Biomedical subjects

Yanjun Zeng

Publications and source records attributed to Yanjun Zeng.

At least 19 recordsLinked to original sources

PubMed2006

The relationship between gestational age and compliance in human umbilical vein and its possible application in vascular grafting.

The aim of this study was to provide a theoretical basis, using biomechanical properties, for the clinical application of human umbilical vein (HUV) as material for vascular grafting. This was a nonrandomized, non-controlled in vitro study. The experiment was conducted in the Laboratory of Medical Biomechanics, Yunyang Medical College. HUVs of 50 normal fetuses were collected on spontaneous miscarriage or labor with the pregnant women's permission by the Department of Obstetrics and Gynecology, Taihe Hospital, Shiyan, Hubei Province. Gestational aged ranged 24-42 weeks, and parturients were 20-30 years old. The pressure-volume (P-V) relationship of HUV was measured on the biomechanical experiment stand for soft tissues, and then compliance was calculated. The P-V relationship of HUV corresponded to a parabolic curve. The compliance of HUV increased gradually with gestational age [24-27 weeks (2.22+/-0.34) x 10(-4) mL/(kPa * cm), 28-32 weeks (3.65+/-0.46) x 10(-4) mL/(kPa * cm), 33-36 weeks (4.22+/-0.55) x 10(-4) mL/(kPa * cm), 37 weeks (7.63+/-0.48) x 10(-4) mL/(kPa * cm), 38 weeks (8.32+/-0.76) x 10(-4) mL/(kPa * cm)]. However, after 39 weeks of gestation, compliance decreased gradually with gestational age [39 weeks 7.61+/-0.46) x 10(-4) mL/(kPa * cm), 40 weeks (7.53+/-0.72) x 10(-4) mL/(kPa * cm), 41 weeks (4.13+/-0.35) x 10(-4) mL/(kPa * cm), 42 weeks (2.25+/-0.62) x 10(-4) mL/(kPa * cm)]. The compliance of HUVs collected at 37-40 weeks of gestational age was similar. When the HUVs older than 42 weeks or under 28 weeks were compared, there was significant difference in their compliance (F=65.84-86.52, p<0.01). The results of the present study suggest that HUVs collected at 37-40 weeks of gestational age have good compliance, i.e., a good P-V relationship, and therefore may be a suitable material for vascular grafting. HUV is one of several graft materials that may be used when autogenous saphenous vein is absent or inadequate. HUV is very biocompatible and shows promise for use in orthopedic implants.

Biomechanical Phenomena↗

PubMed2006

Design of compliance chamber and after-load in apparatus for cultured endothelial cells subjected to stresses.

In order to create a hemodynamic environment that can simulate the physiological condition of arteries, an in vitro experiment apparatus was designed whose key modules were compliance chamber and after-load. These two modules were developed based on the theories of hemodynamics. Both the normal and shear stress to which endothelial cells are exposed can be controlled with these modules, thus facilitating the research of endothelial cells subjected to stresses.

Blood Pressure↗

PubMed2006

A study of maternal hemodynamic change during healthy pregnancy and women with gestation hypertension.

OBJECTIVE: To investigate the maternal hemodynamic changes that occurs during pregnancy. To find out the difference that lie in healthy pregnancy and women with gestational hypertension. To introduce a method that is applied to shift high-risk women of gestational hypertension in pregnancy women. METHOD: Serial hemodynamic investigations (total 8 times) were performed throughout pregnancy period by radioulnar pulse wave electrical monitoring in 182 women (130 with healthy pregnancies, 52 with gestational hypertension). Analysis of variance with repeated measurements was used to evaluate the course of a number of hemodynamic indices. To identify the correlation between these changes and gestational hypertension by using above method. RESULTS: A significant difference in mean arterial pressure (MAP), cardiac output (CO), cardiac index (CI), total Peripheral Resistance (TPR) and heart rat (HR) was observed different between normal pregnancy and women with gestational hypertension. The changes of parameters in normal woman and gestational hypertension were recorded and the mechanism of gestational hypertension was heterogenous. CONCLUSION: These results provide sensitive parameters for use in early risk assessment and as a guide to preventive intervention during pregnancy.

Algorithms↗

PubMed2006

An experimental study on the biomechanical properties of the cancellous bones of distal femur.

OBJECTIVE: To study the comprehensive biomechanical properties of the cancellous bone of distal femur through a series of mechanical tests, and provide relevant subjects with the basic technical data. BACKGROUND: The study on bone mechanics is a commonly used approach to evaluate the biomechanical competency of bone. The biomechanical properties of bone have come to be the precondition of the further research of these relevant clinical subjects. METHOD: In this paper, comprehensive items of mechanical properties of the cancellous bones of distal femur were conducted, and many valuable test results were obtained through a series of mechanical tests, which comprised tensile test, compression test, torsion test, shear test, bending test and impact test. The specimens were extracted from the normal corpses of Chinese donors died from acute head injury. As another key problem in this kind of experiment, the sampling and fixing method of cancellous bones specimens was developed and optimized in this research. RESULT: A series of the experimental data of mechanical properties of cancellous bones were obtained in the tests, these experimental data include tensile strength, compression strength, yield tensile strength, modulus of elasticity, torsion strength, shear strength, torsion modulus, bending strength, yield shear limit and impact toughness, which can reflect the complex mechanical competency of bone, being of great value and practice in clinic and further research on cancellous bones. The mechanical properties of the cancellous bones of distal femur were analyzed and discussed. CONCLUSION: The biomechanical properties of the cancellous bones have a close relationship with individual difference. Comprehensive items of the mechanical properties of the bone can evaluate the mechanical performance of the bone better, and can provide more valuable data to relevant research.

Adult↗

PubMed2006

[Comparisons of hemodynamics in 1-way and 2-way CABG].

For the purpose of improving the hemodynamics of CABG, the authors presented a new amelioration measurement of symmetric 2-way bypass graft. The physiological blood flow in 1-way and 2-way bypass graft of coronary is simulated with finite element method, and the data on computational hemodynamics of these two cases were compared. The temporal-spatial distributions of hemodynamics during the cardiac cycle such as flow patterns and wall shear stress in the vicinity of anastomosis were analyzed. The study results showed that 2-way bypass graft was of more rational hemodynamics when compared with 1-way bypass graft, and it could improve the flow conditions and decrease the probability of restenosis.

Anastomosis, Surgical↗

PubMed2005

Effects of fluid shear stress on apoptosis of cultured human umbilical vein endothelial cells induced by LPS.

The objective of our research was to reveal the effects of shear stress on the apoptosis of cultured human umbilical vein endothelial cells (HUVECs) induced by lipopolysaccharide (LPS). A parallel-plate flow chamber was used to control the strength and duration of shear stress (SS), and apoptosis was measured by immunocytochemistry and radio-immunoassay. Some important conclusions were drawn. In the stationary state, apoptosis of HUVECs could be induced by LPS (50 microg/ml). An SS of 15 dyn/cm(2) could inhibit the apoptosis induced by LPS. However, an SS of 4 dyn/cm(2) had less effect on the same process. At the same time, the experiment demonstrated that the increase in IL-6 secretion by LPS can be inhibited by two different levels of shear stress. Moreover, the inhibition effect was more obvious under high level stress than under low level. We also found that the effect of shear stress on IL-8 was less effective than on IL-6. This research provides data for understanding the mechanism of the contribution of hemodynamic forces to atherosclerosis.

Apoptosis↗

PubMed2005

Simulation of a mathematical model of the role of the TFPI in the extrinsic pathway of coagulation.

Blood coagulation is a complex physiological process. With the development of biochemistry and molecular biology, especially the discovery of the tissue factor pathway inhibitor (TFPI) and further research, the researches of tissue factor (TF) and TFPI have been the hot topics now. Based on this result, we provide a new concept of blood coagulation system and provide a dynamic model to describe the role of TFPI of this pathway. Through stability analysis of the equilibrium point and numerical simulations, we obtain some important conclusions. All these results may have great significance for lesions of cardiac vessels and cerebral vessels, haemophilia, DIC, thrombosis formation and malignancy.

Blood Coagulation↗

PubMed2005

Identification of palm print using dermatoglyphics analysis and detection system.

This paper investigated the biological characteristics of palm print. The preprocessing plays an important role in identifying the ridge characteristics of palm due to the complexity and poor quality of the images. As a functional plug-in of the dermatoglyphics analysis and detection system, the template-based image preprocessing was proposed in this study, including histogram redistribution, ridge orientation, and skeletonization. Using this system, the automatic identification of ridges and triradiuses was accomplished with an effective result. The study demonstrated the feasibility of the method and the potential of the system for being applied as an auxiliary diagnostic tool for heredity diseases (e.g. mammary cancer and neurofibromatosis).

Algorithms↗

PubMed2005

Finding keywords for intergenic and gene regions for human genome.

The analysis of functionally related sequences for conserved patterns is important for further research of different functional regions. This paper presents an analysis of genes and intergenic sequences from the point of view of linguistics analysis, where gene and intergenic regions are regarded as two different subjects written in the four-letter alphabet [A, C, G, T] and high-frequency simple sequences are taken as keywords. A measurement alpha[l(tau)] was introduced to describe the relative repeat ratio of simple sequences. Cutoff values were found for keywords selection. After eliminating "noise," 87 short sequences were selected as keywords for intergenic regions and 76 for gene regions.

Base Sequence↗

PubMed2005

Theoretical approach to blood ejection from the human left ventricle.

An ejection dynamics mathematical model of human left ventricle (LV) based on physiological data of human heart is proposed in this study. The mathematical equations were expressed in terms of vorticity-stream function equations in a prolate spheroidal coordinate system. These equations combined with specified boundary conditions were numerically solved by using an alternating-direction-implicit (ADI) algorithm with second order accuracy. The unsteady aspects of the ejection process were subsequently introduced into the numerical simulation. The numerical results have shown that the present ellipsoidal model could be available to simulate the ejection process of the human LV. Such a model combined with cardiac muscle mechanics could be studied further to determine altered left ventricular function in cardiac diseases.

Adult↗

PubMed2004

Predicting pregnancy-induced hypertension with dynamic hemodynamics.

AIM: To study dynamic changes in the hemodynamic parameters in pregnant women during different weeks of gestation and to comprehend changes to the cardiovascular system in normal pregnant women and in patients with pregnancy-induced hypertension (PIH), with the object of finding predictors of pregnancy-induced hypertension. METHODS: Radialis artery pulse waves of 132 pregnant women were examined from 10 weeks of gestation onward, and the subjects' hemodynamics were examined every 4 weeks. RESULTS: In the women with PIH hemodynamic changes occurred earlier than the onset of disease and even presented in early pregnancy; there might be another mode, and there were factors disturbing the blood pressure modulating mechanism. CONCLUSION: The prediction of PIH from the dynamic changes in hemodynamic parameters has significant implications for clinical practice.

Adult↗

PubMed2004

Quantitative analysis of collagen fiber angle in the submucosa of small intestine.

It is of interest to know how distension changes the angle and content of collagen in the submucosa of small intestine. We describe the application of a two-dimensional quantitative analysis technology to determine the angles between collagen fibers in the submucosa using digital image processing. A polarization microscope was used to obtain a series of animal intestinal slice images. The images were studied by analyzing the relationship between the pixel values of each of the polarized angles to obtain the collagen fiber angle. The statistical distribution of the angle as function of the degree of distension can be analyzed.

Animals↗

PubMed2004

Application of adaptive noise cancellation with neural-network-based fuzzy inference system for visual evoked potentials estimation.

This paper presents an application of adaptive noise cancellation with neural-network-based fuzzy inference system (NNFIS) for rapid estimation of visual evoked potentials (VEPs). Usually a recorded VEP is severely contaminated by background ongoing activities of the spontaneous EEG signal in the human brain. Many approaches have been adopted to enhance the signal-to-noise ratio (SNR) of the recorded signal. However, nonlinear dynamic methods are rarely investigated in view of their complexity, and the fact that the nonlinear characteristics of the signal are hard to determine in general. An adaptive noise cancellation method with NNFIS was carefully designed to estimate the VEP signal. NNFIS, based on Takagi and Sugeno's fuzzy model, has the advantage of being linear-in-parameter; thus the conventional adaptive methods can be efficiently utilized to estimate its parameters. Another advantage of NNFIS lies in that it can track the dynamic behavior of VEP in a real-time fashion because the VEP variation tracking is important for critical patient monitoring in the clinical situation. A series of computer experiments conducted on simulated and real-test responses have confirmed the superiority of the method developed in this paper.

Algorithms↗

PubMed2004

Radial distributions of temperature pressure and velocities for pulsatile blood flow in an axisymmetrical stiff tube.

Using perturbation theory with the assumption that the pulsatile blood flow in an axisymmetrical stiff tube is the first-order term to solve the linear equations of continuity, motion and heat conduction, the equations of the pulsatile flow, including temperature, are derived, and the instantaneous radial distribution of temperature, pressure and velocities for one frequency component are obtained. Using the published geometrical and physiological parameters of a large artery, a numerical analysis of the distribution relationship between the axial velocity and temperature is carried out. The primary studies show that the amplitude of temperature fluctuation in the tube is inversely proportional to the pulsatile frequency, the temperature and velocities gradients are mainly restricted in the near-wall layers with the increase of pulsatile frequency, and there is a close similarity of the radial pulsating distribution between temperature and axial velocity, which indicates that the blood flux in the artery as well as the motion function of heart can be indirectly described by the measurement of temperature fluctuation.

Animals↗

PubMed2004

Nonlinear processing and analysis of ECG data.

A new approach based on a histogram analysis to detect QRS-T complexes of the ECG curve rapidly and reliably is described. The aim consists of a rapid and reliable detection of the P-wave (when atrial fibrillation, AF, is absent) or the f-wave (when AF happens). By means of signal processing techniques such as the fractal dimension method and the Shannon entropy method, two types of ECG signals (with or without AF) were analysed and the significant differences between them documented. Accordingly, the methods allow to determine easily whether AF occurs or not.

Electrocardiography↗

PubMed2003

Stress distribution in the layered wall of the rat oesophagus.

The topic of this study is to obtain the constitutive equations for two layers in the oesophagus from inflation experiment of each layer in the in vivo state and to calculate the corresponding stress distribution referenced to a new stress-free state for multi-layered tissue. The oesophagus is treated as a two-layered structure consisting of an inner submucosa layer and an outer muscle layer. An anisotropic exponential pseudo-strain energy density function is used as the constitutive equation to fit the experimental loading curve and for the calculation of the stress distribution in each layer. Significant differences in the constitutive parameters and zero-stress parameter were found between the submucosa layer and the muscle layer. The stress in the submucosa layer was higher than that in the muscle layer and intact (non-separated) wall under the same loading conditions. The submucosa layer was stiffer than the muscle layer and the intact wall. The zero-stress state of the intact oesophagus and the zero-stress state after separation were used as a reference to compare the stress-strain distributions. The residual strain was discontinuous when using the zero-stress state after separation as a reference. Furthermore, the circumferential stress when using the zero-stress state of the intact wall as a reference was about 100 times higher than that referenced to the zero-stress state after separation. Hence, it is important to use the zero-stress state obtained after the layer separation as the stress-free state in the study of multi-layered tissue.

Animals↗

PubMed2003

Morphological properties of zero-stress state in rat large intestine during systemic EGF treatment.

Systemic treatment with epidermal growth factor (EGF) induce growth of the large intestine. The aim of this study was to investigate the morphological properties early in the course of EGF-induced large intestinal growth. The effects of systemic EGF treatment on the morphological properties at the zero-stress state along the large intestine were investigated. EGF-treated rats and control rats were allocated into group with EGF treatment for 2, 4, 7, and 14 days (N = 6 for each EGF treatment group except N = 4 for the 14-day group). The controls had saline injected (N = 3 for each group). The excised large intestine was subdivided into four segments: the ascending colon, transverse colon, descending colon, and rectum. The length and weight of each segment was measured. The zero-stress state was obtained by cutting rings of the large intestine radially, and the opening angle was measued on video images. The thickness and cross-sectional area of the mucosa and muscle layers, and the inner and outer circumference were measured. The total colon length did not increase, whereas the weight of the large intestine, muscosal thickness and mass, and inner and outer circumference increased significantly (P < 0.05). The increase was most prominent in the proximal colon after 7 days of EGF treatment. Later no further morphological changes were observed, except for a decrease in mucosal thickness in most segments and in mucosal cross-sectional area in the descending colon. In the controls and during the first week of EGF treatment, the opening angle was approximately 100 degrees. After 14 days the opening angle increased significantly in the ascending and transverse colon to approximately 172 and 135 degrees (P < 0.05). In conclusion, this study demonstrates that systemic EGF treatment caused remodeling of the morphology of the zero-stress state in the large intestine in a time-dependent manner. The growth was most pronounced in the ascending and transverse colon and involved mainly the mucosal layer.

Analysis of Variance↗

PubMed2003

[A new approach to detection of QRS complexes based on histogram].

A brief comment on the current methods of detecting QRS complexes from ECG(electrocardiogram) including the wavelet transform method is given, and the shortcomings of those methods are discussed. A simple and effective new approach for detecting QRS complexes based on histogram is developed and presented in this paper with a description of the theory of histogram and the match principle for detecting QRS complexes. This new method is checked up on the data from the MIT/BIH ECG database and that from the Beijing Polytechnic University Hospital.

Algorithms↗