X. laevis oocytes

Messenger RNA isolated from differentiated HL-60 cells is thus a convenient source of transcripts for the receptor, and this mRNA (50-100 ng) can be injected into X. laevis oocytes. These oocytes actively translate foreign mRNA molecules, and often the expressed protein is functional 2-5 days later, functional fMet-Leu-Phe receptors can be detected on the cell surface. The identity of a functional fMet-Leu-Phe receptor was confirmed because ... 

Durieux, M.E., Carlisle, S.J., Salafranca, M.N. and Lynch, K.R., 1993, Responses to sphingosine-1 -phosphate in X. laevis oocytes Similarities with lysophosphatidic add signaling. Am. J. Physiol. 264 C1360-C1364. 

Oatl was cloned by expression cloning using X. laevis oocytes by coexpression of sodium-dicarboxylate transporter, which forms outward concentration gradient of dicarboxylate to drive Oatl-mediated uptake (129). Oatl is predominantly expressed in the kidney, where it is localized in basolateral membrane of the proximal tubules (130). Oatl is a multispecific transporter, and it accepts PAH, a typical substrate for this transporter, and relatively hydrophilic small organic... 

NaPi-1 (SLC17A1), alternatively referred to as NPT1, was originally cloned as a transporter involved in the reabsorption of phosphate in the body. Expression of NaPi-1 in X. laevis oocytes induced saturable uptake of benzylpenicillin (189). This uptake does not depend on Na+ and H+, but on Cl- (190), and increasing extracellular concentration of chloride reduced the uptake of benzyl-penicillin (190). The substrates include faropenem, foscamet, and mevalonate, as well as benzylpenicillin (190). In contrast to the kidney, the expression is localized to the sinusoidal membrane of the liver (190). When the direction of the concentration gradient of Cl- is taken into consideration, the transport direction mediated by NaPi-1 is efflux from inside the cells to the blood and urine in the liver and kidney, respectively. 

Identification of OATP1B/3 substrates is usually performed in stable OATP1B1- or OATPlB3-overexpressing systems, such as Chinese Hamster Ovary (CHO) and Human Embryonic Kidney 293 (HEK293) cells, X. Laevis oocytes, and recombinant virus [80, 82], The criterion for test compounds to be considered as... 

Fig. 4. Microinjection of the GroEL trap D87K into X. laevis oocytes prevents newly translated actin from reaching the native state Hatched bars represent the amount of radiolabeled native actin present after five minutes of labeling. Note that when the trap is injected almost no more native actin is produced (right-hand graph). Reprinted from Farr et al. (1997), with permission.

Lechleiter J. D. Clapham D. 1992. Molecular mechanisms of intracellular calcium excitability in X. laevis oocytes. Cell 69 283-94. 

Lechleiter, J. D. Clapham, D. E. 1992. Molecular Mechanisms of Intracellular Calcium Excilablility in X. laevis Oocytes, Cell 69, 283 294. 

Sweigert, S.E. and D. Carroll. 1990. Repair and recombination of X-irradiated plasmids in Xenopus laevis oocytes. Molec. Cell. Biol. 10 5849-5856. 

Because the fMet-Leu-Phe receptor is present only at low levels in neutrophils (-12 x 10 15 g of receptor per cell), it has proved difficult to purify and characterise. Researchers have therefore turned to molecular cloning techniques to gain insight into the molecular structure of this receptor. This approach itself has not been easy because, in the absence of an antibody that specifically binds to the receptor, or else without some amino acid sequence data that can be used to synthesise oligonucleotide probes, cDNA libraries cannot be screened to isolate relevant clones. Therefore, experimental systems in which functional fMet-Leu-Phe receptors are expressed on the surfaces of transfected cells have been used. Two main systems have been utilised expression of mRNA injected into Xenopus laevis oocytes and cDNA cloning into the COS-cell expression vector. 

In the event that accommodation and care for the frogs is not possible, X laevis surgically extracted ovaries containing oocytes can be ordered through Nasco (Fort Atkinson, WI) however the quantity and quality of the oocytes cannot be guaranteed upon shipping. 

Kleinschmidt, J.A. and Steinbeisser, H. (1991) DNA-dependent phosphorylation of histone H2A.X during nucleosome assembly in Xenopus laevis oocytes involvement of protein phosphorylation in nucleosome spacing. EMBO J. 10, 3043-3050. 

Using two different species of amphibians (X. laevis and X. mulleri), Dawid and Bladder (1972) demonstrated that the hybrid progeny from either reciprocal cross exclusively contained the maternal mt DNA (Table XVIII) in somatic cells as well as in oocytes. Since the X. 

A field and a microcosm study on X laevis reported no relationship between exposure to atrazine and other agricultural chemicals used in com production and gonadal anomalies (27) and the incidence and frequency of testicular oocytes (34), Studies on X. laevis exposed to time-weighted mean concentrations of atrazine of 0,1,12 and 30 fig/L in semi-field microcosms from shortly after hatch until after metamorphosis showed a low frequency of... 

Fig. 5. In situ hybridization of radioactive rRNA with cytological preparations from the ovary of Xenopus laevis. (A) Oogonial stages with a few silver grains located over the centrally placed nucleolus (arrow). X 1275. (B) Two nuclei from leptotene stage oocytes showing a few silver grains over the eccentrically placed nucleoli (arrows). X 1275. (C) Three small unlabeled follicle nuclei and three larger heavily labeled nuclei from pachytene stage oocytes. X1020. [By courtesy of Dr. J. G. Gall, reprinted from Proc. Nat. Acad. Set. 17.S. 63, 378 (1969).]...

Dawid and co-workers (Dawid, 1965 Dawid and Wolstenholme, 1967) presented the first evidence that the extranuclear DNA in frog oocytes was predominantly mt DNA. The refined techniques of this group provided the first reliable data on DNA content of amphibian eggs, i.e., 3.6 0.8 ng per egg for Rana pipiens and 3.1 — 3.8 ng for Xenopus laevis (Dawid, 1965 Chase and Dawid, 1972). This represents 300-600 times the DNA content of a diploid somatic cell in these two amphibian species. This means that more than 99% of the total DNA is mt DNA. A calculation of the average distribution (Table IV) gives about 3800 pg mt DNA and 6.3 pg of n DNA per fertilized oocyte, or about 2 X 10 molecules of mt DNA per cell. 

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