Biomedical subjects

G E Smith

Publications and source records attributed to G E Smith.

At least 55 records · Page 3Linked to original sources

PubMed2000

Usefulness of MRI measures of entorhinal cortex versus hippocampus in AD.

OBJECTIVE: MRI-based measurements of hippocampal atrophy are a sensitive indicator of the early pathologic degeneration of the medial temporal lobe in AD. However, AD pathology appears first in the transentorhinal/entorhinal cortex, not the hippocampus. The authors tested the hypothesis that MRI-based measurements of the entorhinal cortex are more sensitive than measurements of hippocampal volume in discriminating among three clinical groups; controls, patients with a mild cognitive impairment (MCI), and patients with mild probable AD. METHODS: The authors studied 30 controls, 30 patients with MCI, and 30 patients with AD who were matched among clinical groups on age, gender, and education. All underwent a standardized MRI protocol from which the authors made measurements of hippocampal volume, entorhinal cortex volume, and the cumulative length of the medial border of the entorhinal cortex. RESULTS: Pairwise intergroup differences (p < 0.01) were found for all MRI measurements with the exception of the cumulative length of the entorhinal cortex, which did not differentiate controls from MCI patients. Whereas the hippocampal and entorhinal cortex volume measurements provided slightly better intergroup discrimination than the entorhinal distance measurement, overall differences in discriminating ability among the three MRI measurements were minor. CONCLUSIONS: Despite the theoretical rationale for the superiority of entorhinal measurements in early AD, the authors found MRI measurements of the hippocampus and entorhinal cortex were approximately equivalent at intergroup discrimination. Measurements of the hippocampus may be preferable because MRI depiction of the boundaries of the entorhinal cortex can be obscured by anatomic ambiguity, image artifact, or both.

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PubMed2000

Memory and MRI-based hippocampal volumes in aging and AD.

OBJECTIVE: To demonstrate structural-functional relationships between MRI-based volumetric measurements of medial temporal lobe structures and cognitive function. BACKGROUND: Previous work has documented the ability of MRI-based measurements of the hippocampus to discriminate between age-matched control subjects and patients with very mild AD. Relatively less is known about the correlation between medial temporal lobe structures and cognitive functions. METHOD: We evaluated structural-functional relationships among the hippocampal formation, parahippocampal gyrus, and amygdala, and measures of memory, language, and general cognitive performance in 220 probable AD patients and normal control subjects. Standardized instruments of memory and general cognitive function were used to assess subjects enrolled in a longitudinal study of aging and dementia. RESULTS: The volume of the hippocampal formation predicted performance on most acquisition and recall measures across the spectrum of normal aging and AD. If the groups were segregated, most of the expected associations between medial temporal lobe structures and memory measures were observed in the AD patients. CONCLUSION: MRI-based hippocampal volumetry accurately depicts the structural-functional relationships between memory loss and hippocampal damage across the spectrum from normal aging to dementia.

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PubMed2000

Diagnostic accuracy of four approaches to interpreting neuropsychological test data.

The diagnostic accuracy of 4 approaches to interpreting neuropsychological test results are evaluated in 672 cognitively normal and 407 cognitively impaired persons using the Mayo Cognitive Factor Scales (G. E. Smith et al., 1994). The interpretation approaches studied are absolute scores, difference scores, profile variability, and change scores at 1- to 2-year test-retest intervals. All dependent measures were "highly significant" when diagnostic groups were compared on null hypothesis significance testing analyses. In contrast, varied accuracy rates were obtained when each measure's ability to correctly classify individuals was evaluated relative to overall diagnostic accuracy. Odds ratios were also highly varied and ranged from < or = 1.0 (i.e., chance) to 34.9. The clinical usefulness of absolute scores and difference scores in data interpretation is supported. Neither profile variability measures nor measures of change over time were diagnostically useful.

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PubMed2000

Risk factors for nursing home placement in a population-based dementia cohort.

OBJECTIVE: To examine risk factors for nursing home placement in a population-based dementia cohort. METHODS: The Mayo Clinic Medical Records linkage system was used to identify all patients with onset of dementia between 1980 and 1984. The patient group included 314 cases who met DSM-III-R criteria for dementia, including 220 cases who were community dwelling at onset. All dementia patients were followed until death. A control group included 323 patients who did not, at any point, meet DSM-III-R criterion for dementia. The groups were initially matched on age, gender, and year of initial registration. Demographic, medical, social, and functional predictors were examined as static and time-dependent risk factors for nursing home placement in the initial community-dwelling subgroups, using stepwise Cox regression modeling. RESULTS: Of the 314 dementia patients, 282 took residence in licensed skilled nursing homes for at least 6 weeks, suggestive of custodial care, at some point during the course of their illness. In the control group, 162 of the 323 people required nursing home placement. Within controls, the predictor variables of time to nursing home placement included initial age, being divorced, living in a townhome, apartment or assisted living apartment, change in Charlson comorbidity score, and change in amount of daily assistance required. Within the dementia sample, seven predictors were eventually determined to be associated with time to nursing home placement. These included total number of years of education, age at onset of dementia, being single, living in a retirement or supervised apartment at onset, change in Charlson comorbidity score, and a change in the amount of daily assistance required. CONCLUSIONS: Cumulative incidence of placement was 90% in the dementia cohort and 50% in the controls. Certain variables seem to impact time to nursing home placement in all older persons, whether they have dementia or not. Among these are age, living in assisted living settings, increasing comorbidity scores, and increasing need for functional assistance. Certain additional factors may have a specific impact in dementia. Among these is education, which seems to provide a protective effect. These predictors may be important covariates in clinical dementia studies that include time to nursing home placement as an outcome variable.

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PubMed1999

Cowdria ruminantium infection in ticks in the Kruger National Park.

Adult Amblyomma hebraeum ticks, the principle vector of heartwater (cowdriosis) of domestic ruminants in southern Africa, were collected in pheromone traps placed in Kruger National Park, an exclusively wildlife sanctuary in South Africa. These ticks transmitted Cowdria ruminantium, the rickettsial agent causing heartwater, to a susceptible goat, resulting in acute, fatal disease. C ruminantium was isolated in bovine endothelial cell culture from the plasma of this animal during the febrile stage of the disease and transmitted to susceptible goats, causing fatal heartwater. The prevalence of C ruminantium infection in 292 ticks was determined by polymerase chain reaction (PCR) analysis to be 1.7 per cent (95 per cent confidence interval 0.71 to 4.0 per cent). A DNA probe analysis, which is less sensitive than PCR, detected infection in three of the five PCR-positive ticks. The remaining infections were below the detection limit of the DNA probe, which is approximately 70,000 organisms. This is the first evidence that a vector-wildlife cycle of transmission of C ruminantium can be maintained independently of domestic ruminants.

Animals↗

PubMed1999

Prediction of AD with MRI-based hippocampal volume in mild cognitive impairment.

OBJECTIVE: To test the hypothesis that MRI-based measurements of hippocampal volume are related to the risk of future conversion to Alzheimer's disease (AD) in older patients with a mild cognitive impairment (MCI). BACKGROUND: Patients who develop AD pass through a transitional state, which can be characterized as MCI. In some patients, however, MCI is a more benign condition, which may not progress to AD or may do so slowly. PATIENTS: Eighty consecutive patients who met criteria for the diagnosis of MCI were recruited from the Mayo Clinic Alzheimer's Disease Center/Alzheimer's Disease Patient Registry. METHODS: At entry into the study, each patient received an MRI examination of the head, from which the volumes of both hippocampi were measured. Patients were followed longitudinally with approximately annual clinical/cognitive assessments. The primary endpoint was the crossover of individual MCI patients to the clinical diagnosis of AD during longitudinal clinical follow-up. RESULTS: During the period of longitudinal observation, which averaged 32.6 months, 27 of the 80 MCI patients became demented. Hippocampal atrophy at baseline was associated with crossover from MCI to AD (relative risk [RR], 0.69, p = 0.015). When hippocampal volume was entered into bivariate models-using age, postmenopausal estrogen replacement, standard neuropsychological tests, apolipoprotein E (APOE) genotype, history of ischemic heart disease, and hypertension-the RRs were not substantially different from that found univariately, and the associations between hippocampal volume and crossover remained significant. CONCLUSION: In older patients with MCI, hippocampal atrophy determined by premorbid MRI-based volume measurements is predictive of subsequent conversion to AD.

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PubMed1999

REM sleep behavior disorder and dementia: cognitive differences when compared with AD.

OBJECTIVE: To determine whether the dementia associated with REM sleep behavior disorder (RBD) differs from Alzheimer's disease (AD) and, if so, whether differences in cognitive performance between RBD/dementia and AD resemble reported differences between dementia with Lewy bodies (DLB) and AD. METHODS: This retrospective study compares neurocognitive performance between 31 patients with degenerative dementia and polysomnography-confirmed RBD and 31 patients without brainstem Lewy body pathology who met Consortium to Establish a Registry for Alzheimer's Disease (CERAD) clinical and neuropathologic criteria for AD. The patient groups did not differ in dementia severity (based on Global Deterioration Scale score) or duration. RESULTS: RBD preceded or coincided with the onset of cognitive decline in 94% of the patients. All but one patient with RBD/dementia had one or more of the following clinical features of DLB: visual hallucinations, extrapyramidal signs, or fluctuating cognition/alertness. The data revealed significantly worse performance on attention, perceptual organization, visual memory, and letter fluency for the RBD/dementia group, whereas the AD group showed significantly worse performance on confrontation naming and verbal memory. CONCLUSIONS: Patients with RBD and degenerative dementia demonstrate a significantly different pattern of cognitive performance from patients with AD. Most of the patients in the RBD/dementia sample also meet criteria for possible or probable DLB, and the pattern of cognitive differences from AD is similar to reported comparisons between DLB and AD. The cognitive and clinical data provide evidence to suggest that the dementia associated with RBD may represent DLB.

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PubMed1999

Mild cognitive impairment: clinical characterization and outcome.

BACKGROUND: Subjects with a mild cognitive impairment (MCI) have a memory impairment beyond that expected for age and education yet are not demented. These subjects are becoming the focus of many prediction studies and early intervention trials. OBJECTIVE: To characterize clinically subjects with MCI cross-sectionally and longitudinally. DESIGN: A prospective, longitudinal inception cohort. SETTING: General community clinic. PARTICIPANTS: A sample of 76 consecutively evaluated subjects with MCI were compared with 234 healthy control subjects and 106 patients with mild Alzheimer disease (AD), all from a community setting as part of the Mayo Clinic Alzheimer's Disease Center/Alzheimer's Disease Patient Registry, Rochester, Minn. MAIN OUTCOME MEASURES: The 3 groups of individuals were compared on demographic factors and measures of cognitive function including the Mini-Mental State Examination, Wechsler Adult Intelligence Scale-Revised, Wechsler Memory Scale-Revised, Dementia Rating Scale, Free and Cued Selective Reminding Test, and Auditory Verbal Learning Test. Clinical classifications of dementia and AD were determined according to the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition and the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria, respectively. RESULTS: The primary distinction between control subjects and subjects with MCI was in the area of memory, while other cognitive functions were comparable. However, when the subjects with MCI were compared with the patients with very mild AD, memory performance was similar, but patients with AD were more impaired in other cognitive domains as well. Longitudinal performance demonstrated that the subjects with MCI declined at a rate greater than that of the controls but less rapidly than the patients with mild AD. CONCLUSIONS: Patients who meet the criteria for MCI can be differentiated from healthy control subjects and those with very mild AD. They appear to constitute a clinical entity that can be characterized for treatment interventions.

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PubMed1999

Testing normal older people three or four times at 1- to 2-year intervals: defining normal variance.

Normative data were presented that defined the upper and lower standards for deciding if cognitive abilities show reliable change over 2 or more testing occasions when retesting occurs at 1- to 2-year intervals. The Mayo Cognitive Factor Scores (MCFS; G. E. Smith et al., 1994) were analyzed because they permit the quantitation of overall functioning in 5 clinically important cognitive domains: established verbal knowledge, nonverbal reasoning, attention and concentration, new learning, and delayed memory. To the authors' knowledge, this is the first report of both group-level and individual-level data analyses derived from a respectably sized sample of normal persons who have been tested 3 or more times at clinically common test-retest intervals.

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PubMed1999

Optimizing the removal of carbon phases in soils and sediments for sequential chemical extractions by coulometry.

We have developed a coulometric technique to optimize the removal of the carbonate and organic fractions for sequential chemical extractions of soils and sediments. The coulometric system facilitates optimizing these two fractions by direct real-time measurement of carbon dioxide (CO2) evolved during the removal of these two fractions. Further analyses by ICP-MS and alpha-spectrometry aided in interpreting the results of coulometry experiments. The effects of time, temperature, ionic strength and pH were investigated. The sensitivity of the coulometric reaction vessel/detection system was sufficient even at very low total carbon content (< 0.1 mol kg-1). The efficiency of the system is estimated to be 96% with a standard deviation of 8%. Experiments were carried out using NIST Standard Reference Materials 4357 Ocean Sediment (OS), 2704 Buffalo River Sediment (BRS), and pure calcium carbonate. Carbonate minerals were dissolved selectively using an ammonium acetate-acetic acid buffer. Organic matter was then oxidized to CO2 using hydrogen peroxide (H2O2) in nitric acid. The carbonate fraction was completely dissolved within 120 min under all conditions examined (literature suggests up to 8 h). For the OS standard, the oxidation of organic matter self-perpetuates between 45 and 50 degrees C, a factor of two less than commonly suggested, while organic carbon in the BRS standard required 80 degrees C for the reaction to proceed to completion. For complete oxidation of organic matter, we find that at least three additions of H2O2 are required (popular methods suggest one or two).

Carbon↗

PubMed1999

Estimating the size of a transient population.

Migratory populations often stop over for short periods of time at predictable sites along their migration routes. These staging areas can be heavily used and are potentially critical to the survival of the migrants. This paper presents a method for estimating the number of individuals using such an area and their average residence time. The estimator is based on daily population estimates and records of repeat sightings of identifiable individuals. Its application is illustrated with observations on a population of migrating birds, some of which could be identified from bands that were readable from a distance.

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PubMed1999

Patient satisfaction with electroconvulsive therapy.

OBJECTIVE: To determine whether patients who have electroconvulsive therapy (ECT) are satisfied with their treatment and demonstrate more favorable attitudes about ECT compared with controls. PATIENTS AND METHODS: We developed a 44-item survey measuring ECT treatment satisfaction and attitudes. The survey was administered to 24 psychiatric inpatients near the end of ECT treatment and 2 weeks later. A modified survey was administered to 24 outpatient controls who had never received ECT and who were recruited from a psychiatry clinic waiting room. RESULTS: Patients who received ECT had positive attitudes about it. For example, 21 (91%) of 24 patient respondents endorsed the statement, "I am glad that I received ECT." Attitude score was significantly higher for the ECT group compared with controls. A higher degree of satisfaction was associated with a higher level of education and younger age. CONCLUSIONS: Patients who received ECT were satisfied with their treatment and had more favorable attitudes about it than patients who did not receive this treatment.

Attitude↗

PubMed1999

Effect of different liner treatments on postoperative sensitivity of amalgam restorations.

OBJECTIVE: The purpose of this clinical study was to assess the sensitivity experienced and reported by patients following treatment of primary carious lesions with Class I or Class II amalgam restorations. METHOD AND MATERIALS: Only previously untreated teeth were selected. The cavity preparations were treated according to one of four regimens: group 1 = no liner; group 2 = two coats of a copal varnish; group 3 = a dentin adhesive resin liner; group 4 = a resin-modified glass-ionomer liner. Patients were contacted on days 2 and 7 postoperatively and questioned regarding the presence or absence of sensitivity. If sensitivity was experienced, they were asked which stimuli created the sensitivity, the length of time it lasted, and its intensity on a subjective scale. If sensitivity was experienced on day 7, patients were also contacted on days 14, 30, and 90 to assess the degree of sensitivity. Nineteen teeth were included in each of the four groups. RESULTS: By days 2 and 7, no significant difference existed among groups; by day 14, 22% of restorations in group 2 and 17% of those in group 3 were sensitive, while teeth in groups 1 and 4 exhibited no sensitivity reactions. CONCLUSION: Use of a resin-modified glass-ionomer liner or no dentin treatment resulted in short-term sensitivity in fewer than one third of the teeth. Almost one third of the teeth restored with a dentin adhesive resin liner or copal varnish exhibited initial sensitivity, which lasted up to 30 days in a few teeth.

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PubMed1998

Active immunization of patients with HIV infection: a study of the effect of VaxSyn, a recombinant HIV envelope subunit vaccine, on progression of immunodeficiency.

Infection with the human immunodeficiency virus (HIV) leads to a progressive immunodeficiency characterized by decreasing levels of CD4+ T lymphocytes. VaxSyn, a vaccine based on the recombinant envelope glycoprotein subunit (rgp160) of HIV-1IIIB, was used to immunize HIV-infected patients to determine whether its administration was beneficial with respect to slowing disease progression. A 3-year multicenter, randomized, placebo-controlled, double-blinded, efficacy and safety trial of repeated immunization with VaxSyn was used to evaluate the long-term impact on the progression of immunodeficiency. VaxSyn in alum, or alum alone, was given to 278 HIV-infected asymptomatic individuals with initial CD4 counts of > or =500 cells/mm3. Clinical findings, the CD4 count, and both virological and immunological parameters were followed. No significant differences were observed between the treatment and placebo control groups in rate of CD4 T cell decline, time to initiation of antiretroviral therapy, incidence of opportunistic infections, HIV RNA plasma viremia, HIV viral infectivity as measured by quantitative HIV coculture assay, and death. This study revealed no effect on either clinical or laboratory virological parameters from the administration of VaxSyn.

AIDS Vaccines↗

PubMed1998

Hippocampal atrophy and apolipoprotein E genotype are independently associated with Alzheimer's disease.

A variety of anatomic and functional neuroimaging findings are associated with Alzheimer's disease (AD). One of the strongest imaging associations identified is between AD and hippocampal atrophy. The epsilon4 allele of the apolipoprotein E (ApoE) gene increases the risk of developing AD and lowers the mean age of onset of the disease. The purpose of this study was to assess the association between hippocampal volume and ApoE polymorphisms in elderly control subjects and in patients with probable AD. We performed magnetic resonance imaging-based volume measurements of the hippocampus in 125 cognitively normal elderly controls and 62 patients with probable AD. ApoE genotyping was performed by using standard methods. Hippocampal volumes were significantly smaller in AD cases than in control subjects. Hippocampal volumes did not differ significantly within either clinical group on the basis of ApoE genotype. Both the epsilon4 allele of ApoE and hippocampal atrophy were significantly but independently associated with AD.

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PubMed1998

Mayo's older Americans normative studies: category fluency norms.

Age-adjusted normative data are presented for persons over age 55 years on a common measure of category fluency. Further adjustment for education is also provided. These data were obtained as part of a series of projects known collectively as Mayo's Older Americans Normative Studies (MOANS). The normative information provided here should prove useful for characterizing performance on the individual measure of category fluency. In addition, these data should promote greater accuracy in comparing category fluency scores with performance on any other measures with MOANS norms, including tests of letter fluency. Limitations and unique features of MOANS normative data are also discussed.

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PubMed1998

Normative data for the Mattis Dementia Rating Scale.

Age-adjusted normative data are presented for persons over age 55 on the Mattis Dementia Rating Scale. Additional adjustment for the effect of education on test performance is also provided. These data were collected as part of Mayo's Older Americans Normative Studies (MOANS) in a continuing effort to develop age-appropriate norms for older persons on commonly used neuropsychological tests. The normative data presented here should prove more useful in characterizing the presence and severity of general cognitive dysfunction than currently available norms. Limitations and unique features of MOANS normative data are also discussed.

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PubMed1998

Apolipoprotein E genotype influences cognitive 'phenotype' in patients with Alzheimer's disease but not in healthy control subjects.

We examined the association of apolipoprotein E (apo E) genotype with cognitive performance in Alzheimer's disease (AD) and Mild Cognitive Impairment (MCI) patients and in normal subjects. One hundred fifty-seven AD patients, 35 MCI patients who developed AD during longitudinal follow-up, and 341 normal control subjects from the Mayo Clinic Alzheimer's Disease Patient Registry were studied. All participants were typed for apo E using polymerase chain reaction-based assay, epsilon 4+ and epsilon 4- groups were compared on cognitive factor scores of Verbal Comprehension, Perceptual Organization, Attention/Concentration, Learning, and Retention. Raw delayed verbal recall and visual confrontation naming scores supplemented these scores. Multivariate ANOVA was completed for cognitive scores. As expected, a main effect for diagnostic group was present across all scores. Multivariate main effects for age group and apo E genotype were also statistically significant. Subsequent within-group comparisons revealed no genotype differences for control subjects across all cognitive scores except raw delayed recall where an interaction indicated that older epsilon 4+ control subjects actually scored better than younger epsilon 4+ patients. Genotype differences were present for the Retention factor in the MCI sample and for Verbal Comprehension and Learning in the AD sample. In a combined cognitive impairment sample (AD + MCI), genotype differences were present for Verbal Comprehension, Learning, and Retention. Possession of an apo E epsilon 4 allele did not appear to be associated with poorer cognitive performance among normal control subjects. In the AD and MCI samples, epsilon 4+ status was associated with greater memory impairment in analyses including duration of illness as a covariate. In combined AD + MCI analyses, epsilon 4 homozygosity was associated with poorer retention, learning, and verbal comprehension at a given disease duration. Possession of the epsilon 4 genotype may influence cognition in a dose-response relationship.

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