Opiates and medial hypothalamic knife cuts cause hyperphagia through different mechanisms.

In Exp I, male Sprague-Dawley rats were given bilateral parasagittal medial hypothalamic knife cuts (KCs) or a sham procedure and fed a high-fat diet. KC and sham-operated Ss were approximately equally sensitive to the suppressive effects of naloxone (0.1–20 mg/kg, subcutaneously [sc]) on food intake. Ketocyclazocine (0.1–20 mg/kg, sc) generally increased daytime food intake in sham-operated Ss; in contrast, the normal hyperphagia of KC Ss was in most cases either unchanged or decreased by ketocyclazocine. In Exp II, neither diet composition nor hypothalamic KCs significantly affected the feeding responses to naloxone or the stimulatory effects of butorphanol tartrate (0.1–20 mg/kg, sc). It was hypothesized that the differential effects of ketocyclazocine in KC and sham-operated Ss were a consequence of the sedative effects of the drug combined with the elevated baseline of the KC Ss. This hypothesis was supported by Exp III, which showed that ketocyclazocine also reduced nocturnal intake in unoperated Ss and that butorphanol increased intake. That feeding responses to naloxone and butorphanol were essentially unchanged by hypothalamic KCs suggests that the opioid feeding system is independent of the longitudinal feeding inhibitory pathway believed to be involved in KC-induced hyperphagia. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intake of high-fat food is selectively enhanced by mu opioid receptor stimulation within the nucleus accumbens

The present study was designed to further investigate the nature of feeding induced by opioid stimulation of the nucleus accumbens through an examination of the effects of intra-accumbens (ACB) opioids on macronutrient selection. In 3-hr tests of free-feeding (satiated) rats, intra-ACB administration of the mu receptor agonist D-Ala2,N,Me-Phe4, Gly-ol5-enkephalin (DAMGO; 0, 0.025, 0.25 and 2.5 micrograms bilaterally) markedly enhanced the intake of fat or carbohydrate when the diets were presented individually (although the effect on fat intake was much greater in magnitude). Intra-ACB injections of DAMGO, however, produced potent preferential stimulatory effects on fat ingestion with no effect on carbohydrate ingestion when both fat and carbohydrate diets were present simultaneously. Moreover, this selective stimulation of fat intake was independent of base-line diet preference and could be blocked by systemic injection of naltrexone (5 mg/kg). We also examined the effect of 24-hr food deprivation on the pattern of macronutrient intake in rats with access to both carbohydrate and fat. In contrast to the DAMGO-induced selective enhancement of fat intake, food deprivation significantly increased the intake of both diets to the same extent; however, in this case, only the stimulated fat intake was blocked by systemic naltrexone. Intra-ACB administration of DAMGO in hungry rats produced an effect similar to that observed in free-feeding rats; preference was strongly shifted to fat intake. Similarly, the opioid antagonist naltrexone (20 micrograms) infused directly into ACB preferentially decreased fat intake in hungry rats. These findings suggest that endogenous opioids within the ventral striatum may participate in the mechanisms governing preferences for highly palatable foods, especially those rich in fat.     

The magnetic-resonance force microscope: a new tool for high-resolution, 3-D, subsurface scanned probe imaging

The magnetic-resonance force microscope (MRFM) is a novel scanned probe instrument which combines the three-dimensional (3-D) imaging capabilities of magnetic-resonance imaging with the high sensitivity and resolution of atomic-force microscopy. It will enable nondestructive, chemical-specific, high-resolution microscopic studies and imaging of subsurface properties of a broad range of materials. The MRFM has demonstrated its utility for study of microscopic ferromagnets, and it will enable microscopic understanding of the nonequilibrium spin polarization resulting from spin injection. Microscopic MRFM studies will provide unprecedented insight into the physics of magnetic and spin-based materials. We will describe the principles and the state-of-the-art in magnetic-resonance force microscopy, discuss existing cryogenic MRFM instruments incorporating high-Q, single-crystal microresonators with integral submicrometer probe magnets, and indicate future directions for enhancing MRFM instrument capabilities.     

Robust Multivariate Outlier Detection Methods for Environmental Data

Outliers are an inevitable concern that needs to be identified and dealt with whenever one analyzes a large data set. Today’s water quality data are often collected on different scales, encompass several sites, monitor several correlated parameters, involve a multitude of individuals from several agencies, and span over several years. As such, the ability to identify outliers, which may affect the results of the analysis, is crucial. This note presents several statistical techniques that have been developed to deal with this problem, with particular emphasis on robust multivariate methods. These techniques are capable of isolating outliers while overcoming the effects of masking that can hinder the effectiveness of common outlier detection techniques such as Mahalanobis distances (MD). This note uses a comprehensive national metadata set on lake water quality as a case study to analyze the effectiveness of three robust outlier detection techniques, namely, the minimum covariance determinant (MCD), the minimum volume ellipsoid (MVE), and M-estimators. The note compares the results generated from these three techniques to assess the severity of each method when it comes to labeling observations as outliers. The results demonstrate the limitations of using MD to analyze multidimensional water quality data. The analysis also highlighted the differences between the three robust multivariate methods, whereby the MVE method was found to be the most severe when it came to outlier detection, while the MCD was the most lenient. Of the three robust multivariate outlier detection methods analyzed, the M-estimator proved to be the most flexible because it allowed for downweighting rather than censoring many borderline outlier observations.     

Ion beam irradiation of polytetrafluroethylene-loaded polyetheretherketone

Experiments were performed to study the radiation tolerance and mechanical stability of polytetrafluoroethylene (PTFE) loaded polyetheretherketone (PEEK) exposed to alpha particle radiation. Accelerator generated alpha beams were used to provide the extreme upper limit for the radiation environment of actinide sources where the polymer is employed in real applications. Before irradiation, a simplistic approach was used to determine possible exposures/doses a polymer could receive from a variety of actinides. Volatile gas emission from the polymer as a result of alpha radiolysis was measured by a quadruple mass spectrometer. Mechanical properties of irradiated polymer were measured to assure the robustness of the product in radiation environments. Results of all measurements indicate that PEEK performs excellently in alpha particle radiation environments. Volatile fragments generated from the polymer during alpha radiolysis are not observed to interact with nearby reactive metals such as actinides themselves to form undesirable compounds.     

Effects of cholecystokinin on taste preference and sensitivity in rats.

Determined, in 3 experiments with 10 Long-Evans rats, that cholecystokinin octapeptide (CCK-8) reduced the amount consumed or the number of licks of several concentrations of sucrose in short-term tests with Ss that were hungry, satiated, or fed ad lib. The suppressive effect of CCK-8 was generally smaller in the hungry than in the satiated or ad-lib condition. In the satiated and ad-lib conditions, there was no effect of sucrose concentration on the magnitude of the CCK-8 effect. In hungry Ss, the concentration-intake function for sucrose was lowered and flattened by both CCK and natural satiety. To determine whether a taste change is involved in this short-term reduction of sucrose intake, integrated chorda tympani responses were measured before and after iv infusions of CCK-8 or NaCl. The peak response to .3 M sucrose significantly increased after 2 5-μg infusions of CCK-8. Peak and tonic responses to sucrose and saline tended to increase after CCK-8 but not NaCl infusions. Results suggest that CCK-8 reduces sucrose intake in situations in which postingestional factors are minimal and that sucrose concentration has little effect on the size of this suppression. A change in perceived taste intensity or quality may play a role in the inhibitory effect of CCK-8 on intake. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A cubic-to-monoclinic structural transformation in the sesquioxide Dy2O3 induced by ion irradiation

Polycrystalline pellets of the sesquioxide Dy₂O₃ were irradiated at cryogenic temperature with Kr⁺⁺ ions to a fluence of 1 × 10²⁰ Kr/m². The crystal structure of the irradiated Dy₂O₃ was observed to change from a cubic, so-called C-type rare-earth sesquioxide structure to a monoclinic, B-type rare-earth sesquioxide structure upon ion irradiation. This transformation is accompanied by a decrease in molecular volume (or density increase) of approximately 9%.