离子选择电极电位法研究S2O8^2—与I^—反应动力学

用离子选择电极电位法对S_2O_8~(2-)-Ⅰ~-体系反应动力学问题进行了探讨,研究了离子强度对反应速度的影响。结果表明:离子选择电极电位法可用于此体系的动力学研究,并且得到满意的结果;提出了该电极适用的浓度条件;得出生成CuI~+步骤为催化反应决定步骤的新结论;随着离子强度的增加dE/dt值增大,即反应速度加快。     

Distribution of calbindin D-28K and parvalbumin immunoreactivities in the nucleus olfactorius anterior of the rat

The distributions of calbindin D-28K (CaBP) and parvalbumin (PV) in the rat nucleus olfactorius anterior (NOA) were described using monoclonal antibodies and the avidin-biotin-peroxidase method. The NOA showed a high immunoreactivity for CaBP, with a rostrocaudal increase in the positive neurons and fibres. Pars externa (NOAe) was the only subdivision which showed a low CaBP immunostaining. PV-positive elements were less abundant than those CaBP immunostained. The main difference in the distributions for both proteins was observed in the pars medialis which was practically PV negative. PV- and CaBP-stained neurons showed similar morphologies in the subdivisions where they were present. In NOAe, we observed a characteristic PV- and CaBP-positive neuronal type, with an oriented dendritic pattern. Transition areas were clearly observable in both CaBP- and PV-labelled sections.     

对不同月龄雄性大鼠成骨细胞内钙和钙通道电流的实验研究

目的研究不同月龄的雄性大鼠成骨细胞内钙浓度及钙通道电流是否存在差异.方法采用二次酶消化法分离不同月龄(分别为1、2、3、5、7、9、11、13、15)雄性大鼠的原代成骨细胞,通过激光扫描共聚焦技术测定细胞内游离钙浓度([Ca2+]i)(以平均荧光强度表示),同时应用全细胞膜片钳技术记录成骨细胞膜钙电流(ICa)的变化.结果共聚焦结果显示随月龄增加,成骨细胞内[Ca2+]i逐渐降低,但相邻2月龄组之间细胞内[Ca2+]i无显著性差异(P＞0.05);1、2、3月龄组与11、13、15月龄组成骨细胞内[Ca2+]i有显著性差异(P＜0.05),5、7、9月龄组与各组相比均无差异(P＞0.05).应用全细胞膜片钳技术发现刺激电压为+10 mV时,2、7、13月龄组鼠ICa分别为(-392.77±97.07)pA、(-330.33±33.86)pA和(-287.68±71.01)pA,13月龄组鼠与2月龄组鼠相比,ICa明显降低(P＜0.05),而7月龄组鼠与2月龄组鼠和13月龄组鼠相比,ICa均没有明显差异(P＞0.05).结论不同月龄大鼠成骨细胞内[Ca2+]i存在差异,其机制可能与细胞膜上钙通道活性改变相关.     

离子通道与弱精子症

弱精子症是引起男性不育的常见病因之一。随着以精子自身为对象的研究深入,发现离子跨膜转运对精子的生理活动起着重要的作用。离子通道病于20世纪90年代提出,现已逐渐发现临床上许多先天性和/或后天获得性疾病与异常的离子通道有关。因此,关于精子的生理和疾病与离子通道的关系研究逐渐成为当前研究的热点之一。现就近年来与精子运动相关的离子通道,包括阳离子通道和阴离子通道的研究进展作一综述。     

联合补充大豆异黄酮和钙预防去势大鼠骨质疏松的实验研究

目的 研究联合补充大豆异黄酮和钙对去卵巢大鼠骨质疏松的预防作用。方法 将50只3月龄SD雌性大鼠摘除卵巢后按体重随机分成5组：假手术对照组、手术对照组、大豆异黄酮组（40mg／kgBW）、钙组（100mg／kgBW）、钙＋大豆异黄酮组（Ca100mg／kgBW＋SI40mg／kgBW）。连续灌胃饲养3个月后测定大鼠血清骨钙素，左侧股骨测定骨密度和骨钙含量、右侧股骨进行骨组织形态学计量分析。结果 Ca＋SI组血清BGP水平和股骨骨密度均高于其他去卵巢各组（P〈0．05），但低于Sham组（P〈0．05）；Ca＋SI组大鼠股骨的骨钙含量与Ca组、Sham组差异均无统计学意义；在去卵巢各组大鼠中手术对照组、大豆异黄酮组和钙组大鼠的骨小梁数目和骨小梁厚度显著减少，骨小梁间距明显增宽，与钙＋大豆异黄酮组相比有显著差异（P〈0．05）。结论 与单独补充大豆异黄酮或钙相比，大豆异黄酮与钙的联合应用能够更有效地预防去卵巢大鼠骨质疏松的发生。     

Modulation of vertebrate neuronal calcium channels by transmitters

A large number of neurotransmitters have now been shown to reduce the amplitude and slow the activation kinetics of whole cell HVA I_Ca in a great diversity of neurons. These transmitters include l-glutamate (AMPA/kainate, metabotropic and NMDA receptors), G AB A (via GABA_B receptors, NA (via α₂ receptors), 5-HT, N A (via α₂ receptors), DA and several peptides. Both whole-cell and single-channel studies have demonstrated that the N-channel is the most common channel type to be blocked by transmitters, although an inhibition of the L-type channel has also occasionally been reported. The suppression of the N-type Ca current was commonly shown to be voltage-dependent, with a relief at large positive voltages. Strong evidence has been put forward showing that the transmitter action is mediated by a G-protein, with GDP-β-S blocking transmitter action, and GTP-γ-S directly inhibiting the Ca channel. Moreover, pertussis toxin blocked the transmitter action in most neurons, and following such block, injection of the G-protein G₀ restored transmitter action. A direct link between the G-protein and the Ca channel has been widely theorized to mediate the action of transmitters on certain neurons. There is also some evidence that certain transmitters in specific neurons mediate calcium channel inhibition through a 2nd messenger, perhaps protein kinase C.Transmitters have also been found, although uncommonly, to inhibit HVA L-type and LVA T-type channels. In addition, an enhancement of both HVA and LVA, Ca currents by transmitters has been demonstrated, and substantial evidence exists for mediation of this action by cAMP.     

Cobalt-dependent potentiation of net inward current density in Helix aspersa neurons.

A low concentration of transition metal ions Co2+ and Ni2+ increases the inward current density in neurons from the land snail Helix aspersa. The currents were measured using a single electrode voltage-clamp/internal perfusion method under conditions in which the external Na+ was replaced by Tris+, the predominant external current carrying cation was Ca2+, and the internal perfusate contained 120 mM Cs+/0 K+; 30 mM tetraethylammonium (TEA) was added externally to block K+ current. In the presence of Co2+ (3 mM) or Ni2+ (0.5 mM) inward Ca2+ currents were stimulated normally by voltage-dependent activation of Ca2+ channels. There was a 5-10% decrease in the rate of rise of the inward current. The principal effect of Co2+ and Ni2+ in increasing the current density seems to be a decrease in the rate at which the inward currents decline during a depolarizing voltage pulse. The results may be due to a decrease in a voltage-dependent or Ca(2+)-dependent outward current and/or an inhibition of Ca2+ channel inactivation. Outward current under these conditions (zero internal K+) was significant and most likely due to Cs+ efflux through the voltage-activated or Ca(2+)-activated nonspecific cation channels. Co2+ is an extremely effective blocker of this outward current. These results are not an artifact of internal perfusion or the special ionic conditions. Intracellular recording of unperfused neurons in normal Helix Ringer's solution showed that the Ca(2+)-dependent action potential duration was increased significantly by low concentrations of Co2+. This result is consistant with the Co(2+)-dependent increase in inward (depolarizing) current seen in voltage-clamp experiments.     

Analysis of a decreased Na+ conductance by tumor necrosis factor in identified neurons of Aplysia kurodai.

The ionic mechanisms of the effect of extracellularly ejected recombinant human tumor necrosis factor-alpha (rhTNF-alpha) on the membrane of identified neurons R9 and R10 of Aplysia kurodai was investigated with conventional voltage-clamp, micropressure ejection, and ion substitution techniques. Micropressure-ejected rhTNF caused a marked hyperpolarization in the unclamped neuron. Clamping the same neuron at it resting potential level (-60 mV) and reejecting rhTNF-alpha with the same dose produced a slow outward current [Io (TNF)] associated with a decrease in input membrane conductance. Io (TNF) was decreased by depolarization and increased by hyperpolarization. The extrapolated reversal potential of Io (TNF) was approximately +10 mV. Ion substitution and pharmacological experiments suggest that Io (TNF) in identified neurons R9 and R10 of A. kurodai is due to a decreased Na+ conductance but not due to an activation of the Na(+)-K+ pump. Our results demonstrate that the immunomodulator TNF can act directly on the nervous system as well as on the immune system.     

磷脂酶A2激活在鼠急性缺血性脑损伤中的作用机制

目的 探讨急性脑缺血后脑组织内磷脂酶A2（PLA2）激活及细胞内[Ca^2 ]i与脑损伤的关系，为预防和治疗急性缺血性脑损伤提供理论基础和新的思路。方法 将局灶性脑缺血模型大鼠分5组（假手术组、缺血30、60、90、120min组），测定脑组织PLA2活力、脑细胞[Ca^2 ]i、脑含水量及缺血120min组脑组织PLA2表达量的改变。结果 脑缺血120min脑组织PLA2活性、[Ca^2 ]i、脑含水量较假手术组明显升高，并与时间呈正相关，缺血120min后脑组织中出现sPLA2-ⅡAmRNA表达，且cPLA2-ⅣmRNA表达水平较假手术组明显增强。结论 磷脂酶A2激活参与了脑缺血后神经细胞内钙超载及脑损伤的整人病理过程。     

胆结石对肝脏细胞钙稳态影响与调整的实验研究

用低蛋白饮食方法建立豚鼠胆色素结石模型，共设对照、致石、维生素Ｃ修复、丹参修复和对照修复等５组，规定时间内处死动物，用放射免疫、固相酶联免疫、生物化学等方法检测肝细胞内环—磷酸腺甙（ｃＡＭＰ）、环—磷酸鸟嘌呤（ｃＧＭＰ）、钙调素（ＣａＭ）、钙，三磷酸腺甙酶（Ｃａ２＋－ＡＴＰａｓｅ）、磷酸化酶ａ等水平。致石组豚鼠肝脏细胞内ｃＡＭＰ和磷酸化酶ａ升高，而ｃＧＭＰ，ＣａＭ和Ｃａ２＋－ＡＴＰａｓｅ下降，表明肝细胞钙稳态呈失调状态。维生素Ｃ和丹参可调整肝细胞的上述改变，说明维生素Ｃ和丹参具有维持肝细胞钙稳态的作用。