Biomedical subjects

Xiaojun Ma

Publications and source records attributed to Xiaojun Ma.

17 recordsLinked to original sources

PubMed2006

Cytoskeletal reorganization and repolarization of hepatocarcinoma cells in APA microcapsule to mimic native tumor characteristics.

Culture of human hepatocarcinoma cells in three-dimensional structure or spheroid represents a unique opportunity to recapitulate aspects of cell homeostasis and to better reflect the characteristics of native hepatic tumor. In this paper, human hepatocarcinoma SMMC-7721 cells were encapsulated in alginate-poly-l-lysine-alginate (APA) microcapsules and the behavior of the cells in the restricted three-dimensional culture system was investigated. The cells were polygonal-shaped, proliferating with high viability, and formed a single multicellular spheroid in microcapsule. During the assembly of the aggregate in microcapsule, cytoskeletal reorganization and repolorization was occurred, which was absent in cells cultured in monolayer. The in vivo-like cytoarchitecture was confirmed by the phalloidin-FITC labeling of F-actin filaments. The trabecular structure revealed by scanning electron microscope (SEM), and the bile canaliculus with multiple microvilli and tight junctions revealed by transmission electron microscope (TEM) was found in microencapsulated cells, which exhibited the ultrastructural characteristics of native hepatic tissue. It suggested that microcapsule culture provides an in vivo-like model which can be used for the study of the interactions of cell-cell and cell-microenvironment, and the mechanisms of invasion, metastasis and multicellular drug resistance of tumor cells.

Journal Article↗

PubMed2006

K562 cell growth activity and metabolism characteristics in APA microencapsulated culture and modeling study.

Cell microencapsulation is likely to play a major role in cell and transplantation therapies in the next decade. The microcapsules provide a special microenvironment in which cells always have different behaviors compared with free non-encapsulated culture. In this work, the behaviors of K562 leukemia cells were studied once entrapped in solid and liquefied APA microcapsules as well as in free non-encapsulated culture. Glucose pulse culture was employed to characterize the growth and metabolism of microencapsulated K562 cells. And mathematical modeling was presented to develop a basis for the deeper understanding of cells responses to different culture environments. Based on the results of experiments and modeling, it was found that cells presented a better growing pattern and maintain the activity at a higher level for extending time. The concentration of lactate was higher in solid microcapsules culture than that of liquefied microcapsules culture, but the cell number was lower. And the lactate yield coefficients (lactate/glucose) were 0.8129, 0.6978 and 0.601 for free non-encapsulated, solid microcapsules and liquefied microcapsules culture, respectively. An increase of glucose concentration led a decrease of cell activity, The glucose consumption ratio were 99.9%, 86.8%, 49.4% and 28.6% with the decrease in its concentration from 2 to 4, 6, 10 g/L, however, the lactate yield coefficient were 0.7184, 0.6654, 0.8239 and 0.9693, respectively.

Alginates↗

PubMed2006

A normal mucin-binding lectin from the sponge Craniella australiensis.

A lectin, Craniella australiensis (CAL), was isolated from sponge C. australiensis by ion-exchange on DEAE-Sephacel and purified by gel filtration on Sephadex G-150 and HPLC on DEAE-5PW. The purified lectin was a trimeric protein as revealed by SDS-PAGE and MALDI-TOF analysis. SDS-PAGE showed that the CAL protein had a molecular mass of 54 kDa, and consisted of three 18 kDa subunits. Gel filtration of purified lectin on Sephadex G-200 indicates that it exists as a 54 kDa protein in its native state. The amino acid composition was rich in Thr and Glx. CAL was found to agglutinate native and trypsinized human A, B erythrocytes, and agglutinate native erythrocytes of mouse, sheep, rabbit and chicken, and trypsinized erythrocytes of sheep and rabbit. The hemagglutination activity was inhibited by glycoproteins such as PSM and asialo-PSM, but not by any of the monosaccharides tested. The activity was stable between 20 and 70 degrees C. Significant CAL activity was observed between pH 5 and 8. The lectin reaction is independent of the presence of divalent cations Ca2+ and Mg2+. The sequence of N-terminal residues of CAL was determined as TSSCQSIVVE. The lectin showed a potent mitogenic response towards BALB/c splenocytes.

Amino Acid Sequence↗

PubMed2006

Quantitative analysis of fibrosis formation on the microcapsule surface with the use of picro-sirius red staining, polarized light microscopy, and digital image analysis.

Transplantation of microencapsulated cells shows potential to treat a variety of diseases. To improve the quality of microcapsules, efficient methods need to be established and standardized for the evaluation of biocompatibility of microcapsules. To this end, a microscopical method was developed to analyze quantitatively the degree of fibrotic overgrowth (FO), which serves as the index of biocompatibility. In this method, sections were stained with picro-sirius red and illuminated with a polarized light microscope. The images were digitized with the use of a computer-video system in which collagenous content was depicted by gray levels 1 to 255. Both the area of collagen and the thickness of FO were examined. The ratio of Type I/Type III collagen and the thickness were used as indexes of the degree of FO. The data showed that the ratio of Type I/Type III collagen and the thickness increased with time, and FO was not significant 4 weeks after transplantation. In comparison, this new method is more efficient to evaluate FO.

Animals↗

PubMed2006

Proliferation, viability, and metabolism of human tumor and normal cells cultured in microcapsule.

In this study, we investigated the effect of the microenvironment provided by alginate-poly-L-lysine-alginate (APA) microcapsule with liquefied or gelled core on the proliferation, viability, and metabolism of human cells, including anchorage-dependent MCF-7 breast cancer cells and primary fibroblasts, and anchorage-independent K-562 leukemia cells; cells in conventional culture were used as control. The growth pattern of cells in microcapsule was examined by phase-contrast micrography. The cell viability, proliferation, organization, and gene expression were evaluated by 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, hematoxylin and eosin staining, live/dead staining, 5-bromo-20-deoxyuridine labeling, and immunohistochemistry, respectively. Cell metabolism was determined by measuring glucose and lactate concentrations in medium. The results demonstrate that APA microcapsule with liquefied core provides a microenvironment for both anchorage-dependent and anchorage-independent cells to grow into a large cell aggregate and maintain cell viability at a constant level for a period of time. In conclusion, cells in APA microcapsule are alive and have proliferation potential with lower metabolism rate. APA microcapsule may be a useful tool for in vitro tumor cell modeling and anticancer drug screening as well as for cancer gene therapy. In addition, it lays a solid foundation for the use of microencapsulation in cell culture in vitro and cell implantation in vivo.

Alginates↗

PubMed2006

[Study on homogeneity of enzymatic degradation of chitosan as biomaterials by gel permeation chromatography].

Chitosan is an important biomedical material, and its degree of deacetylation is a main parameter of its biodegradation. Gel permeation chromatography was used to investigate the lysozymic degradation of two types of chitosan samples (A and B) with similar degree of deacetylation and relative molecular mass but with different distributions of two units of N-acetyl-D-glucosamine and D-glucosamine. Weight average relative molecular mass, polydispersity and gel permeation chromatograms during the degradation process were obtained. It was found that chitosan sample A with random distribution of the two units underwent a homogeneous degradation process while chitosan sample B with block distribution underwent a heterogeneous degradation process. The results suggest that the homogeneity of the degradation of chitosan materials by lysozyme depends on the distribution type of the two units, which can help to design chitosan-based biomedical devices.

Acetylglucosamine↗

PubMed2005

The enzymatic degradation and swelling properties of chitosan matrices with different degrees of N-acetylation.

In the design of chitosan-based drug delivery systems and implantable scaffolds, the biodegradation rate of the chitosan matrix represents a promising strategy for drug delivery and the function of carriers. In this study, we have investigated the degradation of chitosan with different degrees of N-acetylation, with respect to weight loss, water absorption, swelling behavior, molecular weight loss of bulk materials, and reducing sugar content in the media. Chitosan matrices were prepared by compression molding. The results revealed that the initial degradation rate, equilibrium water absorption, and swelling degree increased with decreasing degree of deacetylation (DD) and a dramatic rise began as DD of the chitosan matrix decreased to 62.4%. Chitosan matrices with DD of 52.6%, 56.1%, and 62.4% had the weight half-life of 9.8, 27.3, and more than 56 days, respectively, and the weight half-life of average molecular weight 8.4, 8.8, and 20.0 days, respectively. For chitosan matrices with DD of 71.7%, 81.7%, and 93.5%, both types of half-life exceeded 84 days because of the much slower degradation rate. The dimension of chitosan matrices during degradation was determined by the process of swelling and degradation. These findings may help to design chitosan-based biomedical materials with predetermined degradation timed from several days to months and proper swelling behaviors.

Absorption↗

PubMed2005

Simultaneous and ultrarapid determination of reactive oxygen species and reduced glutathione in apoptotic leukemia cells by microchip electrophoresis.

A microchip electrophoresis method coupled with laser-induced fluorescence (LIF) detection was established for simultaneous determination of two kinds of intracellular signaling molecules (reactive oxygen species, ROS, and reduced glutathione, GSH) related to apoptosis and oxidative stress. As the probe dihydrorhodamine-123 (DHR-123) can be converted intracellularly by ROS to the fluorescent rhodamine-123 (Rh-123), and the probe naphthalene-2,3-dicarboxaldehyde (NDA) can react quickly with GSH to produce a fluorescent adduct, rapid determination of Rh-123 and GSH was achieved on a glass microchip within 27 s using a 20 mM borate buffer (pH 9.2). The established method was tested to measure the intracellular ROS and GSH levels in acute promyelocytic leukemia (APL)-derived NB4 cells. An elevation of intracellular ROS and depletion of GSH were observed in apoptotic NB4 cells induced by arsenic trioxide (As(2)O(3)) at low concentration (1-2 microM). Buthionine sulfoximine (BSO), in combination with As(2)O(3) enhanced the decrease of reduced GSH to a great extent. The combined treatment of As(2)O(3) and hydrogen peroxide (H(2)O(2)) led to an inverse relationship between the concentrations of ROS and GSH obtained, showing the proposed method can readily evaluate the generation of ROS, which occurs simultaneously with the consumption of the inherent antioxidant.

Apoptosis↗

PubMed2004

Transmembrane/juxtamembrane domain-dependent Dscam distribution and function during mushroom body neuronal morphogenesis.

Besides 19,008 possible ectodomains, Drosophila Dscam contains two alternative transmembrane/juxtamembrane segments, respectively, derived from exon 17.1 and exon 17.2. We wondered whether specific Dscam isoforms mediate formation and segregation of axonal branches in the Drosophila mushroom bodies (MBs). Removal of various subsets of the 12 exon 4s does not affect MB neuronal morphogenesis, while expression of a Dscam transgene only partially rescues Dscam mutant phenotypes. Interestingly, differential rescuing effects are observed between two Dscam transgenes that each possesses one of the two possible exon 17s. Axon bifurcation/segregation abnormalities are better rescued by the exon 17.2-containing transgene, but coexpression of both transgenes is required for rescuing mutant viability. Meanwhile, exon 17.1 targets ectopically expressed Dscam-GFP to dendrites while Dscam[exon 17.2]-GFP is enriched in axons; only Dscam[exon 17.2] affects MB axons. These results suggest that exon 17.1 is minimally involved in axonal morphogenesis and that morphogenesis of MB axons probably involves multiple distinct exon 17.2-containing Dscam isoforms.

Alternative Splicing↗

PubMed2004

Significant changes of peripheral T lymphocyte subsets in patients with severe acute respiratory syndrome.

This report demonstrates that a rapid decrease of peripheral T cell subsets is a unique characteristic in patients with SARS during acute infection, although total white blood cell counts, red blood cell counts, and platelet counts remain relatively normal. In recovering patients, a rapid and dramatic restoration of peripheral T cell subsets was seen in the periphery. Although the underlying mechanism of the acute decrease of peripheral T cell subsets observed in patients with SARS during the acute stage remains unknown, this clinical characteristic can facilitate an earlier and more accurate diagnosis of SARS.

Antigens, CD↗

PubMed2004

Microbial community structure along an altitude gradient in three different localities.

The microbial community structure along an altitude gradient was investigated in different localities, in Kalasi lake, Urumqi river and Sangong river, Xingjiang (China). The mean numbers of DAPI (4',6-diamidino-2-phenylindole)-stained cells were lower in Kalasi lake than that in Urumqi river and Sangong river; these differences were attributed to increasing environmental harshness including lower soil organic carbon and nitrogen content, more acidic pH and lower annual temperature. In each locality, the numbers of bacteria and archaea measured with two fluorescence-labeled 16S rRNA oligonucleotide probes (EUB338 and ARCH915) were higher in a coniferous forest and lower in desert vegetation. A significant and positive relationship was found between microbial and soil organic carbon and total nitrogen along the altitudinal gradient, indicating that plant communities and soil nutrients influence the soil microbial structure. The results show that the microbial population in higher latitudinal site was fewer than lower latitudinal one, soil microorganisms were positively correlated to soil organic carbon and total nitrogen, and plant communities had an obviously impact on soil microbes.

Altitude↗

PubMed2004

Soil microbial counts and identification of culturable bacteria in an extreme by arid zone.

Sixteen samples of two soil cores (about 550 and 180 cm in depth) were drilled at intervals in the lower reach of Heihe river basin (northwest of China) in order to illustrate soil microbial characteristics and diversity of culturable bacteria in an extreme by arid environment. Soil water content, organic matter, total nitrogen, pH, direct cell counts, and culturable microorganism counts were evaluated. The total cell concentration was 19-1120/microg (i.e. 0.19-11.2 x 10(8) per g) soil, the culturable bacteria count being 0.2-10.9 per microg (i.e. 2 x 10(5)-10.9 x 10(6) CFU/g) soil. The number of direct cell counts obtained by 4',6-diamidino-2-phenylindole-staining or the cound of culturable microbes after enrichment with different media were statistically significantly correlated with soil organic matters, total nitrogen content, soil water content and surface vegetation; this partly explained the larger number in the deeper first core than in the shallower one. As part of identification of 228 colonies isolated from the two cores, thirty-two were selected for 16S rDNA amplification, sequencing and molecular identification. These 32 isolates were affiliated to 5 major groups of bacteria: alpha-Proteobacteria, 5-Proteobacteria, gamma-Proteobacteria, the high-G+C G+-bacteria, the low-G+C G- -bacteria, and the Cytophaga-Flexibacter-Bacteroides group. Twenty-eight were rod- or short-rod shaped, which accounted for >87.5% of all species; only 4 of 32 species were cocci (<12.5%).

Bacteria↗

PubMed2004

[The dynamic change of total alkaloids content from Pinellia ternate].

OBJECTIVE: To determine the alkaloids content of Pinellia ternate in different growing time for finding out the best harvest time. METHODS: The alkaloid was extracted by chloroform from Pinellia ternate and tested at 417 nm with the spectroscopy by acid dye. The result was analyzed in One-Way ANOVA. RESULTS: The calibration curve of alkaloid was linear( r = 0.9989). The recovery rate was perfect (100.1%). The alkaloids content in different growing time had very significant difference ( F = 12.789, P < 0.01). CONCLUSION: This method is simple and quick. The alkaloids content in whole seedling stage is higher than that in other growing stages, while the mean total alkaloids output per plant is the highest in intensive seedling-downfallen stage which is considered as the best harvest time.

Alkaloids↗

PubMed2003

Rapid loss of both CD4+ and CD8+ T lymphocyte subsets during the acute phase of severe acute respiratory syndrome.

OBJECTIVE: To study the alteration of peripheral lymphocyte subsets in severe acute respiratory syndrome (SARS) patients and to help improve the early diagnosis of the disease. METHODS: Anti-coagulating blood samples from 98 SARS patients in the acute phase, 56 normal healthy blood donors, and from patients infected by HIV, CMV and EBV were collected. The T lymphocyte subsets were counted by flow cytometry using fluorescence-labeled specific monoclonal antibodies. RESULTS: A significant decrease was observed in all SARS patients in their peripheral CD4(+) and CD8(+) T lymphocyte absolute counts [256 (104) x 10(6)/L and 256 (117) x 10(6)/L, respectively], which were also lower than those of the patients infected with HIV, CMV and EBV. All patients infected with HIV, CMV and EBV had significantly higher CD8(+) T lymphocyte counts in comparison with normal controls. CONCLUSIONS: Decrease of both CD4(+) and CD8(+) T lymphocytes of patients is related to onset of SARS. T lymphocyte subset analysis would help improve the early diagnosis of the disease.

Adult↗

PubMedDate not supplied

Development of an in vitro multicellular tumor spheroid model using microencapsulation and its application in anticancer drug screening and testing.

In this study, an in vitro multicellular tumor spheroid model was developed using microencapsulation, and the feasibility of using the microencapsulated multicellular tumor spheroid (MMTS) to test the effect of chemotherapeutic drugs was investigated. Human MCF-7 breast cancer cells were encapsulated in alginate-poly-l-lysine-alginate (APA) microcapsules, and a single multicellular spheroid 150 mum in diameter was formed in the microcapsule after 5 days of cultivation. The cell morphology, proliferation, and viability of the MMTS were characterized using phase contrast microscopy, BrdU-labeling, MTT stain, calcein AM/ED-2 stain, and H&E stain. It demonstrated that the MMTS was viable and that the proliferating cells were mainly localized to the periphery of the cell spheroid and the apoptotic cells were in the core. The MCF-7 MMTS was treated with mitomycin C (MC) at a concentration of 0.1, 1, or 10 times that of peak plasma concentration (ppc) for up to 72 h. The cytotoxicity was demonstrated clearly by the reduction in cell spheroid size and the decrease in cell viability. The MMTS was further used to screen the anticancer effect of chemotherapeutic drugs, treated with MC, adriamycin (ADM) and 5-fluorouracil (5-FU) at concentrations of 0.1, 1, and 10 ppc for 24, 48, and 72 h. MCF-7 monolayer culture was used as control. Similar to monolayer culture, the cell viability of MMTS was reduced after treatment with anticancer drugs. However, the inhibition rate of cell viability in MMTS was much lower than that in monolayer culture. The MMTS was more resistant to anticancer drugs than monolayer culture. The inhibition rates of cell viability were 68.1%, 45.1%, and 46.8% in MMTS and 95.1%, 86.8%, and 91.6% in monolayer culture treated with MC, ADM, and 5-FU at 10 ppc for 72 h, respectively. MC showed the strongest cytotoxicity in both MMTS and monolayer, followed by 5-FU and ADM. It demonstrated that the MMTS has the potential to be a rapid and valid in vitro model to screen chemotherapeutic drugs with a feature to mimic in vivo three-dimensional (3-D) cell growth pattern.

Breast Neoplasms↗

PubMedDate not supplied

Proliferation and differentiation of mouse embryonic stem cells in APA microcapsule: A model for studying the interaction between stem cells and their niche.

Embryonic stem (ES) cells hold promise either as an in vitro model recapitulating early embryonic development or as a renewable source of therapeutically useful cells. Certain aspects of the microenvironment (or niche) play critical roles in determining the fate of ES cells. Here, we reported the feasibility of using the technique of microencapsulation to study the interaction between ES cells and their tissue niche. ES cells' growth, viability, and differentiation in vitro were evaluated when they were enclosed in solid or liquefied core APA microcapsules. In comparison with those microcapsules with solid cores, the liquefied capsules provided a more suitable culture environment for the growth of ES cells. In addition, behavior of encapsulated ES cells in vivo was observed after their being implanted into mouse peritoneal cavities. In contrast to the prolonged lag phase in vitro, ES cells encapsulated grew much faster in vivo. Typical markers for the undifferentiated ES cells, such as AP, SSEA-1, and Oct-4 gene, were also tracked by immunochemistry and RT-PCR. Results showed that expression of markers remained high over 2 weeks of culture in vitro. However, decreased expression of markers was found in those samples in vivo with time passage. These findings implied that it was the combination of the intrinsic characteristics of ES cells and their microenvironment that regulated their fate. The APA-ES cells system may provide an optimal model to study the interaction between stem cells and their tissue niches.

Alginates↗

PubMedDate not supplied

Scalable producing embryoid bodies by rotary cell culture system and constructing engineered cardiac tissue with ES-derived cardiomyocytes in vitro.

Embryonic stem (ES) cells are of significant interest either as an in vitro model recapitulating early embryonic development or as a renewable source of therapeutically useful cells. ES cells aggregation is important for embryoid bodies (EBs) formation and the subsequent generation of ES cell derivatives. This study was conducted to describe scalable production of EBs by the rotary cell culture system (RCCS, STLV type) and estimate the feasibility of constructing engineered cardiac tissue (ECT). In comparison with suspension culture in a Petri dish, the efficiency of the dynamic process was analyzed with respect to the yield of EB formation and their cardiomyocyte differentiation. Cardiomyocyte differentiation was evaluated by immunohistochemical analysis. After the elementary enrichment by gradient percoll, ES cell-derived cardiomyocytes were applied to construct ECT. Cell gross morphology, spatial distribution, and ultrastructure were evaluated by using histological analysis, confocal laser scanning microscopy, and transmission electron microscopy. Results showed that EB efficiencies in STLV were nearly 1.5-2.0 times higher than that of liquid suspension cultures, and cardiomyocyte differentiation of EBs progressed in a normal course after the dynamic cultivation in STLV. Additionally, the differentiated cultures could be enriched elementarily by gradient percoll. Once cast into the collagen strand, cells grew well and became more matured in Petri dishes. Synchronous contraction of the cell cluster was observed on the surface of the ECT, and cell connection was also established. It was the first report to have beating ES-derived cardiomyocytes on a 3-D collagen scaffold, which might provide a promising model for physiological and pharmacological studies and tissue replacement therapy.

Animals↗