Oocyte system

The Xenopus Oocyte System has Some Limitations as Well. 327... 

The Lester and Dougherty labs, which have collaborated to extend the suppression mutagenesis technique to Xenopus oocytes with remarkable success [30, 31], began with a suppressor tRNA ( MN3 ) designed for in vivo use and demonstrated that it functioned more effectively in the oocyte system than a yeast tRNA -derived suppressor tRNA. They have since developed an alternative suppressor based on tRNA " from Tetrahymena thermophila that has proven to be considerably more versatile, efficient and accurate in the oocyte system [32], as well as showing good suppression efficiency in E. coli transcription-translation reactions [33]. 

The highly successful extension of site-directed suppression mutagenesis to a Xenopus oocyte system by the Dougherty and Lester labs discussed above has permitted structural, functional and kinetic studies of ion channels in intact cells [30-32, 62]. Recently, the introduction of residues that allow photochemical proteolysis and photo deprotection of protein side chains has been applied to the study of ion channels. Miller et al. introduced o-nitrobenzyl-pro-tected tyrosines at three positions in the a-subunit of nAChR [62 c]. The o-nitro-benzyl group was then removed photolytically to produce the wild-type residue during the course of a voltage-clamp study, so that time-resolved measurements could be made. 

The oocyte system has also been utilized by Turcatti et al. to incorporate a fluorescent amino acid into the tachykinin neurokinin-2 receptor (NK2), al-... 

The use of the oocyte system for the assay of a purified mRNA can be illustrated by reference to the reticulocyte hemoglobin mRNA (Burny and Marbaix, 1964 Lockard and Lingrel, 1967 Lane et al, 1971, 1972a). The RNA to be tested (9 S RNA in this case) is dissolved in buffered saline (88 mM NaCl, 1.0 mM KCl, 15 mM Tris-HCl pH 7.6) at a concentration of up to 5 mg/ml. After removal from the frog, the oocytes, which are contained in a sheath of follicle cells, are kept... 

At the time of writing the oocyte system is 10-100 times more sensitive than the most efficient cell-free systems, (Gurdon et al., 1971) the preparations described by Lockard and Lingrel (1972) and Metafora et al., (1972) are almost as active as the oocyte in the short term, but translation occurs for hours as opposed to days. Nonetheless for many purposes cell-free systems are more convenient thus, the ascites cell-free system has a low background compared to that of the oocyte and must be preferred to the oocyte as a simple assay system unless only minute amounts of messenger are available. The oocyte does offer certain spe-... 

Effective Stage of Injected Chemicals in the Oocyte System... 

Using the silkworm oocyte system, screening of mutagenic compounds has been carried out by Tazima and his associates. The chemicals tested were mostly known carcinogens and their allied compounds. The data so far obtained are shown in Table... 

Summarizing the results, the oocyte system could be sufficiently applicable to the testing of direct mutagens and/or carcinogens except for some compounds such as 4-NQO, but for the application of this system to compounds acting indirectly, more investigation is necessary. 

Y. Tazima and K. Onimaru, On an effective stage of chemical mutagens as detected by the silkworm oocyte system, Annu. Rep. Natl. Inst. Genet. Misima 26, 39-40 (1976). 

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