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|a The present study was suggested to explore the impacts of the organochlorine pesticide endosulfan (35% EC) on the developing chick embryos. After 24 hours of eggs incubation, a single dose of 7 or 14 or 21 mg endosulfan/egg was administered through the egg's air space at once. The eggs were opened on embryonic days (EDs) 6 and 12 and the embryos were evaluated for viability, wet body weights, various morphological, morphometric and skeletal changes and the histopathological changes on the developing spinal cord, notochord, liver, and kidney types (mesonephroi and metanephroi). Comparing the three doses with control and with each others, the high dose treatment resulted in statistically significant more embryonic deaths, while the mid-dose caused statistically more malformed embryos. On both EDs, the treated embryos exhibited dose-related growth retardation, as reflected by significant reductions of embryonic wet body weight, anterior-posterior head and crown-rump lengths as well as generalized edema and hematomas formations. Also, on embryonic day 12 significant reductions of beak length, eye diameters and measurements of wing and hind-limb parts were recorded. Abnormal survivors showed high percentages of limb deformities (as limb paralysis, clinodactyly, flexion, and shortness of limbs or digits), microphthalmia, microtia, and omphalocele. The skeleton of treated embryos showed anomalies and incomplete chondrification and/or ossification of some skull parts (interorbital septum, frontals, parietals, palatines, and external auditory apertures), cervicals, scapulae, ribs, sacrals, and caudals. The histopathological changes observed in the spinal cord were dose-dependant and were represented by loss of normal morphology, cellular disorganization, decrease of mitotic figures, neuroepithelium distortion, damage of the neural canal, and cell death and necrosis were frequently seen in the dorsal and ventral horns and roof plate cells. The changes in the notochord were in the form of shrinkage and distortion of the circular shape of the normal notochord. Furthermore, the covering sheath showed disassociation and degeneration of its layers.
|a The endosulfan effects on the liver of the developing chick embryo were dose and embryonic age dependent and were represented by disturbance of hepatic cords arrangement, congestion, retarded compaction and degeneration of hepatic parenchyma and mononuclear cell infiltration, hemorrhage, necrotic changes, an increased incidence of cytoplasmic vacuolization, dilatation and irregularity of sinusoids, an increased incidence of Kupffer cells and lymphocytes. These changes were much severe in ED 6 than in ED 12. In control embryos (on ED 6) the only observed excretory tissue was of the mesonephric kidney type. The endosulfan treatment on ED 6 resulted in dose-dependent histopathological lesions such as a general delay of the L/ and or U-shaped bodies differentiation, a general reduction in the number of mesonephric ducts and tubules, irregular distribution of the renal corpuscles, high rate of degenerative changes with atrophy and/or vacuolization of epithelial cells, pronounced enlargement of the tubules and excessive hemorrhage. In controls of ED 12 both mesonephric and metanephric types of kidney were observed. The mesonephroi were fully developed, enlarged, more compacted and contained much more closely associated components than those of the previously mentioned 6-day-old stage. The effects of endosulfan on ED 12 were also dose-dependent and included regressive changes in mesonephroi. These changes were represented by size reduction, dilatation of collecting tubules, necrosis and apoptosis, damaged renal corpuscle, and persistence of primitive excretory units. Also, the metanephros was either poorly developed or did not show any appearance. These findings suggest that endosulfan exhibits embryotoxic and teratogenic effects on the developing chick embryos in terms of growth retardation, external and skeletal malformations as well as histopathological changes on the developing spinal cord, notochord, liver, and kidney types (mesonephroi and metanephroi).
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