Abnormal display of PfEMP-1 on erythrocytes carrying haemoglobin C may protect against malaria

Haemoglobin C, which carries a glutamate-to-lysine mutation in the beta-globin chain, protects West African children against Plasmodium falciparum malaria. Mechanisms of protection are not established for the heterozygous (haemoglobin AC) or homozygous (haemoglobin CC) states. Here we report a marked effect of haemoglobin C on the cell-surface properties of P. falciparum-infected erythrocytes involved in pathogenesis. Relative to parasite-infected normal erythrocytes (haemoglobin AA), parasitized AC and CC erythrocytes show reduced adhesion to endothelial monolayers expressing CD36 and intercellular adhesion molecule-1 (ICAM-1). They also show impaired rosetting interactions with non-parasitized erythrocytes, and reduced agglutination in the presence of pooled sera from malaria-immune adults. Abnormal cell-surface display of the main variable cytoadherence ligand, PfEMP-1 (P. falciparum erythrocyte membrane protein-1), correlates with these findings. The abnormalities in PfEMP-1 display are associated with markers of erythrocyte senescence, and are greater in CC than in AC erythrocytes. Haemoglobin C might protect against malaria by reducing PfEMP-1-mediated adherence of parasitized erythrocytes, thereby mitigating the effects of their sequestration in the microvasculature.     

Imaging of Titan from the Cassini spacecraft

Titan, the largest moon of Saturn, is the only satellite in the Solar System with a substantial atmosphere. The atmosphere is poorly understood and obscures the surface, leading to intense speculation about Titan's nature. Here we present observations of Titan from the imaging science experiment onboard the Cassini spacecraft that address some of these issues. The images reveal intricate surface albedo features that suggest aeolian, tectonic and fluvial processes; they also show a few circular features that could be impact structures. These observations imply that substantial surface modification has occurred over Titan's history. We have not directly detected liquids on the surface to date. Convective clouds are found to be common near the south pole, and the motion of mid-latitude clouds consistently indicates eastward winds, from which we infer that the troposphere is rotating faster than the surface. A detached haze at an altitude of 500 km is 150-200 km higher than that observed by Voyager, and more tenuous haze layers are also resolved.     

The abundances of constituents of Titan's atmosphere from the GCMS instrument on the Huygens probe

Saturn's largest moon, Titan, remains an enigma, explored only by remote sensing from Earth, and by the Voyager and Cassini spacecraft. The most puzzling aspects include the origin of the molecular nitrogen and methane in its atmosphere, and the mechanism(s) by which methane is maintained in the face of rapid destruction by photolysis. The Huygens probe, launched from the Cassini spacecraft, has made the first direct observations of the satellite's surface and lower atmosphere. Here we report direct atmospheric measurements from the Gas Chromatograph Mass Spectrometer (GCMS), including altitude profiles of the constituents, isotopic ratios and trace species (including organic compounds). The primary constituents were confirmed to be nitrogen and methane. Noble gases other than argon were not detected. The argon includes primordial 36Ar, and the radiogenic isotope 40Ar, providing an important constraint on the outgassing history of Titan. Trace organic species, including cyanogen and ethane, were found in surface measurements.     

Association analysis of NOTCH4 loci in schizophrenia using family and population-based controls

A genetic association between NOTCH4 and schizophrenia has previously been proposed. Unsing all markers previously shown to be associated, we found no evidence for such in three independent family-based samples (n=519 parent-offspring trios), and a case-control sample derived from the same ethnic background as the original observation. These data strongly suggest that NOTCH4 is not a significant susceptibility allele for schizophrenia.     

Phylogenetic divergence in a desert fish: differentiation of speckled dace within the Bonneville, Lahontan, and upper Snake river basins

Historical events have had a great impact on the biogeography of fishes of western North America. We examined the genetic variation of the speckled dace ( Rhinichthys osculus ) to determine the effects on this species of extensive hydrological changes during the last 10 million years in the Bonneville and Lahontan basins of the Great Basin and the upper Snake River Basin. Eight hundred sixty-nine base pairs of the mitochondrial gene cytochrome b were sequenced from 97 individuals representing 22 populations within these 3 basins, as well as from 2 individuals of longnose dace ( Rhinichthys cataractae ) that served as outgroups. Additionally, 13 speckled dace sequences representing 3 Bonneville populations were used from GenBank. Phylogenetic relationships were reconstructed using maximum parsimony and maximum likelihood criteria. Analysis of molecular variance was used to determine population structure and to estimate the amount of gene flow across the community boundaries. Three distinct clades were reconstructed representing the Lahontan Basin, the northern Bonneville and upper Snake River basins, and the southern Bonneville Basin. Additionally, most of the population structuring was explained by variation among basins (65.33%). Speckled dace demonstrated high genetic variation. As hypothesized, the northern and southern Bonneville specimens formed separate clades; however, the southern Bonneville clade was basal to a sister clade formed by the northern Bonneville/upper Snake River and Lahontan clades. These relationships indicate that Pliocene connections between the Snake, Lahontan, and Bonneville drainages, rather than more recent Pleistocene connections, best explain population structuring in speckled dace.     

Acetylcholine induced endothelial-dependent vasodilation increases as artery diameter decreases in the rabbit ear

Summary Isolated resistance vessels in the rabbit ear preconstricted with histamine were relaxed by acetylcholine by a proportionately greater amount than the central ear artery. The relaxation was antagonized by atropine and also by endothelium removal. Our studies represent the first direct evidence that endothelium-dependent dilation can occur in resistance vessels.Acknowledgments. We thank Christine Quinn for her careful technical assistance in the use of the myographs and Daniel Netto for construction of the small vessel myographs. The tungsten wire used for mounting the vessels was given by Westinghouse Corporation Lamp Division. This work was supported by American Heart Association Fellowship 608 and National Heart, Lung, and Blood Institute Grant HL-32985.     

中学生物教师继续教育相关问题的调查研究

职后继续教育的课程设置对教师素质有一定的影响,采用问卷调查、文献分析和访谈等方法,对中学生物教师继续教育所应开设的课程、教学形式等继续教育方面的问题进行研究,并提出相应建议。