Sankara Sethuraman

Intimal Thickness and Layering, and Smooth Muscle Cell Phenotypes in Aorta of Youth

Proneness to the lesions of atherosclerosis varies along the length and circumferential topography of the aorta. Smooth muscle cells, in particular those of the ‘modulated’ synthetic phenotype which are able to proliferate and synthesize matrix proteins, are considered to play an important role in lesion progression. We report on a study of the aortic intima at a lesion-prone site from abdominal aorta and a lesion-resistant site from thoracic aorta in young humans to determine (1) whether the histologic structure and the smooth muscle cell composition show quantitative differences between lesion-prone and lesion-resistant aortic sites; (2) whether there are gender differences, and (3) whether any differences increase in degree with increasing age in this young population. Material for this study was obtained as part of the NIH-funded multicenter study on Pathobiological Determinants of Atherosclerosis in Youth (PDAY) from autopsies of male and female subjects between the ages of 15 and 34, victims of unexpected sudden death, usually from trauma. The samples consisted of strips of abdominal and thoracic aorta, all derived from the same anatomical sites standardized in the PDAY studies. The thickness of total intima (TI) and its elastic hyperplastic (EH) layer was measured. Smooth muscle cells of all types (SMC) and separately those of the synthetic phenotype (SynSMC) were quantified in each site using immunohistochemical procedures in replicate sections of uniform thickness. The intima of the atherosclerotic lesion-prone dorsal half of the abdominal aorta (AD) shows significant differences from the lesion-resistant ventral half of thoracic aorta (TV) in that (1) its EH layer is significantly thicker; (2) its EH layer has a comparatively higher number of both total SMC and SynSMC, even when adjusted for intimal thickness, and (3) the age-related increase in thickness of both TI and EH layer of AD is much greater than that of TV.

Ischemic colitis: A forgotten entity. Results of a retrospective study in 118 patients

The aim of our study was to document our 6‐year experiences in identifing the clinical characteristics, laboratory findings, risk factors and the outcomes of patients with ischemic colitis (IC) in a community hospital setting.

Maximum likelihood estimation for a fractionally differenced autoregressive model on a two-dimensional lattice

Abstract A two-dimensional time series model with long-memory dependence is introduced. The model is based on a fractionally differenced autoregressive process (long-memory) combined with a standard p th order stationary autoregressive process (short-memory). The maximum likelihood estimators for the parameters in the model are derived and their asymptotic distributions are obtained. A novel feature of the derivations is that a new two-dimensional martingale representation is used.

Parameter estimation in a stationary autoregressive process with correlated multiple observations

Abstract An autoregressive process is proposed to model time series data with multiple observations at each time point. The joint autocorrelation function for the model has a product form, the first factor being the autocorrelation function for a stationary AR( p ) process and the second factor involving a constant intraclass correlation ρ. The least-squares and the Gaussian maximum likelihood estimators of the autoregression parameters θ =( θ 1 ,…, θ p ) T and the intraclass correlation ρ are presented and their limit distributions are derived.

Is CT Angiogram of the Abdominal Vessels Needed following the Diagnosis of Ischemic Colitis? A Multicenter Community Study

Background. CT angiogram is frequently obtained after diagnosis of ischemic colitis (IC). Aims. To investigate the vascular findings of CT angiogram as compared to contrast-enhanced CT scan and whether this modality changes the management or prognosis of IC. Methods. We conducted a retrospective analysis of patients with IC from 2007 to 2013. Results. CT angiogram was performed in 34 patients (28.81%), whereas contrast-enhanced CT scan was performed in 54 patients (45.76%). In CT angiogram group, 8 patients (23.5%) had atherosclerotic changes. Stenosis was found in 12 patients (35.3%) (9: celiac trunk, 3: SMA). Among this group, one patient underwent colectomy and another underwent angioplasty of the celiac trunk who died within 30 days. Among contrast-enhanced CT scan group, 5 patients (9.3%) had atherosclerotic changes. Stenosis was found in 5 patients (9.3%) (3: celiac trunk, 1: SMA, and 1: IMA). Among this group, 3 patients had colectomy and one died within 30 days. There was no statistical difference between both groups in all vascular findings except the stenosis which was higher in CT angiogram group (P = 0.0025). Neither the need for surgery nor all-cause mortality was different between both groups. Conclusion. CT angiogram did not provide any useful findings that altered the management or the prognosis of IC.

Large sample inference for a multivariate linear model with autocorrelated errors

Abstract We consider a multivariate linear model with autocorrelated errors. The mean vector of the process is assumed to be linear in the time-trend parameter β and the within-group variation parameter γ. The least-squares estimators of β and γ, and the related estimators of the autoregressive parameter θ and the error covariance matrix Σ are derived and their asymptotic distributions are obtained. Large sample tests of H1:γ=0 and H2:β=0are derived and the limit distributions of the restricted least-squares estimators βH1 and γH2 are obtained under H1 and H2, respectively.

A Simplified Quantitative Method to Measure Brain Shifts in Patients with Middle Cerebral Artery Stroke

A standardized and validated method to measure brain shifts in malignant middle cerebral artery (MCA) stroke with decompressive hemicraniectomy (DHC) could facilitate clinical decision making, prognostication, and comparison of results between studies.

Pre-stroke glycemia in patients with diabetes

AIMS Hyperglycemia in type 2 diabetes mellitus (T2D) remains uncontrolled in approximately 50% of patients in the United States. Uncontrolled T2D is associated with various vascular complications, including stroke. We studied demographic and clinical factors association with pre-stroke glycemia, indicated by glycated hemoglobin (HbA1c), in acute stroke patients with T2D. METHODS Using a questionnaire, we collected demographic, socioeconomic, and clinical information from 300 acute ischemic and hemorrhagic stroke patients in one hospital. We analyzed factors associated with HbA1c in patients with history of T2D. RESULTS There were 111 patients with history of T2D and HbA1c measured on admission. In multivariable analyses factors associated with higher HbA1c were treatment with insulin (p=0.05), history of hyperlipidemia (p=0.01), and total cholesterol level (p=0.02). Poor adherence to T2D treatment was associated with higher HbA1c levels (p=0.006) only in a subgroup of patients with HbA1c ≥8%. CONCLUSION Insulin treatment and hyperlipidemia are associated with higher HbA1c levels in acute stroke patients with T2D. Poor adherence to diabetes treatment is associated with higher HbA1c levels only among patients with HbA1c ≥8%.

Empowering Young Children in Poverty by Improving Their Home Literacy Environments

ABSTRACT An innovative DVD of classic nursery rhymes and stories empowered at-risk kindergarten children to control in the home when and how much they listen, promoting better listening, reading, and overall literacy comprehension skills. Coupled with modest teacher training, and limited use in the classroom, the DVD generated dramatic vocabulary growth in nine months and remarkably higher reading scores three years later. Funded by a Georgia Improving Teacher Quality grant, the study was conducted in 33 kindergarten classrooms in 31 Title I schools, each of which normally produced significantly below average test scores in reading. The study documents 459 kindergarten students’ mean improvement from the 27th to the 47th percentile on the Peabody Picture Vocabulary Test (PPVT-III). The 303 students who remained in the system as 3rd graders and took Georgia’s statewide Criterion Referenced Competency Test in reading failed to meet standards less than half as often (7.6% vs. 16.13%) as their system peers, and scored in the highest range 35% more often (39.6% vs. 27.02%). Forty thousand DVDs have since been distributed and the DVD’s ten hours of audio, text, and pictures are now freely available online at hearatale.org.

Large sample estimation in nonstationary autoregressive processes with multiple observations

The asymptotic distributions of the least-squares estimators of the parameters in autoregressive processes with multiple observations are derived for the two nonstationary cases, viz., (a) the explosive case and (b) the unstable case. It is shown that nonstandard limit distributions are obtained.