Effect and mechanism of melatonin's action on the proliferation of human umbilical vein endothelial cells

Melatonin is the major secretory product of the pineal gland and is considered an important natural oncostatic agent. The anticancer activity of melatonin is due to its immunomodulatory, anti-proliferative and antioxidative effects. At present there are no direct data available as to melatonin's possible influence on angiogenesis, which is a major biological mechanism responsible for tumor growth and dissemination. The current study investigated the influence of melatonin on angiogenesis. Human umbilical vein endothelial cells (HUVECs) were cultured, identified, and purified. Cell growth and viability, DNA fragmentation and cell cycle analyses were determined. To elucidate the mechanism of action of melatonin, Western blot analyses for P53, Bax and Bcl-2 expression were carried out. The results demonstrate the anti-proliferative and apoptosis-inducing effects of melatonin; these changes were associated with cell cycle arrest, upregulation of P53 and Bax and downregulation of Bcl-2. Taken together, our data showed that melatonin in high concentrations markedly reduces HUVECs proliferation, induces cellular apoptosis, and modulates cell cycle length. P53 and Bax/Bcl-2 expression changes may be involved in these actions of melatonin.     

升主动脉扩张的经食管超声心动图研究

为探讨经食管超声心动图（ＴＥ｀Ｅ）对升主动脉扩张疾病的诊断价值，４６例经胸超声心动图（ＴＴＥ）诊断为升主动脉扩张的患者进行了ＴＥＥ的研究。结果表明：（１）ＴＥＥ能清晰显示的升主动脉长度明显高于ＴＴＥ（Ｐ＜０．００１）；（２）ＴＥＥ和ＴＴＥ对升主动脉内径的测值无显著性差异（Ｐ＞０．０５）；（３）ＴＥＥ对升主动脉扩张疾病的病因诊断率（９３．５％）明显高于ＴＴＥ（７３．９％）（Ｐ＜０．０５）；（４）ＴＥＥ能够确定９７．８％的患者的升主动脉的病变范围，而ＴＴＥ仅能确定１７．８％的患者的病变范围（Ｐ＜０．０１）。ＴＥＥ对动脉粥样硬化斑块的检出率也明显高于ＴＴＥ（Ｐ＜０．０１）。因此，我们认为：对于升主动脉扩张，ＴＥＥ是一种十分安全、有效的诊断技术，应作为常规使用。     

FHIT基因异常与消化道恶性肿瘤

目的探讨消化道恶性肿瘤细胞中三联脆组(fragile histidine triad,FHIT)基因的异常转录情况.方法应用巢式逆转录聚合酶链反应(nested RT-PCR)对96例消化道恶性肿瘤(21例食管癌、43例胃癌和32例结肠癌)及相应的癌旁组织,18例正常组织FHIT基因cDNA片断进行扩增.结果在33.3%的食管癌组织,51.2%的胃癌组织和31.3%的结肠癌组织中检出异常FHIT转录,而在相应的食管、胃、结肠癌旁组织中FHIT异常转录检出率分别为4.8%、20.9%和9.4%,二者差异有显著性(P＜0.05);18例正常组织中未见FHIT异常转录.结论食管癌、胃癌和结肠癌组织FHIT基因的异常转录可能与消化道恶性肿瘤的发生、发展有关.     

蛋白酶体抑制剂MG132对结肠癌细胞lovo侵袭力的影响

目的探讨小剂量蛋白酶体抑制剂MG132对结肠癌细胞(lovo)侵袭能力的影响。方法采用不同浓度MG132不同时间点分别作用于lovo细胞,用四甲基偶氮盐比色法(MTT法)检测lovo细胞抑制率;设定MG132浓度为0.5μmol/L、1μmol/L,分别作用lovo细胞24 h,倒置显微镜观察细胞形态学变化,Transwell小室检测MG132对lovo细胞的穿透基底膜能力的影响。结果低剂量MG132对lovo细胞生长无明显抑制,而细胞侵袭力较未处理组明显减弱(P<0.05)。结论低剂量MG132可使结肠癌lovo细胞侵袭能力减弱。     

PTEN下调paxillin的表达抑制胃癌转移

目的检测PTEN(phosphatase and tensin homolog deleted on chromosome10,10号染色体缺失的磷酸酶与张力蛋白同源物)及桩蛋白(paxillin)在胃癌细胞系BGC823中的表达,并探讨PTEN对paxillin的调节作用及其在胃癌的发生、发展中的意义。方法体外培养胃癌细胞BGC823,利用脂质体介导法瞬时转染pEAK8及pEAK8-PTEN质粒,获得pEAK8-BGC823(pE-B)和pEAK8-PTEN-BGC823(pE-P-B)细胞,采用免疫印迹法检测PTEN、paxillin及actin蛋白水平的表达,免疫荧光检测paxillin在细胞内的定位。结果 Western blot显示,pE-P-B细胞PTEN蛋白表达水平(1.013±0.074)明显高于pE-B细胞(0.513±0.006)和BGC823细胞(0.506±0.015),而paxillin的蛋白表达水平(0.883±0.032)明显低于后两者(2.747±0.047,2.663±0.096),BGC823与pE-B相比,PTEN和paxillin蛋白表达差异均无统计学意义(P>0.05),Sperman等级相关分析证明PTEN蛋白与paxillin蛋白的表达呈负相关(r=-0.12,P<0.05);免疫荧光显示,paxillin在pE-B细胞伸出伪足处聚集,在pE-P-B细胞中较少。结论过表达PTEN可能通过下调paxillin的表达从而抑制胃癌的转移。     

联合应用活性氧抑制剂对降低胃癌顺铂耐药性的影响

目的探讨活性氧抑制剂N-乙酰半胱氨酸(NAC)通过Akt(蛋白激酶B)有关的信号途径在胃癌细胞中对顺铂化疗敏感性的影响。方法应用化疗药物顺铂以一系列梯度浓度处理对数期生长的胃癌BGC-823细胞,通过MIT法检测顺铂对BGC-823细胞增殖抑制率的影响,应用顺铂和活性氧抑制剂NAC单独及联合应用处理胃癌BGC细胞后测定细胞的活性氧水平以及Akt及磷酸化Akt的表达水平。结果顺铂对胃癌细胞有明显的抑制作用,呈浓度依赖性。单用顺铂组活性氧水平高于联合用药组;顺铂联合应用活性氧抑制剂NAC组与单用顺铂或活性氧抑制剂组的Akt表达无统计学意义(P>0.05),而磷酸化Akt的表达下调(P<0.05)。结论活性氧抑制剂NAC可能通过阻断P13K/Akt信号途径或其他有关Akt的信号通路以提高癌细胞对顺铂化疗的敏感性。     

Improvement on conventional constant current DC iontophoresis: a study using constant conductance AC iontophoresis.

The purpose of the present study was to compare conventional constant direct current (DC) transdermal iontophoresis with a new constant conductance alternating current (AC) iontophoresis method. The new method was developed with the intent of reducing flux drift during iontophoresis and minimizing skin-to-skin variability. The constant conductance AC iontophoresis studies involved three electrical components: (1) an initial applied potential used to decrease the human epidermal membrane (HEM) electrical resistance to a target level of either 1.5 or 3.0 k Omega cm(2), (2) an applied 50 Hz square-wave AC with a variable potential adjusted to maintain the HEM conductance at the target level during the transport study, and (3) a low voltage DC offset of 0 (passive), 0.25, or 0.40 V applied simultaneously with the AC to assist permeant transport. Current densities of 0.13 and 0.26 mA/cm(2) were chosen for the conventional constant current DC iontophoresis studies. Mannitol was used as the probe permeant for all studies. The constant current DC studies showed significant increases in mannitol flux with time during a given experiment and large skin-to-skin variability. Compared to the constant current DC experiments, the mannitol flux remained more constant during the constant conductance AC iontophoresis and skin-to-skin variability was significantly reduced. On a mechanistic level, changes in the transport properties during constant current DC iontophoresis indicate changes in the membrane parameters such as porosity, effective pore size, and/or pore surface charge density during the conventional method of iontophoresis. The results from the constant conductance AC iontophoresis transport studies imply that this method effectively maintains the membrane parameters that affect transport at a constant state this providing for a relatively constant permanent flux.