A Review of the Macroscopic, Microscopic, and Ultramicroscopic Characteristics of Some Key Oocyte Developmental Processes in Fish Species

Studies involving the reproductive biology of fish have several possibilities of approach, such as the understanding of gonadal development, oocyte development, and the reproductive cycle of the species. In addition, analyses of gonadal morphology can be made at macro-, micro-, and ultramicroscopic levels. This knowledge helps to define factors that determine the different stages of gonadal development, as well as the “triggers” that initiate the reproductive process. In females, the growth and maturation of the ovarian follicles depend on a carefully elaborated communication between the follicular cells and the oocyte and a precisely organized contractile system. Changes in these systems appear to be related to apoptotic cells. This extensive remodeling of gonadal tissue, due to cell proliferation and differentiation, promotes also changes in the extracellular matrix. With this in mind, we provide herein a complementary and in-depth information on cell-cell and cell-matrix interactions related to the process of oocyte development in fish species. This information, together with the existing structural and ultrastructural descriptions of ovaries of different species, will enable a better understanding of the reproductive processes for the group of fish

Development of morphofunctional changes in the ovaries of Astyanax altiparanae Garutti and Britski 2000 (Teleostei, Characidae).

Este estudo apresenta: (1) uma revisão atualizada sobre o desenvolvimento oocitário em teleósteos, as vias de involução no processo de regressão ovariana e a espécie modelo Astyanax altiparanae; (2) a descrição da morfologia ovariana e das células garminativas de A. altiparanae e a caracterização do seu ciclo reprodutivo; (3) a caracterização dos processos de involução de atresia folicular e complexos pós-ovulatórios de A. altiparanae e a localização de proteínas envolvidas nas vias de apoptose e autofagia ao longo desses processos. Foram apresentados neste estudo novos detalhes da oogênese para espécies de Astyanax, sendo que esses novos dados parecem ter aplicação na piscicultura. Além disso, A. altiparanae apresenta um período de desova longo, com pico reprodutivo de outubro a fevereiro, e desenvolvimento oocitário assíncrono. Por fim, parece haver uma interrelação entre as vias de autofagia e apoptose nos processos de involução ovarianos e as vias regulatórias desses processos parecem ser conservadas entre espécies de teleósteos com fertilização externa.This study presents: (1) an updated review on oocyte development in teleosts, the involution pathways during the process of ovarian regression, and the model species Astyanax altiparanae; (2) the description of the ovarian and germ cell morphology of A. altiparanae and the characterization of its reproductive cycle; (3) the characterization of the involution processes of follicular atresia and post-ovulatory complexes of A. altiparanae and the localization of proteins involved in the apoptosis and autophagy pathways throughout these processes. New details of the oogenesis for Astyanax species were presented in this study, and these new data seem to be applied in fish culture. In addition, A. altiparanae presents a long spawning period, with reproductive peak from October to February, and asynchronous oocyte development. Finally, there seems to be a crosstalk between autophagy and apoptosis pathways in ovarian involution processes and the regulatory pathways of these processes seem to be conserved among species of teleosts with external fertilization

Who can save the subaltern? Knowledge and power in Amitav Ghosh�s The Circle of Reason

This article will explore the relationship between subaltern subjectivity, global itineraries and knowledge production in Ghosh's first novel The Circle of Reason, published in 1986. Various discourses both construct and represent the subaltern in the novel: discourses of global migration, national power as bureaucratic fetishism, science as social mission. My argument is that the narrative enacts a tension between these discourses (embodied in the figures of scientists, theorists, bureaucrats) and the local communities of people that this knowledge affects. I am interested in exploring this discrepancy not as a theory/elite versus praxis/subaltern polarity but rather to focus on the effects unleashed by people or groups who represent the subaltern (for good or ill) in the novel

Gonadotropin subunits of the characiform Astyanax altiparanae : Molecular characterization, spatiotemporal expression and their possible role on female reproductive dysfunction in captivity

To better understand the endocrine control of reproduction in Characiformes and the reproductive dysfunctions that commonly occur in migratory fish of this order when kept in captivity, we chose Astyanax altiparanae, which has asynchronous ovarian development and multiple spawning events, as model species. From A. altiparanae pituitary total RNA, we cloned the full-length cDNAs coding for the follicle-stimulating hormone β subunit (fshb), the luteinizing hormone β subunit (lhb), and the common gonadotropin α subunit (gpha). All three sequences showed the highest degree of amino acid identity with other homologous sequences from Siluriformes and Cypriniformes. Real-time, quantitative PCR analysis showed that gpha, fshb and lhb mRNAs were restricted to the pituitary gland. In situ hybridization and immunofluorescence, using specific-developed and characterized polyclonal antibodies, revealed that both gonadotropin β subunits mRNAs/proteins are expressed by distinct populations of gonadotropic cells in the proximal pars distalis. No marked variations for lhb transcripts levels were detected during the reproductive cycle, and 17α,20β-dihydroxy-4-pregnen-3-one plasma levels were also constant, suggesting that the reproductive dysfunction seen in A. altiparanae females in captivity are probably due to a lack of increase of Lh synthesis during spawning season. In contrast, fshb transcripts changed significantly during the reproductive cycle, although estradiol-17β (E2) levels remained constant during the experiment, possibly due to a differential regulation of E2 synthesis. Taken together, these data demonstrate the putative involvement of gonadotropin signaling on the impairment of the reproductive function in a migratory species when kept in captivity. Future experimental studies must be carried to clarify this hypothesis. All these data open the possibility for further basic and applied studies related to reproduction in this fish model