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C Pecoraro

Publications and source records attributed to C Pecoraro.

At least 19 recordsLinked to original sources
PubMed2001

Microbiologic investigation on patients with cystic fibrosis subjected to bilateral lung transplantation.

BACKGROUND: In cystic fibrosis (CF) patients, lung transplantation is the only way to improve both quality and length of life. Data in the literature show that, in 80% of the cases, mortality after lung transplantation in CF patients is due to infections. METHODS: We microbiologically monitored 34 patients subjected to bilateral lung transplantation in during 1996 to 1999 to ascertain whether a change in the bacterial species isolated from the lower respiratory tract took place that might have influenced the clinical conditions of the patients. RESULTS: Our results show that the percentage of nonfermenting Gram-negative bacteria isolated from the lower respiratory tract remains high even in the posttransplantation phase. Nevertheless, the general clinical conditions of most of the patients were good and the three patients who died did not do as a consequence of an infection. CONCLUSIONS: Lung transplantation constitutes a valid therapeutic choice for CF patients because the microorganisms that we isolated from the lungs of the patients in our study behave mostly as contaminants rather than as colonizers. However, the transplanted patients remain at risk and thus require constant microbiological surveillance.

Bronchiolitis Obliterans↗
PubMed2001

Role of the K-channel in the pH-dependence of the reaction of cytochrome c oxidase with hydrogen peroxide.

The reaction of cytochrome c oxidase (COX) from Rhodobacter sphaeroides with hydrogen peroxide has been studied at alkaline (pH 8.5) and acidic (pH 6.5) conditions with the aid of a stopped-flow apparatus. Absorption changes in the entire 350-800 nm spectral range were monitored and analyzed by a global fitting procedure. The reaction can be described by the sequential formation of two intermediates analogous to compounds I and II of peroxidases: oxidized COX + H2O2 --> intermediate I --> intermediate II. At pH as high as 8.5, intermediate I appears to be a mixture of at least two species characterized by absorption bands at approximately 607 nm (P607) and approximately 580 nm (F-I580) that rise synchronously. At acidic pH (6.5), intermediate I is represented mainly by a component with an alpha-peak around 575 nm (F-I575) that is probably equivalent to the so-called F* species observed with the bovine COX. The data are consistent with a pH-dependent reaction branching at the step of intermediate I formation. To get further insight into the mechanism of the pH-dependence, the peroxide reaction was studied using two mutants of the R. sphaeroides oxidase, K362M and D132N, that block, respectively, the proton-conducting K- and D-channels. The D132N mutation does not affect significantly the Ox --> intermediate I step of the peroxide reaction. In contrast, K362M replacement exerts a dramatic effect, eliminating the pH-dependence of intermediate I formation. The data obtained allow us to propose that formation of the acidic form of intermediate I (F-I575, F*) requires protonation of some group at/near the binuclear site that follows or is concerted with peroxide binding. The protonation involves specifically the K-channel. Presumably, a proton vacancy can be generated in the site as a consequence of the proton-assisted heterolytic scission of the O-O bond of the bound peroxide. The results are consistent with a proposal [Vygodina, T. V., Pecoraro, C., Mitchell, D., Gennis, R., and Konstantinov, A. A. (1998) Biochemistry 37, 3053-3061] that the K-channel may be involved in the delivery of the first four protons in the catalytic cycle (starting from reduction of the oxidized form) including proton uptake coupled to reduction of the binuclear site and transfer of protons driven by cleavage of the dioxygen O-O bond in the binculear site. Once peroxide intermediate I has been formed, generation of a strong oxene ligand at the heme a3 iron triggers a transition of the enzyme to the "peroxidase conformation" in which the K-channel is closed and the binuclear site becomes protonically disconnected from the bulk aqueous phase.

Animals↗
PubMed1998

The post-translational modification in cytochrome c oxidase is required to establish a functional environment of the catalytic site.

Mutation of tyrosine-288 to a phenylalanine in cytochrome c oxidase from Rhodobacter sphaeroides drastically alters its properties. Tyr-288 lies in the CuB-cytochrome a3 binuclear catalytic site and forms a hydrogen bond with the hydroxy group on the farnesyl side chain of the heme. In addition, through a post-translational modification, Y288 is covalently linked to one of the histidine ligands that is coordinated to CuB. In the Y288F mutant enzyme, the "as-isolated" preparation is a mixture of reduced cytochrome a and oxidized cytochrome a3. The cytochrome a3 heme, which is largely six-coordinate low-spin in both oxidation states of the mutant, cannot be reduced by cytochrome c, but only by dithionite, possibly due to a large decrease in its reduction potential. It is postulated that the Y288F mutation prevents the post-translational modification from occurring. As a consequence, the catalytic site becomes disrupted. Thus, one role of the post-translational modification is to stabilize the functional catalytic site by maintaining the correct ligands on CuB, thereby preventing nonfunctional ligands from coordinating to the heme.

Binding Sites↗
PubMed1998

Mechanism of inhibition of electron transfer by amino acid replacement K362M in a proton channel of Rhodobacter sphaeroides cytochrome c oxidase.

The three-dimensional structure of cytochrome coxidase (COX) reveals two potential input proton channels connecting the redox core of the enzyme with the negatively charged (N-) aqueous phase. These are denoted as the K-channel (for the highly conserved lysine residue, K362 in Rhodobacter sphaeroides COX) and the D-channel (for the highly conserved aspartate gating the channel at the N-side, D132 in R. sphaeroides). In this paper, it is shown that the K362M mutant form of COX from R. sphaeroides, although unable to turnover with dioxygen as electron acceptor, can utilize hydrogen peroxide as an electron acceptor, with either cytochrome c or ferrocyanide as electron donors, with turnover that is close to that of the wild-type enzyme. The peroxidase activity is similar to that of the wild-type oxidase and is coupled to the generation of a membrane potential and to proton pumping. In contrast, no peroxidase activity is revealed in the D-channel mutants of COX, D132N, and E286Q. Reduction by dithionite of heme a3 in the fully oxidized oxidase is severely inhibited in the K362M mutant, but not in the D132N mutant. Apparently, mutations in the D-channel arrest COX turnover by inhibiting proton uptake associated with the proton-pumping peroxidase phase of the COX catalytic cycle. In contrast, the K-channel appears to be dispensable for the peroxidase phase of the catalytic cycle, but is required for the initial reduction of the heme-copper binuclear center in the first half of the catalytic cycle.

Amino Acid Substitution↗
PubMed1998

[Computerized tomography assessment of replacement of the cruciate ligaments of the knee].

January, 1993, to December, 1995, we examined with CT 44 patients submitted to surgical replacement of knee cruciate ligaments, namely 18 anterior cruciate ligaments (ACL) and 6 posterior cruciate ligaments (PCL). ACL was replaced with a patellar tendon graft (Eriksson technique) in 23 cases and with a semitendinous graft (Lindemann-Bousquet technique) in 7 cases. The autologous new ligament appeared as a laminar structure of intermediate density. The tendon had been covered with a synthetic lining (Leeds-Kejo) in 10 of the above cases, while the new ACL graft was completely synthetic in 8 cases, which synthetic allografts appeared hyperdense relative to autologous new ligaments. PCL replacement had been performed with Augustine technique (patellar tendon graft in a tibial tunnel) in 3 cases, with Hughston technique (medial gastrocnemius graft in a medial condylar tunnel) in 2 cases and with a synthetic graft (Gore-tex) in 1 case. Twelve of 38 new ACLs were injured (7 Eriksson, 3 Lindemann-Bousquet and 2 synthetic grafts): the injured new ligament was enlarged and hypodense, or involved in atrophic absorption. The new ligament was partially calcified in one of the 3 patients with PCL replacement with a patellar tendon graft (Augustine technique). The bone bract was dislocated in the intercondylar notch in a patient submitted to Hughston surgery because of proximal disinsertion of the new ligament. The Gore-tex new PCL was sinuous in the proximal tract, with intra-articular calcified loose bodies. CT adequately depicted surgical results and diagnosed the new ligament injuries and other articular abnormalities. MRI is currently the gold standard in the multiplanar studies of the postoperative knee, but CT can be confidently used to identify ligament injuries and intra-articular calcified loose bodies.

Anterior Cruciate Ligament↗
PubMed1996

[Preoperative assessment of Blount disease].

Osteochondrosis of the medial proximal tibial epiphyseal plate is known as Blount disease. To date, two types have been described: infantile and juvenile disease. Six patients (5 men and 1 woman, mean age: 7.2 years) affected with infantile Blount disease diagnosed with plain radiography were submitted to Magnetic Resonance Imaging (MRI) for preoperative lesion staging. The lesions were bilateral in 5 patients. According to Langenskiöld classification, 2 patients were in stage II-III, 3 in stage III-IV and 1 in stage V-VI. Each patient underwent MRI of the more affected knee and 1 patient, who exhibited a more prominent metaphyseal beak, underwent CT of both knees. MRI depicted proximal tibia varus deformity and the degree of its angulation, which helped plan osteotomy; impaired growth of the medial portion of the proximal tibia involving physeal cartilage, metaphysis and epiphysis; alterations of menisci and ligaments (hypertrophic medial meniscus, medial collateral ligament laxity), the presence of bone bridges; the presence and integrity of unossified epiphysis and of chondral growth plate which was quite completely ossified in one case. To conclude, MRI is a completely atraumatic and noninvasive technique yielding many pieces of information necessary for the preoperative assessment of Blount disease.

Child↗
PubMed1995

The role of cyanide in the removal of type 2 copper from laccase.

We have improved a method for the removal of the type 2 copper from tree laccase under anaerobic reducing conditions and developed a mechanistic model. We identify two key steps in the reaction: (i) dissociation of copper(I) catalyzed by trace levels of cyanide in a weakly acidic medium and (ii) sequestration of the released metal by an appropriate chelator such as 2,9-dimethyl-1,10-phenanthroline. We maintain a steady-state concentration of cyanide in a pH 5.5 acetate buffer under a constantly exchanging nitrogen atmosphere by introducing a cyanometalate ion as a cofactor or by continuously injecting the ion into the protein solution. The type 2-depleted product is identical to previous preparations as regards its spectral properties, activity level and ability to recombine with copper(I). The mechanistic insights appear to be quite general and should form the basis for the development of methods for removing the type 2 copper from other related systems.

Copper↗
PubMed1995

Lysinuric protein intolerance characterized by bone marrow abnormalities and severe clinical course.

STUDY OBJECTIVE: To evaluate phenotypic variability of lysinuric protein intolerance in a cohort of nine Italian patients. DESIGN: Retrospective analysis of patient records. SUBJECTS: Nine Italian patients (seven independent families), all originating from southern Italy, observed during the last 14 years. RESULTS: Some of the patients had unique clinical features, including bone marrow abnormalities featuring erythroblastophagocytosis (five patients) and clinical course and the outcome of the disease, have also been observed: respiratory involvement was present in five cases, with a lethal picture of "alveolar proteinosis" in one. Severe kidney involvement, with both glomerular and tubular damage and rapidly progressing to chronic renal failure, has been observed in one case. CONCLUSION: Lysinuric protein intolerance may cause severe multisystem involvement, which requires early and careful monitoring. Some peculiar clinical findings observed in Italian patients point to a genetic heterogeneity of lysinuric protein intolerance.

Adolescent↗
PubMed1994

Renal tubular dysgenesis without pulmonary hypoplasia.

Only a few cases of renal tubular dysgenesis (RTD) have been diagnosed. RTD is associated with a very early death, always due to lethal pulmonary hypoplasia. We report an additional patient, interesting for two reasons: (1) the rarity of RTD, (2) the absence of microscopic and macroscopic anatomical alterations of the lungs. The infant had only a mild, transient pulmonary maladaptation; after a few days of life the pulmonary function returned to normal. Although renal function dramatically improved after institution of peritoneal dialysis at 6 days of life, the patient died after 2 weeks with an overwhelming Candida sepsis. We suggest that the lack of pulmonary hypoplasia might be due to a short exposure to oligohydramnios.

Fatal Outcome↗