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  • 1
    Electronic Resource
    Electronic Resource
    60 Hz electric field parameters associated with the perturbation of a eukaryotic cell system (1980)
    Springer
    Radiation and environmental biophysics 18 (1980), S. 289-300 
    Details
    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary Roots ofPisum sativum were exposed for seven days to 60 Hz electric fields ranging from 70–430 V/m in an aqueous medium whose conductivity was approximately 0.07 mho/m. (Corresponding current densities in the exposure medium associated with these field strengths ranged from 0.5–3.0 mA/cm2). Control and exposed roots were grown concomitantly in the same tank whose growth medium was continuously circulated. Temperature in the exposure medium was held at a constant 19° C. All experiments were conducted “double blind.” Root growth rates were determined daily. No perturbations in root growth were observed with electric fields of 150 V/m; there was a slight effect at 360 V/m, and a pronounced decrease in growth rate occurred at 430 V/m. Root conductivities are comparable to that of the growth medium. Under conditions in which growth inhibition occurs, it is estimated that induced 60 Hz cell membrane potentials would be of the order of 3–8 mV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01324272
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  • 2
    Electronic Resource
    Electronic Resource
    Relationship of 60-Hz electric-field parameters to the inhibition of growth ofPisum sativum roots (1981)
    Springer
    Radiation and environmental biophysics 19 (1981), S. 227-233 
    Details
    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary Roots ofPisum sativum were chronically exposed to 60-Hz electric fields ranging from 215–430 V/m and current densities from 1.5–2.7 mA/cm2. Adjustments of the exposure medium's conductivity (0.035–0.14 mho/m) allowed for distinction between a field or a current induced perturbation in root growth rates. Inhibition of root growth rates was directly related to the magnitude of the applied field and not the current density. The results are consistent with the postulate that the applied field acts upon the cell membrane and perturbs its function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01324190
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  • 3
    Electronic Resource
    Electronic Resource
    Nitro-blue tetrazolium: A specific stain for photosynthetic activity in protoplasts (1987)
    Springer
    Plant cell reports 6 (1987), S. 70-73 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A qualitative assay for the detection of photosynthetic activity in protoplasts is described. Leaf protoplasts from atrazine resistant and susceptible biotypes of Brassica napus suspended in medium with 0.01% nitro-blue tetrazolium and 10 to 100 µM atrazine showed clear differences in staining. Staining was detectable with 0.001% fluorescein-labelled tetrazolium which, unlike nitro-blue tetrazolium, did not cause collapse of the protoplasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00269743
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  • 4
    Electronic Resource
    Electronic Resource
    Increased totipotency of protoplasts from Brassica oleracea plants previously regenerated in tissue culture (1988)
    Springer
    Plant cell, tissue and organ culture 14 (1988), S. 15-24 
    Details
    ISSN: 1573-5044
    Keywords: Brassica ; genetics of regeneration ; protoplasts ; totipotency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Factors affecting the division of cells derived from leaf and cotyledon protoplasts from Brassica oleracea L. var. italica (‘Green Comet’ hybrid broccoli) were examined to optimize conditions for plant regeneration and to determine whether there was a genetic basis for improved regeneration from protoplasts derived from plants previously regenerated from tissue cultures [15]. When leaf protoplasts from different plants grown from hybrid seed were isolated and cultured simultaneously, division efficiencies of 1–95% were obtained. Cells from some plants showed high division efficiencies in consecutive experiments while cells from other plants had consistently low division rates. More plants from hybrid seed gave high division efficiencies when cotyledon protoplasts were used. However, cotyledon or leaf protoplasts from selfed progeny of regenerated plants produced more vigorous calli and more shoots than protoplasts from hybrid seed. These results suggest that there may be a genetic component to the increased totipotency of Brassica oleracea protoplasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00029571
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  • 5
    Electronic Resource
    Electronic Resource
    Genetic transformation of Norway spruce (Picea abies (L.) Karst) using somatic embryo explants by microprojectile bombardment (1992)
    Springer
    Plant molecular biology 19 (1992), S. 925-935 
    Details
    ISSN: 1573-5028
    Keywords: β-glucuronidase DNA transfer ; kanamycin ; microprojectiles ; Norway spruce ; somatic embryos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Stable transformation of Norway spruce tissue has been obtained following bombardment of mature somatic embryos with pRT99gus, a plasmid that contains neo coding for NPTII, and gusA, coding for β-glucuronidase, both fused to the CaMV 35S promoter. At least 8 lines have been stably transformed (over 15 months in culture) following bombardment and selection on kanamycin. Polymerase chain reaction analyses showed a high frequency of cotransformation of the gusA and neo genes. The frequency of coexpression of the selected and unselected markers was 100%. DNA/DNA hybridization of one transformed line provided conclusive evidence of stable integration and showed copy numbers of over 10 plasmid sequences per genome. None of the transformed lines has remained embryogenic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00040525
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  • 6
    Electronic Resource
    Electronic Resource
    Mapping and expression of a bifunctional thymidylate synthase, dihydrofolate reductase gene from maize (1999)
    Springer
    Plant molecular biology 41 (1999), S. 733-739 
    Details
    ISSN: 1573-5028
    Keywords: bifunctional enzymes ; dihydrofolate reductase ; DNA synthesis ; endoreduplication ; maize ; thymidylate synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A bifunctional gene (ZmDHFR-TS) encoding dihydrofolate reductase (DHFR) and thymidylate synthase (TS) was cloned from a Zea mays cDNA library. Both of these enzymes are involved in nucleotide biosynthesis, specifically in the formation of thymidine monophosphate (TMP). Comparison of the deduced amino acid sequence with DHFR-TS sequences from three other plant sources revealed over 75% similarity and motifs typical of DHFR-TS proteins. Two copies of the gene were mapped to chromosomes 2 and 4. This represents the first DHFR-TS gene cloned from a monocotyledonous plant. Expression of ZmDHFR-TS was examined in developing kernels and various tissues of maize by RNA gel blot hybridization analysis in order to determine the relationship between expression of this gene and DNA synthesis. RNA transcripts for ZmDHFR-TS accumulated to high levels in developing maize kernels when endosperm cells were undergoing endoreduplication and cell division. Meristematic maize tissues had high levels of ZmDHFR-TS mRNA, but transcripts were barely detectable in RNA isolated from the root elongation zone and from mature leaf tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006324328355
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  • 7
    Electronic Resource
    Electronic Resource
    Cotranscription of the wild-type chloroplast atpE gene encoding the CF1/CF0 epsilon subunit with the 3′ half of the rps7 gene in Chlamydomonas reinhardtii and characterization of frameshift mutations in atpE (1990)
    Springer
    Molecular genetics and genomics 221 (1990), S. 155-163 
    Details
    ISSN: 1617-4623
    Keywords: ATP synthase ; atpE ; rps7 ; Chloroplast mutations ; Chlamydomonas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have characterized two independently isolated point mutants in Chlamydomonas reinhardtii, ac-u-a-1-15 and FUD 17, mapping to the chloroplast ac-u-a locus which corresponds to the atpE gene. Both mutants have a single A: T base pair deletion in a sequence of 6 A:T base pairs at nucleotide positions 102 to 107. This causes a frameshift, altering the coding sequence for the next 8 amino acids and creating a termination codon at amino acid position 44, 98 amino acids from the C-terminus of the protein. Assembly of the ATP synthase is impaired in the mutants; less than 5% of the wild-type level of alpha and beta subunits and no gamma or epsilon subunits are associated with thylakoid membranes of the mutants. The genes encoding the beta and epsilon subunits of the chloroplast ATP synthase from C. reinhardtii are not cotranscribed, in contrast to all other photosynthetic organisms examined to date. Four transcripts, of approximately 1.7, 2.9, 3.3 and 7.0 × 103 nucleotides (nt), are found for the atpE gene. S1 nuclease mapping of the 1.7 × 103 nt transcript shows that the atpE gene message is preceded by a leader of about 1250 nt. DNA sequence analysis of this region revealed a 159 by open reading frame corresponding to the 3′ half of the rps7 gene, encoding the S7 protein of the small subunit of the chloroplast ribosome. Only the 5′ portion of this gene is located in the opposite unique sequence region of the C. reinhardtii chloroplast genome where the rps7 gene was previously mapped by heterologous hybridization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261715
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  • 8
    Electronic Resource
    Electronic Resource
    Inhibition and recovery of growth processes in roots of pisum sativum L. Exposed to 60-Hz electric fields (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 2 (1981), S. 329-340 
    Details
    ISSN: 0197-8462
    Keywords: electric fields ; 60 Hz ; biologic effects ; membrane potentials ; recovery ; Pisum sativum ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Roots of Pisum sativum L. were chronically exposed in aqueous inorganic nutrient medium to 60-Hz electric fields between 140 and 490 V/m (growth medium conductivity ∼ 0.08 S/m). The growth rate, meristematic mitotic index, and growth rate recovery of the roots were determined. At 140 V/m there was no perturbation in growth rate or mitotic index. At 430 V/m the growth rate and the mitotic index were reduced. The mitotic index had a maximum depression (∼ 55% of control), which occurred at 4 h. The depression in growth rate was immediate and constant over time. When roots were exposed to an electric field at 430 V/m for 2 days, the growth rate was depressed by about 40%. When the field was terminated, the growth rate steadily increased and was almost normal after 5 days. At 490 V/m root growth rate was almost completely arrested. According to these results, there is a narrow range of induced membrane potentials that span the range from slightly altered to almost completely arrested growth rates.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250020405
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  • 9
    Electronic Resource
    Electronic Resource
    A cytohistological analysis of roots whose growth is affected by a 60-Hz electric field (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 6 (1985), S. 283-291 
    Details
    ISSN: 0197-8462
    Keywords: electric field ; growth ; cell elongation ; tranmembrane potential ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Roots of Pisum sativum were exposed for 48 h to 60-Hz electric fields of 430 V/m in an aqueous inorganic growth medium. The growth in length of the exposed roots was 44% of that for control roots. Root tips were analyzed for mitotic index and cell cycle duration. Mature, differentiated root sections from tissue produced after electrode energization were analyzed for cell lengths and number of files. The major reason for the observation that exposed roots are shorter than control roots is that cell elongation in the former is greatly diminished relative to controls.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250060308
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