槲皮素对食管癌细胞侵袭和中期生长因子基因表达的影响

目的:观察中药提取物槲皮素对食管癌细胞侵袭的影响,并探讨其可能机制.方法:采用不同浓度的槲皮素处理食管癌EC109细胞后,以软琼脂集落培养试验检测癌细胞锚着不依赖性增殖,以Boyden小室模型方法检测癌细胞侵袭能力,采用荧光实时定量RT-PCR检测癌细胞中期因子(midkine,MK)基因mRNA水平,以Western blot方法检测癌细胞MK基因蛋白水平变化.结果:食管癌EC109细胞经槲皮素处理后,恶性增殖和侵袭能力均明显下降,且呈剂量依赖性(均P<0.05).槲皮素处理组MK基因mRNA和蛋白水平均明显下调,且呈时间和浓度依赖性(均P<0.05).结论:槲皮素可明显抑制食管癌EC109细胞侵袭能力,其机制可能与下调MK基因表达有关.     

GABA及GABAA受体激动剂对胰腺癌细胞增殖及MMP-2表达的影响

目的: 探讨γ-氨基丁酸(γ-aminobutyric acid,GABA)及其A受体激动剂THI P对胰腺癌SW1990细胞系增殖及表达基质金属蛋白酶-2(MMP-2)的调控作用.方法: MTT法检测SW1990细胞的生长;免疫共聚焦技术观察不同浓度GABA(80、160、320 μmol/L)、GABA(80 μmol/L)+THIP(20、40、80 μmol/L)作用细胞后MMP-2表达强度;通过荧光定量PCR(real-time PCR)检测MMP-2mRNA的表达.结果: GABA、THIP作用细胞后, 均能促进其生长, 且呈剂量依赖性, GABA组与对照组比差异显著( P<0.01或0.05);与对照组比较,GABA、THIP作用后细胞中MMP-2的表达明显增强(60.15±4.16, 66.28±4.27, 71.23±4.30 vs 26.04±4.54;75.01±4.64, 80.86±4.67,86.35±4.89 vs 26.04±4.54, P<0.01或0.05),MMP-2 mRNA表达也明显增强(39.35±3.24,52.46±4.16, 63.45±5.12 vs 7.34±2.75;78.3±5.39, 84.27±7.64, 97.38±6.64 vs 7.34±2.75, P<0.01或0.05).结论: GABA可能是通过A受体介导胰腺癌SW1990细胞增殖, 并通过促进MMP-2蛋白的表达来影响胰腺癌SW1990细胞的侵袭和转移.     

血管内皮生长因子165基因对人胃癌细胞体外侵袭转移的影响

目的:探讨血管内皮生长因子165基因(vascular endothelial growth factor 165,VEGF165)对胃癌侵袭转移的影响及可能的机制.方法:通过体外培养人胃癌细胞BGC-823,分别转染Ad-GFP及Ad-VEGF165*应用Millicell小室分析VEGF165转染前后胃癌细胞迁移能力的变化:逆转录聚合酶链反应(RT-PCR)研究VEGF懈转染前后BGC-823细胞MMP-2、u-PAmRNA表达变化.结果:迁移实验结果显示Ad-VEGF15组胃癌细胞迁移能力高于Ad-GFP组及对照组(217.53±15.77vs174.07±13.83,167.5±11.5,P＜0.05);RT-PCR结果显示VEGF懈转染后促进了BGC-823细胞MMP-2、u-PA的mRNA表达,Ad-VEGF165组MMP-2、u-PA的mRNA水平明显高于对照组及d-GFP组((MMP-2mRNA:0.6646±0.0486 vs 0.3803±0.0254.0.4096±0.0668;u-PA mRNA:0.8216±0.0798vs0.4043±0.0620,0.406±0.1158,均P＜0.05).结论:经VEGF165转染后,胃癌细胞迁移能力增强,MMP-2、u-PA的mRNA表达增加,MMP-2、u-PA表达的增加可能为VEGF促进胃癌侵袭转移机制.     

整合素β1基因沉默对胰腺癌细胞PANC1体外侵袭能力的影响及机制研究

目的 应用短发夹RNA(shRNA)沉默人胰腺癌细胞株PANC1的整合素α1(integrinβ1)基因表达,观察其对PNAC1细胞体外侵袭能力的影响,探讨其机制.方法 构建靶向integrinβ1基因的shRNA真核表达质粒integrinβ1-shRNA及对照真核表达质粒c-shRNA,转染人胰腺癌PANC1细胞,以未转染质粒的细胞作为对照组.应用实时荧光定量PCR和蛋白质印迹法检测integrinβ1、MMP-2、MMP-9 mRNA和蛋白的表达水平,应用Transwell侵袭小室检测细胞体外侵袭能力.结果 integrinβ1-shRNA 组、c-shRNA组和对照组细胞integrinβ1 mRNA表达量分别为0.0029±0.0004、0.0131±0.0009、0.0138±0.0005;integrinβ1蛋白表达量为0.0159±0.0062、0.3215 ±0.0126、0.3107±0.0094.integrinβ1-shRNA 组integrinβ1 mRNA和蛋白表达抑制率分别为(78.6±7.2)％和(92.9±3.2)％(P＜0.01).而c-shRNA 组与对照组差异无统计学意义(P =0.2999).integrinβ1-shRNA组穿膜细胞数由(52±5)个降低至(21 ±4)个(P＜0.01);MMP-2和MMP-9mRNA表达分别从0.592±0.073和0.847±0.069降低到0.102±0.034和0.273±0.071;MMP-2和MMP-9蛋白表达分别从0.225±0.046和0.416±0.081降低到0.059±0.013和0.106±0.022(P值均＜0.05).结论 重组质粒integrinβ1-shRNA能有效地抑制PANC1细胞integrinβ1基因的表达,并可能通过下调MMP-2和MMP-9基因表达而抑制其体外侵袭能力.     

p15INK4B和p21WAF1基因联合转染对人食管鳞癌细胞系EC109的协同抑制作用

目的:探讨p15INK4B和p21WAF1基因联合转染对人食管鳞癌细胞系EC109细胞增殖和凋亡的影响.方法:脂质体介导PcDNA3.1(+)-p15和pcDNA3.1(+)-p21转染EC109细胞,稳定筛选后用RT-PCR检测转染细胞p15与p21基因mRNA表达,Western blot检测转染细胞P15和P21蛋白的表达.用MTT法和透射电镜检测p15和p21基因分别及联合转染对EC109细胞增殖与凋亡的影响,流式细胞仪检测EC109细胞周期分布与凋亡率.结果:p15和p21转染组EC109细胞生长速度低于空载体组与未转染组,联合转染组与二者单独转染组相比.亦明显抑制EC109细胞体外生长速度.p15和p21转染组EC109细胞发生G1/S阻滞,G1期细胞比例显著高于空载体组和未转染组,S期则显著降低(G1期:60.52%±3.75%,63.12%±2.89% vs 42.17%±5.30%.41.38%±6.54%;S期:22.67%±1.25%,17.96%±2.03% vs 30.96%±3.33%,36.05%±1.78%,均P<0.01),并出现凋亡峰,透射电镜亦发现p15和p21转染组发生细胞凋亡,联合转染组发生更为明显的G1/S阻滞,G1期比例显著升高、S期比例明显降低(G1期:72.83%±2.31% vs60.52%±3.75%,63.12%±2.89%:S期:13.59%±2.59% vs 22.67%±1.25%,17.96%±2.03%.均P<0.05),凋亡率明显升高(21.21%±1.78%vs 4.32±1.74%,10.83%±2.40%,均P<0.01).结论:p15和p21基因联合转染在体外可以进一步增强对人食管鳞癌EC109细胞的抑制与诱导凋亡作用.     

神经型钙黏附蛋白的表达对食管鳞癌侵袭和转移的影响

目的:探讨神经型钙黏附蛋白(N-cadherin)在食管鳞癌组织中的表达及其临床病理意义.以及RNA干扰(RNAi)沉默N-cadherin基因表达对人食管癌细胞系EC9706体外侵袭能力的影响.方法:采用免疫组织化学PV法和RT-PCR检测62例食管鳞癌组织、31例癌旁不典型增生组织及62例正常食管黏膜组织中N-cadherin蛋白和mRNA的表达.将N-cadherin基因的RNA干扰载体稳定转染至EC9706.通过RT-PCR和Western blotting检测RNAi的效果:运用Transwell体外侵袭实验检测RNAi后细胞侵袭能力的改变.结果:正常黏膜组织、癌旁不典型增生组织及食管鳞癌组织中N-cadherin的阳性表达率依次升高,分别为29.0％(18/62)、61.3％(19/31)、75.8％(47/62),组间比较差异有统计学意义(P<0.05);N-cadherin蛋白的阳性表达率与食管鳞癌的浸润深度、分化程度及淋巴结转移密切相关(x2=6.916,6.924,4.486,P<0.05).食管鳞状细胞癌组织中N-cadherinmRNA的相对含量高于癌旁不典型增生组织及正常食管黏膜组织(0.6631±0.0162 vs0.4613±0.0239,0.1538±0.0192),组间比较差异有统计学意义(x2=819.242,P<0.01).RNAi后EC9706中N-cadherin的表达显著下降;Transwell小室体外侵袭实验显示,EC9706的体外侵袭能力也降低.结论:食管鳞癌组织中N-cadherin的高表达与食管鳞癌的浸润、恶化有密切的关系.RNAi沉默N-cadherin基因表达能够使EC9706体外侵袭能力降低.     

VEGF促进肝癌SMMC-7721细胞侵袭性的自分泌机制

目的:探讨促血管内皮生长因子(VEGF)对人肝癌细胞SMMC-7721侵袭力以及对该细胞中基质金属蛋白酶9(MMP-9)的影响,初步研究VEGF对肿瘤侵袭和转移的影响及可能的作用机制.方法:使用VEGF体外培养人肝癌SMMC-7721细胞,通过细胞体外侵袭实验检测细胞侵袭能力的改变,再分别使用30μg/L、10μg/LVEGF培养人肝癌SMMC-7721细胞,以正常培养人肝癌SMMC-7721细胞为空白对照组.使用半定量RT-PCR和Western blot法对3组细胞中MMP-9的mRNA和蛋白表达水平进行分析.结果:细胞体外侵袭实验显示,外加VEGF培养后,细胞侵袭力明显增强(P0.01);MMP-9mRNA和蛋白的表达在外加VEGF组中要明显高于空白对照组(0.479±0.025,0.665±0.024vs 0.315±0.022;0.521±0.026,0.662±0.026vs 0.366±0.025,均P<0.01),且高浓度和低浓度组之间也有明显差别.结论:肝癌SMMC-7721细胞系中存在有自分泌机制,VEGF可通过自分泌机制上调肝癌细胞的MMP-9表达,进而促进肿瘤的浸润转移.     

反义肝素酶基因对胰腺癌细胞体外增殖和侵袭的抑制作用

目的:研究反义肝素酶基因对人胰腺癌SW1990细胞体外增殖和侵袭能力的抑制作用．方法:反义肝素酶基因转染胰腺癌sW1990细胞,并设空载体对照组和空白对照组,以流式细胞仪检测细胞周期;免疫组化、Western blot及RT-PCR检测肝素酶蛋白和mRNA表达;平板克隆形成实验检测细胞增殖活性,Transwell侵袭小室模型检测细胞体外侵袭能力．结果:与空白组和空载组比较,反义组细胞周期中S期比例明显减少(18.8％±2．5％vs 36．3％±2．2％,33．2％±2．1％,P<0．01),G1期细胞比例明显升高(66．0％±2．7％vs30．7％±3．2％,39．8％±4．9％,P<0．01);肝素酶蛋白及mRNA表达分别降低34．3％和37．8％:细胞克隆形成数目减少(12．2±2．8 vs 30．8±4．4,28．3±2．7,P<0．01);Transwell侵袭小室中24 h穿膜细胞数减少(13．0±3．5 vs 34．8±5．8,29．4±5．6．P<0．01)．结论:反义肝素酶基因抑制人胰腺癌SW1990细胞体外增殖及侵袭能力．     

Cdc42基因在表皮生长因子促进HepG2细胞丝状伪足形成中的作用

目的:探讨表皮生长因子(EGF)对HepG2细胞丝状伪足形成和细胞体外侵袭能力的影响以及细胞分裂周期蛋白42(Cdc42)在其中的作用.方法:将Cdc42 siRNA转染HepG2细胞株,RT-PCR和Western blot检测EGF组、EGF+siRNA干扰组、siRNA干扰组及空白对照组细胞Cdc42 mRNA转录以及蛋白的表达水平,微丝绿色荧光探针(actin-tracker green)染色检测HepG2细胞丝状伪足形成,侵袭小室检测细胞体外侵袭能力.结果:经EGF处理后HepG2细胞可见明显丝状伪足形成,EGF组细胞Cdc42 mRNA及总蛋白(Total-Cdc42)表达量无显著变化,但活性Cdc42(Active-Cdc42)显著增高(0.713±0.021vs0.423±0.015,P<0.05),siRNA干扰细Cdc42表达及活性受到明显抑制(0.118±0.017 vs 1.128±0.024;0.351±0.021 vs 0.936±0.024,均P<0.05),并抑制EGF诱导的细胞丝状伪足形成,EGF组细胞体外侵袭能力显著高于其余各组(98.43+3.11vs61,09±3.58,50.53±2.34,62.73±2.64,均P<0.05).结论:EGF通过激活Cdc42诱导HepG2细胞丝状伪足形成并增强其体外侵袭能力.     

亚砷酸诱导人食管癌细胞株EC109细胞p15INK4B基因的表达

目的：研究亚砷酸(As_2O_3)对人食管癌EC109细胞株细胞周期蛋白依赖性激酶抑制因子p15~(INK4B)(p15)基因表达的影响．方法：终浓度2μmol/L的As_2O_3加入食管癌EC109细胞系,采用甲基化特异PCR(MSP)检测食管癌EC109细胞系中p15基因甲基化,采用RT-PCR和Western blot方法检测As_2O_3处理前后p15的mRNA和蛋白质水平的表达情况．用Scion Image软件测量条带灰度值,P15蛋白与ACTB条带的灰度比进行半定量分析．结果：EC109细胞p15基因发生高甲基化,p15基因不表达．As_2O_3作用后p15基因甲基化程度明显下降,As_2O_3作用72,48,24 h组和未加药组之间差异均有统计学意义(37．11±3．62,50．92±5．47,72．07±7．53 vs 97．23±9．80,P＜0．05)．As_2O_3作用24 h后出现p15 mRNA表达,随As_2O_3作用时间延p15 mRNA表达逐渐增强,各个时间组之间比较,除了未加药组和加药24 h组之间及加药24 h组和加药48 h组之间差异无统计学意义外,其余各个时间组之间差异有统计学意义(0．72±0．07 vs 0．58±0．06 vs 0．48±0．07 vs 0．41±0．08,P＜0．05)．As_2O_3作用24 h后P15蛋白出现表达,2μmol/L作用24-72 h中P15蛋白条带灰度逐渐增强,As_2O_3作用72,48,24 h组和未加药组之间差异均有统计学意义(0．51±0．02 vs 0．21±0．01 vs 0．16±0．02 vs 0．06±0．01,P＜0．05),说明其表达随As_2O_3作用时间延长而逐渐增强．结论：As_2O_3可使食管癌EC109细胞p15基因去甲基化,使p15基因表达上调,从而抑制细胞周期进程．     

Erythrocyte-endothelial cell adherence in sickle cell disorders

Detachment of individual sickle erythrocytes from cultured endothelial cell monolayers has been evaluated by a fluid-shearing technique in an effort to quantitate adherence at shear forces that would be anticipated in the in vivo circulation. Nonirreversibly sickled cells (non-ISC) were more adherent at normal oxygen tensions than control cells. More than 1% non-ISC remained attached to the monolayer at forces greater than physiologic shear stresses in capillary and venous circulations, and many of the most avidly attached cells, once separated, immediately reattached to adjacent endothelial cells. These data suggest that hemoglobin S-containing erythrocytes may have a higher frequency of adherence in vivo in regions of low shear stress where prolonged erythrocyte-endothelial cell contact could occur. Some of these cells detached by shear force would subsequently reattach in in vivo conditions. Plasma-enhanced attachment frequency and plasma from blood in a case of sickle crisis caused further increase. These observations further support the concept that sickle erythrocyte- endothelial cell interaction may be a significant factor in initiation of vascular occlusive events in sickle cell disease.     

Liver cell adenoma and liver cell adenomatosis

During the last three decades liver cell adenoma and liver cell adenomatosis have emerged as new clinical entities in hepato-logical practice due to the widespread use of oral contraceptives and increased imaging of the liver. On review of published series there is evidence that 10% of liver cell adenomas progress to hepatocellular carcinoma, diagnosis is best made by open or laparoscopic excision biopsy, and the preferred treatment modality is resection of the liver cell adenoma to prevent bleeding and malignant transformation. In liver cell adenomatosis, the association with oral contraceptive use is not as high as in solitary liver cell adenomas. The risk of malignant transformation is not increased compared with solitary liver cell adenomas. Treatment consists of close monitoring and imaging, resection of superficially located, large (>4 cm) or growing liver cell adenomas. Liver transplantation is the last resort in case of substantive concern about malignant transformation or for large, painful adenomas in liver cell adenomatosis after treatment attempts by liver resection.     

Red cell alloimmunization in sickle cell disease

Alloimmunization to red cell antigens contributes to morbidity in transfused patients. It has been recommended that blood for sickle cell patients need not be matched for antigens other than ABO and Rh(D), as there is no greater incidence of antibody production than in other multitransfused patient populations. Post transfusion alloimmunization was studied in a group of 34 sickle cell disease patients attending a U.K. haemoglobinopathy clinic. Red cell antibodies were formed in 17.6% of the transfused patients and Rhesus and Kell antibodies accounted for 66% of this total. In order to reduce alloimmunization, a policy of performing extended red cell phenotyping on the patients, and providing blood matched for Kell, and in certain circumstances the Rhesus antigens other than Rh(D), is recommended.     

Misdiagnosis of clear cell renal cell carcinoma

Clear cell renal cell carcinoma (RCC) represents the most common histological subtype of malignant kidney tumors. Based on symptoms alone, clear cell RCC is indistinguishable from other histological classes of RCC unless the tumor is present in the context of an RCC syndrome. Histopathological examination is, therefore, important to accurately identify clear cell RCC. Clear cell RCCs have characteristic morphological criteria; these tumors can be easily identified upon typical presentation, but diagnosis can be challenging when tumor cell pattern is unusual or when availability of tissue samples is limited. In this Review, the clinical, radiological and pathological characteristics of clear cell RCCs are described, as well as the potential tumors that can be confused with clear cell RCC and need to be considered in the differential diagnoses. Finally, the importance of an accurate diagnosis is highlighted in the context of the increasing use of preoperative tissue sampling and the prevalence of clear cell tumors associated with hereditary syndromes, which could have different therapeutic and prognostic implications for patients and their families.     

Red cell exchange in sickle cell disease

Red cell exchange transfusion is frequently of use in the management of patients with sickle cell disease either electively or therapeutically. Modern cell separators allow this procedure to be performed rapidly, effectively and safely. These machines have a number of advantages over manual exchange procedures. The patient remains isovolaemic, there is little loss of plasma or platelets, the procedure is relatively short and in elective circumstances can be performed on an outpatient basis. In this series 66 exchanges were performed on 21 patients with an overall increase in HbA of 70%. The COBE Spectra gave a mean increase in HbA of 77%, with the majority of patients achieving an HbA of > 90% post exchange. Automated redcell exchange was well tolerated by most patients, and adverse effects were limited to symptoms of hypocalcaemia which were easily treated, and to transfusion reactions. Cell separators can therefore be recommended for exchange transfusion in patients with sickle cell disease, who require an increase in HbA levels either prophylactically or therapeutically. They are safe, effective, easy and quick to use.     

Sphere-forming cell subpopulations with cancer stem cell properties in human hepatoma cell lines

Background

Cancer stem cells (CSCs) are regarded as the cause of tumor formation and recurrence. The isolation and identification of CSCs could help to develop novel therapeutic strategies specifically targeting CSCs.

Methods

Human hepatoma cell lines were plated in stem cell conditioned culture system allowed for sphere forming. To evaluate the stemness characteristics of spheres, the self-renewal, proliferation, chemoresistance, tumorigenicity of the PLC/PRF/5 sphere-forming cells, and the expression levels of stem cell related proteins in the PLC/PRF/5 sphere-forming cells were assessed, comparing with the parental cells. The stem cell RT-PCR array was performed to further explore the biological properties of liver CSCs.

Results

The PLC/PRF/5, MHCC97H and HepG2 cells could form clonal nonadherent 3-D spheres and be serially passaged. The PLC/PRF/5 sphere-forming cells possessed a key criteria that define CSCs: persistent self-renewal, extensive proliferation, drug resistance, overexpression of liver CSCs related proteins (Oct3/4, OV6, EpCAM, CD133 and CD44). Even 500 sphere-forming cells were able to form tumors in NOD/SCID mice, and the tumor initiating capability was not decreased when spheres were passaged. Besides, downstream proteins DTX1 and Ep300 of the CSL (CBF1 in humans, Suppressor of hairless in Drosophila and LAG1 in C. elegans) -independent Notch signaling pathway were highly expressed in the spheres, and a gamma-secretase inhibitor MRK003 could significantly inhibit the sphere formation ability.

Conclusions

Nonadherent tumor spheres from hepatoma cell lines cultured in stem cell conditioned medium possess liver CSC properties, and the CSL-independent Notch signaling pathway may play a role in liver CSCs.     

Actin filament debranching regulates cell polarity during cell migration and asymmetric cell division

The formation of the branched actin networks is essential for cell polarity, but it remains unclear how the debranching activity of actin filaments contributes to this process. Here, we showed that an evolutionarily conserved coronin family protein, the Caenorhabditis elegans POD-1, debranched the Arp2/3-nucleated actin filaments in vitro. By fluorescence live imaging analysis of the endogenous POD-1 protein, we found that POD-1 colocalized with Arp2/3 at the leading edge of the migrating C. elegans neuroblasts. Conditional mutations of POD-1 in neuroblasts caused aberrant actin assembly, disrupted cell polarity, and impaired cell migration. In C. elegans one-cell−stage embryos, POD-1 and Arp2/3, moved together during cell polarity establishment, and inhibition of POD-1 blocked Arp2/3 motility and affected the polarized cortical flow, leading to symmetric segregation of cell fate determinants. Together, these results indicate that F-actin debranching organizes actin network and cell polarity in migrating neuroblasts and asymmetrically dividing embryos.

Cell polarity is a fundamental feature of virtually all eukaryotic cells and plays crucial roles in a wide range of cellular processes, including cell motility, asymmetric cell division, and cell signaling (1). The establishment of cell polarity involves the asymmetric assembly of distinct cellular components to perform specialized functions. The actin-related protein (Arp) 2/3 complex-dependent branched actin networks and the pushing force they produce provide the principal means for cells to remodel the plasma membrane during cellular polarization (2). For example, in the leading edge of a migrating cell, the local Arp2/3-nucleated actin polymerization powers asymmetric projections of the plasma membrane (3). During asymmetric cell division of the Caenorhabditis elegans zygote, an actomyosin flow is central to the transport of the polarity PAR proteins into defined subcellular domains (4).Actin filaments'' continuous assembly must be balanced by actin depolymerization to ensure a constant supply of actin monomers for new growth. The Arp2/3 complex potency in actin nucleation empowers this complex as an essential regulator to organize the actin cytoskeleton. While Arp2/3 by itself is biochemically inactive, interactions with nucleation-promoting factors (NPFs) such as the Wiskott Aldrich syndrome protein (WASP)/WASP family verproline-homologous (WASP/WAVE) family proteins shift the Arp2/3 complex from its open, inactive conformation to a closed, active conformation (5, 6). The conformationally activated Arp2/3 complex then binds to the side of preexisting actin filaments to nucleate a branch from the mother filament (7–12). Conversely, nucleation by Arp2/3 can be inhibited by several binding partners, including glia maturation factor (GMF), Gadkin, Arpin, and Coronin, whose activities replenish available pools of actin monomers and Arp2/3 complexes for sustained actin assembly (13–18).The coronin family proteins are conserved actin regulators (19). The phylogenetic analysis grouped coronin genes into three types (19, 20). The best-characterized coronin is the Type I coronin (e.g., Coronin 1B) that binds to actin filaments through the β-propeller structure and to the Arp2/3 complex via its N terminus. These interactions block the docking of Arp2/3 onto actin filaments or facilitate debranching the existing actin network (20). Coronin 1B simultaneously interacts with the Slingshot phosphatase to dephosphorylate and activate ADF/Cofilin proteins that sever actin filaments, thereby promoting the actin network disassembly (13). Despite significant progress on Type I coronin, the activity and function of other coronins remain unclear. In particular, Type III coronins, known as POD-1 in C. elegans and Drosophila or Coronin7 in Dictyostelium and humans, contain two tandem coronin repeats, making them distinct from other coronins (19–21). POD-1 was biochemically isolated from C. elegans oocytes (22), and its mutations disrupted the polarity and architecture in early C. elegans embryos and impaired midlife touch sensitivity of the nematode (21, 23). However, it remains unclear how the Type III coronin functions. The Drosophila homolog of POD-1 is required for correct axon guidance, and the purified Dpod-1 cross-links the actin and microtubule cytoskeletons (24), whereas the mammalian Coronin7 was implicated in the Golgi morphology and function (25, 26), demonstrating the functional divergence of this family of coronin. Here, we show that the C. elegans POD-1 debranches Arp2/3-nucleated actin filaments in vitro and that POD-1 regulates cell polarity by remodeling the actin cytoskeleton during cell migration and asymmetric cell division.     

Mechanism of red blood cell aging: Relationship of cell density and cell age

The human red cell has a life span of 120 days. The mechanism that determines cell removal from the circulation with such precision remains unknown. Most studies of red cell aging have been based on analysis of cells of progressively increasing age separated by density. The relationship between red cell age and density has been recently challenged, and the hypothesis has been put forward that cell death is not the result of a progressive deterioration of essential cell constituents. This theory was based on preliminary observations in transient erythroblastopenia of childhood, which could not later be confirmed. When the relationship between cell aging and increasing density is critically reviewed, it appears to be based on firm experimental evidence, confirmed by in vivo demonstration of decreasing survival of cells of increasing age. Analysis of studies using buoyant density gradients reveals that this technique can easily distinguish the single exponential slope of decline for those cell components that change progressively throughout the red cell life span from the biphasic decline of those that decrease drastically at the reticulocyte-mature red cell transition. The view that the aging of the red cell and its removal from the circulation result from a progressive series of events during the 120 days of its life span appears to be the most consistent with the available data. Density separation, validated by much experimental evidence, remains a most useful technique for the study of the mechanism of aging of the red cell. © 1993 Wiley-Liss, Inc.     

Red cell rheology in stomatocyte-echinocyte transformation: roles of cell geometry and cell shape

The influence of the shape of the red blood cell during stomatocyte- echinocyte transformation on its deformability was studied by microsieving through pores with diameters of 2.6, 4.5, and 6.9 micron. A stomatocytic transformation was produced by chlorpromazine (0.02, 0.1, and 0.5 mmol/L) and an echinocytic transformation by sodium salicylate (7.5, 30, and 120 mmol/L). For spherostomatocytes, an increase in filtration resistance through 2.6 and 4.5 micron pores was observed, whereas for spheroechinocytes, a decrease in filtration resistance through 2.6 micron pores was found. Larger pores (6.9 micron) were not sensitive to those shape changes. The changes in deformability can be explained by the fact that the surface area of (sphero)-stomatocytes decreased, whereas that of (sphero)-echinocytes increased; the cell volume remained essentially constant. Echinocytes produced by 24-hour adenosine triphosphate depletion differed from drug- induced echinocytes: they had an increased cell volume at constant surface area and consequently an increased filtration resistance through 2.6- and 4.5-micron filter pores. Shape changes with spicule formation are therefore not a homogeneous entity, and cell geometric factors (eg, surface area and volume) must be assessed with care. The viscosity of red cell suspensions at a hematocrit level of 45% was higher for drug-induced echinocytes than discocytes or stomatocytes at all shear rates tested. We conclude that the normal discocyte represents an optimum shape for the flow in vivo since a stomatocytic transformation could impair the passage through the microcirculation (decrease in cell filterability) and an echinocytic transformation could impair the flow in larger vessels (increase in blood viscosity).     

Automated red cell exchange in sickle cell disease

We used multiple optical trapping to study the mechanism of red cell (dis)aggregation. Two sets of optical 'tweezers' were used to bring two red blood cells together to form a two-cell aggregate and then to pull them apart, to study the interaction between the cells.
We found that cross-bridging occurred in normal reversible aggregation as we observed binding and the occurrence of small tethers between opposite cell membranes. Furthermore, the cells could only be parted by sliding them side by side with a maximum velocity in the order of μm/s indicating accumulation of the cross-bridges.