Behavioral effects of neurotoxic lesions of the ascending monoamine pathways in the rat brain.

Intracranial microinjections of 6-hydroxydopamine or 5,6-dihydroxytryptamine into 6 ascending monoamine pathways produced the expected patterns of depletion of telencephalic serotonin, dopamine (DA), and norepinephrine (NE). Serotonin level was specifically lowered after dorsal or median raphe lesions but not after mesolimbic or nigrostriatal system lesions which lowered both NE and DA. Lesions in the locus coeruleus (LC) or ventral noradrenergic bundle lowered only NE, and LC lesions elevated serotonin level. Behavior was examined in an open field, 1-way active avoidance, and 2 passive avoidance (PA) tasks, and measures were taken of water consumption and body weight. Dorsal raphe lesions had no effect on any of the measures; the other 5 lesion groups exhibited deficient acquisition of the 1-way active avoidance task. In the appetitive PA task, only the substantia nigra lesion group exhibited a deficiency. In the step-through PA task, both the substantia nigra and the median raphe groups exhibited a deficit, with the median raphe group exhibiting hyperactivity in the start box during testing. Water consumption was decreased by lesions in the ventral noradrenergic bundle during the 1st postoperative week and was increased in the median raphe group by the 4th postoperative week. Lastly, lesions in the LC dramatically decreased activity in the open field. Results are discussed in regard to the search for specificity of behavioral functions of the distinct ascending monoamine pathways. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deficient passive and one-way active avoidance acquisition following medial forebrain bundle lesions in rats.

In 3 experiments with 93 Long-Evans male hooded rats, cathodal electrolytic lesions of the medial forebrain bundle (MFB) at posterior hypothalamic levels produced a mild, transient hypodipsia and lowered jump thresholds to footshock. Lesions produced marked deficits in passive avoidance performance in a paradigm that paired discrete, linearly incrementing footshock intensities with contact of a water spout following 48 hrs of water deprivation. Injections of levo-dextro-5-hydroxytryptophan (75 mg g, ip), the immediate metabolic precursor of serotonin, had no effect on the passive avoidance performance of either experimental or operated control Ss. Lesions of the MFB also resulted in deficient acquisition in a 1-trial step-through passive avoidance paradigm not using motivation to drink and caused a severe acquisition deficit in a 1-way active avoidance task. Lesions of the septal nuclei produced lowered jump thresholds but did not affect acquisition in the 1st passive avoidance task. Results are interpreted as indicating a lesion-induced deficiency in fear learning, independent of the serotonergic functions of the MFB. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of molecular weight distribution and branching on rheological properties of polyolefin melts

The objective of this work was to determine the relationships among molecular and melt parameters of polyolefins. The polyolefins studied are polypropylene, poly-1-butene, poly-1-hexene, poly-1-dodecene, these have regularly spaced short-chain branches. Conclusions from previous work, as well as some new data, on polyethylene are given. As the molecular weight increases, the critical shear rate decreases but the melt viscosity and non-Newtonian ratio increase. As the molecular weight distribution broadens, the critical shear rate decreases, whereas the normal forces and the non-Newtonian ratio increase. Increasing the number of short-chain branches increases the energy of activation and the melt viscosity but decreases the non-Newtonian ratio. As the length of the short-chain branches increases, the non-Newtonian ratio increases, but the melt viscosity, critical shear rate, and energy of activation decrease. Increasing the number of long-chain branches decreases the non-Newtonian ratio, but the normal forces and the melt viscosity increase. Such information allows the polymer chemist to design a polyolefin molecule having the critical melt properties required for a given production technique.     

Corticosterone and avoidance in rats with basolateral amygdala lesions.

Produced deficient acquisition of 2-way active and passive avoidance in 15 male Moll-Wistar rats after bilateral electrolytic lesions restricted to the dorsal part of the basolateral nuclei. Other deficits also suggest a general reduction in fear or arousal: less immobility in the open field and during active-avoidance intertrial intervals, and slower escape latencies and less pituitary-adrenal activation during the initial active-avoidance session. Anatomical analysis of the areas producing the greatest deficit suggests that differential involvement of the insula may explain phylogenetic differences between these data from the rat and previous data from the cat, which show only active-avoidance deficiency after basolateral lesions. (26 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for cooxidation of polynuclear aromatic hydrocarbons in soil

The effect of constituent matrix on the degradation of hydrocarbons was characterized and evaluated within the context of cooxidation. Current information concerning the cooxidation process applied to hydrocarbons was evaluated and results were used to define a laboratory approach for studying the effects of constituent matrix on degradation rates of 13 polynuclear aromatic hydrocarbons (PAHs) in soil. Four matrices were studied: (1) single constituents applied and incubated singly; (2) a synthetic mixture of PAHs applied and incubated together; (3) a mixture of oil refinery wastes; (4) and a creosote wood preserving waste. Initial soil concentrations of constituents were similar for each matrix evaluated. One soil was used, a Kidman fine sandy loam (Haplustoll, Utah). Incubation conditions and extraction and analysis methods were similar among the studies. Four and 5-ring PAHs were found to disappear more rapidly from soils amended with complex wastes, while degradation rates for 3-ring compounds in all matrices were similar. These results can be interpreted in the context of cooxidation and suggest a potential tool for bioremediation of PAH contaminated soils and the simultaneous protection of groundwater resources through reduction or mitigation of groundwater contamination due to vadose zone-associated PAHs.     

Polyolefin waxes

The properties of polylefin waxes derived from polypropylene, polybutene, and their copolymers are described, with particular references to those which are useful as coatings and barrier materials. These products can be applied with conventional melt- and curtain-coating machines on paper and other substrates to give coatings with properties comparable to those of extrusion-coated, plastic-grade polyolefins. Because of their low melt viscosity and consequent ease of application, they should find wide application in the packaging industry.     

Conditioning decreases in plasma corticosterone level in rats by pairing stimuli with daily feedings.

Examined the nature of a stimulus-induced decrease in the plasma corticosterone levels of male hooded Long-Evans rats in 3 experiments. Ss maintained on a 23-hr food and water deprivation regimen were fed each morning immediately upon entrance of the experimenter into the otherwise isolated animal quarters. After only 14 feeding trials, Ss showed a marked decrease in corticosterone levels within 10 min of the experimenter's entrance whether fed and watered or not. The acquisition of this decrease was then examined over training trials and by comparing the conditioned animals (Group CD) with a group designed to control for pseudoconditioning, sensitization, and habituation (Group PC) during the use of the more distinctive conditioning stimulus of placing the rat's cage in a sound-attenuating chamber. During training, Group CD was fed .5–6 min after placement in the chamber, and Group PC was fed 1.5–2.5 hrs before or after placement. After 1 training trial, the CD and PC groups showed an increase in corticosterone levels in response to chamber placement when not fed or watered. However, after 14 training trials the CD group exhibited a significant decline, whereas the PC group exhibited a rise in corticosterone levels. Results indicate that external stimuli can cause a decrease in corticosterone level by virtue of prior association with feeding and drinking. This strongly suggests an acquired inhibition of the pituitary-adrenal system. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Derivation and correction of polyethylene melt strength equation

The following equation for the determination of polyethylene melt strength (MS) has been derived: where Δl is the length (inches) of extruded polymer cord required for 50% decrease in diameter of the cord, r₀ is the radius (inches) of the molten polymer cord as it first emerges from the melt indexer die, and MF is melt flow rate in grams/10 min. The required measurements are made on the initially extruded 0.5-in. portion of the polymer cord from a conventional melt indexer using the standard 0.0825-in.-diameter die and 2160-g. load and a temperature of 230°C. This melt strength equation was derived by using the assumption that the melt strength can be expressed as melt viscosity at low shear rates. Melt strengths of polyethylenes having similar melt indices have been shown to have over a 37-fold difference.