Laboratory evaluation of the XR-Bond Dentin/Enamel Bonding System

The shear bond strengths of the XR-Bonding System used in conjunction with Herculite composite, to the dentine of forty extracted human permanent first and second molars were determined after the test specimens were stored in physiological saline at 37 degrees C for 48 hours, one week, two weeks and four weeks, respectively. A shear load was applied to the base of the bonded composite cylinders with a knife-edged rod at a crosshead speed of 0.5 mm/minute. The shear bond strengths were expressed in megapascals (MPa). The quantitative microleakage of Class V preparations in dentine (cementum) in forty-eight extracted human maxillary permanent canines restored with the same dentinal bonding system and after storage in physiological saline at 37 degrees C for the same time intervals as for the shear bond strength tests, was determined. On the final day of each time interval the teeth were thermocycled X 500 in a 2 per cent methylene blue solution between 8 degrees C and 50 degrees C with a dwell time of 15 seconds. Microleakage was determined by a spectrophotometric dye-recovery method and expressed in microgram dye/restoration. There was a significant trend for the shear bond strengths to increase with duration of storage (p = 0.01) but the quantitative microleakage was not significantly different (p = 0.75).     

Annotations and the collaborative digital library: Effects of an aligned annotation interface on student argumentation and reading strategies

Recent research on annotation interfaces provides provocative evidence that anchored, annotation-based discussion environments may lead to better conversations about a text. However, annotation interfaces raise complicated tradeoffs regarding screen real estate and positioning. It is argued that solving this screen real estate problem requires limiting the number of annotations displayed to users. In order to understand which annotations have the most learning value for students, this paper presents two complementary studies examining the effects of annotations on students performing a reading-to-write task. The first study used think-aloud protocols and a within-subjects methodology, finding that annotations appeared to provoke students to reflect more critically upon the primary text. This effect was particularly strong when students encountered pairs of annotations presenting different viewpoints on the same section of text. Student interviews suggested that annotations were most helpful when they caused the reader to consider and weigh conflicting viewpoints. The second study used a between-subjects methodology and a more naturalistic task to provide complementary evidence that annotations encourage more reflective responses to a text. This study found that students who received annotated materials both perceived themselves and were perceived by instructors as less reliant on unreflective summary strategies than students who received the same content but in a different format. These findings indicate that the learning value of an annotation lies in its ability to provoke students to consider and weigh new perspectives on the primary text. When selected effectively, annotations provide a critical scaffolding that can support students’ critical thinking and argumentation activities. Collaborative digital libraries and applications for the Web 2.0 should be designed with this learning framework in mind.     

Multiple pathways are involved in the extracellular processing of MHC class I-restricted peptides

T cell stimulation by certain class I-restricted antigenic peptides, such as the HIV 1 gp160-derived peptide, P18, requires peptide processing by angiotensin-1 converting enzyme (ACE) in FCS. We observed that longer versions of P18 and the murine cytomegalovirus pp89-derived core peptide, pMCMV, which could stimulate T cell hybridomas in FCS, were not as sensitive to the ACE inhibitor captopril as P18. Using cell-free soluble murine class I MHC molecules and protease inhibitors, we found that there are pathways of differing efficiency that use enzymes other than ACE for the proteolytic processing of peptides in serum. The kinetics of the generation of T cell stimulatory activity among P18 variant peptides in serum differed with peptide length, and with the nature of amino and COOH-terminal extensions. Such processing occurs in human plasma as well as in FCS. The understanding of this processing, its kinetics, and its inhibitors can lead to better design of peptide-based therapies, including vaccines.     

Weak interactions and lessons from crystallization

Ideas derived from the study of the process of crystallization may provide insights into molecular recognition in biological systems. Both processes exploit the cooperativity which arises from the formation of a large array of weak interactions.     

Phenotypic analysis of antigen-specific T lymphocytes

Identification and characterization of antigen-specific T lymphocytes during the course of an immune response is tedious and indirect. To address this problem, the peptide-major histocompatability complex (MHC) ligand for a given population of T cells was multimerized to make soluble peptide-MHC tetramers. Tetramers of human lymphocyte antigen A2 that were complexed with two different human immunodeficiency virus (HIV)-derived peptides or with a peptide derived from influenza A matrix protein bound to peptide-specific cytotoxic T cells in vitro and to T cells from the blood of HIV-infected individuals. In general, tetramer binding correlated well with cytotoxicity assays. This approach should be useful in the analysis of T cells specific for infectious agents, tumors, and autoantigens.     

The gill calcium transport cycle in rainbow trout is correlated with plasma levels of bioactive, not immunoreactive, stanniocalcin

The aims of this study were to determine the most appropriate duration for the measurement of the maximal accumulated O2 deficit (MAOD), which is analogous to the anaerobic capacity, to ascertain the effects of mass, fat free mass (FFM), leg volume (Vleg) and lower body volume (V1b) on anaerobic test performance, to examine the reproducibility for peak power output (Wpeak) or maximal anaerobic power using an air-braked cycle ergometer and to produce approximations for the percentages of aerobic and anaerobic metabolism during exercise of short duration but high intensity. A group of 12 endurance trained cyclists [mean age 25.1 (SD 4.6) years; mean body mass 73.43 (SD 7.12) kg; mean maximal oxygen consumption 5.12 (SD 0.35) l.min-1; mean body fat 12.5 (SD 4.1) %] accordingly performed four counterbalanced treatments of 45, 60, 75 and 90 s of maximal cycling on an air-braked ergometer. The mean O2 deficit of 3.52 l for the 45-s treatment was significantly less (P < 0.01) than those for the 60 (3.75 l), 75 (3.80 l) and 90-s (3.75 l) treatments. These data therefore indicate that in predominantly aerobically trained subjects the O2 deficit attains a plateau after 60 s of maximal cycling on an air-braked ergometer. Statistically significant interclass correlation coefficients (P < 0.05) between the anthropometric variables (mass, FFM, Vleg and Vlb) and Wpeak or maximal anaerobic power (0.624-0.748) and MAOD (ml) or anaerobic capacity (0.666-0.772) furthermore would suggest the relevance of taking into account muscle mass during anaerobic tests.(ABSTRACT TRUNCATED AT 250 WORDS)