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  • 1
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    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The unpaired germarium of Dicrocoelium dendriticum contains many female germ cells at different stages of maturation and is enveloped by a fibrous basal lamina-like structure and a multilayered cytoplasmic sheath whose origins and functions are discussed. The maturation process of primary oocytes occurs completely within the prophase of the first meiotic division. It has been divided into three stages, as previously suggested for monogeneans. Stage I corresponds to oogonia and early oocytes which are located in the distal germinative area of the gonad. These cells are characterized by a high nucleo/cytoplasmic ratio and a poorly differentiated cytoplasm. Stage II corresponds to maturing oocytes grouped in the central area of the gonad and exhibiting long synaptonemal complexes and a prominent nucleolus. The main feature of cytoplasmic differentiation is the increase in the number of RER and Golgi complex which are involved in the production of small electron-dense granules. Stage III corresponds to mature oocytes located in the proximal area of the germarium near the origin of the oviduct. In this stage, the granules become regularly distributed in a monolayer in the peripheral ooplasm and make contact with the oolemma. They show a distinctive complex structure, are composed of proteins and glycoproteins and do not contain polyphenols. Their possible role as cortical granules is discussed in relation to chemical composition and previous studies on other Plathelminthes. Neither yolk globules nor glycogen are present in the oocytes.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The in vitro decay of Aextoxicon punctatum and Fagus sylvatica wood by the fungi Trametes versicolor, Ganoderma australe, Phlebia chrysocrea and Lentinus cyathiformis was studied by the agar-block method, and then the decayed woods were analyzed by chemical and spectroscopic techniques. The results demonstrated the strong resistance of the A. punctatum wood to the brown-rot fungus L. cyathiformis; the resistance might be related to the low S/G lignin ratio in this Austral hardwood. Wood decay by the Austral white-rot fungi G. australe and P. chrysocrea was rather limited, and preferential degradation of lignin was not produced although all the fungi studied increased wood digestibility. The most characteristic white and brown-rot decay patterns were observed during the in vitro decay with T. versicolor and L. cyathiformis, respectively. Trametes versicolor caused high weight losses and reduced the lignin content of the wood, whereas L. cyathiformis produced a preferential removal of xylan. No important changes in the solid-state 13C NMR spectra were observed after wood degradation by T. versicolor, but this technique evidenced an increase in aromatic carbon by L. cyathiformis. This increase was higher than that found in the Klason lignin content, suggesting the presence of altered lignin fractions in the brown-rotted wood.
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  • 4
    ISSN: 1432-2048
    Keywords: Calcium and salt stress ; Hordeum (root, salt stress) ; pH (intracellular) ; Salt stress ; Vacuole (Pi content)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Calcium has been demonstrated to ameliorate the inhibitory effects of high salinity on nutrient transport in plants. Time-course experiments were carried out to study the effect of high Ca2+ (6 mM) supply under saline conditions (100 mM NaCl) on the regulation of intracellular pH in excised barley (Hordeum vulgare L. cv Arivat) roots. In-vivo 31P-nuclear magnetic resonance measurements showed an alkalinization of the vacuolar pH after salt treatment. In the presence of high Ca2+ the extent of salt-induced vacuolar alkalinization was lower. High Ca2+ partially mitigated the salt-induced increase in Na+ content and decrease in K+ content of the root. The pattern of change in the vacuolar pH paralleled that of Na+ accumulation in the root. This correlation is consistent with the involvement of a tonoplast Na+/H+ antiporter in Na+ transport and the role of Ca2+ in Na+ uptake. High salt appeared to decrease the Pi content of the vacuole while high Ca2+ increased this content irrespective of the salt treatment.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1420-9071
    Keywords: Acylglycerols ; ichthyotoxins ; nudibranchs ; marine molluscs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Two marine opisthobranchs,Archidoris tuberculata from Asturias (N. Spain) andArchidoris carvi from Patagonia (S. Argentina), contain in their dorsum diasteroisomeric ichthyotoxic acylglycerols esterified in position 1-sn by antipodal diterpenoid acids.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 49 (1993), S. 308-312 
    ISSN: 1420-9071
    Keywords: Amino acids ; β-adrenergic agonist ; protein turnover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The administration of metaproterenol induced an increase in gastrocnemius muscle weight without change in body growth rate or tissue protein concentrations, while epididymal fat was reduced. This effect was accompanied by an enhancement in the levels of intracellular amino acids in muscle. By contrast, liver amino acids were unaffected by treatment with the mixed β-adrenergic agonist.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 49 (1993), S. 179-181 
    ISSN: 1420-9071
    Keywords: Gorgonian ; antitumor agent ; cembranoid diterpene ; Pseudoplexaura porosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Two new cytotoxic antitumor diterpenoids of the cembrane class, named 14-deoxycrassin (3) and pseudoplexaurol (4), have been isolated from the Caribbean gorgonian octocoralPseudoplexaura porosa. The structure of lactone3, possessing the infrequently encountered α-methylene-δ-lactone ring, has been established from spectral and chemical data and that of alcohol4 has been established from spectral data.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 49 (1993), S. 54-56 
    ISSN: 1420-9071
    Keywords: Drosophila-related species ; obscura group ; heat shock ; hsps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effect of heat shock on protein synthesis in three relatedDrosophila species belonging to theobscura group was analyzed on SDS-acrylamide gels. Four major heat shock proteins (hsps) were found in these species, in which synthesis reaches a maximum at 34°C. Although the higher molecular weight proteins are conserved, differences in size were found for the small hsps in these species. By means of in situ hybridization usingD. melanogaster probes for the small hsp genes, it was inferred that the small hsp genes of theobscura group species are clustered at the 27A locus in all three species.
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  • 9
    ISSN: 1420-9071
    Keywords: HLA ; haplotype ; disease ; diabetes ; arthritis ; Berger's disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Extended HLA haplotypes frequencies were estimated from the HLA, C2, Bf and C4 phenotypes of 74 patients with non-insulin-dependent diabetes (NIDD), 92 with juvenile rheumatoid arthritis (JRA), 44 with Berger's disease (BD), 83 with insulin-dependent diabetes (IDD), and 140 healthy controls. The extended HLA haplotype B18 CF130 DR3 DQw2, which is common (around 10% phenotype frequency) in healthy Spaniards and in other populations of paleo-North African origin, was found to be significantly less frequent in NIDD, JRA and BD, whereas its frequency was normal in IDD (although DR3 DQw2 haplotypes were increased in the latter disease). These data support the existence of a common HLA-linked pathogeneic mechanism in NIDD, JRA and BD, and point to a genetic difference between IDD and NIDD at the HLA level. This effect is readily detectable in our population because the uncommon BfF1 allele marks that haplotype instead of the more common BfS, which marks B8 CS01 DR3 DQw2 in other Caucasians. Our results support the hypothesis of strong selective pressures operating at the HLA level to preserve extended HLA haplotypes with advantageous gene sets from dilution by crossing-over. Imbalanced incomplete haplotypes may give rise to inappropriate T-cell repertoire selection in the thymus and/or antigen handling in the periphery, and be partly responsible for the pathogenesis of certain HLA-linked diseases (i.e. NIDD, JRA, and BD).
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 141 (1993), S. 83-100 
    ISSN: 1420-9136
    Keywords: P-waveform inversion ; annealing algorithm ; local stress tensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The determination of a local lithospheric stress pattern from low magnitude seismic activity recorded at a loca array is attempted by means of numerical simulations that include waveform inversion and annealing inversion techniques. A set of flat stratified layers are assumed for the propagating medium. The tests show that the annealing algorithm is a useful tool in this kind of study where collected seismic activity at local arrays could help us better understand local stress distributions in the lithosphere. Although real data recorded at local seismic arrays should be processed, assuming more realistic crust and upper mantle models, many characteristics of the annealing process described here could be used when studying real problems.
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