Biomedical subjects

E E Smith

Publications and source records attributed to E E Smith.

At least 19 recordsLinked to original sources

PubMed2006

Progression of white matter lesions and hemorrhages in cerebral amyloid angiopathy.

OBJECTIVE: To determine the rate of progression of white matter lesions and hemorrhages in a cohort with cerebral amyloid angiopathy (CAA). METHODS: The authors analyzed data from 26 patients with possible (3) or probable (23) CAA, diagnosed by the Boston Criteria. Brain maps of white matter hyperintensities, normalized to head size (nWMH), were created by blinded computer-assisted segmentation of MRI images obtained at baseline and after a median follow-up interval of 1.1 year. RESULTS: There was a substantial nWMH volume increase over the interscan interval (median 0.5 mL/year, interquartile range 0.1 to 2.8, p < 0.001). The median yearly increase, expressed as a percentage of the baseline WMH volume, was 18%. The characteristic most strongly associated with nWMH volume increase was the baseline nWMH volume (r = 0.57, p = 0.002). The volume of nWMH progression was also associated with history of cognitive impairment (median 5.0 mL/year in cognitively impaired subjects vs 0.3 mL/year in cognitively unimpaired, p = 0.02) but not age or hypertension. This association remained present in an analysis stratified by baseline WMH volume. New hemorrhages, including asymptomatic microbleeds, were seen in 46% of subjects. The number of new MRI hemorrhages correlated strongly with baseline nWMH (r = 0.53, p = 0.005) but not with nWMH progression (r = 0.22, p = 0.28). CONCLUSIONS: There is a progressive increase in white matter lesions in subjects with cerebral amyloid angiopathy. The association of white matter lesions with incident lobar hemorrhages suggests that white matter damage may reflect a progressive microangiopathy due to cerebral amyloid angiopathy.

Aged↗

PubMed2006

Sediment TCDD-EQs and EROD and MROD activities in Ranid frogs from agricultural and nonagricultural sites in Michigan (USA).

In vitro studies have demonstrated atrazine-mediated induction of 7-ethoxyresorufin O-deethylase (EROD) activity. EROD is an enzyme active in the metabolism of many compounds, including many xenobiotics. These studies have suggested that atrazine may affect reproductive function by altering steroid metabolism. The goal of this study was to determine whether relationships could be detected between measured atrazine concentrations in surface waters and the liver-somatic index (LSI) and EROD and 7-methoxyresorufin O-deethylase (MROD) activities in the livers of ranid frogs. In addition, sediment dioxin toxic equivalents (TCDD-EQs) were determined using the H4IIE-luc cell bioassay. Adult and juvenile green frogs (Rana clamitans), bullfrogs (R. catesbeiana), and Northern leopard frogs (R. pipiens) were collected from areas with extensive corn cultivation and areas where there was little agricultural activity in south central Michigan in the summer of 2003. Atrazine concentrations at nonagricultural sites ranged from less than the limit of quantification (0.17 microg atrazine/L) to 0.23 microg atrazine/L and did not exceed 1.2 microg atrazine/L at agricultural sites. Sediment TCDD-EQs were measurable only at one agricultural site. Of the measured parameters, only LSI values in adult male frogs differed significantly between agricultural and nonagricultural sites, with greater values observed at agricultural sites. In green frogs, EROD and MROD activities were measurable in both adult and juvenile frogs and were similar among sites. Median EROD activities ranged from 13 to 21 pmol/min/mg protein in adult male green frogs and from 5 to 13 pmol/min/mg protein in adult female green frogs. Juvenile frogs had greater EROD and MROD activities than adult frogs. Bullfrogs and leopard frogs had greater activities than did green frogs. Atrazine concentrations were significantly and negatively correlated with MROD activity in adult male green frogs (Spearman R = -0.800). LSI and EROD and MROD activities of adult female or juvenile green frogs were not significantly correlated with atrazine concentrations. These results suggest that atrazine does not appear to have a consistent association with EROD or MROD activities in wild-caught green frogs.

Agriculture↗

PubMed2006

Antiplatelet use after intracerebral hemorrhage.

BACKGROUND: Survivors of intracerebral hemorrhage are at risk for recurrent intracerebral hemorrhage and ischemic cardiovascular and cerebrovascular disease. OBJECTIVE: To determine whether antiplatelet therapy increases the risk of recurrent intracerebral hemorrhage. METHODS: The authors reviewed data from consecutive survivors of primary intracerebral hemorrhage enrolled in a single-center prospective cohort study. Survivors were followed by telephone interview; recurrent intracerebral hemorrhage and post-index antiplatelet agent use and duration were recorded. Cox proportional hazards models was used with antiplatelet agent exposure as a time-dependent variable to assess the effect of antiplatelet agent use on recurrent intracerebral hemorrhage, stratified by lobar and deep hemispheric location. RESULTS: Recurrent intracerebral hemorrhage was more common in survivors of lobar hemorrhage compared with survivors of deep hemorrhage (cumulative 2-year rate 22% vs 4%; p = 0.007). Antiplatelet agents were prescribed in 22% of intracerebral hemorrhage survivors (27/127 lobar, 19/80 deep hemispheric), most commonly for prevention of ischemic heart disease. Antiplatelet agent use was not associated with intracerebral hemorrhage recurrence in survivors of either lobar hemorrhage (hazard ratio [HR] 0.8, 95% CI 0.3 to 2.3, p = 0.73) or of deep hemorrhage (HR 1.2, 95% CI 0.1 to 14.3, p = 0.88). CONCLUSION: Antiplatelet agent use is relatively common following intracerebral hemorrhage but did not appear to be associated with a large increased risk of intracerebral hemorrhage recurrence in this observational study.

Aged↗

PubMed2006

Plasma steroid hormone concentrations, aromatase activities and GSI in ranid frogs collected from agricultural and non-agricultural sites in Michigan (USA).

The triazine herbicide atrazine has been hypothesized to disrupt sexual development in frogs by up-regulating aromatase activity, resulting in greater estradiol (E2) concentrations and causing feminization in males. The goal of this study was to collect native ranid frogs from atrazine-exposed ponds and determine whether relationships exist between measured atrazine concentrations and the gonadosomatic index (GSI), plasma concentrations of testosterone (T), E2 or 11-ketotestosterone (KT), or with aromatase activity. In the summer of 2002 and 2003, adult and juvenile green frogs (Rana clamitans), bullfrogs (R. catesbeiana) and Northern leopard frogs (R. pipiens) were collected from areas with extensive corn cultivation and areas where there was little agricultural activity in south-central Michigan. Atrazine concentrations were below the limit of quantification at non-agricultural sites. Atrazine concentrations did not exceed 2 microg/L at most agricultural sites, but a concentration of 250 microg atrazine/L was measured in one sample from one site in 2002. Plasma steroid concentrations varied among locations. Aromatase activity was measurable in less than 11% of testes in adult males, and in less than 4% of testes in juvenile males. Median aromatase activities in ovaries of adult females ranged from 3 to 245 pmol/h/mg protein, and maximum activities were 2.5-fold greater in juveniles than in adults. Atrazine concentrations were not significantly correlated with any of the parameters measured in this study. These results indicate that atrazine does not up-regulate aromatase in green frogs in the wild, and does not appear to affect plasma steroid hormone concentrations.

Animals↗

PubMed2006

Working memory for order and the parietal cortex: an event-related functional magnetic resonance imaging study.

Memory for order information has been tied to the frontal lobes, however, parietal activation is observed in many functional neuroimaging studies. Here we report functional magnetic resonance findings from an event-related experiment involving working memory for order. Five letters were presented for storage, followed after a delay by two probe items. Probe items could be separated by zero to three positions in the memory set and subjects had to indicate whether the items were in the correct order. Analyses indicate that activation in left parietal cortex shows a systematic decrease in activation with increasing probe distance. This finding is consistent with an earlier study in which we suggested that parietal cortical regions mediate the representation of order information via magnitude codes.

Adult↗

PubMed2006

Plasma beta-amyloid and white matter lesions in AD, MCI, and cerebral amyloid angiopathy.

BACKGROUND: Microvascular brain injury, typically measured by extent of white matter hyperintensity (WMH) on MRI, is an important contributor to cognitive impairment in the elderly. Recent studies suggest a role for circulating beta-amyloid peptide in microvascular dysfunction and white matter disease. METHODS: The authors performed a cross-sectional study of clinical, biochemical, and genetic factors associated with WMH in 54 subjects with Alzheimer disease (AD) or mild cognitive impairment (AD/MCI) and an independent group of 42 subjects with cerebral amyloid angiopathy (CAA). Extent of WMH was determined by computer-assisted volumetric measurement normalized to intracranial size (nWMH). Biochemical measurements included plasma concentrations of the 40- and 42-amino acid species of beta-amyloid (Abeta40 and Abeta42) detected by specific enzyme-linked immunosorbent assays. RESULTS: Plasma Abeta40 concentrations were associated with nWMH in both groups (correlation coefficient = 0.48 in AD/MCI, 0.42 in CAA, p < or = 0.005). Plasma Abeta40 remained independently associated with nWMH after adjustment for potential confounders among age, hypertension, diabetes, homocysteine, creatinine, folate, vitamin B12, and APOE genotype. The presence of lacunar infarctions was also associated with increased Abeta40 in both groups. nWMH was greater in CAA (19.8 cm3) than AD (11.1 cm3) or MCI (10.0 cm3; p < 0.05 for both comparisons). CONCLUSIONS: Plasma beta-amyloid 40 concentration is independently associated with extent of white matter hyperintensity in subjects with Alzheimer disease, mild cognitive impairment, or cerebral amyloid angiopathy. If confirmed in longitudinal studies, these data would suggest circulating beta-amyloid peptide as a novel biomarker or risk factor for microvascular damage in these common diseases of the elderly.

Aged↗

PubMed2005

Working memory for order information: multiple cognitive and neural mechanisms.

Working memory for order information is mediated by different cognitive mechanisms that rely on different neural circuits. Here we discuss evidence that order memory involves mechanisms that range from general supervisory processes to process that maintenance fine-grained temporal position information. We suggest that neural regions-including the prefrontal cortex, motor cortex, parietal cortex and medial temporal structures-operate at different levels and processing stages to give rise to working memory for order information.

Cerebral Cortex↗

PubMed2005

Atrazine concentrations, gonadal gross morphology and histology in ranid frogs collected in Michigan agricultural areas.

The triazine herbicide atrazine has been suggested to be a potential disruptor of normal sexual development in male frogs. The goals of this study were to collect native ranid frogs from sites in agricultural and non-agricultural areas and determine whether hypothesised atrazine effects on the gonads could be observed at the gross morphological and histological levels. Juvenile and adult green frogs (Rana clamitans), bullfrogs (R. catesbeiana) and leopard frogs (R. pipiens) were collected in the summers of 2002 and 2003. Atrazine concentrations were below the limit of quantification at non-agricultural sites, and concentrations did not exceed 2 microg/L at most agricultural sites. One concentration greater than 200 microg atrazine/L was measured once at one site in 2002. Hermaphroditic individuals with both male and female gonad tissue in either one or both gonads, were found at a low incidence at both non-agricultural and agricultural sites, and in both adults and juveniles. Testicular oocytes (TO) were found in male frogs at most of the sites, with the greatest incidence occurring in juvenile leopard frogs. TO incidence was not significantly different between agricultural and non-agricultural sites with the exception of juveniles collected in 2003. Atrazine concentrations were not significantly correlated with the incidence of hermaphroditism, but maximum atrazine concentrations were correlated with TO incidence in juvenile frogs in 2003. However, given the lack of a consistent relationship between atrazine concentrations and TO incidence, it is more likely the TOs observed in this study result from natural processes in development rather than atrazine exposure.

Agrochemicals↗

PubMed2005

Seasonal exposures to triazine and other pesticides in surface waters in the western Highveld corn-production region in South Africa.

The objective of this study was to characterize concentrations of atrazine, terbuthylazine, and other pesticides in amphibian habitats in surface waters of a corn-production area of the western Highveld region (North-West Province) of South Africa. The study was conducted from November 2001 to June 2002, coinciding with the corn-production season. Pesticide residues were measured at regular intervals in surface water from eight ponds, three in a non-corn-growing area (NCGA) and five within the corn-growing area (CGA). Measured atrazine concentrations differed significantly among sites and between samples. In the five CGA sites, the maximum atrazine concentrations measured during the study ranged from 1.2 to 9.3 microg/L. Although no atrazine was recorded as being applied in the catchment of the three NCGA sites, maximum concentrations from 0.39 to 0.84 microg/L were measured during the study, possibly as a result of atmospheric transport. Maximum measured concentrations of terbuthylazine ranged from 1.22 to 2.1 microg/L in the NCGA sites and from 1.04 to 4.1 microg/L in the CGA sites. The source of terbuthylazine in the NCGA sites may have been in use other than in corn. The triazine degradation products, deisopropylatrazine (DIA) and deethylatrazine (DEA) and diaminochlorotriazine (DACT) were also found in water from both the CGA and NCGA sites. Concentrations of DIA were > or = 1 microg/L throughout the season, while DEA concentrations were mostly <0.5 microg/L before planting but increased after planting and application of herbicides to concentrations >2 microg/L in some locations. Concentrations of DACT were highly variable (LOD to 8 microg/L) both before and after planting and application, suggesting that they resulted from historical use of triazines in the area. Other herbicides such as simazine and acetochlor were only detected infrequently and pesticides such as S-metolachlor, cypermethrin, monocrotophos, and terbuphos, known to be used in the CGA, were not detected in any of the samples. Because of dilution by higher than normal rainfall in the study period, these concentrations may not be predictive of those in years of normal rainfall.

Agriculture↗

PubMed2004

White matter lesions, cognition, and recurrent hemorrhage in lobar intracerebral hemorrhage.

BACKGROUND: Accumulating evidence suggests that white matter lesions are associated with vascular cognitive impairment. The authors investigated the relationships between white matter lesions, cognitive impairment, and risk of recurrent hemorrhage in a prospectively identified cohort of patients with lobar intracerebral hemorrhage (ICH). METHODS: The authors collected clinical and genetic information on 182 consecutive patients age > or = 55 who had CT scan at admission for lobar ICH. White matter disease was graded on CT in all subjects and on MRI in a subset of 82 patients. All scans were interpreted blinded to clinical information. Survivors were followed for recurrent ICH by telephone interview. RESULTS: White matter damage was common (present on CT in 77%) and severe (advanced CT grade in 32%). White matter damage was correlated with the total number of hemorrhages on gradient-echo MRI and with risk of recurrent ICH. Subjects with cognitive impairment prior to their index ICH were more likely to have severe white matter damage on CT (OR 3.6, 95% CI 1.6 to 8.1, p = 0.003) and more likely to have advanced periventricular hyperintensities on MRI. The relationships between white matter damage and cognitive impairment were similar in the subset of 88 subjects meeting criteria for probable or definite cerebral amyloid angiopathy and remained independent after adjustment for age, cortical atrophy, and APOE genotype. CONCLUSIONS: White matter damage in lobar ICH is common and is associated with cognitive impairment. These data support the possibility that an underlying vasculopathy in lobar ICH patients, possibly cerebral amyloid angiopathy, can cause clinically important vascular dysfunction.

Cerebral Amyloid Angiopathy↗

PubMed2004

Hypervariability, suppressed recombination and the genetics of individuality.

We define 'genetic individuality' as intraspecies variation that has substantial heritability and involves traits that are sufficiently common that they can be observed in any modest-sized sampling of individuals. We propose that genetic individuality is largely shaped by the combinatory shuffling of a modest number of genes, each of which exists as a family of functionally and structurally diverged alleles. Unequivocal examples of such allele families are found at the O-antigen-biosynthetic locus in Pseudomonas aeruginosa and the human leucocyte antigen locus in humans. We examine characteristic features of these allele families and explore the possibility that genetic loci with similar characteristics can be recognized in a whole-genome scan of human genetic variation.

Alleles↗

PubMed2004

The where and how of attention-based rehearsal in spatial working memory.

Rehearsal in human spatial working memory is accomplished, in part, via covert shifts of spatial selective attention to memorized locations ("attention-based rehearsal"). We addressed two outstanding questions about attention-based rehearsal: the topography of the attention-based rehearsal effect, and the mechanism by which it operates. Using event-related fMRI and a procedure that randomized the presentation of trials with delay epochs that were either filled with a flickering checkerboard or unfilled, we localized the effect to extrastriate areas 18 and 19, and confirmed its absence in striate cortex. Delay-epoch activity in these extrastriate regions, as well as in superior parietal lobule and intraparietal sulcus, was also lateralized on unfilled trials, suggesting that attention-based rehearsal produces a baseline shift in areas representing the to-be-remembered location in space. No frontal regions (including frontal eye fields) demonstrated lateralized activity consistent with a role in attention-based rehearsal.

Adolescent↗

PubMed2002

Leukoaraiosis is associated with warfarin-related hemorrhage following ischemic stroke.

BACKGROUND AND OBJECTIVES: Prior ischemic stroke is a risk factor for intracerebral hemorrhage (ICH) in patients taking warfarin, but the mechanism is not known. This study investigates radiographic and clinical characteristics of patients with warfarin-related ICH following ischemic stroke. METHODS: In this case-control study, the authors selected all patients with warfarin-related ICH and previous symptomatic ischemic stroke from a prospective cohort of consecutive patients with ICH. Control subjects were similarly aged patients with history of symptomatic stroke randomly chosen from an anticoagulant therapy unit. The 26 eligible ICH cases and 56 controls were compared for vascular risk factors, stroke characteristics, and extent of leukoaraiosis (graded in anterior and posterior brain regions on a validated scale of 0 to 4). RESULTS: The presence and severity of leukoaraiosis on CT scan correlated strongly with the occurrence of ICH. Leukoaraiosis was seen in 24 of 26 cases (92%) compared with 27 of 56 controls (48%), yielding an odds ratio of 12.9 (95% CI 2.8 to 59.8). Other clinical factors associated with ICH included an international normalized ratio >3.0, history of multiple previous strokes, and the presence of carotid artery stenosis. The relationship between leukoaraiosis and ICH persisted in multivariable analyses controlling for these risk factors as well as hypertension and diabetes mellitus. CONCLUSIONS: Leukoaraiosis is an independent risk factor for warfarin-related ICH in survivors of ischemic stroke, including those in the commonly employed range of anticoagulation.

Aged↗

PubMed2001

The neural basis of task-switching in working memory: effects of performance and aging.

We studied the performance of young and senior subjects on a well known working memory task, the Operation Span. This is a dual-task in which subjects perform a memory task while simultaneously verifying simple equations. Positron-emission tomography scans were taken during performance. Both young and senior subjects demonstrated a cost in accuracy and latency in the Operation Span compared with performing each component task alone (math verification or memory only). Senior subjects were disproportionately impaired relative to young subjects on the dual-task. When brain activation was examined for senior subjects, we found regions in prefrontal cortex that were active in the dual-task, but not in the component tasks. Similar results were obtained for young subjects who performed relatively poorly on the dual-task; however, for young subjects who performed relatively well in the dual-task, we found no prefrontal regions that were active only in the dual-task. Results are discussed as they relate to the executive component of task switching.

Adult↗

PubMed2001

Inductive reasoning in Alzheimer's disease.

We evaluated knowledge of basic level and superordinate semantic relations and the role of cognitive resources during inductive reasoning in probable Alzheimer's disease (AD). Nineteen mildly demented AD patients and 17 healthy control subjects judged the truthfulness of arguments with a premise and a conclusion that contain familiar concepts coupled with "blank" predicates, such as "Spiders contain phosphatidylcholine; therefore all insects contain phosphatidylcholine." Like healthy control subjects, AD patients were relatively insensitive to the typicality of the premise category when judging the strength of arguments with a conclusion containing a basic-level concept, but were relatively sensitive to typicality during judgments of arguments containing a superordinate in the conclusion. Moreover, AD patients resembled control subjects in judging arguments with an immediate superordinate in the conclusion compared to arguments with a distant superordinate. AD patients differed from control subjects because they could not take advantage of two premises in an argument containing basic-level concepts. We conclude that semantic knowledge is sufficiently preserved in AD to support inductive reasoning, but that limited cognitive resources may interfere with AD patients' ability to consider the entire spectrum of information available during semantic challenges.

Aged↗

PubMed2001

Subcutaneous emphysema of the thorax heralding colonic perforation.

Subcutaneous emphysema of the thorax may follow thoracic operations for a number of essentially benign reasons and does not usually cause much concern to the thoracic surgeon. We report subcutaneous emphysema of the thorax heralding a retroperitoneal colonic perforation in a patient who had undergone coronary artery bypass grafting 3 days previously.

Aged↗

PubMed2001

Is the dissociability of working memory systems for name identity, visual-object identity, and spatial location maintained in old age?

The dissociability of working memory for name identity (verbal information), visual objects, and spatial location was explored in 3 experiments. Consistent with previous results, the 3 working memory systems were dissociable in younger adults. Both younger and older adults showed involvement of name identity in an object identity task, and older adults showed this involvement in a spatial memory task. Results were interpreted as showing that the systems are generally separable but that involvement of 1 with another is possible and more likely in older adults. A 4th, correlational study showed that there is generalized decline in working memory systems in old age, with the age differences in memory mediated to a moderate extent by age-related differences in speed of processing. It was speculated that the specific, possibly strategic changes are independent of and take place against a backdrop of generalized loss of nervous system integrity.

Acoustic Stimulation↗

PubMed2001

Risk stratification for training in cardiac surgery.

BACKGROUND: There is a potential conflict of interest in providing the best possible outcome for patients undergoing cardiac surgery and good training for junior cardiac surgeons. METHODS: We analysed training with reference to volume of work, risk stratification and outcome for consultant and trainee procedures. The Parsonnet system was used for risk stratification. A retrospective audit was performed for a 6-year period. RESULTS: During the study period, 6037 operations were performed, of which 2166 were carried out by trainees. Direct consultant assistance in a trainee operation varied between 17% and 51% and increased towards the end of the study period. Of the operations performed by trainees, 88% were CABG. The median Parsonnet score for consultant operations was 9 compared with 4 for trainees. Actual mortality was below predicted for all surgeons. Morbidity was also lowest for trainees (10%). CONCLUSIONS: With appropriate case selection, trainees in cardiac surgery can achieve good results. As training changes in the UK, trainees should receive increased supervised exposure to a wider range of procedure to compensate for a lower volume of workload.

Adult↗