Circadian rhythm of phagocytosis in mice.

There has been reported, in some diurnal or equivocal species (man, respectively guinea pig), a circadian rhythm of the phagocytic activity of blood neutrophils, with an acrophase occurring at the end of the light span. The present study, carried out on NMRI adult male mice kept on a LD 12:12 regimen, aimed to assess any circadian variation in the blood neutrophils' phagocytosis level. Basal phagocytic activity was tested against E. coli, every three hours of a 24 h cycle. The results show that phagocytosis in mice's blood neutrophils also presents a rhythmic circadian variation, whose acrophase is delayed with about eight hours compared to that in man, occurring in the second half of the dark period (3:00 h). The occurrence of high circadian phagocytic levels appears to be correlated with the activity type of the species and, of this point of view, mice cannot be used as a model for chronotherapeutical approaches in humans, without keeping in mind the differences between the time structure of the two species.

Influence of bilateral olfactory bulbectomy on the circadian rhythm of phagocytic activity and phagocytic response in mice.

The bilateral olfactory bulbectomy (OB) has been proposed as an animal model of depression. The present study, carried out on NMRI adult male mice kept on a natural LD 12:12 regimen, aimed to assess the influence of OB on the circadian rhythm of blood neutrophils phagocytosis. The results show that OB mice present an about 20% reduction of the basal phagocytic activity at 09.00 hrs, 15.00 hrs. and 21.00 hrs. and a 40% reduction at 03.00 hrs., leading to a flattened circadian phagocytic curve. The results indicate that bilateral olfactory bulbectomy depresses phagocytosis, alters its circadian rhythm and consequently increases susceptibility to infections.

Effects of monosodium glutamate on blood neutrophils phagocytic activity and phagocytic response in mice.

Previous researches of our laboratories (1945, 1946, 1947) have shown that direct electrical stimulation of the tubero-mammillary hypothalamic area in dogs enhances the blood neutrophils phagocytic activity and the phagocytosis exhibiting leukocytes percent. After electrolytic damage of the same area, phagocytic activity decreases and phagocytic response is suppressed (1985, 1988). In the present work, we performed in mice extensive chemical lesions of the arcuate nucleus, by means of the neonatal treatment with monosodium glutamate (MSG). The experiment was carried out on 23 new-born mice. 15 mice were injected with MSG (G group), the other 8, serving as control group, received isotonic saline solution (C group). The studied parameters were, in both groups, the weight evolution of the animals, the blood neutrophils and lymphocytes percentual variation and the neutrophils' phagocytic activity, tested in vitro, expressed through the number of bacteria engulfed by 100 neutrophils and through the phagocyting neutrophils percentage. Phagocytic activity was tested in whole heparinised blood, against E. coli. Phagocytic response was elicited by i.p. injecting 0.05 ml bacterial suspension and was tested four hours later. The results show that the arcuate nucleus has little influence upon maintaining basal phagocytic activity--that does not significantly decrease after its chemical damage--, but plays a decisive role in triggering the phagocytic response. The neonatal MSG treatment also determines a decrease of the blood lymphocytes percentage and induces obesity in up to 30 days old mice pups.