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At least 1,279 records · Page 71Linked to original sources
PubMed2006

Laser-deposited Ti-Nb-Zr-Ta orthopedic alloys.

The complex quaternary Ti-35Nb-7Zr-5Ta orthopedic alloy has been successfully deposited from a powder feedstock consisting of a blend of elemental titanium, niobium, zirconium, and tantalum powders, using the laser engineered net-shaping (LENStrade mark) process. In the as laser-deposited form, these alloys exhibit a substantially higher tensile strength as compared with more conventionally processed counterparts of similar composition, while maintaining excellent ductility and a low modulus. Furthermore, the as-deposited alloys appear to exhibit a <001> texture, with a substantially large number of grains of the beta phase aligning one of their <001> axes nearly normal to the substrate or parallel to the growth direction. The microstructure of the as-deposited as well as tensile-tested alloys have been characterized in detail using scanning electron microscopy (SEM), orientation microscopy (OM), and transmission electron microscopy (TEM). Formation of a high density of shear bands, possibly arising from slip localization due to precipitates of the omega phase in the beta matrix, is clearly evident in the tensile-tested sample. The enhanced tensile strength and low modulus in these laser-deposited alloys coupled with the ability to form near-net shape components makes LENS an attractive processing technology for orthopedic implants.

Alloys↗
PubMed1981

Display of maturation cycles in rat incisor enamel with tetracycline labelling.

Tetracycline was incorporated within seconds of intracardiac injection to form bright yellow fluorescent bands under UV irradiation in maturation zone enamel. The bands were narrow, widening with time. At several hours after subcutaneous injection, the fluorescent bands were wide and of low intensity. It is concluded that tetracycline enters maturing enamel opposite the narrow bands of non-striated border ameloblasts which are probably a main exit route for organic matrix remnants. Tetracycline distribution patterns at hours after injection reflect the diffusion of this substance within enamel and the pattern of its removal, which also occurs in relation to the non-striated border, smooth-ended maturation ameloblasts.

Aging↗
PubMed1984

A histological study of the short-term effects of fluoride on enamel and dentine formation in hamster tooth-germs in organ culture in vitro.

First maxillary molars in early stages of secretory amelogenesis were exposed in vitro to fluoride (F-) concentrations ranging between 2.63 microM and 2.63 mM for up to 3 days. In contrast to the dentine papilla, which seemed unaffected by F- in concentrations up to 1.31 mM, the enamel organ was dose-dependently extremely sensitive for F-. Young ameloblasts which became secretory in vitro were in particular sensitive and did not secrete enamel adjacent to new, in vitro-formed dentine. Hypermineralization of the dentine at the enamel-dentine junction suggested that these ameloblasts still transport and deposit minerals. 52 microM was the lowest concentration of F- that inhibited deposition of enamel in the cervical-loop region. Ameloblasts, secretory at the time of exposure to F-, in concentrations of 52 microM up to 1.31 mM secreted an abnormal, amorphous, von-Kossa-negative enamel matrix. 1.31 mM of F- was the lowest concentration which induced the formation of a hypermineralized band in the pre-exposure enamel. 2.63 mM of F- was highly toxic for the enamel organ but had only moderate effects on the dentine papilla.

Amelogenesis↗
PubMed1983

High molecular mass phosphoproteins in the rat liver nuclear matrix identification of a prominent 110,000 Dalton species.

Purified rat liver nuclei were labelled in vitro in the presence of (32P) ATP and submitted to sequential extraction with DNAse, 0.4 or 2.0 M NaCl and Triton X-100. The residual or matrix structures contained 8-10 phosphoproteins between 76 and 260 kd including a triplet of major bands with 110, 117 and 128 kd. The 110 kd species was purified by chromatography on oligo(dT)-cellulose. It was shown to be identical with the 110 kd phosphoprotein of rat liver or Morris hepatoma free polyribosomes using the technique of limited digestion with S. aureus protease V 8.

Animals↗
PubMed2004

Purification, physicochemical characterization, saccharide specificity, and chemical modification of a Gal/GalNAc specific lectin from the seeds of Trichosanthes dioica.

A new galactose-specific lectin has been purified from the extracts of Trichosanthes dioica seeds by affinity chromatography on cross-linked guar gum. The purified lectin (T. dioica seed lectin, TDSL) moved as a single symmetrical peak on gel filtration on Superose-12 in the presence of 0.1 M lactose with an M(r) of 55 kDa. In the absence of ligand, the movement was retarded, indicating a possible interaction of the lectin with the column matrix. In SDS-PAGE, in the presence of beta-mercaptoethanol, two non-identical bands of M(r) 24 and 37 kDa were observed, whereas in the absence of beta-mercaptoethanol, the lectin yielded a single band corresponding to approximately 55,000 Da, indicating that the two subunits of TDSL are connected by one or more disulfide bridges. TDSL is a glycoprotein with about 4.9% covalently bound neutral sugar. Analysis of near-UV CD spectrum by three different methods (CDSSTR, CONTINLL, and SELCON3) shows that TDSL contains 13.3% alpha-helix, 36.7% beta-sheet, 19.4% beta-turns, and 31.6% unordered structure. Among a battery of sugars investigated, TDSL was inhibited strongly by beta-d-galactopyranosides, with 4-methylumbelliferyl-beta-d-galactopyranoside being the best ligand. Chemical modification studies indicate that tyrosine residues are important for the carbohydrate-binding and hemagglutinating activities of the lectin. A partial protection was observed when the tyrosine modification was performed in the presence of 0.2 M lactose. The tryptophan residues of TDSL appear to be buried in the protein interior as they could not be modified under native conditions, whereas upon denaturation with 8 M urea two Trp residues could be selectively modified by N-bromosuccinimide. The subunit composition and size, secondary structure, and sugar specificity of this lectin are similar to those of type-2 ribosome inactivating proteins, suggesting that TDSL may belong to this protein family.

Amino Acid Substitution↗
PubMed2000

Capillary gel electrophoresis: separation of major erythrocyte membrane proteins.

A new separation method of human erythrocyte membrane proteins by sodium dodecyl sulfate capillary gel electrophoresis (SDS-CGE) is described. In this method, a replaceable gel matrix was used. Seven major erythrocyte membrane proteins, alpha-and beta-spectrin, ankyrin 2.1, band 3 (anion-exchanger), 4.1a and b, and 4.2 (pallidin), were separated and identified by SDS-CGE method. High reproducible migration times of these proteins (inter-assay coefficients of variation less than 2%), as well as quantification (inter-assay coefficients of variation less than 11%) were obtained. This new SDS-CGE method may provide important diagnostic evidence for hereditary spherocytosis. It can be a powerful diagnostic tool in place of SDS polyacrylamide gel electrophoresis for erythrocyte membrane protein analysis.

Electrophoresis, Capillary↗
PubMed2003

Bis(tri-tert-butylsilyl)silylene: triplet ground state silylene.

Upon irradiation with lambda = 254 nm light over the temperature range of 9-80 K, methylcyclohexane glass matrixes of 1a and 1b gave a characteristic broad EPR signal at 845 mT (X-band, 9.4 GHz) due to bis(tri-tert-butylsilyl)silylene, (tBu3Si)2Si: (2). The signal intensity as a function of temperature (9-80 K) gave a linear relation, and the spin multiplicity of 2 in the ground state was established to be a triplet. Product analysis, from which disilacyclobutane derivative 3 and dihydrosilane (tBu3Si)2SiH2 (4) were formed, also supports the conclusion about the multiplicity of 2.

Journal Article↗
PubMed2005

Characterization of paramagnetic species in N-doped TiO2 powders by EPR spectroscopy and DFT calculations.

Electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations are combined for the first time in an effort to characterize the paramagnetic species present in N-doped anatase TiO2 powders obtained by sol-gel synthesis. The experimental hyperfine coupling constants are well reproduced by two structurally different nitrogen impurities: substitutional and interstitial N atoms in the TiO2 anatase matrix. DFT calculations show that the nitrogen impurities induce the formation of localized states in the band gap. Substitutional nitrogen states lie just above the valence band, while interstitial nitrogen states lie higher in the gap. Excitations from these localized states to the conduction band may account for the absorption edge shift toward lower energies (visible region) observed in the case of N-doped TiO2 with respect to pure TiO2 (UV region). Calculations also show that nitrogen doping leads to a substantial reduction of the energy cost to form oxygen vacancies in bulk TiO2. This suggests that nitrogen doping is likely to be accompanied by oxygen vacancy formation. Finally, we propose that the relative abundance of the two observed nitrogen-doping species depends on the preparation conditions, such as the oxygen concentration in the atmosphere and the annealing temperature during synthesis.

Letter↗
PubMed2004

Prostate cancer invasion is influenced more by expression of a CD44 isoform including variant 9 than by Muc18.

The standard form of cell adhesion glycoprotein CD44 is a metastasis suppressor in prostate cancer. However, we previously showed by RT-PCR and Western blotting that cancer overexpresses unique CD44 variant v7-v10 isoforms. Muc18 is another cell adhesion marker reportedly overexpressed by prostate cancer. Matched frozen section-confirmed tumor and benign tissues were harvested from 10 prostatectomy specimens and tumor was microdissected from two lymph node metastases. Tissues were homogenized for RNA preparations, and RT-PCR was performed for the CD44v7-v10 sequence. In cultured prostate cancer cells, we caused RNA interference against CD44v9 and/or Muc18. We used PC3M cells and a derivative cell line called G(s)alpha, that constitutively expresses this G-protein and is more invasive. Lipofection was performed for a green fluorescent protein plasmid and for two 22-mer DNA fragments, cloned into a plasmid expression vector to generate hairpin, interfering dsRNA. Assays for invasion into Matrigel, a basement membrane matrix, were performed in 4-5 experiments. RT-PCR demonstrated expression of a 608 bp band representing CD44v7-v10 or a 638 bp band of CD44v6-v10 in prostate cancer tissues and metastases but not benign tissue. Cultured G(s)alpha cells overexpressed CD44v9 by comparison with PC3M cells. At 90 h after 6-hour lipofection, protein silencing was evident by Western blots. Silencing the CD44v9 expression reduced invasiveness into Matrigel to 21.6+/-7.0% in PC3M cells (P<0.001) and 31.2+/-18.3% in G(s)alpha cells (P=0.001), compared to cells exposed to transfection vehicle alone. Silencing Muc18 expression reduced invasiveness to 76.9+/-13.5% of the control value in PC3M cells (P<0.05) and 84.8+/-29.9% in G(s)alpha cells (P=0.18). Prostate cancer invasion is facilitated more by its overexpression of CD44 variant 9 than by Muc18. Its relative overexpression by G(s)alpha cells is a novel finding, suggesting a link between signal transduction and cell adhesion marker expression.

Antigens, CD↗
PubMedDate not supplied

Open surgical release for frozen shoulder: surgical findings and results of the release.

Over a 5-year period, 75 shoulders that met Codman's criteria for primary frozen shoulder were treated. Nine patients improved with nonoperative treatment, and the remaining 66 patients underwent manipulation under anesthesia. The shoulders in 41 patients successfully released with manipulation. Those in 25 failed to release with manipulation, and therefore, these patients underwent open surgical release of the contracted shoulder. We reviewed the cases of all of the surgically treated patients at 19.52 months' average follow-up, using the history and clinical examination technique recommended by the American Shoulder and Elbow Surgeons. The surgical findings in this group of 25 patients showed a consistent alteration in the rotator interval and coracohumeral ligament. The rotator interval was obliterated, and the coracohumeral ligament was transformed into a tough contracted band. The histology of this contracture was examined in 12 patients and consisted of a dense matrix of type III collagen populated with fibroblasts and myofibroblasts. The contracted coracohumeral ligament was excised with immediate release of the external rotation deficit. Pain scores on visual analogue scale improved from 8.28 to 2.0. The average score for function, with a maximum score of 30, improved from 6.08 to 18.9. Twenty patients had excellent or good results, and 3 had fair results. The shoulders of 2 patients failed to improve: 1 was an insulin-dependent patient with diabetes, and 1 had severe bilateral Dupuytren's contractures. The results in the patients without diabetes were very satisfactory, with visual analogue scale scores of pain decreasing from 8.4 to 1.1, function increasing from 6.4 to 20.1, flexion increasing from an average of 96 degrees to an average of 131 degrees, and external rotation increasing from an average of 10.0 degrees to an average of 46.7 degrees. Surgical release of frozen shoulder is a useful option in those few patients with severe disease whose shoulders fail to release with manipulation under anesthesia. Caution should be used in insulin-dependent patients with diabetes.

Adult↗
PubMed2001

Acoustic wave propagation in a one-dimensional layered system.

Propagation of acoustic waves in a one-dimensional water duct containing many air filled blocks is studied by the transfer matrix formalism. Energy distribution and interface vibration of the air blocks are computed. For periodic arrangement, band structure is calculated analytically, whereas the Lyapunov exponent and its variance are computed numerically for random situations. A distinct collective behavior for localized waves is found. The results are also compared with optical situations.

Journal Article↗
PubMed2003

Waveguide-plasmon polaritons: strong coupling of photonic and electronic resonances in a metallic photonic crystal slab.

Strong coupling between localized particle plasmons and optical waveguide modes leads to drastic modifications of the transmission of metallic nanowire arrays on dielectric waveguide substrates. The coupling results in the formation of a new quasiparticle, a waveguide-plasmon polariton, with a surprisingly large Rabi splitting of 250 meV. Our experimental results agree well with scattering-matrix calculations and a polariton-type model. The effect provides an efficient tool for photonic band gap engineering in metallodielectric photonic crystal slabs. We show evidence of a full one-dimensional photonic band gap in resonant plasmon-waveguide structures.

Journal Article↗
PubMed2004

Complexity of vector spin glasses.

We study the annealed complexity of the m-vector spin glasses in the Sherrington-Kirkpatrick limit. The eigenvalue spectrum of the Hessian matrix of the Thouless-Anderson-Palmer free energy is found to consist of a continuous band of positive eigenvalues in addition to an isolated eigenvalue and (m-1) null eigenvalues due to rotational invariance. Rather surprisingly, the band does not extend to zero at any finite temperature. The isolated eigenvalue becomes zero in the thermodynamic limit, as in the Ising case (m=1), indicating that the same supersymmetry breaking recently found in Ising spin glasses occurs in vector spin glasses.

Journal Article↗
PubMed2002

Expression of alternatively spliced RNA transcripts of amelogenin gene exons 8 and 9 and its end products in the rat incisor.

In addition to seven known exons of the amelogenin gene, recent studies have identified two exons downstream of amelogenin exon 7 in genomic DNA of mouse and rat. Here the spatial and temporal expression of mRNAs and of the translated proteins derived from alternative splicing of the amelogenin gene ending with exon 8 and exon 9 were examined by in situ hybridization (ISH) and immunohistochemistry (IHC). RNA signals for exons 8 and 9 were expressed in the ameloblast layer extending from early presecretory to postsecretory transitional stages of amelogenesis. IHC of amelogenin proteins that include sequences encoded by these exons demonstrated identical localization of these proteins in the ameloblast layer corresponding to RNA signals identified by ISH. There was intense immunostaining of the enamel matrix secreted by these cells. Western blotting analysis of rat enamel proteins revealed three distinct protein bands with sequences encoded by the new exons. These data confirmed the existence of the transcripts of alternatively spliced mRNAs coding for exons 8 and 9 of the amelogenin gene in rat tooth germs and suggest that the translated proteins contribute to the heterogeneity of amelogenins and have some significant roles in enamel formation and mineralization.

Alternative Splicing↗
PubMed1994

Tissue-specific expression of the fibril-associated collagens XII and XIV.

Interstitial collagen fibrils form the supporting scaffold of all connective tissues. The synthesis of this framework is subject to a precise spatial and temporal regulation in order to meet the mechanical needs of every tissue type. A subgroup of non-fibrillar collagens termed FACIT seems to play a role in this regulation by providing specific molecular bridges between fibrils and other matrix components. Collagens XII and XIV represent such FACIT molecules and occur preferentially in tissues containing banded type I collagen fibrils. We have used the techniques of indirect immunofluorescence and in situ hybridization to investigate the expression patterns of the two molecules during chicken embryonic development. We detected specific differences in these patterns, which may be related to the respective functions of the two proteins within the connective tissues. Collagen XIV was expressed at very few sites in the 6-day-old embryo, but occurred in virtually every collagen I-containing tissue (skeletal muscle, cardiac muscle, gizzard, tendon, periosteum, nerve) by the end of embryonic development. In contrast, collagen XII was fairly abundant in the 6-day-old embryo but was, at later stages, restricted to only a few dense connective tissue structures (bone, tendon, gizzard). Thus, our results suggest that collagen XII and collagen XIV serve different functions during embryonic development although their structures are highly similar.

Animals↗
PubMed2003

In vitro surface corrosion of stainless steel and NiTi orthodontic appliances.

Simulated fixed orthodontic appliances were constructed, immersed and incubated in artificial saliva for periods up to three months. Two types of stainless steel archwires and two types of NiTi wires were used. The surface corrosion of the archwires was determined macroscopically, with scanning electron microscopy, and with spectrophotometry. The deposits on the wires were identified with X-ray diffraction. Uniform corrosion was observed on stainless steel wires, and a slight colour change was detected on the NiTi wires beneath stainless steel ligatures. The corrosion product on the stainless steel wires increased with immersion time, and the surface oxide films were easily detached from the underlying matrix. Crevice corrosion was observed under deposits of oxide, and at the interface between bracket and band. Such corrosion may weaken a wire or weld leading to fracture. In contrast, the NiTi archwires did not corrode, and there was no significant difference in surface morphology. The stainless steel archwires showed a significant loss of reflectance after heat treatment and immersion in artificial saliva. The NiTi archwires had the same reflectance before and after the immersion test. NiTi archwires are significantly more stable and resistant to corrosion than stainless steel archwires.

Color↗