1,720,962 research outputs found
Genetic instability and chromosomal aberrations in colorectal cancer: A review of the current models
No full textOur understanding of the pathogenesis of cancer has undergone a revolution over the past decade. Tumors develop by the accumulation of damage to genes that regulate cell growth. Many of the genes responsible for disregulation of cell growth have been identified, as have the processes that lead to the genetic damage. One of the most important concepts that has facilitated our understanding of carcinogenesis is that of genetic or "genomic" instability, which is required to permit a sufficient amount of genetic damage to accumulate to permit the neoplastic phenotype to emerge and evolve. Two mechanisms that lead to genomic instability-one of which involves the loss of chromosomal fragments from the nucleus, and a second which is characterized by microsatellite instability-are discusse
JC virus DNA is present in the mucosa of the human colon and in colorectal cancers
No full textJC virus (JCV) is a polyoma virus that commonly infects humans. We have found T antigen DNA sequences of JCV in the mucosa of normal human colons, colorectal cancers, colorectal cancer xenografts raised in nude mice, and in the human colon cancer cell line SW480. A larger number of viral copies is present in cancer cells than in non-neoplastic colon cells, and sequence microheterogeneity occurs within individual colonic mucosal specimens. The improved yield of detection after treatment with topoisomerase I suggests that the viral DNA is negatively supercoiled in the human tissues. These results indicate that JCV DNA can be found in colonic tissues, which raises the possibility that this virus may play a role in the chromosomal instability observed in colorectal carcinogenesis
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
Expression of human MutS homolog 2 (hMSH2) protein in resting and proliferating cells
No full textThe hMSH2 protein plays an important role in the DNA mismatch repair system. Since this system is involved in the correction of errors that occur during DNA replication, we studied the expression of hMSH2 protein in resting and DNA-replicating cells, as well as through the cell cycle in cell types with different growth characteristics. Using Western blot analysis, we showed that hMSH2 protein was detectable in resting peripheral blood lymphocytes and thymocytes. However, when these cells were induced to proliferate, the protein level increased at least 12-fold. In cell-cycle dependent expression studies we chose two DNA mismatch repair proficient cell lines (HEL and HeLa-S3), and flow cytometry was used to monitor cell-cycle progression. At every phase in the cell cycle, the steady-state level of hMSH2 was higher than in resting lymphocytes or thymocytes, and only minor variations of expression level were observed through the cell cycle. In particular, a two to fourfold decrease in hMSH2 expression occurred at G(1) in HEL and at early S phase in HeLa-S3, but higher expression levels resumed during the replicative and postreplicative phases of the cell cycle. Interestingly, hMSH2 protein expression decreased fourfold when HEL cells were induced to differentiate along the megakaryocyte lineage, when continuous DNA replication occurs without mitosis. These results suggest that a basal level of hMSH2 protein expression is necessary for resting and differentiated cells, and that increased hMSH2 protein expression is required when DNA replication is activated and followed by mitosis
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
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