Tetanus toxin (TeNT) is an extremely potent neurotoxin produced by the vegetative cell of Clostridium tetani in anaerobic conditions, causing tetanus. It has no known function for clostridia in the soil environment where they are normally encountered. It is also called spasmogenic toxin, tentoxilysin, tetanospasmin, or tetanus neurotoxin. The LD50 of this toxin has been measured to be approximately 2.5–3 ng/kg, making it second only to the related botulinum toxin (LD50 2 ng/kg) as the deadliest toxin in the world. However, these tests are conducted solely on mice, which may react to the toxin differently from humans and other animals.
Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defined nervous systems. Their neuroanatomy is therefore better understood. In vertebrates, the nervous system is segregated into the internal structure of the brain and spinal cord and the series of nerves that connect the CNS to the rest of the body. Breaking down and identifying specific parts of the nervous system has been crucial for figuring out how it operates. For example, much of what neuroscientists have learned comes from observing how damage or "lesions" to specific brain areas affects behavior or other neural functions.
Hebbian theory is a neuropsychological theory claiming that an increase in synaptic efficacy arises from a presynaptic cell's repeated and persistent stimulation of a postsynaptic cell. It is an attempt to explain synaptic plasticity, the adaptation of brain neurons during the learning process. It was introduced by Donald Hebb in his 1949 book The Organization of Behavior. The theory is also called Hebb's rule, Hebb's postulate, and cell assembly theory. Hebb states it as follows:
Let us assume that the persistence or repetition of a reverberatory activity tends to induce lasting cellular changes that add to its stability. ... When an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency, as one of the cells firing B, is increased.
A histochemical tracer is a compound used to reveal the location of cells and track neuronal projections. A neuronal tracer may be retrograde, anterograde, or work in both directions. A retrograde tracer is taken up in the terminal of the neuron and transported to the cell body, whereas an anterograde tracer moves away from the cell body of the neuron.
Behavioral neuroscience, also known as biological psychology, biopsychology, or psychobiology, is the application of the principles of biology to the study of physiological, genetic, and developmental mechanisms of behavior in humans and other animals.
In neurology, retrograde amnesia (RA) is the inability to access memories or information from before an injury or disease occurred. RA differs from a similar condition called anterograde amnesia (AA), which is the inability to form new memories following injury or disease onset. Although an individual can have both RA and AA at the same time, RA can also occur on its own; this 'pure' form of RA can be further divided into three types: focal, isolated, and pure RA. RA negatively affects an individual's episodic, autobiographical, and declarative memory, but they can still form new memories because RA leaves procedural memory intact. Depending on its severity, RA can result in either temporally graded or more permanent memory loss. However, memory loss usually follows Ribot's law, which states that individuals are more likely to lose recent memories than older memories. Diagnosing RA generally requires using an Autobiographical Memory Interview (AMI) and observing brain structure through magnetic resonance imaging (MRI), a computed tomography scan (CT), or electroencephalography (EEG).
Retrograde signaling in biology is the process where a signal travels backwards from a target source to its original source. For example, the nucleus of a cell is the original source for creating signaling proteins. During retrograde signaling, instead of signals leaving the nucleus, they are sent to the nucleus. In cell biology, this type of signaling typically occurs between the mitochondria or chloroplast and the nucleus. Signaling molecules from the mitochondria or chloroplast act on the nucleus to affect nuclear gene expression. In this regard, the chloroplast or mitochondria act as a sensor for internal external stimuli which activate a signaling pathway.
Isotopic labeling is a technique used to track the passage of an isotope through chemical reaction, metabolic pathway, or a biological cell. The reactant is 'labeled' by replacing one or more specific atoms with their isotopes. The reactant is then allowed to undergo the reaction. The position of the isotopes in the products is measured to determine what sequence the isotopic atom followed in the reaction or the cell's metabolic pathway. The nuclides used in isotopic labeling may be stable nuclides or radionuclides. In the latter case, the labeling is called radiolabeling.
Neurotransmission is the process by which signaling molecules called neurotransmitters are released by the axon terminal of a neuron, and bind to and react with the receptors on the dendrites of another neuron a short distance away. A similar process occurs in retrograde neurotransmission, where the dendrites of the postsynaptic neuron release retrograde neurotransmitters that signal through receptors that are located on the axon terminal of the presynaptic neuron, mainly at GABAergic and glutamatergic synapses.
Axonal transport, also called axoplasmic transport or axoplasmic flow, is a cellular process responsible for movement of mitochondria, lipids, synaptic vesicles, proteins, and other organelles to and from a neuron's cell body, through the cytoplasm of its axon called the axoplasm. Since some axons are on the order of meters long, neurons cannot rely on diffusion to carry products of the nucleus and organelles to the ends of their axons. Axonal transport is also responsible for moving molecules destined for degradation from the axon back to the cell body, where they are broken down by lysosomes.
Aujeszky's disease, usually called pseudorabies in the United States, is a viral disease in swine that is endemic in most parts of the world. It is caused by Suid herpesvirus 1 (SuHV-1). Aujeszky's disease is considered to be the most economically important viral disease of swine in areas where classical swine fever has been eradicated. Other mammals, such as cattle, sheep, goats, cats, dogs, and raccoons, are also susceptible. The disease is usually fatal in these animal species.
In neuroscience, anterograde tracing is a research method that is used to trace axonal projections from their source to their point of termination. A hallmark of anterograde tracing is the labeling of the presynaptic and the postsynaptic neuron(s). The crossing of the synaptic cleft is a vital difference between the anterograde tracers and the dye fillers used for morphological reconstruction. The complementary technique is retrograde tracing, which is used to trace neural connections from their termination to their source. Both the anterograde and retrograde tracing techniques are based on the visualization of the biological process of axonal transport.
Transneuronal degeneration is the death of neurons resulting from the disruption of input from or output to other nearby neurons. It is an active excitotoxic process when a neuron is overstimulated by a neurotransmitter causing the dysfunction of that neuron which drives neighboring neurons into metabolic deficit, resulting in rapid, widespread loss of neurons. This can be either anterograde or retrograde, indicating the direction of the degeneration relative to the original site of damage. There are varying causes for transneuronal degeneration such as brain lesions, disconnection syndromes, respiratory chain deficient neuron interaction, and lobectomies. Although there are different causes, transneuronal degeneration generally results in the same effects to varying degrees. Transneuronal degeneration is thought to be linked to a number of diseases, most notably Huntington's disease and Alzheimer's disease, and researchers recently have been performing experiments with monkeys and rats, monitoring lesions in different parts of the body to study more closely how exactly the process works.
Retrograde tracing is a research method used in neuroscience to trace neural connections from their point of termination to their source. Retrograde tracing techniques allow for detailed assessment of neuronal connections between a target population of neurons and their inputs throughout the nervous system. These techniques allow the "mapping" of connections between neurons in a particular structure and the target neurons in the brain. The opposite technique is anterograde tracing, which is used to trace neural connections from their source to their point of termination. Both the anterograde and retrograde tracing techniques are based on the visualization of axonal transport.
Biotinylated dextran amines (BDA) are organic compounds used as anterograde and retrograde neuroanatomical tracers. They can be used for labeling the source as well as the point of termination of neural connections and therefore to study neural pathways.
Viral neuronal tracing is the use of a virus to trace neural pathways, providing a self-replicating tracer. Viruses have the advantage of self-replication over molecular tracers but can also spread too quickly and cause degradation of neural tissue. Viruses that can infect the nervous system, called neurotropic viruses, spread through spatially close assemblies of neurons through synapses, allowing for their use in studying functionally connected neural networks.
Neuronal tracing, or neuron reconstruction is a technique used in neuroscience to determine the pathway of the neurites or neuronal processes, the axons and dendrites, of a neuron. From a sample preparation point of view, it may refer to some of the following as well as other genetic neuron labeling techniques,
Pre-locus coeruleus is a small nucleus in the brainstem. This small cluster of neurons also is referred to by the abbreviation "pre-LC". It was named "pre-LC" because it lies just rostral to the locus coeruleus, which is commonly abbreviated "LC".
Vaa3D is an Open Source visualization and analysis software suite created mainly by Hanchuan Peng and his team at Janelia Research Campus, HHMI and Allen Institute for Brain Science. The software performs 3D, 4D and 5D rendering and analysis of very large image data sets, especially those generated using various modern microscopy methods, and associated 3D surface objects. This software has been used in several large neuroscience initiatives and a number of applications in other domains. In a recent Nature Methods review article, it has been viewed as one of the leading open-source software suites in the related research fields. In addition, research using this software was awarded the 2012 Cozzarelli Prize from the National Academy of Sciences.
