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  • 1995-1999  (49)
  • 1900-1904  (1)
  • Chemistry  (44)
  • Biochemistry and Biotechnology  (11)
  • Tyr(P)-containing peptides  (3)
  • flow cytometry  (3)
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  • 1
    ISSN: 1573-7373
    Keywords: brain tumor ; cell kinetics ; PCNA ; Ki-67 ; flow cytometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In an effort to optimize immunocytochemical methods to evaluate cell kinetics in brain tumors, we studied two newly-developed antibodies which react with formalin resistant epitopes of Proliferating Cellular Nuclear Antigen (PCNA) and Ki-67. These results were compared with standard flow cytometric cell cycle data from the same tumor specimens to determine if these methods correlate with each other, and whether retrospective analysis using these antibodies is feasible for cell kinetic analysis of brain tumors. Thirty-one specimens of glial tumors submitted for flow cytometry during 1992 were also reacted with antibodies to PCNA (PC-10) and Ki-67 (MIB-1). Flow cytometry scores for S-phase Fraction were compared with immunocytochemical scores for both antibodies, using an arbitrary rating of 1 (low, 〈 4%), 2 (intermediate, 4–6%), 3 (high, 〉 6%), and 1 (〈 25% positive), 2 (26–75% positive), 3 (〉 75% positive), respectively. MIB-1 results were found to correlate significantly with the S-phase fraction as determined by flow cytometry. The MIB-1 data showed a trend toward underestimating, i.e., lower scores, the proliferative index compared with flow cytometry. There was less of a correlation between PC-10 antibody scores and flow cytometry S-phase fraction, as PC-10 immunostaining typically overestimated the proliferative rate of brain tumors when compared with flow cytometry. There was an exact correlation between PC-10 and MIB-1 in only 4 cases, whereas in the remaining specimens, PC-10 results were always higher than MIB-1. These new immunostaining methods, which react with formalin fixed deparaffinized tissue and require microwave pre-treatment to optimize the results, have demonstrated their usefulness in retrospectively analyzing tumor cell kinetics. For one antibody, namely MIB-1, excellent correlation with standard flow cytometric analysis was achieved. Further studies comparing patient outcome with immunoreactivity to both Ki-67 and PCNA proteins is now possible and may be done on large numbers of achived specimens.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-3017
    Keywords: Trachemys scripta ; flow cytometry ; biomarkers ; sentinel ; pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We used flow cytometry (FCM) to conduct a multiple-tissue assay on slider turtles (Trachemys scripta) inhabiting radioactive seepage basins. Duplicate samples of blood, heart, spleen and kidney were analysed on two different cytometers (Leitz MPV and Coulter Profile II), each employing distinct staining protocols (DAPI and PI, respectively). Both DAPI and PI assays of spleen cells demonstrated significantly greater variation in DNA content for the basin turtles than for ‘control’ animals from nearby, uncontaminated sites. Basin turtles also exhibited significant cell-cycle effects for blood and spleen, again revealed by both assays. These corroborative findings demonstrate the consistency and repeatability of FCM assays in environmental monitoring and identify the particularly sensitive nature of turtle blood and spleen to mutagenic agents. Our survey complements previous FCM studies on sliders from contaminated sites and thereby underscores the species' potential as a sentinel for biomarker assays.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-3017
    Keywords: sea otters ; mink ; flow cytometry ; oil ; genotoxicity ; Exxon Valdez
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Three experiments were conducted to investigate the genotoxic effects of crude oil on mink and sea otters. In the first experiment, the effects on mink of chronic exposure to weathered Prudhoe Bay crude oil were studied. Female mink were fed a diet that included weathered crude oil for a period of 3 weeks prior to mating, during pregnancy and until weaning. Kits were exposed through lactation and by diet after weaning until 4 months of age. Kidney and liver tissues of the kits were examined using flow cytometry (FCM) and it was found that the genome size was increased in kidney samples from the experimental group compared to the control group. This effect was probably due to some type of DNA amplification and it could have been inherited from the exposed mothers or have been a somatic response to oil exposure in the pups. No evidence of clastogenic effects, as measured by the coefficient of variation (CV) of the G1 peak, was found in kidney or liver tissue. In the second experiment, yearling female mink were exposed either by diet or externally to crude oil or bunker C fuel oil. Evidence for clastogenic damage was found in spleen tissue for the exposure groups, but not in kidney tissue. No evidence of increased genome size was observed. In the third experiment, blood was obtained from wild-caught sea otters in Prince William Sound. The sea otters represented two populations: one from western Prince William Sound that was potentially exposed to oil from the Exxon Valdez oil spill and a reference population from eastern Prince William Sound that did not receive oil from the spill. The spill had occurred 1.5 years prior to obtaining the blood samples. Although the mean CVs did not differ between the populations, the exposed population had a significantly higher variance of CV measurements and five out of 15 animals from the exposed population had CVs higher than the 95% confidence limits of the reference population. It is concluded that FCM is a sensitive indicator of the clastogenic effects of oil exposure and that haematopoietic tissues and blood are best for detecting clastogenic damage. Moreover, the observed differences in the genome size of the kidney cells were possibly heritable effects, but this needs further investigation. Lastly, sea otters exposed to spilled oil 1.5 years earlier showed evidence of clastogenic damage in one-third of the individuals sampled.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The small-angle x-ray scattering (SAXS) technique has been applied to investigate solution and gel structures of alginate in the absence and presence of two divalent cations: Ca(II) and Cu(II). We have observed a broad maximum in the scattering curve, a characteristic of polyelectrolyte, for the purified alginate sample. The scattering maximum disappears in excess of added simple salt and shifts toward the higher angle region with increasing alginate concentration. Concentration dependence of the position and intensity of the maximum follows power law relations with exponents close to those predicted by theory. Data analysis shows an increase in correlation length ξ and cross-sectional diameter d0, of polymer chains upon gelation and suggests that a dimeric structure is adopted in the junction zone, consistent with the “egg-box” model previously proposed. In the Ca(II)-alginate system, the molecular parameters ξ and d0 are found to have good correlation with the macroscopic properties of gelation, such as gel point determined by viscosity measurements. However, for the Cu(II)-alginate system there is no clearly transitional behavior observed in ξ and d0, implying that the junction zone may be replaced by a more uniformly distributed site binding of Cu(II) ions to the carboxyl groups of both mannuronate and guluronate residues, in confirmation of previous 13C-nmr results. © 1995 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1215-1218 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal properties of two ferrocene derivatives, substituted by either one or two cholesteryloxycarbonyl units, were investigated. While the monosubstituted ferrocene derivative 1 was found to be non-mesomorphic, the disubstituted ferrocene derivative 2 exhibited a crystal smectic-B phase. This result shows that ferrocene-containing thermotropic liquid crystals, despite the bulkiness of the metallocene core, are not limited to disordered calamitic phases.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 521-525 
    ISSN: 0009-2940
    Keywords: Liquid crystals ; Siloxanes ; Phase behaviors ; Defined topology ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that supermolecules with a tetrahedral symmetry and appropriate side-chains exhibit liquid-crystalline phase behaviour. The use of an optimised hydrosylation reaction allows for the synthesis of materials that have four mesogenic groups attached to a siloxane core, where the conformation and the configuration are unambiguous. The materials show low glass transition temperatures and, depending on the spacer length, complex liquid-crystalline morphologies.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2865-2870 
    ISSN: 0887-624X
    Keywords: phosphine oxide ; aromatic-aliphatic polyamides ; polycondensation ; thermal properties ; fire retardant materials ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The new polymerisation monomer bis[4-(2-aminoethyl)aminophenyl]-phenylphosphine oxide (p-BAPPO) was prepared in good yield by the nucleophilic substitution reaction between bis(4-fluorophenyl)phenylphosphine oxide and a large excess of 1,2-diaminoethane. Five novel polyamides, incorporating phosphine oxide groups within the polymer backbone were synthesised by the condensation reaction of p-BAPPO with a series of aromatic and aliphatic dicarboxylic acids. The thermal properties of these polymers were investigated by differential scanning calorimetry and thermogravimetric analysis. Glass transition temperatures in the 180-215°C range were recorded. Although we observed their thermooxidative stabilities (5% weight loss 〉 345°C) to be lower by 40-70°C than those previously found for wholly aromatic polyamides with phosphine oxide groups within the parent chain, char yields upon prolonged heating at 650°C were still excellent (26-38%). Also, good solubility in aprotic polar solvents was observed for all polyamides synthesised. The new polyamides clearly represent significant progress in the quest for processible fire retardant materials. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2865-2870, 1997
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0887-3585
    Keywords: conformational change ; free energy calculations ; HIV protease ; molecular dynamics simulations ; protein structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Two different structures of ligand-free HIV protease have been determined by X-ray crystallography. These structures differ in the position of two 12 residue, β-hairpin regions (or “flaps”) which cap the active site. The movements of the flaps must be involved in the binding of substrates since, in either conformation, the flaps block the binding site. One of these structures is similar to structures of the ligand-bound enzyme; however, the importance of both structures to enzyme function is unclear. This transformation takes place on a time scale too long for conventional molecular dynamics simulations, so the process was studied by first identifying a reaction path between the two structures and then calculating the free energy along this path using umbrella sampling. For the ligand-free enzyme, it is found that the two structures are nearly equally stable, with the ligand-bound-type structure being less stable, consistent with X-ray crystallography data. The more stable open structure does not have a lower potential energy, but is stabilized by entropy. The transition occurs through a collapse and reformation of the β-sheet structure of the conformationally flexible, glycine-rich flap ends. Additionally, some problems in studying conformational changes in proteins through the use of a single reaction path are addressed. Proteins 32:7-16, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2581-2594 
    ISSN: 0887-624X
    Keywords: grafting ; poly(vinyl alcohol) ; poly(vinyl acetate) ; vinyl acetate ; methine carbon ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The grafting preference of vinyl acetate onto the methine carbon of poly(vinyl alcohol) (PVOH) versus the acetate group of poly(vinyl acetate) (PVAc) was determined as part of an attempt to prepare novel branched PVOH from partially hydrolyzed PVAc. The results showed long chain grafting on the acetate groups of the PVAc units rather than the methine carbons of the PVOH or PVAc units. Decreasing the monomer or initiator concentration decreased the molecular weight of the graft copolymer formed. Of the initiators studied, ammonium persulfate gave the largest increase in copolymer molecular weight. Both hydrolysis and reacetylation combined with gel permeation chromatography (GPC) and 13C-NMR of the fully hydrolyzed material were used to estimate the number and location of grafts. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2267-2272 
    ISSN: 0887-624X
    Keywords: poly(arylene ether)s ; pendant benzoyl groups ; polyxanthenes ; Friedel-Crafts cyclization ; thermal stability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(arylene ether)s (3), (4) containing pendant benzoyl groups as precursors for novel polyxanthenes (7), (8) were prepared by nucleophilic substitution reaction of 2,5-difluoro-4-benzoylbenzophenone (1) or 2,5-difluoro-4-(4-dodecylbenzoyl)-4′-dodecylbenzophenone (2) with hydroquinone derivatives in the presence of potassium carbonate in N,N-dimethylacetamide. The polycondensation proceeded smoothly at 165°C and produced poly(arylene ether)s with inherent viscosities up to 0.80 dL/g. The novel polyxanthenes were synthesized via the reduction of poly(arylene ether)s followed by the Friedel-Crafts cyclization of diol polymers. The structure of the polyxanthenes was characterized by 1H-NMR and IR spectroscopies. Polyxanthene 8 was quite soluble in chloroform and THF. The 10% weight loss temperature of polyxanthene 7 was 510°C in nitrogen and it was 90°C higher than the corresponding poly(arylene ether) 3. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2267-2272, 1997
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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