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  • 1980-1984  (5)
  • 1984  (2)
  • 1982  (3)
  • Life and Medical Sciences  (4)
  • benzo(a)pyrene
  • cyst(e)ine determination
  • 1
    Electronic Resource
    Electronic Resource
    Absorption and fluorescence spectra ofS-quinolylethylated Kunitz soybean trypsin inhibitor (1982)
    Springer
    The protein journal 1 (1982), S. 225-240 
    Details
    ISSN: 1573-4943
    Keywords: protein disulfide bonds ; reductive alkylation ; soybean trypsin inhibitor (Kunitz) ; UV absorption spectra ; fluorescence spectra ; S-β-2-quinolylethylation ; cyst(e)ine determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Disulfide bonds in soybean trypsin inhibitor (Kunitz) were simultaneously reduced and alkylated using tri-n-butylphosphine and 2-vinylquinoline at pH 7.6 in 0.11 M Tris-4.4 M urea, 41% ethanol. The resulting S-β-2-quinolylethylated protein (2-QE-STI) has a new absorption peak at 315–318 nm. Its quinoline fluorescence can be excited above 310 nm independently of intrinsic protein fluorescence. Free 2-quinolylethylcysteine (2-QEC) shows unexpectedly weak fluorescence. Quinoline absorption in 2-QEC and 2-QE-STI changes with pH. The apparentpK values determined spectrophotometrically are near 5 for 2-QEC and 3 for 2-QE-STI. Fluorescence decreased with increasing pH and in the presence of chloride ions. Both structural and charge effects thus appear to influence the absorption and fluorescence of the quinoline group. Corrected fluorescence emission (excited at 316 nm) of neutral 2-QE-STI diluted in 0.1 N H2SO4 was directly proportional to concentration in the range 0.4–8 μm 2-QEC. The 2-QEC content of the protein derivative determined by UV absorption at pH 1.5 was in agreement with the expected value of four residues per mole. Fluorescence measurements ofS-2-quinolylethylated proteins may be especially useful as a sensitive, specific assay for cyst(e)ine residues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025001
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Metabolism of Benzo(a)pyrene by Human Epithelial and Fibroblastic Cells: Metabolite Patterns and DNA Adduct Formation (1982)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 18 (1982), S. 135-148 
    Details
    ISSN: 0730-2312
    Keywords: DNA adduct formation ; benzo(a)pyrene metabolism ; human cells ; mammary fibroblasts ; mammary epithelial cells ; metabolite patterns ; benzo(a)pyrene ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We demonstrate in cell culture that mammary epithelial cells from normal human breast specimens metabolize benzo(a)pyrene (BaP) and form adducts with the bases of their DNA more readily and at lower concentrations of BaP than do fibroblasts from the same specimens. BaP metabolism and adduct formation was determined in the same incubations with epithelial cells grown out in early passage from each of three specimens and with fibroblasts from one of these specimens. The metabolite pattern of the epithelial cells was indicative of preferential formation of 7, 8-dihydrodiol-9, 10-dihydroepoxybenzo(a)pyrene the ultimate carcinogen. In contrast, fibroblasts formed mainly mono- and dihydroxide derivatives of BaP. The metabolite pattern from epithelial cells was compatible with the ease in which adducts between DNA and the diolepoxide of benzo(a)pyrene were formed. These results provide evidence that chemical carcinogens should be considered as possible factors in the induction of breast cancer in women.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.1982.240180202
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of guanethidine-induced sympathectomy on morphology of the pre- and postclosure lleum of the neonatal rat (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 164 (1982), S. 175-186 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The disappearance of the characteristic supranuclear vacuole and extensive apical canalicular system from enterocytes of the ileal villi occurs during the third postnatal week in rats. This phenomenon is associated with loss of permeability of these cells to macromolecules and is therefore termed closure. The present study was designed to analyze the influence of neonatal guanethidine (GTN)-induced sympathectomy on the morphology of the pre- and postclosure ileum of the rat. Light and electron microscopy of control and GTN-sympathectomized rats demonstrated the retention of immature, vacuolated cells on ileal villi as late as 23 days postnatally in GTN-treated rats. Villi from control rats contained only adultlike nonpermeable cells. Electron microscopy further demonstrated no structural differences in the apical canalicular system or storage vacuoles of the delayed cells in GTN rats when compared to the ileal epithelium from preclosure time periods (7 and 15 days) in both GTN-sympathectomized and control rats. Goblet cells were counted on Periodic-Acid-Schiff-stained sections of ileum from 7, 15, and 23-day GTN and control rats. The percentage of goblet cells in the total epithelial cell population of the villus was significantly higher in control versus GTN rats at all time periods. The percentage of goblet cells increased in both groups from day 7 to 15. However, closure in the control group (approximately day 18) was coincident with a steep increase in the percentage of ileal goblet cells which was not evident in the goblet-cell population of the GTN villus. This pattern of change in control versus GTN goblet-cell production was correlated with a similar pattern of variation in the number of crypt cell mitoses between the two groups over the same time period.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001640207
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  • 4
    Electronic Resource
    Electronic Resource
    Gene amplification as a mechanism of reversion at the HPRT locus in V79 chinese hamster cells (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 119 (1984), S. 341-348 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Spontaneous phenotypic revertants of hypoxanthine phosphoribosyl-transferase (HPRT) temperature-sensitive V79 Chinese hamster cells were selected by plating a temperature-sensitive mutant in HAT medium at 39°C. The incidence of such revertants was approximately 2 × 10-4 per cell. The majority of the revertants examined had increases of between three- and tenfold in their specific activity of the enzyme, and they were able to grow continuously in the presence of HAT medium at 39°C. When the revertants were cultivated in the absence of HAT, they recovered their HAT-sensitive phenotype and their lowered level of HPRT. Three of the revertants were examined for their temperature inactivation profiles, and all were found to have profiles identical to the ts parent, and quite different from the V79 wild type. The kinetic properties of the cell lines were studied:the Km for both PRPP and hypoxanthine was significantly different in the temperature-sensitive cells but was not significantly altered in the revertants with respect to the ts mutants. A specific antibody to Chinese hamster brain HPRT was employed in immunoprecipitation experiments. By measuring the point at which the immunoprecipitation of the antibody to HPRT was overcome by increasing concentrations of cell supernatant, it was possible to estimate the relative amount of enzyme molecules in the cell lines. From these data, it could be concluded that the revertants overproduced an enzyme with the same immunological properties as the ts line. Southern blots of the Hind Ill restricted DNA from the ts mutant and two revertant cell lines were examined with an HPRT cDNA probe. This established that the HPRT gene was amplified twofold in one of the revertants, and threefold in the other. However, if the revertants were reintroduced into nonselective medium, the gene copy number declined to one. Finally, northern blots of RNA extracted from the various cell lines demonstrated that the HPRT mRNA was augmented 1.5-fold in one revertant and 1.4-fold in the other. Reintroduction into non-selective medium resulted in a decline in mRNA level for the second mutant, whereas the first mutant appeared to be stabilized.We conclude that gene amplification and concomitant amplification of messenger RNA and enzyme levels are mechanisms of phenotypic reversion at the HPRT locus in Chinese hamster cells.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041190313
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  • 5
    Electronic Resource
    Electronic Resource
    Cerebrovascular permeability to 86Rb in the rat after exposure to pulsed microwaves (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 5 (1984), S. 323-330 
    Details
    ISSN: 0197-8462
    Keywords: pulsed microwaves ; rat ; blood-brain barrier ; 86Rb permeability ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Microwaves (pulsed, 2,450 MHz) at an average power density of 3 W/cm2 were applied directly to the head for 5, 10, or 20 min, producing a peak specific absorption rate of 240 W/kg in the brain, which, after a 10-min exposure, resulted in brain temperatures in excess of 43°C. A bolus of 86Rb in isotonic saline was injected intravenously and an arterial sample was collected for 20 s to determine cardiac output. Compared with unexposed controls, uptake of 86Rb increased most in those regions directly in the path of the irradiation, namely, the occipital and parietal cortex, as well as the dorsal hippocampus, midbrain, and basal ganglia. In a separate group of animals, regional brain-vascular spaces were found to increase with brain temperature. These results support previous observations indicating that reliably demonstrable increases of blood-brain barrier permeability are associated with intense, microwave-induced hyperthermia, and that the observed changes are not due to field-specific interaction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250050305
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