Investigation and comparative characteristic of factors determining human skin elasticity

The results of examining the variation in skin elasticity at its expansion are presented for different skin thickness, different content of collagen and intercellular and intracellular fluids, different venous pressure, and for tension and relaxation of the smooth muscle of skin vessels (vasomotion). Elasticity was determined using the acoustic method by the velocity of the surface shear acoustic wave, the self-resonance method by the frequency of mechanic skin resonance, and the vacuum method by the volume of the skin segment pulled into the aperture of a thin tube by air rarefaction. It is shown that the main factors determining the skin elasticity are its stretching, thickness, and collagen and fluid content. The influence of venous pressure and contractile activity of the vasculature on elasticity is insignificant. This gives grounds for using skin elasticity factors as indicators of systemic and local lesion of connective tissue.     

A study of skin deformation by optical coherence microscopy

The deformation of rat skin in response to cooling and stimulation of nerve fibers innervating the piloerector and vasoconstrictor muscles has been studied by optical coherence microscopy. It has been found that the deformation of skin upon cooling is due to the contraction of collagen fiber bundles rather than the smooth muscle of vessels or piloerectors.     

Physiological characteristics of the smooth muscles vessels of the small circle of blood circulation

Now sireos problem of pulmonology there are the diseases connected with infringement of coordinated regulation of a tone of smooth muscles of vessels and airways of ways that conducts to dissociation of parameters haemodinamyc and ventilation of lungs and as consequence, to infringement airwave-perfusion attitudes. In the review features humoral regulation contractile activity of smooth muscles of vessels of a small circle of blood circulation, a role of endocellular alarm systems in these mechanisms, and endothelium, as the local modulator endocrine functions are considered. Disgusting muscles of a small circle are distinguished from the main vessels of the big circle of blood circulation with predisposition to the raised mechanical pressure. In spite of the fact that endothelium renders modulating relaxe influence on contractile answers of smooth muscles of vessels of a venous and arterial small circle of blood circulation at action corresponding vasoconstriction, pulmonary veins are capable to endothelium-dependent dilatation to a lesser degree, in comparison with pulmonary arteries. And, on the contrary, in absence endothelium, they are characterized with high sensitivity to vasopression to substances--serotonin, histamine, phenylephrine. Features of regulation smooth muscle pressure pulmonary an artery are shown in contractile reactions of its isolated segments in reply to influence beta-adreno agonist--isoprotherenol and phosphoesterase inhibitors. Though, increase in endocellular concentration cyclic nucleotides (cAMP and\or cGMP), on the standard representations, cannot explain growth of a mechanical pressure of smooth muscles, apparently, in contractile reactions of a pulmonary artery to influence biologically and physiologically active substances interfere more complex mechanisms in which basis processes of interaction of smooth muscles cells lay, endothelium and cells of a microenvironment. Finding-out of the contribution cyclic nucleotides in these processes demands the further researches.     

Skin Collagen and Thickness in Simple Obesity

The effects of stretching of the skin on its collagen content and thickness have been studied in a group of subjects with chronic obesity. Despite the increase in skin surface a normal skin thickness, collagen content, and density were maintained. It is concluded that the skin stretching induced by prolonged obesity led to hypertrophy of collagen and that this had maintained both skin thickness and collagen content. It is not known whether this is due to enhanced synthesis or decreased degradation.     

Rapid alignment of collagen fibers in the dermis of undermined and not undermined skin stretched with a skin-stretching device

A controlled, quantitative histochemical study was performed in five piglets to establish changes in undermined and not undermined stretched skin. The skin was stretched with a stretching device for 30 minutes to close a large skin defect. On each flank of the piglet, at a standard position, 9 x 9-cm wounds were created under general anesthesia. On one flank, the surrounding skin was undermined cranially and caudally over a 10-centimeter area. Sections of skin biopsies obtained during stretching were stained with picrosirius red and studied with routine light microscopy and polarized light microscopy in combination with image analysis. The length of collagen fibers was analyzed as a parameter of changes in the dermis resulting from skin stretching. This newly developed quantitative method appeared to be valid, specific, and reproducible, allowing for objective determination of changes in the length of the fibers in the plain of the sections. Changes in the orientation of collagen fibers in the dermis as a result of skin stretching were thereby determined. Epidermal thickness did not change significantly under the influence of stretching forces in both undermined and not undermined skin. However, the orientation of the collagen fibers changed significantly as a result of skin stretching. In undermined wounds, parallel alignment and elongation of the fibers in the plane of the sections was already observed after 15 minutes of stretching. The fibers became aligned in the direction of the stretching force, perpendicular to the wound margin. After 30 minutes of stretching, the mean major axes of the collagen fibers were longest in the plane of the sections (p < 0.001). This meant that elongation and parallel alignment of the collagen fibers had occurred. Stretching of not undermined skin for 15 minutes resulted in significantly stronger parallel alignment in the plane of the sections as compared with undermined skin. This was less well defined after 30 minutes of stretching in not undermined skin. It is concluded that skin stretching with a skin-stretching device for 30 minutes results in significant histomorphological changes of collagen fibers in the dermis of both undermined and not undermined skin. The fibers realign rapidly as a result of stretching forces and become aligned in the direction of the stretching force, perpendicular to the wound margin. These dynamic changes in collagen fibers explain the significantly decreased wound closing tension resulting from skin stretching and explain how skin stretches beyond its inherent extensibility.     

Effect of taurine on the microvessel exchange function and adrenergic response of veins and arteries in the cat skeletal muscle

In cats anesthetized with Uretan and perfused with a constant blood volume, Taurine induced responses of neither arterial nor venous vessels of the skeletal muscle but increased the capillary filtration coefficient without any significant change of the capillary pressure in the skeletal muscle's microvessels. Taurine also increased both the constrictor and the dilatory responses of the arterial and venous vessels. The mechanism of the Taurine effects upon the smooth muscle elements of arteries and veins as well as upon proper mechanisms of capillary pressure control and capillary filtration coefficient, seems to be calcium-dependent.     

Pathological steps of cancer-related lymphedema: histological changes in the collecting lymphatic vessels after lymphadenectomy

Introduction

To date, an electron microscopy study of the collecting lymphatic vessels has not been conducted to examine the early stages of lymphedema. However, such histological studies could be useful for elucidating the mechanism of lymphedema onset. The aim of this study was to clarify the changes occurring in collecting lymphatic vessels after lymphadenectomy.

Methods

The study was conducted on 114 specimens from 37 patients who developed lymphedema of the lower limbs after receiving surgical treatment for gynecologic cancers and who consulted the University of Tokyo Hospital and affiliated hospitals from April 2009 to March 2011. Lymphatic vessels that were not needed for lymphatico venous anastomosis surgery were trimmed and subsequently examined using electron microscopy and light microscopy.

Results

Based on macroscopic findings, the histochemical changes in the collecting lymphatic vessels were defined as follows: normal, ectasis, contraction, and sclerosis type (NECST). In the ectasis type, an increase in endolymphatic pressure was accompanied by a flattening of the lymphatic vessel endothelial cells. In the contraction type, smooth muscle cells were transformed into synthetic cells and promoted the growth of collagen fibers. In the sclerosis type, fibrous elements accounted for the majority of the components, the lymphatic vessels lost their transport and concentrating abilities, and the lumen was either narrowed or completely obstructed.

Conclusions

The increase in pressure inside the collecting lymphatic vessels after lymphadenectomy was accompanied by histological changes that began before the onset of lymphedema.     

Influence of initial collagen and cellular concentrations on the final surface area of dermal and skin equivalents: A box-behnken analysis

Summary Our laboratory has been involved in finding optimal conditions for producing dermal and skin equivalents. As an original approach, a Box-Behnken experimental design was used to study the effects of the initial collagen and fibroblast concentrations and the initial gel thickness on the contraction of dermal and skin equivalents. The final surface area of dermal equivalent varied significantly with the initial concentration of collagen and fibroblast, whereas the initial thickness of gel had no appreciable effect on the contraction of the dermal equivalent. When keratinocytes were grown on these dermal equivalents they produced a very severe contraction, to an extent that all skin equivalents had a similar final surface area. This severe contraction was independent of collagen and fibroblast concentrations. Models for the prediction of the final percentage contraction of dermal and skin equivalents as a function of the initial concentration of collagen, the logarithm of fibroblast concentration, and the initial gel thickness were obtained and analyzed. Keratinocytes grown at the lowest seeding density did not contract the equivalents. However, histologic analysis has shown an incomplete coverage by these cells of the equivalents. The extensive contraction of the skin equivalent presenting adequate morphology is a major drawback toward its clinical utilization for burn wound coverage. The financial supports for this project were received from Canadian NSERC postgraduate scholarship (P. Rompré), Québec FCAR postgraduate scholarship (C.A. López Valle), France-Québec research grant in Biotechnology (F.A. Auger), Canadian MRC grant (F.A. Auger), and NSERC grants (A. LeDuy and J. Thibault).     

Subendocardial vascular plexus of the human ventricular myocardium in ontogenesis studied by scanning electron microscopy]

By means of scanning electron microscopy of native and corrosive preparations peculiarities of endocardium of the papillary-trabecular apparatus of the human heart ventricle and its vessels have been studied in ontogenesis. Folds of the endocardium increase its contact area with blood and also increase reserve of its elasticity at diastole. The subendocardial vascular plexus is formed by capillary-like venous sinusoids. They situate in the direction to the compact myocardium at the depth of 300-500 mcm. They are supposed to perform resorptive functions of nutritive substances and oxygen from blood, which is in the ventricular cavities and to smooth blood pressure between blood in the ventricular cavities and vessels of the compact myocardium.     

Active and passive properties of carotid arteries]

A mathematical model of carotid arteries is constructed from the known experimental data. Passive properties of the vascular wall are characterized by an alternating module of elasticity, the active ones by the specific power of muscle contraction. Its maximum value (0,023 n/m-3) is shown to be reached with intravascular pressure 190 mm Hg. The dependence of inner radius on the power of muscle contraction is studied at different values of intravascular pressure. It is shown that theactive properties of carotid arteries are essentially determined by their passive properties and depend on the stretching of the vessel wall.     

Muscle sound frequencies of the frog are modulated by skeletal muscle tension.

The purpose of this study was to determine the relationships among muscle sound frequencies, muscle tension, and stiffness. Time-frequency transformations of nonstationary acoustic signals provided measures of resonant frequency during isometric contractions of frog (Rana pipiens) semitendinosus and gastrocnemius muscles. A mathematical expression for muscle transverse resonant frequency, elastic modulus and tension, based on elastic beam theory, was formulated by the Rayleigh method adapted for muscles. For thin muscles, the elastic modulus was found to have negligible influence on transverse muscle resonant frequency. Changes in muscle tension were the major determinants of changes in transverse resonant frequency. Consequently, for thin muscles, the time course of muscle tension, but not elastic modulus, can be monitored acoustically during the early phase of contraction when muscles give rise to sounds. Muscles were found to be anisotropic with a modulus of elasticity, EL, measured via length perturbations near 0.1% muscle length peak-to-peak, that was much larger than the modulus of elasticity, Eb, that resists the lateral bending that causes sound production. The elastic and resonant behavior of a thin muscle is similar to a tensioned fibrous cable with distributed mass.     

Occurrence of "elastic" fibres in the invertebrates

The connective tissues of a wide range of invertebrates have been investigated using a potassium permanganate/spirit blue staining technique. The method demonstrates fibres which are distinct from collagen, vertebrate elastic fibres, and reticular fibres. The fibres are variously associated with subepidermal collagen, muscles, basement membrances, the walls of blood vessels and the sheaths around nerve cords; the method also gives a positive reaction with the arborescent mesogloeal fibres of medusoid coelenterates. Their electron microscope appearance is distinctive and they exhibit a physical elasticity. Chemical tests indicate that following pretreatment with acidified potassium permanganate they show many, although not all, of the properties of vertebrate "elastin". It is concluded that they should be regarded as a special category of "elastic" fibre.     

Mastication and the postorbital ligament: dynamic strain in soft tissues

Although the FEED database focuses on muscle activity patterns, it is equally suitable for other physiological recording and especially for synthesizing different types of information. The present contribution addresses the interaction between muscle activity and ligamentary stretch during mastication. The postorbital ligament is the thickened edge of a septum dividing the orbital contents from the temporal fossa and is continuous with the temporal fascia. As a tensile element, this fascial complex could support the zygomatic arch against the pull of the masseter muscle. An ossified postorbital bar has evolved repeatedly in mammals, enabling resistance to compression and shear in addition to tension. Although such ossification clearly reinforces the skull against muscle pull, the most accepted explanation is that it helps isolate the orbital contents from contractions of the temporalis muscle. However, it has never been demonstrated that the contraction of jaw muscles deforms the unossified ligament. We examined linear deformation of the postorbital ligament in minipigs, Sus scrofa, along with electromyography of the jaw muscles and an assessment of changes in pressure and shape in the temporalis. During chewing, the ligament elongated (average 0.9%, maximum 2.8%) in synchrony with the contraction of the elevator muscles of the jaw. Although the temporalis bulged outward and created substantial pressure against the braincase, the superficial fibers usually retracted caudally, away from the postorbital ligament. In anesthetized animals, stimulating either the temporalis or the masseter muscle in isolation usually elongated the ligament (average 0.4-0.7%). These results confirm that contraction of the masticatory muscles can potentially distort the orbital contents and further suggest that the postorbital ligament does function as a tension member resisting the pull of the masseter on the zygomatic arch.     

The mechanism of venom secretion from Duvernoy's gland of the snake Thamnophis sirtalis

The venom glands of snakes of the families Elapidae and Viperidae are thought to have evolved from Duvernoy's gland of colubrid ancestors. In highly venomous snakes elements of the external adductor musculature of the jaw insert fibers directly onto the capsule of the venom gland. These muscles, upon contraction, cause release of contents by increasing intraglandular pressure. In Thamnophis sirtalis, a colubrid, there is no direct connection between Duvernoy's gland and the adductor musculature. The anatomical arrangement of the gland, skull, adductor muscles, and the integument is such that contraction of the muscles may facilitate emptying of the gland. This hypothesis was tested by electrical stimulation of the muscles, which resulted in significantly greater release of secretion than elicited by controls. The results suggest a possible early step in the evolution of a more intimate association between venom glands and adductor musculature in highly venomous snakes.     

Axial stretching of extremity artery induces reversible hyperpolarization of smooth muscle cell membrane in vivo

Circumferential stretch due to increases in pressure induces vascular smooth muscle cell depolarization and contraction known as the myogenic response. The aim of this study was to determine the in vivo effects of axial-longitudinal stretch of the rat saphenous artery (SA) on smooth muscle membrane potential (Em) and on external diameter. Consecutive elongations of the SA were carried out from resting length (L0) in 10% increments up to 140% L0 while changes in membrane potential and diameter were determined in intact and de-endothelized vessels. Axial stretching resulted in a small initial depolarization at 120% of L0 followed by a progressive 20 to 33% hyperpolarizaion of vascular smooth muscle between 130% and 140% of L0. At 140%, an average maximal 10.6 mV reversible hyperpolarization was measured compared to -41.2 +/- 0.49 mV Em at 100% L0. De-endothelialization completely eliminated the hyperpolarization to axial stretching and augmented the reduction of diameter beyond 120% L0. These results indicate that arteries have a mechanism to protect them from vasospasm that could otherwise occur with movements of the extremities.     

Microscopic anatomy of the thin-walled vessels leaving the heart of the lobster Homarus americanus: anterior lateral arteries

Abstract. The anterior lateral arteries are paired vessels leaving the anterior end of the lobster ( Homarus americanus ) heart and proceeding to the antennae and eyestalks, the stomach and hepatopancreas, the gonads, and the thoracic and branchial muscles. These vessels have a trilaminar organization, consisting of a tunica interna with elastic fibrils, a tunica intermedia represented by a bilayered cell mass, and a tunica externa with collagen fibrils. In the tunica intermedia, cells flanking the tunica interna (light cells) show less affinity for basic dyes and electron stains than those flanking the tunica externa (dark cells). Each light cell exhibits an irregularly shaped stress fiber (a bundle of closely packed microfilaments) in the region adjoining the tunica interna. Collectively, these bundles have a circumferential or slightly oblique orientation relative to the lumen of the vessel. The role of the stress fibers is unresolved. If they are static structures, they might contribute to the non-linear elasticity shown by lobster arteries. If they generate force, and small bundles of microfilaments do diverge from the stress fibers to enter filamentous mats applied to the plasmalemmata, a coordinated contraction of the cells might reduce the luminal diameter and, thus, retard the flow of hemolymph. Coordination of contraction would have to occur in the absence of nerves and without the benefit of communicating (gap) junctions between the light and dark cells.     

The dynamics of collagen uncrimping and lateral contraction in tendon and the effect of ionic concentration

Under tensile loading, tendon undergoes a number of unique structural changes that govern its mechanical response. For example, stretching a tendon is known to induce both the progressive “uncrimping” of wavy collagen fibrils and extensive lateral contraction mediated by fluid flow out of the tissue. However, it is not known whether these processes are interdependent. Moreover, the rate-dependence of collagen uncrimping and its contribution to tendon's viscoelastic mechanical properties are unknown. Therefore, the objective of this study was to (a) develop a methodology allowing for simultaneous measurement of crimp, stress, axial strain and lateral contraction in tendon under dynamic loading; (b) determine the interdependence of collagen uncrimping and lateral contraction by testing tendons in different swelling conditions; and (c) assess how the process of collagen uncrimping depends on loading rate. Murine flexor carpi ulnaris (FCU) tendons in varying ionic environments were dynamically stretched to a set strain level and imaged through a plane polariscope with the polarizer and analyzer at a fixed angle. Analysis of the resulting images allowed for direct measurement of the crimp frequency and indirect measurement of the tendon thickness. Our findings demonstrate that collagen uncrimping and lateral contraction can occur independently and interstitial fluid impacts tendon mechanics directly. Furthermore, tensile stress, transverse contraction and degree of collagen uncrimping were all rate-dependent, suggesting that collagen uncrimping plays a role in tendon's dynamic mechanical response. This study is the first to characterize the time-dependence of collagen uncrimping in tendon, and establishes structure–function relationships for healthy tendons that can be used to better understand and assess changes in tendon mechanics after disease or injury.     

Mechanics of caudal artery relaxation in control and hypertensive rats

Alterations of smooth muscle function can just as easily stem from mechanical alterations in its ability to relax as from alteration in contraction. Since a failure of arterial smooth muscle to relax may contribute to the development of hypertension, we felt it necessary to study the relaxation process in greater depth. The effect of load on the time course of relaxation of rat caudal artery smooth muscle was analyzed either by comparing afterloaded contractions against various loads or by imposing abrupt alterations in load. Unlike mammalian striated muscles in which relaxation was reported sensitive to loading conditions, relaxation in the smooth muscle of the rat caudal artery (n = 17) was found to be largely independent of loading conditions. This type of relaxation has been termed "inactivation-dependent" relaxation; it is typical of muscle tissue in which the calcium sequestering apparatus is poorly developed. Our results suggest that calcium resequestration, or some biochemical process downstream to it, is the rate-limiting step during relaxation in arterial smooth muscle and that this is not qualitatively different for hypertensive arterial smooth muscle. These analytic techniques were used in the study of relaxation of hypertensive vessels. Quantitative analysis of the relaxation curves showed that both isometric and isotonic relaxation time was prolonged in hypertensive arterial smooth muscle. Prolonged isotonic relaxation indicates that hypertensive arteries remain narrowed for prolonged periods compared with normotensive vessels. Such narrowed vessels may be a factor in the increased total peripheral resistance seen in genetic hypertension.     

Vascular smooth muscle and neurohypophyseal hormones.

Experimental studies relating to the direct peripheral vascular actions of neurohypophyseal hormones and their synthetic variants are reviewed. In addition, the available data on the comparative pharmacologic actions of these peptides on mammalian vascular smooth muscle are reviewed. Experiments relating to mechanisms by which neurohypophyseal peptides induce contraction of blood vessels are discussed. Neurohypophyseal peptide hormones appear to be able to contract and relax vascular smooth muscle, the exact type of response being dependent on species, vascular bed, and region within a vascular bed. Receptors that subserve both contraction and relaxation may exist on different blood vessels within a species, with a preponderance of receptors that subserve contraction being present in most blood vessels. Concentrations of vasopressin that can be considered physiologic (i.e., 10(-13) to 10(-11) M) are capable of evoking responses on a variety of microscopic as well as large blood vessels. Arginine-vasopressin appears to be, relatively, the most potent contractile substance on rat blood vessels investigated to date; angiotensin is not. Preservative-free oxytocin is a contractile agent on all mammalian arterial and arteriolar vessels so far investigated. A great deal of the controversy surrounding the exact vascular actions elicited by these peptide hormones can be attributed to many factors that were not controlled in older experiments. Moreover, rat pressor assays cannot be utilized to determine structure-activity relationship for neurohypophyseal peptides on vascular smooth muscles. Nuerohypophyseal peptide-induced contractions of vascular smooth muscles can be markedly affected by sex, sex hormones, alcohols, [Ca2+]0, [mg2+]0, oxygen deficit, and glucose-deprivation. Extracellular sodium and potassium ions appear to play relatively little role in vasopressin-induced contractions of rat arterial smooth muscle. The terminal amino group, phenolic hydroxyl, aromatic ring and basicity in positions 1, 2, 3, and 8, respectively, of the neurohypophyseal hormones are important for optimizing hormone-receptor affinity and intrinsic contractile activity on vascular smooth muscle. Basicity in position 8 of these peptide hormones is not an absolute requirement for contractile activation of these smooth muscles. Alterations in molecular structure can result in neurohypophyseal peptides with unique, and selective, microcirculatory effects that may be beneficial in the treatment of low-flow states.     

Mechanism of effect of sympathetic nervous system on skin receptors

While researching the mechanism underlying the effect of the sympathetic nervous system on the operation of skin receptors, we demonstrated that a tremendous role in this process is played by smooth muscles, whose condition also mediates the sympathetic effect on receptors. The increase in the activity of the sympathetic nerve fibers results in an increase in the tonus of the smooth muscles which in turn alters the mechanical condition of the tissues surrounding the receptors. It was established that the change in the tonus of the smooth muscles in the skin itself affects the reaction of the receptors that is evoked by mechanical stimulation. The change in the tonus of the smooth muscles of the vessels affects the response of receptors caused by cooling of the skin.Nizhegorod Medical Institute, Russian Federation Ministry of Health. Translated from Neirofiziologiya, Vol. 24, No. 5, pp. 552–558, September–October, 1992.