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  • Biochemistry and Biotechnology  (10)
  • Cell & Developmental Biology  (6)
  • Lanthanides  (5)
  • 1995-1999  (20)
  • 1950-1954  (1)
  • 1925-1929
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 223 (1995), S. 269-287 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The prenatal development of epidermis, dermis, and hypodermis was studied in embryos of different ago of two delphinid species (Stenella attenuata, Delphinus delphis), using light and transmission electron microscopical methods. The delphinid embryo is covered by a multilayered tissue formed by four different epidermal generations (periderm, stratum intermedium-I, str. intermedium-II, str. spinosum) produced by the str. basale. The first layer appears at about 40-50 mm of body length, the second type (s.i.-I) about 60-160 mm, and the third type (s.i.-II) is present at 160-500 mm. The first spinosal cells are produced at 225-260 mm body length; thenceforth, the epidermis increases continuously in thickness. Epidermal ridge formation begins about 400-mm body length. The development of the dermis is characterized by the early production of thin connective tissue fibers (40- 70-mm body length) and simultaneously the cutaneuous muscle matures in structure. Vascular development intensifies between embryos of 150-225 mm, and collagen production increases markedly in fetuses of 225-260-mm length. These events are paralledled by an increase in dermal thickness. The first elastic fibers can be recognized in the skin from the abdomen at about 600-mm body length. The development of the hypodermis is marked by very rapid and constantly progressing growth, beginning about 60-mm body length. The first typical fat cells appear in animals of 360-400 mm. Regional differences are obvious for all skin layers with regard to the flippers, where structural maturation proceeds more rapidly than in dorsal or abdominal regions. © 1995 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 67-72 
    ISSN: 0886-1544
    Keywords: Nicotiana ; Hordeum ; microtubule ; cell differentiation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Changes in the tubulin-protein and -poly(A)+RNA contents were monitored by means of Western and Northern blot analyses, respectively, during growth and maturation of leaves of a dicotyledonous (tobacco) and monocotyledonous (barley) plant. It was recently argued from immunofluorescence and preliminary biochemical data that the density of microtubular networks and concomitantly the tubulin content are distinctly reduced after cessation of cell growth in leaves [Jung et al., 1993]. The results presented now confirm and extend this view. There appeared to be clear differences between the monocot and the dicot: (1) the loss of tubulin during leaf development was much slower in the dicot than in the monocot leaves (within months instead of days); (2) the degree of loss was more dramatic in the monocot leaf and only very low threshold levels of tubulin were retained in fully differentiated tissues; and (3) the loss of tubulin in the monocot leaf tissue appeared to be correlated with the decrease in the mRNA content, whereas the high level of tubulin-RNA in fully differentiated or even almost senescent dicot leaves indicated a gene expression control at the posttranscriptional level.The comparatively rapid and very distinct tubulin-protein and -RNA disappearance during development of the monocot leaf tissues confirm at the molecular level that differentiation proceeds much faster and is much more determinative in these leaves, as was postulated from histological and physiological data. The differences in the behaviour of the microtubular cytoskeleton perhaps even reflect the differences in the ability of the differentiated leaf cells to dedifferentiate, i.e., to establish new sets of microtubules and to reenter the mitotic cell cycle, e.g., during would response, tumour induction or in vitro culture. © 1995 Wiley-Liss, Inc.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 219-228 
    ISSN: 0006-3592
    Keywords: formate conversion ; mass spectrometer ; anaerobic conversion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dynamics of the anaerobic conversion of formate in a microbial mixed culture taken from an anaerobic fluidized bed reactor was studied using a new stirred micro reactor equipped with a membrane mass spectrometer. The microreactor with a toroidally shaped bottom and pitched blade turbine and a cylindrical flow guide was thermostated and additionally equipped with a pH electrode and pH control. During fed-batch experiments using formate, the dissolved gases (methane, hydrogen, and carbon dioxide), as well as the acid consumption rates for pH control were monitored continuously. Initially and at the end of each experiment, organic acids were analyzed using ion chromatography (IC). It was found that about 50% of the formate was converted to methane via hydrogen and carbon dioxide, 40% gave methane either directly or via acetate. This was calculated from experiments using H13CO3- pulses and measurement of 12CH4 and 13CH4 production rates. About 10% of the formate was converted to lactate, acetate, and propionate, thereby increasing the measured CO2/CH4 production ratio. The nondissociated formic acid was shown to be rate determining. From the relatively high Ks value of 2.5 mmol m-3, it was concluded that formate cannot play an important role in electron transfer. During dynamic feeding of formate, hydrogen concentration always increased to a maximum before decreasing again. This peak was found to be very discriminative during modeling. From the various models set up, only those with two-stage degradation and double Monod kinetics, both for CO2 and hydrogen, were able to describe the experimental data adequately. Additional discrimination was possible with the IC measurement of organic acids. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 127-135 
    ISSN: 0006-3592
    Keywords: membrane mass spectrometer ; kinetic measurements ; anaerobic biofilm ; acetate ; inhibition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A small, stirred, 14.4-mL tank reactor was designed to serve as a measurement cell for short-term investigation of microbial kinetics. A mass spectrometer membrane probe allowed the measurement of the dissolved gases of hydrogen, methane, oxygen, and carbon dioxide. pH was measured by an electrode and controlled by addition of acid or alkali. The highly sensitive measurement of gases with low solubility allowed rapid measurements at very low conversion. In kinetic experiments, a stepwise increase of substrate concentration (method A) and continuous feed of substrate (method B) were used, allowing quick estimation of substrate kinetics. Acetate conversion in mixed culture biofilms from a fluidized bed reactor was investigated. Substrate inhibition was found to be negligible in the concentration range studied. Experiments at various pH values showed that the undissociated acid form was the kinetic determinant. Kinetic parameters for Haldane kinetics of protons were KSH = 1.3 × 10-5 mol m-3 and KIH = 8.1 × 10-3 mol m-3. With free acid (HAc) as the rate determining species, the kinetic parameters for method A were KSHAc = 0.005 mol m-3 and KIHAc = 100 mol m-3 and for method B were KSHAc = 0.2 mol m-3 and KIHAc = 50 mol m-3. The maximum biomass activity occurred at around pH 6.5. Acetate was exclusively converted to methane and CO2 at pH 〉 6. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 127-135, 1998.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 189-202 
    ISSN: 0006-3592
    Keywords: artificial neural network (ANN) ; microfiltration ; cell harvesting ; membrane fouling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Microfiltration is an important unit operation in downstream processing. However, due to the influence of membrane fouling, prediction of the filtration performance for biological suspensions is difficult. This paper describes a modeling approach that allows a comprehensive description of filtration performance. On the basis of experimental data and linguistic information, a specific artificial neural network was developed that predicts the process behavior within a certain range of parameters. This approach allows us to analyze influences of fermentation on filtration. By using extensive simulations, the interactions of 17 parameters were examined and the fouling causes determined. The model was developed for cell harvesting of Escherichia coli through a shear-enhanced module. The method can be applied to any cross-flow filtration process. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:189-202, 1998.
    Additional Material: 15 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 554-559 
    ISSN: 0006-3592
    Keywords: directed evolution ; esterase ; epothilon ; Pseudomonas fluorescens ; stereoselectivity ; mutator strain ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The directed evolution of an esterase from Pseudomonas fluorescens using the mutator strain Epicurian coli XL1-Red was investigated. Mutants were assayed for their ability to hydrolyze a sterically hindered 3-hydroxy ester, which can serve as a building block in the synthesis of epothilones. Screening was performed by plating esterase producing colonies derived from mutation cycles onto minimal media agar plates containing indicator substances (neutral red and crystal violet). Esterase-catalyzed hydrolysis of the 3-hydroxy ester (ethyl or glycerol ester) was detected by the formation of a red color due to a pH decrease caused by the released acid. Esterases isolated from positive clones were used in preparative biotransformations of the ethyl ester. One variant containing two mutations (A209D and L181V) stereoselectively hydrolyzed the ethyl ester resulting in 25% ee for the remaining ester. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 554-559, 1998.
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  • 7
    ISSN: 0006-3592
    Keywords: protein stabilization ; urokinase ; denaturation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Stabilization of proteins through proper formulation is an important challenge for the pharmaceutical industry. Two approaches for stabilization of proteins in solution are discussed. First, work describing the effect of additives on the thermally induced denaturation and aggregation of low molecular weight urokinase is presented. The effects of these additives can be explained by preferential exclusion of the solute from the protein, leading to increased thermal stability with respect to denaturation. Diminished denaturation leads to reduced levels of aggregation. The second approach involves stoichiometric replacement of polar counter ions (e.g., chloride, acetate, etc.) with anionic detergents, in a process termed hydrophobic ion pairing (HIP). The HIP complexes of proteins have increased solubility in organic solvents. In these organic solvents, where the water content is limited, the thermal denautration temperatures greatly exceed those observed in aqueous solution. In addition, it is possible to use HIP to selectively precipitate basic proteins from formulations that contain large amounts of stabilizers, such as human serum albumin (HSA), with a selectivity greater than 2000-fold. This has been demonstrated for various mixtures of HSA and interleukin-4. © 1995 John Wiley & Sons, Inc.
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  • 8
    ISSN: 0730-2312
    Keywords: calbindin-D28k ; 1,25-dihydroxyvitamin D3 ; messenger RNA ; organ culture ; polymerase chain reaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Organ culture of 19-day-old chick embryo duodena was utilized to evaluate the mechanism of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3)-dependent calbindin-D28k (CaBP) expression. Duodenal CaBP and 1,25(OH)2D3 receptor (VDR) expression were assessed by Western blot analysis, while CaBP and VDR mRNA levels were determined by Northen blot analysis. In untreated duodena, both VDR protein and mRNA were present, while CaBP protein and mRNA were undetectable. Treatment of cultured duodena with 25 nM 1,25(OH)2D3 resulted in detectable CaBP mRNA after 4 h which continued to increase during a 24 h time period. Under these conditions, localization of [3H-1β]1α,25(OH)2D3 in duodenal chromatin is rapid (≤ 30 min). Thus, the delayed accumulation of detectable CaBP mRNA cannot be explained by slow nuclear binding of 1,25(OH)2D3. The inclusion of 1.6 μM actinomycin D in the organ culture partially inhibited the 1,25(OH)2D3-regulated increase in CaBP mRNA, which implies that there is a transcriptional component involved in the increased CaBP mRNA levels. Similarly, quantitative polymerase chain reaction studies allowed the detection of CaBP pre-mRNA and mRNA sequences 1 h after hormone treatment, suggesting that CaBP gene transcription is initiated rapidly. Treatment of cultures with 36 μM cycloheximide 1 h prior to 1,25(OH)2D3 addition resulted in superinduction of VDR mRNA levels but sharply reduced CaBP steady-state mRNA levels. This dramatic reduction in CaBP mRNA reveals that 1,25(OH)2D3-mediated CaBP expression is dependent on ongoing protein synthesis. Thus, we propose that a labile auxiliary protein or other cofactor, which may or may not be 1,25(OH)2D3-dependent, is necessary for 1,25(OH)2D3-mediated CaBP gene transcription in chick duodena.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 32 (1995), S. 330-336 
    ISSN: 1059-910X
    Keywords: Scanning electron microscopy ; Teaching ; Computer ; Network ; Remote control ; Ethernet ; Internet ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A laboratory designed for teaching the operation of a scanning electron microscope (SEM) has been developed. The laboratory makes use of a computer network to allow remote operation of the SEM. Movable teaching stations, consisting of a computer, TV monitor, and joystick control, enable students to view the image on the SEM screen, move the sample, control the basic operating parameters of the microscope, and acquire X-ray spectra. Images can also be stored on the computers for image analysis or incorporation into reports. The great advantage of the system is that it has been designed to be flexible enough to allow operation from any location that has access to the Internet. The system is relatively inexpensive and uses nonproprietary computer technology available at any computer store. While the laboratory has been designed for teaching, the concept of a multiuser SEM facility that is inexpensive and easy to install should have applications in both industrial and research settings. © 1995 Wiley-Liss, Inc.
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  • 10
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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