Biomedical subjects

L Liu

Publications and source records attributed to L Liu.

At least 595 records · Page 33Linked to original sources

PubMed1999

[HPLC determination of uracil xanthine, hypoxanthine and uridine in species of animal drugs].

OBJECTIVE: To make further studies on the water-soluble components in animal drugs by determining the contents of uracil, xanthine, hypoxanthine and uridine from ten species of animal drugs. METHOD: The determination was affected by RP-HPLC, using Shim-pack CLC-ODS column(150 mm x 6 mm), 0.05 mol/L dibasic ammonium phosphate solution as mobile phase, flow rate 0.8 ml/min and detection at 254 nm. RESULTS: This method is accurate, rapid and reproducible. Analytical data for Hirudo nipponia, Eupolyphaga sinensis, Scolopendra subspinipes mutilans, Buthus martensii, Bombyx mori, Mylabris cicorri, Aspongopus chinensis, Lytta caraganae, Tabanus bivittatus and Huechys sanguinea are given. CONCLUSION: There are marked discrepancies in the contents of the four components as shown on the chromatograms, a point that may be helpful in identifying the above-cited ten species of animal drugs.

Animals↗

PubMed1999

[Changes and its measurement of intracellular Ca2+ during exposure to hyperbaric oxygen].

Objective. To investigate the rule of change of intracellular Ca2+ and its measurement method during exposure to hyperbaric oxygen (HBO). Method. Microfluorescence method was used to measure the changes of intracellular Ca2+ concentration in co-cultured endothelial cells (EC) and smooth muscle cells (SMC) in a specially designed miniature oxygen chamber. Result. (1) [Ca2+]i changes during HBO exposure can be clearly observed directly in the chamber. (2) Within 5 min during 0.2 MPa and 0.3 MPa HBO exposure, EC[Ca2+]i and SMC[Ca2+]i showed a tendency, to increase at first and then decrease with time throughout the exposures, especially the SMC[Ca2+]i. The EC ruptured under exposure to 0.4 MPa HBO. Conclusion. During HBO exposure, EC[Ca2+]i and SMC[Ca2+]i showed biphasic changes, which increased at first and then decreased. The technique and method used were reliable and suitable for investigating of intracellular [Ca2+]i changes under HBO.

Animals↗

PubMed1999

[An experimental study on bone potentials at fracture site with axial interfragmental gradient compression].

OBJECTIVE: To evaluate the mechanism of stress generated potentials in compressive fixation leading to the primary healing. METHODS: Eighteen fresh sheep tibiae were divided equally into three groups, and all specimen were fractured artificially and imposed "prestressing" at fracture sites with tension device and plate, meanwhile stainless wire tension band was used in the place opposite to plate. The interfragmental pressure was exerted when applied plates, which were 98.62 +/- 19.74 N, 137.93 +/- 8.13 N and 169.20 +/- 11.33 N. Bone potentials at fracture sites were recorded with reference to the potential measurement system by Friedenberg and Brighton (1966). RESULTS: There was no significant statistical difference in bone potentials when made comparison between before and after compression fixation in each group and among groups of different axial interfragmental gradient compressions. CONCLUSION: The mechanism of stress generated potentials may not exist in primary healing with compressive fixation.

Animals↗

PubMed1999

[Analysis of 413 cases of mandibular fractures].

OBJECTIVE: To investigate the characteristics of mandibular fracture. METHODS: 413 patients with mandibular fracture were chosen from patients who received treatment at the department of oral and maxillofacial surgery, College of Stomatology, West China University of Medical Sciences from 1986 to 1995, and a retrospective study was carried out. Chi-square test, t-test and linear regression were used to analyzed age, sex, causes, anatomic site, complicated injury, and treatment of jaw fracture. RESULTS: Fracture of Mandible occurred mainly in male, and during 20 to 29 years old. Mental fracture was common in mandibular fracture, and fracture of central craniofacial bone and craniocerebral injury were often complicated with jaw fracture. CONCLUSION: Mandibular fractures are caused mainly by traffic ever since 1990, and rigid intrafixation is a satisfactory treatment which has been accepted by surgeons.

Accidents, Traffic↗

PubMed1999

[Internal fixation for zygomatic arch fracture with super-high molecular weight poly D, L-lactic acid mini-plates and screws: a study in dogs].

OBJECTIVE: To investigate the internal fixation effects of super high molecular weight (Mv = 6.0 x 10(5) kD) poly D, L-lactic acid(PDLLA) mini-plates and screws. METHODS: 10 dogs were utilized in this experiment with the self-contrast study method, comparing with the titanium mini-plates and screws. RESULTS: The mechanical properties of the PDLLA mini-plates and screws appeared to be sufficient to enable undisturbed healing of depressed zygomatic arch fracture. CONCLUSION: The good fixation effect of PDLLA mini-plates and screws was as same as that of the titanium mini-plates and screws without the need of secondary operation.

Animals↗

PubMed1999

[Tissue reaction and degradation of super-high molecular weight poly D, L-lactic acid mini-plates and screws: an animal experiment].

OBJECTIVE: To investigate the tissue reaction and degradation processes of the super-high molecular weight(Mv = 6.0 x 10(5) kD) poly D, L-lactic acid(PDLLA) mini-plates and screws through the internal fixation for zygomatic arch fracture. METHODS: It was carried out by the self-contrast study method and comparing with the titanium mini-plates and screws. RESULTS: There was no side-effects on bone healing. The reaction of soft and hard tissues to PDLLA mini-plates and screws was similar to that of the titanium mini-plates and screws. No complication had been seen with the use of PDLLA mini-plates and screws, including infection, foreign body reaction and underlying osteolysis. The PDLLA devices had no changes in shape after 3 months, and then became the grains in different sizes after 6 months, and were completely resorbed within 12 months in vivo. CONCLUSION: The super-high molecular weight PDLLA mini-plates and screws has good biocompatibility and proper degradation time. It is safe and effective to use the mini-plates and screws made of the super-high molecular weight PDLLA for internal fixation of bone.

Animals↗

PubMed1999

[Construction of Streptococcus mutans surface protein antigen eukaryotic expression vector pcDNA3-PAc. I. Extraction and purification of plasmid DNA pPC41 and pcDNA3].

OBJECTIVE: To Extract and purify plasmid DNA pPC41 and pcDNA3. METHODS: Bacteria were collected and lyzed by the alkaline lysis method. The plasmid pPC41 carrying structural gene pac and clone expression vector pcDNA3 were extracted and purified from E. coli clone by the polyethylene glycol precipitating method, the electroelution into dialysis bags method, the low melting-temperature agarose gel and glass fiber column chromatography. The concentration, purity and molecular weight were determined by spectrophotometry, restriction enzyme and agarose gel electrophoresis. RESULTS: The concentration of plasmid DNA of this experiment in general was 0.12-0.24 g/L, and A260/A280 of the polyethylene glycol precipitating method, the electroelution into dialysis bags method, the low metling-temperature agrose gel and glass fiber column chromatography were respectively 1.9, 2.2, 2.2 and 2.6. Molecular weight of pPC41 and pcDNA3 was respectively 10.6 kb and 5.4 kb. CONCLUSION: The four methods can obtain pure plasmid DNA. Purity of plasmid DNA obtained by glass fiber column chromatography method is the highest in the four methods. Glass fiber column chromatography is one of the effective methods getting highly purified plasmid DNA.

Antigens, Surface↗

PubMed1999

[Application of derivative technique in the signal processing of gas chromatography].

An application of derivative technique in the signal processing of gas chromatography(GC) is described. TCD's sensitivity of the derivative GC was 270 kV.L/kg, and its susceptibility was 0.3 microgram/L In comparison with the conventional GC, there was a 7-40 fold increase in sensitivity and a 24-40 fold decrease in susceptibility. The noise of the derivative GC was equal to or smaller than the conventional one. The minimum resolution for a pair of substances most difficulty to be separated in conventional GC, which was separated completely in the derivative GC, was 2.8. The linear range of n-butanol was 10(2) and the peak area correlation coefficient of the derivative GC was 0.9991.

1-Butanol↗

PubMed1999

[Effects of human thorax tissues on conduction of electrocardiogram and body surface potential].

In this paper, the forward problem of electrocardiogram(ECG) has been calculated by means of numerical simulating techniques. Firstly, It is focused on the effects of organs and tissues within the thorax on the body surface potentials under a 2-D cross section of thorax in terms of finite element method (FEM). To check the effect of skeletal muscle layers on ECG, the simulating computation of ECG, by a method combining FEM with boundary element method (BEM), has been carried out in terms of a 3-D thorax model.

Algorithms↗

PubMed1999

[The effect of cAMP on the transcription and regulation of angiotensin II type 1 receptor gene in cardiomyocytes of neonatal rats].

OBJECTIVE: To clarify the effect of cAMP on the transcription of angiotensin II type 1 (AT1) receptor mRNA in cardiomyocytes. METHODS: Cardiomyocytes from SD neonatal rats were cultured in DMEM containing 10% fetal bovine serum (FBS) with 0.1 mmol/L 5-bromodeoxyuridine (Brdu). At day 5-7, primary cultured cells were used. FBS and Brdu were deprived 24 h before the stimulation. The levels of AT1 mRNA in primary cultured cardiomyocytes were examined by RT-PCR. RESULTS: Stimulation of forskolin (30 mumol/L) plus 3-isobutyl-1-methyl-xanthine (IBMX, 30 mumol/L) which induced the accumulation of cellular cAMP decreased the expression of AT1 receptor mRNA to (64.4 +/- 20.3)% of control at 6 h treatment; while it increased the expression of AT1 receptor mRNA to (209.6 +/- 24.0)% of control at 48 h treatment. CONCLUSIONS: cAMP regulated the transcription of AT1 receptor gene.

Animals↗

PubMed1999

[Angiotensin II regulates the expression of collagens in rat heart].

OBJECTIVE: To testify the effect of angiotensin (Agn) II on the regulation and expression of collagen I, III genes in rat heart as well as the influence of DMP811 (a novel nonpeptide selective angiotension type 1 antagonist) on the effect of Ang II. METHODS: Six-week-old male SD rats with osmotic minipump subcutaneously containing either Ang II or saline were used. (1) Saline-infused(control) group (n = 6), (2) Ang II-infused group (n = 6). (3) Ang II-infused and DMP811-treated (3 mg.kg-1.d-1, by gavage) group (n = 6). Ang II (200 ng.kg-1.min-1) or saline was continuously infused for 1 week. After extraction of cardiac total RNA, the levels of collagen I, III mRNA and proteins were measured with RT-PCR and Sirius red staining respectively. RESULTS: Cardiac weight, cardiac weight/body weight radio, the mRNA levels of collagen I, III were increased by (4.7 +/- 0.4)%, (4.9 +/- 0.9)%, (22.0 +/- 4.7)% and (20.6 +/- 4.9)% respectively, in group 2 compared with those in group 1. The analysis of collagen on Sirius red-stained sections showed that Ang II increased the deposits of both collagen I and III. The above changes caused by Ang II could be inhibited fully by DMP811. CONCLUSIONS: Ang II up-regulated the expressions of collagen I, III via angiotension type 1 receptor.

Angiotensin II↗

PubMed1999

[The comparison of contents of uracil, xanthine and hypoxanthine in five species of leech].

Three constituents(uracil, xanthine, hypoxanthine) were isolated from five species of leech and determined by reversed phase HPLC. The column employed was Shim-pack CLC-ODS C18(150 mm x 6 mm). The mobile phase was 0.05 mol/l ammonium phophate dibasic solution(pH = 8.4). The flow rate was 0.8 ml/min and detection was effected at 254 nm. This method is accurate, rapid and reproducible. Analytical data for five species and Whitmania pigra samples from different places were given.

Animals↗

PubMed1999

The study on related genes in the neoplastic transformation of immortalized human fetal tracheal fibroblast cells induced by irradiation.

In this study, we investigated the genes related to the transformation of immortalized human fetal tracheal fibroblast cell line induced by alpha particles by means of differential display mRNA method. The result revealed that there were 23 DNA fragments that were expressed intensively in alphaSHTF cells (SHTF cells forming clone on agar after irradiated by alpha particles emitted by 238Pu) only and not in SHTF (SV40-immortalized human fetal tracheal fibroblast) cells. Northern dot confirmed two fragments, C17-5, C23-1 which showed intensive mRNA expression in alphaSHTF cells, but not in SHTF cells. The length of the C17-5 fragment was 310bp. Searching in BLAST database revealed that the C17-5 fragment might be an unknown sequence.

Base Sequence↗

PubMed1999

[Removal of a broken needle in the left pterygoid fossa:report of one case]

OBJECTIVE:To research the application of orthodontic techniques of edgewise brackets to enhance the curative effect of stabilizing the loose teeth.METHODS: Between 1993-1998,we applied orthodontic techniques of Edgewise brackets to treat 35 cases of patients which include 58 loosen teeth caused by trauma factors,most adopting edgewise brackets plus round wire.RESULTS: We have obtained excellent curative effect in 45 teeth,good curative effect in 9 teeth,and 4 teeth failed.CONCLUSION: Orthodontic technique of Edgewidw brackets is a reliable method to stabilize the loose teeth.Compared with conventional arch bar splint fixation,the Edgewise technique has its unique advantage.

Journal Article↗

PubMed1999

[Direct determination of zinc and iron in maize flour using suspension sample introduction by flame atomic absorption spectrometry].

A new FAAS method for the determination of zinc and iron in maize flour using suspension sample introduction is described. The maize flour was suspended in agar sol, and injected into air-acetylene flame by using standard addition method to determine zinc and iron. The results are consistent with those obtained by ashing method. This method is convenient and rapid.

Flour↗

PubMed1999

[Determination of calcium and magnesium in wheat flour by suspension sampling-flame atomic absorption spectrometry].

Suspension sampling technique was applied to flame atomic absorption spectrometry and was successfully used to determine calcium and magnesium in wheat flour. The wheat flour was suspended in agar sol containing dibutyl phthalate and made into suspension. Choice of suspension agent and elimination of chemical interference were studied. The test solution was injected into air-acetylene flame to determine calcium and magnesium by standard addition method. Determination results were consistent with those obtained by ashing method. The t-test showed that no difference was found between the two methods. Displacement of ashing method by suspension sampling method for the sample pretreatment is possible. This method is convenient, rapid and accurate.

Calcium↗

PubMed1999

[Determination of protein in urine by spectral probe of molybdenum(VI) salicylfluoronate complex].

The absorption spectral behavior of binding reaction of molybdenum(VI)-salicylfluoronate on bovine serum albumin was investigated. A novel method for the determination of protein in urine using Mo(VI)-salicylfluoronate complex as a spectroprobe was developed. The maximum binding number (n) of molybdenum complex to BSA was found to be 100. The molar absorptivity of binding product at 575 nm was 2.86 x 10(6) L x mol(-1) x cm(-1). The method possesses high sensitivity as well as high selectivity. It could be used to determine protein in human urine directly. The relative standard deviation for the determination is 1.5%.

Humans↗

PubMed1999

Simultaneous protection of G156A methylguanine DNA methyltransferase gene-transduced hematopoietic progenitors and sensitization of tumor cells using O6-benzylguanine and temozolomide.

O6-Benzylguanine (BG) potentiates temozolomide (TMZ) cytotoxicity in tumors by inactivating O6-alkylguanine DNA alkyltransferase but also increases toxicity in hematopoietic cells. To improve the hematopoietic cell tolerance to alkylating agents, we retrovirally transduced the BG-resistant mutant G156A methylguanine DNA methyltransferase gene (deltaMGMT) into hematopoietic progenitors and evaluated whether deltaMGMT expression in hematopoietic colony-forming units would result in greater drug resistance to TMZ. DeltaMGMT expression in human and mouse colony-forming units followed by BG treatment resulted in a >7.7-fold increase in the TMZ 90% inhibitory concentration (IC90) and a 5.6-fold increase in the 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) IC90 relative to untransduced cells. This degree of protection enabled deltaMGMT-transduced CD34 cells to become much more resistant to BG and TMZ than SW480 cells, which express high O6-alkylguanine DNA alkyltransferase and are normally resistant to TMZ or BCNU alone. DeltaMGMT-transduced long-term culture initiating cells were also resistant to the BG and TMZ combination, as were untransduced long-term culture initiating cells, suggesting that noncycling early progenitors may be partially protected from TMZ. These data indicate that retroviral transduction of deltaMGMT into hematopoietic progenitors followed by BG and TMZ treatment may selectively protect hematopoietic cells more efficiently than BCNU, allowing dose-intensive and repetitive therapy without the risk of cumulative myelosuppression.

Animals↗