Biomedical subjects

Y Moreno

Publications and source records attributed to Y Moreno.

14 recordsLinked to original sources

PubMed2006

Development of a simple and rapid method based on polymerase chain reaction-based restriction fragment length polymorphism analysis to differentiate Helicobacter, Campylobacter, and Arcobacter species.

Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of amplified DNA fragment of the 16S and 23S rRNA genes was performed on 35 Helicobacter, 24 Campylobacter, and 15 Arcobacter strains. PCR amplification generated a 1004-bp fragment of 16S rDNA and a 2.6-Kbp fragment of 23S rDNA from each strain. The amplicons were digested with DdeI and HpaII, respectively. For both assays, distinctive profiles were obtained for each genus. 23S rDNA PCR-RFLP analysis with HpaII enzyme identified Campylobacter and Helicobacter strains at the species level. Analysis of 16S rRNA gene with DdeI enzyme was not useful for the specific identification of Campylobacter and Arcobacter, although it discriminated among Helicobacter species. The PCR-RFLP technique allowed for the discrimination among these three related genus with only one restriction enzyme; therefore it can be a simple, rapid, and useful method for routine identification.

Arcobacter↗

PubMed2006

Landfill leachate treatment using a rotating biological contactor and an upward-flow anaerobic sludge bed reactor.

This paper describes the feasibility of an aerobic system (rotating biological contactor, RBC) and a biological anaerobic system (upward-flow anaerobic sludge bed reactor) at small scale for the treatment of a landfill leachate. In the first phase of the aerobic system study, a cyclic-batch RBC system was used to select perforated acetate discs among three different acetate disc configurations. These discs were chosen on the basis of high COD removal (65%) and biological stability. In the second phase, the RBC system (using four stages) was operated continuously at different hydraulic retention times (HRT), at different rotational speeds, and with varying organic concentrations of the influent leachate (2500-9000mgL(-1)). Forty percent of the total surface area of each perforated disc was submerged in the leachate. A COD removal of about 52% was obtained at an HRT of 24h and a rotational speed of 6rpm. For the anaerobic system, the reactor was evaluated with a volumetric organic load of 3273g-COD m(-3) day(-1) at an HRT of 54, 44, 39, 24 and 17h. At these conditions, the system reached COD removal efficiencies of 62%, 61%, 59%, 44% and 24%, respectively.

Anaerobiosis↗

PubMed2006

Awaking and sleeping of a complex network.

A network with a logistic-like local dynamics is considered. We implement a mean-field multiplicative coupling among first-neighbor nodes. When the coupling parameter is small, the dynamics is dissipated and there is no activity: the network is turned off. For a critical value of the coupling, a non-null stable synchronized state, which represents a turned on network, emerges. This global bifurcation is independent of the network topology. We characterize the bistability of the system by studying how to perform the transition, which is now topology dependent, from the active state to that with no activity, for the particular case of a scale-free network. This could be a naive model for the wakening and sleeping of a brain-like system, i.e., a multi-component system with two different dynamical behaviors.

Animals↗

PubMed2006

Scale-free topologies and activatory-inhibitory interactions.

A simple model of activatory-inhibitory interactions controlling the activity of agents (substrates) through a "saturated response" dynamical rule in a scale-free network is thoroughly studied. After discussing the most remarkable dynamical features of the model, namely fragmentation and multistability, we present a characterization of the temporal (periodic and chaotic) fluctuations of the quasi-stasis asymptotic states of network activity. The double (both structural and dynamical) source of entangled complexity of the system temporal fluctuations, as an important partial aspect of the correlation structure-function problem, is further discussed in light of the numerical results, with a view on potential applications of these general results.

Action Potentials↗

PubMed2003

Use of fluorescent in situ hybridization to evidence the presence of Helicobacter pylori in water.

We have evaluated the use of a fluorescent in situ hybridization (FISH) technique for the detection of Helicobacter pylori in water (river and wastewater) samples. The assay was compared with PCR detection and isolation of cells on selective media. 16S rRNA and UreA+B sequence data were used as oligonucleotide probe and specific primers for FISH and PCR, respectively. Using FISH technique, H. pylori was detected in two river water and one wastewater samples, while PCR yielded only one positive result. H. pylori culture was not possible from any sample. According to these results, FISH technique has the potential to be used as a quick and sensitive method for detection of H. pylori in environmental samples.

DNA, Bacterial↗

PubMed2001

Time dependence of breakdown in a global fiber-bundle model with continuous damage.

A time-dependent global fiber-bundle model of fracture with continuous damage is formulated in terms of a set of coupled nonlinear differential equations. A first integral of this set is analytically obtained. The time evolution of the system is studied by applying a discrete probabilistic method. Several results are discussed emphasizing their differences with the standard time-dependent model. The results obtained show that with this simple model a variety of experimental observations can be qualitatively reproduced.

Journal Article↗

PubMed2000

Fracture and second-order phase transitions.

Using the global fiber bundle model as a tractable scheme of progressive fracture in heterogeneous materials, we define the branching ratio in avalanches as a suitable order parameter to clarify the order of the phase transition occurring at the collapse of the system. The model is analyzed using a probabilistic approach suited to smooth fluctuations. The branching ratio shows a behavior analogous to the magnetization in known magnetic systems with second-order phase transitions. We obtain a universal critical exponent beta approximately = 0.5 independent of the probability distribution used to assign the strengths of individual fibers.

Journal Article↗

PubMed1999

In situ analysis of the bacterial communities associated to farmed eel by whole-cell hybridization.

Bacterial communities in water samples and eel slime were investigated by fluorescence in situ hybridization of whole bacterial cells in an eel intensive culture system over 1 year. A newly developed probe, matching 27 Vibrio spp., and a specific probe for Vibrio vulnificus were used. Phylogenetic probes complementary to selected regions of the 16S and 23S ribosomal RNA revealed that Proteobacteria of the alpha and beta subclass were predominant in water and eel slime. Members of the gamma subclass (e.g. vibrios and aeromonads) were more abundant in eel slime, although no V. vulnificus was detected.

Alphaproteobacteria↗

PubMed1999

Time to failure of hierarchical load-transfer models of fracture.

The time to failure, T, of dynamical models of fracture for a hierarchical load-transfer geometry is studied. Using a probabilistic strategy and juxtaposing hierarchical structures of height n, we devise an exact method to compute T, for structures of height n+1. Bounding T, for large n, we are able to deduce that the time to failure tends to a nonzero value when n tends to infinity. This numerical conclusion is deduced for both power law and exponential breakdown rules.

Journal Article↗

PubMed1999

Modified renormalization strategy for sandpile models.

Following the renormalization-group scheme recently developed by Pietronero et al. [Phys. Rev. Lett. 72, 1690 (1994)] we introduce a simplifying strategy for the renormalization of the relaxation dynamics of sandpile models. In our scheme, five subcells at a generic scale b form the renormalized cell at the next larger scale. Now the fixed point has a unique nonzero dynamical component that allows for a great simplification in the computation of the critical exponent z. The values obtained are in good agreement with both numerical and theoretical results previously reported.

Journal Article↗

PubMed1998

Differences in visual search tasks between congenitally deaf and normally hearing adults.

In order to study the processes of central vision in deaf subjects, 12 congenitally deaf adults and 12 normally hearing adults performed a visual search task. The task consisted of detecting a "Q" target among "O" distractors in variable numbers and the reverse. The method used a paradigm based on the stimulus onset asynchrony (SOA) specifically designed to measure the visual processing time between the visual array and a mask. A different visual search pattern was observed in each group. The hearing subjects showed an asymmetrical visual search pattern (parallel versus serial processing respectively for "Q" and "O" targets). In contrast, the deaf subjects showed a symmetrical search pattern (parallel processing in both experimental conditions). In a visual task selectively supported by central vision, visual processes of the congenitally deaf are more efficient when the task involves the contribution of serial processes.

Adolescent↗

PubMed1988

Alterations in high-density lipoprotein subfractions during postprandial lipidaemia induced by fat with and without ethanol.

1. Serum lipid and apolipoprotein levels, distribution and composition of high-density lipoprotein (HDL) subfractions and lecithin:cholesterol acryltransferase activity were analysed in nine normolipidaemic subjects, in whom a hypertriglyceridaemic state was induced by the acute administration of ethanol (40 g) plus fat (70 g) or of fat only. 2. Triglyceride (TG) levels increased by 180% 4-6 h after fat plus ethanol intake, the hypertriglyceridaemic response being inversely correlated with the basal HDL2 mass (r = -0.82). Serum apolipoprotein (apo) B levels rose by 8%, HDL-cholesterol decreased by 10% and HDL-TG increased by 57% at 6-8 h. 3. When ethanol was omitted, serum cholesterol and TG rose by 6% and 70%, respectively; both apo AI and apo B levels went up by 8%, whereas HDL-cholesterol rose progressively (15%) at 12 h. 4. The flotation rates of both HDL2 and HDL3 increased, reaching a maximum 6-8 h after ethanol plus fat intake. These changes were due to an increase in TG and phospholipid contents, whereas cholesteryl esters and proteins decreased. 5. The alterations in HDL are attributable to the increase in TG-rich lipoproteins, to the stimulated cholesterol esterification (+15%) and to an enhanced transfer of newly formed cholesteryl esters to apo-B-containing lipoproteins in exchange for TG. 6. Changes in HDL properties were evident only when ethanol was given concomitantly with fat. 7. These findings suggest that in the postprandial phase lipoprotein changes may occur, which facilitate an improved removal of cholesterol from tissues.

Adolescent↗

PubMed1985

Effects of storage on the distribution of high density lipoprotein subfractions in human sera.

The current growing interest in the separation of the high density lipoprotein (HDL) subfractions suggested a comparative analysis of the HDL2 and HDL3 distribution in fresh and stored serum samples. Human sera were processed by rate zonal ultracentrifugation in a swinging bucket rotor, immediately after collection and after a 7-day storage at 4 degrees C, both in the presence and in the absence of 5.1 M sodium bromide. Samples stored in absence of salt show a marked decrease of the HDL3 mass, a reduction of its flotation rate, and significant changes in the lipid composition. The HDL2 concentration and composition are not altered by storage. The reported findings indicate that significant HDL3 modifications may occur in serum samples stored at 4 degrees C; these changes can be prevented by the addition of high concentrations of salt before storage.

Adult↗

PubMedDate not supplied

Direct detection of thermotolerant campylobacters in chicken products by PCR and in situ hybridization.

We have evaluated the use of PCR and fluorescent in situ hybridization (FISH) techniques for the detection of thermotolerant campylobacters in naturally contaminated chicken products. 16S rRNA sequence data was used to design two specific primers and an oligonucleotide probe for PCR and FISH analyses, respectively. The PCR protocol amplified a 439-bp fragment corresponding to a portion of specific 16S RNA gene from thermotolerant campylobacters. The detection range of the PCR assay varied between 10 cells (after enrichment) to 10(2) cells per mL (without enrichment). FISH probes were able to identify thermotolerant Campylobacter species in 'spiked' and 'unspiked' naturally contaminated samples. PCR and FISH were performed on naturally contaminated samples and compared with the isolation of cells on selective media. The in situ hybridization technique was less sensitive than PCR, although its sensitivity of detection was increased considerably after 22 h of enrichment. These results confirm the usefulness of 16S rRNA-based techniques for the direct detection of campylobacters in food samples.

Animals↗