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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anatomia, histologia, embryologia 27 (1998), S. 0 
    ISSN: 1439-0264
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A histological and immunohistochemical study of the epididymis of 21 cats which ranged from 7 to 8 months to 2 years of age was made. Five different cell types were observed in the feline epididymis: principal and basal cells, which were the most numerous, apical and narrow, PAS positive cells, which were scarce, and migratory cells, consisting of lymphocytes and macrophages. Four morphologically distinct areas of the cat epididymis were identified. Region I displayed a stellate lumen and the principal cells were tall and presented long and irregular stereocilia. In region II, the lumen was oval and the principal cells were shorter than in the inicial area. Region III displayed characteristics similar to those of region I; the principal difference was the presence of short and regular stereocilia on the surface of the principal cells. In region IV the lumen was very spacious and the epithelium shorter than in the other regions. In regions I, II, and III intraepithelial cavities were observed. With regard to the immunohistochemical results, the basal cells displayed medium immunoreactivity with vimentin. Due to its anti-desmin reactivity, the muscle wall which surrounds the epididymis was seen to become progresively thicker as it nears the tail. Broad-spectrum anti-cytokeratin serum produced intense immunostaining in the basal, apical and narrow, PAS positive cells; the principal cells of region IV also displayed a strong immunoreactivity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    FEBS Letters 136 (1981), S. 127-130 
    ISSN: 0014-5793
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0377-8401
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Using the pyroantimoniate technique, a study was conducted at electron microscope level on the distribution of the calcium ion in the pineal glands of normal adult Sprague-Dawley rats with initial weights of 150–200 g subjected to a 12:12 light dark cycle and others under the same conditions were subjected to modifications in the noradrenergic signal, such as continuous illumination over 7 days, blinding by bilateral enucleation (7 or 90 days) before sacrifice and bilateral superior cervical gangliectomy at 21 days before sacrifice. All the animals were sacrificed by decapitation, half of them at midday and the other half at midnight. Abundant fine precipitations of calcium were found in the intercellular spaces of the pineal glands of the normal rats. By contrast, in the gangliectomized animals subjected to constant illumination and chronic binding these precipitations were few in number. Additionally, two types of pinealocytes were observed regarding the distribution and concentration of intracytoplasmic calcium in both the normal and experimentally manipulated animals. Type I correspond to the classic light pinealocytes, with an absence of intracytoplasmic precipitations, although in the normal and gangliectomized animals sacrificed at midnight it was possible to observe fine deposits inside the mitochondrial matrix. Type II correspond to the classic dark pinealocytes, with a dense cytoplasmic matrix and numerous deposits of intracytoplasmic and intranuclear calcium; these were never seen in the type I pinealocytes.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5117
    Keywords: plant material ; decomposition rates ; leaching ; breakage ; Parana River
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The degradation of plant material in the centre of two plain streams (the Parana Medio River main channel − 0.6 m.s−1 - and the Colorado River − 0.03 m.s.−1) was studied in order to obtain a degradation coefficient for the species Panicum prionitis, Paspalum repens and Eichhornia crassipes, representative of the vegetation of the area of the future man-made lake of the Parana Medio, Dam. The experimental sites were chosen at the limit (minimum and maximum) velocities of the two streams in the valley to be flooded. The plant samples (submerged at different depths) were periodically analysed during 80 days, the experimental data being fitted to an exponential decomposition model. Degradation coefficients ranged from 0.0357 to 0.0682 day−1 (P. prionitis); from 0.0182 to 0.0643 day−1 (P. repens) and from 0.0120 to 0.0425 day−1 (E. crassipes). The incidence of leaching and fragmentation on the decomposition of plant materials was also studied.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 228 (1992), S. 43-54 
    ISSN: 1573-5117
    Keywords: phosphate adsorption ; aluminium ; iron ; calcium ; sediments ; Rio de la Plata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A study of the phosphate adsorption onto the bottom sediments of the Rio de la Plata has been made with the aim to understand the dynamics of this compound in the fluvio-marine system. Previous to the chemical analysis of the phosphate content, an extraction of the different adsorbed phosphate fractions have been made. In addition to phosphate, calcium, iron and aluminium in the sediment samples were determined. The phosphate is associated to the fine fractions of the sediments and good correlations with Al and Fe content in the bottom sediments were found. There is a relative decrease of the adsorbed phosphate on the bottom sediment in the areas where the influence of the marine water is more conspicuous; it is explained by the pH increase of the estuary waters due to the mixture with the marine waters. A hypothesis about the role of the ionic strength and the pH on the phosphate adsorption process is suggested.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5117
    Keywords: phosphate ; sediment ; suspended solid ; redox potential ; pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of redox potential and pH on the phosphate mobility in two sediments were investigated using both consolidated and suspended sediments from the area where the Parana Medio long reservoir (Atgentina) is to be built (Smirnov, 1984). In addition to direct chemical sediment analysis, extraction techniques were carried out with a stepwise NH4Cl-NaOH-HCl shaking method, the latter supposedly separating the weakly bound, the Fe- and Al- bound and the Ca- bound phosphates in the sediments. Phosphate released into water depends upon redox potential and pH, which both were modified in an experimental setup. The source of the phosphate was the fraction of Fe and/or Al bound phosphate present both in the sediment and in the suspended solids.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-5117
    Keywords: plant material ; decomposition rates ; leaching ; nutrient release ; Parana River
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The degradation of plant material was studied in order to obtain degradation coefficients and nutrient release kinetics of the vegetation that will be submerged during the filling of the future Parana Medio man-made lake. A group of 13 plant species representative of the whole vegetation of the area were chosen. The plant samples (submerged at 2.5–4 m in the Setubal lagoon), were periodically analyzed during 97 days. The experimental data were fitted to an exponential decomposition model. The plants were classified according to their velocities of degradation into three groups: fast (K〉0.01), mean (0.01〉K〉0.005) and slow (K〈0.005). The curves of release of P, N, Ca, Mg, Na and K in function of time are presented and discussed.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-5117
    Keywords: Patagonic Coast ; nutritive reserve ; limiting factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Physical and chemical characteristics of the Gulf San Jose (42°ϕ. S.) were studied during two annual cycles. The results indicate a possibility for high primary productivity.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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