Biomedical subjects

Xuejun Liu

Publications and source records attributed to Xuejun Liu.

28 records · Page 2Linked to original sources

PubMed2003

Effects of vehicle impact velocity and front-end structure on dynamic responses of child pedestrians.

To investigate the effects of vehicle impact velocity and front-end structure on the dynamic responses of child pedestrians, an extensive parametric study was carried out using two child mathematical models at 6 and 15 years old. The effect of the vehicle impact velocity was studied at 30, 40, and 50 km/h in terms of the head linear velocity, impact angle, and head angular velocity as well as various injury parameters concerning the head, chest, pelvis, and lower extremities. The variation of vehicle front-end shape was determined according to the shape corridors of modern vehicles, while the stiffness characteristics of the bumper, hood edge, and hood were varied within stiffness corridors obtained from dynamic component tests. The simulation results show that the vehicle impact speed is of great importance on the kinematics and resulting injury severity of child pedestrians. A significant reduction in all injury parameters can be achieved as the vehicle impact speed decreases to 30 km/h. The head and lower extremities of children are at higher injury risks than other body regions. Older children are exposed to higher injury risks to the head and lower leg, whereas younger ones sustain more severe impact loads to the pelvis and upper leg. The results from factorial analysis indicate that the hood-edge height has a significant effect on the kinematics and head impact responses of children. A higher hood edge could reduce the severity of head impact for younger children, but aggravate the risks of head injury for older ones. A significant interaction exists between the bumper height and the hood-edge height on the head impact responses of younger child. Nevertheless, improving the energy absorption performance of the hood seems effective for mitigating the severity of head injuries for children.

Accidents, Traffic↗

PubMed2003

Comparison of the changes in global gene expression of Escherichia coli induced by four bactericidal agents.

DNA microarrays provide a global view of the physiological state of the cell by parallel analysis of the expression levels of all the genes in an organism. The effects of four bactericidal agents on the expression pattern of Escherichia coli MG1655 were assessed. Compounds were chosen on the basis of their different mechanisms of action and included inhibitors of DNA replication and recombination, translation, transcription and cell wall biosynthesis. The addition of rifampin resulted in increased expression of the target, rpoB, as well as several genes involved in nucleotide salvage and purine biosynthesis. The addition of ampicillin resulted in overall changes in gene expression that showed some similarity to changes induced by rifampin. The addition of the antibiotics kanamycin or norfloxacin resulted in the induction of unique gene expression signatures: a heat shock response to kanamycin and an SOS response to norfloxacin. Several genes of unknown function showed expression profiles similar to the genes associated with the SOS or the heat shock response. Thus, these profiles define families of genes with similar expression phenotypes that can be tested for related function.

Ampicillin↗

PubMed2003

[Effect of different cultivation practices on Fe and Cd content in iron plaque outside rice root and Cd content in rice root].

The effects of different cultivation practices-traditional flooding (TF), film mulching (FM), straw mulching (SM), and wetting cultivation (WC)-on Cd concentrations in Indica and Japonica roots and on Cd and Fe concentrations in iron plaque outside the roots were studied at different growth stages (tillering, booting, filling and harvest) with a Cd-polluted soil. The results showed that in all practices, the mean Fe concentration in iron plaque and the mean Cd concentration in roots of Japonica at tillering stage were 6.37 mg.mg-1 and 25.49 mg.kg-1, and greater than those of Indica, which were 4.52 mg.mg-1 and 16.37 mg.kg-1 respectively; at booting stage, the mean Fe and Cd concentrations in iron plaque and the mean Cd concentrations of Japonica were 1.60, 16.35 and 54.68 mg.kg-1, and greater than those of Indica, which were 1.06 mg.mg-1, 9.56 and 43.31 mg.kg-1, respectively; at filling stage, the Fe concentrations in iron plaque of Japonica in SM and WC were 0.89 and 1.00 mg.mg-1, and those of Indica were 0.63 and 0.30 mg.mg-1; in all practices, the mean Cd concentrations in iron plaque and root of Japonica were 15.23 and 73.68 mg.kg-1, and those of Indica were 3.46 and 52.38 mg.kg-1; at harvest stage, the Fe concentration in iron was plaque of Indica in TF was 1.21 mg.mg-1 and that of Japonica was 0.65 mg.mg-1, but that of Japonica in SM was 0.94 mg.mg-1 and that of Indica in SM was 0.55 mg.mg-1; the Cd concentration in iron plaque of Japonica in WC was 7.96 mg.kg-1, and that of Indica was 5.09 mg.kg-1; the mean Cd concentration in root of Japonica was 54.53 mg.kg-1 and that of Indica was 35.91 mg.kg-1 in all practices.

Cadmium↗

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

[Morphology of olfactory bulb, olfactory tract blood supply affected by anthrosclersis and its clinical significance].

OBJECTIVE: In order to provide morphological evidences for olfactory defect cased by olfactory bulb, olfactory tract ischemia, the origins, numbers, distributions and pathological changes about olfactory bulb, olfactory tract arteries were studied. METHOD: The distributions and pathological changes of olfactory bulb, olfactory tract arteries in 80 sides of adult brain specimens were observed with operation microscope, among which the nourishing arteries and nerve of olfactory tract in two sides aged from 60 to 70 were observed pathohistologically. RESULT: The blood supply of olfactory bulb, olfactory tract comes mainly form artery cerebral and posterior communicainy. 10% of these 60 sides arteries were of multi-branch. 86.3% of them had atheroselerosis. 25.0% of the olfactory bulb and olfactory tract artery were blocked or narrow, and pathological changes in olfactory nerve such as atrophy were observed. CONCLUSION: Excluding other diseases, the olfactory defect in different degree of patients over 60 years old were caused possibly by atheroselerosis of the arteries at base of the brain.

Adult↗

PubMed2003

[Soil nitrogen mineralization and its prediction in winter wheat-summer maize rotation system].

The mineralization of soil nitrogen in winter wheat-summer maize growth season was studied with field experiment, and its prediction was made by interval leached aerial incubation combined with first-order dynamic model. The results showed that the amount of soil mineralized nitrogen had a large variation among years and crops. The soil nitrogen mineralization was lower in winter wheat growth season than in summer maize growth season, resulted in the yield increment of summer maize being not significant with increasing nitrogen fertilization rate. The amount of soil mineralized nitrogen occupied 31%-60% of the total nitrogen uptake by winter wheat and 62%-108% by summer maize. It was understandable why crop yield (especially summer maize) was not significantly response to applied nitrogen fertilizer. The amount of soil mineralized nitrogen decreased with increasing soil nitrogen supply. The mineralization was positive in normal nitrogen supply range(0-300 kg N.hm-2). The first order dynamic model could only predict the whole trend of mineralization in growth season, but could not reflect its variation in some growth stages. The role of the model was still important in view of the prediction of nitrogen mineralization before sowing.

Crops, Agricultural↗

PubMed2002

Nuclei and subnuclei gene expression profiling in mammalian brain.

Information on the neuroanatomical expression of a given gene is critical to understanding its function in the central nervous system. The integration of laser capture microdissection (LCM), T7-based RNA amplification and cDNA microarrays allows for this information to be simultaneously generated for thousands of genes. To validate this integrative approach, we catalogued the gene expression profiles of seven rat brain nuclei or subnuclei. A hundred cells from the following seven brain nuclei were analyzed: locus coeruleus (LC), dorsal raphe nucleus (DR), parvocellular division (PA) and magnocellular division (MG) of the hypothalamic paraventricular nucleus (PVN) and CA1, CA3 and dentate gyrus (DG) divisions of the hippocampal formation. Of the 2145 genes investigated, 1402 genes (65%) gave a hybridization signal statistically different from the background level that was defined by non-specific hybridizations to 15 different plant genes. Validation of our microarray data on four arbitrarily selected genes was confirmed by Real-Time PCR. Previous research showing expression patterns of 'signature' genes (n=17) for specific brain nuclei are consistent with our findings. For example, as previously shown, enriched mRNA expression encoding the serotonin transporter or tyrosine hydroxylase was found in DR and LC cells, respectively. Interestingly, expression of the serotonin 5-HT(2B) receptor mRNA was also found in DR cells. We confirmed this new finding by in-situ hybridization. The hierarchical clustering analysis of gene expression shows that the two divisions of the PVN (PA and MG) are closely related to each other, as well as the three regions of the hippocampal formation (CA1, CA3 and DG), which also showed similar gene expression profiles. This study demonstrates the importance, feasibility and utility of cellular brain nuclei profiling.

Animals↗

PubMed2002

[Long-term changes after transplantation of expanded skin in dogs].

OBJECTIVE: To investigate the long-term changes of expanded skin after transplantation. METHODS: The expanded skin in dogs at 0 week, 3 weeks, 6 weeks, 3 months and 6 months after transplantation was observed through areas, histomorphological, electron microscopic, collagen content, biomechanical, and immunohistochemical methods. RESULTS: The expanded skin was close to the control groups in all observations. CONCLUSION: The biological changes after expansion remain in 3 months. The expanded skin will gradually recover to normal in 3-6 months. It is similar to a wound repair process.

Animals↗

PubMed2002

[Clinical results of breast augmentation with polyacrylamide hydrogel injection].

OBJECTIVE: To investigate the complications in 16 patients who had breast augmentation with polyacrylamide hydrogel injection. The distribution and late changes of the injected material was observed. METHODS: The physical signs and symptoms of the 16 patients were classified. Ultrasound and infrared examinations or MRI were used in some cases. RESULTS: Two patients had operations for extraction. The injection material was distributed in the muscles diffusely, or existed in the breast and subcutaneous tissue as many masses. CONCLUSION: The reliability of this injection method for breast augmentation is in doubt.

Acrylic Resins↗

PubMed2002

[The influence of expansion maintenance period upon in vivo skin tension and immediate stretch-back rate of the expanded skin].

OBJECTIVE: The study was to investigate the influence of maintenance period of expansion upon skin tension and immediate stretch-back rate of the expanded skin. METHODS: 30 expanders (240 ml) were implanted in six adult dogs, which were divided into four groups: group A with 2-week saline injection of the expander; group B with 6-week injection; group C with sham-operation and group D as the blank control group. The first two groups were subdivided into three groups respectively according to different maintaining times of one week, two weeks and four weeks. When full inflation was finished, a 4 cm x 7 cm expanded flap was created and in vivo skin tension and stretch-back ratio of the flap were measured. The Comparison was made in terms of in vivo skin tension and immediate stretch-back ratio between different injection and different maintenance periods. RESULTS: With expansion maintenance time increasing, the in vivo skin tension and immediate stretch-back ratio decreased. After the capsule of the expand skin flap was removed, the in vivo skin tension and immediate stretch-back rate significantly reduced. Based on the experimental results, 16 patients were treated with implantation of 23 expanders. Their average expander injection time was 14 days and the average maintenance time was 25 days. All expanders obtained good results except one extrusion. CONCLUSION: In skin and soft tissue expansion, in vivo skin tension and immediate stretch-back ratio can be reduced through prolonged maintenance of expansion and capsule removal from the expanded skin flap.

Adolescent↗