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Role of Cardiac Catecholamines in Embryos and Adults Under Stress
Title
Role of Cardiac Catecholamines in Embryos and Adults Under Stress.
Creator
Baker, Candice, Ebert, Steven, Bossy-Wetzel, Ella, Siddiqi, Shadab, Lambert, Stephen, University of Central Florida
Abstract / Description
Cardiovascular disease is responsible for the loss of one life every 38 seconds and accounts for 26.6 percent of all infants that die of congenital birth defects. Adrenergic hormones are critically important regulators of cardiovascular physiology in embryos and adults. They are key mediators of stress responses and have profound stimulatory effects on cardiovascular function, and dysregulation of adrenergic function has been associated with many adverse cardiac conditions, including...
Show moreCardiovascular disease is responsible for the loss of one life every 38 seconds and accounts for 26.6 percent of all infants that die of congenital birth defects. Adrenergic hormones are critically important regulators of cardiovascular physiology in embryos and adults. They are key mediators of stress responses and have profound stimulatory effects on cardiovascular function, and dysregulation of adrenergic function has been associated with many adverse cardiac conditions, including congenital malformations, arrhythmias, ischemic heart disease, heart failure, and sudden cardiac death. Despite intensive study, the specific roles these hormones play in the developing heart is not well-understood. Further, there is little information available regarding how these important hormones mediate stress responses in adult females (before and after menopause) in comparison to males. My thesis thus has two major foci: (1) What role(s) do catecholamines play in the embryonic heart?, and (2) Do catecholamines differentially influence cardiac function in aging male and female hearts? Initially, we sought to uncover the roles of adrenergic hormones in the embryonic heart by utilizing an adrenergic-deficient (Dbh-/-) mouse model. We found that adrenergic hormones influence heart development by stimulating expression of the gap junction protein, connexin 43, facilitating atrioventricular conduction, and helping to maintain cardiac rhythm. As development progresses, cardiac energy demands increase substantially, and oxidative phosphorylation becomes vital. Adrenergic hormones regulate metabolism in adults, thus we hypothesized they may stimulate energy metabolism during the embryonic/fetal transition period. We examined ATP, ADP, oxygen consumption rate, and extracellular acidification rates and found these metabolic indices were significantly decreased in Dbh-/- hearts compared to Dbh+/+ controls. We employed transmission electron microscopy of embryonic cardiomyocytes and found the mitochondria were significantly larger in Dbh-/- hearts compared to controls, and had more branch points. Taken together, these results suggest adrenergic hormones play a major role mediating the shift from predominantly anaerobic to aerobic metabolism during the embryonic/fetal transition period.Since there are known differential cardiac responses due to sex, age, and menopause to stress, we used echocardiography to measure left ventricular (LV) function in adult (9, 18 and 21 month) male and female mice (pre and postmenopausal) in response to epinephrine, and immobilization stress to investigate the roles of these factors. My results show 9-month premenopausal female mice display significantly decreased LV responsiveness to epinephrine compared to males, and an increased response to epinephrine due to age, especially in the premenopausal females. Similar LV function was also observed between postmenopausal females and males, and this pattern persisted after immobilization stress. I also investigated anatomical differences in the distribution of adrenergic cells within the heart comparing age, sex, and menopausal status. Notably, the density of cells derived from an adrenergic lineage in the heart was significantly increased in postmenopausal mice compared to age-matched males and cycling females. The selective re-appearance of adrenergic cells in the heart following menopause may provide an explanation for the differential stress responses observed in our system, and could have important clinical ramifications for stress-induced cardiomyopathies.
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Date Issued
2014
Identifier
CFE0005458, ucf:50373
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005458
Dubious role of Mycobacterium paratuberculosis in pathogenesis of Type I diabetes
Title
Dubious role of Mycobacterium paratuberculosis in pathogenesis of Type I diabetes.
Creator
Thanigachalam, Saisathya, Naser, Saleh, Singla, Dinender, Siddiqi, Shadab, Jewett, Travis, University of Central Florida
Abstract / Description
INTRODUCTION: Type 1 Diabetes Mellitus (T1DM) is a chronic disorder with unknown etiology and associated with insulin deficiency. Mycobacterium avium subsp. paratuberculosis (MAP), the etiologic agent of paratuberculosis in cattle, has been implicated in many autoimmune diseases including Crohn's disease, TIDM and others. We hypothesize that the molecular mimicry including epitope homology between MAP-Hsp65 and pancreatic Glutamic Acid Decarboxylase65 (GAD65) may play a role in the auto...
Show moreINTRODUCTION: Type 1 Diabetes Mellitus (T1DM) is a chronic disorder with unknown etiology and associated with insulin deficiency. Mycobacterium avium subsp. paratuberculosis (MAP), the etiologic agent of paratuberculosis in cattle, has been implicated in many autoimmune diseases including Crohn's disease, TIDM and others. We hypothesize that the molecular mimicry including epitope homology between MAP-Hsp65 and pancreatic Glutamic Acid Decarboxylase65 (GAD65) may play a role in the auto destruction of pancreatic beta cells leading to insufficient insulin production and the development of TIDM, following exposure to MAP. METHODOLOGY: Peptide sequences of MAP-Hsp65 and GAD65 were analyzed using BLAST and PyMOL bioinformatics tools. Cross reactivity between the two proteins were evaluated using immunoblot and ELISA. Furthermore, coded EDTA blood samples were collected from 18 subjects (12 DM and 6 controls) and investigated for the presence or exposure to MAP. Peripheral leukocytes were investigated for harboring viable MAP using long-term culture followed by nested PCR. Clinical plasma samples were used for measurement of anti-MAP IgG titer as well as glucose and Insulin concentrations. Moreover, coded bovine sera from 100 cattle (50 MAP infected and 50 healthy) were investigated for possible correlation between MAP infection and plasma levels of glucose and insulin. RESULT: Peptide BLAST analysis revealed a 44% identity between MAP Hsp65 and GAD65 proteins with 75% positive identities in a 16 amino acid region. PyMOL 3-D structural analyses identified a shared epitope region within the 16 amino acid motif which is known to be an antigenic site on GAD65 antigen. MAP DNA and anti-MAP IgG were detected in the blood of TD8, a TIDM subject. Strong cross reactivity was observed between plasma from TD8 and MAP Hsp65 in proteins samples from M. tuberculosis, and E. coli recombinant clone expressing MAP Hsp65. A weak cross reactivity was also observed between rat pancreatic tissue homogenate and rabbit anti-MAP IgG. Long term culture of leukocytes from 18 blood samples resulted in the detection of MAP in 3/10 (30%) TIDM and 4/8 (50%) control subjects whereas anti-MAP IgG were detected in 5/10 (50%) TIDM samples compared to 3/8 (37.5 %) controls. In MAP infected cattle, insulin level ranged from below 0.1ng/ml to 2.456 ng/ml with an average of 0.36 +/- 0.57ng/ml compared to 0.1ng/ml to 13.47ng/ml with an average of 2.86 +/- 3.00ng/ml in healthy cattle (P(<)0.0001). CONCLUSION: We identified and confirmed a shared epitope region between MAP Hsp65 and human pancreatic GAD65. The shared epitope is a known antigenic binding site. Although MAP DNA was detected in both TIDM and control subjects, a strong correlation was found between anti-MAP IgG titer and MAP-positive culture in clinical samples, regardless of diagnosis. The correlation between MAP infection and insulin level in cattle is significant. Overall the result is intriguing and requires further investigation of MAP in well-characterized clinical samples.
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Date Issued
2012
Identifier
CFE0004608, ucf:49924
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004608

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