田菁根际促生菌的筛选及其促生耐盐效果

【目的】为探究盐生植物田菁及其根际功能微生物改良盐碱地的效果,本研究从黄河三角洲盐碱区田菁根际土壤中分离促生菌,并明确其耐盐促生效果。【方法】采用选择培养方法从田菁根际土壤中分离固氮菌、解磷菌以及解钾菌,并进行16S rRNA分子生物学鉴定。之后对菌株的耐盐及促生特性进行测定,筛选性状优良菌株进行玉米促生作用研究。【结果】共分离得到105株根际促生菌,其中N102兼具多种促生特性且耐盐性达15%。田菁种子发芽试验表明,N102可显著提高田菁发芽率(47%,P0.05)、芽长(48.5%,P0.05)和根长(60%,P0.05);玉米盆栽试验结果表明,N102对盐胁迫下玉米的株高、根长、叶绿素含量、地上部干重以及根干重具有显著的促进作用。经系统发育分析,N102与Enterobacter soli ATCC BAA-2102 (NR117547)序列相似度为99.30%,鉴定属于Enterobacter属。【结论】菌株N102具有多种植物促生耐盐特性,具有开发成有效促进盐碱地作物生长的微生物肥的良好前景。     

How Does Hemicelluloses Removal Alter Plant Cell Wall Nanoscale Architecture and Correlate with Enzymatic Digestibility?

Thorough understanding of how hemicelluloses removal influences cell wall nanoscale architecture and cellulose digestion is of crucial importance for enabling low-cost industrial conversion of lignocellulosic biomass to renewable biofuels. In this work, delignified poplar cell walls, after various degrees of hemicelluloses removal, were characterized by Fourier transform infrared imaging spectroscopy and atomic force microscopy to evaluate enhancement in cell wall digestibility. There was a gradual decrease in hemicelluloses content with dilute alkali treatment, which resulted in alterations in the nanoscale architecture and crystallinity of cell walls. Removal of hemicelluloses did not disrupt the integrity of microfibrils but resulted in exposure of microfibrils and a decrease in the diameter of microfibrils. X-ray analysis indicated that the increase in crystallinity beyond natural variations in the crystallinity of cellulose was mainly attributable to removal of hemicelluloses. In conclusion, alterations in the architecture and crystallinity of cell walls facilitated enzymatic digestion of delignified poplar, enhancing cellulose conversion from 68.24 to 75.16 %.     

Alpha lipoic acid inhibits oxidative stress‐induced apoptosis by modulating of Nrf2 signalling pathway after traumatic brain injury

Alpha lipoic acid (ALA) is a powerful antioxidant which has been widely used in the treatment of different system diseases, such as cardiovascular and cerebrovascular diseases. But, there are few studies that refer to protective effects and potential mechanisms on traumatic brain injury (TBI). This study was carried out to investigate the neuroprotective effect following TBI and illuminate the underlying mechanism. Weight drop‐injured model in rats was induced by weight‐drop. ALA was administrated via intraperitoneal injection after TBI. Neurologic scores were examined following several tests. Neurological score was performed to measure behavioural outcomes. Nissl staining and TUNEL were performed to evaluate the neuronal apoptosis. Western blotting was engaged to analyse the protein content of the Nuclear factor erythroid 2‐related factor 2 (Nrf2) and its downstream protein factors, including hemeoxygenase‐1 (HO‐1) and quinine oxidoreductase‐1 (NQO1). ALA treatment alleviated TBI‐induced neuron cell apoptosis and improved neurobehavioural function by up‐regulation of Nrf2 expression and its downstream protein factors after TBI. This study presents new perspective of the mechanisms responsible for the neuronal apoptosis of ALA, with possible involvement of Nrf2 pathway.     

Cryopreservation of composite tissues and transplantation: preliminary studies

Despite advances in cryobiology, the reliable cryopreservation of complex tissues has not yet been achieved. This study evaluates the viability of cryopreserved composite flaps and demonstrates the feasibility of their transplantation. Epigastric flaps were harvested from male Lewis rats. 1.5 M dimethyl sulfoxide (Me₂SO) was used as the initial cryoprotectant agent (CPA). Samples were frozen at controlled rate to −140 °C and transferred to liquid nitrogen for at least two weeks. Hematoxylin and eosin (H/E) staining, MTT tetrazolium salt assay, and factor VIII immunostaining were used to evaluate the overall histology, epithelial viability, and vascular endothelial integrity, respectively, of cryopreserved flaps. For the in vivo phase, flaps were isotransplanted to 35 recipient animals, divided into three groups: fresh (n = 10), perfused (n = 8), and cryopreserved (n = 17). Blood vessel patency was assessed via Doppler at 1, 7, and 60 days post-transplantation. For in vitro studies, cryopreserved samples (10/10) retained normal cell architecture and vascular endothelial integrity upon H/E and factor VIII staining. The viability index of cryopreserved composite flap skin (n = 10) was 11.17 ± 2.01, which was not significantly different from fresh controls (n = 10, 12.15 ± 1.32). All transplanted flaps in the fresh and perfusion groups survived with healthy color and hair growth at 60 days after operation. Survival in the cryopreserved group ranged from 2 to 60 days, with a mean of 12 days. These results demonstrate that the long term survival of cryopreserved composite tissue transplants is possible. Further studies are needed to refine protocols for the reliable cryopreservation of composite parts.     

Apoptosis is required during early stages of tail regeneration in Xenopus laevis

The Xenopus tadpole is able to regenerate its tail, including skin, muscle, notochord, spinal cord and neurons and blood vessels. This process requires rapid tissue growth and morphogenesis. Here we show that a focus of apoptotic cells appears in the regeneration bud within 12 h of amputation. Surprisingly, when caspase-3 activity is specifically inhibited, regeneration is abolished. This is true of tails both before and after the refractory period. Programmed cell death is only required during the first 24 h after amputation, as later inhibition has no effect on regeneration. Inhibition of caspase-dependent apoptosis results in a failure to induce proliferation in the growth zone, a mispatterning of axons in the regenerate, and the appearance of ectopic otoliths in the neural tube, in the context of otherwise normal continued development of the larva. Larvae amputated during the refractory stage exhibit a much broader domain of caspase-3-positive cells, suggesting a window for the amount of apoptosis that is compatible with normal regeneration. These data reveal novel roles for apoptosis in development and indicate that a degree of apoptosis is an early and obligate component of normal tail regeneration, suggesting the possibility of the existence of endogenous inhibitory cells that must be destroyed by programmed cell death for regeneration to occur.     

RUS家族对植物生长发育的调控作用

叶绿体基因组编码许多参与光合作用和其他代谢过程的关键蛋白质,在叶绿体中合成的代谢物对于植物正常的生长发育至关重要。根对紫外线-B辐射敏感[Root-UVB (ultraviolet radiation B)-sensitive, RUS]蛋白属于叶绿体蛋白,由高度保守的DUF647结构域组成,在参与植物形态发生、物质运输和能量代谢等多种生命活动的调控中发挥作用。本文就近年来关于RUS家族在植物的胚胎发育、光形态建成、维生素B6稳态、生长素转运和花药发育等生长发育过程中的相关研究进行回顾和总结,为深入研究其在植物生长发育中的分子调控机制提供了参考。     

Physical localization of the 18S-5.8S-26S rDNA and sequence analysis of ITS regions in Thinopyrum ponticum (Poaceae: Triticeae): implications for concerted evolution

Fluorescence in situ hybridization was used in Thinopyrum ponticum, a decaploid species, and its related diploid species, to investigate the distribution of the 18S-5.8S-26S rDNA. The distribution of rDNA was similar in all three diploid species (Th. bessarabicum, Th. elongatum and Pseudoroegneria stipifolia). Two pairs of loci were observed in each somatic cell at metaphase and interphase. One pair was located near the terminal end and the other in the interstitial regions of the short arms of one pair of chromosomes. However, all of the major loci in Th. ponticum were located on the terminal end of the short arms of chromosomes, and one chromosome had only one major locus. The maximum number of major loci detected on metaphase spreads was 20, which was the sum of that of its progenitors. The interstitial loci that exist in the possible diploid genome donor species were probably 'lost' during the evolutionary process of the decaploid species. A number of minor loci were also detected on whole regions of two pairs of homologous chromosomes. These results suggested that the position of rDNA loci in the Triticeae might be changeable rather than fixed. Positional changes of 18S-5.8S-26S rDNA loci between Th. ponticum and its candidate genome donors indicate that it is almost impossible to find a genome in the polyploid species that is completely identical to that of its diploid donors. The possible evolutionary significance of the distribution of the rDNA is also discussed. Internal transcribed spacer (ITS) regions of nuclear DNA in Th. ponticum were investigated by PCR amplification and sequencing. The sequence data from five positive clones selected at random, together with restriction site analysis, indicated that the ITS repeated units are nearly homogeneous in this autoallodecapolypoid species. Combined with in situ hybridization results, the data led to the conclusion that the ITS region has experienced interlocus as well as intralocus concerted evolution. Phylogenetic analyses showed that the sequences from Th. ponticum have concerted to the E genome repeat type.     

Effect of flow baffles on the dialysate flow distribution of hollow-fiber hemodialyzers: a nonintrusive experimental study using MRI

We used an innovative, nonintrusive MRI technique called the two-dimensional (2D) Phase-Contrast (2DPC) velocity-imaging technique to investigate the effect of flow baffles on the dialysate-side flow distribution in two different hollow-fiber hemodialyzers (A and B); each with flow rates between 200 and 1000 mL/min (3.33 x 10(-6) and 1.67 x 10(-5) m3/s). Our experimental results show that (1) the dialysate-side flow distribution was nonuniform with channeling flow occurred at the peripheral cross section of these hollow-fiber hemodialyzers, and (2) the existing designs of flow baffles failed to promote uniform dialysate-side flow distribution for all flow rates studies.