Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1432-0983
    Keywords: RNA plasmids ; Rapeseed ; Maternal inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The large RNAs previously detected in mitochondrial preparations of Brassica plants are shown here to be double-stranded molecules that lack homology to the mitochondrial genome and are synthesized in a DNA-independent manner. In crosses between nuclear isogenic lines, the dsRNAs were transmitted through both seed and pollen, whereas the mtDNA, as expected, was transmitted only from the seed or the maternal parent. In addition, the Brassica dsRNAs did not co-purify with mitochondria during Percoll gradient centrifugation. In identical gradients, however, the maize autonomously replicating species S/Ru-a and S/Ru-b co-purified precisely with mitochondria. The results suggest that, unlike the maize RNAs, the Brassica dsRNAs are not physically or genetically associated with mitochondria and, more generally, that the occurrence of dsRNA in mitochondria may be less widespread than recent reports indicate.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-0983
    Keywords: Cytoplasmic male sterility ; Brassica ; Mitochondrial DNA ; Gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mitochondrial genome of the Polima (pol) male-sterile cytoplasm of Brassica napus contains a chimeric 224-codon open reading frame (orf224) that is located upstream of, and co-transcribed with, the atp6 gene. The N-terminal coding region of orf224 is derived from a conventional mitochondrial gene, orfB, while the origin of the remainder of the sequence is unknown. We show that an apparently functional copy of orfB is present in the pol mitochondrial genome, indicating that the pol CMS is not caused by the absence of an intact, expressed orfB gene. The 5′ termini of orf224/atp6 transcripts present in both sterile and fertility-restored (Rf) pol cytoplasm plants are shown to map to sequences resembling mitochondrial transcription-initiation sites, whereas the 5′ termini of two transcripts specific to restored lines map to sequences which resemble neither one another nor mitochondrial promoter motifs. It is suggested that the complex orf224/atp6 transcript pattern of Rf plants is generated by a combination of multiple transcription initiation and processing events and that the nuclear restorer gene acts to specifically alter orf224/atp6 transcripts by affecting RNA processing. Northern analyses demonstrate that the effect of the restorer gene on orf224/atp6 transcripts is not tissue or developmentalstage specific. However, the expression of the atp6 region is developmentally regulated in pol plants, resulting in decreased levels of monocistronic atp6 transcripts in floral tissue relative to seedlings. It is suggested that this developmental regulation may be related to the absence of overt phenotypic effects of the CMS mutation in vegetative tissues.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1617-4623
    Keywords: Promoters ; Guanylyltransferase ; Gene expression ; ATPase subunit 9
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Transcription initiation sites on the soybean mitochondrial genome have been characterized by sequence analysis of in vitro-capped soybean mtRNAs and corresponding mtDNA regions. The most abundant, discrete soybean mtRNA species labeled by guanylyltransferase and [α-32P]GTP are shown to correspond to the major transcript of the atp9 gene and to a group of small RNAs consisting of a discrete 80 nucleotide (nt) species plus heterogeneous species ranging in size from 133 to 148 nt. The 133-148 nt RNAs represent a set of transcripts with a common 5′ terminus and ragged 3′ ends, while the 80 nt RNA corresponds to positions 53–133 of the 133 nt species. The major, discrete in vitro-capped RNA species thus correspond to primary transcripts originating at three sites located in two regions of the soybean mitochondrial genome. The sequences extending from 13 nucleotides upstream to 8 nucleotides downstream of the initiation sites for the atp9 and 133–148 nt transcripts are identical at 18 of 21 positions. Sequences closely resembling this motif are located at some other 5′ transcript termini of dicot plant mitochondria. Less closely related sequences are found at transcription initiation sites of wheat and maize mitochondria.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The effects of sleep deprivation on the neural substrates of cognition are poorly understood. Here we used functional magnetic resonance imaging to measure the effects of 35 hours of sleep deprivation on cerebral activation during verbal learning in normal young volunteers. On the basis of ...
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-1432
    Keywords: Leghemoglobin ; Gene duplication ; Gene linkage ; Concerted evolution ; Nitrogen fixation ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have analyzed the sequences of soybean leghemoglobin genes as an initial step toward understanding their mode of evolution. Alignment of the sequences of plant globin genes with those of animals reveals that (i) based on the proportion of nucleotide substitutions that have occurred at the first, second, and third codon positions, the time of divergence of plant and animal globin gene families appears to be extremely remote (between 900 million and 1.4 billion years ago, if one assumes constancy of evolutionary rate in both the plant and animal lineages) and (ii) in addition to the normal regulatory sequences on the 5′ end, an approximately 30-base-pair sequence, specific to globin genes, that surrounds the cap site is conserved between the plant and animal globin genes. Comparison of the leghemoglobin sequences with one another shows that (i) the relative amount of sequence divergence in various coding and noncoding regions is roughly similar to that found for animal globin genes and (ii) as in animal globin genes, the positions of insertions and deletions in the intervening sequences often coincide with the locations of direct repeats. Thus, the mode of evolution of the plant globin genes appears to resemble, in many ways, that of their animal counterparts. We contrast the overall intergenic organization of the plant globin genes with that of animal genes, and discuss the possibility of the concerted evolution of the leghemoglobin genes.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1432-2072
    Keywords: Computer modeling ; Impairment of acquisition ; Diazepam
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Hypotheses about the information processes impaired in diazepam-induced amnesia were tested by fitting the output from a computer simulation of list learning to observed serial position curves and to overt rehearsal protocols. Twenty-four subjects received an average weight-relative dosage of 0.18 mg/kg oral diazepam; 24 subjects received placebo. Immediate free recall of 16-word lists was examined at 2- and 8-s presentation times. Subjects receiving diazepam recalled significantly fewer words than placebo subjects (diazepam=6.77 ± 2.39 words; placebo=9.29 ± 1.42 words); their memory impairment was greater at the 8-s than 2-s presentation time. Tests of nonlinear regression models based on computer simulations of list learning performance were consistent with the hypothesis that diazepam reduces rehearsal capacity and disrupts the formation or utilization of contextual and inter-item associations. Among these causes of diazepam-induced amnesia, the disruption of contextual associations appears most important. The results further suggest that quantitative modeling of memory data may complement traditional methods of inferring relationships between brain processes and cognitive dysfunction in amnesic states.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1432-2072
    Keywords: Diazepam ; Amnesia ; Sedation ; Arousal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Forty-eight healthy volunteers received 0.2 mg/kg oral diazepam or a placebo in a double-blind manner. The effect of the drug on memory was assessed by the free recall of unrelated word lists, and arousal was assessed by subjective ratings of drowsiness, multiple trials of a digit cancellation task, and the rate at which subjects rehearsed aloud items from the word lists. As expected, diazepam, depressed both memory functioning and all three measures of arousal. However, within the diazepam group, rehearsal rate was the only arousal measure that correlated with performance on the recall task. When looking at change scores, or the degree to which performance deteriorated from baseline to the diazepam condition, digit cancellation reduction was the only arousal measure that correlated with recall deterioration. Analyses also revealed that the three arousal measures did not correlate with each other. Results support the view that the arousal/attentional system is composed of partially independent subsystems with varying relationships to memory functioning.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1573-5028
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To identify regions of the mitochondrial genome from the polima or pol male-sterile cytoplasm of Brassica napus that are genetically correlated with cytoplasmic male sterility (CMS) we analyzed mtDNAs of three male-sterile somatic hybrids formed by the fusion of broccoli (B. oleracea L. var. italica) and pol CMS B. napus protoplasts. Fragments characteristic of a 4.5 kb DNA segment that comprises the single organizational difference between sterile pol and fertile cam Brassica mitochondrial genomes were found in all three sterile somatic hybrids. One of these hybrids possessed a mitochondrial genome that was, apart from a limited region around this 4.5 kb CMS-associated segment, collinear with B. oleracea mtDNA. Previous studies have indicated that expression of transcripts spanning the atp6 gene and a chimeric gene, orf24, located on this 4.5 kb DNA segment, is associated with male sterility. The present results indicate that the orf224/atp6 gene region is genetically correlated with male sterility and provide significant additional support for the view that this gene region may be involved in specifying the CMS trait.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1573-5028
    Keywords: maize ; mitochondrion ; RNA b ; RNA plasmids ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract RNA b is the most abundant member of a family of autonomously replicating single- and double-stranded RNA plasmids found in maize mitochondria. The extent to which this molecule is associated with proteins was investigated by rate zonal and CsCl equilibrium density gradient centrifugation of clarified lysates of S cytoplasm maize mitochondria. A soluble complex of RNA b, responsible for synthesis of the more abundant (+) RNA b strand in mitochondrial lysates, was identified. The complex had a buoyant density of 1.49 g/cm3, indicating a substantial non-nucleic acids content. The sedimentation coefficient of the complex, however, was only slightly larger than that of deproteinized RNA b. Synthesis of RNA b as well as the larger RNA plasmid, RNA a, was resistant to heparin, suggesting that, for both RNAs, preformed complexes between an RNA template and an RNA-dependent RNA polymerase capable of elongating in vivo preinitiated RNA plasmid strands, were present in the lysate. Only a small fraction of RNA b molecules were bound in the complex; the bulk of RNA b sedimented at the same rate as the deproteinized RNA. Thus, after replication, maize mitochondrial plasmids are not associated with nucleoprotein capsids although their synthesis takes place through ribonucleoprotein replication complexes.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...