Generalised surface waves at the boundary of piezo-poroelastic medium with arbitrary anisotropy.

This study considers the propagation of surface waves along all directions on the plane boundary of piezo-poroelastic half-space with arbitrary anisotropy. This generalised propagation is characterized through an anisotropic phase velocity, which should ensure the decay of wave-field with depth into the medium. A linear homogeneous system of six equations with complex coefficients governs the existence and propagation of surface waves in the considered medium. The real phase velocity of surface waves lies implicit in a complex determinantal equation, which ensures a non-trivial solution to the system of equations. Through a specific transformation, the system of complex equations is modified to yield a real secular equation, with phase velocity being the only unknown. This equation can always be solved numerically for phase velocity of surface wave along any direction on the plane boundary of anisotropic piezo-poroelastic medium. The phase velocity has been used further to calculate the components of energy flux at the boundary. Horizontal components of energy flux define the group velocity and ray direction for the surface wave. A numerical example is solved to analyse the phase/group velocity curves at the boundary of the medium.

Sexual selection drives the evolution of male wing interference patterns.

The seemingly transparent wings of many insects have recently been found to display unexpected structural coloration. These structural colours (wing interference patterns: WIPs) may be involved in species recognition and mate choice, yet little is known about the evolutionary processes that shape them. Furthermore, to date investigations of WIPs have not fully considered how they are actually perceived by the viewers' colour vision. Here, we use multispectral digital imaging and a model of Drosophila vision to compare WIPs of male and female Drosophila simulans from replicate populations forced to evolve with or without sexual selection for 68 generations. We show that WIPs modelled in Drosophila vision evolve in response to sexual selection and provide evidence that WIPs correlate with male sexual attractiveness. These findings add a new element to the otherwise well-described Drosophila courtship display and confirm that wing colours evolve through sexual selection.

Multidrug Therapy for HIV Infection: Dynamics of Immune System.

A mathematical model of the dynamics of the immune system is considered to illustrate the effect of its response to HIV infection, i.e. on viral growth and on T-cell dynamics. The specific immune response is measured by the levels of cytotoxic lymphocytes in a human body. The existence and stability analyses are performed for infected steady state and uninfected steady state. In order to keep infection under control, roles of drug therapies are analyzed in the presence of efficient immune response. Numerical simulations are computed and exhibited to illustrate the support of the immune system to drug therapies, so as to ensure the decay of infection and to maintain the level of healthy cells.

The Drosophila simulans Y chromosome interacts with the autosomes to influence male fitness.

The Y chromosome should degenerate because it cannot recombine. However, male-limited transmission increases selection efficiency for male-benefit alleles on the Y, and therefore, Y chromosomes should contribute significantly to variation in male fitness. This means that although the Drosophila Y chromosome is small and gene-poor, Y-linked genes are vital for male fertility in Drosophila melanogaster and the Y chromosome has large male fitness effects. It is unclear whether the same pattern is seen in the closely related Drosophila simulans. We backcrossed Y chromosomes from three geographic locations into five genetic backgrounds and found strong Y and genetic background effects on male fertility. There was a significant Y-background interaction, indicating substantial epistasis between the Y and autosomal genes affecting male fertility. This supports accumulating evidence that interactions between the Y chromosome and the autosomes are key determinants of male fitness.

Constrained evolution of the sex comb in Drosophila simulans.

Male fitness is dependent on sexual traits that influence mate acquisition (precopulatory sexual selection) and paternity (post-copulatory sexual selection), and although many studies have documented the form of selection in one or the other of these arenas, fewer have done it for both. Nonetheless, it appears that the dominant form of sexual selection is directional, although theoretically, populations should converge on peaks in the fitness surface, where selection is stabilizing. Many factors, however, can prevent populations from reaching adaptive peaks. Genetic constraints can be important if they prevent the development of highest fitness phenotypes, as can the direction of selection if it reverses across episodes of selection. In this study, we examine the evidence that these processes influence the evolution of the multivariate sex comb morphology of male Drosophila simulans. To do this, we conduct a quantitative genetic study together with a multivariate selection analysis to infer how the genetic architecture and selection interact. We find abundant genetic variance and covariance in elements of the sex comb. However, there was little evidence for directional selection in either arena. Significant nonlinear selection was detected prior to copulation when males were mated to nonvirgin females, and post-copulation during sperm offence (again with males mated to nonvirgins). Thus, contrary to our predictions, the evolution of the D. simulans sex comb is limited neither by genetic constraints nor by antagonistic selection between pre- and post-copulatory arenas, but nonlinear selection on the multivariate phenotype may prevent sex combs from evolving to reach some fitness maximizing optima.

Fisher's sons' effect in sexual selection: absent, intermittent or just low experimental power?

The Fisherian sexual selection paradigm has been called the null model of sexual selection. At its heart is the expectation of a genetic correlation (rG ) between female preference and male trait. However, recent meta-analysis has shown estimated correlations are often extremely weak and not statistically significant. We show here that systematic failure of studies to reject the null hypothesis that rG  = 0 is almost certainly due to the low power of most experimental designs used. We provide an easy way to assess experimental power a priori and suggest that current data make it difficult to definitively test a key component of the Fisher effect.

Potential for combination of dipeptidyl peptidase-4 inhibitors and sodium-glucose co-transporter-2 inhibitors for the treatment of type 2 diabetes.

In individuals with advanced type 2 diabetes (T2DM), combination therapy is often unavoidable to maintain glycaemic control. Currently metformin is considered the first line of defence, but many patients experience gastrointestinal adverse events, necessitating an alternative treatment approach. Established therapeutic classes, such as sulphonylureas and thiazolidinediones, have some properties undesirable in individuals with T2DM, such as hypoglycaemia risk, weight gain and fluid retention, highlighting the need for newer agents with more favourable safety profiles that can be combined and used at all stages of T2DM. New treatment strategies have focused on both dipeptidyl peptidase (DPP)-4 inhibitors, which improve hyperglycaemia by stimulating insulin secretion in a glucose-dependent fashion and suppressing glucagon secretion, and sodium-glucose co-transporter-2 (SGLT2) inhibitors, which reduce renal glucose reabsorption and induce urinary glucose excretion, thereby lowering plasma glucose. The potential complimentary mechanism of action and good tolerance profile of these two classes of agents make them attractive treatment options for combination therapy with any of the existing glucose-lowering agents, including insulin. Together, the DPP-4 and SGLT2 inhibitors fulfill a need for treatments with mechanisms of action that can be used in combination with a low risk of adverse events, such as hypoglycaemia or weight gain.

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.

No association between sperm competition and sperm length variation across dung flies (Scathophagidae).

Sperm length is extremely variable across species, but a general explanation for this variation is lacking. However, when the risk of sperm competition is high, sperm length is predicted to be less variable within species, and there is some evidence for this in birds and social insects. Here, we examined intraspecific variation in sperm length, both within and between males, and its potential associations with sperm competition risk and variation in female reproductive tract morphology across dung flies. We used two measures of variation in sperm size, and testis size was employed as our index of sperm competition risk. We found no evidence of associations between sperm length variation and sperm competition or female reproductive tract variation. These results suggest that variation in sperm competition risk may not always be associated with variation in sperm morphology, and the cause(s) of sperm length variation in dung flies remains unclear.

Polymicrobial infections can select against Pseudomonas aeruginosa mutators because of quorum-sensing trade-offs.

Bacteria with increased mutation rates (mutators) are common in chronic infections and are associated with poorer clinical outcomes, especially in the case of Pseudomonas aeruginosa infecting cystic fibrosis (CF) patients. There is, however, considerable between-patient variation in both P. aeruginosa mutator frequency and the composition of co-infecting pathogen communities. We investigated whether community context might affect selection of mutators. Using an in vitro CF model community, we show that P. aeruginosa mutators were favoured in the absence of other species but not in their presence. This was because there were trade-offs between adaptation to the biotic and abiotic environments (for example, loss of quorum sensing and associated toxin production was beneficial in the latter but not the former in our in vitro model community) limiting the evolvability advantage of an elevated mutation rate. Consistent with a role of co-infecting pathogens selecting against P. aeruginosa mutators in vivo, we show that the mutation frequency of P. aeruginosa population was negatively correlated with the frequency and diversity of co-infecting bacteria in CF infections. Our results suggest that co-infecting taxa can select against P. aeruginosa mutators, which may have potentially beneficial clinical consequences.

Male attractiveness, fertility and susceptibility to oxidative stress are influenced by inbreeding in Drosophila simulans.

Inbreeding frequently leads to inbreeding depression, a reduction in the trait values of inbred individuals. Inbreeding depression has been documented in sexually selected characters in several taxa, and while there is correlational evidence that male fertility is especially susceptible to inbreeding depression, there have been few direct experimental examinations of this. Here, we assessed inbreeding depression in male fertility and a range of other male fitness correlates in Drosophila simulans. We found that male fertility and attractiveness were especially susceptible to inbreeding depression. Additionally, levels of testicular oxidative stress were significantly elevated in inbred males, although sperm viability did not differ between inbred and outbred males. Copulation duration, induction of oviposition, and the proportion of eggs hatching did not differ for females mated to inbred or outbred males. Nevertheless, our results clearly show that key male fitness components are impaired by inbreeding and provide evidence that aspects of male fertility are especially susceptible to inbreeding depression.

Female mate preferences in Drosophila simulans: evolution and costs.

Female mate preference is central to sexual selection, and all indirect benefit models require that there is genetic variation in female preference. This has rarely been tested however, with relatively few studies documenting heritable variation in female preference and even fewer that have directly selected on mate preference to unequivocally show that it can evolve. Additionally, costs of mate preference are poorly understood even though these have implications for preference evolution. We selected on female preference for ebony-males in replicate Drosophila simulans lines, and generated a rapid evolutionary response in both replicates, with the proportion of females mating with ebony-males increasing from approximately 5% to 30% after five generations of selection. This increase was independent of changes in ebony-males as only females were included in our selection regime. We could detect no cost to mate preference itself other than that associated with the fitness consequences of mating with ebony males.

Pre and Post-copulatory Selection Favor Similar Genital Phenotypes in the Male Broad Horned Beetle.

Sexual selection can operate before and after copulation and the same or different trait(s) can be targeted during these episodes of selection. The direction and form of sexual selection imposed on characters prior to mating has been relatively well described, but the same is not true after copulation. In general, when male-male competition and female choice favor the same traits then there is the expectation of reinforcing selection on male sexual traits that improve competitiveness before and after copulation. However, when male-male competition overrides pre-copulatory choice then the opposite could be true. With respect to studies of selection on genitalia there is good evidence that male genital morphology influences mating and fertilization success. However, whether genital morphology affects reproductive success in more than one context (i.e., mating versus fertilization success) is largely unknown. Here we use multivariate analysis to estimate linear and nonlinear selection on male body size and genital morphology in the flour beetle Gnatocerus cornutus, simulated in a non-competitive (i.e., monogamous) setting. This analysis estimates the form of selection on multiple traits and typically, linear (directional) selection is easiest to detect, while nonlinear selection is more complex and can be stabilizing, disruptive, or correlational. We find that mating generates stabilizing selection on male body size and genitalia, and fertilization causes a blend of directional and stabilizing selection. Differences in the form of selection across these bouts of selection result from a significant alteration of nonlinear selection on body size and a marginally significant difference in nonlinear selection on a component of genital shape. This suggests that both bouts of selection favor similar genital phenotypes, whereas the strong stabilizing selection imposed on male body size during mate acquisition is weak during fertilization.

Local adaptation of a bacterium is as important as its presence in structuring a natural microbial community.

Local adaptation of a species can affect community composition, yet the importance of local adaptation compared with species presence per se is unknown. Here we determine how a compost bacterial community exposed to elevated temperature changes over 2 months as a result of the presence of a focal bacterium, Pseudomonas fluorescens SBW25, that had been pre-adapted or not to the compost for 48 days. The effect of local adaptation on community composition is as great as the effect of species presence per se, with these results robust to the presence of an additional strong selection pressure: an SBW25-specific virus. These findings suggest that evolution occurring over ecological time scales can be a key driver of the structure of natural microbial communities, particularly in situations where some species have an evolutionary head start following large perturbations, such as exposure to antibiotics or crop planting and harvesting.

Hyperresolving phase-only filters with an optically addressable liquid crystal spatial light modulator.

Hyperresolving (sometimes called 'superresolving' or 'ultraresolving') phase-only filters can be generated using an optically addressable liquid crystal spatial light modulator. This approach avoids the problems of low efficiency, and coupling between amplitude and phase modulation, that arise when using conventional liquid crystal modulators. When addressed by a programmed light intensity distribution, it allows filters to be changed rapidly to modify the response of a system or permit the investigation of different filter designs. In this paper we present experimental hyperresolved images obtained using an optically addressable parallel-aligned nematic LCD with two zone Toraldo type phase-only filters. The images are compared with theoretical predictions.

Holmium-doped optical fiber for filter applications.

We consider the properties of holmium-doped fibers in filter applications. We give spectral properties and model filter characteristics. Experiments on filtering of Raman spectra are presented. The fiber filters exhibit strong rejection in the stop band and sharp absorption cutoffs.

Dyslipidaemia in African Americans, Hispanics and whites with type 2 diabetes mellitus and hypertension.

AIM: To study the pattern of dyslipidaemia in African American, Hispanic, and White patients with type 2 diabetes mellitus and/or hypertension. METHODS: The data were collected retrospectively on 6450 patients followed in the Harris County Hospital District Community Clinics. The information collected from review of the charts included each patient's age, sex, race, body mass index (b.m.i.), duration of type 2 diabetes mellitus and hypertension, medications, fasting plasma glucose, haemoglobin A1c, and fasting lipid profile. Mean lipid and haemoglobin A1c levels in the three ethnic groups were compared. The risk of abnormal cholesterol and triglyceride levels was assessed with logistic regression analysis. RESULTS: The results show that in patients with type 2 diabetes mellitus after correcting for age, sex and b.m.i., African Americans have the lowest serum triglyceride concentrations and Whites have the highest values. This trend holds true even in patients with hypertension and in patients with both hypertension and type 2 diabetes mellitus. The risk of having abnormal triglycerides is 74% lower in African Americans, and 42% lower in Hispanics than Whites based on logistic regression model. Despite better glycaemic control, Whites have a greater increase in serum triglyceride concentrations than Hispanics and African Americans. CONCLUSIONS: Although African Americans are known to be at higher risk for cardiovascular complications than Whites or Hispanics, they appear to have lower triglyceride concentrations than Whites or Hispanics in the presence of type 2 diabetes mellitus. This suggests that an increased prevalence of other adverse factors must contribute to their heightened cardiovascular risk.

Isolation of the novel agent from human stool samples that is associated with sporadic non-A, non-B hepatitis.

The agent(s) responsible for sporadic non-A, non-B hepatitis in humans was serially transmitted in rhesus monkeys by intravenous inoculation of the stool extract from a patient. A novel agent called HFV (hepatitis French [origin] virus) was present as 27- to 37-nm particles in the infectious stool extract. Hepatopathic lesions were noticed in infected monkeys during the acute phase of illness. The purified viral 27- to 37-nm particles consist of a double-stranded DNA of approximately 20 kb and are detected in infected monkey liver. Analysis of cell culture detects the approximately 20-kb-long viral DNA in stool samples from infected monkeys and sporadic enteric non-A, non-B hepatitis patients. Furthermore, the 27- to 37-nm viral particles were able to protect monkeys challenged with infectious stool extract. Our results indicate that 27- to 37-nm virus like particles are responsible for sporadic non-A, non-B hepatitis in rhesus monkeys.

High frequency of serious infections in patients with panhypopituitarism: a case-control study.

We reviewed the records of 65 patients with panhypopituitarism (PHP) for the frequency and types of infections requiring hospitalization, and documented serious infections in 13 of 65 patients with PHP. The increased frequency of serious infectious diseases in patients with PHP is likely to contribute to increased age-specific mortality.

Induction and inhibition of CD40-CD40 ligand interactions: a new strategy underlying host-virus relationships.

Interaction between CD40 and the CD40 ligand (CD40L) is required for mouse mammary tumor virus (MMTV) propagation. We found that Fas was expressed on B cells and CD40L on a small subset of viral superantigen-cognate T cells 12 h after MMTV(SW) infection. CD40L and Fas were down-regulated after 24 h. All CD4 T cells then became resistant to anti-CD3-induced CD40L induction in vitro for 2 wk. Initiation of CD40L expression and its rapid shut-off was associated with IL-12 production and was controlled by IFN-gamma and shedding of soluble CD40. These results suggest that a rapid, transient CD40-CD40L interaction involving a small number of cells is sufficient for MMTV propagation. Modulation of CD40L expression may be a major mechanism regulating the balance between viral propagation and host defenses, allowing mutual survival.