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71.
Production and Release of Acetylcholinesterase by a Primary Cell Culture of Bovine Adrenal Medullary Chromaffin Cells 总被引:7,自引:5,他引:2
Abstract: Bovine adrenal chromaffin cells were isolated and maintained as primary culture monolayers. Total acetylcholinesterase (AChE) activity in the cells increased during the culture period, and AChE activity appeared in the culture medium. We have examined the role of the AChE synthesized by the cells on ACh-evoked release of catecholamine from the cells. A progressive decrease in the efficacy of ACh (5 × 10-5m ) to evoke release of [3H] norepinephrine from day 3–15 cultures suggests that exogenously applied ACh is hydrolyzed by the nascent AChE synthesized by the cells. These findings provide evidence that chromaffin cells produce AChE and release it into their immediate environment. 相似文献
72.
Tatsuo Iwasa Kazuo Takeda Fumio Tokunaga Peter S. Scherrer Lester Packer 《Bioscience reports》1982,2(11):949-958
To elucidate the role of tyrosine residues in the shift of max and the light-driven proton pump of bacteriorhodopsin~ the photochemical reaction of tyrosine-iodinated bacteriorhodopsin (tyr-mod-bR) was investigated by low-temperature spectrophotometry. After 4–5 of 11 tyrosine residues of bacteriorhodopsin were iodinated, the meta-intermediate of tyr-mod-bR in 75% glycerol solution became so stable that its decay could be observed even at room temperature and i t was stable in the dark for several hours at –65°C.Four batho-intermediates were formed by irradiation with green light (500 nm) at –170°C. Like native bacteriorhodopsin, these batho-intermediates were photoreversible at –170°C. Four corresponding meta-intermediates were also formed by irradiation at –60°C. Using the difference spectra between meta-intermediates and tyr-mod-bR, the absorption spectra of four kinds of tyr-mod-bRs, batho-intermediates, and meta-intermediates were estimated. Each was at shorter wavelengths than that of its corresponding type in native bacteriorhodopsin. The results indicate that two or more tyrosine residues have some role in determining color in native bacteriorhodopsin. 相似文献
73.
74.
Changes in the amount of lung and airway phosphatidylcholine in 0.5-12.5-day-old rabbits 总被引:1,自引:0,他引:1
Newborn rabbits delivered spontaneously at term and cared for by the mothers were studied from 0.5 to 12.5 days of age. Curves are constructed to describe the changes in weight, lung and alveolar wash phosphatidylcholine and saturated phosphatidylcholine, and lung protein. The curves are complex and non-linear. However. expressing the increases in lung and alveolar wash phosphatidylcholine and saturated phosphatidylcholine pool sizes relative to animals weight results in a decreasing linear relationship from 0.5 to 12.5 days of age. By 12.5 days the ratios of lung phosphatidylcholine and saturated phosphatidylcholine to weight approximate the ratios measured for adult rabbits. The ratios of saturated to total phosphatidylcholine in the alveolar washes and lungs remained invarient throughout the study period. 相似文献
75.
D Ayusawa K Iwata T Kozu S Ikegami T Seno 《Biochemical and biophysical research communications》1979,91(3):946-954
Mutants that were resistant to aphidicolin were isolated from mutagenized mouse FM3A cells at a frequency of about 10?6. Resistance to aphidicolin in these mutants was not due to an effect on [3H]thymidine incorporation into DNA, DNA synthesis in permeabilized cells, or DNA polymerase α.All the mutants showed a greatly increased dATP pool and decreased ability to incorporate [3H]deoxycytidine into DNA. They also showed cross-resistance to both 1-β-D-arabinofuranosyladenine and 1-β-D-arabinofuranosylcytosine.These results indicate that an enzyme involved in production of dATP or its regulation is altered in these mutants. It is suggested that dATP competes with aphidocolin at its killing site or that dATP reverses the effect of aphidicolin by some unknown mechanism . 相似文献
76.
77.
1. The properties of 3,5-di-tert-butyl-4-hydroxybenzylidenemalononitrile (SF 6847) were studied chemically and spectroscopically. Two molecular species of SF6847 were identified: the undissociated form (SFH; ?363, 10 mM?1) and the dissociated form (SF?; ?454, 35 mM?1). The pKa value of the molecule was determined to be 6.9.2. On the basis of these properties the interactions of SF6847 with liposomes and valinomycin · K+ were studied. The partition constants of SFH (Knp and SF? (K?p) to liposomes were determined separately; Knp was 56 mM?1 and was independent of the pH of the medium, whereas K?p dependend greatly on the pH, being 1.2 mM?1 at pH 7.0 and 2.9 mM?1 at pH 8.0. Using these values, the partition constant of total SF6847 (Kp) was calculated and found to be essentially the same as that calculated from the kinetics of proton uptake. It was concluded that the amount of SF? bound to liposomes is rate limiting for proton uptake.3. The effects of membrane potential on partition constants were studied. The K?p decreased greatly upon generation of a membrane potential negative inside the liposomes but increased upon generation of a membrane potential positive inside the liposomes.4. The interaction of SF6847 with valinomycin in aqueous solution and in liposomes was demonstrated only in the presence of potassium ion. Potassium ion could not be replaced by sodium ion. Evidence was obtained for the formation of the ternary complex valinomycin · K+ · SF? in liposomes and in hexane. It was concluded that SF? became more soluble in the liposomal membranes on formation of this ternary complex. All these results support our proposed mechanism for the proton uptake cycle (Yamaguchi, A. and Anraku, Y. (1978) Biochim. Biophys. Acta 501, 136–149). 相似文献
78.
Circular dichroism (CD) and absorption spectra of squid (Todarodes pacificus) rhodopsin, isorhodopsin and the intermediates were measured at low temperatures. Squid rhodopsin has positive CD bands at wavelengths corresponding the - and β-absorption bands at liquid nitrogen temperature (CD maxima: 485 nm at -band and 348 nm at β-band) as well as at room temperature (CD maxima: 474 nm at -band and 347 nm at β-band). The rotational strength of the -band has a molecular ellipticity about twice that of cattle rhodopsin. The CD spectrum of bathorhodopsin displays a negative peak at 532 nm, the rotational strength of which has an absolute value slightly larger than that of rhodopsin. The reversal in sign at -band of the CD spectrum may indicate that the isomerization of retinal chromophore from twisted 11-cis form to twisted 11-trans form has occurred in the process of conversion from rhodopsin to bathorhodopsin. Lumirhodopsin has a small negative CD band at 490 nm, the maximum of which lies at 25 nm shorter wavelengths than the absorption maximum (515 nm), and a large positive CD band near 290 nm, which is not observed in rhodopsin and the other intermediates. This band may be derived from a conformational change of the opsin. In the process of changing from lumirhodopsin to LM-rhodopsin, the CD bands at visible and near ultraviolet regions disappear. Both alkaline and acid metarhodopsins have no CD bands at visible and near ultraviolet regions. 相似文献
79.
Hypsorhodopsin was formed in frog retina by irradiation at liquid helium temperature and converted into bathorhodopsin above about 29 K. 相似文献
80.
M Ohashi T Taguchi S Ikegami 《Biochemical and biophysical research communications》1978,82(4):1084-1090
Aphidicolin, a tetracyclic diterpenoid, is known to be antiviral and to inhibit the incorporation of thymidine into DNA of cultured human embryonic lung cells. We examined effects of the compound on the activity of several DNA polymerases obtained from subcellular fractions of rat liver. Aphidicolin at a concentration of 15 μg/ml caused a 85% reduction in level of the activity of crude and partially purified DNA polymerases from the cytosol. However, aphidicolin even at a concentration of 75 μg/ml failed to affect the activity of crude and partially purified DNA polymerases from nuclear and mitochondrial fractions. 相似文献