In the last decades, the outstanding role of Thyroid gland in regulating both physiological and pathological operation of cardiovascular system has been acknowledged worldwide. Three main domains of Thyroid function, that is to say, euthyroidism -hyperthyroidism-hypothyroidism, have a direct impact on cardiac response through a variety of mechanisms. Cellular pathways mediate in cardiac contractility, cardiac output, cardiac rhythm, arterial blood pressure and peripheral vessel resistance. Particular biochemical algorithms exist not only between Thyroid hormones' serum concentration and thyroid gland but also between the hormones' serum level and heart muscle genes. These biochemical pathways primarily regulate the appropriate secretion of levothyroxine (T4) and triiodothyronine(T3) via Thyroid- Stimulating-Hormone(TSH) pituitary system, and secondly adjust the cardiac function. In this study, a mathematic model has been developed describing significant aspects of positive or negative feedback mechanisms of THYRO-CARDIAC (THY-CAR) system along with potential applications of novel up-to-date patents in this area of research.

Intoduction: The aim of the study was to investigate whether chaotic phenomena (chaos theory) affects the process of Gene Expression. Methods: Modeling the genes X, Y and Z-which encode a certain protein P-a set of three first order differential equations has been developed and studied in phase-space (x,y,z). Results: The elementary equilibrium points in three dimensional phase portrait analysis, include attractors, saddles and repellors. Conclusions: Attractors indicate a stable equilibrium point which attenuates the production of the protein P, while the saddles and particularly the repellors correspond to an unstable dynamic system, which promotes either the production of a P-flaw protein or totally inhibits gene expression. Among other mechanisms-e.g. patents for gene treatment (US2007000515344) and modulation(US20040014083A1)-chaotic phenomena also seem to regulate in a particular way the DNA encoding , that calls for further theoretical and experimental research(e.g. cardiovascular disease, oncology). Keywords: DNA, chaos, phase-space, gene expression, cardiovascular disease

Objective: To study the impact of pressure drop (PD) which was developed along experimental stenoses on Pulse Wave Velocity (PWV). Methods: Eight, healthy, Landrace pigs were subjected to thoracotomy. In the upper segment of descending thoracic aorta a circumferential symmetric constriction 5 mm in length, was imposed and stabilized so that a pressure drop of 0 (DP-0, control group) 10 (DP-10), 20 (DP-20) and 30 mmHg (DP-30) could be created. respectively. Via catheterization of the vessel with pressure tip catheters, PD could be monitored. Pulse Wave Velocity (PWV) was measured via simultaneous recordings of Electrocardiogram and Doppler pressure waveforms which were received from right carotid and femoral artery. Then the recordings were fed to a computer for analytical estimation of PWV on several occasions: PWV-DP-0=8.27 +/- 0.12 m/sec, PWV-DP-10=8.68 +/- 0.13 m/sec, PWV-DP-20=9.19 +/- 0.13 m/sec and PWV-DP-30=9.51+/-0.14. Results: Significant increase in PWV estimated for all pressure drops compared to the control group. Thus, PWV-DP-0 vs. PWV-DP-10 or PWV-DP-20 or PWV-DP-30 were found to be statistical different (p < 0.05). Conclusions: The observed increase in PWV is proportional to the developed PD along the experimental stenoses. The higher the pressure drop the higher the arterial stenosis and the higher the PWV-increase. The present outcome should be taken into account in patients with atherosclerosis because minor stenoses in the aorta may produce cumulative PWV elevation which undermines coronary flow reserve. Keywords: Aorta, stenosis, pressure drop, Pulse Wave Velocity

Objective: We assessed the radial distribution of elasticity in healthy porcine thoracic aorta. Methods: Cylindrical aortic specimens (n=24) were tested in a uniaxial tension device so that their Stiffness Modulus (SM) could be determined. The specimens were divided into three groups: Group A, radial stretching at zero degrees; Group B, radial stretching at forty five degrees; and Group C, radial stretching at ninety degrees. Results: Stress-Strain analysis showed that (SM-A) vs. (SM-B) and (SM-A vs. SM-C) and (SM-B vs. SM-C) were not statistically different for all strain levels (e=0.5, 1, 1.5, 2.3). Conclusions: In vitro, the radial expansion of aortic tissue appears to be uniform.Thus, diminished elastic properties of the aorta in cases of atheromatosis, would appear in these radial directions where the tissue is atheromatic. So, a useful site prediction could be made for future development of vessel abnormalities (i.e. aneurysm rupture) and the necessary vascular prosthesis might be applied more effectively. Keywords: Elasticity, radial, aorta, distribution, basal plane

OBJECTIVE:To establish a yielding criterion for porcine thoracic aorta. METHODS:The thoracic aortas of three healthy pigs were used in order to form three testing groups: Group D, included aortic Dactyl tissues (n=8); Group C, included aortic Circumferential tissues (n=8); and Group L included aortic Longitudinal tissues (n=8). These groups were tested in a uniaxial tension device in order to determine the mechanical properties of the vessel. RESULTS:Stress-Strain analysis of testing groups showed that for Low strain level (e=0.5) Stress of D group (S-D) was statistically (S, p<0.01) greater than that of C and L groups (S-D>S-C and S-D>S-L, S); for medium strain level (e=1, S-D>S-L, S); for high strain level (e=1.5, S-D>S-C, S-D>S-L, S-C>S-L,S); and for yielding strain level e=2.1 (S-D>S-C, S-D>S-L, S-C>S-L,S). Additionally, mathematical elaboration of yielding data produced a criterion defined as: S-C2+S-L2=(S-C+S-L)/3*S-D. CONCLUSIONS:Although the derived yielding criterion refers to healthy porcine thoracic aorta, however, it predicts that tensile stresses, compressive stresses or a combination of them may simultaneously be present in physiological and pathological situations (i.e. atherosclerosis). Thus, it should be taken into account that patients with seemingly, trivial atherosclerotic stenoses deserve early treatment because certain minor events (i.e. blood pressure fluctuations) may trigger a fatal stress combination that could make aortic wall yield. Since the increased Cu concentration in aortic tissue results in diminished elastic properties of the vessel, it is obvious that, the present outcome along with recent evidence-regarding the effect of high Cu level in atherosclerosis (US2003000388213)-may also contribute to a deeper understanding of plaque rupture behavior.

Objective: To investigate the role of infrasound aortic pressure waves (IPW) in atherosclerotic plaque rupture. Methods: Atherosclerotic plaques have been simulated partly, in two dimensions, as being short or long Conical Intersections(CIS), that is to say elliptic, parabolic or hyperbolic surfaces. Consequently, the course and reflection of the generated aortic pressure wave (infrasound domain-less than 20Hz) has been examined around the simulated plaques. Results: The incidence of IPW on plaque surface results in reflection and "refraction" of the wave. The IPW course within tissue, seems to be enhanced by high Cu-level presence at these areas according to recent evidence (US2003000388213). The "refracted", derived wave travels through plaque tissue and is eventually accumulated to the foci of the respective CIS-plaque geometry. Conclusions: The foci location within or underneath atheroma declares zones where infrasound energy is mostly absorbed. This process, among other mechanisms may contribute to plaque rupture through the development of local hemorrhage and inflammation in foci areas. In future, detection of foci areas and repair (i.e. via Laser Healing Microtechnique) may attenuate atherosclerotic plaque rupture behavior.

The objective of the study was to investigate the alterations of aortic function after interposition of a tubular graft in the descending porcine thoracic aorta. Eight healthy Landrace pigs were subjected to thoracotomy under sterile conditions. A 5-cm-long segment of descending thoracic aorta was replaced with a Dacron graft. Pulse wave velocity (PWV) was measured using simultaneous recordings of electrocardiogram and Doppler pressure waveforms, which were received from right carotid and femoral arteries. Then, the recordings were fed to a computer for analytical estimation of PWV in several occasions: right after the interposition (D0), and after 15 (D15) and 30 (D30) days time. Euthanasia was performed after the D30-recordings and the aortic graft area was removed. "Before graft" (BG) as well as "after graft" (AG) aortic regions were examined under light microscopy in order to determine the aortic thickness (T) and number of lamellar units (LU). Eight sham-operated pigs were used as controls. The results showed that PWV decreased as soon as the graft interposition took place and was maintained, until the end of experiment (P < 0.05). Aortic wall thickness was increased both at pregraft and postgraft areas (P < 0.05), and LUs were also increased at the same regions. It is concluded that the interposition of a tubular graft in the descending thoracic aorta resulted in a decrease in PWV, which may improve left ventricular performance and enhance myocardial perfusion, due to a delay in the arrival of the reflecting diastolic wave.

The objective of the study was to investigate the temperature impact on the elasticity of porcine thoracic aorta. Under general anesthesia, 16 Landrace pigs were subjected to thoracotomy, and the descending thoracic aorta was removed and stored in normal saline. Serial sections of the vessel created cylindrical aortic specimens which were tested in a uniaxial tension device to determine the elastic properties of the aortic wall. In the control, Group A (n = 8), the aortic tissues were tested while immersed in normal saline bath of temperature TA = 37.0 +/- 0.5 degrees C, while in Group B, the temperature was TB = 40.0 +/- 0.5 degrees C. Each experiment took place only after the tissues had remained for 15 min in temperature TA or TB. For the results, the stiffness modulus of Group B showed a significant decrease (P < 0.05) at medium strain level deformation (e = 1, SB1 = 114 +/- 8 Pa) as well as at high strain level deformation (e = 2, SB1 = 1182 +/- 48 Pa) in comparison with the control, Group A (e = 1, SA1 = 147 +/- 15 Pa; e = 2, SA1 = 1479 +/- 64 Pa). It is concluded that temperature increase facilitates, in vitro, the expansion of descending thoracic aorta. We assume that thermal treatment may be another means against the stiffening of aorta, which calls for further research.

OBJECTIVE:To carry out research into the possible changes of the spectral content of pressure pulse wave after the creation of an experimentally induced stenosis in the pig descending thoracic aorta.METHODS:Eight healthy, normotensive Landrace pigs were subjected to thoracotomy under sterile conditions. At the upper segment of the descending thoracic aorta, a 5-mm-long circumferential symmetric constriction was imposed and stabilized; hence, a 15-20 mm Hg pressure gradient was established. Pressure tip catheters were used in order to monitor the pressure gradient. Blood flow disturbances were recorded through a bidirectional Doppler flow meter at pre- and poststenotic areas (A and B, respectively). Measurements were carried out before, 10 min after, and 90 days after the creation of the stenosis. The recorded waveforms were analyzed mathematically by using Fourier Transform, in order to determine their spectral component. Eight sham-operated pigs were used as controls.RESULTS:Fourier Transform analysis showed a significant increase (P < 0.05) of spectral content in A and B areas. Also, the "relative" harmonic amplitudes in nonstenotic subjects were higher than in stenotic animals (P < 0.05).CONCLUSIONS:A minor experimental constriction located at the level of the descending thoracic aorta increased the spectral content of the pressure pulse wave, indicating that spectral analysis may detect slight flow disturbances before developing remarkable signs of an impaired circulation system.