Evaluation of [18F]FNM biodistribution and dosimetry based on whole-body PET imaging of rats.

INTRODUCTION: The aim of this work was to study the biodistribution, metabolism and radiation dosimetry of rats injected with [18F]FNM using PET/CT images. This novel radiotracer targeting NMDA receptor has potential for investigation for neurological and psychiatric diseases. METHODS: Free fraction and stability in fresh human plasma were determined in vitro. PET/CT was performed on anesthetized rats. Organs were identified and 3D volumes of interest (VOIs) were manually drawn on the CT in the center of each organ. Time activity curves (TACs) were created with these VOIs, enabling the calculation of residence times. To confirm these values, ex vivo measurements of organs were performed. Plasma and urine were also collected to study in vivo metabolism. Data was extrapolated to humans, effective doses were estimated using ICRP-60 and ICRP-89 dosimetric models and absorbed doses were estimated using OLINDA/EXM V1.0 and OLINDA/EXM V2.0 (which use weighting factors from ICRP-103 to do the calculations). RESULTS: The [18F]FNM was stable in human plasma and the diffusible free fraction was 53%. As with memantine, this tracer is poorly metabolized in vivo. Ex vivo distributions validated PET/CT data as well as demonstrating a decrease of radiotracer uptake in the brain due to anesthesia. Total effective dose was around 6.11 µSv/MBq and 4.65 µSv/MBq for female and male human dosimetric models, respectively. CONCLUSIONS: This study shows that the presented compound exhibits stability in plasma and plasma protein binding very similar to memantine. Its dosimetry shows that it is suitable for use in humans due to a low total effective dose compared to other PET radiotracers.

Are Tumor Cell Lineages Solely Shaped by Mechanical Forces?

This paper investigates cell proliferation dynamics in small tumor cell aggregates using an individual-based model (IBM). The simulation model is designed to study the morphology of the cell population and of the cell lineages as well as the impact of the orientation of the division plane on this morphology. Our IBM model is based on the hypothesis that cells are incompressible objects that grow in size and divide once a threshold size is reached, and that newly born cell adhere to the existing cell cluster. We performed comparisons between the simulation model and experimental data by using several statistical indicators. The results suggest that the emergence of particular morphologies can be explained by simple mechanical interactions.

A Tyrosine-Hydroxylase Characterization of Dopaminergic Neurons in the Honey Bee Brain.

Dopamine (DA) plays a fundamental role in insect behavior as it acts both as a general modulator of behavior and as a value system in associative learning where it mediates the reinforcing properties of unconditioned stimuli (US). Here we aimed at characterizing the dopaminergic neurons in the central nervous system of the honey bee, an insect that serves as an established model for the study of learning and memory. We used tyrosine hydroxylase (TH) immunoreactivity (ir) to ensure that the neurons detected synthesize DA endogenously. We found three main dopaminergic clusters, C1-C3, which had been previously described; the C1 cluster is located in a small region adjacent to the esophagus (ES) and the antennal lobe (AL); the C2 cluster is situated above the C1 cluster, between the AL and the vertical lobe (VL) of the mushroom body (MB); the C3 cluster is located below the calyces (CA) of the MB. In addition, we found a novel dopaminergic cluster, C4, located above the dorsomedial border of the lobula, which innervates the visual neuropils of the bee brain. Additional smaller processes and clusters were found and are described. The profuse dopaminergic innervation of the entire bee brain and the specific connectivity of DA neurons, with visual, olfactory and gustatory circuits, provide a foundation for a deeper understanding of how these sensory modules are modulated by DA, and the DA-dependent value-based associations that occur during associative learning.

Regionalization of browning revealed by whole subcutaneous adipose tissue imaging.

OBJECTIVE: White and brown adipose tissues play a major role in the regulation of metabolic functions. With the explosion of obesity and metabolic disorders, the interest in adipocyte biology is growing constantly. While several studies have demonstrated functional differences between adipose fat pads, especially in their involvement in metabolic diseases, there are no data available on possible heterogeneity within an adipose depot. METHODS: This study investigated the three-dimensional (3-D) organization of the inguinal fat pad in adult mice by combining adipose tissue clearing and autofluorescence signal acquisition by confocal microscopy. In addition, the study analyzed the expression of genes involved in adipocyte biology and browning at the mARN and protein levels in distinct areas of the inguinal adipose tissue, in control conditions and after cold exposure. RESULTS: Semiautomated 3-D image analysis revealed an organization of the fat depot showing two regions: the core was structured into segmented lobules, whereas the periphery appeared unsegmented. Perilipin immunostaining showed that most of the adipocytes located in the core region had smaller lipid droplets, suggesting a brown-like phenotype. qPCR analysis showed a higher expression of the browning markers Ucp1, Prdm16, Ppargc1a, and Cidea in the core region than at the periphery. Finally, cold exposure induced upregulation of thermogenic gene expression associated with an increase of UCP1 protein, specifically in the core region of the inguinal fat depot. CONCLUSIONS: Altogether, these data demonstrate a structural and functional heterogeneity of the inguinal fat pad, with an anatomically restricted browning process in the core area.

Monitoring the Activation of the DNA Damage Response Pathway in a 3D Spheroid Model.

Monitoring the DNA-Damage Response (DDR) activated pathway in multicellular tumor spheroid models is an important challenge as these 3D models have demonstrated their major relevance in pharmacological evaluation. Herein we present DDR-Act-FP, a fluorescent biosensor that allows detection of DDR activation through monitoring of the p21 promoter p53-dependent activation. We show that cells expressing the DDR-Act-FP biosensor efficiently report activation of the DDR pathway after DNA damage and its pharmacological manipulation using ATM kinase inhibitors. We also report the successful use of this assay to screen a small compound library in order to identify activators of the DDR response. Finally, using multicellular spheroids expressing the DDR-Act-FP we demonstrate that DDR activation and its pharmacological manipulation with inhibitory and activatory compounds can be efficiently monitored in live 3D spheroid model. This study paves the way for the development of innovative screening and preclinical evaluation assays.

Automated image analysis of in vitro angiogenesis assay.

Angiogenesis is the biological process of generating new capillary blood vessels. It is a fundamental component of a number of normal (reproduction and wound healing) and pathological processes (diabetic retinopathy, rheumatoid arthritis, tumor growth, and metastasis). In vitro angiogenesis assays provide a platform for evaluating the effects of pro- or antiangiogenic compounds. One of the most informative assays is the endothelial cells capillary tube formation assay performed on a biological matrix. This assay is based on quantification of the stimulatory and inhibitory effects of various agents, which is estimated through the measurement of the pseudo-tubules network length. This standard measurement is usually carried out manually by trained operators but requires time, attention, and dedication to achieve a reasonable degree of accuracy. Moreover, the screening is operator dependent. In this article, we propose an automated procedure to evaluate the pseudo-tubule network lengths. We propose a series of image analysis procedures developed using a freely available image analysis software library. More than 800 images from 12 experiments were analyzed automatically and manually, and their results were compared to improve and validate the proposed image analysis procedure. The resulting image analysis software is currently running on a dedicated server, with comparable accuracy to manual measurements. Using this new automated procedure, we are able to treat 540 images, or three complete assays per hour.