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PubMed2006

Oxidized, bioactive implants are rapidly and strongly integrated in bone. Part 1--experimental implants.

OBJECTIVES: The study presented was designed to investigate the speed and the strength of osseointegration of oxidized implants at early healing times in comparison which machined, turned implants. MATERIAL AND METHODS: Screw-shaped titanium implants were prepared and divided into two groups: magnesium ion incorporated, oxidized implants (Mg implants, n=10) and machined, turned implants (controls, n=10). Mg implants were prepared using micro-arc oxidation methods. Surface oxide properties of implants such as surface chemistry, oxide thickness, morphology/pore characteristics, crystal structures and roughness were characterized with various surface analytic techniques. Implants were inserted into the tibiae of ten New Zealand white rabbits. After a follow-up period of 3 and 6 weeks, removal torque (RTQ), osseointegration speed (DeltaRTQ/Deltahealing time) and integration strength of implants were measured. Bonding failure analysis of the bone-to-implant interface was performed. RESULTS: The speed the and strength of osseointegration of Mg implants were significantly more rapid and stronger than for turned implants at follow-up periods of 3 and 6 weeks. Bonding failure for Mg implants dominantly occurred within the bone tissue, whereas bonding failure for turned implants mainly occurred at the interface between implant and bone. CONCLUSIONS: Oxidized, bioactive implants are rapidly and strongly integrated in bone. The present results indicate that the rapid and strong integration of oxidized, bioactive Mg implants to bone may encompass immediate/early loading of clinical implants.

Animals↗
PubMed1983

Elevated phosphorus in psoriatic skin determined by energy dispersive x-ray micro-analysis.

Scanning electron-microscopy in combination with secondary electron imaging and x-ray energy spectrometry (electron-probe micro-analysis) was performed on the stratum corneum of involved and uninvolved, psoriatic skin. The significant, elemental alterations included an increase in phosphorus and calcium in the involved skin regions. A composite, chemical, elemental profile of normal and uninvolved, psoriatic stratum corneum is presented.

Electron Probe Microanalysis↗
PubMed1985

Elemental distribution in Rana pipiens retinal rods: quantitative electron probe analysis.

The composition of dark-adapted and illuminated retinal rod outer and inner segments and mitochondria was determined with electron probe X-ray micro-analysis of cryosections. The concentration of Ca in the outer segment was 0.4 mmol/kg dry wt. (0.1 Ca/rhodopsin) and did not measurably change upon illumination with saturating light for 5 min. The non-mitochondrial regions of the inner segment contained the highest concentrations (up to 13 mmol/kg dry wt.) of Ca in rods; these regions probably represent the endoplasmic reticulum. The equilibrium potentials estimated from the measured elemental concentrations and the known water content of dark-adapted outer segments were (mV): ENa = +17, EK = -83, ECl = -27. The respective values in the inner segment were: ENa = +20, EK = -89, ECl = -26. The above values were obtained in frog rods bathed in 0.18 mM-Ca Ringer solution. In the outer segment of toad rods bathed in 1.8 mM-Ca Ringer, ENa = +33 mV. The Mg content of the rods was high. The (computed) concentration in the dark-adapted retinae was 11 mM in the outer segment and 24 mM in the inner segment. Illumination caused a reduction in Mg to 9 mM (outer segment) and 16 mM (inner segment). Illumination caused a highly significant reduction in Na and Cl concentrations, and an increase in K concentration in both outer and inner segments. Exposure to Na-free (choline Ringer) solution resulted in reduction in Na to just-detectable levels (3 +/- 1 mmol/kg dry wt.) in the outer segment and to 5 +/- 1 mM in the inner segment. This was associated with a significant loss of Cl and decrease in ECl to -50 mV. The low Na content of the outer segment in the Na-depleted rods is not compatible with an extracellular concentration (105 mM) of inexchangeable Na in the intradiskal space. Mitochondrial Na and Mg paralleled the changes in the cytoplasmic concentrations: both mitochondrial Na and Mg were significantly decreased in illuminated, compared to dark-adapted rods. There was no detectable Ca (0 +/- 0.2 mmol/kg dry wt.) in mitochondria of dark-adapted rods containing high concentrations of Na; mitochondrial Ca was slightly higher (0.5 +/- 0.2 mmol/kg dry wt.) in the mitochondria that contained low Na following illumination.

Animals↗
PubMed2000

Structure and species composition of mercury-reducing biofilms.

Mercury-reducing biofilms from packed-bed bioreactors treating nonsterile industrial effluents were shown to consist of a monolayer of bacteria by scanning electron microscopy. Droplets of several micrometers in diameter which accumulated outside of the bacterial cells were identified as elemental mercury by electron-dispersive X-ray analysis. The monospecies biofilms of Pseudomonas putida Spi3 initially present were invaded by additional strains, which were identified to the species level by thermogradient gel electrophoresis (TGGE) and 16S rDNA sequencing. TGGE community fingerprints of the biofilms showed that they were composed of the effluent bacteria and did not contain uncultivable microorganisms. Of the 13 effluent bacterial strains, 2 were not mercury resistant, while all the others had resistance levels similar to or higher than the inoculant strain.

Bacteria↗
PubMed1985

Silicon-containing particles in synovial fluid: scanning electron microscopy coupled with analytical techniques allows an easy identification and differentiation from pathologically relevant crystals.

Silicon-containing particles were observed by scanning electron microscopy (SEM) in synovial fluid samples from patients with crystal-induced or inflammatory synovitis, or both. This material was an artefact produced by the technical procedures, but these particles could be easily differentiated from naturally occurring compounds by their morphology and their composition determined by analytical spectrometry.

Electron Probe Microanalysis↗
PubMed2001

Characterization of the interaction between the dark septate fungus Phialocephala fortinii and Asparagus officinalis roots.

Phialocephala fortinii Wang & Wilcox is a member of root-inhabiting fungi known collectively as dark septate endophytes (DSE). Although very common and distributed worldwide, few studies have documented their interaction with roots on a structural basis. The objective of this study was to determine the early colonization events and formation of microsclerotia of P. fortinii in roots of Asparagus officinalis L., a species known to have DSE. A loose network of hyphae accumulated at the root surface, and coils formed around root hairs and external to epidermal cells overlying short cells of the dimorphic, suberized exodermis. Root penetration occurred via swollen, appressorium-like structures into epidermal cells where coiling of hyphae occurred along the periphery of the cells. Hyphae penetrated from the epidermis into short exodermal cells and from these into cortical cells. Hyphae colonized the cortex up to the endodermis and sometimes entered the vascular cylinder. Some root tips were colonized as well. Microsclerotia in epidermal and exodermal short cells accumulated glycogen, protein, and polyphosphate. Energy-dispersive X-ray spectroscopy on distinct bodies visible in microsclerotial hyphae revealed high levels of phosphorus.

Ascomycota↗
PubMed2002

Calcified nanostructured silicon wafer surfaces for biosensing: effects of surface modification on bioactivity.

The growth of known biologically-relevant mineral phases on semiconducting surfaces is one strategy to explicitly induce bioactivity in such materials, either for sensing or drug delivery applications. In this work, we describe the use of a spark ablation process to fabricate deliberate patterns of Ca(10)(PO4)6(OH)2 on crystalline Si (calcified nanoporous silicon). These patterns have been principally characterized by scanning electron microscopy in conjunction with elemental characterization by energy dispersive x-ray analysis. This is followed by a detailed comparison of the effects of fibroblast adhesion and proliferation onto calcified nanoporous Si, calcified nanoporous Si derivatized with alendronate, as well as control samples of an identical surface area containing porous SiO2. Fibroblast adhesion and proliferation assays demonstrate that a higher density of cells grow on the Ca3(PO4)2/porous Si/SiO2 structures relative to the alendronate-modified surfaces and porous Si/SiO2 samples.

Biosensing Techniques↗
PubMed1996

Ultrastructure and characteristics of eggshells of the olive ridley turtle (Lepidochelys olivacea) from Gahirmatha, India.

The structure of a chelonian eggshell is of prime importance for the developing embryo. It acts as a protective covering as well as mediator in the exchange of heat and water. The fresh eggshell of the olive ridley (Lepidochelys olivacea) turtle displays a variety of structural forms in their aragonite framework. Its netted substrate, loose texture and poorly organised crystallites favour the easy exchange of air and water during its development. The shell consists mostly of calcium in carbonate form and K, Mg, Fe, Ni, Pb, Zn, Co, Cr, Cu, Mn and Cd in traces. Ba and Sr in traces are also a feature of the thermal analysis graph. Phosphorous was not detected in the shell and its absence eliminates an earlier suggestion of it being a key factor in the development of aragonite crystals in the inorganic structure of marine turtle eggshells. Its combustion characteristics, which have not been previously reported, are recorded.

Animals↗
PubMed1995

Mineral content of the dentine remaining after chemomechanical caries removal.

Although the dentine remaining after chemomechanical caries removal appears sound by normal clinical criteria, no definitive evidence has yet been obtained to confirm that the dentine surface is in fact mineralised. The aim of this study was to use backscattered electron (BSE) imaging and electron probe micro-analysis (EPMA) to ascertain the level of mineralisation of the dentine remaining in cavities prepared by this technique. Carious dentine was removed from carious lesions by means of N-monochloro-DL-2-aminobutyric acid (NMAB) or NMAB containing 2 mol/l urea. Sections of teeth in which caries removal was complete by normal clinical criteria were examined by EPMA and BSE. Dentine adjacent to the pulp was found to be less mineralised than the surrounding dentine. Although the superficial layer of dentine remaining on the cavity floors frequently appeared to have a slightly reduced mineral content, the results clearly indicated that there was no significant difference between this dentine and the underlying sound dentine.

Aminobutyrates↗
PubMed1997

Formation of brushite, monetite and whitlockite during equilibration of human enamel with acid solutions at 37 degrees C.

The residues of 5 samples of powdered human enamel, each subjected to 5 sequential equilibrations at 37 degrees C with either 17 or 4 mmol/l phosphoric acid, were examined microscopically. With 17 mmol/l acid, both brushite and monetite were found after 1 equilibration but, after further equilibrations, brushite was no longer present and the abundance of monetite crystals increased. Formation of monetite probably contributed to the lower metastability of this system compared to similar low-pH systems at 25 degrees C, where monetite does not form. Neither brushite nor monetite were present after equilibration with 4 mmol/l acid. Whitlockite was identified by transmission electron microscopy and electron diffraction in all residues. In the 4 mmol/l systems, the ionic activity product (IMWH) for magnesium whitlockite, Ca9Mg(HPO4)(PO4)6, became constant after 1-3 equilibrations, at a mean value of 3.6 (+/-0.51 SE).10(-105), which may reflect saturation with respect to this solid. For the 17 mmol/l systems, higher values of IMWH, and supersaturation with respect to monetite, were interpreted as evidence for persistent metastability due to slow crystal growth of whitlockite and monetite. It is concluded that neither brushite nor monetite are likely to form within carious lesions, but the results are consistent with the known association of whitlockite with caries.

Calcium Phosphates↗
PubMed2001

Analytical characterization of collagen- and/or hydroxyapatite-modified polypyrrole films electrosynthesized on Ti-substrates for the development of new bioactive surfaces.

The design and development of new bioactive surfaces on titanium-based materials employed in orthopedic implants is described. The new biosurfaces consist of thin polypyrrole films, directly grown on implant materials and modified by the inclusion of hydroxyapatite and/or collagen during the polymer electrodeposition step. The experimental procedure has been optimized in terms of loading and distribution of the bioactive components. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) investigations have been performed in order to control the effectiveness of film modifications. In particular, XPS has been used to check the presence of biocompounds in the surface and sub-surface region of the polymer film, which is a critical requisite for a positive interface interaction between the biomaterial and the surrounding tissue.

Biocompatible Materials↗
PubMed1987

Molecular mechanism of mucin secretion: I. The role of intragranular charge shielding.

Mucus is an ubiquitous polymer hydrogel that functions as a protective coat on the surface of integument and mucosa of species ranging from simple animals (such as coelenterates) to mammals. The polymer matrix of mucus is made out of long-chain glycoproteins called mucins that are tangled together, forming a randomly woven, highly polyionic network (Lee et al., 1977; Verdugo et al., 1983). Mucin-containing granules, produced by mammalian goblet cells in vitro, undergo massive post-exocytotic swelling. Their swelling kinetics is similar to the swelling of condensed artificial polymer gels (Verdugo, 1984; Tanaka and Fillmore, 1979). We had proposed that mucins must be condensed in the secretory granule and expand by hydration during or after exocytosis (Verdugo, 1984; Tam and Verdugo, 1981). However, the polyionic charges of mucins prevents condensation unless they (the mucins) are appropriately shielded. The present experiments were designed to assert the presence of an intragranular shielding cation and its role in secretion. Giant mucin granules of the slug (Ariolimax columbianus) are released intact from mucus-secreting cells of the slug's skin. They burst spontaneously outside the cell, forming, upon hydration, the typical slug mucus (Deyrup-Olsen et al., 1983). We report here that these granules contain from 2.5 to 3.6 moles calcium/kg dry material, and that calcium is released from the granules immediately before the burst that discharges their secretory product. Therefore, we propose that calcium functions as a shielding cation of polyionic mucins, and that the bursting discharge of mucins from secretory granules must result from the release of calcium from the intragranular compartment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Surface characterization of amalgams using X-ray photoelectron spectroscopy.

This study is the first to report on the use of x-ray photoelectron spectroscopy (XPS or ESCA) for studying the surface films (less than 10 nm thick) of aged amalgams. The concentrations and electron binding energies of the elements on the surfaces of four different amalgams aged for 20 min, one day, seven days, and 30 days were determined quantitatively. For comparison, the bulk compositions of the amalgams aged for seven days were also determined after removal of approximately 5 nm of material from the surface by argon-ion-sputtering. The XPS data revealed that the surface films of aged zinc-containing amalgams were not a simple oxide but were primarily composed of a (hydrated) tin and zinc oxy-hydroxide, whereas, in the zinc-free amalgams, the surface films were primarily a tin oxide. The concentration of mercury in this thin surface film after aging was depleted. This suggests that tin and/or zinc preferentially diffused to the surface and combined with oxygen, forming a surface film and diluting the mercury concentration in the surface. Another probable explanation for the depleted mercury is that a minimal amount of mercury in the surface film evaporated during the aging.

Copper↗
PubMed1989

Effects of thyroxine and dexamethasone on rat submandibular glands.

Glucocorticoids and thyroxine are known to have a marked effect on the flow rate and protein composition of rat parotid saliva in hormonally intact animals. In the present study, the effects of a one-week treatment of male rats with dexamethasone and thyroxine were studied by electron microscopy and x-ray micro-analysis, and by measurement of the flow rate and determination of the chemical composition of pilocarpine-induced submandibular saliva. Thyroxine had the most extensive effects on the submandibular gland. The acinar cells were enlarged and filled with mucus; the cellular calcium concentration was significantly increased. The flow rate of the submandibular saliva was significantly reduced compared with that in saline-injected control animals. Thyroxine caused an increase in the concentrations of protein, total calcium, and potassium in the saliva. Dexamethasone had no significant effects on gland ultrastructure or on the elemental composition of the acinar cells; flow rate was not affected, but the concentrations of protein, calcium, and potassium were significantly increased. The effects of dexamethasone and thyroxine on the flow rate and protein composition of pilocarpine-induced rat submandibular saliva differ from those reported earlier for rat parotid saliva after simultaneous stimulation with pilocarpine and isoproterenol.

Analysis of Variance↗