Sexual Selection on male cuticular hydrocarbons via male-male competition and female choice.

Traditional views of sexual selection assumed that male-male competition and female mate choice work in harmony, selecting upon the same traits in the same direction. However, we now know that this is not always the case and that these two mechanisms often impose conflicting selection on male sexual traits. Cuticular hydrocarbons (CHCs) have been shown to be linked to both social dominance and male attractiveness in several insect species. However, although several studies have estimated the strength and form of sexual selection imposed on male CHCs by female mate choice, none have established whether these chemical traits are also subject to sexual selection via male-male competition. Using a multivariate selection analysis, we estimate and compare sexual selection exerted by male-male competition and female mate choice on male CHC composition in the broad-horned flour beetle Gnatocerus cornutus. We show that male-male competition exerts strong linear selection on both overall CHC abundance and body size in males, while female mate choice exerts a mixture of linear and nonlinear selection, targeting not just the overall amount of CHCs expressed but the relative abundance of specific hydrocarbons as well. We discuss the potential implications of this antagonistic selection with regard to male reproductive success.

Macronutrient intake regulates sexual conflict in decorated crickets.

Sexual conflict results in a diversity of sex-specific adaptations, including chemical additions to ejaculates. Male decorated crickets (Gryllodes sigillatus) produce a gelatinous nuptial gift (the spermatophylax) that varies in size and free amino acid composition, which influences a female's willingness to fully consume this gift. Complete consumption of this gift maximizes sperm transfer through increased retention of the sperm-containing ampulla, but hinders post-copulatory mate choice. Here, we examine the effects of protein (P) and carbohydrate (C) intake on the weight and amino acid composition of the spermatophylax that describes its gustatory appeal to the female, as well as the ability of this gift to regulate sexual conflict via ampulla attachment time. Nutrient intake had similar effects on the expression of these traits with each maximized at a high intake of nutrients with a P : C ratio of 1 : 1.3. Under dietary choice, males actively regulated their nutrient intake but this regulation did not coincide with the peak of the nutritional landscape for any trait. Our results therefore demonstrate that a balanced intake of nutrients is central to regulating sexual conflict in G. sigillatus, but males are constrained from reaching the optima needed to bias the outcome of this conflict in their favour.

Environmental heterogeneity, multivariate sexual selection and genetic constraints on cuticular hydrocarbons in Drosophila simulans.

Sexual selection is responsible for the evolution of many elaborate traits, but sexual trait evolution could be influenced by opposing natural selection as well as genetic constraints. As such, the evolution of sexual traits could depend heavily on the environment if trait expression and attractiveness vary between environments. Here, male Drosophila simulans were reared across a range of diets and temperatures, and we examined differences between these environments in terms of (i) the expression of male cuticular hydrocarbons (CHCs) and (ii) which male CHC profiles were most attractive to females. Temperature had a strong effect on male CHC expression, whereas the effect of diet was weaker. Male CHCs were subject to complex patterns of directional, quadratic and correlational sexual selection, and we found differences between environments in the combination of male CHCs that were most attractive to females, with clearer differences between diets than between temperatures. We also show that genetic covariance between environments is likely to cause a constraint on independent CHC evolution between environments. Our results demonstrate that even across the narrow range of environmental variation studied here, predicting the outcome of sexual selection can be extremely complicated, suggesting that studies ignoring multiple traits or environments may provide an over-simplified view of the evolution of sexual traits.

Genotype-by-environment interactions for cuticular hydrocarbon expression in Drosophila simulans.

Genotype-by-environment interactions (G × Es) describe genetic variation for phenotypic plasticity. Recent interest in the role of these interactions in sexual selection has identified G × Es across a diverse range of species and sexual traits. Additionally, theoretical work predicts that G × Es in sexual traits could help to maintain genetic variation, but could also disrupt the reliability of these traits as signals of mate quality. However, empirical tests of these theoretical predictions are scarce. We reared iso-female lines of Drosophila simulans across two axes of environmental variation (diet and temperature) in a fully factorial design and tested for G × Es in the expression of cuticular hydrocarbons (CHCs), a multivariate sexual trait in this species. We find sex-specific environmental, genetic and G × E effects on CHC expression, with G × Es for diet in both male and female CHC profile and a G × E for temperature in females. We also find some evidence for ecological crossover in these G × Es, and by quantifying variance components, genetic correlations and heritabilities, we show the potential for these G × Es to help maintain genetic variation and cause sexual signal unreliability in D. simulans CHC profiles.

Reagentless identification of single bacterial spores in aqueous solution by confocal laser tweezers Raman spectroscopy.

We demonstrate that optical trapping combined with confocal Raman spectroscopy using a single laser source is a powerful tool for the rapid identification of micrometer-sized particles in an aqueous environment. Optical trapping immobilizes the particle while maintaining it in the center of the laser beam path and within the laser focus, thus maximizing the collection of its Raman signals. The single particle is completely isolated from other particles and substrate surfaces, therefore eliminating any unwanted background signals and ensuring that information is collected only from the selected, individual particle. In this work, an inverted confocal Raman microscope is combined with optical trapping to probe and analyze bacterial spores in solution. Rapid, reagentless detection and identification of bacterial spores with no false positives from a complex mixed sample containing polystyrene and silica beads in aqueous suspension is demonstrated. In addition, the technique is used to analyze the relative concentration of each type of particle in the mixture. Our results show the feasibility for incorporating this technique in combination with a flow cytometric-type scheme in which the intrinsic Raman signatures of the particles are used instead of or in addition to fluorescent labels to identify cells, bacteria, and particles in a wide range of applications.

How events are reviewed matters: effects of varied focus on eyewitness suggestibility.

Witnesses to a crime or an accident perceive that event only once, but they are likely to think or talk about it multiple times. The way in which they review the event may affect their later memory. In particular, some types of review may increase suggestibility if the witness has been exposed to postevent misleading information. In Experiment 1, participants viewed a videotaped crime and then received false suggestions about the event. We found that participants who were then asked to focus on specific details when reviewing the event were more suggestible on a later source memory test than participants asked to review the main points. The findings of Experiment 2 suggest that this effect was not due to a criterion shift at test. These findings indicate that the type of rehearsal engaged in after witnessing an event can have important consequences for memory and, in particular, suggestibility.

Adrenal epinephrine increases alveolar liquid clearance in a canine model of neurogenic pulmonary edema.

Case reports of neurogenic pulmonary edema (NPE) often indicate that the edema resolves quickly. Because plasma epinephrine concentration may be elevated in NPE, and epinephrine has been shown to increase the rate of alveolar liquid clearance (ALC), we determined if ALC was increased in a canine model of NPE produced by the intracisternal administration of veratrine. ALC was determined by instilling autologous plasma into a lower lung lobe and using the increase in instillate protein concentration after 4 h to calculate the volume of fluid cleared from the airspaces by mass balance. To prevent pulmonary hypertension and edema, which would confound the mass balance analysis, carotid arterial blood was allowed to drain into a reservoir as pulmonary arterial pressure started to rise after veratrine administration. ALC in animals administered veratrine (n = 6) was 30.4 +/- 1.6 (SE)% of the instilled volume compared with 14.1 +/- 2.1% observed in control animals. The increase in ALC could be inhibited by adrenalectomy, beta2-adrenergic blockade using ICI 118,551, or sodium channel blockade using amiloride and could be duplicated by infusing epinephrine to increase plasma epinephrine concentration to levels observed in NPE. These data indicate that the increased ALC was mediated by adrenal epinephrine and suggest that edema resolution in patients with NPE might be accelerated by endogenous epinephrine.

Alveolar liquid clearance in multiple nonperfused canine lung lobes.

We evaluated the ability of canine isolated nonperfused lung lobes to absorb fluid from their air spaces by simultaneously measuring alveolar liquid clearance (ALC) in three lobes removed from the same dog. Autologous plasma was instilled in the air spaces of each lobe, and the increase in plasma protein concentration resulting from fluid reabsorption was used to calculate ALC. ALC after 4 h was 16.5 +/- 0.6% (SE) of the instilled fluid volume under baseline conditions and was 30.2 +/- 1.3% after terbutaline (10(-5) M) administration. These values were similar to those previously reported for intact dogs. Propranolol (10(-4) M) and ouabain (10(-3) M) reduced ALC in terbutaline-stimulated lobes to 20.4 +/- 0.8 and 3.9 +/- 1.4%, respectively. There was no significant difference in ALC among the three lobes under either baseline conditions or after terbutaline administration. These data indicate that the sodium and water transport mechanisms of the canine alveolar epithelium remain viable during 4 h of nonperfusion and that there are no intrinsic differences in the transport properties of individual lung lobes. The ability to study several lobes simultaneously without the need for perfusion will allow for the design of experiments in which multiple interventions can be studied by using lung lobes from the same animal.

The recollective experience of cross-modality confusion errors.

There are at least two qualitatively different types of subjective experience that can accompany accurate recognition memory. Sometimes recognition is accompanied by conscious recollection of the learning episode (i.e., it is remembered), and in other cases it is not (i.e., it is simply known that the item is old). In the present study, we assessed the subjective experience that accompanies cross-modality confusion errors (misidentifying words as pictures) by measuring the extent to which subjects claimed to remember versus know that the item was presented as a picture. The results of two experiments demonstrate that cross-modality confusion errors are often accompanied by conscious recollection, although not to the same extent as accurate memories. The findings also show that there is considerable overlap in the recollective experience that accompanies accurate and erroneous memories. Finally, the results support the contention that recollective experience cannot be directly inferred from test performance.

Time course of blood volume changes in an isolated lung lobe after venous pressure elevation.

The elevation of venous pressure (Pv) in isolated perfused organs causes organ weight to increase in a biphasic manner. The initial rapid phase results primarily from an increase in blood volume (BV), whereas the second slower phase is generally considered to reflect fluid filtration. Recent studies have suggested, however, that BV may continue to increase during the slow weight gain phase. To address this question, we made serial measurements of circulating BV by indicator dilution with indocyanine green dye in a canine isolated perfused left lower lung lobe (LLL) preparation during 40 min of Pv elevation. Pv was raised to approximately 18 Torr in six LLLs beginning an average of 28 min after the start of perfusion. After an initial rapid increase, BV continued to increase at a slower rate for approximately 30 min. The increase in BV observed between 3 and 40 min of Pv elevation [4.3 +/- 0.3 (SE) ml] was 47.9 +/- 9.1% of the weight gain that occurred during this period. In six additional LLLs, Pv elevation was delayed until approximately 70 min after the perfusion was started. In these LLLs, BV generally achieved constancy 3 min after Pv was elevated. These data indicate that the dynamics of the BV response of this preparation to Pv elevation is time dependent and that gravimetric determinations of the rate of fluid filtration may substantially overestimate the true filtration rate in the presence of continuing increases in BV. The increases in BV observed in the first group of LLLs appear to be due to vascular recruitment rather than stress relaxation.

Source misattributions and the suggestibility of eyewitness memory.

Although the suggestibility of eyewitness memory is well documented, previous studies have not clearly established the extent to which misled Ss might come to believe they actually remember seeing the suggested details they report. To assess whether Ss confuse misleading suggestions for their "real memories" of a witnessed event, Ss were asked specific questions about their memory for the source of suggested items. The results of 5 experiments showed that misled Ss do sometimes come to believe they remember seeing items that were merely suggested to them, a phenomenon we refer to as the source misattribution effect. Nevertheless, the results also showed that the magnitude of this effect varies and that source misattributions are not an inevitable consequence of exposure to suggestions.

Efficacy of light support pantyhose.

The results of a multicenter, double-blind clinical trial indicate that the use of light support pantyhose significantly reduced the incidence of aches, swelling and fatigue in the lower legs of healthy women. A trend toward reduced foot and leg circumference was noted; however, it did not correlate significantly with subjective symptomatology.

Neutron imaging of laser fusion targets.

Along-term goal of inertial-confinement fusion research is the generation of energy by imploding capsules containing deuterium-tritium fuel. Progress in designing the capsules is aided by accurate imaging of the fusion burn. Penumbral coded-aperture techniques have been used to obtain neutron images that are a direct measurement of the fusion burn region in the capsules.