Acute effect of phenobarbital on escape behavior

Rats were trained to run in a straight alley to escape shock. Subsequently, phenobarbital was administered and more trials given. Phenobarbital retards running at all doses tested in a curve that is positively accelerating as a function of dose on the first trial. The first trial is markedly slower than later trials with the greatest effect occurring at the higher dosages.     

Straight-alley escape behavior in infant mice: effect of shock intensity

Separate groups of Swiss-Webster mice between 5-15 days of age received 25 training trials in a straight-alley escape task at 1 of 4 shock intensities, ranging from .1-.8 mA. An increase in shock level led to better escape performance at all ages, although the amount of improvement varied directly as a function of age. The results supported earlier work suggesting that the competing response measure was the most useful index of improved escape behavior at the early ages. Running speeds did not indicate improved within-session escape performance at any age or shock level, although speeds clearly reflected maturational and motivational differences between groups.     

Protection from habituation of the crayfish lateral giant fibre escape response

1. Habituation of the lateral giant fibre escape response in the crayfish to repetitive tactile stimuli is believed to result from homosynaptic depression at the first synapse of the reflex, between tactile afferents and interneurones. Normally, habituation of escape responses to repeated innocuous stimuli is presumed to be adaptive. Experiments reported here were undertaken to determine whether habituation would occur under circumstances when it would presumably be maladaptive - in particular, when tactile receptors are stimulated by an animal's own tail-flip movements.2. Experiments were carried out on the crayfish isolated abdominal nerve cord, which contains the lateral giant reflex pathway.3. Compound e.p.s.p.s elicited in the lateral giant by electrical stimulation of tactile afferents decline by from 25 to 36% over a series of eleven trials at 1/5 sec (control series).4. To determine whether such a decline would occur when sensory afferents are stimulated during a ;tail-flip', stimuli were given as in the control series but each stimulus occurred 20 msec after direct electrical stimulation of a medial giant or lateral giant escape-command fibre at which time tail flexion movements of an intact animal would be in progress. Under these conditions% e.p.s.p. decline over 11 trials at 1/5 sec was only 16-45% of that occurring on the control series.5. This protective effect starts at about 10 msec after escape command neurone firing, is maximal at 20 msec, and thereafter declines, remaining weakly detectable at 100 msec. This time course is commensurate with that required for execution of a tail-flip movement. Thus, sensory afferent-to-lateral giant transmission is protected from depression if stimuli occur when a tail-flip movement is or should be occurring.6. Giant fibre spikes do not superimpose facilitation upon a depressed reflex pathway, nor accelerate rate of recovery from depression; rather, protection is attributable to actual prevention of development of the depressed state.7. Protection was also examined at the first synapse of the reflex, where the depression responsible for habituation is believed to occur, by recording intracellularly in the largest of the first-order interneurones (interneurone A) of the pathway. In absence of protection, ten stimuli presented at 1/4 sec caused a mean decline of 32% in the e.p.s.p. in interneurone A. When such stimuli followed directly evoked escape command neurone firing by 20 msec this decline was reduced by 59-100%.8. We suggest that protection serves to prevent crayfish from habituating to stimuli produced by their own tail-flip movements.     

A genetic analysis of escape behavior in rats

Three strains of highly inbred rats and their derived F₁ hybrid progeny were tested for escape latencies in a novel test situation at three ages. There were very highly significant differences in escape latencies between genotypes and between ages. There was also a very highly significant genotype by age interaction; the inbreds had increasing latencies with increasing age, whereas the hybrids did not. Heterosis was observed, and it was concluded that this behavioral heterosis was consistent with the hypothesis of selection for an intermediate optimum in latency to escape.     

Genetic analysis of simple water escape behavior: test of a major-gene hypothesis.

Recombinant inbred (RI) strains, progenitor strains, and reciprocal F₁ hybrids were used to test the hypothesis that the recessive condition of the albino gene, when homozygous, exerts a major influence on simple water escape performance in the T maze. The resulting RI strain distribution pattern did not support this hypothesis. One pigmented RI strain exhibited water escape performance which was inferior to that of albino strain BALB/cBy. Two albino RI strains exhibited superior performance relative to progenitor strain BALB/cBy and were equal in performance to two of the best performing pigmented RI strains. Implications of this finding for studies involving color coat mutants and albino strains and stocks are discussed.     

未见多核巨细胞的透明细胞软骨肉瘤一例

患者男,25岁.因不慎跌伤致右髋部剧痛、活动受限1 d于2010年3月5日入院就诊,门诊拟"右股骨颈骨折"收住院.专科检查;右髋部肿胀,压痛,腹股沟中点压痛明显,骨干力丧失,可及异常活动,髋关节活动受限,抬腿乏力,右下肢呈外旋、短缩1 cm畸形,轴冲痛(+),足背动脉搏动好,趾动及血运好.     

Acquisition and retention of multidirectional escape behavior in preweanling rats

The shock-escape behavior of preweanling rats in a multidirectional escape situation was examined in 3 experiments. In Experiment I, 5-, 7-, 9-, and 11-day-old rats were given shock-escape training on each of 3 days. Rats younger than 7 days of age did not improve escape responding within or over sessions. Animals 7 days of age and older, however, showed both an intrasession improvement and an intersession improvement that could not be attributed solely to maturation. In Experiment II, the escape behavior of 3-, 5-, and 7-day-olds was examined in an apparatus modified to take into account the poor locomotor abilities of these animals. They were given escape training on 3 successive days. Again, no within-session improvement was found in rats under 7 days of age. However, an intersession improvement was found in rats whose training began at 5 days of age. This improvement was due to maturation and did not reflect a cumulative effect of training. Experiment III, like Experiment I, demonstrated that the intersession improvement in the older rats was not simply a maturation effect. It also demonstrated that the improvement could not be attributed to the stress of prior handling, shock, or body temperature loss, but was, rather, a retention effect. These results support the contention that the emergence of memory is task specific.     

Modifications of locomotor pattern underlying escape behavior in the lamprey

Two forms of undulatory locomotion in the lamprey (a lower vertebrate) have been described earlier: fast forward swimming (FFS) used for long distance migrations and slow backward swimming (SBS) used for escape from adverse tactile stimuli. In the present study, we describe another form of escape behavior: slow forward swimming (SFS). We characterize the kinematic and electromyographic patterns of SFS and compare them with SBS and FFS. The most striking feature of SFS is nonuniformity of shape and speed of the locomotor waves propagating along the body: close to the site of stimulation, the waves slow down and the body curvature increases several-fold due to enhanced muscle activity. Lesions of afferents showed that sensory information critical for elicitation of SFS is transmitted through the dorsal roots. In contrast, sensory signals that induce SBS are transmitted through the dorsal roots, lateral line nerves, and trigeminal nerves. Persistence of SFS and SBS after different lesions of the spinal cord suggests that the ascending and descending pathways, necessary for induction of SBS and SFS, are dispersed over the cross section of the spinal cord. As shown previously, during FFS (but not SBS) the lamprey maintains the dorsal-side-up body orientation due to vestibular postural reflexes. In this study we have found that the orientation control is absent during SFS. The role of the spinal cord and the brain stem in generation of different forms of undulatory locomotion is discussed.     

Presynaptic inhibition: the mechanism of protection from habituation of the crayfish lateral giant fibre escape response.

1. Mechanism of protection from habituation of the lateral giant escape reflex of the crayfish was studied. Experiments were designed to determine whether presynaptic inhibition of primary afferents for the reflex occurs following escape command neurone firing, and if so, whether it could account for protection of the first synapse from depression. 2. Synaptic transmission between afferents and interneurone A of the escape reflex is strongly inhibited following giant fibre spikes. 3. Giant fibre firing results in post-synaptic inhibition of interneurone A. However, inhibition of afferent input to interneurone A consistently outlasts both i.p.s.p.s and post-synaptic conductance increases in the neurone; the inhibition, therefore, is probably not exclusively post-synaptic. 4. Giant fibre firing results in excitability changes in sensory afferent terminals as measured by the amplitude of antidromic compound action potentials to focal electrical stimuli applied in the region of afferent terminals in the last abdominal ganglion. The time course of this effect parallels those of protection and inhibition of the first synapse. 5. The magnitude and time course of protection and inhibition of transmission to interneurone A parallel each other closely. Both processes considerably outlast measurable signs of post-synaptic inhibition. 6. We conclude that following giant fibre activity the first synapse of the lateral giant reflex is presynaptically inhibited and the presynaptic inhibition is responsible for the protection effect described in the preceding paper.     

Intrapericardial lipoma: successful resection of a giant tumor without cardiopulmonary bypass.

Cardiac lipomas are very rare neoplasms. We describe herein a case of giant intrapericardial extracavitary lipoma in a 67-year-old man who has been previously treated for prostate and kidney cancers. The patient underwent successful resection of the tumor through right anterolateral thoracotomy.     

Influenza H5 virus escape mutants: immune protection and antibody production in mice

Avian H5N1 influenza A viruses are considered to be of high pandemic potential as they are able to cross the avian-human species barrier and cause disease in humans. In the present study we assessed the impact of amino acid substitutions in the hemagglutinin (HA) of antigenic escape mutants of influenza A/Mallard/Pennsylvania/10218/84 (H5N2) (Mld/PA/84-MA) virus on the level of neutralizing antibodies and the ability to protect mice against challenge with the wild type H5 influenza virus. beta-Propiolactone-inactivated vaccines prepared from eight different H5 escape mutants could be separated into two groups based on levels of protection. One group of escape mutants [m46(7), m46(7)-24B9, m46(7)-55, and m46(7)-55-24B9] was characterized by providing high levels of protection (90.0-95.4% survival) to mice against subsequent challenge with 5 LD(50) of wild type Mld/PA/84-MA virus. The other group of escape mutants [m176/26, m55(2), m55(2)-24B9, and m24B9-176/26] provided moderate level of protection (57.1-66.6% survival) in mice. Analysis of the amino acid substitutions in the HA revealed that two amino acid changes in antigenic site B of the HA molecule (D(126)-->N and K(152)-->N) were associated for decreases in the levels of antibody and the immune protection afforded by vaccination with these H5 virus escape mutants. The phenotypic effects of mutations in HA gene of H5 virus may be of importance to appraise the extent and direction of H5 influenza viruses antigenic evolution.     

Cholinergic transmission at the first synapse of the circuit mediating the crayfish lateral giant escape reaction.

1. The chemical synapses between mechanoreceptor neurons and first-order interneurons in the lateral giant (LG) neuron escape circuit of the crayfish have plastic properties, some of which are believed to be the basis for behavioral habituation and sensitization. In this investigation pharmacological experiments were conducted to assess the role of cholinergic synaptic transmission in this pathway. 2. Arterial perfusion of the cholinergic agonist carbachol produced increased activity of many abdominal nerve cord units, including an identified first-order interneuron (interneuron A) in the LG circuit. A general increase in activity of interneurons in this circuit in the presence of certain cholinergic agonists was inferred from an increase in the frequency of occurrence of spontaneous excitatory postsynaptic potentials (EPSPs) recorded in the LG. 3. Cholinergic antagonists reduced the amplitude of spontaneous and evoked sensory neuron-to-interneuron A EPSPs and decreased the disynaptic (via 1st-order interneurons) component of evoked EPSPs in the LG. These effects indicate that postsynaptic cholinergic receptors are utilized in mechanosensory synaptic transmission to the first-order interneurons of this circuit. The relative potencies of the blockers tested (mecamylamine > picrotoxin > curare > atropine) suggest that the receptors on the interneurons belong to a previously characterized class of crustacean cholinergic receptors that resemble the ganglionic nicotinic subtype of vertebrates. 4. Nicotinic agonists (carbachol, tetramethylammonium hydroxide, 1,1-dimethyl-4-phenyl-piperazium iodide) produced depolarizing (decreased input resistance) responses on the LG neuron itself. These responses persisted during blockade of chemical transmission by cobalt. The presence of cholinergic receptors on the LG, a cell in which all known inputs mediating sensory excitation are electrical, is discussed. 5. Application of muscarinic agonists (pilocarpine, oxotremorine) resulted in a long-lasting reduction of the evoked sensory neuron-to-interneuron A EPSP and the disynaptic component of the evoked EPSP in the LG. No effects on the membrane potential or input resistance of the interneurons were detected. It is proposed that presynaptic receptors with a muscarinic profile are present on mechanosensory neurons and that these receptors mediate a reduction of transmitter release.