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Biomedical subjects

W G Liu

Publications and source records attributed to W G Liu.

At least 19 recordsLinked to original sources
PubMed2006

Osteogenic behavior of alginate encapsulated bone marrow stromal cells: an in vitro study.

Sodium alginate is a useful polymer for the encapsulation and immobilization of a variety of cells in tissue engineering because it is biocompatible, biodegradable and easy to process into injectable microbeads. Despite these properties, little is known of the efficacy of calcium cross-linked alginate gel beads as a biodegradable scaffold for osteogenic cell proliferation and differentiation. In this study, we investigated the ability of rabbit derived bone marrow cells (BMCs) to proliferate and differentiate in alginate microbeads and compared them with BMCs cultured in poly-L-lysine (PLL) coated microbeads and on conventional 2D plastic surfaces. Results show that levels of proliferation and differentiation in microbeads and on tissue culture plastics were comparable. Cell proliferation in microbeads however diminished after fortification with a coating layer of PLL. Maximum cell numbers observed were, 3.32 x 10(5) +/- 1.72 x 103; 3.11 x 10(5) +/- 1.52 x 10(3) and 3.28 x 10(5) +/- 1.21 x 10(3 ) for the uncoated, PLL coated and plastic surface groups respectively. Alkaline phosphatase and protein expressions reflected the stage of cell differentiation. We conclude that calcium cross-linked alginate microbeads can act as a scaffold for BMC proliferation and osteogenic differentiation and has potential for use as 3D degradable scaffold.

Alginates↗
PubMed2006

In vitro evaluation of alginate encapsulated adipose-tissue stromal cells for use as injectable bone graft substitute.

This study aims to investigate the survival and osteogenic behavior of murine-derived adipose-tissue stromal cells (ATSCs) encapsulated in alginate microcapsules thereby instigating further studies in this cell delivery strategy for in vivo osteogenesis. Cell viability was quantified using a tetrazolium-based assay and osteogenic differentiation was evaluated by both alkaline-phosphatase (ALP) histochemistry and osteocalcin mRNA analysis. Following microencapsulation, cell numbers increased from 3.9 x 10(3) on day 1 to 7.8 x 10(3) on day 7 and maintained excellent viability in the course of 21-day culture. ALP was 6.9, 5.5, and 3.2 times higher than monolayer cultures on days 7, 14, and 21, respectively. In addition, osteocalcin mRNA was detectable in encapsulated cultures earlier (day 14) than monolayer cultures. We conclude that alginate microcapsules can act as three-dimensional matrix for ATSC proliferation and has potential for use as injectable, biodegradable scaffold in bone tissue engineering.

Adipocytes↗
PubMed2004

A chitosan-arginine conjugate as a novel anticoagulation biomaterial.

Chitosan (CS) was modified with arginine using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as coupling agents. FTIR and 13C NMR spectra showed that arginine was chemically coupled to CS to form a chitosan-arginine conjugate (CS-ArgC). The substitution degree of arginine in CS estimated from elemental analysis was 20.1%. The circular dichroism spectra indicated that the incorporation of arginine significantly altered the conformation of thrombin; while no obvious variation in the conformation of thrombin was observed with the addition of CS. The anticoagulation activity of glucose aldehyde crosslinked CS-ArgC and CS membranes was evaluated by assaying prothrombin time (PT), thrombin time (TT) and activated partial thromboplastin time (APTT). The APTT of CS-ArgC membrane was prolonged two times as that of CS counterpart, suggesting that the CS-ArgC is a promising candidate as an anticoagulation biomaterial.

Anticoagulants↗
PubMed2001

Emission of M2X+ cluster ions in thermal ionization mass spectrometry in the presence of graphite.

The emission of M2X+ cluster ions in thermal ionization mass spectrometry when graphite is loaded on the heating filaments was studied. The emission model of non-reductive thermal ionization of graphite was preliminarily discussed and factors influencing the thermal emission of M2X+ ions were investigated. The results show that the intensities of M2X+ cluster ions are related to ionic radius and crystal lattice energy, and possibly also to the solvation energies of ions. The intensities of M2Cl+ (M stands for K, Rb, and Cs) cluster ions, the M2Cl+/M+ ratios, and the 37Cl/35Cl ratios determined from M2Cl+ ion measurement usually increase with measurement time. The variation of the 37Cl/35Cl ratios determined from Cs2Cl+ ion measurement is lower than those based on K2Cl+ and Rb2Cl+ ion measurement, indicating the lowest isotopic fractionation.

Journal Article↗
PubMed2001

Microbial dechlorination of three PCB congeners in river sediment.

We investigated the potential for the anaerobic degradation of three PCB congeners (2,3,5,6-CB, 2,3,4,5-CB, and 2,3,4,5,6-CB) in sediments collected from five monitoring sites along the Keelung River in northern Taiwan. Optimal conditions for congener dechlorination were 30 degrees C and pH 7.0. Intermediate 2,3,4,5-CB products were identified as 2,3,5-CB, 2,4,5-CB, and 2,5-CB. Intermediate 2,3,4,5,6-CB products were identified as 2,3,5,6-CB, 2,3,6-CB, and 2,5-CB. For 2,3,5,6-CB, intermediate products were identified as 2,3,6-CB and 2,5-CB. Dechlorination rates for PCB congeners were observed as (fastest to slowest): 2, 3, 4-CB > 2, 3, 4, 5-CB > 2, 3, 4, 5, 6-CB > 2, 3, 5, 6-CB > 2, 2', 3, 3', 4, 4'-CB > 2, 2', 4, 4' 6, 6'-CB > 2, 2', 3, 4, 4', 5, 5'-CB > 2, 2', 3, 3', 4, 4', 5, 5'-CB. Rates decreased for mixtures of the eight congeners. Dechlorination rates for the three primary congeners under different reducing conditions occurred in the order of (fastest to slowest): methanogenic condition > sulfate-reducing condition > nitrate-reducing condition. Under methanogenic and sulfate-reducing conditions, dechlorination rates were enhanced by the addition of lactate, pyruvate, or acetate, but delayed by the addition of manganese oxide, or ferric chloride. Under nitrate-reducing condition, dechlorination rates were delayed by the addition of lactate, pyruvate, acetate, manganese oxide or ferric chloride. Treatment with such microbial inhibitors as bromoethanesulfonic acid (BESA) or molybdate revealed that methanogen and sulfate-reducing bacteria were involved in the dechlorination of these three PCB congeners.

Bacteria, Anaerobic↗
PubMed1999

[The early protective effects of basic fibroblast growth factor on acute spinal cord injury in rats].

OBJECTIVE: To study the early protective effects of basic fibroblast growth factor(bFGF) on the experimental acute spinal cord injury. METHODS: Thirty-four SD rats were randomly divided into three groups, and were subjected to contusion of thoracolumbar spinal cord. A thin plastic tube was placed in subarachnoid space below the injury level for perfusion. The bFGF-treated rats were received 20 microliters bFGF(containing bFGF 100 U) at once, 30 min, 1, 2, 3, 4, 6, 12, 24 and 48 hours after injury, and an equal volume of normal saline was given to the control group at the same time. The injured spinal cord was detected by morphological observation and biochemical index after injury. RESULTS: The degree of ionic disorder in bFGF-treated rats was significantly ameliorated and the contents of H2O were also markedly decreased. The morphological finding showed that the damages of gray and white matter in bFGF-treated rats were slighter than those of saline-treated rats. CONCLUSION: bFGF has some protective effects on the secondary lesion of early spinal cord injury in rats.

Animals↗
PubMed1995

Strecker stents in the femoropopliteal arteries: value of duplex ultrasonography in restenosis assessment.

PURPOSE: Experience with Strecker stent implantation in the femoropopliteal arteries has been described; however, few of the reports were prospective studies, and none routinely used site-specific assessment methods for follow-up evaluation of stent patency. The purpose of this study was to evaluate 1-year Strecker stent patency using duplex ultrasound imaging to obtain a more precise delineation of stent restenosis than is possible with other noninvasive assessment modalities. METHODS: A prospective study involved 52 patients with 57 sites treated by angioplasty and Strecker stent deployment in the femoropopliteal arteries. Assessment included clinical evaluation; ankle-brachial index (ABI) measurements at rest and after exercise; and duplex ultrasound imaging preprocedurally and at 3 and 12 months after the intervention. RESULTS: All 74 stents were deployed successfully in the 35 occluded arteries and 22 stenotic lesions. Acute reocclusion occurred in 6 (10%). At 3 months, primary patency was 81% and secondary patency 84%. Mean ( +/- SD) ABIs increased from 0.64 +/- 0.15 at rest and 0.32 +/- 0.17 after exercise to 0.89 +/- 0.14 and 0.68 +/- 0.23, respectively (p < 0.0001). At 12 months, primary patency was 79%, and secondary patency was 82%. Mean ABIs were 0.82 +/- 0.15 at rest and 0.52 +/- 0.22 after exercise at 12 months (p < 0.0002 compared with preprocedural ABIs). Analysis of the length of lesion treated showed betted results with shorter diseased segments, but this was not statistically significant (p > 0.05). Better outcomes were also obtained when one stent was used rather than two stents at 12 months (p = 0.15), but there was no difference at 3 months (p = 0.3). Thirty-four percent of the stented segments progressed from < 20% stenosis at 3 months to > 50% stenosis at 12 months. Overall, 19 (43%) of 44 segments progressed from < 50% stenosis at 3 months to a > 50% stenosis at 12 months. Restenosis seen at 3 months generally was in the native artery just proximal or distal to the stent, but at 12 months, restenosis was mainly inside the stent. CONCLUSIONS: Strecker stents at 1-year demonstrated satisfactory patency in the femoropopliteal arteries when deployed for angioplasty salvage or recurrent disease. The 3- and 12-month evaluations obtained with duplex ultrasound provided site-specific hemodynamic data for stent assessment. Resting ankle pressures were a poor index of restenosis.

Aged↗
PubMed1993

Ocular antivirals.

Explore the source record for details and available documents.

Antiviral Agents↗
PubMed1992

Human gastric cathepsin E gene. Multiple transcripts result from alternative polyadenylation of the primary transcripts of a single gene locus at 1q31-q32.

Genomic clones containing portions of the human cathepsin E (CTSE) gene were isolated from cosmid and lambda recombinant libraries. The regions corresponding to coding, the 5'- and 3'-untranslated, and the exon-intron boundaries of the CTSE gene were identified by sequence and hybridization analysis. The size and placement of the nine exons found in the 17.5-kilobase CTSE gene was highly conserved relative to other aspartic proteinases and provided additional evidence that these proteinases are derived from a common ancestral gene. Segregation and linkage analysis of two informative restriction fragment length polymorphisms (MspI and DraI) indicated that there is a single human CTSE locus located at chromosome 1q31-q32 which is closely linked to the renin gene. Three CTSE transcripts (3.6, 2.6, and 2.1 kilobases) were identified in gastric fundic and antral mucosa poly (A+) RNA, and these appeared identical in size and relative abundance to those contained in poly(A+) RNA from cultured gastric adenocarcinoma cell lines containing CTSE. Sequence analysis of cDNA clones and comparison with the 3'-flanking untranslated region in genomic clones provided evidence that alternative polyadenylation of the primary transcript resulted in the 2.6- and 2.1-kilobase transcripts which constituted greater than 95% of CTSE transcripts found in the stomach.

Amino Acid Sequence↗
PubMed1992

[Development of resistance of herpes simplex virus to antivirus drugs in vitro].

Resistant variants of HSV-1 wt strain to ACV, CC, DHPG and PFA can be selected after several passages in drug-containing cultures. The degree of resistance of different variants varied and emerged at different times. The combination of antiviral agents can delay and even prevent the emergence of drug-resistant variants. At the same time, the concentration, dose and, therefore, toxicity of the antiviral agents can also be reduced. So, it is a feasible method for treating resistant HSV infections. Cross-sensitivity tests showed that ACVr variants are resistant to ACV, DHPG and PFA, but sensitive to CC; PFAr variants are sensitive to ACV, CC and DHPG; CCr variants are sensitive to ACV and DHPG, but resistant to PFA; DHPGr variants are sensitive to ACV, CC and PFA. These results suggest that the study of cross-sensitivity of HSV strains in vitro provide information which will aid the design of suitable therapy for drug-resistant HSV infections.

Acyclovir↗
PubMed1989

Relationship between acupuncture-induced immunity and the regulation of central neurotransmitters in the rabbit: VI. The influence of NDR stimulation on acupuncture regulation of immune function in rabbit.

T-lymphocyte transformation ability decreased and the function of the B-lymphocyte and mononuclear leucocyte/macrophage system increased when the activity of central serotonergic neurons was enhanced by the stimulation of nucleus dorsal raphe (NDR). These changes induced by NDR stimulation were not effected by electroacupuncture (EA) when EA was performed on the background of NDR stimulation. By comparing these results with the previous resultant that immunoreactions were affected by locus coeruleus (LC) stimulation and LC stimulation plus EA, some regularity had been discovered. So, a hypothesis was put forward by us that the catecholaminergic system plays a main role in EA regulation of cellular immunity while the serotonergic system plays such a role in EA regulation of humoral immunity.

Animals↗
PubMed1989

[Experimental studies of 9-(1, 3-dihydroxy-2-propoxymethyl)-guanine(DHPG) against herpes simplex virus].

The antiherpes virus effects of 9-(1,3-dihydroxy-2-propoxymethyl) guanine (DHPG) were studied in cell culture and in experimental herpetic keratitis in rabbits. In plaque reduction assays in Vero cell, the 50% inhibitory concentration (IC50) of DHPG was shown to be 0.1 microgram/ml against HSV-1. Combination of DHPG and Cyclocytidine (CC), produced a synergistic activity against kos strains of HSV-1. Whereas the combination of DHPG and Acyclovir (ACV) or Tai-Ding-An (TDA) resulted in an additive interaction against HSV-1. Topical application of 0.1% or 0.05% DHPG eyedrop was initiated 48h after virus inoculation, significant efficacy was obtained in rabbits with herpetic epithelial keratitis. But 0.025 and 0.01% DHPG eyedrop showed no effect. 0.1% DHPG has been shown to be effective in the topical treatment of herpetic stromal keratitis in the rabbits.

Acyclovir↗
PubMed1988

Relationship between acupuncture-induced immunity and the regulation of central neurotransmitters in the rabbit: I. Effect of central catecholaminergic neurons in regulating acupuncture-induced immune function.

The central catecholaminergic neurons play an important role in the promotion of the T-lymphocyte transformation and the regulation of the positive rate of acid a-naphthylacetate esterase (ANAE) activity with acupuncture. The mechanism by which acupuncture promotes the T-lymphocyte transformation function may be principally by promoting the anabolism of the T-lymphocyte and speeding up the anabolism of the DNA. Judging from the fact that acupuncture increases the positive rate of ANAE, it can be assumed that the quantity of T-lymphocyte was increased markedly. It remains to be clarified what links exist through which the central catecholaminergic neurons can influence the acupuncture induced immunity, and what the effect of other transmitter neurons of the central nervous system are on acupuncture induced immunity.

Acupuncture Therapy↗
PubMed1986

Effects of 2,2'-O-cyclocytidine and acyclovir on latent herpes simplex virus in trigeminal ganglia of mice.

The effects of 2,2'-O-cyclocytidine (CC) and acyclovir (ACV) on latent herpes simplex virus (HSV) in trigeminal ganglia were studied in an in vitro model using reactivation of HSV type 1 (HSV-1) as a model. It was shown that both CC (10 micrograms/ml) and ACV (2.5 micrograms/ml) significantly inhibited the reactivation of the latent HSV-1 in infected ganglia. The effect of CC (25 micrograms/ml), which was as good as that of ACV (10 micrograms/ml), did not last as long as that of ACV after removal of the drugs. The latent state of HSV-1 in vitro was dependent on the continuous presence of either drug. Even though the latent HSV-1 could not be eliminated completely from the trigeminal ganglia by discontinuous administration of either drug, its titers were markedly reduced. The combination of CC and ACV had a synergistic effect on preventing the reactivation of the latent HSV-1 in vitro.

Acyclovir↗