Toxicity of 4-Chloroaniline in Early Life Stages of Zebrafish ( Danio rerio ): II. Cytopathology and Regeneration of Liver and Gills After Prolonged Exposure to Waterborne 4-Chloroaniline

Abstract

Ultrastructural alterations in liver and gills of embryonic and larval zebrafish (Danio rerio) following prolonged exposure to waterborne 0.05, 0.5, and 5 mg/L 4-chloroaniline for up to 31 days as well as after a 14-day regeneration period were investigated by means of light and electron microscopy. Acute toxicity was also tested at 25 and 50 mg/L. Survival of zebrafish embryos and larvae was only impaired from 25 mg/L 4-chloroaniline, but-after a transient stimulation following exposure to 0.5 mg/L-4-chloroaniline hatching was retarded after exposure to >/=5 mg/L, and fish displayed increasing rates of abnormal development and pigmentation. In contrast, hepatocytes displayed a time- and dose-dependent response from 0.05 mg/L 4-chloroaniline, including changes in nuclei, mitochondria, peroxisomes, endoplasmic reticulum, Golgi fields, lysosomes, and hepatic glycogen and lipid stores, as well as invasion of macrophages. In gills, dose-dependent effects were evident from 0.5 mg/L 4-chloroaniline and included deformation of secondary lamellae due to vacuolization and desquamation of respiratory epithelial cells in conjunction with dilation of intercellular spaces. Respiratory epithelial cells displayed progressive mitochondrial changes, induction of cytoplasmic myelinated structures, augmentation of lysosomes, and modifications of Golgi fields. Erythrocytes were severely deformed. A 14-day regeneration period was sufficient for almost complete recovery of pathological symptoms in both liver and gills. Only minor volumetric changes in hepatocellular organelles and a limited number of myelinated bodies, lysosomes, and cytoplasmic vacuoles were reminiscent of prior 4-chloroaniline exposure. In both qualitative and quantitative terms, most effects in hepatocytes after exposure of embryonic and larval zebrafish to waterborne 4-chloroaniline are comparable to the reaction of hepatocytes in adult zebrafish liver after prolonged sublethal exposure as well as in larval zebrafish after microinjection. Morphological changes in erythrocytes indicate disturbance of respiration as an additional mode of action of 4-chloroaniline.

Effect of Intermediate Flush Using Different Devices to Prevent Chemical Smear Layer Formation

“…This layer may affect close adaptation between root canal filling materials and the root canal walls, interfering in the seal of the root canal filling (8,9). In addition, this precipitate changes the color of the tooth and is cytotoxic (10)(11)(12).…”

Using Diazotization to Characterize the Effect of Heat or Sodium Hypochlorite on 2.0% Chlorhexidine

“…These findings might be clinically relevant because PCA has been shown to be toxic (30,31). Toxicologic studies in animals have shown that the hematopoietic system is the major target for PCA (30).…”

“…The primary toxic effect of PCA is the formation of methemogloblin. Studies have shown that methemoglobin formation and hemolytic anemia occurred in animals after 90-day exposure to PCA (31). A carcinogenic effect of PCA in rats, manifested by increased sarcomas in the spleen, was also reported.…”

“…A carcinogenic effect of PCA in rats, manifested by increased sarcomas in the spleen, was also reported. Another reported effect was in exposed zebra fish, in which eggs were hatched later and displayed increased rates of abnormal development and pigmentation (31). In humans, there have been reports of severe methemoglobinemia in neonates exposed to PCA as a result of CHX broken down to PCA by the humidifier heater in neonatal incubators (32).…”

Comparing the Effect of Irrigation With 70% Isopropyl Alcohol, Distilled Water and Saline to Remove the Residual Sodium Hypochlorite before Irrigation with Chlorhexidine in Root Canal Therapy – An In Vitro Study

“…A carcinogenic effect by an increase in sarcoma formation in the spleen has also been reported (8). Another reported adverse effect of PCA was a delay in egg hatching and an increased rate of abnormal development and pigmentation in the hatchlings of zebra fish (18). Adverse effects have also been shown to occur in the embryos of Daphnia magna (19).…”