Search

Objective: Aim: The aim of the work was to study the ef f ect of photobiomodulation therapy on the regulation of disorders in the healing of chronic wounds at the remodeling stage using indicators of platelet aggregation activity, reactive oxygen species, platelet-derived growth factor, and interleukin-1β., Patients and Methods: Materials and Methods: The study included 3 groups of Wistar rats: intact animals and animals of the control and experimental groups, for which chronic wounds were simulated. Rats in the experimental group received photobiomodulation therapy once a day for 5 days. Wound defects of animals in the control group were fictitiously irradiated. The levels of reactive oxygen species, platelet-derived growth factor, and interleukin-1β in the blood serum of animals were studied by enzyme immunoassay. The functional activity of platelets was measured on a computerized platelet aggregation analyzer using the turbidimetric method. Histological studies were carried out., Results: Results: Changes in the expression of the studied indicators were found in the blood serum of animals with chronic wounds when using photobiomodulation therapy: an increase in platelet-derived growth factor concentrations, the levels of reactive oxygen species and interleukin-1β did not have statistically signif i cant differences compared to the corresponding indicators of animals in the control group. There were no significant differences in the indicators of platelet aggregation activity in the control and experimental groups of animals., Conclusion: Conclusions: The findings suggest that photobiomodulation therapy may promote wound healing by increasing platelet-derived growth factor levels. Histological studies have shown that using photobiomodulation therapy helps reduce inflammation and better organization of collagen fibers in animals of the experimental group.

Thrombocytopenia is a major complication in hematopoietic-acute radiation syndrome (H-ARS) that increases the risk of mortality from uncontrolled hemorrhage. There is a great demand for new therapies to improve survival and mitigate bleeding in H-ARS. Thrombopoiesis requires interactions between megakaryocytes (MKs) and endothelial cells. 16, 16-dimethyl prostaglandin E2 (dmPGE2), a longer-acting analogue of PGE2, promotes hematopoietic recovery after total-body irradiation (TBI), and various angiotensin-converting enzyme (ACE) inhibitors mitigate endothelial injury after radiation exposure. Here, we tested a combination therapy of dmPGE2 and lisinopril to mitigate thrombocytopenia in murine models of H-ARS following TBI. After 7.75 Gy TBI, dmPGE2 and lisinopril each increased survival relative to vehicle controls. Importantly, combined dmPGE2 and lisinopril therapy enhanced survival greater than either individual agent. Studies performed after 4 Gy TBI revealed reduced numbers of marrow MKs and circulating platelets. In addition, sublethal TBI induced abnormalities both in MK maturation and in in vitro and in vivo platelet function. dmPGE2, alone and in combination with lisinopril, improved recovery of marrow MKs and peripheral platelets. Finally, sublethal TBI transiently reduced the number of marrow Lin-CD45-CD31+Sca-1- sinusoidal endothelial cells, while combined dmPGE2 and lisinopril treatment, but not single-agent treatment, accelerated their recovery. Taken together, these data support the concept that combined dmPGE2 and lisinopril therapy improves thrombocytopenia and survival by promoting recovery of the MK lineage, as well as the MK niche, in the setting of H-ARS., (©2021 by Radiation Research Society. All rights of reproduction in any form reserved.)

Nitric oxide, NO, has been explored as a therapeutic agent to treat thrombosis. In particular, NO has potential in treating mechanical device-associated thrombosis due to its ability to reduce platelet activation and due to the central role of platelet activation and adhesion in device thrombosis. Nitrite is a unique NO donor that reduces platelet activation in that it's activity requires the presence of red blood cells whereas NO activity of other NO donors is blunted by red blood cells. Interestingly, we have previously shown that red blood cell mediated inhibition of platelet activation by adenosine diphosophate (ADP) is dramatically enhanced by illumination with far-red light that is likely due to photolysis of red cell surface bound NO congeners. We now report the effects of nitrite, far-red light, and their combination on several measure of blood coagulation using a variety of agonists. We employed turbidity assays in platelet rich plasma, platelet activation using flow cytometry analysis of a fluorescently labeled antibody to the activated platelet fibrinogen binding site, multiplate impedance-based platelet aggregometry, and assessment of platelet adhesion to collagen coated flow-through microslides. In all cases, the combination of far-red light and nitrite treatment decreased measures of coagulation, but in some cases mono-treatment with nitrite or light alone had no effect. Perhaps most relevant to device thrombosis, we observed that platelet adhesions was inhibited by the combination of nitrite and light treatment while nitrite alone and far-red light alone trended to decrease adhesion, but the results were mixed. These results support the potential of combined far-red light and nitrite treatment for preventing thrombosis in extra-corporeal or shallow-tissue depth devices where the far-red light can penetrate. Such a combined treatment could be advantageous due to the localized treatment afforded by far-red light illumination with minimal systemic effects. Given the role of thrombosis in COVID 19, application to treatment of patients infected with SARS Cov-2 might also be considered., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Our previous study showed that ultraviolet C (UVC) from xenon (Xe) flash without any photoreactive compounds inactivated bacteria in platelet concentrates (PCs) with less damage to platelets (PLTs) as compared with Xe flash containing ultraviolet A, ultraviolet B, and visible light. Here, we report a UVC irradiation system for PCs under flow conditions consisting of a flow path-irradiation sheet, a peristaltic pump, and a collection bag., Study Design and Methods: Platelet concentrates containing Ringer's solution (R-PCs) inoculated with bacteria were injected into a flow path sheet using a peristaltic pump, being irradiated with UVC from Xe flash. The quality of the irradiated PCs containing platelet additive solution (PAS-PCs) was assessed based on PC variables, PLT surface markers, and aggregation ability., Results: Streptococcus dysgalactiae (12 tests) and Escherichia coli (11) were all negative on bacterial culture, while Staphylococcus aureus (12) and Klebsiella pneumoniae (14) grew in one and two R-PCs, respectively. Bacillus cereus spores were inactivated in 7 of 12 R-PCs. PC variables became significantly different between irradiated and nonirradiated PAS-PCs. P-selectin, first procaspase-activating compound (PAC-1) binding, and phosphatidylserine increased by irradiation. Aggregability stimulated by adenosine diphosphate, collagen, or thromboxane A 2 increased in the irradiated PAS-PCs, while that by thrombin became smaller compared with nonirradiated controls., Conclusion: This newly developed system inactivated bacteria including spores in R-PCs. PAS-PCs irradiated by this system retained acceptable in vitro quality and aggregability. Usage of a peristaltic pump instead of agitator during irradiation may enable this system to be directly combined with an apheresis blood cell separator., (© 2020 AABB.)

Extracorporeal circulation causes many deleterious effects on blood cells. Low-level light therapy (LLLT) in the red/near-infrared spectral range is known for its cytoprotective properties but its use during cardiopulmonary bypass (CPB) has not yet been studied. We aimed to assess whether LLLT protects platelets during CPB. 24 pigs were connected to 1-hour-CPB and observed for the next 23 hours. In 12 animals, blood circulating through the oxygenator was treated with LLLT. Platelet count and function were monitored throughout the experiment. The decrease in platelet count was greater in the control group, especially during CPB and after 24 hours. In LLLT group CD62P expression remained quite stable up to the 12 th hour of the experiment, whereas in the control group it continuously decreased till the end of observation. Platelets in the control group were more prone to aggregation in the postoperative period than at the beginning of the experiment, whereas platelets in the LLLT group aggregated similarly or less intense. Limitation of platelet loss, pattern of aggregation and CD62P expression suggest that LLLT may stabilize platelet function during CPB and diminish the negative effects associated with the interaction of cells with an artificial surface.

Background: Cryopreserved platelets (CPPs) are considered a promising approach for extended platelet storage, bridging inventory shortages of conventionally stored platelets. It is unknown if platelet concentrates exposed to photochemical treatment (PCT) with amotosalen and ultraviolet A (UVA) light, to inactivate pathogens, are suitable for freezing. The objective of this study was to analyze potential effects of PCT on CPPs as compared with untreated CPPs., Study Design and Methods: A total of 12 PCT-treated and 12 untreated platelet units from buffy coats were cryopreserved at -80°C in 5% dimethyl sulfoxide. CPPs of both types were rapidly thawed at 37°C and resuspended in 200 mL fresh plasma. In vitro properties were analyzed prefreezing, postfreezing and thawing, and on Day 1 after thawing., Results: Directly after thawing, no major differences in platelet content, lactase hydrogenase, adenosine triphosphate, mitochondrial membrane potential, CD62P, CD42b, and platelet endothelial cell adhesion molecule were seen between PCT-CPPs and conventional CPPs. Agonist-induced PAC-1 expression and contribution of CPPs to blood coagulation in an experimental rotational thromboelastometry setup were also similar between the groups. On Day 1 after thawing, the CPPs of both types performed less well. The PCT-CPPs tended to be more affected by the freezing process than the conventional CPPs., Conclusions: PCT-CPPs appeared slightly more susceptible to lesion effects by freezing than conventional CPPs, in particular in assays on Day 1 after thawing, but these differences were small relative to the dramatic effects of the freezing process itself., (© 2018 AABB.)

The review of blood optical and rheological parameters plays an important role in many medical routine diagnosis and therapeutic applications and is the best way to understand the mechanism of action of low-level laser irradiation on biological tissues. The aim of this study was to investigate the in vitro effect of laser radiation on platelet count and aggregation. Blood samples were obtained from 30 healthy volunteers; each sample was divided into four aliquots, one of them was considered as a control while the other three were exposed to three different laser doses. A wavelength of 532 nm and a low power of 100 mW were used for irradiation with a 4-mm-diameter beam spot. The irradiation times were 1.8, 3.7, and 6.2 s giving doses of irradiation 1.5, 3, and 5 J/cm 2 , respectively. Microsoft Excel was used for statistical analysis. Low laser irradiation induced significant changes in platelet aggregation in the presence of weak agonists such as adenosine diphosphate (ADP) (P ≤ 0.05) and epinephrine (P ≤ 0.01). Low-level laser therapy has no influence on platelet count; however, it promotes platelet aggregation in response to weak agonists, specifically ADP and epinephrine.

Background: Our previous study revealed that pathogen-reducing filtered xenon flash-treated platelets (fXe-PLTs) showed sustained aggregation in response to adenosine diphosphate (ADP), but apheresis-collected PLTs (Aph-PLTs) showed reversible aggregation., Study Design and Methods: Aph-PLTs, fXe-PLTs, and freshly prepared PLTs (PRP-PLTs) from whole blood were used to investigate the following responses to ADP: concentration response and effects of ADP receptor antagonists on aggregation, the cytosolic calcium (Ca 2+ ) flux downstream of P2Y 1 receptor signaling, and phosphorylation of vasodilator-stimulated phosphoprotein (VASP) and signaling intermediate protein Akt downstream of the P2Y 12 receptor., Results: The aggregation of Aph-PLTs by ADP (10 µM) changed from reversible to sustained in an fXe flash dose-dependent manner. The concentration-response curve of Aph-PLTs showed a fivefold higher 50% effective concentration compared with PRP-PLTs, and fXe treatment decreased it to threefold. While the basal Ca 2+ level was higher both in Aph- and fXe-PLTs than in PRP-PLTs, the increase of cytosolic Ca 2+ by ADP remained unchanged in Aph- and PRP-PLTs, but was slightly reduced in fXe-PLTs. Although the forskolin-induced VASP phosphorylation was significantly reduced in Aph-PLTs, and partially restored by the fXe treatment, ADP stimulation attenuated this phosphorylation to an equivalent extent among the three PLT types. The ADP-stimulated time-dependent Akt phosphorylation was weak in Aph-PLTs, whereas fXe-PLTs and PRP-PLTs showed a marked increase., Conclusion: These results indicate that the reversible aggregation of Aph-PLTs is the consequence of insufficient Akt phosphorylation. The fXe treatment restores the increase of phosphorylated Akt, resulting in the sustained aggregation of fXe-PLTs similar to those of PRP-PLTs., (© 2018 AABB.)

Amotosalen and ultraviolet A (UVA) photochemical-based pathogen reduction using the Intercept™ Blood System (IBS) is an effective and established technology for platelet and plasma components, which is adopted in more than 40 countries worldwide. Several reports point towards a reduced platelet function after Amotosalen/UVA exposure. The study herein was undertaken to identify the mechanisms responsible for the early impairment of platelet function by the IBS. Twenty-five platelet apheresis units were collected from healthy volunteers following standard procedures and split into 2 components, 1 untreated and the other treated with Amotosalen/UVA. Platelet impedance aggregation in response to collagen and thrombin was reduced by 80% and 60%, respectively, in IBS-treated units at day 1 of storage. Glycoprotein Ib (GpIb) levels were significantly lower in IBS samples and soluble glycocalicin correspondingly augmented; furthermore, GpIbα was significantly more desialylated as shown by Erythrina Cristagalli Lectin (ECL) binding. The pro-apoptotic Bak protein was significantly increased, as well as the MAPK p38 phosphorylation and caspase-3 cleavage. Stored IBS-treated platelets injected into immune-deficient nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice showed a faster clearance. We conclude that the IBS induces platelet p38 activation, GpIb shedding and platelet apoptosis through a caspase-dependent mechanism, thus reducing platelet function and survival. These mechanisms are of relevance in transfusion medicine, where the IBS increases patient safety at the expense of platelet function and survival., (Copyright© 2017 Ferrata Storti Foundation.)

Background: Significant concerns are now regularly raised about the safety of excessive mobile phone use. This study was aimed to assess the acute effects of radiofrequency waves emitted by a commercial smartphone on platelet function., Materials and Methods: Two sequential citrated blood samples were collected from 16 healthy volunteers recruited from laboratory staff. The first sample was placed in a plastic rack, 1 cm distant from a commercial smartphone receiving a 30-min call and emitting 900 MHz radiofrequency waves. The second sample was placed in another plastic rack, isolated from radiofrequency wave sources, for the same period. The platelet count and the mean platelet volume were then assessed in all blood samples, whereas platelet function was evaluated using the platelet function analyser-100 (PFA-100)., Results: A 30-min exposure of citrated blood to smartphone radiofrequency waves induced significant prolongation of collagen-epinephrine aggregation (median increase, 10%) and a considerable increase of mean platelet volume (median increase, 5%), whereas collagen-adenosine diphosphate aggregation and platelet count remained unchanged., Discussion: This study demonstrates that smartphone radiofrequency waves induce significant perturbation of platelet structure and function, thus providing further support to concerns regarding excessive use of mobile phones. Caution should also be taken with regards to blood products containing platelets, which should be kept far away from mobile phones and smartphones throughout the production pipeline and storage period.

Background: Ultraviolet (UV) light illumination in the presence of exogenously added photosensitizers has been used to inactivate pathogens in platelet (PLT) concentrates for some time. The THERAFLEX UV-C system, however, illuminates PLT concentrates with UV-C light without additional photoactive compounds. In this study residual PLT function is measured in a comprehensive paired analysis of UV-C-treated, gamma-irradiated, and untreated control PLT concentrates., Study Design and Methods: A pool-and-split design was used with buffy coat-derived PLT concentrates in 65% SSP+ additive solution. Thrombus formation kinetics in microfluidic flow chambers onto immobilized collagen was investigated with real-time video microscopy. PLT aggregation, membrane markers, and cellular metabolism were determined concurrently., Results: Compared to gamma-treated and untreated controls, UV-C treatment significantly affected thrombus formation rates on Days 5 and 7, not Day 2. PLT degranulation (P-selectin) and PLT apoptosis (annexin V binding) was slightly but significantly increased from Day 2 on. UV-C treatment moreover induced integrin αIIb β3 conformational changes reminiscent of activation. However, subsequent integrin activation by either PAR1-activating hexapeptide (PAR1AP) or convulxin was unaffected. This was confirmed by PLT aggregation studies induced with collagen, PAR1AP, and ristocetin at two different agonist concentrations. Finally, UV-C slightly increased lactic acid production rates, resulting in significantly decreased pH on Days 5 and 7, but never dropped below 7.2., Conclusion: UV-C pathogen inactivation treatment slightly but significantly increases PLT activation markers but does not profoundly influence activatability nor aggregation. The treatment does, however, attenuate thrombus formation kinetics in vitro in microfluidic flow chambers, especially after storage., (© 2015 AABB.)

It is shown that during incubation after UV irradiation (22-24 hours at 7-9 degrees C) irradiated isolated rabbit leukocytes release the compound(s) which induces platelets aggregation in the native platelet rich plasma. Treatment of the incubation media of irradiated leukocytes by heat (5 minutes at 100 degrees C) does not significantly change its pro-aggregation activity. Treatment of the platelet-rich plasma by the incubation media of irradiated leukocytes without stirring induces the refractoriness of platelets to ADP. The platelets treated by ADP without stirring do not react to the incubation media of irradiated leukocytes. The absorption spectrum of the incubation media of irradiated leukocytes has the maximum at 260 nm similar to that of the absorption spectra of ADP. It is possible that UVradiation induces the ADP release from leukocytes during post-irradiation incubation. Accumulation of this substance in the incubation media may be the cause of its pro-aggregation activity for native blood platelets.

Background: The adoption of pathogen reduction technology (PRT) is considered for the implementation of safer platelet (PLT) transfusion. However, the effects of PRT treatment on PLT thrombus formation under blood flow have not yet been fully clarified., Study Design and Methods: Leukoreduced PLT concentrates (PCs) obtained by plateletpheresis were treated with riboflavin and ultraviolet light (Mirasol PRT). PC samples were passed through a column filled with collagen-coated beads at a fixed shear rate after 1, 3, and 5 days of storage. The thrombus formation ability was evaluated by measuring collagen column retention rate. The change in the activation state of integrin αIIbβ3 on PLTs during storage was examined by flow cytometry., Results: The retention rate of the PRT-treated PLTs was significantly higher than that of the control PLTs on the day of treatment and decreased with storage but remained higher than those of the control during storage. This modification did not correlate with the total αIIbβ3 or fibrinogen binding on the PLTs but correlated significantly with PAC-1 binding. Mn(2+) -induced αIIbβ3 activation also fully restored the retention rate in the Day 5 PRT-treated PLTs along with the increase in PAC-1 binding., Conclusion: Riboflavin-based PRT treatment of PCs leads to the enhancement of thrombus formation on collagen, which is related to the activation status of αIIbβ3, which does not bind to fibrinogen but binds to PAC-1. The impact of this finding on the hemostatic or even thrombogenic potential in vivo must await clinical evaluation., (© 2014 AABB.)

Platelets are subjected to extremely low frequency electromagnetic fields during standard aggregometry measurements owing to the use of a magnetic stir bar in the instrument. This study evaluates the effects of this magnetic field exposure on platelet aggregation by comparing the results obtained in a modified aggregometer. Blood samples from healthy volunteers were anticoagulated using citrate or heparin. Platelet-rich plasma (PRP) samples were prepared. A mechanical stirring device was attached to the aggregometer instead of the magnetic stir bar system. The PRP samples were stirred using a stirring rod tip that did not produce any magnetic fields in one channel of the aggregometer; in the other channel, a stirring rod carrying a small magnet at its tip was used. As a result, a magnetic field in the extremely low frequency range and in the amplitude range of 1.9-65 mT was applied to the platelets assigned to the channel where the magnetic stirring rod tip was used. Aggregation was induced using adenosine diphosphate (ADP), collagen, or epinephrine. The slopes, maximum aggregation values, and areas under the aggregation curves were compared between the magnetic and neutral stirring rod tip groups. For samples stirred with the magnetic stirring rod tip, a significant decrease was observed in 12 of the 14 parameters evaluated for aggregations induced with ADP or collagen compared to the neutral stirring rod tip, regardless of the method used for anticoagulation. This observation indicates that the magnetic stir bars used in standard aggregometry may significantly alter aggregation parameters and platelets may be possible targets of electromagnetic fields., (Copyright © 2013 Wiley Periodicals, Inc.)

Background: We recently reported that infusion of ultraviolet light B (UVB)-exposed human platelets (HPs) can be the second event that mediates acute lung injury (ALI) in a two-event mouse model of transfusion-related acute lung injury (mTRALI). We have now identified changes in HPs induced by UVB light and responses of the recipient animal that mediate the mTRALI., Study Design and Methods: Effects of UVB on HPs were monitored by flow cytometry and aggregation. HPs exposed to UVB, with or without inhibitors to specific biochemical pathways, were infused into lipopolysaccharide (LPS)-primed severe combined immunodeficient (SCID) mice. ALI was monitored by protein elevations in bronchoalveolar lavage fluid (BALF)., Results: UVB increased fibrinogen binding and potentiated HP aggregation. Infusion of UVB HPs into LPS-primed SCID mice led to macrophage inflammatory protein 2 (MIP-2) elevations in plasma and BALF and resulted in ALI. Protein kinase C (PKC) inhibitors prevented UVB-induced HP changes in vitro and reduced MIP-2 elevation and mTRALI in vivo. Blocking of fibrinogen binding to HP αIIbβ3 with c7E3 monoclonal antibody prevented mTRALI. MIP-2 elevation in vivo in response to UVB HPs was essential for ALI since blocking of MIP-2 receptor in vivo prevented mTRALI., Conclusion: PKC signaling mediates UVB-induced HP fibrinogen binding and aggregation in vitro. The host animal responds to an infusion of UVB HPs by MIP-2 elevation that mediates downstream mTRALI. Elucidation of molecular mechanisms in UVB HP-mediated mTRALI may provide insight into pulmonary adverse events reported with UV-irradiated pathogen-reduced platelets., (© 2012 American Association of Blood Banks.)

Purpose: Electromagnetic fields have various effects on intracellular calcium levels, free oxygen radicals and various enzymes. The platelet activation pathway involves an increase in intracellular calcium levels and protein kinase C activation; and free oxygen radicals play a mediating role in this pathway. This study investigated whether 1 mT and 6 mT, 50 Hz magnetic fields had any effects on platelet aggregation., Materials and Methods: Blood from healthy volunteers was anticoagulated with either citrate or heparin. Each sample was divided in half and assigned to exposure and control groups. Platelet rich plasma samples in the exposure group were exposed to a 1 mT or a 6 mT, 50 Hz magnetic field for 1.5 or 1 h, respectively. The samples from both exposure and control groups were simultaneously evaluated using a modified optical aggregometer. Adenosine-diphosphate, collagen, and epinephrine were used as inducing agents. The slopes of the aggregation curve, the maximum values and the areas under the curves were recorded and compared., Results: A significant effect was observed only in the 1 mT-citrate group. It was found that magnetic field exposure significantly increased the maximum values and slopes of the collagen-induced aggregations., Conclusions: It was found that magnetic field exposure has an activating effect on platelet aggregation.

Background: We previously showed that irradiation to the carotid arteries of ApoE(-/-) mice accelerated the development of macrophage-rich, inflammatory atherosclerotic lesions, prone to intra-plaque hemorrhage. In this study we investigated the potential of anti-inflammatory and anti-coagulant intervention strategies to inhibit age-related and radiation-induced atherosclerosis., Methodology/principal Findings: ApoE(-/-) mice were given 0 or 14 Gy to the neck and the carotid arteries and aortic arches were harvested at 4 or 30 weeks after irradiation. Nitric oxide releasing aspirin (NCX 4016, 60 mg/kg/day) or aspirin (ASA, 30 or 300 mg/kg/day) were given continuously in the chow. High dose ASA effectively blocked platelet aggregation, while the low dose ASA or NCX 4016 had no significant effect on platelet aggregation. High dose ASA, but not NCX 4016, inhibited endothelial cell expression of VCAM-1 and thrombomodulin in the carotid arteries at 4 weeks after irradiation; eNOS and ICAM-1 levels were unchanged. After 30 weeks of follow-up, NCX 4016 significantly reduced the total number of lesions and the number of initial macrophage-rich lesions in the carotid arteries of unirradiated mice, but these effects were not seen in the brachiocephalic artery of the aortic arch (BCA). In contrast, high dose ASA lead to a decrease in the number of initial lesions in the BCA, but not in the carotid artery. Both high dose ASA and NCX 4016 reduced the collagen content of advanced lesions and increased the total plaque burden in the BCA of unirradiated mice. At 30 weeks after irradiation, neither NCX 4016 nor ASA significantly influenced the number or distribution of lesions, but high dose ASA lead to formation of collagen-rich "stable" advanced lesions in carotid arteries. The total plaque area of the irradiated BCA was increased after ASA, but the plaque burden was very low compared with the carotid artery., Conclusions/significance: The development and characteristics of radiation-induced atherosclerosis varied between different arteries but could not be circumvented by anti-inflammatory and anti-coagulant therapies. This implicates other underlying mechanistic pathways compared to age-related atherosclerosis.

Intensive terahertz irradiation at the nitric oxide emission and absorption spectrum frequencies (150.176-150.664 GHz) applied for 60 min to male albino rats subjected to acute immobilization stress enhanced platelet aggregation and induced signs of depression.

Background: To examine if different pathogen-reduction technologies (PRTs) induce different degrees of platelet (PLT) storage lesion., Design: Twenty-seven split triple-dose apheresis PLTs were PRT treated using ultraviolet light with either riboflavin (M) or psoralen (I) or remained untreated (C). Samples taken on days (d) 0 to 8 were analysed for PLT count, blood gas (pH, pO(2) and pCO(2)), metabolism (lactate, glucose, ATP content), in vitro function [swirling, hypotonic shock response (HSR) and aggregation], activation (p-selectin expression) and cellular integrity (JC-1 signal, annexin A5 release)., Results: Platelet counts of all study groups remained unchanged during storage indicating that PRT treatment did not induce relevant cell lysis. Although M units demonstrated the highest values for HSR until d5, PRT treatment lowered all parameters examined with significant differences to untreated controls by d7 of storage. During final storage, M was significantly superior over I for HSR, aggregation with TRAP-6 as agonist (collagen was similar), annexin A5 release and JC-1 signal. Regarding blood gas and metabolic analysis, the most evident effect of PRT was an elevated glycolytic flux combined with higher acidity due to increased lactate accumulation. Most likely due to impaired O(2) consumption, pH and ATP decreased more rapidly in I relative to C and M., Conclusion: Pathogen reduction technology-treated PLTs remained comparable to untreated units throughout 7 days of storage. Mitochondria-based oxidative respiration appeared up-regulated after the riboflavin-based PRT. Compared to the psoralen-based PRT, this resulted in significantly better ATP maintenance and in vitro function during the last storage period (d7, d8).

The experiment with essentially healthy male subjects no older than 50 involved functional load testing and irradiation by a low-energy helium-neon laser according to the standard therapeutic regimen (0.2 ml/V/ 30 min/10 sessions). Biomedical evaluation of hemoaggregation was made by 30 parameters of a multifunctional diagnostic system characterizing three blood aggregation levels: rheological (biophysical), coagulolytic (biochemical) and system (mathematical). The investigation resulted in delineation of a single-vector hypodynamic transformation of biophysical and biochemical modules, i.e. decrease in the rheological and coagulative potential mediated by a moderate platelets disaggregation (24.6%) and hyperactivation of plasmin proferments in euglobulin fraction (126.76 %). Added sessions of percutaneous laser irradiation of blood were shown to induce a medium imbalance of biophysical and biochemical hemoaggregation. At the same time, low-energy laser did not modulate significantly the general functional state of human operator as the rheological and coagulative protective potential of organism remained reasonably high (88.89 and 87.5 %, respectively).

The purpose of the investigation was to study the impact of low-intensity laser therapy (LILT) on platelet aggregatory properties in patients with chronic pancreatitis (CP) on an exacerbation. A total of 105 patients aged 36 to 77 years who were divided into a study group (n = 60) and a control one (n = 45) were examined. Thirty persons who formed a healthy group were additionally examined. In the study group patients, drug therapy was supplemented by LILT via various methods. The control group received only drug therapy. The investigation revealed that patients with CP on an exacerbation showed diverse changes in platelet aggregatory properties towards hyperaggregation. LILT was ascertained to have a normalizing effect on platelet aggregatory properties in the study group patients.

UV-C irradiation has been shown to be effective for pathogen reduction in platelet concentrates, but preliminary work indicated that UV-C irradiation of platelets can induce platelet aggregation. In this study, the mechanism underlying this phenomenon was investigated. Irradiation of platelets with UV-C light (1500 J/m(2)) caused platelet aggregation, which was dependent on integrin alphaIIbbeta3 activation (GPIIb/IIIa). This activation occurred despite treatment with several signal transduction inhibitors known to block platelet activation. UV-C also induced activation of recombinant alphaIIbbeta3 in Chinese hamster ovary (CHO) cells, an environment in which physiologic agonists fail to activate. Activation of alphaIIbbeta3 requires talin binding to the beta3 tail, yet alphaIIbbeta3-Delta724 (lacking the talin binding site) was activated by UV-C irradiation, excluding a requirement for talin binding. The UV-C effect appears to be general in that beta(1) and beta(2) integrins are also activated by UV-C. To explain these findings, we investigated the possibility of UV-C-induced photolysis of disulfide bonds, in analogy with the activating effect of reducing agents on integrins. Indeed, UV-C induced a marked increase in free thiol groups in platelet surface proteins including alphaIIbbeta3. Thus, UV-C appears to activate alphaIIbbeta3 not by affecting intracellular signal transduction, but by reduction of disulfide bonds regulating integrin conformation.

Objective: We investigated the degree and the time course of endothelial injury in mice pretreated with lethal or reduced-intensity irradiation administered before transplantation., Materials and Methods: Six- to eight-week-old female mice were randomly allocated into three groups: lethal-intensity irradiation (8.5 Gy, group 1), reduced-intensity irradiation (5.0 Gy, group 2), or nonirradiated controls (group 3). After conditioning, circulating endothelial cells (CD31+, CD133(-), and CD45low) and peripheral blood CD4+ or CD8+ T-lymphocyte subpopulations were enumerated using flow cytometry at various times. The morphologic changes in endothelium were examined at phase-contrast light microscopy., Results: Circulating endothelial cells showed an earlier and higher peak in the lethal irradiation group compared with the reduced-intensity irradiation group, which exhibited a protean elevation in cell numbers. There were no visible histopathologic changes during the early stage of endothelial damage., Conclusions: Lethal and reduced doses of irradiation induced endothelial injury in a dose-dependent manner. Endothelial damage may occur before graft-vs-host disease and its related complications.

Background: The aim of this study was to examine the effects of a new riboflavin-based pathogen reduction technology (PRT), the Mirasol PRT process (Navigant Biotechnologies) on platelet (PLT) storage lesion development., Study Design and Methods: A three-arm in vitro study was conducted comparing cell quality of apheresis PLTs (n = 12 each) treated with Mirasol PRT (M) to untreated (C) and gamma-irradiated units (X) collected from the same donors and stored for up to 7 days under equal conditions., Results: PLT count, lactate dehydrogenase, and K+ release of M units were not significantly different from C units, indicating retention of cell integrity during storage. The immediate effect (Day 1) of PRT treatment was a significant decrease in hypotonic shock response (M, 80.6 +/- 7.8% vs. 89.2 +/- 8.3%) and aggregation (M, 85.7 +/- 15.2%/min vs. 111.8 +/- 31.5%/min) as well as a significant acceleration of mitochondrial membrane depolarization (M, 1.43 +/- 0.44% vs. 0.91 +/- 0.27%) and P-selectin expression (M, 38.4 +/- 13.8% vs. 15.8 +/- 7.7%) resulting in lower swirl scores on Day 5 (1.5 +/- 0.7 vs. 2.7 +/- 0.4). Significantly higher glucose consumption (60 +/- 13 nmol/10(12) cells/hr vs. 31 +/- 9 nmol/10(12) cells/hr) and lactate production rates (82 +/- 17 nmol/10(12) cells/hr vs. 40 +/- 8 nmol/10(12) cells/hr) caused higher acidity in treated units (pH on Day 5, 6.97 +/- 0.15 vs. 7.42 +/- 0.10). After PRT treatment, oxidative metabolism was still active and, from calculation of oxygen consumption (1.09 +/- 0.23 nmol/min/10(9) PLTs), appeared to be up regulated relative to controls (0.76 +/- 0.27 nmol/min/10(9) PLTs)., Conclusion: Although storage variables clearly showed the effects of PRT treatment, apheresis PLTs treated with Mirasol PRT retained cell quality during 5 days of storage without loss of mitochondria-based oxidative respiration.

The impact of electromagnetic oscillations of the terahertz band at frequencies of NO radiation and absorption molecular spectrum (150.176-150.664 GHz) for the functional activity of platelets was studied in albino rats exposed to immobilization stress. The effect of these waves was sex-specific: females were more sensitive to radiation than males. Relationship between the terahertz waves and phase of estrous cycle in females was detected: estrus females exhibited maximum sensitivity to these waves.

The authors revealed dependence of reaction blood plates to photoeffect on the dose and rate of blood movement at laser radiation of donor blood in vitro. The red light decreases adhesion and aggregation of blood plates both at high and low rate of shift. Infrared laser radiation is effective only at high rate of shift leading to increase of adhesion and decrease of aggregation of blood plates. Blue laser is effective in small doses only and at low rate of sift it leads to decrease of adhesion and at high rate it provokes increase of adhesion. Blue laser do not have a significant influence on aggregation of blood plates. These results make possible to suppose ambiguity of biological response of venous and arterial blood to radiation.

Background: Amotosalen plus ultraviolet A light photochemical treatment (PCT) inactivates high titers of bacteria, and other pathogens, in platelet concentrates (PCs) potentially allowing the storage of platelets (PLTs) for up to 7 days. Adhesion and aggregation of PLTs to injured vascular surfaces are critical aspects of PLT hemostatic function., Study Design and Methods: Two ABO-identical leukoreduced buffy coat-derived PCs in additive solution were mixed and divided: one-half underwent PCT (PCT-PCs) and the other was kept as a control (C-PCs); both were stored under standard conditions. The total number of paired PCs studied was nine. Samples were taken on Day 1 (before PCT) and after 5 and 7 days of storage. The adhesion and aggregation capacities were evaluated under flow conditions in a ex vivo perfusion model., Results: Compared to control, PCT resulted in a decrease in PLT count of 6.5 percent (p = 0.004) and 10.2 percent (p = 0.008) after 5 and 7 days' storage, respectively (n = 9). PLT interaction with subendothelium was mainly in form of adhesion. The surface covered by PCT PLTs on Day 1 was 26.0 +/- 4.2 percent (mean +/- SEM). On Day 5, PCT-PCs showed a covered surface of 20.9 +/- 2.2 percent, and the C-PCs, 20.6 +/- 1.6 percent. After 7 days, PCT-PCs produced a nonsignificant higher PLT deposition compared to control (27.1 +/- 2.9% vs. 21.2 +/- 2.8%, p = 0.06)., Conclusion: PCT of PCs and storage up to 7 days was associated with a 10.2 percent decrease in PLT count due to processing losses compared to C-PC. PLT adhesive and aggregating capacities under flow conditions of PCT-PCs were similar to C-PCs and remained well preserved for up to 7 days of storage.

Background: Photochemical treatment (PCT) prevents replication of pathogens in platelet concentrates (PCs) by cross-linking nucleic acids and thus affects all cells containing DNA or RNA., Study Design and Methods: Fourteen double-dose single-donor PCs were divided into two study arms. The double-dose PCs were split in two identical units, PCT and conventional control PCs. Study Arm A consisted of seven PCT PCs with corresponding untreated controls, whereas Study Arm B consisted of seven PCT PCs with corresponding gamma-irradiated control. Metabolic changes and agonist-induced platelet (PLT) response were evaluated during storage for up to 12 days., Results: Higher rate of PLT destruction, illustrated by reduced PLT content, increased lactate dehydrogenase levels, and higher CD61+ microparticle formation rate, were observed after PCT. Generally PCT accelerated metabolic changes in PCs and reduced agonist-induced (collagen or thrombin receptor activator peptide [TRAP]) aggregation responses. Flow cytometric analysis of CD62P and CD42b (GPIbalpha) expression showed higher spontaneous PLT activation in PCT PCs from 5 days of storage. Correspondingly, a reduced capacity for up regulation of CD62P expression and down regulation of CD42b was observed in PCT PLTs after stimulation by the agonists ADP or TRAP., Conclusion: Generally reduced in vitro PLT quality was observed after PCT during storage for up to 12 days, with marked reduction from 5 days of storage. Compared to conventional PCs, reduced agonist-induced aggregation and glycoprotein expression were observed after PCT during storage, corresponding to significantly higher level of spontaneous PLT activation in PCT PCs. Clinical studies of efficacy and safety of PCT PCs stored for more than 5 days are recommended.

The influence of electromagnetic waves of terahertz range at the frequencies of molecular spectrum o nitric oxide radiation and absorption on functional activity of thrombocytes in white rats under long-term stress has been studied. It has been shown that courses of THzF treatment applied during the stress can prevent and restore disorders in thrombocytes aggregative function. The stress factor does not induce characteristic of stress-reaction disturbances of microcirculation in animals treated with the preventive course of THzF.

The purpose of the study was to evaluate the influence of low-intensive laser therapy (LILT) on the aggregation properties of thrombocytes in patients with exacerbation of peptic ulcer (PU). The subjects, 111 patients aged 18 to 63, were divided into two groups: the main group (n = 81), and the control group (n = 30). In addition there were 15 healthy people who also underwent examination. Patients in the main group received complex treatment with untiulcer drugs and different methods of laser therapy: intravenous laser irradiation of blood, cutaneous irradiation, and a combination of both. The control group was treated with drugs only. The study found various changes in the aggregation properties of thrombocytes in patients with PU exacerbation, which consisted mostly in hyperaggregation. LILT had a normalizing effect on the aggregation properties of thrombocytes in patients of the main group.

Background: Platelet-rich thrombus formation is a critical event in the onset of cardiovascular disease. Because ADP plays a significant role in platelet aggregation, its metabolism is important in the regulation of platelet activation and recruitment. Ectonucleoside triphosphate diphosphohydrolase (E-NTPDase) is a key enzyme involved in vascular ADP metabolism. We recently isolated 2 isoforms of E-NTPDase from the human placenta. The present study examined whether these isoforms suppress platelet aggregation and thrombus formation after adenovirus-mediated gene transfer to vascular smooth muscle cells (SMCs)., Methods and Results: We constructed adenovirus vectors expressing human placental E-NTPDase isoforms I (AdPlac I) and II (AdPlac II) or bacterial beta-galactosidase (AdLacZ). Vascular SMCs infected with AdPlac I expressed significant NTPDase activity and inhibited the platelet aggregation induced by ADP and collagen in vitro. In contrast, SMCs infected with AdPlac II and AdLacZ did not exert antiplatelet effects. To investigate the antithrombotic and antiproliferative effects of placental E-NTPDase isoform I in vivo, we generated thrombosis in rat carotid arteries by systemically administered rose Bengal and transluminal green light 5 days after gene transfer and examined neointimal growth 3 weeks after thrombus formation. Blood flow in AdLacZ-infected arteries rapidly deteriorated and vanished within 96+/-18 seconds of occlusive thrombus formation. In contrast, blood flow in AdPlac I-infected arteries was preserved for at least 10 minutes during irradiation. In addition, thrombus formation and subsequent neointimal growth were obviously suppressed., Conclusions: The local expression of placental E-NTPDase in injured arteries might prevent arterial thrombosis and subsequent neointimal growth.

With the help of a specially designed generator, we have investigated the effect of electromagnetic SWF-oscillation, at nitric oxide molecular spectrum of radiation and absorption, on the function of thrombocytes and erythrocytes of albino rats in the state of immobilizing stress. 5, 15 and 30 min long SWF-radiation treatments were demonstrated to foster various degrees of restoration of thrombocyte and erythrocyte function, the efficiency depending on the period of radiation. It was after a 30 min radiation of rats that a most expressed restoration of thrombocyte and erythrocyte functional activity was observed.

Resveratrol is one of the major polyphenolics in red wine that has been shown to exert the preventive effects against cardiovascular diseases. The effect of trans-resveratrol (t-RES) administered as an ingredient of the diet on the atherothrombotic tendency was assessed in genetically hypercholesterolemic mice after laser-induced damage on endothelium. Mice lacking both apolipoprotein E and low-density lipoprotein receptor (apoE-/-/LDLR-/-) were fed with a high-fat diet with or without t-RES (9.6 and 96 mg/kg diet) for 8 weeks. The atherosclerotic tendency was morphometrically analyzed in their aortae. The thrombotic tendency was determined by inducing thrombus by the irradiation of a helium-neon laser on carotid arteries of these mice with injection of Evans blue. Atherosclerotic area and thrombus size were evaluated by image analyzing in a computer system. Even though the plasma concentrations of lipids (total cholesterol and triacylglycerol) did not change in the control and t-RES groups, a significant decrease (approximately 30%) in the formation of atheroma was observed in the aortae of the t-RES group. The size of laser-induced thrombus that mostly consisted of platelet aggregates was significantly reduced (approximately 25%) in the t-RES group compared with that in the control group. Thus, t-RES orally administrated with a high-fat diet in apoE-/-/LDLR-/- mice significantly suppressed atherosclerosis in their aortae and reduced the laser-induced thrombosis in their carotid arteries.

Intracoronary brachytherapy is the first internationally recognized, evidence-based coronary intervention for in-stent restenosis. But the present and future role of brachytherapy is questioned by the first results of clinical trials with antiproliferative coated stents. This overview compares the status quo of both methods, concluding first practical considerations.

Platelets, a major constituent of thrombus, play a crucial role in the pathogenesis of acute ischemic coronary syndromes. The effect of ultraviolet laser emission on platelets within thrombi is unknown. The effects of increasing levels of laser energy on platelets in whole blood were investigated. Blood samples were obtained by aseptic venipuncture and anticoagulated with 3.8% sodium citrate. Samples were exposed to increased levels (0, 30, 45, 60 mJ/mm2; 25 Hz) of ultraviolet excimer laser fluence (308 nm wave-length) and then tested for ADP and collagen induced platelet aggregation, platelet concentration, and for platelet contractile force (PCF) development. Scanning electron microscopy was used to detect laser induced morphologic changes of platelets and by flow cytometric analysis to detect changes in expression of platelet surface antigens p-selectin (CD 62) and glycoprotein IIb/IIIa (CD 43). Exposure to excimer laser energy produced dose dependent suppression of platelet aggregation and force development ("stunned platelets"). ADP aggregation decreased from 8.0+/-1.1 Ohms (mean+/-SEM) to 3.7+/-0.8 Ohms (p<0.001) to 2.7+/-0.6 Ohms (p <0.001) and to 1.8+/-0.5 Ohms (p <0.001) as the laser energy increased from 0 to 30 to 45 to 60 mJ/mm2, respectively. Collagen induced aggregation decreased from 21.4+/-1.4 Ohms to 15.7+/-1.2 Ohms (p <0.001) to 11.7+/-1.1 Ohms (p <0.001) and to 9.9+/-1.0 Ohms (p <0.001), in response to the same incremental range of laser energy. Platelet contractile forces declined from 34,500+/-3700 to 27.800+/-2700 dynes as laser energy increased from 0 to 60 mJ/mm2 (p <0.03). Platelet concentration did not change with increasing laser energy. The expression of platelet surface antigen p-selectin (CD 62) remained stable through increasing levels of laser energy exposures while the percentage of CD 43 positive platelets significantly increased with exposure to laser energy, yet the level of expression did not exceed 0.5% of cells. Thus, aggregation kinetics are altered in platelets exposed to ultraviolet laser energy as manifested by decreased platelet aggregation and reduction in platelet force development capability. The response is dose dependent and most pronounced at higher energy levels such as 60 mJ/mm2.

Background: The effect of gamma radiation on single-donor apheresis platelet concentrates (SDPs) has been elucidated only incompletely. The only existing report on the function of SDPs stored in the irradiated state found a deterioration in the in vitro aggregability at the end of shelf life in SDPs divided before irradiation with 1500 cGy., Study Design and Methods: The in vitro properties of platelets were examined in four series of irradiated and control platelets, each obtained from the same 15 donors. Irradiation with 3000 cGy was performed on Days 0, 3, and 5. Cellular content, aggregability by ADP alone or ADP and epinephrine, spontaneous and induced CD62 expression, beta-thromboglobulin release, glucose consumption, lactate production, and pH were measured immediately after preparation and on Days 3 and 5 after donation., Results: Comparable in vitro properties were measured in irradiated and control platelets, whether irradiation was performed on Day 3 or Day 5. However, in platelets irradiated on Day 0, we found a significantly better in vitro aggregability by 20 microM: ADP immediately after irradiation and by 10 microM: ADP and 2 microM: epinephrine at the end of shelf life than was found in the other groups (Day 5 results: Day 0 irradiation: 75 +/- 32%; Day 3 irradiation: 45 +/- 45%; Day 5 irradiation: 47 +/- 41%; control: 40 +/- 24%; p<0.05)., Conclusion: Gamma radiation had no adverse effect on platelet quality in extremely WBC-reduced SDPs. On the contrary, a slight, but significantly better in vitro aggregability was found in SDPs irradiated before storage than in platelets irradiated later during storage and in unirradiated platelets. This increased in vitro aggregability persisted until the end of shelf life.

Thrombopoietin (TPO), or megakaryocyte growth and development factor (MGDF), has been shown to potentiate the sensitivity of normal human platelets to various agonists in vitro. The present study investigated the functional and biochemical properties of platelets from mice rendered thrombocytopenic by sublethal irradiation with regard to the reactivity to recombinant murine MGDF (rmMGDF) in vitro. During the course of reversible thrombocytopenia following irradiation, platelets from irradiated mice which had lower platelet counts and reciprocally higher plasma TPO levels showed lower reactivity to rmMGDF in agonist-induced platelet aggregation. Intravenous injections of recombinant soluble murine c-Mpl (sMpl), which has the ability to capture TPO, after irradiation restored the reactivity of platelets at the platelet nadir to rmMGDF. On the other hand, platelets prepared from normal mice 3 h after a single intravenous injection of pegylated rmMGDF did not respond to rmMGDF. There was a marked decrease in c-Mpl and Janus kinase 2 (JAK2) in platelets from irradiated mice at the platelet nadir. Similar results were observed with platelets from mice administered pegylated rmMGDF. JAK2 was only moderately decreased, however, in platelets from mice given sMpl after irradiation. These results indicate that exposure of platelets to increased endogenous TPO levels in vivo in thrombocytopenic mice leads to a reduction in the platelet reactivity to rmMGDF in vitro. Further, these results suggest that the c-Mpl-mediated signaling pathway, which is essential for the priming effect of rmMGDF, is defective in thrombocytopenic murine platelets.

A study was made of the effect of electromagnetic EMI MMD-fluctuation on the frequencies of molecular spectra of radiation, and nitric oxide absorption under in vitro conditions on the functional activity of platelets in patients with unstable angina pectoris, with the help of a specially created generator. At amplitude-modulated and continuous modes of EMI MMD-irradiation of platelet-rich plasma for 5, 15 and 30 min the platelet functional activity decreases, which was shown up in reduction of their activation and fall of aggregative ability. The degree, to which platelet functional activity was inhibited, depended on the mode of irradiation and on duration of EMI MMD effect. The most obvious changes in platelet activation and in their readiness to aggregative response were observed at a continuous mode of irradiation within a 15 min interval.

The molecular informational interaction has been first detected in a system that involves human platelets, exposed to electromagnetic EHF-fluctuations at frequencies of molecular spectra of radiation and absorption of nitric oxide (150.176-150.644 HHz), and native platelets. It has been established that the incubation of a native platelet rich plasma with a similar plasma, exposed to a 5-minute effect of electromagnetic EHF-fluctuations at frequencies of molecular spectra of radiation and absorption of nitric oxide at a mode of peak and frequent modulation of a signal under in vitro conditions, causes a significant (P < 0.05) inhibition of platelet functional activity in the native plasma, in comparison with control. This was displayed by a decreased platelet activation and falling platelet aggregation ability. Some possible mechanisms of interaction are suggested to explain the described effect.

The effect of the intravenous laser blood (ELB) treatment on the sensitivity of blood components with respect to drugs was studied in patients with nonspecific reactive hepatitis and chronic hepatitis. An ELB course reduced the functional activity of thrombocytes in the presence of fibrinogen and adrenaline hydrochloride (collagen inductors), which must be taken into account when these drugs are used as hemostatic agents.

The effect of He-Ne laser irradiation on platelet adhesion, activation and aggregation was investigated. Citrated whole blood was irradiated in vitro by He-Ne laser (632.8 nm, 7 mW) and then subjected to shear stress (1300 s-1) on subendothelial extracellular matrix (ECM)-coated plates. Laser irradiation was followed by a decrease in platelet adhesion and aggregation on ECM under flow conditions in a time exposure-dependent manner (by 30-40%). The inhibiting effect of laser light on platelets was detectable up to 1 h after the termination of irradiation. Laser irradiation of either platelet-rich plasma, gel-filtered platelets, platelet-poor plasma, or packed blood cells followed by whole blood reconstitution revealed a marked decrease in platelet deposition on ECM only in the cases of platelet-rich plasma or gel filtered platelets. In conventional aggregometry, laser-treated platelet-rich plasma demonstrated a diminished platelet response to both thrombin receptor-activating peptide (TRAP), converting a two-wave aggregation curve to reversible, and to the protein kinase C activator PMA (by 45%). In flow cytometry analysis, irradiated platelets presented lower fibrinogen binding and P-selectin expression in response to TRAP. Laser irradiation had no additional inhibitory effect on dibutyryl cGMP- and dibutyryl cAMP-pretreated platelets. A 50% increase in cGMP level was observed in laser-treated gel filtered platelets, both in the presence and in absence of the phosphodiesterase inhibitor, isobuthylmethylxanthine. The results suggest that guanylate cyclase is one of the primary mediators of the laser effect on platelet function.

Infusion of liposome-encapsulated hemoglobin (LEH) induces a transient thrombocytopenia in rats (Rabinovici R, Rudolph AS, Ligler FS, Smith EF, III, Feuerstein G [1992] Biological responses to exchange transfusion with liposome-encapsulated hemoglobin. Circ Shock 37:124). A specific mechanism such as a localization of platelets during this transient LEH-induced thrombocytopenia has not been reported previously in the literature. In this study, platelets were isolated and labeled with indium-111 (111In), then retransfused into the same animal. Fifteen minutes after the 111In platelets were retransfused and allowed to equilibrate with the blood pool, a 10% top load volume of either LEH (1.8 mL, 262 mg phospholipid/kg body weight, 92 mg hemoglobin (Hb)/kg body weight), liposome vehicle (LV) (1.8 mL, 262 mg phospholipid/kg body weight), or free bovine Hb (1.8 mL, 92 mg Hb/kg body weight) (n=6 per group) was infused. Serial blood samples were drawn to determine platelet counts by radioactivity and light scattering methods. LV and Hb demonstrated no significant changes from baseline levels in circulating platelet levels, whereas LEH caused a transient 50% decrease in 111In platelet activity 2-5 minutes postinfusion, which returned to baseline levels by 15 minutes. Platelet counts based on traditional light scattering methods were not significantly different among the three treatment groups over this same time course. Localization of these 111In platelets was monitored with a gamma scintigraphic camera. After infusion of LEH, 111In platelets rapidly moved out of the circulation and sequestered in the lungs and liver with subsequent return to the circulation by 15 minutes. In contrast, no significant changes in 111In platelet activity were noted in the lungs and liver after infusion of LV and Hb. 111In platelet activity in the spleen nearly doubled 30 minutes after Hb infusion and was significantly different than spleen 111In platelet activity in the LEH and LV groups. In vitro platelet aggregation studies were also performed to determine the direct effect of LEH, LV, and Hb on platelet aggregation. The rate of thrombin-induced aggregation did not differ among control samples and samples containing LEH, LV, or Hb; none of these agents induced platelet aggregation. We conclude that LEH-induced thrombocytopenia is associated with a transient (within minutes) sequestration of platelets in the lungs and liver, with subsequent release to the circulation within 15 minutes. Tetrameric bovine Hb is associated with increased platelet accumulation in the spleen. Light scattering methods for measuring platelet levels in blood samples containing LEH are unreliable because of particulate interference.

Effect of garlic on photochemically-induced platelet aggregation in pial microvessels of the mouse, in vivo, was compared to that of acetyl salicylic acid (ASA). Three trials were carried out, in which garlic at doses of 12.5, 25, 50 and 100 mg/kg and ASA doses of 25, 50 and 100 mg/kg were used. Each trial included treatment groups of male mice, approximately 30 g, and a control group. Animals were anesthetized (urethane, 1-2 mg/g, i.p.), the trachea was intubated and a craniotomy was performed. Induction of platelet aggregation was made by activation of circulating sodium fluorescein (0.1 ml of 5% solution/25 g, i.v.) with an intense mercury light. Garlic, ASA and vehicle solutions were injected, i.p., 60 min prior to the photochemical insult. The time for the first platelet aggregate to appear in pial arterioles was significantly delayed (P < 0.001) only by the 100 mg/kg garlic dose and by all ASA doses. The effect of this garlic dose on first aggregate was comparable to that of the 25 and 50 mg/kg ASA doses. Only the ASA doses delayed (P < 0.05) the appearance of first aggregate in venules. Arteriolar and venular diameter changes were not different among groups of all trials. Data of this study documented that garlic was capable of delaying platelet aggregation in mouse pial arterioles, in vivo.

This work examines the effect on the weights of vital body organs, on blood biochemical variables, on neuromuscular coordination and on cerebral microcirculation of aqueous extracts of Teucrium stocksianum, given to mice in drinking water at concentrations of 2 and 4% for 56 days. The treatment caused progressive impairment of neuromuscular coordination, as evidenced by the time spent on the rota-rod. After photochemical challenge, the time for first observable platelet aggregation in arterioles was shorter than for the control group by 22 and 45% in the 2 and 4% T. stocksianum-treated groups, respectively. Platelet aggregation on the venular side was not affected by the treatment nor were microvascular diameters. Treatment with the plant extract produced no statistically significant effect on the plasma biochemical variables that are considered indices of liver and kidney function. Histologically, brains obtained from mice treated with T. stocksianum showed loss of cerebellar Purkinje cells. Although it is likely that the accelerated platelet aggregation might have contributed to an ischaemic effect which could, at least in part, have caused the cytotoxicological changes, this does not exclude the possibility of a direct cytotoxicological effect of the plant extract. Further pharmacological and toxicological investigations on Teucrium species seem warranted.

Background: There are conflicting data on the effect of irradiation and subsequent storage on the quality of platelet components., Study Design and Methods: The retention of platelet properties during storage of gamma-irradiated apheresis suspensions was studied in 22 apheresis components obtained on a cell separator with a specialized centrifugation chamber. Immediately after collection, each suspension was divided equally into two 1-L polyolefin containers. On Day 1 (n = 12) and Day 3 (n = 10) one of each pair of suspension containers was gamma radiated with 2500 cGy. All platelet suspensions were stored for 5 days at 20 to 24 degrees C. Samples were drawn on Day 5 from each of the 22 pairs of containers for evaluation of an array of in vitro properties. Samples were taken from 10 pairs of containers for platelet labeling with either 51Cr or 111In for subsequent transfusion and concurrent in vivo measurement of recovery and survival. Posttransfusion samples were drawn after 24 hours for ex vivo whole blood aggregation., Results: Comparable in vitro and in vivo properties were measured in irradiated and control platelets, whether irradiation was performed on Day 1 or Day 3. The mean +/- 1 SD in vivo recovery and survival time for controls and platelets irradiated on Day 1 was 52 +/- 14 percent and 146 +/- 34 hours and 51 +/- 7 percent and 147 +/- 36 hours, respectively. For Day 3 irradiation, the values were 46 +/- 12 percent and 150 +/- 60 hours and 47 +/- 9 percent and 151 +/- 53 hours, respectively. A small, but measurable adverse effect of irradiation on ex vivo platelet aggregation was present., Conclusion: These data indicate that storage of apheresis platelets after gamma radiation is without clinically significant, demonstrably adverse effects on platelet quality.