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Biomedical subjects

Wei Liu

Publications and source records attributed to Wei Liu.

485 records · Page 27Linked to original sources
PubMed2002

[Intra-arterial thrombolysis in patients with acute ischemic stroke of the cervical internal carotid artery occlusive disease].

OBJECTIVE: To observe the safety and efficacy of local intra-arterial thrombolysis (LIT) in patients with acute ischemic stroke of cervical internal carotid artery occlusive disease. METHODS: 10 patients were treated by LIT. 2 of 10 patients were further treated by either angioplasty or endarterectomy. Primary neuroradiological assessment was performed with CT in all patients. Angiographic recanalization level was classified according to thrombolysis in myocardial infarction (TIMI) grades. Clinical outcome was classified as good for Modified Rankin Scale (MRS) scores of 0 to 3 and as poor for MRS scores of 4 to 6. RESULTS: Complete/partial recanalization after infusion was accomplished in 8 patients, seven of whom had good clinical outcome. Cerebral hemorrhage occurred in 2 of 10 patients. CONCLUSION: The results of this study suggest that LIT may be helpful to improve the outcome in patients with acute cervical internal carotid artery occlusive disease if it is performed within 6 hours of stroke onset.

Adolescent↗
PubMed2002

[Assay of carnitine in plasma and urine of healthy adults].

OBJECTIVE: To determine the levels of carnitine in plasma and daily excretion of carnitine in urine of healthy adults so as to provide the reference standard for studying the changes of carnitine in patients. METHODS: Carnitine in plasma and urine was assayed with high performance liquid chromatography (HPLC). The levels of total carnitine (TC), free carnitine (FC) and acetyl-carnitine (AC) in fasting plasma and the daily excretion of TC, FC and AC in urine were assayed in 40 healthy adults (20 men and 20 women) with standard diet. RESULTS: Good linearity (r 2 > or = 0.999) was observed in assaying TC, FC and AC. The relative standard deviation (RSD) was lower than 9.1% and bias lower than 5.6%. It was showed that the plasmatic levels of TC, FC and AC in healthy men [(53.1 +/- 8.5), (41.2 +/- 6.1), (6.2 +/- 0.6) mumol/L] were significantly higher than those in healthy women [(45.4 +/- 5.6), (35.2 +/- 4.9), (5.7 +/- 0.7) mumol/L] (P = 0.002, 0.002, 0.035). The daily urinary excretion of TC, FC and AC in healthy men [(386.1 +/- 22.9), (180.5 +/- 31.8), (33.8 +/- 3.3) mumol] were also significantly higher than those in healthy women [(240.1 +/- 35.6), (112.7 +/- 22.6), (29.3 +/- 4.3) mumol] (P < 0.0005, < 0.0005, < 0.0005) when the adults were given standard diet. Both the plasmatic levels and the daily urinary excretion of TC, FC and AC were of significantly positive correlation with lean body mass (LBM) (r = 0.501-0.856). The (TC-FC)/FC ratios in plasma were 0.29 +/- 0.05 for male and 0.29 +/- 0.04 for female. CONCLUSION: Good precision and accuracy were observed in assaying carnitine with HPLC. After standard diet, both the level of carnitine in fasting plasma and the daily urinary carnitine excretion of healthy adults were positively correlated with LBM.

Acetylcarnitine↗
PubMed2002

[FTIR and FT-Raman spectroscopic investigation on two complexes of La3+ with galactitol].

FTIR and Raman spectroscopy were used to investigate the two complexes of LaCl3 with galactitol in this paper. The results shows that La ion can complex with galactitol in 1:1 and 2:1 proportion. The FTIR and Raman spectra of the two complexes both exist some differences that prove LaCl3 and galactitol really form two different complexes. In the FTIR spectra nu OH is strong peaks and nu CH peaks are very weak whereas nu CH pband become stronger than nu OH peaks. So FTIR and Raman spectra can provide complementary information.

Chelating Agents↗
PubMed2002

[Study on the aggregation of metal-free tetrasulfophthalocyanine in solutions].

Metal-free tetrasulfophthalocyanine was synthesized by the reaction of triammonium salt of 4-sulfophalic acid with urea, using antimony powder as catalyst. The aggregation of this compound in aqueous and aqueous alcoholic solutions(MeOH, EtOH, ArOH) has been studied by electronic absorption spectra. The result shows that several factors such as the composition of the solvent, the acidity of solution, influence the extent of the aggregation. The dimerisation constant (Kd) of the titled compound in different solvents is reported.

Antimony↗
PubMed2002

[Experimental study of the inducing BMSCs into osteogenesis].

OBJECTIVE: To study the bone tissue osteogenesis ability of bone marrow stromal cells (BMSCs) in vitro and in vivo. METHODS: The BMSCs were separated by gradient centrifugation on Percoll, culture-expanded and induced with a conditional medium. The cells were examined by transmission electron microscopy and histochemistry or immunochemistry stains technique including AKP,Cbfa1,OCN, OPN, BSP and collagen type I. The mRNA of collagen type I in cultured cell was also examined by in situ hybridization. RESULTS: Histochemical studies showed positive stain of AKP,Cbfa1, OCN, OPN,BSP and collagen type I,and in situ hybridization also showed the positive express of mRNA of collagen type I. The excretion of collagen and deposition of calcium salt were observed under transmission electron microscopy. CONCLUSION: BMSCs cultured in conditional medium shows osteoblast-like functions in vitro, which provides an ideal seed cells for bone tissue engineering.

English Abstract↗
PubMed2002

[Immortalization of endothelial cells differentiated from mouse embryonic stem cells].

This study is designed to immortalize endothelial cells differentiated from embryonic stem cells. The embryoid bodies (EB) formed in vitro from embryonic stem cells, were induced to differentiate into many "round cells" (the precursor of endothelial cells) by retinoic acid (RA) and transforming growth factor-beta1 (TGF-beta1). These "round cells" later formed the vascular tube-like structures. Studies by scanning electronic microscopy and light microscopy and immunocytochemistry, demonstrated that these tube-like structures were constituted by a large number of round and flat cells, which were positive for "vWF" and "CD34"staining. These results indicate they are vascular endothelial cells. To immortalize these cells, human telomerase reverse transcriptase (hTERT) cDNA was transfected into "round cells" by lipofectine. hTERT mRNA expression in transfected cells was confirmed by Dot blot, RT-PCR. Furthermore, 95% these transfected cells maintain the characteristic of endothelial cell, can proliferate in large quantity in vitro, and are able to form tubular structures. These results suggest that hTERT cDNA transfection can immortalize the induced endothelial cells and therefore may provide a new source of seed cells for vascular engineering.

Animals↗
PubMed2000

Construction and Characterization of a Mutant of Single-chain Urokinase-type Plasminogen Activator Ser(175)-His(187)-mscu-PA

Single-chain urokinase-type plasminogen activator scu-PA is the precursor of double-chain urokinase tcu-PA , which has a much higher intrinsic catalytic activity than other zymogens of the serine protease family. To restore the "zymogen triad" of Asp-His-Ser in the serine protease family, the mutant gene of scu-PA mscu-PA, Ala(175)right curved arrow Ser(175), Tyr(187)right curved arrow His(187) was constructed by the method of oligonucleotide-directed, site-specific mutagenesis in order to reduce its intrinsic catalytic activity. mscu-PA was expressed in E. coli BL21. After denaturation and renaturation in vitro, the mscu-PA was purified to homogeneity by SP-Sepharose ion-exchange chromatography, Sephacryl S-200 chromatography and Benzamidine-Sepharose affinity adsorption. mscu-PA had the same activity to plasmin as scu-PA. The catalytic efficiency measured by k(cat)/K(m) to synthetic substrate S(2444) was 2.5-fold lower than that of scu-PA, and the activity against Glu-plasminogen was also reduced. After activation by plasmin, mtcu-PA and tcu-PA had similar catalytic efficiency against S(2444) and Glu-plasminogen. The results suggest that the intrinsic catalytic activity of mscu-PA be really reduced after restoring the "zymogen triad".

Journal Article↗
PubMed1998

Comparison of PhoP binding to the tuaA promoter with PhoP binding to other Pho-regulon promoters establishes a Bacillus subtilis Pho core binding site.

The phosphate-deficiency response in Bacillus subtilis is regulated by PhoP and PhoR, a pair of two-component regulatory proteins. PhoR is a histidine kinase and PhoP is a response regulator. Genetic evidence indicates that the Pho-regulon genes, which are induced or repressed under phosphate starvation conditions, are regulated by PhoP and PhoR at the transcriptional level. It has previously been shown that PhoP binds to four Pho-regulon promoters in both unphosphorylated and phosphorylated forms. This study demonstrates that another Pho-regulon gene promoter, the tuaA promoter preceding the operon which is responsible for cell wall teichuronic acid synthesis, is also transcriptionally regulated and is bound by PhoP. The binding affinity for phosphorylated PhoP was about 10-fold higher than that for unphosphorylated PhoP. Both unphosphorylated and phosphorylated PhoP bound upstream of the -20 region in the tuaA promoter. By aligning the PhoP-binding sites within the Pho-regulon promoters, a consensus core PhoP-binding region composed of four TT(A/T)ACA direct repeats, each separated by 5 +/- 2 non-conserved nucleotides was identified. PhoP, phosphorylated or unphosphorylated, binds to such a sequence in all Pho-regulon promoters studied. Phosphorylated PhoP binds to the core binding region with high affinity and to additional regions surrounding this region with similar or lower affinity.

Bacillus subtilis↗
PubMedDate not supplied

Chemiluminescence micro-flow-injection analysis on a chip.

Chemiluminescence microflow-injection analysis (microFIA) systems on a chip have been developed. The technology of laser ablation was used to fabricate the microchannels on the polymethyl methacrylate (PMMA) chip. The three sampling structure, including double-tee sampling structure, microvalve sampling structure and injection pump with accurate time control, were used. The microcolumn for specific molecular recognition, including molecularly imprinted polymer, enzyme and bacteria, were used to enhance selectivity. These microFIA systems have been applied to clinical analysis, assessment of food safety, in vivo and real-time determination of drugs, and pharmacokinetics studies.

Animals↗
PubMedDate not supplied

4-hydroxynonenal triggers multistep signal transduction cascades for suppression of cellular functions.

4-hydroxynonenal (HNE), an aldehyde product of membrane lipid peroxidation, has been suggested to mediate a number of oxidative stress-linked pathological events in humans, including cellular growth inhibition and apoptosis induction. Because HNE is potentially reactive to a number of both cell surface and intracellular proteins bearing sulfhydryl, amino and imidazole groups, it seems that there are multiple signal transduction cascades. Here we briefly review the HNE-triggered signal transduction cascades that lead to suppression of cellular functions and to cell death, based mainly on our own recent study results. We first showed that formation of HNE-cell surface protein adducts, which mimicked ligand-cell surface receptor binding, induced activation of receptor-type protein tyrosine kinases such as epithelial growth factor receptor (EGFR) and that this caused growth inhibition through a cascade of activation of EGFR, Shc and ERK. Next, we showed that HNE-mediated scavenging of cellular glutathione led to activation of caspases and to DNA fragmentation through a Fas-independent and mitochondria-linked pro-apoptotic signal pathway. More recently, we have obtained evidence that the HNE-triggered signal cascade for caspase activation encounters complex positive feedback regulatory mechanisms that are linked to the inhibition of anti-apoptotic signals and are dependent on caspase activity. Underlying multiple regulatory mechanisms, including mechanisms of activation of Akt-dephosphorylating PP2A activity, activities of protein tyrosine kinases have been shown to be biphasically controlled by HNE. In addition, we have obtained results suggesting that HNE inhibits phosphorylation of IkappaB, possibly by targeting some elements upstream of IkappaB, which might downregulate the NF-kappaB-mediated cellular responses, including serum deprivation-induced iNOS expression and generation of anti-apoptotic signals. These results suggest that HNE reacts with multiple cell surface and intracellular sites for triggering a network of signal transduction that is ultimately focused on suppression of cellular functions.

Aldehydes↗
PubMedDate not supplied

Peroxisomal targeting protein 14 (PEX14) from Leishmania donovani. Molecular, biochemical, and immunocytochemical characterization.

Pathogens of the Leishmania and Trypanosoma genera compartmentalize glycolytic and other nutritional pathways in glycosomes, unique subcellular organelles related to the peroxisomes of mammals and yeasts. Most glycosomal proteins are targeted to the glycosomes by a COOH-terminal tripeptide signal similar to the peroxisomal targeting signal-1 (PTS-1). It has been proposed that PTS-1 forms a complex with the PEX5 receptor protein which then docks to the glycosomal membrane through interactions with the membrane associated PEX14 protein. To analyze the role of PEX14 in glycosomal protein import, the gene encoding the L. donovani PEX14 (LdPEX14) was isolated and shown to encode a 464 amino acid protein that exhibited very limited sequence homology with peroxisomal PEX14 proteins. In vitro binding experiments with purified recombinant LdPEX14 and LdPEX5 confirmed that LdPEX14-LdPEX5 interacted with a K(d) of 2.75 microM. When LdPEX5 was preloaded with a PTS-1 peptide, the affinity of the LdPEX14-LdPEX5 interaction affinity increased. Furthermore, binding experiments with truncated forms of LdPEX5 and LdPEX14 showed that the interaction domains localized to the amino terminal region of both proteins. Finally, confocal microscopy, subcellular fractionation, and differential extraction experiments indicated that LdPEX14 is a soluble protein that associates tightly with the glycosomal membrane and further support the role of LdPEX14 in forming a docking complex involved in glycosome biogenesis.

Amino Acid Sequence↗
PubMedDate not supplied

Amyloid fibril formation by peptide LYS (11-36) in aqueous trifluoroethanol.

Peptide LYS (11-36), derived from the beta-sheet region of T4 lysozyme, forms an amyloid fibril in aqueous trifluoroethanol (TFE) at elevated temperature. The peptide has a moderate alpha-helix content in 20 and 50% (v/v) TFE solution; large quantities of fibrils were formed after incubation at 55 degrees C for 2 weeks as monitored by a thioflavin T fluorescence assay. No fibrils were observed when the peptide initially existed predominantly as a random coil or as a complete alpha helix. Our results suggest that a moderate amount of alpha helix and random coil present in the peptide initially facilitates the fibril-formation process, but a high alpha-helix content inhibits fibril formation. Transmission electron microscopy revealed several types of fibril morphologies at different TFE concentrations. The fibrils were highly twisted and consisted of interleaved protofilaments in 50% TFE, while smooth and flat ribbonlike fibrils were found in 20% TFE. In 50% TFE, the fibril growth rate of LYS (11-36) was found to depend strongly on peptide concentration and seeding but was insensitive to solution pH and ionic strength.

Amino Acid Sequence↗
PubMedDate not supplied

Real-time 3D human capture system for mixed-reality art and entertainment.

A real-time system for capturing humans in 3D and placing them into a mixed reality environment is presented in this paper. The subject is captured by nine cameras surrounding her. Looking through a head-mounted-display with a camera in front pointing at a marker, the user can see the 3D image of this subject overlaid onto a mixed reality scene. The 3D images of the subject viewed from this viewpoint are constructed using a robust and fast shape-from-silhouette algorithm. The paper also presents several techniques to produce good quality and speed up the whole system. The frame rate of our system is around 25 fps using only standard Intel processor-based personal computers. Besides a remote live 3D conferencing and collaborating system, we also describe an application of the system in art and entertainment, named Magic Land, which is a mixed reality environment where captured avatars of human and 3D computer generated virtual animations can form an interactive story and play with each other. This system demonstrates many technologies in human computer interaction: mixed reality, tangible interaction, and 3D communication. The result of the user study not only emphasizes the benefits, but also addresses some issues of these technologies.

Art↗
PubMedDate not supplied

An initial study on lip perception of electrotactile array stimulation.

We conducted an initial study on tactile sensory characteristics of the lips by applying electrotactile array stimulation on the center surfaces of the upper and lower lips. We performed experiments of threshold measurement and rating of two-line separation to evaluate the tactile sensitivity and spatial discriminating ability of the lips, respectively. Three stimulator arrays of different sizes presented electrotactile patterns on the lips of eight subjects (six male, two female) to measure the electrotactile performance in relation to stimulator size and spacing. Experimental results showed that the lips required very low intensities for effective electrotactile stimulation. As the stimulator diameter increased from 75 micrometers to 1.55 millimeters, the average stimulation intensity at the threshold level decreased from 12.5 to 6.3 V for the lower lip and from 13.3 to 7.1 V for the upper lip. Meanwhile, the two-line separation rating experiment showed that both upper and lower lips possessed high spatial discriminating ability. The average percentages of correct rating of two adjacent lines ranged from 80.5% to 88.2% on the two stimulator arrays with center-to-center spacing of at least 2.40 mm. In addition, sensitivity analysis indicated that the upper lip slightly outperformed the lower lip in spatial discrimination.

Adult↗
PubMedDate not supplied

Anterior approach for complete isolated caudate lobectomy.

BACKGROUND/AIMS: Complete isolated caudate lobectomy is a technique-demanding procedure that entails the surgeon's judgement and precise knowledge of liver anatomy. METHODOLOGY: All consecutive patients who underwent complete isolated caudate lobectomy were studied. En bloc excisions combined with adjacent hepatic parenchyma (as part of extended hepatectomies) or wedge excisions of the caudate lobe were excluded. All patients were followed-up to date. RESULTS: Thirteen patients met the inclusion criteria (9 male, 4 female). Mean age (+/-SD) was 47 (+/-9) years. Primary diagnoses included hepatocellular carcinoma, hemangioma and adenoma. Margins were negative in all but two patients. Intraoperative US showed no tumor embolus within the main hepatic veins. Mean (+/-SD) operative time was 245 (+/-45) minutes, and estimated blood loss was 680 (+/-210) mL. Median blood transfusion was 420mL (range, 0 approximately 2500mL). Complications included bile leak in one patient, ascites in 2. Median length of hospitalization was 13 days (range, 11-21). There was no perioperative mortality. CONCLUSIONS: Complete isolated resection of the caudate lobe using the anterior approach should be the first choice for treatment of a tumor located in the caudate lobe alone, although the procedure is extremely difficult and highly dangerous.

Adult↗
PubMedDate not supplied

Surgical treatment of primary duodenal adenocarcinoma.

BACKGROUND/AIMS: Our purpose was to review the outcome of the patients with primary duodenal adenocarcinoma and determine factors influencing survival. METHODOLOGY: Over a 10-year period, 43 patients with this disease were identified. Data were analyzed to assess the outcomes of treatment and predictors of survival. RESULTS: Patients had symptoms present for an average of 6 months. The most common symptom was obstructive jaundice, observed in 55.8% of the cases. Based on symptomology, primary duodenal adenocarcinoma may be classified into three categories: icteric, obstructive and illusive. The upper gastrointestinal contrast study and esophagogastroduodenoscopy were the most effective diagnostic tests, showing an accuracy of 79.5% and 86.8%, respectively. A curative resection was performed in 28 of the 43 patients (65.1%), a conventional pancreatoduodenectomy in 11, segmental duodenal resection in 16 and gastroduodenectomy in 1. The overall 5-year survival rate was 27%, which was 42 percent after curative resection. CONCLUSIONS: The respectability of the primary lesion was associated with increased survival. An aggressive surgical approach should be pursued. Pancreaticoduodenectomy is usually required for tumors of the first and second portion of the duodenum. Segmental resection may be appropriate for selected patients, especially for cancers of the distal duodenum.

Adenocarcinoma↗