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At least 1,603 records · Page 89Linked to original sources
PubMed1992

Electron microscopic characterization of calcium-binding physodes in the green alga Mougeotia scalaris.

Effect of the covalently cross-linking agents glutardialdehyde and osmium tetroxide, and of adsorption of the vital dye, neutral red, to the matrix of the calcium-binding "vesicles" from the green alga Mougeotia scalaris has been analysed in situ, both in terms of structural preservation and of the calcium-binding capacity of the vesicles. Upon cell fixation in glutardialdehyde without OsO4, the vesicles appear to dissolve, but upon simultaneous fixation in glutardialdehyde with OsO4 (1% w/v), the vesicles retain a globular form, are evenly stained by osmium and appear to be surrounded by a membrane-like structure. This structure was also observed around the vesicles in cells preincubated for 10 min in 0.1 mM neutral red and then fixed in glutardialdehyde/OsO4 for 1 h. More detailed information of the matrix structure is obtained when simultaneous fixation of the Mougeotia cells was shortened to 15 min: a membrane-like structure was no longer observed around the vesicles. After cell treatment in the presence of neutral red, no calcium at all was found inside the vesicles. A small amount of calcium remained, when cells were fixed simultaneously and extensively in the absence of neutral red. However, calcium was found, to a considerable extent, inside the vesicles after short simultaneous fixation of the cells in the absence of neutral red. Based on the ultrastructural and elemental features presented here, the calcium-binding vesicles in Mougeotia appear to represent a member of the large family of (calcium-binding) physodes in lower plants (CaBP).

Calcium↗
PubMed1977

[Study of the element secretory glands of a tubicolous polychaete (Pectinaria (= Lagis) koreni) with the help of electron microprobe and ion microanalyzer (author's transl)].

Two histophysical methods (electron microprobe and ion microanalyzer) were used on sections of Annelids in order to study the inorganic composition of cement secretory glands. Mg, Ca and P were demonstrated in large amounts in the secretions, associated with organic matter. Traces, or no, Fe, Al and Si were found. Possibilities of artifacts are discussed, and these results are compared with biochemical methods. A hypothesis is proposed in order to explain the differences observed between biochemical and present results, which suggest, for the hardening of cements a different chemical mechanism to that suggested by Vovelle in annelid Sabellaria alveolata.

Animals↗
PubMed1988

Metabolic expression of intrinsic developmental programs for dentine and enamel biomineralization in serumless, chemically-defined, organotypic culture.

Biomineralization was investigated using embryonic mouse mandibular first molars (M1) cultured in the presence or absence of fetal calf serum. Metabolic features including cell division and Ca2+ and phosphate incorporation into dentine and enamel extracellular matrices were analyzed. The relative timing and magnitude of DNA synthesis for serumless cultures was comparable to in vivo controls. Isotopic calcium and phosphate incorporation into the mineral phase of dentine and enamel matrices, in the absence of serum, fluctuated during development. Molar tooth morphogenesis, cytodifferentiation, and extracellular matrix formation approximated late crown-stage development in serumless cultures. Von Kossa histochemical staining indicated calcium phosphate salt formation in serumless cultures. Analysis of anhydrous fixation-prepared enamel and dentine representing serumless cultured explants indicated that crystal size and orientation were comparable to in vivo enamel and dentine. In contrast, serum-supplemented cultures showed atypical crystal size and orientation. Calcium/phosphorous (Ca/P) ratio values for serumless cultures after 21 days showed Ca/P enamel values of 2.03 (SD +/- 0.04, p less than 0.025) and dentine values of 1.89 (SD +/- 0.01, p less than 0.025). Electron diffraction patterns of enamel and dentine formed in serumless cultures were principally those of highly-ordered crystalline hydroxyapatite. Our results suggest that tissue-specific dentine and enamel biomineralization is regulated by endogenous factors intrinsic to the developmental program of embryonic tooth organs during serumless culture.

Animals↗
PubMed1989

Carbohydrate-controlled precipitation of apatite with coprecipitation of organic molecules in human saliva: stabilizing role of polyols.

Addition of common dietary carbohydrates to Millipore-treated human whole saliva either enhances or inhibits the formation of salivary precipitates, some carbohydrates showing no effect. The purpose of this study was to investigate the precipitation conditions more thoroughly and to elucidate the chemical nature of the precipitates formed. D-Xylose either enhanced precipitation (in long-term incubations) or had no appreciable effect (in 10 minute incubations). Other aldo- and keto-sugars and disaccharides (maltose, sucrose, lactose) generally enhanced precipitation, whereas all polyols (xylitol, D-sorbitol, mannitol, and maltitol) retarded the formation of turbidity in saliva. Xylitol inhibited formation of precipitates also in the presence of D-xylose, dextrans, and starch. Fast protein liquid chromatography (FPLC) of EDTA-soluble pellets obtained by centrifugation of the precipitates produced two major protein fractions (I and II) with a molecular weight of 112,000 and 46,000, respectively. The carbohydrates exerted a selective effect on the relative size of I and II in that polyol incubations resulted in a I to II ratio of 1:3, whereas control incubations (without added sugars) and incubations with other carbohydrates gave ratios of 1:6 to 1:10. Both peaks contained large amounts of acidic amino acids, proline, and glycine. The saliva precipitates contained a substantial portion of a crystalline phase that had the crystal structure of apatite, the individual crystallites being extremely small (less than 1 micron) with a Ca:P ratio of 1.46. The carbohydrates had a similar effect on the overall inorganic composition of the precipitates, but they had a clearly selective effect on the rate of formation of precipitates and on the relative amount of coprecipitating salivary proteins. This selectivity indicates that these carbohydrates, when consumed habitually, may exert different effects on the precipitation of Ca-salts at mineral-deficient enamel and dentine sites.

Adult↗
PubMed2003

Transformation behavior, chemical composition, surface topography and bending properties of five selected 0.016" x 0.022" NiTi archwires.

PURPOSE: The aim of this study was to characterize five selected commercial NiTi archwires in terms of their transformation behavior, chemical composition, surface topography and mechanical properties (at temperatures of 22 degrees C, 37 degrees C and 60 degrees C). MATERIAL AND METHODS: The rectangular orthodontic archwires investigated were Neo Sentalloy F80 (GAC, Central Islip, NY, USA), 35 degrees C Thermo-Active Copper NiTi (A-Company/Ormco, Glendora, CA, USA), Rematitan "Lite" (Dentaurum, Pforzheim, Germany), Titanol SE S (Forestadent, Pforzheim, Germany) and Titanal (Lancer, San Marcos, CA, USA) in size 0.016" x 0.022". The chemical composition and surface topography were analyzed by energy dispersive X-ray spectroscopy using an analytical scanning electron microscope (XL30, EDAX SUTW Saphire Detector; Philips, Eindhoven, Netherlands). The transition temperatures were measured by means of differential scanning calorimetry (DSC; Perkin-Elmer Pyris 1, Perkin-Elmer, Fremont, CA, USA) in a range of - 80 degrees C to + 80 degrees C. The mechanical properties and their dependence on temperature were determined by means of 3-point bending tests. The binary archwire materials were characterized by a two-phase structure (NiTi matrix and Ni3Ti4 precipitates). RESULTS: The SEM analyses revealed abradant residues in virtually all archwires, while DSC revealed complex transformation properties. In addition to the martensitic and austenitic transformations, an R-phase transformation was also detected. The bending tests showed pronounced loading and unloading plateaus. The martensitic archwires (Neo Sentalloy F80, 35 degrees C Thermo-Active Copper NiTi) were found to have a lower strength than the martensitic-austenitic (Rematitan "Lite") and the austenitic archwires (Titanol SE S, Titanal). With increasing temperature (in the range from 22 degrees C to 60 degrees C) a linear rise in the plateau forces was recorded. CONCLUSIONS: When assessing the quality of archwires, account should be taken of the surface quality, as it is this that determines corrosion resistance, biocompatibility and friction characteristics. The mechanical properties depend on the initial state; moderate plateau forces and plateau moments can only be achieved with martensitic archwires. In contrast to conventional steel alloys, the strength characteristics are heavily dependent on temperature and need to be known if NiTi archwires are to be used to optimal effect. In addition, the superelastic plateau is used only partially, if at all, when minimum leveling is required.

Calorimetry, Differential Scanning↗
PubMed2006

Lithogenesis: induction of renal calcifications by nanobacteria.

Nanobacteria have been isolated from kidney stones and it has been suggested that they may act as a nucleus for the initiation of the renal stones. In the present study, we examine their role in biocrystallization and their in vivo effects on kidney pathology. Calcium oxalate monohydrate (COM) assay was carried out in the presence of nanobacteria to study biocrystallization. Wistar rats were given an intravenous injection of nanobacteria and the kidneys were examined for pathological changes. The COM assay showed accelerated biocrystallization of (14)C-oxalate in the presence of nanobacteria, indicating them to be efficient candidates for biomineralization. Histopathological studies revealed bacteria induced renal tubular calcifications and various manifestations of infection. Our studies confirm that nanobacteria may be involved in the pathogenesis of renal tubular calcification.

Animals↗
PubMed1995

[Calcinosis of the meniscus. Morphologic and roentgenographic findings for zonal classification].

Primary and secondary meniscal chondrocalcinoses lead to typical changes in X-ray pictures of isolated menisci. Combined X-ray, light and electron microscopic examination of the four menisci in 70 autopsy cases showed calcifications in 13 cases (18.6%). Three types of calcification could be discriminated with the help of topographical and morphological criteria: Type 1 A: disseminated calcification. All four menisci were affected equally. Crystals of calcium pyrophosphate dihydrate (CPPD) were found on light and electron microscopy. Energy-dispersive X-ray analysis (EDX) showed the crystal deposits to consist of 46.5% calcium and 53.5% phosphorus. Type 1 B: Calcification occurring in limited areas. A calcification was found which did affected neither a whole meniscus nor all four menisci of any "quartet" observed. Crystals were found next to areas of stronger meniscal degeneration. EDX showed the same results described for type 1 A. Type 2: Confluent calcification. A cloud-like diffuse calcification was discerned on the X-ray pictures. Light and electron microscopically pseudocystic structures appeared which contained a fine granular amorphous material. No crystals were found. The structures appeared in the neighbourhood of necrotic fibres. EDX showed 44% calcium, 51.2% phosphorus, 2.8% sulphur, 0.74% magnesium and 0.6% potassium. The findings lead to the conclusion that calcification type 1 A represents primary chondrocalcinosis, whereas type 1 B corresponds to secondary chondrocalcinosis. Type 2 was identified as postnecrotic, dystrophic calcification. Careful analysis of X-ray pictures of isolated menisci can yield useful information concerning pathogenetic factors of meniscal calcification.

Calcium Pyrophosphate↗
PubMed1994

The origin and composition of peroxidase-positive granules in cysteamine-treated astrocytes in culture.

Gomori astrocytes, which are prominent in periventricular regions of the brain, contain inclusions that stain with Gomori dyes, and exhibit an orange-red autofluorescence and a non-enzymatic peroxidase activity. Recently, such astrocytes have been induced in dispersed glial cultures by exposure to cysteamine. Using these cells, we have shown that the peroxidase-positive inclusions (Gomori bodies) are multicompartmental, that iron co-localizes with the peroxidase activity, and that the iron is often segregated in one of the compartments of the body. The goal of the present study was to determine the origin and process of formation of these bodies. The results indicate that cysteamine induces aberrations in mitochondrial structure associated with the acquisition of iron and the associated peroxidase activity. Mitochondria thus transformed appear to initiate an autophagic process in which they, and adjacent structures, are sequestered. The presence of acid phosphatase activity in a number of mature Gomori bodies attests to the participation of lysosomal elements in this process. These results indicate, therefore, that the Gomori body is a complex autophagosome in which the iron-containing compartments, putatively responsible for the peroxidase activity, represent undegraded transformed mitochondria.

Acid Phosphatase↗
PubMed1983

Pathogenesis of skeletal muscle necrosis induced by tarantula venom.

The pathogenesis of myonecrosis induced by venoms of the Arkansas tarantula (Dugesiella hentzi, Girard) and the Honduran tarantula (Aphonopelma spp.) was studied using light and electron microscopy, scanning electron microscopy and x-ray microprobe analysis, and histochemistry. White mice were injected intraperitoneally with a sublethal dose of tarantula venom. Gross examination 24 hr after injection revealed white areas of apparent calcification in the diaphragm muscle. Light microscopic examination at 15 min revealed hypercontracted muscle cells, and necrotic masses containing areas of condensed myofibrils and clumps of mitochondria. By 12 hr numerous phagocytic cells were present around degenerated muscle cells. Electron microscopic examination revealed a myonecrosis of rapid onset with plasma membrane rupture and contraction bands 15 min after injection. At 3 hr only small patches of plasma membrane remained and mitochondrial changes such as swelling, dense intracristal spaces, partitioning, and flocculent densities were prominent. By 12 and 24 hr very dark spicular densities were present in mitochondria and numerous phagocytic cells were located within the intact basal lamina of necrotic cells. X-ray analysis and histochemistry of 24 hr samples showed that necrotic cells contained very high levels of calcium and phosphate. These two tarantula venoms caused a rapid onset myonecrosis in which the primary injury was rupture of the plasma membrane followed by inability of mitochondria and sarcoplasmic reticulum to maintain normal levels of calcium in the cytoplasm leading to cell death.

Animals↗
PubMed1991

Ceftriaxone-associated gallbladder sludge. Identification of calcium-ceftriaxone salt as a major component of gallbladder precipitate.

Ceftriaxone, a third-generation cephalosporin, is partially excreted into bile. With its clinical use, the formation of gallbladder sludge detected by ultrasonography has been reported. Four surgical specimens were examined and no gallstones were found. Instead, fine precipitates of 20-250 microns were present. Microscopically, there was a small number of cholesterol monohydrate crystals and bilirubin granules among an abundant amount of granular-crystalline material that was not morphologically cholesterol monohydrate crystals. The chemical composition of the precipitates (n = 4) was determined. There was a small amount of cholesterol (1.7% +/- 0.8%) and bilirubin (13.9% +/- 0.74%). The major component of the precipitate was a residue. On further analysis using thin-layer chromatography, high-performance liquid chromatography, and electron microprobe analysis, the residue was identified as a calcium salt of ceftriaxone. The residue also had identical crystal morphology and chromatographic elution profile as authentic calcium-ceftriaxone standards. It is concluded that ceftriaxone, after excretion and being concentrated in the gallbladder bile, can form a precipitate. The major constituent has been identified as a ceftriaxone-calcium salt.

Bile↗
PubMed1994

Intracytoplasmic eosinophilic hyaline globules in cartilaginous neoplasms: a surgical, pathological, ultrastructural, and electron probe x-ray microanalytic study.

Hyaline globules (HGs), spherical intracytoplasmic eosinophilic droplets, have been associated with a variety of conditions, including hepatocellular carcinoma, lung adenocarcinoma, and Kaposi's sarcoma, but they have not been described in cartilaginous tumors. In specimens of 60 cartilaginous neoplasms we found that 22 of 33 chondrosarcomas (67%), eight of 16 enchondromas (50%), and three of seven soft tissue chondromas (43%) exhibited HGs. HGs were seen more commonly in low grade chondrosarcoma (70%) and were relatively rare in high grade chondrosarcoma (25%). No HGs were identified in three osteochondromas, one synovial chondromatosis, or 15 normal cartilaginous tissues taken from various sites. Cartilage associated HGs ranged in size from 2 to 20 microns, were diastase resistant and periodic acid-Schiff (PAS) stain positive, demonstrated autofluorescence, and variably stained with Mallory's phosphotungstic acid-hematoxylin stain (PTAH). A panel of immunostains did not show any specific staining reactions with HGs. Ultrastructurally the HGs were spherical, non-membrane-bound bodies having complex architectural features associated with profiles of rough endoplasmic reticulum. Electron probe x-ray microanalytic (EPXMA) study showed significant peaks of sulphur and calcium. We conclude that HGs represent secretory products of probable glycoprotein nature, may accumulate in a variety of cartilaginous neoplasms, and may be seen more frequently in low grade chondrosarcomas.

Bone Neoplasms↗
PubMed1993

Surface analysis of titanium implants.

Medical grade titanium samples were examined using X-ray photoelectron spectroscopy before and after immersion in various proteins. Additionally, an implant removed from a patient following clinical failure was examined using scanning ion and electron microscopy. The surface of the as-received samples was found to be mainly TiO2, with contaminants of H2O/OH-, calcium and nitrogen which remained after autoclaving. The immersed proteins adhered to the titanium surface, possibly via a Ca-O link. The failed clinical sample was found to be partially fibrously encapsulated with evidence of calcification. Small amounts of TiOOH were detected at the fibrous periphery, supporting the theory of Tengvall and co-workers that in vivo titanium implants are covered in a gel of this material.

Bone and Bones↗
PubMed1995

Hydroxyapatite-based porous aggregates: physico-chemical nature, structure, texture and architecture.

At the request of medical teams from the maxillofacial sector, a highly porous ceramic support based on hydroxyapatite of around 70-80% porosity was produced with a pore size distribution similar to bone texture (< 10 microns, approximately 3 vol%; 10-150 microns, approximately 110 vol%; > 150 microns, approximately 86 vol%). The ceramic substrates were conceived not only as a fillers for bone cavities, but also for use as drug dispensers and as supports to host cells to produce particular therapeutic agents. A method is suggested to obtain a substrate of high porosity, exploiting the impregnation of spongy substrate with hydroxyapatite ceramic particles. X-ray and scanning electron microscopy analyses were carried out to evaluate the nature of the new ceramic support in comparison with the most common commercial product; pore size distribution and porosity were controlled to known hydroxyapatite ceramic architecture for the different possible uses.

Biocompatible Materials↗
PubMedDate not supplied

The osteogenic stimulating effect of neuroactive calcitonin gene-related peptide.

Silverman and Kruger (Somatosens. Res. 5(2):157-175; 1987) reported that sensory nerve fibers of the dental pulp secrete calcitonin gene-related peptide (CGRP). These are localized exactly where secondary or tertiary dentin calcification occurs. Recently we found that CGRP has an osteogenic stimulating effect by increasing the number and size of bone colonies in vitro. The purpose of this study is to test whether there is a relationship between the effects of different doses of CGRP and bone colony numbers and/or size. Rat CGRP in different dosages (0.4, 4 and 40 micrograms/ml in BGJb medium) was added daily to 3 million light density (LD) bone marrow white cells which were harvested from adult Sprague-Dawley rats with the Ficoll-Paque density gradient separation method, then seeded onto a previously prepared feeder layer of fibroblasts in Petri dishes. Seven days after adding CGRP, in the controls without CGRP there were 2 bone colonies; with 0.4 microgram of CGRP there were 4 colonies; with 4 micrograms of CGRP there were 6 colonies; with 40 micrograms there were 9 colonies, indicating there was a significant increase in number of bone colonies with an increase in dose of CGRP between individual groups, respectively (p less than 0.0005 and p less than 0.0001). In another experiment, intravenous injection of 10 micrograms of rCGRP/kg body weight was performed two hours before surgery. LD bone marrow white cells were collected and seeded onto a feeder layer in Petri dishes exactly as described above.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗