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Non‐specific esterase activity in reactive cells in injured nervous tissue labeled with 3 H‐Thymidine or 125 Iododeoxyuridine injected before injury
Author(s) -
Schelper Robert L.,
Adrian Erle K.
Publication year - 1980
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901940408
Subject(s) - axotomy , hypoglossal nucleus , spinal cord , biology , thymidine , hypoglossal nerve , nucleus , anatomy , central nervous system , microbiology and biotechnology , pathology , endocrinology , medicine , biochemistry , neuroscience , tongue , in vitro
Tritiated thymidine ( 3 H‐TdR) injected before a stab wound of the spinal cord or transection of the hypoglossal nerve has resulted in many labeled reactive cells in the CNS after injury, most of which have the ultrastructural features of microglia. To test for the possible origin of these labeled cells from monocytes, we examined them for the presence of sodium, fluoride‐ (NaF) sensitive non‐specific esterase (NSE), an enzyme characteristic of monocytes. Some of the labeled cells in stab wounds had NaF‐sensitive NSE, but no such cells were found in the nucleus of the injured hypoglossal nerve. To test for the possibility that the NSE‐negative labeled cells had been labeled by reutilization of 3 H‐TdR, we used 125 I‐5‐iodo‐2'deoxyuridine ( 125 I‐UdR), a thymidine analogue with a much lower rate or reutilization, to label blood mononuclear cells prior to either a spinal cord stab wound or hypoglossal axotomy. The number of labeled cells was decreased in the spinal cord wound, but more than half were NSE‐negative. No labeled blood mononuclear cells were found in the hypoglossal nucleus, although there was no decrease in the hyperplasia of unlabeled non‐neuronal cells. When 125 I‐UdR was injected on the fourth day after hypoglossal axotomy, or when both 3 H‐TdR and 125 I‐RdR were injected simultaneously before hypoglossal axotomy, many labeled cells were found in the hypoglosaal nucleus, indicating that 125 I‐UdR can be used by the reactive cells and that it did not inhibit their proliferation. Therefore, the microglial cells that proliferate in response to peripheral nerve injury are not recently derived from any type of circulating large blood mononuclear cell. The most likely explanation for the presence of the 3 H‐TdR‐labeled cells in the nucleus of the injured hypoglossal nerve in that they were proliferating intrinsic labeled by reutilization of 3 H‐TdR.