Natural history of deep vein thrombosis in children

OBJECTIVE

To determine the natural history of deep vein thrombosis in children presented with a first episode in the lower extremity veins.

METHODS

Children with objective diagnosis of acute deep vein thrombosis were followed up with ultrasound and clinical examination. Risk factors and clinical presentation were prospectively collected. The prevalence of recurrent deep vein thrombosis and the development of signs and symptoms of chronic venous disease were recorded.

RESULTS

There were 27 children, 15 males and 12 females, with acute deep vein thrombosis, with a mean age of 4 years, range 0.1-16 years. The median follow-up was 23 months, range 8-62 months. The location of thrombosis involved the iliac and common femoral vein in 18 patients and the femoral and popliteal veins in 9. Only one vein was affected in 7 children, two veins in 14 and more than two veins in 6. Recurrent deep vein thrombosis occurred in two patients, while no patient had a clinically significant pulmonary embolism. Signs and symptoms of chronic venous disease were present at last follow-up in 11 patients. There were nine patients with vein collaterals, but no patient developed varicose veins. Reflux was found in 18 veins of 11 patients. Failure of recanalization was seen in 7 patients and partial recanalization in 11. Iliofemoral thrombosis (p = 0.012) and failure to recanalize (p = 0.036) increased significantly the risk for developing signs and symptoms.

CONCLUSIONS

Children with acute proximal deep vein thrombosis develop mild chronic venous disease signs and symptoms at mid-term follow-up and are closely related with iliofemoral thrombosis and failure to recanalization.

Disappearance of nodal gap across the insulator-superconductor transition in a copper-oxide superconductor

The parent compound of the copper-oxide high-temperature superconductors is a Mott insulator. Superconductivity is realized by doping an appropriate amount of charge carriers. How a Mott insulator transforms into a superconductor is crucial in understanding the unusual physical properties of high-temperature superconductors and the superconductivity mechanism. Here we report high-resolution angle-resolved photoemission measurement on heavily underdoped Bi₂Sr₂-xLaxCuO(₆+δ) system. The electronic structure of the lightly doped samples exhibit a number of characteristics: existence of an energy gap along the nodal direction, d-wave-like anisotropic energy gap along the underlying Fermi surface, and coexistence of a coherence peak and a broad hump in the photoemission spectra. Our results reveal a clear insulator-superconductor transition at a critical doping level of ~0.10 where the nodal energy gap approaches zero, the three-dimensional antiferromagnetic order disappears, and superconductivity starts to emerge. These observations clearly signal a close connection between the nodal gap, antiferromagnetism and superconductivity.

The role of hydrolases in bacterial cell-wall growth

Although hydrolysis is known to be as important as synthesis in the growth and development of the bacterial cell wall, the coupling between these processes is not well understood. Bond cleavage can generate deleterious pores, but may also be required for the incorporation of new material and for the expansion of the wall, highlighting the importance of mechanical forces in interpreting the consequences of hydrolysis in models of growth. Critically, minimal essential subsets of hydrolases have now been identified in several model organisms, enabling the reduction of genetic complexity. Recent studies in Bacillus subtilis have provided evidence for both the presence and absence of coupling between synthesis and hydrolysis during sporulation and elongation, respectively. In this review, we discuss strategies for dissecting the relationship between synthesis and hydrolysis using time-lapse imaging, biophysical measurements of cell-wall architecture, and computational modeling.

Determining the impact of instrument variation and automated software algorithms on the TGT in hemophilia and normalized plasma

BACKGROUND

Despite increasing recognition as a more precise test of in vivo hemostatic conditions, standardization of the thrombin generation test (TGT) continues to hinder its development as routine clinical practice. Prior efforts largely focused on comparing the effects of experimental conditions and different reagents. Commercialized kits, instruments and software have been introduced to calculate the TG curve and its parameters. However, modified versions of the TGT continue to be used worldwide on a variety of microplate reader instruments and processed using individualized algorithms. No prior study has compared the effect of instrument choice and its inherent noise profile on the processing of the TG curve and its common endpoint parameters.

MATERIALS AND METHODS

Hemophilia A plasma supplemented with buffer or Factor VIII, mimicking hemophilic or normalized samples respectively, was monitored for thrombin generation after activation with TF on six different fluorescent microplate readers. Each instrument was optimized for TGT signal recording prior to testing. An automated software package containing various mathematical algorithms was utilized to compute the TG curves and parameters, and compare different TG processing approaches.

RESULTS

Instruments produced unique noise profiles and end-point parameters that were incomparable in absolute signal terms. Similar relative hemophilic responses were obtained across various instruments when the normalized plasma sample was used as an internal standard. Smoothing algorithms corrected destructive instrument noise.

CONCLUSIONS

Instrument-induced errors from numerical differentiation during TG curve processing cannot be eliminated by external calibrators, and require careful qualification of the instrument and implementation of noise-reducing software algorithms.

Correction of microplate location effects improves performance of the thrombin generation test

Background

Microplate-based thrombin generation test (TGT) is widely used as clinical measure of global hemostatic potential and it becomes a useful tool for control of drug potency and quality by drug manufactures. However, the convenience of the microtiter plate technology can be deceiving: microplate assays are prone to location-based variability in different parts of the microtiter plate.

Methods

In this report, we evaluated the well-to-well consistency of the TGT variant specifically applied to the quantitative detection of the thrombogenic substances in the immune globulin product. We also studied the utility of previously described microplate layout designs in the TGT experiment.

Results

Location of the sample on the microplate (location effect) contributes to the variability of TGT measurements. Use of manual pipetting techniques and applications of the TGT to the evaluation of procoagulant enzymatic substances are especially sensitive. The effects were not sensitive to temperature or choice of microplate reader. Smallest location effects were observed with automated dispenser-based calibrated thrombogram instrument. Even for an automated instrument, the use of calibration curve resulted in up to 30% bias in thrombogenic potency assignment.

Conclusions

Use of symmetrical version of the strip-plot layout was demonstrated to help to minimize location artifacts even under the worst-case conditions. Strip-plot layouts are required for quantitative thrombin-generation based bioassays used in the biotechnological field.

Mapping the binding region on the low density lipoprotein receptor for blood coagulation factor VIII

Low density lipoprotein receptor (LDLR) was shown to mediate clearance of blood coagulation factor VIII (FVIII) from the circulation. To elucidate the mechanism of interaction of LDLR and FVIII, our objective was to identify the region of the receptor necessary for binding FVIII. Using surface plasmon resonance, we found that LDLR exodomain and its cluster of complement-type repeats (CRs) bind FVIII in the same mode. This indicated that the LDLR site for FVIII is located within the LDLR cluster. Similar results were obtained for another ligand of LDLR, α-2-macroglobulin receptor-associated protein (RAP), a common ligand of receptors from the LDLR family. We further generated a set of recombinant fragments of the LDLR cluster and assessed their structural integrity by binding to RAP and by circular dichroism. A number of fragments overlapping CR.2-5 of the cluster were positive for binding RAP and FVIII. The specificity of these interactions was tested by site-directed mutagenesis of conserved tryptophans within the LDLR fragments. For FVIII, the specificity was also tested using a single-chain variable antibody fragment directed against the FVIII light chain as a competitor. Both cases resulted in decreased binding, thus confirming its specificity. The mutagenic study also showed an importance of the conserved tryptophans in LDLR for both ligands, and the competitive binding results showed an involvement of the light chain of FVIII in its interaction with LDLR. In conclusion, the region of CR.2-5 of LDLR was defined as the binding site for FVIII and RAP.

Molecular characterization and an infectious clone construction of sweet potato leaf curl virus (SPLCV) isolated from Korea

Sweet potato leaf curl disease (SPLCD) was primarily identified in sweet potato fields in Korea in 2003, and the complete genomic sequence of sweet potato leaf curl virus (SPLCV) has been cloned. The genome of the Korean SPLCV isolate (SPLCV-KR) comprises 2,828 nucleotides with six open reading frames in DNA-A, similar to a monopartite begomovirus. Additionally, neither the genome B genomic component nor the DNA beta sequence was detected. The results of phylogenetic analysis using the maximum parsimony method showed that SPLCV-KR is more closely related to SPLCV-US (US) than SPLCV-CN (China) and SPLCV-JP (Japan). A tandem repeat dimer of SPLCV-KR was cloned and found to be infectious in sweet potatoes (Ipomoea batatas) via biolistic inoculation. The SPLCV-infected sweet potatoes exhibited mild leaf curl symptoms of SPLCD, and the newly-replicated viral DNA was detected via Southern blot analysis. Results of biotic, molecular, and phylogenetic characterization suggest that SPLCV-KR is a new strain of SPLCV and is importantly placed in the evolutionary progression from curtoviruses to begomoviruses.

KEYWORDS

sweet potato leaf curl virus; sweet potato leaf curl disease; phylogenetic analysis; infectious clone; biolistic infection.

Insect cell-based expression and characterization of a single-chain variable antibody fragment directed against blood coagulation factor VIII

A recombinant single-chain variable antibody fragment (scFv) KM33 was previously described as a ligand that can inhibit the function of blood coagulation factor VIII (FVIII). This scFv was previously derived from an individual with anti-FVIII antibodies manifested in FVIII functional deficiency (Hemophilia A) and expressed in bacteria. In the present work, we describe an alternative approach for fast and easy production of KM33 in insect cells (Spodoptera frugiperda). The KM33 gene was codon-optimized and expressed in secreted form using a baculovirus system. The protein was isolated using metal-affinity and size-exclusion chromatography to purity of about 96% and yield of 0.4-1.2 mg per 120 mL of culture, based on several independent expression experiments. In a binding assay using surface plasmon resonance, the insect cell-derived KM33 (iKM33) was qualified as a high-affinity ligand for FVIII. Epitope specificity of iKM33 on FVIII (C1 domain) was confirmed by testing the binding with a relevant mutant of FVIII. In several FVIII functional tests (factor Xa generation, APTT clotting, thrombin generation and video microscopy clot growth assays), iKM33 strongly inhibited FVIII activity in accordance with the clinical effect of the parental antibody. Therefore, the expressed protein was concluded to be fully functional and applicable in various assays with FVIII.

Computational modeling of mammalian signaling networks

One of the most exciting developments in signal transduction research has been the proliferation of studies in which a biological discovery was initiated by computational modeling. In this study, we review the major efforts that enable such studies. First, we describe the experimental technologies that are generally used to identify the molecular components and interactions in, and dynamic behavior exhibited by, a network of interest. Next, we review the mathematical approaches that are used to model signaling network behavior. Finally, we focus on three specific instances of 'model-driven discovery': cases in which computational modeling of a signaling network has led to new insights that have been verified experimentally.

High-throughput, single-cell NF-κB dynamics

Single cells in a population often respond differently to perturbations in the environment. Live-cell microscopy has enabled scientists to observe these differences at the single-cell level. Some advantages of live-cell imaging over population-based methods include better time resolution, higher sensitivity, automation, and richer datasets. One specific area where live-cell microscopy has made a significant impact is the field of NF-κB signaling dynamics, and recent efforts have focused on making live-cell imaging of these dynamics more high-throughput. We highlight the major aspects of increasing throughput and describe a current system that can monitor, image and analyze the NF-κB activation of thousands of single cells in parallel.

Single-cell NF-kappaB dynamics reveal digital activation and analogue information processing

Cells operate in dynamic environments using extraordinary communication capabilities that emerge from the interactions of genetic circuitry. The mammalian immune response is a striking example of the coordination of different cell types. Cell-to-cell communication is primarily mediated by signalling molecules that form spatiotemporal concentration gradients, requiring cells to respond to a wide range of signal intensities. Here we use high-throughput microfluidic cell culture and fluorescence microscopy, quantitative gene expression analysis and mathematical modelling to investigate how single mammalian cells respond to different concentrations of the signalling molecule tumour-necrosis factor (TNF)-alpha, and relay information to the gene expression programs by means of the transcription factor nuclear factor (NF)-kappaB. We measured NF-kappaB activity in thousands of live cells under TNF-alpha doses covering four orders of magnitude. We find, in contrast to population-level studies with bulk assays, that the activation is heterogeneous and is a digital process at the single-cell level with fewer cells responding at lower doses. Cells also encode a subtle set of analogue parameters to modulate the outcome; these parameters include NF-kappaB peak intensity, response time and number of oscillations. We developed a stochastic mathematical model that reproduces both the digital and analogue dynamics as well as most gene expression profiles at all measured conditions, constituting a broadly applicable model for TNF-alpha-induced NF-kappaB signalling in various types of cells. These results highlight the value of high-throughput quantitative measurements with single-cell resolution in understanding how biological systems operate.

A noisy paracrine signal determines the cellular NF-kappaB response to lipopolysaccharide

Nearly identical cells can exhibit substantially different responses to the same stimulus. We monitored the nuclear localization dynamics of nuclear factor kappaB (NF-kappaB) in single cells stimulated with tumor necrosis factor-alpha (TNF-alpha) and lipopolysaccharide (LPS). Cells stimulated with TNF-alpha have quantitative differences in NF-kappaB nuclear localization, whereas LPS-stimulated cells can be clustered into transient or persistent responders, representing two qualitatively different groups based on the NF-kappaB response. These distinct behaviors can be linked to a secondary paracrine signal secreted at low concentrations, such that not all cells undergo a second round of NF-kappaB activation. From our single-cell data, we built a computational model that captures cell variability, as well as population behaviors. Our findings show that mammalian cells can create "noisy" environments to produce diversified responses to stimuli.

CD133+ HCC cancer stem cells confer chemoresistance by preferential expression of the Akt/PKB survival pathway

The recent discovery of cancer stem cells (CSCs) has played a pivotal role in changing our view of carcinogenesis and chemotherapy. Based on this concept, CSCs are responsible for the formation and growth of neoplastic tissue and are naturally resistant to chemotherapy, explaining why traditional chemotherapies can initially shrink a tumor but fails to eradicate it in full, allowing eventual recurrence. Recently, we identified a CSC population in hepatocellular carcinoma (HCC) characterized by their CD133 phenotype. However, the molecular mechanism by which it escapes conventional therapies remains unknown. Here, we examined the sensitivity of these cells to chemotherapeutic agents (doxorubicin and fluorouracil) and the possible mechanistic pathway by which resistance may be regulated. Purified CD133+ HCC cells isolated from human HCC cell line and xenograft mouse models survived chemotherapy in increased proportions relative to most tumor cells which lack the CD133 phenotype; the underlying mechanism of which required the preferential expression of survival proteins involved in the Akt/PKB and Bcl-2 pathway. Treatment of CD133+ HCC cells with an AKT1 inhibitor, specific to the Akt/PKB pathway, significantly reduced the expression of the survival proteins that was normally expressed endogenously. In addition, treatment of unsorted HCC cells with both anticancer drugs in vitro significantly enriched the CD133+ subpopulation. In conclusion, our results show that CD133+ HCC cells contribute to chemoresistance through preferential activation of Akt/PKB and Bcl-2 cell survival response. Targeting of this specific survival signaling pathway in CD133+ HCC CSCs may provide a novel therapeutic model for the disease.

The significance of proline-rich tyrosine kinase2 (Pyk2) on hepatocellular carcinoma progression and recurrence

Understanding the precise molecular mechanisms that trigger liver cancer cell migration and invasion could develop novel therapeutic strategies targeting cancer cell invasion to increase the sensitivity to current treatment modalities. In the current study, 49 patients with hepatocellular carcinoma (HCC) were included prospectively. Liver tumour and adjacent non-tumour tissues were detected for the expression of Proline-rich tyrosine kinase 2 (Pyk2), focal adhesion kinase (FAK), ezrin and fibronectin at protein and/or gene levels. Correlation between the expressions of Pyk2/FAK with the clinical pathological data was analysed. Protein expression of Pyk2 was also examined in a nude mice orthotopic liver tumour model with higher metastatic potential. There were 59% (29 out of 49) and 57% (28 out of 49) of HCC patients with higher levels of Pyk2 and FAK protein/gene expression, respectively. We observed a positive correlation between the protein and gene expression levels of Pyk2 and FAK (P=0.000, r=0.875). Overexpression of Pyk2 and FAK was significantly correlated with shorter disease-free survival. Patients with higher levels of Pyk2/FAK had larger tumour size and advanced Edmonson grading. In the animal studies, Pyk2 overexpression was found in infiltrative tumour cells and lung metastatic nodules. In conclusion, overexpression of Pyk2 and FAK was found in nearly 60% of HCC patients and was significantly correlated with poor prognosis. The significance of Pyk2 in HCC invasiveness was confirmed by animal studies.

AIDA: an adaptive image deconvolution algorithm with application to multi-frame and three-dimensional data

We describe an adaptive image deconvolution algorithm (AIDA) for myopic deconvolution of multi-frame and three-dimensional data acquired through astronomical and microscopic imaging. AIDA is a reimplementation and extension of the MISTRAL method developed by Mugnier and co-workers and shown to yield object reconstructions with excellent edge preservation and photometric precision [J. Opt. Soc. Am. A21, 1841 (2004)]. Written in Numerical Python with calls to a robust constrained conjugate gradient method, AIDA has significantly improved run times over the original MISTRAL implementation. Included in AIDA is a scheme to automatically balance maximum-likelihood estimation and object regularization, which significantly decreases the amount of time and effort needed to generate satisfactory reconstructions. We validated AIDA using synthetic data spanning a broad range of signal-to-noise ratios and image types and demonstrated the algorithm to be effective for experimental data from adaptive optics-equipped telescope systems and wide-field microscopy.

Expression of nitric oxide synthase isoforms in the testes of pigs

This study examined the expression of three isoforms of nitric oxide synthase (NOS) in the testes of pigs. Immunohistochemical studies demonstrated the presence of nNOS, eNOS and iNOS in interstitial cells, primary spermatocytes and spermatids. Positive immunoreactions for eNOS and iNOS were detected in peritubular myoid cells. Some vascular endothelial cells were positive for nNOS and eNOS. The expression of nitrotyrosine was detected in interstitial cells. In addition, the histochemical study revealed that all the interstitial cells were stained positively for NADPH-diaphorase, although some spermatids and vascular endothelial cells displayed moderate enzymatic activity. These findings suggest that three isoforms of NOS are expressed in the testis of pig and that they play important roles in the biology of interstitial cells that produce testosterone, as well as in spermatogenesis in the seminiferous tubules.

Kondo interactions and magnetic correlations in CePt2 nanocrystals

The evolution of the Kondo effect and antiferromagnetic (AF) correlations with size reduction in CePt2 nanoparticles (3.1-26 nm) is studied by analysis of the temperature-dependent specific heat and magnetic susceptibility. The AF correlations diminish with size reduction. The Kondo effect predominates at small particle size with trivalent, small Kondo temperature (TK) magnetic regions coexisting with strongly mixed-valent, large TK nonmagnetic regions. We discuss the role of structural disorder, background density of states and the electronic quantum size effect on the results.

Clinicopathological significance of homeoprotein Six1 in hepatocellular carcinoma

Tumour recurrence and metastases of hepatocellular carcinoma (HCC) after hepatectomy are the major obstacles of long-term survival. The present study investigated the clinicopathological significance of a possible metastasis regulator Six1 in HCC patients who were undergone hepatectomy. Seventy-two pairs of RNA and 103 pairs of protein from tumour and adjacent nontumour liver tissues of HCC patients were examined. About 85 and 60% of HCC tumour tissues were found to overexpress Six1 mRNA and protein, respectively, compared with nontumour liver tissues. No Six1 protein was detected in HCC nontumour liver tissues and normal liver tissues. Increased Six1 protein expression in HCC patients was significantly correlated with pathologic tumour-node-metastasis (pTNM) stage (P=0.002), venous infiltration (P=0.004) and poor overall survival (P=0.0423). We concluded that Six1 is frequently overexpressed in HCC patients and elevated Six1 protein in HCC patients may be an indication of advanced stage and poor overall survival after hepatectomy.

PIN1 expression contributes to hepatic carcinogenesis

The phospho-Ser/Thr-Pro specific prolyl-isomerase PIN1 is over-expressed in more than 50% of hepatocellular carcinomas (HCCs). To investigate its potential oncogenicity, we over-expressed PIN1 in a non-transformed human liver cell line MIHA. This resulted in up-regulation of beta-catenin and cyclin D1, leading to anchorage-independent growth in soft agar and tumorigenicity in nude mice. To further validate the role of PIN1 in hepatocarcinogenesis, PIN was suppressed by RNA interference (siRNA) in the HCC cell line PLC/PRF/5. siRNA-PIN1 transfection of PLC/PRF/5 cells led to repression of PIN1 expression, resulting in decreased levels of beta-catenin and cyclin D1. siRNA-PIN1 transfectants showed lower cell proliferation rates, reduced colony formation, and retarded cell cycle progression, with an increase in cells residing in G0/G1. Furthermore, soft agar colony formation was depressed, and tumorigenicity in nude mice was abrogated. These findings implicate PIN1 expression as an important step in hepatic carcinogenesis.

Evaluation of ketamine abuse using hair analysis: concentration trends in a Singapore population

This paper presents a method for the detection of ketamine in hair. Hair samples (25 mg) were washed, pulverized, and digested in hydrochloric acid (0.5 M) overnight at 45 degrees C. The samples were extracted by an automated solid-phase extraction procedure, and the extracts were subsequently analyzed using gas chromatography-mass spectrometry in selected ion monitoring mode. Linearity up to 120 ng/mg was obtained for both ketamine and norketamine with correlation coefficients of 0.9987 and 0.9985, respectively. Limit of detection was found to be at 0.4 ng/mg for both drugs while the limit of quantitation was found to be 0.6 and 0.8 ng/mg for ketamine and norketamine, respectively. The validated method was used in the analysis of 91 hair segments obtained from 54 ketamine abusers. Based upon the voluntary confession of the ketamine abusers, a correlation between the amount of ketamine detected and the frequency of abuse was observed.

Supersolid phase in spin dimer XXZ systems under a magnetic field

Using the quantum Monte Carlo method, we study, under external magnetic fields, the ground state phase diagram of the two-dimensional spin S=1/2 dimer model with an anisotropic intraplane antiferromagnetic coupling. With the anisotropy 4 greater/approximately Delta greater/approximately 3, a supersolid phase characterized by a nonuniform Bose condensate density that breaks translational symmetry is found. The rich phase diagram also contains a checkerboard solid, an antiferromagnet in the z axis, and a superfluid phase formed by S(z)= +1 spin triplets which has a finite staggered magnetization in the in-plane direction. As we show, the model can be realized as a consequence of including the next nearest neighbor coupling among dimers and our results suggest that spin dimer systems may be an ideal model system to study the supersolid phase.

Right precordial leads and lead aVR at exercise electrocardiography: does it change test results?

BACKGROUND

A recent study on exercise testing (ET) suggested that ST-segment changes in the right precordial leads (RPL) may increase its sensitivity substantially. However, this study looked at a highly selected population of patients who all underwent thallium-201 scintigraphy and coronary angiography. The present study evaluated the clinical utility of ST-segment changes in the RPL and lead aVR in an unselected population of patients undergoing ET.

METHODS

A total of 906 consecutive patients who received ET were included in the study. ET was done using the Bruce Protocol with a 12-lead electrocardiogram (ECG) substituting V(4)R and V(6)R for V(1) and V(6). Leads V(1) and V(6) were selected for omission as these two leads hardly ever manifest changes in isolation. Substituting two leads would obviate the need for a more complex recording system, thus improving clinical utility.

RESULTS

On the basis of horizontal/downsloping ST-segment depression (STD) of 1.0 mm or more (the usually accepted criterion for a positive ET), 159 (17.5%) patients had a positive ET. In those patients with a negative ET (545 patients), 4 patients (0.7%) manifested STD and 5 patients (0.9%) manifested ST-segment elevation (STE) in leads V(4)R and/or V(6)R, respectively. Of note, 44.7% of the positive ET group had STE in lead aVR.

CONCLUSION

The use of ST-segment changes in RPL during exercise stress testing does not appreciably change the test results of a standard ET. If one was to consider an additional marker, STE in aVR may be more useful, as it shows a stronger correlation with positive tests and does not require the recording of additional leads.