Search

We report the ability of Giardia lamblia to modify several of its cellular proteins by isoprenylation. Trophozoites cultured in the presence of [ 3 H]mevalonate synthesized radiolabeled proteins of approx. 50 and 21–26 kDa. Chemical analysis indicated that farnesyl and geranylgeranyl isoprenoids comprised the majority of the radiolabel covalently associated with trophozoite proteins. In addition, antibodies to human p21 ras immunoprecipitated mevalonate-labelled species of approx. 21 kDa. Inhibitors of several enzymatic steps of the mevalonate pathway dramatically affected Giardia metabolism. Protein isoprenylation and cell growth were blocked by compactin and mevinolin, competitive inhibitors of HMG-CoA reductase, the rate-limiting enzyme in isoprenoid biosynthesis. In the presence of these inhibitors, Giardia growth was restored by the addition of mevalonate to the culture medium. In contrast, cell growth was blocked irreversibly by inhibitors of subsequent steps in the protein isoprenylation pathway. Trophozoite growth inhibition by limonene, perillic acid, perillyl alcohol and N -acetyl- S -farnesyl- l -cysteine was not reversed after the addition of mevalonate, dolichol, ubiquinone or cholesterol to the medium. These observations constitute the first description of protein isoprenylation in any protozoan and indicate that this post-translational modification is an important step in the regulation of the growth of this primitive eukaryote.

Adult paired schistosomes incubated for 3 days in radiolabeled mevalonate can effectively label at least 2 major proteins with apparent sizes of 25 and 43 kDa. The 25-kDa mevalonate-labeled proteins comigrated with proteins that could be labeled with GTP. The lipids attached to these proteins were removed and resolved by HPLC and found to comigrate with known samples of farnesol and geranylgeraniol. Homogenates of the schistosome when incubated with labeled farnesol pyrophosphate effectively labeled a protein(s) with an apparent molecular weight of 43 kDa while homogenates incubated in the presence of labeled geranylgeranyl pyrophosphate-labeled schistosome proteins with an apparent molecular weight of 25 kDa. Our results demonstrate that Schistosoma mansoni has the ability to covalently attach farnesol and geranylgeranyl to low-molecular weight proteins.

AIM To establish an extracorporeal bioartificial liver support system (EBLSS) using cultured human liver cells and to study its support effect for fulminant hepatic failure (FHF). METHODS The liver support experiment of EBLSS consisting of aggregates cultured human liver cells, hollow fiber bioreactor, and circulation unit was carried out in dizhepatic dogs. RESULTS The viability of isolated hepatocytes and nonparenchymal liver cells reached 96%. These cells were successfully cultured as multicellular spheroids with synthetic technique. The typical morphological appearance was retained up to the end of the artificial liver experiment. Compared with the control dogs treated with EBLSS without liver cells, the survival time of artificial liver support dogs was significantly prolonged. The changes of blood pressure, heart rate and ECG were slow. Both serum ammonia and lactate levels were significantly lowered at the 3rdh and 5thh . In addition, a good viability of human liver cells was noted after 5h experiment. CONCLUSION EBLSS playing a metabolic role of cultured human hepatocytes, is capable of compensating the function of the liver, and could provide effective artificial liver support and therapy for patients with FHF.

AIM:To evaluate the possibility of using cultured human hepatocytes as a bridge between bioartificial liver and liver transplantation.METHODS:In this experiment,the efficacy of extracorporeal bioartificial liver support system (EBLSS) consisting of spheriodal human liver cells and cultured hepatocytes supernatant was assessed in vivo using galactosamine induced rabbit model of fulminant hepatic failure.RESULTS:There was no difference of survival between the two groups of rabbits, but in the supported rabbits serum alanine aminotransferase, total bilirubin and creatinine were significantly lower and hepatocyte necrosis was markedly milder than those in control animals. In addition, a good viability of human liver cells was noted after the experiment.CONCLUSION:EBLSS plays a biologic role in maintaining and compensating the function of the liver.