Navegando por Assunto "Retina"

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Acesso aberto (Open Access)
Ação da hidroxicloroquina sobre neurônios da retina de embrião de galinha
(Universidade Federal do Pará, 2017-03-22) ROSÁRIO, Aldanete Santos; NASCIMENTO, José Luiz Martins do; http://lattes.cnpq.br/7216249286784978
Hydroxychloroquine (HCQ) is currently used in the treatment of malaria and autoimmune diseases and others therapeutic purposes. However, this drug is known to cause side effects, including producing visual disturbances, which may be irreversible. The mechanisms that produce these visual disorders are not completely known. HCQ - related retinal toxicity may be due to high metabolic rate, being very susceptible to the action of xenobiotics and oxidative damages. Thus, this work aims to evaluate the effects of the HCQ on retinal cells, as well as their possible mechanisms of cytotoxicity. The model used in this work was of cultures of retina cells from chicken embryo. To evaluate cell viability, mitochondrial activity was measured by MTT. The lysosomal function was evaluated by the incorporation rate of the neutral red dye. The levels of reactive species of general oxygen and superoxide anion were evaluated by the CellROX probe and by Nitro Blue Tetrazolium (NBT) and total glutathione levels were quantified using the Ellman reagent. Viability was tested in mixed cultures (glia and neurons) or enriched cultures of neurons and glia after treatment with HCQ and compared with chloroquine (CQ). Cells were exposed to concentrations of 25μM, 50μM and 75μM for 24 hours. The results show that mixed cultures treated with CQ presented a reduction in viability of 36 and 61% at concentrations of 50μM and 75μM, respectively, whereas HCQ did not alter viability at any of the concentrations tested. However, when cultures enriched with glial cells were exposed to HCQ for 24 hours, the concentration of 75μM had a small reduction in cell viability, while that the reduction in neuronal cells was of 20, 33 and 56% at the concentrations of 25μM, 50μM and 75μM, respectively. Even a shorter treatment time (6 hours) there was loss of viability in retinal neurons. The incorporation of neutral red supravital dye was also altered in neuronal cultures treated with HCQ for 24 hours, with reduction of 19 and 32%, compared to the control for the concentrations of 50μM and 75μM, respectively. HCQ significantly reduced the levels of reactive oxygen species produced by the neuronal cells, mainly superoxide anion, 43, 52 and 61% for the concentrations of 25μM, 50μM and 75μM of HCQ in 24 hours of treatment, respectively. In concentrations of 50μM and 75μM of HCQ for 24 for hours, the levels of total glutathione in neuronal cells presented a reduction of 37 and 53%, respectively. When the glial cell conditioned medium was used in neuronal cells for 6 hours after treatment with HCQ, it completely reversed the drug-induced cytotoxicity. When total glutathione levels were measured in culture of glia treated with HCQ for 24 hours no changes were observed. These results suggest cytotoxic action of CQ in mixed culture of chicken embryo retina cells which is not observed in HCQ treatment. However, HCQ showed cytotoxic action when cells are cultured separately, mainly on neurons, which is reversed by some factor released by glial cells in the extracellular environment, and glutathione is a possible candidate to exert this neuroprotective function.
Acesso aberto (Open Access)
Análise morfológica e topográfica das células ganglionares da retina do caititu (Tayassu tajacu)
(Universidade Federal do Pará, 2014-12-22) COSTA, Kelly Helorany Alves; ROCHA, Fernando Allan de Farias; http://lattes.cnpq.br/3882851981484245
In the Amazon there are several different wild animals species, becoming this way a good environment to investigated about compared physiology. Among this species, the caititu, Tayassu tajacu, stood out. This animals is located in central America and Latin America. There are many publications around morphology of sexual organs, meat and blood of the catitu. Although, regarding studies about visual’s morphology are scarce. Facing this reality, the present study investigated a morphology and topography of ganglion cells of Tayassu tajacu’s retina. Were used six retina, from eight animals, Both sexes of the species Tayassu tajacu. The caititu born and raised in captivity in the Brazilian company of research known as Embrapa/Pará. Were slaughtered according to the rules of animals ‘s management to subsequent removal and attachment of eyes. The retinas were dissected and stained using Nissl technique to ganglion cells of view, displaced amacrine, red blood cells, microglia cells and components of vascularization. A count of ganglion cells was made a long the horizontal and vertical axis. Being the number of ganglion cells by field converted into density values. The different regions of the retina were analyzed as the cellular density, obtaining the medium value of the density 351,822 ± 31,434 CG/mm². Verified different of the density between the studies regions : The dorsal region had a medium density and standard deviation 894 ± 44 CG/mm², the ventral region 894 ± 1 CG/mm²; the nasal region 1.403 ± 43; the temporal region with 1596 ± 251. The average peak density located approximately 3.13 mm from the dorsal direction and 6.77 mm in the temporal direction of the optic nerve, was 6767 GC / mm². Check there are two specialized regions, the visual streak region and the area temporalis. The visual streak located in the horizontal direction of the nasal region to temporal, presenting higher cellular density, possibly providing better panoramic vision from the environment and detecting the objects in the horizontal direction. Already the temporalis area, located within the visual range, provides increased visual acuity and spatial resolution, the environment that they live. These results allow to start comparisons between morphophysiological the retina of peccaries with other animal species.
Acesso aberto (Open Access)
Avaliação comportamental e eletrofisiológica do sistema visual em camundongos com anemia a partir de um modelo de colite aguda
(Universidade Federal do Pará, 2017-01-31) GOMES, Luana Aparecida Silva; GOULART, Paulo Roney Kilpp; http://lattes.cnpq.br/7800966999068746; ROCHA, Fernando Allan de Farias; http://lattes.cnpq.br/3882851981484245; https://orcid.org/0000-0002-6148-1050
Inflammatory bowel diseases (IBD) are the main causes of anemia and iron deficiency and tend to affect metabolically active tissues distant from the inflammation areas, such as the retina. From this context, it is interesting to investigate the responsive behavior of the visual system through psychophysical and electrophysiological tests in animals with IBD. The main objective of the present work was to evaluate the behavioral and physiological changes of the visual system in mice with induced anemia, from an acute colitis model. For this purpose, 18 mice were used, divided into three groups: control; Colitis (induced by Dextran Sulfate Sodium (DSS), and colitis mother (animals born from mothers with induced colitis). Induction with DSS was performed 6 days before the tests, which occurred in the period between 60 and 90 days of life of the subjects. After induction, the electrophysiological responses were collected using the full field electroretinogram as an electrophysiological measure. Scotopic responses (rods, mixed 1 and mixed 2) and photoptic responses (from cones 1 Hz, S cones and flicker at 12, 18, 24 and 30 Hz) were measured. In addition, behavioral tests were performed by training with drinking fountain and evaluation of the perception of contrast, through stimulation with sinusoidal grids, arranged in different frequencies. Statistical analysis was performed with one-way ANOVA test, using Tukey post- test, considering (P <0.05) as significant. It was found a reduction in the response amplitudes in microvolts (μV) at 60 days in the following responses: b-wave of mixed 1 (colitis: 28.12 and ± 7.96, mother colitis 42.180 And ± 8,525), cone wave 1 Hz (colitis 39.85 and ± 12.74); Cones S (colitis 36.64 and ± 9.09 μV); 18 Hz Flicker (colitis: 25.12 ± 5.62, mother colitis: 38.37 ± 7.1); 24 hr (colitis: 22.46 ± 8.38, mother colitis: 29.41 ± 9.676) and 30 Hz (colitis: 14.4 ± 3.25, mother colitis: 27.13 ± 5.51). At 90 days, reduction in the b wave of rods (colitis: 57.06 ± 6.7), mixed 1 (colitis: 45.69 ± 7.86 and mother colitis: 56.03 ± 17.130), wave ‘a’ of photopic responses (Colitis, 25.1 ± 5.11) and cones S (colitis 31.04 ± 4.83), Flicker 18 Hz (colitis 29.1 ± 9.01) and Flicker 30 Hz (colitis: 41, 8 ± 5.09, mother colitis: 32.72 ± 11.4). There was an increase in implicit time in miliseconds (ms) in rods (colitis 24.68 ± 3.48 ms) and Flicker response of 12 Hz (colitis: 21.69 ± 4.65, mother colitis 22.14 ± 4.42) At 60 days. E cone S (colitis 13.35 ± 1.18) and Flicker 24Hz (mother colitis 28.4 ± 3.87) at 90 days. The behavioral tests showed a decrease in the responses of the colitis group and a delay in the learning on bar pressure response in comparison to the control group. Therefore, anemia impairs scotopic and photopic visual function, affecting rodent retinal cells with anemia and maternal anemia, as well entails in difficulties performing a behavioral learning task in the training performed at the operant conditioning box.
Acesso aberto (Open Access)
Avaliação do efeito protetor da Euterpe oleracea (açaí) na resposta eletrofisiológica da retina de ratos expostos ao metilmercúrio
(Universidade Federal do Pará, 2013-03-19) COSTA, Alódia Brasil; ROCHA, Fernando Allan de Farias; http://lattes.cnpq.br/3882851981484245; HERCULANO, Anderson Manoel; http://lattes.cnpq.br/8407177208423247
Methylmercury (MeHg) is organic form most toxic of mercury. The MeHg exposure generates oxidative stress may affect the retina, because it has a high vulnerability due to their high content of polyunsaturated fatty acids and oxygen consumption. In this context, administration of exogenous antioxidants obtained from the diet, such as those present in Euterpe oleracea (açaí), could be a way to prevent this imbalance and its consequences. Therefore, the objective of this study was to evaluate the possible protective effect of Euterpe oleracea in electrophysiological changes caused by MeHg in the retina. For this was performed gavage with MeHgCl (5mg/kg) or saline (NaCl 0.9%) for 7 days and pretreatment with açaí (10%) per 28 days. Was used Wistar rats were divided into 4 groups: Group MeHg (received standard diet and MeHgCl); MeHg + Acai (enriched diet with acai and MeHgCl); Acai (enriched diet with açai and NaCl); Vehicle (standard diet and NaCl). One day after the last gavage animals were subjected to full-field electroretinography (ffERG) to obtain the scotopic responses (rods, mixed 1 and mixed 2) and photopic responses (cone and flicker at 12, 18, 24 and 30Hz). The next day to the ffERG was applied open field test to evaluate the animals locomotor activity. Subsequently, measurement of the lipid peroxidation by the method TBARS in retinal tissue. Statistical analysis was done by one-way ANOVA with Tukey post-test, considering significant p<0.05. The open field and body weight results showed no difference between groups. The MeHg reduced the amplitude of the following responses: b-wave in rod response (Vehicle: 114.6 ± 23.6 μV and MeHg: 41.2 ± 9.6 μV); a-wave (Vehicle: 8.4 μV and MeHg ± 1.4: 3.4 ± 0.3 μV) and b-wave (Vehicle: 176.7 ± 17.8 μV and MeHg: 69.5 ± 12.0 μV) in mixed 1 responses; a-wave (Vehicle: 103.1 ± 23.3 μV and MeHg: 40.2 ± 9.6 μV) and b-wave (Vehicle: 281 ±, 38.3 μV and MeHg: 138.6 ± 14μV) in mixed 2 response; a-wave (Vehicle: 27.2 ± 3.6 μV and MeHg: 7.5 ± 1.8 μV) and b-wave (Vehicle: 139.3 ± 16.1 μV and MeHg: 54.4 ± 10μV) of cones response; b-wave in frequencies 12 Hz (Vehicle: 67.7 ± 10μV and MeHg: 28.6 ± 6.9 μV), 18Hz (Vehicle: 31.3 ± 3.4 μV and MeHg : 14.2 ± 2.3 μV), 24Hz (Vehicle: 21.0 ± 1.8 μV and MeHg: 11.0 ± 1.1 μV) and 30Hz (Vehicle: 10.9 ± 0.6 μV and MeHg: 6.0 ± 1.1 μV). While the implicit time of the waves was not altered. The pretreatment with Euterpe oleracea prevented the decrease of amplitude of both waves in mixed 1 (a-wave: 8.3 ± 0.6 μV; b-wave: 144.1 ± 7,1 μV) and mixed 2 responses (a-wave: 106.4 ± 13.6 μV; b-wave: 275,2±27,6 μV), b-wave of cone response (104.5 ± 5.9 μV) and photopic flicker at 12 Hz (67.2 ± 9.1 μV), 18 Hz (29.5 ± 4.8 μV) and 24 Hz (21.9 ± 2.4 μV). Lipid peroxidation in retinal tissue of MeHg group (294.9 ± 205.8%) was higher than that of the Vehicle (100 ± 25.1%) and açaí protected against this oxidative damage (MeHg + Acai = 111.2 ± 26.1%). Our results demonstrate diffuse alteration in the electrophysiological response and increase in lipid peroxidation of the retina induced by MeHg and protection exerted by Euterpe oleracea in these two parameters. Thus, Euterpe oleracea could be used as an important alternative to attenuate the changes in the retina caused by MeHg.
Acesso aberto (Open Access)
Caracterização da cinética de captação de glutamato por cromatografia líquida de alta eficiência em tecido retiniano
(Universidade Federal do Pará, 2011-08-19) MORAES, Edinaldo Rogério da Silva; SILVA, Anderson Manoel Herculano Oliveira da; http://lattes.cnpq.br/8407177208423247
The present study describes a simple and efficient method utilizing high performance liquid chromatography (HPLC) coupled to fluorescence detection for the determination of kinetic parameters of glutamate uptake in nervous tissue. Retinal tissue obtained from 7-day-old chicks was incubated to known concentrations of glutamate (50-2000 μM) for 10 minutes, and the levels of the o-phtaldehyde (OPA)-derivatized neurotransmitter in the incubation medium were measured. By assessing the difference between initial and final concentrations of glutamate in the medium, a saturable uptake mechanism was characterized (Km = 8,2 e Vmax = 9,8 nmol/mg protein/minute). This measure was largely sodium- and temperature-dependent, strongly supporting that the mechanism for concentration decrements is indeed uptake by high-affinity transporters. Added to this, our results also demonstrated that zinc chloride (an inhibitor of glutamate/aspartate transporters) evoked a concentration dependent decrease in the glutamate uptake, demonstrating an elevate specificity of our methodology. Overall, the present work characterizes an alternative methodology to evaluate glutamate uptake in nervous tissue using HPLC. This approach could be an important tool for studies associated to the characterization of glutamate transport related with central nervous system injury
Acesso aberto (Open Access)
Citoproteção do ácido kójico (AK) na morte induzida por LPS em células de Muller de retina de embrião de galinha
(Universidade Federal do Pará, 2017-12-07) CARVALHO, Giselle Cristina Brasil; NASCIMENTO, José Luiz Martins do; http://lattes.cnpq.br/7216249286784978
5-Hydroxy-2-hydroxymethyl-γ-pyrone (AK), a known inhibitor of tyrosinase, an enzyme important for melanin synthesis and therefore used for pigmentation disorders. AK also promotes significant activation of macrophages and promotes cytoplasmic accumulation of reactive oxygen species (ROS), suggesting its role as a potentiator of the immune system and microbicide. There is no work in literature that shows the action of AK in the central nervous system (CNS) as a cellular activator and its possible protective role against infections. To test this hypothesis, it use retinal Muller glia which have similar properties to those of macrophages. Therefore, the present work evaluates the action of AK as a possible protective role in LPS-induced cell death in culture of glial cells from chicken embryos. Cultures enriched with glial cells were treated with AK (10, 25, 50 and 100 μM) and LPS (0.1, 10, 100, and 500 ng / ml) for 24 hours. After treatment, the cells did not show AK-treated cytotoxicity; however, treated with LPS, cell death occurred in a dose-dependent manner. We verified the accumulation of EROs in groups treated with AK (100 μM) and LPS (100 and 500 ng / ml). Cultures co-treated with AK and LPS in the same concentrations there was a reduction of accumulation of EROs. AK was also able to inhibit the activity of antioxidant enzymes, (catalase and Superoxide dismutase) and glutathione levels, while LPS produces an increase in the activity of these antixodants. AK was able to inhibit the antioxidant enzymes and glutathione from the increase induced by LPS. These data show that AK promotes the modulation of oxidative and antioxidative balance as a possible protective mechanism in the cell death produced by LPS in Müller's Glia enriched cells.
Acesso aberto (Open Access)
Dendritic thickness: a morphometric parameter to classify mouse retinal ganglion cells
(2007-10) LOOPUIJT, L.D.; SILVA FILHO, Manoel da; HIRT, B.; VONTHEIN, R.; KREMERS, Joannes Jozef Marie
To study the dendritic morphology of retinal ganglion cells in wild-type mice we intracellularly injected these cells with Lucifer yellow in an in vitro preparation of the retina. Subsequently, quantified values of dendritic thickness, number of branching points and level of stratification of 73 Lucifer yellow-filled ganglion cells were analyzed by statistical methods, resulting in a classification into 9 groups. The variables dendritic thickness, number of branching points per cell and level of stratification were independent of each other. Number of branching points and level of stratification were independent of eccentricity, whereas dendritic thickness was positively dependent (r = 0.37) on it. The frequency distribution of dendritic thickness tended to be multimodal, indicating the presence of at least two cell populations composed of neurons with dendritic diameters either smaller or larger than 1.8 µm ("thin" or "thick" dendrites, respectively). Three cells (4.5%) were bistratified, having thick dendrites, and the others (95.5%) were monostratified. Using k-means cluster analysis, monostratified cells with either thin or thick dendrites were further subdivided according to level of stratification and number of branching points: cells with thin dendrites were divided into 2 groups with outer stratification (0-40%) and 2 groups with inner (50-100%) stratification, whereas cells with thick dendrites were divided into one group with outer and 3 groups with inner stratification. We postulate, that one group of cells with thin dendrites resembles cat ß-cells, whereas one group of cells with thick dendrites includes cells that resemble cat a-cells.
Acesso aberto (Open Access)
Dimorfismo sexual da espessura da retina: uma análise de aprendizagem de máquina
(Universidade Federal do Pará, 2022-03) FARIAS, Flavia Monteiro; SALOMÃO, Railson Cruz; http://lattes.cnpq.br/9518575270670446; SOUZA, Givago da Silva; http://lattes.cnpq.br/5705421011644718; https://orcid.org/0000-0002-4525-3971
The present research compared the accuracy of machine learning algorithms in classifying the thickness and volume measurements of retinal layers as obtained from male and female subjects. The study evaluated the retina of sixty-four healthy participants (38 women and 26 men), with normal vision and without eye or systemic diseases, aged between 20 and 40 years. The data acquisition was obtained with a Spectralis HRA+OCT tomograph in the macular region of the retina and its layers: retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), retinal pigment epithelium (RPE), inner retina (IRL) and outer retina (ORL). The classification accuracy was obtained with the following algorithms: support vector classifier (SVC), logistic regression (LR), linear discriminant analyses (LDA), k-nearest neighbors (kNN), decision tree (DT), gaussian naive bayes (GNB) and random forest (RF). The characteristics attributed to each participant's samples were the thickness values in the nine regions of the macula plus the total macular volume of each retinal layer. The statistical tests Two-way ANOVA and Tukey HSD post-hoc were used in the statistical comparisons between the accuracies for the classifier and retinal layer variables, considering a significance level of < 0.05. All factors (classifier, retinal layer, and their interactions) had significant influences on accuracy (p < 0.05). The main effect of the algorithm type factor resulted in an F ratio of F (6, 630) = 4.527, p = 0.0002. The main effect for the retinal layer produced an F ratio of F (9, 630) = 51.64 and p < 0.0001. The interaction effect was also significant, F(54, 630) = 1.741, p = 0.0012. All algorithms classified with high accuracy (> 0.70) the innermost layers of the retina (total retina, inner retina, RNFL, GCL, INL) according to the gender of the participants, where we observed significant differences between genders in thickness and measurements volume. The SVC, LDA, and LR algorithms produced high accuracy (>0.70) when thickness and volume data came from the RNFL compared to the outermost layers of the retina. The KNN, RF and DT algorithms performed better in correctly classifying the total retina data in relation to the outermost layers. The thickness and volume of the retina and the innermost layers of the retina allow machine learning algorithms to be more accurate in separating data from different sexes.
Acesso aberto (Open Access)
Efeito modulador da glutationa na liberação de gaba induzida por glutamato em retinas de embrião de galinha
(Universidade Federal do Pará, 2012-06-06) PEREIRA, Tiago de Lima; SILVA, Anderson Manoel Herculano Oliveira da; http://lattes.cnpq.br/8407177208423247
The γ-aminobutyric acid (GABA) and glutamate are, respectively, major inhibitory and excitatory neurotransmitters in the central nervous system (CNS) and are essential to the visual processing. Studies show that glutamate induces the release of GABA in the retina, but the mechanisms involved in this release are not well elucidated. Previous work also showed that thiols compounds regulate GABA release, but are not well defined the effects of compounds containing sulfhydryl (-SH) on endogenous levels of this neurotransmitter in the retina. In this context, glutathione (GSH) besides being the most important thiols compounds, have demonstrated perform a neuromodulatory role in the release of neurotransmitters. Thus, the objective of this study was to evaluate a possible modulatory effect of GSH on the release of GABA mediated by glutamate in the retina of chick embryo. For this study, we used as experimental model, retinal tissue intact chick embryo, with seven or eight days of development. In tests of release of GABA, the retinas were treated with GSH (100 and 500 μM), glutamate (50 and 500 μM) and Buthionine Sulfoximine (BSO), an inhibitor of glutathione synthesis, (50 μM) per 15 minutes, and GABA levels released into the extracellular medium were quantified by High Performance Liquid Chromatography (HPLC). For release experiments of thiols compounds, the retinas were incubated with glutamate 100 μM (with or without Na +) per 15 minutes, and their extracellular levels were determined by reaction with DTNB and quantified by spectrophotometry (412 nm). The results show that glutamate, as well as GSH, release GABA. Our data also show that BSO attenuates the release of GABA promoted by glutamate. Furthermore, we demonstrate that glutamate induces release of thiol compounds regardless of sodium. Therefore, it is known that glutamate is able to release thiols and GABA, among them, GSH is most abundant and responsible for also release GABA. It is also known that once inhibited GSH synthesis by BSO, the release of GABA induced by glutamate is attenuated. Then, it is suggested a possible modulation of GSH in the release of GABA induced by glutamate in retina intact chicken embryo.
Acesso aberto (Open Access)
Expressão gênica durante o desenvolvimento ocular e regulação de assimetria de opsinas na espécie Anableps anableps, peixe de quatro olhos
(Universidade Federal do Pará, 2022-11) SOUSA, Daniele Salgado de; SCHNEIDER, Patrícia Neiva Coelho; http://lattes.cnpq.br/9584217233879031
The ocular development is a complex process orchestrated by several events that include: cell specification, morphogenesis and differentiation. All these developmental and functional processes are extremely conserved among living vertebrate species, however, unique adaptations are sometimes observed, such as in fish of the genus Anableps. Unlike most fishes, which use their eyes to explore a submerged world, in Anableps anableps (Anablepidae: Cyprinodontiformes), the eye is adapted for the simultaneous perception of a world above and below the water line. These exceptional adaptations include: duplicated corneas and pupils, as well as a specialized retina region associated with simultaneous aerial and aquatic vision, and which have asymmetrical gene expression. Recently, by transcriptomic analysis of the developing eyes of A. anableps, 20 non-visual opsin genes were identified to be asymmetrically expressed between pre- and post-duplication stages of corneas and pupils. Thus, here, we analyzed by in situ hybridization the gene expression of a bistable opsin (parapinopsin) and a neuropsin (Opn5) in A. anableps larvae. Our data showed that the pattern of gene expression of these opsins is symmetrical between the dorsal and ventral retina, respectively, with expression in the ONL, INL and GCL layers. We also investigated the expression of three non-visual melanopsin genes (opn4x1, opn4x2, opn4m3), one eleost multiple tissue opsin (tmt1b), and two visual opsins (lws and rh2-1) in the dorsal and ventral retinas of juvenile A. anableps, after changing the photic conditions in which the juvenile fish were. Then, we showed that in the transition from an environment of high turbidity to one of clear water, opsins have their expression patterns changed. Additionally, by immunofluorescence, we revealed the expression of Lamin A/C, proteins expressed as part of eye development in A. anableps as well as in other developing organisms, as well as in adult individuals. Therefore, we believe that the information described here elucidates many aspects of the molecular mechanisms behind the development and adaptive plasticity of A. anableps’ eyes.
Acesso aberto (Open Access)
GABA and glutamate transporters: new events and function in the vertebrate retina
(2013) NASCIMENTO, José Luiz Martins do; SAWADA, Luis Armando; OLIVEIRA, Karen Renata Matos; CRESPO LÓPEZ, Maria Elena; SILVA, Anderson Manoel Herculano Oliveira da; HAMOY, Moisés; SILVA, Consuelo Yumiko Yoshioka e; BASTOS, Gilmara de Nazareth Tavares; PANTOJA, Wendell Mauro Soeiro
The neural retina is a highly complex tissue composed of excitatory and inhibitory neurons and glial cells. Glutamate, the main excitatory neurotransmitter, mediates information transfer from photoreceptors, bipolar cells, and ganglion cells, whereas interneurons, mainly amacrine and horizontal cells, use γ-aminobutyric acid (GABA), the main inhibitory neurotransmitter. In this review we place an emphasis on glutamate and GABA transporters as highly regulated molecules that play fundamental roles in neurotransmitter clearance, neurotransmitter release, and oxidative stress. We pharmacologically characterized glutamate transporters in chicken retina cells and identified two glutamate transporters: one Na+-dependent transporter and one Na+-independent transporter. The Na+-dependent uptake system presented characteristics related to the high-affinity xAG- system (EAAT1), and the Na+-independent uptake system presented characteristics related to the xCG- system, which highly contributes to glutamate transport in the retina. Glutamate shares the xCG- system with another amino acid, L-cysteine, suggesting the possible involvement of glutathione. Both transporter proteins are present mainly in Müller glial cells. GABA transporters (GATs) mediate high-affinity GABA uptake from the extracellular space and terminate the synaptic action of GABA in the central nervous system. GABA transporters can be modulated by molecules that act on specific sites to promote transporter phosphorylation and dephosphorylation. In addition to a role in the clearance of GABA, GATs may also release GABA through a reverse transport mechanism. In the chicken retina, a GAT-1 blocker, but not GAT2/3 blocker, was shown to inhibit GABA uptake, suggesting that GABA release from retina cells is mainly mediated by a GAT-1-like transporter.
Acesso aberto (Open Access)
Influência da glutationa (GSH) nos registros eletrorretinográficos de ratos wistar adultos
(Universidade Federal do Pará, 2014-03-26) RABELO, Natielle Ferreira; ROCHA, Fernando Allan Farias; http://lattes.cnpq.br/3882851981484245; GOMES, Bruno Duarte; http://lattes.cnpq.br/4932238030330851
Glutathione (GSH) is a molecule involved in many biological processes, known primarily for its antioxidant. Currently , this tripeptide composed of glutamate , cysteine and glycine has been widely studied for its possible action as a neurotransmitter in the CNS and nuromodulador . The present study evaluated the action of this molecule through the electroretinogram, to evaluate the mass response of the retina, produced after light stimulation. Methods: GSH intravitreal injections were performed at different concentrations (1 , 5 and 10 mM) and PBS ( control) in Wistar rats. The assessment protocol consisted of 6 stimuli in different conditions of adaptation: Scotopic response of rods and Scotopic maximal response after dark adaptation of at least 12h ; photopic cone response after 10 min of adaptation to the course, with the use of filters subpopulations for the evaluation of UV and S cones , and the response to the stimulus flicker at 12 Hz. The main parameters were the amplitudes of the waves -a and- b and their implicit time, and b-wave amplitude of the flicker. RESULTS: The results show changes in response, with decrease in b-wave amplitude of the ERG in all stimuli . When done the test of multiple comparisons, differences were observed between the control group and 5 mM GSH and 10 mM GSH . Changes in the amplitude of a-wave only observed in Scotopic maximal response, with a significant decrease in the amplitude. The latency time of the responses showed no changes in any individual group. DISCUSSION: The retinal Muller cells contains a large amount of GSH and may act actively in the modulation of glutamate and glycinergic responses, also has been shown that GSH induces the release of GABA in the retina, which may explain the decrease of the amplitudes observed by over- activation of an inhibitory pathway. CONCLUSION: The present work supporting the hypothesis that GSH acts as a neuromodulator in the CNS, with significant inibitory changes in the retina after administration .
Acesso aberto (Open Access)
Localização do receptor de melatonina Mel1a e da enzima NRH: quinona redutase 2 em embrião e retinas inteiros de Kinosternon scorpioides
(Universidade Federal do Pará, 2014-06-27) SILVA, Renata Nunes; SAMPAIO, Lucia de Fatima Sobral; http://lattes.cnpq.br/7145234400169550
The pineal and others tissues produced hormone melatonin synchronizes biological clocks with dark light environmental cycle. This hormone has functions on development via Mel1a melatonin receptor and NRH: quinona redutase 2 (QR2) enzyme. The present aim was to initiate an investigation about the localization of the both Mel1a melatonin receptor and QR2 enzyme melatonin binding site in vertebrate development. We taken as a model the fresh water turtle Kinosternon scorpioides (muçuã). Whole 21 days embryos (E21) and retinas from E21 and 60 days posthatched (PH) muçuãs respectively were assayed by immunoassays and immunohistochemistry, using commercial antibodies and the results were revealed by Texas red fluorescence. As Mel1a melatonin receptor as QR2 enzyme were localized in important external morphological characters in E21 and in retinas from both E21 and PH. Results showed Mel1a melatonin receptor in maxillary, mandibula, eye contour, Iris, choroide fissure, neck, elongated forelimb and hindlimb, developing carapace, beyond of the internal part of the tail bud. QR2 fluorescent signals in whole E21 embryos were in the following morphological external characters. In head, QR2 is at maxillary region; in the eye at lens and iris; in elongated forelimb and hindlimb; and in tail bud. No fluorescence was observed in negative controls incubated without the primary antibody. In conclusion, our achievers suggest that melatonin participates in Kinosternon scorpioides development as in ossification, hole of the Mella receptor, as in xenobiotic protection, hole of the QR2 enzyme. Melatonin functions on turtle development disclose are only starting, but we found some interesting answers and future investigations arise from these studies.
Acesso aberto (Open Access)
Losses of immunoreactive parvalbumin amacrine and immunoreactive alphaprotein kinase C bipolar cells caused by methylmercury chloride intoxication in the retina of the tropical fish Hoplias malabaricus
(2006-03) BONCI, Daniela Maria Oliveira; LIMA, Silene Maria Araújo de; GRÖTZNER, Sonia Regina; RIBEIRO, Ciro Alberto de Oliveira; HAMASSAKI, Dânia Emi; VENTURA, Dora Selma Fix
To quantify the effects of methylmercury (MeHg) on amacrine and on ON-bipolar cells in the retina, experiments were performed in MeHg-exposed groups of adult trahiras (Hoplias malabaricus) at two dose levels (2 and 6 µg/g, ip). The retinas of test and control groups were processed by mouse anti-parvalbumin and rabbit anti-aprotein kinase C (aPKC) immunocytochemistry. Morphology and soma location in the inner nuclear layer were used to identify immunoreactive parvalbumin (PV-IR) and aPKC (aPKC-IR) in wholemount preparations. Cell density, topography and isodensity maps were estimated using confocal images. PV-IR was detected in amacrine cells in the inner nuclear layer and in displaced amacrine cells from the ganglion cell layer, and aPKC-IR was detected in ON-bipolar cells. The MeHg-treated group (6 µg/g) showed significant reduction of the ON-bipolar aPKC-IR cell density (mean density = 1306 ± 393 cells/mm2) compared to control (1886 ± 892 cells/mm2; P < 0.001). The mean densities found for amacrine PV-IR cells in MeHg-treated retinas were 1040 ± 56 cells/mm2 (2 µg/g) and 845 ± 82 cells/mm2 (6 µg/g), also lower than control (1312 ± 31 cells/mm2; P < 0.05), differently from the data observed in displaced PV-IR amacrine cells. These results show that MeHg changed the PV-IR amacrine cell density in a dose-dependent way, and reduced the density of aKC-IR bipolar cells at the dose of 6 µg/g. Further studies are needed to identify the physiological impact of these findings on visual function.
Acesso aberto (Open Access)
Manifestações retinianas em pacientes portadores de anemia de células falciformes
(Universidade Federal do Pará, 2011-10) ALMEIDA SOBRINHO, Edmundo Frota de; SARAIVA FILHO, João Carlos de Pina; SILVA, James Nunes da; SILVA, Ana Paula Siqueira da; LIMA, Rafaela Cavalcante de
The World Health Organization counts that more than 5% of the world's population carry some type of hemoglobinopathy. Among them we find the sickle cell aneamia that presents its main harmful effect on the peripheral vasculature. In the retina, the falciform lesions have a well defined physiopathology and classification. To identify the retinal manifestations caused by the falciform aneamia in patients directed to the Bettina Ferro de Souza Hospital from the Hemocenter of the State of Pará – HEMOPA, in the months of September through December of 2006. METHODS: Ophthalmologic examination was performed in the Department of Ophthalmology of the Bettina Ferro de Souza Hospital. and fifty patients with sickle cell aneamia (SS or SC) followed by the department of falciform aneamia of the Hematologia e Hemoterapia do Pará - HEMOPA have been randomly selected and submitted to interview in order to register their: sex; age; color; genotype; ocular alterations; medicines taken. Ophthalmologic examination was performed in the Department of Ophthalmology of the Bettina Ferro de Souza Hospital. It consisted of: evaluation of the acuity of vision with and without correction, indirect biomicroscopy, indirect binocular ophthalmoscopy, and, in case the latter presented alterations, a complementary study witangiofluoresceinography would be carried through. RESULTS: The outcomes have been registered in research protocol and later submitted to the statistic analysis using the Qui-square test, adopting, as level of significance, p<0,05. Eighty-eight percent of the patients did not present any falciform retinal sign, 3% presented peripheral vascular occlusion; in 2%, pigmented plate was shown, and 7% presented injuries which were not compatible with the falciform disease; there was a proportionality of 50% for males and females; there was a higher predominance (38%) of people aged from 11 and 15; 74% had SS genotype and 26% SC genotype; in relation to the use of medicines there was a higher prevalence of ocular alterations in patients who had made use of the folic acid isolated, with 5%, in contrast with those who had used the hidroxyurea association and folic acid, when all (27%) presented normal fundoscopic examination; all the patients (29%) that showed fetal hemoglobin rate above 10% had retina without alterations. CONCLUSION: Few cases of retinal signs have been observed in the studied group, however this research does not diminish the importance of early and periodic ophthalmologic examination, since falciform retinopathy is largely registered and its complications can lead to amaurosis.
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Ontogenia do peixe de quatro olhos Anableps anableps: adaptações ósseas e oculares para a visão simultânea aérea e aquática
(Universidade Federal do Pará, 2015-09-30) PEREZ, Louise Neiva; SCHNEIDER, Patrícia Neiva Coelho; http://lattes.cnpq.br/9584217233879031
The evolution and development of the eye has intrigued developmental biologists for centuries. Aside from partial or complete loss, few vertebrates display substantial modifications to the eye morphology. One example is the Four-eyed fish (Anableps anableps). This species is commonly found from Gulf of Paria in Venezuela to Delta of Parnaíba and reproduces throughout the year. The four-eyed fish consists in a unique model system to study eye Evo-Devo due to its distinctive feature of having divided eye structures, such as pupils and cornea. The retina is a unique structure divided into two regions, dorsal (receives aquatic luminous information) and ventral (receives aerial luminous information). The aim of this study was to describe larval stages of this species, and morphological and molecular description of the retina during eye development. Six larval stages were described. The two earlier stages did not split the cornea and pupil, and from stage three, it is possible to observe this division. It was also described the development and expansion of the frontal bone. The appearance of the frontal bone begins at stage three of development. It has been identified the appearance of an inter-orbital septum cartilaginous, starting four stage of the ocular development. It was observed that the early development of the retinal cellular layers are disorganized and is not possible to distinguish between them, but later during development, these layers become organized, with ventral outer nuclear layer thicker than the dorsal one, and the dorsal inner nuclear layer is thinner than the ventral. The pattern of retinal cell proliferation has been described in three stages of development, before and during ocular division. It was observed that the proliferation is greater at the beginning of the larval development and decreases on later stages. The result of this study will shed light on the molecular basis of this innovative feature.
Acesso aberto (Open Access)
Potencial cortical provocado visual gerado por estímulos pseudoisocromáticos
(Universidade Federal do Pará, 2016-10-11) SALOMÃO, Railson Cruz; SOUZA, Givago da Silva; http://lattes.cnpq.br/5705421011644718
Visual evoked cortical potentials (VECP) are useful the investigation of color vision mechanisms and color vision dysfunctions. Chromatic sinusoidal gratings are generally used to elicit VECP, but they require long psychophysical measurements to match the perceptual brightness between their stripes. An alternative is to replace them by pseudoisochromatic stimuli which make use of luminance noise to mask brightness clues and force the target perception to be dependent of chromatic contrast. In this work, we compared VECPs generated by sinusoidal and pseudoisochromatic gratings. This research was approved by the Comitê de Ética em Pesquisa, Núcleo de Medicina Tropical, Universidade Federal do Pará, Protocol #570434. Seven normal trichromats were tested with chromatic sinusoidal gratings and illusory gratings provided by the pseudoisochromatic design of 0.33, 0.66, 1, 1.33, 1.66, and 2 cpd, presented in pattern reversal (1 Hz) and pattern onset (300 ms) – offset (700 ms) modes. The signals were recorded using surface electrodes, amplified x30,000, digitized at 1 kHz, and filtered between 0.1-100 Hz. Pattern reversal VECPs elicited by pseudoisochromatic gratings had similar amplitude and latency compared to those elicited by sinusoidal gratings. Onsetoffset VECPs elicited by sinusoidal gratings had larger amplitude and shorter latency than those obtained with pseudoisochromatic stimuli. Different visual mechanisms are responsible for the cortical responses evoked by illusory stimuli when presented in different stimulation modes.
Acesso aberto (Open Access)
Potencial cortical provocado visual pseudoaleatório gerado por estímulos compostos: efeito do modo de apresentação e do tempo de adaptação da resposta
(Universidade Federal do Pará, 2016-09-28) RISUENHO, Bárbara Begot Oliveira; SOUZA, Givago da Silva; http://lattes.cnpq.br/5705421011644718
Conventional pattern-reversal visual evoked cortical potential (VECP) shows positivity for luminance and chromatic equiluminant stimuli while conventional pattern-onset VECP shows positivity for luminance pattern-onset and negativity for chromatic pattern-onset. We evaluated how the presentation mode affects VECPs elicited by luminance and compound (luminance plus chromatic) pseudo-random stimulation. Eleven normal trichromats and 17 red-green color-blinds were studied. Pattern-reversal and pattern-onset luminance and compound (luminance plus red-green) gratings were temporally modulated by m-sequence. We used a cross-correlation routine to extract the first order kernel (K1) and the first and second slices of the second order kernel (K2.1 and K2.2, respectively) from the VECP response. We integrated the amplitude of VECP components as a function of time in order to estimate its magnitude for each stimulus condition. We also used a normalized cross-correlation method in order to test the similarity of the VECP components. In order to assess how the interection time afects the VECP’s amplitude we calculate de root mean square (RMS) amplitude into differents time windows and correlated it with the response time interval relative to the sencond order kernel slice avaliated. The VECP components varied with the presentation mode and the presence of red-green contrast in the stimuli. In trichromats, for compound conditions, pattern-onset K1, K2.1, and K2.2, and pattern-reversal K2.1 and K2.2 had negative-dominated waveforms at 100 ms. Small negativity or small positivity were observed in dichromats. Trichromats had larger VECP magnitude than color-blinds for compound pattern-onset K1 (with large variability across subjects), compound pattern-onset and pattern-reversal K2.1, and compound pattern-reversal K2.2. Trichromats and color-blinds had similar VECP amplitude for compound pattern-reversal K1 and compound pattern-onset K2.2, as well as for all luminance conditions. The cross-correlation analysis showed high similarity between waveforms of compound pattern-onset K2.1 and pattern-reversal K2.2 as well as pattern-reversal K2.1 and K2.2. The amplitude of VECP was smaller as higher was the response time interval. We suggest that compound pattern-reversal K2.1 is an appropriate response to study red-green color-opponent activity.
Acesso aberto (Open Access)
Propriedades espaciais das respostas isoladas de cones L e M ao eletrorretinograma: implicações sobre a atividade das vias visuais paralelas
(Universidade Federal do Pará, 2015-06-16) JACOB, Mellina Monteiro; SOUZA, Givago da Silva; http://lattes.cnpq.br/5705421011644718; GOMES, Bruno Duarte; http://lattes.cnpq.br/4932238030330851
We studied the spatial arrangement of L- and M-cone driven electroretinograms (ERGs) reflecting the activity of magno- and parvocellular pathways. L- and M-cone isolating sine wave stimuli were created with a four primary LED stimulator using triple silent substitution paradigms. Temporal frequencies were 8 and 12 Hz, to reflect cone opponent activity, and 30, 36 and 48 Hz to reflect luminance activity. The responses were measured for full-field stimuli and for different circular and annular stimuli. The ERG data confirm the presence of two different mechanisms at intermediate and high temporal frequencies. The responses measured at high temporal frequencies strongly depended upon spatial stimulus configuration. In the full-field conditions, the L-cone driven responses were substantially larger than the full-field M-cone driven responses and also than the L-cone driven responses with smaller stimuli. The M-cone driven responses at full-field and with 70° diameter stimuli displayed similar amplitudes. The L- and M-cone driven responses measured at 8 and 12 Hz were of similar amplitude and approximately in counter-phase. The amplitudes were constant for most stimulus configurations. The results indicate that, when the ERG reflects luminance activity, it is positively correlated with stimulus size. Beyond 35° retinal eccentricity, the retina mainly contains L-cones. Small stimuli are sufficient to obtain maximal ERGs at low temporal frequencies where the ERGs are also sensitive to cone-opponent processing.
Acesso aberto (Open Access)
Valores normativos para o eletrorretinograma de campo total
(Universidade Federal do Pará, 2012-05-02) JACOB, Mellina Monteiro; SOUZA, Givago da Silva; http://lattes.cnpq.br/5705421011644718; GOMES, Bruno Duarte; http://lattes.cnpq.br/4932238030330851
Many visual electrophysiology laboratories don’t have their own normal values for full-field electroretinogram. This impairs the reliability of the diagnosis of various diseases affecting the visual pathways. Thus, the purpose of this study was to establish normative values for the full-field electroretinogram to the Laboratory of Tropical Neurology (LNT) of the Federal University of Pará (UFPA). Were tested using the electroretinogram 68 healthy subjects without visual complaints, divided into three groups according to age group: 36 subjects belonged to group 1 (17 to 30 years), 21 subjects in group 2 (31 to 45 years) and 11 individuals in group 3 (46 to 60 years). Six types of stimulus that follow ISCEV standards were presented. Four dark-adapted: 0.01 cd.s/m2 (rod response), 3.0 cd.s/m2 (mixed response and oscillatory potentials) and 10.0 cd.s/m2 (mixed additional response). Two light-adapted, 3.0 cd.s/m2 (Cone response and Flicker 30Hz), with 30 cd/m2 background adaptation. For analysis, a-wave and b-wave amplitude and implicit times values were calculated. These values were statistically described using the following values: median, confidence interval, 1st and 3rd quartiles, coefficient of variation, mean, standard deviation and minimum and maximum values. The older age groups had lower amplitude and delayed implicit time. Wavelet transform allowed better visualization of waves without change of amplitude and implicit time. Therefore, the normative values obtained can serve as reliable parameters of normality to assist the diagnosis of retinal diseases.