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Biomedical subjects

M Staudt

Publications and source records attributed to M Staudt.

At least 19 recordsLinked to original sources
PubMed2001

Early left periventricular brain lesions induce right hemispheric organization of speech.

Right-hemispheric organization of speech has been observed following early left-sided brain lesions involving the language cortex. The authors studied speech organization in hemiparetic patients with pre- and perinatally acquired lesions in the left periventricular white matter using fMRI, and found that right-hemisphere activation correlated with left facial motor tract involvement. This suggests that the impairment of speech motor output from the left hemisphere plays an important role in this alteration of language representation.

Adolescent↗
PubMed2001

Functional MRI in a 6-year-old boy with unilateral cortical malformation: concordant representation of both hands in the unaffected hemisphere.

Functional magnetic resonance imaging (fMRI) was performed in a 6-year-old boy with a complex malformation of the right hemisphere who suffered from pharmaco-refractory epilepsy. Clinical examination revealed left-sided hemiparesis and marked mirror movements of the opposite hand both during paretic and non-paretic hand movements. Functional MRI of repetitive unimanual grasping demonstrated that the two hands share a common cortical representation located in the central motor region of the unaffected left hemisphere. The affected right hemisphere did not show any activation during either task. This case study demonstrates the feasibility and usefulness of motor fMRI in young children before they undergo epilepsy surgery.

Brain Mapping↗
PubMed2001

Effect of elevated CO2 on monoterpene emission of young Quercus ilex trees and its relation to structural and ecophysiological parameters.

We investigated growth, leaf monoterpene emission, gas exchange, leaf structure and leaf chemical composition of 1-year-old Quercus ilex L. seedlings grown in ambient (350 microl l(-1)) and elevated (700 microl l(-1)) CO2 concentrations ([CO2]). Monoterpene emission and gas exchange were determined at constant temperature and irradiance (25 degrees C and 1000 micromol m(-2) s(-1) of photosynthetically active radiation) at an assay [CO2] of 350 or 700 microl l(-1). Measurements were made on intact shoots after the end of the growing season between mid-October and mid-February. On average, plants grown in elevated [CO2] had significantly increased foliage biomass (about 50%). Leaves in the elevated [CO2] treatment were significantly thicker and had significantly higher concentrations of cellulose and lignin and significantly lower concentrations of nitrogen and minerals than leaves in the ambient [CO2] treatment. Leaf dry matter density and leaf concentrations of starch, soluble sugars, lipids and hemi-cellulose were not significantly affected by growth in elevated [CO2]. Monoterpene emissions of seedlings were significantly increased by elevated [CO2] but were insensitive to short-term changes in assay [CO2]. On average, plants grown in elevated [CO2] had 1.8-fold higher monoterpene emissions irrespective of the assay [CO2]. Conversely, assay [CO2] rapidly affected photosynthetic rate, but there was no apparent long-term acclimation of photosynthesis to growth in elevated [CO2]. Regardless of growth [CO2], photosynthetic rates of all plants almost doubled when the assay [CO2] was switched from 350 to 700 microl l(-1). At the same assay [CO2], mean photosynthetic rates of seedlings in the two growth CO2 treatments were similar. The percentage of assimilated carbon lost as monoterpenes was not significantly altered by CO2 enrichment. Leaf emission rates were correlated with leaf thickness, leaf concentrations of cellulose, lignin and nitrogen, and total plant leaf area. In all plants, monoterpene emissions strongly declined during the winter independently of CO2 treatment. The results are discussed in the context of the acquisition and allocation of resources by Q. ilex seedlings and evaluated in terms of emission predictions.

Carbon Dioxide↗
PubMed2000

Probing the size of a hydrophobic binding pocket within the allosteric site of muscarinic acetylcholine M2-receptors.

Hexane-bisammonium-type compounds containing lateral phthalimide moieties are known to have a rather high affinity for the allosteric site of muscarinic M2 receptors. In order to get more insight into the contribution of the lateral substituents for alloster binding affinity, a series of compounds with unilaterally varying imide substituents were synthesized and tested for their ability to retard allosterically the dissociation of [3H]N-methylscopolamine from the receptor protein (control t1/2 = 2 min; 3 mM MgHCO4, 50 mM Tris, pH 7.3, 37 degrees C). Among the test compounds, the naphthalimide containing agent (half maximum effect at ECs5,diss = 60 nM) revealed the highest potency. Apparently, its affinity for the allosteric site in NMS-occupied receptors is 20fold higher compared with the phthalimide containing parent compound W 84. Analysis of quantitative structure-activity relationships yielded a parabolic correlation between the volume of the lateral substituents and the allosteric potency. The maximal volume was determined to be approximately 600 A3 suggesting that the allosteric binding site contains a binding pocket of a defined size for the imide moiety.

Animals↗
PubMed2000

Ligands for the common allosteric site of acetylcholine M2-receptors: development and application.

Ligands for the allosteric site of acetylcholine M2 receptors are able to retard the dissociation of simultaneously bound ligands for the orthosteric site. This effect promotes receptor occupation by the orthosteric ligand. The allosteric effect opens various therapeutic perspectives, e.g., in organophosphorus poisoning. The aim of our studies was to optimize the affinity of the modulators for the common allosteric binding site of muscarinic M2 receptors, the orthosteric site of which was liganded with the N-methylscolopamine. The phthalimido substituted hexane-bisammonium compound W84 served as a starting point. Previous molecular modelling studies revealed two positive charges and two aromatic imides in a sandwich-like arrangement to be essential for a high allosteric potency. A three-dimensional quantitative structure activity relationship (3D QSAR) analysis predicted compounds with substituents of increasing size on the lateral imide moieties to enhance the affinity for the allosteric binding site. Thus, we synthesized and pharmacologically evaluated compounds bearing "saturated" phthalimide moieties as well as phthalimidines with substituents of systematically increasing size in position 3 or on the aromatic ring at one or both ends of the molecule. Within each series, QSAR could be derived: 1. "Saturation" of the aromatic ring of the phthalimide moiety results in less potent compounds. 2. Increasing the size of the substituents in position 3 of the phthalimide enhances the potency. 3. Putting substituents on the aromatic part of the phthalimide increases the potency more effectively: the introduction of a methyl group in position 5 gave a compound with a potency in the nanomolar concentration range which was subsequently developed as the first radioligand for the allosteric binding site.

Animals↗
PubMed2000

[Normal myelination in childhood brains using MRI--a meta analysis].

PURPOSE: To establish age limits for the assessment of normal myelination of the brain on T1-weighted (T1w) and T2-weighted (T2w) images. METHOD: Comparison of previous publications (Barkovich et al. 1988, Grodd 1993, Hayakawa et al. 1990, Hittmair et al. 1994, Martin et al. 1988/1990/1991, Nakagawa et al. 1998, Staudt et al. 1993/1994, Stricker et al. 1990). RESULTS: Despite technical and methodological differences, these studies principally agreed on the timing of myelination for most regions of the brain. Thus, a common time-table could be established: At 1 month, myelin is visible on both T1w and T2w in the medulla oblongata, tegmentum pontis, cerebellar peduncles and vermis, quadrigeminal plate, decussation of superior cerebellar peduncles, thalamus, posterior limb of internal capsule, optic radiation, corona radiata. Thereafter, the myelin-typical signal in the different regions of the brain should be present at the following ages (M = months): anterior limb of internal capsule (2 M: T1w; 7 M: T2w), splenium of corpus callosum (4 M: T1w; 6 M: T2w), genu of corpus callosum (6 M: T1w; 8 M: T2w), centrum semiovale (2 M: T1w; 7 M: T2w). Branching of myelin into the gyri of the telencephalon (= arborization) appears at the latest at: occipital lobe (5 M: T1w; 12 M: T2w) and frontal lobe (7 M: T1w; 14 M: T2w). CONCLUSION: These extracted age limits can be used for a more reliable assessment of myelination than the time-tables from a single study.

Age Factors↗
PubMed2000

The pyramidal tract in congenital hemiparesis: relationship between morphology and function in periventricular lesions.

Three-dimensional MRI data sets were obtained from 12 young adult patients with congenital spastic hemiparesis caused by unilateral periventricular white matter lesions. The impact of these lesions on corticospinal projections to the upper and lower extremities was assessed on reconstructed semi-coronal planes following anatomical landmarks of somatotopic organization in the precentral gyrus and in the internal capsule: a more anterior plane running through the hand-knob of the precentral gyrus and the anterior portion of the posterior limb of the internal capsule representing projections to the upper extremity, and a more posterior plane running through the top of the precentral gyrus and the middle portion of the posterior limb of the internal capsule representing projections to the lower extremity. In addition, the total lesion extent was determined volumetrically, and Wallerian degeneration was assessed qualitatively in the internal capsule and quantitatively by measuring brainstem asymmetry. We found a strong correlation between motor dysfunction of the upper and lower limb and the lateral extent of the periventricular lesion measured on the respective semi-coronal planes. The total lesion volume and the degree of Wallerian degeneration correlated less strongly, both reaching statistical significance only with motor impairment of the hand.

Adolescent↗
PubMed1999

Predictors of proximal aortic dissection at the time of aortic valve replacement.

BACKGROUND: Type I aortic dissection develops in 0.6% of patients late after aortic valve replacement (AVR), and 13% of patients with type I aortic dissections have a history of AVR. Predictors of aortic dissection at AVR, however, have not been characterized. METHODS AND RESULTS: A study group of 33 patients with type I aortic dissection had aortic surgery 49+/-55 months after routine AVR. A group of 101 controls, who did not have morphological progression of aortic diameters >/=6 years after AVR, was used to identify predictors of postsurgical dissection. Multivariate analysis identified aortic regurgitation (P<0.002) and fragility (P<0.001) or thinning of the aortic wall (P<0.007) at AVR as predictors, associated with a 14%, 22%, and 7% probability of late aortic dissection, respectively. Clamping times, types of valve prostheses, concomitant coronary artery bypass grafting, and mean ascending aortic diameters of 43+/-10 mm at AVR did not predict late dissection. A separate analysis of 29 nondissecting aneurysms of the ascending aorta developing 104+/-64 months after routine AVR revealed younger age at AVR (P<0.003) and congenitally bicuspid aortic valves (P<0.03) as predictors of late aneurysm formation. CONCLUSIONS: Aortic regurgitation combined with fragile and thinned aortic walls in patients with moderate aortic dilation may reflect aortic root disease, with a high risk for postsurgical aortic sequelae if it is treated incompletely by isolated valve replacement.

Adult↗
PubMed1999

Barriers and facilitators to use of services following intensive family preservation services.

The primary caregivers of 101 families that used short-term, intensive home-based services were interviewed 2 months after the services to ascertain use of the recommended aftercare services, perceived barriers to service use, and perceived facilitators of service use. While 88% of the families accessed at least some of the recommended services, more than 50% failed to access all of the recommended aftercare services. The most often noted barriers to service use were enabling factors at the agency or community level. Yet, many of the services were used, and the respondents indicated that professionals played a role in helping them link to services. Researchers should continue to study the use of recommended aftercare services and the relationship between aftercare service use and clinical outcomes.

Adolescent↗
PubMed1999

Hemolytic-uremic syndrome with involvement of basal ganglia and cerebellum.

Hemolytic-uremic syndrome is a microangiopathy often associated with neurologic symptoms. Several patients with persistent lesions in cerebrum and basal ganglia have been reported. We present two children with bilateral basal ganglia and additional unilateral cerebellar lesions in magnetic resonance imaging. These resolved completely in one child. In the other child there were still residuals after 11 weeks. The neurologic symptoms of both improved after several therapeutic plasma exchanges and disappeared after months.

Basal Ganglia↗
PubMed1998

Contribution of lateral substituents in heptane-bisammonium derivatives to the allosteric stabilization of antagonist binding to M2-receptors.

Phthalimide-containing heptane-bisammonium-type compounds retard the dissociation of the antagonist [3H]-N-methylscopolamine ([3H]NMS) from muscarinic M2-receptor allosterically with high potency. To study the contribution of the lateral substituents to this effect, a series of derivatives was synthesized in which the phthalimide moiety was truncated. The potency of the compounds to delay [3H]NMS dissociation was measured in porcine heart homogenates (50 mM Tris-HCl, 3 mM MgHPO4, pH 7.3, 37 degrees C). Potency declined with diminuition of the lateral substituents, e.g. loss of the aromatic ring of the phthalimide resulted in a 400fold reduction in potency. In the hexahydrophthalimide derivatives, the cis-stereoisomer was about fivefold more potent than the trans-isomer. In conclusion, almost flat hydrophobic lateral moieties appear to be pivotal for high allosteric potency, suggesting a hydrophobic interaction of these parts of the molecule with the [3H]NMS occupied receptor protein.

Allosteric Regulation↗
PubMed1997

Pseudoissues in practice evaluation: impediments to responsible practice.

This article reviews often-cited barriers to the implementation of practice evaluation activities and suggests that they are pseudoissues. Five pseudoissues in evaluation are reviewed: (1) time constraints, (2) single-system design issues, (3) gender and ethnic bias, (4) complexity of practice, and (5) incompatibility between the science of evaluation and the art of helping. These pseudoissues result from two misconceptions: First, these issues are sometimes viewed as affecting only the evaluation component of practice, but they pervade all of practice. Second, the confusion about the purpose of single-system designs leads to unwarranted concerns about design and methodology. The article argues that the incorporation of evaluation activities in practice helps practitioners become more aware of and sensitive to legitimate barriers to effective practice and paves the way for overcoming these barriers.

Adolescent↗
PubMed1994

MRI assessment of myelination: an age standardization.

777 cerebral MRI examinations of children aged 3 days to 14 years were staged for myelination to establish an age standardization. Staging was performed using a system proposed in a previous paper, separately ranking 10 different regions of the brain. Interpretation of the results led to the identification of four clinical diagnoses that are frequently associated with delays in myelination: West syndrome, cerebral palsy, developmental retardation, and congenital anomalies. In addition, it was found that assessment of myelination in children with head injuries was not practical as alterations in MRI signal can simulate earlier stages of myelination. Age limits were therefore calculated from the case material after excluding all children with these conditions. When simplifications of the definition of the stages are applied, these age limits for the various stages of myelination of each of the 10 regions of the brain make the staging system applicable for routine assessment of myelination.

Adolescent↗
PubMed1994

Delayed myelination in children with West syndrome: an MRI-study.

Eighteen children with West syndrome underwent MRI-examination of the brain. Five children were examined twice. Myelination of ten regions of the brain was retrospectively assessed on the MRI-examinations. The children could be divided in three groups of main diagnosis (cryptogenic West syndrome, tuberous sclerosis, pre-/perinatally acquired brain lesions). Delays in myelination were found in 17 out of a total of 23 examinations. In children with cryptogenic West syndrome and with tuberous sclerosis myelination was normal or only mildly delayed in the first month after onset of the spasms, but delays seemed to increase in the course of the West syndrome in these groups. In children with pre- or perinatally acquired brain lesions severe delays of myelination could be found already in the first weeks after the onset of the West syndrome. The assessment of myelination can therefore contribute to the diagnosis and understanding of the underlying disease in children with West syndrome.

Age of Onset↗
PubMed1993

Myelination of the brain in MRI: a staging system.

In a retrospective study 516 cranial MRI examinations of children aged 1 month to 14 years were re-evaluated for myelination. An objective staging system for the assessment of the degree of myelination was designed, based on the characteristic patterns of myelin-typical signal which develop in the course of brain maturation. Thus myelination can be estimated using only routine MRI examinations; no additional measurements of signal intensities are necessary. In order to obtain detailed information, ten regions of the brain are ranked separately, with comparisons of the T1- and T2-weighted images for each region. The application of the staging system to the case material revealed typical age ranges for the stages, and retarded myelination in some children. In most cases the observed retardation affected several regions but never the whole brain. Such delays can only be detected by separate assessment of the degree of myelination in each region of the brain.

Adolescent↗
PubMed1992

Epidemiologic and serologic definition of primary and secondary trichinosis in the Arctic.

A large outbreak of trichinosis acquired from walrus in Salluit in 1987 provided the immunologic and epidemiologic data from which two distinct clinical syndromes were identified. The first syndrome is the classic myopathic form with edema, fever, myalgia, and rash. The second is a persistent diarrheal illness with little edema or myalgia. The clinical presentations are paralleled by distinct differences in type and development of antibody response. The clinical and serologic profiles of the two syndromes support the hypothesis that the myopathic form represents a primary infection of Trichinella nativa, while the second represents a secondary infection in previously sensitized individuals.

Adolescent↗