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Signal transduction in olfactory sensory neurons of vertebrates and tools for the computer simulation
Beneš, Martin ; Zápotocký, Martin (advisor) ; Hejnová, Lucie (referee)
The purpose of this thesis is summing up the information about olfactory transduction of vertebrates. This review is divided into four parts, each part focuses on a different aspect of olfactory transduction. First there is an overview of basic electrophysiological methods used for transduction research, followed by a description of a complete transduction on a molecular level. Next is a summary of model types and their use in olfactory transduction simulation, including a detailed description of two models: One of them describes the beginning of olfactory transduction, from the odorant binding on the receptor to the cAMP production, the other deals with the negative feedback of Ca2+. Finally there is an overview of software products designed to create and analyze the models from the preceding section.
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Ca2+ signalling in magnocellular neurones of the rat supraoptic nucleus.
Kortus, Štěpán ; Zápotocký, Martin (advisor) ; Šuta, Daniel (referee) ; Hromádka, Tomáš (referee)
The magnocellular neurosecretory cells (MNCs) of the hypothalamus project axons from the supraoptic nucleus to the posterior pituitary gland, where they secrete either oxytocin or vasopressin into the circulation. Oxytocin is important for delivery at birth and is essential for milk ejection during suckling. Vasopressin primarily promotes water reabsorption in the kidney to maintain body fluid balance. The profile of oxytocin and vasopressin secretion is principally determined by the pattern of action potentials initiated at the cell bodies in the hypothalamus. MNCs principally secrete hormones from terminals in the pituitary, but the secretion also occurs from their dendrites in the supraoptic nucleus, where they diffuse and affect the neighbouring cells. Mechanisms controlling the oxytocin and vasopressin secretion from MNCs have been extensively studied over the last decades and it is assumed that the relationship between Ca2+ signalling, secretion from dendrites, and the firing patterns is essential in understanding the magnocellular neurosecretory system. In this project, we combine mathematical analysis and experimental measurements of Ca2+ activity of MNCs of transgenic rats expressing an arginine vasopressin-enhanced green fluorescent protein (AVP-eGFP) or oxytocin-monomeric red fluorescent...
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Ca2+ signalling in magnocellular neurones of the rat supraoptic nucleus.
Kortus, Štěpán ; Zápotocký, Martin (advisor) ; Šuta, Daniel (referee) ; Hromádka, Tomáš (referee)
The magnocellular neurosecretory cells (MNCs) of the hypothalamus project axons from the supraoptic nucleus to the posterior pituitary gland, where they secrete either oxytocin or vasopressin into the circulation. Oxytocin is important for delivery at birth and is essential for milk ejection during suckling. Vasopressin primarily promotes water reabsorption in the kidney to maintain body fluid balance. The profile of oxytocin and vasopressin secretion is principally determined by the pattern of action potentials initiated at the cell bodies in the hypothalamus. MNCs principally secrete hormones from terminals in the pituitary, but the secretion also occurs from their dendrites in the supraoptic nucleus, where they diffuse and affect the neighbouring cells. Mechanisms controlling the oxytocin and vasopressin secretion from MNCs have been extensively studied over the last decades and it is assumed that the relationship between Ca2+ signalling, secretion from dendrites, and the firing patterns is essential in understanding the magnocellular neurosecretory system. In this project, we combine mathematical analysis and experimental measurements of Ca2+ activity of MNCs of transgenic rats expressing an arginine vasopressin-enhanced green fluorescent protein (AVP-eGFP) or oxytocin-monomeric red fluorescent...
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Activity and Memory in Biologically Motivated Neural Network.
Štroffek, Július ; Maršálek, Petr (advisor) ; Zápotocký, Martin (referee) ; Hozman, Jiří (referee)
This work presents biologically motivated neural network model which works as an auto-associative memory. Architecture of the presented model is similar to the architecture of the Hopfield network which might be similar to some parts of the hippocampal network area CA3 (Cornu Amonis). Patterns learned and retrieved are not static but they are periodically repeating sequences of sparse synchronous activities. Patterns were stored to the network using the modified Hebb rule adjusted to store cyclic sequences. Capacity of the model is analyzed together with the numerical simulations. The model is further extended with short term potentiation (STP), which is forming the essential part of the successful pattern recall process. The memory capacity of the extended version of the model is highly increased. The joint version of the model combining both approaches is discussed. The model might be able to retrieve the pattern in short time interval without STP (fast patterns) or in a longer time period utilizing STP (slow patterns). We know from our everyday life that some patterns could be recalled promptly and some may need much longer time to reveal. Keywords auto-associative neural network, Hebbian learning, neural coding, memory, pattern recognition, short-term potentiation 1
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A diffusion-based model of signal transduction in the vertebrate olfactory sensory neuron, and its sensitivity analysis
Beneš, Martin ; Zápotocký, Martin (advisor) ; Jelínek, Jan (referee)
The goal of this model is to create and to implement qualitative model of the signal track of olfactory sensory neuron, including the feedback with a focus on diffusion of substances that allows to conduct more simulations for the better understanding of dynamics of the signal track. This model is expected to be used for the simulation of influencing during the activation of two receptors in firstly defined distance. Model was created and therefore implemented in a programming language Python with the use of library STEPS. Then I have conducted sensitivity analysis by a method Morris OAT on the model, together with an optimization with the usage of change of individual parameters with a great importance on the output of the model. Model is conducting good and biologically comparable results when there are from 10 to 100 active receptors at the beginning of the track. Unfortunately with a lower numbers, the results are not valid and therefore not to be used for the simulation of influencing of two activated receptors. Despite this is a main benefit of the work the model of signal transduction for the whole signal track with an included feedback and emphasis on diffusion. Another benefit is a set of scripts for the sensitivity analysis by a method Morris OAT and optimization.
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Analysis of dynamical interactions of axon shafts and their biopysical modelling.
Šmít, Daniel ; Zápotocký, Martin (advisor) ; Reingruber, Jūrgen (referee) ; Maršálek, Petr (referee)
in English While axon fasciculation plays a key role in the development of neural networks, very lit- tle is known about its dynamics and the underlying biophysical mechanisms. In a model system composed of neurons grown ex vivo from explants of embryonic mouse olfactory epithelia, we observed that axons dynamically interact with each other through their shafts, leading to zippering and unzippering behaviour that regulates their fasciculation. Taking advantage of this new preparation suitable for studying such interactions, we carried out a detailed biophysical analysis of zippering, occurring either spontaneously or induced by micromanipulations and pharmacological treatments. We show that zippering arises from the competition of axon-axon adhesion and me- chanical tension in the axons. This is upheld on quantitative level by conforming change of network global structure in response to various pharmacological treatments, without active involvement of growth cones. The calibrated manipulations of interacting shafts provide qualitative support for the hypothesis, and also allow us to quantify the mechan- ical tension of axons in our system. Furthermore, we introduce a biophysical model of the zippering dynamics, which efficiently serves the purpose of estimating the magnitude of remaining involved...
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Kinematic analysis of rhythmic motion: the cases of human hand tremor and fly wingbeat.
Chakraborty, Soma ; Zápotocký, Martin (advisor) ; Maršálek, Petr (referee) ; Jech, Robert (referee)
Rhythmic motions, regular or irregular, are an integral part of motor behavior both in health and in disease. Better understanding of its neural control mechanisms helps in developing methods for controlling the progression of diseases manifesting as rhythmic motions. I studied two specific aspects of rhythmic motions: bilateral coordination of hand tremors in human subjects and modular control of locomotion in invertebrates. Many types of tremors, including the physiological tremor (PT) and the essential tremor (ET) occur in limbs on both the sides of the body, with similar fundamental frequency of the oscillation. This raises the possibility that the contralateral tremors may have a common source or are otherwise coupled. However, while significant contralateral interaction is seen in these two types of tremors, only limited evidence of bilateral coherence has been shown in the previous literature. Therefore, in my study I explored the existence of a weak coupling between the left and right oscillators the may lead to intermittent bilateral coherence. I measured triaxial acceleration of the two hands and systematically assessed their bilateral coherence, using both stationary and non-stationary (wavelet-based) analyses methods. Measuring all three axes allowed examination of a more complete set...
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Role of individual chemical compounds of repellent secretion of Graphosoma lineatum towards different predator species
Gregorovičová, Martina ; Horáček, Ivan (advisor) ; Veselý, Petr (referee) ; Zápotocký, Martin (referee)
The chemical defence of Heteroptera is based on the repellent secretion that is very complex and consists of dozens chemical compounds. Heteroptera have good ability to produce/store large amounts of chemical components. The repellent secretion of Graphosoma lineatum is composed of many chemicals, such as short-chained aldehydes, which may signal the unpalatability of the bug to its potential predators or be directly toxic for them. The thesis is aimed at the major components of defensive secretion of Graphosoma lineatum - aldehydes - as well as the whole metathoracic scent-glands secretion of Graphosoma lineatum. The aversive reactions of four selected predators were evaluated: (1) leopard gecko (Eublepharis macularius); (2) green lizard (Lacerta viridis); (3) great tit (Parus major) and (4) blue tit (Cyanistes caeruleus). The following major compounds of the repellent secretion were tested: (1) the mixture of three aldehydes: (E)-hex-2-enal, (E)-oct-2-enal, (E)-dec-2-enal; (2) the mixture of three aldehydes and tridecane; (3) oxoaldehyde: (E)-4-oxohex-2-enal; (4) extracted metathoracic scent-glands secretion of Graphosoma lineatum adults; (5) hexane as a non-polar solvent and (6) pyrazine: 2-isobutyl-3-methoxypyrazine in experiments with leopard geckos as a positive control for excluding the...
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Signal transduction in olfactory sensory neurons of vertebrates and tools for the computer simulation
Beneš, Martin ; Zápotocký, Martin (advisor) ; Hejnová, Lucie (referee)
The purpose of this thesis is summing up the information about olfactory transduction of vertebrates. This review is divided into four parts, each part focuses on a different aspect of olfactory transduction. First there is an overview of basic electrophysiological methods used for transduction research, followed by a description of a complete transduction on a molecular level. Next is a summary of model types and their use in olfactory transduction simulation, including a detailed description of two models: One of them describes the beginning of olfactory transduction, from the odorant binding on the receptor to the cAMP production, the other deals with the negative feedback of Ca2+. Finally there is an overview of software products designed to create and analyze the models from the preceding section.
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