The blood-brain barrier penetration and distribution of PEGylated fluorescein-doped magnetic silica nanoparticles in rat brain

PEGylated PAMAM conjugated fluorescein-doped magnetic silica nanoparticles (PEGylated PFMSNs) have been synthesized for evaluating their ability across the blood-brain barrier (BBB) and distribution in rat brain. The obtained nanoparticles were characterized by transmission electron microscopy (TEM), thermal gravimetry analyses (TGA), zeta potential (ζ-potential) titration, and X-ray photoelectron spectroscopy (XPS). The BBB penetration and distribution of PEGylated PFMSNs and FMSNs in rat brain were investigated not only at the cellular level with Confocal laser scanning microscopy (CLSM), but also at the subcellular level with transmission electron microscopy (TEM). The results provide direct evidents that PEGylated PFMSNs could penetrate the BBB and spread into the brain parenchyma.     

1-Alkanols and membranes: A story of attraction

Although 1-alkanols have long been known to act as penetration enhancers and anesthetics, the mode of operation is not yet understood. In this study, long-time molecular dynamics simulations have been performed to investigate the effect of 1-alkanols of various carbon chain lengths onto the structure and dynamics of dimyristoylphosphatidylcholine bilayers. The simulations were complemented by microcalorimetry, continuous bleaching and film balance experiments. In the simulations, all investigated 1-alkanols assembled inside the lipid bilayer within tens of nanoseconds. Their hydroxyl groups bound preferentially to the lipid carbonyl group and the hydrocarbon chains stretched into the hydrophobic core of the bilayer. Both molecular dynamics simulations and experiments showed that all 1-alkanols drastically affected the bilayer properties. Insertion of long-chain 1-alkanols decreased the area per lipid while increasing the thickness of the bilayer and the order of the lipids. The bilayer elasticity was reduced and the diffusive motion of the lipids within the bilayer plane was suppressed. On the other hand, integration of ethanol into the bilayer enlarged the area per lipid. The bilayer became softer and lipid diffusion was enhanced.     

青海高原二种双腔吸虫尾蚴腺体组织化学的比较观察

本文报道应用组织化学反应方法观察了青海高原中华双腔吸虫尾蚴及暂称为“B”型双腔尾蚴(可能是枝双腔尾蚴)二种单细胞腺体的组化成分及其生理功能。大单细胞腺体12—13对,内含丰富的碳水化合物——蛋白质复合物象粘蛋白之类物质,及酸性粘多糖。小单细胞腺3对,含结合氨基的蛋白质及甲性糖蛋白。二种双腔吸虫在贝类宿主体内子胞蚴及尾蚴组化威分很相似但从尾蚴粘液腺的结构可以区分二虫种。中华双腔吸虫粘球内包绕在尾蚴体外的粘液含丰富的粘蛋白。双腔吸虫幼虫期组化成分与阔盘吸虫相应的幼虫期进行了比较。     

渗透促进剂对5－DSA标记裸鼠皮肤角质层影响的ESR研究

通过测定５－恶唑烷氮氧自由基硬脂酸（５－ＤＳＡ）标记裸鼠皮肤角质层的电子自旋共振（ＥＳＲ）谱,研究某些渗透促进剂如ＡＺ、油酸（ＯＡ）、丙二醇（ＰＧ）、二甲基亚砜（ＤＭＳＯ）等对裸鼠皮肤角质层的影响。促渗剂处理皮肤后,标记物序参数降低,各向同性超精细分裂偶合常数增大,前者表明促渗剂能够引起皮肤角质层细胞间脂质排列有序性降低,流动性增大;后者表明标记物周围脂质区域极性增大。     

Estimates of biomechanical forces in Magnaporthe grisea

The mechanical actions of the fungus Magnaporthe grisea raise many intriguing questions concerning the forces involved. These include: (1) the material properties of the appressorial wall; (2) the strength of the adhesive that keeps the appressorium anchored to the rice leaf surface; and (3) the forces involved in the penetration process whereby a peg is driven through the host cell wall. In this paper we give order of magnitude estimates for all three of these quantities. A simple Young-Laplace law type argument is used to show that the appressorial wall elastic modulus is of order 10–100 MPa; and an adaptation of standard adhesion theory indicates a lower bound on the strength of the appressorial adhesive to be of the order 500 J/m². Drawing on ideas from plasticity theory and ballistics, estimates of the penetration force raise interesting questions about experiments performed on the penetration of inert substrates by the fungus.     

Schistosoma mansoni: description of the head gland of cercariae and schistosomules at the ultrastructural level.

The head gland of the cercaria of Schistosoma mansoni appears to be a relatively large unicellular entity consisting of a fundus tapering into a system of multiple ducts that opens into the integument at the anterior end of the oral sucker. The fundus is located in the posteriodorsal area of the oral sucker and contains most of the secretory granules. The ducts are usually narrow and devoid of secretory granules especially near their integumental junctions in the cercaria. In Schistosomules of S. mansoni the fundus is reduced and the ducts are distended as secretory granules move en masse into the integument during the penetration of cercaria into their host where they may provide material for repair of the integument of the oral sucker damaged during penetration. The head gland has a strong affinity for luxol fast blue and acid hematin stains which suggests the presence of phospholipids.     

Correlation between pectate lyase activity and ability of diazotrophic Klebsiella oxytoca VN 13 to penetrate into plant tissues

Diazotrophic Klebsiella oxytoca VN 13 was able to lyse pectate, but the lytic activity of cultures grown on non-selective media was weak, and the enzyme was located mainly inside the cells. A small fraction of the population (10^-6 to 10^-5) was able to grow in a selective medium with sodium polygalacturonate as sole carbon source, and produced increased amounts of the pectinolytic enzyme pectate lyase. When wheat seeds were inoculated with these bacteria, increased levels of this enzyme correlated with a higher rate of internal colonization of wheat roots and with stimulation of wheat growth resulting in higher biomass. This suggests that colonization occurs via lyzed pectin layers. This revised version was published online in June 2006 with corrections to the Cover Date.     

The behaviour of roots encountering cracks in soil

Summary It is shown that probabilities of root penetration across cracks in soil can be calculated effectively using a mathematical model involving root stress and soil distributions and penetrometer/root stress ratios. Penetration criteria are developed, and it is found that the effective penetrometer/root stress ratios take values of about 4 for crack widths smaller than about 2 mm and about 8 for wider cracks. Root swelling does not appear to contribute significantly to the probability of root penetration through any effect on root buckling stress. Suggestions are made for further work on the effects of soil structure and strength on root behaviour.