Mechanical alterations in smooth muscle from mice lacking desmin

Mice with a null mutation introduced in the desmin gene were used to study the mechanical role of intermediate filaments in smooth muscle cells. Vas deferens (VD), urinary bladder (UB) and portal vein (PV) preparations were obtained from adult animals lacking desmin (Des −/−) and from age- and weight-matched wild-type animals (Des +/+). Active force per cross-sectional area was decreased in the smooth muscle of the Des −/− compared with Des +/+ mice (VD to 42%; UB to 34%). Quantitative gel electrophoresis suggests a marginally lower cellular content of myosin, but the organization of the contractile apparatus appeared unchanged by electron microscopy. A similar reduction in stress was measured in Des −/− skinned fibres showing that altered activation mechanisms were not involved. The results indicate that the reduced active force is caused by low intrinsic force generation of the contractile filaments or subtle modifications in the coupling between the contractile elements and the cytoskeleton. The relationship between length and passive stress was less steep in the Des −/− samples and a second length force curve after maximal extension revealed a loss of passive stress. The maximal shortening velocity was reduced in Des −/− skinned VD and UB preparations by approximately 25–40%. This was associated with an increased relative content of the basic essential myosin light chain, suggesting that alterations in the contractile system towards a slower, more economical muscle had occurred. PV preparations showed no difference in mechanical properties in Des +/+ and Des −/− animals, a result that was consistent with the predominance of vimentin instead of desmin in this vascular tissue. In conclusion, the results show that, although intermediate filaments in smooth muscle are not required for force generation or maintenance of passive tension, they have a role in cellular transmission of both active and passive force. This revised version was published online in September 2006 with corrections to the Cover Date.     

Intermediate filament proteins in developing human arteries

 The distribution of intermediate filament proteins in adult human blood vessels and in human fetal elastic arteries is relatively well-known. However, the distribution of these proteins in the course from neonate to adult has not been established. In this investigation, human postnatal arteries were studied with immunohistochemistry, using antibodies targeted on the intermediate filament proteins desmin, vimentin and cytokeratins 8, 18 and 19. Vimentin was present in most smooth muscle cells in all vessels and at all ages. The proportions of desmin-expressing cells increased in the elastic arteries during the first year of life and was higher in the pulmonary trunk than in the aorta. In the muscular arteries, the proportion of desmin-labelled cells increased in the coronary and the deep femoral arteries, but remained constant in the renal and the cerebral arteries. Cytokeratins were detected in the pulmonary trunk earlier than in the aorta. Cytokeratins were present throughout the wall of the ductus arteriosus, but desmin was present only in some cells. Thus, there are postnatal changes in the distribution of intermediate filament proteins in the elastic arteries and in some muscular arteries, whereas the intermediate filament pattern remains unchanged in other muscular arteries. Accepted: 31 July 1998     

Onset of elastogenesis and downregulation of smooth muscle actin as distinguishing phenomena in artery differentiation in the chick embryo

During development, the arterial system is grossly divided into elastic and muscular vessel types. Apart from local environmental factors, it has been suggested that vascular smooth muscle cell origin (mesoderm or neural crest) is involved in this, as yet poorly understood, arterial differentiation. We describe differentiation of the thoracic arterial system in the chick embryo, using immunohistochemical techniques staining for muscle-specific actin, vinculin and desmin and histological staining to visualise elastin. The initial developmental stages of the vessel wall in all arteries appeared to be highly similar, with all arteries showing peri-endothelial actin and vinculin staining. Major alterations did not occur until the start of elastogenesis, which coincided with complete loss of actin staining from the proximal part of the great arteries. Later in development, however, actin was re-expressed in a subpopulation of medial cells, which also expressed vinculin and desmin. Concomitantly another, nonmuscular, cell type became evident in the great arteries. Transient loss of actin expression and segregation of very distinct cell populations occurred only in vessels prone to elastic development and known to receive a neural crest contribution. In contrast, arteries that developed a muscular phenotype never lost the initially acquired peri-endothelial actin expression. We also show a significant difference in the organisation of elastic fibres between elastic vessels that contain neural crest derivatives and those that do not. The ductus arteriosus still presents as an enigma in the sense that it is the only part of the pharyngeal arch complex that develops a muscular phenotype.     

Ultrastructural features of the distended pulmonary arteries of the normal rat.

Detailed study has been made of the structure of the normal pulmonary artery of rat by both light (1-micrometer sections) and electron microscopy. After tying the pulmonary veins at the hilum, the lungs were fixed by simultaneous injection of glutaraldehyde into the pulmonary trunk and trachea. Study of distended arteries allows precise measurement and assessment of normal lung structure. Four regions of the pulmonary artery can be identified by wall structure and are described here--muscular, partially muscular, non-muscular and the newly described thick-walled oblique muscular. Electron microscopid examination has demonstrated in the non-muscular regions of the partially muscular arteries, an "intermediate" cell and in the non-muscular arteries, a pericyte. The intermediate cell lies internal to the single elastic lamina but external to the endothelial cell, is surrounded by its own basement membrane and contains filaments mainly along the adluminal region of the cell. The pericyte also lies internal to the single elastic lamina, is within the basement membrane of the adjacent endothelial cell and has previously been reported in the lung only in the walls of alveolar capillaries. The structure of the intermediate cell and its position suggest it is a transitional stage between the pericyte and smooth muscle cell.     

Ultrastructural features of the distended pulmonary arteries of the normal rat

Detailed study has been made of the structure of the normal pulmonary artery of rat by both light (1-μ sections) and electron microscopy. After tying the pulmonary veins at the hilum, the lungs were fixed by simultaneous injection of glutaraldehyde into the pulmonary trunk and trachea. Study of distended arteries allows precise measurement and assessment of normal lung structure. Four regions of the pulmonary artery can be identified by wall structure and are described here-muscular, partially muscular, non-muscular and the newly described thick-walled oblique muscular. Electron microscopic examination has demonstrated in the non-muscular regions of the partially muscular arteries, an “intermediate” cell and in the non-muscular arteries, a pericyte. The intermediate cell lies internal to the single elastic lamina but external to the endothelial cell, is surrounded by its own basement membrane and contains filaments mainly along the adluminal region of the cell. The pericyte also lies internal to the single elastic lamina, is within the basement membrane of the adjacent endothelial cell and has previously been reported in the lung only in the walls of alveolar capillaries. The structure of the intermediate cell and its position suggest it is a transitional stage between the pericyte and smooth muscle cell.     

Variations of the celiac trunk branches in the fetus

The study was performed on 60 human foetuses, aged between 4 to 9 months, using as methods dissection and plastic and contrast substances injection. We studied the celiac trunk in what concerns the division into its terminal branches, insisting on the possible morphological variations, some rare collateral branches starting from the common arterial trunk, the dimensional relations between the branches at their origin and the level of the celiac trunk origin from the aorta, in relation with the vertebral column, the diaphragmatic passage of the aorta and with the superior mesenteric artery. We also assessed the dimensional relations (calibers at origin) between the branches of the celiac trunk. Ass possible variations of the division of the celiac trunk, we assessed: gastro-hepatic trunk, with the splenic artery directly from the aorta or from the hepatic artery; gastro-splenic trunk, with the hepatic artery originating from the aorta; hepato-splenic trunk, with origin of the left gastric artery either directly from the aorta or from the hepatic artery. Rare variations: celiaco-mesenteric trunk; two arterial trunks, hepato-splenic and hepato-gastric; separate aortic origin for all three "classic" branches of the celiac trunk; two hepatic arteries, one from the celiac trunk and the other from the aorta or superior mesenteric artery; celiac trunk that divides into several terminal branches; one or two suprarenal arteries originating from the celiac trunk.     

Longitudinally orientated smooth muscle cells in rabbit arteries

Intima formation in vessels, spontaneous or experimentally induced, is generally characterized by the presence of longitudinally orientated smooth muscle cells (LSMC). During an experiment of neo-intima induction in carotid arteries in rabbits, by application of a nonconstrictive silastic cuff, a study was performed to investigate the presence of LSMC in the systemic and pulmonary circulations, in both elastic and muscular arteries. Three patterns could be distinguished: intimai cushions in muscular arteries, single or small groups of LSMC in the intima in elastic and larger muscular arteries, and intra-medially located layers or columns of LSMC in the aorta, the pulmonary artery, at the bifurcation of the aorta and around orifices of branches. In order to understand this peculiar orientation a biomechanical approach was used: this showed that near the lumen the circumferential stress is 4.5 times higher than the longitudinal. Because the cell surface of the smooth muscle cells exposed to this stress per unit vessel length is much less in the longitudinal than in the circular direction we conclude that the LSMC align in the direction which allows them to cope most effectively with the mechanical stresses.     

Lower active force generation and improved fatigue resistance in skeletal muscle from desmin deficient mice

The mechanical effects of the intermediate filament protein desmin was examined in desmin deficient mice (Des−/−) and their wild type control (Des+/+). Active force generation was determined in intact soleus muscles and in skinned single fibres from soleus and psoas. A decreased force generation of skinned muscle fibres from Des−/− mice and a tendency towards decreased active force in intact soleus muscle were detected. Concentrations of the contractile protein actin and myosin were not altered in Des−/− muscles. Ca²⁺-sensitivity of skinned single fibres in Des−/− muscles was unchanged compared to Des+/+. Using a protocol with repeated short tetani an increased fatigue resistance was found in the intact soleus muscles from Des−/− mice. In conclusion, desmin intermediate filaments are required for optimal generation or transmission of active force in skeletal muscle. Although other studies have shown that the desmin intermediate filaments appear to influence Ca²⁺-handling, the Ca²⁺-sensitivity of the contractile filaments is not altered in skeletal muscle of Des−/− mice. Previous studies have reported a switch towards slower myosin isoforms in slow skeletal muscle of Des−/− mice. The increased fatigue resistance show that this change is reflected in the physiological function of the muscle. This revised version was published online in July 2006 with corrections to the Cover Date.     

Age-related changes in arterial wall mechanics and composition of NIA Fischer rats

Segments of carotid and tail arteries and descending thoracic aorta were obtained from the NIA colony of Fischer rats at ages 3, 12, 24 and 30 months. Measurements of pressure and diameter were made on intact cylindrical segments under conditions of active (147 mM K⁺ and pssive (Ca²⁺ -free and 2 mM EGTA) smooth muscle. These data were used to compute active and passive mechanics. Contiguous segments were used for the analysis of connective tissue, water and electrolyte contents. Passive stiffness of the carotid and tail arteries increased monotonically with increasing age. Collagen content in the aorta and tail artery generally increased with age, while elastin content decreased in the aorta and carotid artery. The ratio of collagen to elastin increased at all sites with age. Maximum values of active stress response (force development) increased from 3 to 12 months for the carotid artery, but decreased with age (at 24 and 30 months compared to 3 and 12 months) for the tail artery. Changes in relative cell content were such that active cellular force development was the same at all ages for the carotid artery but was smaller at 24 and 30 months compared to the younger animals for the tail artery. Decreased cellular force development by arterial smooth muscle is not an anatomically uniform finding in this animal model.     

Variations in the source of origin of inferior phrenic artery: a cadaveric study

Introduction: The right and left inferior phrenic arteries perfuse the diaphragm. They may originate either from the aorta, celiac trunk, or from the renal artery. Most textbooks of human anatomy give little information regarding the functional anatomy of the inferior phrenic artery. In the past few years, however, more articles have been published regarding the arterial supply in cases of hepatocellular carcinoma. The inferior phrenic artery is seen as an important source of collateral arterial supply to hepatocellular carcinoma, the hepatic artery being the main source. Materials and methods: A cadaveric study was conducted in the Anatomy Department of Bangalore Medical College during the years 2009–2011. Manual dissection was done to identify the inferior phrenic arteries, and their origins were traced. Results: The inferior phrenic artery arose from the aorta in 53.125%, celiac trunk in 28.125%, renal artery in 15.625%, and the superior mesenteric artery in 3.125% of the 32 cadavers studied. The right inferior phrenic artery arose from aorta in 56.25%, celiac trunk in 18.75%, renal artery in 18.75%, and superior mesenteric artery in 6.25% cases. The left inferior phrenic artery arose from aorta in 50%, from celiac trunk in 37.5%, and the rest arose (12.5%) from the renal artery. Discussion: The results were compared with those of earlier studies so that such findings could be applied in the treatment of hepatocellular carcinoma. The significance of this information is due to the fact that an unresectable hepatocellular carcinoma can be treated by transcatheter embolization of the right inferior phrenic artery, in case it is involved.     

The cytoskeleton of the vertebrate smooth muscle cell

Smooth muscle cells possess a structural lattice composed of two primary parts: the ‘cytoskeleton’ that pervades the cytoplasm and the ‘membrane skeleton’ that provides anchorage for the cytoskeleton and contractile apparatus at the cell surface. The cytoskeleton contains two major components: first, a complement of actin filaments that links the cytoplasmic dense bodies at equispaced intervals in longitudinal fibrils; and second, a network of desmin intermediate filaments that co-distributes with the cytoskeletal actin. The actin filaments of the contractile apparatus are presumed to interface with the cytoskeleton at the cytoplasmic dense bodies and with the longitudinal rib-like arrays of dense plaques of the membrane skeleton that couple to the extracellular matrix. The present report focuses attention on the functional role of intermediate filaments and on the molecular domain structure of the protein calponin, which is found both in the cytoskeleton and the contractile apparatus. New information about the role of intermediate filaments in smooth muscle has come from studies of transgenic mice in which desmin expression has been ablated. These have shown that while desmin is dispensable for normal development and viability its absence has significant consequences for the mechanical properties of muscle tissue. Thus, the visceral smooth muscles develop only 40% of the normal contractile force and the maximal shortening velocity is reduced by 25–40%. Intermediate filaments therefore play an active role in force transmission and do not contribute solely to cell shape maintenance, as has hitherto been presumed. Recent studies on calponin have revealed a second actin binding domain at the C-terminus of the molecule and have also pinpointed an N-terminal domain that shares homology with a growing family of actin binding and signalling molecules. How these newly identified features of calponin relate to its function in vivo remains to be established.     

A case of celiacomesenteric trunk with some other arterial anomalies in a Japanese woman

We found a case of multiple arterial anomalies in a Japanese female cadaver during a routine dissection course. In the present case, a combination of three arterial anomalies was recognized in the abdominal digestive organs: (i) a celiacomesenteric trunk; (ii) a right accessory hepatic artery; and (iii) a left colic artery arising from a portion corresponding to the superior mesenteric artery. The typical celiacomesenteric trunk can be regarded as a variation of the arterial convergence at its origins progressing further between the celiac trunk and the superior mesenteric artery. The celiacomesenteric trunk in the present case included the left colic artery, which is usually one branch of the inferior mesenteric artery. Previously, a case had been reported in which all three arteries supplying the abdominal digestive organs had converged into one trunk, the celiac-bimesenteric trunk. Therefore, the celiacomesenteric trunk in the present case showed an intermediate degree of arterial convergence between that of the typical celiacomesenteric trunk and the celiac-bimesenteric trunk.     

Experimental cerebral aneurysms in the female heterozygous Blotchy mouse

The Blotchy mouse is characterized by an X-linked inherited disorder of connective tissue synthesis. The susceptibility to aneurysm formation in the cerebral arteries of the circle of Willis was compared in female heterozygous 'Blotchy' and control mice subjected to unilateral carotid artery ligation either alone or associated with hypertension. Cerebral aneurysms developed only in hypertensive Blotchy mice (6/31 vs. 0/30 in hypertensive controls). Aneurysms of the aorta and its major branches occurred in normotensive mice only in the Blotchy group in which hypertension increased the incidence of mesenteric and coeliac aneurysms. A light microscopic study of interruptions of the internal elastic lamina (IIEL) showed that they developed in arteries of both Blotchy and control mice but to a greater extent in the Blotchy group where hypertension further increased their incidence. The IIEL incidence in the aortic arch varied in parallel to the occurrence of aneurysms in all the different arterial sites. Thus, in an apparently normally viable animal, the presence of a mutated gene which indirectly leads to defective elastin and collagen fibre synthesis, favours the formation of both peripheral and cerebral aneurysms. However, the development of cerebral aneurysms requires the addition of an increase in haemodynamic stress.     

Aortic origin of right hepatic artery and superior mesenteric origin of splenic artery two rare variations demonstrated angiographically

Abstract Anatomical variations of the celiac trunk and superior mesenteric artery are not infrequent. Knowledge of the existing aberrations is important in planning and conducting surgical or radiological procedures. A case of right hepatic artery arising independently from the aorta supplying an hepatocellular carcinoma was identified, through which transarterial chemoembolization was successfully performed. A second case is presented with a common splenomesenteric trunk branching into the splenic and superior mesenteric arteries. These two cases represent exceptional arterial variations in the upper abdomen.     

Different nerve responses in consecutive sections of the arterial system

Isometric responses to nerve stimulation and to applied noradrenaline were compared in isolated ring preparations of three consecutive types of rat arteries, viz. the aorta, the superior mesenteric artery and 200-micron branches of the latter. Intramural nerves were activated by graded electrical field stimulation; obtained responses were blocked by tetrodotoxin, phentolamine or prazosin. Also direct muscle activation could be accomplished, using impulses of long duration. In the aorta responses to nerve stimulation were sluggish, could reach only 30-40% of the maximal noradrenaline response and single impulses were ineffective. In the small resistance arteries, neurogenic responses matched the maximal noradrenaline responses and distinct, rapid contractions occurred to single nerve impulses. The superior mesenteric artery was intermediate in these respects. By contrast, on direct muscle activation all vessels responded to single impulses with rapid contractions that differed little in velocity. Pharmacological inhibition of transmitter reuptake increased noradrenaline sensitivity most in the small arteries, but nerve responses were most enhanced in the superior mesenteric artery. These regional differences, probably reflecting decreasing neuromuscular distance with decreasing vessel size, imply that generalizations concerning the relation between responses to nerve stimulation and to exogenous noradrenaline cannot be made from one vascular model only.     

Biometry and structure of the left internal thoracic and radial coronary arteries

In an attempt to elucidate the causes of occlusion of radial arteries for coronary artery bypass grafts, we studied the biometry and histology of the coronary, radial and left internal thoracic arteries of 20 anatomical subjects (13 males and 7 females). These specimens were calibrated to the various bypass graft sites using coronary calibrators, and were then submitted to histological examination to determine the structure of the vessel wall. Our preliminary results show no correlation between the internal calibres of these various arteries. Like the coronary arteries and their branches, the radial artery is a muscular artery. In contrast, the left internal thoracic artery like the aorta, is an elastic artery.     

Structural organization of pulmonary arteries in the rat lung

The structure of the normal pulmonary arteries in the rat was studied with light and electron microscopy after use of a newly devised technique of perfusion fixation and tissue preparation. We distinguished two main types of artery in the rat lung on the basis of the structure of the media, an elastic artery and a muscular artery. The elastic artery was characterized by an abundance of extracellular matrix in the media and by an oblique arrangement of smooth muscle cells to connect neighboring elastic laminae. It was subdivided into two segments, a classical elastic and a transitional elastic segment. The muscular artery was distinguished by a paucity of extracellular matrix in the media and by a circumferential arrangement of smooth muscle cells (or pericytes) enclosing the lumina, and was subdivided into four segments, a thick muscular, an ordinary muscular, a partially muscular and a nonmuscular segment. The smooth muscle cells in the muscular artery contained well-developed microfilament bundles compared with those in the elastic artery. Structural differences in smooth muscle cells and in extracellular matrix in the media between the elastic and muscular arteries may reflect the functional heterogeneity of pulmonary arteries in response to hypoxic pulmonary vasoconstriction and to vasoactive substances such as endothelium-derived relaxing and hyperpolarizing factors, and endothelin.     

Coexistence of multiple anomalies in the celiac-mesenteric arterial system

The origins and distribution of arteries of the celiac-mesenteric system were examined by dissection of 52 formalin-fixed human cadavers. Seventy-five percent of the cadavers exhibited the classic Michels' Type I hepatolienogastric pattern; 25% had different branching patterns. Multiple anomalies of the celiac-mesenteric arterial system were observed in one Caucasian female cadaver: a short lienogastric trunk; a common hepatic artery arising directly from the abdominal aorta; an anomalous course of the hepatic arteries; an accessory left hepatic artery arising from the left and right gastric arterial anastomosis along the lesser curvature of the stomach; a double cystic artery; a common inferior phrenic trunk arising from the celiac trunk; and an aberrant arterial channel connecting the proximal segments of the splenic and gastroduodenal arteries. A patent ductus venosus and an anomalous formation of the portal vein by the confluence of the splenic and superior and inferior mesenteric veins was also observed. Although single anomalies of the celiac-mesenteric arterial system are common, complex combinations, such as were observed in the present case, represent a significant deviation from the normal developmental pattern. There seems to be no report in the literature of such a combination of anomalies coexisting in one individual. The developmental and clinical significance of these anomalous vessels is discussed.     

Rare case of the inferior mesenteric artery arising from the superior mesenteric artery

The authors observed a variation of the inferior mesenteric artery, which arose from the superior mesenteric artery, in a 69-year-old Japanese male cadaver during dissection in 1984. In this case, no rudiment of the ordinary inferior mesenteric artery could be found on the abdominal aorta. There are few reports of this variation, and an extensive search of the available literature revealed only four cases, including two in Japan. Such a variation had been somewhat inadequately described as an "absence of the inferior mesenteric artery" in the previous reports, but we avoided this terminology, because all of the cases possessed an artery, which, though arising from the superior mesenteric artery instead of the abdominal aorta, had the same branches as a normal inferior mesenteric artery. Consistent with findings observed in the previous cases, the unusual inferior mesenteric artery arose as the first branch of the superior mesenteric artery, with the common trunk of both mesenteric arteries originating from the abdominal aorta at a level at which an ordinary superior mesenteric artery would arise. It is for this reason that we did not adopt another acceptable name, that is, "the common mesenteric artery," for this variation. The variation can be explained as the result of an unusual development of the embryonic artery system, which comprises a number of ventral splanchnic arteries interconnected by longitudinal anastomotic channels to supply the primitive digestive tube.