Biomedical subjects

S Riva

Publications and source records attributed to S Riva.

At least 19 recordsLinked to original sources

PubMed2006

Randomized trial of basiliximab induction versus steroid therapy in pediatric liver allograft recipients under tacrolimus immunosuppression.

Avoidance of corticosteroids could be beneficial after pediatric liver transplantation (LTx). To test this hypothesis, we performed a randomized prospective study to compare immunosuppression with tacrolimus (TAC) and steroids versus TAC and basiliximab (BAS) after pediatric LTx. Seventy-two patients were recruited, 36 receiving TAC and steroids and 36 TAC and BAS. The primary endpoint was the occurrence of the first rejection episode. Secondary endpoints were the cumulative incidence and severity of rejection, patient and graft survival, and incidence of adverse events. Overall 1-year patient and graft survival rates were 91.4% and 85.5% in the steroid group, and 88.6% and 80% in the BAS group (p = NS). Patients free from rejection were 87.7% in the BAS group and 67.7% in the steroid group (p = 0.036). The use of BAS was associated with a 63.6% reduction in incidence of acute rejection episodes. Overall incidence of infection was 72.3% in the steroid group and 50% in the BAS group (p = 0.035). We conclude that the combination of TAC with BAS is an alternative to TAC and steroid immunosuppression in pediatric LTx, which allows for a significant reduction in the incidence of acute rejection and infectious complications.

Antibodies, Monoclonal↗

PubMed2006

HHH syndrome (hyperornithinaemia, hyperammonaemia, homocitrullinuria), with fulminant hepatitis-like presentation.

We report a 3-year-old Italian patient with the hyperornithinaemia, hyperammonaemia, homocitrullinuria (HHH) syndrome who presented with neurological deterioration after an intercurrent infection. Hyperammonaemia, coagulopathy and moderate hypertransaminasaemia were detected on hospital admission. Severe hepatocellular necrosis with hypertransaminasaemia (aspartate aminotransferase 20,000 UI/L, alanine aminotransferase 18,400 UI/L) and coagulopathy (PT < 5%) rapidly developed within few days, prompting evaluation for liver transplantation. A protein-restricted diet and arginine supplementation were immediately started, with a rapid improvement of the patient's neurological conditions and normalization of liver function tests and blood ammonia. The diagnosis of HHH syndrome was based on the presence of the typical metabolic abnormalities. Molecular analysis of the SLC25A15 gene showed that the patient was heterozygous for two novel mutations (G113C and M273K). The diagnosis of HHH syndrome should be considered in patients with fulminant hepatitis-like presentations. Early identification and treatment of these patients can be life-saving and can avoid liver transplantation.

Alanine Transaminase↗

PubMed2006

In situ split liver transplantation for adult and pediatric recipients: an answer to organ shortage.

BACKGROUND: We report our initial experience with in situ split liver transplantation (SLT) for adult and pediatric patients. PATIENTS AND METHODS: From June 2003 to August 2005, 177 liver transplantations in 165 patients, 133 adults (81%) and 32 children (19%), were performed at our institution. Over this period, 45 liver transplantations (25%) were performed with an in situ split liver technique in 44 patients: 17 (39%) were adults and 27 (61%) children. All of the adult split liver recipients were transplanted with an extended right graft (ERG; segments I + IV-VIII), while pediatric recipients received in 23 cases a left lateral segment (LLS; segments II-III) and in 4 cases an ERG from a pediatric donor. The 45 split liver grafts (21 ERGs and 24 LLSs) were generated from 35 donors. In 10 cases we used both grafts generated with an in situ split procedure to transplant our patients, while in 25 cases the procurement procedure was performed in collaboration with other transplant centers. RESULTS: After a median follow-up of 9 months (range, 1-27 months), the overall patient survival rate was 88% for adult patients and 82% for pediatric patients. Graft survivals were 88% and 79%, respectively. Two adult patients (12%) died from sepsis in the early postoperative period. Five children (18%) died after their transplantations. Only one pediatric recipient (2%) of primary SLT underwent retransplantation. Vascular complications were absent in adult recipients, whereas 4 arterial (14%) and 4 venous (14%) complications developed in the pediatric population. The incidence of biliary complications was 23% in adult and 18% in pediatric recipients. CONCLUSIONS: The use of in situ SLT for adult and pediatric populations allowed us to expand the cadaveric donor pool, significantly eliminating pediatric waiting list mortality without penalizing the adult population.

Adult↗

PubMed2006

Corticosteroid-free immunosuppression in pediatric liver transplantation: safety and efficacy after a short-term follow-up.

BACKGROUND: We report our results with the use of corticosteroid-free immunosuppression after pediatric liver transplantation, evaluating the efficiency and safety of this protocol in the early posttransplantation period. PATIENTS AND METHODS: From July 2003 to October 2005, 34 liver transplantations were performed in 32 pediatric patients (19 boys, 13 girls) at our institution. Recipient median age was 5 years (range, 0.2-14 years), and median body weight was 10 kg (range, 4-49 kg). Twenty-seven patients received a graft from in situ split liver transplantation, 5 a whole graft. Twenty-nine children (90%) received an immunosuppressive therapy based on methylprednisolone IV bolus at reperfusion (10 mg/kg) plus tacrolimus given at an initial dose of 0.08 mg/kg/d and then adjusted to obtain whole blood trough levels of 10 to 15 ng/mL during the first 3 months and 5 to 10 ng/mL after the 3rd month; basiliximab was given on postoperative days 0 and 4. Biopsy-proven acute rejection episodes were treated by methylprednisone IV boluses. RESULTS: After a median follow-up of 9 months (range, 1-27 months), the overall patient survival rate was 84% and graft survival rate was 79%. Three children (9%) died after their transplantations. Three (9%) experienced episodes of biopsy-proven acute rejection, always treated with IV steroid boluses. Mean RAI score was 4. One patient experienced PTLD that resolved with temporary reduction of immunosuppression. Cytomegalovirus infection rate was 14%. Sepsis occurred in 2 cases (6%). CONCLUSIONS: Initial results with a steroid-free immunosuppressive protocol are encouraging, with low rates of acute rejection and infectious complications as in steroid-based protocols.

Adolescent↗

PubMed2005

Light scattered by model phantom bacteria reveals molecular interactions at their surface.

Testing molecular interactions is an ubiquitous need in modern biology and molecular medicine. Here, we present a qualitative and quantitative method rooted in the basic properties of the scattering of light, enabling detailed measurement of ligand-receptor interactions occurring on the surface of colloids. The key factor is the use of receptor-coated nanospheres matched in refractive index with water and therefore optically undetectable ("phantom") when not involved in adhesion processes. At the occurrence of ligand binding at the receptor sites, optically unmatched material adsorbs on the nanoparticle surface, giving rise to an increment in their scattering cross section up to a maximum corresponding to saturated binding sites. The analysis of the scattering growth pattern enables extracting the binding affinity. This label-free method has been assessed through the determination of the binding constant of the antibiotic vancomycin with the tripeptide l-Lys-d-Ala-d-Ala and of the vancomycin dimerization constant. We shed light on the role of chelate effect and molecular hindrance in the activity of this glycopeptide.

Bacteria↗

PubMed2005

Orthotopic liver transplantation for biliary atresia.

Biliary atresia (BA) represents the most frequent indication for liver transplantation (OLTX) in the pediatric population. The aim of this paper was to present a series collected over the last 7 years from October 1997 through July 2004, including 260 pediatric OLTX in 231 patients. BA was the indication in 137 patients. There were 69 boys and 68 girls of mean weight 10.68 kg and median age 0.9 years. As a primary transplant, 99 patients received a LLS graft; 27 a whole graft; four a I+IV-VIII segment, and two a I-IV segment. Mean follow up was 1047 days (range, 1-2496 day). Infections were diagnosed in 45 patients, vascular complications in 27 patients. Surgical complications that required reintervention occurred in 25 patients. In 41 cases biliary complications occurred, 11 requiring reintervention. 16 patients were retransplanted. In two cases another re-OLTx was performed. Currently 126 patients are alive, showing an actuarial 1 year survival of 92% and 5 year 91%, with actuarial graft survivals of 85% at 1 year and 82% at 3 and 5 years. Our results confirm the effectiveness of OLTx for the treatment of children with BA and a failed Kasai procedure. Split liver grafts represent an excellent organ supply for these patients, achieving optimal results with no mortality on the waiting list.

ABO Blood-Group System↗

PubMed2005

Transplantation for acute liver failure in children.

We reviewed the clinical data of 30 children-hospitalized for acute liver failure in the last 6 years. Ten patients were not listed for liver transplantation OLTX. Their clinical conditions gradually improved and they are all alive without deficit. Among 20 patients listed, 15 underwent urgent OLTX. Two children died on the waiting list and three were suspended from waiting list after few days because of improvement. Survival according to age class was analyzed dividing the patients into two groups: A, age 1 year or less versus B, age between 1 and 16 years. The patient survival was 86% at 6 months and 61% both at 1 and 2 years. Survival at 6 months and 1 and 2 years was 88%, 67%, and 45% for the patients in group A and 83%, 83%, and 83% for the patients in group B (P = NS). Observing graft-to-recipient weight ratio and donor-to-recipient weight ratio most patients received an optimal sized graft. The split-liver technique is considered the preferred method of liver transplantation even in the pediatric patients with acute liver failure; especially in the setting of a cooperative system in which all livers that are suitable for split-liver transplantation are shared between centers. In order to have the best chance for survival, children with acute liver failure should be referred as soon as possible to an highly specialized pediatric liver transplantation center that can offer all the treatment modalities that are currently available.

Adolescent↗

PubMed2003

Application of selectively acylated glycosides for the alpha-galactosidase-catalyzed synthesis of disaccharides.

4-Nitrophenyl alpha-D-galactopyranosyl-(1-->3)-6-O-acetyl-alpha-D-galactopyranoside was prepared in a transglycosylation reaction catalyzed by alpha-D-galactosidase from Talaromyces flavus using 4-nitrophenyl alpha-D-galactopyranoside as a glycosyl donor and 4-nitrophenyl 6-O-acetyl-alpha-D-galactopyranoside as an acceptor. 4-Nitrophenyl 6-O-acetyl-alpha-D-galactopyranoside and 4-nitrophenyl 6-O-acetyl-beta-D-galactopyranoside were prepared in a regioselective enzymic transesterification in pyridine-acetone catalyzed by the lipase PS from Burkholderia cepacia. A series of water-miscible organic solvents (acetone, acetonitrile, dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, 2-methoxyethanol, pyridine, 2-methylpropan-2-ol, tetrahydrofuran, propargyl alcohol) were used as co-solvents in this enzymic reaction. Their influence on the activity and stability of the alpha-galactosidase from T. flavus was established. 2-Methylpropan-2-ol and acetone (increasing the solubility of the modified substrate acceptors and displaying the minimum impairment of the activity and stability of the enzyme) were used as co-solvents in transglycosylation reactions.

Burkholderia cepacia↗

PubMed2002

Catheter ablation and antiarrhythmic drugs for haemodynamically tolerated post-infarction ventricular tachycardia; long-term outcome in relation to acute electrophysiological findings.

AIMS: Radiofrequency catheter ablation is effective at terminating ventricular tachycardia, but the overall clinical role of the technique in patients with a prior myocardial infarction is still debated, due to the uncertainties of the long-term reliability of the procedure. The purpose of this study was to prospectively investigate the relationship between acute results obtained by catheter ablation and long-term outcome in a homogeneous population of patients with post-myocardial infarction ventricular tachycardia. METHODS AND RESULTS: One hundred and twenty-four consecutive patients with recurrent, drug-refractory, haemodynamically tolerated ventricular tachycardia were included in the study. This population accounted for 30% of the patients with post-myocardial infarction ventricular tachycardia admitted between April 1992 and September 1997 to the investigating centres. The ablation was successful in eliminating sustained ventricular tachycardia in 91 of them (73%); a partial result was obtained in 21 (17%) and failure in 12 (10%). Low dose amiodarone and/or beta-blockers were maintained in 86% of the patients. Over a median follow-up of 41.5 months (interquartile range 30.5-59.5 months), there were 15 deaths (12%), three of which were sudden (2.4%); the 12 remaining patients died of heart failure. Event-free survival analysis showed a significantly lower ventricular tachycardia recurrence rate in patients with a successful procedure as compared to those with failure or a partial result (19% vs 53% at one year and 27% vs 60% at 3 years, P=0.003). A repeat procedure was performed in 15 patients with early recurrences and was followed in all by long-term success. Of those who submitted to a second procedure, 93/124 patients (75%) are free of ventricular tachycardia recurrences. An implantable cardioverter-defibrillator (ICD), following procedure failure, was implanted in 13 patients (11%) of the study population. CONCLUSIONS: Radiofrequency catheter ablation is effective in a wide population of patients with recurrent tolerated ventricular tachycardia, with very low sudden death and cardiac mortality rates over the long-term. Persistent ventricular tachycardia inducibility after catheter ablation requires an ICD implant and/or repeat ablation.

Adrenergic beta-Antagonists↗

PubMed2002

Non-contact mapping to guide catheter ablation of untolerated ventricular tachycardia.

AIMS: The role of a novel non-contact mapping system (ESI 3000, Endocardial Solutions) to guide radiofrequency catheter ablation of untolerated ventricular tachycardia was investigated in 17 patients; 11 with prior myocardial infarction, three with arrhythmogenic right ventricular dysplasia, and three with idiopathic dilated cardiomyopathy. METHODS: Twenty-seven monomorphic ventricular tachycardias were induced (mean cycle 320+/-60 ms, range 230-450 ms), mapped for 15-20 s, and terminated by overdrive pacing or DC shock. Off-line analysis of isopotential activation mapping was performed to identify the diastolic pathway and/or the exit point of the ventricular tachycardia reentry circuit. Radiofrequency current was applied to create a line of block across the diastolic pathway or around the exit point. RESULTS: All 27 ventricular tachycardias were mapped with the non-contact system. The endocardial exit point (-7+/-15 ms before QRS onset) was defined in 21/21 postinfarction ventricular tachycardias, in 3/3 arrhythmogenic right ventricular dysplasia and in 1/3 idiopathic dilated cardiomyopathy ventricular tachycardias, respectively. The diastolic pathway (earliest endocardial diastolic activity: -65+/-49 ms before QRS onset) was identified in 17/21 postinfarction ventricular tachycardias, in 1/3 arrhythmogenic right ventricular dysplasia and in 1/3 idiopathic dilated cardiomyopathy ventricular tachycardias, respectively. Catheter ablation was performed in 25/27 ventricular tachycardias (93%) in 15/17 patients (88%): 16/25 ventricular tachycardias (64%) were successfully ablated in 10/17 patients (59%). Catheter ablation was not performed in two patients or proved unsuccessful in five patients. At a follow-up of 15+/-5 months, there was no recurrence of documented ventricular tachycardia in all 10 patients with successful catheter ablation; in two of them a previously non-documented ventricular tachycardia occurred. A high recurrence of ventricular tachycardia was observed in patients with a failed procedure (5/7: 71%). No major complication or death occurred. CONCLUSIONS: Non-contact mapping can be effectively used to map and guide radiofrequency catheter ablation of untolerated ventricular tachycardias. Given the favourable acute and clinical long-term results, this approach proves to be more effective in patients with postinfarction ventricular tachycardias, in comparison to patients with arrhythmogenic right ventricular dysplasia and idiopathic dilated cardiomyopathy.

Adult↗

PubMed2002

Atypical atrial flutter: clinical features, electrophysiological characteristics and response to radiofrequency catheter ablation.

AIMS: To evaluate the clinical and electrophysiological features of atypical atrial flutter (AAF) and its response to radiofrequency catheter ablation. METHODS AND RESULTS: In 90 consecutive patients referred for sustained atrial flutter, bipolar recordings were obtained from the tricuspid annulus, coronary sinus, interatrial septum and left atrium. AAF was defined by the absence of concealed entrainment from the inferior vena cava--tricuspid annulus isthmus. Target sites were identified by early, fragmented or double potentials and by concealed entrainment. Linear lesions were created between target sites and nearby anatomical barriers in a temperature-controlled mode: 20 episodes of AAFs were documented in 19/90 (21%) patients. Mitral valve disease and surgery were significantly more frequent in patients with AAF. Target sites were identified in the right atrial free wall (n=8), interatrial septum (n=6), left atrium (n=4) and coronary sinus (n=2). Effective ablation was obtained in 15/19 patients (79%). After a 15.7 +/- 10.7 month follow-up, AAF recurred in 0/15 patients with a successful and 3/4 (75%) with a failed procedure (P<0.05). CONCLUSIONS: Conventional mapping techniques enable identification of critical sites of AAF and allow successful ablation in the majority of cases.

Adult↗

PubMed2002

Electrophysiological characteristics and outcome in patients with idiopathic right ventricular arrhythmia compared with arrhythmogenic right ventricular dysplasia.

BACKGROUND: Idiopathic right ventricular arrhythmias (IRVA) are responsive to medical and ablative treatment and have a benign prognosis. Arrhythmias caused by right ventricular dysplasia (ARVD) are refractory to treatment and may cause sudden death. It is difficult to distinguish between these two types of arrhythmia. OBJECTIVE: To differentiate patients with IRVA and ARVD by a conventional electrophysiological study. METHODS: 56 patients with a right ventricular arrhythmia were studied. They had no history or signs of any cardiac disease other than right ventricular dysplasia. They were classified as having IRVA (n = 41) or ARVD (n = 15) on the basis of family history, ECG characteristics, and various imaging techniques. They were further investigated by standard diagnostic electrophysiology. RESULTS: The two groups were clearly distinguished by the electrophysiological study in the following ways: inducibility of ventricular tachycardia by programmed electrical stimulation with ventricular extrastimuli (IRVA 3% v ARVD 93%, p < 0.0001); presence of more than one ECG morphology during tachycardia (IRVA 0% v ARVD 73%, p < 0.0001); and fragmented diastolic potentials during ventricular arrhythmia (IRVA 0% v ARVD 93%, p < 0.0001). Data from the clinical follow up in these patients supported the diagnosis derived from the electrophysiological study. CONCLUSIONS: Patients with IRVA or ARVD can be distinguished by specific electrophysiological criteria. A diagnosis of ARVD can be made reliably on the basis of clinical presentation, imaging techniques, and an electrophysiological study.

Adolescent↗

PubMed2001

Enzymatic glycosylation using 6-O-acylated sugar donors and acceptors: beta-N-acetylhexosaminidase-catalysed synthesis of 6-O,N,N'-triacetylchitobiose and 6'-O,N,N'-triacetylchitobiose.

p-Nitrophenyl 6-O-acetyl-2-acetamido-2-deoxy-beta-D-glucopyranoside (5a) was used as the glycosyl donor in a beta-N-acetylhexosaminidase-catalysed (from Penicillium brasilianum) glycosylation of GlcNAc yielding 6'-O,N,N'-triacetylchitobiose (6), while 6-O-acetyl-2-acetamido-2-deoxy-beta-D-glucopyranose (3a) served as a selectively protected acceptor in a transglycosylation reaction catalysed by the same enzyme to yield 6-O,N,N'-triacetylchitobiose (4).

Aspergillus oryzae↗

PubMed2001

Regioselective enzymatic glycosylation of natural polyhydroxylated compounds: galactosylation and glucosylation of protopanaxatriol ginsenosides.

Ginsenoside Rg1 (1), the most representative Ginsenoside from Panax Ginseng C.A. Meyer belonging to the protopanaxatriol family, has been galactosylated by action of the beta-(1,4)-galactosyltransferase (GalT) from bovine colostrum, using UDP-galactose as an activated sugar donor. The enzyme showed the well-known specificity for the formation of a beta-linkage with the C-4 OH of the glucose acceptor, but it was not able to discriminate between the two glucose moieties of 1, giving a mixture of mono- and digalactosylated derivatives. Other natural Rg1-analogues such as F1, Rh1, Re, as well as the synthetic derivative 6'-O-acetyl-Rg1 have been also galactosylated, giving monolactosyl derivatives. GalT was also able to accept UDP-glucose as an activated sugar donor, giving rise to cellobiosyl derivatives of Rg1.

Carbohydrate Sequence↗

PubMed2001

Performances of new sugar-bearing poly(acrylamide) copolymers as DNA sieving matrices and capillary coatings for electrophoresis.

We have synthesized two new sugar monomers, allylamine of gluconic and lactobionic acid, by opening the corresponding lactone ring with allylamine. These monomers were copolymerized with acrylamide leading to formation of copolymers with a relative molecular mass of 288000 and 180000 Da, respectively. Double-stranded DNA fragments were separated in entangled solutions of these linear polymers in capillary electrophoresis. Resolution, peak spacing and peak width were the parameters taken into account to evaluate the quality of the separation achieved with the new polymers. This work indicates that the copolymers of acrylamide and allyl gluconic acid have a high sieving capacity and provide a performance similar to that of hydroxyethylcellulose (HEC) of comparable viscosity. Unlike HEC, this copolymer selfcoats onto the capillary wall, allowing DNA fragments to be efficiently separated in an uncoated capillary.

Acrylamides↗

PubMed2001

Biocatalytic modification of natural products.

Natural products are ideal training compounds for enzymatic catalysis. New transformations have become possible on a preparative scale thanks to molecular biology, which has made many new enzymes available. Additionally, new synthetic pathways have been developed to regenerate expensive cofactors in situ and to improve enzyme selectivity.

Amino Acids↗

PubMed2001

Stress-induced nuclear bodies are sites of accumulation of pre-mRNA processing factors.

Heterogeneous nuclear ribonucleoprotein (hnRNP) HAP (hnRNP A1 interacting protein) is a multifunctional protein with roles in RNA metabolism, transcription, and nuclear structure. After stress treatments, HAP is recruited to a small number of nuclear bodies, usually adjacent to the nucleoli, which consist of clusters of perichromatin granules and are depots of transcripts synthesized before stress. In this article we show that HAP bodies are sites of accumulation for a subset of RNA processing factors and are related to Sam68 nuclear bodies (SNBs) detectable in unstressed cells. Indeed, HAP and Sam68 are both present in SNBs and in HAP bodies, that we rename "stress-induced SNBs." The determinants required for the redistribution of HAP lie between residue 580 and 788. Different portions of this region direct the recruitment of the green fluorescent protein to stress-induced SNBs, suggesting an interaction of HAP with different components of the bodies. With the use of the 580-725 region as bait in a two-hybrid screening, we have selected SRp30c and 9G8, two members of the SR family of splicing factors. Splicing factors are differentially affected by heat shock: SRp30c and SF2/ASF are efficiently recruited to stress-induced SNBs, whereas the distribution of SC35 is not perturbed. We propose that the differential sequestration of splicing factors could affect processing of specific transcripts. Accordingly, the formation of stress-induced SNBs is accompanied by a change in the splicing pattern of the adenovirus E1A transcripts.

Adaptor Proteins, Signal Transducing↗

PubMed2000

Characterization of an industrial biocatalyst: immobilized glutaryl-7-ACA acylase.

A batch of the immobilized industrial biocatalyst glutaryl-7-ACA acylase (GA), one of the two enzymes involved in the biotransformation of cephalosporin C (CefC) into 7-aminocephalosporanic acid (7-ACA), was characterized. K(m) value for glutaryl-7-ACA was 5 mM. Enzyme activity was found to be optimal at pH between 7 and 9.5 and to increase with temperature and in buffered solutions. To avoid product degradation, optimal reaction conditions were obtained working at 25 degrees C using a 50-mM phosphate buffer, pH 8.0. Immobilized GA showed good stability at pH value below 9 and at temperature up to 30 degrees C. The inactivation of immobilized GA in the presence of different amounts of H(2)O(2), a side product that might be present in the plant-scale industrial solutions of glutaryl-7-ACA, was also investigated, but the deactivation rates were negligible at H(2)O(2) concentration that might be reached under operative conditions. Finally, biocatalyst performance in the complete two-step enzymatic conversion process from CefC to 7-ACA was determined on a laboratory scale. Following the complete conversion of a 75 mM solution of CefC into glutaryl-7-ACA catalyzed by an immobilized D-amino acid oxidase (DAAO), immobilized GA was used for the transformation of this intermediate into the final product 7-ACA. This reaction was repeated for 42 cycles. An estimation of the residual activity of the biocatalyst showed that 50% inactivation of immobilized GA was reached after approximately 300 cycles, corresponding to an enzyme consumption of 0.4 kU per kg of isolated 7-ACA.

Amidohydrolases↗