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  • Articles  (55)
  • 1995-1999  (49)
  • 1960-1964  (6)
  • Chemistry and Pharmacology  (55)
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  • Articles  (55)
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  • 1
    ISSN: 1573-904X
    Keywords: dissolution ; tablet stability ; solid state reaction ; croscarmellose sodium ; disintegrant ; infrared spectroscopy ; CP/MAS NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To investigate the cause for decrease in delavirdine mesylate 200 mg tablet dissolution upon exposure to high humidity. Methods. Dissolution testing was performed using the USP 2 (paddle) apparatus. Water in tablets was measured by Karl Fischer titration. 13C CP/MAS NMR was used to identify and quantify delavirdine form changes in tablets. FT-IR spectroscopy was used to monitor delavirdine form change in tablets and component mixes, and to investigate a solid state reaction with the disintegrant. Results. Dissolution extent of delavirdine mesylate 200 mg tablets was substantially decreased after exposure to high humidity. This effect is related to the amount of water present in the tablet matrix. 13C CP/ MAS NMR detected about 30% conversion from the mesylate salt of delavirdine to its free base form in the tablet matrix. FT-IR spectroscopy demonstrated that a solid state reaction occurs between the freed methanesulfonic acid and the carboxyl sites on the croscarmellose sodium disintegrant. Conclusions. Water is thought to act as both a reaction medium and a plasticizer for croscarmellose sodium, facilitating protonation of the carboxyl sites on the disintegrant. This reaction has the potential to occur for any acid salt of a free base. The limiting solubility of delavirdine free base formed in the tablets accounts for much of the decrease in the extent of dissolution. A change in inter-particle bonding can explain the reduction in tablet deaggregation during dissolution.
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  • 2
    ISSN: 1573-904X
    Keywords: drug delivery ; diabetes mellitus ; excipient ; insulin ; eye ; nose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Although DNA typing is an accurate, precise, and robust procedure, quality assurance is enhanced by availability of a suitable reference material. The National Institute of Standards and Technology (NIST) recently released a Standard Reference Material (SRM) that meets the calibration and quality assurance needs of laboratories that perform DNA typing. Each step of the analytical process of DNA typing may be verified by one or more of twenty different components of the SRM. As newer, more sensitive methods for DNA typing have been introduced into the human identification laboratory repertoire, new SRMs will be required for quality assurance. A second SRM for PCR-based tests is under development and soon to be available, is also described.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 180 (1998), S. 33-41 
    ISSN: 1573-4919
    Keywords: mitochondrial metabolism ; long chain fatty acids ; acyl carnitine derivitives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The results of clinical and animal studies suggest that a short term period of moderate secondary carnitine deficiency, in and of itself, does not have a major effect on the cardiac contractile function, although substrate oxidation may be altered. However, with longer durations of carnitine deficiency, alterations occur within the heart that may result in impaired contractile performance, particularly at high workloads. At this point, the mechanisms responsible for the cardiac depression are uncertain. We hypothesize that the alterations in substrate metabolism produced by the carnitine deficient state results in inadequate ATP production under high workload conditions which result in impaired cardiac contractile performance. Carnitine deficiency may also induce a number of changes in gene expression of key enzymes required for normal cardiac contractile function and metabolism.
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  • 5
    ISSN: 1573-4919
    Keywords: streptozotocin ; blood vessels ; glycolysis ; glucose oxidation ; palmitate oxidation ; insulin-deficient diabetes ; sodium-potassium ATPase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Several investigators have reported that carbohydrate metabolism is suppressed in blood vessels from diabetic (Db) rats. However, it is not known if metabolites from the reciprocal increase in oxidation of long-chain fatty acids that accompanies insulin-deficiency exacerbates the suppression of this pathway in the Db blood vessels. Such inhibition may have particularly deleterious consequences in vascular smooth muscle since aerobic glycolysis is believed to preferentially fuel the sarcolemmal Na/K ATPase in this tissue. Therefore, this study evaluated the effect of physiological (0.4 mM) and elevated (1.2 mM) concentrations of the long-chain fatty acid palmitate on both carbohydrate utilization and Na/K-ATPase activity in aorta from insulin-deficient Db rat. Thoracic aorta were removed from 10 week Db (streptozotocin 60 mg/Kg , i.v.) or control (C) rats and intima-media aortic preparations were incubated in the absence or presence of palmitate. Glycolysis (μM/g dry wt/h) and glucose oxidation (μM/g dry wt/h) were quantified using 3H-glucose and 14C-glucose, respectively. Na/K-ATPase activity was estimated by the measurement of 86rubidium uptake in the absence and presence of 2 mM ouabain. In the absence of exogenous palmitate, glycolysis (p 〈 0.05), glucose oxidation (p 〈 0.01) and the estimated ATP production from exogenous glucose were decreased in aorta from Db rat. However, despite this diminished rate of glycolysis, Na/K ATPase activity was similar in Db and C aorta. Palmitate (0.4 mM) inhibited Na/K ATPase activity and glucose oxidation to a similar extent in both Db and C but had no effect on glycolysis in either group. Elevation of palmitate to 1.2 mM had no additional inhibitory effect on glucose oxidation, Na/K ATPase activity or glycolysis in either the Db or C aorta. The metabolism of exogenous palmitate restored the ATP production in Db to control values. These data demonstrate that, despite the diminished glycolysis and glucose oxidation demonstrated in the Db tissue, Na/K ATPase activity was comparable in the C and Db aorta, in the absence or presence of exogenous long-chain fatty acid. Therefore, the accelerated oxidation of palmitate in diabetic vascular smooth muscle had no additional inhibitory effect on glycolysis or Na/K ATPase activity. These data suggest that Na/K ATPase activity in vascular smooth muscle is not impaired by the altered pattern of substrate utilization that occurs in insulin-deficient Db rats.
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  • 6
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 845-845 
    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
    Additional Material: 1 Ill.
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  • 8
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; DNA ; Mitochondrial DNA ; Forensic DNA typing ; Polymerase chain reaction analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The polymorphic control region of mitochondrial DNA (mtDNA) is becoming more commonly used in forensic applications to differentiate among individuals in a population. Two hypervariable regions (HV1 and HV2) are often sequenced following amplification of the mtDNA via the polymerase chain reaction (PCR). More rapid screening assays would reduce both the effort and the expenses of comparing two samples. A methodology has been developed that first uses restriction endonuclease digestion of the PCR-amplified mtDNA using RsaI and Mn/I and then capillary electrophoresis (CE) to separate and size the PCR-RFLP fragments. This rapid procedure offers an alternative method for screening of polymorphisms in amplified mtDNA samples. In addition, the presence of a T→C transition at position 16189, which gives rise to the so-called “C-stretch” in HV1, may be predicted from the presence of nonspecific PCR products in the CE results.
    Additional Material: 4 Ill.
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  • 9
    ISSN: 0173-0835
    Keywords: Trypanosoma brucei ; Free-flow electrophoresis ; Endosomes ; Lysosomes ; Transferrin ; Percoll ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: In this paper we demonstrate the power of preparative free-flow electrophoresis (FFE) for the study of endocytosis by African trypanosomes. Endocytosis of extracellular macromolecules by these parasites occurs through a specialized region of the parasite called the flagella pocket. The uptake of fluid phase markers such as horseradish peroxidase (HRP) into the various compartments of the endocytic pathway of bloodstream forms of Trypanosoma brucei brucei was manipulated by regulating the external environment (e.g., by altering the temperature of incubation). The various subcellular compartments were then separated by free-flow electrophoresis (FFE) or isopycnic density gradient centrifugation and analyzed for marker uptake. At low temperatures, HRP was found predominantly in the flagellar pocket. Increasing the temperature resulted in a time-dependent uptake of HRP into more positively charged endosomal fractions. However, little HRP activity was detected in lysosomal compartments, suggesting that either HRP had not yet entered the lysosome or was degraded immediately upon entry. Through the use of FFE we were able to identify and analyze compartments of the endosomal pathway that were not possible to identify by density gradient centrifugation alone. Although the differences in FFE separation of the endocytic compartments as seen in HRP uptake were striking, the minor changes seen within the lysosomal system were more subtle, as depicted in the protease profiles. In conlusion, we show that preparative FFE is a powerful technique for the analysis and separation of flagellar pocket-derived membranes from other endosomal and lysosomal compartments of African trypanosomes.
    Additional Material: 7 Ill.
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  • 10
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic spectrum of germylidene (H2C(Double Bond)Ge), the simplest unsaturated germylene, has been observed for the first time. Jet-cooled H2CGe and D2CGe were produced by an electric discharge through tetramethylgermane diluted in argon at the exit of a supersonic expansion. High-resolution spectra of H2C74Ge and D2C74Ge, obtained from (CH3)4〈sup ARRANGE="STAGGER"〉74Ge prepared from isotopically enriched 74Ge metal, have been rotationally analyzed to yield the following r0 structures: r0″(CGe)=1.7908(2) Å, r0″(CH)=1.1022(5) Å, θ0″(HCH)=115.05(5)°, r0′(CGe)=1.914(4) Å, r0′(CH)=1.082(9) Å, and θ0′(HCH)=139.3(11)°. The 367–354 nm B˜1B2–X˜ 1A1 band system consists of prominent perpendicular bands involving the CGe stretching (ν3) and CH2 scissors (ν2) vibrations and a weaker series of vibronically induced parallel bands involving the CH2 rocking mode (ν6). Vibronic bands involving Δv=2 changes in ν6(b2) and ν4(b1) have also been assigned. The fluorescence decays of single rotational levels of the 000 band of H2C74Ge exhibit molecular quantum beats for about 70% of the levels surveyed. Density of states arguments reveal that most of the beats originate from interactions with high rovibronic levels of the ground state. In one case, hyperfine splittings in the Fourier transform of the beat pattern indicate an accidental coincidence with an excited triplet state level. The less frequent occurrence of quantum beats in germylidene compared to silylidene, where they are almost universal, can be attributed to the smaller density of ground state levels at the zero-point energy of the S2 state in the former. © 1999 American Institute of Physics.
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