Search PubMed⌕ Search

Biomedical subjects

G De Luca

Publications and source records attributed to G De Luca.

At least 37 records · Page 2Linked to original sources
PubMed2003

Hydrogenases in sulfate-reducing bacteria function as chromium reductase.

The ability of sulfate-reducing bacteria (SRB) to reduce chromate VI has been studied for possible application to the decontamination of polluted environments. Metal reduction can be achieved both chemically, by H(2)S produced by the bacteria, and enzymatically, by polyhemic cytochromes c(3). We demonstrate that, in addition to low potential polyheme c-type cytochromes, the ability to reduce chromate is widespread among [Fe], [NiFe], and [NiFeSe] hydrogenases isolated from SRB of the genera Desulfovibrio and Desulfomicrobium. Among them, the [Fe] hydrogenase from Desulfovibrio vulgaris strain Hildenborough reduces Cr(VI) with the highest rate. Both [Fe] and [NiFeSe] enzymes exhibit the same K(m) towards Cr(VI), suggesting that Cr(VI) reduction rates are directly correlated with hydrogen consumption rates. Electron paramagnetic resonance spectroscopy enabled us to probe the oxidation by Cr(VI) of the various metal centers in both [NiFe] and [Fe] hydrogenases. These experiments showed that Cr(VI) is reduced to paramagnetic Cr(III), and revealed inhibition of the enzyme at high Cr(VI) concentrations. The significant decrease of both hydrogenase and Cr(VI)-reductase activities in a mutant lacking [Fe] hydrogenase demonstrated the involvement of this enzyme in Cr(VI) reduction in vivo. Experiments with [3Fe-4S] ferredoxin from Desulfovibrio gigas demonstrated that the low redox [Fe-S] (non-heme iron) clusters are involved in the mechanism of metal reduction by hydrogenases.

Cytochromes↗
PubMed2003

Chiral 3,3'-(1,2-ethanediyl)-bis[2-(3,4-dimethoxyphenyl)-4-thiazolidinones] with anti-inflammatory activity. Part 11: evaluation of COX-2 selectivity and modelling.

Anti-inflammatory/analgesic 3,3'-(1,2-ethanediyl)-bis[2-(3,4-dimethoxyphenyl)-4-thiazolidinones] 1, obtained as racemic mixtures (a) and mesoforms (b), have two equivalent stereogenic centres (C-2 and C-2') and exist as RR, SS and RS isomers. The enantioseparation of 1a provided the single enantiomers that displayed different in vitro cyclooxygenase-1/cyclooxygenase-2 selectivity ratios. In particular the dextrorotatory compound is a highly selective COX-2 inhibitor and the levorotatory one is moderately selective. Instead, RS-meso isomer (1b) exhibited similar levels of inhibitory activity on both COX isozymes. The diastereo- and enantioselectivity has been explained by molecular modelling of RR, SS and RS compounds into COX-1 and COX-2 binding sites. Theoretical results indicated SS>RS>RR affinity order towards COX-2 isoenzyme, in agreement with in vitro and previous in vivo pharmacological results.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2003

Decontamination of dental unit water systems with hydrogen peroxide.

AIMS: Transmission of microbial pathogens to patients from water in dental units is a concern. To reduce this risk, the decontaminating efficiency of hydrogen peroxide was evaluated. METHODS AND RESULTS: Three percent hydrogen peroxide diluted 1 : 4 in distilled water (contact time 15 min) was used daily to disinfect the waterlines of a pilot unit previously contaminated with Pseudomonas aeruginosa or Staphylococcus aureus. The behaviour of the test bacteria was seen to differ over time. Staph. aureus numbers slowly decreased until only low numbers were recovered, after which the levels remained stable. Ps. aeruginosa abatement was more rapid and the density of the bacteria reached a peak when the circuit was empty. CONCLUSIONS: Staph. aureus and Ps. aeruginosa treated with hydrogen peroxide fell from 6 to 4 log. SIGNIFICANCE AND IMPACT OF THE STUDY: Treatment of dental unit waterlines with hydrogen peroxide was seen to be able to keep the number of the bacteria under control, as long as the treatment was repeated daily.

Anti-Infective Agents, Local↗
PubMed2003

Monodomain and polydomain helicoids in chiral liquid-crystalline phases and their biological analogues.

Many natural composites exhibit an architecture known as twisted plywood which imparts to them a superior set of physical properties. The origin of this structure is complex and not yet understood. However, it is thought to involve a lyotropic chiral nematic liquid-crystalline mesophase. Indeed, striking structural similarities have been observed and reported between biological fibrous composites and ordered fluids. In this work, a mathematical model based on the Landau-de Gennes theory has been developed to investigate the role played by constraining surfaces in the structural development of a composite material that experiences a liquid-crystalline state during the early steps of its morphogenesis. The goal of this study is to verify the need for an initial constraining surface in the formation of monodomain twisted plywoods as hypothesized by Neville (Tissue & Cell 20, 133 (1988); Biology of Fibrous Composites (Cambridge University Press, 1993)). The numerical simulations qualitatively confirm this theory and highlight the important role that modelling of liquid-crystalline self-assembly plays in the study of tissue morphogenesis.

Anisotropy↗
PubMed2003

Immunomagnetic assay, classic culture method and fermentation tube test in the recovery of Escherichia coli O157 from sewage.

The diffusion of E. coli O157 was studied in the effluents of a large sewage treatment plant. Three methods were used: the Culture Method, Immunomagnetic Separation (IMS) and Fermentation Tube Test. Vero cells assay and PCR were used to assess toxin production and the presence of virulence genes. E. coli O157 were only detected using IMS and the Fermentation Tubes Test: one strain in raw sewage and 2 in a sample of disinfected effluent. The latter resulted positive for the production of verocytotoxin and possessed genes coding for vt2 and type gamma intimin. The best results were obtained with SMAC-CT-BCIG medium. The use of various different recovery techniques confirmed the difficulty involved in isolating E. coli O157 from water samples.

Bacteriological Techniques↗
PubMed2002

On the hardness evaluation in solvent for neutral and charged systems.

The influence of water on the hardness values of a series of neutral and charged molecules has been studied in the framework of density functional theory using the polarizable continuum model to take into account solvent effects. Three working formulas already widely tested in gas-phase have been used and the results compared. Two of the methods employed going from gas phase to solvent phase give values that do not change, while the results of the third method show remarkable changes. To check the reliability of the hardness behavior found, a test based on the hard-soft/acid-base principle and the calculation of the free energy of reaction has been applied using the adopted procedures.

Journal Article↗
PubMed2002

Sulphydryl groups involved in Na+-Li+ exchange in human erythrocytes.

Oxidative stress causes cellular injury that is thought to be due to increased cytosolic cation levels. Disturbances of a variety of mechanisms which normally maintain intracellular anion/cation homeostasis, occur during oxidative stress. Reactivity of the SH- groups essential for oubain-resistant Na(+)-Li(+) exchange by N-ethylmaleimide (NEM) and selenite was studied in human erythrocytes. In addition, the reactivity of the substances on SH- groups and Li(+) influx have been studied as a function of pH of the medium. The results show that NEM induces an irreversible inhibition of Li(+) influx. It diminishes progressively with the increasing pH of the medium. Whereas we obtain increasing intracellular Li(+) concentration with the rising selenite concentration in the medium. The maximum effect with this substance is reached at about pH 8.0. We can state that the -SH reagents (NEM and selenite) studied behave differently: NEM inhibits Li(+) influx by modifying the essential SH-groups of the membrane proteins in such a way that the exchange is reduced, whereas it maintains the Na(+) permeability almost unaltered. The slight increase in intracellular Na(+) induced by selenite suggests that the oxidative changes in the intracellular sulphydryl groups may constitute an important mechanism for the regulation of the intracellular cations.

Antiporters↗
PubMed2002

Peracetic acid as an alternative wastewater disinfectant to chlorine dioxide.

AIMS: The aim of this study was to compare the efficiency of peracetic acid with that of chlorine dioxide in the disinfection of wastewater from a sewage treatment plant (serving about 650 000 inhabitants) that has been using peracetic acid as a disinfectant since 1998. METHODS AND RESULTS: A total of 23 samplings were made, each consisting of three samples: from secondary effluent, effluent disinfected with 2 mg l(-1) of peracetic acid and effluent disinfected with 2.2 mg l(-1) of chlorine dioxide (contact time 20 min). For each sample, measurements were made of the heterotrophic plate count at 36 degrees C, total and faecal coliforms, Escherichia coli, enterococci, pH, suspended solids and chemical oxygen demand (COD). During the first phase of the experiment the peracetic acid was seen to be less efficient than chlorine dioxide. To improve the disinfectant action a system of mechanical agitation was added which led to a greater efficiency in the inactivation of bacteria of faecal origin. CONCLUSIONS: Both products were found to be influenced by the level of microbial contamination, the amount of suspended solids and COD but not by the pH of the effluent before disinfection. The immediate mixing of the wastewater and disinfectant caused a greater reduction in enterococci. SIGNIFICANCE AND IMPACT OF THE STUDY: Since peracetic acid was seen to produce a high abatement of micro-organisms, it can be considered as a valid alternative to chlorine dioxide in the disinfection of wastewaters.

Bacteria↗
PubMed2002

Oxidation of low-density lipoprotein in atherosclerosis from basic biochemistry to clinical studies.

Although it has been known for long time that atherosclerosis is associated with lipid deposition, only recently it has been accepted that the plasmatic concentration of cholesterol, especially LDL cholesterol, is a risk factor for atherosclerosis. However, chemically modified LDL, but not native LDL, is able to induce the formation of foam cells, the hallmark of atherosclerosis. LDL oxidation is likely to be the most important form of LDL modification in humans. In biochemical terms, LDL oxidation is a free radical driven chain reaction where polyunsaturated fatty acids are converted to lipid peroxides, which easily decompose to many products, including biologically active aldehydes. The assay of LDL oxidation in biological fluids is problematic; direct assays detect a product of LDL oxidation whereas indirect assays give an indicator of LDL oxidation susceptibility. In general, epidemiological studies support the concept that the level of plasmatic lipophilic antioxidants, tocopherols and carotenoids, is low in populations at increased risk for atherosclerosis. However, clinical trials based on vitamin E as antioxidant showed inconclusive results, suggesting that supplementation with vitamin E is not generically recommended for atherosclerotic patients. These results, however, do not contradict that oxidation of lipoprotein is involved in atherosclerosis; rather, this negative outcome raises a number of considerations such as the need for a reliable marker of lipoprotein oxidation in plasma and a more complete information about the physiological triggers of lipoprotein oxidation.

Animals↗
PubMed2001

Direct coronary stenting: effect on coronary blood flow, immediate and late clinical results.

Direct stenting (DS) was attempted in 99 coronary lesions in 94 patients while standard stenting (SS) was attempted in 113 lesions in 103 patients matched for clinical characteristics, stenosis type, and location and stent type. The angiographic result was also evaluated according to TIMI frame count method (TFC) before and after procedure. A clinical follow-up was performed 1 year after the procedure. Before the procedure, TIMI grade 3 flow was detected in 42 cases (42.4%), grade 2 in 40 cases (40.4%), grade 1 in 5 cases (5.1%), and grade 0 in 12 cases (12.1%) in the DS group; these data were similar in SS group. After the procedure, TIMI grade flow was 3 in 90 cases (92.8%) in DS group and in 87 (77.0%) in SS group (P < 0.005); grade 2 was observed in 7 case (7.2%) in DS group and in 25 (22.1%) in SS group (P < 0.005). Major adverse cardiac events during hospitalization and at follow-up were similar in two groups. Radiation exposure time and procedure costs per lesion were significantly reduced in DS group compared to SS group (10.1 +/- 8 min vs. 13.9 +/- 4.7 min, P < 0.001; and 1901 +/- 687 Euro vs. 2352 +/- 743 Euro, P < 0.001, respectively). This study confirms that, in selected patients, direct stenting is a safe and successful procedure, allowing a significant reduction in radiation exposure time and procedural costs compared to standard stenting technique. The angiographic success is confirmed by the improvement in TFC in all cases.

Abciximab↗
PubMed2001

Peripheral neuropathy as the presenting feature of multiple system atrophy.

The authors report a case of multiple system atrophy (MSA) with an onset as a peripheral nerve involvement. Their patient, a 55-year-old man, had a 3-year history of distal weakness and atrophy in upper limbs with dysesthesia in the feet. Other identifiable causes of peripheral neuropathy were ruled out. The authors postulate that peripheral nervous system impairment can anticipate the typical appearance of MSA, and they suggest that, in peripheral neuropathies with autonomic system dysfunction, after excluding main causes of autonomic neuropathy, MSA may need to be suspected.

Autonomic Nervous System↗
PubMed2001

Low-dose oral methotrexate treatment in chronic progressive multiple sclerosis.

We aimed to further assess the safety and efficacy of low-dose oral methotrexate (LDOM) treatment for chronic progressive MS (CPMS). We studied 20 CPMS patients, including 16 with secondary progressive MS who had shown disease progression in the previous year. The mean follow-up was 23 months. The mean EDSS score was 6.3+/-1.1 before treatment and 6.4+/-1.1 after one year of treatment. At one year, 15 of 20 patients were still being treated, and 10 were stable. Twelve patients have completed 18 months of treatment, and eight are stable. Two patients stopped treatment because of side effects, two more because they did not perceive benefit, and one was lost to follow-up. Six patients had mild, transient increases in liver enzymes not requiring treatment interruption, and two had localized herpes zoster. Magnetic resonance imaging (MRI) performed before treatment and at one year remained unchanged in responders. We confirm that LDOM is safe in carefully selected and monitored CPMS patients. MTX is inexpensive and, given its anti-inflammatory and immunomodulatory properties, may be used as add-on therapy in non-responders to interferon beta, although hepatic toxicity may be a problem in long-term treatment.

Adult↗
PubMed2001

Efficacy and safety of Nd:YAG laser for the treatment of bleeding from radiation proctocolitis.

BACKGROUND: Bleeding due to radiation proctocolitis is a frequent and severe complication of radiotherapy in cancers of the pelvis. AIM: The aim of this study was to evaluate the efficacy and safety of endoscopic treatment with Nd:YAG laser in this condition. PATIENTS AND METHODS: A series of 9 patients with radiation-induced damage in the rectum and sigma were treated with endoscopic Nd:YAG laser until significant bleeding stopped and endoscopic features of proctocolitis improved. They received a median of 3 laser treatments (range 1-10) over a maximum time period of 11 months. RESULTS: In 4 cases, bleeding ceased and, in 4, it was reduced to occasional spotting. In the remaining patient, laser therapy led to only a transient improvement, but did not modify the requirement of blood transfusion. In the 5 patients also suffering from urgency, incontinence and/or rectal mucoid discharge, the laser therapy course also relieved these symptoms. No significant treatment-related complications were observed. CONCLUSIONS: Endoscopic Nd: YAG laser is a useful and safe treatment for patients with bleeding due to radiation proctocolitis.

Aged↗
PubMed2001

Evaluation of the efficiency of peracetic acid in the disinfection of sewage effluents.

AIMS: Evaluation of the efficiency of peracetic acid in the disinfection of wastewater in a large treatment plant. METHODS AND RESULTS: Over a period of 18 months 30 sample collections were made, each consisting of three samples taken from: raw incoming sewage, secondary effluent (after 10-12 h) and secondary effluent disinfected with 1.5-2 mg l(-1) of peracetic acid (contact time: 20 min). Total coliforms and Escherichia coli declined from 10(7) MPN 100 ml(-1) in the raw sewage to 10(2) in the disinfected effluent and the enterococci fell from 10(6) MPN 100 ml(-1) to 702 MPN 100 ml(-1). The reduction of bacteria increased with the rise in temperature and decreased with the rise in BOD5. CONCLUSIONS: Disinfection with peracetic acid reduced levels of faecal contamination by 97%, thus attaining the limit recommended by current Italian law (Escherichia coli <or= 5000 MPN 100 ml(-1)) for discharge into surface waters. SIGNIFICANCE AND IMPACT OF THE STUDY: The process of disinfection with peracetic acid is easier to manage than other more common methods and the tests performed confirm that from the bacteriological point of view good results can be obtained for urban effluents.

Bacteria↗
PubMed2001

Taurine and osmoregulation: platelet taurine content, uptake, and release in type 2 diabetic patients.

In this study, plasma and platelet taurine content and fluxes were determined in 38 type 2 diabetic patients and in 26 healthy control subjects. Taurine levels in diabetic patients were significantly lower than in control subjects both in plasma (32.1 v 48.6 micromol/L, P = .000) and platelets (148 v 183 nmol/mg protein, P = .043). Platelet taurine uptake in diabetic patients was significantly reduced (321.2 v 524.9 pmol total taurine 10(8) platelet(-1) min(-20), P = .000), whereas taurine release increased in comparison to healthy controls (38.7 v 29.5% of platelet 3H taurine at the start of incubation, P = .000). These results may reflect modified systems of taurine carriers or a compensatory mechanism in response to an increase of other organic osmolytes.

Blood Platelets↗
PubMed2001

Preliminary report: Amino acid profile in platelets of diabetic patients.

Platelet levels of 19 amino acids were measured in 20 outpatients with type 1 (age [mean +/- SE], 35.5 +/- 2.0 years) and 27 with type 2 (age, 58.4 +/- 1.4 years) diabetes, and 20 young (age 33.7 +/- 1.3 years) and 20 older (age 57.4 +/- 1.5 years) healthy volunteers. Platelet levels of most amino acids tended to be lower in patients with type 1 diabetes than in healthy controls. In particular, asparagine, glycine, taurine, alanine, valine, cysteine, leucine, phenylalanine, and lysine levels, expressed as nmol/10(8) platelets, were significantly lower. Only taurine significantly decreased in patients with type 2 diabetes, whereas threonine, alanine, and isoleucine increased.

Adult↗
PubMed2001

Airborne coagulase negative staphylococci produced by a sewage treatment plant.

Since some coagulase-negative staphylococci species are involved in clinical and environmental situations, the authors carried out a study on the spread of these bacteria in the air of a sewage treatment plant. For these purposes a total of 196 samples were taken from 16 sampling stations, 11 during the day and 5 at night (only at 4 points), using the settle plate technique. Altogether 13 species of coagulase negative staphylococci were isolated: S. haemolyticus, S. xylosus and S. cohnii were particularly common. Station no. 2 (an area almost always kept closed containing the fine screens) was found to be the most contaminated. The presence of coagulase negative staphylococci was favoured by high temperatures and low humidity. No differences were found due to variations in wind speed and direction or between day and night.

Air Pollutants↗