Secretory Hydrolases of Entamoeba histolytica1

ABSTRACT Cells of Entamoeba histolytica grown over a period of four days contained NADP⁺-dependent alcohol dehydrogenase exclusively inside the cells. No activity of this enzyme could be found in the growth medium after harvesting the cells. Under the same conditions, acid phosphatase, β-N-acetylglucosaminidase, esterase, α-glucosidase, and different amylases of the parasite were found both inside the cells and in the medium. The activities present in the cell homogenate and in the medium before and after growth of the amoebas were partially separated by gel filtration on Sephadex G150 and G75, respectively. The comparison of the elution diagrams revealed that NADP⁺-dependent alcohol dehydrogenase, acid phosphatase, esterase, and amylases occurred as multiple forms inside the cells. These activities, as well as β-N-acetylglucosaminidase and α-glucosidase, were released into the extracellular environment to a different degree. The enzymes originating from the parasite were identified and distinguished from those of the ingredients of the growth medium according to their molecular mass and pH optimum. Furthermore, the amoebic origin of the secreted enzymes was shown on the basis of their inhibition by antibodies prepared against the supernatant fraction of the homogenate.     

The effect of mating on phonotactic behaviour in Gryllus bimaculatus (De Geer)

Abstract. Phonotaxis of G. bimaculatus females is expressed by a course-consistent, directional approach to a conspecific model calling song emitted alternatingly at sound intensities of 50–90 dB SPL and appears at the age of 6–7 days, the onset of maturation. Mating abolishes phonotaxis after about 1 h. By that time, the content of the attached spermatophore has migrated into the female's sper-matheca. Removal or emptying of the spermatheca, or severing the ventral nerve cord, fully reinstates phonotaxis, whereas ovariectomy has no effect. We suggest that mechanoreceptors record the expansion of the filled spermatheca and that the inhibitory message is communicated via the ventral nerve cord anteriorly to an unknown control centre in the brain. The loss of phonotaxis is combined with reduced locomotor activity and results in the female no longer being attracted to another calling male.