Audio-visual integration through the parallel visual pathways.

Audio-visual integration has been shown to be present in a wide range of different conditions, some of which are processed through the dorsal, and others through the ventral visual pathway. Whereas neuroimaging studies have revealed integration-related activity in the brain, there has been no imaging study of the possible role of segregated visual streams in audio-visual integration. We set out to determine how the different visual pathways participate in this communication. We investigated how audio-visual integration can be supported through the dorsal and ventral visual pathways during the double flash illusion. Low-contrast and chromatic isoluminant stimuli were used to drive preferably the dorsal and ventral pathways, respectively. In order to identify the anatomical substrates of the audio-visual interaction in the two conditions, the psychophysical results were correlated with the white matter integrity as measured by diffusion tensor imaging.The psychophysiological data revealed a robust double flash illusion in both conditions. A correlation between the psychophysical results and local fractional anisotropy was found in the occipito-parietal white matter in the low-contrast condition, while a similar correlation was found in the infero-temporal white matter in the chromatic isoluminant condition. Our results indicate that both of the parallel visual pathways may play a role in the audio-visual interaction.

A new insight into the zinc-dependent DNA-cleavage by the colicin E7 nuclease: a crystallographic and computational study.

The nuclease domain of colicin E7 metallonuclease (NColE7) contains its active centre at the C-terminus. The mutant ΔN4-NColE7-C* - where the four N-terminal residues including the positively charged K446, R447 and K449 are replaced with eight residues from the GST tag - is catalytically inactive. The crystal structure of this mutant demonstrates that its overall fold is very similar to that of the native NColE7 structure. This implicates the stabilizing effect of the remaining N-terminal sequence on the structure of the C-terminal catalytic site and the essential role of the deleted residues in the mechanism of the catalyzed reaction. Complementary QM/MM calculations on the protein-DNA complexes support the less favourable cleavage by the mutant protein than by NColE7. Furthermore, a water molecule as a possible ligand for the Zn(2+)-ion is proposed to play a role in the catalytic process. These results suggest that the mechanism of the Zn(2+)-containing HNH nucleases needs to be further studied and discussed.

Cortical and subcortical atrophy in Alzheimer disease: parallel atrophy of thalamus and hippocampus.

Brain atrophy is a key imaging hallmark of Alzheimer disease (AD). In this study, we carried out an integrative evaluation of AD-related atrophy. Twelve patients with AD and 13 healthy controls were enrolled. We conducted a cross-sectional analysis of total brain tissue volumes with SIENAX. Localized gray matter atrophy was identified with optimized voxel-wise morphometry (FSL-VBM), and subcortical atrophy was evaluated by active shape model implemented in FMRIB's Integrated Registration Segmentation Toolkit. SIENAX analysis demonstrated total brain atrophy in AD patients; voxel-based morphometry analysis showed atrophy in the bilateral mediotemporal regions and in the posterior brain regions. In addition, regarding the diminished volumes of thalami and hippocampi in AD patients, subsequent vertex analysis of the segmented structures indicated shrinkage of the bilateral anterior thalami and the left medial hippocampus. Interestingly, the volume of the thalami and hippocampi were highly correlated with the volume of the thalami and amygdalae on both sides in AD patients, but not in healthy controls. This complex structural information proved useful in the detailed interpretation of AD-related neurodegenerative process, as the multilevel approach showed both global and local atrophy on cortical and subcortical levels. Most importantly, our results raise the possibility that subcortical structure atrophy is not independent in AD patients.

Comparison of dialysis and clinical characteristics of patients with frequent and occasional hemodialysis-associated hypotension.

BACKGROUND: Symptomatic dialysis hypotension (DH) continues to be a common problem. By comparing patients prone and resistant to DH, several dialysis session and patient related characteristics have been identified that confer susceptibility to DH. Less is known, however, about the comparison of patients with frequent and only occasional DH. The aim of the study was to compare clinical and dialysis-session- (complicated by hypotension) related data between those with frequent (fDH) and those with occasional dialysis hypotension (oDH). METHODS: Nine hundred and fifty-eight patients at 11 dialysis units were followed for 10 months and characteristics of patients with fDH (> or = 10 hypotensive events necessitating medical intervention) (n = 96) were compared to that of patients with oDH (1 or 2 events/10 months) (n = 130). Significant and independent predictors of fDH were obtained by multivariate logistic regression. RESULTS: Significant differences between fDH vs. oDH patients were older age (64.4 vs. 56.9 years, p < 0.001), more females (66 vs. 46%, p < 0.005) in fDH. More fDH patients had diabetes (27 vs. 15%, p < 0.05) and less had glomerulonephritis (15 vs. 35%, p < 0.001) as the cause for ESRD. Coronary artery disease (68 vs. 50%, p < 0.01) and long-acting nitrate treatment (51 vs. 30%, p < 0.001) was more frequent while treatment with ACEI (33 vs. 48%, p < 0.05) or Ca-channel blockers (40 vs. 53%, p < 0.05) were less frequent in patients with fDH. Patients with fDH had higher serum phosphorus levels (1.99 vs. 1.79 mmol, p < 0.005). Dialysis session related data were similar but the hypotensive episode occurred earlier during dialysis in fDH (136 vs. 156 min, p < 0.01). In multivariate analysis, significant independent predictors of fDH were older age (OR = 1.04 [1.02-1.07]), lack of glomerulonephritis as renal diagnosis (2.63 [1.18-5.87]), high phosphorus levels (5.0 [2.45-10.0]), lack of use of Ca-channel blockers (2.09 [1.12-3.91]), and the use of nitrates (2.38 [1.24-4.55]). CONCLUSION: Features of the dialysis sessions complicated by DH seem to be similar between patients with fDH and oDH, while patient characteristics such as older age, renal diagnosis other than glomerulonephritis, higher serum phosphorus levels, use of nitrates, and lack of use of calcium channel blockers are significantly and independently associated with fDH.