Related Experiment Videos
Characterization and biological activity of the monocytosis-producing agent of Listeria monocytogenes
Abstract:
Experiments directed toward determining the lipids in extracts of Listeria monocytogenes containing monocytosis-producing agent (MPA) and the effect of these extracts on several biochemical parameters previously shown to change during experimental Listeria infection were conducted. MPA-containing extracts were found to be a complex of lipids with glycerides, glycolipids, and phospholipid being present. No common cell wall carbohydrates were found. A glyceride, designated glyceride A, was determined to cause the characteristic mononuclear response observed in mice injected with MPA-containing extracts. Fasted MPA-treated animals showed less gluconeogenesis than did controls. Blood glucose levels declined in MPA-treated animals. Increases observed in both blood urea nitrogen and plasma glutamic-pyruvic transaminase were greater in the control groups. Incorporation of (14)C-alanine into liver glycogen was depressed in MPA-treated animals. Liver steroid levels in the control groups increased during fasting and remained elevated for the duration of the experiments, while levels in the MPA-treated groups declined initially and showed no increase until 72 hr after injection. MPA appears to affect steroid metabolism and consequently the animals' homeostatic mechanisms seem to be impaired. Possibly as a consequence, carbohydrate metabolism is altered. The apparent effect of MPA on steroid metabolism and on the gluconeogenic process may indicate participation in the carbohydrate derangement observed in experimental Listeria infection.
Insights
Monocytosis-producing agent (MPA) in Listeria monocytogenes extracts alters lipid metabolism, impacting steroid and carbohydrate pathways. This disruption affects homeostatic mechanisms and gluconeogenesis in experimental infections.
Area of Science:
- Microbiology
- Biochemistry
- Immunology
Background:
- Listeria monocytogenes infection causes significant biochemical changes.
- Monocytosis-producing agent (MPA) is a key component implicated in Listeria pathogenesis.
- Understanding MPA's biochemical effects is crucial for deciphering Listeria's impact on host physiology.
Purpose of the Study:
- To identify lipids in MPA-containing extracts.
- To investigate MPA's effects on host biochemical parameters during experimental Listeria infection.
- To elucidate the role of MPA in metabolic derangements associated with Listeria.
Main Methods:
- Lipid analysis of MPA-containing extracts from Listeria monocytogenes.
- Injection of MPA extracts into animal models to observe biochemical changes.
- Measurement of key metabolic indicators including blood glucose, gluconeogenesis, blood urea nitrogen, plasma glutamic-pyruvic transaminase, liver glycogen, and liver steroid levels.
Main Results:
- MPA extracts contain a complex of lipids, including glycerides, glycolipids, and phospholipids.
- Glyceride A, a specific lipid, induced a mononuclear response in mice.
- MPA-treated animals exhibited reduced gluconeogenesis, declining blood glucose, and depressed incorporation of alanine into liver glycogen.
- Steroid metabolism was significantly affected, with MPA-treated animals showing decreased liver steroid levels compared to controls.
Conclusions:
- MPA significantly impacts lipid composition and host metabolic pathways.
- MPA disrupts steroid metabolism, potentially impairing homeostatic mechanisms.
- Alterations in carbohydrate metabolism, including gluconeogenesis and glycogen synthesis, are linked to MPA's effects on steroid metabolism.
- These findings suggest MPA plays a role in the metabolic disturbances observed in experimental Listeria infections.