Roy Martin

Effects of sophistication and motivation on the detection of malingered memory performance using a computerized forced-choice task.

The present study employed a computerized forced-choice recognition memory task, the Multi-Digit Memory Test (MDMT), to examine the effects of instructional set (i.e., dissimulation information provided subjects) and motivation (i.e., monetary incentive) on simulated malingering behavior in a group of 119 university undergraduate students and 33 patients sustaining varying severity of closed-head injury. For the nonpatient groups, a significant effect of instructional set was revealed. Motivational incentive, however, did not affect forced-choice performance. Overall, significant performance differences emerged between all groups with nonmalingering students performing nearly perfectly, the brain-injured patients performing well above chance levels, sophisticated student malingers performing at chance, and naive student malingers performing well below chance levels. These results suggest the MDMT may offer a clinically useful and convenient addition to a neuropsychological assessment when there is suspicion of feigned memory problems. These data also support the use of naive and sophisticated malingering subjects in further analog studies addressing this topic.

Prospective remembering in younger and older adults: Role of the prospective cue

In these studies, adult age differences in event-based prospective memory were examined using an adapted version of G.O. Einstein and M.A. McDaniels (1990) task. In Experiments 13, we varied prospective cue specificity by assigning a specific target word or an unspecified word drawn from a given taxonomic category. In Experiment 3, we manipulated cue typicality by presenting low or high typicality target words. Results yielded positive effects of cue specificity on prospective performance. Age effects occurred when high typicality target words served as prospective cues (Exps. 1 and 3), but younger and older adults performed comparably with moderate and low typicality words (Exps. 2 and 3). Hierarchical regression analyses indicated that age accounted for a small but significant amount of variance in prospective memory, although the contribution of age was substantially reduced after statistically controlling for recognition memory. Implications of these data for current views on prospective remembering are discussed.

Resistant Starch, Fermented Resistant Starch, and Short-Chain Fatty Acids Reduce Intestinal Fat Deposition in Caenorhabditis elegans

Obesity is a growing global public health dilemma. The objective of this project is to develop and validate a screening mechanism for bioactive compounds that may reduce body fat and promote health. Resistant starch (RS) reduces body fat in rodents. Amylose starch that has a high content of RS, endogenous compounds obtained from the ceca of amylose starch fed mice (fermented RS), and individual short-chain fatty acids (SCFA) were tested. The Caenorhabditis elegans model and Nile red staining were selected to determine the intestinal fat deposition response to bioactive components. The fluorescence intensity of Nile red was reduced to 76.5% (amylose starch), 78.8% (fermented RS), 63.6% (butyrate), or 28-80% (SCFAs) of controls, respectively (P < 0.001). The reduced intestinal fat deposition suggests reduced food intake or increased energy expenditure. C. elegans is a practical animal model to screen for bioactive compounds that may prevent or treat obesity.

Cholesterol secoaldehyde, an ozonation product of cholesterol, induces amyloid aggregation and apoptosis in murine GT1-7 hypothalamic neurons

Aldehydic products from ozonation of cholesterol and peroxidation of phospholipids have been shown to accelerate aggregation of amyloid-beta (Abeta) in vitro. Here, we show that 3beta-hydroxy-5-oxo-5,6-secocholestan-6-al (ChSeco), an ozonation product of cholesterol, induces Abeta aggregation, generation of reactive oxygen species (ROS), and cytotoxicity in murine GT1-7 hypothalamic neurons. The formation of Abeta aggregates in situ was dose-dependent at ChSeco concentrations ranging from 1 to 20 microM. The increase in insoluble Abeta aggregates at increasing concentrations of ChSeco was accompanied by a decrease in soluble Abeta as evidenced by Western blot analysis. The formation of ROS in neuronal cells was found to be dose- and time-dependent with the magnitude being higher at 20 microM compared to 10 microM ChSeco or untreated controls. The increase in ROS was associated with depletion of GSH. The cytotoxicity induced by ChSeco involved changes in phosphatidylserine translocation, DNA fragmentation, and caspase 3/7 activity that are characteristic of apoptosis. Pretreatment of neuronal cells with Trolox, a water-soluble analog of alpha-tocopherol offered partial, but significant protection against ChSeco-induced cell death, whereas, N-acetyl-L-cysteine (NAC) completely prevented the cytotoxic effects of ChSeco. NAC and Trolox were without any effects on ChSeco-induced Abeta aggregation. Fibrillogenesis inhibitors, which inhibited Abeta aggregation, did not inhibit cell death induced by ChSeco, implying that ROS generation, and not Abeta aggregation, plays a major role in the observed cytotoxicity. However, since Alzheimers and other neurodegenerative diseases are slow and progressive, the formation of Abeta aggregates in vivo by ChSeco may have long-term pathological consequences.

Improvement of Obesity Phenotype by Chinese Sweet Leaf Tea (Rubus suavissimus) Components in High-Fat Diet-Induced Obese Rats

Drinking an herbal tea to lose weight is a well-liked concept. This study was designed to examine the possible improvement of obesity phenotype by a new tea represented by its purified components, gallic acid, ellagic acid, and rubusoside (GER). Male obese-prone SD rats were given low-fat diet, high-fat diet, or high-fat diet plus GER at the dose of 0.22 g/kg of body weight for 9 weeks. GER significantly reduced body weight gain by 22% compared to the high-fat diet control group with 48% less abdominal fat gain. Food intake was not affected. Blood glucose was lowered in the GER-treated group, whereas serum triglycerides and cholesterol were significantly reduced by 50%. This improved obesity phenotype may be associated with the attenuated expression of vascular endothelial growth factor in preadipocyte 3T3-L1 cells. Although other underlying, possibly multiple, mechanisms behind the improved phenotype are largely unknown, the observed improvement of multiple obesity-related parameters by the new tea warrants further investigations.

Bacteriology of Indole Production in Shrimp Homogenates Held at Different Temperatures

Homogenized, head-on, white shrimp ( Penaeus setiferus ) were held at 4, 12 and 22°C until putrefactive spoilage occurred. Repetitive bacterial sampling was performed and 1647 bacterial isolations were made from the shrimp homogenates. Of these, 42 isolates (2.6%) produced indole. Isolates that produced indole belonged to the genera Flavobacterium (52.4%), Aeromonas (23.8%), Proteus (21.4%) and Yersinia (2.5%). No Escherichia coli were isolated. Aeromonas and Proteus exhibited proteolysis and were able to produce indole in shrimp extracts without added L-tryptophan. These organisms favored higher growth temperatures. The majority of the Flavobacterium isolates were psychrotrophic, non-proteolytic and could not produce indole in shrimp extracts without added L-tryptophan. Suppression of bacterial reproduction with antibacterial compounds inhibited indole production. Two paths of indole production are suggested based on temperature of decomposition.

Distribution of Soluble Filth in Shrimp During Processing

The objective of this research was to evaluate the distribution of soluble filth in shrimp during different stages of processing. Flies, fed a radioactive glucose isotope, were added to five pounds of headless shell-on shrimp tails (green-headless) and also to five pounds of peeled and deveined shrimp tails. The shrimp were blast frozen as five pound blocks, glazed with distilled water and stored for 10 d at -26°C. After thawing, washing, and rinsing, 44.4% of the total radioactivity from the added flies remained on the green-headless shrimp. Reconditioning of the peeled and deveined shrimp through thawing and multiple washings resulted in 18.2% retention of total activity. Even though cooking caused an additional 8.2% loss of activity, the cooked shrimp still had 10% of the original radioactivity associated with it.