A complete set of hyaluronan fragments obtained from hydrolysis catalyzed by hyaluronidase: Application to studies of hyaluronan mass distribution by simple HPLC devices

Hyaluronan (HA) has different biological functions according to its molar mass; short HA fragments are involved in inflammation processes and angiogenesis, whereas native HA is not. Physicochemically, studies of native HA hydrolysis catalyzed by bovine testicular hyaluronidase (HAase) have suggested that kinetic parameters depend on HA chain length. To study the influence of HA chain length in more detail, and to try to correlate the physicochemical and biological properties of HA, HA hydrolysis catalyzed by HAase was used in a new procedure to obtain HA fragments of different molar masses. HA fragments (10-mg scale) with a molar mass from 800 to 300,000 g mol(-1) were prepared, purified using low-pressure size exclusion chromatography (SEC), lyophilized, and characterized in molar mass by either mass spectrometry or HPLC-SEC-multiangle laser light scattering. The polydispersity index of the purified fractions was less than 1.25. The complete set of HA standards obtained was used to calibrate our routine HPLC-SEC device using only a refractive index (RI) detector. We showed that the N-acetyl-d-glucosamine reducing end assay and the calibrated HPLC-SEC-RI gave equivalent kinetic data. In addition, the HPLC-SEC-RI furnished the mass distribution of the polysaccharide during its hydrolysis.     

大鼠电惊厥后c－fos在中枢神经系统中的表达

本实验应用Ｆｏｓ蛋白免疫组织化方法对大鼠电惊厥后不同时程中枢神经系统内的ｃ－ｆｏｓ表达进行了观察,结果表明;①ｃ－ｆｏｓ表达于电惊厥后３０ｍｉｎ开始,２ｈ达高峰,４ｈ后逐渐下降,１２ｈ基本恢复正常。②Ｆｏｓ阳性神经元呈对称性分布,分布于颞叶听皮质、梨状皮质、内嗅皮质、ｓｔｒ１８区、杏仁体、海马、齿状回、斜角带核、弓状核、下丘脑腹内侧核、．视前区、丘脑、上丘灰质、中央灰质和脑桥腹侧部等结构。③ｃ－ｆｏｓ在颞叶听皮质、梨状皮质和内嗅皮质最先表达,表达程度最强,恢复也最慢,提示这些结构可能是电惊厥发生的起源结构,并呈现皮层结构向皮层下结构播散的过程,主要播及边缘结构。     

Behavioral differentiation during collective building in wild mice Mus spicilegus

Although well documented in social insects, the possibility of behavioral differentiation during collective building has been poorly studied in mammals. In this context, the mound-building mouse Mus spicilegus is an interesting model. Under natural conditions, juveniles from different litters gather vegetal material and build a sophisticated structure, the mound, under which the mice will spend winter. The first steps of this complex building process may be elicited under laboratory conditions by offering cotton balls as building material. Spatio-temporal distribution of both animals and cotton balls was automatically recorded by RFID (Radio-Frequency Identification Device) technique. Our results revealed a behavioral differentiation during a collective building task. In a group of six individuals, only two mice (called carriers) transported 80% of the building material whereas the contribution of the remaining mice was weak or even non-existent. The proportion of carriers was constant in all of the six groups studied. This behavioral differentiation was implemented immediately after the building material was made available and remained stable during the 4 days of experiment. The high contribution level of carriers did not result from resource monopolization, nor did it depend on the gender or parental origin of the mice.     

黑腹果蝇细胞谱系分析方法进展

对动物体内单个细胞的谱系进行分析有助于追踪其在发育过程中的作用,但是体内各种组织都是由很多形态、结构、功能各不相同的细胞构成的复杂系统,这种复杂性严重阻碍了对单个细胞的研究。嵌合克隆技术(Mosaic technique)和标记技术(Labeling technique)的出现为这一研究提供了强有力的手段。文章介绍了近几年来黑腹果蝇(Drosophila melanogaster)研究中常用的7种嵌合克隆标记方法,包括FRT介导的有丝分裂重组(FRT-mediated mitotic recombination)、MARCM(Mosaic analysis with a repressible cell marker)、TSG(Twin spotgenerator)、Twin-spot MARCM、Q-MARCM(Q system-based MARCM)、Coupled MARCM和G-TRACE(Gal4technique for real-time and clonal expression)技术,详述了这些技术的原理及应用,并对不同技术进行了对比。运用这些技术研究者可以从单细胞水平进行遗传学标记和操作,特别是在神经系统等复杂系统中追踪单个细胞的发育过程。果蝇中的这些技术也将为其他模式生物追踪细胞谱系提供参考。     

Influence of spatial structure on effective nutrient diffusion in bacterial biofilms

The main contribution of this paper is to use homogenization techniques to compute diffusion coefficients from experimental images of microbial biofilms. Our approach requires the analysis of several experimental spatial structures of biofilms in order to derive from them a Representative Volume Element (RVE). Then, we apply a suitable numerical procedure to the RVE to derive the diffusion coefficients. We show that diffusion coefficients significantly vary with the biofilm structure. These results suggest that microbial biofilm structures can favour nutrient access in some cases.     

Fabrication and Application of Rose Bengal-chitosan Films in Laser Tissue Repair

Photochemical tissue bonding (PTB) is a sutureless technique for tissue repair, which is achieved by applying a solution of rose bengal (RB) between two tissue edges^1,2. These are then irradiated by a laser that is selectively absorbed by the RB. The resulting photochemical reactions supposedly crosslink the collagen fibers in the tissue with minimal heat production³. In this report, RB has been incorporated in thin chitosan films to fabricate a novel tissue adhesive that is laser-activated. Adhesive films, based on chitosan and containing ~0.1 wt% RB, are fabricated and bonded to calf intestine and rat tibial nerves by a solid state laser (λ=532 nm, Fluence~110 J/cm², spot size~0.5 cm). A single-column tensiometer, interfaced with a personal computer, is used to test the bonding strength. The RB-chitosan adhesive bonds firmly to the intestine with a strength of 15 ± 6 kPa, (n=30). The adhesion strength drops to 2 ± 2 kPa (n=30) when the laser is not applied to the adhesive. The anastomosis of tibial nerves can be also completed without the use of sutures. A novel chitosan adhesive has been fabricated that bonds photochemically to tissue and does not require sutures.     

Improving gel-based proteome analysis of soluble protein extracts by heat prefractionation

The presence of high-abundance proteins in complex protein mixtures often masks low-abundance proteins and causes loss of resolution of 2DE. Protein fractionation steps conducted prior to 2DE can enhance the detection of low-abundance proteins and improve the resolution of 2DE. Here, we report a method to prefractionate soluble protein extracts based on protein thermal denaturation. Soluble proteins were extracted from maize embryos and leaves and Escherichia coli cells. Through heating at 95°C for 5 min, soluble protein extracts were prefractionated as heat stable protein fraction (the supernatant) and heat labile protein fraction (the precipitate). Our results showed that heat prefractionation enhanced the separation of proteins in both fractions by 2DE, thereby increasing the chance of detecting low-abundance proteins, many of which were nonvisible in unfractionated extract. In maize embryo, 330 spots were detected in soluble protein extract, while 577 spots were detected after prefractionation. Furthermore, this prefractionation method facilitated the enrichment, detection, and identification of de novo synthesized stress proteins. Because of its simplicity, the one-step heat prefractionation minimizes protein loss. Finally, heat prefractionation requires no expensive special hardware or reagents, and provides an alternative prefractionation for increasing the resolving power of 2DE.     

大豆血红蛋白基因lba转化根瘤菌工程菌株的构建

以土著大豆根瘤菌接种大豆幼苗45 d后获得的根瘤为材料,提取其总RNA并反转录成cDNA,采用同源序列克隆法扩增大豆血红蛋白基因lba编码区序列。利用DNA重组技术,将lba基因连到lac启动子的下游,利用带有发光酶标记基因luxAB的质粒载体pTR102构建表达载体pTR-Plac-lba。采用三亲本杂交的方式,将表达载体pTR-Plac-lba及作为对照的空载体pTR102分别转化土著大豆根瘤菌,获得根瘤菌工程菌株SFH(pTR-Plac-lba)和SFH(pTR102)。盆栽试验发现,接种SFH(pTR-Plac-lba)的大豆植株各生理指标明显高于接种SFH(pTR102)、土著根瘤菌以及未接菌的大豆植株各生理指标。试验证明,导入大豆血红蛋白基因lba的根瘤菌工程菌株SFH(pTR-Plac-lba)对于提高大豆根瘤的固氮酶活性,增加大豆产量起到显著效果。