Decreased reticuloendothelial system clearance and increased blood half-life and immune cell labeling for nano- and micron-sized superparamagnetic iron-oxide particles upon pre-treatment with Intralipid

Background

Superparamagnetic iron-oxide nanoparticles are useful as contrast agents for anatomical, functional and cellular MRI, drug delivery agents, and diagnostic biosensors. Nanoparticles are generally cleared by the reticuloendothelial system (RES), in particular taken up by Kupffer cells in the liver, limiting particle bioavailability and in-vivo applications. Strategies that decrease the RES clearance and prolong the circulation residence time of particles can improve the in-vivo targeting efficiency.

Methods

Intralipid 20.0%, an FDA approved nutritional supplement, was intravenously administered in rats at the clinical dose (2 g/kg) 1 h before intravenous injection of ultra-small superparamagnetic iron-oxide (USPIO) or micron-sized paramagnetic iron-oxide (MPIO) particles. Blood half-life, monocyte labeling efficiency, and particle biodistribution were assessed by magnetic resonance relaxometry, flow cytometry, inductively-coupled plasma MS, and histology.

Results

Pre-treatment with Intralipid resulted in a 3.1-fold increase in USPIO blood half-life and a 2-fold increase in USPIO-labeled monocytes. A 2.5-fold increase in MPIO blood half-life and a 5-fold increase in MPIO-labeled monocytes were observed following Intralipid pre-treatment, with a 3.2-fold increase in mean iron content up to 2.60 pg Fe/monocyte. With Intralipid, there was a 49.2% and 45.1% reduction in liver uptake vs. untreated controls at 48 h for USPIO and MPIO, respectively.

Conclusions

Intralipid pre-treatment significantly decreases initial RES uptake and increases in-vivo circulation and blood monocyte labeling efficiency for nano- and micron-sized superparamagnetic iron-oxide particles.

General significance

Our findings can have broad applications for imaging and drug delivery applications, increasing the bioavailability of nano- and micron-sized particles for target sites other than the liver.     

Dissecting the causes of variation in intra-inflorescence allocation in a sexually polymorphic species, Fragaria virginiana (Rosaceae)

In this study we dissect the causes of variation in intra-inflorescence allocation in a sexually polymorphic species, Fragaria virginiana. We separated out the effects of resource competition during flowering from those of inflorescence architecture, as well as identified the effects of sex morph and genotype. We found position-based variation in petal length, ovule, pollen, and flower number to be influenced more by architecture than by our resource manipulations during flowering. We also found both genotype- and sex-specific intra-inflorescence patterns. Furthermore, our data indicate that the sex morph-specific intra-inflorescence patterns result from architectural modifications of the basic pattern. In fact, sex-differential intra-inflorescence patterns suggest that fitness through male and female function may be maximized by different resource distribution patterns within the inflorescence and may have been modified by past selection. Specifically, females invested heavily in ovules at positions where fruit set was most likely (primary and secondary), at the expense of flower number and allocation per flower at more distal positions. Whereas functional males invested minimally in ovules at all flower positions and produced the most abundantly flowered inflorescences, hermaphrodites, on the other hand, showed intermediate patterns, implying a compromise between sex functions. We suggest that consideration of intra-inflorescence allocation and inflorescence architecture may reveal the mechanism underlying sexual dimorphism in flower allocation and number.     

Human and mouse macrophage-inducible C-type lectin (Mincle) bind Candida albicans

Candida albicans is a causative agent in mycoses of the skin, oral cavity, and gastrointestinal tract. Identification of receptors, and their respective ligands, that are engaged by immune cells when in contact with C. albicans is crucial for understanding inflammatory responses leading to invasive candidiasis. Mincle is a recently identified macrophage-expressed receptor that is important for host responses to C. albicans. The carbohydrate-recognition domain of human and mouse Mincle were expressed, purified under denaturing conditions, and successfully refolded. In addition to oligomers, there are isolatable monomeric and dimeric forms of the protein that occur under two different buffer solutions. The human and mouse homologues bound yeast extract, and the isolated dimeric and monomeric species also demonstrated the recognition of whole C. albicans yeast cells. The data are indicative of several functional states mediating the interaction of Mincle and yeast at the surface of the macrophage.     

The National Poisons Information Service and hospital admissions for children--the experience in Wales of the Cardiff Centre.

When inquiries to the Cardiff Centre of the National Poisons Information Service were compared with hospital admissions in the eight health authorities in Wales the findings suggested fewer admissions in the area within which the centre is situated and showed a more extensive use in that area than elsewhere. High inquiry rates were associated with high hospital admission rates when the eight areas were compared. If the service were delegated to area level a more complete community use would result.     

A genetic map of Xenopus tropicalis

We present a genetic map for Xenopus tropicalis, consisting of 2886 Simple Sequence Length Polymorphism (SSLP) markers. Using a bioinformatics-based strategy, we identified unique SSLPs within the X. tropicalis genome. Scaffolds from X. tropicalis genome assembly 2.0 (JGI) were scanned for Simple Sequence Repeats (SSRs); unique SSRs were then tested for amplification and polymorphisms using DNA from inbred Nigerian and Ivory Coast individuals. Thus identified, the SSLPs were genotyped against a mapping cross panel of DNA samples from 190 F2 individuals. Nearly 4000 SSLPs were genotyped, yielding a 2886-marker genetic map consisting of 10 major linkage groups between 73 and 132 cM in length, and 4 smaller linkage groups between 7 and 40 cM. The total effective size of the map is 1658 cM, and the average intermarker distance for each linkage group ranged from 0.27 to 0.75 cM. Fluorescence In Situ Hybridization (FISH) was carried out using probes for genes located on mapped scaffolds to assign linkage groups to chromosomes. Comparisons of this map with the X. tropicalis genome Assembly 4.1 (JGI) indicate that the map provides representation of a minimum of 66% of the X. tropicalis genome, incorporating 758 of the approximately 1300 scaffolds over 100,000 bp. The genetic map and SSLP marker database constitute an essential resource for genetic and genomic analyses in X. tropicalis.     

Electrode surface microstructures in studies of biological electron transfer

Specifically designed electrode surfaces that can exchange electrons directly with redox proteins and enzymes are providing new approaches to investigating electrochemical processes in bioenergetics.     

Disorder-to-order transition of the active site of human class Pi glutathione transferase, GST P1-1

Glutathione transferases comprise a large family of cellular detoxification enzymes that function by catalyzing the conjugation of glutathione (GSH) to electron-deficient centers on carcinogens and other toxins. NMR methods have been used to characterize the structure and dynamics of a human class pi enzyme, GST P1-1, in solution. Resonance assignments have been obtained for the unliganded enzyme and the GSH and S-hexylglutathione (GS-hexyl) complexes. Differences in chemical shifts between the GSH and GS-hexyl complexes suggest more extensive structural differences between these two enzyme-ligand complexes than detected by previous crystallographic methods. The NMR studies reported here clearly show that an alpha-helix (alpha2) within the GSH binding site exists in multiple conformations at physiological temperatures in the absence of ligand. A single conformation of alpha2 is induced by the presence of either GSH or GS-hexyl or a reduction in temperature to below 290 K. The large enthalpy of the transition ( approximately 150 kJ/mol) suggests a considerable structural rearrangement of the protein. The Gibbs free energy for the transition to the unfolded form is on the order of -4 to -6 kJ/mol at physiological temperatures (37 degrees C). This order-to-disorder transition contributes substantially to the overall thermodynamics of ligand binding and should be considered in the design of selective inhibitors of class pi glutathione transferases.