EFFECT OF BETA S HAPLOTYPES ON THE RHEOLOGICAL CHARACTERISTICS OF SICKLE RBCS

本研究主要旨在确定β-单倍型和RBC 我们目前的镰状细胞贫血患者的变形能力。 一个主要 具体目的是确定β单倍型（贝宁，CAR， 塞内加尔）对红细胞变形性有无影响。 此外 还将测定α基因数和Hb F水平。 另一个主要 目的是确定镰状红细胞的流变学特性， 稳态和疼痛危象中的患者， 单倍型和α基因数。 第三个目标是确定 羟基脲对镰刀流变性能的影响 体内红细胞。 研究的这一部分将是一个平行项目 羟基脲（HU）治疗镰状细胞性贫血的多中心研究。 基因组DNA将从以下患者的外周白色血细胞制备： 镰状细胞性贫血患者。 α基因数量和 β-单倍型将通过Southern印迹技术确定，或 聚合酶链反应（PCR）。 红细胞的流变特性将 包括：1）用Ektacytometry测定红细胞变形性; 2）红细胞数量 通过在不连续Stractan上离心测定致密细胞 密度梯度和3）RBC阳离子（Na+和K+）通过火焰测定 测光法 流变学研究将在未分级的 细胞以及密度定义的细胞。 预计至少 我们的15名患者将入组HU研究。 多基线 研究（每月至少确定三项）将在 在药物治疗开始前进行。 流变研究 将在开始药物治疗后每月进行一次 研究结束后至少4个月 药物治疗。 此外，51 Cr标记的自体移植的存活率 红细胞、骨髓51 Fe摄取、血浆铁周转和 还将确定铁的利用率。 这些红细胞动力学研究 将在开始羟基脲/安慰剂治疗前进行， 此后每六个月。 他们也将确定4-6个月 在停止药物治疗后。 必须强调的是，在研究过程中， 研究者将无法访问任何数据，例如MCV， 变形指数等，这可能会打破双盲性质的 study. 我们希望这项研究将产生的数据将：1）澄清的因素 影响镰状细胞性贫血临床表型; 2）阐明 在疼痛的镰状细胞病期间发生的病理生理变化 危机;和3）提供深入了解的作用机制，胡及其 不是继发于Hb F水平升高的细胞效应。 此外，测定红细胞的流变学特性， 监测对HU的响应的价值。

This study is primarily designed to determine beta-haplotypes and RBC deformability on our current patients with sickle cell anemia. A major specific objective is to determine if the beta haplotype (Benin, CAR, Senegal) has an effect on RBC deformability or not. In addition the alpha-gene number and Hb F level will also be determined. Another major objective is to determine the rheological properties of sickle RBC in the steady state and during painful crises in patients with different beta-- haplotypes and alpha-gene number. A third objective is to determine the effect of hydroxyurea on the rheological properties of sickle erythrocytes in vivo. This part of the study will be a parallel project to the Multicenter Study of Hydroxyurea (HU) in Sickle Cell Anemia. Genomic DNA will be prepared from peripheral white blood cells from patients with sickle cell anemia. The alpha-gene number and beta-haplotypes will be determined by the Southern blotting technique or by polymerase chain reaction (PCR). Rheological properties of RBC will include: 1) RBC deformability determined by Ektacytometry; 2) number of dense cells determined by centrifugation on discontinuous Stractan density gradient and 3) RBC cations (Na+ and K+) determined by flame photometry. The rheological studies will be performed on unfractionated cells as well as on density-defined cells. It is projected that at least 15 of our patients will enroll in the HU study. Multiple base line studies (at least three determined at monthly intervals) will be performed before the initiation of drug therapy. Rheological studies will be done monthly after the initiation of drug therapy for the period of the study and for a minimum of four months after the discontinuation of drug therapy. In addition, survival of 51Cr-labeled autologous erythrocytes, 51Fe uptake by the bone marrow, plasma iron turnover and iron utilization will also be determined. These erythrokinetic studies will be done before the initiation of Hydroxyurea/placebo therapy and every six months thereafter. They will also be determined 4-6 months after the discontinuation of drug therapy. It must be emphasized that during the course of the study the principal investigator will have no access to any data such as the MCV, deformability index, etc. which may break the double-blind nature of the study. We hope this study will generate data which will: 1) clarify the factors which affect the clinical phenotype of sickle cell anemia; 2) elucidate the pathophysiologic changes that occur during the painful sickle cell crisis; and 3) provide insight into the mechanism of action of HU and its cellular effects which are not secondary to the increased level of Hb F. Moreover, determination of the rheological properties of RBC may be of value in monitoring the response to HU.