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Results for “Homing Behavior”

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At least 199 records · Page 11Linked to original sources
PubMed1999

Calibration of vector navigation in desert ants.

Desert ants (Cataglyphis sp.) monitor their position relative to the nest using a form of dead reckoning [1] [2] [3] known as path integration (PI) [4]. They do this with a sun compass and an odometer to update an accumulator that records their current position [1]. Ants can use PI to return to the nest [2] [3]. Here, we report that desert ants, like honeybees [5] and hamsters [6], can also use PI to approach a previously visited food source. To navigate to a goal using only PI information, a forager must recall a previous state of the accumulator specifying the goal, and compare it with the accumulator's current state [4]. The comparison - essentially vector subtraction - gives the direction to the goal. This whole process, which we call vector navigation, was found to be calibrated at recognised sites, such as the nest and a familiar feeder, throughout the life of a forager. If a forager was trained around a one-way circuit in which the result of PI on the return route did not match the result on the outward route, calibration caused the ant's trajectories to be misdirected. We propose a model of vector navigation to suggest how calibration could produce such trajectories.

Animals↗
PubMed2001

Migratory activity and functional changes of green fluorescent effector cells before and during experimental autoimmune encephalomyelitis.

Homing behavior and function of autoimmune CD4+ T cells in vivo was analyzed before and during EAE, using MBP-specific T cells retrovirally engineered to express the gene of green fluorescent protein. The cells migrate from parathymic lymph nodes to blood and to the spleen. Preceding disease onset, large numbers of effector cells invade the CNS, with only negligible numbers left in the periphery. In early EAE, most (>90%) infiltrating CD4+ cells were effector cells. Migratory effector cells downregulate activation markers (CD25, OX-40) but upregulate several chemokine receptors and adsorb MHC class II on their membranes. Within the CNS, the effector cells are reactivated, with upregulated proinflammatory cytokines and downmodulated T cell receptor-associated structures, presumably reflecting autoantigen recognition in situ.

Animals↗
PubMed1989

Central-place foraging by Rattus norvegicus on a radial maze.

We studied central-place foraging in rats (Rattus norvegicus) by placing food items that varied in size and weight at the ends of a 4-arm radial maze. In Experiments 1-3, rats increasingly tended to carry food to the center of the maze as the size of those items increased. Very large food items often were hoarded in the center. Rats consumed food faster on the arms than in the center, and rats traveled faster when carrying food than when not. Blocking arm entrances increased travel time between the center and the arms and decreased food carrying at every item weight except the largest. In Experiments 4-6, important conditions that influence the degree of food-carrying behavior were discovered; these were the intersection of maze arms, the presence of a conspecific, and the use of open vs. closed maze arms.

Animals↗
PubMed2006

Patient re-training in peritoneal dialysis: why and when it is needed.

The aim of this multicenter, quantitative, observational study was to analyze compliance and re-training needs of patients on peritoneal dialysis (PD) through the assessment of patient knowledge (with a Patient Questionnaire; phase 1) and patient behavior (home visit with a Score Card; phase 2). A total of 353 patients from 11 Italian centers participated in the first phase and 191 patients from nine centers in the second phase. Overall, 66% of questions on the Patient Questionnaire were answered correctly. Correct answers were more frequent in females than males, in patients under 55 years of age, and in those with higher education. The lowest rate of correct answers involved questions related to diet and physical activity (67% and 51%, respectively). Data collected during the home visit showed that 25% of patients were partially compliant with their drug therapy. Twenty-three percent of patients were non-compliant with the exchange protocol procedures, with a significant association between compliance and the incidence of peritonitis, and 11% were non-compliant with the exit-site protocol procedures without a statistically significant correlation to peritonitis. By combining the two evaluations, we found that approximately one-third (29%) of patients needed reinforcement of knowledge and ability to correctly perform PD as related to infection control and 27% for the correct use of drugs. Looking at the combined evaluation of infection control and drug use, results showed that 47% of patients needed re-training. This need for re-training was greater for younger patients (less than 55 years old), patients with lower education degree and patients in the early or late phase of PD therapy (less than 18 months or more than 36 months). Gender and degree of autonomy had no effect on the need for re-training.

Aged↗
PubMed2002

What do you do when they grow up? Approaches to seizures in developmentally delayed adults.

Epilepsy and developmental disabilities (DD) often occur together but affect individuals differently and have a complex causal relationship. Most epilepsy in the population with DD is partial or symptomatic generalized. Seizures and antiepileptic drugs (AEDs) can further delay development, and the DD can complicate treatment and adjustment to epilepsy. Medical care and decision making require careful coordination of health care providers and the family, especially because of the trend for the patients to live in group homes. Behavioral and psychiatric disorders are difficult to diagnose but common in those with DD and epilepsy; psychiatric disorders are perhaps up to sevenfold higher in this group than in the general population. Psychotropic medications-antidepressants, anxiolytics (but use caution with benzodiazepines), antipsychotics, and stimulants-are appropriate for those with psychiatric disorders. Diagnostic difficulties may lead to undertreatment, and the motivation to lessen certain behaviors may lead to overtreatment. Because those with DD may be unusually sensitive to adverse effects of both seizures and AEDs, cognitive and behavioral side effects must be carefully monitored. Few relevant studies exist. For some patients, comorbid psychiatric disorders may be treated with one AED, such as carbamazepine, lamotrigine, or valproate. Phenobarbital and phenytoin may be inappropriate for those with epilepsy and DD. Studies have shown some success with oxcarbazepine (for partial and generalized epilepsy) and with adjunctive lamotrigine. For those on medication regimens, perhaps taking combinations of drugs for numerous years, queries about earlier attempts to reduce AEDs and gradual efforts to substitute less toxic mediations are worthwhile. Vagus nerve stimulation and epilepsy surgery for those with medically refractory epilepsy may be options after careful evaluation.

Adult↗
PubMed2004

How far do animals go? Determinants of day range in mammals.

Day range (daily distance traveled) is an important measure for understanding relationships between animal distributions and food resources. However, our understanding of variation in day range across species is limited. Here we present a day range model and compare predictions against a comprehensive analysis of mammalian day range. As found in previous studies, day range scales near the 1/4 power of body mass. Also, consistent with model predictions, taxonomic groups differ in the way day range scales with mass, associated with the most common diet types and foraging habitats. Faunivores have the longest day ranges and steepest body mass scaling. Frugivores and herbivores show intermediate and low scaling exponents, respectively. Day range in primates did not scale with mass, which may be consistent with the prediction that three-dimensional foraging habitats lead to lower exponents. Day ranges increase with group size in carnivores but not in other taxonomic groups.

Animals↗
PubMed2002

Association patterns and shoal fidelity in the three-spined stickleback.

We investigated pairwise association patterns and shoal fidelity in free-ranging, individual three-spine sticklebacks (Gasterosteus aculeatus) by capturing entire shoals of sticklebacks and tagging each shoal member with a unique individual mark before releasing the shoal at the point of capture. We recaptured tagged fishes in the study area on five subsequent days, noting their identity, their location and the individuals with which they were associated. Stable partner associations between fishes were observed which might provide the basis for shoal fidelity via social networks. These results suggest the potential for the kinds of inter-individual association patterns assumed by models of predator inspection and 'tit-for-tat' behaviours in free-ranging fishes.

Animals↗
PubMed2006

Scale-free foraging by primates emerges from their interaction with a complex environment.

Scale-free foraging patterns are widespread among animals. These may be the outcome of an optimal searching strategy to find scarce, randomly distributed resources, but a less explored alternative is that this behaviour may result from the interaction of foraging animals with a particular distribution of resources. We introduce a simple foraging model where individual primates follow mental maps and choose their displacements according to a maximum efficiency criterion, in a spatially disordered environment containing many trees with a heterogeneous size distribution. We show that a particular tree-size frequency distribution induces non-Gaussian movement patterns with multiple spatial scales (Lévy walks). These results are consistent with field observations of tree-size variation and spider monkey (Ateles geoffroyi) foraging patterns. We discuss the consequences that our results may have for the patterns of seed dispersal by foraging primates.

Animals↗
PubMed1996

Promotion of children's early psychosocial development through primary health care services.

The paper presents the study design of the development and organisation of an EU/WHO multicentre study on the promotion of children's early psychosocial development through primary health care services. The aim of the programme is to develop training for primary health care workers (PHCWs) that improves their ability to assess factors relevant to psychosocial development and gives them preventive approaches to foster that development, building on families' strengths. The focus is on the period from conception to the end of the second year of the child's' life. Two main components are the training of the PHCWs and the semi-structured interviews that guide the workers in practice. The training has content and structure that is feasible within primary health care resources working in collaboration with mental health services. The programme is evaluated in terms of (a) the impact of training on both the PHCWs' knowledge and attitudes with regard to infant behaviour and development, and on practice as assessed by the delivery of the semi-structured interview; and (b) the effect of the intervention on maternal well-being, infant language development and behavior, home environment and mother-infant interaction. The programme is taking place in Cyprus, Greece, the Federal Republic of Yugoslavia, Portugal, Slovenia and Turkey.

Child Development↗
PubMed1982

Range use of gray langurs in highland Nepal.

A 16-month study of foraging and ranging among gray langurs (Presbytis entellus) in the Nepal Himalaya revealed that these animals range over larger areas than other gray langurs so far studied and that they show great seasonal differences in foraging and ranging. A summer monsoon and winter dry season characterize the Himalayan climate. During summer, broadleaf forest provides the basic foraging substrate for the langurs, and when its resources fail during the winter dry season, they radically shift their diet and feed largely in meadow, range over wider areas, use their range more evenly and make longer day journeys. It is hypothesized that the ability of the langurs to make these changes in response to the dry season is vital to their survival at the study site.

Adaptation, Physiological↗
PubMed2004

Differential gene expression by integrin beta 7+ and beta 7- memory T helper cells.

BACKGROUND: The cell adhesion molecule integrin alpha 4 beta 7 helps direct the migration of blood lymphocytes to the intestine and associated lymphoid tissues. We hypothesized that beta 7+ and beta 7- blood memory T helper cells differ in their expression of genes that play a role in the adhesion or migration of T cells. RESULTS: RNA was prepared from beta 7+ and beta 7- CD4+ CD45RA- blood T cells from nine normal human subjects and analyzed using oligonucleotide microarrays. Of 21357 genes represented on the arrays, 16 were more highly expressed in beta 7+ cells and 18 were more highly expressed in beta 7- cells (>/=1.5 fold difference and adjusted P < 0.05). Several of the differentially expressed transcripts encode proteins with established or putative roles in lymphocyte adhesion and chemotaxis, including the chemokine receptors CCR9 and CCR10, the integrin alpha 4 subunit, L-selectin, KLRB1 (CD161), NT5E (CD73), LGALS1 and LGALS2 (galectin-1 and -2), and RGS1. Flow cytometry was used to determine whether differences in levels of transcripts encoding cell surface proteins were associated with differential expression of those proteins. Using this approach, we found that surface expression of KLRB1, LAIR1, and NT5E proteins was higher on beta 7+ memory/effector T cells than on beta 7- cells. CONCLUSIONS: Memory/effector T cells that express integrin beta 7 have a distinct pattern of expression of a set of gene transcripts. Several of these molecules can affect cell adhesion or chemotaxis and are therefore likely to modulate the complex multistep process that regulates trafficking of CD4+ memory T cell subsets with different homing behaviors.

Adult↗