Biomedical subjects

S Yan

Publications and source records attributed to S Yan.

At least 37 records · Page 2Linked to original sources

PubMed2001

HPLC analysis of complete BZ systems. Evolution of the chemical composition in cerium and ferroin catalysed batch oscillators: experiments and model calculations.

In the last few years many new reaction routes and intermediates have been discovered in the mechanism of the Belousov-Zhabotinsky (BZ) reaction with the aid of high performance liquid chromatography (HPLC). These previous HPLC studies, however, were limited to the Ce(4+)-organic substrate (malonic or bromomalonic acid) systems only. Very recently some measurements were made on a cerium catalysed full BZ system but only in its induction period. The present work follows the evolution of the main chemical components in a cerium and in a ferroin catalysed full BZ system from the start until the end of the oscillatory regime in a batch reactor. While recording the potential oscillations of a bromide selective electrode we measured from time to time the concentration of the following components: malonic and bromomalonic acids and bromate as main components; malonyl malonate, ethanetetracarboxylic and bromoethenetricarboxylic acids which are recombination products of organic free radicals; oxidized intermediates: tartronic, oxalic (OA) and mesoxalic (MOA) acids, and brominated products: dibromoacetic and tribromoacetic acids. Recombination products are generated in the intervals when the autocatalytic reaction is "switched off". In the course of the autocatalytic periods, however, the organic radicals react with the inorganic bromine dioxide radical mainly which leads to the formation of MOA and OA. Due to a very fast Ce(4+)-MOA reaction, MOA can be detected in the ferroin catalysed BZ system only. Our model calculations deal exclusively with the cerium catalysed system. The suggested new Marburg-Budapest-Missoula (MBM) model includes both negative feedback loops (bromous acid-bromide ion Oregonator type and bromine dioxide-organic free radicals Radicalator type feedback) and the recently discovered radical-radical recombination reactions. Comparison of the experimental data with the model calculations shows a good qualitative agreement but some open problems still remain. To overcome these problems oxygen atom transfer and other redox reactions are proposed.

Journal Article↗

PubMed2001

Allogeneic transplantation induces expression of cytomegalovirus immediate-early genes in vivo: a model for reactivation from latency.

Reactivation of cytomegalovirus (CMV) from latency is a frequent complication of organ transplantation, and the molecular mechanism by which this occurs is unknown. Previous studies have shown that allogeneic stimulation induces reactivation of human CMV (HCMV) in vitro (64). We find that transplantation of vascularized allogeneic kidneys induces murine CMV (MCMV) and HCMV immediate-early (ie) gene expression. This induction is accompanied by increased expression of transcripts encoding inflammatory cytokines, including tumor necrosis factor (TNF), interleukin-2, and gamma interferon, and by activation of NF-kappaB. TNF alone can substitute for allogeneic transplantation in inducing HCMV and MCMV ie gene expression in some tissues. Our studies suggest that reactivation is a multistep process which is initiated by factors that induce ie gene expression, including TNF and NF-kappaB. Allogeneic transplantation combined with immunosuppression may be required to achieve complete reactivation in vivo.

Animals↗

PubMed2001

Diaphragm activation during exercise in chronic obstructive pulmonary disease.

Although it has been postulated that central inhibition of respiratory drive may prevent development of diaphragm fatigue in patients with chronic obstructive pulmonary disease (COPD) during exercise, this premise has not been validated. We evaluated diaphragm electrical activation (EAdi) relative to maximum in 10 patients with moderately severe COPD at rest and during incremental exhaustive bicycle exercise. Flow was measured with a pneumotachograph and volume by integration of flow. EAdi and transdiaphragmatic pressures (Pdi) were measured using an esophageal catheter. End-expiratory lung volume (EELV) was assessed by inspiratory capacity (IC) maneuvers, and maximal voluntary EAdi was obtained during these maneuvers. Minute ventilation (V E) was 12.2 +/- 1.9 L/min (mean +/- SD) at rest, and increased progressively (p < 0.001) to 31.0 +/- 7.8 L/min at end-exercise. EELV increased during exercise (p < 0.001) causing end-inspiratory lung volume to attain 97 +/- 3% of TLC at end-exercise. Pdi at rest was 9.4 +/- 3.2 cm H(2)O and increased during the first two thirds of exercise (p < 0.001) to plateau at about 13 cm H(2)O. EAdi was 24 +/- 6% of voluntary maximal at rest and increased progressively during exercise (p < 0.001) to reach 81 +/- 7% at end-exercise. In conclusion, dynamic hyperinflation during exhaustive exercise in patients with COPD reduces diaphragm pressure-generating capacity, promoting high levels of diaphragm activation.

Diaphragm↗

PubMed2001

Hepatic artery angiography and embolization for hemobilia after hepatobiliary surgery.

OBJECTIVE: To evaluate the effectiveness of hepatic angiography and embolization in the diagnosis and treatment of hemobilia after hepatobiliary surgery. METHODS: Nine patients had upper gastrointestinal bleeding 7 days to 3 months after surgery. They underwent emergency hepatic artery angiography and were treated by embolization using Gelfoam particles only (8 patients) and Gelfoam particles plus microcoils (1 patient). RESULTS: Hepatic artery angiography revealed hepatic artery pseudoaneurysms in 3 patients, diffuse hemorrhage of the hepatic artery branches in 3, right hepatic artery-bile duct fistulas in 2, and hepatic artery-small intestine fistula in 1. Hemobilia was controlled with embolization in 7 patients, of whom 1 had recurrent bleeding 1 day after treatment. During the follow-up, 3 patients died of multiple organ dysfunction syndrome. Two patients whose hemorrhage could not be controlled due to technical reasons died several days later. CONCLUSION: When hemobilia after hepatobiliary surgery is suspected, patients should receive hepatic angiography as a first diagnostic procedure and be treated with minimally invasive procedure of selective embolization of the involved artery as soon as possible.

Adolescent↗

PubMed2001

[Chromosome t (8; 21) and t (15; 17) in a patient with acute myeloid leukemia].

OBJECTIVE: To report an acute myeloid leukemia (AML) patient with both chromosome t (8; 21) and t (15; 17). METHODS: Chromosome specimen was prepared by short-term culture of bone marrow cells, karyotype analyses by R-banding technique, and fusion genes by reverse transcriptase-polymerase chain reaction (RT-PCR). RESULT: Karyotype analyses showed the appearance of 45, X, -X, t (8; 21), t (15; 17), and RT-PCR assay revealed AML1/ETO and PML-RARalpha fusion gene transcripts. CONCLUSION: AML with both t (8; 21) and t (15; 17) might be recognized as a a novel subtype of acute leukemias.

Bone Marrow Cells↗

PubMed2001

[Effects of olive oil and fish oil on serum lipids and lipid peroxidation in rats].

The effects of olive oil and fish oil on serum lipids and lipid peroxidation were studied in rats. The rats were divided into four groups: negative control, high fat control, fish oil (high fat diet and tube feeding with fish oil 4 ml.kg-1.d-1) and olive oil (high fat diet and tube feeding with olive oil 4 ml.kg-1.d-1) groups. The results showed that the total serum cholesterol and the triglyceride decreased significantly both in fish oil group and olive oil group, and there was a significant increase of serum high-density-lipoprotein (HDL) cholesterol in fish oil group. Both fish oil and olive oil increased superoxide dismutase (SOD) in erythrocyte and decreased serum MDA.

Animals↗

PubMed2001

[A dietary intervention study on the hypertensive high risk population in a northern rural area of Beijing].

To investigate the relationship between optimal living mode, healthy dietary pattern and the incidence of primary hypertension, a dietary intervention study on hte hypertensive high risk population was carried out in Fangshan district of Beijing during 1997-1999. The subjects were divided into two groups: control group and intervention group. A 3-day-dietary-recall combined with weighing method and a healthy diet education program were used in the study. The results indicated that the dietary pattern was not reasonable in the hypertensive high risk population. After two-year-intervention, the dietary pattern of people in the intervention group has changed distinctively. Compared with the results in 1997, the dietary risk factors decreased obviously in the intervention group, but increased in control group, such as high energy, fat, oil and cholesterol which can promote hypertension. Furthermore, in the past two years, the number of over weight + obese people increased by 24.6% in control group, but was no change in the intervention group. The intervention group subjects experienced an average decline of 3.7 and 5.1 mmHg of systolic blood pressure(SBP) and diastolic blood pressure(DBP) respectively, and new cases of hypertension observed in the intervention group were significantly lower than in control group. Thus it can be considered that the dietary intervention may be effective for the high risk population and play a very important role in the prevention of hypertension.

Adult↗

PubMed2000

Class I MHC is stabilized against thermal denaturation by physiological concentrations of NaCl.

Class I MHC molecules are ternary complexes composed of an allotype specific heavy chain, a noncovalently associated protein beta(2)-microglobulin (beta(2)m), and a peptide. The complexes are assembled in the endoplasmic reticulum by a complex series of chaperones and peptide-loading mechanisms. In the absence of beta(2)m or peptide, very little class I heavy chain is transported to the surface of the cell. Complexes that do not contain all three parts of the protein are not made productively in vivo and not at all in vitro. The ability of the complex to withstand thermal denaturation in vitro has been shown to be related to the binding affinity of the peptide. Paradoxically, some low-affinity peptide complexes denature at or below human basal body temperatures in vitro but are effective biological agents in vivo. Here we show that these complexes are stabilized against thermal denaturation by physiological cosolvents and maximally stabilized by 150 mM NaCl. While the degree of stabilization by 150 mM NaCl is greatest for low-affinity peptide/MHC complexes, the mechanism of stabilization is independent of peptide sequence. This effect is hypothesized to occur by multiple mechanisms including increasing the affinity of beta(2)m for the complex and charge screening.

Amino Acid Sequence↗

PubMed2000

[Effects of dietary lipids on serum cholesterol of elder hypercholesterolemic patients].

The intake of dietary lipids of 167 elder hypercholesterolemic patients was collected by a three-day recorded dietary survey. At the mean time, their serum total cholesterol (TC), high density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) levels were detected and analyzed. The results showed the effects of dietary lipids and body mass index (BMI) were great on serum cholesterol levels; BMI, dietary cholesterol and saturated fatty acid were positively related to serum TC and LDL-C; serum HDL-C and HDL-C/TC ratio were positively related with dietary monounsaturated fatty acid, and negatively related with BMI. The results indicate that decreasing the intake of dietary cholesterol and saturated fatty acid, controlling body weight and increasing dietary monounsaturated fatty acid intake will have important benefits on the prevention and treatment of hypercholesterolemia and cardiovascular diseases.

Adult↗

PubMed2000

Enhanced accumbal dopamine release following 5-HT(2A) receptor stimulation in rats pretreated with intermittent cocaine.

This study was conducted to determine whether dopamine (DA) release in the nucleus accumbens (NACC) following 5-HT(2A) receptor stimulation is potentiated by intermittent cocaine. Rats received daily injections of either saline or cocaine (30 mg/kg, s.c.) for 14 days. At the 7th day after withdrawal, microdialysis was performed in the NACC. Infusion of (+/-)-1-(4-iodo-2, 5-dimethoxyphenyl)-2-aminopropane (DOI, 50 microM), a 5-HT(2) receptor agonist, into the NACC produced greater and longer-lasting increases in extracellular DA in the rats pretreated with cocaine than in the rats pretreated with saline. The DOI-induced increases in NACC DA were attenuated by co-perfusion with ketanserin (50 microM), a 5-HT(2A) receptor antagonist. The results are consistent with the concept that intermittent cocaine may cause enhanced sensitivity of 5-HT(2A) receptors within the NACC.

Amphetamines↗

PubMed2000

Perturbation of EGF-activated MEK1 and PKB signal pathways by TGF-beta1 correlates with perturbation of EGF-induced cyclin D1 and DNA synthesis by TGF-beta1 in C3H 10T1/2 cells.

In mouse C3H 10T1/2 cells, we previously reported that TGF-beta1 first delays and later potentiates EGF-induced DNA synthesis corresponding to an inhibition of EGF-induced cyclin D1 expression at t = 13 h. We report here that in accord with DNA synthesis kinetics, TGF-beta1 initially suppresses EGF-induced cyclin D1 expression then later releases the inhibition. Furthermore, TGF-beta1 also first decreases and later potentiates the levels of EGF-activated MEK1/MAPK and PKB, indicating the existence of cross talk between TGF-beta 1- and EGF-activated signal transduction pathways. PD98059, the specific inhibitor of MEK1, significantly blocks EGF-induced DNA synthesis, whereas wortmannin, the PI3K inhibitor, exerts a modest inhibitory effect, which suggests that the activation of MEK1-MAPK pathway plays a major role in EGF-induced DNA synthesis and the activation of PI3K-PKB pathway plays a minor role. Upon examination of mechanisms underlying the cross talk, it was discovered that application of TGF-beta1 triggers a rapid association between Raf-1 and catalytic subunits of PKA, which are reported to be able to inactivate Raf-1 upon activation. Therefore, TGF-beta1 may activate PKA to inhibit the EGF-activated MEK1-MAPK pathway. The wortmannin-sensitive phosphorylation at the thr(389) site is necessary for activation of p70s6K, an important kinase involved in mitogen-stimulated protein synthesis. Although we found that EGF-stimulated p70s6K phosphorylates through a MAPK-dependent and a MAPK-independent (wortmannin-sensitive) pathway, TGF-beta1 failed to block EGF-triggered phosphorylation of p70s6K at thr(389) and thr(421)/ser(424) sites, implying that PKB inhibition by TGF-beta1 may result from inhibition of PDK1 activity instead of inhibition of PI3K activity. These data also suggest that TGF-beta1 may selectively perturb certain EGF-activated MAPK pools.

Animals↗

PubMed2000

Structural identification of two metabolites of catechins and their kinetics in human urine and blood after tea ingestion.

Tea is a popular beverage consumed worldwide. The metabolic fate of its major constituents, catechins, however, is not well-known. In this study, two catechin metabolites were detected in the urine and plasma of human volunteers after ingestion of green tea. These metabolites were identified by LC/ESI-MS and NMR as (-)-5-(3',4', 5'-trihydroxyphenyl)-gamma-valerolactone (M4) and (-)-5-(3', 4'-dihydroxyphenyl)-gamma-valerolactone (M6). The renal excretion of M4 and M6 had a 3 h lag time and peaked 7.5-13.5 h after ingestion of a single dose of green tea, while (-)-epigallocatechin (EGC) and (-)-epicatechin peaked at 2 h. M4 and M6 were two major tea metabolites with urinary cumulative excretions as high as 8-25 times the levels of EGC and (-)-epicatechin in some of our subjects, and accounted for 6-39% of the amounts of ingested EGC and (-)-epicatechin. Both the metabolites appeared to be produced by intestinal microorganisms, with EGC and (-)-epicatechin as the precursors of M4 and M6, respectively. Repeated ingestion of green tea produced a slight accumulative effect of the metabolites. They were also detected in the plasma, exhibiting kinetics similar to those of the urinary metabolites, and in the feces. Study on these metabolites may help us further understand the cancer chemopreventive actions and other beneficial effects of tea.

Adult↗

PubMed2000

Expiratory muscle pressure and breathing mechanics in chronic obstructive pulmonary disease.

Expiratory muscle recruitment is common in stable chronic obstructive pulmonary disease (COPD) patients. Due to airway obstruction, there is little reason to believe that active expiration in COPD would be mechanically effective in lowering operating lung volume. The physiological significance of expiratory muscle recruitment in COPD, therefore, remains unknown. The purpose of this study was to assess, in COPD patients breathing at rest, the effect of expiratory muscle contraction on force generating ability of the diaphragm. The force generating ability of the diaphragm was evaluated from its pressure swing (Pdi) for a given diaphragm electrical activity (Edi), where Edi was normalized as % of its maximal value (Pdi/Edi/Edi,max). Phasic expiratory muscle contraction was measured as the total expiratory rise in gastric pressure (Pga,exp.rise). Nineteen seated patients with moderate to severe COPD, participated in the study and 10 exhibited phasic rise in Pga during expiration with a mean Pga,exp.rise of 1.91+/-0.89 cmH2O. The patients were thus divided into passive expiration (PE) and active expiration (AE) groups. There was no significant difference in various lung function and breathing pattern parameters between the two groups. Pdi/Edi/Edi,max was 0.63+/-0.07 and 0.54+/-0.07 cmH2O/% in PE and AE groups, respectively, and was not significantly different between each other. Compared with PE group, AE group not only recruited expiratory muscles, but also preferentially recruited inspiratory rib cage muscles and derecruited the diaphragm. The results do not support a significant improvement of the force-generating ability of the diaphragm by phasic contraction of expiratory muscles at rest in chronic obstructive pulmonary disease patients.

Aged↗

PubMed2000

Genomic organization and gene function in Leishmania.

Sequencing of the Leishmania major Friedlin genome is well underway with chromosome 1 (Chr1) and Chr3 having been completely sequenced, and Chr4 virtually complete. Sequencing of several other chromosomes is in progress and the complete genome sequence may be available as soon as 2003. A large proportion ( approximately 70%) of the newly identified genes remains unclassified, with many of these being potentially Leishmania- (or kinetoplastid-) specific. Most interestingly, the genes are organized into large (>100-300 kb) polycistronic clusters of adjacent genes on the same DNA strand. Chr1 contains two such clusters organized in a 'divergent' manner, i. e. the mRNAs for the two sets of genes are both transcribed towards the telomeres. Chr3 contains two 'convergent' clusters, with a single 'divergent' gene at one telomere, with the two large clusters separated by a tRNA gene. We have characterized several genes from the LD1 (Leishmania DNA 1) region of Chr35. BT1 (formerly ORFG) encodes a biopterin transporter and ORFF encodes a nuclear protein of unknown function. Immunization of mice with recombinant antigens from these genes results in significant reduction in parasite burden following Leishmania challenge. Recombinant ORFF antigen shows promise as a serodiagnostic. We have also developed a tetracycline-regulated promoter system, which allows us to modulate gene expression in Leishmania.

Animals↗

PubMed2000

Correction of severe congenital epicanthus using the modified square-flap method.

The square-flap method has been gradually adopted for the correction of cicatricial contracture because it effectively relieves the longitudinal shortness in the deformity. Since 1990, the authors have slightly modified the design and employed it for the correction of severe congenital epicanthus. Forty-six cases (23 patients) have been treated by using this modified square flap. Good functional and cosmetic results were obtained. The authors consider it an effective technique with the advantages of rational design, simple operation and fewer incisions. This paper describes the operation design and discusses the advantages and key points of the surgery.

Adolescent↗

PubMed2000

Transcription of human cathepsin B is mediated by Sp1 and Ets family factors in glioma.

Cathepsin B expression is increased at both the mRNA and protein levels in a wide variety of tumors. The mechanisms responsible for this regulation are not well elucidated. We have isolated a 2.2-kb cathepsin B genomic fragment that contains the 5'-flanking region of the cathepsin B gene. Using reporter gene analysis in human glioblastoma U87MG cells, we have mapped a 228-bp fragment (-172 to +56) having high promoter activity. This promoter region has a high G+C content; contains potential Spl, Ets, and USF binding motifs; and lacks canonical TATA and CAAT boxes immediately upstream of the major transcriptional initiation site. Cotransfection experiments demonstrated that Spl and Ets1 could trans-activate cathepsin B transcription, whereas Ets2 could not. Electrophoretic mobility shift assays and supershift assays revealed that three of the four putative Sp1 sites in this promoter region form a specific complex containing the Sp1 transcription factor. Mutating all four of the Spl binding sites individually markedly reduced the promoter activity of transfected reporter genes in U87 cells. Cotransfection of this cathepsin B promoter construct with Spl family expression vectors in Schneider's Drosophila line 2 (SL2) cells demonstrated that Spl and Sp3, but not Sp4, activated cathepsin B transcription. Taken together, these results suggest that Sp1, Sp3, and Ets1 are important factors in cathepsin B transcription. The regulation of cathepsin B transcription by Sp1- and Sp1-related factors is mediated through multiple GC boxes.

Base Sequence↗

PubMed2000

Propofol impairment of mitochondrial respiration in isolated perfused guinea pig hearts determined by reflectance spectroscopy.

OBJECTIVE: To simultaneously determine the effect of propofol on myocardial oxygenation, mitochondrial function, and whole organ function in an isolated heart model, using optical reflectance spectroscopy. DESIGN: Controlled laboratory investigation. SETTING: Research laboratory. SUBJECTS: Twenty adult guinea pigs. INTERVENTIONS: Isolated hearts were perfused alternately with a modified oxygenated Krebs-Henseleit buffer and with buffer containing varied concentrations of propofol. Ninety seconds of ischemia were produced during perfusion with each solution studied. MEASUREMENTS AND MAIN RESULTS: Myoglobin oxygen saturation, cytochrome c and cytochrome a/a3 redox state, and ventricular pressure were continuously measured from isolated guinea pig hearts during a 2-hr period. Myoglobin oxygen saturation increased and both cytochromes became more oxidized in the presence of propofol. During ischemia, myoglobin desaturation and cytochrome reduction were delayed and less complete in the presence of propofol. The mean ischemic time to 50% myoglobin desaturation was, on average, 14.3 secs with buffer perfusion, and increased to 24.5, 27.9, and 41.8 secs, with 50, 100, and 200 microM propofol perfusion, respectively. Ventricular function decreased linearly with increasing propofol concentration. From baseline buffer perfusion, maximal dP/dt per cardiac cycle decreased on average by 30.4%, 40.9%, and 69.4%, with 50, 100, and 200 microM propofol perfusion, respectively. CONCLUSIONS: Propofol impairs either oxygen utilization or inhibits electron flow along the mitochondrial electron transport chain in the guinea pig cardiomyocyte. Propofol also significantly decreases ventricular performance in the isolated perfused heart. These effects are linearly correlated with propofol concentration in the range studied.

Anesthetics, Intravenous↗

PubMed2000

Twitch transdiaphragmatic pressure depends critically on thoracoabdominal configuration.

We measured the effect of thoracoabdominal configuration on twitch transdiaphragmatic pressure (Pdi, t) in response to supramaximal, transcutaneous, bilateral phrenic nerve shocks in three thin normal men. Pdi, t was measured as a function of lung volume (VL) in the relaxation configuration, at functional residual capacity (FRC), and at the same end-tidal VL 1) during relaxation; 2) with the abdomen (Ab) expanded and the rib cage (RC) in its relaxed FRC configuration; 3) with RC expanded and Ab in its relaxed FRC configuration; and 4) in configuration 3 with an active transdiaphragmatic pressure similar to that required to produce configuration 2. In increasing VL from FRC to configuration 1, Pdi, t decreased by 3.6 cmH(2)O; to configuration 2 by 14.8 cmH(2)O; to configuration 3 by 3.7 cmH(2)O; and to configuration 4 by 2.7 cmH(2)O. We argue that changes in velocity of shortening and radius of curvature are unlikely to account for these effects and suggest that changes in diaphragmatic fiber length (L(di)) are primarily responsible. If so, equivolume displacements of Ab and RC change L(di) in a ratio of approximately 4:1. We conclude that Pdi, t is exquisitely sensitive to abdominal displacements that must be rigorously controlled if Pdi, t is to be used to assess diaphragmatic contractility.

Abdomen↗