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Biomedical subjects

J Zeng

Publications and source records attributed to J Zeng.

138 records · Page 8Linked to original sources
PubMed1992

[High performance liquid chromatographic determination of hydroxyphenytoin in human urine].

A high-performance liquid chromatographic method for the determination of p-hydroxyphenytoin (p-HDPH) in human urine was reported. Following acid hydrolysis of urine sample at 90 degrees C for 1 h, an internal standard, nitrophenol, was added. The sample was extracted with n-hexane-ethyl acetate (50:50), and organic layer was evaporated. The residue was dissolved in methanol and chromatographed on an Ultrasphere-ODS column, using a mobile phase of phosphate buffer (0.03 mol/L, pH 6.0): methanol (65:35) at a flow rate of 0.8 ml/min. The eluent was monitored at 240 nm. The standard curve was linear within the range 5.0-200 micrograms/ml (r = 0.9998). Analytical recovery rates were 102.8 +/- 7.3% (p-HDPH 9.70 micrograms/ml, n = 5) and 104.9 +/- 6.4% (p-HDPH 54.70 micrograms/ml, n = 5). The cumulative recovery of p-HDPH in 0-12 h volunteers' urine samples accounted for 20% of the oral dose of 100 mg phenytoin sodium.

Chromatography, High Pressure Liquid↗
PubMed1991

Zinc transfer from transcription factor IIIA fingers to thionein clusters.

The rapid induction of thionein (apometallothionein) by many endogenous stimuli such as steroid hormones, cytokines, and second messengers suggests that this cysteine-rich, metal binding protein participates in an as yet undefined role in cellular regulatory processes. This study demonstrates with DNA and RNA binding assays and in vitro transcription measurements that thionein suppresses the binding of the Xenopus laevis zinc finger transcription factor IIIA (TFIIIA) to 5S RNA and to the 5S RNA gene and abrogates the capacity of TFIIIA to initiate the RNA polymerase III-catalyzed synthesis of 5S RNA. The effect is reversed by the addition of zinc and is not observed in the TFIIIA-independent transcription of a tRNA gene by the same RNA polymerase. In view of the strong tendency of thionein to complex posttransition metals such as zinc, one effect of its enhanced synthesis in vivo could be to reduce the intracellular disposability of zinc and thus modulate the actions of zinc-dependent enzymes and proteins, most notably those of the zinc finger transcription factors.

Animals↗
PubMed1991

Thionein (apometallothionein) can modulate DNA binding and transcription activation by zinc finger containing factor Sp1.

A number of transcription factors contain so-called zinc finger domains for the interaction with their cognate DNA sequence. It has been shown that removal of the zinc ions complexed in these zinc fingers abrogates DNA binding and transcription activation. Therefore we wanted to test the hypothesis that the activity of transcription factors could be regulated by physiological chelators of zinc. A prominent candidate for such a chelator is the Cys-rich protein thionein (apometallothionein) that is inducible by heavy metal loads, and by other environmental stimuli. Here we show with DNA binding and in vitro transcription assays that thionein indeed can inactivate the zinc finger-containing Sp1 in a reversible manner. By contrast, transcription factor Oct-1, which binds DNA via a homeo-domain, i.e. a helix-turn-helix motif not involving zinc ions, is refractory to thionein action. We propose that modulation of intracellular thionein concentration is used for the coordinated regulation of a large subset of genes whose transcription depends on zinc finger proteins.

Animals↗
PubMed1991

[Determination of hydrocortisone and methylprednisolone in plasma by reversed-phase HPLC].

A sensitive and rapid method for the simultaneous measurement of both hydrocortisone (HC) and methylprednisolone (MP) using dexamethasone (DX) as the internal standard was presented. High-performance liquid chromatograph Model 344 (Beckman, USA) with a 254 nm wavelength UV detector and reversed-phase Ultrasphere ODS (5 microns) column was used. Sample was extracted with ethyl acetate and the organic layer was evaporated to dryness under an air stream in a 37 degrees C water bath. The residue was dissolved in 30 microliters mobile phase and 20 microliters injected. The mobile phase of methanol and 0.01 mol/L acetate buffer (pH 3.0) (64:36) was pumped at 1.0 ml/min through the column. The detector was operated at 0.005 aufs. The retention time for HC, MP and DX was 5.43 min, 7.7 min and 11.5 min, respectively. Standard curve was linear in the concentration range of 0.02 to 1.28 mg/L for HC and 0.05 to 12.8 mg/L for MP. Sensitivity was 1 ng for HC and 1.5 ng for MP; extraction recovery 76-83%; within day CV less than 4%, and inter-day CV less than 6% for both steroids.

Animals↗
PubMed1990

Crystallization of a calcium-binding lysozyme from horse milk.

Crystals of the calcium-containing lysozyme from horse milk have been grown by precipitation with sodium phosphate. The crystals are orthorhombic space group P2(1)2(1)2(1) with cell dimensions a = 53.2, b = 57.1, and c = 38.2 A and contain a single molecule in the asymmetric unit. The crystals are suitable for high resolution x-ray structural analysis.

Amino Acid Sequence↗
PubMed1989

Tetragonal crystals of canine myeloperoxidase suitable for X-ray structural analysis.

A new tetragonal crystal form of canine myeloperoxidase grown by precipitation with ammonium sulfate is described. The space group is P4(1)2(1)2 or P4(3)2(1)2 with unit cell dimensions. a = b = 133.0 A, c = 203.6 A, and a single molecule in the asymmetric unit. The crystals diffract to Bragg spacings of 2.5 A and are suitable for a medium-resolution structure determination.

Animals↗
PubMed1989

The effect of IABP ventricular contractility of the normal and ischemic canine heart assessed in situ by T-Emax.

The effects of IABP on the contractile state of the in situ canine heart was evaluated under control conditions and conditions of regional ischemia by determining the transient slope of the end-systolic pressure-volume line, T-Emax. For comparison, the conventional index reflecting contractility, dP/dtmax and other related hemodynamic parameters were also assessed. The results showed that, T-Emax, rather than dP/dtmax, reflected more appropriately the changes in contractile state during activation of the IABP under both conditions. It suggests that IABP has a positive inotropic influence only in the ischemic-state and this is a positive inotropic influence only in the ischemic-state and this is a result of the improvement in the myocardial oxygen supply and demand relation. In addition, the limitations of the new indicator, T-Emax, is discussed.

Animals↗
PubMed1987

Crystal structure determination of mung bean trypsin inhibitor Lys fragment-bovine trypsin complex--molecular replacement, electron density map at 3.0 angstron resolution.

The orientation and position of the trypsin molecule in the complex crystal cell mung bean trypsin inhibitor Lys fragment (MBILF)-bovine trypsin (BTRY) have been successfully determined by molecular replacement method with the model of the refined bovine trypsin molecule. Starting from the BTRY coordinates which were oriented and located in the correct azimuth and position in the complex cell according to the result from rotation function and translation function, sim-weighted Fourier map with coefficients 2/Fo/-/Fc/ at 3.0 A resolution was calculated. Besides the electron density which is obviously attributed to itself, in the vicinity of the active site of BTRY the dense contour levels corresponding to the MBILF and and its boundary could be clearly seen in this map. The size of MBILF was approximately estimated at 15 x 15 x 25 A.

Crystallography↗
PubMed1983

Detection of Epstein-Barr virus IgA/EA antibody for diagnosis of nasopharyngeal carcinoma by immunoautoradiography.

An immunoautoradiographic method was used for the detection of EB virus IgA/EA antibody in sera from NPC patients and other control groups. Ninety-six percent of NPC patients had IgA/EA antibody with a high titer of GMT. The positive rates of IgA/EA antibody in patients with malignant tumours other than NPC and in normal individuals were only 4% and 0%, respectively. Eleven patients histologically diagnosed as having a chronic inflammation and who showed positive for IgA/EA antibody by immunoautoradiography were rebiopsied; six of them were discovered to have squamous cell carcinoma. Fourteen NPC patients had no IgA/EA antibody detected by immunofluorescence and immunoenzymatic testing, but 11 and six of them had IgA/VCA and IgA/EA antibodies detected by immunoautoradiography, respectively. These data indicate that the immunoautoradiographic method is more sensitive than either the immunofluorescence or immunoenzymatic test for the detection of IgA/EA antibody, and can be used for the detection of NPC in the early stages of development.

Antibodies, Viral↗
PubMedDate not supplied

Plasma membrane calcium ATPase gene expression in bovine lens epithelium.

Plasma membrane calcium adenosine triphosphatase (Ca(2+)-ATPase) is an energy-dependent protein responsible for transporting cytosolic calcium across the plasma membrane. Multiple plasma membrane Ca(2+)-ATPase isoforms are expressed from four genes (PMCA1-4) and alternative mRNA splicing. We have studied PMCA gene expression in bovine lens epithelium tissues by reverse transcription-polymerase chain reaction, Southern blot, and Northern blot hybridization. All four PMCA genes are expressed in the lens epithelium, the PMCA3 transcript being the most abundant. The transcripts for PMCA1, PMCA2, and PMCA4 exist in decreasing order of abundance. There is no evidence for the expression of any novel PMCA genes in bovine lens epithelium.

Animals↗