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Biomedical subjects

H Heinrich

Publications and source records attributed to H Heinrich.

At least 19 recordsLinked to original sources
PubMed2006

Measurement of redox potential and steroid concentrations in the follicular fluid of growing and regressing follicles of mares.

The aim of this study was to prove if oxidation-reduction levels in the follicular fluid were new functional indices of follicular health and whether there was a high level of accordance with endocrinological parameters and with the growth stage as detected by ultrasound monitoring of individual follicles during the oestrous cycle in mares. Follicles were classified as growing and regressing follicles using ultrasonography. Altogether 48 follicles with a diameter from 20 to 56 mm were aspirated by transvaginal ultrasound guided follicular aspiration. Follicular concentration of oestradiol and progesterone in relation to the diameter of growing follicles showed correlations of r = 0.64 and r = 0.57, respectively. The redox potential derived index D2 varied from -448 to +431 in the collected fluids of the follicles. The accordance of the judgement of all follicles using both complexes of methods - endocrinological and ultrasonographic parameters vs. analysis of oxidation and reduction levels - reached 72.5%. This finding has shown that parameters of redox reactions do not correlate closely with the stage of follicular growth or regression as determined by in vivo scanning of ovaries or by assessment of follicular steroid concentrations. However, the measurement of redox potentials offers an opportunity to examine the whole process of metabolism in follicular cells and to forecast impairments of cellular performances. Changes of redox parameters in growing follicles enable an earlier prediction of their further development. The data demonstrate that growing and regressing follicles do not represent nonatretic, early atretic and atretic follicles, respectively.

Animals↗
PubMed2004

Bulk interfaces in a Ni-rich Ni-Au alloy investigated by high-resolution Z-contrast imaging.

Interfaces between Au-rich precipitates and the Ni-rich matrix in a decomposed Ni-10 at.% Au alloy were investigated by low-magnification and high-resolution Z-contrast imaging. During aging at 923 K, the originally single crystalline sample decomposed and recrystallized resulting in a microstructure consisting of subgrains separated by small-angle grain boundaries. These small-angle grain boundaries are decorated by Au-rich precipitates. The interfaces between the Au-rich precipitates and the Ni-rich matrix were characterized with respect to the orientation relationship between precipitates and matrix, misfit dislocations and concentration gradients. Two transformation modes were identified that are involved in the decomposition of bulk Ni-rich Ni-Au alloys. While in the first mode the interface is semi-coherent, in the second mode the interface corresponds to an incoherent twin boundary. It is further shown that strain fields around misfit dislocations can result in systematic errors in the determination of the concentration gradients across interfaces between precipitates and matrix.

Journal Article↗
PubMed2003

Questioning inhibitory control as the specific deficit of ADHD--evidence from brain electrical activity.

OBJECTIVE: To investigate motor response control during a cued continuous performance test (CPT-A-X) by performance and ERP parameters in children with hyperkinetic disorder (HD), hyperkinetic conduct disorder (HCD) or oppositional deviant/conduct disorder (ODD/CD), to examine the evidence for an inhibition-specific deficit as indicated by these parameters, and to analyze whether possible deviations are specific for HD/HCD. METHOD: Behavioral parameters and event-related potentials (ERPs) were recorded during a CPT-A-X-task in children (aged 8 to 14 years) with either HD (n = 15), HCD (n = 16), or ODD/CD (n = 15) and normal children (n = 18) and analysed. ICD-10 diagnoses of HD/HCD diagnoses in all children were fully concordant with the DSM-IV diagnosis of ADHD-combined type. RESULTS: Children with HCD committed more dyscontrol errors and differed most from normal children on ERP measures of motor response control, while children with HD-only were more impaired during processing of the warning stimuli for motor preparation. ERP measures specific for response inhibition were not different between the groups. CONCLUSIONS: The results show that ADHD cannot be fully explained by an inhibition-specific deficit and implicate impaired response execution processes as well. This indicates that comorbid children suffer from a reduced ability to control their prepared motor responses. Further, they seem to have difficulties in timely switching attention from monitoring the sensory input stream to the monitoring of own responses and actions.

Adolescent↗
PubMed2003

Methylphenidate and intracortical excitability: opposite effects in healthy subjects and attention-deficit hyperactivity disorder.

OBJECTIVE: To test the effects of a standard dosage of the psychostimulant methylphenidate (MPH) - which significantly enhances intracortical inhibition but had no effects on intracortical facilitation in children with attention-deficit hyperactivity disorder (ADHD) - on intracortical excitability in healthy subjects. METHOD: In 12 healthy subjects, aged 20-40 years, intracortical inhibition and facilitation were investigated before and 70 min after the intake of 10 mg MPH using the technique of transcranial magnetic stimulation (TMS) with the paired-stimulus paradigm. RESULTS: In comparison of the two TMS measurements, a significant enhancement in intracortical facilitation but no effects on intracortical inhibition could be stated under MPH administration. CONCLUSION: This study provides first evidence for opposite effects of MPH on intracortical excitability in healthy adult subjects showing enhanced intracortical facilitation in contrast to ADHD children in whom enhanced intracortical inhibition has recently been shown.

Adult↗
PubMed2001

Time-on-task analysis using wavelet networks in an event-related potential study on attention-deficit hyperactivity disorder.

OBJECTIVE: The aim of this event-related potential (ERP) study was to test time-on-task analysis at the level of single sweeps in a clinical trial. Since inattentiveness is one of the main symptoms of attention-deficit hyperactivity disorder (ADHD), this child psychiatric disorder was chosen as an exemplary application. METHODS: Twenty-four healthy and 24 ADHD boys, aged 9--15 years, performed an auditory selective attention task for about 5 min. ERP single trials were analyzed using wavelet networks. Time-on-task analysis was applied to omission errors, reaction time and slow ERP components (frontal negativity, parietal positivity), represented by a low-frequency wavelet component. RESULTS: Both performance and ERP measures showed distinct temporal dynamics. Time-on-task effects were not only linear, but also of higher order and started after less than 1 min. For ADHD children, earlier time-on-task effects, i.e. an earlier increase of omission errors and frontal negativity, resulted. Healthy children could allocate more attentional resources during the course of the experiment. CONCLUSION: Time-on-task analysis at the level of single trials revealed phenomena probably reflecting ADHD children's attentional deficits. Thus, a more differentiated ERP analysis may provide a better understanding of the pathophysiological background in neuropsychiatric disorders.

Acoustic Stimulation↗
PubMed2001

[Transcranial magnetic stimulation in child and adolescent psychiatry: excitability of the motor system in tic disorders and/or attention deficit hyperactivity disorders].

Motor system excitability can be investigated in vivo by means of single and paired pulse transcranial magnetic stimulation (TMS). Whereas the cortical silent period reflects the general degree of inhibitory mechanisms mainly within the sensorimotor loop, intracortical excitability measures the focused degree of inhibitory and facilitatory mechanisms within the motor cortex. In child and adolescent psychiatric disorders with uncontrollable motor behavior such as tics in tic disorder or motoric hyperactivity in attention deficit hyperactivity disorder (ADHD), different dysfunctional patterns of motor system excitability could be demonstrated compared to age-matched healthy controls: (1) In tic disorder, a shortened cortical silent period was observed, providing evidence of deficient inhibitory mechanisms within the sensorimotor loop, probably primarily at the level of the basal ganglia. (2) In ADHD, a decreased intracortical inhibition was found, probably reflecting deficient inhibitory mechanisms within the motor cortex (but enhancement of intracortical inhibition after oral intake of 10 mg methylphenidate). In order to investigate neurophysiological aspects of comorbidity, (3) motor system excitability was also measured in children with combined ADHD and tic disorder. The findings of a reduced intracortical inhibition as well as a shortened cortical silent period in these comorbid children provide evidence of additive effects at the level of motor system excitability. These decreased inhibitory mechanisms within the entire sensorimotor loop and especially the motor cortex could be essential neurobiological substrates of the deficient inhibitory motor control and regulation, respectively, in tic disorder and ADHD.

Adolescent↗
PubMed2001

Children with comorbid attention-deficit-hyperactivity disorder and tic disorder: evidence for additive inhibitory deficits within the motor system.

For children with attention-deficit-hyperactivity disorder (ADHD) or tic disorder (TD), we recently reported deficient inhibitory mechanisms within the motor system by using transcranial magnetic stimulation. These deficits--stated as reduced intracortical inhibition in ADHD and shortened cortical silent period in TD--could be seen as neurophysiological correlates of motor hyperactivity and tics, respectively. To investigate neurophysiological aspects of comorbidity, we measured motor system excitability for the first time also in children with combined ADHD and TD. The findings of a reduced intracortical inhibition as well as a shortened cortical silent period in these comorbid children provide evidence for additive effects at the level of motor system excitability.

Adolescent↗
PubMed2000

Gamma band response in children is related to task-stimulus processing.

The present study described the functional characteristics of early phase-locked electroencephalographic gamma band (30-60 Hz) responses (GBRs) in 9- to 12-year-old healthy children. GBRs were elicited in an auditory selective-attention task. Target stimuli required motor responding when presented to the right or to the left (attended side). Effects of stimulus type relevance and attended side were evaluated for GBR power and phase-locking within 0-120 ms. GBRs in children were frontally distributed, were larger and better phase-locked to targets relative to non-targets, but did not depend on the attended side. These results demonstrate that the auditory GBR is related to task-stimulus processing and imply that early target selection in children is guided by a sensory or sensorimotor preparatory set, rather than by an internal attentional focus to the side of stimulation.

Attention↗
PubMed2000

Deficient intracortical inhibition in drug-naive children with attention-deficit hyperactivity disorder is enhanced by methylphenidate.

In children with attention-deficit hyperactivity disorder (ADHD), motoric hyperactivity is one of the striking abnormalities. Because this symptom might be due to an insufficient motor control, motor system excitability in 18 drug-naive ADHD-children aged 8-12 years was compared to 18 age-matched healthy children using the technique of transcranial magnetic stimulation (TMS). Whereas motor thresholds, cortical silent period, and intracortical facilitation did not differ between the two groups, ADHD-children had significantly reduced intracortical inhibition compared to healthy controls. In all ADHD-children, a second TMS could be started after their first intake of 10 mg methylphenidate. Under this medication, a significant enhancement in intracortical inhibition could be stated. This study provides the first evidence for inhibitory deficits within the motor cortex in ADHD-children and for an enhancement of inhibitory mechanisms in this brain region by methylphenidate.

Attention Deficit Disorder with Hyperactivity↗
PubMed2000

Comorbidity in ADHD-children: effects of coexisting conduct disorder or tic disorder on event-related brain potentials in an auditory selective-attention task.

In children with attention-deficit hyperactivity disorder (ADHD) some deficits in auditory information processing seem to exist. Further, comorbidity of ADHD with conduct disorder (CD) and tic disorder (Tic) is quite common but not yet fully understood. Thus, we investigated the effects of these two disturbances, when combined with ADHD, on electrophysiological correlates of auditory information processing. An auditory selective-attention task was used, and temporal as well as frontal lobe sensitive event-related electrical brain activity indicators like mismatch negativity (MMN) and negative difference wave (Nd), as well as P300 were registered in four groups of children (healthy controls, ADHD-only, and combined ADHD + CD as well as ADHD + Tic; total number 42). Performance measures showed that ADHD + CD had a higher impact on errors and reaction times than ADHD + Tic. The MMN effect indicated that all ADHD groups showed lower MMN amplitudes compared to normals, but only the group with ADHD + CD suffered from a significant deficiency in automatic auditory information processing. Nd and P300 amplitudes showed no significant group differences. It may be assumed that neurodynamic sufficiency in ADHD-only and ADHD + Tic children seems to be similarly impaired while there might be a greater deficit in ADHD + CD.

Attention↗
PubMed2000

Bloch waves and weak-beam imaging of crystals

The influence of the number of diffracted beams on weak-beam contrast simulations of thickness contour lines and dislocation images is investigated. For large deviation parameters s(g)-->thickness contour lines from two-beam simulations are similar to those from many-beam simulations. In many-beam simulations of wedge-shaped bent samples extra thickness contour lines appear at locations with ((g)-->, 3(g)-->). These extra lines occur between the imaging condition ((g)-->, -(g)-->) and ((g)-->, 3(g)-->). Therefore, in the case of a more symmetrical imaging condition many-beam simulations are mandatory. In bent samples the contributions of different Bloch waves to weak-beam images change as a function of the imaging conditions ((g)-->, x(g)-->). Near ((g)-->, 3.5(g)-->) two Bloch waves dominate. In the case of x <3 two other Bloch waves with different wavelengths are most important for the image contrast. The 'classical' ((g)-->, 3(g)-->) weak-beam condition is not suitable to determine signs and magnitudes of Burgers vectors from terminating thickness contour lines. Higher deviation parameters s(g)--> are necessary, especially for dense dislocation arrangements.

Journal Article↗
PubMed1999

Deficient motor control in children with tic disorder: evidence from transcranial magnetic stimulation.

Decreased motor inhibition was reported in adult patients with tic disorder (TD) using the technique of transcranial magnetic stimulation. Since tics usually begin during childhood, motor threshold, cortical silent period (CSP) and intracortical inhibition/facilitation were measured in 21 TD children and 25 healthy children aged 10-16 years. In TD children motor threshold was normal. The CSP was significantly shortened compared to healthy controls but did not depend on tic localization. Intracortical inhibition and facilitation did not differ between the two groups. This study confirms that the finding of decreased motor control in adult patients also holds true for children wherever the tics in the latter group were located.

Adolescent↗
PubMed1999

[Apoptosis--what is it? Significance in coronary heart disease and myocardial infarct].

Apoptosis is a physiological, highly conserved program of cellular suicide, characterized by nuclear condensation with DNA-fragmentation, by alterations in the distribution of cell membrane phospholipids, and by cellular shrink-age. Apoptotic cellular remnants engulfed by cell membranes are phagocytized largely without activation of inflammatory reactions. The apoptotic program is executed by a cascade of highly specific caspases, activated by complexation of initiatorcaspases in cytosolic signalling complexes at receptors of the TNF family or at impaired mitochondria. In many forms of cellular stress with damage of nuclear DNA and mitochondria, mixed forms of cell death are triggered with regulated activation of the apoptotic program and concomitantly, with induction of catastrophic necrosis. Such a mixed form of myocyte death is observed in myocardial ischemia and reperfusion. Antiapoptotic interventions can delay ischemic myocardial damage in experiments. Therefore, those interventions appear conceivable as future strategy for acutely enhancing the available time interval for therapeutic reperfusion. However, chronic inhibition of apoptosis for ongoing prevention of myocardial ischemic damage may not become a plausible strategy because of disturbances of the immune system, because of putatively infavorable effects on arteriosclerotic lesions and because of likely disturbances in the physiologic elimination of damaged mitochondria.

Apoptosis↗
PubMed1999

Single-sweep analysis of event-related potentials by wavelet networks--methodological basis and clinical application.

OBJECTIVE: Trial-to-trial variabilities in event-related potentials (ERP's), which are neglected by investigating averaged ERP's, can be important to establish group-specific effects in clinical studies. Single ERP responses have to be analyzed to quantify these variations. In order to overcome the disadvantages of existing single-sweep estimators, we have developed a new procedure based on wavelet networks (WN's) and applied this novel approach in a study concerning attention deficit hyperactivity disorder (ADHD) in children. METHOD: WN's represent signals as a linear combination of wavelet nodes, i.e., components characterized by time-frequency features related to the wavelet transformation. In single-sweep analysis, each wavelet node is restricted to a specific region of the time-frequency plane during the recursive WN training process. This is achieved by means of tapering and bandpass filtering with Gaussian functions which are automatically adapted and closely related to the Morlet basis wavelet. The time course of a single event-related response can be reliably estimated. Furthermore, the WN method automatically provides well-defined parameters for single event-related responses, respectively ERP trial-to-trial variabilities. RESULTS: In a psychophysiological study on ADHD using auditory evoked potentials (AEP's), latency and amplitude parameters extracted from averaged ERP's did not reveal any significant differences between 25 control and 25 ADHD boys. In contrast, interesting group-specific differences could be established by WN single-sweep analysis. CONCLUSION: WN single-sweep analysis can be recommended as a sensitive tool for clinical ERP studies which should be applied in addition to the investigation of averaged responses. INDEX TERMS: Attention deficit hyperactivity disorder (ADHD), event-related potentials, single-sweep estimation, single-sweep parameterization, time-frequency method, wavelet networks.

Adolescent↗