Biotransformation of (±)-α-ionone and β-ionone by cultured cells of Caragana chamlagu

Suspension cultures of Caragana chamlagu (Leguminosae) convert (±)-α-ionone (1) into (±)-3-oxo-α-ionone (3) as the major product and β-ionone (2) into 5,6-epoxy-β-ionone (6) as the sole product. It is interesting to note that the cultured cells of C. chamlagu convert regioselectively the cycloolefinic part of 1 into the corresponding unsaturated carbonyl compound, allylic alcohol and epoxide as the oxidation products, whereas the suspension cultures of Nicotiana tabacum (Solanaceae) convert the unsaturated carbonyl of 1 into the corresponding saturated ketones and alcohols as reduction products.     

Characterizing robustness and sensitivity of convolutional neural networks for quantitative analysis of mitochondrial morphology

Background: Quantitative analysis of mitochondrial morphology plays important roles in studies of mitochondrial biology. The analysis depends critically on segmentation of mitochondria, the image analysis process of extracting mitochondrial morphology from images. The main goal of this study is to characterize the performance of convolutional neural networks (CNNs) in segmentation of mitochondria from fluorescence microscopy images. Recently, CNNs have achieved remarkable success in challenging image segmentation tasks in several disciplines. So far, however, our knowledge of their performance in segmenting biological images remains limited. In particular, we know little about their robustness, which defines their capability of segmenting biological images of different conditions, and their sensitivity, which defines their capability of detecting subtle morphological changes of biological objects. Methods: We have developed a method that uses realistic synthetic images of different conditions to characterize the robustness and sensitivity of CNNs in segmentation of mitochondria. Using this method, we compared performance of two widely adopted CNNs: the fully convolutional network (FCN) and the U-Net. We further compared the two networks against the adaptive active-mask (AAM) algorithm, a representative of high-performance conventional segmentation algorithms. Results: The FCN and the U-Net consistently outperformed the AAM in accuracy, robustness, and sensitivity, often by a significant margin. The U-Net provided overall the best performance. Conclusions: Our study demonstrates superior performance of the U-Net and the FCN in segmentation of mitochondria. It also provides quantitative measurements of the robustness and sensitivity of these networks that are essential to their applications in quantitative analysis of mitochondrial morphology.     

氮磷肥配施对冬小麦灌浆期光合参数及产量的影响

在西北绿洲生态条件下, 实验设4个处理, 即165(N₁)和225 kg·hm^-2(N₂)2个氮素(纯氮)水平及105(P₁)和165 kg·hm^-2(P₂)2个磷素(P₂O₅)水平, 研究了氮磷肥配施对冬小麦(Triticum aestivum)品种临抗2号光合特性及产量的影响。结果表明, 低氮(165 kg·hm^-2)处理组的净光合速率(P_n)、气孔导度(G_s)及蒸腾速率(T_r)日变化均呈双峰曲线, 有光合“午休”现象; 高氮(225 kg·hm^-2)处理可减弱甚至使光合“午休”现象消失; 高磷(165 kg·hm^-2)和低磷(105 kg·hm^-2)处理对光合特性的影响差异不显著。N₂P₂具有最高的群体叶面积指数(LAI)、群体光合速率(CAP)、穗粒数、亩穗数、千粒重及产量, 且与N₁P₁和N₁P₂的差异均达显著水平, 与N₂P₁则无显著差异。但N₂P₂水分利用效率(WUE)低于N₂P₁, 显著高于N₁P₁和N₁P₂ (N₁P₁高于N₁P₂, 但无显著差异)。氮肥对光合“午休”的影响大于磷肥, 二者互作效应差异不显著。该实验条件下, 当N、P分别为225和105 kg·hm^-2时有利于提高冬小麦的光合速率及产量。     

Apolipoproteins and amyloid fibril formation in atherosclerosis

Amyloid fibrils arise from the aggregation of misfolded proteins into highly-ordered structures. The accumulation of these fibrils along with some non-fibrillar constituents within amyloid plaques is associated with the pathogenesis of several human degenerative diseases. A number of plasma apolipoproteins, including apolipoprotein (apo) A-I, apoA-II, apoC-II and apoE are implicated in amyloid formation or influence amyloid formation by other proteins. We review present knowledge of amyloid formation by apolipoproteins in disease, with particular focus on atherosclerosis. Further insights into the molecular mechanisms underlying their amyloidogenic propensity are obtained from in vitro studies which describe factors affecting apolipoprotein amyloid fibril formation and interactions. Additionally, we outline the evidence that amyloid fibril formation by apolipoproteins might play a role in the development and progression of atherosclerosis, and highlight possible molecular mechanisms that could contribute to the pathogenesis of this disease.     

Potential Reproductive Advantage of Short-over Long-Winged Adult Males of the Cricket <Emphasis Type="Italic">Velarifictorus ornatus</Emphasis>

A trade-off between flight capability and reproduction is well known in adult females of the wing-dimorphic cricket Velarifictorus ornatus, but it is not clear whether such a trade-off exists in adult males of the species. In the present study, we investigated sexual maturation time, mating frequency, and the fertilization success of spermatophores after sequential mating in long-winged (LW) and short-winged (SW) adult males of V. ornatus to evaluate the potential reproductive advantage of the SW over the LW male morph. We found that the SW males of V. ornatus attained sexual maturity earlier and produced heavier spermatophores during the early stage after adult emergence than their LW counterparts. Additionally, within a 24-h mating period, the SW males showed a higher mating frequency, greater spermatophore weight, and shorter intermating time interval compared with their LW counterparts. Although females copulated with the two male morphs produced eggs of similar size, fertilization success by SW males was significantly higher than by the LW males. These results provide support for a trade-off between dispersal capability and reproduction success in wing-dimorphic males of V. ornatus.     

Prohibitin involvement in the generation of mitochondrial superoxide at complex I in human sperm

Prohibitin (PHB), a major mitochondrial membrane protein, has been shown earlier in our laboratoryto regulate sperm motility via an alteration in mitochondrial membrane potential (MMP) in infertile men with poor sperm quality. To test if PHB expression is associated with sperm mitochondrial superoxide (mROS) levels, here we examined sperm mROS levels, high MMP and lipid peroxidation in infertile men with poor sperm motility (asthenospermia, A) and/or low sperm concentrations (oligoasthenospermia, OA). The diaphorase‐type activity of sperm mitochondrial complex I (MCI) and PHB expression were also determined. We demonstrate that mROS and lipid peroxidation levels are significantly higher in sperm from A and OA subjects than in normospermic subjects, whereas high MMP and PHB expression are significantly lower. A positive correlation between mROS and lipid peroxidation and a negative correlation of mROS with PHB expression, high MMP, and sperm motility were found in these subjects. The finding of similar diaphorase‐type activity levels of sperm MCI in the three groups studied suggests that the catalytic subunits of MCI in the matrix arm may produce mROS on its own. There may be a dysfunction of electron transport at MCI associated with decreased expression of PHB in sperm with poor quality. We conclude that mROS level is increased and associated with decreased PHB expression, and it may regulate sperm motility via increases in low MMP and lipid peroxidation. This is the first report on the involvement of PHB in human sperm motility loss associated with increased generation of mROS at MCI.     

Electric-field-induced spin switch of endohedral dodecahedrane heterodimers H@C<Subscript>20</Subscript>H<Subscript>n</Subscript>–C<Subscript>20</Subscript>H<Subscript>n</Subscript>@M (M= Cu,Ag and Au,n = 15, 18, and 19): a theoretical study

We designed nine endohedral dodecahedrane heterodimers H@C₂₀H_n-C₂₀H_n@M (M = Cu, Ag, and Au, n = 15, 18, and 19) that may act as single-molecule spin switches, and we predicted theoretically that the ground states of the dimmers shift from low-spin states (S = 0) to the high-spin states (S = 1) under an external electric field applied parallel or perpendicular to the molecular symmetry axes, consisting well with the analyses of Stark effect. Molecular orbitals analyses provide an intuitive insight into the spin crossover behavior. This study expands the application of endohedral chemistry and provides new molecules for designing single-molecule spin switch.     

植物病原真菌过氧化物酶体的发生机制及功能

过氧化物酶体（peroxisome,P）是真核细胞中普遍存在的细胞器,参与多种重要的代谢过程。P的产生、增殖及降解是细胞器发生机理研究的重要部分。到目前已知的P发生相关基因有30多个,但其机制仍不完全清楚。作为一种多细胞真核生物,丝状真菌在P发生机制的研究中有重要价值。近年来,随着基因组序列的应用和真菌生物技术的进展,丝状真菌中P功能及发生机制的研究取得了较大进展。同时,作为丝状真菌真菌中的重要类群,植物病原真菌P在致病过程中的作用也引起关注。本文对P发生机制、在丝状真菌中的研究概况,以及与植物病原真菌致病性的关系进行了 综述。