Low-temperature induction of calcium-dependent protein phosphorylation in blood platelets.

Bennett, William F.; Lynch, Gordon S.

doi:10.1083/jcb.86.1.280

Cited by 25 publications

(7 citation statements)

References 18 publications

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“…Newbold & Tume, 1977;Nasu, Sakai, Washibe & Ishida, 1984) and protein phosphorylation (e.g. Bennett & Lynch, 1980) and if these events occurred in the pituitary glands during cold incubation they may have potentiated LH release in response to LHRH during the subsequent hour of incubation at 37°C (Pickering & Fink, 1979;Conn, Rogers, Seay et al 1984). This would account for the apparent anomalies that cold blocks protein synthesis but not the priming effect, and that priming appears to occur as a consequence of exposure to cold alone (group 4, Table 1).…”

Section: Discussionmentioning

confidence: 98%

The priming effect of LH-releasing hormone: effects of cold and involvement of new protein synthesis

Curtis¹,

Lyons²,

Fink³

1985

Journal of Endocrinology

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The possible involvement of protein synthesis in the priming effect of LH-releasing hormone (LHRH) has been investigated in vitro using hemipituitary glands from pro-oestrous rats. Cycloheximide (7.1 mumol/l) blocked the priming effect of LHRH (elicited by 8.5 nmol LHRH/l) and protein synthesis (assessed by gel electrophoresis of 35S-labelled pituitary proteins). Pituitary glands were also incubated at 0-1 degrees C followed by incubation at 37 degrees C. While incubation at 0 degrees C for either 1 or 2 h reduced LH release and blocked protein synthesis, the LH response to LHRH in a subsequent 1-h incubation at 37 degrees C was similar to that during the corresponding period in pituitary glands incubated throughout at 37 degrees C. Incubation with medium alone at 0 degrees C during the first hour followed by incubation with LHRH at 37 degrees C during the second hour resulted in an LH response to LHRH which was similar to that in glands incubated with LHRH for 2 successive hours at 37 degrees C. Two-dimensional gel electrophoresis showed that LHRH priming was associated with the synthesis of a new protein of approximately 69 000 molecular weight and with changes in the isoelectric point of two other high molecular weight proteins. These results suggest that the priming effect of LHRH involves the synthesis of a new protein as well as post-translational changes (possibly phosphorylation) in two other proteins and that exposure to cold may prime the pituitary gland to LHRH possibly by stimulating intracellular Ca2+ release and/or protein phosphorylation.

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Section: Discussionmentioning

confidence: 98%

The priming effect of LH-releasing hormone: effects of cold and involvement of new protein synthesis

Curtis¹,

Lyons²,

Fink³

1985

Journal of Endocrinology

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“…We confirmed the results ofRosenberg et al (10), finding that most of the actin in Triton X-100 lysates of platelets isolated by centrifugation at 4*C is filamentous. However, low temperatures are known to activate platelets, as judged by changes in shape (22), exposure of fibrinogen receptors (23), increased phosphorylation of proteins within platelets (22), and increased polymerization of actin (25).…”

Section: Discussionmentioning

confidence: 99%

“…Second, increased amounts of myosin were associated with actin filaments from platelets isolated at 4°C . Low temperatures have previously been found to induce the phosphorylation ofthe myosin light chain (22), an event that also occurs during activation of platelets with thrombin (26,27), collagen (28), or ionophore A23187 (28); this activity increases the affinity ofmyosin for actin filaments (29). Third, as with thrombin-activated platelets (5,30), increased amounts of actin-binding protein were associated with actin filaments from platelets isolated at 4°C .…”

Section: Discussionmentioning

confidence: 99%

Actin filament content and organization in unstimulated platelets.

Fox¹,

Boyles²,

Reynolds³

et al. 1984

The Journal of Cell Biology

110

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The extent of actin polymerization in unstimulated, discoid platelets was measured by DNase I inhibition assay in Triton X-100 lysates of platelets washed at 37°C by gel filtration, or in Triton X-100 lysates of platelets washed at ambient temperatures by centrifugation in the presence of prostacyclin . About 40% of the actin in the discoid platelets obtained by either method existed as filaments . These filaments could be visualized by electron microscopy of thin sections . Similar results were obtained when the actin filament content of discoid platelets was measured by sedimentation of filaments from Triton X-100 lysates at high g forces (145,000 g for 45 min) . However, few of these filaments sedimented at the lower g forces often used to isolate networks of actin filaments from cell extracts. These results indicate that actin filaments in discoid cells are not highly crosslinked . Platelets isolated by centrifugation in the absence of prostacyclin were not discoid, but were instead irregular with one or more pseudopodia . These platelets also contained -40-50% of their actin in a filamentous form; many of these filaments sedimented at low g forces, however, indicating that they were organized into networks. The discoid shape of these centrifuged platelets could be restored by incubating them for 1-3 h at 37°C, which resulted in the reversal of filament organization . High g forces were then required for the sedimentation of the actin . Approximately 80-90% of the actin in platelets washed at 4°C was filamentous ; this high actin filament content could be attributed to actin polymerization during the preparation of the platelets at low temperatures . These studies show that platelet activation involves mechanisms for the structural reorganization of existing filaments, in addition to those previously described for mediating actin polymerization .

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“…Platelet activation can manifest as shape change, fragmentation and/or microaggregation. During shape change, platelets contract and form pseudopods [8] -protrusions that extend from the cell surface and reduce the speed of the platelets due to increased resistance -and appear to increase in size. Microaggregates are larger, slow-moving particles.…”

Section: Sample Preparationmentioning

confidence: 99%

Characterization of Platelet Concentrates Using Dynamic Light Scattering

Labrie¹,

Marshall

Bedi

et al. 2013

Transfus Med Hemother

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Background: Each year, millions of platelet transfusions save the lives of cancer patients and patients with bleeding complications. However, between 10 and 30% of all platelet transfusions are clinically ineffective as measured by corrected count increments, but no test is currently used to identify and avoid these transfusions. ThromboLUX® is the first platelet test intended to routinely characterize platelet concentrates prior to transfusion. Methods: ThromboLUX is a non-invasive, optical test utilizing dynamic light scattering to characterize a platelet sample by the relative quantity of platelets, microparticles, and other particles present in the sample. ThromboLUX also determines the response of platelets to temperature changes. From this information the ThromboLUX score is calculated. Increasing scores indicate increasing numbers of discoid platelets and fewer microparticles. ThromboLUX uses calibrated polystyrene beads as a quality control standard, and accurately measures the size of the beads at multiple temperatures. Results: Results from apheresis concentrates showed that ThromboLUX can determine the microparticle content in unmodified samples of platelet concentrates which correlates well with the enumeration by flow cytometry. ThromboLUX detection of microparticles and microaggregates was confirmed by microscopy. Conclusion: ThromboLUX provides a comprehensive and novel analysis of platelet samples and has potential as a non-invasive routine test to characterize platelet products to identify and prevent ineffective transfusions.

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Low-temperature induction of calcium-dependent protein phosphorylation in blood platelets.

Cited by 25 publications

References 18 publications

The priming effect of LH-releasing hormone: effects of cold and involvement of new protein synthesis

The priming effect of LH-releasing hormone: effects of cold and involvement of new protein synthesis

Actin filament content and organization in unstimulated platelets.

Characterization of Platelet Concentrates Using Dynamic Light Scattering

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