Biomedical subjects

J Rozga

Publications and source records attributed to J Rozga.

At least 73 records · Page 4Linked to original sources

PubMed1990

Influence of phosphatidylcholine on intra-abdominal adhesion formation and peritoneal macrophages.

Phosphatidylcholine (PC) is the predominant constituent of the surface-active material coating peritoneal mesothelium. Its effects on surgically induced adhesion formation and on peritoneal macrophage viability and superoxide production were studied in rats. Rats treated with intraperitoneal PC liposomes showed more adhesions than controls (p less than 0.01). In vitro incubation with PC had no effect on macrophage viability, but significantly diminished superoxide production (p less than 0.05 and less). It is concluded that PC in its insoluble form is of no value in the prophylaxis of adhesions after abdominal and pelvic surgery and that with the use of the intraperitoneal route it is probably contraindicated in patients undergoing continuous ambulatory peritoneal dialysis.

Animals↗

PubMed1986

Hepatotrophic effect of portal blood during hepatic arterial recirculation.

Portal branch ligation (PBL) is known to induce a rapid and progressive atrophy in the liver parenchyma without portal blood flow and compensatory hyperplasia in the segments receiving the whole portal flow. In this study, the hepatotrophic effect of portal blood was studied in rats with PBL and after this procedure was combined with different portosystemic shunts. After 2 weeks, the most severe atrophy was found in ligated lobes of rats with PBL alone. In shunted animals, the atrophy was significantly inhibited and in relation to the magnitude of portal flow bypassed the liver. This suggests that in shunted rats, the portal-bone hepatotrophic factors undergo systemic recirculation and affect the liver by way of the hepatic artery. Simultaneously, in PBL + shunt rats, the rate of atrophy normally induced by a shunt was also dependent on the amount of portal blood available to this part of the liver. By a balance between these 2 processes, the total liver mass was maintained at the level found in sham PBL + shunt control rats.

Animals↗

PubMed1986

Portal branch ligation in the rat. Reevaluation of a model.

The effects of portal occlusion on the liver have been differently reported in different studies. The authors therefore reevaluated a model of portal branch ligation (PBL) in the rat. Histologic appearance, DNA synthetic activity, labeling count, and mitotic index were serially evaluated in both ligated and nonligated parts of the liver after interruption of the portal flow to one fourth, one third, and two thirds of the liver mass. The authors confirmed the presence of compensatory hyperplasia induced in the nonligated liver lobe(s) by PBL, and its intensity was roughly proportional to the amount of liver tissue devoid of portal perfusion. Portal-deprived liver tissue underwent a rapid and progressive atrophy, and, by the end of the first week, the weight of this part had decreased 10-fold. By a balance between atrophy and compensatory growth, the total liver weight was maintained at the level of sham-operated animals throughout the experiment. PBL invariably resulted in early centrilobular necrosis, which occupied 15-24% of the ligated lobe(s). However, already after 4 days it was almost totally resorbed and did not appear de novo. PBL was not followed by local collateralization.

Animals↗

PubMed1985

Stimulation of DNA synthesis in the rat liver during compensatory renal growth.

The stimulatory effect of a growing kidney upon the liver was studied in rats with renoportal anastomosis (RPA) and contralateral nephrectomy. DNA synthesis, mitotic activity, and index of growth in the renoprival kidneys were independent of the shunt. Hepatic uptake of [Me-3H]thymidine was increased in both RPA-nephrectomized and sham-RPA-nephrectomized rats; however, in the latter group of animals the response was significantly greater. Results of the study suggest that stimulatory substance of renal origin is carried in the venous blood of a growing kidney. A nonspecific interaction between the renotropic and portal-borne hepatotrophic factors seemed to be responsible for stimulation of hepatic DNA synthesis. The study supports the view that mechanisms humoral in nature but not common promote reparative growth in different organs such as the liver and kidney.

Animals↗

PubMed1985

Tumor growth in liver atrophy and growth. An experimental study in rats.

Despite vast knowledge on liver regeneration, little is known about the effect of active liver atrophy and regeneration on tumor growth. Ligation of a branch of the portal vein to the one or two anterior lobes was performed in inbred Wistar rats. This induces acute atrophy of the anterior and regeneration of the other lobes. During the same operation a tumor cell suspension (NGW1--adenocarcinoma) was inoculated in liver lobes undergoing atrophy and regeneration. Tumor volume and weight were measured and the histologic appearance was assessed. During the early and active phases the tumor growth was significantly accelerated in regenerating lobes and partially inhibited in rapidly atrophied segments. After the regeneration and atrophy was completed the normal pattern of growth was re-established in both parts of the liver. The results suggest that tumor growth is affected in proportion to regenerative response. They further suggest that portal branch ligation is of limited value in surgical palliation of liver tumors. The risk for further induction of growth of clinically undetected tumor foci in the remaining liver tissue appears to be small, although a significant, but short-lasting, stimulatory response was found.

Animals↗

PubMed1985

Acute portal vein stenosis. An experimental study on portal circulation and hepatosplenic function.

Portal hypertension was mechanically induced in rats by acute constriction of the portal vein. Using a new "button" technique, a stricture 0.9 mm in diameter was found to be compatible with life in more than 90% of the rats. Angiographic and anatomic studies of portosystemic collaterals confirmed observations in earlier experiments. Oesophageal varices were not seen, despite sustained elevation of portal venous pressure during the four weeks following induction of portal hypertension. Development of paraportal veins bridging the obstacle is suggested to be responsible for maintenance of normal liver structure and for recovery from the transient hepatic dysfunction. Increase of phagocytosis in the germinal centres of the enlarged spleens was found after four weeks, suggesting immunologic changes caused by portal hypertension and/or portosystemic shunt circulation.

Animals↗

PubMed1985

Hepatotrophic factors in liver growth and atrophy.

The hepatotrophic effect of portal blood was studied in rats with portal branch ligation (PBL) simultaneously subjected to mesocaval shunt or total hepatic arterialization. A direct supply of the nonligated liver lobes with pancreatic effluent did not improve DNA synthesis or mitotic response compared to arterialized rats, in which the portal-borne hepatotrophic factors reached the same lobes after systemic recirculation. A comparison with shunted but Sham-PBL rats showed that restorative capacity of the liver was not seriously impaired. In rats with PBL alone the lobes with portal occlusion showed extensive necrosis. In contrast, in PBL + shunt rats necrosis was significantly inhibited, indicating a hepatoprotective role of portal blood during hepatic arterial recirculation. Thus, the study suggests that quality of hepatic blood supply is of vital importance in maintenance of hepatocellular integrity. Hemodynamical factors seem to be of importance, but more in a sense of increased or decreased accessibility of humoral hepatotrophic factors in the blood.

Animals↗

PubMed1984

Portal stump pressure monitorization in the conscious rat after porta-caval shunt and total liver arterialization with the left gastric artery.

A method for portal stump pressure monitorization following arterialization is presented. Both intra and postoperative pressure determinations were performed and a significant difference between intra and postoperative values was observed. The pressure of the arterialized portal stump either using the left gastric artery or one of its branches, when compared to the free portal pressure did not reveal significant differences. According to these data, the proposed method of arterialization seems to create a "physiologic" arterialized stump pressure. This information while contributing to a better understanding of the complex hemodynamics of the arterialized liver represents essential guidelines for further studies on liver trophism and experimental portal hypertension.

Animals↗

PubMedDate not supplied

Artificial liver.

Explore the source record for details and available documents.

Adult↗

PubMedDate not supplied

Artificial liver. Evolution and future perspectives.

Whole organ transplantation is the only clinically effective method of treating fulminant hepatic failure and chronic liver failure due to specific genetic, hepatocellular, and anatomic defects of liver function. However, wider application of liver transplantation is limited by shortage of organ donors, high cost, a relatively high morbidity rate, and need for life long immunotherapy. As a result, investigators have attempted to develop alternative methods to treat liver insufficiency. These ranged from use of plasma exchange to use of detoxification columns and extracorporeal devices loaded with various liver tissue preparations. Several liver support systems were developed in the 1950s and 1960s, but it was not until recently that advances in hepatocyte isolation and culture, improved understanding of hepatocyte-matrix interactions, availability of new biomaterials, improved hollow fiber technology, and better understanding of flow and mass transport across semipermeable membranes resulted in the development of a new generation of liver assist devices. Some of these devices are being tested in the clinical setting. In this article, the authors review past experience with liver support systems, critically examine the current status of the field by drawing primarily on their own experience, and attempt to speculate on the future direction of liver assist system development.

Animals↗

PubMedDate not supplied

Carboxyfluorescein (CFSE) labelling of hepatocytes for short-term localization following intraportal transplantation.

Renewed interest in the transplantation of isolated hepatocytes into the liver as a potential therapy for liver disease has stimulated the development of methods for the identification of donor cells within the recipient organ. We describe a method for cellular tagging and in vivo identification of intraportally transplanted hepatocytes using an intracellular fluorescent dye, 5(6)-carboxyfluorescein diacetate, succinimidyl-ester (CFSE). Rat and porcine hepatocytes were isolated and labelled with CFSE. The optimal conditions for labelling consisted of a buffered saline suspension of hepatocytes (5 x 10(6) cells/mL) in 20.0 microM CFSE incubated for 15 min at 37 degrees C. In vitro, labelled hepatocytes were cultured either on fibronectin-coated chamber slides or in culture flasks. Cultures were evaluated in situ by fluorescence photomicrography or by fluorescence-activated cell sorting (FACS) after cell detachment. Cell viability was assessed serially and cultured, labelled hepatocytes retained the dye for up to 3 wk (last day of study). CFSE did not effect hepatocyte viability and there was no evidence of intercellular diffusion of the dye. In vivo, syngeneic Lewis rats underwent selective portal vein infusion of freshly isolated, labelled hepatocytes (2.0 x 10(7) cells/2.0 mL saline/animal) into the posterior liver lobes. All recipients were sacrificed 48 h and 96 h later and their livers examined. Transplanted hepatocytes were identified by fluorescence microscopy in tissue sections and by FACS following collagenase digestion of the liver tissue. CFSE persisted in a population of viable, engrafted hepatocytes. FACS analysis demonstrated that 9 +/- 3% of the hepatocytes in the posterior liver lobes were labelled 48 and 96 h after transplantation. At 96 h following transplantation, multiple engrafted hepatocytes could be observed by fluorescence microscopy around the central veins. CFSE labelling allows for both in vitro identification and in vivo localization of donor hepatocytes. Furthermore, it appears to be more stable and specific for labelling hepatocytes than other tested dyes (especially DiI).

Animals↗

PubMedDate not supplied

Repeated intraportal hepatocyte transplantation in analbuminemic rats.

The optimal site for implantation of isolated hepatocytes has not been established. We have developed a novel technique which allows repeated infusion of hepatocytes into the portal system via an indwelling catheter. Seven Nagase Analbuminemic rats (NAR) underwent single intraportal infusion of 2 x 10(7) isolated normal albumin-producing rat hepatocytes. Another seven NAR rats underwent placement of indwelling catheters into the portal venous system via the gastroduodenal vein. Each of them received six batches of 5 x 10(6) normal albumin producing hepatocytes. Seven control NAR rats were infused repeatedly (intraportally) with saline only. Plasma albumin (ELISA) showed significant increase in experimental animals and was more pronounced (p < 0.05) in rats transplanted repeatedly than in those given a single dose of cells. Immunohistochemical staining of the liver sections confirmed the presence of transplanted albumin producing hepatocytes. Rats transplanted with a single large batch of isolated hepatocytes showed liver tissue damage, whereas those subjected to repeated cell infusions had normal liver histology. We have developed a novel intraportal transplantation method which allows successful engraftment of a large number of isolated hepatocytes.

Animals↗

PubMedDate not supplied

Long-term correction of albumin levels in the Nagase analbuminemic rat: repopulation of the liver by transplanted normal hepatocytes under a regeneration response.

Numerous studies have reported successful transplantation of hepatocytes with demonstration of function. However, none have shown long-term correction of a liver-related metabolic defect. Male Nagase analbuminemic rats, immunosuppressed with cyclosporin-A, were transplanted with normal hepatocytes (2 x 10(7) cells/rat) isolated from allogeneic male Sprague-Dawley rat donors. Hepatocytes were selectively transplanted via the portal vein tributary into the posterior liver lobes of Nagase analbuminemic rats. Following 2 wk, to allow engraftment, selected transplanted rats (Group I) were reoperated and the portal venous branch supplying the anterior liver lobes was permanently ligated, resulting in their atrophy and induction of regeneration in the residual transplant-bearing lobes. Control rats consisted of: Group II-transplanted with normal hepatocytes without portal branch ligation; Group III-transplanted with analbuminemic hepatocytes with portal branch ligation; and Group IV-nontransplanted analbuminemic rats with portal branch ligation. The experimental period extended to 3 mo posttransplantation. All rats transplanted with normal hepatocytes demonstrated a significant elevation in serum albumin levels (ELISA). Group I rats had dramatic elevations in serum albumin to near normal levels (1.78 +/- 0.20 g/dl), and maintained these levels until the end of the experiment. Albumin levels in Group II rats reached 0.26 +/- 0.07 g/dl (p < 0.001), whereas Group III and IV rats showed no changes in serum albumin levels throughout the experiment. Immunohistology of liver tissue obtained from Group I rats, demonstrated large numbers (22.6 +/- 7.5%) of albumin-positive hepatocytes populating the recipient liver. This is the first report of near-total and sustained correction of a genetic defect in liver function in an experimental animal model following allogeneic hepatocyte transplantation.

Acetylglucosaminidase↗

PubMedDate not supplied

Repeated intraportal injections of subtherapeutic islet cell isografts restore normoglycemia in streptozotocin-diabetic rats.

Poor engraftment and consequent loss of beta-cell mass could be one of the factors that are responsible for function loss after intraportal islet transplantation (Tx). Streptozotocin-diabetic rats were transplanted with syngeneic islets, which were injected into the portal vein via an indwelling catheter connected to a subcutaneous port. In Group I (n = 6), 1,000 islets were injected in a single dose into the liver. In Group II (n = 6), five doses of 200 islets were repeatedly injected over a period of 14 days, for a total of 1,000 islets. In Group III (n = 4), five decreasing doses of islets were injected over a period of 14 days, for a total of 750 islets. Nonfasting blood glucose (n-FBG) and body weight (b.wt.) were determined twice a week and an intravenous glucose tolerance test (IVGTT) was performed at 30 and 90 days. In Group I, n-FBG decreased in 2 wk from the time of first islet injection, averaging 110 +/- 21.9 mg/dl at 1 mo (p < 0.05 vs. normal controls); this value was maintained throughout the 3-mo duration of the study. In Group II, n-FBG was normalized in 2 wk averaging 90.2 +/- 25 mg/dL on day 12 (p = NS vs. normal controls) and 75.8 +/- 14.6 mg/dL at 1 month (p = NS vs. normal controls); this value was maintained throughout the 3-mo duration of the study. In Group III, n-FBG decreased to normal values in 2 wk, averaging 77 +/- 15.7 mg/dL at 1 mo (p = NS vs. normal controls), but normoglycemia was maintained for 40 days and then followed by a progressive increase. Only in Group II, KG (percent/min decline in glucose level) was not significantly different from that of normal controls (1.702 +/- 0.531 at 1 mo and 1.676 +/- 0.891 at 3 mo), while it was significantly lower than normal controls in both Group I and III animals. Body weight increase after Tx correlated with the number of transplanted islets and at 90 days, Group III rats showed less increase than Groups I and II (p < 0.05), while no significant differences in b.wt. were recorded between Group I and II. The findings indicate that intraportal islet Tx, injected repeatedly and in small doses, produced better metabolic effects than injection of the same total number of islets in a single dose.

Animals↗

PubMedDate not supplied

Response of cultured fetal and adult rat hepatocytes to growth factors and cyclosporine.

Hepatocyte transplantation is a promising alternative to orthotopic liver transplantation in experimental animal models with genetic disorders of liver metabolism and liver failure. Fetal hepatocytes have several characteristics that make them potentially suitable as donor cells. In contrast to adult hepatocytes, fetal hepatocytes are thought to be highly proliferative, which may facilitate engraftment, expansion of transplanted cell population, and gene transfer requiring active DNA synthesis. The present study was undertaken to evaluate the proliferative capacity of fetal and adult rat hepatocytes under standardized culture conditions. Fetal (20 days of gestation) and adult hepatocytes were cultured in serum-free media at low densities and treated with growth factors. Proliferation was assessed by [3H]-thymidine incorporation and cell cycle analysis by flow cytometry. In nonstimulated cells, DNA synthesis at 4 h was about x100 higher and after 10 days in culture x20 higher in fetal compared to adult hepatocytes. When epidermal growth factor (EGF) was added, maximal DNA synthesis in fetal hepatocytes was seen at 48 h, whereas in adult hepatocytes at 72 h. For adult hepatocytes, the average increase compared to untreated cells was x13.8 with EGF, x18.5 with transforming growth factor alpha (TGF-alpha), and x7.6 with hepatocyte growth factor (HGF). For fetal hepatocytes, the increase was twofold with either EGF, TGF-alpha or HGF. EGF-, TGF-alpha- and HGF-dependent DNA synthesis was inhibited by transforming growth factor beta-1 (TGF-beta1) in both fetal and adult hepatocyte cultures; this antiproliferative effect was significantly stronger in adult hepatocyte cultures. With cyclosporine, EGF-, TGF-alpha- and HGF-dependent DNA synthesis in fetal hepatocyte cultures decreased by 36-46%, whereas in adult hepatocytes by 19-27 %. These results show that in contrast to adult hepatocytes, fetal hepatocytes have high spontaneous proliferative activity independently of growth factors and are relatively resistant to the inhibitory effect of TGF-beta1. It was also found that cyclosporine suppresses proliferation of cultured fetal hepatocytes.

Animals↗

PubMedDate not supplied

Transplantation of hepatocytes for prevention of intracranial hypertension in pigs with ischemic liver failure.

Intracranial hypertension leading to brain stem herniation is a major cause of death in fulminant hepatic failure (FHF). Mannitol, barbiturates, and hyperventilation have been used to treat brain swelling, but most patients are either refractory to medical management or cannot be treated because of concurrent medical problems or side effects. In this study, we examined whether allogeneic hepatocellular transplantation may prevent development of intracranial hypertension in pigs with experimentally induced liver failure. Of the two preparations tested--total hepatectomy (n = 47), and liver devascularization (n = 16)--only pigs with liver ischemia developed brain edema provided, however, that animals were maintained normothermic throughout the postoperative period. This model was then used in transplantation studies, in which six pigs received intrasplenic injection of allogeneic hepatocytes (2.5 x 10(9) cells/pig) and 3 days later acute liver failure was induced. In both models (anhepatic state, liver devascularization), pigs allowed to become hypothermic had significantly longer survival compared to those maintained normothermic. Normothermic pigs with liver ischemia had, at all time points studied, ICP greater than 20 mmHg. Pigs that received hepatocellular transplants had ICP below 15 mmHg until death; at the same time, cerebral perfusion pressure (CPP) in transplanted pigs was consistently higher than in controls (45 +/- 11 mmHg vs. 16 +/- 18 mmHg; p < 0.05). Spleens of transplanted pigs contained clusters of viable hepatocytes (hematoxylin-eosin, CAM 5.2). It was concluded that removal of the liver does not result in intracranial hypertension; hypothermia prolongs survival time in both anhepatic pigs and pigs with liver devascularization, and intrasplenic transplantation of allogeneic hepatocytes prevents development of intracranial hypertension in pigs with acute ischemic liver failure.

Animals↗

PubMedDate not supplied

Prevention of adhesions by high molecular weight dextran in rats. Re-evaluation in nine experiments.

The efficacy of 32% dextran 70 (Hyskon) in the prevention of postoperative peritoneal adhesions was evaluated in nine different experiments in a total of 320 rats under standardised conditions. Hyskon reduced adhesion formation, only in rats that were also subjected to abrasion of the caecum. In the remaining eight experiments Hyskon was ineffective. We conclude that more extensive experimental and clinical studies are desirable before this agent is recommended for prophylaxis against adhesions; any prophylactic regimen should be tested in a wide range of experiments. In addition, analysis of the control data suggested that the stimulus for inducing adhesions in some experiments was so strong that it could not be countered by any prophylactic regimen. A new microsurgical method that resulted in a 50 per cent response and an equal number of low grade and high grade adhesions was used. This method is well suited for investigation of both the stimulatory and the inhibitory effects of a test agent.

Animals↗

PubMedDate not supplied

Automated liver cell processing facilitates large scale isolation and purification of porcine hepatocytes.

An automated method for large scale isolation and purification of porcine hepatocytes is described. Liver cells were harvested by a two-step portal vein perfusion with ethylenediaminetetraacetate and collagenase. Hepatocyte purification was carried out using either a standard manual processing method (Procedure A) or an automated processing method using a filtration chamber and a programmable cell washer (Procedure B). Both methods produced high cell yields (Procedure A: 1.30 +/- 0.55 x 10(10) viable hepatocytes/liver; Procedure B: 1.38 +/- 0.32 x 10(10) viable hepatocytes/liver) and viability (Procedure A: 89 +/- 6.5%; Procedure B: 92 +/- 3.9%). Hepatocyte purity was significantly greater after Procedure B than after Procedure A (93.1 +/- 3.1% versus 83.1 +/- 3%, p < 0.01). Isolated hepatocytes by either method were morphologically intact, as demonstrated by transmission electron microscopy showing integrity of plasma membranes and intracellular organelles. Cultured hepatocytes isolated by either method were functionally intact, although those isolated by Procedure A showed significantly lower activity of microsomal 7-ethoxycoumarin-O-deethylase activity (p < 0.05) and mitochondrial succinate dehydrogenase activity (p < 0.01). In conclusion, use of the automated hepatocyte processing method resulted in efficient large scale preparation of porcine hepatocytes, with higher purity and greater retention of differentiated liver metabolic functions, and was found to be less time consuming and less labor intensive.

7-Alkoxycoumarin O-Dealkylase↗