Zhao Nanming

Studies on nerve cell affinity of chitosan-derived materials.

Reparation of the central nervous system (CNS) is important because when it is impaired its recovery is difficult and concomitant malfunction of other parts of body occurs. In our previous studies, chitosan was found to be a good material supporting nerve repair. The purpose of this article was to study the ability of chitosan and some chitosan-derived materials to facilitate the growth of nerve cells. Those materials were chitosan, glutaraldehyde-crosslinked chitosan, glutaraldehyde-crosslinked chitosan-gelatin conjugate, a chitosan-gelatin mixture, chitosan coated with polylysine (CAP), and a chitosan-polylysine mixture (CPL). Gelatin and polylysine were used as controls. After nerve cells (gliosarcoma cells and normal cerebral cells) were grown on those materials, their attachment, spread, and growth were observed. The adsorption of some extracellular matrix molecules such as laminin and fibronectin on the materials and the role the molecules play in nerve cell attachment and spreading were also studied by enzyme-linked immunosorbent assay and MTT method. We found that both CAP and CPL have excellent nerve cell affinity, defined as the ability to promote nerve cell to grow and function normally. Those two materials may be promising for the repair of the nervous system. Materials precoated with laminin, fibronectin, and serum were analyzed for their nerve cell affinity. Results suggest that after being precoated with laminin and fibronectin solution or serum, all material have better nerve cell affinity.

Effects of the Degree of Deacetylation on the Physicochemical Properties and Schwann Cell Affinity of Chitosan Films

Chitosan is a potential material for the preparation of nerve repair conduits. In order to find a better chitosan for the application in peripheral nerve regeneration, the effects of the degree of deacetylation (DD) on the physicochemical properties and Schwann cell affinity of chitosan films have been evaluated. Six kinds of chitosan samples with similar molecular weight, but various DD in a range from 70.1 to 95.6% were prepared from one stock chitosan material and fabricated into films. X-ray diffraction analysis showed that there were more crystalline regions in the higher DD chitosan films. Swelling and mechanical property measurements revealed that the swelling index of chitosan films decreased and their elastic modulus and tensile strength increased with the increase in DD. The adsorption amount of fibronectin and laminin on chitosan films was measured by means of enzyme-linked immunosorbent assay (ELISA). Culture of adult rat Schwann cells on the films showed that the chitosan films with higher DD provided better substrata for Schwann cell spreading and proliferation. In conclusion, DD of chitosan plays an important role in their physicochemical properties and affinity with Schwann cells. The results suggest that chitosan with a DD higher than 90% is considered as a promising material for application in peripheral nerve regeneration.

Surface Modification and Characterization of Chitosan Film Blended with Poly-L-Lysine

Biodegradable nerve guidance conduits (NGCs) represent a promising alternative to current clinical nerve repair procedures. Chitosan, a natural polysaccharide that has excellent biocompatibility and biodegradability, can be used as a nerve conduit material. The purpose of this work was to study the nerve cell affinity of chitosan modified by blending with different content of poly-L-lysine. PC12 cells culture was used to evaluate the nerve cell affinity of the chitosan-poly-L-lysine composite materials. The results showed that composite materials had significantly improved nerve cell affinity compared to chitosan as indicated by increased attachment, differentiation, and growth of nerve cells. The improved nerve cell affinity might be due to both the increased surface charge and hydrophilicity of composite materials. Composite material with 3 wt% poly-L-lysine content (PL-3) is an even better material in nerve cell affinity than collagen, suggesting that poly-L-lysine-blended chitosan is a promising candidate material for nerve regeneration.

Regulatory role of DREB transcription factors in plant drought, salt and cold tolerance

Abstractrd29A gene ofArabidopsis encodes a LEA-like hydrophilic protein, its expression is induced by drought, high-salt and cold stress. In the promoter region ofrd29A gene, there are 2 DREcis-acting elements involved in responses to these environmental stresses. 5 cDNAs (DREB1A∼C andDREB2A∼B) encoding DREB transcription factors, which specifically bind to DRE element and control the expression of reporter gene under drought, high-salt and stress, have been isolated by One-Hybrid screening method and with DRE element ofrd29A promoter. DREB transcription factors and DRE element function in signal transduction of drought, high-salt and cold stress. One DREB transcription factor can control the expression of several target functional genes involved in plant tolerance to drought, high-salt and cold stress. Thus, it may be an effective strategy to achieve ideal, multiple and fundamental effect for improving plant stress-resistance by DREB gene transfer.

Study on Mössbauer spectra of hemoglobin in thalassemia

The57Fe Mössbauer spectra of erythrocytes in normal subjects and nine patients of different thalassemias were studied. Together with clinical analysis, the correlation between the components in the spectra and different types of anemias was discussed.

Effects of acid and alkali on the light absorption, energy transfer and protein secondary structures of core antenna subunits CP43 and CP47 of photosystem II

The effects of acid and alkali treatment on the light absorption, energy transfer and protein secondary structure of the photosystem II core antenna CP43 and CP47 of spinach were investigated by the absorption spectra, fluorescence emission spectra and ciruclar dichroism spectra. It has been found that acid treatment caused the appearance of absorption characteristic of pheophytin a (Pheo a), whereas alkali treatment induced a new absorption peak at 642 nm. The energy transfer between β‐carotene and chlorophyll a (Chl a) in CP43 was easily disturbed by alkali, whereas in CP47 was readily affected by acid. As to the effects on the secondary structure of proetins in CP43 and CP47, effects of acid were far less than those of alkali. Both acid and alkali disturbed the microenvironment of Chl a and interfered exciton interaction between Chl a molecules. It was suggested that acid and alkali affect the light absorption, energy transfer and protein secondary structure of CP43 and CP47 in a differenty way. H+ can permeate into the internal space of α‐helix, change Chl a into Pheo a and disturb the microenvironment of pgiments without damaging the secondary structure of protein, whereas OH− can induce the protein unfolding at first, then saponify Chl a to chlorophyllide and disturb the microenvironment of pigments.

Transformation of maize embryogenic calli mediated by ultrasonication and regeneration of fertile transgenic plants.

An insecticidal protein gene isolated fromBacillus thuringiensis was transferred into maize by using ultrasonication. The fertile transgenic plants and their progeny were obtained. The Southern hybridization results indicated that the foreign gene had integrated into the maize genome. It has been found that the acoustic intensity and the duration of treatment are the important parameters influencing transformation efficiency by ultrasonication. The maximum relative transformation frequency of 34.1 % was achieved after 30 min of sonication at 0. 5 W/cm2 acoustic intensity. With appropriate parameters the ultrasonication can make a number of micropores formed on the cell surface and minimize the treatment damage to the foreign DNA molecules, thus facilitating the DNA molecules to enter the cells.

Effects of low frequency electromagnetic fields on osteoblasts proliferation and cell cycle

After primary mouse osteoblasts and ROS osteo-like cells were exposed to 50 Hz low frequency electromagnetic fields (EMF), the MTT method and flow cytometry have been used to determine cell proliferation, cell cycle and apoptosis. The results show that, compared with the control, the cells after exposure are more abundant, have larger S phase ratios and lower apoptosis ratios. The results indicate that EMF has an important biological effect which influences cell proliferation and cell cycle.

Preparation of the selenomethionine derivative of tabtoxin resistance protein

In order to obtain phase information for the X-ray diffraction of tabtoxin resistance protein (TTR) crystal using the MAD phasing method, a selenomethionine (Se-Met) derivative of TTR was overexpressed inE. coli strain M15, with pQE-30 plasmid, through IPTG induction in M9 medium containing Se-Met. The product was purified to an estimated homogeneity of greater than 95% according to SDS-PAGE, by a Ni-NTA metal affinity followed by a Mono Q anion exchange column chromatography. The successful substitution of Se-Met for methionine (Met) was confirmed by MALDI-TOF and ESI-Quadrupole Mass Spectrometry analysis. The derivative crystal was obtained using similar conditions as those for the native.