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21.
Unequal synthesis of globin chains after extended incubation of rabbit reticulocytes with L-O-methylthreonine 总被引:1,自引:0,他引:1
Rabbit reticulocytes were incubated in vitro as long as 20 hr with l-O-methyl threonine, the OMT was removed, and the capacity of the cells to synthesize α- and β-globin chains was determined. After 20 hr incubation in vitro, OMT-treated cells can make β chains about twice as well as cells incubated for 20 hr without OMT. However, the capacity of OMT-treated cells to synthesize α chains was only about 60% that of cells incubated without OMT for 20 hr. These results suggest that the capacity of reticulocytes to produce a specific globin chain after an in vitro incubation correlates positively with the number of ribosomes associated with the specific messenger RNA for that chain during the incubation. 相似文献
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The influence of several ions on the membrane potential of the somatic muscle of Ascaris has been investigated by changing their concentration in the surrounding solution. When [K]o is increased at the expense of [Na]o leaving [Cl]o constant, the membrane potential is first seen to increase. [K]o higher than 45 mM reduces the membrane potential with a slope of 23 mv for a tenfold change in [K]o. However, when [K]o is increased keeping [Na]o and [Cl]o low and constant, the line relating the membrane potential with log [K]o has a slope of almost 50 mv. If [Cl]o is reduced in the absence of external Na, after the [K]o is increased to 45 mM, the membrane potential decreases with a slope of 59 mv per tenfold change in [Cl]o in close agreement with the Nernst equation. If Cl- is replaced by SO4
2-, a depolarization is produced, while chloride replacement by NO3
-, Br-, and I- results in a hyperpolarization of the membrane. Removal of the external Na+ ions increases the average membrane potential by 17 mv. 相似文献
29.
Distribution of diaphragmatic lymphatic stomata 总被引:3,自引:0,他引:3
D Negrini S Mukenge M Del Fabbro C Gonano G Miserocchi 《Journal of applied physiology》1991,70(4):1544-1549
In seven anesthetized rabbits we measured the size, shape, and density of lymphatic stomata on the peritoneal and pleural sides of the diaphragm. The diaphragm was fixed in situ and processed for scanning electron microscopy. Results are from 2,902 peritoneal and 3,086 pleural fields (each 1,620 microns 2) randomly chosen from the various specimens. Stomata were seen in 9% of the fields examined, and in 30% of the cases they appeared grouped in clusters with 2-14 stomata/field. Stoma density was 250 +/- 242 and 72 +/- 57 (SD) stomata/mm2 on peritoneal and pleural sides, respectively, and it was similar over the muscular and tendinous portion of the two surfaces. The maximum diameter ranged from less than 1 to approximately 30 microns, with an average value of 1.2 +/- 3.1 micron. The ratio of the maximum to the minimum diameter and the surface area averaged 2 +/- 1.4 and 0.7 +/- 2.4 micron 2, respectively. The maximum and minimum diameter and surface area values followed a lognormal frequency distribution, suggesting that stomata geometry is affected by diaphragmatic tension. 相似文献
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Valerie Del Thompson 《Zoo biology》1989,8(3):275-297
Twelve species of captive ungulates were studied to determine behavioral responses to the presence of a zookeeper within the exhibit and in front of the exhibit, with and without zoo visitors present. Significant differences in behavior occurred between species for nearly all behaviors observed. A significantly greater occurrence of vigilance and approach behavior was directed toward the zookeeper while within the exhibit relative to when the zookeeper stood in front of the exhibit. A significantly lower occurrence of eating or drinking occurred when the zookeeper was inside the exhibit. Significant differences occurred across size categories in the occurrence of approaching the zookeeper. The most frequently scored behavior was visual orientation. Statistically significant differences in the occurrence of visual orientation directed by females toward the zookeeper existed across size category, with more vigilance by species with larger body size. A statistically higher occurrence of vigilance toward the zookeeper was directed by female ungulates but not by males when the zoo was closed to the public. Although no statistical significance was found regarding the intraspecific vigilance of males, data on females revealed significant differences across species and across size categories. When data regarding vigilance toward the public were analyzed, statistically significant differences existed between species for females only. Likewise, when data regarding interspecific vigilance were examined, statistically significant differences were found across size categories for females, but not for males. The potential roles of vigilance in the wild are discussed in reference to its role in captivity. 相似文献