Characterization of a range of fura dyes with two-photon excitation

Two-photon excitation (TPE) spectra of Fura-2, -4F, -6F, -FF, and Furaptra were characterized using a tunable (750-850 nM) ultra-short pulse laser. Two-photon fluorescence of these dyes was studied in free solution and in the cytosol of isolated rabbit ventricular cardiomyocytes. The TPE spectra of the Ca(2+)-free and Ca(2+)-bound forms of the dyes were measured in free solution and expressed in terms of the two-photon fluorescence cross section (Goppert-Meyer units). The Fura dyes displayed the same Ca(2+)-free TPE spectrum in the intracellular volume of permeabilized and intact cardiomyocytes. Fluorescence measurements over a range of laser powers confirmed the TPE of both Ca(2+)-free and Ca(2+)-bound forms of the dyes. Single-wavelength excitation at 810 nM was used to determine the effective dissociation constants (K(eff)) and dynamic ranges (R(f)) of Fura-2, -4F, -6F, -FF, and Furaptra dyes (K(eff) = 181 +/- 52 nM, 1.16 +/- 0.016 micro M, 5.18 +/- 0.3 micro M, 19.2 +/- 1 micro M, and 58.5 +/- 2 micro M; and R(f) = 22.4 +/- 3.8, 12.2 +/- 0.34, 6.3 +/- 0.17, 16.1 +/- 2.8, and 25.4 +/- 4, respectively). Single-wavelength excitation of intracellular Fura-4F resolved diastolic and peak [Ca(2+)] in isolated stimulated cardiomyocytes after calibration of the intracellular signal using reversible exposure to low (100 micro M) extracellular [Ca(2+)]. Furthermore, TPE of Fura-4F allowed continuous, long-term (5-10 min) Ca(2+) imaging in ventricular cardiomyocytes using laser-scanning microscopy without significant cellular photodamage or photobleaching of the dye.

Imaging mitochondrial organization in living primate oocytes and embryos using multiphoton microscopy

We employed multiphoton laser scanning microscopy (MPLSM) to image changes in mitochondrial distribution in living rhesus monkey embryos. This method of imaging does not impair development; thus, the same specimen can be visualized multiple times at various developmental stages. Not only does this increase the amount of information that can be gathered on a single specimen but it permits the correlation of early events with subsequent development in the same specimen. Here we demonstrate the utility of MPLSM for determining changes in mitochondrial organization at various developmental stages and show that rhesus zygotes possess a distinct accumulation of mitochondria between the pronuclei prior to syngamy. We present evidence that suggests that this pronuclear accumulation may be positively correlated with development to the blastocyst stage-in the same embryo-thereby illustrating how MPLSM can be used to correlate cellular dynamics of primate oocytes and early embryos with their developmental potential. Understanding the relationship between mitochondrial distribution and the subsequent development of mammalian embryos, particularly primates, will increase our ability to improve embryo culture technologies, including those used for human assisted reproduction.