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81.
82.
L. Schachinger U. Hagen H. Klöter Ch. Schippel M. Jaenicke 《Radiation and environmental biophysics》1982,21(2):97-107
Summary In a previous publication it has been shown that the radiation induced physiological inactivation of dibutyryl-cAMP was far more pronounced than the chemical modification (Schachinger et al. 1981). In this paper it will be shown, that irradiation of dib-cAMP in solution resulted in the formation of monobutyryl cAMP and other not yet completely identified hydroxylated derivatives as well as a decomposition of the purine structure. Moreover, irradiated dib-cAMP inhibited the physiological activity of not irradiated dib-cAMP on the smooth muscle. From the data an effectiveK
m
-value for dib-cAMP of 2.4 × 10–5 M was determined and an effectiveK
I
-value of 1.3 × 10–6 M was found for the irradiation products, i.e., a tenfold affinity of the latter compared to unirradiated dib-cAMP. The results are discussed with respect to a better understanding of dose-response curves for chemical and physiological inactivation. 相似文献
83.
The total syntheses of racemic 1,6-dithiabenz[3,4]-estra-3,5(10), 8,14-tetraen-17-one [VII]and 1,6-dithiabenz-[3,4]-D-homoestra-3,5(10),8,14-tetraen-17a-one [IX]starting fron isothiochroman-4-one [I]are described. 相似文献
84.
J. E. Hardebo P. C. Emson B. Falck Ch. Owman E. Rosengren 《Journal of neurochemistry》1980,35(6):1388-1393
The activities of tyrosine hydroxylase, aromatic L-aminoacid decarboxylase, monoamine oxidase, and catechol-O-methyltransferase were measured in microvessel (capillaries and venules), parenchymal arterioles, and pial vessels from rat brains, and the decarboxylase activity was compared in brain microvessels from rabbit, cat, dog, pig, cow, baboon, and man. Cranial sympathectomy was performed to estimate the neuronal contribution to the enzyme activities. All vascular regions had substantial activities of the various enzymes studied. The activity of aromatic L-aminoacid decarboxylase in cerebral microvessels was high in rat, dog, pig, cow, and man; intermediate in rabbit and cat; and low in baboon. In addition to this enzyme, cerebral microvessels also contained tyrosine hydroxylase and monoamine oxidase. Aromatic aminoacid decarboxylase and monoamine oxidase serve an enzymatic barrier function at the microvascular level, whereas the main function of tyrosine hydroxylase is probably to synthesize monoamines within nerve terminals that remain in close association with microvessels under the conditions used for preparation of the microvascular fraction. In larger intracerebral and pial vessels monoamine oxidase was present both in the wall itself and in perivascular sympathetic nerves; the remaining two enzymes had a primarily neuronal localization. The latter types of vessels also contained catechol-O-methyltransferase in their walls. 相似文献
85.
The effect of the local anesthetic tetracaine on some functions of rat heart mitochondria was studied, and the results show that this tertiary amine inhibits the oxidation of NAD-dependent substrates by affecting the mitochondrial membrane in a site located between the NADH dehydrogenase and Co Q span through a process which is not affected by K+, Ca2+, or Mg2+. Also the results show that tetracaine induces sodium uptake probably by a H+/Na+ exchange reaction. 相似文献
86.
The effect of over forty low molecular weight substrates on the growth and synthesis of exocellular neutral proteases was studied in Pseudomonas fluorescens. Neutral exoproteases were found to be regulated enzymes. Glucose did not repress the synthesis of exocellular proteases; the regulation of their synthesis by amino acids involved the mechanism of induction. The data suggest that the primary intracellular inductors of the synthesis of exoproteases are formed for different groups of amino acids at different levels of their utilization by the cells, viz. at the level of transport and at the level of the first steps in the degradation of their carbon backbones. The paper discusses possible molecular mechanisms for integrating the signal of the primary intracellular inductors, which directly regulate the activity of the operon(s) of neutral exocellular proteases. 相似文献
87.
Summary The adventitial cells surrounding the spermatheca of the reproductive system of Sonorella santaritana (Mollusca: Gastropoda) appear to have an unusual system of vesicles. Electron micrographs of the membranes forming these vesicles show that they have multiple openings to the cell's exterior and that each opening has a pore complex. In addition, secondary vesicles appear to be generated by the primary vesicles. Evidence is presented suggesting that these vesicles represent a previously unreported membrane transport system.Southwestern Medical School and Veterous Administration Hospital Dallas, Texas, USA 相似文献
88.
Ch. von der Malsburg 《Biological cybernetics》1979,32(1):49-62
Ontogenetic development of ocularity domains — stripes, patches and layers in cortex, colliculus superior and lateral geniculate nucleus — is the result of organization that may either be intrinsic to the postsynaptic structure or induced to it by the afferents. A specific type of axonal growth behaviour that was recently proposed as a basis for ontogenetic development of retinotopy is sufficient to account also for ocularity domains. No intrinsic organization in the postsynaptic structure is required. The latter merely serves as a propagating medium for markers carried by the presynaptic terminals. Computer simulations demonstrate the mechanism to be complete and consistent. 相似文献
89.
Summary A least squares fit of Feulgen hydrolysis time curves to the Bateman function is performed using an especially adapted parameter transformation together with a standard conjugate gradients iteration procedure. The method has been applied to a large number of measured data, and the use and limits of the computer evaluation are discussed. 相似文献
90.