The Efficacy of Vitamin D Supplementation During a Prolonged Submarine Patrol

Submariners spend prolonged periods submerged without sunlight exposure and may benefit from vitamin D supplementation to maintain vitamin D status. The primary objective of this study was to determine the efficacy of daily vitamin D supplementation on maintenance of 25-hydroxyvitamin D (25(OH)D) during a 3-month submarine patrol. Submariners were randomly divided into three groups: placebo (n = 16), 1,000 IU/day (n = 20), or 2,000 IU/day (n = 17). Anthropometrics, self-reported dietary calcium and vitamin D intake, serum markers of vitamin D and bone metabolism, and peripheral quantitative computed tomography (pQCT) parameters of the tibia were determined before and after the patrol. Prior to departure, 49 % of the subjects were vitamin D insufficient (<50 nmol/L). Following the patrol, 25(OH)D increased in all groups (p < 0.001): 3.3 ± 13.1 (placebo), 4.6 ± 11.3 (1,000 IU/day), and 13 ± 14 nmol/L (2,000 IU/day). The changes in 25(OH)D levels were dependent upon the baseline concentration of 25(OH)D and body mass (p < 0.001). Osteocalcin increased by 38 % (p < 0.01), and pQCT analyses revealed small, yet significant increases in indices of tibial structure and strength (p < 0.05) that were independent of supplementation. These data suggest that vitamin D status was low prior to the patrol, and the subsequent changes in vitamin D status were dependent on the baseline 25(OH)D levels and body mass. Furthermore, short-term skeletal health does not appear to be negatively affected by 3 months of submergence in spite of a suboptimal response to vitamin D supplementation.     

The relative importance of thrombin inhibition and factor Xa inhibition to the antithrombotic effects of heparin

The relative importance of antithrombin and anti-factor Xa activities of heparin fractions required to achieve optimal antithrombotic effects is unknown. To study this, we measured the effects of standard heparin, an octasaccharide heparin fraction (anti-factor Xa activity only), and dermatan sulfate (antithrombin activity only) on the prevention of thrombosis and related this to their anticoagulant effects in vivo in rabbits. Thrombosis was measured as the incorporation of 125I- fibrinogen into tissue thromboplastin-induced thrombi using a Wessler- type model. Ex vivo changes in thrombin clotting time (TCT) were used as an index of antithrombin activity, and a chromogenic anti-factor Xa assay was used to measure anti-factor Xa activity. In addition, the ability of the three sulfated polysaccharides to simultaneously inhibit the generation of thrombin activity and to enhance the inactivation of the factor Xa added to initiate thrombin generation in plasma was determined. Standard heparin, in a dose of 10 anti-factor Xa U/kg, inhibited thrombus formation by 90%, prolonged the TCT by two seconds, and resulted in an anti-factor Xa level of 0.32 U/mL. The octasaccharide heparin fraction, in a dose of 10 anti-factor Xa U/kg, inhibited thrombus formation by 41%, had no effect on the TCT, and resulted in an anti-factor Xa level of 0.28 U/mL. Higher doses of the octasaccharide resulted in a further increase in the anti-factor Xa levels but had no further effect on thrombus formation. Dermatan sulfate, in a dose of 500 micrograms/kg, inhibited thrombus formation by 95%, but had no affect on the TCT. These results indicate that the antithrombotic effect achieved by inhibiting factor Xa is limited and that better antithrombotic effects are achieved by heparin or heparin- like substances capable of influencing the inactivation and/or the generation of thrombin.     

Active surveillance is superior to radical nephrectomy and equivalent to partial nephrectomy for preserving renal function in patients with small renal masses: Results from the DISSRM registry

Purpose

We compared renal function outcomes among patients in the surveillance and intervention arms of the DISSRM registry.

Red cell membrane stiffness in iron deficiency

The purpose of this study was to characterize red blood cell (RBC) deformability by iron deficiency. We measured RBC deformability to ektacytometry, a laser diffraction method for determining the elongation of suspended red cells subjected to shear stress. Isotonic deformability of RBC from iron-deficient human subjects was consistently and significantly lower than that of normal controls. In groups of rats with severe and moderate dietary iron deficiency, RBC deformability was also reduced in proportion to the severity of iron deficiency. At any given shear stress value, deformability of resealed RBC ghosts from both iron-deficient humans and rats was lower than that of control ghosts. However, increase of applied shear stress resulted in progressive increase in ghost deformation, indicating that ghost deformability was primarily limited by membrane stiffness rather than by reduced surface area-to-volume ratio. This was consistent with the finding that iron-deficient cells had a normal membrane surface area. In addition, the reduced mean corpuscular hemoglobin concentration (MCHC) and buoyant density of the iron-deficient rat cells indicated that a high hemoglobin concentration was not responsible for impaired whole cell deformability. Biochemical studies of rat RBC showed increased membrane lipid and protein crosslinking and reduced intracellular cation content, findings that are consistent with in vivo peroxidative damage. RBC from iron-deficient rats incubated in vitro with hydrogen peroxide showed increased generation of malonyldialdehyde, an end-product of lipid peroxidation, compared to control RBC. Taken together, these findings suggest that peroxidation could contribute in part to increased membrane stiffness in iron- deficient RBC. This reduced membrane deformability may in turn contribute to impaired red cell survival in iron deficiency.     

GE Signa Twinspeed 1.5T磁共振肝脏扩散加权成像的技术探讨

目的探讨高场强双梯度磁共振机(GE Signa Twinspeed 1.5T)的肝脏扩散加权成像技术(DWI).方法对20例正常肝脏进行扩散加权成像研究,分别改变重复时间(TR)及扩散敏感系数(b值),测定ADC值、信噪比、图像质量等.结果 b值固定,TR值改变,正常肝组织平均ADC值差异不显著(P>0.05);TR值固定,b值改变,ADC值随b值增大而减小(P<0.05,差异有显著性).b值越大,图像质量越差;b≥800 s/mm2时,图像几乎难以观察.结论 ADC值随b值的增大而减小.行肝脏扩散加权成像时,可适当减小TR值,以缩短扫描时间及患者的屏气时间,减少呼吸运动伪影.     

口服Carvedilol治疗心力衰竭多中心研究(MOCHA)

标题　Ｃａｒｖｅｄｉｌｏｌ对慢性心力衰竭患者左心室功能的改善和存活的提高呈剂量相关性作者　ＢｒｉｓｔｏｗＭＲ,ＧｉｌｂｅｒｔＥＭ,ＡｂｒａｈａｍＷＴ,等　　Ｃｉｒｃｕｌａｔｉｏｎ１９９６,９４：２８０７～２８１６　　研究疾病：充血性心力衰竭。目的：对Ｃａｒｖｅｄｉｌｏｌ治疗慢性心力衰竭患者剂量－疗效特征进行评价。　　设计：随机、双盲、安慰剂对照的多中心研究,剂量效应关系研究。病人资料：共３４５名心力衰竭患者,年龄１８～８５岁,左室射血分数≤０－３５,心力衰竭症状时间≥３月,研究前所有患者必须用利…     

磁共振相位对比电影对蛛网膜囊肿与蛛网膜下腔扩大的鉴别诊断

目的：应用磁共振相位对比法,揭示脑与脑脊液运动的相互关系,以评价此方法对鉴别蛛网膜囊肿与蛛网膜下腔扩大的诊断价值。材料与方法：运用磁共振相位对比电影和流动分析软件,对１０例健康人脑与脑脊液运动规律相关性进行研究和１０例影像学疑蛛网膜囊肿或蛛网膜下腔扩大患者的脑脊液运动进行最化分析,绘出一个心动周期不同时相脑脊液流量贡线和时间、信号强度曲线,并进行分析比较。结果：脑脊液流动是由脑运动驱动引起,而脑运