Clinical evidence for the progressive nature of epilepsy.
Explore the source record for details and available documents.
Amygdala↗
Biomedical subjects
J Engel
Publications and source records attributed to J Engel.
Opioid peptide release and mu-receptor binding during amygdala kindling in rats: regional discordances.
Explore the source record for details and available documents.
Amygdala↗
Outcomes in 248 patients who had diagnostic evaluations for epilepsy surgery.
Surgery for intractable epilepsy is a widely used treatment that is not readily assessed by randomised trials. We evaluated the impact of epilepsy surgery on seizures, medication use, employment, and the quality of life in 248 adults and adolescents consecutively referred to one medical centre between 1974 and 1990. Outcomes were determined through self-administered questionnaire and medical record review for 202 surgery and 46 non-surgery patients whose treatment was usually determined by the presence or absence of an epileptogenic focus. Surgery and non-surgery patients differed at baseline only in median monthly seizure frequency (surgery lower than non-surgery). After adjustment for baseline covariates, surgery patients at follow-up had greater decline in average monthly seizure frequency (-11.9 vs - 1.5; difference -10.4, 95% CI -20.5, -0.3) and took fewer antiepileptic medications (average number 1.4 vs 2.0; difference -0.67, 95% CI -0.94, -0.40). Although quality-of-life scores were higher (p < 0.05) with surgery on 5 of 11 scales that were administered only at follow-up, there were no significant differences in employment status or prospectively assessed quality of life. Relative to a non-surgery group, patients treated surgically had better seizure control with less antiepileptic medication. The impact of epilepsy surgery on quality of life and employment needs to be assessed in larger prospective studies.
Adolescent↗
The C-terminal portion of BM-40 (SPARC/osteonectin) is an autonomously folding and crystallisable domain that binds calcium and collagen IV.
The extracellular glycoprotein BM-40 consists of three domains, an acidic domain I, a follistatin (FS)-like domain II and a calcium-binding EC domain with an EF-hand related motif. BM-40 and several other related proteins (QR1, SC1/hevin, testican and tsc-36/FRP) are members of a novel modular protein family that share the FS domain followed by an EC domain. We have expressed this pair of FS and EC domains (mutant delta I) and the calcium-binding EC domain alone (mutant delta I, II) of human BM-40 as recombinant proteins in human 293 cells. Circular dichroism demonstrated that both mutants were obtained as folded proteins with a distinct three-dimensional conformation. In addition, mutant delta I, II could be readily crystallized and diffraction patterns with a resolution limit of 2.4 A resolution were obtained. Calcium binding to this fragment was ten times weaker (Kd = 0.8 microM) than for the wild-type protein. Identical reversible increases in alpha-helicity upon calcium binding were observed for the 150-residue long mutant delta I, II and for BM-40 (286 residues). A 26-residue synthetic peptide corresponding to the EF-hand related motif exhibited much weaker calcium binding. The apparent dissociation constant decreased with increasing peptide concentration (from Kd 2.4 mM at 1 microM, to Kd 0.3 mM at 100 microM peptide concentration) and calcium binding was accompanied by dimerization of the peptide. This suggests that for strong calcium binding the EF-hand related motif has to be embedded into a larger protein domain that can form an autonomously folding protein module. The EC domain was also shown by surface plasmon resonance assay to be responsible for calcium-dependent binding to collagen IV with an affinity (Kd = 19 microM) only sixfold lower than that of intact human BM-40.
Amino Acid Sequence↗
The function of the NC1 domains in type IV collagen.
At its C terminus, the collagen IV molecule bears a globular NC1 domain, to which two functions have been assigned. In the macromolecular network of collagen IV, two molecules are connected via their NC1 domains, which form a hexameric complex, stabilized by intermolecular disulfide bonds. In addition, the NC1 domains are thought to be responsible for chain selection and assembly. In order to understand the role of the NC1 domains during these steps, hexameric complexes were isolated and further investigated. SDS-polyacrylamide gel electrophoresis and Western blot revealed disulfide-linked alpha 1 (IV)NC1 and alpha 2(IV)NC1 homodimers but no heterodimers. The hexamers were dissociated at low pH, separated into monomers and dimers, and submitted to reconstitution experiments. Only alpha 1(IV)NC1 dimers were able to reconstitute a hexameric complex. alpha(IV)-NC1 and alpha 2(IV)NC1 monomers as well as the alpha 2(IV)NC1 dimers showed only a low tendency to form complexes. It is assumed that during formation of the collagen IV network, lateral aggregation of the molecules via the triple helical domains brings the C termini of two molecules into close vicinity and that subsequently the weak interactions observed between the NC1 subdomains provide the correct alignment for a disulfide exchange. It is, however, questionable whether the low affinity between the NC1 subdomains alone is sufficient for chain assembly and alignment of the alpha(IV) chains before molecule formation.
Collagen↗
Management perspectives. I am the nurse manager in a midsize hospital.
Explore the source record for details and available documents.
Humans↗
Electron microscopic evidence for a mucin-like region in chick muscle alpha-dystroglycan.
alpha-Dystroglycan has been isolated from chicken cardiac muscle and its molecular weight was estimated to be approximately 135 kDa. The avian protein interacts with murine Engelbreth-Holm-Swarm (EHS) tumor laminin via interaction with the C-terminal LG4 and LG5 domains (fragment E3) of the laminin alpha-chain. This laminin binding is calcium-dependent and can be competed by heparin. Electron microscopy investigation on the shape of alpha-dystroglycan suggests that the core protein consists of two roughly globular domains connected by a segment which most likely corresponds to a mucin-like central region also predicted by sequence analysis on mammalian isoforms. This segment may act as a spacer in the dystrophin-associated glycoproteins complex exposing the N-terminal domain of alpha-dystroglycan to laminin in the extracellular space.
Animals↗
Selective chain recognition in the C-terminal alpha-helical coiled-coil region of laminin.
Recombinant fragments alpha, beta, and gamma were prepared comprising about 100 C-terminal residues of the corresponding polypeptide chains in the three-stranded alpha-helical coiled-coil domain of laminin. Circular dichroism spectra, thermal transition profiles, non-denaturing gels, analytical ultracentrifugation, and calorimetry indicated alpha-helicity and high thermal stabilities for the beta gamma heterodimer and homoassociates of beta. Very little or no coiled-coil formation was found for alpha and gamma. The thermal melting profiles and their concentration dependencies were quantitatively described by a two-state mechanism in which two unfolded chains combine to a fully alpha-helical dimer. For the beta gamma dimer the melting temperature was Tm = 42 degrees C at a chain concentration of 25 microM in 5 mM sodium phosphate buffer (pH 7.4). Addition of 100 mM NaCl decreased the Tm slightly but the relative stability of beta gamma and beta beta coiled-coils was not significantly changed, indicating that electrostatic interactions alone are not responsible for chain selection. Upon addition of 1 M urea the Tm value dropped by about 10 degrees C. The enthalpy changes for the formation of the coiled-coil were delta H degrees = -304(+/- 30) kJ/mol for the beta gamma heterodimer and -198(+/- 20) kJ/mol for the beta-homoassociates. Gibbs free energies and entropies amounted to delta G degrees = -42.8 kJ and delta S degrees = -876 J/mol K for the heteroassembly and -37.8 kJ/mol and -537 J/mol K for the homoassembly of beta. This low preference for heteroassociation of the fragment is smaller than the chain selectivity observed for larger fragments and intact laminin. Deletion of ten residues from the C-terminal region of the gamma-fragment which were recently reported as an essential assembly-site was not sufficient to abolish heteroassociation. Interaction of alpha-fragment with double-stranded beta gamma coiled-coils reflected the formation of a three-stranded coiled-coil in laminin but for the small recombinant fragments association between alpha and beta-homoassociates was also observed. The C-terminal 100 residues in the coiled-coil domain are therefore not alone responsible for the high specificity of chain selection in laminin.
Amino Acid Sequence↗
Stabilization of the alpha-helical coiled-coil domain in laminin by C-terminal disulfide bonds.
The long arm of laminin in which three polypeptide chains alpha, beta, and gamma are assembled in an alpha-helical coiled-coil structure is stabilized by non-covalent interactions and disulfide bridges. The stabilizing role of the disulfide linkage between the beta and gamma-chains at the C-terminal region of the assembly domain was investigated with about 100-residue long recombinant fragments. Circular dichroism spectra and electron micrographs were identical for linked and non-linked species and indicated two-stranded coiled-coil structures with about 100% alpha-helicity at 20 degrees C. Thermal transition profiles revealed an increase of the melting temperature from 42 degrees C to 60.4 degrees C upon disulfide formation at a chain concentration of 25 microM. The enthalpy of interaction was identical for the two species but the negative entropy involved in joining the two chains was reduced by the disulfide bonds. At chain concentrations of 10 microM the Gibbs free energy delta G was by 17.5 kJ/mol more negative for the disulfide-linked than for the unlinked chains. Because of the concentration dependence of the entropy of the non-linked chains, this difference decreased with increasing concentration and, by extrapolation at chain concentrations of 10 mM, the stability of both structures would be the same. As a competing reaction, beta-chains associated to four-stranded bundles which probably consist of pairs of two-stranded coiled-coils. After disulfide formation a biphasic transition curve was observed which indicated two different ways of connecting the chains in the bundle.
Circular Dichroism↗
Evidence of a defined spatial arrangement of hyaluronate in the central filament of cartilage proteoglycan aggregates.
Aggregates of proteoglycans from the Swarm rat chondrosarcoma reassembled in vitro have been studied by rotary-shadowing electron microscopy, and shown to be similar to native structures that have never been dissociated [Mörgelin, Engel, Heinegård and Paulsson (1992) J. Biol. Chem. 267, 14275-14284]. A hyaluronate with defined chain length (HAshort) has now been prepared by autoclaving high-Mr hyaluronate and fractionation to a narrow size distribution by gel filtration. Proteoglycan monomers, core protein, hyaluronate-binding region and link protein were combined with HAshort. Free chains of HAshort and reconstituted complexes with proteoglycan, link protein and aggrecan fragments were examined by electron microscopy after rotary shadowing. Length measurements showed that the hyaluronate was condensed to about half of its original length on binding intact aggrecan monomers, any aggrecan fragment or link protein alone. This strongly implies that hyaluronate adopts a defined spatial arrangement within the central filament of the aggregate, probably different from its secondary structure in solution. No differences in length were observed between link-free and link-stabilized aggregates.
Animals↗
Structural comparison of cuticle and interstitial collagens from annelids living in shallow sea-water and at deep-sea hydrothermal vents.
Two types of annelid collagens of different sizes were purified, one from acetic acid extracts of the cuticle (length 2.5 microns) and the other, after pepsin digestion, from interstitial spaces of the body wall (0.3 micron). They were obtained from Alvinella pompejana, Alvinella caudata and Paralvinella grasslei collected at 2600 m depth around anoxic hydrothermal vents and from Arenicola marina and Nereis diversicolor living in shallow sea-water habitats. The length of the corresponding collagens from different species and their amino acid compositions including the hydroxylation of proline were remarkably similar. The melting point of the triple helix, however, differed between the Alvinella species (approximately 45 degrees C), Paralvinella (approximately 35 degrees C) and the shallow sea-water annelids (approximately 28 degrees C), indicating adaption to habitats with different temperatures. The cuticle collagens of the annelids possess a globular domain, which is apparently involved in oligomer formation, and show similar fragment pattern. Almost identical cross-striation patterns of segment-long-spacing segments of the interstitial collagens indicated sequence similarity, which was confirmed by partial Edman degradation of alpha-chains. These data showed almost complete identity between the two Alvinella species and a lower sequence identity with Paralvinella (approximately 95%), Arenicola (67 to 72%) and the vent vestimentiferan Riftia pachyptila (64 to 71%). The data suggest a close evolutionary relationship between these worms, despite a clear separation of habitat preference and thermal stability of the collagens.
Amino Acid Sequence↗
Method of localization and implantation of the lumpectomy site for high dose rate brachytherapy after conservative surgery for T1 and T2 breast cancer.
PURPOSE: This article describes our technique of localization and implantation of the lumpectomy site of patients with T1 and T2 breast cancer. Our method was developed as part of our Phase I/II pilot study of high dose rate (HDR) brachytherapy alone after conservative surgery for early breast cancer. METHODS AND MATERIALS: In March 1992, we started a pilot study of HDR brachytherapy to the lumpectomy site as the sole radiotherapy after conservative surgery for clinical T1 or T2 invasive breast cancer. Initially, the protocol required intraoperative placement of the interstitial needles at the time of definitive surgery to the breast. The protocol was then generalized to allow the implantation of the lumpectomy site after definitive surgery to the breast, either at the time of subsequent axillary nodal dissection or postoperatively. To date, five patients have been implanted intraoperatively at the time of definitive breast surgery. Twelve patients were implanted after definitive breast surgery, with 7 patients being done at the time of axillary nodal dissection and 5 patients postoperatively. We devised a method of accurately localizing and implanting the lumpectomy site after definitive breast surgery. The method relies on the previous placement of surgical clips by the referring surgeon to mark the lumpectomy site. For each patient, a breast mold is made with radio-opaque angiocatheters taped onto the mold in the supero-inferior direction. A planning CT scan is then obtained through the lumpectomy site. The volume of the lumpectomy site, the number of implant planes necessary, and the orientation of the implants are then determined from the CT scan. The angiocatheters provide a reference grid on the CT films to locate the entry and exit points of the interstitial needles on the plastic mold. The entry and exit points for reference needles are then transferred onto the patient's skin enabling implantation of the lumpectomy site. Needle positions with respect to the lumpectomy site are then verified using simulator radiographs. RESULTS: Eight double plane implants and four single plane implants have been done using this method. Five implants were done using direct visualization. It has not been necessary to reorient the implant in any of the patients. If not for the presence of surgical clips, the size of the lumpectomy site cannot be separated from the surrounding normal breast tissue. CONCLUSION: This technique is an accurate way to localize the lumpectomy site for HDR brachytherapy.
Adult↗
Demonstration of non-linear detection in ELISA resulting in up to 1000-fold too high affinities of fibrinogen binding to integrin alpha IIb beta 3.
To clarify the question as to why different solid-phase assays yield different results in terms of interaction strength, we used fibrinogen binding to immobilized alpha IIb beta 3 integrin as a test system. A classical 'three step' enzyme-linked (ELISA), a 'two step' biotin enzyme-linked streptavidin and a 'one step' radioligand assay were compared under otherwise identical conditions. Only the last assay yielded binding constants comparable to earlier data by total internal reflection fluorescence microscopy while the other assays yielded apparent binding constants 5- to 1000-fold too high. These effects are explained by non-linearity of detection signals.
Enzyme-Linked Immunosorbent Assay↗
Outcome assessment for epilepsy surgery: the impact of measuring health-related quality of life.
Epilepsy surgery is an increasingly common treatment for intractable epilepsy; yet there is no clear consensus among experts on how to report epilepsy surgery outcome. Most published outcome reporting systems focus on seizure frequency and type but differ in how they define clinically distinct outcome categories. We used a reliable and valid measure of self-reported health-related quality of life (HRQOL), the Epilepsy Surgery Inventory (ESI)-55, as an external standard by which to evaluate seven previously published, seizure-based outcome classification systems. The ESI-55 was administered to 133 adults who had previously undergone surgery for intractable epilepsy, and results were linked to data on their seizure occurrence before and after surgery (over the year prior to their HRQOL reports). These 133 patients were classified according to each seizure-based outcome system, and variation in HRQOL across outcome groups was evaluated using analysis of variance. Results reveal noteworthy variation in the extent to which different systems reflect patients' HRQOL at follow-up. We modified existing systems to derive a seizure-based surgery outcome system that most closely reflects HRQOL when applied over the latest 1-year postoperative interval.
Adolescent↗
Transesterification reactions of parabens (alkyl 4-hydroxybenzoates) with polyols in aqueous solution.
Accelerated stability tests of aqueous solutions containing parabens and polyols were performed using concentrations similar to pharmaceutical and cosmetic formulations. Reaction products were detected in these solutions by HPLC and identified by chromatographic and spectroscopic means. Using xylitol and methylparaben as model reactants, three unknown peaks having the relation 1:2:4 were obtained together with the hydrolysis product 4-hydroxybenzoic acid. Diode array detection gave identical UV spectra for each peak with a maximum at 255 nm. The structures of the isomeric 1-, 2-, and 3-xylityl 4-hydroxybenzoic acid esters were proved by means of LC-MS, GC-MS, and NMR and correlated to the peaks in the HPLC chromatograms. The rate of the transesterification was shown to be highest in strongly alkaline medium (ph 10-11), whereas equilibration of the reaction was optimally balanced at pH 8-9. An increase of polyol concentration enhanced the formation of the esters. The reactivity of different substituted parabens was higher in the case of parabens with a short alkyl ester function. Similar reaction profiles were observed with C3-C6 polyols, but no transesterification took place when aldoses were used.
Chromatography, High Pressure Liquid↗
Type VI collagen beaded microfibrils from bovine cornea depolymerize at acidic pH, and depolymerization and polymerization are not influenced by hyaluronan.
Type VI collagen beaded microfibrils were extracted from bovine cornea or pig cartilage by limited collagenase digestion. Depolymerization of the microfibril, without strong denaturing reagents linke guanidinium hydrochloride or urea under mild acidic conditions, led to single tetramers and multiples of two to three. However, hyaluronidase digestion in accordance with a published method (Kielty et al. J. Cell Biol. 118:979-990, 1992) was unsuccessful in depolymerizing type VI collagen microfibrils. Also, repolymerization into microfibrils by incubation with hyaluronan was not observed. We further found no binding of native type VI collagen microfibrils to a hyaluronan-Sepharose column. Although a recombinant fragment comprising alpha 3(VI) domains N9-N2 showed apparent binding to the column, electron microscopy did not give any indication of binding of either type VI collagen or fragment N9-N2 to hyaluronan. The present findings suggest that the role of hyaluronan in polymerization of type VI collagen has been overestimated in previous work.
Animals↗
Temperature dependence of Ca2+ wave properties in cardiomyocytes: implications for the mechanism of autocatalytic Ca2+ release in wave propagation.
Digital imaging microscopy of fluo-3 fluorescence was used to study the velocity and shape of intracellular Ca2+ waves in isolated rat cardiomyocytes as a function of temperature. Decreasing the temperature from 37 to 17 degrees C reduced the longitudinal wave velocity by a factor of 1.8 and remarkably slowed the decay of [Ca2+]i in the trailing flank of a wave. Using image analysis, rise times, and half-maximum decay times of local Ca2+ transients, which characterize the processes of local Ca2+ release and removal, were determined as a function of temperature. Apparent activation energies for wave front propagation, local Ca2+ release, and local Ca2+ removal were derived from Arrhenius plots and amounted to -23, -28, and -46 kJ/mol, respectively. The high activation energy of Ca2+ removal, which arises from the activity of the sarcoplasmic reticulum (SR) Ca2+ ATPase, relative to those of longitudinal wave propagation and local Ca2+ release excludes the hypothetical mechanism of regenerative "spontaneous Ca2+ release," in which Ca2+ that has been taken up from the approaching wavefront triggers Ca2+ release at a luminal site of the SR. It is consistent, however, with the hypothesis that Ca2+ wave propagation is based on Ca(2+)-induced Ca2+ release where Ca2+ triggers release on the cytosolic face of the SR.
Aniline Compounds↗
Tennis: dynamics of racket-grip interaction.
Explore the source record for details and available documents.
Equipment Design↗