Identification of a voltage- and calcium-dependent non-selective cation channel in cultured adult and fetal human nasal epithelial cells

The apical membranes of cultured human nasal epithelial cells from adults and fetuses were investigated with the patch-clamp technique. Amiloride-insensitive, calcium- and voltage-dependent, non-selective cation channels were found in 4% of the cell-attached, and 18% of the inside-out and outside-out patches (n=412). Multiple functional channels were present in more than 90% of these patches, with a mean of 3.9 channels per patch (n=55). The current-voltage relationship can be described by the Goldman equations and the single channel conductance was 20.1±0.3 pS (n=29) in adult and 20.7±0.4 pS (n=44) in fetal cells in symmetrical 150mM NaCl solutions. The channels were highly selective for cations: P_Na/P_Cl was 30 in adult and 45 in fetal experiments. They were equally permeable for K⁺ and Na⁺, somewhat less for Cs⁺, and impermeable for choline⁺ and tetraethylammonium⁺. The open probability was voltage dependent: it increased approximately 2-fold with 30mV depolarization in the potential range from −60mV to +60mV. The channels were activated by Ca²⁺ concentrations of about 10⁻⁴M at the cytoplasmic side, but were insensitive to extracellular Ca²⁺ and amiloride (10⁻⁴M). The non-selective cation channels found in apical membranes of cultured fetal nasal epithelial cells were not different from the adult ones.     

Fast and slow blockades of the inward-rectifier K+ channel by external divalent cations in guinea-pig cardiac myocytes

The present patch-clamp study shows that external Mg²⁺, Ca²⁺ and Sr²⁺ decrease the unit amplitude of inward current through the inward-rectifier K⁺ channel in a concentration-dependent manner. Sr²⁺ produces a voltage-dependent flickering block as well, and the fractional electrical distance between the external orifice and the Sr²⁺ binding site () is 0.73. The decrease of unit amplitude is reversible and voltage independent while it does not increase the noise level on the open-channel current. Unit current decreased by Mg²⁺ or Ca²⁺ has a longer mean open time, which is inversely proportional to the unit amplitude. External Mg²⁺ does not decrease the amplitude of unit outward current. A surface potential shift, measured using voltage-dependent Cs⁺ block (=1.60), failed to explain the current decrease. Therefore, we conclude that (1) the external divalent cations cause an extremely fast channel block, which appears as a decreased amplitude of the unit current on the recording system; (2) the blocking site (fast site) is present near the external orifice of the channel, and it is separate from the blocking site (slow site) to which Cs⁺ and Sr²⁺ bind.     

Evidence for a direct and non-receptor-mediated action of 5HT2 antagonists on transmembrane cation transport systems

Summary Changes in transmembrane sodium fluxes have been reported in normotensive and in hypertensive subjects after ketanserin administration. In this study, the effects of the serotonergic system on transmembrane sodium transport mechanisms have been investigated in vitro. In erythrocytes drawn from ten healthy subjects, we studied the effects of serotonin (5HT) on the Na/K pump, Na/K cotransport, Na/Li countertransport, and passive permeability of Na. No significant changes were found. A direct, non-receptor-mediated action of ketanserin was then suspected, and the effects of two concentrations of ketanserin (5×10^-8 and 5×10^-7 M) were evaluated in erythrocytes from 12 normal volunteers. Both concentrations of ketanserin significantly decreased the activity of the Na/K pump and increased the activity of Na/Li countertransport. Na/K cotransport and passive permeability were not affected. Indirect evidence of the action of ketanserin on sodium transmembrane fluxes came from other experiments. In the red blood cells taken from five normal subjects and incubated for 2 hours in a plasma pool, we evaluated the changes in intracellular sodium concentration induced by the presence of 5HT or ketanserin. A significant decrease in intracellular sodium concentration occurred only with ketanserin. This study indicates that ketanserin has a direct influence on transmembrane sodium fluxes. If this action were also present in other cells, it might contribute to the actions of the drug at vascular, nervous, and renal tubular levels.     

Flexural properties of rectangular nickel-titanium orthodontic wires when used as ribbon archwires

Objective:To compare the flexural properties of rectangular nickel-titanium (Ni-Ti) orthodontic wires in occlusoapical and faciolingual orientations using a standardized test method.Materials and Methods:Twenty-two rectangular Ni-Ti wire groups were tested in occlusoapical (ribbon) orientation: eight conventional Ni-Ti products, five superelastic Ni-Ti products, and nine thermal Ni-Ti products (n = 10 per group). Six products of thermal Ni-Ti wire were tested in faciolingual (edgewise) orientation. A three-point bending test was performed to measure deactivation force at 3.0-, 2.0-, 1.0-, and 0.5-mm deflections of each rectangular wire at 37.0 ± 0.5°C. Analysis of variance and post hoc Student-Newman-Keuls tests were used to compare the mean values of the different groups (α = .05).Results:The ranges of deactivation forces varied greatly with different kinds, sizes, products, and deflections of Ni-Ti wires. One product of conventional and superelastic Ni-Ti wires had steeper force-deflection curves. Four products had similarly shaped flat force-deflection curves, whereas the sixth product had a moderately steep force-deflection curve. Thermal Ni-Ti wires had smaller deactivation forces ranging from 0.773 N (78.8 g) to 2.475 N (252.4 g) between deflections of 1.0 and 0.5 mm, whereas wider ranges of force from 3.371 N (343.7 g) to 9.343 N (952.7 g) were predominantly found among conventional Ni-Ti wires between deflections of 3.0 and 2.0 mm.Conclusions:Clinicians should critically select archwires for use in the occlusoapical orientation not only based on Ni-Ti wire type, size (0.022 × 0.016-in or 0.025 × 0.017-in), and product but also with deactivation deflections from 0.5 and 1.0 mm to obtain light forces in the occlusoapical orientation.     

铜吸收转运蛋白介导放射性肠损伤的作用及机制研究

目的 探讨铜吸收转运蛋白（CTR1）在辐射诱导的小肠细胞放射损伤中发挥的作用及机制。方法 采用人小肠上皮细胞（HIEC）和大鼠小肠隐窝上皮细胞（IEC-6）,分别经2、4、6、8 Gy和5、10、15、20 Gy X射线照射,构建放射损伤细胞模型。照后2、4、8、24、48 h收集细胞,通过Western blot检测CTR1蛋白对辐射的时间-剂量响应。将CTR1 shRNA转染入HIEC和IEC-6细胞后进行X射线照射,采用电感耦合等离子体质谱仪（ICP-MS）检测细胞内铜水平。通过克隆形成实验确定CTR1对上述细胞辐射敏感性作用,检测活性氧（ROS）水平和DNA损伤来进一步探讨相关机制。Western blot检测X射线照射以及沉默CTR1对抗氧化蛋白Nrf2、HO-1,铜死亡相关蛋白DLAT、LIAS和FDX1表达的影响,初步确定CTR1的调控机制。结果 Western blot表明两株细胞经不同剂量的X射线照射后CTR1表达均显著上调,并且呈显著的时间剂量响应关系（t=3.53、3.45、6.37、11.11、11.13,P<0.05）。沉默CTR1后的两株细胞放射敏感性均低于对照,增敏比分别为1.146、1.201。沉默CTR1缓解了辐射诱导IEC-6细胞内的铜蓄积（t=3.10,P<0.05）。两株细胞照射沉默组ROS产量显著低于照射对照组（t=5.23、2.96,P<0.05）;并且照射沉默组γ-H2AX蛋白表达较照射对照组有所减少（t=7.50、4.29,P<0.05）。此外,X射线诱导Nrf2、HO-1蛋白表达上调;沉默CTR1后Nrf2和HO-1的表达会进一步增加。电离辐射导致铜死亡标志物DLAT以及铁硫簇蛋白LIAS、FDX1丢失,而沉默CTR1能促进上述蛋白表达水平恢复正常。结论 CTR1沉默后的小肠细胞HIEC和IEC-6辐射抗性增强,涉及的机制可能与氧化应激和铜死亡途径有关。     

铜针与不锈钢针留置于兔耳中央静脉内的比较

目的铜针留置术治疗海绵状血管瘤等血管性疾病,因其特有的优点,临床已开展应用。为了解铜针留置于血管内所发生的病理变化。方法我们用60只家兔的中央静脉行铜针留置,并与不锈钢针留置比较观察血管腔内所发生的病理变化及超微结构改变。结果铜针留置后7天内为急性炎症过程及血栓形成,14天后形成异物性肉芽肿组织,28～60天后瘢痕组织纤维化,血管结构消失。不锈钢针留置诱发的炎症过程轻,血栓形成迟且较小。结论铜针治疗血管性疾病优于不锈钢针。     

铜针与不锈钢针留置于兔耳中央静脉内的比较

目的铜针留置术治疗海绵状血管瘤等血管性疾病,因其特有的优点,临床已开展应用。为了解铜针留置于血管内所发生的病理变化。方法我们用６０只家兔的中央静脉行铜针留置,并与不锈钢针留置比较观察血管腔内所发生的病理变化及超微结构改变。结果铜针留置后７天内为急性炎症过程及血栓形成,１４天后形成异物性肉芽肿组织,２８～６０天后瘢痕组织纤维化,血管结构消失。不锈钢针留置诱发的炎症过程轻,血栓形成迟且较小。结论铜针治疗血管性疾病优于不锈钢针。