Currently, the storage of fish spermatozoa through cryopreservation is widely used. Although it is of common knowledge that the process of freezing / thawing generates DNA fragmentation of spermatozoa, the consequences of this process on embryonary development are unknown. There is great interest in developing methods for in vitro fertilization for the species Prochilodus lineatus using cryopreserved semen. In this paper we study the embryonic development of this fish, to lay the groundwork for the observation of abnormalities in the development of embryos derived from criopreserved spermatozoa. The eggs produced by this species are translucent and have a large perivitelline space, are of the telolecitic type, and presented meroblastic division during the early stages of development. Although the embrionary development of Prochilodus lineatus (Sábalo) took place in less time compared with Danio rerio (Zebrafish) the embryo goes through very similar stages. During the study it was possible to observe the periods of zygote, cleavage, blastula, gastrula, segmentation and hatching of the larvae of Sábalo. The different stages of development were successfully recorded, especially those after the transition of blastula media (TBM), when the embryo begins to transcribe its own genome.

El almacenamiento de espermatozoides de peces por medio de la criopreservación es muy utilizado hoy en día. Si bien se sabe que el proceso de congelamiento/descongelamiento genera la fragmentación del ADN del espermatozoide, no se conocen las consecuencias que esto tiene en el desarrollo embrionario. Actualmente hay un gran interés en el desarrollo de métodos de fecundación in vitro para la especie Prochilodus lineatus utilizando semen criopreservado. En este trabajo estudiamos el desarrollo embrionario de esta especie, a fin de sentar las bases para la observación de anormalidades en el desarrollo de embriones obtenidos a partir de espermatozoides crioconservados. Los huevos producidos por esta especie son translúcidos y poseen un gran espacio perivitelino; son del tipo telolecítico y presentan una división meroblástica durante los primeros estadíos del desarrollo. Si bien el desarrollo embrionario de Prochilodus lineatus (sábalo) se llevó a cabo en menor tiempo en comparación con Danio rerio, las etapas que atravesó el embrión son muy similares. Durante el estudio se observaron los períodos de Cigoto, Clivaje, Blástula, Gástrula, Segmentación y Eclosión de la larva de sábalo. De esta manera se logró registrar los diferentes estadíos de su desarrollo, principalmente aquellos posteriores a la transición de la blástula media (TBM), a partir del cual el embrión comienza a transcribir su propio genoma.

The influence of Fe3O4 and BaTiO3 on dielectric and magnetic properties of Fe3O4/BaTiO3/epoxy composites was studied. Initially, biphasic Fe3O4/epoxy and BaTiO3/epoxy composites were analyzed, and based on these results Fe3O4/BaTiO3/epoxy composite were conformed. In all the cases, dielectric properties were influenced by the frequency and filler concentration. In this way, Fe3O4/epoxy composites with high filler concentration showed high dielectric loss due to percolation effects and semiconducting properties of Fe3O4.

Con el objetivo de estudiar nuevos materiales multipropósito, en este trabajo se analizó la influencia de las partículas de Fe3O4 y BaTiO3 sobre las propiedades magnéticas y dieléctricas de los sistemas Fe3O4/BaTiO3/epoxi. A tal efecto se analizaron los sistemas bifásicos Fe3O4/epoxi y BaTiO3/epoxi y a partir del análisis de los resultados se conformaron los compuestos Fe3O4/BaTiO3/epoxi. En todos los casos los valores de permitividad y pérdidas dieléctricas fueron altamente influenciados por el contenido de carga. En este sentido, los materiales procesados con Fe3O4 presentaron muy elevadas pérdidas dieléctricas para altas concentraciones de carga debido a efectos de percolación y a las propiedades semiconductoras del Fe3O4.

Using biotechnology to increase the growth rates of fish is likely to reduce production costs per unit of food. Among vertebrates, fish appear to occupy a unique position, when growth patterns are considered. With few exceptions, fish species tend to grow indeterminately, implying that size is never fixed. Both hyperplasia and hypertrophy contribute to post-larval muscle growth in fish. Growth hormone (GH) - Insulin-like Growth Factor I (IGF-I) is the most important growth axis in fish. Our experimental model, the pejerrey, Odontesthes bonariensis (Ateriniformes) is a South American inland water fish considered to be a promising species for intensive aquaculture. However, one major drawback to achieve this goal is its slow growth in captivity. In order to understand how growth is regulated in this species, our first objective was to characterized pejerrey GH- IGF-I axis. We first cloned and characterized pejerrey (pj) GH, IGF-I and the growth hormone receptors (GHRs) I and II. In addition to providing valuable data for evolutionary comparison of GH, investigation of GH action in teleosts is particularly important because of its potential application in aquaculture. GH can not only promote the somatic growth in fish but also lower dietary protein requirements. A prerequisite for providing sufficient amounts of GH for basic research and aquaculture application is a large-scale production of GH. For that purpose, recombinant pjGH was expressed in a bacterial system. Protocols for solubilization and proper folding were achieved. Activity of recombinant pjGH was assessed in fish by measuring the liver IGF-I response to different doses of GH. IGF-I transcript was measured in the liver after pjGHr in vivo stimulation by means of quantitative real-time PCR assays. A dose-dependent response of IGF-I mRNA was observed after pjGHr administration, and reached a 6 fold IGF-I maximum increase over control group when 2.5 µg pjGH /g-body weight were injected. Temporal analysis of hepatic IGF-I mRNA levels showed that administration of a single dose of pjGHr into juvenile pejerrey resulted in a significant increase (P<0.02) 9 hours post injection. These results demonstrates that recombinant pjGH could promote a dramatic response in liver, increasing the IGF-I mRNA level. We also study the effect of GH on muscle growth after oral administration. A significant association between GH doses and mean fiber area (MFA) was observed even with a caloric restrictive diet. MFA increased 3.7 µm² per each unit of GH supplied indicating that GH promoted white muscle hypertrophy. These preliminary data indicates that GH could be absorbed by the intestine in an active form and promote somatic growth.