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  • Circadian rhythms  (3)
  • Nitrate reductase  (3)
  • Springer  (6)
  • Blackwell Publishing Ltd
  • Nature Publishing Group
  • Oxford University Press
  • 1990-1994  (6)
  • 1960-1964
  • 1950-1954
Collection
Keywords
Publisher
  • Springer  (6)
  • Blackwell Publishing Ltd
  • Nature Publishing Group
  • Oxford University Press
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Seasonality of circadian locomotor activity in an insect (1993)
    Springer
    Journal of comparative physiology 171 (1993), S. 713-724 
    Details
    ISSN: 1432-1351
    Keywords: Circadian rhythms ; Seasonality ; Locomotor activity ; Carabid beetles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Daily periodic locomotor activity of Carabus auronitens was recorded in a climate-constant laboratory with the animals exposed to naturally changing photoperiods. Most actograms exhibit directed seasonal variations of duration and phase position of daily activity. Seasonal locomotor activity starts in early spring (following dormancy) on a low daily level, first being confined to a short time span around dusk (and even shorter around dawn). In the course of season, the daily onsets of activity become closely related with sunset and the duration of daily activity is steadily extended with both parts of the bimodal phase fusing to a common, unimodal activity band by late spring. Subsequently, it is further extended into forenoon, until in summer (shortly before aestivation), spontaneous phase inversion turns activity periodicity from nocturnality into diurnality within 1 day. Such seasonal variations are paralleled by changes in the precision of synchronization of the individuals' activity rhythms to the entraining light/dark cycle. No geographical differences were detected. The results support the idea of the circadian clock as a system of two dynamically coupled physiological oscillators that invert their phase relation as soon as the natural dark phase falls short of some minimum-tolerable night length.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213068
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  • 2
    Electronic Resource
    Electronic Resource
    Feeding effects on daily locomotor activity in Carabus auronitens (1993)
    Springer
    Journal of comparative physiology 173 (1993), S. 49-55 
    Details
    ISSN: 1432-1351
    Keywords: Circadian rhythms ; Feeding effects ; Locomotor activity ; Ground beetles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Effects of food supply on daily periodic locomotor activity in the ground beetle Carabus auronitens were recorded in the laboratory with the animals exposed to natural daylight and photoperiod. Inspection of individual actograms exhibits that in most cases feeding leads to strongly reduced and more or less irregularly distributed activity for a period of up to 4 days. In terms of quantitative parameters, the animals respond to food supply by an immediate reduction of mean amounts of daily activity. This is achieved through the reduction of duration (as a consequence of reduced burstlengths instead of burstnumber) and, less distinctly, the reduction of intensity. The initial levels of parameters are reattained after 4 days. Direct comparison by means of standardized (i.e. level-independent) relative parameter functions demonstrates close concordance between the amount and duration of daily activity; however, distinct synchronous change of intensity is apparent as a consequence of food supply only. This means that any variation of activity amounts is due to changing duration rather than to intensity variation. In analogy to the feeding-dependent parameter dynamics, also the proportion of animals with strong synchronization to the natural light/dark cycle is considerably reduced by food supply. The feeding-dependent reduction of activity is paralleled by temporarily reduced activity of proteolytic enzymes in the beetles. It is argued that, for the purpose of energy saving, the animals will remain inactive as long as reduced enzyme activity inhibits further consumption and digestion of food.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00209617
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  • 3
    Electronic Resource
    Electronic Resource
    Rhythmicity of chromophore turnover of visual pigment in the Antarctic amphipod Orchomene plebs (Crustacea; Amphipoda) (1993)
    Springer
    Journal of comparative physiology 173 (1993), S. 615-619 
    Details
    ISSN: 1432-1351
    Keywords: Photoreception ; Circadian rhythms ; Visual pigment ; Antarctica ; Crustacea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 1. Relative retinal amounts in the compound eye of the Antarctic amphipod Orchomene plebs were assessed during conditions of continuous summer daylight every 3 h over a period of 48 h. The habitat of the experimental animal is the bottom of the Ross Sea (78°S; 166°E) down to depths of at least 400 m; water temperature is a constant — 1.8° C. A periodicity of 12 h was detected with relative amounts of 11-cis retinal exhibiting peaks at midday and at midnight and troughs at 7.00 h and 19.00 h. 2. The result that 90% of retinoid were insoluble in n-hexane suggests that at least 90% of the measured retinoid were attached to membrane-bound proteins such as opsin. 3. Selective light adaptation showed that the visual pigments were thermostable and photoregenerable. The main absorbance peak of rhodopsin, compared with metarhodopsin, seems to be in the longer wavelengths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197769
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of Tnt1 tobacco retrotransposon insertion on target gene transcription (1991)
    Springer
    Molecular genetics and genomics 228 (1991), S. 233-239 
    Details
    ISSN: 1617-4623
    Keywords: Nicotiana tabacum ; Nitrate reductase ; Retrotransposon ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of Tntl retrotransposon insertion on nitrate reductase (NR) gene transcription have been analyzed in three NR-deficient insertional, mutants of Nicotiana tabacum. In the three mutants, named h9-Nia4, h9-Nia5 and h9-Nia6, Tnt1 was inserted into exon 3, exon 2 and exon 1 of the nia2 NR alloallelle, respectively. The mutants h9-Nia4 and h9-Nia6, which contained Tnt1 insertions that were oriented opposite to the direction of nia2 gene transcription, expressed chimaeric nia2-Tnt1 RNAs, respectively 12 kb and 10 kb long. The size observed in h9-Nia6 was close to the expected size for a full-length hybrid transcript starting and ending under the control of nia2 signals (about 9 kb). The larger transcript found in h9-Nia4 was shown to be due to a failure to splice the nia2 intron 2. The mutant h9-Nia5, which contained a Tntl insertion oriented in parallel with the direction of nia2 transcription expressed two truncated nia2-Tnt1 RNAs, 2 kb and 6.7 kb long. These transcripts arose from termination in the long terminal repeats (LTRs) of Tull. Since no full-length hybrid RNA was detected, we suggest that Tnt1 carries efficient termination signals, which are more efficiently recognized in the 3′ LTR than in the 5′ LTR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00282471
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  • 5
    Electronic Resource
    Electronic Resource
    Interest in and limits to the utilization of reporter genes for the analysis of transcriptional regulation of nitrate reductase (1992)
    Springer
    Molecular genetics and genomics 235 (1992), S. 259-268 
    Details
    ISSN: 1617-4623
    Keywords: Nitrate reductase ; Reporter gene ; Nicotiana tabacum ; Nicotiana plumbaginifolia ; Transgenic plant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Reporter gene techniques and mutant analysis were used to identify the molecular basis of the regulation of the expression of nitrate reductase (NR) by nitrate and nitrate-, or ammonium-derived metabolites (N-metabolites), in the true diploïd species Nicotiana plumbaginifolia and in the amphidiploïd species Nicotiana tabacum. The N. plumbaginifolia mutant E23 results from the insertion of a Tnt1-like retrotransposon (Tnp2) in the first exon of the single-copy nia gene, which encodes nitrate reductase. One of the resulting transcripts ends in the 5′ LTR (long terminal repeat) sequence of this retrotransposon, and another one in the 3′ LTR. Nitrate and N-metabolites modulate the expression of these truncated transcripts, indicating that intron splicing and termination processes are not essential to these regulatory events. A GUS reporter sequence was transcriptionally linked to the promoter of the nia-1 gene of N. tabacum. This fusion was functional in transient expression assays done with protoplasts derived from mesophyll cells of N. tabacum. However none of the regulatory mechanisms known to affect steady-state levels of the nia-1 transcript were operative under these experimental conditions. Transgenic plants carrying either this fusion or translational fusions of GUS linked to the promoter of either the nia-1 or nia-2 gene of N. tabacum were obtained by Agrobacterium-mediated transfer. A low proportion of the transgenic plants (22 out of 105 independent transformants) expressed GUS activity although at a low level. Only 4 plants exhibited a detectable level of GUS mRNA. The concentration of this mRNA increased significantly in an NR-deficient background, indicating regulation by N-metabolites. Only 2 plants, however, showed regulation (induction) by nitrate. Attempts to use aux2 or nptII reporter sequences linked to either the nia-1 or nia-2 promoter as marker genes for the selection of regulatory mutants of the nitrate assimilation pathway were unsuccessful because of our inability to isolate transgenic plants in which these reporter genes were properly regulated by nitrate. The implications of these results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00279369
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  • 6
    Electronic Resource
    Electronic Resource
    Isolation and molecular characterization of dTnp1, a mobile and defective transposable element of Nicotiana plumbaginifolia (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 194-200 
    Details
    ISSN: 1617-4623
    Keywords: Transposable element ; Nitrate reductase ; Nicotiana plumbaginifolia ; γ-Ray mutagenesis ; Nucleotide sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract By Northern blot analysis of nitrate reductase-deficient mutants of Nicotiana plumbaginifolia, we identified a mutant (mutant D65), obtained after γ-ray irradiation of protoplasts, which contained an insertion sequence in the nitrate reductase (NR) mRNA. This insertion sequence was localized by polymerase chain reaction (PCR) in the first exon of NR and was also shown to be present in the NR gene. The mutant gene contained a 565 by insertion sequence that exhibits the sequence characteristics of a transposable element, which was thus named dTnp1. The dTnp1 element has 14 by terminal inverted repeats and is flanked by an 8-bp target site duplication generated upon transposition. These inverted repeats have significant sequence homology with those of other transposable elements. Judging by its size and the absence of a long open reading frame, dTnp1 appears to represent a defective, although mobile, transposable element. The octamer motif TTTAGGCC was found several times in direct orientation near the 5′ and 3′ ends of dTnp1 together with a perfect palindrome located after the 5′ inverted repeat. Southern blot analysis using an internal probe of dTnp1 suggested that this element occurs as a single copy in the genome of N. plumbaginifolia. It is also present in N. tabacum, but absent in tomato or petunia. The dTnp1 element is therefore of potential use for gene tagging in Nicotiana species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391013
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