1,720,986 research outputs found
Comparison between rDNA magnification and bb lethal mutation frequencies in Drosophila melanogaster.
No full textUnequal mitotic sister strand crossing over has been evoked to explain the occurrence of phenotypically bb+ males in the progeny of phenotypically bobbed males during magnification. If this is the case, complementary bbl loci should be obtained together with the bb+. To test this hypothesis we compared the frequency of bb lethal mutations in the sperms of bb males with the percentages of phenotypically bb+ males obtained during magnification of these bb males. We then compared these values with those occurring in phenotypically bb+ control males. We found that, while the number of bb+ males obtained during magnification, though variable, is high, the bb lethal mutation occurs at a very low frequency in all the genetic conditions, whatever the phenotype of the parental male
Molecular genetics of oogenesis in Drosophila melanogaster
No full textGonadal development requires complex differentiation programs leading to the production offunctional female and male gametes. Upon fertilization, while the male germ cell contributes to thenewly formed zygote only its genetic material, the female germ cell also supplies its cytoplasmiccomponents, including fundamental molecular cues on which early embryonic development will rely.Unravelling the mechanisms employed by animal species for building up their eggs is therefore achallenging task in developmental biology. As demonstrated by the impressive body of data producedin recent years, Drosophila melanogaster is a useful model system for attempting a step by stepdissection of the whole oogenesis process. Remarkable opportunities for comparative analyses are inturn expected to be provided by these studies, since it is becoming evident that conserved themesunderlie oogenesis in all animal species. In this review, we focus on few key differentiation eventsoccurring during egg chamber development in Drosophila, outlining our interest in the mechanismsleading to egg polarity establishment, transfer of information between nuclear and cytoplasmic cellcompartments and germ cell apoptosis
The first steps of magnification of DNA complementary to ribosomal RNA in D. melanogaster.
No full text
Protein tyrosine phosphatases of Toxoneuron nigriceps bracovirus as potential disrupters of host prothoracic gland function
No full textThe genomic sequence of the bracovirus associated with the wasp Toxoneuron nigriceps (Hymenoptera, Broconidae) (TnBV), an endophagous parasitoid of the tobacco budworm larvae, Heliothis virescens (Lepidoptera, Noctuidoe), contains a large gene family coding for protein tyrosine phosphatoses (PTPs). Here we report the characterization of cDNAs for two of the viral PTPs isolated by screening a cDNA library from haemocytes of parasitized host larvae. The two encoded proteins show 70% amino acid identity and are expressed in the fat body of parasitized hosts. In addition, one was expressed in inactivated prothoracic glands (PTGs), 24 h after parasitoid oviposition. The rapid block of ecdysteroidogenesis does not appear to be due to inhibition of general protein synthesis, as indirectly indicated by the unaltered S6 kinase activity in the cytosolic extracts of basal PTGs from parasitized host larvae. Rather, TnBV PTP over-expression in inactivated host PTGs suggests that gland function may be affected by the disruption of the phosphorylation balance of key proteins regulating points upstream from the ribosomal S6 phosphorylation in the PITH signaling cascade
rDNA magnification at the bobbed locus of the Y chromosome in Drosophila melanogaster. Cell Differentiation
No full text
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
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
- …
