Effect of transgene introgression site on gene migration from transgenic b. napus to b. rapa [abstract]

Abstract only availableThere is a growing concern of the possible transgenic introgression from GM plants into agricultural weeds, which has stimulated research in the process of crop to weed gene flow. Crop to weed gene flow often involves the hybridization of a polyploidy crop to a diploid weed. An example is canola (Brassica napus with AACC genomes) which can hybridize with B. rapa (AA) to produce fertile triploid F1 hybrids (ACC) in the wild. It is hypothesized that there are "safe sites" on the C genome because the C genome is likely to be lost from wild populations after a few generations of repeated backcrossing with B. rapa. However, there is homoeology between the A and C genomes of Brassica, which allows potential recombination between genomes and the movement of transgenes from the C to A genomes by chromosomal rearrangements. Recent advances in molecular markers and fluorescent in situ hybridization (FISH) now allow us to observe the frequency of homoeologous exchanges following hybridization. Our research is focused on finding safe sites within the B. napus genome which are least likely to be transferred into B. napus and B. rapa hybrids and their progeny. To test this, we have crossed a transgenic B. napus with a natural B. rapa three times to make three different F1events. Then we backcrossed each of the three F1 three times with B. rapa. We are measuring the germination rate of each generation and using transgene specific PCR primers to check the presence or absence of the transgene in hybrids. We will also use molecular cytogenetics (FISH) to count chromosome numbers. This study will help determine the possibilities of a "safe" site in B. napus and offer insight in the mechanisms of crop to weed transgene introgression in B. napus x B. rapa hybrids.MU Monsanto Undergraduate Research Fellowshi

Locally extracting scalar, vector and tensor modes in cosmological perturbation theory

Cosmological perturbation theory relies on the decomposition of perturbations into so-called scalar, vector and tensor modes. This decomposition is non-local and depends on unknowable boundary conditions. The non-locality is particularly important at second- and higher-order because perturbative modes are sourced by products of lower-oder modes, which must be integrated over all space in order to isolate each mode. However, given a trace-free rank-2 tensor, a locally defined scalar mode may be trivially derived by taking two divergences, which knocks out the vector and tensor degrees of freedom. A similar local differential operation will return a pure vector mode. This means that scalar and vector degrees of freedom have local descriptions. The corresponding local extraction of the tensor mode is unknown however. We give it here. The operators we define are useful for defining gauge-invariant quantities at second-order. We perform much of our analysis using an index-free `vector-calculus' approach which makes manipulating tensor equations considerably simpler.Comment: 13 pages. Final version to appear in CQ

Flavor Asymmetry of the Nucleon Sea: Consequences for Dilepton Production

Parton distributions derived from a chiral quark model that generates an excess of down quarks and antiquarks in the proton's sea satisfactorily describe the measured yields of muon pairs produced in proton-nucleus collisions. Comparison of dilepton yields from hydrogen and deuterium targets promises greater sensitivity to the predicted flavor asymmetry.Comment: 11 pages, REVTEX, (Three PostScript figures available by anonymous ftp from fnth06.fnal.gov in directory /pub/Fermilab-Pub/92.264.) FERMILAB-PUB-92/264--T LBL-3298

Prediction of portal and hepatic blood flow from intake level data in cattle

There is growing interest in developing integrated post-absorptive metabolism models for dairy 30 cattle. An integral part of linking a multi-organ post-absorptive model is the prediction of nutrient 31 fluxes between organs, and thus blood flow. It was the purpose of this paper to use a multivariate 32 meta-analysis approach to model portal blood flow (PORBF) and hepatic venous blood flow 33 (HEPBF) simultaneously, with evaluation of hepatic arterial blood flow (ARTBF; ARTBF = 34 HEPBF – PORBF) and PORBF/HEPBF (%) as calculated values. The database used to develop 35 equations consisted of 296 individual animal observations (lactating and dry dairy cows and beef 36 cattle) and 55 treatments from 17 studies, and a separate evaluation database consisted of 34 37 treatment means (lactating dairy cows and beef cattle) from 9 studies obtained from the literature. 38 Both databases had information on DMI, MEI, body weight and a basic description of the diet 39 including crude protein intake and forage proportion of the diet (FP; %). Blood flow (L/h or L/kg 40 BW0.75/h) and either DMI or MEI (g or MJ/d or g or MJ/kg BW0.75/d) with linear and quadratic 41 fits were examined. Equations were developed using cow within experiment and experiment as 42 random effects, and blood flow location as a repeated effect. Upon evaluation with the evaluation 43 database, equations based on DMI typically resulted in lower root mean square prediction errors, 44 expressed as a % of the observed mean (rMSPE%) and higher concordance correlation coefficient 45 (CCC) values than equations based on MEI. Quadratic equation terms were frequently non-46 significant, and the quadratic equations did not out-perform their linear counterparts. The best 47 performing blood flow equations were: PORBF (L/h) = 202 (± 45.6) + 83.6 (± 3.11) × DMI (kg/d) and HEPBF (L/h) = 186 (± 45.4) + 103.8 (± 3.10) × DMI (kg/d), with rMSPE% values of 17.5 and 49 16.6 and CCC values of 0.93 and 0.94, respectively. The residuals (predicted – observed) for 50 PORBF/HEPBF were significantly related to the forage % of the diet, and thus equations for 51 3 PORBF and HEPBF based on forage and concentrate DMI were developed: PORBF (L/h) = 210 52 (± 51.0) + 82.9 (± 6.43) × Forage (kg DM/d) + 82.9 (± 6.04) × Concentrate (kg DM/d), and 53 HEPBF (L/h) = 184 (± 50.6) + 92.6 (± 6.28) × Forage (kg DM/d) + 114.2 (± 5.88) × Concentrate 54 (kg DM/d), where rMSPE% values were 17.5 and 17.6 and CCC values were 0.93 and 0.94, 55 respectively. Division of DMI into forage and concentrate fractions improved the joint Bayesian 56 Information Criterion (BIC) value for PORBF and HEPBF (BIC = 6512 vs. 7303), as well as 57 slightly improved the rMSPE and CCC for ARTBF and PORBF/HEPBF. This was despite 58 minimal changes in PORBF and HEPBF predictions. Developed equations predicted blood flow 59 well, and could easily be used within a post absorptive model of nutrient metabolism. Results also 60 suggest different sensitivity of PORBF and HEPBF to the composition of DMI, and accounting 61 for this difference resulted in improved ARTBF predictions

Chromosomal evolution in Brassicacae: Allopolyploidy, aneuploidy and transgene transmission [abstract]

Abstract only availablePolyploidy is a eukaryotic phenomenon common to plants that serves as an evolutionary mechanism for speciation. Diploid species undergo polyploidization through single genome duplication (autopolyploidy) or by the hybridization of genomes from two or more distinct progenitor species (allopolyploidy). Aneuploidy can arise where offspring possess extra or fewer chromosomes than their progenitors. Over successive generations, changes in chromosomal number and rearrangement can lead to speciation or differentiation of ecotypes within a species. Using advanced molecular cytogenetics and fluorescent in situ hybridization (FISH), we can distinguish chromosomes and genomic markers among different ecotypes and species. In the agricultural industry where genetically modified organisms (GMOs) are used, aneuploidy and homoeologous recombination of transgenic elements presents a potential mechanism of moving transgenes from GMO crops into the genomes of wild diploids. These wild diploids then have the potential to become "superweeds" that can disrupt ecological systems. The goal of this study was to investigate the movement of a transgene from an allopolyploid to a diploid in controlled greenhouse crosses. Transgenic Brassica napus allopolyploid plants (AACC) were backcrossed to natural Brassica rapa (AA) recurrently over three generations. We examined each of the three backcross generations for chromosome number and gene transmission. Molecular cytogenetic analysis was performed on flower buds from each backcross, chromosome numbers were recorded and gene transmission was analyzed by PCR. As expected, we found aneuploidy in Brassica napus x Brassica rapa hybrids suggesting potential for homoeologous recombination of transgenes into non-transgenic diploid species. Surprisingly, despite aneuploidy, we also found a high rate of both germination and transmission of the transgene into wild Brassica rapa, suggesting the need to find safe sites in Brassica napus to insert transgenes

Short-term studies underestimate 30-generation changes in a butterfly metapopulation

Most studies of rare and endangered species are based on work carried out within one generation, or over one to a few generations of the study organism. We report the results of a study that spans 30 generations (years) of the entire natural range of a butterfly race that is endemic to 35 km2 of north Wales, UK. Short-term studies (surveys in single years and dynamics over 4 years) of this system led to the prediction that the regional distribution would be quite stable, and that colonization and extinction dynamics would be relatively unimportant. However, a longer-term study revealed unexpectedly high levels of population turnover (local extinction and colonization), affecting 18 out of the 20 patches that were occupied at any time during the period. Modelling the system (using the 'incidence function model' (IFM) for metapopulations) also showed higher levels of colonization and extinction with increasing duration of the study. The longer-term dynamics observed in this system can be compared, at a metapopulation level, with the increased levels of variation observed with increasing time that have been observed in single populations. Long-term changes may arise from local changes in the environment that make individual patches more or less suitable for the butterfly, or from unusual colonization or extinction events that take metapopulations into alternative states. One implication is that metapopulation and population viability analyses based on studies that cover only a few animal or plant generations may underestimate extinction threats

Does the Isotropy of the CMB Imply a Homogeneous Universe? Some Generalised EGS Theorems

We demonstrate that the high isotropy of the Cosmic Microwave Background (CMB), combined with the Copernican principle, is not sufficient to prove homogeneity of the universe -- in contrast to previous results on this subject. The crucial additional factor not included in earlier work is the acceleration of the fundamental observers. We find the complete class of irrotational perfect fluid spacetimes admitting an exactly isotropic radiation field for every fundamental observer and show that are FLRW if and only if the acceleration is zero. While inhomogeneous in general, these spacetimes all possess three-dimensional symmetry groups, from which it follows that they also admit a thermodynamic interpretation. In addition to perfect fluids models we also consider multi-component fluids containing non-interacting radiation, dust and a quintessential scalar field or cosmological constant in which the radiation is isotropic for the geodesic (dust) observers. It is shown that the non-acceleration of the fundamental observers forces these spacetimes to be FLRW. While it is plausible that fundamental observers (galaxies) in the real universe follow geodesics, it is strictly necessary to determine this from local observations for the cosmological principle to be more than an assumption. We discuss how observations may be used to test this.Comment: replaced with final version. Added discusion and ref

Discontinuation of standard first-line antiretroviral therapy in a cohort of 1434 Malawian children

The standard first-line antiretroviral (ART) regimen in Malawi for both adults and children is a fixed-dose combination tablet containing stavudine (d4T), lamivudine (3TC) and nevirapine (NVP). This regimen has been shown to yield satisfactory virologic and immunologic outcomes in children. Published studies have described insights into discontinuation of first-line regimen and toxicities of ART in adults, but similar studies in paediatric populations are lacking

Self, memory, and imagining the future in a case of psychogenic amnesia

We report a case of psychogenic amnesia and examine the relationships between autobiographical memory impairment, the self, and ability to imagine the future. Case study JH, a 60 year old male, experienced a 6 year period of pervasive psychogenic amnesia covering all life events from childhood to the age of 53. JH was tested during his amnesic period and again following hypnotherapy and the recovery of his memories. JH’s amnesia corresponded with deficits in self-knowledge and imagining the future. Results are discussed with reference to models of self and memory and processes involving remembering and imagining

Calculable Upper Limit on the Mass of the Lightest Higgs Boson in Any Perturbatively Valid Supersymmetric Theory

We show that there is a calculable upper limit on the mass of the lightest Higgs boson in any supersymmetric theory that remains perturbative up to a high scale . There are no restrictions on the Higgs sector, or the gauge group or particle content. We estimate the value of the upper limit to be m_{\hcirc} < 146 GeV for 100 GeV < $M_t$ < 145 GeV, from all effects except possibly additional heavy fermions beyond top (which could increase the limit by 0-20 GeV if any existed); for $M_t$ > 145 GeV the limit decreases monotonically. We expect to be able to decrease the value of the upper limit by at least a few percent by very careful analysis of the conditions. It is not normal in models for the actual mass to saturate the upper limit.Comment: 8 pages, UM-TH-92-24, Plain TeX. (One table available by fax on request to [email protected]