Biomedical subjects

H Ma

Publications and source records attributed to H Ma.

312 records · Page 18Linked to original sources

PubMedDate not supplied

High efficient encapsulation of plasmid DNA in PLGA microparticles by organic phase self-emulsification.

To overcome the drawbacks of encapsulating plasmid DNA (pDNA) in poly (D,L-lactic-co-glycolic acid) (PLGA) by water-in-oil-in-water double-emulsion solvent-evaporation method, we have developed a novel procedure for encapsulating pDNA in PLGA microparticles called DNA organic phase self-emulsification (DOPSM). This method was based on both the extraction plasmid DNA from aqueous phase into organic phase and the spontaneous emulsification DNA in organic phase by solvent diffusion method. The efficiency of extraction plasmid DNA into organic phase is 99% and the concentration of pDNA in organic phase is up to 2.4 mg/ml. The efficiency of microencapsulation of plasmid DNA in PLGA is up to 76% and can be enhanced by lowering the pH of aqueous solution of emulsion. The microparticles size of PLGA of pDNA is in a narrow range of 1-2 microm. This procedure does not involve the high mechanical energy to emulsify which may damage the integrity of pDNA. This method can be applied to encapsulate the pDNA into microparticles of other biocompatible polymers with high efficiency.

Coated Materials, Biocompatible↗

PubMedDate not supplied

Male fertility: a case of enzyme identity.

The plant hormone jasmonate has been implicated in male fertility in Arabidopsis. Recent studies have identified the enzyme required for a critical step of jasmonate synthesis in anthers and shown that this enzyme really is required for male fertility.

Arabidopsis↗

PubMedDate not supplied

Expression of calpain small subunit 2 in mammalian tissues.

PURPOSE: The purpose of the current experiments was to more closely define the distribution and the function of calpain small subunit 2 (css2). Css2 is a newly discovered regulatory protein for the calcium activated proteases, mu- and m-calpains. METHODS: Tissues from rat, monkey, and man of various ages were used to determine expression patterns of css2 by relative quantitative RT-PCR using 18S rRNA as an endogenous standard. Recombinant css2 and the 80 kDa catalytic subunit of m-calpain (80 kDa/css2) were co-expressed in Escherichia coli. Casein zymography was used to measure the enzymatic activity of 80 kDa/css2 proteins. Lens alpha-crystallin and beta B1-crystallin were used as substrates to determine proteolysis by 80 kDa/css2. Computer-based homology modeling was used to predict interactions between the traditional small subunit (css1) or css2 with the 80 kDa catalytic subunit. RESULTS: Css2 appears to be a functional equivalent of css1 in vitro in that the calcium-dependent proteolytic activity of 80 kDa/css2 was similar to recombinant m-calpain (80 kDa/css1). In rat and human lens, css2 transcripts increased with age, whereas css1 transcripts decreased with age. Human beta B1-crystallin and rat alpha A-crystallin were cleaved similarly by 80 kDa/css2 and 80 kDa/css1. Interestingly, alpha A-insert crystallin was not hydrolyzed when css2 was substituted for css1 in the calpain dimer, suggesting that css2 may perform different functions from css1 in terms of proteolysis of lens crystallins during maturational growth of the lens. Css2 may also assist in the proper folding of the 80 kDa subunit and regulate protease activity in the absence of calcium. CONCLUSIONS: The wide distribution of css2 transcripts in rat and monkey suggested that css2 is a second, widely distributed (rather than tissue-specific) calpain small subunit, in addition to the long-recognized css1. Further studies at the protein level will indicate if css2 has unique functions apart from css1.

Adolescent↗

PubMedDate not supplied

Development of a high-performance multiprobe cryosurgical device.

The authors describe the design of the first multiprobe cryosurgical system (AccuProbe system). Compared with prior conventional cryosurgical devices, the new system has the following characteristics: 1) generation of subcooled liquid nitrogen, 2) optional use of up to five independently operated and controlled cryoprobes, 3) use of disposable probes of various sizes and shapes, 4) more accurate placement of the cryoprobes in the lesions due to probe miniaturization (3.4 mm in overall diameter), and 5) higher capacity freezing, which supports more accurate and controllable tissue temperatures. With the use of the newly developed system, numerous cryosurgical procedures, including those in the prostate, brain, and liver, have been successfully performed.

Animals↗

PubMedDate not supplied

Digital subtraction angiography in the diagnosis of congenital heart diseases: analysis of 60 cases.

Ninety-one IVDSA and/or IADSA examinations with 192 injections were performed in 60 patients with congenital heart disease (CHD), including 31 anatomic anomalies. Axial projection was used in 23 patients. Analysis of the results of this series showed that accurate diagnosis by DSA confirmed by cardiac surgery together with definite diagnosis by DSA were obtained in 54 cases (90%). Two cases of nondiagnosis by DSA resulted from a suboptimal DSA method; four cases of partially accurate or mistaken diagnosis determined by cardiac surgery occurred because the axial view was not used and/or the anomalies were too small to be visualized by DSA. To increase the diagnostic accuracy of DSA in CHD, an optimal method of DSA must be selected according to the position of the anomaly and the hemodynamic data, and the axial view should be used to visualize the anomaly clearly in complex cases. In addition, DSA may fail to define a mild anomaly because of its lower spatial resolution.

Adolescent↗

PubMedDate not supplied

High CD44 expression on human mesotheliomas mediates association with hyaluronan.

PURPOSE: Malignant pleural mesothelioma is a rare malignancy with major environmental implications regarding passive asbestos exposure. We have conducted an immunohistochemical and functional study to address three questions: (1) What is the representation of CD44 on tumor cells as detected by immunohistochemistry? (2) Do cultured cell lines derived from malignant pleural mesothelioma tissue express the same CD44 phenotypes as the original tumors, and can they serve as a model for the study of CD44 in mesotheliomas? (3) What is the functional status of the CD44 expressed on mesotheliomas, with regard to hyaluronan anchorage? MATERIALS AND METHODS: Thirty-seven samples of pleural mesothelioma were obtained from patients entered on phase I/II protocols conducted in the Surgery Branch of the National Cancer Institute since 1991. The diagnosis was confirmed in all 37 patients by means of a battery of immunohistochemical tests for markers differentiating malignant pleural mesothelioma from adenocarcinoma. Tumor-positive lymph nodes and distant metastases were also examined in six of the patients. Cell lines, established from tumor tissue of six of the patients described above, were used in these experiments. Four (H2596, H2461, H2373, H2452) were derived from primary solid tumors and two (HP-1 and HP-3) were derived from effusions. RESULTS: Immunohistochemical staining with a monoclonal antibody (H4C4) that recognizes a constant region of human CD44 demonstrated that 34 (92%) of the malignant pleural mesotheliomas examined expressed CD44 on 50% to 100% of their cells. The extent of CD44 expression was apparently related to histologic subtype with the highest expression seen in epithelioid mesotheliomas and the least in sarcomatoid tumors. Tumor cell lines established from the primary tumors or effusions of six of the malignant pleural mesothelioma patients showed high expression of the hematopoietic form of CD44. Four of these cell lines exhibited strong attachment to hyaluronan in an in vitro attachment assay, indicating that their CD44 was functional with respect to hyaluronan anchorage. Hyaluronan attachment was specific in that it could be abolished by preincubation with epitope-specific anti-CD44 antibodies or soluble substrate or by hyaluronidase treatment of attachment surfaces. CONCLUSIONS: We conclude that CD44 is highly expressed on human mesotheliomas, that cell lines adequately represent tumor expression, and that CD44 mediates association with hyaluronan, a major component of pleural fluid.

Antibodies, Monoclonal↗