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  • Zea mays  (43)
  • Calcium  (38)
  • Springer  (81)
  • American Association of Petroleum Geologists (AAPG)
  • Nature Publishing Group
  • 1990-1994  (53)
  • 1980-1984  (28)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    RNA and protein synthesis in sperm cells isolated from Zea mays L. pollen (1993)
    Springer
    Sexual plant reproduction 6 (1993), S. 239-243 
    Details
    ISSN: 1432-2145
    Keywords: Zea mays ; Sperm cell ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sperm cells are thought to be quiescent in pollen and activated upon pollen germination. To test this hypothesis, protein, RNA and DNA synthesis were assessed in Zea mays sperm cells at different times after isolation from pollen. Protein synthesis changed with time; while some proteins were found to be constitutive in both 0 and 24 h cells, others were synthesized and some disappeared. Overall, the number of proteins detected at 24 h doubled compared with freshly isolated cells. Incorporation of [3H]leucine in 24 h cells was about 50 times that in freshly isolated cells, and that of [5, 6-3H]uridine, about 7 times. Very low incorporation of [6-3H]thymidine into the cells was detected; there was no difference between freshly isolated and 24 h cells. It is possible that the differences in synthetic activity between freshly isolated and 24-h-old cells might correspond to sperm cell activation during pollen tube growth. If so, these metabolic changes may play an important role in fertilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231900
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  • 2
    Electronic Resource
    Electronic Resource
    Variation in resistance of Mexican landraces of maize to maize weevil Sitophilus zeamais, in relation to taxonomic and biochemical parameters (1993)
    Springer
    Euphytica 74 (1993), S. 227-236 
    Details
    ISSN: 1573-5060
    Keywords: resistance ; taxonomy ; maize ; maize weevil ; indigenous landraces ; phenolic acids ; life history components ; indirect selection ; Zea mays ; Sitophilus zeamais
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Accessions representing twenty eight landraces of maize were assessed for susceptibility to the maize weevil, Sitophilus zeamais in standardized resistance tests. Susceptibility parameters such as weight loss of grain, number of insect progeny produced, the Dobie index of susceptibility, and oviposition on grain were found to vary significantly by genotype, with exceptional resistance found in accessions representing the Naltel, Chapalote and Palomero landraces. As in improved genotypes, susceptibility was negatively correlated to phenolic and protein content of the variety tested but positively correlated to moisture content. A detailed analysis of the phenolics revealed the presence of diferulate which may contribute to mechanical resistance of the seed by cross-linking of cell wall hemicelluloses. A canonical discriminant analysis of the resistance data suggests that most of the five landrace groupings are significantly different. The ancient indigenous and prehistoric mestisos groupings are sources of resistant genotypes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00040405
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  • 3
    Electronic Resource
    Electronic Resource
    Transient expression of GUS and anthocyanin constructs in intact maize immature embryos following electroporation (1993)
    Springer
    Plant cell, tissue and organ culture 33 (1993), S. 195-201 
    Details
    ISSN: 1573-5044
    Keywords: DNA delivery ; electroporation electrolyte ; heat shock ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Electroporation was used for the delivery and subsequent expression of GUS and anthocyanin reporter genes into intact maize immature embryos. The optimal conditions consisted of culturing immature embryos for 4 days on N6 1-100-25-Ag medium prior to electroporation (375 V/cm; 960 µF capacitance) in EPR buffer containing DNA and 0.07 M sodium glutamate at room temperature (22°C) after a 10 min heat shock at 37°C. Under these conditions, over 40 spots of GUS transient activity were observed per immature embryo. Transient gene expression after electroporation was further demonstrated using an anthocyanin construct, which is specific for expression in plant cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01983234
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  • 4
    Electronic Resource
    Electronic Resource
    Calcium plays a central role in phase shifting the ocular circadian pacemaker of Aplysia (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 415-423 
    Details
    ISSN: 1432-1351
    Keywords: Aplysia ; Calcium ; Circadian ; Light ; Serotonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The eye of the marine mollusk Aplysia californica contains an oscillator that drives a circadian rhythm of spontaneous compound action potentials in the optic nerve. Both light and serotonin are known to influence the phase of this ocular rhythm. The aim of the present study was to evaluate the role of extracellular calcium in both light and serotonin-mediated phase shifts. Low calcium treatments were found to cause phase shifts which resembled those produced by the transmitter serotonin. However, unlike serotonin, low calcium neither increased ocular cAMP levels nor could these phase shifts be prevented by increasing extracellular potassium concentration. Low calcium-induced phase shifts were prevented by the simultaneous application of the translational inhibitor anisomycin and low calcium treatment resulted in changes in [35S]methionine incorporation into several proteins as measured by a two-dimensional electrophoresis gel analysis. Finally, light treatments failed to produce phase shifts in the presence of low calcium or the calcium channel antagonist nickel chloride. These results are consistent with a model in which serotonin phase shifts the ocular pacemaker by decreasing a transmembrane calcium flux through membrane hyperpolarization while light-induced phase shifts are mediated by an increase in calcium flux.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00199249
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  • 5
    Electronic Resource
    Electronic Resource
    Rhythmic dentinogenesis in the rabbit incisor: Allometric aspects (1980)
    Springer
    Calcified tissue international 32 (1980), S. 45-53 
    Details
    ISSN: 1432-0827
    Keywords: Dentin ; Periodicity ; Allometry ; Calcium ; Sulfur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary We have described differences in the aspects of biological rhythms for calcium and sulfur deposition on the labial and lingual sides of the growing rabbit incisor, where growth occurs along a spiral axis. The calcium oscillations appear to be smoother on the labial side than on the lingual side. The lingual side is characterized by high-frequency rhythms with high amplitudes which possess the greatest percent of the power (Fourier analysis). These observations also reflect a difference in behavior of the mean Ca concentration across the labial and lingual sides. Sulfur rhythms on the labial side have higher amplitudes than those on the lingual side, but systematic differences in distribution of power between high and low frequencies is not as pronounced as in the case of Ca. The differences in Ca rhythms reflect differences in the growth rates of incisors on either side of the spiral axis. The labial side grows slightly faster than the lingual side, and its odontoblasts secrete Ca along the spiral axis and toward the pulp cavity at the same time. Thus the resultant direction of growth is more nearly opposite the extension of the occlusal end on the labial side, and Ca is consequently deposited over a wider area relative to that on the lingual surfaces. On the lingual side, Ca is deposited within a more limited area, and growth must therefore be continuous at high frequencies. The distribution of Ca on both sides of the tooth reflects these differences in growth rate and periodicity in two ways. First, given a unit area of tooth, the calcium concentration on the labial side is less than that of the lingual side. Second, whereas the calcium concentration on the labial side declines rapidly from the enamel-dentin junction to the pulp cavity, it is uniformly high across the lingual side because its growth is more continuous at high frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408520
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  • 6
    Electronic Resource
    Electronic Resource
    Rhythmic dentinogenesis in the rabbit incisor: Circadian, ultradian, and infradian periods (1980)
    Springer
    Calcified tissue international 32 (1980), S. 29-44 
    Details
    ISSN: 1432-0827
    Keywords: Rabbit ; Dentin ; Calcium ; Sulfur ; Periodicity ; Circadian ; Ultradian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary We have identified a variety of biological rhythms involved in the apposition and mineralization of dentin in the rabbit incisor. Animals were injected during the day or night with lead acetate at 2-week intervals—to provide biological time markers in forming dentin—and transverse undecalcified sections of the lower incisors were prepared for electron microprobe analysis. The positions of the lead markers were identified, and the continuous distribution of calcium and sulfur was measured at 1 µm intervals between the markers. In thin sections stained with hematoxylin after decalcification, the widths of a series of structural increments (bands) were measured with an ocular micrometer. Fourier analysis of the data revealed spectra of structural and compositional rhythms with a range of periodicities which extended from a matter of hours [ultradian (〈24 h)] to days [infradian (〉24 h) and circadian (approximately 24 h)]. The structural and compositional rhythms appeared to be independent to the extent that they did not necessarily have the same periods, or amplitudes. Nor were there simple phase relationships between all of the rhythms. At some times, Ca and S fluctuations are inversely proportional (180° out of phase), but in other cases they are directly proportional or out of phase by varying degrees other than 180°. The analyses thus suggest that calcium and sulfur deposition (representing mineral and glycosaminoglycan deposition, respectively) are not simply inversely proportional, and that the hematoxylin-stained structural increments did not solely reflect differences in the distribution of the mineral components in dentin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408519
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  • 7
    Electronic Resource
    Electronic Resource
    Amelioration of subsoil acidity in an Oxisol of the humid tropics (1993)
    Springer
    Biology and fertility of soils 15 (1993), S. 153-159 
    Details
    ISSN: 1432-0789
    Keywords: Calcium ; Maize ; Nitrogen ; Brazilian Amazon ; Cation leaching ; Canavalia ensiformes ; Mucuna aterrima
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This work investigated the effectsof amendments of fertilizer N and lime on subsoil acidity and maize rooting depth in an acid soil of the central Amazon basin. A split-plot designed field experiment was conducted on a clayey Oxisol (Typic Acrudox) during a 16-month period. Main plots received 0 or 4 Mt ha-1 of lime. Subplots were four crop sequences: (1) Maize-green manure (Canavalia ensiformes); (2) maize-green manure (Mucuna aterrima); (3) maize-bare fallow, with the maize receiving 300 kg ha-1 of urea-N; and (4) bare fallow, with an application of 300 kg ha-1 of urea-N at the same time as sequence 3. Plots were periodically sampled to 1.2 m. The experimental site received 4265 mm of precipitation during 16 months; approximately 60%–90% of this rain percolated through the profile. Substantial amounts of Ca were leached from the 0–30 cm horizon during the experimental period, but only limited amounts accumulated in the subsoil. Base saturation below 45 cm was less than 50% at the end of the experiment regardless of lime treatment. Roots of maize were concentrated in the 0–30 cm layers in limed plots and the 0–20 cm layers in unlimed plots. In all treatments less than 5% of the roots was found below 50 cm. An acidity balance indicated that considerable acidity was leached below the plow layer and out of the profile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336435
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  • 8
    Electronic Resource
    Electronic Resource
    Differential expression of six glutamine synthetase genes in Zea mays (1993)
    Springer
    Plant molecular biology 23 (1993), S. 401-407 
    Details
    ISSN: 1573-5028
    Keywords: gene-specific probes ; glutamine synthetase ; transcript accumulation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The maize genome has been shown to contain six glutamine synthetase (GS) genes with at least four different expression patterns. Noncoding 3′ gene-specific probes were constructed from all six GS cDNA clones and used to examine transcript levels in selected organs by RNA gel blot hybridization experiments. The transcript of the single putative chloroplastic GS2 gene was found to accumulate primarily in green tissues, whereas the transcripts of the five putative GS1 genes were shown to accumulate preferentially in roots. The specific patterns of transcript accumulation were quite distinct for the five GS1 genes, with the exception of two closely related genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00029015
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  • 9
    Electronic Resource
    Electronic Resource
    Chromosomal location of the catalase structural genes in Zea mays using B-A translocations (1980)
    Springer
    Theoretical and applied genetics 58 (1980), S. 211-218 
    Details
    ISSN: 1432-2242
    Keywords: B-A translocations ; Catalase Mapping ; Structural genes ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary B-A translocations have been used to map the catalase genes, Cat1, Cat2, and Cat3 of Zea mays. Cat1 was found to be on the short arm of chromosome 5, 9.1 map units from brittle endosperm (bt 1). Cat2 was located on chromosome 1S, while Cat3 was located on the distal half of chromosome 1L. There was no linkage between Cat2 and Cat3. The significance of mapping the catalase structural genes is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00288439
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  • 10
    Electronic Resource
    Electronic Resource
    Tentacle contraction inDiscophrya collini: The effects of ionophore A23187 and ruthenium red on Ca2+-induced contraction and uptake of extracellular calcium (1984)
    Springer
    Protoplasma 122 (1984), S. 125-131 
    Details
    ISSN: 1615-6102
    Keywords: Calcium ; Contraction ; Discophrya ; Ionophore A23187 ; Ruthenium red ; Tentacles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The tentacles of the suctorian protozoonDiscophrya collini are stimulated to contract by externally applied Ca2+. The role of extracellular Ca2+ in tentacle contraction was studied by monitoring45Ca2+ uptake, using ionophore A23187 to facilitate membrane transport of calcium and ruthenium red (RR) as an inhibitor of transport. The degree of tentacle retraction was dependent upon external Ca2+ concentration and studies with45Ca2+ using scintillation counting indicated a linear relationship between external Ca2+ concentration and Ca2+ uptake. Uptake of Ca2+ was enhanced in the presence of the ionophore while RR caused little inhibition.45Ca2+ uptake was only partially inhibited by RR when cells were subjected to a Ca2+, ionophore and RR mixture. Grain counts from light microscope autoradiographs after treatment of cells with45Ca2+/ionophore,45Ca2+/RR or45Ca2+ alone showed heavy, light and intermediate labelling respectively. In all instances the grains were evenly distributed within the cell. These observations are interpreted as supporting the suggestion that the ionophore enhances both the uptake of extracellular Ca2+ and release of Ca2+from an internal source, while the RR could only partially prevent movement of Ca2+ through the plasma mebrane. A model is presented suggesting that tentacle retraction is mediated by cytosolic Ca2+ levels which are determined by the fluxing of Ca2+ across the plasma membrane and the membrane of elongate dense bodies which act as internal Ca2+ reservoirs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279445
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