Pesticide 2

Question 1

Nicotine

Answer 1

Interact with human and insect ACh receptors
More toxic to mammals than insects, short lived, protonated at low or neutral pH(resistant to entering insect cuticles), poorly lipophilic

Question 2

Neonicotinoids(NN)

Answer 2

Most widely used pesticide(first imidacloprid), newer NN(thiamethoxam, clothiandin)
Selective for insect nAChRs- low Log P value = LESS lipophilic(NN not toxic dermal)
NOT ionized-increased potency and selectivity for insects
Nitromethylene group
Nitroamine group
Cyanoimine group

Question 3

NN Selectivity

Answer 3

Insect nAChR have + charge, mammalian NAChR is (-) subsite
IMI-imidacloprid
Insects eat plants to absorb them, moderately sol in water-POOR contact insecticides
DO NOT accumulate

Question 4

NN Mech of action

Answer 4

NN are not substrates for acetylcholinesterases, therefore prolong action at synapse
1st gen NNS(imidacloprid(IMI))
Overstim of insect nAChRs lead to desensitization of the recep and paralysis and death of insects
Especially toxic to bees-partial agonist in bee brain structure involved in learning
Metabolite 6-chloronicotinic acid(6-CNA) seems to also be toxic and lead to delayed lethality over a period of 96 hrs or longer=bees sensitive to 6-CNA

2nd gen NNS(thiamethoxam)
Poor insect nAChR agonist-poor nicotinic R
Full agonist at AChR in periphery
May also be muscarinic agonist-atropine works
Clothianidin:metabolite that may be toxic

Question 5

Colony collapse disorder and NNS

Answer 5

Imidacloprid-1st gen: most potent insecticide for bees
First and second gen both cause
Cause of bee deaths
Change in feeding behaviour rather than acute lethality
Don’t respond to normal sugar content that would normally be sufficient to feed the colony
Waggle-dance frequency dramatically decrease-colony mates not informed of food supply

Question 6

Phosphine

Answer 6

Mostly used to kill rodents, fumigant, gas and tablet form(released as phosphine gas when exposed to moisture)
400-600ppm lethal within 30 mins

Question 7

Phosphine mech of action

Answer 7

Block ETC via inhibition of cytochrome C in mito
Prevent oxidative phosphorylation
Result in ROS production
Occurs primarily in heart and lung tissue
Lipid peroxidation and p denaturation
Directly toxic to alveolar capillary membranes
Acute resp distress syndrome
Lung fills with fluid

Question 8

Phosphine Clinical symptoms

Answer 8

Nausea and vomiting
Breathlessness and airway irritation
Anxiety, dizziness, ataxia, paresthesias
Cardiac collapse: common form of death 
First phase-sinus tachycardia
Second phase- ST segment changes and dysrhythmias
No evidence for antidote

Question 9

Biopesticides-Bacillus thuringiensis(Bt)

Answer 9

Bt is a bacterium found in soil that produces insecticidal proteins.
Toxic to only specific insects(pests) while sparing parasitic wasps, bees and ladybugs
Bt crops are GMOs
Express genes that code for the insecticidal proteins Cry(crystal delta endotoxins) and VIP(vegetaitve insecticidal protein)
Target recep on APICAL brush border membrane of insect midgut epithelial cell-cant abs food

Question 10

CRY structure

Answer 10

SEE PIC AND 7a helices in a barrel structure

Question 11

Benefits of Bt-Cry

Answer 11

No effect on humans
Specific for cells of pests
Toxin is biodegradable in light and non-persistent in env
Its effectiveness often results in a decrease in the use of more harmful pesticides
NOT associated with Colony Collapse Disorder
Not allergen/toxic, prot digestible