Investigating the Molecular Rearrangement of Polar Liquid Mixtures Using Terahertz Frequency Domain Reflection Spectroscopy

A special data processing method for the terahertz frequency domain reflection spectroscopy system has been proposed to analyze the characteristics of a polar mixed liquid. This novel and practical measurement system is characterized by a simpler optical structure and a tunable output frequency range of 0.1-1 THz. By Hilbert transform, stationary wavelet transform, and time domain zero setting method, the reflection coefficient that has been eliminated by the noise and the Fabry-Pérot effect can be obtained by the self-reference calibration method. Then, the dielectric function of the ethanol/n-hexane and propanol/n-hexane mixtures with different mixture ratios can be extracted by this method. In addition, a significant deviation can be observed between the imaginary part of the measured dielectric function and the ideal calculated value. These results indicate that during the mixing process of polar and nonpolar liquids, the hydroxyl functional groups of alcohols significantly change the molecular arrangement pattern of the mixture. The arrangement pattern will result in the formation of the new permanent dipole moment. This study lays a solid foundation for future research on the microscopic mechanism of intermolecular interaction using terahertz frequency domain reflection spectroscopy.

Simple Design of Broadband Polarizers Using Transmissive Metasurfaces for Dual Band Ku/Ka Band Applications

Major challenges affecting polarizers for communication systems include the inability to perform over a wide bandwidth with a simple design. Orthogonal outgoing polarization for polarization-diverse applications and stable performances for oblique incidence angles are also major requirements. This paper presents the design of a polarizer that can perform over a wide range of bandwidths in dual frequency bands. The unit cell is uniquely designed using a split circular ring resonator enclosed in a square ring with the addition of three-square patches. As a result, the incoming linearly polarized x(y) wave is converted into a transmitted LHCP (RHCP) wave in the Ku and Ka bands. The operational bandwidths are 11.05~16.75 GHz (41%) and 34.16~43.03 GHz (23%). The proposed polarizer is ultrathin, works in dual wide-bands, is polarization-diverse, and maintains performance over ±45° and ±30° oblique incidences, which makes it a strong candidate for many communication systems.

Transmissive Polarizer Metasurfaces: From Microwave to Optical Regimes

Metasurfaces, a special class of metamaterials, have recently become a rapidly growing field, particularly for thin polarization converters. They can be fabricated using a simple fabrication process due to their smaller planar profile, both in the microwave and optical regimes. In this paper, the recent progress in MSs for linear polarization (LP) to circular polarization (CP) conversion in transmission mode is reviewed. Starting from history, modeling and the theory of MSs, uncontrollable single and multiple bands and LP-to-CP conversions, are discussed and analyzed. Moreover, detailed reconfigurable MS-based LP-to-CP converters are presented. Further, key findings on the state-of-the-arts are discussed and tabulated to give readers a quick overview. Finally, a conclusion is drawn by providing opinions on future developments in this growing research field.

[Analysis of brain perfusion single-photon emission tomography images using an easy Zscore imaging system for early diagnosis of Alzheimer's disease]

OBJECTIVE

To analyze single-photon emission tomography (SPECT) images of cerebral blood flow perfusion using an easy Z-score imaging system (eZIS) and explore the value of SPECT and eZIS in early diagnosis of Alzheimer's disease (AD).

METHODS

We retrospectively analyzed the clinical data of 71 subjects undergoing brain perfusion SPECT examination in our department from September, 2018 to September, 2020 and identified 31 eligible subjects for this study. Among these subjects, according to the NIA-AA criteria (2011 edition), 12 were diagnosed with mild cognitive impairment due to AD (MCI) and 11 with AD dementia stage (AD); 8 elderly subjects were healthy without cognitive impairment (NC). All these subjects underwent brain perfusion SPECT, and eZIS-assisted analysis was used to obtain the index values (severity, range and ratio). The differences in the severity, extent and ratio among the 3 groups were compared, and the diagnostic efficacy of single and joint analysis of the 3 indexes for early AD was analyzed.

RESULTS

There was no significant difference in gender, age and education level among the 3 groups (P>0.05). Compared with those in NC group, the Mini Mental State Examination Scale (MMSE) scores were significantly lowered in AD group and MCI group; the MMSE score was significantly lower in AD group than in MCI group (P < 0.05). The patients with AD had significantly greater disease severity and extent than those with MCI group; the severity, range and ratio in both AD group and MCI group were significantly higher than those of NC group, but the ratio did not differ significantly between AD group and MCI group (P>0.05). In single index analysis, severity had the highest diagnostic performance (AUC=0.911) and sensitivity (87.0%); the diagnostic performance and sensitivity of joint analysis were better than those of single analysis, and joint analysis of range and ratio showed high diagnostic performance (AUC=0.948) and sensitivity (87.0%).

CONCLUSION

The analysis of brain perfusion SPECT using an eZIS program can be useful for early diagnosis of AD.

High-power vacuum terahertz photomixer and integrated circuits based on microscale phototubes

Technologies and industrials in long-distance communication, detection, and imaging applications are still in great need of higher-output-power terahertz sources. This paper proposes two kinds of microscale vacuum phototube based high-power terahertz source: vacuum photomixer and terahertz integrated circuit. The principle of photomixer based on photoemission and field-assisted photoemission is demonstrated. Its capability of producing radiation power beyond 1 mW is estimated based on theoretical analysis and experimental evidence. Simulation and theoretical analysis have shown that the fundamental THz photodiode devices can operate with a space-charge limited current density of 4496 A/cm² at 60 V, and the amplifier circuits are calculated to have a gain performance of around 10 dB. The two photoemission-based roadmaps have the potential to be developed from an emerging and interdisciplinary field to more promising future directions of THz science and technology.

Design of planar distributed three beam electron gun with narrow beam separation for W band staggered double vane TWT

A novel planar distributed three-beam electron gun with narrow beam separations is designed based on grids loaded sheet beam method. The dimensions of the three-beam gun in the y-O-z plane are determined using our basic theoretical design method developed for sheet beam gun. The results show that the profile of focusing electrode in the y-O-z plane is related to the beam width in the x-O-z plane. Then, the characteristics and parameters of three-beam array formation with their stability are analyzed thoroughly by adjustment of control grids in the x-O-z plane. Each of the beamlet obtained is with a small axial deviation of the two transverse waists. Based on the theoretical analysis and simulations, the planar three-beam electron gun is constructed with the beam voltage of 22 kV and the current of 3 [Formula: see text] 0.15 A. The average radius of 0.08 mm at each beam waist is obtained with the compression factor of 4 for the 0.18 mm beam tunnel radius. The beam waist can be achieved at about 4.4 mm away from the cathode with the axis separation about 0.46 mm for each of beamlet. Thus, the design method can be generally used to construct such type of narrow beam separation and planar distributed multiple beam electron gun for the miniaturization and integrated vacuum electron devices in millimeter wave and terahertz band.

von Willebrand factor promotes platelet-induced metastasis of osteosarcoma through activation of the VWF-GPIb axis

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Immunohistochemistry results directly show VWF is increased during tumor progression.

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VWF is expressed as low molecular weight multimer in OS cell line SAOS2.

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VWF promotes platelet-induced metastasis of OS through VWF-GPIb pathway.

von Willebrand factor (VWF) is exclusively expressed in endothelial cells (ECs) and megakaryocytes, which plays a crucial role in the initiation of arterial thrombosis. Recent studies have shown that VWF is also expressed in osteosarcoma (OS) cells and participates in adhesion of cancer cells to platelets, thus promoting metastasis of OS cells. However, it is unclear how OS cell-derived VWF-platelet interaction contributes to the metastasis of OS. We hypothesized that the interaction is mediated by the binding between VWF A1 and GPIbα of platelets, a molecular mechanism similar to that of thrombosis. The increased expression of VWF in SAOS2 cells may contribute to the enhancement of platelet adhesion through the VWF-GPIb pathway, which could promote the migration and invasion capacities of SAOS2 cells in vitro. Antibodies that block the pathway could significantly inhibit the platelet-induced metastasis of OS cells. Our results suggest a theoretical basis for the development of new anti-OS metastasis drugs, and further enrich the mechanism of OS metastasis.

Extremely Sensitive Microwave Sensor for Evaluation of Dielectric Characteristics of Low-Permittivity Materials

In this paper, an extremely sensitive microwave sensor is designed based on a complementary symmetric S shaped resonator (CSSSR) to evaluate dielectric characteristics of low-permittivity material. CSSSR is an artificial structure with strong and enhanced electromagnetic fields, which provides high sensitivity and a new degree of freedom in sensing. Electromagnetic simulation elucidates the effect of real relative permittivity, real relative permeability, dielectric and magnetic loss tangents of the material under test (MUT) on the resonance frequency and notch depth of the sensor. Experiments are performed at room temperature using low-permittivity materials to verify the concept. The proposed design provides differential sensitivity between 102% to 95% as the relative permittivity of MUT varies from 2.1 to 3. The percentage error between simulated and measured results is less than 0.5%. The transcendental equation has been established by measuring the change in the resonance frequency of the fabricated sensor due to interaction with the MUT.

Super Wide Band, Defected Ground Structure (DGS), and Stepped Meander Line Antenna for WLAN/ISM/WiMAX/UWB and other Wireless Communication Applications

This paper presents a new shape (s-shape monopole) of a super wideband antenna using stepped meander lines, a quarter waveguide transformer feeding line, and a defected ground structure (DGS). The antenna will be used for multiple wireless communication applications like WIMAX/WLAN/ISM/UWB, and also for several wireless communication applications. The total dimensions of the proposed antenna are 35 mm × 35 mm × 1.57 mm or 0.36 λo × 0.36 λo × 0.016 λo, which are the corresponding electrical dimensions with free-space wavelength (λo) at the lower operating frequency. The antenna is designed and simulated into two steps: the first (Antenna 1) covers a bandwidth of 18.2 GHz, while the second (Antenna 2, using DGS) covers a super wide bandwidth of 37.82 GHz (3.08-40.9 GHz). The measured fractional bandwidth and bandwidth ratio of the antenna are 174.68% and 13.009:1, respectively, which is operating from 3.09-40.2 GHz. The maximum calculated gain and efficiency are 5.9 dBi and 92.7%, respectively. The time-domain performance is good due to the calculation of the system fidelity factor, group delay, and its linear and constant phase variation.

Optimization of acquisition parameters for reduced-dose thoracic CT: A phantom study

PURPOSE

The purpose of this study was to analyze the impact of different options for reduced-dose computed tomography (CT) on image noise and visibility of pulmonary structures in order to define the best choice of parameters when performing ultra-low dose acquisitions of the chest in clinical routine.

MATERIALS AND METHODS

Using an anthropomorphic chest phantom, CT images were acquired at four defined low dose levels (computed tomography dose index [CTDI_vol]=0.15, 0.20, 0.30 and 0.40mGy), by changing tube voltage, pitch factor, or rotation time and adapting tube current to reach the predefined CTDI_vol-values. Images were reconstructed using two different levels of iteration (adaptive statistical iterative reconstruction [ASIR®]-v70% and ASIR®-v100%). Signal-to-noise ratio (SNR) as well as contrast-to-noise ratio (CNR) was calculated. Visibility of pulmonary structures (bronchi/vessels) were assessed by two readers on a 5-point-Likert scale.

RESULTS

Best visual image assessments and CNR/SNR were obtained with high tube voltage, while lowest scores were reached with lower pitch factor followed by high tube current. Protocols favoring lower pitch factor resulted in decreased visibility of bronchi/vessels, especially in the periphery. Decreasing radiation dose from 0.40 to 0.30mGy was not associated with a significant decrease in visual scores (P<0.05), however decreasing radiation dose from 0.30mGy to 0.15mGy was associated with a lower visibility of most of the evaluated structures (P<0.001). While image noise could be significantly reduced when ASIR®-v100% instead of ASIR®-v70% was used, the visibility-scores of pulmonary structures did not change significantly.

CONCLUSION

Favoring high tube voltage is the best option for reduced-dose protocols. A decrease of SNR and CNR does not necessarily go along with reduced visibility of pulmonary structures.

Measurement and analysis of maxillary anterior teeth color in the chinese population

Background

To measure the difference in the crown color of the maxillary anterior teeth in the Chinese population, to study its potential regularity, and to provide a reference for the colorimetry of oral anterior teeth restoration.

Material and Methods

Using VITA Easyshade Advance4.0 spectrophotometer (the colorimetric system is CIE-1976-L*a*b*), adult patients who were treated in Sanming Integrated Medicine Hospital, Fujian Province, China, from January 2022 to June 2022 160 patients (88 males, 72 females, aged 20-60 years) were used as the survey subjects, and the L*a*b* of 1/3 of the crowns of 6 anterior teeth (central incisors, lateral incisors, canines) were measured Value, statistical analysis was performed with SPSS 26.0 software.

Results

The mean L* values of maxillary central incisors, lateral incisors, and canines in the Chinese population were: (73.02±4.41), (69.96±4.70), (65.14±4.21); the mean a* values were: (-0.54±4.21) 0.35), (0.22±0.63), (1.40±0.62), and the mean values of b* were: (14.50±3.23), (18.60±3.94), (23.64±3.30). 1. There was no significant difference in L*a*b* value between left and right symmetrical teeth with the same name (P>0.05). 2. There was no statistical difference in the L*a*b* value between genders (P>0.05), 3. There was a statistical difference in L*a*b* value between different tooth positions (P< 0.05). 4. There were significant differences in L*a*b* values in different age groups (P< 0.05).

Conclusions

1. The color of the labial crown of maxillary anterior teeth in the Chinese population is related to different age groups and tooth positions but not gender. 2. In the Chinese population, the color of the maxillary anterior teeth on the labial side gradually decreased from the central incisor to the distal end of the dental arch while the chroma gradually increased. 3. With age increase, the L* and a* values of the upper central incisors, upper lateral incisors, and upper canines gradually decrease, and the b* value gradually increases. The teeth became darker, more yellow, and redder. 4. In the clinical colorimetry of the upper anterior teeth, the contralateral tooth with the same name is preferred. Suppose the tooth with the same name is missing at the same time. In that case, when using the adjacent teeth as a reference, the different brightness and chroma between the central incisors, lateral incisors, and canine teeth should be compared. Change trend to determine. 5. A uniform tooth color should not be selected for anterior restoration, and age should be considered when choosing a color for the patient. Key words:Upper anterior teeth, Crown color, CIE-1976-L*a*b*, spectrophotometric colorimeter.

High Efficient and Ultra Wide Band Monopole Antenna for Microwave Imaging and Communication Applications

The paper presents a highly efficient, low cost, ultra-wideband, microstrip monopole antenna for microwave imaging and wireless communications applications. A new structure (z-shape, ultra-wideband (UWB) monopole) is designed, which consists of stepped meander lines to achieve super-wide bandwidth and high efficiency. Three steps are used to design the proposed structure for the purpose to achieve high efficiency and wide bandwidth. The antenna bandwidth is enhanced by varying the length of meander line slots, optimization of the feeding line and with the miniaturization of the ground width. The simulated and measured frequency bands are 2.7-22.5 GHz and 2.8-22.7 GHz (156% fractional bandwidth), respectively. The dimensions of the antenna are 38 mm × 35 mm × 1.57 mm, and its corresponding electrical size is 2.41 λg × 2.22 λg × 0.09 λg, where guided wavelength λg is at the center frequency (12.75 GHz). This antenna achieved a high bandwidth ratio (8.33:1). The realized gain is varying from 1.6-6.4 dBi, while that of efficiency is 70% to 93% for the whole band. Radiation patterns are measured at four operating frequencies. It has an acceptable group delay, fidelity factor, and phase variation results that satisfy the limit of ultra-wideband in the form of the time domain.

Complementary Metamaterial Sensor for Nondestructive Evaluation of Dielectric Substrates

In this paper, complementary metamaterial sensor is designed for nondestructive evaluation of dielectric substrates. The design concept is based on electromagnetic stored energy in the complementary circular spiral resonator (CCSR), which is concentrated in small volume near the host substrate at resonance. This energy can be employed to detect various electromagnetic properties of materials under test (MUT). Effective electric permittivity and magnetic permeability of the proposed sensor is extracted from scattering parameters. Sensitivity analysis is performed by varying the permittivity of MUT. After sensitivity analysis, a sensor is fabricated using standard PCB fabrication technique, and resonance frequency of the sensor due to interaction with different MUT is measured using vector network analyzer (AV3672series). The transcendental equation is derived for the fabricated sensor to calculate relative permittivity for unknown MUTs. This method is very simple and requires calculating only the resonant frequency, which reduces the cost and computation time.

High-Sensitivity Microwave Sensor for Liquid Characterization Using a Complementary Circular Spiral Resonator

This paper describes a low-cost, small size, and high-sensitivity microwave sensor using a Complementary Circular Spiral Resonator (CCSR), which operates at around 2.4 GHz, for identifying liquid samples and determining their dielectric constants. The proposed sensor was fabricated and tested to effectively identify different liquids commonly used in daily life and determine the concentrations of various ethanol–water mixtures at by measuring the resonant frequency of the CCSR. Using acrylic paint, a square channel was drawn at the most sensitive position of the microwave sensor to ensure accuracy of the experiment. To estimate the dielectric constants of the liquids under test, an approximate model was established using a High-Frequency Simulator Structure (HFSS). The results obtained agree very well with the existing data. Two parabolic equations were calculated and fitted to identify unknown liquids and determine the concentrations of ethanol–water mixtures. Thus, our microwave sensor provides a method with high sensitivity and low consumption of material for liquid monitoring and determination, which proves the feasibility and broad prospect of this low-cost system in industrial application.

The In Vitro Effect of Ticlopidine on Fibrinogen and Factor VIII Binding to Human Platelets

The mode of action of the antiplatelet agent ticlopidine is not yet fully understood. Its multiple effects on platelet function include prolongation of the bleeding time, reduction in primary and secondary Waves of ADP-induced aggregation and inhibition of collagen and thrombin-induced aggregation. We have studied the in vitro effects of ticlopidine on fibrinogen binding induced by ADP and adrenaline as well as factor VIII/vWF binding induced by ristocetin.

125I-fibrinogen binding was measured in suspensions of freshly washed normal platelets stimulated by 10 μM ADP or 10 μM adrenaline. The binding of 125I-factor VIII/vWF in the presence of 1 mg/ml ristocetin was measured in both washed and paraformaldehyde-fixed platelets. Ticlopidine at final concentrations of 200, 100, 50 and 25 μM inhibited both ADP and adrenaline-induced fibrinogen binding in a dose-dependent manner. The mean % inhibition of ADP-induced fibrinogen binding was 82, 73, 42 and 32 respectively. The mean % inhibition of adrenaline induced fibrinogen binding was 86, 82, 60 and 35 respectively. In contrast, the factor VIII/vWF binding was unaffected by ticlopidine at all concentrations except at 200 μM using fresh platelets where a slight inhibition (19%) was observed.

These results suggest that ticlopidine either inhibits platelet activation and consequently fibrinogen binding, or inhibits the binding directly, presumably by having an effect on the specific configuration of the platelet membrane required for normal fibrinogen binding.

Clinical and molecular insights into Glanzmann's thrombasthenia in China

Glanzmann's thrombasthenia (GT) is a rare bleeding disorder characterized by spontaneous mucocutaneous bleeding. The disorder is caused by quantitative or qualitative defects in integrin αIIbβ3 (encoded by ITGA2B and ITGB3) on the platelet and is more common in consanguineous populations. However, the prevalence rate and clinical characteristics of GT in non-consanguineous populations have been unclear. We analyzed 97 patients from 93 families with GT in the Han population in China. This analysis showed lower consanguinity (18.3%) in Han patients than other ethnic populations in GT-prone countries. Compared with other ethnic populations, there was no significant difference in the distribution of GT types. Han females suffered more severe bleeding and had a poorer prognosis. We identified a total of 43 different ITGA2B and ITGB3 variants, including 25 previously unidentified, in 45 patients. These variants included 14 missense, 4 nonsense, 4 frameshift, and 3 splicing site variants. Patients with the same genotype generally manifested the same GT type but presented with different bleeding severities. This suggests that GT clinical phenotype does not solely depend on genotype. Our study provides an initial, yet important, clinical and molecular characterization of GT heterogeneity in China.

Exome sequencing identifies highly recurrent somatic GATA2 and CEBPA mutations in acute erythroid leukemia

Acute erythroid leukemia (AEL), characterized by a predominant erythroid proliferation, is a subtype of acute myelogenous leukemia. The genetic basis of AEL remains poorly defined. Through whole-exome sequencing, we identified high frequencies of mutations in CEBPA (32.7%), GATA2 (22.4%), NPM1 (15.5%), SETBP1 (12.1%) and U2AF1 (12.1%). Structure prediction analysis revealed that most of the GATA2 mutations were located at the DNA-binding N-terminal zinc-finger near the DNA-binding interface, suggesting that mutations could result in at least partial inactivation of GATA2 protein. On co-transfection of a GATA-responsive reporter construct together with plasmids expressing either GATA2 wild-type or GATA2 ZF1 mutants (P304H, L321P and R330X) in 293T cells, we found a reduced transcriptional activation in cells transfected with GATA2 mutants. To determine whether reduced GATA2 function is involved in leukemogenesis of AEL, we transfected 32D cells with GATA2 mutants and evaluated the impact of GATA2 mutations on erythroid differentiation. Our data revealed an increased expression of erythroid-related antigens Ter-119, β-globin and βh1-globin, as well as increased hemoglobin positivity in 32D cells transfected with GATA2 mutants compared with control cells. Our results suggest that the decline of GATA2 resulting from mutations contributes to the erythroid commitment, differentiation and the development of AEL.

The glycoprotein Ibalpha-von Willebrand factor interaction induces platelet apoptosis

BACKGROUND

The interaction of glycoprotein (GP) Ibalpha with von Willebrand factor (VWF) initiates platelet adhesion, and simultaneously triggers intracellular signaling cascades leading to platelet aggregation and thrombus formation. Some of the signaling events are similar to those occurring during apoptosis, however, it is still unclear whether platelet apoptosis is induced by the GPIbalpha-VWF interaction.

OBJECTIVES

To investigate whether the GPIbalpha-VWF interaction induces platelet apoptosis and the role of 14-3-3zeta in apoptotic signaling.

METHODS

Apoptotic events were assessed in platelets or Chinese hamster ovary (CHO) cells expressing wild-type (1b9) or mutant GPIb-IX interacting with VWF by flow cytometry or western blotting.

RESULTS

Ristocetin-induced GPIbalpha-VWF interaction elicited apoptotic events in platelets, including phosphatidylserine exposure, elevations of Bax and Bak, gelsolin cleavage, and depolarization of mitochondrial inner transmembrane potential. Apoptotic events were also elicited in platelets exposed to pathologic shear stresses in the presence of VWF; however, the shear-induced apoptosis was eliminated by the anti-GPIbalpha antibody AK2. Furthermore, apoptotic events occurred in 1b9 cells stimulated with VWF and ristocetin, but were significantly diminished in two CHO cell lines expressing mutant GPIb-IX with GPIbalpha truncated at residue 551 or a serine-to-alanine mutation at the 14-3-3zeta-binding site in GPIbalpha.

CONCLUSIONS

This study demonstrates that the GPIbalpha-VWF interaction induces apoptotic events in platelets, and that the association of 14-3-3zeta with the cytoplasmic domain of GPIbalpha is essential for apoptotic signaling. This finding may suggest a novel mechanism for platelet clearance or some thrombocytopenic diseases.

Two novel monoclonal antibodies to VWFA3 inhibit VWF-collagen and VWF-platelet interactions

BACKGROUND

The interaction of collagen-von Willebrand factor (VWF)-GPIb is essential for platelet adhesion, especially under high shear conditions. VWF, which acts as a bridge between platelets and exposed subendothelium, interacts with collagen through its A3 domain, which is a new target for the antithrombotic agent.

OBJECTIVE

To develop functional blockers that specifically inhibit VWF-dependent adhesion of platelets to collagen under high shear stress.

METHODS

To develop murine antihuman VWF A3 monoclonal antibodies (mAbs) by standard hybridoma technology, and characterize their abilities to block interactions between VWF A3 and collagen as well as platelet function.

RESULTS

Thirty anti-VWF-A3 mAbs were obtained. Among them, two mAbs, designated as SZ-123 and SZ-125, were found to inhibit VWF-collagen type III interaction. SZ-123 and SZ-125 inhibited the binding of purified human VWF (1.5 or 3 mug mL(-1)) to human placenta collagen type III (IC(50) = 0.07 +/- 0.02 and 0.15 +/- 0.03 mug mL(-1), respectively) or to calf skin collagen type III (IC(50) = 0.48 +/- 0.06 and 0.51 +/- 0.07 mug mL(-1), respectively) coated on plates. Under flow shear condition (1000 s(-1)), SZ-123 and SZ-125 inhibited platelet adhesion on human placenta collagen- or calf skin collagen-coated surfaces. Both mAbs also inhibited platelet aggregation induced by ristocetin, botrocetin or bovine plasma.

CONCLUSIONS

SZ-123 and SZ-125 inhibited VWF-collagen and VWF-platelet interactions.

ADAMTS-13 plasma level determination uncovers antigen absence in acquired thrombotic thrombocytopenic purpura and ethnic differences

BACKGROUND

The recently discovered plasma enzyme ADAMTS-13 cleaves the A2-domain of von Willebrand factor (VWF). A defective cleaving protease results in unusually large VWF multimers, which cause thrombotic thrombocytopenic purpura (TTP).

AIM

Analysis of the ADAMTS-13 antigen levels in TTP patients compared with normal donors.

METHODS

An antigen ELISA test was built, based on high affinity anti-ADAMTS-13 monoclonal antibodies, which were generated using genetic immunization.

RESULTS

Specificity of the ADAMTS-13 antigen test was confirmed, as (i) plasma from a patient with acquired TTP but presenting without inhibitor did not contain antigen and (ii) the binding of recombinant ADAMTS-13 was inhibited by increasing amounts of normal plasma. The assay is sensitive as it can detect antigen levels as low as 1.6% of normal. The concentration in normal pooled human plasma was determined (1.03 +/- 0.15 microg mL(-1)) and arbitrarily set to 1 U mL(-1). The antigen levels in congenital TTP samples (34 +/- 21 mU mL(-1), n = 2), as well as in samples from patients with acquired TTP (231 +/- 287 mU mL(-1), n = 11), were clearly reduced when compared with normal Caucasian donors (951 +/- 206 mU mL(-1), n = 16). Remarkably, normal Chinese donors have a significantly lower antigen titer (601 +/- 129 mU mL(-1), n = 15), when compared with normal Caucasians.

CONCLUSIONS

Our results show that acquired TTP patients suffer mainly from ADAMTS-13 antigen depletion, thereby indicating the importance of ADAMTS-13 antigen determination in diagnosis and patient follow-up.

Platelet-derived VWF-cleaving metalloprotease ADAMTS-13

The adhesion ligand von Willebrand factor (VWF) is synthesized and stored in vascular endothelial cells and megakaryocytes/platelets. As in endothelial cells, platelet VWF also contains ultra-large (UL) multimers that are hyperactive in aggregating platelets. ULVWF in platelet lysates of thrombin-stimulated platelets was only detected in the presence of EDTA, suggesting that ULVWF is cleaved by a divalent cation-dependent protease. A recent study shows that platelets contain the VWF-cleaving metalloprotease ADAMTS-13, but its activity remains unknown. In this study, we show that platelet lysates cleave endothelial cell-derived ULVWF under static and flow conditions. This activity is inhibited by EDTA and by an ADAMTS-13 antibody from the plasma of a patient with acquired TTP. ADAMTS-13 was detected in platelet lysates and on the platelet surface by four antibodies that bind to different domains of the metalloprotease. Expression of ADAMTS-13 on the platelet surface increases significantly upon platelet activation by the thrombin receptor-activating peptide, but not by ADP. These results demonstrate that platelets contain functionally active ADAMTS-13. This intrinsic activity may be physiologically important to prevent the sudden release of hyperactive ULVWF from platelets and serves as the second pool of ADAMTS-13 to encounter the increase in ULVWF release from endothelial cells.