Ultrastructural changes in rat cornea after prolonged hypobaric hypoxia.

A study was performed to evaluate the effect of prolonged environmental hypobaric hypoxia on the ultrastructure of rat cornea. 60-day-old female Wistar rats were exposed to a simulated altitude of 5,500 m (350 mmHg) and pO2 of 76 mmHg for 30 days. Control rats were exposed to atmospheric sea level pressure (760 mmHg) and pO2 of 150 mmHg, for the same period. Ultrastructural analysis of the corneal epithelium did not reveal any relevant difference between control and treated rats. In contrast, the corneal stroma of rats subjected to hypoxia showed vascularization with advanced vessel differentiation and signs of active proliferation. The endothelium of hypoxic cornea showed swollen mitochondria and large empty cytoplasmic areas. The endothelial intercellular junctions could hardly be identified in the hypoxic condition. Nevertheless, the most evident change in hypoxic cornea was in Descemet's membrane, which was considerably thickened, to approximately twice that of the control specimen. These results suggest that environmental hypobaric hypoxia induces marked alterations in the corneal stroma and endothelium morphology, probably related to reduced oxygen tension in the aqueous humor, consequent to hypoxemia.

[Protective effect of hyperbaric hypoxygenation for paraquat poisoning in the rat]. / Effet protecteur de l'hypoxygénation hyperbarique au cours de l'intoxication par le paraquat, chez le rat.

The effect to paraquat in normobaric conditions and hyperbaric conditions with either a normal or low (10%) oxygen percentage was investigated in rats. Results showed that hyperbaric conditions increased the toxic effect of paraquat on the lung. By contrast, in hypoxic-hyperbaric conditions, the toxic effect of paraquat was decreased either clinically or macro-/microscopically, and lung injury was reduced.