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Biomedical subjects

R M Carlson

Publications and source records attributed to R M Carlson.

At least 19 recordsLinked to original sources
PubMed2001

A novel catalytic pathway for perfluoroacyl peroxide synthesis.

A new catalytic method for synthesis of bis(perfluoroacyl) peroxides (BPFAP) was elaborated by using hydrogen peroxide and perfluoroacyl anhydrides. The desired BPFAP were formed quantitatively in situ when perfluoroacyl anhydride was mixed with hydrogen peroxide (ratio > or = 2:1) in the presence of a catalytic amount of the carboxylate R(f)COO-M+. The essentially irreversible character of this process was shown experimentally and supported on the basis of DFT calculations. The synthesis of new acetyltrifluoroacetyl peroxides is also described. Reaction: see text.

Journal Article↗
PubMed2001

A consecutive double-Criegee rearrangement using TFPAA: stepwise conversion of homoadamantane to oxahomoadamantanes.

Rearrangement of 4-methylhomoadamantan-4-ol (1) with trifluoroperacetic acid (TFPAA) in trifluoroacetic acid (TFAA) proceeds with the formation of 4-oxahomoadamantane 6 and its derivatives (4 and 5). 2-exo-Hydroxy-4-oxahomoadamantane (5) and 6 were identified as a result of consecutive O-insertion Criegee rearrangement processes. The absence of methyl trifluoroacetate and methyl trifluoroperacetate among the reaction products, as well as the presence of acetyltrifluoroacetyl peroxide, is consistent with a double rather that a triple oxygen insertion during the course of the Criegee reaction. A mechanism involving initial Criegee rearrangement followed by a Baeyer-Villiger reaction is also excluded by kinetic considerations. The parallel formation of 4-ethyl-3-oxahomoadamantan-2-one (4) was determined to be the result of 4-methylhomoadmantan-4-ol (3) dehydration, with subsequent epoxidation of 4-methylhomoadamant-4-ene (32) to 4,5-epoxy-4-methylhomoadamantane (33), acid-catalyzed isomerization of 33 to 3-methylhomoadamantan-2-one (34), and Baeyer-Villiger oxidation to 3-methyl-5-oxabishomoadamantan-6-one (35). This sequence of reactions was followed by the acid-catalyzed isomerization to the final product 4. The proposed mechanisms for these transformations are discussed on the basis of model experiments and supporting density functional theory (DFT) calculations.

Journal Article↗
PubMed2001

Flow cytometric evaluation of antiviral agents against human herpesvirus 6.

Antiviral activities of acyclovir (9-[(2-hydroxyethoxy) methyl] guanine, ACV), penciclovir (9-[4-hydroxy-3-(hydroxymethyl) butyl] guanine, PCV), ganciclovir ([9-(1,3-dihydroxy-2-propoxy) methyl] guanine, GCV), and foscarnet (phosphonoformic acid, PFA) were determined against Human Herpesvirus 6 (HHV-6) by flow cytometric technique. The technique is based on the detection of gp116 antigen expression in virus infected cells. Susceptibility was defined in terms of drug concentration which reduced the number of cells expressing HHV-6 gp116 antigen with a mean fluorescent intensity (MFI) by 50% as compared to virus infected untreated cells. GCV was found to be most effective against HHV-6 followed by PFA, PCV and ACV. For HHV-6A, the mean 50% inhibitory concentrations (IC50) of GCV and PFA were found to be 3.4 microM and 34.7 microM respectively, whereas the IC50 of ACV and PCV were found to be 53.7 microM and 37.9 microM respectively. For HHV-6B, the IC50 of GCV and PFA were found to be 5.7 microM and 71.4 microM respectively, whereas the IC50 of ACV and PCV were found to be 119.0 microM and 77.8 microM respectively. Flow cytometry is a valuable technique for the evaluation of antiviral compounds against viruses including HHV-6.

Acyclovir↗
PubMed1990

The identification and quantitation of alkylated nucleobases by high-performance liquid chromatography with UV photodiode array detection.

The application of UV diode array detection in high-performance liquid chromatographic (HPLC) identification and quantitation of several classes of synthetic and commercially available alkylated nucleobases is investigated. Quantitative spectral overlays of these compounds to methyl standard references from a spectral library and absorbance ratios at two maximal wavelengths (lambda max) are found to be useful in categorizing the solutes. They can be grouped into classes of compounds originating from a specific nucleobase and classes of analogs having different alkyl substituents (e.g., methyl, ethyl, propyl, allyl, and benzyl) at the same position of the heterocycle. At a selected wavelength for alkylated nucleobases in the same class, the detector response factors are independent of the alkyl group (+/- 10%). This technique provides a practical means for both qualitative and quantitative analysis of product distribution of DNA base alkylation by using only readily obtainable methylated derivatives as the reference standards.

Adenine↗
PubMed1990

Assessment of the propensity for covalent binding of electrophiles to biological substrates.

Electrophilic character is associated with the ability of external agents to interact with centers of electron density in biological macromolecules and to cause the interruption or alternation of normal activity. With the observation of site specificity in mutagenic events. Pearson's hard/soft acid-based (HSAB) theory is presented as a useful concept in correlating chemical observations in the absence of detailed direct knowledge of the process. Methods for the evaluation of carbon electrophiles (e.g., carbocation character) as reactants are reviewed as potential physical parameters that could be applied in developing quantitative structure-activity relationships.

Alkylating Agents↗
PubMed1988

Separation characteristics of alkylated guanines in high-performance liquid chromatography.

The retention behavior of thirteen alkylated guanines on normal-phase silica gel and amino columns and on reversed-phase ODS and phenyl columns was studied. The larger the alkyl substituent at the same position of guanine the weaker was the retention in the normal-phase chromatographic system and the greater the retention during reversed-phase chromatography. O6-Derivatives possess the lowest polarity in each set of isomers. An amino column was found to be of highest efficiency in terms of separation of the set of ethylguanine isomers and of benzylguanines studied. A phenyl column provided the best resolution of methylated guanines.

Alkylation↗
PubMed1987

A large reservoir of sulfate and sulfonate resides within plasma cells from Ascidia ceratodes, revealed by X-ray absorption near-edge structure spectroscopy.

The study of sulfur within the plasma cells of Ascidia ceratodes [Carlson, R. M. K. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 2217-2221; Frank, P., Carlson, R. M. K., & Hodgson, K. O. (1986) Inorg. Chem. 25, 470-478; Hedman, B., Frank, P., Penner-Hahn, J. E., Roe, A. L., Hodgson, K. O., Carlson, R. M. K., Brown, G., Cerino, J., Hettel, R., Troxel, T., Winick, H., & Yang, J. (1986) Nucl. Instrum. Methods Phys. Res., Sect. A 246, 797-800] has been extended with X-ray absorption near-edge structure (XANES) spectroscopy. An intense absorption feature at 2482.4 eV and a second feature at 2473.7 eV indicate a large endogenous sulfate concentration, as well as smaller though significant amounts of thiol or thioether sulfur, respectively. A strong shoulder was observed at 2481.7 eV on the low-energy side of the sulfate absorption edge, deriving from a novel type of sulfur having a slightly lower oxidation state than sulfate sulfur. The line width of the primary transition on the sulfur edge of a vanadium (III) sulfate solution was found to be broadened relative to that of sodium sulfate, possibly deriving from the formation of the VSO4+ complex ion [Britton, H. T. S., & Welford, G. (1940) J. Chem. Soc., 761-764; Duffy, J. A., & Macdonald, W. J. D. (1970) J. Chem. Soc., 977-980; Kimura, T., Morinaga, M., & Nakano, J. (1972) Nippon Kagaku Zaishi, 664-667]. Similar broadening appears to characterize the oxidized sulfur types in vanadocytes. A very good linear correlation between oxidation state and peak position (in electronvolts) was found for a series of related sulfur compounds. This correlation was used to determine a 5+ oxidation state for the additional sulfur type at 2481.7 eV. (ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

The earlier the better: the importance of equipment planning.

New technologies and medical equipment can constitute up to 25 percent of the cost of developing alternative care services. This article describes a process for integrating equipment planning with the hospital's strategic planning efforts.

Capital Expenditures↗
PubMed1983

Occurrence and seasonal variation of 19-norcholest-4-en-3-one and 3 beta-monohydroxy sterols in the Californian gorgonian, Muricea californica.

The first natural occurrence of 19-norcholestenone is reported, together with 17 sterols and one other delta 4-3-ketone in the extracts of the Californian gorgonian, Muricea californica (Aurivillius). Six additional demethyl sterols and five additional 4-monomethyl sterols which remain unidentified were also detected. Lipid extracts of M. californica from a winter and summer collection were split by various chromatographic methods into free sterol, steryl ester, and steryl conjugate fractions. Sterol compositions (determined by CG and CG-MS) of each fraction, subsequent to hydrolysis, are tabulated and discussed with respect to plausible origins of observed variations. The possible relationship of the Muricea 19-nor-steroidal ketone to other naturally occurring 19-nor-steroids is discussed.

Animals↗
PubMed1983

Marine 4-methyl sterols: synthesis of C-24 epimers of 4 alpha, 24-dimethyl-5 alpha-cholestan-3 beta-ol and 360 MHz 1HNMR comparisons to the natural product from Plexaura homomalla.

Comparison of the highfield 1HNMR spectrum of 4 alpha, 24-dimethyl-5 alpha-cholestan-3 beta-o1 isolated by open column adsorptive chromatography and reversed-phase HPLC from P. homomalla with those of the corresponding synthetic 24 alpha and 24 beta compounds demonstrate that the gorgonian natural product is purely 24 beta, the same C-24 configuration found in sterols related to dinosterol and gorgosterol. 360 MHz 1HNMR data are also reported for synthetic 4 alpha, 24 beta-dimethyl-5 alpha-cholest-22E-en-3 beta-o1 (another P. homomalla natural product). The use of 1HNMR correlations in assigning C-24 configurations of 24-methyl marine sterols possessing various nuclei is examined and discussed. Analyses of the methyl sterol components of P. homomalla are tabulated and discussed with regard to origin and plausible biosynthetic interrelationships in light of the C-24 configurational findings.

Animals↗
PubMed1982

Implications of treating water containing polynuclear aromatic hydrocarbons with chlorine: a gas chromatographic-mass spectrometric study.

The products of aqueous chlorination reactions of 1-methylnaphthalene, fluorene, dibenzofuran, anthracene, phenanthrene, 1-methylphenanthrene, fluoranthene, and pyrene have been determined. The conditions employed for these reactions approximated those that might be encountered in water treatment facilities. Reactions at pH greater than 6 tended to produce oxygenated products (epoxides, phenols, quinones, etc.), and reactions at pH less than 6 tended to produce both oxygenated (quinones) and chlorinated products.

Chemical Phenomena↗
PubMed1978

Hepatic mixed-function oxidase activity in rainbow trout exposed to several polycyclic aromatic compounds.

The effects of polycyclic aromatic hydrocarbons (PAHs) on microsomal liver enzymes were examined in rainbow trout. Various PAHs (naphthalene through benzo(a)pyrene [B(a)P]) were injected ip to screen for mixed-function oxidase (MFO) activity. Chrysene, B(a)P, and Aroclor 1254 caused MFO induction. When fish were also exposed to solubilized pyrene, fluoranthene, and B(a)P in water, bioaccumulation of B(a)P resulted in MFO induction, whereas bioaccumulation of pyrene and fluoranthene did not. Based on water and injection exposure to B(a)P, it was predicted that tissue concentrations in excess of 300 micrograms/kg B(a)P would be accompanied by MFO induction in rainbow trout.

Animals↗
PubMed1976

Minor and trace sterols in marine invertebrates. 1. General methods of analysis.

3beta-Hydroxy sterols occurring at a concentration of at least 0.001% of the sterol mixtures of Pseudoplexaura porosa and Plexaura homomalla have been fractionated using a series of refined techniques and subsequently analyzed using combined gas chromatography-mass spectrometry (GC-MS) in the development of a procedure for examining the minor and trace components of marine sterol mixtures. A total of 49 sterols were found which spanned a molecular weight range of 274 to 440. In addition delta4-3-keto analogs of cholesterol, 24-methylcholesterol and gorgosterol were found in the extracts of P. homomalla. Initial separation of various natural sterol-containing conjugates and free sterols was found to have a number of advantages. Fractional digitonin precipitation and alumina column chromatography were found to possess greater sterol separation abilities than previously recognized. Many of the minor sterols were found to possess novel structures including a series of short side chain sterols, 19-nor sterols, 5beta-stanols and 4-monomethyl sterols for which structure elucidation work is continuing.

Animals↗
PubMed1975

Nuclear magnetic resonance spectrum of living tunicate blood cells and the structure of the native vanadium chromogen.

The 1-H nuclear magnetic resonance spectrum of living tunicate blood cells was examined in an attempt to develop a biophysical assay for the native vanadium chromogen. The living cell spectrum was found to exhibit a broad 21 ppm downfield Gaussian signal which, however, disappears immediately upon cell disruption. Examination of the properties of this extremely low field signal revealed that it corresponds to a labile vanadium (III) aquo complex contained in the cell vacuoles, that vanadium(III) concentrations are rigidly regulated within these vacuoles, and that artifact formation does occur in the hemolysate. The living cell spectrum also indicates the number of ligand-bound vanadium(III) coordination sites in the native blood pigment. Results are discussed relation to the possible functions of the vandium chromogen.

Animals↗