiatric disability.

As part of a systematic research project on the influence of gender factors on age at onset, symptomatology, and course of schizophrenia, data on gender differences in age at onset and symptomatology of schizophrenia from the WHO Collaborative Study "On Assessment and Reduction of Psychiatric Disability" were compared between seven research centres of three different cultural regions. Results on age at onset of five European centres confirmed the well known fact of an earlier onset in men. The earlier onset in women seen in Khartoum and Ankara could be attributed to patient selection because male/female differences in age at onset and male/female ratios in the various samples covary. In the Islamic centres no relevant gender differences in real age at onset and in symptomatology could be detected as probable causes of earlier hospitalisation of women. Major gender differences in symptomatology were found in the Balkan centres of Sofia and Zagreb with a high prevalence of delusional symptoms in women and depression in men. In Western Europe centres, nuclear schizophrenic symptoms were equally prevalent in either sex, while nonspecific symptoms like irritability and tiredness (more frequent in women) and maladaptive illness behaviours like alcohol abuse and social withdrawal (more frequent in men) differed between the sexes. Explanatory hypotheses and the implications of these results are discussed.

Adult↗

PubMed1992

Is age of onset in schizophrenia influenced by marital status? Some remarks on the difficulties and pitfalls in the systematic testing of a "simple" question.

Schizophrenia is a disease characterized by a distinctly higher age at onset and at first admission in females than in males. In a systematic study on gender differences in schizophrenia we have confirmed this finding using different sets of data, in particular through the examination of a large and representative sample of first-admitted patients. The question addressed in this paper is whether marital status influences this sex-specific age difference. Assuming that marriage or a stable relationship is a protective factor in schizophrenia, delaying the onset of the disease or first hospitalization, the hypothesis was formulated that the later age of onset in women is at least partly explained by their generally earlier age of marriage. Testing this hypothesis illustrates some of the methodological problems that often occur when a causal analysis of social data is attempted. The problems emerge especially when both the dependent variable (age of onset/first admission) and the independent variable (marital status) are essentially related to age. First results appearing to indicate an influence of marital status on age at first admission did not bear a critical interpretation.

Adolescent↗

PubMed1992

Transnational stability of gender differences in schizophrenia? An analysis based on the WHO study on determinants of outcome of severe mental disorders.

Gender-specific analyses of the multinational WHO-Determinants of Outcome-Study (including 1,292 cases from 10 countries) demonstrate the transnational stability of major findings on gender differences in schizophrenia: Male patients have an earlier mean age at onset in all countries. In female patients, the distribution of the age at onset shows a second peak after age 40 years. No gender differences on nuclear symptoms of schizophrenia can be detected, but on uncharacteristic symptoms, particularly some aspects of the illness behaviour, differences appear. This investigation supports the transcultural validity of gender differences found in the German ABC-Schizophrenia-Study and in the Danish-German Psychiatric Case Register studies.

Adult↗

PubMed1992

First onset and early symptomatology of schizophrenia. A chapter of epidemiological and neurobiological research into age and sex differences.

In the frame of the ABC (Age, Beginning and Course) Schizophrenia Project we studied the influence of age and sex on first-ever onset, symptom manifestation and early course up to first admission in schizophrenia by using a large, representative sample of first-admitted schizophrenic patients. The results showed that the two variables had surprisingly little bearing upon the core symptoms, particularly on negative and other most frequent symptoms and on first-rank symptoms. In 70% of the cases schizophrenia started solely with negative symptoms, in 20% with negative and positive and in 10% with positive symptoms only. In most of the cases symptoms accumulated exponentially up to the first acute episode with positive symptoms appearing considerably later. The age differences observed concerned secondary phenomena associated with developmental factors. Such phenomena, i.e. anxiety, depression and the cognitive formation of delusions, can be interpreted as responses to the psychosis. Also the sex differences, which culminated in far more frequent socially negative disease behaviour in males, were limited to secondary phenomena. This positive and negative core symptomatology of schizophrenia seems to be astonishingly uniform and fairly independent of age and sex at this early stage of the disease. The only remarkable difference was a three to four years higher mean age of onset in females. We were able to show in animal experiments and to confirm in a clinical study that this finding is attributable to a neuromodulatory effect of estrogens on the sensitivity of D2 receptors in the brain. Apparently, estrogens raise the vulnerability threshold until menopause and have a slight neuroleptic-like effect on the symptomatology in acute schizophrenic episodes.

Adolescent↗

PubMed1992

Differential validity of psychometric tests in dementia of the Alzheimer type.

Forty-nine patients with a clinical diagnosis of probable dementia of the Alzheimer type underwent an extensive test battery designed to evaluate cognitive deficits according to NINCDS/ADRDA criteria. All patients demonstrated signs of impairment on this test battery. One day later, they were administered a second test battery that consisted of the Mini-Mental State Examination (MMS), the Alzheimer's Disease Assessment Scale (ADAS), the SKT test (SKT), and the Brief Cognitive Rating Scale (BCRS) to assess the construct validity, sensitivity, and possible shortcomings of these tests. A control group of 47 age-matched persons was administered the same test battery to allow a comparison with reference values from other studies. Due to the design of the study, values of controls and patients did not overlap. Intercorrelations in patients were above 0.65 (p < 0.05 after Bonferroni correction) for all four cognitive tests. The ADAS and BCRS appeared to document the whole course of the disease in patients studied. The best differentiation with the SKT test could be obtained in mild to moderate dementia; however, due to the test's construction, a floor effect demonstrated its limitations in the case of severe dementia. Results obtained with the MMSE indicated the contrary: a ceiling effect showed its lack of differentiation in mild dementia. Therefore, a combination of tests should be used in the evaluation of cognitive deficits in the course of dementia of the Alzheimer type.

Activities of Daily Living↗