Dagmar Ruffingshofer

Yale University, New Haven, CT, United States

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Publications (14)39.12 Total impact

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    ABSTRACT: Peritoneal dialysis is complicated by mesothelial cell injury due to low biocompatibility of peritoneal dialysis fluid (PDF). We have previously demonstrated that heat shock protein (HSP)-72 is potently up-regulated in response to PDF exposure of mesothelial cells in in vitro and in vivo models of peritoneal dialysis. The aim of this study was to evaluate potential cytoprotective effects of overexpression of HSP-72. Cytoprotection was assessed by comparing cellular viability between pretreated versus nonpretreated human mesothelial cells (Met 5a; ATCC, Manassas, VA, USA, and primary cell cultures) subjected to extended, usually lethal PDF exposure times (120 min, CAPD2; Fresenius, Bad Homburg, Germany). Pretreatment was performed with exposure to PDF (60 min, CAPD2; Fresenius) or heat (15 min, 41.5 degrees C), and by transient transfection with HSP-72. When mesothelial cells were pretreated by nonlethal exposure to PDF or heat, HSP-72 was markedly up-regulated (>5-fold, P < 0.01). Pretreated human mesothelial cells were significantly protected against subsequent "lethal" exposures to PDF, as assessed by dye exclusion (>50% reduction, P < 0.05) and lactate dehydrogenase (LDH) release (>30% reduction, P < 0.05). Comparable cytoprotection (50% reduction by dye exclusion) was indicated by overexpression of HSP-72 in cultered human mesothelial cells (>5-fold) after transient transfection with HSP-72. This cytoprotection was confirmed at a cellular basis by double staining techniques with HSP-72 and ApopTag (apoptosis detection kit). Our study therefore shows that the mesothelial stress response confers cytoprotection in experimental peritoneal dialysis, mediated by the induction of HSP-72, and that the stimulus of the pretreatment does not have to be identical to the subsequent injury. These data offer the basis for an attractive novel therapeutic approach against PDF toxicity.
    Kidney International 12/2004; 66(6):2300-7. · 8.52 Impact Factor
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    ABSTRACT: Currently, there are no data available on long-term effects of angiotensin-converting enzyme inhibitors (ACE-I) on graft function in children after renal transplantation. We therefore analyzed all children who were transplanted at our institution between 1989 and 1998 and followed for at least 2 years. Those treated with ACE-I, mainly because of failure of other antihypertensive medications, were compared to those without ACE-I. The ACE-I-treated children ( n=19) showed significantly better blood pressure control during the 1st year of follow-up ( p<0.05). In children with chronic allograft dysfunction ( n=8), treatment with ACE-I stabilized graft function, with improvement in creatinine clearance in 50% ( p<0.01). Serum potassium and hemoglobin levels remained stable. One patient discontinued ACE-I because of renal artery stenosis. Taken together, ACE-I were effective and safe in the treatment of hypertension in children following renal transplantation. Children with chronic allograft dysfunction experienced a stabilizing effect on graft function.
    Pediatric Nephrology 03/2004; 19(2):222-6. · 2.94 Impact Factor
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    ABSTRACT: Urinary tract infection is a frequent bacterial complication after renal transplantation in adults and children, however there are only very limited data on children beyond the early post-transplant period. In this study we investigated urinary tract infections in pediatric outpatients who had received transplants more than six months previously. Incidence, risk factors and impact on short-term graft function were analyzed. 47 children who had received a total of 58 allografts were analyzed between 1997 and 2000. At the time of analysis they had had their transplants for an average of 3.5 years (range 0.5-9.4). Urinary tract infection was defined as the presence of both significant bacteriuria (> 10(5) CFU/ml) and symptoms. Of the 47 patients, 15 (32%) had from 1 to 7 urinary tract infections each. In total 35 infections were recorded. Median age at urinary tract infection was 5.5 years (range 1.8-24.2). Gender, donor source, immunosuppression and underlying disease (urologic vs non-urologic) did not influence the incidence of urinary tract infection. Creatinine but not C-reactive protein rose significantly during the infection. Our data suggest that urinary tract infection remains a frequent but mostly benign complication in the pediatric transplant population, even beyond the early post-transplant period. More extended studies are needed to assess the long-term effects on graft function.
    Wiener klinische Wochenschrift 06/2003; 115(11):385-8. · 0.81 Impact Factor
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    ABSTRACT: Renal ischemia not only causes injury but also induces repair mechanisms, such as the cellular induction of the 72-kilodalton heat shock protein HSP-72. The aim of this study was to determine whether HSP-72 is excreted in urine after ischemic renal injury. The first urine of six pediatric allograft recipients was examined for proteinuria and urinary HSP-72 excretion. Sprague-Dawley rats were treated with renal ischemia or hyperthermia and renal cortex and urinary HSP-72 levels were determined. HSP-72 was excreted in the first urine of renal allografts. In rats, renal HSP-72 was induced both by renal ischemia or hyperthermia. However, only renal ischemia resulted in urinary excretion of HSP-72. Urinary excretion of HSP-72 indicates an increased renal stress response and loss of tubular cell integrity after clinical and experimental renal ischemia.
    Pediatric Nephrology 03/2003; 18(2):97-9. · 2.94 Impact Factor
  • Wiener Klinische Wochenschrift - WIEN KLIN WOCHENSCHR. 01/2003; 115(11):385-388.
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    ABSTRACT: Recent studies have suggested that heat shock proteins (HSPs) are involved in the restoration of the cytoskeletal anchorage of Na,K-ATPase after renal ischemia. To determine their role in ischemic conditioning, we investigated whether cytoskeletal Na,K-ATPase was stabilized during repeat ischemia concurrent with 25-kD and 70-kD HSPs induction. Anesthetized rats either underwent single unilateral renal ischemia or were conditioned with bilateral renal ischemia and, after 18 h of reflow, were then subjected to repeat unilateral renal ischemia. Renal cortex was harvested, and effects of single versus repeat ischemia were compared by Triton X-100 extraction, by immunohistochemistry, and by an in vitro assay of Na,K-ATPase association with isolated cytoskeletal fractions. In contrast to single ischemia, repeat ischemia did not result in increased Triton X-100 extractability of Na,K-ATPase. Levels of 25-kD and 70-kD HSPs were significantly induced by ischemic conditioning and redistributed into the cytoskeletal fraction after single and repeat ischemia. Immunohistochemistry also showed significant disruption of Na,K-ATPase within proximal tubules only after a single episode of ischemia, whereas repeat ischemia did not alter the pattern of restored Na,K-ATPase localization in conditioned renal cortex. The preserved association of Na,K-ATPase with the cytoskeletal fraction of conditioned renal cortex was effectively abolished in vitro by addition of antibodies against 25-kD or 70-kD HSP. These results suggest that 25-kD and 70-kD HSPs induced by ischemic conditioning stabilize the cytoskeletal anchorage of Na,K-ATPase during repeat renal ischemia.
    Pediatric Research 07/2002; 51(6):722-7. · 2.67 Impact Factor
  • Monatsschrift Kinderheilkunde - MONATSSCHR KINDERHEILK. 01/2002; 150(8):996-997.
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    ABSTRACT: Low biocompatibility of peritoneal dialysis fluids (PDF) contributes to mesothelial injury. We investigated whether the heat shock proteins (HSP)-27, HSP-72, and HSP-90 are differentially induced upon exposure of mesothelial cells to PDF and whether this was affected by selective modulation of the physicochemical properties of PDF. Human mesothelial cells (Met5A and primary human mesothelial cells) were exposed to acidic lactate and glucose-monomer based PDF (CAPD2 and CAPD3), to control culture media, or to a neutral lactate and glucose-monomer-based PDF with reduced levels of glucose degradation products (BALANCE). Expression of HSP-27, HSP-72, and HSP-90 and cellular distribution of HSP-72 were assessed by Western blotting and immunocytochemistry. Mesothelial cells exhibited strong constitutive expression of HSP-27 and to a lesser extent HSP-72 and HSP-90. Exposure of the cells to CAPD2 and CAPD3 resulted in strong up-regulation of HSP-72. HSP-27 levels were slightly increased, but HSP-90 levels were unchanged upon exposure to CAPD2 or CAPD3. In contrast, exposure of the cells to BALANCE did not affect HSP-27 or HSP-72 expression. The acidic pH and glucose degradation products were found to be principal in mediating increased HSP-72 expression upon exposure to PDF. Analysis of HSP expression represents a novel tool to assess biocompatibility of PDF. Among the HSP investigated, HSP-72 is the most predictive and accurate parameter to assess mesothelial cell injury in the early phase of exposure to PDF.
    Kidney International 12/2001; · 8.52 Impact Factor
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    ABSTRACT: Previous data suggested that outcome in small children with cadaveric renal transplantation might be improved with sequential therapy. This protocol combines augmented immunosuppression [by including antibody induction (ATG)] with avoidance of nephrotoxic medication in the immediate postoperative phase (by delayed start of cyclosporin therapy). In this report, we describe effects of this approach in 12 consecutively transplanted small children of less than 5 years of age (mean 3.2 years) who received a cadaveric renal graft at our institution between 1991 and 1998. Up to 1996 triple therapy (prednisolone, azathioprine, cyclosporin) and since 1997 sequential therapy (prednisolone, azathioprine, ATG until serum creatinine <2 mg/dl, then cyclosporin) was used for immunosuppression. Five children had delayed graft function (45.4%), all of whom were treated with triple therapy including cyclosporin from the very beginning, whereas children treated by the sequential protocol gained immediate graft function (P<0.05). There was no statistical difference between the two protocols concerning frequency or severity of rejections (67% vs. 60%, all steroid responsive), difference in the incidence of either bacterial or viral infections, or between the incidence of hypertension. Although not reaching statistical significance, 1-year graft survival rates also increased from 60% for triple therapy to 80% for sequential therapy. In conclusion, our findings confirm previous studies showing that outcome in small children undergoing renal transplantation may be improved by specially tailored treatment protocols such as sequential therapy.
    Pediatric Nephrology 09/2001; 16(8):613-7. · 2.94 Impact Factor
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    ABSTRACT: Research has provided new and potent immunosuppressants which can potentially stop ongoing rejection. Subclinical rejection is a particular problem in the pediatric age group and early identification of children at risk is of the utmost importance. Neopterin has been previously shown to be a non-specific but sensitive marker for immunologic activity. In this study we hypothesized that low serum neopterin in the 1st year after transplantation predicts a low risk of chronic rejection. We retrospectively analyzed serial neopterin data obtained beyond the early postoperative period in 21 children and correlated the peak and average with glomerular filtration rate (GFR) loss during the subsequent years (P = 0.63, NS, r = 0.10). Our results show that serum neopterin did not differ between the majority of children who developed chronic transplant dysfunction and children with stable transplant function beyond the early post-transplant period. Thus serum neopterin failed to delineate a low-risk population who might be spared more invasive diagnostic procedures such as protocol biopsy.
    Pediatric Nephrology 02/2001; 16(1):11-4. · 2.94 Impact Factor
  • Monatsschrift Kinderheilkunde 01/2001; 149(1):60-61. · 0.19 Impact Factor
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    Peritoneal dialysis international: journal of the International Society for Peritoneal Dialysis 23(1):74-7. · 2.21 Impact Factor
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    ABSTRACT: A peritoneal dialysis (PD) catheter is in place at the time of kidney transplantation in children receiving PD. Removal of the catheter eliminates the risk of catheter-related infections. However, the patient benefits from leaving the catheter in place if dialysis is necessary posttransplantation. There is currently no consensus on the proper timing of PD catheter removal after kidney transplantation in children. To identify the risks and benefits of an in-dwelling PD catheter after renal transplantation in children. Retrospective single-center study of infectious complications and posttransplantation PD catheter use in 31 renal transplantations in 26 children. Peritoneal dialysis catheters were used postoperatively in 13 of the 31 transplantations. In 12 instances the catheter was needed during the first month after transplantation, and 2 of the patients involved did not have a catheter in place when needed. Six catheter-related infections occurred in 5 patients posttransplantation, with only 1 infection taking place within 1 month after transplantation. Our data suggest that the need for catheter use occurs predominantly during the first month, while infectious complications usually happen later. This strongly suggests that PD catheters should not be removed until approximately 1 month after kidney transplantation.
    Peritoneal dialysis international: journal of the International Society for Peritoneal Dialysis 21(5):467-70. · 2.21 Impact Factor
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    Peritoneal dialysis international: journal of the International Society for Peritoneal Dialysis 23(5):499-501. · 2.21 Impact Factor