Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Origin Recognition Complex”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,459 records · Page 81Linked to original sources
PubMedDate not supplied

Semisupervised learning for molecular profiling.

Class prediction and feature selection are two learning tasks that are strictly paired in the search of molecular profiles from microarray data. Researchers have become aware how easy it is to incur a selection bias effect, and complex validation setups are required to avoid overly optimistic estimates of the predictive accuracy of the models and incorrect gene selections. This paper describes a semisupervised pattern discovery approach that uses the by-products of complete validation studies on experimental setups for gene profiling. In particular, we introduce the study of the patterns of single sample responses (sample-tracking profiles) to the gene selection process induced by typical supervised learning tasks in microarray studies. We originate sample-tracking profiles as the aggregated off-training evaluation of SVM models of increasing gene panel sizes. Genes are ranked by E-RFE, an entropy-based variant of the recursive feature elimination for support vector machines (RFE-SVM). A Dynamic Time Warping (DTW) algorithm is then applied to define a metric between sample-tracking profiles. An unsupervised clustering based on the DTW metric allows automating the discovery of outliers and of subtypes of different molecular profiles. Applications are described on synthetic data and in two gene expression studies.

Algorithms↗
PubMed1996

Positive selection is not required for thymic maturation of transgenic gamma delta T cells.

Previously published reports describing thymic differentiation in two TCR gamma delta transgenic mouse models have suggested that gamma delta T cells require MHC-mediated positive selection to reach full maturity. Recent studies indicate that recognition of antigen by mature gamma delta T cells is not MHC restricted, raising the issue of why developing gamma delta T cells would even require MHC-driven positive selection. Therefore, we have reinvestigated the requirements for development and selection in G8 gamma delta T cell receptor (TCR) transgenic mice. Analyses of absolute cell numbers, phenotypic subsets, and functional competence of thymic and peripheral G8 gamma delta T cells indicate that these cells can fully mature in class I MHC-deficient mice. Moreover, mixed bone marrow chimeras demonstrate that gamma delta T cells of mutant B2-microglobulin (beta 2m zero) origin are partially deleted in the presence of H-2d-bearing thymocytes (previously believed to be the haplotype mediating positive selection). We conclude that there is no requirement for class I-like molecules for the maturation/development of these transgenic gamma delta T cells and that the differences in thymocyte phenotype and number observed are, instead, attributable to effects of clonal deletion.

Animals↗
PubMed1994

Gene transfer studies of T cell receptor-gamma delta recognition. Specificity for staphylococcal enterotoxin A is conveyed by V gamma 9 alone.

gamma delta T cells bearing the V gamma 9 gene segment have been shown to recognize staphylococcal enterotoxin A (SEA) and a range of other Ags including mycobacterial Ags. We have established an experimental system to analyze the recognition properties of human TCR-gamma delta on a molecular level by transferring the receptor from its original T cell into a Jurkat T cell host that does not express an endogenous TCR. Three groups of transfectants that express the same delta-chain, V delta 1, but different gamma-chains (V gamma 9-J2-C gamma 2, V gamma 3-J2-C gamma 2, and V gamma 9-JP-C gamma 1) together with the endogenous CD3 were obtained. The transfectant T cells each expressing different gamma delta receptors all produced IL-2 after stimulation with plastic bound anti-CD3 Ab, but only those expressing V gamma 9 responded to stimulation with SEA in the presence of an autologous lymphoblastoid B cell line. In addition, transfectants that expressed V delta 2 combined with V gamma 9 could also respond to SEA. These results indicate that the V gamma 9 portion of the receptor, independent of the J region and C region or the delta-chain, is responsible for recognizing SEA.

Amino Acid Sequence↗
PubMed2001

Biophysical analysis of the endoplasmic reticulum-resident chaperone/heat shock protein gp96/GRP94 and its complex with peptide antigen.

Animals vaccinated with heat shock protein (HSP)--peptide complexes develop specific protective immunity against cancers from which the HSPs were originally isolated. This autologous specific immunity has been demonstrated using a number of HSP--peptide antigen complexes. A prototypical HSP-based cancer vaccine is the gp96--peptide antigen complex, which is currently undergoing human clinical trials. Here, we analyzed the structure of a recombinant wild-type and a mutant gp96 protein and their peptide complexes using a number of biophysical techniques. Gel filtration chromatography, dynamic light scattering, and equilibrium analytical ultracentrifugation demonstrated that both a wild-type gp96 and a gp96 mutant lacking a dimerization domain formed higher order structures. More detailed analysis using scanning transmission electron microscopy indicated that both the wild-type and dimerization deletion mutant gp96 protein were organized, unexpectedly, into large aggregates. Size distributions ranged from dimers to octamers and higher. Circular dichroism and intrinsic Trp fluorescence suggested that the gp96 dimerization domain deletion mutant protein was more compact than the wild-type gp96. A fluorescent peptide antigen was synthesized, and the peptide-binding properties of wild-type and the dimerization domain deletion mutant gp96 were studied. Fluorescence lifetime and anisotropy decay showed that the bound antigenic peptide was located in a hydrophobic pocket, with considerable free space for the rotation of the probe. Deletion of the dimerization domain affected the peptide-binding microenvironment, although peptide-binding affinity was reduced by only a small extent. Peptide--gp96 complexes were extremely stable, persisting for many days in the cold. The extraordinary stability of peptide--gp96 complexes and the plasticity of the peptide-binding pocket support the proposed relay of diverse peptides to MHC and/or other molecules via molecular recognition.

Animals↗
PubMed2006

The fundamentals of average local variance--Part I: Detecting regular patterns.

The method of average local variance (ALV) computes the mean of the standard deviation values derived for a 3 x 3 moving window on a successively coarsened image to produce a function of ALV versus spatial resolution. In developing ALV, the authors used approximately a doubling of the pixel size at each coarsening of the image. They hypothesized that ALV is low when the pixel size is smaller than the size of scene objects because the pixels on the object will have similar response values. When the pixel and objects are of similar size, they will tend to vary in response and the ALV values will increase. As the size of pixels increase further, more objects will be contained in a single pixel and ALV will decrease. The authors showed that various cover types produced single peak ALV functions that inexplicitly peaked when the pixel size was 1/2 to 3/4 of the object size. This paper reports on work done to explore the characteristics of the various forms of the ALV function and to understand the location of the peaks that occur in this function. The work was conducted using synthetically generated image data. The investigation showed that the hypothesis originally proposed in is not adequate. A new hypothesis is proposed that the ALV function has peak locations that are related to the geometric size of pattern structures in the scene. These structures are not always the same as scene objects. Only in cases where the size of and separation between scene objects are equal does the ALV function detect the size of the objects. In situations where the distance between scene objects are larger than their size, the ALV function has a peak at the object separation, not at the object size. This work has also shown that multiple object structures of different sizes and distances in the image provide multiple peaks in the ALV function and that some of these structures are not implicitly recognized as such from our perspective. However, the magnitude of these peaks depends on the response mix in the structures, complicating their interpretation and analysis. The analysis of the ALV Function is, thus, more complex than that generally reported in the literature.

Algorithms↗
PubMed1998

L1 makes immunological progress by expanding its relations.

The cell-adhesion molecule L1 was originally described in the nervous system. It has recently been detected in CD4+ T lymphocytes, peripheral B lymphocytes, and granulocytes in the human immune system and in similar leucocyte types in the murine immune system. L1 mediates neural recognition by Ca+2, Mg+2-independent homophilic binding. In the human and murine immune systems, L1 binds to the "classical" vitronectin receptor, alphaVbeta3, and fibronectin receptor, alpha5beta1, respectively, and abstains from homophilic binding. Homophilic L1 binding probably involves antiparallel alignment of several interactive domains. Integrin binding is mediated by a short segment of immunoglobulinlike domain 6, which includes two RGD repeats in rodent L1 and one RGD motif in human L1. L1 is modulated in activated leucocytes in vitro in parallel to L-selectin, and diverse cell types release intact L1 in vivo and in vitro. Released L1 can bind to laminin and adheres to the extracellular matrix of sciatic nerve, M21 melanoma, and possibly spleen and other tissues. It can support integrin-dependent cell migration and preliminary data implicate it in tumor development and transnodal lymphocyte migration.

Amino Acid Sequence↗
PubMed2006

Shuffling of discrete tRNASer regions reveals differently utilized identity elements in yeast and methanogenic archaea.

Seryl-tRNA synthetases (SerRSs) from methanogenic archaea possess distinct evolutionary origin and show minimal sequence similarity with counterparts from bacteria, eukaryotes and other archaea. Here we show that SerRS from yeast Saccharomyces cerevisiae and archaeon Methanococcus maripaludis (ScSerRS and MmSerRS, respectively) display significantly different ability to serylate heterologous tRNA(Ser). Recognition in yeast was shown to be more stringent than in archaeon. While cross-aminoacylation of M. maripaludis tRNA(Ser) (MmtRNA(Ser)) by yeast SerRS barely occurs, yeast tRNA(Ser) (SctRNA(Ser)) was shown to be a good substrate for heterologous MmSerRS. To investigate the contribution of different tRNA regions for the recognition by yeast and archaeal SerRS, chimeric tRNAs bearing separated domains of SctRNA(Ser) in MmtRNA(Ser) framework were produced by in vitro transcription and subjected to kinetic and gel mobility shift analysis with both enzymes. Generally, the recognition in M. maripaludis seems to be relatively relaxed toward tertiary elements of tRNA(Ser) structure and relies on the direct recognition of identity nucleotides. On the other hand, expression of tRNA(Ser) identity elements in yeast seems to be more sensitive toward surrounding sequence context. In both systems variable arm of tRNA was recognized as a major identity region with a strong influence on SerRS:tRNA binding. Acceptor domain of SctRNA(Ser) was also shown to be important for serylation in yeast. We propose that cognate interactions between N-terminal domain of yeast SerRS and variable region of SctRNA(Ser) place the acceptor stem into the enzyme's active site and lead to increased affinity toward serine and efficient serylation of tRNA. The same effect was not observed in M. maripaludis. Unlike its yeast counterpart, MmSerRS forms only one type of covalent complex with MmtRNA(Ser), regardless of the tRNA/SerRS molar ratio. Stoichiometry of the complex, one tRNA per dimeric SerRS, was revealed by mass spectrometry. Our studies indicate that different SerRS:tRNA recognition mode is utilized by these two systems.

Base Sequence↗
PubMedDate not supplied

Uniform remeshing with an adaptive domain: a new scheme for view-dependent level-of-detail rendering of meshes.

We present a new algorithm for view-dependent level-of-detail rendering of meshes. Not only can it effectively resolve complex geometry features similar to edge collapse-based schemes, but it also produces meshes that modern graphics hardware can render efficiently. This is accomplished through a novel hybrid approach: For each frame, we view-dependently refine the progressive mesh (PM) representation of the original mesh and use the output as the base domain of uniform regular refinements. The algorithm exploits frame-to-frame coherence and only updates portions of the output mesh corresponding to modified domain triangles. The PM representation is built using a custom volume preservation-based error function. A simple k-d tree enhanced jump-and-walk scheme is used to quickly map from the dynamic base domain to the original mesh during regular refinements. In practice, the PM refinement provides a view-optimized base domain for later regular refinements. The regular refinements ensure almost-everywhere regularity of output meshes, allowing optimization for vertex cache coherence and caching of geometry data in high-performance graphics memory. Combined, they also have the effect of allowing our algorithm to operate on uniform clusters of triangles instead of individual ones, reducing CPU workload.

Algorithms↗
PubMed1998

Anomalous origin of coronary arteries and risk of sudden death: a study based on an autopsy population of congenital heart disease.

Coronary arteries anomalies may be part of complex congenital malformations of the heart or be an isolated defect. In our anatomic collection of congenital heart disease, an isolated anomalous origin of coronary arteries was observed in 27 of 1,200 specimens (2.2%): left coronary artery from pulmonary trunk in five, origin from the wrong aortic sinus in 12 (both right and left coronary artery from the right sinus in four and from the left sinus in seven, left coronary artery from the posterior sinus in one), left circumflex branch from right aortic sinus or from very proximal right coronary artery in three, high takeoff of right coronary artery in three, stenosis of the coronary ostia attributable to valvelike ridge in four. In 16 (59%) patients (12 males and 4 females, age ranging from 2 months to 53 years; median, 14), the final outcome was sudden death; it occurred in all cases of left coronary artery origin from right aortic sinus, in 43% of right coronary artery origin from left aortic sinus, and in 40% of the left coronary artery from the pulmonary trunk. Sudden death was precipitated by effort in eight (50%) and was the first manifestation of the disease in eight (50%); previous symptoms consisted of recurrent syncope in four, palpitations in three, and chest pain in one. Five patients who died suddenly during effort were athletes. In conclusion, (1) more than half of our postmortem cases with anomalous origin of coronary arteries died suddenly, (2) all but two patients with sudden death had anomalous coronary artery origin from the aorta itself, (3) the fatal event was frequently precipitated by effort, (4) palpitations, syncope, and ventricular arrhythmias were the only prodromic symptoms and signs. Recognition during life of these coronary anomalies, by the use of noninvasive procedures, is mandatory to prevent the risk of sudden death and to plan surgical correction if clinically indicated.

Adolescent↗
PubMed1998

Evidence against the double-arginine motif as the only determinant for protein translocation by a novel Sec-independent pathway in Escherichia coli.

Proteins which are synthesized with a signal peptide containing a 'double-arginine' motif may be translocated across the bacterial cytoplasmic membrane by a mechanism that is different from the known Sec and signal recognition particle pathways. The function of the double-arginine motif as a determinant for this novel pathway was studied by expressions of gene constructs coding for the high potential iron-sulfur protein (HiPIP) from Chromatium vinosum D in Escherichia coli. When the protein was produced with its original double-arginine motif-containing signal peptide, it was in part translocated into the periplasm and thereby processed, as shown by immunoblots after cell fractionation and N-terminal sequencing of purified HiPIP. Processing was not inhibited significantly by 3 mM sodium azide, indicating that translocation of HiPIP occurs by a SecA-independent pathway. Translocation of HiPIP could be altered to the SecA-dependent mode when its signal peptide was substituted by that of PelB from Erwinia carotovora. When the HiPIP double-arginine motif (SRRDAVK) was introduced into the corresponding position of the PelB signal peptide, the transport pathway remained SecA-dependent. This indicates that additional determinants are required for translocation by the Sec-independent pathway.

Adenosine Triphosphatases↗
PubMed1981

The zonal anatomy of the prostate.

Earlier morphologic studies of the prostate, though often extensive, have never systematically delineated its completed structure. Recent comprehensive analysis of 500 prostates has more precisely defined its anatomic composition, identifying previously undetected features and unsuspected complexities. Using a three-dimensional model, these structures and relationships are demonstrated. Four basic anatomic regions are described. The relationship of each to the urethra provides a central anatomic reference point. 1. The peripheral zone constitutes over 70% of the glandular prostate. It forms a disc of tissue whose ducts radiate laterally from the urethra lateral and distal to the verumontanum. Almost all carcinomas arise here. 2. The central zone constitutes 25% of the glandular prostate. Its ducts arise close to the ejaculatory duct orifices and follow these ducts proximally, branching laterally near the prostate base. Its lateral border fuses with the proximal peripheral zone border, completing in continuity with the peripheral zone, a full disc of secretory tissue oriented in a coronal plane. Marked histologic differences between central and peripheral zones suggest important biologic differences. 3. Preprostatic region. The urethral segment proximal to the verumontanum is kinked anteriorly at a 35-degree angle to the distal segment. No major ducts arise in the proximal segment, but the lateral rows of peripheral zone orifices continue. Duct development is aborted here, producing only a small transition zone and several tinier periurethral ducts. The development of these small ducts is possibly determined and limited by their intimate relationship to a periurethral smooth muscle sphincter that exists only proximal to the verumontanum. These small ducts in a restricted area are the exclusive site of nodular hyperplasia (BPH) origin. 4. The anterior fibromuscular stroma forms the entire anterior surface of the prostate as a thick, nonglandular apron, shielding from view the anterior surface of the three glandular regions. Its inseparable fusion to the glandular prostate has probably delayed recognition of the anatomic features described here.

Animals↗
PubMed1981

Antigen-specific T cell clones restricted to unique F1 major histocompatibility complex determinants. Inhibition of proliferation with monoclonal anti-Ia antibody.

The existence of T cells specific for soluble antigens in association with unique F(1) or recombinant major histocompatibility complex (MHC) gene products was first postulated from studies on the proliferative response of whole T cell populations to the antigen poly(Glu(55)Lys(36)Phe(9))(n) (GLphi). In this paper we use the newly developed technology of T lymphocyte cloning to establish unequivocally the existence of such cells specific for GLphi and to generalize their existence by showing that F(1)- specific cells can be isolated from T cell populations primed to poly(Glu(60)Ala(30)Tyr(10))(n) (GAT) where such clones represent only a minor subpopulation of cells. Gl.4b-primed B10.A(5R) and GAT-primed (B10.A x B10)F(1) lymph node T cells were cloned in soft agar, and the colonies that developed were picked and expanded in liquid culture. The GLphi-specific T cells were then recloned under conditions of high-plating efficiency to ensure that the final colonies originated from single cells. T cells from such rigorously cloned populations responded to stimulation with GILphi but only in the presence of nonimmune, irradiated spleen cells bearing (B10.A x B10)F(1) or the syngeneic B 10.A(5R) recombinant MHC haplotype. Spleen cells from either the B10 or B 10.A parental strains failed to support a proliferative response, even when added together. (B10 x B10.D2)F(1) and (B10 x B10.RIII)F(1) spleen cells also supported a proliferative response but (B10 x B10.Q)F(1) and (B10 X B10.S)F(1) spleen cells did not. These results suggested that the T cell clones were specific for GL[phi} in association with the beta(AE)(b)-alpha(E) (k,d,r,) Ia molecule and that recognition required both gene products to be expressed in the same antigen-presenting cells. Support for this interpretation was obtained from inhibition experiments using the monoclonal antibody Y-17 specific for a determinant on the beta(AE)(b)-alphaE Ia molecule. Y-17 completely inhibited the proliferative response of a GLphi-specific clone but had no effect on the response of either a PPD-specific or GAT-specific clone, both of which required the beta(A)-alpha(A) Ia molecule as their restriction element. No evidence could be found for the involvement of suppressor T cells in this inhibition. We therefore conclude that the phenomenon of F(1)-restricted recognition by proliferating T cells results from the presence of antigen- specific clones that must recognize unique F(1) or recombinant Ia molecules on the surface of antigen-presenting cells in addition to antigen in order to be stimulated.

Animals↗
PubMedDate not supplied

Anticoagulation clinics: the Italian experience.

BACKGROUND AND OBJECTIVE: The clinical quality of oral anticoagulant therapy (OAT) depends on how successful physicians and patients are in achieving and maintaining levels of anticoagulation capable of preventing thromboembolic events without increasing the risk of hemorrhagic complications. Concerning the patient, education and compliance are the major problems. As for the physician, on the other hand, the management of patients receiving OAT is a complex task that requires frequent laboratory testing, dosage regulation, prompt diagnosis and treatment of thromboembolic and hemorrhagic events. It requires educated and skilled personnel and a well-organized framework of services. Anticoagulation clinics, which provide patient education, close monitoring of prothrombin time and continuous clinical surveillance, may help in improving the overall quality of OAT. INFORMATION SOURCES: The authors have been working in this field contributing, original papers. In addition, the material examined in this article includes articles published in the journals covered by the Science Citation Index and Medline. STATE OF ART AND PERSPECTIVES: The concept of a coordinated network of medical services specifically devoted to the control of OAT was developed in the Netherlands following the model created by the late Professor Jordan, who in 1949 founded the first thrombosis center at the University of Utrecht. Many other anticoagulant clinics were organized on, a voluntary basis in the following decades in the Netherlands. The Dutch Federation of Thrombosis Centers was founded in 1971 and each affiliated Center is formally recognized and supported by the central Government. Today, there is a nation-wide system of regionally centralized anticoagulant control for outpatients and home patients that counts approximately 70 anticoagulant clinics (thrombosis centers), covering more than 90% of the country. Similar global approaches to the management of patients receiving OAT were proposed in other countries. In the 1950's, a group of internists and surgeons at the University of Michigan, USA, developed a unit specifically devoted to the diagnosis and treatment of thromboembolic disease, and proposed common strategies, teaching and research programs. In 1959, Sevitt and Gallagher were the first to propose a formal recognition of an anticoagulant unit in Great Britain. Finally, the Italian Federation of Centers for the Surveillance of Anticoagulant (FCSA) therapies was founded in 1989. Nowadays, Italian anticoagulation clinics operating in the framework of the FCSA are still voluntary organizations which provide a specific medical service by continuously reorganizing the personnel, structures and resources available to meet increasing demands. Since OAT has a profound social impact, its control should not be left to the good will of dedicated people, but should instead represent a specific task of the public health system. The achievement of a formal recognition of federated centers is essential for their growth, but the unavoidable increase of the expenses needed to support anticoagulation clinics is difficult to bear in a public care system which is currently facing a substantial reduction of financial resources. In a fixed health care budget, a redistribution of existing resources is the only possible solution, but to achieve this goal, public authorities have to be convinced that the management of OAT in specific anticoagulation clinics is cost-effective. A more accurate estimate of costs is needed and should be performed by the FCSA. Finally, the FCSA should strengthen its contacts with patient organizations and other scientific associations in order to develop common action strategies for improving the quality of OAT.

Ambulatory Care Facilities↗
PubMed1997

X-ray structure at 1.76 A resolution of a polypeptide phospholipase A2 inhibitor.

The high resolution crystal structure of a natural PLA2 inhibitor has been determined by Patterson search methods. In the heterodimeric, neurotoxic complex, vipoxin, isolated from the venom of Bulgarian viper, PLA2 inhibitor represents the non-toxic subunit. The model was refined to a crystallographic R-factor of 15.5% for data between 6 and 1.76 A resolution. The packing of the inhibitor in the crystal reveals close contacts between the molecules, which are symmetry-related by the 2-fold axes of the lattice. These pairs associate as a crystallographic dimer, stabilized by a set of interactions, including van der Waals contacts between residues from symmetry-related pairs, denoted as the recognition site and the recognition surface. Residues Ph3, Trp31 and Tyr119 represent the recognition site of inhibitor which possibly fits to the hydrophobic wall of the target PLA2. The topology of the inhibitor represents the PLA2 type of folding: three long helices and a beta-hairpin. Superposition of the structure of the inhibitor shows an almost complete overlap with different mammalian and viper PLA2 in the backbone and in the position of the sidechains of the residues that belong to the active centre and the hydrophobic wall. A "lock and key" mechanism of recognition of its native PLA2 in gland cells and other toxic PLA2 in vitro has been suggested. The mechanism includes complementary "head to tail" interactions between the recognition site of the inhibitor and a recognition surface located on the hydrophobic wall of the target PLA2. Having a high spatial homology with the PLA2 family of enzymes but opposing their action, the inhibitor from vipoxin presents an example of a divergent evolution of an ancient PLA2. The presence of a space for binding calcium in the inhibitor is believed to be a rudiment and proof of a common origin with PLA2.

Amino Acid Sequence↗
PubMed1987

Management of bulbar symptoms in amyotrophic lateral sclerosis.

The bulbar symptoms of ALS include difficulty with the management of swallowing, saliva, aspiration, and communication. These symptoms originate from the disability of the oropharyngeal muscles and actually represent varying degrees of severity of a single problem. The management of these symptoms requires the concerted effort of a rehabilitation team, which should include a surgeon, speech pathologist, neurologist, psychosocial worker, and dietitian. Early education of the patient and patient's family greatly facilitates successful management of bulbar symptoms. Early recognition of the signs of dysphagia, aspiration, and communicative disability are important in order to provide solutions before severe and possibly life-threatening debilitation occurs. The treatments and techniques presented in this chapter must be applied to each patient on an individual basis. The moral and social decisions regarding the providing or withholding of treatment to ALS patients are difficult ones. It is important, however, to realize that management decisions of ALS patients must deal not only with the quantity of life but also the quality of life. This distinction often falls into a 'gray zone' with management of bulbar symptoms since swallowing difficulties are life-threatening as well as uncomfortable. One of the difficulties that we present ourselves as health care providers in ALS is that, more often than not, our patient is in a noncommunicative position and cannot contribute to treatment decisions. If careful and aggressive care is taken to preserve the communicative abilities of our patients, the difficult situation of making decisions based on the family's inclinations and our own inclinations can be avoided. When we are confronted with a decision to maintain or cease support for a patient, the moral and emotional issues that present can be overwhelming. However, the patient's input, if it were direct and included the ability to express complex thoughts, could often provide the information necessary to make the decisions more clear.

Airway Obstruction↗
PubMed1991

The Fraser illusion: complex figures.

The cause of the Fraser illusion, which occurs when a line made up of tilted segments itself appears tilted, is examined further. In this series of experiments, we used figures that resembled the original Fraser illusion; they were more complex than those reported on in our previous paper (Stuart & Day, 1988). The figures were used to explore two theories of the Fraser illusion further: that it is the result of interactions between orientation selective units, and that it is a consequence of the local, distributed processing of orientation. The presence of background elements like those used in the original illusion led to an increase in the strength of the illusion, but the shape of these elements had no differential effect on illusion strength. There was a differential effect of the background on the assimilative and contrast illusions, owing respectively to small and large tilts of the inducing elements. The illusion was markedly reduced at small visual angles when the background was absent, but it was only slightly affected when the background was present. All these findings are difficult to explain in terms of interactions between single units, either at the same or at different scales in the image. The effects of luminance contrast and isoluminance on the illusion were not consistent with either theory, but they indicated that researchers need to consider the role of figure-ground organization in this illusion.

Adolescent↗
PubMed1988

Initiation of lagging-strand synthesis for pBR322 plasmid DNA replication in vitro is dependent on primosomal protein i encoded by dnaT.

The role of the primosome assembly and protein n' recognition site in replication of pBR322 plasmid was examined. The following evidence indicates that the primosome is involved in lagging-strand synthesis of pBR322 plasmid replication in vitro. Early replicative intermediates with newly synthesized leading strand, approximately 1 kilobase pair long, immediately downstream of the replication origin accumulate in products synthesized in extracts from a dnaT strain that lacks primosomal protein i or in wild-type extracts supplemented with anti-protein i antibody. These intermediates are converted efficiently into full-length DNA by addition of purified protein i. Consistent with the previously proposed role of the primosome (Arai, K. and Kornberg, A. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 69-73), an n' site on the lagging strand, but not on the leading strand, is required for efficient replication of the plasmid in vitro. Plasmids lacking an n' site on the lagging strand replicate only to a limited extent in vitro and early replicative intermediates carrying nascent leading strands are accumulated, although a portion of the intermediates complete replication to yield full-length DNA. The latter reaction is completely inhibited by addition of anti-protein i antibody. Insertion of the n' site of phage phi X174 into pBR322 plasmids lacking lagging-strand n' sites restores the replicative ability of the mutant plasmid comparable to that of the wild-type plasmid. These results indicate that protein i is essential for lagging-strand synthesis of pBR322 plasmid in vitro and that it may play an important role in the priming events as a part of either an n' site-dependent primosome or an n' site-independent, as yet unidentified, priming complex.

Bacterial Proteins↗
PubMed2005

Temporal dissociation of early lexical access and articulation using a delayed naming task--an FMRI study.

Neuroimaging studies of overt speech hold an important practical advantage allowing monitoring of subject performance, particularly valuable in disorders like aphasia. However, speech production is not a monotonic process but a complex sequence of stages. Levelt and colleagues have described these as roughly corresponding to two originally independent systems--conceptual and sensorimotor--that are linked in the formulation and expression of spoken language. In the initial stages a word is chosen to match a concept (lexical selection); in the later stages the sound and motor patterns are encoded and the word is uttered (articulation). It has been difficult to discriminate these stages using conventional neuroimaging techniques. We designed a functional magnetic resonance imaging study in an attempt to do this, by introducing a latency into a conventional naming paradigm, delaying the articulated response. Our results showed that left hemisphere perisylvian areas were active throughout, interacting with visual and heteromodal areas during early lexical access and with motor and auditory areas during overt articulation. These results are consistent with the broadest version of the Levelt model and with that derived from Chomsky's minimalist program in which a core language system interacts with conceptual-intentional systems and articulatory-perceptual systems during the early and late stages of lexical access respectively.

Adult↗