Release of [14C]adenosine derivatives from superfused synaptosome preparations. Effects of depolarizing agents and metabolic inhibitors

Adenine 5'-mononucleotides of synaptosome beds from guinea pig neocortex were labelled by incubation with [8-(14)C]adenosine, and excess adenosine was then removed with precursor-free medium. During continuous superfusion, labelled adenosine derivatives were released at a rate of about 0.5% of the synaptosome 14C/min and this rate was increased 2.5-fold by depolarization with 33 mM K+. Some depolarizing agents and metabolic inhibitors were examined for action on the release of [14C)-adenosine derivatives from the synaptosome preparations, and also on the rate of lactate production by these preparations, both before and during K + depolarization. The synaptosome content of adenine 5'-mononucleotides following exposure of the synaptosome beds to these compounds was also estimated. Ouabain, 0.1 mM, brought about an increase in 14C-labelled compounds output, but it caused little alteration in lactate output and some decrease in the adenylate energy charge of the synaptosomes. Veratridine, 80 microM, increased markedly both the output of radioactivity and the lactate production. Tetrodotoxin, 1 microM, when added together with veratridine, completely abolished the effect of veratridine on the efflux of [14C]adenosine derivatives, but this was not associated with a complete blockade of the output of lactate. Sodium cyanide, 2.5 mM, FCCP, 6 muM together with iodoacetate, 2.5 mM, caused an increase in the output of 14C-labelled compounds, and a decrease in the adenylate energy charge. The production of lactate was also increased by sodium cyanide and FCCP, but it was completely inhibited by iodoactate. Oligomycin, 4.65 microM, and amytal, 1 mM, added in the incubation medium before labelling the synaptosome beds with [8-(14)C]adenosine, did not affect very much the output of [14C]adenosine derivatives, while the output of lactate increased independently of the depolarization with 33 mM K+. The release of adenosine derivatives from superfused synaptosome beds induced by depolarizing agents or metabolic inhibitors did not seem to be due either to an effect of membrane permeability changes that follow a decrease of ATP supply, or to an increased metabolic rate occurring during nerve ending stimulation. It is concluded that this release of adenosine derivatives appeared to be a process triggered primarily by the influx of Na+ and the increased intrasynaptosomal calcium, and closely related to the process of neurotransmission.     

Selective hydrogenation of cyclopentadiene over supported metal catalysts

The selective hydrogenation of cyclopentadiene to cyclopentene has been studied in the liquid phase using Pd and Pd Me/Al₂O₃ bimetallic catalysts (Me = Mn, Ni, Co, W). The highest activity was obtained with Pd Co and Pd W/Al₂O₃. For these catalysts, no hydrogen or CO chemisorption was detected although Pd could be seen by XPS at 335·8 eV; it is considered that new species, more active for the selective hydrogenation of cyclopentadiene, appeared at the catalyst surface. The sulfur resistance towards thiophene has also been studied. It was observed that the highest sulfur resistance is coincident with the highest activity. XPS analysis shows that the poisoning species is thiophene adsorbed on the catalyst surface.     

Detecting inappropriate access to electronic health records using collaborative filtering

Many healthcare facilities enforce security on their electronic health records (EHRs) through a corrective mechanism: some staff nominally have almost unrestricted access to the records, but there is a strict ex post facto audit process for inappropriate accesses, i.e., accesses that violate the facility’s security and privacy policies. This process is inefficient, as each suspicious access has to be reviewed by a security expert, and is purely retrospective, as it occurs after damage may have been incurred. This motivates automated approaches based on machine learning using historical data. Previous attempts at such a system have successfully applied supervised learning models to this end, such as SVMs and logistic regression. While providing benefits over manual auditing, these approaches ignore the identity of the users and patients involved in a record access. Therefore, they cannot exploit the fact that a patient whose record was previously involved in a violation has an increased risk of being involved in a future violation. Motivated by this, in this paper, we propose a collaborative filtering inspired approach to predicting inappropriate accesses. Our solution integrates both explicit and latent features for staff and patients, the latter acting as a personalized “fingerprint” based on historical access patterns. The proposed method, when applied to real EHR access data from two tertiary hospitals and a file-access dataset from Amazon, shows not only significantly improved performance compared to existing methods, but also provides insights as to what indicates an inappropriate access.     

Modular Neural Networks for Medical Prognosis: Quantifying the Benefits of Combining Neural Networks for Survival Prediction

This paper describes a medical application of modular neural networks (NNs) for temporal pattern recognition. In order to increase the reliability of prognostic indices for patients living with the acquired immunodeficiency syndrome (AIDS), survival prediction was performed in a system composed of modular NNS that classified cases according to death in a certain year of follow-up. The output of each NN module corresponded to the probability of survival in a given year. Inputs were the values of demographic, clinical and laboratory variables. The results of the modules were combined to produce survival curves for individuals. The NNs were trained by backpropagation and the results were evaluated in test sets of previously unseen cases. We showed that, for certain combinations of NN modules, the performance of the prognostic index, measured by the area under the receiver operating characteristic curve, was significantly improved (p 0.05). We also used calibration measurements to quantify the benefits of combining NN modules, and show why, when and how NNs should be combined for building prognostic models.     

A CDMA‐based radio interface for third generation mobile systems

This paper deals with the use of a CDMA-based radio interface in third generation mobile systems (Universal Mobile Telecommunications System – UMTS, and Future Public Land Mobile Telecommunications System – FPLMTS). The paper is not intended as a detailed analysis of the radio interface performance, but as an overview of the main issues arising in a typical CDMA-based mobile system, discussing the different available technical solutions. First of all, the basic requirements of the radio interface in a third generation mobile system are outlined. In particular, the support of variable bit rate transmission, the adaptability to the different propagation and service environments and the flexibility are felt to be important topics to be discussed. Then, the main characteristics of the CDMA access technique are depicted, in relation with the above mentioned requirements, focusing in particular on the DS-CDMA radio interface designed within the RACE II – CODIT Project. In that context the paper describes some of the technical solutions proposed for the provision of advanced features such as macrodiversity, multibearer transmission and variable bit rate services. This revised version was published online in June 2006 with corrections to the Cover Date.     

Detection of postharvest changes of ascorbic acid in fresh-cut melon, kiwi, and pineapple, by using a low cost telemetric system

The present paper deals with a novel telemetric device combined with a carbon amperometric sensor system to determine postharvest changes of ascorbic acid (AA) in fresh-cut fruits, without displacing products out of the storage rooms. The investigation was performed on kiwi, pineapple and melon, subjected to minimal processing, packaging, cold storage, and simulated shelf life. Results demonstrated that AA content of fresh-cut fruits of all species declines differently during storage. Cold storage notably reduced the degradation rate of AA in comparison with samples stored at 20°C. The cold-chain interruption resulted in a sharp AA content reduction when the optimal storage condition was not rapidly replaced. Unpredicted results showed a high activity of oxidative enzymes, which prevented AA detection in melon samples. Our sensor system allowed us to demonstrate that both ascorbate peroxidase and ascorbate oxidase affected the oxidative stability and the nutritional quality of fresh cut melon fruits.     

A Chimeric UDP-Glucose Pyrophosphorylase Produced by Protein Engineering Exhibits Sensitivity to Allosteric Regulators

In bacteria, glycogen or oligosaccharide accumulation involves glucose-1-phosphate partitioning into either ADP-glucose (ADP-Glc) or UDP-Glc. Their respective synthesis is catalyzed by allosterically regulated ADP-Glc pyrophosphorylase (EC 2.7.7.27, ADP-Glc PPase) or unregulated UDP-Glc PPase (EC 2.7.7.9). In this work, we characterized the UDP-Glc PPase from Streptococcus mutans. In addition, we constructed a chimeric protein by cutting the C-terminal domain of the ADP-Glc PPase from Escherichia coli and pasting it to the entire S. mutans UDP-Glc PPase. Both proteins were fully active as UDP-Glc PPases and their kinetic parameters were measured. The chimeric enzyme had a slightly higher affinity for substrates than the native S. mutans UDP-Glc PPase, but the maximal activity was four times lower. Interestingly, the chimeric protein was sensitive to regulation by pyruvate, 3-phosphoglyceric acid and fructose-1,6-bis-phosphate, which are known to be effectors of ADP-Glc PPases from different sources. The three compounds activated the chimeric enzyme up to three-fold, and increased the affinity for substrates. This chimeric protein is the first reported UDP-Glc PPase with allosteric regulatory properties. In addition, this is a pioneer work dealing with a chimeric enzyme constructed as a hybrid of two pyrophosphorylases with different specificity toward nucleoside-diphospho-glucose and our results turn to be relevant for a deeper understanding of the evolution of allosterism in this family of enzymes.     

Implementation of Lean and Green practices: a supplier-oriented assessment method

Organizations are being pressured to increase productivity, while reducing costs and improving quality. In this matter, lean manufacturing (LM) has been widely adopted by firms to reduce waste and achieve such improvements. However, the shortage of natural resources and the high levels of pollution have forced these organizations to meet several regulations for the control of environmental impacts. In addition, organizations’ environmental initiatives have become a critical factor for market differentiation. The integration of both LM and environmental management (EM) results in an innovative approach, called Lean and Green. Much has been studied about synergies and divergences among LM and EM practices. However, there is still a gap regarding the assessment of the level of integration between both approaches. This research aims at proposing a method for assessing the implementation level of LM and EM practices specifically related to suppliers’ relationship. The proposed method allows the identification of critical practices that corroborate for a synergic implementation of lean and Green approach. Further, these practices are ranked enabling managers to prioritize their improvement initiatives. Our results indicate that for a few practices some trade-offs might emerge according to the type of product, entailing a certain level of adaptation to attend to environmental demands.