A Quantitative Study on the Association Between Stress Tolerance and Exercise Habits among Students Enrolled in a College of Health Professions Program

PURPOSE: The purpose of this study was to gain further knowledge on the effects of stress on students studying health professions by discovering common causes of stress, coping mechanisms utilized for stress of students, and how regular exercise relates to stress tolerance. METHODS: This study was a quantitative, cross-sectional design through a survey distributed via email to undergraduate and graduate students enrolled in a Midwestern university’s College of Health Professions. Embedded in the email was an anonymous link to a survey, which was constructed through the Qualtrics survey platform. The survey included questions relating to stress about major life events occurred, daily hassles, coping mechanisms for stress, symptoms of stress, and current exercise habits. RESULTS: This study found that there was not a significant relationship between stress tolerance ratios and regular exercise (p\u3c0.05, p=0.31). Similarly, no significant difference was determined when comparing academic levels and exercise habits (p\u3c0.05, p=0.316). When examining the association between exercise as a coping mechanism and academic level, there was also not a significant relationship (p\u3c0.05, p=0.40). CONCLUSIONS: Although the results of the study did not yield significant differences between variables, the results of the frequently reported life events, daily hassles, and coping mechanisms agreed with previous research. These findings implicate that undergraduate and graduate students have commonalities in major life events, daily hassles, and coping mechanisms for stress when compared to previous research. Trends were observed in this study, and should be examined further with a larger sample size

Impaired cholecystokinin-induced gallbladder emptying incriminated in spontaneous “black” pigment gallstone formation in germfree Swiss Webster mice

“Black” pigment gallstones form in sterile gallbladder bile in the presence of excess bilirubin conjugates (“hyperbilirubinbilia”) from ineffective erythropoiesis, hemolysis, or induced enterohepatic cycling (EHC) of unconjugated bilirubin. Impaired gallbladder motility is a less well-studied risk factor. We evaluated the spontaneous occurrence of gallstones in adult germfree (GF) and conventionally housed specific pathogen-free (SPF) Swiss Webster (SW) mice. GF SW mice were more likely to have gallstones than SPF SW mice, with 75% and 23% prevalence, respectively. In GF SW mice, gallstones were observed predominately in heavier, older females. Gallbladders of GF SW mice were markedly enlarged, contained sterile black gallstones composed of calcium bilirubinate and <1% cholesterol, and had low-grade inflammation, edema, and epithelial hyperplasia. Hemograms were normal, but serum cholesterol was elevated in GF compared with SPF SW mice, and serum glucose levels were positively related to increasing age. Aged GF and SPF SW mice had deficits in gallbladder smooth muscle activity. In response to cholecystokinin (CCK), gallbladders of fasted GF SW mice showed impaired emptying (females: 29%; males: 1% emptying), whereas SPF SW females and males emptied 89% and 53% of volume, respectively. Bilirubin secretion rates of GF SW mice were not greater than SPF SW mice, repudiating an induced EHC. Gallstones likely developed in GF SW mice because of gallbladder hypomotility, enabled by features of GF physiology, including decreased intestinal CCK concentration and delayed intestinal transit, as well as an apparent genetic predisposition of the SW stock. GF SW mice may provide a valuable model to study gallbladder stasis as a cause of black pigment gallstones.National Institutes of Health (U.S.) (Training Grant T32-OD10978-26)National Institutes of Health (U.S.) (Training Grant P30-ES002109)Kinship Foundation. Searle Scholars Progra

Bioinorganic Chemistry of the Human Host-Defense Protein Calprotectin

Thesis: Ph. D. in Biological Chemistry, Massachusetts Institute of Technology, Department of Chemistry, 2015.Vita. Cataloged from PDF version of thesis.Includes bibliographical references.The human innate immune system responds to bacterial and fungal pathogens by releasing the metal-chelating protein calprotectin (CP) at sites of infection and in the upper layers of the epidermis. CP is a Mn(II)- and Zn(ll)-binding protein. The work described in this thesis elucidates the metal-binding properties of CP, and correlates these properties with in vitro growth inhibition of bacteria and fungi. We report that the metal-binding properties of CP are modulated by Ca(ll), and we propose a working model in which CP responds to physiological Ca(Il)-ion gradients to become a potent Zn(ll)- and Mn(Il)-chelating agent in the extracellular space. Individual chapter summaries follow. Chapter 1: Bioinorganic Chemistry of the Host Pathogen Interaction. Transition metal ions are required for all forms of life. During the course of infection, pathogenic microorganisms must acquire transition metals from the host. Three metals of interest from this standpoint are iron, zinc, and manganese. This chapter describes bacterial metal-ion homeostasis machineries, and metal-requiring processes with a focus on Zn(II) and Mn(II). This chapter then highlights the S100 family of Ca(ll)-binding proteins and discuses the Zn(Il)-, Cu(ll)-, and Mn(Il)-binding properties of S100B, S100A12, S100A7, S10OA15, and S100A8/S100A9. Finally, an overview of the scope of this thesis is presented. Chapter 2: Calcium Ion Gradients Modulate the Zinc(Il) Affinity and Antibacterial Activity of Human Calprotectin. Calprotectin (CP) is a human neutrophil protein that is produced and released by neutrophils at sites of infection, where it prevents the growth of microorganisms by sequestering bioavailable zinc(II) and manganese(II). In this chapter, we present metalbinding studies to elucidate the Zn(ll)-binding properties of CP. We report unique optical absorption and EPR spectroscopic signatures for the interfacial His 3Asp and His 4 sites of human CP by using Co(II) as a spectroscopic probe. Zinc competition titrations employing colorimetric and fluorimetric Zn(II) sensors establish that CP coordinates two Zn(II) ions / CP heterodimer. The Ca(ll)-insensitive Zn(ll) sensor ZP4 is used to determine the Kd of CP for Zn(II) in Ca(Il)-deplete and Ca(Il)-replete conditions. These competition titrations afford apparent Kdsitel = 133 58 pM and Kdsite2 = 185 219 nM in the absence of Ca(II). In the presence of excess Ca(Il) these values decrease to Kd,sitel 5 10 pM and Kd,site2 : 240 pM. In vitro antibacterial assays indicate that the metal-binding sites and Ca(ll)-replete conditions are required to inhibit the growth of Gram-negative and Gram-positive bacteria. We propose a model in which Ca(II) ion gradients modulate the antibacterial activity and Zn(Il)-binding properties of human CP. Chapter 3: High-Affinity Manganese Coordination by Human Calprotectin Is Calcium- Dependent and Requires the Histidine-Rich Site at the Dimer Interface. In this chapter, we report that the His 4 motif at the S10OA8/S100A9 dimer interface of CP is required for high-affinity Mn(II) coordination. We identify a low-temperature EPR spectroscopic signal for this site that is consistent with high-spin Mn(II) in an octahedral coordination sphere. This site could be simulated with zero-field splitting parameters D = 270 MHz and EID = 0.30 (E = 81 MHz). This analysis, combined with studies of mutant proteins, suggests that (A8)Hisl7, (A8)His27, (A9)His9l, (A9)His95 and two as-yet unidentified ligands coordinate Mn(ll) at site 2. These studies support a model in which CP responds to Ca(ll) ion gradients to become a potent metal-ion chelator in the extracellular space. Chapter 4: Contributions of the C-terminal Tail of S100A9 to High-Affinity Manganese Binding by Human Calprotectin. This chapter examines the role of the S100A9 C-terminal tail to high-affinity Mn(ll) coordination by human CP. We present a 16-member mutant family with mutations in the S100A9 C-terminal tail (residues 96-114), which houses three histidine and four acidic residues, to evaluate its contribution to Mn(ll) sequestration. These studies confirm that two His residues at positions 103 and 105 complete the octahedral coordination sphere of CP in solution. Appendix 1: Sequence Alignments of Transition-Metal Binding S100 Proteins. Sequence alignments of S100A7, S100A8, S100A9, S100A12, S100A15, and S100B proteins from multiple organisms are presented. Appendix 2: Characterization of CP Mutant Proteins by Circular Dichroism and Analytical Size Exclusion Chromatography. Additional characterization of CP and mutant proteins employed in Chapters 2-4 is presented. Appendix 3: Structures of Sensors Used In this Work. The structures of Zincon, MagFura-2, Zinpyr-1, and Zinpyr-4 are presented. Appendix 4: Manganese Binding Properties of Human Calprotectin under Conditions of High and Low Calcium. This appendix represents a collaborative work with the Drennan Lab (MIT) and Britt Lab (UC Davis) to study the Mn(Il)-CP complex in low- and high-Ca(II) conditions. We report a crystal structure of Mn(Il)-, Ca(Il)-, and Na(l)-bound CP with Mn(II) exclusively coordinated to the His6 motif. Electron spin-echo envelope modulation and electron-nuclear double resonance experiments demonstrate that the six coordinating histidine residues are spectroscopically equivalent. The observed 15N ( = %/h)y perfine couplings (A) arise from two distinct classes of nitrogen atoms: the coordinating E-nitrogen of the imidazole ring of each histidine (A = [3.45, 3.71, 5.91] MHz) and the distal 6-nitrogen (A = [0.11, 0.18, 0.42] MHz). In the absence of Ca(II), the affinity of CP for Mn(II) drops by two to three orders of magnitude, and Mn(II) coordinates to the His6 site as well as other sites on the protein.by Megan Brunjes Brophy.Ph. D. in Biological Chemistr

Manganese and Microbial Pathogenesis: Sequestration by the Mammalian Immune System and Utilization by Microorganisms

ABSTRACT: Bacterial and fungal pathogens cause a variety of infectious diseases and constitute a significant threat to public health. The human innate immune system represents the first line of defense against pathogenic microbes and employs a range of chemical artillery to combat these invaders. One important mechanism of innate immunity is the sequestration of metal ions that are essential nutrients. Manganese is one nutrient that is required for many pathogens to establish an infective lifestyle. This review summarizes recent advances in the role of manganese in the host−pathogen interaction and highlights Mn(II) sequestration by neutrophil calprotectin as well as how bacterial acquisition and utilization of manganese enables pathogenesis. Metals ions are essential for the proliferation of allkingdoms of life and perform a variety of structural and chemical tasks. In order to establish a virulent lifestyle, pathogens must acquire and concentrate metal ions from the host.1−3 The mammalian innate immune system has evolved t

Employment outcomes of foster youth: The results from the Midwest Evaluation of the Adult Functioning of Foster Youth

Youth emancipated from the foster care system face challenges in securing steady employment and earning a living wage. Using data from the Midwest Evaluation of the Adult Functioning of Former Foster Youth, this article uses Tobit analyses to test the statistical relationship between multiple factors (demographics, human capital, and independent living services) and yearly income for former foster youth at age 21 years. The findings revealed that race, level of education, histories of drug and alcohol use, and histories of mental illness significantly impact yearly earnings within the sampled population. Equally significant, self-reported receipt of help related to employment did not impact yearly earnings. However, the limitations associated with using a non-experimental design and the challenges associated with the endogeneity of the measures of employment-related help suggest areas for future research on this topic.Foster youth Emancipation Transition to adulthood Independent living Employment services Tobit analysis

Assessment of galactose-1-phosphate uridyltransferase activity in cells and tissues

Galactosemias are a family of autosomal recessive genetic disorders resulting from impaired enzymes of the Leloir pathway of galactose metabolism including galactokinase, galactose uridyltransferase, and UDP-galactose 4-epimerase that are critical for conversion of galactose into glucose-6-phosphate. To better understand pathophysiological mechanisms involved in galactosemia and develop novel therapies to address the unmet need in patients, it is important to develop reliable assays to measure the activity of the Leloir pathway enzymes. Here we describe in-depth methods for indirectly measuring Galacose-1-Phosphate Uridyltransferase activity in cell culture and animal tissues

Calcium Ion Gradients Modulate the Zinc Affinity and Antibacterial Activity of Human Calprotectin

Calprotectin (CP) is an antimicrobial protein produced and released by neutrophils that inhibits the growth of pathogenic microorganisms by sequestering essential metal nutrients in the extracellular space. In this work, spectroscopic and thermodynamic metal-binding studies are presented to delineate the zinc-binding properties of CP. Unique optical absorption and EPR spectroscopic signatures for the interfacial His3Asp and His4 sites of human calprotectin are identified by using Co(II) as a spectroscopic probe. Zinc competition titrations employing chromophoric Zn(II) indicators provide a 2:1 Zn(II):CP stoichiometry, confirm that the His[subscript 3]Asp and His[subscript 4] sites of CP coordinate Zn(II), and reveal that the Zn(II) affinity of both sites is calcium-dependent. The calcium-insensitive Zn(II) competitor ZP4 affords dissociation constants of K[subscript d1] = 133 ± 58 pM and K[subscript d2] = 185 ± 219 nM for CP in the absence of Ca(II). These values decrease to K[subscript d1] ≤ 10 pM and K[subscript d2] ≤ 240 pM in the presence of excess Ca(II). The K[subscript d1] and K[subscript d2] values are assigned to the His[subscript 3]Asp and His[subscript 4] sites, respectively. In vitro antibacterial activity assays indicate that the metal-binding sites and Ca(II)-replete conditions are required for CP to inhibit the growth of both Gram-negative and -positive bacteria. Taken together, these data provide a working model whereby calprotectin responds to physiological Ca(II) gradients to become a potent Zn(II) chelator in the extracellular space.National Institutes of Health (U.S.) (Office of the Director, NIH Grant DP2OD007045)Searle Scholars ProgramMassachusetts Institute of Technology. Center for Environmental Health Sciences (NIH Grant P30-ES002109)Massachusetts Institute of Technology. Dept. of Chemistr

High-Affinity Manganese Coordination by Human Calprotectin Is Calcium-Dependent and Requires the Histidine-Rich Site Formed at the Dimer Interface

Calprotectin (CP) is a transition metal-chelating antimicrobial protein of the calcium-binding S100 family that is produced and released by neutrophils. It inhibits the growth of various pathogenic microorganisms by sequestering the transition metal ions manganese and zinc. In this work, we investigate the manganese-binding properties of CP. We demonstrate that the unusual His₄ motif (site 2) formed at the S100A8/S100A9 dimer interface is the site of high-affinity Mn(II) coordination. We identify a low-temperature Mn(II) spectroscopic signal for this site consistent with an octahedral Mn(II) coordination sphere with simulated zero-field splitting parameters D = 270 MHz and E/D = 0.30 (E = 81 MHz). This analysis, combined with studies of mutant proteins, suggests that four histidine residues (H17 and H27 of S100A8; H91 and H95 of S100A9) coordinate Mn(II) in addition to two as-yet unidentified ligands. The His₃Asp motif (site 1), which is also formed at the S100A8/S100A9 dimer interface, does not provide a high-affinity Mn(II) binding site. Calcium binding to the EF-hand domains of CP increases the Mn(II) affinity of the His₄ site from the low-micromolar to the mid-nanomolar range. Metal-ion selectivity studies demonstrate that CP prefers to coordinate Zn(II) over Mn(II). Nevertheless, the specificity of Mn(II) for the His₄ site provides CP with the propensity to form mixed Zn:Mn:CP complexes where one Zn(II) ion occupies site 1 and one Mn(II) ion occupies site 2. These studies support the notion that CP responds to physiological calcium ion gradients to become a high-affinity transition metal ion chelator in the extracellular space where it inhibits microbial growth