Biomedical subjects

Giuseppe Pontoriero

Publications and source records attributed to Giuseppe Pontoriero.

7 recordsLinked to original sources

PubMed2005

Modulation of agonist binding to human dopamine receptor subtypes by L-prolyl-L-leucyl-glycinamide and a peptidomimetic analog.

The present study was undertaken to investigate the role of the hypothalamic tripeptide L-prolyl-L-leucyl-glycinamide (PLG) and its conformationally constrained analog 3(R)-[(2(S)-pyrrolidinylcarbonyl)amino]-2-oxo-1-pyrrolidineacetamide (PAOPA) in modulating agonist binding to human dopamine (DA) receptor subtypes using human neuroblastoma SH-SY5Y cells stably transfected with respective cDNAs. Both PLG and PAOPA enhanced agonist [3H]N-propylnorapomorphine (NPA) and [3H]quinpirole binding in a dose-dependent manner to the DA D2L,D2S, and D4 receptors. However, agonist binding to the D1 and D3 receptors and antagonist binding to the D2L receptors by PLG were not significantly affected. Scatchard analysis of [3H]NPA binding to membranes in the presence of PLG revealed a significant increase in affinity of the agonist binding sites for the D2L, D2S, and D4 receptors. Analysis of agonist/antagonist competition curves revealed that PLG and PAOPA increased the population and affinity of the high-affinity form of the D2L receptor and attenuated guanosine 5'-(beta,gamma-imido)-triphosphate-induced inhibition of high-affinity agonist binding sites for the DA D2L receptor. Furthermore, direct NPA binding with D2L cell membranes pretreated with suramin, a compound that can uncouple receptor/G protein complexes, and incubated with and without DA showed that both PLG and PAOPA had only increased agonist binding in membranes pretreated with both suramin and DA, suggesting that PLG requires the D2L receptor/G protein complex to increase agonist binding. These results suggest that PLG possibly modulates DA D2S, D2L, and D4 receptors in an allosteric manner and that the coupling of D2 receptors to the G protein is essential for this modulation to occur.

Binding, Competitive↗

PubMed2005

Relationship between urea clearance and ionic dialysance determined using a single-step conductivity profile.

BACKGROUND: On-line determination of ionic dialysance (ID) has been used to measure the clearance of small solutes like urea. However, attempts to determine the in vivo relationship between ID and urea clearance have led to discordant findings. The aim of this study was to determine the relationship between the mean values of repeated instantaneous determinations of ID throughout a dialysis session ((m)ID), obtained using a single-step inlet dialysate conductivity profile, and the mean values of urea clearance corrected for access recirculation (K(eu1)), total recirculation (access plus cardiopulmonary recirculation, K(eu2)), and the entire postdialysis urea rebound (K(wb)). METHODS: Eighty-two anuric patients on chronic thrice-weekly hemodialysis were studied using an Integra machine equipped with the Diascan module for the automatic determination of ID. The mean values of repeated ID measurements made at 30-minute intervals were compared with K(eu1) (available for only 31 patients), K(eu2), and K(wb). RESULTS: The results in all 82 patients were: (m)ID = 176 +/- 23 mL/min; K(eu2) = 181 +/- 25 mL/min; K(wb) = 159 +/- 22 mL/min. The mean (m)ID/K(wb) and (m)ID/K(eu2) ratios were, respectively, 1.11 +/- 0.06 and 0.98 +/- 0.06. The results in the 31 patients for whom K(eu1) values were available were: (m)ID = 179 +/- 24 mL/min and K(eu1) = 200 +/- 27 mL/min; the mean (m)ID/K(eu1) ratio was 0.90 +/- 0.05. CONCLUSION: The mean value of repeated ID determinations obtained using a single-step conductivity profile underestimates urea clearance corrected for access recirculation, and may be considered an adequate estimate of urea clearance corrected for total recirculation.

Anuria↗

PubMed2004

Application of dialysis and transplant registries to clinical practice: the Lombardy Registry.

BACKGROUND: Data collected from registries provide a useful source of information for clinical practice. Therefore, several regional and national registries of end-stage renal disease (ESRD) patients have been established. The Lombardy Registry of Dialysis and Transplantation (RLDT) was established in 1982, with participation of all 44 dialysis units that were present at that time within the region. METHODS: Demographic and clinical data on ESRD patients are collected yearly. We present here the results of some of the analyses that have been performed on RLDT data since it was started. RESULTS: Briefly, data on epidemiology of ESRD, cardiovascular disease, patterns of care and patients' outcomes have been considered. Comparisons with international registries have also been performed. CONCLUSIONS: This analysis shows how data collected from a homogeneous patient population receiving similar patterns of care provide precise information on that population. A clear example is provided by the similar results obtained in the comparison of high-flux vs low-flux membranes in a randomized control trial, the HEMO study, and in an analysis of RLDT data. Therefore, analysis of data collected by registries represents an important tool to improve clinical practice and possibly patients' outcomes.

Aged↗

PubMed2004

Ionic dialysance allows an adequate estimate of urea distribution volume in hemodialysis patients.

BACKGROUND: An adequate estimation of urea distribution volume (V) in hemodialysis patients is useful to monitor protein nutrition. Direct dialysis quantification (DDQ) is the gold standard for determining V, but it is impractical for routine use because it requires equilibrated postdialysis plasma water urea concentration. The single pool variable volume urea kinetic model (SPVV-UKM), recommended as a standard by Kidney Disease Outcomes Quality Initiative (K/DOQI), does not need a delayed postdialysis blood sample but it requires a correct estimate of dialyser urea clearance. METHODS: Ionic dialysance (ID) may accurately estimate dialyzer urea clearance corrected for total recirculation. Using ID as input to SPVV-UKM, correct V values are expected when end-dialysis plasma water urea concentrations are determined in the end-of-session blood sample taken with the blood pump speed reduced to 50 mL/min for two minutes (U(pwt2')). The aim of this study was to determine whether the V values determined by means of SPVV-UKM, ID, and U(pwt2') (V(ID)) are similar to those determined by the "gold standard" DDQ method (V(DDQ)). Eighty-two anuric hemodialysis patients were studied. RESULTS: V(DDQ) was 26.3 +/- 5.2 L; V(ID) was 26.5 +/- 4.8 L. The (V(ID)-V(DDQ)) difference was 0.2 +/- 1.6 L, which is not statistically significant (P= 0.242). Anthropometric volume (V(A)) calculated using Watson equations was 33.6 +/- 6.0 L. The (V(A)-V(DDQ)) difference was 7.3 +/- 3.3 L, which is statistically significant (P < 0.001). CONCLUSION: Anthropometric-based V values overestimate urea distribution volume calculated by DDQ and SPVV-UKM. ID allows adequate V values to be determined, and circumvents the problem of delayed postdialysis blood samples.

Hemodialysis Solutions↗

PubMed2003

The quality of dialysis water.

INTRODUCTION: Every week, haemodialysis patients are exposed to approximately 400 l of water used for the production of dialysis fluids which, albeit with the interposition of a semi-permeable artificial membrane, come into direct contact with the bloodstream. It is therefore clearly important to know and monitor the chemical and microbiological purity of dialysis water. METHODS: In this review, we analyse the sources of chemical and microbiological water contamination, and the problems involved in water purification systems and modalities. We also analyse the compliance of dialysis units with the microbiological standards established by the most widely accepted guidelines relating to the quality of dialysis fluids. RESULTS: The risk of chemical contamination is due mainly to the primary pollution of municipal water, whereas the most important microbiological problem is the control of bacterial growth in the water treatment and distribution system. Dialysis water treatment implies various levels of pre-treatment, a final purification module (which, in many cases, is reverse osmosis: RO) and a hydraulic circuit for the distribution of the purified water. RO-based treatment systems produce water of optimal chemical and microbial quality, and so dialysis units need to concentrate on maintaining this quality level in the long term by means of effective maintenance and disinfection strategies. The most widely accepted standards for water purity are those recommended by the Association for the Advancement of Medical Instrumentation and the European Pharmacopea, which respectively allow bacterial growth of <200 and <100 c.f.u./ml, and an endotoxin concentration of <2 and <0.25 IU/ml. However, a number of multicentre studies have reported that 7-35% of water samples have bacterial growth of >200 c.f.u./ml, and up to 44% have endotoxin levels of >5 IU/ml. CONCLUSIONS: The results of multicentre studies indicate that the microbial quality of dialysis fluids is still a too often neglected problem, particularly as there is evidence of a possible relationship between dialysis fluid contamination and long-term morbidity. The time has now come to take advantage of innovations in water treatment processes and improvements in dialysis machines in order to modify clinical practices and start improvement processes aimed at decreasing the risk of microbial contamination to the minimum, as it has already been successfully done in the case of chemical contamination.

Dialysis Solutions↗

PubMed2003

Lanthanum carbonate (Shire).

Shire Pharmaceuticals Group plc, under exclusive license from AnorMED Inc (a subsidiary of Johnson Matthey), is developing lanthanum carbonate, a phosphate-binding lanthanum salt, for the potential treatment of hyperphosphatemia in dialysis patients. It is currently in pre-registration in the US, Canada and Western Europe, and earlier stage clinical trials are ongoing in Japan.

Clinical Trials, Phase I as Topic↗

PubMedDate not supplied

Long-term outcome in hemodialysis: morbidity and mortality.

Despite technical and pharmacological improvements achieved over the past years, long-term prognosis of patients undergoing chronic hemodialysis is still rather poor. Cardiovascular disease is the leading cause of both morbidity and mortality in these patients, mostly because of their severely compromised cardiovascular conditions already at the time of starting hemodialysis. A proper management of factors involved in the development of cardiovascular abnormalities is therefore a basic pre-requisite for improving their clinical outcome. Hypertension and anemia should be adequately evaluated and corrected, in light of their primary involvement in the pathogenesis of left ventricular hypertrophy, whereas treatment of calcium and phosphate metabolism disorders, particularly of high serum phosphorus levels, is needed to prevent the development of severe secondary hyperparathyroidism and mainly vascular calcifications, whose detrimental pathophysiologic consequences on cardiovascular structures are huge. At the same time, the prescription of the hemodialytic treatment should be optimised, with a satisfactory removal of uremic toxins through the delivery of an adequate dialysis dose and with the use of biocompatible membranes, where possible, thus minimizing the inflammatory response secondary to the interaction between blood and the artificial material of the hemodialysis system. The clinical superiority of high-flux membranes, although suggested by all studies performed so far, has still to be demonstrated by well-conducted clinical studies; on-line convective treatments and daily hemodialysis, although promising, also need to be confirmed in randomized trials. In conclusion, long-term outcome of hemodialysis patients may only be improved by a complex, multi-factorial therapeutical approach.

Anemia↗