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  • Occupational Health and Environmental Toxicology  (14)
  • Organic Chemistry  (13)
  • 1
    Electronic Resource
    Electronic Resource
    N-Acetyl-D and L-esters of 5′-AMP hydrolyze at different rates (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 150-153 
    Details
    ISSN: 0899-0042
    Keywords: aminoacyl adenylate esters ; hydrolytic stabilization by intramolecular interaction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies of the properties of aminoacyl derivatives of 5′-AMP are aimed at understanding the origin of the process of protein synthesis. Aminoacyl (2′,3′) esters of 5′-AMP can serve as models of the 3′-terminus of aminoacyl tRNA. We report here on the relative rates of hydrolysis of AC-D- and L-Phe AMP esters as a function of pH. At all pHs above 3, the rate constant of hydrolysis of the AC-L-Phe ester is 1.7 to 2.1 times that of AC-D-Phe ester. The D-isomer seems partially protected from hydrolysis by a stronger association with the adenine ring of the 5′-AMP. © 1993 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050308
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  • 2
    Electronic Resource
    Electronic Resource
    Disposition kinetics of ML-1035 sulfoxide enantiomers and the prochiral sulfide in rats (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 428-435 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric pharmacokinetics ; benzamides ; gastroprokinetic agents ; prochirality ; chiral sulfoxidation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ML-1035, 4-amino-5-chloro-2-[2-(methylsulfinyl)ethoxy]-N-[2-(diethylamino)ethyl]benzamide, is a sulfoxide compound and a racemic gastroprokinetic agent with a chiral center at the sulfur atom. We have investigated the disposition kinetics of (R)-ML-1035 sulfoxide (R) and (S)-ML-1035 sulfoxide (S) after the single enantiomers and the racemic mixture were administered to rats in separate experiments. There was no noticeable chiral inversion after either enantiomer dose. Both enantiomers were rapidly absorbed. After dosing with enantiomers or with the racemate, the resulting plasma concentration-time curve of R was closely parallel to that of S in both intravenous and oral experiments, suggesting that the two enantiomers have approximately the same disposition kinetics. After intravenous enantiomer doses, only S underwent conversion to sulfide, suggesting that sulfidation in the liver is enantioselective. However, the enantioselective sulfidation after intravenous dosing did not introduce a difference in the global plasma disposition profiles between R and S, since the reduction reaction is a minor metabolic process. Other metabolic reactions such as sulfonation and mono-N-desethylations were not enantioselective. After oral administration, conversion to sulfide was observed for both enantioners, implicating the existence of a nonhepatic pathway in sulfidation. Administration of a prochiral sulfide dose was associated with an enantioselective sulfoxidation, in which the R/S concentration ratios increased as a function of time. In addition, enantiomeric interaction causing changes in pharmacokinetic parameters was observed after the oral racemate dose, while the interaction is negligible after an intravenous racemate dose, indicating a route dependency in enantiomeric interaction. © 1993 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050607
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of Aristotelia-Type Alkaloids. Part XVPart XIV: See [1].. Total synthesis of (+)-hobartinol (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 292-300 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic (+)-makomakine (6) was transformed in six steps into (+)-17R,18R)-17,18-dihydrohobartine-17,18-diol ((+)-5) with an overall yield of 38% (Scheme 2). This compound was shown to be identical with natural hobartinol, a monoterpene indole alkaloid from Aristotelia australasica, originally believed to be the (17S)-epimer 1. At the same time, the synthesis of (+)-5 delineates the hitherto unknown absolute configuration of this metabolite.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780204
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  • 4
    Electronic Resource
    Electronic Resource
    Borane Reduction of the Steroid 20-Ketone Group in the Presence of Various Chiral β-Amino Alcohols (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 581-582 
    Details
    ISSN: 0170-2041
    Keywords: 5β-Pregnane, 3α-hydroxy-20-one ; Chiral borane reduction ; Borane reduction ; Steroids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The direction of reduction of 20-carbonyl group of 3α-hydroxy-5β-pregnan-20-one (1) with a complex of borane-methyl sulfide and chiral β-amino alcohols, depends on the chirality of the amino alcohol. Where there is a 2-phenyl or 2-benzyl substituent, then the S enantiomer gives exclusively the steroid 20R alcohol 3. The R enantiomer of 2-amino-2-phenyl-1-ethanol gives the highest steroid 20S (2):20R (3) alcohol ratio.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199319930194
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and oxidation of pregna-3,5-dien-20-ols and -20-one and selective reduction of pregna-3,5-dien-20-one (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 213-215 
    Details
    ISSN: 0170-2041
    Keywords: Steroids ; Pregna-3,5-dien-20-one, oxidation, reduction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pregna-3,5-dien-20-one (4) and (20S)- and (20R)-pregna-3,5-dien-20-ol (2 and 3) were synthesized from progesterone. Oxidation of a mixture of 2 and 3 with Jones reagent gave 4, while a large excess of Jones reagent afforded besides 4, 6-oxoprogesterone (5), 6β-hydroxyprogesterone (6) and 5α-pregnane-3,6,20-trione (7). With L-selectride as reducing agent, reduction of 4 led to 2 and 3 in a ratio of about 1:1. However, some reducing agents gave a higher ratio of isomer 3.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199019900139
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  • 6
    Electronic Resource
    Electronic Resource
    Cerebrovascular permeability to 86Rb in the rat after exposure to pulsed microwaves (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 5 (1984), S. 323-330 
    Details
    ISSN: 0197-8462
    Keywords: pulsed microwaves ; rat ; blood-brain barrier ; 86Rb permeability ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Microwaves (pulsed, 2,450 MHz) at an average power density of 3 W/cm2 were applied directly to the head for 5, 10, or 20 min, producing a peak specific absorption rate of 240 W/kg in the brain, which, after a 10-min exposure, resulted in brain temperatures in excess of 43°C. A bolus of 86Rb in isotonic saline was injected intravenously and an arterial sample was collected for 20 s to determine cardiac output. Compared with unexposed controls, uptake of 86Rb increased most in those regions directly in the path of the irradiation, namely, the occipital and parietal cortex, as well as the dorsal hippocampus, midbrain, and basal ganglia. In a separate group of animals, regional brain-vascular spaces were found to increase with brain temperature. These results support previous observations indicating that reliably demonstrable increases of blood-brain barrier permeability are associated with intense, microwave-induced hyperthermia, and that the observed changes are not due to field-specific interaction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250050305
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of pulsed microwaves on passive electrical properties and interspike intervals of snail neurons (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 14 (1993), S. 503-520 
    Details
    ISSN: 0197-8462
    Keywords: constant temperature ; intracellular recording ; time series ; regression analysis ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The effects of pulsed microwaves (2.45 GHz, 10 μs, 100 pps, SAR: 81.5 kW/kg peak, 81.5 W/kg average) on membrane input resistance and action potential (AP) interval statistics were studied in spontaneously active ganglion neurons of land snails (Helix aspersa), at strictly constant temperature (20.8±.07°C worst case). Statistical comparison with sham-irradiated neurons revealed a significant increase in the mean input resistance of neurons exposed to pulsed microwaves (P ≪ .05 ). Pulsed microwaves had no visible effect on mean AP firing rate; this observation was confirmed by analysis of interspike intervals (ISIs). Using an integrator model for spontaneously active neurons, we found the net input current to be more variable in neurons exposed to pulsed microwaves. The mean input current was not affected. The standard deviation of ISIs and the autocorrelation of the input current were marginally affected, but these changes were not consistent across neurons. Although the observed effects were less obvious than those reported in other studies, they represent evidence of a direct interaction between neurons and pulsed microwaves, in the absence of macroscopic temperature changes. The data do not suggest a single, specific mechanism for such interaction. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250140603
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  • 8
    Electronic Resource
    Electronic Resource
    Studies on microwave and blood-brain barrier interaction (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 1 (1980), S. 313-323 
    Details
    ISSN: 0197-8462
    Keywords: microwave ; blood-brain barrier ; Evans blue ; sodium fluorescein ; brain and body temperatures ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: This investigation was aimed at correlating changes of blood-brain-barrier permeability with the quantity and distribution of absorbed microwave energy inside the brain of adult Wistar rats anesthetized by sodium pentobarbital. Through use of thermographic methods and a direct-contact applicator at the animal's head, the pattern of absorbed microwave energy was determined. Indwelling catheters were placed in the femoral vein and in the left external carotid artery. Evans blue and sodium fluorescein in isotonic saline were used as visual indicators of barrier permeation. Exposure to pulsed 2,450-MHz radiation for 20 min at average power densities of 0.5, 1, 5, 20, 145 or 1,000 mW/cm2, which resulted in average specific absorption rates (SARs) of 0.04, 0.08, 0.4, 1.6, 11.5 or 80.0 mW/g in the brain, did not produce staining, except in the pineal body, the pituitary gland, and the choroid plexus  -  regions that normally are highly permeable. Except for these regions, staining was also absent in the brains of sham-exposed animals. The rectal temperature, as monitored by a copper-constantan thermocouple, showed a maximum increase of less than 0.75°C from a mean pre-exposure temperature of 36.6°C. The highest brain temperature recorded in a similar group of animals using a thickfilm carbon thermistor was less than 41.0°C.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250010307
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  • 9
    Electronic Resource
    Electronic Resource
    In vitro microwave effects on human neutrophil precursor cells (CFU-C) (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 2 (1981), S. 203-215 
    Details
    ISSN: 0197-8462
    Keywords: 2,450-MHz microwaves ; neutrophil ; colony-forming cells ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Human marrow cells were irradiated with 2450-MHz CW microwaves in a fluid-filled waveguide irradiation system. Cell exposure was conducted by placing a marrow cell suspension in 20-μl glass microcapillary tubes that were positioned in the exposure chamber, and irradiated at power densities from 31 to 1,000 mW/cm2 (with corresponding specific absorption rates of 62 to 2,000 mW/g) for 15 minutes. The temperature of the sample was maintained at a fixed point. Sham-irradiated (SI) and microwave-irradiated (MWI) cells were cultured in a methylcellulose culture system for neutrophil colony proliferation. There was no reduction in neutrophil colony number on days 6-7 or 12-14 in cells exposed at 31 or 62 mW/cm2, but as the power density was increased to 1,000 mW/cm2, there was a reduction in colony number of MWI cells compared with SI cells. The microwave interaction with the human neutrophil colony-forming cells was apparently not related to temperature rise, or to the state of cell cycle, and was irreversible.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250020302
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  • 10
    Electronic Resource
    Electronic Resource
    Interaction of ethanol and microwaves on the blood-brain barrier of rats (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 7 (1986), S. 405-414 
    Details
    ISSN: 0197-8462
    Keywords: temperature ; hyperthermia ; Evans-blue ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The combined effects of ethanol and microwaves on the permeation of Evans blue dye through the mammalian blood-brain barrier was studied in male Wistar rats. Anesthetized rats were infused through a cannula in the left femoral vein with 0.1, 0.3, 0.5 or 0.7 grams of absolute ethanol per kilogram of body mass. A control group was given 0.7 g/kg of isotonic saline. The left hemisphere of the brain was irradiated by 3.15-GHz microwave energy at 3.0 W/cm2 rms for 15 min. The rat's rectal temperature was maintained at 37.0°C. Immediately after irradiation, 2% Evans blue dye in saline (2.0 ml/kg body mass) was injected through the cannula. The results show that as the quantity of alcohol was increased, the degree of staining was decreased or eliminated. The temperature of the irradiated area of the brain increased for the first 4 to 5 minutes of irradiation and then stabilized for the remainder of the irradiation period. The steady-state temperature was highest in animals receiving saline or the smallest dose of alcohol. As the quantity of alcohol was increased, the steady-state temperature was reduced. These results indicate that ethanol inhibits microwave-induced permeation of the blood-brain barrier through reduced heating of the brain.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250070408
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