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Melatonin is a hormone secreted by the pineal gland, which is known to modulate biological rhythms in mammals. This study investigated the effect of food access schedule and dietary composition on serum melatonin and pineal NAT activity in adult male Wistar rats. These rats were maintained on a 12:12 h light:dark schedule with lights on at 0800h. The rats were randomly assigned to two dietary groups. A group was simultaneously fed a protein-rich and carbohydrate-rich granulated diet and the other group fed granulated rat chow. Each dietary group was further divided based on dietary feeding schedules. Animals were fed between 0800--1600 h or fed ad libitum. The study revealed that protein intake of rats fed the dietary choice was lower with the restricted access than in the free access. In rats fed dietary choice, the nocturnal melatonin levels and pineal NAT activity were significantly lower under the restricted access feeding when compared to the ad libitum feeding schedule. This was not observed in rats fed single chow diet. In conclusion our data demonstrate that food composition does affect the nocturnal synthesis of melatonin as well as the activity of the enzyme NAT. This could be via dietary intake of tryptophan, which is a precursor melatonin synthesis in the pineal gland.

Animals can associate orosensory characteristics from food with postingestive effects and adjust meal size to prevent energy deficit. By using odor-fasting duration conditioning, two studies were conducted to test the above hypothesis. In the first study, thirteen male and eleven female adult Wistar rats were given 1.5 hours to ingest a casein-based test-meal odorized by either vanilla or chicken flavor prior to a 4-hour short-fast or a 12-hour long-fast. Rats went through the training phase with a pseudo-random sequence of six duplicates of each odor-fasting pairing over four experimental days, followed by an odor preference test. Gender differences may exist regarding hunger perception because only females were capable of adjusting meal size according to the postprandial fast duration. A second study was conducted to examine whether a sugar-rich meal can improve acquisition of anticipatory satiety through memory enhancement. Thirty-two female Sprague-Dawley rats were given either a sugar-rich or a protein-rich test-meal prior to the post-prandial fasts. Rats were conditioned in a similar fashion to the first study except that different odors were used, postprandial fasts were shortened to 3 and 10 hours, whereas training phase was elongated to eleven duplicates and followed by an extinction phase. Both dietary groups acquired the anticipatory satiety. However, probably due to the carbohydrate-induced overeating, the sugar-rich group in contrast to the protein-rich group, exhibited a delayed learning in meal-size adjustment prior to a short fast. The above studies demonstrated the existence of gender and macronutrient differences in food intake regulation.

Dietary selection involves the process of relating the postingestional consequences of eating a food to its sensory characteristics. Diet texture, the most plausible sensory characteristic affecting ingestion, may play an important role in the control of food selection. In this study, we compared the circadian rhythmicity of protein- and carbohydrate-rich diet ingestion of adult male Wistar rats presented with diets in different textural forms (high-protein powder and high-carbohydrate granular (HPP-HCG) diets vs. high-protein granular and high-carbohydrate powder (HPG-HCP) diets) during 15 days. Rats fed HPP-HCG diets selected significantly less protein (kcal) vs. rats fed HPG-HCP diets, during the 24 h, 12 h dark phase and the 4 h early and late dark phases. Carbohydrate intakes of the two dietary groups were not significantly different. Total caloric intake for HPG-HCP group was significantly higher than that of HPP-HCG group during the 24 h and 12 h dark phase. In conclusion, macronutrient-rich diets presented in different textural forms alter the circadian rhythmicity of protein-rich diet ingestion and total energy intake.

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No description available.

No description available.

This research study investigated the level of bone collagen preservation of rat femora from Liang Bua cave on the island of Flores, Indonesia, as well as conducted carbon and nitrogen stable isotopic analyses on well preserved samples. Although Flores is located in a hot intermediate tropical zone and the burial environment of the bone samples within the cave is considered less than optimal for collagen preservation, significant preservation of the bone collagen was found. Collagen yields, C:N ratio and carbon and nitrogen concentrations were investigated. However, this research study argues that carbon and nitrogen concentrations are an appropriate means to determine preservation on its own. According to the carbon and nitrogen concentration data 32 samples were considered well preserved. Carbon and nitrogen stable isotopic analyses were conducted on the 32 preserved samples. According to the carbon data a significant shift in the δ13C values from a C3 signature to a C4 signature occurred prior to 2,750 years ago. This shift is indicative of the introduction of a non-endemic C4 plant, which is believed to be either foxtail millet or sugarcane. Since this shift occurs abruptly it indicates that the introduction of agriculture to Flores occurred at one time and has continued to present day