Expression of extracellular matrix proteins in adenomatoid odontogenic tumor

Altered expression of extracellular matrix (ECM) components has been reported in several pathologies; however, few ECM proteins have been evaluated in adenomatoid odontogenic tumor (AOT). The aim of this study was to analyze the expression and distribution of the ECM proteoglycans: biglycan and decorin; and glycoproteins: osteonectin, osteopontin, bone sialoprotein and osteocalcin in the AOT. Three-micrometer sections from paraffin-embedded specimens were evaluated employing a streptavidin-biotin immunohistochemical method with the antibodies against the proteins previously cited. Only the osteonectin was expressed in the epithelial cells. The eosinophilic amorphous material and the connective tissue showed expression of all components studied. The calcification foci expressed only osteopontin. In conclusion, the low expression of the components studied in neoplastic epithelial cells suggests that the epithelial cells act probably as stimulators of the expression by the stroma, which in turn can act as agonist or antagonist of the tumor growth. These results suggest that the components studied probably have a key role in the biological behavior of the AOT.

Expression of matrix metalloproteinases-2 and-9 and RECK during alveolar bone regeneration in rat

MMPs are endopeptidases that play a pivotal role in ECM turnover. RECK is a single membrane-anchored MMP-regulator. Here, we evaluated the temporal and spatial expression of MMP-2, MMP-9, and RECK during alveolar bone regeneration. The maxillary central incisor of Wistar rats was extracted and the animals were killed at 1, 3, 7, 10, 14, 21, 28, and 42 days post-operatively (n = 3/period). The hemimaxillae were collected, demineralized and embedded in paraffin. Immunohistochemical analysis was performed by the immunoperoxidase technique with polyclonal antibodies. On day 1, polymorphonuclear cells in the blood clot presented mild immunolabeling for MMPs. During bone remodeling, osteoblasts facing new bone showed positive staining for gelatinases and RECK in all experimental periods. MMPs were also found in the connective tissue and endothelial cells. Our results show for the first time that inactive and/or active forms of MMP-2, MMP-9 and RECK are differentially expressed by osteogenic and connective cells during several events of alveolar bone regeneration. This may be important for the replacement of the blood clot by connective tissue, and in the formation, maturation and remodeling of new bone.

Relational learning in children with deafness and cochlear implants

This four-experiment series sought to evaluate the potential of children with neurosensory deafness and cochlear implants to exhibit auditory-visual and visual-visual stimulus equivalence relations within a matching-to-sample format. Twelve children who became deaf prior to acquiring language (prelingual) and four who became deaf afterwards (postlingual) were studied. All children learned auditory-visual conditional discriminations and nearly all showed emergent equivalence relations. Naming tests, conducted with a subset of the: children, showed no consistent relationship to the equivalence-test outcomes.. This study makes several contributions: to the literature on stimulus equivalence. First; it demonstrates that both pre- and postlingually deaf children-can: acquire auditory-visual equivalence-relations after cochlear implantation, thus demonstrating symbolic functioning. Second, it directs attention to a population that may be especially interesting for researchers seeking to analyze the relationship. between speaker and listener repertoires. Third, it demonstrates the feasibility of conducting experimental studies of stimulus control processes within the limitations of a hospital, which these children must visit routinely for the maintenance of their cochlear implants.

Quasi-stationarity in populations that are subject to large-scale mortality or emigration

We shall examine a model, first studied by Brockwell et al. [Adv Appl Probab 14 (1982) 709.], which can be used to describe the longterm behaviour of populations that are subject to catastrophic mortality or emigration events. Populations can suffer dramatic declines when disease, such as an introduced virus, affects the population, or when food shortages occur, due to overgrazing or fluctuations in rainfall. However, perhaps surprisingly, such populations can survive for long periods and, although they may eventually become extinct, they can exhibit an apparently stationary regime. It is useful to be able to model this behaviour. This is particularly true of the ecological examples that motivated the present study, since, in order to properly manage these populations, it is necessary to be able to predict persistence times and to estimate the conditional probability distribution of population size. We shall see that although our model predicts eventual extinction, the time till extinction can be long and the stationary exhibited by these populations over any reasonable time scale can be explained using a quasistationary distribution. (C) 2001 Elsevier Science Ltd. All rights reserved.

Immunolocalization of matrix metalloproteinases-2 and-9 during apical periodontitis development

Objective: The objective of this study was to determine the expression of matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9) during apical periodontitis development. Methods: Using an experimental design of induced periapical lesions in rats and immunohistochemistry assay as investigative tool, the MMP-2 and MMP-9 expression and distribution were evaluated at 3, 7,14, 21, 30,60 and 90 days after coronary access and pulp exposure of the first left mandibular molar to the oral environment. Two blind observers scored the immunoreactivity. A semi-quantitative analysis was performed. Results: Except at day 3, MMP-2 and MMP-9 immunostaining was observed in all experimental periods. The MMP-2 (p = 0.004) and MMP-9 (p = 0.005) immunostaining was higher in the period between 7 and 21 days. They were mainly observed in cells surrounding the apical foramen and adjacent periapical areas. Cells into the hypercementosis areas were strongly stained while both osteoblasts and osteoclasts; presented discrete staining along of this study. No staining was observed on epithelial walls. At 30, 60 and 90 days, the subjacent connective tissue presented intense MMP-2 and MMP-9 immunostaining in mononuclear cells (suggestive of fibroblasts, macrophages, infiltrating neutrophils and lymphocytes). Conclusion: The results observed in this study suggest that MMP-2 and MMP-9 play a critical role in the development of inflammatory periapical lesions, probably involved in the extracellular matrix (ECM) degradation during the initial phase of the lesion development. (C) 2009 Elsevier Ltd. All rights reserved.

Ascorbate-induced osteoblast differentiation recruits distinct MMP-inhibitors: RECK and TIMP-2

The bone formation executed by osteoblasts represents an interesting research field both for basic and applied investigations. The goal of this work was to evaluate the molecular mechanisms involved during osteoblast differentiation in vitro. Accordingly, we demonstrated that, during the osteoblastic differentiation, TIMP-2 and RECK presented differential expressions, where RECK expression was downregulated from the 14th day in contrast with an increase in TIMP-2. Concomitantly, our results showed a temporal regulation of two major signaling cascades during osteoblast differentiation: proliferation cascades in which RECK, PI3 K, and GSK-3 beta play a pivotal role and latter, differentiation cascades with participation of Ras, Rho, Rac-1, PKC alpha/beta, and TIMP-2. Furthermore, we observed that phosphorylation level of paxillin was downregulated while FAK(125) remained unchangeable, but active during extracellular matrix (ECM) remodeling. Concluding, our results provide evidences that RECK and TIMP-2 are involved in the control of ECM remodeling in distinct phases of osteoblast differentiation by modulating MMP activities and a multitude of signaling proteins governs these events.

Stimulus competition in affective and relational learning

Evaluative learning theory states that affective learning, the acquisition of likes and dislikes, is qualitatively different from relational learning, the learning of predictive relationships among stimuli. Three experiments tested the prediction derived from evaluative learning theory that relational learning, but not affective learning, is affected by stimulus competition by comparing performance during two conditional stimuli, one trained in a superconditioning procedure and the other in a blocking procedure. Ratings of unconditional stimulus expectancy and electrodermal responses indicated stimulus competition in relational learning. Evidence for stimulus competition in affective learning was provided by verbal ratings of conditional stimulus pleasantness and by measures of blink startle modulation. Taken together, the present experiments demonstrate stimulus competition in relational and affective learning, a result inconsistent with evaluative learning theory. (C) 2001 Academic Press.

Neural adaptations to resistance training - Implications for movement control

It has long been believed that resistance training is accompanied by changes within the nervous system that play an important role in the development of strength. Many elements of the nervous system exhibit the potential for adaptation in response to resistance training, including supraspinal centres, descending neural tracts, spinal circuitry and the motor end plate connections between motoneurons and muscle fibres. Yet the specific sites of adaptation along the neuraxis have seldom been identified experimentally, and much of the evidence for neural adaptations following resistance training remains indirect. As a consequence of this current lack of knowledge, there exists uncertainty regarding the manner in which resistance training impacts upon the control and execution of functional movements. We aim to demonstrate that resistance training is likely to cause adaptations to many neural elements that are involved in the control of movement, and is therefore likely to affect movement execution during a wide range of tasks. We review a small number of experiments that provide evidence that resistance training affects the way in which muscles that have been engaged during training are recruited during related movement tasks. The concepts addressed in this article represent an important new approach to research on the effects of resistance training. They are also of considerable practical importance, since most individuals perform resistance training in the expectation that it will enhance their performance in-related functional tasks.

Continuous quantum measurement of two coupled quantum dots using a point contact: A quantum trajectory approach

We obtain the finite-temperature unconditional master equation of the density matrix for two coupled quantum dots (CQD's) when one dot is subjected to a measurement of its electron occupation number using a point contact (PC). To determine how the CQD system state depends on the actual current through the PC device, we use the so-called quantum trajectory method to derive the zero-temperature conditional master equation. We first treat the electron tunneling through the PC barrier as a classical stochastic point process (a quantum-jump model). Then we show explicitly that our results can be extended to the quantum-diffusive limit when the average electron tunneling rate is very large compared to the extra change of the tunneling rate due to the presence of the electron in the dot closer to the PC. We find that in both quantum-jump and quantum-diffusive cases, the conditional dynamics of the CQD system can be described by the stochastic Schrodinger equations for its conditioned state vector if and only if the information carried away from the CQD system by the PC reservoirs can be recovered by the perfect detection of the measurements.

Quantum measurement of coherent tunnelling between quantum dots

We describe the conditional and unconditional dynamics of two coupled quantum dots when one dot is subjected to a measurement of its occupation number by coupling it to a third readout dot via the Coulomb interaction. The readout dot is coupled to source and drain leads under weak bias, and a tunnel current flows through a single bound state when energetically allowed. The occupation of the quantum dot near the readout dot shifts the bound state of the readout dot from a low conducting state to a high conducting state. The measurement is made by continuously monitoring the tunnel current through the readout dot. We show that there is a difference between the time scale for the measurement-induced decoherence between the localized states of the dots, and the time scale on which the system becomes localized due to the measurement.

Gag-Pol supplied in trans is efficiently packaged and supports viral function in human immunodeficiency virus type 1

The intracellular trafficking and subsequent incorporation of Gag-Pol into human immunodeficiency virus type 1 (HIV-1) remains poorly defined. Gag-Pol is encoded by the same mRNA as Gag and is generated by ribosomal frameshifting. The multimerization of Gag and Gag-Pol is an essential step in the formation of infectious viral particles. In this study, we examined whether the interaction between Gag and Gag-Pol is initiated during protein translation in order to facilitate the trafficking and subsequent packaging of Gag-Pol into the virion. A conditional cotransfection system was developed in which virion formation required the coexpression of two HIV-1-based plasmids, one that produces both Gag and Gag-Pol and one that only produces Gag-Pol. The Gag-Pol proteins were either immunotagged with a His epitope or functionally tagged with a mutation (K65R) in reverse transcriptase that is associated with drug resistance. Gag-Pol packaging was assessed to determine whether the Gag-Pol incorporated into the virion was preferentially packaged from the plasmid that expressed both Gag and Gag-Pol or whether it could be packaged from either plasmid. Our data show that translation of Gag and Gag-Pol from the same mRNA is not critical for virion packaging of the Gag-Pol polyprotein or for viral function.

Dynamics of a mesoscopic charge quantum bit under continuous quantum measurement

We present the conditional quantum dynamics of an electron tunneling between two quantum dots subject to a measurement using a low transparency point contact or tunnel junction. The double dot system forms a single qubit and the measurement corresponds to a continuous in time readout of the occupancy of the quantum dot. We illustrate the difference between conditional and unconditional dynamics of the qubit. The conditional dynamics is discussed in two regimes depending on the rate of tunneling through the point contact: quantum jumps, in which individual electron tunneling current events can be distinguished, and a diffusive dynamics in which individual events are ignored, and the time-averaged current is considered as a continuous diffusive variable. We include the effect of inefficient measurement and the influence of the relative phase between the two tunneling amplitudes of the double dot/point contact system.

Expecting dirt but saying dart: The creation of a blend memory

During a naming task, time pressure and a manipulation of the proportion of related prime-target pairs were used to induce subjects to generate an expectation to the prime. On some trials, the presented target was orthographically and generally phonologically similar to the expected tal-get. The expectancy manipulation was barely detectable in the priming data but was clearly evident on a final recognition test. In addition, the recognition data showed that the nearly simultaneous activation of an expectation and sensory information derived from the orthographically and phonologically similar target produced a false memory. It is argued that this represents a blend memory.

Using visual spatial search interface for WWW applications

Most Internet search engines are keyword-based. They are not efficient for the queries where geographical location is important, such as finding hotels within an area or close to a place of interest. A natural interface for spatial searching is a map, which can be used not only to display locations of search results but also to assist forming search conditions. A map-based search engine requires a well-designed visual interface that is intuitive to use yet flexible and expressive enough to support various types of spatial queries as well as aspatial queries. Similar to hyperlinks for text and images in an HTML page, spatial objects in a map should support hyperlinks. Such an interface needs to be scalable with the size of the geographical regions and the number of websites it covers. In spite of handling typically a very large amount of spatial data, a map-based search interface should meet the expectation of fast response time for interactive applications. In this paper we discuss general requirements and the design for a new map-based web search interface, focusing on integration with the WWW and visual spatial query interface. A number of current and future research issues are discussed, and a prototype for the University of Queensland is presented. (C) 2001 Published by Elsevier Science Ltd.

Changes in motor planning of feedforward postural responses of the trunk muscles in low back pain

Changes in trunk muscle recruitment have been identified in people with low-back pain (LBP). These differences may be due to changes in the planning of the motor response or due to delayed transmission of the descending motor command in the nervous system. These two possibilities were investigated by comparison of the effect of task complexity on the feedforward postural response of the trunk muscles associated with rapid arm movement in people with and without LBP. Task complexity was increased by variation of the expectation for a command to either abduct or flex the upper limb. The onsets of electromyographic activity (EMG) of the abdominal and deltoid muscles were measured. In control subjects, while the reaction time of deltoid and the superficial abdominal muscles increased with task complexity, the reaction time of transversus abdominis (TrA) was constant. However, in subjects with LBP, the reaction time of TrA increased along with the other muscles as task complexity was increased. While inhibition of the descending motor command cannot be excluded, it is more likely that the change in recruitment M of TrA represents a more complex change in organisation of the postural response.