Design of a static full-ring multi-pinhole collimator for brain SPECT

In clinical practice, brain SPECT is mostly performed using a dual-head SPECT scanner with fan-beam or parallel-beam collimators rotating around the patient's head. The resolution of such a system is typically about 6-8 mm, which is rather poor to image the complex structures of the human brain. We developed a non-rotating multi-pinhole collimator for brain SPECT imaging with a resolution of 4 mm. A full-ring geometry allows for complete transaxial sampling. This enables the use of a stationary collimator. The collimator is a tungsten ring with two rows of pinholes. Each pinhole can individually be opened or closed with shutters. A sequence of shutter movements is performed to obtain an acquisition setup that simulates a rotational movement. The collimator is designed for the LaPET system (a PET detector ring made of 24 LaBr 3 detectors) and is optimized to maximize the system performance, resulting in a collimator radius of 145 mm and a pinhole diameter of 2 mm. This system has a sensitivity that is 4 times lower than a dual-head system with LEHR parallel-beam collimators. However, the resolution is 2 times better, a trade-off that is supported by Muehllehner [1]. Monte-Carlo simulated projections of a resolution phantom are successfully reconstructed and the resulting image shows that a resolution of 4 mm is indeed achieved

Biotechnological Production of Carotenoids and Their Applications in Food and Pharmaceutical Products

Pigments can be divided into four categories: natural, nature-identical, synthetic, and inorganic colors. Artificial colorants are the most used in food and pharmaceutical industries because of their advantages related to color range, price, resistance to oxygen degradation, and solubility. However, many natural pigments present health-promoting activities that make them an interesting option for human use and consumption. Natural colorants are derived from sources such as plants, insects, and microorganisms. Carotenoids are natural pigments with important biological activities, such as antioxidant and pro-vitamin A activity, that can be either extracted from plants and algae or synthesized by various microorganisms, including bacteria, yeasts, filamentous fungi, and microalgae. Advantages of microbial production include the ability of microorganisms to use a wide variety of low cost substrates, the better control of cultivation, and the minimized production time. After fermentation, carotenoids are usually recovered by cell disruption, solvent extraction, and concentration. Subsequent purification steps are followed depending on the application. The most prominent industrial applications of carotenoids, considering their health benefits, are in the food, feed, and pharmaceutical industries

Transcriptional ontogeny of the developing liver

<p>Abstract</p> <p>Background</p> <p>During embryogenesis the liver is derived from endodermal cells lining the digestive tract. These endodermal progenitor cells contribute to forming the parenchyma of a number of organs including the liver and pancreas. Early in organogenesis the fetal liver is populated by hematopoietic stem cells, the source for a number of blood cells including nucleated erythrocytes. A comprehensive analysis of the transcriptional changes that occur during the early stages of development to adulthood in the liver was carried out.</p> <p>Results</p> <p>We characterized gene expression changes in the developing mouse liver at gestational days (GD) 11.5, 12.5, 13.5, 14.5, 16.5, and 19 and in the neonate (postnatal day (PND) 7 and 32) compared to that in the adult liver (PND67) using full-genome microarrays. The fetal liver, and to a lesser extent the neonatal liver, exhibited dramatic differences in gene expression compared to adults. Canonical pathway analysis of the fetal liver signature demonstrated increases in functions important in cell replication and DNA fidelity whereas most metabolic pathways of intermediary metabolism were under expressed. Comparison of the dataset to a number of previously published microarray datasets revealed 1) a striking similarity between the fetal liver and that of the pancreas in both mice and humans, 2) a nucleated erythrocyte signature in the fetus and 3) under expression of most xenobiotic metabolism genes throughout development, with the exception of a number of transporters associated with either hematopoietic cells or cell proliferation in hepatocytes.</p> <p>Conclusions</p> <p>Overall, these findings reveal the complexity of gene expression changes during liver development and maturation, and provide a foundation to predict responses to chemical and drug exposure as a function of early life-stages.</p

Tob1 is a constitutively expressed repressor of liver regeneration

How proliferative and inhibitory signals integrate to control liver regeneration remains poorly understood. A screen for antiproliferative factors repressed after liver injury identified transducer of ErbB2.1 (Tob1), a member of the PC3/BTG1 family of mito-inhibitory molecules as a target for further evaluation. Tob1 protein decreases after 2/3 hepatectomy in mice secondary to posttranscriptional mechanisms. Deletion of Tob1 increases hepatocyte proliferation and accelerates restoration of liver mass after hepatectomy. Down-regulation of Tob1 is required for normal liver regeneration, and Tob1 controls hepatocyte proliferation in a dose-dependent fashion. Tob1 associates directly with both Caf1 and cyclindependent kinase (Cdk) 1 and modulates Cdk1 kinase activity. In addition, Tob1 has significant effects on the transcription of critical cell cycle components, including E2F target genes and genes involved in p53 signaling. We provide direct evidence that levels of an inhibitory factor control the rate of liver regeneration, and we identify Tob1 as a crucial check point molecule that modulates the expression and activity of cell cycle proteins