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Biomedical subjects

L X Xu

Publications and source records attributed to L X Xu.

At least 37 records · Page 2Linked to original sources
PubMed1997

[HPLC determination of six flavonoid constituents in Ginkgo biloba leaves].

Six flavonoid constituents (quercetin, isorhamnetin, kaempferol, bilobetin, ginkgetin and sciadopitysin) were isolated from Ginkgo biloba leaves and determined by reversed phase HPLC using salvianolic acid B as internal standard. The column employed was Zorbax ODS (150 mm x 4 mm ID, 5 microns). The mobile phase consisted of solvent A (methanol) and solvent B [tetrahydrofuran--water--formic acid (34:65:1)] for gradient elution. The flow rate was 1 ml.min-1 and detection was effected at 350 nm. This method is accurate, rapid and reproducible. Analytical data for various samples were given.

Biflavonoids↗
PubMed1996

Osteoclasts in normal and adjuvant arthritis bone tissues express the mRNA for both type I and II interleukin-1 receptors.

Osteoclasts are known to play a crucial role in both physiologic and pathologic bone resorption. Moreover, it is generally agreed that IL-1 has powerful effects on osteoclastic bone resorption, although the precise cellular sites and mechanisms by which IL-1 mediates osteoclastic bone resorption remain unclear. In particular, it is still controversial whether osteoclasts can respond to IL-1 directly. The expression of mRNA for type I IL-1 receptor (IL-1RI) and type II IL-1 receptor (IL-1RII) in osteoclasts was investigated in normal and inflammatory bone tissues by in situ hybridization to determine whether osteoclasts are the target cells for IL-1 and to elucidate the mechanism by which IL-1 induces osteoclastic bone resorption. For this study, normal tibiae were obtained from newborn, young, and adult mice and rats, and inflammatory bone tissues with bone destruction were obtained from adjuvant arthritis rat models. The results showed that (a) both IL-1 receptors (IL-1RI and -II) mRNA were expressed by osteoclasts in all tissue sections of normal tibiae; (b) at the stage of the adjuvant arthritis studied, the IL-1RI mRNA was the most predominant message in osteoclasts present in the area with serious cartilage and bone destruction, whereas the expression level of IL-1RII mRNA in these osteoclasts was weak; and (c) both IL-1RI and -II mRNA were expressed by osteoblasts, as well as by osteocytes localized in the osteoid. In addition, these messages were also expressed by chondrocytes, but the signals were not detected in the chondrocytes in the zones of hypertrophy and provisional calcification. Our present study demonstrates for the first time that mouse and rat osteoclasts express IL-1RI and -II mRNA, which suggest that a primary effect of IL-1 on osteoclasts may be one of the mechanisms by which IL-1 mediates normal bone remodeling and pathologic bone resorption in chronic inflammatory diseases.

Animals↗
PubMed1995

Interleukin-10 selectively inhibits osteoclastogenesis by inhibiting differentiation of osteoclast progenitors into preosteoclast-like cells in rat bone marrow culture system.

Recombinant human interleukin-10 (hIL-10) inhibited the formation of osteoclast-like multinucleated cells in rat whole bone marrow cultures. The effect of hIL-10 on the process of osteoclast formation was further examined, since the process of osteoclast formation includes the proliferation and the differentiation of osteoclast progenitors into mononuclear preosteoclasts and the fusion of preosteoclasts into multinucleated osteoclasts. In the nonadherent bone marrow cell culture system, which was free of stromal cells and formed preosteoclast-like cells, hIL-10 significantly inhibited the formation of preosteoclast-like cells even at a very low concentration (0.5 U/ml). The strong inhibition appeared even after treatment with hIL-10 for only the first 24 h of the culture. However, hIL-10 did not affect the fusion process of preosteoclast-like cells to form osteoclast-like multinucleated cells in the rat coculture system of preosteoclast-like cells with primary osteoblasts. Furthermore, hIL-10 completely inhibited the colony formation induced by granulocyte macrophage colony-stimulating factor (GM-CSF). These findings suggest that the inhibition of osteoclastogenesis by hIL-10 started at the early stage of the differentiation of osteoclast progenitors to preosteoclasts.

Animals↗
PubMed1995

Effects of several tea components on acid resistance of human tooth enamel.

OBJECTIVES: The effects of tea components on the acid resistance of human tooth enamel were investigated by an in vitro experiment. A further study focused on the action of tannin, the main component of tea, in combination with fluoride. RESULTS: Some components such as tannin, catechin, caffeine and tocopherol were demonstrated to be effective for increasing acid resistance, and their effects increased dramatically when they were used in combination with fluoride. A mixed solution of tannic acid and fluoride showed the highest inhibitory effect (98%) on calcium release to an acid solution. Tannin in combination with fluoride showed obvious inhibition of the formation of artificial enamel lesions in comparison with APF as determined by electron probe microanalysis, polarized-light microscopy and Vickers microhardness measurement. CONCLUSIONS: These results demonstrate that besides the fluoride, the organic components of tea also possess the property of increasing the acid resistance of tooth enamel. They also suggest that the organic components appear to play a primary role in their actions rather than fluoride.

Acidulated Phosphate Fluoride↗
PubMed1995

[Expression of exogenous porcine transforming growth factor beta-1 gene in ES cells and its effect on their differentiation in vitro].

A TGF-beta 1 gene expression plasmid was constructed by inserting the porcine 1.7 Kb TGF-beta 1 cDNA into BamHI site of retrovirus vector Dol. The plasmid DNA was introduced into mouse embryonic stem cells (ES-5 line) by calcium phosphate mediated transfection, and transfected ES-5 cells were then selected by stepwise increase in G418 concentration. Finally, we obtained 21 clones that could be stably grown in culture medium with G418 at 500 micrograms/ml and were designated as ES-T cells. Dot blot and Northern analysis of total RNA and polyA+ RNA extracted from those ES-T cells were shown in FIg. 2 and 3, demonstrating that 6 clones could express exogenous porcine TGF-beta 1 mRNA. The stronger hybridized signal in two clones (ES-T6 and ES-T 16) of them were further proved by southern hybridization of genomic DNA from these ES-T cells with 1.7 Kb TGF-beta 1 cDNA probe (Fig. 4). The product of TGF-beta 1 gene overexpression in ES-T 6 cells was shown in Fig. 5 and 6 by SE-LISA for TGF-beta 1 immunoreactivity to TGF-beta 1 antibodies and biological assay for CCL/64 cell growth inhibition, respectively. With respect to some biological characteristics, ES-T 6 cells, like their parent ES-5 cells, retained their pluripotent properties and positive SSEA-1 antigen (Plate I, Fig. 1). ES-T6 cells were expanded and used for studies of in vitro differentiation. Both of ES-T 6 cells and control ES-5 cells could form a lot of simple aggregates and differentiate into embryoid bodies by hanging drop culture for 3 days in the presence of retinoic acid (RA) at 10(-9) mol/L. Then individual embryoid bodies were plated on gelatinized tissue culture wells. On the third day of further culture without RA, a large amounts of epithelial-like and round cells occurred around the embryoid bodies formed either from ES-T 6 cells or ES-5 cells (Plate I, Fig. 4). However, with further culture of embryoid bodies, only the cells differentiated from ES-T6 embryoid bodies could arrange themselves and differentiate into a lot of radially arranged tubular structures (Plate II, Fig. 5). The frequency of tubular structures present in ES-T6 embryoid bodies were about 95.5%, but in ES-5 group there was only about 17.8% cases giving less defined tubular structures (Plate III, Fig. 8).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Localization of endothelin-like immunoreactivity and endothelin binding sites in rabbit eyes.

Immunohistochemistry and in vitro autoradiographic techniques were used to investigate the localization of endothelin (ET)-like immunoreactivity and [125I]ET-1 binding sites in sections of ocular tissues of normal rabbits. ET-like immunoreactivity was localized to the corneal endothelium and the pre-epithelial layer of the cornea, which was specifically inhibited by addition of exogenous ET-1. Immunoreactivity for ET was also observed in the retinal ganglion layer and periocular fat tissues. These, however, were not inhibited in the presence of ET-1. Autoradiography showed binding sites for ET-1 in the iris and ciliary body. Emulsion-dipped slides of sections of rabbit eyes incubated with [125I]ET-1 showed specific labeling for binding sites over structures that were identified from serial sections stained with hematoxylineosin. These were the anterior stroma of the iris root, the walls of capillaries, the circular arteries, and the veins of the ciliary body and extraocular muscles. No binding sites were found in the cornea or conjunctiva. The difference in regional distributions of ET storage and binding sites in rabbit ocular tissue suggests that the peptide may have specific physiologic functions.

Animals↗
PubMed1994

Microvascular architecture within the pig kidney cortex.

Corrosion casts of the plastic (Mercox Cl-2B) filled pig kidney cortex vasculature were sliced either parallel or perpendicular to the kidney surface. Scanning electron microscopy photographs were taken of the casts. Montages of the photographs were analyzed using a digitizing tablet and microcomputer-based software. For vessels having diameters larger than 0.05 mm, their sizes, numbers per unit area, and branching patterns were studied with respect to the kidney cortex depth. Vascular branching diameters and angles within the cortex compare favorably with those reported for other major vascular systems. The microvascular dimensions and densities were used to predict the average blood flow velocity within the kidney cortex. It is expected that the results will facilitate a better insight into the contribution of flowing blood to the heat transfer process in perfused tissues.

Animals↗
PubMed1994

Recent developments in modeling heat transfer in blood perfused tissues.

Successful hyperthermia treatment of tumors requires understanding the attendant thermal processes in both diseased and healthy tissue. Accordingly, it is essential for developers and users of hyperthermia equipment to predict, measure and interpret correctly the tissue thermal and vascular response to heating. Modeling of heat transfer in living tissues is a means towards this end. Due to the complex morphology of living tissues, such modeling is a difficult task and some simplifying assumptions are needed. Some investigators have recently argued that Pennes' interpretation of the vascular contribution to heat transfer in perfused tissues fails to account for the actual thermal equilibration process between the flowing blood and the surrounding tissue and proposed new models, presumably based on a more realistic anatomy of the perfused tissue. The present review compares and contrasts several of the new bio-heat transfer models, emphasizing the problematics of their experimental validation, in the absence of measuring equipment capable of reliable evaluation of tissue properties and their variations that occur in the spatial scale of blood vessels with diameters less than about .2 mm. For the most part, the new models still lack sound experimental grounding, and in view of their inherent complexity, the best practical approach for modeling bio-heat transfer during hyperthermia may still be the Pennes model, providing its use is based on some insights gained from the studies described here. In such cases, these models should yield a more realistic description of tissue locations and/or thermal conditions for which the Pennes' model might not apply.

Blood Physiological Phenomena↗
PubMed1994

Immunohistochemical demonstration of CCAAT/enhancer binding protein (C/EBP) in human liver tissues of various origin.

C/EBP is a sequence-specific DNA-binding protein. In order to identify its distribution and localization, immunohistochemical technique (ABC method) was done using anti-C/EBP polypeptide antibodies 1103#, 425# in liver specimens from 20 normal adults, 5 neonates, 6 patients with hepatitis, 25 with liver cirrhosis, 80 with hepatocellular carcinoma (40 cases were associated with surrounding nontumorous tissues) and 26 patients with cholangiocarcinoma (15 cases were associated with surrounding nontumorous tissues). The results showed that C/EBP was diffusely distributed in nuclei and cytoplasm of differentiated liver cells and very low or undetectable in liver cancer cells. The manifestation of C/EBP correlated with degree of differentiation of tumour cells, and was obviously weaker than that in surrounding nontumorous tissues. C/EBP positive staining has also been found in regenerating epithelial cells of bile ductules. The results suggested that C/EBP should play an important role in establishing and maintaining the differentiation of liver cells.

CCAAT-Enhancer-Binding Proteins↗
PubMed1994

[Determination and significance of C/EBP in hepatoma and various liver tissues].

C/EBP is a sequence-specific DNA-binding protein. In order to identify its distribution, localization and function in liver specimens from 18 normal adult, 5 neonates and 79 hepatocellular carcinoma patients (40 cases associated with surrounding nontumorous tissues), immunocytochemical studies (ABC method) were performed by using anti-C/EBP polypeptide antibodies 1103#, 425#. Northern blot using synthesized C/EBP cDNA probe in liver tissues of 3 normal adult, one neonate and 10 hepatocellular carcinoma tissues (8 cases were associated with surrounding nontumorous tissues) were also studied. The results of immunocytochemical staining showed that C/EBP was diffusely distributed in nuclei and cytoplasm of differentiated liver cells and very low or undetectable in liver cancer cells. The expression of C/EBP was in proportion to the degree of tumor cell differentiation and was much less than in the nontumorous surrounding tissues. C/EBP positive staining has also been found in the regenerating epithelial cells of bile ductules. Northern blot examination matched closely with the immunocytochemical examination. The results suggest that C/EBP may play an important role in establishing and maintaining the differentiation of liver cells and may exert an inhibiting effect against transformation of liver cells and proliferation of neoplastic tissue.

Adult↗
PubMed1993

Identification of a proline residue as a transduction element involved in voltage gating of gap junctions.

Gap junction channels are structurally distinct from other ion channels in that they comprise two hemichannels which interact head-to-head to form an aqueous channel between cells. Intercellular voltage differences together with increased intracellular concentrations of H+ and Ca2+ cause closure of these normally patent channels. The relative sensitivity to voltage varies with the subunit (connexin) composition of the channels. The third of four transmembrane-spanning regions (M3) in connexins has been proposed to form the channel lining, and a global 'tilting' of the hemichannel subunits has been correlated with channel closure. But specific components involved in transduction of channel gating events have not been identified in either gap junctions or other ion channel classes (however, see model in ref. 5). We have examined a strictly conserved proline centrally located in M2 of connexin proteins. Mutation of this proline (Pro 87) in connexin 26 causes a reversal in the voltage-gating response when the mutant hemichannel is paired with wild-type connexin 26 in the Xenopus oocyte system. This suggests that the unique properties associated with this residue are critical to the transduction of voltage gating in these channels.

Amino Acid Sequence↗
PubMed1993

Theoretical analysis of the large blood vessel influence on the local tissue temperature decay after pulse heating.

The influence of a large blood vessel (larger than 500 microns in diameter) on the local tissue temperature decay following a point source heating pulse was determined numerically using a sink/source method. It was assumed that the vessel was large enough so that the temperature of blood flowing within it remained essentially constant and was unaffected by any local tissue temperature transients. After the insertion of a point source heating pulse, the vessel influence on the local tissue transient temperature field was estimated by representing the vessel as a set of negative fictitious instantaneous heat sources with strength just sufficient to maintain the vessel at a constant temperature. In the surrounding tissue, the Pennes' tissue heat transfer equation was used to describe the temperature field. Computations have been performed for a range of vessel sizes, probe-vessel spacings and local blood perfusion rates. It was found that the influence of a large vessel on the local tissue temperature decay is more sensitive to its size and location rather than to the local blood perfusion rate. For a heating pulse of 3s duration and 5mW of power, there is a critical probe-vessel center distance 7R (R, vessel radius) beyond which the larger vessel influence on tissue temperature at the probe can be neglected.

Blood Vessels↗
PubMed1993

The effect of a tannin-fluoride mixture on human dental enamel.

In this study, the effect of a tannin-fluoride mixture (Ta-F, 0.5% tannic acid, 450 ppm fluoride, pH 5.9) on dental enamel has been investigated by using scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD), compared with the effect of acidulated phosphate fluoride (APF, 0.015 M phosphoric acid, 450 ppm fluoride, pH 5.3). Under the SEM, a large number of spherical globules (1-5 microns in diameter) were observed on the enamel surface treated with Ta-F. On a fractured cross section, these large globules showed a columnar appearance, measuring 2.5-5 microns each in height. They had a good range and formed a single coating layer on the enamel, whereas on the APF-treated enamel only very small spherical globules 0.1-0.5 micron in diameter were seen. Moreover, three types of connective patterns were observed between the basal ends of these columnar deposits and the enamel surface: (a) a pattern loosely attached to the enamel surface, (b) a pattern partially connected with the crystals of enamel, and (c) a pattern inserted into the pores of enamel. These columnar deposits also showed very strong resistance either to acid decalcification or to water washing. By EPMA and XRD examinations, a remarkable elevation of the fluoride profile accompanied by a high elevation of calcium was observed and CaF2 peaks were detected on the enamel surface. These results suggest that the columnar deposits might contain the CaF2-like substances and possess unique morphological and qualitative features which are quite different from the deposits found after APF or NaF treatment as described in previous studies.

Acid Etching, Dental↗
PubMed1993

Immunohistochemical studies on the distributions and age-related changes of types I and III collagen in the oral mucosa of mice.

The distribution of types I and III collagen in mouse oral mucosa and the age-related changes over 3 days to 2 years of age were examined by immuno-fluorescence and -electron microscopy, with use of affinity-purified polyclonal antibodies. Immunofluorescence microscopy revealed that types I and III collagen existed in all tissues and at all ages examined. The staining intensity for type I collagen was stronger and increased more markedly in the lamina propria of the hard palate (HPlp) and gingiva (G), compared with that in the submucosa of the hard palate (HPsm) and the buccal mucosa (BM). The staining intensity for type III collagen was strong and increased markedly with age in all connective tissues examined. Examination of immunogold-labeled tissues demonstrated that most of the collagen fibrils were labeled for both type I and type III collagen, which suggests that they were hybrid fibrils containing both types of collagen. The quantitative evaluation of the labeling densities of gold particles revealed that the labeling density of type III collagen in BM and HPsm was higher and increased more rapidly during growth than in HPlp and G, while the labeling density of type I collagen was higher in HPlp and G. The fibril diameters in HPlp were larger and increased more rapidly during growth than in BM and HPsm. These studies are the first to demonstrate the distribution of types I and III collagen and their age-related changes in mouse oral mucosa.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1993

[Determination on of C/EBP in human liver cancer, normal adult liver and various diseased liver tissues].

C/EBP, a heat-stable DNA-binding protein, play a very important role in establishing and maintaining the differentiation state of liver cells as a transcription factor enriched in the liver. In order to identify its distribution, localization and function, immunocytochemical examination (ABC method) was done by using anti-C/EBP polypeptide antibodies 1103#, 425# in 20 normal human adult liver tissues, 5 neonatal liver tissues, 6 hepatitis tissues, 25 liver cirrhosis tissues, 80 hepatocellular carcinoma tissues (40 cases with associated surrounding non-tumor hepatic tissues) and 26 cholangiocarcinoma tissues (15 cases with associated surrounding non-tumor tissues). The results showed that C/EBP expression was restricted to terminally differentiated liver cells, and was very low or undetectable in poorly differentiated liver cells, such as liver tumor cells. Its expression also correlated with the grading of hepatocellular carcinoma. Besides, positive C/EBP stain could be found in all regenerating bile ductules. The C/EBP has a diffuse distribution which could be detected both in nuclei and in cytoplasm, but more abundant in cytoplasm. The results are in accordance with the concept that C/EBP plays an important role in establishing and maintaining the differentiation state of liver cells.

Adult↗
PubMed1992

Vascular anatomy of the pig kidney glomerulus: a qualitative study of corrosion casts.

Pig kidney glomerular vascular anatomy was studied by scanning electron microscopy of vascular corrosion casts. A generalized vascular architecture is presented to describe the pig kidney glomerulus based upon the observation of 3,800 vascular cast glomeruli. The relative simplicity of the pig glomerular vascular architecture has allowed the characterization of different vascular segments more completely than has been possible in other mammals. Based upon relationships to the afferent arteriole, a nomenclature and definition of primary, secondary, tertiary and anastomotic vessels is proposed for the distributing vessels comprising the glomerular tuft. The existence and formation of a large central hemispheric vessel deep within the confines of a glomerular hemisphere is micrographically documented. Micrographic evidence is presented supporting the formation of the single efferent arteriole by the merging of two central hemispheric vessels within the confines of the glomerular tuft. Failure of the merging of these two vessels may result in multiple efferent arterioles.

Animals↗
PubMed1992

[Analysis of isoflavones in Belamcanda chinensis (L.)DC. and Iris tectorum Maxim by square wave voltammetry].

Three isoflavones: irigenin, tectorigenin and tectoridin in Belamcanda chinensis (L.)DC. and Iris tectorum Maxim were determined by square wave voltammetry. At the potential of -1.34 V (vs Ag/AgCl) the isoflavones gave well-defined peaks in the buffer solutions of pH3-5. An excellent linear relationship was obtained between the peak current and concentration. The method can be used to analyze small amounts of sample.

Drugs, Chinese Herbal↗