Image registration in myocardial perfusion MRI

In clinical first-pass myocardial perfusion studies, physiological and patient motions are inevitable. Such motions impair the sensitivity and reliability in assessing myocardial perfusion abnormalities. The current study aims to correct the misregistration of myocardium during first-pass perfusion imaging by using a normalized mutual information approach. Multi-slice registrations were performed in 15 sets of clinical data sets. The proposed registration procedure was found to be fairly robust. With such registration, ROI time courses from normal myocardium and infarcted myocardium were improved, offering potential to quantify myocardial perfusion parameters in a more reliable manner.

catena-Poly[[[cis-aquabis(4-carboxycyclohexane-1-carboxylato-kappa2O,O')cadmium(II)]-mu-4,4'-bipyridine-kappa2N:N] monohydrate]

The title complex, {[Cd(C8H11O4)2(C10H8N2)(H2O)].H2O}(n), consists of linear chains formed through 4,4'-bipyridine ligands linking seven-coordinated Cd(II) ions. Each Cd(II) ion is in a distorted pentagonal-bipyramidal environment, coordinated by one water ligand, two 4-carboxycyclohexane-1-carboxylate ligands and one bridging 4,4'-bipyridine ligand to generate linear chains. The water molecules and the Cd atom on one side, and the 4,4'-bipyridine unit on the other, are bisected by two sets of twofold axes. The carboxylate group of the 4-carboxycyclohexane-1-carboxyl ligand chelates a Cd(II) ion, while the (protonated) carboxyl group forms hydrogen bonds with adjacent chains, resulting in a layered structure. This is the first reported occurrence of a dicarboxycyclohexane ligand exhibiting a non-bridging coordination mode.

The use of comparative genomic hybridization to characterize genome dynamics and diversity among the serotypes of Shigella

Background

Compelling evidence indicates that Shigella species, the etiologic agents of bacillary dysentery, as well as enteroinvasive Escherichia coli, are derived from multiple origins of Escherichia coli and form a single pathovar. To further understand the genome diversity and virulence evolution of Shigella, comparative genomic hybridization microarray analysis was employed to compare the gene content of E. coli K-12 with those of 43 Shigella strains from all lineages.

Results

For the 43 strains subjected to CGH microarray analyses, the common backbone of the Shigella genome was estimated to contain more than 1,900 open reading frames (ORFs), with a mean number of 726 undetectable ORFs. The mosaic distribution of absent regions indicated that insertions and/or deletions have led to the highly diversified genomes of pathogenic strains.

Conclusion

These results support the hypothesis that by gain and loss of functions, Shigella species became successful human pathogens through convergent evolution from diverse genomic backgrounds. Moreover, we also found many specific differences between different lineages, providing a window into understanding bacterial speciation and taxonomic relationships.

BCL2 family in DNA damage and cell cycle control

Individual BCL2 family members couple apoptosis regulation and cell cycle control in unique ways. Antiapoptotic BCL2 and BCL-x(L) are antiproliferative by facilitating G0. BAX is proapoptotic and accelerates S-phase progression. The dual functions in apoptosis and cell cycle are coordinately regulated by the multi-domain BCL2 family members (MCL-1) and suggest that survival is maintained at the expense of proliferation. The role of BH3-only molecules in cell cycle is more variable. BAD antagonizes both the cell cycle and antiapoptotic functions of BCL2 and BCL-x(L) through BH3 binding. BID has biochemically separable functions in apoptosis and S-phase checkpoint, determined by post-translational modification. p53-induced PUMA is known only to have apoptotic function. Inhibition of apoptosis is oncogenic, whereas promotion of cell cycle arrest is tumor suppressive. Paradoxically, selected BCL2 family members can be both oncogenic and tumor suppressive. Which of the dual functions predominates is lineage specific and context dependent.

Genomic compositions and phylogenetic analysis of Shigella boydii subgroup

Comparative Genomic Hybridization (CGH) microarray analysis was used to compare the genomic compositions of all eighteen Shigella boydii serotype representative strains. The results indicated the genomic "backbone" of this subgroup contained 2552 ORFs homologous to nonpathogenic E. coli K12. Compared with the genome of K12199 ORFs were found to be absent in all S. boydii serotype representatives, including mainly outer membrane protein genes and O-antigen biosynthesis genes. Yet the specific ORFs of S. boydii subgroup contained basically bacteriophage genes and the function unknown (FUN) genes. Some iron metabolism, transport and type II secretion system related genes were found in most representative strains. According to the CGH phylogenetic analysis, the eighteen S. boydii serotype representatives were divided into four groups, in which serotype C13 strain was remarkably distinguished from the other serotype strains. This grouping result corresponded to the distribution of some metabolism related genes. Furthermore, the analysis of genome backbone genes, specific genes, and the phylogenetic trees allowed us to discover the evolution laws of S. boydii and to find out important clues to pathogenesis research, vaccination and the therapeutic medicine development.

Interweaving 3D Network with Double Helical Tubes Filled by 1D Coordination Polymer Chains

The hydrothermal reaction of mellitic acid, 4,4'-bipydine, and Cu(CH(3)COO)(2).H(2)O gave rise to a novel 3D supramolecular architecture interpenetrated by three types of coordination polymer motifs. Two independent [[Cu(2)(mellitate)(4,4'-bpy)(H(2)O)(2)](2)(-)] 3D polymers incorporating helical substructures were interwoven into a 3D network with double-stranded helical tubes that host 1D linear polymers [Cu(4,4'-bpy)(H(2)O)(4)](2+)](n).

Bis(μ-ethyl pyridine-2,6-dicarboxylato)bis[diaquachlorocadmium(II)] dihydrate

The reaction of cadmium chloride with pyridine-2,6-dicarboxylic acid (PDA) and 98% H2SO4 in ethanol led to the formation of the title compound, bis[mu-6-(ethoxycarbonyl)pyridine-2-carboxylato]-1:2kappa4O6,N,O2:O2;1:2kappa4O2:O2,N,O6-bis[diaquachlorocadmium(II)] dihydrate, [Cd2(C9H8NO4)2Cl2(H2O)4].2H2O. PDA is esterified to monoethyl pyridine-2,6-dicarboxylate (MEPD) by the catalysis of H2SO4 during the reaction. The dinuclear Cd(II) complex lies about an inversion centre and the unique Cd atom has a pentagonal-bipyramidal geometry. The two Cd atoms are bridged by two carboxylate O atoms, forming a planar Cd2O2 unit. Stair-like chains are formed via O-H.Cl hydrogen bonds and these are further arranged into two-dimensional layers via hydrogen bonds involving solvate water molecules.

Poly[[diaquatris(mu6-benzene-1,2,4,5-tetracarboxylato)tris(mu2-4,4'-bipyridine)hexacopper(II)] dihydrate]

The hydrothermal reaction of an aqueous solution of Cu(CH(3)COO)(2).H(2)O, 1,2,4,5-benzenetetracarboxylic acid and 4,4'-bipyridine gave rise to the interesting title three-dimensional polymer [[Cu(6)(btec)(3)(4,4'-bpy)(3)(H(2)O)(2)].2H(2)O](n) (btec is 1,2,4,5-benzenetetracarboxylate, C(10)H(2)O(8)(4-), and 4,4'-bpy is 4,4'-bipyridine, C(10)H(8)N(2)), in which each btec ligand links six copper(II) cations into a lamellar [Cu(6)(btec)(3)(H(2)O)(2)](n) subpolymer framework. There are two distinct diamine units and two distinct carboxylate units, with one of each lying across an inversion centre.

Overexpression of LIM kinase 1 renders resistance to apoptosis in PC12 cells by inhibition of caspase activation

LIM kinases (LIMKs) regulate actin polymerization by phosphorylating cofilin and are predominantly expressed in neural tissue. In this study, the effect of LIMK1 overexpression in PC12 cell apoptosis was investigated. PC12 cells overexpressing the wild-type LIMK1 were more resistant to serum-withdrawal-induced cell death and the level of caspase 3 activation in these cells was lower than in the control PC12 cells or than in the PC12 cells expressing a mutant LIMK1 lacking the kinase domain. The inhibition of JNK activation was observed in the PC12 cells overexpressing the wild-type LIMK1 after serum withdrawal. These results suggest that the LIMK1 might allow resistance to apoptosis in PC12 cells by inhibiting JNK activation.

Temporal lobe encephalocoele presenting with seizures and hearing loss

A case of a bilateral temporal lobe encephalocoele that presented as seizures and hearing loss for many years. Diagnosis was confirmed on CT and MR imaging, which showed deficiencies in the temporal bone. The patient subsequently underwent surgical repair and recovered from his presenting symptoms.

BAD/BCL-[X(L)] heterodimerization leads to bypass of G0/G1 arrest

The pro-apoptotic molecule BAD binds BCL-[X(L)] or BCL2 and inactivates their survival function. In addition to their anti-apoptotic function, BCL2 and BCL-[X(L)] also delay cell cycle entry from quiescence. We found that the BH3-only molecule BAD also exerted a cell cycle effect. BAD expression resulted in failure to cell cycle block in growth arrest conditions. In low serum and in confluence, fibroblasts constitutively or inducibly expressing BAD persisted in S phase, continued to incorporate BrdU, and exhibited sustained cyclin E/cdk2 activity. Mutation analysis indicated that the cell cycle effect of BAD was not dependent on its phosphorylation status or subcellular localization, but strictly co-segregated with BCL-[X(L)] binding. bclx(-/-) MEFs expressing BAD and bad(-/-) MEFs both arrested in G0/G1 in low serum similar to wild-type controls, suggesting that the ability to overcome the G0/G1 checkpoint resulted from the presence of BAD/BCL-x(L) heterodimers, rather than the absence of BCL-[X(L)] or BAD. These data provide evidence that in addition to regulating apoptosis, the BAD/BCL-[X(L)] heterodimer has a novel cell cycle function.

Cloning of an immunoglobulin family adhesion molecule selectively expressed by endothelial cells

To gain fundamental information regarding the molecular basis of endothelial cell adhesive interactions during vascular formation, we have cloned and characterized a unique cell adhesion molecule. This molecule, named endothelial cell-selective adhesion molecule (ESAM), is a new member of the immunoglobulin superfamily. The conceptual protein encoded by cDNA clones consists of V-type and C2-type immunoglobulin domains as well as a hydrophobic signal sequence, a single transmembrane region, and a cytoplasmic domain. Northern blot analysis showed ESAM to be selectively expressed in cultured human and murine vascular endothelial cells and revealed high level expression in lung and heart and low level expression in kidney and skin. In situ hybridization analysis indicated that ESAM is primarily expressed in the developing vasculature of the embryo in an endothelial cell-restricted pattern. Epitope-tagged ESAM was shown to co-localize with cadherins and catenins in cell-cell junctions. In aggregation assays employing ESAM-expressing Chinese hamster ovary cells, this novel molecule was shown to mediate cell-cell adhesion through homophilic interactions. The endothelial cell-selective expression of this immunoglobulin-like adhesion molecule coupled with its in vitro functional profile strongly suggests a role in cell-cell interactions that is critical for vascular development or function.

Protein phosphatase 2A activates the proapoptotic function of BAD in interleukin- 3-dependent lymphoid cells by a mechanism requiring 14-3-3 dissociation

BAD is a proapoptotic member of the BCL-2 family of proteins, which play a major role in regulating apoptosis in cytokine-dependent hematopoietic cells. The function of BAD is regulated by reversible phosphorylation. Deprivation of survival factors induces BAD dephosphorylation, resulting in apoptosis. Serine-threonine phosphatase activity dephosphorylated BAD in interleukin-3-dependent FL5.12 lymphoid cells. Inhibition of PP2A activity by treatment of cells with PP2A-selective inhibitors, okadaic acid and fostriecin, prevented BAD dephosphorylation in these cells. Conversely, BAD dephosphorylation was not inhibited by the PP1-selective inhibitor tautomycin. In cell-free extracts, BAD phosphatase activity was also inhibited by the PP2A-selective inhibitors okadaic acid and fostriecin, but not by the PP1-specific protein inhibitor I-2. Dissociation of 14-3-3 from BAD was a prerequisite for BAD dephosphorylation in vitro, suggesting a mechanism by which 14-3-3 can regulate the activation of the proapoptotic function of BAD in vivo. Significantly, the inhibition of BAD phosphatase activity rescued cell death induced by survival factor withdrawal in FL5.12 cells expressing wild-type BAD but not phosphorylation-defective mutant BAD. These data indicate that PP2A, or a PP2A-like enzyme, dephosphorylates BAD and, in conjunction with 14-3-3, modulates cytokine-mediated survival.

Rapid induction of senescence in human cervical carcinoma cells

Expression of the bovine papillomavirus E2 regulatory protein in human cervical carcinoma cell lines repressed expression of the resident human papillomavirus E6 and E7 oncogenes and within a few days caused essentially all of the cells to synchronously display numerous phenotypic markers characteristic of cells undergoing replicative senescence. This process was accompanied by marked but in some cases transient alterations in the expression of cell cycle regulatory proteins and by decreased telomerase activity. We propose that the human papillomavirus E6 and E7 proteins actively prevent senescence from occurring in cervical carcinoma cells, and that once viral oncogene expression is extinguished, the senescence program is rapidly executed. Activation of endogenous senescence pathways in cancer cells may represent an alternative approach to treat human cancers.

Structural determinants of aortic regurgitation in type A dissection and the role of valvular resuspension as determined by intraoperative transesophageal echocardiography

Disruption of the aortic root by dissection often produces significant aortic regurgitation (AR). Resuspension of the native valve usually reestablishes competence. The mechanisms of this complex process are poorly understood. We used intraoperative transesophageal echocardiography to characterize the in vivo aortic root structure of type A aortic dissection and the changes brought about by native valve resuspension. Intraoperative transesophageal echocardiograms were obtained from 34 patients with type A dissection and aortic resuspension between January 1990 and April 1997. The severity of AR, aortic root diameter, circumference of the aortic annulus, percentage of the annulus dissected, and presence of leaflet prolapse were assessed in multiple planes. Preoperatively, AR of varying degree was present in 25 patients (73%). Multivariate analysis revealed that preoperative AR was most related to percentage of the annulus dissected (p<0.0001) and less related to root diameter (p<0.01). Leaflet prolapse was predicted by percent aortic annulus dissected (p <0.0001). After resuspension, annular dissection and leaflet prolapse were no longer present. Postoperative AR was significantly decreased from preoperative AR (p<0.0001) and was considered trace to mild. Although postoperative root diameter and annular circumference decreased (p<0.001), individual reductions in AR did not correlate with individual changes in root diameter or annular circumference. The degree of dissection of the valve annulus is the most significant determinant of leaflet prolapse and AR severity. Overall size of the aortic root also contributes to AR. Surgical resuspension significantly decreases root size, but its primary benefit is restoration of the structural integrity of the aortic annulus.

Effects of antigen dose and immunization regimens on antibody responses to a cytomegalovirus glycoprotein B subunit vaccine

The purpose of this phase I study was to evaluate the safety and immunogenicity of 2 doses of cytomegalovirus glycoprotein B (CMV gB)/MF59 vaccine at 3 different immunization schedules. Ninety-five volunteers were randomized to 6 groups. Antibodies to gB represent the majority of the CMV-specific neutralizing response. Three groups received 5 microgram of gB antigen combined with MF59 (a proprietary adjuvant) and 3 groups received a 30-microgram dose at 0, 1, and 2 months; 0, 1, and 4 months; or 0, 1, and 6 months. The vaccine was well tolerated, and there was no significant difference in antibody production between the 2 doses. The vaccine induced highest antibody titers when given at 0, 1, and 6 months. A low dose of CMV gB/MF59 may be the preferred dose for future studies.

Structural examination of autoregulation of multifunctional calcium/calmodulin-dependent protein kinase II

Regulation of Ca(2+)/calmodulin-dependent protein kinase II is likely based on an auto-inhibitory mechanism in which a segment of the kinase occupies the catalytic site in the absence of calmodulin. We analyze potential auto-inhibitory associations by employing charge reversal and hydrophobic-to-charged residue mutagenesis. We identify interacting amino acid pairs by using double mutants to test which modification in the catalytic domain complements a given change in the auto-inhibitory domain. Our studies identify the core pseudosubstrate sequence (residues 297-300) but reveal that distinct sequences centered about the autophosphorylation site at Thr-286 are involved in the critical auto-inhibitory interactions. Individual changes in any of the residues Arg-274, His-282, Arg-283, Lys-291, Arg-297, Phe-293, and Asn-294 in the auto-inhibitory domain or their interacting partners in the catalytic domain produces an enhanced affinity for calmodulin or generates a constitutively active enzyme. A structural model of Ca(2+)/calmodulin-dependent protein kinase II that incorporates these interactions shows that Thr-286 is oriented inwardly into a hydrophobic channel. The model explains why calmodulin must bind to the auto-inhibitory domain in order for Thr-286 in that domain to be phosphorylated and why introduction of phospho-Thr-286 produces the important Ca(2+)-independent state of the enzyme.

The linker domain of Stat1 is required for gamma interferon-driven transcription

Upon binding of gamma interferon (IFN-gamma) to its receptor, the latent transcription factor Stat1 becomes phosphorylated, dimerizes, and enters the nucleus to activate transcription. In response to IFN-alpha, Stat1 binds to Stat2 in a heterodimer that recruits p48, an IRF family member, to activate transcription. A number of functional domains of the STATs, including a C-terminal transactivation domain, a dimerization domain, and an SH2 domain, are known. However, the highly conserved residues between the DNA binding and SH2 domains (463 to 566), recently christened the linker domain on the basis of crystallographic studies, have remained without a known function. In the present study, we report that KE544-545AA point mutants in Stat1 abolish transcriptional responses to IFN-gamma but not to IFN-alpha. We further show that this mutant Stat1 undergoes normal phosphorylation, nuclear translocation, and DNA binding. Taken together with recent structural evidence, these results suggest that the linker domain acts as a critical contact point during the construction of a Stat1-driven transcriptional complex.