Biomedical subjects

Juergen Hennig

Publications and source records attributed to Juergen Hennig.

At least 19 recordsLinked to original sources

PubMed2007

Systematic investigation of balanced steady-state free precession for functional MRI in the human visual cortex at 3 Tesla.

Previous studies have applied balanced steady-state free precession (bSSFP) to functional brain imaging. Methods that exploit the strong frequency dependence of the MR signal in the bSSFP transition band are strongly affected by field inhomogeneity and frequency drifts. Recent bSSFP studies using "on-resonance" (in the bSSFP passband) acquisition claimed that higher sensitivity was achieved compared to traditional fMRI methods. However, the contrast mechanism that generates activation-related signal changes in bSSFP imaging is not yet fully understood. We performed a systematic study of on-resonance bSSFP signal behavior using a multiecho balanced SSFP sequence with different TRs at 3 Tesla. We conclude that intravoxel dephasing, or the off-resonance averaged steady state, dominates the bSSFP signal decay and determines the bSSFP fMRI contrast. Experimental findings were confirmed by simulations based on existing theories for signal formation around blood vessels in inhomogeneous tissues. The activation-induced signal change in on-resonance bSSFP increases with TE, and the TE dependence of the contrast-to-noise ratio (CNR) in bSSFP is similar to that in gradient echo-planar imaging (GE-EPI). However, GE-EPI has a significantly higher CNR efficiency.

Adult↗

PubMed2006

Association between a polymorphism in the promoter region of the TPH2 gene and the personality trait of harm avoidance.

In a genetic association study the role of the -703 G/T (rs4570625) polymorphism, located in the promoter region of the tryptophan hydroxylase 2 gene (TPH2), in personality traits was investigated in a sample of 404 healthy Caucasian subjects. A significant association between harm avoidance (HA), a trait related to anxiety, and the -703 G/T polymorphism was detected supporting the findings by Gutknecht and colleagues.

Adult↗

PubMed2006

S-Citalopram in neuroendocrine challenge-tests: serotonergic responsivity in healthy male and female human participants.

The aim of the present study was to assess the usefulness of the selective serotonin-reuptake-inhibitor S-Citalopram as a serotonergic challenge probe in 24 healthy male and 24 healthy female participants. The participants received a single oral dose of 10 and 20mg of S-Citalopram in a placebo-controlled double blind crossover design. In female subjects phases of the menstrual cycle were controlled. Changes in concentrations of cortisol in saliva were used to indicate serotonergic reactivity. S-Citalopram induced a reliable dose dependent rise in cortisol concentrations. Results reveal a clear dose-response relationship in both sexes. However, in contrast to the 10mg condition the dosage of 20mg led to significantly higher cortisol levels in females, whereas no differences could be observed with respect to different phases of the menstrual cycle (follicular vs. luteal). Adverse side effects were reported only after 20mg. The results clearly indicate that the dosage of 10mg should be preferred when challenging males and females. Results will be discussed with regard to the further use of S-Citalopram in neuroendocrine challenge tests.

Adult↗

PubMed2006

MR-Encephalography: Fast multi-channel monitoring of brain physiology with magnetic resonance.

A new approach to measure activation-related changes in the brain by magnetic resonance is described offering high temporal resolution of 10-100 measurements per second. This is achieved by simultaneous multi-channel reception where the spatial resolution during continuous observation is determined by the sensitive volume of each coil alone without any additional spatial encoding gradients. Experimental results demonstrate the very high sensitivity of this approach, which allows to directly measure and monitor the stimulus-dependent hemodynamic response as well as ECG- and breathing-related signal fluctuations. One-dimensional spatial encoding either parallel or orthogonal to the cortex demonstrates that vascular signals can be identified by the pronounced signal variation at the ECG-frequency. Noise analysis at different frequencies reveals regional signal fluctuations in the frequency range between 2 and 10 Hz. Furthermore, initial results show that frequency changes in the order of <0.03 Hz corresponding to <1 nano Tesla can be detected. In addition to its potential use in neuroscientific studies, this new method opens a wide range of applications for fast physiological monitoring and can be easily combined with conventional high-resolution imaging.

Brain↗

PubMed2006

Association of THR105Ile, a functional polymorphism of histamine N-methyltransferase (HNMT), with alcoholism in German Caucasians.

BACKGROUND: CNS histamine has been shown to have an inhibitory effect on reward and it is implicated in the etiology of addiction and stress. Histamine N-methyltransferase (HNMT) is believed to be the sole pathway for termination of the neurotransmitter action of histamine in mammalian brain. A common, functional polymorphism, a C314T transition in the HNMT gene, results in a Thr105Ile substitution of the protein encoded. A recent study has shown that the frequency of the Ile105 allele was significantly lower in alcoholics compared to that in non-alcoholics in Finns and Plains American Indians. Following up these results, we tested whether the Thr105Ile polymorphism was associated with alcoholism in German Caucasians. METHODS: Thr105Ile was genotyped in n=366 psychiatrically interviewed German Caucasian ICD-10 lifetime alcoholics, along with n=200 ethnically matched controls. RESULTS: No significant difference was found in the frequency of the Ile105 allele between alcoholics (0.11) and controls (0.10) (chi(2)=0.21, d.f.=1, p=0.647). Likewise, genotype distributions did not differ significantly. However, the frequency of the Ile105 allele was significantly lower in male alcoholics with a family history of alcoholism compared to that in male alcoholics without a family history of alcoholism (chi(2)=4.07, d.f.=1, p=0.044). CONCLUSIONS: In German Caucasians the association of the HNMT Thr105Ile polymorphism with alcoholism was not replicated per se, but a congruent association was found between the Ile105 allele and family history of alcoholism supporting the protective role of the Ile105 allele against alcoholism.

Adult↗

PubMed2006

Mirtazapine inhibits salivary cortisol concentrations in anorexia nervosa.

The antidepressant mirtazapine has been demonstrated to acutely inhibit cortisol concentrations in healthy subjects and depressed patients. Since both depressed and anorectic patients are characterized by hyperactivity of the hypothalamo-pituitary-adrenocortical (HPA) system, the clinical usefulness and the endocrinological effects of mirtazapine were investigated in anorexia nervosa (AN). Five female patients suffering from AN restricting subtype (DSM-IV criteria) were admitted to a closed ward and treated with mirtazapine for three weeks receiving 15 mg mirtazapine on day 0; 30 mg mirtazapine on day 1; and 45 mg mirtazapine per day from day 2 up to the end of the study (day 21). Besides weekly determination of clinical parameters (Body Mass Index [BMI], Hamilton Depression Rating Scale [21-HAMD]), salivary cortisol concentrations were measured before treatment (day - 1), at the beginning of treatment (day 0), after 1 week (day 7), and after 3 weeks (day 21) of treatment with mirtazapine. Saliva samples were collected hourly from 0800 up to 1,400 h. Repeated-measures ANOVA revealed a significant inhibition of salivary cortisol levels during 3-week treatment with mirtazapine (p<0.05) which became obvious already after the first mirtazapine administration (day 0). Moreover, a trend for an increase in BMI was seen (p=0.063), whereas no significant changes in 21-HAMD sum scores could be demonstrated. Double-blind, placebo-controlled studies are needed to clarify the question whether the observed changes in BMI are related to the mirtazapine-induced attenuation of HPA axis activity or whether they are due to monitoring of food intake and purgative behaviour on the closed ward.

Adult↗

PubMed2006

MRI myocardial motion and fiber tracking: a confirmation of knowledge from different imaging modalities.

OBJECTIVE: A helical configuration underlies the anatomy of cardiac structure, and a structure/function relationship is needed to determine if the ventricular myocardial band model defines this spatial relationship. This report explores how studies of velocity-encoded phase contrast magnetic resonance imaging (MRI) for myocardial motion and fiber tracking algorithms that imply fiber orientations can (a) quantify regional myocardial wall motion of the entire heart, (b) determine if these motion of implied fiber orientation link with the helical heart model, and (c) reveal if this new knowledge correlates with imaging information from other different imaging modalities. METHODS: Accumulated left ventricular motion patterns that accurately differentiate radial (i.e. contraction and expansion), rotational (i.e. twisting and untwisting), and longitudinal (i.e. lengthening and shortening) motion components are correlated with structure/function data achieved by sonomicrometer crystals, echocardiography, corrosion casts, and MUGA recordings. RESULTS: Acceleration fiber tracking to determine fiber orientation and cardiac motion during the ejection and rapid filling phases of the cardiac cycle corresponded to maximal force displayed by ultrasonic crystals placed into the angulation of the presumed functional units of the descending and ascending segments of the apical loop of the helical ventricular myocardial band, and motion by echocardiographic recordings. These integrated findings imply a favourable interaction of MRI with the myocyte orientation of the helical ventricular myocardial band. CONCLUSIONS: These composite findings indicate that phase contrast MRI techniques for high temporal resolution velocity mapping during cardiac motion and myocardial fiber tracking confirm other technologies, and centralize the capacity of MRI to link other imaging methods together relative to a single helical structural model. The close agreement amongst a spectrum of imaging studies provide a very powerful integration that transcends a single look; the same thing is observed by each component of global technology, thereby implying that the helical ventricular band is the structural basis for these functional changes.

Echocardiography↗

PubMed2006

Quantitative diffusion tensor MR imaging of the brain: field strength related variance of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) scalars.

The objectives were to study the "impact" of the magnetic field strength on diffusion tensor imaging (DTI) metrics and also to determine whether magnetic-field-related differences in T2-relaxation times of brain tissue influence DTI measurements. DTI was performed on 12 healthy volunteers at 1.5 and 3.0 Tesla (within 2 h) using identical DTI scan parameters. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were measured at multiple gray and white matter locations. ADC and FA values were compared and analyzed for statistically significant differences. In addition, DTI measurements were performed at different echo times (TE) for both field strengths. ADC values for gray and white matter were statistically significantly lower at 3.0 Tesla compared with 1.5 Tesla (% change between -1.94% and -9.79%). FA values were statistically significantly higher at 3.0 Tesla compared with 1.5 Tesla (% change between +4.04 and 11.15%). ADC and FA values are not significantly different for TE=91 ms and TE=125 ms. Thus, ADC and FA values vary with the used field strength. Comparative clinical studies using ADC or FA values should consequently compare ADC or FA results with normative ADC or FA values that have been determined for the field strength used.

Analysis of Variance↗

PubMed2006

Myocardial tissue phase mapping with cine phase-contrast mr imaging: regional wall motion analysis in healthy volunteers.

PURPOSE: To establish prospectively a database of normal three-dimensional systolic and diastolic endocardial and epicardial velocity values for all myocardial segments in healthy volunteers by using cine phase-contrast velocity magnetic resonance imaging, also called tissue phase mapping (TPM). MATERIALS AND METHODS: The study was approved by the institutional ethics committee and was conducted according to principles of the Declaration of Helsinki; each subject provided informed written consent. Ninety-six healthy volunteers (57 [59%] men, 39 [41%] women; mean age, 38 years +/- 12 [standard deviation]) underwent cardiac phase-contrast imaging with a black blood segmented k-space gradient-echo sequence for the analysis of three-dimensional myocardial velocity with high spatial resolution at 1.5 T on basal, midventricular, and apical short-axis views. Eighteen consecutive volunteers were imaged twice to determine interstudy reproducibility, and intra- and interobserver variability values were analyzed. Systolic and diastolic velocity curves were analyzed for peak velocity and time to peak velocity in the radial, circumferential, and longitudinal directions, as well as for torsion rate and longitudinal strain rate. Mixed-effects models with a random intercept for volunteers were used to test differences among the three ventricular sections and the transmural, endocardial, and epicardial parameters. RESULTS: TPM enabled reproducible assessment of myocardial velocity with small intra- and interobserver variability values. Systolic peak radial velocity was lowest at the apical level (P < .001); diastolic peak radial velocity was similar at all three myocardial levels (P = .73). As viewed from the apex, a relative counterclockwise rotation during systole was followed by a relative clockwise rotation of the apex against the base. Diastolic and systolic peak longitudinal velocity values decreased from base to apex (P < .001). A gradient between endocardium and epicardium was observed for radial velocity values, with greater endocardial velocity values (P < .001). CONCLUSION: TPM is a reproducible comprehensive modality for assessment of regional wall motion, and intra- and interobserver variability values are low.

Adult↗

PubMed2006

Neural correlates of antinociception in borderline personality disorder.

CONTEXT: A characteristic feature of borderline personality disorder (BPD) is self-injurious behavior in conjunction with stress-induced reduction of pain perception. Reduced pain sensitivity has been experimentally confirmed in patients with BPD, but the neural correlates of antinociceptive mechanisms in BPD are unknown. We predicted that heat stimuli in patients with BPD would activate brain areas concerned with cognitive and emotional evaluation of pain. OBJECTIVE: To assess the psychophysical properties and neural correlates of altered pain processing in patients with BPD. DESIGN: Case-control study. SETTING: A university hospital. PARTICIPANTS: Twelve women with BPD and self-injurious behavior and 12 age-matched control subjects. INTERVENTIONS: Psychophysical assessment and blood oxygen level-dependent functional magnetic resonance imaging during heat stimulation with fixed-temperature heat stimuli and individual-temperature stimuli adjusted for equal subjective pain in all the participants. MAIN OUTCOME MEASURE: Blood oxygen level-dependent functional magnetic resonance imaging signal changes during heat pain stimulation. RESULTS: Patients with BPD had higher pain thresholds and smaller overall volumes of activity than controls in response to identical heat stimuli. When the stimulus temperature was individually adjusted for equal subjective pain level, overall volumes of activity were similar, although regional patterns differed significantly. Patient response was greater in the dorsolateral prefrontal cortex and smaller in the posterior parietal cortex. Pain also produced neural deactivation in the perigenual anterior cingulate gyrus and the amygdala in patients with BPD. CONCLUSION: The interaction between increased pain-induced response in the dorsolateral prefrontal cortex and deactivation in the anterior cingulate and the amygdala is associated with an antinociceptive mechanism in patients with BPD.

Adult↗

PubMed2006

Sex-specific characteristics of cardiac function, geometry, and mass in young adult elite athletes.

PURPOSE: To study young adult elite athletes with age- and sex-matched sedentary controls to assess sex-specific differences for left ventricular (LV) and right ventricular (RV) volumes and mass as well as for LV contraction and relaxation. MATERIALS AND METHODS: A total of 23 male athletes (mean age 25 +/- 4 years, training 22 +/- 7 hours/week in rowing, swimming, or triathlon) and 20 female athletes (mean age 24 +/- 4 years, training 19 +/- 5 hours/week in rowing, swimming, or triathlon) and age- and sex-matched sedentary controls (21 male/17 female) underwent cardiovascular magnetic resonance (CMR) imaging (1.5 Tesla). Cardiac phase contrast imaging using a black-blood k-space segmented gradient echo sequence was used for analysis of cardiac contraction and relaxation and steady-state free-precession cine images were acquired for determination of cardiac volumes and mass. RESULTS: Male and female athletes showed similar increases in LV and RV volume and mass indices when compared to controls (ranging between 15% and 42%). No sex-specific differences in training effect on LV and RV volumes, mass indices, and ejection fractions, as well as LV to RV ratios of these volume and mass indices (parameters of balanced LV and RV dilatation and hypertrophy) were observed (all P for interaction >0.05). Similarly, no sex-specific differences in training effect on cardiac contraction and relaxation were found (all P for interaction >0.05). CONCLUSION: Young adult elite athletes do not show sex-specific adaptive structural and functional changes to exercise training in accordance with the benign nature of the hypertrophy associated with athlete's heart.

Adult↗

PubMed2006

Contrast behavior and relaxation effects of conventional and hyperecho-turbo spin echo sequences at 1.5 and 3 T.

To overcome specific absorption rate (SAR) limitations of spin-echo-based MR imaging techniques, especially at (ultra) high fields, rapid acquisition relaxation enhancement/TSE (turbo spin echo)/fast spin echo sequences in combination with constant or variable low flip angles such as hyperechoes and TRAPS (hyperTSE) have been introduced. Due to the multiple spin echo and stimulated echo pathways involved in the signal formation, the contrast behavior of such sequences depends on both T2 and T1 relaxation times. In this work, constant and various variable flip angle sequences were analyzed in a volunteer study. It is demonstrated that a single effective echo time parameter TE(eff) can be calculated that accurately describes the overall T2 weighted image contrast. TE(eff) can be determined by means of the extended phase graph concept and is practically independent of field strength. Using the described formalism, the contrast of any TSE sequence can be predicted. HyperTSE sequences are demonstrated to show a robust and well-defined T2 contrast allowing clinical routine MRI to be performed with SAR reductions of typically at least 70%.

Adolescent↗

PubMed2006

Fast and quantitative high-resolution magnetic resonance imaging of the optic nerve at 3.0 tesla.

A novel and fast magnetic resonance imaging approach for imaging the optic nerve and the surrounding cerebrospinal fluid sheath is presented. The method provides high contrast between the nerve and cerebrospinal fluid and allows for accurate quantification of the optic nerve and its cerebrospinal fluid sheath diameter within 1.5 seconds scan time. Results of a volunteer study illustrate that measurements can reliably be performed even in the distal part of the intraorbital optic nerve track. Accuracy of quantification of the new technique is demonstrated by the assessment of changes in the optic nerve and CSF sheath diameter between straight gaze and 30 degrees abduction.

Adult↗

PubMed2005

The influence of the dopaminergic system on cognitive functioning: A molecular genetic approach.

Many pharmacological and clinical studies have demonstrated the importance of the dopaminergic (DA) system for cognitive functioning but little is known about the genetic basis of general cognitive ability that has been demonstrated to be highly heritable. Attempts to detect associations between certain gene loci and endophenotypes of general cognitive ability have turned out to be more promising. Therefore, the aim of the present study was to investigate two dopaminergic candidate genes (COMT VAL158MET and DRD2 TAQ IA) for endophenotypes of cognitive functioning i.e. attention, vigilance, interference, time estimation and sensoric and motoric reaction times. Out of a gene data bank of more than 600 healthy Caucasian participants, 96 subjects (n = 48 males and n = 48 females) were recruited according to their genotype/allele pattern, resulting in six independent groups (COMT: VAL/VAL, VAL/MET, MET/MET)x(DRD2: A1-, A1+) of n = 16 subjects each. Results showed associations of the COMT gene with attention and with time estimation but most noteworthy was an interaction effect DRD2xVAL on interference performance as measured by the STROOP-test explaining 13% of the variance. Findings suggest that a balance between DA related catabolic enzyme activity and receptor density are good predictors for the endophenotype of cognitive interference and that the COMT gene is in accordance with previous studies related to cognitive functioning.

Analysis of Variance↗

PubMed2005

Evidence for a common biological basis of the Absorption trait, hallucinogen effects, and positive symptoms: epistasis between 5-HT2a and COMT polymorphisms.

Absorption represents a disposition to experience altered states of consciousness characterized by intensively focused attention. It is correlated with hypnotic susceptibility and includes phenomena ranging from vivid perceptions and imaginations to mystical experiences. Based on the assumption that drug-induced and naturally occurring mystical experiences share common neural mechanisms, we hypothesized that Absorption is influenced by the T102C polymorphism affecting the 5-HT2a receptor, which is known to be an important target site of hallucinogens like LSD. Based on the pivotal role ascribed to the prefrontal executive control network for absorbed attention and positive symptoms in schizophrenia, it was further hypothesized that Absorption is associated with the VAL158MET polymorphism of the catechol-O-methyltransferase (COMT) gene affecting the dopaminergic neurotransmitter system. The Tellegen Absorption Scale was administered to 336 subjects (95 male, 241 female). Statistical analysis revealed that the group with the T/T genotype of the T102C polymorphism, implying a stronger binding potential of the 5-HT2a receptor, indeed had significantly higher Absorption scores (F = 10.00, P = 0.002), while no main effect was found for the COMT polymorphism. However, the interaction between T102C and COMT genotypes yielded significance (F = 3.89; P = 0.049), underlining the known functional interaction between the 5-HT and the dopaminergic system. These findings point to biological foundations of the personality trait of Absorption.

Adult↗

PubMed2005

Association of the functional catechol-O-methyltransferase VAL158MET polymorphism with the personality trait of extraversion.

Across different personality theories, there is agreement that dopamine is the neurochemical basis of extraversion. However, evidence from molecular genetics for the validity of this hypothesis is far from convincing. The functional polymorphism of the catechol-O-methyltransferase gene (COMT VAL158MET) has not been related to extraversion before, although it is a promising candidate gene locus for extraversion because of its great influence on the catabolism of dopamine. In a sample of n=363 healthy study participants, the catechol-O-methyltransferase VAL158MET polymorphism was related to extraversion and novelty seeking.Results showed a significant association between catechol-O-methyltransferase, extraversion and the subscale exploratory excitement (NS1) of novelty seeking but not with the total novelty-seeking scale supporting the psychometric analyses of the personality scales. The findings support the hypothesis that the dopamine system is involved in positive emotionality and incentive motivation, which has implications for the understanding of the neurochemical correlates of normal and psychopathological behaviors.

Adult↗

PubMed2005

Molecular genetics support Gray's personality theory: the interaction of COMT and DRD2 polymorphisms predicts the behavioural approach system.

The present study provides the first direct molecular genetics support for Gray's Reinforcement Sensitivity Theory (RST), which is one of the most influential biologically oriented personality theories. It was investigated whether the DRD2 TaqIA and the COMT polymorphisms were related to the dimensions of Gray's personality theory, as measured by the Carver and White BIS/BAS scales. In a sample of 295 healthy subjects results revealed significant DRD2xCOMT interactions (i.e. epistasis) for the total BAS scale (related to positive emotionality) and for the subscales Drive (D) and Fun Seeking (FS). High BAS scores were observed if the catabolic enzyme activity and the D2 receptor density as indicated by the two polymorphisms were in disequilibrium, i.e. in the presence of the Val-/A1- (low enzyme activity/high receptor density) or the Val+/A1+ (high enzyme activity/low receptor density) alleles. In a random subsample (n=48), it could be demonstrated that those allele combinations of COMT and DRD2 associated with high BAS scores also had significantly lower prolactin levels under resting conditions, indicating high dopamine activity, compared to those allele combinations with low BAS scores. Furthermore, two-way interactions of DRD2 TaqIAxsmoking status and of the Met allele of COMTxsmoking status on FS and Metxgender on BIS could be shown.

Adult↗

PubMed2004

Using Latent Mixed Markov Models for the choice of the best pharmacological treatment.

The choice of the best pharmacological treatment for an individual patient is crucial to optimize convalescence. Due to their effects on pharmacokinetics variables like gender and age are important factors when the pharmacological regimen is planned. By means of an example from anaesthesiology the usefulness of Latent Mixed Markov Models for choosing the optimal anaesthetic considering patient characteristics is demonstrated. Latent Mixed Markov models allow to predict and compare the quality of recovery from anaesthesia for different patient groups (defined by age and gender and treated with different anaesthetic regimens) in a multivariate non-parametric approach. On the basis of observed symptoms immediately after surgery and a few days later the probabilities for the respective dynamic latent status (like health or illness) and the probabilities for transition from one status to another are estimated depending on latent class membership (patient group).

Adolescent↗