Campus & alumni news

Boston University Medicine was published by the Boston University Medical Campus, and presented stories on events and topics of interest to members of the BU Medical Campus community. It followed the discontinued publication Centerscope as Boston University Medicine from 1991-2005, and was continued as Campus & Alumni News from 2006-2013 before returning to the title Boston University Medicine from 2014-present

Morphological Examination of Prairie Turnip (Psoralea Esculenta Pursh) Root

Psoralea esculenta Pursh is an herbaceous perennial legume, native to the Great Plains, that has a tuberous-thickened taproot. Native American populations have long used the roots of this plant as food source. The Psoralea root has a tough outer covering (bark) and a fleshy interior that contains numerous isolated vascular strands. Root tissues from mature and young roots were fixed and embedded in JB-4 plastic. Differential staining methods using Safranin, Toluidine Blue, IKI, and Aniline Blue were used to examine the tissue morphology. Digital pictures were made using a Leaf Microlumina camera attached to an Olympus bright field microscope. The root of Psoralea esculenta possesses a unique arrangement of vascular tissues embedded in secondary parenchyma with regions of cells containing large deposits of either protein or starch. Alteration of protein and starch reserves was observed in mature roots, but absent in young roots. The vascular strands appeared to be randomly arranged in the secondary tissues of the root. Further analysis at different developmental stages will help to clarify the unique anatomical features observed in the root of Psoralea esculenta

An Extremely Lithium-Rich Bright Red Giant in the Globular Cluster M3

We have serendipitously discovered an extremely lithium-rich star on the red giant branch of the globular cluster M3 (NGC 5272). An echelle spectrum obtained with the Keck I HIRES reveals a Li I 6707 Angstrom resonance doublet of 520 milli-Angstrom equivalent width, and our analysis places the star among the most Li-rich giants known: log[epsilon(Li)] ~= +3.0. We determine the elemental abundances of this star, IV-101, and three other cluster members of similar luminosity and color, and conclude that IV-101 has abundance ratios typical of giants in M3 and M13 that have undergone significant mixing. We discuss mechanisms by which a low-mass star may be so enriched in Li, focusing on the mixing of material processed by the hydrogen-burning shell just below the convective envelope. While such enrichment could conceivably only happen rarely, it may in fact regularly occur during giant-branch evolution but be rarely detected because of rapid subsequent Li depletion.Comment: 7-page LaTeX file, including 2 encapsulated ps figures + 1 table; accepted for publication in the Astrophysical Journal Letter

Genetic Predisposition to Higher Body Mass Index or Type 2 Diabetes and Leukocyte Telomere Length in the Nurses' Health Study

Background: Although cross-sectional studies have linked higher body mass index (BMI) and type 2 diabetes (T2D) to shortened telomeres, whether these metabolic conditions play a causal role in telomere biology is unknown. We therefore examined whether genetic predisposition to higher BMI or T2D was associated with shortened leukocyte telomere length (LTL). Methodology: We conducted an analysis of 3,968 women of European ancestry aged 43–70 years from the Nurses' Health Study, who were selected as cases or controls in genome-wide association studies and studies of telomeres and disease. Pre-diagnostic relative telomere length in peripheral blood leukocytes, collected in 1989–1990, was measured by quantitative PCR. We combined information from multiple risk variants by calculating genetic risk scores based on 32 polymorphisms near 32 loci for BMI, and 36 polymorphisms near 35 loci for T2D. Findings: After adjustment for age and case-control status, there was no association between the BMI genetic risk score and LTL (β per standard deviation increase: −0.01; SE: 0.02; P = 0.52). Similarly, the T2D genetic score was not associated with LTL (β per standard deviation increase: −0.006; SE: 0.02; P = 0.69). Conclusions: In this population of middle-aged and older women of European ancestry, those genetically predisposed to higher BMI or T2D did not possess shortened telomeres. Although we cannot exclude weak or modest effects, our findings do not support a causal relation of strong magnitude between these metabolic conditions and telomere dynamics

The White Dwarf in EM Cygni: Beyond The Veil

We present a spectral analysis of the FUSE spectra of EM Cygni, a Z Cam DN system. The FUSE spectrum, obtained in quiescence, consists of 4 individual exposures (orbits): two exposures, at orbital phases phi ~ 0.65 and phi ~ 0.90, have a lower flux; and two exposures, at orbital phases phi =0.15 and 0.45, have a relatively higher flux. The change of flux level as a function of the orbital phase is consistent with the stream material (flowing over and below the disk from the hot spot region to smaller radii) partially masking the white dwarf. We carry out a spectral analysis of the FUSE data, obtained at phase 0.45 (when the flux is maximual, using the codes TLUSTY and SYNSPEC. Using a single white dwarf spectral component, we obtain a white dwarf temperature of 40,000K, rotating at 100km/s. The white dwarf, or conceivably, the material overflowing the disk rim, shows suprasolar abundances of silicon, sulphur and possibly nitrogen. Using a white dwarf+disk composite model, we obtain that the white dwarf temperature could be even as high as 50,000K, contributing more than 90% of the FUV flux, and the disk contributing less than 10% must have a mass accretion rate reaching 1.E-10 Msun/yr.In both cases, however, we obtain that the white dwarf temperature is much higher than previously estimated.Comment: accepted for publication in ApJ, 3 Tables, 12 Figures (including color figures), 33 pages in present format (possibly 10 pages in ApJ format

\u3cem\u3eIn Situ\u3c/em\u3e Nanomechanical Testing in Focused Ion Beam and Scanning Electron Microscopes

The recent interest in size-dependent deformation of micro- and nanoscale materials has paralleled both technological miniaturization and advancements in imaging and small-scale mechanical testing methods. Here we describe a quantitative in situ nanomechanical testing approach adapted to a dualbeam focused ion beam and scanning electron microscope. A transducer based on a three-plate capacitor system is used for high-fidelity force and displacement measurements. Specimen manipulation, transfer, and alignment are performed using a manipulator, independently controlled positioners, and the focused ion beam. Gripping of specimens is achieved using electron-beam assisted Pt-organic deposition. Local strain measurements are obtained using digital image correlation of electron images taken during testing. Examples showing results for tensile testing of single-crystalline metallic nanowires and compression of nanoporous Au pillars will be presented in the context of size effects on mechanical behavior and highlight some of the challenges of conducting nanomechanical testing in vacuum environments

Joint Effects of Colorectal Cancer Susceptibility Loci, Circulating 25-Hydroxyvitamin D and Risk of Colorectal Cancer

Background: Genome wide association studies (GWAS) have identified several SNPs associated with colorectal cancer (CRC) susceptibility. Vitamin D is also inversely associated with CRC risk. Methods: We examined main and joint effects of previously GWAS identified genetic markers of CRC and plasma 25-hydroxyvitamin D (25(OH)D) on CRC risk in three prospective cohorts: the Nurses' Health Study (NHS), the Health Professionals Follow-up Study (HPFS), and the Physicians' Health Study (PHS). We included 1895 CRC cases and 2806 controls with genomic DNA. We calculated odds ratios and 95% confidence intervals for CRC associated with additive genetic risk scores (GRSs) comprised of all CRC SNPs and subsets of these SNPs based on proximity to regions of increased vitamin D receptor binding to vitamin D response elements (VDREs), based on published ChiP-seq data. Among a subset of subjects with additional prediagnostic 25(OH)D we tested multiplicative interactions between plasma 25(OH)D and GRS's. We used fixed effects models to meta-analyze the three cohorts. Results: The per allele multivariate OR was 1.12 (95% CI, 1.06–1.19) for GRS-proximalVDRE; and 1.10 (95% CI, 1.06–1.14) for GRS-nonproxVDRE. The lowest quartile of plasma 25(OH)D compared with the highest, had a multivariate OR of 0.63 (95% CI, 0.48–0.82) for CRC. We did not observe any significant interactions between any GRSs and plasma 25(OH)D. Conclusions: We did not observe evidence for the modification of genetic susceptibility for CRC according to vitamin D status, or evidence that the effect of common CRC risk alleles differed according to their proximity to putative VDR binding sites

Centerscope

Centerscope, formerly Scope, was published by the Boston University Medical Center "to communicate the concern of the Medical Center for the development and maintenance of improved health care in contemporary society.