A model for altered neural network dynamics related to prehension movements in Parkinson disease.

In this paper, we present a neural network model of the interactions between cortex and the basal ganglia during prehensile movements. Computational neuroscience methods are used to explore the hypothesis that the altered kinematic patterns observed in Parkinson's disease patients performing prehensile movements is mainly due to an altered neuronal activity located in the networks of cholinergic (ACh) interneurons of the striatum. These striatal cells, under a strong influence of the dopaminergic system, significantly contribute to the neural processing within the striatum and in the cortico-basal ganglia loops. In order to test this hypothesis, a large-scale model of neural interactions in the basal ganglia has been integrated with previous models accounting for the cortical organization of goal directed reaching and grasping movements in normal and perturbed conditions. We carry out a discussion of the model hypothesis validation by providing a control engineering analysis and by comparing results of real experiments with our simulation results in conditions resembling these original experiments.

A modular neural network architecture for step-wise learning of grasping tasks.

This paper proposes a neural network architecture for learning of grasping tasks. The multineural network model presented in this work, allows acquisition of different neural representations of the grasping task through a successive learning over two stages in a strategy that uses already learned representations for the acquisition of the subsequent knowledge. Systematic computer simulations have been carried out in order to test learning and generalization capabilities of the system. The neural activity at different subparts of the artificial neural network during its performance phase, is compared to the activity of populations of real neurons in areas AIP and F5 of the distributed parieto-frontal biological neural network involved in visual guidance of grasping. A more biologically plausible development of the model presented here is also discussed. The proposed model can be also used as a high level controller for a robotic dextrous hand during learning and execution of grasping tasks.

[Large false aortic aneurysm after 30 years of a coarctation repair]. / Falso aneurisma aórtico 30 años después de la corrección de una coartación: tratamiento quirúrgico bajo hipotermia profunda.

We report a case of a large false aortic aneurysm that had developed in a 43-year-old man who had had coarctation repair 30 years previously. The coarctation repair had been done by inserting an end-to-end Dacron tubular graft which was sutured with silk. The re-operation was successfully performed under deep hypothermic arrest and it was noted that there was complete separation of the graft from both ends and no sutures were visualised. The deep hypothermic technique has considerably improved the ease and safety of this operation. We attribute this complication to the reabsorption of the silk sutures. Patients after coarctectomy with graft material should have regular chest X-rays for life in order to detect false aneurysms.

muARTMAP: use of mutual information for category reduction in Fuzzy ARTMAP.

A new architecture called muARTMAP is proposed to impact a category proliferation problem present in Fuzzy ARTMAP. Under a probabilistic setting, it seeks a partition of the input space that optimizes the mutual information with the output space, but allowing some training error, thus avoiding overfitting. It implements an inter-ART reset mechanism that permits handling exceptions correctly, thus using few categories, especially in high dimensionality problems. It compares favorably to Fuzzy ARTMAP and Boosted ARTMAP in several synthetic benchmarks, being more robust to noise than Fuzzy ARTMAP and degrading less as dimensionality increases. Evaluated on a real-world task, the recognition of handwritten characters, it performs comparably to Fuzzy ARTMAP, while generating a much more compact rule set.

Learning from noisy information in FasArt and FasBack neuro-fuzzy systems.

Neuro-fuzzy systems have been in the focus of recent research as a solution to jointly exploit the main features of fuzzy logic systems and neural networks. Within the application literature, neuro-fuzzy systems can be found as methods for function identification. This approach is supported by theorems that guarantee the possibility of representing arbitrary functions by fuzzy systems. However, due to the fact that real data are often noisy, generation of accurate identifiers is presented as an important problem. Within the Adaptive Resonance Theory (ART), PROBART architecture has been proposed as a solution to this problem. After a detailed comparison of these architectures based on their design principles, the FasArt and FasBack models are proposed. They are neuro-fuzzy identifiers that offer a dual interpretation, as fuzzy logic systems or neural networks. FasArt and FasBack can be trained on noisy data without need of change in their structure or data preprocessing. In the simulation work, a comparative study is carried out on the performances of Fuzzy ARTMAP, PROBART, FasArt and FasBack, focusing on prediction error and network complexity. Results show that FasArt and FasBack clearly enhance the performance of other models in this important problem.

Aortic valve replacement with bioprostheses in liver transplant recipients.

Three cases of aortic valve replacement with porcine bioprostheses are reported in liver transplant recipients at two to six years after transplantation. Indications for aortic valve replacement (AVR) were aortic stenosis (n = 2) and aortic regurgitation (n = 1). The use of bioprostheses was recommended because of patient age, the need for multiple liver biopsies, and contraindication to the use of anticoagulation therapy. The patient who underwent AVR because of aortic regurgitation developed structural valve deterioration (SVD) during the next five years after surgery, and thus replacement of the bioprosthetic valve was required. Recipients of liver transplant who undergo valve replacement with tissue valves should be carefully followed up because of the risk of early SVD. AVR may be performed safely after liver transplantation.

The yeast HAL1 gene improves salt tolerance of transgenic tomato.

Overexpression of the HAL1 gene in yeast has a positive effect on salt tolerance by maintaining a high internal K(+) concentration and decreasing intracellular Na(+) during salt stress. In the present work, the yeast gene HAL1 was introduced into tomato (Lycopersicon esculentum Mill.) by Agrobacterium tumefaciens-mediated transformation. A sample of primary transformants was self-pollinated, and progeny from both transformed and non-transformed plants (controls) were evaluated for salt tolerance in vitro and in vivo. Results from different tests indicated a higher level of salt tolerance in the progeny of two different transgenic plants bearing four copies or one copy of the HAL1 gene. In addition, measurement of the intracellular K(+) to Na(+) ratios showed that transgenic lines were able to retain more K(+) than the control under salt stress. Although plants and yeast cannot be compared in an absolute sense, these results indicate that the mechanism controlling the positive effect of the HAL1 gene on salt tolerance may be similar in transgenic plants and yeast.

A novel target of lithium therapy.

Phosphatases converting 3'-phosphoadenosine 5'-phosphate (PAP) into adenosine 5'-phosphate are of fundamental importance in living cells as the accumulation of PAP is toxic to several cellular systems. These enzymes are lithium-sensitive and we have characterized a human PAP phosphatase as a potential target of lithium therapy. A cDNA encoding a human enzyme was identified by data base screening, expressed in Escherichia coli and the 33 kDa protein purified to homogeneity. The enzyme exhibits high affinity for PAP (K(m)<1 microM) and is sensitive to subtherapeutic concentrations of lithium (IC(50)=0.3 mM). The human enzyme also hydrolyzes inositol-1, 4-bisphosphate with high affinity (K(m)=0.4 microM), therefore it can be considered as a dual specificity enzyme with high affinity (microM range) for both PAP and inositol-1,4-bisphosphate. Hydrolysis of inositol-1,4-bisphosphate was also inhibited by lithium (IC(50)=0.6 mM). Thus, we present experimental evidence for a novel target of lithium therapy, which could explain some of the side effects of this therapy.

A novel mammalian lithium-sensitive enzyme with a dual enzymatic activity, 3'-phosphoadenosine 5'-phosphate phosphatase and inositol-polyphosphate 1-phosphatase.

We report the molecular cloning in Rattus norvegicus of a novel mammalian enzyme (RnPIP), which shows both 3'-phosphoadenosine 5'-phosphate (PAP) phosphatase and inositol-polyphosphate 1-phosphatase activities. This enzyme is the first PAP phosphatase characterized at the molecular level in mammals, and it represents the first member of a novel family of dual specificity enzymes. The phosphatase activity is strictly dependent on Mg2+, and it is inhibited by Ca2+ and Li+ ions. Lithium chloride inhibits the hydrolysis of both PAP and inositol-1,4-bisphosphate at submillimolar concentration; therefore, it is possible that the inhibition of the human homologue of RnPIP by lithium ions is related to the pharmacological action of lithium. We propose that the PAP phosphatase activity of RnPIP is crucial for the function of enzymes sensitive to inhibition by PAP, such as sulfotransferase and RNA processing enzymes. Finally, an unexpected connection between PAP and inositol-1,4-bisphosphate metabolism emerges from this work.

The Arabidopsis HAL2-like gene family includes a novel sodium-sensitive phosphatase.

The yeast HAL2 gene encodes a lithium- and sodium-sensitive phosphatase that hydrolyses 3'-phosphoadenosine-5'-phosphate (PAP). Salt toxicity in yeast results from Hal2 inhibition and accumulation of PAP, which inhibits sulphate assimilation and RNA processing. We have investigated whether the model plant Arabidopsis thaliana contains sodium-sensitive PAP phosphatases. The Arabidopsis HAL2-like gene family is composed of three members: AtAHL and AtSAL2, characterized in the present work, and the previously identified AtSAL1. The AtAHL and AtSAL2 cDNAs complement the auxotrophy for methionine of the yeast hal2 mutant and the recombinant proteins catalyse the conversion of PAP to AMP in a Mg(2+)-dependent reaction sensitive to inhibition by Ca2+ and Li+. The PAP phosphatase activity of AtAHL is sensitive to physiological concentrations of Na+, whereas the activities of AtSAL1 and AtSAL2 are not. Another important difference is that AtAHL is very specific for PAP while AtSAL1 and AtSAL2 also act as inositol polyphosphate 1-phosphatases. AtAHL constitutes a novel type of sodium-sensitive PAP phosphatase which could act co-ordinately with plant sulphotransferases and serve as target of salt toxicity in plants.

Chronic aneurysm of the descending thoracic aorta presenting with right pleural effusion and left phrenic paralysis.

A 62-year-old man was admitted to the emergency department with chronic dysphagia and lower back pain. Chest radiography revealed a wide mediastinal shadow and an elevated left diaphragm, which proved to be secondary to left phrenic paralysis. The patient was diagnosed with an aneurysm of the descending thoracic aorta and was admitted to the hospital. After the patient was admitted, the aneurysm ruptured into the right chest. The patient underwent an emergency operation to replace the ruptured segment with a synthetic graft. Postoperative recovery and follow-up were uneventful. This report describes an unusual presentation of a thoracic aortic aneurysm. Hemidiaphragmatic paralysis caused by compression of the phrenic nerve is an unusual complication that, to our knowledge, has not been previously reported.

Surgical approach for cardiac surgery in a patient with tracheostoma.

The thoracic approach for cardiac surgery in a patient with a tracheostoma can result in difficult problems, such as mediastinitis, stoma necrosis or inadequate operative exposure. We present a distinct approach consisting of an incision at the second intercostal space, transverse sternum transection and longitudinal median sternotomy to the xiphoid process, performed for coronary artery bypass grafting and aortic valve replacement, in a patient with previous tracheotomy. This approach permitted adequate surgical exposure for cardiopulmonary bypass, aortic valve replacement and coronary revascularization procedures.

Coronary angioplasty and stenting following heart transplantation with older donors. Is this a rational approach?

The shortage of ideal donor hearts has led to an extension of the classical donor criteria of age. Higher incidence of focal coronary artery disease has been found in this older donor population requiring conventional angioplasty therapy. The authors present two patients with early coronary angiogram post transplantation, requiring angioplasty and stent in the lesions found.

Infection of a pacemaker by Brucella melitensis.

We report a case that, to the best of our knowledge, is the only published instance of infection of a pacemaker and its leads by Brucella melitensis. Furthermore, this case suggests that B. melitensis may be able to persist around pacemaker devices despite its having been eliminated from the rest of the body. The patient was a sheep shearer who had just undergone a 45-day course of antibiotic therapy for brucella and had been considered cured on the basis of negative blood cultures.