Effect of limited access to sucrose on overeating and patterns of feeding

Four groups of adult rats, housed on a 12-12, light-dark cycle, were allowed access to a nutritionally complete diet and water. Three of these groups were also offered a 32% solution of sucrose. The sucrose was available for either the 24-hour period, the 12 hours of light or the 12 hours of dark. Access to sucrose led to overeating and excessive weight gain. These effects were more pronounced when the sucrose was available for the 24-hour period or during the dark. Limited access to sucrose produced a reversal of the rat's usual circadian pattern of feeding when the sucrose was available during the light and increased the rat's nocturnal hyperphagia when it was available during the dark. Sucrose intake and the proportion of calories taken from sucrose were higher in the 24-hour access group and the dark access group than the light access group. Access to sucrose did not induce a pattern of dietary selection that compromised growth or health. It appears that access to a palatable carbohydrate solution can lead to overeating and major changes in the circadian organization of feeding behavior. These data emphasize the potent role that external factors can play in the control of ingestive behavior.     

Sources of behavioral deviation modeled by early color preferences in quail. III. Developmental stability and normative canalization

Successful artificial selection of quail (C. coturnix japonica) for divergent early approach preferences for, and imprintabilities to, the wavelength characteristics of otherwise identical visual stimuli decreased the trait's developmental stability. The developmental error that resulted from selecting for extreme initial preferences was associated with enhanced imprintabilities. Conversely, the developmental error that resulted from selecting for extreme imprintabilities was associated with enhanced expression of directional gene effects in extreme initial preferences. The data are attributed to selectively relaxed normative canalization of trait development, and to related enhanced expression of genetic, environmental, and stochastic influences in trait deviations.     

双相气道正压无创机械通气上呼吸道影像分析

目的应用多层螺旋CT对患者不同通气状态下上呼吸道放射性成像,证实在全身麻醉无自主呼吸的条件下,双相气道正压(bi-level positive airway pressure,BiPAP)无创机械通气能克服上呼吸道阻力,实施有效的机械通气。方法选择拟实施全身麻醉的择期手术患者10例,分别对患者清醒自主呼吸、麻醉诱导后自主呼吸停止、BiPAP无创通气时头颈部正位和侧位作螺旋CT扫描。监测扫描过程的无创血压(NIBP)、脉搏氧饱和度(SpO2)、心率(HR)、自主呼吸频率(RR)。测量上呼吸道各软组织区(软腭后区RP、舌根后区RG、会厌区EPG)的最窄气道横截面左右径、前后径线长度及相应横截面积。结果头部正位麻醉诱导后各软组织区的最窄横截面左右径、前后径线长度及相应横截面积均比清醒时缩小(P<0.05),BiPAP通气时各截面径线和面积与清醒期比较差异仍有统计学意义(P<0.05,P<0.01)。头部侧位BiPAP通气时各径线和截面积与清醒时比较,差异无统计学意义。EPG区和RG区在BiPAP通气期的侧位截面积明显比正位时增大(P<0.05,P<0.01)。诱导期正、侧位SpO2均明显下降(P<0.01);头部正位BiPAP通气时与诱导期的SpO2比较虽有改善,但差异无统计学意义(P>0.05);头部侧位BiPAP通气时SpO2较诱导期明显升高(P<0.01),基本恢复到清醒期水平(P>0.05)。结论麻醉诱导后上呼吸道的通气面积明显减少,气道通畅度下降;头颈部侧位时上呼吸道各软组织区最狭窄处的通气截面积比正位时显著改善,以会厌区最明显。无明显上呼吸道梗阻性病史的成年患者全身麻醉时,头部侧位BiPAP无创通气能克服上呼吸道阻力,实施有效的机械通气,保证通气和氧合正常。     

Behavioral Profiles of Genetically Selected Aggressive and Nonaggressive Male Wild House Mice in Two Anxiety Tests

Artificially selected aggressive (SAL) and non-aggressive (LAL) male house mice were tested in a hexagonal tunnel maze and light-dark preference (LD) box to determine if the bidirectional selection for aggressive behavior leads to a coselection for different levels of trait anxiety. The tunnel maze consists of an open, brightly lit central arena surrounded by a complex system of interconnecting tunnels. As in the LD box, animals which spend less time and are less active in the brightly illuminated section of the maze are considered to have higher anxiety levels. In the tunnel maze, the LAL mice showed more exploration and spent more time in the central arena than the SAL animals, but only during the final 2 min of the 6-min test. This reduced preference for the central arena was not due to general inactivity or a failure of the SAL to find the central arena and indicates a higher level of state anxiety in the aggressive animals. In contrast, no anxiety-like differences were found in the LD box, either for the percentage of time spent in the light compartment or for the number of crossings. SAL males actually showed higher levels of moving and rearing, and lower levels of freezing, than did LAL males.     

Seven generations of genetic selection for ethanol dependence in mice

An animal model of alcohol dependence is being produced by selecting mice for differences in severity of ethanol withdrawal seizures. Replicate lines of high-dependence (HA), low-dependence (LA), and control (CA) mice are being developed by within-family selection. After seven generations both (replicate) HA and LA lines have separated significantly. Some of the difference between the replicate pairs of HA and LA in the early generations was due to differences in ethanol consumption. This difference in consumption may be attributable to a difference in metabolic rate or activity level rather than to a difference in ethanol preference. Females are more susceptible to seizures than males; this appears to be due partly to their higher consumption of ethanol during treatment.This research was supported in part by Grant AA-03527 from the National Institute of Alcohol Abuse and Alcoholism to the University of Colorado Alcohol Research Center.     

Development of autoimmune insulitis is prevented in E alpha d but not in A beta k NOD transgenic mice

Two lines of E alpha d-expressing NOD mice were established by continuously backcrossing [E alpha d B6 transgenic mice x NOD] F1 to parental NOD or directly microinjecting the E alpha d gene into fertilized NOD eggs. Similarly, A beta k-expressing transgenic NOD mice were produced. Subsequent histological examination of pancreatic tissues revealed that autoimmune insulitis was prevented in E alpha d backcross and transgenic mice but not in A beta k transgenic mice.     

Effectiveness of divergent selection for open-field activity in rabbits and correlated response for body weight and fertility

Two lines deriving from the same rabbit stock were selected for 8 generations for high (H) or low (L) locomotor activity score in the open field (OFS). The divergent selection was most effective up to the 3rd generation in the H line and up to the 4th generation in the L line. In further generations a decrease of OFS in the H line and a floor effect (OFS = 0) in the L line were observed. The mean OFS increased significantly in consecutive trials in the H line, whereas this increase was non-significant in the L line. There was a negative and very high correlation between the latency to enter the open field and the OFS (–0.95 and –0.98 for the H and L line, respectively). The realized heritability of the OFS was 0.46 and 0.23 in generations 0–3 within the L and H line, respectively, and 0.44 and –0.06 in generations 0–8. As calculated on the basis of divergent selection, the heritability was 0.31 and 0.15 for generations 0–3 and 0–8, respectively. The L rabbits were heavier shortly before (4th wk, P < 0.001) and after (8th wk, P < 0.01) weaning, than those of the H line, whereas the H rabbits grew faster (P < 0.05) between the 4th and 20th wk of age. There was a tendency for decreasing weight gains in consecutive generations. Generally, a lower percentage of H females delivered litters than those of the L line, but this was due to a very low percentage of such females in the 3rd and 6th generations. It can be assumed that H and L lines represent different, i.e., active and passive, coping strategies. These lines of rabbits offer increased possibilities for physiologically and ethologically oriented studies, e.g., on the welfare of caged animals.     

Effect of the serotonin agonist buspirone on behaviour and hypothalamic-pituitary-adrenal axis in confident and fearful mink

Behavioural and hypothalamic-pituitary-adrenal (HPA) axis responses were investigated in farm mink (Mustela vison) selected for either confident or fearful behaviour for nine generations.Two groups of 2-year-old confident (n=12) and fearful (n=12) female mink were given the serotonin (5-HT) 1A receptor agonist buspirone (1.25 mg/kg/day), whereas two other groups of 2-year-old confident (n=12) and fearful (n=12) female mink were given saline, continuously for 5 weeks via osmotic minipumps. Behavioural reactions towards a novel object and towards humans were tested after 19-25 days, and HPA axis reactivity [adrenocorticotropic hormone (ACTH), cortisol] was measured after 28-31 days of treatment. Confident mink were more exploratory than fearful mink towards humans and a novel object. Confident mink spent more time in contact with the object than did fearful mink during saline-but not during buspirone-treatment. buspirone increased approach-withdrawal conflict behaviour towards a object in fearful mink only. The chronic dose of buspirone did not reduce fear towards humans and did not affect latencies to reaction, number of contacts, number and duration of manipulations, and stereotypic behaviour in a Novel Object test. Different HPA axis responses have emerged between confident and fearful mink, together with a different degree of fear-related behaviour. Fearful mink have a higher cortisol combined with a lower ACTH secretion than confident mink in response to capture and blood sampling. The central serotonergic system may be involved, and even though the precise underlying mechanisms are presently unknown, treatment with a 5-HT(1A) receptor agonist reduces the difference between confident and fearful mink in HPA axis reactivity.     

Dopamine in the orbitofrontal cortex regulates operant responding under a progressive ratio of reinforcement in rats

Prefrontocortical dopamine (DA) plays an essential role in the regulation of cognitive functions and behavior. The orbitofrontal cortex (OFC) receives a dopaminergic projection from the ventral tegmental area and is particularly important for goal-directed appetitive behaviors and for the neural representation of reward value. We here examined the effects of DA receptor blockers locally infused into the OFC, on instrumental behavior under a progressive schedule of reinforcement. After continuous reinforcement training (lever pressing for casein pellets) rats received bilateral intra-OFC-infusions of the DA D1-receptor antagonist SCH23390 (3 μg/0.5 μl), the DA D2-receptor antagonist sulpiride (3 μg/0.5 μl), or phosphate buffered saline through chronically indwelling cannulae. Immediately after infusion they were tested under a time-constrained progressive ratio schedule of reinforcement (3, 6, 9, 12, … lever presses for 1 casein pellet within 180 s). Both SCH23390 and sulpiride led to a significant reduction of the break point (cessation to respond to the increasing criterion of instrumental effort) compared to vehicle infusions. A food preference test revealed no drug effects on the amount of consumed pellets and on the preference of casein pellets over laboratory chow. Leftward shifts of the break point in progressive ratio tasks indicate a disturbance of the mechanisms that translate motivation into appetitive behavior under conditions of increasing instrumental effort. Therefore, our data indicate that orbitofrontal dopamine is necessary for reward-related instrumental behavior.     

Inbreeding Affects Female Preference for Symmetry in Computer-Animated Sticklebacks

Fluctuating asymmetries are small random deviations from perfect symmetry in bilateral traits caused by the inability of individuals to cope with stress during development. The degree of asymmetry of secondary sexual characters is supposed to convey information about a male's phenotypic and/or genetic quality, and females are thus expected to use bilateral symmetry as a cue in mate choice. We offered female three-spined sticklebacks (Gasterosteus aculeatus L.) that had been inbred for one generation and outbred control females the choice between computer-animated male models differing exclusively in the symmetry of their pelvic spines. Inbred females exhibited a significantly stronger preference for the symmetric model than outbred females, suggesting that females of relatively poor quality are more prepared to pay the costs of choosiness and obtain higher marginal benefits from their discrimination than females of better quality.