Microcirculatory bed of the heart during peripheral arteriovenous shunting

In the experiment performed on 108 test and 28 control dogs, by means of injection and histological methods, the effect of arteriovenous fistula on the cardiac microcirculatory bed has been studied. The arteriovenous blood shunting results in plethora and stasis in the cardiac microcirculatory bed, in dilatation of all its links, in aggregation and adhesion of the blood formed elements, in increased permeability of microvessels, in diapedesis of erythrocytes and in myocardial edema, in winding microvessels, in development of the venoarterial reaction, in hypertrophy of myocytes, recalibration and sclerosis of the microvascular walls.     

The dynamics of morphofunctional changes in the microcirculation of the pelvic extremity after modeling the chief stages of its replantation]

Under study was the effect of autotransplantation in its "pure form" upon the morpho-functional reconstruction and structural mechanisms of adaptation of the blood and lymphatic links of the microcirculatory bed of extremities during early postoperation period up to 10 days. The pathophysiological state of the extremity sufficiently close to its autotransplantation was obtained by means of circular transection of soft tissues of the medial third of the femur together with the nerves and deep collecting lymphatic vessels. It was found that after modeling the main stages of replantation in the fascia and periosteum of the operated extremity there developed a spasm of the arteriolar link and dilatation of the venular and lymphatic links of the microcirculatory bed. The areas of leukocytic infiltration with the phenomena of diapedesis and microhemorrhages were revealed along the course of postcapillaries and venules in the paravasal connective tissue. The amount of functioning arteriole-venular anastomoses was increased. Against the background of pronounced oedema of soft tissues of the operated extremity the venous pressure increased and the rate of the capillary bloodflow in the skin and muscles decreased. The above changes tend to be reduced by the 10th day after modelling the main stages of replantation of the extremity.     

Effect of hypodynamia on the hemomicrocirculatory bed of the triceps muscle and brachial fascia in the rat

By means of amputation of the forearm (the place of the brachial musculus attachment is kept intact) in 30 male rats certain conditions are produced for decreasing force activity in the m. triceps brachii. Anatomical changes in structure and in distribution of links of the hemomicrocirculatory bed (HMCB) are followed in the medial head of the muscle and in the fascia covering it. Time of observations - 1-60 days. The sections of the muscles and some parts of the fascia are impregnated with silver nitrate solution. The greatest changes are observed to occur in the capillary-venular links of the HMCB during the interval of 1.14-4.5 days and are manifested as initial congestion of venous blood in these links. Later (4.5-15.3 and further 60 days) together with stable dilatation of all venous components of the blood bed certain qualitative changes take place in the arteriolar links of the HMCB.     

Morphologic changes in the microcirculatory bed at stages of prolonged experimental fasting in animals

In 40 white male rats with body mass 180-200 g, by means of silver nitrate impregnation, morphological changes have been studied in the blood microcirculatory bed of the small intestine mesentery, spinal trapezoid muscle and eye ball conjunctiva at various stages of a prolonged fasting. With an increasing time of the experiment, a gradual undirected character of the changes in the microvessels is noted. After 3 days of fasting the changes in diameters of the microvessels, comparing to the control ones, have not any significant values in all the organs studied. After 6 days of fasting significant changes in diameters in all the links of the microcirculatory bed of the eye ball conjunctiva and in that of the spinal trapezoid muscle are observed. The microvascular changes are mostly pronounced on the 9th day of fasting. The maximal decrease of the microvessel diameters is noted in the eye ball conjunctiva, and the minimal--in the small intestine mesentery. The changes in the spinal trapezoid muscle are of intermediate character. The highest points of the structural lability gradient fall on the capillary and postcapillary-venular links of the blood microcirculatory bed.     

Morphologic mechanisms of blood flow regulation in the hemomicrocirculatory system of the human heart during ontogenesis

Hearts of 220 human corpses, who had not any cardiovascular system disease during their life, have been distributed into age groups, beginning from fetuses up to old age. By means of injection, silver nitrate impregnation and scanning electron microscopy methods, applied to corrosive preparations, morphological mechanisms of the blood stream regulation in the hemomicrocirculatory bed of the human heart have been revealed in ontogenesis. The first group of the regulation mechanisms includes proper mechanisms inherent in the links of the microbed: spatial orientation of microvessels, precapillary sphincters, anastomoses between these vessels, sequence in arrangement of the endothelial cell nuclei, length, diameter and number of links in the microcirculatory bed. The second group embraces those mechanisms, that depend on structure of the myocardial wall, influencing the microcirculatory bed.     

Morphofunctional transformations of the blood vessels in the transplantation of syngeneic normal tissue and of a tumor

In 360 Fisher rats dynamics of changes in blood vessels, the microcirculatory bed vessels included, have been investigated. An original model of the experiment at implantation of syngenic tissues of the fetus normal intestine and tumorous adenocarcinoma of the small intestine has been used. Specific changes of the blood vessels have been revealed around and in the capsule of the implant, depending on their morphological reorganization. The blood vessels changes can serve as a prognostic sign of possible alterations in the implant structure.     

Ultrastructural regularities of new growth of secondary micro blood vessels in the prenatal period of human morphogenesis

By means of transmissive electron microscopy structural aspects of new formation of secondary blood microvessels in functionally different organs have been studied during fetal period of the human development. Growth buds appear on the basal surface of the endothelial lining of the blood microvessels predominantly in those areas of the vascular wall, where pericytes and adventitial cells are absent. The first stage in formation of the growth bud is separating of small compartments in the lumen of the maternal vessel. Then, connected by means of specialized contacts, endothelial cells of such a compartment move one by one towards periphery of the vessel and form the growth bud, protruding outside. In the area of the growth bud local destruction of the basal membrane is observed. Newly formed microvessels, anastomising, form vascular loops. Further processes in differentiation of separate segments of the newly formed capillary network into links of the hemomicrocirculatory bed are analogous to those, observed in the course of differentiation of the primary protocapillary network into the secondary intraorganic blood bed.     

Sinusoids--elements of the circulatory bed of the human heart

The literature concerning the problems of myocyrdial sinusoids has been analysed and morphological investigation of 98 human hearts has been performed. As demonstrates the comparison of the literature data, the term "sinusoid" in the human heart is applied to different structures. In some cases--to designate dilated areas of the venous part of the blood bed in the ventricular walls, in others--"hollow spaces", "intercellular spaces" and Vieussens--Thebesius vessels. Combining methods of intravascular injections and studying serial histological sections, it has been found that the sinusoids--the "hollow spaces", the "intercellular spaces", the "Veussens--Thebesius vessels" present the areas of intertrabcular spaces, which get into the planes of some sections, not being components of the myocardial blood bed. Spatial angioarchitectonics of the sinusoids--dilated areas in the venous part of the myocardial blood bed have been investigated by means of the plastic reconstruction method. It is suggested to apply the term "sinusoids" only to the given parts of the cardiac blood bed.     

Organizational features and morphometric characteristics of the hemomicrocirculatory bed of the human brain dura mater

By means of silver nitrate impregnation and hematoxylin -- eosin staining the microcirculatory bed of the human brain dura mater (the second half of the mature age) has been investigated. Owing to the analysis of the morphometrical data of module organization of the hemomicrocirculatory bed, an objective quantitative characteristics of its peculiarities in various layers and areas of the dura mater is presented. In three layers of the dura mater in the fornix and skull basis area, falx cerebri and tentorium cerebelli venular links predominate. Most of all morphometrical parameters of the venular vessels increase in the internal layer of the dura mater in the skull basis area. Conditions of functioning for the human brain dura mater are reflected in its blood bed, its specificity manifesting at the microcirculatory level.     

The role of the chromocenter in nonrandom meiotic segregation of nonhomologous chromosomes in Drosophila melanogaster females

The evidence supporting universal significance of physical links between pericentromeric regions of homologous chromosomes for their bipolar orientation during the first meiotic division is discussed. The pericentromeric chiasmata between homologs or (in the absence of the latter) chromocentric links between nonhomologs, which are preserved until prometaphase, compensate for the disturbed binding between homologous pericentromeric regions in both structural or locus mutants. When the links between nonhomologs are involved, interchromosomal effects on chromosome disjunction and nonhomologous pairing were revealed by the genetic methods. An explanation suggested for genetic events observed during Drosophila meiosis conforms with the original, cytogenetically proved model of the orderly two-ring chromocenter formation and reorganization.     

Role of the Chromocenter in Nonrandom Meiotic Segregation of Nonhomologous Chromosomes inDrosophila melanogasterFemales

The evidence supporting universal significance of physical links between pericentromeric regions of homologous chromosomes for their bipolar orientation during the first meiotic division is discussed. The pericentromeric chiasmata between homologs or (in the absence of the latter) chromocentric links between nonhomologs, which are preserved until prometaphase, compensate for the disturbed binding between homologous pericentromeric regions in both structural or locus mutants. When the links between nonhomologs are involved, interchromosomal effects on chromosome disjunction and nonhomologous pairing were revealed by the genetic methods. An explanation suggested for genetic events observed during Drosophilameiosis conforms with the original, cytogenetically proved model of the orderly two-ring chromocenter formation and reorganization.     

Tip-link integrity and mechanical transduction in vertebrate hair cells.

An attractive hypothesis for hair-cell transduction is that fine, filamentous "tip links" pull directly on mechanically sensitive ion channels located at the tips of the stereocilia. We tested the involvement of tip links in the transduction process by treating bundles with a BAPTA-buffered, low-Ca2+ saline (10(-9) M). BAPTA abolished the transduction current in a few hundred milliseconds. BAPTA treatment for a few seconds eliminated the tip links observed by either scanning or transmission electron microscopy. BAPTA also eliminated the voltage-dependent movement and caused a positive bundle displacement of 133 nm, in quantitative agreement with a model for regulation of tension. We conclude that tip links convey tension to the transduction channels of hair cells.     

Patterns in the development of the ultrastructure of elements of the microcirculatory system in the early stages of human embryogenesis

By means of transmissive electron microscopy methods, general regularities in development of the microcirculatory system have been studied at early stages of the human prenatal ontogenesis in functionally different organs. Ultrastructure of two cell types has been described in the mesenchyme of human embryos. Formation mechanisms of the primary blood vessels belonging to the protocapillary type are revealed. Structural peculiarities of the primary protocapillary network differentiating into various links of the secondary organospecific hemomicrocirculatory bed are distinguished. Certain stageness in development of the microcirculatory system is stated, its blood circulatory compartment including. Two stages are determined in development of the microcirculatory system: prevascular and vascular microcirculation. The latter includes the precirculatory and circulatory phases.     

A new one-DOF fully parallel mechanism for modelling passive motion at the human tibiotalar joint

Knowledge on how ligaments and articular surfaces guide passive motion at the human ankle joint complex is fundamental for the design of relevant surgical treatments. The paper presents a possible improvement of this knowledge by a new kinematic model of the tibiotalar articulation. Passive motion, i.e. in virtually unloaded conditions, was captured in vitro in four lower leg specimens by means of a surgical navigation system with cluster of active markers attached to the tibia and talus. The anatomical geometry of the passive structures, i.e. articular surfaces and attachment areas of the ligaments, were taken by digitisation with a pointer. An equivalent spatial mechanism for the passive motion simulation was defined by three sphere-to-sphere contact points and two rigid links. These contact points were identified at the lateral talo-fibular articulation and at the medial and lateral aspects of the articulation between tibial mortise and trochlea tali. The two rigid links were identified by the isometric fibres at the calcaneofibular and tibiocalcaneal ligaments. An optimisation algorithm was developed for the identification of the final geometrical parameters resulting from an iterative refining process, which targets best matching between model predictions and corresponding experimental measurements of the spatial motion. The specimen-specific equivalent spatial mechanisms replicated the original passive motion very well, with mean discrepancies in position smaller than 2.5 mm and in rotation smaller than 1°. The study demonstrates that the articular surfaces and the ligaments, acting together as a mechanism, control the passive kinematics of the ankle joint.     

Arterial pulse attenuation prediction using the decaying rate of a pressure wave in a viscoelastic material model

The present study examines the possibility of attenuating blood pulses by means of introducing prosthetic viscoelastic materials able to absorb energy and damp such pulses. Vascular prostheses made of polymeric materials modify the mechanical properties of blood vessels. The effect of these materials on the blood pulse propagation remains to be fully understood. Several materials for medical applications, such as medical polydimethylsiloxane or polytetrafluoroethylene, show viscoelastic behavior, modifying the original vessel stiffness and affecting the propagation of blood pulses. This study focuses on the propagation of pressure waves along a pipe with viscoelastic materials using the Maxwell and the Zener models. An expression of exponential decay has been obtained for the Maxwell material model and also for low viscous coefficient values in the Zener model. For relatively high values of the viscous term in the Zener model, the steepest part of the pulse can be damped quickly, leaving a smooth, slowly decaying wave. These mathematical models are critical to tailor those materials used in cardiovascular implants to the mechanical environment they are confronted with to repair or improve blood vessel function.     

Development of the hemomicrocirculatory bed of the human gonads during the prenatal period of ontogeny

The formation of the organospecific hemomicrocirculatory bed of the ovaries and testes has been studied by a complex of light, transmissive and scanning electron microscopy in 3--9-month-old human fetuses. The change of the diffusive protocapillary bed is secured by: 1) reduction of some protocapillaries; 2) appearance of secondary capillaries from the growth buds of the preceeding microvessels; 3) formation of arteriolar and venular links of the hemomicrocirculatory bed from the protocapillaries at the expense of differentiation of the developing paravasal connective tissue into cellular elements of the muscular and adventitial tunics. The secondary blood capillaries of the human gonads are predominantly formed intraendothelially. During the prenatal ontogenesis presence of the secondary blood capillaries of somatic uninterrupted type is specific for the human gonads.     

Development of the microcirculatory bed of the human tongue in the prenatal period

Morphofunctional regularities of formation and development of the blood microcirculatory bed in the human tongue have been studied in the prenatal period of morphogenesis. 119 human embryos and fetuses at the age of 5 weeks--9 months have been investigated. A complex of methods have been used: common histological (hematoxylin--eosin, after van Gieson and Mallory), injection of the lingual vessels with 20% suspension of Indian ink--gelatin, transmissive electron microscopy. General regularities of organogenesis, stages of the blood microcirculatory bed development and peculiarities of the process on formation of the primary protocapillary lingual blood bed are revealed. Regularities in structure of the terminal vascular constructions are studied for each structural element of the organ--mucosal membrane, muscles, glands, lingual tonsil. For these elements at the ultrastructural level certain features of the organic specificity in the structure of the blood microcirculatory bed links are determined.     

Microarchitectonics and microtopography of blood vessels of the human rectum

By means of injecting the vessels with 0.2% solution of silver nitrate after Ranvier, solutions of Indian ink and gas soot, impregnation after V.V. Kuprianov, the blood vessels of the rectal wall have been studied. The material has been obtained from 50 corpses of persons of various age, not suffering from any diseases of the gastrointestinal tract. The structural organization of the microcirculatory tract has been studied layer-by-layer, at all levels by means of atraumatic lamination of the tunics. Terminal links of the microcirculatory bed form zonal functional complexes of microvessels specific for each part of the rectum. They regularly repeat in a certain tunic and owing to this the whole organization of the microcirculatory bed acquires features of a definite polymeric structure which consists of homonomic complexes of microvessels. Their regularity, as regards their topography and quantity, definitely differs in each tunic and layer of the rectal wall. Precapillary sphincters and arteriolovenular anastomoses are revealed; they perform an active regulation of blood circulation in the organ. Diameters of the microvessels and density of the microcirculatory network have some slight fluctuations (differences) in functionally poorly active tunics of the rectal wall--the serous and submucous, especially in its rectosigmoid part. Differences of these parameters are especially expressed within the limits of the rectal ampule and its mucous and muscular tunics.     

Morphofunctional characteristics of the hemomicrocirculatory bed of the canine pericardium

The hemomicrocirculatory bed in the canine pericardium is presented by arterioles, precapillaries, capillaries, postcapillaries and venules situating in various connective tissue layers of the pericardium. Certain morphological peculiarities of the structure of the hemomicrocirculatory bed links are revealed in various parts of the pericardium. As demonstrate morphometry data, the diameter of all the vessels of the hemomicrocirculatory bed in various parts of the pericardium has no precise differences. There are some fluctuations in the number of the capillaries per 1 mm2 in various parts of the pericardium. Their number is comparatively greater in the area of the vascular porta (transitional fold), in the left lateral, in the ventral and dorsal parts of the pericardium. In these parts of the pericardium the density of the capillaries is increased, the network is especially dense in the area where the pericardial transitional fold passes into the epicardium. In the pericardial microcirculatory blood bed adaptive mechanisms (glomeruli, arteriolo-venular anastomoses, microsphincters) performing regulation of the organ's blood stream, are widely presented.     

Simple physical model of coronary vasodilation

The coronary diastolic pressure-flow relationship was studied in two groups of dogs; in one group coronary circulation was characterized by normal tone of vascular smooth muscle, while in the other group, complete relaxation of smooth muscle fibres was produced by intravenous infusion of dipyridamole. The coronary flow (CF) was measured in both groups for several values of mean aortic blood pressure (ABP), the variations being obtained by means of a 10 s arterial haemorrhage. The measured CF versus ABP data were found to be well represented by best fit curves calculated by power regression methods. These curves were quite different in the presence and absence of dipyridamole infusion. A simple physical model is proposed for analysis of these curves; the model is based on the Poiseuille equation, modified to take into proper account the variations of the vessel radii under different ABP values during ventricular diastole. These variations are expressed by means of Laplace and Hooke's laws by equating wall tension due to APB, to the sum of tensions due to elastic and smooth muscle forces. Analysis of CF versus APB curves, performed on the basis of this model, shows that to account for the large change of coronary bed conductance observed under dipyridamole infusion one must assume not only that the smooth muscle tone is absent but also that some relevant variations occur in the whole coronary bed, thus pointing to possible recruitment of new blood vessel paths.