Search PubMed⌕ Search

Biomedical subjects

J Hennig

Publications and source records attributed to J Hennig.

At least 37 records · Page 2Linked to original sources
PubMed2004

Guanidinoacetate methyltransferase deficiency: differences of creatine uptake in human brain and muscle.

Deficiency of guanidinoacetate methyltransferase (GAMT), the first described creatine biosynthesis defect, leads to depletion of creatine and phosphocreatine, and accumulation of guanidinoacetate in brain. This results in epilepsy, mental retardation, and extrapyramidal movement disorders. Investigation of skeletal muscle by proton and phosphorus magnetic resonance spectroscopy before therapy demonstrated the presence of considerable amounts of creatine and phosphocreatine, and accumulation of phosphorylated guanidinoacetate in a 7-year-old boy diagnosed with GAMT deficiency, suggesting separate mechanisms for creatine uptake and synthesis in brain and skeletal muscle. The combination of creatine supplementation and a guanidinoacetate-lowering therapeutic approach resulted in improvement of clinical symptoms and metabolite concentrations in brain, muscle, and body fluids.

Arginine↗
PubMed2004

Detection of causal relationships between factors influencing adverse side-effects from anaesthesia and convalescence following surgery: a path analytical approach.

BACKGROUND AND OBJECTIVE: The anaesthesiologist's preoperative interview with the patient is important in preparing the patient for surgery. Its potential protective influence on adverse side-effects from anaesthesia and convalescence is rarely investigated within the context of other perioperative factors. Structural equation modelling allows detection and quantification of all causal relationships and mediator effects in multivariate models. Therefore, this method is presented as a tool and applied to discover the influence of the preoperative interview within socio-demographic variables and duration of surgery on complaints and recovery after anaesthesia. METHODS: The influence of individual satisfaction with the anaesthesiologist's preoperative interview on postoperative events such as nausea/vomiting, difficulties in recovering from anaesthesia, experience of postoperative pain, physical discomfort and satisfaction with convalescence expressed by the patient was analysed by means of structural equation modelling. The variables gender, age and duration of surgery were also included as predictors in the analyses. The model in the total sample of 710 patients was then analysed for structural differences between groups treated either with propofol (n = 204) or with isoflurane + nitrous oxide (n = 267) for maintenance of anaesthesia. RESULTS: The model revealed that the anaesthesiologist's preoperative interview in combination with associated mediating side-effects explains 45% of the variance of 'feeling physical discomfort' and 18% of the variance of 'satisfaction with convalescence'. The same model could be fitted in the propofol and the isoflurane + nitrous oxide group. Moreover, the structure and the strength of causal relations between variables were identical in the two groups. CONCLUSIONS: The anaesthesiologist's efforts to improve the interview with the patient by more reassuring and proper information will result in less side-effects from anaesthesia and better recovery from surgery. It could be demonstrated that structural equation modelling is a powerful tool for detection of causal relationships and mediator effects in perioperative medicine.

Adolescent↗
PubMed2004

Personality and emotion: test of Gray's personality theory by means of an fMRI study.

Although it is known that there are fundamental personality differences in the behavioral responses to emotional stimuli, traits have scarcely been investigated in this context by means of functional imaging studies. To maximize the variance with respect to personality, the authors tested 12 control subjects and 12 subjects who had sadomasochistic experiences with respect to the relationship between J. A. Gray's (1970) personality dimensions, the behavioral approach system (BAS) and the behavioral inhibition system (BIS), and brain activity in regions of interest. The BIS was associated with activity in numerous brain areas in response to fear, disgust, and erotic visual stimuli, whereas few associations could he detected between the BAS and brain activity in response to disgust and erotic stimuli.

Adult↗
PubMed2003

Cortisol as an indicator of dopaminergic effects on nicotine craving.

There is evidence that glucocorticoids mediate the activity of mesencephalic dopaminergic neurons which play an important role in drug-seeking behaviour and that the absence or presence of glucocorticoids determines the intensity of drug self-administration. Moreover, some experiments indicate that corticoids are increased after substance induced dopaminergic stimulation. These findings could imply (a) that differences in basal glucocorticoid levels are associated with differences in craving or (b) that dopamine (DA) induced corticoid release is an indicator of the sensitivity of the dopaminergic system. Therefore, in a sample of 36 male smokers whose DA system was challenged by a DA agonist (lisuride=LIS) and a DA antagonist (fluphenazine=FLU) in a balanced placebo controlled double-blind crossover design, it was investigated if (a) basal cortisol differences and (b) drug induced cortisol responses are related to the amount of nicotine craving after 3.5 h of deprivation from smoking. There were no differences in craving between subjects with high and low basal cortisol levels irrespective of the pharmacological treatment. However, the size of the cortisol change after the DA challenge and deprivation emerged as a good predictor for the amount of craving in that drug condition in which the cortisol response was most pronounced. Findings were interpreted as evidence for the role of cortisol as an indicator of DA sensitivity.

Adult↗
PubMed2003

A voxel-based morphometric MRI study in female patients with borderline personality disorder.

Subtle prefrontal and limbic structural abnormalities have been reported in borderline personality disorder (BPD). In order to further validate the previously reported findings and to more precisely describe the nature of the structural change we performed a voxel-based morphometric (VBM) study in patients with BPD. Twenty female patients with BPD and 21 female healthy controls were investigated. High-resolution 3-D datasets were acquired and analyzed following an optimized protocol of VBM in the framework of statistical parametric mapping (SPM99). Gray matter volume loss was found in the left amygdala. No other differences in gray or white matter volume or density were found anywhere else in the brain. Our findings support the hypothesis that temporolimbic abnormalities play a role in the pathophysiology of BPD. Prefrontal structural alterations in BPD were not observed in this study.

Adult↗
PubMed2003

Background suppression using magnetization preparation for contrast-enhanced 3D MR angiography of the pelvic and lower leg arteries.

PURPOSE: To develop and evaluate non-slab-selective magnetization preparation in contrast-enhanced 3D-MR angiography. METHODS: An ultrafast spoiled mr angiography sequence (FLASH) with non-selective inversion prepulses for background suppression was implemented on a 1.5 T MR system. In 11 patients gadobenate dimeglumine-enhanced mr-angiography of the pelvic and lower leg arteries was performed using the AngioSURF device. Source data was evaluated for contrast-to-noise-ratio, image quality and the extent of background suppression. RESULTS: Background suppression and selective vessel contrast was excellent in all vascular levels. The mr protocol was comfortable and easy-to-handle. Abandonment of precontrast-series acquisition simplified the examination procedure markedly. CONCLUSIONS: Magnetization preparation provides efficient suppression of the background signal in contrast-enhanced 3D mr angiography of the pelvic and lower leg arteries. Since no subtraction technique is needed, moving-bed and whole body MRA-protocols can be simplified significantly.

Adult↗
PubMed2003

Influence of mirtazapine on salivary cortisol in depressed patients.

Unlike other antidepressants, mirtazapine does not inhibit the reuptake of norepinephrine or serotonin but acts as an antagonist at presynaptic alpha(2)-receptors, at postsynaptic 5-HT2 and 5-HT3 receptors, and at histaminergic H1 receptors. Furthermore, mirtazapine has been shown to acutely inhibit cortisol secretion in healthy subjects. In the present study, the impact of mirtazapine treatment on salivary cortisol secretion was investigated in 12 patients (4 men, 8 women) suffering from major depression according to DSM-IV criteria. Patients were treated with mirtazapine for 3 weeks, receiving 15 mg mirtazapine on day 0, 30 mg on day 1 and 45 mg per day from day 2 up to the end of the study (day 21). Response to mirtazapine treatment was defined by a reduction of at least 50% in the Hamilton Rating Scale for Depression after 3 weeks of therapy. 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 08.00 until 20.00 h. The area under the curve values served as parameter for the salivary cortisol secretion. Following analysis of variance with a repeated measures design, tests with contrasts revealed a significant reduction of cortisol concentrations already after 1 day of mirtazapine treatment that was comparable in responders and nonresponders. In addition to new pharmacological approaches such as CRH1 receptor antagonists, mirtazapine therefore appears to be an effective strategy to decrease hypercortisolism and restore HPA system dysregulation in depression. However, the importance of the acute inhibitory effects of mirtazapine on cortisol secretion for its antidepressant efficacy has to be further clarified.

Adrenergic alpha-Antagonists↗
PubMed2003

Auditory-evoked potentials and selective attention: different ways of information processing in cannabis users and controls.

The present study tested the hypothesis that chronic cannabis use leads to persistent attentional dysfunctions and that age of onset of cannabis use is a potential predictor of impaired test performance and information processing. Brain event-related potentials (ERPs) during a complex auditory selective attention task were recorded from 21 cannabis users divided into two groups according to age of onset and from 13 controls comparable with respect to age, IQ and educational background. Participants were instructed to detect target tones of a particular location, pitch and duration from a total sample of random frequencies. The study reveals that the latency of the greatest negative peak of ERPs (200 and 300 ms) to target tones was shorter in controls, while there was no clear difference between target and non-target within cannabis users. In addition, users displayed a reduced P3 to target tones. This was more pronounced in early-onset cannabis users. These data suggest that chronic cannabis use relates to different types of information processing under conditions of selective attention. There is some evidence that users employed different strategies of attention allocation. The results are discussed with respect to possible underlying mechanisms and clinical implications.

Acoustic Stimulation↗
PubMed2002

Frontoorbital volume reductions in adult patients with attention deficit hyperactivity disorder.

Attention deficit hyperactivity disorder (ADHD) is a common psychiatric disorder in childhood and adolescence and in a considerable number of patients it persists into adulthood. A network of brain regions have been shown to be abnormal in ADHD. In the present study we used magnetic resonance volumetry to investigate a possible role of the orbitofrontal cortex (OFC). Eight never medicated male patients fulfilling diagnostic criteria for ADHD and 17 male healthy controls were investigated. There was a significant reduction of the volume of the left OFC in patients with ADHD. It remains unknown whether small volumes are a primary deficit or a result of dysfunctional activation during childhood in terms of a residual deficit or a specific type of adult outcome of the disease.

Adult↗
PubMed2002

Functional magnetic resonance imaging evidence for binocular interactions in human visual cortex.

Using functional magnetic resonance imaging (fMRI), we explored the binocular interactions occurring when subjects viewed dichoptically presented checkerboard stimuli. A flickering radial checkerboard was presented to each eye of the subject, while T2*-weighted images were acquired over the visual cortex with gradient-echo, echoplanar sequences. We compared responses in striate and extrastriate visual cortex under four conditions: both eyes were stimulated at the same time (binocular condition), each eye was stimulated in alternation (monocular condition) or first the one eye then the other eye was stimulated (left eye first - right eye trailing, or vice versa). The results indicate that only the striate area, in and near the calcarine fissure, shows significant differences for these stimulation conditions. These differences are not evident in more remote extrastriate or associational visual areas, although the BOLD response in the stimulation-rest comparison was robust. These results suggest that the effect could be related to inhibitory interactions across ocular dominance columns in striate visual cortex.

Adult↗
PubMed2002

The role of cortisol suppression on craving for and satisfaction from nicotine in high and low impulsive subjects.

The rewarding properties of drug self-administration have been shown to depend on mesolimbic dopamine release but also on the availability of corticosterone, as shown in rats. Since this became particularly evident when tested in rat strains bred for high (HR) and low (LR) reactivity to novel stimuli, the role of cortisol and personality in drug craving was investigated in 60 male nicotine-deprived smokers divided according to questionnaire scores into high and low impulsives, a dimension considered to represent HR/LR rats. They either received the peripheral cortisol blocker metyrapone (MET) or the centrally blocking substance dexamethasone (DEX) or placebo (n=20 each) and were then allowed to smoke. MET more than DEX reduced craving for cigarettes during deprivation. This was only observed in low impulsives while high impulsives developed low craving unmodified by blockade of cortisol. Satisfaction from smoking was less achieved with DEX than with MET and not modified by impulsivity. Differences between MET and DEX in influencing craving during deprivation and satisfaction from smoking were discussed on the basis of different glucocorticoid receptors. The mineralocorticoid receptor (MR) seems to be the 'turn on switch' and the glucocorticoid receptor (GR) the 'turn off switch' in mediating the rewarding properties of dopamine in drug self-administration.

Adult↗
PubMed2002

Fast 31P chemical shift imaging using SSFP methods.

Steady-state free precession (SSFP) methods have been very successful due to their high signal and short imaging times. These properties make them good candidates for applications that intrinsically suffer from low signal such as low gamma nuclei imaging. A new chemical shift imaging (CSI) technique based on the SSFP signal formation has been implemented and applied to (31)P. The signal properties of the SSFP CSI method have been evaluated and the steady-state signal of (31)P has been measured in human muscles. Due to the T(2) and T(1) signal dependence of SSFP, the steady-state signal mainly consists of phosphocreatine (PCr). The technique allows fast CSI acquisitions with high SNR of the PCr signal. The SNR gain for PCr over a FLASH-based CSI method is approx. 4-5. Fast in vivo CSI of human muscle with subcentimeter resolution and high SNR is demonstrated at 2 T.

Magnetic Resonance Imaging↗
PubMed2002

Addictive and nonaddictive smoking as related to responsivity to neurotransmitter systems.

In a double-blind crossover design on 36 male smokers, differences in hormone responses to a serotonergic (citalopram) and dopaminergic (bromocriptine) challenge were tested, to compare transmitter responsivities in addicted and pleasure-motivated smokers with respective controls. A general score of smoking addiction, according to DSM IV criteria, was associated with a blunted prolactin decrease to bromocriptine, indicating a possible nicotine-induced desensitization of DA receptors. The single questionnaire-based symptom of tolerance was associated with a blunted cortisol response to citalopram, indicating a particular desensitization of serotonin receptors. Nontolerant but addicted subjects exhibited increased serotonergic responsivity, interpreted as resulting from low serotonin levels associated with lack of impulse control. The questionnaire-based score of pleasure-motivated (='indulgent') smoking was associated with high dopaminergic activity (pronounced prolactin responses), confirming findings obtained in subjects exhibiting reward-related personality factors.

Adolescent↗
PubMed2001

Attention-deficit disorder in adults with or without hyperactivity: where is the difference? A study in humans using short echo (1)H-magnetic resonance spectroscopy.

The DSM-IV distinguishes three subtypes of attention deficit hyperactivity disorder: The predominantly inattentive subtype (ADD), the hyperactive-impulsive subtype (ADHD) and the combined subtype. We used short echo time (1)H-magnetic resonance spectroscopy (TE=30 ms, TR=3000 ms) for absolute quantification of neurometabolites using the LC model algorithm to investigate a possible metabolic neuropathology in adult patients with ADD and ADHD and compared their spectra with healthy controls (n=5 in each group). Spectra were acquired in the left dorsolateral prefrontal cortex and the left striatum. There was a significant group difference in N-acetylaspartate (NAA) concentration in the left dorsolateral prefrontal cortex distinguishing patients with the ADHD from patients with pure ADD and healthy controls. The absolute NAA concentration was significantly reduced only in the ADHD group. Since NAA-depletion reflects a state of neuronal dysfunction, this finding indicates evidence of subtle left prefrontal neuropathology in ADHD in adults.

Adult↗
PubMed2001

T(1) quantification with inversion recovery TrueFISP.

A snapshot FLASH sequence can be used to acquire the time course of longitudinal magnetization during its recovery after a single inversion pulse. However, excitation pulses disturb the exponential recovery of longitudinal magnetization and may produce systematic errors in T(1) estimations. In this context the possibility of using the TrueFISP sequence to detect the recovery of longitudinal magnetization for quantitative T(1) measurements was examined. Experiments were performed on different Gd-doped water phantoms and on humans. T(1) values derived from inversion recovery TrueFISP were in excellent agreement with the single-point method even for flip angles up to 50 degrees. In terms of T(1) accuracy and SNR, the proposed method seems to be superior to the conventional inversion recovery snapshot FLASH technique. Magn Reson Med 45:720-723, 2001.

Brain↗
PubMed2001

Separation and quantification of perfusion and BOLD effects by simultaneous acquisition of functional I(0)- and T2(*)-parameter maps.

The nature of the coupling between neuronal activity and the hemodynamic response is the subject of intensive research. As a means to simultaneously measure parametric changes of T2(*), initial intensity (I(0)) and perfusion with high temporal resolution, a multi-image EPI technique with slice-selective inversion recovery (ssIR) for arterial spin labeling was developed and implemented. Comparative measurements with and without the preceding slice-selective inversion pulse were performed. I(0) and R2(*) changes induced by primary visual stimulation were separated. For ssIR-multi-image EPI the average change of I(0) over all 12 subjects was 3.4%, corresponding to a perfusion change of 40 ml/min/100 g, whereas only minor I(0) changes were observed without inversion. On average, the R2(*) of the activated pixels changed by -0.62 sec(-1) without inversion, while a significantly reduced average R2(*) change of -0.46 sec(-1) was calculated for ssIR-multi-image EPI due to a decreased BOLD effect contribution of the intravascular compartment.

Brain↗