Stimulated platelets use serotonin to enhance their retention of procoagulant proteins on the cell surface.

Activated platelets bind numerous adhesive and procoagulant proteins by receptor-mediated processes. Although there is little evidence to suggest that these processes are heterogeneous in platelets, we previously found that platelets co-stimulated with collagen and thrombin express functional alpha-granule factor V only on a subpopulation of cells. Here we show that these cells, referred to as 'COAT-platelets', bind additional alpha-granule proteins, including fibrinogen, von Willebrand factor, thrombospondin, fibronectin and alpha2-antiplasmin. These proteins are all transglutaminase substrates, and inhibitors of transglutaminase prevent the production of COAT-platelets. A synthetic transglutaminase substrate (CP15) also binds to COAT-platelets, and analysis by high performance liquid chromatography/mass spectrometry shows that a product is formed with a relative molecular mass (Mr) equal to CP15 plus 176. Serotonin, an abundant component of platelet-dense granules, has an Mr of 176, and fibrinogen isolated from COAT-platelets contains covalently linked serotonin. Synthetic bovine serum albumin-(serotonin)6 binds selectively to COAT-platelets and also inhibits the retention of procoagulant proteins on COAT-platelets. These data indicate that COAT-platelets use serotonin conjugation to augment the retention of procoagulant proteins on their cell surface through an as yet unidentified serotonin receptor.     

Activation of human CD4+ cells with CD3 and CD46 induces a T-regulatory cell 1 phenotype

The immune system must distinguish not only between self and non-self, but also between innocuous and pathological foreign antigens to prevent unnecessary or self-destructive immune responses. Unresponsiveness to harmless antigens is established through central and peripheral processes. Whereas clonal deletion and anergy are mechanisms of peripheral tolerance, active suppression by T-regulatory 1 (Tr1) cells has emerged as an essential factor in the control of autoreactive cells. Tr1 cells are CD4+ T lymphocytes that are defined by their production of interleukin 10 (IL-10) and suppression of T-helper cells; however, the physiological conditions underlying Tr1 differentiation are unknown. Here we show that co-engagement of CD3 and the complement regulator CD46 in the presence of IL-2 induces a Tr1-specific cytokine phenotype in human CD4+ T cells. These CD3/CD46-stimulated IL-10-producing CD4+ cells proliferate strongly, suppress activation of bystander T cells and acquire a memory phenotype. Our findings identify an endogenous receptor-mediated event that drives Tr1 differentiation and suggest that the complement system has a previously unappreciated role in T-cell-mediated immunity and tolerance.     

Impact origin of sediments at the Opportunity landing site on Mars

Mars Exploration Rover Opportunity discovered sediments with layered structures thought to be unique to aqueous deposition and with minerals attributed to evaporation of an acidic salty sea. Remarkable iron-rich spherules were ascribed to later groundwater alteration, and the inferred abundance of water reinforced optimism that Mars was once habitable. The layered structures, however, are not unique to water deposition, and the scenario encounters difficulties in accounting for highly soluble salts admixed with less soluble salts, the lack of clay minerals from acid-rock reactions, high sphericity and near-uniform sizes of the spherules and the absence of a basin boundary. Here we present a simple alternative explanation involving deposition from a ground-hugging turbulent flow of rock fragments, salts, sulphides, brines and ice produced by meteorite impact. Subsequent weathering by intergranular water films can account for all of the features observed without invoking shallow seas, lakes or near-surface aquifers. Layered sequences observed elsewhere on heavily cratered Mars and attributed to wind, water or volcanism may well have formed similarly. If so, the search for past life on Mars should be reassessed accordingly.     

Quantitative study of tectonic geomorphology along Haiyuan fault based on airborne LiDAR

High-precision and high-resolution topography are the fundamental data for active fault research.Light detection and ranging(LiDAR)presents a new approach to build detailed digital elevation models effectively.We take the Haiyuan fault in Gansu Province as an example of how LiDAR data may be used to improve the study of active faults and the risk assessment of related hazards.In the eastern segment of the Haiyuan fault,the Shaomayin site has been comprehensively investigated in previous research because of its exemplary tectonic topographic features.Based on unprecedented LiDAR data,the horizontal and vertical coseismic offsets at the Shaomayin site are described.The measured horizontal value is about 8.6 m,and the vertical value is about 0.8 m.Using prior dating ages sampled from the same location,we estimate the horizontal slip rate as4.0±1.0 mm/a with high confidence and define that the lower bound of the vertical slip rate is 0.4±0.1 mm/a since the Holocene.LiDAR data can repeat the measurements of field work on quantifying offsets of tectonic landform features quite well.The offset landforms are visualized on an office computer workstation easily,and specialized software may be used to obtain displacement quantitatively.By combining precious chronological results,the fundamentallink between fault activity and large earthquakes is better recognized,as well as the potential risk for future earthquake hazards.     

Endoderm contributes to endocardial composition during cardiogenesis

Heart formation commences from a single heart tube, which fuses from bilateral primordial heart fields. The developing heart tube is composed of outerlayer myocardial cells and innerlayer endocardial cells. Several distinct populations of precardiac cells contribute to cardiac morphogenesis. However, it still remains not very clear about the lineage of endocardium at gastrulation stage. Thereby, this study focused on ascertaining the correlation between the hypoblast in gastrulation and endocardium during cardiogenesis. Firstly, the fusing heart tube morphologically is closed to endoderm-derived pharynx floor, implying the possibility that pharynx floor might be wrapped into the formation of endoderm. Secondly, HNK1 is expressed in hypoblast strongly at gastrula stage and subsequently appeared in endocardium of cardiogenesis. Moreover, fate map data displayed that DiI labeled hypoblast was also present in endocardium later on. One more evidence is chickquail chimera of hypoblast transplantation, in which quailhypoblast derivative could be identified in endocardium of cardiogenesis by QCPN antibody. In sum, our current data suggests that endoderrn in gastrula contribute at least partly to the formation of endocardium of cardiogenesis.     

Numeric analysis of the lizard genus Sceloporus with special reference to cranial osteology

Phylogenetic relationships among Sceloporine genera are briefly discussed. Species relationships within the genus Sceloporus are analyzed, and evolutionary lines of descent are proposed. The genus Sceloporus is composed of three monophyletic groups: Group I, the most primitive, probably developed from Sator - like ancestral stock in Miocene times. This group speciated from stock similar to Sceloporus gadoviae in southern Mexico to S. merriami in the North and contains 7 species in 3 species groups. We propose that these species be included in the genus Lysoptychus Cope. Group II arose from Group I and evolved from centrally located Sceloporus pictus in all directions throughout Mexico. This intermediate group contains approximately 19 species in 5 species groups. Group III also arose from the primitive stock of Group I and radiated from several desert refugia created by Pleistocene glaciation. Evolution of this group in Mexico was generally from north to south with Sceloporus malachiticus extending as far south as Panama. This group contains approximately 33 species in 5 species groups.