Oocyte

Ca waves in systems [ike Xenopus laevis oocytes and pancreatic (3 cells fall into this category Electrochemical waves in cardiac and nerve tissue have this origin and the appearance and/or breakup of spiral wave patterns in excitable media are believed to be responsible for various types of arrhythmias in the heart [39, 40]. Figure C3.6.9 shows an excitable spiral wave in dog epicardial muscle [41]. 

Fig. 2. Methods for production of identical catde. (a) Embryo spHtting. A microdissection knife is used to cut an early embryo into two identical halves, (b) Embryo cloning. A cell from a morula stage embryo is removed and then inserted into an oocyte that has had its nucleus removed. EoUowing fusion of the two cells the newly produced one-ceU embryo is identical to the original morula. The procedure can be repeated to give multiple copies of the original...

There should be specific, saturable binding to the receptor, accompanied by pharmacological characteristics appropriate to the functional effects, demonstrable using a radioactive, eg, tritium or iodine-125, ligand to label the receptor. Radioligand binding assays (1,6) have become a significant means by which to identify and characterize receptors and enzymes (see Immunoassays Radioactive tracers). Isolation of the receptor or expression of the receptor in another cell, eg, an oocyte can be used to confirm the existence of a discrete entity. 

Xenobiotic induced disruption of female fertility follows essentially the same pattern as that of the male and can be caused by changes in pituitary-hypothalamic function, primary disruption of ovarian structure or hormone secretion, or changes in the rate of hormone deactivation. In addition, there may be changes in the synthesis of estrogen induced production of the yolk protein by the liver (vitellogenesis), which in turn can lead to failure to lay down sufficient yolk in the developing oocytes. Vitellogenesis provides a valuable biomarker for endocrine dysfunction in both sexes,but is more properly considered as part of the liver function. 

Woodruff, R. I., Miller, A. L., and Jaffe, L. F. (1991). Difference in free calcium concentration between oocytes and nurse cells revealed by corrected aequorin luminescence. Biol. Bull. 181 349-350. 

Heterologous expression systems comprise prokaryotic organisms (e.g., E. coli) and eukaryotic cells (e.g., yeast, HEK293, Xenopus oocytes), which are used to functionally express foreign genes or cDNAs. 

GPR3, GPR6, High constitutive Meiotic arrest of rodent oocytes, increase in synaptic contacts in rat cortical... 

This minimal K+ channel (MinK) encoded by KCNEl consists of 130 amino acid residues and has a single transmembrane segment. A slowly activating K+ current-induced MinK cRNA is expressed in Xenopus oocytes. Coexpression of KvLQTl with MinK induced a current that has characteristics similar to cardiac slowly activating delayed-rectifier K+ current, DCS, in contrast to DCR that has relative fast activation and is composed of hERG/MiRPl. 

Mouse Xenopus oocyte Activation of Ca2+-dependent Cl conductance NT SR 48692 Levocabastine ... 

Mice models reveal that both PR foims are physiologically important. Mice lacking the PR gene fail to ovulate, are infertile, and have impaired thymic function. Selective PRA-deficient female mice are infertile due to reduced oocyte and uterine deficiency... 

The exact subunit composition of the Low Voltage-activated (LVA) Ca2+ channels is unknown [3,6]. Three ai subunits, Cav3.x, have been identified which induce large T-type current after expression in Xenopus oocytes and in HEK cells in the absence of additional subunits. The T-type current can be affected by the a2S and the y6 subunit suggesting a maximal subunit composition of oq/o S./y. 

The nicotinic acetylcholine (nACh) receptor also displays sensitivity to inhalants (Bale et al. 2002). To varying degrees, toluene appeared to antagonize the function of nACh receptors that comprise different subunits. At concentrations of 50 pM to 10 mM, toluene produced a reversible, concentration-dependent inhibition of acetylcholine-induced current in Xenopus oocytes expressing various nicotinic receptor subtypes, with the ol — 2 d ct3—P2 subunit combinations being more sensitive to inhibition than other receptor... 

Similar to alcohol (Lovinger and White 1991) and volatile anesthetics (Machu and Harris 1994), trichoroethane, trichloroethylene, and toluene enhance 5-HT3 receptor function. All three inhalants significantly and reversibly potentiated, in a dose-dependent manner, 5-HT-activated currents, mediated by mouse 5-HT3 receptors expressed in Xenopus oocytes. Another feature common to these drugs is that the acute use of inhalants, as well as alcohol and volatile anesthetics, can produce nausea and vomiting (Meredith et al. 1989). It is believed that 5-HT3 receptors located in the area postrema mediate this action of alcohol and the volatile anesthetics (Aapro 1991). 

Cruz SE, Mirshahi T, Thomas B, et al Effects of the abused solvent toluene on recombinant N-methyl-D-aspartate and non-N-methyl-D-aspartate receptors expressed in Xenopus oocytes. J Pharmacol Exp Ther 286 334-340, 1998 De Rosa E, Bartolucci GB, Sigon M, et al Hippuric acid and ortho-cresol as biological indicators ofoccupational exposure to toluene. Am J Ind Med 11 529—537,1987 Delteil P, Stoesser F, Stoesser R L theromanie. Ann Med Psychol (Paris) 1 329-340, 1974... 

Machu TK, Harris RA Alcohols and anesthetics enhance the function of 5-hydroxy-tryptaminc3 receptors expressed in Xenopus laevis oocytes. J Pharmacol Exp Ther 271 898-905, 1994... 

Unity resulted in 4234 hits. After application of several filters and clustering of the remaining 1975 molecules, compounds from 18 of the 27 clusters were screened in Xenopus oocytes. One compound with an IC50 of 5.6pM belonged to a new class of Kvl.5 blockers and exhibited a favorable pharmacokinetic profile. After further optimization, compound 73 (IC50 = 0.7pM Fig. 16.9) resulted, with good oral bioavailability in rats [145]. 

---