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  • 1
    Electronic Resource
    Electronic Resource
    Morphometric studies demonstrate that aromatase-immunoreactive cells are the main target of androgens and estrogens in the quail medial preoptic nucleus (1994)
    Springer
    Experimental brain research 101 (1994), S. 241-252 
    Details
    ISSN: 1432-1106
    Keywords: Aromatase immunocytochemistry ; Preoptic area ; Sexual behavior ; Morphometry ; Quail
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The volume and cytoarchitectonic organization of the sexually dimorphic medial preoptic nucleus (POM) of the quail are sensitive to plasma levels of testosterone (T). We previously showed that, in castrated quail, T or its estrogenic metabolite, estradiol (E2), increases the size of the large neurons located in the lateral part of POM. Embryonic treatments with estrogens are also known to affect permanently the size of these large neurons. Since the lateral POM also contains a dense population of aromatase-immunoreactive (ARO-ir) cells, and these are known to be a target for steroids, we hypothesized that the effects of steroids identified in previous experiments were primarily directed to these ARO-ir cells. This idea was tested in two experiments in which the size of these cells was measured in male quail under various endocrine conditions. In experiment 1, a detailed analysis of ARO-ir and of non-immunoreactive cells in the POM of adult, sexually mature males revealed that the immunoreactive perikarya are larger than the non-immunoreactive cells and that they constitute the vast majority of the large cells (area 〉 50 μm2) in the POM. In experiment 2, it was shown that T and E2 actually increase the size of ARO-ir cells in the POM while the androgenic metabolite of T, dihydrotestosterone has no effect at this level. Taken together, these data suggest that the sex differences and the steroid-induced changes in cell size previously described in the study of POM sections stained for Nissl material largely concern aromatase-containing cells. Since aromatization of T plays a limiting role in the activation of male copulatory behavior, these changes may represent the morphological signature of the mechanisms causally involved in the control of this behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228744
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  • 2
    Electronic Resource
    Electronic Resource
    Comparative study of micro- and ultrafiltration membranes using STM, AFM and SEM techniques
    Amsterdam : Elsevier
    Ultramicroscopy 41 (1992), S. 235-244 
    Details
    ISSN: 0304-3991
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0304-3991(92)90112-W
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  • 3
    Electronic Resource
    Electronic Resource
    Model for colloidal fouling of membranes (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 368-376 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A proposed theoretical model describes colloids deposition on a membrane surface accounting for surface interactions. A mass-transfer equation links the deposition rate to hydrodynamic conditions (permeation and tangential flow through a boundary layer thickness, δ) and to physicochemical properties of the suspension (diffusion, D, and potential barrier between particles, VB). This equation predicts the existence of a critical flux, Jcrit, for ultrafiltration, reverse osmosis, or microfiltration of large-size colloids as: \documentclass{article}\pagestyle{empty}\begin{document}$$ J_{crit} = \frac{D}{\delta}ln \left({\frac{{V_B}}{\delta}} \right) $$\end{document} Some of the trends observed when processing protein solutions are explained by this model. Previous experimental data for various colloids or our data with a clay suspension in the presence of electrolytes are also compared to predictions of our model. It explains the “flux anomaly” for particle sizes between 10 nm and 1 μm.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410218
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  • 4
    Electronic Resource
    Electronic Resource
    Coagulation of colloids retained by porous wall (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 3523-3532 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The structure of a colloidal deposit retained by a porous wall is described, accounting for surface interactions and hydrodynamic forces. The balance of forces acting over spherical, charged particles allows the calculation of the interparticular distances inside the cake according to the physicochemical conditions (ionic strength, particle potential, pH, particle size) and to the experimental parameters (flux). The model predicts that beyond a critical mass deposited on the porous wall, the structure of the layers near the membrane changes where the particles are in close contact with each other. Experimental data obtained with latex monodisperse particles filtered over various types of ultrafiltration membranes for various physicochemical and flux conditions are compared to the model predictions. These results explain the existence of irreversible colloidal deposits in filtration and suggest strategies to optimize backflush or pulsed pressure procedures often used to improve the efficiency of ultrafiltration or microfiltration.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690421221
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  • 5
    Electronic Resource
    Electronic Resource
    Thermal isoelectric precipitation of α-lactalbumin from a whey protein concentrate: Influence of protein-calcium complexation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 121-130 
    Details
    ISSN: 0006-3592
    Keywords: α-lactalbumin ; whey ; isoelectric precipitation ; calcium complexation ; modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The selective precipitation of α-lactalbumin (α-LA) at a pH around its isoelectric point (4.2) under heat treatment is the basis for a fractionation process of whey proteins. As precipitation is a phenomenon dependent on the protein hydrophobicity, and as the release of the tightly bound calcium occurring at pH around 4 modifies the α-LA hydrophobicity, the specific role of calcium on isoelectric precipitation is investigated. A study of the extent of α-LA precipitation in a whey protein concentrate under various operating conditions of pH, temperature, protein concentration, and calcium content is presented. We propose a mechanism for this phenomenon as a combination of a complexation equilibrium and of an irreversible precipitation, to account for the influence of temperature, α-LA concentration total ionic content, and calcium concentration, and also to estimate the complexation equilibrium constant. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260470202
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  • 6
    Electronic Resource
    Electronic Resource
    Whey protein fractionation: Isoelectric precipitation of α-lactalbumin under gentle heat treatment (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 391-397 
    Details
    ISSN: 0006-3592
    Keywords: whey ; fractionation ; α-lactalbumin ; citrate ; co-precipitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The selective precipitation of α-lactalbumin (α-LA) at a pH around its isoelectric point (4.2) under heat treatment is the basis for a fractionation process of whey proteins. In these conditions, β-lactoglobulin remains soluble, whereas bovine serum albumin and immunoglobulins co-precipitate. Knowledge of the mechanism governing the α-LA precipitation influences the choice of operating conditions and enables optimization of the fractionation process. α-LA is a calcium metallo-protein and its isoelectric precipitation is governed by the protein-calcium complexation equilibrium. Citrate, a sequestrant of calcium, decreases the free calcium concentration and displaces the precipitation phenomenon to a lower temperature range. A study of the effect of citrate on the precipitation phenomena of whey proteins is presented. Whatever the citrate content, precipitation curves for bovine serum albumin (BSA) and α-LA intersect at a temperature around 45°C. For a temperature of heat treatment lower than 40°C, a selective enrichment in α-LA of the precipitated phase is observed. As addition of citrate leads to high α-LA precipitated fractions at a temperature around 35°C, the precipitation step may be performed at this temperature. It results in a reduced heat denaturation of whey proteins and in a higher α-LA purity in the precipitated fraction. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 391-397, 1997.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 7
    Electronic Resource
    Electronic Resource
    Role of some whey components on mass transfer in ultrafiltration (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 171-179 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ultrafiltration through Carbosep M4 mineral membrane of protein solutions of decreasing complexity (whey before and after centrifugation or clarification, β-lactoglobulin) was studied. Mathematical models were used to explain variations in flux with time. Taking into account variations in protein retention and hydraulic resistance of the membrane during ultrafiltration, proteins and lipoproteins were found to be involved not only in the polarization layer (reversible fouling leading to a difference in the osmotic pressure), but also in irreversible fouling by adsorption. Morever, the presence of particles (e.g., inorganic precipitates) in whey explains the build-up of a deposit over and within the membrane which contributes to the decline in flux after 1 h ultrafiltration. The relative importance of these phenomena was quantified.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260340205
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