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  • 1
    Digitale Medien
    Digitale Medien
    Different Effects Of β-Adrenoceptor Desensitization On Inhibitory Actions In Guinea-Pig Trachealis (2002)
    Oxford, UK : Blackwell Science Pty
    Clinical and experimental pharmacology and physiology 29 (2002), S. 0 
    Details
    ISSN: 1440-1681
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: 1. To determine the inhibitory effects of agents that pass through and bypass β-adrenoceptors under conditions of tolerance to β-adrenoceptor agonists, we examined the inhibition by the β-adrenoceptor agonists forskolin and theophylline against contraction induced by methacholine (MCh) after exposure to higher concentrations of a β-adrenoceptor agonist for a long time in guinea-pig tracheal smooth muscle, using isometric tension records.2. After exposure to procaterol (0.0003–3 μmol/L) for 45 min, the inhibitory effect of 0.03 μmol/L procaterol on 1 μmol/L MCh-induced contraction was attenuated in a concentration-dependent manner, whereas after exposure to isoprenaline (0.0003–3 μmol/L) for an equivalent time, the inhibitory effect of isoprenaline was markedly attenuated at each concentration. However, after exposure to 3 μmol/L procaterol for 45 min, the inhibitory actions of forskolin and theophylline were, conversely, augmented.3. These phenomena were observed under conditions whereby the response to MCh returned to control levels 6 h after removal of 3 μmol/L procaterol. The percentage inhibition produced by 0.1 μmol/L forskolin against 1 μmol/L MCh after exposure to normal bathing solution or 3 μmol/L procaterol for 45 min was 9.8 ± 5.5 and 82.8 ± 6.5%, respectively (P 〈 0.001). These values for 100 μmol/L (18 μg/mL) theophylline on MCh resposnes were 9.9 ± 8.5 and 88.0 ± 4.4% (n = 6 for both), respectively (P 〈 0.001).4. The inhibitory action of agents that bypass β-adrenoceptors was markedly augmented under conditions of β-adrenoceptor desensitization in airway smooth muscle.5. In conclusion, procaterol is less potent in causing desensitization of β-adrenoceptors than isoprenaline. The activity of adenylyl cyclase may be enhanced after exposure to a high concentration of β-adrenoceptor agonists.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1440-1681.2002.03715.x
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  • 2
    Digitale Medien
    Digitale Medien
    The evolution of the protein synthesis system, II (1980)
    Springer
    Origins of life and evolution of the biospheres 10 (1980), S. 31-38 
    Details
    ISSN: 1573-0875
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract The sequence of events previously proposed for modern protein synthesis is reviewed. It begins with an abiological synthesis of a template, and evolves through two model autocatalytic systems to a primitive cell that has a rudimentary biological protein synthesis system. A possible scheme for the origin of tRNA's is described so as to fill the gap between the model and the modern system. Fragments of genes that existed in and around the primitive system are proposed to be precursors of tRNA's. Since these fragments must have been undesirable components for the system, the origin and evolution of tRNA's may be regarded as an excellent answer by the primitive system to adverse circumstances.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00928941
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  • 3
    Digitale Medien
    Digitale Medien
    Effect of polynucleotides on the dimerization of glycine (1981)
    Springer
    Origins of life and evolution of the biospheres 11 (1981), S. 237-241 
    Details
    ISSN: 1573-0875
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Polynucleotides were found to suppress the dimerization reaction of aqueous glycine with trimetaphosphate as the condensing agent. Small anions (chloride, acetate, and phosphate) did not show this effect. The reaction was studied at a pH of about 11.5 and at 70°C and room temperature with a 13 mM concentration of glycine and trimetaphosphate. Under these conditions, the effect of the polynucleotides was in the following order: polyguanylic acid 〈 polycytidylic acid 〈 polyadenylic acid 〈 polyuridylic acid. The result may have a significant implication for the understanding of processes of chemical evolution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00931389
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  • 4
    Digitale Medien
    Digitale Medien
    Material cycling and organic evolution (1982)
    Springer
    Origins of life and evolution of the biospheres 12 (1982), S. 369-376 
    Details
    ISSN: 1573-0875
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Intertwined cycles of matters are proposed to be one of the essential characteristics of life. The increase in the amount of recycled matters within biological groups and the complication of the cycling network are considered to be the early development of life soon after its appearance on the Earth. From this point of view, the origin of a cell alone can not sufficiently be regarded as the origin of life. The origin of a cell must be followed by a formation of material cycling among cells, if the cells are to stay on the Earth long enough so that they could be called life. This biogeochemical viewpoint leads to a quantitative analysis of life activity. A formula is presented to exemplify the potential utility of the viewpoint. It is applied to analyses of possible early developments of life and of an impact of present human activity on the global carbon cycle. Further application of the viewpoint to a variety of biogeochemical, sociogeochemical, ecological, and environmental problems should eventually show whether there is some utility in this view.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00927069
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  • 5
    Digitale Medien
    Digitale Medien
    Effect of high atmospheric CO2 concentration on δ13 of algae (1982)
    Springer
    Origins of life and evolution of the biospheres 12 (1982), S. 377-390 
    Details
    ISSN: 1573-0875
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Precambrian reduced carbon is more depleted in13C than what would be expected from the carbon isotopic composition of modern marine algae and algal mats. Since the photosynthetic carbon fixation by algae is the most likely source of the reduced carbon, the depletion has been considered an anomaly. We examined factors that might have contributed to the carbon isotope fractionation from inorganic sources through algae to organic matter in a sedimentary rock, and related laboratory obtainable data to those from Precambrian rocks. Laboratory culture experiments were then performed with nine strains of algae at various concentrations of carbon dioxide, and the result was interpreted according to the relationship. It indicated that the depletion could be understood in terms of a combined effect of fractionation factors, most depletion occurring at the fractionation during the photosynthetic carbon fixation. It also suggested that all but one algal strain incorporated bicarbonate as the source of carbon for its growth. The exception was a thermophilic, acidophilic alga, which must have used carbon dioxide as the carbon source. The present study suggests that Precambrian atmosphere was enriched in carbon dioxide roughly two orders of magnitude more than its present atmospheric level.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00927070
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  • 6
    Digitale Medien
    Digitale Medien
    Errata (1983)
    Springer
    Origins of life and evolution of the biospheres 13 (1983), S. 167-167 
    Details
    ISSN: 1573-0875
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00928895
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  • 7
    Digitale Medien
    Digitale Medien
    The evolution of the protein synthesis system (1977)
    Springer
    Origins of life and evolution of the biospheres 8 (1977), S. 183-219 
    Details
    ISSN: 1573-0875
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract An evolutionary picture of the early protein synthesis was presented in relation to the problem of the origin and the evolution of life. A model of an autocatalytic system was studied in this connection. The system in this model included a template nucleotide and two activated amino acid polymerases with or without a nucleotide polymerase. Variables defining the system were: (1) Catalytic activity of the polymerases, (2) Number of amino acid residues at the activity site of the polymerases, (3) Number of amino acid residues at the selectivity site of the polymerases, (4) Number of the polymerases, (5) Accuracy of polymerization and activity of the polymerases, (6) Number of evolutionary improvements, and (7) The probability of an occurrence of beneficial mutations. The population changes of the systems were obtained by computer calculations. The simulation results indicated that even a very small enzymic activity and specificity of the polymerases could eventually lead the system to the most accurate protein synthesis, as far as transitions to systems with higher accuracy were allowed. The model study would encourage further quantiative investigations on catalytic activities of synthetic peptides, and on interactions between nucleotides and amino acids, and constructions of autocatalytic systems from a chemical evolutionary point of view.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00930682
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  • 8
    Digitale Medien
    Digitale Medien
    Macromolecules and the origin of life (1975)
    Springer
    Origins of life and evolution of the biospheres 6 (1975), S. 139-146 
    Details
    ISSN: 1573-0875
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract From our knonwledge of present day organisms, it is hard to imagine a living assembly, even at its most primitive stage, without macromolecules. In order to look for the macromolecules which possibly participated in the assembly of the primitive organisms, the reaction and formation of polymers in HCN under irradiation of ultraviolet ray of 184.9 nm. was studied. As a example of a simple way of producing an assembly of macromolecules, the mechanism of coacervation was studied by using gelatin as the material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01372398
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  • 9
    Digitale Medien
    Digitale Medien
    Study on the photochemical reaction of HCN and its polymer products relating to primary chemical evolution (1975)
    Springer
    Origins of life and evolution of the biospheres 6 (1975), S. 513-525 
    Details
    ISSN: 1573-0875
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract The photochemical reaction of HCN at 184.9 nm is studied in the gas phase. (CN)2, H2, CH4, NH3, N2H4, C2H6, and CH3NH2 are identified as gas phase products, and a reaction mechanism is proposed. HCN polymers** are also obtained as solid reaction products, and their structure is investigated by Infrared Spectroscopy, UV-Visible Spectroscopy, Mass Spectrometry, and Amino acid Analysis. The process and nature of the formation of the polymers are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00928899
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  • 10
    Digitale Medien
    Digitale Medien
    Carbon isotope composition of CH4 from rice paddies in Japan (1991)
    Springer
    Biogeochemistry 13 (1991), S. 159-175 
    Details
    ISSN: 1573-515X
    Schlagwort(e): carbon isotope ratio ; methane ; rice field ; seasonal variation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract Carbon isotope ratios (δ13C) for bubble CH4 in a submerged paddy soil were studied in Yokohama, Japan, throughout a growing period, and its variation was found. Bubble CH4 collected from other 33 paddy fields in Japan was also measured for its δ13C and the results agreed with Yokohama. Furthermore, the variation occurred irrespective of the amount and the type of supplied organic substances to the fields (whole rice straw, rice stubble, or compost). The δ13C value (average value of -55.9 ± 4.24‰) from these paddy fields was higher than those of the CH4 emitted from African and North American paddies. The higher value was little affected by their difference in the supplied organic substances. CH4 oxidation likely occurs for bubble CH4 in the shallow paddy fields. A rough estimate of the total CH4 production, using isotope mass balance, showed that 17 to 22% of organic carbon supplied to Japanese paddies transforms to CH4.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00002775
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