The effects of riboflavin and ultraviolet light on keratocytes cultured in vitro

ABSTRACT Purpose: To culture quiescent human keratocytes and evaluate the effects of ultraviolet light and riboflavin on human corneal keratocytes in vitro. Methods: Keratocytes were obtained from remaining corneoscleral ring donor corneas previously used in corneal transplant surgeries and cultured in DMEM/F12 with 2% FBS until confluence. Characterization of cultured cells was performed by immunofluorescence analysis for anti-cytokeratin-3, anti-Thy-1, anti-α-smooth muscle actin, and anti-lumican. Immunofluorescence was performed before and after treatment of cultured cells with either ultraviolet light or riboflavin. Corneal stromal cells were covered with collagen (200 µL or 500 µL) and 0.1% riboflavin, and then exposed to ultraviolet light at 370 nm for 30 minutes. After 24 hours, cytotoxicity was determined using MTT colorimetric assays, whereas cell viability was assessed using Hoechst 33342 and propidium iodide. Results: Cell cultures achieved confluence in approximately 20 days. Expression of the lumican was high, whereas no expression of CK3, Thy-1, and α-SMA was observed. After crosslinking, MTT colorimetric assays demonstrated a low toxicity rate, whereas Hoechst 33342/propidium iodide staining demonstrated a low rate of apoptosis and necrosis, respectively, in all collagen-treatment groups. Conclusion: Keratocytes can be successfully cultured in vitro and characterized by immunofluorescence using lumican. MTT colorimetric assays, and Hoechst 33342, and propidium iodide staining demonstrated a higher rate of cell death in cells cultured without collagen, indicating collagen protects keratocytes from the cytotoxic effects of ultraviolet light

Effects of Chronic Video Game Use on Time Perception: Differences Between Sub- and Multi-Second Intervals

Even though video game players frequently report losing track of time while playing, few studies have addressed whether there are long-lasting effects of such activity on time perception. We compared the performance of chronic and occasional video game players in sub-and multi-second time perception tasks. Temporal Discrimination and Temporal Bisection tasks, in the range of 100 to 1,000 milliseconds, and Time estimation and Time production tasks, in the range of 5 to 60 seconds, were used to assess sub-and multi-second time perceptions, respectively. Chronic video game players performed significantly better than occasional players on sub-second tasks, but no group difference was found for the multi-second tasks used. Sub-and multi-second time perceptions are associated to different underlying systems: automatic and cognitive controlled for sub-and multi-second tasks, respectively. We argue that video game use seems to induce more efficient implicit, rather than cognitive controlled, processing of time.Universidade Federal de São Paulo, Dept Psychobiol, BR-04024002 São Paulo, BrazilUniv Fed ABC, Ctr Math Computat & Cognit, Santo Andre, BrazilUniversidade Federal de São Paulo, Dept Psychobiol, BR-04024002 São Paulo, BrazilWeb of Scienc

Visuospatial support for verbal short-term memory in individuals with Down syndrome.

Individuals with Down syndrome (DS) tend to have impaired verbal short-term memory (STM), which persists even when visual support is provided for carrying out verbal tasks. Objective: the current study aims to investigate whether visuospatial support, rather than just visual, can compensate for verbal STM deficits in these individuals. the performance of 25 children and adolescents with DS (mean age = 12.5, SD = 3.8) on five word span tasks was compared with that of two groups of typically developing children, matched for mental age (N = 25; mean age = 6.0, SD = .2) and for receptive vocabulary (N = 25; mean age = 4.0, SD = .8). Four of the five tasks varied in terms of input and output - verbal and/or visual - and the fifth task included a spatial component in addition to visual input and output. DS individuals performed equally bad in the pure verbal task and in those with visual components; however, there was a significant improvement when the spatial component was included in the task. the mental age matched group outperformed DS individuals in all tasks except for that with the spatial component; the receptive vocabulary matched group, outperformed DS individuals only in the pure verbal task. We found that visuospatial support improves verbal STM in individuals With DS. This result may have implications for intervention purposes. (C) 2011 Elsevier B.V. All rights reserved.Univ Presbiteriana Mackenzie, Lab Neurociencia Cognit, Ctr Hlth & Biol Sci, Dev Disorder Program, BR-01241001 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Psychobiol, São Paulo, BrazilUniv Presbiteriana Mackenzie, Dept Psychol, BR-01241001 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Psychobiol, São Paulo, BrazilWeb of Scienc

Maintaining task set against distraction: The role of working memory in multitasking.

Multitasking, a common feature of everyday life, requires simultaneous maintenance and operation of a range of action-controlling task sets. We attempt to investigate the role of working memory in multitasking by means of the embedded task paradigm. This involves setting up a primary task with a variable task set, which then has to be maintained throughout the performance of a second embedded task with a fixed task set before it can be completed. We test the hypothesis that the capacity to maintain the two task sets so as to avoid mutual interference will depend on working memory. We use Baddeley and Hitch’s multicomponent working memory approach to investigate this. Experiment 1 uses articulatory suppression to examine the potential role of subvocal rehearsal, finding no impact on performance. Experiment 2 uses backward counting to impose an additional executive load, finding a major impact on performance even with the simple task of counting back in ones. This took the form of more pervasive effects of stimulus overlap that could be interpreted in terms of a change in the way the two tasks were managed. The differential impacts of the concurrent tasks indicated that multi-tasking is dependent on working memory, where it draws on limited capacity executive resources, but not on the capacity for temporary phonological storage

Análise dos padrões dos movimentos oculares em tarefas de busca visual: efeito da familiaridade e das características físicas do estímulo Analysis of the eye movement patterns in visual search tasks: effect of familiarity and stimulus features

OBJETIVOS: Analisar os movimentos oculares numa tarefa de busca visual assimétrica com letras normais e espelhadas. Explorar o efeito da familiaridade e características do estímulo. MÉTODOS: Oitenta e três universitários emétropes ou com correção óptica foram solicitados a procurar por uma letra normal ou espelhada, num contexto de letras espelhadas ou normais, respectivamente. Foram utilizados quatro tipos de letras (Z, N, E e G) e os movimentos dos olhos foram rastreados por meio de um sistema computacional especializado (eyetracking). As medidas utilizadas para análise foram: tempo de reação, duração e número de fixações, duração e distância dos movimentos sacádicos. RESULTADOS: A análise em função do tipo de letra mostrou diferenças para todas as medidas. O tempo de reação, o número de fixações e a distância média dos movimentos sacádicos foram maiores para encontrar uma letra normal em um conjunto de letras espelhadas. A duração média das fixações, entretanto, foi menor nessa situação. Houve interação dupla entre espelhamento e tipo de letra para o tempo de reação, duração média e número de fixações. O tempo de reação e o número de fixações apresentam função crescente de acordo com o grau de complexidade do estímulo, com aumento acentuado na situação em que o alvo é a letra normal. A duração das fixações, por sua vez, diminui em função da complexidade do estímulo e da situação. CONCLUSÕES: Foi mais fácil encontrar uma letra espelhada entre as normais, que o oposto, sendo que o desempenho também sofreu influência do tipo de letra. Quando o contexto é formado por estímulos não familiares e complexos, a duração média das fixações é menor, indicando um processamento visual com amplitude reduzida. Desta forma, são necessárias mais fixações com menor duração para um contexto não familiar e menos fixações com maior duração, para o familiar.<br>PURPOSE: To analyze eye movements in asymmetric visual search using the task of normal and mirrored position letters. To evaluate the effect of familiarity and stimulus features. METHODS: Eighty-three university students with normal or corrected-to-normal vision were asked to search for a letter in inverted position to the letters in a group of either normal or mirrored letters. Four types of letters were used (Z, N, E and G) and the eye movements were tracked by a specialized computer-based system (eyetracking). The analyzed measurements were: reaction time, fixation number and duration, saccade distance and duration. RESULTS: All measures varied with the type of letter. Reaction time, fixation number, and saccade distance were higher when the task was to find the normal letter in a group of mirrored letters. In this condition, fixation duration was smaller. Interaction was found between familiarity and the type of letter for the reaction time, fixation number and duration. The reaction time and fixation number increased together with the stimulus complexity, with a greater increase for the normal letter target. Fixation duration, however, decreased with the complexity of the stimuli and the search condition. CONCLUSIONS: Finding a mirrored letter among normal letters proved to be easier than the contrary. The letter type also affected the performance. When the context is formed of unfamiliar complex stimuli, the fixation duration is shorter, indicating a narrower span for visual processing. Therefore, a greater number of fixations with shorter duration are needed for the unfamiliar context while less fixations with greater duration are needed for the familiar context

Frequency of anti-Toxoplasma gondii antibodies in dogs and cats from the metropolitan region of Vitória, Espírito Santo, Brazil

Toxoplasmosis, an infection caused by Toxoplasma gondii, is widely distributed worldwide. Seroprevalence in pets is a reliable tool to determine environmental parasite presence and  human risk of infection due to proximity to these animals. In this context, the frequency of anti-T. gondii IgG antibodies in sera of dogs and cats from Espirito Santo, Brazil and risk factors associated with the infection (sex, age, allocation, and breed) were assessed. Antibodies against T. gondii were detected in 39.4% (149/378) and 38.1% (142/373) of the dogs by enzyme-linked immunosorbent assay (ELISA) and by indirect immunofluorescence antibody test (IFAT), respectively. In cats, antibodies were detected in 15.2% (12/79) by ELISA and 7.6% (6/79) by IFAT. Canine infection was associated with stray origin and older ages. Feline females showed a higher chance of infection. There was an agreement between techniques in the detection of antibodies in dogs (k = 0.82) and cats (k = 0.63). These results indicate the parasite presence in the urban environment, suggesting the possibility of infection to humans and other animals. However, this risk is lower while considering pet domiciled animals with a more controlled diet and better hygiene conditions