Use of an indicator sequence of human DNA to study DNA damage by methylbis(2-chloroethyl)amine

A highly reiterated sequence of human DNA was used to determine the sites of modification of DNA caused by the anti-tumor drug methylbis(2-chloroethyl)amine (HN2, mechlorethamine, nitrogen mustard) upon treatment of cells in culture and of purified DNA. The lengths of the breakage products of the DNA treated with HN2 were compared to the lengths of DNA scission products produced by chemical reactions used for DNA sequence determination. HN2 was found to create alkali-labile lesions at positions of guanine. The distribution of the guanine modifications was the same for DNA extracted from cells treated with HN2 and for purified DNA treated with HN2. However, the extent of damage was at least 2-fold greater when purified DNA was used as the substrate. Several nitrogen mustard analogues also produced alkali-labile lesions at positions of guanine.

Studies on the action of dimethoate on the immune system

The actions of the organophosphorous insecticide dimethoate (0.0-dimethyl S-(N-methylcarbamoylmethyl)phosphorodiothioate) on the immune response of mice and rats were studied. There was a decrease of lymphocytes to at 50% of normal. The weights of the thymus and spleen were diminished and the production of antibodies was reduced. 72 h after administration all the parameters measured had returned to normal. Histological examinations show a reduction of the cortex of the thymus and disruption of the thymocytes. The number of rosettes forming cells in rats was reduced after dimethoate. The actions seen after dimethoate administration are identical with the effects observed after glucocorticoid application. These results suggest an indirect depression of the immune system by dimethoate producing a release of glococorticoids.

Effect of two organophosphorus insecticides on the phosphate-dissolving soil bacteria

Dimethoate and malathion added to soil at 10 and 100 microgram/g caused an initial stimulation of CO2 production. Total counts of bacterial propagules were increased. All insecticide applications increased bacteria producing phospholipases from week 1 until week 4 after the application; bacteria then returned to the original levels.

[The effect of organic phosphoric esters on the experimental peptic ulcer (author's transl)]

The authors have investigated some organic phosphoric esters such as dimethoate, malatione, and trichlorphone in order to see whether they influence the genesis of the reserpine ulcer induced in rats or whether they act on the existing ulcer. Another objective of the investigation was to determine whether the aggravating effect of these compounds on the experimental gastric ulcer can be mitigated or prevented with isopropamide and gastrixon, two compounds known to be used in the therapy of ulcers. It was found that 1. dimethoate and trichlorphone considerably aggravate the genesis of the experimental peptic ulcer in rats, and that also malathione exercises this exacerbating effect still to some extent, 2. that the already existing experimental ulcer is aggravated by all three organic phosphoric esters and that 3. the severe experimental damage to the stomach can be reduced or prevented with Isopropamide and even more effectively with Gastrixon. As to the interpretation of the phenomena observed the authors take the view that--provided the effects mentioned apply also to man--with this a new risk was detected in the field of the chemical plant protection which may well gain importance for the health of a population.

The effect of organophosphorus compounds on respiration by rat liver mitochondria

Rat liver mitochondria from normal and chronically intoxicated rats were prepared by standard methods. Three organophosphorus compounds were assayed: Parathion, Malathion and Dimetoate. Oxygen uptake and respiratory control ratio were measured by a polarographic method. The addition of the pesticides at the reaction vessel (containing normal mitochondria) or pretreatment of the animals with these compounds, decreased state 3, state 4 and 2,4-dinitrophenol stimulated respiration with glutamate-malate as substrate in the presence of malonate. The mentioned states were not significantly altered when succinate was used as substrate. Respiratory control ratio decreased in the presence of the pesticides with both substrates. Mitochondrial respiration results obtained in vivo and in vitro suggest that the three mentioned organophosphorus compounds behave as inhibitors of the mitochondrial electron-transport system. The decrease of the respiratory control ratio may be related to a possible change in the permeability of the inner mitochondrial membrane.

[Toxic effect of phosphamide after simultaneous entrance into the body through the gastrointestinal tract and respiratory organs]

The experiment involved an investigation into the action of O,O-dimethyl-S-(N-methyl-carbomoilmethyl)-dithiophosphate (phosphamide), used at the level of the liminal dose (4 mg/kg) and in a concentration of 1.9 mg/m3, as compared with the effect of 1/2 of the liminal dose and 1/2 of the thereshold concentration. Both were simultaneously introduced into the organism of test albino rats for a period of 4 months and their complex action showed an intensification of the toxic effect. In evidence was also a more marked anticholinesterase action, a higher level of the insecticide in biological substrates and greater changes of hematological indices.