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Biomedical subjects

X Fan

Publications and source records attributed to X Fan.

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

[Lymphocyte subset and its apoptosis in chronic hepatitis C].

OBJECTIVE: To explore the autoimmune pathogenesis induced by hepatitis C virus. METHODS: Serum anti-GOR and peripheral blood lymphocyte subset and its apoptosis rate after activated by Pokeweed mitogen (pwm) in vitro were measured by enzyme-linked immunosorbent assay and flow cytometry, respectively. Eighteen individuals with chronic hepatitis C and 16 healthy controls were observed. RESULTS: The positive rates of serum anti-GOR (66.7%) and ANA (44.4%) were significantly higher in chronic hepatitis C than normal controls (chi(2)=26.86, chi(2)=9.30, P<0.005). The apoptosis percentage of PBMCs and CD3(+)T cell was elevated in individuals with chronic hepatitis C when compared with normal controls (t=2.44, P<0.05). However, the apoptosis percentage of CD4(+)T and CD19(+)B cells in PBMCs was significantly decreased in patients with anti-GOR positive compared to anti-GOR negative (t=3.17, P<0.01; t=2.294, P<0.05). Similarly, the percentage of CD4(+)CD8(+) T cells in anti-GOR positive patients was increased and CD3(+)/CD4(+) was decreased (t=2. 18, P<0.05) compared to anti-GOR negative (t=2.44, P<0.05; t=2.18, P<0.05). CONCLUSION: autoimmune response exists in chronic hepatitis C patients. There is an imbalance of lymphocyte subset and its apoptosis, which may be one of the important reasons for the mechanism of autoimmune pathogenesis of chronic hepatitis C.

Adult↗
PubMed2000

[Determination of serum cytokines in individuals with HCV infection].

OBJECTIVE: To investigate the immunopathogenesis of chronic hepatitis C virus (HCV) infection. METHODS: Serum T-helper lymphocyte (Th1) cytokines (IFN-gamma, IL-2) and Th2 cytokines (IL-4, IL-10) were measured by ELISA in 18 individuals with chronic HCV infection 10 persons of chronic HBV infection and 11 normal persons. RESULTS: IL-2 (P <0.05), IL-4 and IL-10 (P <0.025, P <0.001) were significantly increased in HCV infected hosts as compared to 11 normal controls, the production of Th2 cytokines was more predominant. CONCLUSIONS: An enhanced Th2 responses is present in HCV infection, which may he responsible for the chronicity of HCV infection.

Adult↗
PubMed2000

[Telomerase activity of peripheral blood mononuclear cells in patients with acquired immune dysfunction].

OBJECTIVE: To investigate telomerase activity of peripheral blood mononuclear cells (PBMC) in patients with acquired immune dysfunction. METHODS: Telomerase activity of peripheral PBMC isolated from 4 groups including healthy subjects (17), chronic hepatitis B patients (14), diabetic patients (8) and chronic renal failure patients (8) was assayed with PCR-ELISA. RESULTS: (1) Telomerase activity was detectable at low levels in resting PBMC of all the 4 groups. It increased obviously after in vitro phytohemagglutinin (PHA) stimulation; (2) Telomerase activity of the resting PBMC in chronic hepatitis B patients was significantly lower than that in normal subjects, and was upregulated to the same level in the both groups after PHA stimulation; (3) No effect of recombinant human interleukin-12 on telomerase activity of activated T lymphocytes was found. CONCLUSIONS: PBMC may express telomerase activity and the decreased telomerase activity of PBMC in patients with chronic hepatitis B may partially be responsible for immune dysfunction in these patients.

Adolescent↗
PubMed2000

[Study on uptake of fluoroquinolones by Staphylococcus aureus].

This study aimed to investigate the mechanism of Staphylococcus aureus' resistance to fluoroquinolones. The uptake of lomefloxacin, ofloxacin by Staphylococcus aureus and the effect of CCCP on the uptake were studied by the fluorescence method. The uptake of lomefloxacin, ofloxacin by sensitive organisms is higher than that by resistant organisms; CCCP had different influences on different organisms, but no significant difference between the effects of CCCP on sensitive strains and on resistant strains was noted. The uptake of lomefloxacin, ofloxacin by SA2-16 was much lower than that by SA2-16's parent, and after the addition of CCCP, the uptake of both quinolones by SA2-16 increased rapidly, but the concentration did not reach its parent's concentration in stable condition. These results indicate that the decreasing of the uptake of fluoroquinolones is one of the mechanisms responsible for Staphylococcus aureus to resistance fluoroquinolones, and as a mechanism of resistance to drugs, it plays different roles in different strains.

Anti-Infective Agents↗
PubMed2000

[Diagnostic values of MRI in combination with DSA in vascular malformations of the head and neck].

OBJECTIVE: To evaluate prospectively diagnostic values of magnetic resonance imaging (MRI) as the initial examination for vascular malformations of the head and neck, and establish a flowchart based on radiodiagnostic features. METHODS: 45 patients with vascular malformations of the head and neck were evaluated prospectively with MRI. MRI was followed by angiography in 15 patients, contrast-enhanced CT in 15 patients. MRI was performed by using spin-echo pulse sequences with Philips Gyroscan NT 1.0 Teslaunit. RESULTS: In all cases, MRI demonstrated usefully, and there was no other single imaging modality that could provide information about internal structures and flow characteristics as much as MRI. It made differentiation between high-flow and low-flow lesions obvious, however MRI was inferior to angiography in delineation of feeder vessels. CONCLUSION: MRI can be used as the initial methods for diagnosis of vascular malformations in the head and neck, and could be combined with angiography in cases with high-flow or combined-flow lesions.

Adolescent↗
PubMed1999

The Discovery of a High-Redshift Quasar without Emission Lines from Sloan Digital Sky Survey Commissioning Data.

We report observations of a luminous unresolved object at redshift z=4.62, with a featureless optical spectrum redward of the Lyalpha forest region, discovered from Sloan Digital Sky Survey commissioning data. The redshift is determined by the onset of the Lyalpha forest at lambda approximately 6800 Å and a Lyman limit system at lambda=5120 Å. A strong Lyalpha absorption system with weak metal absorption lines at z=4.58 is also identified in the spectrum. The object has a continuum absolute magnitude of -26.6 at 1450 Å in the rest frame (h0=0.5, q0=0.5) and therefore cannot be an ordinary galaxy. It shows no radio emission (the 3 sigma upper limit of its flux at 6 cm is 60 µJy), indicating a radio-to-optical flux ratio at least as small as that of the radio-weakest BL Lacertae objects known. It is also not linearly polarized to a 3 sigma upper limit of 4% in the observed I band. Therefore, it is either the most distant BL Lac object known to date, with very weak radio emission, or a new type of unbeamed quasar, whose broad emission line region is very weak or absent.

Journal Article↗
PubMed1999

Protein kinase C phosphorylated at a conserved threonine is retained in the cytoplasm.

Phosphorylation of calcium-activated protein kinase Cs (PKCs) at threonine 634 and/or threonine 641 increases during long term potentiation or associative learning in rodents. In the marine mollusk Aplysia, persistent activation of the calcium-activated PKC Apl I occurs during long term facilitation. We have raised an antibody to a peptide from PKC Apl I phosphorylated at threonines 613 and 620 (sites homologous to threonines 634 and 641). This antibody recognizes PKC Apl I only when it is phosphorylated at threonine 613. Both phorbol esters and serotonin increase the percentage of kinase phosphorylated at threonine 613 in Aplysia neurons. Furthermore, the pool of PKC that is phosphorylated at threonine 613 in neurons is resistant to both membrane translocation and down-regulation. Replacement of threonine 613 with alanine increased the affinity of PKC Apl I for calcium, suggesting that phosphorylation of this site may reduce the ability of PKC Apl I to translocate to membranes in the presence of calcium. We propose that phosphorylation of this site is important for removal of PKC from the membrane and may be a mechanism for negative feedback of PKC activation.

Amino Acid Sequence↗
PubMed1999

Selective up-regulation of fatty acid uptake by adipocytes characterizes both genetic and diet-induced obesity in rodents.

Long chain fatty acid transport is selectively up-regulated in adipocytes of Zucker fatty rats, diverting fatty acids from sites of oxidation toward storage in adipose tissue. To determine whether this is a general feature of obesity, we studied [(3)H]oleate uptake by adipocytes and hepatocytes from 1) homozygous male obese (ob), diabetic (db), fat (fat), and tubby (tub) mice and from 2) male Harlan Sprague-Dawley rats fed for 7 weeks a diet containing 55% of calories from fat. V(max) and K(m) were compared with controls of the appropriate background strain (C57BL/6J or C57BLKS) or diet (13% of calories from fat). V(max) for adipocyte fatty acid uptake was increased 5-6-fold in ob, db, fat, and tub mice versus controls (p < 0.001), whereas no differences were seen in the corresponding hepatocytes. Similar changes occurred in fat-fed rats. Of three membrane fatty acid transporters expressed in adipocytes, plasma membrane fatty acid-binding protein mRNA was increased 9-11-fold in ob and db, which lack a competent leptin/leptin receptor system, but was not increased in fat and tub, i.e. in strains with normal leptin signaling capability; fatty acid translocase mRNA was increased 2.2-6.5-fold in tub, ob, and fat adipocytes, but not in db adipocytes; and only marginal changes in fatty acid transport protein 1 mRNA were found in any of the mutant strains. Adipocyte fatty acid uptake is generally increased in murine obesity models, but up-regulation of individual transporters depends on the specific pathophysiology. Leptin may normally down-regulate expression of plasma membrane fatty acid binding protein.

Adipocytes↗
PubMed1999

MK-801-induced expression of Fos protein family members in the rat retrosplenial granular cortex.

The N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 has been shown to induce an acute Fos and Fos-related antigen (Fra) expression in the rat retrosplenial granular cortex (RSG), but the exact composition of the Fos protein family and their individual dynamic alterations are unknown. We examined this issue using immunocytochemistry and Western blot analysis with two antibodies that recognize, respectively, Fos and all the identified members of Fos protein family. Immunocytochemistry detected a rapid and transient expression of Fos proteins in some RSG neurons and a delayed and prolonged expression of Fra proteins in most RSG neurons following a single systemic MK-801 injection (1 mg/kg). Multiple MK-801 injections (i.e., ten consecutive injections once every other day; 1 mg/kg) produced a moderate Fra expression but failed to induce detectable Fos expression. Western blot analysis further showed a transient expression of 72-kDa Fos proteins following a single MK-801 injection and a prolonged expression of 46- and 43-kDa Fra proteins after either a single or multiple MK-801 administration. The delayed onset and prolonged expression of these Fra proteins suggest that they may be DeltaFosB. The possible relevance of these results to clinical psychotomimetic effects of the NMDA receptor antagonists phencyclidine and ketamine is discussed.

Animals↗
PubMed1999

Lysophosphatidic acid activates NF-kappaB in fibroblasts. A requirement for multiple inputs.

Lysophosphatidic acid (LPA) is a growth factor that exerts a number of well characterized biological actions on fibroblasts and other cells. In the present study, we investigated the possibility that LPA activates the transcription factor NF-kappaB. NF-kappaB is a target of cytokines, but its activation by other classes of agonists has raised considerable interest in the control of processes such as inflammation and wound healing through varied mechanisms. We find that LPA causes a marked activation of NF-kappaB in Swiss 3T3 fibroblasts as determined by the degradation of IkappaB-alpha in the cytosol and the emergence of kappaB binding activity in nuclear extracts. The EC50 for activation of NF-kappaB is 1-5 microM, a range similar to that reported for reinitiation of DNA synthesis and activation of the serum response element. Activation of NF-kappaB is attenuated by pertussis toxin and inhibitors of protein kinase C, and it is completely blocked by the Ca2+ chelator BAPTA-AM. The combination of phorbol ester and thapsigargin promotes an activation comparable with that of LPA. Activation by LPA is additionally inhibited by tyrphostin A25 but not genistein or AG1478, indicating a selective utilization of protein-tyrosine kinases, and by certain antioxidants, implying a role for reactive oxygen species. The activation is also inhibited by tricyclodecan-9-yl-xanthogenate (D609), implying a requirement for hydrolysis of phosphatidylcholine. The data demonstrate the utilization of multiple pathways in the activation of NF-kappaB by LPA, not inconsistent with the relevance of several families of GTP-binding regulatory proteins.

3T3 Cells↗
PubMed1999

Role of NFkappaB in the regulation of macrophage colony stimulating factor by tumor necrosis factor-alpha in ST2 bone stromal cells.

Expression of MCSF in bone is important to the regulation of osteoclastogenesis. We show here that tumor necrosis factor-alpha (TNFalpha) increases the production of both soluble (sMCSF) and membrane-bound (mMCSF) macrophage colony stimulating factor by ST2 bone stromal cells. Treatment of ST2 cells with TNFalpha caused sMCSF levels to increase by 394+/-5% from basal; mMCSF rose by 316+/-66% from 30+/-10 per 100,000 cells in the same time. These increases were consistent with increased expression of mRNAs encoding both isoforms. Increases in MCSF mRNA are also seen after stimulation with dexamethasone. To investigate the potential role of NFkappaB in this TNFalpha effect, we treated cells with sodium salicylate (NaS), an inhibitor of NFkappaB translocation. NaS decreased TNFalpha-stimulated NFkappaB activation by 50% as assessed by EMSA. Despite inhibition of NFkappaB signaling, NaS enhanced TNFalpha-stimulated MCSF secretion and did not prevent TNFalpha-stimulated increases in sMCSF mRNA, suggesting that NFkappaB was not involved in TNFalpha effect on the gene. TNFalpha failed to stimulate transcription of a 774 nucleotide MCSF promoter-luciferase reporter transfected into ST2 cells which contained the NFkappaB consensus sequence. Deletion of the seven nucleotides containing the NFkappaB homology response sequence from the MCSF promoter increased basal gene transcription by twofold. TNFalpha thus contributes to an osteoclastogenic environment through upregulation of bone expression of both MCSF isoforms. Our data suggests that NFkappaB is not the major signaling pathway through which this occurs.

Bone and Bones↗
PubMed1999

Simplified model and measurement of specific absorption rate distribution in a culture flask within a transverse electromagnetic mode exposure system.

In vitro experiments in bioelectromagnetics frequently require the determination of specific absorption rate (SAR) within a layer of cells on the bottom of a culture flask when the SAR has rapid spatial variation both horizontally within the cell layer and vertically in the medium bathing the cells. This problem has only recently been treated in the literature; and it is here approached differently for another irradiation system. It is shown that a simple two-dimensional frequency-domain guided-wave treatment yields results qualitatively comparable to those of more computationally intensive three-dimensional time-domain free-field scattering treatments. The problem of inferring local SARs from temperature-vs.-time curves is shown to be seriously confounded by thermal diffusion; and specific analytic and numerical results are presented to aid in understanding this effect. A novel experimental technique is introduced for measuring millikelvin temperature offsets with subsecond resolution, and illustrative experimental data are presented. Finally, present experimental and theoretical uncertainties are considered; and it is pessimistically asserted that, in a culture flask where spatial SAR variation is rapid, point SAR measurements by thermal methods may be in error by as much as +/- 3 dB. More reliable thermal determinations will require extreme care, challenging technological innovations, or both.

Cells, Cultured↗
PubMed1999

Osteoclastogenesis is repressed by mechanical strain in an in vitro model.

Functional loading provides a site-specific signal for the regulation of bone mass and morphology. To determine if strain can inhibit the resorptive component of bone remodeling, osteoclast formation was assessed in marrow cultures plated on flexible membranes subjected to 5% strain for 10 cycles/minute, 24 hours per day. Cultures strained during days 2 through 7 inhibited osteoclast formation to 61+/-7% of control cultures (p < 0.05), a degree of inhibition similar to that observed when the cultures were subjected to strains during only days 2 through 4 but also evaluated on day 7 (67+/-4% of control; p < 0.05). In contrast, straining of cultures during days 5 through 7 had little influence on inhibiting the formation of osteoclasts (94+/-5% of control; no significant difference). The nonuniformly strained substrate was subdivided into three concentric rings. and cultures were used to examine the site-specificity of the inhibition caused by strain. Osteoclast formation in the outermost boundary, which was distended from 3.6 to 5%, was 41+/-7% of that observed in outer regions of control wells. The inhibitory potential of mechanical strain was reduced within the middle ring (73+/-6% of control osteoclasts: p < 0.01), where the strain ranged from 0.2 to 3.6%. The central region, which experienced strains equivalent to those in the middle ring (0.2 to -4% strain), showed inhibition of osteoclast formation to a similar degree (75+/-6% of control). Media harvested from strained cultures failed to inhibit osteoclast formation in unstrained cultures; this implies that the inhibitory effect of strain depended on the direct interaction of the cell with the substrate rather than by a humoral factor. A second device, where a uniform strain was delivered at 1.8% throughout the entire plate, inhibited osteoclast recruitment to 48+/-3.6%, emphasizing that uniform strain in the absence of shear stress constrains osteoclast recruitment. These in vitro experiments can but model the complex environment generated by in vivo mechanical strains: however, they provide the first direct evidence that strain must be considered as inhibitory to osteoclast recruitment.

Animals↗
PubMed1999

Ultrasound power deposition model for the chest wall.

An ultrasound power deposition model for the chest wall was developed based on secondary-source and plane-wave theories. The anatomic model consisted of a muscle-ribs-lung volume, accounted for wave reflection and refraction at muscle-rib and muscle-lung interfaces, and computed power deposition due to the propagation of both reflected and transmitted waves. Lung tissue was assumed to be air-equivalent. The parts of the theory and numerical program dealing with reflection were experimentally evaluated by comparing simulations with acoustic field measurements using several pertinent reflecting materials. Satisfactory agreement was found. A series of simulations were performed to study the influence of angle of incidence of the beam, frequency, and thickness of muscle tissue overlying the ribs on power deposition distributions that may be expected during superficial ultrasound (US) hyperthermia of chest wall recurrences. Both reflection at major interfaces and attenuation in bone were the determining factors affecting power deposition, the dominance of one vs. the other depending on the angle of incidence of the beam. Sufficient energy is reflected by these interfaces to suggest that improvements in thermal doses to overlying tissues are possible with adequate manipulation of the sound field (advances in ultrasonic heating devices) and prospective treatment planning.

Computer Simulation↗
PubMed1999

The value of assessing pulmonary venous flow velocity for predicting severity of mitral regurgitation: A quantitative assessment integrating left ventricular function.

Although alteration in pulmonary venous flow has been reported to relate to mitral regurgitant severity, it is also known to vary with left ventricular (LV) systolic and diastolic dysfunction. There are few data relating pulmonary venous flow to quantitative indexes of mitral regurgitation (MR). The object of this study was to assess quantitatively the accuracy of pulmonary venous flow for predicting MR severity by using transesophageal echocardiographic measurement in patients with variable LV dysfunction. This study consisted of 73 patients undergoing heart surgery with mild to severe MR. Regurgitant orifice area (ROA), regurgitant stroke volume (RSV), and regurgitant fraction (RF) were obtained by quantitative transesophageal echocardiography and proximal isovelocity surface area. Both left and right upper pulmonary venous flow velocities were recorded and their patterns classified by the ratio of systolic to diastolic velocity: normal (>/=1), blunted (<1), and systolic reversal (<0). Twenty-three percent of patients had discordant patterns between the left and right veins. When the most abnormal patterns either in the left or right vein were used for analysis, the ratio of peak systolic to diastolic flow velocity was negatively correlated with ROA (r = -0.74, P <.001), RSV (r = -0.70, P <.001), and RF (r = -0.66, P <.001) calculated by the Doppler thermodilution method; values were r = -0.70, r = -0.67, and r = -0.57, respectively (all P <.001), for indexes calculated by the proximal isovelocity surface area method. The sensitivity, specificity, and predictive values of the reversed pulmonary venous flow pattern for detecting a large ROA (>0.3 cm(2)) were 69%, 98%, and 97%, respectively. The sensitivity, specificity, and predictive values of the normal pulmonary venous flow pattern for detecting a small ROA (<0.3 cm(2)) were 60%, 96%, and 94%, respectively. However, the blunted pattern had low sensitivity (22%), specificity (61%), and predictive values (30%) for detecting ROA of greater than 0.3 cm(2) with significant overlap with the reversed and normal patterns. Among patients with the blunted pattern, the correlation between the systolic to diastolic velocity ratio was worse in those with LV dysfunction (ejection fraction <50%, r = 0.23, P >.05) than in those with normal LV function (r = -0.57, P <.05). Stepwise linear regression analysis showed that the peak systolic to diastolic velocity ratio was independently correlated with RF (P <.001) and effective stroke volume (P <.01), with a multiple correlation coefficient of 0.71 (P <.001). In conclusion, reversed pulmonary venous flow in systole is a highly specific and reliable marker of moderately severe or severe MR with an ROA greater than 0.3 cm(2), whereas the normal pattern accurately predicts mild to moderate MR. Blunted pulmonary venous flow can be seen in all grades of MR with low predictive value for severity of MR, especially in the presence of LV dysfunction. The blunted pulmonary venous flow pattern must therefore be interpreted cautiously in clinical practice as a marker for severity of MR.

Aged↗
PubMed1999

Development of apple superficial scald, soft scald, core flush, and greasiness is reduced by MCP.

1-Methylcyclopropene (MCP) was used to evaluate the role of ethylene in development of apple (Malus x domestica Borkh.) physiological disorders during storage. Granny Smith, Red Chief Delicious, and Fuji apple fruit were treated with MCP at a concentration of 1 microL L(-)(1) for 12 h at 20 degrees C. For all varieties stored at 0 degrees C, ethylene production and respiration rates were reduced for several months following MCP treatment, and firmness and titratable acidity of treated fruit were higher compared to controls. Apples treated with MCP did not develop superficial scald or peel greasiness through 6 months storage plus ripening at 20 degrees C for 7 days. Core flush was not observed in MCP-treated fruit until 6 months after treatment when the incidence was still lower compared to control fruit. MCP delayed the rise in production of alpha-farnesene and reduced accumulation of its oxidation products.

Cyclopropanes↗
PubMed1999

Impact of 1-methylcyclopropene and methyl jasmonate on apple volatile production.

Climacteric Fuji apples were treated with 10 microL x L(-1) MCP (1-methylcyclopropene), 2 mmol x L(-1) MJ (methyl jasmonate), or a combination of 10 microL x L(-1) MCP and 2 mmol x L(-1) MJ. Fruit were kept at 20 degrees C for 15 days after treatment. Production of ethylene and other volatile compounds was measured prior to and 3, 7, 11, and 15 days after treatment. Ethylene production decreased 3 days following MJ treatment and then increased. MCP treatment alone or in combination with MJ inhibited ethylene production. MJ and MCP inhibited production of many volatile alcohols and esters. The production of individual alcohols and esters appears to be differentially inhibited by MJ or MCP. MJ and MCP inhibited not only production of alcohols but also formation of esters from alcohols.

Acetates↗