Baroreflex Curve Fitting Using a WYSIWYG Boltzmann Sigmoidal Equation

Arterial baroreflex assessment using vasoactive substances enables investigators to collect data pairs over a wide range of blood pressures and reflex reactions. These data pairs relate intervals between heartbeats or sympathetic neural activity to blood pressure values. In an X-Y plot the data points scatter around a sigmoidal curve. After fitting the parameters of a sigmoidal function to the data, the graph’s characteristics represent a rather comprehensive quantitative reflex description. Variants of the 4-parameter Boltzmann sigmoidal equation are widely used for curve fitting. Unfortunately, their ‘slope parameters’ do not correspond to the graph’s actual slope which complicates the analysis and bears the risk of misreporting. We propose a modified Boltzmann sigmoidal function with preserved goodness of fit whose parameters are one-to-one equivalent to the sigmoidal curve’s characteristics.

Abstract MP18: The Impact Of Perivascular Adipose Tissue On Arterial Stiffness

PVAT is increasingly recognized as an essential layer of the functional vasculature, producing vasoactive substances and assisting arterial stress relaxation. We test the hypothesis that PVAT reduces arterial stiffness. Our model was the thoracic aorta of the male Sprague Dawley rat. Uniaxial mechanical tests for three tissue groups were performed: aorta +PVAT (+PVAT), aorta - PVAT (-PVAT), and PVAT ring separated from aorta (PVAT only) (N=5). Data are reported in the form of a Cauchy stress-stretch curve (fig 1a; line = mean;shaded = SDs). Low-stress stiffness ( E o ), high-stress stiffness ( E 1 ), and the stress corresponding to a stretch of 1.2 (sigma 1.2) were also measured (+PVAT sample in fig 1b) as metrics of distensibility (the higher the stress/stiffness, the less distensible). E 1 and sigma 1.2 for PVAT-only samples could not be quantified. The low-stress stiffness E o was the largest in the -PVAT samples and the smallest in PVAT-only samples (p < 0.05), while the +PVAT samples assumed values in the middle. Both the high-stress stiffness E 1 and the stress at 1.2 stretch (sigma 1.2 ) were significantly higher in -PVAT samples when compared to +PVAT samples (p < 0.05). Taken together these results suggest that -PVAT samples are stiffer both at low stress (not significant) as well as at high stress (significant) when compared to +PVAT samples. Moreover, -PVAT samples appear to also be less distensible (higher values of sigma 1.2 ) when compared to +PVAT samples. Thus, PVAT contributes significantly to decreasing the stiffness of the aortic wall. As such, PVAT should be considered as a target for improving vascular function in diseases with elevated aortic stiffness, including hypertension.

Modern clinical and physiological bases of super microsurgery. The view of a physiologist and surgeons

This paper is a retrospective analysis of the long-term work of a large group of Russian scientists representing various Medical Institutions of St. Petersburg (in the past years of Leningrad) in the period from the 70s of the XX century to the present in the field of theoretical clinical lymphology. We aimed to discuss critical studies of a group of anatomists, in the sphere of the structure of lymphangions and lymph nodes in health and lymphedema of the lower extremities in humans. Experimental data of physiologists are presented, which made it possible for the first time to substantiate the functional mechanisms of active lymph transport in health and in lymphedema of the lower extremities. In addition, there are some results of testing biopsy specimens with various pharmacological agents and vasoactive substances. At last, there is an example of the clinical use of theoretical knowledge in the tactics of choice and expediency of surgical treatment of lymph drainage disorders in patients is given.

ROLE AND PROBLEMATICS OF THE EPIDURAL ANESTHESIA DURING EXTENSIVE LIVER RESECTIONS

In the following article it was evaluated the coagulopathy and/or hypotension incidence rate in patients with the liver extensive resection, who were treated with the thoracal epidural anesthesia and pain management (TEA). Materials and methods. There were enrolled 55 subjects whom the liver extensive resection with TEA both in the intraoperative, and post-operative period was performed at the following site: National Institute of Surgery and Transplantology of the NAMS of Ukraine named after A.A. Shalimov. Influence on the haemodynamics was evaluated on the basis of the mean blood pressure (MBP) decrease lower than 65 mm Hg and appearance of the necessity of vasoactive substances’ administration. We determined the coagulation system’s alteration on the basis of changes of the indicators related to the prothrombotic time (PTT), prothrombotic index (PTI) and international normalization ratio (INR). Vascular platelet hemostasis was evaluated on the basis of the platelets level dynamics. Result. 80% of the 55 subjects required administration of noradrenaline with the aim of the objective MBP control. Execution of the liver extensive resection was characterized by the verifiable decrease of the platelets in the early post-operative period, but this decrease was not clinically significant. It was observed the verifiable increase of the PTT starting from the intraoperative period at the 16,5% (р=0,0001) in comparison with the baseline values, which correlated with the change of PTI and INR.Execution of the liver extensive resection was characterized by the decrease of the blood coagulation properties in early post-operative period, and which led to the verifiable increase of the prothrombotic time, INR and decrease of PTI. Conclusion. Now therefore, the influence of the TEA on the systemic hemodynamics and coagulation system requires of the alternative safe pain management methods’ search for this subjects’ group.

Adaptation to 5 weeks of intermittent local vascular pressure increments; mechanisms to be considered in the development of primary hypertension?

The aims were to study effects of iterative exposures to moderate elevations of local intravascular pressure on arterial/arteriolar stiffness and plasma levels of vasoactive substances. Pressures in the vasculature of an arm were increased by 150 mmHg in healthy men (n=11) before and after a 5-wk regimen, during which the vasculature in one arm was exposed to fifteen 40-min sessions of moderately increased transmural pressure (+65 to +105 mmHg). This vascular pressure training and the pressure-distension determinations were conducted by exposing the subjects arm versus remaining part of the body to differential ambient pressure. During the pressure-distension determinations, venous samples were simultaneously obtained from pressurized and unpressurized vessels. Pressure training reduced arterial pressure distension by 40 ± 23% and pressure-induced flow by 33 ± 30% (p<0.01), but only in the pressure-trained arm, suggesting local adaptive mechanisms. The distending pressure-diameter and distending pressure-flow curves, with training-induced increments in pressure thresholds and reductions in response gains, suggest that the increased precapillary stiffness was attributable to increased contractility and structural remodeling of the walls. Acute vascular pressure provocation induced local release of angiotensin-II (Ang-II) and endothelin-1 (ET-1) (p<0.05), suggesting that these vasoconstrictors limited the pressure distension. Pressure training increased basal levels of ET-1 and induced local pressure release of matrix metalloproteinase 7 (p<0.05), suggesting involvement of these substances in vascular remodeling. The findings are compatible with the notion that local intravascular pressure load acts as a prime mover in the development of primary hypertension.

The mechanism of ions in pulmonary hypertension

Pulmonary hypertension（PH）is a kind of hemodynamic and pathophysiological state, in which the pulmonary artery pressure (PAP) rises above a certain threshold. The main pathological manifestation is pulmonary vasoconstriction and remodelling progressively. More and more studies have found that ions play a major role in the pathogenesis of PH. Many vasoactive substances, inflammatory mediators, transcription-inducing factors, apoptosis mediators, redox substances and translation modifiers can control the concentration of ions inside and outside the cell by regulating the activity of ion channels, which can regulate vascular contraction, cell proliferation, migration, apoptosis, inflammation and other functions. We all know that there are no effective drugs to treat PH. Ions are involved in the occurrence and development of PH, so it is necessary to clarify the mechanism of ions in PH as a therapeutic target for PH. The main ions involved in PH are calcium ion (Ca2+), potassium ion (K+), sodium ion (Na+) and chloride ion (Cl–). Here, we mainly discuss the distribution of these ions and their channels in pulmonary arteries and their role in the pathogenesis of PH.

Beta-Arrestins and Receptor Signaling in the Vascular Endothelium

The vascular endothelium is the innermost layer of blood vessels and is a key regulator of vascular tone. Endothelial function is controlled by receptor signaling through G protein-coupled receptors, receptor tyrosine kinases and receptor serine-threonine kinases. The β-arrestins, multifunctional adapter proteins, have the potential to regulate all of these receptor families, although it is unclear as to whether they serve to integrate signaling across all of these different axes. Notably, the β-arrestins have been shown to regulate signaling by a number of receptors important in endothelial function, such as chemokine receptors and receptors for vasoactive substances such as angiotensin II, endothelin-1 and prostaglandins. β-arrestin-mediated signaling pathways have been shown to play central roles in pathways that control vasodilation, cell proliferation, migration, and immune function. At this time, the physiological impact of this signaling has not been studied in detail, but a deeper understanding of it could lead to the development of novel therapies for the treatment of vascular disease.