Development of an animal model for neuroleptic malignant syndrome: heat-exposed rabbits with haloperidol and atropine administration exhibit increased muscle activity, hyperthermia, and high serum creatine phosphokinase level

The neuroleptic malignant syndrome (NMS) is a life-threatening complication of neuroleptic treatment. To elucidate the pathogenesis of NMS, an animal model has been developed. Experimental rabbits treated with haloperidol (1 mg/kg) by intramuscular injection, were studied for the diagnostic symptoms of increased muscle rigidity, elevated body temperature, and high serum creatine phosphokinase (CPK) level. Administration of haloperiodol (1 mg/kg) and atropine (0.4 mg/kg), and exposure to high ambient temperature (35 degrees C) induced a significant increase in electromyographic activity with muscle rigidity similar to that observed in patients with NMS. Such rabbits also showed elevated body temperature and serum CPK value. In addition to the similarity of the signs and symptoms, all parameters measured (muscle rigidity, body temperature, and serum CPK level) were normalized by dantrolene treatment. The effectiveness of dantrolene in the experimental animal partially confirms the validity of this animal model for NMS. This experimental animal model for NMS may be useful to elucidate the pathogenesis of NMS.     

Cooperative 3D tunnel measurement based on 2D–3D registration of omnidirectional laser light

In this study, we proposed a high-density three-dimensional (3D) tunnel measurement method, which estimates the pose changes of cameras based on a point set registration algorithm regarding 2D and 3D point clouds. To detect small deformations and defects, high-density 3D measurements are necessary for tunnel construction sites. The line-structured light method uses an omnidirectional laser to measure a high-density cross-section point cloud from camera images. To estimate the pose changes of cameras in tunnels, which have few textures and distinctive shapes, cooperative robots are useful because they estimate the pose by aggregating relative poses from the other robots. However, previous studies mounted several sensors for both the 3D measurement and pose estimation, increasing the size of the measurement system. Furthermore, the lack of 3D features makes it difficult to match point clouds obtained from different robots. The proposed measurement system consists of a cross-section measurement unit and a pose estimation unit; one camera was mounted for each unit. To estimate the relative poses of the two cameras, we designed a 2D–3D registration algorithm for the omnidirectional laser light, and implemented hand-truck and unmanned aerial vehicle systems. In the measurement of a tunnel with a width of 8.8 m and a height of 6.4 m, the error of the point cloud measured by the proposed method was 162.8 and 575.3 mm along 27 m, respectively. In a hallway measurement, the proposed method generated less errors in straight line shapes with few distinctive shapes compared with that of the 3D point set registration algorithm with Light Detection and Ranging.     

Postdetection phase combining diversity for reception of faded DPSK signals

A new postdetection diversity scheme for the differential phase detection of faded DPSK signals is proposed. It combines the detector outputs in proportion to the squared value of each branch signal envelope. The average BER of pi /4-shift quaternary differential phase shift keying (QDPSK) with two-branch diversity is obtained through computer simulations assuming Rayleigh fading. It is found that the proposed diversity is superior to selection diversity by approximately 1.5 dB.<>     

Spectroscopic characterization of a high-affinity calmodulin-target peptide hybrid molecule

We describe the properties of a hybrid protein comprising the full length of the Xenopus laevis calmodulin sequence, followed by a pentapeptide linker (GGGGS), and residues 3-26 of M13, the calmodulin binding region of skeletal muscle myosin light chain kinase. The properties of the hybrid protein are compared with those of the complex formed between Drosophila calmodulin and a peptide corresponding to residues 1-18 of the M13 sequence. The addition of calcium to the hybrid protein produces pronounced changes in the near- and far-UV CD spectra, in the fluorescence emission spectrum of the single tryptophan residue at position 4 in the M13 sequence, and in the accessibility of this tryptophan residue to acrylamide quenching. These changes are consistent with the tryptophan residue being immobilized in a hydrophobic environment and with the hybrid protein adopting a more alpha-helical structure when calcium is bound. The increased alpha-helicity derives from changes in both the calmodulin and peptide regions of the hybrid protein. Changes in the circular dichroism and fluorescence properties of the hybrid protein as a function of the calcium to hybrid protein ratio are consistent with the fact that these changes parallel the cooperative binding of all four calcium ions. The hybrid protein shows greatly increased affinity (>250-fold) for calcium compared with calmodulin itself. Macroscopic calcium binding constants (K(1)-K(4)) were determined from calcium titrations performed in the presence of the calcium chelator Quin 2. Values for log(K(1)K(2)) and log(K(3)K(4)) were determined to be 15.4 +/- 0.2 and 15.59 +/- 0.22 (20 degrees C). The corresponding values for Drosophila calmodulin alone are 11.65 +/- 0.15 and 9.66 +/- 0.25. Consistent with this increased affinity for calcium stopped-flow kinetic studies suggest that the dissociation rate for the N-terminal calcium ions is reduced to at least 0.77 s(-1), compared with approximately 700 s(-1) for Drosophila calmodulin in the absence of peptide. This hybrid protein illustrates the principle whereby the binding of a peptide sequence covalently attached to calmodulin can enhance the average calcium affinity by more than 2 orders of magnitude. Conversely, the target sequence in the hybrid protein undergoes a calcium-induced conformational change to bind to the calmodulin in a conformation very similar to that of the corresponding dissociable target sequence binding to calmodulin, but with a greatly enhanced affinity due to its physical proximity to the binding site. This avoidance of the energetic penalty of dissociation may be a key contributory factor in determining the high affinity and specificity of the complex multiple interactions involved in recognition of biological targets by calmodulin.     

Structural basis of calcium-induced E-cadherin rigidification and dimerization

The cadherins mediate cell adhesion and play a fundamental role in normal development. They participate in the maintenance of proper cell-cell contacts: for example, reduced levels of epithelial cadherin (E-cadherin) correlate with increased invasiveness in many human tumour cell types. The cadherins typically consist of five tandemly repeated extracellular domains, a single membrane-spanning segment and a cytoplasmic region. The N-terminal extracellular domains mediate cell-cell contact while the cytoplasmic region interacts with the cytoskeleton through the catenins. Cadherins depend on calcium for their function: removal of calcium abolishes adhesive activity, renders cadherins vulnerable to proteases (reviewed in ref. 4) and, in E-cadherin, induces a dramatic reversible conformational change in the entire extracellular region. We report here the X-ray crystal structure at 2.0 A resolution of the two N-terminal extracellular domains of E-cadherin in the presence of calcium. The structure reveals a two-fold symmetric dimer, each molecule of which binds a contiguous array of three bridged calcium ions. Not only do the bound calcium ions linearize and rigidify the molecule, they promote dimerization. Although the N-terminal domain of each molecule in the dimer is aligned in a parallel orientation, the interactions between them differ significantly from those found in the neural cadherin (N-cadherin) N-terminal domain (NCD1) structure. The E-cadherin dual-domain structure reported here defines the role played by calcium in the cadherin-mediated formation and maintenance of solid tissues.     

Unusual helix-containing greek keys in development-specific Ca(2+)-binding protein S. 1H, 15N, and 13C assignments and secondary structure determined with the use of multidimensional double and triple resonance heteronuclear NMR spectroscopy

Multidimensional heteronuclear NMR spectroscopy has been used to determine almost complete backbone and side-chain 1H, 15N, and 13C resonance assignments of calcium loaded Myxococcus xanthus protein S (173 residues). Of the range of constant-time triple resonance experiments recorded, HNCACB and CBCA(CO)NH, which correlate C alpha and C beta with backbone amide resonances of the same and the succeeding residue respectively, proved particularly useful in resolving assignment ambiguities created by the 4-fold internal homology of the protein S amino acid sequence. Extensive side-chain 1H and 13C assignments have been obtained by analysis of HCCH-TOCSY and 15N-edited TOCSY-HMQC spectra. A combination of NOE, backbone amide proton exchange, 3JNH alpha coupling constant, and chemical shift data has been used to show that each of the protein S repeat units consists of four beta-strands in a Greek key arrangement. Two of the Greek keys contain a regular alpha-helix between the third and fourth strands, resulting in an unusual and possibly unique variation on this common folding motif. Despite similarity between two nine-residue stretches in the first and third domains of protein S and one of the Ca(2+)-binding sequences in bovine brain calmodulin [Inouye, S., Franceschini, T., & Inouye, M. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 6829-6833], the protein S topology in these regions is incompatible with an EF-hand calmodulin-type Ca(2+)-binding site.