isolation-culture-functional-characterization-adult-mouse

Isolation, Culture, and Functional Characterization of Adult Mouse Cardiomyoctyes

The use of primary cardiomyocytes (CMs) in culture has provided a powerful complement to murine models of heart disease in advancing our understanding of ...

Beth Israel Deaconess Medical Center, Harvard Medical School

The various lamellar phases of dipalmitoylphosphadtidylcholine bilayers with and without cholesterol were used to assess the versatility of the fluorescent probe merocyanine 540 through simultaneous measurements of emission intensity, spectral shape, and steady-state anisotropy. Induction of the crystalline phase (Lc') by pre-incubation at 4Â°C produced a wavelength dependence of anisotropy which was strong at 15 and 25Â°C, weak at 38Â°C, and minimal above the main transition (>~41.5Â°C) or after returning the temperature from 46 to 25Â°C. The profile of anisotropy values across this temperature range revealed the ability of the probe to detect crystalline, gel (LÎ²'), and liquid crystalline (LÎ±) phases. The temperature dependence of fluorescence intensity was additionally able to distinguish between the ripple (PÎ²') and gel phases. In contrast, the shape of the emission spectrum, quantified as the ratio of merocyanine monomer and dimer peaks (585 and 621 nm), was primarily sensitive to the crystalline and gel phases because dimer fluorescence requires a highly-ordered environment. This requirement also explained the diminution of anisotropy wavelength dependence above 25Â°C. Repetition of experiments with vesicles containing cholesterol allowed creation of a phase map. Superimposition of data from the three simultaneous measurements provided details about the various phase regions in the map not discernible from any one of the three alone. The results were applied to assessment of calcium-induced membrane changes in living cells.PACS Codes: 87.16.dt.

Combined use of steady-state fluorescence emission and anisotropy of merocyanine 540 to distinguish crystalline, gel, ripple, and liquid crystalline phases in dipalmitoylphosphatidylcholine bilayers.

Assessment of the equilibration kinetics of Patman at the edges of its emission spectra provided additional insights about membrane properties beyond those obtained from end-point fluorescence measurements. Upon introduction of the probe to aqueous suspensions of liposomes, the emission intensity slowly increased about 10-fold (t(Â½)=~100 s). The rate of equilibration depended on emission wavelength, and was usually faster at 500 than at 435 nm. However, this trend was reversed for equilibration with lipids at their phase transition temperature. The apparent rotational motion of the dye also differed between the long and short emission wavelengths but did not display the slow equilibration time dependence observed with intensity measurements. These results suggested that slow equilibration reflects relaxation of the immediate membrane microenvironment around the probe rather than slow insertion into the membrane. The data were rationalized with a model that allows two membrane/probe configurations with distinct microenvironments. The analysis suggests that by monitoring the equilibration pattern of Patman, inferences can be made regarding the polarity of two microenvironments occupied by the probe, the distribution of the probe among those microenvironments, and the kinetics with which they relax to equilibrium.

Article	Year
Combined use of steady-state fluorescence emission and anisotropy of merocyanine 540 to distinguish crystalline, gel, ripple, and liquid crystalline phases in dipalmitoylphosphatidylcholine ... PMC biophysics\| PubMed ID: 21054864	2010
Wavelength dependence of patman equilibration dynamics in phosphatidylcholine bilayers. Biochimica et biophysica acta\| PubMed ID: 22954647	2013

Hannabeth Franchino

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