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  • Articles  (245)
  • General Chemistry  (95)
  • Biochemistry and Biotechnology  (91)
  • Life and Medical Sciences  (59)
  • ENERGY PRODUCTION AND CONVERSION
  • GEOPHYSICS
  • 1995-1999  (188)
  • 1980-1984
  • 1975-1979  (57)
  • 1997  (188)
  • 1977  (57)
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  • 1995-1999  (188)
  • 1980-1984
  • 1975-1979  (57)
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  • 1
    Electronic Resource
    Electronic Resource
    Oxygen transfer coefficients by dynamic model moment analysis (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 19 (1977), S. 853-865 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method to estimate the oxygen transfer coefficient (KLa) from the experimental dynamic response data is presented. Employing a linear model which allows for gas phase, diffusion film, and oxygen electrode dynamics, the first moment of the response curve is simply related to the sum of the model parameters. Two separate experiments are used to characterize the measurement dynamics and to measure the unknown KLa parameter. The simple calculation procedure involves only measuring the area above the response curves.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260190606
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  • 2
    Electronic Resource
    Electronic Resource
    Selective effects of hydrocortisone on intestinal lipoprotein and apolipoprotein synthesis in the human fetus (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 66 (1997), S. 65-76 
    Details
    ISSN: 0730-2312
    Keywords: chylomicron ; very low density lipoprotein ; high density lipoprotein ; apoprotein B-100 ; apoprotein B-48 ; apoprotein A-I ; fat transport ; ontogeny ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Studies employing human fetal intestine have yielded much interesting information on the role of polarized enterocytes in fat absorption and transport. Using the organ culture model, we examined the influence of hydrocortisone on the synthesis and secretion of lipids and lipoproteins. Human jejunal explants were cultured for 5 days at 37°C in serum-free medium containing either [14C]-oleic acid or [14C]-acetate, alone or supplemented with hydrocortisone (25 or 50 ng/ml). The uptake of [14C]-oleic acid was associated with the production of triglycerides, phospholipids, and cholesteryl esters, which were all affected by hydrocortisone. This hormonal agent (50 μg) led to the marked reduction of secreted triglycerides (43%, P 〈 0.01), phospholipids (39%, P 〈 0.01), and cholesteryl esters (36%, P 〈 0.05) without altering the characteristic distribution of tissue and medium lipid classes. Similarly, hydrocortisone significantly (P 〈 0.01) decreased (∼60%) the incorporation of [14C]-acetate into secreted free and esterified cholesterol in the medium. With [14C]-oleic acid as a precursor, hydrocortisone significantly diminished the delivery of chylomicrons and very low density lipoproteins to the medium while consistently enhancing the secretion of high density lipoproteins. In parallel, [35S]-methionine pulse-labeling of jejunal explants revealed the concomitant inhibitory effect of hydrocortisone on apo B-100 synthesis and hydrocortisone's stimulatory effect on apo B-48 and apo A-I. These studies suggest that glucocorticoids play a critical role in lipoprotein processing during intestinal development. J. Cell. Biochem. 66:65-76 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Real-time monitoring and control of glucose and lactate concentrations in a mammalian cell perfusion reactor (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 372-378 
    Details
    ISSN: 0006-3592
    Keywords: glucose ; lactate ; on-line monitoring ; mammalian cell culture ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: On-line monitoring and control of cell culture fermentation is important for optimal and consistent production of biologicals. In this work, glucose and lactate concentrations are monitored on-line using a commercially available analyzer (Model 2700, Yellow Springs Instruments, Yellow Springs, OH) during batch and perfusion hybridoma cell fermentation. Cell free samples from the reactor are obtained using a 0.45 μm hollow fiber filtering system placed in a circulation loop. The samples were analyzed at specified times and the data are collected on a computer. A process control strategy was developed to control the concentrations of glucose and lactate in a perfusion reactor where the feed rate is adjusted to maintain their concentrations at desired set points. Hybridoma cells (A10G10) were cultivated in a high density perfusion culture where cell density increased from 2 to 14 million cells/mL. During this period the control algorithm successfully adjusted the perfusion rate while maintaining constant glucose and lactate concentrations. Glucose consumption and lactate accumulation rates as well as net lactate yield on glucose were monitored continuously during perfusion culture. These metabolic rates were observed to be independent of cell concentration and were used for the estimation of viable cell density in the reactor. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 372-378, 1997.
    Additional Material: 7 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    On-line monitoring and control of methanol concentration in shake-flask cultures of Pichia pastoris (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 279-286 
    Details
    ISSN: 0006-3592
    Keywords: methanol sensor ; methanol monitoring and control ; methylotrophic yeast fermentation ; Pichia pastoris ; transferrin ; shake-flask cultures ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The methylotrophic yeast Pichia pastoris can be used to express recombinant genes at high levels under the control of the methanol-inducible alcohol oxidase 1 (AOX1) promoter. Accurate regulation of the methanol concentration in P. pastoris cultures is necessary to maintain induction, while preventing accumulation of methanol to cytotoxic levels. We developed an inexpensive methanol sensor that uses a gas-permeable silicone rubber tube immersed in the culture medium and an organic solvent vapor detector. The sensor was used to monitor methanol concentration continuously throughout a fed-batch shake-flask culture of a P. pastoris clone producing the N-lobe of human transferrin. The sensor calibration was stable for the duration of the culture and the output signal accurately reflected the methanol concentration determined off-line by HPLC. A closed-loop control system utilizing this sensor was developed and used to maintain a 0.3% (v/v) methanol concentration in the culture. Use of this system resulted in a fivefold increase in volumetric protein productivity over levels obtained using the conventional fed-batch protocol. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 279-286, 1997.
    Additional Material: 7 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of dissolved oxygen on the metabolic profile of a murine hybridoma grown in serum-free medium in continuous culture (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 54 (1997), S. 153-164 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; oxygen ; serum-free medium ; continuous culture ; antioxidant ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The murine B-lymphocyte hybridoma, CC9C10 was grown at steady state under serum-free conditions in continuous culture at dissolved oxygen (DO) concentrations in the range of 10% to 150% of air saturation. Cells could be maintained with this range at high viability in a steady state at a dilution rate of 1 d-1, although with lower cell concentrations at higher DO. A higher specific antibody production measured at higher DO was matched by a decrease in the viable cell concentration at steady state, so that the volumetric antibody titre was not changed significantly. An attempt to grow cells at 250% of air saturation was unsuccessful but the cells recovered to normal growth once the DO was decreased.There was a requirement for cellular adaptation at each step-wise increase in dissolved oxygen. Adaptation to a DO of 100% was associated with an increase in the specific activities of glutathione peroxidase (×18), glutathione S-transferase (×11) and superoxide dismutase (×6) which are all known antioxidant enzymes. At DO above 100%, the activities of GPX and GST decreased possibly as a result of inactivation by reactive oxygen radicals.The increase in dissolved oxygen concentration caused changes in energy metabolism. The specific rate of glucose uptake increased at higher dissolved oxygen concentrations with a higher proportion of glucose metabolized anaerobically. Short-term radioactive assays showed that the relative flux of glucose through glycolysis and the pentose phosphate pathway increased whereas the flux through the tricarboxylic acid cycle decreased at high DO. Although the specific glutamine utilization rate increased at higher DO, there was no evidence for a change in the pattern of metabolism. This indicates a possible blockage of glycolytic metabolites into the TCA cycle, and is compatible with a previous suggestion that pyruvate dehydrogenase is inhibited by high oxygen concentrations.Analysis of the oxygen uptake rate of cell suspensions at steady state under all conditions showed a pronounced Crabtree effect which was manifest by a decrease (up to 40%) in oxygen consumption on addition of glucose. This indicates that the degree of aerobic metabolism in these cultures is highly sensitive to the glucose concentration. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 153-164, 1997.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    The characterization of SV40-transformed cell lines derived from mouse teratocarcinoma: Growth properties and differentiated characteristicsA portion of this work was presented at the Conference on “Regulation of Gene Expression in Development and Neoplasia” which was published in Cancer Research, 36, 4217-4223, 1976. (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 93 (1977), S. 269-276 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Mouse teratocarcinoma cells derived from embryoid bodies of 129SVsl mice were cultured in vitro to permit their differentiation. These cells were then infected with simiam virus 40 (SV40) and 31 cloned cell lines (SVTER) were derived from these cultures. All 31 SVTER cell lines contained the SV40 tumor (T) antigen and grew as permanent lines in culture. Mock-infected embryoid body cultures did not give rise to permanent cell lines. The morphology of each SVTER cell line was distinct and did not change during successive subclonings.The growth properties and tumorigenic potential of all 31 SVTER cell lines were investigated. None of these lines produced tumors in 129SVsl mice. Each cell line was tested for its ability to (1) grow in medium containing 1% serum, (2) plate on a cell monolayer, and (3) form clones in methocel suspension. Only three of the SVTER cell lines were transformed with respect to all three of these criteria. Most of these cell lines were minimal transformation.The SVTER cell lines were tested for creatine phosphokinase (CPK), an enzyme activity characteristic of mouse brain and muscle tissue, and the protease, plasminogen activator (PA) which is found in embryoid bodies and several differentiated cell types. Some of the SVTER cell lines contained high levels of CPK, while others had high levels of PA and a third group of cells contained neither enzyme activity. No SVTER cell line was found with high levels of both these enzyme activities. This result suggests that mutually exclusive sets of genes are expressed in these cells as might be expected from the distinct tissue distribution of the two enzyme activities studied. These SVTER cell lines may be useful in reconstructing developmental pathways of differentiating teratomas in vitro.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040930212
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  • 7
    Electronic Resource
    Electronic Resource
    Calix[4]tubus: ein röhrenförmiger Rezeptor mit hoher Selektivität für Kalium-IonenWir danken dem Engineering and Physical Sciences Research Council (EPSRC) für die Förderung des von uns genutzten Massenspektrometrie-Services an der University of Swansea sowie für die Förderung des Flächendetektors an der University of Reading. P. S. und P. D. S. danken A. W. E. Aldermaston für Stipendien. (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 109 (1997), S. 1926-1928 
    Details
    ISSN: 0044-8249
    Keywords: Alkalimetalle ; Calixarene ; Ionenkanäle ; Kalium ; Supramolekulare Chemie ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19971091709
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  • 8
    Electronic Resource
    Electronic Resource
    Ein neuartiger Zugang zum zentralen Gerüst von CP-225,917 und CP-263,114Diese Arbeit wurde vom The Skaggs Institute for Chemical Biology und von den National Institutes of Health (USA) gefördert. Wir danken Dr. Dee H. Huang und Dr. Gary Siuzdak für die Hilfe bei den NMR-spektroskopischen und den massenspektrometrischen Untersuchungen. (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 109 (1997), S. 2922-2925 
    Details
    ISSN: 0044-8249
    Keywords: Cyclisierungen ; Cyclopropanierungen ; Naturstoffe ; Umlagerungen ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19971092432
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  • 9
    Electronic Resource
    Electronic Resource
    The role of temporal sensing in bioelectromagnetic effects (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 18 (1997), S. 388-395 
    Details
    ISSN: 0197-8462
    Keywords: ornithine decarboxylase ; cell culture ; 60 Hz fields ; “averaging” time ; “memory” time ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Experiments were conducted to see whether the cellular response to electromagnetic (EM) fields occurs through a detection process involving temporal sensing. L929 cells were exposed to 60 Hz magnetic fields and the enhancement of ornithine decarboxylase (ODC) activity was measured to determine cellular response to the field. In one set of experiments, the field was turned alternately off and on at intervals of 0.1 to 50 s. For these experiments, field coherence was maintained by eliminating the insertion of random time intervals upon switching. Intervals ≥ 1 s produced no enhancement of ODC activity, but fields switched at intervals ≥ 10 s showed ODC activities that were enhanced by a factor of approximately 1.7. These data indicate that it is the interval over which field parameters (e.g., amplitude or frequency) remain constant, rather than the interval over which the field is coherent, that is critical to cellular response to an EMF. In a second set of experiments, designed to determine how long it would take for cells to detect a change in field parameters, the field was interrupted for brief intervals (25-200 ms) once each second throughout exposure. In this situation, the extent of EMF-induced ODC activity depended upon the duration of the interruption. Interruptions ≥ 100 ms were detected by the cell as shown by elimination of field-induced enhancement of ODC. That two time constants (0.1 and 10 s) are involved in cellular EMF detection is consistent with the temporal sensing process associated with bacterial chemotaxis. By analogy with bacterial temporal sensing, cells would continuously sample and average an EM field over intervals of about 0.1 s (the “averaging” time), storing the averaged value in memory. The cell would compare the stored value with the current average, and respond to the EM field only when field parameters remain constant over intervals of approximately 10 s (the “memory” time). Bioelectromagnetics 18:388-395, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Quantitative description of migration behavior of porphyrins based on the dynamic complexation model in a nonaqueous capillary electrophoresis system (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 82-91 
    Details
    ISSN: 0173-0835
    Keywords: Nonaqueous capillary electrophoresis ; Dynamic complexation ; Porphyrin ; Additives ; Separation theory ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The effect of an additive (Brij 35) on the mobilities of a group of porphyrin acids is quantitatively characterized based on a 1:1 dynamic complexation model. Varying additive concentration shifts the equilibrium and changes the viscosity of the background electrolyte. The equilibrium constant, the electrophoretic mobility of the free analyte, and the electrophoretic mobility of the complex are identified as the parameters necessary to describe the analytes' migration behavior. Several statistical methods for obtaining these parameters are discussed. The equilibrium constants and complex mobilities are calculated using three different linear regression methods. The weighted y-reciprocal method was preferred because it gives smaller error, and the data points are evenly distributed along the concentration axis. These values are confirmed using a nonlinear regression to ensure that the proper weighting was used in the linear regression plots. The parameters are then used to predict the apparent mobilities of the analytes over the entire additive concentration range, allowing the optimum separation conditions to be identified. For disclike molecules, such as porphyrins, the mobility is determined by the orientation of the molecule in an electric field, in addition to their size and charge. The strength of binding between the porphyrins and Brij 35 depends on the number of binding sites and the solvation shell.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150180117
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