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Biomedical subjects

T A Sears

Publications and source records attributed to T A Sears.

97 records · Page 6Linked to original sources
PubMedDate not supplied

Retrograde response to axotomy of motoneurons in the thoracic spinal cord of the aging cat.

The retrograde response of HRP-labelled intercostal motoneurons was compared in adult (1-2 years) and aging (10-15 years) cats, 64-68 days following crush of intercostal nerves or following nerve transection with proximal ligation. A comparison of the neuroglial response to these two lesions was also made. In both adult and aging cats, 64-68 days following nerve crush, most labelled motoneurons had a normal appearance. In contrast, 64-68 days following nerve transection and ligation the Nissl bodies of labelled motoneurons lacked the highly ordered ultrastructure characteristic of normal and control motoneurons. No axotomy-induced neuronal loss was found in aging cats. A three-fold increase in numbers of microglial cells was quantified in the ipsilateral ventral horn of aging cats following nerve transection and ligation. This increase was not seen following nerve crush in aging cats, nor following either type of nerve injury in adult cats. Numbers of astroglia and oligodendroglia were unaffected by axotomy in adult and aging animals.

Aging↗
PubMedDate not supplied

Ultrastructure of axotomized alpha and gamma motoneurons in the cat thoracic spinal cord.

Using horseradish peroxidase as a retrograde marker, the ultrastructural response of alpha and gamma motoneuronal cell bodies in the cat thoracic spinal cord has been compared 1-8 days following intercostal nerve transection and ligation. By light microscopy, reduction of Nissl body size, together with nuclear and nucleolar alterations were seen in alpha motoneurons 4-8 days following axotomy, but not at any stage in axotomized gamma motoneurons. In the electron microscope, disorganization of Nissl body ultrastructure was seen in both alpha and gamma motoneurons 2 days following axotomy. Only in alpha motoneurons, however, did these disorganized Nissl bodies subsequently fragment into smaller pieces. Both alpha and gamma motoneurons lost synapses following axotomy, but the proportional loss from gamma motoneurons was two-fold greater than that from alpha motoneurons. Loss of synaptic terminals with flattened synaptic vesicles was two-fold higher than that of synaptic terminals with round synaptic vesicles from axotomized gamma motoneurons, whereas axotomized alpha motoneurons lost both types of synaptic terminal equally.

Animals↗