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1

Digitale Medien

Contrasting patterns of genetic diversity in two tropical pines: Pinus kesiya (Royle ex Gordon) and P. merkusii (Jungh et De Vriese) (1996)

Szmidt, A. E. ; Wang, X.-R. ; Changtragoon, S.

Springer

Theoretical and applied genetics 92 (1996), S. 436-441

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ISSN: 1432-2242

Schlagwort(e): Pinus ; Allozymes ; Chloroplast DNA ; Genetic variation ; Evolution

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract We studied allozyme and chloroplast (cp) DNA variation in natural populations of Pinus kesiya and P. merkusii from Thailand and Vietnam. The results showed striking differences between the two species in the amount and distribution of allozyme variation. P. kesiya harboured considerable allozyme variation and showed weak interpopulational differentiation. In contrast, P. merkmii had very low intrapopulational variability but a high level of interpopulational differentiation. The average Nei's genetic distance separating the two species was exceptionally high (0.701) taking into account their close taxonomic placement in the same subsection Sylvestres. The constructed phylogenetic trees revealed very early divergence of P. kesiya and P. merkusii. The present analysis of cpDNA variation also confirmed the dissimilar character of these two species and was compatible with other evidence indicating the outstanding position of P. merkusii as compared to other Asian members of the subsection Sylvestres. Analysis of cpDNA variation in sympatric populations of P. kesiya and P. merkusii revealed that they are pure representatives of the species in question. This result indicates that despite an overlapping distribution P. kesiya and P. merkusii do not hybridise in nature. We suggest that the distinctive character of P. merkusii is a result of an early separation from other Eurasian pines. Despite spatial proximity, P. kesiya and P. merkusii are kept apart by strong reproductive barriers. The low genetic variability of P. merkusii may be explained by previous bottlenecks, reduced gene flow among populations, and an inbreeding due to small population size and asynchronous flowering.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00223690

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2

Digitale Medien

Evolutionary analysis of Pinus densata (Masters), a putative Tertiary hybrid. (1990)

Wang, X. -R. ; Szmidt, A. E.

Springer

Theoretical and applied genetics 80 (1990), S. 641-647

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ISSN: 1432-2242

Schlagwort(e): Pinus ; Species hybridization ; Chloroplast DNA ; Molecular markers ; Evolution

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Summary Restriction fragment analysis and heterologous hybridization of chloroplast (cp) DNA was used to develop species-specific markers for P. tabulaeformis, P. yunnanensis and P. massoniana. Fragment patterns created by the BclI and DraI restriction enzymes and hybridization patterns to the psbC and psbD probes were distinctive among the three species. No intraspecific variation was detected with respect to any of the cpDNA markers developed in this study. The cpDNA markers obtained were subsequently used to examine the parentage of P. densata, a putative Tertiary hybrid between P. tabulaeformis and P. yunnanensis. The analysis demonstrated for the first time that P. densata populations accommodate chloroplast genomes of P. tabulaeformis and P. yunnanensis, which strongly supports earlier suggestions of the hybrid origin of this species. It appears that P. densata represents a stabilized natural hybrid that has become adapted to high mountain environments where neither of the parental species can normally grow.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00224224

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3

Digitale Medien

Evolutionary analysis of Pinus densata Masters, a putative Tertiary hybrid (1990)

Wang, X. -R. ; Szmidt, A. E. ; Lewandowski, A. ; [weitere]

Springer

Theoretical and applied genetics 80 (1990), S. 635-640

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ISSN: 1432-2242

Schlagwort(e): Pinus ; Species hybridization ; Allozymes ; Evolution

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Summary Allozyme differentiation at 13 loci was studied in populations of Pinus tabulaeformis, P. densata, and P. yunnanensis from China. It was previously suggested that P. densata represents a Tertiary hybrid between P. tabulaeformis and P. yunnanensis. The observed levels of allozyme variation within and among the investigated species were comparable to those of other conifers. P. tabulaeformis differed markedly from P. yunnanensis with respect to allozyme frequencies, while P. densata was intermediate between the two putative parents. There was evidence of homozygote excess in embryos from all investigated species, as compared to Hardy-Weinberg expectations. The observed allozyme composition of P. densata conformed to earlier morphological and molecular evidence indicating hybrid origin of this taxon. It was proposed that fusion of gene pools from P. tabulaeformis and P. yunnanensis has led to adaptive evolution of a new species, P. densata.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00224223

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4

Digitale Medien

Molecular systematics and genetic differentiation of Pinus sylvestris (L.) and P. densiflora (Sieb. et Zucc.) (1993)

Szmidt, A. E. ; Wang, X. -R.

Springer

Theoretical and applied genetics 86 (1993), S. 159-165

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ISSN: 1432-2242

Schlagwort(e): Allozymes ; Chloroplast DNA ; Introgression ; Evolution

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Summary Allozyme variation was examined in 22 populations of Pinus densiflora (Sieb, et Zucc.) and four geographic varieties of P. sylvestris (L.): var ‘lapponica’ (Fries, Hartman), var ‘armena’ (Komarov), var ‘mongolica’ (Litvinov) and var ‘sylvestriformis’ (Takenouchi). In addition, we developed paternal chloroplast (cp) DNA markers that distinguish P. densiflora from var ‘lapponica’, var ‘armena’ and var ‘mongolica’. UPGMA cluster analysis based on Nei's distances between all pairwise combinations of the 22 populations revealed patterns corresponding strictly to geographic origin and taxonomic status. Analysis of allozyme variation in var ‘lapponica’, var ‘armena’ and var ‘mongolica’ demonstrated a high level of intrapopulational variability but a low level of interpopulational differentiation. It appears that the late Pleistocene blending of genetically diverse populations was responsible for the observed variation patterns. The constructed phylogenetic trees also showed late divergence of these three varieties. The var ‘sylvestri formis’ was genetically distinct from the other three P. sylvestris varieties. The genetic distances separating var ‘sylvestriformis’ from P. densiflora and the other taxa lend support to a separate taxonomic status for var ‘sylvestriformis’ and a close relation with P. densiflora. We found that var ‘sylvestriformis’ harbors admixtures of allozymes and cpDNA from both P. sylvestris and P. densiflora, which suggests an introgressive nature of this variety. Levels of intrapopulational variability were similar in P. sylvestris and P. densiflora, but interpopulational differentiation was much higher in P. densiflora. In the constructed phylogenetic trees, populations of this species were characterized by relatively long internode distances and branch lengths. The present results suggest that P. densiflora has a more advanced evolutionary age than P. sylvestris.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00222074

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5

Digitale Medien

Contrasting patterns of genetic diversity in two tropical pines: Pinus kesiya (Royle ex Gordon) and P. merkusii (Jungh et De Vriese) (1996)

Szmidt, A. E. ; Wang, X.-R. ; Changtragoon, S.

Springer

Theoretical and applied genetics 92 (1996), S. 436-441

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Details

ISSN: 1432-2242

Schlagwort(e): Key words Pinus ; Allozymes ; Chloroplast DNA ; Genetic variation ; Evolution

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract We studied allozyme and chloroplast (cp) DNA variation in natural populations of Pinus kesiya and P. merkusii from Thailand and Vietnam. The results showed striking differences between the two species in the amount and distribution of allozyme variation. P. kesiya harboured considerable allozyme variation and showed weak interpopulational differentiation. In contrast, P. merkusii had very low intrapopulational variability but a high level of interpopulational differentiation. The average Nei's genetic distance separating the two species was exceptionally high (0.701) taking into account their close taxonomic placement in the same subsection Sylvestres. The constructed phylogenetic trees revealed very early divergence of P. kesiya and P. merkusii. The present analysis of cpDNA variation also confirmed the dissimilar character of these two species and was compatible with other evidence indicating the outstanding position of P. merkusii as compared to other Asian members of the subsection Sylvestres. Analysis of cpDNA variation in sympatric populations of P. kesiya and P. merkusii revealed that they are pure representatives of the species in question. This result indicates that despite an overlapping distribution P. kesiya and P. merkusii do not hybridise in nature. We suggest that the distinctive character of P. merkusii is a result of an early separation from other Eurasian pines. Despite spatial proximity, P. kesiya and P. merkusii are kept apart by strong reproductive barriers. The low genetic variability of P. merkusii may be explained by previous bottlenecks, reduced gene flow among populations, and an inbreeding due to small population size and asynchronous flowering.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/s001220050146

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6

Digitale Medien

On the gel effect in the presence of a chain transfer agent in methyl methacrylate polymerization and its copolymerization with various acrylates (1993)

Wang, X. ; Ruckenstein, E.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 49 (1993), S. 2179-2188

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: The kinetics of methyl methacrylate (MMA) polymerization, and of its copolymerization with various acrylates, at high conversions in the presence of a chain transfer agent, are investigated with a dilatometer over the entire course of reaction. The displacement to higher conversions of the onset of the gel effect in the MMA homopolymerization, in the presence of a chain transfer agent, was determined. Similar information is also provided for the MMA-acrylate copolymerization systems. An increase in polymerization temperature slightly delays the onset of the gel effect in the MMA-acrylate copolymerization, but considerably increases the final conversion. The final conversion in copolymerization for a constant concentration of the chain transfer agent is independent of the initiator concentration, but is a function of the polymerization temperature. The reaction time for reaching the limiting conversion in copolymerization is increased with an increasing amount of the second monomer, as well as with an increasing number of carbon atoms in the acrylate used as the second monomer. © 1993 John Wiley & Sons, Inc.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1993.070491214

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7

Digitale Medien

XPS analysis of hydroxide ion surface reactions on reactions on CeF3 and LaF3 fluoride ion-selective electrodes (1997)

Shen, W. ; Wang, X. D. ; Cattrall, R. W. ; [weitere]

Weinheim : Wiley-Blackwell

Electroanalysis 9 (1997), S. 917-921

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ISSN: 1040-0397

Schlagwort(e): XPS analysis ; Fluoride ; Ion selective electrode ; Surface analysis ; Hydroxide interference ; Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Lanthanum fluoride and cerium fluoride single crystals, used as the sensing membranes of the fluoride ion-selective electrode (F-ISE), were investigated for their hydroxide interference and surface reactions with OH- in high pH conditions. While these membranes show fast response and excellent Nernstian behavior over a wide concertration range in buffered F- solutions, they deviate from the theoretical slope at high pH. CeF3, in particular, exhibits a much larger deviation from the Nernstian slope and a substantially slower response to a F- activity change compared to LaF3. This larger deviation is due to more extensive and faster formation of hydroxo-complexes, with the release of a greater amount of the fluoride ion into the hydrated gel layer. The slower response of the CeF3 membrane after contact with OH- is due to the formation of CeIV oxide on the surface, which acts as a blocking layer to the exchange of F-.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/elan.1140091210

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8

Digitale Medien

Porous-coated titanium implant impregnated with a biodegradable protein delivery system (1997)

Agrawal, C. M. ; Pennick, A. ; Wang, X. ; [weitere]

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 36 (1997), S. 516-521

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ISSN: 0021-9304

Schlagwort(e): porous-coated ; titanium ; PLA-PGA ; protein release ; degradation ; Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Medizin , Technik allgemein

Notizen: Tissue ingrowth into porous-coated orthopedic and dental implants is commonly used as a means to achieve long-term fixation of these prostheses. However, the degree of tissue ingrowth is often inadequate and inconsistent. If the pores of these implants are impregnated with a controlled drug release system delivering relevant growth factors, then it might be possible to stimulate more tissue ingrowth. The present study introduces such a system based on biodegradable polymers and investigates its protein release profile and polymer degradation characteristics. Porous coated titanium implants were impregnated with a mixture of a 50%-50% polylactic acid-polyglycolic acid copolymer and a model protein, soybean trypsin inhibitor. Control implants contained only the polymer and no protein. The implants were subjected to hydrolytic degradation in phosphate buffered saline at 37°C for periods of 3, 6, and 11 weeks. The protein release and the mass and molecular weight of the polymer were monitored. The results indicate that the protein is released in three distinct phases and the polymer loses almost all its mass and molecular weight by 11 weeks. There was a significant difference in the polymer degradation characteristics between the control and test implants, which might be the result of some complex polymer-protein interactions. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res, 36, 516-521, 1997.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

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