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  • 1
    Electronic Resource
    Electronic Resource
    When plant teratomas turn into cancers in the absence of pathogens (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 83 (1991), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Habituated calli have long been classified as neoplasms together with tumors from different origins. The general opinion is that habituation is a reversible process with an epigenetic basis. This is probably true in most cases examined. However, we show here that there might be several degrees of habituation, which can be considered as steps of a neoplastic progression leading to cancerisation in the absence of an introduced oncogenic pathogen. Cell rejuvenation, loss of the capacity to organize meristematic centers, and loss of totipotency are proposed to define plant cancer through this neoplastic progression of a callus.Habituated tissues share many morphological and biochemical similarities with so-called vitreous shoots from micropropagation. Vitrification and hyperhydric malformations of shoots raised in vitro may be considered as steps of another neoplastic progression, which leads to cancerisation also in the absence of introduced oncogenic pathogens. In this case death of the whole organism occurs either through direct apex necrosis or indirectly, from the loss of the capacity for the primary meristems to function normally, which gives rise to completely anarchic structures. As in the animal kingdom, carcinogenesis in plants is the final result of a multistep process involving the irreversible conversion of a stem cell to a terminal-differentiation-resistant cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb02489.x
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  • 2
    Electronic Resource
    Electronic Resource
    Purification of plasma membranes from leaves of conifer and deciduous tree species by phase partitioning and free-flow electrophoresis (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 95 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Purified plasma membrane fractions were obtained from leaves of Picea abies L., Pinus sylvestris L., Fagus sylvatica L. and Quercus robur L., whereas plasma membranes from Pinus halepensis Mill, proved to be more difficult to obtain, perhaps due to the higher content of volatile substances in this plant species. Plasma membranes were purified by both phase partitioning and free-flow electrophoresis from microsomal fractions and identified on the basis of biochemical and in some cases morphological and cytochemical markers. Electron micrographs revealed that membrane vesicles from Pinus sylvestris exhibited a very clear dark-light-dark pattern and measurements of membrane thickness showed that it ranged from 6 to 10 nm. Most membranes were 8 nm thick and stained with phosphotungstic acid at low pH, both typical characteristics of the plasma membrane. Enzymatic identification of plasma membranes consisted in the determination of the vanadate-sensitive ATPase (EC 3.6.1.3) activity. The specific activity in the upper phase (U2) fraction was 10–25 times higher than those in the lower phase and microsomal fractions, depending on plant species. 1,3-β-glucan synthase II (EC 2.4.1.3), another putative plasma membrane marker, was not detected in the plasma membrane-enriched fractions of conifer needles and showed a very low specific activity in membranes of deciduous trees. Contamination by membranes of other origin was determined by analysis of membrane markers: cytochrome c oxidase (EC 1.9.3.1) for mitochondria, inosine diphosphatase (EC 3.6.1.6) for Golgi apparatus, cytochrome c reductase (EC 1.6.2.4) for endoplasmic reticulum, and pyrophosphatase (EC 3.6.1.1) for tonoplasts. The main, but relatively low contamination, was due to tonoplasts, as determined by the activity of pyrophosphatase. Plasma membrane characteristics were quite different depending on the season during which needles were taken. Membrane preparations of better quality were more easily obtained from samples taken during winter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00855.x
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  • 3
    Electronic Resource
    Electronic Resource
    The roles of calcium and manganese ions in the in vitro conversion of 1-aminocyclopropane-1-carboxylic acid to ethylene by lentil root membranes (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 79 (1990), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ca2+ and Mn2+ activate the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) by root microsomes of Vicia lens as they do in other similar systems. The preparation of microsomes in the presence of Mn2+ greatly increases their ability to convert ACC into ethylene, without addition of Mn2+ in the reaction mixture. Ca2+ does not have this property. The effect could not be attributed to Mn2+ entrapping into membrane vesicles (sonication followed by repelleting had no effect) but, possibly, in part to Mn2+-mediated binding to microsomes of a soluble factor favouring the conversion of ACC to C2H4. Although no direct correlation could be established in vitro between ethylene-forming-enzyme (EFE) and peroxidase activities, some soluble peroxidases might be this soluble factor. Mn2+ favoured attachment to membranes of some peroxidase activity from the soluble fraction and from commercial HRP and lipoxygenase. This binding effect of Mn2+ cannot be readily distinguished from its role in the generation of a chain of free radicals and in redox mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1990.tb06738.x
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  • 4
    Electronic Resource
    Electronic Resource
    Glucose-6-phosphate dehydrogenase activity in spinach as measured by image analysis: A new approach for plant enzyme histochemistry (1996)
    Springer
    Journal of molecular histology 28 (1996), S. 25-32 
    Details
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A relatively low-cost computer-assisted image analysis system is described. Software has been specifically written for the continuous monitoring of absorbance readings on cryostat sectons of plant tissues incubated in media to reveal enzyme activities. The equipment was tested by quantify ing glucose-6-phosphate dehydrogenase activity in cryostat sections from shoot apices of spinach plants. The reaction rate of the dehydrogenase activity was monitored at two incubation temperatures, 20°C and 30°C. Control incubations were performed in media lacking substrate. The specific test minus control reaction at 30°C was twice that at 20°C. Variation of the substrate concentration at 30°C yielded a Km value of 0.37 mM. These preliminary results show that our image analysis system can be used for kineti measurements of dehydrogenase activity in froizen tssue sections and constitute a new approach for enzyme histochemistry in the shoot apicla meristem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02331424
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  • 5
    Electronic Resource
    Electronic Resource
    The use of herbarium specimens in DNA phylogenetics: Evaluation and improvement (1995)
    Springer
    Plant systematics and evolution 197 (1995), S. 87-98 
    Details
    ISSN: 1615-6110
    Keywords: Herbarium specimens ; molecular phylogenetics ; ancient DNA ; PCR techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During the last few years we have been confronted with the need to use herbarium specimens in the molecular phylogeny studies, since it is generally difficult to obtain living material of some rare species. Ancient DNA has been sequenced, and there are also reports on successful DNA amplification from herbarium specimens. However, it is not easy to obtain amplified DNA from the first herbarium sample tested. In this paper, experiments are described about trials of DNA amplification from two to 151-year-old herbarium specimens of plant species we needed for our projects. Of the 17 herbarium samples tested only two allowed DNA amplification under standard DNA isolation conditions. Different types of PCR inhibiting activities were demonstrated in DNA extracts. In some of the extracts there was extremely low concentration of template with satisfactory quality. In some instances, PCR inhibiting activities were successfully removed by treating them either with insoluble polyvinylpyrrolidone or by adding bovine serum albumin (BSA) to the amplification mixture. However, some PCR-inhibiting activities were resistant to the treatments described above. When the concentration of template was very low, a second PCR amplification with internal primers was necessary to increase the amount of DNA for sequencing. Nevertheless, contamination of either DNA extract or amplification mixture were sometimes observed, and consequently precautions were taken to minimize them. Finally, successful amplification was obtained in eight samples out of the 17 examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00984634
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