Biomedical subjects

G Zhu

Publications and source records attributed to G Zhu.

At least 145 records · Page 8Linked to original sources

PubMed1999

[Experimental study on the effect of nourishing yin and tranquilizing of yangyin anshen koufuye].

Yangyin Anshen Koufuye could obviously decrease the spontaneous activity of rats, effectively shorten the process of falling into sleep of normal rats which were injected pentobarbital sodium and prolong the sleeping time. The effect of sedation and hypnotism were the same as Zhaoren Anshen Koufuye. Yangyin Anshen Koufuye also could markedly reduce the serum tensity of T3, T4 of hyperthyroid rats, which equaled to TCM's deficiency of yin. It also could prevent the glycogen content of liver from decreasing, decrease heart rate, resist weight losing, thus to show the effect of nourishing Yin and tranquilizing.

Animals↗

PubMed1999

[Fluorescence enhancement of the dysprosium-sulfosalicylic acid system by lanthanum and its application].

A fluorescence enhancement produced by adding lanthanum(III) to dysprosium-sulfosalicylic acid system was observed. La3+ enhanced the fluorescence intensity by two orders of magnitude compared with the system without La3+. The system was used for the determination of trace amount of dysprosium in the range of 3.0 x 10(-7)-1.0 x 10(-5) mol/dm3, and the detection limit was 8.0 x 10(-8) mol/dm3. The procedure was applied to the determination of dysprosium in synthetic rare earth samples and standard rare earth samples with satisfactory results.

English Abstract↗

PubMed1999

[Study on luminescence of the serial new ternary or tetradic complexes complexes of Eu (III) with beta-diketone].

The UV absorption, fluorescence, unstable spectra and quantum yields of five ternary or tetradic complexes of Eu (III) with beta-diketone (dibenzoyl methane, thenoyltrifluoroacetone), acrylic acid and other ligands were reported. The influences of the first and second ligands on absorption and luminescence spectra were found. The lifetimes and the processes of energy transfer of Eu3+ from 5D1 to 5D0 in complex solutions were measured. It was found that the lifetimes of Eu3+ complexes with TTA are approximate to each other and larger than those of complexes with DBM.

English Abstract↗

PubMed1998

The fork head transcription factor Hcm1p participates in the regulation of SPC110, which encodes the calmodulin-binding protein in the yeast spindle pole body.

We previously identified HCM1 as a dosage-dependent suppressor of a calmodulin temperature-sensitive mutant (cmd1-1). Calmodulin performs multiple functions in yeast. Here we demonstrate that the effects of HCM1 are specific to the role of calmodulin at the spindle pole body. Overexpression of HCM1 fully suppresses the temperature sensitivity of a calmodulin mutant (cmd1-3) that only has defects in assembly of the spindle pole body but does not suppress the temperature sensitivity of a calmodulin mutant (cmd1-8) that only affects other functions of calmodulin. The DNA binding specificity of Hcm1p was determined by a selection, amplification and binding protocol. The consensus sequence for an Hcmlp binding site is WAAYAAACAAW. Mutations in the DNA binding domain of Hcm1p abolish the ability of Hcmlp to specifically recognize this binding site and abolish the ability of Hcm1p to act as a suppressor of calmodulin mutants. The promoter of SPC110 contains a match to the consensus binding site. Deletion of HCM1 does not affect the basal level of SPC110 transcription, but reduces the induction that occurs late in G1 of the cell cycle.

Amino Acid Sequence↗

PubMed1998

X-ray studies on two forms of bovine beta-trypsin crystals in neat cyclohexane.

Two orthorhombic forms (Vm values are 2.3 and 3.0 A3/Da) of bovine beta-trypsin crystals in neat cyclohexane were determined to 1.93 A resolution, by X-ray diffraction. Both structures in organic solvent are similar to those in aqueous solution. In the high packing density form, one cyclohexane molecule is found in a hydrophobic site near the active center. One sulfate locates at the active site with hydrogen or salt bond to the Ser-His catalytic diad, and five more sulfates bind on the molecular surface. The conformation of the side chains near the sulfates changed greatly. In the low packing density form, one cyclohexane and three sulfates are found. In both structures, one benzamidine molecule locates at the hydrophobic pocket of the active center. Most water molecules on the enzyme surface are retained except some with high temperature factors.

Animals↗

PubMed1998

Differentiation of oligodendroglial progenitors derived from cortical multipotent cells requires extrinsic signals including activation of gp130/LIFbeta receptors.

We have previously isolated epidermal growth factor (EGF)-responsive multipotent progenitor cells from the early postnatal rodent cerebral cortex independent of generative zones. In this study we have examined the mechanisms regulating the generation of differentiated oligodendrocytes (OLs) from these multipotent cells. Although cultures of primary cortical OL progenitor cells propagated at clonal density spontaneously gave rise to differentiated OLs in defined medium, cultures of multipotent progenitors isolated from identical regions supported the elaboration of OL progenitors but not differentiated OLs. These observations indicate that the terminal maturation of OL progenitors derived from multipotent cells is dependent on signals present within the cellular environment. Application of cytokines such as basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), or neurotrophin 3 (NT3) to clonal density cultures of cortical multipotent progenitors increased the proportion of OL progenitors but failed to support the generation of differentiated OLs. By contrast, application of factors that activate gp130/leukemia inhibitory factor beta (LIFbeta) heterodimeric receptors, such as ciliary neurotrophic factor (CNTF), activated signal transducers and activators of transcription-3 in these OL progenitor cells and promoted the generation of differentiated OLs. Clonal analysis also demonstrated that CNTF directly targets OL progenitors derived from the multipotent cells. These observations suggest that two distinct progenitor cell pathways contribute to the generation of differentiated OLs during postnatal cortical gliogenesis. Although oligodendroglial maturation of classical OL progenitor cells is driven by cell autonomous mechanisms, our findings demonstrate that the generation of differentiated OLs from cortical multipotent progenitor cells is dependent on environmental cues, including activation of gp130/LIFbeta receptors.

Animals↗

PubMed1998

Identification of endogenous outward currents in the human embryonic kidney (HEK 293) cell line.

Human embryonic kidney cells (HEK 293) are widely used as an expression system in studies of ion channels. However, their endogenous ionic currents remain largely unidentified. To characterize these currents, we performed patch clamp experiments on this expression system. In whole-cell voltage clamp mode, the HEK 293 cells showed mainly outward currents using physiological concentrations of Na+ and K+ and symmetric concentrations of Cl- (150 mM) across the plasma membranes. K+ currents contributed to a small portion of these outward currents, since a shift of the reversal potentials of only approximately 20 mV was seen with a change of extracellular K+ concentration from 3 to 150 mM. In contrast, the reversal potential shifted approximately 25 mV when extracellular Cl- was reduced to 50 mM, indicating that most of the outward currents are carried by Cl-. In inside-out patches, several distinct Cl- currents were identified. They were: (1) 350 pS Cl- current, which was voltage-activated and had a moderate outward rectification; (2) 240 pS Cl- current with a weak outward rectification; and (3) 55 pS Cl- current, which was voltage-activated, sensitive to DIDS, and showed a strong outward rectification. Activation of these Cl- currents did not require an elevation of free Ca2+ level in the cytosol. Besides these three currents, we observed two other Cl- currents with much smaller conductances (25 and 16 pS, respectively). Two different K+ currents were seen in the HEK 293 cells, with one of them (125 pS) showing inward rectification and the other (70 pS) outward rectification. Moreover, a 50 pS cation channel was recorded in these cells. The presence of a variety of ion channels in the HEK 293 cells suggests that a great precaution needs to be taken when this expression system is used in studies of several similar ion channels.

Calcium↗

PubMed1998

X-ray studies on cross-linked lysozyme crystals in acetonitrile-water mixture.

Tetragonal crystals of hen egg white lysozyme were cross-linked and subjected to X-ray diffraction study in acetonitrile-water media with different acetonitrile concentrations. Crystals in neat acetonitrile did not scatter X-ray well. Structures of crystals in neat water, in 90% and 95% acetonitrile, and crystal back-soaked from acetonitrile to water, were determined to about 2 A resolution. For crystals in both 90% acetonitrile, and crystal back-soaked from acetonitrile to water, were determined to about 2 A resolution. For crystals in both 90% and 95% acetonitrile, only one protein-bond acetonitrile molecule is found in the active site cleft, and its location and binding-protein mode is similar to the C subunit of polysaccharide. The alteration in conformation and hydrogen-bond pattern involving water as solvent causes the reduction of the protein's flexibility in organic media. The back-soaked crystal regained its ordinary three-dimensional structure in water.

Acetonitriles↗

PubMed1998

In vivo degradation of a poly(propylene fumarate)/beta-tricalcium phosphate injectable composite scaffold.

This study was designed to investigate the in vivo biodegration and biocompatibility of a poly(propylene fumarate) (PPF)-based orthopedic biomaterial. The effects of varying the PPF to N-vinyl pyrrolidinone ratio and PPF to beta-tricalcium phosphate content were studied. The composite mechanical properties and local tissue interactions were analyzed over 12 weeks. An initial increase in both compressive modulus and strength was seen for composite formulations that incorporated beta-tricalcium phosphate. The samples incorporating a higher PPF to N-vinyl pyrrolidinone ratio reached a maximal compressive strength of 7.7 MPa and a maximal compressive modulus of 191.4 MPa at 3 weeks. The lower PPF to N-vinyl pyrrolidinone ratio samples gained a maximum compressive strength of 7.5 MPa initially and a compressive modulus of 134.0 MPa at 1 week. At 6 weeks, all samples for formulations incorporating beta-tricalcium phosphate crumbled upon removal and were not mechanically tested. Samples that did not incorporate beta-tricalcium phosphate were very weak and insufficient for bone replacement at the 4-day time point and beyond. Tissue interactions resulted in a mild inflammatory response at the initial time points and mature fibrous encapsulation by 12 weeks.

Animals↗

PubMed1998

Spectral parameter estimation by an iterative quadratic maximum likelihood method.

An iterative quadratic maximum likelihood (IQML) method is applied to spectral parameter estimation of 1D NMR data. A careful comparison of the linear prediction (LP) method based on the singular value decomposition, the total least squares (TLS) method, and IQML has clearly demonstrated that IQML is superior to both the LP and TLS methods in terms of the accuracy and bias of the estimation. The superiority of the IQML method lies in the fact that constraints on the NMR signal can easily be incorporated into the iterative process. The iterative quadratic maximum likelihood method can be used to analyze NMR data directly or to provide a starting point for further data refinement.

Algorithms↗

PubMed1998

Gradient- and sensitivity-enhanced heteronuclear multiple-quantum correlation spectroscopy.

A gradient- and sensitivity-enhanced HMQC experiment has been developed. The sensitivity of the experiment is increased by factors of the square root of 2 and 2 over the conventional and gradient-enhanced HMQC experiments, respectively. This improvement is achieved by retaining both the x and the y magnetization components in the indirectly detected dimension. This experiment will be particularly useful in NMR studies of large biomolecules as the relaxation time of the multiple-quantum coherence is much longer than that of the single-quantum coherence in the slow motion limit.

Calmodulin↗

PubMed1998

Minimizing DNA recombination during long RT-PCR.

Recent developments have made it possible to reverse transcribe RNA and amplify cDNA molecules of > 10 kb in length, including the HIV-1 genome. To use long reverse transcription combined with polymerase chain reaction (RT-PCR) to best advantage, it is necessary to determine the frequency of recombination during the combined procedure and then take steps to reduce it. We investigated the requirements for minimizing DNA recombination during long RT-PCR of HIV-1 by experimenting with three different aspects of the procedure: conditions for RT, conditions for PCR, and the molar ratios of different templates. We used two distinct HIV-1 strains as templates and strain-specific probes to detect recombination. The data showed that strategies aimed at completing DNA strand synthesis and the addition of proofreading function to the PCR were most effective in reducing recombination during the combined procedure. This study demonstrated that by adjusting reaction conditions, the recombination frequency during RT-PCR can be controlled and greatly reduced.

Cloning, Molecular↗

PubMed1998

Direct isolation of DNA from patient stools for polymerase chain reaction detection of Cryptosporidium parvum.

Although polymerase chain reaction (PCR) can sensitively detect parasitic or other infections, its use with fecal samples is extremely limited, primarily because of the presence of substances that inhibit DNA extension. Here an improved protocol is reported for directly isolating DNA from aged or fresh formalin-fixed stools, which can then be used to detect Cryptosporidium parvum by nested PCR. This method is highly reproducible, sensitive, and specific. It detects <1 pg of C. parvum DNA in human stool, and there are no cross-reactions with other parasites commonly found there.

Animals↗

PubMed1998

Two soluble glycosyltransferases glycosylate less efficiently in vivo than their membrane bound counterparts.

Many Golgi glycosyltransferases are type II membrane proteins which are cleaved to produce soluble forms that are released from cells. Cho and Cummings recently reported that a soluble form of alpha1, 3-galactosyltransferase was comparable to its membrane bound counterpart in its ability to galactosylate newly synthesized glycoproteins (Cho,S.K. and Cummings,R.D. (1997) J. Biol. Chem., 272, 13622-13628). To test the generality of their findings, we compared the activities of the full length and soluble forms of two such glycosyltransferases, ss1,4 N-Acetylgalactosaminyltransferase (GM2/GD2/ GA2 synthase; GalNAcT) and beta galactoside alpha2,6 sialyltransferase (alpha2,6-ST; ST6Gal I), for production of their glycoconjugate products in vivo . Unlike the full length form of GalNAcT which produced ganglioside GM2 in transfected cells, soluble GalNAcT did not produce detectable GM2 in vivo even though it possessed in vitro GalNAcT activity comparable to that of full length GalNAcT. When compared with cells expressing full length alpha2,6-ST, cells expressing a soluble form of alpha2,6-ST contained 3-fold higher alpha2,6-ST mRNA levels and secreted 7-fold greater alpha2,6-ST activity as measured in vitro , but in striking contrast contained 2- to 4-fold less of the alpha2,6-linked sialic acid moiety in cellular glycoproteins in vivo . In summary these results suggest that unlike alpha1,3-galactosyltransferase the soluble forms of these two glycosyltransferases are less efficient at glycosylation of membrane proteins and lipids in vivo than their membrane bound counterparts.

Animals↗

PubMed1998

Chimeric Arabidopsis thaliana ribulose-1,5-bisphosphate carboxylase/oxygenase containing a pea small subunit protein is compromised in carbamylation.

A cDNA of pea (Pisum sativum L.) RbcS 3A, encoding a small subunit protein (S) of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), has been expressed in Arabidopsis thaliana under control of the cauliflower mosaic virus 35S promoter, and the transcript and mature S protein were detected. Specific antibodies revealed two protein spots for the four Arabidopsis S and one additional spot for pea S. Pea S in chimeric Rubisco amounted to 15 to 18% of all S, as judged by separation on two-dimensional isoelectric focusing/sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels from partially purified enzyme preparations and quantitation of silver-stained protein spots. The chimeric enzyme had 11 +/- 1% fewer carbamylated sites and a 11 +/- 1% lower carboxylase activity than wild-type Arabidopsis Rubisco. Whereas pea S expression, preprotein transport, and processing and assembly resulted in a stable holoenzyme, the chimeric enzyme was reproducibly catalytically less efficient. We suggest that the presence of, on average, one foreign S per holoenzyme is responsible for the altered activity. In addition, higher-plant Rubisco, unlike the cyanobacterial enzyme, seems to have evolved species-specific interactions between S and the large subunit protein that are involved in carbamylation of the active site.

Amino Acid Sequence↗

PubMed1998

[Effect of mifepristone on the expression of progesterone receptor messenger RNA and protein in uterine leiomyomata].

OBJECTIVE: To determine the expression of progesterone receptor (PR) mRNA and PR protein levels in the myometrium and leiomyomata from untreated and mifepristone pretreated women with leiomyoma and to examine the mechanism of mifepristone treatment on uterine leiomyomata. METHODS: Expression of PR mRNA and PR protein were determined by Northern blot and HAP of single-dose saturated analysis in myometrium and leiomyomata (center and marginal area) from 27 untreated and 6 mifepristone pretreated women with leiomyomata. RESULTS: PR mRNA abundance and PR protein levels in both myomatous center and marginal area were significantly greater than those in corporal myometrium (P < 0.01) in both follicular and luteal phases, but similar between myomatous center and marginal area (P > 0.05). 6 cases pretreated with mifepristone 25 mg/day for 3 months were operated, all but one patient displayed a decrease in leiomyomata volume. PR mRNA abundance in both myometruim and leiomyomata (center and marginal area) was significantly decreased in 4 patients continuing mifepristone treatment before the operation but not in the other 2 patients stopping RU486 1 month before operation. PR protein levels in these tissues showed significant decrease in all 6 cases. CONCLUSION: There are overexpression of PRmRNA and PR protein in leiomyomata. One of the mechanism of mifepristone action on decreasing leiomyomata volume may be related to suppression on expression of PR gene. It seems that suppression on transcription of PR gene is reversible, but on translation of PR gene may maintain in a relatively longer period.

Adult↗

PubMed1998

[The mechanisms of hyperhomocysteinemia in coronary heart disease].

OBJECTIVE: To identify hyperhomocysteinemia (HHe) as a new and independent risk factor for coronary heart disease (CHD). METHODS: The association of coronary heart disease (CHD) and lipid, homocysteine (HCY) and the factors related to its metabolisms were examined. The mutation of the 677C-->T transition of MTHFR was determined by PCR-based assay. Whole blood and plasma folate (FA) and plasma vitamin B12(B12), as cofactors of those enzymes, were determined by radioimmunologic assay. Plasma HCY was determined by HPLC. RESULTS: Patients with CHD confirmed by coronary angiography had increased plasma HCY concentrations (17.1 +/- 3.6 mumol/L, 7.6 +/- 1.2 mumol/L). In patients with MI, HPT and family history (FH) of CHD, plasma HCY increased significantly. Plasma HCY concentrations had significant non-linear inverse relation with plasma FA and B12 concentrations. Homozygous mutants showed higher plasma HCY concentrations. Patients with CHD had increased serum CHOL and VLDL levels, but plasma HCY concentrations were not correlated with serum lipid levels. CONCLUSION: Hyperhomocysteinemia is an independent risk factor for coronary heart disease.

Adult↗

PubMed1998

[Vascular endothelial growth gene therapy for narrowing of rabbit iliac artery].

OBJECTIVE: To study the mechanism of renarrowing and vascular endothelial growth factor (VEGF) gene therapy to prevent the restenosis caused by balloon angioplasty. METHODS: According to the special function of VEGF that promepts the proliferation of endothelial cell (EC), we constituted an eukaryotic expression vector of pcDNA3/VEGF, and added the pcDNA3/VEGF to the surface of polylysine-balloon. We examined the results of the test by in situ blot, eletromagnetic blood flow mechine, scanning eletromicroscope, and light microscope. RESULTS: There was higher expression of VEGF mRNA and iliac artery intima in the VEGF gene group. The extent of endothelialization was larger, the ratio of intima to media (I/M) was smaller, and the blood flow was more sufficient than in the vector control group. CONCLUSION: VEGF gene local delivery could stimulate the proliferation of EC, accelerate the endothelialization of injury-artery, and inhibite the proliferation of smooth muscle cell (SMC).

Angioplasty, Balloon↗