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Biomedical subjects

Y X Chen

Publications and source records attributed to Y X Chen.

At least 37 records · Page 2Linked to original sources
PubMed2003

The role of citric acid on the phytoremediation of heavy metal contaminated soil.

Adsorption and hydroponics experiments were conducted to study the role of citric acid on the phytoremediation of heavy metal contaminated soil. The results show that addition of citric acid decreased the adsorption of both lead and cadmium, such an effect was bigger for cadmium than for lead. The decrease in the adsorption of Pb and Cd was mainly due to a decrease of pH in the presence of citric acid. The presence of citric acid could alleviate the toxicity of Pb and Cd to radish, and stimulate their transportation from root to shoot. The studies of heavy metal forms using sequential extraction demonstrated that lead was mainly existed as FHAC (a lower bioavailable form) in the root, while F(HCl) was the dominant form in the leaf. The addition of citric acid to the soil changed the concentration and relative abundance of all the forms. The detoxifying effect of citric acid to Pb in shoots might result from the transformation of higher toxic forms into lower toxic forms. Cadmium was mainly present as F(NaCl), therefore, it had higher toxicity than lead. The addition of citric acid increased the abundance of F(H2O) + F(NaCl), indicating that citric acid treatment could transform cadmium into more transportable forms.

Adsorption↗
PubMed2002

Phytotoxicity of dredged sediment from urban canal as land application.

Phytotoxicity of dredged sediment from Hangzhou section of the Grand Canal as land application was evaluated by pakchoi (Brassica chinensis L.) germination tests and pot experiments. Germination rates of pakchoi in the dredged sediment and in sediment-applied soils were both significantly higher than that in the soil controls, while the germination rate between the sediment-applied soils was no significant difference. In pot experiments, plant height and biomass were increased by the dredged sediment application rate in the rate of lower than 540 t ha(-1), but decreased when the application rate was over this rate. Concentrations of Zn and Cu in pakchoi were linearly increased with the increasing of the application rate of the dredged sediment. Both plant height and biomass of pakchoi in sediment-treated red soil were higher than that in sediment-treated paddy soil, regardless the application rate. The results suggest that plant biomass of pakchoi may be used as an indicator of the phytotoxicity of the dredged sediment. It also showed that red soil is more suitable to accept the dredged sediment than paddy soil, and 270 t ha(-1) is a safe application rate both in red soil and paddy soil.

Biomass↗
PubMed2001

Mutation in Bmp7 exacerbates the phenotype of Bmp8a mutants in spermatogenesis and epididymis.

The specificity of bone morphogenetic proteins (BMPs) to their putative heteromeric receptor complexes in vivo is largely unclear. Closely related BMPs may use the same or different receptor complexes for signaling in a time- and space-dependent manner during development and differentiation. We have shown that Bmp7 expression in epididymal epithelium is developmentally regulated. Here, we further show that Bmp7 expression is also developmentally regulated in male germ cells. Bmp7 transcripts are detected in spermatogonia and early primary spermatocytes during early puberty and in stage-7 to -15 spermatids of the adult mice. Since Bmp7 homozygous mutants die perinatally and heterozygotes do not show obvious defects in the testis and the epididymis, the role of Bmp7 in spermatogenesis and epididymal function cannot be revealed by simply examining these mutants. Therefore, we have used a genetic approach by creating Bmp7/Bmp8a double mutants to investigate the role of Bmp7 in spermatogenesis and epididymal function. Here, we report that removal of one allele of Bmp7 exacerbates the phenotype of Bmp8a null mutants in spermatogenesis and epididymis of the adult. These indicate that, similar to Bmp8a, Bmp7 plays a role in both the maintenance of spermatogenesis and epididymal function and it further suggests that BMP8 and BMP7 signal through the same or similar receptors in these two systems.

Animals↗
PubMed2001

Surgical technique for combined intestine-auxiliary liver transplantation in rats: development of a new microsurgical model.

Combined liver-intestine transplantation is an evolving procedure, and auxiliary liver transplantation has several advantages over standard orthotopic liver transplantation. We present a new model of combined intestine-auxiliary liver transplantation in rats. Total small bowel and 60% liver were harvested en bloc. An aortic segment that contained the celiac axis and superior mesenteric artery ensured blood supply to the graft. Venous drainage of the grafted intestine was achieved via the intact portal vein of the graft. The infrahepatic vena cava was cut at different levels during the modification period and at the oblique level of the left renal vein in consecutive series. Revascularization was accomplished by end-to-side anastomosis of the aorta and of the infrahepatic vena cava. The recipient small bowel was resected and the intestine continuity restored by anastomosis. Total operation time averaged 130 min. The overall survival rate of 3 months in the consecutive series was 80% (16/20). Exploratory laparatomy and histologic study in 3 rats on 90 days after transplantation revealed normal and viable grafts. Liver function was normal and both grafted liver and intestine showed normal histologic architectures in 5 rats observed for 12 months after transplantation. The present model is reproducible and allows preclinical research on several aspects of experimental combined intestine-auxiliary liver transplantation.

Animals↗
PubMed2001

Macrophage migration inhibitory factor is an important mediator in the pathogenesis of gastric inflammation in rats.

BACKGROUND & AIMS: Macrophage migration inhibitory factor (MIF) has been shown to play a pivotal role in inflammatory and immune-mediated diseases. This study investigates the role of MIF in gastric inflammation. METHODS: Expression of MIF was examined in a rat gastric ulcer model induced by acetic acid, and the functional role of MIF in acute gastric ulcer was investigated by administration of a neutralizing anti-MIF antibody. RESULTS: MIF messenger RNA and protein were markedly up-regulated in acute gastric ulcer, which correlated with the accumulation of macrophages (P < 0.001) and neutrophils (P < 0.05) at the site of inflammation. Macrophages, like neutrophils, were the major inflammatory cells infiltrating the ulcer base and they strongly expressed inducible nitric oxide synthase. However, macrophages, not neutrophils, were a rich source of MIF production in acute gastric ulcer. In vivo and in vitro blockade of MIF with the neutralizing anti-MIF antibody significantly inhibited the marked up-regulation of MIF, tumor necrosis factor alpha, inducible nitric oxide synthase, and intercellular adhesion molecule-1. This was associated with the marked inhibition of macrophage (70% reduced) and neutrophil (60% reduced) accumulation and activation, thus reducing ulcer sizes and attenuating ulceration. CONCLUSIONS: This study has shown that MIF was markedly up-regulated during acute gastric ulcer. Inhibition of acute gastric ulcer by blockade of MIF indicates that MIF is a key inflammatory mediator and plays a pathogenic role in gastric inflammation.

Acetic Acid↗
PubMed2001

Comparison of continuous and interrupted suture techniques in microvascular anastomosis.

We evaluated the efficacy of the continuous suture technique (CST) in arteries and veins with varying external diameters (ED). In study 1 a direct end-to-end anastomosis was performed in 5 groups of animals (n = 15 in each group): group 1, rabbit carotid artery (ED, 1.8-2.0 mm); group 2, rabbit femoral artery (ED, 1.4-1.6 mm); group 3, rat femoral artery (ED, 0.7-0.9 mm); group 4, rabbit femoral vein (ED, 2.0-2.2 mm); and group 5, rat femoral vein (ED, 1.0-1.2 mm). In study 2 a graft from the femoral vein was interposed into the carotid artery, with a ratio of the diameter of graft to artery of 1.3:1 in the rats (group 6, n = 12) and 1:1 in the rabbits (group 7, n = 12). In each animal the vessel on one side was repaired using CST and the opposite vessel using the interrupted suture technique. Vessel samples were harvested 1, 2, and 4 weeks after anastomosis. The CST significantly reduced anastomosis time by up to 47% in arteries and 41% in veins. Bleeding time and blood loss were also significantly reduced with CST. Similar results were found in study 2. The total thrombosis rate was 8%, but no significant patency difference was noted between the CST and the interrupted suture technique in any vessel category. We conclude that the CST is a reliable and time-saving procedure in microvascular anastomosis of arteries with diameters greater than 0.7 mm and of veins with diameters greater than 1.0 mm.

Anastomosis, Surgical↗
PubMed2001

Macrophage migration inhibitory factor expression in male and female ethanol-fed rats.

Macrophage migration inhibitory factory (MIF) regulates macrophage accumulation at sites of injury and can promote the inflammatory response. We studied MIF expression in the intragastric feeding rat model for alcoholic liver injury. Male and age-matched female rats were fed ethanol or dextrose with fish oil. Two groups of male rats were fed medium-chain triglycerides with ethanol or dextrose. Analysis of liver histopathology, lipid peroxidation, endotoxin, mRNA, and immunohistochemistry for MIF, tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) were carried out. Male and female rats fed fish oil and ethanol showed necroinflammatory liver injury and had the highest expression of MIF, TNF-alpha, and IFN-gamma in the liver. Decreased levels of MIF protein were seen in rats with higher endotoxin levels, suggesting that preformed MIF is released into the circulation. MIF is an important mediator of the inflammatory response in alcoholic liver disease and a potential therapeutic target.

Administration, Oral↗
PubMed2000

De novo expression of macrophage migration inhibitory factor in atherogenesis in rabbits.

Macrophage migration inhibitory factor (MIF) has been shown to play an important role in macrophage-mediated diseases. We investigate the potential role of MIF in atherogenesis using a hypercholesterolemic rabbit model. New Zealand White rabbits fed with a 2% cholesterol diet developed hypercholesterolemia and early fatty streaks at 1 month. The lesions became advanced at 3 months and were associated with de novo MIF expression by vascular endothelial cells (VECs) and smooth muscle cells (SMCs), as demonstrated by immunohistochemistry, reverse transcriptase-polymerase chain reaction, and in situ hybridization. By contrast, there was no increase in MIF levels in rabbits fed a normal diet. In early atherogenesis, marked upregulation of MIF mRNA and protein by VECs and some intimal cells were closely associated with CD68(+) monocyte adhesion onto and subsequent migration into subendothelial space. Of significance, the accumulation of macrophages was exclusively localized to areas of strong MIF expression, which may be associated with the macrophage-rich fatty streak lesion formation. Upregulation of MIF by SMCs is transient during atherogenesis. Importantly, strong MIF expression by activated macrophages may be responsible for the development of foam cell-rich lesions. Finally, the ability of MIF to induce intercellular adhesion molecule-1 expression by VECs implicates its pathogenic role in atherogenesis. In conclusion, the present study provides the first demonstration that MIF is markedly upregulated during atherogenesis. Upregulation of MIF by VECs and SMCs may play a role in macrophage adhesion, transendothelial migration, accumulation, and, importantly, transformation into foam cells. Furthermore, strong MIF expression by macrophages may both initiate and amplify the atherogenesis process.

Animals↗
PubMed2000

[Intravenous infection of C. albicans induces apoptosis of cortical thymocytes in mice].

In this study, we aimed to understand the location of apoptotic cells in murine thymus and phenotype of murine thymocytes involved in C. albicans induced apoptosis. Results showed that significant increase of apoptotic cells in thymus began at 6 h after intravenous injection of C. albicans and kept increased at 12 h, 18 h and 24 h. Quantitative changes of thymocytes with different phenotype measured by flow cytometry revealed that percentage of CD3+ and CD8+ cells were significantly reduced compared to the controls. Moreover in situ cell death detection of thymic tissue revealed that apoptotic cells induced by C. albicans mainly located in the thymic cortex, while in the thymic medulla a very small number of thymocytes was involved. Taken together our study indicates that C. albicans induces apoptosis of murine thymocytes, moreover the apoptosis possibly involves the major immature CD3+ CD4+ CD8+ cells in the thymic cortex and minor mature CD3+ CD4- CD8+ cells in the thymic medulla.

Animals↗
PubMed2000

Synthesis of a new chiral ligand, 6, 6'-dihydroxy-5, 5'-biquinoline (BIQOL) and its applications in the asymmetric addition of diethylzinc to aldehydes.

A new chiral ligand 6, 6'-dihydroxy-5, 5'-biquinoline (BIQOL, 2) was prepared via Cu2+ mediated coupling. The resolution was carried out by separating the corresponding ditrifluomethanesulfonate on chiral column. When applied to the enantioselective addition of diethylzinc to aromatic aldehydes, this ligand induced the reaction with enantioselectivity equivalent to that induced by BINOL. The effects of solvent and reaction temperature on enantioselectivity were also studied.

Journal Article↗
PubMed2000

Angiogenesis and its regulation: roles of vascular endothelial cell growth factor.

Neovascularization is well known to occur in human atherosclerotic plaques, proliferative retinopathies, and malignant neoplasias. However, its pathophysiologic roles and mechanisms still remain unclear. In this study, histochemical examination of atherosclerotic plaques showed that vascular endothelial cell growth factor (VEGF) was expressed by the smooth muscle cells and foamy macrophages in the atherosclerotic intimas. The number of VEGF-positive cells was positively correlated with the number of intimal blood vessels. Moreover, VEGF gene transfer into rabbit carotid arteries using the hemagglutinating virus of Japan (HVJ)-liposomes showed that VEGF overexpression could induce the angiomatoid proliferation. In diabetic rats, VEGF was overexpressed in diabetic retinas, and thus the local overexpression of VEGF seemed to play an important role in the development of blood-retinal barrier breakdown in simple diabetic retinopathy. These results indicated that the VEGF can act as a local and endogenous regulator of endothelial cell functions and that VEGF induces the neovascularization under pathophysiologic conditions. On the other hand, the transfer of a decoy for the cis-element in the promoter region of the angiogenic factors would be an effective method for regulating angiogenesis, because other angiogenic factors' expression promoted by such cis-element could be simultaneously suppressed. Therefore, this method may supply a useful therapeutic tool for the regulation of pathologic angiogenesis.

Animals↗
PubMed2000

Telomerase activity in preleukemia and acute myelogenous leukemia.

The development of acute leukemia from preleukemia involves the appearance of clones with increasing proliferative potential. The studies described here demonstrate that telomerase activity progressively increases as the bone marrow cells acquire increasing proliferative potential. This was demonstrated by measuring telomerase activity in normal bone marrow, in post-treatment lymphoma marrows with skewed Lyonization, and in MDS and AML marrows. The greater telomerase activity in myelodysplastic marrow than in normal marrow is not due to a higher proportion of blast cells or to a higher proliferative rate of the MDS marrow. These data demonstrate that the increasing proliferative potential of the marrow which occurs during the development of AML is associated with a simultaneous increase in telomerase activity.

Adolescent↗
PubMed2000

[Experimental studies on the diel rhythm changes of blood cAMP in growthing rats after mandibular retraction].

OBJECTIVE: To document the effect of orthopedic therapy on the metabolism of rats. METHODS: Exerting backwards force on rats mandible and measuring concentration of rats' blood cAMP in three groups with radio-immunity. Drawing the time-concentration curve and making cosine analysis. RESULTS: In natural state, there was a diel rhythm change of concentration of cAMP in rats' blood(P<0.05); After being imposed orthopedic forces to inhibit mandibular growth, the normal diel rhythm of cAMP in blood still existed(P<0.05). The results of parameter-comparison among groups were more complicated. CONCLUSION: Further research is needed to clarify the mechanism whether local orthopedic forces influence the body metabolism.

English Abstract↗
PubMed1999

Immunohistochemical expression of vascular endothelial growth factor/vascular permeability factor in atherosclerotic intimas of human coronary arteries.

Neovascularization is well known to occur in human atherosclerotic plaques; however, its pathophysiological roles, mechanisms, and stimuli in atherogenesis still remain unclear. In this study, 525 tissue blocks of coronary artery tissue obtained at autopsy from 48 patients ranging in age from 20 to 93 years old (mean+/-SD, 71+/-15 years) were immunohistochemically examined for vascular endothelial growth factor (VEGF) expression in the atherosclerotic intimas. The atherosclerotic lesions were histopathologically classified into types I through VI, as proposed by the American Heart Association Committee, and the numbers of intimal blood vessels and VEGF-positive cells were then morphometrically counted in sections that were immunohistochemically examined with anti-CD34 and human VEGF antibodies, respectively. The more the atherosclerotic lesion type advanced, the more often the lesion contained intimal blood vessels, which were expressed as percentages of the intimal section with intimal microvessels, viz, diffuse intimal thickening (DIT): 0% (0/111); type I, 31% (32/104); II, 42% (10/24); III, 66% (77/117); IV, 72% (48/67); V, 79% (70/89); and VI, 100% (13/13), P<0.0001. The number of VEGF-positive cells per intimal section was also positively correlated with the number of intimal blood vessels (P<0. 0001). The VEGF-positive cells were scattered in the fibrous caps as well as the shoulders and deeper areas of the plaques, and the double-immunostaining method revealed that the VEGF-positive cells were largely spindle-shaped, smooth muscle cells with some macrophage-derived foam cells. These findings thus suggest the possibility that the VEGF expressed by the smooth muscle cells and foamy macrophages in the atherosclerotic intimas can act as a local and endogenous regulator of endothelial cell functions, including intimal neovascularization, in atherosclerotic lesions of human coronary arteries.

Adult↗
PubMed1999

Isolation of deoxycytidine kinase from Ehrlich carcinoma cells by affinity chromatography based on a substrate analog, 2'-C-cyano-2'-deoxy-1-beta-D-arabinofuranosyl-N4-palmitoylcytosine++ +.

Deoxycytidine kinase from Ehrlich carcinoma cells was purified 10400-fold by ammonium sulfate fractionation and affinity chromatography using Sepharose 4B coupled to 2'-C-cyano-2'-deoxy-1-beta-D-arabinofuranosyl-N4-palmitoylcytosine , with a yield of 45%. The purified enzyme preparation showed a single major band with a molecular weight of 32000 on SDS-PAGE. The enzyme phosphorylated deoxyadenosine, deoxyguanosine, cytidine, and several deoxycytidine analogues as well as deoxycytidine. Also, the kinetic parameters of the enzyme for the substrates were estimated.

Animals↗