1,720,975 research outputs found
Investigation of undergraduate and master students’ understanding of gene structure and function
No full textThe concept of gene is constantly changing, becoming increasingly complex and difficult to teach and learn. This study investigates the gene concept acquired by Italian undergraduate and master students in biological/natural sciences. The undergraduate students attended a basic biology course the year before the survey, while the master students attended a general genetics course two years before. Students were asked to answer the open-ended question 'what is a gene?' Answers were analysed in terms of gene concept (structure and function) and gene-trait relationship. The survey was repeated for five academic years to check if the results fluctuated over time. A significant difference was found between the two groups of students with regard to the gene concept: a simplistic Mendelian conception was prevalent among the undergraduates, whereas a more complex modern/molecular conception prevailed among the master students. Surprisingly, there was no significant difference in the gene-trait relationship: most students in both groups described it in a reductionist way (a single gene determines a trait). These results suggest that there is a need to improve the teaching of biology and genetics, to prevent students from losing sight of the complexity and to avoid oversimplification, which could lead to a deterministic view
Epigenetic dysregulation in various types of cells exposed to extremely low-frequency magnetic fields
Full text linkEpigenetic mechanisms regulate gene expression, without changing the DNA sequence, and establish cell-type-specific temporal and spatial expression patterns. Alterations of epigenetic marks have been observed in several pathological conditions, including cancer and neurological disorders. Emerging evidence indicates that a variety of environmental factors may cause epigenetic alterations and eventually influence disease risks. Humans are increasingly exposed to extremely low-frequency magnetic fields (ELF-MFs), which in 2002 were classified as possible carcinogens by the International Agency for Research on Cancer. This review summarizes the current knowledge of the link between the exposure to ELF-MFs and epigenetic alterations in various cell types. In spite of the limited number of publications, available evidence indicates that ELF-MF exposure can be associated with epigenetic changes, including DNA methylation, modifications of histones and microRNA expression. Further research is needed to investigate the molecular mechanisms underlying the observed phenomena
Effect of electromagnetic field exposure on the transcription of repetitive DNA elements in human cells
No full textRepetitive DNA (RE-DNA) was long thought to be silent and inert; only recent research has shown that it can be transcribed and that transcription alteration can be induced by environmental stress conditions, causing human pathological effects. The aim of this study was to determine whether exposure to radiofrequency electromagnetic fields (RF-EMF) could affect the transcription of RE-DNA. To this purpose, three different human cell lines (HeLa, BE(2)C and SH-SY5Y) were exposed to 900 MHz GSM-modulated RF-EMF at specific absorption rate of 1 W/kg or to sham. After exposure, mRNA levels of RE-DNA were evaluated through quantitative real-time PCR. The following RE-DNA types were investigated: Long Interspersed nucleotide Element 1, DNA alpha satellite and Human Endogenous Retroviruses-like sequences. When comparing cells exposed to RF-EMF versus control samples, different results were found for the three cell lines evaluated, indicating that RF-EMF exposure can significantly affect RE-DNA transcription and that the effects strongly depend on the cellular context and the tissue type. Further studies are needed to elucidate which molecular mechanisms could be involved
Long INterspersed element-1 mobility as a sensor of environmental stresses
No full textLong INterspersed element (LINE-1, L1) retrotransposons are the most abundant transposable elements in the human genome, constituting approximately 17%. They move by a “copy-paste” mechanism, involving reverse transcription of an RNA intermediate and insertion of its cDNA copy at a new site in the genome. L1 retrotransposition (L1-RTP) can cause insertional mutations, alter gene expression, transduce exons, and induce epigenetic dysregulation. L1-RTP is generally repressed; however, a number of observations collected over about 15 years revealed that it can occur in response to environmental stresses. Moreover, emerging evidence indicates that L1-RTP can play a role in the onset of several neurological and oncological diseases in humans. In recent years, great attention has been paid to the exposome paradigm, which proposes that health effects of an environmental factor should be evaluated considering both cumulative environmental exposures and the endogenous processes resulting from the biological response. L1-RTP could be an endogenous process considered for this application. Here, we summarize the current understanding of environmental factors that can affect the retrotransposition of human L1 elements. Evidence indicates that L1-RTP alteration is triggered by numerous and various environmental stressors, such as chemical agents (heavy metals, carcinogens, oxidants, and drugs), physical agents (ionizing and non-ionizing radiations), and experiential factors (voluntary exercise, social isolation, maternal care, and environmental light/dark cycles). These data come from in vitro studies on cell lines and in vivo studies on transgenic animals: future investigations should be focused on physiologically relevant models to gain a better understanding of this topic
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Autoaggregation and adhesion ability in a Bifidobacterium suis strain
No full textOn the basis of autoaggregation ability, two different phenotypes (Agg + and Agg -) were selected from a strain (BSu895) of Bifidobacterium suis. The relationship between autoaggregation and adhesion of bacteria to intestinal tissue was investigated by observing the adhesivity of the two phenotypic variants to ileum and colon tissue pieces collected from six new-born piglets. The results suggest that there is a good relationship between autoaggregation and adhesion as variant Agg + (autoaggregating) has a stronger adhesion ability than Agg - (non-autoaggregating)
Relationship between postpartum uterine involution and biomarkers of inflammation and oxidative stress in clinically healthy mares (Equus caballus)
Full text linkTo test the hypothesis that delayed/impaired uterine involution could be associated with oxinflammation, westudied the progression of the uterine involution in association with some biomarkers of inflammation andoxidative stress in clinically healthy mares (N1⁄426) during early postpartum. The examination of the repro-ductive tract was performed on Days 7 and 21 after foaling. Uterine involution was assessed considering: a) theincrease of the gravid uterine horn diameter (GUHD) compared with diameter recorded before pregnancy duringthe previous breeding season; b) the level of endometrial edema (EE); c) the degree of accumulation of intra-uterinefluid (IUFA); d) the status of the cervix (CS). Inflammation and oxidative stress were studied by measuringserum amyloid A (SAA), cortisol, DHEA, AOPP, protein carbonyl groups, malondialdheyde (MDA) and thiols inplasma on Days 7 and 21. By Day 21 after parturition, a significant improvement (P<0.01) was observed forGUHD and EE; while IUFA increased in six animals. Plasma SAA and DHEA concentrations were higher when theclinical parameters indicated a lower degree of uterine involution. On Day 7, the cortisol/DHEA ratio was lower inanimals with higher degree of EE. Plasma AOPP and MDA concentrations were significantly lower (P<0.05) inanimals with the lower GUHD. On Day 21, plasma MDA concentrations were significantly lower (P<0.05) inanimals with the lower IUFA. Our data suggest that a mild condition of inflammation and oxidative stress occur inmares with delayed/impaired uterine involution
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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