No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Retinal image properties such as contrast and spatial frequency play important roles in the development of normal vision. For example, visual environments comprised solely of low contrast and/or low spatial frequencies induce myopia. The visual image is processed by the retina and it then locally controls eye growth. In terms of the retinal neurotransmitters that link visual stimuli to eye growth, there is strong evidence to suggest involvement of the retinal dopamine (DA) system. For example, effectively increasing retinal DA levels by using DA agonists can suppress the development of form-deprivation myopia (FDM). However, whether visual feedback controls eye growth by modulating retinal DA release, and/or some other factors, is still being elucidated. This thesis is chiefly concerned with the relationship between the dopaminergic system and retinal image properties in eye growth control. More specifically, whether the amount of retinal DA release reduces as the complexity of the image degrades was determined. For example, we investigated whether the level of retinal DA release decreased as image contrast decreased. In addition, the effects of spatial frequency, spatial energy distribution slope, and spatial phase on retinal DA release and eye growth were examined. When chicks were 8-days-old, a cone-lens imaging system was applied monocularly (+30 D, 3.3 cm cone). A short-term treatment period (6 hr) and a longer-term treatment period (4.5 days) were used. The short-term treatment tests for the acute reduction in DA release by the visual stimulus, as is seen with diffusers and lenses, whereas the 4.5 day point tests for reduction in DA release after more prolonged exposure to the visual stimulus. In the contrast study, 1.35 cyc/deg square wave grating targets of 95%, 67%, 45%, 12% or 4.2% contrast were used. Blank (0% contrast) targets were included for comparison. In the spatial frequency study, both sine and square wave grating targets with either 0.017 cyc/deg and 0.13 cyc/deg fundamental spatial frequencies and 95% contrast were used. In the spectral slope study, 30% root-mean-squared (RMS) contrast fractal noise targets with spectral fall-off of 1/f0.5, 1/f and 1/f2 were used. In the spatial alignment study, a structured Maltese cross (MX) target, a structured circular patterned (C) target and the scrambled versions of these two targets (SMX and SC) were used. Each treatment group comprised 6 chicks for ocular biometry (refraction and ocular dimension measurement) and 4 for analysis of retinal DA release. Vitreal dihydroxyphenylacetic acid (DOPAC) was analysed through ion-paired reversed phase high performance liquid chromatography with electrochemical detection (HPLC-ED), as a measure of retinal DA release. For the comparison between retinal DA release and eye growth, large reductions in retinal DA release possibly due to the decreased light level inside the cone-lens imaging system were observed across all treated eyes while only those exposed to low contrast, low spatial frequency sine wave grating, 1/f2, C and SC targets had myopic shifts in refraction. Amongst these treatment groups, no acute effect was observed and longer-term effects were only found in the low contrast and 1/f2 groups. These findings suggest that retinal DA release does not causally link visual stimuli properties to eye growth, and these target induced changes in refractive development are not dependent on the level of retinal DA release. Retinal dopaminergic cells might be affected indirectly via other retinal cells that immediately respond to changes in the image contrast of the retinal image.

<p> Chick embryos at stages primitive streak to three somites were explanted on the vitelline membrane and cultured by the method of New (1955) or by Gallera's modification of the method (Nicolet and Gallera. 1963). Antisera produced in rabbits against adult chicken brain extract. adult chicken kidney extract. and embryo brain extract were placed on the uppermost side of the embryo preparation. The embryos were recovered after 24 to 36 hours further incubation. Defects of the central nervous system. the posterior trunk. and the extra-embryonic membranes occurred in embryos exposed to adult brain antiserum. Embryos exposed to adult kidney antiserum developed exactly the same kinds of defects. Embryo brain antiserum produced similar abnormalities which included defects of the central nervous system and of the extra-embryonic membranes, and in addition de-. fective somites. However, embryos exposed to gamma globulin solutions containing antibodies against neural-specific antigens and not against common tissue antigens were normal. In control experiments, embryos exposed to saline solution, to normal rabbit serum, and to normal rabbit serum gamma globulins developed normally. </p> <p> Histological examination of ~epresentative antisera treated embryos revealed that there were extensive areas of disorganization and necrosis of neural tissue. In embryos with short trunks, the caudal proliferation centre was necrotic. Embryos exposed to gamma globulins of absorbed adult brain antiserum were histologically normal. </p> <p> The antisera used in these experiments were characterized by double diffusion in agar gel. It was demonstrated by this method that the antisera contained antibodies against common tissue antigens as well as against tissue-specific antigens. It was also shown that certain antigens common to all adult organs were present in the embryo and in the extra-embryonic membranes during the time that the embryos were exposed to the antisera. </p> <p> Embryos which had been exposed to various of the tissue antisera for 8.5, 21.5 or 32 hours were sectioned. The sections were stained with FITC-labelled goat anti-rabbit gamma globulins in order to localize distribution of the antibodies. Fluorescence was located on the ectoderm of the embryos and of their extra-embryonic membranes, in the lumen of the neural tube and in the cavity of the otic vesicles. This demonstrated that, under the conditions of the experiment, the antibodies were available to the embryo. </p> <p> Antisera which affected the embryo and the extra-embryonic membranes were shown to contain antibodies against antigens actually present in the embryos and in the extra-embryonic membranes during the time of exposure. The only antiserum which had no adverse effects on the embryos was the one which contained only antibodies against antigens not demonstrated to be present in the embryo during the time of exposure. </p> / Thesis / Master of Science (MSc)

Depuis près de dix ans, les lectrices québécoises peuvent retrouver une panoplie de romans de chick lit « Made in Québec » sur le marché. Si l'engouement pour ce type de production est important, très peu d'études se sont consacrées à l'observation de ce phénomène en contexte québécois et francophone. L'objectif de cette recherche est de faire la nomenclature des caractéristiques fondatrices des personnages masculins possédant un potentiel amoureux auprès de l'héroïne et étant issus de la chick lit québécoise. En somme, il s'agit de mettre au jour les traits distinctifs de la chick lit québécoise par le truchement des personnages masculins qui constituent une piste d'analyse des plus riches pour y parvenir. Tout d'abord, afin de bien positionner le sous-genre dans le marché du livre, le premier chapitre retrace l'émergence de la chick lit anglo-saxonne et québécoise, en plus de dresser le portrait actuel de l'édition de chick lit au Québec. Dans le but de bien saisir ses composantes et sa structure narrative, les liens de continuité ou de rupture de la chick lit québécoise avec, d'une part, le roman sentimental et, d'autre part, le roman d'apprentissage sont observés dans le premier chapitre. Même si la quête amoureuse de l'héroïne de chick lit possède une importance non négligeable, elle s'accompagne néanmoins d'une véritable quête d'autonomie. Cependant, malgré les ressemblances soulevées entre le roman d'apprentissage et la chick lit, nous croyons que la quête d'autonomie de l'héroïne achoppe à la fin de ces romances modernes, lorsqu'elle trouve enfin le grand amour. Afin de vérifier cette hypothèse, le deuxième chapitre expose les caractéristiques inhérentes à quatre groupes de personnages masculins possédant un potentiel amoureux, soit les anciens amoureux, les amants, les amis et les amoureux. En outre, ce chapitre présente la fonction de ces personnages masculins dans la trame narrative, en plus de faire ressortir les modalités de leur relation avec l’héroïne. Finalement, le troisième chapitre met en lumière les liens unissant le père de l'héroïne et l’amoureux, puisque la recherche pose, a priori, que le père de l'héroïne de chick lit québécoise possède une relation avec sa fille se distinguant de ce qui se retrouve dans les productions anglophones, relation qui ferait du père un véritable modèle amoureux pour la fille.