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Biomedical subjects

C M Clark

Publications and source records attributed to C M Clark.

At least 37 records · Page 2Linked to original sources
PubMed2000

Structural and functional brain integrity of fetal alcohol syndrome in nonretarded cases.

PURPOSE: To determine the structural and functional integrity of the brain in a sample of nonretarded individuals diagnosed with fetal alcohol syndrome. SUBJECTS: The sample consisted of nineteen individuals who met the diagnostic criteria for fetal alcohol syndrome. METHODS: Intellectual function was assessed using the Wechsler Adult Intelligence Scale-Revised. Structural integrity of the brain was assessed using magnetic resonance imaging whereas functional integrity was assessed using positron emission tomography and (18)F-fluorodeoxyglucose. RESULTS: The mean Full Scale IQ was 80. 2 (range: 66-92). Only 1 magnetic resonance imaging was found to be abnormal. This abnormality was found for the subject with the lowest IQ. Decreases in relative regional cerebral metabolic rates were found in 5 brain regions comprising the thalamus and basal ganglia. CONCLUSION: These results when coupled with previous findings suggest a continuum of neuropathology in fetal alcohol syndrome. For cases with relatively mild intellectual deficits, the cause of the deficit is at a micro-level rather than a macro-level.

Adolescent↗
PubMed2000

Genetic discontinuity revealed by chloroplast microsatellites in eastern North American Abies (Pinaceae).

Development of conservation strategies for Fraser fir (Abies fraseri) in the southern Appalachian Mountains depends in part on recognition of the extent to which Fraser fir is genetically distinct from the closely related balsam (A. balsamea) and intermediate (A. balsamea var. phanerolepis) fir. These sibling species have exhibited intergrading, clinal variation in morphological, chemical, and genetic characteristics in prior research. Chloroplast microsatellite markers were polymerase chain reaction amplified from genomic DNA samples of 78 individuals representing the geographic ranges of Fraser, balsam, and intermediate fir. Gene diversity levels at two loci ranged among taxa from 0.65 to 0.84. Allele frequencies demonstrated significant differentiation among taxa, with R(ST) values of 0.36 and 0.10. Haplotype diversity and D(SH) were highest for balsam fir and lowest for intermediate fir. A haplotype network analysis based on allele size distribution for the two loci revealed two distinct clusters of haplotypes and population-specific haplotypes. Ninety-two percent of the haplotypes in one cluster were from balsam fir and intermediate fir, and 84% of the haplotypes in the other cluster were from Fraser fir and intermediate fir. The genetic differentiation of chloroplast DNA markers provides justification for the recognition of Fraser fir as a distinct Management Unit (MU) for conservation purposes, regardless of its taxonomic classification.

Journal Article↗
PubMed2000

Increased 8,12-iso-iPF2alpha-VI in Alzheimer's disease: correlation of a noninvasive index of lipid peroxidation with disease severity.

The isoprostane 8,12-iso-iPF2alpha-VI is a sensitive and specific marker of in vivo lipid peroxidation. We found elevated levels in the urine, blood, and cerebrospinal fluid of patients with Alzheimer's disease (AD) that correlated with measures of cognitive and functional impairment, established biomarkers of AD pathology (cerebrospinal fluid tau and amyloid) and the number of apolipoprotein E epsilon4 alleles. These results suggest that 8,12-iso-iPF2alpha-VI is a useful biomarker of oxidative damage in AD.

Aged↗
PubMed1999

Influence of lamotrigine on progression of early Huntington disease: a randomized clinical trial.

OBJECTIVE: To assess the efficacy of lamotrigine, a novel antiepileptic drug that inhibits glutamate release, to retard disease progression in Huntington disease (HD). BACKGROUND: Excitatory amino acids may cause selective neuronal death in HD, and lamotrigine may inhibit glutamate release in vivo. METHODS: A double-blinded, placebo-controlled study was conducted of 64 patients with motor signs of less than 5 years' duration who were randomly assigned to either placebo or lamotrigine and assessed at 0 (baseline), 12, 24, and 30 months. The primary response variable was total functional capacity (TFC) score. Secondary response variables included the quantified neurological examination and a set of cognitive and motor tests. Repeated fluorodeoxyglucose measurements of regional cerebral metabolism using PET also were included. RESULTS: Fifty-five patients (28 on lamotrigine, 27 on placebo) completed the study. Neither the primary response variable nor any of the secondary response variables differed significantly between the treatment groups. Both the lamotrigine and the placebo group deteriorated significantly on the TFC, in the lamotrigine group by 1.89 and the placebo group by 2.11 points. No effect of CAG size on the rate of deterioration could be detected. CONCLUSIONS: There was no clear evidence that lamotrigine retarded the progression of early Huntington disease over a period of 30 months. However, more patients on lamotrigine reported symptomatic improvement (53.6 versus 14.8%; p = 0.006), and a trend toward decreased chorea was evident in the treated group (p = 0.08). The study also identified various indices of disease progression, including motor tests and PET studies, that were sensitive to deterioration over time.

Adult↗
PubMed1999

Variability in annual Mini-Mental State Examination score in patients with probable Alzheimer disease: a clinical perspective of data from the Consortium to Establish a Registry for Alzheimer's Disease.

OBJECTIVE: To determine the variability in annual Mini-Mental State Examination scores of patients with Alzheimer disease enrolled in the Consortium to Establish a Registry for Alzheimer's Disease (CERAD). PATIENTS: A total of 372 patients with probable Alzheimer disease with 1 or more years of follow-up. SETTING: Twenty-one CERAD clinical sites throughout the United States. RESULTS: An average annual decline of 3.4 points in CERAD patients returning for longitudinal reassessments was close to the SD of the measurement error of 2.8 points for the Mini-Mental State Examination. There was wide variability in individual rates of decline. Even with 4 years of follow-up, 15.8% of the patients had no clinically meaningful decline in Mini-Mental State Examination score (defined as a change in initial score >3, ie, 1 SD of measurement error). Validity of measurements of the rate of change in Mini-Mental State Examination scores improved with longer observation intervals and was reliable for most patients when observations were separated by 3 or more years. CONCLUSIONS: Although the Mini-Mental State Examination is a useful screening instrument to assess level of cognitive function, it has limited value in measuring the progression of Alzheimer disease in individual patients for periods less than 3 years because of a large measurement error and substantial variation in change in annual score.

Aged↗
PubMed1999

Combination treatment with methotrexate and cyclosporin for severe recalcitrant psoriasis.

An increasingly important approach to the management of patients with severe psoriasis is the concurrent use of two systemic treatments. Previous guidelines have advised against the use of methotrexate and cyclosporin in combination. We report the successful use of a combination of methotrexate and cyclosporin in the treatment of 19 patients with severe, recalcitrant psoriasis, 15 of whom had psoriatic arthropathy. Most patients had previously received two or more systemic treatments. Before combination treatment was started nine of the patients were taking methotrexate and 10 were taking cyclosporin at the maximum tolerated doses. The duration of combination treatment was bimodally distributed, with seven patients having short-term treatment (mean +/- SD duration 18. 9 +/- 15.7 weeks) and 12 patients having long-term treatment (mean +/- SD duration 193.2 +/- 160.6 weeks). Those patients who received short-term treatment did not develop any evidence of toxicity from either agent. Of those patients on long-term treatment, three developed mild impairment of renal function that returned to normal following a reduction in dose of cyclosporin, and three had impairment of renal function (following long-term cyclosporin monotherapy) that improved, but did not normalize, following a reduction in dose of cyclosporin. In each case, combination treatment for psoriasis resulted in good control of both skin and joint problems using lower doses of each agent than would have been used for monotherapy. We conclude that the combination of methotrexate and cyclosporin is an effective treatment for this group of patients.

Adult↗
PubMed1999

Screening and treatment of diabetic nephropathy by primary care physicians.

OBJECTIVE: To describe the practices of Indiana primary care physicians related to diabetic nephropathy screening and management. DESIGN: Cross-sectional, observational. SETTING: The state of Indiana. PARTICIPANTS: Active primary care physicians (defined as general internists, family practitioners, and general practitioners) in Indiana who provided care for diabetic patients at the time of the survey (n = 1,018) MEASUREMENTS AND MAIN RESULTS: Practice patterns relevant to microalbuminuria and overt albuminuria screening and management were assessed along two dimensions: the percentage of patients to whom the practices were applied and the frequency with which the practices were performed. Of 1,141 physicians who responded to the survey, 1,018 were eligible for analysis. Eighty-six percent of physicians reported screening more than half of their patients with type 1 diabetes for overt albuminuria, as did 82% of physicians for their patients with type 2 diabetes. Only 17% of physicians indicated performing microalbuminuria testing on more than half of their type 1 patients. Angiotensin-converting enzyme inhibitor agents were used frequently to treat abnormal urinary albumin excretion when hypertension was present, but less often when hypertension was absent. Physician specialty, year of graduation from medical school, practice location, and familiarity with the results of the Diabetes Control and Complications Trial were significant predictors of screening and treatment practice patterns. CONCLUSIONS: Primary care physicians report practices that allow them to detect overt albuminuria but not microalbuminuria. Angiotensin-converting enzyme inhibitors are frequently used by physicians who test for microalbuminuria, but efforts to increase the detection of early renal damage are needed so that these agents and other therapeutic strategies may be employed at the earliest opportunity.

Clinical Competence↗
PubMed1999

Effects on regional brain metabolism of high-altitude hypoxia: a study of six US marines.

Previous studies of brain glucose metabolism in people indigenous to high-altitude environments uncovered two response patterns: Quechuas native to the high Andes of South America sustained modest hypometabolism in most brain regions interrogated, whereas Sherpas, native to the Himalayas and considered by many biologists to be most effectively high-altitude adapted of all humans, showed brain metabolic patterns similar to lowlanders, with no acclimation effects noted. In the present study, the database was expanded to include hypoxia acclimation effects in lowlanders. Positron emission tomography (PET) and [(18)F]-2-deoxy-2-fluro-D-glucose (FDG) imaging techniques were used to assess regional cerebral glucose metabolic rates (rCMR(glc)) in six US marines (Caucasian lineage) before and after a 63-day training program for operations at high altitudes ranging from 10,500 to 20,320 ft. Significant changes in rCMR(glc) were found for 7 of 25 brain regions examined. Significant decreases in absolute cerebral glucose metabolism after high-altitude exposure were found in five regions: three frontal, the left occipital lobe, and the right thalamus. In contrast, for the right and left cerebellum significant increases in metabolism were found. The magnitudes of these differences, in terms of absolute metabolism, were large, ranging from 10 to 18%. Although the results may not be solely the result of lower oxygen levels at high altitude, these findings suggest that the brain of healthy human lowlanders responds to chronic hypoxia exposure with precise, region-specific fine tuning of rCMR(glc). The observed short-term hypoxia acclimation responses in these lowlanders clearly differ from the long-term hypoxia adaptations found in brain metabolism of people indigenous to high-altitude environments.

Adult↗
PubMed1999

Elevated levels of tau in cerebrospinal fluid: implications for the antemortem diagnosis of Alzheimer's disease elevated levels of tau in cerebrospinal fluid: implications for the antemortem diagnosis of Alzheimer's disease.

Alzheimer's disease (AD) is a heterogeneous group of dementias characterized by progressive cognitive impairments as well as by the accumulation of abundant extracellular deposits of Ass and intra-neuronal neurofibrillary lesions in selective-ly vulnerable regions of the AD brain. The latter abnormalities (e.g. neurofibrillary tangles, dystrophic neurites, neuropil threads) are aggregates of paired helical filaments (PHFs) formed from altered tau proteins (PHFtau). Although PHF tau and normal central nervous system (CNS) tau are phosphorylated at nearly the same sites, PHFtau is phosphorylated to a greater extent, and alterations in the activity of CNS kinases and phosphatases most likely contribute to the pathogenesis of PHFtau. Since the abundance of neurofibrillary lesions correlates with the dementia in AD, the generation of PHFtau and the formation of neurofibrillary lesions may be part of a cell death pathway leading to massive neuron loss and dementia in AD. Building upon these and other insights into altered tau metabolism in AD, a series of studies suggest that the diagnosis of AD may be supported in living patients by determining the concentration of tau in cerebrospinal fluid (CSF). We review these promising studies here, and discuss them in the context of current understanding of the pathobiology of AD.

Journal Article↗
PubMed1998

High cerebrospinal fluid tau and low amyloid beta42 levels in the clinical diagnosis of Alzheimer disease and relation to apolipoprotein E genotype.

OBJECTIVE: To evaluate cerebrospinal fluid (CSF) levels of amyloid beta protein ending at amino acid 42 (Abeta42) and tau as markers for Alzheimer disease (AD) and to determine whether clinical variables influence these levels. DESIGN: Cohort study. SETTING: Six academic research centers with expertise in dementia. SUBJECTS: Eighty-two patients with probable AD, including 24 with very mild dementia (Mini-Mental State Examination score >23/30) (AD group); 60 cognitively normal elderly control subjects (NC group); and 74 subjects with neurological disorders, including dementia (ND group). MAIN OUTCOME MEASURES: Levels of Abeta42 and tau were compared among AD, NC, and ND groups. Relationships of age, sex, Mini-Mental State Examination score, and apolipoprotein E (Apo E) genotype with these levels were examined using multiple linear regression. Classification tree models were developed to optimize distinguishing AD from NC groups. RESULTS: Levels of Abeta42 were significantly lower, and levels of tau were significantly higher, in the AD group than in the NC or ND group. In the AD group, Abeta42 level was inversely associated with Apo E epsilon4 allele dose and weakly related to Mini-Mental State Examination score; tau level was associated with male sex and 1 Apo E epsilon4 allele. Classification tree analysis, comparing the AD and NC subjects, was 90% sensitive and 80% specific. With specificity set at greater than 90%, the tree was 77% sensitive for AD. This tree classified 26 of 74 members of the ND group as having AD. They had diagnoses difficult to distinguish from AD clinically and a high Apo E epsilon4 allele frequency. Markers in CSF were used to correctly classify 12 of 13 patients who later underwent autopsy, including 1 with AD not diagnosed clinically. CONCLUSIONS: Levels of CSF Abeta42 decrease and levels of CSF tau increase in AD. Apolipoprotein E epsilon4 had a dose-dependent relationship with CSF levels of Abeta42, but not tau. Other covariates influenced CSF markers minimally. Combined analysis of CSF Abeta42 and tau levels discriminated patients with AD, including patients with mild dementia, from the NC group, supporting use of these proteins to identify AD and to distinguish early AD from aging. In subjects in the ND group with an AD CSF profile, autopsy follow-up will be required to decide whether CSF results are false positive, or whether AD is a primary or concomitant cause of dementia.

Adult↗