Biomedical subjects

M Heil

Publications and source records attributed to M Heil.

At least 19 recordsLinked to original sources

PubMed1995

Stimulus-induced gamma oscillations: harmonics of alpha activity?

Event-related changes of spectral power of the EEG were studied for each integer frequency between 5 and 100 Hz in three subjects during memory storage and retrieval. Spectra were calculated for successive, overlapping time epochs in seven channels. In one subject a stimulus-locked increase of power was observed at 12 Hz, while in the other two alpha power decreased at the individual peak frequencies of 9 and 11 Hz, respectively. In all subjects corresponding changes of power appeared at frequencies which were integer multiples of the individual dominant alpha frequencies. An analysis of the cross covariance of the alpha, beta and gamma activity revealed high coefficients for harmonic frequencies only while all other covariances were negligibly small. It is argued that event-related gamma activity may be an epiphenomenon of event-related changes within the alpha band.

Adult↗

PubMed1995

Exploring memory functions by means of brain electrical topography: a review.

A series of experiments is reviewed which explored whether the functional brain state of long-term memory retrieval is correlated with specific changes in slow, DC-like event-related brain potentials. The main results are: (1) Retrieving associations from long-term memory is accompanied by a slow negative shift of 5-10 microV which prevails about as long as the retrieval process lasts, i.e., in our experiments, for a period of several seconds: (2) When different types of representations have to be reactivated in memory the slow negative wave shows a clearly distinct topography. The maximum was found in a verbal condition over the left frontal, in a spatial condition over the parietal, and in a color condition over the right occipital to temporal cortex. All these conditions were completely equivalent with respect to the established associative structure, the learning procedure, and the performance criterion. (3) The amplitude of the topographic maximum increases with the number of representations which have to be reactivated. This effect is not due to a non-specific increase of effort but specifically related to the number of activated episodic memory contents which had been experimentally established. In contrast, the reactivation of a priori given semantic association did not become manifest in a specific slow wave effect. These findings are compatible with the idea that memory retrieval implies a reactivation of those cortical cell assemblies in the cortex in which the constituting features of a mnestic entity had originally been processed during perception and learning. The results are also discussed with respect to the possible advantages of EEG and MEG recordings for a cognitive psychophysiology in comparison to other brain imaging techniques as PET or fMRI.

Brain↗

PubMed1995

Patterns of cerebral activation while mental images are rotated and changed in size.

Event-related brain potentials were recorded while subjects performed either a rotation or a size scaling transformation of a mental image. Images had to be rotated 0 degrees, 60 degrees, or 120 degrees or their size had to be enlarged by factors of 1:1, 1:3, or 1:5. Both tasks were accompanied by pronounced negative slow potentials, which extended over several seconds. The relative maximum of these shifts emerged at central to occipital leads. Over the occipital cortex, the negative potential had a similar amplitude level in all conditions and both tasks. However, at parietal and central areas, the negative slow wave changed in relation to the difficulty of the task. The amplitude increased with increasing rotation demands and if the scaling operation required an exact computation of the coordinates of the image. None of these effects could be attributed to an inverse change of P300.

Adult↗

PubMed1994

Safety and efficacy of lifibrol upon four-week administration to patients with primary hypercholesterolaemia.

The efficacy and safety of lifibrol, a novel cholesterol-lowering drug, was investigated in a double-blind clinical study in 168 patients with primary hypercholesterolaemia. Placebo and four lifibrol dose groups (150, 300, 450 and 600 mg/day) were tested over a period of 4 weeks. The mean LDL-cholesterol changes were 5.7%, -11.1%, -27.7%, -34.5% and -35.0%, respectively, after 4 weeks of treatment. No major changes in HDL-cholesterol were seen after this period. With the present study design, a decrease in triglycerides (-28%) was significant in the highest dosage group only. Additionally, it was shown that further independent risk factors for coronary heart disease were favourably influenced. Fibrinogen decreased in all dosage groups with a maximal mean value of 18% and a tendency toward reduction in lipoprotein (a) was observed in patients with high baseline levels (> 30 mg.dl-1). Lifibrol was generally well tolerated in all dosage groups and no serious adverse events were reported. Laboratory parameters did not show any clinically relevant alterations.

Anticholesteremic Agents↗

PubMed1994

Dynamics of activation in long-term memory: the retrieval of verbal, pictorial, spatial, and color information.

Paivio's (1986) dual code theory was tested in 5 experiments with a new paradigm for the FAN effect that enforced genuine memory recall. Subjects had to learn associations between concepts and mediators. The FAN of the concepts in relation to the mediators was varied systematically. Response times (RT) were measured while subjects had to decide whether 2 concepts were linked to each other or not by a common mediator. In Experiment 1 the concepts and mediators were words, whereas in the other experiments the concepts were line drawings. Colors served as mediators in Experiment 2 and spatial locations served as mediators in Experiments 3, 4, and 5. All of the experiments were equivalent with respect to the FAN, the learning procedure, and the retrieval test. In all of the experiments, RT proved to be a linear function of the FAN. These results suggested that the same dynamics hold for all types of information stored in long-term memory.

Adolescent↗

PubMed1993

A correction method for DC drift artifacts.

In order to cope with the problem of drift artifacts in ERP research a new off-line correction method is described. It estimates the DC drift from all prestimulus baselines of an experiment. For this end, an amplifier reset is performed at regular intervals and the DC off-set preceding any reset is stored. A regression is calculated between the prestimulus baseline amplitudes of consecutive trials and the time that has passed by. The amplitude trend which can be explained by either a linear or non-linear regression model is then subtracted from all data points. The power of the method is illustrated by two examples. The first shows that detrending increases the signal-to-noise ratio in ANOVA designs. The second shows that amplitude differences of event-related slow potentials, which appeared between the first and the second half of an experiment, could be explained by a non-linear drift component.

Analysis of Variance↗

PubMed1993

Topographic differences of slow event-related brain potentials in blind and sighted adult human subjects during haptic mental rotation.

Twelve blindfolded sighted, nine congenitally blind, and seven adventitiously blind subjects were tested in a haptic mental rotation task while slow event-related brain potentials in the EEG were recorded from 17 scalp locations. The overall topography of the slow wave pattern which prevailed during the task differed for sighted and for blind, but not for congenitally and adventitiously blind subjects. While the tactile stimuli were encoded, the blind showed a pronounced occipital and the sighted a pronounced frontal activation. The task-specific amplitude increment of a negative slow wave which can be understood as a manifestation of the process of mental rotation proper, showed a different topography for sighted and for blind subjects too. It had its maximum over central to parietal cortical areas in both groups, but it extended more towards occipital regions in the blind. In both groups, the effects were very similar to those observed in former studies with visual versions of the mental rotation task, i.e. the slow wave amplitude over central to parietal areas increased monotonously with an increasing angular disparity of the two stimuli to be compared. These results are discussed with respect to the question of whether visual deprivation in the blind can cause a reorganization of cortical representational maps.

Adult↗

PubMed1993

Imagery-perception interaction depends on the shape of the image: a reply to Farah (1989).

Farah (1989) reported that point threshold stimuli are detected better if they appear at spatial locations in the visual field that are covered by an image. By replicating her experiment with 3 instead of the original 2 images, we found that the effect depends on the shape of the mentally projected image. A second experiment with 9 different shapes revealed that the effect is modulated by the compactness and the size of the image--it is enhanced with increasing compactness and attenuated with increasing size. These findings do not unequivocally support the idea that imagery and perception interact because both processes share the same representational medium. Rather, they suggest that imagery can cause a figure-ground segregation in the visual field and that the shape of the figure may determine the amount of attention that is allocated to different sections in the visual field.

Eidetic Imagery↗

PubMed1993

Monitoring retrieval from long-term memory by slow event-related brain potentials.

Slow event-related brain potentials of nine subjects were recorded in an experimentally controlled long-term memory retrieval task (the Fan paradigm) from electrode sites F3, Fz, F4, Cz, P3, Pz, and P4. In all retrieval conditions, a very pronounced DC-like negative potential appeared over the left frontal cortex. This negativity was switched on with the presentation of the probe stimuli and prevailed in some conditions throughout the total recording epoch of 14 s. Particular retrieval conditions became manifest in distinct slow wave effects. The amplitude of a bilaterally distributed frontal negative slow wave increased when a more diversified associative structure had to be searched. The amplitude of another negative slow wave, which peaked bilaterally over parietal areas, was affected by the type of concepts that had to be retrieved. The amplitude was larger with general concepts (category labels) and smaller with specific concepts (category exemplars). These results suggest that distinct strategies are invoked when subjects are required to draw conclusions about different contents stored permanently in an associative network.

Adult↗

PubMed1993

[Haptic mental rotation in patients with congenital blindness, acquired blindness and normal vision persons].

Nineteen congenitally blind subjects (Ss), eleven Ss who went blind later in their life, and 42 control Ss with normal vision were tested in a tactile version of a "mental rotation" task. A specially constructed tactile display was used which enabled a rotation of the alphanumeric symbols in multiples of 60 degrees without any form distortion. Ss had to compare two successively presented symbols regarding whether the second was just a rotated version or also a mirror image of the first. Decision latencies and errors were recorded. Neither of dependent variables reveal any differences between the three groups of subjects. Moreover, the well known linear increase of decision latency as a function of angular disparity could also be observed with the tactile stimuli in all three groups. Both results are consistent with the assumption that mental rotation effects are neither linked to the visual modality nor to a manipulation of visual-analog representations. If the task is solved by so called analog processes then these seem to operate with non-visual spatial representations.

Adult↗

PubMed1991

Toward a functional categorization of slow waves: taking into account past and future events.

Ruchkin, Johnson, Mahaffey, and Sutton (1988) presented evidence for a frontal positive/posterior negative late slow wave (SW) which they found to be functionally related to conceptual load, i.e., the difficulty of mental calculation problems increased both the positive and negative parts of it. In the present study we replicated the paradigm of Ruchkin et al. with some modifications, and we also found that this late SW pattern is actually due to a superimposition of two slow potentials. Our results suggest that one potential (positive at frontopolar scalp) is related to the mental operation of division. However, the other potential (negative over posterior scalp) is not related to the computational task itself but to the expectation of stimuli that follow the task. In addition, we found that memorizing a digit seems to be associated with a positive slow wave over posterior scalp. Altogether, our data suggest that load imposed on working memory is associated with positive slow waves which show a task specific topography--mental division is associated with a pSW at FPZ, remembering with a pSW at PZ/OZ. On the other hand, the state of stimulus and task anticipation is associated with negative slow waves. The latter reach their amplitude maximum over posterior scalp, if visually presented information is anticipated. Our study demonstrates how functionally distinct slow waves can be disentangled by a systematic manipulation of events which either precede or follow the slow wave activity. Moreover, it shows that recording epochs must be of considerable length, if the functional significance of slow waves is the objective of research.

Adult↗

PubMed1990

[Primary cutaneous Ki-1-lymphoma].

With the help of immunohistochemical techniques and new antibodies developed in the last few years, we were able to identify 2 cases of nodular tumors of the skin as highly malignant Ki-1 lymphomas. The clinical course was characterized by the development of multiple skin tumors without any evidence of systemic involvement. After the excision of several skin tumors; we performed chemotherapy with the MACOP-B regimen. In one of our patients, however, this treatment could not prevent the occurrence of further tumors. Possibly, the cutaneous anaplastic Ki-1 lymphomas presented here are closely related to or even identical with mycosis fungoides d'emblée.

Aged↗

PubMed1989

Mechanism of regulating human leukemia cell growth and differentiation by a lymphokine.

Human myelogenous leukemia cells can be induced to differentiate in vitro along the monocyte-macrophage pathway by a T cell lymphokine maturation inducer. Maturation inducer has now been purified from a human T cell line and determined to be a single chain protein with an approximate molecular weight of 53,500. It induces the differentiation and proliferation of human leukemic HL-60 promyelocytes in a dosage-dependent fashion. Initial interaction with cells at G1 phase induced the cells to enter proliferating S phase. Subsequent differentiation from S phase was dependent on an optimal inducer quantity (18.7 pM - 18.7 nM) which mediated growth cessation and termination differentiation to monocytes-macrophages. When inducer quantity was more or less than this optimal range, the cells did not undergo differentiation but were continuously stimulated to proliferate. This may represent an important proliferation mechanism of leukemic cells.

Cell Cycle↗

PubMed1989

Growth and nutritional intake of infants with congenital heart disease.

Poor weight and length gain of infants with congenital heart disease is generally considered to be related to inadequate nutritional intake, but no longitudinal data on growth and nutritional intake of such infants are available. We compared weight, length, subscapular and triceps skinfold thickness, energy and protein intake (24-h dietary intake records) as well as serum prealbumin and albumin of infants with cyanotic heart disease (n = 8) or isolated left-to-right shunt (n = 8) with those of healthy infants aged (n = 8) 45-365 days. Weight, length, and combined (subscapular and triceps) skinfold thickness of the two groups with congenital heart disease (CHD) were significantly less from 183 through 365 days of age. However, energy and protein intake was similar to that of the control group from 45 through 365 days of age. Normal serum prealbumin and albumin in the infants with CHD ruled out protein-calorie malnutrition. It is concluded that a low level of food intake was not the main cause of inadequate growth and of small subcutaneous fat stores in these two small, but homogeneous, groups of infants with CHD.

Body Height↗

PubMed1989

Is the profile of binding of a panel of neoglycoproteins useful as a diagnostic marker in human lung cancer?

Histomorphological evaluation of the profile of carbohydrate-binding proteins with specificities to alpha- and beta-glucosides (maltose, cellobiose), alpha-L-fucosides (L-fucose), alpha-D-mannosides (D-mannose), a N-acetylated sugar, present in natural glycoconjugates (N-acetyl-D-glucosamine), two negatively charged sugars (glucuronic acid and sialic acid), rhamnose (6-deoxy-L-mannose) or to heparin has been assessed. 133 cases of formalin fixed, paraffin embedded human lung carcinoma specimens (45 cases of epidermoid carcinoma, 24 cases of small cell anaplastic carcinoma, 48 cases of adenocarcinoma, and 16 cases of large cell anaplastic carcinoma) as well as 14 cases with epithelial or biphasic mesothelioma and 7 cases of pleuritis carcinomatosa were incubated with biotinylated, suitably modified neoglycoproteins or heparin for detecting the corresponding endogenous sugar receptors (lectins). Histochemical reaction was demonstrated by use of the avidin-biotin-method. Significant differences were obtained between the different markers used for each cell type as well as between the different cell types. For separating small cell anaplastic carcinoma from non small cell anaplastic carcinoma the markers carrying the histochemically crucial maltose, fucose, and mannose residues are useful, showing a positive reaction to only 4-8% of the small cell anaplastic carcinoma cases compared to 60-80% of the non small cell carcinoma cases. For separation of mesothelioma from pleuritis carcinomatosa a carrier, modified by attachment of N-acetylglucosamine moieties is the most useful marker being negative in all cases of the analyzed mesothelioma cases and being positive in 62-80% of the adenocarcinoma cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomarkers, Tumor↗

PubMed1988

[Preventive use of vitamin D and fluoride in Austria].

The implementation of the recommended daily vitamin D and fluoride supplements for infants in Austria has been investigated during a nationwide infant nutrition survey (n = 1069). 93.9% of the infants received daily vitamin D supplements, whereas only 38% received fluroide. Rejection of fluoride supplemtation was most common among mothers aged between 30 and 45 years and mothers with university education. In Carinthia, Vorarlberg and Styria only 2 out of 10 infants received fluoride supplements. It seems necessary to reconsider the recommendations for fluoride supplementation in Austria.

Adult↗

PubMed1988

Iron intake and iron nutritional status of infants fed iron-fortified beikost with meat.

We compared iron intake and iron nutritional status of two groups of healthy term infants who received meat-containing baby foods fortified with ferrous sulphate (2 mg Fe/100 g). One group received an Fe-fortified formula (1.6 mg Fe/100 kcal) and the other a nonfortified formula. Fe intake of the group fed the nonfortified formula was significantly lower (p less than 0.0001). These infants received Fe mainly from fortification Fe with beikost (75-86%) and less than 10% met the recommended intake of 1 mg.kg-1.d-1; whereas 80-85% of the infants fed the Fe-fortified formula did. Hb, Hct, FEP, and ferritin were similar in both groups with the exception of lower ferritin values at age 365 d (p less than 0.05) in the group fed the nonfortified formula. No infant had hemoglobin less than 100 g/L. We conclude that regular consumption of commercially prepared Fe-fortified beikost with meat prevents most healthy term infants from Fe deficiency even if Fe intake is substantially below the recommended intake.

Breast Feeding↗

PubMed1986

[Lead intake from drinking water in the city of Vienna].

Daily lead intake from drinking water was estimated on the basis of lead concentrations in running and boiled drinking water samples of 42 Viennese households and reported drinking water consumption of adults living in those households. Lead concentration (means, SD, median) in running water samples (15.3 (37.9) micrograms Pb/l, median 6.3) was significantly higher (p less than 0.005) than in boiled water samples (6.4 (11.1) micrograms Pb/l, median 4.1). The highest lead concentrations in running water samples were found in houses built before 1945. Reported drinking water consumption was 1306 (576) ml/day (median 1242); more than 70% of drinking water was consumed at home. Calculated lead intake from drinking water in Vienna was 11.8 (22) micrograms Pb/day (median 5.2). Lead intake from drinking water was highest (19.5 (31.3) micrograms Pb/day, median 7.3) in houses built before 1945. Lead intake with food was calculated using published data on lead concentrations in food items and on food intake and data from the present study. Calculated average lead intake with food (206 micrograms Pb daily) was far below the estimated safe lead intake proposed by WHO 1972. We conclude that lead intake from drinking water in Vienna is low in most households. However, lead intake may be close to toxic levels if persons living in houses built before 1945 are consuming extremely large amounts of drinking water.

Adult↗