Normal and stenotic renal arteries: experimental balloon-expandable intraluminal stenting

Elastic recoil of the vessel wall is a common cause of failure of percutaneous transluminal angioplasty in renal arteries. To oppose such recoil, balloon-expandable metal stents were implanted in artificially stenotic renal arteries in pigs and normal renal arteries in dogs and pigs. The stents were then examined angiographically and histologically at regular intervals. All stents were completely covered with endothelialized neointima in 3 weeks. There was no difference in intimal thickness between the stenotic and nonstenotic renal arteries. A large stent diameter and a large open or nonmetal surface may cause less intimal hyperplasia, but nonturbulent, fast arterial flow is probably the most important factor in ensuring long-term patency of the vessel.     

Gamma-carboxylated isoforms of recombinant human protein S with different biologic properties

Human protein S (HPS), a regulator of hemostasis, is a vitamin K- dependent plasma protein with potential clinical utility. We have obtained high-level expression of the cDNA for HPS in two mammalian cell lines. Both cell lines secreted single chain recombinant HPS (rHPS) in serum-free medium as determined by Western blot analysis. The ability of the rHPS from both cell lines to act as a cofactor for human protein C (HPC) was determined; the rHPS secreted from the human 293 cell line had an activity six times that of the rHPS from the AV12-664 Syrian hamster cell line. Furthermore, the relative specific cofactor activity of rHPS from the 293 cell line was actually 2.5-fold higher than that of single-chain human plasma-derived HPS. Essentially all of the rHPS secreted from the 293 cell line exhibited a calcium-dependent elution profile on anion exchange chromatography, whereas only 25% to 35% of the hamster cell-derived rHPS exhibited this profile. However, the calcium-eluted rHPS from the AV12 cell line had a high specific cofactor activity, equivalent to that of the 293-derived rHPS. A NaCl- elutable rHPS fraction (calcium nondependent) was isolated from the recombinant AV12-664 cell line, further purified, and found to have reduced activity, only 40% that of the calcium-dependent rHPS. The only observable difference in the calcium-dependent and nondependent rHPS molecules was in the content of gamma-carboxyglutamic acid (Gla); the calcium-dependent material contained approximately 10 mol Gla/mol protein whereas the calcium-nondependent material contained only approximately 8 mol Gla/mol of protein. In addition, the calcium- nondependent rHPS had reduced ability to interact with phospholipid vesicles as evidenced by an eightfold increase in the apparent kd. Our data demonstrate the isolation of rHPS with high specific activity, and show that a reduction in as few as two Gla residues dramatically decreases its functional cofactor activity for HPC, due to a reduction in ability to interact with the phospholipid bilayer.     

Enhancement of erythrocyte superoxide dismutase activity: effects on cellular oxidant defense

To delineate further the role of superoxide dismutase (SOD) in red blood cell (RBC) oxidant defense, normal human erythrocytes were osmotically lysed and resealed in the presence of varying concentrations of exogenous SOD. This resulted in a dose-dependent increase in SOD activity in the resealed erythrocytes while maintaining nearly normal RBC hemoglobin concentration (less than 10% decrease from the control value), cell volume, and cellular deformability. Surprisingly, a five- or ninefold increase in SOD activity yielded no additional protection against superoxide-generating drugs (phenazine methosulfate or menadione sodium bisulfite). No significant differences were observed between the control and SOD-loaded RBCs in O2-driven methemoglobin formation or generation of thiobarbituric acid-reactive substances. In contrast, RBCs with elevated SOD activity pretreated with sodium azide (to block catalase activity) or 1-chloro-2,4- dinitrobenzene (to deplete reduced glutathione, GSH) showed significantly enhanced methemoglobin generation in response to superoxide generating drugs. No differential response was noted between the control, control-resealed, and SOD-loaded RBCs to oxidants other than superoxide. Based on our results and other data, we conclude that elevated SOD activity may imbalance cellular oxidant defense, resulting in enhanced oxidation due to the accelerated generation of H2O2, the product of O2- dismutation. This effect is significantly exacerbated under conditions in which H2O2 catabolism is altered.     

Infection of human T-cell leukemia virus type I and development of human T-cell leukemia lymphoma in patients with hematologic neoplasms: a possible linkage to blood transfusion

Among 354 adult patients with either hematological malignancy or aplastic anemia, eight were positive for anti-HTLV-I antibodies; six of eight had received multiple transfusions. There was an approximately 3.5-fold increase (P less than .001) of HTLV-I seropositivity in the patients with hematologic disease (8 of 354, 2.23%) compared to the healthy adults older than 20 years (34 of 5252, .65%). Two hematological patients, one with Hodgkin's disease and one with acute promyelocytic leukemia, were found to be positive for HTLV-I, and developed and died of adult T-cell leukemia/lymphoma (ATL) subsequently. Both were long-term survivors of the primary disease and had received multiple transfusions. The latent period from blood transfusion to onset of ATL was 6 months and 11 years, respectively. Immunocompromised patients, who were seropositive for HTLV-I, may be at increased risk for ATL compared to healthy carriers of HTLV-I, and the latent period may be shorter.     

Markedly reduced beta-cell function does not result in insulin resistance in islet autografted dogs.

Autotransplantation of islets of Langerhans has resulted in long-term normoglycemia in pancreatectomized dogs. This canine model is useful in evaluating both the progress of islet transplantation and the effect of a reduced islet mass upon the determinants of glucose tolerance: i.e., insulin secretion, insulin sensitivity, and glucose effectiveness. To determine the effect of a reduced islet mass on these factors, we measured the acute insulin response to arginine (AIRa) and glucose (AIRg), the slope of glycemic potentiation of AIRa (SP), insulin sensitivity (Sl), and glucose effectiveness (SG) in control (CN), diabetic (DM), and pancreatectomized dogs rendered normoglycemic with transplanted autografts of islets of Langerhans (TX). Normal fasting plasma glucose (FPG) (TX 4.7 +/- 0.2 mM; CN 4.9 +/- 0.1 mM; P greater than 0.05) was maintained despite a markedly reduced insulin secretion in TX (AIRa 24%, AIRg 15%, and SP 11% of CN). All measures of insulin secretion were significantly correlated (SP vs. AIRg, r = 0.80, P less than 0.0001; AIRa vs. AIRg, r = 0.92, P less than 0.0001) across all animals, but none of the measures of secretion were significantly correlated with either the number of islets transplanted or time posttransplant (P greater than 0.10). Insulin sensitivity was normal in islet autografted dogs (TX: 136 +/- 12 min-1/(nmol/ml); CN: 101 +/- 11 min-1/(nmol/ml), P greater than 0.05) but SG was reduced (TX: 1.93 +/- 0.28 x 100 min-1; CN: 3.53 +/- 0.35 x 100 min-1, P less than 0.05), as determined by the minimal-model method. In diabetic animals (FPG = 16.1 +/- 1.3 mM), insulin secretion was negligible by all measures (P greater than 0.05), and was associated with insulin resistance (Sl = 28 +/- 8 min-1/(nmol/ml)) and reduced SG (1.72 +/- 0.11 x 100 min-1). These studies indicate that across a range of insulin secretion in dogs, the secretagogues arginine and glucose provide similar estimates of beta-cell function. This markedly reduced beta-cell function does not result in insulin resistance when fasting normoglycemia is maintained, but is associated with a decrease in glucose action at basal insulin.