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D Abendroth

Publications and source records attributed to D Abendroth.

At least 19 recordsLinked to original sources
PubMed2006

Renal ischemia/reperfusion and its influence on telomere length and expression of cell cycle regulatory genes.

The aim of the study was to evaluate the influence of renal ischemia/reperfusion (I/R) on telomere (T) length and tissue expression of cyclin-dependent kinase inhibitor genes (CDKIG). An experimental model of ex-vivo hemoperfusion of the kidney was used as described earlier. Telomere length measurement and expression of p16((INK4a)), p21((WAF1/CIP1)) and p27((Kip1)) CDKIGs was studied immunohistochemically in kidney biopsy samples at baseline and different time points after the reperfusion. The mean T length decreased after reperfusion from 5.56+/-0.60 kbp to 5.46+/-0.36 kbp (p=NS). All 3 genes were up-regulated in kidney tissue however their activation was different in diverse renal cells according to the reperfusion time. Expression of p16 significantly increased in tubular cells at 180 min of reperfusion as compared with the baseline. Activation of the p27 in glomerular cells was significantly higher at 60, 120 and 180 min of reperfusion as compared with 0 and 15 min. The marker started increasing in tubular cells at 15 min and was elevated at every time point afterwards. p21 was significantly over-expressed in all renal cells after the reperfusion. The current study shows that renal I/R causes T shortening and over-expression of CDKIGs indicating on substantial DNA damage and/or accelerated tissue senescence. The tissue expression of CDKIGs is positively related with the reperfusion time.

Animals↗
PubMed2005

Cyclosporine-based immunosuppressive strategies for kidney recipients: interim analysis of German data from the Multinational Observational Study (MOST).

INTRODUCTION: We collected data from kidney recipients with a functioning graft at German kidney transplant centers in order to analyze the efficacy of various cyclosporine (CsA)-based immunosuppressive strategies, the effects of different perioperative and maintenance regimens, and the impact of donor source on clinical outcome. METHODS: As part of the ongoing prospective Multinational Observational Study in Transplantation (MOST), data for both prospective and retrospective analysis were collected from kidney recipients over 18 years bearing a functioning graft that was transplanted at 21 German kidney transplant centers between 1987 and 2002. RESULTS: Data from 1223 renal graft recipients, including their CsA-based immunosuppressive regimens, were stratified as: 402 de novo patients (median 6.8 months posttransplant) and 821 patients on maintenance therapy (median 71 months posttransplant). Triple regimens with CsA + mycophenolate mofetil (MMF) + steroids (Ste) currently comprise the major perioperative immunosuppressive strategies in Germany (de novo 65%). IL-2 receptor antagonist (IL-2Ra) use is increasing (de novo 18%, maintenance 4%), while mono and dual regimen use de novo is declining (de novo 4%, maintenance 20%). Among 689 patients transplanted between 1987 and 2002 with outcome data, the mean incidence of acute rejection during the first posttransplant year was 21.6%. Rejection rates on initial therapy with CsA + MMF + Ste +/- antibodies (n = 517) averaged 17.8%. CONCLUSIONS: Between 1987 and 2002, CsA-based immunosuppression combined with MMF and Ste became the most commonly used strategy for both initial and maintenance therapy after kidney transplantation in Germany, yielding the low acute rejection rates particularly when combined with IL-2Ra.

Adult↗
PubMed2005

Cyclosporine C2 levels in de novo renal allograft recipients: a German multicenter prospective observational study.

This ongoing multicenter prospective observational study was undertaken in de novo renal allograft recipients managed with cyclosporine (CsA) trough (C0) and 2-hour postdose (C2) level monitoring at defined times so as to assess the risk for an acute rejection episode or allograft dysfunction. The renal transplant recipients (n = 159) were enrolled at 11 German centers. The 6-month posttransplant data from 138 patients were evaluable for this interim analysis. Mean C2 levels (ng/mL), which were measured by liquid chromatography-tandem mass spectrometry at a central laboratory, were: days 3 to 5: 873.1 +/- 391.9; days 7 to 10: 939.1 +/- 422.8; days 14 to 28: 1116.3 +/- 497.6; 3 months: 905.0 +/- 316.8; and after 6 months: 787.0 +/- 276.5. To identify patients at higher risk for acute rejection or allograft dysfunction, we calculated the relative CsA absorption capacity (C2 [ng/mL]/morning dose [mg/kg]; CsA-Abs), yielding mean values on days 3 to 5: 284.4 +/- 115.1; days 7 to 10: 306.7 +/- 134.8; days 14 to 28: 382.5 +/- 164.7; month 3: 501.5 +/- 168.8; month 6: 512.7 +/- 176.5. Three groups were distinguished by CsA-Abs at days 7 to 10: low absorbers (CsA-Abs < 200), normal absorbers (CsA-Abs 200 to 350), and high absorbers (CsA-Abs > 350). A between-group comparison of absorption level at 6 months posttransplant revealed the incidences of biopsy-proven acute rejection and Cockcroft-Gault formula-based mean glomerular filtration rates of 23.8% and 54.7 +/- 19.0 mL/min, 22.6% and 59.5 +/- 20.7 mL/min, and 17.6% and 67.7 +/- 23.5, respectively. In conclusion, mean C2 levels >1000 ng/mL are attained within 2 to 4 weeks, with CsA-Abs increasing continuously over the first 6 posttransplant months. High CsA absorbers show a propensity toward good allograft function and lower acute rejection rates at 6 months after renal transplantation.

Area Under Curve↗
PubMed2004

Experience with therapeutic drug monitoring of cyclosporine.

During the past 20 years, cyclosporine (CsA) has become the main part of immunosuppressive protocols. Its impact to improve the quality and quantity of transplantation surgery has been enormous. Immunosuppression in allograft recipients 10 years after renal transplantation CsA continued to demonstrate benefits on graft survival without evidence of long-term morbidity. The pharmacokinetic properties of CsA show wide interpatient variation. After being subject of intense investigation for more than 20 years, it only recently has the full potential of the drug been realized, primarily due to two advances: first, the development of a microemulsified formulation, (Neoral), that improves drug delivery; second, substantial improvements in CsA monitoring. Sparse-sampling algorithms were developed specifically to predict AUCs. We prospectively investigated the practicality, intrapatient variability, and impact on the outcomes of toxicity and rejection episodes using an algorithm. Rejection episodes were diminished by 43.5% in the first 3 months compared to the results in the previous 3 years. Furthermore, the relation of the trough versus C2 concentrations performed at day 3 to 5 and 10 to 12 predicted the probability of an acute rejection episode. Using a truncated AUC to identify patients at risk for rejection episodes early provides optimal and individualized immunosuppression. This pharmacokinetic rationale has now eventuated in an international consensus statement that represents a further step toward optimal immunosuppression.

Area Under Curve↗
PubMed2001

Urinary endotoxin excretion and urinary tract infection following kidney transplantation.

Following kidney transplantation, urine endotoxin levels were measured among 44 patients and compared to bacterial cultures. Urine samples were collected either via transurethral catheters or - after removal of the catheter on postoperative day 4 - by midstream void. In a control group of ten healthy volunteers, urine endotoxin levels were measured daily for 10 days. Urinary endotoxin concentration was measured by means of a chromogenically modified Limulus amebocyte lysate (LAL) test. The levels among patients with positive bacteriological findings (n = 21) were always elevated ( > 0.7 EU/ml). Furthermore, there was a marked, statistically significant difference in endotoxin values between samples with bacterial growth and samples with fungal or without any growth (P < 0.001). All 21 of the 44 patients with urinary tract infection (UTI) were endotoxin-positive. Seven more patients who received antibiotics had elevated urinary endotoxin levels, but no bacterial growth in the urine culture. No bacterial infection or significant urinary endotoxin was found in the control group. In summary, the detection of urinary endotoxin in samples obtained by either suprapubic/transurethral catheters or midstream void is an early, sensitive, and specific means of diagnosis that can be carried out even during antibiotic treatment.

Bacteria↗
PubMed2001

Ex-vivo hemoperfusion (eHPS) of pig-lungs with whole human blood: effects of complement inhibition with a soluble C1-esterase-inhibitor.

OBJECTIVES: Xenotransplantation could be a future alternative to allotransplantation due to increasing organ shortage. Complement activation plays a major role in hyperacute rejection (HAR) in pig-to-human combinations. We developed an ex-vivo hemoperfusion (EHP) system to investigate pathophysiology of HAR in the lung. After standardizing the model, the effect of a soluble complement inhibitor (C1-INH, Berinert) was investigated. METHODS: Pig lungs were harvested following cold perfusion with Celsior preservation solution. EHP was performed using fresh heparinized human blood plus C1-INH (n = 6) or heparinized human blood as control (n = 4). Bloodgas analyses (BGA), pulmonalarterial pressure (PAP) were monitored. P-selectin and L-selectin were measured. Tissue samples were taken and microscopic changes evaluated. RESULTS: BGA, PAP, macroscopic and microscopic changes in the control group showed HAR, while the C1-INH group showed significantly longer function. Leucocytes and platelets were markedly activated in the control, whereas in the treated group L-selectin and P-selectin values indicated lower activation. HE stainings showed maintained lung architecture after perfusion of pig-lungs with human blood plus C1-INH. Immunohistochemistry showed less C1q, C3, C5b-9 activation in the C1-INH group. CONCLUSIONS: Investigation of interaction of human blood with pig lung endothelium could be done in this model. C1-INH attenuates HAR in a pig-to-human lung transplantation model by decreasing the activation of adhesion molecules. C1-INH could play a role in induction therapy of future lung xenotransplantation.

Animals↗
PubMed2000

Development and application of a high-performance liquid chromatography-based assay for determination of the activity of inosine 5'-monophosphate dehydrogenase in whole blood and isolated mononuclear cells.

With the objective of pharmacodynamic monitoring of the immunosuppressive efficacy of mycophenolate mofetil (MMF) (CellCept, Hoffman-LaRoche, Grenzach-Wyhlen, Germany), a method for determination of the inosine monophosphate dehydrogenase (IMPDH) activity in whole blood cell (WBC) lysates and mononuclear cells (MNCs) was developed. The assay is based on the incubation of WBC lysates or lysed MNCs in the presence of supplemented inosine 5'-monophosphate (IMP) and nicotimamide adenine dinucleotide (NAD). The formation of xanthosine 5'-monophosphate (XMP) was determined by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. The analytical method was validated, and the obtained data demonstrated that the amount of XMP in WBC and MNC lysates can be reliably determined by this method. Under assay conditions the rate of XMP formation remained constant within the incubation period of 60 minutes and a quantification of product formation at 30 and 60 minutes proved to be sufficient to reliably characterize the IMPDH activity. Applications of this assay with whole blood indicated extremely high IMPDH-activities in samples from patients with renal transplant receiving MMF. IMPDH monitoring within 10 hours after administration of the morning dose demonstrated a marked enzyme inhibition between 2 hours and 3 hours postdosing, but the activities returned to predose levels within one dose interval. The analysis of isolated cell fractions indicated that the IMPDH-activity is predominantly located in erythrocytes. The contribution of MNCs to the whole blood activity remained below 10%. In order to simulate the in vivo exposure of MNCs to mycophenolic acid, an "erythrocyte- and platelet-free" whole blood was reconstituted by resuspension of isolated MNCs with plasma. This strategy allowed for the reliable measurement of IMPDH activity in the target cells of immunosuppression.

Chromatography, High Pressure Liquid↗
PubMed1999

Screening for basiliximab exposure-response relationships in renal allotransplantation.

The immunosuppressant basiliximab--a chimeric monoclonal antibody specific to the interleukin-2 receptor on activated T-lymphocytes--significantly reduces the incidence of acute cellular rejection following renal transplantation. Screening for exposure-response relationships was performed within a randomized, blinded, placebo-controlled efficacy trial in which patients received 40 mg basiliximab (20 mg on days 0 and 4) by intravenous infusion in addition to cyclosporine and corticosteroids. In a subset of patients, serum samples were collected pre-transplant and once in weeks 2, 3 and 4 for determination of basiliximab concentrations. A population pharmacostatistical model was used to derive individual empirical Bayes estimates of each patient's pharmacokinetic parameters. Biopsy-confirmed acute rejection episodes were recorded to month 6 post-transplant. Forty basiliximab-treated patients were evaluated, 30 men and 10 women, aged 48 +/- 12 yr (range, 24-73) and weighing 72.4 +/- 12.9 kg (range, 52.5-107.5). The basiliximab distribution volume was 7.5 +/- 1.7 L, the half-life 7.5 +/- 2.5 d and the clearance 33 +/- 12 mL/h. There was no clinically relevant influence of weight, age, or gender on basiliximab disposition. Receptor-saturating serum basiliximab concentrations (> 0.2 microgram/mL) were maintained for 41 +/- 23 d. Twenty-five patients remained rejection-free over the 6-month observation period, while a total of 26 biopsy-confirmed acute rejection episodes occurred in the remaining 14 patients. Of these episodes, 12 occurred during receptor blockade. No apparent relationship to basiliximab concentration on the day of onset was observed range, 0.1-9.0 microgram/mL) nor did the time of suppression offset represent a period of increased risk for rejection episodes. Fourteen rejection episodes occurred after basiliximab had cleared from the serum. The durations of receptor suppression preceding these events did not differ compared with those in patients who remained rejection-free: 32 +/- 11 versus 45 +/- 26 d, respectively (p = 0.1269). Given the durations of receptor saturation achieved with the chosen basiliximab regimen, this screen for exposure-response relationships did not identify the duration of receptor saturation in peripheral blood as a predictive factor for acute rejection episodes. Further exploration for exposure-effect relationships in a larger population is warranted.

Adult↗
PubMed1999

[Human xenogenic kidney transplantation from the clinical viewpoint].

Pig-to-primate transplantations of hDAF-transgenic kidneys achieved survival times of up to 70 days. Pilot projects for clinical kidney xenotransplantation seem to be possible in the near future. The problems of hyperacute rejection seem to be solved. Delayed xenograft rejection remains a serious problem. Further medical, ethical and practical issues have to be solved, before Phase-I-studies can be anticipated. In contrast to other organs, kidney xenotransplantation is associated with low operative risk. Xenotransplant dysfunction or rejection could be treated with conventional hemodialysis.

Animals↗
PubMed1998

Cardiovascular risk profile after simultaneous pancreas and kidney transplantation.

The positive influence of simultaneous pancreas and kidney transplantation (PKT) on the development of diabetic microvascular lesions is well established. On the other hand, little is known on its impact on diabetic macrovascular disease, which is still the major cause of death in diabetes, including patients after PKT. In order to evaluate the influence of PKT on the cardiovascular risk profile, we performed a cross-sectional study on 55 patients. Special attention was given to the hemorheological parameters fibrinogen and plasma viscosity, two important cardiovascular risk factors, which so far have found no attention in the field of PKT research. The patients were subdivided into three groups according to their graft function: group 1-26 patients after successful PKT (no insulin dependency, serum creatinine <2 mg%), group 2-23 patients after PKT and rejection of the pancreas graft (insulin dependency, serum creatinine <2 mg%), group 3-6 patients after PKT with pancreas rejection and renal insufficiency (insulin dependency, serum creatinine >2 mg%, no dialysis). There was a high prevalence of arterial hypertension after PKT (group 1: 65%, group 2: 70%, group 3: 100%). Serum lipids were in the normal range as long as renal function was intact. In renal insufficiency, however, LDL-cholesterol and triglycerides were significantly elevated (p < 0.05). Fibrinogen was significantly raised after PKT (p < 0.001), as was plasma viscosity when the pancreas graft was rejected (p < 0.02). There was a tendency towards elevated fibrinogen levels with decreasing graft function. In conclusion, a number of cardiovascular risk factors were identified in patients after PKT, predominantly arterial hypertension and impaired hemorheology, with elevated fibrinogen levels and plasma viscosity. There is a further enhancement with decreasing graft function.

Adult↗
PubMed1998

[Prevention of ischemia before cold ischemia by pharmcologic donor conditioning--experimental findings].

The loop-diuretic piretanide was used to study the influence of pharmacological donor pretreatment on immediate postischemic function in a pig model of kidney transplantation based on the results of a clinical pilot study [4]. Following laparotomy, both kidneys were flushed via a transaortal catheter with Eurocollins-solution and surgically removed. A cold ischemic period of 1 or 24 h was chosen. After that period, kidneys were reperfused with intraoperatively drawn heparinized blood for one hour. We used a special instrument for hemoperfusion of isolated organs which allows perfusion for several hours under steady-state conditions. Four groups were formed: Control and piretanide, 1 or 24 h cold ischemia. The perfusion of piretanide-treated organs resulted in a lower perfusion-resistance, calculated as pressure/flow-ratio or as pressure/glomerular filtrationratio. The flow in the pretreated group was higher, thus excluding a higher shunt-volume. In parallel, oxygen consumption as a parameter of postischemic function start and creatinine clearance were higher in the piretanide treated groups. The experiments demonstrate a superior postischemic function of pretreated kidneys in comparison to control organs after 1 and 24 hours of cold ischemia in this model.

Animals↗
PubMed1998

[Transgenic swine as potential organ donors? Results of the ex-vivo hemoperfusion hDAF transgenic kidney with human blood].

Kidney xenotransplantation is not yet a realistic clinical treatment modality. However, during the last decades more than 30 kidneys from other species have been transplanted into humans; some of the kidneys sustained some function up to 60 days. Recent progress in genetic engineering has raised the possibility to create large transgenic animals which express human complement regulatory proteins (CRP). Since early complement activation is believed to be the main triggering event for xenograft destruction, complement regulation by species-specific CRP should avoid hyperacute rejection in transspecies transplantation. The perfusion of hDAF-transgenic pig kidneys with human blood was not associated with the morphological signs of hyperacute rejection when compared to non-transgenic control organs. Specific immunohistology could demonstrate that the transgene was sufficient to regulate complement activation beyond C3 despite the endothelial deposition of xenoantibodies. In the future, these organs could be further optimized and ultimately tested in a clinical pilot protocol under appropriate immunosuppression.

Animals↗
PubMed1997

Immunopathological observations after xenogeneic liver perfusions using donor pigs transgenic for human decay-accelerating factor.

BACKGROUND: Donor pigs transgenic for human decay-accelerating factor (hDAF) were used in a xenogeneic ex vivo liver perfusion model to study the effect of this modification on the development of hyperacute rejection. METHODS: Three transgenic pigs were hepatectomized after hypothermic portal and transaortal gravity perfusion. Livers from six nontransgenic pigs served as controls. All livers were perfused for 3 hr with human blood from two donors diluted to a hematocrit of 30%. Particular importance was placed on the use of an optimal perfusion technique incorporating the floating suspension of the organs in a waterbath and intermittent external pressurization. Biochemical, physiological, and immunological parameters were assessed. Tissue specimens taken before and after perfusion were analyzed using routine histology, electron microscopy, and immunohistology. RESULTS: Complement activation was more pronounced in the control group. AP50 and CH50 values fell to about 60% of the initial levels in control experiments, whereas they remained at 80% of the initial levels during perfusion of hDAF livers. After 180 min, pig tumor necrosis factor alpha levels were 7862+/-1645 pg/ml for unmodified livers and 2830+/-734 pg/ml in the hDAF group. Human tumor necrosis factor alpha levels were similar in both groups. Control livers showed marked morphological alterations and distinct deposition of complement factors, whereas livers expressing hDAF showed no signs of hepatocellular necrosis and almost no complement deposition beyond C3 activation. CONCLUSIONS: These results confirm that the transgenic expression of the human complement regulatory protein hDAF reduces complement activation and prevents hyperacute rejection in a xenogeneic liver perfusion model over the 3-hr evaluation period used in this study.

Animals↗
PubMed1997

Morphology of hDAF (CD55) transgenic pig kidneys following ex-vivo hemoperfusion with human blood.

Discordant xenotransplantation of pig kidneys into man may be possible in the future using transgenic organs which regulate complement activity. It was the aim of this experimental study to characterize morphologic alterations of organs transgenic for human decay accelerating factor (hDAF/CD55) perfused with human blood since no data on function of these organs after exposure to human blood are available. An ex-vivo system was developed that allows computer driven pressure-controlled perfusion of kidneys including a separate cartridge oxygenator circuit. Following cold ischemia time of 1-4 hr, 8 kidneys from heterozygote transgenic animals (TG) and 9 control kidneys (C) were perfused with 500 ml freshly drawn heparinized human blood at physiological conditions. A histologic grading system from 0 to +4 was used to describe the histologic findings. Using a mouse antihuman DAF moAB, hDAF was stained on all TG kidneys both on glomerular capillary (4+) and vascular endothelium (2+), but there was no detectable hDAF-expression on controls. No difference in xenoantibody deposition on vascular endothelium was seen between both groups. There was comparable staining for complement fraction C4 in both groups, but significant reduction of C3 and C9 staining on glomerular and vascular endothelium in TG. P-selectin was expressed on a higher level in C (+4) compared with TG (+2). Neutrophil extravasation [NP-57 elastase] was higher in C (80.2 vs. 32.2 C vs. TG [values as n/high power field]). Tubular epithelial cell swelling and mild necrosis was paralleled by glomerular hemorrhage and platelet microthrombus formation in both groups as seen in transmission electron microscopy. The observed results allow the conclusion that hDAF expression on transgenic pig kidneys was sufficient to inhibit complement activation beyond C3 during xenoperfusion with human blood despite xenoantibody deposition.

Animals↗