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Longman Dictionary of Contemporary English
▪ This has led to difficulties in interpretation of the possible sequence of events in the development of enhanced platelet reactivity in diabetics.
▪ The above studies have attempted to assess the presence of circulating platelet aggregates.
▪ Along with this there was a significant reduction in circulating platelet aggregates.
▪ Other authors found similar findings with regard to circulating platelet aggregates.
▪ Formalin fixes platelet aggregates which would be removed during the centrifugation to produce platelet-rich plasma.
▪ Therefore the platelet-aggregate ratio would be low in the presence of circulating platelet aggregates.
▪ Thus diminution of prostacyclin production and stimulation of platelet aggregation both mediated by lipid peroxides could contribute to thrombosis on atheromatous plaques.
▪ Biological activity of platelet activating factor was measured by platelet aggregation using a Chrono-log Corporation aggregometer.
▪ The L-arginine-NO system exerts various biological actions including vascular smooth muscle relaxation and inhibition of platelet aggregation.
▪ A positive correlation was found between glycosylated haemoglobin concentration and the prostacyclin concentration necessary to inhibit ADP-induced platelet aggregation by 50 percent.
▪ Spontaneous platelet aggregation Several studies have attempted to assess whether there is evidence of increased circulating platelet aggregates in diabetic subjects.
▪ Platelets were resuspended in washing buffer at appropriate concentrations for platelet aggregation measurement.
▪ However, this suggestion depends on the assumption that prostacyclin is continually produced by arterial wall to prevent platelet aggregation.
▪ Other cell types - leucocytes and blood platelets - spend much of their time circulating freely and thus showing no adhesive interactions.
▪ It can also be readily extracted from out-of-date human blood platelets.
▪ Prostacyclin has powerful metabolic effects on blood platelets.
▪ Correlation with platelet count was particularly good in colonic disease.
▪ For instance, there is no absolutely satisfactory test of platelet function.
▪ This would enable prospective studies to be performed to determine the importance of platelet function in the development of vascular disease.
▪ Studies in this field are difficult to interpret due to the inherent variability of the measurements of platelet function.
▪ The mechanism of lipid-induced effects of platelet function has received considerable attention.
▪ In addition to problems intrinsic to the methodology of platelet function, problems also arise from the diabetic groups studied.
▪ For these reasons studies detailing the effects of diabetic control on platelet function must be interpreted with caution.
▪ Gliclazide is the sulphonylurea that has received most study in terms of possible effects on platelet function.
▪ These authors have shown that colonic platelet activating factor content was significantly increased irrespective of colonic inflammation.
▪ Therefore we suggest that platelet activating factor should be considered as a global mucosal activity marker.
▪ These results suggest the involvement of platelet activating factor in the endothelin induced fibrinolytic activation and subsequently developed mucosal haemorrhagic lesion.
▪ This suggests that platelets must possess very sophisticated intracellular control mechanisms.
▪ A minor fraction of phosphatidylserine may be present at the outer surface of platelets, but this can not usually be detected.
▪ An ion exchange process creates an aqueous slurry of platelets of molecular dimensions.
▪ Maternity blues linked to platelet receptors TWO-THIRDS of women suffer from postnatal depression, accompanied by crying, confusion and tension.
▪ The distributional asymmetries of phospholipids in the plasma membrane of erythrocytes and platelets are shown in Fig. 2.
▪ The earliest finding is the platelet adhesion to collagen fibres followed by aggregation and formation of a platelet plug.
▪ The L-arginine-NO system exerts various biological actions including vascular smooth muscle relaxation and inhibition of platelet aggregation.
▪ These findings suggest that lipoprotein abnormalities in the diabetic state may also indirectly affect platelet function by damaging vascular endothelium.
▪ This would enable prospective studies to be performed to determine the importance of platelet function in the development of vascular disease.
Douglas Harper's Etymology Dictionary

1895, formed in English from plate + diminutive suffix -let.


n. (context hematology cytology English) A small colorless disk-shaped particle found in the blood of mammals, which plays an important role in the formation of blood clots.


n. tiny bits of protoplasm found in vertebrate blood; essential for blood clotting [syn: blood platelet, thrombocyte]


Platelets, also called thrombocytes (thromb- + -cyte, "blood clot cell"), are a component of blood whose function (along with the coagulation factors) is to stop bleeding by clumping and clotting blood vessel injuries. Platelets have no cell nucleus: they are fragments of cytoplasm that are derived from the megakaryocytes of the bone marrow, and then enter the circulation. These unactivated platelets are biconvex discoid (lens-shaped) structures, 2–3 µm in greatest diameter. Platelets are found only in mammals, whereas in other animals (e.g. birds, amphibians) thrombocytes circulate as intact mononuclear cells. On a stained blood smear, platelets appear as dark purple spots, about 20% the diameter of red blood cells. The smear is used to examine platelets for size, shape, qualitative number, and clumping. The ratio of platelets to red blood cells in a healthy adult is 1:10 to 1:20.

The main function of platelets is to contribute to hemostasis: the process of stopping bleeding at the site of interrupted endothelium. They gather at the site and unless the interruption is physically too large, they plug the hole. First, platelets attach to substances outside the interrupted endothelium: adhesion. Second, they change shape, turn on receptors and secrete chemical messengers: activation. Third, they connect to each other through receptor bridges: aggregation. Formation of this platelet plug (primary hemostasis) is associated with activation of the coagulation cascade with resultant fibrin deposition and linking (secondary hemostasis). These processes may overlap: the spectrum is from a predominantly platelet plug, or "white clot" to a predominantly fibrin clot, or "red clot" or the more typical mixture. The final result is the clot. Some would add the subsequent clot retraction and platelet inhibition as fourth and fifth steps to the completion of the process and still others a sixth step wound repair.

Low platelet concentration is thrombocytopenia and is due to either decreased production or increased destruction. Elevated platelet concentration is thrombocytosis and is either congenital, reactive (to cytokines), or due to unregulated production: one of the myeloproliferative neoplasms or certain other myeloid neoplasms. A disorder of platelet function is a thrombocytopathy.

Normal platelets can respond to an abnormality on the vessel wall rather than to hemorrhage, resulting in inappropriate platelet adhesion/activation and thrombosis: the formation of a clot within an intact vessel. These arise by different mechanisms than a normal clot. Examples are: extending the fibrin clot of venous thrombosis; extending an unstable or ruptured arterial plaque, causing arterial thrombosis; and microcirculatory thrombosis. An arterial thrombus may partially obstruct blood flow, causing downstream ischemia; or completely obstruct it, causing downstream tissue death.

Usage examples of "platelet".

I was too far away to make out the platelet parasites around them, but a sense of diffused light there -- like dust floating -- suggested their presence by the thousands or millions.

Perhaps it is odd to admit, but my mind wandered all that afternoon, even while the alien cuttlefish swam alongside within swallowing range and alien platelet creatures danced and hovered within meters of the kayak and parasail.

I could see the internal organs more clearly now -- pulsing and absorbing, moving in peristaltic waves, some of them filled with the green platelet creatures.

The alien Akerataeli appeared to be missing until Aenea pointed to a place far out among the branches where the microgravity was even less, and there -- between the gossamers and glowbirds -- floated the platelet beings.

Henry had had two platelet and two red-cell transfusions in the past two months, and he had been on Anadrol, a steriod to boost his blood counts, for two and a half years.

For instance, one study has shown that depression increases platelet aggregation, which means that being depressed may make you more prone to arterial clotting and arterial aging.

Goldstein shuffled to the last page, past the tests confirming malaria: decreased hemoglobin, hemocrit, platelet count and haptoglobin.

It raised up even higher as they watched, yellow-brown in the harsh sunlight, its two sets of horns searching as its upper body waved from side to side, revealing a light external shell, a platelet with the merest hint of a spire.

His platelet counts dropped alarmingly and his viral count from the hepatitis soared.

In a short time, his platelet counts were back to normal, his viral count had subsided, and there were no symptoms of any disease.

Even here, at the one moment my entire life should have trained me forIntensive Care, 5W, North Tower, Green Wingobscenely lacerated, lost: wanting, needing, but not knowing how to hear the makeshift, temporary metronome measuring out so obvious a rhythm, the meter of the faltering human platelet pump.

He pressed the sensor platelet into the hollow under his ribs on his right side, and saw that the powerpack implant in that location still had a .

The only comment on the smear is that the platelets are markedly decreased and that no reticulocytes are seen.

The refrain thundered so loudly within his skull that the meager assembly of platelets left to guard the vascular borders of his brain might be fatally dislodged by the sheer vibrations of the thunderous noise.

But should his platelets manage to stave off a lethal flood, his cells would suffocate.