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R Du

Publications and source records attributed to R Du.

At least 19 recordsLinked to original sources
PubMed2000

Coronary nitric oxide production in response to exercise and endothelium-dependent agonists.

BACKGROUND: Endothelium-derived nitric oxide (NO) contributes to epicardial coronary artery vasodilation during exercise. However, blockade of NO production does not impair the increase in coronary blood flow (CBF) during exercise, suggesting that NO is not obligatory for exercise-induced coronary resistance vessel dilation. In contrast, the increases in CBF produced by endothelium-dependent agonists are decreased after NO blockade. Consequently, this study was performed to determine whether the increase in coronary NO production in response to agonists is greater than that which occurs during exercise. METHODS AND RESULTS: We measured the oxidation products of NO (nitrate+nitrite=NO(x)) in aortic and coronary sinus plasma using chemiluminescence to assess NO(x) production across the coronary circulation in chronically instrumented dogs during a 3-stage treadmill exercise protocol and in response to intracoronary administration of the endothelium-dependent agonists acetylcholine (37.5 microg/min) and bradykinin (3.0 microg/min). No coronary NO(x) production could be detected at rest or during the first 2 stages of exercise; only at the highest level of exercise was a small increase in coronary NO(x) production measured. In contrast, coronary production of NO(x) was significantly increased in response to endothelium-dependent agonists. CONCLUSIONS: Coronary NO production in response to endothelium-dependent agonists is greater than in response to the increase in shear stress associated with exercise. These findings support previous studies suggesting that NO is not required for the coronary vasodilation that occurs in the normal heart during exercise.

Acetylcholine↗
PubMed2000

MSY2: a slowly evolving minisatellite on the human Y chromosome which provides a useful polymorphic marker in Chinese populations.

We present the second human Y-specific minisatellite, MSY2 (DYS440). It consists of three or four copies of a 99-110bp repeat unit and is located about 1kb upstream of the DBY gene. The most common allele contains four units, but a three-unit allele has arisen on at least four occasions; in chimpanzees and orangutans, MSY2 contains only two units. It is therefore evolving slowly and provides a particularly useful polymorphic marker for Chinese populations.

Alleles↗
PubMed1999

Distribution of two HIV-1-resistant polymorphisms (SDF1-3'A and CCR2-64I) in East Asian and world populations and its implication in AIDS epidemiology.

Chemokine receptor CCR2 and stromal-derived factor (SDF-1) are involved in HIV infection and AIDS symptom onset. Recent cohort studies showed that point mutations in these two genes, CCR2-64I and SDF1-3'A, can delay AIDS onset > or = 16 years after seroconversions. The protective effect of CCR2-64I is dominant, whereas that of SDF1-3'A is recessive. SDF1-3'A homozygotes also showed possible protection against HIV-1 infection. In this study, we surveyed the frequency distributions of the two alleles at both loci in world populations, with emphasis on those in east Asia. The CCR2-64I frequencies do not vary significantly in the different continents, having a range of 0.1-0.2 in most populations. A decreasing cline of the CCR2-64I frequency from north to south was observed in east Asia. In contrast, the distribution of SDF1-3'A in world populations varies substantially, and the highest frequency was observed in Oceanian populations. Moreover, an increasing cline of the SDF1-3'A frequency from north to south was observed in east Asia. The relative hazard values were computed to evaluate the risk of AIDS onset on the basis of two-locus genotypes in the east Asian and world populations.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Y-Chromosome evidence for a northward migration of modern humans into Eastern Asia during the last Ice Age.

The timing and nature of the arrival and the subsequent expansion of modern humans into eastern Asia remains controversial. Using Y-chromosome biallelic markers, we investigated the ancient human-migration patterns in eastern Asia. Our data indicate that southern populations in eastern Asia are much more polymorphic than northern populations, which have only a subset of the southern haplotypes. This pattern indicates that the first settlement of modern humans in eastern Asia occurred in mainland Southeast Asia during the last Ice Age, coinciding with the absence of human fossils in eastern Asia, 50,000-100,000 years ago. After the initial peopling, a great northward migration extended into northern China and Siberia.

Africa↗
PubMed1998

Models of protein interactions: how to choose one.

BACKGROUND: There have been many attempts to approximate realistic protein interaction energies by coarse graining (i.e. considering interactions between amino acids rather than those between atoms). In particular, many 20-letter models have been derived (corresponding to the 20 naturally occurring amino acids). Because such models remain computationally infeasible, many two-letter models have been proposed as further simplifications. The choice of which model to use remains arbitrary, however. In this work, we formulate the framework within which the quality of approximate interaction potentials with respect to folding can be defined explicitly. RESULTS: Using a recently proposed criterion for comparing interaction matrices, we compare various 20 x 20 interaction matrices and obtain the two-letter model that most closely approximates each 20 x 20 matrix. We find that there are considerable differences among the 20 x 20 matrices. In particular, some matrices are much more similar to the hydrophobic model than others. Furthermore, we find that although the best two-letter approximation of a 20-letter model is a significantly better approximation than a random two-letter model, it is still a poor approximation of realistic protein interactions. CONCLUSIONS: The determination of the best two-letter approximations of various 20-letter models of protein interaction energies reveals the degree to which hydrophobic interactions dominate in each of the models and hence in proteins.

Models, Chemical↗
PubMed1998

Monitoring working memory load during computer-based tasks with EEG pattern recognition methods.

We assessed working memory load during computer use with neural network pattern recognition applied to EEG spectral features. Eight participants performed high-, moderate-, and low-load working memory tasks. Frontal theta EEG activity increased and alpha activity decreased with increasing load. These changes probably reflect task difficulty-related increases in mental effort and the proportion of cortical resources allocated to task performance. In network analyses, test data segments from high and low load levels were discriminated with better than 95% accuracy. More than 80% of test data segments associated with a moderate load could be discriminated from high- or low-load data segments. Statistically significant classification was also achieved when applying networks trained with data from one day to data from another day, when applying networks trained with data from one task to data from another task, and when applying networks trained with data from a group of participants to data from new participants. These results support the feasibility of using EEG-based methods for monitoring cognitive load during human-computer interaction.

Adult↗
PubMed1998

The pathogenetic role of endogenous angiotensin II in stress ulcer in obstructive jaundice rats.

OBJECTIVE: To investigate the pathogenetic role of endogenous angiotensin II (Ang II) in the mechanism of stress ulcer in obstructive jaundice rats and to detect the effect of angiotensin converting enzyme inhibitor (ACEI) on stress ulcer in obstructive jaundice rats. METHODS: After common bile duct ligation (CBDL) in Wistar rats, the content of plasma and gastric mucosal Ang II, gastric mucosal blood flow (GMBF) and gastric mucosal damage were measured, and the relationship among them was analyzed. RESULTS: The plasma Ang II contents increased much more significantly at 1, 3, 7 and 14 days following CBDL than those in non-CBDL rats (P < 0.05, < 0.01, < 0.01 and < 0.01, respectively). Within 120 minutes following cold-restraint stress, plasma and gastric mucosal Ang II contents were elevated, GMBF decreased, and ulcer index and gastric mucosal damage increased more significantly than those in non-cold-restraint stress rats (P < 0.05, < 0.05, < 0.01, < 0.01 and < 0.05, respectively). Administration of an ACEI, enalaprili, to CBDL rats (5 mg.kg-1.day-1, orally for two days) before stress reduced both the plasma and gastric mucosal Ang II levels, inhibited the decrease of GMBF and decreased ulcer index and gastric mucosal damage (P < 0.001, < 0.01, < 0.01, < 0.01 and < 0.05, respectively). CONCLUSION: The endogenous Ang II plays a significant pathogenetic role in the development of stress ulcer in obstructive jaundice rats, and ACEI may prevent stress ulcer.

Angiotensin II↗
PubMed1997

[Treatment of atrial fibrillation using maze procedure by radiofrequency ablation].

From May 1994 to May 1996, 20 cases of atrial fibrillation were treated by means of Maze procedure by radiofrequenncy ablation, at the same time 19 cases of these patients were complicated with rheumatic heart valve disease and valve replacement operations were perfomned, in the other case atrial septal defect was repaired. Yoshio Kosakai's operation route was adopted in radiofrequency ablation procedure. After operation 16 patients of atrial fibrillation resumed sinus rhythm (80%), in 4 casess of atrial fibrillation sinus rhythm was unsuccessfully restored, two patients remained atrial fibrillation, one patient was of atrial flutter, the other was of nodal rhythm. Short time was needed in radiofrequency ablation Maze procedure, average time increase of aortic clamping was 20.5 minutes, and there was no danger of hemorrhage related to this kinds of Maze procedure. During 7-10 days after operation, there appeared superventricular arrhythmia which might be related to ill-distribution of radiofrequency ablation, and interference of atrial electric activity.

Adult↗
PubMed1997

[Polymorphism of group specific component (Gc) in nine Han subpopulations in China].

Isoelectric focusing (IEF) followed by immunofixation in thin layer polyacrylamide gels (pH4-6) was used to analyse the Gc subtypes of 1841 individuals from nine Han geographically distributed populations in China. The Gc1F gene frequencies in these Han subpopulations from Lanzhou, Huhhot, Harbin, Xi'an, Zhengzhou, Chengdu, Guiyang, Zhangzhou and Harras in Guangdong Province were 0.3905, 0.4333, 0.4193, 0.4146, 0.4182, 0.4035, 0.4045, 0.4381 and 0.4347 respectively; Gc1S were 0.3071, 0.2190, 0.2734, 0.2261, 0.2182, 0.2871, 0.2889, 0.2738 and 0.2764 respectively; Gc2 were 0.2786, 0.3357, 0.2917, 0.3367, 0.3295, 0.2896, 0.3065, 0.2667, and 0.2814 respectively. GcV were 0.0238, 0.0119, 0.0156, 0.0226, 0.0341, 0.0198, 0.0000, 0.0214 and 0.0075 respectively. The results of present study indicated a clear cline of linear change from north to south China in allelic frequency at the Group-Specific Component (Gc) locus among nine Chinese populations. Three alleles, Gc1F, Gc2 and GcV, showed frequencies varying from 0.3905 to 0.4381, from 0.2786 to 0.3367 and from nil to 0.0341, respectively, over these geographical subpopulations. In addition, some rare variant phenotypes of Gc in Chinese populations were discussed.

China↗
PubMed1996

High resolution evoked potential imaging of the cortical dynamics of human working memory.

High resolution evoked potentials (EPs), sampled from 115 channels and spatially sharpened with the finite element deblurring method, were recorded from 8 subjects during working memory (WM) and control tasks. The tasks required matching each stimulus with a preceding stimulus on either verbal or spatial attributes. All stimuli elicited a central P200 potential that was larger in the spatial tasks than in the verbal tasks, and larger in the WM tasks than in the control tasks. Frequent, non-matching stimuli elicited a frontal, positive peak at 305 msec that was larger in the spatial WM task relative to the other tasks. Irrespective of whether subjects attended to verbal or spatial stimulus attributes, non-matching stimuli in the WM tasks also elicited an enhanced P450 potential over the left frontal cortex, followed by a sustained potential over the superior parietal cortex. A posterior P390 potential elicited by infrequent, matching stimuli was smaller in amplitude for both spatial and verbal WM tasks compared to control tasks, as was a central prestimulus CNV. These results indicate that WM is a function of a distributed system with both task-specific and task-independent components. Lesion studies and course temporal resolution functional imaging methods, such as PET and fMRI, tend to paint a fairly static picture of the cortical regions which participate in the performance of WM tasks. In contrast, the fine-grain time resolution provided by imaging brain function with EP methods provides a dynamic picture of subsecond changes in the spatial distribution of WM effects over the course of individual trials, as well as evidence for differences in the activity elicited by matching and non-matching stimuli within sequences of trials. This information about the temporal dynamics of WM provides a critical complement to the fine-grain spatial resolution provided by other imaging modalities.

Acoustic Stimulation↗
PubMed1996

[Serum adrenaline and noradrenaline levels in cirrhosis patients with portal hypertension].

High Pressure Liquid chromatography was used to measure serum adrenaline (E) and noradrenaline (NE) concentrations in 38 portal hypertensive patients, 28 idiopathic hypertensive patients, and 34 controls, respectively. It was found that peripheral E in portal hypertensive patients and controls was 57.5 +/- 37.4 pg/ml and 23.5 +/- 11.2 pg/ml respectively (P < 0.01), and peripheral NE was 451.1 +/- 381.2 pg/ml and 183.0 +/- 83.3 pg/ml (P < 0.01). Compared with controls, peripheral E and NE in idiopathic hypertensive patients were also significantly increased (54.9 +/- 39.9 pg/ml vs. 23.6 +/- 11.2 pg/ml, P < 0.01, and 524.3 +/- 219.9 pg/ml vs. 183.0 +/- 83.3 pg/ml, P < 0.01). E and NE in superior vena cava (SVC), portal vein, and peripheral artery in portal hypertensive patients were also increased, but only the elevation of E in SVC was significant (207.2 +/- 55.4 pg/ml vs. 83.7 +/- 46.7 pg/ml, P < 0.05). Our results reveal significant metabolic disorders of E and NE in portal hypertensive patients, which may play an important role in the pathogenesis of portal hypertension.

Adult↗
PubMed1995

Mapping cognitive brain function with modern high-resolution electroencephalography.

High temporal resolution is necessary to resolve the rapidly changing patterns of brain activity that underlie mental function. While electroencephalography (EEG) provides temporal resolution in the millisecond range, which would seem to make it an ideal complement to other imaging modalities, traditional EEG technology and practice provides insufficient spatial detail to identify relationships between brain electrical events and structures and functions that are visualized by magnetic resonance imaging (MRI) or positron emission tomography (PET). Recent advances overcome this problem by recording EEGs from more electrodes, by registering EEG data with anatomical information from each subject's MRI, and by correcting the distortion that is caused by volume conduction of EEG signals through the skull and scalp. Along with its ability to record how brains think when performing everyday activities in the real world, these advances make modern EEG an invaluable complement to other functional neuroimaging modalities.

Brain↗
PubMed1995

Towards measurement of brain function in operational environments.

In operational environments that demand sustained vigilance or that involve multiple tasks competing for limited attentional resources, continuous monitoring of the mental state of the operator could decrease the potential for serious errors and provide valuable information concerning the ergonomics of the tasks being performed. There is widespread discussion and appreciation of the basic feasibility of utilizing neurophysiological measurements to derive accurate, reliable, rapid and unobtrusive assessments of mental state. However, progress in transitioning this idea into practical applications has been impeded by the fact that at present no convenient, inexpensive and effective means exists to derive a meaningful index of brain activity outside of laboratory settings. In this paper, we review some recent advances in recording technology and signal processing methods that will help overcome this limitation. For example, rapid progress is being made in the engineering of recording systems that are small, rugged, portable and easy-to-use, and thus suitable for deployment in operational environments. Progress is also being made in the development of signal processing algorithms for detecting and correcting recording artifacts and for increasing the amount of useful information that can be derived from brain signals. Finally, results from basic research studies suggest that accurate and reliable inferences about the mental load and alertness of an individual can be derived from neurophysiological measures in a practical fashion. These research and engineering successes suggest that it is reasonable to expect that in the near term a basic enabling technology will be deployed that will permit routine measurement of brain function in operational environments.

Arousal↗
PubMed1995

[Analysis of the causes of recurrence of atrioventricular reentry tachycardia in patients treated with radiofrequency current ablation].

The recurrence rate of atrioventricular reentry tachycardia (AVRT) after radiofrequency current ablation (RFCA) of 124 accessory atrioventricular pathways (AP) in 122 patients were reported and the possible causes of recurrence of AVRT were analyzed. Of the 122 patients, 81 were male, 41 female. The average age of the patients was 46.3 +/- 14.4 (14-71) hears. There were 81 manifest AP in 80 patients, 43 concealed AP in 42 patients. 13 of the 124 AP were located in left anterior wall, 59 left lateral wall, 8 left posterior wall, 10 left posterior interventricular septum. 14 right anterior interventricular septum, 2 mid-septum, 14 righy posterior interventricular septum and 4 right free wall. All patients had no organic heart disease. The total recurrence rate of 124 AP in the 122 patients during a follow-up period of 2-25 (13.5 +/- 7.1) months was 4.03% (5/124), with manifest and concealed AP 1.23% (1/81) and 9.30% (4/43), respectively (P < 0.05); left free wall and interventricular septum AP were 2.5% (2/80) and 7.5% (3/40), respectively (P > 0.05); left and right AP were 3.3% (3/90) and 3.1% (1/32), respectively (P > 0.05). The recurrence time was from 0.5 to 60 (15.4 +/- 25.4) days. The recurrence may be related to inaccurate ablation target site, functional and anatomical characteristics of AP, locations of AP, and insufficient ablation energy, etc. It is suggested that AVRT patients receiving RFCA should be followed up for a certain period.

Adolescent↗
PubMed1995

[The level of serum gastrin and ulceration in cirrhotic patients with portal hypertension].

A higher incidence of gastric and duodenum ulcer was well recognized in patients with liver cirrhosis, but the mechanism has not been fully identified. In this study, serum gastrin, free portal pressure (FPP) were measured in 24 consecutively admitted cirrhotic portal hypertensive patients, and preoperative basic acid output (BAO) was measured in 13 randomized patients. Among the 24 patients, concomitant duodenal ulcers were found in 3 by both gastroduodenoscopy and barium series, and gastritis was found in all patients. It was found that most patients (71%) with liver cirrhosis have a elevated level in serum gastrin, whereas BAO is lower than normal in all patients, and the higher the FPP, the lower the BAO is. We believe that the congestive gastroduodenal mucosal lesion was underlying the ulceration most often seen in patients with portal hypertension.

Adult↗
PubMed1995

[A survey on distribution of red cell blood group systems in naxi and primi ethnic groups].

A survey of distribution of red cell blood group systems, including ABO, MNSs, Rh and P, was carried out on the Naxi and Primi ethnic groups in Yunnan province. The results based on 104 cases in each of the two ethnic groups showed that both Naxi and Primi possessed a high gene frequency r of 0.6082 and 0.6882, respectively, with gene frequency p = q. The gene frequency m of Naxi (0.8509) was found to be very high among the populations studied in China until now, only next to that of Lizu (0.8709). The most common phenotype of Rh system was CcDE- in both Naxi and Primi, with a quite high cDE frequency. No case of Rh negative was observed in the two ethnic groups. The P1 in Naxi approximated to that in Primi. The red cell blood group systems and their genetic distances suggested that the Naxi and Primi was genetically close to ethnic groups of North China, but different from those of South China. This fact suggests that these two ethnics groups originated from the North China.

ABO Blood-Group System↗
PubMed1995

Polymorphism of phosphoglucomutase 1 (PGM1) in five Han subpopulations in China.

PGM1 polymorphism in five Han subpopulations in China was investigated by polyacrylamide gel isoelectric focusing. The frequency of PGM1*1A was 0.6256 for Xi'an Han, 0.5982 for Zhengzhou Han, 0.6429 for Huhhot Han, 0.6232 for Lanzhou Han, and 0.6000 for Hakka in Guangdong Province. There was a north to south cline of PGM1*1A frequency.

Alleles↗