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Biomedical subjects

A Ebel

Publications and source records attributed to A Ebel.

At least 19 recordsLinked to original sources
PubMed2006

Robust analysis of short echo time (1)H MRSI of human brain.

Short echo time proton MR Spectroscopic Imaging (MRSI) suffers from low signal-to-noise ratio (SNR), limiting accuracy to estimate metabolite intensities. A method to coherently sum spectra in a region of interest of the human brain by appropriate peak alignment was developed to yield a mean spectrum with increased SNR. Furthermore, principal component (PC) spectra were calculated to estimate the variance of the mean spectrum. The mean or alternatively the first PC (PC(1)) spectrum from the same region can be used for quantitation of peak areas of metabolites in the human brain at increased SNR. Monte Carlo simulations showed that both mean and PC(1) spectra were more accurate in estimating regional metabolite concentrations than solutions that regress individual spectra against the tissue compositions of MRSI voxels. Back-to-back MRSI studies on 10 healthy volunteers showed that mean spectra markedly improved reliability of brain metabolite measurements, most notably for myo-inositol, as compared to regression methods.

Adult↗
PubMed2006

Comprehensive processing, display and analysis for in vivo MR spectroscopic imaging.

Image reconstruction for magnetic resonance spectroscopic imaging (MRSI) requires specialized spatial and spectral data processing methods and benefits from the use of several sources of prior information that are not commonly available, including MRI-derived tissue segmentation, morphological analysis and spectral characteristics of the observed metabolites. In addition, incorporating information obtained from MRI data can enhance the display of low-resolution metabolite images and multiparametric and regional statistical analysis methods can improve detection of altered metabolite distributions. As a result, full MRSI processing and analysis can involve multiple processing steps and several different data types. In this paper, a processing environment is described that integrates and automates these data processing and analysis functions for imaging of proton metabolite distributions in the normal human brain. The capabilities include normalization of metabolite signal intensities and transformation into a common spatial reference frame, thereby allowing the formation of a database of MR-measured human metabolite values as a function of acquisition, spatial and subject parameters. This development is carried out under the MIDAS project (Metabolite Imaging and Data Analysis System), which provides an integrated set of MRI and MRSI processing functions. It is anticipated that further development and distribution of these capabilities will facilitate more widespread use of MRSI for diagnostic imaging, encourage the development of standardized MRSI acquisition, processing and analysis methods and enable improved mapping of metabolite distributions in the human brain.

Algorithms↗
PubMed2005

Computational intelligence-based optimisation of wastewater treatment plants.

Methods of computational intelligence (CI), especially fuzzy control and neuronal networks, are used for controlling and optimising of wastewater treatment plants. Areas of application are the control of sludge water dosage, of phosphate elimination by optimal precipitant dosage as well as an optimal aeration in the nitrification zone. In two municipal wastewater treatment plants with 60,000 and 12,600 person equivalents the controllers have been installed and optimised and they have been in operation for several years. Results of operation of the plants are presented in comparison to previously used classical control. Performance increased significantly and the outflow values could be kept securely below the government requirements without increase of the energy consumption. Peak loads in the inflow were eliminated in the plant and did not increase outflow concentrations. Results of operation for more than three years clearly show that the CI controller is a cost-efficient method for a sustainable rise of performance in municipal wastewater treatment plants.

Artificial Intelligence↗
PubMed2001

Comparison of methods for reduction of lipid contamination for in vivo proton MR spectroscopic imaging of the brain.

In vivo proton MR spectroscopic imaging (MRSI) of human brain is complicated by the presence of a strong signal from subcutaneous lipids, which may result in signal contamination in metabolite images obtained following Fourier-transform reconstruction. In this study, two approaches for reduction of lipid contamination--using postprocessing and additional data acquisition--are compared. The first uses extrapolation of k-space information for subcutaneous lipid, which has been applied to data obtained using conventional fully phase-encoded MRSI with circularly sampled k-space or echo-planar spectroscopic imaging (EPSI). The second uses a dual EPSI technique that combines multiple-averaged central k-space data with a single EPSI acquisition of additional information that is used for improved lipid reconstruction. Comparisons are carried out with data obtained from human brain in vivo at 1.5 T with short and medium TEs. Results demonstrate that the performance of both methods for reducing the effects of lipid contamination is similar, and that both are limited by the effects of instrumental instabilities and subject motion, which also depend on the acquisition method used.

Artifacts↗
PubMed2001

Assessment of 3D proton MR echo-planar spectroscopic imaging using automated spectral analysis.

For many clinical applications of proton MR spectroscopic imaging (MRSI) of the brain, diagnostic assessment is limited by insufficient coverage provided by single- or multislice acquisition methods as well as by the use of volume preselection methods. Additionally, traditional spectral analysis methods may limit the operator to detailed analysis of only a few selected brain regions. It is therefore highly desirable to use a fully 3D approach, combined with spectral analysis procedures that enable automated assessment of 3D metabolite distributions over the whole brain. In this study, a 3D echo-planar MRSI technique has been implemented without volume preselection to provide sufficient spatial resolution with maximum coverage of the brain. Using MRSI acquisitions in normal subjects at 1.5T and a fully automated spectral analysis procedure, an assessment of the resultant spectral quality and the extent of viable data in human brain was carried out. The analysis found that 69% of brain voxels were obtained with acceptable spectral quality at TE = 135 ms, and 52% at TE = 25 ms. Most of the rejected voxels were located near the sinuses or temporal bones and demonstrated poor B0 homogeneity and additional regions were affected by stronger lipid contamination at TE = 25 ms.

Brain↗
PubMed2000

A fast variant of (1)H spectroscopic U-FLARE imaging using adjusted chemical shift phase encoding.

So far, fast spectroscopic imaging (SI) using the U-FLARE sequence has provided metabolic maps indirectly via Fourier transformation (FT) along the chemical shift (CS) dimension and subsequent peak integration. However, a large number of CS encoding steps N(omega) is needed to cover the spectral bandwidth and to achieve sufficient spectral resolution for peak integration even if the number of resonance lines is small compared to N(omega) and even if only metabolic images are of interest and not the spectra in each voxel. Other reconstruction algorithms require extensive prior knowledge, starting values, and/or model functions. An adjusted CS phase encoding scheme (APE) can be used to overcome these drawbacks. It incorporates prior knowledge only about the resonance frequencies present in the sample. Thus, N(omega) can be reduced by a factor of 4 for many (1)H in vivo studies while no spectra have to be reconstructed, and no additional user interaction, prior knowledge, starting values, or model function are required. Phantom measurements and in vivo experiments on rat brain have been performed at 4.7 T to test the feasibility of the method for proton SI.

Animals↗
PubMed2000

Validation of the INNO-LIA syphilis kit as a confirmatory assay for Treponema pallidum antibodies.

The commercially available diagnostic tests for syphilis are mostly based on the use of extracted antigens of Treponema pallidum. Pronounced cross-reactivities with other spirochete antigens are often reported. The aim of this study was to validate a novel multiparametric assay (the assay performed with the kit) INNO-LIA Syphilis for the confirmation of syphilis antibodies in a set of 840 documented human serum samples. All serum samples were previously tested at the French World Health Organization reference center for venereal diseases (Institute Alfred Fournier, Paris, France), with a consensus result provided for each sample. The study was conducted in two phases, with each phase involving a validation set (500 well-documented serum samples) and an exploratory set (340 serum samples) of serum samples, respectively. By measuring the sensitivity and specificity, we compared the result of the new assay with the consensus result on the basis of the results of a variable number of classical serological methods and clinical information when available. A sensitivity of 99.6% (95% confidence internal [CI], 98.5 to 99.9%) and a specificity of 99.5% (95% CI, 98.1 to 99.9%) were found for the new line immunoassay. Six of seven samples with indeterminate results by classical serology tested positive with the INNO-LIA Syphilis kit. This single multiparametric assay provides reliable confirmatory diagnostic information that must currently be obtained by the performance and interpretation of results of a combination of serological assays.

Antibodies, Bacterial↗
PubMed1998

Evaluation of a new competitive immunoassay (BioElisa Syphilis) for screening for Treponema pallidum antibodies at various stages of syphilis.

The BioElisa Syphilis, a new competitive enzyme immunoassay (EIA) for Treponema pallidum whole antigen that uses specific human immunoglobulin G (IgG) antibodies as the competitor, was evaluated for potential use in screening for syphilis at various stages. The results obtained by this competitive EIA were compared with those obtained by the fluorescent treponemal antibody absorption (FTA-abs) test and the T. pallidum hemagglutination assay (TPHA). Serum samples from 434 patients with positive TPHA and FTA-abs test results, including patients with primary, latent, secondary, and tertiary syphilis and neurosyphilis, were investigated. Two samples tested negative by competitive EIA but were weakly reactive by the TPHA and the FTA-abs test. Sixteen serum samples from patients with clinically documented active syphilis, including several patients infected with human immunodeficiency virus, tested positive by the competitive EIA. There was a direct inverse correlation between EIA indices and titers in the TPHA and the FTA-abs test for all samples that tested positive. Specificity was assessed by testing 358 serum samples which tested negative for syphilis by TPHA and the FTA-abs test, including 100 serum samples from patients with documented infectious or autoimmune diseases. Only two serum samples gave a weakly positive EIA result. Thus, competitive EIA had a sensitivity of 99.5% and a specificity of 99.4% relative to the results of the FTA-abs test and TPHA. Our evaluation shows that BioElisa Syphilis is a sensitive, specific, and simple assay for screening for syphilis.

Antibodies, Bacterial↗
PubMed1994

Cholinergic modulation through biogenic amines during development of the chick spinal cord.

Our previous analyses of the functional maturation of cholinergic neurotransmission in the chick embryo spinal cord showed that 12 days of development represents a crucial stage in the maturation of cholinergic neurotransmission. Since supraspinal inputs are essential for the modulation of motoneuron activity in the embryo, we studied, using a pharmacological approach, the regulatory effects of biogenic amines on the developing cholinergic neurotransmission. We show that, in spite of the early occurrence of serotonin and norepinephrine in the developing spinal cord, the modulatory influences of these biogenic amines on motoneurons can only be effective from 12 days of incubation onwards. It also appears that the inputs of biogenic amines on cholinergic activity is a sequential event. Whereas serotonin (5-HT) begins to stimulate cholinergic activity from 12 days of incubation, norepinephrine inputs are only observed at later stages (17 days of development). These observations underline the specific turning point in the functional maturation of motoneurons, we noted in our previous studies. At the end of embryonic life a specific interrelationship between the biogenic amines was noted, its effect on the cholinergic system may lead to a more precise motor control, preparing the chick embryo for hatching.

Animals↗
PubMed1992

Distribution of cholinergic neurons in the chick spinal cord during embryonic development. Comparison of ChAT immunocytochemistry with AChE histochemistry.

The location of cholinergic neurons was studied during the development of the chick embryo spinal cord. A comparison between choline acetyltransferase (ChAT) immunocytochemistry and acetylcholinesterase (AChE) histochemistry was performed. ChAT-positive neurons could be detected only from embryonic day 9 (E9) onwards by the FITC technique and from E12 onwards by the PAP technique. These neurons were located mainly in the medial and lateral motor columns in the ventral horn of the gray matter and some of them were observed in the intermediate region of the spinal cord. AChE-containing cell bodies were much more numerous than the ChAT immunoreactive ones and were distributed in the ventral horn of the gray matter, the intermediate gray region and mostly off the apical part of the dorsal horn. ChAT should provide a reliable and specific marker for cholinergic neurons.

Acetylcholinesterase↗
PubMed1991

Are chronic alcohol-induced central vasopressin changes determinant in strain dependency of tolerance in mice?

As vasopressin (VP) has been related to tolerance, we were interested in following central VP levels after chronic alcohol exposure of two selected mouse lines (C57Bl and Balb/c). Strongly elevated VP and VP mRNA levels have been noted, in particular in the hypothalamus. The phenomenon is much more marked in Balb/c mice than in C57Bl; in extrahypothalamic areas in the changes in VP noted in septum and amygdala are only apparent in Balb/c mice. Hypothalamic norepinephrine and serotonin, known to partly control VP release, also reacts in a strain dependent manner to alcohol. This study provides neurochemical evidence that long term ethanol intoxication selectively activates central vasopressinergic and aminergic neurons in mice. Such activation appears to be strain dependent; therefore it may be related to the unequal capacities of these strains to adapt to chronic alcohol intoxication. Such phenomena may partly account for differences between individuals in tolerance to chronic alcohol in men.

Animals↗
PubMed1990

Alcohol withdrawal-induced changes in brain biogenic amines in mice: influence of the genotype.

Alterations in striatal and hippocampal dopamine (DA) and serotonin (5HT) activities were investigated in two inbred strains of mice (C57B1 and Balb/c) after 3 withdrawal periods following 5 months chronic ethanol administration. Two groups of animals with different levels of ethanol administration (15% and 30%, v/v) were examined. A striking strain dependency has been noted. Striatal dopaminergic mechanisms of the Balb/c strain are profoundly disturbed in both groups. In contrast no changes were noted for either transmitter activities in C57B1 mice at any withdrawal time studied. Strain dependency has also been noted for hippocampal serotonin neurotransmission, since only Balb/c mice showed a progressive decrease in 5HT levels. These impairments observed in striatum and hippocampus could be involved in motor incoordinations and convulsions often associated with the withdrawal syndrome. The differences in withdrawal effects we noted between the two strains may be linked to the specific chemical neuroanatomy of the strains. Such specificities could be implied in the well known variability of withdrawal induced behavior in man.

Animals↗
PubMed1989

Effects of basic fibroblast growth factor (bFGF) on choline acetyltransferase activity and astroglial reaction in adult rats after partial fimbria transection.

Adult rats received a partial and unilateral transection of the fimbria. They received then intracerebroventricular (i.c.v.) injections of 5 microliters of Tris, half of them containing 2.5 ng of basic fibroblast growth factor (bFGF). They were injected twice a week for 4 weeks. At the end of this period, choline acetyltransferase (ChAT) activity was measured in the hippocampus. ChAT activity, which was decreased by the fimbria transection, was higher (by about 20%) in medial hippocampus of the bFGF group compared with the Tris group. In addition, bFGF enhanced the lesion-induced astroglial reaction by changing the morphology of the astrocytes and increasing the apparent number of these reactive astrocytes.

Animals↗
PubMed1988

Responses of cholinergic markers to a pre- or a postsynaptic pharmacological blockage in the developing chick embryo spinal cord.

The response of cholinergic markers to pre- or postsynaptic blockage was followed during development of the chick embryo spinal cord, to understand better the maturation sequence of the developing cholinergic synapse. It has been shown that the developing neurotransmitter system is able to react to pre- or postsynaptic disturbances by compensatory mechanisms, as early as 7.5 days of incubation. From 12.5 days of incubation the synaptic reactivity to such blockage changes in complexity as well as in nature. At this developmental stage muscarinic receptors show capacity for intrinsic regulation, similar to that of the adult nervous system. These results together with our previous studies clearly demonstrate that 12.5-15.5 days of embryonic life appears to be a crucial period in ontogenesis of the cholinergic neurotransmission in the chick embryo spinal cord.

Animals↗
PubMed1987

Influence of mouse genotype on responses on central neurotransmitters to long-term alcohol exposure in striatum and hippocampus.

A striking strain dependency in response of central neuromediators (dopamine, serotonin, acetylcholine activities and somatostatin) to various periods of alcohol treatment has been noted in striatum and hippocampus in mice. For biogenic amines the C57Bl strain loses tolerance to prolonged alcohol injury earlier than the Balb/c strain. At the opposite the Balb/c strain exhibits a remarkable long lasting tolerance for cholinergic activity. The unequal capacity to adapt, also appears to depend on the nervous structure and the neurotransmitter considered. Such discrepancies may underly differences in behavioral changes observed in alcoholics.

Animals↗
PubMed1986

Effects of hormone therapy on the central cholinergic neurotransmission of the Snell dwarf mouse.

Effects of growth and thyroid hormone therapy on central cholinergic neurotransmission has been followed in the cholinergic-deficient Snell dwarf mouse. Growth hormone and thyroxine can reverse the neurotransmission impairment even in adulthood. Furthermore, it appears that in the dw/dw mouse, hormone deficiency becomes determinant only after the critical period of neurogenesis, in a late postnatal developmental stage. At first sight, these observations show that the disturbed cholinergic neurotransmission of the mutant might be linked to the pituitary and thyroxine deficiency that is characteristic of this mouse. Hormone therapy selectively stimulates cholinergic activity in cholinergic-deficient structures, where it reactivates presynaptic markers. The differential responsiveness of the neuroanatomical and neurochemical targets could be linked to different regulatory hormone effects or to timing in respect to sensitivity to hormones during development.

Acetylcholinesterase↗
PubMed1986

Genotypic differences in age and chronic alcohol exposure effects on somatostatin levels in hippocampus and striatum in mice.

Somatostatin contents of striatum, hippocampus, and pons medulla have been followed in two inbred strains of mice (C57B1/6J and Balb/cJ) with aging and long term alcohol exposure (over a 25 month period of intoxication). Marked strain dependent differences in basic levels of somatostatin and genotypic variations in reactivity of this neuropeptide to aging processes and chronic alcohol exposure were demonstrated. The Balb/c strain exhibits a significant age dependent decrease in striatal and hippocampal somatostatin levels whereas the C57B1 mice remain unchanged until the 27 month. Moreover, only the Balb/c strain reacts to chronic alcohol exposure, showing a significant increase in somatostatin levels in those structures affected by the aging process. Such genotypic differences may be involved in man in specific pathologies in aged individuals and in alcohol induced behavioral alterations in alcoholics.

Aging↗