Regular ArticleDetection of Platelet Aggregates with a Particle Counting Method Using Light Scattering
Abstract
A novel method to detect platelet aggregation by means of the particle counting technique using light scattering has been developed. An optical device designed to focus on a limited area of platelet-rich plasma measured the intensity of light scattered by particles passing through the area, minimizing multiple light scattering. The use of polystyrene spheres of different diameters confirmed that the light scattering intensity increases in proportion to the particle size in a suspension. Platelet activation induced by various agonists resulted in light scattering of higher intensities, which correlated well with the number and size of aggregates as observed under a microscope. These findings confirmed that the intensity of light scattering detected by the new device provides information on the number and size of aggregates in a suspension. The new method was compared with conventional platelet aggregometry using overall light scattering or changes in light transmission (optical density). The new device appeared to be particularly sensitive to small aggregates such as those formed in platelet activation induced by low concentrations of agonists. Furthermore, the new method has an advantage over the conventional aggregometry, in that it allows the aggregate size distribution and the extent of aggregation to be estimated.
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Safety of Tailored Transfemoral Carotid Artery Stenting for Symptomatic Elderly Patients: A Single Center Observational Study
2024, World NeurosurgeryTransfemoral carotid artery stenting (TFCAS) in symptomatic elderly patients (≥70 years old) may have a high periprocedural stroke rate. This study was performed to examine whether tailored TFCAS for symptomatic elderly patients is as safe as that for symptomatic nonelderly patients.
The subjects were 185 patients with symptomatic internal carotid artery stenosis. Tailored TFCAS including postoperative management was performed based on preoperative examinations of vascular anatomy, plaque imaging, platelet aggregation activity, and cerebral hemodynamic impairment. The major 30-day perioperative stroke rates were examined.
The patients included 51 (27.6%) <70 (group Y) and 134 (72.4%) ≥70 (group E) years old. Group E included significantly more cases with an elongated aortic arch, tortuous target lesion, and longer plaques (all P < 0.05). Among all cases, 181 (97.8%) procedures were performed as per preoperative planning. Group E had more frequent use of a proximal embolic protection device and a closed-cell or dual-layer micromesh stent (all P < 0.05). Seven patients (3.8%) had major stroke. Rates of major ischemic stroke (2.0% vs. 3.0%, P = 1.00) and intracranial hemorrhage (2.0% vs. 0.8%, P = 0.48) were low and did not differ significantly between groups Y and E.
Symptomatic elderly patients have several unfavorable factors. However, tailored TFCAS for each patient based on preoperative examinations in symptomatic elderly patients may be as safe as that in symptomatic nonelderly patients.
Bidirectional effects of dexmedetomidine on human platelet functions in vitro
2015, European Journal of PharmacologyPlatelets express the imidazoline (I)-receptor, I1 and I2, as well as the α2-adrenoceptor. Although dexmedetomidine, a selective α2-adrenoceptor agonist with some affinity for the I-receptor is expected to affect platelet function, the effects of dexmedetomidine on platelet functions remain unclear. In the present study, we investigated the effects of dexmedetomidine on human platelet functions in vitro. The effects of dexmedetomidine on platelet aggregation were examined using aggregometers. The formation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in platelets was measured by an enzyme immunoassay. In addition, P-selectin expression in platelets was estimated by flow cytometry. We showed that dexmedetomidine enhances platelet aggregation. But in the presence of yohimbine, an α2-antagonist, dexmedetomidine suppressed platelet aggregation. Efaroxan, an I1-antagonist, and methylene blue, a soluble guanylate cyclase inhibitor, abolished the suppressive effect of dexmedetomidine, whereas idazoxan, an I2-antagonist, showed no effect. Dexmedetomidine suppressed cAMP formation and enhanced P-selectin expression in platelets, and these effects were inhibited by yohimbine. Dexmedetomidine increased cGMP formation in platelets in the presence of yohimbine, and this increase was suppressed by efaroxan. These results demonstrated that dexmedetomidine has both enhancing and suppressive effects on human platelet functions through its action on the α2-adrenoceptor and on the I1-imidazoline receptor, respectively.
Form From Projected Shadow (FFPS): An algorithm for 3D shape analysis of sedimentary particles
2013, Computers and GeosciencesIn this paper we present a simple and effective method based on measuring the projected shadow of sedimentary particles by means of a digital image processing algorithm that enables the three principal axes of the particle to be determined from a single 2D color image. The method consists in projecting the shadow of the particle when it is resting on the maximum projection area (“c” axis pointing almost vertical, since in this configuration minimal distance from the center of mass to the floor is achieved minimizing the gravitational potential energy), by means of an oblique incident illumination system. Using HSL (hue-saturation-lightness) color space segmentation, two axes of the particle are measured directly from the maximum projected area. The length of the shadow provides the third axis of the particle. Multiple textured and colored sedimentary particles can be easily segmented from a green background and their corresponding shadows by means of a single space color transformation. This simple method enables the lengths of the three main axes of several particles to be determined at the same time without expensive equipment (the software is provided free by the authors). The axis lengths can span a broad range of sizes, and are measured with low experimental error (less than 5%).
Platelet aggregometry in the presence of PGE<inf>1</inf> provides a reliable method for cilostazol monitoring
2012, Thrombosis ResearchCitation Excerpt :The aggregation experiments were completed within 2.5 hours after blood sampling. Platelet aggregation was performed using light transmittance aggregometry (LTA) according to the method previously reported [16]. In brief, platelet aggregation was assessed using PRP by light transmittance in a four channel aggregometer (PA-200, Kowa Corp.
Cilostazol has been shown to be effective for prevention and treatment of cerebral infarction. However, there appears to be no widely accepted method appropriate for monitoring cilostazol. We attempted to establish an assay system for cilostazol monitoring, using platelet aggregation induced by arachidonic acid (AA) in the presence of PGE1 which upregulates intracellular cyclic AMP.
Blood was drawn from stroke patients before and after cilostazol intake. AA-induced platelet aggregation after pretreatment with 0 ~ 30 nM PGE1 for 2 minutes was measured by light transmittance aggregometry.
AA-induced platelet aggregation was 73.1 ± 2.2% in the absence of PGE1, and pretreatment with 30 nM PGE1 had virtually no inhibitory effect on platelet aggregation prior to cilostazol intake. In contrast, after cilostazol intake, 30 nM PGE1 significantly inhibited platelet aggregation to 12.7 ± 4.5% (p = 7.8 × 10(− 11)) , while in the absence of PGE1 platelet aggregation remained similar to that of prior-to-cilostazol value (70.6 ± 3.5%). The plasma concentration of cilostazol ranged from 0.55 to 3.51 μM. In the presence of 30 nM PGE1, all the patients with cilostazol concentrations exceeding 1 μM had their platelet aggregation inhibited almost completely. ROC analysis suggests that AA-induced platelet aggregation in the presence of 30 nM PGE1 had the excellent sensitivity (90.5%) and specificity (88.4%) for monitoring cilostazol.
AA-induced platelet aggregation in the presence of 30 nM PGE1 could give good estimate on plasma concentrations of cilostazol. It is suggested that this system is a good tool for monitoring cilostazol.
Spontaneous platelet aggregation evaluated by laser light scatter in patients with type 2 diabetes: Effects of short-term improved glycemic control and adiponectin
2012, Translational ResearchSpontaneous platelet aggregation (SPA) is enhanced in patients with type 2 diabetes. Adiponectin may inhibit platelet aggregation. The aims of the current study were to identify factors associated with in vitro SPA measured by a laser light scattering method and to investigate the effects of short-term glycemic control and adiponectin on SPA. In study 1, we investigated platelet aggregation in 20 healthy control subjects and 82 patients with type 2 diabetes. In study 2, we evaluated the changes of SPA and serum high-molecular-weight (HMW) adiponectin after 2 weeks of improved glycemic control in 20 hospitalized diabetic patients. In study 3, using washed platelets from 10 healthy subjects, in vitro SPA was measured over 15 min in the absence or presence of recombinant adiponectin (20 μg/mL). Platelet aggregation was assessed with a laser light scatter aggregometer that measured the size of platelet aggregates. SPA was defined as formation of small aggregates under constant stirring in the absence of any agonists. The area under the curve was calculated for SPA and also for agonist-induced small, medium, and large aggregates. SPA was increased in diabetic patients compared with control subjects. In diabetic patients, SPA was correlated positively with plasma fibrinogen, fasting plasma glucose, glycated albumin, and high-sensitivity C-reactive protein. A stepwise multivariate analysis showed that plasma fibrinogen was the strongest independent determinant of SPA in diabetic patients. In 20 diabetic patients, SPA decreased significantly after 2 weeks of glycemic control. A significant negative correlation was found between changes of SPA and those of HMW adiponectin during treatment. The in vitro study showed that adiponectin inhibited the spontaneous aggregation of washed platelets. In conclusion, hyperfibrinogenemia and hyperglycemia are associated independently with SPA in patients with type 2 diabetes. SPA is reduced after even short-term improvement of glycemic control and adiponectin also inhibits SPA directly.
Non-invasive diffuse optical neuromonitoring during cardiopulmonary resuscitation predicts return of spontaneous circulation
2021, Scientific Reports