Syndicate content
Recent documents in eScholarship@UMMS
Updated: 2 hours 20 min ago

An observational study of social and emotional support in smoking cessation Twitter accounts: content analysis of tweets

Mon, 03/30/2015 - 10:28am

BACKGROUND: Smoking continues to be the number one preventable cause of premature death in the United States. While evidence for the effectiveness of smoking cessation interventions has increased rapidly, questions remain on how to effectively disseminate these findings. Twitter, the second largest online social network, provides a natural way of disseminating information. Health communicators can use Twitter to inform smokers, provide social support, and attract them to other interventions. A key challenge for health researchers is how to frame their communications to maximize the engagement of smokers.

OBJECTIVE: Our aim was to examine current Twitter activity for smoking cessation.

METHODS: Active smoking cessation related Twitter accounts (N=18) were identified. Their 50 most recent tweets were content coded using a schema adapted from the Roter Interaction Analysis System (RIAS), a theory-based, validated coding method. Using negative binomial regression, the association of number of followers and frequency of individual tweet content at baseline was assessed. The difference in followership at 6 months (compared to baseline) to the frequency of tweet content was compared using linear regression. Both analyses were adjusted by account type (organizational or not organizational).

RESULTS: The 18 accounts had 60,609 followers at baseline and 68,167 at 6 months. A total of 24% of tweets were socioemotional support (mean 11.8, SD 9.8), 14% (mean 7, SD 8.4) were encouraging/engagement, and 62% (mean 31.2, SD 15.2) were informational. At baseline, higher frequency of socioemotional support and encouraging/engaging tweets was significantly associated with higher number of followers (socioemotional: incident rate ratio [IRR] 1.09, 95% CI 1.02-1.20; encouraging/engaging: IRR 1.06, 95% CI 1.00-1.12). Conversely, higher frequency of informational tweets was significantly associated with lower number of followers (IRR 0.95, 95% CI 0.92-0.98). At 6 months, for every increase by 1 in socioemotional tweets, the change in followership significantly increased by 43.94 (P = .027); the association was slightly attenuated after adjusting by account type and was not significant (P = .064).

CONCLUSIONS: Smoking cessation activity does exist on Twitter. Preliminary findings suggest that certain content strategies can be used to encourage followership, and this needs to be further investigated.

Testing item response theory invariance of the standardized Quality-of-life Disease Impact Scale (QDIS) in acute coronary syndrome patients: differential functioning of items and test

Mon, 03/30/2015 - 10:28am

PURPOSE: The Quality-of-life (QOL) Disease Impact Scale (QDIS(R)) standardizes the content and scoring of QOL impact attributed to different diseases using item response theory (IRT). This study examined the IRT invariance of the QDIS-standardized IRT parameters in an independent sample.

METHOD: The differential functioning of items and test (DFIT) of a static short-form (QDIS-7) was examined across two independent sources: patients hospitalized for acute coronary syndrome (ACS) in the TRACE-CORE study (N = 1,544) and chronically ill US adults in the QDIS standardization sample. "ACS-specific" IRT item parameters were calibrated and linearly transformed to compare to "standardized" IRT item parameters. Differences in IRT model-expected item, scale and theta scores were examined. The DFIT results were also compared in a standard logistic regression differential item functioning analysis.

RESULTS: Item parameters estimated in the ACS sample showed lower discrimination parameters than the standardized discrimination parameters, but only small differences were found for thresholds parameters. In DFIT, results on the non-compensatory differential item functioning index (range 0.005-0.074) were all below the threshold of 0.096. Item differences were further canceled out at the scale level. IRT-based theta scores for ACS patients using standardized and ACS-specific item parameters were highly correlated (r = 0.995, root-mean-square difference = 0.09). Using standardized item parameters, ACS patients scored one-half standard deviation higher (indicating greater QOL impact) compared to chronically ill adults in the standardization sample.

CONCLUSION: The study showed sufficient IRT invariance to warrant the use of standardized IRT scoring of QDIS-7 for studies comparing the QOL impact attributed to acute coronary disease and other chronic conditions.

Quadrimodal distribution of death after trauma suggests that critical injury is a potentially terminal disease

Mon, 03/30/2015 - 10:28am

BACKGROUND: Patterns of death after trauma are changing due to advances in critical care. We examined mortality in critically injured patients who survived index hospitalization.

METHODS: Retrospective analysis of adults admitted to a Level-1 trauma center (1/1/2000-12/31/2010) with critical injury was conducted comparing patient characteristics, injury, and resource utilization between those who died during follow-up and survivors.

RESULTS: Of 1,695 critically injured patients, 1,135 (67.0%) were discharged alive. As of 5/1/2012, 977/1,135 (86.0%) remained alive; 75/158 (47.5%) patients who died during follow-up, died in the first year. Patients who died had longer hospital stays (24 vs. 17 days) and ICU LOS (17 vs. 8 days), were more likely to undergo tracheostomies (36% vs. 16%) and gastrostomies (39% vs. 16%) and to be discharged to rehabilitation (76% vs. 63%) or skilled nursing (13% vs. 5.8%) facilities than survivors. In multivariable models, male sex, older age, and longer ICU LOS predicted mortality. Patients with ICU LOS >16 days had 1.66 odds of 1-year mortality vs. those with shorter ICU stays.

CONCLUSIONS: ICU LOS during index hospitalization is associated with post-discharge mortality. Patients with prolonged ICU stays after surviving critical injury may benefit from detailed discussions about goals of care after discharge.

Chocolate-candy consumption and 3-year weight gain among postmenopausal U.S. women

Mon, 03/30/2015 - 10:28am

OBJECTIVE: To test the hypothesis that greater chocolate-candy intake is associated with more weight gain in postmenopausal women.

METHODS: A prospective cohort study involved 107,243 postmenopausal American women aged 50-79 years (mean = 60.7) at enrollment in the Women's Health Initiative, with 3-year follow-up. Chocolate-candy consumption was assessed by food frequency questionnaire, and body weight was measured. Linear mixed models, adjusted for demographic, socio economic, anthropomorphic, and behavioral variables, were used to test our main hypotheses.

RESULTS: Compared with women who ate a 1 oz ( approximately 28 g) serving of chocolate candy < 1 per month, those who ate this amount 1 per month to < 1 per week, 1 per week to < 3 per week and > =3 per week showed greater 3-year prospective weight gains (kg) of 0.76 (95% CI: 0.66, 0.85), 0.95 (0.84, 1.06), and 1.40 (1.27, 1.53), respectively, (P for linear trend < 0.0001). Each additional 1 oz/day was associated with a greater 3-year weight gain (kg) of 0.92 (0.80, 1.05). The weight gain in each chocolate-candy intake level increased as BMI increased above the normal range (18.5-25 kg/m(2) ), and was inversely associated with age.

CONCLUSIONS: Greater chocolate-candy intake was associated with greater prospective weight gain in this cohort of postmenopausal women.

Lessons Learned from the Development and Implementation of Two Internet-enhanced Culturally Relevant Physical Activity Interventions for Young Overweight African-American Women

Mon, 03/30/2015 - 10:28am

This research team has designed and implemented 2 culturally relevant, Internet-enhanced physical activity (PA) interventions for overweight/obese African-American female college students. Presumably, these are the only prospectively designed, culturally relevant interventions using the Internet to promote PA among African-American women. Due to the limited research on this topic, the experiences associated the design and implementation of these studies were syntesized and 5 key lessons learned from this research were formulated. Findings provide insight for researchers to consider when developing Internet-based PA promotion interventions for African-American women. Lessons learned included: 1) Elicit and incorporate feedback from the target population throughout development of an Internet-based PA promotion tool; 2) Incorporate new and emerging technologies into Internet-enhanced PA programs; 3) Maintain frequent participant contact and provide frequent incentives to promote participant engagement; 4) Supplement Internet-based efforts with face-to-face interactions; 5) Include diverse images of African-American women and culturally relevant PA-related information in Internet-based PA promotion materials.

Thirty day hospital re-admissions in patients with non ST-segment elevation acute myocardial infarction

Mon, 03/30/2015 - 10:28am

BACKGROUND: Limited data exist about relatively recent trends in the magnitude and characteristics of patients who are rehospitalized shortly after admission for a non ST-segment elevation acute myocardial infarction (NSTEMI). This observational study describes decade-long trends (1999-2009) in the magnitude and characteristics of patients readmitted to the hospital within 30 days of hospitalization for an incident (initial) episode of NSTEMI.

METHODS: We reviewed the medical records of 2,249 residents of the Worcester (MA) metropolitan area who were hospitalized for an initial NSTEMI in 6 biennial periods between 1999 and 2009 at 3 central MA medical centers.

RESULTS: The average age of our study population was 72 years, 90% were white, and 46% were women. The proportion of patients who were readmitted to the hospital for any cause within 30 days after discharge for a NSTEMI remained unchanged between 1999 and 2009 (approximately 15%) in both crude and multivariable adjusted analyses. Slight declines were observed for cardiovascular disease-related 30-day readmissions over the ten-year study period. Women, elderly patients, those with multiple chronic comorbidities, a prolonged index hospitalization, and patients who developed heart failure during their index hospitalization were at higher risk for being readmitted within 30-days than respective comparison groups.

CONCLUSIONS: Thirty day hospital readmission rates after hospital discharge for a first NSTEMI remained stable between 1999 and 2009. We identified several groups at higher risk for hospital readmission in whom further surveillance efforts and/or tailored educational and treatment approaches remain needed.

Diet quality and history of gestational diabetes mellitus among childbearing women, United States, 2007-2010

Mon, 03/30/2015 - 10:28am

INTRODUCTION: Women with a history of gestational diabetes mellitus (GDM) have elevated risk of developing type 2 diabetes. Diet quality plays an important role in the prevention of type 2 diabetes. We compared diet quality among childbearing women with a history of GDM with the diet quality of childbearing women without a history of GDM.

METHODS: We used data from the National Health and Nutrition Examination Survey for 2007 through 2010. We included women without diabetes aged 20 to 44 years whose most recent live infant was born within the previous 10 years and who completed two 24-hour dietary recalls. The Healthy Eating Index (HEI)-2010 estimated overall and component diet quality. Multivariable linear regression models estimated the association between a history of GDM and current diet quality, adjusting for age, education, smoking status, and health risk for diabetes.

RESULTS: A history of GDM was reported by 7.7% of women. Compared with women without a history of GDM, women with a history of GDM had, on average, 3.4 points lower overall diet quality (95% confidence interval [CI], -6.6 to -0.2) and 0.9 points lower score for consumption of green vegetables and beans (95% CI, -1.4 to -0.4). Other dietary component scores did not differ by history of GDM.

CONCLUSION: In the United States, women with a history of GDM have lower diet quality compared with women who bore a child and do not have a history of GDM. Improving diet quality may be a strategy for preventing type 2 diabetes among childbearing women.

Whole-exome sequencing identifies tetratricopeptide repeat domain 7A (TTC7A) mutations for combined immunodeficiency with intestinal atresias

Mon, 03/23/2015 - 2:58pm

BACKGROUND: Combined immunodeficiency with multiple intestinal atresias (CID-MIA) is a rare hereditary disease characterized by intestinal obstructions and profound immune defects.

OBJECTIVE: We sought to determine the underlying genetic causes of CID-MIA by analyzing the exomic sequences of 5 patients and their healthy direct relatives from 5 unrelated families.

METHODS: We performed whole-exome sequencing on 5 patients with CID-MIA and 10 healthy direct family members belonging to 5 unrelated families with CID-MIA. We also performed targeted Sanger sequencing for the candidate gene tetratricopeptide repeat domain 7A (TTC7A) on 3 additional patients with CID-MIA.

RESULTS: Through analysis and comparison of the exomic sequence of the subjects from these 5 families, we identified biallelic damaging mutations in the TTC7A gene, for a total of 7 distinct mutations. Targeted TTC7A gene sequencing in 3 additional unrelated patients with CID-MIA revealed biallelic deleterious mutations in 2 of them, as well as an aberrant splice product in the third patient. Staining of normal thymus showed that the TTC7A protein is expressed in thymic epithelial cells, as well as in thymocytes. Moreover, severe lymphoid depletion was observed in the thymus and peripheral lymphoid tissues from 2 patients with CID-MIA.

CONCLUSIONS: We identified deleterious mutations of the TTC7A gene in 8 unrelated patients with CID-MIA and demonstrated that the TTC7A protein is expressed in the thymus. Our results strongly suggest that TTC7A gene defects cause CID-MIA. Mosby, Inc. All rights reserved.

Cryptococcosis-IRIS is associated with lower cryptococcus-specific IFN-gamma responses before antiretroviral therapy but not higher T-cell responses during therapy

Mon, 03/23/2015 - 2:58pm

BACKGROUND: Cryptococcosis-associated immune reconstitution inflammatory syndrome (C-IRIS) may be driven by aberrant T-cell responses against cryptococci. We investigated this in human immunodeficiency virus (HIV)-infected patients with treated cryptococcal meningitis (CM) commencing combination antiretroviral therapy (cART).

METHODS: Mitogen- and cryptococcal mannoprotein (CMP)-activated (CD25+CD134+) CD4+ T cells and -induced production of interferon-gamma (IFN-gamma), IL-10, and CXCL10 were assessed in whole blood cultures in a prospective study of 106 HIV-CM coinfected patients.

RESULTS: Patients with paradoxical C-IRIS (n = 27), compared with patients with no neurological deterioration (no ND; n = 63), had lower CMP-induced IFN-gamma production in 24-hour cultures pre-cART and 4 weeks post-cART (P = .0437 and .0257, respectively) and lower CMP-activated CD4+ T-cell counts pre-cART (P = .0178). Patients surviving to 24 weeks had higher proportions of mitogen-activated CD4+ T cells and higher CMP-induced CXCL10 and IL-10 production in 24-hour cultures pre-cART than patients not surviving (P = .0053, .0436 and .0319, respectively). C-IRIS was not associated with higher CMP-specific T-cell responses before or during cART.

CONCLUSION: Greater preservation of T-cell function and higher CMP-induced IL-10 and CXCL10 production before cART are associated with improved survival while on cART. Lower CMP-induced IFN-gamma production pre-cART, but not higher CMP-specific T-cell responses after cART, were risk factors for C-IRIS.

A rare presentation of hypertrophic olivary degeneration secondary to primary central nervous system lymphoma

Mon, 03/23/2015 - 2:58pm

Case report: A 71-year-old man presented with a 2-week history of nausea, vomiting, unsteady gait, and diplopia.

Targeted expression of human folylpolyglutamate synthase for selective enhancement of methotrexate chemotherapy in osteosarcoma cells

Mon, 03/23/2015 - 2:58pm

The antifolate methotrexate (MTX) is an important chemotherapeutic agent for treatment of osteosarcoma. This drug is converted intracellularly into polyglutamate derivates by the enzyme folylpolyglutamate synthase (FPGS). MTX polyglutamates show an enhanced and prolonged cytotoxicity in comparison to the monoglutamate. In the present study, we proved the hypothesis that transfer of the human fpgs gene into osteosarcoma cells may augment their MTX sensitivity. For this purpose, we employed the human osteocalcin (OC) promoter, which had shown marked osteosarcoma specificity in promoter studies using different luciferase assays in osteosarcoma and non-osteosarcoma cell lines. A recombinant lentiviral vector was generated with the OC promoter driving the expression of fpgs and the gene for enhanced green fluorescent protein (egfp), which was linked to fpgs by an internal ribosomal entry site (IRES). As the vector backbone contained only a self-inactivating viral LTR promoter, any interference of the OC promoter by unspecific promoter elements was excluded. We tested the expression of FPGS and enhanced green fluorescent protein (EGFP) after lentiviral transduction in various osteosarcoma cell lines (human MG-63 cells and TM 791 cells; rat osteosarcoma (ROS) 17/2.8 cells) and non-osteogenic tumor cell lines (293T human embryonic kidney cells, HeLa human cervix carcinoma cells). EGFP expression and MTX sensitivity were assessed in comparison with non-transduced controls. Whereas the OC promoter failed to enhance MTX sensitivity via FPGS expression in non-osteogenic tumor cell lines, the OC promoter mediated a markedly increased MTX cytotoxicity in all osteosarcoma cell lines after lentiviral transduction. The present chemotherapy-enhancing gene therapy system may have great potential to overcome in future MTX resistance in human osteosarcomas.

A small jab - a big effect: nonspecific immunomodulation by vaccines

Mon, 03/23/2015 - 2:58pm

Recent epidemiological studies have shown that, in addition to disease-specific effects, vaccines against infectious diseases have nonspecific effects on the ability of the immune system to handle other pathogens. For instance, in randomized trials tuberculosis and measles vaccines are associated with a substantial reduction in overall child mortality, which cannot be explained by prevention of the target disease. New research suggests that the nonspecific effects of vaccines are related to cross-reactivity of the adaptive immune system with unrelated pathogens, and to training of the innate immune system through epigenetic reprogramming. Hence, epidemiological findings are backed by immunological data. This generates a new understanding of the immune system and about how it can be modulated by vaccines to impact the general resistance to disease.

Accuracy of Dietary Reference Intakes for determining energy requirements in girls

Mon, 03/23/2015 - 2:58pm

BACKGROUND: The most recent Dietary Reference Intakes (DRIs) (2002) for energy were based on pooled data from convenience samples of individuals with energy expenditure determined by using doubly labeled water (DLW). To our knowledge, the accuracy of these intake estimates has not been assessed in children.

OBJECTIVE: We assessed the accuracy of DRI prediction equations for determining daily energy needs in girls by comparing the individual-level prediction of estimated energy requirements with the measured value of total energy expenditure (TEE) from DLW, which is considered the gold standard.

DESIGN: In this cross-sectional analysis, we measured the resting metabolic rate (RMR) by using indirect calorimetry and TEE by using DLW in 161 nonobese premenarcheal girls aged 8-12 y. The activity factor TEE/RMR was used to categorize the physical activity level used in DRI equations.

RESULTS: We observed a strong linear relation between TEE by using DLW and estimated energy requirements predicted from DRI equations (Pearson's r = 0.78, P < 0.0001, R(2) = 0. 61). The DRI-predicted energy requirements underestimated measured TEE by ~120 kcal on average. The overall mean (+/-SD) error in the sample was -121.3 +/- 163.9 kcal. The average (+/-SD) percentage error in the sample was -5.8 +/- 7.9%. Seventy percent of participants had predicted TEE values < /=10% of measured TEE.

CONCLUSIONS: DRI equations for girls predict well for the group. The use of these equations for individuals may result in the underestimation of energy requirements for a significant percentage of girls.

Post-translational modification by cysteine protects Cu/Zn-superoxide dismutase from oxidative damage

Mon, 03/23/2015 - 2:58pm

Reactive oxygen species (ROS) are cytotoxic. To remove ROS, cells have developed ROS-specific defense mechanisms, including the enzyme Cu/Zn superoxide dismutase (SOD1), which catalyzes the disproportionation of superoxide anions into molecular oxygen and hydrogen peroxide. Although hydrogen peroxide is less reactive than superoxide, it is still capable of oxidizing, unfolding, and inactivating SOD1, at least in vitro. To explore the relevance of post-translational modification (PTM) of SOD1, including peroxide-related modifications, SOD1 was purified from postmortem human nervous tissue. As much as half of all purified SOD1 protein contained non-native post-translational modifications (PTMs), the most prevalent modifications being cysteinylation and peroxide-related oxidations. Many PTMs targeted a single reactive SOD1 cysteine, Cys111. An intriguing observation was that unlike native SOD1, cysteinylated SOD1 was not oxidized. To further characterize how cysteinylation may protect SOD1 from oxidation, cysteine-modified SOD1 was prepared in vitro and exposed to peroxide. Cysteinylation conferred nearly complete protection from peroxide-induced oxidation of SOD1. Moreover, SOD1 that has been cysteinylated and peroxide oxidized in vitro comprised a set of PTMs that bear a striking resemblance to the myriad of PTMs observed in SOD1 purified from human tissue.

Inhibition of heat shock protein 90 alleviates steatosis and macrophage activation in murine alcoholic liver injury

Mon, 03/23/2015 - 2:58pm

BACKGROUND and AIMS: Heat shock protein 90 (hsp90) is an emerging therapeutic target in chronic liver diseases. Hsp90 plays an important role in liver immune cell activation; however its role in alcoholic liver disease (ALD) remains elusive. Here we hypothesize that hsp90 is crucial in alcohol induced steatosis and pro-inflammatory cytokine production. To test this hypothesis, we employed a pharmacological inhibitor of hsp90, 17-DMAG (17-Dimethylamino-ethylamino-17-demethoxygeldanamycin) in an in vivo mouse model of acute and chronic alcoholic liver injury.

METHODS: C57BL/6 mice were given either a single dose of ethanol via oral gavage (acute) or chronically fed alcohol for 2 weeks followed by oral gavage (chronic-binge). 17-DMAG was administered during or at the end of feeding. Liver injury parameters, inflammatory cytokines and lipid metabolism genes were analysed.

RESULTS: Our results reveal increased expression of hsp90 in human and mouse alcoholic livers. In vivo inhibition of hsp90, using 17-DMAG, not only prevented but also alleviated alcoholic liver injury, determined by lower serum ALT, AST and reduced hepatic triglycerides. Mechanistic analysis showed that 17-DMAG decreased alcohol mediated oxidative stress, reduced serum endotoxin, decreased inflammatory cells, and diminished sensitization of liver macrophages to LPS, resulting in downregulation of CD14, NFkappaB inhibition, and decreased pro-inflammatory cytokine production. Hsp90 inhibition decreased fatty acid synthesis genes via reduced nuclear SREBP-1 and favoured fatty acid oxidation genes via PPARalpha.

CONCLUSIONS: Inhibition of hsp90 decreased alcohol induced steatosis and pro-inflammatory cytokines and inhibited alcoholic liver injury. Hsp90 is therefore relevant in human alcoholic cirrhosis and a promising therapeutic target in ALD. Elsevier B.V. All rights reserved.

Post-transplant lymphoproliferative disease (PTLD): risk factors, diagnosis, and current treatment strategies

Mon, 03/23/2015 - 2:58pm

Post-transplant lymphoproliferative diseases (PTLD) are heterogeneous lymphoid disorders ranging from indolent polyclonal proliferations to aggressive lymphomas that complicate solid organ or hematopoietic transplantation. Risk factors for PTLD include viral infections, degree of immunosuppression, recipient age and race, allograft type, and host genetic variations. Clinically, extra-nodal disease is common including 10-15 % presenting with central nervous system (CNS) disease. Most PTLD cases are B cell (5-10 % T/NK cell or Hodgkin lymphoma), while over one-third are EBV-negative. World Health Organization (WHO) diagnostic categories are: early lesions, polymorphic, and monomorphic PTLD; although in practice, a clear separation is not always possible. Therapeutically, reduction in immunosuppression remains a mainstay, and recent data has documented the importance of rituximab +/- combination chemotherapy. Therapy for primary CNS PTLD should be managed according to immunocompetent CNS paradigms. Finally, novel treatment strategies for PTLD have emerged, including adoptive immunotherapy and rational targeted therapeutics (e.g., anti-CD30 based therapy and downstream signaling pathways of latent membrane protein-2A).

Role of Astrocytes in Sculpting Neuronal Circuits in the Drosophila CNS: A Dissertation

Sun, 03/22/2015 - 10:26pm

The nervous system is composed of neurons and glia. Glial cells have been neglected and thought to have only a supportive role in the nervous system, even though ~60% of the mammalian brain is composed of glia. Yet, in recent years, it has been shown that glial cells have several important functions during the development, maintenance and function of the nervous system. Glial cells regulate both pre and post mitotic neuronal survival during normal development and maintenance of the nervous system as well as after injury, are necessary for axon guidance, proper axon fasciculation, and myelination during development, promote synapse formation, regulate ion balance in the extracellular space, are required for normal synaptic function, and have immune functions in the brain. Although glia have crucial roles in nervous system development and function, there are still much unknown about the underlying molecular mechanisms in glial development, function and glial-neuronal communication.

Drosophila offers great opportunity to study glial biology, with its simple yet sophisticated and stereotypic nervous system. Glial cells in flies show great complexity similar to the mammalian nervous system, and many cellular and molecular functions are conserved between flies and mammals. In this study, I use Drosophila as a model organism to study the function of one subtype of glia: astrocytes. The role of astrocytes in synapse formation, function and maintenance has been a focus of study. However, their role in engulfment and clearance of neuronal debris during development remains unexplored.

I generated a driver line that enables the study of astrocytes in Drosophila.In chapter two of this thesis, I characterize astrocytes during metamorphosis, when extensive neuronal remodeling takes place. I found that astrocytes turn into phagocytes in a cell-autonomous, steroid-dependent manner, by upregulating the phagocytic receptor Draper and forming acidic phagolysosomal structures. I show that astrocytes clear neuronal debris during nervous system remodeling and that this is a novel function for astrocytes during the development of nervous system. I analyzed two different neuronal populations: MB γ neurons that prune their neurites and vCrz+ neurons that undergo apoptosis. I discovered that MB γ axons are engulfed by astrocytes using the Draper and Crk/Mbc/dCed-12 pathways in a partially redundant way. Interestingly, Draper is required for clearance of vCrz+ cell bodies, while Crk/Mbc/dCed-12, but not Draper, are required for clearance of vCrz+ neurites. Surprisingly, I also found that loss of Draper delayed vCrz+ neurite degeneration, suggesting that glia facilitate neurite destruction through engulfment signaling.

Taken together, my work identifies a novel function for astrocytes in the clearance of synaptic and neuronal debris during developmental remodeling of the nervous system. Additionally, I show that Crk/Mbc/dCed-12 act as a new glial signaling pathway required for pruning, and surprisingly, that glia use different engulfment pathways to clear neuronal debris generated by cell death versus local pruning.

Activity Regulates Neuronal Connectivity and Function in the C. elegans Motor Circuit: A Dissertation

Sun, 03/22/2015 - 10:26pm

Activity plays diverse roles in shaping neuronal development and function. These roles range from aiding in synaptic refinement to triggering cell death during traumatic brain injury. Though the importance of activity-dependent mechanisms is widely recognized, the genetic underpinnings of these processes have not been fully described. In this thesis, I use the motor circuit of Caenorhabditis elegans as a model system to explore the functional and morphological consequences of modulating neuronal activity.

First, I used a gain-of-function ionotropic receptor to hyperactivate motor neurons and asked how increased excitation affects neuronal function. Through this work, I identified a cell death pathway triggered by excess activation of motor neurons. I also showed that suppression of cell body death failed to block motor axon destabilization, providing evidence that death of the cell body and of motor axons can be genetically separated.

Secondly, I removed excitatory drive from a simple neural circuit and asked how loss of excitatory activity alters circuit development and function. I identified excitatory motor neurons as master regulators of inhibitory synaptic connectivity. Additionally, I was able to identify previously undescribed activity-dependent mechanisms for regulating inhibitory synapses in both developing and mature neural circuits.

Finally, I show data to implicate the highly conserved genes neurexin and neuroligin in determining inhibitory synapse connectivity. Collectively this work has lent insight into activity-dependent mechanisms in place to regulate neuronal development and function, a core function of neurobiology that is relevant to the study of a wide range of neurological disorders.

Caspase-8 and RIP Kinases Regulate Bacteria-Induced Innate Immune Responses and Cell Death: A Dissertation

Sun, 03/22/2015 - 10:26pm

Yersinia pestis (Y. pestis), as the causative agent of plague, has caused deaths estimated to more than 200 million people in three historical plague pandemics, including the infamous Black Death in medieval Europe. Although infection with Yersinia pestis can mostly be limited by antibiotics and only 2000-5000 cases are observed worldwide each year, this bacterium is still a concern for bioterrorism and recognized as a category A select agent by the Centers for Disease Control and Prevention (CDC). The investigation into the host-pathogen interactions during Y. pestis infection is important to advance and broaden our knowledge about plague pathogenesis for the development of better vaccines and treatments.

Y. pestis is an expert at evading innate immune surveillance through multiple strategies, several mediated by its type three secretion system (T3SS). It is known that the bacterium induces rapid and robust cell death in host macrophages and dendritic cells. Although the T3SS effector YopJ has been determined to be the factor inducing cytotoxicity, the specific host cellular pathways which are targeted by YopJ and responsible for cell death remain poorly defined. This thesis research has established the critical roles of caspase-8 and RIP kinases in Y. pestis-induced macrophage cell death. Y. pestis-induced cytotoxicity is completely inhibited in RIP1-/- or RIP3-/-caspase-8-/- macrophages or by specific chemical inhibitors. Strikingly, this work also indicates that macrophages deficient in either RIP1, or caspase-8 and RIP3, have significantly reduced infection-induced production of IL-1β, IL-18, TNFα and IL-6 cytokines; impaired activation of NF-κB signaling pathway and greatly compromised caspase-1 processing; all of which are critical for innate immune responses and contribute to fight against pathogen infection. Y. pestis infection causes severe and often rapid fatal disease before the development of adaptive immunity to the V bacterium, thus the innate immune responses are critical to control Y. pestis infection. Our group has previously established the important roles of key molecules of the innate immune system: TLR4, MyD88, NLRP12, NLRP3, IL-18 and IL-1β, in host responses against Y. pestis and attenuated strains. Yersinia has proven to be a good model for evaluating the innate immune responses during bacterial infection. Using this model, the role of caspase-8 and RIP3 in counteracting bacterial infection has been determined in this thesis work. Mice deficient in caspase-8 and RIP3 are very susceptible to Y. pestis infection and display reduced levels of pro-inflammatory cytokines in spleen and serum, and decreased myeloid cell death. Thus, both in vitro and in vivo results indicate that caspase-8 and RIP kinases are key regulators of macrophage cell death, NF-κB and caspase-1 activation in Yersinia infection. This thesis work defines novel roles for caspase-8 and RIP kinases as the central components in innate immune responses against Y. pestis infection, and provides further insights to the host-pathogen interaction during bacterial challenge.

Putting the Pieces Together: Exons and piRNAs: A Dissertation

Sun, 03/22/2015 - 10:26pm

Analysis of gene expression has undergone a technological revolution. What was impossible 6 years ago is now routine. High-throughput DNA sequencing machines capable of generating hundreds of millions of reads allow, indeed force, a major revision toward the study of the genome’s functional output—the transcriptome. This thesis examines the history of DNA sequencing, measurement of gene expression by sequencing, isoform complexity driven by alternative splicing and mammalian piRNA precursor biogenesis. Examination of these topics is framed around development of a novel RNA-templated DNA-DNA ligation assay (SeqZip) that allows for efficient analysis of abundant, complex, and functional long RNAs. The discussion focuses on the future of transcriptome analysis, development and applications of SeqZip, and challenges presented to biomedical researchers by extremely large and rich datasets.