Relieving efforts in palm‐tree tissue sampling for population genetics analyses

1. The young leaves are the main source of nucleic acids for population genetic studies in palm‐trees; however, the access to this tissue may be limited by specific features of each species. Using root tissues as an alternative source of nucleic acids could facilitate the sampling in large populations.
2. This study tests root tissue viability as an alternative nucleic acid source (root versus. leaf) and explores different protocols (tissue storage and DNA extraction methods) to obtain high‐quality DNA samples.
3. The results showed no significant differences in DNA concentration (603.7 vs. 599.1 ng/μl) and quality ratios (A260/280:2.1 vs. 1.9, and A260/230:2.1 vs. 2.0) for the comparisons of tissue source (leaf vs. root) and DNA extraction method (manual vs. kit). For tissue storage method, DNA concentration was significantly higher for root tissues stored in 70% and 90% alcohol solutions (692.8 and 822.6 ng/μl, respectively) versus those obtained from leaf tissue (603.7 ng/μl); however, for the quality parameters, no differences were found.
4. Results showed the effective potential of using root tissue as an alternative source for nucleic acids, which could facilitate population sampling of palm‐tree species for future studies, and this methodological alternative could be applied to other plant systems with similar sampling challenges.

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Anatomical Studies of Citrus jambhiri Lush. Roots Infected by Pratylenchus coffeae

All motile stages of Pratylenchus coffeae infected mature and immature tissues of Citrus jambhiri (rough lemon) seedling tap roots. The nematodes fed primarily in the cortex and colonized in pockets or cavities. Intra- and intercellular migration within the cortex occurred in either direction from the point of entry. When P. coffeae invaded a root tip the meristem often was destroyed and lateral root initiation usually occurred near the destroyed root tip. Males were essential for reproduction and survived at least 2 1/2 months within root tissues, but with males alone used as inoculum, no cortical pockets were formed. On infected trees in the field P. coffeae were most numerous in C. jambhiri feeder roots.     

运用《生物化学》歌曲，辅助《生物化学》教学

《生物化学》以生物体为对象,研究其生命的化学本质,是生命科学领域的核心课程。长期以来,由于生物化学课程知识点多、范围广和内容抽象,在一定程度上会影响学生学习的自信心,压抑其学习过程中的兴趣,致使学习的积极性不高。最近10～20年里,国外将科学（science）、技术学（technology）、工程学（engineering）及数学（mathematics）的教育与艺术学（arts）,特别是与艺术学中的音乐结合实施教学,形成一种所谓的STEAM (STEM + Arts) 策略,对STEM教育进行辅助,取得了不错的效果。基于以上情况,结合国内生物化学教学实际,笔者尝试将生物化学歌曲应用于课堂教学过程中,辅助教学。生物化学歌曲可以将抽象难懂的生物化学知识转变成悦耳动听的歌曲,在教学过程中能激发学生的学习兴趣,活跃课堂气氛,使学生在学习过程中爱上生物化学;在生物化学歌曲的创作过程中,能促进学生的思考创新,内化重点难点,使深奥的问题形象化;在学习过程中用歌声展现生物化学的魅力,让知识成为有趣的知识,让其成为有趣的学习者。本文介绍了国内生物化学歌曲发展壮大历程,结合具体实例从利用生物化学歌曲引入教学、理解生物化学内容、密切联系生活三方面评论了生物化学歌曲在辅助生物化学教学中的应用,并从歌词的改编、旋律的选择、歌曲的传唱、教学的设计等方面需要注意的问题进行讨论。     

Isolation of Avian Trypanosomes by Selective Centrifugation and Subsequent Processing for Electron Microscopy

Paraffin sections are usually rehydrated before staining. It is possible to apply aqueous dye solutions without first removing the wax. Staining then occurs more slowly, and only if the embedding medium has not melted or become unduly soft after catting. To avoid this problem, sections are flattened on water no hotter than 45 C and dried overnight at 40 C. Minor technical modifications to the staining procedures are needed. Mercury deposits are removed by iodine, and a 3% solution of sodium thiosnlfate in 60% ethanol is used to remove the iodine from paraffin sections. At room temperature, progressive staining takes 10–20 tunes longer for sections in paraffin than for hydrated sections; at 45 C, this can be shortened to about three times the regular staining time. After staining, the slides are rinsed in water, air dried, dewaxed with xylene, and coverslipped in the usual way. Nuclear staining in the presence of wax was achieved with toluidine blue, O, alum-hematoxylin and Weigert's iron-hematoxylin. Eosin and van Gieson's picric acid-acid fuchsine were effective anionic counterstains. A one-step trichrome mixture containing 3 anionic dyes and phosphomolybdic acid was unsuitable for sections in wax because it Imparted colors that were nninformative and quite different from those obtained with hydrated sections. Advantages of staining in the presence of wax include economy of solvents, reduced risk of overstaining and strong adhesion of sections to slides.     

Adaptive morphological shifts to novel habitats in marine sculpin fishes

Sculpin fishes of the North American Pacific Coast provide an ideal opportunity to examine whether adaptive morphological character shifts have facilitated occupation of novel habitat types because of their well‐described phylogeny and ecology. In this group, the basal‐rooted species primarily occupy the subtidal habitat, whereas the species in the most distal clades are found in the intertidal. We tested multiple evolutionary models to determine whether changes in body size and changes in number of scales are adaptive for habitat use in sculpins. Based on a statistically robust, highly resolved molecular phylogeny of 26 species of sculpins, in combination with morphometric and habitat affinity data, our analyses show that an adaptive model based on habitat use best explains changes in body size and number of scales. The habitat model was statistically supported over models of neutral evolution, stabilizing selection across all habitats, and three clade‐based models. We suggest that loss of scales and reduction of body size in the intertidal may facilitate cutaneous breathing in air when tidepools become hypoxic during low tides. This study demonstrates how the combined use of phylogenetic, ecological and statistical approaches helps to identify traits that are likely adaptive to novel habitats.     

Adaptive Finite Element Analysis of the Anisotropic Biphasic Theory of Tissue-Equivalent Mechanics

Abstract

The nonlinear partial differential equations of the anisotropic biphasic theory of tissue-equivalent mechanics are solved with axial symmetry by an adaptive finite element system. The adaptive procedure operates within a method-of-lines framework using finite elements in space and backward difference software in time. Spatial meshes are automatically refined, coarsened, and relocated in response to error indications and material deformation. Problems with arbitrarily complex two-dimensional regions may be addressed. With meshes graded in high-error regions, the adaptive solutions have fewer degrees of freedom than solutions with comparable accuracy obtained on fixed quasi-uniform meshes. The adaptive software is used to address problems involving an isometric cell traction assay, where a cylindrical tissue equivalent is adhered at its end to fixed circular platens; a prototypical bioartificial artery; and a novel configuration that is intended as an initial step in a study to determine bioartificial arteries having optimal collagen and cell concentrations.