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A Neonatal Imaging Model of Gram-Negative Bacterial Sepsis
Published on: August 12, 2020
Cytologic and biochemical changes associated with inoculation of amniotic fluid and meconium into lungs of neonatal
J Martínez-Burnes1, A López, B Horney
1Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Tamaulipas, México.
Objective:
To evaluate the effect of homologous amniotic fluid and meconium inoculated intratracheally into the lungs of neonatal rats.
Animals:
153 male 7-day-old Fischer-344 rats.
Procedure:
Amniotic fluid was obtained by cesarean section from the uterus of pregnant rats and meconium was collected at the time of birth from the gastrointestinal tract of neonatal rats. Neonatal rats were randomly allocated into 5 treatment groups. Two groups received 0.05 ml of saline (0.9% NaCl) solution; the third and fourth groups received 0.05 ml of 50% or 100% amniotic fluid, respectively; the fifth group was inoculated with 0.05 ml of a 20% suspension of meconium. Six or 7 rat pups/group were euthanatized by exsanguination under halothane anesthesia at postinoculation days 1, 3, 7, and 14. The magnitude of injury and inflammatory response was determined by biochemical and cytologic analyses of bronchoalveolar lavage fluid.
Results:
Inoculation with saline solution and amniotic fluid did not induce pulmonary injury or inflammatory response. Inoculation with meconium induced significant (P < 0.01) injury and inflammatory response, characterized by the release of cytosolic enzymes and recruitment of neutrophils in the lung.
Conclusions:
Saline solution is an innocuous vehicle that can be safely used in intratracheal inoculations in neonatal rats. Homologous amniotic fluid, despite containing keratin and epidermal cells, does not cause acute injury or inflammation in the lung. In contrast, meconium acts as a toxic substance injuring respiratory cells and causing a vigorous but transient leukocytic inflammatory reaction in the lungs.
Insights
Meconium causes lung injury and inflammation in neonatal rats, while amniotic fluid does not. This study highlights meconium
Area of Science:
- Neonatal physiology and toxicology
- Pulmonary research
- Experimental pathology
Background:
- Understanding the effects of inhaled substances in newborns is crucial for neonatal care.
- Meconium aspiration syndrome is a significant cause of neonatal respiratory distress.
- The potential pulmonary effects of amniotic fluid and meconium require detailed investigation.
Purpose of the Study:
- To investigate the pulmonary effects of intratracheal inoculation of homologous amniotic fluid and meconium in neonatal rats.
- To compare the inflammatory and injury responses induced by amniotic fluid versus meconium.
- To establish a reliable model for studying neonatal lung injury.
Main Methods:
- Seventy-day-old Fischer-344 rats were intratracheally inoculated with saline, amniotic fluid (50% or 100%), or meconium (20% suspension).
- Bronchoalveolar lavage fluid was analyzed for biochemical and cytologic markers of injury and inflammation.
- Evaluations were conducted at 1, 3, 7, and 14 days post-inoculation.
Main Results:
- Intratracheal inoculation with saline or amniotic fluid did not result in pulmonary injury or inflammation.
- Meconium inoculation induced significant pulmonary injury and inflammatory response (P < 0.01).
- Meconium-induced effects included cytosolic enzyme release and neutrophil recruitment in the lungs.
Conclusions:
- Saline is a safe vehicle for intratracheal inoculations in neonatal rats.
- Homologous amniotic fluid is non-injurious to the neonatal lung, even with cellular content.
- Meconium acts as a toxic substance, causing acute lung injury and a transient inflammatory response in neonatal rats.
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