Computational determination of refractive index distribution in the crystalline cones of the compound eye of Antarctic krill (Euphausia superba)

In order to understand how a compound eye channels light to the retina and forms an image, one needs to know the refractive index distribution in the crystalline cones. Direct measurements of the refractive indices require sections of fresh, unfixed tissue and the use of an interference microscope, but frequently neither is available. Using the eye of the Antarctic krill Euphausia superba (the main food of baleen whales) we developed a computational method to predict a likely refractive index distribution non-invasively from sections of fixed material without the need of an interference microscope. We used a computer model of the eye and calculated the most realistic spatial distribution of the refractive index gradient in the crystalline cone that would enable the eye to produce a sharp image on the retina. The animals are known to see well and on the basis of our computations we predict that for the eyes of the adult a maximum refractive index of 1.45-1.50 in the centre of the cone yields a better angular sensitivity and light absorption in a target receptor of the retina than if N(max) were 1.55. In juveniles with a narrower spatial separation between dioptric structures and retina, however, an N(max) of 1.50-1.55 gives a superior result. Our method to determine the most likely refractive index distribution in the cone without the need of fresh material and an interference microscope could be useful in the study of other invertebrate eyes that are known to possess good resolving power, but for a variety of reasons are not suitable for or will not permit direct refractive index measurements of their dioptric tissues to be taken.     

香港大埔滘天然次生林鸟类群落结构变化

观察了香港最大的大埔滘天然次生林内鸟类群落结构在10a间的变化。用t檢验比较了1993~1995年和2003~2005年间的10种数量最高的鸟类的密度变化。所有的泛生境留鸟种类的密度均呈显著减少。两种树林种类的密度有显著増加,其中一种是本土种,另一种是外来种。香港树林鸟类群落的变化趋势主要受到两个因素的影响,包括缺少有树林种类鸟居住的树林,和外来种的入侵。     

Changes of a forest bird community in Hong Kong of China in 10 years

The changes in the bird community structure of the largest natural secondary forest of Hong Kong over 10 years were investigated. Densities of the 10 most abundant species in 1993–1995 and 2003–2005 were compared using t-test. All resident habitat generalists showed significant decline in densities. Two forest specialists showed significant increase in densities: one is native and the other is exotic species. The trend of changes in the forest bird community of Hong Kong is mainly related to the absence of nearby forests that could act as “source” of forest dependent species to colonize the local secondary forests, and the invasion of exotic species.     

Isolation of Laribacter hongkongensis, a novel bacterium associated with gastroenteritis, from drinking water reservoirs in Hong Kong

AIMS: Freshwater fish has been found to be the reservoir of Laribacter hongkongensis, a recently discovered bacterium associated with community-acquired gastroenteritis. However, little is known about the ecology of this bacterium in the aquatic environment. We carried out a surveillance study to investigate the presence of L. hongkongensis in water and freshwater fish from 10 drinking water reservoirs in Hong Kong. METHODS AND RESULTS: Using membrane filtration, L. hongkongensis was isolated from the waters of six reservoirs, with numbers ranging from 1 to 12 CFU l(-1). Higher recovery rates were observed in summer and during days of higher water and ambient temperatures. Of 27 freshwater fish collected from the reservoirs, L. hongkongensis was recovered from the intestines of two fish, a Goldfish and a Nile tilapia. Overall, 35 different pulsed-field gel electrophoresis patterns are found among the 59 isolates recovered from water and the two isolates from freshwater fish. CONCLUSIONS: The present report represents the first to demonstrate the presence of L. hongkongensis in natural water environments. SIGNIFICANCE AND IMPACT OF THE STUDY: Although it is unlikely that treated, drinking water is an important source of L. hongkongensis-associated gastroenteritis, one should be aware of the possibility of other contaminated water as a source of human infection.     

Selection of Stable Reference Genes for Quantitative Real-Time PCR on <i>Paeonia ostii</i> T. Hong et J. X. Zhang Leaves Exposed to Different Drought Stress Conditions

The definition of relatively stable expressed internal reference genes is essential in both traditional blotting quantification and as a modern data quantitative strategy. Appropriate internal reference genes can accurately standardize the expression abundance of target genes to avoid serious experimental errors. In this study, the expression profiles of ten candidate genes, ACT1, ACT2, GAPDH, eIF1, eIF2, α-TUB, β-TUB, TBP, RNA Pol II and RP II, were calculated for a suitable reference gene selection in Paeonia ostii T. Hong et J. X. Zhang leaves under various drought stress conditions. Data were processed by the four regularly used evaluation software. A comprehensive analysis revealed that RNA Pol II was the most stable gene and eIF2 was the least stable one. In addition, the geNorm program provided the optimal choice of two reference gene combination, RNA Pol II and β-TUB, for qRT-PCR normalization in P. ostii subjected to different drought stress levels. Our research provided convenience for gene expression analysis in P. ostii under drought stress and promoted research of effective methods to alleviate P. ostii drought stress in the future.     

海洋浮游植物与生物碳汇

系统描述了浮游植物与海洋碳汇相关的几个过程:初级生产、浮游植物沉降、浮游动物粪球打包沉降、经典食物链碳汇、溶解有机碳生产和转化、透明胞外聚合颗粒物(TEP)凝聚网,和CO₂分压升高(海水酸化)影响下浮游植物功能群转变及中国海可能的生物碳汇前景展望。提出海洋初级生产过程和TEP凝聚网过程是中国海生物碳汇的关键过程,而中国海的黄海中部及长江口区域是生物碳汇研究的重点区域,建议将硅藻及其碳汇过程作为今后研究的重点。     

康惠尔水胶体透明贴对阿奇霉素引起的静脉炎的预防作用

目的:观察康惠尔水胶体透明贴对使用阿奇霉素引起的静脉炎的疗效与效果。方法:从我院2009年1月-2010年1月的呼吸内科患者中选择100例使用阿奇霉素静脉输液治疗的患者。分为观察组与对照组,每组50名使用阿奇霉素静脉输液治疗的患者。普通组使用普通透明贴,对照组患者使用康惠尔水胶体透明贴。对两组患者进行比对。结果:观察组的50名患者使用普通透明贴,16例未发生静脉炎,发生静脉炎为34例;对照组的50名患者使用康惠尔水胶体透明贴,仅有2例发生静脉炎的患者。对照组与普通组相比,对照组结果好于普通组,P<0.05差距有显著统计学意义。结论:使用康惠尔水胶体透明贴可以有效的减少呼吸内科患者使用阿奇霉素造成的静脉炎发生率。     

Scales of spatiotemporal variation in macroinvertebrate assemblage structure in monsoonal streams: the importance of season

1. We assessed the relative importance of different scales of spatial and temporal variability on benthic macroinvertebrate assemblage structure in six unpolluted streams in monsoonal Hong Kong using ordination and complementary multivariate analyses. The spatial scales were regions, sites (streams) and sections (riffles) within sites. The temporal scales were years (three, including one with unusually high rainfall), seasons (dry versus wet) and days within seasons. 2. Significant differences in assemblage structure were manifested at all temporal scales. Those at the site scale were most obvious, whereas demarcation of assemblage structure at the section (riffle) scale was smaller, and there was no significant regional differentiation in assemblage structure. Seasonal variability in assemblage structure was greater than that among years or days. 3. Inter‐year differences in assemblage structure were recorded at all sites, and were noted among all years at some sites but not at others. They were recorded more frequently during the dry season, although their occurrence (in pair‐wise comparisons between years) appeared to be related to differences in the monsoonal (wet season) rainfall. 4. Seasonal differences in assemblage structure were strongly evident at all sites. Inter‐site differences were more apparent during the dry season when local (site‐scale) influences on assemblages were stronger. By contrast, wet‐season samples were more variable because of spate‐induced disturbance, and inter‐site differentiation was less distinct. 5. Differences among days at all sites were relatively minor, but shifts attributable to repeated spate‐induced disturbance were evident at some sites during the wet season. 6. Differences at the section scale were recorded more frequently during the dry season, when the extent of within‐site variability among sections was higher, reflecting increased patchiness within sections resulting from increased substratum heterogeneity and/or greater intensity of biotic interactions. 7. Seasonal shifts in macroinvertebrate assemblage structure at a variety of scales in Hong Kong streams are likely to be attributable to monsoonal rains affecting the relative intensity of abiotic disturbance and biotic interactions in accordance with the harsh‐benign hypothesis.     

Bridging the gap between chemistry, physiology, and evolution: quantifying the functionality of sperm whale myoglobin mutants

This work merges a large set of previously reported thermochemical data for myoglobin (Mb) mutants with a physiological model of O₂-transport and -storage. The model allows a quantification of the functional proficiency of myoglobin (Mb) mutants under various physiological conditions, i.e. O₂-consumption rate resembling workload, O₂ partial pressure resembling hypoxic stress, muscle cell size, and Mb concentration, resembling different organism-specific and compensatory variables. We find that O₂-storage and -transport are distinct functions that rank mutants and wild type differently depending on O₂ partial pressure. Specifically, the wild type is near-optimal for storage at all conditions, but for transport only at severely hypoxic conditions. At normoxic conditions, low-affinity mutants are in fact better O₂-transporters because they still have empty sites for O₂, giving rise to a larger [MbO₂] gradient (more varying saturation curve). The distributions of functionality reveal that many mutants are near-neutral with respect to function, whereas only a few are strongly affected, and the variation in functionality increases dramatically at lower O₂ pressure. These results together show that conserved residues in wild type (WT) Mb were fixated under a selection pressure of low P_O2.