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  • Kinetics  (55)
  • American Association for the Advancement of Science (AAAS)  (48)
  • Springer  (7)
  • 1980-1984  (55)
  • 1970-1974
Collection
Publisher
  • American Association for the Advancement of Science (AAAS)  (48)
  • Springer  (7)
  • Wiley-Blackwell  (1)
Years
Year
  • 1
    Publication Date: 1981-12-04
    Description: Leucine catabolism is regulated by either of the first two degradative steps: (reversible) transamination to the keto acid or subsequent decarboxylation. A method is described to measure rates of leucine transamination, reamination, and keto acid oxidation. The method is applied directly to humans by infusing the nonradioactive tracer, L-[15N,1-13C]leucine. Leucine transamination was found to be operating several times faster than the keto acid decarboxylation and to be of equal magnitude in adult human males under two different dietary conditions, postabsorptive and fed. These results indicate that decarboxylation, not transamination, is the rate-limiting step in normal human leucine metabolism.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Matthews, D E -- Bier, D M -- Rennie, M J -- Edwards, R H -- Halliday, D -- Millward, D J -- Clugston, G A -- AM-25994/AM/NIADDK NIH HHS/ -- HD-10667/HD/NICHD NIH HHS/ -- RR-00954/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 1981 Dec 4;214(4525):1129-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7302583" target="_blank"〉PubMed〈/a〉
    Keywords: Adult ; Carbon Isotopes ; Humans ; Kinetics ; Leucine/*metabolism ; Male ; Models, Biological ; Nitrogen Isotopes ; Oxidation-Reduction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 1983-12-23
    Description: Endotoxin-free thymosin fraction 5 elevated corticotropin, beta-endorphin, and cortisol in a dose- and time-dependent fashion when administered intravenously to prepubertal cynomolgus monkeys. Two synthetic component peptides of thymosin fraction 5 had no acute effects on pituitary function, suggesting that some other peptides in thymosin fraction 5 were responsible for its corticotropin-releasing activity. In agreement with these observations, total thymectomy of juvenile macaques was associated with decreases in plasma cortisol, corticotropin, and beta-endorphin. These findings indicate that the prepubertal primate thymus contains corticotropin-releasing activity that may contribute to a physiological immunoregulatory circuit between the developing immunological and pituitary-adrenal systems.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Healy, D L -- Hodgen, G D -- Schulte, H M -- Chrousos, G P -- Loriaux, D L -- Hall, N R -- Goldstein, A L -- CA 24974/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1983 Dec 23;222(4630):1353-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6318312" target="_blank"〉PubMed〈/a〉
    Keywords: Adrenocorticotropic Hormone/*blood ; Animals ; Dose-Response Relationship, Drug ; Endorphins/blood ; Female ; Hydrocortisone/blood ; Kinetics ; Macaca fascicularis ; Thymectomy ; Thymosin/analogs & derivatives/*pharmacology ; Thymus Gland/*physiology ; beta-Endorphin
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 1983-03-25
    Description: Microinfusions of rat prolactin into the dorsal midbrain of estrogen-treated, ovariectomized rats increased lordosis behavior. Midbrain microinfusions of antiserum to prolactin into rats displaying maximum lordosis had the opposite effect. The distribution of a prolactin-like substance in the brain was studied immunocytochemically. The results suggest that a hypothalamic neuronal system projecting to the midbrain contains a prolactin-like substance that plays a role in facilitating this behavior and therefore may mediate some of the effects of estrogen on the brain. These data, together with others from studies of the prolactin gene and its regulation, indicate that it may be possible to analyze a sequence of molecular events in the brain that facilitate a behavioral response.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harlan, R E -- Shivers, B D -- Pfaff, D W -- HD-05585/HD/NICHD NIH HHS/ -- HD-05737/HD/NICHD NIH HHS/ -- New York, N.Y. -- Science. 1983 Mar 25;219(4591):1451-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6828874" target="_blank"〉PubMed〈/a〉
    Keywords: Adrenalectomy ; Animals ; Castration ; Cerebral Cortex/drug effects/*physiology ; Cosyntropin/pharmacology ; Estradiol/pharmacology ; Female ; Growth Hormone/pharmacology ; Immune Sera ; Kinetics ; Mesencephalon/*physiology ; Oxytocin/pharmacology ; Posture ; Prolactin/administration & dosage/*pharmacology ; Rats ; Sexual Behavior, Animal/*drug effects ; Vasopressins/pharmacology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 1980-06-06
    Description: A protein that binds spermine specifically was separated from normal rabbit serum by affinity chromatography. Immunoelectrophoresis, the Ouchterlony immunodiffusion test, and gradient gel electrophoresis indicated that this protein has immunoglobulin characteristics and consists of several populations of antibodies to spermine. These were sequentially released from Sepharose-spermine gel by step-wise elution with solutions ranging in pH from 4 to 1. The binding constants varied from 5.0 x 10(8) to 11.1 x 10(8) liters per mole. These globulins did not react with monoacetylputrescine, L-ornithine, L-lysine, and histamine. Negligible cross-reactivity was detected with spermidine, putrescine, N8-monoacetylspermidine, cadaverine, and diaminopropane. Since perturbations in polyamine metabolism have been identified in several diseases, the study of extracellular polyamine homeostasis may reveal an important regulatory function for this protein.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bartos, D -- Bartos, F -- Campbell, R A -- Grettie, D P -- Smejtek, P -- New York, N.Y. -- Science. 1980 Jun 6;208(4448):1178-81.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7375929" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antibodies/*isolation & purification ; Binding Sites, Antibody ; Chromatography, Affinity ; Homeostasis ; Immunoglobulin G/isolation & purification ; Kinetics ; Rabbits ; Spermine/*immunology/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 1982-07-02
    Description: Liposomes were used to deliver ribosomal RNA's from the different organisms into cultivated mouse plasmacytoma cells. Ribosomal RNA from Escherichia coli was degraded intracellularly within 1 hour, whereas mouse and yeast ribosomal RNA's were degraded more slowly. This indicates that cells can discriminated between different ribosomal RNA's.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lavelle, D -- Ostro, M J -- Giacomoni, D -- GM 27935/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1982 Jul 2;217(4554):59-61.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6178157" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Line ; Escherichia coli ; Kinetics ; *Liposomes ; Mice ; Molecular Weight ; Neoplasms, Experimental/metabolism ; Plasmacytoma/*metabolism ; RNA, Bacterial/metabolism ; RNA, Ribosomal/*metabolism ; Saccharomyces cerevisiae ; Species Specificity
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 36 (1984), S. 48-59 
    ISSN: 1432-0827
    Keywords: Salivary proteins ; Adsorption ; Thermodynamics ; Kinetics ; Hydroxyapatite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Equilibrium and kinetic experiments were conducted to investigate the factors determining the adsorption of salivary macromolecules onto hydroxyapatite. Using amino acids and other small adsorbates, it was determined that the carboxyl attached to the α carbon does not appear to adsorb onto HA and the affinities of side-chain carboxyls are much smaller than that of the phosphate group (phosphoserine). Hydroxyl (serine) displays an extremely high affinity, but its adsorption site on HA is different and the number of such sites is much smaller than found for the rest of the functional groups investigated. It is shown that the information obtained from small molecules cannot be readily applied to prediction of the adsorption behavior of salivary macromolecules and polypeptides. The kinetics of adsorption of the salivary phosphopeptide statherin, a polyaspartate, and the salivary prolinerich phosphoprotein PRP3 are consistent with the reversibility of the adsorption process; no conclusion was possible in the case of the protein PRP1. Apparent irreversibility cannot be explained on the basis of multipoint binding or the properties of the carboxyl versus phosphate group; it appears that secondary structure determines to a significant extent the adsorption properties of the macromolecules. Calculation of the thermodynamic molar quantities of adsorption of PRP1, PRP3, andl-ASP onto HA showed that the process is entropically driven. The functional relationship between partial molar entropy and adsorption coverage is similar for the two proteins, but quite different from that for aspartate. Explanations for these results are advanced on the bases of changes in structure configurations and displacement of water from the adsorbate and the adsorbent surface, the second factor being the dominant one in the adsorption of a small molecule such asl-ASP.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 9 (1983), S. 145-170 
    ISSN: 1432-1017
    Keywords: Viroids ; Thermodynamics ; Kinetics ; Hydrodynamics ; Function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Viroids are an independent class of plant pathogens which are distinguished from viruses by the absence of a protein coat and by their unusually small size. They are single-stranded circular RNAs composed of about 360 nucleotide residues. Sequence analysis and physicochemical studies of the potato spindle tuber viroid (PSTV) have shown that, as a result of intra-molecular base pairing, viroids form a unique rod-like secondary structure which is characterized by a serial arrangement of double-helical sections and internal loops. There is no indication for an additional tertiary structure because all parts of the molecule are freely accessible to ligand interaction. During the denaturation all of the native base pairs of viroids are dissociated in one highly cooperative transition, and in the same process very stable hairpins which are not present in the native structure are newly formed. Most of the properties of the structure and structural transitions of PSTV have been found also in citrus exocortis viroid, chrysanthemum stunt viroid and four different viroid-like RNAs associated with the cadang-cadang disease. The close similarity between these viroids is more expressed in the overall structure and in thermodynamic and functional domains than in the primary sequence. The stiffness of all viroids can be described by an unique persistence length of 300 å. Characteristically, regions of premelting, regions of stable hairpins, and the sequence UACUACCCGGUGG which is opposite to one of the stable hairpins, are the most conservative sequences in the molecules. Current hypotheses about the function of viroids are discussed on the basis of their structural and thermodynamic features. The suggestion that viroid RNA has features similar to DNA has been supported by the finding that they are replicated in vitro by the DNA-dependent RNA polymerase II of the host plant. The highly conserved sequence in viroids mentioned above corresponds very closely to a segment at the 5′-end of the small nuclear RNA U1 of eukaryotes. Because this segment is discussed in recent models, to be involved in the splicing process, a hypothesis is proposed in which viroids interfere with the splicing process leading to a pathogenic misregulation of mRNA processing.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 8 (1981), S. 23-34 
    ISSN: 1432-1017
    Keywords: Light-scattering ; Flash photometry ; Kinetics ; Visual transduction ; Biomembranes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract A recent development of kinetic light-scattering and -absorption photometry is described. Essential points are: 1) In the scattering experiment, amplitude resolution of 2 · 10−5 (single flash) by application of a differential detector, stability of the same magnitude due to optical compensation, high intensity at the detector due to special optics for the scattered light and semiconductor sources. 2) In the absorption measurement, elimination of scattering contributions by the dual wavelength-method and by high aperture optics. 3) Simultaneous measurement of absorption and scattering. The application of the method is described in using signals from isolated bovine rod outer segments. A reliable procedure is described by the use of which the originally measured light-scattering effects can be split up into single signals. The method allows comparative kinetic analysis of absorption and scattering signals. The possible causal connections between pigment and membrane structure processes can be selected.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1434-4475
    Keywords: Arginine ; Catalysis ; Kinetics ; Mechanism ; Oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Oxidation erfolgt sowohl mit als auch ohne Cu(II)-Katalysator in erster Ordnung bezüglich des Oxidationsmittels und des Substrats; inverse Ordnung wird bezüglich der Alkalikonzentration beobachtet. Bis zu einer Cu(II)-Konzentration von≤2×10−5 M ist die Geschwindigkeitskonstante der Katalysatorkonzentration proportional; darüber wird eine konstantbleibende Geschwindigkeit beobachtet, die nun von der Cu(II)-Konzentration unabhängig ist. Neutralsalze haben keinen Effekt auf die Geschwindigkeitskonstante. Es wird für den katalysierten und unkatalysierten Reaktionsablauf ein Mechanismus vorgeschlagen und ein mathematischer Ansatz präsentiert.
    Notes: Abstract The kinetics of uncatalysed and Cu(II) catalysed oxidation of arginine monohydrochloride was investigated. Both reactions follow a singular order dependence each in oxidant and substrate. An inverse order dependence is reported with the alkali concentration. A plot of observed rate constant versus Cu(II) concentrations Cu(II)≤2.0×10−5 M is linear; from the intercept the rate constant for the uncatalysed pathway was calculated. However, at high copper ion concentrations i.e. Cu(II)〉2.0×10−5 M a fixed value of rate constant was found for all catalyst concentrations. Added neutral salts show an insignificant effect on the reaction rate. Mechanisms were proposed for both cases and rate expressions were derived by applying steady state assumptions.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 260 (1982), S. 641-642 
    ISSN: 1435-1536
    Keywords: Kinetics ; Nucleation ; Water ; Emulsion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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