Development of a PET Tracer for OGA with Improved Kinetics in the Living Brain

O-GlcNAcylation is thought to play a role in the development of tau pathology in Alzheimer's disease because of its ability to modulate tau's aggregation propensity. O-GlcNAcylation is regulated by 2 enzymes: O-GlcNAc transferase and O-GlcNAcase (OGA). Development of a PET tracer would therefore be an essential tool for developing therapeutic small-molecule inhibitors of OGA, enabling clinical testing of target engagement and dose selection. Methods: A collection of small-molecule compounds was screened for inhibitory activity and high-affinity binding to OGA, as well as favorable PET tracer attributes (multidrug resistance protein 1 efflux, central nervous system PET multiparameter optimization, etc.). Two lead compounds with high affinity and selectivity for OGA were selected for further profiling, including OGA binding to tissue homogenate using a radioligand competition binding assay. In vivo pharmacokinetics were established using a microdosing approach with unlabeled compounds in rats. In vivo imaging studies were performed in rodents and nonhuman primates (NHPs) with 11C-labeled compounds. Results: Two selected candidates, BIO-735 and BIO-578, displayed promising attributes in vitro. After radiolabeling with tritium, [3H]BIO-735 and [3H]BIO-578 binding in rodent brain homogenates demonstrated dissociation constants of 0.6 and 2.3 nM, respectively. Binding was inhibited, concentration-dependently, by homologous compounds and thiamet G, a well-characterized and structurally diverse OGA inhibitor. Imaging studies in rats and NHPs showed both tracers had high uptake in the brain and inhibition of binding to OGA in the presence of a nonradioactive compound. However, only BIO-578 demonstrated reversible binding kinetics within the time frame of a PET study with a 11C-labeled molecule to enable quantification using kinetic modeling. Specificity of tracer uptake was confirmed with a 10 mg/kg blocking dose of thiamet G. Conclusion: We describe the development and testing of 2 11C PET tracers targeting the protein OGA. The lead compound BIO-578 demonstrated high affinity and selectivity for OGA in rodent and human postmortem brain tissue, leading to its further testing in NHPs. NHP PET imaging studies showed that the tracer had excellent brain kinetics, with full inhibition of specific binding by thiamet G. These results suggest that the tracer [11C]BIO-578 is well suited for further characterization in humans.

18F-Trifluoromethanesulfinate Enables Direct C-H 18F-Trifluoromethylation of Native Aromatic Residues in Peptides

18F labeling strategies for unmodified peptides with [18F]fluoride require 18F-labeled prosthetics for bioconjugation more often with cysteine thiols or lysine amines. Here we explore selective radical chemistry to target aromatic residues applying C-H 18F-trifluoromethylation. We report a one-step route to [18F]CF3SO2NH4 from [18F]fluoride and its application to direct [18F]CF3 incorporation at tryptophan or tyrosine residues using unmodified peptides as complex as recombinant human insulin. The fully automated radiosynthesis of octreotide[Trp(2-CF218F)] enables in vivo positron emission tomography imaging.

Anticancer Gold(III) Peptidomimetics: From Synthesis to in vitro and ex vivo Biological Evaluations

Five new Au^III -peptidodithiocarbamato complexes of the type [Au^III Br₂ (dtc-AA₁ -AA₂ -OR] (in which AA₁ =N-methylglycine (Sar), l/d-Pro; AA₂ =l/d-Ala, α-aminoisobutyric acid (Aib); R=OtBu, triethylene glycol methyl ether), differing with regard to the amino acid sequence and/or the chiral amino acid configuration, were designed to enhance tumor selectivity and bioavailability. The gold(III)-based moiety was functionalized to exploit the targeting properties of the peptidomimetic ligand toward two peptide transporters (namely PEPT1 and PEPT2), which are upregulated in several tumor cells. The compounds were synthesized and fully characterized, mainly by means of elemental analysis, one- and two-dimensional NMR spectroscopy, FT-IR, and UV/Vis spectrophotometry. The crystal structures of three compounds were also solved by X-ray diffraction. In vitro cytotoxicity studies using a panel of human tumor cell lines (A549 [non-small-cell lung carcinoma], MCF-7 [breast cancer], A2780 [ovarian carcinoma], H1975 [non-small-cell lung carcinoma], H460 [large-cell lung carcinoma], and A431 [human epidermoid carcinoma]) showed the dtc-Pro-Aib-OtBu derivative to be very effective, with GI₅₀ values much lower than those of cisplatin. This complex was thus selected for evaluating stability under physiological conditions and possible interactions with serum albumin, as well in PARP-1 enzyme inhibition assays and preliminary ex vivo toxicity experiments on healthy rat tissues.

Use of carbon-11 labelled tool compounds in support of drug development

The pharmaceutical industry is facing key challenges to improve return on R&D investment. Positron emission tomography (PET), by itself or in combination with complementary technologies such as magnetic resonance imaging (MRI), provides a unique opportunity to confirm a candidate's ability to meet the so-called 'three pillars' of drug development. Positive confirmation provides confidence for go/no-go decision making at an early stage of the development process and enables informed clinical progression. Whereas fluorine-18 has probably gained wider use in the community, there are benefits to using carbon-11 given the greater flexibility the use of this isotope permits in adaptive clinical study design. This review explores the scope of available carbon-11 chemistries and provides clinical examples to highlight its value in PET studies in support of drug development.

CCK8 peptide-labeled Pluronic® F127 micelles as a targeted vehicle of gold-based anticancer chemotherapeutics

A sparingly water-soluble gold(iii) complex was encapsulated in micelles functionalized with the CCK8-targeting moiety for the selective delivery of an anticancer drug.

Beyond platinums: gold complexes as anticancer agents

The accidental discovery of the anticancer properties of cisplatin in the mid-1960s triggered the development of alternative platinum-based drugs. However, the platinum-based treatment of tumor diseases is massively hampered by severe side-effects and development of resistance. Sulfur-containing biomolecules play a significant role in platinum anticancer chemotherapy because of their high affinity to the platinum(II) ion. Sulfur is involved in the entire metabolic processing of platinum drugs. Strong and irreversible binding of cisplatin to intracellular thiolato ligands is considered a major step of inactivation, and reactions with sulfur donors in proteins are believed to affect enzymatic processes. Consequently, the development of novel metal-based compounds with a pharmacological profile different from that of clinically-established platinum drugs is a major goal of modern medicinal chemistry and drug design. Among the non-platinum antitumor agents, gold(III) complexes have recently gained increasing attention due to their strong tumor cell growth-inhibiting effects, generally achieved by exploiting non-cisplatin-like mechanisms of action. The real breakthrough is not simply the use of gold compounds to treat cancer, but the rational design of gold-based drugs which may be very effective, non-toxic and potentially selective towards cancer cells, their potential impact relying on the possible site-specific delivery in localized cancer, thus strongly improving cellular uptake and minimizing unwanted side-effects. Cancer cells are known to overexpress specific proteins and receptors needed for tumor growth. Among them, two integral plasma membrane proteins mediate the cellular uptake of di- and tripeptides and peptide-like drugs. They are present predominantly in epithelial cells of the small intestine, bile duct, mammary glands, lung, choroid plexus, and kidney but are also localized in other tissues and are up-regulated in some types of tumors. Accordingly, we have been designing gold(III)-peptide dithiocarbamato derivatives which combine both the antitumor properties and reduced side-effects of the previously reported gold(III) analogues with enhanced bioavailability and tumor selectivity achieved by exploiting peptide transporters. Our compounds showed interesting cytotoxic properties towards a number of cancer cell lines in vitro and in vivo on xenograft models, together with negligible organ and acute toxicity. With respect to their mechanisms of action, we identified mitochondria and proteasome as major in vitro and in vivo targets. These results allowed the filing of an international patent for the use of gold(III) peptidomimetics in cancer chemotherapy, as well as providing a solid starting point for them to enter phase I clinical trials in a few months.

Insights into the reactivity of gold-dithiocarbamato anticancer agents toward model biomolecules by using multinuclear NMR spectroscopy

Some gold(III)-dithiocarbamato derivatives of either single amino acids or oligopeptides have shown promise as potential anticancer agents, but their capability to interact with biologically relevant macromolecules is still poorly understood. We investigated the affinity of the representative complex [Au(III)Br2(dtc-Sar-OCH3)] (dtc: dithiocarbamate; Sar: sarcosine (N-methylglycine)) with selected model molecules for histidine-, methionine-, and cysteine-rich proteins (that is, 1-methylimidazole, dimethylsulfide, and N-acetyl-L-cysteine, respectively). In particular, detailed mono- and multinuclear NMR studies, in combination with multiple (13)C/(15)N enrichments, allowed interactions to be followed over time and indicated somewhat unexpected reaction pathways. Whereas dimethylsulfide proved to be unreactive, a sudden multistep redox reaction occurred in the presence of the other potential sulfur donor, N-acetyl-L-cysteine (confirmed if glutathione was used instead). On the other hand, 1-methylimidazole underwent an unprecedented acid-base reaction with the gold(III) complex, rather than the expected coordination to the metal center by replacing, for instance, a bromide. Our results are discussed herein and compared with the data available in the literature on related complexes; our findings confirm that the peculiar reactivity of gold(III)-dithiocarbamato complexes can lead to novel reaction pathways and, therefore, to new cytotoxic mechanisms in cancer cells.

[Effects of dose of erythropoiesis stimulating agents on cardiovascular outcomes, quality of life and costs of haemodialysis. the clinical evaluation of the DOSe of erythropoietins (C.E. DOSE) Trial]

BACKGROUND

Anaemia is a risk factor for death, adverse cardiovascular outcomes and poor quality of life in patients with chronic kidney disease (CKD). Erythropoietin Stimulating Agents (ESA) are the most used treatment option. In observational studies, higher haemoglobin (Hb) levels (around 11-13 g/dL) are associated with improved survival and quality of life compared to Hb levels around 9-10 g/dL. Randomized studies found that targeting higher Hb levels with ESA causes an increased risk of death, mainly due to adverse cardiovascular outcomes. It is possible that this is mediated by ESA dose rather than haemoglobin concentration, although this hypothesis has never been formally tested.

METHODS

We present the protocol of the Clinical Evaluation of the Dose of Erythropoietins (C.E. DOSE) trial, which will assess the benefits and harms of a high versus a low ESA dose therapeutic strategy for the management of anaemia of end stage kidney disease (ESKD). This is a randomized, prospective open label blinded end-point (PROBE) design trial due to enroll 900 haemodialysis patients. Patients will be randomized 1:1 to 4000 UI/week i. v. versus 18000 UI/week i. v. of epoetin alfa, beta or any other epoetin in equivalent doses. The primary outcome of the trial is a composite of cardiovascular events. In addition, quality of life and costs of these two strategies will be assessed. The study has been approved and funded by the Italian Agency of Drugs (Agenzia Italiana del Farmaco (AIFA)) within the 2006 funding plan for independent research on drugs (registered at www.clinicaltrials.gov (NCT00827021)).

[Chronic renal failure after hematopoietic stem cell transplantation]

Hematopoietic stem cell transplantation, autologous or allogeneic, is a well established hematology procedure. There can be a number of renal complications in this setting, which may occur in every phase but all strongly influence prognosis. Among the late complications, there is the well-known possibility of progressive chronic renal failure, appearing together with hypertension and modest alterations of the urinary sediment, and characterized by pathological findings of thrombotic microangiopathy, often without the corresponding clinical aspects. This clinical picture must be distinguished from other forms of clinically more severe thrombotic microangiopathy, such as those occurring in the early post-transplant period, and from other causes of renal disease in the hematopoietic stem cell transplantation setting. Total body irradiation, chemotherapeutic drugs, calcineurin inhibitors and opportunistic infections have all been considered as causal factors. The nosological classification is still poorly defined, as are the real prognosis and the best treatment. Kidney biopsy is a necessary tool to make a correct diagnosis, assess the frequency of the condition, make a prognostic judgment, and set up rational treatment.

Effects of Successful Renal Transplantation on Left Ventricular Mass

Left ventricular hypertrophy is an independent cardiovascular risk factor in the general population and in patients with chronic renal failure. Relatively little is known about the effects of renal transplantation on left ventricular hypertrophy. The aim of this study was to determine the changes in left ventricular mass after successful renal transplantation and to evaluate the importance of some clinical, laboratory, and echocardiographic variables on the trend to left ventricular hypertrophy. Twenty-three patients with end-stage renal disease were studied by ambulatory blood pressure monitoring and echocardiography before and 2 years following renal transplantation. After 24 months of follow-up, all transplant recipients had adequate renal function (serum creatinine <2 mg/dL). At the end of the study, we observed a significant decrease in left ventricular mass and left ventricular mass index compared to the pretransplantation period. In renal transplant recipients, the prevalence of left ventricular hypertrophy significantly decreased (78% versus 44%, P < .03) after 2 years of follow-up. Systolic 24-hour blood pressure was the only predictor of left ventricular mass and of left ventricular mass index at 2 years after transplantation. In conclusion, successful renal transplantation produces a regression of left ventricular hypertrophy. This beneficial effect depends on a decrease in systolic pressure levels.

Renoprotective Effect of Early Inhibition of the Renin-Angiotensin System in Renal Transplant Recipients

The aim of this work was to study the effect of early administration of angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II type-I receptors blockers (ARB) on renal function and proteinuria in renal transplant recipients with good, stable renal function and mild proteinuria. Twenty four patients started ACEI/ARB therapy within 14 months after surgery (RAS-). Before (T0) and every month for 2 years after the initiation of ACEI/ARB we evaluated creatinine clearance (CrCl), proteinuria/day (UP), UP/CrCl (FUP), arterial blood pressure, and serum lipid levels. Twenty-eight patients who never received ACEI/ARB (RAS+) were studied in the same fashion. In the RAS+ CrCl was reduced after 2 years compared with T0 (64.5 +/- 2.6 vs 75.0 +/- 3.2 mL/min, P < .003); UP and FUP were both significantly increased (666 +/- 65 vs 132 +/- 20 mg/day 8.8 +/- 1.2 vs 2.6 +/- 0.6 mg/mL x 10(3); P < .001 and .002) compared with T0. Moreover, UP (P < .04), FUP (P < .03), and the percentage reduction of CrCl (11.4% +/- 5% vs 4.6% +/- 1.8%; P < .05) were greater in RAS+ than RAS- subjects at 2 years of the study. The values of other parameters did not show significant differences between the two groups. In conclusion, this study suggested that ACEI/ARB have renoprotective effects, when used in patients with good stable renal function and mild proteinuria. These drugs may play a role to prevent chronic allograft nephropathy.

Renal allograft protection with early angiotensin-converting enzyme inhibitors administration

Twenty renal transplant recipients (RTx) with a normal ultrasound pattern of renal artery who began angiotensin-converting enzyme inhibitor (ACEI) therapy within 14 months after surgery (ACEI(+)) were studied retrospectively to evaluate endogenous creatinine clearance/1.73 m(2) body surface area (CrCl), proteinuria (UP), UP/CrCl (FUP), mean arterial pressure (MBP), total cholesterol, LDL, HDL, and triglycerides. Before (T(0)) and every month for 2 years after initiation of ACEI. Twenty-four RTx who never received ACEI (ACEI(-)) were studied in the same fashion. No differences in the parameters were noted at T(0); all RTx had CrCl >60 mL/min, Up less than 0.5 g/d, and stable renal function for 3 months before the study. In the ACEI cohort CrCl was reduced after 2 years compared with T(0) (65.6 +/- 2.8 vs 76 +/- 3.2 mL/min, P <.004), UP and FUP were both increased (660 +/- 60 vs 130 +/- 20 mg/d, 8.9 +/- 1.3 vs 2.8 +/- 0.6 mg/mL x 10(3); P <.001 and.002, respectively). UP >0.5 g/d was present in three cases. After 2 years the ACEI(+) group showed a decrease in CrCl (68.2 +/- 3.1 vs 73 +/- 2.2 mL/min) and the increase in UP (181 +/- 21 vs 139 +/- 18 mg/d) and in FUP (3.1 +/- 0.7 vs 2.6 +/- 0.9 mg/mL x 10(3)), which were not significantly different from the values at T(0). No cases showed UP >0.5 g/d. Moreover UP (P <.04), FUP (P <.03) and the percent reduction of CrCl (11.2 +/- 2.5% vs 4.6 +/- 1.8%, P <.05) were greater among ACEI(-) than ACEI(+) patients at 2 years. ACEI(-) patients showed correlation between the percent reduction of CrCl and UP (r =.51, P <.04). The values of MBP and lipids did not reveal any significant difference between the two groups. In conclusion, this study suggests that ACEI have a renoprotective effect, when used early, and may also prevent chronic allograft nephropathy.

[Surgical complications after kidney transplantation]

Chronic renal failure needs substitutive treatment such as haemodialysis and peritoneal dialysis for the patient to survive. Kidney transplantation (KTx) improves survival of the patient with chronic renal failure. Since the first KTx, performed by Merrill in Boston in 1959, advances in medical therapy, immunosuppressive therapy and refinements in surgical technique have improved the quality of life of the transplant patient. We present a review of the incidence, diagnosis and therapy of surgical complications after KTx reported in the literature and a retrospective analysis of 297 consecutive cadaveric donor kidney transplants done in our institution from September 1993 to September 2002. Vascular complications represent 5-10% of postoperative complications. Our experience showed an incidence of 1.7% renal artery thrombosis, 1.4% renal vein thrombosis, 1.7% renal artery stenosis, 1.4% arterial rupture due to fungal arteritis, 0.7% spontaneous graft ruptures and 12% lymphoceles. Urological complications account for 10-15% of postoperative complications. In our series we found an incidence of 7.4% urinary leakage, 2.7% urinary obstruction and 3% urinary reflux. Gastrointestinal complications represent 16% of postoperative complications. Our series showed 1% pancreatitis with an overall mortality of 33% and an incidence of 1.7% intestinal perforations. Surgical complications still represent a challenge that increments morbidity and mortality among kidney transplant recipients. Data shown may offer some guidance on how to deal with early and late post-transplant surgical complications.

[Cardiovascular disease after renal transplantation]

Cardiovascular disease is the leading cause of morbidity and mortality following renal transplantation. Because many renal transplant recipients die with functioning grafts, deaths resulting from cardiovascular disease have became an increasingly important cause of graft loss, particularly after the first post-transplantation year. Moreover, a contribution of some cardiovascular risk factors to renal allograft dysfunction has been demonstrated. A number of observational studies suggest that cardiovascular disease is more common in renal transplant patients than in the general population. The excessive risk for cardiovascular disease is related to a high prevalence and accumulation of atherogenic risk factors before and after transplantation. Hypertension, post-transplantation diabetes and hyperlipidemia are well-recognized risk factors for the development of cardiovascular events after renal transplantation and are strongly associated with immunosuppressive therapy. Progressive renal dysfunction may also influence the risk of cardiovascular complications after renal transplantation. The elevated risk may also be caused by non- traditional risk factors such as anaemia, adhesion molecules, hyperhomocysteinemia, microinflammatory state, abnormal coagulation and oxidative stress. To prevent post-transplantation cardiovascular disease it is crucial to define the etiological risk factors. Some risk factors can be modified, and for some of these, there is strong evidence from studies in the general population that intervention improves survival. Given the significant morbidity and mortality of cardiovascular disease in renal transplant recipients, aggressive treatment intervention for potentially modifiable factors are strongly advocated after transplantation. In addition to treatment intervention, risk management should also involve tailoring the immunosuppressive regimen to minimize both direct and indirect cardiovascular risks. In this article we attempted to review and quantify the post-transplant risk factors for cardiovascular disease as well as offer suggestions on optimizing the therapy or treatment strategies to minimize the risk of cardiovascular complications in renal transplant patients. Reduction of cardiovascular morbidity and mortality can improve not only the life expectancy and quality of life of the transplant recipients but also their graft function and survival.

[Clinicopathologic correlations in acute renal graft rejection]

Although the diagnostic and therapeutic outcome of renal transplantation has successfully improved during the last decades, acute graft rejection (AGR) is still an ongoing cause of concern being often associated with irreversible graft dysfunction. Renal biopsy remains a valuable tool in the initial assessment of the potential graft malfunction especially during the early post-transplant period. It is an accurate and sensitive means for detecting prognostically relevant microscopic abnormalities, and assisting in subsequent patient management. For long time, the histopathologic evaluation of AGR has suffered from an irreducible bias with poor interobserver rates. Nowadays, the classification schemes of AGR include the BANFF approach and the National Institute of Heath Collaborative Clinical Trials in Transplantation (NIH-CCTT) system: both have been originally designed in order to improve the diagnostic reproducibility of AGR among pathologists. Arteritis and tubulitis, along to clinical information, constitute the cardinal features of the BANFF classification. Distinguishing features of the traditional NIH-CCTT system includes microscopic criteria such as assessment of interstitial hemorrhage, extent and quality of inflammatory infiltrate, and acute glomerulitis, in addition to tubulitis and arteritis. The BANFF classification has apparently gained more popularity than the time-honored NIH-CCTT system since, if used in the appropriate clinical context, it allows a more accurate assessment of AGR, provides prognostically relevant information, and has a better reproducibility rate among pathologists. Nevertheless, the accuracy trend has not significantly improved during the last few years.

Acid production and base balance in patients on chronic haemodialysis

Acid generation and elimination processes were compared with total base (bicarbonate plus metabolizable anions) turnover in 18 anuric patients undergoing post-dilutional haemofiltration. The study was conducted during the second haemodialysis session of the week by means of a whole-body base balance technique. The results showed that the mean rates of base loss and base gain during dialysis did not differ (i.e. the dialysis base balance approximated to zero). The concurrent mean rate of intestinal base absorption was 66+/-26 mmol/2 days, as calculated from the whole-body balance of the various inorganic cation and anion differences in a metabolic steady state. This level of intestinal base absorption would be capable of neutralizing the 59+/-21 mmol of H(+) ions/2 days that is contributed by sulphuric acid, which is the most important endogenous acid produced in anuric patients. In spite of the fact that intestinal base supply was adequate to neutralize endogenous acid production completely, our patients presented with pre-dialysis non-carbonic acidosis. The depression of plasma bicarbonate levels could not, however, be explained by increased concentrations of the anion gap and organic acids, which were within normal limits both before and after dialysis. We suggest as an alternative hypothesis that this pre-dialysis acidosis may represent an isotonic dilution acidosis that is induced by the ingestion of base-free tap water in order for plasma tonicity to be protected from the accumulation of impermeant dietary solutes, which takes place during the interdialysis period in anuric patients.

Long-term therapy for postrenal transplant erythrocytosis with ACE inhibitors: efficacy, safety and action mechanisms

SUBJECTS AND METHODS

Eleven patients with postrenal transplant erythrocytosis were treated with angiotensin-converting enzyme inhibitors for 18 months.

RESULTS

Indices of red blood cell production and destruction, renal function and kalemia were followed-up during the treatment. Angiotensin-converting enzyme inhibitors (ACEi) led to a progressive and significant fall in hemoglobin and hematocrit compared to the basal values at every time interval considered with a maximum reduction at 12th month for hemoglobin ( 17.04 +/- 0.21 vs. 15.10 +/- 0.42 g/dl, p < 0.0001) and at the 6th month for hematocrit (53.74 +/- 0.56 vs. 45.7 +/- 1.19 %, p < 0.0001). Serum erythropoietin levels were reduced significantly after the first month of therapy (13.56 +/- 2.7 vs. 7.48 +/- 1.6 mUI/dl, p < 0.05) after which no further variations were recorded. In the course of ACEi therapy, there was an inverse correlation between percentage reduction in erythropoietin values and those of hemoglobin emerged (r = 0.24, p < 0.05) and hematocrit (r = 0.39, p < 0.01). Indices of red blood destruction including haptoglobin, bilirubin and lactic dehydrogenase, were unaffected by ACE inhibitors treatment, as was creatininemia and kalemia. Treatment was well tolerated by all patients who completed the study without major adverse side-effects. No patient required phlebotomy and no thromboembolic event occurred during angiotensin-converting enzyme therapy.

CONCLUSIONS

Our results suggest that angiotensin-converting enzyme inhibitors are a safe and effective long-term therapy of postrenal transplant erythrocytosis. These agents decrease the erythropoietin synthesis but this effect is not the sole mechanism by which angiotensin-converting enzyme inhibitors act in postrenal renal transplant erythrocytosis.

Balance of non-metabolizable base in continuous peritoneal dialysis patients

Acid generation and elimination processes compared to titratable non-metabolizable base (NaOH equivalents, NB) turnover in end-stage renal disease patients are examined in the light of the Law of electroneutrality. The application over 2 days of the whole-body NB balance technique to 18 patients undergoing continuous ambulatory peritoneal dialysis is evaluated. The results show that the mean rate of NB loss with peritoneal effluent (as bicarbonate and organic acid anions) exceeded the mean rate of NB gain with the dialysis fluid (as salts of lactic acid) by 24 (27), m (SD), mmol per 2 days. In spite of this, the bicarbonate and pH of the plasma remained stable and within normal limits. The concurrent mean rate of the intestinal NB absorption was about 61 (27) mmol per 2 days, as calculated from the whole body balances of the several electrolytes in the metabolic steady-state. This intestinal absorption was more than sufficient to restore the body base consumed in neutralizing endogenous acid generation: 37 (14), 2H2SO4 mmol per 2 days, the remaining NB being eliminated as bicarbonate and organic acid anions. The ample spectrum of plasma acid-base (A B) values appears to some extent influenced by patient-related factors, such as the rate of drinking water intake and the set point deviation for organic acid turnover.

Insertion of a straight peritoneal catheter in an arcuate subcutaneous tunnel by a tunneler: long-term experience

OBJECTIVE

This study describes the results of the insertion of a straight Tenckhoff peritoneal catheter (PC) in an arcuate, caudally concave tunnel using a tunneler designed by the authors. It has a semicircular shape and a bending radius of 4.5 cm.

SETTING

A hospital renal unit.

PATIENTS

From June 1988 to February 1994, 112 straight Tenckhoff PCs, 62 with one deep cuff (single-cuff PC) and 50 with two cuffs (double-cuff PC), were inserted as first catheters in 112 patients (mean age 62 +/- 13 years), who underwent continuous ambulatory peritoneal dialysis (CAPD). The follow-up was 1099 months (mean 18 +/- 13 months) for single-cuff PCs and 1264 months (mean 25 +/- 15 months) for double-cuff PCs, respectively.

INTERVENTIONS

After intraperitoneal placement of the PCs by median laparotomy, a 180 degrees arc bend tunnel, with both external and peritoneal exits directed downwards, was created by means of the tunneler.

RESULTS

The rate of exit-site infection (ESI) was 0.27 episodes/year (epis/year). The probability of remaining ESI-free was 76%, 60%, and 55% at 1, 2, and 3 years. The rate of tunnel infection (TI) was 0.046 epis/year. The incidence of the double-cuff PC-related ESI and TI tended to be lower than the incidence observed with the single-cuff PC. Episodes of peritonitis were 60 (0.30 epis/year), where 6 were subsequent to ESI and/or TI. Two PCs were lost due to ESI, 3 due to TI, and 11 due to peritonitis. Drainage failure, due to displacement of the PC caused by straightening, involved 3 PCs; 2 were lost. PC survival was 92%, 82%, and 74% at 1, 2 and 3 years, respectively.

CONCLUSIONS

By an easily used semicircular tunneler, the standard straight Tenckhoff PC can be stably positioned in an arcuate tunnel with both inner and outer exits directed downwards. This tunnel shape, as already suggested by some authors, appears to be an effective technical solution to reducing the PC-related complication rates.

Renal involvement in acro-renal-ocular syndrome: interstitial nephritis, unlikely pyelonephritis

We describe a case, seemingly sporadic, in which ocular and acral malformations were associated with an interstitial nephropathy; we made a diagnosis of acro-renal-ocular syndrome. There was no stasis, reflux, or urinary tract infection in our patient. We believe that interstitial nephritis in acro-renal-ocular syndrome may not always be pyelonephritis, as previously reported.

Atrial natriuretic peptide and hemodynamic changes after concentrated ascitic fluid reinfusion in cirrhotic patients

In order to assess the role, if any, of atrial natriuretic peptide (ANP) and hemodynamic changes in diuretic response to concentrated ascitic fluid reinfusion (CAFR) in cirrhotic patients, we studied 10 patients with liver cirrhosis before and after aspiration, concentration and intravenous reinfusion of their ascitic fluid. Basal ANP levels were higher than in normal subjects, but not related to the degree of water and sodium excretion. CAFR induced a variable degree of ANP changes and diuretic response, and these two parameters were strictly correlated to each other. No major changes of cardiac output and systemic vascular resistances were observed after CAFR. In conclusion, the apparent resistance to ANP diuretic action observed in basal condition in cirrhotic patients seems to revert after expanding blood volume by CAFR.