Contact zone dynamics and the evolution of reproductive isolation in a North American treefrog, the spring peeper (Pseudacris crucifer)

Despite over seven decades of speciation research and 25 years of phylogeographic studies, a comprehensive understanding of mechanisms that generate biological species remains elusive. In temperate zones, the pervasiveness of range fragmentation and subsequent range expansions suggests that secondary contact between diverging lineages may be important in the evolution of species. Thus, such contact zones provide compelling opportunities to investigate evolutionary processes, particularly the roles of geographical isolation in initiating, and indirect selection against hybrids in completing (reinforcement), the evolution of reproductive isolation and speciation. The spring peeper (Pseudacris crucifer) has six well-supported mitochondrial lineages many of which are now in secondary contact. Here I investigate the evolutionary consequences of secondary contact of two such lineages (Eastern and Interior) in Southwestern Ontario using genetic, morphological, acoustical, experimental, and behavioural evidence to show accentuated divergence of the mate recognition system in sympatry. Mitochondrial and microsatellite data distinguish these two lineages but also show ongoing hybridization. Bayesian assignment tests and cline analysis imply asymmetrical introgression of Eastern lineage nuclear markers into Interior populations. Male calls are divergent between Eastern and Interior allopatric populations and show asymmetrical reproductive character displacement in sympatry. Female preference of pure lineage individuals is also exaggerated in sympatry, with hybrids showing intermediate traits and preference. I suggest that these patterns are most consistent with secondary reinforcement. I assessed levels of post-zygotic isolation between the Eastern and Interior lineages using a laboratory hybridization experiment. Hybrid tadpoles showed equal to or greater fitness than their pure lineage counterparts, but this may be countered through competition. More deformities and developmental anomalies in hybrid tadpoles further suggest post-zygotic isolation. Despite evidence for pre-mating isolation between the two lineages, isolation appears incomplete (i.e. hybridization is ongoing). I hypothesize that potentially less attractive hybrids may circumvent female choice by adopting satellite behaviour. Although mating tactics are related to body size, genetic status may play a role. I show that pure Eastern males almost always engage in calling, while hybrids adopt a satellite tactic. An absence of assortative mating, despite evidence of female preference, suggests successful satellite interception possibly facilitating introgression.

Mouse Uterine Natural Killer Cell Functions During Early Pregnancy

Early pregnancy is characterized by complex interactions between blood vessels, leukocytes, and conceptus-derived trophoblasts within the gestational uterus. Uterine Natural Killer (uNK) cells become the most abundant leukocyte during decidualization and produce a wide array of angiogenic factors, yet little is known regarding their early pregnancy functions. To characterize the role(s) of uNK cells, whole mount in situ immunohistochemistry of live early implant sites was performed. A timecourse examination of murine early pregnancy (virgin, and gd4.5-9.5) implantation sites was performed. Comparison of Gd6.5, 8.5 and 9.5 implant sites from BALB/c+/+ controls (BALB/c) and BALB/c-Rag2-/-Il2rg-/- (alymphoid) identified anomalies that result from the absence of lymphocytes. In alymphoid decidua basalis, mesometrial angiogenesis was widespread but pruning of nascent vessels within alymphoid decidua basalis was deficient. As early gestation progressed, vessels of alymphoid decidua basalis showed no evidence for remodeling. Alymphoid implantation sites showed ~24h delay in uterine lumen closure and embryonic development. To determine if uNK cells would normalize the anomalies observed in alymphoid implantation sites, adoptive cell transfer of NK+ B- T- marrow to alymphoid mice was performed. All of the above anomalies were reversed by adoptive transfer of NK+B-T- marrow. My results suggest that uNK cells support vascular growth and development which ensures the decidua can support the growing conceptus early in pregnancy prior to formation and function of the placenta. Human decidual NK cells may fill similar roles and be important targets for strategies designed to correct intra-uterine growth restriction.

Cytohesin Binder and Regulator (Cybr) is Not Essential for T- and Dendritic-Cell Activation and Differentiation

Cybr (also known as Cytip, CASP, and PSCDBP) is an interleukin-12-induced gene expressed exclusively in hematopoietic cells and tissues that associates with Arf guanine nucleotide exchange factors known as cytohesins. Cybr levels are dynamically regulated during T-cell development in the thymus and upon activation of peripheral T cells. In addition, Cybr is induced in activated dendritic cells and has been reported to regulate dendritic cell (DC)-T-cell adhesion. Here we report the generation and characterization of Cybr-deficient mice. Despite the selective expression in hematopoietic cells, there was no intrinsic defect in T- or B-cell development or function in Cybr-deficient mice. The adoptive transfer of Cybr-deficient DCs showed that they migrated efficiently and stimulated proliferation and cytokine production by T cells in vivo. However, competitive stem cell repopulation experiments showed a defect in the abilities of Cybr-deficient T cells to develop in the presence of wild-type precursors. These data suggest that Cybr is not absolutely required for hematopoietic cell development or function, but stem cells lacking Cybr are at a developmental disadvantage compared to wild-type cells. Collectively, these data demonstrate that despite its selective expression in hematopoietic cells, the role of Cybr is limited or largely redundant. Previous in vitro studies using overexpression or short interfering RNA inhibition of the levels of Cybr protein appear to have overestimated its immunological role.

Investigation of dead-layer thickness in SrRuO3/Ba0.5Sr0.5TiO3/Au thin-film capacitors

Thin-film capacitors, with barium strontium titanate (BST) dielectric layers between 7.5 and 950 nm in thickness, were fabricated by pulsed-laser deposition. Both crystallography and cation chemistry were consistent with successful growth of the BST perovskite. At room temperature, all capacitors displayed frequency dispersion such that epsilon (100 kHz)/epsilon (100 Hz) was greater than 0.75. The dielectric constant as a function of thickness was fitted, using the series capacitor model, for BST thicknesses greater than 70 nm. This yielded a large interfacial d(i)/epsilon (i) ratio of 0.40 +/-0.05 nm, implying a highly visible parasitic dead layer within the capacitor structure. Modeled consideration of the dielectric behavior for BST films, whose total thickness was below that of the dead layer, predicted anomalies in the plots of d/epsilon against d at the dead-layer thickness. In the capacitors studied here, no anomaly was observed. Hence, either (i) 7.5 nm is an upper limit for the total dead-layer thickness in the SRO/BST/Au system, or (ii) dielectric collapse is not associated with a distinct interfacial dead layer, and is instead due to a through-film effect. (C) 2001 American Institute of Physics.

The production and characterisation of dinitrocarbanilide antibodies raised using antigen mimics.

Polyclonal antibodies were produced to detect the coccidiostat nicarbazin. Due to structural constraints of the active component of nicarbazin, dinitrocarbanilide (DNC), three different compounds that shared a common substructure with DNC were used as antigen mimics. The compounds (N-suceinyl-L-alanyl-L-alanyl-L-alanine 4-nitroanilide (SAN), L-glutamic acid gamma-(p-nitroanilide) (GAN) and p-nitrosuccinanilic acid (NSA)) were conjugated to a carrier protein and used in the immunisation of rabbits. Five different polyclonal sera were produced and consequently characterised. The antibodies exhibited an IC50 range of 2.3-7.6 ng/ml using a competitive ELISA procedure, Serum from one rabbit, R555, exhibited an IC50 of 2.9 ng/ml for DNC and cross-reactivity studies showed that this serum was specific for DNC and did not cross-react with other coccidiostats such as halofuginone, toltrazuril or ronidazole. (C) 2002 Elsevier Science B.V. All rights reserved.

The production and characterisation of an antibody to detect the coccidiostat toltrazuril and its metabolite ponazuril.

The production of an antibody to detect toltrazuril or its metabolite ponazuril is complicated due to structural constraints of conjugating these coccidiostats to a carrier protein. Therefore a search was carried out for a compound that shared a common substructure to use as an antigen mimic. The chosen compound, trifluoraminoether, was conjugated to two carrier proteins (HSA and BTG) and used in the immunisation of six rabbits. Two immunogen doses (1 mg and 0.1 mg) were also used. All six rabbits produced an immunological response to the hapten regardless of the carrier protein or immunogen dose used. The most sensitive polyclonal antibody produced, designated R609, was subsequently characterised. This antiserum exhibited an IC50 of 18 ng ml-1 using a competitive ELISA format. Cross reactivity studies show that this serum is specific for toltrazuril and its metabolites (toltrazuril sulfoxide and toltrazuril sulfone) but does not cross-react with other coccidiostats such as halofuginone, nitroimidazoles or nicarbazin. This is the first reported production of an antibody capable of specifically binding toltrazuril and ponazuril.

Clinical Features of Dominant and Recessive Interferon γ Receptor 1 Deficiencies

Background Interferon ? receptor 1 (IFN? R1) deficiency is a primary immunodeficiency with allelic dominant and recessive mutations characterised clinically by severe infections with mycobacteria. We aimed to compare the clinical features of recessive and dominant IFN?R1 deficiencies. Methods We obtained data from a large cohort of patients worldwide. We assessed these people by medical histories, records, and genetic and immunological studies. Data were abstracted onto a standard form. Findings We identified 22 patients with recessive complete IFN?R1 deficiency and 38 with dominant partial deficiency. BCG and environmental mycobacteria were the most frequent pathogens. In recessive patients, 17 (77%) had environmental mycobacterial disease and all nine BCG-vaccinated patients had BCG disease. In dominant patients, 30 (79%) had environmental mycobacterial disease and 11 (73%) of 15 BCG-vaccinated patients had BCG disease. Compared with dominant patients, those with recessive deficiency were younger at onset of first environmental mycobacterial disease (mean 3·1 years [SD 2·5] vs 13·4 years [14·3], p=0·001), had more mycobacterial disease episodes (19 vs 8 per 100 person-years of observation, p=0·0001), had more severe mycobacterial disease (mean number of organs infected by Mycobacterium avium complex 4·1 [SD 0·8] vs 2·0 [1·1], p=0·004), had shorter mean disease-free intervals (1·6 years [SD 1·4] vs 7·2 years [7·6], p

Low-frequency electrical response to microbial induced sulfide precipitation

We investigated the sensitivity of low-frequency electrical measurements to microbe-induced metal sulfide precipitation. Three identical sand-packed monitoring columns were used; a geochemical column, an electrical column and a control column. In the first experiment, continuous upward flow of nutrients and metals in solution was established in each column. Cells of Desulfovibrio vulgaris (D. vulgaris) were injected into the center of the geochemical and electrical columns. Geochemical sampling and post-experiment destructive analysis showed that microbial induced sulfate reduction led to metal precipitation on bacteria cells, forming motile biominerals. Precipitation initially occurred in the injection zone, followed by chemotactic migration of D. vulgaris and ultimate accumulation around the nutrient source at the column base. Results from this experiment conducted with metals show (1) polarization anomalies, up to 14 mrad, develop at the bacteria injection and final accumulation areas, (2) the onset of polarization increase occurs concurrently with the onset of lactate consumption, (3) polarization profiles are similar to calculated profiles of the rate of lactate consumption, and (4) temporal changes in polarization and conduction correlate with a geometrical rearrangement of metal-coated bacterial cells. In a second experiment, the same biogeochemical conditions were established except that no metals were added to the flow solution. Polarization anomalies were absent when the experiment was replicated without metals in solution. We therefore attribute the polarization increase observed in the first experiment to a metal-fluid interfacial mechanism that develops as metal sulfides precipitate onto microbial cells and form biominerals. Temporal changes in polarization and conductivity reflect changes in (1) the amount of metal-fluid interfacial area, and (2) the amount of electronic conduction resulting from microbial growth, chemotactic movement and final coagulation. This polarization is correlated with the rate of microbial activity inferred from the lactate concentration gradient, probably via a common total metal surface area effect.

Geophysical imaging of stimulated microbial biomineralization

Understanding how microorganisms influence the physical and chemical properties of the subsurface is hindered by our inability to observe microbial dynamics in real time and with high spatial resolution. Here, we investigate the use of noninvasive geophysical methods to monitor biomineralization at the laboratory scale during stimulated sulfate reduction under dynamic flow conditions. Alterations in sediment characteristics resulting from microbe-mediated sulfide mineral precipitation were concomitant with changes in complex resistivity and acoustic wave propagation signatures. The sequestration of zinc and iron in insoluble sulfides led to alterations in the ability of the pore fluid to conduct electrical charge and of the saturated sediments to dissipate acoustic energy. These changes resulted directly from the nucleation, growth, and development of nanoparticulate precipitates along grain surfaces and within the pore space. Scanning and transmission electron microscopy (SEM and TEM) confirmed the sulfides to be associated with cell surfaces, with precipitates ranging from aggregates of individual 3-5 nm nanocrystals to larger assemblages of up to 10-20 m in diameter. Anomalies in the geophysical data reflected the distribution of mineral precipitates and biomass over space and time, with temporal variations in the signals corresponding to changes in the aggregation state of the nanocrystalline sulfides. These results suggest the potential for using geophysical techniques to image certain subsurface biogeochemical processes, such as those accompanying the bioremediation of metal-contaminated aquifers.

Teachers’ perception of visual deficiencies and their impact on students

The sense of vision is people’s main source of information acquisition, hence the importance of a right diagnosis and correction, if necessary, of any faults for proper learning, especially in the early years of schooling. This article discusses the results of a survey of teachers in Andalusian schools that aimed at highlighting their knowledge of their students’ possible visual deficiencies, and its possible impact on school performance. The results indicate that such knowledge is generally limited to the type of refractive anomalies, and that they think that such anomalies are well treated in their students. Despite the importance they attach to these deficiencies on school learning, they think that other factors may have a greater role. They also consider that better training on this topic is necessary.

Validation of urinary cortisol as an indicator of hypothalamic-pituitary-adrenal function in the bearded emperor Tamarin (Saguinus imperator subgrisescens)

The use of cortisol levels as a measure of stress is often complicated by the use of invasive techniques that may increase hypothalamic-pituitary-adrenal (HPA) axis activity during sample collection. The goal of this study was to collect samples noninvasively and validate an enzyme-immunoassay (EIA) for the measurement of cortisol in urine to quantify HPA axis activity in the bearded emperor tamarin (Saguinus imperator subgrisescens). Urine samples were collected from trained subjects between 0700 and 0730 hr during a 1-month period, and were pooled for immunological validation. We validated the assay immunologically by demonstrating specificity, accuracy, precision, and sensitivity. For biological validation of the assay, we showed that levels of urinary cortisol (in samples collected between 0700 and 1700 hr) varied significantly across the day. Cortisol concentration was lowest at 0700 hr, increased to a mid-morning peak (0900 hr), and declined across the remainder of the day in a typical mammalian circadian pattern. We thus demonstrate that urinary cortisol can be used to quantify HPA activity in S. i. subgrisescens. (C) 2004 Wiley-Liss, Inc.

Collision strengths for transitions in Ni XIX

In this paper we present calculations of electron impact excitation collision strengths for transitions among the 89 fine-structure levels of the 2S(2) 2p(,)(6) 2S(2) 2P(5) 3l, 2s(2)p(6) 3l, 2s(2) 2p(5) 4l, and 2s(2)p(6) 2l configurations of Ni XIX, for which flexible atomic code (FAC) has been adopted. Comparisons are made with the earlier available results in the literature, and the anomalies observed have been discussed.

Bimanual coordination in chronic schizophrenia

Anomalies of movement are observed both clinically and experimentally in schizophrenia. While the basal ganglia have been implicated in its pathogenesis, the nature of such involvement is equivocal. The basal ganglia may be involved in bimanual coordination through their input to the supplementary motor area (SMA). While a neglected area of study in schizophrenia. a bimanual movement task may provide a means of assessing the functional integrity of the motor circuit. Twelve patients with chronic schizophrenia and 12 matched control participants performed a bimanual movement task on a set of vertically mounted cranks at different speeds (1 and 2 Hz) and phase relationships. Participants performed in-phase movements (hands separated by 0 degrees) and out-of-phase movements (hands separated by 180 degrees) at both speeds with an external cue on or off. All participants performed the in-phase movements well. irrespective of speed or cueing conditions. Patients with schizophrenia were unable to perform the out-of-phase movements, particularly at the faster speed, reverting instead to the in-phase movement. There was no effect of external cueing on any of the movement conditions. These results suggest a specific problem of bimanual coordination indicative of SMA dysfunction per se and/or faulty callosal integration. A disturbance in the ability to switch attention during the out-of-phase task may also be involved. (C) 2001 Academic Press.