[Cryosurgery in diffuse hepatic diseases]

Comparative studying, using histological and biomicroscopic methods, of the dosed cryohepatodestruction (CHD), periarterial cryodenervation of hepatic artery (CDHA) and their concomitant application influence on the dynamics of hepatic restoration processes in experimental cirrhosis was performed. The investigations were done on 215 male rats owing body mass 200-280 g in a not changed and pathologically changed liver. There was shown, that CDHA promotes changes in hepatic tissue microhemocirculation, as well as the enhancement of the sinusoidal vessels diameter and relative square of vascular bed. CHD stimulates the reparative processes course in a pathologically changed organ. There was established, that while simultaneous application of two cryosurgical methods, the velocity and grade of restoration processes in cirrhotically-changed liver are enhanced in comparison with such indices changes while separate usage of these two methods.

Three-dimensional organization of the hepatic artery terminal branches: a scanning electron microscopic study of vascular corrosion casts of rat liver

The hepatic artery plays an important role in the nourishment of liver parenchyma. The arterial distribution generates debate on where the artery terminates in the liver although is accepted that terminal branching of hepatic artery opened into sinusoids and form arterio-portal anastomosis. This implies that sinusoids are fed by both arterial and portal vessels characterized by different pressures. The presence of a double feeding to the sinusoids from the vena porta, at a pressure of 6-7 cm H2O, and from the hepatic artery, at a pressure of 12-25 cm H2O, has generated many studies for the need to explain the prevalence of flow from the vena porta. For this reason, we have studied the terminal hepatic artery branches in the rat by using special microvascular corrosion casting procedure which makes possible to better follow the hepatic artery terminal branches. Twelve young sexually mature male and female Wistar rats were used in this study. More than one hundred vascular corrosion casts of terminal hepatic arterioles were studied by Scanning Electron Microscopy. Histological samples were prepared using standard techniques for light microscopy. The experimental approach allow to easily follow the three-dimensional course of hepatic artery branches which is extremely difficult in standard injections. In all our observations of the rat liver vascular corrosion casts, terminal hepatic artery branches do not end directly in the sinusoidal beds. Terminal hepatic artery branches end into peribiliary plexus, periportal plexus and single capillaries of the portal space. We have not found any arterio-venous shunt nor any arterial vessel flowing into a venous vessel or a sinusoid. This means that only venous blood at a lowered pressure reaches the vena porta branches and the sinusoids.

Cholangiocytes and blood supply

The microvascular supply of the biliary tree, the peribiliary plexus (PBP), stems from the hepatic artery branches and flows into the hepatic sinusoids. A detailed three-dimensional study of the PBP has been performed by using the Scanning Electron Microscopy vascular corrosion casts (SEMvcc) technique. Considering that the PBP plays a fundamental role in supporting the secretory and absorptive functions of the biliary epithelium, their organization in either normalcy and pathology is explored. The normal liver shows the PBP arranged around extra- and intrahepatic biliary tree. In the small portal tract PBP was characterized by a single layer of capillaries which progressively continued with the extrahepatic PBP where it showed a more complex vascular network. After common duct ligation (BDL), progressive modifications of bile duct and PBP proliferation are observed. The PBP presents a three-dimensional network arranged around many bile ducts and appears as bundles of vessels, composed by capillaries of homogeneous diameter with a typical round mesh structure. The PBP network is easily distinguishable from the sinusoidal network which appears normal. Considering the enormous extension of the PBP during BDL, the possible role played by the Vascular Endothelial Growth Factor (VEGF) is evaluated. VEGF-A, VEGF-C and their related receptors appeared highly immunopositive in proliferating cholangiocytes of BDL rats. The administration of anti-VEGF-A or anti-VEGF-C antibodies to BDL rats as well as hepatic artery ligation induced a reduced bile duct mass. The administration of rVEGF-A to BDL hepatic artery ligated rats prevented the decrease of cholangiocyte proliferation and VEGF-A expression as compared to BDL control rats. These data suggest the role of arterial blood supply of the biliary tree in conditions of cholangiocyte proliferation, such as it occurs during chronic cholestasis. On the other hand, the role played by VEGF as a tool of cross-talk between cholangiocytes and PBP endothelial cells suggests that manipulation of VEGF release and function could represent a therapeutic strategy for human pathological conditions characterized by damage of hepatic artery or the biliary tree.

Development of liver size and perfusion after reduced-size liver transplantation in children

The technique of segmental liver transplantation (s-LTx) provides a method to overcome the shortage of suitable livers for small recipients. Patient survival rates are parallel to those obtained with whole liver transplantation (w-LTx). For long-term rehabilitation, adaptive liver growth and adequate perfusion is crucial; however, morphometric and hemodynamic parameters in growing children with s-LTx are not available. Seventeen children who received a s-LTx and 25 with a w-LTx who had follow-up evaluation 1 and 2 yr after LTx were studied. Mean age at time of transplantation was 4.3 +/- 3.5 yr for s-LTx and 10.3 +/- 6.0 yr for w-LTx, mean height 98 +/- 21 cm and 122 +/- 30 cm respectively. At follow-up evaluation mean values for liver enzymes, bilirubin and prothrombin time were in the normal ranges for both groups. Liver dimensions were measured by gray scale ultrasound, and hemodynamic parameters by Doppler sonography in the portal vein and hepatic artery using an Acuson 128 machine. Maximal (Vmax), minimal (Vmin) and time-average velocity (TAV) were measured and the resistive index (RI) calculated. We found that 1 and 2 yr after LTx liver dimensions were at a mean in the upper normal range of healthy controls. Spleen size was above the normal range and did not show any tendency towards regression. Mean Vmax in the hepatic artery in s-LTx and w-LTx was 48 cm/sec vs. 28 cm/sec after 1 yr and 30 cm/sec vs. 35 cm/sec after 2 yr, the RI 0.66 vs. 0.55 and 0.59 vs. 0.73, respectively (p for all parameters > 0.05). Maximal portal vein flow was 25 cm/sec in s-LTx vs. 29 cm/sec in w-LTx. Blood flow calculated by vessel diameter and TAV showed no statistical difference between both groups. In conclusion, liver size after s-LTx and w-LTx was increased to the upper normal range, and portal vein blood flow velocities were within the normal range. Vmax in the hepatic artery was reduced in s-LTx; however, the reduction was to the same extent as in w-LTx. In the view of long-term functional adaptation, s-LTx is not inferior to w-LTx.

Hepatic neovascularization after partial portal vein ligation: novel mechanism of chronic regulation of blood flow

The present study was undertaken to investigate hepatic microcirculatory response following partial portal vein ligation (PPVL) in rats. Portal pressure was markedly increased 2-6 wk after PPVL, but no significant reduction in sinusoidal perfusion and hepatocellular injury were detected. However, marked neovascularization was observed in PPVL rats using intravital microscopy and scanning electron microscopy (SEM). Extremely high red blood cell velocity (2,000-4,900 microm/s) was seen in these vessels. Injection of fluorescein sodium via the carotid artery revealed that the neovessels originated from the hepatic arterial vasculature. This was further confirmed by clamping the common hepatic artery and phenylephrine injection from the carotid artery. These vessels maintained sufficient flow after massive sinusoidal shutdown elicited by the portal infusion of endothelin receptor B agonist IRL-1620. SEM also showed extensive neovascularization at the hilum. Additionally, clamping the portal vein decreased sinusoidal perfusion only by 9.5% in PPVL, whereas a 71.2% decrease was observed in sham. These results strongly suggest that the liver maintains its microcirculatory flow by vascular remodeling from the hepatic arterial vasculature following PPVL.

Vascular pattern of a metastatic liver tumor in a dog:--a scanning electron microscopic study of resin casts

Metastasis of a malignant mixed tumor occurring in the abdominal wall was found in the liver of a 15-year-old dog male. The vascular system of the metastatic lesion was examined by scanning electron microscopy using the resin cast technique. The existence of arterio-portal shunts was confirmed. The shunts arose from branches of the hepatic artery in retrograde or vertical direction and merged into the capillary plexus replacing the branches of the portal vein, forming the so-called thread and streaks vessel in the field of hepatic angiography. Vessels with the thread and streaks appearance histologically represented tumor emboli growing in the lumen of a large branch of the portal vein. There were capillaries running inside along the portal vein and forming a longitudinal dense network in the vein. Branches of the hepatic artery feeding the metastatic lesion were well developed and formed a coarse arterial network in their course. Tributaries of the hepatic vein from the lesion were also well developed.

Segmental mediolytic arteritis involving hepatic arteries

Segmental mediolytic arteritis is a rare, noninflammatory arteriopathy that involves the splanchnic arteries of adults with shock and the coronary arteries of neonates with hypoxemia. We report the first case (to our knowledge) of segmental mediolytic arteritis involving the hepatic arteries. The lesion begins with cytoplasmic vacuolar degeneration of the arterial smooth-muscle cells, which then progresses to coalescence of vacuoles, leading to disruption of the media, intramural hemorrhage, and periadventitial fibrin deposition. Segmental mediolysis results in arterial wall defects, which can lead to dissecting aneurysms or hemorrhage due to arterial rupture. The intima and internal elastica are spared from the lytic process, and there is minimal periadventitial inflammation. Segmental mediolytic arteritis is not a true arteritis; therefore, segmental mediolytic arteriopathy may be a preferable term. Morphological similarities exist between segmental mediolytic arteritis and arterial fibromuscular dysplasia. In our case, hepatic ischemia correlated with mediolysis involving the hepatic arterial branches. Segmental mediolytic arteritis is thought to be due to an inappropriate vasospastic response, developing in the setting of hypoperfusion and hypoxemia.

Observation of microvascular casts of human hepatocellular carcinoma by scanning electron microscopy

The microcirculation of hepatocellular carcinomas (HCCs) and surrounding tissue was observed three-dimensionally by scanning electron microscopy of vascular casts made from 10 livers at autopsy. The livers were perfusion-washed and cast with resin through both the hepatic artery and portal vein branches. The HCCs observed ranged from several millimeters to 3 cm in size. A vascular plexus proliferated around the HCC nodules in all cases. Both portal vein and hepatic artery branches proliferated markedly to form the plexus in 5 patients. These vessels communicated directly with the blood sinuses of the HCCs as feeder vessels. HCC cells replaced normal cells while maintaining the liver's trabecular structure in 2 cases. At the borders of these HCCs, there was direct communication between the hepatic sinusoids and the tumor blood sinuses. Efferent vessels of the tumors were generally difficult to identify but vessels resembling hepatic vein branches were detected in one 4-mm HCC nodule after microdissection. Thus, HCC was demonstrated to be supplied not only by the hepatic artery but also by the portal vein and hepatic sinusoids. This may be one of the reasons why cancer cells survive in the tumor margins and daughter nodules after transcatheter arterial embolization of HCC.

Scanning electron microscopy of intrahepatic microvasculature casts following experimental hepatic artery embolization

The initial site of occlusion of the intrahepatic microvasculature in rats following hepatic artery embolization was studied by scanning electron microscopy of microvasculature casts. The rats were divided into four groups: embolization with gelatin powder (n = 3), polyvinyl alcohol (n = 3, 125-150 microns), gelatin sponge (n = 3, 212-250 microns), and ionized oil. Not only the hepatic arteries but also vessels in the peribiliary plexus were occluded. However, the size of the hepatic arteries and vessels of the peribiliary plexus occluded correlated with the size of the embolic material, except in the case of the gelatin powder which occluded vessels smaller than the particle size.

Scanning electron microscopic examinations of microvascular casts of the rat liver and bile duct

Microvascular features of normal rat livers and bile duct system were examined with the vascular casts using methacrylated resin. Portal vein branches not only showed regular tapered down bifurcations but also had many side branches, some of which were directly connected with sinusoids. Terminations of hepatic arterial branches were divided into three types: 1) Many branches pouring into peribiliary capillary plexus (PBP), 2) branches directly pouring into periportal sinusoids and/or peripheral portal vein branches via arterio-portal anastomoses, and 3) anastomoses with periportal vascular plexus. PBP was composed of rich vascular networks. In large portal tracts, the plexus showed two layers, that is, the inner layer made up of a close network of capillary vessels and the outer layer consisting of a loose network of arteries and veins, while the PBP in the small portal tracts was composed of only a single layer of loose capillary network. Transitional features of these two patterns were found in the medium-sized portal tracts. PBP was supplied by afferent vessels from the interlobular hepatic artery as described above, and were directly connected with interlobular branches of the portal vein (internal root). The extrahepatic bile duct revealed a much richer vasculature than the intrahepatic bile duct. Both arterial and venous branches were ramified at almost right angle from a pair of arteries and veins running parallel with the bile duct. Occasional strictures, which might have been sphincter portions of the media, were noted at the branching sites of the artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Vascular plexus around intrahepatic bile ducts in normal livers and portal hypertension

Vessels around the intrahepatic large bile ducts (peribiliary vascular plexus) were examined by histologic, immunohistochemical and scanning electron microscopic observations. The vessels within duct walls were mainly capillaries, while those around the duct walls were composed of capillaries and venules. A majority of vessels was positive for factor VIII-related antigen and Ulex europaeus lectin I. Scanning electron microscopy of hepatic arterial and biliary casts revealed that bile ducts were surrounded by the vascular plexus derived from hepatic arterial branches, and serial section observations in addition disclosed the vessels connecting the peribiliary plexus with portal venous branches ('internal roots'). The peribiliary vascular plexus was increased considerably in livers with portal hypertension, especially idiopathic portal hypertension, extrahepatic portal venous obstruction and hepatocellular carcinoma with portal venous tumor thrombi. Internal roots were also frequently found in the livers with portal hypertension. These results suggest that altered intrahepatic hemodynamics in portal hypertensive conditions involves the peribiliary vascular plexus, resulting in an increase of the number and frequent occurrence of 'internal roots', these vessels probably operating as intrahepatic collaterals.

Neuroeffector transmission of the hepatic and pancreatico-duodenal isolated arteries of the dog

Direct evidence has been obtained that the neurogenic responses of the hepatic and pancreatico-duodenal arteries of the dog are mainly due to norepinephrine released from varicosities and that this effect is mediated via alpha 1-adrenoceptors. In addition, there is a prazosin-resistant response to nerve stimulation that is certainly not mediated via alpha 2-adrenoceptors. These vessels are 10-100 times less sensitive to applied norepinephrine than the great majority of peripheral arteries; however, the pA2 value for prazosin (7.5) is the same as in other systems. The varicose terminal plexus is located deep in the media, as shown by electron microscopic study. Findings indicate that these gastrointestinal arteries are mainly controlled by adrenergic innervation, that their density is as high as that of any other vessel, and that these arteries might be much less influenced by the circulating catecholamines than others. The neuroeffector transmission of hepatic and pancreatico-duodenal arteries is subject to presynaptic modulation. Muscarinic (oxotremorine) and P1 (adenosine) receptor agonists are effective inhibitors of transmission, whereas xylazine surprisingly has no effect.

[Hepatic artery of the rat in experimental cirrhosis of the liver]

In 30 male rats of Wistar strain (20 more rats served as controls) thickness of the internal elastic membrane, that of the media, cross section area of the media and that of the lumen were define 3, 4, 5 and 6 months after the experiment was started. The initial changes in the hepatic artery structure are noted on the 4th month, however, differences in the parameters are not yet statistically significant. On the 5th month certain signs of hypertrophy in the smooth muscle cells of the media are clearly seen, as well as an increasing thickness of the internal elastic membrane and that of the tunica media. Simultaneously, the index of labelling the myocyte nuclei reaches its maximum. The increasing thickness of the arterial wall causes certain decrease in the lumen cross section area. The changes of all the parameters are statistically significant. In 6 months after the beginning of the experiment, a pronounced hyperelastosis develops in the wall of the hepatic artery; a part of the smooth muscle cells in the tunica media undergoes atrophy. The area of the vascular lumen decreases by 16%, comparing to the age control. The experimental data confirm certain clinical observations and reveal some features in the mechanism of pathological changes occurring in the hepatic artery wall at cirrhosis.

Perinodular arteriolar plexus in liver cirrhosis. Scanning electron microscopy of microvascular casts

The blood supply to regenerative nodules in liver cirrhosis was studied by scanning electron microscopy of microvascular casts. Cirrhotic nodules are surrounded by many arterioles with rich anastomoses that form a perinodular arteriolar plexus: these arterioles connect with sinusoids in the nodules. The portal vein branches, on the contrary, are distorted and compressed by connective tissue. These findings illustrate how the regenerative nodules in liver cirrhosis are mainly nourished by hepatic arterial blood via a perinodular arteriolar plexus.

Changes in the rat liver induced by total portal vein ligation

An enlargement of the hepatic arterial tree with dilation of the main branches, rich ramification of smaller branches and marked tortuosity were seen in rats after total portal vein ligation (compensatory hypertrophy). The normal architecture and histochemistry of the liver showed no evident changes, but some definite alterations were seen in the sinusoids. There was a mild hyperplasia of the reticulum framework. Electron microscopy disclosed capillarization of sinusoids in animals with prolonged portal vein ligation and the presence of hyperfibers of collagen in Disse's space. It is concluded that these changes resulted from hepatic arterialization.

Scanning electron microscopy of normal rat liver: the surface structure of its cells and tissue components

Scanning electron microscopy (SEM) allows the surface ultrastructure of intrahepatic cells and other tissue components of liver to be delineated. Excellent depth of focus of the SEM makes it possible to visualize surfaces of intact cells in their native configurations. This report details the surface characteristics and inter-relationships of hepatocytes and hepatic plates, sinusoidal endothelial cells and sinusoids, presumed Kupffer cells, vessels, bile ducts, connective tissue, and the capsule of rat liver. Hepatocytes present three structurally distinctive faces--the intercellular face containing flat surfaces and bile canaliculus, the sinusoidal face, and the connective tissue face which abuts portal tracts and hepatic veins. Sinusoidal endothelium is penetrated by large (1 to 3 mum) and small (0.1 mum) fenestrae, the latter occurring in clusters of up to 50. The width of bile canaliculi and distribution of large fenestrae vary proximodistally along hepatic plate or sinusoid. The cells of portal bile ductules contain microvilli located in linear rows and sparse cilia. Endothelium of hepatic artery and of portal vein is sparsely fenestrated.