Biomedical subjects

Hai-Bo Zhang

Publications and source records attributed to Hai-Bo Zhang.

8 recordsLinked to original sources

PubMed2005

Capacity of human beta-defensin expression in gene-transduced and cytokine-induced cells.

The purpose of this study was to determine the capacity of cells transduced with human beta-defensins (HBDs) to express antimicrobial peptides, since sufficient expression level is required for effective antimicrobial activity. Retroviral vector pBabeNeo and lentiviral vector SIN18cPPTRhMLV (SIN18) carrying HBDs were utilized to transduce non-HBD-expressing cells such as fibroblasts or HBD-producing oral epithelial cells. We found that HBD-3 gene transfer to fibroblasts was possible not via retrovirus but by direct vector transfection. SIN18 had high transduction efficiencies (80.9-99.9%) and transduced cells expressed higher amounts of HBD-2 than those by pBabeNeo. Primary human gingival epithelial cells (HGECs) expressed greater amounts of HBD-2 than primary fibroblasts after lentiviral transduction. Additionally, HBD-2 secretion from transduced HGECs cells was further increased when stimulated with IL-1 or TNFalpha. Our data indicate that while HBD-2 expression is limited in primary fibroblasts, its expression in HGECs may be maximized by gene transduction plus cytokine induction.

Animals↗

PubMed2005

The top-bottom effect of a tilted thick specimen and its influence on electron tomography.

We present the top-bottom effect (TBE) of a 5 microm thick amorphous specimen in a 3 MV ultrahigh voltage electron microscope (ultra-HVEM) and its influence on the quality of electron tomography (ET). The 40-nm gold particles on the top surface of the specimen tilted at different angles have been observed to be of poorer image quality than those on the symmetrical bottom surface obtained by tilting and turning over the specimen. The point spread function of the gold-particle images was calculated using the increment Wiener filter and the image-quality variation was then evaluated. The TBE is shown to become more remarkable with the increase of the effective thickness of the tilted specimen or the decrease of the magnification of the ultra-HVEM. The ET simulation indicates that the TBE may generate approximately 4% distortion in the radial direction of a reconstructed sphere model.

Journal Article↗

PubMed2005

Photosynthetic acclimation in rice leaves to free-air CO2 enrichment related to both ribulose-1,5-bisphosphate carboxylation limitation and ribulose-1,5-bisphosphate regeneration limitation.

Net photosynthetic rates (Pns) in leaves were compared between rice plants grown in ambient air control and free-air CO2 enrichment (FACE, about 200 micromol mol(-1) above ambient) treatment rings. When measured at the same CO2 concentration, the Pn of FACE leaves decreased significantly, indicating that photosynthetic acclimation to high CO2 occurs. Although stomatal conductance (Gs) in FACE leaves was markedly decreased, intercellular CO2 concentrations (Ci) were almost the same in FACE and ambient leaves, indicating that the photosynthetic acclimation is not caused by the decreased Gs. Furthermore, carboxylation efficiency and maximal Pn, both light and CO2-saturated Pn, were decreased in FACE leaves, as shown by the Pn-Ci curves. In addition, the soluble protein, Rubisco (ribulose-1,5-bisphosphate caboxylase/oxygenase), and its activase contents as well as the sucrose-phosphate synthase activity decreased significantly, while some soluble sugar, inorganic phosphate, chlorophyll and light-harvesting complex II (LHC II) contents increased in FACE leaves. It appears that the photosynthetic acclimation in rice leaves is related to both ribulose-1,5-bisphosphate (RuBP) carboxylation limitation and RuBP regeneration limitation.

Acclimatization↗

PubMed2005

[Detection of gene expression alteration of myeloma cells treated with arsenic trioxide].

OBJECTIVE: To investigate the effect of arsenic trioxide on multiple myeloma (MM) cell gene expression and explore the molecular mechanism of arsenic trioxide therapy for MM. METHODS: U266 cells were divided into two groups, group A as control group and group B as test group. Cells were cultured for 48 hours, and total RNA and mRNA were extracted. Suppression subtractive hybridization (SSHs) was performed to distinguish the differentially expressed genes. The products were cloned into pGEM-T Easy Vector, and transfected into the competent host JM109 to construct two subtractive libraries. Positive colonies were selected by blue-white screening, and the plasmids were extracted. Homologous comparison was conducted in GenBank. RESULTS: Five downregulated clones were isolated in the first SSH: (1) Aminopeptidase N, (2) Homosapiens tumor translationally-controlled protein 1, (3) Human ATP synthetase A chain, (4) Signal recognition particle A10, (5) Mitochondrial ATP synthetase/ATPase subunit 6. Four upregulated clones were isolated in the second SSH: (1) Calcium-binding protein A10, (2) Keratin 6A, (3) 45 kD MIP repetitive element containing splicing factor and (4) poly(A)-binding protein. CONCLUSIONS: Arsenic trioxide exerts proliferation inhibition and apoptosis induction on MM cells by regulating genes expression.

Antineoplastic Agents↗

PubMed2004

Influence of the image quality deterioration of a tilted thick specimen on electron tomography.

In electron tomography (ET) based on a transmission electron microscope, the effective thickness of a specimen increases with the tilt angle and, therefore, the projection quality may deteriorate because of electron scattering. The information-missing region, however, can be reduced by broadening the specimen tilt range. To clarify the general influence of these effects on ET, the projection quality varying with the tilt angle was quantitatively evaluated for a 5-microm thick specimen observed with a 3 MV ultrahigh-voltage electron microscope. Simulations of three-dimensional reconstruction were then performed for different specimen thicknesses and tilt ranges. As a result, the ET accuracy was shown to decrease as the specimen thickness increased. However, an optimum specimen-tilt range, at which ET could reach its highest accuracy, was found to exist and become small with the increase of the specimen thickness. The presented results are helpful for determining the specimen thickness limitation on the ET resolution and improving the ET fidelity of thick specimens.

Computer Simulation↗

PubMed2004

Utilizing the charging effect in scanning electron microscopy.

The charging effect of an insulating specimen from electron beam (e-beam) irradiation may be utilized to facilitate imaging in the scanning electron microscope (SEM). This has been confirmed by a great deal of experimental work during the last three decades. Particularly, recent investigations indicate that even located underneath insulating thin films that a low energy e-beam cannot penetrate, conductors not biased and overlay marks, are observable through a novel imaging pattern, charging contrast. Unlike conventional SEM contrasts, which usually reflect surface characteristics, the dynamic charging contrast can reveal information of underlying structures without any external exciting signal. The authors consider that this kind of charging contrast arises from the different redistribution rates of secondary electrons returning to the surface under the surface local field of the charged specimen. The charging contrast has the prospect of extending the SEM application and forming new testing methods matched with the fast development of integrated circuits.

Animals↗

PubMed2003

Quantitative analysis of static capacitance contrast in scanning electron microscopy.

A one-dimensional model is proposed for analysing static capacitance contrast (SCC) in scanning electron microscopy. For the large-scale integrated specimen covered by an insulating thin film, the imaging signal is calculated considering the redistribution of secondary electrons (SEs) and the charging process of the equivalent effective capacitance between the irradiation point and substrate. The calculated SCC as a function of the irradiation charge density is in good agreement with the experimental SCC. It is confirmed that the SCC arises from the redistribution of SEs and the difference in the effective capacitance of irradiation points under the condition of positive charging.

Journal Article↗

PubMed2002

A model for antimicrobial gene therapy: demonstration of human beta-defensin 2 antimicrobial activities in vivo.

We transfected host cells with an antimicrobial peptide/protein-encoding gene as a way to enhance host defense mechanisms against infection. The human beta-defensin 2 (HBD-2) gene was chosen as a model because its protein does not require cell type-specific processing. Using a retroviral vector carrying HBD-2 cDNA, we treated several mouse or human cell lines and primary cell cultures including fibroblasts, salivary gland cells, endothelial cells, and T cells. All transduced cells produced detectable HBD-2. In Escherichia coli gel overlay experiments, secreted HBD-2 from selected cell lines showed potent antimicrobial activity electrophoretically identical to that of purified HBD-2. We then used a mouse model (nonobese diabetic/severely compromised immunodeficient [NOD/SCID]) to test HBD-2 antimicrobial activities in vivo. HT-1080 cells carrying HBD-2 or control vector were implanted subcutaneously into NOD/SCID mice to allow tumor formation. Escherichia coli was then injected into each tumor mass. Tumors were resected after 16 hr and homogenized for bacterial colony-forming unit analysis. Compared with control tumors, HBD-2-bearing tumors contained only 7.8 +/- 3.3% viable bacteria. On the basis of this demonstration of HBD-2 in vivo antimicrobial activity, enhancement of antibacterial host defense by HBD-2 gene therapy may be feasible.

Animals↗