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  • 1
    Electronic Resource
    Electronic Resource
    Gene conversion of ribosomal DNA in Nicotiana tabacum is associated with undermethylated, decondensed and probably active gene units (2000)
    Springer
    Chromosoma 109 (2000), S. 161-172 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. We examined the structure, intranuclear distribution and activity of ribosomal DNA (rDNA) in Nico-tiana sylvestris (2n=2x=24) and N. tomentosiformis (2n=2x=24) and compared these with patterns in N. tabacum (tobacco, 2n=4x=48). We also examined a long-established N. tabacum culture, TBY-2. Nicotiana tabacum is an allotetraploid thought to be derived from ancestors of N. sylvestris (S-genome donor) and N. tomentosiformis (T-genome donor). Nicotiana sylvestris has three rDNA loci, one locus each on chromosomes 10, 11, and 12. In root-tip meristematic interphase cells, the site on chromosome 12 remains condensed and inactive, while the sites on chromosomes 10 and 11 show activity at the proximal end of the locus only. Nicotiana tomentosiformis has one major locus on chromosome 3 showing activity and a minor, inactive locus on chromosome 11. In N. tabacum cv. 095-55, there are four rDNA loci on T3, S10, S11/t and S12 (S11/t carries a small T-genome translocation). The locus on S12 remains condensed and inactive in root-tip meristematic cells while the others show activity, including decondensation at interphase and secondary constrictions at metaphase. Nicotiana tabacum DNA digested with methylcytosine-sensitive enzymes revealed a hybridisation pattern for rDNA that resembled that of N. tomentosiformis and not N. sylvestris. The data indicate that active, undermethylated genes are of the N. tomentosiformis type. Since S-genome chromosomes of N. tabacum show rDNA expression, the result indicates rDNA gene conversion of the active rDNA units on these chromosomes. Gene conversion in N. tabacum is consistent with the results of previous work. However, using primers specific for the S-genome rDNA intergenic sequences (IGS) in the polymerase chain reaction (PCR) show that rDNA gene conversion has not gone to completion in N. tabacum. Furthermore, using methylation-insensitive restriction enzymes we demonstrate that about 8% of the rDNA units remain of the N. sylvestris type (from ca. 75% based on the sum of the rDNA copy numbers in the parents). Since the active genes are likely to be of an N. tomentosiformis type, the N. sylvestris type units are presumably contained within inactive loci (i.e. on chromosome S12). Nicotiana sylvestris has approximately three times as much rDNA as the other two species, resulting in much condensed rDNA at interphase. This species also has three classes of IGS, indicating gene conversion has not homogenised repeat length in this species. The results suggest that methylation and/or DNA condensation has reduced or prevented gene conversion from occurring at inactive genes at rDNA loci. Alternatively, active undermethylated units may be vulnerable to gene conversion, perhaps because they are decondensed and located in close proximity within the nucleolus at interphase. In TBY-2, restriction enzymes showed hybridisation patterns that were similar to, but different from, those of N. tabacum. In addition, TBY-2 has elevated rDNA copy number and variable numbers of rDNA loci, all indicating rDNA evolution in culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050424
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular cytogenetic analyses and phylogenetic studies in the Nicotiana section Tomentosae (2000)
    Springer
    Chromosoma 109 (2000), S. 245-258 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Phylogenetic schemes based on changing DNA sequence have made a major impact on our understanding of evolutionary relationships and significantly built on knowledge gained by morphological and anatomical studies. Here we present another approach to phylogeny, using fluorescent in situ hybridisation. The phylogenetic scheme presented is likely to be robust since it is derived from the chromosomal distribution of ten repetitive sequences with different functions and evolutionary constraints [GRS, HRS60, NTRS, the Arabidopsis-type telomere repeat (TTTAGGG)n, 18S-5.8S-26S ribosomal DNA (rDNA), 5S rDNA, and four classes of geminiviral-related DNA (GRD)]. The basic karyotypes of all the plant species investigated Nicotiana tomentosiformis, N. kawakamii, N. tomentosa, N. otophora, N. setchellii, N. glutinosa (all section Tomentosae), and N. tabacum (tobacco, section Genuinae) are similar (x=12) but the distribution of genic and non-genic repeats is quite variable, making the karyotypes distinct. We found sequence dispersal, and locus gain, amplification and loss, all within the regular framework of the basic genomic structure. We predict that the GRD classes of sequence integrated into an ancestral genome only once in the evolution of section Tomentosae and thereafter spread by vertical transmission and speciation into four species. Since GRD is similar to a transgenic construct that was inserted into the N. tabacum genome, its fate over evolutionary time is interesting in the context of the debate on genetically modified organisms and the escape of genes into the wild. Nicotiana tabacum is thought to be an allotetraploid between presumed progenitors of N. sylvestris (maternal, S-genome donor) and a member of section Tomentosae (T-genome donor). Of section Tomentosae, N. tomentosiformis has the most similar genome to the T genome of tobacco and is therefore the most likely paternal genome donor. It is known for N. tabacum that gene conversion has converted most 18S-5.8S-26S rDNA units of N. sylvestris origin into units of an N. tomentosiformis type. Clearly if such a phenomenon were widespread across the genome, genomic in situ hybridisation (GISH) to distinguish the S and T genomes would probably not work since conversion would tend to homogenise the genomes. The fact that GISH does work suggests a limited role for gene conversion in the evolution of N. tabacum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120000074
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of coatings which inhibit epoxy bleeding in electronic packaging (1997)
    Springer
    Journal of materials science 8 (1997), S. 73-77 
    Details
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The bleeding of epoxy resin around surfaces, undergoing bonding in electronic packaging assembly, has for long caused sporadic yield-loss. This loss is more severe in advanced and dense packages. Previously it has been supposed that the loss results from surface contaminants which are reduced by vacuum bakeout. In fact, that procedure generates coatings of hydrocarbons as we show by surface analysis. The coatings very strongly affect the wettabilities and measured surface energies of substrates. In particular, the comparatively low surface energy of hydrocarbon films on gold surfaces shows how the surfaces can be engineered, with coatings of “appropriate cleanliness”, to systematically inhibit epoxy bleeding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018561106025
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  • 4
    Electronic Resource
    Electronic Resource
    ‘Complete’ trisomy 5p; de novo translocation t(2;5)(q36;p11) with isochromosome 5p (1979)
    Springer
    Human genetics 〈Berlin〉 46 (1979), S. 271-278 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A case of complete trisomy 5p due to a de novo translocation t(2;5)(q36;p11) with an isochromosome 5p is described. Complete trisomy 5p has been reported only once (Brimblecombe et al., 1977). The confusing literature relating to partial trisomy 5p is reviewed. Comparison of our case with the patients reported by Brimblecombe et al. (1977) and by Opitz and Patau (1975) is suggestive for a distinct clinical syndrome if (almost) the complete short arm of chromosome 5 is present in a trisomic state. Unfortunately the clinical findings in the case of Brimblecombe (1966, 1977) are poorly documented. The main features of this syndrome are: macrocephaly, psychomotor retardation, hypotonia, postnatal growth failure, tracheobronchial involvement, mongoloid slant of the eyes, epicanthus, low-set ears, depressed nasal bridge, short first toe, and seizures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00273310
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  • 5
    Electronic Resource
    Electronic Resource
    Gemeinsame Einwirkung von elementarem Schwefel und Äthylenimin auf Diäthylketon (1968)
    Springer
    Monatshefte für Chemie 99 (1968), S. 2090-2094 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract 2-Methyl-3-ethyl-5.6-dihydro-4H-1.4-thiazine (1) may be synthesised in 75% yield by the concomitant action of sulphur and ethylene imine upon diethyl ketone.
    Notes: Zusammenfassung 2-Methyl-3-äthyl-5,6-dihydro-4H-1,4-thiazin (1) läßt sich in 75proz. Ausb. durch die gemeinsame Einwirkung von Schwefel und Äthylenimin auf Diäthylketon darstellen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00904344
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  • 6
    Electronic Resource
    Electronic Resource
    Gemeinsame Einwirkung von elementarem Schwefel und Äthylenimin auf Ketone, 3. Mitt.: Über die gemeinsame Einwirkung von elementarem Schwefel und gasförmigem Ammoniak auf Ketone, 74. Mitt. (1971)
    Springer
    Monatshefte für Chemie 102 (1971), S. 321-332 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract The reaction of ethylenimine and sulfur with methyl ethyl ketone, methyl isopropyl ketone and ethyl isopropyl ketone, resp., yields the structurally isomeric 5.6-dihydro-1.4-thiazines (1–6) and as by-products the thiazolidines (7–9) derived from the corresponding ketones. The 5.6-dihydro-1.4-thiazines are converted with formic acid to the N-formyl thiomorpholines10–15, which are easily hydrolyzed with dilute hydrochloric acid to the corresponding thiomorpholines (16–21). The ratio of the pairs of structurally isomeric thiomorpholines is determined by quantitative gas chromatography.
    Notes: Zusammenfassung Bei der Einwirkung von Äthylenimin und Schwefel auf Methyläthylketon, Methylisopropylketon und Äthylisopropylketon entstehen strukturisomere 5,6-Dihydro-1,4-thiazine (1–6) und als Nebenprodukte die dem jeweiligen Keton entsprechenden Thiazolidine (7–9). Die 5,6-Dihydro-1,4-thiazine werden mit Ameisensäure in N-Formylthiomorpholine (10–15) übergeführt, die mit verd. HCl glatt zu den entsprechenden Thiomorpholinen (16–21) hydrolysiert werden. Das Verhältnis der Thiomorpholin-Isomerenpaare wird gaschromatographisch quantitativ bestimmt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00909244
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  • 7
    Electronic Resource
    Electronic Resource
    Genomic characterisation and the detection of raspberry chromatin in polyploid Rubus (1998)
    Springer
    Theoretical and applied genetics 97 (1998), S. 1027-1033 
    Details
    ISSN: 1432-2242
    Keywords: Key words Rubus ; Allopolyploid ; rDNA ; Karyotype ; Rosaceae ; FISH ; GISH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  This paper reports genomic in situ hybridization (GISH) and fluorescent in situ hybridization (FISH) data for chromosomes of raspberry (Rubus idaeus 2n=2x=14), blackberry (Rubus aggregate, subgenus Eubatus. 2n=2–12x=14–84) and their allopolyploid derivatives used in fruit breeding programmes. GISH was used to discriminate labelled chromosomes of raspberry origin from those of blackberry origin in allopolyploid hybrid plants. The raspberry chromosomes were labelled by GISH at their centromeres, and 1 chromosome was also labelled over the short arm. In one allopentaploid plant a chromosome carried a terminal signal. Karyotype analysis indicated that this is a blackberry chromosome carrying a raspberry translocation. GISH analysis of an aneuoctaploid blackberry cv ‘Aurora’ (2n=8x=58) showed that both whole and translocated raspberry chromosomes were present. The basic Rubus genome has one ribosomal DNA (rDNA) locus, and in all but one case all levels of ploidy had the expected multiples of rDNA loci. Interestingly, in the blackberry cv ‘Aurora’, there were only six sites, two less than might be predicted from its aneuoctaploid chromosome number. Our results highlight the potential of GISH and FISH for genomic designation, physical mapping and introgression studies in Rosaceous fruit crops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050987
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  • 8
    Electronic Resource
    Electronic Resource
    Gemeinsame Einwirkung von elementarem Schwefel und Äthylenimin auf Ketone, 2. Mitt. (1970)
    Springer
    Monatshefte für Chemie 101 (1970), S. 1281-1294 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract The interaction of sulfur and ethylenimine with 4-heptanone, cyclopentanone, cyclohexanone, and cyclooctanone leads to 5.6-dihydro-4H-1.4-thiazines (3–6) in good yields. As byproducts of3, 4 and5 2.2-dialkylated thiazolidines (7–9, resp.) are isolated. When this reaction is carried out with phenyl isopropyl ketone, however, the main product is 2-isopropyl-2-phenylthiazolidine (12), the corresponding 5.6-dihydro-2H-1.4-thiazine (11) is but formed in a small quantity. The mechanisms of the formation of 5.6-dihydro-1.4-thiazines, as well as the formation of the thiazolidines are discussed. Reaction of 5.6-dihydro-1.4-thiazines (1, 3–5, 11) with excess formic acid leads to N-formylthiomorpholines (13–17) which can be easily saponified with dil. HCl to the corresponding thiomorpholines (18–22).
    Notes: Zusammenfassung Bei der gemeinsamen Einwirkung von Schwefel und Äthylenimin auf 4-Heptanon, Cyclopentanon, Cyclohexanon und Cyclooctanon bilden sich in glatter Reaktion 5,6-Dihydro-4H-1,4-thiazine (3–6). Als Nebenprodukte von3, 4 und5 fallen die dem jeweiligen Keton zugrunde liegenden 2,2-dialkylierten Thiazolidine (7–9) an. Bei Einsatz von Phenylisopropylketon in diese Reaktion wird dagegen das 2-Isopropyl-2-phenylthiazolidin (12) zum Hauptprodukt, während das entsprechende 5,6-Dihydro-2H-1,4-thiazin (11) nur in untergeordnetem Maße entsteht. Die Reaktionsmechanismen sowohl der 5,6-Dihydro-1,4-thiazin-als auch der Thiazolidin-Bildung werden diskutiert. Die Umsetzung der 5,6-Dihydro-1,4-thiazine (1, 3–5, 11) mit überschüss. Ameisensäure führt zu N-Formylthiomorpholinen (13–17), die sich mit verd. HCl glatt zu den entsprechenden Thiomorpholinen (18–22) verseifen lassen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00911394
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  • 9
    Electronic Resource
    Electronic Resource
    Comparative analysis of DNA methylation in tobacco heterochromatic sequences (2000)
    Springer
    Chromosome research 8 (2000), S. 527-541 
    Details
    ISSN: 1573-6849
    Keywords: chromatin ; chromatin condensation ; cytosine methylation ; repetitive sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cytosine methylation levels and susceptibility to drug-induced hypomethylation have been studied in several Nicotiana tabacum (tobacco) DNA repetitive sequences. It has been shown using HapII, MspI, BamHI and Sau3AI methylation-sensitive restriction enzymes that the degree of 5′-mCmCG-3′ methylation varied significantly between different repeats. There were almost saturation levels of 5-methylcytosine at the inner (3′) cytosine position and variable degrees of methylation at the outer (5′) cytosine at the enzyme recognition sites. The non-transcribed high copy satellite sequences (HRS60, GRS) displayed significant heterogeneity in methylation of their basic units while middle repetitive sequences (R8.1, GRD5, 5S rDNA) were more uniformly modified at both cytosine residues. Dihydroxypropyladenine (DHPA) treatment, which is thought to reduce DNA methyltransferase activity by increasing S-adenosylhomocysteine levels, resulted in extensive demethylation of the outer cytosine in all repeats, and the partial hypomethylation of cytosines at the inner positions in less densely methylated repeats such as HRS60 and GRS. The results suggest that hypomethylation of 5′-mCmCG-3′ sites with DHPA is a gradual non-random process proceeding in the direction mCmCG→CmCG→CCG. The 18S-5.8S-25S rDNA was remarkably hypomethylated relative to the 5S rDNA at all restriction sites studied. Fluorescence in-situ hybridization showed that DNA decondensation within and between the 18S-5.8S-25S and 5S rDNA loci was variable in different nuclei. All nuclei had condensed and decondensed sequence. The chromatin of 18S-5.8S-25S rDNA was more readily digested with micrococcal nuclease than the 5S rDNA suggesting that the overall levels of decondensation were higher for 18S-5.8S-25S rDNA. Variable decondensation patterns within and between loci were also observed for GRS and HRS60. Cytosine methylation of the tobacco repeats is discussed with respect to transcription, overall levels of condensation and overall structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009223823327
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  • 10
    Electronic Resource
    Electronic Resource
    Superconductivity in bulk A15 Nb3Si under pressure (1981)
    Springer
    Journal of low temperature physics 45 (1981), S. 575-580 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have determined the effect of hydrostatic pressureP on the superconducting transition temperatureT c of bulk, A15 Nb3Si. For 0≤P≤20 kbar (2 GPa),T c decrease linearly with increasing pressure at a rate ∂T c/∂P=−2.67×10−5 K/bar. From an estimate of ∂T c/∂P obtained using recent band structure calculations for the density-of-electronic-states change as a function of lattice parameter in Nb3Si, we conclude that the pressure dependence of the electron-phonon interaction primarily determines ∂T c/∂P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654500
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