Effects of Insecticides on Spiracle Movements in Insect

We studied the effects of permethrin and DDVP on thoracic spiracle movements of the male cockroach. Permethrin increased, rather than decreased, the average open time of thoracic valve 1 in low or lethal doses, with no large change in the frequency of the opening and closing. In thoracic spiracle 2, the average open time was reduced by 1/3 of the control, but the opening frequency was markedly increased. DDVP had a similar effect on thoracic spiracle 1. The action of DDVP was only transiently and partially antagonized by atropine. These results suggest that the thoracic spiracle 1 valve tends to open, probably by a peripheral control mechanism, rather than to close, during permethrin or DDVP poisoning in insects

An Assay of Histamine Applied from the Mucosal Surface of Isolated Intestine

1) In order to observe the effects of some drugs applied from the intestinal mucosal surface on the intestinal motility, an everted intestine method is described in detail. 2) In this method, the excised and everted intestinal segment was used, and the intestinal movements were recorded as being the same as in the MAGNUS' method. So the results obtained by this method are favorable when compared with the results obtained by MAGNUS' method (drug action on the serosal surface), but this method is unfavorable for observing the intestinal movements for a long time, because it is not able to enclose sufficient oxygen volume into the sac without evoking peristalses. 3) Histamine (more than 5×10^<-7>g/ml), using the everted intestine method, caused delayed, slow contractions and increased the tone of the intestine. The latent period decreased in step with the increase of the dosage of histamine administered. 4) By shaving the mucosal surface of the everted intestine, the histamine action was potentiated and the latent period became very short comparing with the results obtained by using the only, everted intestine. 5) Mechanical distension of the intestinal wall potentiated the action of histamine applied from the mucosal surface