Brain mechanisms in fatal cardiac arrhythmia.

Intravenous injection of histamine to rabbits was used as a prototype in an investigation of the mechanism of sudden death due to anaphylaxis and other causes. The "dive" reflex, bradycardia due to activation of the ophthalmic branch of the fifth cranial nerve, was induced in thirty-seven of the animals while they inhaled a very small amount of cigarette smoke. Associated with the resulting bradycardia were lowered blood pH and increased serum content of lactic acid and potassium and increased peripheral arterial constriction with elevation of diastolic blood pressure. Intravenous injection of 1 ml of histamine in the presence of the dive reflex induced potentially fatal ventricular arrhythmia, but no cardiac disturbance when administered while the dive reflex was inactive, thereby strongly suggesting that sudden death in anaphylaxis may involve an overzealous response to a normally protective neural reflex.     

Treatment of PAT

It has been suggested that the dive reflex (elicited by face immersion in water with breath-hold) may be employed to induce vagally-mediated bradycardia in individuals with paroxysmal atrial tachycardia. However, in several cases the use of this reflex is reported to have led to exacerbation of the cardiac dysfunction. Examination of heartrate and EKG T-wave amplitude changes during the dive in healthy, college-aged individuals indicated that warming the water (10° through 20° C to 40° C) decreased the bradycardia, but did not alter theattenuation (approximately 100 μv) of the T-wave. The latter effect was taken to indicate that sympathetic activity, as indexed by T-wave amplitude, was not reduced by increases in water temperature. On the other hand, a 90° head-up to head-down body tilt produced a bradycardia response of some 30 bpm as well as a T-wave amplitudeincrease (sympathetic withdrawal) in the order of 100 μv. These data suggest that individuals who exhibit symptoms of ventricular sympathetic irritability may be adversely affected by the dive maneuver, regardless of water temperature. The body-tilt induced reflex in such individuals may thus be more appropriate given the large-magnitude bradycardia and absence of T-wave attenuation. At the present, however, the body-tilt preparation has been used only with healthy normal subjects, so this suggestion remains to be directly tested.     

Data on the role of the frontal cortex in vegetative behavior

A homeostatic conditional reflex (CR) was elaborated to the effect of repeated inhalations in rats of a gas mixture containing 8 per cent oxygen. The effect of the conditional response was opposite to that of the unconditional one. After ablation of the frontal cortex, the conditional reaction disappeared. The repeated administration of 40 mg/kg of histamine resulted in a tolerance to the temperature lowering effect of histamine similar to the habituation. An injection of distilled water brought about dishabituation. Tolerance was not influenced by the ablation of the frontal cortex, but the dishabituating effect of distilled water was absent.     

七氟醚与氯胺酮做基础麻醉在婴幼儿先天性唇腭裂手术中的应用比较

为了寻找婴幼儿先天性唇腭裂手术比较理想的基础麻醉方式,将该类手术患儿60例随机均分为氯胺酮肌肉注射基础麻醉组（K组）和高浓度七氟醚吸入基础麻醉组（S组）。患儿入手术室后常规监测生命体征,记录其哭闹时间、睫毛反射消失时间和疼痛反射消失时间,观察基础麻醉期间患儿的合作情况和有无并发症的发生。术后随访并发症的发生情况。S组与K组患儿相比,哭闹时间、睫毛反射时间、疼痛反射消失时间均显著缩短。K组患儿基础麻醉期间发生的并发症明显多于S组,且．术后呕吐的发生率亦显著高于S组。因此,高浓度七氟醚吸入做基础麻醉是婴幼儿先天性唇腭裂手术时较为理想的基础麻醉方式。     

The somatic and vegetative-regulatory behavior of the healthy organism during conditioning of the insulin effect

Symptoms produced by repeated daily injection of insulin (3 units/kg i.v.) in dogs revealed the principle of fractional conditioning: the general behavior and changes in the cortical EEG characteristic of insulin action could become a conditional reflex (evoked by the injection of physiological saline i.v. and a CS)—while the blood sugar level, the heart rate, the EKG, and body temperature did not become CRs. This split illustrates the principle shown by Gantt that centrally-mediated effects of an agent are conditionable while those resulting only from direct peripheral action cannot become CRs. From this principle it may be assumed that the effects of insulin (behavioral, EEG) are mediated through the central nervous system, while other insulin effects (those not conditionable) are a result of peripheral action. Two methods of blood sugar determination (Hagedorn-Jensen and glucose oxidase) in both venous and arterial blood were used in these experiments, and the data resulting from 14,056 determinations were analyzed.     

Living with Long QT Syndrome: A Qualitative Study of Coping with Increased Risk of Sudden Cardiac Death

Long QT syndrome (LQTS) is a congenital disorder associated with increased risk of sudden cardiac death; LQTS patients and their families are offered diagnostic or predictive genetic testing. The purpose of this qualitative study was to investigate the psychosocial aspects of living with LQTS, to identify LQTS patients’ daily life challenges and coping strategies, and to describe their experiences with healthcare services. In-depth interviews were conducted with seven individuals who had been tested for long QT genetic mutation. Four of these participants had an implantable cardiac defibrillator (ICD). The participants reported that early and gradually acquired knowledge of the syndrome was an advantage. They also reported experiencing worries and limitations in daily life, but their main concern was for their children or grandchildren. Healthcare providers’ minimal knowledge of LQTS resulted in uncertainty, misinformation, and even wrong advice regarding treatment. The results suggest that regional centers, with the appropriate expertise, should investigate and counsel LQTS patients and their families.     

Time and direction preparation of the long latency stretch reflex

This study investigated time and direction preparation of motor response to force load while intending to maintain the finger at the initial neutral position. Force load extending or flexing the index finger was given while healthy humans intended to maintain the index finger at the initial neutral position. Electromyographic activity was recorded from the first dorsal interosseous muscle. A precue with or without advanced information regarding the direction of the forthcoming force load was given 1000 ms before force load. Trials without the precue were inserted between the precued trials. A long latency stretch reflex was elicited by force load regardless of its direction, indicating that the long latency stretch reflex is elicited not only by muscle stretch afferents, but also by direction-insensitive sensations. Time preparation of motor response to either direction of force load enhanced the long latency stretch reflex, indicating that time preparation is not mediated by afferent discharge of muscle stretch. Direction preparation enhanced the long latency stretch reflex and increased corticospinal excitability 0–20 ms after force load when force load was given in the direction stretching the muscle. These enhancements must be induced by preset of the afferent pathway mediating segmental stretch reflex.     

Role of Secondary Stressors in the Parental Death–Child Distress Relation

This study examined the psychological consequences and secondary stressors associated with death of a parent. The sample (N = 116) consisted of 26 youths who had lost a parent to homicide, 45 youths who had lost a parent to natural death, and 45 nonbereaved youths. Youngsters completed face-to-face interviews, while their guardians completed measures assessing the children's functioning. Results based on both child and guardian reports indicated that parental death was associated with an increase in secondary stressors, regardless of the mode of death. Findings based on guardian reports also revealed that parental death was related to increased internalizing distress, and that parental death due to homicide was related to increased externalizing distress. Furthermore, secondary stressors mediated the parental death–child distress relation such that parental death led to an increase in stressors, which in turn led to increased child distress. Implications for secondary and tertiary preventive interventions are discussed.     

Crib death: a biobehavioral phenomenon?

In developed countries, more children under 1 year of age die of crib death (sudden infant death syndrome, SIDS) than of all other causes combined. Researchers and clinicians have proposed many possible causes of SIDS, but the abrupt, unexpected death of some babies remains mysterious and frightening. Although infant behavior may explain some of these deaths, scant attention has addressed behavioral characteristics of babies who die without medical explanation. Any explanation of SIDS must account for the fact that most SIDS deaths occur at 2 to 5 months of age, acknowledging that a protective mechanism appears to spare babies before 2 months but then disappears. The respiratory occlusion reflex serves as an initial defense against smothering and can provide such an explanation. Infantile reflexes wane, after providing opportunities for learned responses to be acquired. During this well-documented neurobehavioral transition from subcortical to cortically mediated responding, some babies, viable for the first 2 months, may become especially vulnerable if they fail to acquire sufficiently strong defensive behaviors needed to prevent occlusion after the waning of the life-preserving reflex. Recent success of back-to-sleep directives, urging that babies sleep on their backs to avoid smothering, supports this hypothesis.     

Medium-chain acyl CoA dehydrogenase deficiency: Its relationship to SIDS and the impact on genetic counseling

Sudden infant death syndrome (SIDS) is defined as the sudden and unexpected death of an apparently healthy infant under 1 year of age. Routine autopsies often provide few clues as to the cause of death and rarely include a biochemical evaluation. Genetic counseling for SIDS can be difficult as recurrence risks vary depending on the age at death and the number of deaths which have occurred in the family. Biochemical disorders may account for up to 5% of SIDS. Of the metabolic disorders known to be involved in SIDS, the most commonly found is medium-chain acyl CoA dehydrogenase deficiency (MCAD). MCAD is an autosomal recessive disorder of fatty acid oxidation which accounts for up to 1% of SIDS. For some families, the addition of a postmortem biochemical investigation can identify an unsuspected metabolic disorder as the cause of death. Once the diagnosis is established, accurate genetic counseling can then be provided. Metabolic testing of the surviving siblings of victims of sudden death, and the subsequent identification of those due to MCAD can prevent the tragedy of recurrent SIDS in some families. In addition, screening the survivors of an acute life threatening event (ALTE) may also prevent a recurrence.     

Endocrine reactions and cognitive performance at 60 metres hyperbaric pressure

Endocrine reactions and cognitive performance were examined in a dive to 60 metres hyperbaric pressure ( N = 29). There was a significant increase for prolactine and growth hormone, and a significant decrease for epinephrine and testosterone. Memory was significantly reduced at 60 metres. The factor pattern of the endocrine postdive measures showed a cortisol, a catecholamine, and a testosterone factor similar to previous stress-studies at 1 atmosphere. Confirming previous studies there was a correlation between perceptual defense reactions as tested by the Defense Mechanism (DMT) and cortisol. DMT also correlated with performance on a reasoning test when learning was controlled. Furthermore, for the postdive samples there was a correlation between cortisol and performance on the arithmetic test, while prolactine correlated to memory reduction. These results indicate that the endocrine reactions and the reduction in cognitive performance is due to an effect of the emotional reaction to the dive situation in addition to direct effects of the nitrogen narcosis.     

Punishment and the potential for negative reinforcement with histamine injection

The present study examined punishment of responding with histamine injection, and its potential to generate avoidance of punishment. Sprague–Dawley rats were trained under concurrent schedules in which responses on one lever (the punishment lever) produced food under a variable‐interval schedule, and under some conditions intermittent injections of histamine, which suppressed behavior. Responses on a second (avoidance) lever prevented histamine injections scheduled on the punishment lever. After stabilization of punished responding, a variable‐interval 15‐s schedule of cancellation of histamine (avoidance) was added for responding on the second/avoidance lever, without subsequent acquisition of responding on that lever. Progressive decreases in the length of the punishment variable‐interval schedule increased suppression on the punishment lever without increases in response rates on the avoidance lever. Exchanging contingencies on the levers ensured that response rates on the avoidance lever were sufficiently high to decrease the histamine injection frequency; nonetheless response rates on the avoidance lever decreased over subsequent sessions. Under no condition was responding maintained on the avoidance lever despite continued punishing effectiveness of histamine throughout. The present results suggest that avoidance conditioning is not a necessary condition for effective punishment, and confirm the importance of empirical rather than presumed categorization of behavioral effects of stimulus events.     

A choice procedure to assess the aversive effects of drugs in rodents

The goal of this series of experiments was to develop an operant choice procedure to examine rapidly the punishing effects of intravenous drugs in rats. First, the cardiovascular effects of experimenter‐administered intravenous histamine, a known aversive drug, were assessed to determine a biologically active dose range. Next, rats responded on each of two levers with concurrently available fixed‐ratio 1 schedules of food reinforcement. Intravenous histamine was delivered along with food when responses were made on one of the options, and the lever on which both food and histamine were contingent was switched on a regular basis. A dose of 1.0 mg/kg/inj of histamine was effective in moving responding to the alternate lever, whereas saline, 0.1, or 0.3 mg/kg/inj of histamine were not. Histamine injections produced reliable selection of the alternate lever when they were presented on the same lever for three consecutive sessions, but not when they were switched between levers on each session. In addition, histamine produced greater selection of the alternate lever when it was presented with shorter intertrial interval durations. These findings indicate that, with appropriate parameters, the aversive effects of histamine and perhaps other drugs can be established rapidly using a concurrent choice procedure.     

Lexical Decision Paradigms do not Differentiate between Fearful and Non-fearful Individuals

Thirty-two spider-fearful, 33 blood/injury/injection fearful, and 28 non-fearful individuals (N = 93) participated in dual-task study. Participants were presented with blood, spider, neutral, positive and pseudo-word stimuli while having to also verbally identify numbers as either even or odd. Blood-fearful individuals responded slower than spider and non-fearful individuals. However, there was no interaction of group membership with stimuli type. This study replicates the results of two previous studies that have used a lexical decision task in an effort to differentiate between fearful and non-fearful individuals and found no significant differences between these two groups on this task. These results suggest that the lexical decision task in general may not be sensitive enough to elicit processing differences in non-clinical samples.     

Biobehavioral factors in sudden cardiac death

The authors examine the recent literature on psychological factors and sudden cardiac death and explore the mediating psychophysiological processes by which these variables may be associated. Direct evidence that psychosocial stressors and their correlates may be causally linked with sudden cardiac death in humans is not conclusive, but there is abundant convergent evidence that several physiological precursors of sudden death may be promoted by psychological challenge, especially in persons with coronary heart disease. The authors call for increased attention to the acute effects of psychological events on cardiovascular health.     

Histamine reverses a memory deficit induced in rats by early postnatal maternal deprivation

Early partial maternal deprivation causes long-lasting neurochemical, behavioral and brain structural effects. In rats, it causes a deficit in memory consolidation visible in adult life. Some of these deficits can be reversed by donepezil and galantamine, which suggests that they may result from an impairment of brain cholinergic transmission. One such deficit, representative of all others, is an impairment of memory consolidation, clearly observable in a one-trial inhibitory avoidance task. Recent data suggest a role of brain histaminergic systems in the regulation of behavior, particularly inhibitory avoidance learning. Here we investigate whether histamine itself, its analog SKF-91844, or various receptor-selective histamine agonists and antagonists given into the CA1 region of the hippocampus immediately post-training can affect retention of one-trial inhibitory avoidance in rats submitted to early postnatal maternal deprivation. We found that histamine, SKF-91844 and the H2 receptor agonist, dimaprit enhance consolidation on their own and reverse the consolidation deficit induced by maternal deprivation. The enhancing effect of histamine was blocked by the H2 receptor antagonist, ranitidine, but not by the H1 receptor antagonist pyrilamine or by the H3 antagonist thioperamide given into CA1 at doses known to have other behavioral actions, without altering locomotor and exploratory activity or the anxiety state of the animals. The present results suggest that the memory deficit induced by early postnatal maternal deprivation in rats may in part be due to an impairment of histamine mediated mechanisms in the CA1 region of the rat hippocampus.     

Sudden Unexpected Versus Violent Death and PTSD Symptom Development

Changes to posttraumatic stress disorder (PTSD) trauma criterion in the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM–5) have been an area of much scrutiny and debate. One of the proposed changes included removing sudden unexpected death (SUD) from the list of potentially traumatic events. This study tested the extent to which unexpected death differed from violent death and other traumas as measured by PTSD symptoms. Our results indicated a significant difference in symptom development between those experiencing sudden violent death and sudden unexpected, but nonviolent, death. Additional analyses at the DSM–IV symptom cluster level, as well as with Simms, Watson, and Doebbeling’s (2002) factor structure of PTSD symptoms, suggested further distinctions between event types and symptom development. The extent to which SUD should be included in the trauma criterion is considered.     

Relationship between absolute body-fluid deficits and fluid intake in the rat.

Acute absolute body-fluid deficits were induced in rats by injection of the diuretic drug furosemide, which caused up to 20% reduction of extracellular fluid volume and up to 2% reduction of intracellular fluid volume. Water and .3 M NaCl were subsequently made available to allow the rats to replace their body fluids by drinking. The rats increased their intake of both fluids, but replaced less than half of the total deficit, thereby tolerating larger and larger voluntary body-fluid deficits as the size of the diuretic fluid loss increased. Plasma measures showed that the rats sustained hypovolemia after drinking, while intracellular fluid volume was apparently restored. Fluid-depleted rats drank normally in response to intracellular dehydration induced by a sodium chloride load. Incomplete restoration of body-fluid balance after body-fluid depletion is due to a failure to drink in response to extracellular dehydration.     

Effects of a Classwide Interdependent Group Contingency Designed to Improve the Behavior of an At-Risk Student

When students display disruptive behaviors, it interferes with their own, and other students’ learning and with the teacher’s ability to instruct during academic activities. This study investigated the effects of a classwide interdependent group contingency on the on/off-task behaviors of an at-risk student in a first-grade classroom in a private Midwestern school. The student was referred for intervention due to his high rates of off-task behavior and low levels of academic engagement. An ABAB withdrawal design was used to evaluate the effectiveness of the intervention to improve the target student’s behavior as well as that of his classroom peers. Results suggested that the intervention decreased the individual student’s off-task behavior and increased academic engagement while also having positive effects on overall behavior in the classroom.     

The Kurt Cobain Suicide Crisis: Perspectives from Research,Public Health,and the News Media

The suicide of rock star Kurt Cobain in 1994 raised immediate concerns among suicidologists and the public at large about the potential for his death to spark copycat suicides, especially among vulnerable youth. The Seattle community, where Cobain lived and died, was especially affected by his sudden death. An overview of Cobain's life and death is presented and various crisis center and community-based interventions that occurred are discussed. Preliminary data collected from the Seattle Medical Examiner's Office and from the Seattle Crisis Center to assess the potential impact of Cobain's death on completed suicides and the incidence of suicide crisis calls are presented. The data obtained from the Seattle King County area suggest that the expected “Werther effect” apparently did not occur, but there was a significant increase in suicide crisis calls following his death. It is hypothesized that the lack of an apparent copycat effect in Seattle may be due to various aspects of the media coverage, the method used in Cobain's suicide, and the crisis center and community outreach interventions that occurred. The Cobain suicide and the role of media influence on copycat suicides are further discussed in commentaries from public health and news media perspectives.