The crystal structure of CD8 in complex with YTS156.7.7 Fab and interaction with other CD8 antibodies define the binding mode of CD8 alphabeta to MHC class I

The CD8αβ heterodimer interacts with class I pMHC on antigen-presenting cells as a co-receptor for TCR-mediated activation of cytotoxic T cells. To characterize this immunologically important interaction, we used monoclonal antibodies (mAbs) specific to either CD8α or CD8β to probe the mechanism of CD8αβ binding to pMHCI. The YTS156.7 mAb inhibits this interaction and blocks T cell activation. To elucidate the molecular basis for this inhibition, the crystal structure of the CD8αβ immunoglobulin-like ectodomains were determined in complex with mAb YTS156.7 Fab at 2.7 Å resolution. The YTS156.7 epitope on CD8β was identified and implies that residues in the CDR1 and CDR2-equivalent loops of CD8β are occluded upon binding to class I pMHC. To further characterize the pMHCI/CD8αβ interaction, binding of class I tetramers to CD8αβ on the surface of T cells was assessed in the presence of anti-CD8 mAbs. In contrast to YTS156.7, mAb YTS105.18, which is specific for CD8α, does not inhibit binding of CD8αβ to class I tetramers, indicating the YTS105.18 epitope is not occluded in the pMHCI/CD8αβ complex. Together, these data indicate a model for the pMHCI/CD8αβ interaction similar to that observed for CD8αα in the CD8αα/pMHCI complex, but in which CD8α occupies the lower orientation (membrane proximal to the antigen presenting cell), and CD8β occupies the upper position (membrane distal). The implication of this molecular assembly for the function of CD8αβ in T cell activation is discussed.     

Diversity, relative abundance, new locality records and population structure of Antarctic demersal fishes from the northern Scotia Arc islands and Bouvetøya

A primary objective of the ICEFISH 2004 cruise was to collect and study notothenioid fishes from remote localities in the Atlantic sector of the Southern Ocean. Nearly 1 month was devoted to bottom trawling for fishes on the shelf and upper slope (to 1,000 m) areas around Shag Rocks, South Georgia, South Sandwich Islands and Bouvetøya. The focus was on the latter two locations, because their faunas are more poorly known. Eight species were collected at Shag Rocks with Patagonotothen guntheri most abundant; 17 at South Georgia with Lepidonotothen nudifrons, L. larseni and Gobionotothen gibberifrons most abundant; 13 at the South Sandwich Islands with L. larseni, L. nudifrons and G. gibberifrons most abundant; and 11 at Bouvetøya with L. larseni, Macrourus holotrachys and L. squamifrons most abundant. Ten new locality records were established: Shag Rocks (1), South Georgia (1), South Sandwich Islands (5), South Sandwich Trench at 5,350 m (1) and Bouvetøya (2). Total known demersal fish diversity on the shelf and upper slope at Shag Rocks/South Georgia, South Sandwich Islands and Bouvetøya is 42, 31 and 17 species, respectively. To examine population structure in the four most abundant notothenioids at Bouvetøya (L. larseni, L. squamifrons, Notothenia coriiceps and Chaenocephalus aceratus), we examined the ND2 portion of mitochondrial DNA. Chaenocephalus aceratus, N. coriiceps and L. larseni exhibited no significant genetic differentiation in comparison with samples from localities in the Scotia Sea and the Antarctic Peninsula. However, L. squamifrons showed significant genetic differentiation between the South Shetlands and Bouvetøya populations (F _ST = 0.189, P = 0.015). Thus, these data combined with previous studies of two other notothenioids suggest that five of the six notothenioid species at Bouvetøya are not genetically differentiated from other localities in the Atlantic sector of the Southern Ocean. The location of Bouvetøya within the Antarctic Circumpolar Current and the long (1–2 years) pelagic stages of the notothenioids at Bouvetøya may be at least partly responsible for this genetic homogeneity.     

Construction of a first genetic map of distylous Turnera and a fine-scale map of the S-locus region

As a prelude to discovery of genes involved in floral dimorphism and incompatibility, a genetic map of distylous Turnera was constructed along with a fine-scale map of the S-locus region. The genetic map consists of 79 PCR-based molecular markers (48 AFLP, 18 RAPD, 9 ISSR, 4 RAMP), 5 isozyme loci, one additional gene, and the S-locus, spanning a total distance of 683.3 cM. The 86 markers are distributed in 5 linkage groups, corresponding to the haploid chromosome number. Molecular markers tightly linked or co-segregating with the S-locus in an initial mapping population of 94 individuals were used to assay an additional 642 progeny to construct a map of the S-locus region. The fine-scale map consists of 2 markers (IS864a and RP45E9) flanking the S-locus at distances of 0.41 and 0.54 cM, respectively, and 3 additional markers (OPK14c, RP45G18, and RP81E18) co-segregating with the S-locus in the total mapping population of 736 individuals. The genetic map constructed will serve as a framework for localization of genes outside the S-locus affecting distyly, while molecular markers of the fine-scale map will be used to initiate chromosome walking to find the genes residing at the S-locus.     

Tropomyosin 4 defines novel filaments in skeletal muscle associated with muscle remodelling/regeneration in normal and diseased muscle

The organisation of structural proteins in muscle into highly ordered sarcomeres occurs during development, regeneration and focal repair of skeletal muscle fibers. The involvement of cytoskeletal proteins in this process has been documented, with nonmuscle gamma-actin found to play a role in sarcomere assembly during muscle differentiation and also shown to be up-regulated in dystrophic muscles which undergo regeneration and repair [Lloyd et al.,2004; Hanft et al.,2006]. Here, we show that a cytoskeletal tropomyosin (Tm), Tm4, defines actin filaments in two novel compartments in muscle fibers: a Z-line associated cytoskeleton (Z-LAC), similar to a structure we have reported previously [Kee et al.,2004], and longitudinal filaments that are orientated parallel to the sarcomeric apparatus, present during myofiber growth and repair/regeneration. Tm4 is upregulated in paradigms of muscle repair including induced regeneration and focal repair and in muscle diseases with repair/regeneration features, muscular dystrophy and nemaline myopathy. Longitudinal Tm4-defined filaments also are present in diseased muscle. Transition of the Tm4-defined filaments from a longitudinal to a Z-LAC orientation is observed during the course of muscle regeneration. This Tm4-defined cytoskeleton is a marker of growth and repair/regeneration in response to injury, disease state and stress in skeletal muscle.     

不同种类可吸收性外科缝线的体外降解性能评价

目的研究3种不同种类的可吸收性缝线的体外降解性能,分析其体外降解产物。方法将3种可吸收性缝线分别按比例浸入Sorensen缓冲液中进行体外降解实验,设3个降解周期组,每组设3个重复,分别过滤分离试样、碎片和溶液,计算试样的质量损耗率。并对其体外降解产物进行定性定量分析。结果3种试样体外降解的质量损耗率均逐期增大;不同种类缝线的体外降解液成分不同,且其主要成份含量逐期增加。结论：不同种类的可吸收性缝线应采用不同的定性定量分析方法,根据产物推断缝线的生物安全性。     

MRI典型和特殊故障排除方法

介绍了GE公司的磁共振机（Signa Mri 1．OT）的主机显示器、磁体监视器故障排除方法,以及解决伪影干扰的经验。     

Pet owners' views of pet behavior problems and willingness to consult experts for assistance

Prior research has found that dog obedience training and the receipt of advice regarding companion animal (pet) behavior reduce the risk of nonhuman animal relinquishment to an animal shelter and increase human-companion animal interactions, but research also finds that only a minority of pet guardians participates in such activities. The researchers for this study asked 170 dog and cat guardians to assess the seriousness of common problem behaviors and how likely they were to seek help. The researchers also asked them to rate different methods of obtaining expert advice. The dog and cat guardians saw behaviors directly affecting humans as most severe; those involving the destruction of property were next in severity; and those affecting the animal more than the human were least severe. There were no significant differences in ratings by participants' gender or income. Participants indicated they were more likely to use free help options than fee-based services. The lack of a clear correlation between the seriousness of a behavior problem and likelihood of seeking help suggests that other factors may play a role in pet guardians' interest in obtaining expert advice.     

Electrochemical sensing of dihydrogen phosphate and adenosine-5′-triphosphate anions by self-assembled monolayers of (ferrocenylmethyl)trialkylammonium cations on gold electrodes

The effective electrochemical sensing of dihydrogen phosphate and adenosine-5′-triphosphate anions could be achieved in organic electrolytes using self-assembled monolayers of a (ferrocenylmethyl)trialkylammonium cation. The electrochemical response of these modified electrodes was found to be similar to that of the receptor in homogeneous solution. This observation showed that the electrochemical recognition properties of the redox active cationic receptor were fully retained after immobilization on the electrode surface. The recognition abilities of this redox assembly are based on strong ion pairing effects, further reinforced upon oxidation of the ferrocene centres to ferrocenium. The complexation events could be detected and amperometrically quantified through the emergence of new differential pulse voltammetric peaks corresponding to the electroactivity of the (ferrocenylmethyl)alkylammonium-anion complexes.     

Molecular shape, architecture, and size of P2X4 receptors determined using fluorescence resonance energy transfer and electron microscopy

P2X receptors are ATP-gated nonselective cation channels with important physiological roles. However, their structures are poorly understood. Here, we analyzed the architecture of P2X receptors using fluorescence resonance energy transfer (FRET) microscopy and direct structure determination using electron microscopy. FRET efficiency measurements indicated that the distance between the C-terminal tails of P2X(4) receptors was 5.6 nm. Single particle analysis of purified P2X(4) receptors was used to determine the three-dimensional structure at a resolution of 21A(;) the orientation of the particle with respect to the membrane was assigned by labeling the intracellular C termini with 1.8-nm gold particles and the carbohydrate-rich ectodomain with lectin. We found that human P2X(4) is a globular torpedo-like molecule with an approximate volume of 270 nm(3) and a compact propeller-shaped ectodomain. In this structure, the distance between the centers of the gold particles was 6.1 nm, which closely matches FRET data. Thus, our data provide the first views of the architecture, shape, and size of single P2X receptors, furthering our understanding of this important family of ligand-gated ion channels.