PubMed HealthSearch

PubMed · 6821315

Platelet aggregation testing.

Abstract

The authors review the methods currently used for platelet aggregation testing, which are mainly grouped in two classes: 1. methods measuring the sensitivity of platelets to aggregating agents and to mechanical stimulation in vitro and 2. methods measuring the spontaneous tendency of platelets to aggregate in vivo. Their advantages, their pitfalls and their potential usefulness are reported. The platelet behavior as assessed by the available methods is not strictly related to the true platelet behavior in circulating blood. Therefore much criticism is requested in the interpretation of the results obtained for a given group of subjects with a given method and any unallowed extrapolation must be avoided.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

G Gensini, A Fortini, R Laureano. 1981. Platelet aggregation testing.. https://pubmed.ncbi.nlm.nih.gov/6821315/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

A novel DPH5-related diphthamide-deficiency syndrome causing embryonic lethality or profound neurodevelopmental disorder.

PURPOSE: Diphthamide is a post-translationally modified histidine essential for messenger RNA translation and ribosomal protein synthesis. We present evidence for DPH5 as a novel cause of embryonic lethality and profound neurodevelopmental delays (NDDs). METHODS: Molecular testing was performed using exome or genome sequencing. A targeted Dph5 knockin mouse (C57BL/6Ncrl-Dph5em1Mbp/Mmucd) was created for a DPH5 p.His260Arg homozygous variant identified in 1 family. Adenosine diphosphate-ribosylation assays in DPH5-knockout human and yeast cells and in silico modeling were performed for the identified DPH5 potential pathogenic variants. RESULTS: DPH5 variants p.His260Arg (homozygous), p.Asn110Ser and p.Arg207Ter (heterozygous), and p.Asn174LysfsTer10 (homozygous) were identified in 3 unrelated families with distinct overlapping craniofacial features, profound NDDs, multisystem abnormalities, and miscarriages. Dph5 p.His260Arg homozygous knockin was embryonically lethal with only 1 subviable mouse exhibiting impaired growth, craniofacial dysmorphology, and multisystem dysfunction recapitulating the human phenotype. Adenosine diphosphate-ribosylation assays showed absent to decreased function in DPH5-knockout human and yeast cells. In silico modeling of the variants showed altered DPH5 structure and disruption of its interaction with eEF2. CONCLUSION: We provide strong clinical, biochemical, and functional evidence for DPH5 as a novel cause of embryonic lethality or profound NDDs with multisystem involvement and expand diphthamide-deficiency syndromes and ribosomopathies.

Adenosine Diphosphate

Mechanism of regulation of the Epac family of cAMP-dependent RapGEFs.

Epac1 (cAMP-GEFI) and Epac2 (cAMP-GEFII) are closely related guanine nucleotide exchange factors (GEFs) for the small GTPase Rap1, which are directly regulated by cAMP. Here we show that both GEFs efficiently activate Rap2 as well. A third member of the family, Repac (GFR), which lacks the cAMP dependent regulatory sequences, is a constitutive activator of both Rap1 and Rap2. In contrast to Epac1, Epac2 contains a second cAMP binding domain at the N terminus, as does the Epac homologue from Caenorhabditis elegans. Affinity measurements show that this distal cAMP binding domain (the A-site) binds cAMP with much lower affinity than the cAMP binding domain proximal to the catalytic domain (the B-site), which is present in both Epac1 and Epac2. Deletion mutant analysis shows that the high affinity cAMP binding domains are sufficient to regulate the GEFs in vitro. Interestingly, isolated fragments containing the B-sites of either Epac1 or Epac2, but not the A-site from Epac2, inhibit the catalytic domains in trans. This inhibition is relieved by the addition of cAMP. In addition to the cAMP binding domains, both Epac1 and Epac2 have a DEP domain. Deletion of this domain does not affect regulation of Epac1 activity but affects membrane localization. From these results, we conclude that all three members of the Epac family regulate both Rap1 and Rap2. Furthermore, we conclude that the catalytic activity of Epac1 is constrained by a direct interaction between GEF and high affinity cAMP binding domains in the absence of cAMP. Epac1 becomes activated by a release of this inhibition when cAMP is bound.

Adenosine Diphosphate

The activation state of alphavbeta 3 regulates platelet and lymphocyte adhesion to intact and thrombin-cleaved osteopontin.

Cleavage of osteopontin by thrombin has been reported to enhance cell adhesion. We asked whether thrombin could regulate the alpha(v)beta(3)-mediated adhesion of platelets and B lymphocytes to this substrate. Although there was no difference in the extent or the avidity of thrombin- and ADP-stimulated platelet adhesion to intact or thrombin-cleaved human osteopontin, both the extent and avidity of phorbol ester-stimulated B cell adhesion to thrombin-cleaved osteopontin was significantly increased. Thus, these data suggest that the ability of alpha(v)beta(3) to recognize osteopontin can be differentially regulated in a cell-specific manner. To localize the alpha(v)beta(3) binding site on osteopontin, we measured cell adhesion to the two thrombin cleavage products of osteopontin and to a series of nested RGD-containing osteopontin peptides cross-linked to albumin. Whereas ADP-stimulated platelets adhered to the amino-terminal but not the carboxyl-terminal osteopontin fragment and to the osteopontin peptide RGDSVVYGLR, phorbol ester-stimulated B cells did not adhere to this peptide, although they did so in the presence of 1 mm Mn(2+). Thus, our data confirm that thrombin cleavage enhances the accessibility of the binding motif for alpha(v)beta(3) on osteopontin, but this enhancement is also a function of the activation state of alpha(v)beta(3). Moreover, they indicate that the sequence RGDSVVYGLR contains sufficient information to specify activation-dependent alpha(v)beta(3)-mediated platelet and lymphocyte adhesion.

Adenosine Diphosphate