Biomedical subjects

D Liu

Publications and source records attributed to D Liu.

At least 379 records · Page 21Linked to original sources

PubMed1999

[Changes in chloroquine resistance of Plasmodium falciparum in Hainan province].

AIM: To observe the variation in resistance of Plasmodium falciparum after the cessation of chloroquine medication. METHODS: WHO standard in vitro microtest and in vivo test were used. RESULTS: In vitro test showed that the rate of chloroquine-resistant P. falciparum dropped from 97.9% in 1981 to 26.7% in 1997 (P < 0.001). The mean concentration of chloroquine for complete inhibition of schizont formation declined from 10.46 +/- 7.14 pmol/ul blood in 1981 to 1.63 +/- 1.47 pmol/microliter blood in 1997(P < 0.001). In vivo test showed that the rate of chloroquine-resistant P. falciparum decreased from 84.2% in 1981 to 18.4% in 1997(P < 0.001). The proportion of R III cases to the total resistant cases dropped from 53.1% in 1981 to 14.3% in 1997. CONCLUSION: A tendency of progressive decline of resistance of the parasite was revealed after the cessation of chloroquine medication.

Adolescent↗

PubMed1999

[Molecular cloning of a cDNA encoding an antigenic polypeptide containing repeat units of Spirometra erinaceieuropaei plerocercoid].

AIM: To study the gene structure encoding some antigenic polypeptides of plerocercoid of Spirometra erinaceieuropaei (SEP). METHODS: A cDNA library constructed from SEP was immunoscreened using mouse anti-SEP polyclonal antibody. The gene structure was analyzed by computer after the insert of positive clone was subcloned and the nucleotide sequences of the insert were determined. The length of mRNA hybridized with cDNA was detected by Northern blotting. RESULTS: A cDNA clone of 1,084 bp encoding an antigenic polypeptide was isolated. The clone contained one open reading frame composed of 828 bp encoding 276 amino acids. The open reading frame contained tandem repeating unit of 123 bp which appeared 5 times in this clone. The 41 amino acids deduced from 123 bp repeating unit consisted of 53.7% of hydrophobic amino acid residues. In Northern blot assay of poly (A)+RNA, a strong band of about 1.1 kb and a weak band of about 1.7 kb were found in the plerocercoids but no band was found in the adult worms. CONCLUSION: The repeating element derived from the plerocercoids may be associated with the migration of the plerocercoids in the host tissue. The polypeptides with repeating element may act as evasive antigens of the parasite to escape from the destruction of host immune reactions.

Amino Acid Sequence↗

PubMed1999

[Assay of sensitivity of Plasmodium falciparum to chloroquine, amodiaquine, piperaquine, mefloquine and quinine in Yunnan province].

AIM: To determine the sensitivity of P. falciparum to chloroquine, amodiaquine, piperaquine, mefloquine and quinine in Yunnan Province of China in 1992-1995. METHODS: Rieckmann's in vitro microtechnigue was used. The sensitivity of P. falciparum was tested to the above-mentioned antimalarials. RESULTS: The resistance rates of isolates of P. falciparum from the south, southeast and the west part of Yunnan to chloroquine and amodiaquine were 96.7% (29/30), 78.9% (30/38), 95.7% (22/23) and 100% (30/30), 85.3% (29/34), 8/9, respectively, with their corresponding ID50 of 125 nmol/L, 136 nmol/L and 176 nmol/L, and 52 nmol/L, 64 nmol/L and 72 nmol/L, respectively. All the isolates were sensitive to quinine and their ID50 were 480 nmol/L, 352 nmol/L, 608 nmol/L, respectively. The resistance rates of P. falciparum from the south part and southeast part of Yunnan to piperaquine were 96.4% (27/29), 72.9 (27/37), respectively, their ID50 were 320 nmol/L and 228 nmol/L; all the cases were sensitive to mefloqine, their ID50 were 68 nmol/L and 88 nmol/L. CONCLUSION: P. falciparum generally produces resistance to chloroquine, amodiaquine and piperaquine in Yunnan Province; the degree of resistance to chloroquine of P. falciparum from the west part of Yunnan were higher than the P. falciparum from the southeast part of Yunnan; all the isolates were sensitive to mefloquine and quinine in this region.

Amodiaquine↗

PubMed1999

[Clinical observation of curative effect of neartotal larynegectomy for advance laryngeal cancer].

OBJECTIVE: To explore a method how to preserve the speech function affer larynegectomy for advance laryngeal cancer and to improve the patients' life quality. METHOD: 17 cases with advance laryngeal cancer (T3 11 cases, T4 6 cases, glottic region 8 cases, supraglottic region 5 cases, pyriform recess 4 cases) were treated with neartotal larynegectomy (Pearson operation) in our department from February 1990 to July 1995. In the operations the remained monolateral arytenoid cartilage and an about 1.5 cm-wide mucomembranous flap, which joined to trachea, reconstructed vocal duct, lymphoglandulae near the branch of neck artery were checked routinely in those N0 cases, and the radical neck dissection was taken or not according the result of frozen section. RESULT: After the operation good speech function was obtained in 12 cases. All patients, except one, had good swallowing. Survival rate of 2, 3 and 5 year was 70.6%, 64.2% and 50% respectively. CONCLUSION: It is key that neck dissection should be performed rightly and the principle of surgery should be carried out for successful Pearson operation.

Adult↗

PubMed1999

[Prevention of keloids of the earlobes].

OBJECTIVE: To investigate the causing of keloids of the earlobes. METHOD: We have treated 41 keloides of earlobes in 28 cases, and analyzed the factors. RESULT: It has been found that infections, inappropriate supporter, allergy to nickel and gold, local delayed allergy are the chief factors to form keloides of the earlobes. CONCLUSION: Some measures to prevent those cousing mentioned above have been proposed.

Adolescent↗

PubMed1999

[Construction and in vivo expression of the recombinant adenovirus containing human pro-UK cDNA].

OBJECTIVE: To construct the recombinant adenovirus which contained human pro-UK cDNA and to provide experimental basis for clinical gene therapy. METHODS: The recombinant plasmid pCA14-pro-UK and the plasmid pJM17 were cotransfected into cultured 293 cells and the replication-deficient adenovirus were harvested, identified, propagated and titered. The recombinant virus were then transferred into balloon-injured femoral arteries of rabbits and the pro-UK expression was detected by immunohistochemistry and Western Blot. RESULTS: PCR amplification and in vitro transfection of A549 cells confirmed that pro-UK had been inserted into adenovirus genome correctly, and immunohistochemistry and Western blot analysis showed that pro-UK expressed evidently in the balloon-injured sites of the rabbit femoral arteries. CONCLUSIONS: The recombinant adenovirus that constructed could express pro-UK cDNA in vivo successfully.

Adenoviridae↗

PubMed1999

[Establishment of A + G ligation mediated polymerase chain reaction and its application in in vivo footprinting study].

OBJECTIVE: To establish a new ligation mediated PCR method for the work in in vivo footprinting study of some regions of low G-residue content or some regions of G-residue free. METHODS: The A > G chemical cleavage method of Maxam-Gilbert sequencing was modified for ligation mediated PCR after A + G chemical cleavage and separate the PCR products by sequencing PAGE. RESULTS: A new A + G ligation mediated method was established and could be used in vivo footprinting study. CONCLUSIONS: Our results indicated that the newly developed method could analyze the DNA-Protein interaction at both A-residue and G-residue, enabled us to get more information and enlarged the scope of its application.

Animals↗

PubMed1999

[Experimental studies in vitro on the alpha-fetoprotein-specific promoter mediated target gene therapy of hepatocellular carcinoma].

OBJECTIVE: To investigate the alpha-fetoprotein (AFP)-specific promoter mediated target gene therapy of hepatocellular carcinoma in vitro. METHODS: Retroviral vector (LX2.2CD) in which the cytosine deaminase (CD) gene was driven by the 2.2 kb recombinant human AFP TRS. After transfecting three human hepatoma cell lines and one non-hepatoma cell line with LX2.2 CD, anti-G418 clones integrated CD gene were selected, and inhibitory experiment of cell growth was performed. RESULTS: 5-fluorocytosine (5FC) could confer the chemosensitivity to transduced AFP-producing hepatoma cells (HuH-7 and huH-1/c1-2), but not to AFP-nonproducing hepatoma cells (HLE) or nonhepatoma cells (GLC). On the other hand, when transfecting the above four tumor cell lines with another retroviral vector pCD2 (CD gene was driven by 5'LTR internal promoter), no cell selection was found in 5FC-induced cell grow inhibition. CONCLUSIONS: Recombinant retrovival transfer of the CD gene under the control of the AFP TRS followed by 5FC may well be a promising trageted gene therapy for hepatoma.

Antineoplastic Agents↗

PubMed1999

[Minimally invasive treatment in early glottic cancer and vocal cord dysplasia].

OBJECTIVE: To investigate the pathologic and clinical diagnosis of early stage glottic carcinoma and the vocal cord dysplasia and the results of the minimally invasive treatment. METHODS: Thirty-two cases of early glottic cancer (T1N0M0) and 20 cases of vocal dysplasia were treated with mucous stripping and minimally invasive cordectomy under the micro-suspension laryngoscope. The pathomorphology was observed with continuous sections. RESULTS: After 3-4 years follow-up, 26 cases of early glottic cancer remained tumor free, 3 cases relapsed and 2 cases received the re-stripping operation. twenty cases of vocal cord dysplasia were classified as: leucoplakia of vocal cord, mild atypical hyperplasia, moderate atypical hyperplasia and advanced hyperplasia. None of them had malignant change after 3 years follow-up. CONCLUSION: The laryngeal micro-operation under the micro-suspension laryngoscope is an effective and safe cure procedure, it provides a definite diagnostic method for the early stage glottic carcinoma and the vocal cord dysplasia.

Combined Modality Therapy↗

PubMed1999

[Endoscopic CO2 laser arytenoidectomy in the treatment of bilateral vocal cord paralysis].

OBJECTIVE: To evaluate endoscopic CO2 laser arytenoidectomy(ECO2LA) for the treatment of bilateral vocal cord paralysis (BVCP). METHODS: Eight cases have been operated upon and observed for 6 to 40 months. Three of them were extralaryngeal approach artenoidectomy failures. All of them had tracheostomy before. The technique was to modification of Ossoff ECO2LA model. A small part of ventricular fold and posterior part of vocal cord was vaporized by laser. The mucoperichondrium overlying the arytenoid was reserved and sutured. After 3 months the opposite arytenoid was treated similarly. RESULTS: There were no aspiration and no granulation at the surgical site postoperatively. All cases kept satisfactory voice. Five of 8 patients were decannulated. Two patients still had laryngeal stridor during sleep and they had to plug the tracheotomy tube only on daytime. One patient had cannula retained for waiting operation on the opposite side. CONCLUSION: ECO2LA is currently a most reliable and efficient technique for treatment of patients with BVCP.

Adolescent↗

PubMed1998

Identification of two regions in the cytoplasmic domain of CD44 through which PMA, calcium, and foskolin differentially regulate the binding of CD44 to hyaluronic acid.

CD44 contains two clustered basic residues of three arginines and three lysines in the membrane-proximal region of its cytoplasmic domain. These two clusters are conserved among different species and different splicing forms. The function of these two motifs is not known. We substituted either the three-arginine or the three-lysine motif with alanine (CD44.3R3A and CD44.3K3A) and established stable CD44 transfectants. The effects of these mutations on the binding of CD44 to one of its ligands, hyaluronic acid (HA), were studied. When stimulated with PMA, transfectants bearing CD44.3K3A and CD44.3R3A proteins have reduced HA-binding capacity. When stimulated with forskolin, an activator of cAMP-dependent PKC, CD44.3R3A transfectants were able to bind low but detectable level of fluorescent-conjugated HA (F-HA). In contrast, CD44.3K3A transfectants were unable to bind any F-HA. Elevation of intracellular calcium concentrations either by ionomycin or thapsigargin also induced binding of HA in CD44.3R3A but not in CD44. 3K3A transfectants. These results provide evidence that both the arginine and the lysine motifs are important in the binding of CD44 to high levels of HA when stimulated with PMA. In contrast, when transfectants were stimulated with either forskolin or a Ca2+ mobilizer to bind a low level of F-HA, the lysine cluster, but not the arginine cluster, is required. These two closely located basic clusters are, therefore, differentially involved in the binding of CD44 to HA, depending on the level of ligand binding and the nature of the stimulatory signals.

Arginine↗

PubMed1998

The Arabidopsis CHL1 protein plays a major role in high-affinity nitrate uptake.

The CHL1 (NRT1) gene of Arabidopsis encodes a nitrate-inducible nitrate transporter that is thought to be a component of the low-affinity (mechanism II) nitrate-uptake system in plants. A search was performed to find high-affinity (mechanism I) uptake mutants by using chlorate selections on plants containing Tag1 transposable elements. Chlorate-resistant mutants defective in high-affinity nitrate uptake were identified, and one had a Tag1 insertion in chl1, which was responsible for the phenotype. Further analysis showed that chl1 mutants have reduced high-affinity uptake in induced plants and are missing a saturable component of the constitutive, high-affinity uptake system in addition to reduced low-affinity uptake. The contribution of CHL1 to constitutive high-affinity uptake is higher when plants are grown at more acidic pH, conditions that increase the level of CHL1 mRNA. chl1 mutants show reduced membrane depolarization in root epidermal cells in response to low (250 microM) and high (10 mM) concentrations of nitrate. Low levels of nitrate (100 microM) induce a rapid increase in CHL1 mRNA. These results show that CHL1 is an important component of both the high-affinity and the low-affinity nitrate-uptake systems and indicate that CHL1 may be a dual-affinity nitrate transporter.

Anion Transport Proteins↗

PubMed1998

NMR structure of the histidine kinase domain of the E. coli osmosensor EnvZ.

Bacteria live in capricious environments, in which they must continuously sense external conditions in order to adjust their shape, motility and physiology. The histidine-aspartate phosphorelay signal-transduction system (also known as the two-component system) is important in cellular adaptation to environmental changes in both prokaryotes and lower eukaryotes. In this system, protein histidine kinases function as sensors and signal transducers. The Escherichia coli osmosensor, EnvZ, is a transmembrane protein with histidine kinase activity in its cytoplasmic region. The cytoplasmic region contains two functional domains: domain A (residues 223-289) contains the conserved histidine residue (H243), a site of autophosphorylation as well as transphosphorylation to the conserved D55 residue of response regulator OmpR, whereas domain B (residues 290-450) encloses several highly conserved regions (G1, G2, F and N boxes) and is able to phosphorylate H243. Here we present the solution structure of domain B, the catalytic core of EnvZ. This core has a novel protein kinase structure, distinct from the serine/threonine/tyrosine kinase fold, with unanticipated similarities to both heatshock protein 90 and DNA gyrase B.

Amino Acid Sequence↗

PubMed1998

Fractionation of rat hepatocyte subpopulations with varying metabolic potential, proliferative capacity, and retroviral gene transfer efficiency.

The liver contains hepatocytes with varying ploidy and gene expression. To isolate cells on the basis of ploidy for analyzing mechanisms concerning cell proliferation and differentiation, we used Percoll gradients to separate F344 rat hepatocyte subpopulations. Specific fractions were enriched in polyploid (H2 fraction) or diploid (H3 and H4 fractions) hepatocytes containing glycogen and glucose-6-phosphatase. H4 cells were relatively smaller with greater nuclear/cytoplasmic ratios, less complex cytoplasm, and higher serum albumin or ceruloplasmin biosynthetic rates. H2 fraction cells were larger with lesser nuclear/cytoplasmic ratio, more complex cytoplasm, and more cytochrome P450 activity. Phenotypic marking showed that H4 cells originated in zone one and H2 cells in zones two or three of the liver lobule. H4 cells showed much greater mitogenic responsiveness to human hepatocyte growth factor. Retroviral gene transfer, which requires both viral receptors and cellular DNA synthesis, was significantly more efficient in H4 cells. The findings indicated that small diploid and large polyploid hepatocytes show unique biological differences. The ability to isolate hepatocytes of varying maturity is relevant for mechanisms concerning liver growth control and hepatic gene expression.

Animals↗

PubMed1998

Solution structure of a TBP-TAF(II)230 complex: protein mimicry of the minor groove surface of the TATA box unwound by TBP.

General transcription factor TFIID consists of TATA box-binding protein (TBP) and TBP-associated factors (TAF(II)s), which together play a central role in both positive and negative regulation of transcription. The N-terminal region of the 230 kDa Drosophila TAF(II) (dTAF(II)230) binds directly to TBP and inhibits TBP binding to the TATA box. We report here the solution structure of the complex formed by dTAF(II)230 N-terminal region (residues 11-77) and TBP. dTAF(II)230(11-77) comprises three alpha helices and a beta hairpin, forming a core that occupies the concave DNA-binding surface of TBP. The TBP-binding surface of dTAF(II)230 markedly resembles the minor groove surface of the partially unwound TATA box in the TBP-TATA complex. This protein mimicry of the TATA element surface provides the structural basis of the mechanism by which dTAF(II)230 negatively controls the TATA box-binding activity within the TFIID complex.

Amino Acid Sequence↗

PubMed1998

Identification and functional characterization of DR6, a novel death domain-containing TNF receptor.

Tumor nectosis factor (TNF) receptors are key players in inflammation and immune regulation. A new member of this family, termed death receptor-6 (DR6), has been identified. Like other death receptors, DR6 is a type I transmembrane receptor, possesses four extracellular cysteine-rich motifs and a cytoplasmic death domain. DR6 is expressed in most human tissues and abundant transcript was detected in heart, brain, placenta, pancreas, thymus, lymph node and several non-lymphoid cancer cell lines. DR6 interacts with TRADD, which has previously been shown to associate with TNFR1. Furthermore, ectopic expression of DR6 in mammalian cells induces apoptosis and activation of both NF-kappaB and JNK.

Amino Acid Sequence↗

PubMed1998

Prion protein expression in different species: analysis with a panel of new mAbs.

By immunizing prion knockout mice (Prnp-/-) with recombinant murine prion protein (PrPc), we obtained a panel of mAbs specific for murine PrPc. These mAbs can be applied to immunoblotting, cell surface immunofluorescent staining, and immunohistochemistry at light and electron microscopy. These mAbs recognize both the normal (PrPc) and protease-resistant (PrPres) isoforms of PrP. Some mAbs are species restricted, while others react with PrP from a broad range of mammals including mice, humans, monkeys, cows, sheep, squirrels, and hamsters. Moreover, some of the mAbs selectively recognize different PrP glycoforms as well as the metabolic fragments of PrPc. These newly generated PrPc antibodies will help to explore the biology of PrPc and to establish the diagnosis of prion diseases in both humans and animals.

Animals↗

PubMed1998

Mechanisms regulating the binding activity of CD44 to hyaluronic acid.

CD44 is a cell surface glycoprotein present on many cell types. Many CD44 isoforms have been identified. All CD44 isoforms utilize identical transmembrane and cytoplasmic domains. The hematopoietic form of CD44 (CD44H) is the major CD44 protein present on normal human lymphocytes and monocytes. One of the ligands for CD44 is hyaluronic acid (HA), a polymer consisting of repeat units of disaccharide; N-acetyl-D-glucosamine and N-acetyl-D-glucuronic acid. Since HA is present ubiquitously in extracellular matrix and in circulation, promiscuous binding of HA to CD44 may have undesirable affect. Similar to other adhesion molecules, binding of HA to cell surface CD44 requires regulation. In this review, we summarized our studies using a human lymphoma cell line, Jurkat. We found that binding of CD44+ Jurkat transfectants to HA requires cellular activation. Cellular activation induces the reorganization of the cytoskeleton proteins. Reorganization of cytoskeletal proteins results in clustering of CD44 on the cell surface. Clustering of CD44 on the cell surface is a prerequisite for the homodimerization of CD44. Our studies on Jurkat transfectants and results from other investigators suggest that interactions between CD44 and HA is a dynamic process and requires the participation of different cellular components; depending of the nature of the cell type and/or the nature of the activation signals.

Amino Acid Sequence↗