Brain-suboesophageal Ganglion Complexes Research Articles

Pheromonotropic activity in the gypsy moth Lymantria dispar: evidence for a neuropeptide

The brain-suboesophageal ganglion complex of the gypsy moth, Lymantria dispar, contains pheromonotropic activity detectable using a Helicoverpa zea in vivo bioassay for pheromone-biosynthesis-activating neuropeptide. Pheromonotropic activity was detected as early as the third larval instar and was present throughout development and through day 6 post-eclosion. Activity in the adult is presumably associated with pheromone production, while it is speculated that larval activity may be related to melanization. Adult pheromonotropic activity is associated with a peptide of approximately 3.500 kDa. It is heat labile and only partially stable when incubated at 35°C or exposed to freeze-thawing. Isolation of L. dispar pheromonotropic factor should facilitate the elucidation of the mechanism of pheromone production in this insect pest.

The distribution of pheromone-biosynthesis-activating neuropeptide (PBAN) immunoreactivity in the central nervous system of the corn earworm moth, Helicoverpa zea

Production of sex pheromone in several species of moths has been shown to be under the control of a neuropeptide termed pheromone-biosynthesis-activating neuropeptide (PBAN). We have produced an antiserum to PBAN from Helicoverpa zea (Lepidoptera: Noctuidae) and used it to investigate the distribution of immunoreactive peptide in the brain-suboesophageal ganglion complex and its associated neurohemal structures, and the segmental ganglia of the ventral nerve cord. Immunocytochemical methods reveal three clusters of cells along the ventral midline in the suboesophageal ganglion (SOG), one cluster each in the presumptive mandibular (4 cells), maxillary (12–14 cells), and labial neuromeres (4 cells). The proximal neurites of these cells are similar in their dorsal and lateral patterns of projection, indicating a serial homology among the three clusters. Members of the mandibular and maxillary clusters have axons projecting into the maxillary nerve, while two additional pairs of axons from the maxillary cluster project into the ventral nerve cord. Members of the labial cluster project to the retrocerebral complex (corpora cardiaca and cephalic aorta) via the nervus corpus cardiaci III (NCC III). The axons projecting into the ventral nerve cord appear to arborize principally in the dorsolateral region of each segmental ganglion; the terminal abdominal ganglion is distinct in containing an additional ventromedial arborization in the posterior third of the ganglion. Quantification of the extractable immunoreactive peptide in the retrocerebral complex by ELISA indicates that PBAN is gradually depleted during the scotophase, then restored to maximal levels in the photophase. Taken together, our findings provide anatomical evidence for both neurohormonal release of PBAN as well as axonal transport via the ventral nerve cord to release sites within the segmental ganglia.

Spatial and temporal distribution of pheromone biosynthesis‐activating neuropeptide in Helicoverpa (Heliothis) armigera using RIA and in vitro bioassay

A [3H]-PBAN (pheromone biosynthesis-activating neuropeptide) analog was synthesized, and binding of the radioligand to a specific PBAN-antiserum was achieved. The inhibition of binding of the radioligand by unlabeled PBAN, several PBAN analogs, and other competitors was studied and a specific radio-immunoassay was developed. Using this radioimmunoassay we found PBAN-like immunoreactivity in methanol extracts of hemolymph and neural tissues from females. Higher levels of PBAN-like immunoreactivity in extracts of brain-suboesophageal ganglion complexes, corpora cardiaca, thoracic ganglia, and abdominal ganglia were observed during the 4-5th h scotophase when compared to the PBAN-like immunoactivity levels during the 6-11th h photophase. On the other hand, the concentrations of PBAN-like immunoreactivity, in the terminal abdominal ganglion were higher during the photophase relative to minimal levels observed during the scotophase, indicating an accumulation before the onset of pheromone production. These differences in concentrations of PBAN were also reflected in the stimulation of in vitro pheromone glands, whereby significant stimulations were obtained by scotophase and photophase brain extracts, scotophase thoracic ganglia extracts, and photophase terminal abdominal ganglia extracts. No detectable levels of PBAN were found in hemolymph extracts during the sampling periods.

GABAergic control of the release of diapause hormone from the suboesophageal ganglion of the silkworm, Bombyx mori

Brain-suboesophageal ganglion complexes and suboesophageal ganglia were isolated from silkworm pupae destined to lay diapause eggs and pupae destined to lay non-diapause eggs and incubated in Grace's insect medium for 24 h. Diapause hormone released into the medium was determined by bioassay. Brain-suboesophageal ganglion complexes of diapause-egg-producing pupae secreted diapause hormone into the medium, whereas those of non-diapause-egg-producing pupae secreted little hormone. The suboesophageal ganglia of diapause-egg-producing and non-diapause-egg-producing pupae also released diapause hormone into the medium, and the amount of hormone was about 70% of that released by the brain-suboesophageal ganglion complexes of diapause-egg-producing pupae. Diapause hormone released from the brain-suboesophageal ganglion complexes of diapause-egg-producing was significantly reduced when the complexes were incubated in a medium containing more than 1 mM of γ-aminobutyric acid (GABA), an inhibitory neurotransmitter. The secretion of diapause hormone from the suboesophageal ganglia of both diapause-egg-producing and non-diapause-egg-producing pupae was also suppressed by GABA. Pictrotoxin, a specific blocker for GABA, induced diapause hormone release from the brain-suboesophageal ganglion complexes of non-diapause-egg-producing pupae in a dosedependent manner. When the concentration of picrotoxin was increased to 16.6 μM, these complexes secreted almost the same amount of diapause hormone as the complexes of diapause-egg-producing pupae. These lines of evidence showed the GABAergic neurones played a key role in the cerebral control of diapause hormone release from the suboesophageal ganglion.

In vivo and in vitro photoperiodic induction of diapause using isolated brain-suboesophageal ganglion complexes of the silkworm, Bombyx mori

By use of a bivoltine silkworm race which shows a long-day photoperiodic response after induction during the last (5th) instar, we tried to programme photoperiodic induction in the isolated brain-suboesophageal ganglion complex in vivo and in vitro. A pair of the complexes from a newly ecdysed 5th-instar female was transplanted into the abdomen of a late 5th-instar larva and exposed to long-day (20 h light: 4 h dark) or short-day (8 h light: 16 h dark) conditions for 3 cycles. The short-day-exposed complexes elicited the production of diapause eggs in the recipient silkworms destined to become non-diapause egg producers, whereas the long-day-exposed brain complexes produced non-diapause eggs. Transplant experiments of the brain-suboesophageal ganglion complex using isolated abdomens showed a similar result. The brain complexes from newly ecdysed females of the 5th-instar were cultured in Grace's insect medium under 20 h light: 4 h dark or 8 h light: 16 h dark for 4 cycles, respectively. After in vitro culture, a pair of complexes was implanted into the abdomen of a late 5th-instar larva destined to become a non-diapause egg producer, and the diapause incidence in the resultant moths was examined. The brain complexes which received the short-day cycles induced a large portion of diapause eggs, whereas those which received the long-day conditions induced non-diapause eggs. The connection of corpora cardiaca and corpora allata with the brain complex had no influence on the result. Suboesophageal ganglia which had been cultured in vitro and implanted elicited a remarkable production of diapause eggs, but cultured brains were ineffective in producing diapause eggs, regardless of the photoperiod experienced. These results demonstrate that photoperiodic induction of the silkworm can be programmed in in vivo and in vitro culture systems, and that components of the photoperiodic clock (photoreceptor, clock, and counter system) are located in the brain-suboesophageal ganglion complex, possibly in the brain itself.

Relationship between photoperiod and secretion of the diapause hormone during larval stages of the silkworm, Bombyx mori L., reared on an artificial diet

The suboesophageal ganglion of the silkworm, Bombyx mori synthesizes sufficient diapause hormone to produce diapause eggs, regardless of the photoperiodic conditions experienced during the larval stages. When larvae destined to produce non-diapause eggs are implanted with the brain-suboesophageal ganglion complex from larvae which have been reared under short-day conditions, the resulting adults lay diapause eggs. The larvae receiving the complex from larvae reared under long-day conditions gave rise to adults which did not produce any diapause eggs. The brains from pupae which have been reared under long-day conditions show an activity inhibiting the secretion of diapause hormone by the suboesophageal ganglion. The mechanism through which the brain controls the secretion of diapause hormone from the suboesophageal ganglion can be modified by photoperiodic conditions during the larval stages.

Elektrophysiologische Untersuchungen am Frontalganglion von Periplaneta americana L.

The frontal ganglion is an important part of the stomodeal division of the visceral nervous system. It is involved in the control of intake of food and water and of crop emptying as well as in the control of production and/or release of neurosecretory materials. Consequently it also has an influence upon the waterbalance, oocyte development, vitellogenesis etc. Investigations on the electrophysiological activities in the stomatogastric nervous system have not been published until now. This study deals with the spontaneous activities of the frontal ganglion of the cockroach, Periplaneta americana. Extracellular recordings were made with suction electrodes. From both frontal connectives as well as from the recurrent nerve one can detect clear irregular activities coming from the isolated ganglion. Newly moulted animals show in 70% of the cases volley like discharges, which are identical with the rhythm in the nervus connectivus (see below) and are lost in a higher ground activity at the latest four hours after ecdysis. The nervus connectivus consists of only two axons and its cell bodies are located in the protocerebrum. Each axon splits into three branches inside the neuropile of the frontal ganglion. One branch goes to the recurrent nerve, the others to the frontal connectives. From this nerve one can detect extreme regular volley-like discharges from the ganglion ( in vitro and in vivo) to the cell bodies in the protocerebrum (antidromic transmission!). Each cycle lasts 1–4 sec separated by a silent period of few seconds. The volleys consist in our records with suction electrodes of two types of spikes differing in height. Each type supplies half of the total spike number and may relate with the two axons of the nerve. At the end of each volley both the spike types show an increase in frequency and at the same time a decrease in amplitude. From the nerves N1, N2, N3 and N5, only in the cases of N3 and N5 is there spontaneous activity coming from the ganglion. The nerve N3 is more active than N5. From the tritocerebrum heavy spontaneous activity occurs between the frontal connectives and the frontal ganglion. This is similar to the activity detected in the opposite direction. It is essential that the brain-suboesophageal ganglion complex remains undamaged. If the two connectives between subesophageal ganglion and the first thoracic ganglion are dissected carefully and successively the activity may remain. These experiments are performed in situ. The recurrent nerve as well as the other nerves (N. connectivus, N1, N2, N3 and N5) never show spontaneous activity in the direction of the frontal ganglion.

Function of the Brain through Nerve Commissures on the Suboesophageal Ganglion in Bombyx mori L.

Fukuda and Hasegawa have verified1–3 that voltinism in the silkworm is probably controlled by a hormone from the suboesophageal ganglion. Hasegawa has claimed that voltinism may be determined by the function of the suboesophageal ganglion alone, while Fukuda has assumed that it may be determined by that of the brain-suboesophageal ganglion complex at the pupal stage. It can be inferred from Fukuda's experiments that the brain controls the secretion of the suboesophageal ganglion. When the brain completely suppresses the secretion of the suboesophageal ganglion, the silkworm moths lay batches of non-diapausing eggs. When the brain accelerates the secretion of the suboesophageal ganglion, on the other hand, the moths lay batches of diapausing eggs. Fukuda concluded that the centre which controls voltinism lies in the pupal brain. Morohoshi4 later recognized that inhibitory and accelerating functions of the brain are not completely absent but act only weakly.

Studies On the Mode of Action of the Diapause Hormone in the Silkworm, Bombyx Mori L

ABSTRACT The action of the diapause hormone has been studied by injecting extracts of the heads of male moths or of the brain-suboesophageal ganglion complexes of pupae into pupae expected to produce non-diapause eggs. The effect of the injection of hormone upon young oocytes is to make them develop into diapause eggs. Older oocytes, which have already acquired non-diapause characters, are not affected. The hormone is almost completely inactivated when injected on the day of pupation. The hormone is most effective when injected into pupae 2-3 days old, at which stage the ovarioles have started to grow vigorously. It is ineffective 1-2 days before adult emergence, by which time all the oocytes have acquired non-diapause characters. The hormone is inactivated in all pupae irrespective of whether they are destined to produce diapause eggs or non-diapause eggs. Inactivation of diapause hormone (in contrast to that of juvenile hormone) is partially relieved by exposure to low temperature or by simultaneous injection of indian ink. The extracts prepared as in (1) above do not serve as a stimulant for the brain causing the suboesophageal ganglion to produce diapause hormone. The action of the extract faithfully reflects the function of the diapause hormone which originates in the suboesophageal ganglion.

Hormonal studies on the diapause and non-diapause eggs of the silkworm, Bombyx mori L.

It is known that the brain-suboesophageal ganglion complex in the silkworm converts the non-diapause egg into the diapause egg. It has been found that the corpus allatum is concerned not only with the number of moults but also with the production of non-diapause eggs. The influence of the suboesophageal ganglion differs with each voltine race, and it gradually becomes stronger with age, whereas the influence of the corpus allatum differs with each moulting race and becomes weaker with age. The brain does not perfectly control the secretion of both the suboesophageal ganglion and the corpora allata, but weakly inhibits and also weakly promotes their secretory activity. The corpus allatum and suboesophageal ganglion hormones consist not only of non-diapause and diapause hormones, but also of growth-promoting and inhibitory hormones.

Functions of the Central Nervous System in Relation to Quantitative Characters in a W-Translocated strain of Silkworm, <i>Bombyx mori</i> L.

(1) Although the silk-layer weight of females is usually heavier than that of males in the common silkworm strain, this relation is reversed in the W-translocated strain.(2) The functional relationships among the three organs, brain, suboesophageal ganglion and corpora allata which are related to quantitative characters such as the weight of the silk-layer and voltinism were examined in a series of experiments in organ transplantation.(3) By transplantation of the brain-suboesophageal ganglion complex of females of the W-translocated silkworm strain to “non-diapause larvae” the silk-layer weight of the recipient is more decreased and voltinism is more strongly changed in non- diapause direction than in the case of transplantation of suboesophageal ganglion alone.(4) By transplantation of the brain-suboespohageal ganglion complex of males of the W-translocated silkworm strain to “non-diapause larvae” the silk-layer weight of the recipients is more increased and the voltinism is more strongly changed in diapause direction than in the case of transplantation of the suboesophageal ganglion alone.(5) By transplantation of the brain-corpora allata complex of females of the W-translocated silkwrom strain to “diapause larvae” the silk-layer weight of the recipients is more decreased and the frequency of non-diapause eggs within one batch becomes higher than by transplantation of corpora allata alone.(6) By transplantation of the brain-corpora allata complex of males of the W- translocated silkworm strain to “diapause larvae” the silk-layer weight of the recipient is more increased and the percentage of non-diapause eggs in one batch (laid by one moth) is more decreased than in the case of transplantation of corpora allata alone.(7) It is assumed from the above-mentioned findings that the brain of females of the W-translocated strains weakly inhibits the functional activity of suboesophageal ganglion and weakly acclerates that of corpora allata through nerve commissures. It seems, on the contrary, that the brain of males of the same strain weakly accelerates the functional activity of suboesophageal ganglion and weakly inhibits that of corpora allata through the nerve commissures.

Function of the Brain-Suboesophageal Ganglion Complex in the Silkworm, Bombyx mori

Function of the Brain-Suboesophageal Ganglion Complex in the Silkworm, Bombyx mori