Histological and ultrastructural changes in sea bass(Dicentrarchus labrax) larvae muscle in response to high dietary content of DHA

【Author】

Mónica B.Betancor;M José Caballero;Tibiábin Benítez-Santana;Reda Saleh;Eyad Atalah;Javier Roo;Marisol Izquierdo;

【Abstract】

<正>It is widely known that highly unsaturated fatty acids(HUFA) are beneficial for fish larvae in terms of growth,survival and resistance to stress.Nevertheless,these fatty acids are highly susceptible to oxidation and so,a higher addition of antioxidants must be included in formulated diets.Vitamin E is considered to be one of the most efficient physiological antioxidant protections for fish being a structural component of cell membranes.In previous studies we observed dystrophic alterations in muscle of 48 day-old sea bass fed imbalanced DHA and vitamin E diets for 2 weeks.In order to better understand the whole pathological process associated to free radicals,a deeper histological study was performed feeding 14 day-old sea bass larvae with microdiets containing different ratios of DHA/vitamin E(1/150,5/150 and 5/300) for three weeks. Larvae were sampled each week and fixed in 10%buffered formalin or in 2.5%glutaraldehyde 0.2M phosphate buffer.Longitudinal paraffin sections of these larvae were employed to study the incidence of muscle dystrophy among dietary treatments.Larvae fed diet 1/150 showed no lesions in contrast to larvae fed diet 5/150 and 5/300 where the highest incidence of muscle lesions was observed(around 19%).Semithin sections showed that focal lesions consisted of degenerated fibres and an extensive sarcoplasm vacuolization affecting both red and white muscle.Ultrathin sections of these degenerating muscle fibres showed a diffuse dilatation of the sarcoplasmic reticulum,disorganized miofibres and autophagic vacuoles eventually containing myelin figures and dense bodies.Besides,some monocyte - macrophage cells were observed among lesioned fibres as numerous satellite cells.The results of the present study reinforced the conclusions observed in our previous study and demonstrate the pathological potential of free radicals in sea bass larvae musculature,which could not be attenuated by dietary vitamin E.The implication of other nutrients related to cell protection against oxidative stress is being studied at present.

【Keywords】

Sea bass larvae;;oxidative stress;;muscle dystrophy;;ultrastructure

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