Navegando por Orientadores "SCHNEIDER, Igor"

Agora exibindo 1 - 2 de 2

Acesso aberto (Open Access)
Análise morfológica e molecular dos filamentos das nadadeiras pélvicas do peixe pulmonado Lepidosiren paradoxa
(Universidade Federal do Pará, 2015-12-18) LIMA, Sérgio Queirós; SCHNEIDER, Igor; http://lattes.cnpq.br/4453558334183860
The Lepidosiren paradoxa species belongs to Dipnoi order, along with two genre and are considered true lungfishes. Adult males of L. paradoxa differ from females by the presence of filaments in the pelvic fin. These filaments resemble those found in gills of fish and neotenic salamanders. These filaments are grow and become vascularized during the reproduction period. In this work we tested the hypothesis that the pelvic filament of L. paradoxa share morphological and molecular characteristics with gill filaments. Thus, we performed morphological and molecular analyses of the filaments of the pelvic fins between the dry and rainy seasons. Morphological analysis was perfomed through hematoxylin and eosin (HE) and scanning electron microscopy (SEM). Finally, we quantified gene expression of gill markers by RT-PCR using pectoral fin as reference. The mean length and standard deviation of the filaments during rainy and dry season were 4,31mm of ± 0.186 and 1,63mm ± 0.104, respectively. In the SEM images, we observed with a few cell microvilli and/or microplicae and some smaller cells. In the HE analyzes we found that the filaments have uniform epithelium formed with four layers of cells being filled by connective tissue and finally become more vascularized the rainy season. Molecular analysis through RT-PCR did not show any change when compared to the pectoral fin and between the stations. In conclusion, despite morphological and molecular similarities between gill filaments and pelvic fin filaments, our findings do not support a role for L. paradoxa pelvic filaments in gas exchange.
Acesso aberto (Open Access)
Um mecanismo molecular compartilhado na padronização de nadadeiras em peixes pulmonados e membros em tetrápodes
(Universidade Federal do Pará, 2019-05-03) AMARAL, Danielson Baia; SCHNEIDER, Igor; http://lattes.cnpq.br/4453558334183860
The first known tetrapods to emerge already display a specifically arranged limb, composed of proximal endoskeletal elements (humerus, radius and ulna) plus distal elements (wrist bones and digits). While limbs with digits have been regarded as an evolutionary novelty, part of their skeletal organization was already in place in fish fins, as the closest relatives to tetrapods, sarcopterygian fishes, possess three proximal bones and a distal endoskeletal region composed of segmented radials. Among modern lungfish, the genus Neoceratodus has retained distal radials whereas Lepidosirenids (Protopterus e Lepidosiren) have lost them. Genetic or pharmacological inactivation of Sonic Hedgehog signaling (SHH) in developing limbs and fins leads to loss of distal endoskeleton, digits or distal radials, respectively. Shh expression during appendage development is controlled by a highly conserved enhancer element termed ZRS, present in all vertebrates including snakes. Here, we investigate the role of SHH signaling during lungfish fin regeneration by: (i) cloning and in silico analysis of ZRS from lungfish species of the three living genera; (ii) Semiquantitative PCR for Shh, Ptch1 and Gli1 and (iii) pharmacological modulation of SHH signaling during lungfish fin regeneration. Comparative analysis of vertebrate ZRS sequences revealed a 17 bp deletion of a key ETS transcription factor binding site in Lepidosirenid lungfish but not in Neoceratodus. Furthermore, as seen in salamander limb regeneration, SHH signaling is activated and is necessary for lungfish fin regeneration. Last, we show that SHH activation increases the number of distal radials in lungfish fin. Overall, our data suggests that SHH signaling, a key pathway underlying digit development in tetrapods, also controls distal radial development in lungfish fins, providing support for the homology of digits and distal radials.