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31.
Host immunoglobulin G titre and antibody activity in haemolymph of the tick, Ornithodoros moubata 总被引:1,自引:0,他引:1
Immunoglobulin G (IgG) in tick haemolymph was analysed immunochemically and biochemically for its antigenicity, antibody activity and relative concentration in a soft tick, Ornithodoros moubata (Murray) sensu Walton 1962 (Acari: Argasidae). Ouchterlony immunodiffusion tests showed that haemolymph from a tick engorged on rabbit IgG (or human IgG) through an artificial membrane, reacted with anti-rabbit IgG (anti-human IgG) but not with anti-human IgG (anti-rabbit IgG). This indicates that haemolymph of the fed tick contains IgG with a similar antigen specificity to host blood IgG. IgG from tick haemolymph was demonstrated by enzyme immunoassay to have the same antibody activity as ingested IgG. The IgG concentration in tick haemolymph was measured by a quantitative single immunodiffusion test. Changes of IgG titre after a bloodmeal were correlated with IgG activity, which was low for 5 days after a bloodmeal and then suddenly increased. The IgG titre reached a maximum 7 days post-engorgement, and remained high for over 4 months during and after oviposition. 125I-labelled IgG was injected into the tick haemocoel to determine the persistence of IgG in the haemolymph. Recovery of labelled IgG was low at 1 and 3 days, and high at 5, 8 and 16 days after engorgement. The data suggest that IgG in haemolymph disappears quickly soon after engorgement possibly by degradation and/or absorption (adhesion to tissues). 相似文献
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34.
The effects of moderate light at chilling temperature on the photosynthesis of unhardened (acclimated to +18° C) and hardened (cold-acclimated) spinach (Spinacea oleracea L.) leaves were studied by means of fluorescence-induction measurements at 20° C and 77K and by determination of quantum yield of O2 evolution. Exposure to 550 mol photons·m-2·s-1 at +4° C induced a strong photoinhibition in the unhardened leaves within a few hours. Photoinhibition manifested by a decline in quantum yield was characterized by an increase in initial fluorescence (F
o) and a decrease in variable fluorescence (F
v) and in the ratio of variable to maximum fluorescence (F
V/F
M), both at 77K and 20° C. The decline in quantum yield was more closely related to the decrease in the F
V/F
M ratio measured at 20° C, as compared with F
V/F
M at 77K. Quenching of the variable fluorescence of photosystem II was accompanied by a decline in photosystem-I fluorescence at 77K, indicating increased thermal de-excitation of pigments as the main consequence of the light treatment. All these changes detected in fluorescence parameters as well as in the quantum yield of O2 evolution were fully reversible within 1–3 h at a higher temperature in low light. The fast recovery led us to the view that this photoinhibition represents a regulatory mechanism protecting the photosynthetic apparatus from the adverse effects of excess light by increasing thermal energy dissipation. Long-term cold acclimation probably enforces other protective mechanisms, as the hardened leaves were insensitive to the same light treatment that induced strong inhibition of photosynthesis in unhardened leaves.Abbreviations
F
0
initial fluorescence
-
F
M
maximum fluorescence
-
F
V
variable fluorescence (F
M-F
0
- PFD
photon flux density
- PS
photosystem 相似文献
35.
Phorbol esters are known to alter microfilaments but it is not clear if the changes correspond to modulation of the phosphoinositide turnover/protein kinase C system. The novel technique of laser scanning confocal epifluorescence was used to study fiber orientation in phorbol ester treated cells. We treated endothelial cells with control agents and agents known to stimulate protein kinase C: 4 alpha-phorbol, phorbol 12-myristate 13-acetate (PMA), phorbol dibutyrate (PDB), or lipopolysaccharide. After incubation with the test agents, the endothelial cell microfilaments were stained with rhodamine pholloidin and viewed by conventional epifluorescence and by laser scanning confocal epifluorescence microscopy. The images obtained by the confocal microscopy corresponded to a thin optical section through the cells, 300 nm or more in thickness. The microfilaments extended predominantly in the plane of focus. After exposure of the cells to phorbol esters, the stress fibers became more nearly parallel in arrangement or were shortened, but remained in the plane of focus. The modification of microfilaments in response to phorbol esters was quantitated by a single blind analysis. In order to compare the morphological changes with a biochemical action of the phorbol esters, we measured phosphoinositide turnover. The dose-dependence of morphological changes was compared and contrasted to the dose-dependent effect of phorbol esters on bradykinin-stimulated phosphoinositide turnover. PMA had about the same EC50 (1-5 nM) for both biochemical and morphological processes. PDB was less potent in inducing the disruption of microfilament structure than in inhibiting phosphoinositide turnover. Lipopolysaccharide was ineffective in inducing a morphological change under these conditions. A simple activation of protein kinase C is insufficient to explain the dose-dependent effects of phorbol esters. Thus a morphometric analysis can help distinguish the potency of cytoskeleton modulators. 相似文献
36.
Summary The secondary and tertiary structural features of botulinum neurotoxin (NT) serotype A, a dichain protein (Mr 145 000), and its two subunits, the heavy (H) and light (L) chains (Mr 97 000 and 53 000, respectively) were examined using circular dichroism and fluorescence spectorscopy. Nearly 70% of the amino acid residues in each of the three polypeptide preparations were found in ordered structure (sum of helix, sheet and turns). Also, the helix, sheet, turns and random coil contents of the dichain NT were nearly equal to the weighted mean of each of these secondary structure parameters of the L and H chains; e.g., sum of helix of L chain (22%) and H chain (18.7%), as weighted mean, 19.8% was similar to that of NT (20%). These agreements suggested that the secondary structures of the subunits of the dichain NT do not significantly change when they are separated as isolated L and H chains. Fluorescence emission maximum of L chain, 4 nm less (blue shift) than that of H chain, suggested relatively more hydrophobic environment of fluorescent tryptophan residue(s) of L chain. Tryptophan fluorescence quantum yields of L chain, H chain and the NT, 0.072, 0.174 and 0.197, respectively, suggested that a) an alteration in the micro-environment of the tryptophan residues was possibly caused by interactions of L and H chain subunits of the NT and b) quantum yields for L and H chains were altered when they are together as subunits of the NT. Possible implications of structural features of the L and H chains, their interactions and the molecular mechanism of action of botulinum NT are assessed. 相似文献
37.
Giorgio Di Marco Nicola D'Ambrosio Maria T. Giardi Angelo Massacci Domenico Tricoli 《Photosynthesis research》1989,21(2):117-122
We investigated several photosynthetic parameters of a virescent mutant of durum wheat and of its wild-type. Electron transport rate to ferricyanide was the same in the two genotypes when expressed on leaf area basis while O2 evolution of the leaf tissue in saturating light and CO2 was slightly higher in the yellow genotype. RuBPCase was also slightly higher. Quantum yield per absorbed light was similar in the two genotypes. P700 and Cyt f were less concentrated in the mutant while PS II was only marginally lower. The light response curve of CO2 assimilation indicated higher level of photosynthesis of the mutant in high light, which corresponded to a lower non-photochemical quenching compared to the wild-type. It is concluded that the reaction centres, cyt f and chlorophyll are not limiting factors of electron transport in wheat seedlings and that electron transport capacity is in excess with respect to that needed for driving photosynthesis. Since the differences in photosynthesis reflect differences in RuBPCase activity, it is suggested that this enzyme limits photosynthesis in wheat seedlings also at high light intensities.Abbreviations cyt f
cytochrome f
- chl
chlorophyll
- PS II
photosystem II
- Pnmax
maximum photosynthesis
- RuBCase
Ribulose, 1-5,bisphosphate carboxylase 相似文献
38.
A. J. W. G. Visser A. van Hoek D. J. O'Kane J. Lee 《European biophysics journal : EBJ》1989,17(2):75-85
Time-resolved fluorescence on lumazine protein from Photobacterium phosphoreum was performed with synchrotron radiation as a source of continuously tunable excitation. The experiments yielded structural and dynamic details from which two aspects became apparent. From fluorescence anisotropy decay monitoring of lumazine fluorescence with different excitation wavelengths, the average correlation times were shown to change, which must indicate the presence of anisotropic motion of the protein. A similar study with 7-oxolumazine as the fluorescent ligand led to comparable results. The other remarkable observation dealt with the buildup of acceptor fluorescence, also observed with 7-oxolumazine although much less pronounced, which is caused by the finite energy transfer process between the single donor tryptophan and the energy accepting lumazine derivatives. Global analytical approaches in data analysis were used to yield realistic correlation times and reciprocal transfer rate constants. It was found that the tryptophan residue has a large motional freedom as also reported previously for this protein and for the related protein from P. leiognathi (Lee et al. 1985; Kulinski et al. 1987). The average distance between the tryptophan residue and the ligand donor-acceptor couple has been determined to be 2.7 nm for the same donor and two different acceptors. 相似文献
39.
Summary Hepatic-FABP was labelled at cysteine-69 with the fluorescent environmentally sensitive reporter group AEDANS. The labelled protein had an emission maximum at 465 nm indicating that cysteine-69 was buried in a non-polar environment. The modified protein was still able to bind ligands such as oleic acid, oleoyl CoA and haem. The affinity of AEDANS-FABP for haem was unaltered as compared with the native protein indicating that cysteine-69 must be remote from the ligand binding site. The binding of oleic acid did not significantly perturb the fluorescence emission spectrum of the fluorescent reporter group suggesting that there are not large conformational changes in the region of cysteine-69 on fatty acid binding. The binding of stoichiometric amounts of oleoyl CoA was accompanied by a small fluorescence enhancement which suggests that fatty acyl CoAs may interact with other regions of the FABP molecule not involved in fatty acid binding.Abbreviations FABP
Fatty Acid-Binding Protein
- AEDANS
5-[2-(Acetyl)aminoEthyl]Aminonaphthalene-1-Sulphonic Acid
- AAEDANS
5-[2-(Iodoacetyl-AminolEthyl] aminonaphthalene-1-Sulphonic Acid
- DTNB
5,5Dithiobis-(2-Nitrobenzoic acid) 相似文献
40.
Summary The identity of monoamine-emitted, formaldehyde-induced fluorescence in some pancreatic islet cells was studied in pancreatic tissue of male chickens by fluorescence and immunohistochemistry either on the same tissue section or on serial tissue sections. Pancreatic islet cells emitting intense formaldehyde-induced fluorescence also react immunohistochemically with antisera directed against glucagon, serotonin and aromatic L-amino acid decarboxylase. These results show that chicken pancreatic islet A cells contain glucagon, serotonin, and aromatic L-amino acid decarboxylase, an enzyme involved in the synthesis of serotonin. The islet B cells identified with anti-insulin immunoreactivity, which displayed a very weak formaldehyde-induced fluorescence, did not react with anti-serotonin serum. 相似文献