RtcB2-PrfH Operon Protects E. coli ATCC25922 Strain from Colicin E3 Toxin

In the bid to survive and thrive in an environmental setting, bacterial species constantly interact and compete for resources and space in the microbial ecosystem. Thus, they have adapted to use various antibiotics and toxins to fight their rivals. Simultaneously, they have evolved an ability to withstand weapons that are directed against them. Several bacteria harbor colicinogenic plasmids which encode toxins that impair the translational apparatus. One of them, colicin E3 ribotoxin, mediates cleavage of the 16S rRNA in the decoding center of the ribosome. In order to thrive upon deployment of such ribotoxins, competing bacteria may have evolved counter-conflict mechanisms to prevent their demise. A recent study demonstrated the role of PrfH and the RtcB2 module in rescuing a damaged ribosome and the subsequent re-ligation of the cleaved 16S rRNA by colicin E3 in vitro. The rtcB2-prfH genes coexist as gene neighbors in an operon that is sporadically spread among different bacteria. In the current study, we report that the RtcB2-PrfH module confers resistance to colicin E3 toxicity in E. coli ATCC25922 cells in vivo. We demonstrated that the viability of E. coli ATCC25922 strain that is devoid of rtcB2 and prfH genes is impaired upon action of colicin E3, in contrast to the parental strain which has intact rtcB2 and prfH genes. Complementation of the rtcB2 and prfH gene knockout with a high copy number-plasmid (encoding either rtcB2 alone or both rtcB2-prfH operon) restored resistance to colicin E3. These results highlight a counter-conflict system that may have evolved to thwart colicin E3 activity.     

Effect of Cardiotonic Steroid Marinobufagenin on Vascular Remodeling and Cognitive Impairment in Young Dahl-S Rats

The hypertensive response in Dahl salt-sensitive (DSS) rats on a high-salt (HS) diet is accompanied by central arterial stiffening (CAS), a risk factor for dementia, and heightened levels of a prohypertensive and profibrotic factor, the endogenous Na/K-ATPase inhibitor marinobufagenin (MBG). We studied the effect of the in vivo administration of MBG or HS diet on blood pressure (BP), CAS, and behavioral function in young DSS rats and normotensive Sprague–Dawley rats (SD), the genetic background for DSS rats. Eight-week-old male SD and DSS rats were given an HS diet (8% NaCl, n = 18/group) or a low-salt diet (LS; 0.1% NaCl, n = 14–18/group) for 8 weeks or MBG (50 µg/kg/day, n = 15–18/group) administered via osmotic minipumps for 4 weeks in the presence of the LS diet. The MBG-treated groups received the LS diet. The systolic BP (SBP); the aortic pulse wave velocity (aPWV), a marker of CAS; MBG levels; spatial memory, measured by a water maze task; and tissue collection for the histochemical analysis were assessed at the end of the experiment. DSS-LS rats had higher SBP, higher aPWV, and poorer spatial memory than SD-LS rats. The administration of stressors HS and MBG increased aPWV, SBP, and aortic wall collagen abundance in both strains vs. their LS controls. In SD rats, HS or MBG administration did not affect heart parameters, as assessed by ECHO vs. the SD-LS control. In DSS rats, impaired whole-heart structure and function were observed after HS diet administration in DSS-HS vs. DSS-LS rats. MBG treatment did not affect the ECHO parameters in DSS-MBG vs. DSS-LS rats. The HS diet led to an increase in endogenous plasma and urine MBG levels in both SD and DSS groups. Thus, the prohypertensive and profibrotic effect of HS diet might be partially attributed to an increase in MBG. The prohypertensive and profibrotic functions of MBG were pronounced in both DSS and SD rats, although quantitative PCR revealed that different profiles of profibrotic genes in DSS and SD rats was activated after MBG or HS administration. Spatial memory was not affected by HS diet or MBG treatment in either SD or DSS rats. Impaired cognitive function was associated with higher BP, CAS, and cardiovascular remodeling in young DSS-LS rats, as compared to young SD-LS rats. MBG and HS had similar effects on the cardiovascular system and its function in DSS and SD rats, although the rate of change in SD rats was lower than in DSS rats. The absence of a cumulative effect of increased aPWV and BP on spatial memory can be explained by the cerebrovascular and brain plasticity in young rats, which help the animals to tolerate CAS elevated by HS and MBG and to counterbalance the profibrotic effect of heightened MBG.     

全球聚氨酯涂料市场:技术已臻成熟

2019年,聚氨酯(PU)涂料的全球总需求量超过了250万t.据涂料研究协会(Paint Research Association, PRA)独立涂料专家估计,97％的聚氨酯涂料用于工业领域,聚氨酯涂料占全球化学涂料总量的16％以上.在工业应用领域中(见表1、表2),单组分和双组分聚氨酯技术的使用已经非常成熟,而在木器...     

Failure mechanisms and bending strength of Fuchsia magellanica var. gracilis stems

In the course of biological evolution, plant stems have evolved mechanical properties and an internal structure that makes them resistant to various types of failure. The mechanisms involved during damage development and failure in bending are complex and incompletely understood. The work presented builds on a theoretical framework outlined by Ennos and van Casteren, who applied engineering mechanics theory to explain why different woody stems fail in different ways. Our work has extended this approach, applying it to a detailed analysis of one particular species: Fuchsia magellanica var. gracilis. When subjected to three-point bending, stems of this species exhibited one of two failure mechanisms: a plastic hinge or a greenstick fracture. We developed a predictive model using a computer simulation and a mathematical analysis using the theory of plastic bending. Required material properties were obtained from tests, the literature and imaging techniques. We found that greenstick fractures are more likely to occur in more lignified stems with a higher density. We discovered a new failure mode: an internal crack caused by tensile transverse stress. This work helps in understanding how plants have evolved their bending resistance and may assist in the creation of novel engineering structures inspired by these principles.     

Effect of different organic additives on the shape,size and scintillation properties of Bi4Ge3O12 powders synthesized by the microwave-hydrothermal method

A route for production of fine Bi₄Ge₃O₁₂ (BGO) powder is sought after to lower the cost of scintillation devices and make their shapes more versatile. A systematic study of highly dispersed BGO crystallization under the hydrothermal-microwave (HTMW) conditions was carried out in the present work. Anionic, cationic and non-ionic surfactants, chelating agents and polyols were used to modify the synthesis and their respective effects on phase composition and morphology were determined. It was shown that chelating agents or other additives that are capable of forming complexes with the bismuth ions allow the production of smaller, non-aggregated particles and have the procedure be scaleable. BGO powders of various morphology were synthesized and study of the optical properties of the product discovered their advantages over traditional single-crystal material. The BGO powders obtained in optimal HTMW conditions are characterized by the presence of a single intense fast scintillation component with a flash time of about 11 ns which is by an order of magnitude less than that observed in single-crystal BGO (327 ns). This suggests the suitability of these powders for the production of scintillation materials with improved properties. This material is promising for creating highly sensitive composite detectors with a high rate of counting events.     

Timing of ICSI with Respect to Meiotic Spindle Status

The aim of this study was to evaluate the efficiency of using meiotic spindle (MS) visibility and relative position to the polar body (PB) as indicators of oocyte maturation in order to optimize intracytoplasmic sperm injection (ICSI) timing. This was a cohort study of patients younger than 40 years with planned ICSI, the timing of which was determined by MS status, compared with those without MS evaluation. The angle between PB and MS and MS visibility were evaluated by optical microscope with polarizing filter. Oocytes with MS evaluation were fertilized according to MS status either 5–6 h after ovum pick-up (OPU) or 7–8 h after OPU. Oocytes without MS evaluation were all fertilized 5–6 h after OPU. For patients over 35 years visualization of MS influenced pregnancy rate (PR): 182 patients with MS visualization had 32% PR (58/182); while 195 patients without MS visualization had 24% PR (47/195). For patients under 35 years, visualization of MS did not influence PR: 140 patients with MS visualization had 41% PR (58/140), while 162 patients without MS visualization had 41% PR (66/162). Visualization of MS therefore appears to be a useful parameter for assessment of oocyte maturity and ICSI timing for patients older than 35.     

Function-based visualization and haptic rendering in shared virtual spaces

We seek to further expand the collaborative potential of shared virtual spaces by using haptic force-feedback. We propose how to define tangible physical properties of the objects, together with their geometry and appearance, by using mathematical functions. We illustrate this concept by developing software which allows us to touch and feel surfaces of VRML and X3D objects, convert them to solid objects, as well as create any other solid objects using the function-based extension of VRML and X3D. We define geometry, appearance and tangible physical properties of the solid objects by implicit, explicit and parametric functions straight in the VRML/X3D code or in loadable libraries. Since the function-defined models are small in size, it is possible to perform their collaborative interactive modifications with concurrent synchronous visualization at each client computer with any required level of detail. We illustrate the proposed models with several application examples.     

Solid-state V NMR and its potentiality in investigation of vanadia systems with paramagnetic centres

In this article we will discuss the potentiality of solid-state ⁵¹V NMR technique to characterize heterogeneous catalysts containing paramagnetic cations located on the surface or incorporated in the bulk of heterogeneous catalysts. ⁵¹V NMR data for a number of 3d and rare earth vanadates, where paramagnetic effects are caused by the presence of paramagnetic cations, are considered. We also summarize results available for vanadium bronzes, where some vanadium is in a paramagnetic V⁴⁺ state, and for some vanadium compounds, where closely spaced paramagnetic centers form diamagnetic pairs. The comprehensive ⁵¹V chemical shift scale (database) for paramagnetic solids was compiled.