[HISTOGENESIS AND PECULIARITIES OF STRUCTURAL ORGANIZATION OF THE CARDIAC MUSCLE TISSUE IN THE WALLS OF HUMAN CAVAL AND PULMONARY VEINS].

To study the structural organization and histogenesis of the cardiac muscle tissue in the walls of human caval and pulmonary veins, the heart was examined in 3 human embryos (at weeks 6-7 of development) and 20 fetuses (at weeks 9-10, 16, 19, 22 and 24 of development), as well as segments of caval and pulmonary veins of adult men and women (n = 50) located at various distances from the heart. The methods of light and electron microscopy were used in this work. To obtain the isolated cells from the walls of caval and pulmonary veins, the method of tissue alkaline dissociation was used. An immunohistochemical study with the monoclonal antibodies against cardiac troponin T was performed. It was found that the cardiomyocytes in humans were located in the middle and outer tunics of caval and pulmonary veins, where they formed thick layers. In the pulmonary veins of the adult humans, cardiac muscle fibers did not reach the intrapulmonary areas, in the inferior vena cava their layer did not extend beyond the pericardium, in the superior vena cava, its length was 2.5-3.0 cm. The formation of the pulmonary vein orifices occured by sequential inclusion of the wall of the common pulmonary vein, and later--of the right and left pulmonary veins into the wall of the left atrium. During the formation of the orifices of the caval veins, the gradual inclusion of the wall of the venous sinus in the wall of the right atrium was observed, resulting in caval veins opening directly into the cavity of the right atrium. The veins studied were referred to the veins of the muscular type with the strong development of muscular elements containing the myocardial component.

[Efferent innervation of pulmonary blood vessels and bronchi in rat (an immunohistochemical study)].

In this investigation the peculiarities of innervation of bronchi and blood vessels of the lung were studied in 20 rats using immunohistochemical demonstration of synaptophysin and alpha-actin. The results obtained have showen that the densest innervation is typical for bronchial walls, particularly, for the muscular lamina. Synaptophysin-immunoreactive terminals (SFIT) were detected in the bronchi in close association with both circular bundles of smooth muscle cells and microganglia. Dense network of SFIT was found in the pulmonary vein--in its middle tunic formed by cardiomyocytes. In contrast to the bronchi and pulmonary vein, large branches of the pulmonary artery contained no SFIT. We briefly discuss the problem of the origin of the nerve fibers described and their functions and suggest that SFIT are formed by efferent fibers (axons) of neurons arising from either the intrapulmonary parasympathetic ganglia.

[Modern conceptions of the atrial fibrillation development. The role of the myocardial sleeves in the pulmonary veins].

Atrial fibrillation (AF) is the most common supraventricular cardiac arrhythmia. In this review several conceptions focused on the mechanisms of the AF initiation are discussed. At present time viewpoint that the ectopical activity in the pulmonary vien myocardial sleeves (PVs) account for AF in prevailing. PVs myocardium has been the subject of many anatomical and physiological investigations. PVs myocardium differs from left atria tissue and has many moprhological properties that make in convenient substrate for AF initiation and maintenance. PVs cardiomyocytes were shown to have great variability of electrophysiological properties (action potential duration, resting potential, upstroke velocity, etc.). Attempt to discuss afterdepolarization, triggered activity and abnormal automaticity as initiators of AF in PVs was made. It was shown that as in experimental condition, as in vivo in PVs can exist er-entry. Possibly, re-entry from PVs could be the one mechanism by which AF is initiated. In review big attention to the innervations of PVs and role of the sympathetic and the parasympathetic nerves in PVs ectopical activity is paid. Combined influence of autonomic nerves may be critical to initiating AF in PVs. Pharmacological intervention as a possible way to suppress or prevent the activity in the PVs that leads to AF is discussed.

Presence of Ganglia and Telocytes in Proximity to Myocardial Sleeve Tissue in the Porcine Pulmonary Veins Wall.

Ganglia and telocytes were identified inside the porcine pulmonary veins wall near myocardial sleeve tissue at the atriopulmonary junction. These structures are reported to play a role in the initiation of pulses from outside the heart, which potentially can cause cardiac conduction disorders such as atrial fibrillation. In-depth knowledge on the fine structure of the pulmonary vein wall is a pre-requisite to better understand the underlying pathophysiology of atrial fibrillation and the origin and conduction of ectopic pulses. The importance of pulmonary vein myocardial sleeves as triggering foci for atrial fibrillation has been shown in human patients. In this context, the fine structure of the pulmonary vein wall was investigated qualitatively by light and transmission electron microscopy in the pig, which is a frequently used animal model for development of new treatment strategies. Additionally, intra and extramural ganglia, containing telocytes that create a network near the neurone cell bodies, were identified in pigs. Detailed illustration of the distribution and organization of tissues and cell types, potentially involved in the origin and propagation of ectopic stimuli originating from the pulmonary veins, might lead to a better insight on the actual composition of the tissues affected by ablation as studied in pigs.

[Ultrastructural study of the pulmonary veins in pigs].

OBJECTIVE: To explore the possible relationship between the ultrastructural characteristics of pulmonary veins and the pathogenesis of atrial fibrillation originating from pulmonary veins. METHODS: The pulmonary veins from domestic pigs were serially sectioned (2 mm) transversely along the vessels. The odd number sections were fixed in 10% phosphate buffered formalin solution and the even number sections were fixed in 3% Glutaral for further electron microscopy observations. RESULTS: Two cell types were found in the pulmonary veins of pigs. One cell type was the P-like cells that had an empty-appearing cytoplasm containing only sparse myofibrils and small mitochondria, both of which were randomly distributed. Another cell type was slender transitional cells with plenty of longitudinally displayed myofibrils. CONCLUSION: P-like cells in the pig pulmonary veins were found using electron microscopy in this study and ectopic beats from P-like cells in the myocardial sleeves in the pulmonary veins might be responsible for atrial fibrillation originating from pulmonary veins.

Dynamics of the pulmonary venous flow in the fetus and its association with vascular diameter.

BACKGROUND: The usual positioning of the Doppler sample volume to assess fetal pulmonary vein flow is in the distal portion of the vein, where the vessel diameter is maximal. This study was performed to test the association of the pulmonary vein pulsatility index (PVPI) with the vessel diameter. METHODS AND RESULTS: Twenty-three normal fetuses (mean gestational age, 28.6+/-5.3 weeks) were studied by Doppler echocardiography. Pulmonary right upper vein flow was assessed adjacent to the venoatrial junction ("distal" position) and in the middle of the vein ("proximal" position). The vessel diameter was measured by 2D echocardiography with power Doppler, and the PVPI was obtained by the ratio (maximal velocity [systolic or diastolic peak]-minimal velocity [presystolic peak])/mean velocity. The statistical analysis used t test and exponential correlation studies. Mean distal diameter was 0.33+/-0.10 cm (0.11 to 0.57 cm), and mean proximal diameter was 0.16+/-0.08 cm (0.11 to 0.25 cm) (P<0.0001). Mean distal PVPI was 0.84+/-0.21 (0.59 to 1.38), and mean proximal PVPI was 2.09+/-0.59 (1.23 to 3.11) (P<0.0001). Exponential inverse correlation between pulmonary vein diameter and pulsatility index was highly significant (P<0.0001), with a determination coefficient of 0.439. CONCLUSIONS: In the normal fetus, the pulmonary venous flow pulsatility decreases from the lung to the heart, and this parameter is inversely correlated to the diameter of the pulmonary vein, which increases from its proximal to its distal portion. This study emphasizes the importance of the correct positioning of the Doppler sample volume, adjacent to the venoatrial junction, to assess pulmonary venous flow dynamics.

[A new view of anatomic substrate, electrophysiological mechanisms of atrial fibrillation, and results of interventional treatment].

Literature data on anatomic and electrophysiological properties of pulmonary veins (PVs) are very scarce. The study included an investigation of 20 human autopsy hearts with and without cardiovascular pathology. In addition, biopsy samples from the right superior PV were taken from 5 patients with atrial fibrillation (AF) for ultrastructural study. The investigation found myocardial sleeves (MS) in 86.3% of cases, an additional PV between right PVs--in 15%, a collector type of superior and inferior PV--in 25% of cases. MS were situated on the adventitial side of PVs; along the whole length of the PVs the MS myocyte fascicles ran in different directions. Local changes, such as productive myocarditis, fibrosis and fibro-lipomatosis, were observed in MS of PV of patients with AF. 106 patients (80 of whom were male; middle age 42.9 +/- 12.5 years) with symptomatic AF underwent clinical examination. Electrophysiological features of the PVs were evaluated in 30 patients. Effective and functional refractory periods of PVs were found to be shorter than those of the left atrium and non-arrhythmogenic PVs. Radiofrequency ablation (RA) with application of electrophysiological criteria proved to be effective in all patients with frequent ectopy from PVs. The use of electroanatomical mapping allowed successful RA in 82% of patients with persistent and chronic AF. The study demonstrates that the changes in MS of PV, discovered by means of light and electron microscopy, as well as their complex three-dimensional morphological structure may cause and maintain AF. Very distinct electrophysiological features, found in AF patients, probably play a major role in arrhythmogenicity.

Tissue structure and connexin expression of canine pulmonary veins.

OBJECTIVE: Rapid electrical activity in pulmonary veins (PVs) has been proposed as a mechanism for focal atrial fibrillation. The way in which the myocardial sleeve inside PVs can form a substrate for focal activity is not well understood. Therefore, we have studied tissue structure and connexin distribution at the veno-atrial transition in the dog. METHODS: In adult mongrel dogs, the anatomy of the PV area was studied. Tissue structure in individual veins was assessed in formalin fixed sections using Masson's Trichrome staining. Gap junction protein distribution was examined using antibodies against connexin40 (Cx40) and connexin43 (Cx43). The ultrastructure of myocytes in myocardial sleeves was studied using electron microscopy. RESULTS: Individual PVs in the dog had a gross morphology similar to that observed in the human, with myocardial sleeves extending into the veins for 4-20 mm. In all veins examined, myocytes in myocardial sleeves had a normal atrial morphology and anti-desmin staining pattern. Cx43 was expressed throughout the sleeve at levels comparable to normal atrial myocardium. By contrast, Cx40 expression was lower in myocardial sleeves than in the rest of the left atrium. Myocytes in the sleeve, which were ultrastructurally similar to normal atrial myocytes, were predominantly organized in a circumferential pattern. CONCLUSIONS: PVs in the dog and various canine models of heart disease will be a suitable model for (patho)physiology of the veno-atrial transition. Myocytes in myocardial sleeves are similar to normal atrial myocytes. The circumferential orientation of these myocytes may provide a substrate for rapid circular reentry.

Pulmonary veno-occlusive disease secondary to granulomatous venulitis.

Pulmonary veno-occlusive disease is a rare disorder characterized by an obliterative fibrosing venulitis. The etiology and pathogenesis of this disease is not well understood. This case is one secondary to granulomatous venulitis. Ultrastructural study demonstrated reduplication of capillary basal laminae, endothelial swelling, and granuloma formation, but shed no light on the etiology of the disease. The formation of noncaseating granulomas involving only intralobular veins is most unusual and has not been previously described in pulmonary veno-occlusive disease.

Differential expression of connexin43 gap junctions in cardiomyocytes isolated from canine thoracic veins.

We investigated the phenotypic features of cardiomyocytes, including the gap junctions, in the myocardial sleeve of thoracic veins. Single cardiomyocytes, isolated from the canine pulmonary veins (PV) and superior vena cava (SVC) using digestive enzymes, were examined by immunoconfocal microscopy using antisera against connexin43 (Cx43), Cx40, and other cell markers. The results showed that isolated cardiomyocytes displayed rod shapes of various sizes, ranging from <50 microm to >200 microm in length, and all the cells expressed alpha-actinin and vinculin. Gap junctions made of various amounts of Cx43 and Cx40 were found at the cell borders. These two connexins were extensively co-localized. Comparison between the thoracic veins showed that cells of the SVC contained more Cx43 gap junctions (total Cx43 gap junctions area per cell surface area, 4.0 +/- 0.2% vs 1.5 +/- 0.2%; p<0.01). In addition, for single-nucleus cells, those from the PV were longer (103.7 +/- 3.6 vs 85.0 +/- 3.1 microm; p<0.01) but narrower (14.4 +/- 0.5 vs 16.9 +/- 0.9 microm; p<0.01). In conclusion, canine thoracic veins contain cardiomyocytes with differences in shape and gap junctions, suggesting that the electrical conduction properties may be different between the thoracic veins.

Ultrastructure of lung in pulmonary veno-occlusive disease.

A 17-year-old boy died of severe pulmonary hypertension due to pulmonary veno-occlusive disease. The condition was diagnosed in a lung biopsy specimen and confirmed at necropsy. The lung specimen was studied by electron microscopy and immunofluorescence microscopy. The occluded pulmonary veins were lined by intact endothelial cells, beneath which was a haphazard proliferation of collagen fibrils and smooth muscle cells. The alveolar capillaries showed thickening of the endothelial cell basement membrane with an increase in the number of cytoplasmic processes of pericytes. Electron-dense deposits were located within the thickened basement membrane. These deposits were considered to represent disintegrating extravasated erythrocytes rather than immune complexes because immunofluorescence microscopy showed no immunoglobulin or complement deposition within the lung.

Endothelin-1 focally constricts pulmonary veins in rats.

Serum endothelin levels increase during sepsis, ischemia, reperfusion, pulmonary operations, and systemic hypertension after surgery. Despite extensive study, the site and extent of action of endothelin on the pulmonary microcirculation are not well established. To assess the effect of endothelin on the pulmonary vasculature, especially the veins, the circulation of the lung was cast with methyl methacrylate 10 minutes after endothelin-1 was given intravenously to rats. Endothelin-1, at concentrations of 0.1, 1.0, and 10.0 micrograms/kg of body weight, increased the mean systemic arterial blood pressure 8%, 7%, and 17% (p < 0.01) and mean pulmonary arterial blood pressure 15%, 28%, and 53%, respectively (p < 0.01). The proportional increases in the pulmonary pressures were greater than those of the systemic pressures (p < 0.01). Scanning electron microscopy of cast blood vessels showed more contraction of the veins than the arteries. For doses of 0, 0.1, 1.0, and 10.0 micrograms/kg, the respective focal contraction of small veins was 6.7% (+/- 4.4), 15.4% (+/- 9.1), 23.3% (+/- 10.1), and 14.4% (+/- 9.0) of the vessel diameter (p < 0.01). In addition, the diameter of capillaries increased (p < 0.01) and the capillary interspaces decreased (p < 0.01) after endothelin administration, but not in a linear dose-dependent manner. The dose of endothelin correlated with the change in the mean systemic (r = 0.82, p < 0.01) and the mean pulmonary (r = 0.80, p < 0.01) blood pressures. The mean pulmonary pressure change correlated with the focal venous contraction on the casts (r = 0.35, p < 0.01), capillary diameter (r = 0.64, p < 0.01), and capillary interspace distance (r = -0.34, p < 0.01). The venous contraction was related to the capillary diameter (r = 0.26, p < 0.01). The most notable effect of endothelin-1 in rat pulmonary microcirculation is focal constriction of small veins. Because this effect may lead to pulmonary edema, endothelin antagonists may be of benefit in a variety of clinical situations.

Structure of intercellular junctions in different segments of the intrapulmonary vasculature.

Freeze-fracture studies have shown that there is a segmental differentiation of the structure of intercellular junctions of intraacinar pulmonary vessels. Tight junctions vary in complexity, being composed in the arterial segment of the most highly interconnected and most numerous (two to seven) rows of tight junction particles, which are present in E face grooves. In capillaries, they consist of one to three rows of particles, which, in the venular segment, show some discontinuities. Tight junctions in intraacinar veins consist of one to five rows of particles in the E face. Large gap junctions are numerous and are intimately associated with arterial tight junctions. They are absent from capillaries, and are fewer in number and smaller in size in veins than in arteries. The above observations suggest that, as in the systemic circulation, the venular segment is likely to be the most permeable to small, water-soluble solutes. The presence of numerous gap junctions, particularly in the arteries, suggests that in this segment there is a high degree of electrotonic and/or metabolic coupling between endothelial cells.

Effects of lipopolysaccharide on human endothelial cells in culture.

Lipopolysaccharide (LPS) in concentrations up to 10 micrograms/ml did not induce detectable direct cytotoxicity in human umbilical vein, pulmonary artery, or pulmonary vein endothelial cells. By contrast, significant cytotoxicity was observed in bovine aortic endothelial cells exposed to LPS 0.01 micrograms/ml. Transmission electron microscopy of human umbilical vein cells exposed to LPS 10 micrograms/ml for 4 days revealed no significant ultrastructural abnormalities compared to control cells. Whereas human umbilical vein endothelial cell cytotoxicity was observed when neutrophils were stimulated with phorbol myristate acetate, LPS-stimulated neutrophils did not induce significant cytotoxicity even in the presence of fresh human serum as a complement source. Moreover, human umbilical vein endothelial cell factor VIII-antigen and fibronectin release, angiotensin-converting enzyme activity, and PGI2 release were unaffected by a 24-hour exposure to LPS. Cytotoxicity, however, was produced when human umbilical vein endothelial cells were coincubated with LPS and cycloheximide. The proliferation of human umbilical vein endothelial cells was also inhibited after prolonged, continuous exposure to LPS 10 micrograms/ml. We conclude that LPS with or without complement or neutrophils does not induce significant human endothelial cell lysis or detachment. Moreover, brief exposure to LPS has minimal, direct effect on several functions of human endothelial cells in vitro.

The cardiac muscle in the pulmonary vein of the rat: a morphological and electrophysiological study.

The pulmonary veins of albino Wistar rats were studied by means of light and electron microscopy. The media of larger veins consists of cardiac muscle fibers which extend until the vessels attain about 100 mu in diameter. This coat consists of external longitudinal fibers and internal circular fibers. The vasa vasorum are well developed and the capillaries show pseudofenestrations. The numerous adrenergic and cholinergic nerve endings do not form typical motor end-plates as seen in skeletal muscles. The ultrastructure of these media muscle fibers is similar to that of the rat hearts. The smooth muscle layer of larger pulmonary veins is not continuous as it is in smaller veins where it forms cushions. Comparison of albino rats and other rodents reveal striking differences. Action potential shape and propagation velocity (0.5-1.2 m/s) along the myocardial coat of the pulmonary vein were similar to those observed in the left atrium and so was their sensitivity to locally applied acetylcholine. The physiological direction of propagation in rat pulmonary veins is toward the lung. This fingind lends support to the hypothesis of a rhythmic, valve-like action of the striated musculature of the pulmonary venous wall during the systole and a possible role in the capacitance of the pulmonary circulation.

Pulmonary lymphatic filling is increased in spontaneously hypertensive rats.

Extravascular lung liquid must rely on tissue-space pressure gradients to drive it into the lymphatics because the fluid is outside the lymphatic contractile pumping and valve control. Focal tissue pressure changes could result from muscular contraction in the blood vessel walls. Perivascular lymphatics usually lie within the adventitia of pulmonary blood vessels, and are generally more noticeable in veins than arteries. Spontaneously hypertensive rats have exaggerated focal pulmonary venous muscle (venous sphincters). These muscular tufts are often near initial lymphatics; if their contraction was important for lymph transport, spontaneously hypertensive rats could have more lymphatic filling in the areas of the pulmonary venous sphincters than normotensive rats. Because the focal muscularity is found in pulmonary veins more than arteries, veins may have more focal lymphatic filling than arteries. To test these hypotheses, lung histology and vascular and lymphatic casts of spontaneously hypertensive and normotensive rats were examined. Contracted venous sphincters were found on 108 of 127 veins with lymphatics in the spontaneously hypertensive rats and 5 of 41 in the normotensive rats P<0.01). The spontaneously hypertensive rats had deeper venous contractions and more lymphatic filling around both arteries and veins (P<0.01). In the hypertensive rats, the venous was greater than the arterial lymphatic filling (P<0.01). On the pleural surface, hypertensive rats also had greater lymphatic filling than controls (P<0.01). This anatomic evidence suggests that pulmonary venous sphincters are associated with focal lymphatic filling, and perivascular muscle action might be a component of the pulmonary lymphatic system.

Three-dimensional cytoarchitecture of rat pulmonary venous walls: a light and scanning electron microscopic study.

The three-dimensional architecture of the rat pulmonary veins was studied by light microscopy (LM) and scanning electron microscopy (SEM). For LM, the left lungs were fixed with formalin, sectioned and immunostained with an anti-alpha-smooth muscle actin (alpha-SMA) antibody in addition to conventional staining. For SEM, the specimens were fixed with glutaraldehyde and immersed in 30% KOH solution for 8 min followed by treatment of collagenase solution for more than 5 h. By LM, the smooth muscle cells stained with anti-alpha-SMA showed discontinuous, periodical thickenings of circular bundles in the wall of the venules, but they became thin and continuous in the larger vessels (or veins) that had a cardiac muscle layer on the outside. Under SEM, the smooth muscle cells formed circular-oriented bundles at constant intervals along the venules less than 100 microm in diameter. These bundles had circumferential constrictions in the lumen. The cardiac muscle cells, which appeared in large pulmonary veins of more than 100 microm, ran in a circular or oblique direction and completely surrounded the vessel wall outside of the thin continuous layer of smooth muscle cells. The muscle arrangements were considered to play a significant role in the return blood flow in rat pulmonary veins.

Immunohistochemical study of the innervation of pulmonary vessels and smooth muscles in the respiratory tract of two frog species.

The innervation of the respiratory tract of amphibians is still poorly understood. Therefore, the respiratory tracts of the frogs Rana esculenta and Discoglossus pictus have been investigated in order to describe non-adrenergic non-cholinergic (NANC) and adrenergic innervation, and the localization of neuromediators that are possibly involved. Immunohistochemical staining of many bioactive substances was found in neuroepithelial cells of the buccopharynx, larynx, lung septa, nerves and neurons throughout the airway system. The findings indicate the occurrence of vasoactive intestinal peptide (VIP)-immunopositive nerve fibers in fibromuscular septa and the vasculature, nitrergic innervation of the large pulmonary veins showing a plexus of nNOS-immunopositive nerve fibers that also innervate the lung wall and the localization of neuronal nitric oxide synthase (nNOS) in neurons in the lung wall. In addition, laryngeal blood vessels and small arteries in the wall of septa that form capillary networks are supplied by enkephalin-immunopositive nerve terminals. We conclude that the airway system of the two frog species studied is innervated by a parasympathetic NANC system. Adrenergic innervation was also found that was immunostained for tyrosine hydroxylase. Adrenergic fibers were mainly present in muscles in septal edges, arteries present in septa and the wall of the lung. It is suggested that nNOS-positive and leu-enkephalin-positive neurons mediate vasodilation via the release of NO, but the nature of the NANC innervation remains obscure. Despite the many pharmacological studies of the lungs of amphibians, the physiological role of pulmonary autonomic innervation remains poorly understood.

Pulmonary hypertension of the newborn and urogenital anomalies in two male siblings: a new family with misalignment of pulmonary vessels.

The association of pelvi-ureteric junction obstruction (PUJO) and rapidly fatal persistent pulmonary hypertension of the newborn (PPHN) has been observed in two male siblings. PUJO was also observed in a maternal uncle, whose daughter suffered from vesico-ureteral reflux (VUR). In both patients, histopathologic study of the lungs showed misalignment of pulmonary veins (MAPV), which is a rare autosomal recessive condition leading to severe PPHN and death within the neonatal period. It has occasionally been described associated with PUJO. The authors point out that: i: MAPV has to be carefully searched in case of PPHN; ii: PUJO could be an important finding associated with MAPV, and the only prenatal indication of this lethal condition.

Cardiac musculature of the cranial and caudal venae cavae and the pulmonary vein in the fowl.

The cardiac musculature of cranial and caudal venae cavae and pulmonary vein was examined to clarify its distribution pattern in the fowl using both light and electron microscopies. The musculature was distributed from the heart to the root of subclavian vein in the cranial vena cava, to the cranial margin of the liver in the caudal vena cava, and to the left and right distal pulmonary veins in the pulmonary vein, respectively. Judging from the morphology and distribution pattern in the venous wall, the cardiac musculature in the fowl is thought to share the same phylogenic origin with that in mammals. The ultrastructure of cardiac myocytes including transitional cells in the cranial vena cava and the pulmonary vein resembled that of atrial myocytes. While, the typical specialized myocytes such as Purkinje fiber were found in the caudal vena cava of the fowl.