Dieldrin: interaction with nerve components of cockroaches

DNA sequence and site of mutation of the GABA receptor of cyclodiene-resistant red flour beetle, Tribolium castaneum

Using polymerase chain reactions (PCR) on cDNA, the DNA sequence of a membrane spanning region of a GABA receptor of the red flour beetle, Tribolium castaneum was identified. The deduced amino acid sequence indicates that its basic structure is similar to the GABA receptor of Rdl type subunits of Drosophila melanogaster and of Blattella germanica. Particularly conserved are M1, M2 and M3 segments. Within this 146 amino acid stretch, the GABA receptor from the red flour beetle differed from corresponding ones from Drosophila and Rdl subunit of B. germanica by 12 and eight amino acids, respectively. By using an identical approach, the corresponding DNA region was sequenced from the cDNA of a cyclodiene-resistant strain of T. castaneum. While two points of mutation were found only one mutation in DNA was found to result in an amino acid shift. The site of mutation was at the 5th amino acid of the M2 cylinder where G to T conversion of the GCT codon resulted in a conversion of alanine to serine. This is qualitatively the same mutational switch of alanine to serine in resistant strains previously reported to have occurred in cyclodiene-resistant Drosophila melanogaster, Aedes aegypti and Blattella germanica, indicating that this amino acid change is the likely cause for evolution of the nerve insensitive type of resistance to cyclodiene insecticides.

DDT: participation in ultraviolet-detectable, charge-transfer complexation

The chlorophenyl groups of DDT and several of its metabolites are capable of participating in a charge-transfer interaction with tetracyanoethylene detectable in the ultraviolet region of the spectrum. In addition, during a change of state DDT undergoes ultraviolet spectral alterations that closely resemble those previously claimed to support the hypothesis suggesting charge-transfer interaction between this pesticide and a component of insect nerve tissue. The pesticide DDT possesses structural characteristics that would permit it to participate in several types of molecular association.

Antagonism by DDT of the effect of valinomycin on a synthetic membrane

The potassium conductance which is induced by 10(-6) molar valinomycin in a lecithin-decane membrane is reversed by 3 x 10(-6) molar DDT. Membranes not treated with valinomycin are not affected by DDT. This blockade of potassium conductance parallels the effect of DDT on axonic conduction. Dieldrin and lindane, whose physiological actions are in some ways like those of DDT, do not affect valinomycin-induced conductance of lecithin-decane membranes.

Improved extraction of chlorinated hydrocarbon pesticides from animal tissues

An improved procedure Is presented whereby greater concentrations of chlorinated hydrocarbon pesticides are removed from fatty animal tissue. This procedure employs surfactants such as Span 80 and crude lecithin in the presence of petroleum ether to extract the fat and pesticide.

Inhibition of electron transport enzymes and cholinesterases by Endrin

Two enzymes involved in mitqchondrial electron transport in the catfish,Ictalurus melas, have been shown to be inhibited by endrin. Succinate dehydrogenase and cytochrome oxidase were both inhibited, and the extent of inhibition depended ypon endrin concentration and the specific activity ef the enzyme preparation. No appreciable effect of endrin on acetylcholinesterase or NADH-cytochrome c reductase was seen. Binding to lipoprotein components essential for mitochondrial oxidation has been proposed as a logical site for endrin action.

Dieldrin: degradation by soil microorganism

An attempt was made to discover microorganisms that degrade dieldrin, an extremely stable chlorinated hydrocarbon insecticide. Examination of more than 500 isolates from soil that had been heavily contaminated with various insecticides revealed the existence of a few microbes that are very active in degrading this compound to various metabolites.