抗衰老药物对线虫生存曲线影响的荟萃分析

随着世界人口老龄化步伐的加快,衰老机制及抗衰老药物的研究日益成为生物医学领域的热点前沿之一.国内外已有大量研究报道抗衰老药物能够延长多种模式生物包括线虫、果蝇、小鼠、大鼠及灵长类等的寿命,然而,这些药物延缓衰老方式的差异仍缺乏系统研究.因此,本研究以衰老研究的热点模式生物线虫为对象,搜集1990年以来国内外刊物上正式发表的有关抗衰老药物寿命试验的研究文献及其涉及的生存曲线,利用荟萃分析比较了不同抗衰老药物与生存曲线变化类型间的关系,并结合药物的药理作用探讨其延寿机制.生存曲线特征聚类结果与药物生物学分类交叉分析结果表明,药理作用类型与增益类型具有很强相关性,提示这2种分类方法的结果是匹配的.抗氧化剂类药物和控制血糖类药物对生存曲线的改善总体增益虽然不是最高,但相对于正常组生存曲线其增益部分呈平移形,表明该类药物可以通过改善年龄结构对整个群体产生显著增益,且其衰老曲线的特征与自然衰老相似.抗癫痫药物及胃肠道菌群相关药物总体增益较大,其曲线增益形状呈梯形,提示该类药物(尤其是胃肠道菌群相关药物)尽管显著延长了少数个体的最大寿命,但是从整个群体来看,大多数个体寿命延长程度并不明显,受益的少数个体可能需要较长的外界资源支持方能保持较长时间的存活状态,这种模式既不大众化也不经济.综上所述,清除自由基和控制血糖类药物对健康老年有着更为积极合理的作用与效应.     

Oxygen supply limits the heat tolerance of lizard embryos

The mechanisms that set the thermal limits to life remain uncertain. Classically, researchers thought that heating kills by disrupting the structures of proteins or membranes, but an alternative hypothesis focuses on the demand for oxygen relative to its supply. We evaluated this alternative hypothesis by comparing the lethal temperature for lizard embryos developing at oxygen concentrations of 10–30%. Embryos exposed to normoxia and hyperoxia survived to higher temperatures than those exposed to hypoxia, suggesting that oxygen limitation sets the thermal maximum. As all animals pass through an embryonic stage where respiratory and cardiovascular systems must develop, oxygen limitation may limit the thermal niches of terrestrial animals as well as aquatic ones.     

Relationships of fungal spore concentrations in the air and meteorological factors

High concentrations of airborne fungal spores are associated with human health concerns. Environmental variables, such as temperature and moisture, can influence growth and reproduction in fungi and airborne spore concentrations can fluctuate seasonally. However, we do not understand how long-term changes in climate affect fungal abundance in the air. Here, we sampled annually (at peak season, in September, over a 20-yr period) for airborne fungal spores in two North American cities (New York and Toronto), and related fungal abundance to local variation in climate. We found that at both locations, the total precipitation during the 2- month period prior to sampling (Jul.–Aug.) was negatively related to observed fungal spore concentrations. Considering that climate predictions for these two regions indicate an increase in drought events in summer, we expect airborne fungal concentrations to increase in future years, potentially exacerbating human health concerns.     

Formation of Thick Dense Yttrium Iron Garnet Films Using Aerosol Deposition

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% of the bulk. The primary advantage of AD is that the deposition takes place entirely at ambient temperature; thereby enabling film growth in material systems with disparate melting temperatures. This report describes in detail the processing steps for preparing the powder and for performing AD using the custom-built system. Representative characterization results are presented from scanning electron microscopy, profilometry, and ferromagnetic resonance for films grown in this system. As a representative overview of the capabilities of the system, focus is given to a sample produced following the described protocol and system setup. Results indicate that this system can successfully deposit 11 µm thick yttrium iron garnet films that are  > 90% of the bulk density during a single 5 min deposition run. A discussion of methods to afford better control of the aerosol and particle selection for improved thickness and roughness variations in the film is provided.     

Thermal tolerance and climate warming sensitivity in tropical snails

Tropical ectotherms are predicted to be especially vulnerable to climate change because their thermal tolerance limits generally lie close to current maximum air temperatures. This prediction derives primarily from studies on insects and lizards and remains untested for other taxa with contrasting ecologies. We studied the HCT (heat coma temperatures) and ULT (upper lethal temperatures) of 40 species of tropical eulittoral snails (Littorinidae and Neritidae) inhabiting exposed rocky shores and shaded mangrove forests in Oceania, Africa, Asia and North America. We also estimated extremes in animal body temperature at each site using a simple heat budget model and historical (20 years) air temperature and solar radiation data. Phylogenetic analyses suggest that HCT and ULT exhibit limited adaptive variation across habitats (mangroves vs. rocky shores) or geographic locations despite their contrasting thermal regimes. Instead, the elevated heat tolerance of these species (HCT = 44.5 ± 1.8°C and ULT = 52.1 ± 2.2°C) seems to reflect the extreme temperature variability of intertidal systems. Sensitivity to climate warming, which was quantified as the difference between HCT or ULT and maximum body temperature, differed greatly between snails from sunny (rocky shore; Thermal Safety Margin, TSM = −14.8 ± 3.3°C and −6.2 ± 4.4°C for HCT and ULT, respectively) and shaded (mangrove) habitats (TSM = 5.1 ± 3.6°C and 12.5 ± 3.6°C). Negative TSMs in rocky shore animals suggest that mortality is likely ameliorated during extreme climatic events by behavioral thermoregulation. Given the low variability in heat tolerance across species, habitat and geographic location account for most of the variation in TSM and may adequately predict the vulnerability to climate change. These findings caution against generalizations on the impact of global warming across ectothermic taxa and highlight how the consideration of nonmodel animals, ecological transitions, and behavioral responses may alter predictions of studies that ignore these biological details.     

Interactions with successional stage and nutrient status determines the life‐form‐specific effects of increased soil temperature on boreal forest floor vegetation

The boreal forest is one of the largest terrestrial biomes and plays a key role for the global carbon balance and climate. The forest floor vegetation has a strong influence on the carbon and nitrogen cycles of the forests and is sensitive to changes in temperature conditions and nutrient availability. Additionally, the effects of climate warming on forest floor vegetation have been suggested to be moderated by the tree layer. Data on the effects of soil warming on forest floor vegetation from the boreal forest are, however, very scarce. We studied the effects on the forest floor vegetation in a long‐term (18 years) soil warming and fertilization experiment in a Norway spruce stand in northern Sweden. During the first 9 years, warming favored early successional species such as grasses and forbs at the expense of dwarf shrubs and bryophytes in unfertilized stands, while the effects were smaller after fertilization. Hence, warming led to significant changes in species composition and an increase in species richness in the open canopy nutrient limited forest. After another 9 years of warming and increasing tree canopy closure, most of the initial effects had ceased, indicating an interaction between forest succession and warming. The only remaining effect of warming was on the abundance of bryophytes, which contrary to the initial phase was strongly favored by warming. We propose that the suggested moderating effects of the tree layer are specific to plant life‐form and conclude that the successional phase of the forest may have a considerable impact on the effects of climate change on forest floor vegetation and its feedback effects on the carbon and nitrogen cycles, and thus on the climate.     

不同温度条件下香水文心兰花香气的成分分析及感官评定

Flower aromatic components and their relative contents of Oncidium Sharry Baby ‘Sweet Fragrance ’ at full flowering stage under conditions of 10 ℃, 20 ℃ and 30 ℃ were analyzed by solid phase micro-extr...     

Estimating striae of Retzius periodicity nondestructively using partial counts of perikymata

Accurate age estimations for enamel formation and the timing of enamel hypoplasia have traditionally only been available through histological analyses of dental thin sections, which is a difficult and destructive process. However, an association between striae of Retzius periodicity, crucial for accurate aging, and the total number of striae in imbricational enamel has been reported in the literature. This means periodicity can be estimated nondestructively but is reliant on all perikymata being visible along the crown surface. Therefore, crowns with worn or damaged surfaces may not be able to be assessed, potentially limiting sample sizes. We tested this relationship in a modern New Zealand sample and investigated whether reliable associations might be identified using only partial perikymata counts from the cervical half of the crown. Using mandibular canines (n = 11), the distribution of perikymata per decile was recorded using high definition replica surfaces. Thin sections of the same crowns were used to assess periodicity histologically along with striae of Retzius distributions. A strong correlation between total striae numbers and periodicity was also identified in our sample. Furthermore, we report strong correlations that allow periodicity to be estimated from perikymata counts using only 10% of crown height when certain deciles are used. Based on these findings, we propose a simple matrix that can be developed for nondestructively estimating periodicity based on the range of perikymata counts in the sixth to ninth deciles. Am J Phys Anthropol 154:251–258, 2014. © 2014 Wiley Periodicals, Inc.     

Modulation of CD6 function through interaction with Galectin-1 and -3

CD6 is a lymphocyte glycoprotein receptor that physically associates with the antigen-specific receptor complex at the center of the immunological synapse, where it interacts with its ligand CD166/ALCAM. The present work reports the carbohydrate-dependent interaction of CD6 and CD166/ALCAM with Galectin-1 and -3, two well-known soluble mammalian lectins. Both galectins interfered with superantigen-induced T cell proliferation and cell adhesion phenomena mediated by the CD6-CD166/ALCAM pair, while CD6 expression protected cells from galectin-induced apoptosis. The results suggest that interaction of Galectin-1 and -3 with CD6 and CD166/ALCAM might modulate some relevant aspects of T cell physiology.