Multiple indices of diffusion identifies white matter damage in mild cognitive impairment and Alzheimer's disease

The study of multiple indices of diffusion, including axial (DA), radial (DR) and mean diffusion (MD), as well as fractional anisotropy (FA), enables WM damage in Alzheimer's disease (AD) to be assessed in detail. Here, tract-based spatial statistics (TBSS) were performed on scans of 40 healthy elders, 19 non-amnestic MCI (MCIna) subjects, 14 amnestic MCI (MCIa) subjects and 9 AD patients. Significantly higher DA was found in MCIna subjects compared to healthy elders in the right posterior cingulum/precuneus. Significantly higher DA was also found in MCIa subjects compared to healthy elders in the left prefrontal cortex, particularly in the forceps minor and uncinate fasciculus. In the MCIa versus MCIna comparison, significantly higher DA was found in large areas of the left prefrontal cortex. For AD patients, the overlap of FA and DR changes and the overlap of FA and MD changes were seen in temporal, parietal and frontal lobes, as well as the corpus callosum and fornix. Analysis of differences between the AD versus MCIna, and AD versus MCIa contrasts, highlighted regions that are increasingly compromised in more severe disease stages. Microstructural damage independent of gross tissue loss was widespread in later disease stages. Our findings suggest a scheme where WM damage begins in the core memory network of the temporal lobe, cingulum and prefrontal regions, and spreads beyond these regions in later stages. DA and MD indices were most sensitive at detecting early changes in MCIa

Glial activation in white matter following ischemia in the neonatal P7 rat brain

This study examines cell death and proliferation in the white matter after neonatal stroke. In post-natal day 7 injured rat, there was a marked reduction in myelin basic protein (MBP) immunostaining mainly corresponding to numerous pyknotic immature oligodendrocytes and TUNEL-positive astrocytes in the ipsilateral external capsule. In contrast, a substantial restoration of MBP, as indicated by the MBP ratio of left-toright, occurred in the cingulum at 48 (1.27 +- 0.12) and 72 (1.30 +- 0.18, p<0.05) hours of recovery as compared to age-matched controls (1.03 +- 0.14). Ki-67 immunostaining revealed a first peak of newly-generated cells in the dorsolateral hippocampal subventricular zone and cingulum at 72 hours after reperfusion. Double immunofluorescence revealed that most of the Ki-67-positive cells were astrocytes at 48 hours and NG2 pre-oligodendrocytes at 72 hours of recovery. Microglia infiltration occurs over several days in the cingulum and a huge quantity of macrophages reached the subcortical white matter where they engulfed immature oligodendrocytes. The overall results suggest that the persistent activation of microglia involves a chronic component of immunoinflammation, which overwhelms repair processes and contributes to cystic growth in the developing brain.Comment: 30 page

Cerebral differences in explicit and implicit emotional processing - An fMRI study

The processing of emotional facial expression is a major part of social communication and understanding. In addition to explicit processing, facial expressions are also processed rapidly and automatically in the absence of explicit awareness. We investigated 12 healthy subjects by presenting them with an implicit and explicit emotional paradigm. The subjects reacted significantly faster in implicit than in explicit trials but did not differ in their error ratio. For the implicit condition increased signals were observed in particular in the thalami, the hippocampi, the frontal inferior gyri and the right middle temporal region. The analysis of the explicit condition showed increased blood-oxygen-level-dependent signals especially in the caudate nucleus, the cingulum and the right prefrontal cortex. The direct comparison of these 2 different processes revealed increased activity for explicit trials in the inferior, superior and middle frontal gyri, the middle cingulum and left parietal regions. Additional signal increases were detected in occipital regions, the cerebellum, and the right angular and lingual gyrus. Our data partially confirm the hypothesis of different neural substrates for the processing of implicit and explicit emotional stimuli. Copyright (c) 2007 S. Karger AG, Basel

Talon cusp affecting primary dentition in two siblings: a case report

The term talon cusp refers to a rare developmental dental anomaly characterized by a cusp-like structure projecting from the cingulum area or cement-enamel junction. This condition can occur in the maxillary and mandibular arches of the primary and permanent dentitions. The purpose of this paper is to report on the presence of talon cusps in the primary dentition of two southern Chinese siblings. The 4 years and 2 months old girl had a talon cusp on her maxillary right primary central incisor, while her 2 years and 9 months old brother had bilateral talon cusps on the maxillary primary central incisors. The presence of this rare dental anomaly in two siblings has scarcely been reported in the literature and this may provide further evidence of a hereditary etiology.Article Link: http://www.rjme.ro/RJME/resources/files/540113211213.pd

Distinct subdivisions of the cingulum bundle revealed by diffusion MRI fibre tracking: Implications for neuropsychological investigations

The cingulum is a prominent white matter tract that supports prefrontal, parietal, and temporal lobe interactions. Despite being composed of both short and long association fibres, many MRI-based reconstructions ( tractography ) of the cingulum depict an essentially uniform tract that almost encircles the corpus callosum. The present study tested the validity of dividing this tract into subdivisions corresponding to the ‘parahippocampal’, ‘retrosplenial’, and ‘subgenual’ portions of the cingulum. These three cingulum subdivisions occupied different medial–lateral locations, producing a topographic arrangement of cingulum fibres. Other comparisons based on these different reconstructions indicate that only a small proportion of the total white matter in the cingulum traverses the length of the tract. In addition, both the radial diffusivity and fractional anisotropy of the subgenual subdivision differed from that of the retrosplenial subdivision which, in turn, differed from that of the parahippocampal subdivision. The extent to which the radial diffusivity scores and the fractional anisotropy scores correlated between the various cingulum subdivisions proved variable, illustrating how one subdivision may not act as a proxy for other cingulum subdivisions. Attempts to relate the status of the cingulum, as measured by MRI-based fibre tracking, with cognitive or affective measures will, therefore, depend greatly on how and where the cingulum is reconstructed. The present study provides a new framework for subdividing the cingulum, based both on its known connectivity and MRI-based properties

Bysmatrum granulosum sp. nov., a new benthic dinoflagellate from the southwestern Indian Ocean

A new benthic marine dino¯agellate, Bysmatrum granulosum Ten-Hage, Turquet, Quod & Couté, sp. nov., was obtained from sediment and coral samples from sites of La Réunion Island (SW Indian Ocean). This new species is described and illustrated by light and scanning electron micrographs. Cells are 40-50 µm long and 40-46 µm wide. The epitheca is conical and smaller than the hypotheca, which is trapezoidal with convex sides. Plate tabulation is typical for the genus (Pₒ, X, 4', 3a, 7'', 6c, 5s, 5''', 2''''); epithecal plates 3’ and 4’’ separate the intercalary plates 2a and 3a. Thecal plates are perforated by pores and covered by both small and minute wart-like projections, linearly arranged, radiating from the apical pore. This new species differs from the three others of the genus Bysmatrum in the following characters: cell shape and size, size of the apical pore complex and features of thecal plates (plate shapes and ornamentations

Uppermost Pleistocene shrews (Mammalia, Soricidae) from Vaskapu Cave (N-Hungary)

Three shrew species (Sorex araneus LINNAEUS1758, Sorex minutus LlNNAEUS1766 and Sorex alpinus SHINZ1837) were found in the fossiliferous sediments of Vaskapu Cave, near Felsötárkány. The probable stratigraphical position of the sample is Upper Pleistocene, Pilisszántó Horizon (Upper Würm), about 15,000 years B.P. A cold period of the Late Pleistocene with wooded environment is indicated by the soricid assemblage