Unique method of tooth replacement in durophagous placodont marine reptiles,with new data on the dentition of Chinese taxa

The placodonts of the Triassic period (~252–201 mya) represent one of the earliest and most extreme specialisations to a durophagous diet of any known reptile group. Exceptionally enlarged crushing tooth plates on the maxilla, dentary and palatine cooperated to form functional crushing areas in the buccal cavity. However, the extreme size of these teeth, combined with the unusual way they occluded, constrained how replacement occurred. Using an extensive micro‐computed tomographic dataset of 11 specimens that span all geographic regions and placodont morphotypes, tooth replacement patterns were investigated. In addition, the previously undescribed dental morphologies and formulae of Chinese taxa are described for the first time and incorporated into the analysis. Placodonts have a unique tooth replacement pattern and results follow a phylogenetic trend. The plesiomorphic Placodus species show many replacement teeth at various stages of growth, with little or no discernible pattern. On the other hand, the more derived cyamodontoids tend to have fewer replacement teeth growing at any one time, replacing teeth unilaterally and/or in functional units, thus maintaining at least one functional crushing area at all times. The highly derived placochelyids have fewer teeth and, as a result, only have one or two replacement teeth in the upper jaw. This supports previous suggestions that these taxa had an alternative diet to other placodonts. Importantly, all specimens show at least one replacement tooth growing at the most posterior palatine tooth plates, indicating increased wear at this point and thus the most efficient functional crushing area.     

荧光染色技术在艾滋病患者活检标本病原学诊断中的应用

目的探讨快速真菌与抗酸分枝杆菌荧光技术在艾滋病患者活检标本病原体诊断中的应用价值及意义。方法选取艾滋病患者500例活检标本,采用快速真菌荧光染色及六胺银、PAS染色对300例可疑真菌感染的活检标本进行检测,采用抗酸分枝杆菌荧光染色及萋尼抗酸染色对200例可疑结核的活检标本进行检测,并对检测结果进行对比。结果（1）快速真菌荧光镜检法检出阳性205例（阳性率68.3%）,六胺银染色法检出阳性209例（阳性率69.7%）,PAS染色法检出阳性97例（阳性率39.5%）,快速真菌荧光染色与六胺银染色检出阳性率差异无统计学意义（P>0.05),但高于PAS染色法;（2）抗酸分枝杆菌荧光染色检出阳性179例（阳性率89.5%）,萋尼抗酸染色法检出阳性117例（阳性率58.5%）,抗酸分枝杆菌荧光染色阳性率高于萋尼抗酸染色法,两者差异有统计学意义（P<0.01）;（3）荧光染色比常规特殊染色操作更快速、简便、显示更清晰。结论艾滋病患者并发机会性感染病原体种类多样,普通的特殊染色阳性率不高并且费时费力,而快速真菌及抗酸荧光染色特别是抗酸荧光染色的阳性率明显增高,为活检组织诊断真菌及结核分枝杆菌感染提供一种快速、准确、经济、对比更清晰的染色方法,能够为真菌感染及结核病患者诊断提供可靠的指导依据,值得在病原体诊断工作中广泛使用。     

From the Cover: Accumulation and enhanced cycling of polyphosphate by Sargasso Sea plankton in response to low phosphorus

Phytoplankton alter their biochemical composition according to nutrient availability, such that their bulk elemental composition varies across oceanic provinces. However, the links between plankton biochemical composition and variation in biogeochemical cycling of nutrients remain largely unknown. In a survey of phytoplankton phosphorus stress in the western North Atlantic, we found that phytoplankton in the phosphorus-depleted subtropical Sargasso Sea were enriched in the biochemical polyphosphate (polyP) compared with nutrient-rich temperate waters, contradicting the canonical oceanographic view of polyP as a luxury phosphorus storage molecule. The enrichment in polyP coincided with enhanced alkaline phosphatase activity and substitution of sulfolipids for phospholipids, which are both indicators of phosphorus stress. Further, polyP appeared to be liberated preferentially over bulk phosphorus from sinking particles in the Sargasso Sea, thereby retaining phosphorus in shallow waters. Thus, polyP cycling may form a feedback loop that attenuates the export of phosphorus when it becomes scarce, contributes bioavailable P for primary production, and supports the export of carbon and nitrogen via sinking particles.Phosphorus (P) is an essential element for all living organisms. However, P can be extremely scarce in open-ocean surface waters such as in the subtropical western North Atlantic (the Sargasso Sea), where soluble reactive P (SRP) concentrations are routinely <10 nmol⋅L⁻¹ and turnover rates are on the order of hours (1). Despite this scarcity, primary production by phytoplankton in the Sargasso Sea does not appear to be limited primarily by P (2, 3), reflecting the intensity of P recycling by the microbial community (4, 5) and the exquisite adaptations of marine phytoplankton to low P conditions, which remain to be fully characterized.Phytoplankton respond to low P by producing enzymes such as alkaline phosphatase to hydrolyze extracellular dissolved organic P molecules (4, 6, 7), increasing the affinity and rate of P uptake (8, 9) and reducing their inventory of P-containing biochemicals (1, 10). In contrast, when P is abundant, phytoplankton take up excess P and store it as a luxury reserve that is generally thought to be composed of polyphosphate (polyP) (10–12). This modulation of P-containing biochemicals results in basin-scale relationships between P availability and biomass carbon-to-phosphorus (C:P) ratios (13). Presently, the only class of molecules known to consistently contribute to these gradients in cellular P are lipids because P stress in phytoplankton triggers substitution of non–P-membrane lipids for phospholipids, such as the sulfolipid sulfoquinovosyldiacylglycerol (SQDG) for the phospholipid phosphatidylglycerol (PG) (1, 14). However, lipid substitution alone probably cannot account for the full range of C:P observed in the ocean, and yet an understanding of other biochemical drivers of the C:P gradient remains elusive. Further, it is unknown how changes in plankton biochemical composition influence the recycling of nutrients.Polyphosphate (polyP), a ubiquitous inorganic P polymer of three to hundreds of residues, has diverse physiological roles and complex dynamics in microbes. It is critical for surviving nutritional stress and stationary phase (15–17) but is also important for P homeostasis: microbes produce polyP when P is more abundant than required for growth, so-called luxury uptake, and break down this polyP store upon P stress (18). Moreover, if P-stressed cells experience a spike in P availability, they overproduce polyP in excess of luxury uptake levels, the so-called “overplus” response (19). Given these complex dynamics, it has been hypothesized that polyP might be either virtually absent, or particularly abundant, in oligotrophic marine systems (20).     

深海真菌Phomopsis tersa的次级代谢产物及其细胞毒活性研究

目的 研究深海真菌Phomopsis tersa FS441的次级代谢产物及其细胞毒活性。方法 采用正、反相硅胶柱、凝胶柱和高效液相等多种色谱技术对菌株FS441的固体发酵产物进行分离纯化,并通过NMR、MS等波谱方法鉴定化合物结构,采用SRB法对得到的单体化合物进行细胞毒活性测试。结果 从发酵物中分离纯化得到11个化合物,分别鉴定为：5α, 8α-表二氧麦角甾-6,22-二烯-3β-醇（1）、麦角甾醇（2）、12-hydroxydehydrobotrydienol（3）、5,6-二羟基-2,3,6-三甲基环己-2-烯酮（4）、1,2-二羟基-3,4-脱氢蒽酮（5）、（1S,2S,3S,4R） -3-氯-4-（2-羟基丙吡啶-2-基）-1-甲基环己烷-1,2-二醇（6）、（-）-5-methylmellein（7）、酪醇（8）、胸腺嘧啶核苷（9）、（R）-（+）-甘油1-9 （Z）,12 （Z）-十八碳二烯酸酯（10）、亚油酸（11）。结论 化合物3～6为首次从Phomopsis属分离得到,化合物1和2对SF-268、MCF-7、HepG-2和A549 4种肿瘤细胞株具有弱的细胞毒活性。     

南海深海沉积环境来源真菌Aspergillus flavus SCSIO F025的次生代谢产物及活性研究

目的 对采集自南海中部1781 m沉积环境的1株曲霉属真菌Aspergillus flavus SCSIO F025进行次生代谢产物及活性研究。方法 通过优化培养条件对菌株进行规模发酵,发酵产物采用硅胶柱层析、Sephadex LH-20、HPLC等色谱学方法进行化学分离,利用NMR、MS等波谱学技术并结合文献进行化合物的结构鉴定,应用纸片扩散法及DPPH自由基清除法对化合物进行初步抗氧化和抗菌活性测试。结果 从菌株SCSIO F025中分离鉴定5个单体化合物：penicillivinacine(1),arthrographol(2),dehydroxypaxilline(3),ditryptophenaline(4),kojic acid(5)。其中化合物1和2为首次从黄曲霉中分离得到。化合物1对溶藻弧菌和藤黄微球菌有弱的抑制活性,化合物2表现出显著抗氧化及溶藻弧菌和藤黄微球菌抑制活性,化合物3对溶藻弧菌和肺炎克雷伯杆菌有抑制活性。     

Climate change and the selective signature of the Late Ordovician mass extinction

Selectivity patterns provide insights into the causes of ancient extinction events. The Late Ordovician mass extinction was related to Gondwanan glaciation; however, it is still unclear whether elevated extinction rates were attributable to record failure, habitat loss, or climatic cooling. We examined Middle Ordovician-Early Silurian North American fossil occurrences within a spatiotemporally explicit stratigraphic framework that allowed us to quantify rock record effects on a per-taxon basis and assay the interplay of macrostratigraphic and macroecological variables in determining extinction risk. Genera that had large proportions of their observed geographic ranges affected by stratigraphic truncation or environmental shifts at the end of the Katian stage were particularly hard hit. The duration of the subsequent sampling gaps had little effect on extinction risk, suggesting that this extinction pulse cannot be entirely attributed to rock record failure; rather, it was caused, in part, by habitat loss. Extinction risk at this time was also strongly influenced by the maximum paleolatitude at which a genus had previously been sampled, a macroecological trait linked to thermal tolerance. A model trained on the relationship between 16 explanatory variables and extinction patterns during the early Katian interval substantially underestimates the extinction of exclusively tropical taxa during the late Katian interval. These results indicate that glacioeustatic sea-level fall and tropical ocean cooling played important roles in the first pulse of the Late Ordovician mass extinction in Laurentia.     

Cultural adaptation, compounding vulnerabilities and conjunctures in Norse Greenland

Norse Greenland has been seen as a classic case of maladaptation by an inflexible temperate zone society extending into the arctic and collapse driven by climate change. This paper, however, recognizes the successful arctic adaptation achieved in Norse Greenland and argues that, although climate change had impacts, the end of Norse settlement can only be truly understood as a complex socioenvironmental system that includes local and interregional interactions operating at different geographic and temporal scales and recognizes the cultural limits to adaptation of traditional ecological knowledge. This paper is not focused on a single discovery and its implications, an approach that can encourage monocausal and environmentally deterministic emphasis to explanation, but it is the product of sustained international interdisciplinary investigations in Greenland and the rest of the North Atlantic. It is based on data acquisitions, reinterpretation of established knowledge, and a somewhat different philosophical approach to the question of collapse. We argue that the Norse Greenlanders created a flexible and successful subsistence system that responded effectively to major environmental challenges but probably fell victim to a combination of conjunctures of large-scale historic processes and vulnerabilities created by their successful prior response to climate change. Their failure was an inability to anticipate an unknowable future, an inability to broaden their traditional ecological knowledge base, and a case of being too specialized, too small, and too isolated to be able to capitalize on and compete in the new protoworld system extending into the North Atlantic in the early 15th century.     

苦参素治疗低病毒载量慢性乙型肝炎患者的疗效观察

目的 观察序贯应用苦参素胶囊和苦参素注射液治疗低病毒载量慢性乙型肝炎的疗效.方法 选择60例低病毒载量慢性乙型肝炎患者,随机分为对照组和治疗组各30例,对照组给予常规保肝治疗,治疗组同时序贯应用苦参素胶囊和苦参素注射液治疗,总疗程24周,观察两组治疗4、12、24周时的ALT、HBV DNA转阴率及HBeAg/抗-HBe血清转换率.结果 治疗组在改善肝功能、HBV DNA转阴率及HBeAg/抗-HBe血清转换率方面优于对照组.结论 序贯应用苦参素胶囊和苦参素注射液治疗低病毒载量慢性乙型肝炎患者可以获得较高的应答率.