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  • 1
    Electronic Resource
    Electronic Resource
    The Impermeant Ion Methylammonium Blocks K+ and NH+ 4 Currents through KAT1 Channel Differently: Evidence for Ion Interaction in Channel Permeation (1998)
    Springer
    The journal of membrane biology 163 (1998), S. 25-35 
    Details
    ISSN: 1432-1424
    Keywords: Key words: KAT1 — Potassium channel — Permeation — Block — Ammonium (NH+4) — Methylammonium (MA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. The permeation properties of KAT1, an inward rectifying potassium channel from plant cells, were investigated with different ions in the external medium. With either K+, NH+ 4 or methylammonium (MA) in the external solution, the channel, expressed in Xenopus oocytes, appeared permeable to K+ and, to a lesser extent, to NH+ 4 but not to the slightly bigger, methylated analogue of NH+ 4, MA. Substituting NH+ 4 for K+ shifted the voltage dependency of channel activation further negative and hastened activation kinetics. This suggests that channel operation depends on the transported substrate. In mixed solution (50 mm K+, 50 mm MA) MA inhibited K+ current in a voltage-independent manner. The maximum block did not exceed 50% of the K+ current. In contrast, when NH+ 4 was the permeant ion (50 mm NH+ 4, 50 mm MA) MA caused a voltage-dependent, slowly developing open channel block, achieving complete inhibition at very negative voltages. The latter block could be partially overcome by the addition of K+ in the external solution. The data support a model in which ions, after entering the channel pore, compete with different affinities for binding sites on their permeation pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900367
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  • 2
    Electronic Resource
    Electronic Resource
    Hydroxyapatite Coated Stainless-Steel External Fixation Pins (1997)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 250 (Sept. 1997), p. 231-0 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/02/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.250.231.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Quantitative analysis of the bone-hydroxyapatite coating interface (1995)
    Springer
    Journal of materials science 6 (1995), S. 455-459 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: The bone implant interface in stainless steel pins coated with hydroxyapatite, used in a monoaxial fracture external fixation system was examined. The pins were transversally inserted into sheep tibial diaphyses where a defect was created, and they were loaded for 6 weeks. Uncoated pins were implanted as control. The microscopic relation between bone and implant was quantified through image analysis: the residual thickness of the hydroxyapatite coating, pin-bone contact surface and bone ingrowth value in between the threads were measured. The bone tissue at the interface appeared regularly mineralized and viable both in the implants of coated pins and in the control uncoated ones. The ceramic coating showed a slight and not statistically significant increase in thickness. The ceramic coated pins presented contact with bone higher than the uncoated pins (75.6±20.0 versus 47.5±19.4); they also induced a higher bone ingrowth (86.6±22.4 versus 78.7±13.5). Both differences are not statistically significant, but suggestive of a trend. The authors concluded that the hydroxyapatite coating of the pins might improve the performance of external fixators, by favouring bone apposition and reducing rate of loosening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00123370
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  • 4
    Electronic Resource
    Electronic Resource
    X-ray diffraction of bone at the interface with hydroxyapatite-coated versus uncoated metal implants (1998)
    Springer
    Journal of materials science 9 (1998), S. 109-115 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The microstructural characteristics of the newly formed bone tissue at the interface with hydroxyapatite-coated and uncoated stainless steel pins used in an external fracture fixation system have been evaluated. The bone far from the interface was used as a control. Pins were transversally inserted into the diaphyses of sheep tibiae and were loaded in for six weeks. Three sheep received coated pins and two received uncoated pins. Crystallographic habit and mineralization of the implant-facing bone were evaluated. Moreover, lattice parameters of bone apatite were measured and hydroxyapatite (HA) coating degradation was investigated, by means of conventional and microbeam X-ray diffraction (XRD). In coated pins, six weeks after the implantation the newly formed bone tissue at the interface did not reach complete maturation, but the presence of the implant did not alter the apatite lattice structure; the lattice parameters did not show statistically significant variations with respect to those observed in the control bone. In uncoated pins, bone tissue rarely appeared totally mineralized and lattice parameters were significantly different with respect to those observed in the bone far from the implant. HA particles were observed spreading in the bone-facing coated pins; the XRD pattern of bone apatite surrounding HA particles was unmodified. It was concluded that HA coatings improved the bone remodelling process during pin fixation in comparison to uncoated pins and did not alter the crystallographic habit of apatite. © 1998 Chapman & Hall
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008855216755
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  • 5
    Electronic Resource
    Electronic Resource
    A non-destructive selection method for resistance to fusicoccin in Arabidopsis thaliana (1998)
    Springer
    Plant cell reports 18 (1998), S. 255-259 
    Details
    ISSN: 1432-203X
    Keywords: Key words Fusicoccin ; Arabidopsis thaliana ; Selection method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A mutagenised population of seeds of Arabidopsis thaliana was allowed to germinate in the presence of the positively charged aminoglycoside hygromycin (4 μg/ml) and the fungal toxin fusicoccin (5×10–6 m). This hygromycin concentration, which is non-toxic by itself, becomes toxic when used together with fusicoccin, which stimulates cation uptake. Seeds that had germinated after 3–5 days and produced seedlings with green cotyledons were potentially resistant to fusicoccin and were therefore transferred into sterile Magenta vessels containing 1/2-strength Murashige and Skoog medium. This selection procedure is non-destructive, i.e. it allows the recovery of viable seedlings and their growth into adult plants thus permitting direct physiological characterisation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990050567
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  • 6
    Electronic Resource
    Electronic Resource
    The seismic history of Catania (1999)
    Springer
    Journal of seismology 3 (1999), S. 235-252 
    Details
    ISSN: 1573-157X
    Keywords: Catania ; damage ; earthquakes ; eastern Sicily ; history ; macroseismics ; seismic hazard ; seismic risk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A detailed study of the most significant seismic effects that took place in the city of Catania has been performed in order to build up a site catalogue, to assess seismic hazard directly from it and to provide the picture of damage scenarios which happened in the past. In the last 1000 years Catania was destroyed twice (1169 and 1693) and more or less severely damaged twelve times (e.g., 1542, 1818, 1848, etc.). Destruction or severe damage are mainly related to earthquakes occurring in the coastal sector of the Hyblean foreland, while slighter, moderate effects are usually due to earthquakes taking place in the seismogenic sources of the Messina Straits and in the inner Hyblean region. The analysis of the historical reports allowed to delineate the damage scenarios of the most relevant events. In particular, for the 1693 case-history it has also been possible to map the damage distribution with reference to the existing urban settlement of the city. The site catalogue was used for assessing seismic hazard; the obtained estimates show that the probability of occurrence for intensity 7 and 10 exceeds 99.9% for 150 and 500 years, respectively. These values, associated with the high vulnerability caused by the city growth which occurred mainly before the introduction of the seismic code (1981) and without ad-hoc planning policies, implies that the urban system is exposed to high seismic risk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009818313629
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  • 7
    Electronic Resource
    Electronic Resource
    Protein synthesis and Golgi-mediated vesicle traffic is not required to maintain a polarised membrane voltage in the presence of auxin (1997)
    Springer
    Protoplasma 197 (1997), S. 182-187 
    Details
    ISSN: 1615-6102
    Keywords: Auxin ; Maize coleoptiles ; Membrane potential ; Cycloheximide ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The contribution of protein synthesis and secretion to indol acetic acid (IAA) induced polarisation of the plasma membrane voltage (V M) was investigated. TheV M of coleoptiles fromZea mays was measured in the presence of known inhibitors of protein- and RNA synthesis, as well as those of Golgi-mediated vesicle secretion. Inhibitors were applied under conditions at which they are known to abolish IAA stimulated H+ secretion and cell elongation effectively. Cycloheximide (CHI), an inhibitor of protein synthesis, caused depolarisation ofV M with a half maximal concentration of approximately 20 μM. At 100 μM CHI,V M depolarised to a new stable voltage with a half time of 9.8 ± 0.6 min. The temporal similarity of CHI-induced depolarisation and cessation of coleoptile elongation suggests that the induced change inV M underlies inhibition of elongation. CHI evoked membrane depolarisation to a final voltage of about −100 mV irrespective of the presence or absence of auxin in the external medium. Thus, CHI probably affected constitutive membrane transport properties independently of IAA-induced modulation of transport proteins. Cordycepin (COR), an inhibitor of RNA synthesis, had no significant effect at 400 μM onV M of IAA-treated cells, suggesting that gene transcription for transport- or regulatory protein synthesis was not essential for IAA-generated polarisation ofV M. Brefeldin-A (BFA), an inhibitor of Golgi-mediated vesicle secretion in maize coleoptiles, had no perceivable effect at 20 mg/1 onV M of IAA-treated coleoptile cells, demonstrating that constitutive or IAA-stimulated protein secretion was not essential for the mechanism underlying IAA-evokedV M polarisation. Hence, IAA-stimulated and COR/BFA-depressed H+ extrusion in elongating coleoptiles may not be entirely mediated by auxin-enhanced ATPase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01288027
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  • 8
    Electronic Resource
    Electronic Resource
    An approach for the processing engineer: Rheotechnics (1974)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 651-655 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Processing involves complex polymer flow problems, either in the melt or in solution. Rheologists have developed many studies with the aim of correlating polymer structure with flow properties and polymer processing. Most of these studies, however, have had relatively little impact on practical processing because of the difficulty in solving the mathematical equations involved. Recently, a relatively few papers have been published with the aim of bridging the gap between theoretical rheology and technology. The first part of the paper presents an account of works which have dealt with the process of filling a mold cavity. The second part discusses briefly some experimental results which provide a correlation between moldability and rheological properties. By analogy with the terms “electrology” and “electrotechnics,” the term “rheotechnics” is suggested for this new area of study.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760140911
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  • 9
    Electronic Resource
    Electronic Resource
    The interface of bone microstructure and an innovative coating: An X-ray diffraction study (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 86-91 
    Details
    ISSN: 0021-9304
    Keywords: X-ray diffraction ; ceramic ; external fixation ; coating ; biocompatibility ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The in vivo compatibility and degradation aspects of an innovative coating to be sprayed onto titanium implants were investigated. The surface of fluorinated apatite (fHA), consisting of fluorhydroxyapatite plasma sprayed in a vacuum atmosphere, was treated with carbonate to improve its biological compatibility. fHA coating was compared with titanium implants coated (a) with hydroxyapatite (HA) by the traditional plasma spraying, and (b) with titanium oxide (TiOx). Screw-shaped implants were inserted in the cortical bone of sheep tibiae. X-ray diffraction (XRD) analysis of bone tissue and coatings was carried out at 2, 4, 12 and 36 weeks after surgery. The crystallographic habit of the implant-facing bone, as well as the structural stability of the coating, were evaluated. For each time period and type of ceramic bone apatite lattice at the interface, no significantly different reference apatite lattice and no foreign peak were recorded. Two weeks after implantation, the bone at the interface was strongly unmineralized in all samples; after 4 weeks, poorly mineralized bone microareas decreased. At 12 weeks, the newly formed bone tissue at the interface with both the new coating and HA coating was shown to be fully mineralized; this crystallographic habit was retained at 36 weeks, when particle release from the tested material was lower compared to the controls. The XRD pattern of bone apatite surrounding the coating particles was unmodified. The innovative coating did not alter the mineralization process at the interface. It improved implant osteointegration, mainly due to a limited release of particles. Consequently, clinical performance of external fixation treatment could be improved by modifying the chemical composition of the implant surface. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 86-91, 1998.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Microhardness of bone at the interface with ceramic-coated metal implants (1995)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 695-699 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We evaluated bone microhardness at the interface with hydroxyapatite-coated stainless-steel pins used in an external fracture fixation system. Pins were transversally inserted into the diaphyses of sheep tibiae and were loaded in for 6 weeks. Uncoated pins were implanted as controls. Microhardness analysis, based on the measure of the resistance of the bone to the penetration of a small diamond pyramid, yielded an accurate and reproducible measure of the mineralization degree and of the orientation of collagen fibers. Bone tissue close to the pin is less hard than bone tissue far from it. Moreover, the presence of hydroxyapatite coating on the pins did not significantly affect bone hardness; actually, the mean hardness at the interface with the pins was 56.9 Vickers degrees, whereas at the interface with the uncoated pins it was 62.2. It can be concluded that, 6 weeks postsurgery, the bone growing into the threadings of a loaded screwed implant reached maturity at a degree lower than that of the host both uncoated and coated implants. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820290604
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