R. Moreau

Endocrine control of hemolymph carbohydrates in Locusta migratoria: Comparison between effects of two endogenous hormonal extracts and effects of insulin and glucagon

Abstract 1. 1. In adult male Locusta , effects of corpora cardiaca extracts, intestinal insulin-like molecule, glucagon and insulin were tested on hemolymph carbohydrates. 2. 2. Carbohydrates were separated by gas-liquid chromatography. 3. 3. CC extracts and glucagon mainly increase trehalose and melibiose levels; they have no effect upon glucose concentration. 4. 4. Intestinal insulin-like molecule and insulin decrease all hemolymph carbohydrates. 5. 5. These results suggest that in Locusta , like in mammals, hemolymph carbohydrates are controlled by a double system of regulation: a hyperglycemic system present in CC and a hypoglycemic factor localized in midgut.

Locust neuropeptides stimulating sex pheromone production in female European corn borer moth, Ostrinia nubilalis

Abstract The presence of a pheromonotropically active hormone (PBAN-like substance) from locust organs, ( Locusta migratoria ) has been demonstrated. Extracts of brain, corpora cardiaca, corpora allata, suboesophageal ganglia and thoracic ganglia of L. migratoria caused highly pheromonotropic responses in decapitated females of the European corn borer moth ( Ostrinia nubilalis ). The highest activity per unit weight of tissue was found in the corpora cardiaca and corpora allata of the locust followed by the brain plus suboesophageal ganglion of O. nubilalis . Following 8 days of disconnection, separating the corpora allata from the corpora cardiaca and suboesophageal ganglion, the pheromonotropic activity of the corpora allata was maintained at a level similar to that observed in intact organs, while that of the corpora cardiaca and suboesophageal ganglion was decreased. The corpora allata extract was heat stable but destroyed by proteases. Thus, the pheromonotropic hormone from locust cerebral organs which displays potent PBAN activity could be a peptide originating principally in the corpora allata.

An intestinal insulin-like molecule in Apis mellifica L. (Hymenoptera)

Abstract 1. 1. In worker honeybee (Apis mellifica), an insulin-like substance reacting with the guinea-pig anti-insulin antibody has been found in haemolymph and in midgut tissue exclusively. 2. 2. Quantitative estimation of this factor has been made with an insulin radioimmunoassay. 3. 3. A purified tissue extract showed a molecular weight by liquid chromatography and electrophoresis of 18,000 daltons 4. 4. The curves of decreasing percentage of bound insulin as a function of decreasingly diluted midgut extracts are superimposable. This strongly suggests that insect insulin-like molecule may be very similar to mammals insulin.

Effects of honeybee insulin-immunoreactive peptide on haemolymph lipid and carbohydrate: Interaction of vertebrate somatostatin

Abstract The haemolymph lipid and carbohydrate concentrations were determined in emerging worker honeybees following injection of [ I ] saline, [ II ] a bee insulin-immunoreactive peptide ( BIRP ) and [ III ] BIRP + vertebrate somatostatin. BIRP promptly lowered trehalose, glucose, diacylglycerol and phospholipid concentrations, and increased the levels of fatty acid and triacylglycerol. It also induced a positive correlation between 1,2-diacylglycerol and short chain triacylglycerol, and completely reversed a negative correlation between long chain triacylglycerol and fatty acid, as well as a positive correlation between 1,3-diacylglycerol and steroid, both of the latter correlation appearing following treatment [ I ]. In all correlations except those between fatty acid, phospholipid and diacylglycerol, injection of vertebrates somatostatin together with BIRP partially neutralizes the specific effects of BIRP injected alone, a result similar to the action of somatostatin in vertebrates. BIRP is an endogenous intestinal insulin-like peptide whose physiological activity may be modulated by somatostatin-like molecules.

Variations de la pression interne au cours de l'émergence et de l'expansion des ailes chez Bombyx mori et Pieris brassicae

Abstract During the final stage of development the haemolymph of Lepidoptera does not seem to undergo great variations of pressure. At most, sudden rises of 10 to 15 mm Hg were noted during violent movements or at ecdysis. With an improved and very sensitive apparatus, a pressure eighteen times higher than the pressure measured normally was recorded. This sudden variation of blood pressure corresponds to the erectile stage of the extension of the wings. The study under different conditions has shown the importance of the part played by the abdominal muscles in the pressure of the haemolymph.

Effects on growth and respiration due to the ingestion of the rapeseed meal glucosinolates in young larvae of Tenebrio molitor

Abstract 1. 1. We investigated the effects of the ingestion of naturally occurring glucosinolates in rapeseed meal on growth rate, metabolic efficiency and respiratory rate in larvae of the yellow mealworm, Tenebrio molitor L. 2. 2. In our feeding studies, larvae were reared on one of seven different diets, including a whole ground wheat control diet and rapeseed meal from six rapeseed varieties. Dry weight gain of larvae and dry food assimilated were measured after 4 weeks of rearing, and the conversion of food into insect biomass was determined. The results may be explained by variations in the glucosinolates content of the diets. 3. 3. The effect of glucosinolates on food consumption, larval growth, expired carbon dioxide, oxygen uptake and respiratory quotient were studied. 4. 4. Glucosinolates did not reduce food assimilation or growth after 1 day of experimentation, but they caused some inhibition of respiratory exchanges and increased the RQ ratio.

Rôle des organes pulsatiles thoraciques et du cœur pendant l'émergence et l'expansion des ailes des lépidoptères

Abstract Electrograms of the thoracic pulsatile organs and of the heart during emergence and expansion of the wings have been made. The mesotergal and metatergal organs function in a similar way: active periods are interrupted by short periods of rest, but the two organs contract with different but apparently independent rhythms. During emergence and expansion, the rate of contraction of the pulsatile organs increases twofold, and the resting periods disappear during the entire period of expansion of the wings. When the wings are removed or cut short, the activity of the pulsatile organs is inhibited.

Changes of biogenic amine levels in haemolymph during diapausing and non-diapausing status in Pieris brassicae L.

During the larval development of Pieris brassicae, photoperiod status induces either direct (non-diapausing) development or diapausing development. Biogenic amines such as dopamine and serotonin and their derivatives may be implicated in the physiological control and adaptation of these insects to different photoperiods. High performance liquid chromatography coupled with electrochemical detection was used to measure biogenic amine concentrations in insect haemolymph in different photoperiod conditions. At the end of the higher photosensitivity phase, dopamine levels were two-fold higher in diapausing (0.914 pmol/microl+/-0.025) as compared to non-diapausing insects (0.415 pmol/microl+/-0.02; P<0.001). Globally, dopamine catabolites are found in higher levels in non-diapausing insects (in prepupa, near seven times more for NADA, and 25 times more for DOPAc), thus indicating a higher dopamine turn-over. Serotonin levels were detected only at the beginning of this instar in diapausing insects but not in direct development insects. During pupal life, dopamine levels were significantly higher in diapausing than in non-diapausing insects (in 3-day pupae, dopamine was 28 times higher), and remained at high levels throughout diapausing life. At the beginning of diapause, serotonin levels were higher in diapausing insects than in non-diapausing insects (in 3-day pupae, serotonin was 13 times higher). These levels decreased in the middle of diapause period, and then increased just before its breaking. Dopamine and serotonin levels presented the typical kinetics of diapause development and may be used as an indicator of the evolution of diapause status.

Carbohydrate metabolism in Pieris brassicae L. (Lepidoptera); variations during normal and diapausing development

Abstract 1. 1. Glycogen and trehalose metabolisms are studied with [U- 14 C] glucose during the normal and diapausing development in Pieris brassicae L. 2. 2. During pupal diapause trehalose is accumulated, its storage being accompanied with a strong turnover. If the diapausing pupae are maintained at a cold temperature (+5°C), this phenomenon is amplified. 3. 3. Diapause appears to be a period of the development where metabolic activity is very unequal; some metabolic pathways are inhibited, on the contrary others remain very active.

Hemolymph trehalose and carbohydrates in starved male adult Locust a migratoria: Possibility of endocrine modification

Abstract 1. 1. Starvation during a period from 1 to 6 days induced a strong decrease of total hemolymph carbohydrates in Locusta 25-day-old male adults. 2. 2. The trehalose concentration remained constant during the first fasting day, after which it dramatically decreased: trehalose is the most used sugar during starvation. 3. 3. Injections of saline CC extracts, during the fasting period, are always able to increase hemolymph carbohydrates, especially trehalose. The fourth-fasting-day insects have the highest reactions. 4. 4. The effects of injecting glucagon are comparable with those of CC extracts but are noticeable earlier.