Bright-field to fluorescence microscopy image translation for cell nuclei health quantification.

Microscopy is a widely used method in biological research to observe the morphology and structure of cells. Amongst the plethora of microscopy techniques, fluorescent labeling with dyes or antibodies is the most popular method for revealing specific cellular organelles. However, fluorescent labeling also introduces new challenges to cellular observation, as it increases the workload, and the process may result in nonspecific labeling. Recent advances in deep visual learning have shown that there are systematic relationships between fluorescent and bright-field images, thus facilitating image translation between the two. In this article, we propose the cross-attention conditional generative adversarial network (XAcGAN) model. It employs state-of-the-art GANs (GANs) to solve the image translation task. The model uses supervised learning and combines attention-based networks to explore spatial information during translation. In addition, we demonstrate the successful application of XAcGAN to infer the health state of translated nuclei from bright-field microscopy images. The results show that our approach achieves excellent performance both in terms of image translation and nuclei state inference.

Infectious microbial diseases and host defense responses in Sydney rock oysters.

Aquaculture has long been seen as a sustainable solution to some of the world's growing food shortages. However, experience over the past 50 years indicates that infectious diseases caused by viruses, bacteria, and eukaryotes limit the productivity of aquaculture. In extreme cases, these types of infectious agents threaten the viability of entire aquaculture industries. This article describes the threats from infectious diseases in aquaculture and then focuses on one example (QX disease in Sydney rock oysters) as a case study. QX appears to be typical of many emerging diseases in aquaculture, particularly because environmental factors seem to play a crucial role in disease outbreaks. Evidence is presented that modulation of a generic subcellular stress response pathway in oysters is responsible for both resistance and susceptibility to infectious microbes. Understanding and being able to manipulate this pathway may be the key to sustainable aquaculture.

Phenoloxidase-associated cellular defence in the Sydney rock oyster, Saccostrea glomerata, provides resistance against QX disease infections.

The enzyme phenoloxidase is a critical component of the immunological defence of invertebrates. Previously, we have shown that the activity of phenoloxidase in Sydney rock oysters (Saccostrea glomerata) correlates with the severity of QX disease outbreaks. The aetiological agent of QX disease is the opportunistic protozoan parasite, Marteilia sydneyi. In this study, we examined the response of oyster haemocytes to challenge with M. sydneyi. Granular haemocytes were able to rapidly phagocytose parasite sporonts. Phagocytosis stimulated intracellular associated phenoloxidase activity that led to the complete melanisation of phagosomes. Significant differences in phagocytic indexes and phenoloxidase activities were observed between oysters selected for resistance to QX disease (QXR) and non-selected wild-type oysters. The data suggest that phagocytosis and cellular melanisation are critical defensive responses of Sydney rock oysters infected with M. sydneyi.

Breeding for QX disease resistance negatively selects one form of the defensive enzyme, phenoloxidase, in Sydney rock oysters.

QX disease in Sydney rock oysters (Saccostrea glomerata) is caused by the paramyxean protozoan, Marteilia sydneyi. Disease outbreaks occur during summer (January to May) and can result in up to 95% mortality. The New South Wales Department of Primary Industries has been selectively breeding S. glomerata for resistance to QX disease since 1996. Previous work suggests that this breeding program has specifically affected the defensive phenoloxidase enzyme system of oysters. The current study more thoroughly characterises the effect of selection on the different forms of phenoloxidase found in oyster populations. Native polyacrylamide gel electrophoresis (native-PAGE) identified five discrete types of phenoloxidase in non-selected (wild type) and fourth generation QX disease resistant (QXR4) oysters. One electrophoretically distinct form of phenoloxidase, POb, is significantly less frequent in resistant oysters when compared to the wild type population. The frequency of POb also decreased in both the wild type and QXR4 populations over the course of a QX disease outbreak. This suggests that possession of POb makes oysters susceptible to QX disease and that breeding for resistance has resulted in negative selection against this form of phenoloxidase.