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Biomedical subjects

X Du

Publications and source records attributed to X Du.

At least 73 records · Page 4Linked to original sources
PubMed2000

Effects of pH on glucose measurements with handheld glucose meters and a portable glucose analyzer for point-of-care testing.

OBJECTIVES: To determine pH effects on glucose measurements obtained with the latest generation of glucose devices, to quantitate changes in glucose measurements obtained over a wide pH range, and to assess the potential clinical risks of pH effects with use of point-of-care glucose testing. DESIGN: Paired differences of glucose measurements between pH-altered and parallel control samples with target pH 7.40 were calculated. SETTING: A pH range of 6.94 to 7.84 was used to evaluate pH effects on glucose measurements in vitro with 6 handheld glucose meters and a portable glucose analyzer at both normal, 4.81 mmol/L (86.6 mg/dL), and high, 11.16 mmol/L (201 mg/dL), glucose levels. MAIN OUTCOME MEASURES: Glucose measurements obtained from test samples and control samples were compared by calculating paired differences, which were plotted against pH to show pH effects on glucose meter measurements. RESULTS: At the normal glucose level, different pH levels did not interfere significantly with glucose measurements. At the high glucose level, a trend whereby low pH decreased and high pH increased glucose measurements was observed on the Precision G and the Precision QID glucose meters. CONCLUSION: Because of potential risk in diabetic patients with ketoacidosis and in other patients with acid-base disorders, we recommend that clinicians choose glucose devices carefully and interpret the measurements cautiously when point-of-care glucose testing is performed in critically ill patients with acidemia, alkalemia, or changing acid-base status.

Blood Chemical Analysis↗
PubMed2000

Three novel mammalian toll-like receptors: gene structure, expression, and evolution.

We describe three novel genes, encoding members of the Toll-like receptor (Tlr) family (TLR7, TLR8, and TLR9). These Tlr family members, unlike others reported to date, were identified within a genomic database. TLR7 and TLR8 each have three exons, two of which have coding function, and lie in close proximity to one another at Xp22, alongside a pseudogene. The remaining gene (TLR9) resides at 3p21.3 (in linkage with the MyD88 gene), and is expressed in at least two splice forms, one of which is monoexonic and one of which is biexonic, the latter encoding a protein with 57 additional amino acids at the N-terminus. The novel Tlrs comprise a cluster as nearest phylogenetic neighbors. Combining all sequence data related to Toll-like receptors, we have drawn several inferences concerning the phylogeny of vertebrate and invertebrate Tlrs. According to our best estimates, mammalian TLRs 1 and 6 diverged from a common mammalian ancestral gene 95 million years ago. TLR4, which encodes the endotoxin sensor in present-day mammals, emerged as a distinct entity 180 million years ago. TLRs 3 and 5 diverged from a common ancestral gene approximately 150 million years ago, as did Tlr7 and Tlr8. Very likely, fewer Tlrs existed during early vertebrate evolution: at most three or four were transmitted with the primordial vertebrate line. Phylogenetic data that we have adduced in the course of this work also suggest the existence of a Drosophila equivalent of MyD88, and indicate that the plasma membrane protein SIGIRR is close functional relative of MyD88 in mammals. Finally, a single present-day representative of the Toll-like proteins in Drosophila has striking cytoplasmic domain homology to mammalian Tlrs within the cluster that embraces TLRs 1, 2, 4, and 6. This would suggest that an ancestral (pre-vertebrate) Tlr may have adopted a pro-inflammatory function 500 million years ago.

Alternative Splicing↗
PubMed2000

Endotoxin-mimetic effect of antibodies against Toll-like receptor 4.

Monospecific, affinity-purified polyclonal antibodies reacting with the amino-terminal half of the mouse Toll-like receptor 4 (Tlr4) ectodomain failed to block LPS effects and, to the contrary, were capable of inducing TNF synthesis when applied to mouse macrophages and cross-linked with a secondary antibody. This effect was observed with macrophages derived from C3H/HeN and C57BL/10ScSn mice, but not with macrophages derived from C3H/HeJ or C57BL/10ScCr mice, indicating a specific, Tlr4-dependent effect. Neither primary nor secondary antibody caused any response if administered in the absence of the other reagent, nor was any response observed in cells from mice lacking Tlr4, or bearing the Lps(d) mutation of Tlr4. These findings support several conclusions. Tlr4, the essential transducer of LPS responses, may act independently of LPS itself. LPS needs not be internalized, nor must it bind to a secondary target within the cell in order to exert its effect; rather, the receptor alone is required for initiation of a signal. The data are consistent with the hypothesis that a conformational change in Tlr4 is required for activation via this receptor, and reveal that the amino-terminal half of the Tlr4 ectodomain is a target sufficient for antibody-mediated activation.

Animals↗
PubMed2000

[Evaluation on soil anti-erodibility of soil and water conservation forest].

Indexes including organic matter content, water stable aggregate content, mean weight diameter of water stable aggregate, aggregate degree and disperse coefficient were selected to evaluate soil anti-erodibility of soil and water conservation forests component of different tree species at different ages. The results showed that soil and water conservation forest played an important role in improving soil anti-erodibility, especially to the topsoil. Compared with that of Chinese pine pure forests, Chinese pine-broadleaved mixed forests had higher soil organic matter content, and water stable aggregate content increased by 1.71%-38.53%, and soil anti-erodibility was also increased with increasing stand age.

China↗
PubMed2000

[Clinical experience of long-distance electronic fetal heart rate monitoring system by telephone].

OBJECTIVE: To explore the value of the long-distance electronic fetal heart rate monitoring system by telephone and explore a new way of self-monitoring at home for pregnant woman. METHOD: 204 high risk pregnant women came to our clinic were enrolled in this study. Complications included pregnancy induced hypertension (PIH), intrauterine growth retardation (IUGR), anemia, diabetes, hemolysis, nephropathy. In the study group, 97 women took the terminal part of the fetal heart rate monitoring system home and were requested to auscultate and count fetal heart rate three times a day, while another 107 cases did the self monitoring by fetal movement counting daily and served as control group. For the study group, whenever woman felt any abnormality of her baby, she could contact the long-distance electronic fetal heart rate (FHR) monitoring center in hospital by telephone immediately. The signal of fetal heart beat and fetal movement was converted and analyzed in the electronic FHR monitoring center by computer at the same time. The fetal heart rate curve was printed out, and diagnosis and management could be made. Age, gestational weeks, high risk factors, abnormal non-stress test (NST), Apgar score and birth weight of newborn were analyzed between the experimental and control group retrospectively. RESULTS: There were no obviously differences in age, gestational weeks, weight of newborn, high risk factors between the 2 groups. The incidence of abnormal NST and Apgar score of newborn were significantly higher in the study group than that in the control group, while the incidence of neonatal asphyxia was significantly lower. CONCLUSIONS: This study suggested that the long-distance electronic FHR monitoring by telephone was a reliable, sensitive and applicable method of self-monitoring for pregnant woman at home, use of this system could decrease the incidence of fetal distress, brain damage and perinatal mortality, thus improves the quality of perinatal care.

Adult↗
PubMed2000

[Ultrasonically guided radio-frequency ablation of liver tumors with a clustered electrode: a report of 100 cases].

OBJECTIVE: To evaluate the efficacy of ultrasonically guided radio-frequency (RF) thermal ablation of liver tumors with a clustered electrode. METHODS: Clinical records of 100 consecutive patients who underwent RF tissue ablation 120 times were analysed. Image data, tumor size, clinic manifestation, and AFP value before and after the procedure were compared. RESULTS: A hundred cases at 10 days, thirty at 30 days, ten at 60 days after the procedure were subjected to color ultrasonography and CT scans, respectively. The tumor size decreased by 20% at 10 days in 70% patients, decreased by 30% at 30 days in 80% patients, decreased by 50% at 60 days in 3 patients. AFP value decreased in 50% of patients, no operative death was noted, and the rate of operative complication was 23% after ablation. CONCLUSION: Ultrasound guided RF thermal ablation of hepatic tumors is safe, applicable and effective.

Adolescent↗
PubMed2000

[A molecular epidemiological investigation on Leptospira interrogans serovar hebdomadis and australia in China].

OBJECTIVE: In order to confirm whether cattle serve the source of infection for patients with Leptospira interrogans serovar hebdomadis and australia. METHODS: 12 field strains of leptospira interrogans serovar hebdomadis and australia were isolated from blood samples of patients with leptospirosis and farm cattle urine. An analysis of chromosome DNA restriction endonuclease patterns (REP) and restriction fragments length polymorphism (RFLP) of 16S + 23S rRNA gene were processed by digestion of chromosome DNA using EcoR I. RESULTS: The same serovar field strains of Leptospira interrogans from blood samples of patients with leptospirosis and farm cattle urine resulted in unique restriction endonuclease patterns (REP) and ribosomal types (RT). The chromosome DNAs from field strains that belonged to different serovars of Leptospira interrogans caused different restriction endonuclease patterns and ribosomal types. CONCLUSION: In accordance with this results, we recognize that farm cattle serve the infectious source of leptospirosis serovar hebdomadis and australia thus may have realistic significance in the control of leptospirosis serovar epidemic of hebdomadis and australia in China.

Animals↗
PubMed2000

[The expression and effects of isoforms of macrophage colony stimulating factor in human leukemic cell lines].

OBJECTIVE: To explore the expression and effects of isoforms of macrophage colony-stimulating factor (M-CSF) in human leukemic cell lines. METHODS: Three normal human peripheral blood mononuclear cells (PBMCs) and 4 human myelomonocytic leukemic cell lines including J6-1, J6-2, K562 and HL-60 were studied using ABC immunoperoxidase assay, indirect immunofluorescence staining, flow cytometry, Western blot and reverse enzyme-linked DNA-protein interaction assay (reverse ELDIA). RESULTS: M-CSF was noticed to be localized in the cytoplasm, nucleus and at the cell membrane in 4 human leukemic cell lines; expression of M-CSF was not detected in normal human PBMCs without PHA stimulation. Human PBMCs stimulated by PHA expressed a low level of M-CSF. Frequencies of membrane bound M-CSF expression in J6-1, J6-2, K562 and HL-60 were 71.6%, 69.7%, 42.7% and 57.4% respectively. Frequencies of cytoplasm and nucleus associated M-CSF were 65.7%, 45.4%, 36.5% and 72.5% respectively. The cytosolic bound M-CSF was expressed in J6-1 cell as four isoforms with a molecular weight of 14,000, 16,000, 20,000 and 44,000. While nucleus associated M-CSF expressed as two isoforms with a molecular weight of 16,000 and 20,000. Anti-M-CSF monoclonal antibody could dramatically inhibit proliferation of leukemic cells and its inhibitory effect was related to the levels of membrane bound M-CSF expression in leukemic cells. Reverse ELDIA showed that M-CSF could bind with DNA in vitro. CONCLUSIONS: Expression of M-CSF isoforms is heterogeneous and polymorphous in leukemic cells. Membrane bound M-CSF is crucial for the proliferation of leukemic cells, which might be a DNA-bound protein and could be involved in the transformation and tumorigenesis of hematopoietic cells.

Antibodies, Monoclonal↗
PubMed2000

[The clinical significance of lung resistance protein (LRP) gene expression in patients with acute leukemia].

OBJECTIVE: To investigate the relationship between the expression of lung resistance protein (LRP) gene and drug resistance in patients with acute leukemias (AL). METHODS: Semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR)was used to examine the expression of LRP gene in AL patients and 15 normal subjects. Beta(2) microglobulin (beta(2)MG) was used as internal reference. LRP/beta(2)MG ratio >or= 0.3 was defined as LRP positive. RESULTS: The positivity percentage of LRP gene expression in newly diagnosed group was 32.4%. The first complete remission rate was 84.0% and 33.0% in LRP negative and LRP positive patients, respectively. The difference was significant (P < 0.005). The expression level of LRP mRNA and the positivity percentage of LRP in relapsed/refractory group were significantly higher than that in newly diagnosed group (P < 0.01). The expression level of LRP gene in normal subjects and long-term survival groups was very low and correlated with FAB subtypes. The mdr-1 gene was examined simultaneously in 61 AL patients. No significant correlation was found between the expression of LRP and mdr-1 gene (P > 0.5). Coexpression of LRP and mdr-1 genes in the same AL patient might result in the worst prognosis. CONCLUSION: High expression of LRP gene leads to clinical drug resistance and is an unfavorable factor to AL patients of prognosis.

Acute Disease↗
PubMed2000

[Evidence for TCR Vbeta clonal expansion T cells in a patient with cGVHD after unrelated donor BMT].

OBJECTIVE: To investigate the distribution and clonal expansion of TCR Vbeta subfamily T cells in patients with cGVHD after unrelated donor bone marrow transplantation (BMT). METHODS: The CDR3 of 24 TCR Vbeta subfamily genes were amplified from peripheral mononuclear cells of a patient with cGVHD after unrelated BMT. RT-PCR was used for detection of the distribution of TCR Vbeta repertoire, and the PCR products were further analyzed by genescan technique for the CDR3 size, to evaluating clonality of the detectable TCR VbetaT cells. RESULTS: Only 8 Vbeta subfamily T cells could be identified in the patient, clonal expansion T cells could be found of Vbeta2, 3, 8 and 13 subfamilies. CONCLUSIONS: The skew distribution and clonal expansion of TCR Vbeta subfamily T cells could be found in the patient. It may relate to the initiation of cGVHD.

Acute Disease↗
PubMed2000

[Descending cervical mediastinitis: report of 15 cases].

OBJECTIVE: To analyze the cause, diagnosis and treatment of descending cervical mediastinitis. METHODS: Fifteen cases of descending cervical mediastinitis, which were treated from January 1985 to December 1997, were retrospectively reviewed. There were 10 males and 5 females, ranging in age from 2.5 to 82 years. RESULTS: The cause of descending cervical mediastinitis included odontogenic infection, suppurative tonsillitis, suppurative otitis media (cholesteatoma) complicating Mouret abscess, pharyngeal injury by foreign body and esophageal perforation. Different ways of drainage were adopted. Twelve cases were cured and three died. CONCLUSION: The key to successful management of descending cervical mediastinitis is early recognition, prompt and effective surgical drainage and appropriate antibiotics.

Adolescent↗
PubMed1999

Analysis of the roles of 14-3-3 in the platelet glycoprotein Ib-IX-mediated activation of integrin alpha(IIb)beta(3) using a reconstituted mammalian cell expression model.

We have reconstituted the platelet glycoprotein (GP) Ib-IX-mediated activation of the integrin alpha(IIb)beta(3) in a recombinant DNA expression model, and show that 14-3-3 is important in GPIb-IX signaling. CHO cells expressing alpha(IIb)beta(3) adhere poorly to vWF. Cells expressing GPIb-IX adhere to vWF in the presence of botrocetin but spread poorly. Cells coexpressing integrin alpha(IIb)beta(3) and GPIb-IX adhere and spread on vWF, which is inhibited by RGDS peptides and antibodies against alpha(IIb)beta(3). vWF binding to GPIb-IX also activates soluble fibrinogen binding to alpha(IIb)beta(3) indicating that GPIb-IX mediates a cellular signal leading to alpha(IIb)beta(3) activation. Deletion of the 14-3-3-binding site in GPIbalpha inhibited GPIb-IX-mediated fibrinogen binding to alpha(IIb)beta(3) and cell spreading on vWF. Thus, 14-3-3 binding to GPIb-IX is important in GPIb-IX signaling. Expression of a dominant negative 14-3-3 mutant inhibited cell spreading on vWF, suggesting an important role for 14-3-3. Deleting both the 14-3-3 and filamin-binding sites of GPIbalpha induced an endogenous integrin-dependent cell spreading on vWF without requiring alpha(IIb)beta(3), but inhibited vWF-induced fibrinogen binding to alpha(IIb)beta(3). Thus, while different activation mechanisms may be responsible for vWF interaction with different integrins, GPIb-IX-mediated activation of alpha(IIb)beta(3) requires 14-3-3 interaction with GPIbalpha.

14-3-3 Proteins↗
PubMed1999

The cytoplasmic domain of the platelet glycoprotein Ibalpha is phosphorylated at serine 609.

The alpha chain of the platelet von Willebrand factor receptor, glycoprotein (GP) Ib, is not known to be phosphorylated. Here, we report that the cytoplasmic domain of GPIbalpha is phosphorylated at Ser(609); this was detected by immunoblotting with an anti-phosphopeptide antibody, anti-pS609, that specifically recognizes the GPIbalpha C-terminal sequence S(606)GHSL(610) only when Ser(609) is phosphorylated. Immunoabsorption with anti-pS609 removed almost all of the GPIbalpha from platelet lysates, indicating a high proportion of GPIbalpha phosphorylation. Anti-pS609 inhibited GPIb-IX binding to the intracellular signaling molecule, 14-3-3zeta. Dephosphorylation of GPIb-IX with potato acid phosphatase inhibited anti-pS609 binding and also 14-3-3zeta binding. A synthetic phosphopeptide corresponding to the GPIbalpha C-terminal sequence (SIRYSGHpSL), but not a nonphosphorylated identical peptide, abolished GPIb-IX binding to 14-3-3zeta. Thus, phosphorylation at Ser(609) of GPIbalpha is important for 14-3-3zeta binding to GPIb-IX. In certain regions of spreading platelets, particularly at the periphery, there was a reduction in GPIbalpha staining by anti-pS609 as observed under a confocal microscope, indicating that a subpopulation of GPIbalpha molecules in these regions is dephosphorylated. These data suggest that phosphorylation and dephosphorylation at Ser(609) of GPIbalpha regulates GPIb-IX interaction with 14-3-3 and may play important roles in the process of platelet adhesion and spreading.

14-3-3 Proteins↗
PubMed1999

Calpain cleavage of integrin beta cytoplasmic domains.

We showed previously that the calcium-dependent protease, calpain, cleaves the cytoplasmic domain of the integrin beta3 subunit. To investigate whether susceptibility to calpain is a common feature of all integrin beta subunits, and to map calpain cleavage sites in different integrin beta tails, we treated recombinant cytoplasmic domains of integrin beta1A, beta1D, beta2, beta3 and beta7 subunits with purified calpain in vitro. We found that the cytoplasmic domains of all these integrin chains were cleaved by calpain. HPLC followed by mass spectrometry was used to identify calpain cleavage sites. These sites were clustered in the C-terminal half of the integrin beta cytoplasmic domains in regions flanking the two NXXY motifs, suggesting the possibility that the structural framework provided by these motifs is recognized by calpain. We used the knowledge of these cleavage sites to develop cleavage site-specific antibodies and to demonstrate cleavage of the beta1A cytoplasmic domain in intact platelets stimulated with calcium ionophore or thrombin. Thus susceptibility to calpain cleavage is common to integrin beta subunits, can be induced in intact cells, and appears to favor regions surrounding two conserved NXXY motifs.

Amino Acid Sequence↗
PubMed1999

Functional studies of a glucagon receptor isolated from frog Rana tigrina rugulosa: implications on the molecular evolution of glucagon receptors in vertebrates.

In this report, the first amphibian glucagon receptor (GluR) cDNA was characterized from the liver of the frog Rana tigrina rugulosa. Functional expression of the frog GluR in CHO and COS-7 cells showed a high specificity of the receptor towards human glucagon with an EC(50) value of 0.8+/-0.5 nM. The binding of radioiodinated human glucagon to GluR was displaced in a dose-dependent manner only with human glucagon and its antagonist (des-His(1)-[Nle(9)-Ala(11)-Ala(16)]) with IC(50) values of 12.0+/-3. 0 and 7.8+/-1.0 nM, respectively. The frog GluR did not display any affinity towards fish and human GLP-1s, and towards glucagon peptides derived from two species of teleost fishes (goldfish, zebrafish). These fish glucagons contain substitutions in several key residues that were previously shown to be critical for the binding of human glucagon to its receptor. By RT-PCR, mRNA transcripts of frog GluR were located in the liver, brain, small intestine and colon. These results demonstrate a conservation of the functional characteristics of the GluRs in frog and mammalian species and provide a framework for a better understanding of the molecular evolution of the GluR and its physiological function in vertebrates.

Amino Acid Sequence↗
PubMed1999

Global protein synthesis shutdown in Autographa californica nucleopolyhedrovirus-infected Ld652Y cells is rescued by tRNA from uninfected cells.

Global protein synthesis arrest occurs in Autographa californica nucleopolyhedrovirus (AcNPV)-infected Ld652Y cells at late times postinfection (p.i.). A Lymantria dispar nucleopolyhedrovirus gene, hrf-1, precludes this protein synthesis arrest. We used in vitro translation assays to characterize the translation defect. Cell-free lysates prepared from uninfected Ld652Y cells, AcNPV-infected cells harvested at early times p.i., and cells infected with vAchrf-1, a recombinant AcNPV bearing hrf-1, all supported translation. Lysates prepared from AcNPV-infected Ld652Y cells at late times p.i. did not support translation, but activity was restored by adding small RNA species from mock-, vAchrf-1- (24 or 48 h p.i.), and AcNPV- (6 h p.i. ) infected cells. Small RNA species (24 and 48 h p.i.) from AcNPV-infected cells did not rescue translation. Assays of RNA species further fractionated by ion exchange chromatography demonstrated that tRNA rescued translation. Although specific defective tRNA species were not revealed by comparative two-dimensional gel analysis, analysis of (32)P-labeled tRNAs showed a reduction in de novo synthesis of small RNA isolated from AcNPV-infected cells compared with mock- and vAchrf-1-infected cells. This study suggests a mechanism of translation arrest involving defective or depleted tRNA species in AcNPV-infected Ld652Y cells.

Animals↗
PubMed1999

A protein phosphatase methylesterase (PME-1) is one of several novel proteins stably associating with two inactive mutants of protein phosphatase 2A.

Carboxymethylation of proteins is a highly conserved means of regulation in eukaryotic cells. The protein phosphatase 2A (PP2A) catalytic (C) subunit is reversibly methylated at its carboxyl terminus by specific methyltransferase and methylesterase enzymes which have been purified, but not cloned. Carboxymethylation affects PP2A activity and varies during the cell cycle. Here, we report that substitution of glutamine for either of two putative active site histidines in the PP2A C subunit results in inactivation of PP2A and formation of stable complexes between PP2A and several cellular proteins. One of these cellular proteins, herein named protein phosphatase methylesterase-1 (PME-1), was purified and microsequenced, and its cDNA was cloned. PME-1 is conserved from yeast to human and contains a motif found in lipases having a catalytic triad-activated serine as their active site nucleophile. Bacterially expressed PME-1 demethylated PP2A C subunit in vitro, and okadaic acid, a known inhibitor of the PP2A methylesterase, inhibited this reaction. To our knowledge, PME-1 represents the first mammalian protein methylesterase to be cloned. Several lines of evidence indicate that, although there appears to be a role for C subunit carboxyl-terminal amino acids in PME-1 binding, amino acids other than those at the extreme carboxyl terminus of the C subunit also play an important role in PME-1 binding to a catalytically inactive mutant.

3T3 Cells↗