How the RNA isolation method can affect microRNA microarray results

The quality of RNA is crucial in gene expression experiments. RNA degradation interferes in the measurement of gene expression, and in this context, microRNA quantification can lead to an incorrect estimation. In the present study, two different RNA isolation methods were used to perform microRNA microarray analysis on porcine brain tissue. One method is a phenol-guanidine isothiocyanate-based procedure that permits isolation of total RNA. The second method, miRVana? microRNA isolation, is column based and recovers the small RNA fraction alone. We found that microarray analyses give different results that depend on the RNA fraction used, in particular because some microRNAs appear very sensitive to the RNA isolation method. We conclude that precautions need to be taken when comparing microarray studies based on RNA isolated with different methods.     

Curtailing transmission of severe acute respiratory syndrome within a community and its hospital

Severe acute respiratory syndrome (SARS) has been transmitted extensively within hospitals, and healthcare workers (HCWs) have comprised a large proportion of SARS cases worldwide. We present a stochastic model of a SARS outbreak in a community and its hospital. For a range of basic reproductive numbers (R(0)) corresponding to conditions in different cities (but with emphasis on R(0) approximately 3 as reported for Hong Kong and Singapore), we evaluate contact precautions and case management (quarantine and isolation) as containment measures. Hospital-based contact precautions emerge as the most potent measures, with hospital-wide measures being particularly important if screening of HCWs is inadequate. For R(0) = 3, case isolation alone can control a SARS outbreak only if isolation reduces transmission by at least a factor of four and the mean symptom-onset-to-isolation time is less than 3 days. Delays of a few days in contact tracing and case identification severely degrade the utility of quarantine and isolation, particularly in high-transmission settings. Still more detrimental are delays between the onset of an outbreak and the implementation of control measures; for given control scenarios, our model identifies windows of opportunity beyond which the efficacy of containment efforts is reduced greatly. By considering pathways of transmission in our system, we show that if hospital-based transmission is not halted, measures that reduce community-HCW contact are vital to preventing a widespread epidemic. The implications of our results for future emerging pathogens are discussed.     

Modelling strategies for controlling SARS outbreaks

Severe acute respiratory syndrome (SARS), a new, highly contagious, viral disease, emerged in China late in 2002 and quickly spread to 32 countries and regions causing in excess of 774 deaths and 8098 infections worldwide. In the absence of a rapid diagnostic test, therapy or vaccine, isolation of individuals diagnosed with SARS and quarantine of individuals feared exposed to SARS virus were used to control the spread of infection. We examine mathematically the impact of isolation and quarantine on the control of SARS during the outbreaks in Toronto, Hong Kong, Singapore and Beijing using a deterministic model that closely mimics the data for cumulative infected cases and SARS-related deaths in the first three regions but not in Beijing until mid-April, when China started to report data more accurately. The results reveal that achieving a reduction in the contact rate between susceptible and diseased individuals by isolating the latter is a critically important strategy that can control SARS outbreaks with or without quarantine. An optimal isolation programme entails timely implementation under stringent hygienic precautions defined by a critical threshold value. Values below this threshold lead to control, but those above are associated with the incidence of new community outbreaks or nosocomial infections, a known cause for the spread of SARS in each region. Allocation of resources to implement optimal isolation is more effective than to implement sub-optimal isolation and quarantine together. A community-wide eradication of SARS is feasible if optimal isolation is combined with a highly effective screening programme at the points of entry.     

Transmission dynamics of carbapenemase-producing Klebsiella pneumoniae and anticipated impact of infection control strategies in a surgical unit

Background

Carbapenemase-producing Klebsiella pneumoniae (CPKP) has been established as important nosocomial pathogen in many geographic regions. Transmission from patient to patient via the hands of healthcare workers is the main route of spread in the acute-care setting.

Methodology/Principal Findings

Epidemiological and infection control data were recorded during a prospective observational study conducted in a surgical unit of a tertiary-care hospital in Greece. Surveillance culture for CPKP were obtained from all patients upon admission and weekly thereafter. The Ross-Macdonald model for vector-borne diseases was applied to obtain estimates for the basic reproduction number R₀ (average number of secondary cases per primary case in the absence of infection control) and assess the impact of infection control measures on CPKP containment in endemic and hyperendemic settings. Eighteen of 850 patients were colonized with CPKP on admission and 51 acquired CPKP during hospilazation. R₀ reached 2 and exceeded unity for long periods of time under the observed hand hygiene compliance (21%). The minimum hand hygiene compliance level necessary to control transmission was 50%. Reduction of 60% to 90% in colonized patients on admission, through active surveillance culture, contact precautions and isolation/cohorting, in combination with 60% compliance in hand hygiene would result in rapid decline in CPKP prevalence within 8–12 weeks. Antibiotics restrictions did not have a substantial benefit when an aggressive control strategy was implemented.

Conclusions/Significance

Surveillance culture on admission and isolation/cohorting of colonized patients coupled with moderate hand hygiene compliance and contact precautions may lead to rapid control of CPKP in endemic and hyperendemic healthcare settings.     

Immigrant inviability produces a strong barrier to gene flow between parapatric ecotypes of Senecio lautus

Speciation proceeds when gene exchange is prevented between populations. Determining the different barriers preventing gene flow can therefore give insights into the factors driving and maintaining species boundaries. These reproductive barriers may result from intrinsic genetic incompatibilities between populations, from extrinsic environmental differences between populations, or a combination of both mechanisms. We investigated the potential barriers to gene exchange between three adjacent ecotypes of an Australian wildflower to determine the strength of individual barriers and the degree of overall isolation between populations. We found almost complete isolation between the three populations mainly due to premating extrinsic barriers. Intrinsic genetic barriers were weak and variable among populations. There were asymmetries in some intrinsic barriers due to the origin of cytoplasm in hybrids. Overall, these results suggest that reproductive isolation between these three populations is almost complete despite the absence of geographic barriers, and that the main drivers of this isolation are ecologically based, consistent with the mechanisms underlying ecological speciation.     

Specific regulatory role of phosphorylation of calf thymus DNA-topoisomerase I smaller forms on the relaxational activity expression

Calf thymus Topo I is found to be associated with three active breakdown products, resolved from intact enzyme, which do not appear to be unique to one extraction procedure. They are phosphoproteins, whose enzymatic activity can be modulated through changes in phosphorylation, and which can be phosphorylated 'in vitro', by N II protein kinase, in the same five sites as the intact enzyme. Different amounts of 32P incorporated are observed however, in the corresponding sites. We conclude: 1. proteolysis is probably an 'in vivo' phenomenon, as the Topo I smaller species are observed, during isolation from the earlier crude fractions, and as a minimum of them is always present, even if precautions are taken to minimize proteolysis; 2. a specific regulatory role in the DNA relaxational activity might be played by N II protein kinase phosphorylation, indeed, in the smaller species; 3. the different degrees of 32P incorporation, in analogous phosphorylation sites, might represent a different signal for modulating the gene expression.     

动物外泌体分离方法的研究进展*

外泌体是一种由细胞分泌的细胞外囊泡,其广泛存在于各类生物液中,是细胞间信息交流的途径之一。由于外泌体内携带的核酸、蛋白质及脂质等功能性物质可作为生物标记用于动物生理诊断,也可作为信息传输载体用于调节动物生理状态以及治疗动物疾病,因而受到广泛的研究,开发潜力巨大。建立成熟稳定且方便快捷的外泌体分离手段是保证外泌体相关研究顺利开展的前提。以下对当前动物外泌体分离的主要方法进行了综述,比较了不同分离手段的特点,以此为相关技术的进一步开发与后续的动物外泌体研究提供方法及理论参考。     

Obligatory precautions against infection

If we have a duty not to infect others, how far does it go? This question is often discussed with respect to HIV transmission, but reflection on other diseases like influenza raises a number of interesting theoretical issues. I argue that a duty to avoid infection not only yields requirements for persons who know they carry a disease, but also for persons who know they are at increased risk, and even for those who definitely know they are completely healthy. Given the numerous ways in which human interaction facilitates the spread of communicable diseases, a maximum level of precaution would be very demanding – possibly unreasonably demanding. The ‘over‐demandingness problem’ is mostly invoked as a criticism of utilitarianism, as this theory requires moral agents to always maximise general welfare, even at significant cost for themselves. However, I argue that, with respect to precautions against infectious diseases like influenza, utilitarianism is able to avoid the over‐demandingness problem. A contractualist account, on the other hand, whilst able to explain how one's obligations to avoid infection can be limited, given that other persons have opportunities and responsibilities to protect themselves, in the end requires precautions that raise the over‐demandingness problem.     

Floral isolation is the main reproductive barrier among closely related sexually deceptive orchids

Floral isolation is an important component of pollinator-driven speciation. However, up to now, only a few studies have quantified its strength and relative contribution to total reproductive isolation. In this study, we quantified floral isolation among three closely related, sympatric orchid species of the genus Ophrys by directly tracking pollen flow. Ophrys orchids mimic their pollinators' mating signals, and are pollinated by male insects during mating attempts. This pollination system, called sexual deception, is usually highly specific. However, whether pollinator specialization also conveys floral isolation is currently under debate. In this study, we found strong floral isolation: among 46 tracked pollen transfers in two flowering seasons, all occurred within species. Accounting for observation error rate, we estimated a floral isolation index ≥0.98 among each pair of species. Hand pollination experiments suggested that postpollination barriers were effectively absent among our study species. Genetic analysis based on AFLP markers showed a clear species clustering and very few F(1) hybrids in natural populations, providing independent evidence that strong floral isolation prevents significant interspecies gene flow. Our results provide the first direct evidence that floral isolation acts as the main reproductive barrier among closely related plant species with specialized pollination.     

Laboratory studies of the effects of short‐term isolation on aggressive behaviour in fish

A review of the literature on the effects of short‐term isolation on aggressive behaviour in a variety of fishes reveals different approaches and often conflicting results. This diversity is attributed to a number of factors, including different experimental conditions and specific differences in habitat, behavioural repertoire and social system. Some common trends are identified and the main hypotheses proposed to account for the different results are discussed. Some methodological issues as well as proximate and ultimate mechanisms are examined, and the importance of a standard experimental paradigm in comparative research emphasised.     

Teeth-derived stem cells: A source for cell therapy

Cell therapy is one of the important therapeutic approaches in the treatment of many diseases such as cancer, degenerative diseases, and cardiovascular diseases. Among various cell types, which could be used as cell therapies, stem cell therapy has emerged as powerful tools in the treatment of several diseases. Multipotent stem cells are one of the main classes of stem cells that could originate from different parts of the body such as bone marrow, adipose, placenta, and tooth. Among several types of multipotent stem cells, tooth-derived stem cells (TDSCs) are associated with special properties such as accessible, easy isolation, and low invasive, which have introduced them as a good source for using in the treatment of several diseases such as neural injuries, liver fibrosis, and Cohrn’s disease. Here, we provided an overview of TDSCs particular stem cells from human exfoliated deciduous teeth and clinical application of them. Moreover, we highlighted molecular mechanisms involved in the regulation of dental stem cells fate.     

A note on the effect of different storage procedures on the ability of Preston medium to recover campylobacters

The effect of different storage procedures on the ability of Preston medium to recover campylobacters was investigated. Freshly poured media was shown to recover more campylobacters than media stored under aerobic or anaerobic conditions at room temperature or at 4 degrees C. The growth of Campylobacter laridis was greatly reduced by storage of media and although most strains of C. jejuni and C. coli were not markedly affected, the growth of one strain of C. jejuni was considerably reduced. It is recommended that freshly prepared media be used whenever possible, but if storage is necessary, then plates should be held at 4 degrees C, preferably under anaerobic conditions. These precautions may not be necessary for workers interested solely in C. jejuni or C. coli, but are essential for the optimum isolation of C. laridis.     

A note on the effect of different storage procedures on the ability of Preston medium to recover campylobacters

The effect of different storage procedures on the ability of Preston medium to recover campylobacters was investigated. Freshly poured media was shown to recover more campylobacters than media stored under aerobic or anaerobic conditions at room temperature or at 4dEC. The growth of Campylobacter laridis was greatly reduced by storage of media and although most strains of C. jejuni and C. coli were not markedly affected, the growth of one strain of C. jejuni was considerably reduced. It is recommended that freshly prepared media be used whenever possible, but if storage is necessary, then plates should be held at 4dEC, preferably under anaerobic conditions. These precautions may not be necessary for workers interested solely in C. jejuni or C. coli , but are essential for the optimum isolation of C. laridis.     

Stem cell therapies in cardiac diseases: Current status and future possibilities

Cardiovascular diseases represent the world’s leading cause of death. In this heterogeneous group of diseases, ischemic cardiomyopathies are the most devastating and prevalent, estimated to cause 17.9 million deaths per year. Despite all biomedical efforts, there are no effective treatments that can replace the myocytes lost during an ischemic event or progression of the disease to heart failure. In this context, cell therapy is an emerging therapeutic alternative to treat cardiovascular diseases by cell administration, aimed at cardiac regeneration and repair. In this review, we will cover more than 30 years of cell therapy in cardiology, presenting the main milestones and drawbacks in the field and signaling future challenges and perspectives. The outcomes of cardiac cell therapies are discussed in three distinct aspects: The search for remuscularization by replacement of lost cells by exogenous adult cells, the endogenous stem cell era, which pursued the isolation of a progenitor with the ability to induce heart repair, and the utilization of pluripotent stem cells as a rich and reliable source of cardiomyocytes. Acellular therapies using cell derivatives, such as microvesicles and exosomes, are presented as a promising cell-free therapeutic alternative.     

Etiology of suppurative bacterial meningitis

The results of the laboratory examination of 2034 patients with meningococcal infection and purulent meningitides, hospitalized during the period of June 1980 to October 1983, revealed that three main etiological agents were responsible for these diseases: meningococci, pneumococci and Haemophilus influenzae. The susceptibility of the patients to different etiological agents was found to depend on their age. Children aged up to 3 years constituted 75% of the patients with meningitis caused by H. influenzae; 50% of the patients with meningococcal infection were children aged up to 5 years; pneumococcal meningitis occurred more frequently in adults. Serogroup A meningococci were found to prevail in patients with meningococcal infection. Besides, in children serogroup C meningococci could be isolated in 24% of cases. Since 1983 the cases of the isolation of strains belonging to serogroup B increased in number. Among the pneumococci responsible for the disease serotypes 1, 19, 6 and in children serotype 12 occurred most frequently.     

LMPCR for detection of oligonucleotide-directed triple helix formation: a cautionary note.

We note that precautions are necessary when ligation-mediated PCR (LMPCR) is applied to the detection of oligonucleotide-directed triple helix formation in vitro and in vivo. Synthetic oligonucleotides applied to cell cultures can persist after chemical treatment and genomic DNA isolation and inhibit a key step in LMPCR, causing an artifact that simulates a triplex footprint. Residual oligonucleotides apparently form triplexes during LMPCR, blocking ligation of the unidirectional linker in a site-specific manner. We show that careful removal of residual oligonucleotide prior to LMPCR alleviates this problem.     

3种同域分布的杓兰属植物的种子及杂交种子特征分析

杂交种子研究在一定程度上能说明是否存在杂种不活机制,在植物生殖隔离研究中具有重要意义。通过对同域分布的西藏杓兰(Cypripedium tibeticum)、黄花杓兰(C.flavum)和褐花杓兰(C.calcicola)的自交、异交、杂交种子的形态特征及活性进行分析,发现3种杓兰属植物两两之间均可产生杂交种子,且杂交种子活性较高,杂交种子与其他处理所得种子的外观、表面纹饰无显著性差异;种子宽度、种子长度、有胚率、着色率并没有比自交或异交种子显著低。这一结果表明这3种同域杓兰属植物种与种之间具有相当高的亲和性,它们之间不存在明显的杂种不活机制。黄花杓兰与西藏杓兰或褐花杓兰间的传粉者大小明显不同,黄花杓兰由丽蝇和熊蜂工蜂传粉,而西藏杓兰和褐花杓兰由体形较大的熊蜂蜂王传粉,传粉者隔离已使得它们之间的物种界限比较清晰,因此已经没有必要再产生杂种不活等其他隔离机制。而西藏杓兰与褐花杓兰的传粉者相同,又没有明显的杂种不活隔离机制,暗示它们之间有其他合子后隔离机制或应将其合并为一个种。     

Large Scale Preparation of Myelin Basic Protein from Central Nervous Tissue of Several Mammalian Species

The wide-spread use of and demand for myelin basic protein for immunologic studies has prompted us to re-examine the details of its isolation from CNS tissue of various species. The procedure described in this communication for the isolation and purification of myelin basic protein does not require column chromatography and is therefore suitable for large scale preparation of a reasonably pure product with simple laboratory equipment. If certain precautions are taken, the yield and quality of the product are reproducible. Certain contaminants which may accompany myelin basic protein during purification by procedures currently in use are pointed out, and their possible influence on the immunologic behavior of myelin basic protein is discussed. Suitable electrophoretic techniques for the detection of these contaminants as well as details for their removal from the myelin basic protein are described.     

Neural stem cells in inflammatory CNS diseases: mechanisms and therapy

Autoimmune inflammatory diseases of the central nervous system (CNS) are highly complex in their interaction of different cell populations. The main therapy focus in the last years has been the inhibition of the immune system. Recent progress has shown that endogenous as well as transplanted neural stem cells might positively influence the outcome of such diseases. In this review, we discuss the current concept of the underlying pathogenesis with a specific focus on local CNS cells and potential treatment options.