Age-related changes in mitochondrial membrane composition of Nothobranchius furzeri.: comparison with a longer-living Nothobranchius species.

Membrane compositions, particularly of mitochondria, could be critical factors in the mechanisms of growth and aging, especially during phases of high oxidative stress that result in molecular damage. Changes affecting lipid class or fatty acid (FA) compositions could affect phospholipid (PL) properties and alter mitochondrial function. In the present study, mitochondrial membrane PL compositions were analysed throughout the life-cycle of Nothobranchius furzeri, a species with explosive growth and one of the shortest-lived vertebrates. Mitochondrial PLs showed several changes with age. Proportions of total PLs and PC were reduced while an increase in PS, CL and PE was observed, mainly between the 2.5 and 5 months of fish age, the time during which animals doubled their weight. FA compositions of individual PLs in mitochondria were also significantly affected with age suggesting the existence of increasing damage to mitochondrial lipids during the life-cycle of N. furzeri that could be one of the main contributors to degraded mitochondrial function associated with aging. The peroxidation index values from N. furzeri mitochondrial PLs were significantly lower than those reported in N. rachovii, a species with a twofold longer life span than N. furzeri, which seems to contradict the membrane pacemaker theory of animal metabolism.

Both pineal and lateral eyes are needed to sustain daily circulating melatonin rhythms in sea bass.

This study investigates the role of the pineal organ and lateral eyes (the two most important sources of melatonin in vertebrate species) on daily melatonin rhythms of sea bass, a fish exhibiting reversed melatonin profiles, as well as their contribution to circulating melatonin levels. To this aim, the pineal and/or the eyes were surgically removed (Exp. 1), the optic nerve sectioned and retinal dopaminergic neurons damaged with injections of 6-hydroxydopamine (Exp. 2), and the pineal or the eyes covered with aluminium foil (Exp. 3). The results show that plasma and ocular melatonin display opposing profiles. In Experiment 1, pinealectomized fish displayed lower nightly plasma melatonin levels (66+/-22 pg/ml) than intact or sham-operated groups (131+/-14 pg/ml), as it occurred in ophthalmectomized fish (64+/-12 pg/ml). Fish that were both pinealectomized and ophthalmectomized showed a further decrease in plasma melatonin levels (1.4+/-0.4 pg/ml), which approached daytime levels. In Experiment 2, plasma melatonin levels in both optic nerve-sectioned and ophthalmectomized fish were lower than control levels, while injection of 6-hydroxydopamine did not modify plasma melatonin concentrations. In Experiment 3, covering only the pineal made melatonin drop after a light pulse at MD, and covering only the eyes had a similar effect. In conclusion, these findings suggest that even though sea bass eyes do not directly contribute to plasma melatonin, the pineal organ, which unlike that of mammals is a direct photoreceptor in fish, requires light information from the lateral eyes to normally secrete melatonin into the bloodstream.