Steemann Nielsen and the zooplankton

E. Steemann Nielsen is remembered by most biological oceanographers and limnologists as having introduced the ¹⁴C method for measuring photosynthesis in 1952. The present paper is to recall that he was interested in the phytoplankton as part of the plankton community and was much aware of the role of grazing in affecting, if not determining, the concentrations of phytoplankton and, thus, also its rate of production. His principal statements to this effect were made with the open, oligotrophic subtropical and tropical oceans in mind where phytoplankton concentrations exhibit little seasonal change. This paper shows that Steemann Nielsen's sentiment also applies to non-static situations, especially phytoplankton blooms. Of the blooms in Cushing's North Sea Calanus patches of 1949 and 1954 and the two low-latitude, open-sea iron fertilization experiments (IronEx I, II) of the 1990s, more than half or even most of the newly formed cells were lost daily. In these examples, the same water was revisited, mixing was considered, and sinking was an unimportant loss term, so that grazing was the principal cause of mortality. Because of the grazing losses and the subsequent regeneration the CO₂ draw down in the fertilized water was much lower than the ¹⁴C uptake. Moreover the examples show that over the course of the blooms, the rate and even the sign of temporal change of phytoplankton abundance had little relation to the rate of cell division, as already postulated by Riley's 1946 model of the seasonal cycle of phytoplankton on Georges Bank. Thus, in most situations in the open sea and, presumably, large lakes, the rates of cell division (instead of photosynthesis by itself) and of mortality (most often from grazing) are needed for understanding and predicting the temporal change of phytoplankton abundance, a principal goal of biological oceanography. The mechanism maintaining the actual abundance of phytoplankton in the quasi-steady state prevailing over most of the ocean much of the time is still unclear.     

紫草的化学成分及其药理活性研究概况

本文对国内外有关药用植物紫草的化学成分、它们的提取分离及生物合成以及药理活性等方面的研究进行了综述,为研究和开发利用紫草提供依据。     

MapGene2Chrom基于Perl和SVG语言绘制基因物理图谱

遗传图谱表现形式简洁明了,为分析遗传规律、克隆基因提供了便利。Gbrowse、MapViewer等工具虽然能够协助研究人员绘制相似形式的物理图谱,但有很大的局限性:(1)数据需提前布置好;(2)输出结果无法灵活修改。鉴于此,文章基于Perl和SVG语言,开发了一款生物辅助作图软件MapGene2Chrom的本地版与网页版,该软件能够依据输入数据快速绘制相应的物理图谱。该软件输入数据格式简单,输出结果易于修改,图片格式为SVG矢量图,具有很好的移植性,以期为研究人员绘制物理图谱提供便利。     

The coincidence of rarity and richness and the potential signature of history in centres of endemism

We investigate the relative importance of stochastic and environmental/topographic effects on the occurrence of avian centres of endemism, evaluating their potential historical importance for broad‐scale patterns in species richness across Sub‐Saharan Africa. Because species‐rich areas are more likely to be centres of endemism by chance alone, we test two null models: Model 1 calculates expected patterns of endemism using a random draw from the occurrence records of the continental assemblage, whereas Model 2 additionally implements the potential role of geometric constraints. Since Model 1 yields better quantitative predictions we use it to identify centres of endemism controlled for richness. Altitudinal range and low seasonality emerge as core environmental predictors for these areas, which contain unusually high species richness compared to other parts of sub‐Saharan Africa, even when controlled for environmental differences. This result supports the idea that centres of endemism may represent areas of special evolutionary history, probably as centres of diversification.     

Relationships of hepatic and pancreatic biomarkers with the cholestatic syndrome and tumor stage in pancreatic cancer

We analyzed relationships of hepatic and pancreatic biomarkers with the cholestatic syndrome and tumor stage in exocrine pancreatic cancer (N = 183). Information on laboratory tests and on signs and symptoms was obtained from medical records and patient interviews. Bilirubin, aspartate aminotransferase (AST), γ-glutamyltransferase (GGT) and alkaline phosphatase were lower in tumor stage IV. The association was due to the relationship between cholestatic syndrome and earlier presentation of patients. There was no association between hepatic biomarkers and stage when adjusting by cholestatic syndrome. Relationships of hepatic and pancreatic biomarkers with pancreatic symptoms and tumor stage must be controlled in “-omics” and other studies using biomarkers.     

Synthetic Spider Silk Production on a Laboratory Scale

As society progresses and resources become scarcer, it is becoming increasingly important to cultivate new technologies that engineer next generation biomaterials with high performance properties. The development of these new structural materials must be rapid, cost-efficient and involve processing methodologies and products that are environmentally friendly and sustainable. Spiders spin a multitude of different fiber types with diverse mechanical properties, offering a rich source of next generation engineering materials for biomimicry that rival the best manmade and natural materials. Since the collection of large quantities of natural spider silk is impractical, synthetic silk production has the ability to provide scientists with access to an unlimited supply of threads. Therefore, if the spinning process can be streamlined and perfected, artificial spider fibers have the potential use for a broad range of applications ranging from body armor, surgical sutures, ropes and cables, tires, strings for musical instruments, and composites for aviation and aerospace technology. In order to advance the synthetic silk production process and to yield fibers that display low variance in their material properties from spin to spin, we developed a wet-spinning protocol that integrates expression of recombinant spider silk proteins in bacteria, purification and concentration of the proteins, followed by fiber extrusion and a mechanical post-spin treatment. This is the first visual representation that reveals a step-by-step process to spin and analyze artificial silk fibers on a laboratory scale. It also provides details to minimize the introduction of variability among fibers spun from the same spinning dope. Collectively, these methods will propel the process of artificial silk production, leading to higher quality fibers that surpass natural spider silks.