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Biomedical subjects

B Viswanathan

Publications and source records attributed to B Viswanathan.

16 recordsLinked to original sources
PubMed2001

Diagnostic plots for assessing the frailty distribution in multivariate survival data.

In biomedical studies, frailty models are commonly used in analyzing multivariate survival data, where the objective of the study is to estimate both the covariate effect and the dependence between the multivariate survival times. However, inference based on these models are dependent on the distributional assumption of frailty. We propose a diagnostic plot for assessing the frailty assumption. The proposed method is based on the cross-ratio function and the diagnostic plot suggested by Oakes (1989). We use kernel regression smoothing with bandwidth choice by cross-validation, to obtain the proposed plot. The resulting plot is capable of differentiating between the gamma and positive stable frailty models when strong association is present. We illustrate the feasibility of our method using simulation studies under known frailty distributions. The approach is applied to data on blindness for each eye of diabetic patients with adult onset diabetes and a reasonable fit to the gamma frailty model is found.

Blindness↗
PubMed1990

Endothelial cells enhance spontaneous metastasis of human lung carcinoma cells in athymic mice.

The process of adhesion to endothelial cells is an important step in the progression to metastatic disease. The use of human neoplastic cell lines (now increasingly used in the study of the mechanisms of metastasis) in studying interactions with normal endothelial cells is therefore pertinent. In this report, the enhanced ability of a metastatic variant, MV522, of a human lung carcinoma cell line to adhere to endothelial cell monolayers is demonstrated. The ability to spontaneously metastasize from subcutaneous sites in athymic mice, of in vitro selected endothelial adhesive subpopulations of MV522 is also shown.

Animals↗
PubMed1985

Right ventricular myxoma.

This report describes a patient with right ventricular myxoma in whom two-dimensional echocardiography was the sole means of diagnosis and provided sufficient justification for surgical intervention without further invasive workup. A review of the literature also is presented.

Adult↗
PubMed1983

Hemodynamic assessment of the circulation in 200 normal hands.

The frequent use of arterial puncture, cannulation, and A-V shunting has demonstrated a greater degree of safety than could be predicted from previous anatomic and angiographic studies. Using a noninvasive technique, the status of the superficial palmar arch (SPA) and relative contributions of radial and ulnar arteries were determined in 100 volunteers with no history of vascular disease. Although there was no significant difference in the diameter of the vessels at the wrist, the flows showed statistically significant ulnar dominance, suggesting that the difference is a factor of a lower distal resistance on the ulnar side. The lower resistance across the ulnar bed probably is responsible for the clinically observed ease of sacrifice of the radial artery contribution to palmar flow. The SPA was found to be incomplete in 11.0% of the hands.

Adult↗
PubMed1975

Peripheral iridectomy with scleral cautery for glaucoma.

Peripheral iridectomy with cautery (Scheie operation) was carried out on 113 eyes with glaucoma. The results were so favorable and the complications so few that we believe this operation still has an important place in the surgical management of the glaucomas and is noteworthy in the light of the trend to more precise surgery of the canal of Schlemm and the trabeculae.

Anesthesia, Local↗
PubMedDate not supplied

Physiologic anatomy of the palmar circulation in 200 normal hands.

The functional capacity of the Superficial Palmar Arch (SPA) was evaluated in 200 normal hands by a non-invasive narrow beam ultrasonic technique. Peak systolic velocity of flow with radial artery occlusion increased in all SPAs except for 22 (11%) which were considered incomplete. Ulnar artery occlusion resulted in a more variable response including 89 (45%) SPAs with bidirectional flow. SPA blood flow is complex but understandable in terms of hand blood flow and vascular bed resistance. The use of tobacco does not increase the incidence of incomplete SPAs.

Adult↗