Resistant cells

The aperture impedance principle of blood cell counting and sizing, also called the Coulter principle (5), exploits the high electrical resistivity of blood cell membranes. Red blood cells, white blood cells, and blood platelets can all be counted. In the aperture impedance method, blood cells are first diluted and suspended ia an electrolytic medium, then drawn through a narrow orifice (aperture) separating two electrodes (Fig. 1). In the simplest form of the method, a d-c current flows between the electrodes, which are held at different electrical potentials. The resistive cells reduce the current as the cells pass through the aperture, and the current drop is sensed as a change in the aperture resistance. 

Sorcin (soluble resistance-related calcium binding protein) was isolated from multidrug-resistant cells and is expressed in a few mammalian tissues such as skeletal muscle, heart, and brain. In the heart, sorcin interacts with the ryanodine receptor and L-type Ca2+-channels regulating excitation in contraction coupling. 

Success in regenerating salt-resistant plants from salt-resistant cells has been limited (Table 4). The most extensively quoted example is the work of Nabors et al. (1980) who found that tobacco plants regenerated from NaCl-resistant cell lines survived salinity better than did plants regenerated from unselected lines. The authors themselves were justifiably cautious. 

Erythromycin Ribosomes from resistant cells have lower affinity, resulting from enzymatic methylation of adenine in 23S rRNA... 

Bilzer, M. and Lauterburg, B.H. (1991). Effects of hypoch-lorous acid and chloramines on vascular resistance, cell integrity, and biliary glutathione disulfide in the perfused rat liver modulation by glutathione. J. Hepatol. 13, 84-89. 

Cancer chemotherapy and the treatment of cancers are analogous to anti-infectives and the treatment of infections. Cancer cells may be sensitive to certain chemotherapy agents, but then with repeated exposure, the cells become resistant to treatment. The resistant cells then grow and multiply. While tumors may be tested for chemotherapy sensitivity, this area is still developing. Today, tumor sensitivity can demonstrate tumor resistance so that needless exposure to an inadequate therapy and its toxicity can be avoided. 

In cultures of the more resistant cell line, MDCK, the predominant effect of Tyv-specific monoclonal antibodies is to exclude larvae from the monolayer. This exclusion is associated with the formation of cap-like structures that cover the stoma of the larva. Such caps were first described... 

When examining cytotoxicity data it is important to bear in mind that they are based on a general assessment of cytotoxicity, and thus may account for more than one acting mechanism in the resistant cells used [36],... 

Fig. 20.10. Enhancement of doxorubicin cytotoxicity in LoVo-resistant cells by verapamil and analogues. (Adapted from Ref. [77]). The results are expressed as fold increase in cytotoxicity represented by the ratio of doxorubicin IC50 in the absence and presence of verapamil and analogues (solid bars). The verapamil concentrations used were the minimal cytotoxic concentrations (IC20)-The compounds used were verapamil (1) ...

Safa, A. R., Roberts, S., Agresti, M., Fine, R. L., Tamoxifen aziridine, a novel affinity probe for P-glycoprotein in multidrug resistant cells, Biochem. Biophys. Res. Commun. 1994, 202, 606-612. 

Cutler, G. B., Fojo, T., Bates, S. E., Steroid treatment, accumulation, and antagonism of P-glycoprotein in multidrug-resistant cells, Biochemistry 1996, 35, 4820-4827. 

Drug efficacy is directly related to its intracellular concentration level, so it is necessary to evaluate the MTX concentration in cells. In particular, MTX is a folate antagonist, thus it binds to dihydrofolate reductase in competition with folate [71-77]. A low intracellular level of MTX caused by high efflux and low uptake in resistant cells is also the main disadvantage of MTX medication [78,79]. This leads to a high dosage of MTX for cancer treatment, which is also directly associated with adverse effects. 

Fig. 7. Effect of light on the IC50 values for the inhibition of cell growth of various cancer cell lines by platinum(IV) diazido complexes, (a) toxicity of the cis-complexes 4 and 5 on human bladder cancer cell lines (5637-CDDP, cisplatin-resistant cell line) (b) comparison of cytotoxicities of the cis- and rarcs-isomers 4 and 6 in the dark and upon irradiation cisplatin is included for comparison. Data from Ref. (30).

Fig. 1 Transfer of plasmid by conjugation and generation of a new resistant cell...

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