Morphological and morphometrical characteristics of cattle heart structure

The paper presents the results of macro- and microscopic structure of cattle heart on the organ-, tissue- and cell levels. The samples of the selected material (n = 5) were preserved in a 10–12 % water solution of neutral formaline with its further charging into wax. Histologic sections not more than 10 mkm were made from wax blocks by using a sliding microtome MC-2. Hematoxilin- and eosin staining of histological sections by Heydengine technique was used for studying cell morphology, carrying out morphometrical studies and for receiving review samples. Histoarchitecture of the structural parts of the heart (ventricle and auricle) and their morphometrical parameters were studied on the histological preparations using the light microscopy technique. The experimantal part of the scientific research was carried out in compliance with the requirements of “European Convention for the Protection of Vertebrate Animals used for Experimantal and other Scientific Purposes” (Strussburg, 1986). The cattle heart is located in a thorax between two lungs, in front of a diaphragm and shifted left. In the 3rd–4th rib region the heart adjacents to a thoracic wall. The heart apex is in the 5th rib region. The absolute weight of a cattle heart equals 2143.27 ± 38.76 g, the relative weight equals – 0.43 ± 0.006 %. The net weight of the heart without the epicardial fat equals 1926.12 ± 31.12 g. Herewith, the weight of the aortic ventricle equals 978.54 ± 19.52 g, the weight of the pulmonic ventricle equals 554.17 ± 14.21 g, the weight of both ventricles equals 1539.08 ± 49.74 g. The auricles weight was the least and equaled 397.18 ± 11.21 g. The ratio of the ventricle weight of the heart to its net weight equals 1:0.2, and the ratio of the weight of the auricle myocard to the weight of the ventricle myocard equals 1:0.26. The heart height equaled 23.08 ± 0.11 сm, width – 13.9 ± 0.18 cm and the circumference – 38.08 ± 0.9 cm. According to the analysis of such liniar measurements, the cattle heart in the animals of the experimental group is characterized as that of an enlarged- and short form. The heart wall consists of three sacs – endocardium, myocard and epicardium. The dominating weight of the heart wall is in a muscular layer (myocard), which consists of transversus stripe muscular fibers which are formed on the basis of mononuclear cells – cardiomyocytes which are interlinked into muscular fibers. According to the cytometric analysis of cardiomyocytes, their largest volume – (11225.73 ± 824.42 mkm3) is observed in the aortic ventricle, smaller – (7963.60 ± 627.09 mkm3) – in a pulmonic ventricle and the smallest – (5361.60 ± 583.91 mkm3) in the auricle cardiomyocytes. Herewith, the volumes of cardiomyocytes nuclei in an aortic ventricle (124.55 ± 7.99 mkm3 and in a pulmonuc ventricle (121.67 ± 7.02 mkm3) are nearly the same, and in the auricle cardiomyocytes the nuclei volume is significantly smaller and it equals 101.05 ± 6.04 mkm3 respectively. Such morphometrical parameters of cardiomyocytes and their nuclei are evidenced in their nuclei-cytoplasmatic ratio, which is the smallest in the cardiomyocytes of an aortic ventricle – 0.0113 ± 0.0068, somewhat larger in a pulmonic ventricle – 0.0156 ± 0.0054 and the largest – 0.0234± 0.0058 in the auricle cardiomyocytes, that is connected with the special properties of the muscular tissue of a myocard which is capable of spontaneous rythmic beatings depending on their morphofunctional load: the ventricles pump the blood from the heart to the body performing the gratest load (the aortic ventricle acts a s a pump, and the pulmonic ventricle acts as a container), the auricles receive the blood which returns to the heart from the animal body, performing somewhat smaller load.

Transmural Distribution of Coronary Perfusion and Myocardial Work Density Due to Alterations in Ventricular Loading, Geometry and Contractility

Myocardial supply changes to accommodate the variation of myocardial demand across the heart wall to maintain normal cardiac function. A computational framework that couples the systemic circulation of a left ventricular (LV) finite element model and coronary perfusion in a closed loop is developed to investigate the transmural distribution of the myocardial demand (work density) and supply (perfusion) ratio. Calibrated and validated against measurements of LV mechanics and coronary perfusion, the model is applied to investigate changes in the transmural distribution of passive coronary perfusion, myocardial work density, and their ratio in response to changes in LV contractility, preload, afterload, wall thickness, and cavity volume. The model predicts the following: (1) Total passive coronary flow varies from a minimum value at the endocardium to a maximum value at the epicardium transmurally that is consistent with the transmural distribution of IMP; (2) Total passive coronary flow at different transmural locations is increased with an increase in either contractility, afterload, or preload of the LV, whereas is reduced with an increase in wall thickness or cavity volume; (3) Myocardial work density at different transmural locations is increased transmurally with an increase in either contractility, afterload, preload or cavity volume of the LV, but is reduced with an increase in wall thickness; (4) Myocardial work density-perfusion mismatch ratio at different transmural locations is increased with an increase in contractility, preload, wall thickness or cavity volume of the LV, and the ratio is higher at the endocardium than the epicardium. These results suggest that an increase in either contractility, preload, wall thickness, or cavity volume of the LV can increase the vulnerability of the subendocardial region to ischemia.

Changes Caused by Low Doses of Bisphenol A (BPA) in the Neuro-Chemistry of Nerves Located in the Porcine Heart

Bisphenol A (BPA) contained in plastics used in the production of various everyday objects may leach from these items and contaminate food, water and air. As an endocrine disruptor, BPA negatively affects many internal organs and systems. Exposure to BPA also contributes to heart and cardiovascular system dysfunction, but many aspects connected with this activity remain unknown. Therefore, this study aimed to investigate the impact of BPA in a dose of 0.05 mg/kg body weight/day (in many countries such a dose is regarded as a tolerable daily intake–TDI dose of BPA–completely safe for living organisms) on the neurochemical characterization of nerves located in the heart wall using the immunofluorescence technique. The obtained results indicate that BPA (even in such a relatively low dose) increases the number of nerves immunoreactive to neuropeptide Y, substance P and tyrosine hydroxylase (used here as a marker of sympathetic innervation). However, BPA did not change the number of nerves immunoreactive to vesicular acetylcholine transporter (used here as a marker of cholinergic structures). These observations suggest that changes in the heart innervation may be at the root of BPA-induced circulatory disturbances, as well as arrhythmogenic and/or proinflammatory effects of this endocrine disruptor. Moreover, changes in the neurochemical characterization of nerves in the heart wall may be the first sign of exposure to BPA.

MEMBRANE FINITE ELEMENT FOR MODELING HEART WALL

Modeling of heart wall deformation remains a challenge due to complex structure of tissue, which contains different group of cells and connective tissue. Muscle cells are dominant where, besides stresses coming from tissue deformation, active stresses are generated representing the load which produces heart motion and function. These cells form a helicoidal structure within so- called wall sheets and are considered as tissue fibers. Usual approach in the finite element (FE) discretization is to use 3D isoparametric elements. The dominant stresses lie in the sheet planes, while normal stresses in the wall normal directions are of the order smaller. Taking this stress state into account, we explore a possibility to model heart wall by membrane finite elements, hence considering the wall as a thick membrane (shell without bending effects). The membrane element is composite, containing layers over the thickness and variation of the direction of fibers. The formulated element is applied to a simplified left ventricle geometry to demonstrate a possibility to simulate heart mechanics by models which are much smaller and simpler for use than 3D conventional models.

Microstructural deformation observed by Mueller polarimetry during traction assay on myocardium samples

Despite recent advances, the myocardial microstructure remains imperfectly understood. In particular, bundles of cardiomyocytes have been observed but their three-dimensional organisation remains debated and the associated mechanical consequences unknown. One of the major challenges remains to perform multiscale observations of the mechanical response of the heart wall. For this purpose, in this study, a full-field Mueller polarimetric imager (MPI) was combined, for the first time, with an in-situ traction device. The full-field MPI enables to obtain a macroscopic image of the explored tissue, while providing detailed information about its structure on a microscopic scale. Specifically it exploits the polarization of the light to determine various biophysical quantities related to the tissue scattering or anisotropy properties. Combined with a mechanical traction device, the full-field MPI allows to measure the evolution of such biophysical quantities during tissue stretch. We observe separation lines on the tissue, which are associated with a fast variation of the fiber orientation, and have the size of cardiomyocyte bundles. Thus, we hypothesize that these lines are the perimysium, the collagen layer surrounding these bundles. During the mechanical traction, we observe two mechanisms simultaneously. On one hand, the azimuth shows an affine behavior, meaning the orientation changes according to the tissue deformation, and showing coherence in the tissue. On the other hand, the separation lines appear to be resistant in shear and compression but weak against traction, with a forming of gaps in the tissue.

A biodegradable microneedle sheet for intracorporeal topical hemostasis

Management of bleeding is critical for improving patient outcomes. While various hemostatic products are used in daily practice, technical improvement is still needed. To addresses this problem, we newly developed a microneedle hemostatic sheet based on microneedle technology. We demonstrated the unique features of this microneedle hemostatic sheet, including reduced hemostatic time, biodegradable polymer composition that allows intracorporeal use without increasing infectious risk incorporation of microneedles to fix the sheet to the wound even on the left ventricular wall of a swine while beating, and a mesh structure with flexibility comparable to that of bonding surgical tape and sufficient rigidity to penetrate human aorta tissue and swine left ventricular wall. One potential application of the microneedle hemostatic sheet is intracorporeal topical hemostasis for parenchymatous organs, large vessels, and heart wall during trauma or surgery, in addition to new, widespread applications.

Modeling esophageal protection from radiofrequency ablation via a cooling device: an analysis of the effects of ablation power and heart wall dimensions

Background Esophageal thermal injury can occur after radiofrequency (RF) ablation in the left atrium to treat atrial fibrillation. Existing methods to prevent esophageal injury have various limitations in deployment and uncertainty in efficacy. A new esophageal heat transfer device currently available for whole-body cooling or warming may offer an additional option to prevent esophageal injury. We sought to develop a mathematical model of this process to guide further studies and clinical investigations and compare results to real-world clinical data. Results The model predicts that the esophageal cooling device, even with body-temperature water flow (37 °C) provides a reduction in esophageal thermal injury compared to the case of the non-protected esophagus, with a non-linear direct relationship between lesion depth and the cooling water temperature. Ablation power and cooling water temperature have a significant influence on the peak temperature and the esophageal lesion depth, but even at high RF power up to 50 W, over durations up to 20 s, the cooling device can reduce thermal impact on the esophagus. The model concurs with recent clinical data showing an 83% reduction in transmural thermal injury when using typical operating parameters. Conclusions An esophageal cooling device appears effective for esophageal protection during atrial fibrillation, with model output supporting clinical data. Analysis of the impact of ablation power and heart wall dimensions suggests that cooling water temperature can be adjusted for specific ablation parameters to assure the desired myocardial tissue ablation while keeping the esophagus protected.