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CooPPS: a system for the cooperative prediction of protein structures.

Predicting the three-dimensional structure of proteins is a difficult task. In the last few years several approaches have been proposed for performing this task taking into account different protein chemical and physical properties. As a result, a growing number of protein structure prediction tools is becoming available, some of them specialized to work on either some aspects of the predictions or on some categories of proteins; however, they are still not sufficiently accurate and reliable for predicting all kinds of proteins. In this context, it is useful to jointly apply different prediction tools and combine their results in order to improve the quality of the predictions. However, several problems have to be solved in order to make this a viable possibility. In this paper a framework and a tool is proposed which allows: (i) definition of a common reference applicative domain for different prediction tools; (ii) characterization of prediction tools through evaluating some quality parameters; (iii) characterization of the performances of a team of predictors jointly applied over a prediction problem; (iv) the singling out of the best team for a prediction problem; and (v) the integration of predictor results in the team in order to obtain a unique prediction. A system implementing the various steps of the proposed framework (CooPPS) has been developed and several experiments for testing the effectiveness of the proposed approach have been carried out.

Algorithms↗

A factor-analytic investigation of computer 'addiction' and engagement.

Evidence supporting the application of Brown's (1991, 1993) conception of behavioural addiction to computing behaviour is presented. Questionnaire items tapping Brown's addiction criteria were factor-analysed along with others, including computer apathy-engagement and computer anxiety-comfort items of Charlton and Birkett (1995). Items relating to some of Brown's criteria (tolerance, euphoria, and cognitive salience) were found to be complex, an Addiction factor loading upon them but an Engagement factor loading more highly. Items tapping other criteria (conflict, withdrawal, behavioural salience, and relapse and reinstatement) were shown to be factor pure, with only the addiction factor loading highly upon them. It is concluded that Brown's conception of behavioural addiction can be applied to computer-related behaviour, although the relationship of milder facets of addiction, which are also merely indicative of high engagement, to computer-related addictions is non-unique. It is also concluded that classifying individuals as exhibiting pathological computer use using checklists based upon adaptations of DSM criteria for pathological gambling is likely to overestimate the number of people addicted to computing activities.

Adolescent↗

Record linkage in the Cancer Registry of Tyrol, Austria.

OBJECTIVE: Record linkage of patient data originating from various data sources and record linkage for checking uniqueness of patient registration are common tasks for every cancer registry. In Austria, there is no unique person identifier in use in the medical system. Hence, it was necessary and the goal of this work to develop an efficient means of record linkage for use in cancer registries in Austria. METHODS: We adapted the method of probabilistic record linkage to the situation of cancer registries in Austria. In addition to the customary components of this method, we also took into consideration typing errors commonly occurring in names and dates of birth. The method was implemented in a program written in DELPHI(TM) with interfaces optimised for cancer registries. RESULTS: Applying our record linkage method to 130,509 linkages results in 105,272 (80.7%) identical pairs. For these identical pairs, 88.9% of decisions were performed automatically and 11.1% semi-automatically. For results decided automatically, 6.9% did not have simultaneous identity of last name, first name and date of birth. For results decided semi-automatically, 48.4% did not have an identical last name, 25.6% did not have an identical date of birth and 83.1% did not have simultaneous identity of last name and date of birth and first name. CONCLUSIONS: The method implemented in our cancer registry solves all record linkage problems in Austria with sufficient precision.

Austria↗

Ductular reaction after submassive necrosis in humans. Special emphasis on analysis of ductular hepatocytes.

The ductular reaction to acute submassive necrosis was studied in human livers removed at the time of orthotopic liver transplantation. Single, double, and triple immunohistochemical labeling in combination with morphometry was used to analyze the phenotype and proliferative and apoptotic rates of various epithelial cell compartments. These were divided on the basis of immunohistochemistry and morphology into three subtypes: 1) CK19+/AE1+ mature bile duct epithelium, 2) HEP-PAR+ mature hepatocytes (HEPs), and 3) CK19+/AE1+ ductular hepatocyte (DH) cells lying at the interface between the portal tract connective tissue and the hepatic lobules. Cycling cells were defined as those showing Ki-67+ (MIB-1) nuclear labeling. Apoptotic cells were identified with in situ labeling using the terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling assay. Special emphasis was placed on DHs that appeared at the interface between the portal tracts and hepatic lobules. During the recovery phase from submassive hepatic necrosis, subtraction of the rate of cell death from the proliferative index shows that all of the epithelial compartments experience a net increase in the number of cells. The highest proliferation rate occurs in the DHs, which is significantly (P < 0.0001) higher than the proliferation rate seen in either the HEP or bile duct epithelium compartments. Immunohistochemical analysis of the highly proliferative DH compartment shows it to be a heterogeneous population with unique phenotypic features. Like epithelial cells in the ductal plate of fetal liver and cholangiocarcinomas, DHs are positioned on a laminin-rich matrix and focally express vimentin and Lewis(x) and show up-regulation of bcl-2 and type IV collagenase. However, unlike ductal plate cells, DHs are CD34 and alpha-fetoprotein negative. Although a subpopulation of DHs share phenotypic features with mature bile duct epithelium (AE1/cytokeratin 19 and type IV collagenase positive) or HEP (HEP-PAR, albumin, and alpha-1-antitrypsin positive), they are also clearly separate from both populations; DHs are negative or only weakly stain for glutathione-S-transferase-pi and are type IV collagenase positive. Moreover, occasional DHs also co-expressed HEP-PAR or alpha-1-antitrypsin and AE1, indicative of both hepatocyte and ductular differentiation. These findings suggest that DHs seen in human livers after submassive necrosis may represent a transient amplifying population arising from a progenitor population located in or near the canals of Herring. In addition, injured hepatocytes can express cytokeratin 19 and AE1, which normally are biliary intermediate filaments.

Adult↗

Dual function for a unique site within the beta2I domain of integrin alphaMbeta2.

Integrin activation has been postulated to occur in part via conformational changes in the I domain of the beta subunit (the betaI domain), especially near the F-alpha(7) loop, in response to "inside-out" signaling. However, direct evidence for a role of the F-alpha(7) loop in ligand binding and activity modulation is still lacking. Here, we report our finding that the F-alpha(7) loop (residues 344-358) within the beta(2)I domain has dual functions in ligand binding by alpha(M)beta(2). On the one hand, it supports intercellular adhesion molecule 1 (ICAM-1) binding to alpha(M)beta(2) directly as part of a recognition interface formed by five noncontiguous segments (Pro(192)-Glu(197), Asn(213)-Glu(220), Leu(225)-Leu(230), Ser(324)-Thr(329), and Glu(344)-Asp(348)) on the apex of the beta(2)I domain. On the other hand, it controls the open and closed conformation of the alpha(M)beta(2) receptor, thereby indirectly affecting alpha(M)beta(2) binding to other ligands. Switching the five constituent sequences of the ICAM-1-binding site within the beta(2)I domain to their beta(1) counterparts destroyed ICAM-1 binding but had no effect on the gross conformations of the receptor. Of the five ICAM-1 binding-defective mutants, four had normal or even stronger interaction with Fg and C3bi, as reported in our previous study. Synthetic peptides derived from the identified site inhibited alpha(M)beta(2)-ICAM-1 interaction and supported direct binding to ICAM-1. Most importantly, perturbation of the F-alpha(7) loop caused conformational changes within the beta(2)I domain, which was further propagated to other regions of alpha(M)beta(2). Altogether, our data demonstrate that inside-out signaling could modulate ligand binding directly by changing the ligand-binding pocket per se and/or indirectly by inducing multiple conformational changes within the receptor.

Antibodies, Monoclonal↗

Nanocrystal targeting in vivo.

Inorganic nanostructures that interface with biological systems have recently attracted widespread interest in biology and medicine. Nanoparticles are thought to have potential as novel intravascular probes for both diagnostic (e.g., imaging) and therapeutic purposes (e.g., drug delivery). Critical issues for successful nanoparticle delivery include the ability to target specific tissues and cell types and escape from the biological particulate filter known as the reticuloendothelial system. We set out to explore the feasibility of in vivo targeting by using semiconductor quantum dots (qdots). Qdots are small (<10 nm) inorganic nanocrystals that possess unique luminescent properties; their fluorescence emission is stable and tuned by varying the particle size or composition. We show that ZnS-capped CdSe qdots coated with a lung-targeting peptide accumulate in the lungs of mice after i.v. injection, whereas two other peptides specifically direct qdots to blood vessels or lymphatic vessels in tumors. We also show that adding polyethylene glycol to the qdot coating prevents nonselective accumulation of qdots in reticuloendothelial tissues. These results encourage the construction of more complex nanostructures with capabilities such as disease sensing and drug delivery.

Animals↗

Simultaneous host and parasite expression profiling identifies tissue-specific transcriptional programs associated with susceptibility or resistance to experimental cerebral malaria.

BACKGROUND: The development and outcome of cerebral malaria (CM) reflects a complex interplay between parasite-expressed virulence factors and host response to infection. The murine CM model, Plasmodium berghei ANKA (PbA), which simulates many of the features of human CM, provides an excellent system to study this host/parasite interface. We designed "combination" microarrays that concurrently detect genome-wide transcripts of both PbA and mouse, and examined parasite and host transcriptional programs during infection of CM-susceptible (C57BL/6) and CM-resistant (BALB/c) mice. RESULTS: Analysis of expression data from brain, lung, liver, and spleen of PbA infected mice showed that both host and parasite gene expression can be examined using a single microarray, and parasite transcripts can be detected within whole organs at a time when peripheral blood parasitemia is low. Parasites display a unique transcriptional signature in each tissue, and lung appears to be a large reservoir for metabolically active parasites. In comparisons of susceptible versus resistant animals, both host and parasite display distinct, organ-specific transcriptional profiles. Differentially expressed mouse genes were related to humoral immune response, complement activation, or cell-cell interactions. PbA displayed differential expression of genes related to biosynthetic activities. CONCLUSION: These data show that host and parasite gene expression profiles can be simultaneously analysed using a single "combination" microarray, and that both the mouse and malaria parasite display distinct tissue- and strain-specific responses during infection. This technology facilitates the dissection of host-pathogen interactions in experimental cerebral malaria and could be extended to other disease models.

Animals↗

Motor rehabilitation using virtual reality.

Virtual Reality (VR) provides a unique medium suited to the achievement of several requirements for effective rehabilitation intervention. Specifically, therapy can be provided within a functional, purposeful and motivating context. Many VR applications present opportunities for individuals to participate in experiences, which are engaging and rewarding. In addition to the value of the rehabilitation experience for the user, both therapists and users benefit from the ability to readily grade and document the therapeutic intervention using various systems. In VR, advanced technologies are used to produce simulated, interactive and multi-dimensional environments. Visual interfaces including desktop monitors and head-mounted displays (HMDs), haptic interfaces, and real-time motion tracking devices are used to create environments allowing users to interact with images and virtual objects in real-time through multiple sensory modalities. Opportunities for object manipulation and body movement through virtual space provide frameworks that, in varying degrees, are perceived as comparable to similar opportunities in the real world. This paper reviews current work on motor rehabilitation using virtual environments and virtual reality and where possible, compares outcomes with those achieved in real-world applications.

Journal Article↗

A database manager of biomedical images.

In order to allow an efficient archiving and retrieval of biomedical images, PACS would include an image DBMS. As biomedical images have complex structures we developed a specific DBMS over a relational one. The medical image database manager ensures a data description that takes into account data semantics so that consistency or existential constraints may be verified. It provides a unique language to retrieve images no matter what their storage format. It encompasses the queries of the user which constitute a filter over associated data. The manager can handle changes in the environment of the image. We implemented a manager prototype to show the validity of logical access possibilities. The user need no longer know the structure of the image database to access data. The logical access allows retrieval of images, whatever the architecture of the base. An automatic query construction consists of three functional levels including the interfaces towards the external environment which ensure a logical independence from the database, a query generator which creates the correspondence between the user's query and physical access queries, a dictionary which contains the structure of the image data and consistency constraints.

Computer Systems↗

Designing effective siRNAs with off-target control.

Successful gene silencing by RNA interference requires a potent and specific depletion of the target mRNA. Target candidates must be chosen so that their corresponding short interfering RNAs are likely to be effective against that target and unlikely to accidentally silence other transcripts due to sequence similarity. We show that both effective and unique targets exist in mouse, fruit fly, and worm, and present a new design tool that enables users to make the trade-off between efficacy and uniqueness. The tool lists all targets with partial sequence similarity to the primary target to highlight candidates for negative controls.

Algorithms↗

BAGEL: a web-based bacteriocin genome mining tool.

A common problem in the annotation of open reading frames (ORFs) is the identification of genes that are functionally similar but have limited or no sequence homology. This is particularly the case for bacteriocins, a very diverse group of antimicrobial peptides produced by bacteria and usually encoded by small, poorly conserved ORFs. ORFs surrounding bacteriocin genes are often biosynthetic genes. This information can be used to locate putative structural bacteriocin genes. Here, we describe BAGEL, a web server that identifies putative bacteriocin ORFs in a DNA sequence using novel, knowledge-based bacteriocin databases and motif databases. Many bacteriocins are encoded by small genes that are often omitted in the annotation process of bacterial genomes. Thus, we have implemented ORF detection using a number of published ORF prediction tools. In addition, BAGEL takes into account the genomic context, i.e. for each potential bacteriocin-encoding ORF, the sequence of the surrounding region on the genome is analyzed for genes that might encode proteins involved in biosynthesis, transport, regulation and/or immunity. These innovations make BAGEL unique in its ability to detect putative bacteriocin gene clusters in (new) bacterial genomes. BAGEL is freely accessible at: http://bioinformatics.biol.rug.nl/websoftware/bagel.

Amino Acid Motifs↗

DisProt: the Database of Disordered Proteins.

The Database of Protein Disorder (DisProt) links structure and function information for intrinsically disordered proteins (IDPs). Intrinsically disordered proteins do not form a fixed three-dimensional structure under physiological conditions, either in their entireties or in segments or regions. We define IDP as a protein that contains at least one experimentally determined disordered region. Although lacking fixed structure, IDPs and regions carry out important biological functions, being typically involved in regulation, signaling and control. Such functions can involve high-specificity low-affinity interactions, the multiple binding of one protein to many partners and the multiple binding of many proteins to one partner. These three features are all enabled and enhanced by protein intrinsic disorder. One of the major hindrances in the study of IDPs has been the lack of organized information. DisProt was developed to enable IDP research by collecting and organizing knowledge regarding the experimental characterization and the functional associations of IDPs. In addition to being a unique source of biological information, DisProt opens doors for a plethora of bioinformatics studies. DisProt is openly available at http://www.disprot.org.

Databases, Protein↗

Three-dimensional virtual dissection at CT colonography: unraveling the colon to search for lesions.

Computed tomographic (CT) colonography is a promising noninvasive examination for colorectal cancer screening; however, the optimal interpretation strategy remains undecided. Virtual dissection is an innovative technique whereby the three-dimensional (3D) model of the colon is virtually unrolled, sliced open, and displayed as a flat 3D rendering of the mucosal surface, similar to a gross pathologic specimen. This technique has the potential to reduce evaluation time by providing a more rapid 3D image assessment than is possible with an antegrade and retrograde 3D endoluminal fly-through. It may also ultimately improve accuracy by reducing blind spots present with 3D endoluminal displays and by reducing reader fatigue. A disadvantage of virtual dissection is the potential for distortion of colonic lesions and normal anatomy. To avoid potential pitfalls in image interpretation, the radiologist must be familiar with the unique appearance of the normal colon anatomy and of various pathologic findings when using virtual dissection with two-dimensional axial and 3D endoluminal CT colonographic image data sets.

Colonic Diseases↗

Designing and Evaluating Home-Based, Just-in-Time Supportive Technology.

At MIT, a multi-disciplinary team of researchers is studying how to create pervasive computing environments for the home. We are developing technologies and design strategies that use context-aware sensing to empower people with information by presenting it at precisely the right time and place. Contrary to many visions of future home environments in the literature, we advocate an approach that uses technology to teach as opposed to using technology primarily for automated control. We have constructed a "living laboratory" that will provide a unique, flexible infrastructure for scientifically studying the power of pervasive computing for motivating learning and behavior change in the home. This facility, called the PlaceLab, is being used to study technology for creating homes that are supportive.

Biomedical Technology↗

Working memory and image guided surgical simulation.

We report on a study that investigates the relationship between visual working memory and verbal working memory and a performance measure in endoscopic instrument navigation in MIST and GI Mentor II (a simulator for gastroendoscopy). Integrated cognitive neuroscience in state-of-the-art simulator training curriculum will take safety science in health care one step ahead. Current simulator validation focuses on how to train. In the light of recent research it is now prime time to ask why in search of mechanisms rather than to repeatedly show that training has effect. This will help tailor training to maximize individual output in procedures that require a high level of dexterity. WM training is a unique learning aid in simulator training and should be used alongside clinical practice in order to improve the quality of complex clinical intervention in the field of image guided surgical simulation.

Computer Simulation↗

The ultrastructure of the neonatal pig colon.

The neonatal pig colon has several unique structural and developmental features. At birth it has a variable population of epithelial cells which in their arrangement on villus-like protrusions and in their capability for protein uptake into large preformed supranuclear vacuoles closely resemble neonatal ileal cells. Such villus-like protrusions and vacuolated cells are not present in the 2-day-old piglet. On the first day after birth absorptive epithelial cells which lack supranuclear vacuoles transiently accumulate a large number of lipid droplets, each separated from the cytoplasm only by a proteolipid interface. None of the much smaller lipid droplets bounded by a unit membrane of the smooth endoplasmic reticulum and characteristic of normal small intestinal fat uptake were ever seen in these cells. Very few of the large lipid drops remain on the second day after birth. This initial capacity of the colon for protein and lipid uptake never reappears. The pattern of colonic amino acid transport also changes markedly in the first four days of independent life and this may be correlated with the observation that the absorptive cells at birth have microvilli which are twice the length of those on similar cells at and after two days old. These morphological results are discussed in terms of implied functional changes in the neonatal period.

Amino Acids↗

The monomeric orphan nuclear receptor Schistosoma mansoni Ftz-F1 dimerizes specifically and functionally with the schistosome RXR homologue, SmRXR1.

In an attempt to understand development and differentiation processes of the parasitic blood fluke Schistosoma mansoni, several members of the nuclear receptor superfamily were cloned, including SmFtz-F1 (S. mansoni Fushi Tarazu-factor 1). The Ftz-F1 nuclear receptor subfamily only contains orphan receptors that bind to their response element as monomers. Whereas SmFtz-F1 displays these basic functional properties, we have identified an original and specific interaction between SmFtz-F1 and the schistosome RXR homologue, SmRXR1. The mammalian two-hybrid assay showed that the D, E, and F domains of SmFtz-F1 were capable of interacting specifically with the E domain of SmRXR1 but not with that of mouse RXRalpha. Using three-dimensional LBD homology modelling and structure-guided mutagenesis, we were able to demonstrate the essential role of exposed residues located in the dimerization interfaces of both receptors in the maintenance of the interaction. Cotransfection experiments with constructions encoding full-length nuclear receptors show that SmRXR1 potentiates the transcriptional activity of SmFtz-F1 from various promoters. Nevertheless, the lack of identification of a dimeric response element for this SmFtz-F1/SmRXR1 heterodimer seems to indicate a "tethering" mechanism. Thus, our results suggest for the first time that a member of the Ftz-F1 family could heterodimerize functionally with a homologue of the universal heterodimerization partner of nuclear receptors. This unique property confirms that SmFtz-F1 may be involved in the development and differentiation of schistosome-specific structures.

Amino Acid Sequence↗

alpha-Conotoxin EI, a new nicotinic acetylcholine receptor antagonist with novel selectivity.

We report the isolation and characterization of a novel nicotinic acetylcholine receptor (nAChR) ligand. The toxin is an 18 amino acid peptide and is the first reported alpha-conotoxin from an Atlantic fish-hunting Conus. The peptide was purified from the venom of Conus ermineus and is called alpha-conotoxin EI. The sequence diverges from that of previously isolated alpha-conotoxins. We demonstrate that this structural divergence has functional consequences. In Torpedo nAChRs, alpha-conotoxin EI selectively binds the agonist site near the alpha/delta subunit interface in contrast to alpha-conotoxin MI which selectively targets the alpha/gamma agonist binding site. In mammalian nAChRs alpha-conotoxin EI shows high affinity for both the alpha/delta and alpha/gamma subunit interfaces (with some preference for the alpha/delta site), whereas alpha-conotoxin MI is highly selective for the alpha/delta ligand binding site. The sequence of the peptide is: Arg-Asp-Hyp-Cys-Cys-Tyr-His-Pro-Thr-Cys-Asn-Met-Ser-Asn-Pro-Gln-Ile-Cys- NH2, with disulfide bridging between Cys4-Cys10 and Cys5-Cys18, analogous to those of previously described alpha-conotoxins. This sequence has been verified by total chemical synthesis. Thus, alpha-conotoxin EI is a newly-available tool with unique structure and function for characterization of nAChRs.

Amino Acid Sequence↗