Since the collapse of the pelagic fisheries off southwest Africa in the late 1960s, jellyfish biomass has increased and the structure of the Benguelan fish community has shifted, making the bearded goby (Sufflogobius bibarbatus) the new predominant prey species. Despite increased predation pressure and a harsh environment, the gobies are thriving. Here we show that physiological adaptations and antipredator and foraging behaviors underpin the success of these fish. In particular, body-tissue isotope signatures reveal that gobies consume jellyfish and sulphidic diatomaceous mud, transferring "dead-end" resources back into the food chain.

Sandvik GK, Nilsson GE, Jensen FB. Dramatic increase of nitrite levels in hearts of anoxia-exposed crucian carp supporting a role in cardioprotection. Am J Physiol Regul Integr Comp Physiol 302: R468 -R477, 2012. First published November 30, 2011 doi:10.1152/ajpregu.00538.2011 Ϫ ) functions as an important nitric oxide (NO) donor under hypoxic conditions. Both nitrite and NO have been found to protect the mammalian heart and other tissues against ischemia (anoxia)-reoxygenation injury by interacting with mitochondrial electron transport complexes and limiting the generation of reactive oxygen species upon reoxygenation. The crucian carp naturally survives extended periods without oxygen in an active state, which has made it a model for studying how evolution has solved the problems of anoxic survival. We investigated the role of nitrite and NO in the anoxia tolerance of this fish by measuring NO metabolites in normoxic, anoxic, and reoxygenated crucian carp. We also cloned and sequenced crucian carp NO synthase variants and quantified their mRNA levels in several tissues in normoxia and anoxia. Despite falling levels of blood plasma nitrite, the crucian carp showed massive increases in nitrite, S-nitrosothiols (SNO), and ironnitrosyl (FeNO) compounds in anoxic heart tissue. NO 2 Ϫ levels were maintained in anoxic brain, liver, and gill tissues, whereas SNO and FeNO increased in a tissue-specific manner. Reoxygenation reestablished normoxic values. We conclude that NO 2 Ϫ is shifted into the tissues where it acts as NO donor during anoxia, inducing cytoprotection under anoxia/reoxygenation. This can be especially important in the crucian carp heart, which maintains output in anoxia. NO 2 Ϫ is currently tested as a therapeutic drug against reperfusion damage of ischemic hearts, and the present study provides evolutionary precedent for such an approach. nitric oxide; S-nitrosothiols; anoxia/reoxygenation; cytoprotection; nitric oxide synthase NITRIC OXIDE (NO) is an important regulator of many biological functions in vertebrates. In normoxic conditions, NO is produced from L-arginine and O 2 by NO synthases (NOS). The classical role is in vasodilation, where NO binds to the heme of the guanylyl cyclase in smooth muscle cells, leading to a rise in cGMP and subsequent muscle relaxation (35). NO also binds to heme groups of other proteins and is involved in reactions with thiols and secondary amines of different proteins, leading to formation of iron-nitrosyls (FeNO), S-nitrosothiols (SNO), and N-nitrosamines (NNO), respectively (26). Through formation of FeNO and SNO, NO can activate and inactivate enzymes or modify protein function (17,73). NO is inactivated by oxidation to nitrate (NO 3 Ϫ ) in reaction with oxygenated hemoglobin and myoglobin, and it is metabolized to nitrite (NO 2 Ϫ ) in reaction with O 2 (48). Nitrite was previously considered an inert end product of this oxidation, but nitrite can be reduced back to NO, and it has become clear that nitrite functions as a NO storage pool that is activated by va...

No golden standard exists for normalization of real-time reverse transcriptase polymerase chain reaction (RT PCR) data and procedures used are often not validated. Numerous studies have indicated that current approaches are inadequate. Here, we report the development of an external RNA control approach. It is the first to add external RNA to tissue on a per unit weight basis, and we demonstrate its accuracy, suitability, and necessity in experiments involving severe physiological challenges. We utilized the approach to examine the expression of the internal RNA control genes (reference genes) beta-actin, cyclophilin A, and glyceraldehyde 3-phospate dehydrogenase in brain and heart of normoxic and anoxic crucian carp (Carassius carassius). The internal RNA control genes differed significantly in expression in experimental groups, especially in heart. We also demonstrate that the external RNA control approach provides a more accurate normalization of target genes. For example, it revealed a 2.5-fold increase in the expression of the stress-response gene HSC70, which was not detected using beta-actin or geNorm. Further, we demonstrate and discuss the need for using the optimized and standardized external RNA control protocol reported. Collectively, our data suggest that the normalization of real-time RT PCR data is considerably improved by adding an external RNA control to the samples.

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