Mitochondrial DNA Polymerase IB: Functional Characterization of a Putative Drug Target for African Sleeping Sickness

Trypanosoma brucei and related parasites are causative agents of severe diseases that affect global health and economy. T. brucei is responsible for sleeping sickness in humans (African trypanosomiasis) and a wasting disease in livestock. More than 100 years after T. brucei was identified as the etiological agent for sleeping sickness, available treatments remain inadequate, complicated by toxicity, lengthy and expensive administration regiments, and drug-resistance. There is clear need for the development of a new antitrypanosomal drugs. Due to the unique evolutionary position of these early diverging eukaryotes, trypanosomes posses a number of biological properties unparalleled in other organisms, including humans, which could prove valuable for new drug targets. One of the most distinctive properties of trypanosomes is their mitochondrial DNA, called kinetoplast DNA (kDNA). kDNA is composed of over five thousand circular DNA molecules (minicircles and maxicircles) catenated into a topologically complex network. Replication of kDNA requires an elaborate topoisomerase-mediated release and reattachment mechanism for minicircle theta structure replication and at least five DNA polymerases. Three of these (POLIB, POLIC, and POLID) are related to bacterial DNA polymerase I and are required for kDNA maintenance and growth. Each polymerase appears to make a specialized contribution to kDNA replication. The research described in this dissertation is a significant contribution to the field of kDNA replication and the advancement of kDNA replication proteins as putative drug targets for sleeping sickness. Functional characterization of POLIB indicated that it participates in minicircle replication but is likely not the only polymerase contributing to this process. Gene silencing of POLIB partially blocked minicircle replication and led to the production of a previously unidentified free minicircle species, fraction U. Characterization of fraction U confirmed its identity as a population of dimeric minicircles with non-uniform linking numbers. Fraction U was not produced in response to silencing numerous other previously studied kDNA replication proteins but, as we demonstrated here, is also produced in response to POLID silencing. This common phenotype led us to hypothesize that POLIB and POLID both participate in minicircle replication. Simultaneously silencing both polymerases completely blocked minicircle replication, supporting a model of minicircle replication requiring both POLIB and POLID. Finally, we demonstrate that disease-causing trypanosomes require kDNA and the kDNA replication proteins POLIB, POLIC, and POLID. These data provide novel insights into the fascinating mechanism of kDNA replication and support the pursuit of kDNA replication proteins as novel drug targets for combating African trypanosomiasis

Claw-free t-perfect graphs can be recognised in polynomial time

A graph is called t-perfect if its stable set polytope is defined by non-negativity, edge and odd-cycle inequalities. We show that it can be decided in polynomial time whether a given claw-free graph is t-perfect

The impact of reduction of doublet well spacing on the Net Present Value and the life time of fluvial Hot Sedimentary Aquifer doublets

This paper evaluates the impact of reduction of doublet well spacing, below the current West Netherlands Basin standard of 1000 to 1500 m, on the Net Present Value (NPV) and the life time of fluvial Hot Sedimentary Aquifer (HSA) doublets. First, a sensitivity analysis is used to show the possible advantage of such reduction on the NPV. The parameter value ranges are derived from West Netherlands Basin HSA doublet examples. The results indicate that a reduction of well spacing from 1400 to 1000 m could already influence NPV by up to 15%. This effect would be larger in more marginally economic HSA doublets compared to the West Netherlands Basin base case scenario. The possibility to reduce well spacing is supported by finite element production simulations, utilizing detailed facies architecture models. Furthermore, our results underline the necessity of detailed facies architecture models to assess the potential and risks of HSA doublets. This factor significantly affects doublet life time and net energy production of the doublet

Use of a Simulated-Virtual Training Module to Improve Dental Hygiene Students\u27 Self-Reported Knowledge, Attitudes, and Confidence in Providing Care to Children with Autism Spectrum Disorder: A Pilot Study

Purpose: Autism spectrum disorder (ASD) is a developmental disorder affecting an individual\u27s ability to communicate, interact, behave, and learn. The purpose of this study was to determine knowledge, attitudes, and confidence of dental hygiene students in providing care to children with ASD as a mechanism for evaluating dental hygiene curricula for patients with special needs. Methods: A simulated-virtual training (SVT) intervention was developed as an interactive approach for educating dental hygiene students on providing care to a child patient with ASD. The SVT intervention consisted of a scenario in which the clinician interacted with a child with ASD who was having difficulty in the dental environment. Pre- and post-test surveys measured students\u27 knowledge, attitudes, and perceived confidence related to providing dental hygiene services to children with ASD prior to and following the intervention. The Wilcoxon Signed Rank was used to determine statistical significance at the p=.05 level. Results: Thirty-three second year dental hygiene students completed the pre- and post-test surveys for a response rate of 97%. Statistically significant differences were observed for self-reported confidence to provide care to patients with ASD upon graduation, assessment of the unique needs of children with ASD, and an understanding of the dental needs for children with ASD (p\u3c0.05). Participants\u27 confidence with performing dental hygiene services on children with ASD greatly increased, with statistically significant difference found for almost all services (i.e., oral exam, oral hygiene instruction, oral photos, radiographs, scaling, fluoride treatment; p\u3c0.05) except selective polishing. Most (90%) agreed that there is a need for additional/elective resources to help increase comfort in providing care to children with ASD. Conclusion: Results indicate the SVT intervention increased students\u27 knowledge, attitudes, self-perceived confidence, and comfort. Dental and dental hygiene curricula could include technologies and intervention methods to advance access to dental care by children with ASD

Tectonic geomorphology and late Quaternary deformation on the Ragged Mountain fault, Yakutat microplate, south coastal Alaska

The 33 km-long Ragged Mountain fault (RMF) forms the northwestern corner of the Yakutat Terrane, which is colliding with the North American plate in south coastal Alaska at ~5.5 cm/yr. The fault zone contains three types of scarps in a zone up to 175 m wide: (1) antislope scarps on the lower range front, (2) a sinuous thrust scarp at the toe of the range front, and (3) a swarm of flexural-slip scarps on the footwall. Trenches across the first two scarp types reveal evidence for two Holocene surface ruptures, plus several late Pleistocene ruptures. In the antislope scarp trench, ruptures occurred at 0.5–3.9 ka; slightly younger than 8.3 ka; and at 18.1–21.8 ka (recurrence intervals 4.4–8 kyr and 9.8–13.3 kyr). Displacements per event ranged from 15 to 40 cm. In the thrust trench ruptures are dated at 2.8–5.9 ka; 5.9–17.2 ka, and 17.2–44.9 ka (mean recurrence intervals 7.2 kyr and 19.5 kyr). Displacements per event ranged from 26 to 77 cm. We interpret the thrust fault as the primary seismogenic structure, and its largest trench displacement (77 cm) equates to the average displacement expected for a 33 km-long reverse rupture. The flexural-slip scarp, in contrast, was rapidly formed ca. 4 ka but its sag pond sediments have continued to slowly fold up to present. The southern third of the fault is dominated by large gravitational failures of the range front (as large as 2.5 km wide, 0.6-0.7 km long, and 200–250 m thick), which head in a linear, 40 m-deep range-crest trough filled with lakes, a classic expression of deep-seated gravitational slope deformation

Cryogenic silicon detectors with implanted contacts for the detection of visible photons using the Neganov-Luke Effect

There is a common need in astroparticle experiments such as direct dark matter detection, 0{\nu}\b{eta}\b{eta} (double beta decay without emission of neutrinos) and Coherent Neutrino Nucleus Scattering experiments for light detectors with a very low energy threshold. By employing the Neganov-Luke Effect, the thermal signal of particle interactions in a semiconductor absorber operated at cryogenic temperatures, can be amplified by drifting the photogenerated electrons and holes in an electric field. This technology is not used in current experiments, in particular because of a reduction of the signal amplitude with time which is due to trapping of the charges within the absorber. We present here the first results of a novel type of Neganov-Luke Effect detector with an electric field configuration designed to improve the charge collection within the semiconductor.Comment: 6 pages, 5 figures, submitted to Journal of Low Temperature Physic