Essays on Health and Retirement

The essays in this dissertation explore issues related to health and retirement of older Americans, using longitudinal data on older Americans from ten waves of the Health and Retirement Study (1992-2010). The first essay explores the effect of both subjective and relatively more objective physical and mental health conditions on the probability of exit from full-time employment. Eight health indices (factors) are created from a wide range of health measures by principal component analysis. The effect of these health factors on the time until exit from full-time employment is empirically examined in a proportional hazard model. Single and competing risk specifications are estimated that allow for multiple spells of full-time employment and control for unobserved heterogeneity. The main results suggest that increase in functional limitation factor makes an individual more likely to exit via any route in general and the complete retirement route in particular. For mental health problems, increase in the depression factor increases the likelihood of exit from full-time employment via the complete retirement, part-time work and unemployment routes. While increase in cognitive disorders factor has no significant effect on the likelihood of exit via complete retirement, but increases the likelihood of exit via the disability route. These results have implications for public policies targeted towards retaining older workers within the labor market. The second essay examines the effect of retirement on post retirement physical and mental health and the extent to which the effects differ across these different health outcomes. The inherent issue of reverse causality between health and retirement that leads to endogeneity is addressed by using multiple sample stratification and instrumental variable estimation strategies. The stratified samples include individuals who are physically and mentally healthy prior to their retirement so that pure effect of retirement on post retirement health may be found. Five different instruments for complete retirement are also used to deal with endogeneity. The sample stratification results unanimously indicate that complete retirement has adverse effect on post retirement physical and mental health. While the instrumental variables approach results are mixed and are based on the choice of instrument for complete retirement

Endogenous hydrogen peroxide production in the epithelium of the developing embryonic lens

Purpose Hydrogen peroxide (H2O2) is an endogenously produced reactive oxygen species (ROS) present in a variety of mammalian systems. This particular ROS can play dichotomous roles, being beneficial in some cases and deleterious in others, which reflects the level and location of H2O2 production. While much is known about the redox regulation of ROS by antioxidant and repair systems in the lens, little is known about the endogenous production of H2O2 in embryonic lens tissue or the physiologic relevance of endogenous H2O2 to lens development. This gap in knowledge exists primarily from a lack of reagents that can specifically detect endogenous H2O2 in the intact lens. Here, using a recently developed chemoselective fluorescent boronate probe, peroxyfluor-6 acetoxymethyl ester (PF6-AM), which selectively detects H2O2 over related ROS, we examined the endogenous H2O2 signals in the embryonic lens. Methods: Embryonic day 10 chick whole lenses in ex vivo organ culture and lens epithelial cells in primary culture were loaded with the H2O2 probe PF6-AM. To determine the relationship between localization of mitochondria with active membrane potential and the region of H2O2 production in the lens, cells were exposed to the mitochondrial probe MitoTracker Red CMXRos together with PF6-AM. Diphenyleneiodonium (DPI), a flavin inhibitor that blocks generation of intracellular ROS production, was used to confirm that the signal from PF6-AM was due to endogenous ROS production. All imaging was performed by live confocal microscopy. Results: PF6-AM detected endogenous H2O2 in lens epithelial cells in whole lenses in ex vivo culture and in lens epithelial cells grown in primary culture. No endogenous H2O2 signal could be detected in differentiating lens fiber cells with this probe. Treatment with DPI markedly attenuated the fluorescence signal from the peroxide-specific probe PF6-AM in the lens epithelium, suggesting that basal generation of ROS occurs in this region. The lens epithelial cells producing an endogenous H2O2 signal were also rich in actively respiring mitochondria. Conclusions: PF6-AM can be used as an effective reagent to detect the presence and localization of endogenous H2O2 in live lens cells

Differentiation state-specific mitochondrial dynamic regulatory networks are revealed by global transcriptional analysis of the developing chicken lens.

The mature eye lens contains a surface layer of epithelial cells called the lens epithelium that requires a functional mitochondrial population to maintain the homeostasis and transparency of the entire lens. The lens epithelium overlies a core of terminally differentiated fiber cells that must degrade their mitochondria to achieve lens transparency. These distinct mitochondrial populations make the lens a useful model system to identify those genes that regulate the balance between mitochondrial homeostasis and elimination. Here we used an RNA sequencing and bioinformatics approach to identify the transcript levels of all genes expressed by distinct regions of the lens epithelium and maturing fiber cells of the embryonic Gallus gallus (chicken) lens. Our analysis detected more than 15,000 unique transcripts expressed by the embryonic chicken lens. Of these, more than 3000 transcripts exhibited significant differences in expression between lens epithelial cells and fiber cells. Multiple transcripts coding for separate mitochondrial homeostatic and degradation mechanisms were identified to exhibit preferred patterns of expression in lens epithelial cells that require mitochondria relative to lens fiber cells that require mitochondrial elimination. These included differences in the expression levels of metabolic (DUT, PDK1, SNPH), autophagy (ATG3, ATG4B, BECN1, FYCO1, WIPI1), and mitophagy (BNIP3L/NIX, BNIP3, PARK2, p62/SQSTM1) transcripts between lens epithelial cells and lens fiber cells. These data provide a comprehensive window into all genes transcribed by the lens and those mitochondrial regulatory and degradation pathways that function to maintain mitochondrial populations in the lens epithelium and to eliminate mitochondria in maturing lens fiber cells

Increased mTOR activity and metabolic efficiency in mouse and human cells containing the African-centric tumor-predisposing p53 variant Pro47Ser

The Pro47Ser variant of p53 (S47) exists in African-descent populations and is associated with increased cancer risk in humans and mice. Due to impaired repression of the cystine importe

The Identification of CELSR3 and Other Potential Cell Surface Targets in Neuroendocrine Prostate Cancer.

UNLABELLED Although recent efforts have led to the development of highly effective androgen receptor (AR)-directed therapies for the treatment of advanced prostate cancer, a significant subset of patients will progress with resistant disease including AR-negative tumors that display neuroendocrine features [neuroendocrine prostate cancer (NEPC)]. On the basis of RNA sequencing (RNA-seq) data from a clinical cohort of tissue from benign prostate, locally advanced prostate cancer, metastatic castration-resistant prostate cancer and NEPC, we developed a multi-step bioinformatics pipeline to identify NEPC-specific, overexpressed gene transcripts that encode cell surface proteins. This included the identification of known NEPC surface protein CEACAM5 as well as other potentially targetable proteins (e.g., HMMR and CESLR3). We further showed that cadherin EGF LAG seven-pass G-type receptor 3 (CELSR3) knockdown results in reduced NEPC tumor cell proliferation and migration in vitro. We provide in vivo data including laser capture microdissection followed by RNA-seq data supporting a causal role of CELSR3 in the development and/or maintenance of the phenotype associated with NEPC. Finally, we provide initial data that suggests CELSR3 is a target for T-cell redirection therapeutics. Further work is now needed to fully evaluate the utility of targeting CELSR3 with T-cell redirection or other similar therapeutics as a potential new strategy for patients with NEPC. SIGNIFICANCE The development of effective treatment for patients with NEPC remains an unmet clinical need. We have identified specific surface proteins, including CELSR3, that may serve as novel biomarkers or therapeutic targets for NEPC

Effects of antibiotic resistance, drug target attainment, bacterial pathogenicity and virulence, and antibiotic access and affordability on outcomes in neonatal sepsis: an international microbiology and drug evaluation prospective substudy (BARNARDS)

Background Sepsis is a major contributor to neonatal mortality, particularly in low-income and middle-income countries (LMICs). WHO advocates ampicillin–gentamicin as first-line therapy for the management of neonatal sepsis. In the BARNARDS observational cohort study of neonatal sepsis and antimicrobial resistance in LMICs, common sepsis pathogens were characterised via whole genome sequencing (WGS) and antimicrobial resistance profiles. In this substudy of BARNARDS, we aimed to assess the use and efficacy of empirical antibiotic therapies commonly used in LMICs for neonatal sepsis. Methods In BARNARDS, consenting mother–neonates aged 0–60 days dyads were enrolled on delivery or neonatal presentation with suspected sepsis at 12 BARNARDS clinical sites in Bangladesh, Ethiopia, India, Pakistan, Nigeria, Rwanda, and South Africa. Stillborn babies were excluded from the study. Blood samples were collected from neonates presenting with clinical signs of sepsis, and WGS and minimum inhibitory concentrations for antibiotic treatment were determined for bacterial isolates from culture-confirmed sepsis. Neonatal outcome data were collected following enrolment until 60 days of life. Antibiotic usage and neonatal outcome data were assessed. Survival analyses were adjusted to take into account potential clinical confounding variables related to the birth and pathogen. Additionally, resistance profiles, pharmacokinetic–pharmacodynamic probability of target attainment, and frequency of resistance (ie, resistance defined by in-vitro growth of isolates when challenged by antibiotics) were assessed. Questionnaires on health structures and antibiotic costs evaluated accessibility and affordability. Findings Between Nov 12, 2015, and Feb 1, 2018, 36 285 neonates were enrolled into the main BARNARDS study, of whom 9874 had clinically diagnosed sepsis and 5749 had available antibiotic data. The four most commonly prescribed antibiotic combinations given to 4451 neonates (77·42%) of 5749 were ampicillin–gentamicin, ceftazidime–amikacin, piperacillin–tazobactam–amikacin, and amoxicillin clavulanate–amikacin. This dataset assessed 476 prescriptions for 442 neonates treated with one of these antibiotic combinations with WGS data (all BARNARDS countries were represented in this subset except India). Multiple pathogens were isolated, totalling 457 isolates. Reported mortality was lower for neonates treated with ceftazidime–amikacin than for neonates treated with ampicillin–gentamicin (hazard ratio [adjusted for clinical variables considered potential confounders to outcomes] 0·32, 95% CI 0·14–0·72; p=0·0060). Of 390 Gram-negative isolates, 379 (97·2%) were resistant to ampicillin and 274 (70·3%) were resistant to gentamicin. Susceptibility of Gram-negative isolates to at least one antibiotic in a treatment combination was noted in 111 (28·5%) to ampicillin–gentamicin; 286 (73·3%) to amoxicillin clavulanate–amikacin; 301 (77·2%) to ceftazidime–amikacin; and 312 (80·0%) to piperacillin–tazobactam–amikacin. A probability of target attainment of 80% or more was noted in 26 neonates (33·7% [SD 0·59]) of 78 with ampicillin–gentamicin; 15 (68·0% [3·84]) of 27 with amoxicillin clavulanate–amikacin; 93 (92·7% [0·24]) of 109 with ceftazidime–amikacin; and 70 (85·3% [0·47]) of 76 with piperacillin–tazobactam–amikacin. However, antibiotic and country effects could not be distinguished. Frequency of resistance was recorded most frequently with fosfomycin (in 78 isolates [68·4%] of 114), followed by colistin (55 isolates [57·3%] of 96), and gentamicin (62 isolates [53·0%] of 117). Sites in six of the seven countries (excluding South Africa) stated that the cost of antibiotics would influence treatment of neonatal sepsis

APPLICATION OF MULTIMEDIA IN E-LEARNING: LECTURE VIDEOS AND MULTIMODAL SYSTEMS

Ph.DDOCTOR OF PHILOSOPHY (SOC

Signaling pathways crucial in differentiation initiation and terminal differentiation during lens development

Precise regulation of signaling pathways that are involved in cell differentiation is crucial for the proper development of a tissue. Here we studied the regulatory mechanisms that control the initiation of differentiation in lens epithelial cells and terminal differentiation of lens fiber cells. Previously the caspase-3 protease, when activated at low levels downstream to the canonical mitochondrial death pathway, was shown to be a requisite non-apoptotic signal for lens epithelial cell differentiation initiation. However, it was not known how this caspase-3 signal is regulated and maintained at the low levels of activation necessary for its function as a differentiation and not a death signal. From our studies we discovered that a coordinated α6 integrin/IGF-1R survival signal mediated the level of caspase-3 activation. This α6 integrin/IGF-1R pathway activates NFκB, a transcription factor that induces expression of survival proteins in both the Bcl-2 and Inhibitor of Apoptosis (IAP) families, which in turn regulate caspase-3 activity. When IGF-1R activation is blocked, NFκB signaling is compromised and, both the Bcl-2 and IAP families fail to be induced. α6 integrin was found to be responsible for transactivation of IGF-1R and induction of its downstream effectors. Releasing these cellular controls on caspase-3 results in high levels of caspase-3, blocking lens cell differentiation and instead inducing cell death. Investigation of the signal responsible for activating the mitochondrial death pathway for its non-apoptotic function in differentiation-initiation suggests that generation of endogenous hydrogen peroxide (H2O2), a reactive oxygen species (ROS), is a good candidate for inducing caspase-activation in the developing lens. We also investigated the signals that lead to tightly programmed elimination of nuclei and organelles from the lens during terminal differentiation to form the organelle free zone (OFZ). We have discovered that the formation of the organelle free zone (OFZ) involves induction of an autophagic pathway. The mechanism responsible for inducing the autophagy process that leads to OFZ formation involves inhibition of a c-Jun NH2-terminal kinases (JNK)-regulated mTOR signal. mTOR, the mechanistic target of rapamycin, is a classical regulator of autophagy induction. Inhibition of JNK or mTOR signaling induces premature formation of OFZ by autophagy, with JNK signaling upstream of mTOR. This role for JNK as negative regulator of autophagy in the context of development represents a paradigm shift for the known signaling roles for JNK in autophagy. Collectively, our studies revealed essential regulatory mechanisms that control lens differentiation and development and are expected to have a wide applicability to other cell types

Factors Influencing Healthcare Choices by the Elderly in India: Role of Social Interactions

Purpose: The primary objective of this paper is to identify and analyze factors that influence choice and quality of healthcare of the elderly population in two northern and two southern states in India. The purpose of this paper is to look beyond the obvious factors that influence choice and therefore the quality of healthcare and seek to find whether there are some additional indirect factors that also influence choice and quality of healthcare. Design/methodology/approach: This paper utilizes data from the Longitudinal Aging Study in India pilot project, which was a cross-sectional survey of men and women aged 45 and over focusing on two northern states (Punjab and Rajasthan) and two southern states (Kerala and Karnataka). In this paper the authors carry out a Probit analysis to estimate the factors that influence the elderly\u27s choice of healthcare. Findings: The authors find that social activity via different types of social interactions outside the home and access to a phone (which is one of the cheapest and most commonly used methods of communication used by people in India) are statistically significant in influencing better quality of healthcare for the elderly. Moreover, gender-segregated results suggest that social activity is particularly important for elderly females. Relative price of healthcare is also an important determinant of the quality of healthcare sought. The authors also find some consistent regional influences on healthcare choices by the elderly. Research limitations/implications:The main limitation is the data itself which is cross-sectional in nature. However, as further rounds of survey are conducted the authors hope to be able to build on the results of this paper using a longitudinal approach. A second limitation is the lack of variables available for carrying out an instrumental variables analysis. The results imply that elderly males and females are influenced by different things when it comes to healthcare choices. Thus for policy to be effective, the government needs to pursue avenues that would be most likely to succeed. Practical implications: One of the most important practical implications of this research is the understanding that informal channels of knowledge transmission are important especially for the elderly in India. Traditional methods of knowledge transmission such as education, media, and income are less likely to be effective in a country where majority of the people are illiterate and poor. Social interactions appear to be most effective in influencing healthcare choices of elderly females. Social implications: The most obvious social implications of this paper are the importance of social interactions via social activities outside the home and ability for social communication via access to a phone for the elderly population in India to make better healthcare choices and therefore receive better healthcare. Originality/value: The literature on elderly healthcare is limited when it comes to developing countries. What makes matters worse for India is that up until recently there have been no comprehensive efforts to collect reliable data on the elderly population in India. As a result there is extremely limited availability of policy-relevant research dedicated to issues relating to the older population. Most of the existing literature looks at self-reported health and healthcare status or utilization. This paper would be among the first to address factors influencing quality of healthcare received by the elderly population in India