APP substitutions V715F and L720P alter PS1 conformation and differentially affect Abeta and AICD generation

The 37-43 amino acid Abeta peptide is the principal component of beta-amyloid deposits in Alzheimer's disease (AD) brain, and is derived by serial proteolysis of the amyloid precursor protein (APP) by beta- and gamma-secretase. gamma-Secretase also cleaves APP at Val50 in the Abeta numbering (epsilon cleavage), resulting in the release of a fragment called APP intracellular domain (AICD). The aim of this study was to determine whether amino acid substitutions in the APP transmembrane domain differentially affect Abeta and AICD generation. We found that the APPV715F substitution, which has been previously shown to dramatically decrease Abeta40 and Abeta42 while increasing Abeta38 levels, does not affect in vitro generation of AICD. Furthermore, we found that the APPL720P substitution, which has been previously shown to prevent in vitro generation of AICD, completely prevents Abeta generation. Using a fluorescence resonance energy transfer (FRET) method, we next found that both the APPV715F and APPL720P substitutions significantly increase the distance between the N- and C-terminus of presenilin 1 (PS1), which has been proposed to contain the catalytic site of gamma-secretase. In conclusion, both APPV715F and APPL720P change PS1 conformation with differential effects on Abeta and AICD production.     

Large,Omega-3 Rich,Pelagic Diatoms under Arctic Sea Ice: Sources and Implications for Food Webs

Pelagic primary production in Arctic seas has traditionally been viewed as biologically insignificant until after the ice breakup. There is growing evidence however, that under-ice blooms of pelagic phytoplankton may be a recurrent occurrence. During the springs of 2011 and 2012, we found substantial numbers (201–5713 cells m⁻³) of the large centric diatom (diameter >250 µm) Coscinodiscus centralis under the sea ice in the Canadian Arctic Archipelago near Resolute Bay, Nunavut. The highest numbers of these pelagic diatoms were observed in Barrow Strait. Spatial patterns of fatty acid profiles and stable isotopes indicated two source populations for C. centralis: a western origin with low light conditions and high nutrients, and a northern origin with lower nutrient levels and higher irradiances. Fatty acid analysis revealed that pelagic diatoms had significantly higher levels of polyunsaturated fatty acids (mean ± SD: 50.3±8.9%) compared to ice-associated producers (30.6±10.3%) in our study area. In particular, C. centralis had significantly greater proportions of the long chain omega-3 fatty acid, eicosapentaenoic acid (EPA), than ice algae (24.4±5.1% versus 13.7±5.1%, respectively). Thus, C. centralis represented a significantly higher quality food source for local herbivores than ice algae, although feeding experiments did not show clear evidence of copepod grazing on C. centralis. Our results suggest that C. centralis are able to initiate growth under pack ice in this area and provide further evidence that biological productivity in ice-covered seas may be substantially higher than previously recognized.     

Laccase immobilization on enzymatically functionalized polyamide 6,6 fibres

Polyamide matrices, such as membranes, gels and non-wovens, have been applied as supports for enzyme immobilization, although in literature the enzyme immobilization on woven nylon matrices is rarely reported. In this work, a protocol for a Trametes hirsuta laccase immobilization using woven polyamide 6,6 (nylon) was developed. A 2⁴ full factorial design was used to study the influence of pH, spacer (1,6-hexanediamine), enzyme and crosslinker concentration on the efficiency of immobilization. The factors enzyme dosage and spacer seem to have played a critical role in the immobilization of laccase onto nylon support. Under optimized working conditions (29 U mL⁻¹ of laccase, 10% of glutaraldehyde, pH = 5.5, with the presence of the spacer), the half-life time attained was about 78 h (18% higher than that of free enzyme), the protein retention was 30% and the immobilization yield was 2%. The immobilized laccase has potential for application in the continuous decolourization of textile effluents, where it can be applied into a membrane reactor.     

Homing endonuclease mediated gene targeting in Anopheles gambiae cells and embryos

Homing endonuclease genes (HEGs) are ‘selfish’ genetic elements that combine the capability to selectively disrupt specific gene sequences with the ability to rapidly spread from a few individuals to an entire population through homologous recombination repair events. Because of these properties, HEGs are regarded as promising candidates to transfer genetic modifications from engineered laboratory mosquitoes to wild-type populations including Anopheles gambiae the vector of human malaria. Here we show that I-SceI and I-PpoI homing endonucleases cleave their recognition sites with high efficiency in A. gambiae cells and embryos and we demonstrate HEG-induced homologous and non-homologous repair events in a variety of functional assays. We also propose a gene drive system for mosquitoes that is based on our finding that I-PpoI cuts genomic rDNA located on the X chromosome in A. gambiae, which could be used to selectively incapacitate X-carrying spermatozoa thereby imposing a severe male-biased sex ratio.     

BRCTx is a novel, highly conserved RAD18-interacting protein

The BRCT domain is a highly conserved module found in many proteins that participate in DNA damage checkpoint regulation, DNA repair, and cell cycle control. Here we describe the cloning, characterization, and targeted mutagenesis of Brctx, a novel gene with a BRCT motif. Brctx was found to be expressed ubiquitously in adult tissues and during development, with the highest levels found in testis. Brctx-deficient mice develop normally, show no pathological abnormalities, and are fertile. BRCTx binds to the C terminus of hRAD18 in yeast two-hybrid and immunoprecipitation assays and colocalizes with this protein in the nucleus. Despite this, Brctx-deficient murine embryonic fibroblasts (MEFs) do not show overt sensitivity to DNA-damaging agents. MEFs from Brctx-deficient embryos grow at a similar rate to wild-type MEF CD4/CD8 expressions, and the cell cycle parameters of thymocytes from wild-type and Brctx knockout animals are indistinguishable. Intriguingly, the BRCT domain of BRCTx is responsible for mediating its localization to the nucleus and centrosome in interphase cells. We conclude that, although highly conserved, Brctx is not essential for the above-mentioned processes and may be redundant.     

Determinants of Survival in Malignant Pleural Mesothelioma: A Surveillance,Epidemiology, and End Results (SEER) Study of 14,228 Patients

Introduction

Left untreated, malignant pleural mesothelioma (MPM) is associated with uniformly poor prognosis. Better survival has been reported with surgery-based multimodality therapy, but to date, no trial has demonstrated survival benefit of surgery over other therapies. We evaluated whether cancer-directed surgery influenced survival independently from other predictors in a large population-based dataset.

Methods

The SEER database was explored from 1973 to 2009 to identify all cases of pathologically-proven MPM. Age, sex, race, year of diagnosis, histology stage, cancer-directed surgery, radiation, and vital status were analyzed. The association between prognostic factors and survival was estimated using Cox regression and propensity matched analysis.

Results

There were 14,228 patients with pathologic diagnosis of MPM. On multivariable analysis, female gender, younger age, early stage, and treatment with surgery were independent predictors of longer survival. In comparison to no treatment, surgery alone was associated with significant improvement in survival [adjusted hazard ratio (adj HR) 0.64 (0.61–0.67)], but not radiation [adj HR 1.15 (1.08–1.23)]. Surgery and radiation combined had similar survival as surgery alone [adj HR 0.69 (0.64–0.76)]. Results were similar when cases diagnosed between 1973 and 1999 were compared to cases diagnosed between 2000 and 2009.

Conclusions

Despite developments in surgical and radiation techniques, the prognosis for MPM patients has not improved over the past 4 decades. Cancer-directed surgery is independently associated with better survival, suggesting that multimodal surgery-based therapy can benefit these patients. Further research in adjuvant treatment is necessary to improve prognosis in this challenging disease.     

An alternative method for assessing early mortality in contemporary populations

Biological anthropologists are interested in a population's early mortality rates for a variety of reasons. Early mortality (infant or juvenile) is of obvious importance to those interested in demography, but early mortality statistics are useful for life history analysis, paleodemography, and human adaptability studies, among others. In general, the form of mortality statistics is derived from demography, where chronological age is the gold standard for statistical calculation and comparison. However, there are numerous problems associated with the collection, analysis, and interpretation of early mortality statistics based on age, particularly for anthropological research, which is often conducted in small or non-calendrical-age numerate populations. The infant mortality rate (IMR), for example, is notoriously difficult to determine in populations where accurate accounting of age is not routine, and yet it is widely used in demography, public health, medicine, and social science research. Here we offer an alternative to age-based early mortality statistics that makes use of human biologists' interest in, and skill at, assessing human growth and development. Our proposal is to use developmental stages of juveniles instead of relying exclusively on age as the basis for mortality statistics. Death or survival according to a developmental stage (such as crawling or weaning) may provide more accurate data that are also more closely related to the cause of death. Developmental stages have the added advantage of putting infants and children back at the center of the discussion of early mortality by focusing on their activities in relation to their environment. A case study from the Turkana population of Kenya illustrates the use of developmental stages in describing early mortality. Am J Phys Anthropol 107:315–330, 1998. © 1998 Wiley-Liss, Inc.     

In vitro physical mutagenesis of giant reed (Arundo donax L.)

Giant reed (Arundo donax L.) is a C₃ perennial, warm‐season, rhizomatous grass of emerging interest for bioenergy and biomass derivatives production, and for phytoremediation. It only propagates vegetatively and very little genetic variation is found among ecotypes, basically precluding breeding efforts. With the objective to increase the genetic variation in this species, we developed and applied a mutagenesis protocol based on γ‐irradiation of in vitro cell cultures from which regenerants were obtained. Based on a radiosensitivity test, the irradiation dose reducing to 50% the number of regenerants per callus (RD₅₀) was estimated at 35 Gy. A large mutagenic experiment was carried out by irradiating a total of 3120 calli with approx. 1×, 1.5× and 2× RD₅₀. A total of 1004 regenerants from irradiated calli were hardened in pots and transplanted to the field. Initial phenotypic characterization of the collection showed correlated responses of biomass‐related quantitative traits to irradiation doses. Approx. 10% of field‐grown clones showed remarkable morphological aberrations including dwarfism, altered tillering, abnormal inflorescence, leaf variegation and others, which were tested for stability over generations. Clone lethality reached 0.4%. Our results show for the first time that physical mutagenesis can efficiently induce new genetic and phenotypic variation of agronomic and prospective industrial value in giant reed. The methodology and the plant materials described here may contribute to the domestication and the genetic improvement of this important biomass species.     

Proximity to canopy mediates changes in the defensive chemistry and herbivore loads of an understory tropical shrub,Piper kelleyi

Phytochemical traits are a key component of plant defense theory. Chemical ecology has been biased towards studying effects of individual metabolites even though effective plant defenses are comprised of diverse mixtures of metabolites. We tested the phytochemical landscape hypothesis, positing that trophic interactions are contingent upon their spatial location across a phytochemically diverse landscape. Specifically, intraspecific phytochemical changes associated with vertical strata in forests were hypothesised to affect herbivore communities of the neotropical shrub Piper kelleyi Tepe (Piperaceae). Using a field experiment, we found that phytochemical diversity increased with canopy height, and higher levels of phytochemical diversity located near the canopy were characterised by tradeoffs between photoactive and non‐photoactive biosynthetic pathways. For understory plants closer to the ground, phytochemical diversity increased as direct light transmittance decreased, and these plants were characterised by up to 37% reductions in herbivory. Our results suggest that intraspecific phytochemical diversity structures herbivore communities across the landscape, affecting total herbivory.