VOLTAGE-CLAMP PREDICTIONS BY GOMPERTZ KINETICS MODEL RELATING SQUID-AXON NA+-GATING AND IONIC CURRENTS

Gompertz kinetics is a simple, realistic, accurate, and computationally parsimonious alternative for prediction of macroscopic changes in Na⁺ conductance during voltage clamp. Conductance delay and time course depend on initial amplitudes and decay rates of surrogates for the macroscopic gating currents. The model is tested by the fit to published data of other authors. The proposed physical basis for the model is that membrane potential perturbation triggers motion of charged “gating” components of the axon membrane at rapid (activating) and at slow (inactivating) rates. The resulting distortion increases and more slowly diminishes the probability that conduction channels will be open.     

鱿鱼软骨Ⅱ型胶原蛋白提取方法及结构分析

目的从鱿鱼软骨中分离纯化非变性II型胶原蛋白,并对其进行结构表征。方法将鱿鱼软骨冻干后粉碎成200目软骨粉,用4%(w/w)Na OH溶液去除多糖、0.5 M EDTA溶液脱灰对软骨进行前处理,采用胃蛋白酶水解提取,Na Cl盐析用纯水透析后冷冻干燥得到II型胶原蛋白样品。通过氨基酸组成分析、SDS-PAGE电泳、紫外吸收光谱、电镜扫描等对制备的样品鉴定。结果制备的II型胶原蛋白具有3条α1链,分子量112 k Da,在224.5 nm波长处有最大紫外吸收,具有三螺旋结构特征。     

乌贼墨多糖抗肿瘤作用及其机制研究进展

近年来,针对海洋来源的生物物质的药用价值进行开发,特别是用于治疗严重危害人类健康的恶性肿瘤的研究,已成为药学领域的热点之一。乌贼散布于世界各大洋,乌贼墨多糖是乌贼墨中的1种重要的生物活性成分,具有抗肿瘤、抗氧化、抗菌、抗逆转录病毒等多种功效。本文就2013-2018年国内外对乌贼墨多糖抗肿瘤功效及作用机制的研究作了系统的归纳和总结,旨在为乌贼墨多糖的深入研究、开发提供理论依据。     

Axonal transport and the movement ofCa inside the giant axon of squid

⁴⁵Ca was microinjected directly into the giant axon of squid, and the radioisotope profile along the axon was determined after 2–12 h. Our results indicated that the intracellular Ca ions at the axon, unlike those at the cell body, were not axonally transported at a fast rate. The implication of this finding on the involvement of Ca in the axonal transport system is discussed.     

Water diffusion in the giant axon of the squid: Implications for diffusion-weighted MRI of the nervous system

To clarify the result that marked diffusional anisotropy had been found in nonmyelinated nerve, and in completion of an evaluation of the role of all longitudinal axonal structures, we report NMR measurements of water diffusion in the giant axon of the squid, where diffusional anisotropy is determined by the neurofilamentary structure. The diffusion coefficients of water parallel and perpendicular to the long axis of the squid giant axon at 20°C are (1.61 ± 0.06) × 10^?5 cm² s^?1 and (1.33 ± 0.09) × 10^?5 cm² s^?1, respectively, which yield an anisotropic diffusion ratio of 1.2 2 0.1. Water diffusion in the squid giant axon is therefore quite rapid and nearly isotropic, thus eliminating the possibility of a significant role for the longitudinally oriented neurofilaments in producing diffusional anisotropy within the axoplasm. In conjunction with our work on garfish nerves therefore, only membranes, either as numerous axonal membranes or as myelin (if present), remain to fulfill the role of the primary determinant of anisotropic water diffusion in nerve and in white matter.     

Trafficking of axonal K+ channels: potential role of Hsc70

Voltage-gated potassium ion channels in axons underlie the repolarization phase of the membrane action potential and help to set the resting potential. In addition to being present in the axolemma, they are also found in axoplasm in small vesicles, 30-50 nm in diameter, which may serve as a reserve pool of K+ channel protein (Clay and Kuzirian [2000] J Neurobiol 45:172-184). We have developed a novel technique for extracting these vesicles from axoplasm, which relies on the ability of Texas red to bind to them, thereby reducing their buoyancy so that they are amenable to pelleting by ultracentrifugation (Clay and Kuzirian [2000] J Neurobiol 45:172-184). The mechanism underlying this process may be binding of Texas red to Hsc70, which is primarily a cytosolic protein. However, a small portion of it is located on the surface of vesicles. Kinesin is also on the vesicle surface. This protein is membrane bound in our in vitro vesicle preparation when solutions that do not contain MgATP are added to extruded axoplasm. The addition of MgATP to the solution appears to release a significant amount of kinesin from the vesicles, possibly by the Hsc70-MgATP catalysis mechanism recently proposed by Tsai et al.     

改良稀碱法从鱿鱼肝脏中提取核酸

用改良稀碱法对从鱿鱼肝脏中提取核酸的工艺进行了摸索。结果表明：20g/L液破膜、调节pH=6、1％C液沉淀蛋白为改良稀碱法提取核酸的最佳条件。该方法成本低,提取效果好,具有一定的实用价值。     

鱿鱼内脏的综合利用研究

综合利用鱿鱼加工中废弃的内脏开发出具有经济效益的产品是有意义的。本研究利用鱿鱼内脏自身酶水解内脏及其它废弃物,开发出价廉的鱿鱼油、内脏水解液,并成功地低成本地解决了从水解液中去除镉的难题。鱿鱼内脏水解液可作为调味品原料或动物的氨基酸添加剂。     

Molecular cloning and characterization of a novel mRNA present in the squid giant axon

Previously, we reported the presence of a heterogeneous population of mRNAs in the squid giant axon. The construction of a cDNA library to this mRNA population has facilitated the identification of several of the constituent mRNAs which encode several cytoskeletal and motor proteins as well as enolase, a glycolytic enzyme. In this communication, we report the isolation of a novel mRNA species (pA6) from the axonal cDNA library. The pA6 mRNA is relatively small (550 nucleotides in length) and is expressed in both nervous tissue and skeletal muscle. The axonal localization of pA6 mRNA was unequivocally established by in situ hybridization histochemistry. The results of quantitative RT-PCR analysis indicate that there are 1.8 × 10⁶ molecules of pA6 mRNA (≈0.45 pg) in the analyzed segment of the giant axon and suggest that the level of pA6 mRNA in the axonal domain of the giant fiber system might be equal to or greater than the level present in the parental cell soma. Sequence analysis of pA6 suggests that the mRNA encodes an integral membrane protein comprising 84 amino acids. The putative protein contains a single transmembrane domain located in the middle of the molecule and a phosphate-binding loop situated near the N terminus. The C-terminal region of the protein contains two potential phosphorylation sites. These four structural motifs manifest striking similarity to domains present in the ryanodine receptor, raising the possibility that pA6 represents a cephalopod intracellular calcium release channel protein. J. Neurosci. Res. 49:144–153, 1997. © 1997 Wiley-Liss, Inc.