Biomedical subjects

Ashok Patel

Publications and source records attributed to Ashok Patel.

8 recordsLinked to original sources

PubMed2006

Microstructural white matter abnormalities in nodular heterotopia with overlying polymicrogyria.

Nodular heterotopia (NH) with overlying polymicrogyria can result in medically uncontrolled seizures. Most patients also exhibit deficits of function related to the location of the abnormal cortex. However, functional imaging studies show that the abnormal cortex can retain some function, making surgical planning difficult. It is not known if the connectivity of the abnormal cortex is normal. In this article, we performed an evaluation of molecular diffusion within the white matter in a patient with refractory epilepsy due to NH with overlying polymicrogyria. We observed that the white matter underlying the polymicrogyric area shows signs of microstructural abnormalities. This result suggests that the deficit of function from polymicrogyria result from both the structurally abnormal cortex and from its impaired connectivity.

Adult↗

PubMed2006

Correlation of the turbo-MP RIA with ImmunoCAP FEIA for determination of food allergen-specific immunoglobulin E.

It has been reported that in vitro measurement of food-specific IgE can be used to accurately predict food allergy and reduce the risk associated with double-blinded placebo-controlled food challenges (DBPCFC). Our objective was to assess the performance characteristics of the Hycor Turbo-MP quantitative radioimmunoassay for food-specific IgE and to determine this method's comparability to another assay, the Pharmacia ImmunoCAP fluorescence enzyme immunoassay (FEIA). The dynamic range of the Turbo-MP assay is 0.05 to 100 IU/ml, compared to 0.35 to 100 IU/ml for the FEIA. Performance characteristics of the Turbo-MP assay (ie, reproducibility of the calibration curve, within-run precision, total precision, parallelism, and linearity) were determined using samples from the Hycor serum bank. The precision (CV) of IgE calibrator replicates was <10%. The total precision (CV) of the Turbo-MP assay ranged from 8.8% to 18.4% for specific IgE concentrations between 0.28 to 31.4 IU/ml. Testing of serial dilutions of sera with IgE specificities for egg white, cow's milk, codfish, wheat, peanut, and soybean showed that the assay is linear over the entire dynamic range. Serial dilution data (slopes of 1.01 to 1.10) showed parallelism to serial dilutions of the IgE calibrator (slope of 0.96). The Turbo-MP and FEIA methods were both used for quantitative assays of food-specific IgE in 457 serum samples obtained from a clinical reference laboratory. Comparison of specific IgE results by the Turbo-MP and FEIA methods for 6 major food allergens exhibited a slope of 0.99 (0.92 to 1.03) with a correlation coefficient of 0.81.

Allergens↗

PubMed2005

Prostate cancer in patients with screening serum prostate specific antigen values less than 4.0 ng/dl: results from the cooperative prostate cancer tissue resource.

PURPOSE: Prostate cancer can occur in patients with low screening serum prostate specific antigen (PSA) values (less than 4.0 ng/ml). It is currently unclear whether these tumors are different from prostate cancer in patients with high PSA levels (greater than 4.0 ng/ml). MATERIALS AND METHODS: From the Cooperative Prostate Cancer Tissue Resource database through March 2004, 3,416 patients with screening PSA less than 16.0 ng/ml diagnosed with prostate cancer between 1993 and 2004 were stratified in groups based on screening serum PSA. These subsets were compared for race, age at diagnosis, clinical and pathological stage, Gleason score, positive surgical margins, posttreatment recurrent disease, and vital status. RESULTS: We identified 468 (14%) patients with screening PSA less than 4.0 ng/ml, 142 (4.2%) of whom had a PSA of less than 2.0 ng/ml. This group included 40 black and 376 white patients. Men with low screening PSA treated with radical prostatectomy had smaller cancers, lower Gleason scores, lower pathological tumor (T) stage and lower PSA recurrence rates than men with high PSA levels (4 ng/ml or greater). These differences held true for men who were younger than 62 years or were white, whereas older or black men had tumor characteristics and outcomes similar to those with higher PSA levels. CONCLUSIONS: Young (younger than 62 years) or white patients with screening serum PSA less than 4.0 ng/ml had smaller, lower grade tumors and lower recurrence rates than patients with PSA 4.0 ng/ml or greater. This was not true for those older than 62 years and for black men.

Humans↗

PubMed2004

Long-term fracture risk among children with asthma: a population-based study.

UNLABELLED: Fracture risk among patients diagnosed with asthma in childhood is greater in males and oral corticosteroid users, but most fractures are of the appendicular skeleton and may relate to impaired skeletal development. INTRODUCTION: There are no population-based data on fracture outcomes among the growing number of patients with asthma diagnosed in childhood. MATERIALS AND METHODS: We conducted a population-based retrospective (historical) cohort study among 279 Rochester, Minnesota, residents who were <35 years of age (mean, 6.2 years) when first diagnosed with asthma. Fractures were ascertained by review of comprehensive community medical records, and cases were compared directly with age- and sex-matched controls in a stratified proportional hazards model. Risk factors for fractures among the asthma cases were assessed using Andersen-Gill time-to-fracture regression models. RESULTS: During 6649 person-years of follow-up (median, 24.3 years/subject), 107 asthma patients experienced 189 fractures, for a crude fracture incidence rate of 2.8 per 100 person-years. The actuarially estimated cumulative fracture incidence after 20 years was 40% compared with 34% among controls (p = 0.122). There was no significant increase in overall fracture risk among cases compared to their age- and sex-matched controls (hazard ratio [HR], 1.3; 95% CI, 0.9-1.9), but males with asthma had a 2.6-fold greater risk of hand and finger fractures than control males. The independent predictors of overall fracture risk among the asthma patients included male gender (HR, 2.2; 95% CI, 1.5-3.2) and use of oral corticosteroids (HR, 2.0; 95% CI, 1.2-3.1) or anti-cholinergic agents (HR, 3.9; 95% CI, 1.5-10). CONCLUSIONS: Rather than osteoporotic fractures of the axial skeleton, oral corticosteroid therapy was associated here with limb fractures, suggesting a relationship with impaired development of a biomechanically competent skeleton. Additional studies are needed to assess this possibility.

Adolescent↗

PubMed2004

The tissue microarray data exchange specification: implementation by the Cooperative Prostate Cancer Tissue Resource.

BACKGROUND: Tissue Microarrays (TMAs) have emerged as a powerful tool for examining the distribution of marker molecules in hundreds of different tissues displayed on a single slide. TMAs have been used successfully to validate candidate molecules discovered in gene array experiments. Like gene expression studies, TMA experiments are data intensive, requiring substantial information to interpret, replicate or validate. Recently, an open access Tissue Microarray Data Exchange Specification has been released that allows TMA data to be organized in a self-describing XML document annotated with well-defined common data elements. While this specification provides sufficient information for the reproduction of the experiment by outside research groups, its initial description did not contain instructions or examples of actual implementations, and no implementation studies have been published. The purpose of this paper is to demonstrate how the TMA Data Exchange Specification is implemented in a prostate cancer TMA. RESULTS: The Cooperative Prostate Cancer Tissue Resource (CPCTR) is funded by the National Cancer Institute to provide researchers with samples of prostate cancer annotated with demographic and clinical data. The CPCTR now offers prostate cancer TMAs and has implemented a TMA database conforming to the new open access Tissue Microarray Data Exchange Specification. The bulk of the TMA database consists of clinical and demographic data elements for 299 patient samples. These data elements were extracted from an Excel database using a transformative Perl script. The Perl script and the TMA database are open access documents distributed with this manuscript. CONCLUSIONS: TMA databases conforming to the Tissue Microarray Data Exchange Specification can be merged with other TMA files, expanded through the addition of data elements, or linked to data contained in external biological databases. This article describes an open access implementation of the TMA Data Exchange Specification and provides detailed guidance to researchers who wish to use the Specification.

Confidentiality↗

PubMed2004

Long-term fracture risk following adult-onset asthma: a population-based study.

There are few data on skeletal outcomes in the growing population of patients with adult-onset asthma. We conducted a population-based retrospective (historical) cohort study among 226 residents of Rochester, Minnesota, USA, who were 35 years of age or older when first diagnosed with asthma. Fractures were ascertained by review of comprehensive community medical records, and observed fractures were compared with expected numbers based on incidence rates in the local population (standardized incidence ratios, SIR). During 4,022 person-years of follow-up, 100 patients experienced 211 fractures, for an actuarially estimated cumulative incidence of 63% after 30 years compared with 59% expected ( p=0.004). Statistically significant increases were seen for moderate trauma fractures of the vertebrae (SIR, 2.9; 95% CI, 2.1 to 3.8) and ribs (SIR, 2.0; 95% CI, 1.2 to 3.2), as well as the proximal femur (SIR, 1.8; 95% CI, 1.02 to 2.8). As assessed by proportional hazards models, the only independent predictors of any subsequent moderate trauma fracture were age (hazard ratio [HR] per 10-year increase, 1.7; 95% CI, 1.5 to 2.1) and cumulative corticosteroid dose greater than the median of 1,775 mg (HR, 1.8; 95% CI, 1.1 to 3.0). In another multivariate analysis, the predictors of a moderate trauma vertebral fracture were older age (HR, 1.6; 95% CI, 1.3 to 2.1), concomitant chronic obstructive pulmonary disease (HR, 2.4; 95% CI, 1.2 to 4.9), cigarette smoking (HR, 2.3; 95% CI, 1.2 to 4.8), and cumulative corticosteroid dose greater than the median (HR, 2.6; 95% CI, 1.4 to 5.0). Other asthma therapies did not contribute significantly to these models. Thus, a 70% increase in overall fracture risk among unselected community patients with adult onset asthma was mainly confined to the subset who also had chronic obstructive pulmonary disease and was influenced by substantial corticosteroid use.

Accidental Falls↗

PubMed2003

Association between the cholesteryl ester transfer protein TaqI-detectable B polymorphism and low high-density lipoprotein cholesterol concentration in Saudis.

Plasma concentrations of HDL (high-density lipoprotein) cholesterol are low in the Saudi Arabian population. A B polymorphism at the CETP (cholesteryl ester protein transfer) locus that is detectable with the restriction enzyme Taq I is a genetic determinant of the plasma HDL cholesterol concentration. We assessed the relationship between the Taq I B CETP polymorphism and lipid and apolipoprotein concentrations in a study sample of 335 Saudi residents. The Taq I B1 and B2 allele frequencies were 0.54 and 0.46 respectively, similar to those in other populations. HDL cholesterol levels in B2B2 homozygotes were significantly higher than in B1B1 homozygotes [1.01 (0.3) compared with 0.92 (0.2) mmol/l; mean (S.D.); P=0.03]. There was also a significant difference between the B2B2 and B1B1 homozygotes with regard to apolipoprotein AI concentration [123.6 (16.4) compared with 113.7 (13.9) mg/dl; P=0.04]. This genetic variation was independent of metabolic risk factors known to influence HDL cholesterol levels. The allele frequency of the Taq I B CETP polymorphism and its relatively modest impact on HDL cholesterol concentrations argue against an important role for this allele, or for strongly linked loci, in determining the low levels of HDL cholesterol seen in the Saudi population.

Adult↗

PubMedDate not supplied

Stochastic resonance in noisy spiking retinal and sensory neuron models.

Two new theorems show that small amounts of additive white noise can improve the bit count or mutual information of several popular models of spiking retinal neurons and spiking sensory neurons. The first theorem gives necessary and sufficient conditions for this noise benefit or stochastic resonance (SR) effect for subthreshold signals in a standard family of Poisson spiking models of retinal neurons. The result holds for all types of finite-variance noise and for all types of infinite-variance stable noise: SR occurs if and only if a sum of noise means or location parameters falls outside a 'forbidden interval' of values. The second theorem gives a similar forbidden-interval sufficient condition for the SR effect for several types of spiking sensory neurons that include the Fitzhugh-Nagumo neuron, the leaky integrate-and-fire neuron, and the reduced Type I neuron model if the additive noise is Gaussian white noise. Simulations show that neither the forbidden-interval condition nor Gaussianity is necessary for the SR effect.

Algorithms↗