Intranuclear ubiquitin immunoreactivity in the pigmented neurons of the substantia nigra in fire fatalities

Abstract

To evaluate the significance of immunohistochemical staining of ubiquitin (heat shock protein) in the midbrain for medico-legal investigation of death in fires, we examined forensic autopsy cases of fire fatalities (n = 35) in comparison with controls (n = 27; brain stem injury, acute myocardial infarction and carbon monoxide poisoning other than fire fatality). There were two intranuclear staining patterns in the nuclei of pigmented substantia nigra neurons: a type of inclusion (possible Marinesco bodies) and a diffuse staining. Percentage of nuclear ubiquitin positivity (Ub-positive %) in fire fatalities (2.7-44.7%; mean, 18.5%) was significantly higher than in brain stem injury (n = 9; 0-10.4%; mean, 4.5%) and myocardial infarction (n = 14; 1.5-14.6%; mean, 6.9%), independently of blood carboxyhemoglobin (COHb) levels. Age-dependent increase in Ub-positive % was observed in lower COHb (< 60%) cases. The intranuclear diffuse ubiquitin staining was not observed in cases of high blood cyanide level (> 1.0 microg/ml). These observations showed that intranuclear ubiquitin immunoreactivity of the pigmented substantia nigra neurons in the midbrain was induced by severe stress in fires.

Evaluation of the agonal stress: can immunohistochemical detection of ubiquitin in the locus coeruleus be useful?

“…This can point to a direct neuronal toxicity with an obviously higher neuronal ubiquitin immunopositivity. However, Quan et al could not establish a correlation of the ubiquitin-positivity in the pigmented neurons of the substantia nigra with the blood carboxyhaemoglobin (COHb) level in fatal CO poisoning cases [13]. Since this is in opposition to our results, a higher susceptibility of the locus coeruleus to the agonal stress may be assumed.…”

“…1), most of the neurons demonstrate ubiquitin-immunoreactivity in the nucleus. This is also confirmed by the literature, since it [13][14][15] and presumably bind to the histones [22]. One could assume that the longer the agony lasts, the more neurons will show ubiquitinimmunoreactivity in the nucleus and less in the cytoplasm.…”

“…The IHC staining of the ependymal cells [13,14] and the corpora amylacea [21] served as an internal positive control.…”

“…Immunohistochemical (IHC) staining of ubiquitin may indicate the possible activation and redistribution of ubiquitin to form larger aggregates rather than a de novo synthesis, since there is a hypothesis that ubiquitin can move rapidly from the cytoplasm into the nucleus [13][14][15]. Dickson et al researched in 1990 the ubiquitin-immunoreactive structures in the normal human brain: Immunostaining was seen both in the neurons and in the glia cells.…”

“…very few structures were ubiquitinimmunoreactive in young children [16]. Quan et al evaluated the intra-nuclear ubiquitin-immunoreactivity in the pigmented neurons of the substantia nigra in fire fatalities [13] and in fatal acute mechanical asphyxia and drowning [14]: These authors substantiated that the stress on the central nervous system resulting from the physical activity could be evaluated by these means [13,14]. These two articles led us to further investigate ubiquitin localisation, namely in the locus coeruleus.…”