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Biomedical subjects

W Liu

Publications and source records attributed to W Liu.

At least 631 records · Page 35Linked to original sources
PubMed1998

[Abuse of "pheticol" and its interference to the analysis of methamphetamine].

The study was to eliminate interference from ephedrine in the analysis of methamphetamine. The extraction procedure for methamphetamine was modified to include an oxidation step (2 ml urine specimen was treated with 0.5 ml of 1 mol/L phosphate buffer (pH 6.8) and 0.5 ml 0.3 mol/L sodium periodate). Results showed that ephedrine could be oxidized in the presence of periodate ions into smaller fragments while leaving methamphetamine intact. It is recommended that specimens be treated with sodium periodate prior to extraction in order to eliminate any interference caused by ephedrine.

Central Nervous System Stimulants↗
PubMed1998

[Determination of triazolam in human urine by GC/ECD].

A GC/ECD method was established to determine triazolam in human urine qualitatively and quantitatively. The triazolam was extracted from 2 ml urine with 2 x 2 ml chloroform. The retention time of triazolam was 10.74 min. The limit of the determination was 0.5 ng/ml. The recovery of the procedure in 5 ng/ml was 95.98%, CV = 7.85% (n = 5). The limit of quantitation is 2-50 ng/ml.

Adult↗
PubMed1998

[Determination of diflunisal in plasma by RP-HPLC after solid-liquid extraction].

A RP-HPLC method was developed with solid-liquid extraction technique. Plasma sample was extracted on a macroreticular resin cartridge with methanol--glacial acetic acid (99:1) as elution solvent. After extraction, the assay was carried out on a Spherisorb C18 column with p-phenylphenol as internal standard. The mobile phase is a mixture of methanol--water--glacial acetic acid (66:30:4). UV detection was performed at 250 nm. The flow rate was 1.0 ml.min-1. A good linearity was found at the concentration range from 0.5 to 100 micrograms.ml-1, with the lowest detection limit 0.02 microgram.ml-1 (S/N = 2). The extraction and method recoveries were 91.65% and 97.25% respectively, while the RSD for the within-day and between-day precision were all less than 10%. The above method was applied to determine the plasma concentration of difunisal in three human volunteers after a single oral dosage of 300 mg. Two hours after administration, the plasma concentration of diflunisal reached maximum level. A two compartment method was used to study the pharmacokinetic parameters. The T1/2 alpha and T1/2 beta were 1.40 h and 17.85 h, respectively.

Chromatography, High Pressure Liquid↗
PubMed1998

[Study on mechanical performance of the cerebral aneurysm clip].

Blood vessel tissue mechanical performance and cerebral aneurysm clip mechanical property are investigated. Results show that physical character of cerebral aneurysm clip, such as pressure value, maximum opening width of the blade tip, width, thickness and material is very important for its medical purpose. Surveying instrument is devised successfully.

Biomechanical Phenomena↗
PubMed1998

[Studies on the biomedical sensor techniques for real-time and dynamic simultaneous detection and measurements of respiratory gases carbon dioxide and oxygen].

Based on the studies of the direct detection of electro-inactive gas CO2 by amperometry and the mechanism of oxygen interference, a new modulated potential pulse coulometry/amperometry (MPPC/MPPA), which combines the fast modulated potential technique with the microelectrode method, has been advanced and established for the rapid determination of both CO2 and O2. The influence of modulated potential-time waveforms on the electrode activity, the accuracy and range of detection was investigated. Results were obtained which demonstrate that the novel biomedical sensor techniques can be used for the non-invasive, real-time and dynamic simultaneous monitoring of respiratory gases CO2 and O2.

Biosensing Techniques↗
PubMed1998

[Comparative research on two different killer strains of Saccharomyces cerevisiae].

Using two different killer strains SK4(K1 type) and ERR1(K2 type), their killer characters were analysed and find two strains compete with each other when they are mixed and killer characters are related with the growth of strains. Different M-dsRNA plasmids in different killer strains have different molecular lengths, being 1.7 kb and 1.5 kb in SK4 and ERR1, respectively. L-dsRNA plasmids in both strains have the same molecular lengths, 4.0 kb. Cured by high temperature (38 degrees C) and U.V. (15 W, 30 cm, 5 min), killer strains lose their killer characters with the disappearance of M-dsRNA, the curing rate of killer activity is associated with strains and curing conditions. Killer toxins produced by two strains have different killer effects. Toxins of SK4 and ERR1 have the different highest killer activity at pH 4.8, 16 degrees C and pH4.2, 22 degrees C, but both of two toxins have the greatest effect on the sensitive strain in the late-log phase.

Hydrogen-Ion Concentration↗
PubMed1998

[Construction and identification of recombinant fowlpox virus for expressing haemagglutinin-neuraminidase glycoprotein of Newcastle disease virus strain F48E8].

For the construction of transfer vector pFGHN1175-1, the gene encoding haemagglutinin-neuraminidase(HN) glycoprotein of newcastle disease virus(NDV) strain F48E8 was removed from plasmid pGEMHN, and inserted into the HindIII site of insertion vector pFG1175-1, downstream of P7.5 promotor. Chicken embryo fibroblast (CEF) cell cultures which had been infected with fowlpox virus (FPV) Chinese vaccine strain 282E4 for 3-4 hours were transfected with pFGHN1175-1 plasmid DNA by liposomal transfection. Recombinant FPV with blue plaques were selected and purified 3 times in CEF cell cultures overlaid agarose containing X-gal. PCR analysis and DNA dot-blotting hybridization assay indicated that the HN gene had inserted into the FPV genomic DNA. The expression of the NDV HN gene in recombinant FPV was confirmed by indirect immunofluorescence assay with specific monoclonal antibody.

Animals↗
PubMed1998

[Study on pharmacological actions of pingxiaozhitong pill].

Pingxiaozhitong pill was administered ig. once daily for 7 successive days at dosages (4,2,2 g/kg). It was shown markelly suppressive effects on solid sarcoma 180 (S180) and Ehrlich aseites carcinoma (EAC) and synergism effect on cytoxan inhibiting S180 in mice. It had significant analgesic effect. 4,2 g/kg pingxiaozhitong pill enhanced effects on phagocysis of monocyte macrophage and value of hemagglutinin in serum in mice.

Adjuvants, Immunologic↗
PubMed1998

[Management of very complicated retinal detachment].

PURPOSE: To evaluate the management for a group of complicated retinal detachment in very severe conditions including(A) rhegmatogenous retinal detachment associated with severe posterior and anterior PVR, (B) giant retinal tear (GRT) retinal detachment with severe PVR, (C) severe perforating eye injury with tractional retinal detachment. METHODS: A total number of 31 eyes from 31 patients was included, in which 14 eyes were in group A, 8 eyes were group B and 9 eyes group C. Procedures including scleral buckling, encircling, cryotherapy, total vitrectomy, epiretinal membrane peeling/excision, relaxing retinectomy, use of perfluorocarbon liquid and silicone oil were applied to all patients. Patients were followed up for three to 16 months. RESULTS: Retinas of 21 out of 31 eyes(67.7%) were completely reattached and 5 eyes (16.1%) were partially reattached, 5 eyes were failed(16.1%). Postoperative vision was significantly improved in 25 eyes. The visual acuity of 19 eyes was better than 0.02, while before operation only two eyes were better than 0.02. PVR and GRT patients had better results. CONCLUSION: The results showed that a big part of very complicated retinal detachment which was called as hopeless cases could still be successfully treated with comprehensive procedures, more than half of them may have useful vision which may obviously improve their life quality.

Adolescent↗
PubMed1998

The immunological studies on proliferative intraocular disorders: investigation of activated lymphocytes, macrophages and HLA-DR.

PURPOSE: To investigate whether activated B lymphocytes (CD23), activated T lymphocytes (CD25), macrophages (CD68) and human leucocyte antigen class II antigen (HLA-DR) were existed in epiretinal membranes (ERMs) and subretinal membranes (SRMs) of proliferative intraocular disorders (PID). METHODS: Twenty specimens of ERMs from rhegmatogenous retinal detachment with proliferative vitreoretinopathy (PVR), traumatic PVR and secondary traction retinal detachment, and two specimens of SRMs from rhegmatogenous retinal detachment with PVR and traumatic PRV were studied using immunohistochemical staining. RESULTS: CD68 and HLA-DR were found in all specimens, CD23 and CD25 in 4 cases of ERMs and in 1 case of SRMs, respectively. CONCLUSIONS: 1. The ERMs and SRMs of different etiology shared a common basis of inflammation and immunopathology. 2. There would be secondary cellular and humoral immunity in the ERMs and the SRMs of PID.

Antigens, CD↗
PubMed1998

[Determination of the content of serum calcium with methylthymol blue as chromogenic reagent].

It is reported in this paper that calcium can be determined with MTB as chromogenic reagent by isoabsorption dual-wavelength elimination. The measuring wavelength and referential wavelength were 613.7 and 590.0nm, respectively. No masking reagent was necessary in the analysis. The average recovery and RSD of calcium are 98.98% and 0.81%, respectively. Compared with titration, this method is rapid, simple and precise.

Absorption↗
PubMed1998

Upregulation of p21WAF1/CIP1 in human breast cancer cell lines MCF-7 and MDA-MB-468 undergoing apoptosis induced by natural product anticancer drugs 10-hydroxycamptothecin and camptothecin through p53-dependent and independent pathways.

Recently, natural product DNA topoisomerase I inhibitors 10-hydroxycamptothecin (HCPT) and camptothecin (CPT) have been shown to have therapeutic effects in both in vitro and in vivo models of human breast cancer. In the present study, we characterized the in vitro and in vivo apoptotic pathways induced by HCPT and CPT in the human breast cancer cell lines MCF-7 and MDA-MB-468. Using various DNA fragmentation analyses and the terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay, the apoptosis induced by HCPT and CPT was shown to be dose- and time-dependent. The MDA-MB-468 cells were more sensitive to both HCPT and CPT than MCF-7 cells. HCPT induced apoptosis in MDA-MB-468 cells more effectively than CPT; however, in MCF-7 cells, CPT was more effective than HCPT. The levels of p53 and p21WAF1/CIP1 protein increased in MCF-7 cells treated with HCPT or CPT in a dose- and time-dependent manner. The levels of p21WAF1/CIP1 protein also increased in a dose- and time-dependent manner in MDA-MB-468 cells treated with HCPT or CPT, whereas the mutated p53 protein levels had no significant change. The elevation of p53 protein levels in MCF-7 cells treated with CPT was significantly inhibited by preincubation with DNA breaks inhibitor aphidicolin, while the elevation of p21WAF1/CIP1 protein levels was not inhibited. The elevation of p21WAF1/CIP1 in MDA-MB-468 cells treated with CPT was not inhibited by aphidicolin. Using Northern blot analysis, the transcription of p21WAF1/CIP1 was shown to increase in a dose-dependent manner in MCF-7 and MDA-MB-468 cells treated with HCPT or CPT. These results suggest that treatment with HCPT and CPT results in increased levels of p21WAF1/CIP1 protein and mRNA, and that they induce apoptosis in human breast cancer cells through both p53-dependent and -independent pathways. These findings may be significant in further understanding the mechanisms of actions of camptothecins in the treatment of human cancers.

Antineoplastic Agents, Phytogenic↗
PubMed1998

Significance of platelet-derived endothelial cell growth factor in the angiogenesis of human gastric cancer.

We have previously shown that platelet-derived endothelial cell growth factor (PD-ECGF) is associated with angiogenesis of human colon cancer; this factor is expressed at high levels in vascular tumors that express low levels of vascular endothelial growth factor (VEGF). In these colon cancers, the major source of PD-ECGF is the infiltrating cells. In this study, we examined the role of PD-ECGF in the angiogenesis of human gastric cancer. Immunostaining for PD-ECGF was done on 93 gastric cancers previously stained for VEGF, basic fibroblast growth factor, and factor VIII-related antigen (specific for endothelial cells). To determine the cell type expressing PD-ECGF, double staining was done using antibodies to both PD-ECGF and CD68 (specific for macrophages). PD-ECGF was expressed more frequently in infiltrating cells (positive CD68 staining; 53.8%) than in tumor epithelium (9.7%; P < 0.0001). Infiltrating cells simultaneously stained positive for both PD-ECGF and CD68. An association between PD-ECGF expression in infiltrating cells, VEGF expression in tumor epithelium, and vessel count was observed in intestinal-type gastric cancer but not in diffuse-type gastric cancer. Vessel count was greater in tumors with high expression of both PD-ECGF and VEGF than in those with high expression of either factor alone (P = 0.002). Multiple angiogenic factors expressed by both tumor cells and infiltrating cells may play a role in the regulation of angiogenesis in intestinal-type gastric cancer.

Adult↗
PubMed1998

Mammalian auditory hair cell regeneration/repair and protection: a review and future directions.

Regeneration/repair and protection of auditory hair cells and auditory neurons is an exciting, rapidly evolving field. Simultaneous developments in the fields of otobiology and surgical otology have led to new and exciting possibilities in inner ear medicine and surgery; specifically, the treatment or prevention of a variety of types of hearing losses in the foreseeable future. Sensorineural hearing loss in humans is commonly associated with a loss of auditory hair cells. It has been generally accepted that hearing loss resulting from hair cell damage is irreversible because the human ear has been considered to be incapable of regenerating or repairing these sensory elements following severe injury. An organ of Corti explant study has shown that it is possible to initiate the regeneration/repair of mammalian hair cells. In this study, ototoxin-damaged organ of Corti explants from juvenile rats were treated with a combination of retinoic acid (10-8M) and fetal calf serum (10%). TGF-alpha has been identified as a growth factor capable of evoking auditory hair cell regeneration/repair in ototoxin-damaged organ of Corti explants. Preliminary in vitro experiments with juvenile rat organ of Corti explants and in vivo studies in the cochleae of adult guinea pigs indicate that pretreatment followed by continuous treatment of the inner ear with a combination of retinoic acid and TGF-alpha can protect the auditory hair cells from the ototoxic effects of aminoglycosides. Because the integrity of spiral ganglion neurons is also essential for normal auditory function, there is a parallel series of in vitro and in vivo studies of the effects of neurotrophic factors on the survival of auditory neurons and the regeneration of injured neuronal processes. Clinical studies have demonstrated that it is now possible to perform surgeries on the inner ear, i.e., partial or total labyrinthectomies, and maintain hearing. The field of cochlear implantation has also provided insights into both the short- and long-term effects of cochlear fenestration on inner ear function. Administration of growth factors to the inner ears of animals is now possible with the use of implanted catheters and miniature infusion pumps. These advances suggest that localized application of drugs to the human inner ear may be feasible. The aim of this paper has been to provide an overview of advances in the study of the biology of auditory hair cells and auditory neurons, as well as recent relevant surgical advances. Taken together, these advances in otobiology and surgery will, in the future, be combined to devise new and innovative treatments for inner ear disorders.

Adult↗
PubMed1997

[Phe21]big endothelin-1(18-34) and [Ala31]big endothelin-1(18-34) inhibit the human endothelin-converting enzyme-1 (ECE-1) expressed in CHO-K1 cells in a different fashion.

Endothelin-converting enzyme-1 (ECE-1) is one of the most important enzymes to convert big endothelin-1 (big ET-1) to ET-1. To identify the inhibitors of ECE-1, we examined the effects of variously substituted analogues of big ET-1 on ECE-1 activity using solubilized membranes prepared from human ECE-1-expressed CHO-K1 cells. Among the big ET-1 analogues tested, [Phe21]big ET-1(18-34) and [Ala31]big ET-1(18-34) exhibited a significant inhibition of ECE-1. A kinetic analysis revealed [Phe21]big ET-1(18-34) to be a competitive inhibitor (Ki=20.6 microM) and [Ala31]big ET-1(18-34) to be a noncompetitive inhibitor (Ki=35.6 microM). These results not only support the concept that ECE-1 recognizes big ET-1 both at the P1 position and at the C-terminal region but also revealed that these two regions are recognized by this enzyme in a different manner.

Animals↗
PubMed1997

Chemosignal transduction in the vomeronasal organ of garter snakes: Ca(2+)-dependent regulation of adenylate cyclase.

Earthworm shock secretion contains a 20-kDa vomeronasally mediated chemoattractive protein for garter snakes. Both the ligand-receptor binding and the chemoattractivity of ES20 are Ca(2+)-dependent. When ES20 binds to its G-protein-coupled receptors in the vomeronasal epithelium, the inositol 1,4,5-trisphosphate (IP3) level is increased, but the level of cAMP is reduced. Furthermore, forskolin-stimulated levels of cAMP are completely blocked by ES20-receptor binding or by Ca2+ alone and the effect of calcium ions can be nullified by EGTA. Previously, we hypothesized that the decrease in cAMP was due to activation of a Ca(2+)-dependent phosphodiesterase. In the present study, we provide evidence that the decrease in cAMP is due mainly to the regulation of adenylate cyclase (AC) activity by Ca2+ or is indirectly mediated by ES20. Results obtained with intact vomeronasal sensory epithelium suggest that the binding of ES20 to its receptors facilitates generation of IP3 which mobilizes intracellularly sequestered Ca2+, resulting in an increase of cystosolic Ca2+. A further increase in cytosolic Ca2+ occurs through Ca2+ influx from extracellular sources. Garter snake vomeronasal AC does not require calmodulin for its activity and shows a biphasic response to increasing concentrations of Ca2+; its activity is modulated both positively and negatively by this bivalent cation.

Adenylate Cyclase Toxin↗
PubMed1997

PTEN/MMAC1 mutations and EGFR amplification in glioblastomas.

Loss of heterozygosity (LOH) from chromosome 10 is a hallmark of glioblastoma, the most malignant (grade IV) form of glioma. A candidate tumor suppressor gene, PTEN/MMAC1, that may be targeted for deletion in association with chromosome 10 LOH has recently been identified. Here we have investigated 63 glioblastomas for PTEN/MMAC1 alterations and identified DNA sequence changes that would affect the encoded protein in 17 (27%) tumors. Microsatellite analyses of normal-tumor DNA pairs were performed on 14 of these cases and revealed LOH at locations flanking and/or near PTEN/MMAC1 in all but 1 instance, suggesting that deletion of the remaining wild-type allele had occurred in the large majority of tumors with PTEN/MMAC1 mutations. Competitive PCR assays were developed to address the possible occurrence of PTEN/MMAC1 homozygous deletions in glioblastomas, and this analysis identified three samples having loss of both PTEN/MMAC1 alleles. EGFR amplification was determined to occur at similar frequencies among cases with or without PTEN/MMAC1 homozygous deletions or mutations, suggesting that a growth-promoting effect resulting from amplification-associated increases in epidermal growth factor receptor signaling is not necessarily dependent on the inactivation of PTEN/MMAC1.

Alternative Splicing↗