RESUMO
Similar to mammals, spermatogenesis in fish is initiated by spermatogonial stem cells (SSCs) which either self-renew or gradually differentiate to produce mature sperm. SSCs are located in a particular testis microenvironment called SSC ni che, formed by Sertoli and peritubular myoid cells, the basement membrane and other cellular components/factors from the intertubular compartment that regulate SSCs maintenance and fate. Considering the great variation in testis structure/arrangemen t across fish species, the study of the niche components is crucial to understand SSCs physiology. Additionally, the germ cell transplantation technique, which has been applied to fish in the last decade, is a unique approach to elucidating important functional aspects of SSCs biology such as: (i) the capacity of SSCs to colonize the testis of recipient species (syngeneic and xenogeneic transplantation) giving rise to donor sperm; (ii) the plasticity of these cells, considering that spermatogonia and oogonia can be derived from SSCs collected from the opposite sex; and (iii) the possibility of genetically manipulating SSCs before transplantation to produce transgenic fish. However, fish SSC isolation and characterization has been lim ited so far by the lack of specific molecular markers fo r these cells. Therefore, various research groups are currently investigating specific SSCs markers and, up to date, few proteins have been identified in different spermatogonial populations from distinct fish species (e.g. Notch1, Ly75, Plzf, Oct-4, SGSA -1). Furthermore, the development of a fish SSC culture system would allow the investigation of important regulatory aspects of the SSC physiology in well-defined conditions as well as to in vitro amplify these rare cells. Overall, the study of SSC physiology, niche and transplantation in fish has opened up new scenarios for the development of aquaculture and reproductive biotechnologies such as germplasm conservation of endangered or commercially important species and the possibility of generating transgenic fish.
Assuntos
Animais , Aquicultura/tendências , Espermatogênese/fisiologia , Espermatozoides/citologia , Fisiologia , Biotecnologia/métodos , Peixes/classificaçãoRESUMO
Avaliaram-se diferentes variávies biométricas de vacas mestiças F1 Holandês x Zebu de diferentes bases genéticas maternas, suplementadas com concentrado (T1) ou não (T2) durante o pré-parto, durante as estações chuvosa e seca. A suplementação no pré-parto, durante a estação chuvosa, aumentou o peso ao parto e os escores da condição corporal ao final do pré-parto e ao parto. Entretanto, não houve diferença entre as vacas suplementadas ou não no ganho de peso total ou diário durante o pré-parto. Durante a estação seca, apesar da suplementação não ter afetado o peso ao parto, ela aumentou o escore da condição corporal ao final do período pré-parto e ao parto. Durante a estação chuvosa, as vacas de base Guzerá apresentaram maior peso corporal final do pré-parto em relação às de base Gir ou Indubrasilada, enquanto que, na estação seca, as vacas de base Guzerá foram mais no início e ao final do pré-parto e também ao parto. A suplementação no pré-parto, em vacas mestiças, deve ser usada de forma estratégica, com o intuito de aumentar o escore da condição corporal ao parto, especialmente durante a estação chuvosa.
It was evaluated different biometric variables of crossbred F1 Holstein x Zebu cows supplemented or not with concentrate during the transition period, during the dry and the rainy season. The supplementation increased the weitgh and body condition score at the end of the transition period and at calving, although there was not difference in the total and daily weight gains. During the dry season the supplementation did not affect the weight at calving. In the other hand, the supplemented cows presented higher body condition scores at the end of the transition period and at calving. During the rainy season, Guzera based cows had higher weights at the end of the transition period and at calving than the Gir or Indubrasil based cows. The supplemetation of crossbred dairy cows during the transition period must be done strategically, specially during the rainy season.
Assuntos
Feminino , Animais , Bovinos , Bovinos/classificação , Parto , Técnicos em Manejo de Animais , Aumento de Peso/fisiologia , Estação Chuvosa , Estação Seca , Fenômenos Fisiológicos da Nutrição do Lactente , Hibridização Genética/fisiologiaRESUMO
A psicologia do trabalho é uma disciplina que sofreu transformações em seu corpo teórico e técnico no presente século. Estas mudanças são analisadas em três momentos, o que serve de base para discutir-se a interdisciplinaridade e as principais atividades do psicólogo do trabalho(AU)