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.     

Seasonal distribution of the invasive snail, <Emphasis Type="Italic">Bithynia tentaculata,</Emphasis> within infested waterbodies in Minnesota,USA, including waterfowl migration

The introduction of the invasive faucet snail (Bithynia tentaculata) and its associated trematodes, Cyathocotyle bushiensis, Sphaeridiotrema spp., and Leyogonimus polyoon, has resulted in recurring waterfowl die-offs during spring and fall migration in the Great Lakes Region, especially of Lesser scaup (Aythya affinis) and American coots (Fulica americana). Here we evaluated faucet snail habitat use and abundance in infested waterbodies in northcentral Minnesota (USA) during spring, summer, and fall of 2011–2013. We collected snail samples, along with data on abiotic and biotic variables, at 12 snail-infested waterbodies. We used Generalized Estimating Equations to develop models that explain variability in the distribution and abundance of snails within waterbodies. Models containing water depth consistently received considerable support in waterbodies where depth varied substantially; however the specific shape of these relationships varied among waterbodies. Snails used a wide range of depths, but were more likely to be present in deep portions (~6 m) of large lakes in all seasons. We found seasonal differences in the location of rafts of migrating scaup, with use of areas closer to shore in the spring, and use of areas shallower than those used most by faucet snails. Patterns in snail distribution likely influenced the availability of snails for consumption by migrating waterfowl; differences in portions of large lakes used by migratory waterfowl as stopover sites and by faucet snails may reduce exposure of migrating waterfowl to trematodes in infested lakes. However, some spatio-temporal overlap between snails and scaup occurs and explains the continuing loss of waterfowl to trematodiasis.     

Investigating the mechanical function of the cervix during pregnancy using finite element models derived from high-resolution 3D MRI

Preterm birth is a strong contributor to perinatal mortality, and preterm infants that survive are at risk for long-term morbidities. During most of pregnancy, appropriate mechanical function of the cervix is required to maintain the developing fetus in utero. Premature cervical softening and subsequent cervical shortening are hypothesized to cause preterm birth. Presently, there is a lack of understanding of the structural and material factors that influence the mechanical function of the cervix during pregnancy. In this study we build finite element models of the pregnant uterus, cervix, and fetal membrane based on magnetic resonance imagining data in order to examine the mechanical function of the cervix under the physiologic loading conditions of pregnancy. We calculate the mechanical loading state of the cervix for two pregnant patients: 22 weeks gestational age with a normal cervical length and 28 weeks with a short cervix. We investigate the influence of (1) anatomical geometry, (2) cervical material properties, and (3) fetal membrane material properties, including its adhesion properties, on the mechanical loading state of the cervix under physiologically relevant intrauterine pressures. Our study demonstrates that membrane–uterus interaction, cervical material modeling, and membrane mechanical properties are factors that must be deliberately and carefully handled in order to construct a high quality mechanical simulation of pregnancy.     

Importance of alignment between local DC magnetic field and an oscillating magnetic field in responses of brain tissue in vitro and in vivo

The frequency dependence of the electric and magnetic (EM)-field-induced release of calcium ions from an in vitro brain tissue preparation has been shown to be a function of the density of the local DC magnetic field (Bdc). In this study, we demonstrate that the relative orientation of the Bdc and the magnetic component (Bac) of a 315-Hz EM signal (15 Vrms/m and 61 nTrms) are crucial for the induced release to be observed. The induced release occurs only when the Bdc and the Bac are perpendicular, and not when they are parallel. This finding is consistent with a magnetic resonance-like transduction mechanism for the conversion of EM energy into a physicochemical change, and contrasts with the requirement for parallel Bdc and Bac components in the diatom-mobility experiments of Smith et al. A review of the exposure conditions in the rat behavioral experiments conducted by Thomas et al. identifies unhydrated calcium and zinc ions as alternatives to lithium ions as candidates for interaction under parallel magnetic-field orientations but fails to reject perpendicular orientations as an alternative basis for the phenomenon. Investigators that attempt to confirm the rat behavioral experiments should be aware of the conflicting exposure conditions that can be assumed to be operative, and they should design their experiments to test all conditions accordingly.     

Proton translation in submitochondrial vesicles

An investigation of proton translocation in submitochondrial vesicles from rat liver has been made under simple experimental conditions. Choline chloride was used both as the oxidizable substrate and the ionic medium for the measurement of activity during oxygen pulse experiments:

1. The passive permeability measured from the decay of proton efflux after an oxygen pulse could be described by a first-order equation. An H⁺/O ratio of 2·5 was obtained for choline oxidation in the presence of oligomycin and/or MgCl₂. Oligomycin decreased the passive proton permeability and respiration, concomitant with an increase in proton uptake. Respiratory control was directly related to the passive proton permeability and inversely related to the magnitude of the proton gradient. The decreased respiration and passive permeability reflecting respiratory control is most evident in the pH rang 5·8–7·5.
2. Preparation of submitochondrial vesicles in the presence of EDTA resulted in proton production during an oxygen pulse given at alkaline pH. Cytochromec enhanced proton uptake by approximately 1 H⁺/cytochromec, but only in the presence of Triton X-100. These results are indicative of the asymmetric behavior of the coupling membrane and provide direct evidence of the participation of electron transport components in proton translocation.

     

The influence of basic residues on the substrate specificity of protein kinase C

The substrate specificity of protein kinase C has been examined using a series of synthetic peptide analogs of glycogen synthase, ribosomal protein S6, and the epidermal growth factor receptor. The glycogen synthase analog peptide Pro1-Leu-Ser-Arg-Thr-Leu-Ser-Val-Ala-Ala10 was phosphorylated at Ser7 with a Km of 40.3 microM. Peptide phosphorylation was strongly dependent on Arg4. When lysine was substituted for Arg4 the Km was increased approximately 20-fold. Addition of basic residues on either the NH2-terminal or COOH-terminal side of the phosphorylation site of the glycogen synthase peptide improved the kinetics of peptide phosphorylation. The analog Pro-Leu-Ser-Arg-Thr-Leu-Ser-Val-Ala-Ala-Lys-Lys was phosphorylated with a Km of 4.1 microM. Substitution of Ser7 with threonine increased the apparent Km to 151 microM. The truncated peptide Pro1-Leu-Ser-Arg-Thr-Leu-Ser-Val8 was phosphorylated with similar kinetic constants to the parent peptide, however, deletion of Val8 increased the apparent Km to 761 microM. The ribosomal peptide S6-(229-239) was phosphorylated with a Km of approximately 0.5 microM predominantly on Ser236 and is one of the most potent synthetic peptide substrates reported for a protein kinase. The apparent Km for S6 peptide phosphorylation was increased by either deletion of the NH2-terminal 3 residues Ala229-Arg-231 or by substitution of Arg238 on the COOH-terminal side of the phosphorylation site with alanine. This analog peptide, [Ala238]S6-(229-239) was phosphorylated with an approximate 6-fold reduction in Vmax and a switch in the preferred site of phosphorylation from Ser236 to Ser235. These results support the concept that basic residues on both sides of the phosphorylation site can have an important influence on the kinetics of phosphorylation and site specificity of protein kinase C.     

The autologous mixed lymphocyte reaction in strains of mice with autoimmune disease

We have studied the autologous mixed lymphocyte reaction (AMLR) in 3 strains of mice with autoimmune disease. T cell proliferation to autologous non-T cells occurs in young mice of these 3 strains (as it does in normal mice) but is absent or greatly reduced in older mice of strains with autoimmune disease. Reciprocal mixing experiments revealed that the defect in the AMLR of the older mice resides in the responder T cell population. Further analysis of the cells participating in the AMLR of young mice of the B/W F1 strain revealed that: 1) a Thy 1- and Ly1-positive responder cell was necessary at the start of the culture to initiate the AMLR; 2) the cells present after 5 days of culture contained very few, if any, Ly123 cells in the B/W F1 strain compared with the normal C57BL/6 strain; and 3) the stimulating cell appear to be a macrophage, and an Ia-bearing cell must be present for the reaction to occur.     

Light dependent reduction of nitrate by pea chloroplasts in the presence of nitrate reductase and C4-dicarboxylic acids

In the presence of purified nitrate reductase (NR) and 1 mM NADH, illuminated pea chloroplasts catalysed reduction of NO₃^? to NH₃ with the concomitant evolution of O₂. The rates were slightly less than those for reduction of NO₂^? to NH₃ and O₂, evolution by chloroplasts in the absence of NR and NADH (ca 6 μg atoms N/mg Chl/hr). Illuminated chloroplasts quantitatively reduced 0.2 mM oxaloacetate (OAA) to malate. In the presence of an extrachloroplast malate-oxidizing system comprised of NAD-specific malate dehydrogenase (NAD-MDH), NAD, NR and NO₃^?, illuminated chloroplasts supported OAA-dependent reduction of NO₃^? to NH₃ with the evolution of O₂. The reaction did not proceed in the absence of any of these supplements or in the dark but malate could replace OAA. The results are consistent with the reduction of NO₃^?by reducing equivalents from H₂O involving a malate/OAA shuttle. The ratios for O₂, evolved: C₄-acid supplied and N reduced: C₄-acid supplied in certain experiments imply recycling of the C₄-acids.