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Brain Cell Biology - The olfactory epithelium of the adult hamster (Mesocricetus auratus) was studied using the scanning electron microscope. A method that produced fractures in the epithelium... 相似文献
144.
Brain Cell Biology - The olfactory epithelium of the adult hamster (Mesocricetus auratus) was examined with the scanning electron microscope following olfactory nerve axotomy. Axotomy results in... 相似文献
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146.
Summary We have investigated the ion permeability properties of sodium channels purified from eel electroplax and reconstituted into liposomes. Under the influence of a depolarizing diffusion potential, these channels appear capable of occasional spontaneous openings. Fluxes which result from these openings are sodium selective and blocked (from opposite sides of the membrane) by tetrodotoxin (TTX) and moderate concentrations of the lidocaine analogue QX-314. Low concentrations of QX-314 paradoxically enhance this channel-mediated flux. N-bromoacetamide (NBA) and N-bromosuccinimide (NBS), reagents which remove inactivation gating in physiological preparations, transiently stimulate the sodium permeability of inside-out facing channels to high levels. The rise and subsequent fall of permeability appear to result from consecutive covalent modifications of the protein. Titration of the protein with the more reactive NBS can be used to produce stable, chronically active forms of the protein. Low concentrations of QX-314 produce a net facilitation of channel activation by NBA, while higher concentrations produce block of conductance. This suggests that rates of modifications by NBA which lead to the activation of permeability are influenced by conformational changes induced by QX-314 binding. 相似文献
147.
Edward E. Schilling 《Biochemical Systematics and Ecology》1989,17(7-8):535-538
Distribution of external flavonoid aglycones supports other data to suggest that Viguiera series Viguiera (series Dentatae Blake) is a mixed taxonomic grouping. Two species, V. dentata and V. potosina, lack external flavonoid aglycones, whereas the remaining species of the series all produce external flavonoid aglycones and appear to form a natural taxonomic group. The latter group, which consists of species from Baja California and nearby xeric areas, exhibits a diversity of flavonoid types, with different diploid species variously producing flavonols, simple flavones, 6-methoxyflavones, 6-hydroxy,7-methoxyflavones and a chalkone as major compounds. Polyploid species exhibit combinations of flavonoid types from possible diploid ancestors. Compounds of the 6-hydroxy,7-methoxyflavone type appear to characterize the group of species from Baja California and nearby areas within Viguiera. 相似文献
148.
149.
EDU and ozone protection: Foliar glycerolipids and steryl lipids in snapbean exposed to O3 总被引:1,自引:0,他引:1
Effects of the antiozonant EDU, N-[2-(2-oxo-1-imidazolidinyl) ethyl]-N'-phenylurea, on the content and composition of foliar lipids in snapbean ( Phaseolus vulgaris L. cv. Bush Blue Lake 290) before and after a single, acute ozone (O3 ) exposure were assessed. Pretreatment with EDU conferred protection against O3 -induced necrosis and losses of glycerolipids and chlorophyll. Systemic treatment of snapbean plants with EDU did not significantly alter membrane lipids in the first trifoliate leaf. Leaves of untreated controls had lost ca 50% of both galacto- (GL) and phospholipids (PL) by the end of a 3 h exposure to 0.4 μl l−1 O3 . A decline in the ratio of mono- to di-galactosyldiacylglycerol (MGDG/DGDG) was associated with the loss of GL, and a decline in the ratio of linoleic to linolenic acid (18:2/18:3) was associated with the loss of PL in untreated controls. EDU-treated plants showed no significant loss of foliar GL and PL. The MGDG/DGDG ratio declined only slightly, and the 18:2/18:3 ratio in PL increased during O3 exposure of EDU-treated seedlings. The level of total membrane sterols, including free sterols (FS), acylated steryl glycosides (ASG) and steryl glycosides (SG), did not change during O3 exposure of either treated or untreated plants. However, in the controls the proportions of ASG and SG increased at the expense of FS, and the ratio of stigmasterol/sitolsterol increased in FS and SG. In EDU-treated plants, a relatively small increase in SG was offset by a decrease in FS, and there was no change in the stigmasterol/sitosterol ratio in ASG, SG or FS. The results indicate that EDU may confer tolerance to O3 through induction of enzyme systems involved in the elimination of activated oxygen species and free radicals. 相似文献
150.
Edward B. Tucker 《Planta》1990,182(1):34-38
The effect of microinjected calcium-loaded 1,2-bis(2-aminophenoxy) ethane-N,N,N,N-tetraacetic acid (CaBAPTA) on cell-to-cell diffusion of carboxyfluorescein (CF) was examined in staminal hairs of S. purpurea Boom. The CaBAPTA was microinjected into the cytoplasm of the staminal hairs either with CF or prior to a subsequent microinjection of CF. The cell-to-cell diffusion of CF along the hair was monitored using enhanced-fluorescence video microscopy. Cytoplasmic streaming stopped in cells treated with CaBAPTA, indicating that intracellular Ca2+ had increased. Cell-to-cell diffusion of CF was blocked in cells treated with Ca-BAPTA. An inhibition of cytoplasmic streaming and cell-to-cell diffusion was observed in the cells adjoining the CaBAPTA-microinjected cell, indicating that the Ca-BAPTA appeared to pass through plasmodesmata. While cytoplasmic streaming resumed 5–10 min after CaBAPTA treatment, cell-to-cell diffusion did not resume until 30–120 min later. These data support an involvement of calcium in the regulation of cell-to-cell communication in plants.Abbreviations BAPTA
1,2-bis(2-aminophenoxy)ethane-N,N,N, N-tetraacetic acid
- CF
carboxyfluorescein
This work was supported by Professional Staff Congress-City University (PSC-CUNY) of New York grant No. 667180 and U.S. Department of Agriculture grant No. 87-CRCR-1-244. 相似文献