The experimental toxicity of zirconium compounds is examined in the Mouse (acute toxicity) and in the Rat (short time toxicity). The absorption, the distribution and the elimination of zirconium are evaluated by zirconium cation assay in some biological fluids and tissues. After a single oral dose, zirconium oxyd is not toxic, zirconium oxychlorure slightly toxic and zirconium chlorure moderately toxic. At certain concentrations, cerebral and pulmonary disorders are observed, particularly with zirconium chlorure. In considering molar toxicity, the studied zirconium compounds are more toxic than certain aluminium salts mentioned in the literature. The zirconium oxychlorure doesn't influence the growth curve after iterative administrations (0.23 g zirconium/kg/day). Only a weak fraction of administered zirconium is absorbed and is electively fixed in the ovaries, in a lesser degree in the lung and the bone. In the ovary the zirconium induces vascular variation (hypervascularization) which appear one month after the end of the treatment. The absorbed zirconium is eliminated by the urinary tract. The fecal elimination can be essentially explained by an important quantity of non absorbed zirconium.

Animals↗

PubMedDate not supplied

[The pores of Kohn in pulmonary alveoli].

The pores of Kohn are apertures in the alveolar septum, which allow the communication of two adjacent alveoli. Their existence has been most disputed, but was lastly supported in man and adult mammalians by observations from electron microscopy. Located between the meshes of the capillary network, these alveolar apertures are circular or oval, and are bordered by extensions of type I pneumocytes. Type II pneumocytes are often located close to the pores of Kohn. The presence of two near apertures gives a "double-barrelled gun" aspect, frequently observed in the old animal. The specific connections of the pore of Kohn with the septal components, particularly by the myofibroblasts, are analysed. The quantification of the pores of Kohn in various species shows great variations according to the fixation technique, animals age and site of alveoli in the lung and the lobules. The size of these apertures also depends on species, varying from 0.8 to 15 micrograms. Histogenesis of these apertures is still poorly understood and various processes can be evoked. Ventilation, which differs according to the site of the alveoli in the lung, is a determinant factor, proved by the great number of pores of Kohn in the hyperventilated areas. The role of the macrophages (synthesis and excretion of proteases and lipases) is also discussed. The formation of pores of Kohn is linked with renewing and dehiscence of alveolar epithelial cells. The role of alveolar pores in collateral ventilation seems relatively weak in the physiological state, whereas it is certain in lung pathology, contributing to the propagation of bacterial infections in the adult and to changes of local ventilatory conditions in atelectasis and asthmatic bronchoconstriction. The alveolar apertures can explain the specific propagation of some epitheliotropical peripheral cancers (bronchiolo-alveolar carcinoma). The pore of Kohn is one of the first signs of parenchymatous senescence of the pulmonary alveolus; its part in the appearance and extension of emphysematous disorders is also discussed.

Adult↗

PubMedDate not supplied

Immunohistochemical localization of insulin-like growth factor I (IGF-I) in the rat epididymis.

The distribution of insulin-like growth factor I (IGF-I) was studied by immunohistochemistry during postnatal development of the rat epididymis. At 2 weeks the immunoreactivity was mainly located along the cytoplasmic apical border in both the caput and the cauda epididymidis. A slight immunolabeling was present in the myofibroblastic cells. Afterward, the epithelial immunoreactivity was minimal at 4 weeks and increased progressively after the 6th week, especially in the apical and subapical cytoplasmic compartments of the caput epididymidis. The labeling of the epithelial cells of the cauda epididymidis was restricted to the apical cytoplasmic area. Immunolabeling was also found in the myofibroblastic cells and was more intense after 6 weeks. The variations of the pattern of distribution support the hypothesis of a physiological role for IGF-I in the regulation of epididymal functions.

Animals↗