PCR primers for polymorphic microsatellite loci in the desert locust,Schistocerca gregaria (Orthoptera: Acrididae)

Nine pairs of polymerase chain reaction (PCR) primers that amplify polymorphic microsatellite loci in the desert locust, Schistocerca gregaria (Forskal), were developed using a magnetic bead‐based enrichment protocol. A sample of 48 locusts collected during the 1993 and 1995 upsurge periods in Eritrea, East Africa, were genotyped. The number of alleles per locus ranged from six to 20; the average was 12.67. Allelic distributions were significantly different between samples from different localities.     

Life cycle changes during 12 successive generations of laboratory colonisation of the leafroller Cnephasia jactatana (Walker) (Lepidoptera: Tortricidae) on artificial diet

Abstract

Close monitoring of the lepidopteran leafroller Cnephasia jactatana under laboratory colonisation revealed few distinct effects of successive rearing on artificial diet on the life cycle. The second laboratory generation had a prolonged development time and altered sex synchronism in pupation and eclosion patterns. Some deleterious changes were observed in later generations, including decreases in fertility, egg hatch and sperm motility, failure of mating adults to separate, and pupal and adult malformations. These changes were not adaptive, but were due to incompatibility with the general purpose diet (GPD) used; they were absent under sub-colonisation on a sheepnut-bean based diet (SBD). Success in the laboratory colonisation of C. jactatana is attributed to a random mating protocol, choice of environmental conditions representing the wild habitat, and a rapid rate of population growth.     

Voltage-dependent depolarization of bacterial membranes and artificial lipid bilayers by the peptide antibiotic nisin

The peptide antibiotic nisin is shown to disrupt valinomycin-induced potassium diffusion potentials imposed on intact cells of Staphylococcus cohnii 22. Membrane depolarization occurred rapidly at high diffusion potentials while at low potentials nisin-induced depolarization was slower suggesting that nisin requires a membrane potential for activity. This assumption was proven in experiments with planar lipid bilayers (black lipid membranes). Macroscopic conductivity measurements indicated a voltage-dependent action of nisin. The potential must have a trans-negative orientation with respect to the addition of nisin (added to the cis-side) and a sufficient magnitude (ca. -100 mV). With intact cells the threshold potential was lower (-50 to -80 mV at pH 7.5 and below -50 mV at pH 5.5). Single channel recordings resolved transient multistate pores, strongly resembling those introduced by melittin into artificial bilayers. The pores had diameters in the range of 0.2–1 nm, and lifetimes of few to several hundred milliseconds. The results indicate that nisin has to be regarded as a membrane-depolarizing agent which acts in a voltage-dependent fashion.Abbreviations BLM Black lipid membranes - CCCP carbonyl cyanide m-chlorophenylhydrazone - DOPC dioleoyl phosphatidylcholine - PS phosphatidylserine - TPP⁺ tetraphenylphosphonium cation     

飞蝗复眼生理和结构上的节律变化

采用细胞内记录和光镜方法研究了飞蝗(Locusta migratoria)夜间和日间在暗适应和明适应状态下小网膜细胞角敏感度以及晶锥和小网膜细胞之间区域结构上的变化.结果表明小网膜细胞角敏感度的变化不仅仅由于晶锥周围主色素细胞色素颗粒的移动,而且也由于小眼感杆束结构上的节律变化.     

Feeding postures of suspension-feeding larval black flies: the conflicting demands of drag and food acquisition

Summary We tested whether larval black flies actively control the positioning of their feeding appendages (labral fans), and if so, whether their posture represents a balance between the conflicting demands of drag and feeding. We compared the postures of live larvae with the postures of larvae killed by heat-shock in three different flow regimes in a laboratory experiment; we assumed that the postures of heat-killed larvae approximated a passive response to drag. The average height of the labral fans above the bed declined significantly in faster flows, and was significantly greater in live than dead larvae. There was also a significant interaction effect, since the difference between the fan heights of live and dead larvae was greater in slower flows. Two mechanisms may contribute to this result. Larvae in slower flows have to increase their fan heights more than larvae living in faster flows to achieve comparable increases in velocity and thus particle flux. In addition, muscular strength may limit the feeding postures larvae can assume. The fan heights of live larvae also varied depending on the concentration of food particles: larvae exposed to low food concentrations held their fans higher above the bed than did larvae exposed to high food concentrations in the same flow regime. This change in posture is due neither to an uneven particle concentration in the boundary layer nor to added drag from particles trapped in the labral fans. Collectively, our results indicate that these suspension feeders actively control their feeding posture, and suggest that these varying postures represent a dynamic balance between the conflicting needs of minimizing drag and maximizing feeding.     

Capacitance--voltage relationship in phospholipid bilayers containing gangliosides

Changes in the position of the minimum of the parabolic capacitance-voltage curve allow the measurement of the amount of ganglioside present in artificial bilayers made with phosphatidylcholine-ganglioside mixtures and asymmetrically shielded with Ca2+. The screening effect of the ionic solution must be considered. With ganglioside/phospholipid molar ratios of up to 15%, all glycolipids can be found at the membrane surfaces.     

Isolation of the vitellogenin-binding protein from locust ovaries

A rapid, efficient procedure for the isolation and purification of the vitellogenin binding protein from locust ovarian membranes is described. After solubilization with the nonionic detergent octyl-β-D-glucoside and removal of the detergent, the binding protein is subjected to affinity chromatography on vitellogenin coupled covalently to Affi-Gel 15. The binding protein is eluted with suramin and EDTA at low pH value. Sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis reveals a polypeptide with a molecular weight of 156,000 in the eluted fraction. By ligand blotting this polypeptide could be identified as the vitellogenin binding protein. It retains its high-affinity binding properties. The specific binding of vitellogenin increases from 4.8 μg (intact ovarian membranes) to 170.9 μg (affinity purified binding protein) per mg membrane protein, which corresponds to a purification factor of 35.     

Effects of plant odor on oviposition by the black swallowtail butterfly,Papilio polyxenes (Lepidoptera: Papilionidae)

Black swallowtail females laid more eggs on plant models treated with contact stimulants and volatiles from carrot leaves than on models treated only with contact stimulants. The volatiles enhanced landing rates and females alighted more frequently on artificial leaves treated with host volatiles than on adjacent control leaves. Volatiles from cabbage, a nonhost, inhibited landing rates on artificial leaves treated with carrot contact stimulants. Examination of antennae revealed two major types of sensilla, believed to be olfactory in function. Electroantennogram preparations responded more strongly to carrot volatiles than to cabbage volatiles and several shared responses at particular retention times to carrot volatile components eluting from a gas chromatograph. Our results are consistent with a long-standing hypothesis that behavioral responses to essential oil components characteristic of the larval food plants have facilitated host shifts in the genus Papilio.     

Resetting biological oscillators—A stochastic approach

We present a stochastic approach to phase-resetting of an ensemble of oscillators. In order to describe stimulation-induced dynamical phenomena we develop a stochastic model which consists of an ensemble of phase oscillators interacting via random forces. Every single oscillator is submitted to a phase stimulus. The ensemble's dynamics is determined by a Fokker-Planck equation. The stationary states are calculated explicitly, whereas the transients are analysed numerically. If the stimulus of a given (non-vanishing) intensity is administered at a critical initial cluster phase for a critical duration T _crit the ensemble's synchronized oscillation is annihilated. A transition from type 1 resetting to type 0 resetting occurs when the stimulation duration exceeds T _crit. Stimulation causes a shift of the mean frequency of every single oscillator. This frequency shift is explicitly calculated by deriving the mean first passage time. The model shows that there is a subcritical intensity which is connected with an enhanced vulnerability to stimulation. The desynchronized states, the so-called black holes, are typically associated with a double peak in the ensemble's phase distribution. This is important for analysing experimental data because simple peak-detection algorithms are not able to extract the underlying dynamics.Our results are discussed from the experimentator's point of view so that the insights derived from our model can improve data analysis and design of stimulation experiments.