Thrombin-dependent Incorporation of von Willebrand Factor into a Fibrin Network

Attachment of platelets from the circulation onto a growing thrombus is a process involving multiple platelet receptors, endothelial matrix components, and coagulation factors. It has been indicated previously that during a transglutaminase reaction activated factor XIII (FXIIIa) covalently cross-links von Willebrand factor (VWF) to polymerizing fibrin. Bound VWF further recruits and activates platelets via interactions with the platelet receptor complex glycoprotein Ib (GPIb). In the present study we found proof for binding of VWF to a fibrin monomer layer during the process of fibrinogen-to-fibrin conversion in the presence of thrombin, arvin, or a snake venom from Crotalus atrox. Using a domain deletion mutant we demonstrated the involvement of the C domains of VWF in this binding. Substantial binding of VWF to fibrin monomers persisted in the presence of the FXIIIa inhibitor K9-DON, illustrating that cross-linking via factor XIII is not essential for this phenomenon and suggesting the identification of a second mechanism through which VWF multimers incorporate into a fibrin network. Under high shear conditions, platelets were shown to adhere to fibrin only if VWF had been incorporated. In conclusion, our experiments show that the C domains of VWF and the E domain of fibrin monomers are involved in the incorporation of VWF during the polymerization of fibrin and that this incorporation fosters binding and activation of platelets. Fibrin thus is not an inert end product but partakes in further thrombus growth. Our findings help to elucidate the mechanism of thrombus growth and platelet adhesion under conditions of arterial shear rate.     

Genetic variation in IncI1-co1Ib plasmids

Nucleotide sequences of portions of three plasmid genes (cib, cir, and abi) present in IncI1-Co1Ib colicin plasmids obtained from strains of Salmonella typhimurium isolated in either 1974 (Barker strains) or between 1935 and 1941 (Murray strains) were examined along with sequences of the chromosomal gene for 6-phosphogluconate dehydrogenase (gnd). Our principal findings were: (1) The plasmid genes were virtually identical to those in IncI1-CoIIb plasmids from E. coli, suggesting that Salmonella and E. coli share overlapping pools of these plasmids. (2) The plasmid genes were much less polymorphic than gnd or any other known chromosomal gene from Salmonella, further suggesting horizontal transfer with rapid transmission and turnover. (3) No characteristic differences were found in either the plasmid genes or the chromosomal gene between the 1974 isolates and the Murray strains, indicating that these plasmids have been stable for at least several decades. (4) There was an excess of amino-acid replacement polymorphisms, relative to synonymous polymorphisms, in the plasmid genes, which is consistent with the hypothesis of diversifying selection among colicin-producing plasmid families. (5) The abi (abortive infection) gene present in each of the plasmids contained two single-nucleotide insertions relative to the published sequence. These result in a putative abi protein of 114 amino acids instead of 89.     

油桐叶品质对油桐尺蠖生长发育的影响

用上年受害树和未受害树的当年新发叶在室内饲养油桐尺蠖幼虫,并用Folin－Denis分析方法测定了当年受害叶,受害后新发叶和未受害叶的总单宁含量。结果表明,取食受害叶的幼虫比取食未受害叶者存活率低20．5％,发有速度慢2天,体长短5.0mm,蛹重轻25．3％。叶内总单宁含量不因受害而上升,反而呈下降趋势,说明叶内成分中影响幼虫生长发育的是非单宁物质。     

A new Late Pleistocene non-anthropogenic vertebrate assemblage from the northern Iberian Peninsula: Artazu VII (Arrasate,Basque Country)

Late Pleistocene palaeontological sites without human intervention are limited in the Cantabrian region, and even more so those with a good state of preservation and rich biodiversity. A new vertebrate fossiliferous locality discovered at Kobate Quarry (Arrasate, northern Iberian Peninsula) is presented in this article. This site, in which remains of 40 different vertebrate taxa were accumulated, acted as a natural trap. The preliminary vertebrate faunal list includes five amphibian taxa, four reptiles, seven species of birds and 24 mammalian taxa. While small mammals are represented by 13 small mammal taxa (seven in the Order Rodentia, five in the Order Eulipotyphla, and one in the Order Chiroptera), the large mammal fauna comprises eleven species, including ungulates and carnivores. The palaeoecology inferred from this faunal assemblage suggests the existence of large forested areas with some grassland and a watercourse nearby, within a notably warm and humid climate. These palaeoenvironmental conditions, combined with AMS and AAR results carried out in macrofaunal bone samples, suggest that the deposit from Artazu VII would be located in the first half of the Late Pleistocene, in the Marine Isotope Stage (MIS) 5c.     

Schistosoma mansoni: TGF-beta signaling pathways

Schistosome parasites have co-evolved an intricate relationship with their human and snail hosts as well as a novel interplay between the adult male and female parasites. We review the role of the TGF-beta signaling pathway in parasite development, host-parasite interactions and male-female interactions. The data to date support multiple roles for the TGF-beta signaling pathway throughout schistosome development, in particular, in the tegument which is at the interface with the host and between the male and female schistosome, development of vitelline cells in female worms whose genes and development are regulated by a stimulus from the male schistosome and embryogenesis of the egg. The human ligand TGF-beta1 has been demonstrated to regulate the expression of a schistosome target gene that encodes a gynecophoric canal protein in the schistosome worm itself. Studies on signaling in schistosomes opens a new era for investigation of host-parasite and male-female interactions.     

Le gisement rupestre de Siega Verde, Salamanque: Une vision de synthèse

The Paleolithic shelter Art in the open air of Siega Verde, Salamanca, is the unitary group better endowed with paleolithic shelter manifestations in the bleakness of the whole Iberian Peninsula. Its study, consequence of more than 10 years of works on the land, has culminated with the recent publication of a complete monograph. In the following lines, we intend to synthesize the content of that, with special emphasis in the internal analysis of the representations and in their relationship with its cultural immediate environment, the Upper Paleolithic of the Castilian Plateau. The results of so long investigation process suppose a new interpretation way, not only of the own site, but also of the whole Paleolithic shelter phenomenon inside the Peninsula, and in a more general environment, of the graphic system of the European Upper Paleolithic.     

PAFAH Ib phospholipase A2 subunits have distinct roles in maintaining Golgi structure and function

Recent studies showed that the phospholipase subunits of Platelet Activating Factor Acetylhydrolase (PAFAH) Ib, α1 and α2 partially localize to the Golgi complex and regulate its structure and function. Using siRNA knockdown of individual subunits, we find that α1 and α2 perform overlapping and unique roles in regulating Golgi morphology, assembly, and secretory cargo trafficking. Knockdown of either α1 or α2 reduced secretion of soluble proteins, but neither single knockdown reduced secretion to the same degree as knockdown of both. Knockdown of α1 or α2 inhibited reassembly of an intact Golgi complex to the same extent as knockdown of both. Transport of VSV-G was slowed but at different steps in the secretory pathway: reduction of α1 slowed trans Golgi network to plasma membrane transport, whereas α2 loss reduced endoplasmic reticulum to Golgi trafficking. Similarly, knockdown of either subunit alone disrupted the Golgi complex but with markedly different morphologies. Finally, knockdown of α1, or double knockdown of α1 and α2, resulted in a significant redistribution of kinase dead protein kinase D from the Golgi to the plasma membrane, whereas loss of α2 alone had no such effect. These studies reveal an unexpected complexity in the regulation of Golgi structure and function by PAFAH Ib. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism.     

忽地笑酌-生育酚甲基转移酶基因LaTMT的克隆与表达分析

采用RACE技术从忽地笑也Lycoris aurea ( L'Hér.) Herb.页叶片中克隆获得γ-生育酚甲基转移酶(γ-TMT)基因,命名为LaTMT。序列分析结果显示：该基因cDNA全长1458 bp,其中开放阅读框( ORF)长1017 bp,编码338个氨基酸残基。 LaTMT基因编码蛋白质的理论相对分子质量37560,理论等电点pI 8.70,为亲水性蛋白,无跨膜结构但具有信号肽结构;并具有S-腺苷甲硫氨酸( SAM)甲基转移酶保守结构域,包含3个SAM结合位点;该蛋白的二级结构中包含44.08%的α-螺旋、32.84%的无规则卷曲、12.72%的延伸链和10.36%的β-转角。序列比对和系统进化树分析结果显示：LaTMT蛋白属于S-腺苷甲硫氨酸-依赖性γ-生育酚甲基转移酶家族,与其他植物γ-TMT蛋白的一致性为64%~75%;在 NJ系统树上, LaTMT蛋白与单子叶植物γ-TMT蛋白聚为同一大类,并与油棕( Elaeis guineensis Jacq.) EgTMT和美洲油棕也Elaeis oleifera ( Kunth) Cortés页EoTMT聚为同一类,亲缘关系最近。基因表达分析结果显示：LaTMT基因可在大肠杆菌中成功表达,且表达量随异丙基硫代半乳糖苷( IPTG)诱导时间的延长而增加;在忽地笑的根、叶片、花苞、子房、雄蕊、花瓣和鳞茎中LaTMT基因均可表达,其中在叶片中的相对表达量最高,在子房、雄蕊和鳞茎中的相对表达量相对较低,具有明显的组织特异性。研究结果表明：忽地笑LaTMT基因在进化过程中具有很高的保守性;该基因主要定位于叶绿体中,并与忽地笑对非生物逆境胁迫的抗性相关。     

Ability of Different Glycoprotein IIb-IIIa Ligands to Support Platelet Aggregation Induced by Activating Antibody CRC54

The ability of different ligands of glycoprotein (GP) IIb-IIIa (alphaIIb/beta3-integrin) to support platelet aggregation stimulated by activating anti-GP IIb-IIIa monoclonal antibody (monoAB) CRC54 has been investigated. Antibody CRC54 stimulated aggregation of washed platelets not only in the presence of fibrinogen, the main GP IIb-IIIa ligand, but also in the presence of von Willebrand factor (vWF). Unlike these ligands, fibronectin failed to support CRC54-induced aggregation. Fibrinogen and vWF dependent platelet aggregation was completely suppressed by GP IIb-IIIa antagonists--preparations Monafram (F(ab')2 fragments of monoAB that blocked GP IIb-IIIa receptor activity) and aggrastat (RGD-like peptidomimetic). However, aggregation stimulated in the presence of vWF was also completely inhibited by monoAB AK2 directed against GP Ib and capable of blocking its binding with vWF. CRC54-induced aggregation of platelets from patient with GP Ib deficiency in the presence of vWF was significantly lower than aggregation of platelets from normal donors and was not inhibited by anti-GP Ib antibody but still blocked by GP IIb-IIIa antagonist Monafram. Monafram also suppressed CRC54-stimulated platelet adhesion to plastic-adsorbed fibrinogen, vWF, and fibronectin. Unlike CRC54-induced platelet aggregation supported by fluid phase vWF, CRC54-induced adhesion to adsorbed vWF was not affected by anti-GP Ib antibody. Aggregation induced by CRC54 in the presence of fibrinogen and vWF was only partially suppressed by prostaglandin E1, an inhibitor of platelet activation, and was associated with serotonin release from platelet granules only when Ca2+ concentration was decreased from 1 mM (physiological level) to 0.1 mM. The data indicate that vWF supports CRC54-induced platelet aggregation via interaction with two receptors--GP IIb-IIIa and GP Ib. Aggregation induced by CRC54 in the presence of vWF or fibrinogen is only partially dependent on platelet activation and is accompanied with granule secretion only at low Ca2+ concentrations.