Imaging Techniques in Large Animals

Imaging techniques in large animals bridges the gap between preclinical and clinical research.  The same scanners can be used for large laboratory animals and for human beings and, with few  modifications, the same scanning protocols can also be used. Therefore, knowledge obtained from imaging  techniques in animal research can readily be used in humans. Similarly, medical hypotheses and problems  from clinical experience with humans can often be tested and studied in large animals. Imaging techniques  create either anatomical images (Computerized Tomography, CT or Magnetic Resonance Imaging, MRI) or  functional images of the body (Positron Emission Tomography, PET). While X-ray radiation is used to get  a cross-sectional CT image of the body, MRI involves the use of a magnetic field that forces the hydrogen  cellular nuclei to align in different positions. PET utilizes radiation emitted from the animal after injection  of radioactive tracers. The most commonly used large animals in imaging research are dogs, sheep, goats,  pigs and nonhuman primates. These laboratory animals have large organs and blood volumes that allow  repeated blood sampling, which is needed in most PET studies, while blood sampling is unnecessary for  CT and MRI imaging. Large animals are outbreed, and so many animals are typically needed in each study,  due to marked individual variation. That situation is unfavourable, because imaging studies of large animals  are expensive and time consuming. Except for nonhuman primates, large animals must be anaesthetised for  scanning procedures, and this may influence the experiments.

Carbon dioxide dynamics in an agricultural headwater stream driven by hydrology and primary production

Headwater streams are known to be hotspots for carbon dioxide (CO2) emissions to the atmosphere and are hence important components in landscape carbon balances. However, surprisingly little is known about stream CO2 dynamics and emissions in agricultural settings, a land use type that globally covers ca. 40% of the continental area. Here we present hourly measured in situ stream CO2 concentration data from a 11.3 km(2) temperate agricultural headwater catchment covering more than 1 year (in total 339 d excluding periods of ice and snow cover). The stream CO2 concentrations during the entire study period were generally high (median 3.44 mg C L-1, corresponding to partial pressures (pCO(2)) of 4778 mu atm) but were also highly variable (IQR = 3.26 mgC L-1). The CO2 concentration dynamics covered a variety of different timescales from seasonal to hourly, with an interplay of hydrological and biological controls. The hydrological control was strong (although with both positive and negative influences dependent on season), and CO2 concentrations changed rapidly in response to rainfall and snowmelt events. However, during growing-season base flow and receding flow conditions, aquatic primary production seemed to control the stream CO2 dynamics, resulting in elevated diel patterns. During the dry summer period, rapid rewetting following precipitation events generated high CO2 pulses exceeding the overall median level of stream CO2 (up to 3 times higher) observed during the whole study period. This finding highlights the importance of stream intermittency and its effect on stream CO2 dynamics. Given the observed high levels of CO2 and its temporally variable nature, agricultural streams clearly need more attention in order to understand and incorporate these considerable dynamics in large-scale extrapolations

18Fluorodeoxyglucose Accumulation in Arterial Tissues Determined by PET Signal Analysis

BACKGROUND: Arterial 18fluorodeoxyglucose (FDG) positron emission tomography (PET) is considered a measure of atherosclerotic plaque macrophages and is used for quantification of disease activity in clinical trials, but the distribution profile of FDG across macrophages and other arterial cells has not been fully clarified. OBJECTIVES: The purpose of this study was to analyze FDG uptake in different arterial tissues and their contribution to PET signal in normal and atherosclerotic arteries. METHODS: Wild-type and D374Y-PCSK9 transgenic Yucatan minipigs were fed a high-fat, high-cholesterol diet to induce atherosclerosis and subjected to a clinical FDG-PET and computed tomography scan protocol. Volumes of arterial media, intima/lesion, macrophage-rich, and hypoxic tissues were measured in serial histological sections. Distributions of FDG in macrophages and other arterial tissues were quantified using modeling of the in vivo PET signal. In separate transgenic minipigs, the intra-arterial localization of FDG was determined directly by autoradiography. RESULTS: Arterial FDG-PET signal appearance and intensity were similar to human imaging. The modeling approach showed high accuracy in describing the FDG-PET signal and revealed comparable FDG accumulation in macrophages and other arterial tissues, including medial smooth muscle cells. These findings were verified directly by autoradiography of normal and atherosclerotic arteries. CONCLUSIONS: FDG is taken up comparably in macrophage-rich and -poor arterial tissues in minipigs. This offers a mechanistic explanation to a growing number of observations in clinical imaging studies that have been difficult to reconcile with macrophage-selective FDG uptake.This study was supported by the Danish Council for Independent Research/Medical Sciences, Lundbeck Foundation, Danish Heart Foundation, and Aarhus University Research Foundation (AU IDEAS). The CNIC is supported by the Ministerio de Ciencia, Innovación y Universidades, and the Pro CNIC Foundation; and is a Severo Ochoa Center of Excellence (SEV-2015-0505). Dr. Bentzon has served as a consultant for Novo Nordisk A/S; and has within the last 5 years received an investigator-initiated preclinical research grant from Regeneron PharmaceuticalsS

Neuropeptide Y and religious commitment in healthy young women

The present study explores the relationship between neuroactive hormones and religious commitment. We hypothesised that religious commitment is mediated by neuropeptide Y and oxytocin. These neurohormones have a well-established role in general well-being, anxiety regulation, stress-resilience, social affiliation and spirituality.Methods Sixty healthy women (median age 21) participated in the study and completed the Religious Commitment Inventory and other psychometric surveys. Blood was sampled from each participant and serum levels of neuropeptide Y were measured using radioimmunoassay. Oxytocin, stress and sex hormones were measured using enzyme-linked immunosorbent assay. Correlations were tested using non-parametric statistical methods.Results We found a positive correlation between serum neuropeptide Y levels and religious commitment, but not between oxytocin and religious commitment.Conclusions The present study provides preliminary evidence that neuropeptide Y is a biological correlate of religious commitment.</p

A robust method for the detection of small changes in relaxation parameters and free water content in the vicinity of the substantia nigra in Parkinson’s disease patients

Alterations in the substantia nigra are strongly associated with Parkinson’s disease. However, due to low contrast and partial volume effects present in typical MRI images, the substantia nigra is not of sufficient size to obtain a reliable segmentation for region-of-interest based analysis. To combat this problem, the approach proposed here offers a method to investigate and reveal changes in quantitative MRI parameters in the vicinity of substantia nigra without any a priori delineation. This approach uses an alternative method of statistical, voxel-based analysis of quantitative maps and was tested on 18 patients and 15 healthy controls using a well-established, quantitative free water mapping protocol. It was possible to reveal the topology and the location of pathological changes in the substantia nigra and its vicinity. Moreover, a decrease in free water content, T1 and T2* in the vicinity of substantia nigra was indicated in the Parkinson’s disease patients compared to the healthy controls. These findings reflect a disruption of grey matter and iron accumulation, which is known to lead to neurodegeneration. Consequently, the proposed method demonstrates an increased sensitivity for the detection of pathological changes—even in small regions—and can facilitate disease monitoring via quantitative MR parameters

Clinical Evaluation of the Accuracy and Precision of the CDI 500 In-line Blood Gas Monitor With and Without Gas Calibration

During cardiopulmonary bypass blood gases can be analyzed with laboratory equipment or with an in-line monitor giving instant results. The manufacturer of the CDI 500 in-line blood gas monitor recommends gas calibration before use. In acute cases there may not be time to perform a gas calibration. We hypothesized that after calibration against laboratory results, the CDI values of pH, pO2, and pCO2 will keep the same level of accuracy, whether the CDI has been gas calibrated or not. We performed a prospective randomized observational study using a study group without gas calibration (29 patients) and a control group with gas calibration (29 patients). Blood sampling was done at the beginning of bypass, and 30 minutes later. After each blood sample the CDI was in-vivo calibrated to the values simultaneously obtained from the ABL. Before in-vivo calibration values from the CDI without gas calibration were significantly different from the ABL-values in accuracy as well as precision, whereas the results from the gas calibrated CDI were largely consistent with the ABL. Before in-vivo calibration, the CDI without gas calibration was completely unreliable. After in-vivo calibration there was no statistical difference between the values of the CDI with and without calibration. We recommend gas calibration of the CDI before use in the period before in-vivo calibration