Bioimaging and Biodistribution of the Metal-Ion-Controlled Self-Assembly of PYY3–36 Studied by SPECT/CT

The controlled self-assembly of peptide- and protein-based pharmaceuticals is of central importance for their mode of action and tuning of their properties. Peptide YY_3–36 (PYY_3–36) is a 36-residue peptide hormone that reduces food intake when peripherally administered. Herein, we describe the synthesis of a PYY_3–36 analogue functionalized with a metal-ion-binding 2,2’-bipyridine ligand that enables self-assembly through metal complexation. Upon addition of Cu^II, the bipyridine-modified PYY_3–36 peptide binds stoichiometric quantities of metal ions in solution and contributes to the organization of higher-order assemblies. In this study, we aimed to explore the size effect of the self-assembly in vivo by using non-invasive quantitative single-photon emission computed tomography/computed tomography (SPECT/CT) imaging. For this purpose, bipyridine-modified PYY_3–36 was radiolabeled with a chelator holding ¹¹¹In^III, followed by the addition of Cu^II to the bipyridine ligand. SPECT/CT imaging and biodistribution studies showed fast renal clearance and accumulation in the kidney cortex. The radiolabeled bipyridyl-PYY_3–36 conjugates with and without Cu^II presented a slightly slower excretion 1 h post injection compared to the unmodified-PYY_3–36, thus demonstrating that higher self-assemblies of the peptide might have an effect on the pharmacokinetics.     

Reference groups, membership groups, and attitude change.

"The present study is an examination of the attitude changes which occur over time when reference groups and membership groups are identical and when they are disparate… . The Ss were women students at a large private coeducational university… . In the social context of the lives of the subjects, and in a natural social experiment which provided randomization of the relevant condition effects, the influence of both membership and reference groups on attitude change was assessed. All subjects shared a common reference group at the start of the period of the study. When divergent membership groups with disparate attitude norms were socially imposed on the basis of a random event, attitude change in the subjects over time was a function of the normative attitudes of both imposed membership groups and the individuals' reference groups. The greatest attitude change occurred in subjects who came to take the imposed initially nonpreferred, membership group as their reference group." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feeding trials in organic food quality and health research

Feeding experiments comparing organically and conventionally produced food are performed to assess the overall impact on the animals' health as a model for the effects experienced by the human consumers. These experiments are based on systems research and characterized by their focus on production methods, whole food testing and procedures in accordance with the terms of organic farming. A short review of such experiments shows that the majority of these tests revealed effects of the organically produced feed on health parameters such as reproductive performance and immune responses. Systems research is not just about simple cause–effect chains, but rather about the pluralism of interactions in biological networks; therefore, the interpretation of the outcome of whole food experiments is difficult. Furthermore, the test diets of organic and conventional origin can be constituted in different ways, compensating for or maintaining existing differences in nutrient and energy contents. The science‐based results suggest positive influences from organic feeds, but there is still a need for confirmation in animals and, finally, in humans. For this purpose animal feeding trials with feed from different production systems should be conducted, with the aims to define health indicators and to establish biomarkers as a basis for future dietary intervention studies in humans. Copyright © 2009 Society of Chemical Industry     

Enzymatic degradation of starch thermoplastic blends using samples of different thickness

The material studied was a thermoplastic blend of corn starch with a poly(ethylene-vinyl alcohol) copolymer, SEVA-C. The influence of both the material's exposed surface and enzyme concentration on degradation kinetics was studied. As alpha-amylase is present in the blood plasma, experiments were performed, varying the material thickness and the alpha-amylase between 50 and 100 units/l, at 37 degrees C, lasting up to 90 days. Four different batches using SEVA-C and starch samples of different thickness were performed. The positive correlation between degradation rate and the exposed material surface was confirmed, since thin films with larger exposed surfaces were degraded faster than thick square plates having the same total mass. The degradation extent depends on the total amount of amorphous starch present in the formulation rather than on the amount of enzyme used and the minimum thickness to ensure maximum degradation was estimated to be close to 0.25 mm.     

Optical characterization of double layers containing epitaxial ZnSe and ZnTe films

In this paper results of the optical characterization of double layers consisting of ZnTe and ZnSe thin films prepared by molecular beam epitaxy onto GaAs single crystal substrates are presented. For this optical characterization the optical method based on combining variable angle spectroscopic ellipsometry and near-normal spectroscopic reflectometry is used in the multi-sample modification applied within the spectral region 230–850?nm. Using this method the spectral dependences of the optical constants of the upper ZnTe thin films are determined within the spectral region mentioned above. Spectral dependences of the optical constants of the lower ZnSe thin films were determined within the spectral region 450–850?nm. Boundary roughness of these double layers and overlayers is respected. RMS values of the heights of the irregularities of the boundaries and thicknesses and optical constants of the overlayers are determined by means of the combined optical method as well. The uppermost boundaries of the double layers are, moreover, analysed using atomic force microscopy because of verification of the RMS values of these boundaries obtained by the optical method. The spectral dependences of the optical constants of the upper ZnTe films and lower ZnSe films determined in this paper are compared with those presented for ZnTe single layers and ZnSe single layers in the literature.