Nitrogen-Cycling Genes in Epilithic Biofilms of Oligotrophic High-Altitude Lakes (Central Pyrenees,Spain)

Microbial biofilms in oligotrophic environments are the most reactive component of the ecosystem. In high-altitude lakes, exposed bedrock, boulders, gravel, and sand in contact with highly oxygenated water and where a very thin epilithic biofilm develops usually dominate the littoral zone. Traditionally, these surfaces have been considered unsuitable for denitrification, but recent investigations have shown higher biological diversity than expected, including diverse anaerobic microorganisms. In this study, we explored the presence of microbial N-cycling nirS and nirK (denitrification through the conversion of NO₂ ^? to NO), nifH (N₂ fixation), anammox (anaerobic ammonium oxidation), and amoA (aerobic ammonia oxidation, both bacterial and archaeal) genes in epilithic biofilms of a set of high-altitude oligotrophic lakes in the Pyrenees. The concentrations of denitrifying genes determined by quantitative PCR were two orders of magnitude higher than those of ammonia-oxidizing genes. Both types of genes were significantly correlated, suggesting a potential tight coupling nitrification-denitrification in these biofilms that deserves further confirmation. The nifH gene was detected after nested PCR, and no signal was detected for the anammox-specific genes used. The taxonomic composition of denitrifying and nitrogen-fixing genes was further explored by cloning and sequencing. Interestingly, both microbial functional groups were richer and more genetically diverse than expected. The nirK gene, mostly related to Alphaproteobacteria (Bradyrhizobiaceae), dominated the denitrifying gene pool as expected for oxygen-exposed habitats, whereas Deltaproteobacteria (Geobacter like) and Cyanobacteria were the most abundant among nitrogen fixers. Overall, these results suggest an epilithic community more metabolically diverse than previously thought and with the potential to carry out an active role in the biogeochemical nitrogen cycling of high-altitude ecosystems. Measurements of activity rates should be however carried out to substantiate and further explore these findings.     

Leaf traits from stomata to morphology are associated with climatic and edaphic variables for dominant tropical forest evergreen oaks

热带森林优势种青冈叶片气孔、解剖和形态性状与气候、土壤因子的关联 了解优势树种叶片多水平的功能性状沿海拔梯度的变化及其内在关联,有助于预测优势种应对气候变化的响应与适应。本文研究了青冈属树种叶片气孔、解剖和形态性状沿海拔梯度的变化及其与环境调控因子的关联,探究了其生态策略是否随海拔发生改变。在海南尖峰岭热带森林,沿海拔梯度(400–1400 m)采集了6种常绿青冈：竹叶青冈(Cyclobalanopsis bambusaefolia)、雷公青冈(C. hui)、托盘青冈 (C. patelliformis)、饭甄青冈(C. fleuryi)、吊罗山青冈(C. tiaoloshanica)和亮叶青冈(C. phanera)叶片,用于气孔、解剖和形态性状的测定。研究结果表明,随海拔升高,青冈树种叶片气孔密度、气孔孔隙度指数和叶面积显著增加,但海绵组织厚度比和干物质含量则显着降低。叶片气孔、解剖和形态性状沿海拔梯 度的变化主要受年均温、年降水量和土壤pH 值调控。在低海拔和高海拔处,青冈属采取“耐受”和“竞 争”策略,而在中海拔处,则是“竞争”策略。土壤磷含量和土壤pH 值随海拔的变化可能是驱动其生态 策略转变的主要原因。该结果揭示,热带森林优势树种青冈可通过从气孔细胞-组织解剖结构-叶片水平功能性状的改变来响应环境变化。     

Predicting walnut (Juglans spp.) crop yield using meteorological and airborne pollen data

Crop yield determines economy by influencing prices on the trade market, and so accurate forecasts of the yield are important for planning various aspects of agricultural production. The main aim of this study is to construct a model for predicting walnut yield in an important walnut production area (the region of Novi Sad in Northern Serbia). Relationships between the amount of walnuts produced annually (2000–2011) and abiotic (e.g. meteorological) and biotic (e.g. airborne pollen data) factors were examined using Pearson correlation analysis. Walnut yield data were then entered into linear regression models with variables that had the highest correlations. The models were constructed using 10 years of data, and tested using 2 years of data not included in constructing the model. This paper has shown that walnut yield is greatly dependent on weather conditions, particularly during fertilisation and seed growth, but the amount of available airborne pollen also plays an important role. The introduction of the seasonal pollen index, as a proxy for the amount of pollen available for fertilisation, improved the performance of models predicting walnut yield.     

High-Melting Lipid Mixtures and the Origin of Detergent-Resistant Membranes Studied with Temperature-Solubilization Diagrams

The origin of resistance to detergent solubilization in certain membranes, or membrane components, is not clearly understood. We have studied the solubilization by Triton X-100 of binary mixtures composed of egg sphingomyelin (SM) and either ceramide, diacylglycerol, or cholesterol. Solubilization has been assayed in the 4–50°C range, and the results are summarized in a novel, to our knowledge, form of plots, that we have called temperature-solubilization diagrams. Despite using a large detergent excess (lipid/detergent 1:20 mol ratio) and extended solubilization times (24–48 h) certain mixtures were not amenable to Triton X-100 solubilization at one or more temperatures. DSC of all the lipid mixtures, and of all the lipid + detergent mixtures revealed that detergent resistance was associated with the presence of gel domains at the assay temperature. Once the system melted down, solubilization could occur. In general adding high-melting lipids limited the solubilization, whereas the addition of low-melting lipids promoted it. Lipidomic analysis of Madin-Darby canine kidney cell membranes and of the corresponding detergent-resistant fraction indicated a large enrichment of the nonsolubilized components in saturated diacylglycerol and ceramide. SM-cholesterol mixtures were special in that detergent solubilization was accompanied, for certain temperatures and compositions, by an independent phenomenon of reassembly of the partially solubilized lipid bilayers. The temperature at which lysis and reassembly prevailed was ∼25°C, thus for some SM-cholesterol mixtures solubilization occurred both above and below 25°C, but not at that temperature. These observations can be at the origin of the detergent resistance effects observed with cell membranes, and they also mean that cholesterol-containing detergent-resistant membrane remnants cannot correspond to structures existing in the native membrane before detergent addition.     

Effects of shock waves on oxidative stress and some trace element levels of rat liver and diaphragm muscles

This study was designed to investigate whether the short-term extracorporeal shockwave lithotripsy (ESWL) exposure to kidney produces an oxidative stress and a change in some trace element levels in liver and diaphragm muscles of rats. Twelve male Wistar albino rats were divided randomly into two groups, each consisting of six rats. The animals in the first group did not receive any treatment and served as control group. The right-side kidneys of animals in group 2 were treated with two-thousand 18 kV shock waves while anesthetized with 50 mg kg(-1) ketamine. The localization of the right kidney was achieved after contrast medium injection through a tail vein under fluoroscopy control. The animals were killed 72 h after the ESWL treatment, and liver and diaphragm muscles were harvested for the determination of tissue oxidative stress and trace element levels. Although the malondialdehyde level increased, superoxide dismutase and glutathione peroxidase enzyme activities decreased in the livers and diaphragm muscles of ESWL-treated rats. Although glutathione level increased in liver, it decreased in diaphragm muscles of ESWL-treated animals. Fe, Mg and Mn levels decreased, and Cu and Pb levels increased in the livers of ESWL-treated animals. Fe and Cu levels increased, and Mg, Pb, Mn and Zn levels decreased in the diaphragm muscles of ESWL-treated animals. It also causes a decrease or increase in many mineral levels in liver and diaphragm muscles, which is an undesirable condition for the normal physiological function of tissues.     

Length of human constitutive heterochromatin in relation to chromosomal contraction

Summary Linear measurement of blocks of constitutive heterochromatin and the euchromatin portion 1q-h in three members of a family was used to study the dependence of the size of C blocks on the degree of chromosomal contraction. The results demonstrate that the size of heterochromatin portions decrease regularly with an increases of the degree of euchromatin contraction. The dependence was found to be linear, except for mitoses with an extremely high or low degree of contraction. The finding was used for the development of a new method of evaluation of constitutive heterochromatin.     

Conformation and structure of 2-amino-8-(β-d-ribofuranosyl)imidazo [1,2-a]-s-triazin-4-one (5-aza-7-deaza guanosine), a potent antiviral nucleoside

The crystal and molecular structure of one imidazo[1,2-a]-s-triazine nucleoside and its antiviral activity are described. The crystal structure of 2-amino-8-(β-d-ribofuranosyl)imidazo-[1,2-a]-s-triazin-4-one monohydrate (C₁₀H₁₃N₅O₅·H₂O) was solved by X-ray counter data. The compound crystallizes in the monoclinic space group P2₁ with cell dimensions a = 7.353 (1), b = 6.465 (1), c = 13.701 (1) Å, β = 104.64 (1)°. The structure was solved by direct methods and refined by full matrix least-squares technique to a final value of the conventional R-factor of 0.049 using 1998 observed intensities. The orientation of the base relative to the sugar ring defined in terms of rotation about the C(1′)-N(8) glycosyl bond is anti (47.8°). The ribose moiety exhibits C(2′)-endo, ²E conformation. The conformation around C(4′)-C(5′) is gauche^?. Molecular packing is dominated by hydrogen bonds. Base stacking occurs long the b axis. 5-Aza-7-deazaguanosine has shown a marked antiviral activity in vitro against herpes simplex virus despite the fact that N(3) is effective as the hydrogen acceptor only.     

草鱼人工繁殖中一年多次产卵的生物学基础

草鱼在人工培育条件下,一年可以进行多次催情产卵。草鱼一年多次产卵的生物学基础主要是: (1)成熟草鱼卵母细胞发育的不完全同步性。由于卵母细胞由第Ⅲ时相过渡到第Ⅳ时相不是完全同步,所以,在第一次催产产空后的卵巢中保留有相当数量第Ⅲ时相卵母细胞,它们经过人工培育一段时间后,能够发育成熟而在第二次催产时产出。(2)第一次催产后保留在卵巢中的第Ⅲ时相卵母细胞向第Ⅳ时相发育的过程中,呈现明显的AKP酶活性反应而没有ACP酶活性反应,表明这些卵母细胞正在进行着旺盛的物质代谢活动,生长发育正常。(3)第一次催产后垂体间叶嗜硷性细胞还有一部份保留着分泌颗粒,表明促性腺激素的分泌活动尚在持续进行,这是第Ⅲ时相卵母细胞能够发育成熟的重要生理因素。       

Phospholipase Dδ assists to cortical microtubule recovery after salt stress

The dynamic microtubule cytoskeleton plays fundamental roles in the growth and development of plants including regulation of their responses to environmental stress. Plants exposed to hyper-osmotic stress commonly acclimate, acquiring tolerance to variable stress levels. The underlying cellular mechanisms are largely unknown. Here, we show, for the first time, by in vivo imaging approach that linear patterns of phospholipase Dδ match the localization of microtubules in various biological systems, validating previously predicted connection between phospholipase Dδ and microtubules. Both the microtubule and linear phospholipase Dδ structures were disintegrated in a few minutes after treatment with oryzalin or salt. Moreover, by using immunofluorescence confocal microscopy of the cells in the root elongation zone of Arabidopsis, we have shown that the cortical microtubules rapidly depolymerized within 30 min of treatment with 150 or 200 mM NaCl. Within 5 h of treatment, the density of microtubule arrays was partially restored. A T-DNA insertional mutant lacking phospholipase Dδ showed poor recovery of microtubule arrays following salt exposition. The restoration of microtubules was significantly retarded as well as the rate of root growth, but roots of overexpressor GFP-PLDδ prepared in our lab, have grown slightly better compared to wild-type plants. Our results indicate that phospholipase Dδ is involved in salt stress tolerance, possibly by direct anchoring and stabilization of de novo emerging microtubules to the plasma membrane, providing novel insight into common molecular mechanism during various stress events.     

Mesoscopic Segregation of Excitation and Inhibition in a Brain Network Model

Neurons in the brain are known to operate under a careful balance of excitation and inhibition, which maintains neural microcircuits within the proper operational range. How this balance is played out at the mesoscopic level of neuronal populations is, however, less clear. In order to address this issue, here we use a coupled neural mass model to study computationally the dynamics of a network of cortical macrocolumns operating in a partially synchronized, irregular regime. The topology of the network is heterogeneous, with a few of the nodes acting as connector hubs while the rest are relatively poorly connected. Our results show that in this type of mesoscopic network excitation and inhibition spontaneously segregate, with some columns acting mainly in an excitatory manner while some others have predominantly an inhibitory effect on their neighbors. We characterize the conditions under which this segregation arises, and relate the character of the different columns with their topological role within the network. In particular, we show that the connector hubs are preferentially inhibitory, the more so the larger the node''s connectivity. These results suggest a potential mesoscale organization of the excitation-inhibition balance in brain networks.