Selective reduction of N-acetylaspartate in medial temporal and parietal lobes in AD

BACKGROUND

Both AD and normal aging cause brain atrophy, limiting the ability of MRI to distinguish between AD and age-related brain tissue loss. MRS imaging (MRSI) measures the neuronal marker N-acetylaspartate (NAA), which could help assess brain change in AD and aging.

OBJECTIVES

To determine the effects of AD on concentrations of NAA, and choline- and creatine-containing compounds in different brain regions and to assess the extent NAA in combination with volume measurements by MRI improves discrimination between AD patients and cognitively normal subjects.

METHODS

Fifty-six patients with AD (mean age: 75.6 +/- 8.0 years) and 54 cognitively normal subjects (mean age: 74.3 +/- 8.1 years) were studied using MRSI and MRI.

RESULTS

NAA concentration was less in patients with AD compared with healthy subjects by 21% (p < 0.0001) in the medial temporal lobe and by 13% to 18% (p < 0.003) in parietal lobe gray matter (GM), but was not changed significantly in white matter and frontal lobe GM. In addition to lower NAA, AD patients had 29% smaller hippocampi and 11% less cortical GM than healthy subjects. Classification of AD and healthy subjects increased significantly from 89% accuracy using hippocampal volume alone to 95% accuracy using hippocampal volume and NAA together.

CONCLUSION

In addition to brain atrophy, NAA reductions occur in regions that are predominantly impacted by AD pathology.

Effects of abstinence on the brain: quantitative magnetic resonance imaging and magnetic resonance spectroscopic imaging in chronic alcohol abuse

BACKGROUND

Structural brain damage, especially to white matter, is well documented in chronic alcohol abuse. There is also evidence for brain metabolic abnormalities in this condition. It is unknown, however, to what extent these structural and metabolic changes are present in treated alcohol abusers who achieve long-term abstinence versus treatment-naïve, heavily drinking individuals.

METHODS

This study compared 12 recovering alcoholics with 8 actively heavily drinking subjects. Participants underwent magnetic resonance (MR) imaging and proton MR spectroscopic imaging of the brain. Semiautomated image segmentation techniques yielded volumes for gray matter, white matter, white matter lesions, and cerebral spinal fluid in multiple brain regions defined by Talairach stereotaxic coordinates. Automated spectral processing methods yielded gray and white matter concentrations of the metabolites N-acetylaspartate, creatine, and choline for the same regions.

RESULTS

Recovering alcoholics had greater volumes of frontal white matter, but the opposite was true for white matter in a "remainder" region encompassing the basal frontal and temporal lobes, the cerebellum, and the brainstem. Recovering alcoholics also had smaller volumes of white matter lesions in whole brain, in occipital and mesial parietal regions, and in the remainder region. Recovering alcoholics had greater gray matter volumes in the orbital frontal pole and postcentral gyrus, but smaller gray matter volumes in the anterior cingulate. Whole-brain and regional metabolite concentrations did not differ significantly between the two groups.

CONCLUSIONS

White and gray matter volumes in different regions of the brain were greater or smaller in recovering, treated alcoholics. The findings suggest region-specific structural recovery from chronic alcohol-induced brain injury, but also region-specific long-term structural damage in abstinent alcoholics. White matter lesions were widespread in active drinkers and may partly resolve during long-term abstinence. Proton MR spectroscopic measures, as applied in this cross-sectional study, were largely ineffective in revealing metabolic effects of abstinence on the alcohol-damaged brain.

Health motivation: a determinant of older adults' attendance at health promotion programs

The primary purpose of conducting this study was to determine if there is a significant relation between health motivation and participation in health promotion programs in a sample of community-dwelling older adults (n = 106). Health motivation was measured using Cox's (1985) Health Self-Determinism Index, and participation in health promotion programs was measured by tallying the self-reported number of programs attended within the past year by each individual. The effects of selected demographic variables on these two variables were also examined. The conceptual framework guiding the study was the Health-Promoting Self-Care System Model (Simmons, 1990). Intrinsically motivated older persons attended fewer programs (p < .01) than those who were more extrinsically motivated. Higher educational level (p < .001) and fewer health problems (p < .01) emerged as significant predictor variables for intrinsic health motivation, and those with less formal education attended more health promotion programs (p < .05).

Separate and interactive effects of cocaine and alcohol dependence on brain structures and metabolites: quantitative MRI and proton MR spectroscopic imaging

The effects of chronic cocaine and alcohol abuse on human brain structure and metabolites are not fully known. We studied controls (n = 13) and abstinent subjects dependent on cocaine (8), alcohol (12), and cocaine and alcohol (17) using quantitative MRI and proton MR spectroscopic imaging. Talairach-based techniques yielded tissue and CSF volumes and gray- and white-matter concentrations of N-acetylaspartate (NAA), creatine and choline metabolites in multiple brain regions. Alcohol dependents had lower gray-matter NAA concentrations and more sulcal CSF than non-alcohol dependents throughout the brain. They also had less subcortical gray matter and (regionally) less white matter. Cocaine dependents compared with non-cocaine dependents had higher posterior parietal white-matter creatine concentration. They also had less gray and white matter in the prefrontal lobes and in a region encompassing the temporal lobes and cerebellum. Structural white-matter deficits in cocaine dependents were greater with longer duration of cocaine use. Subjects with concurrent cocaine and alcohol dependence had less prefrontal white matter, especially in the anterior cingulate, than subjects dependent on only one substance. Chronically abused cocaine and alcohol each leave multiple metabolic and structural brain defects after long-term abstinence. Concurrent dependence on both substances may aggravate white-matter structural defects, primarily in frontal brain.

Differential sensitivity to the wake-promoting actions of norepinephrine within the medial preoptic area and the substantia innominata

Mapping studies were conducted to delineate the site(s) of action for the arousal-enhancing actions of norepinephrine (NE) within the basal forebrain region encompassing the medial preoptic area (MPOA) and the substantia innominata (SI). Varying doses of NE, the beta-agonist, isoproterenol, or the alpha1-agonist, phenylephrine, were infused into the MPOA or SI in the resting rat. Infusions of NE (4 nmol, 16 nmo/150 nl), isoproterenol (15 nmol/150 nl), and phenylephrine (40 nmol/250 nl) into the MPOA elicited robust increases in waking. In contrast, neither isoproterenol or phenylephrine infusions into the SI altered behavioral state. NE infusions into the SI increased waking only at the highest dose, and at this dose there was an anatomical gradient for NE-induced waking, with infusions placed farther from the MPOA, producing smaller increases in waking. Thus, in contrast to the MPOA, the SI is relatively insensitive to the wake-promoting actions of NE.

Superoxide dismutase and catalase do not affect the pulmonary hypertensive response to group B streptococcus in the lamb

The purpose of this study was to determine whether treatment with conjugated antioxidant enzymes could attenuate or abolish pulmonary hypertension induced by group B streptococcus (GBS). Lambs, 3-7 d old, were anesthetized and ventilated. Intravascular catheters were placed in the left ventricle, descending aorta, right atrium, and pulmonary artery for continuous monitoring of intravascular pressures. Cardiac output was measured with radiolabeled microspheres. Measurements were obtained at baseline and 15 and 60 min into a 60-min GBS infusion, and 60 min after GBS was stopped. Blood gas values were held constant and PaO(2) was maintained >100 mm Hg. The control group received saline vehicle only (n = 6), the GBS group received GBS infusion only (n = 9), the enzymes (ENZ) group received polyethylene glycol-superoxide dismutase (PEG-SOD) and polyethylene glycol-catalase (PEG-CAT) treatment only (n = 6), and the ENZ+GBS group received PEG-SOD and PEG-CAT then GBS (n = 9). Plasma samples were obtained to confirm increased superoxide dismutase and catalase activities in the groups receiving enzymes. Compared with baseline, pulmonary vascular resistance increased by 119% and 101% at 15 min and 87% and 81% at 60 min in the GBS and ENZ+GBS groups, respectively. Sixty minutes after the termination of the GBS infusion, PVR returned to baseline in the GBS group but did not in the ENZ+GBS group. Enzyme infusions resulted in at least a ninefold increase in plasma enzyme activities. As opposed to previously published data from endotoxin models, PEG-CAT and PEG-SOD were ineffective in altering the GBS-induced pulmonary hypertensive response in this model. This suggests that acute administration of antioxidant enzymes may not be effective in ameliorating GBS-induced pulmonary hypertension.

Ask trustees who know. Interview by Laurie Larson

Five of your trustee peers share their expertise on board education, fundraising, community representation, what it means to be a board chair, and what physicians can bring to your board.

Creating a hospital-community infrastructure: challenges and benefits

With rising public expectations and demands for increased accountability, hospitals will be even more challenged by their local communities to implement strategies such as those developed at SMH to enable community participation that assists the hospital in serving its local population into the future. In response to unique health needs of its local community, SMH created an Inner City Health (ICH) Program in the early 1990s to provide comprehensive inpatient, ambulatory, and community outreach services. To build on its philosophy to reduce barriers to health for disadvantaged populations, the ICH Research Program, the only one of its kind in Canada, was also established. This paper will describe and explore the formalised infrastructure between SMH and the community; its evolution, as well as SMH's involvement with its community in context of the hospital's relationships with its Board of Directors, the Toronto teaching hospital system, media and advocacy groups. The role of ICH research in influencing evidence-based clinical practice, innovations in health science education and government policy will also be discussed as part of the SMH's hospital-community infrastructure.

Effects of guanfacine on three forms of distraction in the aging macaque

alpha-2 adrenoceptor agonists, such as clonidine and guanfacine, enhance attention in aged animals. According to one theory, alpha-2 receptor agonists improve attention by decreasing distractibility to task-irrelevant stimuli. In two healthy aging bonnet macaques, we investigated the effects of low-(0.001 mg/kg) and high-dose (0.05 mg/kg) acute intramuscular guanfacine versus saline control on accuracy (number of trials correct) in three tasks requiring attention: delayed matching-to-sample, one-target visual tracking (test of focused attention) and two-target visual tracking (test of divided attention). Each task employed distracting stimuli in a different paradigmatic context. One monkey responded to guanfacine at both doses with significant rises in accuracy on all three tasks. The second monkey showed significant accuracy improvement for high-dose guanfacine only. No sedation was observed. These results suggest that guanfacine improves attention and reduces distractibility in multiple task contexts in healthy aging primates.

Effects of muscarinic and adrenergic agonism on auditory P300 in the macaque

Homologs of human endogenous evoked potentials are known in several species of nonhuman primates, but the neurotransmitter substrates of these potentials remain uncertain. In particular, the role of central cholinergic and adrenergic systems is not yet clearly defined. We recorded cognitive evoked potentials from the scalp in four adult bonnet macaque monkeys during a passive version of the auditory oddball paradigm with unique novel stimuli under saline control conditions. In two subjects each, cognitive evoked potentials were also recorded following intramuscular administration of the m1 muscarinic agonist AF102B or of the alpha-2A noradrenergic agonist guanfacine. On saline, large positivities resembling the human P300 were recorded over midline sites in response to rare or novel auditory stimuli in all four monkeys. The amplitude of these positivities was sensitive to the delivery of fruit-juice reward in association with rare stimuli in three monkeys tested. At cognition-enhancing doses, AF102B enlarged the amplitude of P300-like positivities in both monkeys tested; guanfacine enlarged the amplitude of P300-like positivities in one of two monkeys tested. These results add to existing evidence of human-like endogenous late positivities in monkeys that are influenced by the cholinergic and adrenergic systems, and suggest a possible role of m1 muscarinic and alpha-2A noradrenergic receptor subtypes.

A clinical evaluation of a locking orthodontic facebow

Standard orthodontic facebows may accidentally detach from the appliance buccal tubes at night; this could reduce the effectiveness of extra oral traction and occasionally cause an injury. To try and prevent facebow detachment at night a facebow with a locking mechanism was introduced. This study assessed the ability of 706 consecutively treated patients to learn to wear and use this facebow. The facebows were fitted in 9 different practices supervised by 12 orthodontists. Data from the patients and orthodontists were collected over a 2-year period and covered approximately 166,550 nights. All the orthodontists were able to fit and adjust the facebow; a total of 697 patients successfully used the facebow. Accidental detachment of the facebow at night was reported to be less than 1%. This indicates a significant improvement in the safety of the facebow and should help to improve compliance by increasing the number of hours of wear achieved by the patients.

Method to correlate 1H MRSI and 18FDG-PET

The in vivo neuronal contribution to human cerebral metabolic rate of glucose (CMRglc), measured by 18FDG-PET, is unknown. Examining the effect of 1H MRSI-derived N-acetyl aspartate (NAA) concentration on positron emission tomography (PET) measures of metabolic activity might indicate the relationship of CMRglc to neuron density. In a population of 19 demented, cognitively impaired, and control subjects, the Miller-Gartner algorithm was applied to whole-brain PET data to isolate the PET signal originating in cortical gray matter alone (GMPET). An analogous procedure applied to multislice proton MRSI data yielded the N-acetyl aspartate concentration in cortical gray matter (GMNAA). In 18 of 19 subjects, a significant linear regression (P < 0.05) resulted when GMPET was plotted against GMNAA, whereby GMPET was higher for higher GMNAA. This suggests that CMRglc rises linearly with increasing neuron density in gray matter. This method may be used to investigate the relationship of CMRglc to neurons in various conditions.

The unveiling of traumatic brain injury in an HIV/AIDS population

This study examines the frequency of traumatic brain injury (TBI) in an HIV/AIDS population and its associated symptomatology. A panel of 173 individuals with HIV were split into two groups--those who have experienced a blow to the head within their lifetime (n = 128) and those who have not (n = 45). Self-reported symptoms from the TIRR Symptom Checklist were compared across both HIV panels, individuals who identified as traumatically brain injured (n = 416), and individuals with no disability (n = 282). Six clusters of symptoms (total, cognitive, physical, affective/behavioural, five symptoms sensitive and specific to TBI in general and 25 symptoms sensitive and specific to mild TBI) were analysed in a MANOVA, controlling for the demographic variables that were correlated with total symptoms, including panel membership, education, annual household income and substance use history. Significant main effects were found for panel membership. Individuals with HIV and a history of blow to the head reported a higher number of total symptoms and the 25 symptoms specific to mild TBI. The significance of these findings acknowledges the need to recognize the frequency of TBI in an HIV population and the subsequent need to provide the appropriate interventions that will lead to an enhanced overall quality of life.

Environmental covariates: effects on the power of sib-pair linkage methods

The effect of inclusion of environmental risk factors on the power of sib-pair linkage methods was tested for a qualitative trait. It was found that inclusion of an environmental variable did not increase the power of the Haseman-Elston (H-E) sib-pair nonparametric linkage analysis test. However, a significant increase in power was observed for both the H-E and affected-sib-pair tests, even in small samples, when persons unexposed to the environmental risk factor were coded as unknown.

Possible linkage of alcoholism, monoamine oxidase activity and P300 amplitude to markers on chromosome 12q24

Multipoint linkage analysis was used to screen for evidence of linkage between alcoholism and five alcoholism-related quantitative traits. The results suggest that a susceptibility locus that influences monoamine oxidase activity and P300 amplitude at the Pz lead, and increases the risk of alcohol dependence may be linked to markers in the 12q24 region. Furthermore, the susceptibility for alcoholism may be associated with allele 3 (allele size 144) of D12S392.

Levomepromazine (methotrimeprazine) and the last 48 hours

Levomepromazine (previously known as methotrimeprazine) has a broad range of beneficial effects in the terminal phase of many illnesses, resulting from its combined antipsychotic, anxiolytic and sedative actions. Levomepromazine can safely be administered in a continuous subcutaneous infusion with most other commonly used drugs in palliative care.

Divided attention-enhancing effects of AF102B and THA in aging monkeys

The effects of cholinergic drugs proposed for treatment of cognitive impairment in normal aging and dementia on divided attention have been little studied in non-human primates. We tested the hypothesis that cholinergic drugs improve spatial divided attention in primates via a computer task requiring simultaneous tracking of two visual targets in three young and two aged healthy bonnet macaques. Task accuracy (number of correct responses) and reaction time (RT) were measured 2 h after administration of either the m1 agonist +/- -cis-2-methyl-spiro(1,3-oxathiolane-5,3')quinuclidine (AF102B; 0.1-2.1 mg/kg IM) or the cholinesterase inhibitor 9-amino-1,2,3,4-tetrahydroamino-acridine (THA; 0.5-2.0 mg/kg orally). Accuracy increased for four of five monkeys at appropriate doses of one or both cholinomimetics, accompanied in two monkeys by a drop in RT. Responses were less uniform to THA than to AF102B. For the five-monkey group at Best dose, accuracy increased 34% (THA) or 43% (AF102B) above baseline (P<0.05 for both drugs), respectively, with no significant change in RT and with minimal untoward effects. Cholinotherapy may improve divided attention in young and aged healthy primates.