Biomedical subjects

Yanjun Zeng

Publications and source records attributed to Yanjun Zeng.

29 records · Page 2Linked to original sources

PubMed2003

[Biomechanical properties of skin expanded by different methods in vivo].

In plastic surgery, people hope the conventional expansion will be replaced by rapid expansion, which can shorten greatly the expansion period. Also people are concerned about whether the skin properties after rapid expansion approach that after conventional expansion. So we designed and made an apparatus for in vivo measurement of tension, and then measured the biomechanical properties of skin in vivo for the first time. The experimental results showed there was no significant difference between the rapid expansion method and conventional expansion method in respect to the area gain of expanded skin surface. Both the tension in vivo and the instant stretch-back ratio increased during the expansion, but fell almost to the control values after four weeks' maintaining period. So, rapid skin expansion did not produce any deleterious effect when compared with the conventional expansion. Extension of the maintaining period can improve the biomechanical properties of expanded skin and effectively reduce the stretch-back ratio. Therefore, rapid expansion with an extended maintaining period is clinically acceptable.

Animals↗

PubMed2003

[Soil seed banks of different grassland types of Alashan arid desert region, Inner Mongolia].

Investigations on the soil seed banks of different grassland types of Alashan arid desert region in Inner Mongolia showed that when the altitudes of sampling plots increased from 1,370 m to 1,750 m, the soil seed densities of natural grasslands decreased from 326 grain.m-2 to 76 grain.m-2. At the altitude of 1,100 m, the soil seed density was 56 grain.m-2 in typical desert plot, but only 8 grain.m-2 in the sand dune plot. After the vegetation was restored with Artemisa sphaerocephala on sand dune, its soil seed density increased obviously, almost as 17-29 times as sand dune's. In this study, 31 seeds m-2 were sampled, which belonged to 11 families. Among them, annual plants accounted for 77%, 100% and 70%, perennial plants accounted for 21%, 0 and 16%, and semi-shrubs accounted for 2%, 0 and 14%, respectively for natural grassland, sand dune and sown grassland. Shrub seeds were not found in all the soil seed bank plots. When the altitudes of sampling plots increased from 1,100 m to 1,750 m, the species richness (Margalet index) of soil seed banks of natural grasslands increased from 1.49 to 2.77, and the species diversity (Shannon-Winner index) increased from 0.697 to 0.917.

Biodiversity↗

PubMed2002

Silicone implant in augmentation rhinoplasty.

During the past 6 years the authors have treated 406 patients with classic silicone augmentation rhinoplasty. The types and incidence of complications after subcutaneous or subfascial implantation are examined and discussed. They propose that most complications are related to the depth of the implant and the character of the tissues. To improve their operation and to prove their hypothesis, they performed subperiosteal augmentation rhinoplasty in 22 patients with satisfactory results. At the same time, they investigated the biomechanical properties of human nasal periosteum and fascia, including tensile strength, the stress-strain relationship, and stress relaxation characteristics under uniaxial tension. Although it has less failure strain, the periosteum has more tensile strength than fascia. So, in the view of biomechanics, the periosteum is thicker, tougher, and stiffer than fascia, and thus more suitable for covering silicone implants.

Adolescent↗

PubMed2002

[An alternative method of strain analysis on arterial walls].

As is well known, the zero stress state of an artery is brought by cutting a ring of the artery radically and then the ring segment springs open into a sector. The zero stress state is a foundation of strain analysis of an artery. There are two methods to measure the dimensions of a blood vessel in the zero stress state. First, it is a way to measure immediately an opening angle. Second, it is a method of assuming that a cut-open, stress-free specimen forms a circular sector and there are two edge angles. In this paper, we proposed a new method to measure the dimensions of an arterial wall in the zero stress state. The new method is to measure immediately the curve length of an arterial wall in zero stress state by computer image process (CIP). We used the curve lengths to define a standard circle for the strain analysis. We compared these three methods on descending thoracic aortas, common carotid arteries, and femoral arteries of white rabbits. Conclusions are: (1) the new method, that is the strain analysis method from the curve length, is the best method among the three methods of strain analysis; (2) the lengths of a ring segment (the length between D/2 and 2D) do not affect the dimensions of the zero stress state.

Animals↗

PubMed2002

Fluid shear stress induces the secretion of monocyte chemoattractant protein-1 in cultured human umbilical vein endothelial cells.

In this study we investigated the patterns of fluid shear stress on induction of monocyte chemoattractant protein-1 (MCP-1) secretion in cultured human umbilical vein endothelial cells (HUVECs). MCP-1 is a potent special chemoattractant, which recruits monocytes into the sub-endothelium. This process is one of the early events of atherosclerosis. We examined the pattern of fluid shear stress inducing the secretion of MCP-1 in cultured HUVECs from the view of biomechanics. In our experiments, HUVECs were subjected to controlled levels of shear stress (4, 10, 20 dyn/cm(2)) in a parallel plate flow chamber. MCP-1 in HUVECs of different periods was measured by an immunohistochemistry method and digital image analysis; MCP-1 in perfusion was measured by sandwich ELISA. The results demonstrated the increase of MCP-1 synthesis and secretion by shear stress was time- and force-dependent. The accumulated level of MCP-1 in HUVECs under lower shear stress (4 dyn/cm(2)) for 4-5 hrs was 3-fold compared with that for static cells. When the shear stress lasted to 6 hrs, the secretion of MCP-1 was reduced to normal levels and could not be increased even when the shear stress lasted for 12 hours. 10 dyn/cm(2) had less effect on the secretion of MCP-1 compared with 4 dyn/cm(2). This research provides data for understanding the mechanism of the contribution of hemodynamic forces to atherosclerosis.

Chemokine CCL2↗

PubMed2002

Effects of fluid shear stress on expression of proto-oncogenes c-fos and c-myc in cultured human umbilical vein endothelial cells.

The objective of our research was to reveal the effects of different shear stresses on the expression of proto-oncogenes c-fos and c-myc in cultured human umbilical vein endothelial cells (HUVEC). A parallel plate flow chamber was used to control the value and duration of shear stress (SS), and the expression of c-fos and c-myc protein was measured by immunocytochemistry methods and image analysis software. Some important conclusions were drawn. In the stationary state, c-fos protein levels were very low. The SS's of 4 dyn/cm(2) and 10 dyn/cm(2) induced rapid increases of c-fos protein levels, especially the SS of 10 dyn/cm(2). The levels peaked at 1.0 h. Then, c-fos protein levels began to decrease, after 2.5 h, they declined to almost basal levels. In the stationary state, the c-myc protein levels were also very low slowly increasing after the onset of shear stress. The effects of 4 dyn/cm(2) and 10 dyn/cm(2) SS on c-myc protein expression levels had no difference and apparently were less than the effect on c-fos protein levels. The c-myc protein levels peaked at 1.5 h. Subsequently, they fell to basal levels at 2.5 h. Increased expression of these proto-oncogenes mediated by shear stress may have important effects on the regulation of critical cell activities, such as proliferation and differentiation.

Blood Circulation↗

PubMed2002

Application and development of palm print research.

The palm print contains a great deal of information which is of great research and application value. This paper provides palm print research methods, application, and the relationship between the palm print and cancer.

Adult↗

PubMed2002

[Response of seed germination of three xeromorphic shrubs to drought stress].

The seed germination, seedling growth and water absorption characteristic of Caragana korshinskii, Hedysarum scoparium, and Artemisia sphearocephala were investigated under different osmotic potentials (PEG 6000, -0.3(-) -2.7 MPa). The results showed that under drought stress, C. korshinskii had the highest germination rate, while A. sphearocephala had the lowest one. Under -0.3(-) -0.6 MPa, the root length of 10-day-old A. sphearocephala seedling was significantly longer than that of H. scoparium and Caragana korshinskii(P < 0.05), and the length reached 7.9, 4.5 and 3.1 cm, respectively. There existed a significant positive correlation between seed germination rate and 72 h water absorption rate of the three shrub seeds(P < 0.01). The relationships among germination characteristics, root length, and survive percentage of seedlings were also discussed.

Artemisia↗

PubMed2002

[Water distribution patterns in different degraded desert grasslands of Reaumuria soongorica].

Water distribution pattern and water use-efficiency in soil-plant-atmosphere system for light, medium, and heavy degraded Reaumuria soongorica grasslands were studied in Alashan region of Inner Mongolia. The total precipitation in 2001 was 124.3 mm, of which 119.4 mm occured during experimental period. Soil water content (SWC) in 10-40 cm layer was greatly affected by the evapotranspiration. The SWC in 10-20 cm layer of medium degraded grassland paddock was significantly lower (P < 0.05), and the SWC in 20-40 cm layer of light degraded paddock was lower than that of other paddocks due to different transpiration rate and root distribution depth between the main co-existing plant species of R. soongorica and Cleistogenes soongorica in the paddocks. The annual average bare land evaporation and R. soongorica population transpiration were 30.6 mm and 11.9 mm, respectively. As the grassland further degraded, the bare land evaporation and transpiration through Peganum nigellastrum population, a degradation indicating plant species, increased, while the transpiration of R. soongorica decreased. In addition, the water use-efficiency of the grassland and dominant plant species markedly decreased with the increasing grassland degradation. Compared to the light degraded paddocks, for instance, the water use-efficiency of medium and heavy degraded paddocks were reduced by 14.6% and 46.1% for total biomass production, and by 37.8% and 73.8% for R. soongorica, respectively.

Agriculture↗

PubMed2002

[Comparison of biomechanical properties between human nasal periosteum and fascia].

There has been a lot of controversies on which layer the silastic implants should be inserted in the augmentation rhinoplasty, i.e. subperiosteal or deep subfascial. This study is to investigate the biomechanical properties of human nasal periosteum and deep fascia, including tensile strength, stress-strain and stress relaxation characters under uniaxial tension system. The periosteum is stronger in tensile strength than that of the fascia, but it is less elastic. Under a sudden increase of load, the periosteum relaxes far less than the fasia. Therefore, in view of biomechanics, the periosteum is thicker, tougher, stiffer and less relaxation than facia, thus has a better fixation effect.

Biomechanical Phenomena↗

PubMedDate not supplied

Silicone implants in augmentation rhinoplasty.

During the past six years, we have treated 406 patients with classical silicon augmentation rhinoplasty. The types and incidence of complications after subcutaneous or subfascial implantation were examined and discussed. We proposed that most complications are related to the depth of the implant and the character of the tissues. In order to improve our operation and prove our hypothesis, we performed subperiosteal augmentation rhinoplasty in 22 cases with satisfactory results. At the same time, we investigated the biomechanical properties of human nasal periosteum and fascia, including tensile strength, stress-strain relationship and stress relaxation characters under uniaxial tension. Although less elastic, the periosteum has more tensile strength than fascia. So, in the view of biomechanics, the periosteum is thicker, tougher, and stiffer than fascia, thus more suitable for covering silicon implants.

Adolescent↗