Activation of a non-specific cation conductance by intracellular injection of inositol 1,3,4,5-tetrakisphosphate into identified neurons of Aplysia

The ionic mechanism of the effect of intracellulary injected inositol 1,3,4,5-tetrakisphosphate (IP₄) on the membrane of identified neurons (R9–R12) of Aplysia kurodai was investigated with conventional voltage-clamp, pressure injection, and ion-substitution techniques. Intracellular injection of IP₄ into a neuron voltage-clamped at −45 mV reproducibly induced a slow inward current (20–60 s in duration, 3–5 nA in amplitude) associated with a conductance increase. The current was decreased by depolarization and increased by hyperpolarization. The extrapolated reversal potential was −21 mV. The IP₄-induced inward current was sensitive to changes in the external Na⁺, Ca²⁺ and K⁺ concentration but not to changes in Cl⁻ concentration, and was resistant to tetrodotoxin (50 μM). When the cell was perfused with tetraethylammonium (5 mM) but not with 4-aminopyridine (5 mM), the IP₄-induced inward current recorded at −45 mV slightly increased. The IP₄-induced inward current was partially reduced by calcium channel blockers (Co²⁺ and Mn²⁺). These results suggest that intracellularly injected IP₄ can activate a non-specific cation conductance.     

Independent folding of autolytic fragments of thermolysin and their domain-like properties

High molecular weight autolysis products from thermolysin have been isolated and identified. The primary fragments correspond to residues 1 to 187–204 (21kD) and residues 187–204 to 316 (12kD), respectively. The fragments are both capable of independent refolding upon removal of denaturant. On the basis of these results, we suggest that the first step in the unfolding pathway of thermolysin involves unfolding of an interdomain region and domain separation. Bound calcium ions at sites 1, 2 and 4 play a major role in protecting the protein against both autolysis and unfolding, probably by stabilizing the interdomain region and enhancing domain-domain interactions.     

Effect of divalent cations and proteases on skin sulfhydryl oxidase activity

Crude skin sulfhydryl oxidase was independently isolated from the living cell layer, the granular cell layer, and the lower living cell layer (spinous and basal) of cow snout. The properties of this enzyme were subsequendy investigated. The addition of 1 mM CuCl₂ and FeCl₂ stimulated the enzyme activity to 216% and 166% of the initial activity, respectively. Neither CaCl₂ nor MgCl₂ had much effect on the activity, and ZnCl₂ inhibited it. Diethyldithiocarbamate (DEDTC), a copper ion chelating agent, inhibited the activity in a dose and pre-incubation time-dependent manner: however, other divalent cation chelators such as EDTA, EGTA, o-phenanthrolin and α,α'-dipyridyl did not have any effect on the enzyme's behavior. From these findings, it was determined that Cu²⁺ was essential for the activity of skin sulfhydryl oxidase. This enzyme was stimulated to 130–150% of its initial activity by treatment with 1 mg/ml trypsin, chymotrypsin or urokinase but was not affected by plasmin, elastase or cathepsin D. Trypsin treatment enhanced the activity in a dose and treatment-time dependent manner. Skin sulfhydryl oxidase from the lower living cell layer (spinous and basal) was more highly activated by trypsin treatment than was that from the granular cell layer. These findings suggest that this enzyme may be activated by some kind of serine proteases during the keratinocytes autolysis process in the granular cell layer.     

Passive and Carrier-Mediated Intestinal Absorption Components of Two Angiotensin Converting Enzyme (ACE) Inhibitor Prodrugs in Rats: Enalapril and Fosinopril

The intestinal absorption mechanism of two ACE inhibitor prodrugs, enalapril and fosinopril, was investigated in rats using a single-pass perfusion method. A modified boundary layer solution was applied to determine the apparent intestinal wall permeability. The prodrug enalapril is well absorbed from rat jejunum, whereas the parent drug, enalaprilat, is poorly absorbed. The permeability of enalapril is concentration dependent and is decreased by the dipeptide Tyr-Gly and by cephradine but not by the amino acids L-leucine or L-phenylalanine, indicating a nonpassive absorption mechanism via the small peptide carrier-mediated transport system. In contrast, fosinopril is readily absorbed by a concentration-independent mechanism without the involvement of the peptide carrier.     

中医药调控线粒体功能防治肝衰竭的研究进展

肝衰竭（LF）作为一种肝细胞严重损害及肝脏功能障碍的临床综合征，其高死亡率、高发病率与高医疗资源耗竭呈现出三重叠加，成为阻碍人类健康的重大疑难重症。深入研究其疾病发生的核心因素及补充治疗手段以提高LF生存率具有十分重大的意义。LF发病机制复杂，线粒体是肝细胞内较敏感的细胞器之一，作为细胞内能量代谢的中心环节，已有大量研究显示，在LF中，肝细胞内线粒体在结构和功能上发生了改变，线粒体结构和功能异常在LF疾病进程中发挥着重要作用。其中线粒体呼吸链障碍、线粒体DNA损伤、线粒体通透性转换孔开放、线粒体质量控制失衡及线粒体氧化应激等多种因素交织成网络，构成一个复杂而统一的整体，成为影响LF病程进展的关键节点。近年来，研究人员开始着力于研究能够通过调节肝脏线粒体功能，防治LF的药物。随着研究的深入，中医药在LF防治中不断有新的突破，诸多研究证实了中医药可通过保护线粒体功能来发挥防治LF的效用，其作用效果可概括为减轻肝细胞损伤、抑制肝细胞死亡及促进肝细胞再生3个方面，以有效代偿肝功能，促进肝实质质量与功能的恢复。该文对线粒体的结构与功能、LF与线粒体的关系及中医药领域干预线粒体功能防治LF的研究进...     

Outcome of the isolated SLAP lesions and analysis of the results according to the injury mechanisms

Superior labral anterior posterior (SLAP) lesions of the shoulder arise from various causes and have some controversies in their treatment. The purpose of this study is to evaluate the outcomes of arthroscopic SLAP repair and the relationship between injury mechanisms and outcomes. We evaluated the clinical results of 24 patients (mean 33 months follow-up) who had an arthroscopic isolated SLAP (type II: 21, type III: 1, type IV: 2 patients) repair with suture anchors. These labral tears were arthroscopically repaired with 1–4 anchors (mean 1.8). All patients were evaluated with University of California, Los Angeles (UCLA) and Visual Analogue Scale (VAS) scores. There were the following injury mechanisms: compression-type, 10; traction-type, 9; combined or other-type, 5 patients. We also compared the clinical results according to the injury mechanisms. Preoperatively, the mean of UCLA and VAS scores were 22.7 and 6.4 points, respectively. At an average of 33 months postoperatively, the mean of UCLA and VAS scores were 29.9 and 2.1 points, respectively. There was statistical improvement in the subjective scores from the pre- to post-operation. UCLA and VAS scores of the pre- and post-operation were not statistically different according to the injury mechanisms. Arthroscopic repair is effective in the treatment of isolated SLAP lesion and injury mechanisms do not affect the clinical outcomes.     

数控凸轮

针对机械凸轮的某些不足，提出了数控凸轮的概念．介绍了数控凸轮的工作原理、实现方法及应用前景．     

Some Properties of Pineal Gland Hydroxyindole-O-Methyltransferase From Black Rhinoceros (Diceros bicornis)

Pineal glands were obtained from two young female black rhinoceri that had died as a result of postcapture trauma during a translocation exercise. Hydroxyindole-O-methyltransferase (HIOMT) from these pineal glands showed a peak activity at pH 8.2, although high activity extended over a fairly wide pH range (7.8-8.4). N-acetylserotonin was the best hydroxyindolic substrate for the enzyme, although other hydroxyindoles were methylated, the relative affinities being similar to values previously reported for bovine HIOMT. Kinetic analyses revealed that black rhinoceros HIOMT was subject to substrate inhibition by both substrates at high concentration; this observation is unlikely to have physiological significance. The catalytic mechanism was found to be ordered Bi-Bi, in which S-adenosylmethionine is the obligatory first substrate to bind to the enzyme, such binding allowing for binding of the hydroxyindolic substrate followed by catalysis, products again leaving the catalytic site in a sequential fashion.     

墓头回止血作用机制的探讨

大、小鼠 P.0给予墓头回(PSB)20g/kg、26g/kg,qd×4d 或 qd×7d,能有效地防治5-FU 所致血小板减少。ip PSB3g/kg、5g/kg 可明显促进家兔循环血小板聚集。小鼠 P.0给予PSB14g/kg、20g/kg,qd×5d,其能显著降低毛细血管通透性;PSB 对大鼠、蟾蜍下肢血管具收缩作用。初步认为,PSB 止血作用机制可能与其对血小板和血管的作用有关。     

Molecular interactions, internal structure and drug release kinetics of rationally developed polymer–lipid hybrid nanoparticles

This paper presents the first study of molecular interactions of ingredients and internal nanostructure in relation to drug loading and release mechanisms/kinetics of rationally designed solid polymer–lipid hybrid nanoparticles (PLN). The PLN were prepared by using a rationally selected composition that was found in our previous work to provide optimized interactions of verapamil hydrochloride (VRP) with dextran sulfate sodium (DS) and then the VRP–DS complex with dodecanoic acid (DA). The solid-state properties of the components, their molecular interactions and the morphology, particle size and internal structure of PLN were determined by use of differential scanning calorimetry, powder X-ray diffraction, ¹³C nuclear magnetic resonance, Fourier transform infrared spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering. The distribution of VRP in PLN was examined by TEM imaging using a cationic gold tracer. Drug release studies were conducted in various media. Drug loading as high as 36% and loading efficiencies up to 99% were achieved in the rationally formulated PLN. Hydrogen bonding between drug, polymer and lipid and a uniform distribution of amorphous VRP within the solid lipid matrix were evident. Sustained drug release from the PLN was mainly controlled by ion exchange and diffusion processes. The results demonstrated that strong molecular interactions among the drug, the polymer and the lipid in the optimized formulation were responsible for the improved drug loading and release performance of the PLN.