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Biomedical subjects

D Song

Publications and source records attributed to D Song.

142 records · Page 8Linked to original sources
PubMed1994

Effects of formulation, processing and storage parameters on the characteristics and stability of perflubron emulsion.

In this study, the effects of formulation, processing and storage parameters on perflubron (perfluorooctyl bromide; PFOB) emulsions were investigated. Emulsions with varying concentrations of perflubron and egg yolk phospholipid (EYP) were prepared with different processing parameters and placed at different storage temperatures. Their characteristics and stability were compared. The emulsion droplet growth rate was nearly proportional to the perflubron percentage in the range of 15-110% w/v. The initial droplet size of perflubron emulsions was inversely proportional to the concentration of EYP until a certain lower limit of droplet size was reached. The initial droplet size and droplet growth rate of perflubron emulsion were strongly dependent upon the processing parameters. The logarithmic value of the droplet growth rate decreased linearly with l/T in the range of 5-40 degrees C. The formulation and processing parameters are the key variables to be optimized to achieve better emulsion characteristics and stability.

Drug Stability↗
PubMed1992

Molecular cloning and expression of Bacillus subtilis bglS gene in Saccharomyces cerevisiae.

A 2.7-kb EcoRI DNA fragment carrying a Bacillus subtilis endo-beta-1,3-1, 4-glucanase gene (bglS) from the E. coli plasmid pFG1 was cloned into an Escherichia coli/yeast shuttle vector to construct a hybrid plasmid YCSH. The hybrid plasmid was used to transform Saccharomyces cerevisiae, and the bglS gene was expressed. Variation between levels of bglS gene expression in S. cerevisiae was about 2.3-fold, depending on the orientation of the 2.7-kb DNA fragment. Assay of substrate specificity and optimal pH of the enzyme demonstrated that the enzyme encoded by YCSH (bglS) was identical with that found in B. subtilis, but the expression level of bglS gene in S. cerevisiae (YCSH) was much lower than that in E. coli (YCSH).

Bacillus subtilis↗
PubMed1992

Aging Koreans' perceived conflicts in relationships with their offspring as a function of age, gender, cohabitation status, and marital status.

The Youn Scale was used to assess aging Koreans' perceived conflicts in relationships with their adult offspring. The sample consisted of 623 elderly Koreans between the ages of 55 and 84 years. Results indicated that aging Koreans experienced significantly more conflicts in their relationships as they grew older. There were also differences in the perceptions of problems in relationships with their offspring between those who lived together with their adult children and the those who did not, and also between those who were married and those who were single. The findings imply that aging Koreans want to have qualitatively better (i.e., warmer and closer) relationships with their offspring, regardless of their bereavement status and cohabitation status.

Age Factors↗
PubMed1992

Drop size stability assessment of fluorocarbon emulsions.

The aging of fluorocarbon emulsions prepared with natural egg yolk phospholipids (EYP) has been studied and a linear variation (r2 greater than 0.95) of the mean average volume of the droplets with time has been observed. The slope of the experimental lines, called "Stability Parameter, S" can thus be taken as a representation of the rate of aging of the emulsions. Examples are given of use of parameter S to assess the effect of formulation and processing parameters on the stability of diverse fluorocarbon emulsions. S is a useful tool to compare emulsions and ascertain any factors of stabilization/destabilization.

Blood Substitutes↗
PubMed1992

Inhibition of 11 beta-hydroxysteroid dehydrogenase by gossypol and bioflavonoids.

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) oxidizes hydrocortisone to inactive cortisone in the kidney and is an important regulator of renal K+ clearance. Gossypol, in clinical trials as an antifertility drug for men in China, was associated with episodes of hypokalemia. To learn whether gossypol and other structurally similar compounds in plants can inhibit 11 beta-OHSD activity, purified enzyme from rat liver and in human renal cortical microsomes was studied. Rat liver enzyme was inhibited by glycyrrhetinic acid > gossypol >> morin > quercetin >> rutin. Glycyrrhetinic acid, gossypol, and morin inhibited activity of the human kidney enzyme. Enzyme in microsomes from five human kidneys had an IC50 (S.D.) of 1.5 (1.2) mumol/L for glycyrrhetinic acid; enzyme in microsomes from six human kidneys had a 50% inhibitory doses of 147 (25) mumol/L for gossypol. Our observations indicate that gossypol and other compounds in plants can inhibit 11 beta-OHSD activity and may thereby increase K+ excretion.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1992

[Effects of benzyltetrahydropalmatine on rat portal vein and guinea pig myocardium].

In isolated rat portal vein, benzyltetrahydrophalmatine (BTHP) 0.3-100 mumol.L-1 dose-dependently increased the spontaneous mechanical activity. However, BTHP 300 mumol.L-1 showed an inhibitory effect on the spontaneous contraction. BTHP 200 mumol.L-1 reversed positive staircase phenomenon to negative ones in left atrium of guinea pig and inhibited the amplitude and Vmax and shortened the action potential duration (APD50) of the slow action potentials induced by high K+ (24 mmol.L-1) in guinea pig papillary muscles. BTHP reduced also the contractile force in papillary muscles of guinea pig. These results suggest that BTHP possesses calcium antagonistic effect in high concentration.

Action Potentials↗
PubMed1991

Pheromone-dependent phosphorylation of the yeast STE12 protein correlates with transcriptional activation.

Haploid a and alpha cells of yeast respond to the pheromones alpha- and a-factor, respectively, by increasing the transcription of many genes whose products are essential for mating. The STE12 protein acts in this process by binding to the DNA sequence that mediates the increased transcription of pheromone-responsive genes. We show here that a hybrid protein containing STE12 fused to the DNA-binding domain of GAL4 can activate transcription of a reporter gene containing GAL4-binding sites but only after treatment of cells with pheromone. Thus, STE12 alone, when bound to DNA, is sufficient to mediate pheromone-induced transcription. By constructing hybrids of different STE12 regions with the GAL4 domain, we map the domain of STE12 necessary for this activation to the central third of the protein. Upon alpha-factor treatment, the hybrid of GAL4 with the complete STE12 sequence is rapidly phosphorylated, with kinetics consistent with the observed transcriptional induction of pheromone-responsive genes. The domain of STE12 necessary for this phosphorylation correlates with that involved in transcriptional activation. We propose that induction of pheromone-responsive genes is mediated by phosphorylation of STE12 to alter its activation function but not its DNA-binding ability.

Binding Sites↗
PubMedDate not supplied

Fine mapping of the antigen-antibody interaction of scFv215, a recombinant antibody inhibiting RNA polymerase II from Drosophila melanogaster.

A bacterially expressed single chain antibody (scFv215) directed against the largest subunit of drosophila RNA polymerase II was analysed. Structure and function of the antigen binding site in scFv215 were probed by chain shuffling and by site-specific mutagenesis. The entire variable region of either the heavy or light chain was replaced by an unrelated heavy or light chain. Both replacements resulted in a total loss of binding activity suggesting that the antigen binding site is contributed by both chains. The functional contributions of each complementarity determining region (CDR) were investigated by site specific mutagenesis of each CDR separately. Mutations in two of the CDRs, CDR1 of light chain and CDR2 of heavy chain, reduced the binding activity significantly. Each of the amino acids in these two CDRs was replaced individually by alanine (alanine walking). Seven amino acid substitutions in the two CDRs were found to reduce the binding activity by more than 50%. The data support a computer model of scFv215 which fits an epitope model based on a mutational analysis of the epitope suggesting an alpha-helical structure for the main contact area.

Alanine↗