交联透明质素特性的研究

目的研究交联透明质素的特征和性能,为其应用于临床提供理论依据。方法采用扫描电镜-能谱仪分析交联透明质素的化学成分。采用傅立叶变换红外光谱法对交联透明质素结构进行分析。使用旋转流变仪测定交联透明质素凝胶的储能模量、耗能模量及粘度等流变学性能的动态变化。采用激光粒度仪测定凝胶中微粒的大小及分布。结果能谱分析显示交联透明质素中主要成分与天然透明质素相同,但多了硫原子,该元素来自交联剂。红外光谱测定显示,交联透明质素的吸收特征基本与未交联透明质素相似,只是在示硫砜键振动的吸收加强。交联透明质素凝胶的储能模量、耗能模量显著高于天然透明质素凝胶,与频率的依赖性不明显,表现为强凝胶弹性体特征,凝胶微粒平均粒径约为500μm。结论交联透明质素是天然透明质素与二乙烯基砜交联反应形成的多聚物,该多聚物溶胀于水后生成水不溶性凝胶。交联透明质素微粒凝胶制剂具有稳定性好和粘弹性高等优点,有利于进一步拓展其临床应用。     

交联透明质素特性的研究

目的 研究交联透明质素的特征和性能,为其应用于临床提供理论依据.方法 采用扫描电镜-能谱仪分析交联透明质素的化学成分.采用傅立叶变换红外光谱法对交联透明质素结构进行分析.使用旋转流变仪测定交联透明质素凝胶的储能模量、耗能模量及粘度等流变学性能的动态变化.采用激光粒度仪测定凝胶中微粒的大小及分布.结果 能谱分析显示交联透明质素中主要成分与天然透明质素相同,但多了硫原子,该元素来自交联剂.红外光谱测定显示,交联透明质素的吸收特征基本与未交联透明质素相似,只是在示硫砜键振动的吸收加强.交联透明质素凝胶的储能模量、耗能模量显著高于天然透明质素凝胶,与频率的依赖性不明显,表现为强凝胶弹性体特征,凝胶微粒平均粒径约为500 μm.结论 交联透明质素是天然透明质素与二乙烯基砜交联反应形成的多聚物,该多聚物溶胀于水后生成水不溶性凝胶.交联透明质素微粒凝胶制剂具有稳定性好和粘弹性高等优点,有利于进一步拓展其临床应用.     

黑皮质素受体的研究进展

综述了近年来对黑皮质素受体的研究进展 ,包括五型受体 (MC1R MC5R)的基因克隆及染色体定位、分子结构特点及其细胞内信号转导途径、药理学特性、体内分布和介导的生物学效应等。     

肾上腺髓质素的研究进展

肾上腺髓质素是一种在体内广泛分布的内源性血管活性肽。具有扩张血管 ,降低血压 ,排钠利尿 ,抑制某些血管收缩肽释放 ,促进某些炎性介质释放及损伤修复上皮更新等多种生物学作用。调节和参予多系统疾病的发生和发展。     

肾上腺髓质素的心血管作用

肾上腺髓质素 (Adrenomedullin)是一种广泛分布于机体组织的活性多肽 ,具有扩张血管、降低血压等作用 ,以自分泌或旁分泌方式参与机体的多种生理、病理调节 ,可能在心血管系统疾病 (如充血性心衰、高血压、急性心肌梗塞、动脉粥样硬化 )的发生发展中发挥重要的代偿作用。作为一种监测指标对上述疾病病情的评估具有重要的意义 ,有望成为其诊断的辅助指征 ,也为相关疾病的预防与治疗提供新的思路。     

肾上腺髓质素的抗感染和炎症调节作用

肾上腺髓质素 (adrenomedullin ,ADM )是 1993年从人的嗜铬细胞瘤中发现的一种活性肽 ,由 5 2个氨基酸残基组成 ,在 16位与 2 1位半胱氨酸残基间通过二硫键形成环状结构[1] 。ADM具有扩张血管、利钠利尿、抑制血管平滑肌细胞增殖等作用 ,是循环稳态重要的调节因子 ,在高血压、心力衰竭等过程中起保护效应[2 ] 。心血管活性肽是维持循环稳态的重要因素 ,近期研究发现活性肽参与机体的防御反应 ,本文综述ADM抗感染和炎症调节作用。1　肾上腺髓质素抗感染作用　　皮肤粘膜是机体防御微生物感染的第 1道屏障。皮肤及其表皮角质、毛囊、皮肤…     

下丘脑黑皮质素系统对机体能量代谢的调控

下丘脑黑皮质素系统是中枢神经系统调控机体能量代谢的关键神经环路。既往研究证实其在调控机体摄食行为中发挥重要的作用,近几年的研究进一步阐明其在调控机体糖脂代谢中的作用和机制。最新的研究发现黑皮质素系统通过交感神经系统,调控棕色脂肪组织的产热以及白色脂肪米色化,在促进机体能量消耗的过程中发挥重要的作用。本文将主要对下丘脑黑皮质素系统及其相关的神经环路在调控机体能量代谢中的作用和机制对最新的研究进展做一综述,同时讨论临床抗肥胖和降糖药物的中枢作用机制,为对抗肥胖和糖尿病提供新思路。     

组织透明技术

正近年来是组织透明技术(Tissue optical clearing technique)弥补了传统机械切片技术的不足,新兴起来的一种组织学技术,受到越来越多科研人员的关注与青睐。所谓组织透明技术是利用化学或物理的原理与方法将大块组织或完整器官透明化处理的技术,通过光学仪器直接对组织或器官内的细胞等结构进行观察研究。迄今为止,脊髓是组织透明技术应用最有成效的器官。     

透明清洁灌肠器的研究

1998年5月,我们根据几十年临床上用的搪瓷不透明的灌肠器操作不便等因素,设计了透明的清洁灌肠器,该器采用聚甲基丙烯酸甲酯高分子材料、经三套凹凸模具注射成型的外壳、大盖、小盖和液体排出管、吊带组成。外壳上有100ml进位的透明容量标记100－1500ml,便于观察灌肠器内液量变化,液体排出管内直径6mm透明PVC塑料管,便于观察灌肠液的流动情况,设计的盖子减少了污染机会,又保持了液体的温度。满足了临床的应用。     

肾上腺髓质素的中枢作用研究进展

肾上腺髓质素 (ADM)存在于外周及中枢神经系统。ADM作为一种神经递质或调质在中枢神经系统内主要参与机体电解质、体液平衡及心血管活动的调节。     

Effect of hyaluronan on xenotransplanted breast cancer

Hyaluronan is a major glycosaminoglycan component of the extracellular matrix and CD44 is its principal ligand. In previous in vitro studies we have shown that CD44 and hyaluronan are involved in the invasive properties of the human breast cancer cell line Hs578T. The aim of this study was to test whether experimental therapy with hyaluronan interferes with tumor invasion and has an inhibitory effect on tumor growth in vivo. The Hs578T cell line was xenotransplanted orthotopically into the mammary fat pad of nu/nu mice. After tumor growth reached a maximum size of 5 x 5 mm, 50 microg of hyaluronan was injected intratumorally. The tumors of control nu/nu mice were injected with PBS. Four of 12 tumors from the hyaluronan-treated group regressed completely. This effect could be due to a saturation of the hyaluronan-binding sites on tumor cells or to an acceleration of tumor rejection by a non-T-cell-dependent mechanism. This study gives a rationale for future work on the antineoplastic effects of hyaluronan.     

Immunologic roles of hyaluronan

Hyaluronan (HA), a large glycosaminoglycan composed of d-N-acetylglucosamine and d-glucuronic acid, is expressed in virtually all tissues and has long been considered to serve as a structural component or filling material in the tissue interstitium (Filler Theory). This idea was revised with the discovery of HA-binding proteins that introduced the concept that HA may also serve as an adhesive substrate for cellular trafficking (Adhesion Theory). Most recently, it has been shown that HA fragments can deliver maturational signals to dendritic cells (DCs) and high molecular weight HA polymers can deliver costimulatory signals to T-cells (Signaling Theory). Thus, HA may represent an important component of the immune system. Recently, we have evaluated the impact of HA on Langerhans cell (LC) maturation and migration using a novel peptide inhibitor of HA function, termedPep-1 (GAHWQFNALTVR). As skin-specific members of the DC family, LCs are crucial for the initiation of cutaneous immune responses. Local injections of Pep1 prevented hapten-induced LC migration from, the epidermis, providing the first experimental evidence that HA facilitates their emigration. Moreover, Pep-1 also significantly inhibited the hapteninduced maturation of LCs in vivo as assessed by cell morphology, costimulatory molecule expression, and their ability to induce proliferation of allogeneic T-cells. HA therefore has dual functionality to facilitate LC migration and maturation, the two critical events for the initiation of adaptive immune responses. Finally, we have observed that DC-dependent, antigen-specific T-cell proliferation and cytokine secretion is blocked by Pep-1. These results have revealed a previously unrecognized role for HA in antigen presentation. Thus, far from an inert structural biopolymer, HA represents a multifunctional carbohydrate mediator of immune processes.     

Hormonal regulation of renomedullary hyaluronan

Aim: Hyaluronan (HA) is involved in renomedullary water handling through its water‐binding capacity. This study addressed the effect of hormones involved in regulating fluid‐electrolyte homeostasis on renomedullary HA content in vivo and in vitro. Methods: The kidneys from rats treated with l ‐NAME, indomethacin, vasopressin (AVP) or methylprednisolone (MP) during euvolaemia or water loading were analysed for HA by RIA, ELISA and histochemical staining. HA was measured in renomedullary interstitial cells treated with AVP, angiotensin II (Ang II) or a combination of AVP and Ang II. Results: Baseline renal cortical and medullary HA content was unaffected by 2 h of intravenous treatment with l ‐NAME (NOS inhibitor) or indomethacin (cyclo‐oxygenase inhibitor), whereas AVP reduced medullary HA by 33%. During 2 h of acute water loading, diuresis was accompanied by an increase in renomedullary HA (+45%), but cortical HA was unaffected. In both l ‐NAME‐ and indomethacin‐treated animals, the water loading‐induced increase in renomedullary HA was absent, indicating involvement of NO and prostaglandins. After 7 days of MP treatment, medullary HA was reduced by 40%, but the water loading‐induced elevation in HA remained. In cultured renomedullary interstitial cells, AVP reduced the HA content in the supernatant by 63%, and simultaneous treatment with Ang II reduced the HA content even further (95%). Conclusion: AVP reduces HA content, and NO and prostaglandins are needed for the increase in HA during water loading.     

Delivery of a vector encoding mouse hyaluronan synthase 2 via a crosslinked hyaluronan film

We have developed a crosslinked hyaluronic acid (HA) film with DNA incorporated within its structure and have characterized this system for its efficacy in sustained transferring of a vector encoding mouse hyaluronan synthase 2 (Has2). Analysis of the DNA release kinetics indicated that the HA films degraded when treated with hyaluronidase and that they released DNA over a prolonged period of time. Gel electrophoresis revealed that this DNA was intact and immunohistochemical analysis verified the transfection capabilities of DNA release samples. The ability of released DNA encoding Has2 to promote HA synthesis was confirmed by quantifying the amount of HA produced by COS-1 cells that were transfected with release samples. The intended future application of the HA films is in prevention of post-operative peritoneal adhesions. In addition to serving as a physical barrier, the film would function as a vehicle for sustained delivery of DNA encoding Has2, which would promote the synthesis of HA in transfected tissues.     

Smooth muscle cell adhesion on crosslinked hyaluronan gels

Hyaluronic acid (HA)-based polymers (hylans) are highly biocompatible and can be structurally modified to obtain desired mechanical properties. This study evaluated divinyl sulfone-crosslinked solid and particulate hylans as cellular scaffolds. These two hylan types differ in surface characteristics, mode of preparation, HA content, and extent of crosslinking. Neonatal rat aortic smooth muscle cells were cultured on hylan gels coated with matrix factors including collagen I, ECM gel, laminin, and fibronectin and on uncoated controls for < or =4 weeks. Cell attachment was sparse on uncoated controls but significantly enhanced on coated gels. Cell morphology was influenced by the identity of the matrix factors coated and the surface topography of the hylan gels. Cells attached to coated particulate gels appeared either highly spread (collagen, fibronectin) or irregularly shaped (ECM gel, laminin). Cells on laminin and fibronectin-coated solid gels were rounded and nonproliferative. Cells proliferated most rapidly on ECM gel-coated gels. The uneven surface of particulate gels induced more protein deposition and the subsequent attachment and active proliferation of cells. This study shows that surface texturizing and subsequent surface treatment with matrix factors enhances cell attachment and proliferation of hylans. These results are useful toward developing bioengineered materials based on cell-hylan composites.     

Lubricating effect of sialomucin and hyaluronan on pleural mesothelium

Coefficient of kinetic friction (μ) between rabbit visceral and parietal pleura, sliding in vitro at physiological velocities and load, increases markedly after blotting mesothelial surface with filter paper; this increase is only partially reduced by wetting blotted mesothelium with Ringer solution. Given that mesothelial surface is covered by a thick coat with sialomucin and hyaluronan, we tested whether addition of sialomucin or hyaluronan solution after blotting lowers μ more than Ringer alone. Actually, these macromolecules lowered μ more than Ringer, so that μ was no longer significantly higher than its preblotting value. Moreover, Ringer addition, after washout of macromolecule solution, increased μ, in line with their dilution. These findings indicate that mesothelial blotting removes part of these molecules from the coat covering mesothelial surface, and their relevance for pleural lubrication. Transmission electron micrographs of pleural specimens after mesothelial blotting showed that microvilli were partially or largely removed from mesothelium, consistent with a substantial loss of macromolecules normally entrapped among them.     

Molecular control of the hyaluronan biosynthesis

Hyaluronan (HA) is the only unsulfated glycosaminoglycan (GAG) composed of repeating units of D-glucuronic acid and N-acetylglucosamine. The amount and the molecular weight of HA are important factors that regulate the physiology and pathology in several mammalian tissues. In fact hydrated HA makes ECM an ideal environment in which cells can move and proliferate. HA interacting with several receptors at the cellular level plays a critical role in signal transduction responses. The control of the HA synthesis is therefore a critical aspect in ECM and cells biology, but so far the information about this question is scanty. The synthesis of HA is due to several enzymes activities which not only involves its synthetic enzymes on the membranes of the cells (HA synthases 1, 2, 3, isoforms) but also the cytoplasmatic enzymes producing the UDP-sugar precursors. The UDP-sugars availability in cytoplasm is a critical point for the GAG synthesis and it seems to affect particularly the HA production. Eventually, the activity control of the enzymes involved in HA metabolism is obtained throughout both enzyme amount and their postsynthetic covalent modification, as phosphorylation. In fact, it was recently reported that HA synthase 3 may be phosphorylated after specific stimuli, and an increasing body of evidence supports the idea that the synthetic pathway of HA may be carefully regulated in all steps.     

Attachment of hyaluronan to metallic surfaces

Metal implants are in general not compatible with the tissues of the human body, and in particular, blood exhibits a severe hemostatic response. Herein we present results of a technique to mask the surface of metals with a natural biopolymer, hyaluronan (HA). HA has minimal adverse interactions with blood and other tissues, but attachment of bioactive peptides can promote specific biological interactions. In this study, stainless steel was cleaned and then surface-modified by covalent attachment of an epoxy silane. The epoxy was subsequently converted to an aldehyde functional group and reacted with hyaluronan through an adipic dihydrazide linkage, thus covalently immobilizing the HA onto the steel surface. Fluorescent labeling of the HA showed that the surface had a fairly uniform covering of HA. When human platelet rich plasma was placed on the HA-coated surface, there was no observable adhesion of platelets. HA derivatized with a peptide containing the RGD peptide sequence was also bound to the stainless steel. The RGD-containing peptide was bioactive as exemplified by the attachment and spreading of platelets on this surface. Furthermore, when the RGD peptide was replaced with the nonsense RDG sequence, minimal adhesion of platelets was observed. This type of controlled biological activity on a metal surface has potential for modulating cell growth and cellular interactions with metallic implants, such as vascular stents, orthopedic implants, heart valve cages, and more.     

Effects of cyclosporin on serum hyaluronan levels in collagen arthritis

Serum hyaluronan (HA) levels were measured in a rat model of collagen arthritis using a sandwich enzyme-linked immunosorbent assay. Values became elevated as the arthritis developed, correlating with its severity. Daily subcutaneous treatment with cyclosporin at the dose of 25 mg/kg per day for fourteen days completely prevented anti-type II collagen antibody production and the serum HA increase as well as development of collagen arthritis. HA in the blood may thus provide a good quantitative marker for joint disease in rat collagen arthritis with potential as a tool for evaluation of drug efficacy in this experimental model.