Pathogenic Etiology of Atherosclerosis

Pathogenic Etiology of AtherosclerosisAtherosclerosis Heart CoronarySpecial Topics in PathophysiologyIntroduction to the Comp whizznts of the cardiovascular SystemTo understand the basis of this paper, the pathophysiology of atherosclerosis, it is vital to appreciate the basic physiology of the boldness, circulatory system, and most importantly, the coronary thrombosis thrombosis arteries. This fundamental comprehension will lay the foundation to break in understand the devastation caused to the coronary arteries by the pathogenesis of atherosclerosis. This may also provide insight into prevention and treatment strategies to counteract the destructive mechanism of this unsoundness.The plaza is a very small, vitally important organ composed of four muscular chambers the right and left atria, and the right and left ventricles. The atria baffle relatively supple muscular walls, allowing them to be utmostly distensible 1 whereas the ventricles atomic number 18 of greater muscul ar thickness, which is vital for suming the line of business to the pulmonary and systemic circuits. A normal muscular heart has two main functions to pump tear to the pulmonary circuit where the subscriber line becomes oxygenated and to pump the oxygen-rich blood to the systemic circuit. The heart is essentially a small, muscular pump that is responsible for propelling deoxygenated blood to the lungs, while correspondingly pumping nutrient rich, oxygenated blood to the body. Once the blood leaves the left ventricle, it enters the aorta and corresponding network of arteries that constitute the circulatory system. argument vessels be divided into four categories arteries (take oxygenated blood away from the heart to the body), arterioles (branch out from the arteries attracting into the capillaries), capillaries (smallest of blood vessels where gas and nutrient exchange occurs), and veins (carry deoxygenated blood from the body to the heart). Arteries and veins live differen t functions but, they both are composed of three distinct layers tunica intima, tunica media, and the tunica adventita 2. The tunica intima is the innermost layer of any given blood vessel it includes the endothelial lining and a layer of connective tissue containing variable amounts of elastic fibers 3. The tunica media is the middle layer which contains concentric sheets of flavourless muscle builder composed of elastin and collagen fibers 3. It is this flavourless muscle that when stimulated by the sympathetic nervous system both constricts, decreasing the diam of the lumen (vasoconstriction), or it relaxes, increasing the diameter of the vessel lumen (vasodilation) 2 the role of these vasoactivators will be discussed later in this paper. Lastly, the tunica adventitia is the outer most layer, which is composed of collagen and elastin fibers. Often, this outer layer is intermix into adjacent tissues allowing the anchoring and stabilization of some vessels 2.As the heart is an organ continuously doing work, the cardiac muscle cellular phones are in need of a constant sum of oxygen and nutrients. It is the coronary circulation that is responsible for the blood supply to the cardiac tissues, via an extensive network of coronary arteries. Both the left and right coronary arteries originate from the domicile of the ascending aorta in spite of appearance the aortic sinus 1,3. The autonomic nervous system (ANS) plays an important role as neurogenic stimuli have the king to restrain the completion of coronary vasodilation. This neuromodulation governs the rate of reverse of vasoconstrictor norepinephrine (NE), which is summationd by the adrenergic medicine energizing and angiotension II (AII) 1. Other vasoconstrictors include 1 and 2 adrenergic activity, AII, and endothelin. Vasoconstrictive stimuli are also responsible for an increase in free cytosolic calcium in the vascular smooth muscle, endingant roleing in the homeostasis of myocardial contr action 4.Importantly, these vasoconstrictive adrenergic influences are opposed by vasodilatory influences such(prenominal) as -adrenergic vascular receptors and metabolic mechanisms such as nitric oxide (NO), adenosine (ATP) and the activation of vascular ATP hooklike potassium channels (KATP) 1. With this, there are three essential regulators of coronary tone i) the metabolic vasodilatory system ii) the neurogenic control system (more vasoconstrictive than vasodilatory) and iii) the vascular epithelium, which can be either vasodilatory by releasing NO or vasoconstrictive by releasing endothelin-1 1, 4. Thus, we must keep in mind that endothelin-1 is one of the more powerful vasoconstrictors, especially when endothelial damage is extensive 1, 4. These vasoactive substances are activated by their respective and very different, signaling passageways thus contributing to the complexities of atherosclerosis, devising it a true multifactorial affection.As with other vessels within the body, when there is an increased demand for oxygen, vasodilation of the coronary arteries occurs. This vasodilation is usually mediated by the release of NO from healthy endothelium in contrast, when the endothelium is damaged, it releases vasoconstrictive endothelin 1. It is because of their vital importance that the coronary arteries have gained popular attention when they are divulgeially or completely occluded by atherosclerotic plaques. These atherosclerotic plaques cause inadequate oxygen supply to the cardiac tissue resulting in tissue close (myocardial infarction), and versatile other forms of heart unsoundnesss 1. so without an adequate supply of oxygen and nutrients to the myocardial muscle, the heart will cease to function properly.This basic foundation will give us a bust idea on how a healthy cardiovascular system functions. Therefore allowing us to understand the drastic cause a illness such as atherosclerosis can have on this system. The main focus of thi s paper will be on atherosclerosis however other forms of heart disease will be discussed to solidify the idea of how destructive atherosclerosis can be. Thus, the remainder of this paper will focus on the cellular mechanisms behind atherosclerosis, on with old and new thoughts in regards to the aetiology and treatment options for this type of heart disease.Their Underlying Relation of Atherosclerosis to Other Coronary Heart DiseasesCardiovascular disease (CVD) has emerged as the dominant chronic disease in many parts of the world, and early in the 21st century it is predicted to become the main cause of constipation and death worldwide 5. CVD represents a very broad category of conditions that affect the heart and circulatory system. Common lay on the line factors include blood pressure (hypertension), agree cholesterol (LDL and HDL), diabetes, obesity, left ventricular hypertrophy, and genetic predisposition 6. The most prominent and worrisome of these diseases are those that contribute to coronary heart disease. The coronary heart diseases of care include ischemic heart disease, angina pectoris, myocardial infarction, and most importantly, atherosclerosis. As a result of these coronary heart diseases, cardiac output is practically demoralise and often increases the oxygen demand needed by the cardiac tissues. Therefore the effects of coronary heart disease cannot be taken lightly, as the effects can be highly variable, ranging from diffuse damage, to localized contract or stenosis of the coronary arteries 7. Importantly, these coronary diseases have direct vasodilatory effects of the coronary circulation, acting by the formation of adenosine and NO, and the opening of the KATP channels also the vascular endothelium is damaged, make the vasodilatory stimuli to be overcome by the vasoconstrictors such as endothelin and AII 1. By discussing these other forms of coronary heart disease, the reader will better understand the relationship between thes e diseases and atherosclerosis allowing a better understanding of the importance for prevention and treatment strategies of coronary heart disease.Traditionally, it has been thought that the major cause of myocardial ischemia is the result of fixed vessel narrowing and abnormal vascular tone, caused by atherosclerosis-induced endothelial cell dysfunction 6. This narrowing of the coronary arteries minifys the blood and oxygen flow to the myocardial tissues. It is the cessation of the myocardial blood flow ascribable to atherosclerotic stoppages that results in the warm physiological and metabolic changes. Unfortunately, the heart cannot increase oxygen extraction on demand, therefore any additional oxygen requirements are met by increasing the blood flow and autoregulation of the coronary vasculature 6. This oxygen imbalance may also be an key cause for not only myocardial ischemia, but contractile cardiac dysfunction, arrhythmias, infarction, and sometimes death 5. However, im portant to note is the hearts unique ability to adapt to these sudden changes in coronary blood flow by correspondingly decreasing the rate of cardiac contraction 1,5. Thus, the decreased work during ischemia proportionately decreases the oxygen demand and helps conserve the underperfused myocardium 1 this protective mechanism prevents move on damage and cell death due to decreased oxygen levels.Besides physiological factors, there are also metabolic changes that occur immediately afterward the initial on great deal of ischemia. The myocardial energy metabolism shifts from aerobic (mitochondrial) metabolism to anaerobic glycolysis within a few seconds 5 simultaneously, the energy depletion causes the myocardial contraction to diminish, finally ceasing altogether. Consequently, due to the inhibited mitochondrial metabolism, there is an increase in adenosine concentrations which causes the adenosine to bind to the smooth muscle receptors, decreasing calcium entry into the cells, th us causing relaxation due to vasodilation 7,8. Overall, the inability to meet the myocardial oxygen demand often results in severe, vice-like federal agency pain, or more super acidly known as angina pectoris. angina pectoris often is an associated symptom of myocardial ischemia and is the common medical term used to describe chest pain or discomfort due to coronary heart disease without myocardial necrosis. Interestingly, angina can also occur in people with valvular disease, hypertrophic cardiomyopathy, and uncontrolled high blood pressure (hypertension). currently there are three major variations of angina pectoris. The first is known as stable angina, or more commonly, chronic stable angina. This form of angina is characterized by a fixed, obstructive atheromous plaque in one or more coronary arteries 1,7,9. Patients who suffer from chronic stable angina usually have episodes of discomfort that are usually predictable. The discomfort is experienced shortly after over exertion and/or mental or emotional stress these symptoms are usually relieved by rest, nitroglycerin, or a combination of both. Again, the major contributing factor in stable angina is due to the coronary vasoconstriction caused by atherosclerotic endothelial dysfunction 7.A second form of angina is known as unstable angina. Unstable angina is characterized by unexpected chest pain which usually occurs at rest without any type of physical exertion. This chest pain is due to coronary artery stenosis caused by atherosclerotic plaque or the narrowing of the vessels obstructed by blood clots. Also other key factors in unstable angina include inflammation and transmission 7,9. The last form of angina is the variant angina, or more commonly known as Prinzmetals Angina 7. This form of angina is manifested by episodes of central coronary artery spasm in the absence of atherosclerotic lesions 7,9. The coronary vasospasm alone reduces coronary oxygen supply and is thought to be caused in response to abnormal endothelial dependent vasodilators (Acetylcholine ACh, and serotonin) 1,7. These coronary spasms are often manifested by the coronary atheroma which damages the vascular endothelium, causing a decreased growthion of vasodilators (NO and prostaglandin PGI2) and an increase in vasoconstrictive factors such as endothelin and AII 1. Often when someone is diagnosed with either form of angina, they are usually monitored closely, as they are at an increased risk of a heart attack (myocardial infarction), cardiac arrest, or sudden cardiac death.A myocardial infarction (heart attack) is the resultant complication when the blood supply to part of the heart is interrupted. This ischemic oxygen shortage causes damage and sometimes death to the heart tissues. Important associated risk factors include atherosclerosis, previous heart attack or stroke, smoking, high LDL and low HDL cholesterol levels, diabetes, obesity, and high blood pressure 10. Often referred to as an acute myoca rdial infarction, it is part of the acute coronary syndromes which includes ST segment elevation myocardial infarction (STEMI), non-ST segment elevation myocardial infarction (NSTEMI) and unstable angina 1,7,10.As with angina, the pain experienced may result from the release of mediators such as adenosine and lactate from the ischemic myocardial cells onto the local nerve endings 7. This ischemic persistence triggers a process called the ischemic cascade 5, which usually results in tissue death due to necrosis. Certain factors such as psychological stressors and physical exertion have been identified as major triggering factors heterogeneous with acute myocardial infarctions. Often these acute myocardial infarctions are brought on by the rupturing of atherosclerotic plaques, which then promote thrombus (blood clot) formation causing further occlusion of the arteries. This atherosclerotic blockage thus initiates myocardial necrosis, which in turn activates systemic responses to infl ammation causing the release of cytokines interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF) 7,10. disgraced caused by myocardial necrosis includes i) going of critical amount of ATP, ii) membrane damage induced metabolically or mechanically, iii) formation of free radicals, iv) calcium overload, and v) sodium pump inhibition 1.Apart from damaging the myocardial tissue, an acute myocardial infarction can cause varying pathophysiological changes in other organ systems. whatever of these changes include decreased pulmonary function gas exchange, ventilation, and distribution of perfusion, decreased vital capacity reduction in hemoglobins affinity for oxygen, causes hyperglycaemia and stricken glucose function, increases the plasma and urinary catecholamine levels (thus enhancing platelet aggregation), and also has been found to increase blood viscosity 5. From the above evidence, we can suppose that coronary heart disease should not be looked at light heartedly. It is due to their similarity that the different coronary heart diseases can be diagnosed using a given set of molecular markers and other diagnostic tools.Serum cardiac markers have become widely used when it comes to diagnosing the extent and type of coronary heart disease a patient is symptomatic of. Also, these tests have allowed physicians to diagnose an additional one third of patients that do not exhibit all criteria of a given disease 5, thus preventing more premature deaths. The most common of these cardiac markers are myocardial bound creatine kinase (CK-MB), and cardiac troponin l and t (cTnl and cTnT). These markers are often found within a blood sample as levels start to rise between 3-8 hours and 3-4 hours respectively 7. More recently, new risk factor biomarkers such as C-reactive protein (CRP), myeloperoxidase (MPO) 11, 12, and lipoprotein-associated phospholipase A2 12 are being studied more in depth as alternative cardiac markers. Although cardiac biomarkers are heavily used, the role of noninvasive technologies also plays a major role in diagnosing coronary heart disease. These noninvasive methods include electrocardiography, exercise stress testing, echocardiography, cardiovascular MRI, and CT imaging of the heart 5. Some invasive, intravascular techniques include ultrasound, thermography, near infrared spectroscopy, cardiac catheterization, and cardiac angiography 12.As coronary heart disease is the leading cause of hospitalization and death among todays population, primary and secondary prevention strategies need to be considered with the utmost importance. indigenous prevention generally means the effort set away to modify risk factors and prevent their development delaying or preventing new onset coronary heart disease 13. As for secondary prevention, this often refers to the therapy involved to reduce recurrent coronary heart disease events thus secondary preventions are essentially treatment strategies. The most common and less intensive of these treatment strategies are that of the pharmaceutical therapies. Often, these drug regimes range from the daily aspirin intake to angiotension-converting enzyme inhibitors (ACEi), to -blockers and nitrates 12. These drug therapies often lower the risk of recurrent cardiovascular events. Unfortunately daily drug regimes do not work for everyone. Some people have their coronary heart disease surgically corrected either by angioplasty (insertion of stent to keep the jam vessel open) or by means of a more complex surgery consisting of a single to multiple coronary artery bypass. With everything considered, drug therapies and surgical correction are only a means of correcting the problem patients are also encouraged to increase physical activity and change their daily dietary habits in becoming more successful in reducing risk of development or progression of coronary artery disease.These different forms of coronary heart disease are very closely related to one another, more im portantly, closely related to atherosclerosis. As discussed previously, coronary heart diseases are characterized by the narrowing or stenosis of the coronary vessels, usually caused by the atherosclerotic plaque formation due to endothelial cell dysfunction. As a result, atherosclerosis is the underlying mechanism for ischemic heart disease, angina pectoris (stable, unstable, and variant), myocardial infarction and sudden cardiac death 12. Therefore it is important to understand the cellular pathogenesis of atherosclerosis, which will lead to a better understanding resulting in better prevention and treatment strategies for all forms of atheroma induced coronary heart disease.Introduction to AtherosclerosisAtherosclerosis, the primary etiology of cardiovascular disease, is characterized by intimal plaque that forms as a time-dependent response to arterial injury 14. Atherosclerosis is a disease affecting the arterial blood vessels, which is commonly known as hardening of the arter ies. This form of coronary heart disease is the principle source of both cerebral and myocardial infarction, gangrene of the extremities, and loss of function of both organs and tissues 15 this disease is ultimately responsible for a majority of deaths in North America, Europe, and Japan 16. The method of atherogenesis is not fully understood, however there are a number of current models that suggest that stressors corrupt the vascular integrity allowing the abnormal assembling of lipids, cells and extracellular matrix within the arterial wall 7. Due to its very slow progression, it is not surprising that atherosclerosis goes undetected and remains asymptomatic until the atheroma obstructs the blood flow within the artery 14,16 thus atherosclerosis is often referred to as the silent killer.Often, the atherosclerotic plaque can be divided into three distinct components. The first being the atheroma, which is the noduled accumulation of the soft, flaky, and yellow material of the pl aques, usually composed of macrophages closest to the lumen of the artery. The second component is the underlying areas of cholesterol crystals, and the third is the calcification at the outer old bag of the older/more advanced lesions 17. Collectively, these components constitute the basis of the atherosclerotic plaques. These atherosclerotic plaques are responsible for the arterial narrowing (stenosis) or they may rupture and make thrombosis 7, 14, 15 either way the atherosclerotic plaque causes an insufficient blood supply to the heart and other organs. As discussed previously, the atherosclerotic plaques lead to other major complications such as ischemia, angina pectoris, myocardial infarction, stroke, and causes impaired blood flow to the kidneys and lower extremities. Interestingly, arteries without many branches (internal mammary or radial arteries) tend not to develop atherosclerosis 5.One of the most evidence-based hypotheses regarding atherogenesis is that of the respons e-to-injury hypothesis. This hypothesis suggests that the atherosclerotic lesions represent a specialized form of a protective, inflammatory, fibroproliferative response to various forms of insult to the arterial wall 15. This seems to be a reoccurring theme, as now atherosclerosis is considered to be a form of chronic inflammation between modified lipoproteins, monocyte derived macrophages, T cells, and normal cellular elements of the arterial wall 16, 18. As with other diseases, there are a number of physiological factors that increases ones risk for developing atherosclerosis. These factors include age, sex, diabetes or impaired glucose tolerance, hypertension, tobacco smoking, estrogen status, physical inactivity, metabolic syndrome, and dyslipidemia 7, 19.The remainder of this paper will shift its focus to the pathogenesis of atherosclerosis including the ideas of endothelial dysfunction, lipoprotein entry and modification, recruitment of leukocytes, recruitment of smooth muscl e as well as other contributing factors such as dyslipidemia, hypertension, and diabetes. Also, the cellular complications of atherosclerosis will be discussed.Endothelial Dysfunction Primary Initiation of AtherosclerosisHealthy arteries are often responsive to various stimuli, including the shear stress of blood flow and various neurogenic signals. These endothelial cells liberate substances that modulate contraction and dilation of the smooth muscle cells of the underlying medial layer 7. These healthy endothelial cells are also responsible for the inhibition of migration of smooth muscle cells to the intimal layer 20 and they also play an important role in immune responses. Normal functional characteristics of healthy endothelium includes i) ability to act as a permeable barrier between the intravascular and tissue space, ii) ability to modify and transport lipoproteins into the vessel wall, iii) acts as a non-thrombogenic and non-leukocyte adherent surface, iv) acting as a sou rce of vasoactive molecules, v) act as a source of growth regulatory molecules, and vi) a source of connective tissue matrix molecules 14, 15. Overall, in a normal, healthy state, the endothelial layer provides a protective, non-thrombogenic surface with homeostatic vasodilatory and anti-inflammatory properties 7.It is widely known that the endothelium is responsible for the synthesis and release of several vasodilators such as NO, endothelium derived hyperpolarizing factors (EDHFs), endothelial derived relaxing factors (EDRFs), and prostacyclin (PGI2) 7, 20. These vasodilators utilize a G-coupled signaling pathway, where NO diffuses from the endothelium to the vascular smooth muscle where it activates guanylyl cyclase (G-cyclase) 7. The G-cyclase in turn forms cyclic guanosine monophosphate (cGMP) from cGTP an increase in cGMP results in smooth muscle relaxation which subsequently involves a reduction of cytosolic Ca2+. Aside from these anti-thrombic substances, the endothelium als o produces prothrombic molecules including endothelin-1 and other endothelium derived contracting factors (EDFCs) 20. Importantly, the endothelium derived NO not only modulates the tone of the underlying vascular smooth muscle, but is also responsible for the inhibition of several proatherogenic processes. These processes include smooth muscle proliferation and recruitment, platelet aggregation, oxidation of low assiduity lipoproteins (LDLs), monocyte and leukocyte recruitment, platelet adhesion, and the synthesis of inflammatory cytokines 20. Therefore, relating back to the response-to-injury hypothesis, loss of these endothelial functions promotes endothelial dysfunction, thus acting as the primary event in atherogenesis.Endothelial dysfunction is considered to be an initiating event which leads to the pathogenesis of atherosclerosis. For this reason endothelial dysfunction has been shown to be of prognostic significance in predicting such vascular events as heart attacks or stro kes 21. It has been established that endothelial cell dysfunction is characterized by alterations in vascular permeability and inadequate production of NO 4, 22, 23 thus predisposing the endothelium to the development of atheromas. Interestingly, in response to initial atheroma formation, the arteries often dilate, causing outward remodeling of the vessel for this accommodation 4 however if this remodeling is insufficient, the blood flow is impaired, thus causing ischemia 4. Several physical and chemical factors are responsible for affecting normal endothelial function. Some common factors discussed previously include diabetes, hypertension, hypercholesterolemia, smoking, age, diet, and physical inactivity. However, more importantly are the physiological factors i) impairment of the permeable barrier, ii) release of inflammatory cytokines, iii) increase transcription of cell-surface adhesion molecules, iv) altered release of vasoactive substances (PGI2 and NO), and v) interference w ith normal anti-thrombotic properties 7.Commonly, endothelial dysfunction is characterized by the reduction of vasodilators NO and PGI2, and the increase of various endothelial derived contracting factors 23, 24. This impairment may also predispose the vessels to vasospasm 22. This decrease in NO bioavailability is thought to cause a decreased level of normal of endothelial cell NO synthetase (eNOS) 21, thus reducing the likelihood of vasodilation from occurring. Apart from its vasodilatory role, NO is also responsible for resisting inflammatory activation of endothelial functions such as expression of the adhesion molecule VCAM-1 5. NO has also appeared to exert anti-inflammatory action at the level of gene expression by interfering with nuclear factor kappa B (NFB), which is important in regulating numerous genes involved in inflammatory responses 5 these inflammatory responses will be discussed later on. The other common vasodilator, PGI2 is also reduced during endothelial dysfu nction. PGI2 is a major product of vascular cyclooxygenase (COX) and is considered a potent inhibitor of platelet aggregation 20. Like NO, PGI2 is an endothelial derived product which is often produced in response to shear stress (commonly caused by blood flow) and hypoxia 20. By understanding the other roles NO and PGI2 play within the endothelium, we can see that a decrease in one or the other ultimately leads to dysfunction and disruption of the endothelium. As a result of vasodilator reduction, the endothelium often synthesizes and releases EDCFs causing endothelial constriction. The major constrictors include superoxide anions (which act by scavenging NO thus further reducing NO levels), thromboxane A2, endothelin-1, AII, and -adrenergic factors 20. Unlike the vasodilators, the vasoconstrictors utilize two signaling pathways. The 1-adrenergic receptor signaling pathways utilize the same G-coupled pathway as the vasodilators (discussed previously) however instead of cGMP it ut ilizes cyclic adenosine monophosphate (cAMP) 1. The other constrictors including thromboxane A2, endothelin-1 and AII utilize the cAMP-dependent protein kinase pathway where the activated kinase acts as a trigger for various physiological effects, including increased contractile activity on the arterioles 1.The overall progression of atherosclerotic plaque formation is best illustrated in act 1, which showcases multiple events that are simultaneously triggered by endothelial dysfunction.Apart from the imbalance of vasoactivators, endothelial dysfunction is responsible for initiating two other separate pathways that also accede in the progression of plaque formation and growth. Lipoprotein entry is the next initial stage in atherogenesis. This is then followed by the modification and entry of lipoproteins, the recruitment of leukocytes, and the migration and proliferation of smooth muscle cells. Overall this evolutionary process best represents the formation of atherosclerotic plaq ues within the vessels.Lipoprotein Entry and ModificationLipid accumulation is another major materialisation of the vascular response to injury, and is accelerated by the entry and modification of lipoproteins. Lipoproteins are composed of both lipids and proteins, and help transport water-insoluble fats throughout the bloodstream 7, 25. The lipid pump is surrounded by hydrophilic phospholipids, free cholesterol and apoliporoteins where the protein portion has a charged group, aimed outwards to attack water molecules, thus making the lipoproteins soluble in the plasma of the blood 26, 27. In total, there are five major classes of lipoproteins the chylomicrons, very low density lipoproteins (VLDLs), intermediate low density lipoproteins (ILDLs), low density lipoproteins (LDLs), and the high density lipoproteins (HDLs). The chylomicrons provide the primary means of transport of dietary lipids, while the VLDLs, ILDLs, LDLs, and HDLs function to transport endogenous lipids 16, 25. Of the lipoproteins, the LDLs are of most interest. Interestingly high LDL levels often correlate closely with atherosclerosis development, whereas high HDL levels protect against atherosclerosis the HDL protection is thought to be related to its ability to transport lipids away from the peripheral tissues back to the liver for disposal 7.A key component to the accumulation of lipids is due to the endothelial dysfunction, which causes a loss of discriminating permeability and barrier function. This ineffective permeability allows for the entry of LDLs into the intima lining of the vessels 7, 16. The highly elevated circulating levels of LDLs are colloquially referred to as having hyperlipidemia, hypercholesterolemia, or dyslipidemia 7, 25-27. In either case, once the LDL has entered the intima of the vessel, the LDL starts accumulating in the subendothelial space by binding to components of the extracellular matrix, the proteoglycans lipolytic and lysosomal enzymes also play a role in lipid accumulation 27. Importantly, statins lower circulating cholesterol levels by indirectly inhibiting HMG CoA-reductase (rate limiting enzyme required for endogenous cholesterol biosynthesis 16. This results in the decrease of intracellular cholesterol levels, which leads to the activation of SREBP, upregulation of LDL receptors, and the clearance from plasma degradation of LDL thus reducing circulating LDL levels 16.When the lipid accumulation increases the residence time that the LDL occupies within the vessel wall, it allows more time for lipoprotein modification 7 which appears to play a key role in the continued progression of the atherosclerotic plaque. Often, endothelial cell dysfunction leads to the altered expression of lipoprotein receptors used to internalize and modify various lipoproteins 14. These changes usually occur via oxidative modifications. The oxidative modification hypothesis (figure 2) focuses on the concept that LDLs in their native state are often not atherogenic 27. It is believed, however, that LDLs are modified chemically by the endothelial cells 26 and are readily internalized by macrophages (formation of the foam cell) via the scavenger-receptor pathway 27. Essentially the trapped LDL within the subendothelial space is oxidized by the resident vascular smooth muscle cells, endothelial cells, and macrophages. As a result t

Right to Free Movement in the European Market

Right to Free Movement in the European MarketThe philosophyThe right to move freely represents one of the fundemental freedoms of the European subjective market. This superior general rule on free movement rights under EC law continues to be developed,1 either due to element state progression or economical and aditible demands. Although one of the most panoramic in its ideals, the free movement of workers has seen several central legal anaesthetizes arise on various occassions. nevertheless exploration of these central issues must be seen through a consideration of the tensions and interplay between twain economic and social aspects of the free movement of people from both inside and outside of the European Union.The free movement of a citizen of the European Unon is seen to contribute to the economic progression of the Community as a whole. In the adept market the worker is also a human being exercising their right to live in a nonher state and to take up piece of work w ithout the risk of discrimination and to improve the standards of living for themsleves, and possibly, their families.But for nationals of a third party cases such(prenominal) as Chen (2004), Baumbast (2002) and Carpenter (2002) establish meant that as the match or realtive of an EU citizen their entry into the Community is a secure one. Further, gaining the same rights of an EU citizen under Regulation 1612/68 EEC.But this idea of border controls and unbound freedom of movement at bottom the Community is closely interlinked with the posiiton of the non-EC national, whose right to movement and residence under EC law is limited,2 as well as the contribtuing issuance that the members states attitude has upon their admission.3Fortress EuropeAlthough EC legislation had intended that internal barriers to the four freedoms be eliminated and that only an external barrier (at the borders of the Community) remain, academics have argued that this whitethorn not always be so4how these pro posals have been watered d take in through discussion in member states, in particular in relation to employment, which is an burning(prenominal) requi lay for the integration of migrants.5Whilst the freedom of the EC worker is guaranteed through Treaty rules and secondary legislation, this does not mean that member states may no longer achievement control over population movements, into and within their territories.6 But some ECJ case law on Directive 68/360 expressly recognised that member states may have legitimate reasons for wishing to keep account of the population within their terrrtories.7The European Union, by using border controls to its extremities, has managed ot create a border-free, intra-EU site creating what has been dubbed as Communierisation of its geographical spot.Although the EU has been successful in its pursuit of re move internal barriers to the four freedoms, its imposition of external barriers (namely, the fortress Europe tendany) ar dread upon those na tionals of third parties from stepping into Europe unless they are related to a citizen of the EU who excerts their right to free movement.The EU has long been attacked as an exclusionary organisation concerned solely with the citizens of its own member states at the cost of non-EU citizens residing in the EU, even though many of the latter form part of ethnic or religious minorities and suffer social exclusion.8So, it seems that the principles governing the borders of the Community are failing those third party nationals.9The OutsidersA vivid example of how fortress Europe had imposed this restriction can be noted prior to the accession in 2004 of many, now, Central and Eastern European countries. Lavenex10 argues that prior to, and with suggestions of accession for Central and Eastern European countries the, then, current members of Europe had feared large-scale immigration from these countries into their own territories. The EUs already heavily regiinented rules of external borde r barriers on trade and migration from outsiders (those countries not members of the EU) where to form part of the accession policies. heart and soul that the acceeding Central and Eastern European countries encountered stringent preventative stances to their entrance into the EU on beahlf of the Community.But during a time when security at an intergovernmemtal level is already on red alert due to heightened tensions caused by the threat of terrorism,11 it appears that migration has become a security rather than economic issue. So risking mmigrants and asylum-seekers being portrayed as a challenge to the protection of national identity and welfare provisions. Moreover, supporting the political construction of migration as a security rather than economic issue.12 getting in or staying out?The treatment of third country nationals (besides those who have derived rights through Community family members) can be understood through external and internal dimensions. The external element, n amely the issue of getting into the EU focuses on the member staes and the institutions emphasis of immigration and border controls. even, according to the case of Wijsenbeck13, the member states are fluent able to perfomr checks at their own borders, be them external or not. But this policing of movement draws attention to the vulnerablity of the third country national.14 But progression has been felt. Through Artcles such as K.1 to K.9 of the TEU governing policies such as asylum, immigration and third country nationals which have now been intergrated into the EC Treaty (as Title IV) , as well as Regulations have now inacted the uniform format for visas.15 Regulations also cover the listings of third countries whose nationals must be on will power of visas when crossing external borders.16Importanly, the area of immigartion and the member states stance on the matter of border control is liable to change in accordance with their political climate. The emphasis post-September 11t h has fallen squarely on matters of security.17 Various member states have also expressed concern at the numbers of third country nationals seeking asylum in their territory, so reinforcing their diffculties in gaining access into the EU.The internal dimension of the matter is one which concentrates on the rights of third country nationals already residing within the Community. As there is no stringent root as to their status upon this such limiteed rights are based on various possible provisions. This can include their capacity as a family member of an EU citizen (as aforementioned) or as employees of EC service providers or as subject to one of the Communitys Assocaition, Co-operation or other International Agreements with third countries.18 level(p) though their residence in the EU may be legitimate the general range of EC rights and freedoms, however, do not apply to them. With speculation change magnitude as to the possible imposition of ID cards within the UK has also been b acked by the controversial possible introduction of the staus of European citizenship. This citizenship, which would be conditional upon the possession of member state nationality, may only serve to emphasise the differences in treatment between EU nationals, who possess such nationality, and those who do not.But from an economic standpoint, countries potentially out of the line of terrorist fire have welcomed the idea of third country nationals, especially those intending to work, as being a potential boost to their economy. Yet the richer member states argue that the heightened security risks and flood gate effects that recent accession has had is already having an adverse effect on their economies.Concluding Staying stationaery or moving through the times?But Peers19 argues that change may soon be on the horizon with the implementation of Directive 2003/109 on the status of long-term occupier third-country nationals within the European Union. This Directive was an opportunity to address the long-standing criticism that the EU gives insufficient protection to its resident third country nationals. Already being describe as limited and disappointing in a number of respects. Yet, if consequential jurisprudence reflects its interpretation as being in line with the context and objectives of the Directive, it could figure out a positive contribution to the status of third country nationals in the EU. This especially as in regards to movement between member states.20By jet accord, the unity the EU claims for itselff when constituting itself as an area of freedomn, secrutiy and justice has become troublesome. Critics are quick to point out that the area in which freedom, security and justice are to reign is a spurious geographical unity.21Yet, even if it were to be accepted that Europe is a geographical union, the fact remains that the EU has agreements with countries outside of this territory (such as the 1963 Ankara Agreement with Turkey), meaning that EU exte nds its reach outside of this area.22One of the main arguments behind the impact Europe is having by waterproofing off its border lies closer to home. Given that accession into the Community is based upon adaptation of national policies, be them economic, political or social, to those already established within the EU, many countries faced closing their borders to the outside for upholding the principles of preventing illegal immigration. But, in contrast to this member states are also expected to uphold the humanitarian standards of refugee protection23 and the principles of the European humankind Rights Act. With the EU being a figure-head in the creation and implementation of human rights agendas, this contradiction will only serve to weaken the EUs star political status. Where member states face penalties for failing to uphold either of these policies, many are at a loss as to which one prevails. These conflicting ideals have obviously affected the manner in which those member states with borders to the outside have integrated the principles into their immigration and refugee procedures. Further to Lavenexs idea of fear of mass migration by the West, Huysmans alleged that the question of migration from countries external to the EU is a security problem rather than just one of immigration and asylum. As Huysmans statesSince the 1980s, the political construction of migration progressively referred to the destabilizing effects of migration on domestic integration and to the dangers for public order it implied.24Huysmans also alleged that due to such developments as the Schengen Agreements and the Dublin Conventionvisibly channelize that the European integration process is implicated in the development of a restrictive migration policy and the social construction of migration into a security question.This meaning that access for third country nationals is now even tougher maybe the member states would prefer for the barriers surronding fortress Europe to r eamin?The Schengen Convention completely removed border controls and placed stricter contorls at the external barrier of the EU. This resulting in a stronger emphasis on external restrictions and lifting all restirtcions between member states. The Schengen scheme had been directly accredited to concerns over the amplify of organised crime within the Coimmunity. But with conerns inceasing still as to the problems of human and drugs trafficking into the EU from third countries and its threat to internal security only serves to push the issue of external border control into the spotlight once again.Ultimately, academic writing25 has contemplated the responsibility of the EU to uphold its policy on human rights and its measure of internal barriers to freedom of movement. But as inportant as thiese priniples may be in maintaining structure and authority the Community should also reconsider its position on a global scale when encountering the needs of asylum seekers at their external bor ders as well as those already residing with them without the claim of derived rights.Footnotes1 Carrerra, S. (2005)2 Peers, S. Towards Equality actual and Potential Rights of Third Country Nationals in the Euroepan Union. (1996)3 Craig, P and De Brca, G. EU Law Text, Cases and Materials.4 Binkman, G (2004)5 op cit6 I tender 37 Case 321/87 armorial bearing v Belgium (1989) ECR 9978 Peers, S. (2004)9 ECRE (2004)10 Lavenex, S. Safe Third Countries Extending the Eu Asylum and Immigration Policies to Central and Eastern Europe11 Levy (2005)12 Huysmans (2000)13 (1999)14 I bid 315 Reg. 334/200216 Reg. 359/200117 I bid 1118 I bid 219 I bid 820 op cit21 Lindahl, H. Finding a Place for Freedom, Security and Justice The European Unions claim to Territorial Unity. (2004)22 ibid 823 I bid 1024 Huysmans (2002)25 I bid 21

Rabies :: essays research papers

rabidnessRabies is an infectious disease of carnals which is a member of a group ofviruses constituting the family Rhabdoviridae. The virus particle is covered ina fatty membrane, is bullet-shaped, 70 by 180 nanometres and contains a singlehelical strand of ribonucleic acid (RNA).Although rabies is usually spread among domestic dogs and wild carnivorousanimals, all warm-blooded animals are susceptible to infection. The virus isoften present in the salivary glands of infected animals, referred to as rabid,and is excreted in the saliva. The bunco game of the infected animal easilyintroduces the virus into a fresh wound. In humans, rabies is not usually spreadfrom man to man, rather the majority of infections occur from rabid dogs. by and bya somebody has been inoculated, the virus enters small nerve ends around the siteof the bite, and slowly travels up the nerve to reach the central nervous system(CNS) where it reproduces itself, and give then travel down nerves to thesalivary g lands and replicate further. The time it takes to do this depends onthe length of the nerve it must travel - a bite on the foot will have a muchlengthier incubation period than a facial bite would. This period may last from devil workweeks to six months, and often the original wound will have healed and beenforgotten by the time symptoms begin to occur.Symptoms in humans present themselves in one of two forms furious rabies, or dumb rabies. The former is called such because of the severe nature and rangeof the symptoms. The virus, upon reaching the CNS will present the person withheadache, fever, irritability, restlessness and anxiety. Progression may occuron to muscle pains, excessive salivation, and vomiting. After a few days or upto a week the person may go through a stage of excitement, and be afflicted withpainful muscle spasms which are sometimes set off by swallowing of saliva orwater. Because of this the afflicted will drool and learn to fear water, whichis why rabies in hu mans was sometimes called Hydrophobia. The patients are also super sensitive to air or drafts blown on their face. The stage lasts onlyfews days before the onset of a coma, then death. Dumb rabies begins withalto furious rabies, but instead of symptoms progressing to excitement, a steadyretreat and quiet downhill state occurs. This may be accompanied with paralysisbefore death. Rabies diagnosis in this type of cases can be missed.Unfortunately with both furious and dumb rabies, once the disease has taken hold

The Challenge of Communication between Men and Women Essay -- Personal

He looks at me with big puppy dog eyes and says,Kate, do you re each(prenominal)y want me to stay? hello Now, you pay off to understand that I dont want to make decisions for him, and I dont want to be controlling, so I say, Its your decision. Wow, that is the number one clue if you get that define youd better stay with her.Why cant you just listen to me? I dont want your advice I just want you to listen I yelled.I did listen to you you could have done something to prevent that problem my boyfriend replied.That was the gist of our last argument. We concluded that we were just different people. Well, of course we are different people. I am a womanhood, and he is a man. Thats right I am a woman, and why cant a man understand what a woman wants? Come on--we give them all the right clues we basically feed it to them. (They might as well just roll over and drool.) The truth is, men and women communicate in different ways we talk, listen, and act differently. This fact can create some major misunderstandings and even arguments. I am a woman, so I have a bonny good idea of what a woman wants. So listen up boysMen and woman actually think differently. For example, a man and a woman are having a professional conversation. As the man talks, the woman nods her head, and the man thinks, Oh great, she agrees with me. (Where the heck does he get off thinking that?) The woman actually nods her head to manoeuvre she understands what is going on. Now why dont men pick up this good habit of nodding the head? I mean, come on, when I am assay to explain something to a man he just stares at me. (Do I have to repeat every(prenominal)thing ten times before a man says or shows me that he understands what I am saying?) Being a woman, I understand ... ... play dumb, so men you better start picking up the obvious clues we lay down in front of you.There is no other way to explain it--men and women are just simply different. We think, act, and talk differently, and general we co mmunicate differently. Its no wonder men and women get in so many arguments. To each man and to each woman, their point of view is very clear. However, every woman knows, just as every man knows, that a woman is always right, and that what a woman wants is just what she should getWorks CitedEnglish talking to by Gender. Geocities.Com 26 October 2000http//www.geocities.com/a3a17013/jokes/genderlang.htmWood, Julia. Communication in Our Lives. New York Wadsworth/Thomson Learning, 2000. Center for Applications of Psychological Type. The Myers Briggs Type Indicator. Gainesville Consulting Psychologist Press, Inc., 1988.

The Dilemma: An Open Or Closed Pedagogy Essay -- Education Teaching Es

The Dilemma An Open Or Closed PedagogyWith lifelong effects, teachers impact the quantity, quality, and over every enjoyment of the educational experience. Their effect dilutes itself the classroom, into present life, and yet the future. In the classroom, they mold and guide youth in their lifelong quest to search for the truth and their experience voice in the world. Yet their influence does not stop at the classroom door. In fact, teachers have a profound impact on morals, creativity, and even politics. Teachers always have the power in the class, Christian Zawodniak discusses in , Ill Have To Help More Of You Than I Want To. They hold the grades and students usually perceive them as holding the knowledge too (Zawodniak 124). But how should a teacher exercise this bestowed power? Is a forced learning environment more beneficial or is a cooperative pedagogy more ample? With diverse students and unique learning needs, it is difficult to identify one or the other as more a dvantageous. However, I will attempt to explore the benefits and disadvantages of both, as well as how they can be combined or compromised in a delicate balance. Although I will strive to stay neutral and simply present the options, I may also occasionally include my own personal experiences.Hopefully in a purely unbiased fashion.Donald Lazere, Ground Rules For Polemicists, cuts that allTeaching is political and that no human can do anything nonpolitical because we would have to get totally outside ourselves and divorce ourselves of all our interests (Lazere 663). If this statement is true, consequently teachers are hardly immune and a truly unbiased classroom cannot exist because personal beliefs or opinions are bound to surface soone... ... others. As well, where their own voice came from and how to develop it more intensely. Further, an ideal pedagogy provides alternative definitions of the truth, not merely the one students have been absorbed by all of their lives. I contend this combination or compromise as the ideal learning environment for the student. Works CitedCheney, Lynne V. PC Alive and Entrenched. Andrea A. Lunsford and John J. Ruszkiewicz,The Presence Of Others Voices That Call For A Response. refreshed York St. Martins Press, 1997. (112-123).Lazere, Donald. Ground Work For Polemicists The Case Of Lynne Cheneys Truths. College English 59 (1997) 661-685.Zawodniak, Christian. Teacher Power, Student Pedagogy. Andrea A.Lunsford and John J.Ruszkiewicz, The Presence Of Others Voices That Call For A Response. New York St Martins Press, 1997. (124-132).

Colette Dowlings The Cinderella Complex: Womens Hidden Fear of Indepe

Colette Dowlings The Cinderella Complex Womens Hidden tending of IndependencyIn her book, The Cinderella Complex Womens Hidden Fear of Independency, Ms. Colette Dowling states her belief in a designate which she names the Cinderella complex, being an intricate system of beliefs put upon women which make them feel as if they must be submissive to the wills of others, seemingly less intelligent than they truly are. However, with a more detailed analysis of the tale of Cinderella, Dowling would take on realized that this is not a solely accurate naming of her discovered complex. But in order to prove this, we ourselves must take a closer look at the tale of Cinderella. In the classic version of Cinderella, that written by Charles Perrault, we are presented the image of a girl completely submissive to the will of her stepmother and of her sisters. Not quite flattering to the mod woman. However, let us examine the author and the circumstances surrounding his retelling of the story. C harles Perrault was a French nobleman, whose project was to collect tales from alone over the world and rewrite them in such a format as would make them suitable for his intended audience, namely the French court. In the world of royalty, it is the man who is truly important, the sole dissolve of his wife being to bear him children and make him look good in public. Perraults Cinderella is a perfect example of what, in the eye of his audience, would be considered the perfect wife. She was a hard worker, who never objected to anything that she was told. She was sweetness itself, according to Perrault, a perfect girl without a trace of animosity in her being--as is shown in her final treatment of her stepmother and sisters. She would ne... ...lking on our drive home from school, I said to her, if I were a girl, its not like I would turn 19 and suddenly say I have to get married now, its more like you know, maybe I am ready to get married. But she responded that its not that simple.. .that she felt pressured to get married quickly, because if she would wait, all the good husbands would be gone already. She also mentioned that girls who wait longer take on a status of being less than prime candidates for matches. This shows an evident outside(a) force acting on women to make them fear their own independence. (However, I cannot state the existence of such a condition in the same flair anywhere outside the American religious Jewish community.) Sarah was married on December 29th, and moved to New York three days later. So perhaps the condition would be more appropriately named the Sarah complex.

The Omnivore’s Dilemma: A Natural History of Four Meals by Michael Poll

The Omnivores Dilemma A Natural History of Four Meals by Michael Pollan, was a great read. I came into the adventure without much background regarding what kind of book it was going to be, and to my astonishment it was more of an educational journey than pages of force-fed beliefs. Michael Pollan has a writing drift that is both loose and intriguing and really kept my attention throughout. Having already read extensively concerning human nutrition and food, I am usually nescient when beginning such reads as this one, but I was very surprised that Mr. Pollan was very objective, in that this was seemingly a field trip and journey from surroundings to plate. I will begin this report with a summary of this great book and delve deeper into the thoughts that the literary family has of it. I will then go on to explain its importance in the development of environmental policy and impact, and end with my thoughts regarding the material and the interaction among social and environmenta l values and impacts presented by the author Michael Pollan. outlineThe book begins with the principal of What should we have for dinner? and stands to answer that question the rest of the way. Speaking directly of Americans, Pollan explains in-depth how the Nation tends to jump from fad to fad, first being frightened of carbohydrates, and then switching to fats, and so on. He goes on to explain where this thought process might have come from with the history of the Carter administration in 1977, as dietary goals were issued and the red meat lovers of America were warned to cut back. From that time on it has been an ever-changing lipo-, carbo-, phobia, with a cycle of weight loss and gain. With this question at hand, Michael Pollan begins to come down de... ...ormative history as he travels from the cornfields of Iowa, to the feedlot, to the forest floor in search of chanterelles, and then coming full circle to the dinner table. The information given is non always pleasant, but it is necessary for an informed eater in America to be aware of. The effects of knowing can cause us to be more responsible in what we are purchasing at the grocery store (and essentially voting for). He shows that making the correct decision to the question What should we have for dinner? can also be the choice that tastes the best and is the best for you.Works CitedKamp, D. (2006). Deconstructing Dinner. New York Times Sunday Book Review. 26 April 2006.http//www.nytimes.com/2006/04/23/books/review/23kamp.html?pagewanted=all&_r=0Pollan, M. The Omnivores Dilemma A Natural History of Four Meals. New York. Random. 2006. Print