|
|
Nicol, C. J., Adachi, M., Akiyama, T. E., & Gonzalez, F. J. (2005). PPARgamma in endothelial cells influences high fat diet-induced hypertension. Am J Hypertens, 18(4 Pt 1), 549–556.
Abstract: BACKGROUND: Peroxisome proliferator-activated receptor gamma (PPARgamma) ligands improve human hypertension. However, the mechanism and site of this effect remains unknown, confounded by PPARgamma expression in many cell types, including endothelial cells (ECs). METHODS: To evaluate the vascular role of PPARgamma we used a conditional null mouse model. Specific disruption of PPARgamma in ECs was created by crossing Tie2-Cre+ transgenic (T2T+) and PPARgamma-floxed (fl/fl) mice to generate PPARgamma (fl/fl)T2T+ (PPARgamma E-null) mice. Conscious 8- to 12-week-old congenic PPARgamma (fl/fl)Cre- (wild type) and PPARgamma E-null mice were examined for changes in systolic blood pressure (BP) and heart rate (HR), untreated, after 2 months of salt-loading (drinking water), and after treatment for 3 months with high fat (HF) diet alone or supplemented during the last 2 weeks with rosiglitazone (3 mg/kg/d). RESULTS: Untreated PPARgamma E-nulls were phenotypically indistinguishable from wild-type littermates. However, compared to similarly treated wild types, HF-treated PPARgamma E-nulls had significantly elevated systolic BP not seen after normal diet or salt-loading. Despite sex-dependent baseline differences, salt-loaded and HF-treated PPARgamma E-nulls of either sex had significantly elevated HR versus wild types. Interestingly, rosiglitazone improved serum insulin levels, but not HF diet-induced hypertension, in PPARgamma E-null mice. CONCLUSIONS: These results suggest that PPARgamma in ECs not only is an important regulator of hypertension and HR under stressed conditions mimicking those arising in type 2 diabetics, but also mediates the antihypertensive effects of rosiglitazone. These data add evidence supporting a beneficial role for PPARgamma-specific ligands in the treatment of hypertension, and suggest therapeutic strategies targeting ECs may prove useful.
|
|
|
|
Cole, P. D., & Adamo, S. A. (2005). Cuttlefish (Sepia officinalis: Cephalopoda) hunting behavior and associative learning. Anim. Cogn., 8(1), 27–30.
Abstract: Because most learning studies in cephalopods have been performed on octopods, it remains unclear whether such abilities are specific to octopus, or whether they correlate with having a larger and more centrally organized brain. To investigate associative learning in a different cephalopod, six sexually mature cuttlefish (Sepia officinalis) participated in a counterbalanced, within-subjects, appetitive, classical conditioning procedure. Two plastic spheres (conditioned stimuli, CSs), differing in brightness, were presented sequentially. Presentation of the CS+ was followed 5 s later by a live feeder fish (unconditioned stimulus, US). Cuttlefish began to attack the CS+ with the same type of food-acquisition seizures used to capture the feeder fish. After seven blocks of training (42 presentations of each CS) the difference in seizure probability between CS+ and CS- trials more than doubled; and was found to be significantly higher in late versus early blocks. These results indicate that cuttlefish exhibit autoshaping under some conditions. The possible ecological significance of this type of learning is briefly discussed.
|
|
|
|
Zentall, T. R. (2005). Configural/holistic processing or differential element versus compound similarity. Anim. Cogn., 8(2), 141–142.
Abstract: Before accepting a configural or holistic account of visual perception, one should be sure that an analytic (elemental) account does not provide an equal or better explanation of the results. I suggest that when one forms a compound of a color and a line orientation with one element previously trained as an S+ and the other as an S-, the resulting transfer found will depend on the relative salience of the two elements, and most important, the similarity of the compound to each of the training stimuli. Thus, if a line orientation is placed on a colored background (a separable compound), it will appear more like the colored field used in training, and color will control responding. However, if the line itself is colored (an integral compound), the compound will appear more like the line used in training, and line orientation will control responding. Not only does this account do a better job of explaining the data but it is simpler and it is testable.
|
|
|
|
Lansade, L., Bertrand, M., & Bouissou, M. - F. (2005). Effects of neonatal handling on subsequent manageability, reactivity and learning ability of foals. Appl. Anim. Behav. Sci., 92(1-2), 143–158.
Abstract: Behaviour is an important factor to be taken into account in the various uses of horses. Today horses are mainly used for sport and leisure activities. They should therefore be easy to manage, calm and not fearful. Early handling is known to improve manageability and learning ability and to reduce fearfulness in various species. It has become fashionable in the horse industry to use an early training procedure, referred to as “imprint training”, which is said to produce durable if not permanent effects. However, no studies concerning the long-term effects of such neonatal handling have been carried out in horses. The present study examines the short- and long-term effects of neonatal handling on manageability, general reactivity and learning ability of foals. Twenty-six Welsh foals were studied: 13 were handled daily for 14 days from birth and 13 were non-handled controls. The handling procedure consisted of fitting a halter, gently patting all parts of each foal's body, picking up feet and leading over 40 m. Two days, 3 months, 6 months and 1 year after the end of the handling period, foals underwent behavioural tests to measure their manageability and various aspects of their reactivity. The results showed that neonatal handling has only short-term effects on manageability: 2 days after the handling period, handled animals were significantly easier to handle than controls for the four parameters measured during this test (time to fit a halter, time to pick up feet, walk ratio that is time during which foal walks under constraint/total time measured during leading and number of defensive reactions). Two parameters (time to fit a halter and walk ratio) were still lower in handled foals than in non-handled foals 3 months later and only one 6 months later (walk ratio). One year later there was no difference between groups. In addition, there was no effect of handling on reactivity at any time of testing or in any of the tests (reaction to isolation from conspecifics, presence of a human, presence of a novel object and to a surprise effect). Finally, neonatal handling did not improve the spatial or discriminative learning abilities measured at 14 months of age. To conclude, the effects of neonatal handling are only temporary.
|
|
|
|
Stevens, J., Vervaecke, H., de Vries, H., & Van Elsacker, L. (2005). The influence of the steepness of dominance hierarchies on reciprocity and interchange in captive groups of bonobos (Pan paniscus). Behaviour, 142(7), 941–960.
Abstract: Biological market models explain variability in reciprocity and interchange between groups. In groups with a shallow dominance gradient, grooming will be mostly exchanged for itself (i.e. exchange will occur). In groups with steep dominance hierarchies, interchange is expected: individuals will groom higher ranking individuals to get access to limited resources or commodities such as support in conflicts, and grooming will be traded for these commodities. We examine patterns of reciprocity in grooming and support, and of interchange of grooming for support or for tolerance in six captive groups of bonobos. We test whether differences between groups in patterns of reciprocity and interchange can be attributed to differences in a measure of steepness of dominance hierarchies, which is based on dyadic agonistic interactions. We found that grooming was reciprocal in some, but not all groups. Support was highly reciprocal, but this was a side effect of dominance in most groups. Interchange between grooming and support was observed in some groups. Corroborating earlier findings, this was a side effect of individuals preferring high ranking individuals as grooming and support partners, possibly because these high-ranking individuals provide more efficient support in conflicts. There was no evidence for interchange of grooming for tolerance. Variability in grooming reciprocity was explained by differences in steepness of dominance hierarchies, as predicted by the biological market models. In groups with a shallow dominance hierarchy, grooming was more reciprocal. This was not true for reciprocity in support. There was some evidence that individuals groomed dominants more frequently in groups with a steep dominance hierarchy. The variation in interchange relations between grooming and support did not depend on the steepness of dominance hierarchies. We suggest that grooming in itself is a valuable commodity in bonobos, especially under captive conditions, which can be exchanged reciprocally. Bonobos may interchange grooming for another value equivalent, with food sharing as a very likely candidate. This interchange effects seem more dependent on potential to monopolise food than on steepness of dominance hierarchies per se.
|
|
|
|
Fripp, D., Owen, C., Quintana-Rizzo, E., Shapiro, A., Buckstaff, K., Jankowski, K., et al. (2005). Bottlenose dolphin (Tursiops truncatus) calves appear to model their signature whistles on the signature whistles of community members. Anim. Cogn., 8(1), 17–26.
Abstract: Bottlenose dolphins are unusual among non-human mammals in their ability to learn new sounds. This study investigates the importance of vocal learning in the development of dolphin signature whistles and the influence of social interactions on that process. We used focal animal behavioral follows to observe six calves in Sarasota Bay, Fla., recording their social associations during their first summer, and their signature whistles during their second. The signature whistles of five calves were determined. Using dynamic time warping (DTW) of frequency contours, the calves' signature whistles were compared to the signature whistles of several sets of dolphins: their own associates, the other calves' associates, Tampa Bay dolphins, and captive dolphins. Whistles were considered similar if their DTW similarity score was greater than those of 95% of the whistle comparisons. Association was defined primarily in terms of time within 50 m of the mother/calf pair. On average, there were six dolphins with signature whistles similar to the signature whistles of each of the calves. These were significantly more likely to be Sarasota Bay resident dolphins than non-Sarasota dolphins, and (though not significantly) more likely to be dolphins that were within 50 m of the mother and calf less than 5% of the time. These results suggest that calves may model their signature whistles on the signature whistles of members of their community, possibly community members with whom they associate only rarely.
|
|
|
|
Lonsdorf, E. V. (2005). Sex differences in the development of termite-fishing skills in the wild chimpanzees, Pan troglodytes schweinfurthii, of Gombe National Park, Tanzania. Anim. Behav., 70(3), 673–683.
Abstract: By the age of 5.5 years, all of the young chimpanzees of Gombe National Park have acquired a skill known as 'termite fishing'. Termite fishing involves inserting a flexible tool made from vegetation into a termite mound and extracting the termites that attack and cling to the tool. Although tool use is a well-known phenomenon in chimpanzees, little is known about how such skills develop in the wild. Prior studies have found adult sex differences in frequency, duration and efficiency of tool-using tasks, with females scoring higher on all measures. To investigate whether these sex differences occurred in youngsters, I performed a 4-year longitudinal field study during which I observed and videotaped young chimpanzees' development of the termite-fishing behaviour. Critical elements of the skill included identifying a hole, making a tool, inserting a tool into a hole and extracting termites. These elements appeared in the same order during the development of all subjects, but females typically peaked at least a year earlier than males in their performance of the skills that precede termite fishing. In addition, young females successfully termite-fished an average of 27 months earlier than young males and were more proficient at the skill after acquisition had occurred. Furthermore, the techniques of female offspring closely resembled those of their mothers whereas the techniques of male offspring did not, suggesting that the process by which termite fishing is learned differs for male and female chimpanzees.
|
|
|
|
Earley, R. L., Druen, M., & Alan Dugatkin, L. (2005). Watching fights does not alter a bystander's response towards naive conspecifics in male green swordtail fish, Xiphophorus helleri. Anim. Behav., 69(5), 1139–1145.
Abstract: Bystanders are capable of extracting cues from signalling interactions between others and appear to use information gained via eavesdropping when confronted with the watched individuals. A question that has gained little attention is whether observing fights affects bystander behaviour outside the context of interacting with the watched individuals. Our aim was to determine whether watching fights elicits general changes in bystander aggression levels in Xiphophorus helleri. We manipulated the bystanders' ability to witness encounters using clear, one-way-mirror and opaque partitions. After watching (or not watching) an initial contest, the bystanders were pitted against naive conspecifics instead of the animals they had seen fight. Observing fights did not alter the bystanders' propensity to initiate aggression, escalate, or win against naive individuals, indicating that bystanders do not experience general changes in aggressive behaviour after watching a fight. Earlier work in this species, however, has shown that bystanders respond in predictable ways to individuals they have witnessed winning or losing a fight. Taken together, these data support the notion that bystanders consistently modify their behaviour towards previously watched winners or losers in response to information gained via eavesdropping. We discuss our results in light of some recent work on the behavioural and endocrinological responses triggered by watching fights and suggest that comparative approaches to understanding networking phenomena may be productive.
|
|
|
|
Zentall, T. R., & Kaiser, D. H. (2005). Interval timing with gaps: gap ambiguity as an alternative to temporal decay. J Exp Psychol Anim Behav Process, 31(4), 484–486.
Abstract: C. V. Buhusi, D. Perera, and W. H. Meck (2005) proposed a hypothesis of timing in rats to account for the results of experiments that have used the peak procedure with gaps. According to this hypothesis, the introduction of a gap causes the animal's memory for the pregap interval to passively decay (subjectively shorten) in direct proportion to the duration and salience of the gap. Thus, animals should pause with short, nonsalient gaps but should reset their clock with longer, salient gaps. The present authors suggest that the ambiguity of the gap (i.e., the similarity between the gap and the intertrial interval in both appearance and relative duration) causes the animal to actively reset the clock and prevents adequate assessments of the fate of timed intervals prior to the gap. Furthermore, when the intertrial interval is discriminable from the gap, the evidence suggests that timed intervals prior to the gap are not lost but are retained in memory.
|
|
|
|
Young, L. E., Rogers, K., & Wood, J. L. N. (2005). Left ventricular size and systolic function in Thoroughbred racehorses and their relationships to race performance. J Appl Physiol, 99(4), 1278–1285.
Abstract: Cardiac morphology in human athletes is known to differ, depending on the sports-specific endurance component of their events, whereas anecdotes abound about superlative athletes with large hearts. As the heart determines stroke volume and maximum O(2) uptake in mammals, we undertook a study to test the hypothesis that the morphology of the equine heart would differ between trained horses, depending on race type, and that left ventricular size would be greatest in elite performers. Echocardiography was performed in 482 race-fit Thoroughbreds engaged in either flat (1,000-2,500 m) or jump racing (3,200-6,400 m). Body weight and sex-adjusted measures of left ventricular size were largest in horses engaged in jump racing over fixed fences, compared with horses running shorter distances on the flat (range 8-16%). The observed differences in cardiac morphologies suggest that subtle differences in training and competition result in cardiac adaptations that are appropriate to the endurance component of the horses' event. Derived left ventricular mass was strongly associated with published rating (quality) in horses racing over longer distances in jump races (P < or = 0.001), but less so for horses in flat races. Rather, left ventricular ejection fraction and left ventricular mass combined were positively associated with race rating in older flat racehorses running over sprint (<1,408 m) and longer distances (>1,408 m), explaining 25-35% of overall variation in performance, as well as being closely associated with performance in longer races over jumps (23%). These data provide the first direct evidence that cardiac size influences athletic performance in a group of mammalian running athletes.
|
|
