Impaired phosphate handling of renal allografts is aggravated under rapamycin-based immunosuppression

BACKGROUND

Impaired phosphate handling of the renal allograft is a common problem and of multifactorial origin. The aim of the study was to elucidate whether a rapamycin- or a mycophenolate-based immunosuppressive therapy aggravates the renal phosphate leak in kidney transplant recipients.

METHODS

Renal phosphate handling was determined in thirty-eight cadaveric allograft recipients, with good renal function at 8, 12, 20 and 28 weeks after transplantation. Nineteen patients (group 1) received triple immunosuppression with rapamycin, cyclosporine and prednisolone, nineteen other transplant recipients received mycophenolate mofetil, cyclosporine and prednisolone immunosuppression (group 2), and six healthy subjects (group 3) served as controls. After 12 weeks of stable graft function, group 1 patients were divided further into two subgroups. Ten patients were kept on their immunosuppressive regimen (group 1A), whereas the remaining nine randomly chosen subjects had their cyclosporine withdrawn; they were thus maintained on a dual immunosuppression regimen with prednisolone and a higher dosage of rapamycin (group 1B).

RESULTS

Renal phosphate reabsorption was significantly lower in group 1 at 8 and 12 weeks after transplantation as compared with groups 2 and 3. At 20 weeks after transplantation, patients with rapamycin-based immunosuppression (groups 1A and 1B) continued to exhibit hypophosphataemia and impaired renal phosphate handling. Group 1B had the lowest TmP/ GFR compared with all groups. At 28 weeks, renal phosphate reabsorption and plasma phosphate levels were no longer different between patient groups and controls.

CONCLUSION

These data suggest that rapamycin-based immunosuppression prolongs the phosphate leak of the allografted kidney, leading to low serum phosphate levels during the first weeks after transplantation.

Informational contribution of noninvasive screening tests for coronary artery disease in patients on chronic renal replacement therapy

The prevalence of coronary artery disease (CAD) is high in patients on renal replacement therapy; therefore, reliable noninvasive screening tests are needed. We retrospectively determined the sensitivity, specificity, and positive and negative likelihood ratios (LRs) for a history of chest pain, resting and exercise electrocardiography (ECG), thallium dipyridamole scintigraphy, and echocardiography in 42 patients undergoing chronic hemodialysis and 42 patients after renal transplantation who also underwent coronary angiography. In addition, the prognostic power of each test for the occurrence of a cardiovascular event after angiography (therapeutic intervention, myocardial infarction, or cardiovascular death) was evaluated during a follow-up of 37 months. Forty-three patients had significant CAD on angiography. Angina pectoris had a sensitivity of 65% and specificity of 66%, corresponding to a positive LR of 1.9 and a negative LR of 0.5. A variable number of patients underwent noninvasive tests before angiography. Results were similar in patients undergoing hemodialysis and after renal transplantation and in patients with or without angina pectoris. Exercise ECG could not be performed in the majority of patients, and resting ECG (sensitivity, 67%; specificity, 52%; corresponding to a positive LR of 1.4 and negative LR of 0.6) and scintigraphy (sensitivity, 80%; specificity, 37%; positive LR, 1.3; negative LR, 0.5) in patients on renal replacement therapy were not useful for the diagnosis of CAD. Angina also markedly increased the relative odds for the occurrence of a cardiovascular event during follow-up (relative odds, 4.6) compared with other noninvasive tests. Angina pectoris had the best informational and prognostic value of noninvasive screening methods, but angiography seems to be the only method to clearly document CAD in patients on renal replacement therapy.

Hypothyroidism as a cause of tacrolimus intoxication and acute renal failure: a case report

The nephrotoxic side effects of cyclophilin-binding agents like cyclosporine A and tacrolimus are well characterized. In severe cases nephrotoxicity may profoundly deteriorate kidney function and even induce acute renal failure. In this report we describe the first case of excessive tacrolimus intoxication caused by hypothyroidism. The patient had undergone single-lung transplantation 6 months earlier, developed hypothyroidism, and was admitted with acute anuric renal failure. Thyroxin is a potent activator of the cytochrome P-450- CYP 3A enzyme system, which is crucial for tacrolimus metabolism. Hence, hypothyroidism reduces cytochrome P-450 activity and may result in drug accumulation. Rapid reversal of toxic drug levels could be achieved by reducing drug intake and increasing thyroxin levels by substitution therapy. In conclusion, it is important to consider thyroid function when prescribing medications with a narrow therapeutic range, which are metabolized by the cytochrome P-450 system such as tacrolimus, and the possible devastating effect of impaired drug metabolism during hypothyroidism.

The Erlangen Endo-Trainer: life-like simulation for diagnostic and interventional endoscopic retrograde cholangiography

The Erlanger Endo-Trainer offers a large spectrum of training possibilities in endoscopic techniques using life-like biological specimens. We organised the first pilot study of interventions at the papilla and the bile duct under x-ray control. Specially prepared upper visceral porcine organ packages including the esophagus, stomach, duodenum, liver, gallbladder and bile ducts were implanted into the Endo-Trainer. Furthermore, small stones were introduced into the bile duct. The test study was carried out by a senior endoscopist assisted by his endoscopy nurse. The following steps could therefore be carried out as a structured team-training scheme: Introduction of the side-viewing endoscope and passage into the duodenum; identification and adjustment at the papilla; cannulation of the papilla; selective bile duct imaging with contrast application under x-ray vision; placement of a guidewire; papillotomy; stone extraction and finally placement of a plastic stent. The special value of this type of simulation is the fact that endoscopic techniques can be trained in the usual manner with real tissue-feeling using regular commercial instruments. Although there is general consent that individual practice on the patient cannot be completely replaced by simulator training, a suitable and realistic simulation model can be of great value, for initial steps prior to "real" patient contact as well as for refining techniques and tactics.

Thymic humoral factor-gamma 2 augments immune cell response and exerts antitumor activity in murine model systems

The immunomodulatory and antimetastatic/antitumor activity of thymic humoral factor-gamma 2 (THF-gamma 2) was evaluated in BALB/c-mice. Daily subcutaneous applications (7 consecutive days, 20, 200 ng of THF-gamma 2 per injection/mouse) upregulated counts of thymocytes and peripheral blood cells in tumor bearing mice. To check the influence of THF-gamma 2 treatment on the growth of experimental metastases, RAW 117 H10 lymphosarcoma cells or L-1 sarcoma cells were intravenously inoculated into BALB/c-mice to establish liver or lung metastases, respectively. Local tumor growth was induced by subcutaneous injection of L-1 sarcoma cells. THF-gamma 2 was subcutaneously administered daily for 7 consecutive days starting 24 hrs after tumor cell challenge. Organ colonization as well as local tumor growth were investigated on day 14 after tumor cell inoculation and demonstrated a statistically significant (p < 0.05) reduction of experimental liver and lung metastases and local tumor growth for THF-gamma 2 treated mice.

Thymosin alpha(1) application augments immune response and down-regulates tumor weight and organ colonization in BALB/c-mice

The immunomodulatory and antimetastatic/antitumor activity of thymosin alpha(1) (Talpha(1)) was evaluated in BALB/c-mice. Daily subcutaneous application (7 consecutive days, 0.01-10 microg of Talpha(1)/injection per mouse) upregulated the number of thymocytes and peripheral blood cells in tumor bearing mice. To check the influence of Talpha(1) treatment on growth of experimental metastases, RAW H10 lymphosarcoma cells or L-1 sarcoma cells were intravenously injected into BALB/c-mice to establish liver or lung metastases. Local tumor growth was induced by subcutaneous injection of L-1 sarcoma cells. Talpha(1) was subcutaneously administered daily for 7 consecutive days starting 24 h after tumor cell challenge. Organ colonization, as well as local tumor growth, were investigated on day 14 after tumor cell inoculation, and demonstrated a statistically significant (P<0.05) reduction of experimental liver and lung metastases and local tumor growth for Talpha(1) treated mice.

Angiotensin-converting enzyme gene polymorphism determines the antiproteinuric and systemic hemodynamic effect of enalapril in patients with proteinuric renal disease. Austrian Study Group of the Effects of Enalapril Treatment in Proteinuric Renal Disease

Angiotensin-converting enzyme (ACE) inhibitors are known to reduce blood pressure and proteinuria in a variety of different glomerular diseases. Nonetheless, a marked interindividual difference in the efficacy of these agents exists. The activity of the ACE and therefore of the renin-angiotensin-aldosterone system (RAAS) has been shown to be under genetic influence. Patients with a deletion genotype at the intron 16 of the ACE gene have been shown to exhibit higher activity of plasmatic ACE when compared to patients with the insertion genotype. We therefore studied prospectively the hemodynamic and antiproteinuric effect of a 6-month therapy with enalapril in patients with biopsy-proven proteinuric glomerular diseases and the DD (n = 10) and ID/II (n = 26) genotype. Although patients with the DD genotype received a slightly higher dose of enalapril, blood pressure and proteinuria did not change significantly. However, both were significantly reduced in the II/ID group after 10 weeks and 6 months of therapy. Creatinine clearance decreased steadily in DD patients. In II/ID patients, creatinine clearance was reduced significantly after 10 weeks of therapy but increased again thereafter and the value at 6 months was again comparable to the one obtained in the DD patients. We conclude from our study that the ACE genotype influences the blood pressure-lowering and antiproteinuric effect of enalapril in patients with proteinuric glomerular disease.

Low molecular thymic peptides stimulate human blood dendritic cells

Dendritic cells are considered to be the most potent antigen-presenting cells and are thus promising new tools for the immunotherapy of cancer. They respond to various stimuli by differentiation (expression of CD83) and up-regulation of costimulatory surface molecules. Thymic peptides have immunostimulatory and immunomodulating properties. Their therapeutic potential in immunotherapy of cancer has been discussed. To test whether thymic peptides act on dendritic cells, we examined the effects of a standardized thymic peptide preparation on cultured human monocyte-derived dendritic cells. Addition of thymic peptides resulted in enhanced expression of the specific differentiation marker CD83 in a dose dependent manner. Moreover, thymic peptides induced the up-regulation of costimulatory molecules including CD86, CD80, HLA-DR and HLA-ABC. After priming with thymic peptides dendritic cells showed an enhanced expression of IL-8 and TNF-alpha mRNA and protein release. Dendritic cells stimulated with thymic peptides were able to induce proliferation of autologous T cells as measured by 3H-thymidine incorporation in mixed Lymphocyte reaction. In combination with a low dosage of keyhole limpet hemocyanin, thymic peptides showed additive effects in the up-regulation of CD83 and costimulatory surface markers. Our findings indicate that thymic peptides per se act on professional antigen-presenting cells in a stimulatory manner and were presented by these cells. Furthermore, thymic peptides enhance the response of dendritic cells to low dosages of a standard nominal antigen. Therefore, thymic peptides could improve the immunological activity especially against low amounts of endogenous antigens.

Nucleic acid aptamers-from selection in vitro to applications in vivo

Aptamers are nucleic acid ligands which are isolated from combinatorial oligonucleotide libraries by in vitro selection. They exhibit highly complex and sophisticated molecular recognition properties and are capable of binding tightly and specifically to targets ranging from small molecules to complex multimeric structures. Besides their promising application as molecular sensors, many aptamers targeted against proteins are also able to interfere with the proteins' biological function. Recently developed techniques facilitate the intracellular application of aptamers and their use as in vivo modulators of cellular physiology. Using these approaches, one can quickly obtain highly specific research reagents that act on defined intracellular targets in the context of the living cell.

Detection of HIV-1 infection in dried blood spots from a 12-year-old ABO bedside test card

BACKGROUND AND OBJECTIVES

We tested dried blood from an ABO bedside test card which had been stored at room temperature for 12 years, to prove that a patient with HIV-1 infection had been infected by blood transfusion.

MATERIALS AND METHODS

Immunoblots for HIV-1 antibodies and threefold PCRs with half-nested primers for the HIV-1 integrase gene were done with eluates from the dried blood spots.

RESULTS

HIV-1 antibodies and HIV-1 DNA could be detected in the sample from one unit of blood, but not from the two other units or from the recipient before transfusion.

CONCLUSION

Further studies should be done on the validity of stored dried blood as an alternative to the storage of frozen donor serum for several years for 'look-back' studies.

The recombinant human histones H1 zero and H1.2 cause different toxicity profiles on the human leukemia cell line K562

The human histones H1 zero and H1.2 were expressed in E. coli and purified to homogenity. Their cytotoxicity on the human leukemia cell line K562 and on PBMC from healthy volunteers was compared with the cytotoxic effect of a bovine histone H1 preparation. In this preparation, histone H1.2 was identified as the main compound. All three histone preparations induced a significant dose-dependent toxicity on the leukemia cell line. Compared with the recombinant histone H1 zero, the bovine preparation and recombinant H1.2 showed stronger cytotoxicities. Cytotoxic effects on K562 cells were observed immediately after addition of the histones, whereas the histone preparations failed to induce significant cytotoxicity on PBMC during the first hour of incubation. However, after 24 hours all three histone preparations induced toxic effects on PBMC which were comparable to those observed on the leukemia cell line.

Bacteriological and serological findings in a further case of transfusion-mediated Yersinia enterocolitica sepsis

A 13-year-old patient developed severe shock due to administration of a Yersinia enterocolitica-contaminated red blood cell concentrate. Y. enterocolitica (serotype O:9, biotype II) was cultivated from the residual blood in the blood bag and from a stool sample of the blood donor. In the donor's plasma immunoglobulin M (IgM), IgA, and IgG antibodies against Yersinia outer proteins (YopM, -H, -D, and -E) were found. Since the donor remembered a short-lasting, mild diarrhea 14 days prior to blood donation, a transient attack of Yersinia enteritis may be associated with a longer than expected period of asymptomatic bacteremia that causes contamination of donor blood. Serological screening for IgM antibodies against Yersinia outer proteins might offer a way to reduce the risk of transfusion-associated Y. enterocolitica sepsis.

Colocalization of chaperone Cpn60, proinsulin and convertase PC1 within immature secretory granules of insulin-secreting cells suggests a role for Cpn60 in insulin processing

Many of the mechanisms that control insulin processing and packaging by interaction with different elements along the secretory pathway remain poorly understood. We have investigated the possibility that Cpn60, a member of the heat shock protein family, may be present in rat insulin-secreting cells, participating in the proinsulin-insulin maturation process. Immunofluorescence and high resolution immunocytochemical studies revealed the presence of the Cpn60 protein all along the insulin secretory pathway, being particularly abundant over the proinsulin-containing immature secretory granules. Double-labeling experiments showed associations between Cpn60 and proinsulin, as well as between Cpn60 and PC1 convertase, with a preferential binding to proinsulin. These findings paralleled those of coimmunoprecipitation studies showing the Cpn60 chaperone and the mature form of the PC1 convertase in proinsulin immunoprecipitates, as well as the PC1 in Cpn60 immunoprecipitates from total islet cell extracts. In vitro binding of Cpn60 to proinsulin, insulin and glucagon was also documented. Cpn60, significantly abundant in proinsulin-containing secretory granules where conversion of proinsulin to insulin takes place, and the colocalization of the chaperone with proinsulin and PC1 convertase suggest that the Cpn60 protein may play a role directing precise molecular interactions during insulin processing and/or packaging.

Introduction of a novel HRP substrate-Nanogold probe for signal amplification in immunocytochemistry

Amplification of immunological signals with catalyzed reporter deposition (CARD) allows improved detection of scarce tissue antigens in light and electron microscopy. The technique takes advantage of the oxidation ability of horseradish peroxidase (HRP), in the presence of hydrogen peroxide, to yield the accumulation of one of its specific reporter-tagged substrates. This immunocytochemical approach continues to be improved by the introduction of new reporter molecules tagged to tyramine or to other HRP substrates. In this study we introduced a novel HRP substrate tagged to Nanogold particles. The amplification protocol is based on the application of a specific primary antibody, a biotinylated secondary antibody, streptavidin-HRP, and an HRP substrate coupled to Nanogold, followed by silver intensification. In addition to amplification of immunological signals of high resolution, direct accumulation of Nanogold particles at target sites by enzymatic activity of HRP improves the efficiency of the technique compared to other amplification protocols. Moreover, this approach combines the CARD amplification potentials with the ultrasmall gold probe and the silver intensification method. Immunolabeling obtained by light and electron microscopy, as well as immunodot assay using this new amplification strategy, appear to be highly sensitive, specific, and of enhanced intensity.

Endoscopic mucosal resection of early cancer and high-grade dysplasia in Barrett's esophagus

BACKGROUND & AIMS

In view of the mortality and morbidity rates of esophagectomy and the relatively large group of inoperable patients, local therapeutic techniques are required for high-grade dysplasia and early Barrett's cancer.

METHODS

A prospective investigation of endoscopic mucosal resection was conducted in 64 patients (mean age, 65 +/- 10 years) who had early carcinoma (61 patients) or high-grade dysplasia (3 patients) in Barrett's esophagus. Thirty-five patients met the criteria for low risk: macroscopic types I, IIa, IIb, and IIc; lesion diameter up to 20 mm; mucosal lesion; and histological grades G1 and G2 and/or high-grade dysplasia (group A). The remaining 29 patients were included in group B (high risk).

RESULTS

A total of 120 resections were performed, with no technical problems encountered. The mean number of treatment sessions per patient was 1. 3 +/- 0.6 in group A and 2.8 +/- 2.0 in group B (P < 0.0005). Only one major complication occurred, a case of spurting bleeding, which was managed endoscopically. Complete local remission was achieved significantly earlier (P = 0.008) in group A than in group B. In May 1999, complete remission had been achieved in 97% of the patients in group A and in 59% of those in group B; however, 1 patient in group A and 9 in group B are still undergoing treatment or awaiting the first check-up. During a mean follow-up of 12 +/- 8 months, recurrent or metachronous carcinomas were found in 14%.

CONCLUSIONS

Endoscopic mucosal resection of early carcinoma in Barrett's esophagus is associated with promisingly low morbidity and mortality rates. The procedure may offer a new minimally invasive therapeutic alternative to esophagectomy, especially in low-risk situations. Comparisons with surgical results will need to be done when the long-term results of this procedure become available.

High-performance liquid chromatographic determination of p-aminohippuric acid and iothalamate in human serum and urine: comparison of two sample preparation methods

A high-performance liquid chromatography method applied to determine p-aminohippuric acid (PAH) and iothalamate (IOT) in serum and urine samples of patients was evaluated according to recovery, reproducibility and linearity utilizing narrow-bore columns. The mobile phase consisted of 0.15 M sodium dihydrogenphosphate with 1.2 mM tetrabutylammonium sulphate, the pH was adjusted to pH 4.6, acetonitrile was added to a final ratio of 95:5 (v/v), the flow-rate was set at 0.3 ml/min. The separation was achieved on a ODS Hypersil column (200 x 2.1 mm I.D.). The UV detector was set at 254 nm. PAH and IOT are used for evaluation of kidney function [effective renal plasma flow (ERPF) and glomerular filtration rate (GFR)]). Under the described chromatographic conditions two sample preparation techniques, ultrafiltration and acetonitrile precipitation were compared. The results demonstrate the accuracy of both methods in evaluation of ERPF and GFR. Due to its cost-effectiveness we recommend the acetonitrile precipitation method in clinical routine.

Mechanisms of hypertension after renal transplantation

Hypertension is extremely prevalent after renal transplantation, affecting up to 70% of all patients. An elevation in blood pressure is associated with an increased cardiovascular risk and may also contribute to chronic allograft failure. Renal transplantation provides interesting insights into the pathogenesis of hypertension. Experimental and human data show that the kidney is an essential organ for blood pressure regulation. In clinical practice a differential diagnosis that is based on excretory allograft function has proved useful.

Biomonitoring of human genotoxicity induced by complex occupational exposures

Sensitivity, specificity and correlations among several biomarkers for monitoring occupational exposure to complex mixtures of genotoxic agents were assessed in occupational environments in Hungarian study populations. The studies have been focused on DNA adduct formation, urinary metabolites, mutations and micronuclei induced by exposures to complex organic mixtures. In two Hungarian aluminium plants, increased DNA adduct and 1-hydroxypyrene (1-OH-PY) levels were observed in workers as compared to controls. However, no association between the biomarker levels was evident on an individual basis. In Hungarian garage mechanics, DNA adduct determinations did not show increased genotoxic exposure as compared to the controls. However, ambient air measurements, significantly enhanced 1-OH-PY levels, and slightly enhanced frequency of micronuclei indicated increased polycyclic aromatic hydrocarbon (PAH) exposure in the garages, as compared to the general environment. In a Hungarian vulcanizing plant, DNA adduct determinations and 1-OH-PY did not show significantly elevated exposure levels as compared to controls. The glycophorin A (GPA) somatic mutation assay was also negative for this occupational exposure. The results support previous observations of a lack of correlation between DNA adducts detectable by 32P-postlabelling and those measured by the PAH-DNA immunoassay in the same DNA sample. These studies also demonstrate a lack of close correlation between levels of DNA adducts and urinary 1-OH-PY in the same individual.