Postmating isolation and genetically variable host use in ecologically divergent host forms of Neochlamisus bebbianae leaf beetles.

Ecological speciation studies have more thoroughly addressed premating than postmating reproductive isolation. This study examines multiple postmating barriers between host forms of Neochlamisus bebbianae leaf beetles that specialize on Acer and Salix trees. We demonstrate cryptic isolation and reduced hybrid fitness via controlled matings of these host forms. These findings reveal host-associated postmating isolation, although a nonecological, 'intrinsic' basis for these patterns cannot be ruled out. Host preference and performance results among cross types further suggest sex-linked maternal effects on these traits, whereas family effects indicate their genetic basis and associated variation. Genes of major effect appear to influence these traits. Together with previous findings of premating isolation and adaptive differentiation in sympatry, our results meet many assumptions of 'speciation with gene flow' models. Here, such gene flow is likely asymmetric, with consequences for the dynamics of future ecological divergence and potential ecological speciation of these host forms.

The use of recombinant human activated protein C (drotrecogin alpha) in solid organ transplant recipients: case series and review of the literature.

Septic shock occurs frequently in solid organ transplant (SOT) recipients. Standard therapy includes fluid resuscitation, the administration of antimicrobials, and source control of the infection. Adjunctive therapy with recombinant human activated protein C (rhaPC), also called drotrecogin alpha, is another treatment that is used in patients but has not been studied in SOT patients. Concerns regarding the use of this drug in this patient population include the risk of bleeding and the potential to adversely affect graft survival. Here we report the largest case series of SOT recipients with septic shock who received rhaPC. This was a retrospective chart review that looked at the impact of this drug in the SOT population. In this single-center study, we identified 17 patients with a SOT and septic shock who received rhaPC. Six of the patients underwent kidney transplants, 5 received lung transplants, 4 received cadaveric liver transplants, and 2 received combined kidney/pancreas transplants. The average APACHE II score was 26.6 ± 5.5; all patients were undergoing mechanical ventilation and receiving vasopressors at the time of rhaPC administration. Overall mortality in the group was 23.5% (4/17) at 28 days post infusion. All of the deaths were due to complications of septic shock. Allograft survival was present in 13/17 (76.5%) of the patients at 28 days. Bleeding occurred in 17.6% of patients (3/17). The use of rhaPC appears to be associated with a favorable effect on mortality, with the potential for increased risk of bleeding. Clinicians must balance this risk with the potential benefit of this drug until further research can be conducted.

Intraspecific variation in symbiont genomes: bottlenecks and the aphid-buchnera association.

Buchnera are maternally transmitted bacterial endosymbionts that synthesize amino acids that are limiting in the diet of their aphid hosts. Previous studies demonstrated accelerated sequence evolution in Buchnera compared to free-living bacteria, especially for nonsynonymous substitutions. Two mechanisms may explain this acceleration: relaxed purifying selection and increased fixation of slightly deleterious alleles under drift. Here, we test the divergent predictions of these hypotheses for intraspecific polymorphism using Buchnera associated with natural populations of the ragweed aphid, Uroleucon ambrosiae. Contrary to expectations under relaxed selection, U. ambrosiae from across the United States yielded strikingly low sequence diversity at three Buchnera loci (dnaN, trpBC, trpEG), revealing polymorphism three orders of magnitude lower than in enteric bacteria. An excess of nonsynonymous polymorphism and of rare alleles was also observed. Local sampling of additional dnaN sequences revealed similar patterns of polymorphism and no evidence of food plant-associated genetic structure. Aphid mitochondrial sequences further suggested that host bottlenecks and large-scale dispersal may contribute to genetic homogenization of aphids and symbionts. Together, our results support reduced N(e) as a primary cause of accelerated sequence evolution in Buchnera. However, our study cannot rule out the possibility that mechanisms other than bottlenecks also contribute to reduced N(e) at aphid and endosymbiont loci.

Intraspecific phylogenetic congruence among multiple symbiont genomes.

Eukaryotes often form intimate endosymbioses with prokaryotic organisms. Cases in which these symbionts are transmitted cytoplasmically to host progeny create the potential for co-speciation or congruent evolution among the distinct genomes of these partners. If symbionts do not move horizontally between different eukaryotic hosts, strict phylogenetic congruence of their genomes is predicted and should extend to relationships within a single host species. Conversely, even rare 'host shifts' among closely related lineages should yield conflicting tree topologies at the intraspecific level. Here, we investigate the historical associations among four symbiotic genomes residing within an aphid host: the mitochondrial DNA of Uroleucon ambrosiae aphids, the bacterial chromosome of their Buchnera bacterial endosymbionts, and two plasmids associated with Buchnera. DNA sequence polymorphisms provided a significant phylogenetic signal and no homoplasy for each data set, yielding completely and significantly congruent phylogenies for these four genomes and no evidence of horizontal transmission. This study thus provides the first evidence for strictly vertical transmission and 'co-speciation' of symbiotic organisms at the intraspecific level, and represents the lowest phylogenetic level at which such coevolution has been demonstrated. These results may reflect the obligate nature of this intimate mutualism and indicate opportunities for adaptive coevolution among linked symbiont genomes.

Intraspecific differences in olfactory sensilla in relation to diet breadth in Uroleucon ambrosiae (Homoptera: Aphididae).

The olfactory plate organs found on the proximal segments of aphid antennae, the secondary rhinaria, were studied in apterae of the aphid Uroleucon ambrosiae. The numbers and shapes of these structures are important taxonomic characters in Aphididae, but they also show intraspecific variation within a morph. In this study, numbers were found to vary with aphid size but, independent of size, were greater in aphids collected in the eastern than in the southwestern United States. In addition, the sizes of rhinaria were greater in eastern than in southwestern aphids. These differences correlate with previously recorded differences in diet breadth and the efficiency of finding and settling on food: eastern aphids specialize on the host Ambrosia trifida, on which they settle relatively efficiently, while southwestern aphids are more generalized and less efficient. Greenhouse experiments demonstrated that differences in rhinaria are partly determined genetically. Southwestern aphids showed bilateral asymmetry in length of antennal segments though not in numbers of rhinaria, but only on certain adopted hosts that were apparently inferior for growth. The significance of these intraspecific differences is discussed in relation to the physiology, ecology, and evolution of host range.

Infrared complex refractive index measurements and simulated reflection mode infrared absorption spectroscopy of shock-compressed polymer thin films.

Thin film interference effects complicate the interpretation of reflection-mode infrared absorption spectra obtained in shock-compressed thin film materials and must be carefully accounted for in any analysis attempting to unravel shock-induced energy transfer or reactivity. We have calculated such effects for spectrally simple model systems and also, to the extent possible, for real systems such as polymethylmethacrylate (PMMA) and nitrocellulose (NC). We have utilized angle-dependent infrared (IR) reflectometry to obtain the ambient spectral complex index for PMMA and NC for use in the calculations and to interpret experiments. A number of counter-intuitive spectral effects are observed versus film thickness and during uniaxial shock compression: absorption band shifts, changes of shape, and changes in both absolute and relative peak intensities. The film thickness effects can be predicted by thin film interference alone, while additional assumptions are required to predict the effects due to shock compression. Since it is very difficult to obtain the complex index in the shock state, we made very simple assumptions regarding the change in vibrational spectra upon shock load-ing. We illustrate general thin film interference effects that could be expected and compare them to experimental results for the antisymmetric NO2 stretch mode of NC.

Compromised development of calves (Bos gaurus) derived from in vitro-generated embryos and transferred interspecifically into domestic cattle (Bos taurus).

Advanced reproductive technologies, incuding IVF and interspecies embryo transfer, are becoming increasingly important for the preservation of endangered species. Previous attempts at interspecies transfers between Bos gaurus and Bos taurus have yielded compromised offspring. The goal of this investigation was to characterize the effects of interspecies transfer of IVF-derived embryos on subsequent neonatal outcome. To achieve this goal, fresh Bos gaurus IVF-derived embryos were transferred into Holstein (Bos taurus) recipients. Four fetuses were carried to term. Calf weight, temperature, heart rate, and respiration rate were recorded after birth. Blood samples also were obtained for determination of blood glucose, pH, packed cell volume (PCV), total hemoglobin (tHB), PO2, and PCO2. After parturition, milk production and health status of the recipients were recorded. Two calves were alive at birth, and two calves were stillborn. One of the calves that was born alive died within minutes after birth, while the other lived until approximately 26 h of age. Blood samples obtained from the calf that lived for 26 h showed it to be extremely acidotic and hypoglycemic; this calf also had marked difficulty thermoregulating. At necropsy, all calves showed evidence of in utero gasping and hypoxia, suggestive of premature placental separation. None of the recipient cows showed typical signs of impending parturition. After parturition, lactogenesis in all recipient cows was markedly decreased. On gross examination, placentae resulting from the interspecies transfers had fewer cotyledons that were also much larger in size compared to cotyledons from normal gaur placentae. Calves in this study had abnormalities consistent with those noted from previous interspecies transfers and with IVF and nuclear transfer (cloned) calves. Due to the design of this study, it is not possible to differentiate between problems resulting from the IVF process and those resulting from potential interspecies incompatibilities. However, interspecies transfers of in vitro-produced gaur embryos into Bos taurus are strongly discouraged.

Shock temperature measurement using neutron resonance spectroscopy.

We report a direct measurement of temperature in a shocked metal using Doppler broadening of neutron resonances. The 21.1-eV resonance in 182W was used to measure the temperature in molybdenum shocked to approximately 63 GPa. An explosively launched aluminum flyer produced a planar shock in a molybdenum target that contained a 1-mm thick layer doped with 1.7 at. %(182)W. A single neutron pulse, containing resonant neutrons of less than 1 mus duration, probed the shocked material. Fits to the neutron time-of-flight data were used to determine the temperature of the shocked molybdenum.

Molecular systematics of cytochrome oxidase I and 16S from Neochlamisus leaf beetles and the importance of sampling.

If a gene tree is to be judiciously used for inferring the histories of closely related taxa, (1) its topology must be sufficiently resolved and robust that noteworthy phylogenetic patterns can be confidently documented, and (2) sampling of species, populations, and pertinent biological variation must be sufficiently broad that otherwise misleading sources of genetic variation can be detected. These principles are illustrated by the complex gene tree of Neochlamisus leaf beetles that I reconstructed using 90,000 bp of cytochrome oxidase I (COI) and 16S mitochondrial DNA (mtDNA) sequences from over 100 specimens. Cytochrome oxidase I haplotypes varied up to 25.1% within Neochlamisus and up to 11.1% within the gibbosus species group, while exhibiting very low A + T bias for insect mtDNA (63%), low transition saturation, and conservative patterns of amino acid variation. 16S exhibited lower sequence divergences and greater A + T bias and transition saturation than COI, and substitutions were more constrained in stems than in loops. Comparisons with an earlier study of Ophraella leaf beetles highlighted conservative and labile elements of molecular evolution across genes and taxa. Cytochrome oxidase I parsimony and neighbor-joining analyses strongly supported a robust mtDNA genealogy that revealed the monophyly of Neochlamisus and of the gibbosus species group. Phylogeographic relationships suggested that the eastern U.S. gibbosus group derives from southwestern velutinus group ancestors. Haplotypes from individual velutinus group species clustered monophyletically, as expected. However, haplotypes from each of several gibbosus group taxa were polyphyletically distributed, appearing in divergent parts of the tree. 16S provided a less-resolved gibbosus group topology that was congruent with the COI tree and corroborated patterns of mitochondrial polyphyly. By subsampling haplotypes corresponding to particular species, populations, and ecological variants of gibbosus group taxa, I demonstrate that recovered topologies and genetic distances vary egregiously according to sampling regime. This study thus documents the potentially dire consequences of inadequate sampling when inferring the evolutionary history of closely related and mitochondrially polyphyletic taxa.

Broadly tunable difference-frequency generation of VUV using two-photon resonances in H(2) and Kr.

We report generation of tunable VUV radiation in the range 117-150 nm by four-wave difference-frequency mixing of a tunable ArF excimer laser with an Nd:YAG-pumped dye laser. The four-wave mixing occurs through two-photon resonant enhancement of X((3)) through the E,F(1)Sigma(g)+ (E,' = 2, J' = 0-3) state(s) of H(2) or the 4p(5)6p(3/2)(2) state of Kr in the process (2omega(193) - omega(dye) = omega(VUV)). An estimate of energy efficiency yields 3 x 10(-5) near 133 nm for both H(2) and Kr. Even though several rotational resonances fall within the natural 193-nm bandwidth, mixing with broadband ArF output in H(2) yields single-line VUV output with a FWHM of 3.5 cm(-1) at half the efficiency compared with that of line-narrowed operation.

Fourier-transform spectroscopy using liquid-crystal technology.

We report the use of a ferroelectric liquid-crystal (FLC) mask as an optical encoder for development of a solid-state Fourier-transform spectrometer. For this demonstration a 1x64 element array was striped and used as a 1x4 element device. The device intersected dispersed radiation and encoded each spectral component with a carrier signal by applying half-wave potential to each of the four striped (1x16) FLC elements, which varied the transmitted amplitude of the light from 0.03% to 28% of full scale. The light was spectrally recombined and imaged onto a photomultiplier and the resulting carriers (and their amplitudes) detected by Fourier transformation of the time-varying signal. Spectra of colored-glass filters were taken to demonstrate the possibilities of the instrument.

Mitochondrial DNA sequences and multiple data sets: a phylogenetic study of phytophagous beetles (Chrysomelidae: Ophraella).

This paper presents the phylogenetic infrastructure for an integrated historical and experimental study of host use evolution in the chrysomelid leaf beetle genus Ophraella. We report the collection of sequence data from the 16S ribosomal RNA (446 bp) and the cytochrome oxidase subunit I (420 bp) mitochondrial genes from 12 species of Ophraella and two outgroups. Sequence analysis revealed a strong A + T nucleotide bias, high interspecific COI sequence divergences (up to 21.4%) that greatly exceeded those for 16S (up to 5.9%), high intraspecific COI divergences (up to 3.8%), a dearth of amino acid substitutions in COI, and differing substitution patterns in ribosomal stems and loops. Intraspecific variation in COI haplotypes generally supported the genealogical coherence of Ophraella lineages, while suggesting two cases of paraphyletic species. Separate phylogenetic analyses of 16S and COI data sets yielded largely congruent trees. A combined 16S + COI analysis yielded a single shortest tree under maximum parsimony that was identical to trees provided by successive approximations, neighbor-joining, and maximum-likelihood methods. This topology proved robust to various forms of weighting and most nodes were highly supported (by bootstrap analysis). Separate parsimony analyses of mtDNA and previously collected morphological and electromorphic data sets revealed congruent estimates of all cladistic relationships except those within one clade. Analysis of the pooled data sets in a combined approach additionally provided support for the basal placement of two species from this clade, although the topology for the remaining species was weakly supported and incongruent with the mtDNA tree. Each data set contained significantly structured phylogenetic signal with respect to this clade, and data sets exhibited limited conflict (character incongruence) with each other. The combined data set, however, was found to lack phylogenetic signal. These observations may imply that pooling heterogeneously evolving classes of data obscured the phylogenetic signal in each, a potential limitation of the combined approach.

Evolving FROGS: phase retrieval from frequency-resolved optical gating measurements by use of genetic algorithms.

We present a new technique based on genetic algorithms for retrieving the electric field and the phase of ultrashort pulses from frequency-resolved optical gating (FROG) traces. We have successfully applied a very basic genetic algorithm to the two most common beam geometries: polarization gate and second-harmonic generation (SHG). In the case of SHG FROG, the genetic algorithm returns a lower error than the standard iterative composite algorithm.

Measurement of shock wave rise times in metal thin films.

We have measured the rise time of laser-generated shock waves in vapor plated metal thin films using frequency-domain interferometry with subpicosecond time resolution. 10%- 90% rise times of <6.25 ps were found in targets ranging from 0.25 to 2.0 microm in thickness. Particle and average shock velocities were simultaneously determined. Shock velocities of approximately 5 nm/ps were inferred from the measured free surface velocity, corresponding to pressures of 30-50 kbar. Thus, the shock front extends only a few tens of lattice spacings.

Terahertz emission via ultrashort-pulse excitation of magnetic metal films.

We observe terahertz emission by optical rectification of an intense 1.5-eV, 50-fs pulse in single-crystal iron thin films grown by molecular beam epitaxy. The azimuthal dependence of the emission indicates the presence of a magnetic nonlinearity and a nonmagnetic surface nonlinearity.