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81.
The specificity of the collagenolytic enzyme from the fungus Entomophthora coronata toward some inhibitors and the B chain of oxidized insulin was investigated and compared to that of the bacterial collagenase from Achromobacter iophagus. The fungal enzyme was completely inhibited by diisopropylfluorophosphate, tosyl-l-lysine chloromethyl ketone, and tosyl-amino-2-phenylethyl chloromethyl ketone but not at all by ethylenediaminetetraacetate. This indicates that it is not a metalloenzyme like the bacterial Achromobacter collagenase. The B chain of insulin was not hydrolysed at all by the bacterial enzyme under conditions where extensive digestion was observed with the Entomophthora enzyme. The fungal enzyme cleaves preferentially the bonds as determined by automatic sequencing; the secondary cleavages were identified by a systematic analysis of the digestion mixture; thus, the fungal collagenolytic enzyme from Entomophthora coronata differs both structurally and functionally from the bacterial Achromobacter collagenase. 相似文献
82.
Carbon and nitrogen stable isotope analyses have improved our understanding of food webs and movement patterns of aquatic
organisms. These techniques have recently been applied to diet studies of elasmobranch fishes, but isotope turnover rates
and isotope diet–tissue discrimination are still poorly understood for this group. We performed a diet switch experiment on
captive sandbar sharks (Carcharhinus plumbeus) as a model shark species to determine tissue turnover rates for liver, whole blood, and white muscle. In a second experiment,
we subjected captive coastal skates (Leucoraja spp.) to serial salinity reductions to measure possible impacts of tissue urea content on nitrogen stable isotope values.
We extracted urea from spiny dogfish (Squalus acanthias) white muscle to test for effects on nitrogen stable isotopes. Isotope turnover was slow for shark tissues and similar to
previously published estimates for stingrays and teleost fishes with low growth rates. Muscle isotope data would likely fail
to capture seasonal migrations or diet switches in sharks, while liver and whole blood would more closely reflect shorter
term movement or shifts in diet. Nitrogen stable isotope values of skate blood and skate and dogfish white muscle were not
affected by tissue urea content, suggesting that available diet–tissue discrimination estimates for teleost fishes with similar
physiologies would provide accurate estimates for elasmobranchs. 相似文献
83.
Postural sway was compared for humans touching an external object while standing on an immobile or slowly moving posturographic platform. When the platform moves, the central nervous system may interpret the movement of the point of the contact with the external object as the movement of the body relative to the support or as the movement of the support itself. Thus, the information concerning the body position that is provided by the touch becomes ambiguous. It was demonstrated that contact with an external object during standing on an unstable support leads to a decrease in support sway. When a subject stands on a moving platform, this decrease is smaller than in the case of an immobile platform. Contact with an external object causes a decrease in postural responses to shank muscle vibrations on an immobile platform. On a moving platform, this decrease is nonsignificant. The change in postural sway depending on the unambiguity of afferent information is discussed in terms of the interaction between afferent signals of different modalities on the basis of the body scheme in subjects maintaining balance.Translated from Fiziologiya Cheloveka, Vol. 31, No. 1, 2005, pp. 59–65.Original Russian Text Copyright © 2005 by Kazennikov, Shlykov, Levik. 相似文献
84.
S Sayama R V Iozzo G S Lazarus N M Schechter 《The Journal of biological chemistry》1987,262(14):6808-6815
The subcellular localization of human skin chymase to mast cell granules was established by immunoelectron microscopy, and binding of chymase to the area of the dermo-epidermal junction, a basement membrane, was demonstrated immunocytochemically in cryosections incubated with purified proteinase prior to immunolabeling. Because heparin and heparan sulfate proteoglycans are major constituents of mast cell granules and basement membranes, respectively, the ability of chymase to bind to glycosaminoglycans (GAG) was investigated. Among a variety of GAGs, only binding of chymase to heparin and heparan sulfate appears physiologically significant. Binding was ionic strength-dependent, involved amino groups on the proteinase, and correlated with increasing GAG sulfate content, indicating a predominantly electrostatic association. Interaction with heparin was observed in solutions containing up to 0.5 M NaCl, and interaction with heparan sulfate was observed in solutions containing up to 0.3 M NaCl. Binding of heparin did not detectably affect catalysis of peptide substrates, but may reduce accessibility of proteinase to protein substrates. Measurements among a series of serine class proteinases indicated that heparin binding was a more common property of mast cell proteinases than proteinases stored in other secretory granules. Binding of chymase to heparin is likely to have a storage as well as a structural role within the mast cell granule, whereas binding of chymase to heparan sulfate may have physiological significance after degranulation. 相似文献
85.
86.
Comparative tissue ascorbic acid studies in fishes 总被引:1,自引:0,他引:1
Comparative tissue ascorbic acid levels in four species of major carp viz., Labeo rohila, L. calbasu, Cirrhina tnrigala and Catla catla , were investigated. The ascorbic acid level was found to be the highest in the spleen in the four species studied (range 430–380 μg/g) followed by the anterior (adrenal) kidney, gonads, liver, renal kidney, brain and/or eye. Heart and blood had the lowest levels (range 26–18 μg/ml) amongst the tissues studied. Overall tissue ascorbic acid levels were the highest in L. rohita and the lowest in C. mrigala . Investigation on seasonal variations in blood and kidney ascorbic acid levels of Notopterus notopterus revealed peak levels in spring (February-April) and the lowest levels in the postspawning period (August-September). 相似文献
87.
88.
Ia I Serkiz A I Lipskaia L B Pinchuk V V Trishin Iu F Kataevski? G N Koval' 《Radiobiologiia》1991,31(5):629-634
Irradiation conditions in which laboratory animals were kept in experimental laboratories of Chernobyl and Kiev after the accident at the Chernobyl A.P.S. are described. The data are presented on the spectral structural and activity of radionuclides in the diet as well as in the organs and tissues of the animals. The radiation loads have been estimated with regard to an external gamma component and the internal one contributed by the incorporated radionuclides. It has been shown that radiation doses received by the animals during their lifetime due to these contributions do not exceed units of cGy. 相似文献
89.
90.