Fluorimetric multiparameter cell assay at the single cell level fabricated by optical tweezers.
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A fluorimetric multi-parameter cell sensor at the single cell level is presented which makes it possible to observe the physiological behavior of different cell lines, different physiological parameters, and statistical data at the same time. Different cell types were immobilized at predefined positions with high accuracy using optical tweezers and adhesion promoting surface layers. The process is applicable to both adherent and non-adherent cells. Coating of the immobilization area with mussel adhesive protein was shown to be essential for the process. Intracellular proton and calcium concentrations in different cell classes were simultaneously imaged and the specific activation of T lymphocytes was demonstrated. This method should be especially useful for drug screening due to the small sample volume and high information density. (+info)
In vitro comparison of the retention capacity of new aesthetic brackets.
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Tensile bond strength and bond failure location were evaluated in vitro for two types of aesthetic brackets (non-silanated ceramic, polycarbonate) and one stainless steel bracket, using bovine teeth as the substrate and diacrylate resin as the adhesive. The results show that metallic bracket had the highest bond strength (13.21 N) followed by the new plastic bracket (12.01 N), which does not require the use of a primer. The non-silanated ceramic bracket produced the lowest bond strength (8.88 N). Bond failures occurred mainly between bracket and cement, although a small percentage occurred between the enamel-cement interface with the metal and plastic brackets and within the cement for the plastic bracket. With the ceramic bracket all the failures occurred at the bracket-cement interface. This suggests that the problems of enamel lesions produced by this type of bracket may have been eliminated. The results also show that the enamel/adhesive bond is stronger than the adhesive/bracket bond in this in vitro study. (+info)
Autoclaving impairs the connector-tube bond of the laryngeal mask airway but not its airtightness.
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The general-purpose laryngeal mask airway (LMA) is re-usable when undamaged, and cleaned and autoclaved correctly. We had found weakening of the silicone adhesive that bonds the connector of the LMA to the tube. We report that repeated autoclaving damaged the adhesive such that the connector could be rotated in the tube after the 12th autoclave cycle in almost all of the LMA tested. The damage to the adhesive did not affect the airtightness of the junction, which appears to be maintained by the material properties of the connector and tube and by the shape of the join. (+info)
Abnormal liver function tests following inadvertent inhalation of volatile hydrocarbons.
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The use of aerosols containing volatile hydrocarbons in conditions of poor ventilation can result in accidental overexposure which can cause central nervous system effects and hepatic injury. We present a case in which inadvertent usage of an adhesive spray used to make greeting cards resulted in vague neurological symptoms and abnormal liver function tests both of which fully resolved on discontinuation. (+info)
A laboratory investigation to compare enamel preparation by sandblasting or acid etching prior to bracket bonding.
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A laboratory investigation to compare the mean shear debonding force and mode of bond failure of metallic brackets bonded to sandblasted and acid-etched enamel is described. The buccal surfaces of 30 extracted human premolars were sandblasted for 5 seconds with 50 mu alumina and the buccal surfaces of a further 30 human premolars were etched with 37 per cent phosphoric acid for 15 seconds. Following storage for 24 hours at 37 degrees C in distilled water, shear debonding force was measured using an Instron Universal Testing Machine with a cross-head speed of 10 mm/minute. Mean shear debonding force was significantly lower for brackets bonded to sandblasted enamel compared to acid etched enamel (P < 0.001). Weibull analysis showed that at a given stress the probability of failure was significantly greater for brackets bonded to sandblasted enamel. Brackets bonded to etched enamel showed a mixed mode of bond failure whereas following sandblasting, failure was adhesive at the enamel/composite interface (P < 0.01). (+info)
Factors affecting the shear bond strength of orthodontic brackets to porcelain.
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The aim of this investigation was to establish a regime for orthodontic bonding to feldspathic porcelain, which ensures adequate bond strength (6-8 MPa) with minimal damage on debond and consisted of an ex vivo investigation measuring the effects of porcelain surface preparation and thermocycling on shear bond strength of orthodontic brackets. One-hundred-and-twenty feldspathic porcelain bonded crown surfaces were divided into 12 equally-sized groups to assess the effects of: (1) glaze removal, (2) application of hydrofluoric acid, phosphoric acid, or omission of acid treatment, and (3) silane priming upon the bond strength of premolar brackets bonded with Right-on (TM) composite resin adhesive. Specimens were subjected to thermocycling and then to shear debonding forces on an Instron machine. Removal of the porcelain glaze, or use of hydrofluoric acid, prior to bonding were found to be unnecessary to secure the target bond strength. Hydrofluoric acid application was associated with increased porcelain surface damage. Thermocycling caused a significant reduction in shear bond strength to porcelain (P < 0*001). The best regime for orthodontic bonding to feldspathic porcelain was to apply phosphoric acid for 60 seconds, and prime with silane prior to bonding. Usually the porcelain surfaces could be repolished. Refereed Paper (+info)
Differentiation of mucilage secretory cells of the Arabidopsis seed coat.
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In some plant species, including Arabidopsis, fertilization induces the epidermal cells of the outer ovule integument to differentiate into a specialized seed coat cell type with a unique morphology and containing large quantities of polysaccharide mucilage (pectin). Such seed coat mucilage cells are necessary for neither viability nor germination under normal laboratory conditions. Thus, the Arabidopsis seed coat offers a unique system with which to use genetics to identify genes controlling cell morphogenesis and complex polysaccharide biosynthesis and secretion. As a first step in the application of this system, we have used microscopy to investigate the structure and differentiation of Arabidopsis seed coat mucilage cells, including cell morphogenesis and the synthesis, secretion, and extrusion of mucilage. During seed coat development in Arabidopsis, the epidermal cells of the outer ovule integument grow and differentiate into cells that produce large quantities of mucilage between the primary cell wall and plasma membrane. Concurrent with mucilage production, the cytoplasm is shaped into a column in the center of the cell. Following mucilage secretion the cytoplasmic column is surrounded by a secondary cell wall to form a structure known as the columella. Thus, differentiation of the seed coat mucilage cells involves a highly regulated series of events including growth, morphogenesis, mucilage biosynthesis and secretion, and secondary cell wall synthesis. (+info)
1H-NMR studies of the interaction of dental adhesive monomer, 4-META with calcium.
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Our objective was to determine whether high-resolution proton-nuclear magnetic resonance (500 MHz) could be utilized for detection of ionic binding interaction of the 4-META resin system with calcium derived from hydroxyapatite. The stability of 4-META in aqueous medium was studied, findings indicated that 4-META was rapidly converted to 4-MET, a hydrate product of 4-META in 10% D2O/DMSO-d6. The 1H-NMR signals of the methacryloyloxyethoxy group of 4-MET remained intact following the addition of both monocalcium phosphate (MCP) and dicalcium phosphate dihydrate (brushite) solution, whereas those of its trimellitic portion were markedly shifted upfield depending on the phosphate concentration. The shielding effect followed by upfield shifts was due to the localization of electron density surrounding the carboxylate anions that were dissociated by the interaction with calcium counter cation. The shielding effect of 4-MET with brushite was larger than that with MCP. An ionic interaction of 4-MET derived from 4-META with calcium was demonstrated. (+info)