Salmonella effectors translocated across the vacuolar membrane interact with the actin cytoskeleton

A family of nine Salmonella typhimurium type III secretion effectors with a conserved amino-terminus have been defined. Three family members (SifA, SifB and SseJ) have previously been demonstrated to localize to the Salmonella-containing vacuole and to Salmonella-induced filaments. In contrast, we demonstrate that two other family members, SspH2 and SseI, co-localized with the polymerizing actin cytoskeleton. These proteins also interacted with the mammalian actin cross-linking protein filamin in the yeast two-hybrid assay through their highly conserved amino-terminal domains. This amino-terminus was sufficient to direct localization to the polymerizing actin cytoskeleton, suggesting that the interaction with filamin is important for this subcellular localization. In addition, SspH2 co-localized with vacuole-associated actin polymerizations (VAP) induced by intracellular bacteria through the Salmonella pathogenicity island (SPI)-2 type III secretion system (TTSS). SspH2 interacted with the actin-binding protein profilin in the yeast two-hybrid assay and by affinity chromatography. This interaction was highly specific to SspH2 and was mediated by its carboxy-terminus. Furthermore, SspH2 inhibited the rate of actin polymerization in vitro, suggesting that it functions to reduce or remodel VAP. Strains with mutations in sspH2 and sseI retained the ability to form VAP. However, a third intracellular virulence factor, spvB, which ADP-ribosylates actin, strongly inhibited VAP formation in HeLa cells, suggesting a more subtle effect for SspH2 and SseI on the actin cytoskeleton.     

A peritoneal mesothelioma in a captive aardwolf (Proteles cristatus)

A 10-year-old male aardwolf (Proteles cristatus) was presented abdominal distention and emaciation for 3 months. Physical examination revealed firm abdominal masses with effusions. Cytologic assessment of the effusion showed uniform round tumor cells with a surface brush border. Necropsy showed white velvety masses covering the peritoneal surface of the liver, gall bladder, stomach, omentum, mesentery, spleen, intestine, abdominal wall and diaphragm. Histologic examination demonstrated papillary projections, lined with cuboidal tumor cells supported by fibrous connective tissue cores, arising from the serosa of visceral organs. Cytoplasmic vacuolation and a surface brush border were evident on some cells under light microscopy. Tumor cells stained positive for both cytokeratin (AE1/AE3) and vimentin. Electron microscopy showed prominent surface microvilli, rough endoplasmic reticulum, mitochondria and desmosomes in tumor cells. This may be the first reported case of peritoneal mesothelioma in a captive wild aardwolf.     

小切口微创手术治疗新鲜跟腱断裂的临床价值

目的：探讨小切口微创手术治疗新鲜跟腱断裂的一晦床价值。方法：选取我院新鲜闭合性跟腱断裂患者50例,随机分为实验组和对照组各25例。实验组行小切口手术,对照组行常规切口手术。术后对患者进行随访,采用美国足踝协会（AOFAS）推荐的评分标准对患者术后功能恢复情况进行评价,观察并记录完全恢复患者例数、完全恢复时间、小腿最大周长差和术后并发症发生情况。结果：实验组AOFAS评分为（98．6±9．7）分,痊愈率96．00％,痊愈时间（20．2±3．2）周,两侧小腿最大周长差为（0．79＋0．68）cm,共有1例患者出现并发症,并发症发生率8％;而对照组的AOFAS评分为（91．4±11．5）分,痊愈率92．00％,痊愈时间（22．4±3．8）周,两侧小腿最大周长差为（0．91~0．76）cm;共有6例患者出现并发症,并发症的发生率为24％。两组患者的痊愈率、两侧小腿最大周长差比较差异无统计学意义（痊愈率：x2=-0．355,P=0．552;侧小腿最大周长差：t=O．588,P=0．559）;而与对照组比较,实验组AOFAS评分明显升高,完全恢复时间明显缩短,术后并发症的发生率显著降低,差异均有统计学意义（AOFAS评：t=2．393,P=0．021;恢复时间：t=2．150,P=0．037;并发症发生率：xⅫ．153,P=0．042）。结论：小切口手术与常规切口手术治疗新鲜跟腱断裂的疗效相当,但小切口手术术后恢童时间曼短．并发症更少．临床价值相对更高．     

Instrumented Indentation Investigation on the Viscoelastic Properties of Porcine Cartilage

Articular cartilage lubricates the contact surfaces in human joints and provides a shock-absorbing effect which protects the joint under dynamic loading. However, this shock-absorbing effect is gradually reduced as the result of normal wear, tear and aging-related cartilage loss. Thus, with the increasing average human life expectancy, the issue of joint health has attracted significant interest in recent decades. In developing new materials for the repair or regeneration of damaged articular cartilage, it is essential that the difference in the mechanical properties of healthy and damaged cartilages is well-understood. In the present study, the hardness and Young＇s modulus of damaged and healthy porcine articular cartilage samples are evaluated via a quasi-static nanoindentation technique. A dynamic mechanical analysis method is then applied to determine the viscoelastic properties of the two samples. The results presented in this study provide a useful insight into the mechanical properties of articular cartilage at the mesoscale, and therefore fill an important gap in the literature.     

Modular synthesis of Petri nets for modeling flexible manufacturing systems

This paper proposes a modular Petri net synthesis method for modeling flexible manufacturing systems based on synchronization among control processes of the manufacturing resources (such as robots and machines). In the method, the target system is modeled in a bottom-up and uniform manner by first describing the system's control processes using strongly connected state machines (SCSMs) as the basic modules. Each SCSM may contain multiple tokens to represent resources from the same type such as spaces in a buffer. Next, the common transitions and common transition subnets of the modules are merged to represent their synchronization. The system model constructed is proven to be conservative and thus bounded. Moreover, a restricted class of merged nets is proven to be live and reversible. For general classes of merged nets, this paper shows theorems that easily calculateP-invariants of the final net without solving the linear system equations. TheseP-invariants can be used to help in verifying the model's qualitative properties such as liveness.     

Low dose electron microscopy of the crotoxin complex thin crystal

The crotoxin complex from Crotalus d. terrificus rattlesnake venom was crystallized in the form of thin platelets. These crystals were prepared by the glucose embedding technique and examined by low dose electron microscopy. Electron diffraction patterns and images have been recorded to 2.2 and 4.5 A, respectively. By a combination of electron and X-ray diffraction techniques, the space group of this crystal was determined to be P4(2)22 with eight crotoxin complex molecules in one unit cell with dimensions of 38.8 A x 38.8 A x 256.8 A. The Patterson maps and the symmetry reliability factors calculated from the electron diffraction intensities clearly showed the existence of three types of electron diffraction patterns in different crystals. The phases in the computer-calculated transform of the low dose images also show the variation in symmetry among crystals. These phenomena are explained by the presence of crystals consisting of one-half, three-quarter and one unit cell in thickness. The interpretation of the computer reconstructed two-dimensional density map was limited, partly because of the similarity in density between the protein and the embedding glucose and partly because of the non-uniqueness in relating projected structure to the three-dimensional structure.     

Establishment of a human ovarian clear cell carcinoma cell line (RMG-I) and its single cell cloning--with special reference to the stem cell of the tumor

A cell line, designated RMG-I, has been established from ascites of a patient with ovarian clear cell carcinoma. RMG-I cells have grown well for more than 6 years with mirror ball formation. Chromosome analysis revealed aneuploidy with a modal number of 47 and 3 marker chromosomes. The histological characteristics of the transplanted tumor were similar to those observed in the original tumor which was composed of dark cells, clear cells, and hobnail cells. Thus, the RMG-I cell line was identified to be an ovarian clear cell carcinoma. Immunohistochemically, basic fetoprotein (BFP) and ferritin were demonstrated in the original tumor, the cultured cells, and the transplanted tumor. Furthermore, in order to clarify whether these 3 kinds of cells originate from one stem cell or not, monoclonal cell population were transplanted into nude mice, and its histological investigation revealed that 3 types of cells existed in the transplanted tumor, proving that they originate from one stem cell.     

Phosphorylation of neurofilament proteins by protein kinase C

The low molecular mass (70 kDa) subunit of neurofilaments (NF-L) contains at least three phosphorylation sites in vivo and is phosphorylated by multiple kinases in a site-specific manner [(1987) J. Neurochem. 48, S101; Sihag, R.K. and Nixon, R.A. submitted]. In this study, we observed that the three subunits of neurofilament proteins from retinal ganglion cell neurons are substrates for purified mouse brain protein kinase C. Two-dimensional alpha-chymotryptic phosphopeptide map analyses of the NF-L subunit demonstrated that protein kinase C phosphorylates four polypeptide sites, two of which incorporate phosphate when retinal ganglion cells are pulse-radiolabeled with [32P]orthophosphate in vivo.