Novel complex hydrogels based on N-carboxyethyl chitosan and quaternized chitosan and their controlled in vitro protein release property

A novel pH-responsive hydrogel (CHC) composed of N-carboxyethyl chitosan (CEC) and N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride (HTCC) was synthesized by the redox polymerization technique. Turbidimetric titrations were used to determine the stoichiometric ratio of these two chitosan derivatives. The hydrogel was characterized by FT-IR, thermal gravimetric analysis (TGA), X-ray diffractometry (XRD), and scanning electron microscopy (SEM). The dynamic transport of water showed that the hydrogel reached equilibrium within 48 h. The swelling ratio of CHC hydrogel depended significantly on the pH of the buffer solution. The performance of the CHC as a matrix for the controlled release of BSA was investigated. It was found that the release behavior was determined by pH value of the medium as well as the intermolecular interaction between BSA and the hydrogels.     

冰冻切片技术在海滨锦葵细胞学研究中的应用

为解决普通石蜡切片观察植物样品繁琐与耗时长的问题,利用改进的蔗糖保护—液氮速冻切片法,进行海滨锦葵不同器官细胞学研究。结果表明:(1)适合于海滨锦葵不同器官的最适蔗糖浓度不同,适于含水量较大的营养器官(根、茎和叶)的最适蔗糖浓度比含水量较小的花器官(柱头裂片、花柱、子房和花药)高。(2)利用最适蔗糖浓度的蔗糖保护-液氮速冻切片方法,获得了完整而清晰的海滨锦葵各器官组织细胞结构的切片;海滨锦葵具有典型的双子叶草本植物营养器官的组织细胞结构特征,花柱为闭合型花柱,子房为多室复子房。表明基于蔗糖保护-液氮速冻的冰冻切片技术在植物细胞学研究中具有广阔的应用前景。     

不同灌溉方式对杂交稻同化产物运转与分配特性的研究

采用盆钵实验和^14C-同位素示踪技术,在节水、淹水、干旱三种灌溉方式下对杂交稻组合C两优396、威优46不同生育期的光合特性及同化产物的运转与分配进行研究。结果表明：在生育前期节水处理的叶绿素含量、净光合速率、同化产物分配比例与淹水处理的差异不显著;水稻抽穗后,淹水处理叶绿素含量与净光合速率下降幅度均大于节水处理,同化产物分配比例显著低于节水处理,最终导致产量也低于节水处理。而十旱处理在整个生育期的剑叶叶绿素含量、净光合速率、同化产物分配比例均低于节水、淹水处理,最终产量显著低于前两种处理。     

AGS3蛋白对吗啡慢性处理大鼠前额叶皮层神经元瞬时外向钾电流的影响

目的:研究吗啡对大鼠皮层神经元瞬时外向钾电流(IA)的影响,并在此基础上,用G蛋白信号转导激活因子3(AGS3)的抗体阻断AGS3作用,观察其对瞬时外向钾电流(IA)的影响,从而探讨AGS3蛋白在吗啡成瘾中的机制。方法:采用全细胞膜片钳技术记录IA;吗啡对神经元IA电流密度-电压曲线(I-V曲线)的影响;在全细胞构型下,观察三种不同浓度AGS3抗体对吗啡处理大鼠前额叶皮层神经元IA的影响。结果:吗啡能引起大鼠皮质神经元IA增强;当膜电位+55mV时,10-3μg/L、10-2μg/L、10-1μg/L三种不同浓度的AGS3抗体作用于吗啡处理的神经元,10-3μg/L对电流密度的抑制没有显著差异;10-2μg/L、10-1μg/L的抗体能显著抑制吗啡引起的电流密度升高,有统计学差异。结论:吗啡能引起神经元I的增强,AGS3蛋白在成瘾机体中参与了对I通道进行调节的信号转导通路。     

Docosahexaenoic Acid Production and Lipid-Body Formation in Schizochytrium limacinum SR21

Schizochytrium limacinum SR21, a thraustochytrid (Labyrinturomycota), is a heterotrophic marine microorganism. SR21 has attracted recent attention because of the production of docosahexaenoic acid (DHA). We obtained highly concentrated SR21 zoospores and successfully observed synchronous growth. We investigated changes of lipid content and fatty acid composition during the growth. The morphological features of the lipid bodies were also described via fluorescent and electron microscopy. The cells developed quickly after zoospore settlement. Lipid bodies developed in accordance with an increase in lipid content during the 8-h synchronous growth. The total lipid was composed mainly of triacylglycerol, sterol esters, and phosphatidylcholine. The proportion of neutral lipids (triacylglycerol and sterol esters) in the total lipid was fairly constant during growth. The fatty acid composition of neutral lipids, primary components of the lipid body, and phospholipids, primary components of the cell membranes, was nearly unchanged during the synchronous growth. However, the DHA content of the phospholipids decreased drastically after a 10-day culture. Electron micrographs prepared using a high-pressure freeze substitution technique revealed a fine structure of light- and dark-staining bands inside the lipid bodies in many stages of the cells.     

Region- and strand-specific mutagensis of a recombinant plasmid

Techniques were developed to mutagenize a single DNA strand in a specific region of the tetracycline-resistance (tetr) gene of the plasmid pKB280 that also carries the lambda repressor gene. Separate annealings of complementary single strands gave two isomeric, circular plasmids containing a 275-nucleotide, single-stranded region (gap) in the tetr gene. One of the isomeric, gapped plasmids was mutagenized specifically with sodium bisulfite such that an estimated 98% of the molecules had suffered at least one C to U conversion in the gap. The mutagenized gap was filled in with DNA polymerase. These molecules transformed Escherichia coli strain MM294 to lambda-immunity with the same frequency as unmutagenized, gap-filled pKB280. Of the lambda-immune transformants, 32% were Tcr and 68% were Tcs. Restriction analysis of plasmids from some Tcs transformants showed losses of restriction sites within the gap and at the gap termini, but none outside the gap. No deletions were detected.     

Optocardiographic recording of heart rate in Talitrus saltator (Amphipoda: Talitridae)

Abstract.  An optocardiographic non-invasive technique was used to monitor heart activity in small arthropods. Heart rate was recorded in adult individuals of the supralittoral amphipod Talitrus saltator after 3 h of immersion in marine artificial water (0, 11 and 33‰, t  = 15 ± 1 °C). Mean heart rate (± SE) ranged from 210 ± 26 beats min⁻¹ (at 33‰) to 276 ± 15 beats min⁻¹ (at 0‰) and, despite the small increase in temperature (0.5 °C) due to the infrared beam, the heart frequency remained constant for several hours. Neither the glue used to apply the sensor to the animal nor the beating of the pleopods affected heart rate. This technique could be a useful tool for the investigation of ecophysiological aspects in T. saltator , which is already well known for its ecology and behaviour.     

Establishing a lung cancer stem cell culture using autologous intratumoral fibroblasts as feeder cells

Human LCSCs (lung cancer stem cells) were first isolated from lung cancer patients and cultured using serum-free culture methods. To recreate the intratumoural microenvironment to sustain LCSC growth, autologous intratumoral fibroblasts were used as feeder cells. In this study, we investigated the growth and maintenance of pluripotency in prolonged LCSCs culture on autologous intratumoural fibroblasts. LCSCs isolated from three clinical samples all showed vigorous growth on feeder cells for 16 weeks of continuous cultures with a doubling time of 41-47 h. The cells continued expressing stem cell marker CD133 and remained undifferentiated. Pluripotency was demonstrated by tumour formation in immunodeficient mice. In a feeder-free culture system, growth of LCSCs spheres was retarded and would cease when the diameter reached 100 μm if immediate passage was not performed. Moreover, spontaneous differentiation was more frequently seen in a serum-free culture system. In conclusion, we have successfully established a culture system using autologous intratumoural fibroblast cells as feeder cells for prolonged culture of undifferentiated LCSCs in vitro.     

Dendrochronological assessment of the time since death of dead wood in an old growth Magellan's beech forest,Navarino Island (Chile)

The present study investigated the relationship between time since death and the morphological characteristics of fallen dead trees in a Nothofagus betuloides forest stand located on the island of Navarino (Chile). In this unmanaged forest, there were 399 m³ ha^?1 of dead wood, which represented about half of the living tree volume. At the investigation site, 18 living trees were selected and increment cores were collected from them to build master ring‐width chronologies. Cross sections were also collected from 48 fallen dead trees. The samples collected were then assigned to observable decay classes and their death date was determined dendrochronologically. Cross‐dating techniques were used and it was found that the fallen dead trees cross‐dated significantly with standard chronologies. A year of death was successfully determined for 75% of the sampled fallen dead trees. However, this study demonstrated that, in the standard classification, the transition rate from one class of decay to another was highly variable. Furthermore, the inconsistencies found in the decay rates of the fallen dead trees demonstrated that the existing decay classification schemes were unsuitable for this type of forest stand and that the relationship between qualitatively assessed decay classes and the time since death of trees in this extreme environment was rather weak. In addition, the analysis of the time since death, in this old growth forest, was indicative of the persistence of dead wood on the forest floor in austral cold ecosystems and of its contribution to long‐term carbon storage.