Advanced single molecule localization microscopy for imaging cellular nuclei

In this PhD research, single molecule localization microscopy (SMLM) was used to image nuclear structures with a resolution down to several nanometers.The scope of this PhD research is to develop a 3D SMLM microscope which can overcome several principle limitations in imaging nuclei in 3D. The advanced improvements during this PhD research include a broad range of research subjects associated to SMLM techniques. Firstly, one of the most common problems of a super-resolution microscope is sample drift, because a small sample drift may result in artefacts and can hamper the resolution. A speckle-based method was developed to correct sample drift without changing the standard design of the SMLM setup. This drift correction method can achieve a resolution of several nanometers. Secondly, another principle problem is that commonly used organic fluorophores are restricted in their photon budget. It is often observed that the chemical structure of fluorophores change after high laser irradiance resulting in photobleaching. A patterned illumination technique was developed which allows the user to define arbitrary regions of interest for illumination with a flat-top intensity profile. Thirdly, for SMLM in particular, a carefully adjusted chemical environment in the sample is recommended to induce sufficiently blinking signals of the organic fluorophores in combination with an appropriate laser irradiance. However, such an imaging buffer can degrade over time and may not be suitable for long time imaging. Nanographene was presented as a new class of fluorophores which have blinking properties without an imaging buffer. Therefore, the nanographenes facilitate a wide range of SMLM applications including bio-imaging and material science. These advanced developments are not only for imaging nuclei, but also applicable to applications in other biological researches and in material science

Effect of Insurance on Prescription Drug Use by ESRD Beneficiaries

In this article the author reviews the prescription drug coverage policy in the Medicare End Stage Renal Disease (ESRD) program and examines the relationship between secondary insurance status and the number of medications prescribed for dialysis patients who had Medicare as their primary payer. Negative binomial models were used to examine this relationship. Findings in this study indicate that the number of secondary payers has a significant impact on the number of prescription drugs received by Medicare ESRD patients. Further research is needed to determine whether Medicare beneficiaries without secondary insurance are obtaining fewer prescriptions than needed or if those with greater coverage are obtaining more than needed

Factors Associated with the Income Distribution of Full-Time Physicians: A Quantile Regression Approach: Income Distribution of Full-Time Physicians

Physician income is generally high, but quite variable; hence, physicians have divergent perspectives regarding health policy initiatives and market reforms that could affect their incomes. We investigated factors underlying the distribution of income within the physician population

Use of Home Health Care by ESRD and Medicare Beneficiaries

The use of home health care (HHC) services among Medicare end stage renal disease (ESRD) enrollees remains an understudied area. In this article, the authors report sociodemographic characteristics and patterns of HHC utilization by Medicare-covered ESRD patients. The authors found that those who were female, age 85 or over, diabetic, and residing in the New England or West South Central census divisions were more likely to use HHC services and were also more intensive users. Analysis of use patterns in such high-risk populations is necessary to ensure that health policy changes do not have unintended consequences for vulnerable patients

Using Rare Earth Elements to Constrain Particulate Organic Carbon Flux in the East China Sea

Fluxes of particulate organic carbon (POC) in the East China Sea (ECS) have been reported to decrease from the inner continental shelf towards the outer continental shelf. Recent research has shown that POC fluxes in the ECS may be overestimated due to active sediment resuspension. To better characterize the effect of sediment resuspension on particle fluxes in the ECS, rare earth elements (REEs) and organic carbon (OC) were used in separate two-member mixing models to evaluate trap-collected POC fluxes. The ratio of resuspended particles from sediments to total trap-collected particles in the ECS ranged from 82-94% using the OC mixing model, and 30-80% using the REEs mixing model, respectively. These results suggest that REEs may be better proxies for sediment resuspension than OC in high turbidity marginal seas because REEs do not appear to undergo degradation during particle sinking as compared to organic carbon. Our results suggest that REEs can be used as tracers to provide quantitative estimates of POC fluxes in marginal sea

Protein kinase CK2 localizes to sites of DNA double-strand break regulating the cellular response to DNA damage

<p>Abstract</p> <p>Background</p> <p>The DNA-dependent protein kinase (DNA-PK) is a nuclear complex composed of a large catalytic subunit (DNA-PKcs) and a heterodimeric DNA-targeting subunit Ku. DNA-PK is a major component of the non-homologous end-joining (NHEJ) repair mechanism, which is activated in the presence of DNA double-strand breaks induced by ionizing radiation, reactive oxygen species and radiomimetic drugs. We have recently reported that down-regulation of protein kinase CK2 by siRNA interference results in enhanced cell death specifically in DNA-PKcs-proficient human glioblastoma cells, and this event is accompanied by decreased autophosphorylation of DNA-PKcs at S2056 and delayed repair of DNA double-strand breaks.</p> <p>Results</p> <p>In the present study, we show that CK2 co-localizes with phosphorylated histone H2AX to sites of DNA damage and while CK2 gene knockdown is associated with delayed DNA damage repair, its overexpression accelerates this process. We report for the first time evidence that lack of CK2 destabilizes the interaction of DNA-PKcs with DNA and with Ku80 at sites of genetic lesions. Furthermore, we show that CK2 regulates the phosphorylation levels of DNA-PKcs only in response to direct induction of DNA double-strand breaks.</p> <p>Conclusions</p> <p>Taken together, these results strongly indicate that CK2 plays a prominent role in NHEJ by facilitating and/or stabilizing the binding of DNA-PKcs and, possibly other repair proteins, to the DNA ends contributing to efficient DNA damage repair in mammalian cells.</p