Biomedical subjects

X Guo

Publications and source records attributed to X Guo.

At least 271 records · Page 15Linked to original sources

PubMed1998

D1/D2 dopamine receptor interaction in membrane abolished by 6-hydroxydopamine lesion.

D1/D2 interaction in rat striatum was investigated by examining the effect of the D2 antagonist spiperone on the binding of [3H]SCH23390 to D1 dopamine (DA) receptors. In the presence of endogenous DA, spiperone blocked D2 receptors, then caused the increase of the binding of [3H]SCH23390 in rat striatal homogenate. After the 6-hydroxydopamine (6-OHDA) lesion, the increase was not found even if in the addition of exogenous DA. The results suggest that the D2 antagonist can modify the interaction between endogenous DA and D1 receptors labeled with [3H]SCH23390, while 6-OHDA lesion may change the state of D1/D2 interaction operating at the receptor level.

Adrenergic Agents↗

PubMed1998

Measurement error in dietary data: implications for the epidemiologic study of the diet-disease relationship.

OBJECTIVES: To examine the effect of measurement error in dietary data on the relationship between diet and body mass index (BMI). To correct for the effect of measurement error on diet-BMI association by using replicate measurements of diet. The effect of measurement error on diet--BMI relationship was simulated, and its implications are discussed. DESIGN: Prospective study design. SETTING: The first and second China Health and Nutrition Survey conducted in 1989 and 1991, respectively. SUBJECTS: Three thousand, four hundred and seventy-nine adults age 20-45 y at the 1989 survey. METHODS: Statistical methods were used to demonstrate the effect of measurement error in dietary data on the diet-BMI association. RESULTS: By using the average of three replicate 24 h dietary recalls, the attenuation of diet-BMI association was reduced substantially. The regression coefficients of fat and energy intakes differed markedly from those computed by using only single measurement of diet. CONCLUSIONS: Measurement error in dietary data may significantly attenuate the diet-disease association. Where appropriate, specific emphasis may be needed to address the problem of measurement error in the study of diet-disease relationship.

Adult↗

PubMed1998

QT interval and QT dispersion measured with the threshold method depend on threshold level.

Various computerized methods with multiple parameter options for measurements of the QT interval now are available. The optimum parameter setting for most algorithms is not known. This study evaluated the influence of the threshold level applied on the T wave differential on the QT interval and its dispersion measured in normal and abnormal electrocardiograms (ECGs). Seven hundred sixty ECGs recorded in 76 normal subjects and 630 in 63 patients with hypertrophic cardiomyopathy (HCM) (10 consecutive recordings in each individual) were analyzed. In each lead of each ECG, the QT interval was measured by the threshold method applied to the first differential of the T wave. The threshold level was varied between 5% and 30% of the T wave maximum in 1% steps, resulting in 26 different choices of QT measurements. With each choice the maximum QTc and the QT dispersion (QTd, standard deviation of the QT in all 12 leads) were obtained for each recording. The maximum QTc was significantly longer in HCM patients than in normal subjects (P < 0.001) at all threshold levels except between 5% and 7%. The QTd was significantly greater in HCM patients at all threshold levels. The QTc and QTd changed significantly with the threshold level. The maximum QTc varied up to 60 ms in normal subjects and up to 70 ms in HCM patients, depending on the threshold level. Thus, the QT interval and its dispersion measured with the threshold method applied to the first T wave differential depended significantly on the threshold level in both normal and diseased hearts. All programmable options of available automatic instruments should be examined carefully before any study, and all algorithmic details should by systematically presented.

Adult↗

PubMed1998

Comparative reproducibility of QT, QT peak, and T peak-T end intervals and dispersion in normal subjects, patients with myocardial infarction, and patients with hypertrophic cardiomyopathy.

Abnormal repolarization is associated with arrhythmogenesis. Because of controversies in existing methodology, new computerized methods may provide more reliable tools for the noninvasive assessment of myocardial repolarization from the surface electrocardiogram (ECG). Measurement of the interval between the peak and the end of the T wave (TpTe interval) has been suggested for the detection of repolarization abnormalities, but its clinical value has not been fully studied. The intrasubject reproducibility and reliability of automatic measurements of QT, QT peak, and TpTe interval and dispersion were assessed in 70 normal subjects, 49 patients with acute myocardial infarction (5th day; MI), and 37 patients with hypertrophic cardiomyopathy (HC). Measurements were performed automatically in a set of 10 ECGs obtained from each subject using a commercial software package (Marquette Medical Systems, Milwaukee, WI, U.S.A.). Compared to normal subjects, all intervals were significantly longer in HC patients (P < 0.001 for QT and QTp; p < 0.05 for TpTe); in MI patients, this difference was only significant for the maximum QT and QTp intervals (P < 0.05). In both patient groups, the QT and QTp dispersion was significantly greater compared to normal subjects (P < 0.05) but no consistent difference was observed in the TpTe dispersion among all three groups. In all subjects, the reproducibility of automatic measurement of QT and QTp intervals was high (coefficient of variation, CV, 1%-2%) and slightly lower for that of TpTe interval (2%-5%; p < 0.05). The reproducibility of QT, QTp, and TpTe dispersion was lower (12%-24%, 18%-28%, 16%-23% in normal subjects, MI and HC patients, respectively). The reliability of automatic measurement of QT, QTp, and TpTe intervals is high but the reproducibility of the repeated measurements of QT, QTp and TpTe dispersion is comparatively low.

Adult↗

PubMed1998

T wave complexity in patients with hypertrophic cardiomyopathy.

The complexity of the T wave assessed by principal component analysis (PCA) has been proposed to reflect abnormal repolarization, which may be arrhythmogenic. To determine whether PCA can differentiate patients with hypertrophic cardiomyopathy (HCM) from normal subjects and whether PCA is of prognostic importance in HCM, 112 patients with HCM (41 +/- 14 years, 64 males) and 72 healthy subjects (39 +/- 9 years, 41 males) were studied. Patients with sinus node dysfunction, AV conduction block, flat T waves, QRS > 140 ms, and those < 15 years were excluded from this study. Standard 12-lead ECGs were recorded digitally using the MAC-VU system (Marquette Medical Systems). PCA parameters were computed using the QT Guard software package by Marquette. PCA ratio was significantly greater in HCM patients than in normal controls (23.9% +/- 12.4% vs 16.1% +/- 7.6%, P < 0.0001) and was correlated with QT-end dispersion (r = 0.24, P = 0.01) and QT peak (Q point to T peak) dispersion (r = 0.35, P < 0.0001). HCM patients with syncope (n = 23) had increased PCA ratios compared with those without syncope (29.1% +/- 11.5% vs 22.5% +/- 12.3%, P = 0.01). PCA ratio was similar in patients with and without nonsustained ventricular tachycardia on Holter (25.9% +/- 11.4% vs 22.7% +/- 12.1%, P = 0.2), as well as in patients treated with amiodarone or sotalol versus those not on therapy. In conclusion, assessment of the complexity of the T wave by PCA differentiates HCM patients from normal subjects. PCA ratio correlated with QT dispersion and an increased PCA ratio was associated with a history of syncope in HCM.

Adult↗

PubMed1998

Evolution of changes in the ventricular rhythm during paroxysmal atrial fibrillation.

Changes in the RR interval within episodes of paroxysmal atrial fibrillation (PAF) have not been fully characterized. A database of 177 24-hour Holter recordings were created from patients with PAF in the CRAFT studies. PAF episodes of > or = 1 minute duration containing < or = 20% noise and preceded by > or = 1 minute of sinus rhythm with < or = 20% noise were selected. Sections of each AF episode containing 10 and 25 RR intervals were identified at the onset, middle, and termination of each episode. Descriptive characteristics (mean, SD, and RMSSD of RR intervals) were calculated within each section, and compared using a nonparametric, paired Wilcoxon test. In 25 patients (17 men, 60.6 +/- 12.2 years old), 231 episodes from 44 recordings met the selection criteria. The mean RR interval increased slightly between the onset and mid-portion of AF episodes (565.9 +/- 128.3 vs 580.3 +/- 144.7 ms, P < 0.001). The RR interval at the termination of AF was significantly greater than that at the start (627.1 +/- 156.1 vs 565.9 ms, P < 10-11) or mid-portion (627.1 +/- 156.1 vs 580.3 +/- 144.7 ms, P < 10-13). SD of the RR interval increased significantly between onset and mid-portion (111.1 +/- 60.2 vs 118.2 +/- 66.7 ms, P < 0.001) and more substantially between mid-portion and termination (118.2 +/- 66.7 vs 201.8 +/- 93.7 ms, P < 10-21). During paroxysms of AF, the mean RR interval and the variability of RR intervals increases. Termination of a paroxysm is preceded by a marked increase in RR interval variability.

Anti-Arrhythmia Agents↗

PubMed1998

Age and gender influences on rate and duration of paroxysmal atrial fibrillation.

UNLABELLED: The influence of age and gender on the character of paroxysmal atrial fibrillation (PAD) has not been described. METHODS: The heart rate (HR) during PAF in patients receiving placebo or antiarrhythmic therapy was analyzed. Data from 177 24-hour Holter recordings were analyzed to mark the onset and termination of PAF and converted into RR interval files. PAF episodes lasting at least 2 minutes and containing < or = 20% noise were included. HR during the first 30-second segment versus during the remainder of the episode, and the duration of PAF episodes were compared among groups of different ages and sex (Wilcoxon test). RESULTS: 236 episodes from 55 recordings in 32 patients (all patients: 61.4 +/- 12.8 years; men (19): 58.5 +/- 12.6 years; women (13) 65.5 +/- 12.4 years, P = ns for difference in age) fulfilled the inclusion criteria. Women had a higher mean heart rate at AF onset (123 +/- 35 beats/min vs 115 +/- 20 beats/min, P = 0.02) and during the remainder of the episode (120 +/- 25 beats/min vs 112 +/- 22 beats/min at the start, P = 0.01, and 116 +/- 26 beats/min vs 108 +/- 18 beats/min subsequently, P = 0.01). Episodes tended to be longer in women (mean 89.8 min vs 50.5 min, P = NS) and in the aged (mean 83.8 min vs 46.9 min, P = NS). CONCLUSION: PAF episodes are associated with faster heart rates and last longer in women, which may reflect differing autonomic responses to AF. A slower ventricular rate during PAF in older patients probably reflects an increasing prevalence of impaired atrioventricular conduction.

Age Factors↗

PubMed1998

Metabolism of 2',3'-dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine and its activity in combination with clinically approved anti-human immunodeficiency virus beta-D(+) nucleoside analogs in vitro.

2',3'-Dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine [L(-)Fd4C] has been reported to be a potent inhibitor of the human immunodeficiency virus (HIV) in cell culture. In the present study the antiviral activity of this compound in two-drug combinations and its intracellular metabolism are addressed. The two-drug combination of L(-)Fd4C plus 2',3'-didehydro-2'-3'-dideoxythymidine (D4T, or stavudine) or 3'-azido-3'-deoxythymidine (AZT, or zidovudine) synergistically inhibited replication of HIV in vitro. Additive antiviral activity was observed with L(-)Fd4C in combination with 2',3'-dideoxycytidine (ddC, or zalcitabine) or 2',3'-dideoxyinosine (ddI, or didanosine). This beta-L(-) nucleoside analog has no activity against mitochondrial DNA synthesis at concentrations up to 10 microM. As we previously reported for other beta-L(-) nucleoside analogs, L(-)Fd4C could protect against mitochondrial toxicity associated with D4T, ddC, and ddI. Metabolism studies showed that this drug is converted intracellularly to its mono-, di-, and triphosphate metabolites. The enzyme responsible for monophosphate formation was identified as cytoplasmic deoxycytidine kinase, and the K(m) is 100 microM. L(-)Fd4C was not recognized in vitro by human mitochondrial deoxypyrimidine nucleoside kinase. Also, L(-)Fd4C was not a substrate for deoxycytidine deaminase. L(-)Fd4C 5'-triphosphate served as an alternative substrate to dCTP for incorporation into DNA by HIV reverse transcriptase. The favorable anti-HIV activity and protection from mitochondrial toxicity by L(-)Fd4C in two-drug combinations favors the further development of L(-)Fd4C as an anti-HIV agent.

Anti-HIV Agents↗

PubMed1998

[Relationship between blood glucose, insulin and hypertension in 60 obese children].

OBJECTIVE: To study the relationship between blood glucose, insulin and hypertension in children. METHODS: Fasting serum glucose (GS), insulin (IS) and high-density lipoprotein (HDL) were determined in 60 obese children and 60 normal controls, and oral glucose tolerance test was performed for half of them. RESULTS: It showed that there were no significant differences in fasting GS, HDL and GS after glucose load between the two groups, and fasting IS, IS after glucose load, an area and a ratio of IS to GS under the insulin curve all were higher in the obese group than those in the control one. There were 43 obese children (71.7%) with hypertension. CONCLUSION: There existed hyper-insulinemia and insulin resistance in obese children and there also was close relationship between obesity and hypertension in them.

Adolescent↗

PubMed1998

CD 80(B7-1) expression on human tumor cell lines and its costimulatory signals for T cell proliferation and cytokine production.

OBJECTIVE: To investigate CD 80 expression on human tumor cell lines and establish stable CD 80 expression transfectants to illustrate CD 80 costimulation on the T cell proliferation and cytokine production. METHODS: Raji, MDA-453, MCF-7, Hela, 3AO, MKN-45 and EBV transformed B cell were detected for CD 80 expression by RT-PCR. CD 80 cDNA subcloned to retrovirus vector pLXSN, with them stable CD 80 transfectanants were established. With specific mAb BB1 and FACS assay, the expression of CD 80 were detected. Anti-CD3 induced T lymphocyte proliferation and IL-2, IFN-r production were performed to evaluate CD 80 costimulatory activity in the presence of calcium ionophore A23187 and phorbol ester PMA. RESULTS: CD 80 (B7-1) expression of MDA-453, MCF-7, Hela, 3AO, MKN-45 was negative, and that of Raji and EBV transformed B cell was positive by RT-PCR and FACS methods. Cocultured with CD 80 transfected human breast carcinoma cell line MDA-453, anti-CD3 induced T cells proliferation and cytokine production were significantly increased in the presence of A23187 and PMA, but not with parental MDA-453. CONCLUSIONS: CD 80 expression is absent on most human tumor cell line except for Raji and EBV transformed B cell. Full activation of T cell needs CD 80 costimulation. Influence of CD 80 costimulation on cytokine production is mainly regulated via IL-2 and IFN-r.

B7-1 Antigen↗

PubMed1998

Enhancement of (-)-stepholidine on protein phosphorylation of a dopamine- and cAMP-regulated phosphoprotein in denervated striatum of oxidopamine-lesioned rats.

AIM: To study effects of (-)-stepholidine (SPD) on the phosphorylation of a dopamine- and cAMP-regulated phosphoprotein (DARPP-32) in the striatum of oxidopamine-lesioned rats. METHODS: The amount of dephospho-DARPP-32 was measured by a back-phosphorylation assay. RESULTS: In the striatum of control rats, SPD per se had no effect on the phosphorylation of DARPP-32, but it antagonized the decrease by 28% of dephospho-DARPP-32 induced by the D1 agonist SK&F-38393. In the denervated striatum of oxidopamine-lesioned rats, SPD decreased the amount of dephospho-DARPP-32 by 44%. The effect of SPD was completely counteracted by the concomitant administration of the D1 antagonist Sch-23390. CONCLUSION: SPD exhibits D1 agonistic action on DARPP-32 phosphorylation in the denervated striatum of oxidopamine-lesioned rats, but it acts as a D1 antagonist in normal striatum.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed1998

Oxidized low-density lipoproteins induce apoptosis in vascular smooth muscle cells.

AIM: To examine whether oxidized low density lipoproteins (ox-LDL) could induce apoptosis in rabbit aortic smooth muscle cells (VSMC). METHODS: Low density lipoproteins (n-LDL) were isolated from healthy human plasma by gradient ultracentrifugation and oxidized by CuSO4 10 mumol.L-1. VSMC were exposed to ox-LDL, n-LDL, or phosphate-buffer solution (PBS) as control. Morphological changes were observed under fluorescene microscope after Hoechst 33258 staining. Extracted DNA was electrophoresized on agarose gel. RESULTS: Incubation of VSMC with ox-LDL 300 mg.L-1, not n-LDL, for 24 h induced morphological apoptosis changes (chromatin condensation, nucleus fragmentation) and DNA fragmentation, which was furthered with the incubation time up to 48 h or at a concentration of 400 mg.L-1. Dextran sulfate, a scavenger receptor blocker and butylated hydroxytoluene (BHT), an antioxidant, exhibited no effect on DNA fragmentation. Lysophosphatidylcholine (LPC) at a concentration up to 125 mumol.L-1 (equivalent to ox-LDL 300 mg.L-1) did not elicit DNA fragmentation. CONCLUSION: Ox-LDL induced apoptosis in VSMC without involving oxygen free radicals and LPC.

Animals↗

PubMed1998

[Membrane guided tissue regeneration in the treatment of bone defect].

Membrane guided tissue regeneration is new biological concept. The basic theory of this concept includes the belief that during the healing process of wound, the different cells will show different speed of cell migration and regeneration in the wound. If an appropriate membrane being placed to form a mechanical barrier, so that only the needed cells can grow into that area and prevent others from going in, thus resulting in the creation of a guided area where the needed cells can undergo proliferation and differentiation under protection in completing an ideal tissue regeneration and repair. In this article, the experimental researches on the application of membrane guided tissue regeneration in the repair of tubular bone defects, skull defects and faciomaxillary defects were reviewed from literatures, and the degradable and non-degradable materials were introduced, particularly. The pros and cons of this method and the materials were evaluated. It is believed that this technique will push forward the progress in bone biology and reconstructive surgery.

Animals↗

PubMed1998

[Expectant treatment of placenta previa with ritodrine].

OBJECTIVE: To investigate the effectiveness of the expectant treatment in placenta previa with adrenergic agonist ritodrine. METHODS: 50 women with placenta previa of preterm labor were randomly assigned into two groups. 26 patients treated with magnesium sulfate were served as control group. 24 patients were enrolled in the study group, receiving ritodrine 100 mg in 5% glucose 500 ml intravenous. The drip speed was started at 8 drips per minute routinely, then adjusted according to the treatment response, and oral ritodrine was used after vaginal bleeding and uterine contraction disappeared 12 hours. If contraction reappeared, the i.v. infusion would be restarted. RESULTS: The study group prolonged the gestational period to an average of 28.24 days and increased the birth weight of newborn to an average of 2,913.68 g (P < 0.05). CONCLUSION: Ritodrine is highly effective and safe for expectant treatment of placenta previa.

Adrenergic beta-Agonists↗

PubMed1998

[Study on the human dietary intake of minerals, energy, fiber and phytic acid].

Duplicate diets of three days were collected. The diets represented general living standard of male adults. There were three types of subjects: city inhabitants in group 1, northern peasants in group 2, and southern peasants in group 3. The diets were analyzed to calculate the average per capita intake of various minerals, energy, fiber and phytic acid. The assessment of intake according to the values of RDA, ESADDI and ADI shows the following results: Zn is low, Ca comes up to 2/3 of RDA, P reaches 88%-133% of RDA, Fe appears enough to attain the standard, but the availability should be considered. The contents of Se and I in each group was varied. Even though the intake of Se is low, it reaches the minimum requirement. Since I is being supplemented for all the people, it would not be deficient. The intake levels of Cu, Mo and Cr achieve or surpass the minimum values of ESADDI. Mn intake exceeds the maximum value of ESADDI, but the highest intake was only 10. 5 mg, which is far from poisoning level. High Na and low K intakes are specific defects of Chinese diets. The level of Cd, Hg and Pb is far apart from toxicosis. As for the amount of As intake, only in group 3 is higher than ADI by 29%. The energy is full. Dietary fiber is suitable. The intake of phytic acid of northern peasants is higher than that of southern peasants and city inhabitants, but it would be harmless.

Adult↗

PubMed1998

[Analysis of amino acids, vitamins and inorganic elements in Dictyophora indusiata].

Fifteen amino acids(total content: 13.37 mg.100 ml-1), 12 inorganic elements(Zn 37.3 micrograms.g-1, Mn 56.9 micrograms.g-1, Cr 4.88 micrograms.g-1, Fe 370 micrograms.g-1, Se 0.81 microgram.g-1, Cu 28.2 micrograms.g-1, Co 0.78 microgram.g-1, Ni 2.09 micrograms.g-1, etc.), and vitamin E(73.2 micrograms.g-1) in Dictyophora indusiata were determined. Seven amino acids, including valine 0.61, leucine 1.04, isoleucine 0.66, threonine 0.74, methionine 0.20, lysine 0.52, and pheuylalanine 0.64(mg.100 mg-1), were found to be essential. The possible medical significance of Dictyophora indusiata is discussed.

Amino Acids↗

PubMed1998

[Evaluation of the intubating conditions and maintenance doses of rocuronium].

OBJECTIVE: To assess intubating conditions after administration of rocuronium 0.6 mg/kg at 60 or 90 s and neuromuscular blocking effects of rocuronium. METHODS: Thirty-two patients were randomly designated to two groups: 60 s group and 90 s group. Anesthesia consisted of thiopentone, fentanyl, N2O/O2 and enflurane. After a 2 x ED95 dose the trachea was intubated at 60 or 90 s and the intubating conditions were recorded. After intubation was finished, patients were allocated randomly to receive either intravenous infusion or bolus injection of rocuronium to maintain surgical relaxation. RESULTS: Intubating conditions were not different between the two groups and were found to be clinically acceptable (good or excellent) in all patients. The maintenance of surgical relaxation was satisfactory either with repeated bolus and infusion of rocuronium. CONCLUSION: Intubation can be performed under good to excellent conditions within 60-90 seconds after a bolus dose of 0.6 mg/kg rocuronium. This indicates that rocuronium may be a suitable alternative to succinycholine during rapid-sequence induction of anesthesia.

Adjuvants, Anesthesia↗

PubMed1998

[The pharmacokinetic study of desflurane, sevoflurane, isoflurane and enflurane in general anesthesia].

OBJECTIVE: To compare pharmacokinetics of desflurane, sevoflurane, isoflurane and enflurane in general anesthesia. METHODS: 40 patients scheduled for abdominal hysterectomy under general anesthesia were randomly divided into desflurane(D), sevoflurane(S), isofluane(I) and enflurane(E) groups. After induction of anesthesia and endotracheal intubation, desired fraction (Fd) of desflurane(6%), sevoflurane(2%), isoflurane (1.15%) and enflurane(1.7%) in oxygen and nitrous oxide(1:2) were inhaled in D, S, I and E groups, respectively. The fractional end tidal alveolar concentration (Fa) was adjusted to 1MAC during the maintenance of anesthsia. Fa and the fractional inspired concentration of inhaled anesthetics (Fi) were monitored continuously. During operation, fentanyl was infused continuously and pancuronium was injected intermittently. RESULTS: After the beginning of inhalational anesthesia, the time required for Fa/Fi = 1:2 and Fa = 1MAC in D and S groups was significantly shorter than that in E and I groups. The rates of Fa/Fi in D and S groups were significantly higher than those in E and I groups during the maintenance of anesthesia, so were those of Fa/Fd. After cessation of inhalational anesthesia, the time required for Fa equaled to 50% of Fa0(the last Fa during stoping administration of the inhalational anesthesia) in D group was significantly faster than that in the other three groups. CONCLUSIONS: The rates of desflurane wash-in and wash-out are faster than those of other inhaled anesthetics. The depth of anesthesia is easy to control when desflurane is used in general anesthesia.

Anesthesia, General↗