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  • Polymer and Materials Science  (8)
  • Key wordsSchizosaccharomyces pombe  (2)
  • Somatic embryogenesis  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Agrobacterium-mediated genetic transformation of California poppy, Eschscholzia californica Cham., via somatic embryogenesis (2000)
    Springer
    Plant cell reports 19 (2000), S. 1006-1012 
    Details
    ISSN: 1432-203X
    Keywords: Key words Agrobacterium tumefaciens ; Benzylisoquinoline alkaloids ; California poppy ; Eschscholzia californica Cham. ; Genetic transformation ; Somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  An efficient Agrobacterium-mediated protocol for the stable genetic transformation of Eschscholzia californica Cham. (California poppy) via somatic embryogenesis is reported. Excised cotyledons were co-cultivated with A. tumefaciens strain GV3101 carrying the pBI121 binary vector. Except for the co-cultivation medium, all formulations included 50 mg l−1 paromomycin as the selective agent and 200 mg l−1 timentin to eliminate the Agrobacterium. Four to five weeks after infection, paromomycin-resistant calli grew on 80% of explants in the presence of 2.0 mg l−1 1-naphthaleneacetic acid (NAA) and 0.1 mg l−1 6-benzylaminopurine (BAP). Calli were cultured on somatic embryogenesis induction medium containing 1.0 mg l−1 NAA and 0.5 mg l−1 BAP, and somatic embryos were visible on 30% of the paromomycin-resistant calli within 3–4 weeks. Three to four weeks after the somatic embryos were transferred to phytohormone-free plant regeneration medium, 32% converted to paromomycin-resistant plants. Detection of the neomycin phosphotransferase gene and high levels of β-glucuronidase (GUS) mRNA and enzyme activity, and the cytohistochemical localization of GUS activity in all plant tissues confirmed the integrative transformation of the regenerated plants. The normal alkaloid profile of California poppy was unaffected by the transformation process; thus, the reported protocol could serve as a valuable tool to investigate the molecular and metabolic regulation of the benzophenanthridine alkaloid pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990000213
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  • 2
    Electronic Resource
    Electronic Resource
    High-efficiency somatic embryogenesis and plant regeneration in California poppy, Eschscholzia californica Cham. (2000)
    Springer
    Plant cell reports 19 (2000), S. 421-426 
    Details
    ISSN: 1432-203X
    Keywords: Key words California poppy ; Eschscholzia californica ; Plant regeneration ; Somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The development of a rapid protocol for high-efficiency somatic embryogenesis and plant regeneration from seed-derived embryogenic callus cultures of California poppy (Eschscholzia californica Cham.) is reported. The optimized procedure required less than 13 weeks from the initiation of seed cultures to the recovery of plantlets and involved the sequential transfer of cultures onto solid Murashige and Skoog basal medium containing three different combinations of growth regulators. All steps were performed at 25  °C. Friable primary callus was induced from seeds of E. californica cultured on medium supplemented with 1.0 mg l−1 2,4-dichlorophenoxyacetic acid. The primary callus was transferred to medium containing 1.0 mg l−1 1-naphthaleneacetic acid and 0.5 mg l−1 6-benzylaminopurine to establish embryogenic callus and promote somatic embryogenesis. Regenerated plantlets were recovered after the conversion of somatic embryos on medium containing 0.05 mg l−1 6-benzylaminopurine and showed normal development. Embryogenic callus was induced at a frequency of 85%, an average of 45 somatic embryos were produced per callus, 90% of the somatic embryos converted, and about 70% of the plantlets were recovered in soil. The growth rate of somatic embryo-derived shoots could be increased by gibberellic acid treatment, but the resulting plantlets were hyperhydritic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990050750
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  • 3
    Electronic Resource
    Electronic Resource
    Identification of the DNA damage-responsive elements of the rhp51 + gene, a recA and RAD51 homolog from the fission yeast Schizosaccharomyces pombe (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 167-175 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsSchizosaccharomyces pombe ; DNA-damage inducibility ; Damage-responsive element ; Upstream activating sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Schizosaccharomyces pombe rhp51 + gene encodes a recombinational repair protein that shares significant sequence identities with the bacterial RecA and the Saccharomyces cerevisiae 1RAD51 protein. Levels of rhp51 + mRNA increase following several types of DNA damage or inhibition of DNA synthesis. An rhp51:: ura4 fusion gene was used to identify the cis-acting promoter elements involved in regulating rhp51 + expression in response to DNA damage. Two elements, designated DRE1 and DRE2 (for damage-responsive element), match a decamer consensus URS (upstream repressing sequence) found in the promoters of many other DNA repair and metabolism genes from S. cerevisiae. However, our results show that DRE1 and DRE2 each function as a UAS (upstream activating sequence) rather than a URS and are also required for DNA-damage inducibility of the gene. A 20-bp fragment located downstream of both DRE1 and DRE2 is responsible for URS function. The DRE1 and DRE2 elements cross-competed for binding to two proteins of 45 and 59 kDa. DNase I footprint analysis suggests that DRE1 and DRE2 bind to the same DNA-binding proteins. These results suggest that the DRE-binding proteins may play an important role in the DNA-damage inducibility of rhp51 + expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02172915
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  • 4
    Electronic Resource
    Electronic Resource
    Isolation and characterization of hrp1 +, a new member of the SNF2/SWI2 gene family from the fission yeast Schizosaccharomyces pombe (1998)
    Springer
    Molecular genetics and genomics 257 (1998), S. 319-329 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsSchizosaccharomyces pombe ; SNF2/SWI2 protein family ; ATPase/helicase domains ; DNA-binding domain ; Chromodomain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The SNF2/SWI2 ATPase/helicase family comprises proteins from a variety of species, which serve a number of functions, such as transcriptional regulation, maintenance of chromosome stability during mitosis, and various types of DNA repair. Several proteins with unknown functions are also included in this family. The number of genes that belong to this family is rapidly expanding, which makes it easier to analyze the common biological functions of the family members. This study was designed to clone the SNF2/SWI2 helicase-related genes from the fission yeast Schizosaccharomyces pombe in the hope that this would help to elucidate the common functions of the proteins in this family. The hrp1 + (helicase-related gene from S. p ombe) gene was initially cloned by PCR amplification using degenerate primers based on conserved SNF2 motifs within the ERCC6 gene, which encodes a protein involved in DNA excision repair. The hrp1 + ORF codes for an 1373-amino acid polypeptide with a molecular mass of 159 kDa. Like other SNF2/SWI2 family proteins, the deduced amino acid sequence of Hrp1 contains DNA-dependent ATPase/7 helicase domains, as well as a chromodomain and a DNA-binding domain. This configuration is similar to that of mCHD1 (mouse chromo-ATPase/helicase-DNA-binding protein 1), suggesting that Hrp1 is a S. pombe homolog of mCHD1, which is thought to function in altering the chromatin structure to facilitate gene expression. Northern blot analysis showed that the hrp1 + gene produces a 4.6-kb transcript, which reaches its maximal level just before the cells enter the exponential growth phase, and then decreases gradually. DNA-damaging agents, such as MMS, MNNG and UV, decrease the rate of transcription of hrp1 +. Deletion of the hrp1 + gene resulted in accelerated cell growth. On the other hand, overexpression of Hrp1 caused a reduction in growth rate. These results indicate that hrp1 + may act as a negative regulator of cellular growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380050653
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  • 5
    Electronic Resource
    Electronic Resource
    Einfluß der Korngröße auf mechanische Eigenschaften und den ungeschmierten reversierenden Gleitverschleiß von Al2O3-Keramik (1992)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 329-338 
    Details
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Influence of grain size on mechanical properties and dry oscillating sliding wear of Al2O3-ceramicsSpecimens with average grain sizes varying between about 0.8 μm and 12 μm were produced by cold isostatic pressing of high purity Al2O3-powder followed by sintering between 1300°C and 1700°C. Hardness, Young's modulus, bending strength and fracture toughness were measured as a function of average grain sizes. Tribological tests were carried out on the different microstructures at normal laboratory air and room temperature by using a ring-on-block tribometer.Experimental results showed the dependence of mechanical properties on grain size, hardness and bending strength obeying a Hall-Petch type relation, approximately. Coefficient of friction was relatively independent of grain size under the test conditions used. However, wear intensity increased substantially if a critical grain size was surpassed. This was due to a change in mechanisms of material removal which was confirmed by scanning electron microscopical studies of the worn surfaces.
    Notes: Aus hochreinem Al2O3-Pulver wurden durch kaltisostatisches Pressen und Variation der Sintertemperatur zwischen 1300°C und 1700°C Formkörper mit unterschiedlichen mittleren Korngrößen zwischen etwa 0,8 und 12 μm hergestellt. Untersucht wurde der Einfluß der Korngröße auf mechanische und tribologische Eigen-schaften.Die Ergebnisse zeigten, daß mechanische Eigenschaften wie Härte, E-Modul, Biegebruchfestigkeit und Bruchzähigkeit von der Korngröße bzw. den Sintertemperaturen abhingen, wobei im Fall der Härte und Bruchfestigkeit näiherungsweise eine Hall-Peteh-Beziehung vorlag. Während die Reibungszahl relativ unabhängig von der Korngröße war, trat in der Verschleißintensität aufgrund geänderter Mechanismen ein starker Anstieg mit zunchmender Korngröße auf. Rasterelektronenmikroskopische Untersuchungen zeigten, daß der Verschleiß durch plastische Verformung, Mikrobruch, Kornfragmentierung und Deckschichten beeinflußt wurde.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19920230909
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  • 6
    Electronic Resource
    Electronic Resource
    Application of extracorporeal shock wave lithotripter (ECSWL) in orthopaedics. III. In Vitro and In Vivo studiesPart of this work was presented to the Society for Biomaterials and Orthopedic Research Society annual meetings. (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 171-181 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The present study was conducted to compare the push-out strength of the treated and control samples obtained after implantation of intramedullary rod in canine femurs with bone cement to simulate the femoral stem implantation for 2 weeks, 3 and 6 months. Contralateral femur served as control. The result showed a significant decrease in push-out interfacial strength after shock wave treatment (average 48.4% decrease compared with control, p 〈 0.0001) which is similar to the in vitro results. There was no significant difference if the shock treatment was applied and left for 2 weeks or 4 weeks compared to the ones tested immediately after sacrifice. There were some soft tissue damage immediately following shock treatment in the focal area but this returned to normal in 2 weeks. Human cadaveric femoral bones and the canine bone (the dosage level was higher for the human bone than canine). The number of impacts used to extract the bone cement plug out of a human femur segment (5-cm long) decreased about 68% at 23 and 25 kV treatment power level. These preliminary studies indicate that the shock wave can be utilized to reduce the interfacial strength of the bone and bone cement although more studies are needed to assess its efficacy in terms of cost, long-term effect on patients and the exact mechanism of the loosening before this technique can be used clinically.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770020305
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  • 7
    Electronic Resource
    Electronic Resource
    Application of extracorporeal shock wave lithotripter (ECSWL) in orthopaedics. II. Dose-response and pressure distribution measurements (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 161-170 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In order to apply the extracorporeal shock wave lithotripter (ECWSL) technique to the loosening of the bone-cement interface for the extraction of the cement during revision arthroplasty it is essential to know the dose-response characteristics. The present study shows that the number of shocks needed to break the interface between a 2- and 6-mm-thick bovine femoral bone and bone cement is similar to the fatigue behavior of a material, that is, Log(N) = C(kV) + D, where N is the number of shock impulses, kV is the power setting of the lithotripter machine in kilovolts, and C and D are constants. Iso-pressure distribution of the traveling shock wave front through a simulated bone in a Plexiglass® tube using Fuji® pressure film showed quantitative pressure contours from which one can understand the effective area of shock wave and its distribution. The most effective area of the shock wave was about 1.5 cm in diameter at 23 and 25 kV with pressure at least 7.0 MPa which is more than sufficient to break the bone-cement interface in tension.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770020304
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  • 8
    Electronic Resource
    Electronic Resource
    Application of extracorporeal shock wave lithotripter (ECSWL) in orthopedics. I. Foundations and overviewParts of this paper were presented at the Society for Biomaterials and Orthopedic Research Society Annual meetings. (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 115-126 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In this paper we have reviewed the feasibility of using a shock wave lithotripter to loosen the interface between the bone and acrylic bone cement for revision arthroplasty. We have reviewed the physics of shock wave and its applications in medicine, especially its interaction with tissues. The calculations show that the energy is greatly reduced at the interface both in the soft tissue-bone interface and cement-bone interface. On the other hand, a tensile and compressive pressure can be operated at the cement-bone interface that can cause the interface to break if the pressure exceeds the tensile strength of the cement-bone interface.Subsequent papers will deal with in vitro and in vivo application of the shock wave in the treatment of the cement-bone interface in order to weaken it and consequently for easier extraction of bone cement from the intramedullary canal.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770020207
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  • 9
    Electronic Resource
    Electronic Resource
    Biodegradable sponges for hepatocyte transplantation (1995)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 959-965 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Liver cell transplantation may provide a means to replace lost or deficient liver tissue, but devices capable of delivering hepatocytes to a desirable anatomic location and guiding the development of a new tissue from these cells and the host tissue are needed. We have investigated whether sponges fabricated from poly-L-lactic acid (PLA) infiltrated with polyvinyl alcohol (PVA) would meet these requirements. Highly porous sponges (porosity = 90-95%) were fabricated from PLA using a particulate leaching technique. To enable even and efficient cell seeding, the devices were infiltrated with the hydrophilic polymer polyvinyl alcohol (PVA). This reduced their contact angle with water from 79 to 23°, but did not inhibit the ability of hepatocytes to adhere to the polymer. Porous sponges of PLA infiltrated with PVA readily absorbed aqueous solutions into 98% of their pore volume, and could be evenly seeded with high densities (5 × 107 cells/mL) of hepatocytes. Hepatocyte-seeded devices were implanted into the mesentery of laboratory rats, and 6 ± 2 × 105 of the hepatocytes engrafted per sponge. Fibrovascular tissue invaded through the devices' pores, leading to a composite tissue consisting of hepatocytes, blood vessels and fibrous tissue, and the polymer sponge. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820290807
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  • 10
    Electronic Resource
    Electronic Resource
    Potentiometric anion selectivities of polymer membranes doped with indium(III)-porphyrins (1991)
    Weinheim : Wiley-Blackwell
    Electroanalysis 3 (1991), S. 909-916 
    Details
    ISSN: 1040-0397
    Keywords: Indium ; potentiometry ; membrane ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potentiometric anion responses of polymeric membranes doped with various indium (III)-porphyrin structures are examined. The appropriate membranes are prepared by incorporating 1.0 wt % of the In(III)-porphyrins in plasticized poly(vinyl chloride) films. When such membranes are incorporated within standard ion selective electrode bodies, the resulting electrodes display non-Hofmeister anion selectivity, with a particularly enhanced and super-Nernstian response to chloride. Among those porphyrins investigated, membranes doped with chloro(octaethylporphyrinato)indium(III) yield the largest and most reproducible potentiometric anion responses. These same membrane electrodes exhibit negligible response to protons (or hydroxide) in the range of pH 4.5-9.0. When utilized as a flow-injection detector in conjunction with a protein diluent/buffer stream, the In(III)-porphyrin based electrodes may be used to determine chloride levels in human serum samples.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140030906
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