甾体激素对C6细胞摄取甘氨酸的快速作用

目的 :探讨甾体激素对C6细胞摄取甘氨酸快速作用的非基因组织机制。方法 :应用液体闪烁技术 ,通过检测C6细胞在加入了甾体激素和 /或其它试剂后摄入标记甘氨酸量的改变 ,确定甾体激素的作用。结果 :C6细胞高亲合力的甘氨酸依赖于钠离子和氯离子。皮质酮 ,孕酮 ,地塞米松可快速抑制这种摄取 ,雌二醇 ,脱氧皮质酮无显著的抑制作用 ,表明甾体激素作用有特异性。皮质酮的作用在 10 4 -8～ 10 -6 mmol/L范围内效应与浓度成正相关。皮质酮偶联牛血清蛋白后作用依然存在。RU38486 能部分阻断皮质酮的效应。细胞外液钙离子缺乏时皮质酮的作用基本消失。结论 :虽然皮质酮 ,孕酮 ,地塞米松神经胶质细胞和神经元摄取甘氨酸的快速作用不一样 ,但均是非基因组机制。     

SKF38393抑制大鼠DRG分离神经元GABA-激活电流

在大鼠新鲜分离ＤＲＧ神经元标本上应用全细胞膜片箝记录,观察了多巴胺Ｄ１受体的选择性激动剂ＳＫＦ３８３９３ＨＣＩ对ＧＡＢＡ－激活电流的作用。大部分受检细胞对ＧＡＢＡ敏感,１０＾－６－１０＾－３－ｍｏｌ／Ｌ ＧＡＢＡ可于引起呈剂量依赖性的明显去敏感作用的内向电流。     

抗心律失常药UK－68798对家兔心脏房室结区不同细胞的电生理作用

在离体家兔ＡＶＮ区标本上,用微电极技术研究了Ⅲ类抗心律失常新药ＵＫ－６８７９８对ＡＮ,Ｎ,ＮＨ,Ｈ４种细胞的电生理效应。浓度５×１０－９至５×１０－６ｍｏｌ／Ｌ的ＵＫ－６８７９８对４种细胞的动作电位幅值（ＡＰＡ）、静息膜电位（ＲＰ）皆无影响。对ＡＶＮ的自搏率有剂量依赖性减慢作用,但不改变Ａ－Ｈ传导时间。在５×１０－８－５×１０－６ｍｏｌ／Ｌ剂量范围,此药使动作电位时程（ＡＰＤ５０）和（ＡＰＤ９０）发生剂量依赖性延长。４种细胞中以Ｎ细胞的ＡＰＤ５０和ＡＰＤ９０延长百分率最高。各种细胞ＡＰＤ９０延长百分率的排列次序为Ｎ＜ＡＮ＜Ｈ＜ＮＨ,当浓度为５×１０－６ｍｏｌ／Ｌ时的延长百分率分别为９５±２６％（Ｎ）,７５±２２％（ＡＮ）,６３±２６％（Ｈ）,４６±２６％（ＮＨ）。在ＵＫ－６８７９８的作用下,４种细胞的有效不应期（ＥＲＰ）也发生剂量依赖性延长,但不存在像ＡＰＤ延长百分率那样的差别。此外,４种细胞ＥＲＰ所相当的复极化膜电位未受药物影响,从而避免了由于兴奋性恢复的不均一性,使ＡＶＮ区成为折返性心律失常的发源地．     

佛波醇对大鼠大脑皮层突触体及人多形胶质瘤细胞株BT-325摄取谷氨酸的促进作用

采用大鼠大脑皮层突触体,人神经母细胞瘤细胞２株ＳＫ－Ｎ－ＳＨ及人多形胶质瘤细胞株ＢＴ－３２５作氚标谷氨酸高亲和摄取实验,探讨蛋白激酶Ｃ及蛋白激酶Ａ对于神经元性及胶质细胞性谷氨酸摄取的影响。     

白介素-2促进RC-4B/C垂体瘤细胞系增殖

采用细胞培养方法,以＾３Ｈ－ＴｄＲ掺入率反映细胞增殖水平,研究了白介素－２（ＩＬ－２）对大鼠源的ＲＣ－４Ｂ／Ｃ垂体瘤细胞系增殖的影响,并初步分析了ＩＬ－２的作用机制。结果表明：⑴ＩＬ－２（１０－１０００Ｕ／ｍｌ）剂量依赖性地显著提高ＲＣ－４８／Ｃ细胞＾３Ｈ－ＴｄＲ掺入率。⑵特异性酪氨酸蛋白激酶（ＰＴＫ）抑制剂ｔｙｒｐｈｏｓｔｉｎ（１μｍｏｌ／Ｌ）可明显降低ＲＣ－４Ｂ／Ｃ细胞＾３Ｈ－ＴｄＲ掺入率,并     

正常的和转化的C3H小鼠胚胎成纤维细胞neu基因结构的初步研究

应用ＰＣＲ－ＳＳＣＰ技术并结合Ｓｏｕｔｈｅｒｎ印迹杂交从基因水平对正常和￣３Ｈ－ＴｄＲ恶性转化小鼠胚胎成纤维细胞ＮＣ３Ｈ１０和ＴＣ３Ｈ１０中ｎｅｕ基因进行研究。Ｓｏｕｔｈｅｒｎ印迹杂交结果表明恶性转化的ＴＣ３Ｈ１０细胞ｎｅｕ基因出现重排和扩增,ＳＳＣＰ分析未发现ＴＣ３Ｈ１０细胞ｎｅｕ基因跨膜区突变。上述结果说明ＴＣ３Ｈ１０细胞ｎｅｕ基因结构异常可能在跨膜区外,ｎｅｕ基因异常在￣３Ｈ－ＴｄＲ诱导的细胞恶性转化过程中可能有重要的作用,ＥＧＦ可促进ｎｅｕ基因表达增高,研究发现在ＥＧＦ持续作用下,ＮＣ３Ｈ１０细胞ｎｅｕ基因甲基化水平无显著变化,说明ＥＧＦ可能是通过其它途径调控ｎｅｕ基因表达增高的,排除了ＥＧＦ通过改变ｎｅｕ基因甲基化水平而调控ｎｅｕ基因表达的可能性。     

正常的和转化的C3H小鼠胚胎成纤维细胞neu基因结构的初步研究

应用ＰＣＲ－ＳＳＣＰ技术并结合Ｓｏｕｔｈｅｒｎ印迹杂交从基因水平对正常和＾３Ｈ－ＴｄＲ恶生转化小鼠胚胎成纤维细胞ＮＣ３Ｈ１０和ＴＣ３Ｈ１０中ｎｅｕ基因进行研究,Ｓｏｕｔｈｅｒｎ印迹杂交结果表明恶性转化的ＴＣ３Ｈ１０细胞的ｎｅｕ基因出现重排和扩增,ＳＳＣＰ分析未发现ＴＣ３Ｈ１０细胞ｎｅｕ基因跨膜区突变,上述结果说明ＴＣ３Ｈ１０细胞ｎｅｕ基因结构异常可能在跨膜区外,ｎｅｕ基因异常在＾３Ｈ－ＴｄＲ诱导的     

转TK基因的人结肠癌细胞对多种原药敏感性的研究

构建了含有单纯疱疹病毒胸苷激酶基因（ＨＳＶ－ＴＫ）的重组逆转录病毒载体ＬＴＫＳＮ,经ＰＡ３１７细胞包装后,感染人结肠癌细胞株ＬｏＶｏ．用Ｇ４１８筛选到稳定表达ＨＳＶ－ＴＫ基因的细胞克隆ＬｏＶｏ／ＬＴＫＳＮ,ＬｏＶｏ／ＬＴＫＳＮ与野生型ＬｏＶｏ细胞相比,生长曲线无明显差异,细胞形态亦无改变,细胞毒试验证明ＬｏＶｏ／ＬＴＫＳＮ对ＧＣＶ的敏感性很高,半杀伤浓度ＩＣ５０为０．５μｍｏｌ／Ｌ,比野生型细胞提     

一氧化氮抑制内皮素促血管平滑肌细胞增殖作用的信号转导途径

培养的家兔胸主动脉血管平滑肌细胞（ＶＳＭＣ）分别以内皮素（ＥＴ－１）、一氧化氮（ＮＯ）前体Ｌ－Ａｒｇ和ＮＯ供体ＳＩＮ－１刺激,或用ＥＴ－１＋Ｌ－Ａｒｇ、ＥＴ－１＋ＳＩＮ－１联合刺激,测ＶＳＭＣ＾３Ｈ－ＴｄＲ掺入、丝裂素活化蛋白激酶（ＭＡＰＫ）活性及蛋白激酶Ｃ（ＰＫＣ）活性的改变,以研究ＮＯ抑制ＥＴ－１促ＶＳＭＣ增殖作用的信号转导途径。结果表明：（１）ＥＴ－１ １０＾－８ｍｏｌ／Ｌ单独刺激,＾３Ｈ－     

P物质对大鼠骶髓后连合核神经元甘氨酸激活的氯电流的调控

采用制霉菌素穿孔膜片箍技术,研究了Ｐ物质对急性分离的大鼠骶髓后的核神经元士的宁敏感性甘氨酸反应的调控作用。在箍制电压为－４０ｍＶ时,ＳＰ时１ｍｍｏｌ／Ｌ－１μｍｏｌ／Ｌ之间呈浓度依赖性地增强３０μｍｏｌ／Ｌ甘氨酸激活的氯电流。ＳＰ既不改变ＩＧｌｙ的翻转电位,也不是影响Ｇｌｙ与其受体的亲和力。Ｓｐａｎｔｉｄｅ和选择性Ｎ中受体拮抗剂,Ｌ－６６８,１６９,可阻断ＳＰ的增强作用,而选择性ＮＫ２受体拮抗剂,     

Corticosterone acutely prolonged N-methyl-d-aspartate receptor-mediated Ca2+ elevation in cultured rat hippocampal neurons

This work reports the first demonstration that corticosterone (CORT) has a rapid and transient effect on NMDA receptor-mediated Ca2+ signaling in cultured rat hippocampal neurons. Using single cell Ca2+ imaging, CORT and agonists of glucocorticoid receptors were observed to modulate the NMDA receptor-mediated Ca2+ signals in a completely different fashion from pregnenolone sulfate. In the absence of steroids, 100 micro m NMDA induced a transient Ca2+ signal that lasted for 30-70 s in 86.1% of the neurons prepared from postnatal rats (3-5 days old). After pre-treatment with 0.1-100 micro m CORT for 10-20 min, NMDA induced extremely prolonged Ca2+ elevation. This prolonged Ca2+ elevation was terminated by the application of MK-801 and followed by washing out of CORT. The proportion of CORT-modulated neurons within the NMDA-responsive cells increased from 25.1 to 95.5% when the concentration of CORT was raised from 0.1 to 50 micro m. Substitution of BSA-conjugated CORT produced essentially the same results. When hippocampal neurons were preincubated with 10 micro m cortisol and 1 micro m dexamethasone for 20 min, a very prolonged Ca2+ elevation was also observed upon NMDA stimulation. The CORT-prolonged Ca2+ elevation caused a long-lasting depolarization of the mitochondrial membrane, as observed with rhodamine 123. In contrast, incubation with 100 micro m pregnenolone sulfate did not considerably alter the time duration of NMDA-induced transient Ca2+ elevation, but caused a significant increase in the peak amplitude of Ca2+ elevation in hippocampal neurons. These results imply that high levels of CORT induce a rapid and non-genomic prolongation of NMDA receptor-mediated Ca2+ elevation, probably via putative membrane surface receptors for CORT in the hippocampal neurons.     

Acute effect of corticosterone on N-methyl-D-aspartate receptor-mediated Ca2+ elevation in mouse hippocampal slices

We examined the rapid effects of corticosterone (CORT) on N-methyl-D-aspartate (NMDA) receptor-mediated Ca2+ signals in adult mouse hippocampal slices by using Ca2+ imaging technique. Application of NMDA caused a transient elevation of intracellular Ca2+ concentration followed by a decay to a plateau within 150s. The 30min preincubation of CORT induced a significant decrease of the peak amplitude of NMDA-induced Ca2+ elevation in the CA1 region. The rapid effect of CORT was induced at a stress-induced level (0.4-10microM). Because the membrane non-permeable bovine serum albumin-conjugated CORT also induced a similar rapid effect, the rapid effect of CORT might be induced via putative surface CORT receptors. In contrast, CORT induced no significant effects on NMDA-induced Ca2+ elevation in the dentate gyrus. In the CA3 region, CORT effects were not evaluated, because the marked elevation of NMDA-induced Ca2+ signals was not observed there.     

Uptake and Release of Glycine in the Guinea Pig Cochlear Nucleus

This study attempts to determine if the cochlear nucleus (CN) contains glycinergic synaptic endings. The uptake and release of exogenous radiolabeled glycine were measured in vitro in the three major subdivisions of the guinea pig CN: anteroventral, posteroventral, and dorsal. A kinetic analysis of [3H]glycine uptake revealed the presence in each CN subdivision of a high- and a low-affinity uptake mechanism. The high-affinity mechanism had a Km of 25.2-30.5 microM and a Vmax of 3.8-4.8 nmol/10 mg of cell water/5 min, whereas the low-affinity mechanism had a Km of 633-718 microM and a Vmax of 26.6-37.1 nmol/10 mg of cell water/5 min. At steady state, the high-affinity mechanism accumulated 10 microM [3H]glycine from the medium, achieving tissue concentrations that were 13-24 times that in the medium. The high-affinity uptake was dependent on the temperature and on the concentrations of NaCl and glucose in the incubation medium. It exhibited a high degree of substrate specificity, as determined by the effects of structural analogues of glycine on the uptake of [3H]glycine. Each CN subdivision also contained two mechanisms mediating [14C]glycine release. One was activated by depolarizing electrical stimuli, produced a rapid transient release of [14C]glycine, and was dependent on the presence of extracellular Ca2+. The other was continuous, producing a slow spontaneous efflux of [14C]glycine. Released glycine could be removed primarily by uptake, because during release measurements, the amount of [14C]glycine detected in the medium decreased when glycine uptake activity was optimized. The electrically evoked, Ca2+-dependent release and the high-affinity uptake of glycine may mediate the synaptic release and inactivation of glycine, respectively. These findings, therefore, support the presence of glycinergic synaptic endings in each CN subdivision.     

Calcium influx mediated by nicotinic receptors and voltage sensitive calcium channels in SK-N-SH human neuroblastoma cells

When SK-N-SH human neuroblastoma cells were exposed to nicotine (NIC) or KCl they showed a dose-dependent transient increase (2- to 4-fold) in intracellular Ca2+ concentration ([Ca2+])i as detected by quin-2 fluorescence, with half maximal effects (EC50) observed at 13 microM and 26 mM, respectively. Tubocurarine and 1-isodihydrohistrionicotoxin potently blocked the NIC-evoked (IC50 congruent to 1 microM and 0.3 microM, respectively), but not the high [K+]o-evoked [Ca2+]i accumulation. The KCl-induced response was inhibited by verapamil and diltiazem (IC50 = 1.4 and 10.9 microM, respectively). Tetrodotoxin (3 microM) and tetraethylammonium (10 microM) had no effect on [Ca2+]i accumulation induced by either agent. Increases in [Ca2+]i could be evoked sequentially by NIC and KCl in the same cells suggesting independent mechanisms of Ca2+ entry. In a Ca2+-free medium, no response to either KCl or NIC was observed. However, when Ca2+ ions were restored, [Ca2+]i accumulation was enhanced to the same extent as cells suspended in a Ca2+-containing buffer. Long-term (18 hr) pretreatment of SK-N-SH cells with pertussis (100 ng/ml) or cholera toxins (10 nM) had no effect on NIC or KCl-induced [Ca2+]i accumulation. Together, these data demonstrate the presence of NIC receptors and voltage-sensitive Ca2+ channels on SK-N-SH neuroblastoma cells, through which [Ca2+]i may be modulated.     

Influence of Ca2+ on the plasma membrane potential and electrogenic uptake of glycine by myeloma cells. Involvement of a Ca2+-activated K+ channel

The involvement of Ca2+-activated K+ channels in the regulation of the plasma membrane potential and electrogenic uptake of glycine in SP 2/0-AG14 lymphocytes was investigated using the potentiometric indicator 3,3'-diethylthiodicarbocyanine iodide. The resting membrane potential was estimated to be -57 +/- 6 mV (n = 4), a value similar to that of normal lymphocytes. The magnitude of the membrane potential and the electrogenic uptake of glycine were dependent on the extracellular K+ concentration, [K+]o, and were significantly enhanced by exogenous calcium. The apparent Vmax of Na+-dependent glycine uptake was doubled in the presence of calcium, whereas the K0.5 was not affected. Ouabain had no influence on the membrane potential under the conditions employed. Additional criteria used to demonstrate the presence of Ca2+-activated K+ channels included the following: (1) addition of EGTA to calcium supplemented cells elicited a rapid depolarization of the membrane potential that was dependent on [K+]o; (2) the calmodulin antagonist, trifluoperazine, depolarized the membrane potential in a dose-dependent and saturable manner with an IC50 of 9.4 microM; and (3) cells treated with the Ca2+-activated K+ channel antagonist, quinine, demonstrated an elevated membrane potential and depressed electrogenic glycine uptake. Results from the present study provide evidence for Ca2+-activated K+ channels in SP 2/0-AG14 lymphocytes, and that their involvement regulates the plasma membrane potential and thereby the electrogenic uptake of Na+-dependent amino acids.     

Rapid Elevation of Calcium Concentration in Cultured Dorsal Spinal Cord Astrocytes by Corticosterone

In addition to the classic genomic effects, increasing evidence suggests that GC can generate multiple rapid effects on many tissues and cells through nongenomic pathway. In the present study, the effects of corticosterone (CORT) on the intracellular calcium concentration ([Ca²⁺]i) in cultured dorsal spinal cord astrocytes were detected with confocal laser scanning microscopy using fluo-4/AM as a calcium fluorescent indicator that could monitor real-time alterations of [Ca²⁺]i. CORT (0.01–10 μM) caused a rapid increase in [Ca²⁺]i with a dose-dependent manner in cultured dorsal spinal cord astrocytes. The action of CORT on astrocytic [Ca²⁺]i was blocked by pertussis toxin (a blocker of G protein activation, 100 ng/ml), but was unaffected by RU38486 (glucocorticoid receptor antagonist, 10 μM). In addition, cycloheximide (protein-synthesis inhibitor, 10 μg/ml) pretreatment could not impair the CORT-evoked [Ca²⁺]i elevation. Furthermore, Ca²⁺ mobilization induced by CORT was abolished by chelerythrine chloride (protein kinase C inhibitor, 10 μM), but was not impaired by H89 (protein kinase A inhibitor, 10 μM). These observations suggest that a nongenomic pathways might be involved in the effect of CORT on [Ca²⁺]i in cultured dorsal spinal cord astrocytes. In addition, our results also raise a possibility that a putative pertussis toxin-sensitive mGCR (G-protein-coupled membrane-bound glucocorticoid receptor) and the downstream activation of protein kinase C may be responsible for CORT-induced Ca²⁺ mobilization in cultured dorsal spinal cord astrocytes.     

Development of a scintillation proximity assay for analysis of Na+/Cl- -dependent neurotransmitter transporter activity

Human placental choriocarcinoma (JAR) cells endogenously expressing glycine transporter type 1a (GlyT1a) have been cultured in 96-well scintillating microplates to develop a homogenous screening assay for the detection of GlyT1 antagonists. In these microplates uptake of [14C]glycine was time dependent and saturable with a Michaelis-Menten constant (Km) of 27+/-3 microM. The GlyT1 transport inhibitors sarcosine, ALX-5407, and Org-24598 were tested and shown to block [14C]glycine uptake with expected IC50 values of 37.5+/-4.6 microM, 2.8+/-0.6 nM, and 6.9+/-0.9 nM, respectively. The [14C]glycine uptake process was sensitive to membrane Na+ gradient as blockade of membrane Na+/K+-ATPase by ouabain or Na+ exchanger by benzamil-disrupted glycine accumulation in JAR cells. Glycine influx was not affected by concentration of dimethyl sulfoxide up to 2%. The versatility of this technological approach was further confirmed by the characterization of a saturable [14C]taurine uptake in JAR cells. Taurine transport was of high affinity with a Km of 10.2+/-1.7 microM and fully inhibited by ALX-5407 (IC50=522 +/-83 nM). The developed assay is homogenous, rapid, versatile and amenable to automation for the discovery of new neurotransmitter transporter inhibitors.     

皮质酮对原代培养海马神经元的毒性作用及NMDA受体亚基表达的改变

目的研究皮质酮对大鼠海马神经元的毒性作用及NMDA受体亚基表达的影响.方法以体外原代培养的大鼠海马神经元为研究对象,根据影响因素,即给予的不同浓度皮质酮和其它因素分为8个组:对照组、10-7mol/L皮质酮组(简称10-7组)、10-6mol/L皮质酮组(简称10-6组)、10-5mol/L皮质酮组(简称10-5组)、10-6 高糖组、10-5 高糖组、10-6mol/L MK801组和10-5mol/L MK801组,镜下观察不同浓度皮质酮作用下海马神经元形态学的变化,并采用MTT方法测量各组细胞存活率,利用免疫细胞化学结合图象分析对原代培养海马神经元NMDA受体亚基的表达进行观察.结果 10-6、10-5浓度的皮质酮对海马神经元影响较大,细胞存活率较对照组明显降低,但10-6 高糖组、 10-5mol/L 高糖组、10-6mol/L MK801及10-5mol/L MK801 4个组,分别与相同皮质酮浓度处理组比较,细胞存活率显著提高.10-6和10-5组海马神经元上NMDA受体亚基表达较对照组明显降低.10-7mol/L浓度的皮质酮对上述指标影响不大.结论过量的皮质酮对大鼠海马神经元具有损伤作用,NMDA受体参与了此过程,NMDA受体拮抗剂和高浓度葡萄糖可保护海马神经元.