Cell body, growth

Neurons have three parts the cell body and dendrites, the axon, and axon terminals. The cell body contains the nucleus and the organelles needed for metabolism, growth, and repair. The dendrites are branched extensions of the cell body membrane. The axon is a long, thin structure which transfers electrical impulses down to the terminals. The axon divides into numerous axon terminals and it is in this specialized region that neurotransmitters are released to transmit information from one neuron to its neighbors. The synapse has been defined as the space between two subsequent interrelated neurons. ... 

Although mast cells and basophils probably account for >90% of stored histamine in the body, histamine is also present in platelets, enterochromaffin-like cells, endothelial cells, and neurons. Histamine can act as a neurotransmitter in the brain. Histaminergic nerves have their cell bodies within a very small area of the brain (the magnocellular nuclei of the posterior hypothalamus) but have axons in most areas of the forebrain. There is also evidence for axons projecting into the spinal (Fig. 1) cord. Finally, there is evidence that histamine synthesis can be induced in tissues undergoing rapid tissue growth and repair. In certain neonatal tissues (e.g. liver), the rate of synthesis of this unstored diffusable histamine (termed nascent histamine) is profound and may point to a role for histamine is cell proliferation. 

A cognate property of this continuous production throughout life is the repair of damaged parts of the neurone axonal and or dendritic re-growth readily occurs, an ability retained even by higher primates (Graziadei et al., 1980). Such a regenerational capacity is probably due to the peripheral site of the cell body, since those within the CNS mostly lack this property. 

Rickettsia are more difficult to produce in quantity than bacteria. Similar to viruses, they are strict obligate parasites and require living cells for growth. They cannot survive long outside a host. They also have a selective affinity for specific types of cells in the body. They are normally transmitted by an arthropod vector (i.e., ticks, lice, fleas, mites), which also serves as either the primary or intermediate host. 

Foetal development promotes growth and differentiation of foetal cells and organogenesis Promotes longitudinal body growth and increased body weight Promotes enhanced functioning of the male and female reproductive tissue Promotes growth and differentiation of neuronal tissue... 

The receptor for NGF is TrkA, a 140 kDa cell surface protein that specifically binds NGF, but not other neurotrophins [5, 6, 9]. TrkA is expressed on the neuronal cell body and on neuronal processes. In its action as a target-derived trophic factor, NGF is secreted within the target organ and it then binds to TrkA receptors present on the growing neuronal process or synapse. The NGF-TrkA complex is then internalized and subsequently translocated to the cell body by retrograde axonal transport. In those cells that respond to NGF through autocrine or paracrine mechanisms, the growth factor can bind to any of the widely distributed TrkA molecules on the neuronal membrane. 

The size and extent of many neurons presents a special set of challenges. Since protein synthesis for the entire neuron takes place in the cell body, which may represent only 0.1% of the total cell volume, growth and maintenance of neuronal processes requires timely, efficient delivery of material to axonal and dendritic domains. The idea that materials must be transferred from cell body to axon was suggested by Ramon y Cajal and other pioneers during the early part of this century. For many years, the existence of such transport processes could only be inferred. 

FIGURE BO-2 Wallerian degeneration in the PNS. After an axon is injured, resulting chromatolysis, i.e. stress reaction and increased protein synthesis, occurs in the neuronal cell body, with axonal and myelin degeneration distal to the injury. Growth-permissive Schwann cells secrete growth factors that stimulate axons to regenerate. 

Perhaps one of the most exciting areas in neuroscience to which in situ hybridization has made significant contributions in recent years is the discovery that specific mRNA transcripts can be localized to certain compartments of neuronal cells (Steward and Schuman, 2003), such as axons (Tohda, 2003), dendrites (Ma and Morris, 2002 Bockers et al., 2004), cell bodies (Lu et al., 1998), and growth... 

It stimulates growth directly and in conjunction with other hormones. It stimulates the multiplication of the cells of epiphyseal cartilage and thus increases the length of the cartilage bone. After administration, there is an increased body growth due to its direct effect on the tissues. It stimulates the growth of muscles. It also increases the secretion of milk during lactation. 

Vimentin is not the only IF type that is moved in this manner. Neural IFs, including both the type III peripherin proteins and type IV neural IF proteins, have also been demonstrated to be moved by molecular motors. In the case of peripherin, particles and squiggles were observed to translocate rapidly within PCI 2 cell bodies, neurites, and growth cones. The movements were bidirectional and dependent on microtubules, kinesin, and cytoplasmic dynein. The authors suggest that peripherin particles are... 

Once the nutrients enter the bloodstream, they are transported to various parts of the body for vital body functions. Nutrients are used to maintain essential functions such as breathing, circulation of blood and muscle movement, replacement of worn-out cells (maintenance), growth, reproduction and egg production. 

Fig. 2.12. Scolex of Diphyllobothrium dendriticum plerocercoid. The neural elements have been labelled with growth hormone releasing factor (GRF), a vertebrate neuropeptide. In the main nerve cord (n) one GRF-immunoreactive cell body can be seen (large arrow) in the peripheral nervous system (P) several GRF-immunoreactive cells bodies occur (large arrows). The small arrows point to nerve terminals beneath the basal lamina of the tegument along the inner border of the bothridia. Sections stained with Stemberger s immunoperoxidase-antiperoxidase (PAP) technique. (Courtesy Dr Margaretha K. S. GustafFson.)...

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