37 resultados para 725.35


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Effects of La3+ and Gd3+ on Ca2+ influx were investigated in rat hepatoma H-35 cells by measuring the initial rate of Ca-45(2+) uptake. It was found that the maximum initial rate of Ca2+ uptake was increased six- to ten-fold at low concentrations of La3+ and Gd3+. Kinetic analyses by measuring the initial rate of Ca2+ influx at different external Ca2+ concentrations indicated the existence of two intracellular exchangeable components in the basal Ca2+ system, with low and high affinities for Ca2+, and only one class of Ca2+ binding sites was observed in the La3+- or Gd3+-treated cells. For high affinity, La3+ and Gc(3+) increased both kinetic parameters K-m and V-max of basal Ca2+ influx. La3+ and Gd3+ compete directly with Ca2+ for Ca2+ binding site for low affinity. The kinetics is competitive.

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通过测定 4 5Ca2 +摄取初速度的变化研究了La3+和Gd3+对鼠肝癌H 3 5细胞Ca2 +内流的影响 .发现低浓度La3+和Gd3+能增加肝癌H 3 5细胞Ca2 +内流初速度达 6~ 10倍 .Ca2 +内流的初速度随Ca2 +浓度变化的动力学研究表明 ,肝癌H 3 5细胞中存在 2类Ca2 +亲和部位的通道 ,即高亲和位和低亲和位Ca2 +内流通道 ,而La3+和Gd3+刺激的肝癌H 3 5细胞则只有 1类Ca2 +亲和位通道 ,La3+和Gd3+增加高亲和位Ca2 +结合通道的Km和Vmax,而对于低亲和位的Ca2 +结合通道Ca2 +内流的作用是竞争性的.

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The concentrations of five major and 28 trace elements in 35 marine algae collected along the coast of China were determined by instrumental neutron activation analysis. The concentrations of halogens, rare earth elements and many transition metal elements in marine algae are remarkably higher than those in terrestrial plants. The concentration factors for 31 elements in all collected algae were calculated, those for tri- and tetra-valent elements were higher than those of the mono- and di-valent elements in marine algae. The biogeochemical characteristics of inorganic elements in marine algae were investigated. In addition, the seasonal variation of inorganic elements in Sargassum kjellmanianum was also studied. (C) 1998 Elsevier Science B.V. All rights reserved.

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本文对真鲷心跳期胚胎对5种常用渗透性抗冻剂(DMSO、甘油、甲醇、丙二醇、乙二醇)和3种非渗透性抗冻剂(PVP、PEG-8000、蔗糖)的耐受性进行了研究。渗透性抗冻剂分6个浓度梯度(5%;10%;15%;20%;25%;30%)和3个时间组(10min;30min;1h)。非渗透性抗冻剂中,PVP、PEG-8000分3个浓度梯度(5%、10%、15%)和2个时间组(10min、30min),蔗糖为4个浓度梯度(5%、10%、15%、20%)和2个时间组(10min、30min)。实验结果表明,在渗透性抗冻剂组中,浓度为5%的处理组的孵化率(>90%)与对照组差异均不显著,随着抗冻剂浓度增大及处理时间的延长,真鲷心跳期胚胎的孵化率显著下降(P<0.05),在最高浓度的最长处理时间中胚胎孵化率均降到了0。总体上,真鲷心跳期胚胎对五种渗透性抗冻剂的耐受性从小到大依次为:甲醇 < 甘油 < 乙二醇 < DMSO < 丙二醇。对影响胚胎孵化率的三个因素(抗冻剂、浓度、时间)进行的因素效应分析结果表明,三种因素对孵化率的影响显著(P<0.05),并且浓度效应 > 时间效应 > 抗冻剂效应。在非渗透性抗冻剂组中,蔗糖组胚胎孵化率未呈显著变化;PVP组随着浓度及时间的增大,孵化率显著下降(P<0.05);PEG-8000组随着浓度增大孵化率显著下降(P<0.05),但在两个时间组间差异不显著。相同处理情况下PEG-8000对真鲷心跳期胚胎的毒性要小于PVP。因素效应分析比较结果表明仅时间效应不显著,且抗冻剂效应 > 浓度效应 > 时间效应。 对所用各种抗冻剂进行了渗透压测量,实验中使用的渗透性抗冻剂(5%-30%)的渗透压值在959-7980mOsm/kg之间,均高于使用海水的渗透压值(919mOsm/kg);使用的非渗透性抗冻剂的渗透压值在316-1040mOsm/kg之间,除20%蔗糖渗透压值(1040mOsm/kg)高于海水外,其他非渗透性抗冻剂的渗透压值均要低于海水。对孵化率与相应的溶液渗透压值进行相关回归分析结果表明,渗透性抗冻剂的渗透压与孵化率呈显著的负相关(P<0.05),而非渗透性抗冻剂的渗透压与孵化率相关不显著。渗透性抗冻剂组的回归分析结果表明,二次方程的曲线拟合度最高,得到的回归方程分别为:Y10min = -2×10-8X2 10min - 6×10-5 X 10min + 1.5635 (R2 = 0.713),Y30min= 5×10-8X2 30min-0.0007 X 30min + 2.097(R2 = 0.681),Y1h = 7×10-8X2 1h-0.0008 X 1h+ 2.0397(R2= 0.725)。 在真鲷胚胎对抗冻剂耐受性实验的基础上,挑选五种抗冻剂--10%DMSO、5%甘油、10%甲醇、20%丙二醇、10%乙二醇,浸泡真鲷心跳期胚胎30min后,分别以超速(130℃/min)、快速(20℃/min)、慢速(3℃/min)的速度降温并使用低温显微镜进行观察,依次记录Toif(油球结冰)、Teif(胚胎外部结冰)、Tiif(胚胎内部结冰)等结冰点,Toif值在-9~-23℃之间;Teif值在-21~-35℃之间;Tiif值在-21~-52℃之间。结冰顺序为先油球结冰,然后胚胎外部结冰随之内部马上瞬间变黑形成内部冰晶。随着降温速度的提高,各结冰温度值显著下降。各抗冻剂之间的Teif及Tiif值不同,Toif值之间没有显著差异。对两种玻璃化冷冻方法进行模拟观察,发现胚胎冰晶形成的顺序与非玻璃化过程不同--先内部结冰然后逐渐蔓延至外部形成外部冰晶,而且模拟玻璃化的内部结冰温度Tiif值(-52.56℃)显著(P<0.05)低于使用低浓度的同种抗冻剂超速降温组的Tiif值(-40.11℃)。在快速及慢速降温组中,20%丙二醇组的Tiif要显著的低于其他组(P<0.05);在超速降温中,甲醇组的Tiif值要显著的低于其他组(P<0.05)。在Tiif小于30℃的实验组中获得形态完整胚胎的比例平均仅有30.77%;在Tiif大于30℃的实验组中获得形态完整胚胎的平均比例高达70.37%,模拟玻璃化组达到100%。各抗冻剂之间,复温后胚胎形态完整率10%甲醇组最高(77.78%);其次依次为10%乙二醇(66.67%)、20%丙二醇(55.56%)和10%DMSO(55.56%);5%甘油组最低(11.11%);推测甲醇的对胚胎的渗透效果要好于其他组。综上推测:使用丙二醇、甲醇作为抗冻剂以及玻璃化冷冻保存方法对真鲷心跳期胚胎超低温保存也许较为合适。 我们对低温保存的真鲷精子核DNA损伤进行了研究以期为下一步胚胎遗传物质稳定性研究提供参考依据。研究方法为单细胞凝胶电泳(SCGE),针对研究对象,在实验过程中对传统的碱性单细胞凝胶电泳在铺胶方法、电泳条件等进行了改进。对精子细胞进行预处理,在碱性电泳液中使核DNA双链解链变性后电泳,EB染色lOmin后,在荧光显微镜下观察,每次随机观察50个左右的核DNA。结果表明,对荧光显微镜下观察到的精子核按彗尾长度及荧光强度划分等级,出现损伤的精子核DNA的损伤程度主要为轻度损伤和中度损伤,很少见有完全损伤的真鲷精子核。经5%、10%、18%、20%、25%、30%DMSO冷冻保存后的精子彗星率分别为33.47% ± 8.95%; 35.91% ± 19.44%; 48.95% ± 8.90%; 43.33% ± 11.19%; 55.80% ± 38.94%。鲜精彗星率为31.43 % ± 2.68%。对比真鲷冷冻精液与新鲜精液的精子DNA的损伤状况,表明仅用30% DMSO冷冻精子DNA损伤状况与鲜精差异显著(P<0.05)。 综上所述,渗透性抗冻剂对胚胎的毒性与其渗透压值呈显著的负相关关系。丙二醇对真鲷心跳期胚胎毒性最小,甲醇较其他抗冻剂能更好的渗透入胚胎;玻璃化方法能显著降低Tiif值并能更好的保持超低温保存后胚胎的形态完整性,因此,使用丙二醇、甲醇作为抗冻剂以及玻璃化冷冻保存方法对真鲷心跳期胚胎超低温保存也许较为合适。常规使用的用于超低温保存真鲷精子的DMSO(浓度<15%)不会对精子核物质稳定性造成明显影响。由于胚胎较精子结构要复杂许多,对于真鲷胚胎损伤机理的研究还有大量工作可以开展。

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A series of MCM-22/ZSM-35 composites has been hydrothermally synthesized and characterized by XRD, SEM, particle size distribution analysis, N-2 adsorption and NH3-TPD techniques. Pulse and continuous flow reactions were carried out to evaluate the catalytic performances of these composites in aromatization of olefins, respectively. It was found that MCM-22/ZSM-35 composites could be rapidly crystallized at 174 degrees C with an optimal gel composition of SiO2/Al2O3=25, Na2O/SiO2=0.11, HMI/SiO2=0.35, and H2O/SiO2=45 (molar ratio), of which the weight ratio of ZSM-35 zeolite in the composite relied on the crystallization time. The coexistence of MCM-22 and ZSM-35 in the composite (MCM-22/ZSM-35=45/55 wt/wt) was observed to exert a notable synergistic effect on the aromatization ability for butene conversion and FCC gasoline updating, possibly due to the intergrowth of some MCM-22 and ZSM-35 layers.