A Fluid Dynamic Analysis Using Flow Visualization of the Baylor/NASA Implantable Axial Flow Blood Pump for Design Improvement

Abstract: The Baylor/NASA Axial Blood Flow Pump has been developed for use as an implantable left ventricular assist device (LVAD). The pump is intended as an assist device for either pulmonary or systemic circulatory support for more than 3-months' duration. To date the pump provides acceptable results in terms of thrombus formation and hemolysis (IH of 0.018 g/100 L). A fluid dynamics analysis using flow visualization was performed to investigate the flow fields and to determine areas within the pump that could be improved. These studies focused upon the inflow area in front of the pump. A prototype axial flow pump assembly was constructed to facilitate the flow visualization studies. Particle image tracking velocimetry techniques were used to measure Amberlite particles suspended in a blood analog fluid composed of 63% water and 37% glycerin. This method used a pulsed (612 Hz) laser light to determine flow velocity profiles, shear stress, Reynolds numbers, and stagnant areas within the axial pump. These studies showed that the flow straightener (a vaned assembly in the pump inflow) reduced Reynolds numbers from 4,640 to 2,540 (at 8.5 L/min) and that the flow straightener exacerbates a discontinuity found between it and the impeller. Within the inflow area, a maximum of 80 N/m² shear stress was measured, which is well below published blood damage thresholds. Design variations were investigated resulting in a smoother flow transition between flow straightener and impeller. These variations must be investigated further to establish a correlation with hemolysis and thrombus formation.     

Histamine in Cerebrospinal Fluid of Children with Febrile Convulsions

Summary: Febrile convulsions (FC) are frequent acute neurologic disturbances of childhood. The cellular and neurochemical mechanisms causing FC are unclear. Among other mechanisms, the CNS histamine (HA) has been suggested to participate in seizure control and thermoregulation. We evaluated the possible role of HA in regulation of FC by measuring HA and tele-methylhis- tamine (t–MH) concentrations in the cerebrospinal fluid (CSF) of children with FC. The study group consisted of 35 children treated for acute FC in the hospital. The control groups consisted of (a) feverish children without seizures ( n =23), (b) convulsive children without fever ( n =7), and (c) children with neither fever nor convulsions ( n =21). HA was assayed by high-performance liquid chromatography (HPLC) with fluorescence detection, and t-MH was measured by gas chromatography-mass spectrometry. CSF HA concentration in the group of febrile Convulsions occur rather frequently in connection with febrile children without seizures was significantly higher (0.69 ± 0.16 pmol/ml, mean k SE) than in children with FC (0.36 ± 0.07 pmol/ml, p <0.05, analysis of variance, ANOVA). HA concentration was 0.37 ± 0.18 pmoVml in the group of nonfebrile convulsive children and 0.36 k 0.08 pmol/ml in the nonfebrile nonconvulsive group. No statistical differences in t–MH were detected between groups. The increased susceptibility to seizures during fever may be connected to the lack of increase in CSF HA in the FC group. The data support the hypothesis that the central histaminergic neuron system may be involved in inhibition of seizures associated with febrile illnesses in childhood.     

脑膜癌病的临床与脑脊液细胞学分析

目的:探讨脑脊液细胞学在诊断治疗脑膜癌病中的价值。方法:对自1996年以来确诊的脑膜癌病患者的临床资料及脑脊液细胞学检查进行对照分析。结果:13例病人中发现脑脊液查白细胞总数升高10例,余3例正常。9例首次检查时发现癌细胞,4例于2～5次检查发现,经相应辅助检查后确诊原发病,肺癌5例,淋巴瘤3例,胃癌2例,乳腺癌1例。结论:脑脊液细胞学检查发现癌细胞是诊断脑膜癌病的最重要的依据。     

Evidence for rapid fluid flow from the subarachnoid space into the spinal cord central canal in the rat

Horseradish peroxidase (HRP) was used as a CSF tracer in Sprague-Dawley rats. One group of rats received an injection of HRP in the cistema magna and a second group was injected in the thoracic spinal subarachnoid space. The animals were sacrificed 0, 10 or 30 min after HRP injection by rapid perfusion with paraformaldehyde and glutaraldehyde. In both groups, there was rapid HRP labeling of brain and spinal cord perivascular spaces. HRP was present in the central canal in a pattern that was not consistent with flow from the fourth ventricle: in both groups there were segments of unlabeled central canal between the fourth ventricle and central canal segments containing HRP. HRP-labeled perivascular spaces were seen in the central gray matter adjacent to the central canal. There was a distinctive pattern of interstitial HRP between perivascular spaces and the central canal. The results suggest that there is a normal flow of fluid from the subarachnoid space, into the perivascular spaces, across the interstitial space and into the central canal. The function of this flow may be to clear metabolites from the interstitial space. The existence of such a flow would add considerable support to the theory that non-communicating syringomyelia develops in segments of central canal isolated by occlusion or stenosis at each end.     

~（99m）Tc－ECD脑SPECT显像和CT扫描对脑部疾病应用价值的对比研究

比较了脑病患者的９９ｍＴｃ-乙撑双半胱氨酸二乙酯（ＥＣＤ）脑ＳＰＥＣＴ显像和脑ＣＴ扫描结果，并对其临床意义进行初步评价．方法：２１９例脑病患者进行了９９ｍＴｃ-ＥＣＤＳＰＥＣＴ和ＣＴ检查，两者间隔时间在２周之内．结果：ＣＴ探查脑出血或梗塞、脑肿瘤和脑血肿等颅内结构性损伤非常灵敏．但不能探查到尚未引起脑结构异常的代谢和功能性损伤．９９ｍＴｃ-ＥＣＤＳＰＥＣＴ对后者的优越性很大，可以灵敏地探查到损伤部位的血流灌注变化．这在急性脑梗塞早期、短暂性缺血发作、偏头痛、痴呆、锥体外系疾病、脑外伤后遗症和癫痫病人中尤为明显．部分脑外伤和癫痫患者经保守治疗改善局部脑血流而取得显著效果．结论：９９ｍＴｃ-ＥＣＤＳＰＥＣＴ在许多脑病的诊断和治疗中可起重要作用．     

鼠侧向液压脑损伤后脑血流量和葡萄糖利用率的改变

目的：探讨液压冲击脑损伤后脑血流量（ＣＢＦ），局部脑血流量（ｒＣＢＦ）与局部葡萄糖利用率（ｒＣＧＵ）的变化及其对神经元继发性损伤的影响。方法：应用激光多普勒流量计和定量放射自显影技术。结果：液压冲击脑损伤导致６０秒内ＣＢＦ短暂升高然后显著下降，且持续６０分钟低于正常，同侧和对侧大脑半球的ＣＢＦ相应降为正常值的７９％和９３％。外伤后１小时，损伤侧脑皮层，丘脑及海马的ｒＣＢＦ下降１２％～５９％，对侧大脑半球相应区域则下降１０％～４０％。相反，ｒＣＧＵ在冲击区周围脑皮质及同侧丘脑和海马区升高２７％～１０１％，在对侧大脑半球相应区域则升高２０％～９１％，海马区由液压冲击引起的ｒＣＢＦ和ｒＣＧＵ分离性变化十分显著，同侧海马ＣＡ１和ＣＡ２－３区存活的神经元数量在损伤后两星期时显著减少。结论：ｒＣＢＦ和ｒＣＧＵ的分离性变化是引起外伤后神经元尤其是海马区神经元继发损伤的主要因素。     

Angiotensin-(1–7) and nitric oxide synthase in the hypothalamo-neurohypophysial system

The organization of angiotensin (Ang)-(l-7) immunoreactivity with respect to neurons containing the nitric oxide synthase, nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d), in the hypothalamo-neurohypophysial (HNS) system was examined. The majority of neurons in this system were single labeled with Ang-(1–7) or NADPH-d and were found localized in two separate populations of neurons within the HNS. A small number of double-labeled neurons were observed in the supraoptic (SO) and paraventricular (PV) nuclei. Double-labeled accessory neurosecretory neurons were also found distributed between the SO and PV. Although a well-defined function for nitric oxide in the magnocellular hypothalamic system has not been determined, the codistribution and limited coexistence of Ang-(1–7), a heptapeptide involved in antidiuresis, and NADPH-d in the HNS suggests a potential role for these substances in mechanisms modulating fluid homeostasis.     

安徽省三座风景名山土壤中天然放射性核素调查研究

本文对三座风景名山土壤中天然放射性核素进行了研究．研究表明：三座名山土壤中天然放射性核素的含量高出正常本底地区水平。由三座名山土壤中放射性核素的含量估算的年有效剂量当量为６０３μＳｖ，比正常地区居民受到的外照射年有效剂量当量为６５０μＳｖ偏低。可见三座风景名山土壤中天然放射性核素的含量对当地居民及旅游者并无损害。     

心外管道全腔静脉肺动脉连接术后肺血分布的研究

目的　探讨心外管道全腔静脉肺动脉连接手术对肺血分布的确切影响。方法　应用99锝 大颗粒聚合蛋白 ( 99mTc MAA)肺灌注显像 ,对 17例心外管道全腔静脉肺动脉连接术病人手术前、后肺血灌注情况进行定量研究。结果　 17例病人术后肺放射性核素计数值为 ( 313 7± 40 1)× 10 3,显著高于术前的 ( 2 6 6 8± 33 6 )× 10 3(t=2 2 3,P <0 0 5 )。术后右肺与左肺血流灌注量比值为 1 14± 0 15 ,高于术前的 1 0 2± 0 12。术后肺野上段血流灌注量显著降低 (t=2 93,P <0 0 1) ,下段血流灌注量显著增加 (t=3 14,P <0 0 1)其上 /下段比值为 0 2 3± 0 0 9。显著低于术前为 0 43± 0 0 8(t=3 19,P <0 0 1)。结论　心外管道全腔静脉肺动脉连接手术仍可保持右肺的相对优势灌注血流。术后明显的坠积性肺淤血状态可能与远期肺动静脉瘘并发症发生率增加 ,以及活动耐力受限有关 ,但仍有待于进一步随访证实。     

荷瘤裸鼠整合素αv β3受体显像的实验研究

目的探讨99Tcm标记精氨酸-甘氨酸-天冬氨酸（RGD）小分子多肽（GY11）作为肿瘤显像剂的可能性.方法利用SnCl2直接还原法进行GY11的^99Tcm标记.建立荷人黑色素瘤A375、肺癌H460和宫颈癌HeLa BALB/c裸鼠肿瘤模型,分别进行体内分布和肿瘤显像研究.结果GY11的^99Tcm标记率为80%.黑色素瘤A375荷瘤裸鼠体内分布显示,^99Tcm-GY11主要经肾脏快速从血液中清除,注射后2 h肿瘤摄取量为3.13%ID/g,肿瘤/血和肿瘤/骨骼肌比值随时间的推移而增加,注射后1和6 h比值分别为3.0、4.3和8.1、15.1.对于黑色素瘤A375和肺癌H460荷瘤裸鼠,^99Tcm-GY11静脉注射后2 h肿瘤均能清楚显示,24 h后显像更清晰;2 h后宫颈癌HeLa肿瘤能显影,但6 h后肿瘤放射性基本清除.结论^99Tcm-GY11有望成为肿瘤αvβ3受体显像剂.