Satiety, hunger and regional brain content of cholecystokinin/gastrin and met-enkephalin immunoreactivity in sheep

Cholecystokinin (CCK) and met-enkephalin (MEK) related peptides have been shown to alter feeding behavior subsequent to their injection into the peripheral circulation or directly into the brains of several species. To evaluate the potential role of endogenous brain pools of these peptides in feeding, groups of sheep were sacrificed either immediately following a meal (satiated) or after various intervals of food deprivation (hungry). Content of CCK-gastrin immunoreactivity in the anterior hypothalami of satiated sheep was elevated compared to 2, 4, or 24 hours of food deprivation. Content of MEK increased progressively with longer intervals of fasting (4 and 24 hours) in the amygdala and basomedial hypothalamus, whereas olfactory bulb content decreased with a similar time course. The results support a potential role for anterior hypothalamic CCK/gastrin in behaviors of satiety, whereas MEK neurons of limbic/rhinencephalic regions appear to form part of a separate circuit gradually activated by increasing hunger. Results are discussed in terms of potential target regions of the peptides, as well as the regional levels and feeding response of sheep as compared to available data from other species.     

Effects of Ramadan upon Fluid and Food Intake,Fatigue, and Physical,Mental, and Social Activities: A Comparison between the UK and Libya

Two studies were performed during Ramadan, one in the UK (N=31) and the other in Libya (N=33). The aims were to assess some changes to lifestyle that are produced by fasting as well as effects due to culture. Subjects were studied on eight separate occasions: four control days (two before and two after Ramadan) and four days during the four weeks of Ramadan itself. A questionnaire was answered that asked about naps and fluid and food intake. The questions elicited if an individual had slept, drank, or eaten, plus the reasons for doing or not doing so. Also, subjects were asked to describe their physical, mental, and social activities, their fatigue, and their perceived abilities to perform physical or mental work. The questionnaire was answered five times per day: at sunrise, at 10:00 h, at 14:00 h, at sunset, and on retiring to sleep at night. Urine samples were collected at sunset and measured for osmolality. Differences between control and Ramadan days, as well as between subjects studied in UK and Libya, were assessed by analysis of variance. Correlations between fatigue and physical, mental, and social activities were also assessed, as were differences in urine osmolality. Fasting during Ramadan resulted in fewer activities and increased fatigue and frequency of napping during daytime. Changes in fluid and food intake indicated some degree of preparation for fasting before sunrise and a marked “recuperation” from fasting after sunset. The reasons given for napping in the daytime, for drinking or not drinking, and for eating or not eating, changed during Ramadan compared with control days; as a result, links between fatigue and activities, and fatigue and fluid and food intake, were all altered during Ramadan, particularly after sunset. Subjects become dehydrated during the daytime, but this was not reduced when females who were menstruating drank during this time. Several differences between the two studies were found. There was a greater frequency of napping during the daytime in the Libya study, and evidence for the conservation of energy during the daytime and reduced physical, mental, and social activities. Subjects' preparations for fasting and recovering from it—their fluid and food intakes and associated reasons for these—also differed. Possible explanations of these differences are discussed. (Author correspondence: waterhouseathome@hotmail.com)     

Nutritional state influences shoaling preference for familiars

Preferences for grouping with familiar individuals are shown in many animal species, including the three-spined stickleback (Gasterosteus aculeatus). Shoaling with familiars is advantageous because of more precise anti-predator behaviours or more stable dominance hierarchies. Additionally, associations with familiar individuals facilitate the evolution of altruistic behaviour. Thus, in situations of increased competition one might expect an increased preference for familiar fish. We gave single juvenile sticklebacks of different nutritional state the choice between shoals composed either of familiar or unfamiliar individuals. Satiated fish preferred to shoal with familiar individuals. A comparative analysis of 8 stickleback studies with 15 different tests using familiars showed that all tests gave similar results, i.e. sticklebacks of all age classes preferred to shoal with familiars in a non-sexual context. In contrast, hungry test fish did not prefer to shoal with familiar fish, but even showed a preference for the unfamiliar group. Because sticklebacks use early-life familiarity to recognize kin, the results suggest the avoidance of competition with relatives. To our knowledge, this is the first study showing an impact of nutritional state on social interactions with familiar individuals.     

Transient changes in the pattern of food intake following a simulated time-zone transition to the east across eight time zones

Twelve healthy adults were studied, singly or in groups of up to four, in an Isolation Unit before (control days) and for 3 days after a simulated time-zone transition to the east across 8 time zones (the clock being changed from 15:00 to 23:00 h). Subjects were free to choose how to pass their waking hours (though naps were forbidden), and to eat what and when they wanted. A wide selection of food was provided, though the subjects had to prepare it. Subjects completed food intake questionnaire on waking and at 3 h intervals during the waking day. This questionnaire assessed the reasons for choosing not to eat a meal or, if a meal was eaten, the reasons for doing so, the type of meal chosen and the reasons for this choice, and subjective responses to the meal (hunger before, enjoyment during, and satiety afterwards). Subjects also recorded the incidence and degree of indigestion and jet lag at 3 h intervals after the time-zone transition. Following the time-zone transition, the subjects experienced significant amounts of jet lag and recorded a significant increase in the incidence of indigestion. They also showed significant changes in their pattern of food intake, but, whereas the patterns of food intake were no longer significantly different from control days by the third post-shift day, the symptoms of jet lag and indigestion were still present then. The distribution of daytime meals was significantly affected on the first post-shift day, with a redistribution of the times that the main, hot meals were eaten; these times indicated some influence of an unadjusted body clock. On this day also, the reasons for determining food intake continued to be dominated by hunger and appetite (hunger even increasing in the frequency with which it was cited), and the reason for not eating a meal, by a lack of hunger. On both control and post-shift days, there was a marked effect of meal type upon the responses to food intake, with cold food being rated least and large hot meals most when appetite before the meal, enjoyment during it, and satiety afterward were considered. However, evidence suggested that the degree to which larger hot meals were preferred to cold meals was significantly less marked after the time-zone transition. On control days, sleep was unbroken; whereas, after the time-zone transition, all subjects woke on at least one of the 3 nights studied. During the first post-shift night, about half of the subjects ate a meal, the reason given being that they were “hungry.” On those occasions when subjects woke but did not eat a meal, the reason cited was because they “could not be bothered” as frequently as because they were “not hungry.”. A simulated time-zone transition is associated with significant changes to the incidence of indigestion, pattern of food intake, and subjective responses to food. However, these changes are generally transient and are only weakly linked to the sensation of jet lag.     

饥饿胁迫对小鼠学习记忆、SOD和心肌丙二醛的影响

给小鼠断绝食物,观察小鼠学习记忆能力的变化及生理应激反应。结果表明,饥饿后小鼠的体重明显减轻,学习能力明显增强,记忆能力和大脑5－羟色胺含量无明显改变,心肌丙二醛含量下降,肝组织超氧化物歧化酶（SOD）活性无明显改变,血浆SOD活性提高,血浆SOD同工酶变带无明显改变。提示饥饿胁迫使小鼠产生适应性的生理反应,使小鼠学习能力提高,加强延缓机体衰退的生理功能;这些应激反应有利于小鼠在逆境下的生存。     

Energetic stress in the honeybee Apis mellifera from Nosema ceranae infection

Parasites are dependent on their hosts for energy to reproduce and can exert a significant nutritional stress on them. Energetic demand placed on the host is especially high in cases where the parasite-host complex is less co-evolved. The higher virulence of the newly discovered honeybee pathogen, Nosema ceranae, which causes a higher mortality in its new host Apis mellifera, might be based on a similar mechanism. Using Proboscis Extension Response and feeding experiments, we show that bees infected with N. ceranae have a higher hunger level that leads to a lower survival. Significantly, we also demonstrate that the survival of infected bees fed ad libitum is not different from that of uninfected bees. These results demonstrate that energetic stress is the probable cause of the shortened life span observed in infected bees. We argue that energetic stress can lead to the precocious and risky foraging observed in Nosema infected bees and discuss its relevance to colony collapse syndrome. The significance of energetic stress as a general mechanism by which infectious diseases influence host behavior and physiology is discussed.     

The relative importance of refugia in determining the drift and habitat selection of predaceous stoneflies in a sandy-bottomed stream

Patch structure in sandy, compared to rocky streams, is characterized by isolated snags that can only be colonized by drifting. By measuring drift from patches (snags) of various quality we determined the factors that influence habitat selection and drift of the predaceous stoneflies Acroneuria abnormis and Paragnetina fumosa. The presence of refugia (loose bark and leaf packs) was more important than hunger level and modified the effects of increased predator densities and aggressive interactions. Stoneflies concentrated to 8x natural densities with access to refugia remained longer on snags than a single stonefly without access to refugia. During periods of activity, refugia were defended with larger stoneflies always displacing smaller nymphs. During long periods of inactivity, two and sometimes three nymphs would rest side-by-side sharing the same refuge. Hunger level (starved versus satiated stoneflies), an indirect measure of a predator's response to prey availability, had no significant effect on drift or habitat selection regardless of the presence of refugia. Stonefly predators had a uniform distribution while their prey were clumped. Drift was deliberate and almost always delayed until night, usually at dusk or dawn. An examination of previous research plus the results of this study suggest that non-predatory intra- and interspecific interactions can be an important mechanism causing drift in streams.     

Responses of Acilius sulcatus (Coleoptera: Dytiscidae) to chemical cues from perch (Perca fluviatilis)

In this study we tested the hypothesis that the presence of chemical stimuli from a hungry predator would initiate anti-predator responses, while stimuli from a satiated predator would not. We used chemical stimuli released from starved perch (Perca fluviatilis) and from satiated perch (predator). As prey we used adult Acilius sulcatus (Coleoptera: Dytiscidae). The reaction of the beetles to different predator conditions was tested during daytime. We also tested the reaction to starved perch during the night. A. sulcatus activity decreased when it was exposed to stimuli released from starved perch during daytime when visibility was poor, due to the presence of artificial vegetation. There was, however, no reaction to satiated perch under the same experimental conditions. These results indicate that A. sulcatus can discriminate between chemical cues from hungry and satiated fish predators. When visibility was good and the concentration of chemical cues was constant, the beetles did not react to starved perch in the daytime, but their activity decreased at night in response to stimuli released from starved perch. Visual as well as chemical cues seem to be important for detecting a potential predator. When visibility is good, beetles seem to rely on visual stimuli, while in darkness they seem to use chemical stimuli to detect the presence of predators. Received: 4 October 1996 / Accepted: 7 February 1997     

Does individual internal state affect the presence of a barrier web in Argiope bruennichii (Araneae: Araneidae)?

A barrier web created by some orb-web spiders has a three-dimensional web structure made of nonsticky threads, which is believed to provide a defensive function against predators. To test for a possible antipredatory function, we investigated relationships between the presence of a barrier web and an individuals internal state in the orb-web spider Argiope bruennichii, which builds orb-webs with and without a barrier web. Hunger level and molting as measures of internal state were represented by relative abdominal width and relative web size, respectively. Field survey showed that individuals with a wider abdomen and a smaller web tended to construct a barrier web. The positive relationship between body width and the presence of a barrier web supports the hypothesis of an antipredatory function as well-fed individuals are likely to expend more effort for defense. The small web size, however, may not be representative of molting because a correlation existed between web size and potential web substrates; therefore, the effect of molting on the presence of barrier web remains unclear.     

Trading off safety against food: state dependent habitat choice and foraging in crucian carp

The influence of hunger level and predation risk on habitat choice and foraging in crucian carp, Carassius carassius, were studied in a laboratory experiment. Experiments were carried out in aquaria with or without a predator (pike, Esox lucius). Habitat use and foraging activity of three-fish foraging groups of either fed or hungry crucian carp were studied. Fish were allowed to choose between an open (risky) habitat with Tubifex worms and a habitat with dense vegetation (safe) without food. Habitat use was significantly affected by both risk of predation and hunger level. Crucian carp spent less time in the open habitat when there was a predator present and they also spent less time there when fed than when hungry. Furthermore, there was a significant interaction between risk of predation and hunger level, indicating a state-dependent trade-off between food acquisition and predator avoidance.