Human IVF blastocyst at approximately the 100 cell stage. The outer layer of cells is the trophectoderm layer that contributes to the placenta. The ball of cells at the lower left of the image is the inner cell mass (ICM) from which the fetus develops or from which the embryonic stem cells are derived upon ICM removal followed by culturing in vitro. Courtesy of Dr. Richard Scott, Reproductive Medicine Associates of New Jersey, Morristown, NJ, USA.

Images of adult rhesus stromal stem cells. (a) Phase contrast image (40×) of a passage 14 stem cell that has differentiated or deteriorated into a cell containing numerous lipid droplets (arrow). (b) Measurement of Mitotracker fluorescence intensity in a passage 11 cell with perinuclear mitochondrial arrangement (600×). The cell periphery is outlined (dotted line). Cells with a predominantly perinuclear arrangement of mitochondria have a very high fluorescence intensity near the nucleus which drops precipitously toward the cell periphery (graph inset). Because there is such a large variation in intensity at the two ends of the transect line, the standard deviation is numerically high, resulting in a low fluorescence intensity/standard deviation ratio. (c) In a cell with a homogeneous distribution of mitochondria (passage 14, 600×), the fluorescence intensity is relatively constant along the transect line (graph inset) and the standard deviation is numerically low, resulting in a higher ratio. (d) Representative image of a passage 11 perinuclear mitochondrial arrangement (600×), (e) image of a passage 14 homogeneous mitochondrial arrangement (600×), and (f) image of passage 17 an aggregated mitochondrial arrangement (600×). Reproduced with permission from Lonergan et al. (2006).

Hamster two-cell stage embryo stained with Rhodamine 123. Mitochondria are clustered around each nucleus. Bar equals 10 µm. Reproduced with permission from Barnett et al. (1996).