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PubMedDate not supplied

The great escape: junctional escape-capture bigeminy.

Escape-capture bigeminy is a bigeminal rhythm in which each escape beat is followed by a captured beat. This dysrhythmia is very rare, because its manifestation requires the sinus interval to be longer than the escape interval. This is possible only with severe sinus nodal disease, where the intrinsic sinus rate is extremely low, or with a sinus rhythm associated with an accelerated junctional rhythm. The authors review the case of a 75-year-old man who presented with occasional dizziness and near-syncopal episodes. He was diagnosed with escape-capture bigeminy and subsequently underwent pacemaker placement.

Aged↗
PubMed2005

De novo generation of escape variant-specific CD8+ T-cell responses following cytotoxic T-lymphocyte escape in chronic human immunodeficiency virus type 1 infection.

Human immunodeficiency virus type 1 (HIV-1) evades CD8(+) T-cell responses through mutations within targeted epitopes, but little is known regarding its ability to generate de novo CD8(+) T-cell responses to such mutants. Here we examined gamma interferon-positive, HIV-1-specific CD8(+) T-cell responses and autologous viral sequences in an HIV-1-infected individual for more than 6 years following acute infection. Fourteen optimal HIV-1 T-cell epitopes were targeted by CD8(+) T cells, four of which underwent mutation associated with dramatic loss of the original CD8(+) response. However, following the G(357)S escape in the HLA-A11-restricted Gag(349-359) epitope and the decline of wild-type-specific CD8(+) T-cell responses, a novel CD8(+) T-cell response equal in magnitude to the original response was generated against the variant epitope. CD8(+) T cells targeting the variant epitope did not exhibit cross-reactivity against the wild-type epitope but rather utilized a distinct T-cell receptor Vbeta repertoire. Additional studies of chronically HIV-1-infected individuals expressing HLA-A11 demonstrated that the majority of the subjects targeted the G(357)S escape variant of the Gag(349-359) epitope, while the wild-type consensus sequence was significantly less frequently recognized. These data demonstrate that de novo responses against escape variants of CD8(+) T-cell epitopes can be generated in chronic HIV-1 infection and provide the rationale for developing vaccines to induce CD8(+) T-cell responses directed against both the wild-type and variant forms of CD8 epitopes to prevent the emergence of cytotoxic T-lymphocyte escape variants.

CD8-Positive T-Lymphocytes↗
PubMed2000

Escape behaviour in the stomatopod crustacean Squilla mantis, and the evolution of the caridoid escape reaction.

The mantis shrimp Squilla mantis shows a graded series of avoidance/escape responses to visual and mechanical (vibration and touch) rostral stimuli. A low-threshold response is mediated by the simultaneous protraction of the thoracic walking legs and abdominal swimmerets and telson, producing a backwards 'lurch' or jump that can displace the animal by up to one-third of its body length, but leaves it facing in the same direction. A stronger response starts with similar limb protraction, but is followed by partial abdominal flexion. The maximal response also consists of limb protraction followed by abdominal flexion, but in this case the abdominal flexion is sufficiently vigorous to pull the animal into a tight vertical loop, which leaves it inverted and facing away from the stimulus. The animal then swims forward (away from the stimulus) and rights itself by executing a half-roll. A bilaterally paired, large-diameter, rapidly conducting axon in the dorsal region of the ventral nerve excites swimmeret protractor motoneurons in several ganglia and is likely to be the driver neuron for the limb-protraction response. The same neuron also excites unidentified abdominal trunk motoneurons, but less reliably. The escape response is a key feature of the malacostracan caridoid facies, and we provide the first detailed description of this response in a group that diverged early in malacostracan evolution. We show that the components of the escape response contrast strongly with those of the full caridoid reaction, and we provide physiological and behavioural evidence for the biological plausibility of a limb-before-tail thesis for the evolution of the escape response.

Animals↗
PubMed1975

Physiological responses during escape and non-escape from stress in field independent and field dependent subjects.

Psychophysiological responses (GSP, GSR, heart rate and respiration) were monitored while the subjects viewed stressful stimuli. In balanced order the subjects were exposed to a condition in which they viewed the stimuli for 15 sec and a condition in which they could escape the stimulus. The subjects were divided into four groups according to level of trait anxiety and rod and frame scores. The results suggested that escape from stress produced different patterns of physiological activity than non-escape conditions. The changes were most noticeable for tonic GSP, non-specific GSR and heart rate. Field independent subjects differentiated the conditions physiologically and behaviorally to a greater extent than field independent subjects. It was speculated that field independent subjects are more dependent upon physiological cues to evaluate their perceptions and emotions than field dependent subjects.

Anxiety↗
PubMed1992

Autologous HIV-1 neutralizing antibodies: emergence of neutralization-resistant escape virus and subsequent development of escape virus neutralizing antibodies.

The capacity of consecutive human sera to neutralize sequentially obtained autologous virus isolates was studied. HIV-1 was isolated three times over a 48-164-week period from three individuals immediately after seroconversion and from two individuals in later stages of infection. Development of neutralizing antibodies to the primary virus isolates was detected 13-45 weeks after seroconversion. Emergence of escape virus with reduced sensitivity to neutralization by autologous sera was demonstrated. The patients subsequently developed neutralizing antibodies against the escape virus but after a delay. Titers of neutralizing antibodies against late virus isolates were generally low compared to initial neutralizing titers against primary virus isolates. The delay in appearance of neutralizing antibodies to the dominant viral strain at any time in the patient and the emergence of neutralization resistant escape virus may be part of the explanation of the apparent failure of the immune system to control HIV infection.

HIV Antibodies↗
PubMed1997

Promoter escape by RNA polymerase II. Formation of an escape-competent transcriptional intermediate is a prerequisite for exit of polymerase from the promoter.

Shortly after initiating promoter-specific transcription in vitro, mammalian RNA polymerase II becomes highly susceptible to arrest in a promoter-proximal region 9-13 base pairs downstream of the transcriptional start site (Dvir, A., Conaway, R. C., and Conaway, J. W. (1996) J. Biol. Chem. 271, 23352-23356). Arrest by polymerase in this region is suppressed by TFIIH in an ATP-dependent reaction (Dvir, A., Conaway, R. C., and Conaway, J. W. (1997) Proc. Natl. Acad. Sci. U. S. A. 94, 9006-9010). In this report, we present evidence that, in addition to TFIIH and an ATP cofactor, efficient transcription by RNA polymerase II through this promoter-proximal region requires formation of an "escape-competent" transcriptional intermediate. Formation of this intermediate requires template DNA 40-50 base pairs downstream of the transcriptional start site. This requirement for downstream DNA is transient, since template DNA downstream of +40 is dispensable for assembly of the preinitiation complex, for initiation and synthesis of the first 10-12 phosphodiester bonds of nascent transcripts and for further extension of transcripts longer than approximately 14 nucleotides. Thus, promoter escape requires that the RNA polymerase II transcription complex undergoes a critical structural transition, likely driven by interaction of one or more components of the transcriptional machinery with template DNA 40-50 base pairs downstream of the transcriptional start site.

Adenosine Triphosphate↗
PubMed1982

Mathematical modelling of reaction latency. Part II: A model of escape reaction and escape learning.

The results of fitting the linear-dynamic-stochastic model to the latency data from escape conditioning experiment are presented. Two processes can be distinguished: (i) an increase in parameters of the dynamic part of the model (called the static gain and the dynamic gain) which results in a decrease in the reaction latency during learning, (ii) an increase in parameter of the decision part of the model (mean value of the threshold), which results simultaneously in an increase in the reaction latency and a decrease in the inter-trial responses probability. The reaction latency decreases during the learning because the first phenomenon prevails over the second one, but the latter is the only reason of inter-trial responses decrease during learning. Analysis of the results of surgical treatment on the learning process is also presented.

Animals↗
PubMed1994

Treatment of escape-maintained aberrant behavior with escape extinction and predictable routines.

We evaluated the effects of two daily activity schedules on 2 participants' rates of aberrant behavior and their compliance. Functional analysis identified the operant function of the participants' aberrant behaviors to be escape from tasks. Participants were taught to use stimuli contained in daily schedules, and were tested based on a modified stimulus-equivalence model that consisted of flash cards and activity schedules comprised of words or photographs that corresponded to the participants' daily activities. On pretests, the participants demonstrated simple and conditional discriminations with the photographs but not with the printed stimuli. A time-delay procedure was used to teach the participants to name the flash cards. Following training, the printed activity schedules corresponded to lower rates of problem behavior and higher rates of compliance than the photographic activity schedules. Performance on posttests indicated the establishment of functional classes of stimuli involving the flash cards and activity schedules even though this type of correspondence was not directly trained.

Journal Article↗
PubMed2000

Effects of escape to alone versus escape to enriched environments on adaptive and aberrant behavior.

Escape-maintained aberrant behavior may be influenced by two outcomes: (a) a break from the activity and (b) subsequent access to preferred activities. To assess this hypothesis, a treatment was developed that analyzed response allocation across two break options: break alone and break with access to preferred social activities. The break with preferred activities decreased aberrant behavior and increased appropriate behavior.

Adaptation, Psychological↗