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Hepatitis B Virus (HBV) e antigen (HBeAg), HBV DNA and precore mutations affecting HBeAg expression during active replication were studied in 72 Tunisian hepatitis B surface antigen (HBsAg) positive individuals: 30 asymptomatic carriers of the virus, 37 with chronic hepatitis and 5 with acute hepatitis. HBV DNA was detected in 44 patients, but only 20% of them expressed HBeAg. Precore mutant strains, with mutations at position 1896 or at positions 1896 and 1899, were detected by PCR-hybridization in 86 and 36% of patients, respectively. Wild-type strains were detected in 54% of patients. Precore mutants were found in chronically and in acutely infected individuals, in patients with severe and asymptomatic infections, in HBeAg positive as well as HBeAg negative individuals. These results show the high frequency of HBV precore mutants in Tunisia.

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Pathological and biochemical investigations were performed on femoral veins used as fresh autografts and allograft substitutes in the carotid arteries of dogs from the same litter and separated in two groups described as compatible and incompatible after a mixed leukocyte culture (MLC). After 5 months of implantation, all the arterial substitutes were patent. The analyses gave the following results: 1. The haematologic parameters were not affected by the grafts. 2. Light microscopy (LM) and scanning electron microscopy (SEM) indicate a thrombotic accumulation and the presence of inflammatory cells in the compatible and the incompatible allografts. The occurrence of pathological changes was more pronounced in the incompatible group. 3. Immunostaining of anti-factor VIII-related antigen reveals a better preservation of the endothelial cell wall on the autograft. 4. The 6-keto-PGF1 alpha/TXB2 ratios of the autografts and the compatible allografts were similar.

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One of the techniques used to avoid preclotting a porous textile arterial prosthesis is to coat the graft with a layer of a bioerodible polymer. The efficacy of this treatment is dependent in part on the rate at which the polymer degrades after implantation. The focus of this study was therefore to investigate the rate of in vivo degradation of albumin-coated polyester (Dacron)-knitted vascular prostheses. Two types of cross-linked albumin were included: one using glutaraldehyde, the other using carbodiimide as the cross-linking agent. Radioactively labeled albumin-coated prostheses were implanted in the thoracic aorta and peritoneal cavity of dogs, and their rates of biodegradation in vivo were monitored over a 4-week period. The rate of biodegradation was found to depend upon the site of implantation. It occurred more rapidly in the peritoneal cavity where less than 20% of the albumin coating remained after 4 weeks in vivo in comparison to the approximately 30% in the thoracic aorta. The nature and intensity of the cellular response appeared to be related to the cytotoxic potential of the cross-linking agent. Glutaraldehyde induced an inflammatory response and a delay in healing, whereas carbodiimide caused only a mild tissue reaction.

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Preclotting is mandatory prior to implanting a knitted polyester arterial graft, unless the structure is made impermeable to blood by coating with a bioerodible material. Before achieving wide-spread clinical acceptance, the technique of impregnating with cross-linked albumin must be optimized in order to develop a graft that is immediately implantable, easy to handle and suture and has improved healing characteristics. The choice of the chemical to cross-link the albumin is of paramount importance. In this study two alternative candidates have been evaluated by using a series of tests to measure the physical properties, the morphology and the cytocompatibility of albumin-coated grafts. A carbodiimide cross-linking agent appears more promising than glutaraldehyde, since it is equally effective in producing a blood impermeable prosthesis, yet presents improved biocompatibility and provokes a less intense inflammatory response from the host.

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Previous in vitro studies have predicted that the type of chemical used to cross-link albumin-coated polyester arterial prostheses may influence the rate of bioerosion of the albumin layer in vivo. This study has confirmed that the healing process of this type of compound prosthesis does indeed depend on the nature and concentration of the cross-linking agent used. Four series of implantations in the thoracic aorta of dogs for scheduled periods for 4 h up to 6 months were conducted using 1.6% glutaraldehyde, 2.5% glutaraldehyde and 0.2 M carbodiimide as the alternative cross-linking agents plus a nonalbuminated preclotted polyester prosthesis which served as the control. The pathology of the explanted grafts revealed that in the short and medium term the rate of healing and the extent of tissue ingrowth was dependent initially on the presence of and later on the rate of bioerosion of the albumin layer. After 3 months in situ, the prostheses coated with albumin cross-linked with 1.6% glutaraldehyde and carbodiimide had healed more rapidly and were invaded by more extensive tissue ingrowth than the one cross-linked with 2.5% glutaraldehyde or the preclotted control. Moreover, the migration of cells over the carbodiimide-treated surface was the most fully developed and most regularly organized of all four series. Immunostaining revealed that the presence of glutaraldehyde induced an inflammatory response which failed to support the growth of normal luminal cells with the endothelial phenotype.

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A novel, microporous, hydrophilic polyether urethane-urea (PEUU) vascular graft was compared with expanded PTFE in the canine carotid artery. At implantation times ranging from 4 h to 6 months, all the PEUU grafts were found to be occluded while of the PTFE grafts, only those implanted for 1 week and 6 months were blocked. Histopathological analysis of the explanted grafts and their capsules revealed an ongoing inflammatory reaction at the anastomotic sites of the PEUU grafts.

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This paper adds a new dimension to the series of studies concerned with the development of an albumin-coated polyester vascular prosthesis by addressing the question of the origin of the albumin. Previous experiments in dogs have used canine albumin-coated polyester arterial grafts. This study evaluated the biocompatibility of xenogenic material by implanting in dogs prostheses coated with bovine albumin and cross-linked with glutaraldehyde. Two series of albuminated grafts, one gamma radiation sterilized, the other ethylene oxide sterilized, as well as a preclotted control series were undertaken. The origin of the albumin did not appear to be significant. In fact, the healing pattern of the xenogenic albumin coated grafts was identical to that found previously with isogenic albumin. Nor did the method of sterilization produce significantly different pathological results. However, a slower rate of healing with the coated grafts compared to the preclotted controls did appear to be related to the slow rate of albumin erosion and the potentially cytotoxic effect of the glutaraldehyde cross-linking agent.

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