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Biomedical subjects

Lei Liu

Publications and source records attributed to Lei Liu.

At least 127 records · Page 7Linked to original sources
PubMed2004

Epitheliotrophic capacity of a growth factor preparation produced from platelet concentrates on corneal epithelial cells: a potential agent for the treatment of ocular surface defects?

BACKGROUND: Topical application of serum eye drops has been reported to accelerate healing of persistent ocular surface defects. It is supposed that growth factors in serum support the wound healing process. Platelets (PLTs) are rich in growth factors and easily available as PLT concentrates (PCs) from blood banks. Therefore, growth factor preparations from PCs may serve as a new and superior therapeutic agent for such defects. STUDY DESIGN AND METHODS: After thrombin stimulation for growth factor release, the cell-free supernatant (PLT releasate) of washed PCs (n = 8) was analyzed for epitheliotrophic factors and its wound healing capacity in comparison to serum (n = 8). Human corneal epithelial cells were used as a model to investigate cell growth, migration, and differentiation in response to both blood products. RESULTS: PLT releasate contains more epithelial growth factor, PLT-derived growth factor, and transforming growth factor-beta, but less hepatocyte growth factor, fibronectin, and vitamins. Cell growth was significantly better in response to PLT releasate. Migration and differentiation were slightly better supported by serum. CONCLUSION: Possibly owing to its high content of growth factors, PLT releasate has a distinct superior effect on cell growth. Stimulation of migration and differentiation was slightly inferior but still acceptable. PLT releasate could therefore be a novel treatment option for ocular surface defects.

Adenosine Triphosphate↗
PubMed2004

Transformation of verapamil by Cunninghamella blakesleeana.

A filamentous fungus, Cunninghamella blakesleeana AS 3.153, was used as a microbial model of mammalian metabolism to transform verapamil, a calcium channel antagonist. The metabolites of verapamil were separated and assayed by the liquid chromatography-ion trap mass spectrometry method. After 96 h of incubation, nearly 93% of the original drug was metabolized to 23 metabolites. Five major metabolites were isolated by semipreparative high-performance liquid chromatography and were identified by proton nuclear magnetic resonance and electrospray mass spectrometry. Other metabolites were characterized according to their chromatographic behavior and mass spectral data. The major metabolic pathways of verapamil transformation by the fungus were N dealkylation, O demethylation, and sulfate conjugation. The phase I metabolites of verapamil (introduction of a functional group) by C. blakesleeana paralleled those in mammals; therefore, C. blakesleeana could be a useful tool for generating the mammalian phase I metabolites of verapamil.

Biotransformation↗
PubMed2004

[Biomechanical study of open bite treatment with tip forward bend].

OBJECTIVE: To verify whether it is effective to treat open bite cases with tip-forward bend. METHODS: Three-dimensional finite element (TDFE) models of the lower left central incisor and first molar were set up by means of CT. Stress distribution in root, PDL and alveolar bone, and the tendency of the tooth movement were obtained by calculation under different orthodontic forces. RESULTS: (1) The molar model revealed that the tensile stress concentration was at the distal cervix and the compressive stress concentration at mesial cervix. (2) The incisor model showed that the tensile stress was concentrated at apical tip and the compressive stress concentration was at the lingual side of the cervix. (3) The incisor had the tendency to elongate and move lingually. The molar tended to tip mesially and buccally. CONCLUSIONS: Arch wire with tip forward bend depends on the elongation and lingual movement of anterior teeth to treat open bite, but the anchorage molar will incline mesially further, which is not consistent with the mechanism to treat open bite.

Biomechanical Phenomena↗
PubMed2004

[Clinical study on repairing depressed fracture of frontal part with hydroxylapatite particulate artificial bone].

OBJECTIVE: To study the effect and complication of repairing depressed fracture of frontal part with hydroxylapatite particulate artificial bone. METHODS: From January 1994 to December 2002, 13 patients were all diagnosed as having depressed fracture of frontal part with clinical and X-ray examinations. The small incision before the hair-edge or local small incision was made. After opening the incision, we performed creeping decollement. Then the hydroxylapatite particulate artificial bone was implanted into the sites of the depressed fracture. The effect and complication were observed with clinical and X-ray examinations in all patients 1 week, 1 month, 3 months after operation. RESULTS: The quantity of hydroxylapatite implanted was 10-30 g. Primary healing was obtained in all cases without any complication. All cases were followed up for 3 months. The contours of the frontal part were restored well. CONCLUSION: It is a good method to repair depressed fracture of frontal part with hydroxylapatite particulate artificial bone.

Adolescent↗
PubMed2004

[Biomechanical study of medical hard tissue adhesive bonding butterfly fracture fragment in middle part of fresh human tibia].

A medical hard tissue adhesive, octyl-a-cyanoacrylate, was tested in 6 fresh human tibiae. A 90 degrees butter-fly fracture fragment was made in the middle part of tibia by bandsaw. The compressive stress, torsional stress and angular deflection were assessed before and after osteoectomy respectively. After adhesive bonding, the compressive stress, torsional stress and angular deflection were tested again. The butterfly fracture fagment decreased the bending strength, torsion strength, yielding strength of tibia bone. In torsion test, the torque of tibia before osteoectomy is greater than bonded tibia, the bonded tibia is greater than that of the unbonded tibia. In compression test, before adhesive bonding broken, the compressive curve slope of tibia before osteoectomy is greater than that of bonded tibia, the bonded tibia is greater than that of the unbonded tibia. In angular deflection test before adhesive bonding of broken,the curve slope of tibia before osteoectomy is not different from that of bonded tibia (P>0.05), the slope the bonded tibia is greater than the slope of unbonded tibia(P<0.05). The elastic modulus, rigidity coefficient and moment of area inertia show no statistical difference between the bonded tibia and intact tibia. The used of medical hard tissue adhesive to bond the fracture fragment could improve the bending strength, torsion strength, yielding strength of tibia bone. In operation, it can reduce the soft tissue injury when the fracture fragment is being fixed, and this will benefit bone healing.

Biomechanical Phenomena↗
PubMed2004

[Gene delivery system based on low molecular weight polyethylenimine and its transfection activity in the skin tissue].

Low molecular weight polyethylenimine (LMW-PEI) was linked to an expressing plasmid contains a green fluorescence protein (GFP) reporter gene and effective gene transfer was observed in CM7221 cell line tested. We examined the relationship among the molecular weight, structure of PEI and their transfection activity and cytotoxicity on CM7221 cell line. We also examined the position and continuance time of the GFP reporter gene expressed in the skin tissue of mouse. Results showed that LMW-PEI/DNA complexes led to high levels of expression in the CM7221 cell line (about 55%). However, with the increasing of PEI molecular weight, the transfection activity of PEI was decreasing. There was an increasing cytotoxicity with the larger PEI molecules. Further research showed that LMW-PEI induced a significant and long-lasting (7 days) expression of the GFP reporter gene in the hair vesicle, sweat, gland, sebaceous gland in the mouse skin tissues. The LMW-PEI described here is a new, highly efficient and non-cytotoxic vector. It would be a useful non-viral vector for gene delivery technology, particular useful as simple skin-specific vehicles of therapeutic genes.

Animals↗
PubMed2004

[In vitro culture and biological characteristics of cranial neural crest stem cell].

OBJECTIVE: According to development biology, cranial neural crest stem cell (CNCSC) can differentiate into precursor cells of tooth, jaw and peripheral nerve system, but in vitro study is less reported. In the present study, CNCSC were dissociated and cultured in vitro, and the biological characteristics of CNCSC was investigated. METHODS: Cranial neural tubes, dissected from mouse E9d, were explanted onto fibronectin-coated dishes. CNCSCs emigrated from the explanted neural tubes, cultured in a serum-free medium containing modified DMEM/F12. Biological characteristics of CNCSC were detected by morphology, nuclear labeled with BurdU and immunocytochemistry. RESULTS: Fibroblast-like CNCSCs demonstrated the characteristics of stem cell, such as clonality, self-renewal and multipotentiality. The result of immunocytochemical stain showed that CNCSC expressed HNK-1 antigen. CONCLUSION: CNCSC were cultured successfully, providing a experimental basis for study on tooth/jaw-like differentiation of CNCSC in vitro, especially providing a cell source for investigating tooth/jaw regeneration.

Animals↗
PubMed2004

[Establishment of a culture system of chick embryo for mouse tooth germ development].

OBJECTIVE: To establish a new culture system for mouse tooth germs in chick embryo. METHODS: The mandibular first molar germ fragments of 15 embryonic days' Kunming mouse embryo were implanted into the lateral mesenchyme of 4-5 days' chick embryo wing buds in ove. Eggs were reincubated and implanted tissues were examined by histochemistry. RESULTS: The cultured tooth germ development continued from cap stage to latest bell stage. The ameloblast and the odontoblast all differentiated maturely and secreted matrix. CONCLUSION: 4-5 days' wing buds chick embryo could serve as developing the mouse tooth germs and demonstrate well physiological process of differentiation and morphogenesis.

Ameloblasts↗
PubMed2004

[Effects of antisense human telomerase reverse-transcript protein subunit (hTERT) gene on biological characteristics of hepatoblastoma cell line in vitro].

OBJECTIVE: Telomerase, a complex of ribose and nucleoprotein, is a specific marker of tumor, which expresses in 98% infinite cell lines and 90% malignant tumor organizations and whose function is to maintain the length of telomere. Human telomerase reverse-transcript protein subunit (hTERT) is the key element and rate-limiting factor of telomerase activity. Our study was to investigate the effects of antisense hTERT gene on biological characteristics of hepatoblastoma cell line in vitro. METHODS: The sense and antisense hTERT eukaryotic expression vectors that we had constructed before were transfected into hepatoblastoma cell line HepG2 by using the SuperFect transfection reagent (Qiagen) according to the manufacturer's instructions, then the HepG2-s and HepG2-as of G418-resistant colonies were obtained with G418 and identified for the presence of hTERT insert by PCR with T7 and pcDNA3.1/BGH reverse primers. After that, we have detected the endogenous hTERT mRNA expression and telomerase activity by quantitative real-time RT-PCR and TRAP-silver staining assay in cells from each group. Meanwhile, MTT cellular proliferation assay, soft agar colony formation assay and flow cytometry were employed to analyze if the proliferation capacity of liver cancer cells was affected in vitro and the tumor cells could be induced to apoptosis by antisense hTERT. RESULTS: Antisense hTERT significantly down-regulated the endogenous hTERT mRNA expression (15.35 +/- 1.72/HepG2-as, 43.8 +/- 2.89/HepG2-s, 45.2 +/- 3.46/HepG2) (n = 10, t = 7.61, P < 0.01) and telomerase activity in HepG2, compared to blank control and sense hTERT. After 20 passages of three group cells, a 7-day cell growth curve and the numbers (size) of soft agar colony formation showed the proliferation and the anchorage-independent growth in HepG2-as were significantly suppressed (50.6 +/- 4.8/HepG2-as, 113.52 +/- 8.15/HepG2-s, 119.12 +/- 10.82/HepG2) (n = 10, t = 4.54, P < 0.01 and n = 10, t = 3.96, P < 0.01), compared to HepG2 and HepG2-s. However there was a significant increase in apoptosis percentage of HepG2-as by flow cytometry (n = 10, t = 9.24, P < 0.01 and n = 10, t = 8.37, P < 0.01), compared to control group. CONCLUSIONS: Antisense hTERT could significantly suppress the hepatoblastoma cell growth and reverse its malignant phenotypes in vitro and cause the increase in apoptosis percentage of HepG2, thus it might be applied in malignant tumor gene therapy through the telomerase-targeted molecular mechanism.

Cell Division↗
PubMed2004

[Experimental study on the fabrication of bioactive membrane for inducing bone regeneration].

The aim of this study was to develop a bioactive membrane for inducing bone regeneration. The membrane was composed of polylactic acid, collagen, recombinant human bone morphogenetic protein-2 (rhBMP-2). The PLA + collagen + rhBMP-2 membrane was fabricated by solvent-casting and cool-drying. The mechanic properties of this compound membrane were tested. The two surfaces of membrane were observed by SEM. Degradability of PLA was evaluated by SEM observation and molecular weight measure in vitro and in vivo. The compound membranes were implanted in rabbit muscles. The samples were obtained when animals were sacrificed at different periods: 2 weeks, 1, 2, 3, 6 months after surgery. The biodegradability and biocompatibility of the membrane were evaluated. The heterotopic bone inducing activity of BMP was identified. The results indicated that the strength at extension to failure of the compound membrane was 36.4MPa at 2.3% strain. The compound membrane was found bearing active factor on its coarse side, which can induce bone regeneration. After implantation in vivo, the membrane maintained the structure for three months and degraded in 6 months. Based on histological analysis, there was no obvious inflammation. Heterotopic bone was induced. We could conclude that the PLA + collagen + rhBMP-2 membrane is an absorbable compound membrane that possesses good biocompatibility, adequate mechanic properties and excellent property of bone induction. It could be applied as an ideal membrane for inducing bone regeneration.

Animals↗
PubMed2004

Observation and establishment of an animal model of tractive spinal cord injury in rats.

OBJECTIVE: To establish an animal model of tractive spinal cord injury in rats in order to investigate its pathophysiological changes and clinical significance. METHODS: T(12)-L(3) spines were tracted longitudinally with a special spinal retractor that was put on the proccessus transverses of T(12)-L(3) vertebrae of the rat after exposing T(13)-L(2) spinal cord via dual laminectomy. At the same tine, the spinal cord function was monitored by cortical somatosensory evoked potential (CSEP). Rats were randomly divided into four groups according to the amplitude of CSEP P(1)-N(1) wave, the amount of the decreasing P(1)-N(1) wave was 30% (the 30% group), 50% (the 50% group) and 70% (the 70% group), respectively. After traction, the changes of the neural behavioral function in rats were observed and the morphological structure of the spinal cord was analyzed quantitatively with image analysis system of computer. RESULTS: With traction of spine, compared with the control group, the 30% group had no marked difference in combined behavioral score (CBS), neuron count, section area of neuron and Nissl body density, but the 50% and 70% groups had marked difference (P<0.01). Light microscope showed that the neuron volume was slightly small and the Nissl body was reduced lightly in the 30% group; the neuron space was enlarged and the neuron was degenerative, reductive, and dissolved, and the spinal cord structure was destroyed in the 50% and 70% groups. CONCLUSIONS: The animal model of tractive spinal cord injury in rats is a reproducible, graded and clinic mimic. The model in this article provides a valuable assistance in further understanding etiopathology and screening effective measures of therapy and prophylaxis of the injury.

Animals↗
PubMed2004

[Study on chronic toxicity to rats of implantation of super-high molecular weight polylactate].

OBJECTIVE: To make sure whether super-high molecular weight polylactate is toxic to the body after it has been implanted into the body for a long period. METHODS: We implanted super-high molecular weight polylactate into the rats and took the specimens of blood at 3, 6, 9, 12 months after the operation. The changes of proteins, electrolyte, enzyme and other indices were observed. At the same time, the tissue around the implants were taken out to carry out the histological observation. RESULTS: At 3, 6, 9, 12 months after the operation, the levels of albumin, globulin, total bilirubin, direct bilirubin, triglyceride, glucose, K+, Na+, Cl-, Ca2+, alkaline phosphatase, glutamic-pyruvic transaminase in the blood plasma were all in the normal range; there were no significant differences between the experimental group and the control group. The level of lactate dehydrogenase increased slightly, but there was no statistically significant difference between the experimental group and the control group. There were no non-reversible immune rejection around the implants in the histological observation. CONCLUSION: Super-high molecular weight polylactate is not toxic to the body after it has been implanted into the animals for a long period.

Animals↗
PubMed2003

Blue-shifted lithium bonds.

A number of lithium bonding systems (X-LiY) have been found in which the X-Li bond is shortened due to the lithium bond formation.

Journal Article↗
PubMed2003

Molecular cloning and characterization of rainbow trout (Oncorhynchus mykiss) C5a anaphylatoxin receptor.

In the course of suppression subtractive hybridization between the cDNA of phytohemagglutinin-stimulated and non-stimulated head kidney cells in rainbow trout (Oncorhynchus mykiss), a cDNA clone was obtained that showed most similarity to mammalian receptor for the anaphylatoxin of the fifth complement component (C5aR). The rainbow trout C5aR cDNA contains a 1,679-bp nucleotide sequence that encodes a 350-amino-acid putative protein with 29.0-31.5% identity to mammalian C5aR. Rainbow trout C5aR has seven putative transmembrane domains that are common to mammalian C5aR. A cysteine residue in the second cytoplasmic domain in mammalian C5aR, required for formation of disulfide-linked dimers, is seen in trout C5aR but not in other similar rhodopsin-like receptors. An arginine residue in the fifth transmembrane domain, which is critical for activation of the C5aR by C5a, is also conserved in rainbow trout C5aR. The rainbow trout C5aR gene has a 1.9-kb intron in the position 12 bp upstream of the start codon, which is similar to that seen right after the start codon in human C5aR gene. These results indicate that the clone is a rainbow trout homologue of mammalian C5aR. Southern blot hybridization suggested that C5aR is a single-copy gene. Northern blotting and RT-PCR analyses detected higher amounts of the transcript in head kidney and posterior kidney, but much lower levels in peripheral blood leukocytes and spleen, faint expression in brain and gills, heart, intestine and very faint expression in liver and muscle.

Amino Acid Sequence↗
PubMed2003

Extracellular matrix protein 1 (ECM1) is over-expressed in malignant epithelial tumors.

The extracellular matrix protein 1 (ECM1) is a secreted protein that has been implicated with cell proliferation, angiogenesis and differentiation. In the present study, we used immunohistochemical staining to examine the expression of ECM1 in a panel of human tumors and found that it was closely correlated with some types of tumors including: invasive breast ductal carcinoma (83%), esophageal squamous carcinoma (73%), gastric cancer (88%) and colorectal cancer (78%). Significantly, ECM1expression was correlated with the metastatic properties of the tumors. Primary breast cancers that had formed metastases were 76% positive while those that had not metastasized were only 33% positive. ECM1 expression was also correlated with PCNA a marker for proliferation, but not with CD34, a marker for endothelial cells. These results indicate that ECM1 tends to be preferentially expressed by metastatic epithelial tumors.

Antigens, CD34↗
PubMed2003

Dendrimeric pyridoxamine enzyme mimics.

PAMAM dendrimers from generations 1-6 were synthesized with pyridoxamine in their core. They transaminated pyruvic and phenylpyruvic acids in water to alanine and phenylalanine, respectively, with Michaelis-Menten kinetics and high effectiveness compared with simple pyridoxamine. The largest dendrimers-similar in size to some globular proteins-were comparable in effectiveness to a previous polyethylenimine (PEI)-pyridoxamine catalyst, and to a protein-pyridoxamine catalyst, but not as effective as a previous PEI-pyridoxamine carrying lauryl hydrophobic groups. The new catalysts showed both general acid/base catalysis by their amino groups and hydrophobic binding of the phenylpyruvate substrate.

Biomimetic Materials↗
PubMed2003

Neural expression and regulation of NSSR1 proteins.

Neural salient serine-/arginine-rich protein 1 (NSSR1) is a newly identified SR protein that regulates pre-mRNA splicing. In the present study, we demonstrated the neural specialization of NSSR1 protein expression in humans and mice. Strong immunoreactive signals to NSSR1 were observed in mouse cerebral neurons, cerebellar Purkinje cells, pyramidal neurons in CA1, CA2 and CA3 regions of the hippocampus and granule cells in the dentate gyrus. In primarily cultured mouse neural progenitor cells (NPCs), at the undifferentiated status, NSSR1 transcripts were detected, but not the proteins. In comparison, in differentiated NPCs both NSSR1 transcripts and proteins were expressed and significantly up-regulated. The results suggest that NSSR1 is important in regulation of brain function and neural differentiation, possibly via regulating the neural-specific alternative splicing of genes.

Animals↗