Expression of pax-6 during urodele eye development and lens regeneration.

Regeneration of eye tissues, such as lens, seen in some urodeles involves dedifferentiation of the dorsal pigmented epithelium and subsequent differentiation to lens cells. Such spatial regulation implies possible action of genes known to be specific for particular cell lineages and/or axis. Hox genes have been the best examples of genes for such actions. We have, therefore, investigated the possibility that such genes are expressed during lens regeneration in the newt. The pax-6 gene (a gene that contains a homeobox and a paired box) has been implicated in the development of the eye and lens determination in various species ranging from Drosophila to human and, because of these properties, could be instrumental in the regeneration of the urodele eye tissues as well. We present data showing that pax-6 transcripts are present in the developing and the regenerating eye tissues. Furthermore, expression in eye tissues, such as in retina, declines when a urodele not capable of lens regeneration (axolotl) surpasses the embryonic stages. Such a decline is not seen in adult newts capable of lens regeneration. This might indicate a vital role of pax-6 in newt lens regeneration.

Evidence for a hypothalamothalamocortical circuit mediating pheromonal influences on eye and head movements.

A method for simultaneous iontophoretic injections of the anterograde tracer Phaseolus vulgaris leukoagglutinin and the retrograde tracer fluorogold was used to characterize in the rat a hypothalamothalamocortical pathway ending in a region thought to regulate attentional mechanisms by way of eye and head movements. The relevant medial hypothalamic nuclei receive pheromonal information from the amygdala and project to specific parts of the thalamic nucleus reuniens and anteromedial nucleus, which then project to a specific lateral part of the retrosplenial area (or medial visual cortex). This cortical area receives a convergent input from the lateral posterior thalamic nucleus and projects to the superior colliculus. Bidirectional connections with the hippocampal formation suggest that activity in this circuit is modified by previous experience. Striking parallels with basal ganglia circuitry are noted.

Prenatal monocular enucleation induces a selective loss of low-spatial-frequency cortical responses to the remaining eye.

During early development, interactions between the two eyes are critical in the formation of eye-specific domains within the lateral geniculate nucleus and the visual cortex. When monocular enucleation is done early in prenatal life, it induces remarkable anatomical and functional reorganizations of the visual pathways. Behavioral data have shown a loss in sensitivity to low-spatial-frequency gratings in cats. To correlate the behavioral observations with a possible change in the analysis of contrast at the level of primary visual areas we recorded visual evoked potentials at the 17/18 border in two cats enucleated prenatally (gestational age at enucleation, 39-42 days), three neonatal, two control animals, and one animal with a surgical removal of Y-ganglion fibers. Our results show a strong attenuation in the amplitude of response at all contrast values for gratings of low spatial frequency in prenatally enucleated cats, whereas neonatally enucleated and control animals present responses of comparable amplitude. We conclude that the behavioral results reflect the reduced sensitivity for low frequencies of visual cortical neurons. In addition, we define a critical period for the development of the contrast-sensitivity function that seems to be limited to the prenatal gestation period. We suggest that the prenatal interruption of binocular interactions leads to a functional elimination of the Y-ganglion system.

Pancreatic digestive enzyme secretion in the rabbit: rapid cyclic variations in enzyme composition.

The role and mechanism of nonparallel pancreatic secretion of digestive enzymes, in which enzyme proportions change in rapidly regulated fashion, remain controversial. Secretion was collected from male 2.2-kg New Zealand rabbits in 5-min intervals for 3 h under basal conditions or constant stimulation with cholecystokinin (CCK; 0.1 microgram per kg per h i.v.) or methacholine chloride (MCh; 40 micrograms per kg per h i.v.). Both CCK and MCh produced an 8-fold stimulation of protein output. Enzymes were separated by SDS/PAGE and quantitated by densitometry of Coomassie blue-stained gels. Under both basal conditions and constant MCh infusion, rapid neurosecretory-like 12-min cyclic changes occurred in the proportions of amylase, lipase I, chymotrypsinogen, and trypsinogen. During constant infusion their percentages changed as much as 10-fold, and their ratios cycled by as much as 30-fold. The mean percentage for the entire infusion period for lipase I declined > 25% with CCK or MCh, for amylase it rose approximately 30%, and for chymotrypsinogen and trypsinogen it doubled (for all, P < 0.05). CCK and MCh elicited subtly but significantly different mean enzyme percentages and enzyme ratios (P < 0.05) for amylase, chymotrypsinogen, and trypsinogen; these differences were also confirmed by regression and correlation analyses. The changes in enzyme percentages and ratios were explicitly consistent with secretagogue-caused shifts in the intrapancreatic enzyme secretory sources. Nonparallel secretion of digestive enzymes occurs routinely, even during constant stimulation, and is due to cyclic neurosecretory-like secretion from heterogeneous intrapancreatic sources.

Estudo morfológico e eletrofisiológico dos efeitos da injeção intravítrea de ácido micofenólico em coelhos utilizando um modelo de uveíte crônica experimental

Uveítes são inflamações intra-oculares geralmente crônicas e constituem uma das principais causas de cegueira no mundo. Os corticosteroides são a droga de primeira escolha para o tratamento das uveítes não infecciosas, mas muitas vezes há necessidade do uso de outras drogas imunossupressoras. O micofenolato de mofetila (MMF) é um potente imunossupressor administrado por via oral que vem sendo utilizado com sucesso no tratamento das uveítes, mas cujos efeitos colaterais muitas vezes tornam necessária sua suspensão. O MMF é uma pró-droga, que é transformada no fígado em ácido micofenólico (MPA), o imunossupressor ativo. Para minimizar os efeitos colaterais do uso do MPA e permitir que o olho receba uma dose maior da droga, testamos os efeitos da injeção intravítrea do MPA em um modelo de uveíte crônica experimental (UCE) em olhos de coelhos. Os objetivos deste estudo foram: 1) reproduzir um modelo de UCE em coelhos através da injeção intravítrea de M. tuberculosis; 2) estabelecer uma dose segura de MPA a ser injetada no vítreo; e 3) analisar os efeitos morfológicos, clínicos e eletrofisiológicos da injeção intravítrea de MPA em coelhos utilizados como modelo de UCE. O modelo de UCE reproduzido apresentou uma inflamação autolimitada, possuindo um pico de inflamação no 17° dia após a indução da uveíte. As doses de MPA testadas (0,1 e 1mg) não foram toxicas para a retina do coelho. O modelo de UCE recebeu uma injeção intravítrea de 0,1mg de MPA e as análises clinicas demonstraram uma redução na inflamação. As análises realizadas com o eletrorretinograma (ERG) também apontaram uma melhora na inflamação através da recuperação da latência das ondas-a e b (fotópicas e escotópica) e recuperação da amplitude da onda-a (fotópica). As análises morfológicas com HE não apresentaram alterações na estrutura retinia, porem a imunohistoquimica para proteína GFAP evidenciou gliose das células de Müller, sinalizando um processo inflamatório. Concluímos que o modelo de UCE reproduziu uma uveíte anterior semelhante à uveíte causada em humanos e a dose de MPA utilizada apresentou efeitos terapêuticos durante o pico de inflamação, mostrando uma diminuição da inflamação e promovendo a recuperação de fotorreceptores e células bipolares-ON. Este resultado faz das injeções intravítreas de MPA um recurso promissor no tratamento de uveítes. Porém, novos experimentos são necessários para padronizar os resultados encontrados

Privy Private Eye: A Guidebook for Travelers Who Have to Go

This creative Capstone project, Privy Private Eye: A Guidebook for Travelers Who Have to Go, contains a nonfiction compendium of brief reviews of public restrooms in the Dallas, Texas area. To inform readers about facilities that are safe (and a few that should be avoided), Privy Private Eye contains reviews and ratings of restrooms in gas stations, restaurants, and retail centers. These appraisals will be featured in a full-length manuscript that may be published in the near future as a travel guide. Also contained herein, before the creative portion of the project itself, is a reflective paper describing the project, its creation, and its position within the context of published travel guides.

Kinematics of eyelid movement and eye retraction in the blinking

Resumen del póster expuesto en el 6th EOS Topical Meeting on Visual and Physiological Optics (EMVPO 2012), Dublín, 20-22 Agosto 2012.

Kinematics of eyelid movement and eye retraction in the blinking [Poster]

Póster presentado en el 6th EOS Meeting on Visual and Physiological Optics (EMVPO 2012), Dublín, 20-22 Agosto 2012.

Analysis of fixational eye micromovements through pupil tracking

Póster presentado en OPTYKA Optical Fair 2012, Poznan, Polonia, 9-10 noviembre 2012.

Intrasubject repeatability in keratoconus-eye measurements obtained with a new Scheimpflug photography–based system

Purpose: To evaluate in keratoconus eyes the intrasubject repeatability of anterior and posterior corneal curvature and of other anterior segment anatomic measurements obtained with a new topography system combining Scheimpflug-photography and Placido-disk technology. Setting: Vissum Corporation, Alicante, Spain. Design: Evaluation of technology. Methods: All keratoconus eyes had a comprehensive ophthalmologic examination including analysis with the Sirius system. Three consecutive measurements were obtained to assess the intrasubject repeatability of the following parameters: anterior and posterior corneal curvature and shape factor, white-to-white (WTW) corneal diameter, central and minimum corneal thickness, and anterior chamber depth (ACD). The within-subject standard deviation (Sw) and intraclass correlation coefficient (ICC) were calculated. Results: This study comprised 61 eyes of 61 patients ranging in age from 14 to 64 years. For anterior and posterior corneal curvatures and power vector components, the Sw was 0.29 mm or less in all cases. The ICC was above 0.990 in all cases except the flattest curvature of the posterior corneal surface at 3.0 mm, which was 0.840 (moderate agreement), and the posterior power vector J0, which was 0.665 (poor agreement), 0.752, and 0.758 (moderate agreement) for 3.0 mm, 5.0 mm, and 7.0 mm, respectively. In shape factor measurements, the Sw was 0.12 or less in all cases and the ICC ranged between 0.989 and 0.999. Pachymetry, ACD, and WTW had ICC values very close to 1. Conclusion: The new topography system provided repeatable measurements of corneal shape and other anatomic parameters in eyes with keratoconus.

Correlation of the Corneal Toricity Between Anterior and Posterior Corneal Surfaces in the Normal Human Eye

Purpose: To evaluate the correlation of the magnitude of corneal toricity and power vector components of both corneal surfaces measured with a Scheimpflug photography-based system. Methods: A total of 117 healthy normal eyes of 117 subjects selected randomly with ages ranging from 7 to 80 years were included. All eyes received an anterior segment and corneal analysis with the Sirius system (CSO) evaluating the anterior and posterior mean toricity for 3 and 7 mm (aAST and pAST). The vector components J0 and J45 as well as the overall strength blur (B) were calculated for each keratometric measurement using the procedure defined by Thibos and Horner. Results: The coefficient of correlation between aAST and pAST was 0.52 and 0.62 and the mean anteroposterior ratio for toricity was 0.46 ± 0.39 and 0.57 ± 0.75 for 3 and 7 mm, respectively. These ratios correlated significantly with aAST, anterior corneal J0, and manifest refraction J0 (r ≥ 0.39, P < 0.01). The coefficient of correlation was 0.69 and 0.81 between anterior and posterior J0 for 3 and 7 mm, respectively. For J45, the coefficients were 0.62 and 0.71, respectively. The linear regression analysis revealed that the pAST and power vectors could be predicted from the anterior corneal data (R2 ≥ 0.40, P < 0.01). Conclusions: The toricity and astigmatic power vector components of the posterior corneal surface in the human healthy eye are related to those of the anterior and therefore can be predicted consistently from the anterior toricity and astigmatic power vectors.

Modeling the role of fixational eye movements in real-world scenes

Our eyes never remain still. Even when we stare at a fixed point, small involuntary movements take place in our eyes in an imperceptible manner. Researchers agree on the presence of three main contributions to eye movements when we fix the gaze: microsaccades, drifts and tremor. These small movements carry the image across the retina stimulating the photoreceptors and thus avoiding fading. Nowadays it is commonly accepted that these movements can improve the discrimination performance of the retina. In this paper, several retina models with and without fixational eye movements were implemented by mean of RetinaStudio tool to test the feasibility of these models to be incorporated in future neuroprostheses. For this purpose each retina model has been stimulated with natural scene images in two experiments. Results are discussed from the point of view of a neuroprosthesis development.

Advanced techniques for the human eye study: ocular aberrometry

Lectures about the course module "Advanced techniques for the human eye study: ocular aberrometry".

A high-resolution binocular video-oculography system: assessment of pupillary light reflex and detection of an early incomplete blink and an upward eye movement

Background: The pupillary light reflex characterizes the direct and consensual response of the eye to the perceived brightness of a stimulus. It has been used as indicator of both neurological and optic nerve pathologies. As with other eye reflexes, this reflex constitutes an almost instantaneous movement and is linked to activation of the same midbrain area. The latency of the pupillary light reflex is around 200 ms, although the literature also indicates that the fastest eye reflexes last 20 ms. Therefore, a system with sufficiently high spatial and temporal resolutions is required for accurate assessment. In this study, we analyzed the pupillary light reflex to determine whether any small discrepancy exists between the direct and consensual responses, and to ascertain whether any other eye reflex occurs before the pupillary light reflex. Methods: We constructed a binocular video-oculography system two high-speed cameras that simultaneously focused on both eyes. This was then employed to assess the direct and consensual responses of each eye using our own algorithm based on Circular Hough Transform to detect and track the pupil. Time parameters describing the pupillary light reflex were obtained from the radius time-variation. Eight healthy subjects (4 women, 4 men, aged 24–45) participated in this experiment. Results: Our system, which has a resolution of 15 microns and 4 ms, obtained time parameters describing the pupillary light reflex that were similar to those reported in previous studies, with no significant differences between direct and consensual reflexes. Moreover, it revealed an incomplete reflex blink and an upward eye movement at around 100 ms that may correspond to Bell’s phenomenon. Conclusions: Direct and consensual pupillary responses do not any significant temporal differences. The system and method described here could prove useful for further assessment of pupillary and blink reflexes. The resolution obtained revealed the existence reported here of an early incomplete blink and an upward eye movement.