Browsing by Subject "Stress"

A series of experiments and mathematical models explore the response of the bacteria E. coli to stressors. Experimentally, the effect of L-homocysteine, a non-protein amino acid, is explored, and via math models, the effect of trimethoprim, a common antibiotic, is also explored. Previous work on L-homocysteine labels it a stressor, and this assertion is refined via the presented work. A mathematical model that improves on a previous work published by Kwon et al. (2008) explores the response of E. coli to various supplementations of amino acids when exposed to trimethoprim. New methods of developing antibiotics and therapeutic drug treatments are also explored.

As an opportunistic Gram-negative pathogen, Pseudomonas aeruginosa must be able to adapt to changes and survive stressors in its environment during the course of infection. To aid survival in the hostile host environment, P. aeruginosa has evolved a myriad of virulence factors including the production of an exopolysaccharide capsule, as well as secretion of degradative proteases and lipases that also function as defense mechanisms. Outer membrane vesicles (OMVs) acts as a secretion system to disseminate virulence factors and function as a general bacterial stress response to remove accumulated periplasmic waste. Despite the growing insights of the field into the potential functions of OMVs, the mechanism for formation remains to be fully elucidated. The three proposed mechanisms for OMV formation in P. aeruginosa are mediated by the Pseudomonas quinolone signal PQS, the AlgU envelope stress response pathway, and the periplasmic chaperone MucD. This report investigates how P. aeruginosa responds to sublethal physiological stressors with regards to OMV production levels and whether the proposed mechanisms for OMV formation are required for stress-induced OMV formation. We concluded that exposure to cell wall directed stressors increased OMV production and activity of the sigma factor that controls MucD expression, AlgU. AlgU was shown to be sufficient to induced OMV production upon overexpression; however, stress-induced OMV production was not dependent on activation of AlgU as vesiculation could be induced in strains lacking AlgU. Furthermore, MucD levels were not inversely proportional to OMV production under acute stress, and the ability to produce PQS was not required for OMV production. Finally, an investigation of the response of P. aeruginosa to oxidative stress revealed that hydrogen peroxide-induced OMV production requires the presence of B-band but not A-band lipopolysaccharide. We also demonstrated that the ability for P. aeruginosa to sense oxidative stress via OxyR, was important for hydrogen peroxide-induced OMV production, by a yet to be determined method. Together these results demonstrate that current proposed mechanisms for OMV formation do not universally apply under all stress conditions, and that additional mechanisms for OMV formation are still to be identified and fully elucidated during acute stress in P. aeruginosa.

In the following document, I will describe two distinct strategies that poliovirus

(PV) deploys to manage host antiviral responses. In the first section, I report on a role of

the constitutive repressor of eIF2α phosphorylation (CReP) in translation of PV and the

endoplasmic reticulum (ER)-resident chaperone binding immunoglobulin protein (BiP)

at the ER. Functional, proximity-dependent labeling and cell fractionation studies

revealed that CReP, through binding of the eukaryotic translation initiation factor eIF2α,

anchors translation initiation machinery at the ER and enables protein synthesis in this

compartment. This ER site was protected from the suppression of cytoplasmic protein

synthesis by acute stress responses. I propose that partitioning of translation initiation

machinery at the ER enables cells to maintain active translation of PV during stress.

In the second section, I report that PV 2A protease cleaves all three members of

the YTHDF protein family, cytosolic N6-methyladenosine (m6A) ‘readers’ that regulate

target mRNA fate. These cleavages occurred early during infection, and preemptive

YTHDF3 depletion enhanced viral replication. This corresponded with diminished type-

I interferon (IFN) receptor (IFNAR) expression and IFN-stimulated gene induction,

while IFN production was not significantly changed. I propose that 2A protease cleaves

YTHDF proteins, in part, to interfere with IFNAR expression and antagonize the host

antiviral response.

*Designated as an Exemplary Master's Project for 2014-15*

Exposure to psychosocial stress is a robust predictor of subsequent psychopathology. However, only a portion of individuals with these experiences will develop psychiatric symptoms. The concept of gene-environment interaction (GxE) has provided one theoretical framework for reconciling these observations, but the empirical findings from this literature are mixed and often fail to replicate across studies. This dissertation explores the use of a relatively new approach to measuring the mental-health effects of environmental stress (the “p-factor”), and examines whether this approach has the potential to advance and consolidate studies of gene-environment interaction and psychopathology. First, I present lifetime prevalence data from The Dunedin Multidisciplinary Health and Development Study indicating that mental disorder is near-ubiquitous, consistent with the notion that liability to these conditions is distributed quantitatively throughout the population. Second, I present analyses from the Environmental Risk Longitudinal Twin Study showing that the mental-health effects of victimization exposure (one of the most common and severe types of psychosocial stress) are both non-specific and likely causal. These data suggest that stressful life experiences increase risk of psychopathology largely through effects on general liability. Third, I examine whether victimization’s effects on general psychopathology vary as a function of multiple measures of genetic propensity. Results consistently indicate that they do not, suggesting minimal gene-environment interaction. Implications for future research that seeks to identify the genetic and non-genetic factors that determine vulnerability and resilience to the mental-health effects of environmental stress are discussed.

MicroRNAs are key post-transcriptional regulators that have been found to play critical roles in the regulation of cellular functions. There is an emerging concept that microRNAs may be just as essential for fine-tuning physiological functions and responding to changing environments and stress conditions as for viability or development. In this dissertation, two studies are presented: The first study demonstrates a role for microRNA in the regulation of oxidative stress response in erythroid cells and the functional consequences of dysregulated microRNA expression in Sickle Cell Disease (SCD) pathobiology. The second study examines a functional role for microRNA in the cellular response to changes in cellular iron concentration. Together these studies illustrate the scope of importance of microRNAs in the coordination of cellular responses to diverse stresses.

Homozygous Sickle Cell (HbSS) erythrocytes are known to have reduced tolerance for oxidative stress, yet the basis for this phenotype has remained unknown. Here we use erythrocyte microRNA expression profiles to identify a subset of HbSS patients with higher miR-144 expression and more severe anemia. We reveal that in K562 erythroid cells and primary erythroid progenitor cells, miR-144 directly regulates NRF2, a central regulator of cellular response to oxidative stress, and modulates the oxidative stress response. We further demonstrate that increased miR-144 is associated with the reduced NRF2 levels, decreased glutathione regeneration, and attenuated antioxidant capacity found in HbSS erythroid progenitors, thereby providing a mechanism for the reduced oxidative stress tolerance and increased anemia severity seen in HbSS patients.

The post-transcriptional regulation of the IRP2 regulon in the cellular response to iron deficiency is well characterized. Here we examine the potential role for microRNA-mediated regulation in the coordinated response to cellular iron deficiency.

Animals must coordinate development with fluctuating nutrient availability. Nutrient availability governs post-embryonic development in Caenorhabditis elegans: larvae that hatch in the absence of food do not initiate post-embryonic development but enter "L1 arrest" (or "L1 diapause") and can survive starvation for weeks, while rapidly resume normal development once get fed. Insulin-like signaling (IIS) has been shown to be a key regulator of L1 arrest and recovery. However, the C. elegans genome encodes 40 insulin-like peptides (ILPs), and it is unknown which peptides participate in nutritional control of L1 arrest and recovery. Work in other contexts has identified putative receptor agonists and antagonists, but the extent of specificity versus redundancy is unclear beyond this distinction.

We measured mRNA expression dynamics with high temporal resolution for all 40 insulin-like genes during entry into and recovery from L1 arrest. Nutrient availability influences expression of the majority of insulin-like genes, with variable dynamics suggesting complex regulation. We identified 13 candidate agonists and 8 candidate antagonists based on expression in response to nutrient availability. We selected ten candidate agonists (daf-28, ins-3, ins-4, ins-5, ins-6, ins-7, ins-9, ins-26, ins-33 and ins-35) for further characterization in L1 stage larvae. We used destabilized reporter genes to determine spatial expression patterns. Expression of candidate agonists was largely overlapping in L1 stage larvae, suggesting a role of the intestine, chemosensory neurons ASI and ASJ, and the interneuron PVT in systemic control of L1 development. Transcriptional regulation of candidate agonists was most significant in the intestine, as if nutrient uptake was a more important influence on transcription than sensory perception. Scanning in the 5' upstream promoter region of these 40 ILPs, We found that transcription factor PQM-1 and GATA putative binding sites are depleted in the promoter region of antagonists. A novel motif was also found to be over-represented in ILPs.

Phenotypic analysis of single and compound deletion mutants did not reveal effects on L1 recovery/developmental dynamics, though simultaneous disruption of ins-4 and daf-28 extended survival of L1 arrest without enhancing thermal tolerance, while overexpression of ins-4, ins-6 or daf-28 shortened L1 survival. Simultaneous disruption of several ILPs showed a temperature independent, transient dauer phenotype. These results revealed the relative redundancy and specificity among agonistic ILPs.

TGF- β and steroid hormone (SH) signaling have been reported to control the dauer formation along with IIS. Our preliminary results suggest they may also mediate the IIS control of L1 arrest and recovery, as the expression of several key components of TGF-β and SH signaling pathway genes are negatively regulated by DAF-16, and loss-of-function of these genes partially represses daf-16 null phenotype in L1 arrest, and causes a retardation in L1 development.

In summary, my dissertation study focused on the IIS, characterized the dynamics and sites of ILPs expression in response to nutrient availability, revealed the function of specific agonistic ILPs in L1 arrest, and suggested potential cross-regulation among IIS, TGF-β signaling and SH signaling in controlling L1 arrest and recovery. These findings provide insights into how post-embryonic development is governed by insulin-like signaling and nutrient availability.

Introduction: Hypertension, the primary risk factor for the leading cause of mortality, cardiovascular diseases, is increasing in all parts of the world, including low-income countries. This thesis explores the prevalence and predictors of elevated blood pressure in rural farmers in northeastern Madagascar. The prevalence of hypertensive blood pressure was compared as defined by two commonly used hypertension standards, the World Health Organization (WHO), and the American College of Cardiology & the American Heart Association (ACC/AHA). The hypothesized drivers of systolic and diastolic blood pressure were investigated, focusing specifically on age, gender, body mass index (BMI), salt intake, and stress. Methods: Over 1,200 surveys were conducted from 2019 to 2022 in four villages in the Sava Region of Madagascar, where blood pressure readings were obtained on each participant. A subset of the sample in the last field season, participated in additional questions related to salt consumption and a measurement of salt taken over the course of seven days. A subsample of forty-eight participants completed an additional survey regarding stress. Generalized linear mixed models were run to assess associations involving blood pressure, salt intake and stress, and other predictions involving age, gender, and BMI. Results: The different standards of hypertension, as defined by the WHO and the ACC/AHA, changed the respective prevalence of elevated blood pressure for this population markedly, nearly doubling the prevalence of hypertension if the more stringent American standard was used (WHO=29.7%, ACC/AHA=59.6%). Age was found to be a strong predictor of blood pressure as well as BMI, while salt intake, stress, and gender had weaker associations. Conclusion: The prevalence of elevated blood pressure in this population was markedly higher than that found in other studies conducted in this region and globally. Findings regarding lifestyle factors, salt intake and stress, as individual drivers of blood pressure were found to be inconclusive. Further research should be performed in this population to determine the predictors and lifestyle factors associated with blood pressure and the extent of their influence in this region. Consideration for standards of practice and diagnosis should be carefully considered in this population, as the burden of hypertension would potentially increase with a change in practice standard.

This dissertation investigates racial differences in individual stress processes and health as well as the ways social networks characteristics mediate these relationships. I explore (1) the stress trajectories of victims and non-victims from adolescence to adulthood across racial groups, (2) how particular network configurations determine the probability of adolescents experiencing victimization, and finally, (3) the ways racial homophily and social cohesion together, determine depressive symptoms. I conduct three studies all using relevant demographic, mental, and physical health data from the National Longitudinal Study of Adolescent to Adult Health. In my first study I find that black respondents have a unique relationship with the stress incurred from victimization, such that black victims and non-victims have virtually equal allostatic loads. In my second study I find that delinquency and integration shape the probability of victimization for adolescents, net of several common correlates of delinquency. Finally, results from my third chapter show that racial homophily mediates the well establish relationship between social cohesion and depression. These findings contribute to the sociology of race and ethnicity, network sociology, and to medical sociological inquires concerned with the vulnerable period of adolescence. Together, these three chapters show that race and networks govern opportunities that individuals have to form positive social relationships and the resulting health consequences of both successful and unsuccessful navigation of one’s social environment.

Apoptotic dysregulation is a hallmark of cancer cells. The inability of cancer cells to undergo apoptosis may lead to therapeutic resistance. Inflammatory breast cancer (IBC) is a highly aggressive subtype of breast cancer that is often characterized by ErbB2 overexpression and ErbB2 activation. ErbB-targeting is clinically relevant using trastuzumab (anti-ErbB2 antibody) and lapatinib (small molecule ErbB1/2 inhibitor). However, acquired resistance is a common outcome even in IBC patients who show an initial clinical response, which limits the efficacy of these agents. Little is known about the molecular mechanisms of therapeutic resistance in IBC cells. We hypothesized that apoptotic dysregulation leads to therapeutic resistance of IBC cells to therapeutic agents, including ErbB-targeting agents. To determine whether apoptotic dysregulation and changes in anti-apoptotic proteins leads to resistance of IBC cells to therapeutic agents, we performed a variety of in vitro-based studies using agents that are used in the clinic to treat IBC patients. The sensitivity of both ErbB2 overexpressing and ErbB1 activated IBC cells to various therapeutic agents was evaluated using various cell death and apoptosis assays, and anti-apoptotic protein expression post-treatment was determined using western blot analysis. The overarching theme observed was that x-linked inhibitor of apoptosis protein (XIAP) expression inversely correlated with sensitivity of cells to therapeutic agents with various mechanisms of action, including TNF-related apoptosis inducing ligand (TRAIL), doxorubicin, cisplatin, paclitaxel, and two ErbB-targeting agents: trastuzumab and a lapatinib-analog (GW583340). Moreover, there was a specific and marked overexpression of XIAP in cells with de novo resistance to trastuzumab and with acquired resistance to GW583340. The observed overexpression was identified to be caused by IRES-mediated XIAP translation. Stable XIAP overexpression using a lentiviral system reversed sensitivity to therapeutic agents (TRAIL and GW583340) in parental IBC cells. Moreover, XIAP downregulation in cells resistant to therapeutic agents (TRAIL, trastuzumab, and GW583340) resulted in decreased viability and increased apoptosis, demonstrating that XIAP is required for survival of cells with resistance to these agents. A novel mechanism of GW583340 oxidative stress-induced mediated apoptosis was identified, and resistant cells had increased antioxidant expression and capability. Interesting, inhibition of XIAP function overcame this increase in antioxidant potential, demonstrating a new function for XIAP in oxidative stress-induced apoptosis. These studies establish the feasibility of development of an XIAP inhibitor that potentiates apoptosis for use in IBC patients with resistance to therapeutic agents.

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Adolescent girls in sub-Saharan Africa must transition through puberty in the context of heightened risk for reproductive tract infections and mental illness. At the same time, girls experience menstrual stigma and a lack of resources to manage menstruation. Although menstruation and other puberty-specific stressors may negatively impact girls’ well-being, little is known about the relationships between puberty-specific stressors, coping, mental health, and reproductive health among girls in sub-Saharan Africa. The present dissertation seeks to fill this gap by investigating the types of puberty-specific stressors experienced by adolescent girls and young women in Tanzania, how girls cope with stressors, and the associations between stress and coping and mental health and reproductive health. A qualitative interview study and cross-sectional survey study were conducted to explore stress, coping, and health among adolescent girls in Tanzania. Both studies showed that girls experienced significant and disruptive puberty-specific stressors, with sexual pressure and menstrual pain constituting two of the most common stressors. Stressors were associated with depression, anxiety, and reproductive tract infections. Active coping and avoidant coping showed inconsistent relationships with stressors and mental health. Overall, psychosocial interventions are needed to reduce the negative impact of puberty-specific stressors on mental health and reproductive health among adolescent girls in Tanzania.

Traditional in-person psychotherapies are proving incapable of addressing mental health needs globally. Computer-based interventions are one promising solution to closing the large gap between mental health treatment need and actual treatment received. The overarching aim of this study is to contribute to the body of literature focused on providing new insights into effective ways of leveraging technology to implement large-scale mental health initiatives that are financially feasible, easily transportable and quickly scalable in low-resource setting. Although many meta-analyses have provided evidence to support the efficacy of self-guided, computer-based interventions, most report low rates of treatment engagement (high attrition, low adherence). Accordingly, this dissertation investigates the efficacy of an adjunctive treatment component that uses task-sharing, where mental health care is provided by non-specialist providers (NSP; e.g., nurses, clergy, community members), to enhance engagement in a self-directed, web-based mindfulness intervention for stress and depression among Chinese students.

Fifty-four students from 36 universities across China reporting at least mild stress, anxiety and/or depression were randomly assigned to a brief (4-week online mindfulness intervention (MIND) or to the intervention plus NSP support (MIND+). Fifty-six volunteer NSP candidates without formal training in the delivery of mental health services were screened, ten were invited to participate in a 1-day training, and four were selected. NSPs were instructed to provide six brief (15-20 minute) weekly meetings, with the intention of supporting and encouraging participants in their completion of the online intervention. NSPs received weekly online group supervision. Participants completed daily monitoring of mindfulness practice and mood, as well as baseline and post-treatment self-report packet assessing depression, anxiety and stress symptoms and trait mindfulness.

The study found that participants assigned to the MIND+ (vs. MIND) condition showed significantly less attrition and more adherence, as indicated by a greater likelihood of completing post-treatment assessments and a greater percentage of course completion, respectively. There were no significant between-group differences in daily self-reports of frequency and duration of mindfulness practice across the trial. However, results indicated that participation in the online intervention was associated with significant improvements in pre- to post-treatment mindfulness and mental health outcomes. In addition, individuals in the MIND+ condition reported significant improvements in daily ratings of stress and depression across the trial, compared to individuals in the MIND condition. These findings suggest that volunteer NSPs receiving brief training and weekly supervision may significantly improve participants’ indices of treatment engagement and mental health outcomes in an online mindfulness intervention among college and graduate students in China.

This dissertation offers an account of precarious neoliberal subjectivity by examining the suffering of the privileged as it relates to the practice of Western yoga in California's Silicon Valley. Yoga culture underlines creating connections and community. But my research, based on twenty-seven month fieldwork in an epicenter of the global high-tech economy, reveals that yoga practitioners actually seek to experience and create "space." I suggest that yoga practitioners often cultivate an interiority aimed at giving themselves room from the judgment and expectations of others.

This dissertation portrays the complicated lives of people who are more privileged than most. In so doing, this study questions the separation between "real" and "privileged" suffering; and it explores the ethical and political implications of the problems of the well-off. I suggest that the destructive aspects of neoliberal capitalism and late modernity do not hurt only the marginalized traditionally studied by anthropologists, but also--albeit in very different ways--those who supposedly benefit from them. The social scenes of modern yoga are sites of ambivalently embodied neoliberal logic, where clusters of promises and recipes for an "art of living" are critical about aspects of capitalism while enjoying its comfort. Even though the yogic ethic and politics do not adhere to the anthropological ideals of political action, Western yoga is often an ethical practice that does not simply reproduce neoliberal logic, but also shifts it slightly from within. By creating disruption of subjectivity and gaining space from old and habitual ways of being, yoga sometimes opens up a new territory of change and reflection.