What Drives Embryo Development? Chromosomal Normality or Mitochondria?

Objective. To report the arrest of euploid embryos with high mtDNA content. Design. A report of 2 cases. Setting. Private fertility clinic. Patients. 2 patients, 45 and 40 years old undergoing IVF treatment. Interventions. Mature oocytes were collected and vitrified from two ovarian stimulations. Postthaw, survived mature oocytes underwent fertilization by intracytoplasmic sperm injection (ICSI). Preimplantation genetic screening (PGS) and mitochondrial DNA (mtDNA) copy number were done using next generation sequencing (NGS). The only normal embryo among the all-biopsied embryos had the highest “Mitoscore” value and was the only arrested embryo in both cases. Therefore, the embryo transfer was cancelled. Main Outcome Measures. Postthaw survival and fertilization rate, embryo euploidy, mtDNA copy number, and embryo development. Results. In both patients, after PGS only 1 embryo was euploid. Both embryos had the highest mtDNA copy number from all tested embryos and both embryos were arrested on further development. Conclusions. These cases clearly demonstrate the lack of correlation between mtDNA value (Mitoscore) and chromosomal status of embryo

Zinc Transporters YbtX and ZnuABC Are Required for the Virulence of \u3cem\u3eYersinia pestis\u3c/em\u3e in Bubonic and Pneumonic Plague in Mice

A number of bacterial pathogens require the ZnuABC Zinc (Zn2+) transporter and/or a second Zn2+ transport system to overcome Zn2+ sequestration by mammalian hosts. Previously we have shown that in addition to ZnuABC, Yersinia pestis possesses a second Zn2+ transporter that involves components of the yersiniabactin (Ybt), siderophore-dependent iron transport system. Synthesis of the Ybt siderophore and YbtX, a member of the major facilitator superfamily, are both critical components of the second Zn2+ transport system. Here we demonstrate that a ybtX znu double mutant is essentially avirulent in mouse models of bubonic and pneumonic plague while a ybtX mutant retains high virulence in both plague models. While sequestration of host Zn is a key nutritional immunity factor, excess Zn appears to have a significant antimicrobial role in controlling intracellular bacterial survival. Here, we demonstrate that ZntA, a Zn2+ exporter, plays a role in resistance to Zn toxicity in vitro, but that a zntA zur double mutant retains high virulence in both pneumonic and bubonic plague models and survival in macrophages. We also confirm that Ybt does not directly bind Zn2+in vitro under the conditions tested. However, we detect a significant increase in Zn2+-binding ability of filtered supernatants from a Ybt+ strain compared to those from a strain unable to produce the siderophore, supporting our previously published data that Ybt biosynthetic genes are involved in the production of a secreted Zn-binding molecule (zincophore). Our data suggest that Ybt or a modified Ybt participate in or promote Zn-binding activity in culture supernatants and is involved in Zn acquisition in Y. pestis

TMG 1 (2014): Pandemic Disease in the Medieval World: Rethinking the Black Death, ed. Monica Green

The plague organism (Yersinia pestis) killed an estimated 40% to 60% of all people when it spread rapidly through the Middle East, North Africa, and Europe in the fourteenth century: an event known as the Black Death. Previous research has shown, especially for Western Europe, how population losses then led to structural economic, political, and social changes. But why and how did the pandemic happen in the first place? When and where did it begin? How was it sustained? What was its full geographic extent? And when did it really end? Pandemic Disease in the Medieval World is the first book to synthesize the new evidence and research methods that are providing fresh answers to these crucial questions. It was only in 2011, thanks to ancient DNA recovered from remains unearthed in London’s East Smithfield cemetery, that the full genome of the plague pathogen was identified. This single-celled organism probably originated 3000-4000 years ago and has caused three pandemics in recorded history: the Justinianic (or First) Plague Pandemic, around 541-750; the Black Death (Second Plague Pandemic), conventionally dated to the 1340s; and the Third Plague Pandemic, usually dated from around 1894 to the 1930s. This ground-breaking book brings together scholars from the humanities and social and physical sci­ences to address the question of how recent work in genetics, zoology, and epi­de­miology can enable a rethinking of the Black Death\u27s global reach and its larger historical significance. It forms the inaugural double issue of The Medieval Globe, a new journal sponsored by the Program in Medieval Studies at the University of Illinois at Urbana-Champaign. This issue of The Medieval Globe is published with the support of the World History Center at the University of Pittsburgh.https://scholarworks.wmich.edu/medieval_globe/1000/thumbnail.jp

Using Selectively Applied Accelerated Molecular Dynamics to Enhance Free Energy Calculations

Accelerated molecular dynamics (aMD) has been shown to enhance conformational space sampling relative to classical molecular dynamics; however, the exponential reweighting of aMD trajectories, which is necessary for the calculation of free energies relating to the classical system, is oftentimes problematic, especially for systems larger than small poly peptides. Here, we propose a method of accelerating only the degrees of freedom most pertinent to sampling, thereby reducing the total acceleration added to the system and improving the convergence of calculated ensemble averages, which we term selective aMD. Its application is highlighted in two biomolecular cases. First, the model system alanine dipeptide is simulated with classical MD, all-dihedral aMD, and selective aMD, and these results are compared to the infinite sampling limit as calculated with metadynamics. We show that both forms of aMD enhance the convergence of the underlying free energy landscape by 5-fold relative to classical MD; however, selective aMD can produce improved statistics over all-dihedral aMD due to the improved reweighting. Then we focus on the pharmaceutically relevant case of computing the free energy of the decoupling of oseltamivir in the active site of neuraminidase. Results show that selective aMD greatly reduces the cost of this alchemical free energy transformation, whereas all-dihedral aMD produces unreliable free energy estimates

Siderophore-Mediated Zinc Acquisition Enhances Enterobacterial Colonization of the Inflamed Gut

Zinc is an essential cofactor for bacterial metabolism, and many Enterobacteriaceae express the zinc transporters ZnuABC and ZupT to acquire this metal in the host. However, the probiotic bacterium Escherichia coli Nissle 1917 (or “Nissle”) exhibits appreciable growth in zinc-limited media even when these transporters are deleted. Here, we show that Nissle utilizes the siderophore yersiniabactin as a zincophore, enabling Nissle to grow in zinc-limited media, to tolerate calprotectin-mediated zinc sequestration, and to thrive in the inflamed gut. We also show that yersiniabactin’s affinity for iron or zinc changes in a pH-dependent manner, with increased relative zinc binding as the pH increases. Thus, our results indicate that siderophore metal affinity can be influenced by the local environment and reveal a mechanism of zinc acquisition available to commensal and pathogenic Enterobacteriaceae

Investigation of chemistry graduate teaching assistants’ teacher knowledge and teacher identity

Graduate students play an integral role in undergraduate chemistry education at doctoral granting institutions where they routinely serve as instructors of laboratories and supplementary discussion sessions. Simultaneously, graduate teaching assistants (GTAs) balance major research and academic responsibilities. Although GTAs have substantial instructional facetime with large numbers of undergraduate students, little is known about their conceptions of teaching or their identities as teachers. To investigate the knowledge that GTAs have regarding teaching in this unique context, their teaching identities, and how these developed, we conducted 22 interviews with graduate students from several universities at various levels in their graduate school career using a modified Teacher Beliefs Interview. Interviews were analyzed for two overarching teacher learning constructs: teacher knowledge and teacher identity. We characterized chemistry GTAs’ teacher knowledge and identity and determined major influencing factors. We found that chemistry GTAs often identified as a tutor or lab manager, which hindered their self‐investment in developing as teachers. The results presented herein contribute to an understanding of GTAs’ teacher knowledge, teacher identity, and their teaching context, from which training can be designed to best support GTA development.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155950/1/tea21618_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155950/2/tea21618.pd

Intramyocardial Transplantation of Undifferentiated Rat Induced Pluripotent Stem Cells Causes Tumorigenesis in the Heart

BACKGROUND: Induced pluripotent stem cells (iPSCs) are a novel candidate for use in cardiac stem cell therapy. However, their intrinsic tumorigenicity requires further investigation prior to use in a clinical setting. In this study we investigated whether undifferentiated iPSCs are tumorigenic after intramyocardial transplantation into immunocompetent allogeneic recipients. METHODOLOGY/PRINCIPAL FINDINGS: We transplanted 2 × 10(4), 2 × 10(5), or 2 × 10(6) cells from the established rat iPSC line M13 intramyocardially into intact or infarcted hearts of immunocompetent allogeneic rats. Transplant duration was 2, 4, or 6 weeks. Histological examination with hematoxylin-eosin staining confirmed that undifferentiated rat iPSCs could generate heterogeneous tumors in both intracardiac and extracardiac sites. Furthermore, tumor incidence was independent of cell dose, transplant duration, and the presence or absence of myocardial infarction. CONCLUSIONS/SIGNIFICANCE: Our study demonstrates that allogeneic iPSC transplantation in the heart will likely result in in situ tumorigenesis, and that cells leaked from the beating heart are a potential source of tumor spread, underscoring the importance of evaluating the safety of future iPSC therapy for cardiac disease

Molecular Dynamics Simulations Suggest that Electrostatic Funnel Directs Binding of Tamiflu to Influenza N1 Neuraminidases

Oseltamivir (Tamiflu) is currently the frontline antiviral drug employed to fight the flu virus in infected individuals by inhibiting neuraminidase, a flu protein responsible for the release of newly synthesized virions. However, oseltamivir resistance has become a critical problem due to rapid mutation of the flu virus. Unfortunately, how mutations actually confer drug resistance is not well understood. In this study, we employ molecular dynamics (MD) and steered molecular dynamics (SMD) simulations, as well as graphics processing unit (GPU)-accelerated electrostatic mapping, to uncover the mechanism behind point mutation induced oseltamivir-resistance in both H5N1 “avian” and H1N1pdm “swine” flu N1-subtype neuraminidases. The simulations reveal an electrostatic binding funnel that plays a key role in directing oseltamivir into and out of its binding site on N1 neuraminidase. The binding pathway for oseltamivir suggests how mutations disrupt drug binding and how new drugs may circumvent the resistance mechanisms