Assuntos
Humanos , Melanócitos , Melanose , Pele , Queratinócitos , Opsinas de Bastonetes , FibroblastosRESUMO
ABSTRACT Cichlid fishes are an important group in evolutionary biology due to their fast speciation. This group depends widely of vision for feeding and reproduction. During the evolutionary process it plays a significant role in interspecific and intraspecific recognition and in its ecology. The molecular basis of vision is formed by the interaction of the protein opsin and retinal chromophore. Long-wavelength sensitive opsin (LWS) gene is the most variable among the opsin genes and it has an ecological significance. Current assay identifies interspecific variation of Neotropical cichlids that would modify the spectral properties of the LWS opsin protein and codons selected. Neotropical species present more variable sites for LWS gene than those of the African lakes species. The LWS opsin gene in Crenicichla britskii has a higher amino acid similarity when compared to that in the African species, but the variable regions do not overlap. Neotropical cichlids accumulate larger amounts of variable sites for LWS opsin gene, probably because they are spread over a wider area and submitted to a wider range of selective pressures by inhabiting mainly lotic environments. Furthermore, the codons under selection are different when compared to those of the African cichlids.
Assuntos
Animais , Variação Genética , Opsinas de Bastonetes/genética , Ciclídeos/genética , Filogenia , Especificidade da Espécie , Brasil , Códon/genética , Reação em Cadeia da Polimerase , Análise de Sequência de DNA , África , Ciclídeos/classificaçãoRESUMO
Vertebrates have a central clock and also several peripheral clocks. Light responses might result from the integration of light signals by these clocks. The dermal melanophores of Xenopus laevis have a photoreceptor molecule denominated melanopsin (OPN4x). The mechanisms of the circadian clock involve positive and negative feedback. We hypothesize that these dermal melanophores also present peripheral clock characteristics. Using quantitative PCR, we analyzed the pattern of temporal expression of Opn4x and the clock genes Per1, Per2, Bmal1, and Clock in these cells, subjected to a 14-h light:10-h dark (14L:10D) regime or constant darkness (DD). Also, in view of the physiological role of melatonin in the dermal melanophores of X. laevis, we determined whether melatonin modulates the expression of these clock genes. These genes show a time-dependent expression pattern when these cells are exposed to 14L:10D, which differs from the pattern observed under DD. Cells kept in DD for 5 days exhibited overall increased mRNA expression for Opn4x and Clock, and a lower expression for Per1, Per2, and Bmal1. When the cells were kept in DD for 5 days and treated with melatonin for 1 h, 24 h before extraction, the mRNA levels tended to decrease for Opn4x and Clock, did not change for Bmal1, and increased for Per1 and Per2 at different Zeitgeber times (ZT). Although these data are limited to one-day data collection, and therefore preliminary, we suggest that the dermal melanophores of X. laevis might have some characteristics of a peripheral clock, and that melatonin modulates, to a certain extent, melanopsin and clock gene expression.
Assuntos
Animais , Proteínas CLOCK/metabolismo , Melanóforos/fisiologia , Melatonina/farmacologia , Opsinas de Bastonetes/metabolismo , Fatores de Transcrição ARNTL/genética , Fatores de Transcrição ARNTL/metabolismo , Proteínas CLOCK/genética , Relógios Circadianos/efeitos dos fármacos , Relógios Circadianos/genética , Relógios Circadianos/fisiologia , Proteínas do Olho/genética , Proteínas do Olho/metabolismo , Melanóforos/efeitos dos fármacos , Reação em Cadeia da Polimerase , Proteínas Circadianas Period/genética , Proteínas Circadianas Period/metabolismo , RNA Mensageiro , Opsinas de Bastonetes/efeitos dos fármacos , Xenopus laevis , Proteínas de Xenopus/genética , Proteínas de Xenopus/metabolismoRESUMO
<p><b>BACKGROUND</b>Glaucoma can cause progressive damage to retinal ganglion cells. These cells can be classified as cells projecting to the superior colliculus and melanopsin-containing retinal ganglion cells, which project to the suprachiasmatic nucleus. This study was to investigate the effects of chronic intraocular pressure elevation on melanopsin-containing retinal ganglion cells in rats.</p><p><b>METHODS</b>Chronic intraocular pressure elevation was induced in one eye of adult Wistar rats by cauterization of three episcleral veins. Intraocular pressure was measured at different intervals with a rebound tonometer. Superior collicular retinal ganglion cells were retrogradely labeled from the superior colliculus with Fluorogold. Melanopsin-containing retinal ganglion cells were visualized by free-floating immunohistochemistry on whole-mount retinas. The number of labeled superior collicular and melanopsin-containing retinal ganglion cells were counted in the sample areas on flat-mounted retinas.</p><p><b>RESULTS</b>Compared with contralateral control eyes, the numbers of both superior collicular and melanopsin-containing retinal ganglion cells were significantly reduced after 12 weeks of experimental intraocular pressure elevation ((2317.41 +/- 29.96)/mm(2) vs (1815.82 +/- 24.25)/mm(2); (26.20 +/- 2.10)/mm(2) vs (20.62 +/- 1.52)/mm(2), respectively). The extent of cell loss of the two types of retinal ganglion cells was similar. However, no morphologic changes were found in melanopsin-containing retinal ganglion cells.</p><p><b>CONCLUSION</b>Both melanopsin-containing and superior collicular retinal ganglion cells were damaged by chronic ocular hypertension, indicating that glaucomatous neural degeneration involves the non-image-forming visual pathway.</p>