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Leon I. Cohen 《American journal of botany》1970,57(4):477-485
The pistillate flowers of Arceuthobium show a high degree of uniformity and structural simplicity. Because of their simplicity certain structures such as the carpel and the placenta have been difficult to interpret. From this study, the placenta is interpreted as a composite structure consisting of two united ovules fused basally with the tissues of the receptacle. Pollen tube penetration of the placenta at its tip, development of the zygote at the distal pole, and early endosperm formation at the basal pole of the former megagametophyte indicate that the ovule is orthotropous. A theoretical interpretation of gynoecial phylogeny in Arceuthobium is discussed. 相似文献
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A new cyanogenic glycoside isolated from pods of Acacia sieberiana var. woodii has been shown by chemical and spectroscopic methods to be (2S)-2-[(6-O-α-l-arabinopyranosyl-β-d-glucopyranosyl)oxy]-3-methylbut-3-enenitrileo. Acid-catalysed hydrolysis of the glycoside afforded arabinose and proacacipetalin, and base-catalysed double-bond migration gave 2- [(6-O-α-l-arabinopyranosyl-β- d-glucopyranosyl)oxy ]-3-methylbut-2-enenitrile. 相似文献
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Leon Wong Yu‐An Huang Zhu‐Hong You Zhan‐Heng Chen Mei‐Yuan Cao 《Journal of cellular and molecular medicine》2020,24(1):79-87
LncRNA and miRNA are key molecules in mechanism of competing endogenous RNAs(ceRNA), and their interactions have been discovered with important roles in gene regulation. As supplementary to the identification of lncRNA‐miRNA interactions from CLIP‐seq experiments, in silico prediction can select the most potential candidates for experimental validation. Although developing computational tool for predicting lncRNA‐miRNA interaction is of great importance for deciphering the ceRNA mechanism, little effort has been made towards this direction. In this paper, we propose an approach based on linear neighbour representation to predict lncRNA‐miRNA interactions (LNRLMI). Specifically, we first constructed a bipartite network by combining the known interaction network and similarities based on expression profiles of lncRNAs and miRNAs. Based on such a data integration, linear neighbour representation method was introduced to construct a prediction model. To evaluate the prediction performance of the proposed model, k‐fold cross validations were implemented. As a result, LNRLMI yielded the average AUCs of 0.8475 ± 0.0032, 0.8960 ± 0.0015 and 0.9069 ± 0.0014 on 2‐fold, 5‐fold and 10‐fold cross validation, respectively. A series of comparison experiments with other methods were also conducted, and the results showed that our method was feasible and effective to predict lncRNA‐miRNA interactions via a combination of different types of useful side information. It is anticipated that LNRLMI could be a useful tool for predicting non‐coding RNA regulation network that lncRNA and miRNA are involved in. 相似文献
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Jean-Marc Bielser Leon Kraus Orlando Burgos-Morales Hervé Broly Jonathan Souquet 《Biotechnology progress》2020,36(5):e3026
Media preparation for perfusion cell culture processes contributes significantly to operational costs and the footprint of continuous operations for therapeutic protein manufacturing. In this study, definitions are given for the use of a perfusion equivalent nutrient feed stream which, when used in combination with basal perfusion medium, supplements the culture with targeted compounds and increases the medium depth. Definitions to compare medium and feed depth are given in this article. Using a concentrated nutrient feed, a 1.8-fold medium consumption (MC) decrease and a 1.67-fold increase in volumetric productivity (PR) were achieved compared to the initial condition. Later, this strategy was used to push cell densities above 100 × 106 cells/ml while using a perfusion rate below 2 RV/day. In this example, MC was also decreased 1.8-fold compared to the initial condition, but due to the higher cell density, PR was increased 3.1-fold and to an average PR value of 1.36 g L−1 day−1 during a short stable phase, and versus 0.46 g L−1 day−1 in the initial condition. Overall, the performance improvements were aligned with the given definitions. This multiple feeding strategy can be applied to gain some flexibility during process development and also in a manufacturing set-up to enable better control on nutrient addition. 相似文献
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Leon Green Jan Niemax Jens‐Peter Herrmann Axel Temming Charlotta Kvarnemo 《Ecology and evolution》2020,10(18):9981-9999
During male–male competition, evolution can favor alternative reproductive tactics. This often results in a dominant morph that holds a resource, such as a nest for egg laying, which competes with a smaller sneaker morph that reproduces by stealing fertilizations. The salinity environment can influence male growth rates, for example, via osmoregulatory costs, which in turn may influence the use of sneaker tactics for small males competing for mating opportunities. Salinity can also affect sperm directly; however, little is known of how salinity influences sneaker tactics through sperm performance. We sampled males of the invasive round goby (Neogobius melanostomus) from two environments, a freshwater river and a brackish estuary. This fish has two male morphs: nest‐holding dark males and non‐nest‐holding light males. We examined the role of water salinity of 0, 8, and 16 on sperm performance and found that for estuarine males, a salinity of 0 reduced sperm velocity compared to a salinity of 8 and 16. Riverine males had low velocity in all salinities. Sperm viability also decreased by over 30% in 0 salinity, compared to 8 and 16, for fish from both environments. Gobies produce ejaculate contents in specialized glands that could in theory shield sperm in an adverse environment. However, gland contents did not improve sperm performance in our tests. Body mass and age estimates indicate that riverine males invested more in somatic growth compared to estuarine males. Estuarine light morph males had a high enough gonadosomatic index to indicate sneaker tactics. We propose that when sperm performance is low, such as for the riverine males, sneaker tactics are ineffective and will be selected against or phenotypically suppressed. Instead, we interpret the increased investment in somatic growth found in riverine males as a life‐history decision that is advantageous when defending a nest in the next reproductive season. 相似文献
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Desai Chirag S. Khan Aisha Bellio Michael A. Willis Micah L. Mahung Cressida Ma Xiaobo Baldwin Xavier Williams Brittney M. Baron Todd H. Coleman Leon G. Wallet Shannon M. Maile Robert 《Molecular and cellular biochemistry》2021,476(12):4331-4341
Molecular and Cellular Biochemistry - Plasma-derived extracellular vesicles (EV) can serve as markers of cell damage/disease but can also have therapeutic utility depending on the nature of their... 相似文献