Biomedical subjects

G Zhu

Publications and source records attributed to G Zhu.

At least 73 records · Page 4Linked to original sources

PubMed2001

[Clinical observation of astigmatism induced by corneal incision after phacoemulsification].

OBJECTIVE: To evaluate the changes of astigmatism induced by corneal incision after phacoemulsification. METHODS: Phacoemulsification was performed on 62 cases (78 eyes) without suture for a corneal incision. The changes of corneal astigmatism before and after operation in group A (incision at the superior nasal or superior temporal) and B (incision at the steepest corneal meridian) were compared. RESULTS: Three months after the operation, the surgical induced astigmatism was (0.83 plus minus 0.65) D and (0.72 plus minus 0.55) D in group A and B respectively. There was no significant difference, statistically (P > 0.05). The changes of corneal astigmatism were 0.11 D and 0.39 D in group A and B respectively, the difference being statistically significant (P < 0.05). CONCLUSION: Surgically induced astigmatism is very small after a corneal incision in phacoemulsification without a suture. If the incision is placed on the steepest meridian, the corneal astigmatism can be significantly reduced postoperatively.

Adolescent↗

PubMed2001

[Detection of DNA of Toxoplasma gondii in rat by using polymerase chain reaction].

OBJECTIVE: To study the significance of DNA of Toxoplasma gondii in peripheral blood. METHODS: DNA of T. gondii in peripheral blood of 50 infected rats was detected by polymerase chain reaction. A pair of primers was designed, according to the sequence P30 gene specific to T. gondii, to amplify DNA from T. gondii by PCR. RESULTS: The primers amplified DNA specifically from T. gondii and could not amplify DNA from humans, uninfected rat and mouse and from Trichomonas vaginalis and Entamoeba histolytica. DNA of two Toxoplasma parasites was detected by 35 cycles of amplification, indicating a fair sensitivity of the PCR system. CONCLUSION: PCR may have a value for early diagnosis of T. gondii infection in rat.

Animals↗

PubMed2001

[Ultrastructure of surfactant-like multilamellar bodies in the human nose].

OBJECTIVE: To study the distribution of the surfactant-like multilamellar bodies in the human nose. METHODS: Fourteen specimens obtained from the inferior turbinate, middle turbinate, uncinate process and maxillary sinus were examined under the electron microscope. RESULTS: The surfactant-like multilamellar bodies were identified in the epithelium on the lateral wall and maxillary sinus. CONCLUSION: The existence of surfactant-like multilamellar bodies in the human lateral nasal wall and maxillary sinus were confirmed. It is necessary to have further study for its effect in the nose both physiologically and pharmacologically.

Adolescent↗

PubMed2001

Interleukin 10 inhibits the rat VSMC proliferation and collagen secretion stimulated by angiotensin II.

OBJECTIVE: To study the effect of interleukin 10 (IL-10) on the angiotensin II (AngII) stimulated rat VSMC proliferation and collagen secretion, and furthermore, explore its mechanism. METHODS: On cultured VSMC of rat, 3H-thymine (3H-TdR) and 3H-proline incorporations were used to evaluate the DNA and collagen synthesis, respectively. Western blot and immunoprecipitation were applied to assay the expression and activity of focal adhesion kinase (FAK), respectively. RESULTS: IL-10 (10(-8) approximately 10(-10) g/ml) inhibited the increase of 3H-TdR and 3H-proline incorporation as well as FAK activity, which was induced by 10(-7) mol/L AngII (P < 0.05 or P < 0.01). IL-10 also obviously downregulated the synthesis and secretion of collagen by AngII stimulated VSMC. But there was no difference in the protein expression of FAK among all the groups (P > 0.05). CONCLUSION: IL-10 antagonizes the VSMC proliferation and collagen synthesis by regulating FAK activity stimulated by AngII.

Angiotensin II↗

PubMed2001

[Pulmonary surfactant impairment in the development of ventilator-induced lung injury in rats].

OBJECTIVE: To evaluate whether pulmonary surfactant (PS) impairment plays a role in the development of ventilator-induced lung injury (VILI). METHODS: Thirty-two healthy adult Sprague-Dawley rats were randomly allocated to four groups ( n = 8, each group ) and mechanically ventilated (MV). (1) P7 group: with settings [expressed as peak inspiratory pressure (PIP, cm H2O)/frequency (cpm)/inspiratory:expiratory ratio/positive end expiratory pressure (PEEP, cm H2O)] of 7/40/1:1/0, (2) P45 group: with settings of 45/ 20/1:1/0, (3) PS group: 100 mg/kg of a porcine PS administered intra-tracheally and with the same settings as P45 group, (4) PEEP group: with settings of 45/20/1: 1/10. After 20 minutes of MV, all animals were killed. Another 8 animals were killed immediately after surgical procedure to serve as nonventilated controls (CON group). Arterial blood O2 partial pressure (PaO2) and maximum thorax-lung compliance (C(max)) were measured, and total proteins (TP), total phospholipids (TPL), small and large aggregates (SA, LA), and minimum surface tension (ST min) of bronchoalveolar lavage fluid (BALF) were analyzed. RESULTS: P45 group had decreased PaO2, C(max), TPL/TP all P < 0.01), increased TP, SA/LA and ST min of ABLF (all P < 0.01) as compared with P7 group. Both PS group and PEEP group had improved PaO2, C(max), BALF analyses as compared with P45 group (P < 0.05 or P < 0.01). There was no significant difference between P7 group and CON group in any parameter described above. CONCLUSIONS: A short period of mechanical ventilation with high PIP alone can cause VILI in rats that is associated with PS impairment; both exogenous PS and PEEP can restore or preserve alveolar space PS composition and function, attenuate abnormalities of lung oxygenation and mechanics, indicating PS impairment may play an important role in the development of VILI.

Animals↗

PubMed2000

Quantitation of basic fibroblast growth factor by immunoassay using BIAcore 2000.

A sensitive, accurate, and efficient immunoassay using a BIAcore 2000 biosensor instrument for the quantitation of basic fibroblast growth factor (bFGF) in HEPES-buffered saline containing 100 microg/ml heparin (HHBS) has been developed and validated. In this method, anti-bFGF monoclonal antibody 48.1 (MAb 48.1) was selected as a binding ligand and immobilized to the matrix surface of Sensor Chip CM5 by amine coupling. A high immobilization level of MAb 48.1 (12643+/-816 RU, mean +/- S.D., n = 5) was achieved with high reproducibility (i.e. coefficient of variation (CV) was 6.5%). This immobilized MAb 48.1 sensor surface was used to detect and quantity bFGF. This assay has a range of reliable BIAcore response from 5.65 to 1440 ng/ml bFGF in HHBS. which was well fitted with a sigmoidal model. The immobilized MAb 48.1 was found to be stable for at least 150 regeneration cycles and for at least 9 days at room temperature. Intra- and interassay CVs ranged from 0.9 to 5.9%, and from 2.7 to 8.5%, respectively. Matrices such as serum, bovine serum albumin (BSA), and two pharmaceutical excipients (Pluronic F127 surfactant and sodium carboxymethylcellulose) did not interfere with bFGF analysis over the sensor surface. Therefore, this validated assay has good precision, accuracy and specificity, and has been found useful in quantifying bFGF in several research and development studies.

Antibodies, Monoclonal↗

PubMed2000

Dysfunction of M-channel enhances propagation of neuronal excitability in rat hippocampus monitored by multielectrode dish and microdialysis systems.

To explore the pathogenesis of benign familial neonatal convulsions (BFNC), we determined effects of KCNQ-related M-channels (KCNQ-channels) on hippocampal glutamate (Glu) and gamma-aminobutyric acid (GABA) releases using microdialysis, and propagation of evoked field-potentials (FP) using multielectrode (64-ch)-dish system as two-dimensional monitoring. KCNQ-channel inhibitor, Dup996, enhanced hippocampal K(+)-evoked Glu and GABA releases without affecting basal releases of them. Dup996 unaffected FP-amplitude, but enhanced FP-propagation. The GABA(A)-receptor antagonist, bicuculline, enhanced the stimulatory effects of Dup996 on FP-propagation, however, this stimulatory effects of Dup996 were abolished by the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/glutamate-receptor antagonist, DNQX. These results suggest that the occurrence of BFNC cannot be produced by KCNQ-channel dysfunction alone, but by reciprocal action between impaired KCNQ-channel and other unknown elements (possibly dysfunction of inhibitory neurotransmission system).

Action Potentials↗

PubMed2000

Costimulation of T cells by B7-H2, a B7-like molecule that binds ICOS.

This report describes a new human B7-like gene designated B7-H2. Cell surface expression of B7-H2 protein is detected in monocyte-derived immature dendritic cells. Soluble B7-H2 and immunoglobulin (Ig) fusion protein, B7-H2Ig, binds activated but not resting T cells and the binding is abrogated by inducible costimulator Ig (ICOSIg), but not CTLA4Ig. In addition, ICOSIg stains Chinese hamster ovary cells transfected with B7-H2 gene. By suboptimal cross-linking of CD3, costimulation of T-cell proliferation by B7-H2Ig is dose-dependent and correlates with secretion of interleukin (IL)-2, whereas optimal CD3 ligation preferentially stimulates IL-10 production. The results indicate that B7-H2 is a putative ligand for the ICOS T-cell molecule. (Blood. 2000;96:2808-2813)

Abatacept↗

PubMed2000

Gating of inward rectifier K+ channels by proton-mediated interactions of N- and C-terminal domains.

Ion channels play an important role in cellular functions, and specific cellular activity can be produced by gating them. One important gating mechanism is produced by intra- or extracellular ligands. Although the ligand-mediated channel gating is an important cellular process, the relationship between ligand binding and channel gating is not well understood. It is possible that ligands are involved in the interactions of different protein domains of the channel leading to opening or closing. To test this hypothesis, we studied the gating of Kir2.3 (HIR) by intracellular protons. Our results showed that hypercapnia or intracellular acidification strongly inhibited these channels. This effect relied on both the N and C termini. The CO(2)/pH sensitivities were abolished or compromised when one of the intracellular termini was replaced. Using purified N- and C-terminal peptides, we found that the N and C termini bound to each other in vitro. Although their binding was weak at pH 7.4, stronger binding was seen at pH 6.6. Two short sequences in the N and C termini were found to be critical for the N/C-terminal interaction. Interestingly, there was no titratable residue in these motifs. To identify the potential protonation sites, we systematically mutated most histidine residues in the intracellular N and C termini. We found that mutations of several histidine residues in the C but not the N terminus had a major effect on channel sensitivities to CO(2) and pH(i). These results suggest that at acidic pH, protons appear to interact with the C-terminal histidine residues and present the C terminus to the N terminus. Consequentially, these two intracellular termini bound to each other through two short motifs and closed the channel. Thus, a novel mechanism for K(+) channel gating is demonstrated, which involves the N- and C-terminal interaction with protons as the mediator.

Amino Acid Motifs↗

PubMed2000

Two yeast forkhead genes regulate the cell cycle and pseudohyphal growth.

There are about 800 genes in Saccharomyces cerevisiae whose transcription is cell-cycle regulated. Some of these form clusters of co-regulated genes. The 'CLB2' cluster contains 33 genes whose transcription peaks early in mitosis, including CLB1, CLB2, SWI5, ACE2, CDC5, CDC20 and other genes important for mitosis. Here we find that the genes in this cluster lose their cell cycle regulation in a mutant that lacks two forkhead transcription factors, Fkh1 and Fkh2. Fkh2 protein is associated with the promoters of CLB2, SWI5 and other genes of the cluster. These results indicate that Fkh proteins are transcription factors for the CLB2 cluster. The fkh1 fkh2 mutant also displays aberrant regulation of the 'SIC1' cluster, whose member genes are expressed in the M-G1 interval and are involved in mitotic exit. This aberrant regulation may be due to aberrant expression of the transcription factors Swi5 and Ace2, which are members of the CLB2 cluster and controllers of the SIC1 cluster. Thus, a cascade of transcription factors operates late in the cell cycle. Finally, the fkh1 fkh2 mutant displays a constitutive pseudohyphal morphology, indicating that Fkh1 and Fkh2 may help control the switch to this mode of growth.

Binding Sites↗

PubMed2000

Involvement of histidine residues in proton sensing of ROMK1 channel.

ROMK channels are inhibited by intracellular acidification. This pH sensitivity is related to several amino acid residues in the channel proteins such as Lys-61, Thr-51, and His-206 (in ROMK2). Unlike all other amino acids, histidine is titratable at pH 6-7 carrying a positive charge below pH 6. To test the hypothesis that certain histidine residues are engaged in CO(2) and pH sensing of ROMK1, we performed experiments by systematic mutations of all histidine residues in the channel using the site-directed mutagenesis. There are two histidine residues in the N terminus. Mutations of His-23, His-31, or both together did not affect channel sensitivity to CO(2). Six histidine residues are located in the C terminus. His-225, His-274, His-342, and His-354 were critical in CO(2) and pH sensing. Mutation of either of them reduced CO(2) and pH sensitivities by 20-50% and approximately 0.2 pH units, respectively. Simultaneous mutations of all of them eliminated the CO(2) sensitivity and caused this mutant channel to respond to only extremely acidic pH. Similar mutations of His-280 had no effect. The role of His-270 in CO(2) and pH sensing is unclear, because substitutions of this residue with either a neutral, negative, or positive amino acid did not produce any functional channel. These results therefore indicate that histidine residues contribute to the sensitivity of the ROMK1 channel to hypercapnia and intracellular acidosis.

Carbon Dioxide↗

PubMed2000

Effects of HFE C282Y and H63D polymorphisms and polygenic background on iron stores in a large community sample of twins.

The aim of this study was to assess and to compare the role of HFE polymorphisms and other genetic factors in variation in iron stores. Blood samples were obtained from 3,375 adult male and female twins (age range 29-82 years) recruited from the Australian Twin Registry. There were 1,233 complete pairs (562 monozygotic and 571 dizygotic twins). Serum iron, transferrin, transferrin saturation with iron, and ferritin were measured, and the HFE C282Y and H63D genotypes were determined. The frequency of the C282Y allele was.072, and that of the H63D allele was.141. Significant sources of variation in the indices of iron status included age, sex, age-sex interaction, body-mass index, and both the C282Y and H63D genotypes. The iron, transferrin, and saturation values of CC and CY subjects differed significantly, but the ferritin values did not. After correction for age and body-mass index, 23% and 31% of the variance in iron, 66% and 49% of the variance in transferrin, 33% and 47% of the variance in transferrin saturation, and 47% and 47% of the variance in ferritin could be explained by additive genetic factors, for men and women, respectively. HFE C282Y and H63D variation accounted for <5% of the corrected phenotypic variance, except for saturation (12% in women and 5% in men). We conclude that HFE CY and HD heterozygotes differ in iron status from the CC and HH homozygotes and that serum transferrin saturation is more affected than is serum ferritin. There are highly significant effects of other as-yet-unidentified genes on iron stores, in addition to HFE genotype.

Adult↗

PubMed2000

NMR studies of Bacillus subtilis tRNA(Trp) hyperexpressed in Escherichia coli. Assignment of imino proton signals and determination of thermal stability.

15N-Labeled Bacillus subtilis tRNA(Trp) wild type and a series of mutants were hyperexpressed in Escherichia coli and purified for NMR studies with the use of two-dimensional nuclear Overhauser effect spectroscopy (NOESY) and heteronuclear single quantum correlation (HSQC) and three-dimensional NOESY-HSQC techniques. These made possible chemical shift assignments of imino protons and determination of the thermal stability of the tRNA(Trp) molecules. Almost all of the imino protons in the helical regions and the tertiary base pairs were assigned, except three imino protons of the AU base pairs whose peaks were not clearly observed. Several base triplets found in the crystal structure of tRNA were observed in the present study as well. These studies also revealed two components of tRNA(Trp), which could not be separated by high pressure liquid chromatography, corresponding to s(4)U and U at position 8 of the tRNA(Trp), as indicated by two different sets of peaks for the TpsiC and D arms. The modification at position 8 altered the local conformation of the core region of the tRNA. Thermal unfolding experiments showed that the unfolding process is cooperative in the presence of a high concentration of magnesium ions and that the component corresponding to the s(4)U8 is more stable than the U8 component, thus providing evidence that the thiolation of U8 stabilizes the tertiary structure of tRNA.

Anticodon↗

PubMed2000

Molecular analysis of a Type I fatty acid synthase in Cryptosporidium parvum.

We report here the molecular analysis of a Type I fatty acid synthase in the apicomplexan Cryptosporidium parvum (CpFAS1). The CpFAS1 gene encodes a multifunctional polypeptide of 8243 amino acids that contains 21 enzymatic domains. This CpFAS1 structure is distinct from that of mammalian Type I FAS, which contains only seven enzymatic domains. The CpFAS1 domains are organized into: (i) a starter unit consisting of a fatty acid ligase and an acyl carrier protein; (ii) three modules, each containing a complete set of six enzymes (acyl transferase, ketoacyl synthase, ketoacyl reductase, dehydrase, enoyl reductase, and acyl carrier protein) for the elongation of fatty acid C2-units; and (iii) a terminating domain whose function is as yet unknown. The CpFAS1 gene is expressed throughout the life cycle of C. parvum, since its transcripts and protein were detected by RT-PCR and immunofluorescent localization, respectively. This cytosolic Type I CpFAS1 differs from the organellar Type II FAS enzymes identified from Toxoplasma gondii and Plasmodium falciparum which are targetted to the apicoplast, and are sensitive to inhibition by thiolactomycin. That the discovery of CpFAS1 may provide a new biosynthetic pathway for drug development against cryptosporidiosis, is indicated by the efficacy of the FAS inhibitor cerulenin on the growth of C. parvum in vitro.

Amino Acid Motifs↗

PubMed2000

Developmental changes in neural progenitor cell lineage commitment do not depend on epidermal growth factor receptor signaling.

Multipotent neural progenitor cells become progressively more biased towards a glial fate during development coincident with an increase in expression of the epidermal growth factor receptor (EGFR). To determine whether differences in lineage commitment of neural progenitor cells from different stages are causally related to expression of the EGFR and whether generation of glia is EGFR-dependent, we used an EGFR-specific tyrosine kinase inhibitor, PD158780, to block the activation of EGFR in progenitor cells. Treatment of cultured neonatal progenitor cells with PD158780 completely blocked EGF-induced proliferation of the cells but did not affect bFGF-induced proliferation. Nevertheless, treatment with the inhibitor failed to inhibit the generation of astroglia in the presence of either EGF or bFGF. Treatment with bone morphogenetic protein-2 (BMP2) enhanced astroglial differentiation and suppressed oligodendroglial (OL) differentiation. PD158780 treatment had no effect on the BMP2-induced astroglial differentiation or OL suppression. These observations suggest that the generation of astroglia is not dependent on EGFR activation. Because it was still possible that the progenitor cell responses reflected a prior history of EGFR signaling, rat forebrain cells were cultured in the presence of PD158780 from a time (E12.5) preceding expression of the EGFR. After time in culture, the E12.5 cells expressed EGFR by Western analysis both in the presence and in the absence of PD158780, but activation of EGFR kinase (receptor autophosphorylation) was undetectable in the presence of PD158780 and the cells did not proliferate in response to EGF. Nevertheless, astroglial differentiation was normal in PD158780-treated cells both in the absence and in the presence of BMPs or CNTF. Furthermore, the propensity towards glial differentiation increased with time in culture even in the absence of EGFR signaling. This suggests that the increased bias towards glial differentiation during development does not depend on EGFR signaling.

Animals↗

PubMed2000

CO(2) inhibits specific inward rectifier K(+) channels by decreases in intra- and extracellular pH.

Hypercapnia has been shown to affect cellular excitability by modulating K(+) channels. To understand the mechanisms for this modulation, four cloned K(+) channels were studied by expressing them in Xenopus oocytes. Exposures of the oocytes to CO(2) for 4-6 min produced reversible and concentration-dependent inhibitions of Kir1.1 and Kir2.3 currents, but had no effect on Kir2.1 and Kir6.1 currents. Intra- and extracellular pH (pH(i), pH(o)) dropped during CO(2) exposures. The inhibition of Kir2.3 currents was mediated by reductions in both intra- and extracellular pH, whereas the suppression of Kir1.1 resulted from intracellular acidification. In cell-free excised inside-out patches with cytosolic-soluble factors washed out, a decrease in pH(i) produced a fast and reversible inhibition of macroscopic Kir2.3 currents. The degree of this inhibition was similar to that produced by hypercapnia when compared at the same pH(i) level. Exposure of cytosolic surface of patch membranes to a perfusate bubbled with 15% CO(2) without changing pH failed to inhibit the Kir2.3 currents. These results therefore indicate that (1) hypercapnia inhibits specific K(+) channels, (2) these inhibitions are caused by intra- and extracellular protons rather than molecular CO(2), and (3) these effects are independent of cytosol-soluble factors.

Animals↗

PubMed2000

Cryptosporidium parvum: functional complementation of a parasite transcriptional coactivator CpMBF1 in yeast.

We report here the identification of a novel multiprotein bridging factor type 1 from the apicomplexan Cryptosporidium parvum (CpMBF1), one of the opportunistic pathogens in AIDS patients. In slime molds, insects, and humans, MBF1-regulated systems have been associated with cell differentiation, which indicates that CpMBF1 could be responsible for the activation of similar systems in C. parvum during its complex life cycle. Because of the difficulties and high cost in obtaining sufficient and purified C. parvum material for molecular and biochemical analyses, well-characterized yeast genetic systems may be useful for investigating the functions of C. parvum genes. In this study, the function of CpMBF1 as an interconnecting element between a DNA-binding regulator and TATA-box-binding protein (TBP) was confirmed using a yeast complementation assay. Under conditions of histidine starvation, an MBF1-deficient strain of Saccharomyces cerevisiae was unable to activate the HIS3 gene, which encodes imidazoleglycerol-phosphate dehydratase (IGPDH), and thus became sensitive to 3-amino triazole, an inhibitor of this enzyme. Upon introduction of parasite CpMBF1 into S. cerevisiae, 3-amino triazole resistance of the MBF1-deficient strain was restored to wild-type levels, and Northern blot analysis revealed that CpMBF1 was able to activate HIS3 transcription in response to histidine starvation.

Amino Acid Sequence↗

PubMed2000

Protein dynamics measurements by TROSY-based NMR experiments.

The described TROSY-based experiments for investigating backbone dynamics of proteins make it possible to elucidate internal motions in large proteins via measurements of T(1), T(2), and NOE of backbone (15)N nuclei. In our proposed sequences, the INEPT sequence is eliminated and the PEP sequence is replaced by the ST2-PT sequence from the HSQC-based experiments. This has the benefit of shortening the pulse sequences by 5.4 ms (=1/2J) and results in an increase in the intrinsic sensitivity of the proposed TROSY-based experiments. The TROSY-based experiments are on average of 13% more sensitive than the corresponding HSQC-based experiments on a uniformly (15)N-labeled Xenopus laevis calcium-bound calmodulin sample on a 750-MHz spectrometer at 5 degrees C. The amide proton linewidths of the TROSY-based experiments are 2-13 Hz narrower than those of the HSQC experiments. More sensitivity gain and higher resolution are expected if the protein sample is deuterated.

Amides↗