Forskolin-insensitive adenylate cyclase in cultured cells of Choristoneura fumiferana (Insecta)

Adenylate cyclase from a spruce budworm cell line, IBRI-Cfl, is activated by octopamine (Ka = 50 microM), guanine nucleotides and sodium fluoride but not by forskolin. In addition, forskolin does not potentiate the octopamine-sensitive response. To our knowledge, this is the first published report of a hormone-sensitive adenylate cyclase, with a functional guanine nucleotide regulatory protein, that is insensitive to forskolin both in intact cells and washed membrane preparations.     

Pharmacology of octopamine-, dopamine-, and 5-hydroxytryptamine-stimulated cyclic amp accumulation in the corpus cardiacum of the american cockroach,Periplaneta americana L

A variety of potential receptor agonists were incubated with isolated corpora cardiaca from the American cockroach Periplaneta americana to determine their effects on cyclic AMP production in this gland. Octopamine, dopamine, and 5-hydroxytryptamine elevated cyclic AMP levels in a dose-dependent manner with estimated K_a values of 15.8, 1.7, and 1.1 m?M, respectively, and their stimulation was found to be additive. Several vertebrate receptor antagonists were tested against the three amines and a preliminary pharmacological profile developed.     

Surface-bound biomembranes incorporating receptors: electrochemical and structural characterization.

A generic method is described for forming surface-bound structures that incorporate protein receptors in a membrane-like environment. Silane reagents (octadecyltrichlorosilane and dimethyloctadecylchlorosilane) were used to produce primed substrates bearing full and partial monolayers, respectively. Biomembranes were formed by dialysis of detergent-solubilized membranes in the presence of two different alkylsilanized substrates: Si/SiO2 electrodes and glass microspheres. Electrochemical analysis of the capacitance was used to determine apparent thickness and degree of surface coverage at each stage in the deposition process. Elemental analysis on glass beads gave the hydrocarbon incorporation. Glass bead substrates were also examined by Fourier transform infrared spectroscopy to evaluate the alkylsilanized substrate before and after dialysis. Both vertebrate rhodopsin and the nicotinic acetylcholine receptor could be incorporated into structures with composition and dimensions similar to natural bilayer membranes. The techniques reported here are applicable for coupling membrane receptors to a variety of transducing substrates used in biosensors.     

Taurine inhibits octopamine-stimulated cAMP production in cockroach haemocytes

Taurine and the taurine analogue guanidinoethanesulfonic acid interact with octopamine receptors of cockroach hemocytes to decrease octopamine-stimulated cAMP production. Dopamine-, synephrine- and tyramine-stimulated cAMP production in the haemocytes are also inhibited by taurine.     

Temperature-induced changes in lipid composition and transition temperature of flight muscle mitochondria of Schistocerca gregaria

The lipid composition of flight muscle mitochondria was determined in adult male $\text{Schistocerca gregaria}$ acclimated for 30 days at 31°C and 45°C respectively. Locusts held at 31°C showed lower levels of phosphatidylcholine and higher levels of phosphatidylethanolamine than the 45°C-acclimated insects. A trend towards an increased cholesterol:phospholipid ratio was also observed at the higher temperature. Wide angle X-ray diffraction procedures indicated a difference of 5°C in the lipid phase transition temperatures of mitochondrial preparations derived from the two groups of insects with the 45°C-acclimated samples demonstrating the higher transition temperature.     

Ecological cues, gestation length, and birth timing in African buffalo (Syncerus caffer)

We examined annual variation in the timing of conception andparturition in the African buffalo (Syncerus caffer) and thesynchrony of birth timing with resource cues, using 8 yearsof monthly birth, rainfall, and vegetation data, measured asNormalized Difference Vegetation Index (NDVI). Monthly birthshad the strongest significant correlations with NDVI and rainfalllevels 12 and 13 months in the past, respectively. In addition,the synchrony of current year births corresponds most stronglyto the synchrony of the previous year's NDVI distribution. Becausethe gestation period of buffalo has been estimated to be around11 months, these findings suggest that improved protein levels,occurring approximately a month after the first green flushof the wet season, are either a trigger for conception or conceptionhas evolved to be synchronous with correlated environmentalcues that ensure females enter a period of peak body conditionaround the time of conception and/or parturition. With a gestationperiod of approximately 340 days, parturition occurs to takeadvantage of the period when forage has its highest proteincontent. A comparative analysis of gestation periods withinthe subfamily Bovinae indicates that African buffalo have aprotracted gestation for their body size, which we suggest isan adaptation to their seasonal environment. We also found thatinterannual variation in the birth distribution suggests a degreeof plasticity in the date of conception, and variation in thenumber of calves born each year suggest further synchrony ata timescale longer than a single year.     

α-Glucosidase activity in haemolymph of the American cockroach, Periplaneta americana

α-Glucosidase activity of whole haemolymph has been investigated in adult males of the American cockroach, Periplaneta americana. Two electrophoretically distinguishable enzymes capable of hydrolysing α-glucosidic linkages are present in the serum component of the haemolymph, and one of these hydrolyses trehalose. Trehalase activity is also present in haemocytes, and the haemocyte enzyme shares an identical electrophoretic mobility and similar pH sensitivity with the serum trehalase. Furthermore, both enzymes are inhibited to the same extent by sodium ethylene diamine tetracetate (EDTA); thus it is suggested that the same enzyme may be responsible for trehalase activity in the two components. The K_m of EDTA-inhibited trehalase is 3·3 mM and this value is reduced to 1·8 mM upon activation of the enzyme by calcium ions. The properties of the trehalase are discussed in light of the possible rôle of the enzyme in regulating haemolymph trehalose and glucose concentrations.     

Serotonin Inhibits Protein Feeding in the Blow Fly, Phormia regina (Meigen)

Serotonin is an important signaling molecule involved in the control of feeding in flies and other animals. In this study, a potential neurohemal release site for serotonin and the effects of exogenous serotonin on protein feeding were examined in the black blow fly, Phormia regina. A dense network of varicose neural processes exhibiting serotonin-like immunoreactivity was identified on the dorsal region of the thoracico-abdominal ganglion in P. regina. This dorsal region of the central nervous system is a likely site for the release of serotonin into the hemolymph. Circulating serotonin may have multiple systemic effects on fly physiology, including modulating or regulating feeding related processes and diuresis. Injections of exogenous serotonin reduced protein meal size in female flies at all doses and at all time points examined within a 24 h period relative to control and saline injected flies. Similar results were observed in serotonin-injected males at 35 min post injection. The injection of 50 μg serotonin resulted in the greatest amount of protein feeding inhibition. Serotonin injected flies also experienced greater weight loss than control or saline-injected flies during the 24 h post-injection period, possibly due to increased diuresis.