Biomaterials, artificial cells, and immobilization biotechnology : official journal of the International Society for Artificial Cells and Immobilization Biotechnology最新文献

Although the main function of an arterial graft is to restore distal blood flow, there is evidence that certain local parameters of blood flow, particularly wall shear stresses, are important in determining the graft's long-term patency. Wall shear stresses were associated with intimal hyperplasia, intimal proliferation, and endothelial cell development, morphology, and attachment. Here we present a detailed method which permits the investigation of the wall shear stress acting on arteries and prostheses in dogs. The theory takes into account the nonlinear terms of the Navier-Stokes equations as well as the nonlinear behaviour and large deformation of the arterial wall. It is based on the numerical resolution of the nonlinear equations by the Crank-Nicolson method which was selected for its unconditional stability. Through the locally measured values of the pressure, pressure gradient, radius and flow rate, the velocity distribution and wall shear stress at a given location along the artery or the prosthesis, can be determined. Complete results on the same dog are presented for the distal aorta and for the middle of a chemically processed prosthesis, implanted as substitute in the thoracic aorta.

Many anticancer drugs require oxygen to be cytotoxic, or are selectively cytotoxic toward cells under oxygenated conditions. The effects of the dilute perfluorochemical emulsion Fluosol-DA with a wide variety of chemotherapeutic agents have been explored; however, it has not been possible to determine the optimal level of circulating perfluorochemical emulsion with anticancer drugs because the volume of Fluosol that may be administered in limited. Using a concentrated 90% Perflubron emulsion, Oxygent, a wide range of perfluorochemical emulsion doses have been examined in combination with melphalan, cyclophosphamide and BCNU in a murine solid tumor model. When Oxygent was administered by injection i.v. just prior to the injection of melphalan (10 mg/kg), the greatest tumor growth delays were obtained with Oxygent levels between 4 and 12 g PFC/kg. With each of these drugs the greatest tumor growth delays were obtained when the drug was prepared in the emulsion and the combination injected i.v. In each case, each dose of drug was followed by 6 h. of breathing carbogen.

Perflubron (perfluoroocytlbromide, PFOB) emulsion concentrations of 100%, 90%, or 60% w/v were administered to mice with and without 3 types of murine malignant tumor implants, and the distribution in blood, tumor, lung, liver and spleen were studied 48 hours after a dose of 10 or 3 g/Kg of PFOB. The most important changes were seen in the blood where the PFOB concentration [PFOB] was decreased in tumor bearing mice (TBM). Blood [PFOB] was also decreased in TBM and normal mice (NM) that received the 60% emulsion. Liver [PFOB] was increased in TBM. Lung [PFOB] was directly proportional to the emulsion concentration with the 10g/Kg dose. No major differences were seen in the biodistribution between the 100% and 90% emulsions using 10g/Kg, in spite of differences in composition and manufacturing history.

We examined how changes in oxygen affinity brought about by different chemical modifications of hemoglobins affect their oxidation-reduction reactions. The three modified hemoglobins studied were HbA-FMDA, HbBv-FMDA, produced by the reaction of human or bovine oxyHb with fumaryl mono-dibromoaspirin; and HbA-DBBF, produced by the reaction of human deoxyHb with bis(3,5-dibromosalicyl) fumarate. Exposure of oxyHb to H2O2 causes generation of free radicals capable of cleaving dimethylsulfoxide (Me2SO) to produce formaldehyde (HCHO). Relative to the reaction rate for HbAo (630 +/- 130 M/min) the rates of HCHO formation were roughly 70% for HbA-DBBF, 50% for HbA-FMDA and 16% for HbBv-FMDA. Exposure to H2O2 also caused spectral changes at varied rates for the HBOCs analyzed. Although these rates were not directly correlated with the rates of free radical formation, addition of mannitol or thiourea slowed both the rate of spectral changes and HCHO formation. The relative ability of the ferric derivatives of the HBOCs to participate in free radical reactions was monitored by assays of non-enzymatic NADPH oxidation and aniline hydroxylation. HbBv-FMDA showed significantly slower rates than the other HBOCs in both assays. The observed differences between HBOCs in these assays indicate differences in their ability to generate or interact with free radicals.

To assess the potential immunogenicity of human diaspirin cross-linked hemoglobin (DCLHb) solution, repetitive doses of this material were given intravenously to rhesus monkeys at monthly intervals and the immune response to this challenge was assessed. Serum samples collected at multiple intervals throughout the study showed no evidence of DCLHb specific IgG or IgM production. Intradermal skin tests performed one month after the final DCLHb infusion were also negative. These data demonstrate that DCLHb is not antigenic when administered intravenously to rhesus monkeys. In addition, screening of a panel of normal human sera for pre-existing anti-DCLHb IgG antibodies was negative, suggesting that this modified hemoglobin is unlikely to be antigenic in humans.

We bled 25% of estimated total blood volume, then infused pyridoxalated polymerized human stroma-free hemoglobin solution (PP-SFH) (10 g/dl) to dogs under anesthesia in a volume equal to the blood removed. Central hemodynamics, blood flow distribution to organs, and renal function were studied up to 2-3 hours following the infusion. Mean arterial pressure was reduced from 120 +/- 3 to 86 +/- 7 mmHg at the end of the 30-minute hypovolumic period and the cardiac output was reduced by 27%. Immediately following the PP-SFH infusion we observed a further fall in blood pressure (43%) caused by a fall in cardiac output which lasted for 10 minutes. Blood pressure was restored gradually with the continuation of the infusion and the cardiac output was restored and maintained well. During the hypovolumic period, blood flow to the heart, renal cortex, and liver were reduced, whereas normal flow to the renal medulla and brain were maintained. After the resuscitation, blood flow to the heart, brain, liver, and renal medulla significantly exceeded the normal range, but remained subnormal in the renal cortex. Glomerular filtration rate (GFR), urine flow, and electrolyte excretion were all reduced during the hypovolumic period and were not restored to the pre-bleed levels after the infusion.

Fluosol has been shown to alter the disposition of several drugs immediately after its administration. Investigations in this laboratory established that the disposition of several drug markers requiring the hepatic microsomal cytochrome P-450 isoenzymes was time dependent for 72 hours. It was an additional purpose of the research to determine if the nonmicrosomal sulfation and acetylation pathways were also influenced by Fluosol hemodilution in a time dependent manner. Rats were moderately hemodiluted with Fluosol and received an intravenous dose of a drug marker 24, 48, or 72 hours after hemodilution. The formation clearance (ClF) of specific metabolites was used as the pharmacokinetic measure of a specific enzymatic activity. 3-Hydroxymethyl antipyrine ClF (phenobarbital inducible microsomal cytochrome P-450 isoenzymes) increased 300% only at 48 hours. Acetylsulfamethazine ClF (nonmicrosomal acetylation) increased 287% and 162% at 24 and 48 hours, respectively. Acetaminophen sulfate ClF (nonmicrosomal sulfation) decreased 30% only at 48 hours. Substantial evidence shows that cytochrome P-450 content is induced at 72 hours and remains induced for an unprecedented length of time by the PFCs in Fluosol. Therefore, it was unexpected that 3-hydroxymethyl antipyrine ClF was not increased at 72 hours. Several possible explanations are discussed for the unexpected findings.

In view of the potential application for hemoglobin-based oxygen carriers (HBOCs) in organ perfusion under hypothermic conditions, we examined the temperature dependence of oxygen equilibrium curves (OECs) at 15-37 degrees C of three HBOCs: HbA-FMDA and HbBv-FMDA, produced by the reaction of human or bovine oxyHb with fumaryl mono-dibromoaspirin, and HbA-DBBF, produced by the reaction of human deoxyHb with bis(3,5-dibromosalicyl) fumarate. OECs for HbA-DBBF, HbA-FMDA and HbBv-FMDA at 37 degrees C were right shifted (P50 = 24.5, 17 and 35 torr, respectively). van't Hoff's rule gave HbA-DBBF (-12.2 +/- 2.8), HbA-FMDA (-12.0 +/- 2.0), HbBv-FMDA (-10.5 +/- 1.8); these values do not significantly differ from that for native HbAo (-11.5 +/- 2.4). Among the hemoglobins included in this study, HbBv-FMDA had the most favorable oxygenation characteristics at low temperatures (a P50 of 6.0 torr at 15 degrees C as compared to only 2-3 torr for the other hemoglobins in the study). Recently, however, a human hemoglobin crosslinked with bis-pyridoxyl tetraphosphate was reported to have a P50 of 15 torr at 16 degrees C (Keipert et al, Transfusion 1989; 29: 768-773). Therefore, precise knowledge of the oxygen delivering capacity of any potential HBOC should be explored under hypothermic conditions as performance under these conditions may determine its usefulness as an organ perfusate.

Pyridoxalated hemoglobin polymerized with glutaraldehyde has been proposed as a hemoglobin based blood substitute. The preparations contain significant amounts of unpolymerized hemoglobin. We have prepared polymerized pyridoxalated hemoglobin labelled with 14C by reductive methylation free of unpolymerized hemoglobin and pyridoxalated hemoglobin labelled with 3H by reductive methylation to compare the handling of the two forms after infusion into dogs. Four dogs were examined sequentially. After three hours, 52.4 +/- 8.9% of the 3H label had disappeared from plasma whereas 21.7 +/- 5.8 of the 14C label had disappeared. The decrease of both labels occurred in a very close to linear fashion over the time period examined. From radioactivity in collected urine, it was calculated that 30.7 +/- 6.3% of the 3H and 9.0 +/- 2.7 of the 14C that had been cleared from plasma appeared in urine. The ratio of the specific radioactivity in tissue to the specific radioactivity of plasma indicated that extravascular accumulation of 3H label from unpolymerized hemoglobin occurred in kidney, heart and liver, with the kidney cortex exhibiting a very high concentration of the label. The specific radioactivity of both 3H and 14C label in liver suggested the substantial involvement of the reticuloendothelial system in the removal of both unpolymerized and polymerized hemoglobin from the circulation.