Evolution and function of anterior cervical vertebral fusion in tetrapods

The evolution of vertebral fusion is a poorly understood phenomenon that results in the loss of mobility between sequential vertebrae. Non‐pathological fusion of the anterior cervical vertebrae has evolved independently in numerous extant and extinct mammals and reptiles, suggesting that the formation of a ‘syncervical’ is an adaptation that arose to confer biomechanical advantage(s) in these lineages. We review syncervical anatomy and evolution in a broad phylogenetic context for the first time and provide a comprehensive summary of proposed adaptive hypotheses. The syncervical generally consists of two vertebrae (e.g. hornbills, porcupines, dolphins) but can include fusion of seven cervical vertebrae in some cetaceans. Based on the ecologies of taxa with this trait, cervical fusion most often occurs in fossorial and pelagic taxa. In fossorial taxa, the syncervical likely increases the out‐lever force during head‐lift digging. In cetaceans and ricochetal rodents, the syncervical may stabilize the head and neck during locomotion, although considerable variation exists in its composition without apparent variability in locomotion. Alternatively, the highly reduced cervical vertebral centra may require fusion to prevent mechanical failure of the vertebrae. In birds, the syncervical of hornbills may have evolved in response to their unique casque‐butting behaviour, or due to increased head mass. The general correlation between ecological traits and the presence of a syncervical in extant taxa allows more accurate interpretation of extinct animals that also exhibit this unique trait. For example, syncervicals evolved independently in several groups of marine reptiles and may have functioned to stabilize the head at the craniocervical joint during pelagic locomotion, as in cetaceans. Overall, the origin and function of fused cervical vertebrae is poorly understood, emphasizing the need for future comparative biomechanical studies interpreted in an evolutionary context.     

The relationship between the electromyogram-amplitude and isometric extension torques of neck muscles at different positions of the cervical spine

A group of 12 healthy men volunteered for the experiment. Electromyograms (EMG) were obtained from semispinalis capitis, splenius capitis, levator scapulae, and trapezius muscles. The flexion angle of the cervical spine was precisely adjusted to 0°, 10°, 20°, and 30° relative to the horizontal, with a constant angle of the atlanto-occipital joint. The subjects made eight short (about 2 s) vertical extension forces (6%, 12%,18%, 24%, 30%, 36%, 42%, and 48% of maximal voluntary peak contraction force). For each position, the centre of pressure under the head was determine as the basis for the calculation of the external lever arm. The presence of motor endplate regions was ascertained by multiple surface electrodes. The slopes of individual linear regression lines for the root mean square (rms)-values were dependent on the existence of endplates in the area of the electrodes — endplates caused smaller rms values per Newton metres of external torque. Significant intersubject differences between regression equations could not be eliminated by the normalization of EMG-parameters and/or torques. The elimination of gravity, the continuous monitoring of positions, and the consideration of localization of motor endplate regions were essential prerequisites for the acquisition of reliable relationships between EMG of different neck muscles and external torques. Two important conclusions were derived for the prediction of torques from EMG measurements: firstly, individual regression equations which take into account the position of the head and neck should be used; secondly, normalization procedures do not justify the application of average regressions to a group of subjects.     

The management of episiotomy technique and its effect on pelvic floor muscles during a malposition childbirth

Vaginal childbirth is the leading cause of pelvic floor muscles injury, which contributes to pelvic floor dysfunction, being enhanced by fetal malposition. Therefore, the aim of the present study is to verify the influence of mediolateral episiotomies in the mechanics of the pelvic floor with the fetus in occiput posterior position when compared to the occiput anterior position. Numerical simulations of vaginal deliveries, with and without episiotomy, are performed based on the Finite Element Method. The biomechanical model includes the pelvic floor muscles, a surface to delimit the anterior region of the birth canal and a fetus. Fetal malposition induces greater extension of the muscle compared to the normal position, leading to increases of stretch. The faster enlargement may be responsible for a prolonged second stage of labor. Regarding the force required to achieve delivery, the difference between the analyzed cases are 35 N, which might justify the increased need of surgical interventions. Furthermore, episiotomy is essential in reducing the damage to values near the ones obtained with normal position, making the fetal position irrelevant. These biomechanical models have become extremely useful tools to provide some understanding of pelvic floor function during delivery helping in the development of preventative strategies.     

耕作扰动对喀斯特土壤可溶性有机质及其组分迁移淋失的影响

土壤可溶性有机质(DOM)及其组分淋失特征研究对深入理解干扰作用下土壤碳氮养分损失机制具有重要意义,本研究基于翻耕模拟试验,分析喀斯特石灰土可溶性有机碳(DOC)、可溶性有机氮(DON)、及DOM官能团组分的淋失动态特征及其对不同耕作频率的响应,并探讨其影响因子。结果表明:(1)土壤DOC与DON的淋失量均随翻耕频率的增加而增加,但4个官能团特征参数对翻耕频率响应均不显著;DOC/DON淋失比随翻耕频率的增大而减少,DON占淋溶水可溶性总氮(TDN)比例随翻耕频率增加而增加。(2)DOC和DON月淋失量同时受翻耕处理与季节变化及其交互作用的影响,4个官能团特征参数仅受季节变化的影响;翻耕处理实施后,DOC月淋失量表现为初期大、后期小,各处理间差异性逐渐降低;但DON月淋失量初期小、后期大,各处理间差异性逐渐增大。(3)DOC淋失量与4个官能团特征参数呈显著负相关(P0.05),与Ca~(2+)、NH_4~+-N的淋失量呈显著正相关;DON淋失量与4个官能团参数无显著相关关系,与Mg~(2+)淋失量呈显著正相关关系。以上结果表明耕作扰动会加剧土壤DOM淋失,但淋失组分中稳定性组分没有变化,意味着耕作干扰将导致土壤有机质的持续损失,且由于其淋失组分碳氮比(DOC/DON)随扰动频率增加而降低,DON/TDN比随扰动频率增加而增加,持续的耕作干扰将大大增加水体氮素污染风险。     

葛根素对糖尿病致肺损伤的保护作用及其机制的研究

目的:探讨糖尿病对肺脏损伤及葛根素对肺组织影响的可能机制。方法:腹腔注射链脲佐菌素(STZ)建立大鼠糖尿病(DM)模型,SD大鼠随机分为对照组(C组)、糖尿病组(DM组)、糖尿病 葛根素组(DM Pur组)。检测注药前及模型成立后第20d、40d、60d的血糖及体重的改变。检测肺组织中一氧化氮(NO)和丙二醛(MDA)的含量、超氧化物歧化酶(SOD)活性。结合光镜、电镜、免疫组织化学染色方法综合评价。结果:①DM组NO、MDA高于C组(P<0.01),SOD活性低于C组(P<0.01),DM Pur组NO含量明显低于DM组(P<0.01),MDA含量40d开始显著降低(P<0.01),SOD活性高于DM组(P<0.01)。②光镜下见肺泡隔增厚,炎性细胞浸润;电镜下见Ⅱ型肺泡上皮细胞微绒毛数量明显减少,嗜锇性板层小体数量明显减少,细胞间质胶原纤维增生,葛根素可减轻肺组织上述病理性改变。③免疫组织化学染色结果:DM组细胞胞质中可见ONOO-特征性代表物硝基酪氨酸(ni-trotyrosine,NT)黄染阳性信号表达,且较对照组略为增强,DM Pur组黄染信号较DM组略为减弱。结论:①DM时可发生肺组织损伤,可能与长期高血糖诱导产生大量自由基有关。②NO/ONOO-通路是DM造成肺组织细胞损伤的机制之一。③初步证实葛根素能在一定程度上抑制高血糖诱导肺组织中自由基的过量生成,降低肺组织中的ONOO-的过度表达,这可能是其抗DM时肺组织损伤的作用机制之一。     

西瓜胚乳衰退过程中的超微结构变化及其对胚发育的作用

西瓜胚乳细胞衰退过程中 ,质膜、液泡膜突起、形成体积较大的囊泡 ,内质网断裂形成体积较小的囊泡 ;细胞质和细胞核降解形成电子致密的碎片沿细胞壁分布 ;细胞壁在衰退过程逐渐变薄 ,由于部分区域分解而使整个壁呈波浪型 ,细胞降解后的物质可直接穿越薄壁处或通过宽约 5 0 nm的胞间连丝向近胚端的胚乳细胞转移。胚乳与珠心组织分界壁 -胚囊壁上有发达的壁内突 ,有利于珠心组织内的物质向胚乳内转运 ;胚乳发育早期与胚共有的壁上内外两侧均有胼胝质沉积 ,壁上无外连丝型的胞间连丝存在 ,胚乳发育后期共有壁上的胼胝质消失 ,胚乳细胞降解物可穿越共有壁进入胚细胞内。实验结果表明西瓜胚乳在发育后期对胚的发育具有重要的作用。     

The role of erythropoietin and its receptor in growth,survival and therapeutic response of human tumor cells: From clinic to bench — a critical review

Recombinant human erythropoietin (rhEPO) has been used clinically to alleviate cancer- and chemotherapy-related anemia. However, recent clinical trials have reported that rhEPO also may adversely impact disease progression and survival. The expression of functional EPO receptors (EPOR) has been demonstrated in many human cancer cells where, at least in vitro, rhEPO can stimulate cell growth and survival and may induce resistance to selected therapies.