Microaggregate Formation Research Articles

Plateletpheresis: What's new?

1995 has brought several novelties into the field of thrombocytapheresis. The most important is the presentation by Baxter of the Amicus CFC apparatus that, in a two-vein collection time of 51-53 min, collects 3.93-4.13 x 10(11) platelets contaminated by 0.2 x 10(6) white blood cells (WBC) with an efficiency of 72-74%. Similar results are obtained in 55 min, in single-needle procedures, with a collection efficiency of 70.7%, a total yield of 4.3 x 10(11) and a contamination of 0.9 x 10(6) WBC. Presently the machine cannot collect red blood cells (RBC), along with platelets, as does the DFC Haemonetics MCS3p. With this machine in mandatory single-needle procedures lasting 80-85 min, approximately 4.5 x 10(11) platelets can be collected with a WBC contamination of 3.1 x 10(6). Along with the platelet cells (PC), with the SDP PRC protocol at the end of each pass it is possible to collect aliquots of plasma red blood cells (PRBC) (10-50 mL) with a haematocrit of 65%. Depending on the number of passes and on the donor's body weight (BW), from 1 and 2 U/PRBC containing approximately 55 g of haemoglobin (Hb) each can be obtained. This method not only costs less but also immunological and viral risks for the patients are more efficiently addressed since it is possible to reduce the number of allogeneic exposures in the same transfusion event. PRBC can also be collected with the Fresenius AS104 and the Dideco Excel apparatuses. Dideco is presently using the "Genova" separation chamber, which can collect an average of 4.8 x 10(11) platelets contaminated with 0.5 x 10(6) WBC, in approximately 55 min. The ACD-A-to-blood ratio may be as low as 1/20 since the very last belts and lines are coated with non-thrombogenic substances. Therefore, there is no alteration of the quality of the platelets as evaluated with monoclonal antibodies (MoAbs) anti-CD 62, 63, 36 and 51, no extra haemorrhagic risk for the donors and citrate reactions and microaggregate formation are totally eliminated. In 1995 there has also been some rejuvenation of the older cell separators. The CS3000+ uses the TN6/PLT 30 combination of separation collection chambers. Platelets are collected in only 30 mL of plasma, and non-plasma solutions containing acetate can be used for their resuspension. The Fresenius AS204 is ready for better-quality combined platelet collection, and RBC-PC collection with Cobe Spectra is under evaluation along with the leucocyte reduction system that apparently brings leucocyte contamination down to 0.35 x 10(5). This interest in thrombocytapheresis is also the result of the challenge that thrombopoietin phase I and II trials have promoted.

Plateletpheresis: What's new?

1995 has brought several novelties into the field of thrombocytapheresis. The most important is the presentation by Baxter of the Amicus CFC apparatus that, in a two-vein collection time of 51–53 min, collects 3.93–4.13 × 10 11 platelets contaminated by 0.2 × 10 6 white blood cells (WBC) with an efficiency of 72–74%. Similar results are obtained in 55 min, in single-needle procedures, with a collection efficiency of 70.7%, a total yield of 4.3 × 10 11 and a contamination of 0.9 × 10 6 WBC. Presently the machine cannot collect red blood cells (RBC), along with platelets, as does the DFC Haemonetics MCS3p. With this machine in mandatory single-needle procedures lasting 80–85 min, approximately 4.5 × 10 11 platelets can be collected with a WBC contamination of 3.1 × 10 6. Along with the platelet cells (PC), with the SDP PRC protocol at the end of each pass it is possible to collect aliquots of plasma red blood cells (PRBC) (10–50 mL) with a haematocrit of 65%. Depending on the number of passes and on the donor's body weight (BW), from 1 to 2 U/PRBC containing approximately 55 g of haemoglobin (Hb) each can be obtained. This method not only costs less but alsoimmunological and viral risks for the patients are more efficiently addressed since it is possible to reduce the number of allogeneic exposures in the same transfusion event. PRBC can also be collected with the Fresenius AS 104 and the Dideco Excel apparatuses. Dideco is presently using the “Genova” separation chamber, which can collect an average of 4.8 × 10 11 platelets contaminated with 0.5 × 10 6 WBC, in approximately 55 min. The ACD-A-to-blood ratio may be as low as 1 20 since the very last belts and lines are coated with non-thrombogenic substances. Therefore, there is no alteration of the quality of the platelets as evaluated with monoclonal antibodies (MoAbs) anti-CD 62, 63, 36 and 51, no extra haemorrhagic risk for the donors and citrate reactions and microaggregate formation are totally eliminated. In 1995 there has also been some rejuvenation of the older cell separators. The CS3000+ uses the TN6/PLT 30 combination of separation collection chambers. Platelets are collected in only 30 mL of plasma, and non-plasma solutions containing acetate can be used for their resuspension. The Fresenius AS204 is ready for better-quality combined platelet collection, and RBC-PC collection with Cobe Spectra is under evaluation along with the leucocyte reduction system that apparently brings leucocyte contamination down to 0.35 × 10 5. This interest in thrombocytapheresis is also the result of the challenge that thrombopoietin phase I and II trials have promoted.

Activation of human platelets by protein kinase C antibody: role for surface phosphorylation in homeostasis.

A monoclonal antibody that inhibits protein kinase C (PKC) activity, as well as PKC pseudosubstrate inhibitory peptides, was found to cause aggregation of human platelets followed by granular secretion. Binding of this antibody to the platelet surface was demonstrated directly by flow cytometry and immunofluorescence microscopy. Assays of ecto-protein kinase activity revealed that this antibody inhibits the phosphorylation of five proteins on the platelet surface. The platelet aggregation induced by extracellular PKC inhibitors could be blocked by the addition of the membrane-impermeable phosphatase inhibitor, microcystin. Thus the inhibition of surface protein phosphorylation together with continuous dephosphorylation, namely, a decrease in the phosphorylation state of surface proteins, causes the activation of platelets. The aggregation caused by decreased surface phosphorylation appears to be initiated by the exposure of active fibrinogen-binding sites on the platelet surface, as demonstrated by the formation of fibrinogen-dependent microaggregates, as the first step in this process. We conclude that the phosphorylation of surface proteins by a platelet ecto-protein kinase C protects platelets from spontaneous aggregation and thus can play an important role in homeostatic mechanisms that maintain circulating platelets in a resting state.

Carbon Dynamics of Aggregate-Associated Organic Matter Estimated by Carbon-13 Natural Abundance

A major factor controlling soil organic matter dynamics is believed to be the differing degrees of protection from decomposition afforded by the spatially hierarchical organization of soil aggregate structure. Changes in the natural 13 C content and in the concentration of soil organic C resulting from the growth of C3 pasture grasses (low δ 13 C PDB ) on former C4 cropland (high δ 13 C PDB ) were used to investigate the turnover and inputs of organic C in water-stable aggregates of different sizes. After removal of free and released particulate organic matter (POM) in aggregate size separates (POM with a density ≤1.85 g cm -3 that was either exterior to aggregates in situ or released from unstable aggregates by slaking), organic C concentrations were greater in macroaggregates (>212 μm) than in microaggregates (53-212 μm). The turnover time (1/k) for C4-derived C was 412 yr for microaggregates, compared with an average turnover of 140 yr for macroaggregates, indicating that old C associated with microaggregates may be both biochemically recalcitrant and physically protected. Net input rates of C3-derived C increased with aggregate size (0.73-1.13 g kg -1 yr -1 ), supporting the concept of an aggregate hierarchy created by the binding of microaggregates into increasingly larger macroaggregates. The net input rate for microaggregates, however, was equal to the rates for small macroaggregates, suggesting that the formation and degradation of microaggregates may be more dynamic than is predicted by their stability in cultivated soils or by the observed turnover times for old C.

ＲＣ‐Ｍ・Ａ・Ｐの微小凝集塊について 構成成分の検討

The presence of microaggregates in transfusion blood is a well known cause of adverse effects in recipient patients. Few studies, however, have examined in datail microaggregate formation in Red cell Concentrate preserved in MAP solution (RC-M·A·P). This situation contrasts with the many reports concernings macroaggregates in these products.In this study we analyzed microaggregates in RC-M·A·P stored two or three weeks using light and scanning electron microscopic observation, immunofluoressent detection of constituents, and PCR analysis. The microaggregates consisted of disrupted platelets, granulocytes, monocytes, lymphocytes, small quantities of DNA, and, importantly, fibrin fibers. This composition suggested that, in RC-M·A·P, fibrin but not DNA played a major role in microaggregate formation, causing adhesion of blood cell debris. These findings contrast with those of previous studies of macroaggregates in RC-M·A·P, which indicated leukocyte DNA to be the adhesive core.Further, this study indicates the importance of the improved cytocentrifugation technique we developed and used here. Without this method, collection of microaggregates would have been a laborious and time-consuming proccess.

Surface Chemical Control of Ultra-Fine Coal to Improve Dewatering

Lowering of filter cake moisture of ultra-fine (d50 = 25 µm) coal to a 20 percent level using the conventional vacuum filtration could be achieved using a combination of metal ions and surfactants. Pretreating coat slurry with about 0.2 Kg/ton of a surfactant and 50 ppm of copper or 10 ppm of aluminum ions provided filter cake containing 22.8 percent moisture. The lowering of moisture is explained due to formation of hydrophobic micro-aggregates which facilitates dewatering.

Junctional sites of erythrocyte skeletal proteins are specific targets of tert-butylhydroperoxide oxidative damage

The oxidative denaturation of the erythrocyte membrane, which is considered a major cause of the haemolytic process, 'was evaluated upon ‘in vitro’ oxidative stress with tert-butylhydroperoxide. Biochemical and ultrastructural analyses were performed to point out the effect of this substance on the skeletal network, which is mainly responsible for red cell shape and viability. Moreover, cell morphology was observed by scanning electron microscopy and membrane rigidity assessed by EPR measurements. The most relevant features of the membrane denaturation were, (i) lipid peroxidation, as assessed by malonildialdehyde production, (ii) spectrin and ankyrin degradation with simultaneous globin binding to the membrane, as evidenced by electrophoretic pattern of red cell ghosts. These phenomena were related to the drug concentration in the incubation medium, and accompanied by depletion of intracellular reduced glutathione. The denaturation of protein components hindered the release of spectrin in a hypotonic extraction medium and could be only partially reversed by dithiothreitol. The extensive membrane protein and lipid degradation, at high drug concentration, was coherent with a marked increase of membrane order (membrane ‘rigidity’). No clustering of intramembrane proteins was shown by the transmission electron microscopy images. At the same time scanning electron microscopy demonstrated shrinking and disco-stomatocytic deformation of erythrocytes. Ultrastructural analysis of the membrane skeleton by fluorescence-labelling of spectrin and actin, allowed to point out that exposure to t-BHP caused the marginalization of spectrin and the rearrangement of actin molecules with formation of micro aggregates, so that a detachment of actin from the spectrin network was suggested. In addition to the generalized damage of red cell membrane, tert-butylhydroperoxide was found to induce a specific alteration of the skeletal network at the horizontal junction sites involving spectrin, actin, and protein 4.1 and thus to modify the cytoskeletal assembly. This effect on the membrane skeletal components was consistent with the hypothesis that oxidative stress plays a key role in the haemolytic process.

Transport of bacteria in porous media: I. An experimental investigation

The convective transport of concentrated suspension of bacteria in porous media is of interest for several processes such as microbial enhanced oil recovery and in situ bioremediation. The parameters which affect the transport of the bacterium Bacillus licheniformis JF-2, a candidate microorganism for microbial enhanced oil recovery, were investigated experimentally in sandpacks. Bacteria retention and permeability reduction occurred primarily in the first few centimeters upon entering the porous medium. In downstream sections of the sandpack, the permeability reduction was low, even in cases in which high cell concentrations (10(8) cfu/mL) were detected in the effluent. The effect of (i) addition of a dispersant, (ii) linear velocity of injection, (iii) cell concentration, (iv) salinity (v) temperature, and (vi) the presence of a residual oleic phase were determined experimentally. A lower reduction in permeability and a higher effluent bacterial concentration were obtained in the presence of dispersant, high injection velocities, low salinities, and at a higher temperature. Macroscopic measurements at different linear velocities and in the presence or absence of dispersants suggest that the formation of reversible microaggregates and multiparticle hydrodynamic exclusion may be the primary mechanisms for bacterial retention and permeability reduction. (c) 1994 John Wiley & Sons, Inc.

Promotion of human platelet adhesion and aggregation by a synthetic, triple-helical “mini-collagen”.

Platelet activation and aggregation by fibrillar collagens are based on substrate primary, secondary, tertiary, and quaternary structure. Although several peptides incorporating sequences from the triple-helical domains of types I and III collagen inhibit collagen-mediated platelet aggregation, none independently promote platelet activation and aggregation. It is believed that the absence of these platelet activities is due to the lack of proper substrate tertiary and quaternary structures. We have utilized a synthetic, triple-helical "mini-collagen" that incorporates a known cell adhesion site (alpha 1(IV)1263-1277) to better understand the relationship between substrate primary, secondary, tertiary, and quaternary structure and platelet activation and aggregation. The promotion of platelet adhesion, activation, and aggregation was compared for this triple-helical polypeptide (THP), fibrillar and type IV collagens, and a single-stranded peptide (SSP) incorporating the alpha 1(IV)1263-1277 sequence. Glass-coated fibrillar and type IV collagens and the THP supported platelet adhesion at substrate concentrations of 0.33 nM, 0.20 nM, and 0.89 microM, respectively. When platelets were stirred with 10 micrograms/ml of fibrillar (0.33 nM) and type IV (0.20 nM) collagen, SSP (2.1 microM), and THP (0.89 microM), only the fibrillar collagen caused 3H-labeled arachidonic acid release, elevation of cytosolic calcium, irreversible aggregation, and secretion of granule contents. The THP (0.45-1.8 microM) effectively inhibited fibrillar collagen-mediated platelet aggregation, while the SSP did not. At a substrate concentration of 40 micrograms/ml, the THP (3.6 microM) was as effective as fibrillar collagen (1.3 nM) at inducing 3H-labeled oleic acid-labeled platelet activation and microaggregate formation, while the SSP and type IV collagen were relatively ineffective. Rotary shadowing images indicated that aggregates of the THP could form distinct quaternary structures, while the type IV collagen used here could not. These results are the first demonstrations of a synthetic peptide promoting platelet adhesion, activation, and aggregation and suggest that the combination of THP primary, secondary, tertiary, and quaternary structural features are required for platelet aggregation.

Soil structure and carbon cycling

Samples from the surface horizons of six virgin soils were collected and separated into density fractions. Based on the spatial distribution of organic materials within the mineral matrix of soil, the soil organic matter (SOM) contained in various density fractions was classified as: (a) free particulate OM, (b) occluded particulate OM, and (c) colloidal or clay-associated OM. The compositional differences noted among these three components of SOM were used to describe the changes that OM undergoes during decomposition when it enters the soil, is enveloped in aggregates and eventually is incorporated into microbial biomass and metabolites and associated with clay minerals. The occluded organic materials, released as a result of aggregate disruption, were in various stages of decomposition and had different degrees of association with mineral particles. Changes in the degree of association of occluded organic materials and mineral particles with decomposition are discussed and form the basis of a model which illustrates the simultaneous dynamics of microaggregates and their organic cores. This model indicates a major role for carbohydrate-rich plant debris in formation and stabilization of microaggregates.

Aggregation of band 3 in hereditary ovalocytic red blood cell membranes Electron microscopy and protein rotational diffusion studies

Microaggregation of band 3 proteins in hereditary ovalocytic membranes was investigated by rotational diffusion measurements and by electron microscopy. It was previously shown that band 3 in ovalocytic membranes has decreased rotational mobility compared with band 3 in normal cells (Tilley, L., Nash, G.B., Jones, G.L. and Sawyer, W.L. (1991) J. Membr. Biol. 121, 59-66). This result could arise from either altered interactions with cytoskeletal proteins or from band 3 microaggregation. In the present study it was found that removal of spectrin and actin from the membrane had no effect on the rotational mobility of ovalocytic band 3. Additional removal of ankyrin and band 4.1, as well as cleavage of the cytoplasmic domain of band 3 with trypsin, did enhance band 3 mobility, as is the case in the membranes from normal cells. However, the rotational mobility of ovalocytic band 3 was always considerably less than that of normal band 3 under the same conditions. Scanning electron microscopy and low power electron micrographs of freeze-fracture replicas revealed that the surfaces of ovalocytes were more irregular than those of normal erythrocytes. At higher magnification, numerous linearly arranged intramembranous particles were observed on the P-faces of freeze-fractured ovalocytes but not on normal cells. These clusters consist of straight or slightly curved lines of 10-15 particles in single rows. From these results it is deduced that the reduced rotational mobility of band 3 in ovalocytes is a consequence of the formation of microaggregates, which are very probably induced by the mutation in the membrane-bound domain of ovalocytic band 3.

Transformation of the soil structure through Pontoscolex corethrurus (Oligochaeta) intestinal tract

Pontoscolex corethrurus is a geophagous tropical earthworm whose population in a Mexican pasture can ingest annually 400 Mg of dry soil ha −1. A comparative study of the soil before ingestion, the gut content and casts of P. corethrurus using transmission or scanning electron microscopy (TEM and SEM) showed that the soil structure was completely destroyed. In the control soil the organo-mineral material was compact, while the soil in the anterior gut was dispersed in a semi-liquid medium with a great amount of free polysaccharides (intestinal mucus) and swollen clays by the increase of water content. At the end of the gut and in the casts the soil had retaken a similar structure than before its ingestion. Although in the gut a great reorganization of the soil occurred, as formation of new aggregates like microbial colonies surrounded by polysaccharides and clays, or activation of some dormant microorganisms. These observations supported with other physico-chemical (pH, water content) and microbial activity measurements showed how P. corethrurus had a dramatic impact on soil macro- and microstructure. This destructuration and restructuration of the soil made that organic elements that were protected were recycled and others, on the contrary, were protected by the formation of new microaggregates.

The influence of organic matter, cation bridges and Fe‐ and Al‐oxides and hydroxides on the aggregation of three Alfisols

AbstractThe effects of organic matter, cation bridges, and Fe‐ and Al‐oxides and hydroxides on binding soil particles were studied for three aggregate sizes of three different Alfisols. The binding effect was evaluated from changes in particle size distribution and from changes in surface area caused by selective removal of binding agents. Organic matter oxidation resulted in both clay fraction and surface area increase. The selective removal of cation bridges or dithionite‐extractable Fe‐ and Al‐oxides and hydroxides had no effect on particle size distribution but caused a considerable decrease in surface area. Ammonium oxalate treatment resulted in a decrease of both clay fraction and surface area of the aggregates. The findings of the present study are discussed in the context of formation of primary and secondary structural units as well as of the formation and stabilisation of microaggregates in soils.

Thermal behaviour and physicochemical properties of naproxen in mixtures with polyvinylpyrrolidone

The thermal behaviour (DSC, TGA) of naproxen (NAP) and various grades of polyvinylpyrrolidone (PVP; Mr ≈ 10000, 25000, 40000 and 360000), and their mixtures was investigated. A profound modification of the NAP melting peak, observed in the DSC curves of simply blended systems (physical mixtures) with PVP, was attributed to a solid-state interaction. This interaction proved to be influenced by the composition of the mixture, the PVP average molecular weight and the type of manipulation of the sample (grinding, compaction, heating). The high dispersion of NAP within the PVP matrix probably gives rise to the formation of crystalline drug microaggregates (molecular clusters) responsible for the thermal behaviour. The chemical and physical stability (dissolution rate, crystallinity) of NAP was not significantly affected in the mixtures with PVP.

Model for the regulation of platelet volume and responsiveness by the trans-membrane Na+/K(+)-pump.

The correspondence between K+ uptake in platelets to their responsiveness was studied using 86Rb+ as an analogue of K+. An average 86Rb+ uptake rate of 0.73 (+/- 0.140) x 10(-15) mole Rb+/min-plt (n = 20) was observed. By the use of K(+)-influx inhibitors, we were able to distinguish three distinct 86Rb+ uptake pathways: an ouabain-sensitive (61% +/- 2% inhibitable) pump and two equivalent channels, only one of which is sensitive to furosemide. Other platelet parameters were also examined in conjunction with K(+)-uptake. Platelets incubated with ouabain exhibited an overall rise in their cell volume (MPV) with incubation time (delta MPV = 7.4 x 10(-17) L/min-1 plt-1). Concomitantly, over 24 hours, a steady decrease in platelet number was recorded by blood cell coulter, which correlated inversely with the counts of particles, which by their size resemble white blood cells (r = 0.89). On a cellular level, incubation with ouabain induced greater expression of surface fibrinogen-receptor (GPIIb), increased binding of FITC-labelled fibrinogen, and increased responsiveness to ADP. Our observations suggest the following sequence of events: Ouabain turns off the Na+/K(+)-ATPase pump, which leads to water accumulation in platelets and concomitant increased MPV. Greater expression of fibrinogen receptors on the distended platelet surface corresponds to spontaneous microaggregate formation as well as greater responsiveness to agonists. Our model links volume regulation, the expression of fibrinogen receptors, and the sensitivity of platelets to agonists to the activity of the Na+/K(+)-ATPase pump.

遠心ポンプを用いた実験的左心バイパス: 各種抗凝血剤の微小血栓発生, 血小板減少防止効果についての比較検討

遠心ポンプを用いた実験的左心バイパス: 各種抗凝血剤の微小血栓発生, 血小板減少防止効果についての比較検討

A prospective clinical study on the pathogenesis of multiple organ failure in severely burned patients

This study has shown that multiple organ failure (MOF) is one of the major causes of death in patients with severe burns. Both the plasma and visceral levels of TXB 2 and the TXB 2/6-keto-PGF 1α ratio were significantly increased. The changed plasma levels of TXB 2 and the TXB 2/6-keto-PGF 1α ratio paralleled the deterioration of the general condition in MOF patients. The circulatory platelet aggregation ratios (CPAR) in the MOF patients initially declined then dropped profoundly at 5–7 days postburn, indicating more microaggregate formation. CPK, LDH and GOT had increased markedly by 1 day, were elevated further at 2–3 days, and remained at supranormal levels for the first 7 days postburn. Degeneration, destruction, oedema, haemorrhage and thrombosis were observed in tissues from patients who died due to heart, lung, renal and hepatic failure. Clinically, 13 of the 16 MOF cases developed organ failure and 11 died between 3 and 7 days postburn. These findings confirmed that the increases of TXA 2 and the TXA 2/PGI 2 ratio in plasma and visceral tissues can be an important factor in the genesis and development of postburn MOF.

Clinical studies on postburn multiple organ failure: its aetiological factors and monitoring

This study demonstrated that multiple organ failure (MOF) developed in 16 of 57 severely burned patients (28.1 per cent). When expressed as a percentage of the 590 patients admitted during the same period, the incidence became 2.7 per cent. Fifteen of the 16 MOF cases died, with a mortality of 93.8 per cent. In those patients with TBSA over 80 per cent with inhalation injury, severe shock and systemic infection, the incidence of MOF was significantly higher. Systemic infection and severe shock were the most important complications. These results indicated that the severity of the burn is the prime prerequisite of MOF, while severe shock and systemic infection are secondary but very important factors in the genesis and development of postburn MOF. The circulatory platelet aggregate ratio (CPAR) started to decrease significantly at 12 h postburn, remaining at low levels and declining further at 5–7 days postburn. However the values of the myocardial enzyme spectrum (MES) remained at significantly higher levels, indicating significant and continuous increases of microaggregate formation and the continuous existence of visceral and tissue ischaemia and cellular destruction. Changes of CPAR and MES in MOF patients were directly related to the development of MOF. It is advisable to use CPAR and MES to monitor the possible development of postburn MOF.

The Use of Laser-Light Scattering and Controlled Shear in Platelet Aggregometry

Laser-light scattering was used to observe and quantify the dynamics of human blood platelet aggregation in platelet-rich plasma (PRP). Aggregation was performed in a controlled shear environment by placing the PRP in the annular space between a rotating cylindrical rod and a stationary cylindrical tube. The instrument was capable of very sensitive continuous semi-quantitative measurements of chemically-induced microaggregation. As a demonstration of the technique, results are presented for ADP-induced aggregation at doses of 10, 1, and 0.1 microM and collagen-induced aggregation at a dose of 5 micrograms/ml, each at shear rates of 1,000 s-1 and 500 s-1. Extensive aggregation was observed in response to ADP at even the low dose of 0.1 microM, indicating a high sensitivity to microaggregates. The sensitivity of the ultimate size of the ADP-induced aggregates to ADP concentration was shear dependent. The formation of microaggregates by collagen stimulation was shown to be almost immediate, as contrasted with a 10-20 s typical lag when observed turbidometrically. Disaggregation was observed with 1 microM ADP, but this was only partial, as contrasted with the complete recovery of transmittance observed in the turbidometric technique. Electronic particle sizing and counting was employed to semiquantitatively verify the aggregate size distributions found from mathematical conversion of the laser-light scattering data.

Enhanced Platelet Reactivity in Cats Experimentally Infected with Feline Infectious Peritonitis Virus

Platelet function was evaluated in six specific-pathogen-free cats prior to and following intraperitoneal inoculation with feline infectious peritonitis virus (FIPV). By 4 days post-inoculation, platelet samples from five of six cats responded with irreversible platelet aggregation to threshold concentrations of adenosine diphosphate (ADP). This was accompanied by enhanced platelet 14C-serotonin release (greater than 10%) in two cats. Compared to one of six baseline samples, five of five post-inoculation samples exhibited microaggregate formation in response to 20 microM epinephrine. Enhanced platelet 14C-serotonin release did not accompany these responses. Enhanced platelet responses to ADP and epinephrine were also observed on day 11 post-inoculation and day 16 (when one cat died) or 21 (the end of the study). Platelet 14C-serotonin release in response to 20 microM epinephrine increased markedly in three of five cats on day 21. Enhanced collagen-induced platelet responses were not demonstrated. Although the mechanism for the enhanced platelet responses observed on day 4 was unknown, a direct effect on the virus on platelets, mononuclear inflammatory cells, and endothelial cells must be considered.