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ACUTE VASCULAR LESIONS IN MICE FOLLOWING INJECTIONS OF PNEUMOCOCCI
1Pathological Laboratory and Medical Clinic of Johns Hopkins University, Baltimore.
Abstract:
Mice dying several days after injections of pneumococci, both living and dead, frequently show at autopsy large intrathoracic hemorrhages. The histological study of the thoracic organs indicates that there occurs in each case a sharply circumscribed, acute degeneration of the wall of some large vessel, usually the ascending aorta or one of the pulmonary arteries. This degenerated portion is torn out by the pressure of the blood with almost complete disappearance of the vessel wall, leading to a gross hemorrhage. A similar change is occasionally found in the walls of the veins which contain cardiac instead of smooth muscle. We have found this lesion only in mice which had been recently inoculated with pneumococci. Negative cultures at autopsy, the lack of inflammatory reaction, and the occurrence of the conditions after injection of dead pneumococci suggest the cause to be a toxic degeneration of the vessel wall brought about by the poisons of the injected organisms.
Insights
Pneumococci injections in mice cause toxic degeneration of blood vessel walls, leading to fatal intrathoracic hemorrhages. This occurs even with dead bacteria, suggesting a poison-induced vascular injury.
Area of Science:
- Pathology
- Toxicology
- Vascular Biology
Background:
- Intrathoracic hemorrhages are observed in mice post-pneumococci inoculation.
- The precise mechanism of hemorrhage in these cases requires elucidation.
Purpose of the Study:
- To investigate the cause of large intrathoracic hemorrhages in mice following pneumococci inoculation.
- To determine the pathological changes in thoracic organs and blood vessels.
Main Methods:
- Histological examination of thoracic organs from mice inoculated with live and dead pneumococci.
- Autopsy and microbiological cultures to identify causative agents and inflammatory responses.
Main Results:
- Acute, localized degeneration of large vessel walls (aorta, pulmonary arteries) was observed.
- Hemorrhage resulted from the tearing of degenerated vessel walls due to blood pressure.
- Lesions were linked to pneumococci inoculation, irrespective of bacterial viability, and lacked inflammatory signs.
Conclusions:
- Pneumococci-derived toxins likely cause acute degeneration of vessel walls.
- This toxic vascular injury is the primary cause of observed intrathoracic hemorrhages in mice.
- The findings highlight a non-inflammatory, toxin-mediated vascular pathology induced by pneumococci.
