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  • Polymer and Materials Science  (11)
  • pharmacokinetics  (3)
  • METEOROLOGY AND CLIMATOLOGY  (2)
  • Chlorophylls
  • Surface physics, nanoscale physics, low-dimensional systems
  • 1990-1994  (16)
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  • 1
    ISSN: 1573-8744
    Keywords: diclofenac sodium ; biliary excretion ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Diclofenac sodium is a widely used drug with interesting absorption and disposition features when administered to laboratory animals. The present study was undertaken to assess the pharmacokinetics of the drug after iv and gastrointestinal dosing to rats. Renal excretion of unchanged drug was negligible, but biliary excretion of the drug (unchanged and conjugated) was detected in bile duct-cannulated rats; it accounted for 27.2 and 31.2% of the total dose following iv and intraduodenal administration, respectively. Most of the drug excreted in the bile was conjugated diclofenac; unchanged drug accounted for only 4.7 and 5.4% of total diclofenac excreted in the bile after iv and intraduodenal dosing, respectively. In normal animals, intestinal absorption of the drug excreted in the bile resulted in higher drug concentrations in plasma than those obtained in bile duct-cannulated rats, but only after 60 min of dosing. When administered directly into the duodenum, diclofenac absorption was extremely fast and the maximum plasma diclofenac concentration was reached within 2 min. After oral dosing, an early peak was also observed, but it was lower than that obtained after intraduodenal dosing: 71% diclofenac hioavailability was found in bile duct-cannulated rats intraduodenally dosed, whereas in normal animals dosed by mouth a bioavailability of 79% was obtained. In normal animals intraduodenally dosed, an apparent bioavailability of 106% was observed. All of these features, particularly the influence of enterohepatic circulation on drug bioavailability, are discussed.
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 1579-1592 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Differential scanning calorimetry (DSC) has been utilized in several studies on polymerization kinetics, at different heating rates. However, there are several factors affecting the precision of kinetic parameters. In this work, the activation energy of urethane-bond formation between 2,6-tolylene diisocyanate and diethylene glycol is reported, the latter being in excess in order to minimize problems such as thermal transitions and incomplete reaction in the final step. The DSC technique was applied at different heating rates. Both the equal conversion and equal conversion rate options of the method are discussed. The latter appears to be a more adequate option for the system studied here. The results obtained show a good agreement with the model used.
    Additional Material: 8 Ill.
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  • 3
    ISSN: 1573-904X
    Keywords: enterohepatic recirculation ; pharmacokinetics ; bioavailability ; clearance ; biliary excretion ; first-pass effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A general treatment of enterohepatic recirculation of drugs has been developed based on the fraction of drug in systemic circulation that is excreted in the bile and the fraction of drug reabsorbed from the gut that reaches systemic circulation in each enterohepatic cycle. The deduced equations make it possible to establish mathematical relationships between the areas under the blood level curves (AUC) of a drug when administered to normal and bile duct-cannulated animals and to predict the effect of enterohepatic recycling on bio-availability and clearance. The results were compared with those obtained by other authors using different approaches to enterohepatic recirculation, and some discrepancies were found in the equations describing the effect of enterohepatic recycling on AUC and bioavailability of drugs. The cause of such discrepancies and the problems associated with the prediction of hepatic extraction ratio from in vitro studies are discussed.
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  • 4
    ISSN: 1573-904X
    Keywords: permanent cannulation ; pharmacokinetics ; amoxycillin ; antipyrine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of chronic cannulation of the rat jugular vein on the pharmacokinetics of amoxycillin and antipyrine administered by the i.v. and oral routes has been evaluated. Animals that received the i.v. dose of amoxycillin on the eighth day after jugular vein cannulation showed decreased clearance (4.0 ± 0.3 ml/min) and steady-state volume of distribution (105 ± 8 ml) compared to animals that received the i.v. dose on the fourth day (5.5 ± 1.1 ml/min and 155 ± 17 ml, respectively). Rats first dosed by the i.v. route showed an oral bioavailability of 54 ± 12%, whereas for those first dosed by the oral route the calculated bioavailability was 31 ± 6%. Antipyrine was administered to rats by the i.v. and oral routes on the first and fourth days after jugular vein cannulation. Animals intravenously dosed on the fourth day showed a decreased clearance (1.9 ± 0.3 ml/min) compared to rats intravenously dosed on the 1st day (2.7 ± 0.6 ml/min). Antipyrine bioavailability was larger in animals first dosed by the i.v. route than in animals first dosed by the oral route (173 ± 43 and 74 ± 15%, respectively). These results argue against the use of crossover studies in rats with permanently implanted cannulas since kinetic changes induced by cannulation can be larger than previously proposed.
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 959-970 
    ISSN: 0887-6266
    Keywords: laser-induced processes in conducting polymer precursors ; interaction of dyes with polyelectrolytes ; lithography ; microelectronics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The elimination reaction of polyelectrolyte films of poly(phenylene vinylene) precursor polymers into the fully conjugated chain was induced by irradiation with an Ar+ laser emitting at 514.5 nm. The experiments were conducted using as cast precursor polyelec-trolyte films of both the unsubstituted poly(phenylene vinylene), H-PPV, and its 2,5-dimethoxyphenylene derivative, DMEO-PPV. Precursor polymer films impregnated with an azosulfonic dye, which had a strong absorption at the laser emission wavelength, were also irradiated. The elimination reaction was followed by comparing the elemental analysis and the infrared and visibleultraviolet spectra of the irradiated and nonirradiated areas. With the unsubstituted PPV film no elimination was detected even at power fluence levels up to approximately 350 W/cm-2, but elimination and conversion to the conjugated polymer could be observed at 10 W/cm-2 when the dye was present. For DMEO-PPV the elimination reaction occurred with or without dye impregnation, and similar marking threshold values were measured in both cases. The molecular mechanism used to explain such observations and the possible application in the area of microelectronics are also discussed. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 777-792 
    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: Binary blends of poly(vinyl alcohol) (PVA) with poly(acrylic acid) (PAA) and polyacrylamide (PAAm) were characterized by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and infrared spectroscopy (IR). Molecular weight, blend composition, and heating time at 150°C were the variables used. Results obtained by DSC indicated that PAA/PVA blends are miscible in the full range of composition. Similarly, TGA traces showed that thermal stability was higher for blends than for pure polymers. Blends of PVA with high molecular weight PAA exhibited a hydrogel behavior after drying at relatively low temperature (100°C), whereas blends containing low molecular weight PAA behaved as hydrogels only after they were heated at 150°C. Hydrogel character was increased for these two PVA/PAA blends with the heating time at higher temperature (150°C). IR spectra revealed that esterification took place in these blends after thermally treated at this temperature. In contrast, addition of glyoxal in combination with heating was necessary to produce hydrogels from PAAm/PVA blends. Furthermore, the crosslinking degree of these hydrogels was estimated from their absorbency values by applying the Flory-Rehner equation. © 1993 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 47 (1993), S. 53-59 
    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: Graft starch-polyacrylonitrile copolymers have been obtained from cassava starch (yucca starch or tapioca), which was pre-heated at 65 and 95°C for different lengths of time. The copolymerization was carried out by using ceric ion as initiator at different concentrations (2.0 to 8.0 mmol/L) and also varying both the length of time of copolymerization and the ratio of monomer to starch. The composition, or grafting parameters, of all the obtained copolymers was determined by weight difference after they were extracted with dimethylformamide and hydrolyzed with an acidic solution. Samples of these copolymers were also hydrolyzed with an aqueous solution of potasium bydroxide to produce the corresponding hydrogels, and its absorbency in water was determined. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 47 (1993), S. 37-44 
    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: In this article we report results of the evaluation of the reactivity of polyphenolic extracts of coconut husk with formaldehyde in both acidic and alkaline media. The objective of this evaluation was to determine if the extracts could be used in the preparation of phenol-formaldehyde-type resins. Extracts were obtained using aqueous solutions of NaOH (with and without anthraquinone) and NH4OH. Because of their low Stiasny's Number values, these extracts are not suitable for phenol-formaldehyde resin preparation in acidic conditions unless they are mixed with phenol or phenolic derivatives. Nevertheless, extracts obtained with NaOH, especially at 100 and 120°C, showed sufficient reactivity with form-aldehyde in basic conditions and may therefore be considered suitable for resin preparation in an alkaline medium. The resins were characterized using infrared spectroscopy (IR), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). A transition temperature prior to decomposition was not detected; their thermal stability was similar to phenol-formaldehyde-type resins. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 645-653 
    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: Results of the characterization of coconut husk lignin by infrared (IR) and proton nuclear magnetic resonance (H-NMR) spectroscopy are presented. Lignin was extracted with both alkaline and organosolv liquors. The IR spectra of dioxane lignin were very similar to those reported for hardwood lignins. Furthermore, these results combined with those obtained from the H-NMR studies suggest that coconut husk lignin can be classified into the Lm-type lignins. These lignins are characteristic of the monocotyledon class, of which the coconut palm is a member. The H-NMR studies showed that anthraquinone significantly inhibited the occurrence of lignin condensation during the alkaline extraction with sodium hydroxide solutions. This inhibition was more intense in the lignin extracted at 150°C than in that extracted at 100°C.
    Additional Material: 7 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 931-937 
    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 mechanical properties of network molecular systems, prepared through visible (Ar+) laser-induced polymerization of multifunctional acrylates, were studied as a function of some of the photopolymerization parameters. The properties investigated were the Young's modulus of elasticity and the stress-at-break, both derived from the stress versus strain test of dogbone-shaped photopolymerized samples. The parameters studied included the dye and co-initiator concentrations, and the laser power. We also compared the mechanical properties of samples made using different types of fluorone dyes and using two different amines as co-initiator. Better polymers are formed by the dyes with low fluorescence quantum yield. The three photopolymerization parameters modify the mechanical properties in a very similar way: they initially tend to increase both the Young's modulus and the stress-at-break but have a deleterious effect on the material strength if used in excess. N-phenylglycine, NPG, was shown to form stronger polymers (higher Young's modulus) than if N,N-dimethyl-2,6-diisopropylaniline, DIDMA, was used as co-initiator. We discuss the possible molecular mechanisms for such observations. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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