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  • 1980-1984  (40)
  • Polymer and Materials Science  (29)
  • Life and Medical Sciences  (11)
  • 1
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(propylene) has been oxidized at temperatures between 240 and 289°C. The products were GC separated and on-line identified by an interfaced GC peak identification system. The major products are CO2, H2O, acetaldehyde, acetone, butanal, formaldehyde, methanol and other ketones and aldehydes. Most of the products can be accounted for by well-known reactions of alkoxyl and peroxyl radicals; the major products are derived from the secondary alkoxy and peroxy species. Oxygen starvation is manifested in diffusion limited products of olefins and dienes, and the increase of CO2 and H2O formation in pure oxygen atmosphere. The first order rate constant at 240°C is 2,4·10-3 S-1 with an overall activation energy of ca. 16 kcal·mol-1 (67 kJ·mol-1). If one assumes the oxidative pyrolysis to share the same reaction pathways as autoxidation at lower temperatures, then the observed rate constants and activation energy may be calculated from kinetic parameters measured earlier for autoxidation of poly(propylene) from 71 to 140°C. Good agreement was obtained implying a similarity of oxidative degradation of the polymers spanning a large temperature range.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 3067-3077 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A perturbation chromatography apparatus has been designed and constructed for determining the vapor-liquid equilibrium between a two-component (solvent/helium) vapor phase and a two-component (polymer/solvent) liquid phase. The apparatus performed very well, giving reproducible and reliable results that agree with independent, previously reported studies. All tests of the equipment indicated that it was successful in meeting the conditions of low column pressure drop, small perturbations, and slow flow rate that are required for perturbation chromatography. Binary polymer/solvent data were obtained for polybutadiene (PBD)/benzene or polybutadiene/cyclohexane systems at solvent partial pressures to 40 kPa and for n-hexane at infinite dilution, all at the three temperatures of 333.15, 355.00, and 373.15 K. The experimental data for each system can be represented within experimental error by the Flory-Huggins polymer solution theory using a single binary interaction parameter that is independent of temperature and concentration.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 18 (1982), S. 135-148 
    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
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 499-512 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The B-to-A conformational transition of calf thymus DNA fibers was followed employing Raman spectroscopy. The transition was induced by soaking DNA fibers in water/ethanol mixtures increasing from 60 to 85% ethanol (v/v). Intensity changes of 17 Raman vibrational bands were quantified in the region from 400 to 860 cm-1. Two bands at 500 and 784 cm-1 were employed as internal standards. These bands do not appear to change in intensity with ethanol concentration. Large intensity changes relative to these two bands are observed between 70 and 74% ethanol for backbone vibrations at 708, 808, and 835 cm-1, and base vibrations at 682, 730, and 750 cm-1. These results indicate that a highly cooperative conformational change takes place between different portions of DNA in the B-to-A transition. Relative intensity changes preceding the onset of the major transition are observed in only two bands; at 835 cm-1, assigned to a ribose-phosphate vibration, and at 750 cm-1, assigned to thymine. The implications of these pretransition changes are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 197 (1980), S. 205-211 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Studies of Sertoli cell structure, maturation, and function have been aided by the use of in vitro systems. Although numerous papers have appeared that utilize the Sertoli cell culture model, few papers have dealt with the characterization of these cells under various culture environments. Recently, it has been reported that the addition of serum to the culture medium prevents induction of long cytoplasmic appendages in cultured Sertoli cells that have been treated with FSH, TSH, or c-AMP. The purpose of this investigation was to determine which serum components, obtained by gel filtration, are capable of inhibiting the morphological response induced by FSH, TSH, or c-AMP. Sertoli cell-enriched cultures were prepared using collagenase and trypsin digestion, each followed by gravity sedimentation. Untreated cells grown on plastic or glass substrates assumed an epithelioid appearance after several days. Cells treated with FSH, TSH, or c-AMP formed long cytoplasmic appendages after 1-2 days. This response was prevented or reversed by the addition of fetal calf serum (10%), crystallized bovine serum albumin (0.25%-2%), or purified albumin obtained by gel filtration of whole serum (0.25%). It was also found that fractions that elute between the void volume and the initial albumin fractions (molecular weights of approximately 50,000 and greater) mimic the hormone-induced response after only 10-12 hours. The results of this investigation indicate that albumin is the primary serum component responsible for inhibiting morphological alterations induced by FSH, TSH, and c-AMP. Furthermore, it is apparent that the production of long filamentous cytoplasmic appendages in Sertoli cells can be induced by a wide variety of substances.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 176 (1983), S. 249-259 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development of middle-ear structures in the mouse was examined in nine groups of pups between 1 and 45 days of age. The area of the tympanic membrane (pars tensa and pars flaccida), the length of the lever arms of the malleus and incus, the surface area of the oval window, and the volume of the bulla all showed systematic changes during neonatal life. The area of the oval window reached maturity first and the lever arms achieved 90% of their adult size on day 11. The tympanic membrane achieved the same criterion on day 18. These data help us further to understand the processes that contribute to the functional ontogeny of the middle ear.
    Additional Material: 9 Ill.
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  • 7
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The monomer 2-butenyl acrylate was reacted with starch by exposure to either 60Co irradiation or ceric ion initiation. Monomer conversion in the presence of starch is greater than in the absence of starch, indicating that a starch initiating mechanism takes place for 60Co irradiated samples. Acetone extraction indicates little or no soluble homopolymer in the grafts. Portions of the samples soluble in dimethyl sulfoxide (DMSO) appear to be low-level 2-butenyl acrylate-grafted starch by infrared analysis. DMSO-insoluble portions (usually more than 50% of each sample) are somewhat more soluble in 1N NaOH at room temperature. This indicates that the 2-butenyl acrylate acts as an easily hydrolyzed crosslink for starch in samples containing as low as 5 wt % grafted poly(2-butenyl acrylate).
    Additional Material: 1 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 2227-2233 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dynamic mechanical experiments have been conducted on an epoxy system made with tetraglycidyl 4,4′-diaminodiphenyl methane (TGDDM) and polyglycidyl ether of Bisphenol A Novalac that were cured with 4,4′-diaminodiphenyl sulfone (DDS) in the presence of Boron trifluoride monoethylamine catalyst (BF3:EtNH2). As the concentration of BF3:EtNH2 increased, the low temperature β-transition magnitude increased slightly. The α1-transition observed in the uncatalyzed system decreased significantly with the addition of BF3:EtNH2 catalyst. The α2 or glass transition temperature of this system increased with increasing catalyst concentration. Both the catalyzed and uncatalyzed epoxy formulations studied in this work are important due to their similarity to systems used commercially in epoxy matrix composites.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 164 (1982), S. 175-186 
    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.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 119 (1984), S. 341-348 
    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.
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