Biomedical subjects

B C McDonald

Publications and source records attributed to B C McDonald.

4 recordsLinked to original sources

PubMed2006

Regional brain atrophy in cognitively intact adults with a single APOE epsilon4 allele.

OBJECTIVE: To determine whether cognitively intact adults with the APOE epsilon3/epsilon4 genotype show reduced gray matter density on voxel-based morphometry (VBM) vs those homozygous for the epsilon3 allele. METHODS: Participants were healthy, cognitively intact, right-handed adults, age 19 to 80, who completed genotyping, neuropsychological testing, and MRI. Forty-nine participants had the epsilon3/epsilon3 genotype and 27 had the epsilon3/epsilon4 genotype. Gray matter data were analyzed using the general linear model as implemented in the Statistical Parametric Mapping package, adjusting for age and sex. RESULTS: The epsilon3/epsilon4 participants showed lower gray matter density than the epsilon3/epsilon3 participants in right medial temporal and bilateral frontotemporal regions as well as other areas. There were no regions in which epsilon3/epsilon4 participants showed higher gray matter density than epsilon3/epsilon3 participants. CONCLUSIONS: Regionally reduced gray matter density is detectable in cognitively intact adults with a single copy of the APOE epsilon4 allele.

Adult↗

PubMed2004

Brain activation patterns associated with working memory in relapsing-remitting MS.

BACKGROUND: Patients with multiple sclerosis (MS) show changes in brain activation patterns during visual and motor tasks that include decreases in the typical local network for a function and increases in other brain regions. OBJECTIVE: To determine whether brain activation patterns associated with working memory are affected by MS. METHODS: Activation of working memory circuitry was examined using an fMRI n-back task in adults with mild relapsing-remitting MS (RRMS; n = 10) and demographically matched healthy controls (n = 10). RESULTS: Group differences in brain activation emerged during both low- and high-demand conditions (p < 0.001). Overall, patients showed less activation than controls in core prefrontal and parietal regions of working memory circuitry, and greater activation in other regions within and beyond typical working memory circuitry, including bilateral medial frontal, cingulate, parietal, bilateral middle temporal, and occipital regions. CONCLUSIONS: Relative to controls, patients with mild RRMS showed shifts in brain activation patterns within and beyond typical components of working memory circuitry.

Adult↗

PubMed2003

Chronic deep brain stimulation for the treatment of tremor in multiple sclerosis: review and case reports.

BACKGROUND: Deep brain stimulation (DBS) offers a non-ablative alternative to thalamotomy for the surgical treatment of medically refractory tremor in multiple sclerosis. However, relatively few outcomes have been reported. OBJECTIVE: To provide a systematic review of the published cases of DBS use in multiple sclerosis and to present four additional patients. METHODS: Quantitative and qualitative review of the published reports and description of a case series from one centre. RESULTS: In the majority of reported cases (n=75), the surgical target for DBS implantation was the ventrointeromedial nucleus of the thalamus. Tremor reduction and improvement in daily functioning were achieved in most patients, with 87.7% experiencing at least some sustained improvement in tremor control postsurgery. Effects on daily functioning were less consistently assessed across studies; in papers reporting relevant data, 76.0% of patients experienced improvement in daily functioning. Adverse effects were similar to those reported for DBS in other patient populations. CONCLUSIONS: Few of the studies reviewed used highly standardised quantitative outcome measures, and follow up periods were generally one year or less. Nonetheless, the data suggest that chronic DBS often produces improved tremor control in multiple sclerosis. Complete cessation of tremor is not necessarily achieved, there are cases in which tremor control decreases over time, and frequent reprogramming appears to be necessary.

Adult↗

PubMed1996

Prenatal alcohol exposure influences the effects of neuroactive steroids on separation-induced ultrasonic vocalizations in rat pups.

Fetal alcohol exposure has been reported to be associated with hyper-responsiveness to stress. Using a maternal separation paradigm, this study examined whether prenatal alcohol exposure affected sensitivity to neurosteroid modulation of stress. We have shown that the neuroactive steroid allopregnanolone reduces ultrasonic vocalizations (USVs) after brief maternal separation in week-old rat pups. Prenatal alcohol exposure, however, resulted in reduced sensitivity to this neurosteroid. In this study's first experiment, the behavioral effects of pregnenolone sulfate, a neurosteroid with reportedly opposite modulatory effects on the GABAA receptor, were characterized. Pregnenolone sulfate had a triphasic effect on the production of ultrasonic vocalizations and on open field activity. Blockade of conversion of pregnenolone sulfate to allopregnanolone via the 5 alpha-reductase inhibitor 4-MA also blocked the drug-related reduction in USVs, but not the higher-dose augmentation. The enzyme inhibitor alone had no significant effects on USV production, nor did progesterone. These results suggest that the neuroactive steroid pregnenolone sulfate may play an independent role in the stress response after maternal separation as well as being a precursor for the anxiolytic neurosteroid allopregnanolone. In the second experiment, prenatal alcohol exposure was found to eliminate both the low dose USV-reducing effect and the higher dose USV-increasing effect. These results support previous results demonstrating that prenatal alcohol exposure may cause an altered sensitivity to the neuromodulatory effects of neurosteroids.

Androgen Antagonists↗