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Biomedical subjects

Feng Liu

Publications and source records attributed to Feng Liu.

242 records · Page 14Linked to original sources
PubMed2002

Preparation and degradation characteristic study of bone repair composite of DL-polylactic acid/hydroxyapatite/decalcifying bone matrix.

OBJECTIVE: To explore the preparative method and study the degradation characteristics of bone repair composite of DL-polylactic acid (PDLLA)/hydroxyapatite(HA)/decalcifying bone matrix (DBM) in vitro. METHODS: An emulsion blend method was developed to prepare the composite of PDLLA/HA/DBM in weight ratio of PDLLA:HA:DBM = 1.5-2:1-1.5:1. The dynamic changes of weight, biomechanical property and pH value of PDLLA/HA/DBM and PDLLA in phosphate buffered saline (PBS, pH 7.4) were studied respectively through degradation tests in vitro. RESULTS: Without being heated, PDLLA, HA and DBM could be synthesized with the emulsion blend method as bone composite of PDLLA/HA/DBM, which had both osteoconductive and osteoinductive effects. The diameter of the aperture was 100-400 microm and the gap rate was 71.3%. During degradation, the pH value of PDLLA solution decreased lightly within 2 weeks, but decreased obviously at the end of 4 weeks and the value was 4.0. While the pH value of PDLLA/HA/DBM kept quite steady and was 6.4 at the end of 12 weeks. The weight of PDLLA changed little within 4 weeks, then changed obviously and was 50% of its initial weight at the end of 12 weeks. While the weight of PDLLA/HA/DBM changed little within 5 weeks, then changed obviously and was 60% of the initial weight at the end of 12 weeks. The initial biomechanical strength of PDLLA was 1.33 MPa, decreased little within 3 weeks, then changed obviously and kept at 0.11 MPa at the end of 12 weeks. The initial biomechanical strength of PDLLA/HA/DBM was 1.7 MPa, decreased little within 4 weeks, then changed obviously and kept at 0.21 MPa at the end of 12 weeks. CONCLUSIONS: The emulsion blend method is a new method to prepare bone repair materials. As a new bone repair material, PDLLA/HA/DBM is more suitable for regeneration and cell implantation, and the environment during its degradation is advantageous to the growth of bone cells.

Biocompatible Materials↗
PubMed2002

[Purification and immunogenicity identification of the recombinant protein related with specific IgE against Schistosoma japonicum].

OBJECTIVE: To purify the specific IgE antibody-related recombinant protein of Schistosoma japonicum and to identify its immunogenicity. METHODS: The recombinant plasmid Sj43B/pGEX-6p-1 was expressed in E. coli BL 21. The inclusion body of the fusion protein was washed by TNMFX buffer and separated by FPLC. After renaturation, the fusion protein was used to vaccinate the mice. The specific IgG and IgE antibodies were detected by dot-ELISA and Western blotting analysis, respectively. RESULTS: Most of the proteins mixed with the inclusion body of the recombinant protein could be eliminated by washing with TNMFX buffer. The purified recombinant fusion protein could be obtained by FPLC separation. The experiment on mice immunized with the fusion protein showed that the specific IgE antibody was generated against the target part of the fusion protein, but not the specific IgG antibody. CONCLUSION: The fusion protein expressed by the recombinant plasmid Sj43B/pGEX-6p-1 could induce specific IgE response of the immunized mice.

Animals↗
PubMed2002

Identification of genes required for immortalization in human papillomavirus-infected human oral keratinocytes.

The early stages of head and neck cancer are presumed to require a senes of genetic alterations that are not represented by a distinct clinical phenotype. Therefore, genes with altered expression in the preneoplasia may be useful for the early detection of this highly recurrent cancer. In this study, we immortalized normal human oral keratinocytes (NHOK) by retroviral-mediated infection of HPV 16 transforming oncogenes, E6 and E7 (HOK16E6E7). Using the Affymetrix gene chip (U95Av2), we identified 177 known genes and EST that were overexpressed at least 3-fold or above in the immortalized cells, while 133 were down-regulated compared to NHOK. Northern blot analysis showed elevated levels of p55CDC in the immortalized cells, while NHOK showed high basal expression of small proline rich protein (SPRR2). The altered expression of these genes maybe associated with cellular proliferation or differentiation and the early stages of oral carcinogenesis.

Blotting, Northern↗
PubMed2002

[Laryngeal reinnervation for unilateral traumatic recurrent laryngeal nerve injuries].

OBJECTIVE: To investigate 5 procedures of laryngeal reinnervation for unilateral vocal cord paralysis induced by traumatic recurrent laryngeal nerve injury. METHODS: 35 cases were selected for our study, all patients had unilateral recurrent laryngeal nerve injury, including 8 for nerve decompression, 6 for end to end anastomosis of recurrent laryngeal nerve, 16 for main branch of ansa cervicalis anastomosis to recurrent laryngeal nerve, 3 for nerve muscular pedicle and 2 for nerve implantation. All cases have been subjected to preoperative and postoperative voice recording, acoustic analysis, videolaryngoscopy, strobscopy and electromyography. RESULTS: It is found the adductory and abductory motion of the vocal cord restored in 5 cases with less than 4 months course who received nerve decompression. Although functional motion of vocal cord was not seen in two patients who received nerve decompression with a course longer than 4 months and one less than 4 months, and in all cases who received ansa cervicalis anastomosis and end to end anastomosis of recurrent laryngeal nerve, these procedures resulted in medialization of vocal cord and the mass and tension of the reinnervated vocal cord may become much the same as the contralateral normal vocal cord, thus resuming symmetric vibration of the vocal cords and physiological phonation. Nerve muscular pedicle technique and nerve implantation enabled adductory muscles to be reinnervated, thus improving severe hoarseness, but they didn't restore normal voice. CONCLUSIONS: (1) Nerve decompression seems to be the best procedure in laryngeal reinnervation; (2) Main branch of ansa cervicalis technique raises satisfactory reinnervation of adductor muscles; (3) Selection of the laryngeal reinnervation protocols should depend on the course, severity and type of nerve injury.

Adult↗
PubMedDate not supplied

Numerical evaluation of the fields induced by body motion in or near high-field MRI scanners.

In modern magnetic resonance imaging , both patients and health care workers are exposed to strong, non-uniform static magnetic fields inside and outside of the scanner, in which body movement may be able to induce electric currents in tissues which could be potentially harmful. This paper presents theoretical investigations into the spatial distribution of induced E-fields in a tissue-equivalent human model when moving at various positions around the magnet. The numerical calculations are based on an efficient, quasi-static, finite-difference scheme. Three-dimensional field profiles from an actively shielded 4 T magnet system are used and the body model projected through the field profile with normalized velocity. The simulation shows that it is possible to induce E-fields/currents near the level of physiological significance under some circumstances and provides insight into the spatial characteristics of the induced fields. The methodology presented herein can be extrapolated to very high field strengths for the evaluation of the effects of motion at a variety of field strengths and velocities.

Computer Simulation↗
PubMedDate not supplied

A modelling study on discrimination tasks.

We investigate the discrimination capacity of a single neuron model including the integrate-and-fire (IF) model and the IF-FHN model [Neural Networks, 14 (2001) 955], both theoretically and numerically. Both magnitude and frequency discrimination tasks are considered. It is found that for the magnitude discrimination task, with a small fraction of coherent inputs, an IF model and an IF-FHN model with inhibitory inputs can tell one input from the other. The total probability of misclassifications (TPM) is considerably reduced with the increasing of inhibitory inputs. However, the IF model and the IF-FHN model are incapable of performing the frequency discrimination task.

Discrimination, Psychological↗
PubMedDate not supplied

Characterization of the aldehyde dehydrogenase gene families of Zea mays and Arabidopsis.

Cytoplasmic male sterility is a maternally transmitted inability to produce viable pollen. Male sterility occurs in Texas (T) cytoplasm maize as a consequence of the premature degeneration of the tapetal cell layer during microspore development. This sterility can be overcome by the combined action of two nuclear restorer genes, rf1 and rf2a. The rf2a gene encodes a mitochondrial aldehyde dehydrogenase (ALDH) that is capable of oxidizing a variety of aldehydes. Six additional ALDH genes were cloned from maize and Arabidopsis. In vivo complementation assays and in vitro enzyme analyses demonstrated that all six genes encode functional ALDHs. Some of these ALDHs are predicted to accumulate in the mitochondria, others in the cytosol. The intron/exon boundaries of these genes are highly conserved across maize and Arabidopsis and between mitochondrial and cytosolic ALDHs. Although animal, fungal, and plant genomes each encode both mitochondrial and cytosolic ALDHs, it appears that either the gene duplications that generated the mitochondrial and the cytosolic ALDHs occurred independently within each lineage or that homogenizing gene conversion-like events have occurred independently within each lineage. All studied plant genomes contain two confirmed or predicted mitochondrial ALDHs. It appears that these mitochondrial ALDH genes arose via independent duplications after the divergence of monocots and dicots or that independent gene conversion-like events have homogenized the mitochondrial ALDH genes in the monocot and dicot lineages. A computation approach was used to identify amino acid residues likely to be responsible for functional differences between mitochondrial and cytosolic ALDHs.

Aldehyde Dehydrogenase↗