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181.
Quinone and inhibitor binding to Rhodopseudomonas sphaeroides (R-26 and GA) reaction centers were studied using spectroscopic methods and by direct adsorption of reaction centers onto anion exchange filters in the presence of 14C-labelled quinone or inhibitor. These measurements show that as secondary acceptor, QB, ubiquinone (UQ) is tightly bound in the semiquinone form and loosely bound in the quinone and quinol forms. The quinol is probably more loosely bound than the quinone. o-Phenanthroline and terbutryn, a triazine inhibitor, compete with UQ and with each other for binding to the reaction center. Inhibition by o-phenanthroline of electron transfer from the primary to the secondary quinone acceptor (QA to QB) occurs via displacement of UQ from the QB binding site. Displacement of UQ by terbutryn is apparently accessory to the inhibition of electron transfer. Terbutryn binding is lowered by reduction of QB to Q?B but is practically unaffected by reduction of QA to Q?A in the absence of QB. UQ-9 and UQ-10 have a 5- to 6-fold higher binding affinity to the QB site than does UQ-1, indicating that the long isoprenoid chain facilitates the binding to the QB site. 相似文献
182.
The Effects of Volatile Compounds from Nematodes on Trap Formation by a Nematode-Trapping Fungus
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Although the presence of prey induced trap formation by nematode-trapping fungi, it is improbable that the activity was associated with volatile compounds of nematode origin. 相似文献
183.
Monolayer preparations used in cell image analysis show some peculiarities as compared with conventional cytologic smears, such as homogeneous distribution of cells, distinct appearance of cells and a reduced number of background elements. However, for use in gynecologic cytology, monolayer preparations must be accessible to visual examination and classification. To investigate the consequences of the special features of these preparations on the strategy of visual evaluation, we estimated the minimum number of cells needed for a diagnostic decision. Cell counts were made of gynecologic monolayer preparations from 50 women with no suspicion of malignancy and 50 women with invasive squamous-cell carcinoma of the uterine cervix and its precursors. Our results showed that the more serious the lesion, the lower the number of cells needed for a diagnostic decision. The highest mean values of numbers of cells needed for an effective diagnosis were estimated in cases of mild and moderate dysplasia (734 cells) and in non-suspicious cases (731 cells). The number of cells needed did not exceed 1,700 in any case. The false-negative and false-positive rates were 6% and 2%, respectively, including the cases of mild to moderate dysplasia. 相似文献
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LY165163, a ligand reported to be selective for the 5HT1A subtype of serotonin receptor, was examined for its ability to interact with 5HT2 receptors in the rat jugular vein and alpha-receptors in the rat aorta. In these smooth muscle preparations, no agonist activity of LY165163 occurred in concentrations up to 10(-5) M. However, LY165163 was an antagonist of serotonin-induced contractions in the jugular vein and of norepinephrine-induced contractions in the rat aorta. The dissociation constant calculated for LY165163 at 5HT2 receptors in the rat jugular vein was 10(-8) M and at alpha-receptors in the rat aorta was 2 X 10(-7) M. Thus, LY165163 is a relatively potent antagonist at vascular 5HT2 sites and possesses appreciable affinity at alpha-receptors. Based on these data, the multiple receptor interactions of LY165163 must be taken into consideration when utilizing this agent as a probe for the 5HT1A subtype of serotonin receptor. 相似文献
186.
U Schenck B Reuter P V?hringer 《Analytical and quantitative cytology and histology / the International Academy of Cytology [and] American Society of Cytology》1986,8(1):35-45
In order to elucidate the process of visual cytoscreening, graphic and electronic recordings of the stage movements in visual screening of conventional gynecologic smears were carried out. More than 400 recordings have been evaluated. The screening consisted of alternating movements, with a mean duration of 180 milliseconds, and stops of about 230 milliseconds. Variations of the screening pattern due to the specimen diagnosis were hidden behind the rather obvious individual behavior and reactions to inhomogenity of material distribution. The detection threshold was found to vary with the diagnostic situation. A lowering of the detection threshold was especially reflected by an increase of the overlap in screening direction and an increased number of fields of view with stop times of more than 350 milliseconds. A substantial part of the specimen was only seen during movements; the fraction of the specimen area covered during the stops was found to vary between 41% and 93% for screenings in the daily routine work. 相似文献
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