Ligand density effect on biorecognition by PEGylated gold nanoparticles: regulated interaction of RCA120 lectin with lactose installed to the distal end of tethered PEG strands on gold surface

PEGylated gold nanoparticles (diameter: 20 nm) possessing various functionalities of lactose ligand on the distal end of tethered PEG ranging from 0 to 65% were prepared to explore the effect of ligand density of the nanoparticles on their lectin binding property. UV-visible spectra of the aqueous solution of the nanoparticles revealed that the strong steric stabilization property of the PEG layer lends the nanoparticles high dispersion stability even under the physiological salt concentration (ionic strength, I = 0.15 M). The number of PEG strands on a single particle was determined to be 520 from thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) observation under controlled acceleration voltage revealed the thickness of the PEG layer on the nanoparticle to be approximately 7 nm. The area occupied by a single lactose molecule on the surface of PEGylated gold nanoparticles was then calculated based on TGA and SEM results and was varied in the range of 10-34 nm2 depending on the lactose functionality (65 approximately 20%). PEGylated gold nanoparticles with 40% and 65% lactose functionality showed a selective and time-dependent aggregation in phosphate buffer with the addition of Ricinus communis agglutinin (RCA120) lectin, a bivalent galactose-specific protein. The aggregates can be completely redispersed by adding an excess amount of galactose. Time-lapse monitoring of UV-visible spectra at 600-750 nm revealed that the aggregation of PEGylated gold nanoparticles was accelerated with an increase in both RCA120 concentration in the solution and the lactose density of the nanoparticles. Furthermore, the sensitivity of lectin detection could be controlled by the regulation of lactose density on the particle surface. Interestingly, there was a critical lactose density (>20%) observed to induce detectable particle aggregation, indicating that the interaction between the particles is triggered by the multimolecular bridging via lectin molecules.     

Reanalysis of the phylogenetic status of Nipponosaurus sachalinensis (Ornithopoda: Dinosauria) from the Late Cretaceous of Southern Sakhalin

Nipponosaurus sachalinensis is the only definitive lambeosaurine hadrosaurid from Sakhalin Island of Russia. Previous studies suggested it was a member of Lambeosaurini (derived lambeosaurines). However, its phylogenetic status within Lambeosaurini remains controversial. In addition, some studies argued the juvenile ontogenetic stage of the holotype and regarded Nipponosaurus as an invalid taxon. In order to solve these problems, its definite growth stage is determined through histological studies. Absence of a line of arrested growth, presence of osteons with large vascular spaces, and presence of primary bone remnants even in the highly modified regions of the femur confirm that the holotype was a juvenile. More than a hundred of the 350 characters used to determine the phylogenetic position of Nipponosaurus are ontogenetically variable characters based on the different ontogenetic stages of Hypacrosaurus stebingeri. Our phylogenetic analysis reveals that Nipponosaurus is a basal lambeosaurine hadrosaurid, much further down in the tree than previously suggested, and shows a polytomy with Blasisaurus and Arenyisaurus. This study also indicates that Nipponosaurus is a valid taxon because it possesses unique characters within the Lambeosaurinae (presence of massive surangular anterodorsal process, presence of lateral shelf of the dentary, and a relatively short ulna), which are independent of ontogeny.     

Central noradrenergic inhibition of gastric mucosal blood flow and acid secretion in rats

To investigate the role of central noradrenaline (NA) in gastric functions, changes in mucosal blood flow (MBF) and acid secretion following electrical stimulation of the lateral hypothalamic area (LHA) and the effects of NA on these parameters were examined in rats anesthetized with urethane. NA 10 μg/animal injected into the lateral ventricle decreased the basal value of both the gastric MBF and acid output, while the same dose of acetycholine or dopamine was without effect. Repetitive electrical stimulation of LHA at 10 cycles/sec, 0.5 mA, 2 msec for 10 min elicited a significant, reproducible increase in both gastric MBF and acid output. NA 10 μg/animal injected into the lateral ventricle completely blocked these increases induced by the electrical stimulation. These data suggest that a central noradrenergic inhibitory mechanism is involved in regulation of the gastric MBF and acid secretion.