Functional Fractionation of Platelets: Aggregation Kinetics and Glycoprotein Labeling of Differing Platelet Populations

SummaryPlatelet heterogeneity has been studied with a technique called functional fractionation which employs gentle centrifugation to yield subpopulations (“reactive” and “less-reactive” platelets) after exposure to small doses of aggregating agent. Aggregation kinetics of the different platelet populations were investigated by quenched-flow aggregometry. The large, “reactive” platelets were more sensitive to ADP (Ka = 1.74 μM) than the smaller “less-reactive” platelets (Ka = 4.08 μM). However, their maximal rate of aggregation (Vmax, % of platelets aggregating per sec) of 23.3 was significantly lower than the “less-reactive” platelets (Vmax = 34.7). The “reactive” platelets had a 2.2 fold higher level of cyclic AMP.Platelet glycoproteins were labeled using the neuraminidase-galactose oxidase – [H3]-NaBH4 technique. When platelets were labeled after reversible aggregation, the “reactive” platelets showed a two-fold decrease in labeling efficiency (versus control platelets). However, examination of whole cells or membrane preparations from reversibly aggregated platelets revealed no significant difference in Coomassie or PAS (Schiff) staining.These results suggest that the large, “reactive” platelets are more sensitive to ADP but are not hyperaggregable in a kinetic sense. Reversible aggregation may cause a re-orientation of membrane glycoproteins that is apparently not characterized by a major loss of glycoprotein material.

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Reversible aggregation kinetics of poly(N-isopropylacrylamide-co-N-vinylpyrrolidone) in aqueous solutions revealed by elastic light scattering spectroscopy

Journal of Wuhan University of Technology-Mater Sci Ed ◽

10.1007/s11595-013-0766-6 ◽

2013 ◽

Vol 28 (4) ◽

pp. 766-772 ◽

Cited By ~ 1

Author(s):

Yuanjun Xia ◽

Yunwei Huang ◽

Guobin Yi ◽

Xihong Zu ◽

Qingshui Yin ◽

...

Keyword(s):

Light Scattering ◽

Aqueous Solutions ◽

Aggregation Kinetics ◽

Elastic Light Scattering ◽

Reversible Aggregation ◽

Light Scattering Spectroscopy ◽

Kinetics Of

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Identification of a Thrombin Proteolytic Receptor on Human Platelets

10.1055/s-0039-1682635 ◽

1977 ◽

Cited By ~ 1

Author(s):

David R. Phillips ◽

Patricia Poh Agin

Keyword(s):

Membrane Surface ◽

Human Platelets ◽

Complete Loss ◽

Surface Proteins ◽

Galactose Oxidase ◽

Membrane Glycoproteins ◽

Hydrolytic Product ◽

A 23187 ◽

Labeling Method ◽

Kinetics Of

Thrombin is one of the most potent physiological agents causing platelet stimulation. It would appear that proteolysis is intimately linked to stimulation because trypsin, but not thrombin inactivated with PMSF, also stimulates platelets. Our approach to identifying the proteolytic substrate was to radioactively label the membrane surface proteins and determine which of these were hydrolyzed by thrombin. A glycoprotein labeling method (neuraminidase/galactose oxidase/(3H)-NaBH4) was employed. Twelve membrane glycoproteins were labeled, including most of those labeled by 1actoperoxidase-catalyzed iodination. Secretion and aggregation experiments showed that platelets labeled by this procedure are equally responsive to thrombin, collagen, and ADP as unlabeled platelets.Of the glycoproteins labeled by this procedure, only glycoprotein V (Mr = 89,000) was decreased as a result of thrombin action. Although low thrombin concentrations (0.2 U/ml) were sufficient to obtain significant hydrolysis, the complete loss of glycoprotein V occurred at the ratio of 1 U thrombin per 109 platelets; no further changes were observed when the thrombin concentration was increased to 10 U/109 platelets. A soluble glycopeptide hydrolytic product (Mr = 70,000) was released into solution. The kinetics of glycoprotein V hydrolysis were comparable to those of secretion and aggregation. Glycoprotein V hydrolysis was not observed when platelets were aggregated by collagen, ADP, or the Ca++ ionophore A-23187. It is proposed that glycoprotein V is a proteolytic receptor of thrombin.

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Shear-induced reaction-limited aggregation kinetics of Brownian particles at arbitrary concentrations

The Journal of Chemical Physics ◽

10.1063/1.3361665 ◽

2010 ◽

Vol 132 (13) ◽

pp. 134903 ◽

Cited By ~ 33

Author(s):

Alessio Zaccone ◽

Daniele Gentili ◽

Massimo Morbidelli

Keyword(s):

Aggregation Kinetics ◽

Brownian Particles ◽

Kinetics Of ◽

Induced Reaction

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Rheological behaviour and aggregation kinetics of EG/water based MCNT nano-suspension for sub-zero temperature cold storage

Energy Procedia ◽

10.1016/j.egypro.2019.01.709 ◽

2019 ◽

Vol 158 ◽

pp. 4846-4851

Author(s):

Yaoting Huang ◽

Chunping Xie ◽

Chuan Li ◽

Yongliang Li ◽

Yulong Ding

Keyword(s):

Cold Storage ◽

Rheological Behaviour ◽

Aggregation Kinetics ◽

Zero Temperature ◽

Water Based ◽

Kinetics Of

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The impact of stabilization mechanism on the aggregation kinetics of silver nanoparticles

The Science of The Total Environment ◽

10.1016/j.scitotenv.2012.03.041 ◽

2012 ◽

Vol 429 ◽

pp. 325-331 ◽

Cited By ~ 110

Author(s):

Amro M. El Badawy ◽

Kirk G. Scheckel ◽

Makram Suidan ◽

Thabet Tolaymat

Keyword(s):

Silver Nanoparticles ◽

Aggregation Kinetics ◽

Stabilization Mechanism ◽

The Impact ◽

Kinetics Of

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Determinants of mRNA stability in Dictyostelium discoideum amoebae: differences in poly(A) tail length, ribosome loading, and mRNA size cannot account for the heterogeneity of mRNA decay rates.

Molecular and Cellular Biology ◽

10.1128/mcb.8.5.1957 ◽

1988 ◽

Vol 8 (5) ◽

pp. 1957-1969 ◽

Cited By ~ 23

Author(s):

R A Shapiro ◽

D Herrick ◽

R E Manrow ◽

D Blinder ◽

A Jacobson

Keyword(s):

Steady State ◽

Dictyostelium Discoideum ◽

Mrna Decay ◽

Decay Rates ◽

Time Dependent ◽

Translational Efficiency ◽

Cdna Clones ◽

Dependent Manner ◽

Significant Difference ◽

Kinetics Of

As an approach to understanding the structures and mechanisms which determine mRNA decay rates, we have cloned and begun to characterize cDNAs which encode mRNAs representative of the stability extremes in the poly(A)+ RNA population of Dictyostelium discoideum amoebae. The cDNA clones were identified in a screening procedure which was based on the occurrence of poly(A) shortening during mRNA aging. mRNA half-lives were determined by hybridization of poly(A)+ RNA, isolated from cells labeled in a 32PO4 pulse-chase, to dots of excess cloned DNA. Individual mRNAs decayed with unique first-order decay rates ranging from 0.9 to 9.6 h, indicating that the complex decay kinetics of total poly(A)+ RNA in D. discoideum amoebae reflect the sum of the decay rates of individual mRNAs. Using specific probes derived from these cDNA clones, we have compared the sizes, extents of ribosome loading, and poly(A) tail lengths of stable, moderately stable, and unstable mRNAs. We found (i) no correlation between mRNA size and decay rate; (ii) no significant difference in the number of ribosomes per unit length of stable versus unstable mRNAs, and (iii) a general inverse relationship between mRNA decay rates and poly(A) tail lengths. Collectively, these observations indicate that mRNA decay in D. discoideum amoebae cannot be explained in terms of random nucleolytic events. The possibility that specific 3'-structural determinants can confer mRNA instability is suggested by a comparison of the labeling and turnover kinetics of different actin mRNAs. A correlation was observed between the steady-state percentage of a given mRNA found in polysomes and its degree of instability; i.e., unstable mRNAs were more efficiently recruited into polysomes than stable mRNAs. Since stable mRNAs are, on average, "older" than unstable mRNAs, this correlation may reflect a translational role for mRNA modifications that change in a time-dependent manner. Our previous studies have demonstrated both a time-dependent shortening and a possible translational role for the 3' poly(A) tracts of mRNA. We suggest, therefore, that the observed differences in the translational efficiency of stable and unstable mRNAs may, in part, be attributable to differences in steady-state poly(A) tail lengths.

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The Conformation and the Aggregation Kinetics of α-Synuclein Depend on the Proline Residues in Its C-Terminal Region

Biochemistry ◽

10.1021/bi1010927 ◽

2010 ◽

Vol 49 (43) ◽

pp. 9345-9352 ◽

Cited By ~ 41

Author(s):

Jessika Meuvis ◽

Melanie Gerard ◽

Linda Desender ◽

Veerle Baekelandt ◽

Yves Engelborghs

Keyword(s):

Terminal Region ◽

Aggregation Kinetics ◽

Kinetics Of

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REGENERATION OF VISUAL PURPLE IN SOLUTION

The Journal of General Physiology ◽

10.1085/jgp.23.1.21 ◽

1939 ◽

Vol 23 (1) ◽

pp. 21-39 ◽

Cited By ~ 19

Author(s):

Aurin M. Chase ◽

Emil L. Smith

Keyword(s):

Order Process ◽

First Order ◽

Color Changes ◽

Violet Light ◽

Frog Retina ◽

Significant Difference ◽

Kinetics Of ◽

Photosensitive Substance ◽

Subsequent Regeneration

1. Measurements of visual purple regeneration in solution have been made by a procedure which minimized distortion of the results by other color changes so that density changes caused by the regenerating substance alone are obtained. 2. Bleaching a visual purple solution with blue and violet light causes a greater subsequent regeneration than does an equivalent bleaching with light which lacks blue and violet. This is due to a photosensitive substance which has a gradually increasing effective absorption toward the shorter wavelengths. It is uncertain whether this substance is a product of visual purple bleaching or is present in the solution before illumination. 3. The regeneration of visual purple measured at 560 mµ is maximal at about pH 6.7 and decreases markedly at more acid and more alkaline pH's. 4. The absorption spectrum of the regenerating material shows only a concentration change during the course of regeneration, but has a higher absorption at the shorter wavelengths than has visual purple before illumination. 5. Visual purple extractions made at various temperatures show no significant difference in per cent of regeneration. 6. The kinetics of regeneration is usually that of a first order process. Successive regenerations in the same solution have the same velocity constant but form smaller total amounts of regenerated substance. 7. In vivo, the frog retina shows no additional oxygen consumption while visual purple is regenerating.

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