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Query: UMLS:C0276640 (TEM)
 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An excellent durability of adhesion was obtained in the adhesion of 2% 4-META/MMA-TBB resin to dentin pretreated with EDTA 3-2 (NH4/Fe). Such high bond strength as 15 MPa did not change for up to one year even when they were immersed in water at 37 degrees C. The resin reinforced dentin, a hybrid, was identified between dentin and the cured resin by TEM. The collagen and hydroxyapatite were encapsulated with the copolymer and the crystals were not removed by the demineralization with either HCl or electronic staining. Tensile fracture between the hybrid and dentin like the adhered samples to 10-3 treated dentin did not occur and the cohesive failure in the resin was observed here after the storage in water for a year. EDTA 3-2 (NH4/Fe) could not completely demineralize the hydroxyapatite especially at the deeper portion and the width of the demineralized dentin became thinner than 1 micron. The encapsulated crystals with the resin could improve the resistance of collagen against deterioration in water and such good bonding durability could be obtained.
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PMID:[Stable adhesion to dentin. Combination of EDTA 3-2 (NH4/Fe) pretreatment and 2% 4-META/MMA-TBB resin]. 213 47

High resolution transmission electron microscopy (Hr TEM) studies on biological and synthetic calcium phosphate have provided information on the dissolution process at the crystal level. The purpose of this study was to investigate the dissolution of ceramic hydroxyapatite (HA) after implantation using Hr TEM. Recovered HA ceramic implanted in bony and nonbony sites in animals and in periodontal pockets in humans were used for the study. For comparison, sections of human fluorotic enamel with caries and sections of shark enameloid previously exposed to 0.1 HCl were similarly investigated. Hr TEM studies demonstrated that in both the biological and ceramic apatites, the lattice and atomic defects were the starting points in the dissolution process. However, significant differences in the process of dissolution were observed: (1) biological apatite crystals showed preferential core dissolution whereas ceramic apatite crystals showed nonspecific dissolution at the cores and at the surfaces; (2) the dissolution of biological apatites appeared to consistently extend along the crystal's c-axis whereas dissolution of the ceramic HA did not appear to be correlated with the crystal's c-axis. The observed differences in crystal dissolution between biological and ceramic apatites may be attributed to the following: (1) the unique crystal/protein interaction present with biological apatites but absent in ceramic HA; (2) differences in defect distribution between biological and ceramic apatites which are due to the differences in the original of these defects; and (3) the longer morphological c-axis of biological apatites compared with that of ceramic apatites.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Crystal dissolution of biological and ceramic apatites. 250

Rat stomachs were studied after intragastrically administered, repeated doses of 0.1 N HCl, 100 mmol/l NaF, 50 mmol/l CaF2 in 0.1 N HCl, respectively. NaF produced extensive desquamation and cell injury, while CaF2 caused some desquamation and a slight decrease in secretory activity as revealed by light microscopic, SEM and TEM examinations.
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PMID:Comparison of the effects of NaF and CaF2 on rat gastric mucosa. A light-, scanning- and transmission electron microscopic study. 251 44

The methods reviewed here include: scanning electron microscopy (SEM) of vascular corrosion casts, SEM of intact tissue, SEM of HCl-collagenase treated tissues, light microscopy (LM) of India ink or silicon rubber injected tissues, with stereomicrography, LM of tissue stained by perfusion with hematoxylin, and a correlative study of intravital microscopy with SEM of vascular corrosion casts or LM of India ink-injected tissue. The last technique allowed for both the examination of the microvascular architecture and blood flow in a particular tissue area. This paper shows that an adequate understanding of the microvasculature of the pancreas can only be gained when a variety of SEM techniques, together with other LM and TEM techniques are employed in a coordinated fashion. The intralobular arterioles of the pancreas supply the islets of Langerhans, exocrine acini, and duct system. Blood leaving the islets flows into the capillaries in the exocrine region through the insulo-acinar portal system and insulo-ductular portal system, although some fraction of the blood drains through venules into nearby veins. Thus, these studies in the pancreas indicate that the islets of Langerhans are situated in the center of the pancreatic microcirculatory bed so that the insular secretions are transferred in high concentrations through short vascular routes to the exocrine region of both the duct system and acini, presumably to act upon these structures.
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PMID:Review of scanning electron and light microscopic methods in microcirculation research and their application in pancreatic studies. 638 19

At the onset of the mineralization of bone, small membranous matrix vesicles are often observed. The information available on the production and release of these vesicles is limited. When treated with 10-20 nM of the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA), the human osteosarcoma cell line U-2 OS developed long cytoplasmic processes connecting adjacent cells. SEM and TEM show that TPA triggers a production and release of matrix vesicle-like membrane vesicles, mainly from the cellular processes. Tetracycline HCl was used to label intracellular bound calcium. The tetracycline HCl label was primarily localized to the end-feet of the cytoplasmic processes, indicating that these contain high concentrations of Ca2+, and to endoplasmic reticulum-like structures in the cell bodies. Together with our previous demonstration of the release of alkaline phosphatase-containing vesicles into the culture medium (Ringbom-Anderson T, Akerman KEO 1992 Calcif Tissue Int 50:533-540), the results presented here indicate that TPA induces a rapid induction of the primary steps of mineralization in U-2 OS osteosarcoma.
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PMID:Production and release of matrix vesicles in the cell processes of TPA-treated human osteoblast-like cells. 805 95

Results on surfactant gels containing densely packed multilamellar vesicles are reported. The gels form spontaneously when the bilayers of L alpha or L3 phases of alkyldimethylaminoxide and cosurfactant are charged up by the addition of ionic surfactant or HCl. The rheological behaviour on addition of excess salt was studied by dynamic rheological measurements for systems with surfactants of different chainlengths. Both the storage modulus, G', and the yield stress, sigma y, decay with rising salinity. This effect is caused by the reduction of both the electrical contribution of the bending constants of the bilayers and the compression modulus of the vesicles. The influence of the charge density on the rheological properties was determined. G' and sigma y increase with charge density and reach a plateau that depends on the chainlength of the surfactant. Measurements on samples prepared with waterglycerol mixtures show that the moduli and the yield stress value are independent of the solvent viscosity. Photographs of the surfactant gels that were taken with the interference contrast microscopy technique are presented. They reveal that some of the vesicles are much bigger than expected on the basis of TEM micrographs. The mean size of the vesicles can be estimated on basis of conductivity data. This method yields an average number of 5-6 shells per vesicle and corresponds with the value taken from the electron micrograph. The rheological data are explained with a model that was recently introduced by van der Linden. In connection with a model due to Lekkerkerker for the electric contribution of the bending constant of the bilayers and our own calculations of the osmotic pressure the van der Linden formula yields good results for describing the experimental data.
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PMID:Gels from surfactant solutions with densely packed multilamellar vesicles. 880 25

Phosphoprotein appears to play an important role in the mineralization of dentin during tooth development and remineralization after demineralization by dental caries. To better understand this role, we describe the extraction and characterization of phosphoprotein from immature, human root apex dentin during and after EDTA demineralization. The extraction procedure included dissociation of the demineralized dentin matrix by guanidine hydrochloride (Gdn.HCl) followed by subsequent digestion with cyanogen bromide (CNBr) and collagenase. Characterization of these extracts included 'Stains-All' staining of SDS polyacrylamide gels (SDS-PAGE) and amino acid, protein and phosphorus analyses. The ability of these matrices to remineralize was determined by TEM and measuring calcium levels in the remineralized tissue by atomic absorption spectroscopy. The staining of SDS-PAGE gels and amino acid analysis showed that an intact phosphophoryn was extracted from the dentin of the immature apices during EDTA demineralization and that it had an apparent Mr approximately 140,000. In the subsequent extracts and digests, the phosphoprotein has a range of molecular weights, some of which may have been degraded products of the intact phosphoprotein. A greater quantity of phosphoprotein was found in the EDTA-demineralized dentin matrices than in dentin after Gdn.HCl, CNBr and collagenase digests. These EDTA-demineralized matrices also remineralized to a greater extent than those dissociated with Gdn.HCl. The differences in both the quantity and the quality, as defined by the amino acid residue profile, of the phosphoprotein in the sequential extracts of the root apex dentin may be important in affecting the ability of this tissue to remineralize.
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PMID:Phosphoprotein analysis of sequential extracts of human dentin and the determination of the subsequent remineralization potential of these dentin matrices. 970 61

The phase diagram of the ternary surfactant system tetradecyldimethylamine oxide (TDMAO)/HCl/1-hexanol/water shows with increasing cosurfactant concentration an L(1) phase, two L(alpha) phases (a vesicle phase L(alpha1) and a stacked bilayer phase L(alphah)), and an L(3) phase, which are separated by the corresponding two-phase regions L(1)/L(alpha) and L(alpha)/L(3). In this investigation, the system was studied where some of the TDMAO was substituted by the protonated TDMAO. Under these conditions, one finds for constant surfactant concentration of 100 mM TDMAO a micellar L(1) phase, an L(alpha1) phase (consisting of multilamellar vesicles), and an interesting isotropic L(1)(*) phase in the middle of the L(1)/L(alpha) two-phase region. The L(1)(*) phase exists at intermediate degrees of charging of 30-60% and for 40-120 mM TDMAO and 70-140 mM hexanol concentration. At surfactant concentrations less than 80 mM the L(1)(*)-phase borders directly on the L(1) phase. The phase transition between the L(1) phase and the L(1)(*) phase was detected by electric conductivity and rheological measurements. The conductivity values show a sharp drop at the L(1)/L(1)(*) transition, and the zero shear viscosity of the L(1)(*) phase is much lower than in L(1) phase. The form and size of the aggregates in L(1)(*) were detected with FF-TEM and SANS. This phase contains small unilamellar vesicles (SUV) of about 10 nm and some large multilamellar vesicles with diameters up to 500 nm. The system exhibits another peculiarity. For 100 mM surfactant, the clear L(alpha1)-phase exists only at chargings below 30%. With oscillating rheological measurements a parallel development of the storage modulus G' and the loss modulus G" was observed. Both moduli are frequency independent and the system possesses a yield stress. The storage modulus is a magnitude larger than the loss modulus. Copyright 2000 Academic Press.
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PMID:Phase Behavior, Structure, and Physical Properties of the Quaternary System Tetradecyldimethylamine Oxide, HCl, 1-Hexanol, and Water. 1063 Oct 21

Colloidal dispersions of tungstic acid (H(2)WO(4)) have been prepared in water/(TX-100+alkanol)/n-heptane water-in-oil microemulsion media by reacting Na(2)WO(4) with HCl. The effects of alkanol chain length, TX-100/alkanol mass ratio, temperature, and dilution at different [water]/[TX-100] mole ratios (omega) have been studied by the dynamic light scattering technique. The formation of H(2)WO(4) in the microwater pool has been established by FT-IR measurements. The particle sizes and shapes in microemulsion media and in isolated states have been measured by TEM and SEM techniques. The enthalpy of formation of H(2)WO(4) in the water pool of the microemulsions has also been determined microcalorimetrically. Copyright 2001 Academic Press.
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PMID:Dispersed Molecular Aggregates. 1125 94

We report studies of the effect of hydrothermal treatment on physical properties such as crystalline phase, size, and morphology of nanosized cadmium sulfide (CdS) particles. CdS precipitates have been synthesized by the reaction of Cd(NO(3))(2) with Na(2)S at room temperature. These CdS precipitates have been hydrothermally treated in the range 120-240 degrees C with variation of the treatment time. The effects of acid catalysts and other additives were also investigated. The particles prepared were characterized by XRD, TEM, and BET methods. With increased hydrothermal treatment temperature and time, crystallization from amorphous to crystalline form, cubic or hexagonal, and an increase of particle size occurred. CdS particles of well-developed hexagonal form were obtained at a hydrothermal treatment temperature of 240 degrees C; the primary hexagonal grain size was on the order of 20-30 nm. The addition of an acid catalyst, HCl, or of Cd(NO(3))(2) into the precipitate sol promoted crystal growth and phase transformation during the hydrothermal treatment, but another additive, Na(2)S, showed the opposite trend. It appears that hydrothermal treatment combined with proper additives could be an effective method for preparation of nanosize crystalline CdS particles. Copyright 2001 Academic Press.
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PMID:Preparation of Nanosized Crystalline CdS Particles by the Hydrothermal Treatment. 1133 25


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