Multipoint Schur algorithm and orthogonal rational functions: convergence properties, I

Classical Schur analysis is intimately connected to the theory of orthogonal polynomials on the circle [Simon, 2005]. We investigate here the connection between multipoint Schur analysis and orthogonal rational functions. Specifically, we study the convergence of the Wall rational functions via the development of a rational analogue to the Szeg\H o theory, in the case where the interpolation points may accumulate on the unit circle. This leads us to generalize results from [Khrushchev,2001], [Bultheel et al., 1999], and yields asymptotics of a novel type.Comment: a preliminary version, 39 pages; some changes in the Introduction, Section 5 (Szeg\H o type asymptotics) is extende

Steroid-free immunosuppression after renal transplantation

Concerns about the side effects of chronic steroid therapy have prompted increasing interest in steroid-free immunosuppression for renal transplant recipients who are maintained on cyclosporine-based regimens. Studies to date suggest that at least 50% of cyclosporine-treated patients can be managed without steroid therapy. Reported benefits of avoiding or withdrawing steroid therapy have included improvements in hyperlipidemia, hypertension, and glucose intolerance and accelerated growth in children. Whether these effects will increase patient or allograft survival remains to be proved. Furthermore, the benefits of steroid-free immunosuppression must be weighed against the risk of precipitating allograft rejection. Although the elimination of steroids clearly increases the short-term risk of acute rejection, further studies are needed to determine the effects of steroid-free immunosuppression on long-term allograft function and to identify clinical or immunologic factors that can predict a successful outcome after the elimination of steroids

Cost-utility analysis of living-donor kidney transplantation followed by pancreas transplantation versus simultaneous pancreas-kidney transplantation

For a type I diabetic with end-stage renal disease, the choice between a kidney-alone transplant from a living-donor (KA-LD) and a simultaneous pancreas kidney (SPK) transplant remains a difficult one. The prevailing practice seems to favor KA-LD over SPK, presumably due to the superior long-term renal graft survival in KA-LD and the elimination of the lengthy waiting time on the cadaver transplant list. In this study, two treatment options, KA-LD followed by pancreas-after-kidney (PAK) and SPK transplant, are compared using a cost-utility decision analysis model. The decision tree consisted of a choice between KA-LD + PAK and SPK. The analysis was based on a 5-yr model and the measures of outcome used in the model were cost, utility and cost-utility. The expected 5-yr cost was $277,638 for KA-LD + PAK and$288,466 for SPK. When adjusted for utilities, KA-LD + PAK at a cost of $153,911 was less cost-effective than SPK at a cost of$110,828 per quality-adjusted year. One-way sensitivity analyses were performed by varying patient and graft survival probabilities, utilities and cost. SPK remained the optimal strategy over KA-LD + PAK across all variations. Two-way sensitivity analysis showed that in order for KA-LD + PAK to be at least as cost-effective as SPK, 5-yr pancreas and patient survival rates following PAK would need to surpass 86 and 80%. In conclusion, according to the 5-yr cost-utility model presented in this study, KA-LD followed by PAK is less cost-effective than SPK as a treatment strategy for a type I diabetic with end-stage renal disease. For patients interested in the benefits of a pancreas transplant, it would be reasonable to offer SPK as the optimal treatment, even if a living kidney donor is available

Effect on renal function of change from high to moderate protein intake in type I diabetic patients

The effects on renal function of moderate restriction in protein intake were studied in 14- to 20-yr-old type I diabetic patients who had no clinical renal disease or hypertension; matched normal subjects served as controls. After assessment of protein intake and renal function, studies were conducted at the completion of each of two consecutive dietary periods of 1 wk. Diets containing 3.5 and 1.5 g X kg-1 X day-1 protein were provided during the first and second periods, respectively. Baseline protein intakes were substantial in both controls (1.86 g X kg-1 X day-1) and diabetics (2.17 g X kg-1 X day-1). Baseline creatinine clearance was increased in diabetics (P = .043). At the end of the high-protein intake period, both diabetics and controls showed similar high values of glomerular filtration rate (GFR) and renal plasma flow (RPF). GFR and RPF decreased markedly (P less than .001) and to a similar degree in both groups after normal protein intake. GFR and RPF in diabetics were not higher than in controls at this point, but filtration fraction was increased in diabetics. Albumin excretion rates were similar in both groups and not influenced by renal function changes. GFR and RPF values correlated significantly with the quantity of protein intake, as estimated from the urea nitrogen appearance rate in both groups. The results suggest that the functional response to variations in protein intake is not altered in the diabetic kidney. In addition, increased renal function in diabetics may be related partly to the excessive protein content in commonly prescribed diabetic diets

Randomized Trial of Thymoglobulin Versus Alemtuzumab (with Lower Dose Maintenance Immunosuppression) Versus Daclizumab in Living Donor Renal Transplantation

We performed a randomized trial evaluating Alemtuzumab, a humanized anti-CD52 monoclonal antibody, in living donor (LD) kidney transplantation. Thirty-eight LD first renal transplant recipients were randomized into three single-agent antibody induction groups: thymoglobulin (group A); alemtuzumab (group B); and daclizumab (group C). In groups A and C, target tacrolimus trough levels were 6 to 8 ng/mL, with 1 gm mycophenolate mofetil (MMF) administered twice daily, and maintenance methylprednisolone. In group B, the target tacrolimus trough level was 4 to 6 ng/mL, with 500 mg MMF administered twice daily, without methylprednisolone. With 29/38 patients now followed beyond 36 months posttransplantation, we observed no graft failures and only one death with a functioning graft (in group B). Acute rejection episodes were low: 0/13, 1/13, and 1/12 patients in groups A, B, and C. Biopsy-proven chronic allograft injury was higher among group B (3/13) versus groups A (0/13) or C (0/12; P = .01). Poorer renal function was observed in group B; the mean calculated creatinine clearance at 3 months posttransplantation was significantly poorer: 63.3 ± 3.0 versus 85.4 ± 7.2 and 82.2 ± 8.2 in groups A and C ( P = .01). No differences in the incidence of adverse events were observed

Removal of lymphocytotoxic antibodies by pretransplant immunoadsorption therapy in highly sensitized renal transplant recipients

A high level of panel-reactive antibodies (PRA) in potential renal transplant recipients is associated with a long waiting time until transplantation and correlates inversely with graft outcome. We report our experience with the employment of immunoadsorption (IA) using a column composed to sepharose-bound staphylococcal protein A (which has a relatively selective affinity for binding IgG compared with other immunoglobulins) to decrease the PRA levels and expedite transplantation in 6 highly sensitized potential renal transplant recipients (1 primary and 5 awaiting second transplants). All patients had PRA levels of greater than or equal to 70% for a duration of 1 year prior to IA. Only patients with antibody specificity localized to 1 or 2 HLA A or B antigens were accepted for the study. IA procedures were performed on alternate days until a twofold decrease in antibody titer had occurred (maximum: 6 procedures). Repeat procedures were initiated if the HLA antibody titer returned to its baseline value. Intravenous cyclophosphamide (CY) (10 mg/kg/day every 3 weeks) and methylprednisolone (MP) (0.5 mg/kg/day) were provided as adjunctive immunosuppression until transplantation. A total of 44 immunoadsorption procedures were performed (27 primary and 17 repeat) with treatment of 2.49 +/- 0.02 plasma volumes per session. Serum IgG concentration decreased 95 +/- 3% and PRA activity decreased 75 +/- 16% after the primary treatment course. Four patients received cadaveric grafts within 3.7 +/- 1.2 months following the last IA procedure. Three grafts are functioning at 1 year, 8 months, and 8 weeks posttransplant. The remaining graft demonstrated primary nonfunction. All four patients had a past positive crossmatch using pre-IA sera with their respective donors. Patients not transplanted exhibited rapid resynthesis of IgG and a return of the PRA towards baseline levels within a few weeks after IA. We conclude that IA can effectively remove HLA antibodies and expedite graft availability in highly sensitized patients