Effects of heat shock and ambient temperature on female soldier production in a polyembryonic parasitic wasp

Larval castes are well known in both sexes of polyembryonic parasitic wasps, in which sterile soldier larvae are clonally produced from a single egg and thousands of reproductive larvae develop into adults. The proportion of soldier larvae in Copidosoma floridanum is first determined genetically in both sexes but subsequently increases in females as a result of environmental disturbances, such as the presence of competitive parasitoids. Because temperature is the most influential environmental factor affecting ectotherms, we hypothesize that an increase in ambient temperature also affects the production of female soldier larvae. Conversely, we hypothesize that there would be no effect of temperature on the production of male soldier larvae. In the present study, we show that heat stress experienced by C. floridanum at an early stage in host development increases the number of female soldier larvae produced during the last instar stage of the host. We also show that rearing at extreme (high and low) temperatures induces an increase in the number of female soldiers produced. The effect of heat stress and ambient temperature on soldier production is found only in females, as is the response to heterospecific competitors. By contrast, no responses are detected in males for either heat stress or ambient temperature. The adaptive effect of these phenomena is not known, although the results of the present study imply the existence of a common physiological cascade that causes an increase in the number of soldier larvae in females.     

Inhibitory effects of tryptamine on tolbutamide-induced hypoglycemia in mice: Mediation by 5-HT receptors

Effects of tryptamine on tolbutamide-induced hypoglycemia were investigated in mice. Tryptamine significantly inhibited hypoglycemia elicited by tolbutamide. The inhibitory effects of tryptamine were strongly blocked by the 5-HT₁ and 5-HT₂ receptor antagonist methysergide and the 5-HT₂ receptor antagonist ketanserin, while the 5-HT₃ receptor antagonist ICS 205–930 was without effect. Tryptamine induced hyperglucagonemia in tolbutamide-treated mice, and this effect elicited by tryptamine was strongly inhibited by the 5-HT₂ receptor antagonist ketanserin. These results suggest that the inhibitory effects of tryptamine on tolbutamide-induced hypoglycemia are mediated by 5-HT₂ receptors and that tryptamine is involved in glucagon release.     

Difficulties of molecular dissociation of Clostridium botulinum type G progenitor toxin

Clostridium botulinum type G progenitor toxin was chromatographed on DEAE-Sephadex and Q-Sepharose equilibrated with 0.05 M Tris-HCl buffer, pH 8.0, containing 0.2 M urea. The toxin was eluted in a single protein peak from DEAE-Sephadex, but it was eluted in four protein peaks from Q-Sepharose; the third peak was toxic and the others were nontoxic. The third peak, appearing to be the toxic component, had a molecular mass of 150,000. In SDS-polyacrylamide gel electrophoresis, purified type G progenitor toxin migrated in six bands, with molecular masses of 150,000, 140,000, 58,000, 10,800, 10,600, and 10,400. Type G progenitor toxin may be composed of a toxin component with a molecular mass of 150,000 and a nontoxic component in a manner similar to progenitor toxins of other types. Type G toxic component, whether it was reduced or not, migrated in a single band to the same relative positions in SDS-PAGE; type A toxic component reduced with 2-mercaptoethanol migrated in two bands.