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  • 1
    ISSN: 1573-5168
    Keywords: fat deposition ; GH ; GH ontogeny ; IGF-I ; immune function ; nutrient regulation ; phagocytic cells ; proliferative role ; sea bream
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of this mini-review is to provide a comprehensive survey of the physiological role of growth hormone (GH) in the Mediterranean sea bream (Sparus aurata). For this purpose, sea bream GH is now available as a recombinant and bioactive protein in a practically unlimited amount. In juvenile and adult fish, the liver is the most important target for the direct action of GH. Nevertheless, it must be noted that in sea bream larvae the greater concentration of GH-binding sites occurs in the head region, which also exhibits a fast growth. This finding suggests that GH exerts at this early stage of development a direct action on growing tissues rather than a systemic one mediated by hepatic IGF-I. However, the GH-liver axis is later a sensitive marker of growth performance, and seasonal changes in circulating GH levels and hepatic GH-binding are well characterized. The effect of age, water temperature and feeding regimes has also been studied. As a characteristic feature, fasting and malnourished fish show a decrease in hepatic GH-binding and circulating IGF-I, which increases pituitary GH release due to a lack of negative feedback inhibition. Interestingly, the up-regulation of plasma GH levels has also been described in fish fed to visual satiety. This, together with a decreased feed conversion, is more evident in fish fed high energy diets, and it has been suggested that this metabolic derangement is an adaptive response to protect adipose tissue and perhaps other organs and tissues from the excessive lipid deposition, when abundant energy is available. Experimental evidence also indicates that GH is able to exert a direct effect on sea bream erythroid and immunocytes. It is now recognized that GH receptors are present in erythroid, lymphoid and myeloid cells, and both GH and IGF-I have a mitogenic effect. GH also acts as a phagocytic-activating factor, and the presence of GH transcripts in the head kidney has been demonstrated by RT-PCR. All this provides suitable evidence for a pleiotropic and crucial role of GH in a lower vertebrate species such as sea bream.
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  • 2
    ISSN: 1573-5168
    Keywords: cortisol ; ACTH ; α-MSH ; GH ; head kidney ; pituitary ; temperature ; stress ; Sparus aurata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study investigated the effects of a drop in water temperature (18 °C to 9 °C in 24 h) on the pituitary and interrenal hormones of the gilthead sea bream Sparus aurata. The in vitro sensitivity of the interrenal tissue to ACTH, plasma levels of cortisol, ACTH, α-MSH, GH, glucose, lactate and ions were determined. In vitro ACTH, stimulated the release of cortisol from isolated interrenal glands from control gilthead sea bream in a concentration dependent fashion. However, the interrenal cells were less sensitive to ACTH as soon as 24 h following the onset of the temperature drop. At this time, plasma cortisol and ACTH levels were raised, and plasma GH concentrations were decreased, whereas no significant changes were found in plasma α-MSH. After 96 h plasma ACTH levels had recovered whereas plasma cortisol levels were still higher than controls after 8 days of the beginning of the experiment. Interrenal sensitivity had recovered after 8 days. The results may help to clarify the relationship between the stress response and the aetiology of the winter syndrome in sea bream.
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  • 3
    ISSN: 0886-9383
    Keywords: Principal components ; Multiple and stepwise regression ; Non-parametric density and regression estimation ; Bootstrap inference ; Canonical correlation ; PLS regression ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A statistical study of the dependence between various critical fusion temperatures of a certain kind of coal and its chemical components is carried out. As well as using classical dependence techniques (multiple, stepwise and PLS regression, principal components, canonical correlation, etc.) together with the corresponding inference on the parameters of interest, non-parametric regression and bootstrap inference are also performed.
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 560-567 
    ISSN: 0006-3592
    Keywords: phenol degradation ; Pseudomonas putida ; inhibition model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A semiempirical model, based on the presence of an inhibitory intermediate metabolite excreted to the broth, was developed to better predict the dynamic responses to shock loadings of Pseudomonas putida Q5 degrading phenol. Compared to the Haldane equation, the new model exhibited better prediction capabilities for a broad range of inlet concentration and dilution rate step changes. The experiments were performed at 10° and 25°C and ranged from stable responses to washouts. The time delays observed experimentally were successfully predicted with the dual-inhibition model and a very good agreement with the observed phenol profile also was found in a pulse experiment. A possible intermediate metabolite was detected by HPLC analyses based on the high correlation shown with the predicted inhibitory intermediate metabolite in the model. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 560-567, 1998.
    Additional Material: 10 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 847-856 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This work reports on the photodegradation of low-density polyethylene films formulated with titanium (IV) oxide actylacetonate (TAc) and titanium dioxide pigment in different proportions; no previous reports on the photoactivity of this acetylacotonate have been found. Samples of blow-extruded films were submitted to accelerated UV aging with fluorescent lamps and the polymer degradation measured. The changes in carbonyl groups, molecular weight, and film elongation at break are discussed. The results show that TAc can promote photooxidation and accelerate the film degradation. The retention percent of elongation at break (EB) is apparently proportional to the carbonyl index irrespective of the formulation but has different relations with molecular weight (Mn), time, or the number of chain scissions (n), probably as a result of microstructural differences. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 4 (1993), S. 99-105 
    ISSN: 1042-7147
    Keywords: Proton-conducting polymer ; Sol-gel process ; Battery ; Supercapacitor ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A new proton-conducting polymer electrolyte - poly-(benzylsulfonic acid)siloxane (PBSS) - has been prepared by sol-gel process. Both the hydrolysis and the condensation reactions of triethoxybenzylsilane have been studied under different catalysis conditions. The basic material - polybenzylsiloxane (PBS) - is always soluble, no matter what the experimental conditions, reaching an average molecular weight - Mw - of 20,000 and a polydispersity index close to 5. Good yields of a water-soluble polyelectrolyte - PBSS-thermally stable up to 300°C in air according to thermogravimetric analysis (TGA), and for which the exchange capacity is close to 4.4, can be obtained by sulfonation of PBS. Conductivities ranging from 2 × 10-3 to 10-2 S/cm at room temperature have been determined by a.c. impedance spectroscopy. These high conductivities, as well as the tensile strength of the PBSS, allow its use in several electrochemical devices.
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 413-424 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The accelerated UV photodegradation process of low-density polyethylene films, formulated with two photostabilizers and two antioxidants, was studied to evaluate the effect of different combinations of UV stabilizers and antioxidants on the overall photodegradation process. An experimental design, consisting of 33 formulations with different additive ratios and a blank, was used to evaluate the performance of the four mixed additives. From each formulation, 200 micron-thick films were produced by the extrusion-blowing process. Samples from these films were submitted to accelerated UV aging, and the polymer degradation was measured by carbonyl group evolution, molecular weight distribution changes, and maximum elongation loss. The effect of the additive combination on the different degradation reactions is discussed qualitatively by using “relative variables” and a triangular diagram. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 1511-1517 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The hardening process of natural (Hevea brasiliensis) rubber, that takes place when this rubber is stored in dry conditions over long periods of time, has been correlated with the presence of reactive “abnormal” groups directly grafted on the polymeric chain and in the serum of the latex. In the present work, natural Hevea (HR) and Guayule (Parthenium argentatum) rubber (GR) were stored under accelerated conditions and the changes in Mooney viscosity and molecular weight measured. The results showed that while HR undergoes hardening, GR keeps its Mooney viscosity constant, as does a constant viscosity (CV) Hevea rubber. These results are explained by the absence of functional “abnormal” groups that sustain the hardening reactions.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 655-661 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The uptake and activation of FXII from blood plasma was studied in small-diameter polyethylene tubing, surface-modified by end-point immobilization of heparin. Two preparations of heparin were used to modify the contact-activating properties of the plastic tubing: unfractionated, functionally active heparin and low-affinity heparin, lacking the specific antithrombin-binding sequence and virtually devoid of anticoagulant activity. The uptakes of FXII on the two heparin surfaces were similar. No activated FXII could be demonstrated on the unfractionated heparin surface, whereas on the low-affinity heparin surface nearly all FXII underwent spontaneous activation. The suppression of FXII activation on the unfractionated heparin surface was investigated by using plasma depleted of antithrombin, complement C1 esterase inhibitor, or both. The removal of antithrombin resulted in extensive activation of FXII, whereas the depletion of C1 esterase inhibitor had only a minor effect. Experiments with recalcified plasma showed rapid clot formation during exposure to the low-affinity heparin surface. After depletion of antithrombin, but not complement C1 esterase inhibitor, the recalcified plasma clotted in contact with the unfractionated heparin surface as well. We conclude that antithrombin and the antithrombin-binding sequence in the surface-immobilized heparin are essential for the prevention of surface activation of FXII and triggering of the intrinsic coagulation system. © 1995 John Wiley & Sons, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 37 (1997), S. 37-42 
    ISSN: 0021-9304
    Keywords: heparin surface ; contact activation system ; antithrombin ; factor XII ; systemic heparin ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: End-point immobilization of heparin to artificial materials gives rise to a surface that prevents triggering of the plasma contact activation system and, presumably as a result thereof, generally has thrombo-resistant properties. The present investigation was undertaken to determine what density of immobilized heparin molecules expressing functionally intact antithrombin binding sites is required to achieve these blood compatible properties. Six different heparin surfaces were prepared on polyethylene tubing and studied in contact with human plasma. The content of bound heparin was the same on all surfaces while the densities of antithrombin binding sites ranged from 1 to 28 pmol/cm2. The surfaces expressing 4 pmol/cm2 or more of specific anti-thrombin binding sites generated no measurable enzymatic activity in contact with plasma, either on the exposed surfaces or in the plasma phases. Below this level, the degree of activation gradually increased with decreasing densities, and in parallel the thrombo-resistant properties deteriorated. Addition of heparin to the plasma phase reduced the capacity of the heparin surfaces to bind antithrombin, leading to a diminished ability of the surfaces to prevent contact activation. This finding supports the hypothesis that antithrombin is the critical coagulation inhibitor for the suppression of contact activation on end-point immobilized heparin. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res, 37, 37-42, 1997.
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