In vitro growth, differentiation and biological characteristics of neural stem cells

OBJECTIVE： To summarize the biological characteristics of neural stem cells, and the separation, purification. differentiation and source of neural stem cells. DATA SOURCES ： An online search of Pubmed database was undertaken to identify English articles about the growth of neural stem cells in vitro published from January 2000 to October 2006 by using the keywords of ＂neural stem cells, bone marrow mesenchymal stem cells （BMSCs）, umbilical cord blood stem cells, embryonic stem cells （ESC）, separation methods, neural growth factor＂. And relevant articles published in IEEE/IEE Electronic Library （IEL） database, Springer Link database and Kluwer Online Journals were also searched, Chinese relevant articles published between January 2000 to October 2006 were searched with the same keywords in Chinese in Chinese journal full-text database. STUDY SELECTION ： The articles were primarily screened, and then the full-texts were searched. Inclusive criteria： （1） Articles relevant to the biological characteristics and classification of neural stem cells; （2） Articles about the source, separation and differentiation of the ESCs, BMSCs and umbilical cord blood stem cells. The repetitive studies and reviews were excluded. DATA EXTRACTION ： Thirty articles were selected from 203 relevant articles according to the inclusive criteria Articles were excluded because of repetition and reviews. DATA SYNTHESES ： Neural stem cells have the ability of self-renewing and high differentiation, and they are obtained from ESCs, nerve tissue, nerve system, BMSCs and umbilical cord blood stem cells. ESCs can be separated by means of mechanical dissociation is better than that of the trypsin digestion, BMSCs by density gradient centrifuge separation, hemolysis, whole-blood culture, etc., and umbilical cord blood stem ceils by Ficoil density gradient centrifugation, hydroxyethyl starch （HES） centrifugation sedimentation, etc. Neural growth factor （NGF） and other factors play an important role in the growth of NSCs, such as transforming growth factor （TGF） is an important player in repairing organs, NGF accelerates the process of growth, insulin-like growth factor serves importantly in the differentiation of stem cells into neuron-like cells. CONCLUSION ： As unipotent stem cells, NSCs have the abilities of self-renewal and potential of high differentiation. The method of mechanical dissociation is better than trypsin digestion in e separating ESCs. However, density gradient centrifuge separation is better than other methods in the separation of the BMSCs. NGF and other factors play an important role in the growth of NSCs.

Effect of Different Nitrogen Application Rate on Rice Stem Characteristics

The effects of different nitrogen application rate on the physical characteristics and anatomic structure of rice stems were investigated with rice cultivars Guangliangyou 1128 （with high resistance） and Zhunliangyou 527 （with low resistance） as materials. The results showed that, firstly, plant height, gravity center height and basal internode length of the 2 rice cultivars increased with the increase of nitrogen application rate, while wall thickness and internode filling degree decreased. The breaking-resistance strength per stem and thrust-resistance strength of plants declined with the increase of nitrogen application rate. Secondly, as nitrogen input increased, the number of vascular bundles and the area of vascular bundles increased between the 2 rice cultivars. Thirdly, with the increase of nitrogen application rate, the stem section area of Guangliangyou 1128, which had strong lodging resistance, gradually increased, while that of Zhunliangyou 527 increased firstly and then decreased. The maximum application amount of nitrogen was 240 kg/hm 2. Nitrogen fertilizer mainly affected the relative gravity center height, stem wall thickness and internode filling degree of the 2 cultivars, thereby reducing the basal stem breaking resistance and plant thrust-resistance strength.

Comparison of stem cell characteristics between perichondral-derived stem cells and periosteal stem cells in postnatal rats

Bone marrow mesenchymal stem cells(BMSCs),periosteal stem cells(PSCs),and other bone stem cells originate from embryonic bone formation,but their function and stem cell characteristics such as proliferation ability and differentiation ability change at different anatomical locations.Perichondral-derived stem cells(PCSCs)are more closely related to PSCs in origin and function,usually used to be studied together with PSCs as one type of stem cell.However,this leads to the ignoration of the PCSCs'characteristics.Since the anatomical locations of these two types of stem cells diverse,PCSCs should have some differences from PSCs.In this study,the PCSCs in the perichondrium surrounding the growth plate cartilage expressed CTSK and CD200 same as PSCs.However,when compared the stem cell characteristics of PCSCs with that of PSCs,PCSCs were more elongated than PSCs in morphology and have stronger self-renewal ability,as well as stronger chondrogenic and adipogenic differentiation potentials.This study revealed the stem cell characteristics of PCSCs distinguished from PSCs,which may indicate PCSCs and PSCs should not be treated as one type of cell to research in the future.

Lignin metabolism regulates lodging resistance of maize hybrids under varying planting density

Hybrids and planting density are the main factors affecting maize lodging resistance.Here,we aimed to elucidate the mechanism of the regulation of maize lodging resistance by comparing two hybrids at various planting densities from the perspective of lignin metabolism.Our results showed that compared to lodging-susceptible hybrid Xundan 20(XD20),lodging-resistant hybrid Denghai 605(DH605)showed a lower center of gravity and culm morphological characteristics that contributed to the higher lodging resistance of this hybrid.Lignin content,activities of key lignin synthesis-related enzymes and G-,S-and H-type monomer contents were significantly higher in hybrid DH605 than in hybrid XD20.Stalk mechanical strength,lignin accumulation and enzyme activity decreased significantly with increasing planting density in the two hybrids.While G-type monomers first decreased with increasing planting density but then remained stable,S-type monomers showed a decreasing trend,and H-type monomers showed an increasing trend.Correlation analysis showed that lodging rate was significantly correlated with plant traits and lignin metabolism.Therefore,maize hybrids characterized by high lignin accumulation,high lignin synthesis-related activities,high S-type monomer content,low center of gravity,high stem puncture strength,high cortical thickness,and small vascular bundle area are more resistant to lodging.High planting densities reduce stalk lignin accumulation,relevant enzyme activities and mechanical strength,thereby,ultimately increasing the lodging rate significantly.