Occlusion of experimental artery aneurysms by intrasaccular injection of fibrin sealant.

Aneurysms were produced by grafting a vein pouch onto the cervical carotid artery of rabbits following the removal of an elliptical piece of the arterial wall. The diameter of the opening was 3-4 mm and the maximum height 8 mm. Through direct puncture of the aneurysm a clot of the fibrin sealant Tissucol was injected into the aneurysm. The sequential morphological changes were studied by light microscopy. One case was examined after 3 weeks by scanning electron microscopy. Complete resorption of the fibrin sealant was observed. The aneurysm cavity was filled with a dense connective tissue covered by a layer of newly formed endothelial cells.

Experimental aneurysms in the rabbit: occlusion by intrasaccular injection of fibrin sealant.

Experimental aneurysms of the carotid artery were produced using the microsurgical technique of grafting a venous sack onto the artery in the neck of rabbits after the removal of an elliptical piece of arterial wall. Twenty-five aneurysms were occluded with the fibrin sealant Tissucol. Microscopic examination showed complete resorption of the fibrin clot and the formation of dense granulation tissue within the aneurysm, which was covered with a layer of endothelial cells after 2 weeks. The results are only tentative and require further experimental studies.

Hyperplastic foci in the atrophic liver of rats after portacaval anastomosis.

Hyperplastic focal areas were investigated in livers of male rats 1 and 9 months after portacaval anastomosis (PCA) by light and electron microscopy. These alterations, predominantly found in periportal areas, were characterized by light microscopy as clusters of enlarged hepatocytes along narrowed sinusoids, contrasting in the remaining liver acinus with smaller hepatocytes along widened sinusoids. No differences were observed between 1 and 9 months PCA except for glycogen content, which was homogeneously distributed in the liver at 1 month but completely lacking in foci at 9 months. The most striking ultrastructural alterations were the sinusoids delimited in these hyperplastic areas by a thickened barrier consisting of thick endothelial cells encircled by numerous subendothelial processes of the perisinusoidal fat-storing cells. Deep and widened recesses of the sinusoidal lumen separated the two-cell-thick plates of the hyperplastic cells. Hepatocytes in foci, thought to represent regenerative areas, tend to increase their exchange surface. Their progressive loss in glycogen and their two-cell-thick plates architecture should be in favour of a potential malignancy. However, the spontaneous evolution of these foci which do not necessarily give rise to nodules, as well as the lack of other features of transformation, do not support this possibility.

Ultrastructural characteristics of hyperplastic alterations in the liver of congenital portacaval-shunt rats.

A congenital portacaval shunt was discovered in five rats. In these animals the hepatic artery was the only blood vessel perfusing the liver; the portal vein was absent. The livers were small and mainly hypoplastic, but light microscopy revealed the occurrence of focal hyperplastic alterations and occasional hyperplastic nodules. TEM and SEM showed these areas to be composed of clustered hepatocytes, separated by widened intercellular spaces. The cell membranes carried numerous pleomorphic microvilli, and the cytoplasma contained densely packed mitochondria, some of which were giant sized. Liver cells in the centrilobular region were hypoplastic. Comparison with findings of experimental portacaval anastomosis suggest that in congenital-shunt animals, the overall hypoplasia of the liver with the formation of hyperplastic areas is a consequence of the lack of portal blood.

Neoplastic surface changes in urothelium of rats after portacaval anastomosis. A combined light and scanning electron microscopic study.

The development of preneoplastic and neoplastic alterations in the urinary tract was investigated by light and scanning electron microscopy in rats after portacaval anastomosis. The changes consisted of slight hyperplasia to papillary hyperplasia after 24 weeks. Carcinomas were present in all animals after 52 weeks. Surface characteristics can be correlated with the sequence of changes in urothelial cells. Short uniform microvilli appear in moderate hyperplasia and a cobblestone formation of the cells is typical of papillary hyperplasia. In transitional cell carcinomas the cells varied in shape and size and they were densely covered with pleomorphic microvilli. Although the cause of tumour induction after portacaval anastomosis is not clearly understood, possible mechanisms are discussed.

Morphological aspects of mesotheliomas after intratracheal instillations of fibrous dusts in Syrian golden hamsters.

After intratracheal instillation of glass fibres and crocidolite in male Syrian golden hamsters, besides lung carcinomas a number of mesotheliomas of the epitheloid type occurred. These were examined with light microscopy (LM) and scanning electron microscopy (SEM); the characteristics of the tumours are described.

The scanning electron microscope as a diagnostic tool in liver pathology.

Diagnostic scanning electron microscopic (SEM) investigations can be performed in human liver biopsies after perfusion fixation. For needle and wedge biopsies transparenchymal perfusion techniques have been developed. The perfusion fluid is brought into the tissue through special cannulas and removed by suction. By means of this 'push and pull' method, a directional flow is achieved and the tissue specimens are cleaned of blood. Thus the inner surfaces of the parenchymal tissue are accessible and can be observed with SEM. Vascular changes in different liver diseases, such as sinusoidal stenosis or sinusoidal capillarization, are easily detectable. New aspects are obtained on the morphology, arrangement and the functional role of perisinusoidal cells during mesenchymal reaction. This gives new insights into the pathophysiology of the microcirculation. SEM is also of great significance in diagnosing liver tumours. It may aid in deciding the origin and differentiation of carcinomas or sarcomas. Moreover, for the first time the sinusoidal haemangioendothelioma , consisting of fenestrated sinusoidal cells, could be demonstrated with SEM. Cholestasis can be diagnosed with SEM. However, we were unable to obtain useful information with SEM for the differential diagnosis of intra- and extrahepatic cholestasis.

In vivo and electron microscopic observations of the hepatic microvasculature in the rat following portacaval anastomosis.

The livers of rats subjected to end-to-side portacaval anastomoses were studied 3 to 5 months postoperatively by in vivo and electron microscopy. Compared with sham-operated controls, the livers of portacaval anastomoses animals contained dilated, tortuous networks of sinusoids. The velocity of blood flow in these vessels tended to be slower and more variable than controls, but always progressed toward the hepatic venules. Blood entered the sinusoids from portal venules and from arteriosinus twigs which terminated in the initial segments of some of the sinusoids at the periphery of the lobule. Together, the arteriosinus twigs and the short, initial segments of these sinusoids formed functional arterioportal anastomoses. These, in combination with the lack of portal venous flow, resulted in retrograde blood flow in portal venules. Nevertheless, blood still flowed from these portal venules into the sinusoids unless the sinusoid was fed by an arteriosinus twig. In addition to these microcirculatory alterations, the number of Kupffer cells that phagocytized latex particles was less in the animals with portacaval anastomoses, as was the number of particles ingested by these cells. Scanning and transmission electron microscopy confirmed the paucity of Kupffer cells. Those seen appeared inactive since they were flattened, exhibited few microplicae and filopodia and contained few latex particles. The endothelial cells of the sinusoid lining were perforated by increased numbers of large fenestrate which may be a reflection of elevated intrasinusoid pressures generated by the expanded arterialization of the sinusoid bed. The observed dilated sinusoid network interspersed by narrowed plates of hepatocytes is also consistent with this hypothesis. Finally, scattered nodular foci were observed which contained enlarged hepatocytes, narrow sinusoids, active Kupffer cells, and more normal rates of blood flow. Such sites may represent attempts by the liver to regenerate its normal architecture.

A scanning electron microscopic study of the liver of the monkey Macaca speciosa. I. Vascular system of the hepatic lobule.

The vasculature of the hepatic lobule of the monkey was investigated by scanning and transmission electron microscopy. The vessel walls of the portal and terminal hepatic (central) veins consist of a closed endothelium, a continuous basement membrane and a connective tissue layer. Sinusoids, however, show endothelia with typical fenestrations, and connective tissue fibres are only sparsely distributed in the space of Disse. Kupffer cells are present in the sinusoids, and occasionally in the terminal hepatic and sublobular veins, but are never present in the portal veins. They are characterized by a ruffled surface and special processes--filopodia and lamellipodia--which anchor them to the endothelial cells and also connect them with adjacent Kupffer cells. Flat branches of perisinusoidal cells, which encircle the endothelia, occur in the space of Disse, and are presumed to have a pericyte-like function.

A scanning electron microscopic study of the liver of the monkey Macaca speciosa. II. Intra- and extrahepatic biliary system.

The bile canalicular network of the monkey was studied by fracturing fixed liver tissue and examination by scanning electron microscopy. Bile canaliculi do not differ remarkably from those described in other species. Their course and luminal diameter vary, depending on their position in the liver lobule. In one specimen the continuity of a canaliculus with a terminal bile ductule (canal of Hering) is presented. Several constrictions occur in this part of the ductular lumen. The interlobular bile duct wall shows two kinds of niches. A single cilium arises from a primary niche. The walls of secondary niches contain numerous primary niches. Simple columnar epithelium lines the common bile duct, the main pancreatic duct and the Several constrictions occur in this part of the ductular lumen. The interlobular bile duct wall shows two kinds of niches. A single cilium arises from a primary niche. The walls of secondary niches contain numerous primary niches. Simple columnar epithelium lines the common bile duct, the main pancreatic duct and the Several constrictions occur in this part of the ductular lumen. The interlobular bile duct wall shows two kinds of niches. A single cilium arises from a primary niche. The walls of secondary niches contain numerous primary niches. Simple columnar epithelium lines the common bile duct, the main pancreatic duct and the gallbladder. A common feature is the presence of microplicae on their lateral cell surfaces.

Laser coagulation in the upper GI tract: a preliminary light and scanning electron microscopic study.

Experimentally intact as well as artificially damaged mucosa of porcine stomach was endoscopically coagulated with Nd:YAG laser beams. Energy, intensity pattern, and time of application of the irradiation was varied and supracellular changes of the coagulated mucosa were subsequently investigated with the scanning electron microscope. The mucosa, damaged by laser beams, showed three typical zones: 1. a superficial, central carbonisation zone protected with a thin layer of coagulated mucus; 2. an elevated hyperemic ring with complete loss of superficial epithelium, but intact basement membrane and a blood clotting of the mucosal capillaries; 3. normal mucosa. After coagulating artificially induced bleeding of the mucosa the irradiated centre showed a deep depression with a carbonized surface. Two weeks later regeneration had occurred and there was complete reepithelialisation of the mucosa to about two-thirds of normal thickness.

An improved method for transparenchymal fixation of human liver biopsies for scanning electron microscopy.

A method for fixing surgical liver biopsies is described. Hepatic tissue is perfused with a needle which is introduced directly into the parenchyma. Fixation is carried out at constant pressure using a perfusion apparatus. The sinusoids of the liver samples, which weigh up to 5g, are flushed completely clean so that the sinusoidal lining cells may be examined by SEM. This technique is particularly suitable for studying the cellular changes which take place in microcirculation disturbances of the human liver.