1,720,976 research outputs found
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
Effect of cytidine analogs on cell growth and differentiation on a human neuroblastoma line.
No full textThe cytidine analog 5-AZA-2'-deoxycytidine (5-AZA-CdR) has been demonstrated to induce cellular differentiation; on the other hand, induction of differentiation has been suggested as a possible form of therapy for leukemic cells. We have evaluated the possibility that the neuroblastoma malignant tumor growth could be controlled by treatment that promotes the differentiation of immature tumor cells. We have previously reported on differentiation of murine neuroblastoma cells (41A3) treated with 5-AZA-CdR. In this paper, we describe the effect of 5-AZA-CdR on human neuroblastoma cell line CHP-100. The drug-treated cells show some degree of differentiation, demonstrated by morphological and biochemical markers. A significant DNA hypomethylation and partial inhibition of DNA synthesis and cell proliferation is also observed. This effect is more stable than that caused by another cytidine analog, Cytosine-beta-D-Arabinofuranoside (ARA-C)
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
Gene deletions in an infertile man with sperm fibrous sheath dysplasia
No full textBACKGROUND:
Asthenozoospermia may sometimes be related to genetic structural defects of the sperm tail detectable by transmission electron microscopy. Dysplasia of the fibrous sheath (DFS) is a genetic sperm defect, characterized by dysplastic development of the axonemal and periaxonemal cytoskeleton. We report the case of an infertile man with normal sperm count and total sperm immotility in which dysplasia of the fibrous sheath, Akap3, Akap4 gene deletions, meiotic segregation of chromosomes 18, X and Y and Y microdeletions were investigated.
METHODS:
A 32-year-old man with a 3-year history of primary infertility presented at our Regional Referral Center for Male Infertility. Family medical history, lymphocyte karyotype, PCR analysis, physical examination, hormone assays and semen analysis were performed.
RESULTS:
Ultrastructural sperm evaluation showed dysplasia of the fibrous sheath. Immunostaining of AKAP4 protein was negative in sperm tails. PCR analysis revealed intragenic deletions of the Akap3 and Akap4 genes. Fluorescence in situ hybridization on sperm showed a high frequency of XY disomy.
CONCLUSION:
In this infertile patient, our results suggest a possible relationship between dysplasia of the fibrous sheath, partial deletions in the Akap3 and Akap4 genes and absence of AKAP4 protein in the fibrous sheath. These findings, however, were not detected in another four patients with dysplasia of the fibrous sheath. Our results require future confirmatory molecular analyses
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
Infertile spermatozoa in a human carrier of Robertsonian translocation (14;22)
No full textObjective: To present the ultrastructural, functional, and chromosomal analyses of spermatozoa from an infertile man with normal phenotype and chromosomal translocation 14;22.
Design: Case report.
Setting: Regional Reference Center for Male Infertility in Siena, Italy.
Patient(s): A 36-year-old man with primary infertility for 3 years and his parents.
Intervention(s): Family history and lymphocytic karyotypes, physical and hormonal assays, and semen analysis.
Main Outcome Measure(s): Morphological sperm evaluation was performed by light, fluorescent, and electron microscopy; chromosomal constitution was examined by the fluorescence in situ hybridization (FISH) technique. The penetration ability of spermatozoa was checked by the hamster test.
Result(s): The spermatozoa of the patient showed unusual ultrastructural defects. The nuclei were large, spheroidal, and generally uncondensed; the acrosomes were frequently absent or reduced; and the axonemes were often devoid of dynein arms or central singlet tubules. These characteristics are related to immaturity. The lymphocytic karyotype revealed a robertsonian translocation 14;22 in the sterile patient and his mother. FISH sperm analysis demonstrated a high frequency of diploidy for the chromosome 18,XY. The hamster penetration test gave negative results.
Conclusion(s): The unusual structural sperm immaturity is associated with the translocation 14;22. This chromosomal anomaly may therefore negatively influence the spermatogenesis; an interchromosomal effect on meiosis segregation is also suggested
5-Aza-2'-deoxycytidine as inducer of differentiation and growth inhibition in mouse neuroblastoma cells
No full textWe studied the effect of 5-aza-2'-deoxycytidine (5-AZA-CdR) on the differentiation of murine 41A3 neuroblastoma cells. Neuroblastoma cells treated with 0.1-1.0 microM 5-AZA-CdR underwent differentiation; markers of neuronal functions, such as acetylcholinesterase activity and growth of nerve fibers, were expressed at a higher level in the drug-treated cells than in the controls. This increased expression was accompanied by significant hypomethylation of newly synthesized DNA. A secondary event seemed to be a partial inhibition of DNA synthesis, cell proliferation and colony-forming activity. These effects were more pronounced than those caused by the related cytidine analog, 1-beta-D-arabinosil-cytosine (ARA-C). The results obtained suggest that 5-AZA-CdR may be an effective agent for the growth control of human neuroblastoma cells
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