Poor metabolic control is a major health concern for children and adolescents with type 1 diabetes, particularly for African American youth. The aims of this study were to test the mediating relationship between two variables consistently related to metabolic control, depressive symptoms and adherence, as well as to attempt to explain racial disparities in metabolic control. The study sample consisted of 53 European American youth and 33 African American youth ages 5 to 20 (M = 13.59, SD = 3.49) with type 1 diabetes. Information on depressive symptoms, adherence, and HbA1c was collected during routine outpatient clinic visits. Significant associations were found between depressive symptoms and metabolic control, depressive symptoms and adherence, and adherence and metabolic control. When included together in a regression model, adherence mediated the relationship between depressive symptoms and metabolic control. This mediation pathway did not significantly differ between African American youth and European American youth; however, African American youth had significantly higher HbA1c levels. These findings indicate the importance of considering depressive symptoms during treatment for type 1 diabetes. This study also supports previous research findings of racial disparities in metabolic control among youth with type 1 diabetes. Future studies should further examine mechanisms by which these racial disparities emerge. / acase@tulane.edu

The goal of this qualitative study was to use archival data from a participatory action research (PAR) project to construct a local, culturally informed model of African American children and adolescents' stressors and reactions to stress specifically representative of an elementary and a secondary school in New Orleans, Louisiana. Low-income urban African American youth face chronic conditions including economic problems, exposure to community violence, racial stereotyping and discrimination rare in the lives of youth of other communities, yet the extent to which extant findings on stress can be generalized to this population is unclear. Focus group data from students from grades K-2 (n = 42) and grades 9-10 (n = 44) in two charter schools in New Orleans were coded deductively to identify stressors and stress reactions in this sample. Themes across the two groups were examined for patterns in the data that explain variations in definitions of stress and reactions to stress due to age and ecological contexts (e.g. family, school, peer group). Understanding stressors and reactions to stress is a first step in working toward planning culturally relevant and culturally acceptable intervention programs to equip the students to effectively deal with stress, provide resources and, create conditions for them to cope adaptively. / acase@tulane.edu

acase@tulane.edu

Rodents solve dual-solution tasks that require navigation to a goal by adopting either a hippocampus-dependent place strategy or a striatum-dependent stimulus–response strategy. The current experiments investigated the preference for learning strategy as a function of biological sex and anxiety level in rats prior to the onset of puberty, before the activational effects of gonadal hormones influence these processes. In the first experiment, a significant proportion of prepubertal males preferred a stimulus-response strategy on a dual-solution visible platform water maze task at 28 days of age, in contrast to age-matched prepubertal females or adult males. In the second experiment, prepubertal males categorized as high in trait anxiety on an open field task exhibited a bias toward stimulus–response strategy, whereas age-matched females exhibited no preference in strategy regardless of anxiety level. In the third experiment, pups were separated from dams for either 15 or 180 min per day during the first 2 weeks of life and tested for anxiety and learning strategy preference. Prolonged maternal separations were linked to elevated anxiety and a bias for stimulus-response strategy in prepubertal males but not females. In the fourth experiment, prepubertal males and rats preferring a stimulus-response strategy expressed a lower ratio of muscarinic binding in the hippocampus relative to the striatum compared to prepubertal females and place learners, respectively. In the fifth experiment, prepubertal females masculinized by injections of testosterone shortly after birth preferred a stimulus-response strategy similar to that of prepubertal males and unlike vehicle-treated females. In the sixth experiment, prepubertal females expressed greater dendritic complexity and spine density in the CA1 region of the hippocampus than males at the exact age at which sex differences in learning strategy preference were found in the first five experiments. This series of experiments indicates that, in contrast to prepubertal female rats, prepubertal males displayed a clear preference for a striatum-based stimulus-response strategy when learning a dual-solution task. Furthermore, several variables were identified as contributing to this sex difference, including the impact of male anxiety on strategy preference, lower male hippocampus-to-striatum ratios of muscarinic binding, and delayed structural development of the male hippocampus. / acase@tulane.edu

To date, not much is known about why past research has found that Latino youth report higher levels of internalizing symptoms than White non-Latino youth. At a more basic level, our current understanding of phenomenology of internalizing problems in Latino youth is limited. This study explored the relationship among anxiety, depression, and somatic symptoms and investigated the influence of cultural acceptability on somatic symptom expression within a school-based sample (5th through 8th grade) of Latino and White non-Latino youth. Anxiety and depression uniquely explained variability in somatic symptom expression. Contrary to past research, Latino and White non-Latino youth did not report different somatic symptoms levels. Cultural acceptability did not vary by ethnicity. Cultural acceptability also did not predict somatic symptoms. Exploratory analyses were conducted including African-American youth and with male only samples. Cultural acceptability predicted somatic symptoms among the male only samples. Future studies should further explore possible interactions between gender and culture on the expression of psychological distress. / acase@tulane.edu

Research using the adult mammalian model shows that regeneration in the limb is limited to the distal most portion of the terminal phalanx. Recent studies suggest that the cellular contributions made to the regenerating system are lineage restricted and that the niche bone marrow hematopoietic stem cell population’s contributions are minimal. These studies however, do not address other residing populations within the bone marrow, specifically the mesenchymal and endothelial stem cell populations. One of the residing populations, the reputed pericyte or perivascular cells, possesses the ability to differentiate into multiple other cell types. To assess the potential contribution of perivascular cells to the regeneration competency of the terminal phalanges, we began by identifying perivascular cells within the terminal phalanx by using two accepted pericyte markers: nerve-glial antigen 2 (NG2) and endosialin (TEM1). Using NG2 and TEM1 in conjunction with vascular marker Tie2 in the Tie2-EGFP murine reporter line, we confirm a large number of perivascular cells in the bone marrow’s unusually well-developed and organized vasculature and a lower density within the connective tissue microvasculature; implicating a great potential contribution from the bone marrow. Post-amputation, we observe a large population of NG2+ and TEM1+ cells within the regenerating blastema region. Co-immunohistochemical studies reveal the blastema have cells that co-express osteogenic and pericyte markers; strongly suggestive of a transdifferentiation event. We attempt to confirm our hypotheses made in our initial assessment by utilizing two independent cell tracing studies: a DiI labeling of the bone marrow of the terminal phalanx to identify a marrow derived cellular contribution to the regenerate and a genetic fate tracing study using transgenic NG2CreERTamR26REYFP mice to confirm a transdifferentiation event. Using a novel in vivo method , we DiI-label the bone marrow content before amputation and trace DiI labeled bone marrow derived cellular contributions to the regenerate. DiI labeled cells were observed within the blastema expressing either endothelial, perivascular, or osteogenic markers, confirming the bone marrow contributes multiple cell types during the regeneration process. Using a similar experimental design, we genetically label the terminal phalanx NG2 expressing cells using systemic tamoxifen induction of NG2CreERTamR26REYFP mice. We fate trace the initially labeled population during blastema formation and re-differentiation and observed transdifferentiation events of the perivascular cells into two distinctive lineages, endothelial and osteoprogenitor cells. Establishing a direct correlation between peri-vasculature and re-differentiation, we address NG2/perivascular necessity with a series of temporal loss of function studies using a blocking antibody (iNG2). We implant iNG2 soaked microcarrier beads into various regions of the terminal phalanx and during different stages of the regeneration process. The experiments confirm the necessity of NG2 expression for distal bone elongation, as well as ascertain the temporal nature of the NG2 expression in different microenvironments. These results establish the importance of NG2+ cells in the bone marrow during early stages of regeneration, with early iNG2 bone marrow implantation resulting in a complete failure of the regeneration process. In an attempt to rescue this iNG2 failed regeneration we employ an established position-specific fibroblast cell line that displays a surprising plasticity as a cell-based therapeutic. Through a series of RNAi lentiviral transfection of inhibitors of the TGFβ-BMP pathway we induce osteogenic plasticity in the line. These results reveal regeneration competency associated with the mammalian terminal phalanx is in part due to the ability to recruit local perivascular multipotent populations, which has great translational relevancy. / acase@tulane.edu

acase@tulane.edu

Stereotypes associating men more strongly with science compared to women have harmful implications for women’s science, technology, engineering, and math (STEM) outcomes. Exposure to successful female STEM role models can buffer women from the effect of these stereotypes and lead to better performance and greater interest in STEM fields. Moreover, role model identification is especially important for improving women’s STEM outcomes. The current study posits that encouraging women to reflect on the ways in which they identify with a role model will improve women’s STEM identification, STEM sense of belonging, weaken explicit STEM stereotypes, and will strengthen implicit associations between women and science over the course of a semester, which will then lead to increased desire to pursue STEM opportunities and improved STEM GPA. Seventy-two incoming freshmen women interested in majoring in STEM completed the study. Participants read two role model biographies at different time points during the semester, and at both time points were asked to either write about the ways in which they identified with the role model, asked to write facts about the role model, or asked to write facts about a woman whose hobbies they read about (i.e., control condition). Results revealed that encouraging women to identify with a role model weakened explicit stereotypes and strengthened implicit women-science associations compared to merely exposing women to a role model. Furthermore, encouraging women to identify with a role model and merely exposing women to a role model tended to increase STEM sense of belonging compared to not exposing women to a role model. These findings suggest that encouraging women to identify with a role model is important for improving women’s STEM attitudes. / acase@tulane.edu

An understanding of the pathways responsible for differentiation in pluripotent stem cells (PSCs) would accelerate their translation to medical therapies. Specifically, studies that identify criteria for the better design of experiments targeting certain phenotypes would allow for the generation of cell sources adequate for transplantation. In this dissertation, we aimed at elucidating the role of the cytoskeleton in the spontaneous differentiation of PSCs in two dimensional (2D) and three dimensional (3D) microenvironments. First, we quantified the expression of the cytoskeleton in ESCs, iPSCs, and the iPSC source phenotype, showing that there were indeed differences in the expression of microfilaments and certain intermediate filaments among all three phenotypes. Next, we found that there were inherent differences in ESC differentiation when cultured in 2D and 3D microenvironments. Lastly, alterations in the cytoskeleton were found to decrease mesodermal differentiation in 3D culture, while increase both mesodermal and endodermal differentiation in 2D culture. Taken together, we identified the cytoskeleton as a regulator of differentiation to the mesodermal and endodermal lineages in both 2D and 3D culture. / acase@tulane.edu

Disparities in health and achievement are greater for low income ethnic minorities. There is a growing evidence base that supportive teacher-child relationships are associated with positive socioemotional outcomes and can act as a protective factor for children, including those at risk for poorer outcomes due to their racial/ethnic backgrounds and socioeconomic status. Research suggests that the reverse is also true. Specifically, children’s behaviors can also reciprocally impact the quality of teacher-child relationships. While there is an abundance of research on associations between the teacher-child relationship and child outcomes in school-aged children, this is one of the first studies to focus on these associations in a low-income, ethnically diverse population of preschoolers. In the current study, data on preschoolers (N = 2152) and their teachers (N = 229) were gathered during the beginning and end of the preschool year in the context of a larger study evaluating a kindergarten readiness program (Baker, Kupersmidt, Voegler-Lee, Arnold, & Willoughby, 2010). Teachers completed questionnaires about preschooler social skills, inattention, and oppositional/defiant behaviors. Project staff conducted assessments of preschooler behavior regulation and also gathered information about the teacher-child relationship using observational measures. The influence of teacher-child relationships on preschooler functioning was examined using hierarchical linear modeling. The influence of preschooler functioning on teacher-child relationships was analyzed using linear regression. Results indicate that teacher-child relationships established early in the preschool school year impact preschooler social skills, behavior regulation and oppositional/defiant behaviors later in the same school year. Additionally, behaviors exhibited by preschoolers early in the year appear to influence the levels of sensitivity and permissiveness in teacher-child relationships later in the year. These reciprocal relationships were also moderated by preschooler age, gender and race/ethnicity. Limitations of the study and implications of the findings as they relate to the professional development and training of professionals in preschool settings are also described. / acase@tulane.edu