血清岩藻糖测定方法学研究

本文对血清岩藻糖测定方法进行了系统研究。血清用量由200μL减至50μL,显色反应4h内稳定。吸收峰在396nm。岩藻糖浓度40μg/mL内线性良好,批间CV=2.1％。以Sephadex-G200层析,血清岩藻糖主要存在于分子量为500kD的组分中。以本法测得30例健康人血清岩藻糖浓度为588.1±172.0μmol/L。     

红毛五加多糖对腹腔巨噬细胞作用的定量细胞化学研究

中药红毛五加(Acanthopanax giraldii Harms)属五加科植物,本文通过细胞化学定性、定位、定量研究探讨红毛五加多糖(AGPS)对腹腔巨噬细胞的作用及机理。实验证明AGPS能使巨噬细胞数量明显增多,细胞体积增大,伪足增多,吞噬能力增强,细胞内醣类、酸性磷酸酶、三磷酸腺昔酶、酸性酯酶和琥珀酸脱氢酶活性显著增强。用显微分光光度计对上述单个细胞的化学成分进行定量测定。实验组和对照组结果有显著差异。提示红毛五加的扶正固本作用十分明显,本研究为AGPS的应用和作用机理提供了一定的实验依据。     

Partial migration: niche shift versus sexual maturation in fishes

Summary Many fish populations have both resident and migratory individuals. Migrants usually grow larger and have higher reproductive potential but lower survival than resident conspecifics. The decision about migration versus residence probably depends on the individual growth rate, or a physiological process like metabolic rate which is correlated with growth rate. Fish usually mature as their somatic growth levels off, where energetic costs of maintenance approach energetic intake. After maturation, growth also stagnates because of resource allocation to reproduction. Instead of maturation, however, fish may move to an alternative feeding habitat and their fitness may thereby be increased. When doing so, maturity is usually delayed, either to the new asymptotic length, or sooner, if that gives higher expected fitness. Females often dominate among migrants and males among residents. The reason is probably that females maximize their fitness by growing larger, because their reproductive success generally increases exponentially with body size. Males, on the other hand, may maximize fitness by alternative life histories, e.g. fighting versus sneaking, as in many salmonid species where small residents are the sneakers and large migrants the fighters. Partial migration appears to be partly developmental, depending on environmental conditions, and partly genetic, inherited as a quantitative trait influenced by a number of genes.     

Estimating tree-based dynamic treatment regimes using observational data with restricted treatment sequences

A dynamic treatment regime (DTR) is a sequence of decision rules that provide guidance on how to treat individuals based on their static and time-varying status. Existing observational data are often used to generate hypotheses about effective DTRs. A common challenge with observational data, however, is the need for analysts to consider “restrictions” on the treatment sequences. Such restrictions may be necessary for settings where (1) one or more treatment sequences that were offered to individuals when the data were collected are no longer considered viable in practice, (2) specific treatment sequences are no longer available, or (3) the scientific focus of the analysis concerns a specific type of treatment sequences (eg, “stepped-up” treatments). To address this challenge, we propose a restricted tree–based reinforcement learning (RT-RL) method that searches for an interpretable DTR with the maximum expected outcome, given a (set of) user-specified restriction(s), which specifies treatment options (at each stage) that ought not to be considered as part of the estimated tree-based DTR. In simulations, we evaluate the performance of RT-RL versus the standard approach of ignoring the partial data for individuals not following the (set of) restriction(s). The method is illustrated using an observational data set to estimate a two-stage stepped-up DTR for guiding the level of care placement for adolescents with substance use disorder.     

Vertically stratified frugivore community composition and interaction frequency in a liana fruiting across forest strata

Vertical stratification is a key feature of tropical forests and structures plant–frugivore interactions. However, it is unclear whether vertical differences in plant-frugivore interactions are due to differences among strata in plant community composition or inherent preferences of frugivores for specific strata. To test this, we observed fruit removal of a diverse frugivore community on the liana Marcgravia longifolia in a Peruvian rain forest. Unlike most other plants, Marcgravia longifolia produces fruits across forest strata. This enabled us to study effects of vertical stratification on fruit removal without confounding effects of plant species and stratum. We found a high number of visits of a few frugivore species in the understorey and a low number of visits of many different frugivores in the canopy and midstorey. Whereas partial and opportunistic frugivores foraged across strata with differing frequencies, obligate frugivores were only found eating fruits in the higher strata. Avian frugivores foraging in the canopy were mainly large species with pointed wings, whereas under- and midstorey avian foragers were smaller with rounded wings. Our findings suggest a continuous shift in the frugivore community composition along the vertical gradient, from a few generalized frugivores in the understorey to a diverse set of specialized frugivores in the canopy. This shift in the frugivore community leads to correlated, reciprocal changes from specialized to generalized plant-frugivore interactions. Thus, we conclude that vertical niche differentiation between species in tropical forests persists even when food resources are available across strata. This highlights its role for promoting biodiversity and ecosystem functioning.     

Surface imprinted bio-nanocomposites for affinity separation of a cellular DNA repair protein

Apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional DNA repair protein localized in different subcellular compartments. The mechanisms responsible for the highly regulated subcellular localization and “interactomes” of this protein are not fully understood but have been closely correlated to the posttranslational modifications in different biological context. In this work, we attempted to develop a bio-nanocomposite with antibody-like properties that could capture APE1 from cellular matrices to enable the comprehensive study of this protein. By fixing the template APE1 on the avidin-modified surface of silica-coated magnetic nanoparticles, we first added 3-aminophenylboronic acid to react with the glycosyl residues of avidin, followed by addition of 2-acrylamido-2-methylpropane sulfonic acid as the second functional monomer to perform the first step imprinting reaction. To further enhance the affinity and selectivity of the binding sites, we carried out the second step imprinting reaction with dopamine as the functional monomer. After the polymerization, we modified the nonimprinted sites with methoxypoly (ethylene glycol) amine (mPEG-NH₂). The resulting molecularly imprinted polymer-based bio-nanocomposite showed high affinity, specificity, and capacity for template APE1. It allowed for the extraction of APE1 from the cell lysates with high recovery and purity. Moreover, the bound protein could be effectively released from the bio-nanocomposite with high activity. The bio-nanocomposite offers a very useful tool for the separation of APE1 from various complex biological samples.     

Regulation of Nitrogen Metabolism,Photosynthetic Activity,and Yield Attributes of Spring Wheat by Nitrogen Fertilizer in the Semi-arid Loess Plateau Region

It is critical for spring wheat (Triticum aestivum L.) production in the semi-arid Loess Plateau to understand the impact of nitrogen (N) fertilizer on changes in N metabolism, photosynthetic parameters, and their relationship with grain yield and quality. The photosynthetic capacity of flag leaves, dry matter accumulation, and N metabolite enzyme activities from anthesis to maturity were studied on a long-term fertilization trial under different N rates [0 kg ha^?1(N1), 52.5 kg ha^?1 (N2), 105 kg ha^?1 (N3), 157.5 kg ha^?1 (N4), and 210 kg ha^?1 (N5)]. It was observed that N3 produced optimum total dry matter (5407 kg ha^?1), 1000 grain weight (39.7 g), grain yield (2.64 t ha^?1), and protein content (13.97%). Our results showed that N fertilization significantly increased photosynthetic parameters and N metabolite enzymes at all growth stages. Nitrogen harvest index, partial productivity factor, agronomic recovery efficiency, and nitrogen agronomic efficiency were decreased with increased N. Higher N rates (N3–N5) maintained higher photosynthetic capacity and dry matter accumulation and lower intercellular CO₂ content. The N supply influenced NUE by improving photosynthetic properties. The N3 produced highest chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate, grain yield, grain protein, dry matter, grains weight, and N metabolite enzyme activities compared to the other rates (N1, N2, N4, and N5). Therefore, increasing N rates beyond the optimum quantity only promotes vegetative development and results in lower yields.