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Biomedical subjects

M Bartels

Publications and source records attributed to M Bartels.

At least 37 records · Page 2Linked to original sources
PubMed2002

Genetic and environmental influences on the development of intelligence.

Measures of intelligence were collected in 209 twin pairs at 5, 7, 10, and 12 years of age, as part of a longitudinal project on intelligence, brain function, and behavioral problems. Intelligence was measured at 5, 7, and 10 years of age with the RAKIT, a well-known Dutch intelligence test, consisting of 6 subscales. At 12 years of age, the complete WISC-R was administered (12 subscales). Both intelligence tests resulted in a measure of full-scale IQ (FSIQ). Participation rate is around 93% at age 12. Correlation coefficients over time are high: (r(5-7) = .65; r(5-10) = .65; r(5-12) = .64; r(7-10) = .72; r(7-12) = .69 and r(10-12) = .78). Genetic analyses show significant heritabilities at all ages, with the expected increase of genetic influences and decrease of shared environmental influences over the years. Genetic influences seem to be the main driving force behind continuity in general cognitive ability, represented by a common factor influencing FSIQ at all ages. Shared environmental influences are responsible for stability as well as change in the development of cognitive abilities, represented by a common factor influencing FSIQ at all ages and age-specific influences, respectively.

Child↗
PubMed2002

Heart-rate variability (HRV) in the ECG trace of routine EEGs: fast monitoring for the anticholinergic effects of clozapine and olanzapine?

Drug monitoring in psychiatry usually serves psychoactive drug plasma concentration measurement. Anticholinergic properties offer a faster approach to monitoring pharmacodynamic intraindividual effects of the drug by measuring their effects on heart rate variability (HRV), which is sympathetically and parasympathetically controlled via cholinergic synapses. The plasma concentrations of the atypical antipsychotics clozapine and olanzapine correlated with parameters of HRV in 59 patients suffering from schizophrenia or schizoaffective disorder. HRV during 4 minutes at rest was extracted from the ECG trace of a routine digital EEG registration in addition to blood sampling for plasma concentration measurement (HPLC method). We calculated sympathetically and parasympathetically controlled heart frequency bands (low, medium and high frequency) and other HRV parameters, coefficient of variation (CV), and root mean square of successive differences (RMSSD). All HRV parameters were significantly more impaired in clozapine patients (n = 33, mean clozapine plasma concentration 331 +/- 294 ng/ml) than in olanzapine patients (n = 26, mean olanzapine plasma concentration 42 +/- 32 ng/ml) and demonstrated 1.7 - 4.8 times the cardiac anticholinergic properties of clozapine in vivo. 14 out of 14 patients with a CV beyond 3.2 % had clozapine plasma concentrations below the proposed optimal therapeutic concentration of 350 ng/ml. All HRV parameters were inversely and significantly correlated with the clozapine plasma concentrations (such as lgCV: r = - 0.73, p < 0.001) and, to a lesser extent, with the olanzapine plasma concentrations (lgCV r = - 0.44, p < 0.05). These results underline the potential clinical value of HRV parameter extraction from routine ECGs in predicting plasma concentrations and objective individual neurocardiac effects of drugs with anticholinergic properties.

Adolescent↗
PubMed2002

Increased serum levels of CD95 in Alzheimer's disease.

There is growing evidence for a role of apoptosis in Alzheimer's disease (AD). Recent findings suggest an increased susceptibility of lymphocytes to apoptosis in AD. To prove the hypothesis of systemic alterations in the apoptotic balance in AD, serum and cerebrospinal fluid levels of soluble CD95, which is known to mediate apoptosis, were measured. In the serum, AD patients exhibited significantly higher levels of CD95 than the controls (p = 0.017), suggesting an involvement of peripheral markers in AD.

Aged↗
PubMed2001

Differential activation in parahippocampal and prefrontal cortex during word and face encoding tasks.

Episodic encoding is the first step in the formation of a memory trace. The relation between type of stimulus material and regional brain activation is not fully understood. We measured brain activation using fMRI in 12 healthy subjects during two experiments, word and face encoding. A widespread network of common activations in both tasks was present in the bilateral frontal (BA44/45), occipital (BA17/18/19) and fusiform gyri (BA37) as well as the right hippocampal formation (BA30). A region-of-interest-analysis for the hippocampal formation and dorsolateral prefrontal cortex (DLPFC) was performed additionally. During face encoding the right dorsal and during word encoding the bilateral ventral hippocampal region was activated. In the prefrontal cortex a lateralization to the left side was present only for word encoding. During encoding, activation in the inferior frontal and hippocampal cortex is modulated by the type of stimulus material.

Adult↗
PubMed2001

Noradrenergic modulation of human cortex excitability by the presynaptic alpha(2)-antagonist yohimbine.

The objective of this study was to determine if yohimbine, a central norepinephrine enhancing drug, increases cortico-motoneuronal excitability in intact humans. Transcranial magnetic stimulation was used to assess excitability of the motor system reflected in the parameters motor threshold, recruitment curve, intracortical inhibition and intracortical facilitation before and after oral administration of 20 and 40 mg yohimbine. Oral intake of 40 but not 20 mg yohimbine increased slope and plateau of the recruitment curve and intracortical facilitation. Motor threshold and intracortical inhibition remained unchanged. The data show that pharmacological enhancement of central norepinephrine in humans is effective to increase the cortico-motoneuronal excitability. Since cortical excitability is closely linked to neuroplasticity, this observation might be of possible relevance for strategies to enhance rehabilitative processes after cortical lesions by pairing noradrenergic drugs with motor training.

Adrenergic alpha-Antagonists↗
PubMed2001

Are emotions contagious? Evoked emotions while viewing emotionally expressive faces: quality, quantity, time course and gender differences.

In human interactions, frequently one individual becomes 'infected' with emotions displayed by his or her partner. We tested the predictions by Hatfield et al. (1992) (Primitive emotional contagion. Review of Personal and Social Psychology 14, 151-177) that the automatic, mostly unconscious component of this process, called 'primitive emotional contagion', is repeatable and fast, that stronger facial expressions of the sender evoke stronger emotions in the viewer and that women are more susceptible to emotional contagion than men. We presented photos from the Pictures of Facial Affect (Ekman and Friesen, 1976). (Pictures of Facial Affect. Consulting Psychologists Press, Palo Alto) on a PC varying the affective content (happy and sad), the expressive strength and the duration of presentation. After each photo, subjects rated the strength of experienced happiness, sadness, anger, disgust, surprise, fear and pleasure. Feelings of happiness or sadness were significantly, specifically and repeatedly evoked in the viewer - even with presentations lasting only 500 ms. Stronger expressions evoked more emotion. The gender of the viewer had weak effects. We hypothesize that this fast and repeatable reaction is likely to have a 'prewired' neural basis. We propose that the induction of emotional processes within a subject by the perception of emotionally expressive faces is a powerful instrument in the detection of emotional states in others and as the basis for one's own reactions. Detailed knowledge of emotional reactions to faces is also valuable as a basis for psychiatric studies of disorders in affect and/or communication and in studies using functional imaging (fMRI or PET) where faces are increasingly used as stimuli.

Adult↗
PubMed2001

Investigation of contemporary gilded forgeries of ancient coins.

Four contemporary forgeries of ancient gold coins were investigated regarding techniques used for gilding, and the composition of the gold cover and the base metal core. The forged coins are a Daric of the Persian Empire, a Gold Stater in the name of Alexander, and two Solidi of the late Roman Empire. A combination of modern analytical methods such as Scanning Electron Microscopy (SEM), Electron Probe Micro Analysis (EPMA), X-Ray Fluorescence Spectrometry (XRF), and SecondaryIon Mass Spectrometry (SIMS) was used. The results demonstrate that the coins represent the main three technologies of gilding used in antiquity. The core of the Daric is a silver Siglos, plated by leaf gilding. The Gold Stater was forged by foil gilding using a silver core. The Roman Solidi have a core of either silver or copper and were plated by fire gilding. On account of our results it is possible to compare the forgers' profits made by use of the different technologies of forging.

Journal Article↗
PubMed2001

Dynamic regulation of EEG power and coherence is lost early and globally in probable DAT.

Electroencephalographic (EEG) findings in dementia of Alzheimer type (DAT) include slowing of alpha frequency, loss of alpha band power, increased theta and delta power and reduced coherence. Here it is evaluated whether a) EEG acquisition during different functional states facilitates the detection of DAT-associated EEG changes, and b) EEG changes in mild DAT are topographically confined or global. Power spectra and coherence of EEGs from 29 patients with mild probable DAT and 28 age- and sex-matched controls were compared during three cognitive states. Group differences in power spectra and coherence were largest during resting with eyes open, yielding a 77% correct classification result. Already in early stages of probable DAT, EEG changes were topographically wide-spread. The task-related up- and down-regulation of power and coherence was impaired already in mild probable DAT. We propose to augment clinical EEG assessment by including a quantitative analysis of the dynamic power and coherence changes from rest, eyes closed to eyes open in suspected DAT.

Aged↗
PubMed2001

Recognizing one's own face.

We report two studies of facial self-perception using individually tailored, standardized facial photographs of a group of volunteers and their partners. A computerized morphing procedure was used to merge each target face with an unknown control face. In the first set of experiments, a discrimination task revealed a delayed response time for the more extensively morphed self-face stimuli. In a second set of experiments, functional magnetic resonance imaging (fMRI) was used to measure brain activation while subjects viewed morphed versions of either their own or their partner's face, alternating in blocks with presentation of an unknown face. When subjects viewed themselves (minus activation for viewing an unknown face), increased blood oxygenation was detected in right limbic (hippocampal formation, insula, anterior cingulate), left prefrontal cortex and superior temporal cortex. In the partner (versus unknown) experiment, only the right insula was activated. We suggest that a neural network involving the right hemisphere in conjunction with left-sided associative and executive regions underlies the process of visual self-recognition. Together, this combination produces the unique experience of self-awareness.

Adult↗
PubMed2001

Activation of right fronto-temporal cortex characterizes the 'living' category in semantic processing.

It is a vital ability for humans to distinguish between living and non-living objects. Whether the semantic features of these two classes of objects are represented in distinct brain areas, is unknown. In our study, words belonging to the categories 'living' and 'non-living' were presented visually to twelve right-handed volunteers, while brain activation was measured with event-related fMRI. Subjects had to judge whether the item belonged to one of these categories. Common areas of activation (P<0.05, corrected) during processing of both categories include the inferior occipital gyri bilaterally (BA 17/18), left inferior frontal gyrus (BA 44/45) and left inferior parietal lobe (BA 40). During processing of 'living' minus 'non-living' items, signal changes (P<0.05, corrected) were present in the the right inferior frontal (BA 47), middle temporal (BA 21) and fusiform gyrus (BA 19). Our results are in line with findings from patients with a deficit in semantic processing of living things, who specifically suffer from right hemispheric lesions.

Adult↗
PubMed2001

[Chronic cholecystitis simulating gallbladder tumor with liver abscess. Case report].

We report on a 58 year-old male who presented with nausea, a painful tumor palpable in the upper right epigastrium, moderate fever without leukocytosis. Both ultrasonic scan and subsequent computerized tomography lead to the primary diagnosis of a malignant tumor of the gall bladder infiltrating the liver and inducing an intrahepatic abscess formation in segments 4b and 3. The patient was scheduled for emergency operation, i.e. abscess drainage, cholezystectomy, and hemihepatectomy. However, at operation a purulent chronic cholezystitis was found without involvement of the liver itself. Consequently, a cholezystectomy was necessary and performed. Histological examination of the gall bladder revealed no signs of malignancy. The patient had an uneventful recovery and was discharged on post-operative day seven. This case report shows the difficulties in the differential diagnosis of inflammable processes and malignancies, which affect the gall bladder and adhering structures. A chronic inflammable process can mimic solid tumors. Despite cost-effective diagnostic tools the correct diagnosis was finally found by surgery.

Cholecystectomy↗
PubMed2001

[Surgical therapy of cystic echinococcosis of the liver].

This study analyses the results of a surgical deroofing technique that was used for the treatment of cystic echinococcosis of the liver in our institution during the last 18 years. The deroofing technique was used on 106 of 132 patients from January 1981 to December 1998. Other operative techniques (pericystectomy, hemihepatectomy) were performed on 26 patients. In 12 cases (9%) the operative procedure was completed by interventions at the extrahepatic bile ducts. 99 patients (75%) showed one or two cysts, and the remaining 33 patients (25%) had three or more cysts in the liver. 18 (14%) patients had to be reoperated on account of complications: in 5 cases a postoperative hemorrhage, in 11 cases a bile duct leakage and in 2 cases an intraabdominal abscess had to be treated operatively. The follow-up of 74 patients (81%) revealed recurrent disease in 14 (19%) cases. Surgical deroofing of cystic echinococcosis of the liver is easy to perform and in contrast to other minor surgical interventions universally applicable. The recurrence rate and the rate of postoperative complications are comparable to other minor surgical techniques. Therefore in our view this procedure represents the therapy of choice.

Adolescent↗
PubMed2001

[Which patients with major depression benefit from prefrontal repetitive magnetic stimulation].

Antidepressive benefit of prefrontal repetitive magnetic stimulation (RTMS) for one or two weeks varies between 6 % and 60 % (mean 37 %) improvement of the Hamilton depression scale vs. 12 % improvement following sham RTMS. This variance is probably caused by study specific stimulus parameters but also by genetic, psychopathological and neuropsychological characteristics of the patients as well as by the functional state of the cortex area below the stimulation coil. Data from 10 open and 7 sham controlled studies including two own studies comprising more than 300 patients with major depression have been published to date. In synopsis several positive predictors for antidepressive response of prefrontal RTMS become apparent: 1) younger age, 2) somatic signs of anxiety, 3) lack of cortical hyperactivity below the magnetic coil pulsed by 10 Hz stimuli, 4) cortical hypermetabolism below the 1 Hz pulsed coil. Negative predictors of response to prefrontal RTMS were: 1) Advanced age, 2) prefrontal atrophy, 3) cognitive impairment in neuropsychological tasks assigned to the prefrontal cortex, 4) psychotic symptoms, 5) cortical hyperactivity below 10 Hz pulsed coil 6) non-response to electroconvulsive therapy (ECT). While prefrontal RTMS will probably not replace ECT in severe major depression with psychotic symptoms it could be beneficial especially in younger anxious patients without cognitive impairment.

Clinical Trials as Topic↗
PubMed2001

Surgical removal of a distinct subcutaneous metastasis of multilocular hepatocellular carcinoma 2 months after initial percutaneous ethanol injection therapy.

Subcutaneous tumor seeding after percutaneous ethanol injection therapy (PEI) for hepatocellular carcinoma is a rarely seen complication. It is reported due to needle track seeding during PEI after a distance of 6-46 months. Metastatic tumor spread is described subcutaneously, to the chest wall, abdominal wall and diaphragm. We report the case of a 76-year-old patient with chronic hepatitis B infection and cirrhosis which let to a multilocular hepatocellular carcinoma who underwent PEI. This patient developed 2 months after primary PEI a subcutaneous tumor formation confined to the right lower chest wall. Surgical tumor resection was performed. The histopathological evaluation confirmed subcutaneous seeding of the preknown hepatocellular carcinoma with a maximum of 30 mm in diameter. As a risk of PEI subcutaneous metastasis of the primary tumor should be considered even in early stage of therapy and close follow-up of the patient during treatment is required. Surgical tumor resection to ensure the curative intention of PEI is advisable.

Aged↗
PubMed2001

Microglia/macrophages proliferate in striatum and neocortex but not in hippocampus after brief global ischemia that produces ischemic tolerance in gerbil brain.

The current study determined whether short durations of ischemia that produce ischemia-induced tolerance stimulate glial proliferation in brain. Adult male gerbils were injected with BrdU (50 mg/kg) and dividing cells were detected using immunocytochemistry after sham operations, 2.5 or 5 minutes of global ischemia, or ischemia-induced tolerance. The 2.5-minute ischemia and the ischemia-induced tolerance did not kill hippocampal CA1 pyramidal neurons, whereas the 5-minute ischemia did kill the neurons. At 4 days after 2.5-minute global ischemia, when cell proliferation was maximal, BrdU-labeled cells increased in striatum and in neocortex, but not in hippocampus. The majority of the BrdU-labeled cells were double-labeled with isolectin B4, showing that these dividing cells were primarily microglia or macrophages, or both. Similarly, BrdU-labeled microglia/macrophages were found in striatum and neocortex but not in hippocampus of most animals 4 days after ischemia-induced tolerance (2.5 minutes of global ischemia followed 3 days later by 5 minutes of global ischemia). No detectable neuronal cell death existed in striatal and cortical regions where the microglia/macrophage proliferation occurred. Though 3 of 7 animals subjected to 2.5 minutes of ischemia showed decreased myelin-associated glycoprotein (MAG) immunostaining and increased numbers of adenomatous polyposis coli-stained oligodendrocytes in lateral striatum, this did not explain the microglia/macrophage proliferation. Data show that ischemia-induced tolerance in the gerbil is associated with proliferation of microglia/macrophages in striatum and cortex but not in hippocampus. Because there is no apparent neuronal death, it is postulated that the microglia/macrophage proliferation occurs in response to an unknown nonlethal injury to neurons or glia and may be beneficial.

Adenomatous Polyposis Coli Protein↗
PubMed2000

Both pain and EEG response to cold pressor stimulation occurs faster in fibromyalgia patients than in control subjects.

Pain-evoked brain potentials elicited by laser stimulation have been repeatedly shown to be abnormal in fibromyalgia syndrome. However, to our knowledge this is the first study assessing enduring (cold pressor) pain and correlated EEG changes in fibromyalgia. EEG power and subjective pain ratings during the cold pressor test were analyzed and contrasted with tasks not involving sensory stimulation (rest, mental arithmetic and pain imagery) in 20 patients with fibromyalgia and 21 healthy control subjects. Fibromyalgia patients both perceived pain and judged pain as intolerable earlier than control subjects, while pain intensity ratings and EEG power changes during subjective awareness of pain were similar in both groups. In patients and control subjects, pain was correlated with a rise in delta, theta and beta power. EEG power spectra during pain imagery and mental arithmetic were significantly different from those observed during the cold pressor test. In conclusion, fibromyalgia patients seem to process painful stimuli abnormally in a quantitative sense, thus producing both the sensation of pain, as well as the associated EEG patterns, much earlier than control subjects. However, the quality of the pain-associated EEG changes seems similar.

Cold Temperature↗