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PubMedDate not supplied

An in vitro caries inhibition of photopolymerized glass ionomer liners.

Caries inhibition of traditional chemical cure glass ionomers has been established. The newer photopolymerized glass ionomers demonstrate a different composition that may impair the ability of providing prevention to secondary caries at restoration margins. The purpose of this study was to evaluate the caries inhibition of photopolymerized glass ionomers (Vitrebond-3M Dental Products, Photac Bond-ESPE/Premier Dental Products) compared to a photopolymerized composite resin (Pertac Universal Bond-ESPE/Premier) control. Two standardized Class V preparations were placed in thirty permanent molars, the gingival margin placed below the cementoenamel junction. Equal numbers of preparations were restored with Vitrebond, Photac Bond and Pertac Universal Bond, according to manufacturer's instructions. The teeth were coated with an acid resistant varnish to within 2 mm of the restoration margins. All teeth were subjected to an artificial caries challenge (pH 4.2) for five days, then axial sections of 100 microns were cut longitudinally through the restored margins and photographed under polarized light microscopy. The polarized micrographs were projected onto a digitizing pad, where demineralized areas adjacent to the restoration margins were quantitated. Results demonstrated the mean (+/- S.D.) area (microns2) demineralization 100 microns from the restoration gingival margin to be: Photac Bond 66.1 +/- 27.8; Vitrebond 47.2 +/- 37.2; Pertac Universal Bond 120.9 +/- 66.0. Duncan's multiple range test indicated there was no statistically significant difference in demineralization inhibition between the two photopolymerized glass ionomers Photac Bond and Vitrebond (p < 0.05), but both photopolymerized glass ionomers demonstrated significantly less demineralization than the Pertac Universal Bond composite resin control (p < 0.05).

Dental Caries↗
PubMed1996

Treatment of root fracture by CO2 and Nd:YAG lasers: an in vitro study.

The purpose of this in vitro study was to use scanning electron microscopy and polarized light microscopy to evaluate the feasibility of using either the CO2 laser or an Nd:YAG laser in combination with air/water surface cooling to effect fusion of fractured tooth roots. The experimental unit consisted of 81 single-rooted teeth, each with an induced root fracture. Fifty-six teeth that had been reapproximated in dental stone and 25 teeth that had been reapproximated with C-clamps were assigned to untreated control groups or groups for treatment using CO2 and Nd:YAG lasers. Laser treatment consisted of multiple passes along the line of fracture, which was inspected using a dissecting microscope after each pass until a visual indication of fusion or irreparable damage resulted. Scanning electron microscopy evaluation of the treated lines revealed heat-induced fissures and cracks, areas of cementum meltdown and resolidification, crater formation, and separation of cementum from underlying dentin. In no instance-regardless of reapproximation technique, laser type, energy, and other parameters-did the treatment effect fusion of the fractured root halves.

Argon↗
PubMed2002

Rapid alignment of collagen fibers in the dermis of undermined and not undermined skin stretched with a skin-stretching device.

A controlled, quantitative histochemical study was performed in five piglets to establish changes in undermined and not undermined stretched skin. The skin was stretched with a stretching device for 30 minutes to close a large skin defect. On each flank of the piglet, at a standard position, 9 x 9-cm wounds were created under general anesthesia. On one flank, the surrounding skin was undermined cranially and caudally over a 10-centimeter area. Sections of skin biopsies obtained during stretching were stained with picrosirius red and studied with routine light microscopy and polarized light microscopy in combination with image analysis. The length of collagen fibers was analyzed as a parameter of changes in the dermis resulting from skin stretching. This newly developed quantitative method appeared to be valid, specific, and reproducible, allowing for objective determination of changes in the length of the fibers in the plain of the sections. Changes in the orientation of collagen fibers in the dermis as a result of skin stretching were thereby determined. Epidermal thickness did not change significantly under the influence of stretching forces in both undermined and not undermined skin. However, the orientation of the collagen fibers changed significantly as a result of skin stretching. In undermined wounds, parallel alignment and elongation of the fibers in the plane of the sections was already observed after 15 minutes of stretching. The fibers became aligned in the direction of the stretching force, perpendicular to the wound margin. After 30 minutes of stretching, the mean major axes of the collagen fibers were longest in the plane of the sections (p < 0.001). This meant that elongation and parallel alignment of the collagen fibers had occurred. Stretching of not undermined skin for 15 minutes resulted in significantly stronger parallel alignment in the plane of the sections as compared with undermined skin. This was less well defined after 30 minutes of stretching in not undermined skin. It is concluded that skin stretching with a skin-stretching device for 30 minutes results in significant histomorphological changes of collagen fibers in the dermis of both undermined and not undermined skin. The fibers realign rapidly as a result of stretching forces and become aligned in the direction of the stretching force, perpendicular to the wound margin. These dynamic changes in collagen fibers explain the significantly decreased wound closing tension resulting from skin stretching and explain how skin stretches beyond its inherent extensibility.

Animals↗
PubMed1990

Collagen in submucous fibrosis: an electron-microscopic study.

A comparison of the electron-microscopic features of 11 examples of submucous fibrosis in its moderately advanced and advanced stages with 15 control specimens revealed no obvious abnormality of the collagen fibrils. The notable feature of the collagen in this disease is the densely packed bundles in the lamina propria, reaching close to the epithelial-connective tissue junction, to blood vessel walls, salivary glands and muscle fibers. The width and the periodicity of fibrils vary in both groups of specimens, noticeably so, next to the junction and close to blood vessels, salivary glands and muscles. This is due to the presence of the thinner Type III collagen fibrils in these sites and the natural variation of Type I fibrils. Immunofluorescent microscopy and special staining with sirius red and polarization microscopy demonstrate both types, confirming that Type I collagen forms the bulk of the collagen and that Type III is localized in the sites mentioned above. It is concluded that although there is an excessive increase of collagen, especially Type I, in submucous fibrosis, the fibrils are still morphologically normal.

Collagen↗
PubMed1986

[Structural changes in the contractile proteins of muscle fiber studied by polarization ultraviolet fluorescence microscopy. IX. The effect of the pH and ionic strength of the solution on the conformational restructurings of F-actin induced by the binding of heavy meromyosin].

The dependence of F-actin conformational changes induced by the F-actin-HMM complex on pH and ionic strength was found by polarized ultraviolet fluorescence microscopy. It is discovered that pH affects sufficiently the cooperativity of F-actin structural changes, while the ionic strength affects their depth. The actomyosin complex was supposed to be at least in two structural states, differing in their orientation as well as in flexibility of F-actin monomers.

Actins↗
PubMed1988

Identification of collagen, elastic, elaunin and oxytalan fibres in ganglia of the myenteric plexus of the human oesophagus.

The connective tissue associated with the myenteric plexus of the human oesophagus was studied by light and electron microscopy. Collagen fibres were identified by picrosirius staining with polarization microscopy and from their fine structural morphology. A capsule of connective tissue invests the ganglia while septa of connective tissue separate groups of ganglion neurons, surrounding each individual ganglion neuron and each nerve bundle. Collagen fibrils surround the ganglia, each ganglion neuron and each nerve bundle. The fibrils are disposed in various orientations forming networks. Elastic, elaunin and oxytalan fibres were identified by their staining characteristics and fine structural morphology. The bulk of the ganglion sheath consists of coarse elastic fibres and elaunin fibres. Elaunin and oxytalan fibres form the intraganglionic network. Oxytalan, elaunin and elastic fibres appear to be located in areas related to different stresses and deformation to which the ganglia of the myenteric plexus are exposed during the contraction of the esophageal wall. The ganglia of the myenteric plexus of the human oesophagus show structural organisation of the connective tissue component similar to that seen in sympathetic and parasympathetic ganglia.

Aged↗
PubMed2003

Diagnosing acute monoarthritis in adults: a practical approach for the family physician.

Acute monoarthritis can be the initial manifestation of many joint disorders. The first step in diagnosis is to verify that the source of pain is the joint, not the surrounding soft tissues. The most common causes of monoarthritis are crystals (i.e., gout and pseudogout), trauma, and infection. A careful history and physical examination are important because diagnostic studies frequently are only supportive. Examination of joint fluid often is essential in making a definitive diagnosis. Leukocyte counts vary widely in septic and sterile synovial fluids and should be interpreted cautiously. If the history and diagnostic studies suggest an infection, aggressive treatment can prevent rapid joint destruction. When an infection is suspected, culture and Gram staining should be performed and antibiotics should be started. Light microscopy may be useful to identify gout crystals, but polarized microscopy is preferred. Blood tests alone never confirm a diagnosis, and radiographic studies are diagnostic only in selected conditions. Referral is indicated when patients have septic arthritis or when the initial evaluation does not determine the etiology.

Acute Disease↗
PubMed2005

Gold nanorods as novel nonbleaching plasmon-based orientation sensors for polarized single-particle microscopy.

By monitoring the polarized light scattering from individual gold nanorods in a darkfield microscope, we are able to determine their orientation as a function of time. We demonstrate time resolution of milliseconds and observation times of hours by observing the two-dimensional rotational diffusion of gold rods attached to a glass surface. The observed orientational diffusion shows a fast component of about 60 ms and "sticky times" of seconds. The large signal-to-noise ratio, chemical and photochemical stability, fast time response, and small size of these gold nanorods make them an ideal probe for orientation sensing in material science and molecular biology.

Gold↗
PubMed1989

[Anatomical studies on a supernumerary tooth considered to be a successional tooth of the lower first molar].

The purpose of this study is to investigate features of the successional tooth of the lower first molar. Materials investigated in this study deal with a supernumerary tooth formed at the distolingual deep part to the lower right first molar of a male patient aged twenty-four. It was observed with binocular microscopy and under X-ray. The occlusal surface of it was observed with scanning electron microscopy. Horizontal ground sections of it were prepared and observed with polarizing microscopy, fluorescent microscopy, and scanning electron microscopy. It is thought that this supernumerary tooth is a true successional tooth of the lower first molar because it was formed at the distolingual deep part to the lower first molar and the fissure of it is Y-shaped and it has five cusps. It is considered that two impressions at buccal and distal surfaces of it isn't original hereditary features but was accidentally formed by pressures of mesial and distal roots of the lower first molar. The rough form of it has most resemblance to the lower second premolar and distal and lingual parts of it are smaller than that of the lower first molar. But fundamental features of the lower first molar are preserved in it. It is thought that the center of the molarization field of human lower successional teeth lies at the successional tooth of the lower first molar because the form of the occlusal surface of it is more complex and functional than those of the lower first and second premolars.

Adult↗
PubMed2005

Recent advances in atomic-scale spin-polarized scanning tunneling microscopy.

The Mn3N2 (010) surface has been studied using spin-polarized scanning tunneling microscopy at the atomic scale. The principle objective of this work is to elucidate the properties and potential of this technique to measure atomic-scale magnetic structures. The experimental approach involves the use of a combined molecular beam epitaxy/scanning tunneling microscopy system that allows the study of atomically clean magnetic surfaces. Several key findings have been obtained. First, both magnetic and non-magnetic atomic-scale information has been obtained in a single spin-polarized image. Magnetic modulation of the height profile having an antiferromagnetic super-period of c = 12.14 A (6 atomic rows) together with a non-magnetic superstructure having a period of c/2 = 6.07 A (3 atomic rows) was observed. Methods of separation of magnetic and non-magnetic profiles are presented. Second, bias voltage-dependent spin-polarized images show a reversal of the magnetic modulation at a particular voltage. This reversal is clearly due to a change in the sign of the magnetic term in the tunnel current. Since this term depends on both the tip's as well as the sample's magnetic local density of states, the reversal can be caused by either the sample or the tip. Third, the shape of the line profile was found to vary with the bias voltage, which is related to the energy-dependent spin contribution from the 2 chemically inequivalent Mn sites on the surface. Overall, the results shown here expand the application of the method of spin-polarized scanning tunneling microscopy to measure atomic-scale magnetic structures.

Algorithms↗
PubMed2004

Effects of titanium-coated micromachined grooved substrata on orienting layers of osteoblast-like cells and collagen fibers in culture.

Osteogenic cells from newborn rat calvariae were cultured on titanium surfaces on which cell orientation could be manipulated. Substrata included smooth surfaces and substrata with smooth regions (gaps) flanked by grooves of 47-microm pitch and 3-, 10-, or 30-microm depth. Orientation angles of the cells were measured over time using propidium-iodide staining and confocal laser scanning microscopy. In addition, collagen fibers were identified using picro-sirius staining and reflected light polarization microscopy. Grooves proved effective in orienting cells, but their orienting ability decreased above the ridge level. Cells on the smooth surface showed no preferred orientation. Cells in the gaps became oriented as a result of cell-cell interactions with the cells on the flanking grooves. Cells in grooves produced oriented collagen fibers, but in the gaps, fibers could be parallel, perpendicular, or diagonal to the grooves. Collagen fibers on the smooth surfaces formed arrays of parallel fibers in a crisscross pattern. In long-term cultures, bone-like nodules were formed, but mostly above the ridge level. These data demonstrate that grooved surfaces can influence cell orientation both in cell populations above the cells in contact with the grooves and in cell populations adjacent to the grooves.

Animals↗
PubMed1982

[Structural changes in muscle fiber contractile proteins studied by polarization ultraviolet fluorescence microscopy. VI. Conformational restructurings of F-actin induced by the binding of heavy meromyosin].

Decrease in tryptophan fluorescence anisotropy of a single ghost muscle fibre was found at the binding of heavy meromyosin (HMM) to actin. Polarized fluorescence revealed its peak changes at a molar ratio of HMM/actin equal to 0.1. The changes observed in polarized fluorescence at F-actin-HMM interaction were found to depend on the state of HMM. The changes in anisotropy fluorescence under the same conditions were assumed to be independent of tryptophane residues in HMM, reflecting cooperative changes in F-actin conformation. Changes in the conformation of F-actin are of great importance in muscular contraction.

Actins↗
PubMed2004

Minipump induced hyperoxaluria and crystal deposition in rats: a model for calcium oxalate urolithiasis.

PURPOSE: Unraveling the mechanisms leading to clinically active calcium oxalate (CaOx) stone disease and the development of effective medical therapies to treat it have been hampered by the lack of appropriate animal models. To address this problem we developed a model of hyperoxaluria and calcium oxalate crystal deposition by implanting osmotic minipumps subcutaneously into male rats, that is minipump induced hyperoxaluria and crystal deposition in rats. MATERIALS AND METHODS: Male Harlan-Sprague Dawley rats (225 to 290 gm) were implanted subcutaneously with 1-week 2 ml osmotic minipumps containing 1.5 M potassium oxalate (360 microM KOx/24 hours, [KOx-trt], 11) or phosphate buffered saline (PBS-trt, 9) on days 1 and 7. The 24-hour urine collections were performed on days 0, 4, 7, 11 and 14. Data were analyzed by ANOVA and Tukey's HSD. Urinary crystals were analyzed by light microscopy. Kidneys were harvested on day 14 and processed for light and polarizing microscopy, and RNA analysis.RESULTS Mean overall creatinine excretion +/- SEM (PBS-trt 107 +/- 7 and KOx-trt 123 +/- 6 microM/24 hours, p >0.07) and day 14 serum creatinine (PBS-trt 83 +/- 4 and KOx-trt 83 +/- 5 microM, p >or=0.9) were similar in the 2 treatment groups. Overall urinary volume (PBS-trt 11.3 +/- 0.8 and KOx-trt 18.0 +/- 1.5 ml/24 hours, p <or=0.001) and oxalate (OX) excretion (PBS-trt 9.2 +/- 0.6 and KOx-trt 44 +/- 4.2 microM/24 hours, p <or=0.001) were higher in KOx-trt vs PBS-trt rats. In KOx-trt rats OX excretion on day 0 was significantly less than on any day after implantation (p <or=0.01). All KOx-trt rats excreted calcium oxalate dihydrate crystals by day 4 and had intrarenal deposits of birefringent crystals by day 14. Overall the morphology of kidneys of OX rats was normal, although localized regions of inflammation and tubular debris were occasionally observed. Reverse transcriptase-polymerase chain reaction and Northern blot analysis revealed that the expression of 3 distress molecules tumor necrosis factor receptor, osteopontin and kidney injury molecule were up-regulated in KOx-trt kidneys. CONCLUSIONS: The model of minipump induced hyperoxaluria and crystal deposition in rats reliably induces hyperoxaluria, CaOx crystalluria and CaOx crystal deposition. These characteristics make it an appropriate model for investigations of the effects of OX on renal physiology as well as investigating the efficacy of new therapeutics.

Animals↗
PubMed2001

Interactions of phospholipid bilayer with chitosan: effect of molecular weight and pH.

Chitosan has demonstrated its potentials as a gene carrier and a membrane perturbant for subsequent drug delivery to cells. However, there is currently a lack of experimental correlation between the physiochemical properties of chitosan and the resulting degree of lipid bilayer destabilization. In this study, the effect of pH and chitosan molecular weight on the interaction between chitosan and dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayer was examined with cross-polarization microscopy, differential scanning calorimetry (DSC), and Fourier transform- (FT-) Raman spectroscopy. Cross-polarized images showed that the direct hydration of the DPPC/chitosan mixture led to the formation of larger DPPC multilamellar vesicles (MLV), and pure chitosan also induced fusions of individual MLV. Under the influence of chitosan, the calorimetric enthalpy of DPPC was reduced in a concentration-dependent manner, and a new phase appeared at 28 degrees C during sample cooling. Even the lowest chitosan mole fraction of 0.04% reduced the cooperative unit of the DPPC bilayer by more than 70%. In addition, the electrostatic effect between chitosan and DPPC tuned the degree of membrane bilayer perturbation. Reduction of pH increased the number of protonated amines on the chitosan backbone and caused further disruption on the membrane organization. Mixing DPPC with chitosan in an organic medium before hydration enhanced the hydrophobic interactions between the two molecules and greatly reduced the cooperative unit among individual lipids during the main phase transition. The increase of chitosan molecular weight also affected the cooperativity in the thermotropic transition of DPPC bilayer. FT-Raman spectroscopy provided additional evidence that chitosan directly perturbed the organizations of the hydrophobic inner core of the DPPC bilayer.

1,2-Dipalmitoylphosphatidylcholine↗