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  • Lolium  (5)
  • Electron microscopy  (4)
  • Springer  (9)
  • American Chemical Society (ACS)
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  • Springer  (9)
  • American Chemical Society (ACS)
Years
  • 1
    Electronic Resource
    Electronic Resource
    Time-related changes in the ultrastructure of osteoclasts after injection of parathyroid hormone in young rats (1979)
    Springer
    Calcified tissue international 27 (1979), S. 129-135 
    Details
    ISSN: 1432-0827
    Keywords: Parathyroid hormone ; Osteoclasts ; Electron microscopy ; Morphometry ; Metaphysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The effects of parathyroid hormone (PTH) on the size of the osteoclasts, nuclei, ruffled borders, and clear zones in long bones of thyroparathyroidectomized (TPTX) rats were quantitated as a function of time. These data were compared with the number of osteoclasts in the bone and with plasma calcium levels. A significant increase in the average size of the ruffled borders was demonstrated 30 min after injection of 50 U of purified bovine PTH, and of the clear zones 30–90 min after PTH. This was followed at 90 min by an increase in the average size of the cells. The sizes of ruffled borders and clear zones dropped sharply to control levels after 6 h, whereas the size of the cells remained elevated up to 12 h and returned to control values at 24 h. Plasma calcium levels were increased, but not significantly, between 30 min and 6 h. An increase in the number of osteoclasts was significant after 12 h. Removal of the parathyroid glands did not diminish the normal activity of osteoclasts. In animals with intact glands injection of 50 U of PTH did not cause a significant change in cell size or resorbing apparatus. It is concluded that PTH acts to rapidly stimulate the bone resorptive activity of osteoclasts and to cause a delayed increase in their number.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02441175
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  • 2
    Electronic Resource
    Electronic Resource
    Gibberellin structure and florigenic activity in Lolium temulentum, a long-day plant (1990)
    Springer
    Planta 182 (1990), S. 97-106 
    Details
    ISSN: 1432-2048
    Keywords: Lolium ; Gibberellin and flowering ; Flowering and gibberellins ; Stem elongation and gibberellins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Structural requirements for florigenic activity among gibberellins (GAs) and GA derivatives, including several new ones, applied once to leaves of Lolium temulentum, were examined. The compounds were applied to plants kept either in non-inductive short days (SD) or exposed to one inductive long day (LD). Inflorescence initiation and stem-elongation responses were assessed three weeks later. Among the GAs used, the range in effective dose for inflorescence initiation was more than 1000-fold, but substantially less for stem elongation. Some GAs promoted both stem elongation and inflorescence initiation, some promoted one without the other, and some affected neither. The structural features enhancing florigenic activity were often different from those enhancing stem elongation. Except in the case of 2,2-dimethyl GA4, a double bond in the A ring at either C-1,2 or C-2,3 was essential for high florigenic activity, though not for stem elongation. A free carboxy group was needed for both. Inflorescence initiation in Lolium was enhanced by hydroxylation at C-12, −13 and −15, whereas hydroxylation at C-3 reduced the effect on inflorescence initiation but increased that on stem elongation. A 12β-hydroxyl was more effective than the α epimer for inflorescence initiation whereas the reverse was true for stem elongation. Although such differential effectiveness of GAs for inflorescence initiation and for stem elongation could reflect differences in uptake, transport or metabolism, we suggest that it is indicative of specific structural requirements for inflorescence initiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239990
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  • 3
    Electronic Resource
    Electronic Resource
    The differential effects of C-16,17-dihydro gibberellins and related compounds on stem elongation and flowering in Lolium temulentum (1994)
    Springer
    Planta 193 (1994), S. 107-114 
    Details
    ISSN: 1432-2048
    Keywords: Lolium ; Gibberellin ; Flowering ; Day-length ; Stem elongation ; 16,17-dihydro gibberellins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plants of Lolium temulentum L. cv. Ceres grown under short days (SDs) can be induced to initiate inflorescences either by exposure to one long day (LD) or by single applications of some gibberellins (GAs), which also enhance the flowering response to one LD. Single doses of up to 25 μg per plant of C-16, 17-dihydro-GA5 were about as effective as GA5 for promoting flowering after one LD but inhibited stem elongation by up to 40% over three weeks. The promotion of flowering but not the inhibition of elongation by 16, 17-dihydro-GA5 was reduced in SDs or in LDs low in far-red (FR) radiation. With shoot apices cultured in vitro, 16, 17-dihydro-GA5 was more florigenic than GA3 for apices excised after one LD of 14 h or more, but less florigenic for apices excised from plants in shorter days. 16, 17-Dihydro-GA5 was ineffective compared with GA1, GA3 and GA5 for α-amylase production by half-seeds of Lolium, a response concordant with its effect on stem elongation. As with GA5, 16, 17-dihydro derivatives of GA1, GA3, GA20 and several other GAs were more effective for flowering and less effective for stem elongation than the GAs from which they were derived. Hydroxylation at C-17 and/or C-16 generally reduced the effectiveness of 16, 17-dihydro-GA5 for flowering. These results extend the known features of GA structure which favour flowering relative to stem elongation in L. temulentum. Moreover, C-16, 17-dihydro-GA5 mimics, in its daylength- and wavelength-dependence and lack of stem elongation, characteristics of the LD stimulus in L. temulentum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191613
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  • 4
    Electronic Resource
    Electronic Resource
    Floral determination and in-vitro floral differentiation in isolated shoot apices of Lolium temulentum L. (1991)
    Springer
    Planta 185 (1991), S. 9-16 
    Details
    ISSN: 1432-2048
    Keywords: Floral determination and evocation ; Flower development in-vitro ; Gibberellin and flower development ; Lolium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Shoot apices of Lolium temulentum excised after exposure of the plants to one long day (LD) undergo floral development in vitro, whereas those excised from plants in short days (SD) remain vegetative. Floral differentiation in vitro is reasonably normal and responds quantitatively to the preceding LD induction when three conditions are met. First, excision must not precede the arrival at the apex of the LD stimulus from the leaves. This appears to begin about 22 h after the start of the LD and is completed after a further 14 h, by which time all isolated apices have become capable of initiating inflorescence differentiation, i.e. florally determined. Second, for apices excised on the day after the LD (Day II) or early on Day III, the presence of gibberellic acid in the medium is required for floral differentiation to occur in most explants. By contrast, neither kinetin (N6-furfurylaminopurine) nor indole-3-acetic acid is required or beneficial, while abscisic acid in the medium is inhibitory to both survival and floral differentiation in excised apices. The third requirement is for an adequate supply of sugar, particularly after floral differentiation begins. Sucrose is taken up rapidly to reach high levels in the excised apices, but high sugar concentration in the medium, either alone or with gibberellic acid, does not suffice for floral differentiation to begin, and there is an absolute requirement for receipt of the LD stimulus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194508
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  • 5
    Electronic Resource
    Electronic Resource
    The relative significance for stem elongation and flowering in Lolium temulentum of 3β-hydroxylation of gibberellins (1993)
    Springer
    Planta 192 (1993), S. 130-136 
    Details
    ISSN: 1432-2048
    Keywords: Lolium ; Gibberellin ; Flowering ; Stem elongation ; 3β-Hydroxylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In previous experiments with many gibberellins (GAs) and GA derivatives applied to Lolium temulentum L., quite different structural requirements were evident for stem elongation on the one hand and for the promotion of flowering on the other. Whereas hydroxylation at carbons 12, 13 and 15 enhanced flowering relative to stem growth, the reverse was the case at carbon 3 (L.T. Evans et al. 1990, Planta 182, 97–106). The significance of hydroxylation at carbon 3 is examined in this paper. The application of inhibitors of 3β-hydroxylation, including C/D-ring-rearranged GAs, reduced stem growth but, in the case of the two acylcyclohexanediones, increased the flowering response when applied on the inductive long day. Later applications of the acylcyclohexanediones, made after floral initiation had occurred, were inhibitory to flowering, suggesting that subsequent inflorescence development requires 3β-hydroxylated GAs. Applications of the 3α-hydroxy epimers of GA1, GA3 and GA4 gave slightly less promotion of flowering in comparison with the 3β-hydroxy GAs, but far less promotion of stem elongation, except in the case of 3-epi-GA4, which was comparable to GA4. The 3α-hydroxy epimer of 2,2-dimethyl GA4 gave less promotion of flowering than its 3β-hydroxy epimer but almost no promotion of stem elongation. The 3α-hydroxy epimers of GA3 and 2,2-dimethyl GA4 did not act as competitive inhibitors of the stem elongation elicited by GA3 and 2,2-dimethyl GA4, respectively. These results extend the differences in GA structure which favour flowering as opposed to stem elongation, and indicate that 3-hydroxylation and its epimeric configuration are of much greater importance to stem elongation than to flower initiation in Lolium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198703
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  • 6
    Electronic Resource
    Electronic Resource
    The fine structure of neuroglial cells and pericytes in the primate red nucleus and substantia nigra (1970)
    Springer
    Cell & tissue research 106 (1970), S. 309-321 
    Details
    ISSN: 1432-0878
    Keywords: Red nucleus ; Substantia nigra ; Neuroglia ; Pericytes ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The morphology of perivascular and perineuronal cells in the substantia nigra and red nucleus was studied in Nissl, silver carbonate, and electron microscopic preparations. In light microscopic preparations of the red nucleus and substantia nigra oligodendrocytes and astrocytes are located adjacent to blood vessels and nerve cells. Pericytes are also found adjacent to blood vessels. Scattered perineuronal oligodendrocytes and astrocytes are present in the magnocellular portion of the red nucleus and in the substantia nigra, whereas a distinguishing morphological feature of the parvocellular portion of the red nucleus is the clustering of perineuronal oligodendrocytes around a single neuron. In the present electron micrographs of the red nucleus and substantia nigra oligodendrocytes are separated from the vascular basement membrane (basal lamina) by astrocyte processes and therefore are not truly perivascular. Pericytes are easily identified by the basement membrane which encompasses their cell bodies and processes. Characteristic of the neuropil in the red nucleus are astrocytic processes that approximate dendrites. In contrast, astrocytic processes in the substantia nigra rarely contact dendrites which are covered by a mosaic of synaptic endings. A “third type of neuroglial element” is also present in the neuropil of the substantia nigra and the red nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335775
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  • 7
    Electronic Resource
    Electronic Resource
    The effects of host deprivation on the calyx cells of Nasonia vitripennis (walker) (hymenoptera: Pteromalidae) (1972)
    Springer
    Cell & tissue research 134 (1972), S. 529-538 
    Details
    ISSN: 1432-0878
    Keywords: Calyx cells ; Nasonia vitripennis ; Effects of host deprivation ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The changes in the ultrastructure of the cells of the calyx in the female reproductive system of Nasonia vitripennis are described during a period extending from a condition when host puparia are readily available to a condition of prolonged host deprivation. 2. In conditions when host puparia are available, the calyx cells resemble typical secretory cells with rough endoplasmic reticulum, Golgi complex and mitochondria. After periods of host deprivation the calyx cells increase in size, the organelles change and become reorientated and cytolysomes appear producing a configuration of cells undergoing autophagy. 3. When host puparia become available again, the cells show an ability to recover and recommence production of secretory droplets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307672
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  • 8
    Electronic Resource
    Electronic Resource
    Transformations of hypothalamic arcuate neurons (1974)
    Springer
    Cell & tissue research 153 (1974), S. 497-515 
    Details
    ISSN: 1432-0878
    Keywords: Arcuate nucleus ; Hypothalamus ; Sexual cycle ; Ribbon-rolls ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Changes in subcellular structures of arcuate neurons correlated in a consistent way with stages of the estrous cycle of the rat. Associated with the rough endoplasmic reticulum short ribbons of moderately electron dense material appeared at metestrus and circular or elliptical bodies termed “ribbon-rolls” at diestrus and proestrus. Although present in proestrus, the ribbon-rolls were smaller at this stage. In a few neurons in diestrous females and in ovariectomized animals one to seven months before perfusion multiple large ribbon-rolls occupied much of the cytoplasm. Also, frequency of dense granules and lysosomes increased in diestrus. The significance of the ribbon-rolls and changes in other structures during the estrous cycle are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231543
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  • 9
    Electronic Resource
    Electronic Resource
    Comparison of ribosomal DNA sites inLolium species by fluorescencein situ hybridization (1996)
    Springer
    Chromosome research 4 (1996), S. 486-490 
    Details
    ISSN: 1573-6849
    Keywords: in situ hybridization ; Lolium ; phylogeny ; rDNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The position of the 18S-5.8S-26S and 5S rRNA genes have been physically mapped on the chromosomes of sevenLolium taxa. 18S-5.8S-26S sites were seen on two pairs of chromosomes in the inbreeding taxa. In the outbreeding taxa six sites were found in theL. multiflorum, seven inL. perenne and nine inL. rigidum var.rigidum. Two 5S sites were found in each of the taxa. In the inbreeders, the 5S sites were found adjacent to the 18S-5.8S-26S sites on chromosome 2. InL. multiflorum andL. perenne the 5S sites were on the short arm of chromosome 3. However, inL. rigidum var.rigidum the 5S rDNA site was found in either of the two positions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02261775
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