بایگانی برچسب برای: Cardiovascular

Mitochondrial.Dynamics.in.Cardiovascular.[taliem.ir]

Mitochondrial Dynamics in Cardiovascular Medicine

Mitochondria in cardiac myocytes are densely packed to form a cell-wide network of communicating organelles that accounts for about 35% of the myocyte’s volume . The lattice-like arrangement of mitochondria, mostly in long and dense rows parallel to the cardiac myocyte myoflaments, has the structural features of a highly ordered network . This specifc mitochondrial network architecture ensures that the large demand of adenosine triphosphate (ATP) of cardiac myocytes is met and appropriately distributed. Mitochondria synthesize approximately 30 kg of ATP each day to both provide energy for the basic cellular metabolism and to secure basic physiological functions of the cardiovascular system such as the maintenance of pulmonary and systemic blood pressure during heart contractions . Their intracellular position is closely associated with the sarcoplasmic reticulum and the myoflaments to facilitate cellular distribution of ATP . However, the role of mitochondrial structure and function is not only limited to ATP generation; mitochondria participate in and control numerous metabolic pathways and signaling cascades such as the calcium signaling, redox oxidation, β-oxidation of fatty acids, oxidative phosphorylation, the synthesis of aminoacids, heme and steroids, and cellular apoptosis . Their structural and functional diversity thus surpasses any other cellular organelle.
Complexity.and.Nonlinearity.in.Cardiovascular.[taliem.ir]

Complexity and Nonlinearity in Cardiovascular Signals

This chapter aims at providing a brief overview of the main aspects in cardiovascular physiology that have encouraged and justified the use of advanced nonlinear signal processing methodologies for the study of the cardiovascular system. This system, in fact, constantly adapts to changes in internal and external conditions to maintain blood pressure homeostasis through complex and dynamic feedback mechanisms that simultaneously affect several processes such as heart rate, cardiac output, blood pressure, respiration, peripheral resistance etc. Therefore, there is a need for nonlinear, non-stationary, and multivariate approaches to assess cardiovascular interactions and their causal structure in health and disease. This chapter aims at providing a brief overview of the main aspects in cardiovascular physiology that have encouraged and justified the use of advanced nonlinear signal processing methodologies for the study of the cardiovascular system. This system, in fact, constantly adapts to changes in internal and external conditions to maintain blood pressure homeostasis through complex and dynamic feedback mechanisms that simultaneously affect several processes such as heart rate, cardiac output, blood pressure, respiration, peripheral resistance etc. Therefore, there is a need for nonlinear, non-stationary, and multivariate approaches to assess cardiovascular interactions and their causal structure in health and disease. This introduction focuses on short-term regulation of the cardiovascular function, whose primary aim is to ensure that blood pressure allows oxygen and nutrients supply to match body’s needs. The most important parameters that determine the cardiovascular function as well as their normal range are reported in Table 1.1.
Exosomes.in.Cardiovascular.Diseases.Biomarkers.[taliem.ir]

Exosomes in Cardiovascular Diseases

Cytoplasm of eukaryotic cells contains several compartments, including transGolgi network, mitochondria, peroxisomes, endoplasmic reticulum, having different functions. Transport of macromolecules among these dynamic structures is mediated by vesicles moving in a densely populated microenvironment . In some instances, part of these vesicles are released into the extracellular milieu. Extracellular vesicles (EVs) are part of mechanism of intercellular communication, a function of vital importance for multicellular organisms. For decades, intercellular communication has been thought to be solely regulated by cell-to-cell contact and release of soluble molecules into the extracellular space. These molecules transmit the signal through their uptake or binding to specifc receptors on target cells. However, the discovery of vesicular structures released into the extracellular space containing a multitude of factors including signaling molecules, proteins and nucleic acids, has opened a new frontier in the study of signal transduction, thereby adding a new level of complexity to our understanding of cell-to-cell communication. Body fluids (e.g., blood, urine, saliva, amniotic fluid, bronchoalveolar lavage fluid, synovial fluid, breast milk) contain various types of membrane- enclosed vesicles recognizing different pathways of biogenesis. These vesicles possess different biophysical features and functions in health, e.g., protein clearance, immune regulation , cell signaling , as well as in disease, such as in infections and cancer . Originally, EVs were thought to be garbage bags through which cells eject their waste. Today, it is widely accepted that EVs are key components of the intercellular communication network.
Cardiovascular.Biomechanics.2017.Peter.[taliem.ir]

Cardiovascular Biomechanics

An understanding of the functioning of the cardiovascular system draws heavily on principles of fluid flow and of the elastic behaviour of tissues. Indeed, much of the cardiovascular system consists of a fluid (blood), flowing in elastic tubes (arteries and veins). This chapter will introduce basic principles of fluid flow and of solid mechanics. This area has developed over many centuries and Appendix 1 provides details of key scientists and their contribution. The concept of a fluid and a solid is familiar from everyday experience. However, from a physics point of view, the question arises as to what distinguishes a fluid from a solid? For a cubic volume element there are two types of forces which the volume element experiences (Fig. 1.1); a force perpendicular to a face and a force in the plane of a face. The forces perpendicular to the face cause compression of the material and this is the case whether the material is liquid or solid. The force parallel to the face is called a shear force. In a solid, the shear force is transmitted through the solid and the solid is deformed or sheared. The shear force is resisted by internal stresses within the solid and, provided the force is not too great, the solid reaches an equilibrium position. At the nano level the atoms and molecules in the solid retain contact with their neighbours. In the case of a fluid, a shear force results in continuous movement of the material. At the nano level the atoms and molecules in the fluid are not permanently connected to their neighbours and they are free to move. The key distinction between a fluid and a solid is that a solid can sustain a shear force whereas a fluid at rest does not.