Now showing items 41-60 of 2006

    • Metagenome and Metatranscriptome Analysis of the Subgingival Bacteria in Periodontal Disease. A Systematic Narrative Review

      Wohl, Hirschel; Aichelmann-Reidy, Mary Beth (2021)
      The main purpose of this systematic narrative review is to determine the difference in abundance of bacteria and bacterial genes of subgingival microflora of human periodontal pockets compared to healthy sites, via Metagenomic and Metatranscriptomic analyses. Databases EMBASE and MEDLINE were searched for articles, with earliest records from 1978. Main outcome measures included: 1) Bacterial genera and/or species significantly increased 2) Most prevalent or significantly upregulation of genes. Ten studies met selection criteria and were included in the study. Nine studies were cross-sectional, and one was longitudinal. Main results showed trends of specific bacteria and genes found in periodontal pockets. However, within the limitations of this narrative review, trends of abundant bacteria and genes does not imply these specific species or genes are actively participating in disease progression. Nine of ten included studies were cross-sectional in design with eight studies being metagenome based and not able to measure gene expression.
    • The Color Stability of 3D-Printed and Milled Zirconia Crowns

      Spatz, Harrison; Masri, Radi, 1975-; 0000-0002-3583-7674 (2021)
      Purpose: This is an in vitro study on the color stability of 3D-printed and milled zirconia crowns. Materials and Methods: A total of 18 samples were tested, 9 milled and 9 printed zirconia crowns. Change in color (ΔE) was assessed before and after samples were soaked in solutions of coffee, chlorhexidine and distilled water for a simulated period of 1 week. Two-way ANOVA was used to compare between the groups. Results: There was a significant difference (P = .003) between ΔE of samples soaked in chlorohexidine (4.24 ±3.62) versus coffee (8.84 ±7.48) and between ΔE of samples milled (1.64 ±1.12) versus printed (11.11 ±3.96, P ≤ .0001). Conclusion: Printed zirconia crowns are more susceptible to staining than milled crowns. Printed zirconia crowns appeared noticeably darker when soaked in coffee and lighter when soaked in distilled water and chlorohexidine.
    • The Impact of Sex and Cognition on Recovery and Mortality Post Hip Fracture

      Mutchie, Heather; Gruber-Baldini, Ann L.; 0000-0002-6964-5283 (2021)
      Introduction The overall objective of this work was to estimate misclassification of cognitive impairment (CI) by sex among hip fracture patients. The effects of sex and identified CI on hip fracture recovery outcomes, including trajectories of cognitive and physical function and mortality (all-cause and cognition-specific), were subsequently examined. Methods This study used secondary data from a cohort of hip fracture patients recruited from 8 Baltimore-area hospitals between 2006-2011 (N=339), with frequency matched enrollment of females (n=171) and males (n=168), tested within 22 days of hip fracture admission and at 2, 6, and 12 months. Death data were derived from the National Death Index 2006-2018 (n=260; females=113, females=147). Analyses differentiated source of CI identification (SCI, n=330) between clinical diagnosis/documentation and direct testing [Modified Mini Mental State Examination (3MS)] of cognition at baseline by patient sex. Analyses identified cognitive and functional recovery using group-based trajectory modeling (GBTM) and joint trajectory models; and estimated time to death for all-cause and cognition-related cause of death (CR-COD) by SCI and sex. Results Males had increased odds of CI identified by both hospital record and 3MS after adjusting for age, education, and comorbidities. There were 2-4 distinct groups of recovery for cognitive and functional recovery. In joint models of recovery, high levels of cognitive function were only seen in high physical functioning groups. Significantly more men died than women (147 vs 113, p<.0001) and died sooner from all-cause mortality (41 vs 54 months, p=0.001) but not CR-COD. Males and those with SCI Both were independently at increased risk for all-cause mortality but there was not a significant interaction. Those with SCI Both were 14 times more likely to die of CR-COD (p<.0001). Conclusions There is clinical underdiagnosis of active CI in males. Additional CI ascertainment can identify a sub-population of patients at excess risk for mortality and CR-COD. Cognitive testing after hip fracture should be instituted as standard practice to avoid sex bias in identification of CI. Cognition changes little over 12 months post fracture. Pre-fracture functional status informs pattern of physical function recovery. Sex and CI increase mortality risk, and to some extent cause-specific mortality.
    • Tongue Asymmetry and Muscle Shortening During Speech in Partial Glossectomy Patients and Controls

      Miller, Natalie; Stone, Maureen L. (2021)
      Tumors of the tongue are routinely removed by partial glossectomy surgery. This study examines the extent of anatomical asymmetries caused by the glossectomy surgery and its effects on the tongue’s resting position and motor symmetry. Magnetic resonance imaging (MRI) data of ten control subjects and ten glossectomy patients were obtained. 3D tongue volumes were extracted from high-resolution MRI data using Matlab. Using cine- and tagged-MRI data, shortening of the genioglossus, transverse, and verticalis muscles were calculated during a speech task involving /∫/ and /l/. Anatomical asymmetries were observed in the control subjects, although they were generally small and less than in glossectomy patients. Glossectomy patients aimed to distribute their tongue volume evenly in the oral cavity, irrespective of anatomical asymmetry, by posturing their tongue towards the resected side. Glossectomy patients shortened more muscles when executing the speech task. Muscle shortening asymmetry was observed in both control and patient groups.
    • Optimal Antero-Posterior Position of the Maxillary Central Incisors and its Relationship to the Forehead in Adult Asian Males

      Kocan, Jessica; Sanchez, Dina (2021)
      Objective: To determine an optimal antero-posterior (AP) position of the maxillary central incisors (CI) and its relationship to the forehead in Asian males. Methods: Smiling profile photographs of 60 Asian males were obtained and divided into three groups based on the judged AP position of CI (“just about right,” “too far forward,” “too far back”), as evaluated by orthodontists and laypersons. CI position and forehead inclination (FI) were measured relative to glabella vertical (GV). Statistical analysis tested for differences among groups, differences between orthodontists and laypersons, and the relationship between CI position and FI. Results: Optimal CI position was 0.86mm anterior to GV. There were statistical differences between orthodontists and laypersons in the study groups. CI position and FI showed moderate positive correlation. Conclusions: In Asian males, the AP position of the CI can be evaluated relative to the forehead, to plan for optimized CI position and maximized facial harmony.
    • μ-Crystallin: A Novel Protein Regulator of Mammalian Metabolism

      Kinney, Christian; Bloch, Robert J.; 0000-0002-9799-9097 (2021)
      Thyroid hormones control many aspects of physiology such as metabolism and thermogenesis. Because thyroid hormones control such crucial bodily functions, their levels in the body are tightly regulated. Hypo- and hyperthyroidism can result when the level of thyroid hormone is too low or too high, respectively, with potentially serious pathophysiological consequences. µ-Crystallin is an NADPH-regulated thyroid hormone binding protein. The protein is minimally expressed in the skeletal muscle of most people; however, some individuals express relatively high baseline levels of µ-crystallin. We generated a transgenic mouse, the Crym tg mouse, that expresses high levels of µ-crystallin in its skeletal muscle, in order to explore the consequences of expressing high levels, comparable to those seen in some humans. The Crym tg mouse expresses mouse µ-crystallin at levels 2.6-147.5-fold higher than control mice in their skeletal muscle. Consequently, intramuscular triiodothyronine (T3) levels are elevated ~190-fold in the tibialis anterior, while serum thyroxine levels are decreased by 1.2-fold. Crym tg mice have a decreased respiratory exchange ratio that corresponds to a 13.7% increase in fat utilization as an energy source. Female Crym tg mice gained weight faster on high fat or high simple carbohydrate diets. Gene ontology enrichment analysis of transcriptomic and proteomic data revealed alterations to the expression of genes associated with metabolism and fiber type, while the fiber sizes of Crym tg soleus muscle are significantly smaller than those of controls. Taken together, these results suggest that µ-crystallin may play a role in regulating metabolism, perhaps through the control of thyroid hormone in muscle. Thus, humans who naturally express higher levels of µ-crystallin in their skeletal muscle may have an altered metabolism, comparable to the Crym tg mice.
    • Parents’ Experiences and Perspectives of Early Childhood Mental Health Services and Child Welfare

      Keyser, Daniel; Ahn, Haksoon; 0000-0002-7812-7496 (2021)
      Children birth to five in the child welfare system often experience trauma and are at risk for mental health problems and developmental delays (Barth, Scarborough et al., 2007; Cooper, Banghart & Aratani, 2010; Painter & Scannapieco, 2013; Whitaker, 2015). However, despite the high need for services, few children in child welfare receive them (Horwitz et al., 2012; Stahmer et al., 2005). Qualitative studies have used interviews with service providers to identify themes related to mental health service barriers (Hoffman, 2016). However, a gap remains in understanding birth parents’ experience accessing mental health services for children birth to five involved in child welfare. The purpose of this dissertation is to understand the experiences and perspectives of parents of toddlers and preschoolers in child welfare accessing mental health services. A mixed-methods study using qualitative methods as the primary method was conducted. Ten African American birth parents participated. Participants had children 1.5 to 5 years old and involved in child welfare when accessing mental health services. The qualitative data explored parents’ experiences and perspectives of mental health and child welfare services. The quantitative data provided descriptive statistics to assess child behavior, parent stress, parent psychological distress, and mental health service satisfaction compared to national norms. The qualitative data and the quantitative data were integrated to understand parents’ experience with early childhood mental health and child welfare services. The qualitative results of this study showed three major qualitative themes; complex mental health needs, navigating systems: child welfare and mental health, and equity and understanding. Quantitative results suggested most participants had their children placed in foster care, a high level of mental health need for participants’ children, participants had lower psychological distress, but had elevated levels of parenting stress. The integrated data showed participants referred to early childhood mental health services did not immediately seek services, but when they did, they often navigated through several barriers before receiving services. Some participants did not seek services until a major traumatic incident. A conceptual model was developed for early childhood mental health service utilization. Implications for practice, policy, and future research are discussed.
    • Multi-omic analysis of hearing difficulty risk loci and gene regulatory networks in the mammalian cochlea

      Kalra, Gurmannat; Ament, Seth A.; 0000-0002-4176-6489 (2021)
      The sensory cells of the mammalian cochlea do not have the capacity to regenerate. Studies have identified some genes and pathways that are critical for hair cell formation; however, the conditions necessary to regenerate fully functional hair cells remain unknown, as the genetic and genomic architecture of hearing loss and hair cell regeneration is only partially defined due to different experimental conditions and models used in each study. This dissertation improves our understanding of these conditions by taking a systems biology approach, combining diverse multi-omic data into genome-scale models for predicting target genes in the mammalian cochlea and in vitro systems. Using a meta-analysis of summary statistics from hearing-related traits, I identified 31 genome-wide significant risk loci for self-reported hearing difficulty. I then investigated the regulatory and cell specific expression for these loci and found that risk-associated genes were most strongly enriched for expression in cochlear epithelial cells, as well as for genes related to sensory perception and known Mendelian deafness genes, supporting their relevance to auditory function. My epigenomic and statistical fine-mapping most strongly supported 50 putative risk genes. To derive target genes from a model of hair cell regeneration, I characterized cochlear organoids derived from murine progenitor cells through bioinformatic analysis of single-cell RNA sequencing and bulk RNA sequencing data. For comparison, I integrated data from six previous studies of cochlear and utricular cell types in vivo and report an improved list of marker genes for each inner ear cell type. I found that cells in organoids mimic nearly all subtypes of supporting cells and hair cells in the cochlea and that the resulting hair cells reach a mature identity. I reconstructed a gene regulatory model from these data to gain insight into the transcription factors driving the trans-differentiation of progenitors to hair cells. My model identified known regulators of hair cell development and predicts novel regulatory factors. I validated these networks across transcriptional datasets, demonstrating dynamic changes in the expression of these transcription factors. Overall, I report new risk genes for hearing difficulty and new transcription factors that play a role in hair cell regeneration.
    • Comparing the impact of community-based mediation vs. prosecution on assault recidivism among adults

      Harmon-Darrow, Caroline; Bright, Charlotte Lyn; Sharpe, Tanya L.; 0000-0001-5553-1034 (2021)
      Although violence continues to damage community and family life, crime reduction victories over the past 30 years have come with the cost of expanding criminalization of human life, especially in communities of color. Solutions that reduce both violence and over-criminalization are urgently needed. Community-based mediation for diversion of misdemeanor assault cases has been practiced around the country since the 1970s, but little is known about its ability to prevent further violence between participants or reduce assault recidivism. Secondary analysis was conducted with assault cases (n = 162) within a Maryland Judiciary dataset from a quasi-experimental longitudinal comparison group study of criminal court mediation recidivism. Bivariate analyses and logistic regression with inverse proportion of treatment weighting were conducted. Semi-structured qualitative phone interviews (n = 19) were conducted with mediation participants in three counties of Maryland’s Eastern Shore and Baltimore City. Community-based mediation for misdemeanor assault had a small and statistically non-significant association with return to court at six months, versus usual court processes. Had assaults between couples been excluded, recidivism for mediation cases would have been one third of those treated as usual. For interviewees, the justice system was capable of protection and of worsening the danger and damage, and in mutual cases, respondents wanted to cut ties with it. Mediation could only resolve the conflict if participants were offered: safety; free expression; clarity about the incident; solutions; and active, neutral mediators. Outcomes included no further violence or court charges between participants, little interaction, and for some: loss of housing and livelihood, emotional closure, or endings that needed to happen. Mediators, community mediation centers, and local prosecutors’ offices could improve screening for intimate partner violence and work together to divert more mediatable cases earlier in the process via police officers and court commissioners. Future studies of mediation recidivism should consider comparison groups of people who chose to use the service but their fellow participant declined, and mediation evaluations with a dependent variable of self-reported violence would be best suited to understanding community mediation’s ability to meet its founding mission of community-created peace.
    • Evaluating Oropharyngeal Airway Volume in Patients with Class II Dental Relationships with Extractions vs Non-Extraction Orthodontic Treatment

      Feizi, Ariana Gabriela; Schneider, Monica, D.D.S., M.S. (2021)
      Purpose: The purpose of this study is to support the position of the AAO by demonstrating that the oropharyngeal volume does not decrease as a result of premolar extractions and orthodontic treatment. Materials and Methods: Cone-beam CT’s were obtained for twenty-seven orthodontic patients before and after treatment. Nine patients were treated with four premolar extractions, and eighteen treated non-extraction. Total oropharyngeal airway volume and minimum area of constriction were measured using InVivo Anatomage Software. Results: The initial and final airway volumes of the non-extraction group were correlated (p = 0.61). The total airway volume in the non-extraction cases showed a significant increase (p = .037). Conclusion: There was no significant change in oropharyngeal volume in Class II patients that underwent orthodontic treatment with extractions, however; patients that were treated non-extraction had a significant increase in oropharyngeal volume. There was no significant change in area of minimum constriction in either group.
    • Identifying the Molecular Mechanisms of Thymine DNA Glycosylase (TDG) Substrate Specificity

      Dow, Blaine Jacob; Drohat, Alexander Clark (2021)
      Thymine DNA glycosylase (TDG) helps maintain genomic integrity by removing thymine from G·T mispairs arising via deamination of 5-methylcytosine (mC). TDG employs strict regulation for both the opposing guanine, as well as the base downstream of the target thymine, in order to limit removal of thymine from canonical A·T pairs, as erroneous removal of thymine from A·T pairs is mutagenic and cytotoxic. TDG also excises 5-formylcytosine (fC) and 5-carboxylcytosine (caC), oxidation products of mC generated by ten-eleven translocation (TET) enzymes during active DNA demethylation. Remarkably, using single-turnover kinetics reactions to determine the maximum rate of substrate removal, k¬max, we find that TDG activity for fC and caC shows little dependence on the opposing base or the downstream base, revealing a major difference in specificity for excision of fC and caC relative to T. Using a novel 19F NMR approach to determine the flipping equilibrium for thymine into the TDG active site, we establish that specificity during thymine excision manifests largely by modulating the stability for thymine flipping in the active site. Structure-function analysis employing a variety of opposing bases reveals that both the thermodynamic stability (ΔH) of A·T pairs, as well as direct contacts between TDG and the opposing base, contribute to opposing base specificity. The differences in specificity observed for thymine versus fC or caC are likely explained by interactions between these substrates and the TDG active site. Structural information obtained from x-ray crystallography, combined with TDG mutational studies, identified several TDG active site residues that form stabilizing interactions with fC and caC, helping to both stabilize base flipping into the active site, as well as enhance the chemical steps of base excision. Conversely, two conserved residues in TDG, A145 and H151, limit stability of thymine in the active site, and destabilize thymine as a leaving group. As a result, additional contacts between both the opposing guanine, as well as the guanine downstream of the target thymine, appear necessary to orient thymine in a manner which produces stable, productive flipping into the active site.
    • Identification of core genes involved in Streptococcus pneumoniae host-pathogen interactions under diverse infections, and their potential as therapeutic targets

      D'Mello, Adonis; 0000-0001-6995-3617; Tettelin, Hervé (2021)
      Streptococcus pneumoniae (the pneumococcus) is a human-specific opportunistic pathogen that asymptomatically colonizes the nasopharynx. It is the leading cause of otitis media, communityacquired pneumonia, bacteremia and meningitis, as it can spread from the nasopharynx. It has been estimated that ~500,000 children under the age of 5 die annually due to pneumococcal infection and pneumococcal bacteremia and meningitidis has over 60% mortality rates in the elderly. It has also been established that influenza A co-infections enhance the progression from asymptomatic colonization to invasive disease, with clinically worsened outcomes. Utilization of antibiotics and pneumococcal conjugate vaccines has resulted in the rise of antibiotic resistance and emergence of non-vaccine serotypes, requiring identification of novel therapeutic targets. We hypothesized that there exist pneumococcal conserved genes, that are involved in these diverse forms of colonization, infection, and influenza co-infection. We sought to identify such genes using a combination of in silico, in vivo and ex vivo approaches. Through pangenomics and reverse vaccinology (in silico), and multi-species transcriptomics on a mouse model of pneumococcal colonization and invasive disease (in vivo), and a primary human lung epithelial model of pneumococcal and influenza co-infection (ex vivo), we observed mechanisms underlying diverse host-pathogen interactions and identified novel potential avenues for therapy from both the host and bacterial perspectives.
    • Targeting the Activator Protein-1 Complex to Inhibit Airway Smooth Muscle Cell Hyperproliferation in Asthma

      Defnet, Amy Elizabeth; Shapiro, Paul, Ph.D.; Kane, Maureen A. (2021)
      Hyperproliferation of airway smooth muscle (ASM) cells leads to increased ASM mass causing airway obstruction in inflammatory diseases such as asthma. Currently, there are no effective therapies to modulate ASM cell proliferation that contributes to debilitating bronchoconstriction in severe asthmatics. Previous studies suggest that activator protein-1 (AP-1) transcription factor expression is upregulated in airway cells in asthma and inhibition of AP-1 could mitigate the hyperproliferation of ASM cells. AP-1 activity has been shown to be enhanced by upstream extracellular signal-regulated kinase (ERK1/2) signaling or antagonized by retinoic acid receptor (RAR)-mediated signaling. The overall goal of the current study was to evaluate the therapeutic potential of a combination therapy of an ERK1/2 inhibitor and RAR agonist to modulate AP-1 complex formation and activation. Aim 1 studies tested the hypothesis that a novel function-selective ERK1/2 inhibitor, referred to as SF-3-030, would mitigate off-target toxicity while regulating platelet-derived growth factor (PDGF) induced AP-1 activity and ASM cell proliferation. In Aim 2 studies we evaluated the role of retinoids in controlling AP-1 complex formation and identified a RARγ isoform-specific agonist, CD1530, as a potential therapeutic option for inhibition of AP-1 activity and ASM cell hyperproliferation. Aim 3 studies determined whether a polypharmacological approach of combining ERK1/2 inhibition and RAR agonism to target two different aspects of the AP-1 complex activation and formation would have an additive effect in preventing ASM hyperproliferation. Overall, these studies help further our understanding of how AP-1 signaling causes the hyperproliferation of ASM cells while elucidating possible therapeutic treatment options through ERK1/2 inhibition and RAR agonism.
    • Tongue Muscle Shortening Differences in Glossectomy Versus Non-Glossectomy Patients

      Dao, Anh; Stone, Maureen L. (2021)
      In cancers that affect the tongue, the most common treatment is glossectomy, a procedure that can have substantial effects on a patient’s intelligibility. We are seeking to identify the effect of this resection on the use of four muscles – genioglossus, transversus, verticalis, and superior longitudinal, which comprise the bulk of the tongue. MRI data was used to study differences in tongue muscle shortening patterns during the speech task “a thing” between patients who have undergone glossectomies and controls who have not. Speech data was collected from 2D tagged-MRI movies and reconstructed into 3D volumes at 26 timeframes. Velocity fields and tissue points were extracted and shortening was calculated to study how the muscles were used by glossectomies vs. controls to protract and retract the tongue during /θ/. The results reveal differences in function between the two groups, and potential compensation strategies for glossectomy patients.
    • MyD88 Co-stimulation in CD8+ T Cells Improves Tumor Immunotherapy in Allogeneic and Syngeneic Models

      Ciavattone, Nicholas; Cao, Xuefang; Davila, Eduardo, Ph.D.; 0000-0001-9265-8202 (2021)
      Improving the efficacy of T cell therapies for solid tumors and leukemias could improve clinical outcomes. In leukemia, allogeneic hematopoietic cell transplantation and donor lymphocyte infusions can be potentially curative, however, tumor evasion of the graft-versus-leukemia effects still limit their efficacy. In the solid tumor microenvironment, immune suppressive myeloid cells inhibit T cell activation which can be detrimental to anti-tumor T cell responses. Toll-like Receptor/MyD88 signaling in cytotoxic T cells can provide a strong co-stimulation signal to improve T cell activation, function, and efficacy to counteract evasion mechanisms in hematopoietic and solid tumors. Unfortunately, TLR agonists lack specificity to T cells and may induce hyper inflammation or induce pro-tumor effects. Rather than provide TLR agonist therapy in leukemia and solid tumors, there exists potential to modify or engineer T cells to provide a direct MyD88 co-stimulus. Our research group developed a CD8α:MyD88 T cell co-receptor that mimics TLR co-stimulation in conjunction with T cell receptor activation. Our goal was to first determine whether this engineered T cell co-receptor could enhance graft-versus-leukemia responses in allogeneic hematopoietic cell transplantation and donor lymphocyte infusion therapies. In a suppressive solid tumor, we asked if MyD88 co-receptor could improve T cell activation and function in a suppressive tumor microenvironment. Using multiple experimental transplant models, we found that MyD88 co-stimulation in donor CD8+ T cells could improve the graft versus tumor response with some non-lethal increases in graft-versus-host disease. Looking further, we found that the CD8α:MyD88 co-receptor increased donor cytotoxic T cell proliferation, survival, and function in vivo. Donor CD8α:MyD88 T cells were able to directly kill tumor better than transduced controls. In the second part of this project we found that cytotoxic T cells receiving a synthetic MyD88 co-stimulation maintained strong basal activation in the presence of myeloid suppression. In the suppressive B16-GMCSF melanoma model, CD8α:MyD88 T cell were able to control tumor growth and reduce populations of suppressive myeloid cells in the tumor. These data show that augmented MyD88 co-stimulation in cytotoxic T cells could benefit patients undergoing both autologous and allogeneic T cell therapies.
    • Epidemiology of Plasmodium falciparum infection and clinical malaria among infants in Malawi

      Andronescu, Liana; Laufer, Miriam K.; 0000-0003-3342-7820 (2021)
      Background: Few malaria interventions are designed to target infants under six months. The burden of malaria in infancy and its long-term health impact needs to be better characterized to inform surveillance and treatment guidelines for this age group. Objectives: The aims of this study were to (a) assess the effect of intermittent preventive treatment during pregnancy (IPTp) regimens on the risk of malaria in infancy, (b) characterize P. falciparum infection and clinical malaria in the first six months and the risk of subsequent malaria, and (c) assess effects of P. falciparum infection and clinical malaria exposure in first six months on weight and hemoglobin concentration after six months. Methods: Longitudinal cohort data collected from infants in southern Malawi between 2016 and 2019 was analyzed using Cox proportional hazards models, Poisson generalized estimating equations with a log link function, and linear mixed effects models. Results: Maternal IPTp regimen had no effect on infant incidence of clinical malaria (IRR=1.03; 95%CI: 0.58–1.86) or incidence of P. falciparum infection (IRR=1.18; 95%CI: 0.92–1.55) before two years. Maternal IPTp was not significantly associated with infant’s time to first infection (HR=1.05; 95%CI: 0.8–1.39) or clinical malaria (HR=0.92; 95%CI: 0.58–1.48). Exposure to any malaria before six months was associated with higher incidence of any malaria (IRR=1.27; 95%CI: 1.06–1.52) and clinical malaria (IRR=1.76; 95%CI: 1.42–2.19) between 6 and 24 months. Clinical malaria exposure before first six months was also associated with higher incidence of any malaria (IRR=1.64; 95%CI: 1.38–1.94) and clinical malaria (IRR=1.85, 95%CI:1.48–2.32) between 6 and 24 months. Exposure to asymptomatic P. falciparum infection before six months was associated with lower weight-for-age z-scores during follow-up (p=0.02) and exposure to clinical malaria before six months was associated with lower hemoglobin concentrations during follow-up (p=0.02). Conclusion: Prevention of malaria during pregnancy does not reduce infant risk of malaria and malaria infection before six months is associated with higher malaria incidence, lower weight-for-age Z-scores, and lower hemoglobin concentrations in early childhood. Early malaria infection may be an indication of high exposure risk and a marker for downstream health outcomes.
    • Characterizing the Influence of Resident Microbiota and Mosquito Factors on Plasmodium Infections of Anopheles Mosquitoes

      Bogale, Haikel; Serre, David; 0000-0002-1907-788X (2021)
      Pathogens transmitted by mosquitoes are responsible for illnesses that cause nearly 700 million cases every year. A significant proportion of this morbidity is due to malaria, a disease caused by Plasmodium parasites and spread through the bites of infected Anopheles mosquitoes. While we have seen a reduction in malaria mortality rates thanks to the development of antimalarial therapeutics and entomological controls, there is a potential of malaria resurgence associated with the emergence and spread of antimalarial and insecticide resistance, highlighting the need for additional malaria control strategies. Malaria transmission occurs only if one Plasmodium parasite develops through key stages in the mosquito, including passing through the midgut, which harbors a microbial community that can influence Plasmodium transmission. Despite the opportunities they present for novel interventions, the development of Plasmodium sporozoites and the factors that shape the microbiota in mosquitoes are incompletely understood. Here, I sought to provide new insights into the microbial variations of wild-caught mosquitoes and the transcriptional regulatory programs of Plasmodium sporozoites. To this end, I simultaneously characterized the bacterial composition of 665 individual field-caught Anopheles mosquitoes in addition to their species, insecticide resistance genotype, blood-meal status, and infection status. My analyses revealed that mosquito collection site is the main driver of the microbial diversity, while other factors showed marginal or non-significant contribution. I also generated scRNA-seq data from 36,958 sporozoites of three Plasmodium species and collected from multiple anatomical sites of the mosquito and developmental stages of the parasite in an effort to better understand parasite developmental processes critical for malaria transmission. I identified transcriptional variations among salivary gland sporozoites of different Plasmodium species, patterns of gene regulation accompanying the journey of Plasmodium berghei sporozoites, and novel candidates potentially critical for mechanisms involved in sporozoite maturation. In addition, my analyses highlighted novel extensive transcriptional heterogeneity among sporozoites isolated from the same anatomical site, indicating asynchronous sporozoite development in the mosquito, that is regulated by intrinsic and environmental factors. Altogether, my findings improve our understanding of factors that influence malaria parasite transmission and lay the groundwork for identifying key transmission components, to inform development of novel intervention strategies.
    • Probiotic Use for the Primary Prevention of Clostridioides difficile infection

      Heil, Emily; Leekha, Surbhi; 0000-0002-6644-6684 (2020)
      Primary prevention of C. difficile infection (CDI) is a priority for hospitals and probiotics have the potential to interfere with colonization and/or infection with C. difficile offering an opportunity to enhance ongoing primary prevention strategies. The overall objective of this study was to evaluate the impact of a hospital-wide computerized clinical decision support system tool to prescribe probiotics to eligible adult patients receiving antibiotics for the primary prevention of CDI. After implementation of the tool, the odds of CDI was 1.41 in eligible patients compared to the pre-intervention time period (aOR 1.41, 95% CI 1.11, 1.79). A propensity score matched analysis showed that patients who received probiotics did not have lower rates of CDI compared to those who did not (OR 1.46, 95% CI 0.87, 2.45). Based on these findings, the use of probiotics for the primary prevention of CDI is not supported.
    • Discovery of a thalamic integrator for action reinforcement

      Cover, Kara; Mathur, Brian N. (Brian Neil); 0000-0003-3938-9669 (2020)
      The pursuit and acquisition of rewards is essential for survival. The input nucleus of the basal ganglia, the striatum, facilitates the selection, execution, and reinforcement of reward obtaining actions. The contributions of excitatory input from cortical regions and the influence of dopaminergic signaling on corticostriatal synapses to these vital functions has been studied extensively. A relative underappreciation for thalamic contributions to striatal signaling has consequently excluded this major excitatory input from basal ganglia models of action selection and reinforcement. I investigated the contributions of the rostral intralaminar thalamic nuclei to striatal-mediated action sequence performance using a combination of ex vivo physiological and in vivo behavioral assays. In the present dissertation, I characterize mechanisms by which this thalamic projection interacts with striatal neuronal populations and modulates dopaminergic signaling to sculpt output activity. I further identify that the rostral intralaminar nuclei causally contribute to action execution in the pursuit of rewards. This work serves to further understanding of how thalamic inputs participate in action selection and reinforcement.
    • Melanocyte stem cell subpopulations show distinct pigmentation and regenerative potential

      Tandukar, Bishal; Hornyak, Thomas; 0000-0002-9650-1664 (2020)
      Melanocyte stem cells (McSCs) are key components of the hair follicle (HF) stem cell system. They are derived from neural crest during embryogenesis and are responsible for regeneration of differentiated melanocytes during successive HF cycles. We have described McSC subsets that can be distinguished by CD34 expression. CD34+ McSCs are located within the bulge/lower permanent portion (LPP) while CD34- McSCs are in the secondary hair germ (SHG) during the resting stage (telogen). Whether these two cell subpopulations are maintained separately or exist in a developmental hierarchy is not yet known. The goal of my thesis is to explore whether (a) the two McSC subpopulations are functionally distinct, (b) if they are maintained independently throughout the HF cycle and (c) their role in generation of mature melanocytes. To study McSCs, we engineered the Dct-H2BGFP bitransgenic mouse. We confirm that this animal model accurately identifies melanoblasts, McSCs and mature melanocytes by constitutive GFP expression that can be regulated by doxycycline. Using our Dct-H2BGFP mouse, we compared the transcriptomes of bulge and SHG McSC subsets by genome-wide expression profiling (RNA-seq). This study, along with functional in vitro and in vivo assays, confirms that CD34+/bulge share characteristics of neural crest stem cells with multilineage potential while CD34-/SHG McSCs represent a stem cell population that is more committed to melanocyte differentiation. To further understand the relationship between two McSC subpopulations, we traced their proliferation throughout the HF cycle and found that proliferation of SHG McSCs gives rise to mature melanocytes. The analysis also surprisingly revealed quiescent CD34- melanocytes maintained outside of the HF bulge region throughout anagen retaining the stem cell phenotype, identifying a SHG McSC-like population outside telogen suggesting independent or quasi-independent maintenance of the two McSC subpopulations. Taken together, our study identifies heterogeneous McSC subpopulations with distinct pigmentation and regenerative potential for the first time. Strikingly, CD34+/bulge McSCs exhibited the ability to myelinate neurons in vivo, revealing a novel therapeutic possibility for demyelinating disorders and traumatic nerve injury.