COS-1 cells

Fig. 19. Self-discharge at ambient temperatures for a 35 A-h cell, NTS-2 prototype Sanyo Electric Co. cell.

When measuring CO concentration, the reference signal is obtained when the beam is passed through the sample chamber and the CO cell. The absorption is then saturated due to the high CO concentration in the cell. Consequently, the reference signal is practically nondependent on the CO concentration in the sample gas. When the beam passes through the sample chamber and the N2 filter, the absorption is dependent on the CO concentration in the sample chamber, as the N2 filter does not absorb energy from the infrared beam. 

Transiently transfected COS cells Constitutive activity SR 48692 NT Levocabastine... 

Besides this purported action on DAT, amphetamine has also been suggested to act upon the vesicular transporter as well. Pifl et al.87 examined COS cells transfected with cDNA for either DAT or the vesicular transporter, or both. A marked increase in DA release was noted in cells that expressed both DAT and the vesicular transporter when compared to the release from cells that express only DAT or the vesicular transporter. The mechanism of action for amphetamine was further defined with the work of Giros et al.59 In transgenic mice lacking the DAT, amphetamine did not produce hyperlocomotion or release DA. 

Nicotine increased DA levels both in vivo11,193 and in vitro. 94 196 Nicotine197 and its metabolites198 were found to both release and inhibit the reuptake of DA in rat brain slices, with uptake inhibition occurring at a lower concentration than that required for DA release. In addition, the (-) isomer was more potent than the (+) isomer.197 However, the effects of nicotine upon DA release and uptake were only apparent when brain slices were utilized because nicotine was unable to affect DA when a synaptosomal preparation was utilized.197 These results indicate that nicotine exerts its effects upon the DAT indirectly, most likely via nicotine acetylcholine receptors. This finding was supported by the results of Yamashita et al.199 in which the effect of nicotine on DA uptake was examined in PC 12 and COS cells transfected with rat DAT cDNA. Nicotine inhibited DA uptake in PC 12 cells that possess a nicotine acetylcholine receptor. This effect was blocked by the nicotinic antagonists hexamethonium and mecamylamine. Additionally, nicotine did not influence DA uptake in COS cells, which lack nicotinic acetylcholine receptors. 

Edwards, C.P. and Aruffo, A. (1993) Current applications of COS cell based transient expression systems. Current Opinion in Biotechnology, 4 (5), 558-563. 

Cloning of the rat pi opioid receptor was somewhat easier than the cloning of the <5 receptor since it was based on the knowledge of what the 3 receptor sequence was and on the assumption that 3 and pi receptors had high amino acid sequence similarity. Chen et al. [18] used probes directed against conserved regions of the 6 receptor to screen a rat brain cDNA library. cDNAs identified by this approach were cloned into expression vectors, transfected into COS cells and pi receptor expression detected with radioactive pi receptor selective ligands. 

While chronic morphine treatment uncouples the // receptor from K+ channels, it did not affect the coupling of ft receptors to adenylyl cyclase. Pretreatment of the cloned ft receptor expressed in HEK 293, AtT-20, CHO and COS cells with morphine or DAMGO for up to 16h did not alter the subsequent ability of fi agonists to inhibit cAMP accumulation [25, 65, 80-82]. These findings suggest that morphine treatment induces a selective desensitization of the coupling of the fi receptor to K+ channels. 

Assembles SGs, not PBs Disassembles both SGs and PBs Induces SGs in COS cells but does not localize to SGs Useful SG/PB diagnostic... 

Lakowicz, J. R., Szmacinski, H., Nowaczyk, K., Lederer, W. J., Kirby, M. S. and Johnson, M. L. (1994). Fluorescence lifetime imaging of intracellular calcium in COS cells using Quin-2. Cell Calcium 15, 7-27. 

Also consistent with this labeling in SERT, antibodies raised against EL2 and EL4 of NET showed reactivity with intact COS cells expressing NET, as assessed by immunofluorescence, whereas antibodies against the amino and carboxyl terminal regions reacted only after cells were permeabilized (21). 

Recombinant GM-CSF (produced in Escherichia coli, yeast or COS cells) has been tested for its ability to affect haematopoiesis in primates and humans. Because of its relatively short half-life in the circulation, daily administration (usually via intravenous infusion) is required. Administration results in a transient neutropenia, monocytopenia and eosinopenia within 30 min of administration, presumably because of the ability of GM-CSF to stimulate the expression of adhesins and hence increase the numbers of leukocytes adhered to the capillary endothelium in the marginated pool. Additionally, these leukocytes may accumulate in the lungs after GM-CSF administration, which may contribute to the decrease in the observed numbers... 

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. 

Figure 1.9, Intensity left) and calcium images (right) of Quin-2 fluorescence in COS cells.

While only a limited amount of testing has been performed on cells made with Cu—Co mixtures, the initial results were intriguing. The addition of even 5% Co to Cu significantly increased the performance of the cells for operation in H2 at 973 K, from 220 mW/cm on the Cu-based anode to more than 310 mW/cm on the Cu0.95Co0.05 anode. A Cu—Co cell also exhibited a power density of 360 mW/cm in pure n-butane at 1073 K, suggesting that bimetallic anodes are worth considering for fuel cells that operate on hydrocarbons. 

In 1991 bile-acid secretion was shown to be energy driven by a 110-kDa glycoprotein that was dependent on ATP. This protein was subsequently characterised as liver ecto-ATPase by Sippel and co-workers. However, while further work with COS cells showed that expression of ecto-ATPase enhanced secretion of bile acids purified canalicular membranes lacking this enzyme efficiently exported bile acids showing that at least one other bile-acid transporter existed. ... 

Carnosine can affect gene expression. Ikeda et al. (1999) showed that carnosine markedly upregulates vimentin synthesis in cultured rat fibroblasts, while an association between carnosine and vimentin, a cytoskele-tal, intermediate filament protein has been noted in glial cells and neurons (Bonfanti et al., 1999). Interestingly, it has also been shown that the protease, oxidized protein hydrolase (OPH), is coexpressed with vimentin in COS cells (Shimizu et al., 2004). Thus, it is at least possible that carnosine could induce synthesis of OPH in the cultured human fibroblasts and thereby increase the cellular ability to eliminate oxidized... 

The first transient expression system for cytochrome P450 expression was the COS cell system which couples monkey cells with an SV40-based expression vector (Zuber et al., 1986). The cDNA of interest is introduced into a plasmid expression vector under control of a heterologous promoter. The vector is introduced into COS cells via electroporation or another method allowing DNA uptake. The plasmid vector replicates within the cells and cDNA-derived protein accumulates within the cell. 

The principal advantage of COS cell transient cDNA expression systems is that they provide a rapid means for producing catalytically active protein. The introduction of the cDNA into the vector is simple, based on rapid bacteria-based molecular biology. The vector DNA is then used to directly transfect the host cells. COS cell expression suffers from limitations in expression level (which tends to be low) and overall yield, since a limited number of cells can be transfected and only about 10% of the cells take up the transfected vector molecule. The practical aspects of COS cell expression are discussed in Clarke and Waterman (1991). 

The first member of a new subfamily of RhoGEFs was identified simultaneously by affinity chromatography of COS cell lysates with RhoA in the absence of nucleotide (Hart et al, 1996) and by expression cloning in 3T3... 

---