Multiscale Coupling of One-dimensional Vascular Models and Elastic Tissues.

We present a computational multiscale model for the efficient simulation of vascularized tissues, composed of an elastic three-dimensional matrix and a vascular network. The effect of blood vessel pressure on the elastic tissue is surrogated via hyper-singular forcing terms in the elasticity equations, which depend on the fluid pressure. In turn, the blood flow in vessels is treated as a one-dimensional network. Intravascular pressure and velocity are simulated using a high-order finite volume scheme, while the elasticity equations for the tissue are solved using a finite element method. This work addresses the feasibility and the potential of the proposed coupled multiscale model. In particular, we assess whether the multiscale model is able to reproduce the tissue response at the effective scale (of the order of millimeters) while modeling the vasculature at the microscale. We validate the multiscale method against a full scale (three-dimensional) model, where the fluid/tissue interface is fully discretized and treated as a Neumann boundary for the elasticity equation. Next, we present simulation results obtained with the proposed approach in a realistic scenario, demonstrating that the method can robustly and efficiently handle the one-way coupling between complex fluid microstructures and the elastic matrix.

Macroscopic and histological investigation of guanaco footpads (Lama guanicoe, Müller 1776).

The surface of guanaco footpads is characterized by hairless skin with up to 4-mm-thick stratum corneum that protects from abrasion. The horny layer is pliable and elastic, and ensures firm contact with irregular ground. It is padded with a particular structure of the subcutaneous layer, the digital cushion. The flat cushions of each of the two digits are of elongated ovate shape, each about 45-mm long, up to 20-mm wide, and 8-mm thick. The cushions are lined by a 1-2-mm-thick capsule that resembles a tunica albuginea. The capsule consists of coarse collagen fibers, with elastic fibers absent. The cushion capsule and dermis approach each other, and fuse along a line that runs parallel to the longitudinal axes of cushion and digit. Loose connective tissue rich in elastic fibers and acidic glycosaminoglycans separates dermis and cushion capsule lateral to the narrow interconnecting zone. The cushion capsule encloses cloudy yellowish, gelatinous material. Microscopy shows bundles of elastic fibers in abundant mucinous matrix. Tightly gathered elastic bundles adjoin the inner surface of the capsule. Rough cords of elastic fibers branch out from there and traverse to the opposite side. The cushion is pressed flat, and elastic fibers are stretched when bearing weight. With relief of load, elastic fibers contract and reset the cushion's shape. Contractile cells are absent. A resistant capsule and easily malleable mucinous contents establish the functioning as a gel pad. Mucinous connective tissue between elastic fiber bundles contains abundant basophilic matrix. Hyaluronan, chondroitin sulfate, and dermatan sulfate are main matrix constituents. Spindle-shaped or stellate fibroblasts contain vimentin, S100 protein, and neuron specific enolase. Moprhology, staining characteristics and synthesis activities of these cells meet the criteria to be classified as myxoid cells. The connective tissue in guanaco digital cushions represents myxoid tissue.

Venous invasion in oesophageal adenocarcinoma: enhanced detection using elastic stain and association with adverse histological features and clinical outcomes.

AIMS: In oesophageal adenocarcinoma, detection rates of venous invasion using haematoxylin and eosin (H&E) and elastic stains have not been compared. The aims of this study were to investigate whether or not elastic stains facilitate the detection of venous invasion, and to determine the prognostic significance of venous invasion following review with elastic stains. METHODS AND RESULTS: One hundred and three resection specimens containing oesophageal adenocarcinoma, all reported originally as negative for venous invasion, were examined for the presence of venous invasion using H&E and subsequently Movat pentachrome stains. Venous invasion was detected in eight cases with H&E and an additional 66 cases using Movat pentachrome; overall, 72% of cases contained venous invasion. Venous invasion was associated with advanced stage, tumour size, lymphatic and perineural invasion and subsequent distant metastases. Venous invasion, stage, size, grade, lymphatic invasion and perineural invasion were prognostically significant on univariate analysis. Only tumour stage was independently prognostic. Two of eight patients with venous invasion but no other indication for adjuvant treatment died of recurrent disease. CONCLUSIONS: Elastic stains improve detection of venous invasion significantly in oesophageal adenocarcinoma. Venous invasion is associated with multiple adverse clinicopathological features. Its identification may facilitate the stratification of patients at risk for visceral metastases and disease-related death.

Pulse wave analysis and arterial stiffness.

Assessment of the pulse character is one of the earliest recorded medical skills, but objective recordings of the pulse waveform--sphygmography--emerged only in the nineteenth century. This technique fell into disuse with the advent of the sphygmomanometer, but interest has recently been rekindled with the introduction of computer technology and applanation tonometry. Pulse wave analysis (PWA) is a technique that allows the accurate recording of peripheral pressure waveforms and generation of the corresponding central waveform, from which the augmentation index and central pressure can be derived. In clinical studies, we have shown that PWA is a highly reproducible technique and easy to apply. Together with ECG-gated assessment of pulse wave velocity, also using PWA, these measures provide important information about arterial stiffness. Stiffness may be partly under the functional control of the endothelium, which releases a number of vasoactive mediators, as well as being structurally determined. Increased stiffness is associated with most cardiovascular risk factors and established atherosclerosis. However, increased stiffness may be more than a marker for occult atheroma. It may be involved in the pathogenesis of cardiovascular disease by a number of mechanisms. Assessment of stiffness, perhaps using PWA, may therefore provide better risk assessment and allow treatment to be targeted to those most in need.

A controlled hematoxylin-eosin for actinic elastosis-lysis. Its versatility and use for vascular damage (actinic arteriopathy) in the skin and orbit.

To demonstrate elastic tissue and its reactions in the skin and other organs, the hematoxylin-eosin staining method had been modified in two ways: (a) the hematoxylin solution is used once only to obtain its full potential, and (b) aqueous eosin is given greater selectivity by controlling its pH with a buffer. This stain highlights the broad supporting role of elastic tissue, particularly in pressure-containing blood vessels. It also helps to define the hyperplasia, degeneration, and elastolysis that arise from its peculiar sensitivity to actinic radiation.

Benign vascular invasion in vasitis nodosa.

Vasovasostomy specimens were examined for vascular changes in 50 cases of vasitis nodosa. In five, benign gland- or ductule-like structures were seen invading small veins and, in one, also the small arteries. The intravascular ductules appeared benign, and there was no clinical evidence of malignancy. The presence of ductules in the blood vessels always was accompanied by marked elastosis. In 12 additional cases, elastosis of arteries and veins was seen without intravascular ductules. These changes suggest that proliferating ductules in vasitis nodosa invade the blood vessels after they have become obliterated by regressive and reparative processes.

Transient pressure-flow responses in the resting canine hindlimb--analysis as responses to rapid stretching of the resistance microvessels.

The transient hyperaemia caused by sudden elevation of arterial pressure and reactive hyperaemia after interruption of arterial pressure for 3, 5, 10, 20 and 40 s were studied in the perfused resting hindlimb of anaesthetized areflexic dogs. Experiments were performed using steady-state pressures ranging from 50-150 mmHg. The component of the hyperaemia response (delta Q) that was attributable to resistance vessel distension by a sudden rise in pressure (delta P), was measured as the difference between peak hyperaemic flow change and the flow change predicted for that delta P in a system having constant resistance. Over the range of steady-state pressures used, vascular conductance was approximately constant, indicating that steady-state flow autoregulation was weak. delta Q was a linear function of delta P for both the hyperaemia of sudden pressure elevation and reactive hyperaemia, and the delta Q/delta P relationships were independent of steady-state perfusion pressure. The delta Q/delta P relationships for sudden pressure elevation and reactive hyperaemia after 40 s occlusion did not differ significantly. For a given delta P, however, delta Q decreased with decreasing occlusion time. The magnitude of reactive hyperaemia after brief occlusion depended not only on the degree of resistance vessel relaxation achieved during occlusion but also on the pressure step resulting from restoration of pressure. Using data from these experiments in a simple mathematical model of an idealized resistance vessel, a series of distensibility curves were constructed that showed that as active wall tension increased with increasing steady-state pressure, resistance vessel distensibility decreased.

[Arterial vascular bed of the human mesenteric lymph nodes]. / Arterial'noe sosudistoe ruslo bryzheechnykh limfaticheskikh uzlov cheloveka.

The anatomy of the blood vessels has been studied in 394 mesenteric lymph nodes macro- and microscopically. Morphometrical measurements of the size and diameter of the nodes have been performed in the intraorganic arteries of all orders of branching. Correlative connections existing between the size of the nodes and the number of the arteries supplying them with blood, between the size of the nodes and the diameter of the arteries feeding them, between the number of the hiluses and the number of the arteries supplying the lymph node with blood have been determined. As the results of the investigation demonstrate, the mesenteric lymph nodes having various localization differ in their size and form. The number and diameters of the arteries getting into the nodes via the hilus and the capsule vary within a wide range. There are two (often) or three (seldom) hiluses. One - three arteries get into one hilus. The structure of the intraorganic arterial vessels in the mesenteric lymph nodes is complex and variable, depended on the form of the nodes, number and position of the hiluses, on the type of blood supply and on the branching of the arteries getting into the nodes via the hiluses. In most of the mesenteric lymph nodes there are four orders of branching of the intraorganic arteries, each of them having a specific type of division into branches. All the intraorganic arteries either are situated within the trabecular connective tissue or are surrounded with elastic and collagenous fibres. The arteries of various order are differently connected with the structural-tissue elements of the lymph nodes. There are various variants in blood supply of the lymph node folliculi. The arterial vessels of the human mesenteric lymph nodes have a twisty course.

Elastosis in breast carcinoma.

Elastosis, the significant increase of elastic tissue, was identified by histochemical methods in 45 (53.5%) cases of an unselected series of breast cancers. They were all invasive ductal carcinomas with or without tubular differentiation. The highest proportion of tumors with elastosis was found in the "scirrhous" type of carcinomas. Elastosis was preponderantly of the focal variety, periductal and perivenous. The affected ducts were of large calibre, containing a normal, benign hyperplastic or carcinomatous epithelium. There were not observed correlations with the grade of malignancy and the extent of axillary lymph node metastases.

[Plastic properties of the arterial bed of the cervical area in the dog]. / Plasticheskie svoistva arterial'nogo rusla sheinoi oblasti sobaki.

In 12 dogs sources of blood supply for certain cervical organs have been studied in norma. Anastomoses between them are grouped according to their origin as intersystemic and intrasystemic. The main intersystemic anastomoses are situated in the superficial ventral muscles, and the intrasystemic ones--in the superficial dorsal muscles, trachea and esophagus. In 24 dogs both the common carotid and vertebral arteries have been ligated simultaneously. The main compensatory-adaptive mechanisms contribute for the collaterals to develop, dilate and acquire their winding character, for the angle of the collateral branches alteration to change. Main and additional by-pass ways of the blood stream have been revealed.

Actinic granuloma. An annular connective tissue disorder affecting sun- and heat-damaged (elastotic) skin.

Ring-shaped inflammatory lesions sometimes develop in the abnormal "elastotic" connective tissues of skin damaged by sun and heat. The lesions, which commence as papules and nodules, enlarge very slowly and may persist for years. Microscopical sections show that there is an infiltrate composed mainly of foreign-body giant cells, the cells being engaged in digesting and absorbing the abnormal elastotic fibers. The disorder, which occurs on several continents, should probably be regarded as a phenomenon of repair within damaged connective tissue. The name actinic granuloma indicates its external or environmental origin and distinguishes it from other granulomas with which it is constantly being confused. Actinic granuloma and granuloma annulare appear to be related. In granuloma annulare, a productive and resorptive process also occurs, but its nature remains obscure. Actinic granuloma may be misdiagnosed as "atypical necrobiosis lipoidica" or as a sarcoidosis. The subject of actinic damage to blood vessels deserves study.

Chick vincula: elastic structures with a check-rein mechanism.

From their mode of attachment and their elastic composition, it is clear that the vincula of the chick serve other functions besides that of carrying blood vessels to the digital flexor tendons within their synovial sheaths. Evidence is presented in support of the argument that elastic fibres bear the brunt of rapidly applied tensile forces and that the interweaving collagen fibres only become taut when the vincula are stretched to the limit and about to tear. Our hypothesis is that the collagen serves as a check-rein mechanism in an otherwise elastic structure.