Biomedical subjects

Stylianos Nicolaidis

Publications and source records attributed to Stylianos Nicolaidis.

4 recordsLinked to original sources

PubMed2006

Metabolic mechanism of wakefulness (and hunger) and sleep (and satiety): Role of adenosine triphosphate and hypocretin and other peptides.

The concurrent background level of metabolic activity may control state of vigilance, promoting wakefulness (and hunger) when it is low, or sleep (and satiety) when it is high. In a series of experiments, we have shown that sleep is dependent on feeding, but only because of the metabolic consequences of food ingestion. These consequences are sensed by glioneuronal populations (at least in the rostromedial hypothalamus), which probably respond to channel-bound adenosine triphosphate/diphosphate turnover (ischymetric monitoring) rather than to the binding of such downstream molecules as adenosine and cytochrome c oxidase. This basic signal is communicated to the vigilance-controlling centers by a cascade of peptidic and nonpeptidic messengers-messengers that promote wakefulness and hunger, possibly via a hypometabolic action (as in the case of neuropeptide Y or hypocretins), or somnolence and satiety, possibly via a hypermetabolic action (as in the case of leptin or certain serotonergic agents).

Adenosine Diphosphate↗

PubMed2005

Depression and neurosurgery: past, present, and future.

Neurosurgery has been used to treat depression since 1935, when open surgery was first used to isolate relatively large areas of the limbic system from the rest of the brain. Soon thereafter, more selective leucotomies were performed based on a growing knowledge of the role played by brain limbic circuitry in processing the emotions. Subsequent discovery of the effectiveness in depression of both electroconvulsive therapy and various pharmacotherapies raised serious doubts about "psychosurgical" treatments, but the introduction of stereotactic techniques revived interest in the selective-lesion, neurobiology-based approach. However, neurosurgery has only come to be regarded as an appropriate treatment of severe depression since Benabid introduced the frequency-dependent chronic electric stimulation technique. Because of its nondestructive nature, this procedure will undoubtedly be favored in the future. One can anticipate that, eventually, frequency-dependent chronic electric stimulation will be complemented by newer techniques such as microdialysis and reverse dialysis, with concomitant functional magnetic resonance imaging and/or positron emission tomography scanning, and the use of chemodes for microinfusion or for in situ insertion of reactivated-stem cells. To optimize success, these modern methods will require a new taxonomy of "depressions" based on up-to-date neurobiological criteria.

Brain↗

PubMed2002

Body weight, body composition, and energy metabolism in lean and obese Zucker rats fed soybean oil or butter.

BACKGROUND: Dietary fat composition is thought to affect body weight regulation independent of the amount of fat ingested. OBJECTIVE: We analyzed the feeding behavior, body weight gain, body composition, and energy metabolism in lean and obese rats fed a diet in which fat was in the form of either butter or soybean oil. DESIGN: Ten lean (Fa/?) and 10 obese (fa/fa) adult Zucker rats were divided into 4 groups according to a 2 x 2 experimental design. They were fed a normally balanced diet over 11 wk in which 30% of energy was either soybean oil or butter. Food intake, body weight gain, and body composition were measured. Indirect calorimetry was used to study energy metabolism at rest and in relation to feeding and activity. RESULTS: Food intake increased similarly in lean and obese rats after butter feeding. Body weight gain increased in obese rats and decreased in lean rats after butter feeding. Body weight gain in obese rats was due mainly to an increase in the weight of lean tissues besides muscle, whereas adiposity and distribution of fat between the various pads did not change. Resting metabolic rates and postprandial lipid oxidation increased in butter-fed obese rats. Lipid oxidation during exercise was not significantly different between obese and lean rats. Fat oxidation increased in butter-fed lean rats during treadmill running at moderate intensity. CONCLUSIONS: In obese rats, basal metabolism and postprandial lipid oxidation increased during butter feeding, which appeared to prevent fat accumulation in the long term. In lean rats, butter feeding favored lipid utilization by working muscles, an observation that deserves further investigation in terms of endurance and performance.

Animals↗

PubMed2002

Behavioral, plasma, and calorimetric changes related to food texture modification in men.

We hypothesized that food texture modifications might alter anticipatory reflexes, feeding behavior, and the postabsorptive consequences of ingestion. Two sets of complete meals with different textures but the same macronutrient composition were prepared. The first set was either a soup containing chunks of food (mixture) or the same soup blended until smooth (purée). The second set was either a rusk (R), a sandwich loaf (SL), or a liquid rusk meal (LR). We measured hunger and fullness feelings after ingestion of each food in a calibrated lunch, the ingestion rate, the duration between lunch and a spontaneous dinner request, the energy value, and the macronutrient composition of the ad libitum dinner. We also studied plasma modifications and respiratory gas exchanges from lunch to dinner. Feelings of hunger and fullness were not affected by texture modifications. The purée soup was consumed faster than the mixture (P < 0.05), and insulin, triacylglycerol, and energy expenditure were greater with the purée (P < 0.05). LR was less palatable than the other rusk lunch versions (P < 0.001), and R was ingested more slowly (P < 0.05). The lowest increase in plasma glucose occurred with SL, and the highest energy expenditure was seen with LR (P < 0.05). In humans, food texture modification affects not only eating patterns and palatability of ingestants but also metabolic management.

Adult↗