Influence of mild cognitive impairment and body mass index on white matter integrity assessed by diffusion tensor imaging.

Mild cognitive impairment (MCI), a prodromal stage of Alzheimer's disease, is characterized by decreased memory and cognition, which are linked to degenerative changes in the brain. To assess whether white matter (WM) integrity is compromised in MCI, we collected diffusion-weighted images from 60 healthy older adults (OA) (69.16 ± 0.7) and 20 older adults with amnestic MCI (72.45 ± 1.9). WM integrity differences were examined using Tract-Based Spatial Statistics (TBSS). We hypothesized that those with MCI would have diminished WM integrity relative to OA. In a whole-brain comparison, those with MCI showed higher axial diffusivity in the splenium (SCC) and body of the corpus callosum (BCC), superior corona radiata (SCR), and the retrolenticular part of the internal capsule (RLIC) (p's < .05 TFCE-corrected). Additionally, significant between-group connectivity differences were observed using probabilistic tractography between the SCC, chosen from the TBSS results, and forceps major and minor (p-value's < .05). To further relate a physical health indicator to WM alterations, linear regression showed significant interactions between cognitive status and body mass index (BMI) on diffusivity outcome measures from probabilistic tractography (p-value-'s < .05). Additionally, we examined the association between relational memory, BMI, and WM integrity. WM integrity was positively associated with relational memory performance. These findings suggest that these regions may be more sensitive to early markers of neurodegenerative disease and health behaviors, suggesting that modifiable lifestyle factors may affect white matter integrity.

Hippocampal subfield viscoelasticity in amnestic mild cognitive impairment evaluated with MR elastography.

Hippocampal subfields (HCsf) are brain regions important for memory function that are vulnerable to decline with amnestic mild cognitive impairment (aMCI), which is often a preclinical stage of Alzheimer's disease. Studies in aMCI patients often assess HCsf tissue integrity using measures of volume, which has little specificity to microstructure and pathology. We use magnetic resonance elastography (MRE) to examine the viscoelastic mechanical properties of HCsf tissue, which is related to structural integrity, and sensitively detect differences in older adults with aMCI compared to an age-matched control group. Group comparisons revealed HCsf viscoelasticity is differentially affected in aMCI, with CA1-CA2 and DG-CA3 exhibiting lower stiffness and CA1-CA2 exhibiting higher damping ratio, both indicating poorer tissue integrity in aMCI. Including HCsf stiffness in a logistic regression improves classification of aMCI beyond measures of volume alone. Additionally, lower DG-CA3 stiffness predicted aMCI status regardless of DG-CA3 volume. These findings showcase the benefit of using MRE in detecting subtle pathological tissue changes in individuals with aMCI via the HCsf particularly affected in the disease.

The role of adherent cells in the immunosuppressed state of mouse progeny transplacentally exposed to benzo(alpha)pyrene.

In recent studies, we showed that murine fetal liver cells from progeny exposed to benzo(alpha)pyrene in utero by intraperitoneal injection of the dam at midpregnancy (12 d) suppressed cell proliferation in an allogeneic mixed lymphocyte response. On the other hand, fetal liver cells from the corn oil (vehicle for the carcinogen)-exposed progeny (control) appeared to enhance proliferation. Suppression or enhancement appeared to be mediated by fetal liver bearing CD8+ and Lyt 1+ (CD5+) cells. Despite these manifestations, the role of third-party cells needs to be considered. As a first premise, adherent cells were targeted as possible third-party cells. To test the role of the adherent cells, liver cells from benzo(alpha)pyrene-exposed fetuses were treated with ficoll-hypaque, and the interface cells were fractionated through glass wool or nylon wool. It is known that adhering cells, macrophages and B cells, readily attach to glass or nylon wool. The effluent cells and the adherent cells were cultured with syngeneic responder cells and allogeneic stimulator cells in a mixed lymphocyte response. The results showed that benzo(alpha)pyrene-effluent cells led to the enhancement of proliferation in the mixed lymphocyte response, while benzo(alpha)pyrene-adherent cells led to suppression. The effluent and adherent cells of corn oil controls did not modify cell proliferation in the mixed lymphocyte response. These data suggest that a third-party cell, reasonably the macrophage or possibly B cells or both, since these are adherent cells, play a decided role in mediating suppression in the benzo(alpha)pyrene-exposed progeny.