Analysis of Cell Size in the Gastrula of Ten Frog Species Reveals a Correlation of Egg with Cell Sizes, and a Conserved Pattern of Small Cells in the Marginal Zone.

We investigated the relationship between egg and cell sizes in the early gastrula of ten species of frogs with eggs of 1,100-3,500 µm diameters. We asked whether differences in cell size of the vegetal region, blastocoel roof, and marginal zone of the early gastrula were associated with egg size. Alternatively, we proposed that cell size differences may associate with gastrulation characteristics. The analyzed species were as follows: Xenopus laevis, Engystomops randi, Engystomops coloradorum, Espadarana callistomma, Epipedobates machalilla, Epipedobates anthonyi, Epipedobates tricolor, Dendrobates auratus, Gastrotheca riobambae, and Eleutherodactylus coqui. A positive correlation between egg and cell size was detected in the three regions of the gastrula. The correlation was strong in the vegetal region and blastocoel roof, and weak in the marginal zone. Large eggs allowed the evolution of frog terrestrial reproductive modes by storing nourishment for the developing embryos. Large cells, laden with yolk, occur in the vegetal region. However, small cell size characterized the marginal zone and blastocoel roof. We proposed that small cells of the marginal zone are required for involution and blastopore formation. The evolution pressure toward small cells in the marginal zone contributed to maintain the blastopore as a universal feature of frog gastrulation in eggs of different sizes and gastrulation modes. Our comparative analysis revealed two fundamental and conserved properties of the frog early gastrula, the correlation of egg with cell sizes, and the general small size of cells in the marginal zone.

The gastrocoel roof plate in embryos of different frogs.

The morphology of the gastrocoel roof plate and the presence of cilia in this structure were examined in embryos of four species of frogs. Embryos of Ceratophrys stolzmanni (Ceratophryidae) and Engystomops randi (Leiuperidae) develop rapidly, provide comparison for the analysis of gastrocoel roof plate development in the slow-developing embryos of Epipedobates machalilla (Dendrobatidae) and Gastrotheca riobambae (Hemiphractidae). Embryos of the analyzed frogs develop from eggs of different sizes, and display different reproductive and developmental strategies. In particular, dorsal convergence and extension and archenteron elongation begin during gastrulation in embryos of rapidly developing frogs, as in Xenopus laevis. In contrast, cells that involute during gastrulation are stored in the large circumblastoporal collar that develops around the closed blastopore in embryos of slow-developing frogs. Dorsal convergence and extension only start after blastopore closure in slow-developing frog embryos. However, in the neurulae, a gastrocoel roof plate develops, despite the accumulation of superficial mesodermal cells in the circumblastoporal collar. Embryos of all four species develop a ciliated gastrocoel roof plate at the beginning of neurulation. Accordingly, fluid-flow across the gastrocoel roof plate is likely the mechanism of left-right asymmetry patterning in these frogs, as in X. laevis and other vertebrates. A ciliated gastrocoel roof plate, with a likely origin as superficial mesoderm, is conserved in frogs belonging to four different families and with different modes of gastrulation.

Embryogenesis and laboratory maintenance of the foam-nesting túngara frogs, genus Engystomops (= Physalaemus).

The vast majority of embryological research on amphibians focuses on just a single genus of frogs, Xenopus. To attain a more comprehensive understanding of amphibian development, experimentation on non-model frogs will be essential. Here, we report on the early development, rearing, and embryological analysis of túngara frogs (genus Engystomops, also called Physalaemus). The frogs Engystomops pustulosus, Engystomops coloradorum, and Engystomops randi construct floating foam-nests with small eggs. We define a table of 23 stages for the developmental period in the foam-nest. Embryos were immunostained against Lim1, neural, and somite-specific proteins and the expression pattern of RetinoBlastoma Binding Protein 6 (RBBP6) was analyzed by in situ hybridization. Due to their brief life-cycle, frogs belonging to the genus Engystomops are attractive for comparative and genetic studies of development. Developmental Dynamics 238:1444-1454, 2009. (c) 2009 Wiley-Liss, Inc.

Expression of Brachyury during development of the dendrobatid frog Colostethus machalilla.

The expression of Brachyury (Bra) during development of Colostethus machalilla was analyzed with a polyclonal antibody. The observed molecular mass of Bra was of 48 kDa, as in Xenopus laevis. During cleavage, low levels of Bra were expressed. In contrast, in the blastula Bra became up-regulated, and Bra protein was present in a wide ring of surface cells. The surface expression of Bra disappeared in the gastrula, and a new ring of Bra-positive nuclei was detected in deep cells around the closing blastopore. The C. machalilla external and internal rings of Bra-positive nuclei apparently mark the prospective mesoderm in the blastula and gastrula, respectively. The two Bra expression rings were dissociated in time in the fairly slow developing embryos of this frog. Brachyury expression in the notochord became visible only after the blastopore closed, in contrast with X. laevis. In addition, Bra expression in the notochord indicated that dorsal convergence and extension occurred after blastopore closure. The C. machalilla Bra-positive notochord was originally exposed on the gastrocoel roof, in agreement with a superficial component of the prospective mesoderm.

Alteraciones de la nefrogénesis y vasculogénesis renal en anfibios tratados con inhibidores de la enzima convertidora de la Angiotensina 1 / Alterations of the renal nephrogenesis and vasculogenesis in amphibia treat with of the Angiotensin 1 converting enzyme inhibitors

El sistema renina-angiotensina (SRA) parece influir en el desarrollo renal fundamentalmente en su vasculogenésis. Recientes trabajos indican que el SRA es estimulado durante la organogenésis renal y el crecimiento renal neonatal, las células del SRA son activadas y/o redistribuidas en muchas situaciones que evidencian crecimiento renal. Con el objeto de evaluar este efecto veinte ejemplares de Rana Catesbeiana en período de prometamofosis, cuyo peso medio fue de 4,8 + - 0,1g fueron criados en bateas plásticas con agua libre de cloro a una temperatura que osciló entre 22 y 25 grados C con un fotoperíodo de 12 horas día 12 horas noches. A diez de estos animales se los mantuvo en condiciones similares pero al agua se le agregó 20 mg/litro de enalapril (ENAL). Dos semanas después del período denominado climax metamórfico los animales se pesaron y se sacrificaron por decapitación. Se realizaron estudios morfométricos e inmunohistoquímicos (AU)

Alteraciones de la nefrogénesis y vasculogénesis renal en anfibios tratados con inhibidores de la enzima convertidora de la Angiotensina 1 / Alterations of the renal nephrogenesis and vasculogenesis in amphibia treat with of the Angiotensin 1 converting enzyme inhibitors

El sistema renina-angiotensina (SRA) parece influir en el desarrollo renal fundamentalmente en su vasculogenésis. Recientes trabajos indican que el SRA es estimulado durante la organogenésis renal y el crecimiento renal neonatal, las células del SRA son activadas y/o redistribuidas en muchas situaciones que evidencian crecimiento renal. Con el objeto de evaluar este efecto veinte ejemplares de Rana Catesbeiana en período de prometamofosis, cuyo peso medio fue de 4,8 + - 0,1g fueron criados en bateas plásticas con agua libre de cloro a una temperatura que osciló entre 22 y 25 grados C con un fotoperíodo de 12 horas día 12 horas noches. A diez de estos animales se los mantuvo en condiciones similares pero al agua se le agregó 20 mg/litro de enalapril (ENAL). Dos semanas después del período denominado climax metamórfico los animales se pesaron y se sacrificaron por decapitación. Se realizaron estudios morfométricos e inmunohistoquímicos (AU)

Alteraciones de la nefrogénesis y vasculogénesis renal en anfibios tratados con inhibidores de la enzima convertidora de la Angiotensina 1 / Alterations of the renal nephrogenesis and vasculogenesis in amphibia treat with of the Angiotensin 1 converting enzyme inhibitors

El sistema renina-angiotensina (SRA) parece influir en el desarrollo renal fundamentalmente en su vasculogenésis. Recientes trabajos indican que el SRA es estimulado durante la organogenésis renal y el crecimiento renal neonatal, las células del SRA son activadas y/o redistribuidas en muchas situaciones que evidencian crecimiento renal. Con el objeto de evaluar este efecto veinte ejemplares de Rana Catesbeiana en período de prometamofosis, cuyo peso medio fue de 4,8 + - 0,1g fueron criados en bateas plásticas con agua libre de cloro a una temperatura que osciló entre 22 y 25 grados C con un fotoperíodo de 12 horas día 12 horas noches. A diez de estos animales se los mantuvo en condiciones similares pero al agua se le agregó 20 mg/litro de enalapril (ENAL). Dos semanas después del período denominado climax metamórfico los animales se pesaron y se sacrificaron por decapitación. Se realizaron estudios morfométricos e inmunohistoquímicos

The relationship between the red cell forms and surface area during thyroxine induced metamorphosis in Rana cyanophlyctis.

A study of the effect of exogenous thyroxine on the red cell form and surface area during Rana cyanophyctis metamorphosis is made. Haemoglobin presents changes in its affinity for O2 with age. A loss of 35 per cent in the mean surface is recorded on the eleventh day after thyroxine treatment. The early appearance of adult erythrocytes, compared with control is due to a change in the time scale of metamorphosis.