Biomedical subjects

Li Ma

Publications and source records attributed to Li Ma.

150 records · Page 9Linked to original sources

PubMed2002

[Transplantation of mesenchymal derived stem cells followed by G-CSF injection can reconstitute hematopoiesis of lethally irradiated BALB/c mice].

OBJECTIVE: To explore the hematopoietic reconstitution potential of mesenchymal derived stem like cells. METHODS: We transplanted bone marrow mesenchymal derived stem like cells into lethally irradiated BALB/c mice. Hematopoietic cells were derived from the non-adherent bone marrow cells 24 hours after initial culture while murine mesenchymal derived stem like cells from bone marrow of donor mice were cultured for 10 days before the transplantation. RESULTS: All mice of group 1 and 3 died in 7-8 days post irradiation following transplantation, while all the mice from group 2 and 4 survived. The time course of hematopoietic reconstitution was then observed. The peripheral blood and bone marrow cell count recovered in the MSC + G-CSF transplanted group and the BM transplanted group after 3 weeks. Interestingly, CFU-GM number in the MSC + G-CSF transplanted group increased significantly after 2 weeks and even more than that in the BM transplanted group after 3 weeks while as CFU-GM colony dropped 2 weeks after in the BM transplanted group. Spleen colony (CFU-S) number and size of the MSC + G-CSF transplanted group was significantly greater than the BM transplanted group. Furthermore, PCR analysis was performed using peripheral blood cells to determine if any male-derived cells were present. No male-derived cells were found in any of the mice from group 1 and 3. Y-chromosome-specific src gene was found to be dominant in the MSC + G-CSF transplanted group and the BM transplanted group by week 4 post transplantation. In addition, we demonstrated that induction with G-CSF lead to CFU-GM colony formation from MSC compartment in vitro. CONCLUSION: These results indicate that under stimulation of G-CSF, mesenchymal derived stem like cells might differentiate into hematopoietic primitive stem cells in vivo and have the capacity to re-establish hematopoiesis in lethally irradiated mice. This study should provide an alternative transplantation treatment for malignancy.

Animals↗

PubMed2002

[Identification and isolation of mesenchymal stem cells from human fetal pancreas].

OBJECTIVE: To isolate and identify the phenotype and biological characteristics of pancreas derived mesenchymal stem cell. METHODS: Fresh pancreas of 4-5 months old aborted fetus was dissected free from connective tissue, and was cut into small pieces. The adherent cells were harvested and subcultured, after the third subculture, the cells were used for examination. Cell cycle was analyzed by measuring DNA content by FACScan flow cytometer. Phenotype of MSCs was analyzed by immunohistochemical SA technique and differentiated cells were identified by relevant specific staining. RESULTS: Fetal pancreas derived cells gave rise to a population of adherent cells characterized by the presence of a predominant cell type with a typical fibroblast like morphology. By transmission electron microcopy, MSC had few endoplasmic reticulums and mitochondrias. During the log phase of growth, MSC proliferated with a two fold population at 30 h. MSC can be ex vivo expanded by successive cycles of trypsinization, seeding, and culture. Under these conditions, MSC had capability of passaging up to 30 times without displaying significant changes in morphology, with 2-fold increase in cell number after each passage. This indicates the high ex vivo expansion potential of MSC. The results showed that the yield of CFU-Fs was above 200 clones even after the 6th passage. Cell cycle analysis by flow cytometry revealed that more than 83% of cells were in the G0/G1 phases, while a small population of cells were actively engaged in proliferation (S + G2 + M = 17%). We also showed that more than 86% of cells were positive stained by FITC labeled CD44, CD29, CD13, and only about 1% of cells were positive for CD34, HLA-DR. Expression of collagen I, III was positive while vWF was negative. In the differentiation study, we found culture-expanded pancreas MSCs could be directed into the osteogenic lineage as detected by osteoblastic morphology, expression of alkaline phosphatase, modulation of osteocalcin mRNA production and the formation of a mineralized extracellular matrix. We also found that MSCs could give rise to the adipogenic and chondrogenic lineage as evidenced by accumulation of lipid-rich vacuoles within cells and the expression of lipoprotein lipase mRNA or the expression of collagen II and the deposition of proteoglycans. CONCLUSION: Mesenchymal stem cells existing in human pancreas can be isolated by their adherent ability and should be essential to sustain a steady supply of primitive cells in tissue remodeling.

Cell Differentiation↗

PubMed2002

[Determination of procaine hydrochloride by fluorimetry].

Use of fluorescence spectrophotometry for the determination of procaine hydrochloride in injection solution of procaine hydrochloride in suggested based on fluorescence property of 4-aminobenzoate which is a hydrolysis product of the procaine hydrochloride in pH 12, with exciatation wavelength and emission wavelength at 268 and 340 nm, respectively. Under this condition, a linear relationship is obtained between procaine hydrochloride and the relative fluorescence intensity. The linear regression equation of the calibration graph is c = 0.022I-0.081, with a linear regression correlative coefficient of 0.9996 and relative standard deviation (RSD) of 3.4%. Influences of pH, foreign ions, kanamycin, gentamycin, benylpencillin, streptomycin and standing for time on the determination of procaine hydrochloride have been examined. The reasons that the relative fluorescence intensity of procaine hydrochloride increases with a rise in pH and with standing for time are discussed. The detection limit of this method is 49 ng.mL-1. The results obtained by the method agreed with those by the official method. The method is simple, and available to be used in the determination of procaine hydrochloride in injection solution.

4-Aminobenzoic Acid↗

PubMed2001

Expression, Purification and Biological Activity Analysis of Human Vascular Endothelial Growth Factor (VEGF(165)) in Pichia pastoris.

The human VEGF(165) cDNA was amplified by PCR, and was inserted, after confirming by DNA sequence analysis, into the Pichia pastoris expression vector pPIC9K containing AOX1 promoter and lead sequence of alpha factor gene to form a recombinant expression plasmids pPIC9K/hVEGF(165). This recombinant plasmid was transformed into KM71. Transformants were screened, cultured inflasks and induced by the addition of 1% methanol. After 4 days of methanol induction, the expressed hVEGF(165) came up to 60% of total proteins in medium supernatant as shown by SDS-PAGE. Western blot assay proved that the expressed hVEGF(165) had good antigenicity and high specificity. The recombinant protein was further purified by using Heparin-Sepharose CL6B affinity chromatography, and was proved that it had good biological activity to stimulate HUVEC proliferation and to promote collateral blood vessel formation in an acquired limb artery occlusion animal model.

Journal Article↗

PubMed2000

Ligand Binding Domains of human Vascular Endothelial Growth Factor Receptor.

Four cDNA clones, encoding truncated Flt-1 mutants consisting of loop 2, 1-2, 2-3 and 1-3, were amplified by PCR from human placenta cDNA library and the corresponding gene fragments were named Flt-1(2) Flt-1(1-2) Flt-1(2-3) and Flt-1(1-3). In order to detect which part of the extracellular domain was involved in ligand binding, the interaction between Flt-1 mutants and hVEGF(165) was studied with yeast two-hybrid system. The data presented here suggest that both Flt-1(2-3) and Flt-1(1-3) were able to bind hVEGF(165). Two recombinant expression plasmids, pPIC9K/Flt-1(1-3) and pPIC9K/Flt-1(2-3), were constructed and transformed into Pichia pastoris strain GS115, respectively. After 4 days of methanol induction, the amount of the expressed Flt-1s reached 60% of total proteins in supernatant by SDS-PAGE. Recombinant proteins were purified with CM-Sepharose Fast Flow and Sephacryl S-100 chromatography. Biological activities analysis proved that 1-3 loop had slightly better biological activity than 2-3 loop in VEGF(165) binding and in inhibition of HUVEC proliferation stimulated by hVEGF(165).

Journal Article↗

PubMedDate not supplied

Enhancement effect of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and cationic surfactant on the chemiluminescence of poly(3, 4, 5-trihydroxybenzoate ester)dendrimers.

In the presence of l-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), the chemiluminescence (CL) intensities of poly(3, 4, 5-trihydroxybenzoateester)dendrimers, 1 and 2, having 1,2-pyrocatechol and 1,3,5-trihydroxybenzene as core molecules and also six and nine gallic acid units in the periphery, were respectively 7.4- and 2.4-fold stronger than those of 1 and 2 in the absence of EDC. Similarly, the CL intensities of 1 and 2 in the presence of cetyltrimethylammonium bromide (CTAB) were respectively 4- and 1.7-fold stronger than those of 1 and 2 in the absence of CTAB.

Ethyldimethylaminopropyl Carbodiimide↗