Efficiency of CO2 fixation in a glycollate oxidoreductase mutant of Alcaligenes eutrophus which exports fixed carbon as glycollate

Mutant strains of the facultative autotrophic bacterium Alcaligenes eutrophus blocked in glycollate utilization were isolated and characterized. One of the strains, AE161, which lacked glycollate oxidoreductase activity, excreted up to 1.2mol glycollate/mg cell protein per hour during autotrophic growth. This mutant strain was used to study the efficiency of CO₂ fixation in terms of how much of the fixed carbon was excreted as glycollate under different conditions. Glycollate excretion was not detected during heterotrophic growth. Only 1% of the total CO₂ fixed was excreted as glycollate in an atmosphere of 4% CO₂ plus 20% O₂. The rate of glycollate excretion showed a large increase and CO₂ fixation decreased as the CO₂ concentration was lowered. Almost half (40–50%) of the total CO₂ fixed was excreted as glycollate in an atmosphere of 0.07% CO₂ plus 20% O₂.Abbreviations HPMS 2-pyridyl-hydroxymethane sulphonic acid - RuBP ribulose 1,5-bisphosphate To whom offprint requests are to be sent     

How hydrological and hydraulic conditions affect performance of ponds

During the 1990s there has been a growing interest in (re)constructed wetlands and ponds for treatment of agricultural runoff, sewage water, and stormwater. Some of these facilities, however, are poorly designed in terms of hydrological and hydraulic performance, which strongly affects their treatment capacity. This paper gives an overview of the present knowledge regarding pond hydraulics in terms of effective volume ratio and dispersion. The importance of these parameters is demonstrated by modelling of nitrogen removal in 13 ponds of different design. The results show that effective volume ratio has a clear influence, which increases when removal rate coefficients increase, while dispersion is of minor importance for removal efficiency. Finally, the concept of hydraulic efficiency is discussed in the light of these results.     

Rod Visual Pigment Optimizes Active State to Achieve Efficient G Protein Activation as Compared with Cone Visual Pigments

Most vertebrate retinas contain two types of photoreceptor cells, rods and cones, which show different photoresponses to mediate scotopic and photopic vision, respectively. These cells contain different types of visual pigments, rhodopsin and cone visual pigments, respectively, but little is known about the molecular properties of cone visual pigments under physiological conditions, making it difficult to link the molecular properties of rhodopsin and cone visual pigments with the differences in photoresponse between rods and cones. Here we prepared bovine and mouse rhodopsin (bvRh and mRh) and chicken and mouse green-sensitive cone visual pigments (cG and mG) embedded in nanodiscs and applied time-resolved fluorescence spectroscopy to compare their G_t activation efficiencies. Rhodopsin exhibited greater G_t activation efficiencies than cone visual pigments. Especially, the G_t activation efficiency of mRh was about 2.5-fold greater than that of mG at 37 °C, which is consistent with our previous electrophysiological data of knock-in mice. Although the active state (Meta-II) was in equilibrium with inactive states (Meta-I and Meta-III), quantitative determination of Meta-II in the equilibrium showed that the G_t activation efficiency per Meta-II of bvRh was also greater than those of cG and mG. These results indicated that efficient G_t activation by rhodopsin, resulting from an optimized active state of rhodopsin, is one of the causes of the high amplification efficiency of rods.     

一种平末端连接的有效方法

转化效率与质粒大小成反比,而当质粒大于１５ｋｂ时,转化效率将成为限制因素,此时提高连接效率极为必要,特别是对于具有普遍性而效率又低的平末端连接。我们在连接反应体系中,加入相应的产生平末端质粒载体的限制性内切酶Ｈｐａ Ｉ、或ＥｃｏＲ Ｖ,与不加Ｈｐａ Ｉ,或ＥｃｏＲ Ｖ的连接反应相对照,连接产物转化大肠杆菌ＪＭ１０９后,产生的转化子比率分别为１９．９％和１０．３％（ｐＦｐ７）,３２．６％和９．７％（     

Two-dimensional informative array testing

Summary Array-based group-testing algorithms for case identification are widely used in infectious disease testing, drug discovery, and genetics. In this article, we generalize previous statistical work in array testing to account for heterogeneity among individuals being tested. We first derive closed-form expressions for the expected number of tests (efficiency) and misclassification probabilities (sensitivity, specificity, predictive values) for two-dimensional array testing in a heterogeneous population. We then propose two "informative" array construction techniques which exploit population heterogeneity in ways that can substantially improve testing efficiency when compared to classical approaches that regard the population as homogeneous. Furthermore, a useful byproduct of our methodology is that misclassification probabilities can be estimated on a per-individual basis. We illustrate our new procedures using chlamydia and gonorrhea testing data collected in Nebraska as part of the Infertility Prevention Project.     

Efficient Estimation for Rank‐Based Regression with Clustered Data

Summary Rank‐based inference is widely used because of its robustness. This article provides optimal rank‐based estimating functions in analysis of clustered data with random cluster effects. The extensive simulation studies carried out to evaluate the performance of the proposed method demonstrate that it is robust to outliers and is highly efficient given the existence of strong cluster correlations. The performance of the proposed method is satisfactory even when the correlation structure is misspecified, or when heteroscedasticity in variance is present. Finally, a real dataset is analyzed for illustration.     

Fasciola hepatica: Comparison of the sedimentation and FLOTAC techniques for the detection and quantification of faecal egg counts in rats

We compared the sedimentation and FLOTAC techniques for the detection and quantification of Fasciola hepatica eggs in faecal samples obtained from 120 experimentally-infected rats before intervention, and in 42 rats after drug administration. Additionally, the average time for a single test was determined. A single FLOTAC showed a higher sensitivity (92.6%) than 2, 4 and 8 sedimentation readings (63.0-85.2%) for detecting F. hepatica eggs in rat faeces post-treatment. On average, it took 21 min to prepare and examine a single FLOTAC, whereas 114 min were needed for the sedimentation method including the reading of 8 slides. In both treated and untreated rats, the sedimentation method resulted in higher mean faecal egg counts (FECs) than FLOTAC (P < 0.05). In view of the high sensitivity and efficiency, the FLOTAC technique holds promise for experimental work in the F. hepatica-rat model. Additional research is needed to determine the reasons for the observed differences in FECs.     

Simulation of evolution implemented in the mutualistic symbioses towards enhancing their ecological efficiency, functional integrity and genotypic specificity

We created the mathematical model for the evolution of the Efficiency of Mutualistic Symbioses (EMS) which was estimated as the microsymbiont impacts on the host’s reproductive potential. Using the example of rhizobia–legume interaction, the relationships were studied between EMS and Functional Integrity of Symbiosis (FIS) which is represented as a measure for concordance of changes in the partners’ genotypic frequencies under the environmental fluctuations represented by the minor deviations of the systemic model parameters. The FIS indices correlate positively with EMS values suggesting an enhancement of FIS via the natural selection operating in the partners’ populations in favor of high EMS. Due to this selection, nodular habitats may be closed for colonization by the non-beneficial bacterial strains and the Genotypic Specificity of Mutualism (GSM) in partners’ interactions is enhanced: the selective advantage of host-specific vs non-host-specific mutualists is increasing. The novelty of our model is to suggest a selective background for macroevolutionary events reorganizing the structure and functions of symbiotic systems and to present its evolution as a result of shifting the equilibrium between different types of mutualists under the impacts of the symbiosis-stipulated modes of natural selection.     

Novel insights for improving the therapeutic safety and efficiency of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have attracted great interest in the field of regenerative medicine. They can home to damaged tissue, where they can exert pro-regenerative and anti-inflammatory properties. These therapeutic effects involve the secretion of growth factors, cytokines, and chemokines. Moreover, the functions of MSCs could be mediated by extracellular vesicles (EVs) that shuttle various signaling messengers. Although preclinical studies and clinical trials have demonstrated promising therapeutic results, the efficiency and the safety of MSCs need to be improved. After transplantation, MSCs face harsh environmental conditions, which likely dampen their therapeutic efficacy. A possible strategy aiming to improve the survival and therapeutic functions of MSCs needs to be developed. The preconditioning of MSCs ex vivo would strength their capacities by preparing them to survive and to better function in this hostile environment. In this review, we will discuss several preconditioning approaches that may improve the therapeutic capacity of MSCs. As stated above, EVs can recapitulate the beneficial effects of MSCs and may help avoid many risks associated with cell transplantation. As a result, this novel type of cell-free therapy may be safer and more efficient than the whole cell product. We will, therefore, also discuss current knowledge regarding the therapeutic properties of MSC-derived EVs.