Do predators have a role to play in wetland ecosystem functioning? An experimental study in New England salt marshes

The historical ecological paradigm of wetland ecosystems emphasized the role of physical or “bottom‐up” factors in maintaining functions and services. However, recent studies have shown that the loss of predators in coastal salt marshes can lead to a significant reduction in wetland extent due to overgrazing of vegetation by herbivores. Such studies indicate that consumers or “top‐down” factors may play a much larger role in the maintenance of wetland ecosystems than was previously thought. The objective of this study was to evaluate whether altering top‐down control by manipulating the presence of predators can lead to measurable changes in salt marsh ecosystem properties. Between May and August of 2015 and 2016, we established exclosure and enclosure cages within three New England coastal wetland areas and manipulated the presence of green crab predators to assess how they and their fiddler and purple marsh crab prey affect changes in ecosystem properties. Predator presence was associated with changes in soil nitrogen and aboveground biomass at two of the three field sites, though the magnitude and direction of these effects varied from site to site. Further, path analysis results indicate that across field sites, a combination of bottom‐up and top‐down factors influenced changes in measured variables. These results challenge the growing consensus that consumers have strong effects, indicating instead that predator impacts may be highly context‐dependent.     

Biomass production of hairy roots of Artemisia annua and Arachis hypogaea in a scaled‐up mist bioreactor

Hairy roots have the potential to produce a variety of valuable small and large molecules. The mist reactor is a gas phase bioreactor that has shown promise for low‐cost culture of hairy roots. Using a newer, disposable culture bag, mist reactor performance was studied with two species, Artemisia annua L. and Arachis hypogaea (peanut), at scales from 1 to 20 L. Both species of hairy roots when grown at 1 L in the mist reactor showed growth rates that surpassed that in shake flasks. From the information gleaned at 1 L, Arachis was scaled further to 4 and then 20 L. Misting duty cycle, culture medium flow rate, and timing of when flow rate was increased were varied. In a mist reactor increasing the misting cycle or increasing the medium flow rate are the two alternatives for increased delivery of liquid nutrients to the root bed. Longer misting cycles beyond 2–3 min were generally deemed detrimental to growth. On the other hand, increasing the medium flow rate to the sonic nozzle especially during the exponential phase of root growth (weeks 2–3) was the most important factor for increasing growth rates and biomass yields in the 20 L reactors. A. hypogaea growth in 1 L reactors was µ = 0.173 day^?1 with biomass yield of 12.75 g DW L^?1. This exceeded that in shake flasks at µ = 0.166 day^?1 and 11.10 g DW L^?1. Best growth rate and biomass yield at 20 L was µ = 0.147 and 7.77 g DW L^?1, which was mainly achieved when medium flow rate delivery was increased. The mist deposition model was further evaluated using this newer reactor design and when the apparent thickness of roots (+hairs) was taken into account, the empirical data correlated with model predictions. Together these results establish the most important conditions to explore for future optimization of the mist bioreactor for culture of hairy roots. Biotechnol. Bioeng. 2010;107: 802–813. © 2010 Wiley Periodicals, Inc.     

Scaling‐up of complex whole‐cell bioconversions in conventional and non‐conventional media

The use of whole cells is becoming a more common approach in pharmaceutical and agrochemical industries in order to obtain pure compounds with fewer production steps, higher yields, and cleaner processes, as compared to those achieved with traditional strategies. Whole cells are often used as enzymes pools, in particular when multi‐step reactions and/or co‐factor regeneration are envisaged. Nonetheless, published information on the scale‐up of such systems both in aqueous and in two‐phase aqueous–organic systems is relatively scarce. The present work aims to evaluate suitable scale‐up criteria in conventional and non‐conventional medium for a whole‐cell bioconversion that uses resting cells of Mycobacterium sp. NRRL B‐3805 to cleave the side chain of β‐sitosterol, a poorly water‐soluble substrate. The experiments were performed in 24‐well microtiter plates and in 250 mL shaken flasks as orbital stirred systems, and in 300 mL stirred tanks as mechanically stirred systems. Results show that productivity yields were similar in all scales tested, when maintaining oxygen mass transfer coefficients constant in aqueous systems, or when maintaining constant volumetric power consumption in aqueous–organic two‐phase systems. Biotechnol. Bioeng. 2010;106: 619–626. © 2010 Wiley Periodicals, Inc.     

Left ventricular dysfunction due to right ventricular stimulation: is biventricular upgrade really necessary?

Left ventricular (LV) dysfunction can occur due to chronic right ventricular apical pacing. Upgrading of the pacemaker to biventricular pacing is an option to reverse LV dysfunction but reprogramming of the atrioventricular (AV) timing can also be favourable. In this case report we describe the effect of AV-time reprogramming in a patient with LV function deterioration that emerged two years after implantation of a dual chamber system for sick sinus syndrome. Echocardiographc studies demonstrated a tremendous improvement in LV function during two years follow-up whereas the percentage of right ventricular pacing diminished dramatically. Careful analysis of the cause of LV deterioration can avoid unnecessary upgrading to biventricular pacing. (Neth Heart J 2010;18:604–5.)     

农村留守孩心理健康的家庭因素研究

青少年时期是儿童个性发展的一个重要时期,个性发展有较大的可塑性。目前农村劳动力迁移导致了大批留守儿童亲子教育缺失和家庭教育缺位。本文对留守儿童心理健康的相关研究进行了整理,分析了影响留守儿童心理健康状况的四个主要家庭因素,并总结了关于为留守儿童建立社区学校和家庭的三维支持系统的建议。     

The importance of catch-up growth after early malnutrition for the programming of obesity in male rat

Objective: To investigate whether catch‐up growth after maternal malnutrition would favor the development of obesity in adulthood. Research Methods and Procedures: Pregnant rats were submitted to protein or calorie restriction during the course of gestation. During lactation, pups were protein‐restricted, normally fed, or overfed [reduced litter size, control (C) diet]. At weaning, rats were transferred to chow or to a hypercaloric diet (HCD) known to induce obesity. Body weight, food intake, blood parameters, glucose tolerance, adipocyte cellularity, and adipose factors contributing to cardiovascular disease development were measured. Results: Protein and calorie restriction during gestation led to growth retardation at birth. If malnutrition was prolonged throughout lactation, adult body weight was permanently reduced. However, growth‐retarded offspring overfed during the suckling period underwent a rapid catch‐up growth and became heavier than the normally fed Cs. Offspring of calorie‐restricted rats gained more weight than those of dams fed protein‐restricted diet. Feeding an HCD postnatally amplified the effect of calorie restriction, and offspring that underwent catch‐up growth became more obese than Cs. The HCD was associated with hyperphagia, hyperglycemia, hyperinsulinemia, glucose intolerance, insulin resistance, and adipocyte hypertrophy. The magnitude of effects varied depending on the type and the timing of early malnutrition. The expression of genes encoding factors implicated in cardiovascular disease was also modulated differently by early malnutrition and adult obesity. Discussion: Catch‐up growth immediately after early malnutrition should be a key point for the programming of obesity.     

Enclosed outdoor photobioreactors: light regime,photosynthetic efficiency,scale-up,and future prospects

Enclosed outdoor photobioreactors need to be developed and designed for large-scale production of phototrophic microorganisms. Both light regime and photosynthetic efficiency were analyzed in characteristic examples of state-of-the-art pilot-scale photobioreactors. In this study it is shown that productivity of photobioreactors is determined by the light regime inside the bioreactors. In addition to light regime, oxygen accumulation and shear stress limit productivity in certain designs. In short light-path systems, high efficiencies, 10% to 20% based on photosynthetic active radiation (PAR 400 to 700 nm), can be reached at high biomass concentrations (>5 kg [dry weight] m(-3)). It is demonstrated, however, that these and other photobioreactor designs are poorly scalable (maximal unit size 0.1 to 10 m(3)), and/or not applicable for cultivation of monocultures. This is why a new photobioreactor design is proposed in which light capture is physically separated from photoautotrophic cultivation. This system can possibly be scaled to larger unit sizes, 10 to >100 m(3), and the reactor liquid as a whole is mixed and aerated. It is deduced that high photosynthetic efficiencies, 15% on a PAR-basis, can be achieved. Future designs from optical engineers should be used to collect, concentrate, and transport sunlight, followed by redistribution in a large-scale photobioreactor.     

Effect of membrane morphology on system capacity during normal flow microfiltration

Understanding the effects of membrane fouling on system capacity is critical for the successful design and scale-up of microfiltration systems. The underlying morphology and structure of the microfiltration membrane can have a significant effect on system capacity by altering the rate and extent of fouling. Experimental data were obtained for system capacity during protein microfiltration using several model membranes with both homogeneous and composite structures. Data were compared with predictions of a new model that can account for both pore blockage and cake formation, and also includes the effects of membrane morphology on internal flow profiles within the membrane. Membranes with highly interconnected pores have a significantly higher capacity due to the reduction in flux decline arising from the fluid flow under and around any surface blockage. The model calculations are in good agreement with the flux decline data, allowing far more accurate predictions of system capacity than for the commonly used V(max) analysis.     

Scale-up of pseudo solid-phase enzymatic synthesis of alpha-methyl glucoside acrylate

The successful scale-up of the enzymatic synthesis of alpha-methyl glucoside acrylate from laboratory-scale (milliliter) to pilot-scale (liter) was examined. Specifically, Candida antarctica lipase B (Novozym 435) was used as a biocatalyst to produce alpha-methyl glucoside acrylate via the transesterification of alpha-methyl glucoside (MG) with vinyl acrylate (VA) using acetone as a solvent. This is a pseudo-solid-phase synthesis; only a fraction of the alpha-methyl glucoside and the product are soluble in acetone. Molecular sieves were used to remove traces of water in the reaction medium and to increase enzyme stability by removing the acetaldehyde by-product. A general method was also developed to purify and recover the monoacrylate product from unreacted sugar and undesired diester by a simple crystallization and precipitation process.     

Scale-up and optimization of an acoustic filter for 200 L/day perfusion of a CHO cell culture

Acoustic cell retention devices have provided a practical alternative for up to 50 L/day perfusion cultures but further scale-up has been limited. A novel temperature-controlled and larger-scale acoustic separator was evaluated at up to 400 L/day for a 10(7) CHO cell/mL perfusion culture using a 100-L bioreactor that produced up to 34 g/day recombinant protein. The increased active volume of this scaled-up separator was divided into four parallel compartments for improved fluid dynamics. Operational settings of the acoustic separator were optimized and the limits of robust operations explored. The performance was not influenced over wide ranges of duty cycle stop and run times. The maximum performance of 96% separation efficiency at 200 L/day was obtained by setting the separator temperature to 35.1 degrees C, the recirculation rate to three times the harvest rate, and the power to 90 W. While there was no detectable effect on culture viability, viable cells were selectively retained, especially at 50 L/day, where there was a 5-fold higher nonviable washout efficiency. Overall, the new temperature-controlled and scaled-up separator design performed reliably in a way similar to smaller-scale acoustic separators. These results provide strong support for the feasibility of much greater scale-up of acoustic separations.