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R N Bryan

Publications and source records attributed to R N Bryan.

At least 19 recordsLinked to original sources
PubMed2001

Association between blood pressure level and the risk of myocardial infarction, stroke, and total mortality: the cardiovascular health study.

BACKGROUND: Recent reports have drawn attention to the importance of pulse pressure as a predictor of cardiovascular events. Pulse pressure is used neither by clinicians nor by guidelines to define treatable levels of blood pressure. METHODS: In the Cardiovascular Health Study, 5888 adults 65 years and older were recruited from 4 US centers. At baseline in 1989-1990, participants underwent an extensive examination, and all subsequent cardiovascular events were ascertained and classified. RESULTS: At baseline, 1961 men and 2941 women were at risk for an incident myocardial infarction or stroke. During follow-up that averaged 6.7 years, 572 subjects had a coronary event, 385 had a stroke, and 896 died. After adjustment for potential confounders, systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse pressure were directly associated with the risk of incident myocardial infarction and stroke. Only SBP was associated with total mortality. Importantly, SBP was a better predictor of cardiovascular events than DBP or pulse pressure. In the adjusted model for myocardial infarction, a 1-SD change in SBP, DBP, and pulse pressure was associated with hazard ratios (95% confidence intervals) of 1.24 (1.15-1.35), 1.13 (1.04-1.22), and 1.21 (1.12-1.31), respectively; and adding pulse pressure or DBP to the model did not improve the fit. For stroke, the hazard ratios (95% confidence intervals) were 1.34 (1.21-1.47) with SBP, 1.29 (1.17-1.42) with DBP, and 1.21 (1.10-1.34) with pulse pressure. The association between blood pressure level and cardiovascular disease risk was generally linear; specifically, there was no evidence of a J-shaped relationship. In those with treated hypertension, the hazard ratios for the association of SBP with the risks for myocardial infarction and stroke were less pronounced than in those without treated hypertension. CONCLUSION: In this population-based study of older adults, although all measures of blood pressure were strongly and directly related to the risk of coronary and cerebrovascular events, SBP was the best single predictor of cardiovascular events.

Aged↗
PubMed2000

CPT-EIA assays for the detection of vancomycin resistant vanA and vanB genes in enterococci.

Cycling Probe Technology (CPT) was combined with a colorimetric enzyme-immuno assay (EIA) to develop two assays for the detection of vanA and vanB genes in vancomycin resistant enterococci (VRE). The CPT-EIA assay employs a gene-specific fluorescein labeled DNA-RNA-DNA probe that gets cleaved within the probe : target duplex. The cleaved DNA probe fragments dissociate from the target, making it available for further cycling. Following the separation of cleaved probe fragments, anti-fluorescein-horseradish peroxidase antibodies are used for the detection of uncleaved probes. The two CPT-EIA assays were used to screen a collection of 440 clinical isolates (Modrusan et al., 1999). All of the 154 VanA and 131 VanB isolates were correctly identified in the vanA and vanB CPT-EIA, respectively. The VanA and VanB isolates were differentiated from vancomycin sensitive enterococci (VSE) and also from the VanC isolates. In addition, an accurate VRE detection in the CPT-EIA assay was shown with cultures grown on eight different media.

Anti-Bacterial Agents↗
PubMed2000

Neuroimaging variables related to development of Secondary Attention Deficit Hyperactivity Disorder after closed head injury in children and adolescents.

OBJECTIVE: To characterize children who develop Secondary Attention Deficit Hyperactivity Disorder (S-ADHD) after severe and moderate closed head injury (CHI) according to neuroimaging variables. METHOD: Ninety-nine children from 4-19 years who suffered severe and moderate CHI were prospectively followed for a year after injury. Premorbid psychiatric status was determined by administration to the parent of a structured psychiatric interview. This interview was readministered 1 year after injury to determine the presence of post-closed head injury S-ADHD. An MRI was performed 3 months after injury to define lesion locations and volumes. RESULTS: A set of multiple logistic regression models determined that the odds of developing S-ADHD were 3.64 times higher among children with thalamus injury, and 3.15 times higher among children with basal ganglia injury. There was no significant difference in lesion volumes in any of the locations of interest between the group who developed S-ADHD and the group who did not develop S-ADHD. CONCLUSION: The data support an association between S-ADHD and injury in either or both the thalamus and basal ganglia, but they do not definitively demonstrate whether injury in either structure has an effect on S-ADHD in the absence of injury in the other.

Adolescent↗
PubMed2000

One-year age changes in MRI brain volumes in older adults.

Longitudinal studies indicate that declines in cognition and memory accelerate after age 70 years. The neuroanatomic and neurophysiologic underpinnings of cognitive change are unclear, as there is little information on longitudinal brain changes. We are conducting a longitudinal neuroimaging study of nondemented older participants in the Baltimore Longitudinal Study of Aging. This report focuses on age and sex differences in brain structure measured by magnetic resonance imaging during the first two annual evaluations. Cross-sectional results from 116 participants aged 59-85 years reveal significantly larger ventricular volumes and smaller gray and white matter volumes in older compared with younger participants and in men compared with women. Regional brain volumes show that the effects of age and sex are not uniform across brain regions. Age differences are greatest for the parietal region. Sex differences tend to be larger for frontal and temporal than parietal and occipital regions. Longitudinal analysis demonstrates an increase of 1526 mm(3) in ventricular volume over 1 year, but no detectable change in total or regional brain volumes. Definition of the pattern and rate of longitudinal brain changes will facilitate the detection of pathological brain changes, which may be predictors of dementia.

Age Factors↗
PubMed1999

Neuroanatomic and functional correlates of depressed mood: the Cardiovascular Health Study.

Although a number of studies suggest an association between stroke and depression, few have examined the relation between magnetic resonance imaging (MRI)-identified lesions and depression among community-dwelling older adults. This cross-sectional study sought to assess the association between MRI infarcts in the basal ganglia and non-basal-ganglia areas, potential functional consequences of these lesions, and depressive symptomatology in 3,371 US men and women aged 65 years or older who participated in the Cardiovascular Health Study between 1992 and 1994. By using multiple linear regression models, the authors found that after adjustment for age, gender, and stroke history, Center for Epidemiologic Studies Depression Scale scores were independently associated with non-basal-ganglia lesions (p = 0.04) but were not independently associated with basal ganglia lesions (p = 0.11). When measures of physical disability and cognitive impairment were added to the models, these measures displaced MRI-identified infarcts in their association with depressive symptoms. In additional models, hemispheric location and size of the basal ganglia lesion were found to have no relation to depression levels. These results suggest that the functional consequences of cerebrovascular disease may be the causal pathway by which basal ganglia and non-basal-ganglia lesions are associated with depressive symptomatology.

Activities of Daily Living↗
PubMed1999

Relation of education to brain size in normal aging: implications for the reserve hypothesis.

OBJECTIVE: To examine the relations between education and age-related changes in brain structure in a nonclinical sample of elderly adults. BACKGROUND: Education may protect against cognitive decline in late life--an observation that has led to the "reserve" hypothesis of brain aging. Little is known, however, about the effect of education on age-related changes in brain structure. METHODS: Quantitative MRI of the brain was performed in 320 elderly volunteers (age range, 66 to 90 years) living independently in the community (Mini-Mental State Examination scores > or =24), all of whom were participants in the Cardiovascular Health Study. Blinded measurements of global and regional brain size were made from T1-weighted axial images using computer-assisted edge detection and trace methodology. High measurement reliabilities were obtained. RESULTS: Regression analyses (adjusting for the effects of intracranial size, sex, age, age-by-sex interactions, and potential confounders) revealed significant main effects of education on peripheral (sulcal) CSF volume-a marker of cortical atrophy. Each year of education was associated with an increase in peripheral CSF volume of 1.77 mL (p<0.03). As reported previously, main effects of age (but not education) were observed for all of the remaining brain regions examined, including cerebral hemisphere volume, frontal region area, temporoparietal region area, parieto-occipital region area, lateral (Sylvian) fissure volume, lateral ventricular volume, and third ventricle volume. CONCLUSIONS: The authors' findings demonstrate a relation between education and age-related cortical atrophy in a nonclinical sample of elderly persons, and are consistent with the reserve hypothesis as well as with a small number of brain imaging studies in patients with dementia. The neurobiological basis and functional correlates of this education effect require additional investigation.

Aged↗
PubMed1999

Detection of vancomycin resistant genes vanA and vanB by cycling probe technology.

Cycling Probe Technology (CPT) has been used to develop gene-based assays for detection of vancomycin resistance genes vanA and vanB in enterococci (VRE). Cycling Probe Technology utilizes a chimeric DNA-RNA-DNA probe that is cleaved by the enzyme RNase H when hybridized to its complementary DNA target. Conversion of full-length probe into the cleaved probe fragments is the basis for detection and quantification of the CPT reaction. Two gene-specific probes, each one unique to either the vanA or vanB gene, were utilized for development of vanA and vanB CPT assays, respectively. Both vanA and vanB CPT assays were used to determine the presence or absence of the corresponding gene in 440 clinical enterococcal isolates. The presence of vanA and vanB gene sequences was detected in 154 and 131 isolates, respectively. Phenotypic characterization of all isolates was determined through interpretation of conventional susceptibility data obtained with the disk diffusion method. Comparison between disk diffusion characterization and CPT assays revealed 11 discrepant isolates. The identity of these isolates was resolved by polymerase chain reaction (PCR) which confirmed the vanA and vanB CPT assay data. Therefore, compared to conventional phenotyping, both the vanA and vanB CPT assays appeared superior for accurate identification of VanA and VanB isolates.

Bacterial Proteins↗
PubMed1999

Rapid detection of the mecA gene in methicillin resistant staphylococci using a colorimetric cycling probe technology.

A Cycling Probe Technology (CPT) assay was developed for the detection of the mecA gene from methicillin resistant staphylococcal cultures. The assay is based on a colorimetric enzyme-immuno-assay (EIA) and uses a mecA probe (DNA-RNA-DNA) labeled with fluorescein at the 5'-terminus and biotin at the 3'-terminus. The reaction occurs at a constant temperature that allows the target DNA to anneal to the probe. RNase H cuts the RNA portion, allowing the cut fragments to dissociate from the target, making it available for further cycling. CPT-EIA uses streptavidin-coated microplate wells to capture uncut probe followed by detection with horseradish-peroxidase conjugated anti-fluorescein antibody. The assay was compared to PCR and shown to accurately detect the presence or absence of the mecA gene in 159 staphylococcal clinical isolates. The CPT-EIA assay takes two hours starting from cultured cells compared with the 24-48 h required for detection of methicillin resistance by conventional susceptibility tests.

Bacterial Proteins↗
PubMed1999

Nonlinear elastic registration of brain images with tumor pathology using a biomechanical model.

A biomechanical model of the brain is presented, using a finite-element formulation. Emphasis is given to the modeling of the soft-tissue deformations induced by the growth of tumors and its application to the registration of anatomical atlases, with images from patients presenting such pathologies. First, an estimate of the anatomy prior to the tumor growth is obtained through a simulated biomechanical contraction of the tumor region. Then a normal-to-normal atlas registration to this estimated pre-tumor anatomy is applied. Finally, the deformation from the tumor-growth model is applied to the resultant registered atlas, producing an atlas that has been deformed to fully register to the patient images. The process of tumor growth is simulated in a nonlinear optimization framework, which is driven by anatomical features such as boundaries of brain structures. The deformation of the surrounding tissue is estimated using a nonlinear elastic model of soft tissue under the boundary conditions imposed by the skull, ventricles, and the falx and tentorium. A preliminary two-dimensional (2-D) implementation is presented in this paper, and tested on both simulated and patient data. One of the long-term goals of this work is to use anatomical brain atlases to estimate the locations of important brain structures in the brain and to use these estimates in presurgical and radiosurgical planning systems.

Biomechanical Phenomena↗
PubMed1999

TCD, MRA and MRI in acute cerebral ischemia.

OBJECTIVES: The aim of this study was to determine accuracy of transcranial Doppler ultrasound (TCD) and compare efficacy of three non-invasive tests [TCD, magnetic resonance angiography (MRA), and magnetic resonance imaging (MRI)] in patients with acute cerebral ischemia. MATERIAL AND METHODS: This prospective study involved 30 patients. MRI, MRA, and TCD were performed within 24 h after onset of ictus. The 2nd MRI was repeated at 48-72 h and was used as the standard for the evaluation of sensitivity and specificity of MRA, TCD, and initial MRI. RESULTS: TCD showed a sensitivity of 96% and a specificity of 33% for recognizing abnormal cerebral blood flow velocities. MRA showed a sensitivity of 46% and a specificity of 75% for assessing intracranial vascular anatomy, while initial MRI revealed a sensitivity of 84% and a specificity of 100% for evaluation of ischemic parenchymal changes. CONCLUSION: Our results revealed that TCD is an accurate indicator of blood flow status and correlated well with MRI, MRA abnormalities in acute stroke.

Adult↗
PubMed1999

Is the spatial distribution of brain lesions associated with closed-head injury predictive of subsequent development of attention-deficit/hyperactivity disorder? Analysis with brain-image database.

PURPOSE: To determine whether there is an association between the spatial distribution of lesions detected at magnetic resonance (MR) imaging of the brain in children after closed-head injury and the development of secondary attention-deficit/hyperactivity disorder (ADHD). MATERIALS AND METHODS: Data obtained from 76 children without prior history of ADHD were analyzed. MR images were obtained 3 months after closed-head injury. After manual delineation of lesions, images were registered to the Talairach coordinate system. For each subject, registered images and secondary ADHD status were integrated into a brain-image database, which contains depiction (visualization) and statistical analysis software. Using this database, we assessed visually the spatial distributions of lesions and performed statistical analysis of image and clinical variables. RESULTS: Of the 76 children, 15 developed secondary ADHD. Depiction of the data suggested that children who developed secondary ADHD had more lesions in the right putamen than children who did not develop secondary ADHD; this impression was confirmed statistically. After Bonferroni correction, we could not demonstrate significant differences between secondary ADHD status and lesion burdens for the right caudate nucleus or the right globus pallidus. CONCLUSION: Closed-head injury-induced lesions in the right putamen in children are associated with subsequent development of secondary ADHD. Depiction software is useful in guiding statistical analysis of image data.

Adolescent↗
PubMed1999

Early and delayed MR and PET changes after selective temporomesial radiosurgery in mesial temporal lobe epilepsy.

We report a patient with medically refractory mesial temporal lobe epilepsy treated by gamma knife radiosurgery. In lieu of a microsurgical procedure, an entorhinoamygdalohippocampectomy was performed with a gamma knife and low marginal doses (25 Gy). The clinical and imaging studies, including CT, MR imaging, 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), and long-term follow-up MR examinations, are reported. The patient has been seizure-free since the day of treatment, with no clinical complications. MR studies accurately depicted the effect on the target structures and the transient secondary changes around them. FDG-PET scans showed decreased metabolism after gamma knife surgery throughout the anteromesial part of the epileptogenic temporal lobe. This metabolic decrease was reversible in the lateral temporal cortex. Our case suggests that gamma knife surgery is a promising tool for use as a minimally invasive approach to the treatment of epilepsy.

Adult↗
PubMed1999

MR perfusion imaging.

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Cerebrovascular Circulation↗
PubMed1999

Prevalence and anatomic characteristics of infarct-like lesions on MR images of middle-aged adults: the atherosclerosis risk in communities study.

BACKGROUND AND PURPOSE: MR imaging has revealed putative evidence of subclinical cerebrovascular disease (CVD) as reflected by white matter signal changes and infarct-like lesions (ILLs). Nonetheless, the prevalence of this condition in the general population has been defined only to a limited extent. We herein report the prevalence and anatomic characteristics of ILLs seen on cranial MR images obtained as part of a population-based study of cardiovascular disease in middle-aged adults. These results are contrasted to those of previous similar studies, particularly those of an elderly population in the Cardiovascular Health Study (CHS). METHODS: This Atherosclerosis Risk in Communities (ARIC) cohort consists of a probability sample of community-living persons who were 55 to 72 years old at the time of MR examination. MR imaging of 1890 participants was performed at two ARIC field centers, based on a common protocol. MR studies were evaluated by trained readers at the MR Reading Center using original digital data displayed on a high-resolution workstation. The measures of lesion size, anatomic location, and signal intensity were collected. The definition for an ILL was a non-mass, hyperintense region with an arterial vascular distribution on spin-density and T2-weighted images. RESULTS: Two hundred ninety participants had ILLs, for an overall prevalence of 15.3%. Eighty-two percent of participants with ILLs had lesions that were 3 mm or larger in maximal dimension, although 87% of these lesions were 20 mm or smaller in maximal dimension. The prevalence of ILLs increased with age, from 7.9% in the 55- to 59-year-old age group to 22.9% in the 65- to 72-year-old age group (P < .001). Lesion prevalence was greater in black (20.7%) than in white persons (10.2% [P < .0001]), but did not differ significantly between male and female participants. The basal ganglia and thalamic region was the most commonly affected anatomic site, accounting for 78.9% of the lesions. CONCLUSION: Considering that the prevalence of self-reported stroke or transient ischemic attack in ARIC participants is 1.5%, these results suggest that there is significantly more subclinical than clinical CVD in the general population. Furthermore, the prevalence of this subclinical disease increases with age, and is greater in black persons. ILLs are dominated by "lacunae" in the basal ganglia and thalamus. These results are, in general, similar to those of a comparable study of elderly participants in the CHS, except for a 60% lower prevalence of ILLs in this younger population.

Age Factors↗
PubMed1998

Sex differences in brain aging: a quantitative magnetic resonance imaging study.

BACKGROUND: Little is known about the effect of sex on age-related changes in brain structure. METHODS: Quantitative magnetic resonance imaging of the brain was performed in 330 elderly (age range, 66-96 years) volunteers living independently in the community, all of whom were participants in the Cardiovascular Health Study. Blinded measurements of global and regional brain size were made from T1-weighted axial images by means of computer-assisted edge detection and trace methods. High measurement reliabilities were obtained. RESULTS: Age-specific changes in brain size were significantly greater in men than women for the peripheral (sulcal) cerebrospinal fluid volume, the lateral (sylvian) fissure cerebrospinal fluid volume, and the parieto-occipital region area. Main effects of age were observed for all the remaining brain regions examined (cerebral hemisphere volume, frontal region area, temporoparietal region area, lateral ventricular volume, and third ventricle volume), but these effects were similar in men and women. Asymmetries in brain structures were not affected by aging in either sex. CONCLUSIONS: Our results are generally consistent with the few published studies on sex differences in brain aging and suggest that, for at least some structures, aging effects may be more apparent in men than women. The neurobiological bases and functional correlates of these sex differences require further investigation.

Age Distribution↗
PubMed1998

Craniocerebral magnetic resonance imaging measurement and findings in Lesch-Nyhan syndrome.

OBJECTIVE: To provide the first comprehensive magnetic resonance imaging (MRI) assessment of brain in a series of patients with Lesch-Nyhan syndrome (LNS), with emphasis on basal ganglia measurements. DESIGN: Routine readings of MRI studies, repeated reading in random order blinded to subject diagnosis, and 3-dimensional volumetric measures of basal ganglia regions. SETTING: The Johns Hopkins Hospital, Baltimore, Md. PATIENTS: Seven patients with LNS who have hypoxanthine guanine phosphoribosyltransferase levels less than 1.6% and characteristic clinical features of the disorder, which include hyperuricemia, cognitive impairment, and dystonic movement disorder, were compared with 7 age-matched control subjects. Five of the 7 patients demonstrated self-injurious behavior. MRI studies were performed using general anesthesia because of the severity of the movement disorder. MAIN OUTCOME MEASURES: Measurement of brain regions from MRI-obtained images. RESULTS: Routine readings described mild cerebral atrophy in 2 of 7 patients, but no caudate or putamen abnormalities were reported. However, on the directed blinded rereading, small caudates were suspected in 5 of 7 cases, and abnormalities in cerebral size and cranium were identified. Volumetric studies of the patients with LNS confirmed a 34% decrease in caudate volume (P<.001), a 17% decrease in total cerebral volume (P<.03), and a 12% decrease in putamen volume (P=.19). CONCLUSIONS: To our knowledge, this is the first demonstration of consistent neuroanatomic abnormalities in LNS. The findings of reduced basal ganglia volume are consistent with the dystonic movement disorder.

Adult↗