Biomedical subjects

Xiang Ma

Publications and source records attributed to Xiang Ma.

26 records · Page 2Linked to original sources

PubMed2004

[The morphologic changes of Amplatzer asymmetric ventricular septal defect occluder after transcatheter closure of perimembrane ventricular septal defect].

OBJECTIVE: Catheter closure of perimembrane ventricular septal defect (PMVSD) using the Amplatzer asymmetric ventricular septal defect occluder (AAVSDO) is a potential alternative for open surgical repair. However, the profile of the device obtained after closure probably continues to change some concerns regarding its safety. This study was designed to evaluate the morphologic changes of AAVSDO by transthoracic echocardiography examination (TTE) and X-ray examination after transcatheter closure of PMVSD. METHODS: A total of 23 patients, aged 2.5 - 47.0 years, with PMVSDs underwent transcatheter closure with the AAVSDO. Each patient underwent TTE and X-ray examination with same radiography system immediately, 72 hours, 6 months and 1 year after the transcatheter closure procedures, respectively. Seven parameters were measured by TTE and X-ray to evaluate the morphologic changes of AAVSDO: the distance between superior edge of left disk of AAVSDO and aortic valve (L(1)), the distance between superior extremity edge of two disks of the occluder (L(2)), the distance between inferior extremity edge of two disks of the occluder (L(3)), the distance between two marks on the left and right disks (L(4)), the diameter of left disk (D(1)), the diameter of left disk (D(2)), and the degree of angle between left and right disks (alpha). In the meantime, the influences of occluder's morphologic changes were evaluated by TTE. RESULTS: The PMVSD diameter ranged from (8.53 +/- 4.82) mm (3.91 - 17.0 mm). The device diameter ranged from 6 - 18 (10.34 +/- 7.16) mm. AAVSDO was performed successfully in all the 23 patients who underwent immediately, 72 hours and 6 months follow-up after catheter closure, and 12 patients accomplished 1-year follow-up. L(2), L(4) and alpha were shorter at 6-months than 72-hours after procedures, but D(1) and D(2) were greater at 6-months than 72-hours after procedures in all patients. Alpha was decreased further 1 year after the procedure, but other parameters did not change significantly compared with those at 6-months after procedures. The lower profile and smaller thickness of AAVSDO were observed in the follow-up. Meanwhile, D(1) and D(2) changed significantly during the follow-up. L(4) had a weak positive correlation with device size (r = 0.47, 0.33 and 0.39, respectively) and with alpha (r = 0.47, 0.53 and 0.49, respectively), and had weak negative correlation with D1 (r = -0.27, -0.45 and -0.29, respectively). After deployment of the prosthesis there was no residual shunt in 20 of 23 patients (87%). There was a trivial residual shunt that disappeared at the six month follow up in two patients, and a small residual shunt that disappeared at the one year follow up in one patient. The morphologic changes of AAVSDO did not influence the structure near PMVSD. CONCLUSION: The morphologic changes of Amplatzer occluder were observed in the follow-up. The change of the occluder was safe and beneficial to improve short-term curative effect.

Adolescent↗

PubMed2004

[Determination of chemical components in tobacco leaves by FT-NIR spectroscopy: study of influence of spectral ranges on PLS modeling].

NIR spectra of tobacco leaves were measured in the range of 12000 to 4000 cm(-1) using a Bruker MPA FT-NIR spectrometer. PLS calibration models were developed and optimized for rapid quantitative analysis of nicotine alkaloids, total sugar and total nitrogen contents in tobacco leaves. It was found that the prediction errors of the same component were significantly different when different spectral regions were used for PLS modeling, and the best spectral range is also different for each component. The study demonstrated that wavelength range selection is one of the important keys to optimizing the NIR calibration model. In this study it was found that the optimized calibration ranges for nicotine alkaloids, total sugar and total nitrogen are 9500-4231.2 cm(-1), 7502.1-4246.7 cm(-1) and 7502.1-4597.7 cm(-1), respectively. The Root Mean Square Error of Cross Validation (RMSECV) of the three calibration models are 0.081 5, 0.808 and 0.056, respectively.

Algorithms↗

PubMed2003

[Application of two-dimensional electrophoresis and mass spectrometry in the research of testicular proteins].

OBJECTIVES: To evaluate the application of two-dimensional electrophoresis and mass spectrometry in the research of proteins expressed in testis. METHODS: Protein from adult ICR mouse testes was extracted by two-dimensional electrophoresis. Two protein spots were cut from the gel, then the proteins were digested in-gel by enzyme and the generated peptides were measured by matrix assisted laser desorption/ionization-time of flight mass spectrometry. The proteins were identified through database searching. RESULTS: Two spots in Commasie Brilliant Blue-stained gel were identified as serum albumin and protein disulfide isomerase by database searching. CONCLUSIONS: This rapid high resolution and efficient method is a very powerful way to analyze testicular proteins.

Animals↗

PubMed2003

[Suppression of corneal neovascularization by conditioned culture medium of human amniotic membrane].

OBJECTIVE: To investigate the effects of the conditioned culture medium (CCM) of human amniotic membrane (AM) on corneal neovascularization (CNV) induced by basic fibroblast growth factor (bFGF) in mice. METHODS: AM (with epithelium side up) was cultured in EGM basic medium for 3 days, and the CCM was collected. The CCM consisted of three groups: control (EGM only), AM with epithelium (AM) and AM without epithelium (De-AM). Corneal neovascularization was induced in mice by using micropocket assay with Hydron polymer pellets containing 100 ng bFGF. Migration and proliferation of human umbilical cord vein endothelial cells (HUVEC) were measured in Boyden chambers and by CyQUANT fluorescence binding assay, respectively. The levels of tissue inhibitors of metalloproteinase 1 and 2 (TIMP-1, TIMP-2) in the CCM were determined by ELISA assay. RESULTS: CNV induced by bFGF was significantly suppressed by the CCM of amniotic membrane. When CCM was applied as an eyedrop 4 times a day for 7 days, the area of CNV was (2.48 +/- 0.76) mm(2), (0.64 +/- 0.52) mm(2) and (1.96 +/- 0.65) mm(2) in control, AM and De-AM groups, respectively. The migration and proliferation of HUVEC were strongly inhibited by the CCM of AM with epithelium, while the De-AM had no effect on the migration of HUVEC cells. A high level of TIMP-2 was found in AM group, but not in De-AM group. There were no differences in the amount of TIMP-1 in medium among these three groups. CONCLUSIONS: CCM of amniotic membrane significantly suppresses the CNV induced by bFGF. One of the mechanisms of CCM-mediated suppression is that a high level of TIMP-2 protein is secreted or released into the CCM by AM, which can inhibit the migration and growth of vascular endothelial cells.

Amnion↗

PubMed2002

Crystal structure of a staphylokinase: variant a model for reduced antigenicity.

Staphylokinase (SAK) is a 15.5-kDa protein from Staphylococcus aureus that activates plasminogen by forming a 1 : 1 complex with plasmin. Recombinant SAK has been shown in clinical trials to induce fibrin-specific clot lysis in patients with acute myocardial infarction. However, SAK elicits high titers of neutralizing antibodies. Biochemical and protein engineering studies have demonstrated the feasibility of generating SAK variants with reduced antigenicity yet intact thrombolytic potency. Here, we present X-ray crystallographic evidence that the SAK(S41G) mutant may assume a dimeric structure. This dimer model, at 2.3-A resolution, could explain a major antigenic epitope (residues A72-F76 and residues K135-K136) located in the vicinity of the dimer interface as identified by phage-display. These results suggest that SAK antigenicity may be reduced by eliminating dimer formation. We propose several potential mutation sites at the dimer interface that may further reduce the antigenicity of SAK.

Antigens, Bacterial↗

PubMed2002

Delay of corneal epithelial wound healing and induction of keratocyte apoptosis by platelet-activating factor.

PURPOSE: To examine the role of the lipid mediator platelet-activating factor (PAF) in epithelial wound healing. METHODS: A 7-mm central de-epithelializing wound was produced in rabbit corneas, and the tissue was incubated with 125 nM carbamyl PAF (cPAF), an analogue of PAF. Rabbit corneal epithelial and stromal cells were also cultured in the presence of cPAF. Cell adhesion, proliferation, and migration assays were conducted. Apoptosis was assayed by TUNEL staining on preparations of corneal tissue sections and in cells in culture. RESULTS: Twenty-four hours after injury, 50% of the wounded area was covered by new epithelium, whereas only 30% was covered in the presence of cPAF. At 48 hours, the epithelium completely closed the wound, but only 45% of the original wound was covered in corneas treated with cPAF. Similar inhibition of epithelial wound closure was found with human corneas incubated with PAF in organ culture. Moreover, addition of several growth factors involved in corneal wound healing, such as epidermal growth factor, hepatocyte growth factor, and keratinocyte growth factor, could not overcome the inhibitory action of PAF in wound closure. Three PAF antagonists, BN50727, BN50730, and BN50739, abolished the effect of PAF. A significant increase in TUNEL-positive staining occurred in corneal stromal cells (keratocytes), which was inhibited by preincubating the corneas with PAF antagonists. However, no TUNEL-positive staining was found in epithelial cells. TUNEL-staining results in cultured stromal cells (keratocytes) and epithelial cells in first-passage cell culture were similar to those in organ-cultured corneas. In addition, PAF caused 35% to 56% inhibition of adhesion of epithelial cells to proteins of the extracellular matrix: collagen I and IV, fibronectin, and laminin. There were no significant changes in proliferation or migration of epithelial cells induced by the lipid mediator. CONCLUSIONS: The results suggest PAF plays an important role in preventing corneal wound healing by affecting adhesion of epithelial cells and increasing apoptosis in stromal cells. PAF antagonists could be of therapeutic importance during prolonged ocular inflammation, helping to avoid loss of corneal transparency and visual acuity.

Animals↗

PubMed2002

[Non-penetrating trabecular surgery with application of mitomycin C].

OBJECTIVE: To evaluate the clinical effect of non-penetrating trabecular surgery (NPTS) with mitomycin C (MMC) in primary open-angle glaucoma (POAG). METHODS: Twenty-five eyes of 18 patients with POAG underwent NPTS with MMC during the operation. The mean follow-up was 16.6 months (6 - 28 months). RESULTS: The mean preoperative intraocular pressure (IOP) was (27.93 +/- 7.62) mm Hg (1 mm Hg = 0.133 kPa) which decreased to a mean postoperative IOP of (14.62 +/- 3.53) mm Hg (P < 0.001). After operation, there was an obvious diffuse bleb in each eye, in the 3 months after operation, there were functional blebs in 21 eyes, and the successful filtration was ceased in 4 eyes. The anterior chamber reaction was mild. Hyphema occurred in 1 eye after operation. Intra-operatively, in 4 eyes microperforations occurred in the trabecular meshwork without iris prolapse, and after operation, under the gonioscope, the perforation could be observed in these eyes. In another 2 eyes, there was no intra-operative perforation, but a small fissure was seen by gonioscopy. CONCLUSIONS: NPTS with application of MMC can lower the IOP effectively in this group of patients. The recovery of vision after operation is quick. A few complications occurred after operation. It is a promising technique to treat POAG.

Adolescent↗

PubMedDate not supplied

Traceless solid-phase synthesis of nitrogen-containing heterocycles and their biological evaluations as inhibitors of neuronal sodium channels.

The preparation of pyrimidine-2-thione, pyrimidine-2-one, pyrimidine, and benzo[b][1,4]diazepine derivatives using traceless solid-phase sulfone linker strategy is described. Key steps involved are (i) sulfinate S-alkylation, (ii) sulfone anion alkylation with an epoxide, (iii) gamma-hydroxyl sulfone --> gamma-ketosulfone oxidation, and (iv) traceless product release by a one-pot elimination-cyclization process. Elimination-cyclization was carried out under basic conditions with thiourea, methyl thiourea, methyl urea, guanidine hydrochloride, benzamidine hydrochloride and ortho-phenylene diamine. Twenty-three compounds were prepared, and 14 of them were evaluated by the Batrachotoxin (BTX) radioligand binding assay for their binding affinity to neuronal sodium channels. Compound 7c was found to be a potential neuronal sodium channels blocker.

Animals↗