Biomedical subjects

J Feng

Publications and source records attributed to J Feng.

At least 109 records · Page 6Linked to original sources

PubMed2000

Stochastic resonance tuned by correlations in neural models.

The idea that neurons might use stochastic resonance (SR) to take advantage of random signals has been extensively discussed in the literature. However, there are a few key issues that have not been clarified and thus it is difficult to assess that whether SR in neuronal models occurs inside plausible physiology parameter regions or not. We propose and show that neurons can adjust correlations between synaptic inputs, which can be measured in experiments and are dynamical variables, to exhibit SR. The benefit of such a mechanism over the conventional SR is also discussed.

Animals↗

PubMed2000

Impact of correlated inputs on the output of the integrate- and-fire model.

For the integrate-and-fire model with or without reversal potentials, we consider how correlated inputs affect the variability of cellular output. For both models, the variability of efferent spike trains measured by coefficient of variation (CV) of the interspike interval is a nondecreasing function of input correlation. When the correlation coefficient is greater than 0.09, the CV of the integrate-and-fire model without reversal potentials is always above 0.5, no matter how strong the inhibitory inputs. When the correlation coefficient is greater than 0.05, CV for the integrate-and-fire model with reversal potentials is always above 0. 5, independent of the strength of the inhibitory inputs. Under a given condition on correlation coefficients, we find that correlated Poisson processes can be decomposed into independent Poisson processes. We also develop a novel method to estimate the distribution density of the first passage time of the integrate-and-fire model.

Action Potentials↗

PubMed2000

Chronic toxicity of rare-earth elements on human beings: implications of blood biochemical indices in REE-high regions, South Jiangxi.

Blood analyses for rare-earth element (REE)-high background regions in South Jiangxi show that the population averages of many of the biochemical indices deviate markedly from normal values in the normal region. These deviations are thought to be caused by prolonged intake of REE through food chains in view of that the toxicity of other harmful metals such as Pb and Cd can be neglected because of their insignificant amounts in the environment. In comparison with the normal region, blood biochemical indices abnormal in the REE-high regions are manifested as low total serum protein (TSP), albumin, beta-globulin, glutamic pyruvic transitanase, serium triglycerides, and immunoglobulin, but high cholesterol. These deviations may be related to the REE concentration and composition of food chains, and are sex dependent. Certain blood indices (such as TSP) of different age groups in the LREE-high region indicate that the influence of REE on males is a one-way irreversible process, whereas females show a strong ability of restoration.

Adult↗

PubMed2000

Rare-earth element distribution characteristics of biological chains in rare-earth element-high background regions and their implications.

The rare-earth element (REE) contents of water and vegetables from two typical REE-high background regions and a normal region in Gannan, Jiangxi Province, indicated that the REE contents were significantly different from those of water and vegetables, respectively. The average values are 0.03 mg/L and 0.11 mg/L REE for water from regions A and B. As the REE contents of vegetables from region A are different from region B, it is suggested that there are a number of factors controlling the REE distribution from those among plants. By comparing with the normal region, the soluble REE contents of water from the REE-high background regions are higher than those of the normal region by factors of 18 and 68, respectively. The REE contents of most plants and crops from regions A and B are higher than those of the normal region. It is clear that the REEs are the indispensable elements of plants during their growing period. Why are the REE contents of some plants from regions A and B usually higher than those from the normal region? The answer is that the plants and crops have passively absorbed REE during their growth.

China↗

PubMed2000

Bacteriostatic effects of cerium-humic acid complex: an experimental study.

The bacteriostatic potency of the cerium-humic acid complex was evaluated by experimental measurement of this complex interaction with E. coli, Bacillus pyocyaneus, Staphylococcus aureus, Leuconostoc and Streptococcus faecalis, and by comparison bacteriostatic effects with the cerium-citrate complex. The experimental results indicated that the cerium-humic acid complex strongly inhibited growth of all five bacterial strains, and its diameter of bacteriostatic circles were more than 30 mm. The minimal bacteria-inhibiting concentration were 1 x 10(-3), 2 x 10(-3) and 1 x 10(-2) mol/L for E. coli and Bacillus pyocyaneus, Staphylococcus aureus, and Leuconostoc and Streptococcus faecalis individually, and the measured minimal bactericidal concentrations were 2 x 10(-3) and 1 x 10(-2) mol/L for Bacillus pyocyaneus, E. coli, and Leuconostoc. To kill Staphylococcus aureus and Streptococcus faecalis, the concentration had to be more than 1 x 10(-20 mol/L. On the contrary, we found that cerium-citrate complex did not inhibit the growth of the above five bacteria, but stimulated bacterial growth. The completely different bacteriostatic results of two cerium complexes may hint that the association and chemical properties of the two complexes were different.

Anti-Bacterial Agents↗

PubMed2000

Mutation profile of the p53, fhit, p16INK4a/p19ARF and H-ras genes in Indian breast carcinomas.

Breast cancer is the second most prevalent cancer affecting Indian women. Genetic alterations of oncogenes and tumor suppressor genes were attributed to the development of breast carcinomas. In the present study, human breast tumor DNAs from untreated, non-familial, Indian patients were analysed for the presence of mutations in p53, fhit, p16INK4a/p19ARF and H-ras genes. Polymerase chain reaction-single strand conformation polymorphism and sequencing analysis were used to detect point mutations. Exons 5-8 of p53, exons 1-2 of p16INK4a, exon 2 of p19ARF, exons 5-9 of fhit gene and exons 1-2 of H-ras genes were amplified and analysed individually using exon-flanking primers. Only 12% of the tumors had mutation in p53, 8% had mutation in fhit gene and none of the tumors showed evidence for mutation in p16INK4a/p19ARF and H-ras genes. Tumor B18 exhibited two novel mutations in the p53 gene, ATGright curved arrow GTG (Metright curved arrow Val) at codon 237 and AATright curved arrow GAT (Asnright curved arrow Asp) at codon 263. Both of these mutations are hitherto unreported in breast carcinomas. Tumor B20 had a non-sense mutation CGAright curved arrow TGA (Argright curved arrow Stop) at codon 306 of p53 gene. In fhit gene, tumor B1 exhibited TTCTright curved arrow TACT mutation at intron 8 and tumor B15 had a silent mutation GAGright curved arrow GAA (Gluright curved arrow Glu) at codon 123. Our results indicate that, among the genes analysed, the p53 gene was more frequently mutated than fhit, p16INK4a/p19ARF and H-ras genes in Indian mammary tumors. Transcribable point mutations of fhit gene were found to be extremely uncommon in these tumors. Mutations in the above genes are mutually exclusive and are infrequent in fhit, p16INK4a/p19ARF and H-ras genes suggesting that these genes may not play a major role in Indian breast carcinomas. However, the significant frequency of mutations in the p53 gene suggest that p53 could be one of the genes involved in the genesis of sporadic breast carcinomas in Indian women.

Acid Anhydride Hydrolases↗

PubMed2000

Induction of CD36 expression by oxidized LDL and IL-4 by a common signaling pathway dependent on protein kinase C and PPAR-gamma.

CD36, a class B scavenger receptor, is a macrophage receptor for oxidized low density lipoprotein (OxLDL) and may play a critical role in atherosclerotic foam cell formation. We have previously demonstrated that OxLDL, macrophage-colony stimulating factor (M-CSF), and interleukin-4 (IL-4) enhanced expression of CD36. The effect of OxLDL on CD36 is due, in part, to its ability to activate the transcription factor, PPAR-gamma (peroxisome proliferator activated receptor-gamma). Other PPAR-gamma ligands (15-deoxyDelta(12,14) prostaglandin J(2) (15d-PGJ(2)) and the thiazolidinedione class of antidiabetic drugs) also increase CD36 expression. We have now evaluated signaling pathways involved in the induction of CD36. Treatment of RAW264.7 cells (a murine macrophage cell line) with protein kinase C (PKC) activators (diacylglycerol and ingenol) up-regulated CD36 mRNA expression. Specific inhibitors of PKC reduced CD36 expression in a time-dependent manner, while protein kinase A (PKA) and cyclic AMP agonists had no effect on CD36 mRNA expression. PKC inhibitors reduced basal expression of CD36 and blocked induction of CD36 mRNA by 15d-PGJ(2), OxLDL and IL-4. In addition, PKC inhibitors decreased both PPAR-gamma mRNA and protein expression and blocked induction of CD36 protein surface expression by OxLDL and 15d-PGJ(2) in human monocytes, as determined by FACS. 15d-PGJ(2) had no effect on translocation of PKC-alpha from the cytosol to the plasma membrane. These results demonstrate that two divergent physiological or pathophysiological agonists utilize a common pathway to up-regulate of CD36 gene expression. This pathway involves initial activation of PKC with subsequent PPAR-gamma activation. Defining these signaling pathways is critical for understanding and modulating expression of this scavenger receptor pathway.

Animals↗

PubMed2000

Pulmonary function changes following surgical correction for pectus excavatum.

OBJECTIVE: To assess whether and to what extent pulmonary function returns to normal after surgical correction for pectus excavatum. METHODS: Twenty-seven patients who could be examined in person at the outpatient department of our hospital were included in this study. Of these patients, 24 were boys and 3 were girls, with age ranging from 3 to 16 years (mean: 8.67 years). The mean age at surgery was 4 years and mean years at follow-up was 6.8. Pulmonary function measurements included inspiratory vital capacity (IVC), total lung capacity (TLC), residual volume (RV), functional residual capacity (FRC), RV/TLC ratio, maximal voluntary ventilation (MVV), forced ventilatory capacity (FVC), forced expiratory volume in one second (FEV1), maximal mid-expiratory flow (MMEF), maximal expiratory flow at 75% vital capacity (V75), maximal expiratory flow at 50% vital capacity (V50), maximal expiratory flow at 25% vital capacity (V25) and breathing reserve ratio (BR). RESULTS: TLC, FRC, MVV, MMEF, V75 and V50 were not different from normal values. IVC, FVC, FEV1 and V25 were significantly decreased compared with normal values. RV and RV/TLC were high in 87.5% cases. CONCLUSIONS: Preoperative symptoms improved substantially after operation. Little airway obstruction was observed postoperatively, suggesting that patients with pectus excavatum should have surgery as early in life as possible, preferably by age 3.

Adolescent↗

PubMed2000

Effect of prenatal tetrandrine therapy on pulmonary vascular structural remodeling in the nitrofen-induced CDH rat model.

OBJECTIVE: To examine the effects of prenatal tetrandrine (Tet) therapy on pulmonary arterial structural remodeling in nitrofen-induced congenital diaphragmatic hernia (CDH). METHODS: CDH was induced in fetal rats by maternal administration of 100 mg nitrofen by gavage on day 9.5 of gestation (term, day 22). Control animals received olive oil (OO). Tet (24 mg/kg per day) or normal saline (NS) was given by gavage every day from 16 to 20 days of gestation, and fetuses were delivered by caesarean section on day 21.5. Lung sections from 3 fetuses in each group were studied. The number of vessels were calculated, the external diameter (ED), medial wall thickness (MT), percent of medial wall thickness, and wall structure were evaluated by image analysis software. RESULTS: In the pre-acinar arteries, CDH-NS pups had a significantly increased %MT compared with the OO-NS group (P < 0.05), while CDH-Tet animals had a reduced %MT compared with the CDH-NS rats (P < 0.05). Similar results were seen in the intra-acinar level. Significant differences were observed between CDH-NS animals and OO-NS controls in the percentage of muscularized intra-acinar blood vessels (P < 0.001). Tet-treated CDH pups had a reduced percentage of muscularized intra-acinar arteries compared with CDH-NS animals. CONCLUSIONS: Medial hypertrophy is present in both the pre-acinar and intra-acinar arteries in the nitrofen-induced CDH rat model. Tet treatment inhibits medial hypertrophy and reduces the percentage of muscularized intra-acinar vessels. Prenatal Tet therapy may be efficacious in reducing the risk of PH in human newborns with CDH.

Alkaloids↗

PubMed2000

Modified sternal elevation for children with pectus excavatum.

OBJECTIVE: To describe our experience in the treatment of pectus excavatum (PE) using a modified sternal elevation procedure. METHODS: From Oct. 1986 to Dec. 1997, 171 patients with PE were admitted to the Department of Pediatric Surgery of the First Hospital of West China University of Medical Sciences. All patients were diagnosed through a history and physical examination. Cardiopulmonary function was assessed by M-mode echocardiography and instrument of pulmonary function in 40 patients before and 4.2 years after surgery which was performed between 1989 and 1994. We performed the following three procedures in the sternal elevation: (1) forming the metal strut in a "arch" shape, (2) suturing the perichondrium into a "pipe" shape, and (3) encouraging patients to do chest expansion exercise after operation. All patients were followed up for 1 to 12 years. RESULTS: The normal contour of the costal cage was enlarged in all but one patient. Exercise tolerance was improved, and cardiac function recovered to the same level as in healthy children, while pulmonary function recovered very slowly after surgery. CONCLUSION: The normal appearance of chest wall can be recovered and normal cardiopulmonary function can be restored by the modified sternal elevation procedure in children with PE.

Adolescent↗

PubMed2000

[The significance and the role of TNFalpha and NO in the early renal damage in burned rats complicated with endotoxemia].

OBJECTIVE: To explore the role and the significance of TNFalpha and NO in the early renal damage in burned rats complicated with endotoxemia. METHODS: The rats inflicted with 20% TBSA III degree burn and injected intraperitoneally with endotoxin (1 mg/kg) were employed as the model of MOD. The renal pathomorphology was observed at 0.5, 1, 3, 6, 12, 24, 48, 72 postburn hours. Concomitantly, the changes of renal and serum TNFalpha and NO were investigated and in situ hybridization for TNFalpha mRNA and immunohistochemical staining for iNOS were performed. RESULT: The expressions of renal iNOS and TNFalpha mRNA, the NO synthesis and the serum levels of NO and TNFalpha in BCEG (burns complicated with endotoxin group) were obviously higher and appeared earlier than those in SBG (simple burns group) and SEG(simple endotoxin group). CONCLUSION: The renal TNFalpha and NO increased significantly in rats subjected to burn complicated with endotoxemia, which might be important factors causing renal damage and the alterations in renal hemodynamics.

Animals↗

PubMed2000

[Histochemical study on the nitric oxide synthase in the intestinal myenteric plexus of burned rats].

OBJECTIVE: To elucidate the postburn change in the activity and the distribution of nitric oxide synthase (NOS) in rat intestinal myenteric plexus. METHODS: The activity and distribution of NOS were quantitatively and locationally studied by histochemical staining with NADPH-diaphorase (NDP), a marker for NOS, and whole mount preparation technique. RESULTS: NOS was widely distributed in whole intestine wall, especially in myenteric plexus. The majority of NOS positive neurons displayed either round or oval shape. There were some varicosities string of bead-like structure in the nerve fibers and which were accompanied by blood vessels and muscular fibers. There was no significant postburn change in the density of NOS positive neurons in myenteric plexus (P < 0.05). Nevertheless the NOS activity of neurons decreased obviously (P < 0.05 similar 0.01). Meanwhile, it was found after injury that there were indistinction of the structure of NOS positive neuron, more breaking of nerve fibers, leading to the lack of integral web of nerve fibers and obvious decrease of NOS positive varicosities in nerve fibers. CONCLUSION: After burn injury, the NOS positive neural structure in myenteric plexus of rat small intestine was damaged with the decrease in NOS activity. Simultaneously, there was impairment of the releasing route of nitric oxide (NO). All these changes might be closely related to intestinal structural damage and dysfunction after burn injury.

Animals↗

PubMed2000

[Influence of pravastatin on expression of platelet CD(62P) and CD(41) in patients with hypercholesterolemia in vitro and in vivo].

OBJECTIVE: To study in vitro and in vivo effect of hypercholesterolemia (HC) on expression of platelet CD(62P) and CD(41) and their changes after treatment with pravastatin. METHODS: Twenty patients with HC were given 10 - 20 mg/d pravastatin orally for 4 - 8 weeks. Changes of blood cholesterol and expression of platelet CD(62P) and CD(41) were detected by flow cytometry. RESULTS: After 4 and 8 weeks' treatment, blood cholesterol level and platelet aggregation function decreased. The expression of CD(62P) average fluorescence intensity decreased from 31.8 +/- 7.8 to 27.2 +/- 6.9 and 26.8 +/- 4.9; CD(62P) (%) from (31.3 +/- 9.3)% to (26.4 +/- 7.4)% and (25.3 +/- 9.1)% (P < 0.05); CD(41) from 483.2 +/- 263.9 to 348.1 +/- 192.4 and 306.8 +/- 128.0 (P < 0.05), respectively. Similar results were obtained in vitro study. CONCLUSION: Improvement of platelet function and expressions of CD(62P) and CD(41) in HC patients after prevastatin treatment may be resulted from enhancing arteriosclerosis regression. It suggested from the in vitro result that pravastatin might play a direct effect on platelet function.

Adult↗

PubMed2000

[Determination of glycyrrihizin in rats plasma and pharmacokinetics after oral administration of si-jun-zi-tang].

OBJECTIVE: To study the pharmacokinetics of glycyrrhizin after oral administration of Si-jun-zi-tang in rats and provide the experimental evidences for the prescription pharmacokientics of traditional Chinese medicine. METHOD: A RP-HPLC method was established for rapid determination of glycyrrhizin in rats plasma. After obtaining the blood sample at different time, the plasma concentration of GL were detected respectively. The data were processed by the software named 3P87 to find the pharmacokinetic parameters. RESULTS: A good linear relationship existed in the range of GL from 1.224 micrograms/ml to 38.656 micrograms/ml. Whole blood concentration-time course of GL after oral administration Si-jun-zi-tang was fitted to be a two-compartment model. GL in rats plasma which came from Si-jun-zi-tang was absorbed and distributed rapidly, but excreted slowly. CONCLUSION: This RP-HPLC method was sensitive, raliable and rapid, it can be used in absorption and metabolism of GL, also in detection of GL preparation. This experiment is prepared for further study of the tradtional Chinese medicine prescription pharmacokinetics.

Administration, Oral↗

PubMed2000

Dynamic changes of serum vascular endothelial growth factor levels in a rat myocardial infarction model.

OBJECTIVE: To investigate the dynamic changes of serum vascular endothelial growth factor (VEGF) levels in a rat model of acute myocardial infarction. MATERIALS AND METHODS: Eighty-eight adult male Sprague-Dawley rats weighing approximately 270 g we used in this study. Eighty rats were subjected to left coronary artery ligation, with 8 rats for each different duration of infarct. Eight sham-operated animals in which the left coronary artery was surgically exposed without ligation were used as controls. Blood samples were drawn from the right atrium before (sham animals) and 1, 3, 6, 12, 24 h and 2, 3, 5, 7, 14 d after myocardial infarction. The concentrations of serum VEGF were measured by a sensitive enzyme-linked imosorbent assay with a rabbit polyclonal antibody specific for VEGF. RESULTS: In the 8 control animals, the mean concentration of serum VEGF was 66.99 +/- 17.83 pg/ml. Six hours after myocardial infarction, the level of serum VEGF significantly increased to 125.68 +/- 28.07 pg/ml (P < 0.01 vs x sham controls), and reached a peak (240.61 +/- 70.63 pg/ml. P < 0.01 vs x sham animals) at 24 h after ligation and then decreased gradually over the remaining 2 weeks. However, the level remained significantly elevated for 14 d (107.64 +/- 30.13 pg/ml, P < 0.01 vs x sham controls). CONCLUSION: The present study shows that the levels of serum VEGF are markedly increased until 14 d in the rat model of acute myocardial infarction. The increased serum VEGF level may play an important role in the angiogenesis associated with myocardial infarction.

Animals↗

PubMed2000

Serum levels of vascular endothelial growth factor in patients with angina pectoris and acute myocardial infarction.

OBJECTIVE: To determine whether serum vascular endothelial growth factor (VEGF) concentrations are altered in several kinds of coronary heart disease patients. MATERIALS AND METHODS: Using a VEGF enzyme-linked immunosorbent assay (ELISA), serum VEGF concentrations were determined in antecubital venous blood of 16 patients with stable angina pectoris (SAP), 16 with unstable angina pectoris (UAP) and 16 with acute myocardial infarction (AMI) before and after thrombolytic therapy, and of 16 age- and sex-matched healthy volunteers who used as controls. RESULTS: The concentrations of serum VEGF in patients with SAP (98.60 +/- 26.99 pg/ml) and UAP (103.61 +/- 24.89 pg/ml) tended to be higher than those in control subjects (80.44 +/- 24.57 pg/ml), but the differences did not reach statistical significance (P > 0.05 for each). Before thrombolytic therapy, the concentrations of serum VEGF in patients with AMI (285.92 +/- 125.15 pg/ml) were significantly higher than those in patients with SAP, UAP or control subjects (P < 0.01, respectively), and correlated with synchronous serum creatine kinase (CK) and its MB isoenzyme (CK-MB) contents (r = 0.866, P < 0.001 and r = 0.948, P < 0.001; respectively). Three hours after thrombolysis, the concentrations of VEGF had fallen to 111.57 +/- 31.29 pg/ml (P < 0.01 vs x before thrombolytic therapy and P < 0.05 vs x control subjects). CONCLUSION: The present study shows that serum concentrations of VEGF in patients with AMI are markedly elevated and that increased serum VEGF levels may be one of the most sensitive indexes in diagnosing AMI and judging reperfusion.

Adult↗

PubMed1999

Inhibitory phosphorylation site for Rho-associated kinase on smooth muscle myosin phosphatase.

It is clear from several studies that myosin phosphatase (MP) can be inhibited via a pathway that involves RhoA. However, the mechanism of inhibition is not established. These studies were carried out to test the hypothesis that Rho-kinase (Rho-associated kinase) via phosphorylation of the myosin phosphatase target subunit 1 (MYPT1) inhibited MP activity and to identify relevant sites of phosphorylation. Phosphorylation by Rho-kinase inhibited MP activity and this reflected a decrease in V(max). Activity of MP with different substrates also was inhibited by phosphorylation. Two major sites of phosphorylation on MYPT1 were Thr(695) and Thr(850). Various point mutations were designed for these phosphorylation sites. Following thiophosphorylation by Rho-kinase and assays of phosphatase activity it was determined that Thr(695) was responsible for inhibition. A site- and phosphorylation-specific antibody was developed for the sequence flanking Thr(695) and this recognized only phosphorylated Thr(695) in both native and recombinant MYPT1. Using this antibody it was shown that stimulation of serum-starved Swiss 3T3 cells by lysophosphatidic acid, thought to activate RhoA pathways, induced an increase in Thr(695) phosphorylation on MYPT1 and this effect was blocked by a Rho-kinase inhibitor, Y-27632. In summary, these results offer strong support for a physiological role of Rho-kinase in regulation of MP activity.

3T3 Cells↗

PubMed1999

D(2) dopamine receptors induce mitogen-activated protein kinase and cAMP response element-binding protein phosphorylation in neurons.

Dopamine, by activating D(1)- and D(2)-class receptors, plays a significant role in regulating gene expression. Although much is known about D(1) receptor-regulated gene expression, there has been far less information on gene regulation mediated by D(2) receptors. In this study, we show that D(2) receptors can activate the mitogen-activated protein kinase (MAPK) and the cAMP response element-binding protein (CREB) in neurons. Treatment of brain slices with the D(2) receptor agonist quinpirole induced rapid phosphorylation of MAPK and CREB. The neuroleptic drug eticlopride, a highly selective D(2) receptor antagonist, blocked the quinpirole-induced phosphorylation of MAPK and CREB. D(2) receptor-induced MAPK phosphorylation depended on intracellular Ca(2+) elevation, protein kinase C activation, and MAPK kinase activation, but not on the protein tyrosine kinase Pyk2, even though quinpirole stimulated Pyk2 phosphorylation. D(2) receptor-induced CREB phosphorylation was mediated by activation of protein kinase C and Ca(2+)/calmodulin-dependent protein kinase, but not MAPK. The dopamine and cAMP-regulated phosphoprotein DARPP-32 also was required for the regulation of MAPK and CREB phosphorylation by D(2) receptors. Our results suggest that MAPK and CREB signaling cascades are involved in the regulation of gene expression and other long-term effects of D(2) receptor activation.

Animals↗