Biomedical subjects

Yan-Jun Zeng

Publications and source records attributed to Yan-Jun Zeng.

10 recordsLinked to original sources

PubMed2006

Biomechanical properties of different segments of human umbilical cord vein and its value for clinical application.

No satisfactory effects have been obtained with the use of synthetic blood vessels (diameter <6 mm) as substitutes for human small arteries or veins for the purpose of clinical vascular reconstruction. Therefore, blood vessels of human origin, for example, umbilical cord blood vessels, with their wide availability, still should be considered. However, little information on biomechanical properties of human umbilical cord blood vessels is available. The objective was to provide a theoretical basis for the clinical application of umbilical cord veins as optional material for small-caliber grafts. This was a nonrandomized, noncontrolled in vitro study. The experiment was conducted in the Laboratory of Medical Biomechanics, Yunyang Medical College. Umbilical cord veins of 20 normal fetuses of spontaneous labor were collected by the Department of Obstetrics and Gynecology, Taihe Hospital in Shiyan City, Hubei Province. The fetuses aged 37-40 weeks, and the parturients were 20-30 years old. Umbilical cord veins of the 20 fetuses were used and the placental ends were treated as proximal ends while the fetal ends as distal ends. The fetal ends were divided into three segments: proximal, middle, and distal segments. The relationship between pressure of umbilical cord veins segments and the diameters was measured on the biomechanical experiment stand for soft tissues, and then the elastic modulus was calculated. The materials were transversely extracted, refrigerated, and sliced up before HE staining. The geometrical morphology indexes were measured by a computer image analysis system (Leica-Q500IW). The main outcome measures were: incremental elastic modulus (E(inc)), pressure-strain elastic modulus (E(p)), volume elastic modulus (E(v)), diameter, and wall thickness of the veins. E(inc), E(p), and E(v) of umbilical cord veins of proximal, middle, and distal segments increased with the pressure elevated. The three kinds of elastic modulus of proximal segments (E(inc): 26.98 +/- 3.21, E(p): 16.58 +/- 2.12, E(v): 8.31 +/- 2.35) were all lower than those of distal segments (E(inc): 33.20 +/- 4.21, E(p): 119.45 +/- 2.87, E(v): 9.71 +/- 1.32) (F = 95.74-126.52, p < 0.05), and a tendency to increase was shown from proximal segments to distal segments. Media thickness [(0.30 +/- 0.05)] mm, (0.24 +/- 0.03) mm] and the diameters [(3.07 +/- 0.12) mm, (2.30 +/- 0.13) mm] decreased gradually from proximal to distal segments (F = 12.76, p < 0.01). It is feasible to use umbilical cord veins as substitutes for the transplantation of small-caliber arteries in terms of basic biomechanical properties. On vascular grafting, different segments of umbilical cord veins should be chosen cautiously so that the biomechanical characteristics of umbilical cord vein grafts could be in accordance with those of host to increase the long-term patency rate of transplanted blood vessels.

Adult↗

PubMed2005

Measuring blood flow velocities based on three image processing techniques.

The classification of microcirculation can be based on the size of the capillary and the velocity of the blood flow. For each type of microcirculation, the ad hoc method is required to measure the blood flow velocity. In this paper, the correlation method is used to measure blood flow velocity in the small-size capillary. The large-size capillaries are classified into three types based on the blood velocities, say low-speed, high-speed, and unstable one. The template-matching algorithm, the Fast Fourier Transform algorithm and a high-speed video camera measurement are used to measure the blood velocities corresponding to those three types of large-size capillary. It was shown by several experiments that fairly good results for different types of capillary may be obtained by using the proposed three image processing algorithms.

Algorithms↗

PubMed2005

A nonlinear adaptive fuzzy approximator technique with its application to prediction of non-stationary EEG dynamics and estimation of single-sweep evoked potentials.

In this paper, we apply a fast training paradigm to the optimization of fuzzy approximator and a nonlinear adaptive fuzzy approximator (NAFA) is constructed. Using TSK fuzzy rules, the structured knowledge along with numerical information are parameterized and utilized in the NAFA, which can be easily configured as a multi-layer network when its transparency is desired. We propose a fast training paradigm, which is actually a combination of Kalman filtering and LMS adaptation, to optimize the linear and nonlinear parameters of the NAFA separately. The NAFA is characterized by concise representation of structured knowledge, fast learning capability, as well as universal approximation property. The NAFA is applied to forecast the non-stationary EEG time-series and to estimate single-sweep evoked potentials (EPs). The corresponding simulation results are given. It is concluded that the NAFA technique can provide efficient nonlinear separation of single-sweep EPs, which allows for quantitative examination of the cross-trial variability of clinical EPs.

Artifacts↗

PubMed2004

Morphologic and biomechanical changes of rat oesophagus in experimental diabetes.

AIM: To study morphologic and biomechanical changes of oesophagus in diabetes rats. METHODS: Diabetes was induced by a single injection of streptozotocin (STZ). The type of diabetes mellitus induced by parenteral STZ administration in rats was insulin-dependent (type I). The samples were excised and studied in vitro using a self-developed biomaterial test machine. RESULTS: The body mass was decreased after 4 d with STZ treatment. The length of esophagus shortened after 4, 7, 14 d. The opening angle increased after 14 d. The shear, longitudinal and circumferential stiffness were obviously raised after 28 d of STZ treatment. CONCLUSION: The changes of passive biomechanical properties reflect intra-structural alteration of tissue to a certain extent. This alteration will lead to some dysfunction of movement. For example, tension of esophageal wall will change due to some obstructive disease.

Animals↗

PubMed2004

Biomechanical properties of skin in vitro for different expansion methods.

OBJECTIVE: In plastic surgery, clinicians are interested in replacing conventional expansion by rapid expansion, because the expansion period could be shortened greatly. Also people are concerned that skin properties after rapid expansion might not approach those after conventional expansion. DESIGN: Biomechanical testing of skin for different expansion methods. BACKGROUND: It would be useful to know how much the mechanical properties of skin have been altered during rapid and conventional expansion and during different maintaining times. METHODS: Tensile strength, stress-strain relationship, stress relaxation, and creep were measured by a material testing machine. RESULT: The biomechanical properties of experimental specimens differ significantly from those of their controls immediately after expansion, however, the difference is reduced with time. With the same maintaining period, the biomechanical properties of rapidly expanded skin are similar to conventionally expanded skin. CONCLUSION: Rapid skin expansion did not demonstrate any deleterious effect when compared with the conventional expansion. Extension of the maintaining period can improve the biomechanical properties of expanded skin. Therefore, rapid expansion with an extended maintaining period is acceptable in clinical practice.

Animals↗

PubMed2003

Mechanical properties of nasal fascia and periosteum.

OBJECTIVE: To determine under which layer the silicone implants should be inserted into, the biomechanical properties of fascia and periosteum were investigated. DESIGN: Biomechanical testing of cadaveric tissues. BACKGROUND: In silicone augmentation rhinoplasty, most complications are closely related to the depth of implant and the mechanical character of the tissue surrounding the implant. METHODS: Biomechanical properties of human nasal periosteum and fascia were studied, including tensile strength, stress-strain relationship and stress relaxation under uniaxial elongation.Result. Although with less failure strain, the periosteum has more tensile strength than fascia. The slope of the linear part of stress-strain curve of the periosteum is bigger than that of fascia, which indicates the periosteum is stiffer than fascia. The stress-relaxation slope of periosteum is smaller than that of fascia. CONCLUSION: In the view of biomechanics, the periosteum is thicker, stronger and stiffer than fascia. Under periosteum the silicone implants are easier to be fixed at desired position, thus periosteum is more suitable for covering silicone implants. RELEVANCE: The periosteum is more suitable than fascia for covering silicone implants in augmentation rhinoplasty.

Adolescent↗

PubMed2003

Biomechanical properties of ileum after systemic treatment with epithelial growth factor.

AIM: Systemic treatment with epidermal growth factor (EGF) leads to growth of all parts of the small intestine in normal functioning rats. In this study, we investigated the effect of this growth process on morphometric and biomechanical parameters of ileum. METHODS: Rats were treated with EGF (150 microg.kg(-1)day(-1))or placebo via osmotic minipumps for 2, 4, 7, and 14 days. A segment of ileum was removed. The morphology at no-load state and zero-stress state was measured and passive biomechanical properties were assessed using a biaxial test machine (combined inflation and axial stretching). RESULTS: The ileum weight increased after EGF administration. After 4 days' EGF treatment, the wall thickness was increased. Significantly smaller inner perimeters were seen in 4 day and 7 day EGF treatment groups. The opening angle and residual strain began to increase after 7 days' EGF treatment. Wall stiffness, evaluated from the stress-strain curves, showed a continuous decrease in circumferential direction during the first 7 days' EGF treatment. The longitudinal stiffness increased during the first 7 days. The stress-strain curves for both circumferential and longitudinal direction tended to shift back to normal 14 days after starting EGF administration. CONCLUSION: EGF can cause significant changes both in the morphology and in the passive mechanical properties of the rat ileum.

Animals↗

PubMed2003

Collagen fiber angle in the submucosa of small intestine and its application in Gastroenterology.

AIM: To propose a simple and effective method suitable for analyzing the angle and distribution of 2-dimensional collagen fiber in larger sample of small intestine and to investigate the relationship between the angles of collagen fiber and the pressure it undergoes. METHODS: A kind of 2-dimensional visible quantitative analyzing technique was described. Digital image-processing method was utilized to determine the angle of collagen fiber in parenchyma according to the changes of area analyzed and further to investigate quantitatively the distribution of collagen fiber. A series of intestinal slice's images preprocessed by polarized light were obtained with electron microscope, and they were processed to unify each pixel. The approximate angles between collagen fibers were obtained via analyzing the images and their corresponding polarized light. The relationship between the angles of collagen fiber and the pressure it undergoes were statistically summarized. RESULTS: The angle of collagen fiber in intestinal tissue was obtained with the quantitative analyzing method of calculating the ratio of different pixels. For the same slice, with polarized light angle's variation, the corresponding ratio of different pixels was also changed; for slices under different pressures, the biggest ratio of collagen fiber area was changed either. CONCLUSION: This study suggests that the application of stress on the intestinal tissue will change the angle and content of collagen fiber. The method of calculating ratios of different pixel values to estimate collagen fiber angle was practical and reliable. The quantitative analysis used in the present study allows a larger area of soft tissue to be analyzed with relatively low cost and simple equipment.

Animals↗

PubMed2003

[The genome comparison of SARS-CoV and other coronaviruses].

The genome comparison of inter-species and intra-species can give us much information about the origin and evolution of viruses. There are 137 mutation sites in the 17 genomes of SARS-CoV,and the mutation rate is about 8.04 x 10(-3) substitution/site/year. The distribution of the segregating sites is not steady,the most variable region appears in S1 protein,and the nucleotide sequence of RNA-dependent RNA polymerase has very few mutation sites. The substitution bias of nucleotide acids and amino acids indicates the non-random drift products. The comparison of genome structures of SARS-CoV and other coronaviruses shows that SARS-CoV and IBV share the same genome structure. Phylogenetic analyses of conserved genes of coronaviruses indicate that SARS-CoV is a new branch of coronaviruses and appears more close to the group II coronaviruses. Interestingly,SARS-CoV shares some different features with different groups of coronaviruses. Additional analyses show that the first ORFs between S and E genes of some coronaviruses are transmembrane proteins and share the common motif,indicating the possible common ancestor. From the host distribution of different groups of coronaviruses and the phylogeny of s2m,we can deduce that avian is the probable natural host of SARS-CoV.

English Abstract↗

PubMed2000

Mechanosensitive Channel Currents Recorded in Rat Brain Microvascular Endothelial Cells with Whole-cell Mode.

Using the whole-cell patch-clamp technique, delayed outward currents were recorded in rat brain microvascular endothelial cells(RBMECs), which were nearly completely inhibited by extracellular TEA-Cl at a concentration of 20 mmol/L. Whole-cell currents were elicited by 2 100 ms depolarizing voltage pulses applied every 7 s between -100 mV to +90 mV, with 10 mV increment, from a holding potential of -100 mV. The currents were similar with delayed rectified K(+) currents (IKv)which were inhibited in a concentration-dependent manner by both application of TEA-Cl, with an IC(50) approximately 2.0 mmol/L. In the presence of mechanical force, outward currents were increased in amplitude as compared with controls. These mechanical force-induced currents were also defined as IKv, which were different from previous described mechanosensitive currents induced by mechanical force with characteristic of inward rectifier.

Journal Article↗