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Effects of 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT) on gonadal development in the chick embryo: a
Abstract:
Fertile white Leghorn chicken eggs were exposed via intravitelline injections to dosages of 5.0, 10.0, or 20 mg 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT) in olive oil prior to incubation. Control embryos received only the olive oil vehicle. Eggs were placed in a forced-draft incubator for either 5 or 12 days. Embryos were removed and their gonadal areas prepared for histological or histochemical evaluation. Histological examination of DDT-exposed 5-day embryos revealed no significant differences in the number of primordial germ cells aggregating in the gonadal area and in the localization of acid and alkaline phosphatase activity. Embryos exposed to DDT for 12 days revealed significant alterations in both ovaries and testes. The testes of DDT-exposed embryos consisted of mostly stroma with fewer seminiferous cords than controls while ovaries of exposed embryos contained a larger number of distended medullary cords as well as a difference in the distribution of these cords when compared to controls. There was an increased alkaline phosphatase activity in the stromal cells of female gonads. Increased amounts of alkaline phosphatase activity found in the stroma at 12 days might be due to a DDT-induced stimulation of these cells to differentiate more rapidly. Acid phosphatase activity was found in the secondary sex cords of control 12-day ovaries, but was much reduced or absent in those of pesticide-exposed embryos. These results indicate that a single dosage of DDT administered to a chick embryo prior to incubation does not affect early stages of gonadal development but that effects on both ovaries and testes occur 12 days following exposure.
Insights
Exposure to the pesticide DDT in chick embryos did not impact early gonadal development. However, significant alterations in both testes and ovaries were observed after 12 days, suggesting DDT affects later stages of reproductive organ development.
Area of Science:
- Developmental toxicology
- Reproductive biology
- Environmental health
Background:
- Pesticide exposure during embryonic development can disrupt normal growth.
- 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT) is a persistent organic pollutant with known endocrine-disrupting effects.
- Understanding the impact of DDT on avian reproductive development is crucial for ecological risk assessment.
Purpose of the Study:
- To investigate the effects of prenatal DDT exposure on early gonadal development in white Leghorn chicken embryos.
- To evaluate histological and histochemical changes in gonads following DDT exposure at different developmental time points.
Main Methods:
- Fertile chicken eggs were injected with varying doses of DDT (5.0, 10.0, or 20 mg) or a vehicle control prior to incubation.
- Embryos were incubated for 5 or 12 days.
- Gonadal tissues were analyzed using histological and histochemical techniques to assess germ cell number, cord formation, and enzyme activity (acid and alkaline phosphatase).
Main Results:
- No significant differences in primordial germ cells or phosphatase activity were observed at 5 days post-exposure.
- At 12 days, DDT-exposed testes showed reduced seminiferous cords, while ovaries exhibited altered medullary cord distribution and increased alkaline phosphatase activity in stromal cells.
- Acid phosphatase activity was reduced in the secondary sex cords of DDT-exposed ovaries compared to controls.
Conclusions:
- Prenatal DDT exposure does not affect initial gonadal differentiation in chick embryos.
- Prolonged exposure (12 days) to DDT leads to significant histological and histochemical alterations in both male and female gonads.
- DDT may interfere with the normal differentiation and development of avian reproductive organs during later embryonic stages.