Measurement of ionized calcium in blood platelets with a new generation calcium indicator

Rao, Gundu H. R.; Peller, Janet D.; White, James G.

doi:10.1016/0006-291x(85)91182-9

Cited by 70 publications

(15 citation statements)

References 14 publications

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“…Although the difference between the groups was not statistically significant without correction (109.7± 18.4 vs. 94.9±9.2 nM, p>0.1), corrected basal [Ca 2+ ]j was significantly higher in SHR than WKY rats (61.6±5.6 vs. 54.0±3.9 nM, p<0.02). As before (Figure 1), fura-2 leakage (the ratio of extracellular fura-2 to total fura-2) was not different between SHR and WKY rats (17 observed within 6-9 seconds. Time to reach the peak was similar in both groups (SHR vs. WKY rats: 8.0±0.5 vs. 7.9±0.8 seconds in the presence of calcium; 7.4±1.2 vs. 7.6±0.9 seconds in the absence of calcium.…”

Section: Resultssupporting

confidence: 79%

Abnormal calcium handling by platelets of spontaneously hypertensive rats.

et al. 1990

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Section: Resultssupporting

confidence: 79%

Abnormal calcium handling by platelets of spontaneously hypertensive rats.

et al. 1990

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“…The quinolone nucleus has adjacent carbonyls at C-2 and C-3 which form a potential divalent-cation-chelating site. Changes in the fluorescence of chelating compounds often indicate the binding of metals and have been used to measure levels of cations in biological systems (19). Accordingly, changes in the fluorescence of fleroxacin were seen with divalent, but not monovalent, cations (Fig.…”

Section: Discussionmentioning

confidence: 99%

Routes of quinolone permeation in Escherichia coli

Chapman

Georgopapadakou

1988

Antimicrob Agents Chemother

235

157

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The uptake of quinolone antibiotics by Escherichia coli was investigated by using fleroxacin , AM 833) as a prototype compound. The uptake of fleroxacin was reduced and its MIC was increased in the presence of magnesium. Quinolones induced lipopolysaccharide release, increased cell-surface hydrophobicity and outer membrane permeability to l-lactams, and sensitized cells to lysis by detergents. These effects were also antagonized by magnesium and were very similar to those seen with EDTA and gentamicin. MICs of quinolones in porin-deficient strains were increased relative to those of the parent strain, consistent with a porin pathway of entry. However, MICs were further increased in the presence of magnesium; the size of the additional increase showed a positive correlation with quinolone hydrophobicity in an OmpF-OmpCOmpA-strain. When quinolones were mixed with divalent cations in solution, changes in quinolone fluorescence suggestive of metal chelation were observed. The addition of fleroxacin to a cell suspension resulted in a rapid initial association of fluorescence with cells, foUlowed by a brief decrease and a final time-dependent linear increase in cell-associated fluorescence. We interpret these results as representing chelation of outer membrane-bound magnesium by fleroxacin and other quinolones, dissociation of the quinolone-magneum complex from the outer membrane, and diffusion of the quinolone through both porins and exposed lipid domains on the outer membrane. For a given quinolone, the contribution of the porin and nonporin pathways to total uptake is influenced by the hydrophobicity of the quinolone.Quinolones are broad-spectrum antibacterial agents whose primary mechanism of action is inhibition of DNA gyrase activity (2). Access to the target site is a major determinant of antibacterial activity, the outer membrane being the major permeability barrier in gram-negative bacteria. Quinolones are known to penetrate the outer membrane of Escherichia coli through the OmpF and OmpC porins; this has been demonstrated by both the use of defined porindeficient strains (8) and the isolation of quinolone-resistant mutants that lack porins (9, 10). However, the size of the quinolone MIC increase in porin-deficient mutants relative to the wild type is rarely more than fourfold. In similar porin-deficient mutants, the MIC increases of hydrophilic cephalosporins, which are restricted to the use of porins (18,25), may be as much as 64-fold (11). Hirai et al. (8) noted that the MIC of quinolones was decreased in lipopolysaccharidedeficient (rough) mutants as compared with the wild type, and the size of the decrease correlated with the hydrophobicity of the quinolone. These observations suggested that the passage of quinolones through the outer membrane was not limited to porins.Several classes of antibiotics, including the aminoglycosides and polymyxin B, are known to penetrate the outer membrane by pathways other than porins (6). These molecules displace divalent cations which bridge adjacent lipopolysaccharide ...

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“…Fluorescent calcium-sensitive intracellular probes have enabled receptor-mediated cytosolic calcium transients to be examined in a variety of cells (14)(15)(16)(17)(18)(19)(20). However, obtaining these measurements from anchorage-dependent cells has usually required that the cells be physically or enzymatically detached from their culture surface to form a suspension suitable for spectrofluorometry.…”

Section: Introductionmentioning

confidence: 99%