Publication: Microscopic changes induced by the intratracheal inoculation of amniotic
fluid and meconium in the lung of neonatal rats
Authors
Martínez Burnes, J. ; Lopez, A. ; Wright, Glenda M. ; Ireland, William P. ; Wadowska, D.W. ; Dobbin, G.V.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
Meconium aspiration syndrome is a major
contributor to neonatal respiratory distress in infants and
it has been sporadically recognized in neonatal animals.
This investigation was designed to study the short and
long term effects of meconium and amniotic fluid in the
lungs of neonatal rats. Seven-day-old rats (n=123)
divided in three groups were intratracheally inoculated
with saline solution, amniotic fluid or meconium. Rats
were euthanatized on 1, 3, 7, 14, 28, 56 and 112
postinoculation days (PID) and the lungs were examined
by light microscopy. Saline solution did not induce any
change while amniotic fluid elicited only a mild foreign
body response which disappeared by PID 14. In contrast,
meconium induced an exudative alveolitis characterized
by recruitment of neutrophilsn in the bronchoalveolar
spaces. Meconium also induced atelectasis,
hyperinflation and thickening of alveolar septa all of
which had disappeared by PID 14. Starting at PID 7,
neutrophils were progressively replaced by
macrophages, giant cells, and some fibroblasts. There
were sporadic foci of mineralization starting at PID 14
and lasting up to PID 112. Some mineralized foci
became lined with cuboidal epithelial cells at PID 28.
Meconium was slowly degraded but still evident by PID
112. It was concluded that inoculation of meconium in
neonatal rats induces acute microscopic changes typical
of meconium aspiration syndrome. The long term lesions
induced by meconium consisted of persistent multifocal
histiocytic alveolitis and bronchiolitis reaction with
occasional foci of calcification.
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