Controlling the Oxygen Microenvironment: The Role of HIF-1α in Early Tumor Progression

Cancer drug efficacy has remained a critical obstacle for researchers as it has one of the lowest probabilities of success compared to other diseases. One method to help improve this success rate is to create better tumor models on which to perform the drug testing. With growing interesting in microphysiological systems, scientists can create more advanced in vitro models of human organ systems as well as diseased states. These “organ-on-a-chip” platforms aim to improve drug response prediction for both efficacy and toxicity. One underappreciated characteristic of many disease states is that they are often at a lower oxygen tension that normal tissue (a condition known as hypoxia). Not only is this the case for cancer, but it is thought to be one of the main reasons why cancer treatment fails. Furthermore, cancer can experience two types of hypoxia: chronic (sustained low oxygen tension) or intermittent (varying cycles of hypoxia and normoxia). In both conditions, the vasculature determines the spatial and temporal dynamics of oxygen. If the tumor cells expand far enough away from the vasculature, this diffusion-limited oxygen condition will lead to chronic hypoxia. On the other hand, if the tumor cells encourage rapid vasculature growth that tends to be tortuous and leaky, then this will lead to intermittent hypoxia. Under both hypoxic conditions, tumor cells upregulate hypoxia inducible factor 1α (HIF-1α), a transcription factor which affects many downstream processes that encourages cell survival. In this dissertation, we investigate our ability to use a microfluidic platform to mimic some of these key features in the hypoxic tumor microenvironment and test if it can recapitulate some known biological responses. First, we created a microfluidic device that can control both spatial and temporal gradients of oxygen via an oxygen scavenger line. As tumor angiogenesis is a major concern during tumor progression, we examined angiogenesis in the device. Vasculature was grown in the central chamber of the device, and stromal cells were grown in compartments on both sides of the vasculature. Lastly, the oxygen scavenger was flown in a channel adjacent to the left stromal chamber to create an oxygen gradient across the device. By controlling the flow the of oxygen scavenger, we could simulate both chronic and intermittent hypoxia. Our results demonstrate that stromal cells under hypoxia conditions encourage biased angiogenesis, which is in agreement with previous studies. Second, using our microfluidic device platform, we investigated how knocking down HIF-1α affects the survival and progression of breast cancer cells (MDA-MB-231) under various oxygen gradients. By varying the scavenger concentration, we found a threshold for chronic hypoxia that the knockdown cells could no longer survive. Interestingly, by modulating the length of the hypoxic and normoxic cycles during intermittent hypoxia, we could dictate tumor cell survival. This result emphasizes the importance of understanding the temporal variations of oxygen, especially with cancer treatments that target HIF-1α. Altogether, our results further our understanding of how to control spatial and temporal oxygen gradients for disease modeling. Hopefully with this understanding, future studies will be able to more effectively assess drug efficacy

Alone in Paradise: A Review of the Literature Related to Single, Immigrant Mothers in Canada

In most studies, the phenomena of immigration and single motherhood are examined and explored in isolation from each other. In this manuscript, we adopted intersectionality theory as the framework for examining the literature related to the lived experiences of single, immigrant mothers in Canada. We explored single motherhood and immigration in relation to multiple points of intersection concerning dimensions of cultural identity. We began by examining how intersections of gender and ethnicity affect single, immigrant mothers in terms of self-perception, sociocultural experiences, and acculturation processes. Single, immigrant mothers receive specific gendered messages from their families, cultures of origin, and Canadian culture. These messages, specific to the context of mothering, shape their cultural identity and role in society.We also examined the impact of Canadian and country of origin mothering ideologies on single, immigrant mothers, how discourses around these ideologies endorse potentially unrealistic images of the ideal or good mother, and how they affect the mother-child relationship. Single, immigrant mothers hold multiple, nondominant intersecting identities and may not portray adherence to the dominant mothering ideologies, from either Canada or their country of origin. As a result, they are more vulnerable to marginalization, discrimination, and mental health problems. We considered how the intersections of gender, ethnicity, single motherhood, social class, and immigration affected single, immigrant mothers’ labour market participation, social support, mental health, and acculturation. We offer insights into the challenges that single, immigrant mothers face and point to ways to improve social and mental health services for these women

Application of WGS data for O-specific antigen analysis and <i>in silico </i>serotyping of <i>Pseudomonas aeruginosa </i>isolates

Accurate typing methods are required for efficient infection control. The emergence of whole-genome sequencing (WGS) technologies has enabled the development of genome-based methods applicable for routine typing and surveillance of bacterial pathogens. In this study, we developed the Pseudomonas aeruginosa serotyper (PAst) program, which enabled in silico serotyping of P. aeruginosa isolates using WGS data. PAst has been made publically available as a web service and aptly facilitates high-throughput serotyping analysis. The program overcomes critical issues such as the loss of in vitro typeability often associated with P. aeruginosa isolates from chronic infections and quickly determines the serogroup of an isolate based on the sequence of the O-specific antigen (OSA) gene cluster. Here, PAst analysis of 1,649 genomes resulted in successful serogroup assignments in 99.27% of the cases. This frequency is rarely achievable by conventional serotyping methods. The limited number of nontypeable isolates found using PAst was the result of either a complete absence of OSA genes in the genomes or the artifact of genomic misassembly. With PAst, P. aeruginosa serotype data can be obtained from WGS information alone. PAst is a highly efficient alternative to conventional serotyping methods in relation to outbreak surveillance of serotype O12 and other high-risk clones, while maintaining backward compatibility to historical serotype data

Texture-Modified Diet for Improving the Management of Oropharyngeal Dysphagia in Nursing Home Residents: An Expert Review.

Abstract Objectives This paper provides evidence-based and, when appropriate, expert reviewed recommendations for long-stay residents who are prescribed texture-modified diets (TMDs), with the consideration that these residents are at high risk of worsening oropharyngeal dysphagia (OD), malnutrition, dehydration, aspiration pneumonia, and OD-associated mortality, poorer quality of life and high costs. Design Nestlé Health Science funded an initial virtual meeting attended by all authors, in which the unmet needs and subsequent recommendations for OD management were discussed. The opinions, results, and recommendations detailed in this paper are those of the authors, and are independent of funding sources. Setting OD is common in nursing home (NH) residents, and is defined as the inability to initiate and perform safe swallowing. The long-stay NH resident population has specific characteristics marked by a shorter life expectancy relative to community-dwelling older adults, high prevalence of multimorbidity with a high rate of complications, dementia, frailty, disability, and often polypharmacy. As a result, OD is associated with malnutrition, dehydration, aspiration pneumonia, functional decline, and death. Complications of OD can potentially be prevented with the use of TMDs. Results This report presents expert opinion and evidence-informed recommendations for best practice on the nutritional management of OD. It aims to highlight the practice gaps between the evidence-based management of OD and real-world patterns, including inadequate dietary provision and insufficient staff training. In addition, the unmet need for OD screening and improvements in therapeutic diets are explored and discussed. Conclusion There is currently limited empirical evidence to guide practice in OD management. Given the complex and heterogeneous population of long-stay NH residents, some 'best practice' approaches and interventions require extensive efficacy testing before further changes in policy can be implemented

A Bacteriophage-Acquired O-Antigen Polymerase (Wzy_β) from <i>P. aeruginosa </i>Serotype O16 Performs a Varied Mechanism Compared to Its Cognate Wzy_α

Pseudomonas aeruginosa is a Gram-negative bacterium that produces highly varied lipopolysaccharide (LPS) structures. The O antigen (O-Ag) in the LPS is synthesized through the Wzx/Wzy-dependent pathway where lipid-linked O-Ag repeats are polymerized by Wzy. Horizontal-gene transfer has been associated with O-Ag diversity. The O-Ag present on the surface of serotypes O5 and O16, differ in the intra-molecular bonds, α and β, respectively; the latter arose from the action of three genes in a seroconverting unit acquired from bacteriophage D3, including a β-polymerase (Wzyβ). To further our understanding of O-polymerases, the inner membrane (IM) topology of Wzyβ was determined using a dual phoA-lacZα reporter system wherein random 3’ gene truncations were localized to specific loci with respect to the IM by normalized reporter activities as determined through the ratio of alkaline phosphate activity to β-galactosidase activity. The topology of Wzyβ developed through this approach was shown to contain two predominant periplasmic loops, PL3 (containing an RX10G motif) and PL4 (having an O-Ag ligase superfamily motif), associated with inverting glycosyltransferase reaction. Through site-directed mutagenesis and complementation assays, residues Arg254, Arg270, Arg272 and His300 were found to be essential for Wzyβ function. Additionally, like-charge substitutions, R254K and R270K, could not complement the wzyβ knockout, highlighting the essential guanidium side group of Arg residues. The O-Ag ligase domain is conserved among heterologous Wzy proteins that produce β-linked O-Ag repeat units. Taking advantage of the recently obtained whole-genome sequence of serotype O16 a candidate promoter was identified. Wzyβ under its native promoter was integrated in the PAO1 genome, which resulted in simultaneous production of α- and β-linked O-Ag. These observations established that members of Wzy-like family consistently exhibit a dual-periplasmic loops topology, and identifies motifs that are plausible to be involved in enzymatic activities. Based on these results, the phage-derived Wzyβ utilizes a different reaction mechanism in the P. aeruginosa host to avoid self-inhibition during serotype conversion

Parental Decision-Making on Childhood Vaccination

A growing number of parents delay vaccinations or are deciding not to vaccinate their children altogether. This increases the risk of contracting vaccine-preventable diseases and disrupting herd immunity, and also impair the trust in the capacities of health care systems to protect people. Vaccine hesitancy is related to a range of both psychological and demographic determinants, such as attitudes towards vaccinations, social norms, and trust in science. We focus on parents and our aim is to understand those determinants, because they are a special group in this issue – proxy decision makers – as they are deciding for their children, who are unable to do so themselves. The fact that deciding to vaccinate is a socially forced choice that concerns a child’s health makes vaccine-related decisions highly important and involving for parents. This high involvement might lead to parents overemphasizing the potential side effects that they know to be vaccine-related, and by amplifying those, parents are more focused on the potential outcomes of vaccine-related decisions, which can yield specific pattern of the outcome bias. We propose two related studies to investigate factors which promote vaccine hesitancy, protective factors that determine parental vaccination decisions, and outcome bias in parental vaccination intentions. We will explore demographic and psychological factors, and test parental involvement related to vaccine hesitancy using an online battery in a correlation panel design study. The second study is an experimental study, in which we will investigate the moderating role of parents’ high involvement in the specific domain of vaccination decision making. We expect that higher involvement among parents, compared to non-parents, will shape the pattern of the proneness to outcome bias. The studies will be conducted across eight countries in Europe and Asia (Finland, Germany, Hong Kong, the Netherlands, Serbia, Slovenia, Spain, and the United Kingdom), rendering findings that will aid with understanding the underlying mechanisms of vaccine hesitancy and paving the way for developing interventions that are custom-made for parents.Peer reviewe

Maternal taurine supplementation in rats partially prevents the adverse effects of early-life protein deprivation on b-cell function and insulin sensitivity

Dietary protein restriction during pregnancy and lactation in rats impairs b-cell function and mass in neonates and leads to glucose intolerance in adult offspring. Maternal taurine (Tau) supplementation during pregnancy in rats restores b-cell function and mass in neonates, but its long-term effects are unclear. The prevention of postnatal catch-up growth has been suggested to improve glucose tolerance in adult offspring of low-protein (LP)-fed mothers. The objective of this study was to examine the relative contribution of b-cell dysfunction and insulin resistance to impaired glucose tolerance in 130-day-old rat offspring of LP-fed mothers and the effects of maternal Tau supplementation on b-cell function and insulin resistance in these offspring. Pregnant rats were fed i) control, ii) LP, and iii) LPCTau diets during gestation and lactation. Offspring were given a control diet following weaning. A fourth group consisting of offspring of LP-fed mothers, maintained on a LP diet following weaning, was also studied (LP-all life). Insulin sensitivity in the offspring of LP-fed mothers was reduced in females but not in males. In both genders, LP exposure decreased b-cell function. Tau supplementation improved insulin sensitivity in females and b-cell function in males. The LP-all life diet improved b-cell function in males. We conclude that i) maternal Tau supplementation has persistent effects on improving glucose metabolism (b-cell function and insulin sensitivity) in adult rat offspring of LP-fed mothers and ii) increasing the amount of protein in the diet of offspring adapted to a LP diet after weaning may impair glucose metabolism (b-cell function) in a gender-specific manner.Fil: Tang, Christine. University Of Toronto; Canadá;Fil: Marchand, K.elly. University of Western Ontario. Lawson Health Research Institute; Canadá;Fil: Lam, Loretta. University Of Toronto; Canadá;Fil: Lux, Victoria Adela R.. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Thyssen, Sandra M.. University of Western Ontario. Lawson Health Research Institute; Canadá;Fil: Guo, June. University Of Toronto; Canadá;Fil: Giacca, A.dria. University Of Toronto; Canadá;Fil: Arany, Edith. University of Western Ontario. Lawson Health Research Institute; Canadá

Maternal taurine supplementation in rats partially prevents the adverse effects of early-life protein deprivation on β-cell function and insulin sensitivity

Dietary protein restriction during pregnancy and lactation in rats impairs β-cell function and mass in neonates and leads to glucose intolerance in adult offspring. Maternal taurine (Tau) supplementation during pregnancy in rats restores β-cell function and mass in neonates, but its long-term effects are unclear. The prevention of postnatal catch-up growth has been suggested to improve glucose tolerance in adult offspring of low-protein (LP)-fed mothers. The objective of this study was to examine the relative contribution of β-cell dysfunction and insulin resistance to impaired glucose tolerance in 130-day-old rat offspring of LP-fed mothers and the effects of maternal Tau supplementation on β-cell function and insulin resistance in these offspring. Pregnant rats were fed i) control, ii) LP, and iii) LP+Tau diets during gestation and lactation. Offspring were given a control diet following weaning. A fourth group consisting of offspring of LP-fed mothers, maintained on a LP diet following weaning, was also studied (LP-all life). Insulin sensitivity in the offspring of LP-fed mothers was reduced in females but not in males. In both genders, LP exposure decreased β-cell function. Tau supplementation improved insulin sensitivity in females and β-cell function in males. The LP-all life diet improved β-cell function in males. We conclude that i) maternal Tau supplementation has persistent effects on improving glucose metabolism (β-cell function and insulin sensitivity) in adult rat offspring of LP-fed mothers and ii) increasing the amount of protein in the diet of offspring adapted to a LP diet after weaning may impair glucose metabolism (β-cell function) in a gender-specific manner. © 2013 Society for Reproduction and Fertility

The protection of Victoria Harbour in Hong Kong : an analysis of civic engagement strategies

published_or_final_versionPolitics and Public AdministrationMasterMaster of Public Administratio