10-20-2007, 01:59 AM
anyone explain plz,,thanks
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retrograde chromatolysis?? - pmle
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10-20-2007, 02:34 AM
Neuron cell bodies undergo retrograde chromatolysis in response to axotomy.
1. Chromatolytic changes are accompanied by increases in RNA and synthesis of proteins in an attempt to regenerate the axon. 2. In the first few days after axotomy, the Nissl substance breaks up and becomes dispersed. 3. The nucleus moves from a central position in the cell to an eccentric position adjacent to the cell membrane. 4. The cell body may swell, and the dendrites may shrink. 5. Axon terminals in synapse with the affected neuron may withdraw from the cell body and dendrites. 6. The chromatolytic process results in the growth of multiple sprouts from the proximal part of the cut axon as the neuron attempts to regenerate its axon (from Road Map Neuroscience)
10-20-2007, 02:37 AM
same question i asked few days back with no response..cudn`t even find it in google.
NEUROPATHOLOGY MINI-COURSE FOR RESIDENTS Presented by William I. Rosenblum, MD CHAPTER 1 PATHOLOGY OF THE NEURON AND ITS PROCESSES PRETEST: Answers can be found in the text of this chapter or click on link at end of these questions The basophilic, Nissl positive material in neurons is____________________________. Axonal injury may result in what change in the distribution of this material ? What is the location of the inclusion body of Parkinson's disease? of rabies infection? Neuronophagia results in______________________ and is carried out by_______________. What is Wallerian degeneration? The two principal histological hallmarks of Alzheimer disease are________________________. ANSWERS TO QUESTIONS The cellular elements of the central nervous system are neurons and glia. All of these cells have processes in addition to their cell bodies. The neuronal processes are called axons and dendrites. In the peripheral nervous system, there are no glia. There are Schwann cells which surround the axons and produce myelin in the same manner as the oligodendroglia of the CNS. Interestingly, the Schwann cells also become phagocytes, devouring the debris from injured peripheral nerves, and this property is not shared by the oligodendroglia. NEURONAL CELL BODY The image above is an example of a normal anterior horn nerve cell. The normal anterior horn cell serves as a good illustration of a normal neuron. The nucleus is centrally placed and contains a large, prominent nucleolus. In the cytoplasm, large clumps of blue-black material are seen which represent the prominent aggregates of ribonucleoprotein (RNA). This material is often called Nissl substance, after the man who devised special stains for staining it. One such stain, cresyl violet, has been used in this image. The image above, with the more routine hematoxylin and eosin stain, also discloses Nissl substance, which is a shade of purple. Although the neurons illustrated in this image are typical of large neurons, please remember that neurons of all sizes exist in the central nervous system. In response to transection or destruction of the axons, whether by mechanical trauma or by other means, a characteristic change known as central chromatolysis occurs in the neuronal cell body. The nucleus moves to an eccentric position, the Nissl material is visible only peripherally, and the central area of the neuron is free of stainable material. This is a reversible change and electron microscopy shows that the ribonucleoprotein is dispersed rather than aggregated as in the normal neuron. |
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