Living donor kidney transplantation after desensitization in cross-match positive high sensitized patients

BACKGROUND

We aimed to evaluate the long-term results of the patients who had positive cross-match (XM) test results and underwent living donor renal transplantation after desensitization with different combinations of intravenous immunoglobulin (IVIG), plasmapheresis (PP), and rituximab.

MATERIAL AND METHODS

Forty-nine patients who were positive for complement-dependent cytotoxicity (CDC), flow cytometric (FC), and Luminex-XM test were included in the study. Renal transplantation was performed in 16 patients who had XM (-) test after desensitization with different combinations of IVIG (n =15), PP (n =13), and rituximab (n =10). Anti-human leukocyte antigens (HLA) antibodies (anti-HLA Abs) were detected by the Luminex single antigen bead assay. Anti-thymocyte globulin was used for induction, and tacrolimus, mycophenolic acid, and prednisolone were used for maintenance therapy. Also, we evaluated the relationship between different donor-specific anti-HLA Abs and the parameters mentioned above.

RESULTS

Antibody-mediated rejection (AMR) and acute T cell-mediated rejection rates were 18.8 % and 6.3 %, respectively. Graft survival rates at the first, third, and fifth years post-transplantation were 93.8 %, 85.2 %, and 85.2 %, respectively, and the patients' survival rates were found to be 100 %. Serum creatinine level and glomerular filtration rate were 1.5 ± 1.2 mg/dl and 69.9 ± 30.4 ml/min, respectively. The mean follow-up time was 39 ± 24 months.

CONCLUSIONS

Our study showed that kidney transplantation could be performed by effective desensitization in XM test positive patients. It was also shown that donor-specific anti-HLA DQ Ab and non-HLA Ab determination might be useful in diagnosing patients with positive cross-test and/or diagnosis of AMR. HIPPOKRATIA 2020, 24(4): 182-190.

Expression Profile of MicroRNA Biogenesis Components in Renal Transplant Patients

BACKGROUND

MicroRNAs (miRNAs) and the miRNA biogenesis components are potential biomarkers of some prevalent diseases, such as cancer and diabetes. In light of this information, we aimed to investigate the expression profiles of miRNA biogenesis components in renal transplant patients before and after transplantation and how these profiles are related to immunosuppressive treatment and clinical outcomes of these patients.

METHODS

In this study, gene and protein expression profiles of Dicer, Drosha, Pasha (DGCR8), Exportin5 (XPO5), and Argonaute2 (AGO2) in peripheral blood mononuclear cells (PBMCs) of renal transplant patients were evaluated by means of real-time quantitative polymerase chain reaction and Western blot methods before and 3 months after transplantation. Patients who had transplant procedures for the first time were included in the study.

RESULTS

Gene expressions were significantly reduced after transplantation. The reduction rate of expressions in 1 patient undergoing chronic rejection was higher. In addition, in patients under everolimus treatment, gene expression of Dicer did not change and gene expression of AGO2 increased. Dicer, Drosha, DGCR8, and AGO2 protein expressions were reduced in all patients, but no change was observed in XPO5 protein expression in nonrejecting patients. Interestingly, in the patient undergoing chronic rejection, protein expression profiles other than Dicer were distinctive from nonrejecting patients. However, XPO5 protein expression was higher in that patient.

CONCLUSIONS

Our study shows the importance of the global effect of immunosuppressive treatment on the miRNA biogenesis pathway. miRNA biogenesis components are potential biomarkers indicative of graft outcome and pharmacologic target molecules.

Outcomes of Renal Transplantation in Patients With Alport Syndrome

AIM

We evaluated the outcomes of patients who underwent renal transplantation (Rtx) due to end-stage renal disease (ESRD) related to Alport syndrome in our study.

MATERIALS AND METHODS

Twenty-five patients (female/male: 9 [36%]/16 [64%]) who underwent Rtx at our center between 2002 and 2014 were enrolled in the study. Mean ages of patients and donors (cadaveric/living: 8 [32%]/17 [68%]) were 28.2 ± 11.6 and 42.3 ± 15.8 years, respectively. As immunosuppressive therapy, tacrolimus plus mycophenolic acid were used for 17 (68%) patients and cyclosporin plus mycophenolic acid were used for 8 (32%) patients where induction therapy was basiliximab 20 mg (day 0 and 4) for 11 (44%) patients and anti-thymocyte globulin for 8 (32%) patients. Acute rejection was diagnosed using biopsy and evaluated with Banff classification. Analyses were performed by using SPSS 20.0 software with outcomes of mean 75.4 ± 31.4 months follow-up. Patient and graft survival were measured by using Kaplan-Meier survival curve and compared by using log-rank test.

RESULTS

Graft survival rate was 89%, patient survival rate was 92.9%, and acute rejection rate was 12% (3 cases; 1 was cellular and 2 were antibody-mediated). Delayed graft function was observed in 4 (16%) cases, 1 patient (4%) had BK virus nephropathy and 2 (8%) patients required hemodialysis and had cytomegalovirus infection. At the last follow-up, mean serum creatinine level was 1.57 ± 1.23 mg/dL, spot urine protein creatinine ratio was 0.13 (0.04-1.84), and glomerular filtration rate was 71.7 ± 34.9 mL/min.

CONCLUSION

Rtx is an effective and successful treatment modality for ESRD cases related to Alport syndrome.

A Successful Renal Transplantation Case After Stem Cell Transplantation

Renal transplantation is the most effective treatment method for end-stage renal disease (ESRD). However, new treatment modalities are being investigated, such as immunotoleration, to avoid the acute and chronic side effects of immunosuppressant drugs. We report a case in which a man had undergone allogenic stem cell transplantation from his brother 16 years ago due to chronic myeloid leukemia, and who then developed ESRD due to arterial hypertension and underwent renal transplantation (Rtx) from the same brother. The patient was followed up without immunosuppression due to full chimerism.

Drug interaction between tacrolimus and ertapenem in renal transplantation recipients

To show drug interactions between tacrolimus and ertapenem, we retrospectively evaluated 13 renal transplant recipients who had been treated with ertapenem for urinary tract infections during prescription of a constant dose. The mean dose of tacrolimus to achieve desired therapeutic concentrations decreased significantly after beginning ertapenem. The decrease from 0.079 mg/kg to 0.043 mg/kg occurred 2 days after initiation of ertapenem (P < .005). These results suggest that ertapenem, which is not metabolized through the cytochrome (CYP) P450 3A metabolic pathway, interacts with tacrolimus by an unknown mechanism. This report recommends tacrolimus concentration monitoring and dose reductions when the two drugs are administered in combination.

Hox-C9 activates the intrinsic pathway of apoptosis and is associated with spontaneous regression in neuroblastoma

Neuroblastoma is an embryonal malignancy of the sympathetic nervous system. Spontaneous regression and differentiation of neuroblastoma is observed in a subset of patients, and has been suggested to represent delayed activation of physiologic molecular programs of fetal neuroblasts. Homeobox genes constitute an important family of transcription factors, which play a fundamental role in morphogenesis and cell differentiation during embryogenesis. In this study, we demonstrate that expression of the majority of the human HOX class I homeobox genes is significantly associated with clinical covariates in neuroblastoma using microarray expression data of 649 primary tumors. Moreover, a HOX gene expression-based classifier predicted neuroblastoma patient outcome independently of age, stage and MYCN amplification status. Among all HOX genes, HOXC9 expression was most prominently associated with favorable prognostic markers. Most notably, elevated HOXC9 expression was significantly associated with spontaneous regression in infant neuroblastoma. Re-expression of HOXC9 in three neuroblastoma cell lines led to a significant reduction in cell viability, and abrogated tumor growth almost completely in neuroblastoma xenografts. Neuroblastoma growth arrest was related to the induction of programmed cell death, as indicated by an increase in the sub-G1 fraction and translocation of phosphatidylserine to the outer membrane. Programmed cell death was associated with the release of cytochrome c from the mitochondria into the cytosol and activation of the intrinsic cascade of caspases, indicating that HOXC9 re-expression triggers the intrinsic apoptotic pathway. Collectively, our results show a strong prognostic impact of HOX gene expression in neuroblastoma, and may point towards a role of Hox-C9 in neuroblastoma spontaneous regression.

Collagen Synthesis, Nitric Oxide and Asymmetric Dimethylarginine in Diabetic Subjects Undergoing Hyperbaric Oxygen Therapy

The main pathological condition in patients with impaired wound healing is diabetes mellitus. These patients have significantly low circulating nitric oxide (NO) levels because the stimulatory action of insulin on NO synthesis is absent. Additionally, asymmetric dimethylarginine (ADMA), an inhibitor of NO synthase, is increased owing to the generation of oxidative stress. NO was thought to contribute to wound healing. Hyperbaric oxygen (HBO) treatment is generally used in order to accelerate the healing of wounds. The aim of this study was to determine the changes in plasma procollagen type I and III N-terminal peptides (PINP and PIIINP), total nitrite/nitrate (NOx) and ADMA levels; and to evaluate their relation to healing during the HBO treatment of foot ulcers. Data obtained from 18 diabetic patients before and after the HBO therapy were compared statistically by the Wilcoxon test. NOx was increased in 11 and ADMA was decreased in 12 patients following HBO treatment. Both PINP (32.6±29.4 μg/l vs 44.3±33.4 μg/l) and PIIINP (6.97±3.01 μg/l vs 7.92±2.49 μg/l) were significantly increased (p<0.05). Progressive reductions were observed in wound areas, as assessed by the digital wound imaging. In 12 patients, wounds healed by 50 % or higher; whereas only two subjects had minimal improvements (15 % or less healing). The duration of diabetes correlated negatively with wound healing (r = -498, p<0.05). This study suggests that increased collagen synthesis is associated with wound healing during hyperbaric oxygen therapy. Nitric oxide generation may also contribute to the healing process.

Relationship between carotid artery intima-media thickness and brachial artery flow-mediated dilation in peritoneal dialysis patients

BACKGROUND AND AIM

Carotid artery intima-media thickness (CIMT) and brachial artery flow-mediated dilation percentage (FMD%) are two commonly used parameters for detecting subclinical atherosclerosis. However, studies investigating the relationship between CIMT and brachial artery FMD% in different populations have produced conflicting results. The aim of this study was to determine the relationship between CIMT and brachial artery FMD% in patients on peritoneal dialysis (PD) METHODS: Fifty-two PD patients without known cardiovascular disease and 30 age-gender matched controls were included in the study. Endothelial function was determined using ultrasonography (US) to measure the FMD of the brachial artery, and this parameter was expressed as the percentage change from the baseline diameter of the brachial artery (FMD%). We also measured CIMT by US and analysed the relationship between CIMT and brachial FMD%.

RESULTS

The CIMT was significantly higher in patients than in the control group (0.84 +/- 0.08 vs. 0.75 +/- 0.06 mm, P < 0.01), whereas brachial artery FMD% was lower in patients than in the controls (8.2 +/- 5.0 vs. 11.7 +/- 5.5%, P < 0.01). There was no significant correlation between CIMT and FMD% (r = -0.004, P = 0.94).

CONCLUSION

Although PD patients are known to be characterized by an impaired flow-mediated vasodilatation of brachial artery and increased in CIMT, we did not find a significant correlation between FMD% and CIMT in our PD patient cohort. One possible explanation for our results is that each method measures a different aspect and stage of atherosclerosis.

Comparison of harmonic scalpel and high-frequency electrocautery in radial artery harvesting

AIM

We evaluated the effects of the radial artery on the functional outcomes and endothelium when the harvest was made either by harmonic scalpel or by high-frequency electrocautery.

METHODS

Between 2002 and 2007, 982 patients with coronary artery diseases were operated for coronary artery revascularization. The radial arteries were harvested for 101 of these patients and divided into two groups depending on the use of the harmonic scalpel (Group A; N=51) and the high-frequency electrocautery (Group B; N=50). Harvesting time, use of hemostatic clips, frequency of spasm, in situ free flow, and endothelial damage were compared between the two groups.

RESULTS

Conventional high-frequency electrocautery technique used 8.7+/-3.9 hemostatic clips versus 1.5+/-1 clips (P<0.001). In situ free blood flow was 85+/-5.5 mL/min for Group B versus 114+/-21.7 mL/min for Group A (P<0.006). The endothelial damage of the radial arteries taken down with the harmonic scalpel was significantly less than when taken down with the high-frequency electrocautery (P<0.05). There was no statistically significant difference in terms of harvesting time and spasm between the two groups (P>0.05).

CONCLUSION

Ultrasonic dissection with harmonic scalpel of the radial artery is associated with a decreased use of hemostatic clips. Moreover, the harmonic scalpel has a positive effect on endothelial preservation and it was associated with increased free blood flow of the radial artery.

Oxidative stress and asymmetric dimethylarginine is independently associated with carotid intima media thickness in peritoneal dialysis patients

BACKGROUND

Oxidative stress (OS) and asymmetric dimethylarginine (ADMA) are accepted as nonclassical cardiovascular risk factors in end-stage renal disease patients. To clarify the role of these factors in the atherosclerotic process, we investigated if OS and ADMA are associated with common carotid artery intima media thickness (CIMT) in peritoneal dialysis (PD) patients.

METHODS

Thirty PD patients without known atherosclerotic disease and classical cardiovascular risk factors as well as age- and gender-matched 30 healthy individuals were included. We measured serum thiobarbituric acid-reactive substances (TBARS), malondialdehyde (MDA), advanced glycation end product (AGE), pentosidine, advanced oxidation protein products (AOPP), ADMA and CIMT in each subjects.

RESULTS

TBARS, MDA, AOPP, AGE, pentosidine and ADMA levels were significantly higher in PD patients than in controls (p < 0.001). CIMT in patients was higher than in the control group (0.83 +/- 0.09 vs. 0.77 +/- 0.06 mm; p < 0.01). CIMT was independently correlated with TBARS (beta = 0.33, p < 0.01), MDA (beta = 0.27, p < 0.01), AOPP (beta = 0.22, p < 0.02), AGE (beta = 0.45, p < 0.01), pentosidine (beta = 0.56, p < 0.01) and ADMA (beta = 0.54, p < 0.01).

CONCLUSIONS

OS markers and serum ADMA levels independently predict the CIMT level in PD patients.

Ganglioglioma with lytic skull lesions: A case report

Gangliogliomas represent only 0.4% of central nervous system neoplasms and 1.3% of brain tumors. They are benign neoplasms with low morbidity and mortality and the patients usually present with seizures, but there has been no adult ganglioglioma with lytic skull lesion. A 49-year-old right handed woman suffering from generalized epileptic seizures was admitted to our hospital. She had also left hemiparesis with 4/5 motor strength. Magnetic resonance imaging and immunohistochemical studies revealed WHO Grade II ganglioglioma. Skull X-ray showed the lytic skull lesions. We have to consider gangliogliomas in the differential diagnosis of lytic skull lesions.

EDC/NHS cross-linked collagen foams as scaffolds for artificial corneal stroma

In this study, a highly porous collagen-based biodegradable scaffold was developed as an alternative to synthetic, non-degradable corneal implants. The developed method involved lyophilization and subsequent stabilization through N-ethyl-N'-[3-dimethylaminopropyl] carbodiimide/N-hydroxy succinimide (EDC/NHS) cross-linking to yield longer lasting, porous scaffolds with a thickness similar to that of native cornea (500 microm). For collagen-based scaffolds, cross-linking is essential; however, it has direct effects on physical characteristics crucial for optimum cell behavior. Hence, the effect of cross-linking was studied by examining the influence of cross-linking on pore size distribution, bulk porosity and average pore size. After seeding the foam with human corneal keratocytes, cell proliferation, cell penetration into the scaffold and ECM production within the scaffold were studied. After a month of culture microscopical and immunohistochemical examinations showed that the foam structure did not undergo any significant loss of integrity, and the human corneal keratocytes populated the scaffold with cells migrating both longitudinally and laterally, and secreted some of the main constituents of the corneal ECM, namely collagen types I, V and VI. The foams had a layer of lower porosity (skin layer) both at the top and the bottom. Foams had an optimal porosity (93.6%), average pore size (67.7 microm), and chemistry for cell attachment and proliferation. They also had a sufficiently rapid degradation rate (73.6+/-1.1% in 4 weeks) and could be produced at a thickness close to that of the natural corneal stroma. Cells were seeded at the top surface of the foams and their numbers there was higher than the rest, basically due to the presence of the skin layer. This is considered to be an advantage when epithelial cells need to be seeded for the construction of hemi or full thickness cornea.

Assessment and comparison of endothelial function between dialysis and kidney transplant patients

Dialysis and kidney transplant patients display endothelial dysfunction. Previous studies concerning comparisons of endothelial function in dialysis and kidney transplant patients included subjects with cardiovascular risk factor(s) that alone may lead to endothelial dysfunction. In this study, we compared endothelial function between dialysis and transplant patients who did not show known cardiovascular risk factors that lead to endothelial dysfunction. We studied age- and gender-matched cohorts: 30 hemodialysis (HD), 30 peritoneal dialysis (PD), and 30 kidney transplant patients. We also included 20 age- and gender-matched healthy controls. We assessed the endothelial function of patients and controls by a noninvasive technique. Serum biochemistry profiles of patients were also similar to controls in terms of lipid profile and fasting blood glucose level. Although mean FMD% levels of HD and PD patients were similar (6.6% +/- 3.1% vs 6.8% +/- 3.0%, P > .05), the mean percent of flow-mediated endothelium-dependent dilatation (FMD%) level in transplant patients was higher than those in HD or PD patients (10.50% +/- 3.0% vs 6.6% +/- 3.1% and 6.8% +/- 3.0%, respectively; P < .01). In addition, the mean FMD% level in healthy controls was higher than those in HD, PD, and transplant patients (14.0% +/- 2.3% vs 6.6% +/- 3.1%, 6.8% +/- 3.0% and 10.50% +/- 3.0%; P < .01, respectively). In conclusion, endothelial functions in transplant patients were better than those in dialysis patients.

Relation of C-2 monitoring with serum lipid profile in stable renal transplant patients

C-2 monitoring has been proposed as a more effective strategy than C-0 to predict the risk of acute rejection in the early stages posttransplantation. However, cyclosporine (CsA) is associated with posttransplant dyslipidemia. The aim of this retrospective study was to evaluate the correlations of C-0 and C-2 levels with atherogenic risk factors in the first 6 months versus after 6 months posttransplantation. We evaluated the data from 127 stable renal transplant recipients (89 males, 38 females) of mean age 38.10 +/- 12.79 years who received Neoral-based immunosuppression to investigate the relation of C-2 levels to serum lipid profile compared with C-0 values in the early and late posttransplantation periods. Receiver operating characteristic (ROC) analyses were performed to define a C-2 cutoff level that identified subjects with hypercholesterolemia, defined as a total cholesterol (TC) >200 mg/dL. There were significant positive correlations between both C-0 and C-2 levels and TC as well as the ratio of total cholesterol/HDL cholesterol (TC/HDL) in the late period. When the C-2 levels in the late posttransplantation period were stratified, serum TC concentrations showed statistically significant differences between the groups. Whole blood C-2 levels above 850 ng/mL were associated with increased serum TC concentrations; the C-2 cutoff level leading to hypercholesterolemia was 888 ng/mL. Maintenance immunosuppressive therapy under the proposed whole blood C-2 level of 888 ng/mL seemed to preserve graft function while preventing atherogenic risks for cardiovascular diseases in the late posttransplantation period.

Tacrolimus plus low-dose mycophenolate mofetil in renal transplant recipients: better 2-year graft and patient survival than with a higher mycophenolate mofetil dose

OBJECTIVES

Mycophenolate mofetil (MMF) has become more widely prescribed in recent years, but its adverse effects on the gastrointestinal system and bone marrow restrict its use in certain settings. The aim of this study was to compare the demographic features and clinical data for 173 renal transplant recipients who received tacrolimus (TAC) plus 1 g/d MMF (group I, n = 112) versus TAC plus 2 g/d MMF (group II, n = 61 patients) over a 2-year period. Each patient received similar TAC doses.

METHODS

We compared demographic data and clinical data for each case: acute rejection (AR) episodes, chronic rejection (CR) episodes, death, graft loss, development of posttransplantation diabetes mellitus (PTDM), and posttransplantation hypertension rates.

RESULTS

Demographic features were similar. There were also no significant differences between groups I and II with respect to number of AR episodes (17/112 vs 12/61, respectively), number of CR episodes (4/112 vs 1/61, respectively), PTDM, and hypertension rate (P > .05). Kaplan-Meier survival analysis revealed 2-year graft survival rates of 94% in group I versus 83% in group II. The corresponding 2-year patient survival rates were 100% in group I versus 91% in group II. The graft survival and patient survival rates in group I were significantly higher than those in group II (log-rank 0.005 and 0.001, respectively).

CONCLUSIONS

The 2-year graft and patient survival rates for the renal transplant recipients in this study suggest that the combination of a full TAC dose with 1 g/d MMF is a better choice than 2 g/d MMF.

Sirolimus as Primary Immunosuppression Agent in Kidney Transplant Recipients: Akdeniz University Experience

OBJECTIVES

Recently usage of sirolimus as the primary immunosuppressant is widening among kidney transplant recipients. We reviewed the clinical follow-up of patients transplanted at our center using sirolimus protocols.

METHODS

Sirolimus including primary immunosuppressive treatment protocols were begun in February 2002. Among the 21 patients (15 men, six women) who received sirolimus, six patients were prescribed sirolimus + prednisolone; seven, sirolimus + mycophenolate mofetil + prednisolone; and eight, sirolimus + cyclosporine + prednisolone. The mean age of the patients was 32.9 +/- 7.3 years and the mean posttransplantation follow-up, 13.2 +/- 4.5 months.

RESULTS

Three patients experienced acute rejection episodes, which were treated successfully with steroids. None of the patients had either hematologic or wound healing problems. Lymphoceles developed in eight patients. Serum creatinine level was 1.4 +/- 0.5 mg/dL at 12 months. There was a serious increase in serum cholesterol and triglyceride levels starting from the first month posttransplant (total cholesterol levels pretransplant and at 1 month, respectively: 159.3 +/- 29.5 and 255.7 +/- 52.3 mg/dL, P = .0001; triglycerides pretransplant and at 1 month, respectively: 146.9 +/- 89.5 and 215.1 +/- 102.5 mg/dL, P = .001). Despite routine antihyperlipemic treatment those high levels were maintained for 12 months.

CONCLUSIONS

We achieved 100% graft and patient survival rates for 1 year among patients who were using sirolimus. But the most important role in defining the morbidity and mortality in this group of patients is cardiovascular events; for this reason the abnormalities in the lipid profile must be taken seriously.

Simvastatin Therapy in Lymphocyte Cross-Match–Positive Kidney Transplantation Candidates

OBJECTIVES

Recent identification of several mechanisms by which statins decrease recruitment of monocytes and T cells into the arterial wall and inhibit both T-cell and B-cell activation and proliferation in vitro prompted us to study the immunomodulatory effects of statins. In this study, we examined the effect of simvastatin therapy on lymphocyte cross-match positivity in kidney transplantation candidates.

METHODS

Simvastatin therapy (20 mg/d) was administered to 25 patients (18 men, 7 women of mean age 34 +/- 11.7 years who displayed positive lymphocyte cross-matches between July 2002 and October 2004. The etiologies of end-stage renal disease were vesicoureteral reflux (n = 5), urinary stone disease (n = 4), glomerulonephritis (n = 6), amyloidosis secondary to familial Mediterranean fever (n = 1), and unknown (n = 9).

RESULTS

The lymphocyte cross-match became negative in 10 patients 4-9 months, and successful kidney transplantation was performed in 6 of them. The serum creatinine levels of these patients ranged between 0.8 and 1.4 mg/dL. Two patients required higher doses, but none suffered from adverse effects. The remaining 4 patients are still undergoing pretransplantation evaluation.

CONCLUSION

Simvastatin therapy seems to be a cost-effective and useful method for lymphocyte cross-match-positive kidney transplantation candidates compared with immunoadsorption or intravenous immunoglobulin use.

Implications of certain genetic polymorphisms in scarring in vesicoureteric reflux: importance of ACE polymorphism

Polymorphisms of the renin-angiotensin system (RAS) have been shown to affect renal prognosis in a number of diseases. We examined the influence of deletion (D) and insertion (I) polymorphism in the angiotensin I-converting enzyme (ACE) gene and the other polymorphic markers of RAS, and that of plasminogen-activator inhibitor-1 (PAI-1) on renal scarring in reflux nephropathy. Ninety-four children with third- or fourth-degree reflux were the subject of the study. They were stratified into two groups according to the technetium-99m-dimercaptosuccinic acid (DMSA) findings: the first group consisted of 41 patients with no scar formation. In the second group (n = 53), there was significant scar formation in the refluxing units. ACE levels, ACE gene, angiotensin-1 receptor (AT1) A1166C, angiotensinogen (ATG) M235T, and PAI-1 4G/5G polymorphisms were studied. In the second group with scarred kidneys, 18 patients had decreased renal function. The frequency of patients homozygous for the D allele was significantly greater in the second group with scar formation in the refluxing units compared with the first group of patients (P < 0.005). On multivariate analysis, the DD genotype was the only factor that had a significant impact on renal scar formation, introducing a 4.9-fold risk (P < 0.05, 95% confidence interval). We were unable to find any correlation with the presence ofDD genotype and hypertension, decreased renal function, proteinuria, or sex of the patient. DDgenotype correlated with the serum ACE levels (P < 0.005). AT1and ATGpolymorphisms and PAI-1 polymorphism did not correlate with scar formation or any of the parameters. This study provides evidence that the DDgenotype of ACE may be a genetic susceptibility factor contributing to adverse renal prognosis in reflux nephropathy; namely, scar formation. The role of the synergism between the aforementioned genetic polymorphisms can be enlightened with larger patient groups, possibly through multicenter studies.

Chaos: a potential problem in the biological control of insect pests

Erratic variations are normally observed in the populations of insect pests that destroy crop plants. To establish a scientific basis for developing effective control procedures, we have developed a model system for the European Corn Borer (ECB) (Ostrinia nubilalis) for which extensive field data, as well as laboratory results, have been accumulated during the past four decades. The model includes both a natural ECB pathogen and a genetically engineered toxin-producing agent as possible means of biological control. Our aim was to determine the conditions that could cause the population to vary erratically, as observed in the field. The erratic behavior in our simulations was analyzed to determine whether it is chaotic; chaos is a distinct type of erratic behavior which shows extreme sensitivity to initial conditions, i.e., the starting size of the population. Our simulations show that an increase in the death rate of the infected ECB, or a decrease in the birth rate of uninfected ECBs from infected ones, variables that are known to be affected by weather conditions, can induce a chaotic regime in which ECB population peaks reach values far higher than before chaos set in. Population peaks are even greater in the presence of both biological control agents. The results show that a biological control regime cannot be effective under conditions that induce chaotic population dynamics. Microcosm studies could be used to determine whether this situation would occur in the field.