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Biomedical subjects

S He

Publications and source records attributed to S He.

At least 109 records · Page 6Linked to original sources
PubMed2000

Detection and analysis of intracoronary artery stent after PTCA using contrast-enhanced three-dimensional electron beam tomography.

We evaluated several three-dimensional methods of contrast-enhanced electron beam tomography (EBT) for evaluation of intracoronary stent characteristics after percutaneous transluminal coronary angioplasty (PTCA). Twenty-six patients who had undergone PTCA and stenting (31 stents) were investigated by using contrast-enhanced, electrocardiographically (ECG) triggered EBT scanning. EBT results were compared with conventional selective coronary arteriography (SCA). Overall, 27 intracoronary stents had been identified on EBT images (87.1%), while 4 stents could not be evaluated because of impaired image quality. EBT correctly identified the only case in which there was a residual stenosis at the distal portion of the stent. As compared with SCA results, EBT showed an over-estimation of intracoronary stent diameter (p < 0.001) and accurate measurement on the visualized length of the stents (p > 0.05). Fifty Hu, 100 Hu and 150 Hu were used as the observed window levels on three-dimensional (3-D) images; the accuracy for stent assessment increased with ascending window levels. EBT can reliably characterize coronary artery stents and may become a useful non-invasiveive method for patency evaluation of stented coronary segments after PTCA.

Adult↗
PubMed2000

[Radiation-induced apoptosis and p53, bcl-2 gene expression products in QGY-7703 cell line in vitro].

OBJECTIVE: To investigate the dose response and time course of radiation-induced apoptosis and gene expression products of p53, bcl-2 genes in human hepatocarcinoma cell line QGY-7703 in vitro. METHODS: Apoptosis was induced by radiation and quantitated by Flow Cytometry. The oncoproteins of p53 and bcl-2 genes after radiation were detected immunocytochemically on cell cytospinned slides. The data were analyzed with Sony Mias-300 Spato Immage Analyzer. RESULTS: The percentage of apoptosis in unradiation QGY-7703 was 4. 79%. After radiation, the apoptotic fraction increased with incubation time and radiation dose. Both gene expression products increased with incubation time and reached plateau at 6h post-radiation. CONCLUSION: After radiation, the response and time course of radiation-induced apoptosis in QGY-7703 cell line are similar to those of p53, bcl-2 oncoproteins. The later proceeds by the apoptosis peak about 6 h. The results suggest that p53 and bcl-2 genes are the regulating factors partially in radiation-induced apoptosis of QGY-7703 cell line.

Apoptosis↗
PubMed2000

Peroxisome proliferator-activated receptor-gamma ligands inhibit choroidal neovascularization.

PURPOSE: To determine the antiangiogenic effects of peroxisome proliferator-activated receptor (PPAR)-gamma agonists on ocular cells involved in the pathogenesis of choroidal neovascularization (CNV) in vitro and on experimental laser photocoagulation-induced CNV in vivo. METHODS: PPAR-gamma expression in human retinal pigment epithelial (RPE) cells and bovine choroidal endothelial cells (CECs) was determined using an RNase protection assay and Western blot analysis. Two PPAR-gamma ligands, troglitazone (TRO) and rosiglitazone (RSG; 0.1-20 microM), were used to assess effects on RPE and CEC proliferation and migration and CEC tube formation in response to vascular endothelial growth factor (VEGF). The effects of intravitreal injection of TRO on laser photocoagulation-induced CNV lesions in rat eyes (15 experimental, 15 control, nine burns per eye) and cynomolgus monkey eyes (two experimental, two control, seven paramacular burns per eye) was assessed by fluorescein angiography and histologic evaluation. RESULTS. PPAR-gamma1 was expressed in both RPE and CEC. PPAR-gamma ligands significantly inhibited VEGF-induced migration and proliferation in both cell types and tube formation of CEC in a dose-response manner. CNV in rats was markedly inhibited by intravitreous injection of TRO (P < 0.001). Lesions showed significantly less fluorescein leakage and were histologically thinner in the TRO-treated animals. Similar findings were present in the TRO-treated lesions in two monkey eyes. The drug showed no apparent adverse effects in the adjacent retina or in control eyes. CONCLUSIONS: The inhibition of VEGF-induced choroidal angiogenesis in vitro, and CNV in vivo by PPAR-gamma ligands suggests the potential application of these agents in the large group of patients with age-related macular degeneration complicated by CNV.

Animals↗
PubMed2000

Selective killing of RPE with a vascular endothelial growth factor chimeric toxin.

PURPOSE: To determine the sensitivity of retinal pigment epithelial (RPE) cells to a vascular endothelial growth factor (VEGF) chimeric toxin. METHODS: A targeted toxin was developed using recombinant methods to fuse VEGF165 to the diphtheria toxin (DT) translocation and enzymatic domain (DT390-VEGF165). Human RPE cells, choroidal endothelial cells (CECs), and scleral fibroblasts were isolated, and a dose-response for DT390-VEGF165 was determined by measurement of cell proliferation and cell number. In parallel experiments, cultures were pretreated with transforming growth factor (TGF)-beta2. VEGF-receptor (VEGFR-1 and -2) expression was determined using reverse transcription-polymerase chain reaction and fluorescence-activated cell sorting, and affinity was measured using Scatchard analysis. RESULTS: RPE cells and CECs were similarly prone to killing by the VEGF-toxin, but scleral fibroblasts were unaffected. Pretreatment with TGF-beta2 selectively increased the sensitivity of RPE cells to the VEGF-toxin. RPE cells expressed both VEGFR-1 and -2 in vitro; however, the expression of VEGFR-1 was very low. Pretreatment with TGF-beta2 (10 ng/ml) was associated with increased expression of the VEGFR-1 in RPE cells and increased receptor affinity for VEGF detected by Scatchard analysis. CONCLUSIONS: Dose-dependent killing of RPE cells by the DT390-VEGF165 conjugate is selectively enhanced by pretreatment with TGF-beta2. This study provides further strong support for the presence of functional VEGFRs on human RPE cells, and demonstrates for the first time the ability to target a normal nonendothelial cell type through VEGFR expression.

Cell Division↗
PubMed2000

Geometric distribution of chordae tendineae: an important anatomic feature in mitral valve function.

BACKGROUND AND AIM OF THE STUDY: This study examined the geometric distribution of chordae tendineae and their importance in compensating for papillary muscle (PM) displacement. METHODS: Anatomic, chordal mechanics and hemodynamic measurements were performed with porcine mitral valves. For hemodynamic measurements, physiological pulsatile flow conditions were maintained, and PM positions varied. Leaflet coaptation was documented by 2-D echocardiography, and regurgitation measured directly. RESULTS: Anatomic measurements showed the sum of marginal leaflet and marginal chordal lengths to exceed basal chordal length (1.8+/-0.4 versus 2.8+/-0.7 cm for anterior leaflets; 1.6+/-0.3 versus 2.5+/-0.6 cm for posterior leaflets). Triangular structures existed between basal chordae and marginal chordae with the marginal leaflet as the third side. Basal chordae resisted apical PM displacement in static experiments, while marginal chordae governed leaflet closure in hemodynamic experiments. Under pulsatile flow conditions, apical PM displacement decreased leaflet coaptation length and increased regurgitation (9.4+/-2.1 versus 4.0+/-1.6 ml). When marginal chordae were fused to the basal chordae, eliminating the role of the marginal chordae, severe regurgitation resulted (28.5+/-5.0 ml with apical PM displacement). CONCLUSION: Based on triangular structures involving the basal and marginal chordae, a compensatory mechanism was described which explains how the severity of mitral regurgitation can vary following PM displacement. Basal chordae provide a constant connection between the annulus and papillary muscles, while marginal chordae maintain marginal leaflet flexibility, governing proper valve closure. This study relates chordal distribution to normal valve function, and provides a better understanding of breakdown in valve function under pathophysiological conditions.

Animals↗
PubMed2000

Promotion of adhesion and migration of RPE cells to provisional extracellular matrices by TNF-alpha.

PURPOSE: Adhesion and migration of retinal pigment epithelial (RPE) cells to provisional extracellular matrices (ECM) is important in the development of epiretinal membranes found in proliferative vitreoretinopathy (PVR). Tumor necrosis factor alpha (TNF-alpha) is found in PVR membranes and regulates many functions of RPE cells. In this study, the effects of TNF-alpha on adhesion and migration of RPE cells to various components of ECM were examined and elucidation of the mechanism of the response was attempted. METHODS: Mitogen activated protein kinase (ERK1/2; MAPK) activation was measured by immunoblot. RPE cells pretreated with TNF-alpha (10 ng/ml) or TNF-alpha + PD98059 (a specific inhibitor of MAPK, 30 microM) for 24 hours were compared with control RPE. Attachment was measured by modified MTT assay on fibronectin and collagen types I and IV. Spreading was measured by staining with fluo3-AM and confocal laser scanning microscopy. Migration of RPE cells on substrates was determined by Boyden chamber assay using PDGF-BB (20 ng/ml) as a chemotactic factor. Integrin expression was determined by flow cytometry and RT-PCR. RESULTS: TNF-alpha rapidly activated MAPK and increased the extent of attachment, spreading and migration on fibronectin and collagen type I (P < 0.01) but not on collagen type IV. TNF-stimulated RPE cells showed increased mRNA and surface protein expression for alpha1 and alpha5 integrin (P < 0.01) but not alpha3 integrin subunit. Neutralizing the anti-alpha1 antibody inhibited migration on collagen type I, whereas alpha5 antibody inhibited fibronectin-induced migration. Treatment with both TNF and PD98095 reduced attachment and migration on provisional ECM and reduced the upregulated integrin expression to control levels. CONCLUSIONS: After treatment with TNF-alpha, there is increased expression of specific integrins associated with increased adhesion and migration on provisional ECM (fibronectin and collagen type I). This effect is mediated, at least in part, by activation of MAPK signaling pathway.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed2000

Electron beam tomography with three-dimensional reconstruction in the diagnosis of aortic diseases.

BACKGROUND: This study was performed to evaluate the protocols of electron beam tomographic angiography and three-dimensional reconstruction for assessing the diagnostic value of aortic diseases. METHODS EXPERIMENTAL DESIGN: Retrospective and comparative study. SETTINGS: University hospital. PATIENTS: Between 1996 and 1998, 189 cases who underwent electron beam tomographic angiography and diagnosed with aortic diseases were analyzed retrospectively. The results were compared with surgical and pathological findings in 68 cases. Electron beam tomographic angiography was used single-slice-scanning with ECG-triggering for screening of the thoracic aorta, continuous-volume-scanning, permitted by continuous X-ray exposure with table incremention, was performed for the abdominal aorta scanning without ECG-triggering. Three-dimensional reconstructions were performed with shaded-surface display, multiplanar reformatting and/or maximum intensity projection methods. RESULTS: Electron beam tomography angiography with ECG-triggered sections of single-slice-scanning improved the image quality of the ascending aorta without motion artifacts. Continuous-volume-scanning was suitable for screening of the abdominal aorta because of minimizing exposure time (10-14 sec) and saving contrast media (total contrast material of 45.5+/-6.6 ml was needed). One hundred eighty-nine cases were diagnosed with aortic dissection (97 cases), aortic aneurysm (26 cases), pseudoaneurysm (8 cases), Marfan's syndrome (39 cases), Takayasu's arteritis (5 cases) and congenital aortic malformations (14 cases). Electron beam tomography results were compared with the findings of surgery (as gold standard) in 68 cases, the diagnostic accuracy was 97% (2 cases with aortic aneurysm were erroneously diagnosed with pseudoaneurysm). CONCLUSIONS: Electrocardiographically triggered, contrast-enhanced electron beam tomography is feasible for the diagnosis of all kinds of aortic diseases, with excellent three-dimensional images competitive in quality with conventional selective aortic angiography or digital subtraction angiography.

Adolescent↗
PubMed2000

[The growth inhibitory effects by transfection of p16 gene on human pancreatic cancer cell line].

OBJECTIVE: To elevate the growth inhibitory effects by transfection of p16 gene on human pancreatic cancer cell line JF305. METHODS: Recombinant eukaryotic expression vector pDOR-p16 containing exogenous human wt-p16 cDNA and vector containing neomycin resistance gene only were introduced by Liposomes-mediated gene transfection into JF305 cell line which did not express endogenous p16. By using PCR amplification, in situ hybridization, and immunocytochemistry, the clones obtained were detected for efficiency of transfection and effect of vector expression and observed for the changes of their biologic characteristics. RESULTS: Exogenous wt-p16 was successfully transferred into JF305 cells and obtained permanent expression. The growth rate of these transfected JF305 cells in regular medium and soft agar was inhibited. The percentage of phage G(1) cells increased and that of phage S cells decreased by analysing cell cycle. The ultrastructural changes of the cells observed under electron-microscope revealed growth retardation. CONCLUSION: p16 is a candidate for cancer gene replacement therapy of human pancreatic cancer.

Cell Division↗
PubMed2000

[Studies on intercellular communication of rabbit lens epithelial cells in vitro].

OBJECTIVE: To investigate the intercellular communication in rabbit lens epithelial cells and effect of dexamethasone and heparin on it. METHODS: Rabbit lens epithelial cells were cultured and exposed to different concentrations of dexamethasone (10, 100, 300 mg/L), heparin (1 x 10(5), 2 x 10(5), 4 x 10(5) U/L) for 48 hours at 37 degrees C. The fluorescence redistribution after photobleaching (FRAP) was used for the analysis. The mean fluorescence recovery rate (MFRR, %/min) of the cells labelled with 6-carboxy fluorescein diacetate (CFDA) after photobleaching was measured with laser scanning cytometry ACAS Ultima. RESULTS: MFRR (%/min) of the cells after exposure to dexamethasone was 0.375 +/- 0.236 in the control group, 0.491 +/- 0.239 in the group of dexamethasone 10 mg/L, 0.996 +/- 0.447 in the group of dexamethasone 100 mg/L, 0.984 +/- 0.379 in the group of dexamethasone 300 mg/L, respectively (F = 26.07, P < 0.05). The MFRR after exposure of heparin was 0.375 +/- 0.236 in the control group, 0.694 +/- 0.491 in the group of heparin 1 x 10(5) U/L, 1.097 +/- 0.504 in the group of heparin 2 x 10(5) U/L, 1.082 +/- 0.501 in the group of heparin 4 x 10(5) U/L, respectively (F = 19.01, P < 0.05). CONCLUSION: It is discovered that there is intercellular communication in rabbit lens epithelial cells with FRAP analysis. Dexamethasone and heparin can enhance the intercellular communication of rabbit lens epithelial cells in dose dependent manner.

Animals↗
PubMed2000

[The effect of dactinomycin on retinal injury induced by argon laser in mouse].

OBJECTIVE: To determine that the administration of RNA synthesis inhibitor (dactinomycin) prevents retinal photoreceptor cell injury induced by green wavelength of argon laser in SD mice. METHODS: At various time (0, 8, 20 h) after the exposure to laser, eyes of the mice were injected intraocularly with dactinomycin in experimental eyes, and saline in control ones, and the concentration of the drug were 10 g/L, 5 g/L, 2.5 g/L. The eyes were taken at 24 h after the exposure, the slices of the retina were stained with methyl green-pyronin (MG-P), and pyknotic (violet) as well as surviving cells (green) were counted in the laser burns. RESULTS: Intraocular administration of dactinomycin diminished the degeneration induced by argon laser, there were marked differences between the experimental group and the control group, dactinomycin showed to be more effective if administered immediately after exposure and 8 h later, after this time the higher concentration of the drug could not result in higher effect. CONCLUSION: Dactinomycin can inhibit the occurrence of the laser injury, but the time selected for the administration is critical for its efficacy.

Animals↗
PubMed2000

[Factor XIIa-inhibited diluted thromboplastin time can reflect coagulation process].

OBJECTIVE: To establish a screening test that can reflect two stages of coagulation process. METHODS: With FXII a being blocked, the effects of various dilution of thromboplastin on clotting time were observed. FX a activity was determined by chromogenic assay. RESULTS: (1) At high concentration of thromboplastin, FXII a-inhibited diluted thromboplastin time (FXII ai DTT) of pooled normal plasma and FXI deficient plasma was very similar, but at low concentration, FXII ai DTT was in order of FVIII and FIX deficient plasma > FXI deficient plasma > pooled normal plasma. (2) FXI consumption by immunologic method induced FXII ai DTT of pooled normal plasma prolonged, and addition of FXI to FXI deficient plasma shortened FXII ai DTT. (3) Alpha-thrombin blocked by hirudin at different time (10 - 80 seconds) resulted in decreased FXa generation, and the earlier the block, the more the decrease. Under the same condition, the amount of FXa generation was in order of platelet-rich plasma > platelet-poor plasma > FXI deficient plasma. CONCLUSION: (1) Our data support the two-stage hypothesis and confirm the important role of FXI in the amplification stage. (2) FXII ai DTT as a screening test for coagulation process may be practicable.

Blood Coagulation↗
PubMed1999

A laboratory method for determination of overall haemostatic potential in plasma. I. Method design and preliminary results.

The aim of this study was to design a simple laboratory method that can screen the overall haemostatic potential in plasma (OHPP) when a hyper- or hypocoagulable state is present. A fibrin time curve was made via spectrophotometric registration of fibrin generation and lysis in plasma, to which exogenous thrombin and tissue type plasminogen activator was added. The area under the curve, calculated by the sum of absorbance (ABS-sum), varied in correlation to the concentrations of platelets or purified pro-/anticoagulants: tissue factor, von Willebrand factor, fibrinogen, antithrombin, plasminogen, or plasminogen activator inhibitor type 1. The ABS-sums also changed in positive relation to the haemostatic function investigated in 16 menopausal women and 14 young healthy nonpregnant women (controls). The findings imply that the ABS-sums not only offer a general information about fibrin generation and lysis in vitro, but also reflect the OHPP (i.e., final combined effects of platelet activity, coagulation, and fibrinolysis in vivo). Preliminary results were satisfactory; the levels of OHPP, expressed as the ABS-sums, were higher in normal pregnant women than in the controls, and even higher in preeclamptic patients than in pregnant women with no complications, which corresponds to the different grades of hypercoagulability in the three groups. Moreover, the level of OHPP was considerably lower in an untreated infant with von Willebrand's disease type 3 and in factor VIII- or factor IX-deficient plasma samples.

Adult↗
PubMed1999

The nondiscriminating zone of directionally selective retinal ganglion cells: comparison with dendritic structure and implications for mechanism.

We have studied, at high resolution, the sizes and pattern of dendrites of directionally selective retinal ganglion cells in the rabbit. The dendrites had a distinctive pattern of branching. The major dendritic trunks were relatively thick, beginning at approximately 1 micrometer and tapering to approximately 0.5 micrometer in diameter. Higher order dendrites exiting from them generally stepped abruptly to a diameter of 0.4-0.6 micrometer, which they maintained throughout their length. Recording confirmed the existence of a zone within the receptive field, usually occupying 20-25% of its area, where direction of movement was only weakly discriminated. The dendritic arbors of cells, injected with Lucifer yellow after recording, revealed no difference in dendritic structure between the discriminating and nondiscriminating zones. The nondiscriminating zone was located on the preferred side of the receptive field (the side from which movement in the preferred direction originates). This is consistent with a mechanism of direction selectivity based on inhibition generated by movement in the null direction but not with feedforward excitation, as occurs in flies and is postulated in some models of mammalian direction selectivity.

Animals↗
PubMed1999

X-ray crystallography and mass spectroscopy reveal that the N-lobe of human transferrin expressed in Pichia pastoris is folded correctly but is glycosylated on serine-32.

The ferric form of the N-lobe of human serum transferrin (Fe(III)-hTF/2N) has been expressed at high levels in Pichia pastoris. The Fe(III)-hTF/2N was crystallized in the space group P41212, and X-ray crystallography was used to solve the structure of the recombinant protein at 2.5 A resolution. This represents only the second P. pastoris-derived protein structure determined to date, and allows the comparison of the structures of recombinant Fe(III)-hTF/2N expressed in P. pastoris and mammalian cells with serum-derived transferrin. The polypeptide folding pattern is essentially identical in all of the three proteins. Mass spectroscopic analyses of P. pastoris- hTF/2N and proteolytically derived fragments revealed glycosylation of Ser-32 with a single hexose. This represents the first localization of an O-linked glycan in a P. pastoris-derived protein. Because of its distance from the iron-binding site, glycosylation of Ser-32 should not affect the iron-binding properties of hTF/2N expressed in P. pastoris, making this an excellent expression system for the production of hTF/2N.

Animals↗
PubMed1999

[Studies on photochemical disinfectant enamelled-ware of toxicity experiments].

In order to understand the toxicity of photochemical disinfectant enamelled-ware to human body, systematic toxicity studies were carried out. The results showed that the concentrations of toxic metal stibium (Sb) and cadmium(Cd) in photochemical disinfectant enamelled-ware 0.01 ml/L and 0.02 mg/L and lead (Pb) was non-detectable. The amount of LPO lipid peroxides in the experiment group and control group had no significant difference(t = 0.3481, P > 0.05). The drinking water of photochemical disinfectant had no effect on gene mutation in Ames test, and didn't make increase micronucleus formation of mice bone marrow and sperm deformity in the teratogenesis test of mice. It suggested that the photochemical disinfectant enamelled-ware was not toxic to human body. It was safe to human and could be used widely.

Animals↗
PubMed1999

Chordal force distribution determines systolic mitral leaflet configuration and severity of functional mitral regurgitation.

OBJECTIVES: The purpose of this study was to investigate the impact of the chordae tendineae force distribution on systolic mitral leaflet geometry and mitral valve competence in vitro. BACKGROUND: Functional mitral regurgitation is caused by changes in several elements of the valve apparatus. Interaction among these have to comply with the chordal force distribution defined by the chordal coapting forces (F(c)) created by the transmitral pressure difference, which close the leaflets and the chordal tethering forces (FT) pulling the leaflets apart. METHODS: Porcine mitral valves (n = 5) were mounted in a left ventricular model where leading edge chordal forces measured by dedicated miniature force transducers were controlled by changing left ventricular pressure and papillary muscle position. Chordae geometry and occlusional leaflet area (OLA) needed to cover the leaflet orifice for a given leaflet configuration were determined by two-dimensional echo and reconstructed three-dimensionally. Occlusional leaflet area was used as expression for incomplete leaflet coaptation. Regurgitant fraction (RF) was measured with an electromagnetic flowmeter. RESULTS: Mixed procedure statistics revealed a linear correlation between the sum of the chordal net forces, sigma[Fc - FT]S, and OLA with regression coefficient (minimum - maximum) beta = -115 to -65 [mm2/N]; p < 0.001 and RF (beta = -0.06 to -0.01 [%/N]; p < 0.001). Increasing FT by papillary muscle malalignment restricted leaflet mobility, resulting in a tented leaflet configuration due to an apical and posterior shift of the coaptation line. Anterior leaflet coapting forces increased due to mitral leaflet remodeling, which generated a nonuniform regurgitant orifice area. CONCLUSIONS: Altered chordal force distribution caused functional mitral regurgitation based on tented leaflet configuration as observed clinically.

Animals↗
PubMed1999

Retinoic acid modulates gap junctional permeability between horizontal cells of the mammalian retina.

In the retina, all-trans retinoic acid (at-RA) could function as a light signal because its production increases with the level of illumination. Given the well-established effects of retinoic acid on cell coupling in other tissues, it is possible that the changing levels of at-RA modulate the gap junctional permeability between retinal neurons. This study examines the effects of retinoic acid on horizontal cell coupling, which is known to be modulated by the ambient light level. Single horizontal cells were injected under visual control with either Neurobiotin (mouse retina) or Lucifer yellow (rabbit retina) and the extent of tracer coupling or dye coupling was used to monitor the gap junctional permeability. In the mouse retina, the injection of Neurobiotin revealed a network of approximately 150-250 tracer-coupled horizontal cells. The tracer coupling was completely abolished by incubating the retina in 150 microM at-RA for 35 min. In the rabbit retina, the injection of Lucifer yellow into A-type horizontal cells revealed networks of approximately 15-30 dye-coupled horizontal cells. Incubation in 150 microM at-RA reduced the dye coupling within 12 min and complete uncoupling was achieved after 35 min. The uncoupling effects of at-RA in the mouse and rabbit retinas were concentration- and time-dependent and they were reversible after washout. The coupling was not affected by either the 9-cis form of retinoic acid or by at-RA that had been isomerized by intensive light. The uncoupling effect of at-RA persisted following treatment with a D1 receptor antagonist and thus was dopamine-independent. This study has established that at-RA is able to modulate the gap junctional permeability between horizontal cells in the mammalian retina, where its light-dependent release has already been demonstrated.

Animals↗