Figure 6. Granules are synthesized,... | Rockefeller University Press

Figure 6.

$Figure 6. Granules are synthesized, packaged, and continue to sort in released proplatelets. (A) High magnification electron micrographs show the presence of MVBs in released preplatelets (top) and proplatelets (bottom). (B and C) Mouse preplatelet/proplatelet labeled with a fluorescent human fibrinogen conjugate, which is taken up and stored in α-granules. The distribution and dynamics of the labeled α-granules were followed using time-lapse fluorescence microscopy and demonstrate ongoing, bidirectional α-granule movement during preplatelet to proplatelet conversion. (C) Red dots highlight α-granule movement toward the top end of the proplatelet, whereas green dots highlight movement toward the bottom end. Labeled organelles moved bidirectionally along the microtubule tracks of cytoplasmic bridges and cortices of developing proplatelets at a rate of ∼0.13–0.26 µm/min, implying continued organization of platelet contents through late stages of the maturation process. The width of the field is 10 µm. (D) Released proplatelet/platelet fraction from second gradient sedimentation probed with a rabbit monoclonal antibody against serotonin. Fluorescence and DIC images were overlaid and merged. Images are exhibited as a montage of representative cells from the same sample slide. Dense granules distribute evenly within the preplatelet and along the cytoplasmic bridges and bulbous tip of released proplatelets and continue to translocate throughout maturation.$

Granules are synthesized, packaged, and continue to sort in released proplatelets. (A) High magnification electron micrographs show the presence of MVBs in released preplatelets (top) and proplatelets (bottom). (B and C) Mouse preplatelet/proplatelet labeled with a fluorescent human fibrinogen conjugate, which is taken up and stored in α-granules. The distribution and dynamics of the labeled α-granules were followed using time-lapse fluorescence microscopy and demonstrate ongoing, bidirectional α-granule movement during preplatelet to proplatelet conversion. (C) Red dots highlight α-granule movement toward the top end of the proplatelet, whereas green dots highlight movement toward the bottom end. Labeled organelles moved bidirectionally along the microtubule tracks of cytoplasmic bridges and cortices of developing proplatelets at a rate of ∼0.13–0.26 µm/min, implying continued organization of platelet contents through late stages of the maturation process. The width of the field is 10 µm. (D) Released proplatelet/platelet fraction from second gradient sedimentation probed with a rabbit monoclonal antibody against serotonin. Fluorescence and DIC images were overlaid and merged. Images are exhibited as a montage of representative cells from the same sample slide. Dense granules distribute evenly within the preplatelet and along the cytoplasmic bridges and bulbous tip of released proplatelets and continue to translocate throughout maturation.