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Biomedical subjects

D Candinas

Publications and source records attributed to D Candinas.

At least 55 records · Page 3Linked to original sources
PubMed1996

Effect of repetitive high-dose treatment with soluble complement receptor type 1 and cobra venom factor on discordant xenograft survival.

Hyperacute xenograft rejection may be modified by the activation and depletion of complement (C) using cobra venom factor (CVF). This method of prolonging xenograft survival is toxic and associated with systemic inflammation, which may potentially contribute to the pathologic features of delayed xenograft rejection. Soluble complement receptor type 1 (sCR1) inhibits both the classical and alternative C pathways and thus limits the production of proinflammatory products such as the anaphylatoxins. Hence, we investigated the effects of various sCR1 and CVF regimens, and combinations thereof, in the discordant guinea pig-to-Lewis rat cardiac xenograft model. Mean graft survival time (MST) was significantly prolonged with repetitive dosing (MST=22 hr) or continuous infusion of sCR1 (MST=32 hr) as compared with unmodified controls (MST=15 min). However, sCR1 did not prevent intragraft deposition of C3 or neutrophil infiltration and resulted in only partial inhibition of C-mediated hemolytic activity in vitro. Grafts in rats treated with a single dose of CVF (MST=67 hr) or repetitive doses of CVF (MST=69 hr) survived significantly longer than those treated with sCR1 alone, and lacked C3 deposition or neutrophil accumulation. Sera from these animals were completely depleted of C-mediated hemolytic activity. Animals treated with a single dose of CVF, or sCRI plus a single dose of CVF (MST=64 hr), had similar xenograft survival times. However, immunohistologic studies showed that addition of sCR1 to a single dose of CVF resulted in decreased macrophage activation and reduced levels of cytokines (tumor necrosis factor-alpha and interleukin-1beta) within xenografts as compared with that in recipients treated with CVF alone. Such decreased macrophage activation may result from the binding of C4b by sCR1, since combination therapy was associated with decreased intragraft C4b as compared with either therapy alone. High doses of sCR1 were well tolerated by rats and significantly prolonged discordant xenograft survival (MST=32 hr), although not to the same extent as CVF. The modification of the intragraft immune responses seen with CVF/sCR1 combination therapy may augment further therapeutic manipulations to achieve discordant xenograft survival without the attendant toxicity associated with repeated CVF administration.

Animals↗
PubMed1996

Inhibition of platelet integrin GPIIbIIIa prolongs survival of discordant cardiac xenografts.

The integrin GPIIbIIIa is known to be crucial to the formation of platelet aggregates and potentiates adhesion to subendothelial matrices via fibrin(ogen), von Willebrand factor, and vitronectin. Given the demonstration by us and others of widespread platelet aggregation during xenograft rejection, we hypothesized that platelet thrombi might contribute to graft dysfunction during development of hyperacute rejection (HAR), as well as during what we have termed delayed xenograft rejection (DXR), e.g., as seen in complement-depleted rat recipients of guinea pig cardiac xenografts. We therefore tested the effects of a specific GPIIbIIIa antagonist (SDZ GPI 562) during xenograft rejection. Lewis rats received heterotopic guinea pig cardiac xenografts and were treated with GPI 562 alone (HAR model) or in combination with cobra venom factor (CVF) (DXR model). A high (0.5 mg/kg) or a low dose (0.1 mg/kg) of GPI 562 was administered perioperatively and then given twice daily in the same dose until rejection. CVF was given daily until rejection. Plasma drawn after the first dose of GPI 562 and at the time of rejection was tested for the ability to inhibit ADP-stimulated platelet aggregation in vitro. Rejected grafts were analyzed by immunohistology. Plasma from animals in the high-dose group completely inhibited platelet aggregation in vitro, whereas plasma from the low-dose group resulted in only partial inhibition. Similarly, whereas low-dose GPI 562 failed to prolong graft survival, high-dose GPI 562 showed a statistically significant increase in graft survival in both HAR and DXR groups. Immunohistologic studies of HAR showed little effect of GPI 562 on platelet aggregation or activation and no effect on fibrin deposition. However, the combination of high-dose GPI 562 and CVF resulted in a significant decrease in intragraft platelet aggregation, P-selectin expression, and leukocyte infiltration compared with CVF alone. In conclusion, GPIIbIIIa antagonist therapy can inhibit platelet aggregation in vitro and prolong xenograft survival. The diminution of intragraft platelet microthrombi formation and leukocyte infiltration suggests an important role for platelet-dependent mechanisms in leukocyte recruitment during DXR.

Animals↗
PubMed1996

Thrombin inhibition in an ex vivo model of porcine heart xenograft hyperacute rejection.

Prominent components of vascularized xenograft rejection such as platelet activation and microvascular thrombosis may be dependent upon thrombin generation in vivo. To study potential therapeutic benefits of a synthetic low-molecular-weight thrombin inhibitor, SDZ MTH 958, in hyperacute porcine heart rejection by human blood ex vivo, a working model of hyperacute rejection of porcine by fresh, heparinized (6 microM/ml) human blood with or without 1 microM SDZ MTH 958 was used. Thrombin-antithrombin complexes (TAT) and prothrombin fragment F1.2 levels as markers of thrombin activation were determined, and biopsies from rejected hearts were analyzed by immunohistopathology. Control porcine hearts (n=8) underwent a rapid and consistent decline in cardiac output, ceasing function by 60 min. Experimental cardiac output values of 14 ml/g (SEM 1.2) were significantly higher than seen in controls (5 ml/g SEM 0.6) after 5 min of cardiac work, and prolonged survival times up to 120 min were noted (P<0.05). Activity of SDZ MTH 958 was confirmed by functional assays throughout perfusion. Levels of TAT and F1.2 increased consistently in control samples when compared with plasma samples containing SDZ MTH 958. Immunohistopathological examination confirmed diminished fibrin deposition, reduced leukocyte adherence to endothelium, impaired diapedesis and less tissue necrosis in the hearts perfused with SDZ MTH 958. SDZ MTH 958, in this xenoperfusion model, prolonged survival, enhanced function of the explanted organ, and improved histological features at the time of rejection. Effective and specific antagonism of thrombin may be useful as an adjunct therapy to complement inhibition for xenograft rejection

Acute Disease↗
PubMed1996

Preoperative risk assessment in elective general surgery.

Despite improved surgical techniques there is still a risk of mortality in elective general surgery. In a prospective study preoperative data from 3250 patients were collected and compared with postoperative systemic complications, using univariate chi 2 analysis. Highly significant (P < 0.00001) variables were subjected to stepwise logistic regression analysis. The severity of operative procedure, higher American Society of Anesthesiologists (ASA) grade, symptoms of respiratory disease and malignancy were found to be significant risk factors predicting postoperative morbidity (P < 0.05). Using these four variables, a simple preoperative risk scoring system has been defined. Class A (up to 5 points) was defined as a low-risk group (systemic complication rate 5.0 per cent), class B (5-7 points) was intermediate risk (systemic complication rate 17.9 per cent) and class C (8-10 points) was high risk (systemic complication rate 33.3 per cent). Patients at high risk for perioperative and postoperative complications are more likely to be identified by this analysis than by using the ASA classification alone.

Elective Surgical Procedures↗
PubMed1996

A novel dextran 40-based preservation solution.

Although the University of Wisconsin (UW) solution has become the standard solution for the preservation of kidneys for transplantation, the importance of the colloid hydroxyethylstarch (HES), one of the key compounds of the UW solution, has been questioned repeatedly. It is now established that HES is not necessary for routine kidney preservation. However, colloids may still be advantageous in UW like solutions for the purpose of multiorgan procurements and the preservation of organs from marginal donors. It has been shown in various experimental models that dextran 40 may successfully substitute for HES. Dextran 40 is not only cheaper but also has a variety of biological effects that may be beneficial during the graft reperfusion phase. The aim of this clinical study was to examine the efficacy of a dextran 40-based preservation solution (Dex-PS) for its use in human kidney graft preservation and to compare the transplantation results with kidneys preserved with UW solution. A total of 87 kidneys were preserved with Dex-PS and matched with 87 kidneys preserved with UW solution. Both groups were comparable in terms of donor and recipient characteristics and both had a high proportion of kidneys from nonheart-beating donors. Patient survival and graft survival after 1 year were 95% and 86% for the Dex-PS group and 94% and 90% for the UW group, respectively (P = NS). Primary nonfunction, delayed graft function, postoperative need for dialysis, and follow-up of serum creatinine were statistically comparable between these two groups. We conclude that dextran 40 can safely replace HES in UW solution for the purpose of clinical kidney preservation. There were no statistically detectable differences in graft performance between the kidneys preserved with UW and those preserved with Dex-PS.

Adenosine↗
PubMed1996

Loss of rat glomerular ATP diphosphohydrolase activity during reperfusion injury is associated with oxidative stress reactions.

Endothelial cell ATP diphosphohydrolases or ATPDases degrade extracellular inflammatory mediators ATP and ADP, thus inhibiting the formation of platelet thrombi, but the modulation of these ecto-enzymes during vascular injury remains largely undetermined. Renal glomerular ATPDase levels were determined in the rat following ischemia-reperfusion or systemic complement activation, by direct biochemical methods and histochemistry. Ischemia followed by reperfusion times over 30 min were associated with loss of glomerular ATPDase activity. Cobra Venom Factor (CVF) inhibited ATPDase activity and potentiated the deleterious effects of reperfusion. Treatment with either soluble complement receptor type 1 (sCR1), an inhibitor of complement activation, or antioxidants prior to the ischemia-reperfusion was largely protective. Expression of rat glomerular ATPDase activity appears susceptible to the inflammatory injury associated with systemic complement activation and ischemia/reperfusion processes. Oxidative stress could, at least in part, result in the loss of ATPDase activity and thus thrombotic consequences of vascular injury.

Adenosine Diphosphate↗
PubMed1996

[Efficacy of organ exchange rules in a 7 million population nation].

The suitability of organ exchange rules were analysed retrospectively in a country with a population of 7 million not connected to international organ sharing organisations following the opening of a national coordination centre 2 years previously. The results demonstrate that the sharing rules work frictionless and efficiently, and that compulsory registration of every organ donor (cadaveric and living) guarantees entire transparency of organ source and exchange, therefore preventing any illegal activity. An unacceptably high mortality rate for patients awaiting a highly urgent organ (specifically heart or liver) shows that connection to an international organ exchange organisation is desirable in this respect.

Health Care Rationing↗
PubMed1996

Thirty-two years of renal transplantation in Zurich.

This overview of the last 3 decades of renal transplantation at our center depicts the development from the early phase of clinical transplantation to the development of a standardized multiorgan transplant program. Between 1964 and 1996, a total of 1,703 kidney transplants were performed at the University of Zurich Hospital in Switzerland. Due to a relatively active program in the early years of renal transplantation our data provide some useful information on the long-term results of renal transplantation. We observed a steady improvement in outcomes following transplantation during the first 2 decades of our program paralleled by an improvement in graft half-life. In the last decade, however, the demographic characteristics of our recipient population have changed gradually, leading to an increased proportion of diabetics and elderly patients. Thus, during the past decade, transplant outcomes, in terms of early graft and patient survival, have stagnated. The increased proportion of diabetics being accepted for transplantation has helped to establish simultaneous kidney and pancreas transplantation as a routine procedure, thereby offering these patients the prospect of long-term rehabilitation. In order to increase the number of available kidneys for transplantation we have adopted 2 strategies. First, we have successfully used donor kidneys from non-heart-beating donors. Results achieved with this method can be equivalent to transplantation of organs from heart-beating donors when certain criteria are respected. Second, we are increasingly performing kidney transplants from living-related donors and hope to further expand our activities in this direction in the future.

Adolescent↗
PubMed1995

Sex mismatch as a risk factor for chronic rejection of liver allografts.

Chronic irreversible rejection is a major cause of graft loss and retransplantation after orthotopic liver allotransplantation. To identify risk factors we retrospectively analysed 423 adult consecutive primary liver allograft recipients. The endpoint of the study was graft failure due to chronic rejection leading either to retransplantation or death. Chronic rejection developed in 22 (5.2%) patients. Pretransplant diagnosis of primary biliary cirrhosis or autoimmune hepatitis, recipient age less than 30 years, 1 or more episodes of acute cellular rejection, and transplantation of an organ from cytomegalovirus (CMV). IgG positive donor to an IgG negative recipient were identified as risk factors for chronic rejection. Transplantation of a liver from a male donor into a female recipient was also associated with an increased probability of chronic rejection. By logistic regression analysis, the probability of chronic rejection was predicted by: sex and cytomegalovirus match of donor and recipient, the presence of acute rejection, recipient age, transplantation for autoimmune hepatitis or primary biliary cirrhosis, and recipients receiving no azathioprine during the third month after transplantation. Sensitisation to antigens expressed by bile-duct epithelium as in primary biliary cirrhosis or exposure to donor bile-duct minor histocompatibility antigens, such as the male sex related H-Y antigen, may provide an explanation. More selective allocation of donor organs may allow a reduction in the incidence of ductopaenic rejection and graft loss.

ABO Blood-Group System↗
PubMed1995

The immunomodulatory effect of leflunomide in rat cardiac allotransplantation.

Leflunomide, a novel immunosuppressant, has been the subject of recent preclinical studies using solid organ allo- and xenotransplantation models. The objectives of this study were to evaluate the efficacy and toxicity of leflunomide using a rat cardiac allotransplant model in two different strain combinations (DA x PVG and DA x Lew). Leflunomide, at doses ranging between 5 and 30 mg/kg, prolonged graft survival in both strain combinations as effectively as CsA and FK506 1 mg/kg (P < 0.05). A dose-dependent effect was seen only after a longer treatment course. When ongoing rejection was intercepted early (postoperative day 2), 5 mg/kg was as effective as 1 mg/kg FK506 (P > 0.05) but was inferior to CsA in the DA x PVG combination (P < 0.05). However, in the DA x Lew combination, leflunomide was equally as efficacious as 15 mg/kg CsA and 1 mg/kg FK506 (P > 0.05). If ongoing rejection was treated at postoperative day 4, 10 mg/kg leflunomide was not only as effective as 15 mg/kg CsA and 1 mg/kg FK506, but demonstrated a dose-dependent increase in graft survival in both strain combinations. The toxicity of leflunomide at doses of especially 5-20 mg/kg was minimal in comparison to therapeutic doses of CsA and FK506 using body weight and biochemical parameters of renal and liver function. These in vivo observations convincingly show leflunomide to be equally as potent an immunosuppressant as CsA and FK506 in transplant rejection. It is also well tolerated on long-term administration and, by virtue of this fact, is a potentially suitable candidate for clinical transplantation.

Animals↗