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  • 1
    Electronic Resource
    Electronic Resource
    Evidence for a direct relationship between mitochondrial genome organization and regeneration ability in hexaploid wheat somatic tissue cultures (1988)
    Springer
    Current genetics 14 (1988), S. 387-394 
    Details
    ISSN: 1432-0983
    Keywords: Triticum aestivum ; Genomic variability ; Mitochondrial DNA ; Somatic tissue culture ; Regeneration ability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Embryogenic and non-embryogenic long-term callus cultures of hexaploid wheat exhibit differences in the organization of their mitochondrial genome. Embryogenic and non-embryogenic fractions of callus cultures initiated from immature embryos of the wheat cultivar “Chinese Spring” have been isolated and subsequently subcultured. DNA-DNA hybridization experiments using labelled cloned wheat mitochondrial DNA fragments have shown that the mitochondrial DNA organization of embryogenic subcultures derived from embryogenic parts of “Chinese Spring” calli is closely related to that of the initial “Chinese Spring” calli, while non-embryogenic subcultures derived from non-embryogenic fragments of “Chinese Spring” calli exhibit a mitochondrial DNA organization similar to that found in non-embryogenic calli derived from cultivar “Aquila”. In addition, somatic tissue cultures initiated from three other non-embryogenic wheat cultivars (“Talent”, “Thésée” and “Capitole”) display mitochondrial DNA arrangements similar to those found in cultivar “Aquila”. These results strongly suggest that, in wheat callus cultures, a particular mitochondrial genome organization is correlated with the ability of cultured cells to regenerate whole plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00419997
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  • 2
    Electronic Resource
    Electronic Resource
    Nuclear genes control changes in the organization of the mitochondrial genome in tissue cultures derived from immature embryos of wheat (1992)
    Springer
    Current genetics 21 (1992), S. 515-520 
    Details
    ISSN: 1432-0983
    Keywords: Nuclear-cytoplasmic interactions ; Mitochondrial genome ; Chondriome variability ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Although the mitochondrial genomes of the Chinese Spring and Aquila varieties of wheat are normaly similar in organization, this is not so in tissue cultures initiated from their immature embryos where the mitochondrial genomes of both are rearranged and in different, characteristic, ways. However, the mitochondrial genomes of tissue cultures of reciprocal F1 crosses between these varieties were almost identical to one another, showing that nuclear genes control the rearrangement processes. These rearrangements are either due to the appearance of new structures or else result from changes in the relative amounts of subgenomic components. The severe reduction in the amount of certain molecular configurations in tissue cultures from reciprocal crosses is probably due to the presence of dominant information in the Aquila nuclear genome. Data obtained from tissue cultures initiated from F2 embryos of the cross Aquila x Chinese Spring suggest that at least two complementary genes are involved in this control. In contrast, the presence of new molecular arrangements appears to be under the control of a dominant allelic form of a Chinese Spring gene or genes. Thus, this study demonstrates that at least two sets of nuclear genes control the reorganization of the mitochondrial genome which occurs when tissue cultures are initiated from the immature embryos of wheat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351662
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  • 3
    Electronic Resource
    Electronic Resource
    Extensive mitochondrial DNA variation in somatic tissue cultures initiated from wheat immature embryos (1987)
    Springer
    Current genetics 12 (1987), S. 369-376 
    Details
    ISSN: 1432-0983
    Keywords: Triticum aestivum ; Tissue culture ; Mitochondrial DNA ; Genomic variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Wheat mitochondria) DNA has been isolated from callus cultures initiated from both immature embryos and the corresponding parental cultivar. A Sall restriction pattern study has shown that the organization of callus culture mitochondria) DNA underwent extensive change, characterized by either the disappearance or the decrease in the relative stoichiometry of several restriction bands. Hybridization of labelled mitochondrial fragments obtained from a recombinant cosmid library to Southern blots of callus and parental line restricted mitochondria) DNAs has shown that a fraction of the mitochondria) genome was lost in callus cultures. Data from a Sall + HindIII restriction map of a defined part of the wheat mitochondria) genome concerned with some of these variations strongly suggest that the observed variations correspond to the disappearance of at least one mitochondria) DNA subgenomic molecule in callus cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00405759
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  • 4
    Electronic Resource
    Electronic Resource
    Mitochondrial DNA variability detected in a single wheat regenerant involves a rare recombination event across a short repeat (1994)
    Springer
    Current genetics 25 (1994), S. 456-464 
    Details
    ISSN: 1432-0983
    Keywords: Reciprocal recombination ; Mitochondrial genome ; Chondriome variability ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mitochondrial genome of the selfed progeny of a plant regenerated from long-term somatic tissue culture displays specific structural rearrangements characterized by the appearance of novel restriction fragments. A mitochondrial DNA library was constructed from this selfed progeny in the SalI site of cosmid pHC79 and the novel fragments were subsequently studied. They were shown to arise from reciprocal recombination events involving DNA sequences present in the parental plant. The regions of recombination were sequenced and the nucleotide sequences were aligned with those of the presumptive parental fragments. We characterized an imperfect short repeated DNA sequence, 242 bp long, within which a 7-bb DNA repeat could act as a region of recombination. The use of PCR technology allowed us to show that these fragments were present in both parental plants and tissue cultures as low-abundance sequence arrangements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351786
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  • 5
    Electronic Resource
    Electronic Resource
    Detailed kinetics of titanium nitride synthesis (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 377-388 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A thermogravimetric analyzer is used to study the synthesis of TiN from Ti powder over a wide range of temperature, conversion and heating rate, and for two Ti precursor powders with different morphologies. Conversions to TiN up to 99% are obtained with negligible oxygen contamination. Nonisothermal initial rate and isothermal data are used in a nonlinear least-squares minimization to determine the most appropriate rate law. The logarithmic rate law offers an excellent agreement between the experimental and calculated conversions to TiN and can predict afterburning, which is an important experimentally observed phenomenon. Due to the form of the logarithmic rate law, the observed activation energy is a function of effective particle size, extent of conversion, and temperature even when the intrinsic activation energy remains constant. This aspect explains discrepancies among activation energies obtained in previous studies. The frequently used sedimentation particle size is a poor measure of the powder reactivity. The BET surface area indicates the powder reactivity much better.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410219
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  • 6
    Electronic Resource
    Electronic Resource
    Noncatalytic gas-solid reactions and mechanical stress generation (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1235-1250 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The reaction rate in gas-solid systems can be affected by mechanical stresses that arise as the reaction proceeds. Stresses develop due to differences between precursor and product molar volumes and thermal expansion coefficients. Experimental evidence on the interaction of reaction rate and mechanical stress for the Ti/N2 and Ti/O2 systems is provided. A detailed and consistent mathematical model is developed for the reaction taking place at the constrained precursor/product interface. An elastic formulation for the stresses is adopted, and stress generation due to mismatches in linear thermal expansion coefficients and equivalent volume (Pilling-Bedworth ratio) for the precursor and product are considered. The effect of surface energy, which becomes significant for particle sizes below 1 μm, is also included in the model. Both experimentally and theoretically, conditions exist where the mechanical stresses exceed the strength of the material, leading to mechanical breakdown of the product layer, thus causing a discontinuity in the observed reaction rate. The entire processing history, including the reaction, temperature, and pressure profiles, plays an important role in determining the overall reaction kinetics of the powder.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410519
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  • 7
    Electronic Resource
    Electronic Resource
    Reaction rate modeling in noncatalytic gas-solid systems: Species transport and mechanical stress (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2614-2624 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A detailed model to describe the overall reaction rate of the oxidation of titanium is developed. The mathematical model consists of two facets, the first of which involves a detailed description of species transport that accounts for the formation of charged species. This is augmented by a description of the occurrence of mechanical stress due to a Pilling - Bedworth ratio that differs significantly from I as well as differences between precursor and product thermal expansion coefficients. A self imposed electric field is formed across the oxide layer due to different mobilities of the species considered. This field opposes the transport of electrons and enhances the transport of anion vacancies, thus increasing the overall reaction rate compared to a pure diffusion process, while also ensuring that electrical charge is conserved. Large growth stresses result from the unmatched precursor and product volumes, significantly affecting the overall process. These results show that the incorporation of a consistent treatment of mechanical stress forms a necessay part of any accurate description of the overall behavior of a reacting particle.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411210
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