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Biomedical subjects

D Liu

Publications and source records attributed to D Liu.

At least 577 records · Page 32Linked to original sources
PubMed1996

[Effects of selective nitric oxide synthase inhibitor in sheep with endotoxic shock].

OBJECTIVE: To investigate the effects of S-methylisothiourea sulfate (SMT), a selective inducible nitric oxide synthase (iNOS) inhibitor, on hyperdynamic endotoxic shock sheep. METHODS: Endotoxic shock was induced by Escherichia coli endotoxin in both control (n = 8) and SMT groups (n = 8). SMT was given intravenously. Hemodynamic data, oxygen delivery derived parameters and intramucosal pH (pHi) were measured. RESULTS: The control group had a hyperdynamic state, similar to that of human septic shock. In the SMT group, blood pressure was maintained at baseline, and cardiac index (CI) was lower than that in the control group (P < 0.05). Oxygen extraction ratio (O2 ext) was increased up to 40% +/- 5% and was much higher than that of the control group (P < 0.01). Pulmonary artery pressure (PAP) was higher than that of the control group (P < 0.01), and pHi decreased gradually similarly to the control group. CONCLUSION: SMT restored the blood pressure and increased O2 extespecially in the gut, but decreased CI and oxygen delivery and increased PAP. So over inhibition of iNOS should be cautiously considered.

Animals↗
PubMed1996

[Constant composition study on kinetics of enamel demineralization].

The aim of this work was to investigate the kinetic behaviour of whole enamel demineralization compared with that of powder enamel. Constant composition technique was used to maintain a constant undersaturation degree with respect to hydroxyapatite in the demineralizing solutions. The demineralizing processes were monitored by recording the volume of adding titrant solution. Finally, sections were measured for lesion depth by microradiography, and blocks were tested for microhardness. The results showed that demineralization of enamel powder nearly completed within 40 minutes, while demineralization of whole enamel was much slower and with a constant rate within the experimental time. It was also found there were significant increases of concentrations of calcium and phosphate in solutions during the first 40 hours of whole enamel demineralization. It suggests that the kinetic behaviour of whole enamel demineralization is different from that of powder enamel, which is not only due to the unique transport process in whole tissue, but also possible due to a different phase transformation before and after formation of a surface layer.

Calcium↗
PubMed1996

Nonlinear property membrane rectifier potassium channel and inhibitory effects of oxygen free radical.

There are at least eight kinds of different potassium channels on cardiac cell membrane. This paper presents a nonlinear property membrane outward current going rectifying potassium channel and the inhibitory effects of oxygen free radical on this channel. The current-voltage relation of this nonlinear-membrane can be defined by an equation I = 8a3/(0.01v2 + 4a2)2 and the maximum conductance of this channel is -75.3 pS.

Animals↗
PubMed1996

[Clinicopathological study of 34 autopsy cases of mycobacteriosis in patients with acquired immunodeficiency syndrome].

OBJECTIVE: Clinicopathological features of mycobacteriosis were studied by means of microscopical examination of 34 autopsy cases in patients with acquired immunodeficiency syndrome (AIDS) and the diagnostic methods were evaluated. METHODS: All cases were anatomized, sampled, fixed and embedded routinely and stained with hematoxylin-eosin. Acid fast stain was applied to identify the mycobacteria. The pathological sections and files were reviewed systemically and retrospectively. RESULTS: Thirty-four cases of mycobacteriosis, including Mycobacterium avium-intracellular complex (MAI) infection (20 cases) and Mycobacterium tuberculosis (10 cases) and mixed infection of both pathogens (4 cases) were found out of 151 autopsy AIDS patients. MAI infection involved mostly the lymph nodes (21 cases) and followed by spleen, liver and lung, etc. The infection were often disseminated and characterized by proliferation of histocytes with foamy or vacuolar cytoplasm containing acid fast bacilli and formation of granulomatous nodules. Tuberculosis often involved the lung (10 cases) and lymph node (8 cases), the typical manifestations of which were caseous necrosis and tuberculation. Other opportunistic infections and neoplasmas occurred with mycobacteriosis in 25 cases. CONCLUSIONS: Mycobacteriosis, especially the tuberculosis and MAI infection are common in patients with AIDS, which are often disseminated and involved the lung and lymph node. The diagnosis can be made according to the specific pathological appearances and positive acid fast stain.

Acquired Immunodeficiency Syndrome↗
PubMed1996

[The evaluation of clinical staging by preoperative CT examination in patients with bladder cancer].

50 patients with bladder cancer, treated from september 1988 to September 1994 was analysed to compare preoperative CT examination with postoperative pathological diagnosis. The coincident staging of CT and pathological finding was found to be 86% (43/50). In the remaining 7 patients, 4 were of overstaging and 3 were of understaging respectively. The cause of incorrecting staging by preoperative CT was usualy due to the difficulty in determing if lymph node metastasis occurs. It is suggested that to improve the preoperative CT staging, the thin phase scanning to the area of lymph nodes around the iliac artery and obsturatorius should be carried out if the patient has been confirmed to have hydronephrosis.

Adult↗
PubMed1996

[The correlation between gastric intramucosal pH and oxygen delivery in patients with septic shock].

We studied the correlation of intramucosal pH (pHi), oxygen delivery (DO2) and oxygen consumption (VO2) in 21 patients with septic shock, and found that pHi decreased dramatically (P < 0.05) in nonsurvivors while it had no significant change in survivors. In survivors, there was a positive correlation between pHi and DO2 (r = 0.71, P < 0.001), pHi and VO2 (r = 0.63, P < 0.001) when DO2 was below the critical level of 641 ml/min/m2. We concluded that the change of pHi is related with the prognosis of septic shock. The correlation between pHi and DO2 proves the oxygen supply dependency of VO2. The hypoxia in tissue level is the main factor which results in a high mortality of septic shock patients. pHi is a reliable and useful parameter not only for prognosis, but also for titrating the therapy in septic shock if pHi is monitored serially together with DO2.

Adult↗
PubMed1996

[Retroviral-mediated transfer of beta-globin gene into human hematopoietic cells].

Transferring beta-globin gene and its enhancer into human hematopoietic cells is the basis for applying beta-thalassemia gene therapy in clinical practice. We isolated ecotropic virus producing clones and amphotropic virus producing clones by using a replication-defective retrovirus vector containing beta-globin gene and its enhancer to transfect ecotropic packaging cell line phi-2 and amphotropic packaging cell line PA317. Then by ping-ponging supernatant infection between ecotropic producer clone and amphotropic producer clone, we obtained high titer amphotropic PA317 producer clones with the highest titer up to 5.9 x 10(6) CFU/ml. Human mononuclear bone marrow cells were infected repeatly with this high titer virus vector under stimulation of hematopoietic growth factors IL-3, IL-6 and SCF, Southern blot hybridization analysis showed that beta-globin gene and its enhancer had been integrated into the genome of human hematopoietic cells.

Enhancer Elements, Genetic↗
PubMed1996

[Construction of the wt-p53 gene recombinant retroviral vector. Inhibiting the growth of laryngocarcinoma cell line].

We have constructed wt-p53 gene recombinant retroviral vector. The p53 cDNA with positive regulative sequence was subcloned into the Xho I site between the two LTRs of the N2A retroviral vector which contained the cytomegalovirus promotor/enhancer for expression and a neomycin resistance gene allowing G418 selection in reverse orientation and established the PA317 packaging cell line producing virus. The recipient cell line of Hep2 (laryngocarcinoma) containing the abnormal p53 gene was transfected in vitro with fresh retroviral stock produced. The result showed that the constructed wt-p53 gene recombinant retroviral vector was able to suppress growth of laryngocarcinoma cell in vitro. These observations indicate that recombinant retrovirus expressing wild-type p53 may be the useful vectors for gene therapy of human laryngocarcinoma.

DNA, Recombinant↗
PubMed1996

[Study clinical application to determine heparin requirements during hemodialysis].

A de nove Weighted Stepwise Linear Model based on Gotch's heparin pharmacokinetic model has been designed to determine the heparin elimination rate constant during hemodialysis (HD). 100 times of HD in 26 patients with unstable dosage requirements of heparin were performed according to the computing method and the new heparin pharmacokinetic Weighted Stepwise Linear Model monitored be program of pocket calculator. The results showed not only stable anticoagulation but also successful prevention of patients's bleeding and avoidance of coagulation in hemodialyzer and blood tubing. The computer diagram presented in this paper is useful for propramming with different computer languages to calculate the heparin dosage requirements of patients undergoing HD.

Computers↗
PubMed1996

[Relationship between the abnormal expression of CD44 gene and bladder cancer].

Reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot hybridization were used to detect exon V6-containing isoforms of CD44 gene in 42 surgical bladder specimens (20 cases of bladder cancer, 10 cases of corresponding normal bladder tissue, 8 non-neoplastic bladder tissue from the benign prostatic hyperplasia, and 4 cystitis). All samples of bladder cancer tissue showed over-expression of many abnormal alternatively-spliced products containing transcripts from exon V6 of the CD44 gene except those from 22 non-neoplastic tissue. Furthermore, the band pattern permitted differentiation between the 2 cases of metastatic bladder tumors and the 18 cases of non metastatic tissue. Our results suggest that there is a remarkable relationship between the abnormal CD44 gene expression (inappropriate splicing and overexpression) and malignant phenotype and metastasis of bladder cancer. The CD44 splice variants may prove to be a more ideal tumor marker for the early diagnosis of bladder cancer and for the early detection of metastatic potential in surgical biopsy specimens, which deserves further evaluation.

Adult↗
PubMed1996

[Influence of age on serum prostate specific antigen concentration].

322 men who had not prostatic diseases were selected at random for defining the characteristics of serum prostate specific antigen (PSA) in order to use PSA more appropriately in detecting clinically significant prostate cancer. The serum PSA concentration is correlated with patient age (r = 0.301; P < 0.0001), PSA is increased with age. The recommended upper limits (mean +2 standard deviations) for serum PSA for men aged 20-49 years was 2.71 ng/ml; for 50-59 years, 5.01ng/ml; for 60-69 years, 6.05 ng/ml; and for greater than or equal to 70 years, 7.92 ng/ml. Our findings led to proposals for using age-specific PSA reference range instead of a single reference range for men of all age groups. These age-specific reference ranges have the potential to increase the specificity of using PSA for detecting prostate cancer.

Adult↗
PubMed1996

[Clinical study of imposed work of breathing caused by the breathing apparatus].

OBJECTIVE: The imposed work of breathing caused by the breathing apparatus (endotracheal tube, breathing circuit tubing, and ventilator's valves) may increase patient's work of breathing. To evaluate the imposed work may be useful to determine weaning. METHODS: Work of breathing was observed by Bicore CP-100 breathing monitor at different levels pressure support (PS), T piece and after extubation, and the PS level to compensate imposed work of breathing was computed. RESULTS: When PS level decreased, patient's work of breathing increased significantly. At PS O kPa, the patient's work of breathing increased 57%, which was caused by imposed work of apparatus. Because of the resistance of endotracheal tube, the patient's work of breathing increased 41% at T piece. The PS level that compensated for the imposed work was 0.7 kPa. CONCLUSIONS: When PS level was too low or T piece was applied, the imposed work of breathing caused by apparatus could markedly increase patient's work of breathing.

Adult↗
PubMed1995

Evaluation of rhBMP-2 with an OPLA carrier in a canine posterolateral (transverse process) spinal fusion model.

STUDY DESIGN: Posterolateral L4-L5 transverse process fusions were done on 14 adult beagles. Six were implanted with recombinant human bone morphogenetic protein-2 carried by open-cell polylactic acid polymer delivery vehicle. Six received autogenous iliac bone graft. Two received carrier alone. Eleven were killed 3 months after implantation. One in each group was maintained for 8 months. OBJECTIVES: To compare recombinant human bone morphogenetic protein-2 and open-cell polylactic acid polymer with autogenous iliac bone for inducing transverse process fusion in the canine by 3 months and to determine whether transverse process decortication and implantation of carrier alone causes spontaneous transverse process fusion in the canine. SUMMARY OF BACKGROUND DATA: Recombinant human bone morphogenetic proteins have healed segmental long bone defects in several models. They have induced interlaminar and facet fusions in canines. Interlaminar and facet fusions have occurred after sham decortications in canines. Recombinant human bone morphogenetic protein-2 has not been evaluated for transverse process fusion in canines. Transverse process fusion is a preferred clinical method for achieving posterior lumbar fusion. METHODS: Fusion sites were evaluated by serial computed tomography scans. After the dogs were killed, explanted spines were subjected to manual testing, mechanical testing, high resolution radiography, and histologic analysis. RESULTS: One hundred percent of recombinant human bone morphogenetic protein-2-implanted sites had solid transverse process fusion by 3 months according to all measures. No autografted sites were fused at this interval. Osseous bridging of posterolateral gutters occurred in the recombinant human bone morphogenetic protein-2-implanted sites after 2 months, the earliest radiographic measure. None of the carrier-only sites showed bone formation. CONCLUSIONS: Recombinant bone morphogenetic protein-2 carried by open-cell polyactic acid polymer is superior to autogenous iliac bone for producing radiographically and mechanically solid transverse process fusions in canines by 3 months. Spontaneous transverse process fusion does not occur in canines after decortication and open-cell polylactic acid polymer implantation.

Acetates↗
PubMed1995

Liposome clearance from blood: different animal species have different mechanisms.

The kinetics of blood clearance and the mechanisms of liposome uptake by the reticuloendothelial system (RES) were compared in two animal species (mice and rats). By employing an in situ liver perfusion technique with selected liposome compositions (PC/Chol, PC/Cho/PS, PC/Chol/GM1 and PC/Chol/PEG5000-PE), we demonstrated that liposomes with same lipid composition exhibited different blood circulation half-lives in different animal species. Although liver is the major organ responsible for the clearance of liposomes from blood in both animal species, the specific mechanisms differ. In mice, liposome uptake by the liver did not involve specific serum opsonins. In contrast, liposome uptake by the rat liver was strongly dependent on serum opsonins. Further, the activity of serum opsonins for a given liposome composition differed among animal species. Human serum exhibited higher opsonin activities for PC/Chol and PC/Chol/GM1 liposomes than bovine sera, while rat serum displayed a high opsonizing activity for GM1 liposomes and none for liposomes composed of PC and Chol. The opsonin activity of human serum could be removed or decreased by treatment with EGTA/Mg2+, EDTA or cobra venom factor, suggesting that the activity is likely due to complement components. It is likely that C3 of the human complement system plays an important role in mediating the uptake of liposomes by the liver.

Animals↗
PubMed1995

Expression and purification of the light chain of botulinum neurotoxin A: a single mutation abolishes its cleavage of SNAP-25 and neurotoxicity after reconstitution with the heavy chain.

Botulinum neurotoxin type A (BoNT/A) selectively and irreversibly inhibits acetylcholine release from peripheral nerve endings. While the toxin's heavy (H) chain contributes to neuronal binding and internalization, its light (L) chain is a Zn(2+)-dependent endoprotease that intracellularly cleaves synaptosomal-associated protein of M(r) = 25 kDa (SNAP-25). For research and clinical exploitation of this uniquely-acting neurotoxin, recombinant wild-type L chain was produced together with a mutant in which His227 in the Zn(2+)-binding motif was substituted by Tyr. The PCR-amplified wild-type and mutant L chain genes were cloned, fused to the gene for maltose-binding protein, and expressed at high levels in Escherichia coli. The soluble fusion proteins were purified using amylose affinity chromatography, and, after factor Xa cleavage, the free L chains were isolated. The wild-type was shown to proteolyze SNAP-25 at a rate approaching that of the native chain while the mutant was inactive. Reconstitution of the pure wild-type L chain with native homogeneous H chain yielded a disulfide-linked dichain form that inhibited neuromuscular transmission in vitro and produced the symptoms of botulism in vivo. After reconstitution with the H chain, the Tyr227 mutant L chain failed to show any neuroparalytic activity in either of these assays. This methodology allows, for the first time, routine preparation of recombinant forms of the L chain that are needed to decipher the molecular details of its interaction with substrate and, thereby, assist the design of effective inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)

ATP-Binding Cassette Transporters↗
PubMed1995

Intrafamily fragment analysis of the T cell receptor beta chain CDR3 region.

The length distributions of the third complementarity determining region (CDR3) of the T cell receptor (TCR) beta chain were determined quantitatively from peripheral blood lymphocytes of healthy donors. RT-PCR products of 26 V beta families and subfamilies were analyzed by an A.L.F. DNA sequencer and Fragment Manager software. We established a normal reference of CDR3 lengths for most of the V beta families and subfamilies. The known range of CDR3 lengths for the V beta chain was expanded to 24 amino acids, and quantitative measurements were made for each fragment length allowing intrafamily CDR3 fragment length comparisons. Importantly, we were able to analyze intrafamily CDR3 fragment distribution without optimizing PCR conditions, thereby circumventing a major obstacle found in intrafamily TCR beta chain comparisons.

Adult↗
PubMed1995

Characterization and regulation of a chloride channel from bovine tracheal epithelium.

1. The patch-clamp technique was used to characterize chloride channels from the apical membranes of bovine tracheal epithelial cells. Application of GTP gamma S or NaF to excised patches revealed the existence of a novel type of Cl- channel regulated by G-proteins in a membrane-delimited manner. 2. The channel had a linear current-voltage relationship, with a conductance of 100-120 pS. Its open probability was independent of voltage. 3. The channel was highly anion selective (permeability ratio, PNa/PCl = 0.06 +/- 0.04) and had the halide permeability sequence: I- > Br- > or = Cl- > F-, corresponding to the Eisenman I sequence. This suggested that neither ionic size nor diffusion rate determined ion permeation through the channel. 4. The mole fraction behaviour was studied using fluoride and chloride ions. Mixtures of ions produced currents that would be expected from the linear combination of the two ions acting independently, indicating relatively simple permeation through the pore and compatible with a single ion binding site. 5. The channel was inhibited by the stilbene disulphonates SITS (4-acetamido-4'-isothiocyanatostilbene-2, 2'-disulphonic acid) and DNDS (4,4'-dinitrostilbene-2,2'-sulphonic acid). SITS introduced voltage dependence to channel gating and indicated the possible involvement of lysine residues in the channel permeation pathway. 6. NaF was unable to activate Cl- channels in the presence of the aluminum chelator, deferoxamine mesylate. This indicates that Al3+ ions play an important role in chloride channel activation by fluoride. NaF activation was not dependent on the presence of calcium ions. 7. The channel was insensitive to alkaline phosphatase and to the specific inhibitors of protein phosphatase types I and 2A, okadaic acid and calyculin A. 8. The channels could be activated by GTP gamma S or by NaF in the presence of the phospholipase A2 inhibitor quinacrine, indicating that this enzyme is not involved in channel regulation.

Animals↗