Tetrapod-like middle ear architecture in a Devonian fish

Few fossils show the incipient stages of complex morphological transformations. For example, the earliest stages in the remodelling of the spiracular tract and suspensorium (jaw suspension) of osteolepiform fishes into the middle ear of tetrapods have remained elusive. The most primitive known tetrapods show a middle ear architecture that is very different from osteolepiforms such as Eusthenopteron, with little indication of how this transformation took place. Here we present an analysis of tetrapod middle ear origins that is based on a detailed study of Panderichthys, the immediate sister taxon of tetrapods. We show that the spiracular region is radically transformed from osteolepiforms and represents the earliest stages in the origin of the tetrapod middle ear architecture. The posterior palatoquadrate of Panderichthys is completely tetrapod-like and defines a similarly tetrapod-like spiracular tract. The hyomandibula has lost its distal portion, representing a previously unrecognized advance towards a stapes-like morphology. This spiracular specialization suggests that the middle ear of early tetrapods evolved initially as part of a spiracular breathing apparatus.     

水通道蛋白1,4,5型在中耳腔液体平衡中作用机制的实验观察

观察水通道蛋白1、4、5（AQP-1,4,5）在正常豚鼠中耳腔粘膜的表达和分布情况,探讨AQP-1,4,5在豚鼠中耳液体转运和水平衡中的作用机制.用逆转录聚合酶链反应（RT-PCR）,免疫印迹（Western-blotting）和免疫组织化学的方法观察正常豚鼠中耳腔粘膜AQP1、4、5的表达和分布情况.AQP-1,4,5的mRNA在正常豚鼠中耳腔粘膜内有确定表达,AQP-1,4的蛋白质在正常豚鼠中耳粘膜内有确定表达,AQP-1的细胞定位发现：AQP-1在所有的中耳腔内被覆的扁平上皮,立方上皮,粘膜下层的毛细血管内皮和此层的纤维母细胞的胞浆中均有分布.AQP-1可能通过上述分布,在调节纤周粘液系统的厚度、粘膜下毛细血管与周围组织的水分交换、纤维母细胞层保持渗透压差的活动过程中与离子通道介导的离子流运动一起来积极参与中耳腔的水转运.由于相关基因和蛋白表达的存在,也初步揭示了AQP-4和AQP-5在中耳腔粘膜组织中可能存在.AQP-1,4,5共同参与了中耳腔的液体平衡过程,参与了保持中耳腔正常情况下的无液体积聚状态.     

中耳正向与逆向压力增益模拟

为分析中耳的声传递特性,采用声场与结构耦合的人耳有限元模型模拟声音在中耳中正向和逆向传递过程,分别获得外耳道声音激励经听骨链传递到耳蜗的中耳正向压力增益,以及耳蜗声音激励经中耳传递到外耳道的逆向压力增益．通过中耳正、逆向压力增益的乘积来分析声音在中耳往返传递的压力增益,评价中耳对耳声发射传递的影响．在1-3kHz范围内,计算结果显示中耳往返压力增益平均值为-18dB．     

人中耳听骨链置换数值模型

在人耳三维有限元模型的基础上,建立了听骨链置换三维有限元模型.模型中置换物将替代听骨链,将声音从鼓膜传递至镫骨底板.利用此数值模型研究了完全听骨链置换、锤骨保留与否及鼓膜重建对镫骨底板振动的影响.用数值方法解释了听骨链置换对传声的影响,以期为中耳疾病治疗及置换物设计提供力学参考.     

Transitional mammalian middle ear from a new Cretaceous Jehol eutriconodont

The transference of post-dentary jaw elements to the cranium of mammals as auditory ossicles is one of the central topics in evolutionary biology of vertebrates. Homologies of these bones among jawed vertebrates have long been demonstrated by developmental studies; but fossils illuminating this critical transference are sparse and often ambiguous. Here we report the first unambiguous ectotympanic (angular), malleus (articular and prearticular) and incus (quadrate) of an Early Cretaceous eutriconodont mammal from the Jehol Biota, Liaoning, China. The ectotympanic and malleus have lost their direct contact with the dentary bone but still connect the ossified Meckel's cartilage (OMC); we hypothesize that the OMC serves as a stabilizing mechanism bridging the dentary and the detached ossicles during mammalian evolution. This transitional mammalian middle ear narrows the morphological gap between the mandibular middle ear in basal mammaliaforms and the definitive mammalian middle ear (DMME) of extant mammals; it reveals complex changes contributing to the detachment of ear ossicles during mammalian evolution.     

基于CT图像构建听骨链三维有限元模型

目的:初步探讨中耳听骨链传声机制的力学特点。方法:采用1例听力正常者CT图像,建立中耳的三维有限元模型,进行中耳力学分析,观察不同频率下中耳主应变、主应力和位移的变化。结果:低频和中频中耳主应变、主应力变化较大,而在高频阶段变化并不明显,其中200 Hz和在1 000~2 000 Hz阶段变化最为明显,中耳主应力与主应变变化趋势相一致。当刺激音高于2 000 Hz时,中耳听骨链没有位移产生。结论:通过中耳有限元模型可以无创性地研究听骨链传声机制,有利于术前及术后对听骨链进行临床评估。     

Ecology. Global amphibian population declines

The decline and disappearance of relatively undisturbed populations of amphibians in several high-altitude regions since the 1970s suggests that they may have suffered a global decline, perhaps with a common cause or causes. Houlahan et al. examined means of trends for 936 amphibian populations and concluded that global declines began in the late 1950s, peaked in the 1960s, and have continued at a reduced rate since. Here we re-analyse their data using a method that accounts for the sampling of different populations over different time periods, and find evidence of a mean global decline in monitored populations only in the 1990s. However it is calculated, the global mean not only masks substantial spatial and temporal variation in population trends and sampling effort, but also fails to distinguish between a global decline with global causes and the cumulative effects of local declines with local causes.     

快速气压变化及呼吸纯氧对耳气压功能和听力的影响

观察了经快速气压变化、呼吸纯氧后耳气压功能和听力随时间变化的情况。被试者提前舱内吸氧并利用低压舱营造快速气压变化环境,对其进行低压舱耳气压功能检查试验,试验前后行主观感觉记录、耳镜检查、声抗导检查(包括鼓室导抗图、声反射阈及咽鼓管功能)和纯音测听。对不同试验时间点的声导抗指标和纯音听阈情况进行统计学分析。综合各项检测指标分析各时间点耳气压功能和听阈变化情况,总体看来出舱和出舱3 h各项指标偏离基础值但无显著差异,至出舱24 h基本恢复正常。试验中被试呼吸纯氧后经历快速气压变化对耳气压功能和听力的影响在24 h后基本回复。     

Polarity of structure and of ordered nerve connections in the developing amphibian brain.

Tectal polarity for retinal connections remains reversible long after the anatomical pattern of neural structures has been determined. Cells in the diencephalon seem to control this polarity. Following certain embryonic operations, the diencephalon developed behind the tectum. In such cases, the polarity of the retino-tectal projection was reversed.     

Dynamics of folded proteins.

The dynamics of a folded globular protein (bovine pancreatic trypsin inhibitor) have been studied by solving the equations of motion for the atoms with an empirical potential energy function. The results provide the magnitude, correlations and decay of fluctuations about the average structure. These suggest that the protein interior is fluid-like in that the local atom motions have a diffusional character.