Electrospun water-soluble carboxyethyl chitosan/poly(vinyl alcohol) nanofibrous membrane as potential wound dressing for skin regeneration

Biocompatible carboxyethyl chitosan/poly(vinyl alcohol) (CECS/PVA) nanofibers were successfully prepared by electrospinning of aqueous CECS/PVA solution. The composite nanofibrous membranes were subjected to detailed analysis by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). SEM images showed that the morphology and diameter of the nanofibers were mainly affected by the weight ratio of CECS/PVA. XRD and DSC demonstrated that there was strong intermolecular hydrogen bonding between the molecules of CECS and PVA. The crystalline microstructure of the electrospun fibers was not well developed. The potential use of the CECS/PVA electrospun fiber mats as scaffolding materials for skin regeneration was evaluated in vitro using mouse fibroblasts (L929) as reference cell lines. Indirect cytotoxicity assessment of the fiber mats indicated that the CECS/PVA electrospun mat was nontoxic to the L929 cell. Cell culture results showed that fibrous mats were good in promoting the cell attachment and proliferation. This novel electrospun matrix would be used as potential wound dressing for skin regeneration.     

Genomic Sequence and Evolution of Marine Cyanophage P60: a New Insight on Lytic and Lysogenic Phages

The genome of cyanophage P60, a lytic virus which infects marine Synechococcus WH7803, was completely sequenced. The P60 genome contained 47,872 bp with 80 potential open reading frames that were mostly similar to the genes found in lytic phages like T7, phi-YeO3-12, and SIO1. The DNA replication system, consisting of primase-helicase and DNA polymerase, appeared to be more conserved in podoviruses than in siphoviruses and myoviruses, suggesting that DNA replication genes could be the critical elements for lytic phages. Strikingly high sequence similarities in the regions coding for nucleotide metabolism were found between cyanophage P60 and marine unicellular cyanobacteria.     

In vitro and in vivo transfection and expression of plasmid-based non-viral vector for erythropoietin gene therapy

A non-viral gene therapy vector, pcDNA3-EPO, was constructed by subcloning erythropoietin (EPO) cDNA into plasmid pcDNA3. After liposome-mediated transfection of the NIH 3T3 cells in vitro, EPO expression in the culture medium was detected by ELISA and amounted to 1.25 ± 0.3 IU ml^–1. The biological activity of this EPO in the medium was detected after intramuscular injection of BALB/c mice. PCR of genomic DNA and RT-PCR of total RNA also confirmed that the plasmid pcDNA3-EPO had been transfected into the cells. A pool of pcDNA3-EPO transfectants, which stably expressed EPO, was obtained by G418 selection. When pcDNA3-EPO was combined into liposomes and intramuscularly injected into BALB/c mice, the reticulocyte ratio in the positive mice was three times higher than that in the control mice. In vivo expression was maintained in mice for at least one month.     

利用重组Pichia pastoris生产腺苷甲硫氨酸

为改造甲醇利用型酵母Pichia pastoris来生产腺苷甲硫氨酸（SAM,S－adenosyl-L-methionine),我们将一个带有SAM合成酶基因的胞内表达质粒转化入Pichia pastoris菌株GS115,经过G418抗性筛选得到一株有两个基因拷贝的转化子。该菌在含有甲醇和甲硫氨酸的培养基中生长5d后,其细胞内的SAM的产量比原始菌株提高了30余倍。对该菌生产SAM的培养基中的碳源与氮源进行了优化,结果显示碳源的控制对该菌SAM产量的影响很大。在试管水平,该菌在含有0．75％的L-methionine并且碳源和有机氮源经过一定程度优化的培养基中,生长6d后SAM产量达到1．58g/L。     

中国大羽羊齿植物分叉蕨叶的首次发现--兼论亚洲与北美大羽羊齿植物之异同

东亚与北美大羽羊齿植物间的主要差异在于蕨叶的结构：北美大羽羊齿植物的蕨叶为单叶或二歧分叉叶,而东亚的大羽羊齿植物以往只知为羽状复叶或不分叉的单叶,因之,二歧分叉蕨叶在中国的发现具有十分重要的意义,它使东亚与北美大羽羊齿植物之间的关系变得更为密切,虽然其间仍存在不实质性的差异,同时,对东亚和北美华夏羊齿Cathaysiopteris之间的异同作了较详的讨论。     

非损伤微测技术在植物根系生长发育研究中的应用

进出组织和细胞的无机离子的运输对植物生命极为重要。膜片钳和荧光成像等传统方法技术要求高、设备要求先进且测得的数据很难直接用于样品植株上。"非损伤微测技术"因其具有非损伤性、高的时空分辨率的特点,使其可以在不破坏样品的前提下测到样品的生理特征和生命活动规律,测得的数据生理真实性高,可以直接应用于样品植株上。文章较详细地介绍了运用非损伤微测技术,尤其是用于测量离子流的SIET技术和MIFE技术,及其在测量植物根部净离子流量以研究植物根系生长发育的一些报告。     

CD4+-T-Cell and CD20+-B-Cell Changes Predict Rapid Disease Progression after Simian-Human Immunodeficiency Virus Infection in Macaques

Simian-human immunodeficiency virus 89.6PD (SHIV_89.6PD) was pathogenic after intrarectal inoculation of rhesus macaques. Infection was achieved with a minimum of 2,500 tissue culture infectious doses of cell-free virus stock, and there was no evidence for transient viremia in animals receiving subinfectious doses by the intrarectal route. Some animals experienced rapid progression of disease characterized by loss of greater than 90% of circulating CD4⁺ T cells, sustained decreases in CD20⁺ B cells, failure to elicit virus-binding antibodies in plasma, and high levels of antigenemia. Slower-progressing animals had moderate but varying losses of CD4⁺ T cells; showed increases in circulating CD20⁺ B cells; mounted vigorous responses to antibodies in plasma, including neutralizing antibodies; and had low or undetectable levels of antigenemia. Rapid progression led to death within 30 weeks after intrarectal inoculation. Plasma antigenemia at 2 weeks after inoculation (P ≤ 0.002), B- and T-cell losses (P ≤ 0.013), and failure to seroconvert (P ≤ 0.005) were correlated statistically with rapid progression. Correlations were evident by 2 to 4 weeks after intrarectal SHIV inoculation, indicating that early events in the host-pathogen interaction determined the clinical outcome.     

Ovarian steroids and serotonin neural function

The serotonin neural system originates from ten nuclei in the mid- and hindbrain regions. The cells of the rostral nuclei project to almost every area of the forebrain, including the hypothalamus, limbic regions, basal ganglia, thalamic nuclei, and cortex. The caudal nuclei project to the spinal cord and interact with numerous autonomic and sensory systems. This article reviews much of the available literature from basic research and relevant clinical research that indicates that ovarian steroid hormones, estrogens and progestins, affect the function of the serotonin neural system. Experimental results in nonhuman primates from this laboratory are contrasted with studies in rodents and humans. The sites of action of ovarian hormones on the serotonin neural system include effects within serotonin neurons as well as effects on serotonin afferent neurons and serotonin target neurons. Therefore, information on estrogen and progestin receptor-containing neurons was synthesized with information on serotonin afferent and efferent circuits. The ability of estrogens and progestins to alter the function of the serotonin neural system at various levels provides a cellular mechanism whereby ovarian hormones can impact mood, cognition, pain, and numerous other autonomic functions.     

Geology and geochemistry of the Paleoproterozoic borate deposits in Liaoning-Jilin,northeastern China: evidence of metaevaporites

The borate deposits in Liaoning, Jilin province, China, are hosted in the Paleoproterozoic meta-volcanic-sedimentary sequence which comprises magnetite-microcline rocks, K- and Na-rich leptynites and leptites, magnesium marbles and amphibolites. The borates are exclusively hosted in the magnesium carbonates and Mg-silicate rocks. The association of these rocks, their sedimentary structures and unusual chemical composition suggest that their protolithes were sediments deposited in evaporite basins: red beds, zeolitized tuffs and evaporites. Therefore, the borate deposits are metamorphosed evaporites. The initial precipitates were magnesium carbonates and hydrous magnesium borates, reflecting a MgSO_4 brine stage in a playa lake environment. During the subsequent metamorphism, these borates were dehydrated to form anhydrous borates, e.g. suanite and ludwigite. These deposits are analogous to many modern evaporite sequences in rift systems. Mineralogically, these borates are comparable to the borates in the saline lakes in the Qinghai-Xizang (Tibet) plateau. This revised version was published online in July 2006 with corrections to the Cover Date.     

施肥进步在粮食增产中的贡献及其地理分异

采用中长期田间试验对８种模拟施肥模型在温带的海伦试验站、暖温带的沈阳试验站和亚热带的桃源试验站进行了６～１０年试验,以比较、评价施肥在粮食生产中的贡献．结果发现,施肥在作物产量形成中的贡献随施肥制度和气候的热量因素所影响;在最佳施肥条件下,施肥在产量中的贡献率分别为海伦（温带）３０％、沈阳（暖温带）３８％、桃源（亚热带）４４％．按这一实验结果可以一般地估计：当其他技术条件不变时,施肥在产量形成中的贡献率最高可达３０～４５％,随所在地区气候的热量条件而不同．