Genetic variation in the cellular response of Daphnia magna (Crustacea: Cladocera) to its bacterial parasite

Linking measures of immune function with infection, and ultimately, host and parasite fitness is a major goal in the field of ecological immunology. In this study, we tested for the presence and timing of a cellular immune response in the crustacean Daphnia magna following exposure to its sterilizing endoparasite Pasteuria ramosa. We found that D. magna possesses two cell types circulating in the haemolymph: a spherical one, which we call a granulocyte and an irregular-shaped amoeboid cell first described by Metchnikoff over 125 years ago. Daphnia magna mounts a strong cellular response (of the amoeboid cells) just a few hours after parasite exposure. We further tested for, and found, considerable genetic variation for the magnitude of this cellular response. These data fostered a heuristic model of resistance in this naturally coevolving host–parasite interaction. Specifically, the strongest cellular responses were found in the most susceptible hosts, indicating resistance is not always borne from a response that destroys invading parasites, but rather stems from mechanisms that prevent their initial entry. Thus, D. magna may have a two-stage defence—a genetically determined barrier to parasite establishment and a cellular response once establishment has begun

Minimal Trinification

We study the trinified model, SU(3)_C x SU(3)_L x SU(3)_R x Z_3, with the minimal Higgs sector required for symmetry breaking. There are five Higgs doublets, and gauge-coupling unification results if all five are at the weak scale, without supersymmetry. The radiative see-saw mechanism yields sub-eV neutrino masses, without the need for intermediate scales, additional Higgs fields, or higher-dimensional operators. The proton lifetime is above the experimental limits, with the decay modes p -> \bar\nu K^+ and p -> \mu^+ K^0 potentially observable. We also consider supersymmetric versions of the model, with one or two Higgs doublets at the weak scale. The radiative see-saw mechanism fails with weak-scale supersymmetry due to the nonrenormalization of the superpotential, but operates in the split-SUSY scenario.Comment: 23 pages, uses axodra

X-ray image reconstruction from a diffraction pattern alone

A solution to the inversion problem of scattering would offer aberration-free diffraction-limited 3D images without the resolution and depth-of-field limitations of lens-based tomographic systems. Powerful algorithms are increasingly being used to act as lenses to form such images. Current image reconstruction methods, however, require the knowledge of the shape of the object and the low spatial frequencies unavoidably lost in experiments. Diffractive imaging has thus previously been used to increase the resolution of images obtained by other means. We demonstrate experimentally here a new inversion method, which reconstructs the image of the object without the need for any such prior knowledge.Comment: 5 pages, 3 figures, improved figures and captions, changed titl

Generation and analysis of expressed sequence tags (ESTs) for marker development in yam (Dioscorea alata L.)

Background: Anthracnose (Colletotrichum gloeosporioides) is a major limiting factor in the production of yam (Dioscorea spp.) worldwide. Availability of high quality sequence information is necessary for designing molecular markers associated with resistance. However, very limited sequence information pertaining to yam is available at public genome databases. Therefore, this collaborative project was developed for genetic improvement and germplasm characterization of yams using molecular markers. The current investigation is focused on studying gene expression, by large scale generation of ESTs, from one susceptible (TDa 95-0310) and two resistant yam genotypes (TDa 87-01091, TDa 95-0328) challenged with the fungus. Total RNA was isolated from young leaves of resistant and susceptible genotypes and cDNA libraries were sequenced using Roche 454 technology. Results: A total of 44,757 EST sequences were generated from the cDNA libraries of the resistant and susceptible genotypes. Greater than 56% of ESTs were annotated using MapMan Mercator tool and Blast2GO search tools. Gene annotations were used to characterize the transcriptome in yam and also perform a differential gene expression analysis between the resistant and susceptible EST datasets. Mining for SSRs in the ESTs revealed 1702 unique sequences containing SSRs and 1705 SSR markers were designed using those sequences. Conclusion: We have developed a comprehensive annotated transcriptome data set in yam to enrich the EST information in public databases. cDNA libraries were constructed from anthracnose fungus challenged leaf tissues for transcriptome characterization, and differential gene expression analysis. Thus, it helped in identifying unique transcripts in each library for disease resistance. These EST resources provide the basis for future microarray development, marker validation, genetic linkage mapping and QTL analysis in Dioscorea species

Coherent X-ray Diffractive Imaging; applications and limitations

The inversion of a diffraction pattern offers aberration-free diffraction-limited 3D images without the resolution and depth-of-field limitations of lens-based tomographic systems, the only limitation being radiation damage. We review our experimental results, discuss the fundamental limits of this technique and future plans.Comment: 7 pages, 8 figure

Effects of a College-Mentored Physical Activity Program for Elementary Students

Health risks of a sedentary lifestyle for children, defined as being less than 5,000 steps per day, include unfavorable indicators of body composition and cardio-metabolic risk. Results of school-based physical activity interventions to increase physical activity levels have been mixed. However, mentorship programs have shown promise. Previous mentorship programs have relied on peer-to-peer mentorships, with participants being of a similar age group. College mentors present an alternative and low-cost resource that may also provide positive results, yet have been largely ignored in research studies to date. PURPOSE: The purpose of this study was to investigate the impact of a novel, individualized college-mentored physical activity program on physical activity levels among older elementary school students. METHODS: Fifth grade students (n = 12) were paired one-to-one with local college mentors for 30 minute bi-weekly running sessions on the elementary school campus for six weeks. Multiple assessments from activity trackers were compared on intervention versus non-intervention days using paired-samples t-tests. RESULTS: Significant increases in steps (t(11) = 8.056; p ≤ .001) and moderate-to-vigorous activity (t(11) = 5.202; p ≤ .001) were seen on intervention days, as compared to non-intervention days. The average increase in step count on intervention days (6,381) versus non-intervention days (3,158) also resulted in students being elevated out of a sedentary classification. CONCLUSION: Individualized mentoring from college students significantly increased multiple assessments of physical activity, including minutes of moderate-to-vigorous activity and number of steps taken. Perhaps most notably, the mentored physical activity program promoted students from a sedentary to active lifestyle on intervention days as determined by step count. This novel high-impact and low-cost approach should be further developed for future school-based physical activity programs and research