PubMed Health⌕ Search

Biomedical subjects

W Guan

Publications and source records attributed to W Guan.

46 records · Page 3Linked to original sources
PubMed1995

[Experimental study on rapid expansion of soft tissue].

Nine white pigs weighing about 15 kg were divided into three groups: rapid expansion group (REG), conventional expansion group (CEG) and control group (CON). Expansion was carried out under monitoring of interal pressure of the expander and blood flow of the skin over the expander. After completion of expansion, hemodynamic, physical, histologic and ultrastructure changes of the expanded skin were measured and recorded. The study showed: (1) The immediate retraction ratios of skin of three groups were 41.37%, 20.82% and 10.01%, respectively (P < 0.01). (2) The thickness of the epidermis of the three groups was not statistically different, though the dermis of the expanded skin was thinner than that of the control (P < 0.01). (3) The density of collagen in the dermis of the three groups was 80.57 +/- 5.47, 79.49 +/- 6.31 and 82.72 +/- 2.69, respectively; the density of elastin of the three groups was 2.88 +/- 1.24, 2.77 +/- 0.74 and 2.56 +/- 0.63, respectively (P < 0.05). We concluded that the delay phenomenon of the expanded flap depends mainly on the intensity of expansion. The immediate retraction ratio of the rapidly expanded skin was greater than that of conventionally expanded skin. Rapid expansion also results in tissue hypertrophy but does not cause destruction of collagen. With proper calculating the size of the defect and estimating immediate skin retraction, rapid expansion is feasible in clinical applications.

Animals↗
PubMed1995

[Adherent mechanism of the mutans of Actinomyces viscosus T14V].

Three mutans of Actionmyces viscous T14V lacking type1 (5951), type 2 (5519) and both types of fimbriae (147) were selected in this study. We compared the ability of their adsorption to the test-tube wall, the result of the cellular coaggregation between these mutant strains and Streptococcus sanguis 34, Streptococcus sanguis black bova, Streptococcus mutans ingbritte, Streptococcus sobrinus 6715 and analysed the chemical characterization of cell walls of the three mutans. We found that the specific fimbriae and cell hydrophobicities had great effect on the bacteria adsorption or coaggregation.

Actinomyces viscosus↗
PubMed1994

[Experimental study on adipocyte culture in vitro].

The adipocyte belongs to a kind of end cells. Most people take a skeptical attitude to its ability of proliferation in vitro. Based on foreign scientists' experience in this aspect. We isolated rats' adipocytes with percoll-density-gradient procedure. Using compound medium of DMEM and F12 with glucocorticoid, insulin and basic fibroblast growth factor (bFGF), we have succeeded in culturing fat cells in vitro.

Adipocytes↗
PubMed1994

[Mandibular advancement for the treatment of micrognathia with obstructive sleep apnea].

Fifteen patients with micrognathia and obstructive sleep apnea syndrome (OSAS) are presented. All patients were evaluated before and after surgery by physical examinations, cephalometric, fibroptic pharyngoscopy and oxygen saturation (SaO2). A method that allows isolated advancement of the genial tubercle and genioglossus muscle is described. The operation could enlarge the pharyngeal airway space at the base of the tongue (P < 0.05), increase SaO2 and decrease MP-H (P < 0.05) so that the symptoms of OSAS improved or disappeared. The facial symmetry and chin prominence also improved significantly. This method is simple and effective for the treatment of OSAS due to micrognathia and obviates the need for intermaxillary fixation. But it is not indicated for patients with severe malocclusion or airway obstruction on more than one sites.

Adolescent↗
PubMed1994

Mechanisms of up-regulation of D2L dopamine receptors by agonists and antagonists in transfected HEK-293 cells.

Mechanisms underlying agonist- and antagonist-induced up-regulation in HEK-293 cells transfected to express D2 dopamine receptors were investigated. We have reported previously that exposure of cells to agonists and antagonists led to an increase in the density of receptors. The time course of up-regulation on exposure to (-)-sulpiride, a D2 dopamine-selective antagonist, was measured. A lag in the effect of antagonists not seen with up-regulation induced by exposure to agonists was observed. Effects of N-propylnorapomorphine were synergistic with those of cyclic AMP analogs, however, synergistic effects between (-)-sulpiride and cyclic AMP analogs were not observed. These findings suggest that separate mechanisms may be involved in agonist- and antagonist-induced up-regulation. Changes in mRNA levels did not appear to account for the increase in receptors after agonist or antagonist treatment. Results of experiments with cycloheximide, a protein-synthesis inhibitor, suggest that increased protein synthesis, and not decreased protein degradation, is responsible for up-regulation by both NPA and (-)-sulpiride. Studies monitoring receptor recovery after treatment with N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline, an irreversible alkylating agent, suggest that rates of receptor incorporation into membranes are increased after treatment with either an agonist or an antagonist.

Apomorphine↗
PubMed1994

[Experimental study of changes in biomechanical properties of pig skin after rapid expansion].

The purpose is to evaluate the biomechanical properties of conventional skin expansion, rapid expansion and unexpanded skin. In four pigs, 240 ml expanders of square shape are placed. The flaps are divided into three groups: (1) Rapid expansion flap: the expander is inflated daily until maximum volume is obtained. (2) Conventional expansion flap: inflation is done weekly. (3) Unexpanded skin is used as control. By using the tensometer, the skin is evaluated for stress strain, stress relaxation, density of strain energy, parameters of strength, and a mathematical model is obtained. We conclude that the biomechanical properties of the expanded skin are different from that of the unexpanded skin. But the biomechanical properties of conventional expanded skin are similar to that of rapid expanded skin. It is shown that the rapid expansion may be accepted in the practice.

Animals↗
PubMed1993

Paradoxical regulation of dopamine receptors in transfected 293 cells.

Selective expression of subtypes of receptors in mammalian cell lines permits the study of the regulation of receptors in a homogeneous population of cells growing under controlled conditions. cDNAs encoding the human D2L and D2S receptors were ligated into a eukaryotic expression vector, pRc/CMV. The resulting plasmid, which contains a cytomegalovirus promoter for high expression levels, was used for stable transfection of 293 cells, a human kidney cell line. Expression of D2L and D2S receptors in 293 cells was confirmed by radioligand binding assays with [125I]NCQ 298. The pharmacological properties of the expressed receptors were comparable to those of receptors in rat striatal homogenates and in other transfected cell lines. D2L and D2S receptors were coupled to inhibition of cAMP accumulation in 293 cells. Incubation of 293-D2L cells with agonists resulted in an increase in the density of D2 receptors without a change in the affinity of the receptors for [125I]NCQ 298. This effect was time dependent, with a t1/2 of approximately 6 hr. The dose dependence of up-regulation followed the pharmacological profile expected of a D2 receptor, with an order of potency of N-propylnorapomorphine (NPA) > quinpirole > dopamine. The density of receptors was further increased by incubation of cells with agonist together with forskolin or 8-bromo-cAMP. D2S receptors responded similarly to D2L receptors to treatment with NPA and forskolin. Exposure of 293-D2L cells to the beta-adrenergic receptor agonist isoproterenol did not change the density of D2L receptors. Similarly, NPA had no effect on levels of endogenously expressed beta-adrenergic receptors in 293-D2L cells, as assayed by binding of [125I]iodocyanopindolol. Levels of beta-adrenergic receptors in transfected 293-beta 2 or 293-D2L cells did not increase after exposure to NPA but decreased after exposure to isoproterenol. Cells expressing D2L receptors were incubated with antagonists, including SCH-23390, sulpiride, haloperidol, clozapine, and epidepride, alone or in combination with NPA. Incubation of cells with SCH-23390 had no effect on the density of D2 receptors, and SCH-23390 did not block the effect of NPA. D2-selective antagonists increased the density of receptors. D2L receptor mRNA levels were unchanged during agonist treatment. This suggests a role for translational or post-translational mechanisms in the regulation of D2 receptor levels in transfected cell lines.

8-Bromo Cyclic Adenosine Monophosphate↗