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  • Articles  (196)
  • Life and Medical Sciences  (120)
  • Biochemistry and Biotechnology  (76)
  • 1980-1984  (188)
  • 1960-1964  (8)
  • 1983  (115)
  • 1980  (73)
  • 1960  (8)
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  • Articles  (196)
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  • 1980-1984  (188)
  • 1960-1964  (8)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 177 (1983), S. 245-254 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Striking ultrastructural and hormonal parameters of premature menopause and aging are reported in female Xyleborus ferrugineus fed cholesterol, rather than 7-dehydrocholesterol, as a sole dietary sterol. The titer of free ecdysteroids in such 63-day-old females remained abnormally elevated through the period of the ovarian cycle. A similar plateauing of such elevated titer also occurred in 147-day-old, irregularly cycling females fed only cholesterol as the dietary sterol. These hormonal changes in menopausing X. ferrugineus females seem especially analogous to the maintenance of an elevated concentration of 17-β-estradiol through the estrous, as well as the proestrous, ovary of aged irregularly cycling rats. The highly abnormal ultrastructure of ovaries of X. ferrugineus females aged 216 days on a diet containing cholesterol as the sole sterol seems quite analogous to that of the nonovulatory follicles in older, irregularly cycling rats. Our new findings involving aging X. ferrugineus females indicate further the usefulness of an insect model to study aging processes.
    Additional Material: 8 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 1 (1980), S. 159-162 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 3 (1983), S. 1-19 
    ISSN: 0886-1544
    Keywords: cytoplasmic transport ; Saltation ; microtubules ; keratocytes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We report the first direct demonstration that the cytoplasmic transport of organelles and vesicles (collectively called particles) takes place along microtubules. Living keratocytes from the corneal stroma of the frog, Rana pipiens, were observed with Allen video-enhanced constrast, differential interference constrast (AVEC-DIC) microscopy [Allen et al, 1981]. In sufficiently thin regions of these cells a network of linear elements was visible. When particles were observed in motion, they always moved along these linear elements. The linear elements remained intact and in focus on the microscope when lysed in a cell lysis solution that stabilized microtubules. Preparations were then fixed in formaldehyde, washed with phosphate-buffered saline (PBS), incubated with rabbit antitubulin, washed with PBS, stained with rhodamine-conjugated goat antirabbit, and washed with PBS. The extracted cells continued to remain in place and in focus on the microscope throughout these procedures. The same cells were then observed using epifluorescence optics and a silicon-intensified target (SIT) video camera. A network of fluorescent linear elements was seen to correspond in number, form, and position to the linear elements seen in the live AVEC-DIC image. Taken together, the AVEC-DIC and fluorescence microscopy observations prove that the linear elements along which particles move are microtubules (MTLEs). The observed particle speeds, pause times, and distances moved varied widely, even for the same particle on the same microtubule. Particles were also observed to switch from one microtubule to another as they were transported. The polarity of the microtubules did not seem to affect the particle direction, since particles were observed to move in both directions on the same MTLE. When not in motion these particles behaved as if anchored to the microtubules since they showed negligible Brownian motion. Finally, it was observed that an elongate particle could move onto two intersecting linear elements such that it was deformed into an inverted “Y” shape. This indicates that there may be more than a single site of attachment between the force generator and the particle.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 1 (1980), S. 63-71 
    ISSN: 0886-1544
    Keywords: Physarum polycephalum ; myosin light chains ; polyacrylamide gel electrophoresis ; calcium ; cytoplasmic streaming ; actomyosin ATPase regulation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Myosin from the slime mold Physarum polycephalum contains three sizes of polypeptides: a heavy chain and two light chains, LC-1 and LC-2. Using a simple qualitative test for calcium binding by comparing electrophoretic migration of the polypeptides in sodium dodecy1 sulfate (SDS) acrylamide gels in the presence and absence of calcium, we have found that Physarum myosin light chain LC-2 migrates with an apparent molecular weight of 16,900 daltons in the presence of the metal ion chelator ethylene glycol bis (B-aminoethyl ether) N,N′-tetraacetic acid (EGTA). However, if calcium chloride is added to the sample prior to electrophoresis, the apparent molecular weight decreases to 16,100. Lanthanide and cadmium ions, but not magnesium, can substitute for calcium. Because the ionic radii of Ca2+, La3+, and Cd2+ are almost identical, we conclude that Physarum myosin LC-2 possesses a very size-specific binding site for calcium. Physarum myosin LC-1 and the heavy chain give no evidence for binding calcium by this test. Since cytoplasmic streaming in the plasmodium of Physarum requires calcium, our evidence indicates that the calcium-binding property of Physarum myosin LC-2 may be important in regulating the production of force by actomyosin in the ectoplasm. Unexpectedly, the myosin light chain in Physarum capable of binding calcium, LC-2, is the essential light chain, while LC-1 is a member of the regulatory class of myosin light chains [V. T. Nachmias, personal communication]. Until now, essential myosin light chains have not been shown to have high affinity divalent cation binding sites. This means a new version of the myosin-based model for actomyosin regulation by calcium may be required to explain cytoplasmic movement in Physarum, and perhaps in other motile systems involving cytoplasmic myosins as well.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 22 (1980), S. 1237-1247 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The reaction kinetics of the enzymatic of cephalexin from 7-aminodea-cetoxy cephalosporanic acid and phenylglycine methylester was studied using the synthesizing enzyme obtained from Xanthomonas citri. The activation energy, Km value for 7-aminodeacetoxy cephalosporanic acid and phenylglycine methylester, and Ki value for phenylglycine methylester were determined as 8.63 kcal/mol, 3.7mM, 14.5mM, and 70mM, respectively. The enzyme was found to be constitutive and susceptible to deactivation.
    Additional Material: 7 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 123-131 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Industrialized nations face a critical problem in replacing the sources of liquid fuels that traditionally have been supplied by petroleum. One solution that has gained increasing support in this country is the use of ethanol produced by fermentation of renewable biomass as an extender in, or supplement to, gasoline for transportation fuel. Distillation, the present method of separating ethanol from the fermentation broth, is an energy-intensive one and frequently uses more energy than is available from the ethanol recovered. There are many investigations under way to find alternative, less energy-intensive techniques for the ethanol-water separation. The separations method described in this article involves the use of solid materials to preferentially remove ethanol from fermentation broths. Subsequent stripping of the ethanol from the sorbent with a dry gas reduces dramatically the energy required for the separation. Three solid sorbents have been investigated experimentally. Their sorption/desorption characteristics are described, and their incorporation in an ethanol recovery process is evaluated. Three sorbents were investigated: two commercially available divinylbenzene crosslinked polystyrene resins in bead form (one with a nominal surface area of 300 m2/g, the other with 750 m2/g) and an experimental proprietary molecular sieve with hydrophobic properties. Equilibrium adsorption isotherms for two of the sorbents were obtained at ambient temperature (21°C) for ethanol-water solutions containing up to 12 wt. % ethanol. In addition, 40°C isotherms were obtained for the polystyrene sorbents. Although different, the equilibrium isotherms for the sorbents indicated that ethanol could be preferentially sorbed from a dilute solution. Column breakthrough curves indicated very favorable kinetics. Desorption of the ethanol was readily effected with warm (60-80°C), dry nitrogen.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 329-340 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lysine decarboxylase (L-lysine carboxylyase, E.C.4.1.1.18) is immobolized on a carbon dioxide gas-sensing electrode, by copolymerization with gelatin using the bifuncitional agent glutaraldehyde. The enzyme electrodes thus prepared are used in a continuous flow system to measure the concentration of L-lysine in a mixture of amino acids. The measuring time for each sample is about 3 min, including response and rinsing times. The electrode response is linear between 0.01-1 g/L and has a high specificity for L-lysine. The enzyme electrode response to lysine at concentrations below 0.5 g/L is stable on repeated use for at least 500 assays.
    Additional Material: 13 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 387-401 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pseudomonas PG-1 cultivated on pristane produced in good amount a heat-stable polymeric substance which showed strong hydrocarbon emulsifying and solubilizing properties. The substance was isolated in crude form and was found to contain 34% protein, 16% carbohydrate, and 40% lipid. The hydrocarbon solubilizing activity of the isolate was strongly inhibited by EDTA but the chelating agent had no effect on the hydrocarbon emulsifying activity. Both activities of the isolate were strongly inhibited by chymotrypsin treatment indicating the importance of the protein moiety for its activity. Hydrocarbon solubilization by the isolate showed a certain degree of specificity to pristane in modest agitation generally used in microbial cultivation, but this specificity was lost by vigorous agitation in a Waring blender. It was proposed that in the first case, solubilization was effected by a solubilizing factor specific to pristane, whereas in the latter case, nonspecific solubilization occurred due to the action of the emulsifying factor. The rate of pristane solubilization by heat-treated culture broth under the conditions of agitation used in cultivation (rotary shaker, 120 rpm) was found to be ca. 750 mg L-1 h-1 which was much larger than the maximal pristane uptake rate of 170 mg L-1 h-1 observed during microbial growth on the substrate. It was concluded that hydrocarbon solubilization could satisfactorily account for the substrate uptake and growth.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 2503-2518 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A computer-controlled headspace gas chromatograph was used to monitor the progress of ethanol production from both aerobic batch and anaerobic continuous fermentations. Using an automatic, electropneumatic sampling system, aliquots of fermentation headspace gas were injected directly onto the column for quantitative ethanol determinations every six minutes. A sample volume of 1 mL permitted liquid ethanol concentrations from 2 to 100 g/L to be measured with better than 3% standard deviation on five repeated injections. Provided fermenter liquid temperature and ionic strength were maintained constant, the signal-tohyphen;concentration ratio remained linear to 80 g/L ethanol. This quantitative gas chromatographic (GC) method is suitable for accurate, precise analysis of multiple solvent fermentations, and is limited only by the elution rate and separating capacity of the GC column.
    Additional Material: 11 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 2929-2943 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The mode of uptake of sterols, which are nearly insoluble in water by an Arthrobacter species, was studied on the basis of substrate transfer via the aqueous phase (solubilization/pseudosolubilization) and through direct contact with sterol particles. Growth of the organism, on stero powder was predominantly in nonlogarithmic in character, indicating a possible limitation of substrate transfer. Soluble sterol was shown to be the preferential form of the substrate for assimilation by the organism. Evidence was obtained for increased solubilizition of β-sitosterol and cholesterol during microbial growth on these substrates. But the rate of solubilization of β-sitosterol (3.06 mg L-1 h-1) was too inadequate to account for the observed substrate uptake rare (107 mg L-1 h-1) during growth. A cholesterol solubilization rate of 44 mg L-1 h-1 could, however, account to an appreciable extent for the observed cholesterol uptake rate of 140 mg L-1 h-1 during growth. Increasing attachement of cells to sterol particles during growth was observed by microscopic examination, indicating that growth may take place over the surface of sterol particles. By using the synthetic surfactant HYOXYD AAO (alkyl aryl polyglycol ether), which prevented attachment of cells to sterol particles without affecting the metabolic integrity of the cells, it was shown that growth indeed took place predominantly on the surface of the sterol particles. Increased generation of finer particles of sterol, which provides increased substrate surface area during growth, was demonstrated. It was concluded that with β-sitosterol, growth takes place almost entirely by attachement, whereas with cholesterol, about 30% of the growth take place on solubilized substrate and the rest through attachament.
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