Matching Items (6)

132773-Thumbnail Image.png

The Gender Differences in Heart Disease and the Cardiovascular Benefits of Estrogen

Description

Heart disease is the number one killer of men and women in the world. The incidence of cardiovascular disease is known to be much higher in men than women until around the ages of 60-75 years, when the occurrence of

Heart disease is the number one killer of men and women in the world. The incidence of cardiovascular disease is known to be much higher in men than women until around the ages of 60-75 years, when the occurrence of the disease becomes approximately equal in both sexes. Additionally, the occurrence of heart disease is significantly lower in premenopausal women than postmenopausal women. Since men have a higher risk for heart disease than women until 10-15 years after the average age of menopause and postmenopausal women have a higher risk of cardiovascular disease than premenopausal women, it is hypothesized that endogenous estrogen exposure throughout the fertile period of a woman's life postpones the onset of cardiovascular disease. Research shows estrogen has beneficial effects on the cardiovascular system by regulating multiple metabolic processes including lipid metabolism, vasodilation, nitric oxide synthesis, cytochrome c apoptosis, and mitochondrial antioxidant production. Though estrogen has been found to have cardiovascular benefits on individual metabolic processes, the treatment of synthetic estrogen on postmenopausal women and men to reduce the overall risk of heart disease is very controversial. The controversy of synthetic estrogen is partially due to the fact that most studies done using estrogen replacement therapy on postmenopausal women and men resulted in either no effects or harmful effects on the cardiovascular system. Hormone replacement therapy has also been associated with a higher risk of multiple medical conditions, especially venous thromboembolism and breast cancer. This review will explore these topics and consider the costs and benefits of estrogen replacement therapy.

Contributors

Created

Date Created
2019-05

135592-Thumbnail Image.png

A Comparison of the Effect of Acute vs. Chronic Stress on the Cardiovascular System

Description

The stress levels of the average person in today's society are extremely high and this can have a massive effect on health, especially on the cardiovascular system. The two most common types of stress, acute and chronic, effect the cardiovascular

The stress levels of the average person in today's society are extremely high and this can have a massive effect on health, especially on the cardiovascular system. The two most common types of stress, acute and chronic, effect the cardiovascular system differently. Acute stress comes from a short term source of perceived danger, such as giving a presentation in front of a crowd, or being chased by a wild animal. Chronic stress is the dull anxiety that hangs around consistently and comes from long-term sources of stress, such as a negative work environment or feeling trapped in a poor relationship. A review of the available research literature shows that while acute stress can have positive or negative effects on the body, chronic stress is consistently damaging to cardiovascular health. The adrenaline rush associated with acute stress can increase focus and improve performance through a variety of physiological reactions such as increased heart rate and changes in blood flow to support the most vital organs. Chronic stress sufferers have an increased chance of heart disease, heart attack, and a variety of other problems due to the negative consequences of chronic stress such as high blood pressure. The high negative impact chronic stress and excessive amounts of acute stress can have leads to the conclusion that stress needs to be regulated and limited. Prioritizing health by getting sufficient sleep, taking time to exercise, and practicing relaxation techniques such as meditation can all help to minimize stress levels and the dangerous potential consequences of excess stress.

Contributors

Agent

Created

Date Created
2016-05

151800-Thumbnail Image.png

Selenium supplementation and cardiovascular outcome markers in hemodialysis patients: a randomized, controlled trial

Description

Background Hemodialysis (HD) patients elicit an oxidant-antioxidant imbalance in addition to a selenium deficiency, possibly contributing to cardiovascular disease (CVD) mortality. Objective To evaluate the effect of selenium supplementation on CVD outcomes and antioxidant status in HD patients. Design A

Background Hemodialysis (HD) patients elicit an oxidant-antioxidant imbalance in addition to a selenium deficiency, possibly contributing to cardiovascular disease (CVD) mortality. Objective To evaluate the effect of selenium supplementation on CVD outcomes and antioxidant status in HD patients. Design A randomized controlled intervention trial conducted from October 2012 to January 2013. Participants/setting The study included 27 maintenance HD patients (61.1+17.5y, 14M, 13F) receiving HD in the greater Phoenix, AZ area. Intervention Patients received one of three treatments daily: 2 Brazil nuts, (5g, 181µg/day of selenium as selenomethionine [predicted]), 1 tablet of selenium (200µg/day of selenium as selenomethionine), or control (3 gummy bears). Main outcome measures Antioxidant status outcome measures included total antioxidant capacity, vitamin C, and RBC and plasma glutathione peroxidase (GSH-Px). CVD outcomes measures included brain natriuretic peptide; plasma cholesterol, high density lipoprotein, low density lipoprotein, triglycerides; blood pressure, and thoracic cavity fluid accumulation. Statistical analyses performed Repeated measures ANOVA analyzed changes over time and between groups at months 0 and 2 and months 0 and 3. Results Independent analysis showed the Brazil nuts provided 11µg of selenium/day and the pill provided 266µg of selenium/day. Consequently, the Brazil nut group was combined with the placebo group. 21 patients completed 2 months of the study and 17 patients completed the study in its entirety. Data was analyzed for months 0, 1 and 2. No significant differences were noted for antioxidant status outcome measures with the exception of plasma GSH-Px. Patients receiving the selenium pill had a significant increase in plasma GSH-Px compared to the placebo group (6.0+11 and -4.0+7.6, respectively, p=0.023 for change between month 0 and month 2). No significant differences were seen in total antioxidant capacity or for CVD outcome measures over time or between groups. Conclusions These data indicate that selenium supplementation increased plasma GSH-Px concentration in HD patients; however, oxidative stress was not altered by selenium supplementation. The low vitamin C status of HD patients warrants further research, specifically in conjunction with selenium supplementation.

Contributors

Agent

Created

Date Created
2013

154322-Thumbnail Image.png

Blood supply and vascular reactivity of the spinal cord under normal and pathological conditions

Description

The unique anatomical and functional properties of vasculature determine the susceptibility of the spinal cord to ischemia. The spinal cord vascular architecture is designed to withstand major ischemic events by compensating blood supply via important anastomotic channels. One of the

The unique anatomical and functional properties of vasculature determine the susceptibility of the spinal cord to ischemia. The spinal cord vascular architecture is designed to withstand major ischemic events by compensating blood supply via important anastomotic channels. One of the important compensatory channels of the arterial basket of the conus medullaris (ABCM). ABCM consists of one or two arteries arising from the anterior spinal artery (ASA) and circumferentially connecting the ASA and the posterior spinal arteries. In addition to compensatory function, the arterial basket can be involved in arteriovenous fistulae and malformations of the conus. The morphometric anatomical analysis of the ABCM was performed with emphasis on vessel diameters and branching patterns.

A significant ischemic event that overcomes vascular compensatory capacity causes spinal cord injury (SCI). For example, SCI complicating thoracoabdominal aortic aneurysm repair is associated with ischemic injury. The rate of this devastating complication has been decreased significantly by instituting physiological methods of protection. Traumatic spinal cord injury causes complex changes in spinal cord blood flow (SCBF), which are closely related to a severity of injury. Manipulating physiological parameters such as mean arterial pressure (MAP) and intrathecal pressure (ITP) may be beneficial for patients with a spinal cord injury. It was discovered in a pig model of SCI that the combination of MAP elevation and cerebrospinal fluid drainage (CSFD) significantly and sustainably improved SCBF and spinal cord perfusion pressure.

In animal models of SCI, regeneration is usually evaluated histologically, requiring animal sacrifice. Thus, there is a need for a technique to detect changes in SCI noninvasively over time. The study was performed comparing manganese-enhanced magnetic resonance imaging (MEMRI) in hemisection and transection SCI rat models with diffusion tensor imaging (DTI) and histology. MEMERI ratio differed among transection and hemisection groups, correlating to a severity of SCI measured by fraction anisotropy and myelin load. MEMRI is a useful noninvasive tool to assess a degree of neuronal damage after SCI.

Contributors

Agent

Created

Date Created
2016

151209-Thumbnail Image.png

An experimental replication and refinement of the undoing hypothesis of positive emotions

Description

Broaden and build theory (BBT; Fredrickson, 1998; 2001) postulates that positive emotions expand the scope of one's attention and thought-action repertoires (Fredrickson & Branigan, 2005). Within the boundaries of BBT, the undoing hypothesis (Fredrickson, 1998, Fredrickson & Levenson, 1998) argues

Broaden and build theory (BBT; Fredrickson, 1998; 2001) postulates that positive emotions expand the scope of one's attention and thought-action repertoires (Fredrickson & Branigan, 2005). Within the boundaries of BBT, the undoing hypothesis (Fredrickson, 1998, Fredrickson & Levenson, 1998) argues that positive emotions themselves do not bring forth specific action tendencies or urges; therefore, they do not consequently require an increase in cardiovascular activity to carry out the urge. On the other hand, positive emotions have evolved to subdue the cardiovascular response previously initiated by negative emotions. This dissertation proposes that the real power of positive emotions might be to undo not the effects of negative emotions themselves, however, but simply reduce the arousal itself. This dissertation used minor physiological arousal (e.g., a step-stool task) to simulate the cardiovascular effects of the stress manipulations used in previous tests of the undoing hypothesis by Fredrickson and colleagues. This dissertation asks if positive emotions undo the cardiovascular reactivity of an emotionally neutral stimulus. Positive emotions were induced through one film clip (i.e., a happy film clip) and was compared to a neutral film clip (no emotion elicited). An experimental design measured the effects of arousal induction and film clip on participants' cardiovascular activity. Results indicated that positive emotions had the same effect as no emotions on participants' cardiovascular activity. Implications for theory and research are provided, as well as an assessment of the study's strengths and limitations. Finally, several directions for future research are offered.

Contributors

Agent

Created

Date Created
2012

154254-Thumbnail Image.png

Improved techniques for cardiovascular flow experiments

Description

Aortic pathologies such as coarctation, dissection, and aneurysm represent a

particularly emergent class of cardiovascular diseases and account for significant cardiovascular morbidity and mortality worldwide. Computational simulations of aortic flows are growing increasingly important as tools for gaining understanding of these

Aortic pathologies such as coarctation, dissection, and aneurysm represent a

particularly emergent class of cardiovascular diseases and account for significant cardiovascular morbidity and mortality worldwide. Computational simulations of aortic flows are growing increasingly important as tools for gaining understanding of these pathologies and for planning their surgical repair. In vitro experiments are required to validate these simulations against real world data, and a pulsatile flow pump system can provide physiologic flow conditions characteristic of the aorta.

This dissertation presents improved experimental techniques for in vitro aortic blood flow and the increasingly larger parts of the human cardiovascular system. Specifically, this work develops new flow management and measurement techniques for cardiovascular flow experiments with the aim to improve clinical evaluation and treatment planning of aortic diseases.

The hypothesis of this research is that transient flow driven by a step change in volume flux in a piston-based pulsatile flow pump system behaves differently from transient flow driven by a step change in pressure gradient, the development time being substantially reduced in the former. Due to this difference in behavior, the response to a piston-driven pump can be predicted in order to establish inlet velocity and flow waveforms at a downstream phantom model.

The main objectives of this dissertation were: 1) to design, construct, and validate a piston-based flow pump system for aortic flow experiments, 2) to characterize temporal and spatial development of start-up flows driven by a piston pump that produces a step change from zero flow to a constant volume flux in realistic (finite) tube geometries for physiologic Reynolds numbers, and 3) to develop a method to predict downstream velocity and flow waveforms at the inlet of an aortic phantom model and determine the input waveform needed to achieve the intended waveform at the test section. Application of these newly improved flow management tools and measurement techniques were then demonstrated through in vitro experiments in patient-specific coarctation of aorta flow phantom models manufactured in-house and compared to computational simulations to inform and execute future experiments and simulations.

Contributors

Agent

Created

Date Created
2015