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Biomedical subjects

Q Du

Publications and source records attributed to Q Du.

At least 55 records · Page 3Linked to original sources
PubMed1997

Investigations on the protective action of Condonopsis pilosula (Dangshen) extract on experimentally-induced gastric ulcer in rats.

The action of Codonopsis pilosula extract in 5 animal models of gastric ulcer was investigated. It was found that the extract had higher efficacy on gastric ulcer induced by stress, acetic acid and sodium hydroxide and little significant effect on ulcers induced by pyloroligature and indomethacin. The C. pilosula extract was also capable of reducing gastric acid pepsin secretion. It is possible that inhibition of gastrointestinal movement and propulsion is one of the mechanisms underlying the antiulcer action of C. pilosula extract.

Acetic Acid↗
PubMed1997

Heuristic lipophilicity potential for computer-aided rational drug design.

In this contribution we suggest a heuristic molecular lipophilicity potential (HMLP), which is a structure-based technique requiring no empirical indices of atomic lipophilicity. The input data used in this approach are molecular geometries and molecular surfaces. The HMLP is a modified electrostatic potential, combined with the averaged influences from the molecular environment. Quantum mechanics is used to calculate the electron density function rho(r) and the electrostatic potential V(r), and from this information a lipophilicity potential L(r) is generated. The HMLP is a unified lipophilicity and hydrophilicity potential. The interactions of dipole and multipole moments, hydrogen bonds, and charged atoms in a molecule are included in the hydrophilic interactions in this model. The HMLP is used to study hydrogen bonds and water-octanol partition coefficients in several examples. The calculated results show that the HMLP gives qualitatively and quantitatively correct, as well as chemically reasonable, results in cases where comparisons are available. These comparisons indicate that the HMLP has advantages over the empirical lipophilicity potential in many aspects. The HMLP is a three-dimensional and easily visualizable representation of molecular lipophilicity, suggested as a potential tool in computer-aided three-dimensional drug design.

Drug Design↗
PubMed1997

The role of cytoskeletal elements in the two-phase denucleation process of mammalian erythroblasts in vitro observed by laser confocal scanning microscope.

The cytoskeletal elements in the denucleation processes were observed using immunofluorescence and laser confocal scanning microscopy in the Friend virus (FVA) infected splenic erythroblasts of BALB/c mice. When cultured in the presence of erythropoietin (EPO), it was shown that the synchronized erythroid precursor cells proceeded to an autonomous nuclear extrusion when the three types of cytoskeletal elements were observed contributing to different phases of that process. The vimentin intermediate filament (IF) was shown as the nuclear anchorage elements with binding sites anchored from the nuclear lamina to the center as well as to the plasma membrane periphery. A dense perinuclear layer of vimentin fluorescence in erythroblasts was observable during the periods of 12, 24 and 36 hrs. in vitro culture. The amount of vimentin IF per cell was higher than that of tubulin and F-actin at 12-24 hrs. culture, but the vimentin filaments were observed to brake down and decreased steadily when the cells became differentiated into late erythroblasts at 36-48 hrs. Such an attenuation of vimentin filaments may facilitate the eccentric movement of the nucleus which can be regarded as the initial step (phase) of denucleation. The fluorescent intensity of tubulin and actin exhibited a significant rise and aggregated between the extruding nucleus and the incipient reticulocyte prior to and during the processes of denucleation, what indicated that the actin filaments and microtubules may play roles in the second phase of the denucleation process, or final commitment of enucleation. The erythroid differentiation-denucleation factor (EDDF), as an intrinsic factor, involved in the denucleation events, was also discussed.

Animals↗
PubMed1996

Modeling lipophilicity from the distribution of electrostatic potential on a molecular surface.

Molecular lipophilicity L is represented as a function of four surface electrostatic potential descriptors: L = f(B+F, B-F, B+R, B-R). Each B descriptor is computed from the products of elements of molecular surface area, delta(si), and the molecular electrostatic potential (MEP), V(ri), at the center of an area element: B = sigma(i) delta(si) V(r(i)). Octanol-water partition coefficients (P(ow)) are correlated with these four surface-MEP descriptors: log P(ow) = c0 + c1B+F + c2B-F + c3B+R + c4B-R. Good correlations are obtained for homologous series of aliphatic alcohols, amines and acids, as well as for a set of aromatic compounds with various functional groups. Within this approach, we find that the molecular fragment contributions of surface-MEP descriptions to log P are approximately additive. We have computed the values for the following fragments: -CH2-, -CH3, _COOH, -OH and -NH2. These contributions can be used to estimate the molecular lipophilicity and partition coefficients of new compounds, without additional quantum-mechanical calculations. The proposed approach provides a reasonably accurate tool that can be useful in quantitative structure-activity relations for computer-aided rational drug design. More importantly, the correlation model is conceptually simpler than previous work in the literature and can be improved systematically.

Alcohols↗
PubMed1996

Preliminary studies on the role of plasminogen activator in seminal plasma of human and rhesus monkey.

Two types of plasminogen activators (PA), tissue type (tPA) and urokinase type (uPA), were identified in the seminal plasma of both the human and the rhesus monkey. We studied the possible relationship between PA activities in the seminal plasma and the sperm counts and motility and demonstrated that: (i) PA activity in human seminal plasma from infertile patients was associated with immotile spermatozoa; (ii) the treatment of fertile men with testosterone enanthate (TE) to induce azoospermia was accompanied by an increase in seminal PA activity; (iii) when monomer T4 (isolated from multiglycosides of Tripterygium wilforddi) was administered to fertile male rhesus monkeys to induce azoospermia, PA activities in seminal plasma increased considerably; and (iv) immunocytochemistry studies showed that both uPA and PAI-1 antigens were localized on the surface of human spermatozoa, indicating that human spermatozoa were capable of binding uPA and PAI-1 through their receptors or forming a complex. These data demonstrate that seminal PA activity may be related to azoospermia, and possibly, to the fertilizing capability of spermatozoa in primates.

Adult↗
PubMed1996

Regulation of tissue-type plasminogen activator and plasminogen activator inhibitor type-1 in cultured rat Sertoli and Leydig cells.

New data are provided to show that (i) rat Sertoli cells produce two types of plasminogen activators, tissue type (tPA) and urokinase type (uPA), and a plasminogen activator inhibitor type-1 (PAI-1); (ii) both tPA (but not uPA) and PAI-1 secretion in the culture are modified by FSH, forskolin, dbcAMP, GnRH, PMA and growth factors (EGF and FGF), but not by hCG and androstenedione (delta 4); (iii) in vitro secretion of tPA and PA-PAI-1 complexes of Sertoli cells are greatly enhanced by presence of Leydig cells which produce negligible tPA but measurable PAI-1 activity; (iv) combination culture of Sertoli and Leydig cells remarkably increases FSH-induced PAI-1 activity and decreases hCG- and forskolin-induced inhibitor activity as compared with that of two cell types cultured alone. These data suggest that rat Sertoli cells, similar to ovarian granulosa cells, are capable of secreting both tPA and uPA, as well as PAI-1. The interaction of Sertoli cells and Leydig cells is essential for the cells to response to hormone stimulation for tPA and PAI-1 secretion.

Animals↗
PubMed1995

Interrelation between electrostatic and lipophilicity potentials on molecular surfaces.

Molecular electrostatics and lipophilicity are two important properties included in quantitative structure-activity relationships (QSARs) employed for rational drug design. The molecular electrostatic potential (MEP) provides information on the position, distribution, and extent of electrophilic and nucleophilic regions around a molecule. Similarly, the solvent affinity can be represented by a local phenomenological potential of semiempirical nature: the molecular lipophilicity potential (MLP). Although a simultaneous, three-dimensional display of MEP and MLP is possible, it may not provide a practical tool for comparing molecules. In this work, we deal with the simpler two-dimensional maps of the entire molecular surface projected onto an MEP-MLP plane. We analyze how these maps change with the following factors: (1) composition and molecular geometry, (2) the quality of the computation of MEP, and (3) the parameter set used for evaluating the lipophilicity potential. The approach is used to compare series of pyrazole derivatives. The methodology is useful in assessing molecular similarity, as well as in establishing the nature of differences between compounds.

Chemical Phenomena↗
PubMed1995

Hormonal regulation of tissue-type plasminogen activator and plasminogen activator inhibitor type-1 in cultured monkey Sertoli cells.

Sertoli cells play a central role in the control and maintenance of spermatogenesis. Isolated Sertoli cells of mouse and rat testes have been shown to secrete plasminogen activator (PA) and a plasminogen activator inhibitor type-1 (PAI-1) in culture. In this study, we have investigated the hormonal regulation of PA and PAI-1 activities in cultured monkey Sertoli cells. Sertoli cells (5 x 10(5) cells/well) isolated from infant rhesus monkey testes were preincubated at 35 degrees C for 16 h in 24-well plates precoated with poly(D-lysine) (5 micrograms/cm2) in 0.5 ml McCoy's 5a medium containing 5% of fetal calf serum and further incubated for 48 h in 0.5 ml serum-free medium with or without various hormones or other compounds. PA as well as PAI-1 activities in the conditioned media were assayed by fibrin overlay and reverse fibrin autography techniques respectively. The Sertoli cells in vitro secreted only tissue-type PA (tPA), no detectable amount of urokinase-type PA (uPA) could be observed. Monkey Sertoli cells were also capable of secreting PAI-1. Immunocytochemical studies indicated that both tPA and PAI-1 positive staining localized in the Sertoli cells, spermatids and residual bodies of the seminiferous epithelium; Northern blot analysis further confirmed the presence of both tPA and PAI-1 mRNA in monkey Sertoli cells. Addition of follicle-stimulating hormone (FSH) or cyclic adenosine monophosphate (cAMP) derivatives or cAMP-generating agents and gonadotrophin-releasing hormone (GnRH) agonist or phorbol ester (PMA) to the cell culture significantly increased tPA activity.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗
PubMed1994

Purification of (-)-epigallocatechin from enzymatic hydrolysate of its gallate using high-speed counter-current chromatography.

Epigallocatechin gallate (EGCG) was hydrolyzed at various concentrations of tannase under pH 6.0 at 35 degrees C, and the reaction mixtures were separated by high-speed counter-current chromatography with a two-phase solvent system composed of hexane-ethyl acetate-water (1:13:20). The best results were obtained when 2 mg/ml of the enzyme buffer solution was added to 0.3 M EGCG buffers at a rate of 0.1 ml/min. Using 10 mg of the enzyme, 342 mg of epigallocatechin were obtained at a purity of 99.1%.

Carboxylic Ester Hydrolases↗
PubMed1993

Hormonal regulation of tissue-type plasminogen activator and plasminogen activator inhibitor type-1 gene expression in cultured mouse Sertoli cells.

We have demonstrated for the first time that (i) mouse Sertoli cells predominantly secrete tPA under the action of FSH and cAMP-generating agents, whereas Leydig cells mainly produce uPA; (ii) Sertoli cells are also capable of secreting PAI-1, as well as FSH, growth factors and GnRH increase PAI-1 gene expression; (iii) the increases in tPA and PAI-1 activities by different hormones in the conditioned media of Sertoli cells correspond to the increases in the levels of tPA and PAI-1 mRNA in the cultured cells, suggesting that the synthesis of the activator-inhibitor in mouse Sertoli cells is regulated at a transcriptional level and the tPA secreted by Sertoli cells may be involved in the spermatogenesis.

Animals↗
PubMed1992

[Research on sterilization of pathogens by high electrostatic voltage method].

An experimental research has been carried out on the sterilization of four kinds of pathogens by high electrostatic method along with an inquiry into the influence of voltage waveform and the treated time on sterilization. It is concluded that pathogens can be killed efficiently by corona discharge field.

Candida albicans↗