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Oocyte development and egg envelope formation in Oreochromis niloticus, a mouth-brooding cichlid fish
No full textThe development of the oocyte and of its associated follicle cells in the Nile tilapia, Oreochromis niloticus, has been examined by optical and transmission electron microscopy. During oocyte development the female gamete of Orochromis niloticus increases in size because of the accumulation of yolk in its cytoplasm. As the accumulation of yolk proceeds, the organization of cortex of the oocyte becomes very complex; all of the cytoplasmic organelles and several populations of vesicles can be found. On the other hand follicle cells also undergo a series of modifications: they first become cuboidal then cylindrical and their cytoplasm become densely populated with organelles. The mature egg of Oreochromis niloticus is surrounded by a thin acellular envelope (chorion) assembled during oocyte development. Biochemical analysis of isolated and purified chorions from mature females was also performed. SDS-PAGE under reducing conditions showed a reproducible pattern of three major polypeptides (121, 66 and 50 kD), most of which being glycosylated. The pattern of synthesis and assembly of the egg envelope in Oreochromis niloticus, a mouth-brooding cichlid fish, is also discussed
Neurogenic role of prox1 in the CNS and lateral line development
No full textIn teleost, the lateral line is a sensory organ composed of neuromasts containing hair cells, expressing athl, and surrounded by supporting cells, expressing notch3. notch3 signalling seems to limit the number of cells that are allowed to adopt the hair cell fate while failure of notch3 signal generates an overproduction of athl expressing hair cells in the middle of the neuromast. In this report we analyze the role of prox1 in zebrafish (z-prox1) on neural and proneural genes in the neuromasts of the posterior lateral line. We have examinated the z-prox1 interaction with ath1 and notch3 in the lateral line system of zebrafish by both z-prox1 morpholino-mediated inactivation and z-prox1 mRNA overexpression. This gene is expressed in the migrating primordium, and its inactivation results in a reduced number of neuromasts at 48 hpf but does not affect the primordium migration. In particular, lack of prox1 inhibits the differentiation of ath1 expressing hair cells, while enhances the number of the supporting cells, expressing notch3. Injection of prox1 synthetic mRNA generates the opposite phenotype: the number of the pre-determined ath1 expressing hair cells is increased, while notch3 expression in the supporting cells is reduced. Moreover prox1 could have a role in timing regulation of the neuromasts development because morphant embryos rigenerate neuromasts after 48 hpf
Myogenic determination in Zebrafish is entirely dependent upon myf5 and myod but can be rescued by exogenous mrf4
No full textMuscle regulatory factors activate myogenesis in all vertebrates, but their role has been studied in great detail only in the mouse embryo, where all but myogenin – Myod, Myf5 and Mrf4 – are sufficient to activate (albeit not completely) skeletal myogenesis. In the zebrafish embryo, myod and myf5 are required for induction of myogenesis because their simultaneous ablation prevents muscle development. Here we show that mrf4 but not myog can fully rescue myogenesis in the myod/myf5 double morphant via a selective and robust activation of myod, in keeping with its chromatin remodelling function in vitro. Rescue does not happen spontaneously, because the gene, unlike that in the mouse embryo, is expressed only at the onset of muscle differentiation, Moreover, because of the transient nature of morpholino inhibition, we were able to investigate how myogenesis occurs in the absence of a myotome. We report that in the complete absence of a myotome, subsequent myogenesis is abolished, whereas myogenesis does proceed, albeit abnormally, when the morpholino inhibition was not complete. Therefore our data also show that the early myotome is essential for subsequent skeletal muscle differentiation and patterning in the zebrafish
LOCALIZATION AND DISTRIBUTION OF ACTIN IN MAMMALIAN SPERM HEADS
No full textActin was identified in boar and mole spermatozoa by utilizing indirect immunofiuorescence, immunoelectron microscopy, and SDS-PAGE, followed by blot and screening with an anti-actin monoclonal antibody. Actin was detected in two places in the sperm head: the equatorial segment of the acrosome and the postacrosomal region. The protein was present in a nonfilamentous form and was localized under the plasma membrane. A small amount of actin was also detected in the sperm tail. The function of actin in the sperm head is discussed. © 1986
Induced early expression of mrf4 but not myogenin rescues myogenesis in the myod/myf5 double morphant zebrafish embryo
No full textMuscle regulatory factors activate myogenesis in all vertebrates, but their role has been studied
in great detail only in the mouse embryo, where all but myogenin – Myod, Myf5 and Mrf4 – are
sufficient to activate (albeit not completely) skeletal myogenesis. In the zebrafish embryo, myod
and myf5 are required for induction of myogenesis because their simultaneous ablation prevents
muscle development. Here we show that mrf4 but not myog can fully rescue myogenesis in the
myod/myf5 double morphant via a selective and robust activation of myod, in keeping with its
chromatin-remodelling function in vitro. Rescue does not happen spontaneously, because the
gene, unlike that in the mouse embryo, is expressed only at the onset of muscle differentiation.
Moreover, because of the transient nature of morpholino inhibition, we were able to investigate
how myogenesis occurs in the absence of a myotome. We report that in the complete absence
of a myotome, subsequent myogenesis is abolished, whereas myogenesis does proceed, albeit
abnormally, when the morpholino inhibition was not complete. Therefore our data also show
that the early myotome is essential for subsequent skeletal muscle differentiation and patterning
in the zebrafish
Caratterizzazione funzionale del gene numb durante la formazione del sistema vascolare/ematopoietico in zebrafish
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