被视为恐龙的鸟(英文)

尽管于 2 0世纪 2 0年代在亚洲地表层首次发现长有羽毛的恐龙和著名的“龙骨突位点” ,关于鸟类起源的争论仍没有休止。来自化石的证据表明 ,鸟类在进化分支上应归于兽脚类的特殊分支。本文主要阐明完好无损的化石揭示的鸟和非鸟类恐龙的亲密关系和鸟类羽毛及鸟类出现以前的羽毛的起源证据 。

晚白垩世真兽类Zalamdalestes揭示哺乳动物独特的枢椎及其复杂的进化过程

The typical mammalian neck consisting of seven cervical vertebrae(C1–C7)was established by the Late Permian in the cynodont forerunners of modern mammals.This structure is precisely adapted to facilitate movements of the head during feeding,locomotion,predator evasion,and social interactions.Eutheria,the clade including crown placentals,has a fossil record extending back more than 125 million years revealing significant morphological diversification in the Mesozoic.Yet very little is known concerning the early evolution of eutherian cervical morphology and its functional adaptations.A specimen of Zalambdalestes lechei from the Late Cretaceous of Mongolia boasts exceptional preservation of an almost complete series of cervical vertebrae(C2–C7)revealing a highly modified axis(C2).The significance of this cervical morphology is explored utilizing an integrated approach combining comparative anatomical examination across mammals,muscle reconstruction,geometric morphometrics and virtual range of motion analysis.We compared the shape of the axis in Zalambdalestes to a dataset of 88 mammalian species(monotremes,marsupials,and placentals)using three-dimensional landmark analysis.The results indicate that the unique axis morphology of Zalambdalestes has no close analog among living mammals.Virtual range of motion analysis of the neck strongly implies Zalambdalestes was capable of exerting very forceful head movements and had a high degree of ventral flexion for an animal its size.These findings reveal unexpected complexity in the early evolution of the eutherian cervical morphology and suggest a feeding behavior similar to insectivores specialized in vermivory and defensive behaviors in Zalambdalestes akin to modern spiniferous mammals.

SHP-1是IL-4诱导的IL-4R在脾脏细胞中表达所必需的

为了探索包含SH-2功能域的蛋白酪氨酸磷酸酶(SH-2-containing protein tyrosine phosphatase1,SHP-1)在IL-4诱导的IL-4受体(IL-4receptor,IL-4R)表达中的作用,用Na3VO4处理野生型(wildtype,WT)实验小鼠的脾脏细胞以及用IL-4刺激可育Motheaten小鼠(viable motheatenmice,mev/mev)的脾脏细胞,并检测IL-4RαmRNA的表达.我们发现IL-4诱导的IL-4RαmRNA表达在经Na3VO4处理后野生型小鼠的脾脏细胞以及用IL-4刺激的mev/mev小鼠的脾脏细胞中降低了.结果表明,IL-4诱导的IL-4RαmRNA表达的降低是由于IL-4R的低水平表达导致的STAT6信号转导缺陷.实验进一步证实,在mev/mev小鼠的脾脏细胞中IL-4Rα蛋白表达的降低是由于细胞组成的改变.在mev/mev小鼠脾脏组织中,表达相对高水平IL-4R的CD4+,CD8+和CD19+的细胞比例显著下降,相反表达低水平IL-4R的Mac-1+和Gr-1+细胞比例明显升高.尽管IL-4R蛋白表达是明显下降的,但在同窝对照小鼠(+/?)和mev/mev小鼠的脾脏细胞中IL-4RαmRNA的表达未发现明显的差异.在B细胞、T细胞和巨噬细胞中也没有显著差异.这提示在巨噬细胞中IL-4R表达细胞类型特异性下调是通过转录后水平的调控来实现的.研究结果提示,在脾脏细胞中SHP-1对于IL-4诱导的IL-4R表达是必需的,并且通过影响血细胞生成而间接地调控相应的功能.

SH-2-containing protein tyro-sine phosphatase 1 is required for IL-4-induced IL-4R expression in spleen cells

To investigate the role of SH-2-containing pro- tein tyrosine phosphatase 1, SHP-1, in IL-4-induced IL-4 receptor (IL-4R) expression, we examined IL-4 receptor α-chain (IL-4Rα) mRNA expression in Na3VO4-treated wild type (WT) spleen cells and measured IL-4R mRNA in IL-4-stimulated spleen cells of viable motheaten mice (mev/mev). It is found that IL-4-induced IL-4R mRNA ex- pression was impaired in Na3VO4-treated WT spleen cells and IL-4-stimulated mev/mev spleen cells. Here we show that the impaired IL-4-induced IL-4Rα mRNA expression was due to reduced expression of IL-4R that led to impaired STAT6 signaling. We further demonstrate that reduction of IL-4Rα protein expression in mev/mev spleen cells was due to alteration in cell compositions. In mev/mev spleen, the per- centages of CD4+, CD8+, and CD19+ cells expressing rela- tively high levels of IL-4R were reduced dramatically while the percentages of Mac-1+ and Gr-1+ cells with relative low levels of IL-4R increased greatly. Despite the profound effect of reduced expression of IL-4R protein, the IL-4Rα mRNA expression was comparable in spleen cells of littermate con- trol mice (+/?) and mev/mev mice and no differences were found in B cells, T cells, and macrophages, suggesting cell type-specific downregulation of IL-4R expression in macro- phages through a posttranscriptional mechanism. Our study suggests that SHP-1 is required for IL-4-meidated function and indirectly regulates IL-4-meidated function in spleen cells by affecting hematopoiesis.