Biomedical subjects

D M Soderlund

Publications and source records attributed to D M Soderlund.

24 records · Page 2Linked to original sources

PubMed1984

Mouse brain synaptosomal sodium channels: activation by aconitine, batrachotoxin, and veratridine, and inhibition by tetrodotoxin.

Batrachotoxin, veratridine and aconitine, activators of the voltage-dependent sodium channel in excitable cell membranes, increase the rate of 22Na+ uptake by mouse brain synaptosomes. Batrachotoxin was both the most potent (K0.5, 0.49 microM) and most effective activator of specific 22Na+ uptake. Veratridine (K0.5, 34.5 microM) and aconitine (K0.5, 19.6 microM) produced maximal stimulations of 22Na+ uptake that were 73% and 46%, respectively, of that produced by batrachotoxin. Activation of 22Na+ uptake by veratridine was completely inhibited by tetrodotoxin (I50, 6 nM ), a specific blocker of nerve membrane sodium channels. These results identify appropriate conditions for measuring sodium channel-dependent 22Na+ flux in mouse brain synaptosomes. The pharmacological properties of mouse brain synaptosomal sodium channels described here are distinct from those previously described for sodium channels in rat brain synaptosomes and mouse neuroblastoma cells.

Aconitine↗

PubMed1983

Receptor-like stereospecific binding of a pyrethroid insecticide to mouse brain membranes.

A heterogeneous particulate fraction of mouse brain homogenates binds NRDC 157 (3-phenoxybenzyl [1R, cis]-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate), a potent pyrethroid insecticide, stereospecifically and with high affinity. Stereospecific binding is a minor component of total binding (2.8%); the remainder of observed binding is predominantly nonspecific and unsaturable. Stereospecific binding is half-saturated at 4 X 10(-8)M and fully saturated at concentrations in excess of 1 X 10(-7)M. The stereospecific binding capacity of this preparation was 200-250 pmoles of NRDC 157 per gram equivalent of brain tissue (2.3-2.8 pmol/mg protein). This binding site may represent the neural receptor involved in the stereospecific toxic action of pyrethroids.

Animals↗

PubMed1983

Effects of non-neural mechanisms on pyrethroid structure-activity relationships.

Structural requirements for high insecticidal activity in pyrethroid insecticides are very stringent. Observed structure-activity relationships may arise either from specificity at the site of pyrethroid action in the nervous system, from selectivity in the pharmacokinetic processes governing the appearance and persistence of compounds at that site, or from a combination of these mechanisms. Recent studies of the metabolism of trans and cis isomers of pyrethroids in insect tissue preparations in vitro and of their pharmacokinetic behavior in insects in vivo permit an assessment of the impact of non-neural mechanisms on the toxicity differences observed between these isomers.

Animals↗

PubMed1977

Separation and analysis of the pyrethrins by combined gas-liquid chromatography-chemical ionization mass spectrometry.

Pyrethrins, the 6 naturally occurring insecticidal esters of pyrethrum extract, were analyzed by combined gas-liquid chromatography-chemical ionization mass spectrometry. Separation was best on an OV-25 column with temperature programming; The chemical ionization mass spectra for the 6 esters as well as for the thermally isomerized pyrethrins I and II are reported and discussed. Using selective ion monitoring, a lower limit of detectability of all 6 esters was 114 ng of total extract injected on the column.

Chromatography, Gas↗

PubMedDate not supplied

Structure-biodegradability relationships in pyrethroid insecticides.

The metabolism of 20 pyrethroids has been examined to evaluate the contribution of detoxification in their selective action between insects and mammals. The studies utilized living houseflies, mice, or rats, or esterase and oxidase systems derived from these organisms. Pyrethroid-hydrolyzing esterases cleave the primary alcohol trans-substituted-cyclopropanecarboxylates much faster than the corresponding cis-isomers but are ineffective in hydrolyzing secondary alcohol esters. Microsomal enzymes oxidize the (+)-trans-chrysanthemate moiety at the trans-methyl group of the isobutenyl substituent and at one of the gem-dimethyl groups whereas the (+)-cis-isomer is attacked at either of the isobutenyl methyl groups. Products isomerized at C3 of the cyclopropane are also detected but only after ester cleavage and oxidation of an isobutenyl methyl group. Each alcohol moiety has its own unique sites for oxidation involving pentadienyl, allyl, benzylic methylene, and aromatic substituents. An enhancement of insecticidal activity is expected on replacement of the biodegradable groupings with substituents relatively resistant to metabolism but this may also increase the mammalian toxicity.

Animals↗

PubMedDate not supplied

Metabolic considerations in pyrethroid design.

1. Synthetic pyrethroids, based on the naturally-occurring insecticidal components of pyrethrum extract, emerged in the 1970s as the fourth major chemical class of synthetic insecticides. They are widely used today in the control of agriculture and household pests and disease vectors. 2. Early efforts in the design of synthetic analogues focused on the need to identify novel structural moieties that preserved or enhanced intrinsic insecticidal activity while eliminating known sites of metabolic and photolytic attack in the natural compounds. Subsequent efforts focused on achieving high levels of insecticidal activity while minimizing costs of synthesis and retaining desirable levels of selective toxicity. 3. The synthetic compounds obtained in these efforts constitute a group of insecticides having unprecedented biological activity against target species with low acute toxicity to mammals. 4. The evolutionary development of the pyrethroids illustrates how knowledge of metabolic fate can contribute to the design of novel insecticides with improved insecticidal activity and selective toxicity.

Animals↗