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At least 721 records · Page 40Linked to original sources
PubMed1992

Increased plasma FFA uptake and oxidation during prolonged exercise in trained vs. untrained humans.

We studied the effect of local muscle adaptations on free fatty acid (FFA) metabolism during prolonged exercise in trained and untrained subjects. Six trained (T) and six untrained (UT) young human males exercised for 3 h at 60% of their individual maximal dynamic knee extension capacity. The contribution of blood and plasma metabolites as well as intramuscular substrates to oxidative metabolism in the thigh was calculated from arteriovenous differences and femoral-venous blood flow as well as from muscle biopsies in subjects that were continuously infused with [1-14C]palmitate. Arterial plasma FFA concentration increased over time in both T and UT. Fractional uptake of FFA across the thigh remained unchanged over time in T (15%) but decreased in UT (from 15 to 7%), especially during the last hour of exercise. Thus FFA uptake increased linearly over time in T (96 +/- 20 to 213 +/- 20 mumol.min-1.kg-1), whereas it leveled off after 2 h in UT (74 +/- 16 to 133 +/- 46) even though FFA delivery increased similarly in T and UT. Percentage oxidation was similar in T and UT; thus total FFA oxidation was higher in T. Glucose uptake increased in both groups over time and was significantly higher in UT during the last hour of exercise. In conclusion, during prolonged knee extension exercise, FFA uptake increases linearly with FFA delivery in the trained thigh, whereas in the untrained thigh uptake becomes saturated with time. This difference partly explains the increased lipid oxidation in T vs. UT and suggests, furthermore, that local muscle adaptations to training are important for the utilization of FFA during prolonged exercise.

3-Hydroxybutyric Acid↗
PubMed2001

Melatonin for preventing and treating jet lag.

BACKGROUND: Jet-lag commonly affects air travellers who cross several time zones. It results from the body's internal rhythms being out of step with the day-night cycle at the destination. Melatonin is a pineal hormone that plays a central part in regulating bodily rhythms and has been used as a drug to re-align them with the outside world. OBJECTIVES: To assess the effectiveness of oral melatonin taken in different dosage regimens for alleviating jet-lag after air travel across several time zones. SEARCH STRATEGY: We searched the Cochrane Controlled Trials Register, MEDLINE, EMBASE, PsychLit and Science Citation Index electronically, and the journals 'Aviation, Space and Environmental Medicine' and 'Sleep' by hand. We searched citation lists of relevant studies for other relevant trials. We asked principal authors of relevant studies to tell us about unpublished trials. Reports of adverse events linked to melatonin use outside randomised trials were searched for systematically in 'Side Effects of Drugs' (SED) and SED Annuals, 'Reactions Weekly', MEDLINE, and the adverse drug reactions databases of the WHO Uppsala Monitoring Centre (UMC) and the US Food & Drug Administration. SELECTION CRITERIA: Randomised trials in airline passengers, airline staff or military personnel given oral melatonin, compared with placebo or other medication. Outcome measures should consist of subjective rating of jet-lag or related components, such as subjective wellbeing, daytime tiredness, onset and quality of sleep, psychological functioning, duration of return to normal, or indicators of circadian rhythms. DATA COLLECTION AND ANALYSIS: : Ten trials met the inclusion criteria. All compared melatonin with placebo; one in addition compared it with a hypnotic, zolpidem. Nine of the trials were of adequate quality to contribute to the assessment, one had a design fault and could not be used in the assessment. Reports of adverse events outside trials were found through MEDLINE, 'Reactions Weekly', and in the WHO UMC database. MAIN RESULTS: : Nine of the ten trials found that melatonin, taken close to the target bedtime at the destination (10pm to midnight), decreased jet-lag from flights crossing five or more time zones. Daily doses of melatonin between 0.5 and 5mg are similarly effective, except that people fall asleep faster and sleep better after 5mg than 0.5mg. Doses above 5mg appear to be no more effective. The relative ineffectiveness of 2mg slow-release melatonin suggests that a short-lived higher peak concentration of melatonin works better. Based on the review, the number needed to treat (NNT) is 2. The benefit is likely to be greater the more time zones are crossed, and less for westward flights. The timing of the melatonin dose is important: if it is taken at the wrong time, early in the day, it is liable to cause sleepiness and delay adaptation to local time. The incidence of other side effects is low. Case reports suggest that people with epilepsy, and patients taking warfarin may come to harm from melatonin. REVIEWER'S CONCLUSIONS: Melatonin is remarkably effective in preventing or reducing jet-lag, and occasional short-term use appears to be safe. It should be recommended to adult travellers flying across five or more time zones, particularly in an easterly direction, and especially if they have experienced jet-lag on previous journeys. Travellers crossing 2-4 time zones can also use it if need be. The pharmacology and toxicology of melatonin needs systematic study, and routine pharmaceutical quality control of melatonin products must be established. The effects of melatonin in people with epilepsy, and a possible interaction with warfarin, need investigation.

Antioxidants↗
PubMed1982

Role of locally generated prostaglandins in adaptive gastric cytoprotection.

This study was designed to determine the role of mucosal generation of prostaglandins (PGs) in the ability of mild irritants (20% ethanol or 5% NaCl) to protect against the formation of mucosal lesions caused by necrotizing agents (100% ethanol or 25% NaCl) or acidified aspirin (ASA). Mild irritants protected damage from necrotizing agents but not from ASA. This protection was accompanied by increased mucosal generation of PGE2 and PGI2-like substances. Exogenous PGE2 and PGI2 applied topically to the gastric mucosa in a nonantisecretory dose greatly inhibited the formation of lesions induced by either necrotizing agents or ASA. Pretreatment with indomethacin, which suppressed the generation of mucosal PGs augmented formation of lesions by necrotizing agents and partly counteracted the protective effect of mild irritants. We conclude that mild irritants, and exogenous PGs inhibit the formation of gastric lesions by necrotizing agents, at least in part, by mucosal generation of PGs.

Animals↗
PubMed2004

Massively parallel networks for edge localization and contour integration--adaptable relaxation approach.

The paper describes a new adaptive neural network for edge-based pattern extraction problems. In the model, each neuron represents an edge with continuous state variables describing its location and orientation. The post-synaptic distribution is dependent on the state variables. Each neuron adjusts its state to increase its membrane potential, which results in highly adaptive dynamics of the synaptic weight distribution. The network allocates multiple neurons with different orientation modes for each edge. The strategy allows accurate modeling of multi-modal distributions at key-points such as corners and junctions. As a result, the network delineates edges at sub-pixel accuracy while preserving key-points. It is also capable of processing a sequence of images and following moving objects. The network is extended for contour integration and key-point detection tasks. The paper presents experiments conducted on both synthetic and non-synthetic data to demonstrate the effectiveness of the technique.

Artificial Intelligence↗
PubMed2003

The dynamics of local rules in hospital admission processes.

This paper reports on research into admission practices at a sub acute extended care hospital. A system dynamics simulation model of the patient flow from feeder hospitals to the hospital was built to show the impact of the local rules used by the medical registrar. Local rules are behaviours that are local, and often idiosyncratic, adaptations to the local environment. The model showed these adaptations had a significant impact on the acuity of patients being admitted as a result of the separation policies of the feeder hospitals. This patient mix in turn affected the hospital ability to meet its budget.

Admitting Department, Hospital↗
PubMed2006

A silicon retina that reproduces signals in the optic nerve.

Prosthetic devices may someday be used to treat lesions of the central nervous system. Similar to neural circuits, these prosthetic devices should adapt their properties over time, independent of external control. Here we describe an artificial retina, constructed in silicon using single-transistor synaptic primitives, with two forms of locally controlled adaptation: luminance adaptation and contrast gain control. Both forms of adaptation rely on local modulation of synaptic strength, thus meeting the criteria of internal control. Our device is the first to reproduce the responses of the four major ganglion cell types that drive visual cortex, producing 3600 spiking outputs in total. We demonstrate how the responses of our device's ganglion cells compare to those measured from the mammalian retina. Replicating the retina's synaptic organization in our chip made it possible to perform these computations using a hundred times less energy than a microprocessor-and to match the mammalian retina in size and weight. With this level of efficiency and autonomy, it is now possible to develop fully implantable intraocular prostheses.

Algorithms↗
PubMed1984

Binaural phase differences and binaural auditory adaptation.

In order to determine the relationship between binaural phase localization and auditory adaptation, subjects were asked to perform a series of phase-based localization tasks, as well as an SDLB adaptation task. A binaurally presented 400 Hz tone was used for midplane localization tasks, and adaptation balances. The tone was presented monaurally during adaptation after binaural localization and the SDLB pre-test. Following 7 min exposure, subjects readjusted phase to centre the binaural stimulus in the midline, and then adjusted intensity to determine dB of adaptation. No consistent or statistically significant change in phase settings occurred. There was a significant decline in the balance intensity as a function of adaptation. A further re-establishment of the midline by phase manipulation also showed no localization effect. For the stimulus values used in the present study, there was no inter-effect of binaural phase localization, and SDLB auditory adaptation.

Adaptation, Physiological↗
PubMed2001

[Ultrastructural localization of calcium pyroantimonate in Mauthner neurons of goldfish fry adapted to natural stimulation].

The localization of Ca2+ in control and adapted goldfish fry Mauthner cells (M-cells) revealed by sedimentation with potassium pyroantimonate technique was investigated. It has been shown the following. 1. In the control M-cells electron dense precipitates are present in the extracellular space, commonly within the active zone clefts of chemical synapses, throughout the whole apposition of the mixed synapses and in the synaptoplasm of both type afferent boutons. No precipitates were seen in the cytoplasm of M-cells. 2. After long term natural (vestibular) stimulation (LTNS), resulting in a strong functional suppression of M-cells, precipitates disappeared entirely from active zones but remained numerous in the cytoplasm of M-cells. The distribution of precipitates within the cytoplasm was non-uniform, the highest density was observed on the surfaces of intracellular organelles and elements of the cytoskeleton. 3. In fatigued M-cells after LTNS and after a subsequent one day rest the distribution of precipitates was less intensive, while in the whole it resembled that of fatigued M-cells. 4. In adapted M-cells the distribution of precipitates was similar to that observed in control. M-cells after LTNS, but the amount and size of the precipitated grains were noticeably increased. 5. The most numerous precipitates were seen in adapted M-cells after LTNS. They were localized throughout the postsynaptic cytoplasm and in a lesser order in the presynaptic cytoplasm. 6. After one day rehabilitation the intensitivity of cytochemical reaction of Ca2+ ion precipitation restored to the initial stage characteristic of adapted M-cells before LTVS. The results obtained suggest that the total concentration of Ca2+ ions in adapted M-cells and the dynamics of their exchanges between cytosole and intracellular depots, such as the smooth endoplasmic reticulum, may increase to keep a normal or even increased functional activity of M-cells, both before and after the LTNS.

Acoustic Stimulation↗
PubMedDate not supplied

Validation of a new method for stereotactic localization using MR imaging.

Magnetic resonance is recognized as potentially the best imaging procedure for localization in stereotactic neurosurgery. However, special difficulties necessitate specific adaptation to localize targets in the stereotactic frame. We developed a new method for stereotactic localization. The MR studies were performed using a 0.5 T imager. Four small boxes filled with CuSO4 solution were inserted into the intracranial holders of a Talairach frame. Using fast sequences, thirty 7-mm thick contiguous sagittal slices and twenty 5-mm thick axial slices enabled us to image the entire brain. The image data were transferred for analysis to an image processing station, including special software to handle stereotactic calculations. The accuracy of the origin of the trihedron and systematic geometrical errors were carefully evaluated using a cubic phantom, and corrective algorithms were applied when needed. Moreover, checks have been designed to detect geometrical distortion due to ferromagnetic artifacts, alterations in gradient calibration, or movements made by the patient. This localization method does not necessitate the use of stereotactic frames and appears to be precise enough for clinical use. Duration of MR examination is not a restricting factor, mainly because the patient can be positioned easily.

Calibration↗
PubMed2006

Evolutionary responses of natives to introduced species: what do introductions tell us about natural communities?

Biological invasions dramatically affect the distribution, abundance and reproduction of many native species. Because of these ecological effects, exotic species can also influence the evolution of natives exposed to novel interactions with invaders. Evolutionary changes in natives in response to selection from exotics are usually overlooked, yet common responses include altered anti-predator defenses, changes in the spectrum of resources and habitats used, and other adaptations that allow native populations to persist in invaded areas. Whether a native population is capable of responding evolutionarily to selection from invaders will depend on the demographic impact of the invader, the genetic architecture and genetic variability of the native population and potentially the history of previous invasions. In some cases, natives will fail to evolve or otherwise adapt, and local or global extinction will result. In other cases, adaptive change in natives may diminish impacts of invaders and potentially promote coexistence between invaders and natives. Here, we review the evidence for evolutionary responses of native species to novel community members. We also discuss how the effects of introduced species may differ from those caused by natural range expansions of native species. Notably, introduced species may come from remote biotas with no previous evolutionary history with the native community. In addition, the rate of addition of introduced species into communities is much greater than all but the most extreme cases of historical biotic exchange. Understanding the evolutionary component of exotic/native species interactions is critical to recognizing the long-term impacts of biological invasions, and to understanding the role of evolutionary processes in the assembly and dynamics of natural communities.

Animals↗
PubMed2004

Questing height of nymphs of the bush tick, Haemaphysalis longicornis, and its closely related species, H. mageshimaensis: correlation with body size of the host.

The questing height (i.e. ambush height) of ticks on a plant plays an important role in host selection. To test the hypothesis that the questing height of ticks in a locality had adapted to the body size of the host in that locality, we examined the questing height of nymphs of the ticks, Haemaphysalis longicornis and H. mageshimaensis, at 7 locations in Japan. Sika deer, Cervus nippon, is the primary host of these ticks and there is considerable geographical variation in the body size of sika deer. Multiple regression analysis revealed that the questing height in the field was influenced by the height of the plants and by the body size of deer at a location. However, the questing height of ticks at some locations may have been constrained by the height of the plants and might not be the same as their intrinsic questing height. When ticks were placed in vertical glass tubes in the laboratory, the questing height of ticks from a locality was correlated with the mean body size of deer at that locality. Therefore, the prominent cue determining the questing height of H. longicornis and H. mageshimaensis seems to be the body size of the host deer.

Adaptation, Psychological↗
PubMed1995

Functional separation of global and local stereopsis investigated by cross-adaptation.

Reports that brain lesions may differentially affect global and local stereopsis suggest that anatomically separate mechanisms underlie these two functions. We demonstrate here that adaptation to global stereograms induces an after-effect on local stereopsis as well as on global stereopsis, showing that the two mechanisms cannot be entirely separate. We suggest that global stereopsis depends upon an interaction between primary visual area V1 and higher brain areas such as inferotemporal cortex.

Adolescent↗