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Temperature and Chemicals
Published in Sue Binkley, Biological Clocks, 2020
There are a number of surgical procedures that have produced arrhythmia, a loss of circadian rhythms, in constant conditions. Either the circadian pacemaker was removed. Or, alternatively, the measurable rhythm (the hands) were disconnected from the pacemaking oscillation (clock). Ablations which have abolished rhythms include removing the pineal gland from a house sparrow, lesioning the suprachiasmatic nuclei of the hypothalamus of the brain of a rat or hamster, removing the optic lobe from a cockroach. Thus, these structures—the pineal gland, the suprachiasmatic nuclei, and the optic lobes—are candidates for biological oscillators (circadian pacemakers, biological clocks).
Glutaminases
Published in Elling Kvamme, Glutamine and Glutamate in Mammals, 1988
Elling Kvamme, Gerd Svenneby, Ingeborg Aasland Torgner
Since glutamine is believed to function as a precursor to the excitatory transmitter pool of glutamate, the structural localization of PAG in the brain has created considerable interest. PAG activity has been detected all over the brain, but in humans much higher activities are found in cortical areas compared to subcortical ones and the cerebellum with an exception of caudate nucleus which show high activity.64 Chick cerebral hemispheres also show higher PAG activity than the optic lobe and cerebellum.61 Immunocytochemical investigations have been done using antibodies raised against brain or rat kidney PAG. Such studies are based on the conviction that high PAG-like immunoreactivity is a marker for glutamatergic neurons. However, this view is open for discussion, since PAG is a general mitochondrial enzyme and a relationship between functional enzyme activity and amount of mitochondrial enzyme protein never has been demonstrated (see Section VILA, B).
Markers of Cholinergic Dysfunction in Alzheimer Disease
Published in Robert E. Becker, Ezio Giacobini, Alzheimer Disease, 2020
Ezio Giacobini, Kiminobu Sugaya, Rodger J. Elble
Although α-BTX has proved to be a useful cholinergic ligand in the peripheral nervous system, mainly at the neuromuscular junction, it is not suitable as a marker for the CNS (Morley et al., 1983). Experiments performed with iontophoretic techniques do not support the hypothesis that α-neurotoxins such as α-BTX bind to functional NIC receptors in mammalian CNS (Morley and Kemp, 1981; Chiappinelli, 1985). Consequently, characterization and quantitation of nicotinic cholinergic binding sites in the brain has met with difficulty. Recent studies have indicated differences between central and peripheral nicotinic receptors (Marks and Collins, 1982; Shimohama et al., 1985; Sugiyama and Yamashita, 1986). Chiappinelli (1985) and Wolf et al. (1987) have used a BTX that they named kappa-bungarotoxin (K-BTX) to characterize central nicotinic receptors in the chicken and in the rat. Kappa-bungarotoxin has been recently isolated from snake venom (Chiappinelli, 1985). It was shown to be a potent and selective antagonist of neuronal nicotinic receptors (Chiappinelli, 1985) including CNS sites in the chicken optic lobe (Wolf et al., 1987). We have observed that using 3H-NIC, 125I-α-BTX and 125I-K-BTX, at least three putative categories of nicotinic receptor are present in the human brain. Our studies suggest that each type of these receptors may have different kinetics, distribution and localization. Kappa-bungarotoxin or neuronal BTX has been shown to block nicotinic synaptic transmission in a variety of neuronal preparations where α-BTX has no effect. Vidal and Changeux (1989) have demonstrated that the effect of NIC applied by iontophoresis to the prefrontal cortex of the rat is blocked by K-BTX but not by other nicotinic antagonists. The agonistic actions of ACh in cerebellar neurons is also selectively blocked by K-BTX (de la Garza et al., 1989).
A deep learning analysis of Drosophila body kinematics during magnetically tethered flight
Published in Journal of Neurogenetics, 2023
Geonil Kim, JoonHu An, Subin Ha, Anmo J. Kim
Besides the T4/T5-to-HS pathway through the lobula plate, the lobula represents another major visual structure that conveys visual signals to central brain structures from the optic lobe via a large number of visual projection neurons (VPNs). In particular, a large number of VPNs project from the lobula to the posterior ventrolateral protocerebrum (PVLP), forming discrete neuropils termed optic glomeruli (Kim et al.,2023; Ryu et al.,2022; Wu et al.,2016). These neurons are thought to act as feature-detecting neurons in Drosophila vision and thus are a good candidate for bar detection. Indeed, a recent study showed that LC15 neurons respond selectively to the horizontal movement of a dark vertical bar (Städele et al.,2020). Besides LC15 neurons, bar-sensitive VPNs include LC4, LC12, LC21, and LC25. Although no behavioral studies have been carried out regarding the function of these neurons during the bar fixation behavior, it is likely that some of these neurons, if not all, contribute to bar fixation. Besides the lobula, there are also VPNs that carry visual signals directly from the medulla to a central brain region, akin to the role of the MC61 neurons in color vision (Otsuna et al.,2014).
Studying complex brain dynamics using Drosophila
Published in Journal of Neurogenetics, 2020
Sophie Aimon, Ilona C. Grunwald Kadow
Large scale activity changes can be elicited by a perturbation such as a stimulus or a change in behavior. The perturbation will generate a change in some brain regions that will then affect connected regions and thus propagate throughout the network (O’Connell, Shadlen, Wong-Lin, & Kelly, 2018). This temporal aspect of information processing can be captured by maps of activation delays. For example, Figure 1(D) presents the activation time of different brain regions of the fly in response to an onset of light (bottom) or after the fly starts walking (top). Brain regions directly innervated by primary sensory or motor neurons such as areas of optic lobe (for the response to the flash) or the primary motor areas (for the walk) are activated first, while medial regions such as the mushroom body (an important center for learning and memory in the fly brain) are activated later.
Finding a place and leaving a mark in memory formation
Published in Journal of Neurogenetics, 2020
Divya Sitaraman, Holly LaFerriere
While, such cells within specific regions have not yet been identified in invertebrates, circuit analysis of spatial navigation has largely relied on visual pathways. For example, navigation using polarized skylight as a visual compass cue have identified neurons (POL neurons) that are tuned to specific polarized light angles and signal via the optic lobe and central complex (cx). This neural architecture has been found in bees, butterflies, locusts and beetles (Dacke, Nilsson, Scholtz, Byrne, & Warrant, 2003; Heinze & Reppert, 2011; Homberg, Heinze, Pfeiffer, Kinoshita, & el Jundi, 2011; Homberg et al., 2004; Merlin, Heinze, & Reppert, 2012; Stone et al., 2017; Warrant & Dacke, 2016). Evidence from Drosophila has taken these studies a step further by identifying cell types specifically, a set of columnar neurons termed ‘wedge-neurons’ that relay information from single identified domains of ellipsoid body (eb) to protocerebral bridge (pb) in flies walking on a ball in a virtual reality arena (Seelig & Jayaraman, 2015). In addition to the processing of sensory information, memory plays a central role in these navigational strategies.