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J Engel

Publications and source records attributed to J Engel.

At least 163 records · Page 9Linked to original sources
PubMed1998

Classifications of the International League Against Epilepsy: time for reappraisal.

Recent advances in neurodiagnostic technology, new insights into fundamental neuronal mechanisms of epilepsy, and rapid developments in molecular genetics have greatly improved our understanding of epileptic seizures and epileptic disorders since 1981, when the current International Classification of Epileptic Seizures was adopted, and since 1989, when the International Classification of Epilepsies, Epileptic Syndromes, and Related Disorders was adopted. Although both have been universally accepted and have proven to be of considerable clinical value, it has become clear that more is needed for specific applications of growing importance, such as presurgical evaluation, clinical pharmacology trials, and epidemiological studies. Therefore, an International League Against Epilepsy (ILAE) task force has evaluated the need for revising our current classification and terminology and has begun developing four specific documents. The first is a descriptive terminology for ictal phenomena, incorporating some of the concepts included in the preceding paper by Dr. Hans Lüders; however, this will be a glossary, not a classification. The second is a classification of epileptic seizures based on known or presumed pathophysiological and anatomic substrates, to replace the current classification, which is based entirely on phenomenology. The third is a classification of epileptic syndromes and epileptic diseases, adapted from the current Classification of Epilepsies, Epileptic Syndromes, and Related Disorders, which will take into account the fact that disorders with unique etiologies, such as a single gene, should be considered diseases, and which will be reorganized for maximum practical application to differential diagnosis. The fourth is a new classification of functional disability due to seizures or epilepsy, based on a new impairment classification for neurological disorders being developed by the World Health Organization. Working groups are currently in the process of developing each of these documents, and their chairs would benefit from any comments or suggestions from those who ultimately will be using these systems of classification and terminology.

Epilepsy↗
PubMed1998

Fusion of Chlamydia trachomatis-containing inclusions is inhibited at low temperatures and requires bacterial protein synthesis.

The human pathogen Chlamydia trachomatis is an obligate intracellular bacterium with a unique developmental cycle. Within the host cell cytoplasm, it resides within a membrane-bound compartment, the inclusion. A distinguishing characteristic of the C. trachomatis life cycle is the fusion of the chlamydia-containing inclusions with each other in the host cell cytoplasm. We report that fusion of inclusions does not occur at 32 degreesC in multiple mammalian cell lines and with three different serovars of C. trachomatis. The inhibition of fusion was inclusion specific; the fusion with sphingolipid-containing secretory vesicles and the interaction with early endosomes were unaffected by incubation at 32 degreesC. The inhibition of fusion of the inclusions was not primarily the result of delayed maturation of the inclusion, as infectious progeny was produced in host cells incubated at 32 degreesC, and the unfused inclusions remained competent to fuse up to 48 h postinfection. The ability to reverse the inhibition of fusion by shifting the infected cells from 32 to 37 degreesC allowed the measurement of the rate and the time of fusion of the inclusions after entry of the bacteria. Most significantly, we demonstrate that fusion of inclusions with each other requires bacterial protein synthesis and that the required bacterial protein(s) is present, but inactive or not secreted, at 32 degreesC.

Animals↗
PubMed1998

Sex differences in patients with mesial temporal lobe epilepsy.

Possible sex differences in the pattern of interictal hypometabolism were investigated, and also seizure spread in patients with mesial temporal lobe epilepsy (n=48) and hippocampal sclerosis (MTLE). Male patients (n=21) more often had a frontal lobe hypometabolism ipsilateral to the seizure onset (p<0.0001) and a spread of epileptiform activity to this region (p=0.001). By contrast, female patients more often exhibited hypometabolism (p=0.0052) and an ictal spread to the contralateral temporal lobe (p=0.0097). These findings suggest sex differences in spatial distribution of brain dysfunction in MTLE, perhaps reflecting sexual dimorphism in regional cerebral connectivity.

Adult↗
PubMed1998

Spinalin, a new glycine- and histidine-rich protein in spines of Hydra nematocysts.

Here we present the cloning, expression and immunocytochemical localization of a novel 24 kDa protein, designated spinalin, which is present in the spines and operculum of Hydra nematocysts. Spinalin cDNA clones were identified by in situ hybridization to differentiating nematocytes. Sequencing of a full-length clone revealed the presence of an N-terminal signal peptide, suggesting that the mature protein is sorted via the endoplasmic reticulum to the post-Golgi vacuole in which the nematocyst is formed. The N-terminal region of spinalin (154 residues) is very rich in glycines (48 residues) and histidines (33 residues). A central region of 35 residues contains 19 glycines, occurring mainly as pairs. For both regions a polyglycine-like structure is likely and this may be stabilized by hydrogen bond-mediated chain association. Similar sequences found in loricrins, cytokeratins and avian keratins are postulated to participate in formation of supramolecular structures. Spinalin is terminated by a basic region (6 lysines out of 15 residues) and an acidic region (9 glutamates and 9 aspartates out of 32 residues). Western blot analysis with a polyclonal antibody generated against a recombinant 19 kDa fragment of spinalin showed that spinalin is localized in nematocysts. Following dissociation of the nematocyst's capsule wall with DTT, spinalin was found in the insoluble fraction containing spines and the operculum. Immunocytochemical analysis of developing nematocysts revealed that spinalin first appears in the matrix but then is transferred through the capsule wall at the end of morphogenesis to form spines on the external surface of the inverted tubule and the operculum.

Amino Acid Sequence↗
PubMed1997

Nerve growth factor signal transduction in mature pig oligodendrocytes.

It has previously been shown that nerve growth factor (NGF) is of functional significance for mature pig oligodendrocytes (OLs) in culture. The present data give evidence for the expression of TrkA, the so-called high-affinity NGF receptor, and of p75NTR, the so-called low-affinity NGF receptor. TrkA is upregulated during culturing, in contrast to the p75 receptor. Exposure of OLs to NGF induces an autophosphorylation of TrkA via its intrinsic tyrosine kinase. K-252a inhibits the TrkA autophosphorylation, which reduces the OL process formation to control levels. To the tyrosine-phosphorylated sites of TrkA several proteins, such as phospholipase C-gamma1, the adaptor protein SHC, the phosphotyrosine phosphatase SH-PTP2 (SYP) associate via their SH2 phosphotase SH-PTP2 domain. The association of SHC to TrkA is shown by co-immunoprecipitation. Indirect evidence for a possible activation of PLC-gamma1 is given by an NGF-induced increase of oligodendroglial [Ca2+]i. Downstream from TrkA, a mitogen-activated protein kinase cascade, which includes Erk1 and Erk2, is operating. An in-gel myelin basic protein kinase assay revealed that NGF activates predominantly Erk1. Finally, it is shown that NGF stimulates expression of c-fos.

Animals↗
PubMed1997

Calcium binding and homoassociation of E-cadherin domains.

Cadherins are single pass transmembrane glycoproteins which mediate calcium dependent cell-cell adhesion by homophilic interactions. To reveal the molecular details of calcium binding and homoassociation, we recombinantly expressed in Escherichia coli a domain pair consisting of the first two domains of E-cadherin (ECAD12) and the single domains 1, 2, and 5. ECAD12 encompasses the most N-terminal of the four putative calcium-binding pockets in the extracellular region of E-cadherin. Equilibrium dialysis experiments revealed that the single domains do not bind Ca2+, but ECAD12 was found to bind three calcium ions. ECAD12 dimerizes (Kd = 0.08 +/- 0.02 mM) in the presence of Ca2+ as we could demonstrate by analytical ultracentrifugation. Calcium binding to ECAD12 induces conformational changes which were monitored by electrophoretic mobility and by circular dichroism. By analyzing our equilibrium dialysis data with a single binding site model, we found an average Kd of 460 microM for the three bound Ca2+. Assuming a model for three binding sites, which slightly increased the quality of the fit, we obtained two identical Kds of 330 microM and a third much higher Kd of 2 mM. The entire extracellular region of E-cadherin, which was recombinantly expressed in mammalian cells, binds nine Ca2+ with a much lower average Kd of 30 microM. Therefore, we conclude that the four calcium binding pockets are not identical. Since binding to ECAD12 occurs at Ca2+ concentrations close to those in the extracellular space, we suggest that the N-terminal domain pair might be involved in calcium regulation of E-cadherin mediated cell-cell adhesion.

Animals↗
PubMed1997

Integrin alphaIIb beta3 reconstituted into lipid bilayers is nonclustered in its activated state but clusters after fibrinogen binding.

Integrin activation, ligand binding, and integrin clustering were analyzed using alphaIIb beta3 reconstituted into phospholipid vesicles and into supported planar lipid bilayers. Strong and specific binding of fibrinogen and the gamma-chain dodecapeptide of fibrinogen to alphaIIb beta3 indicated that the integrin is in an activated state after membrane reconstitution. Cryoelectron and fluorescence microscopy suggested a nonclustered state of the protein in the vesicle membrane. Supported planar lipid membranes were generated by fusion of vesicles in which approximately equal fractions of integrins were pointing inside-out and outside-in. This distribution led to an immobilization of about 40% of the integrin in supported bilayers due to attachment of the large extracellular domains to the quartz support. Fluorescence recovery after photobleaching indicated a diffusion coefficient of D = (0.70 +/- 0.06) x 10(-8) cm2/s, consistent with a nonclustered state of the mobile integrin. Upon fibrinogen binding, the integrins became immobile, and fluorescence micrographs showed a patchy distribution of fibrinogen-integrin complexes consisting of approximately 250 molecules. In addition to the expected dimer formation by bivalent fibrinogen, additionally induced fibrinogen clustering may account for the large size of the complexes. In contrast, binding of monovalent GRGDS pentapeptide or the gamma-chain dodecapeptide of fibrinogen altered neither the mobile fraction nor the association state of alphaIIb beta3. Our data indicate that integrin alphaIIbb3 is activated while monodisperse, and became clustered upon fibrinogen binding, leading to an irreversibly bound state.

Amino Acid Sequence↗
PubMed1997

Dimer model for the microfibrillar protein fibulin-2 and identification of the connecting disulfide bridge.

Fibulin-2 is a novel extracellular matrix protein frequently found in close association with microfibrils containing either fibronectin or fibrillin. The entire protein and its predicted domains were obtained as recombinant products and examined by ultracentrifugation and electron microscopy. This demonstrated a disulfide-linked homodimer of 175 kDa subunits. Partial reduction to monomers identified specifically an odd Cys574 residue responsible for dimer formation in one of three anaphylatoxin-like modules that constitute the central globular domain I (13 kDa) of fibulin-2. Furthermore, a Cys574-Ser mutation abolished disulfide connection but not non-covalent dimerization of fibulin-2. The C-terminal region (85 kDa) was shown to represent a 35-nm-long rod consisting of 11 calcium-binding EGF-like modules (domain II) and a small terminal globe (domain III). The unique N-terminal domain N (55 kDa) was also rod-shaped (approximately 38 nm) and rich in galactosamine indicating extensive O-glycosylation. A dimer model is proposed indicating mainly a rod-like shape of 80 nm length based on an anti-parallel association of two subunits through their domains I. This model also implies alignment of domains II and N between different subunits. This was demonstrated by surface plasmon resonance assay which showed a distinct interaction between domains N and II with a Kd of approximately 0.7 microM.

Amino Acid Sequence↗
PubMed1997

The N-terminal region of alpha-dystroglycan is an autonomous globular domain.

The structure of the N-terminal region of mouse alpha-dystroglycan (DGN) was investigated by expression of two protein fragments (residues 30-180 and 30-438) in Escherichia coli cells. Trypsin susceptibility experiments show the presence of a stable alpha-dystroglycan N-terminal region (approximately from residue 30 to 315). In addition, guanidinium hydrochloride (Gdn/HCl) denaturation of DGN-(30-438)-peptide, monitored by means of tryptophan fluorescence, produces a cooperative transition typical of folded protein structures. These results strongly suggest that the alpha-dystroglycan N-terminal is an autonomous folding unit preluding a flexible mucin-like region and that its folding is not influenced by the absence of glycosylation. In order to obtain more information on the structural features of the N-terminal domain we have also used circular dichroism, analytical sedimentation and electron microscopy analysis. Circular dichroic spectra show the absence of typical secondary structure (e.g. alpha-helix or beta-sheet) and closely resemble those recorded for loop-containing proteins. This is consistent with a sequence similarity of the alpha-dystroglycan domain with the loop-containing protein elastase. Analytical ultracentrifugation and electron microscopy analysis reveal that the N-terminal domain has a globular structure. DGN-(30-438)-peptide does not bind in the nanomolar range to an iodinated agrin fragment which binds with high affinity to tissue purified alpha-dystroglycan. No binding was detected also to laminin. This result suggests that the alpha-dystroglycan N-terminal domain does not contain the binding site to its extracellular matrix binding partners. It is less likely than the lack of glycosylation reduces its binding affinity, because the N-terminal globular domain only contains two glycosylation sites.

Agrin↗
PubMed1997

Investigation of the stereoselective in vitro metabolism of the chiral antiasthmatic/antiallergic drug flezelastine by high-performance liquid chromatography and capillary zone electrophoresis.

An achiral HPLC method using a silica gel column as well as two independent chiral analytical methods by HPLC and capillary zone electrophoresis (CZE) were developed in order to investigate the in vitro metabolism of the racemic antiasthmatic/antiallergic drug flezelastine. The chiral HPLC analysis was performed on a Chiralpak AD column, which also allowed the simultaneous separation of the N-dephenethyl metabolite. The chiral separation by CZE was achieved by the addition of beta-cyclodextrin to the run buffer. The stereoselectivity of the in vitro biotransformation of flezelastine was investigated using liver homogenates of different species. Depending on the species, diverse stereoselective aspects were demonstrated. The determination of the enantiomeric ratios of flezelastine and of N-dephenethylflezelastine after incubations of racemic flezelastine with liver microsomes revealed that porcine liver microsomes showed the greatest enantioselectivity of the biotransformation. (-)-Flezelastine was preferentially metabolized. After incubations with bovine liver microsomes the enantiomer of N-dephenethylflezelastine formed from (+)-flezelastine dominated. Incubations of the pure enantiomers of flezelastine with induced rat liver microsomes resulted in the stereoselective formation of a hitherto unknown metabolite, which was only detected in samples of (+)-flezelastine. Initial structure elucidation of the compound indicated that the new metabolite was most likely an aromatically hydroxylated derivative of the N-dephenethylflezelastine.

Animals↗
PubMed1997

Doing What Everybody Does? A Procedure for Investigating Behavioural Synchronization

Behavioural synchronization means that the behaviour of several individuals is related in time. They may show the same behaviour either at the same time (synchrony) or explicitly at different moments (anachrony). Here, a procedure is presented, which not only allows quantitative investigation of behavioural synchronization in groups of any size, but also a separate evaluation with respect to each individual and behaviour pattern. The method distinguishes between the purely descriptive degree of concurrence and the degree of synchrony, which takes into account synchrony or anachrony occurring by chance on the basis of particular behaviour frequencies. Some recommendations for the application of the procedure are given and its limitations discussed. Copyright 1997 Academic Press Limited

Journal Article↗
PubMed1997

Pattern of interictal hypometabolism in PET scans with fludeoxyglucose F 18 reflects prior seizure types in patients with mesial temporal lobe seizures.

BACKGROUND: Interictal hypometabolism is routinely used as an indicator of the epileptogenic zone in patients with complex partial seizures (CPSs). However, the regional pattern of hypometabolism varies without obvious reasons, even among patients with identical epileptogenic zones and causes. OBJECTIVE: To investigate whether this pattern may be related to the electroencephalographic and clinical features of the seizure that precedes the positron emission tomographic (PET) scan with fludeoxyglucose F 18. PATIENTS AND METHODS: Fifty-three patients with CPSs were first classified into 4 groups, depending on the features of the seizure that preceded the PET scan (determined from findings from electroencephalography and videotelemetry). In 14 patients, this seizure was focal limbic (characterized by aurae or staring spells); in 18, the CPS was widespread limbic (including automatisms). Ten patients had a CPS with posturing, and 11 had a secondarily generalized CPS. Regions with a hemisphere-normalized concentration of fludeoxyglucose F 18 below the 95% confidence interval of values from 8 control subjects were defined as hypometabolic. The location of these regions was then compared among the 4 groups, and the degree of hypometabolism was related to the time from the seizure to the PET scan with fludeoxyglucose F 18. RESULTS: The hypometabolic area was limited to the epileptogenic zone if the preceding seizure was focal limbic, whereas in patients with widespread limbic seizures, it included one or several additional areas of the limbic cortex (P = .03). Patients with posturing differed from both previous groups by having hypometabolism in the extralimbic frontal lobe (P < .001), and subjects with secondarily generalized seizures differed from all others because of cerebellar (P < .001) and parietal lobe (P < .05) reductions. The time between the seizure and the performance of the PET scan did not correlate with the degree or extent of hypometabolism. CONCLUSIONS: Mechanisms involved in the generation of a seizure that precedes a PET scan with fludeoxyglucose F 18 seem to influence the "interictal" hypometabolic pattern. Therefore, caution should be used when interpreting scans that are preceded by a nonhabitual seizure.

Adolescent↗