Mean LD50 Research Articles

Susceptibility to three organophosphorus insecticides of Wiseana spp. larvae (Lepidoptera: Hepialidae)

When test groups of Wiseana larvae were standardised by weight, estimates of susceptibility to fenitrothion applied topically in 1‐μlitre volumes of isopropyl alcohol to batches of 10 showed no essential differences between the populations examined, nor between larvae in the weight range 85–1177 mg. Mean LD50 values for fenitrothion (11 larval populations) and for diazinon and trichlorfon (3 larval populations) were 0.84, 2.31, and 1.39 μg/g respectively. Single LD50 estimates for the same toxicants ingested on clover leaflets were 1.29, 4.57, and 1.5 μg/g respectively. The close relationship between weight and susceptibility would allow small batches of larvae of almost any weight to be used for the detection of resistance, for which the following discriminating doses (based on 2 × LD100 in μg/g) are proposed: fenitrothion 3.0; diazinon 8.0; trichlorfon 5.0.

Effects of ultraviolet radiation on carotenoid containing and albino strains of Neurospora crassa

To determine the influence of carotenoids on UV sensitivity of Neurospora crassa conidia, the dose-response curves of 3 albino strains were compared to that of the wild type. In a control experiment the genetic background effects were eliminated by irradiating the wild type in which carotenoid synthesis had been inhibited by β-ionone, and comparing the dose-response curve to that of untreated wild type. All strains used had similar γ-ray survival curves and nuclei per conidium which precluded differences in UV sensitivity due to morphological differences. The albinos and β-ionone-treated strains showed a greater sensitivity (mean LD50 4.35·103 erg/mm2) to UV irradiation than the wild type (LD50 7.30·103 erg/mm2).

Effects of ultraviolet radiation on carotenoid-containing and albino strains of Neurospora crassa.

Abstract To determine the influence of carotenoids on UV sensitivity of Neurospora crassa conidia, the dose-response curves of 3 albino strains were compared to that of the wild type. In a control experiment the genetic background effects were eliminated by irradiating the wild type in which carotenoid synthesis had been inhibited by β-ionone, and comparing the dose-response curve to that of untreated wild type. All strains used had similar γ-ray survival curves and nuclei per conidium which precluded differences in UV sensitivity due to morphological differences. The albinos and β-ionone-treated strains showed a greater sensitivity (mean LD50 4.35·10 3 erg/mm 2 ) to UV irradiation than the wild type (LD50 7.30·10 3 erg/mm 2 ).

Toxicity of some pyrethroids to the adult desert locust, Schistocerca gregaria forsk

AbstractThe toxicity of a number of topically applied pyrethroids has been tested against adult male desert locusts, Schistocerca gregaria: the most potent proved to be 5‐benzyl‐3‐furylmethyl (+)‐trans‐chrysanthemate (bioresmethrin) with a weighted mean LD50 of 4.0 μg/g. The remaining compounds may be ranked in order of toxicity as follows: 5‐benzyl‐3‐furylmethyl (±)‐cis‐trans‐chrysanthemate (resmethrin) > 4‐allyl‐2,6‐dimethyl‐benzyl(+)‐trans‐chrysanthemate > 4‐allylbenzyl (+)‐trans‐chrysanthemate > 2,4,6‐trimethylbenzyl (+)‐cis‐trans‐chrysanthemate > 2,3,4‐trimethylbenzyl (+)‐cis‐trans‐chrysanthemate > 2,4‐dimethylbenzyl (±)‐cis‐trans‐chrysanthemate; 2‐methylbenzyl (±)‐cis‐trans‐chrysanthemate. A small factor of synergism (4.2) was obtained with bioresmethrin following pre‐treatment with sesamex, but with resmethrin the synergistic ratio (1.6) was of little practical significance.

Venom of the lionfish Pterois volitans

Extracts prepared from the venomous dorsal spines of lionfish ( Pterois volitans) were investigated in mice and rabbits. Intravenous injection into mice produced death in from less than a minute up to about one-half hour. The primary action in rabbits was a fall in blood pressure, accompanied by increase in respiratory rate; with larger doses there was evidence of myocardial ischemia or injury. After injection of fatal doses a variety of electrocardiographic changes occurred and the blood pressure fell to zero; respiratory arrest occurred terminally, but artificial respiration did not prolong the life of the animal. The active material was nondialyzable and the extracts contained considerable amounts of protein. Extracts retained substantial activity after lyophilization or addition of glycerol when stored for over a year at –20°C. The mean ld50 following intravenous injection into mice was about 1 mg of protein/kg.

The antigenicity of cholera vaccine prepared in fluid medium.

Cholera vaccine prepared in a chemically defined fluid medium (containing tyrosine, asparagine, glycine, and inorganic salts) was compared antigenically in mice with vaccines prepared by standard methods. The mean LD50 for normal mice was 108 ± 9.1 V. comma of the strain employed for challenging. Both vaccines afforded a high degree of protection. Mice immunized with bivalent (Ogawa and Inaba) Standard vaccine had a mean LD50 of 40.0 ± 4.7 million V. comma. Mice protected by bivalent fluid-prepared vaccine had a mean LD50 of 32.7 ± 6.0 million V. comma. The difference is not statistically significant. Vaccines prepared in fluid medium were relatively unstable.