Liver transplantation for fulminant liver failure in children

The mortality rate of fulminant hepatic failure (FHF) in childhood has remained between 70% and 95% despite recent improvements in medical therapy. Liver transplantation has become an important therapeutic option in adults with this entity, but has been infrequently performed in children. Many children do not receive transplants because of the rapid progression of the illness and the lack of suitable donor livers. We present our experience in liver transplantation in children with FHF. Between March 1988 and December 1989, seven children aged between 15 months and 12 years received eight liver transplants. The aetiology of FHF was viral hepatitis in five and drug hepatotoxicity (carbamazepine) in two. Five of our patients were in grade III-IV coma. Reduced-sized livers were used in six of the eight transplants. The post-operative morbidity included viral and fungal infections, and abdominal bleeding. Two patients died from graft-versus-host disease and one from brain aspergillosis. Four patients (57%) survived a median follow-up of 15 months. Liver transplantation should be the therapeutic option in children with FHF where the chances of medical recovery are poor.

Biochemical and histochemical analysis of 71 kDa dystrophin isoform (Dp71f) in rat brain

Dp71 is a member of the dystrophin family and the most abundant dmd gene product in the brain. In the present study, we focused on a short dystrophin transcript named Dp71f, which is alternatively spliced when exon 78 is absent The topographic localization of this protein in the encephalon has not been properly described yet, nor its cellular or subcellular localization, and even less its functions. Dp71f was found to be a cytoplasmic 70 kDa protein and localized in all encephalon regions studied. Double labeling using specific markers for various cell types confirmed Dp71f distribution in the cytoplasm of all cell types studied. Labeling was more conspicuous near the nucleus and diminished towards the periphery of cells. In some cases, we observed cells that were positive for actin and Dp71f in regions corresponding to lamellipodia-like structures. Dp71f and Dp71d isoforms were differently distributed. Our study is the first specific and unambiguous description of the topography and cellular localization patterns of Dp71f in brain, suggesting that Dp71f is a ubiquitous protein.

Genotypic analysis of Toxoplasma gondii isolates from pigs

To determine the prevalence of the 3 primary clonal lineages of Toxoplasma gondii (strain types I, II, and III) in a potential food source of infection for humans, we analyzed 43 isolates of T. gondii that had been collected from pigs at an abattoir in Iowa. Parasites were harvested as in vitro-grown tachyzoites, and their genotypes were determined at the SAG1 and SAG2 loci. On the basis of the allele identified at the SAG2 locus, isolates were grouped into 1 of the 3 primary lineages. Type II strains were by far the most prevalent, accounting for 83.7% of the isolates. The type III genotype was identified in only 16.3% of the isolates. These prevalences differ significantly from a previous sampling of isolates from animals but are similar to the frequencies with which they occur in human disease cases. Similar to the previously characterized strain P89, strains P62 and P105 appeared to have recombinant genotypes. The type I genotype was not identified in the isolates from pigs although these strains have previously been shown to account for approximately 10-25% of toxoplasmosis cases in humans.

Ca(2+)-dependence of conoid extrusion in Toxoplasma gondii tachyzoites

The role of Ca2+ in conoid extrusion was investigated in isolated Toxoplasma gondii tachyzoites by treatment with Ca(2+)-ionophores, Ca(2+)-chelating agents and an inhibitor of the Ca(2+)-ATPase at the endoplasmic reticulum. The results were evaluated by light phase-contrast microscopy and electron microscopy. Ionomycin (0.5-1 microM) caused an immediate and sustained extrusion of the conoid in up to 80% of the tachyzoites, depending on the concentrations of ionophore and Ca2+ in the medium. However, over 50% of the tachyzoites extruded the conoid when treated with ionomycin in Ca(2+)-free saline complemented with EGTA. The effect of ionomycin was reversible and could be induced a second time in about half of the responsive population. Similar results were obtained with A23187. Conoid extrusion induced by ionomycin in Ca(2+)-free medium was almost completely abolished when the tachyzoites were previously loaded with a permeable compound known to chelate intracellular Ca2+ (BAPTA/AM; 25 microM). On the other hand, exposure of tachyzoites to the Ca(2+)-ATPase inhibitor thapsigargin (0.5-1 microM) produced significant extrusion of the conoid. Tachyzoites loaded with BAPTA/AM as well as those treated with ionomycin, i.e. with conoids paralyzed in opposite positions, had a diminished capacity to invade cultured epithelial cells. A substantial reduction in the response to stimulation by ionomycin was found also in parasites treated with cytochalasin-D, a drug that depolymerizes actin-filaments. The results suggest that Ca(2+)-release from internal stores may act as a key signal to activate a mechanism of conoid extrusion probably mediated, at least in part, by actin-filaments.

Divalent cation and ATP dependent motility of Toxoplasma gondii tachyzoites after mild treatment with trypsin

Large percentages of Toxoplasma gondii tachyzoites could be induced to display two types of movement associated with active invasive behavior by exposing them for 1 min to 0.002% trypsin in phosphate-buffered saline (PBS). The motile activity, consisting of clockwise rotation around the posterior end (about 20 revolutions per min) and twirling-gliding over a poly-L-lysine substrate (1.2 +/- 0.2 microns/s standard deviation), was observed and recorded by video-enhanced contrast microscopy. The number of active tachyzoites reached a maximum 1 min after trypsinization; the motile response of the population lasted for about 5 min. Activation was prevented by soybean trypsin-inhibitor, and could not be induced again in previously treated specimens. Electronmicroscopy of trypsinized tachyzoites fixed in the presence of ruthenium-red revealed discrete discontinuities of the plasma membrane, which sealed within 90 min after washing with PBS. Treated tachyzoites were able to invade cultured epithelial cells with a higher relative infectivity than that of untreated parasites. Perfusion of trypsinized tachyzoites with 1 mM of either CaCl2 or MgCl2 and 1 mM ATP increased the number of activated parasites to over 60%; on the other hand, all induced motility was inhibited or blocked by agents that chelate divalent cations. The present preparation, which provided the first serial illustrations of T. gondii movements induced by a defined chemical stimulus, may offer a useful experimental model for the study of motility in this parasite.

A new portal venous shunt for bypass in orthotopic hepatic grafting

A new heparin bonded portal venous cannula is described for use during orthotopic hepatic transplantation. This new shunt has a "shoulder" 4 centimeters from the caged tip, allowing it to be securely maintained within the portal vein. With a 60 degree curvature 7 centimeters from the tip, the shunt can conveniently be positioned away from the operative field.