Supramolecular quantum dot-porphyrin assemblies for biological oxygen sensing

Thesis (S.M. in Inorganic Chemistry)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013.Vita. Cataloged from PDF version of thesis.Includes bibliographical references.Generating metabolic profiles of tumors provides a spatiotemporal map of the concentration of key species to assess and quantify tumor growth, metabolism, and response to therapy. Because the tumor microenvironment is characterized by hypoxia, the concentration of oxygen is an important indicator of tumor health. Understanding how this parameter changes as a function of disease progression is critical to develop novel targeted therapeutics. New non-invasive sensors must be developed that are small enough to penetrate into the tumor and monitor dynamic changes with high resolution. To this end, this thesis presents new oxygen sensors that are a supramolecular assemblies of a quantum dot (QD) and a palladium(II) porphyrin. High spectral overlap between QD emission and porphyrin absorption results in efficient Förster resonance energy transfer (FRET) for signal transduction in these sensors. Porphyrins with meso pyridyl substituents bind to the surface of the QD to produce self-assembled nanosensors. Since these macrocycles are sensitive in the 0-160 torr range, they are ideal phosphors for in vivo biological oxygen quantification. The QD serves as a two-photon antenna to enable sensing under two-photon excitation. Multiphoton imaging is a powerful technique that is nondestructive to tissue and provides high-resolution images of live tissue at depths of several hundred microns with submicron spatial resolution. Having studied the photohysical properties of these sensors under both one- and two-photon excitation in organic solvents, these sensors were then encapsulated in lipid micelles to quantify oxygen in aqueous media. In these constructs, the quantum dot also serves as an internal intensity standard, furnishing a ratiometric oxygen sensor. Preliminary in vivo multiphoton imaging and oxygen measurements were conducted using mice with chronic dorsal skinfold chambers or cranial windows. Together, the properties of this sensor establish a ratiometric two-photon oxygen sensor for applications in probing biological microenvironments.by Christopher M. Lemon.S.M.in Inorganic Chemistr

The Chimpanzee Model of Viral Hepatitis: Advances in Understanding the Immune Response and Treatment of Viral Hepatitis

Chimpanzees (Pan troglodytes) have contributed to diverse fields of biomedical research due to their close genetic relationship to humans and in many instances due to the lack of any other animal model. This review focuses on the contributions of the chimpanzee model to research on hepatitis viruses where chimpanzees represented the only animal model (hepatitis B and C) or the most appropriate animal model (hepatitis A). Research with chimpanzees led to the development of vaccines for HAV and HBV that are used worldwide to protect hundreds of millions from these diseases and, where fully implemented, have provided immunity for entire generations. More recently, chimpanzee research was instrumental in the development of curative therapies for hepatitis C virus infections. Over a span of 40 years, this research would identify the causative agent of NonA,NonB hepatitis, validate the molecular tools for drug discovery, and provide safety and efficacy data on the therapies that now provide a rapid and complete cure of HCV chronic infections. Several cocktails of antivirals are FDA approved that eliminate the virus following 12 weeks of once-per-day oral therapy. This represents the first cure of a chronic viral disease and, once broadly implemented, will dramatically reduce the occurrence of cirrhosis and liver cancer. The recent contributions of chimpanzees to our current understanding of T cell immunity for HCV, development of novel therapeutics for HBV, and the biology of HAV are reviewed. Finally, a perspective is provided on the events leading to the cessation of the use of chimpanzees in research and the future of the chimpanzees previously used to bring about these amazing breakthroughs in human healthcare

Reassessing immune control of hepatitis A virus

There is renewed interest in hepatitis A virus (HAV) pathogenesis and immunity after 2–3 decades of limited progress. From a public health perspective, the average age at infection has increased in developing countries, resulting in more severe hepatitis that is poorly understood mechanistically. More fundamentally, there is interest in comparing immunity to HAV and hepatitis C virus (HCV): small, positive-strand RNA viruses with very different infection outcomes. Here, we review evidence that circulating HAV virions are cloaked in membranes, with consequences for induction of innate immunity and antibody-mediated neutralization. We also consider the contribution of CD4+ helper versus CD8+ cytotoxic T cells to antiviral immunity and liver injury, and present a model of non-cytotoxic immune control of HAV infection

Two-Photon Oxygen Sensing with Quantum Dot-Porphyrin Conjugates

Supramolecular assemblies of a quantum dot (QD) associated to palladium(II) porphyrins have been developed to detect oxygen (pO2) in organic solvents. Palladium porphyrins are sensitive in the 0–160 torr range, making them ideal phosphors for in vivo biological oxygen quantification. Porphyrins with meso pyridyl substituents bind to the surface of the QD to produce self–assembled nanosensors. Appreciable overlap between QD emission and porphyrin absorption features results in efficient Förster resonance energy transfer (FRET) for signal transduction in these sensors. The QD serves as a photon antenna, enhancing porphyrin emission under both one– and two–photon excitation, demonstrating that QD–palladium porphyrin conjugates may be used for oxygen sensing over physiological oxygen ranges.Chemistry and Chemical Biolog

Metabolic Tumor Profiling with pH, Oxygen, and Glucose Chemosensors on a Quantum Dot Scaffold

Acidity, hypoxia, and glucose levels characterize the tumor microenvironment rendering pH, pO2, and pGlucose, respectively, important indicators of tumor health. To this end, understanding how these parameters change can be a powerful tool for the development of novel and effective therapeutics. We have designed optical chemosensors that feature a quantum dot and an analyte-responsive dye. These noninvasive chemosensors permit pH, oxygen, and glucose to be monitored dynamically within the tumor microenvironment by using multiphoton imaging.National Cancer Institute (U.S.) (Grant R01-CA126642

Hepatitis C Virus Indirectly Disrupts DNA Damage-Induced p53 Responses by Activating Protein Kinase R

ABSTRACT Many DNA tumor viruses promote cellular transformation by inactivating the critically important tumor suppressor protein p53. In contrast, it is not known whether p53 function is disrupted by hepatitis C virus (HCV), a unique, oncogenic RNA virus that is the leading infectious cause of liver cancer in many regions of the world. Here we show that HCV-permissive, liver-derived HepG2 cells engineered to constitutively express microRNA-122 (HepG2/miR-122 cells) have normal p53-mediated responses to DNA damage and that HCV replication in these cells potently suppresses p53 responses to etoposide, an inducer of DNA damage, or nutlin-3, an inhibitor of p53 degradation pathways. Upregulation of p53-dependent targets is consequently repressed within HCV-infected cells, with potential consequences for cell survival. Despite this, p53 function is not disrupted by overexpression of the complete HCV polyprotein, suggesting that altered p53 function may result from the host response to viral RNA replication intermediates. Clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9-mediated ablation of double-stranded RNA (dsRNA)-activated protein kinase R (PKR) restored p53 responses while boosting HCV replication, showing that p53 inhibition results directly from viral activation of PKR. The hepatocellular abundance of phosphorylated PKR is elevated in HCV-infected chimpanzees, suggesting that PKR activation and consequent p53 inhibition accompany HCV infection in vivo . These findings reveal a feature of the host response to HCV infection that may contribute to hepatocellular carcinogenesis. IMPORTANCE Chronic infection with hepatitis C virus (HCV) is the leading cause of liver cancer in most developed nations. However, the mechanisms whereby HCV infection promotes carcinogenesis remain unclear. Here, we demonstrate that HCV infection inhibits the activation of p53 following DNA damage. Contrary to previous reports, HCV protein expression is insufficient to inhibit p53. Rather, p53 inhibition is mediated by cellular protein kinase R (PKR), which is activated by HCV RNA replication and subsequently suppresses global protein synthesis. These results redefine our understanding of how HCV infection influences p53 function. We speculate that persistent disruption of p53-mediated DNA damage responses may contribute to hepatocellular carcinogenesis in chronically infected individuals

Human pDCs preferentially sense enveloped hepatitis A virions

Unlike other picornaviruses, hepatitis A virus (HAV) is cloaked in host membranes when released from cells, providing protection from neutralizing antibodies and facilitating spread in the liver. Acute HAV infection is typified by minimal type I IFN responses; therefore, we questioned whether plasmacytoid dendritic cells (pDCs), which produce IFN when activated, are capable of sensing enveloped virions (eHAV). Although concentrated nonenveloped virus failed to activate freshly isolated human pDCs, these cells produced substantial amounts of IFN-α via TLR7 signaling when cocultured with infected cells. pDCs required either close contact with infected cells or exposure to concentrated culture supernatants for IFN-α production. In isopycnic and rate-zonal gradients, pDC-activating material cosedimented with eHAV but not membrane-bound acetylcholinesterase, suggesting that eHAV, and not viral RNA exosomes, is responsible for IFN-α induction. pDC activation did not require virus replication and was associated with efficient eHAV uptake, which was facilitated by phosphatidylserine receptors on pDCs. In chimpanzees, pDCs were transiently recruited to the liver early in infection, during or shortly before maximal intrahepatic IFN-stimulated gene expression, but disappeared prior to inflammation onset. Our data reveal that, while membrane envelopment protects HAV against neutralizing antibody, it also facilitates an early but limited detection of HAV infection by pDCs

Bodyweight Perceptions among Texas Women: The Effects of Religion, Race/Ethnicity, and Citizenship Status

Despite previous work exploring linkages between religious participation and health, little research has looked at the role of religion in affecting bodyweight perceptions. Using the theoretical model developed by Levin et al. (Sociol Q 36(1):157–173, 1995) on the multidimensionality of religious participation, we develop several hypotheses and test them by using data from the 2004 Survey of Texas Adults. We estimate multinomial logistic regression models to determine the relative risk of women perceiving themselves as overweight. Results indicate that religious attendance lowers risk of women perceiving themselves as very overweight. Citizenship status was an important factor for Latinas, with noncitizens being less likely to see themselves as overweight. We also test interaction effects between religion and race. Religious attendance and prayer have a moderating effect among Latina non-citizens so that among these women, attendance and prayer intensify perceptions of feeling less overweight when compared to their white counterparts. Among African American women, the effect of increased church attendance leads to perceptions of being overweight. Prayer is also a correlate of overweight perceptions but only among African American women. We close with a discussion that highlights key implications from our findings, note study limitations, and several promising avenues for future research

Metabolic Tumor Profiling with pH, Oxygen, and Glucose Chemosensors on a Quantum Dot Scaffold

Acidity, hypoxia and glucose levels characterize the tumor microenvironment rendering pH, pO2 and pGlucose, respectively, important indicators of tumor health. To this end, understanding how these parameters change can be a powerful tool for the development of novel and effective therapeutics. We have designed optical chemosensors that feature a quantum dot and an analyte-responsive dye. These non-invasive chemosensors permit pH, oxygen, and glucose to be monitored dynamically within the tumor microenvironment by using multiphoton imaging.Chemistry and Chemical Biolog

FAST INdiCATE Trial protocol. Clinical efficacy of functional strength training for upper limb motor recovery early after stroke : neural correlates and prognostic indicators

© 2013 The Authors. International Journal of Stroke published by John Wiley & Sons Ltd on behalf of World Stroke Organization. Funded by: Efficacy and Mechanism Evaluation programme. Grant Number: 10/60/30 Medical Research Council (MRC)Peer reviewedPublisher PD