壳聚糖的止血机理和应用

壳聚糖在医学领域的应用越来越广泛。本文简述了壳聚糖止血机理研究的进展 ,指出它的止血机理不是常规的依赖于血小板和凝血因子的瀑布机制。壳聚糖止血机制中的重要一环是通过对红细胞作用 ,使红细胞发生粘附聚集从而使血液凝固。另外 ,本文对壳聚糖在止血剂中的应用也作了简要的介绍。     

壳聚糖的止血机理和应用

壳聚糖在医学领域的应用越来越广泛。本简述了壳聚糖止血机理研究的进展，指出它的止血机理不是常规的依赖于血小板和凝血因子的瀑布机制。壳聚糖止血机制中的重要一环是对红细胞作用，使红细胞发生粘附聚集从而使血液凝固。另外，中对壳聚糖在止血剂中的应用也作了简要的介绍。     

壳聚糖醋酸溶液对凝血作用的研究

研究了不同脱乙酰度和不同分子量壳聚糖醋酸溶液的凝血作用。发现壳聚糖醋酸溶液使抗凝血液中红细胞发生了明显的聚集和变形。通过不同分子量和脱乙酰度壳聚糖的促红细胞聚集实验,证明了低脱乙酰度壳聚糖(60%~70%)使红细胞聚集效果更好,分子量在105~106范围内作用不十分明显。对血液的凝血酶时间(TT)、凝血酶原时间(PT)、活化部分促凝血酶原激酶时间(APTT)和纤维蛋白原浓度(FIB)的测定结果验证了壳聚糖醋酸溶液凝血机理不依赖于血小板和常规“瀑布”凝血机制。     

胶原/壳聚糖复合膜的制备及止血效果的研究

目的以胶原和壳聚糖制备复合膜,检验其止血效果,并探讨其止血原因.材料与方法以酸解法从牛腱中提取胶原,用甲壳素制得壳聚糖,以胶原和壳聚糖制成复合膜,通过动物实验测不同配比的复合膜对出血创面的止血时间,并与其它止血材料做对比.结果各种配比的复合膜的止血效果均比明胶等一般止血材料好.结论胶原/壳聚糖复合膜有良好的止血作用,可望在外科手术上得到广泛应用.     

胶原/壳聚糖复合膜的制备及止血效果的研究

目的以胶原和壳聚糖制备复合膜,检验其止血效果,并探讨其止血原因.材料与方法:以酸解法从牛腱中提取胶原,用甲壳素制得壳聚糖,以胶原和壳聚糖制成复合膜,通过动物实验测不同配比的复合膜对出血创面的止血时间,并与其它止血材料做对比.结果:各种配比的复合膜的止血效果均比明胶等一般止血材料好.结论:胶原/壳聚糖复合膜有良好的止血作用,可望在外科手术上得到广泛应用.     

胶原／壳聚糖复合膜的制备及止血效果的研究

目的以胶原和壳聚糖制备复合膜，检验其止血效果，并探讨其止血原因。材料与方法以酸解法从牛腱中提取胶原，用甲壳素制得壳聚糖，以胶原和壳聚糖制成复合膜，通过动物实验测不同配比的复合膜对出血创面的止血时间，并与其它止血材料做对比。结果各种配比的复合膜的止血效果均比明胶等一般止血材料好。结论胶原／壳聚糖复合膜有良好的止血作用，可望在外科手术上得到广泛应用。     

甲壳素/壳聚糖生物抗菌敷料在皮肤组织工程中的应用

目的:探讨甲壳素/壳聚糖生物抗菌敷料的性能及其在皮肤组织工程中的应用。方法:由作者应用计算机检索中国知网(CNKI)与万方医学网中与生物抗菌敷料特性及临床应用有关的文献,检索时限为1996/2010。检索关键词:生物抗菌敷料,甲壳素/壳聚糖,皮肤组织工程,安全性,性能特点。纳入标准:①甲壳素/壳聚糖生物抗菌敷料的性能。②甲壳素/壳聚糖生物抗菌敷料在皮肤组织工程中的应用。③同一领域选择近期发表或在权威杂志上发表的文章。排除标准:排除重复研究和较陈旧文献。对资料进行初审,并查看每篇文献后的引文。结果:根据纳入排除标准,共纳入20篇相关文献。甲壳素/壳聚糖安全性和可降解性良好,吸湿性、抑菌性强,并具有止血和止痛、抑制瘢痕形成、促进细胞生长、加速伤口创面愈合和促进机体非特异性免疫的功能。从其在皮肤组织工程中的应用研究来看,甲壳素/壳聚糖可有效促进烧伤创面的愈合和皮肤再生,且不增加创面感染的机率。结论:甲壳素/壳聚糖生物抗菌敷料性能良好,能有效促进烧伤创面愈合和增强皮肤再生,在皮肤组织工程及其他医学领域中具有广泛常规应用的可能性。     

青紫型先天性心脏病患儿血液流变学和血小板聚集功能的变化

本文观察了45例青紫型先天性心脏病(CCHD)患儿血液流变学和血小板聚集功能的变化。结果显示:与对照组比较红细胞压积和全血粘度显著提高,红细胞聚集功能及刚性增强,变形运动能力减低,血小板聚集功能降低,纤维蛋白原减少,血浆比粘度增高。提示CCHD患儿存在着严重的血液流变学异常,不仅有血液粘度的变化,而且有血小板和红细胞的生理功能异常。本文对其临床意义进行了讨论。     

等剪切场中剪切条件与红细胞流变性质对全血血小板自发聚集性的影响

本文采用剪切激活血小板的方法观察了等剪切场中剪切率、剪切时间、红细胞浓度与刚度对大鼠全血血小板自发聚集性的影响。结果提示,等剪切场中剪切率与剪切时间对全血血小板的自发聚集率呈双向性的影响,剪切率在46s~(-1)或剪切时间在20min时血小板的自发聚集率不受剪切时间或剪切率的影响;红细胞浓度增高使全血血小板的自发聚集率升高(r=0.8235,P<0.001),而刚化红细胞的影响则较小(r=0.6321,P<0.001)。     

53例糖尿病血液流变学观察

本文对53例Ⅱ型糖尿病患者作血液流变学检测,并与92例健康人比较;红细胞压积,全血比粘度,血浆比粘度有极显著差异(P<0.01)。体外血栓形成,血小板聚集率有显著性差异(P<0.05)。提示糖尿病患者血液呈高粘、高凝、高聚状态,并对其产生机理作简要讨论。     

Local hemostatic effects of microcrystalline partially deacetylated chitin hydrochloride

The hemostatic effects of microcrystalline partially deacetylated chitin hydrochloride (DAC-HCl) were compared with those of cotton and collagen hydrochloride (collagen-HCl). The DAC-HCl had excellent physical properties as a hemostatic agent such as its ability to absorb and retain blood. In canine blood it induced the release of substances involved in the process of platelet activation, such as beta-thromboglobulin and platelet factor 4, and it also had excellent hemoagglutinative properties. Moreover, in a hemostatic study on bleeding from cancellous bone in canines it exhibited a hemostatic effect comparable to that exhibited by collagen-HCl. Because it also has an intrinsic promotive effect on wound healing, chitin hydrochloride is considered to be a promising hemostatic material.     

水溶性止血纺织材料对血小板和血栓形成的影响

水溶性止血纺织材料是脱脂纤维素经化学处理而成，具有生物止血活性。作者研究了该类止血材料对血小板粘附及体外血栓形成的影响。止血纺织材料在液体中形成胶体颗粒并吸附激活血小板，参与止血过程，血小板粘附率约５０％。体外血栓形成试验表明，在凝血机制发生障碍的情况下，Ｓ－９９和Ｓ－１００止血纺织材料仍能形成血栓，明显比海藻类止血材料要好。     

Platelet interaction with a pancreatic ascites tumor

The mechanism leading to the hypercoagulability in pancreatic carcinoma is unclear. The rapid progress of the disease after its diagnosis and the inaccessibility of the tumor make studies on the mechanism difficult in man. With the successful induction of this malignancy and conversion of it into an ascites tumor in Syrian golden hamsters, interactions between isolated tumor cells and individual hemostatic components can be investigated. In this paper, studies on in vitro tumor cell-platelet interactions and some hemostatic changes in hamsters following intravenous injection of isolated tumor cells are described. Freshly isolated tumor cells and tumor-cell sonicates, but not those that had been kept at 4 or -70 C overnight, induced comparable aggregation of human platelets in both heparinized and citrated platelet-rich plasmas (hPRP and cPRP). The aggregation was not followed by clot formation; a specific synthetic thrombin inhibitor had no effect on the aggregation in either hPRP or cPRP. Washed and gel-filtered platelets, even in the presence of 5% of citrated or heparinized platelet-poor plasma (cPPP or hPPP) failed to be aggregated by tumor cells. Tumor-cell-induced platelet aggregation was accompanied by thromboxane formation and serotonin release, both of which were several orders of magnitude greater in cPPP than in hPRP. Aspirin, apyrase, and PGI2 all inhibited tumor-cell-induced platelet aggregation in both PRPs, but the inhibition by aspirin was minimal. Intravenous infusion of isolated tumor cells into normal hamsters resulted in a 50% reduction of platelet count and a 20-30% decline in antithrombin III and fibrinogen. Platelet aggregates and fibrin strands were seen in the lungs of these animals.     

Effect of chitosan molecular weight and deacetylation degree on hemostasis

Comparative studies have been carried out among solid-state chitosan soliquoid, chitosan acetic acid physiological saline solution, and carboxymethyl chitosan physiological saline solution to discover the hemostatic effect of molecular weight (M(w)) and deacetylation degree (DA) of chitosan. It was found that solid-state chitosan and chitosan acetic acid physiological saline solution performed different hemostatic mechanisms. When blood mixed with chitosan acetic acid physiological saline solution, the erythrocytes aggregated and were deformed. The DA, especially a low DA, in the chitosan acetic acid physiological saline solution, had a significant effect on the unusual aggregation and deformation of erythrocytes, compared with the effect of M(w) within a range between 10(5) and 10(6). However, this phenomenon could not be observed in solid-state chitosan soliquoid. Solid-state chitosan with a low DA absorbed more platelets and was more hemostatic. Carboxymethyl chitosan physiological saline solution had nothing to do with the aggregation and deformation of erythrocytes but caused local rouleau. The values of thrombin time (TT), prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen concentration (FIB) were measured after the blood was mixed with solid-state chitosan soliquoid, chitosan acetic acid physiological saline solution, and carboxymethyl chitosan physiological saline solution, separately. The results demonstrated that coagulation factors might not be activated by them.     

Chitin-based tubes for tissue engineering in the nervous system

The purpose of this study was to investigate chitin and chitosan as potential materials for biodegradable nerve guides. Transparent chitin hydrogel tubes were synthesized, for the first time, from chitosan solutions using acylation chemistry and mold casting techniques. Alkaline hydrolysis of chitin tubes resulted in chitosan tubes, with the extent of hydrolysis controlling the resulting amine content. This, in turn, impacted compressive strength and cell adhesion. Chitosan tubes were mechanically stronger than their chitin origins, as measured by the transverse compressive test, where tubes having degrees of acetylation of 1%, 3%, 18% (i.e. chitosan) and 94% (i.e. chitin) supported loads at a 30% displacement of 40.6 +/- 4.3, 25.3 +/- 4.5, 10.6 +/- 0.8, and 8.7 +/- 0.4 g, respectively. However, the chitin processing methodology could be optimized for compressive strength, by either incorporating reinforcing coils in the tube wall, or air-drying the hydrogel tubes. Chitin and chitosan supported adhesion and differentiation of primary chick dorsal root ganglion neurons in vitro. Chitosan films showed significantly enhanced neurite outgrowth relative to chitin films, reflecting the dependence of nerve cell affinity on the amine content in the polysaccharide: neurites extended 1794.7 +/- 392.0 microm/mm(2) on chitosan films vs. 140.5 +/- 41.6 microm/mm(2) on chitin films after 2 days of culture. This implies that cell adhesion and neurite extension can be adjusted by amine content, which is important for tissue engineering in the nervous system. The methods for easy processing and modification of chitin and chitosan described herein, allow the mechanical properties and cyto-compatibility to be controlled and provide a means for a broader investigation into their use in biomedical applications.     

Plasma from rheumatoid patients taking low dose methotrexate enhances platelet aggregation

Methotrexate (MTX) in low doses is commonly used to treat rheumatoid arthritis (RA). At least 36 deaths have been attributed to bone marrow cytotoxicity associated with low dose MTX. The goal was to determine if plasma from arthritis patients taking low dose MTX induces platelet aggregation in platelet rich plasma from healthy volunteers. Plasma from patients on MTX alone caused a 3-fold increase in aggregation vs plasma from controls (P<0.05). Plasma from patients not taking MTX or taking MTX with diclofenac caused aggregation to a lesser extent. Diclofenac, along with several others NSAIDs and cyclooxygenase inhibitors, depressed aggregation produced by arachidonic acid in platelet rich plasma from healthy volunteers. A precise mechanism for amplification of aggregation by MTX plasma and its relationship to MTX toxicity remains unknown. However, a serum factor may be produced by MTX that modulates the activity of cyclooxygenase, thereby influencing aggregation.     

甲壳素和甲壳胺对聚乳酸体外降解的影响

考察了ＤＬ－聚乳酸（ＤＬ－ＰＬＡ）／甲素（ＣＨＩ）,ＤＬ－ＰＬＡ／甲壳胺（ＣＨＳ）两种复合物在生理盐水降解过程中生理盐水的ｐＨ值、试样的失重率和外观形态以及ＤＬ－ＰＬＡ分子量的变化,结果表明：ＣＨＩ和ＣＨＳ对ＤＬ－ＰＬＡ的降解速度有明显的抑制作用,并对抑制机理进行了探讨。     

壳聚糖作为基因输送载体的最新研究进展

基因治疗是一种非常有前景的医学治疗技术，然而目前尚不能广泛地应用于临床，安全高效的基因输送载体的缺乏是其临床推广应用的主要限制因素之一。壳聚糖作为一种天然存在的阳离子多聚物，具有较好的生物相容性和生物降解性，可以与DNA通过快速混合形成纳米颗粒，从而具有作为基因输送载体的重大潜力。就壳聚糖作为基因输送载体的最新研究进展进行系统综述，重点讨论纳米粒子进入体内后需要跨越的各个生物屏障以及如何克服这些生物屏障。     

The effects of "anti-platelet" drugs on bleeding time and platelet aggregation in normal human subjects.

The effects on hemostasis of several commonly used drugs previously described as inhibiting platelet function were evaluated in a randomized, double-blind study of 54 normal volunteers. The subjects were each given a single dose of aspirin, chlorpromazine, glyceryl guaiacolate, diphenhydramine, indomethacin or lactose placebo. A single dose of aspirin significantly prolonged the template bleeding time and inhibited secondary platelet aggregation two and 24 hours after ingestion. Single doses of indomethacin and chlorpromazine affected aggregation at two hours but had no effect on bleeding time, although multiple doses of indomethacin did prolong bleeding time. Glyceryl guaiacolate inhibited aggregation one hour after ingestion but had no effect on bleeding time. Diphenhydramine did not affect either. These findings suggest that standard doses of many commonly used "anti-platelet" drugs may have little clinical effect on the hemostatic mechanism in normal man. Results of in-vitro platelet-drug incubations may not be directly applicable to in-vivo hemostasis.