几何形态测量方法在古代人类遗骸研究中的应用

几何形态测量方法基于对样本标志点的数据采集和分析，近10年来该方法在国内人类遗骸研究中得到了很好的应用。古人类化石研究取得的很多进展中，都应用到了几何形态测量方法。本文中我们结合具体的研究案例，简要梳理了几何形态测量方法在人类遗骸研究中的应用，并展望了该方法在古代儿童体质研究中的应用前景。     

搏动灌注研究现状

在体外循环应用中，对搏动灌注进行了大量研究和讨论，但争议较多，应用尚未普及。本文对近年有关搏动灌注的论文做了综述，介绍搏动灌注的各种理论基础和搏动灌注的研究情况，提出了目前研究中存在的问题。     

搏动灌注研究现状

在体外循环应用中，对搏动灌注进行了大量研究和讨论，但争议较多，应用尚未普及。本文对近年有关搏动灌注的论文做了综述，介绍了搏劝灌注的各种理论基础和搏劝灌注的研究情况，提出了目前研究中存在的问题。     

酶性DNA（deoxyribozyme）研究进展

Deoxyribozyme（酶性DNA0自发现以来，正由基因研究开始走向应用，本综述了deoxyribozyme研究的发展过程，并探讨了deoxyribozyme的理论及应用价值。     

近距离放射治疗技术的进展

近距离放射治疗是治疗癌症的一种有效的手段，是现代放射治疗的重要组成部分。它在国外研究和应用较多，在放射治疗中应用约占１５％，而国内在应用和研究上还存在差距。本文介绍了近距离放射治疗技术的发展、特点以及它与外照射的关系，概述了它在国内外的现状，指出了其发展应用前景。     

时间分辨荧光各向异性及其在生物大分子研究中的应用

概述了时间分辨荧光各向异性（TRAMS）的工作原理和发展概况，描述了常用荧光探针，标记物及大分子的一般标记方法，讨论了其测定方法，研究特点及生物大分子中的构象及结构变化等研究方面的应用，展望了未来的应用前景。     

图像归档和通讯系统（PACS）的发展与应用

图像归档和通讯系统，是经通讯网络获取、存储、管理和显示放射医学图像的集成信息系统。近年来，国外的ＰＡＣＳ技术和应用已逐步进入成熟期，有大量的研究成果和应用实例；但我国的ＰＡＣＳ研究和应用因起步较晚，尚处在相对落后的局面。本介绍了ＰＡＣＳ系统发展历程，概述了国外ＰＡＣＳ研究和应用的现状，最后分析了国内ＰＡＣＳ的发展状况，展望了其在我国医疗信息系统发展中的应用前景。     

晶体上皮细胞培养技术及其应用

晶体上皮细胞的研究是晶体研究中的重点。利用晶体上皮细胞培养技术对晶体进行了广泛、深入的研究，但国内起步较晚。本文详细地介绍了这一技术，并将其应用的现状进行总结，为晶体上皮细胞培养技术的进一步应用及发展提供了线索     

骨组织工程种子细胞的研究进展

随着骨组织工程研究的进展，选择什么细胞作为其种子细胞成为年来研究的热点，目前，骨组织工程应用中种子细胞有五种来源：骨、骨膜、骨髓，内外组织和早期胚胎，本介绍了五种来源种子细胞的研究状况，并对种子细胞各自存在的问题及应用前景进行了分析。     

形状记忆合金在医学上应用研究的新动向

近年来形状记忆合金，主要是具有优异形状记忆和超弹性性能的ＮｉＴｉ合金，在医学上的应用研究取得了显著进展。本文简要指出了有关形状记忆合金在医学基础研究，力学行为模拟，新多孔合金，表面改性，以及医疗器械和临床应用方面的某些重要进展和重点问题。     

Polyclonal catalytic antibodies

Polyclonal catalytic antibodies offer advantages in the evaluation of immunogens and in the ease of production of large quantities of antibodies. They comprise the entire immune response of an animal to an immunogen where monoclonals represent a subset. Polyclonal antibodies are consequently particularly suitable for evaluating catalytic antibody responses generated by different haptens or a group of structurally related haptens. The authors reported the first polyclonal catalytic antibodies in 1990. An unexpected finding is that polyclonal catalytic antibodies show single-site kinetic behaviour, i.e. whatever structural heterogeneity exists, the kinetic behaviour is homogeneous. Many groups worldwide have since published work in this area. Three groups are prominent. The authors' group, a group based in Austin, Texas, and led by Iverson, and a Shanghai group. The authors' group works with sheep antibodies and has published mechanistic studies and, more recently, specificity studies that revealed the catalysis of a beta-lactam. Most of this work over a 10-year period was performed by using a single bleed from a single sheep, which gives an indication of the ease of production and utility of such catalytic antibodies. Iverson's group works with rabbit antibodies and has published much work on the evaluation of catalytic antibodies generated by structurally related haptens. The Shanghai group has concentrated on the studies of polyclonal catalytic antibodies for electrocyclic reactions where any danger of contaminating enzymes is reduced. The use of immunisation to generate therapeutically useful catalytic antibodies (necessarily polyclonal) in a host animal is an attractive target. Several groups are working towards this. The authors themselves have published in this area and promising recent studies come from a group working in France on immunisation to protect against nerve agents and a Texas group (based in Houston) that has demonstrated active immunisation to generate antibodies that catalyse the hydrolysis of a carbamate insecticide.     

Negative regulation by amidase PGRPs shapes the Drosophila antibacterial response and protects the fly from innocuous infection

Peptidoglycan recognition proteins (PGRPs) are key regulators of insect immune responses. In addition to recognition PGRPs, which activate the Toll and Imd pathways, the Drosophila genome encodes six catalytic PGRPs with the capacity to scavenge peptidoglycan. We have performed a systematic analysis of catalytic PGRP function using deletions, separately and in combination. Our findings support the role of PGRP-LB as a negative regulator of the Imd pathway and brought to light a synergy of PGRP-SCs with PGRP-LB in the systemic response. Flies lacking all six catalytic PGRPs were still viable but exhibited deleterious immune responses to innocuous gut infections. Together with recent studies on mammalian PGRPs, our study uncovers a conserved role for PGRPs in gut homeostasis. Analysis of the immune phenotype of flies lacking all catalytic PGRPs and the Imd regulator Pirk reveals that the Imd-mediated immune response is highly constrained by the existence of multiple negative feedbacks.     

Two basic residues, Lys-107 and Lys-118, of RuvC resolvase are involved in critical contacts with the Holliday junction for its resolution

BACKGROUND: Crystallographic and mutational studies of Escherichia coli RuvC Holliday junction resolvase have revealed that a catalytic site of each subunit is composed of four acidic residues at the bottom of the putative DNA-binding cleft, whose surface contains eight basic residues. RESULTS: To elucidate the functional roles of the basic residues on the cleft surface, we constructed a series of mutant ruvC genes and characterized their properties in vivo and in vitro. Among them, two RuvC mutants with a single alteration, K107A and K118A, were defective in UV-repair and showed a dominant negative effect. The purified K107A and K118A proteins showed reduced binding activity to the junction DNA in the presence of Mg2+ under high salt conditions. Mn2+ increased both the junction binding and cleaving activities of the mutant proteins. In the absence of a divalent cation, the wild-type, K107A and K118A proteins did not bind to junction DNA under high salt conditions, but the D7N mutant, with an alteration of the catalytic centre, was able to bind to the junction efficiently. CONCLUSION: The results presented here, in conjunction with previous crystallographic studies, suggest that the catalytic complex which is formed through interactions of acidic residues, Mg2+ and a cleavable phosphodiester bond, is stabilized by Lys-107 and Lys-118 via electrostatic interactions with the DNA backbone, a process which is critically important for the cleavage reaction to take place. One or two basic residues near the catalytic centre have also been found in other RNase H superfamily proteins, indicating that this is the conserved reaction mechanism in this superfamily.     

Comparison of three microbial hosts for the expression of an active catalytic scFv

Antibodies represent an interesting protein framework on which catalytic functions can be grafted. In previous studies, we have reported the characterization of the catalytic antibody 4B2 obtained on the basis of the "bait and switch" strategy which catalyzes two different chemical reactions: the allylic isomerization of beta,gamma-unsaturated ketones and the Kemp elimination. We have cloned the antibody 4B2 and expressed it as a single-chain Fv (scFv) fragment in different expression systems, Escherichia coli and two yeasts species, in order to elicit the most suitable system to study its catalytic activity. The scFv4B2 was secreted as an active form in the culture medium of Pichia pastoris and Kluyveromyces lactis, which led respectively to 4 and 1.3mg/l after purification. In E. coli, different strategies were investigated to increase the cytoplasmic soluble fraction, which resulted, in all cases, in the expression of a low amount of functional antibodies. By contrast, substantial amount of scFv4B2 could be purified when it was expressed as inclusion bodies (12mg/l) and submitted to an in vitro refolding process. Its catalytic activity was measured and proved to be comparable to that of the whole IgG. However, the instability of the scFv4B2 in solution prevented from an exhaustive characterization of its activity and stabilization of this protein appears to be essential before designing strategies to improve its catalytic activity.     

Antioxidants as potential therapeutics for lung fibrosis

Interstitial lung disease encompasses a large group of chronic lung disorders associated with excessive tissue remodeling, scarring, and fibrosis. The evidence of a redox imbalance in lung fibrosis is substantial, and the rationale for testing antioxidants as potential new therapeutics for lung fibrosis is appealing. Current animal models of lung fibrosis have clear involvement of ROS in their pathogenesis. New classes of antioxidant agents divided into catalytic antioxidant mimetics and antioxidant scavengers are being developed. The catalytic antioxidant class is based on endogenous antioxidant enzymes and includes the manganese-containing macrocyclics, porphyrins, salens, and the non-metal-containing nitroxides. The antioxidant scavenging class is based on endogenous antioxidant molecules and includes the vitamin E analogues, thiols, lazaroids, and polyphenolic agents. Numerous studies have shown oxidative stress to be associated with many interstitial lung diseases and that these agents are effective in attenuating fibroproliferative responses in the lung of animals and humans.     

Role of insulin-induced reactive oxygen species in the insulin signaling pathway

Oxidants, including hydrogen peroxide (H2O2), have been recognized for years to mimic insulin action on glucose transport in adipose cells. Early studies also demonstrated the complementary finding that H2O2 was elaborated during treatment of cells with insulin, suggesting that cellular H2O2 generation was integral to insulin signaling. Recently, reactive oxygen species elicited by various hormones and growth factors have been shown to affect signal transduction pathways in various cell types. We recently reported that insulin-stimulated H2O2 modulates proximal and distal insulin signaling, at least in part through the oxidative inhibition of protein tyrosine phosphatases (PTPases) that negatively regulate the insulin action pathway. Nox4, a homologue in the family of NADPH oxidase catalytic subunits, was found to be prominently expressed in insulin-sensitive cells. By various molecular approaches, Nox4 was shown to mediate insulin-stimulated H2O2 generation and impact the insulin signaling cascade. Overexpression of Nox4 also significantly reversed the inhibition of insulin-stimulated receptor tyrosine phosphorylation by PTP1B, a widely expressed PTPase implicated in the negative regulation of insulin signaling, by inhibiting its catalytic activity. These recent studies have provided insight into Nox4 as a novel molecular link between insulin-stimulated reactive oxygen species and mechanisms involved in their modulation of insulin signal transduction.     

Catalytic antibodies in clinical and experimental pathology: human and mouse models

Most of the data accumulated through studies on natural catalytic autoantibodies indicate that production scales up markedly in pathological abnormalities. We have previously described an increased level of DNA-hydrolyzing autoantibodies in the sera of patients with various autoimmune disorders [systemic lupus erythematosus (SLE), rheumatoid arthritis, scleroderma], HIV infection and lymphoproliferative diseases accompanied by autoimmune manifestations. In the present study, we show that an increased level of catalytic activity of autoantibodies can be observed in the sera of autoimmune mice, thus providing a fundamental insight into the medical relevance of abzymes. Polyclonal autoantibodies purified from sera of NZB/W, MRL-lpr/lpr and SJL/J mice show proteolytic and DNA-hydrolyzing activities, as opposed to those harvested from non-autoimmune BALB/c mice. The expressiveness of the catalytic activity was strongly dependent on the age of the animal. The highest levels of catalytic activity were found in the sera of mice aged between 8 and 12 months; the lowest level was typical of younger animals whose age ranged from 6 to 8 weeks. Specific inhibition assays of the catalytic activities were performed to throw light on the nature of the abzyme activity. Within a cohort of aging animals, a strong correlation between marked autoimmune abnormalities and levels of catalytic activities has been established. Nonimmunized SJL/J mice revealed specific immune responses to myelin basic protein (MBP), skeletal muscle myosin (skMyo) and cardiac myosin (Myo), and highly purified antibodies from their serum show specific proteolytic attack against the target antigens. This finding prompted us to undertake a more detailed study of specific antibody-mediated proteolysis in diseased humans. A targeted catalytic response was originally demonstrated against MBP and Myo in multiple sclerosis and myocarditis patients, respectively.     

Idiotypic mimicry of a catalytic antibody active site

We have previously described three catalytic antibodies (Ab1s) raised against human erythrocyte acetylcholinesterase (AChE). These antibodies both recognise and resemble AChE in their reaction with substrates and appear with a relatively high frequency. We do not know, however, why catalytic activity should have developed in response to a ground state antigen. This question has implication for autoimmune disorders, which are frequently characterised by the presence of catalytic antibodies, many of which have cytotoxic effects. In this study, we raised anti-idiotypic (Ab2) and anti-anti-idiotypic (Ab3) antibodies to a catalytic Ab1 and examined their properties. None of the Ab2s showed catalytic activity, whereas four of the Ab3s did, an incidence of 1.26%. No contamination of antibody preparations with either AChE or butyrylcholinesterase (BChE) was found. Immunisation of mice with AChE, as well as AChE complexed with various inhibitors, resulted in a significant increase in catalytic immunoglobulins in the serum, compared with non-immunised mice and mice immunised with the Ab1. There appears to be considerable resemblance between Ab1s and Ab3s, but there are also significant differences between the two groups. All the antibodies were inhibited by phenylmethylsulphonyl fluoride (PMSF), indicating the presence of a serine residue in their active sites and were inhibited by the cholinesterase active site inhibitors tetraisopropyl pyrophosphoramide (iso-OMPA) and pyridostigmine. The Ab3s resembled the Ab1s in their ability to hydrolyse both acetylthiocholine (ATCh) and butyrylthiocholine (BTCh). However, the Ab3s appear to be better catalysts, having significantly reduced K(M) values (for ATCh but not BTCh) and increased turnover numbers (K(cat)), rate enhancements (K(cat)/K(uncat)) and K(cat)/K(M) ratios. The Ab3s also had reduced affinities for cholinesterase anionic site inhibitors (edrophonium, tetramethylammonium and BW284c51) and no affinity at all for the AChE peripheral anionic site (PAS) inhibitor fasciculin. All the antibodies recognise, to some degree, the PAS of AChE, shown by their ability to inhibit AChE, to compete with peripheral site inhibitors and to block AChE-mediated cell adhesion, a property of the site. These results indicate idiotypic mimicry of the catalytic antibody's active site, suggesting that the catalytic activity is due to affinity maturation of immunoglobulin genes in response to a specific antigen, namely, the PAS of AChE. Further studies are required to determine the structural features of this ground state antigen responsible for the development of catalytic activity.     

EhGEF2, a Dbl-RhoGEF from Entamoeba histolytica has atypical biochemical properties and participates in essential cellular processes

Dbl proteins are a family of factors that exchange the guanine nucleotide which promote the activation of Rho small GTPases. This paper reports the molecular, structural, biochemical and functional characterization of EhGEF2, a new member of the Dbl family. EhGEF2 is the second GEF studied in parasites and in the protozoan Entamoeba histolytica, and it is also the first member of the Dbl family that was found to have Arm repeats. The catalytic domain (DH) of EhGEF2 has the conserved residues T421, N590 and E591, which are important for the activation of the GTPases. Biochemical studies on EhGEF2 showed that it could activate in vitro the amoebic GTPases EhRacA, EhRacB, EhRacC, EhRacD, EhRacG, EhRacH and EhCdc42, being EhRacG its main target. It was found that the DH domain binds specifically phosphatidic acid (PA); docking and lipid dot blot studies indicated that this binding does not interfere with the contact surface of EhRacG. Functional studies showed that both the Arm repeats and the catalytic domain of EhGEF2 participate in its localization at the amoebic membrane. Expression of a negative dominant version of EhGEF2 protein in E. histolytica provoked a 30% decrease in its ability to phagocyte human erythrocytes as well as severe effects on both the proliferation and the cellular chemotaxis which suggest that EhGEF2 participates in these cellular processes.