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Biomedical subjects

M F Zhang

Publications and source records attributed to M F Zhang.

11 recordsLinked to original sources
PubMed1992

Chemical synthesis, molecular cloning, and expression of the gene coding for the Trichosanthes trypsin inhibitor--a squash family inhibitor.

The gene coding for a Trichosanthes trypsin inhibitor analog (Ala-6-TTI) in which methionine at position 6 was replaced by alanine was synthesized chemically. The synthetic gene was cloned into plasmid pWR590-1 and expressed in Escherichia coli as a fusion protein composed of beta-galactosidase fragment of 590 amino acid residues and (Ala-6)-TTI, with methionine as a connecting residue. After cyanogen bromide cleavage and reduction of the fusion protein, followed by refolding with trypsin-Sepharose 4B as a matrix and affinity chromatography on the immobilized enzyme, the fully active (Ala-6)-TTI was obtained. The trypsin inhibitory activity and amino acid composition of the recombinant (Ala-6)-TTI were consistent with those of the natural one. The (Ala-6)-TTI gene was also cloned into the secretion expression vector, pVT102U/alpha, in Saccharomyces cerevisiae. In order to make the reading frame of the gene compatible with the vector, a nucleotide was inserted into the (Ala-6)-TTI gene via site-directed mutagenesis. The secreted (Ala-6)-TTI was purified and found to be correctly processed at the junction between the alpha-factor leader peptide and (Ala-6)-TTI downstream. Of the two expression systems, the latter is more advantageous in the high yield (greater than 2 mg/liter), easy purification and needlessness of disulfide refolding.

Amino Acid Sequence↗
PubMed1992

Sensitive and selective liquid-chromatographic assay of fluoxetine and norfluoxetine in plasma with fluorescence detection after precolumn derivatization.

We determined fluoxetine (Prozac) and its major metabolite norfluoxetine in plasma by liquid chromatography with fluorescence detection. After liquid-liquid extraction from 1 mL of plasma, the extract was derivatized at room temperature with dansyl chloride, and the highly fluorescent derivatives were chromatographed with a reversed-phase C18 column and a mobile phase of phosphate buffer and acetonitrile. Dansylated fluoxetine, norfluoxetine, and the internal standard were eluted in less than 14 min with no interference from endogenous material. The calibration curve was linear over the concentration range 25-800 micrograms/L with inter- and intra-assay imprecision (CV) of less than 10%. Validity of the assay was checked by comparing results for 110 patients' samples with those by a liquid-chromatographic method with ultraviolet detection (r = 0.993 for fluoxetine, 0.957 for norfluoxetine). The identity of the dansylated derivatives was verified by positive chemical ionization mass spectroscopy. The lower limit of detection was approximately 3 micrograms/L. Because no major antidepressant, neuroleptic, or respective drug metabolites interfere with the quantification of fluoxetine and norfluoxetine, this is a useful procedure for pharmacokinetic studies and in clinical settings.

Chromatography, Liquid↗
PubMed1990

[Studies on sensor for L-ascorbic acid using biotissue slice].

Bioselective membrane electrode for L-ascorbic acid has been made with tissue slices. It is made from porcine liver tissue slice covering an oxygen electrode. The influence of buffer mediator, pH, temperature, antiseptics, slice thickness, etc. on the response characteristics of the electrode was examined. In the presence of copper ions, a linear relationship between dynamic response of the electrode and the logarithm of concentration of L-ascorbic acid was observed for the range of 21.14 micrograms/ml to 352.3 micrograms/ml, with a correlation coefficient of 0.9996 and the Michaelis constant of 0.8 mmol/L. The electrode has been used to determine L-ascorbic acid in drugs, the analytical results were satisfactory.

Animals↗
PubMed1989

Treatment of typhoid fever with ofloxacin.

Ofloxacin, 300 mg 12-hourly, was given orally to 64 patients with typhoid fever, all with positive blood cultures. Almost 80% of the isolates were resistant to chloramphenicol, ampicillin and co-trimoxazole, but sensitive to ofloxacin and norfloxacin. Fever subsided within five days in most patients (mean 3.2 +/- 1.1), rates of clinical effectiveness and bacteriological cure both being 100%. Thirty patients were followed for 1-3 months after the completion of therapy with no occurrence of relapse.

Adolescent↗
PubMed1989

A study on tea-pigment in prevention of atherosclerosis.

Since Lou Fu-qing et al first reported that tea had effect on the prevention of atherosclerosis (AS) in the 1960s, we have conducted experimental and clinical studies, and found that tea-pigment (TP) could reduce blood coagulability, increase fibrinolysis, prevent platelet adhesion and aggregation, and decrease cholesterol content in aortic walls in vivo (P less than 0.01). In addition, TP was shown to inhibit the proliferation of cultured human aortic smooth muscle cells in normal and elevated LDL circumstance in vitro (P less than 0.01), and decreased the level of T x B2 in platelet-rich plasma and remote myocardial infarction patients (P less than 0.01). TP can be used in the prevention of AS.

Animals↗
PubMed1989

[Efficacy of ofloxacin in treating typhoid fever].

We studied 75 patients (36 males and 39 females), suffering from typhoid fever. 64 patients were treated with ofloxacin and 11 with amikacin, dosage regimens of the two drugs were 300 mg and 300-400 mg twice daily. Clinical effective rate was 100% with ofloxacin and 36.4% with amikacin. A total of 72 strains of salmonella typhi was isolated from all the patients of both groups. Bacteriological elimination rate was 100% with ofloxacin after treatment. Sensitive rates for S. Typhi isolated was 100% with ofloxacin, norfloxacin and ceftriaxone, 98.6% with amikacin and 20-21.4% with chloramphenicol, ampicillin and sulfamethoxazole Co. There were fewer adverse reactions and better acceptance, one had skin rash and one had gastrointestinal disturbance. In amikacin group, abnormality of urine routine and serum creatinine was observed. Ofloxacin was well absorbed orally. Its high bioavailability, satisfactory therapeutic efficacy excellent tolerability and convenience for use make it a very useful medication in the therapy of typhoid fever resulted from multiresistant strains.

Adolescent↗
PubMed1989

[Antidiarrheal and anti-inflammatory effects of berberine].

Berberine sulfate (Ber) 40 and 80 mg/kg ig reduced the purging effects of castor oil or Cassia angustifolia leaf in mice, but did not affect the gastrointestinal transport function of Chinese ink in normal mice. Ber 60 mg/kg ig significantly inhibited the increased vascular permeability induced by ip 0.7% acetic acid in mice. Ber 20 and 50 mg/kg sc markedly inhibited the increased vascular permeability induced by histamine 100 micrograms/0.1 ml ic in rats. Ber 4 and 8 mg/kg sc produced obvious inhibition in the xylene-induced swelling of mouse ear. The anti-inflammatory effects were enhanced in a dose-dependent manner. It is suggested that the antidiarrheal effect of Ber is relative to its restriction against exudative inflammation to a certain extent.

Animals↗