Search PubMed⌕ Search

Biomedical subjects

Yi Wang

Publications and source records attributed to Yi Wang.

At least 181 records · Page 10Linked to original sources
PubMed2004

[Expression of proteinase cathepsin L1 gene of Schistosoma japonicum in Escherichia coli].

OBJECTIVE: To express the proteinase cathepsin L1 gene of Schistosoma japonicum (SjCL1) in Escherichia coli JM109 cells. METHODS: The SjCL1 gene was amplified from the recombinant plasmid pcDNA3-SjCL1 by PCR. The gene was cloned into a prokaryotic expression vector pGEX4T-1 to construct a recombinant plasmid pGEX-SjCL1. The E. coli JM109 cells were transformed with the recombinant plasmid pGEX-SjCL1 and the transformants were induced by IPTG to express the recombinant protein, the target protein was then identified by SDS-PAGE and Western blotting. RESULTS: A 1 kb length PCR product was obtained and a recombinant plasmid pGEX-SjCL1 was constructed. The expression product was detected by SDS-PAGE and Western blotting and an expression band about 62000 was found. CONCLUSION: The SjCL1 gene is effectively expressed in the E. coli JM109 cells.

Animals↗
PubMed2004

Efficient synthesis of imidazoles from aldehydes and 1,2-diketones using microwave irradiation.

[reaction: see text] A simple, high-yielding synthesis of 2,4,5-trisubstituted imidazoles from 1,2-diketones and aldehydes in the presence of NH(4)OAc is described. Under microwave irradiation, alkyl-, aryl-, and heteroaryl-substituted imidazoles are formed in yields ranging from 80 to 99%. Short syntheses of lepidiline B and trifenagrel illustrate the utility of this approach.

Aldehydes↗
PubMed2004

Fast photoacoustic imaging system based on 320-element linear transducer array.

A fast photoacoustic (PA) imaging system, based on a 320-transducer linear array, was developed and tested on a tissue phantom. To reconstruct a test tomographic image, 64 time-domain PA signals were acquired from a tissue phantom with embedded light-absorption targets. A signal acquisition was accomplished by utilizing 11 phase-controlled sub-arrays, each consisting of four transducers. The results show that the system can rapidly map the optical absorption of a tissue phantom and effectively detect the embedded light-absorbing target. By utilizing the multi-element linear transducer array and phase-controlled imaging algorithm, we thus can acquire PA tomography more efficiently, compared to other existing technology and algorithms. The methodology and equipment thus provide a rapid and reliable approach to PA imaging that may have potential applications in noninvasive imaging and clinic diagnosis.

Acoustics↗
PubMed2004

Activating mechanism of transcriptor NF-kappaB regulated by hepatitis B virus X protein in hepatocellular carcinoma.

AIM: To investigate the mechanism and significance of NF-kappaB activation regulated by hepatitis B virus X protein (HBx) in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC). METHODS: The expression levels of HBx, p65, IkappaB-alpha and ubiquitin were detected by immunohistochemistry in HCC tissue microarrays (TMA) respectively, and IkappaB-alpha was detected by Western blot in HCC and corresponding liver tissues. RESULTS: The percentage of informative TMA samples was 98.8% in 186 cases with a total of 367 samples. Compared with corresponding liver tissues (60.0%), the HBx expression was obviously decreased in HBV-associated HCC (47.9%, u=2.24, P<0.05). On the contrary, the expressions of p65 (20.6% vs 45.3%, u=4.85, P<0.01) and ubiquitin (8.9% vs 59.0%, u=9.68, P<0.01) were notably elevated in HCC. In addition, IkappaB-alpha had a tendency to go up. Importantly, positive relativity was observed between HBx and p65 (chi2=10.26, P<0.01), p65 and IkappaB-alpha (chi (2)=16.86, P<0.01), IkappaB-alpha and ubiquitin (chi2=8.90, P<0.01) in HCC, respectively. CONCLUSION: Both active and non-active forms of NF-kappaB are increased in HBV-associated HCC. Variant HBx is the major cause of the enhancement of NF-kappaB activity. The activation always proceeds in nucleus and the proteasome complexes play an important role in the activation.

Carcinoma, Hepatocellular↗
PubMed2004

Regulation of signal peptidase by phospholipids in membrane: characterization of phospholipid bilayer incorporated Escherichia coli signal peptidase.

Prokaryotic signal peptidases are membrane-bound enzymes. They cleave signal peptides from precursors of secretary proteins. To study the enzyme in its natural environment, which is phospholipid bilayers, we developed a method that allows us effectively to incorporate full-length Escherichia coli signal peptidase I into phospholipid vesicles. The membrane-bound signal peptidase showed high activity on a designed substrate. The autolysis site of the enzyme is separated from its catalytic site in vesicles by the lipid bilayer, resulting in a dramatic decrease of the autolysis rate. Phosphotidylethanolamine, which is the most abundant lipid in Escherichia coli inner membrane, is required to maintain activity of the membrane-incorporated signal peptidase. The maximal activity is achieved at about 55% phosphotidylethanolamine. Negatively charged lipids, which are also abundant in Escherichia coli inner membrane, enhances the activity of the enzyme too. Its mechanism, however, cannot be fully explained by its ability to increase the affinity of the substrate to the membrane. A reaction mechanism was developed based on the observation that cleavage only takes place when the enzyme and the substrate are bound to the same vesicle. Accordingly, a kinetic analysis is presented to explain some of the unique features of phospholipid vesicles incorporated signal peptidase, including the effect of lipid concentration and substrate-vesicle interaction.

Bacteriolysis↗
PubMed2004

Association of Vimentin overexpression and hepatocellular carcinoma metastasis.

The poor prognosis of hepatocellular carcinoma (HCC) has been associated with recurrence and metastasis. Recently, we established a pair of HCC cell lines from a primary (H2-P) and its matched metastatic (H2-M) HCC tumors. A high density of cDNA microarray with 9184 human cDNA was used to identify the differentially expressed genes between H2-P and H2-M. Comparing with H2-P, eight upregulated and six downregulated genes were detected in H2-M. One interesting finding is the overexpression of Vimentin (VIM), a well-defined intermediate filament, which has been linked to a more aggressive status in various tumors. The correlation of overexpression of VIM and HCC metastasis was studied by immunohistochemistry using a tissue microarray with 200 primary HCCs and 60 pairs of primary and matched metastatic HCC samples. Tissue microarray demonstrated that the overexpression of VIM was significantly associated with HCC metastasis (P<0.01). This finding strongly suggests that the overexpression of VIM may play an important role in the metastasis of HCC.

Adult↗
PubMed2004

Characterization of HBV integrants in 14 hepatocellular carcinomas: association of truncated X gene and hepatocellular carcinogenesis.

Although the integration of hepatitis B virus (HBV) into human DNA has been found to be associated with the development of hepatocellular carcinoma (HCC), the molecular mechanism remains unclear. In order to obtain additional insight into the correlation of HBV integration and HCC development, integrated HBV in 14 primary HCC cases was isolated and characterized by sequencing analysis. Our findings in this study showed that: (1) none of the known cellular oncogene or tumor suppressor gene was affected by the HBV integration; (2) although the integration of HBV is random, the integration site was often within or close to human repetitive sequences; (3) integrated HBV may possess the capacity to transpose to another chromosome region through reintegration; (4) rearrangements of HBV sequence were observed in all the 14 integrants, involving (most frequently) X (12/14 integrants), P (8/14), S (7/14), and C (7/14) genes; and (5) 3'-deleted X gene and consequent C-terminal truncated X protein caused by HBV integration was observed in 10 cases. These deletions cause the losses of p53-dependent transcriptional repression binding site, transcription factor Sp1 binding site, and growth-suppressive effect domain, leading to cell proliferation and transformation. This finding suggests that 3'-deleted X gene caused by the HBV integration may play an important role in the HCC development.

Adolescent↗
PubMed2004

Fine mapping and identification of a candidate gene SSH1 in disseminated superficial actinic porokeratosis.

Disseminated superficial actinic porokeratosis (DSAP) is an uncommon autosomal dominant chronic keratinization disorder, characterized by multiple superficial keratotic lesions surrounded by a slightly raised keratotic border. Thus far, although two loci for DSAP have been identified, the genetic basis and pathogenesis of this disorder have not been elucidated yet. In this study, we performed a genome-wide linkage analysis in three Chinese affected families and localized the gene in an 8.0 cM interval defined by D12S330 and D12S354 on chromosome 12. Upon screening 30 candidate genes, we identified a missense mutation, p.Ser63Asn in SSH1 in one family, a frameshift mutation, p.Ser19CysfsX24 in an alternative variant (isoform f) of SSH1 in another family, and a frameshift mutation, p.Pro27ProfsX54 in the same alternative variant in one non-familial case with DSAP. SSH1 encodes a phosphatase that plays a pivotal role in actin dynamics. Our data suggested that cytoskeleton disorganization in epidermal cells is likely associated with the pathogenesis of DSAP.

Age of Onset↗
PubMed2004

Simultaneously multi-parameter determination of hematonosis cell apoptosis by two-photon and confocal laser scanning microscopy.

Flow cytometry (FCM), TdT-mediated dUTP Nick End Labeling (TUNEL), and DNA ladder are conventional methods to detect apoptosis of drug-treated cells. However, the assumption of cell number restricts their applications in clinics. In this paper, we report a cell-saving imaging method for quick identification of the hematonosis cell apoptosis induced by chemotherapeutic drugs. By the combination of two-photon and confocal microscopy, three main apoptosis parameters (the change of nuclear morphology, collapse of mitochondrial membrane potential, and increase of intracellular calcium) were recorded simultaneously for single As2O3-induced Molt-4 cells. The results are highly in accordance with those produced by classical flow cytometry. This work suggests that this new imaging method would be promising in the quick identification of hematonosis cell apoptosis.

Apoptosis↗
PubMed2004

Soft tissue enhancement on time-resolved peripheral magnetic resonance angiography.

PURPOSE: To evaluate the incidence and locations of soft tissue enhancement on time-resolved two-dimensional projection magnetic resonance angiography (MRA) of the calf and foot. MATERIALS AND METHODS: Time-resolved two-dimensional projection MRA of the knee, calf, and foot, performed at 1.5 Tesla using the head coil, was retrospectively reviewed in 326 patients. Soft tissue enhancement of the foot was identified and graded by blinded review. Subsequently, patient medical records were reviewed to determine the presence or absence of diabetes, cellulitis, gangrene, and ulceration of the foot and presence of neuropathic joints. RESULTS: Enhancing spots were identified in 228 patients. For those feet without clinical abnormalities, diabetic patients had an average of 1.2 enhancing spots per foot, while nondiabetics had only 0.6 (P < 0.001). Higher-grade lesions were more prevalent in diabetics and in heavier patients. Of 64 patients with follow-up, 8 (13%) developed cellulitis (N = 4) or ulceration (N = 4) at the location of an enhancing spot, including 5 diabetic and 3 nondiabetic patients. CONCLUSION: Pedal soft tissue enhancement frequently occurs on time-resolved gadolinium (Gd):MRA of the feet. The etiology is uncertain, but the high frequency in diabetic patients and observation of progression to cellulitis/ulceration suggest this soft tissue enhancement may identify sites of subclinical pedal soft tissue injury.

Adult↗
PubMed2004

Three-dimensional MR angiography in imaging platinum alloy stents.

PURPOSE: To evaluate visualization inside platinum stents with three-dimensional contrast-enhanced magnetic resonance angiography (CE-MRA). MATERIALS AND METHODS: Breath-hold three-dimensional gadolinium (Gd) MRA was performed on 18 patients with 22 platinum stents in the renal (n = 18), celiac (n = 1), superior mesenteric (n = 1), and iliac (n = 2) arteries. Electronic calibers were used to measure the lumen diameter within the stent and just distal to the stent to calculate percent stenosis. MRA accuracy was determined from the difference between percent stenosis measured on MRA and digital subtracted angiography (DSA). The patients were imaged at flip angles of 45 degrees , 60 degrees , 75 degrees , 90 degrees , and 150 degrees . RESULTS: MRA demonstrated the stent lumen in all of the patients, with a mean difference between MRA and DSA of 21%. For stents oriented parallel to B0 (iliac arteries) the difference was only 10%, as compared to 22% for stents perpendicular to B0. The flip angle with the best agreement between MRA and DSA was 75 degrees (16%). CONCLUSION: The lumen of a platinum stent can be imaged with three-dimensional CE-MRA, although grading of restenosis has limited accuracy. The best results were obtained with a flip angle of 75 degrees and for stents in the iliac arteries parallel to B0.

Aged↗
PubMed2004

Novel RF coil geometry for lower extremity imaging.

A receive-only phased-array coil was designed to image the lower extremities. The array consists of four volume coils placed on two cylindrical formers. The coil array has the ability to image both legs simultaneously over a 40 cm longitudinal field of view (FOV). Experiments using phantoms show an increase in signal-to-noise ratio (SNR) in regions of interest through the center of the coil by an average factor of 2.8 over the body coil and 1.5 over the GE 4-channel torso array. In vivo data acquired from 10 subjects show that the X array provided similar SNR improvement in spin-echo images and more vascular details in angiographic images compared to the torso array.

Equipment Design↗
PubMed2004

Improved magnetization preparation for navigator steady-state free precession 3D coronary MR angiography.

The purpose of this work was to investigate a new magnetization preparation scheme for navigator steady-state free precession (SSFP) 3D coronary MR angiography (MRA) that executes the navigator and fat saturation pulses in steady state after the dummy RFs in order to minimize the delay between the magnetization preparation and the image echoes. Compared to the previous preparation scheme that executes the navigator and fat saturation pulses before the dummy RFs, the new scheme was found to provide more effective motion suppression, significantly improved blood-to-myocardium contrast-to-noise ratio (46%, P < 0.001) at slightly but insignificantly decreased blood signal-to-noise ratio (SNR) (2%, P = 0.73), significantly reduced fat SNR (32%, P < 0.001), and better overall image quality (P = 0.05; Wilcoxon paired sample signed rank test).

Adipose Tissue↗
PubMed2004

Multiprocessor scheduling implementation of the simultaneous multiple volume (SMV) navigator method.

The simultaneous multiple volume (SMV) approach in navigator-gated MRI allows the use of the whole motion range or the entire scan time for the reconstruction of final images by simultaneously acquiring different image volumes at different motion states. The motion tolerance range for each volume is kept small, thus SMV substantially increases the scan efficiency of navigator methods while maintaining the effectiveness of motion suppression. This article reports a general implementation of the SMV approach using a multiprocessor scheduling algorithm. Each motion state is regarded as a processor and each volume is regarded as a job. An efficient scheduling that completes all jobs in minimal time is maintained even when the motion pattern changes. Initial experiments demonstrated that SMV significantly increased the scan efficiency of navigator-gated MRI.

Algorithms↗
PubMed2004

High temporal and spatial resolution 4D MRA using spiral data sampling and sliding window reconstruction.

Contrast-enhanced magnetic resonance angiography (CE-MRA) requires high spatial resolution to demonstrate detailed vasculature and high temporal resolution to capture the contrast bolus. Sparse bright voxels in MRA permit substantial undersampling in MRI data acquisition, allowing simultaneous high temporal and spatial resolution. We developed a time-resolved 3D MRA technique using the efficient spiral sampling trajectory, and performed off-resonance corrections using inhomogeneity field maps. View sharing and sliding window reconstruction were utilized to generate high temporal resolution. High-resolution 3D angiograms were generated at 1-2 s per frame, with a 5-8 ml gadolinium dose, in patients with vascular disease.

Arteriosclerosis↗
PubMed2004

View ordering for magnetization prepared steady state free precession acquisition: application in contrast-enhanced MR angiography.

Magnetization prepared segmented acquisition requires a view order that maximizes signal contrast during the acquisition of the central portion of k-space. Steady state free precession (SSFP) acquisition further requires a view order that minimizes changes in phase-encoding gradients from one repetition to the next in order to minimize eddy current artifacts. In this article, optimal view ordering schemes satisfying these two requirements are formulated and applied to inversion prepared 3D SSFP contrast-enhanced MR angiography (MRA). Experiments on phantoms and pigs demonstrated improved background suppression and reduced image artifacts.

Animals↗
PubMed2004

Self-calibrated spiral SENSE.

Current standard sensitivity-encoded parallel imaging (SENSE) utilizes a fully sampled low-resolution reference scan to estimate the coil sensitivities. This reference scan adds scan time and may introduce misregistration artifacts. The purpose of this study was to investigate the feasibility of estimating the coil sensitivities for spiral SENSE directly from an undersampled k-space center. The limited spatial frequencies of the coil sensitivities, and the undersampling beyond the Nyquist radius cause image artifacts. A point spread function (PSF) analysis and experiments on both phantoms and humans identified an optimal radius for the k-space center by minimizing these image artifacts. The preliminary data indicate that self-calibrated SENSE is as accurate as standard SENSE, which uses a fully sampled reference scan.

Algorithms↗