RNA splicing in lower eukaryotes.

Recently, cis-acting elements and trans-acting RNA and protein factors necessary for splicing nuclear pre-mRNAs, group II introns or group III introns, have been discovered, and new roles for the splicing factors have been elucidated. Parallels among the pathways for splicing these different classes of introns have been identified.     

EGF and TGF-alpha stimulate retinal neuroepithelial cell proliferation in vitro.

Peptide growth factors have been shown to have diverse effects on cells of the CNS, such as promoting neuronal survival, neurite outgrowth, and several other aspects of neuronal differentiation. In addition, some of these factors have been shown to be mitogenic for particular classes of glial cells within the brain and optic nerve, and recently two peptide growth factors, fibroblast growth factor and nerve growth factor, have been shown to have mitogenic activity on the CNS neuronal progenitors. We now report that two members of another peptide growth factor, epidermal growth factor and transforming growth factor-alpha, are mitogenic for retinal neuroepithelial cells in primary cultures and provide evidence for the presence of both of these factors in normal developing rat retina.     

Lineage Specifiers： New Players in the Induction of Pluripotency

Pluripotency-associated factors and their rivals,lineage specifers,have long been considered the determining factors for the identity of pluripotent and differentiated cells,respectively.Therefore,factors that are employed for cellular reprogramming in order to induce pluripotency have been identifed mainly from embryonic stem cell(ESC)-enriched and pluripotency-associated factors.Recently,lineage specifers have been identifed to play important roles in orchestrating the process of restoring pluripotency.In this review,we summarize the latest discoveries regarding cell fate conversion using pluripotency-associated factors and lineage specifers.We highlight the value of the‘‘seesaw’’model in defning cellular identity,opening up a novel scenario to consider pluripotency and lineage specifcation.     

肌腱再生相关转录因子研究进展

肌腱作为骨骼和肌肉的连接往往容易受到损伤,目前对肌腱基本生物学有限的了解妨碍了肌腱修复技术的发展。最近,一系列肌腱生长相关因子被发现,其中Scleraxis(Scx)和Mohawk(Mkx)已被确定为肌腱生长和分化中的关键转录因子,Sox9和EGR1/2也被报道参与肌腱的生长。然而,目前研究尚未明确这些转录因子的生物学功能及其分子机制。本文就上述转录因子的分布与功能,及转录因子相关分子进行综述,为肌腱的修复提供生物学基础并探讨肌腱损伤治疗的未来发展方向。     

Understanding the interacting factors that determine ecological effectiveness of terrestrial protected areas

Protected areas are recognized as an essential tool to safeguard habitat integrity and biodiversity in the Anthropocene. Substantial efforts have been made to clarify the conditions under which they deliver conservation outcomes effectively. Location, spatial design, management strategy and threats, have commonly been identified as key factors. The impacts of these factors have, however, often been evaluated independently, and there is limited information on how their combined and interactive effects can improve or hinder protected area effectiveness. Here we develop a framework for understanding the combined effects of these factors. This has important implications for how protected areas are established and maintained.     

Uridine insertion/deletion RNA editing in trypanosome mitochondria: a complex business

The basic mechanism of uridine insertion/deletion RNA editing in mitochondria of kinetoplastid protists has been established for some time but the molecular details remained largely unknown. Recently, there has been significant progress in defining the molecular components of the editing reaction. A number of factors have been isolated from trypanosome mitochondria, some of which have been definitely implicated in the uridine insertion/deletion RNA editing reaction and others of which have been circumstantially implicated. Several protein complexes have been isolated which exhibit some editing activities, and the macromolecular organization of these complexes is being analyzed. In addition, there have been several important technical advances in the in vitro analysis of editing. In this review we critically examine the various factors and complexes proposed to be involved in RNA editing.     

Distribution of "classic" virulence factors among Salmonella spp

Whether an infection with Salmonella spp. leads to a disease largely depends on the virulence of the strain and the constitution of the host. The virulence of the strain is determined by so-called virulence factors. Whereas a number of virulence factors of Salmonella have been identified only recently, others have been studied for decades. These latter virulence factors i.e., virulence-plasmids, toxins, fimbriae and flagella are therefore referred to as "classic" virulence factors. Here we present an overview on the distribution of (genes coding for) these virulence factors among Salmonella spp. The pathogenicity islands of Salmonella are also reviewed, all be it briefly, since they contain a major part of the virulence genes.     

Persistence of bacterial pathogens as a physiological phenomenon

The complex ecosystem of humans and microbes has been presented as an associative symbiosis based on a mutual support of symbionts with different consequences for them. Conditions for the persistence of bacteria have been defined: their resistance to environmental factors, antagonism in biocenosis, and stability to withstand host defense mechanisms. The key role of bacterial peptidoglycan has been defined for their survival in an infected organism, and the classification for persistent mechanisms of pathogens has been given. The group of bacterial secreted protease providing microbial resistance to defense factors of the organism has been described. Host colonizing resistance has been presented as a physiological regulatory system controlling bacterial penetration into an organism. Regulatory mechanisms for bacterial persistence have been discussed.     

Six distinct nuclear factors interact with the 75-base-pair repeat of the Moloney murine leukemia virus enhancer.

Binding sites for six distinct nuclear factors on the 75-base-pair repeat of the Moloney murine leukemia virus enhancer have been identified by an electrophoretic mobility shift assay combined with methylation interference. Three of these factors, found in WEHI 231 nuclear extracts, which we have named LVa, LVb, and LVc (for leukemia virus factors a, b, and c) have not been previously identified. Nuclear factors that bind to the conserved simian virus 40 corelike motif, the NF-1 motif, and the glucocorticoid response element were also detected. Testing of multiple cell lines showed that most factors appeared ubiquitous, except that the NF-1 binding factor was found neither in nuclear extracts from MEL cells nor in the embryonal carcinoma cell lines PCC4 and F9, and core-binding factor was relatively depleted from MEL and F9 nuclear extracts.     

Factors affecting the genetic engineering of plants by microprojectile bombardment

Since its development in the mid-1980s, microprojectile bombardment has been widely employed as a method for direct gene transfer into a wide range of plants, including the previously difficult-to-transform monocotyledonous species. Although the numerous instruments available for microprojectile-mediated gene delivery and their applications have been widely discussed, less attention has been paid to the critical factors which affect the efficiency of this method of gene delivery. In this review we do not wish to describe the array of devices used for microprojectile delivery or their uses which have already been definitively described, but instead wish to report on research developments investigating the factors which affect microprojectile-mediated transformation of plants.     

Development of regional characterization factors for aquatic eutrophication

Background, aim, and scope  

Life cycle assessment (LCA) has traditionally been considered a site-independent tool, but nowadays, there is a trend towards making LCA more site-dependent. Site-dependent characterization factors have been calculated for regional impact categories such as acidification, terrestrial and aquatic eutrophication, and smog. Specifically, for aquatic eutrophication, characterization factors have been proposed for large geographical areas (mainly European and North American countries). Those factors are not detailed enough for countries which present large geographical, climatic, and economical variability such as Spain. Therefore, this work aims to calculate the characterization factors and the normalization reference for aquatic eutrophication at a regional level, using Galicia (NW Spain), a region with increasing problems of eutrophication, as a case study. Finally, the comparison of the factors obtained here with literature values will be used to analyze the influence of spatial differentiation with increasing coverage of the causality chain.     

A simple procedure for isolation of eukaryotic mRNA polyadenylation factors.

We have devised a simple chromatographic procedure which isolates five polyadenylation factors that are required for polyadenylation of eukaryotic mRNA. The factors were separated from each other by fractionation of HeLa cell nuclear extract in two consecutive chromatographic steps. RNA cleavage at the L3 polyadenylation site of human adenovirus 2 required at least four factors. Addition of adenosine residues required only two of these factors. The fractionation procedure separates two components that are both likely to be poly(A) polymerases. The candidate poly(A) polymerases were interchangeable and participated during both RNA cleavage and adenosine addition. They were discriminated from each other by chromatographic properties, heat sensitivity and divalent cation requirement. We have compared our data with published information and have been able to correlate the activities that we have isolated to previously identified polyadenylation factors. However, we have not been able to assign one of the candidate poly(A) polymerases to a previously identified poly(A) polymerase. This simple fractionation procedure can be used for generating an in vitro reconstituted system for polyadenylation within a short period of time.     

Determining the number of factors in P-technique factor analysis

Determining the number of factors is a critical first step in exploratory factor analysis. Although various criteria and methods for determining the number of factors have been evaluated in the usual between-subjects R-technique factor analysis, there is still question of how these methods perform in within-subjects P-technique factor analysis. A novel feature of P-technique data is that observations are usually sequentially dependent in some way. The current study evaluates 10 criteria for determining the number of factors for data simulated to resemble intensive repeated-measures data for which P-technique is usually applied. The number of factors, loading size, observed-to-latent ratio, serial-dependency, and sample size were simulation design factors with conditions simulated to resemble P-technique data. The methods are compiled from various statistical techniques and have been demonstrated in previous R-technique simulations. Finally, a real data example demonstrates applying the acceleration factor method to several time series data sets.