1,721,137 research outputs found
La tomba del Tifone: effetti speciali etruschi
No full textGli autori esaminano la Tomba del Tifone di Tarquinia da tre diversi punti di vista archeologici: architettura e impaginato (G. Bagnasco Gianni); pittura tombale (M. Marzullo); scelte iconografiche legate a creature mostruose (L. Perego
Molecular cloning and tissue-specific expression of the mouse homolog of the rat brain 14-3-3 theta protein: characterization of its cellular and developmental pattern of expression in the male germ line
No full textThe highly conserved 14-3-3 family of proteins, originally reported as brain-specific and then found in various somatic cells and oocytes, interacts with several important signal transduction kinases so that actually the 14-3-3 proteins ave considered as modulators of multiple signal transduction pathways. Here we show that a 14-3-3 protein is also expressed in the male germ cells, thus extending the protein cellular distribution to a cell line never reported to express 14-3-3 proteins. Screening of a mouse spermatogenic cells lambda gt11 cDNA library with affinity-purified polyclonal antibodies to the tyrosine kinase SP42 allowed the isolation of several positive clones. Sequencing of a positive cDNA clone revealed a 735-nucleotide open reading frame encoding a protein of 245 amino acids (27,778 Da). The predicted protein was found to be identical to the most recently discovered 14-3-3 isoform, the theta subtype from a rat brain. Here we demonstrate that 14-3-3 theta mRNA is highly expressed in testis and brain only. Western immunoblot analyses confirm the Northern blot data. Developmental Northern and Western blot analyses are consistent with an expression and translation of the 14-3-3 theta gene throughout spermatogenesis. However, analysis of RNA from purified populations of spermatogenic cells at different developmental stages and immunohistochemistry on adult testis sections reveal that within the testis the 14-3-3 theta gene products are most abundant in meiotic prophase spermatocytes, and, above all, in differentiating spermatids. Both testicular and epididymal spermatozoa are negative. The present study is the first report on the presence and molecular characterization of the 14-3-3 theta gene product in the male germ line. Our observations suggest that this specific member of the 14-3-3 protein family could play distinct modulatory roles in the complex development of the mammalian male germ cell lineage
In vitro manipulation of cryopreserved gametes in the domestic cat
No full textThe availability of preserved gametes would greatly enhance reproductive technologies aimed to the diffusion of valuable cat breeds or to the preservation of biodiversity in wild feline species. In the domestic cat, in vitro fertilization (IVF) or intracytoplasmic injection of frozen spermatozoa resulted in embryo development up to the blastocyst stage. By contrast, cryopreservation of oocytes has met with very little success in animals and humans, due to the unique morphological characteristics of the cells. Various types of cell damage (i.e. cytoskeleton disorganization, DNA abnormality, premature granule exocitosis, etc.) may occur during freezing and meiotic stages vary in their response to cryopreservation. In fact, IVF of frozen cat oocytes resulted in embryo development to the blastocyst stage only when mature (Metaphase II) oocytes were cryopreserved. The cryopreservation of immature oocytes, as donors of germinal vesicles (GVs) for transfer to fresh enucleated oocytes, could be an opportunity to overcome the problem of freezing injuries to the cytoplasm. The transferred GV could respond to meiosis promoting factors present in the recipient cytoplasm, as demonstrated in other species. Our recent results show that high proportions of cat immature oocytes are still viable and their GVs are well preserved after thawing. Removal and transfer of the cryopreserved GVs would allow a better understanding of the physiological mechanisms involved in cat oocyte maturation and a future application of this procedure may aid in the conservation of female valuable germplasm
Intracellular immunolocalization of mouse and rat sp42 and developmental pattern of protein expression in male germ cells
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
Preparation of karyoplasts and cytoplasts from feline oocytes at the germinal vesicle stage
No full textIntroduction. The homologous transfer of oocyte nucleus stage I or germinal vesicle (GV-karyoplast) into an enucleated mouse oocyte (cytoplast) at the same developmental stage, resulted in resumption of meiosis (1) and embryo development in vitro (2) of the reconstructed GV-oocytes. The transfer of GVs derived from cryopreserved oocytes also resulted in a normal progression to metaphase II (MII) in vitro of the reconstructed mouse and bovine oocytes (3,4). It has been shown that the GV is potentially more resilient to cooling than the spindle of MII, because chromosomes are decondensed and enclosed within the nuclear membrane. However, thawed immature cat oocytes show a poor developmental competence in vitro (5), probably due to the occurrence of chilling-induced damages to the cytoplasm. This compartment has a pivotal role in the resumption and completion of oocyte maturation, which is essential for the developmental competence of the embryo. Since the integrity of the oocyte nucleus may be better preserved than the cytoplasm after cryopreservation, the transfer of cryopreserved GVs into fresh enucleated oocytes could improve the chance of embryo development in culture. In the feline species there are no reports in the literature concerning GV transfer. Hence, the purpose of this work was to make a preliminary evaluation of the feasibility of enucleating immature oocytes in order to produce GV-karyoplasts and cytoplasts for GV transfer in cat oocytes.
Materials and methods. A total of 156 immature (GV) cat oocytes collected from anestrous queens after ovariectomy were mechanically deprived of cumulus cells with a small-bore pipette. The oocytes were centrifuged at 14000 rpm for 16 min to obtain the polarization of the cytoplasm and a better visualization of the GV. The nucleus was measured in order to prepare adequate microtools for manipulation. Prior to enucleation, the oocytes were incubated for 30 min at room temperature in a specific medium containing 7.5 g/mL of cytochalasin B (Sigma Chemical Co., USA) for inducing an increase of the oolemmal elasticity and 50 g/mL of 3-isobutyl-1-methylxanthine (IBMX, Sigma) in order to prevent the GV breakdown (1). Following lancing of the zona pellucida with a sharp-tipped pipette, GV nuclei were extruded using a bevelled glass pipette with a diameter adequate to the size of GV in cat oocytes. The GV was surrounded by a small amount of cytoplasm and encapsulated by a membrane (GV-karyoplast). The enucleated oocytes were considered as cytoplasts.
Results. The mean average of GV diameter in oocytes > 120 m of diameter was 35.4 + 5.3 m. A bevelled glass pipette, with inner diameter of 40-45 m, allowed the extrusion of intact and morphologically normal karyoplasts and related cytoplasts in 17.3% (27/156) of micromanipulated oocytes. However, the lancing of the zona pellucida or the extrusion of the karyoplast resulted in rates of 40.4% (63/156) and 42.3% (66/156) of severely damaged oocytes, respectively.
Conclusion. These results suggest that is possible to prepare karyoplasts and cytoplasts from feline oocytes, although the efficiency of the technique is low compared to what has been obtained in mouse (around 90%, 1). This is likely due to the thickness and hardness of zona pellucida, and to the larger diameter of the GV of cat oocytes compared to that of mouse (15 m) or bovine (25-30 m) oocytes. Further experiments based on the partial dissection of the zona pellucida with an acidic solution in order to reduce the oocyte damage and to improve the efficiency of GV transfer in feline oocytes, are in progress in our laboratory.
References
1) 1) Liu et al., Human Reprod 1999; 14:2357-61. 2) Takeuchi et al., Hum Reprod 2004;19:975–81.
3) Moffa et al., Human Reprod 2002;17:178-83. 4) Luciano et al., Reprod Fertil Dev 2006;18:138. 5) Luvoni and Pellizzari, Theriogenology 2000;53:1529-40
Cell viability and germinal vesicle morphological integrity of cryopreserved feline oocytes
No full textVariations 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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