Modulating Glutathione Thiol Status Alters Pancreatic β-cell Morphogenesis in the Developing Zebrafish (Danio rerio) Embryo

Emerging evidence suggests that redox-active chemicals perturb pancreatic islet development. To better understand potential mechanisms for this, we used zebrafish (Danio rerio) embryos to investigate roles of glutathione (GSH; predominant cellular redox buffer) and the transcription factor Nrf2a (Nfe2l2a; zebrafish Nrf2 coortholog) in islet morphogenesis. We delineated critical windows of susceptibility to redox disruption of beta-cell morphogenesis, interrogating embryos at 24, 48 and 72 h post fertilization (hpf) and visualized Nrf2a expression in the pancreas using whole-mount immunohistochemistry at 96 hpf. Chemical GSH modulation at 48 hpf induced significant islet morphology changes at 96 hpf. Pro-oxidant exposures to tert-butylhydroperoxide (77.6 mu M; 10-min at 48 hpf) or tert-butylhydroquinone (1 mu M; 48-56 hpf) decreased beta-cell cluster area at 96 hpf. Conversely, exposures to antioxidant N-acetylcysteine (bolsters GSH pools; 100 mu M; 48-72 hpf) or sulforaphane (activates Nrf2a; 20 mu M; 48-72 hpf) significantly increased islet areas. Nrf2a was also stabilized in beta-cells: 10-min exposures to 77.6 mu M tert-butylhydroperoxide significantly increased Nrf2a protein compared to control islet cells that largely lack stabilized Nrf2a; 10-min exposures to higher (776 mu M) tert-butylhydroperoxide concentration stabilized Nrf2a throughout the pancreas. Using biotinylated-GSH to visualize in situ protein glutathionylation, islet cells displayed high protein glutathionylation, indicating oxidized GSH pools. The 10-min high (776 mu M) tert-butylhydroperoxide exposure (induced Nrf2a globally) decreased global protein glutathionylation at 96 hpf. Mutant fish expressing inactive Nrf2a were protected against tert-butylhydroperoxide-induced abnormal islet morphology. Our data indicate that disrupted redox homeostasis and Nrf2a stabilization during pancreatic beta-cell development impact morphogenesis, with implications for disease states at later life stages. Our work identifies a potential molecular target (Nrf2) that mediates abnormal beta-cell morphology in response to redox disruptions. Moreover, our findings imply that developmental exposure to exogenous stressors at distinct windows of susceptibility could diminish the reserve redox capacity of beta-cells, rendering them vulnerable to later-life stresses and disease

A dramatic isotope effect in the reaction of ClSiH with trimethylsilane-1-d: experimental evidence for intermediate complexes in silylene Si-H(D) insertion reactions

A kinetic isotope effect (kD/kH) of 7.4 has been found for the reaction of chlorosilylene with trimethysilane (Me3SiD vs Me3SiH). Such a value can be accounted for by theoretical modelling, but only if an internal rearrangement of the initially form complex is included in the mechanism. This provides the first concrete evidence for such complexes

Beyond deficit-based models of learners' cognition: Interpreting engineering students' difficulties with sense-making in terms of fine-grained epistemological and conceptual dynamics

Researchers have argued against deficit-based explanations of students' troubles with mathematical sense-making, pointing instead to factors such as epistemology: students' beliefs about knowledge and learning can hinder them from activating and integrating productive knowledge they have. In this case study of an engineering major solving problems (about content from his introductory physics course) during a clinical interview, we show that "Jim" has all the mathematical and conceptual knowledge he would need to solve a hydrostatic pressure problem that we posed to him. But he reaches and sticks with an incorrect answer that violates common sense. We argue that his lack of mathematical sense-making-specifically, translating and reconciling between mathematical and everyday/common-sense reasoning-stems in part from his epistemological views, i.e., his views about the nature of knowledge and learning. He regards mathematical equations as much more trustworthy than everyday reasoning, and he does not view mathematical equations as expressing meaning that tractably connects to common sense. For these reasons, he does not view reconciling between common sense and mathematical formalism as either necessary or plausible to accomplish. We, however, avoid a potential "deficit trap"-substituting an epistemological deficit for a concepts/skills deficit-by incorporating multiple, context-dependent epistemological stances into Jim's cognitive dynamics. We argue that Jim's epistemological stance contains productive seeds that instructors could build upon to support Jim's mathematical sense-making: He does see common-sense as connected to formalism (though not always tractably so) and in some circumstances this connection is both salient and valued.Comment: Submitted to the Journal of Engineering Educatio

The acquisition of Sign Language: The impact of phonetic complexity on phonology

Research into the effect of phonetic complexity on phonological acquisition has a long history in spoken languages. This paper considers the effect of phonetics on phonological development in a signed language. We report on an experiment in which nonword-repetition methodology was adapted so as to examine in a systematic way how phonetic complexity in two phonological parameters of signed languages — handshape and movement — affects the perception and articulation of signs. Ninety-one Deaf children aged 3–11 acquiring British Sign Language (BSL) and 46 hearing nonsigners aged 6–11 repeated a set of 40 nonsense signs. For Deaf children, repetition accuracy improved with age, correlated with wider BSL abilities, and was lowest for signs that were phonetically complex. Repetition accuracy was correlated with fine motor skills for the youngest children. Despite their lower repetition accuracy, the hearing group were similarly affected by phonetic complexity, suggesting that common visual and motoric factors are at play when processing linguistic information in the visuo-gestural modality

An alu-based phylogeny of gibbons (hylobatidae)

Gibbons (Hylobatidae) are small, arboreal apes indigenous to Southeast Asia that diverged from other apes ∼15-18 Ma. Extant lineages radiated rapidly 6-10 Ma and are organized into four genera (Hylobates, Hoolock, Symphalangus, and Nomascus) consisting of 12-19 species. The use of short interspersed elements (SINEs) as phylogenetic markers has seen recent popularity due to several desirable characteristics: the ancestral state of a locus is known to be the absence of an element, rare potentially homoplasious events are relatively easy to resolve, and samples can be quickly and inexpensively genotyped. During radiation of primates, one particular family of SINEs, the Alu family, has proliferated in primate genomes. Nomascus leucogenys (northern white-cheeked gibbon) sequences were analyzed for repetitive content with RepeatMasker using a custom library. The sequences containing Alu elements identified as members of a gibbon-specific subfamily were then compared with orthologous positions in other primate genomes. A primate phylogenetic panel consisting of 18 primate species, including 13 gibbon species representing all four extant genera, was assayed for all loci, and a total of 125 gibbon-specific Alu insertions were identified. The resulting amplification patterns were used to generate a phylogenetic tree. We demonstrate significant support for Symphalangus as the most basal lineage within the family. Our findings also place Nomascus as a derived lineage, sister to Hoolock, with the Nomascus-Hoolock clade sister to Hylobates. Further, our analysis groups N. leucogenys and Nomascus siki as sister taxa to the exclusion of the other Nomascus species assayed. This study represents the first use of SINEs to determine the genus level phylogenetic relationships within the family Hylobatidae. These relationships have been resolved with robust support at most internal nodes, demonstrating the utility of SINE-based phylogenetic analysis. We postulate that hybridization and rapid radiation may have contributed to the complex and contradictory findings of the previous studies. Our findings will aid in the conservation of these threatened primates and inform future studies of the biogeographical history and distribution of modern gibbon species. © 2012 The Author

A systematic review and meta-analysis of gene therapy in animal models of cerebral glioma:why did promise not translate to human therapy?

BACKGROUND: The development of therapeutics is often characterized by promising animal research that fails to translate into clinical efficacy; this holds for the development of gene therapy in glioma. We tested the hypothesis that this is because of limitations in the internal and external validity of studies reporting the use of gene therapy in experimental glioma. METHOD: We systematically identified studies testing gene therapy in rodent glioma models by searching three online databases. The number of animals treated and median survival were extracted and studies graded using a quality checklist. We calculated median survival ratios and used random effects meta‐analysis to estimate efficacy. We explored effects of study design and quality and searched for evidence of publication bias. RESULTS: We identified 193 publications using gene therapy in experimental glioma, including 6,366 animals. Overall, gene therapy improved median survival by a factor of 1.60 (95% CI 1.53–1.67). Study quality was low and the type of gene therapy did not account for differences in outcome. Study design characteristics accounted for a significant proportion of between‐study heterogeneity. We observed similar findings in a data subset limited to the most common gene therapy. CONCLUSION: As the dysregulation of key molecular pathways is characteristic of gliomas, gene therapy remains a promising treatment for glioma. Nevertheless, we have identified areas for improvement in conduct and reporting of studies, and we provide a basis for sample size calculations. Further work should focus on genes of interest in paradigms recapitulating human disease. This might improve the translation of such therapies into the clinic

Healthcare costs in women with metastatic breast cancer receiving chemotherapy as their principal treatment modality

<p>Abstract</p> <p>Background</p> <p>The economic costs of treating patients with metastatic breast cancer have been examined in several studies, but available estimates of economic burden are at least a decade old. In this study, we characterize healthcare utilization and costs in the US among women with metastatic breast cancer receiving chemotherapy as their principal treatment modality.</p> <p>Methods</p> <p>Using a large private health insurance claims database (2000-2006), we identified all women initiating chemotherapy for metastatic breast cancer with no evidence of receipt of concomitant or subsequent hormonal therapy, or receipt of trastuzumab at anytime. Healthcare utilization and costs (inpatient, outpatient, medication) were estimated on a cumulative basis from date of chemotherapy initiation ("index date") to date of disenrollment from the health plan or the end of the study period, whichever occurred first. Study measures were cumulated over time using the Kaplan-Meier Sample Average (KMSA) method; 95% CIs were generated using nonparametric bootstrapping. Findings also were examined among the subgroup of patients with uncensored data.</p> <p>Results</p> <p>The study population consisted of 1444 women; mean (SD) age was 59.1 (12.1) years. Over a mean follow-up of 532 days (range: 3 to 2412), study subjects averaged 1.7 hospital admissions, 10.7 inpatient days, and 83.6 physician office and hospital outpatient visits. Mean (95% CI) cumulative total healthcare costs were $128,556 ($118,409, $137,644) per patient. Outpatient services accounted for 29% of total costs, followed by medication other than chemotherapy (26%), chemotherapy (25%), and inpatient care (20%).</p> <p>Conclusions</p> <p>Healthcare costs-especially in the outpatient setting--are substantial among women with metastatic breast cancer for whom treatment options other than chemotherapy are limited.</p