Quantitative encapsulation and retention of 227Th and decay daughters in core-shell lanthanum phosphate nanoparticles.

Targeted alpha therapy (TAT) offers great promise for treating recalcitrant tumors and micrometastatic cancers. One drawback of TAT is the potential damage to normal tissues and organs due to the relocation of decay daughters from the treatment site. The present study evaluates La(227Th)PO4 core (C) and core +2 shells (C2S) nanoparticles (NPs) as a delivery platform of 227Th to minimize systemic distribution of decay daughters, 223Ra and 211Pb. In vitro retention of decay daughters within La(227Th)PO4 C NPs was influenced by the concentration of reagents used during synthesis, in which the leakage of 223Ra was between 0.4 ± 0.2% and 20.3 ± 1.1% in deionized water. Deposition of two nonradioactive LaPO4 shells onto La(227Th)PO4 C NPs increased the retention of decay daughters to >99.75%. The toxicity of the nonradioactive LaPO4 C and C2S NP delivery platforms was examined in a mammalian breast cancer cell line, BT-474. No significant decrease in cell viability was observed for a monolayer of BT-474 cells for NP concentrations below 233.9 µg mL-1, however cell viability decreased below 60% when BT-474 spheroids were incubated with either LaPO4 C or C2S NPs at concentrations exceeding 29.2 µg mL-1. La(227Th)PO4 C2S NPs exhibit a high encapsulation and in vitro retention of radionuclides with limited contribution to cellular cytotoxicity for TAT applications.

Three-dimensional reconstruction of biological macromolecular complexes from in-lens scanning electron micrographs.

Two helical samples: F-actin and the bacteriophage T4 tail sheath were reconstructed in three dimensions from contrast enhanced (rotational shadowing and negatively stained) in-lens cryo-field emission scanning electron micrographs, using the iterative real-space helical reconstruction method. The F-actin--and bacteriophage T4 reconstructions compare favourably to an atomic model refined against fibre diffraction data and a cryo-electron microscopy reconstruction, respectively. These results show that single-particle methods, developed for macromolecules imaged in the transmission electron microscope can be applied to cryo-field emission scanning electron micrographs data with appropriate symmetry.

Helical structure of unidirectionally shadowed metal replicas of cyanide hydratase from Gloeocercospora sorghi.

The helical filaments of the cyanide hydratase from Gloeocercospora sorghi have been reconstructed in three dimensions from freeze dried, unidirectionally shadowed specimens using iterative real-space helical reconstruction. The average power spectrum of all selected images has three clear reflections on different layer lines. The reconstruction is complicated by the fact that three possible indexing schemes are possible and reconstructions using the starting symmetries based on each of these indexing schemes converge on three-dimensional volumes which appear plausible. Because only one side is visible in shadowed specimens, it is necessary to examine the phases from a single filament by cryo-electron microscopy in order to make an unequivocal assignment of the symmetry. Because of the novel nature of the reconstruction method used here, conventional cryo-EM methods were also used to determine a second reconstruction, allowing us to make comparisons between the two. The filament is shown to have a left-handed one-start helix with D(1) symmetry, 5.46 dimers per turn and a pitch of 7.15nm. The reconstruction suggests the presence of an interaction across the groove not previously seen in nitrilase helical fibres.

Study of the structure of the air and blood capillaries of the gas exchange tissue of the avian lung by serial section three-dimensional reconstruction.

We have previously reconstructed the gas exchange tissue of the adult muscovy duck, Cairina moschata using a method of manually aligning sections and tracing the contours of the components of the gas exchange tissue. This reconstruction method demonstrated that the air capillaries are comprised of an expanded globular part interconnected by narrow air channels. The blood capillaries completely surround the air capillaries forming an anastomosing meshwork of short segments. However, the resulting reconstruction was limited in scope because of the laborious process of tracing the profiles of each component through the sequence of micrographs. We have now reconstructed a larger proportion of the exchange tissue by using a cross-correlation based alignment strategy and have demonstrated that the staining intensity of each of the exchange tissue components is sufficiently different to allow them to be identified by simple filtering and thresholding. The resulting reconstructions sample a much larger proportion of the exchange tissue and demonstrate the heterogeneity of structures from different locations in the parabronchus. We have shown that a sheet-flow-type arrangement of blood capillaries surrounds the infundibulum; this represents an unexpected functional convergence with the arrangement of blood capillaries surrounding the mammalian alveoli. It is feasible, using this reconstruction strategy, to analyse the exchange tissue of a large number of avian species in order to determine structural correlates of function. The resulting reconstructions could be analysed in order to determine the basis of the functional efficiency and rigidity of the avian lung.

Synthesis and characterization of lanthanum phosphate nanoparticles as carriers for (223)Ra and (225)Ra for targeted alpha therapy.

INTRODUCTION: Targeted alpha therapy (TAT) has the potential for killing micro-metastases with minimum collateral damage to surrounding healthy tissue. In-vivo generator radionuclides, such as(223)Ra, (225)Ra, and (225)Ac, are of special interest for radiotherapeutic applications as they emit multiple α-particles during their decay. Utilizing appropriate carriers capable of retaining both the parent radioisotope as well as daughter products is important for the effective delivery of the radioisotope to the tumor site while mitigating global in vivo radiotoxicity. In this work, LaPO4 core and core+2 shells nanoparticles (NPs) (NPs with 2 layers of cold LaPO4 deposited on the core surfaces) were synthesized containing either (223)Ra or(225)Ra/(225)Ac, and the retention of the parents and daughters within the NPs in vitro was investigated. METHODS: Core LaPO4 NPs were synthesized in aqueous solution by reacting 1 equivalent of La(NO3)3, along with few microcuries of either (223)Ra or (225)Ra/(225)Ac, with 1 equivalent of sodium tripolyphosphate (TPP) under moderate heating and purified by membrane dialysis. Core-shell NPs were also synthesized with one (core+1 shell) and two (core+2 shells) cold LaPO4 layers deposited onto the radioactive cores. The NPs were then characterized by transmission electron microscopy (TEM) and powder x-ray diffraction (XRD). Identification and quantification of radioactive parents and daughters released from the NPs in vitro were investigated using gamma-ray spectroscopy. RESULTS: XRD and TEM analysis revealed that the NPs crystallized in the rhabdophane phase with mean diameters of 3.4 and 6.3nm for core and core+2 shells, respectively. The core LaPO4 NPs retained up to 88% of (223)Ra over 35days. However, in the core+2 shells NPs, the retention of (223)Ra and its daughter, (211)Pb, was improved to >99.9% over 27days. Additionally, the retention of (225)Ra/(225)Ac parents was >99.98% and ~80% for the (221)Fr and (213)Bi daughters over 35days for the core+2 shells NPs. CONCLUSIONS: The in vitro retention of both parents and daughters results suggests that LaPO4 NPs are potentially effective carriers of radium isotopes.

Denture marking for identification.

A method for including the patient's name in the denture base material for identification purposes has been described. This simple procedure takes little time, has almost no cost, and is effective.

Macromolecular 3D SEM reconstruction strategies: signal to noise ratio and resolution.

Three-dimensional scanning electron microscopy generates quantitative volumetric structural data from SEM images of macromolecules. This technique provides a quick and easy way to define the quaternary structure and handedness of protein complexes. Here, we apply a variety of preparation and imaging methods to filamentous actin in order to explore the relationship between resolution, signal-to-noise ratio, structural preservation and dataset size. This information can be used to define successful imaging strategies for different applications.

Tomography of asymmetric bulk specimens imaged by scanning electron microscopy.

The scanning electron microscope produces nanometer-resolution surface images of biological samples preserved in a life-like state. Extracting three-dimensional information from these two-dimensional images has been the subject of long and ongoing research. We present here a general method and theoretical basis for reconstructing the surfaces of SEM specimens imaged from multiple directions by back-projection. The resulting reconstructions are faithful representations of the original specimen geometry, even when the input images are blurred and have low signal-to-noise ratio.

Conditioned compensatory response to ethanol as indicated by locomotor activity in rats.

Spontaneous motor activity (SMA) was used to investigate conditioned tolerance to the depressant effect of ethanol, and conditioned responses to stimuli predicting ethanol injection. Rats were injected with saline or ethanol at 800 or 1600 mg/kg, on alternate days, in two distinctly different locations, over a period of 20 conditioning days. The two ethanol doses were administered to separate groups of rats, but conditioned effects were determined by within-subject comparisons. Conditioned SMA responses (rearing and ambulatory activity) were measured after injection of saline in the location previously paired with ethanol treatment, and conditioned tolerance was determined by observing ethanol effects in rats tested in the environment previously paired with saline treatment. Ethanol-paired stimuli increased SMA (both activity measures, both dose-groups) during the conditioned response test. Absence of these conditioned stimuli during the tolerance test resulted in greater behavioral depression with the 800 mg/kg ethanol dose for both the rearing and ambulation measures; however, this effect was seen with the 1600 mg/kg dose for the rearing measure only. These results provide further evidence that Pavlovian conditioning is involved in tolerance to the depressant action of ethanol on overt behavior, and demonstrate the presence of such conditioned compensatory responses in the absence of ethanol treatment.

[Ni(terpy)(H2O)]-trans-[Ni-(mu-CN)2-(CN)2]n, a one-dimensional linear tetracyanonickelate chain.

The one-dimensional chain catena-poly[[aqua(2,2':6',2"-terpyridyl-kappa(3)N)nickel(II)]-mu-cyano-kappa(2)N:C-[bis(cyano-kappaC)nickelate(II)]-mu-cyano-kappa(2)C:N], [Ni(terpy)(H(2)O)]-trans-[Ni-mu-(CN)(2)-(CN)(2)](n) or [Ni(2)(CN)(4)(C(15)H(11)N(3))(H(2)O)], consists of infinite linear chains along the crystallographic [10-1] direction. The chains are composed of two distinct types of nickel ions, paramagnetic octahedral [Ni(terpy)(H(2)O)](2+) cations (with twofold crystallographic symmetry) and diamagnetic planar [Ni(CN)(4)](2-) anions (with the Ni atom on an inversion center). The [Ni(CN)(4)](2-) units act as bidentate ligands bridging through two trans cyano groups thus giving rise to a new example of a trans-trans chain among planar tetracyanonickelate complexes. The coordination geometry of the planar nickel unit is typical of slightly distorted octahedral nickel(II) complexes, but for the [Ni(CN)(4)](2-) units, the geometry deviates from a planar configuration due to steric interactions with the terpyridine ligands.