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Biomedical subjects

T Gasser

Publications and source records attributed to T Gasser.

At least 181 records · Page 10Linked to original sources
PubMed1991

[Neurogenetics--the challenge for neurology. 1. Neurogenetic diseases].

Progress in molecular genetics has provided insight into a number of neurogenetic disorders. The chromosomal location of the genes for Huntington's disease, Wilson's disease, myotonic dystrophy and Friedreich's ataxia are now known. In families affected by these illnesses, linkage analysis can now be employed for presymptomatic or prenatal diagnosis. The genes for Duchenne and Becker muscular dystrophy and neurofibromatosis I have been cloned and sequenced, allowing the direct analysis of the genetic defect in many cases, and thereby providing further insight into the pathophysiology. In addition, the classification of several neurogenetic diseases, such as the hereditary motor and sensory neuropathies or the spinal muscular atrophies can now be based on the chromosomal location of the affected gene(s).

Chromosome Mapping↗
PubMed1990

EEG power and coherence while male adults watch emotional video films.

Quantitative EEG analysis recorded at F3, F4, T3, T4, P3, P4 was performed for a group of healthy right-handed male adults (n = 9) viewing video films varying in their inductiveness on the affective valence dimension. Digital EOG-correction permitted the inclusion of trials with eye movements. Muscle artifacts were statistically treated by means of analysis of covariance (ANCOVA). The configuration of topographically motivated EEG parameters corresponded to the subjective valence rating of different video films. Low broad band coherences (COHs) ranked films along the subjective ratings within each hemisphere by the fronto-temporal COHs and interhemispherically by the T4-T3 COH, as did, restricted to the right hemisphere, similarity of beta 2 band power topography over time. High frequencies may be involved in the processing and low frequencies in the transmission of differential affective information, which to integrate seemed to utilize resources of both hemispheres. Alpha 2 and beta 1 COHs were sensitive to variations in an integrality/disassociation dimension with regard to the arrangement of verbal-visual affective cues. Power fluctuations at frontal leads pointed to difficulties in interpreting interhemispheric EEG asymmetries in emotion research, if information on time dynamics is discarded.

Adult↗
PubMed1990

Pubertal growth in chronic renal failure.

We evaluated the growth records of 15 boys and 14 girls who developed end-stage renal failure before or during puberty and who were regularly followed from the onset to the end of their pubertal growth spurt. Height data were smoothed by using the kernel estimation method. Mean values for age, height, and height velocity at defined points of the pubertal growth period were compared with those of normal children entering puberty both at an average and late age. The start of the pubertal growth spurt was delayed by 2.5 y in both sexes. Its duration and intensity were significantly reduced. Mean pubertal height gain was 17.3 cm in boys and 13.9 cm in girls, i.e. 58 and 48% of that observed in the late maturing control group. Mean height at the onset of the pubertal spurt in the patients was the same as that in the late maturing healthy girls and 1.0 SD below that of corresponding boys. During the pubertal growth spurt, mean height declined to -2.9 SD in boys and -2.3 SD in girls. Although skeletal maturation was increasingly retarded, we did not observe accelerated growth velocity during late puberty. Our data indicate that most patients reaching end-stage renal failure before or during puberty irreversibly lose growth potential during this period. Renal transplantation did not consistently improve pubertal growth.

Adolescent↗
PubMed1988

Effect of carbamazepine on stimulus-evoked Ca2+ fluxes in rat hippocampal slices and its interaction with A1-adenosine receptors.

In rat hippocampal slices superfused with a medium lacking Mg2+ ions, CA1 neurons generated burst discharges which were sensitive to blockade by 2-amino-5-phosphonovaleric acid (APV) and antagonized by 20-50 microM carbamazepine (CBZ). Decreases of [Ca2+]o (delta Ca), evoked by repetitive synaptic activation, were reduced in the presence of CBZ by 20-50%, associated with a reduced membrane depolarization. CBZ also abolished an APV-sensitive increase of delta Ca in the synaptic area elicited by theophylline. CBZ inhibited binding of the A1-adenosine receptor antagonist, [3H]8-cyclopentyl-1,3-dipropylxanthine [( 3H]DPCPX), in a dose-dependent manner. The displacement curve was shifted to the left in the presence of guanine nucleotide, suggesting that CBZ acts as an antagonist at A1-receptors. It is concluded that CBZ exerts its electrophysiological actions in the hippocampus at a site beyond the ligand recognition moiety.

2-Amino-5-phosphonovalerate↗
PubMed1988

Development of the EEG of school-age children and adolescents. I. Analysis of band power.

Development in quantitative EEG parameters is studied for a sample of 158 normal children and adolescents aged 6-17 years. This is of interest both for increasing basic knowledge of human neurophysiology and for obtaining age standardized norms, useful in clinical research and applications. After selecting an appropriate epoch and correcting for EOG artifacts, the EEG at 8 derivations was submitted to spectral analysis in order to extract broad-band parameters in absolute and relative power. Change in EEG band power across age was quantified by polynomial regression analysis. This opened automatically the possibility to obtain age-standardized EEG norms. Development was for most EEG parameters non-linear, with more pronounced changes for absolute than for relative power. No sex differences and no pubertal spurt could be identified in contrast to most somatic quantities. A detailed statistical analysis revealed, however, that this might be due to using cross-sectional data. All bands except for alpha 2 decreased in absolute power, whereas the fast bands increased and the slow bands decreased in relative power. Strong evidence was found for a substituting process between theta activity and fast alpha activity.

Adolescent↗
PubMed1988

Development of the EEG of school-age children and adolescents. II. Topography.

Topographic aspects of EEG development of normal children and adolescents from 6 to 17 years are investigated with respect to various spectral parameters. The topographic distribution of spectral band power does not change between hemispheres across age. Changes take place, however, in the antero-posterior dimension. For the bands theta, alpha 1 and alpha 2 (and less so for delta) maturation starts at posterior derivations and ends at anterior derivations. For the band beta 2 (and to some extent also for beta 1), development progresses from Cz to Pz and further to occipital, lateral, central and frontal derivations. Principal component analysis (PCA) leads to a more parsimonious and better interpretable description of broad-band power and of its topographic distribution. Broad-band coherences increase with age, though to a modest degree. The different magnitudes of coherence between different regions can be largely accounted for by the interelectrode distances. Coherences, too, can be described in a more parsimonious and better interpretable way via PCA. The 3 components extracted reflect firstly the overall level of coherence, secondly the coherences of the occipital regions with all other regions and thirdly antero-posterior versus left-right coherences.

Adolescent↗
PubMed1988

CT scans and neuroleptic response in schizophrenia: a multidimensional approach.

Structural brain abnormalities in schizophrenia have been reported in a number of studies using computed tomography (CT). However, the prevalence and the localization of the abnormalities vary widely among studies. These discrepancies might stem from clinical and demographic differences among samples, from the choice of the CT parameters, or from the use of different criteria to define abnormalities. In an attempt to overcome these difficulties, we studied 12 CT parameters in 30 schizophrenic patients and 30 sex- and age-matched controls, and evaluated the data simultaneously through multidimensional scaling (MDS). MDS offers a graphic representation in which subtle deviations in the different CT parameters can be detected, independently of predetermined criteria for the definition of abnormalities. MDS distinguished 13 patients from the controls as having deviant values in one or more CT parameters. Five of these patients were first-onset schizophrenics. Patients with deviant CT parameters showed significantly poorer response to haloperidol therapy over 3 weeks than did patients without deviant CT parameters. Our results suggest that the MDS approach might be useful in identifying more precisely patients with and without structural brain abnormalities.

Adult↗
PubMed1988

Clinical course of subacute HIV encephalitis.

A subacute encephalitis is increasingly recognized to be the most frequent cerebral manifestation of human immunodeficiency virus (HIV) infection. Contradictory reports are given in the literature concerning its clinical course. In the present study, a group of 19 patients with subacute encephalitis was followed for an average of 210 days. A steady progression of the disease was documented using the Karnofsky index. An advanced disease, rated according to the Walther Reed staging classification, but not isolated immunological parameters such as the ratio of OKT4/8 subsets are associated with more rapid progression of the encephalitis. Age, social status, duration of HIV positivity and antibody titers to cytomegalovirus could not be identified as contributing factors.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Visual evoked potentials of mildly mentally retarded and control children.

Visual evoked potentials (VEPs) were recorded from 25 10- to 13-year-old mildly mentally retarded children and compared with those from 31 control children of the same age-range. Correlations of VEPs with age were weak, but a relationship between VEPs and IQ was demonstrated for the control group. The retarded group had significantly longer latencies and higher amplitude peaks than the control group, with the differences occurring primarily over non-specific cortex and for secondary components. Analysis also showed that the retarded group were neurophysiologically heterogeneous. Since the same children had been analyzed earlier by quantitative EEG methods, comparisons are made with respect to these two methods of investigating brain function.

Adolescent↗
PubMed1987

EEG coherence at rest and during a visual task in two groups of children.

EEG coherence was studied in a group of n = 31 normal children (NG) and in a group of n = 25 mildly mentally retarded children (EG), 10-13 years old. This was done for a recording at rest, eyes closed, and one during which a visual matching task was presented. Coherence showed little structure across frequency, apart from a slow decline towards higher frequencies. For the EEG at rest, coherence was higher for the EG and a slight increase with age was found. The visual task changed the coherence pattern in a complex way, and differently for the two groups. Coherence decreased in the fronto-central region (about the same in both groups) and increased in occipito-parietal central combinations (more so for the NG). The delta band showed predominantly an increase for the NG.

Adolescent↗
PubMed1987

The intra-individual reproducibility of flash-evoked potentials in a sample of children.

Visual evoked potentials (VEPs) to flash stimuli were recorded twice from 26 children aged 10-13 years, with an intersession interval of about 10 months. Test-retest reliability was poor for recordings taken from scalp locations overlying non-specific cortex and somewhat better for specific cortex. The size of consistency coefficients (i.e. correlations within session) showed that noise and artefacts were not the decisive factors which lower reliability. A comparison with retest correlations of broad band parameters of the EEG at rest for the same sample showed, to our surprise, smaller retest reliability for VEP parameters. Variability of the VEP in children over time seems to be a substantial as its well-known inter-individual variability.

Adolescent↗
PubMed1987

Does smoking interfere with the effect of histamine H2-receptor antagonists on intragastric acidity in man?

The interaction between smoking and the effect of histamine H2-antagonists on intragastric acidity was examined in a double blind double dummy placebo controlled study. Healthy volunteers, 11 smokers and 10 non-smokers, were given, on four separate days at least one week apart, either placebo or cimetidine 800 mg nocte or ranitidine 2 X 150 mg per day or ranitidine 300 mg nocte. Tablets were taken at 2115 and 0900 h. Smokers smoked a cigarette hourly from 0700 to 2300 h. Breakfast, lunch, and dinner were standardised. Intragastric acidity was measured with a combined intragastric glass electrode and a solid state recorder. The subjects were fully ambulatory. The three histamine H2-receptor antagonist regimens were less effective (p = 0.04) in smokers than in non-smokers, but the difference between acidity of smokers and non-smokers was small. Means of medians of pH during a 24-h period with placebo, cimetidine 800 mg, ranitidine 2 X 150 mg and ranitidine 300 mg were 1.6, 2.3, 3.1, and 2.7 in smokers and 1.5, 2.7, 3.2, and 3.1 in non-smokers, respectively. In a second part of the study seven chronic smokers were reexamined after acutely stopping smoking: inhibition of gastric acidity by histamine H2-receptor antagonists was similar before and after withdrawal. Smoking does not affect intragastric acidity in untreated volunteers and only slightly decreases the effectiveness of histamine H2-receptor antagonists on intragastric acidity. This effect best in part explains the unfavourable effect of smoking on healing of peptic ulcer in patients treated with these drugs.

Adult↗
PubMed1987

Reduction of gastric acidity with ranitidine or famotidine: early evening dosage is more effective than late evening dosage.

The antisecretory effect of a once daily dose of ranitidine and famotidine was examined after administration of the drugs either immediately after dinner or 3 h after dinner. A placebo-controlled multiple cross-over study was performed in 7 healthy ambulatory volunteers. They were given, on 6 separate days at least 1 week apart, either placebo, ranitidine 300 mg or famotidine 40 mg, either immediately after dinner or 3 h later. Breakfast, lunch and dinner were standardized. 24-Hour intragastric acidity was measured with a combined glass electrode. Duration of secretory inhibition by a drug was defined as the nighttime period between the first rise of pH above and the final fall below 3.5. This value represents the 95% upper confidence limit of nighttime pH values during placebo treatment. Secretory inhibition with early and late administration of ranitidine lasted for 10.7 and 7.3 h, respectively (p = 0.012). With famotidine it lasted for 10.1 and 7.1 h, respectively (p = 0.005). Gastric acidity after dinner was decreased by early but not late intake of ranitidine and famotidine. Thus, both ranitidine and famotidine were more effective when taken early, immediately after dinner, than when taken late in the evening. This observation might affect the mode of ulcer treatment with these drugs.

Adult↗
PubMed1987

Trial-to-trial variability of single potentials: methodological concepts and results.

Variability of single visual evoked potentials was investigated by means of three statistical tests sensitive to amplitude variations, gradual changes, and latency jitter, respectively. In a sample of (n = 78) normal children, a considerable number of inhomogeneous responders was found, and most prominent were gradual potential changes and latency jitter. Removal of latency jitter demonstrated that the gradual changes are not of latency type and only partly of the amplitude type. As found from empirical densities, there is strong indication that there were subpopulations differing in their response style. On the whole, however, it was concluded that there was no clear, interindividually stable type of response variation in these data.

Adolescent↗