ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    pH equilibration in human erythrocyte suspensions (1980)
    Springer
    The journal of membrane biology 54 (1980), S. 81-88 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A stopped-flow rapid reaction apparatus was used to study the rate of pH equilibration in human red cell suspensions. Flux of OH− or H+ was determined over a wide range of extracellular pH (4–11) in CO2-free erythrocyte suspensions. In these experiments, an erythrocyte suspension at pH 7.3 is rapidly mixed with an equal volume of NaCl solution at 3.0〉pH〉11.5. The pH of the extracellular fluid of the mixture changes rapidly as OH− or H+ moves across the red cell membrane. Flux and velocity constants can be calculated from the initiald pH/dt using the known initial intra- and extracellular pH. It was found that the further the extracellular pH is from 7.3 (in either direction from 4–11), the greater the absolute value of total OH− and/or H+ flux. Pretreatment with SITS (4-acetamido-4′-isothiocyanostilbene-2,2′-disulfonic acid), a potent anion exchange inhibitor, greatly reduces flux over the entire pH range, while exposure to valinomycin, a potassium ionophore, has no measurable effect. These data suggest that (i) both H+ and OH− may be moving across the red cell membrane at all pH; (ii) the species dominating pH equilibration is probably dependent on the extracellular pH, which determines the magnitude of the driving gradient for each ion; and (iii) the rapid exchange pathway of the erythrocyte membrane may be utilized for both H+ and OH− transport during CO2-free pH equilibration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01940562
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Exchange of HCO 3 − for monovalent anions across the human erythrocyte membrane (1980)
    Springer
    The journal of membrane biology 52 (1980), S. 173-179 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A stopped-flow rapid reaction apparatus was used for measuring changes in extracellular pH (pH o ) of red cell suspensions under conditions wheredpH o /dt was determined by the rate of HCO 3 − /X − exchange across the membrane (X −=Cl−, Br−, F−, I−, NO 3 − or SCN−). The rate of the exchange at 37°C decreased forX − in the order: Cl−〉Br−〉F−〉I−〉NO 3 − 〉SCN−, with rate constants in the ratios 1∶0.86∶0.77∶0.55∶0.52∶0.31. When HCO 3 − is exchanged for Cl−, Br−, F−, NO 3 − or SCN−, a change in the rate-limiting step of the process takes place at a transition temperature (T T ) between 16 and 26°C. In I− medium, however, no transition temperature is detected between 3 and 42°C. AlthoughT T varies withX −, the activation energies both above and belowT T are similar for Cl−, Br−, NO 3 − and F−. The values of activation energy are considerably higher whenX −=I− or SCN−. The apparent turnover numbers calculated for HCO 3 − /X − exchange (except forX −=I−) at the correspondingT T ranged from 140 to 460 ions/site ·sec for our experimental conditions. These findings suggest that: (i) HCO 3 − /X − exchange for allX − studied takes place via the rapid anion exchange pathway; (ii) the rate of HCO 3 − /X − exchange is influenced by the specific anions involved in the 1∶1 obligatory exchange; and (iii) the different transition temperatures in the Arrhenius diagrams of the HCO 3 − /X − exchange do not seem to be directly related to a critical turnover number, but may be dependent upon the influence ofX − on protein-lipid interactions in the red blood cell membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869123
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    HCO 3 − /Cl− exchange across the human erythrocyte membrane: Effects of pH and temperature (1979)
    Springer
    The journal of membrane biology 50 (1979), S. 23-41 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Changes in extracellular pH (pHo) in red cell suspensions were monitored in a stopped-flow rapid reaction apparatus under conditions wheredpHo/dt was determined by the rate of HCO 3 − /Cl− exchange across the membrane. Experiments were performed at 5°C〈T〈40°C using either untreated cells or cells exposed to 0.11mm SITS (4-acetamido-4′-isothiocyanostilbene-2,2′-disulfonic acid). Although SITS exposure reduced the rate of exchange by 90%, both untreated and SITS-treated cells are similarly affected by changes in pH0 and temperature. The rate of HCO 3 − /Cl− exchange exhibits a minimum at about pHo 5 and a maximum at about pH0 7.4 at all temperatures. A transition temperature of 17°C was observed in the Arrhenius relationship for all pH0. The activation energies (E a) in kcal/mol are 19.6 below and 11.7 above 17°C for 5〈pH0〈8. These findings, similar to those reported for Cl− self-exchange, suggest that: (i) a change in the rate-limiting step for HCO 3 − /Cl− exchange occurs at 17°C, possibly due to an altered interaction between the transport pathway and membrane lipids; (ii) the carrier system can be titrated by either H+ or SITS from the outside of the membrane, but the untitrated sites continue to transport normally; (iii) the pH0 dependence of the rate of exchange is consistent with the titratable carrier having its most alkaline pK in the range expected for amino groups; and (iv) below pH0 5, the nature of the exchange is markedly altered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868786
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Horseradish Peroxidase Transport Across Rat Alveolar Epithelial Cell Monolayers (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 1331-1335 
    Details
    ISSN: 1573-904X
    Keywords: protein transport ; pinocytosis ; fluid-phase endocytosis ; alveolar epithelium ; drug delivery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To evaluate the transport characteristics of horseradish peroxidase (HRP, a nonspecific fluid-phase endocytosis marker) across an in vitro model of tight (〉 2,000 ohm-cm2) rat alveolar epithelial cell monolayers grown on tissue culture-treated polycarbonate filters. Methods. Unidirectional HRP fluxes were estimated from the appearance rate of HRP in the receiver fluid following instillation in the donor fluid as a function of donor [HRP] and temperature. Molecular species present in either bathing fluid were determined at the end of flux experiments using fluorescein isothiocyanate (FITC)-labeled HRP by gel permeation chromatography. Cell-associated HRP activity at the end of the transport experiment was determined, as were the rates of recycling and transcellular movement of HRP. An enzymatic assay was used to quantify HRP activity in the bathing fluid and cells. Results. Unidirectional HRP fluxes were symmetric and increased linearly with up to 50 µM donor [HRP]. The apparent permeability coefficient of HRP was reduced by 3.5 times upon lowering the temperature from 37 to 4°C. About 50% of the FITC-labeled species present in either receiver fluid was intact HRP. Cell-associated HRP estimated from apical HRP incubation was about 4 times greater than that from basolateral incubation. Recycling into apical fluid of cell-associated HRP following apical incubation occurred rapidly with a half-time (T1/2) of ~5 min, reaching a plateau at ~67% of the initial cell-associated HRP, while transcellular movement of HRP (into basolateral fluid) took place with a T1/2 of ~20 min, attaining a steady-state at ~13% of the initial cell-associated HRP. Basolateral recycling of HRP was also rapid (T1/2 = ~5 min) reaching a steady-state at ~35% of the initial basolaterally-bound HRP. Transcellular movement of HRP following basolateral incubation was slower (T1/2 = ~70 min), leveling off at 50% of the initial cell-associated HRP. Conclusions. HRP appears to be transported relatively intact (~50%) across rat alveolar epithelial barrier via nonspecific fluid-phase endocytosis. The transepithelial pinocytotic rate of alveolar epithelial cells is estimated to be about 25 nL/cm2/h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016013731237
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Studies on the mechanisms of active ion fluxes across alveolar epithelial cell monolayers (1992)
    Springer
    Methods in cell science 14 (1992), S. 187-193 
    Details
    ISSN: 1573-0603
    Keywords: transport ; epithelium ; edema ; beta-agonist ; barrier ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To investigate the cell physiologic and biological properties of the alveolar epithelium, we studied rat alveolar epithelial cell monolayers grown on permeable supports in primary culture. Type II alveolar epithelial cells were disaggregated using elastase, and partially purified on a discontinuous metrizamide gradient. These isolated cells were plated onto tissue culture-treated Nuclepore membrane filters at 1.5×106 cells/cm2 and maintained in a humidified incubator (5% CO2 in air, 37° C). After 2 days in culture, the bathing media on both sides of the cell monolayers were changed to fresh culture medium, thus removing nonadherent cells (mostly leukocytes). These monolayers exhibit a high transmonolayer resistance (〉2000 Ω-cm2) and actively transport ions. Radionuclide flux studies indicate that Na+ is the predominant ionic species absorbed actively under baseline conditions, accounting for about 80% of the total active ion transport. Cl− seems to be passively transported across the epithelium. However, when the epithelium is exposed to a beta-agonist (terbutaline), active absorption of Na+ is increased and active absorption of Cl− occurs. Although it is clear that both active Na+ and Cl− transport are dependent on Na+/K+-ATPase activity, and that Na+ enters cells predominantly through channels, the specific mechanisms by which Cl− enters and exits the alveolar epithelial cells remain unclear. The stimulated reabsorption of Na+ and Cl− may be important in helping to remove excess fluid from alveolar air spaces in the lung.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01409010
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    An application of adaptive control to a continuous stirred tank reactor (1965)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 11 (1965), S. 930-936 
    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: This paper reports on an investigation of the effect of adaptive control on a closed-loop chemical plant. The plant controlled was a simple closed-loop feedback system, the elements of which were a proportional controller and an elementary continuous stirred-tank reactor. The reaction involved was an exothermic, single-reactant decomposition, with the control criterion being the integral of the square of the deviation of the output composition from a value determined by a reference model. The adaptive control system incorporated an automatic identification scheme and a decision process, and operated in the presence of disturbances in cooling water temperature and/or catalyst activity.The adaptive control system yielded excellent results. For all disturbances, the output of the adaptive controlled plant remained much closer to the reference model output than did the output of the simply controlled plant. Inclusion of an adaptive capability in a control system thus appears to be desirable and often feasible.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690110534
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Multiparameter adaptive process control via constrained objective functions (1971)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 17 (1971), S. 326-335 
    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 method has been developed for applying classical minimization techniques to forms of algebraic performance indices for use in optimal adaptive control systems. Essentially, the derivative of a general objective function is constrained to be equal to the integrand of a desired integral performance index. This generates a set of linear algebraic equations, the solution of which results in an algebraic objective function which is explicit in the system parameters. Derivatives of this function can be taken with respect to the controllable parameters, set equal to zero, and solved for the settings which minimize the performance index over time. Alternatively, the function itself may be searched for its minimum on the controllable parameters.The method has been applied to a stirred tank chemical reactor with an exothermic first-order reaction in which heat removal was accomplished by cooling coils. The cooling water flow rate was controlled by a proportional-plus-integral controller and by a three-mode controller. The adaptive control system adjusted the controller settings periodically. The plant, which was third-order, was controlled to a second-order dynamic reference model. The responses to both initial offsets (start-up problem) and disturbances in system parameters were investigated. In all cases, the adaptive control system performance was markedly superior to that for the unadapted, ordinary feedback control system.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690170218
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Local and average interphase heat transfer coefficients in a randomly packed bed of spheres (1968)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 14 (1968), S. 483-490 
    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: Local and average heat transfer coefficients have been measured for a sphere in a randomly packed bed. A steady state technique was employed in which internally heated spheres were placed in a bed 35 in. deep and 12 in. sq. Air passed through the bed in downflow, the range of Reynolds numbers being from 120 to 1,700 based on the sphere diameter and the superficial velocity.Average heat transfer coefficients have been measured at twenty-five positions permitting the assessment of the effect of position. An entrance region limited to the first two particle layers in the bed has been verified.Distributions of the local heat transfer coefficient on the surface of a single sphere in the top layer and in the nineteenth layer of the bed have also been measured. These distributions indicate that a laminar boundary layer exists over portions of the sphere surface.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690140326
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    facet.materialart.
    Unknown
    Transcriptional control of lung alveolar type 1 cell development and maintenance by NK homeobox 2-1 (2019)
    National Academy of Sciences
    Details
    Publication Date: 2019-09-23
    Description: The extraordinarily thin alveolar type 1 (AT1) cell constitutes nearly the entire gas exchange surface and allows passive diffusion of oxygen into the blood stream. Despite such an essential role, the transcriptional network controlling AT1 cells remains unclear. Using cell-specific knockout mouse models, genomic profiling, and 3D imaging, we found that NK homeobox 2-1 (Nkx2-1) is expressed in AT1 cells and is required for the development and maintenance of AT1 cells. Without Nkx2-1, developing AT1 cells lose 3 defining features—molecular markers, expansive morphology, and cellular quiescence—leading to alveolar simplification and lethality. NKX2-1 is also cell-autonomously required for the same 3 defining features in mature AT1 cells. Intriguingly, Nkx2-1 mutant AT1 cells activate gastrointestinal (GI) genes and form dense microvilli-like structures apically. Single-cell RNA-seq supports a linear transformation of Nkx2-1 mutant AT1 cells toward a GI fate. Whole lung ChIP-seq shows NKX2-1 binding to 68% of genes that are down-regulated upon Nkx2-1 deletion, including 93% of known AT1 genes, but near-background binding to up-regulated genes. Our results place NKX2-1 at the top of the AT1 cell transcriptional hierarchy and demonstrate remarkable plasticity of an otherwise terminally differentiated cell type.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 10
    facet.materialart.
    Unknown
    Enhancement of Insulin Transport Across Primary Rat Alveolar Epithelial Cell Monolayers by Endogenous Cellular Factor(s) (2007)
    Springer
    Details
    Publication Date: 2007-04-19
    Print ISSN: 0724-8741
    Electronic ISSN: 1573-904X
    Topics: Chemistry and Pharmacology
    Published by Springer
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...