1. ©Chaves, Hofelt, Shea. Environmental Toxicology and Chemistry Environmental Toxicology and Chemistry Intoxication Mechanisms II

2. ©Chaves, Hofelt, Shea. Intoxication Mechanisms II

3. ©Chaves, Hofelt, Shea. Plant-Specific Mechanisms

4. ©Chaves, Hofelt, Shea. Photosynthesis One of the main distinctive features of plants is its ability to use sunlight to generate energy (ATP) and reducing power (NADPH) from water in a process known as photosynthesis. One of the main distinctive features of plants is its ability to use sunlight to generate energy (ATP) and reducing power (NADPH) from water in a process known as photosynthesis. Plants capture solar energy using a system of pigments. Plants capture solar energy using a system of pigments.

5. ©Chaves, Hofelt, Shea. Photosynthesis

6. Photosynthesis Herbicides such as Simazine, Propanil, Bromacil, Metribuzin and Diuron inhibit photosynthesis mostly by affecting the Hill reaction. Herbicides such as Simazine, Propanil, Bromacil, Metribuzin and Diuron inhibit photosynthesis mostly by affecting the Hill reaction. 2H 2 O + 4Fe +3 → O 2 + 4H + + 4Fe +2. 2H 2 O + 4Fe +3 → O 2 + 4H + + 4Fe +2.

7. ©Chaves, Hofelt, Shea.

8. Paraquat High reduction potential. High reduction potential. Competes with chlorophyll a for electrons. Competes with chlorophyll a for electrons. P 2+ + e - → P +· → ·O-O + P 2+ P 2+ + e - → P +· → ·O-O + P 2+

9. ©Chaves, Hofelt, Shea. Amino Acid Biosynthesis Glyphosate It inhibits synthesis of aromatic amino acids by affecting the enzyme 5- enolpyryvylshikimate-3-phosphate (EPSP) synthase. It inhibits synthesis of aromatic amino acids by affecting the enzyme 5- enolpyryvylshikimate-3-phosphate (EPSP) synthase.

10. ©Chaves, Hofelt, Shea. Amino Acid Biosynthesis Sulfonylureas Inhibit the synthesis of valine, leucine and isoleucine by inhibiting the enzyme acetolactate synthase (ALS). Inhibit the synthesis of valine, leucine and isoleucine by inhibiting the enzyme acetolactate synthase (ALS).

11. ©Chaves, Hofelt, Shea.

12. Microbe-Specific Mechanisms

13. ©Chaves, Hofelt, Shea. Cell Wall Synthesis

14. ©Chaves, Hofelt, Shea. Cell Wall Synthesis

15. ©Chaves, Hofelt, Shea. Cell Wall Synthesis Murein Structure.

16. ©Chaves, Hofelt, Shea.

17. Cell Wall Synthesis Penicillin acts by inhibiting the enzyme transpectidase involved in the synthesis of the cross-linked network of murein. Penicillin acts by inhibiting the enzyme transpectidase involved in the synthesis of the cross-linked network of murein.

18. ©Chaves, Hofelt, Shea. Penicillin

19. Toxicity via Sulfhydryl Groups

20. ©Chaves, Hofelt, Shea. Sulfhydryl Groups Copper compounds are very efficient in controlling fungal infections. Copper compounds are very efficient in controlling fungal infections. They bind tightly to SH groups in a way similar to arsenic compounds in mammals. They bind tightly to SH groups in a way similar to arsenic compounds in mammals. They enter the cell by forming lipid- soluble chelates with natural amino- and hydroxy-acids. They enter the cell by forming lipid- soluble chelates with natural amino- and hydroxy-acids.

21. ©Chaves, Hofelt, Shea. Mechanism of Toxic Action of Copper Fungicides

22. ©Chaves, Hofelt, Shea. Fungicides Dithiocarbamates: some of the most common fungicides. Dithiocarbamates: some of the most common fungicides. Easy and cheap to make. Easy and cheap to make. Broad range. Broad range. Safe for animals and plants. Safe for animals and plants.

23. ©Chaves, Hofelt, Shea. Nabam Toxicity

24. ©Chaves, Hofelt, Shea. Special Topic Chemical Carcinogenesis

25. ©Chaves, Hofelt, Shea. Cancer 1-uncontrolled cell proliferation. 1-uncontrolled cell proliferation. 2- genotoxicity (the toxic effect is related to damage cause at the DNA level). 2- genotoxicity (the toxic effect is related to damage cause at the DNA level). 3- long latency period. 3- long latency period.

26. ©Chaves, Hofelt, Shea. Chemical Carcinogen Ultimate Carcinogen Damaged DNA Latency Tumor Formation DNA Repair Detoxication Replication Growth, Promotion And Progression

27. ©Chaves, Hofelt, Shea. Metabolic Activation The ultimate carcinogen is normally an electrophile. The ultimate carcinogen is normally an electrophile. Most of the time it is metabolic activation what causes the formation of electrophiles. Most of the time it is metabolic activation what causes the formation of electrophiles. Alkylation of DNA is known to affect directly the stability of H bonds within the DNA strand. Alkylation of DNA is known to affect directly the stability of H bonds within the DNA strand.

28. ©Chaves, Hofelt, Shea. Conclusions The toxic interaction of a xenobiotic with a target is basically a chemical process. The toxic interaction of a xenobiotic with a target is basically a chemical process. Toxicants interact with specific receptors. Toxicants interact with specific receptors. There is a high degree of variation in the possible toxic responses observed. There is a high degree of variation in the possible toxic responses observed. Even individuals of the same species may respond differently to the same toxic insult. Even individuals of the same species may respond differently to the same toxic insult.

29. ©Chaves, Hofelt, Shea. References 1-Crosby, D.G. Environmental Toxicology and Chemistry. 2000. Oxford University Press, New York. 1-Crosby, D.G. Environmental Toxicology and Chemistry. 2000. Oxford University Press, New York.

30. ©Chaves, Hofelt, Shea. Additional Resources National Toxicology Program Report on Carcinogens: National Toxicology Program Report on Carcinogens: http://ntp- server.niehs.nih.gov/NewHomeRoc/AboutRo C.html http://ntp- server.niehs.nih.gov/NewHomeRoc/AboutRo C.html http://ntp- server.niehs.nih.gov/NewHomeRoc/AboutRo C.html http://ntp- server.niehs.nih.gov/NewHomeRoc/AboutRo C.html Information of Photosynthesis: Information of Photosynthesis: http://photoscience.la.asu.edu/photosyn/educ ation/learn.html http://photoscience.la.asu.edu/photosyn/educ ation/learn.html