Species Specificity of the Insect Prothoracicotropic Hormone (PITH): the Presence of Bombyx-and Samia-Specific PTTHs in the Brain of Bombyx mori: (prothoracicotropic hormone (PTTH)/peptide hormone species specificity/Bombyx mori/Samia Cynthia ricini).

Crude extracts of Bombyx mori brains can provoke adult development when injected into brain-removed dormant pupae of Bombyx mori and Samia Cynthia ricini. From this fact the prothoracicotropic hormone (PTTH) of Bombyx has long been thought to be species-nonspecifically active on Samia. Chemical fractionation of Bombyx brain or head extracts by fractional precipitation with acetone, Sephadex G-50 gel-filtration, and DEAE-Sepharose CL-6B chromatography, however, separated the fractions which activated Bombyx brainless pupae from those which activated Samia.

Prothoracicotropic Hormone Bioassay: Pupal-Adult Bombyx Assay: (prothoracicotropic hormone (PTTH)/Bombyx mori/Samiu cynthia ricini/pupal assay).

Blockage of adult development by brain removal and its resumption by application of the prothoracicotropic hormone (PTTH) were studied using pupae of a racial hybrid J-122 × C-115 of Bombyx mori. A log-linear dose-response relationship was obrained after injection of a PTTH solution. The Bombyx-unit of PTTH has been defined from this dose-response curve.