Acetylcholine receptor and calcium leakage activity in nondystrophic and dystrophic myotubes (MDX)

To determine whether the lack of dystrophin alters the occurrence of calcium leakage activity (CLA) and acetylcholine receptor (AChR) activity, the frequency of each event class was determined from several cell attached patches on nondystrophic and dystrophic (mdx) myotubes. The frequency of CLA observed in the presence of ACh was significantly (P < 0.05) elevated in mdx myotubes, an effect which was partly due to a significant (P < 0.05) increase in the proportion of cell attached patches that exhibited 100% CLA with no AChR activity. Areas of mdx and nondystrophic membrane that exhibited reduced or absent AChR activity had significantly (P < 0.01) and substantially elevated calcium leakage event frequencies. This inverse and discontinuous relationship between CLA and AChR activity provides further evidence that some CLA in dystrophic muscle is produced by clusters of AChRs that form unusual physical associations with the dystrophic cytoskeleton during the processes associated with receptor localization and stabilization. © 1996 John Wiley & Sons, Inc.     

Regioselective Approach to Characterizing Increased Edge Availability in Layered Crystal Materials following Layer Expansion: Reaction of Kaolinite with Octadecyltrimethylammonium Salts

In this paper, the regioselective reactions of kaolinite and methoxy-modified kaolinite (MeO-Kaol), methanol-expanded kaolinite, with octadecyltrimethylammonium salts are compared. This study mainly concerns the reactions of kaolinite or MeO-Kaol with octadecyltrimethylammonium chloride (C18TAC) in methanol and the subsequent exhaustive washing of the resultant products with ethanol. X-ray diffraction patterns of the products reveal no intercalation of C18TAC between pristine kaolinite layers. Additionally, intercalation and subsequent deintercalation of C18TAC proceed in the product using MeO-Kaol. In the Fourier-transform infrared spectra, the intensities of CH₂ stretching bands of the product prepared using MeO-Kaol drastically increase compared to those using kaolinite. In addition, CH₂ stretching bands of the product using kaolinite are hardly observed without enlarging the spectrum. The product using MeO-Kaol also displays mass loss in the range of 200–300 °C in the thermogravimetric curve and a nitrogen content with 0.15 mass% estimated using the CHN analysis. These results therefore demonstrate an increase in the available reactive edges in the layered crystal material following an expansion of the stacked layers.     

钙离子在疼痛和抗伤害性感受中的作用

1钙通道的结构与分类钙离子广泛地参与各种生命活动的调节。通过细胞膜上的钙通道、离子泵的转运或细胞内钙库释放钙离子使胞浆钙离子浓度急剧升高,促使突触囊泡释放神经递质,引起膜兴奋性的改变。钙离子内流主要经由3种不同类型的钙通道:电压依从型钙通道(VOCC)、配体门控非特     

钾离子浓度对离体毛细胞凋亡的影响

目的 探讨钾离子浓度对离体毛细胞凋亡的作用.方法 采用胶原酶制备离体耳蜗毛细胞,模拟病理状态下的钾离子浓度(100mmol/L)环境,用倒置显微镜、荧光显微镜下观察毛细胞凋亡改变.结果 病理状态钾环境下离体耳蜗毛细胞的凋亡改变类似于Hank′s液下毛细胞的凋亡改变,即胞核皱缩;纤毛泡状或倒伏;胞质内可见布朗运动.荧光显微镜下凋亡毛细胞呈红色或红黄色荧光,毛细胞形态完整,无胞膜破裂或胞质溢出.随着时间延长毛细胞凋亡数逐步增多,二者凋亡率差异无统计学意义(P＞0.05).结论 在离体环境下,此种病理状态下的钾离子浓度(100mmol/L)对离体毛细胞的凋亡无显著性影响.     

Synthesis and Properties of Nitrogen-Doped Carbon Quantum Dots Using Lactic Acid as Carbon Source

Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized in a one-step hydrothermal technique utilizing L-lactic acid as that of the source of carbon and ethylenediamine as that of the source of nitrogen, and were characterized using dynamic light scattering, X-ray photoelectron spectroscopy ultraviolet-visible spectrum, Fourier-transformed infrared spectrum, high-resolution transmission electron microscopy, and fluorescence spectrum. The generated N-CQDs have a spherical structure and overall diameters ranging from 1–4 nm, and their surface comprises specific functional groups such as amino, carboxyl, and hydroxyl, resulting in greater water solubility and fluorescence. The quantum yield of N-CQDs (being 46%) is significantly higher than that of the CQDs synthesized from other biomass in literatures. Its fluorescence intensity is dependent on the excitation wavelength, and N-CQDs release blue light at 365 nm under ultraviolet light. The pH values may impact the protonation of N-CQDs surface functional groups and lead to significant fluorescence quenching of N-CQDs. Therefore, the fluorescence intensity of N-CQDs is the highest at pH 7.0, but it decreases with pH as pH values being either more than or less than pH 7.0. The N-CQDs exhibit high sensitivity to Fe³⁺ ions, for Fe³⁺ ions would decrease the fluorescence intensity of N-CQDs by 99.6%, and the influence of Fe³⁺ ions on N-CQDs fluorescence quenching is slightly affected by other metal ions. Moreover, the fluorescence quenching efficiency of Fe³⁺ ions displays an obvious linear relationship to Fe³⁺ concentrations in a wide range of concentrations (up to 200 µM) and with a detection limit of 1.89 µM. Therefore, the generated N-CQDs may be utilized as a robust fluorescence sensor for detecting pH and Fe³⁺ ions.     

Compositional Effects on Indentation Mechanical Properties of Chemically Strengthened TiO2-Doped Soda Lime Silicate Glasses

TiO₂ is an important oxide for property modifications in the conventional soda lime silicate glass family. It offers interesting optical and mechanical properties, for instance, by substituting heavy metals such as lead in consumer glasses. The compositional effects on the hardness, reduced elastic modulus and crack resistance as determined by indentation of chemically strengthened (CS) TiO₂-doped soda lime silicate glass was studied in the current paper. The CS, which was performed by a K⁺ for Na⁺ ion exchange in a molten KNO₃ salt bath at 450 °C for 15 h, yielded significant changes in the indentation mechanical properties. The hardness of the glass samples increased, and this was notably dependent on the SiO₂, CaO and TiO₂ content. The reduced elastic modulus was less affected by the CS but showed decrease for most samples. The crack resistance, an important property in many applications where glasses are subjected to contact damage, showed very different behaviors among the series. Only one of the series did significantly improve the crack resistance where low CaO content, high TiO₂ content, high molar volume and increased elastic deformation favored an increased crack resistance.     

不同部位诱发癫痫动物模型对比研究

目的 探讨铁离子不同部位诱发外伤性癫痫动物模型的稳定性和可靠性.方法 健康成年雄性大鼠50只,随机分为5组:SDA、SDB、SDC、SDD、SDE,各10只,其中SDA、SDB为对照组;SDC、SDD、SDE为癫痫模型组,采用不同方法制备癫痫模型,点燃成功后,收集行为表现、脑电图、组织病理等3方面资料,行统计学分析.结果研究结果显示SDC、SDD、SDE均能点燃癫痫动物模型,其中SDD点燃动物模型出现早,持续时间短,不适合作为人类癫痫基础研究;组织病理方面,SDA和SDB比较P＞0.05,差异无统计学意义,排除实验干扰导致海马CA1神经元细胞丢失;SDC、SDD、SDE均能使CA1区锥体细胞数减少,与对照组相比P＜0.01,差异有统计学意义;对侧相比P＜0.01,差异有统计学意义;3组同侧之间比较P＞0.05,差异无统计学意义.结论 额叶皮层运动区注射铁离子操作简单、成功率高、可靠性好,相比于其他两种,更为适合外伤性癫痫基础研究和药物研究.     

Direct evidence for the presence of GABAA receptors on the cytoplasmic side of the Deiters' neurone membrane

A newly developed micromethod has been used for studying the rate of passage of³⁶Cl⁻ ions across single nerve membranes from rabbit Deiters' neurones. The application of γ-aminobutyric acid (GABA) on the cytoplasmic side of those membranes increases the rate of passage of³⁶Cl⁻ ions from that side to the other one across the membrane. The maximal effect is exerted by 10⁻⁶ M GABA and it fades at higher neurotransmitter concentrations (10⁻⁵M to3.3 × 10⁻³M). The cause of this fading of the effect appears to be a receptor desensitization phenomenon. The 10⁻⁶ M GABA effect is reversed by both 10⁻⁴ M picrotoxin and 10⁻⁵ M bicuculline. The overall pattern of the data indicates the presence of GABA_A receptors on the cytoplasmic side of these nerve membranes.     

Podophyllum hexandrum Offers Radioprotection by Modulating Free Radical Flux: Role of Aryl-Tetralin Lignans

We have evaluated the effect of variation in aryl-tetralin lignans on the radioprotective properties of Podophyllum hexandrum. Two fractionated fractions of P. hexandrum [methanolic (S1) and chloroform fractions (S2)], with varying aryl-tetralin lignan content were utilized for the present study. The peroxyl ion scavenging potentials of S1 and S2 were found to be comparable [i.e. 45.88% (S1) and 41% (S2)] after a 48 h interval in a time-dependent study, whereas in a 2 h study, S2 exhibited significant (P < 0.05) antioxidant activity in different metal ion + flux states. In the aqueous phase, S2 exhibited non-site-specific reactive oxygen species scavenging activity, i.e. 73.12% inhibition at 500 mug ml(-1). S1 exhibited 58.40 +/- 0.8% inhibition (at 0.025 mug ml(-1)) of the formation of reactive nitrite radicals, comparable to S2 (52.45 +/- 0.825%), and also showed 45.01% site-specific activity (1000 mug ml(-1)), along with significant (P < 0.05) electron donation potential (50-2000 mug ml(-1)) compared to S2. Such activities of S1 could be attributed to the significantly (P < 0.05) higher levels of podophyllotoxin beta-d-glucopyranoside (16.5 times) and demethyl podophyllotoxin glucoside (2.9 times) compared with S2. Together, these findings clearly prove that aryl-tetralin lignan content influences the radiation protective potential of the Podophyllum fractions to a great extent.