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Biomedical subjects

Z L Wang

Publications and source records attributed to Z L Wang.

At least 19 recordsLinked to original sources
PubMed1992

Reflection electron energy-loss spectroscopy and imaging for surface studies in transmission electron microscopes.

A review is given on the techniques and applications of high-energy reflection electron energy-loss spectroscopy (REELS) and reflection electron microscopy (REM) for surface studies in scanning transmission electron microscopes (STEM) and conventional transmission electron microscopes (TEM). A diffraction method is introduced to identify a surface orientation in the geometry of REM. The surface dielectric response theory is presented and applied for studying alpha-alumina surfaces. Domains of the alpha-alumina (012) surface initially terminated with oxygen can be reduced by an intense electron beam to produce Al metal; the resistance to beam damage of surface domains initially terminated with Al+3 ions is attributed to the screening effect of adsorbed oxygen. Surface energy-loss near-edge structure (ELNES), extended energy-loss fine structure (EXELFS), and microanalysis using REELS are illustrated based on the studies of TiO2 and MgO. Effects of surface resonances (or channeling) on the REELS signal-to-background ratio are described. The REELS detection of a monolayer of oxygen adsorption on diamond (111) surfaces is reported. It is shown that phase contrast REM image content can be significantly increased with the use of a field emission gun (FEG). Phase contrast effects close to the core of a screw dislocation are discussed and the associated Fresnel fringes around a surface step are observed. Finally, an in situ REM experiment is described for studying atomic desorption and diffusion processes on alpha-alumina surfaces at temperatures of 1,300-1,400 degrees C.

Aluminum Oxide↗
PubMed1992

[Experimental study of preventing liver cirrhosis by using four kinds of Chinese herbs].

UNLABELLED: 55 rats were divided into six groups; (1) normal control, (2) cirrhosis control, (3-6) Chinese herbs groups, 2-6 groups were liver cirrhosis model caused by combined factor dominated by CCl4, and 3-6 groups were given Chinese herbs simultaneously until the end of sixth week. Radix Salviae miltlorrhizae (RSM) were used in group 3, Flos Carthami (FC) in group 4, Radix Angelicae sinensis (RAS) in group 5, Semen persicae (SP) in group 6. THE RESULTS: in group 2, 7 out of 9 rats developed into cirrhosis, the degree of fibrosis was 2.55+ and collagen protein content was 35.3 mg/g.liver, SGPT 387u. In group 3(RSM), no cirrhosis was found, the degree of the fibrosis was 0.43+ (compared with group 2, P < 0.01, collagen protein content was 16.7 mg/g.liver (P < 0.01), SGPT 132u (P < 0.01). In group 4(FC), 8 out of 9 rats did not develop into cirrhosis, collagen content 21.1 mg/g.liver, compared with group 2, P < 0.05. In the group of 5 and 6, some rats were developed into cirrhosis. The result showed that RSM and FC possessed an inhibitory effect on fibrogenesis. The effect of RSM was remarkable. It could prevent experimental cirrhosis. The effect of RAS and SP were uncertain. This experiment predicted that RAM would become the promising drug to restrain chronic hepatic disease from developing into cirrhosis clinically.

Animals↗
PubMed1992

[Effect of intraventricular administration of histamine and its receptor agonists on pentagastrin-induced gastric acid secretion in rats].

The present study shows the dual effects of intraventricularly injected histamine (0.25-2.0 micrograms/5 microliters) on pentagastrin-induced gastric acid secretion. Male Wistar rats weighing 200-300 g were anesthetized with intraperitoneal sodium pentobarbital. Gastric acid was continuously washed out with 37 degrees C saline solution by means of a perfusion pump. On the background of continuous intravenous infusion of pentagastrin [7.5 micrograms/(kg.h),] histamine (0.25 microgram/5 microliters) or 2-pyridylethylamine (PEA, 10 micrograms/5 microliters), a H1-receptor agonist, was injected into the third ventricle through a chronically implanted canula. The acid output decreased 10 min after injection and did not recover at 90 min. When the dose of histamine was increased to 1.0 micrograms or 2.0 micrograms, dual effects appeared. The acid output decreased respectively in 73% or 50% of the animals, while in the rest 27% and 50% of the animals, the acid output increased. H2-receptor agonist dimaprit (10 micrograms/5 microliters, i.c.v.) or impromidine (0.1 micrograms/5 microliters, i.c.v.) had no pronounced effect on pentagastrin-induced acid secretion. Pretreatment with diphenhydramine (16 micrograms/0.2 ml or 32 micrograms/0.2 ml, i.m.) abolished the inhibitory effect of histamine and PEA on acid secretion. These results suggest that histamine may be involved in the central regulation of gastric acid secretion, and the inhibitory effect may be mediated by H1-receptors in the brain. The mechanism underlying the production of the dual effects of histamine is unknown.

Animals↗
PubMed1992

HDL and apolipoprotein A1 (apo A1). Their effects on retardation of lipid deposition in aortic intima.

The aim of this study is to clarify whether apo A1 displays a similar role as that of HDL in preventing the development of experimental atherosclerosis. Results were obtained from 4 groups of experiments. (1) Result from 4 successive experiments of tree shrews indicated that high serum HDL level is the main factor in preventing the development of experimental atherosclerosis; (2) Results from 4 successive experiments in rabbits showed that both HDL and apo A1 were able to decrease the extent of lipid deposition and atheromatous lesion developed in the aortic intima; (3) Apo A1 also inhibited the number of monocytes/macrophages infiltrated in aortic intima at the initial stage of fatty streak formation; (4) Similar as HDL, apo A1 phospholipid liposomes promoted markedly the clearance ability of smooth muscle cells on intracellular cholesterol. Conclusively, apo A1 is effective in preventing the development of experimental atherosclerosis. Further study, however, is required to detect an ideal combination of apo A1 with other component, e.g., phospholipid.

Animals↗
PubMed1992

[Interaction of foamy cells from experimental hyperlipemia rabbits with smooth muscle cells and the endothelial surface of intima preparation].

In the development of atherosclerosis (AS), circulating monocytes emigrate into and accumulate in the intima as foamy cells. Interaction of the lipid laden macrophage (M phi) with cells of the arterial wall may contribute to the formation of atheromatous plaque. Using subcutaneous and peritoneal foamy cells (FC) collected from diet-induced hyperlipemia rabbits, the authors observed the influence of lipid laden on macrophage's functions relevant to AS lesion formation. In comparison with normal M phi, peritoneal FC were 4.8 and 5.4 fold more adhesive to the endothelial surface of intima preparation and the smooth muscle cells (SMC), while the adhesion rate produced by subcutaneous FC were increased 0.79 and 0.16 fold. SMC migration stimulated by both FC-conditioned medium slowed 5.78 and 5.90 fold increased respectively as in comparing with the control's, whereas normal M phi-conditioned medium only gave a 2.3 fold increase of SMC migration stimulation. In addition, both FC-conditioned medium stimulated SMC growth making 1.96 and 2.59 fold increase, and normal M phi-conditioned medium produced a 1.3 fold increase as compared with the control's. The results suggest that lipid-laden macrophages, may accelerate AS development due to changes of their biological properties. Since more than 95% of peritoneal macrophages as well as macrophages in the pleura, pericardial and synovial cavities from experimental hyperlipidemia rabbits are fully filled with lipid assuming the morphologic characteristics of atheromatous intimal foamy cells, it is considered that these cells will be valuable as the model.

Animals↗
PubMed1991

Vascular effects of tetramethylpyrazine: direct interaction with smooth muscle alpha-adrenoceptors.

The interaction of tetramethylpyrazine, a vasoactive ingredient of a Chinese traditional medicinal plant, with the vascular muscle alpha 1-adrenoceptors was investigated by a direct radioligand binding technique using [3H]prazosin and vascular smooth muscle microsomes isolated from dog aorta and mesenteric artery. Tetramethylpyrazine inhibited the binding of [3H]prazosin to vascular muscle membranes in a concentration-dependent manner at a suboptimal concentration of prazosin. Scatchard analysis of the effect of tetramethylpyrazine on the saturation profile of [3H]prazosin binding to vascular muscle microsomes of either arterial muscle indicated a substantial increase of Kd values (the affinity for prazosin) without a change in Bmax (maximal binding sites for prazosin). Thus, the present results provide supporting evidence that the inhibitory effect of tetramethylpyrazine on the vasoconstriction of dog mesenteric artery induced by phenylephrine in the earlier studies may be, at least, in part due to a direct action at the recognition sites of alpha 1-adrenoceptors. Amiloride and amiloride-related compounds, which shares a common pyrazine ring structure with tetramethylpyrazine and other related derivatives, also inhibits the binding of [3H]prazosin to aortic muscle microsomal membranes. Functional studies of dog saphenous vein also indicated that both tetramethylpyrazine and its ethyl derivatives inhibited the responses induced by phenylephrine and B-HT 920 in the presence and absence of extracellular Ca2+. Together with our earlier findings that amiloride also inhibits [3H]prazosin and [3H]rauwolscine binding to vascular muscle alpha 1- and alpha 2-adrenoceptors, the present radioligand binding study in canine arteries and functional study in saphenous veins suggest that the above compounds containing the pyrazine nucleus indeed interacted at the alpha-adrenoceptor sites.

Adrenergic alpha-Agonists↗
PubMed1991

Imaging friction tracks at diamond surfaces using reflection electron microscopy.

Reflection electron microscopy (REM) is applied to image the structure of polished natural diamond (001) surfaces (of 5 x 4 mm size) after friction experiments under a pressure below the critical value. Friction tracks marked by a diamond needle after a single pass movement under a pressure of 13 GPa can be seen in REM images and show non-uniform contrast. The surface shows relatively dark image contrast at the light contacted area, which is possibly due to the structural modification at the top atomic layer. The high local contacting pressure pushes part of the needle into the surface which causes fracture, resulting in the formation of grooves at the surface. It is possible to have plastic deformation in this process, but no evidence has been found for the presence of cracking. The observations support the adhesion frictional mechanism rather than the micro-cleavage model.

Carbon↗
PubMed1991

Inhibitory effects of tetramethyl and tetraethyl derivatives of pyrazine on dog saphenous vein.

The effects of two structurally similar pyrazine derivatives, tetramethylpyrazine (TMP) and tetraethylpyrazine (TEP) on the contractile responses of dog saphenous vein to KCl (via membrane depolarization), phenylephrine (PHE, alpha 1-adrenergic agonist), and B-HT 920 (alpha 2-adrenergic agonist) were investigated. The relaxant or inhibitory effect of TMP and TEP was most potent on KCl-induced responses and least potent on PHE-induced responses. Their effect on KCl-induced responses was more prominent at 30 mM KCl than at 100 mM KCl. In Ca(2+)-free medium, PHE and B-HT 920 elicited transient responses, which were also markedly and reversibly inhibited by TMP and TEP. Similar results were also obtained when prostaglandin F2 alpha was used as an agonist. In all four types of contractile responses involving different receptors, the inhibitory effect of TEP was consistently more potent than that of TMP. We conclude that both TMP and TEP behave as a nonselective smooth muscle relaxant having similar and multiple actions including their general interference with the processes involving both Ca2+ entry and intracellular Ca2+ release.

Animals↗
PubMed1991

Alpha-adrenoceptors in vascular smooth muscle: all is not well.

Studies of binding interactions and contractile responses of vascular muscles at alpha 1- and alpha 2-adrenoceptors revealed the following. (1) Agonists at alpha 1- and alpha 2-adrenoceptors may achieve selectivity by virtue of different efficacies despite similar affinities at the two receptors as well as by differing affinities. This implies that their potencies in binding studies may not correlate with potencies in response and that an agonist may produce positive or negative interactions by occupying both alpha 1- and alpha 2-receptors. (2) Agonists at alpha 2-adrenoceptors have the ability in some vascular muscles to release internal Ca2+ (implying an inositol triphosphate mechanism) as well as open Ca2+ channels. However, their contractile abilities are not closely related to function of Na+/H+ or Na+/Ca2+ exchange sites. Amiloride derivatives probably inhibit contractile effects of alpha-agonists and K+ elevation by an action at sites distal to the receptor or Ca channels. (3) The failure of alpha 2-agonists to contract arteries in vitro is not related to the absence of these receptors but most likely to their uncoupling from contractile responses, possibly owing to changes related to the in vitro condition (loss of modulating endogenous substances present in vivo such as angiotensin II or endothelins or to changed physical conditions such as may alter function of stretch-activated channels).

Amiloride↗
PubMed1991

[The study of major anaerobic bacteria from subgingival plaques of juvenile periodontitis].

The studies of the subgingival plaques from juvenile periodontitis (JP) have shown that JP is associated with Haemophilus actinomycetemcomitans (H. a), Capnocytophaga (Capno.) and other species. This study was designed to study these species with Chinese JP patients using selective cultivable technique. The media used include TSBV to support H. a, TBBP to support Capno. and selective media for Bacteroides gingivalis. A total of 303 subgingival samples were collected from 43 JP, 31 gingivitis and 13 normal juvenile. It was found that the recovery rates of H. a and Capnocytophaga in JP group were higher than that in two other groups. The Black-pigmented Bacteroides had a similar recovery rate in JP and gingivitis groups, but higher than that in periodontal healthy group. The bacterial counts and the correlation analysis between bacteria findings and clinical indices were consistent with the above results.

Adolescent↗
PubMed1990

Electrophoresis and movements of fluorescence pattern after photobleaching of large DNA fragments in agarose gels.

By combining electrophoresis with movements of fluorescence pattern after photobleaching (MOFPAP), which is abbreviated as EMOFPAP, we are able to measure electrophoretic mobilities of large DNA fragments in an agarose gel within a fairly short time scale (about 10 min or even down to 1 min). The new method represents a significant improvement in experiment time when compared with the time (typically on the order of hours) required to determine the average electrophoretic mobility of large DNA fragments in agarose gels by means of either conventional gel electrophoresis or pulsed-field gel electrophoresis. In this article, we present the EMOFPAP experimental setup and consider optical conditions, including beam profile geometry and fluorescence pattern formation. A realistic formula that can explain the parameters governing the EMOFPAP method using our present optical setup has been derived. A comparison of results between experimental and computer simulation data is made, and an optimization of the EMOFPAP method is proposed.

DNA↗
PubMed1990

Surface microanalysis by reflection electron energy-loss spectroscopy.

Several basic physical concepts of applying eq. Ik = I sigma Nxt to surface microanalysis by reflection electron energy-loss spectroscopy (REELS) are clarified. Here Ik and I are the integrated intensities of the core ionization edge and the low loss part, sigma is the scattering cross section of element x with atomic concentration Nx, and t is the specimen thickness. The reflected inelastic electrons are found to be distributed almost symmetrically around the Bragg spots and can be reasonably described by a Lorentzian function. EELS microanalysis can be performed by using the diffracted spots. The omega correction, arising from the angular contributions of the neighbouring spots into the spectrometer collecting aperture, is required to be considered.

Magnesium Oxide↗
PubMed1990

Inhibitory effects of amiloride on alpha adrenoceptors in canine vascular smooth muscle.

Amiloride inhibits vascular smooth muscle contractions from canine aorta and saphenous vein. The mechanisms were studied using radioligand binding and functional techniques. Amiloride inhibited [3H]prazosin and [3H]rauwolscine binding to alpha-1 and alpha-2 adrenoceptors in a concentration-dependent manner. Amiloride increased Kd values for [3H]rauwolscine without affecting the maximum binding of [3H]prazosin. These results suggest that the drug interacts with the alpha-1 adrenoceptor binding sites in a competitive manner and with the alpha-2 adrenoceptor binding sites in a noncompetitive manner. Amiloride reduced maximal contractile responses to agonists selective for both alpha adrenoceptors and to elevated K+, the EC50 values were increased by about 10-fold in the presence of amiloride. In Ca+(+)-free Krebs' solution, contractions induced in saphenous vein after addition of Ca++ in saphenous vein in the presence of adrenoceptor agonists were inhibited by amiloride. Our results suggest that amiloride reduced alpha-1 and alpha-2 adrenoceptor-mediated responses and inhibited Ca++ influx.

Adrenergic alpha-Antagonists↗
PubMed1990

[A preliminary study on the role of interleukin-1 in chronic lung disease].

Pulmonary alveolar macrophages (PAM) obtained by bronchoalveolar lavage in 13 normal individuals, 17 lung cancer patients and 10 patients with chronic obstructive pulmonary disease (COPD) were incubated in vitro for 24 hours. Every specimen was divided into two portions and lipopolysaccharides were used to stimulate PAMs to produce interleukin-1 (1L-1) in one. The levels of 1L-1 in normal subjects were 5547.65 +/- 2420.42 cpm/10(6) cells (stimulated) and 718.46 +/- 472.25 (unstimulated), which were higher than the 2733.20 +/- 1611.17 (stimulated, P less than 0.01) and 327.57 +/- 226.86 (unstimulated, P less than 0.05) in lung cancer patients, but lower than that of 8716.26 +/- 2977.66 (stimulated, P less than 0.05) in COPD patients. The enhanced 1L-1 activity in COPD patients might contributed to the active inflammatory process and tissue destruction of COPD. Our findings that 1L-1 activity in patients with bronchogenic carcinoma was decreased may reflect the local immune deficiency in malignant disease. The release of 1L-1 by PAMs stimulated by smoking was suggested to be associated with the development of COPD, but its role in immune response has to be determined.

Aged↗
PubMed1989

Experimental conditions for surface microanalysis with reflection electron energy-loss spectroscopy.

Experimental conditions for obtaining the optimum signal-to-background (S/B) ratio in reflection electron energy-loss spectroscopy (REELS) are investigated. It is shown that the S/B ratio can be improved by lowering the incident energy of the electrons. The spectra taken from the GaAs (660) specular reflection spot under the surface resonance condition is demonstrated to have the best S/B ratio and lowest surface plasma excitation, which is capable of providing structural information on the top few atomic layers.

Electron Probe Microanalysis↗