Ultrastructure of resting and activated storage pool deficient platelets from animals with the Chédiak-Higashi syndrome
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Platelets from Chédiak-Higashi (CH) syndrome animals lack dense granules. While CH platelets aggregate similarly, their activation during aggregation differs from normal platelets.
Area of Science:
- Hematology
- Cell Biology
- Genetics
Background:
- Chédiak-Higashi (CH) syndrome is a rare genetic disorder affecting various cell types.
- Platelet dysfunction is a known complication, impacting hemostasis.
- Ultrastructural analysis provides insights into cellular morphology and function.
Purpose of the Study:
- To investigate the ultrastructural differences in platelets from CH animals compared to normal controls.
- To examine the impact of CH syndrome on platelet granule content and morphology.
- To assess the behavior of CH platelets during aggregation.
Main Methods:
- Transmission electron microscopy was used to examine resting platelets from normal and CH cattle, mink, and cats.
- Ultrastructural analysis focused on granule content, mitochondria, microtubules, and other organelles.
- Platelet aggregation was induced using ADP and thrombin, followed by ultrastructural evaluation at different stages.
Main Results:
- Platelets from CH animals exhibited a near-complete absence of dense granules.
- Giant CH granules, characteristic of the syndrome in other cells, were not observed in platelets.
- CH bovine platelets showed similar numbers and appearance of alpha granules, mitochondria, and microtubules compared to normal platelets.
- During ADP-induced aggregation, CH platelets aggregated similarly to normal platelets initially but showed reduced activation during irreversible aggregation.
- Thrombin-treated CH and normal platelets displayed similar morphology with centrifugal granule movement.
Conclusions:
- The primary ultrastructural defect in CH platelets is the absence of dense granules.
- Despite granule deficiency, CH platelets can undergo aggregation, though their activation state differs from normal platelets.
- These findings highlight specific platelet abnormalities in CH syndrome, contributing to understanding its hemostatic implications.
Abstract:
The ultrastructural of platelets from Chédiak-Higashi (CH) and normal cattle, mink, and cats at rest was studied. Platelets from CH animals had a virtual absence of platelet dense granules. Alpha granules, amorphous membrane-surrounded structures, mitochondria, and microtubules of CH bovine platelets were similar in number and appearance to those in normal bovine platelets. Giant CH granules, present in other cells and considered diagnostic of the syndrome, could not be identified in platelets from CH animals. The open canalicular system and dense tubule system were not readily identifiable in resting bovine platelets. The ultrastructure of normal and CH cattle platelets was evaluated at various stages of ADP-induced aggregation. After platelets changed shape during the first phase of aggregation, the ultrastructural appearance of CH platelets was similar to that of normal platelets. The CH platelets composing the aggregates during irreversible aggregation did not appear as activated as did normal platelets, even though the aggregation tracings were similar. Normal and CH cattle platelets treated with thrombin appeared morphologically similar and were characterized by centrifugal movement of granules.