Automated Fiber Diameter and Porosity Measurements of Plasma Clots in Scanning Electron Microscopy Images

Scanning Electron Microscopy (SEM) is a powerful, high-resolution imaging technique widely used to analyze the structure of fibrin networks. Currently, structural features, such as fiber diameter, length, density, and porosity, are mostly analyzed manually, which is tedious and may introduce user bias. A reliable, automated structural image analysis method would mitigate these drawbacks. We evaluated the performance of DiameterJ (an ImageJ plug-in) for analyzing fibrin fiber diameter by comparing automated DiameterJ outputs with manual diameter measurements in four SEM data sets with different imaging parameters. We also investigated correlations between biophysical fibrin clot properties and diameter, and between clot permeability and DiameterJ-determined clot porosity. Several of the 24 DiameterJ algorithms returned diameter values that highly correlated with and closely matched the values of the manual measurements. However, optimal performance was dependent on the pixel size of the images—best results were obtained for images with a pixel size of 8–10 nm (13–16 pixels/fiber). Larger or smaller pixels resulted in an over- or underestimation of diameter values, respectively. The correlation between clot permeability and DiameterJ-determined clot porosity was modest, likely because it is difficult to establish the correct image depth of field in this analysis. In conclusion, several DiameterJ algorithms (M6, M5, T3) perform well for diameter determination from SEM images, given the appropriate imaging conditions (13–16 pixels/fiber). Determining fibrin clot porosity via DiameterJ is challenging.

The effect of the Rochagan on radiolabeling with (99m)Tc

Radionuclides are used in nuclear medicine by variety of diagnostic procedures. The labeling of red blood cells (RBC) with (99m)Tc is a current method applied in clinical nuclear medicine. Drugs can alter this labeling and modify the disposition of the radiopharmaceuticals. The influence of Rochagan on the labeling of blood constituents with (99m)Tc was reported. Samples of blood were incubated with different concentrations of Rochagan (0%; 6.25%; 12.5%; 25%; 50%; 100%). Stannous chloride and (99m)Tc (3.7MBq/mL) were added. Plasma (P) and (RBC) were isolated and precipitated with thricloroacetic acid 5%. The insoluble (IF) and soluble fractions (SF) were separated. The %ATI in RBC, IF-P and IF-RBC were calculated. The %ATI on RBC decreased significantly (p<0.05) from control to all concentrations of Rochagan, respectively: 90.15 + or - 0.14(control) to 70.80 + or - 4.21; to 64.36 + or - 0.33; to 57.30 + or - 1.56; to 50.28 + or - 2.71; to 42.41 + or - 2.24; on IF-RBC, respectively: 84.70 + or - 0.87(control) to 67.16 + or - 4.38; to 63.63 + or - 2.92; to 59.02 + or - 3.17; to 43.75 + or - 1.00; to 24.15 + or - 0.94 and also on IF-P, respectively: 83.46 + or - 1.09(control) to 50.90 + or - 3.36; to 35.46 + or - 4.13; to 35.78 + or - 2.31; to 28.74 + or - 3.09; to 19.66 + or - 1.34. The analyses were performed by T-Student and Mann Whitney tests, p<0.05. This effect was probably due to products present in Rochagan that may complex with ions or have a direct/indirect effect on intracellular stannous ion concentration.

Brain and whole-body imaging in nonhuman primates with [11C]MeS-IMPY, a candidate radioligand for β-amyloid plaques

[(11)C]MeS-IMPY ([S-methyl-(11)C]N,N-dimethyl-4-(6-(methylthio)imidazo[1,2-a]pyridine-2-yl)aniline) is a potential radioligand for imaging beta-amyloid plaques with positron emission tomography (PET). The aims of this study were to evaluate [(11)C]MeS-IMPY uptake in nonhuman primate brain and to estimate radiation exposure from serial whole-body images. Eight PET studies were performed in rhesus monkeys to measure the brain uptake and washout of [(11)C]MeS-IMPY. Time-activity data were analyzed with one-tissue and two-tissue compartmental models using radiometabolite-corrected plasma input function. In addition, two whole-body PET scans were acquired for 120 min to determine the biodistribution of [(11)C]MeS-IMPY. Tomographic PET images were compressed into a single planar image to identify organs with the highest radiation exposures. Estimates of the absorbed dose of radiation were calculated using OLINDA 1.0. Injection of [(11)C]MeS-IMPY caused little change in pulse rate, blood pressure, respiratory rate and temperature. [(11)C]MeS-IMPY showed high standardized brain uptake values of approximately 500% and 600% between 2 and 3 min in cortical regions and the cerebellum, respectively. The brain uptake of [(11)C]MeS-IMPY was widespread and quite uniform across all cortical regions. Activity rapidly washed out of the brain, with 20% of peak activity remaining at 40 min. Thus, all brain regions showed minimal retention of radioactivity, consistent with these healthy young animals having negligible amyloid plaques. Regional brain activity fitted well into a one-tissue compartment model. The average volume of distribution in all brain regions was 7.66+/-2.14 ml/cm(3) (n=4). The organs with the highest radiation exposure (muSv/MBq) were the gallbladder wall (33.4), urinary bladder (17) and lungs (12.9), with a resulting effective dose of 4.9 microSv/MBq (18 mrem/mCi). The high brain uptake, rapid washout and quantifiable volume of distribution in nonhuman primate brain further support the evaluation of [(11)C]MeS-IMPY. Calculated dosimetry results are comparable with those for other (11)C-labeled brain imaging radioligands.

Measurement of the ultrasonic attenuation coefficient of human blood plasma during clotting in the frequency range of 8 to 22 MHz

The blood coagulation mechanism consists of a series of concatenated chemical reactions, governed by the coagulation factors present in the blood plasma, after the activation of the clot mechanism. The last reaction corresponds to the fibrinogen conversion into fibrin, followed by the fibrin polymerisation and production of a stable fibrin network. During the clotting process, there is a sol-gel transformation of the medium. The subject of the present paper is the measurement of the ultrasonic attenuation coefficient for human blood plasma during the coagulation process, in the frequency range of 8 to 22 MHz. The clot was obtained after the procedure to measure the prothrombin time (approximately 12 s): mixing 150 microL of reconstituted lyophilised normal plasma with 300 microL of reconstituted lyophilised thromboplastin immersed in a water bath with the temperature controlled at 36.5 degrees C. The attenuation coefficient for pure plasma remained constant within the measurement period of 10 s and at frequencies of 8, 9, 10, 15, 20, 21 and 22 MHz. On the other hand, there is a detectable time-decay of the attenuation coefficient for samples of plasma going through the coagulation process and at frequencies of 8, 9, 10 and 15 MHz. The time-decay becomes less and less detectable as the frequency increases and it becomes completely undetectable at 20, 21 and 22 MHz.

Clinical significance of optimal red cell mass and plasma volume estimation methods

BACKGROUND

The aim of this study was to present and compare the results of proposed methods for optimal red cell mass and plasma volume (RCM&PV) estimation, and their influence on the interpretation of obtained results.

MATERIAL AND METHODS

In 120/280 patients with polycythaemia rubra vera, subjected to RCM&PV determination with autologous erythrocytes in vitro labelled with 51Cr-sodium chromate, optimal volumes were determined using: 1. traditional ml/kg of: --the real body weight method (ml/kg RBW); --the optimal body weight method (ml/kg OBW). 2. the body weight, height, and sex based method (Retzlaff's tables), 3. the method recommended by the International Council for Standardization in Haematology (ICSH), based on body surface area.

RESULTS

Different interpretation of the same results of 120 RCM&PV measurements was registered in 48/120 patients (40%). The greatest disagreement existed between ml/kg RBW and ml/kg OBW methods (in 39/120 subjects, 32.5%). In underweight patients the ml/kg RBW method, and in overweight patients the ml/kg OBW method, offered better agreement with ICSH&Retzlaff's methods. The ml/kg RBW method disagreed with ICSH&Retzlaff's methods and ml/kg OBW in 25% and 19.2% of patients respectively. ICSH and Retzlaff's methods disagreed in 10/120 patients (8.3%). The ICSH method yielded significantly lower optimal volumes than Retzlaff's.

CONCLUSION

Three methods for optimal RCM&PV estimation lead to different interpretations of the same results of RCM&PV measurements with 51Cr-erythrocytes in 40% of patients. Two ml/kg body weight methods show greater disagreement in comparison with ICSH and Retzlaff's methods, which differ significantly. The ICSH method yields lower optimal values compared to Retzlaff's.

Evaluation of DNA aptamers directed to thrombin as potential thrombus imaging agents

Two DNA aptamers directed against two separate exosites on human alpha-thrombin were evaluated for thrombus-imaging potential. Aptamer ODN 1 is directed to the thrombin substrate binding site (exosite 1). Our finding that ODN 1 competes with fibrin for binding to exosite 1 on thrombin suggests that ODN 1 will not be useful for thrombus imaging. Aptamer ODN 2 is directed against the thrombin heparin binding site (exosite 2). ODN 2 bound to model thrombi that were formed either by clotting purified fibrinogen with thrombin, or by recalcifying citrated plasma. As the thrombin content of thrombi was increased the rate of ODN 2 uptake into preformed thrombi increased, whereas the rate of release of ODN 2 out of preformed thrombi decreased. This in vitro data suggested that ODN 2 might be useful for thrombus imaging because it can bind to exosite 2 on fibrin-bound thrombin. However, in a rabbit jugular vein model using thrombus supplemented with human thrombin, ODN 2 uptake was equal to the ovalbumin control, and did not reflect thrombin content. While the in vitro results with ODN 2 were consistent with thrombus imaging, the rapid clearance of ODN 2 from circulation, combined with slow mass transfer in the clot, seem to work against in vivo thrombin-dependent imaging or washout analysis.

Enhancement of the relative uptake of 18F-FDG in mouse fibrosarcoma by rolipram

The effect of rolipram, a selective phosphodiesterase type 4 inhibitor, on the uptake of 18F-fluorodeoxyglucose (18F-FDG) in tumor tissue was examined in mice transplanted with NFSa fibrosarcoma. The uptake indexes of 18F-FDG in the heart, skeletal muscle and brain remarkably decreased after treatment with 3 mg/kg of rolipram (heart: 13%, skeletal muscle: 14%, brain: 31%), but fibrosarcoma tissue showed only a 50% reduction in the uptake index of 18F-FDG. The tumor/muscle ratio of radioactivity 30 min after 18F-FDG injection was consequently enhanced from 1.9 to 6.5 by rolipram. This indicates the possible use of rolipram to enhance the sensitivity of tumor detection, as well as characterization of tumors in 18F-FDG PET.

Ultrasound enhancement of fibrinolysis at frequencies of 27 to 100 kHz

Ultrasound (US) accelerates enzymatic fibrinolysis in vitro and in animal models, and may be a useful adjunctive therapy for clinical thrombolysis. Successful clinical application will depend on the selection of appropriate US parameters to optimize fibrinolytic enhancement while limiting adverse effects, including heating. Most studies have been done at megahertz frequencies, but tissue penetration is better and heating less at lower frequencies. We have, therefore, now investigated the effects of continuous-wave and pulsed US on fibrinolysis at midkilohertz frequencies. Fibrinolysis with tissue plasminogen activator (t-PA) was measured by solubilization of radiolabeled fibrin exposed to a calibrated US field in a temperature-controlled water bath. There was significant enhancement of fibrinolysis at frequencies of 27, 40 and 100 kHz, with the greatest effect observed at 27 kHz. The largest effect was observed with continuous-wave US, but significant acceleration was also observed with peak intensities of 1 W/cm(2) duty cycles of 10% and 1%. At a 10% duty cycle, there was approximately 60% of the fibrinolytic enhancement observed with continuous-wave exposure, indicating a clear advantage of pulsing to optimize fibrinolytic effect and limit exposure. We conclude that US in the range of 27 to 100 kHz is effective in accelerating fibrinolysis at intensities and pulsing conditions that minimize the probability of heating and cavitation in clinical applications.

Plasma preparation from whole blood using ultrasound

A technique to efficiently separate plasma from human whole blood is described. Essentially, 3-mL samples are held on the axis of a tubular transducer and exposed for 5.7 min to an ultrasonic standing wave. The cells concentrate into clumps at radial separations of half wavelength. The clumps grow in size and sediment under gravity. A distinct plasma/cell interface forms as the cells sediment. The volume of clarified plasma increases with time. The separation efficiencies of transducers of 29-mm and 23-mm internal diameters driven, by test equipment, at radial resonances of 3.4 and 1.5 MHz, respectively, were compared. The average efficiency of separation was 99.6% at 1.5 MHz and 99.4% with the 3.4-MHz system. The cleared plasma constituted 30% of the sample volume at 1.5 MHz and 25% at 3. 4 MHz. There was no measurable release of haemoglobin or potassium into the suspending phase, indicating that there was no mechanical damage to cells at either frequency. A total of 114 samples from volunteers and patients were subsequently clarified in a 1.5-MHz system driven by an integrated generator. The average efficiency of clarification of blood was 99.76% for the latter samples. The clarification achieved is a significant improvement on that previously reported (98.5%) for whole blood exposed to a planar ultrasonic standing wave field (Peterson et al. 1986). We have, therefore, now achieved a six-fold reduction of cells in plasma compared to previous results.

Inhibition of red cell aggregation prevents spontaneous echocardiographic contrast formation in human blood

BACKGROUND

Spontaneous echocardiographic contrast (SEC) is a pattern of blood echogenicity that has been attributed to ultrasonic backscatter from blood cell aggregates that form under low shear conditions. Patients with left atrial SEC have an increased thromboembolic risk. This study examined the role of red cell and platelet aggregates in the pathogenesis of SEC in human blood and the effects on SEC of antithrombotic therapy and red cell disaggregatory agents.

METHODS AND RESULTS

Blood echogenicity was examined with the use of quantitative videodensitometry over a controlled range of flow velocities in an in vitro model characterized by nonlaminar flow conditions. One hundred ninety study samples were prepared from single fresh blood donations (40 to 120 mL) from 24 healthy volunteers and 11 patients. Whole blood echogenicity was unaltered by depletion of platelets, stimulation of platelet aggregation with adenosine diphosphate, or inhibition of platelet aggregation with aspirin. Low flow-related echogenicity increased with increasing hematocrit (P<.001) but was abolished when red cells were lysed selectively with saponin (P<.001). In the presence of red cells, low flow-related echogenicity increased with increasing fibrinogen concentration (P<.001) and with plasma paraproteins. Low flow-related echogenicity in whole blood was unaltered by heparin and warfarin but was reduced in a dose-dependent manner by dextran 40 (40 mg/mL, 70% reduction, P<.001) and poloxamer 188 (8 mg/mL, 47% reduction, P<.001), which inhibited red cell aggregation.

CONCLUSIONS

These results support protein-mediated red cell aggregation as the mechanism of SEC in human blood. Inhibition of red cell aggregation, indexed by resolution of SEC, may provide an alternative to anticoagulant and antiplatelet therapy to reduce cardiac thromboembolic risk.

Allergen-induced biphasic plasma exudation responses in guinea pig large airways

In this study involving sensitized guinea pigs (anesthetized intramuscularly with a 3:2 mixture of ketamine+xylazine, 1 ml/kg), we applied allergen (ovalbumin) selectively to the tracheobronchial mucosa (sparing the nasal passages and the terminal airways) and examined the occurrence of immediate and late-phase inflammatory exudation of plasma and plasma-derived mediators (bradykinins) into the airway lumen. The experiments were terminated 10 to 480 min after challenge. A selective lavage that sampled the surface liquids of the extrapulmonary bronchi and the lower trachea was performed. The amount of plasma (microliter) was determined by analysis of a plasma tracer, [125I]albumin, in lavage fluid and blood (plasma) samples. Ovalbumin, 3 to 12 pmol, and histamine, 5 and 10 nmol, produced a dose-dependent immediate exudation response (p < 0.001). The effects were nonneurogenic because they were not affected by topical lidocaine given in a dose (3 nmol) that prevented the exudative effect of capsaicin. The 6- and 12-pmol doses of ovalbumin (but not 3 pmol) produced a significant late-phase exudative response at 5 h (p < 0.001), and both the immediate and late phases were associated with increased (p < 0.01 to p < 0.001) levels of bradykinin in the lavage fluids. Histamine, even in doses that produced a greater early response than the allergen, did not produce a late-phase response. A single topical dose of an antiasthma steroid (budesonide, 12 mumol/kg) administered just before ovalbumin (6 pmol) had little effect on the immediate response but inhibited the late-phase response (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

C-13 NMR spectroscopy of plasma reduces interference of hypertriglyceridemia in the H-1 NMR detection of malignancy. Application in patients with breast lesions

We have previously described the application of water-suppressed proton nuclear magnetic resonance (H-1 NMR) spectroscopy of plasma for detection of malignancy. Subsequently, hypertriglyceridemia has been identified as a source of false positive results. We now describe a confirmatory, adjunctive technique--analysis of the carbon-13 (C-13) NMR spectrum of plasma--which also identifies the presence of malignancy but is not sensitive to the plasma triglyceride level. Blinded plasma samples from 480 normal donors and 208 patients scheduled for breast biopsy were analyzed by water-suppressed H-1 and C-13 NMR spectroscopy. Triglyceride levels were also measured. Among the normal donors, there were 38 individuals with hypertriglyceridemia of whom 18 had results consistent with malignancy by H-1 NMR spectroscopy. However, the C-13 technique reduced the apparent H-1 false positive rate from 7.0% to 0.6%. Similarly, in the breast biopsy cohort, C-13 reduced the false positive rate from 2.8% to 0.9%. Furthermore, the accuracy of the combined H-1/C-13 test in this blinded study was greater than 96% in 208 patients studied.

Abnormalities of von Willebrand factor multimers in thrombotic thrombocytopenic purpura and the hemolytic-uremic syndrome

PURPOSE

To analyze and review von Willebrand factor (vWF) multimeric patterns in patients with single-episode thrombotic thrombocytopenic purpura (TTP), intermittent TTP (episodes at infrequent, irregular intervals), chronic relapsing TTP (episodes at frequent, regular intervals), and the hemolytic-uremic syndrome (HUS).

PATIENTS AND METHODS

Platelet-poor plasma samples were obtained in EDTA, citrate, or citrate-hirudin-aprotinin-leupeptin from 36 patients with single-episode TTP, eight patients with intermittent TTP, four patients with chronic relapsing TTP, and 26 patients with HUS. The samples were separated by sodium dodecyl sulfate-agarose gel electrophoresis, overlaid with rabbit 125I-anti-human vWF IgG, and analyzed by autoradiography.

RESULTS

Abnormalities of vWF multimers were found in platelet-poor plasma samples from 31 of 36 found in platelet-poor plasma samples from 31 of 36 patients (86%) at the onset of and during their single TTP episode. vWF multimers larger than those in normal plasma, and similar to vWF forms observed within normal human endothelial cells (unusually large vWF multimers), were demonstrated in 31% of the patients; 19% had either unusually large vWF multimers or a relative decrease in the largest plasma vWF forms in different serial samples; 36% had a relative decrease in the largest plasma vWF forms. These results imply that endothelial cell injury or intense stimulation, along with the attachment of unusually large vWF multimers and the largest plasma vWF forms to platelets, occurred during the single TTP episodes in most patients. Patterns of vWF multimers were normal in 92% of patients with single-episode TTP studied after recovery. All eight patients with intermittent TTP and the four patients with chronic relapsing TTP had unusually large vWF multimers in their plasma between episodes, and these multimers decreased or disappeared during relapses. Of 26 children and adults with HUS, 14 had a relative decrease in the largest plasma vWF multimeric forms and one had unusually large vWF multimers during the episode (vWF multimeric abnormalities in 58% of the patients).

CONCLUSION

It is probable that vWF was involved in the pathophysiology of TTP in most of these patients with the single-episode, intermittent, or chronic relapsing types of TTP, and in more than 50% of the patients with HUS.

[Energy dependence of Hounsfield numbers]

The linear absorption co-efficient of various tissues, as determined by Phelps, was converted into Hounsfield units. This demonstrated their close energy-dependence; the possibility of tissue characterization and differentiation by CT is pointed out.

Attenuation coefficients of various body tissues, fluids, and lesions at photon energies of 18 to 136 keV

Radioactive sources of 241Am, 125I, 153Gd, 170Tm, and 57Co were used to measure the attenuation coefficient muL of various body tissues (gray and white matter, fat, liver, pancreas, and muscle), fluids (water, cerebrospinal fluid, plasma, and red blood cells), and cerebral lesions (blood clots, edematous brain tissue, and eight types of brain tumors) at 16 different energies in the range 18-136 keV. Experimental accuracy was about 0.1-0.3% and 0.2-0.4% in the energy ranges 18-60 keV and 60-136 keV, respectively. Comparisons with values determined in vivo and in vitro with an EMI scanner showed excellent agreement. It is hoped that these findings will provide a better understanding of the photon interactions at the sensitivity level of computed tomography.