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31.
Perturbations induced by a toxic lectin (ricin) on lipid organisation of model membranes prepared with DPPC and DPPC-cerebrosides mixtures have been analysed by Raman and infrared spectroscopy, two powerful and non-invasive methods. Our approach involves the observation of changes in the vibrational spectra of liquid multilayers in the PO
2
-
, C=0 and CH2 spectral regions for two lipid: ricin molar ratios (225:1, 75:1).The interfacial and polar regions of the multilayers, analysed by FTIR, appear to be perturbed by the protein. With both kinds of membranes, ricin mainly perturbs the C=0 ester groups of the sn-2 acylchain of DPPC. In the PO
2
-
stretching region, the frequency shifts are correlated with changes in polar group hydration.In the hydrophobic core of the multilayer membrane studied by Raman spectroscopy, the interaction of ricin is associated with changes in lipid packing. These perturbations depend upon the lipid composition of the membrane. With DPPC membranes, an affect is detected at temperatures lower than T
m
.It corresponds to a decrease of the lipid ordering. With DPPC-cer membranes, the protein increases the acylchain packing order regardless of the temperature of the experiments (10°C<T<75°C). No perturbation of T
m
is observed after addition of ricin to either DPPC or DPPC-cer membranes.The different perturbations detected by Raman and FTIR suggest that ricin mainly interacts with the interfacial domains of the membranes. 相似文献
32.
The effect of short chain fatty acids on the cellular permeability of embryonic axis inGcer arietinum seeds was studied. Octanoic (OCT) and nonanoic (NON) adds, which reduce both germination and growth of the embryonic axis and raise the inhibitor effects of the supraoptimal temperatures (30?C), induce a greater ionic efflux into the medium (conductivity). NON reduces glucose (3-0-MG) and K+ (86Rb) uptake during the germinative process, this action being counteracted by fusicoccin (FC) at optimal (25?C) and supraoptimal temperatures (30 ?C). Tonoplast and plasmalemma increase their permeability to the K+ efflux when NON is present. Addition of NON+FC gives rise to higher values in the efflux rate, the vacuolar compartment being the most affected. Temperatures around zero (2 ?C) notably reduce the isotope efflux from cytosol and vacuole. NON acid does not significantly affect the efflux of3H-ABA, suggesting that it does not cause any important changes in the phytohormone compartmentation. 相似文献
33.
To determine whether male worms provide any specific polypeptides to females, we produced extruded alginate fibers that resembled the size and shape of mature female worms. Males clasped these surrogate "female worms" and remained "paired" with them for long periods. On polyacrylamide gel electrophoresis, fibers clasped for several days showed bands at approximately 40 and 46 kDa which were never found in fibers incubated in the same medium but not clasped by males. We believe that these may be substances transferred from male worms during normal pairing. Males biosynthetically labeled with [14C]leucine were permitted to pair with fibers, which took up a broad range of polypeptides visualized on long autoradiographic exposure to gels. 相似文献
34.
E Tosoni-Pittoni I Joab J C Nicolas M Perricaudet 《Biochemical and biophysical research communications》1989,158(3):676-684
The gene which encodes the Epstein-Barr gp 220/340 was inserted into a eukaryotic expression vector. A cDNA clone corresponding to the mature mRNA coding for gp 220 was isolated from an Epstein-Barr virus cDNA library and inserted in the same expression vector, enabling us to identify the precise location of the intron within the gp 220/340 coding sequence. The recombinant plasmids direct the expression of membrane proteins detected by immunofluorescence experiments using an anti-gp 220/340 monoclonal antibody in transfected human cells. The region of the gp 220/340 gene encoding the domain for membrane anchorage was removed from the two recombinant plasmids and the sequence containing the intron produced secreted forms of both truncated gp 220 and gp 340 whereas only the former was obtained with the intronless sequence. 相似文献
35.
A new cellular model of response to estrogens: a bioluminescent test to characterize (anti) estrogen molecules 总被引:12,自引:0,他引:12
With the aim of quickly and easily characterizing new estrogen or anti-estrogen molecules, we developed a cellular model in which estrogenic action can be detected by bioluminescence. This model is based on MCF-7 cells stably transfected with a receptor gene which allows expression of the firefly luciferase enzyme under control of the estrogen regulatory element of the Xenopus vitellogenin A2 gene. A stably transfected cell line (cultured for more than eight months without loss of the chimeric estrogenic response) was established by cotransfection of a neomycin resistance gene and cloning under selective pressure. Subcloning luminescent clones was accomplished by using a single-photon detecting camera. This cellular model allowed the study of an estrogenic activity either in whole-cell or in cell-free experiments by detection of the induced luciferase. Estradiol induced the luciferase activity in a dose-dependent manner at subnanomolar concentrations. The induced luciferase activity reached a maximum level as early as 24 hours after the cells were incubated with estradiol. The antiestrogen 4-hydroxy-tamoxifen inhibited the luciferase activity induced by estradiol. The cross-reactivity of ligands, such as dexamethasone, progesterone, testosterone, aldosterone, calcitriol, oxysterol and retinoic acid, were also studied, showing an estradiol specificity for a 24-hour incubation time. 相似文献
36.
Fos-Jun and the primary genomic response in the nervous system 总被引:3,自引:0,他引:3
37.
J Mouecoucou C Villaume H M Bau J P Nicolas L Mejean 《Reproduction, nutrition, development》1990,30(4):541-547
Male 21 d-old Wistar rats, were fed for 4 wk with diets containing casein or soybean proteins (10%) with 0.5, 1, 2 or 3% sodium alginate or sodium carrageenan or without any alginate or carrageenan. Daily protein intake and weight gain of casein-fed rats were not significantly different (P less than 0.05) from those of rats fed soybean meal with alginate, whatever the dose received. Rats fed 3% carrageenan in soybean meal had significantly higher feed intake than that of rats fed casein. At the levels studied, alginate had no effect on the Protein Efficiency Ratio (PER), but carrageenan did. The addition of increased quantities of carrageenan to soybean meal followed by heating the mixture led to a progressive and significant decrease in PER at all levels of carrageenan compared to casein feeding. The addition of 3% carrageenan to heated soybean meal, corresponding to 0.62% of meal diet, led to a significant decrease in PER. These results confirm the precipitating role of carrageenans on proteins. 相似文献
38.
D. R. J. Grootjen R. G. J. M. van der Lans K. Ch. A. M. Luyben 《Biotechnology Techniques》1990,4(3):149-154
Summary In some fermentations micro-aerobic conditions are desirable. The controlled addition of trace amounts of oxygen may be achieved by bubble free oxygen supply using silicon membrane tube, operated in dead-end mode. The small oxygen uptake rate is accurately determined with this self-constructable device. 相似文献
39.
1. In vitro studies have indicated that several transmitters present in the striatum can regulate presynaptically the release of dopamine (DA) from nerve terminals of the nigrostriatal DA neurons. 2. The receptors involved in these local regulatory processes are located or not located on DA nerve terminals. 3. Recent in vivo investigations have demonstrated that the corticostriatal glutamatergic neurons facilitate presynaptically the release of DA and have allowed the analysis of the respective roles of presynaptic events and nerve activity in the control of DA transmission. 相似文献
40.
Effects of training at simulated altitude on performance and muscle metabolic capacity in competitive road cyclists 总被引:1,自引:0,他引:1
Nicolas Terrados Jan Melichna Christer Sylvén Eva Jansson Lennart Kaijser 《European journal of applied physiology and occupational physiology》1988,57(2):203-209
Differences between the effects of training at sea level and at simulated altitude on performance and muscle structural and biochemical properties were investigated in 8 competitive cyclists who trained for 3-4 weeks, 4-5 sessions/week, each session consisting of cycling for 60-90 min continuously and 45-60 min intermittently. Four subjects, the altitude group (AG), trained in a hypobaric chamber (574 torr = 2300 m above sea level), and the other four at sea level (SLG). Before and after training work capacity was tested both at simulated altitude (574 torr) and at sea level, by an incremental cycle ergometer test until exhaustion. Work capacity was expressed as total amount of work performed. Venous blood samples were taken during the tests. Leg muscle biopsies were taken at rest before and after the training period. AG exhibited an increase of 33% in both sea level and altitude performance, while SLG increased 22% at sea level and 14% at altitude. Blood lactate concentration at a given submaximal load at altitude was significantly more reduced by training in AG than SLG. Muscle phosphofructokinase (PFK) activity decreased with training in AG but increased in SLG. All AG subjects showed increases in capillary density. In conclusion, work capacity at altitude was increased more by training at altitude than at sea level. Work capacity at sea level was at least as much improved by altitude as by sea level training. The improved work capacity by training at altitude was paralleled by decreased exercise blood lactate concentration, increased capillarization and decreased glycolytic capacity in leg muscle. 相似文献