Circadian rhythm in the light response of rat retinal disk-shedding and autophagy

Under a light-dark cycle, disk-shedding and autophagy in the rat retina peak in the early and mid light phase, respectively. Under constant conditions, disk-shedding and autophagy responses after light stimulation were elicited at different time points of a 24-h cycle. The greatest magnitude of response occurred in the late dark and early light phase. Thus there is a circadian variation of the light response of important metabolic parameters in the mammalian retina. Inhibition of dopamine synthesis during the early light phase caused a significant dampening of the light responses of both disk-shedding and autophagy.

Decreased plasma fibronectin during starvation in man

This study evaluated the effect of 5 days of starvation followed by 5 days of refeeding on immunoreactive plasma and serum fibronectin and associated opsonic activity as studied by peritoneal macrophage monolayer bioassay in 12 healthy women volunteers. The temporal alteration of fibronectin was compared with the serum albumin, total iron-binding capacity, and retinol-binding protein levels. Fibronectin concentration and opsonic activity were also determined in two cachectic patients who were 61 and 78% of their ideal body weight. Prior to starvation, plasma fibronectin was 292 +/- 20 micrograms/ml and serum fibronectin was 182 +/- 16 in all subjects. After 5 days of starvation, immunoreactive fibronectin decreased (p less than 0.05) by 20-25%. This decrease was not great enough to impair opsonic activity as tested by the in vitro macrophage assay. Starvation caused no decrease in serum albumin or total iron-binding capacity, although retinol-binding protein decreased by 35%. During refeeding, subjects were randomized to a diet with (n = 6) and without (n = 6) carbohydrate. After 5 days of refeeding, fibronectin levels were normalized on the carbohydrate-containing diet, but were still low (82% of normal) on the carbohydrate-free diet. Retinol-binding protein did not fully normalize after 5 days of refeeding. In the two cachectic patients, fibronectin levels prior to total parenteral nutrition were 25 and 75% of normal. Thus, starvation can lower fibronectin levels and this protein is rapidly restored with adequate nutrition.