Oxygen-induced retinopathy in the mouse.

PURPOSE: To develop oxygen-induced retinopathy in the mouse with reproducible and quantifiable proliferative retinal neovascularization suitable for examining pathogenesis and therapeutic intervention for retinal neovascularization in retinopathy of prematurity (ROP) and other vasculopathologies. METHODS: One-week-old C57BL/6J mice were exposed to 75% oxygen for 5 days and then to room air. A novel fluorescein-dextran perfusion method has been developed to assess the vascular pattern. The proliferative neovascular response was quantified by counting the nuclei of new vessels extending from the retina into the vitreous in 6 microns sagittal cross-sections. Cross-sections were also stained for glial fibrillary acidic protein (GFAP). RESULTS: Fluorescein-dextran angiography delineated the entire vascular pattern, including neovascular tufts in flat-mounted retinas. Hyperoxia-induced neovascularization occurred at the junction between the vascularized and avascular retina in the mid-periphery. Retinal neovascularization occurred in all the pups between postnatal day 17 and postnatal day 21. There was a mean of 89 neovascular nuclei per cross-section of 9 eyes in hyperoxia compared to less than 1 nucleus per cross-section of 8 eyes in the normoxia control (P < 0.0001). Proliferative vessels were not associated with GFAP-positive astrocyte processes. CONCLUSIONS: The authors have described a reproducible and quantifiable mouse model of oxygen-induced retinal neovascularization that should prove useful for the study of pathogenesis of retinal neovascularization as well as for the study of medical intervention for ROP and other retinal angiopathies.

Effect of light on oxygen-induced retinopathy in the mouse.

PURPOSE: To examine the effect lf light on retinal neovascularization and vasculogenesis in a reproducible and quantifiable model of oxygen-induced proliferative retinopathy in the mouse. METHODS: C57Bl/6J mice were reared in room air, 68% oxygen, or 75% oxygen and were exposed to darkness, low cyclical light (200-350 lux), or high-intensity continuous light (3000-4500 lux). The entire retinal vascular pattern was visualized in fluorescein-dextran perfused flat-mount preparations. Proliferative retinopathy was quantified by counting neovascular nuclei in 6 microns cross-sections of whole eyes. RESULTS: Light exposure did not exacerbate the proliferative retinopathy that was seen after 68% oxygen exposure, which induced a meager proliferative response, nor after 75% oxygen exposure, which induced an exuberant proliferative response. In room air, retinas from all three illumination groups had normal vascular patterns. CONCLUSIONS: In this model of oxygen-induced retinopathy, under the conditions tested, light neither exacerbated the hyperoxia-induced neovascularization nor affected normal retinal vascular development.

Microscopic visualization of the retina by angiography with high-molecular-weight fluorescein-labeled dextrans in the mouse.

Methods currently available for the examination of the retinal vasculature of laboratory animals have significant drawbacks. Fluorescein angiography of rodent eyes is hampered by a poor view of the peripheral retina and difficulty in performing fundus photography. Methods of staining or filling retinal vessels are unreliable, labor-intensive, or have high backgrounds. We have developed a novel technique that is quick, simple, and accurate. Fluorescein-labeled 2 million molecular weight dextrans are used to fill the retinal vasculature of mice in vivo, followed by removal of the retina, fixation in paraformaldehyde, and examination of the vascular pattern in whole mount preparations by fluorescence microscopy. We found that fluorescein and fluorescein-labeled low-molecular-weight dextrans (40,000-500,000) are not suitable as they leak out of the vasculature to stain the entire retina in whole mount preparations. By contrast, fluorescein-labeled 2 million molecular weight dextrans remain in the vasculature for many months without diffusion or decay. Under low magnification, the entire retinal vasculature can be visualized at one time. By focusing from one plane to another, the superficial, connecting, or deep vascular layers are delineated. The background fluorescence is very low. We have successfully used this technique in over 20 mice per day to document retinal angiogenesis in a model of oxygen-induced proliferative retinopathy.

Modulation by neonatal thymectomy of the reproductive axis in male and female rats during development.

The effects of neonatal thymectomy, at 3 days of age, on parameters of the reproductive axis were examined in male and female Sprague-Dawley rats. Gonadal and accessory sex tissue (male: epididymis, seminal vesicle, and ventral prostate; female: uterus) weights as well as anterior pituitary, spleen, and adrenal weights were determined in the thymectomized and sham-thymectomized animals at 20, 30, 40, 50, 60, and 90 days of age. Plasma gonadotropin concentrations as well as pituitary content of the gonadotropins and prolactin were assessed at each of these time intervals. No significant difference in gonad and accessory sex tissue weights was detected in thymectomized versus sham-operated controls at each of these times. Adrenal weights were increased in thymectomized animals compared with controls at 50 days of age and older in male rats and at 90 days in females. Spleen weights were decreased in the thymectomized males at 50 and 60 days of age. Thymectomy did not affect the spleen weight of females. Plasma concentrations of gonadotropins were unaffected in thymectomized males but were altered in females during the pre- and peripubertal period (Days 20-40). Vaginal opening, however, occurred at the same time in the thymectomized and control females. Pituitary gonadotropin and prolactin content were unaffected by thymectomy of the females, except at 90 days when pituitary luteinizing hormone (LH) content was lower in thymectomized than in control animals. LH and prolactin content were significantly reduced in the males at 60 and 90 days of age. These results demonstrate that there are sexual differences in the effects of thymectomy on parameters of the reproductive axis.(ABSTRACT TRUNCATED AT 250 WORDS)