A zebrafish model of tauopathy allows in vivo imaging of neuronal cell death and drug evaluation

Our aging society is confronted with a dramatic increase of patients suffering from tauopathies, which include Alzheimer disease and certain frontotemporal dementias. These disorders are characterized by typical neuropathological lesions including hyperphosphorylation and subsequent aggregation of TAU protein and neuronal cell death. Currently, no mechanism-based cures are available. We generated fluorescently labeled TAU transgenic zebrafish, which rapidly recapitulated key pathological features of tauopathies, including phosphorylation and conformational changes of human TAU protein, tangle formation, neuronal and behavioral disturbances, and cell death. Due to their optical transparency and small size, zebrafish larvae are well suited for both in vivo imaging and drug development. TAU-induced neuronal cell death was imaged by time-lapse microscopy in vivo. Furthermore, we used this zebrafish model to identify compounds targeting the TAU kinase glycogen synthase kinase 3beta (GSK3beta). We identified a newly developed highly active GSK3beta inhibitor, AR-534, by rational drug design. AR-534 reduced TAU phosphorylation in TAU transgenic zebrafish. This transgenic zebrafish model may become a valuable tool for further studies of the neuropathology of dementia.

Psychologic stress, vasodepressor (vasovagal) syncope, and sudden death

Giving up in the face of emotional arousal and psychologic uncertainty are conditions conducive both to vasodepressor syncope and sudden death. Under such circumstances there may be simultaneous activation of two emergency biologic regulatory systems, flight-fight and conservation-withdrawal. In the healthy person this may result in vasodepressor syncope, benign arrhythmias, or both. In the presence of factors lowering the threshold for conduction disturbances, dangerous arrhythmias and sudden death rather than, or as well as, vasodepressor syncope may result. Although active myocardial damage by itself may provide the necessary and sufficient conditions for lethal arrhythmias, psychic uncertainty must be considered an additional risk factor. The implications of this concept for patient care and prevention of sudden death are a challenge for future research.

Rapid evolution of escape ability in Trinidadian guppies (Poecilia reticulata)

Predators are widely assumed to create selection that shapes the evolution of prey escape abilities. However, this assumption is difficult to test directly due to the challenge of recording both predation and its evolutionary consequences in the wild. We examined these events by studying natural and experimental populations of Trinidadian guppies, Poecilia reticulata, which occur in distinct high-predation and low-predation environments within streams. Importantly, in the last two decades several populations of guppies have been experimentally introduced from one type of predatory environment into the other, allowing measurements of the consequences of change. We used this system to test two hypotheses: First, that changes in predatory environments create phenotypic selection favoring changes in escape ability of guppies, and second, that this selection can result in rapid evolution. For the first test we compared escape ability of wild caught guppies from high- versus low-predation environments by measuring survival rates during staged encounters with a major predator, the pike cichlid Crenicichla alta. We used guppies from three streams, comparing two within-stream pairs of natural populations and three within-stream pairs of an introduced population versus its natural source population. In every comparison, guppies from the high-predation population showed higher survival. These multiple, parallel divergences in guppy survival phenotype suggest that predatory environment does create selection of escape ability. We tested our second hypothesis by rearing guppies in common garden conditions in the laboratory, then repeating the earlier experiments using the F2 generation. As before, each comparison resulted in higher survival of guppies descended from the high-predation populations, demonstrating that population differences in escape ability have a genetic basis. These results also show that escape ability can evolve very rapidly in nature, that is, within 26-36 generations in the introduced populations. Interestingly, we found rapid evolutionary loss of escape ability in populations introduced into low-predation environments, suggesting that steep fitness trade-offs may influence the evolution of escape traits.

Omega-3 fatty acids and rodent behavior

This paper reviews the role of the n-3 fatty acids in the regulation of cognitive functions, locomotor and exploratory activity and emotional status in rodents. There are disparate data on the performance of n-3 fatty acid deficient animals in the open field test and elevated plus maze. Results obtained in our laboratory indicated slower habituation to the open field in deficient mice, which affects total locomotor and exploratory parameters. We also observed no change in plus maze performance of deficient mice under low-stress but elevated anxiety under high-stress conditions. There is some evidence of elevated aggression and increased immobility time in the forced swimming test caused by n-3 fatty acid deficiency in rodents. Effects of n-3 fatty acid deficiency and supplementation on learning in several tests such as the Morris water maze, two odor olfactory discriminations, radial arm maze performance and avoidance tasks are reviewed in detail. There is some evidence of an enhanced vulnerability to stress of n-3 fatty acid deficient animals and this factor can influence performance in a variety of tests. Thus, behavioral tasks that involve a higher level of stress may better differentiate behavioral effects related to brain docosahexaenoic acid (DHA) status. It is suggested that a fruitful area for future investigations of functional alterations related to brain DHA status will be the delineation of the factors underlying changes in performance in behavioral tasks. The possible role of non-cognitive factors like emotionality and attention in the impaired performance of n-3 fatty acid deficient animals also requires further investigation.

A quantal analysis of the synaptic depression underlying habituation of the gill-withdrawal reflex in Aplysia

Habituation, one of the simplest behavioral paradigms for studying memory, has recently been examined on the cellular level in the gill-withdrawal reflex in the mollusc Aplysia and in the escape response in cray-fish. In both cases short-term habituation involved a decrease in excitatory synaptic transmission at the synapses between the sensory neurons and their central target cells. To analyze the mechanisms of the synaptic depression in Aplysia, we applied a quantal analysis to synaptic transmission between the sensory and motor neurons of the gill-withdrawal reflex. Our results indicate that short-term habituation results from a presynaptic mechanism: a decrease in the number of transmitter quanta released per impulse. The sensitivity of the postsynaptic receptor remains unaltered.

Coupled contagion dynamics of fear and disease: mathematical and computational explorations

Background

In classical mathematical epidemiology, individuals do not adapt their contact behavior during epidemics. They do not endogenously engage, for example, in social distancing based on fear. Yet, adaptive behavior is well-documented in true epidemics. We explore the effect of including such behavior in models of epidemic dynamics.

Methodology/Principal Findings

Using both nonlinear dynamical systems and agent-based computation, we model two interacting contagion processes: one of disease and one of fear of the disease. Individuals can “contract” fear through contact with individuals who are infected with the disease (the sick), infected with fear only (the scared), and infected with both fear and disease (the sick and scared). Scared individuals–whether sick or not–may remove themselves from circulation with some probability, which affects the contact dynamic, and thus the disease epidemic proper. If we allow individuals to recover from fear and return to circulation, the coupled dynamics become quite rich, and can include multiple waves of infection. We also study flight as a behavioral response.

Conclusions/Significance

In a spatially extended setting, even relatively small levels of fear-inspired flight can have a dramatic impact on spatio-temporal epidemic dynamics. Self-isolation and spatial flight are only two of many possible actions that fear-infected individuals may take. Our main point is that behavioral adaptation of some sort must be considered.

Escaping or connecting? Characteristics of youth who form close online relationships

We used data from a US national sample of Internet users, ages 10-17 (N=1501), to explore the characteristics of youth who had formed close relationships with people they met on the Internet (n=210). Girls who had high levels of conflict with parents or were highly troubled were more likely than other girls to have close online relationships, as were boys who had low levels of communication with parents or were highly troubled, compared to other boys. Age, race and aspects of Internet use were also related. We know little about the nature or quality of the close online relationships, but youth with these sorts of problems may be more vulnerable to online exploitation and to other possible ill effects of online relationships. At the same time, these relationships may have helpful aspects.

Decision making under stress: Scanning of alternatives under controllable and uncontrollable threats

This study tested the proposition that deficient decision making under stress is due, to a significant extent, to the individual's failure to fulfill adequately an elementary requirement of the decision-making process, that is, the systematic consideration of all relevant alternatives. One hundred one undergraduate students (59 women and 42 men), aged 20-40, served as subjects in this experiment. They were requested to solve decision problems, using an interactive computer paradigm, while being exposed to controllable stress, uncontrollable stress, or no stress at all. There was no time constraint for the performance of the task. The controllability of the stressor was found to have no effect on the participants' performance. However, those who were exposed to either controllable or uncontrollable stress showed a significantly stronger tendency to offer solutions before all available alternatives had been considered and to scan their alternatives in a nonsystematic fashion than did participants who were not exposed to stress. In addition, patterns of alternative scanning were found to be correlated with the correctness of solutions to decision problems.

Four dimensions of fear of dental injections

In 1995, students and staff at the University of Washington were surveyed regarding avoidance of dental care and fear of dental injections. More than 25 percent of adults surveyed expressed at least one clinically significant fear of injections. Almost one in 20 respondents indicated avoiding, cancelling or not appearing for dental appointments because of fear of dental injections. Fear of dental injections consists of four dimensions. General fear of dental injections including pain of injection and of bodily injury from injection are the two most common dimensions of dental injection fear. Many people also express fears of acquired disease. Fear related to local anesthetic (such as side effects, inadequate anesthesia) is less frequent. Some respondents have fears that must be categorized using more than one of these dimensions. Understanding the nature of a patient's fear of injection may suggest strategies to address his or her concerns.

Getting even or moving on? Power, procedural justice, and types of offense as predictors of revenge, forgiveness, reconciliation, and avoidance in organizations

A field study and an experimental study examined relationships among organizational variables and various responses of victims to perceived wrongdoing. Both studies showed that procedural justice climate moderates the effect of organizational variables on the victim's revenge, forgiveness, reconciliation, or avoidance behaviors. In Study 1, a field study, absolute hierarchical status enhanced forgiveness and reconciliation, but only when perceptions of procedural justice climate were high; relative hierarchical status increased revenge, but only when perceptions of procedural justice climate were low. In Study 2, a laboratory experiment, victims were less likely to endorse vengeance or avoidance depending on the type of wrongdoing, but only when perceptions of procedural justice climate were high.

Multiple benefits of multiple mating in guppies

The rewards of promiscuity for males are undisputed. But why should a female mate promiscuously, particularly when her partners offer no resources other than sperm and increase her chances of succumbing to predation or disease? This question has been hotly debated but at present remains largely unresolved [Jennions, M. D. & Petrie, M. (2000) Biol. Rev. 75, 21-64]. One possibility is that females exploit postcopulatory mechanisms, such as sperm competition, to increase both the quality and quantity of their offspring. In this paper, we use the Trinidadian guppy, a species with a resource-free mating system, to test the hypothesis that females gain multiple benefits from multiple mating. Our results indicate that multiply mated females secure substantive advantages: They have shorter gestation times and larger broods, and they produce offspring with better developed schooling abilities and escape responses than their singly mated counterparts.

Formation of a place learning-set by the rat: a new paradigm for neurobehavioral studies

The Morris water swimming task provides an ideal way of studying spatial navigational abilities in rats. It requires that rats swim to find a platform located just below the surface of the water in a swimming pool, and rats will learn and perform the task readily without being subject to nutrient deprivation. A novel adaption of the task, in which rats are shown to form a place learning-set, is described in the present paper. The learning-set paradigm can be used for the repeated evaluation of spatial navigation abilities in the same animals over a long period of time. The procedure is based on the finding that once trained, rats can acquire a new place response each day. Each new response can be learned within one or two trials, given within the time period of a few seconds, and once acquired, the response can be retained for a number of days, or until the problem is changed. The procedure can be usefully applied to the study of recovery of function following brain damage, the study of memory processes following brain damage, the changes in memory processes accompanying aging, or it can be used for the screening of pharmacological compounds, etc. The technique may be especially useful for the study of the performance of individual rats.

Acceptance and Commitment Therapy in the Treatment of Posttraumatic Stress Disorder

The current article describes the application of a behavioral psychotherapy, acceptance and commitment therapy (ACT), to the treatment of post-traumatic stress disorder (PTSD). It is argued that PTSD can be conceptualized as a disorder that is developed and maintained in traumatized individuals as a result of excessive, ineffective attempts to control unwanted thoughts, feelings, and memories, especially those related to the traumatic event(s). As ACT is a therapeutic method designed specifically to reduce experiential avoidance, it may be a treatment that is particularly suited for individuals with PTSD. The application of ACT to PTSD is described, and a case example is used to demonstrate how this therapy can be successfully used with individuals presenting for life problems related to a traumatic event.

An open trial of an acceptance-based behavior therapy for generalized anxiety disorder

Research suggests that experiential avoidance may play an important role in generalized anxiety disorder (GAD); see . Expanding our conceptualization of and treatment for generalized anxiety disorder: Integrating mindfulness/acceptance-based approaches with existing cognitive-behavioral models. Clinical Psychology: Science and Practice, 9, 54-68, for a review). Therefore, a treatment that emphasizes experiential acceptance, as well as intentional action, may lead to both reduced symptomatology and improved quality of life and functioning for individuals with this chronic disorder. In an open trial of a newly developed acceptance-based behavior therapy for GAD, 16 treated clients demonstrated significant reductions in clinician-rated severity of GAD and reports of anxiety and depressive symptoms and fear and avoidance of their internal experience, as well as significant improvements in reports of quality of life, at both posttreatment and 3-month follow-up. Directions for future treatment development and research are discussed.

The role of neurohormonal octopamine during 'fight or flight' behaviour in the field cricket Gryllus bimaculatus

Octopamine has been called the 'fight or flight' hormone of insects. We tested this hypothesis by measuring octopamine levels in the haemolymph of field crickets after fighting, flying, courting and escape behaviours. Octopamine levels in the cricket Gryllus bimaculatus increased during aggressive (agonistic) behaviour from baseline levels of 4.5 +/- 2.1 pg microliters-1 haemolymph to 24.3 +/- 15.2 pg microliters-1 haemolymph, regardless of whether the cricket won or lost the encounter. Octopamine levels also increased after 5 min of flying (to 44.6 +/- 22.3 pg microliters-1) and during courtship. However, crickets did not exhibit an increase in their haemolymph octopamine levels after performing an escape run. Therefore, neurohormonal octopamine shows some, but not all, of the characteristics that would be expected if it were a component of a nonspecific 'arousal' system. Rather, octopamine may be released as a neurohormone to prepare the animal for a period of extended activity or to assist the animal in recovering from a period of increased energy demand. Antennal contact with conspecifics may provide a sensory cue that results in the release of octopamine into the haemolymph.

Learned helplessness in the rat: time course, immunization, and reversibility

Rats, like dogs, fail to escape following exposure to inescapable shock. This failure to escape does not dissipate in time; rats fail to escape 5 min, 1 hr., 4 hr., 24 hr., and 1 wk. after receiving inescapable shock. Rats that first learned to jump up to escape were not retarded later at bar pressing to escape following inescapable shock. Failure to escape can be broken up by forcibly exposing the rat to an escape contingency. Therefore, the effects of inescapable shock in the rat parallel learned helplessness effects in the dog.

Behavioral genetic approaches to visual system development and function in zebrafish

The zebrafish is a recent vertebrate model system that shows great potential for a genetic analysis of behavior. Early development is extraordinarily rapid, so that larvae already display a range of behaviors 5 days after fertilization. In particular the visual system develops precociously, supporting a number of visually mediated behaviors in the larva. This provides the opportunity to use these visually mediated behaviors to screen chemically mutagenized strains for defects in vision. Larval optokinetic and optomotor responses have already been successfully employed to screen for mutant strains with defects in the visual system. In the adult zebrafish a visually mediated escape response has proved useful for screening for dominant mutations of the visual system. Here, I summarize visually mediated behaviors of both larval and adult zebrafish and their applicability for genetic screens, and present, the approaches and results of visual behavior carried out to date.

Inescapable footshocks induce progressive and long-lasting behavioural changes in male rats

Long-term behavioural consequences of exposure to a brief (15 min) session of inescapable footshocks (10 x 6 s, 1 mA) were investigated in male rats. The time course of the effects of inescapable footshocks was assessed by studying the behaviour of groups of rats at different post-stress intervals. Footshocked rats (S) did not differ from control (C) rats (exposed to the shock box for 15 min) in their behavioural response to an open field whether tested 1 h or 4 h post-stress. However, one day after shocks, S rats showed less locomotion and rearing, and more immobility and attention as compared to C rats. At 7 days or 14 days post-stress, S rats exhibited decreased locomotion, rearing, sniffing, and grooming, and increased immobility, attention, and defecation relative to C rats. In a second experiment, we investigated whether footshocks affect the behavioural response to a sudden drop in background noise during exposure to a novel environment. At 21 days post-stress, S rats showed a markedly enhanced immobility response to this stimulus as compared to C rats. In order to investigate whether rats could be exposed repeatedly to the open field without affecting the differences in behaviour between the two treatment groups, C and S rats were tested in an open field for the first time at 7 days post-stress, which yielded the typical effects of footshocks. When these rats were exposed to a second open-field test one week later, the behavioural responses of C and S rats were not different.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclic AMP-induced repair of zebrafish spinal circuits

Neurons in the human central nervous system (CNS) are unable to regenerate, as a result of both an inhibitory environment and their inherent inability to regrow. In contrast, the CNS environment in fish is permissive for growth, yet some neurons still cannot regenerate. Fish thus offer an opportunity to study molecules that might surmount the intrinsic limitations they share with mammals, without the complication of an inhibitory environment. We show by in vivo imaging in zebrafish that post-injury application of cyclic adenosine monophosphate can transform severed CNS neurons into ones that regenerate and restore function, thus overcoming intrinsic limitations to regeneration in a vertebrate.