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At least 1,081 records · Page 60Linked to original sources
PubMed2003

Calcification of degenerating tissues in the periodontal ligament during tooth movement.

OBJECTIVE: Calcification of degenerating tissues in the periodontal ligament (PDL) during tooth movement was investigated longitudinally. MATERIALS AND METHODS: Upper first molars of male Wistar rats were moved lingually for 1, 7 and 21 d, following which unfixed undecalcified sections of the lingual PDL (in the pressure zone) were examined histologically, histochemically (autoradiography and electron probe microanalysis). RESULTS: On d 1 of tooth movement, degenerating tissues, together with some calcified particles, were visible in the pressure zone of the lingual PDL. On d 7, substantial calcified aggregations were seen in the degenerating tissues, predominantly situated between the bone and root. This was confirmed by the 45Ca autoradiography. On d 21 of tooth movement, large calcified aggregations were still clearly evident between the bone and root. CONCLUSIONS: This calcification of the degenerating tissues is a self-defense response of the living body to prevent direct contact between alveolar bone and the tooth root during compression of the PDL, so preventing friction between them and the development of ankylosis.

Alveolar Process↗
PubMed2000

Trichosanthin induced calcium-dependent generation of reactive oxygen species in human choriocarcinoma cells.

The type-I ribosome-inactivating protein trichosanthin (TCS) has a broad spectrum of biological and pharmacological activities, including abortifacient, anti-tumor and anti-HIV. We found for the first time that TCS induced the generation of reactive oxygen species (ROS) in human choriocarcinoma cells (JAR cells) at the level of the single cell by using the fluorescent probe 2',7'-dichlorofluorescein diacetate with confocal laser scanning microscopy. TCS-induced ROS formation was shown to be dependent on the presence of extracellular Ca2+ and was further reduced when cytosolic Ca2+ was chelated by BAPTA-AM. The production of ROS increased rapidly after the application of TCS, which paralleled TCS-induced increase in intracellular calcium monitored using fluo 3-AM. Simultaneous observation of the nuclear morphological changes via two-photon laser scanning microscopy and production of ROS via confocal laser scanning microscopy revealed that ROS were involved in the apoptosis of JAR cells. The contribution of ROS was confirmed by experiments in which the antioxidant alpha-tocopherol prevented TCS-induced ROS formation and cell death. The finding that TCS induced calcium-dependent generation of ROS in JAR cells and that ROS were involved in the apoptosis of JAR cells might provide new insight into the anti-tumor and anti-HIV mechanism of TCS.

Antineoplastic Agents, Phytogenic↗
PubMed1995

Contribution of the mitochondrial permeability transition to lethal injury after exposure of hepatocytes to t-butylhydroperoxide.

We have developed a novel method for monitoring the mitochondrial permeability transition in single intact hepatocytes during injury with t-butylhydroperoxide (t-BuOOH). Cultured hepatocytes were loaded with the fluorescence probes, calcein and tetramethylrhodamine methyl ester (TMRM). Depending on loading conditions, calcein labelled the cytosolic space exclusively and did not enter mitochondria or it stained both cytosol and mitochondria. TMRM labelled mitochondria as an indicator of mitochondrial polarization. Fluorescence of two probes was imaged simultaneously using laser-scanning confocal microscopy. During normal incubations, TMRM labelled mitochondria indefinitely (longer than 63 min), and calcein did not redistribute between cytosol and mitochondria. These findings indicate that the mitochondrial permeability transition pore ('megachannel') remained closed continuously. After addition of 100 microM t-BuOOH, mitochondria filled quickly with calcein, indicating the onset of mitochondrial permeability transition. This event was accompanied by mitochondrial depolarization, as shown by loss of TMRM. Subsequently, the concentration of ATP declined and cells lost viability. Trifluoperazine, a phospholipase inhibitor that inhibits the permeability transition in isolated mitochondria, prevented calcein redistribution into mitochondria, mitochondrial depolarization, ATP depletion and cell death. Carbonyl cyanide m-chlorophenylhydrazone (CCCP), a mitochondrial uncoupler, also rapidly depolarized mitochondria of intact hepatocytes but did not alone induce a permeability transition. Trifluoperazine did not prevent ATP depletion and cell death after the addition of CCCP. In conclusion, the permeability transition pore does not 'flicker' open during normal incubation of hepatocytes but remains continuously closed. Moreover, mitochondrial depolarization per se does not cause the permeability transition in intact cells. During oxidative stress, however, a permeability transition occurs quickly which leads to mitochondrial depolarization and cell death.

Adenosine Triphosphate↗
PubMed2001

Reactive oxygen species involved in trichosanthin-induced apoptosis of human choriocarcinoma cells.

The type-I ribosome-inactivating protein trichosanthin (TCS) has a broad spectrum of biological and pharmacological activities, including abortifacient, anti-tumour and anti-HIV activities. We have found for the first time that TCS stimulated the production of reactive oxygen species (ROS) in JAR cells (a human choriocarcinoma cell line) in a time- and concentration-dependent manner by using the fluorescent probe 2',7'-dichlorofluorescein diacetate with confocal laser scanning microscopy. ESR spectral studies and the inhibition of ROS formation by the superoxide radical anion (O(2)(-.)) scavenger superoxide dismutase, the H(2)O(2) scavenger catalase and the hydroxyl radical (OH(.)) scavenger mannitol suggested the involvement of O(2)(-.), H(2)O(2) and OH(.). TCS-induced ROS formation was shown to be dependent on the presence of both extracellular and intracellular Ca(2+); moreover, ROS production paralleled the intracellular Ca(2+) elevation induced by TCS, suggesting that ROS production might be a consequence of Ca(2+) signalling. TCS-induced activation of caspase-3 was initiated within 2 h; however, TCS-induced production of ROS was initiated within 5 min, suggesting that the production of ROS preceded the activation of caspase-3. Simultaneous observation of the nuclear morphological changes via two-photon laser scanning microscopy and ROS production via confocal laser scanning microscopy revealed that ROS is involved in the apoptosis of JAR cells. The involvement of ROS was also confirmed by the inhibition of TCS-induced cell death by the antioxidant Trolox and the ROS scavengers catalase and mannitol. Diethylenetriaminepenta-acetic acid, an inhibitor of metal-facilitated OH(.) formation, markedly inhibited TCS-induced cell death, suggesting that TCS induced OH(.) formation via the Fenton reaction. The finding that ROS is involved in the TCS-induced apoptosis of JAR cells might provide new insight into the anti-tumour and anti-HIV mechanism of TCS.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Imaging of monolayers composed of palmitic acid and lung surfactant protein B.

Near-field scanning optical microscopy and atomic force microscopy are used to probe the sub-micrometre phase structure in palmitic acid monolayers containing the 25 peptide amino terminus of lung surfactant protein B (SP-B(1-25)). Monolayers deposited onto mica substrates at a surface pressure of 15 mN m-1 exhibit a two-phase coexistence across a broad range of SP-B(1-25) concentrations. Monolayers containing 5 wt.% SP-B(1-25) or less exhibit an expanse of liquid condensed phase in which elliptical liquid expanded (LE) domains with areas of approximately 25 microm2 coexist. By contrast, monolayers containing 20 wt.% SP-B(1-25) exhibit an expanse of liquid expanded phase in which circular liquid condensed domains coexist. The phase distribution dependence on SP-B(1-25) concentration suggests that the peptide induces disorder in the monolayer.

Amino Acid Sequence↗
PubMed1989

Movement of endogenous calcium in the elongating zone of graviresponding roots of Zea mays.

Endogenous calcium (Ca) accumulates along the lower side of the elongating zone of horizontally oriented roots of Zea mays cv. Yellow Dent. This accumulation of Ca correlates positively with the onset of gravicurvature, and occurs in the cytoplasm, cell walls and mucilage of epidermal cells. Corresponding changes in endogenous Ca do not occur in cortical cells of the elongating zone of intact roots. These results indicate that the calcium asymmetries associated with root gravicurvature occur in the outermost layers of the root.

Calcium↗
PubMed2000

Morphology and structure of various phases at the bonding interface of Al/steel formed by explosive welding

The bonding interface of explosively-welded aluminium and steel in three explosive conditions have been investigated by using scanning electron microscopy, transmission electron microscopy, electron diffraction and electron probe microanalysis methods. The results show that all the interfaces have the shape of waves with curled front formed by process of superplasticity and some discontinuous reacted zones. They consist of amorphous and nano sized crystals and quasi-crystals as well as the compounds such as AlFe, Al2Fe, Al3Fe and Al6Fe with various shapes. The basal steel crystal near the interface has structure of martensite and perlite crystals which are deformed by the process of superplasticity. The size of reacted zone becomes large with increasing amount of explosive charge powder and separation of the driver Al plate from the basal steel plate.

Journal Article↗
PubMed1992

High-resolution imaging of chromosome-related structures by atomic force microscopy.

An atomic force microscope (AFM) was combined with a conventional optical microscope. The optical microscope proved to be very convenient for locating objects of interest. In addition, the high-resolution AFM image can be compared directly with the traditional optical image. The instrument was used to study chromosome structures. High-resolution chromosome images revealed details of the 30-nm chromatide structure, confirming earlier electron microscopic observations. Chromosomes treated with trypsin revealed a banding pattern in height which is very similar to the optical image observed after staining with Giemsa. Furthermore, it is shown that the AFM can be used to locate DNA probes on in situ hybridized chromosomes. Images of the synaptonemal complex isolated from rat spermatocytes revealed details that improve the understanding of the three-dimensional structure of this protein.

Animals↗
PubMed1980

Electron microprobe analysis of zinc incorporation into rumen protozoa.

With the aid of electron microprobe analysis on ciliate spreads, we detected zinc in ciliates and its accumulation in the endoplasm. A correlation was found between the amount of zinc accumulation and its concentration in the medium. By the same microprobe analysis of of ultrathin sections, we determined semiquantitatively the zinc accumulation in the intracytoplasmic granules and its presence in macronuclei and in intra- and extracellular bacteria.

Animals↗
PubMed2006

Osteoblast-like cells are sensitive to submicron-scale surface structure.

OBJECTIVES: Studies showing that osteoblasts exhibit a more differentiated phenotype on rough titanium (Ti) surfaces and osteoclast-resorbed bone surfaces used materials characterized by average peak to valley distance (Ra). Other surface features impacting the cells include distance between peaks, curvature of the valleys, and relative distribution of flat and smooth regions. We used novel Ti surfaces prepared by electrochemical micromachining as models to examine specific contributions of individual design features to osteoblast response. Results show that micron-scale topography modulates cell number, cell morphology and prostaglandin E2 (PGE2). In the presence of the appropriate microtopography, submicron-scale rugosity modulates differentiation and transforming growth factor-beta1 (TGF-beta1) levels. In this study, we examined the role of different types of submicron-scale structures. MATERIAL AND METHODS: Thirty micrometer diameter craters on Ti disks were produced by photolithography resulting in an electropolished smooth surface, and arranged so that inside crater area vs. outside flat area was 6 (30/6). Submicron-scale structures were superposed by acid etching and porous anodization. Ra's were 700, 400, 60 nm on acid-etched, porous anodized and smooth 30/6 surfaces, respectively. RESULTS: MG63 osteoblast-like cells were sensitive to submicron-scale architecture. Cell morphology on anodized surfaces was similar to morphology on smooth surfaces, whereas on etched surfaces, cells had a more elongated differentiated shape. Cell number was greatest on smooth surfaces > anodized > etched. Osteocalcin and PGE2 were affected in a reverse manner. Active TGF-beta1 was greatest on etched 30/6 surfaces > anodized > smooth; latent TGF-beta1 was elevated on all rough surfaces. CONCLUSIONS: These results support our previous observations that submicron-scale structures modulate osteoblastic phenotype and show that the physical properties of the submicron-scale structures are important variables in determining osteoblast response to substrate topography.

Acid Etching, Dental↗
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↗
PubMed2005

Nodal quasiparticles and antinodal charge ordering in Ca2-xNaxCuO2Cl2.

Understanding the role of competing states in the cuprates is essential for developing a theory for high-temperature superconductivity. We report angle-resolved photoemission spectroscopy experiments which probe the 4a0 x 4a0 charge-ordered state discovered by scanning tunneling microscopy in the lightly doped cuprate superconductor Ca2-xNaxCuO2Cl2. Our measurements reveal a marked dichotomy between the real- and momentum-space probes, for which charge ordering is emphasized in the tunneling measurements and photoemission is most sensitive to excitations near the node of the d-wave superconducting gap. These results emphasize the importance of momentum anisotropy in determining the complex electronic properties of the cuprates and places strong constraints on theoretical models of the charge-ordered state.

Journal Article↗
PubMed1977

Electron probe microanalysis in the study of gallstones.

Detailed information on the structure and composition of gallstones was obtained using an electron probe microanalyser in conjunction with the other methods. Gallstones were studied layer by layer without greatly disturbing the arrangement of the materials present. Elements, including trace elements such as copper, iron, and manganese, were identified and their distributions mapped. The range of the method was extended to determine the character and distribution of certain chemical groups present by treating sections of gallstone with reagents which contained easily detected elements. The nature of the bonding of the sulphur in the stones was studied by examining the sulphur-X-ray spectrum. Pigmented sulphur-containing deposits were found to contain sulphur in a low valence state but taurine conjugates and the sulphate groups of mucosubstances were not detected. Microcrystalline apatite present in the stones contained some manganese and seemed to be implicated in the absorption of the low valence sulphur compound and in the nucleation of some stones.

Calcium↗
PubMed1989

Tension and electrolyte changes with Na+-K+ pump inhibition in rat papillary muscle.

Myocardial ischemic injury results in altered membrane integrity, energy depletion, and electrolyte shifts leading to accumulation of intracellular Ca. However, analysis of the direct effects of Ca accumulation is complicated by other concomitant cellular changes produced by ischemia. The purpose of this study was to examine the effects of Ca loading in rat papillary muscles produced by Na+-K+ pump inhibition in oxygenated K+-free buffer. Changes in contractile characteristics, high energy phosphate, and elemental concentrations of subcellular compartments were measured. Electron probe X-ray microanalysis was used to assess elemental concentrations in cryosections. After 3 h of Na+-K+ pump inhibition, resting tension (RT) increased to 164% and developed tension (DT) fell to 16.8% of control values. One hour after return to complete buffer, RT and DT partially recovered but remained significantly different from the 180 to 240-min values for the control muscles. Electron probe X-ray microanalysis showed increases in cytoplasmic and mitochondrial Na and Ca and a decrease in K during Na+-K+ pump inhibition. Mitochondrial Ca was greater than 100-fold greater than Ca in control mitochondria. Morphologically, the majority of cells showed ultrastructural damage. The mean ATP level was 20% of control. After 1 h of recovery, the cells appeared more heterogeneous, and the mean mitochondrial Ca decreased, whereas mean cytoplasmic Ca increased. Further statistical analysis showed a bimodal distribution for Na, Ca, K, Mg, and Cl, which coincided with the morphologically mixed population of cells. This suggests that replacement of extracellular K+ was associated with restored electrolyte gradients in some cells and the persistent or further alteration of electrolytes in others. These results suggest that variable Ca accumulation and associated ATP depletion without the compounding effects of ischemia lead to cell injury similar to reperfusion injury reported in ischemic myocardium.

Adenosine Triphosphate↗
PubMed1983

Ionic distribution in dopamine-stimulated NaCl fluid-secreting cockroach salivary glands.

The compound, racemose, innervated salivary glands of the cockroach Periplaneta americana closely resemble in structure and function the mammalian salivary glands (C.R. House, Biol. Rev. 55: 417-473, 1980). The quantitative distribution of Na, K, Cl, Ca, Mg, P, and S was investigated in the P-cells secreting isotonic NaCl and in duct lumens by using electron probe X-ray microanalysis of frozen-hydrated and frozen-dried cryosections. In the unstimulated glands in vitro the cells had (mmol/l cell-H2O) Na, 10; K, 110; Cl, 39 while the primary saliva had Na, 153; K, 4; Cl, 151. With 1 mumol dopamine in the bathing Ringer solution the P-cells had Na, 25; K, 177; Cl, 58 and the primary saliva, Na, 153; K, 26; Cl, 172. During passage through the ducts, the primary saliva was modified by an absorption of NaCl: more in unstimulated than in stimulated glands. It is proposed that the cells have a Na-K-ATPase both in the apical and basal cell membrane, as in vertebrate choroid plexus, and dopamine might increase the K and Na conductance of the basal cell membrane.

Animals↗