Relationship between firing activity of bombyxin-producing neurosecretory cells and hemolymph bombyxin titer in the silkworm Bombyx mori.
Isolated brain-retrocerebral neurohemal complex of the silkworm of Bombyx mori was stimulated electrically and the released bombyxin (an insulin-like neuropeptide) was measured using time-resolved fluoroimmunoassay. The amount of bombyxin release depended on the number of stimulus pulses delivered to the axonal tract of the bombyxin-producing (BP) neurosecretory cells, and 17 fg of bombyxin per pulse was released from a cell. The titer of bombyxin in the hemolymph of bombyxin-II injected pupae decreased exponentially, the half-life being 170 min. To relate firing activity of a population of BP cells to the hormone titer in the hemolymph, bombyxin titer and its change in the hemolymph were calculated numerically. We assumed that the amount of bombyxin release was proportional to the firing rate of BP cells and the released bombyxin was inactivated with the same time course of injected bombyxin. Our calculations suggested that the hemolymph bombyxin titer may fluctuate dynamically and the mean titer is 380 pg/ml, a level which is close to the actually determined bombyxin titer at middle stages of pupal-adult development.
Suenobu
Akiko
A
Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan.
Mizoguchi
Akira
A
Ichikawa
Toshio
T
D000818:Animals; D012831:Bombyx / Q000254:growth & development / Q000502:physiology*; D001921:Brain / Q000502:physiology; D004558:Electric Stimulation; D004594:Electrophysiology; D015200:Fluoroimmunoassay; D006458:Hemolymph / Q000737:chemistry*; D007700:Kinetics; D009479:Neuropeptides / Q000008:administration & dosage / Q000096:biosynthesis* / Q000097:blood*; D009490:Neurosecretory Systems / Q000166:cytology / Q000378:metabolism*; D011679:Pupa / Q000737:chemistry / Q000254:growth & development
D009479:Neuropeptides; C075028:bombyxins; C077536:bombyxin II