姜试管苗移栽过程中的蒸腾及光合性能变化

用TPS-1型光合测定仪测定了移栽驯化过程中姜试管苗的光合速率、蒸腾速率等生理指标变化,结果表明：姜试管苗在移栽过程中叶片表观量子产额、羧化效率、净光合速率逐渐增加,而蒸腾速率和气孔导度则呈下降趋势,这有利于试管苗适应外界环境和自养。     

Phenotypic Characterization of a Female Sterile Mutant in Rice

A female sterile mutant, derived from a spontaneous mutation, was first discovered In rlce （Oryzs satlvs L. sep. Indlca） restorer llne 202R. Wlth normal fiowerlng, the mutant exhlblts an extremely low seed-sattlng rate. When the mutant Is crossed as a pollen donor, the seeds set normally; whereas when It Is used as a pollen recelver, no seeds are obtalned even wlth mlxed pollen gralns of dlfferent varletles sprlnkled over the atlgmas. The fioret of the mutant, conslatlng of slx stamens and one platll, looks the same as that of the wlld type In the malefemale organs, except that less than 10% of the mutant florets have three atlgmas on the ovary. Although the mutant has a low seed-setting rate, Its pollen fertility Is approximately 87.1%, which Is equal to that of the wild type. In addition, more than 90% of the mature embryo sacs of the mutant have complete Inner structures. At every stage after pollination, the sperm, embryo, and endosperm are not found In the mutant embryo sac, whereas the disintegration of the egg cell that does not accomplish fertilization Is visible. Through observetlons with a fluorescence microscope, we have found that the pollen grains germinate normally, whereas the pollen tube abnormally elongates in the style-transmitting tissue. The mutant pollen tubes display various defects In the style, such as slower elongation, conversed elongation, distorted elongation, swollen tips, or branched tips. As a result, the growth of the pollen tubes ceases In the style, and, therefore, the pollen tubes cannot reach the embryo sac and the process of double fertilization Is blocked. Based on these observations, we conclude that this mutant, designated as fs-202R, Is a novel type of female sterile mutation In rice, which causes the arrest of the elongation of the pollen tube.     

洗胃研究进展

概述洗胃的方法、影响洗胃效果的相关因素及采取的相应措施。应根据患者的具体情况,正确选择洗胃时间及时机、采用合适的体位、洗胃液、胃管、置管途径、适当延长胃管插入长度,以提高洗胃效果,减少并发症的发生。     

‘弥河银瓜’高效植株再生体系的建立

建立了以薄皮甜瓜品种‘弥河银瓜’子叶为外植体的高效再生体系。取生长5d的甜瓜子叶为外植体,置于MS+2.0mg·L-16-BA+0.5mg·L-1IBA+3.5%蔗糖+0.7%琼脂(pH5.8)的诱导培养基上培养,可获得100%芽分化频率。在不定芽伸长过程中,生长调节剂最佳浓度为0.5mg·L-16-BA+0.1mg·L-1IAA。潮霉素是较合适的筛选抗生素。     

Folate concentrations and folic acid supplementation among women in their first trimester of pregnancy in a rural area with a high prevalence of neural tube defects in Shanxi, China

BACKGROUND: Although an information campaign concerning periconceptional folic acid supplementation was launched in 1998 in Shanxi Province, China, the prevalence of neural tube defects in rural areas was reported as high as 140 per 10,000 births in 2002. The blood folate concentrations and the practice of folic acid supplementation among pregnant women in rural areas of the province are described. METHODS: A total of 483 pregnant women (mean gestation, 8.1 weeks) in a rural area of Shanxi were interviewed. Nonfasting blood samples and information on folic acid supplementation were collected. Folate concentrations in plasma and erythrocytes were determined by a microbiological assay. RESULTS: The mean concentrations of plasma and erythrocyte folate for pregnant women was 10.4 nmol/liter and 375.8 nmol/liter, respectively. Deficiencies of plasma and erythrocyte folate were observed in 20.9% and 47.6% of women, respectively. Seasonal variations were noted in the prevalence of folate deficiency, with significantly lower plasma folate concentrations in spring and summer and lower erythrocyte folate concentrations in seasons other than summer. Among pregnant women, <10% reported having taken or currently taking folic acid, and virtually no women (0.6%) took folic acid as recommended. CONCLUSIONS: Women in rural areas had low plasma and erythrocyte folate levels, and folate deficiency was highly prevalent in the area. Few women followed the recommendations regarding folic acid supplementation, and the information campaign in Shanxi was unsuccessful. These findings suggest the urgent need for combined strategies in rural areas to fortify grain with folic acid and promote folic acid supplements for childbearing-age women.     

A role for LORELEI,a putative glycosylphosphatidylinositol‐anchored protein,in Arabidopsis thaliana double fertilization and early seed development

In plants, double fertilization requires successful sperm cell delivery into the female gametophyte followed by migration, recognition and fusion of the two sperm cells with two female gametes. We isolated a null allele (lre‐5) of LORELEI, which encodes a putative glycosylphosphatidylinositol (GPI)‐anchored protein implicated in reception of the pollen tube by the female gametophyte. Although most lre‐5 female gametophytes do not allow pollen tube reception, in those that do, early seed development is delayed. A fraction of lre‐5/lre‐5 seeds underwent abortion due to defect(s) in the female gametophyte. The aborted seeds contained endosperm but no zygote/embryo, reminiscent of autonomous endosperm development in the pollen tube reception mutants scylla and sirene. However, unpollinated lre‐5/lre‐5 ovules did not initiate autonomous endosperm development and endosperm development in aborted seeds began after central cell fertilization. Thus, the egg cell probably remained unfertilized in aborted lre‐5/lre‐5 seeds. The lre‐5/lre‐5 ovules that remain undeveloped due to defective pollen tube reception did not induce synergid degeneration and repulsion of supernumerary pollen tubes. In ovules, LORELEI is expressed during pollen tube reception, double fertilization and early seed development. Null mutants of LORELEI‐like‐GPI‐anchored protein 1 (LLG1), the closest relative of LORELEI among three Arabidopsis LLG genes, are fully fertile and did not enhance reproductive defects in lre‐5/lre‐5 pistils, suggesting that LLG1 function is not redundant with that of LORELEI in the female gametophyte. Our results show that, besides pollen tube reception, LORELEI also functions during double fertilization and early seed development.     

Regional neural tube closure defined by the Grainy head-like transcription factors

Primary neurulation in mammals has been defined by distinct anatomical closure sites, at the hindbrain/cervical spine (closure 1), forebrain/midbrain boundary (closure 2), and rostral end of the forebrain (closure 3). Zones of neurulation have also been characterized by morphologic differences in neural fold elevation, with non-neural ectoderm-induced formation of paired dorso-lateral hinge points (DLHP) essential for neural tube closure in the cranial and lower spinal cord regions, and notochord-induced bending at the median hinge point (MHP) sufficient for closure in the upper spinal region. Here we identify a unifying molecular basis for these observations based on the function of the non-neural ectoderm-specific Grainy head-like genes in mice. Using a gene-targeting approach we show that deletion of Grhl2 results in failed closure 3, with mutants exhibiting a split-face malformation and exencephaly, associated with failure of neuro-epithelial folding at the DLHP. Loss of Grhl3 alone defines a distinct lower spinal closure defect, also with defective DLHP formation. The two genes contribute equally to closure 2, where only Grhl gene dosage is limiting. Combined deletion of Grhl2 and Grhl3 induces severe rostral and caudal neural tube defects, but DLHP-independent closure 1 proceeds normally in the upper spinal region. These findings provide a molecular basis for non-neural ectoderm mediated formation of the DLHP that is critical for complete neuraxis closure.     

Dynamic imaging of mammalian neural tube closure

Neurulation, the process of neural tube formation, is a complex morphogenetic event. In the mammalian embryo, an understanding of the dynamic nature of neurulation has been hampered due to its in utero development. Here we use laser point scanning confocal microscopy of a membrane expressed fluorescent protein to visualize the dynamic cell behaviors comprising neural tube closure in the cultured mouse embryo. In particular, we have focused on the final step wherein the neural folds approach one another and seal to form the closed neural tube. Our unexpected findings reveal a mechanism of closure in the midbrain different from the zipper-like process thought to occur more generally. Individual non-neural ectoderm cells on opposing sides of the neural folds undergo a dramatic change in shape to protrude from the epithelial layer and then form intermediate closure points to “button-up” the folds. Cells from the juxtaposed neural folds extend long and short flexible extensions and form bridges across the physical gap of the closing folds. Thus, the combination of live embryo culture with dynamic imaging provides intriguing insight into the cell biological processes that mold embryonic tissues in mammals.