Microphotometric analysis of NADH-tetrazolium reductase and alpha-glycerophosphate dehydrogenase in human quadriceps muscle.

Synopsis In serial cross-sections of human skeletal muscles stained for either NADH-tetrazolium reductase (NADH-TR) or -glycerophosphate dehydrogenase (-GPD), a linear relation was found between the total content of enzyme in a cell (expressed as the thickness of the section) and the absorbance of the formazan reaction product formed. Little variation (<4.8%) was found in the concentration of formazan (absorbance per unit thickness) when the same cell was measured in serial cross-sections of various thicknesses (2–10 m) along a longitudinal distance of at least 200 m along the cell. The reduction in enzyme activity was found to be negligible after aqueous preincubation. A maximum of 10–12% of the formazan produced in the NADH-TR reaction might be the result of nothing dehydrogenase activity, whereas this unspecific reaction might account for up to 20% of the formazan deposited in the -GPD reactions after 30 min incubation. The diffusion of Nitro BT into the tissue during the incubation period was found to be unhindered. The rates of formazan production decreased with increasing incubation time, especially in the -GPD reaction in both fibre types. The ratio of the mean absorbance of the formazan in type I fibres to that in type II fibres (in the same section) was 1.41 (coefficient of variation, 2.5%) in the NADH-TR reaction and 0.68 (coefficient of variation, 3.8%) in the -GPD reaction. These values were not affected either by variations in the incubation time (5–40 min) or by the thickness of the section (2–8 m). The concentrations of NADH-TR and -GPD seem to be constant along the length of the muscle fibre. The histochemical reactions reported, together with measurements of the thickness of the sections, seem suitable for the microphotometric quantification of the two enzymes in single fibres of human skeletal muscles.     

SOMA: A Single Oligonucleotide Mutagenesis and Cloning Approach

Modern biology research requires simple techniques for efficient and restriction site-independent modification of genetic material. Classical cloning and mutagenesis strategies are limited by their dependency on restriction sites and the use of complementary primer pairs. Here, we describe the Single Oligonucleotide Mutagenesis and Cloning Approach (SOMA) that is independent of restriction sites and only requires a single mutagenic oligonucleotide to modify a plasmid. We demonstrate the broad application spectrum of SOMA with three examples. First, we present a novel plasmid that in a standardized and rapid fashion can be used as a template for SOMA to generate GFP-reporters. We successfully use such a reporter to assess the in vivo knock-down quality of morpholinos in Xenopus laevis embryos. In a second example, we show how to use a SOMA-based protocol for restriction-site independent cloning to generate chimeric proteins by domain swapping between the two human hRMD5a and hRMD5b isoforms. Last, we show that SOMA simplifies the generation of randomized single-site mutagenized gene libraries. As an example we random-mutagenize a single codon affecting the catalytic activity of the yeast Ssy5 endoprotease and identify a spectrum of tolerated and non-tolerated substitutions. Thus, SOMA represents a highly efficient alternative to classical cloning and mutagenesis strategies.     

Das Leben der V?gel

Ohne Zusammenfassung(Bruchstücke aus dem Mss. eines unter obigem Titel vorbereiteten populären Buches.)     

No support for the emergence of lichens prior to the evolution of vascular plants

The early‐successional status of lichens in modern terrestrial ecosystems, together with the role lichen‐mediated weathering plays in the carbon cycle, have contributed to the long and widely held assumption that lichens occupied early terrestrial ecosystems prior to the evolution of vascular plants and drove global change during this time. Their poor preservation potential and the classification of ambiguous fossils as lichens or other fungal–algal associations have further reinforced this view. As unambiguous fossil data are lacking to demonstrate the presence of lichens prior to vascular plants, we utilize an alternate approach to assess their historic presence in early terrestrial ecosystems. Here, we analyze new time‐calibrated phylogenies of ascomycete fungi and chlorophytan algae, that intensively sample lineages with lichen symbionts. Age estimates for several interacting clades show broad congruence and demonstrate that fungal origins of lichenization postdate the earliest tracheophytes. Coupled with the absence of unambiguous fossil data, our work finds no support for lichens having mediated global change during the Neoproterozoic‐early Paleozoic prior to vascular plants. We conclude by discussing our findings in the context of Neoproterozoic‐Paleozoic terrestrial ecosystem evolution and the paleoecological context in which vascular plants evolved.     

The role of shaded cocoa plantations in the maintenance of epiphytic orchids and their interactions with phorophytes

生境丧失和破碎化是热带森林生物多样性的主要威胁。遮荫的可可种植园(SCP)等农业生态系统为热带森林生物群提供了庇护。然而,在这些转化后的生境中是否还维持种间生态的相互作用,目前尚鲜为人知。我们评定附生兰花群落的多样性、繁殖状态和光合代谢(CAM或C₃),以及与热带雨林(TRF)相比,它们与SCP中寄主树种(附生植物)之间的相互作用。在墨西哥东南部,对TRF和SCP中各三个采样地点进行研究。每个采样地点建立了4个400平方米的样地,调查记录所有兰花及其附生植物。我们依据花/果实(或残体)是否存在来确定每个兰花个体的繁殖(成体)或非繁殖(幼体)状态,并根据文献确定每种兰花的光合作用途径。我们采用真正的分集和生态网络的方法分别分析兰花的多样性以及兰科与附生植物间的相互作用。我们一共记录了47个兰花种的607个个体。在TRF (19个有效物种)中的兰花多样性高于SCP (11个有效物种),两个生境之间仅共享7个物种。SCP (53%)中的CAM兰花物种比TRF (14%)更常见。在群落水平上,SCP维持了非生殖兰花和生殖兰花的比例以及TRF兰科附生植物网络的嵌套结构和特异化水平。然而,SCP中仅保留一部分的TRF附生兰花,突显出保护TRF的重要性。尽管存在这种差异,诸如SCP类型的遮荫农业生态系统仍然可以维持天然林的一些多样性和功能,因为SCP附生兰花群落主要由CAM物种组成,其附生植物构成了一个嵌套的相互作用网络,对干扰形成了更强的抗性。