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Biomedical subjects

X Reynaud

Publications and source records attributed to X Reynaud.

7 recordsLinked to original sources
PubMed1999

Rod photoreceptors in infant rats with a history of oxygen exposure.

PURPOSE: To study in an infant rat model of retinopathy of prematurity, the rod photoreceptors, which are known to have attenuated photoresponses. METHODS: Rhodopsin was extracted from whole retinas, the thickness of the rod outer segment (ROS) layer was measured, large phagosomes were counted, and the ROS ultrastructure was examined in the retinas of oxygen-exposed and control rats, ages 13 and 18 days. Rhodopsin absorbances in the ROS were measured by microspectrophotometry at age 20 days. RESULTS: The rhodopsin content did not differ significantly between the oxygen-exposed and control rats at either 13 or 18 days. The thickness of the ROS layer was equal in 13-day-old oxygen-exposed and control rats; however, at 18 days, the ROS layer was significantly thinner in the oxygen-exposed rats than in the control rats. The number of phagosomes did not vary significantly among the oxygen-exposed and control groups. Opsin immunoreactivity was seen only in the ROS layer in oxygen-exposed and control rats. The ROS were disorganized in oxygen-exposed rats. The rhodopsin absorbances of the oxygen-exposed ROS were significantly more variable and higher than in the control rats. CONCLUSIONS: Attenuation of the rod photoresponse parameters does not result simply from shortening of the outer segments and consequent low rhodopsin content. Rather, the structure of the outer segments is altered. A fault in the synthesis of the outer segments, rather than disposal of outer segment discs, is suspected.

Animals↗
PubMed1996

Correlation of vascular permeability factor/vascular endothelial growth factor with extraretinal neovascularization in the rat.

OBJECTIVE: To determine whether neovascularization was spatially correlated with the distribution of messenger RNA for vascular permeability factor/vascular endothelial growth factor (VPF/VEGF). METHODS: Neonatal rats were raised 8 days in 80% oxygen with daily intervals of relative hypoxia in room air, then transferred to room air for 5, 7, or 10 additional days. In situ hybridization for VPF/VEGF expression and avascular area were examined in retinas from oxygen-exposed animals and room-air controls. Severity of neovascularization was scored. RESULTS: The inner nuclear layer of oxygen-exposed retinas exhibited a continuous intense band of VPF/VEGF messenger RNA expression across the peripheral avascular zone that dropped sharply in vascular retina. Neovascularization occurred adjacent to regions of greatest expression. Controls had much lower expression and smaller avascular regions. The VPF/VEGF messenger RNA expression was most intense in Müller cells, scattered astrocytes, and amacrine cells, strong in retinal pigment epithelium, and moderate in the remaining inner nuclear layer and ganglion cell layer. CONCLUSION: The expression of VPF/VEGF message was spatially and quantitatively correlated with the neovascularization.

Animals↗
PubMed1995

Effect of prior oxygen exposure on the electroretinographic responses of infant rats.

PURPOSE: To study electroretinographic responses of infant rats with a history of exposure to high-ambient oxygen. METHODS: Electroretinographic responses to a range of full-field stimuli were recorded from 13-day-old (n = 8) and 18-day-old (n = 10) rats with a history of intermittent exposure to 80% oxygen and age-matched controls. The a-waves were fitted with a model of rod cell sensitivity and saturated response amplitude. The amplitudes and implicit times of the b-wave and oscillatory wavelets were examined as a function of stimulus energy. Response parameters in oxygen-exposed rats were compared to those in controls. RESULTS: The amplitude of the saturated rod response was reduced in oxygen-exposed 13-day-old but not 18-day-old rats. The sensitivity of the rod response was reduced in both 13- and 18-day-old oxygen-exposed rats. The saturated amplitude and sensitivity of the b-wave did not differ significantly between oxygen-exposed and control rats age 13 days, but both amplitude and sensitivity were significantly decreased in 18-day-old oxygen-exposed rats. Oscillatory potentials, which could be investigated only in 18-day-old rats, showed significant attenuation of OP3 but not OP4 amplitudes in the oxygen-exposed rats. The sensitivity of OP2 did not differ significantly between oxygen-exposed and control rats. The avascular area in the oxygen-exposed rats was not correlated with any of the rod cell, b-wave, or oscillatory potential response parameters. CONCLUSION: The function of the rod photoreceptors, as well as the inner retina, is altered in infant rats with a history of oxygen exposure.

Aerobiosis↗
PubMed1994

Extraretinal neovascularization induced by hypoxic episodes in the neonatal rat.

PURPOSE: To test the hypothesis that hypoxia induces retinal neovascularization. METHODS: To produce relative hypoxia in the avascular retina, newborn rats were exposed for 11 days to 80% oxygen interrupted daily by short episodes in room air. Episodes in room air lasted 1/2 hour or 1 hour followed by abrupt reintroduction, or 1/2 hour followed by progressive reintroduction to 80% oxygen lasting 3 hours to prolong the period of hypoxia. At the end of the 11 days of interrupted oxygen exposure, the animals were left in room air for 6 days. RESULTS: The incidence of neovascularization exhibited a dose-response relationship to the period out of 80% oxygen. Periods of approximately 3 hours produced neovascularization (in at least one eye) in 94% of the animals. The total area of the peripheral avascular retina was larger in animals exposed to prolonged periods of hypoxia than in those exposed for shorter periods. The incidence of neovascularization was strongly associated with the total area of the peripheral avascular retina and occurred in the inferior quadrant in 78% of the cases. Additional features of stage 3 retinopathy of prematurity (ROP), including arteriovenous shunts and ridges, were observed in some retinas. CONCLUSIONS: These data demonstrate that hypoxic episodes can induce extraretinal neovascularization in the rat and suggest that brief periods of oxygen deficiency could exacerbate progression of ROP. With the high incidence and predictability of localization of neovascularization, this model could be useful for the study of angiogenesis and for evaluation of antiangiogenic or antioxidant substances.

Animals↗
PubMed1991

Characterization of functional changes in macular holes and cysts.

Precise characterization of functional loss in small retinal lesions is difficult with conventional techniques. Using the scanning laser ophthalmoscope, the authors evaluated functional changes and fixation behavior in 26 eyes with macular holes and 15 eyes with macular cysts. A dense scotoma was present over all macular holes; 24 had no detectable functional alteration at the margins of the hole, and fixation was above the horizontal meridian in all eyes. Nine eyes with cysts had no detectable functional loss over the cyst. Only two eyes had small areas of dense scotoma within the cyst area, and four had areas of relative scotoma. Fixation was central in all eyes. Characterization of functional changes is helpful in differentiating holes from cysts. Photocoagulation at the margin of the holes may result in further functional damage.

Aged↗