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At least 19 recordsLinked to original sources
PubMed1989

Pre-escape and escape aircraft maneuvers and gyrations: a critical under-reported problem affecting escape system performance and aircrew safety.

A major problem confronting both the requirements formulators and the designers of aircrew escape systems is defining the systems' operational emergency conditions. For years the community has relied on computerized compilations of such data. However, increasingly, examination of original records reveals that the report originators are not sufficiently thorough in completing the block sections of the form. As a consequence computerized searches for pre-escape and escape aircraft maneuvering and gyrations show these conditions to be dramatically under-reported. Several recent studies suggest this under-reporting approximates 100%. This is critical because the associated aircraft motions may adversely affect seat separation from the aircraft, degrading system stability, and aircrew safety.

Aerospace Medicine↗
PubMed1999

Escape trajectories of the brown shrimp crangon crangon, and a theoretical consideration of initial escape angles from predators

Tail-flip escape trajectories of the brown shrimp Crangon crangon have been investigated in response to a natural predator, the cod Gadus morhua, and an artificial stimulus. Shrimps escaped by rolling to their left or right during the initial tail-flip of a response, and thereafter swam on their side. As a result of the laterally directed first tail-flip, initial escape angles always lay between 75 degrees and 156 degrees with respect to the (pre-escape) longitudinal axis (anterior=0 degrees) of the shrimp. Symmetrical attacks from either head-on or tail-on produced escapes to the shrimp's left or right in equal proportions, although a contralateral bias did occur if the shrimp experienced a looming object from one side before a symmetrical attack was applied. Lateral attacks produced a significantly greater proportion of contralateral responses than ipsilateral ones. Empirical and theoretical analyses indicate that the initial escape direction is influenced by an interaction between the range of first tail-flip escape angles that the shrimp is capable of performing and the risk of being intercepted by a predator during the initial stage of an escape. Thus, the unpredictability ('protean behaviour') of the response may be affected by the conditions of the interaction. Subsequent tail-flips of an escape usually directed the response away from the stimulus, but sometimes escapes were instead steered to the side of the stimulus and then behind it. The probability of each type of escape occurring changed with attack direction. The elements of protean behaviour that have been identified in both the initial and subsequent stages of the escape may prevent predators from learning a fixed pattern of response, but a trade-off occurs when escape trajectories infringe upon zones of high capture risk.

Journal Article↗
PubMed1975

Fixed-ratio escape and avoidance-escape from naloxone in morphine-dependent monkeys: effects of naloxone dose and morphine pretreatment.

Lever pressing by rhesus monkeys was maintained by morphine injections during four equally spaced sessions each day. During other periods, lever pressing was maintained by timeout from a continuous naloxone infusion (escape), or by timeout from a stimulus that preceded naloxone injections, or termination of the injections (avoidance-escape). As naloxone dose increased in the escape procedure, response rate increased to a maximum and then decreased. In the avoidance-escape procedure, response rate generally increased as naloxone dose increased, but the changes in rate were small compared to the excape procedure. Substitution of saline for naloxone in the escape procedure led to a very low response rates within three sessions. In the avoidance-escape procedure, rate decrements produced by saline substitution appeared to be related to the behavioral history of the monkey. Previous escape experience led to more rapid decreases in responding when saline was introduced, whereas responding was maintained for 15 sessions in a monkey without prior escape conditioning. Morphine pretreatment produced comparable, dose-dependent decreases in response rates in both procedures. The rate-decreasing effects of morphine were exacerbated when no naloxone was delivered in the escape procedure.

Animals↗
PubMed2004

Consequences of cytotoxic T-lymphocyte escape: common escape mutations in simian immunodeficiency virus are poorly recognized in naive hosts.

Cytotoxic T lymphocytes (CTL) are associated with control of immunodeficiency virus infection but also select for variants that escape immune recognition. Declining frequencies of epitope-specific CTL frequencies have been correlated with viral escape in individual hosts. However, escape mutations may give rise to new epitopes that could be recognized by CTL expressing appropriate T-cell receptors and thus still be immunogenic when escape variants are passed to individuals expressing the appropriate major histocompatibility complex class I molecules. To determine whether peptide ligands that have been altered through escape can be immunogenic in new hosts, we challenged naïve, immunocompetent macaques with a molecularly cloned simian immunodeficiency virus (SIV) bearing common escape mutations in three immunodominant CTL epitopes. Responses to the altered peptides were barely detectable in fresh samples at any time after infection. Surprisingly, CTL specific for two of three escaped epitopes could be expanded by in vitro stimulation with synthetic peptides. Our results suggest that some escape variant epitopes evolving in infected individuals do not efficiently stimulate new populations of CTL, either in that individual or upon passage to new hosts. Nevertheless, escape variation may not completely abolish an epitope's immunogenicity. Moreover, since the mutant epitope sequences did not revert to wild type during the study period, it is possible that low-frequency CTL exerted enough selective pressure to preserve epitope mutations in viruses replicating in vivo.

Amino Acid Sequence↗
PubMed2003

Escape from viscosity: the kinematics and hydrodynamics of copepod foraging and escape swimming.

Feeding and escape swimming in adult females of the calanoid copepod Temora longicornis Müller were investigated and compared. Swimming velocities were calculated using a 3-D filming setup. Foraging velocities ranged between 2 and 6 mm s(-1), while maximum velocities of up to 80 mm s(-1) were reached during escape responses. Foraging took place at Reynolds numbers between 2 and 6, indicating that viscous forces are considerable during this swimming mode. Inertial forces are much more important during escape responses, when Reynolds numbers of more than 100 are reached. High-speed film recordings at 500 frames s(-1) of the motion pattern of the feeding appendages and the escape movement of the swimming legs revealed that the two swimming modes are essentially very different. While foraging, the first three mouth appendages (antennae, mandibular palps and maxillules) create a backwards motion of water with a metachronal beating pattern. During escape movements the mouth appendages stop moving and the swimming legs beat in a very fast metachronal rhythm, accelerating a jet of water backwards. The large antennules are folded backwards, resulting in a streamlined body shape. Particle image velocimetry analysis of the flow around foraging and escaping copepods revealed that during foraging an asymmetrical vortex system is created on the ventral side of the animal. The feeding motion is steady over a long period of time. The rate of energy dissipation due to viscous friction relates directly to the energetic cost of the feeding current. During escape responses a vortex ring appears behind the animal, which dissipates over time. Several seconds after cessation of swimming leg movements, energy dissipation can still be measured. During escape responses the rate of energy dissipation due to viscous friction increases by up to two orders of magnitude compared to the rate when foraging.

Animals↗
PubMed2002

Inhibition of chaotic escape from a potential well by incommensurate escape-suppressing excitations.

Theoretical results are presented concerning the reduction of chaotic escape from a potential well by means of a harmonic parametric excitation that satisfies an ultrasubharmonic resonance condition with the escape-inducing excitation. The possibility of incommensurate escape-suppressing excitations is demonstrated by studying rational approximations to the irrational escape-suppressing frequency. The analytical predictions for the suitable amplitudes and initial phases of the escape-suppressing excitation are tested against numerical simulations based on a high-resolution grid of initial conditions. These numerical results indicate that the reduction of escape is reliably achieved for small amplitudes and at, and only at, the predicted initial phases. For the case of irrational escape-suppressing frequencies, the effective escape-reducing initial phases are found to lie close to the accumulation points of the set of suitable initial phases that are associated with the complete series of convergents up to the convergent giving the chosen rational approximation.

Journal Article↗
PubMed2001

Exploitation of an ancient escape circuit by an avian predator: relationships between taxon-specific prey escape circuits and the sensitivity to visual cues from the predator.

The painted redstart Myioborus pictus uses visual displays to flush, pursue, and then capture an abundance of brachyceran Diptera that are equipped with giant fiber escape circuits. This paper investigates the relationships between features of the giant fiber system, the structure of visual stimuli produced by redstarts and their effectiveness in eliciting escape reactions by flies. The results show that dipterous taxa having large-diameter giant fibers extending short distances from the brain to motor neurons involved in escape are flushed at greater distances than taxa with longer and small-diameter giant fibers. The results of behavioral tests show the importance of angular acceleration of expanding image edges on the compound eye in eliciting escape responses. Lateral motion of stimulus profile edges as well as structured visual profiles additionally contribute to the sensitivity of one or more neural systems that trigger escape. Retinal subtense and angular velocity are known to trigger physiological responses in fly giant fiber circuits, but the contributions of edge length and lateral motion in a looming stimulus suggest that escape pathways might also receive inputs from circuits that are tuned to different types of motion. The present results suggest that these several properties of escape pathways have contributed to the evolution of foraging displays and plumage patterns in flush-pursuing birds.

Animals↗
PubMed2004

Escape behavior and escape circuit activation in juvenile crayfish during prey-predator interactions.

The neural systems that control escape behavior have been studied intensively in several animals, including mollusks, fish and crayfish. Surprisingly little is known, however, about the activation and the utilization of escape circuits during prey-predator interactions. To complement the physiological and anatomical studies with a necessary behavioral equivalent, we investigated encounters between juvenile crayfish and large dragonfly nymphs in freely behaving animals using a combination of high-speed video-recordings and measurements of electric field potentials. During attacks, dragonfly nymphs rapidly extended their labium, equipped with short, sharp palps, to capture small crayfish. Crayfish responded to the tactile stimulus by activating neural escape circuits to generate tail-flips directed away from the predator. Tail-flips were the sole defense mechanism in response to an attack and every single strike was answered by tail-flip escape behavior. Crayfish used all three known types of escape tail-flips during the interactions with the dragonfly nymphs. Tail-flips generated by activity in the giant neurons were predominantly observed to trigger the initial escape responses to an attack, but non-giant mediated tail-flips were often generated to attempt escape after capture. Attacks to the front of the crayfish triggered tail-flips mediated either by the medial giant neuron or by non-giant circuitry, whereas attacks to the rear always elicited tail-flips mediated by the lateral giant neuron. Overall, tail flipping was found to be a successful behavior in preventing predation, and only a small percentage of crayfish were killed and consumed.

Action Potentials↗
PubMed1980

Differential effects of inescapable shock on escape performance and discrimination learning in a water escape task.

The effects of inescapable shock on subsequent T-maze water escape and position discrimination performance were evaluated in seven experiments. Escapable shock did not disrupt water escape performance; however, escape performance was retarded 24 hr after inescapable shock. These deficits were not apparent if escape was possible upon stress inception; however, pronounced deficits were noted if sustained active responding was necessitated by briefly (3-5 sec) preventing escape. When water escape testing was conducted in relatively warm water (20 degrees C), the disruptive effects of preshock were not apparent. In colder water (15 degrees C), which increases the motor difficulty of the task, the disruptive effects of preshock were noted. When the motor difficulty of the task was increased further, by testing mice in 10 degrees C water, or when the associative difficulty was increased by using a vigorous reversal learning task, the differences between the preshocked and nonpreshocked groups were obviated. Exposure to inescapable shock did not disrupt position discrimination performance regardless of the motor difficulties of the task. Similarly, deficits of discrimination performance were not apparant in mice exposed to inescapable shock even when the associative difficulty of the task was increased by removing intramaze cues or by testing animals in a position discrimination reversal task. It is concluded that inescapable shock results in deficits of response maintenance but probably has a minor, if any, influence on cognitive/associative processes.

Animals↗
PubMed1994

Chlordiazepoxide microinjected into the region of the dorsal raphe nucleus eliminates the interference with escape responding produced by inescapable shock whether administered before inescapable shock or escape testing.

Systemic administration of benzodiazepines before exposure to inescapable shock (IS) blocks the enhanced fear conditioning and escape learning deficits that follow exposure to IS, whereas administration before the subsequent behavioral testing eliminates the enhanced fear but not the interference with escape. The failure of benzodiazepines to reduce the IS-produced escape learning deficit when given before testing is inconsistent with a recent proposal that interference with escape is mediated by an IS-induced sensitization of dorsal raphe nucleus (DRN) activity. The present experiments demonstrate that chlordiazepoxide will block both the enhancement of fear and interference with escape responding when given before either IS or testing if microinjected in the region of the DRN. This suggests that systemic benzodiazepines fail to block escape deficits when given before testing because action at a site distant from the DRN counters the effect of the drug at the DRN.

Animals↗
PubMed1995

Zona pellucida escape by hamster blastocysts in vitro is delayed and morphologically different compared with zona escape in vivo.

The timing and mode of hamster blastocyst escape from the zona pellucida in vitro ("hatching") and in vivo were compared on the basis of dynamic and static images captured on videotape and computer, respectively. In vivo, most embryos (> or = 80%) escaped between 0030 h and 0600 h on Day 4 of pregnancy. The zona gradually thinned globally and greatly increased in diameter, eventually disappearing. Attachment of blastocysts to the uterine epithelium followed within 4 h. Retarded embryos also showed global zona lysis. In contrast, zona escape in vitro was delayed > or = 29 h both in blastocysts cultured from 1-cell embryos and in blastocysts flushed from uteri of mated, naturally cycling hamsters at 2330 h on Day 3. Zonae were focally lysed; then blastocysts egressed through the hole, leaving most of the zona intact. Global zona lysis never occurred, and retarded embryos did not escape. In conclusion, the striking morphological and temporal differences in zona escape indicate that the hatching behavior routinely observed in cultured hamster blastocysts is not representative of normal events, and implicate a uterine contribution to normal zona escape that is lacking in culture.

Animals↗
PubMed1979

Relationship of scores on the Escapism Scale of the MMPI to escape from minimum security federal custody.

Investigated the ability of the Escapism (Ec) scale of the MMPI to differentiate between escape and non-escape minimum security federal prisoners. At the .05 level there was no difference between the scores of the two groups on the Ec scale or on comparisons of other correctional data, age, and ethnic composition. It appears that the Ec scale alone or in combination with other data will be a poor predictor of escape. Also, the rate of escape was so low as to make accurate prediction from any criteria extremely unlikely.

Adult↗
PubMed1993

The wind-elicited escape response of cockroaches (Periplaneta americana) is influenced by lesions rostral to the escape circuit.

When the escape response of the cockroach (Periplaneta americana) is triggered by wind, it is mediated by the cercal-to-giant interneuron pathway and leg motor circuitry, within the abdominal and thoracic portions of the ventral nerve cord. We have found that a lesion rostral to the thorax (transection of a cervical connective) produces specific changes in wind-evoked escape. Lesioned animals reliably displayed short-latency responses to wind. However, the orientation of the initial turning component of escape was altered and the duration of subsequent running was reduced. Preliminary physiological study suggests that changes in the orientation of escape reflect changes in the integration of wind-sensory signals by thoracic circuitry. These findings imply that rostral centers influence sensorimotor integration underlying wind-evoked escape.

Abdomen↗
PubMed1989

Overcoming unlearned response biases: delayed escape following errors facilitates acquisition of win-stay and win-shift working memory water-escape tasks in rats.

Previous research has demonstrated that perseveration in escape situations is an unlearned response bias of rats and mice which is difficult to overcome. In Experiment I, Sprague-Dawley rats were trained to a criterion of nine correct choices in 10 consecutive trials in a win-stay working memory water-escape task wherein an escape platform was hidden in one of two compartments. Subjects were given a forced choice on an Information Trial followed by a free choice on a Test Trial 5 min later. Subjects who were given a 30-s forced swim in the incorrect section following errors on the Test Trial showed faster acquisition and less use of response perseveration than control subjects. In Experiment II, the delayed escape procedure was used to compare acquisition of win-stay and win-shift strategies. Contrary to previous research both groups learned the tasks, although the win-stay group showed better performance. It is concluded that unlearned response biases of perseverating and returning to previous escape sites can be overcome if experimental conditions are appropriately arranged.

Animals↗
PubMed1984

Effects of pimozide on escape and discrimination performance in a water-escape task.

The effects of pimozide (0.2 and 0.4 mg/kg) on discrimination learning were evaluated by a water-escape paradigm in which the degree of motor difficulty was manipulated by varying water temperature. Treatment with the drug marginally affected escape latencies in relatively warm water (25 degrees C) but markedly disrupted escape latencies when the task was more demanding (e.g., 15 degrees C and 20 degrees C water). The escape deficits, however, were not accompanied by disturbances in the acquisition of a position discrimination response or of a cue discrimination response when mice were required to make the highly prepared response of swimming to light or the contraprepared response of swimming to dark. These data were taken to suggest that in tasks involving aversive motivation pimozide influences performance through its effects on response maintenance but does not appear to affect either associative or motivational processes.

Animals↗
PubMed2000

Escape from shock versus escape from shock accompanied by a visual stimulus in rats.

Two groups of 15 rats each were trained in a shuttle box to escape foot-shock either unsignalled or presented in compound with a visual cue: darkness. The visual cue presented in shock compartment amplifies the behavioral tendency actually prevailing in the response repertory of the rat. During the 1st session the compound enhanced the species-specific flight resulting in shortening of the rat's escape latency. Thereafter, during subsequent sessions, darkness exaggerated resistance to enter the other compartment; thus escape latencies were longer under compounded than under unsignalled procedure. The darkness cue reduces the intertrial response rate relative to the unsignalled group. This latter finding supports the discrimination model of the effect, since the compound helps the animals to discriminate the illuminated "safe" period between trials from the aversive shock period. Our data seem to suggest that the darkness presented synchronously with escapable grid-shock acquires aversive properties.

Animals↗