Novel zebrafish behavioral assay to identify modifiers of the rapid,nongenomic stress response

When vertebrates face acute stressors, their bodies rapidly undergo a repertoire of physiological and behavioral adaptations, which is termed the stress response. Rapid changes in heart rate and blood glucose levels occur via the interaction of glucocorticoids and their cognate receptors following hypothalamic‐pituitary‐adrenal axis activation. These physiological changes are observed within minutes of encountering a stressor and the rapid time domain rules out genomic responses that require gene expression changes. Although behavioral changes corresponding to physiological changes are commonly observed, it is not clearly understood to what extent hypothalamic‐pituitary‐adrenal axis activation dictates adaptive behavior. We hypothesized that rapid locomotor response to acute stressors in zebrafish requires hypothalamic‐pituitary‐interrenal (HPI) axis activation. In teleost fish, interrenal cells are functionally homologous to the adrenocortical layer. We derived eight frameshift mutants in genes involved in HPI axis function: two mutants in exon 2 of mc2r (adrenocorticotropic hormone receptor), five in exon 2 or 5 of nr3c1 (glucocorticoid receptor [GR]) and two in exon 2 of nr3c2 (mineralocorticoid receptor [MR]). Exposing larval zebrafish to mild environmental stressors, acute changes in salinity or light illumination, results in a rapid locomotor response. We show that this locomotor response requires a functioning HPI axis via the action of mc2r and the canonical GR encoded by nr3c1 gene, but not MR (nr3c2). Our rapid behavioral assay paradigm based on HPI axis biology can be used to screen for genetic and environmental modifiers of the hypothalamic‐pituitary‐adrenal axis and to investigate the effects of corticosteroids and their cognate receptor interactions on behavior.     

Temporal variation in condition index and meat quality of Lunella undulata (Turbinidae), in relation to the reproductive cycle

ABSTRACT

Lunella undulata is a subtropical-temperate marine gastropod which is harvested commercially from temperate reefs in Australia. This paper aimed to evaluate monthly variation in the condition index (CI) and biochemical composition of the foot tissue of L. undulata in relation to the spawning cycle. The gonadosomatic index (GSI) varied significantly between males and females and across months (P?=?0.0001), ranging from 43% to 70% in males and 41% to 71% for females. The highest GSI, as well as the highest CI for both sexes was recorded in December and April, whilst meat yield peaked in January, September and October. Protein, lipid, fatty acid and heavy metals in the foot tissue also significantly varied between months (P?<?0.05). Throughout all 14 months of sampling, the foot tissue of L. undulata showed good nutritional quality, with high levels of protein and the polyunsaturated fatty acids, docosapentaenoic acid, eicosapentaenoic acid and arachidonic acid. Overall, despite some temporal variability in the biochemical composition, L. undulata could be harvested at any time of the year for human consumption, although it may be best to avoid peak spawning times, which occur around January in northern NSW.     

Saltwater Intrusion Modifies Microbial Community Structure and Decreases Denitrification in Tidal Freshwater Marshes

Ecosystems - Environmental changes can alter the interactions between biotic and abiotic ecosystem components in tidal wetlands and therefore impact important ecosystem functions. The objective of...     

Blood treatment of Lyme borreliae demonstrates the mechanism of CspZ‐mediated complement evasion to promote systemic infection in vertebrate hosts

Lyme disease, caused by the spirochete Borrelia burgdorferi, is the most common vector‐borne disease in the United States and Europe. The spirochetes are transmitted from mammalian and avian reservoir hosts to humans via ticks. Following tick bites, spirochetes colonize the host skin and then disseminate haematogenously to various organs, a process that requires this pathogen to evade host complement, an innate immune defence system. CspZ, a spirochete surface protein, facilitates resistance to complement‐mediated killing in vitro by binding to the complement regulator, factor H (FH). Low expression levels of CspZ in spirochetes cultivated in vitro or during initiation of infection in vivo have been a major hurdle in delineating the role of this protein in pathogenesis. Here, we show that treatment of B. burgdorferi with human blood induces CspZ production and enhances resistance to complement. By contrast, a cspZ‐deficient mutant and a strain that expressed an FH‐nonbinding CspZ variant were impaired in their ability to cause bacteraemia and colonize tissues of mice or quail; virulence of these mutants was however restored in complement C3‐deficient mice. These novel findings suggest that FH binding to CspZ facilitates B. burgdorferi complement evasion in vivo and promotes systemic infection in vertebrate hosts.