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Nicos Maglaveras

Publications and source records attributed to Nicos Maglaveras.

14 recordsLinked to original sources
PubMed2006

Methylation and repeats in silent and nonsense mutations of p53.

All exonic CG sequences in p53 are methylated; this epigenetic modification is correlated with frequent G:C-->A:T transitions in p53. Recent reports reveal the presence in p53 of non-CG methylation in CC and CCC sequences, complementary to sites of selective guanosine adduct formation (GG and GGG), and the association of genetic instability with methylation at repetitive sequences. We presently investigated the distribution of methylation sites and repetitive elements in silent and nonsense p53 mutations (2051) among the IARC's TP53 somatic mutation database for exons 5-8. Silent mutations are nonrandom, but mostly involve G:C-->A:T transitions (62%); in particular C-->T mutations (39% of all silent mutations) are mostly correlated with CC and CCC sequences, while G-->A mutations with GG sequences. Sequence analysis of all non-G:C-->A:T silent mutations reveals the frequent formation of new methylation sites (CG), new CCC and GGG sequences in the resulting sequence, refinement of symmetry elements at interrupted microsatellite-like sequences and formation of small repeats (55.3%). The G:C-->A:T silent mutations characterize cancers associated with cigarette smoking (e.g. bladder or lung and bronchus cancer versus colorectal cancer); on the contrary, non-G:C-->A:T silent mutations have similar frequencies in most cancers. Nonsense mutations in exons 5-8, all resulting in mutants lacking amino acids 307-393, which are crucial for p53 activity, were also analyzed. The frequency of nonsense mutations is higher at methylated sites or repeats 1-2 nucleotides removed from methylation sites. Frameshift mutations are also more frequent at repeated sequences. The frequent G:C-->A:T silent mutations could indicate that CC and CCC sequences of exons 5-8 are occasionally targets of non-CpG methylation of cytosine. This process of de novo methylation in the presence of microsatellite-like sequences and small repeats might influence the genetic stability of a variety of genes.

Base Sequence↗
PubMed2006

In-vivo validation of spatially correct three-dimensional reconstruction of human coronary arteries by integrating intravascular ultrasound and biplane angiography.

OBJECTIVES: The in-vivo validation of geometrically correct three-dimensional reconstruction of human coronary arteries by integrating intravascular ultrasound and biplane coronary angiography has not been adequately investigated. The purpose of this study was to describe the reconstruction method and investigate its in-vivo feasibility and accuracy. METHODS: In 17 coronary arteries (mean length, 85.7+/-17.1 mm) from nine patients, an intravascular ultrasound procedure along with a biplane coronary angiography was performed. From each angiographic projection, a single end-diastolic frame was selected in order to reconstruct the intravascular ultrasound catheter trajectory in space. In each end-diastolic intravascular ultrasound image, the lumen and media-adventitia contours were detected semi-automatically by an active contour algorithm. Each pair of contours was located on the catheter trajectory appropriately and interpolated with the adjacent pairs creating a three-dimensional volume of the arterial lumen and wall. The reconstructed lumen was back-projected onto both angiographic planes and the agreement between the back-projected and the angiographic luminal outlines was calculated. RESULTS: The angiogram-derived catheter length showed very high correlation (y=0.97 x + 1.8, P<0.001) and agreement with the corresponding pullback-derived values. Accordingly, the semi-automated segmentation of intravascular ultrasound images was also in significant correlation (r> or =0.96, P<0.001) and agreement with the reference manual tracing. The back-projected luminal borders showed good overall association with the corresponding angiographic ones (r=0.78, P<0.001) as well as remarkable agreement. CONCLUSIONS: Spatially correct three-dimensional reconstruction of human coronary arteries constitutes an imaging method with considerably high in-vivo feasibility and accuracy.

Coronary Angiography↗
PubMed2006

Constructing a semantically enriched biomedical service space: a paradigm with bioinformatics resources.

Biomedical applications are becoming increasingly reliant on resource integration and information exchange within global solution frameworks that offer seamless connectivity and data sharing in distributed environments. Resource autonomy and data heterogeneity are the most important impediments towards this potential. Aiming to overcome these limitations, we propose an implementation of the service-oriented model towards the construction of an open, semantically enriched biomedical service space that enables advanced service registration, selection and access capabilities, as well as service interoperability. The proposed system is realised by defining service annotation ontologies and applying software agent technology as the means for service registration, matchmaking and interfacing in a Grid environment. The applicability of the envisioned biomedical service space is illustrated on a set of bioinformatics resources, addressing computational identification of protein-coding genes.

Computational Biology↗
PubMed2006

Fuzzy Hidden Markov Models: a new approach in multiple sequence alignment.

This paper proposes a novel method for aligning multiple genomic or proteomic sequences using a fuzzyfied Hidden Markov Model (HMM). HMMs are known to provide compelling performance among multiple sequence alignment (MSA) algorithms, yet their stochastic nature does not help them cope with the existing dependence among the sequence elements. Fuzzy HMMs are a novel type of HMMs based on fuzzy sets and fuzzy integrals which generalizes the classical stochastic HMM, by relaxing its independence assumptions. In this paper, the fuzzy HMM model for MSA is mathematically defined. New fuzzy algorithms are described for building and training fuzzy HMMs, as well as for their use in aligning multiple sequences. Fuzzy HMMs can also increase the model capability of aligning multiple sequences mainly in terms of computation time. Modeling the multiple sequence alignment procedure with fuzzy HMMs can yield a robust and time-effective solution that can be widely used in bioinformatics in various applications, such as protein classification, phylogenetic analysis and gene prediction, among others.

Base Sequence↗
PubMed2005

A novel approach for incremental uncertainty rule generation from databases with missing values handling: application to dynamic medical databases.

Current approaches for mining association rules usually assume that the mining is performed in a static database, where the problem of missing attribute values does not practically exist. However, these assumptions are not preserved in some medical databases, like in a home care system. In this paper, a novel uncertainty rule algorithm is illustrated, namely URG-2 (Uncertainty Rule Generator), which addresses the problem of mining dynamic databases containing missing values. This algorithm requires only one pass from the initial dataset in order to generate the item set, while new metrics corresponding to the notion of Support and Confidence are used. URG-2 was evaluated over two medical databases, introducing randomly multiple missing values for each record's attribute (rate: 5-20% by 5% increments) in the initial dataset. Compared with the classical approach (records with missing values are ignored), the proposed algorithm was more robust in mining rules from datasets containing missing values. In all cases, the difference in preserving the initial rules ranged between 30% and 60% in favour of URG-2. Moreover, due to its incremental nature, URG-2 saved over 90% of the time required for thorough re-mining. Thus, the proposed algorithm can offer a preferable solution for mining in dynamic relational databases.

Algorithms↗
PubMed2005

A multiagent system enhancing home-care health services for chronic disease management.

In this paper, a multiagent system (MAS) is presented, aiming to enhance monitoring, surveillance, and educational services of a generic medical contact center (MCC) for chronic disease management. In such a home-care scenario, a persistent need arises for efficiently monitoring the patient contacts and the MCC's functionality, in order to effectively manage and interpret the large volume of medical data collected during the patient sessions with the system, and to assess the use of MCC resources. Software agents were adopted to provide the means to accomplish such real-time information-processing tasks, due to their autonomous, reactive and/or proactive nature, and their effectiveness in dynamic environments by incorporating coordination strategies. Specifically, the objective of the MAS is to monitor the MCC environment, detect important cases, and inform the healthcare and administrative personnel via alert messages, notifications, recommendations, and reports, prompting them for actions. The main aim of this paper is to present the overall design and implementation of a proposed MAS, emphasizing its functional model and architecture, as well as on the agent interactions and the knowledge-sharing mechanism incorporated, in the context of a generic MCC.

Artificial Intelligence↗
PubMed2005

The Citizen Health System (CHS): a modular medical contact center providing quality telemedicine services.

In the context of the Citizen Health System (CHS) project, a modular Medical Contact Center (MCC) was developed, which can be used in the monitoring, treatment, and management of chronically ill patients at home, such as diabetic or congestive heart failure patients. The virtue of the CHS contact center is that, using any type of communication and telematics technology, it is able to provide timely and preventive prompting to the patients, thus, achieving better disease management. In this paper, we present the structure of the CHS system, describing the modules that enable its flexible and extensible architecture. It is shown, through specific examples, how quality of healthcare delivery can be increased by using such a system.

Database Management Systems↗
PubMed2004

Contact centers, pervasive computing and telemedicine: a quality health care triangle.

The Citizen Health System (CHS) is a European Commission (CEC) funded project in the field of IST for Health. Its main goal is to develop a generic contact center which in its pilot stage can be used in the monitoring, treatment and management of chronically ill patients at home in Greece, Spain, and Germany. Such contact centers, using any type of communication technology, and providing timely and preventive prompting to the patients are envisaged in the future to evolve into well-being contact centers providing services to all citizens. In this paper, we present the structure of such a generic contact center and present its major achievements, and their impact to the quality of health delivery.

Biomedical Technology↗
PubMed2003

Citizen Health System: telehealth homecare.

The Citizen Health System (CHS) is a European Commission (CEC) funded project in the field of IST for Health. Its main goal is to develop a generic contact center which in its pilot stage can be used in the monitoring, treatment, and management of chronically ill patients at home in Greece, Spain, and Germany. Such contact centers, using any type of communication technology, and providing timely and preventive prompting to the patients, are envisaged in the future to evolve into well-being contact centers providing services to all citizens. In this paper, we present the structure of such a generic contact center and in particular the telecommunication infrastructure, the communication protocols and procedures, and finally the educational modules that are integrated into this contact center. We present the procedures followed for two target groups of patients, namely diabetic patients, and congestive heart failure patients, in which two randomized controlled clinical trials are under way. We present examples of the communication means between the contact center medical personnel and these patients, and elaborate on the educational, user, and telecommunication issues involved.

Chronic Disease↗
PubMed2002

Model-based processing scheme for quantitative 4-D cardiac MRI analysis.

In this paper, we present an integrated model-based processing scheme for cardiac magnetic resonance imaging (MRI), embedded in an interactive computing environment suitable for quantitative cardiac analysis, which provides a set of functions for the extraction, modeling, and visualization of cardiac shape and deformation. The methods apply four-dimensional (4-D) processing (three spatial and one temporal) to multiphase multislice MRI acquisitions and produce a continuous 4-D model of the myocardial surface deformation. The model is used to measure diagnostically useful parameters, such as wall motion, myocardial thicking, and myocardial mass measurements. The proposed model-based shape extraction method has the advantage of integrating local information into an overall representation and produces a robust description of cardiac cavities. A learning segmentation process that incorporates a generating-shrinking neural network is combined with a spatiotemporal parametric modeling method through functional basis decomposition. A multiscale approach is adopted, which uses at each step a coarse-scale model defined at the previous step in order to constrain the boundary detection. The representation accuracy starts from a coarse but smooth estimation of the approximate cardiac shape and is gradually increased to the desired detail. The main advantages of the proposed methods are efficiency, lack of uncertainty about convergence, and robustness to image artifacts. Experimental results obtained from application to clinical multislice multiphase MRI examinations of normal volunteers and patients with medical record of myocardial infarction were satisfactory in terms of accuracy and robustness.

Heart↗
PubMed2002

DIABCARD CCMIS--a portable and scalable CPR for diabetes care.

The aim of this paper is to introduce the main software module of the DIABCARD Chip Card Medical Information System (DIABCARD CCMIS) that provides an online, portable diabetes medical record information system based on a high performance object-oriented rapid application development language such as Borland Delphi. A chip card based medical information system was developed as a good possibility to create a portable electronic patient record. In particular the patient data card makes the up-to-date patient's record available whenever needed. The developed DIABCARD Core System, described in this paper, includes a patient record management system that has the ability to handle topics such as administrative and medical data, medical anamnesis, and physical examination data. Issues tackled were simplicity, data security and reporting, customization, and internationalization. Especially for the two last issues (customization and internationalization) a novel approach based on using native initialization table files is presented. Proper care has been addressed during the development of the software modules for matters of security, data integrity and confidentiality.

Database Management Systems↗
PubMed2002

WEB-WAP based telecare.

We have developed two telecare applications based on mobile telephony (WAP) and WEB. The first can be used to request Basic Life Support (BLS) guidelines any time by using a WAP device and to teach people and non-professionals involved in health care emergency situations. The second is a WEB-WAP based tool for medical data retrieval and at-home health care monitoring of chronically ill patients with congestive heart failure (CHF) or diabetes. Medical education content related to these diseases is available on the WEB and on the WAP device. The WAP application uses the features found in the last generation of mobile phones such as better multimedia information presentations, better interactivity capabilities, and enhanced ease of use. Based on these two applications, a promising platform is offered for developing applications in health care, home care, medical monitoring and health education ensuring continuity of care. In the paper we present the preliminary results of a pilot test at Thessaloniki University (Greece) where the WEB-WAP based tool is used to monitor patients with diabetes or CHF.

Chronic Disease↗
PubMed2002

Agent-based monitoring and alert generation for a home care telemedicine system.

In the present paper, a multi-agent system is proposed, which can be integrated in the home care telemedicine system that was developed in the context of the Citizen Health System (CHS) European project, functioning as a contact center for diabetic and congestive heart failure patients. The objective of the multi-agent system is to provide a set of alert/notification mechanisms for the clinicians, helping them to classify the clinical condition of each patient. Therefore, despite the huge amount of data managed by the system, due to the daily use of the contact center's services, these alert mechanisms provide the clinician with an overview of the cases that need further examination and save him/her time from the trivial cases. The multi-agent system consists of different types of agents, each one assigned with specific tasks, which communicate with each other, in order to share knowledge.

Computer Systems↗