Butter, which is naturally enriched in cis-9, trans-11 conjugated linoleic acid (rumenic acid; RA) and vaccenic acid (VA), has been shown to be an effective anticarcinogen in studies with animal models; however, there has been no examination of the effects of a naturally derived source of VA and RA on atherosclerosis-related biomarkers. The current study was designed to determine the effect of a diet containing VA/RA-enriched butter on plasma lipoproteins and tissue fatty acid profiles in cholesterol-fed hamsters. Male Golden Syrian hamsters were fed diets containing 0.2% cholesterol and 20% added fat as: 1) Control, 20% standard butter (CT); 2) 5% standard butter + 15% VA/RA-enriched butter (EB); 3) 15% standard butter + 5% partially-hydrogenated vegetable oil (VO). After 4 wk, plasma lipoproteins were isolated, cholesterol quantified, and tissue fatty acid profiles determined. Tissue concentrations of VA and RA were increased by consumption of the EB diet compared with both the CT and VO diets, whereas the VO diet increased their concentration compared with the CT diet only. Total and LDL cholesterol concentrations were significantly reduced in hamsters fed EB and VO compared with CT, whereas VLDL cholesterol concentrations were reduced in hamsters fed EB compared with those fed CT and VO. HDL cholesterol concentrations did not differ among treatments. The ratio of potentially atherogenic lipoproteins [VLDL + intermediate density lipoproteins (IDL) + LDL] to antiatherogenic HDL was significantly lower in hamsters fed VA/RA-enriched butter (0.60) than in those fed either control diet (1.70) or the diet containing partially hydrogenated vegetable oil (1.04). Thus, increasing the VA/RA concentration of butter results in a plasma lipoprotein cholesterol profile that is associated with a reduced risk of atherosclerosis.
We used a passive avoidance to active avoidance negative transfer design to investigate the contextand dose-dependent effects of glucose on reactivated memories in rats. Memory reactivation consisted of reexposing rats 24 h after passive avoidance training to contextual and learning cues that had been present during training. Immediate postreactivation glucose administration was followed 24 h later by active avoidance (discrimination reversal) training. The memory reactivation treatments were designed to reactivate the rats' memories with different degrees of fidelity. We found a direct relationship between the effectiveness of the memory reactivation treatment and the further enhancement of memory by postreactivation administration of glucose (100 mg/kg). In another experiment, we found that changes in memory strengthening or retrievability were both dose (glucose: 100, 320, or 1,000 mg/kg) and reactivation context dependent. Our results demonstrate that modulation of a reactivated memory or second experience is the combined effect of both an exogenous environmental context-dependent and an endogenous glucose-dependent memory-modulating system.
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