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  • 1990-1994  (1.689)
  • 1975-1979  (407)
  • Biochemistry and Biotechnology  (763)
  • Engineering  (536)
  • Rat  (304)
  • Atomic, Molecular and Optical Physics  (299)
  • Magnetic resonance imaging  (194)
Materialart
Erscheinungszeitraum
Jahr
Schlagwörter
  • 1
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 11 (1993), S. 79-86 
    ISSN: 0263-6484
    Schlagwort(e): Aldehyde dehydrogenase ; alcohol dehydrogenase ; aldehyde reductase ; glutathione-S-transferase ; hepatoma ; 4-hydroxynonenal ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: 4-Hydroxynonenal (4-HNE), produced during the oxidative lipid breakdown of biological membranes, modulates various biochemical processes in normal liver and in hepatoma cells. It is very probable that the effects of 4-HNE are related to the quantity formed in the cells and the cells' ability to metabolize it. Aldehyde catabolism takes place within the cells through oxidative and reductive enzymes, and through conjugation with intracellular glutathione. In this paper, the various enzymatic pathways involved in the metabolism of 4-HNE were studied in normal hepatocytes and in hepatoma cells. The hepatocyte pathway undergoes a complex variety of change during neoplastic transformation.In hepatoma cells, generally, 4-HNE metabolism was due mainly to aldehyde dehydrogenases, whereas in normal hepatocytes 4-HNE metabolism was mainly due to alcohol dehydrogenase and glutathione-S-transferase. The increase in oxidative enzymes compared to normal tissue was not the same in all types of hepatoma: in HTC hepatoma cells, the enzyme levels were considerably higher; in AH-130 hepatoma cells of Yoshida, they were lower in subcellular particles and similar in the cytosol. Indeed, consumption of externally-added 4-HNE in hepatoma cells was proportional to their content of 4-HNE metabolizing enzymes.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1432-1912
    Schlagwort(e): Pharmacokinetics ; [3H]-Hexahydro-siladifenidol ; Sila-drug ; Rat ; Autoradiography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The pharmacokinetics of tritiated hexahydrosila-difenidol ([3H]-HHSiD) were examined in rats. Furthermore, the distribution of radioactivity was studied by means of whole body autoradiography. After i. v. administration of 2.9 mg/kg HHSiD plus [3H]-HHSiD to anaesthetized rats bearing a catheter implanted in the ductus choledochus and receiving a mannitol infusion, HHSiD was rapidly distributed and metabolized. Only 5% of the radioactivity was recovered in blood after 23 s and 0.4% after 2.5 h. 64% of the plasma radioactivity could be extracted with hexane from the samples taken 23 s after administration. 52% of the radioactivity was eliminated within 2.5 h, 13% by urinary and 39% by biliary excretion. Following oral administration of 8.6 mg/kg HHSiD plus [3H]-HHSiD there was an absorption of approximately one fourth of the administered radioactivity within 4 h. By means of whole body autoradiography (i. v. injection) as well as by tissue distribution measurement the highest levels of radioactivity were found in bile, urine, lung, kidney, adrenals, liver and pancreas. Thus, after i. v. administration to rats HHSiD is rather quickly distributed, metabolized and excreted. This explains its low antimuscarinic potency in vivo.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1432-1920
    Schlagwort(e): Acute traumatic central cord syndrome ; Magnetic resonance imaging ; Pathology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The acute traumatic central cord syndrome (ATCCS) is commonly stated to result from an injury which affects primarily the center of the spinal cord and is frequently hemorrhagic. To test the validity of this widely disseminated hypothesis, the magnetic resonance images [MRI] of 11 consecutive cases of ATCCS caused by closed injury to the spine were analyzed and correlated with the gross pathological and histological features of 3 cervical spinal cords obtained at post mortem from patients with ATCCS, including 2 of patients studied by MRI. The MRI studies were performed acutely (18 h to 2 days after injury) in 7 patients and subacutely (3–10 days after injury) in 4. Ten of the 11 patients had pre-existing spondylosis and/or canal stenosis. The 11th suffered a cervical fracture. All patients exhibited hyperintense signal within the parenchyma of the cervical spinal cord on gradient echo MRI. None showed MRI features characteristic of hemorrhage on T1-weighted spin echo or T2*-weighed gradient echo studies. Gross and histological examination of the necropsy specimens showed no evidence of blood or blood products within the cord parenchyma: the primary finding was diffuse disruption of axons, especially within the lateral columns of the cervical cord in the region occupied by the corticospinal tracts. The central gray matter was intact. In patients with ATCCS, the predominant loss of motor function in thedistal muscles of the upper limbs may reflect the importance of the corticospinal tract for hand and finger function in the primate. In this study, the MRI and pathological observations indicate that ATCCS is predominantly a white matter injury and that intramedullary hemorrhage is not a necessary feature of the syndrome; indeed, it is probably an uncommon event in ATCCS. We suggest that the most common mechanism of injury in ATCCS may be direct compression of the cervical spinal cord by buckling of the ligamenta flava into an already narrowed cervical spinal canal; this would explain the predominance of axonal injury in the white matter of the lateral columns.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    ISSN: 1432-2072
    Schlagwort(e): Sensitization to drug reward ; Morphine ; Place conditioning ; Taste conditioning ; Abuse potential ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Male Sprague Dawley rats were injected daily with saline (morphine naive rats) or 20 mg/kg morphine (morphine experienced rats), starting at least 12 days before training. Subsequent place and taste conditioning indicated that 2.5 mg/kg morphine caused a significant increase in the amount of time spent on the least preferred side by morphine experienced but not by morphine naive rats; furthermore, saccharin consumption was markedly decreased and slightly increased by 10–20 mg/kg morphine in naive and experienced rats, respectively. It was concluded that morphine experience enhances the reinforcing efficacy of morphine and broadens the conditions under which the drug is reinforcing; thus it possibly increases morphine abuse potential.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 1432-0878
    Schlagwort(e): Key words: Pituitary ; Pars tuberalis ; α-Subunit ; Immunocytochemistry ; In situ hybridization ; Rat ; Mouse ; Guinea-pig
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The nature of the hormone(s) secreted by the pars tuberalis (PT) is still unknown. This pituitary lobe is mainly formed by specific glandular cells that differ in their ultrastructural features from the other adenohypophysial cell types. Data from the literature indicate the presence of thyroid-stimulating hormone immunoreactivity in the PT-specific cells of the rat and the Djungarian hamster but not of other species, including the mouse and guinea-pig. The PT also encloses variable numbers of pars distalis cells, essentially gonadotrophs that are mainly dispersed in its caudal area. We studied the expression of the glycoprotein hormone α-subunit in the PT of the rat, mouse and guinea-pig by in situ hybridization and immunocytochemistry. In situ hybridization, using an oligonucleotide probe complementary to rat cDNA sequence 196–237 revealed the expression of the α-subunit gene throughout the PT of the rat and the mouse; in the guinea-pig, the probe labelled no pituitary cells. Light- and electron-microscopic immunocytochemistry demonstrated α-subunit immunoreactivity in the secretory granules of the PT-specific cells in the three species examined. These cells did not react with a specific antibody against the β-subunit of luteinizing hormone, an antibody that labelled scattered gonadotrophs. The present data suggest that hormone(s) produced by the PT-specific glandular cells are, at least partly, related to glycoprotein hormones.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    ISSN: 1432-0878
    Schlagwort(e): Pituitary ; Pars tuberalis ; α-Subunit ; Immunocytochemistry ; In situ hybridization ; Rat ; Mouse ; Guinea-pig
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The nature of the hormone(s) secreted by the pars tuberalis (PT) is still unknown. This pituitary lobe is mainly formed by specific glandular cells that differ in their ultrastructural features from the other adenohypophysial cell types. Data from the literature indicate the presence of thyroid-stimulating hormone immunoreactivity in the PT-specific cells of the rat and the Djungarian hamster but not of other species, including the mouse and guinea-pig. The PT also encloses variable numbers of pars distalis cells, essentially gonadotrophs that are mainly dispersed in its caudal area. We studied the expression of the glycoprotein hormone α-subunit in the PT of the rat, mouse and guinea-pig by in situ hybridization and immunocytochemistry. In situ hybridization, using an oligonucleotide probe complementary to rat cDNA sequence 196–237 revealed the expression of the α-subunit gene throughout the PT of the rat and the mouse; in the guinea-pig, the probe labelled no pituitary cells. Light-and electron-microscopic immunocytochemistry demonstrated α-subunit immunoreactivity in the secretory granules of the PT-specific cells in the three species examined. These cells did not react with a specific antibody against the β-subunit of luteinizing hormone, an antibody that labelled scattered gonadotrops. The present data suggest that hormone(s) produced by the PT-specific glandular cells are, at least partly, related to glycoprotein hormones.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 16 (1979), S. 485-500 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The model systems of molecular nitrogen fixation [N2 + H]⋅, [N2 + H]+, [N2 + H]-, [N2 + H2], [N2 + H2]+, and [N2 + H2]- were studied by the semiempirical INDO method. The study was based on the formal analogy between the catalytic reactions and the photochemical, radical, and ionic reactions on the other side. Symmetrical and donor-acceptor properties of necessary catalytic systems were proposed using the dependence of energy characteristics and electron structure on reaction coordinate. On the basis of this MO study we have proposed the appropriate symmetry types of catalysts for each of acceptable models of nitrogen fixation. For one of the proposed systems there was realised a model MO computation with explicit inclusion of atoms of transition metals (Fe, V).
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    ISSN: 0006-3592
    Schlagwort(e): enzymatic peptide synthesis ; N-terminal protecting groups ; α-chymotrypsin ; experimental design ; partition constant ; reaction rate ; log P ; molecular refractivity ; response surfaces ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The influence of five different N-terminal protecting groups (For, Ac, Boc, Z, and Fmoc) and reaction conditions (temperature and dimethylformamide content) on the α-chymotrypsin-catalyzed synthesis of the dipeptide derivative X-Phe-Leu-NH2 was studied. Groups such as For, Ac, Boc, and Z always rendered good peptide yields (82% to 85%) at low reaction temperatures and DMF concentrations, which depended on the N-α protection choice. Boc and Z were the most reactive N-α groups and, in addition, the most suitable for peptide synthesis. On the other hand, the use of empirical design methodologies allowed, with minimal experimentation and by multiple regression, to deduce an equation, which correlates the logarithm of the first order kinetic constant (log k') with reaction temperature, DMF concentration, and hydrophobicity (log P values) of the different protecting groups. The predictive value of the equation was tested by comparing the performance of another protective group, such as Aloc, with the performance predicted by said equation. Experimental and calculated k' values were found to be in good agreement.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 727-732 
    ISSN: 0006-3592
    Schlagwort(e): lipase kinetics ; Candida cylindracea ; hydrolysis of triacetin ; hollow-fiber membrane reactor ; immobilization ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The aptitude of a hollow-fiber membrane reactor to determine lipase kinetics was investigated using the hydrolysis of triacetin catalyzed by lipase from Canadida cylindracea as a model system. The binding of the lipase to the membrane appears not to be very specific (surface adsorption), and probably its conformation is hardly altered by immobilization, resulting in an activity comparable to that of the enzyme in its native form. The reaction kinetics defined on the membrane surface area were found to obey Michaelis-Menten kinetics. The specific activity of the lipase in the membrane reactor was found to be significantly higher than in an emulsion reactor. The activity and stability of the enzyme immobilized on a hydrophilic membrane surface seem not to be influenced significantly by the choice of the membrane material. The hollow-fiber membrane reactor is a suitable tool to assess lipase kinetics in a fast and convenient way.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 552-556 
    ISSN: 0006-3592
    Schlagwort(e): stirring ; turbulence ; shear effects ; lysine fermentation ; Brevibacterium flavum ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Excess turbulence caused by high-intensity stirring inhibited microbial growth and metabolism. In stirred tank bioreactors, the growth rate and lysine biosynthesis decreased in Brevibacterium flavum beyond 900 rpm, the growth rate of Trichoderma reesei on wheat straw beyond 150 rpm, and the growth rate of Saccharomyces cerevisae beyond 800 rpm. The term turbohypobiosis was introduced to describe this inhibition. Turbohypobiosis was characterized by a stress factor Fstr expressing the interaction of medium flow with microbial cells in local turbulent zones, dependent on the energy distribution of the stirring regime. Lysine synthesis was inhibited at significantly lower Fstr values than the growth of B. flavum. The main reason for the inhibition was shear effects causing decreased adenosine triphosphate (ATP) generation, lower O2 uptake, and lower specific growth rate of bacteria.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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