Biomedical subjects

Ming Ma

Publications and source records attributed to Ming Ma.

26 records · Page 2Linked to original sources

PubMed2005

Sesquiterpenes from the red alga Laurencia tristicha.

Seven new sesquiterpenes (1-7), together with seven known sesquiterpenes, aplysin (8), aplysinol (9), gossonorol (10), 7,10-epoxy-ar-bisabol-11-ol (11), 10-epi-7,10-epoxy-ar-bisabol-11-ol (12), johnstonol (13), and laurebiphenyl (14), have been isolated from the red alga Laurencia tristicha. The structures of new compounds were established as laur-11-en-2,10-diol (1), laur-11-en-10-ol (2), laur-11-en-1,10-diol (3), 4-bromo-1,10-epoxylaur-11-ene (4), cyclolauren-2-ol (5), laurentristich-4-ol (6), and ar-bisabol-9-en-7,11-diol (7) by means of spectroscopic methods including IR, HRMS, and 1D and 2D NMR techniques. Compound 6 possessed a novel rearranged skeleton. All compounds were tested against several human cancer cell lines including lung adenocarcinoma (A549), stomach cancer (BGC-823), hepatoma (Bel 7402), colon cancer (HCT-8), and HELA cell lines. Laurebiphenyl (14) showed moderate cytotoxicity against all tested cell lines, with IC(50) values of 1.68, 1.22, 1.91, 1.77, and 1.61 microg/mL, respectively. Other compounds were inactive (IC(50) > 10 microg/mL).

Antineoplastic Agents↗

PubMed2005

Therapeutic effect of Fe2O3 nanoparticles combined with magnetic fluid hyperthermia on cultured liver cancer cells and xenograft liver cancers.

The therapeutic effect of Fe2O3 nanoparticles combined with magnetic fluid hyperthermia (MFH) on human hepatocarcinoma SMMC-7721 cells in vitro and xenograft liver cancer in nude mice is studied. We examined growth and apoptosis of SMMC-7721 cells treated with MFH containing Fe2O3 nanoparticles at various concentrations (2, 4, 6, and 8 g/liter) for 30-60 min by using MTT, flow cytometry (FCM), and transmission electron microscopy (TEM). We also observed weight and volume inhibitory rates of the tumors of SMMC-7721-bearing nude mice by using animal experiments. The results showed that Fe2O3 nanoparticles combined with MFH could significantly inhibit the proliferation and increase the ratio of apoptosis of SMMC-7721 cells, and the effect was dose-dependent. The inhibitory rate was 26.5%, 33.53%, 54.4%, and 81.2%, respectively, and the apoptosis rate was 30.26%, 38.65%, 50.28%, and 69.33%, respectively. Animal experiments showed that tumors became small. The weight inhibitory ratio was 42.10%, 66.34%, 78.5%, and 91.46%, and the volume inhibitory ratio was 58.77%, 80.44%, 93.40%, and 98.30%, respectively. Compared with the control and experimental groups, each group had statistically significant difference (p < 0.05). So, Fe2O3 nanoparticles combined with MFH could inhibit the proliferation and induce apoptosis of SMMC-7721 cells and also has a significant inhibitory effect on the weight and volume of xenograft liver cancer. However, the mechanism remains to be further investigated.

Animals↗

PubMed2005

Prevention of central cell damage to isolated islets of Langerhans in hamsters by low temperature preconditioning.

BACKGROUND: The efficacy of clinical islet transplantation has been demonstrated with autografts, and although islet allografts have established insulin independence in a small number of IDDM patients, the treatment is confounded by the necessity of central cell damage immunosuppression, the lack of donor tissue, and recurring islet immunogenicity. These limitations underscore a need to develop therapies to serve the large population of diabetic patients. This study was designed to document central cell damage to isolated islets of Langerhans in hamsters and its prevention. METHODS: Islets were cultured at 37 degree centigrade for 7-14 days after isolation, and then at 26 degree centigrade for 2,4 and 7 days before additional culture at 37 degree centigrade for an additional 7 days. Central cell damage in the isolated islets was monitored by video-microscopy and analyzed quantitatively by a computer-assisted image analysis system. The analysis included daily measurement of the diameter and the area of the isolated islets and the area of the central cell damage that developed in those islets over time during culture. Histological examination and TdT-mediated dUTP-biotin nick end labeling (TUNEL) assay were used to characterize cell damage and to monitor islet function. RESULTS: Microscopic analysis showed that during the 7 to 14 days of culture at 37 degree centigrade, central cell damage appeared in the larger islets with diameters greater than 200 microm, which included both necrotic and apoptotic cell death. Low temperature (26 degree centigrade) culture prevented central cell damage of isolated islets. The 7-day culture procedure at 26 degree centigrade could inhibit most of the central cell (excluding diameters greater than 300 microm) damage when the islets were rewarmed to 37 degree centigrade. CONCLUSIONS: Our results indicate that central cell damage to isolated islets of Langerhans correlates with the size of the islets. Low temperature (26 degree centigrade) culture can prevent central cell damage to the isolated islets, and is capable to successfully precondition these islets for 37 degree centigrade culture. These novel findings may help to understand the pathophysiology of early loss of islet tissue after transplantation, and may provide a new strategy to improve graft function in the clinical setting of islet transplantation.

Animals↗

PubMed2005

[Determination of sildenafil and vardenafil in human plasma by high performance liquid chromatography coupled with liquid-liquid-liquid microextraction].

High performance liquid chromatography coupled with liquid-liquid-liquid microextraction was developed for the simultaneous determination of sildenafil and vardenafil in human plasma. The effects of extraction solvent, the volume of organic solvent, dropsize of acceptor phase, stirring rate and extraction time on the enrichment factors of analytes were investigated. The optimized experimental conditions, 300 microL toluene as the organic phase, 2 microL 0.2 mol/L HCl as the acceptor phase, 600 r/min of the stirring rate, and 40 min of the extraction time, were gotten. Under these conditions, high enrichment factors were obtained. The linear range of studied analytes was from 5 microg/L to 1.0 mg/L. The relative standard deviation was lower than 5%. The limits of detection were 1 microg/L for sildenafil and 0.5 microg/L for vardenafil at signal-to-noise ratio of 3. The method with little solvent consumption may provide high analyte preconcentration and excellent sample clean-up, and it is a sensitive and suitable method for simultaneous determination of the above two substances in human plasma.

Chemical Fractionation↗

PubMed2004

Simultaneous analysis of theanine, chlorogenic acid, purine alkaloids and catechins in tea samples with the help of multi-dimension information of on-line high performance liquid chromatography/electrospray-mass spectrometry.

A reverse phase high performance liquid chromatography (RP-HPLC) separation coupled with photo diode array detection (DAD) and electrospray ionization mass spectrometry (ESI-MS) detection was established for the analyzing of multiple bioactive compounds in tea and tea extracts. Theanine, chlorogenic acid, purine alkaloids and catechins were identified with authentic standard compounds and with MS-spectra. The content of theanine and catechins was measured by employing DAD and caffeine, chlorogenic acid, theobromine and theopylline by protonated molecular ion on selective ion recording (SIR) mode. The unity of LC/ESI-MS provides more qualitative and quantitative information comparing with general HPLC in the analysis of multi-components in tea, and complex extraction or sample pretreatment is unnecessary. The chromatogram acquired by using this method can be used as a bioactive components fingerprint for the quality control of tea and its extracts. With the help of multi-dimension information of HPLC-DAD-ESIMS, the compounds owning different chemical structure such as amino acid, catechins, etc. in tea and its extracts could be identified and determined in one run successfully.

Alkaloids↗

PubMed2004

[Expression of MAGE genes and MAGE gene products in human renal and urinary bladder tumor].

OBJECTIVE: To observe the expression of MAGE-1 MAGE-3 genes and MAGE-3 gene product in renal and urinary bladder tumor, and to explore the possibility of MAGE-1 and MAGE-3 genes encoding proteins or MAGE-3 gene product used as a target for immunotherapy in renal and urinary bladder tumor patients. METHODS: Reverse transcriptase polymerase chain reaction for MAGE-1 and MAGE-3 genes was performed using 39 renal and urinary bladder tumor specimens. Immunohistochemical technique for MAGE-3 antigen was performed using formal infixed paraffin embedded section of 121 renal and urinary bladder tumor specimens. RESULTS: MAGE-1 and MAGE-3 mRNAs were detected in 23(59.0%) and 22(56.4%) of 39 patients with renal and urinary bladder tumor without expression in 10 tumor surrounding tissues.MAGE-3 antigen was detected in 56(46.3%) of 121 patients with renal and urinary bladder tumor without expression in 10 tumor surrounding tissues. The expression rates of MAGE-1 and MAGE-3 mRNA and MAGE-3 gene product were significantly higher in renal and urinary bladder tumors tissues than in tumor surrounding tissues. The frequency of MAGE-3 gene product expression was examined according to clinical stage and differentiation of histopathology. The results revealed no significant differences in MAGE gene product expression among the clinical stage and the grade of differentiation of histopathology according to Logistic Regression test(P>0.05). CONCLUSION: The tumor-specific antigens might be used as molecular markers and targets for human renal and urinary bladder tumor.

Adult↗

PubMed2003

Size dependence of second-order optical nonlinearity of CdS nanoparticles studied by hyper-Rayleigh scattering.

The second-order optical nonlinearity of CdS nanoparticles with different mean diameters of 28.0, 30.0, 31.5, 50.0, and 91.0 A was studied by the incoherent hyper-Rayleigh scattering technique. Results show that the first-order hyperpolarizability beta value per CdS particle decreases with decreasing size from 91.0 to 31.5 A; however, as CdS particle size further decreases, this trend is reversed and the beta value increases. Substantially, the normalized value of the first-order hyperpolarizability per CdS formula unit, beta(0), exhibits systematic enhancement with decreasing size. This is interpreted in terms of a so-called surface contribution mechanism. The two aspects of quantum size effects, the size dependence of optical band-gap and oscillator strength, cannot be adopted to explain the size dependence of the second-order optical nonlinearity of CdS nanoparticles.

Journal Article↗

PubMed2003

Identification and molecular phylogeny of Epulorhiza isolates from tropical orchids.

24 isolates of Epulorhiza were obtained from the roots and protocorms of orchids in Singapore. Two groups were distinguished based on morphological and cultural characteristics. Group 1 comprised 20 isolates which were identified as E. repens, while those in group 2 were identified as E. calendulina-like Rhizoctonia. The ITS-5.8S rDNA sequence identity ranged from 88-100% among isolates of E. repens and six sub-groups were further delineated. The sequence identity was 98-100% among E. calendulina-like Rhizoctonia isolates. The sequence identity between E. repens isolates and E. calendulina-like Rhizoctonia isolates ranged from 18-44%. Apparently, isolates from both groups 1 and 2 were genetically distinct. Phylogenetic analysis showed that the distribution of the isolates correlated with the sites and the hosts from which the fungi were isolated. No matching sequences have been found in the GenBank database for the ITS region of E. repens and E. calendulina-like Rhizoctonia.

Basidiomycota↗