This study was designed to determine optimal operating conditions of a bioartificial liver (BAL) based on mass transfer of representative hepatotoxins and mediators of immune damage. A microprocessor-controlled BAL was used to study mass transfer between patient and cell compartments separated by a hollow fiber membrane. Membrane permeability (70, 150, or 400 kDa molecular weight cut-off-MWCO), membrane convection (high: 50 mL/min; medium: 25 mL/min; low: 10 mL/min; diffusion: 0 mL/min), and albumin concentration in the cell compartment (0.5 or 5 g%) were considered for a total of 24 test conditions. Initially, the patient compartment contained pig plasma supplemented with ammonia (0.017 kDa), unconjugated bilirubin (0.585 kDa), conjugated bilirubin (0.760 kDa), TNF-α (17 kDa), pig albumin (67 kDa), pig IgG (147 kDa), and pig IgM (900 kDa). Mass transfer of each substance was determined by its rate of appearance in the cell compartment. Membrane fouling was assessed by dextran polymer technique. Of the three tested variables (membrane pore size, convection, and albumin concentration), membrane permeability had the greatest impact on mass transfer (P < 0.001). Mass transfer of all toxins was greatest under high convection with a 400 kDa membrane. Transfer of IgG and IgM was insignificant under all conditions. Bilirubin transfer was increased under high albumin conditions (P = 0.055). Fouling of membranes ranged from 7% (400 kDa), 24% (150 kDa) to 62% (70 kDa) during a 2-h test interval. In conclusion, optimal toxin removal was achieved under high convection with a 400-kDa membrane, a condition which should provide adequate immunoprotection of hepatocytes in the BAL.

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SYNOPSIS. Mechanically released sporocyts of Eimeria bovis, E. ellipsoidalis and E. auburnensis readily excysted when incubated in a mixture of trypsin, steapsin, and bovine bile. Excystation of intact E. bovis, E. ellipsoidalis and E. auburnensis oocysts occurred after pretreatment at 37°C in aqueous 0.02 M cysteine hydrochloride under an atmosphere of CO2‐air or CO2‐N2, followed by incubation in an enzyme‐bile mixture. Nine % of E. bovis oocysts were activated after 6 hr of incubation at 37 C in a mixture of 0.5% (w/v) trypsin, 0.5% (w/v) steapsin, and 5.0% (v/v) bile at pH 7.5 with 10 hr pretreatment under air and 20% CO2; with 30% CO2, 80% activation occurred; with 50% CO2, 91% of the oocysts were activated. At CO2 levels from 10 to 40%, pretreatment with CO2 and N2 yielded less activation than CO2 and air. Pretreatment with CO2‐N2 (50–50) for 2 hr resulted in 37% activation; for 6 hr, 60%; for 10 hr, 94%; and for 14 hr, 99%. After pretreatment under 50% CO2 for 10 hr, 95% excystation was obtained by incubation for 6 hr in 0.5% trypsin and 5.0% bile. Only 76 or 69% excystation occurred when 0.25% trypsin or 1.0% bile, respectively, was substituted. Addition of steapsin to this mixture caused little change in the results. In oocysts pretreated 14 to 21 hr with steapsin, 2% or less excystation occurred after 6 hr in a trysinbile or bile mixture. E. ellipsoidalis oocysts, pretreated for 10 hr under CO2‐N2 (50–50), underwent 61 and 80% excystation when incubated for 2 and 6 hr, respectively, in trypsin, steapsin, and bile. E. bovis oocysts enclosed in a dialysis bag inside an intestinal fistula became thinned or flattened at the micropyle after 24 hr, and excystation occurred when these oocysts were mixed with trypsin, steapsin, and bile and returned to the fistula for 4 hr. No excystation occurred when oocysts without added enzymes were left 48 hr in the fistula. Sporozoites escaped first from sporocysts and then from oocysts.