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From praise of danger to “reasoned” risk-taking
Published in Guy André Boy, Edwige Quillerou, Risk-Taking, Prevention, and Design, 2023
Take sensation-seeking. It was in 1964 that Zuckerman, who was studying the individual valence of responses from subjects under conditions of isolation or sensory over-stimulation, used the concept of optimal level of stimulation in terms of activation based on the work of Hebb (1955) (see Figure 2.1; Zuckerman et al., 1964) to conceptualize his first theory of sensation-seeking. His first version of the theory posited that sensation-seekers function in a way as to maintain “an optimal high level of stimulation”. According to Zuckerman, every human being has an optimal level of stimulation corresponding to his/her threshold. When we fall below our “threshold” (e.g., mild sensations induced in daily life), we experience boredom and disinterest. However, when our feelings exceed the threshold, we feel anguish, anxiety, or pain. Thus, individuals who have a very high threshold (high sensation-seekers) will be sensitive to the monotony of everyday life and tend to seek activities, behaviors or substances allowing them to feel sensations corresponding to their own personal threshold. Zuckerman, who later shifted toward a psychobiological model of sensation-seeking, changed the concept of an optimal level of activation to an optimal level of activity within the catecholaminergic system and particularly the dopaminergic system (Zuckerman, 1995).
High Information Content Physiological Biosensors
Published in George K. Knopf, Amarjeet S. Bassi, Smart Biosensor Technology, 2018
Guenter W. Gross, Joseph J. Pancrazio, Kamakshi Gopal
Attention-deficit hyperactivity disorder (ADHD) is thought to result from a disturbance in catecholaminergic neurotransmission with emphasis on dopamine (DA) and norepinephrine (NE) neurotransmitters (Pliszka et al., 1996). D,L-Methylphenidate (MPH) is a psychostimulant, which is commonly administered to treat ADHD. Subjects with ADHD are reported to have increased expression of dopamine transporters in the brain, leading to greater removal of dopamine from the extracellular space and decreasing the levels of dopamine at the synapses (Dougherty et al., 1999; Krause et al., 2000). MPH seems to preferentially block these transporters and inhibit the presynaptic uptake of dopamine (Volkow et al., 2001, 2003; Kuczenski and Segal 2002; Overtoom et al., 2003), thus decreasing the spontaneous neuronal activity in the postsynaptic neurons and leading to enhanced attention and motivation for specific tasks.
Dedifferentiation as a cell source for organ regeneration
Published in David M. Gardiner, Regenerative Engineering and Developmental Biology, 2017
The dedifferentiation process, as defined by Hall (2005), is “a process in which a cell loses its specialized morphology, function and biochemistry to initiate cell division and reverts to a less differentiated state in order to redifferentiate again.” Although cellular dedifferentiation has been known to be involved in regeneration processes for several decades, it is only in recent years that it has received serious attention. Part of the problem might have been that the early researches were done in regenerating amphibian limbs, and thus, investigators were reticent about ascribing a similar process to mammals. However, the main problem most likely stems from the fact that cellular dedifferentiation goes against the reigning dogma that views embryological development as a linear, irreversible process, where cell progenitors move from a less differentiated phenotype to a more differentiated phenotype. This implies that cells acquire their morphological, biochemical, and physiological properties in a stepwise manner controlled by the activation of a specific genetic profile. This differentiation pathway is usually accompanied by a loss of cellular plasticity; therefore, as cells acquire a specific phenotype, concomitantly, they are thought to lose the possibility of acquiring other alternative phenotypes (Figure 17.1). An example of this is the cells from the ectoderm embryological layer that can initially give rise to epidermis or nervous system if they take the nervous system route, which, later in development, will become either neurons or glia, and if they choose the neuronal route, later, they will have to choose what type of neuron to form (e.g., cholinergic vs. catecholaminergic). The outcome of the differentiation process is the formation of organs made up of cells that have reached their final differentiated state, which, in many cases, is considered irreversible.
Experimental models of chemically induced Parkinson’s disease in zebrafish at the embryonic larval stage: a systematic review
Published in Journal of Toxicology and Environmental Health, Part B, 2023
Paola Briñez-Gallego, Dennis Guilherme da Costa Silva, Marcos Freitas Cordeiro, Ana Paula Horn, Mariana Appel Hort
According to a recent review by Kin et al. (2019), 6-OHDA and MPTP are currently the most widely used toxins to induce experimental parkinsonism. This compound, unlike MPTP, cannot cross the BBB (Zeng, Geng, and Jia 2018), and this is why in non-adult zebrafish models, exposure needs to be between 24 and 72 hpf, since the BBB start to develops at 3 dpf (Jeong et al. 2008). 6-OHDA is a highly oxidizable DA analog that can be captured through DAT, which gives this neurotoxic agent specificity to affect catecholaminergic neurons, such as dopaminergic ones in the SNpc (Blandini and Armentero 2012). 6-OHDA is rapidly auto-oxidized, generating ROS including superoxide and hydroxyl radicals, hydrogen peroxide, and quinones, contributing to neurotoxic effects (Kin et al. 2019). It is known that the 6-OHDA-induced model does not perfectly mimic the pathology of PD since it lacks the formation of Lewy bodies but presents other typical characteristics of PD such as dopaminergic cell death, alteration of the mitochondrial complex I, and behavioral disturbances, for example, tremors and bradykinesia (Schober 2004).
Fatigue: Is it all neurochemistry?
Published in European Journal of Sport Science, 2018
Manipulations aiming to influence the catecholaminergic brain neurotransmitters have yielded a wide array of outcomes depending on the neurotransmitter that was manipulated and the ambient temperature in which this manipulation took place. Methylphenidate, a dopaminergic reuptake inhibitor, did not influence endurance performance in a normal ambient temperature (Roelands, Hasegawa, et al., 2008). When the ambient temperature was elevated (30°C), however, subjects performed 16% faster on a self-paced time trial compared with the placebo situation. Furthermore, their average core temperature reached 40.0°C. Most strikingly, no differences were observed in the subjects’ perceptions. They did not feel they were pushing much harder, nor did they feel they were getting much warmer (Roelands, Hasegawa, et al., 2008). Swart et al. (2009) also showed that methylphenidate allowed subjects to sustain higher work rates and greater levels of metabolic and cardiorespiratory stress for longer, while perceiving the exercise stress to be identical, indicating that subjects terminated the placebo trial with a metabolic and cardiorespiratory reserve that was not accessible without the use of methylphenidate.
Ractopamine hydrochloride induces behavioral alterations and oxidative status imbalance in zebrafish
Published in Journal of Toxicology and Environmental Health, Part A, 2018
Adrieli Sachett, Fernanda Bevilaqua, Rafael Chitolina, Cristiane Garbinato, Henrique Gasparetto, Jacir Dal Magro, Greicy M Conterato, Anna M Siebel
β-adrenergic signaling is significantly involved in the ability of organisms to respond to stressful situations suggesting that chronic exposure to RAC might impair, for example, zebrafish ability to respond effectively to a predatory threat. Further, chronic administration of β-adrenoreceptor agonists may induce alterations in catecholaminergic balance and neurochemical signaling mediated by the dopamine (D1) receptor, also a catecholaminergic G-coupled protein receptor type (Poletto et al. 2010, 2011). Thus, additional studies investigating chronic exposure of zebrafish to RAC are necessary since zebrafish is an adequate model organism to examine the effects of contaminants on behavior and physiology of exposed organisms.