Connectivity-Enforcing Hough Transform for the Robust Extraction of Line Segments

Global voting schemes based on the Hough transform (HT) have been widely used to robustly detect lines in images. However, since the votes do not take line connectivity into account, these methods do not deal well with cluttered images. In opposition, the so-called local methods enforce connectivity but lack robustness to deal with challenging situations that occur in many realistic scenarios, e.g., when line segments cross or when long segments are corrupted. In this paper, we address the critical limitations of the HT as a line segment extractor by incorporating connectivity in the voting process. This is done by only accounting for the contributions of edge points lying in increasingly larger neighborhoods and whose position and directional content agree with potential line segments. As a result, our method, which we call STRAIGHT (Segment exTRAction by connectivity-enforcInG HT), extracts the longest connected segments in each location of the image, thus also integrating into the HT voting process the usually separate step of individual segment extraction. The usage of the Hough space mapping and a corresponding hierarchical implementation make our approach computationally feasible. We present experiments that illustrate, with synthetic and real images, how STRAIGHT succeeds in extracting complete segments in several situations where current methods fail.Comment: Submitted for publicatio

Evaluation of three iterative algorithms for phase modulation regarding their application in concentrating light inside biological tissues for laser induced photothermal therapy

Grant No. UIDB/00645/2020The focusing of light through turbid media like biological tissues is strongly hindered by the scattering of light which limits its safe practice and application in medicine. In order to control this phenomenon, we shaped the incident wavefront using three algorithms including a four-element division algorithm, a partitioning algorithm, and simulated annealing to control, iteratively, a spatial light modulator (SLM). We have tested two different convergence criteria to achieve a focal point inside a turbid environment, made up of a mixture of agar and milk, set to mimic a specific depth of human skin, and provide comparison results. A camera and a lens are used to visualize the focal area and give feedback information to the algorithms. A discussion on the use of these algorithms and convergence criteria is presented, being focused on its convergence time and performance. Depending on the algorithm and operational parameters, improvements of 29% to 46% of the irradiance in the region of interest were accomplished.publishersversionpublishe

Characterization of fish scale regeneration: environmental and endocrine control

Fish scales are calcified structures present in skin which have a protective function but which are also implicated in calcium homeostasis. Information about the molecular and cellular organisation of scales and the endocrine factors which regulate their turnover is scarce. In the present study as a first step to studying the influence of hormones on scale metabolism we aimed to characterize elasmoid scales from the sea bream (Sparus auratus), the dynamics of scale regeneration and the possible regulation of this process by calcium availability. Regenerating scales were evident 7 days after their removal in fish maintained in seawater (SW) and brackish water (BW). In BW, the activity of enzymes involved in scale turnover, tartrate resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP), increased indicating active remodelling. The higher activity of TRAP compared to ALP suggests that the reduced calcium availability in BW led to calcium mobilization from the scales. The results suggest that the scales can be used as a regulated reservoir of calcium in this fish.info:eu-repo/semantics/publishedVersio

Metabolic responses and resilience to environmental challenges in the sedentary Batrachoid Halobatrachus didactylus (Bloch & Schneider, 1801)

In the context of climate change, warming of the seas and expansion of hypoxic zones are challenges that most species of fish are, or will be subjected to. Understanding how different species cope with these changes in their environment at the individual level can shed light on how populations and ecosystems will be affected. We provide first-time estimates on the metabolic rates, thermal, and oxygen-related limits for Halobatrachus didactylus, a coastal sedentary fish that lives in intertidal environments of the Northeast Atlantic. Using respirometry in different experimental designs, we found that this species is highly resistant to acute thermal stress (CTmax: 34.82 ± 0.66 °C) and acute hypoxia (Pcrit: 0.59–1.97 mg O2 L−1). We found size-specific differences in this stress response, with smaller individuals being more sensitive. We also quantified its aerobic scope and daily activity patterns, finding this fish to be extremely sedentary, with one of the lowest standard metabolic rates found in temperate fish (SMR: 14.96 mg O2 kg−1h−1). H. didactylus activity increases at night, when its metabolic rate increases drastically (RMR: 36.01 mg O2 kg−1h−1). The maximum metabolic rate of H. didactylus was estimated to be 67.31 mg O2 kg−1h−1, producing an aerobic scope of 52.35 mg O2 kg−1h−1 (77.8% increase). The metrics obtained in this study prove that H. didactylus is remarkably resilient to acute environmental variations in temperature and oxygen content, which might enable it to adapt to the extreme abiotic conditions forecasted for the world’s oceans in the near future.info:eu-repo/semantics/publishedVersio

Evaluating the repetitive mucus extraction effects on mucus biomarkers, mucous cells, and the skin-barrier status in a marine fish model

Among all the mucosal barriers, the skin and its surrounding mucus are possibly the main defensive tool against changes in the environment that can be harmful for fish. Due to the extraction of this mucus being less invasive, the study of its production and functions has attracted great interest in recent years. However, there are still many gaps concerning the sampling process as well as the possible alterations in skin integrity and mucus composition. In the current study, the effects of skin mucus extraction were determined by comparing the effects of a single extraction (single extraction group, SEG) with those of three successive extractions separated by 3 days (repetitive extractions group, REG). Intact skin histology without mucus extraction (ØEG) and both plasma and skin mucus biomarkers and antibacterial capacities were also assessed. Regarding the skin histology and skin barrier properties, both the SEG and REG did not show differences in the intact skin. Interestingly, repetitive mucus extractions seemed to activate skin mucus turnover, significantly increasing the number of small-sized mucous cells (cell area 150 µm2). Repetitive extractions significantly decreased the amounts of soluble protein and increased cortisol secretion. These metabolites remained unaltered in the plasma, indicating different responses in the plasma and mucus. Despite changes in the mucus biomarkers, antibacterial capacity against pathogenic bacteria (Pseudomonas anguilliseptica and Vibrio anguillarum) was maintained in both the plasma and mucus irrespective of the number of mucus extractions. Overall, the mucus sampling protocol had little effect on skin integrity and mucus antibacterial properties, only modifying the amounts of soluble protein exuded and stimulating mucous cell replacement. This protocol is a feasible and minimally invasive way of studying and monitoring fish health and welfare and can be used as an alternative or a complement to plasma analysis. This methodology can be transferred to farm culture conditions and be very useful for studying threatened species in order to preserve fish welfare.info:eu-repo/semantics/publishedVersio

Transcriptomic down-regulation of immune system components in barrier and hematopoietic tissues after lipopolysaccharide injection in antarctic notothenia coriiceps

The environmental conditions and isolation in the Antarctic have driven the evolution of a unique biodiversity at a macro to microorganism scale. Here, we investigated the possible adaptation of the teleost Notothenia coriiceps immune system to the cold environment and unique microbial community of the Southern Ocean. The fish immune system was stimulated through an intraperitoneal injection of lipopolysaccharide (LPS 0111:B4 from E. coli) and the tissue transcriptomic response and plasma biochemistry were analyzed 7 days later and compared to a sham injected control. Gene transcription in the head-kidney, intestine and skin was significantly modified by LPS, although tissues showed different responsiveness, with the duodenum most modified and the skin the least modified. The most modified processes in head-kidney, duodenum and skin were related to cell metabolism (up-regulated) and the immune system (comprising 30% of differentially expressed genes). The immune processes identified were mostly down-regulated, particularly interleukins and pattern recognition receptors (PRRs), nucleotide-binding oligomerization domain-like receptors and mannose receptors, unlike the toll-like receptors response commonly described in other teleost fish. The modified transcriptional response was not mirrored by a modified systemic response, as the circulating levels of enzymes of innate immunity, lysozyme and antiproteases, were not significantly different from the untreated and sham control fish. In conclusion, while the N. coriiceps immune system shares many features with other teleosts there are also some specificities. Further studies should better characterize the PRRs and their role in Antarctic teleosts, as well as the importance of the LPS source and its consequences for immune activation in teleosts.info:eu-repo/semantics/publishedVersio

Environmental salinity modifies mucus exudation and energy use in European Sea Bass Juveniles

The European sea bass (Dicentrarchus labrax) is a euryhaline marine teleost that can often be found in brackish and freshwater or even in hypersaline environments. Here, we exposed sea bass juveniles to sustained salinity challenges for 15 days, simulating one hypoosmotic (3‰), one isosmotic (12‰) and one hyperosmotic (50‰) environment, in addition to control (35‰). We analyzed parameters of skin mucus exudation and mucus biomarkers, as a minimally invasive tool, and plasma biomarkers. Additionally, Na+/K+ -ATPase activity was measured, as well as the gill mucous cell distribution, type and shape. The volume of exuded mucus increased significantly under all the salinity challenges, increasing by 130% at 50‰ condition. Significantly greater amounts of soluble protein (3.9 ± 0.6 mg at 50‰ vs. 1.1 ± 0.2 mg at 35‰, p < 0.05) and lactate (4.0 ± 1.0 µg at 50‰ vs. 1.2 ± 0.3 µg at 35‰, p < 0.05) were released, with clear energy expenditure. Gill ATPase activity was significantly higher at the extreme salinities, and the gill mucous cell distribution was rearranged, with more acid and neutral mucin mucous cells at 50‰. Skin mucus osmolality suggested an osmoregulatory function as an ion-trap layer in hypoosmotic conditions, retaining osmosis-related ions. Overall, when sea bass cope with different salinities, the hyperosmotic condition (50‰) demanded more energy than the extreme hypoosmotic condition.UIDB/04326/2020, ALG-01-0145-FEDER-022121,info:eu-repo/semantics/publishedVersio

Active removal of inorganic phosphate from cerebrospinal fluid by the choroid plexus

The P-i concentration of mammalian cerebrospinal fluid (CSF) is about one-half that of plasma, a phenomenon also shown here in the spiny dogfish, Squalus acanthias. The objective of the present study was to characterize the possible role of the choroid plexus (CP) in determining CSF P-i concentration. The large sheet-like fourth CP of the shark was mounted in Ussing chambers where unidirectional P-33(i) fluxes revealed potent active transport from CSF to the blood side under short-circuited conditions. The flux ratio was 8: 1 with an average transepithelial resistance of 87 +/- 17.9 Omega . cm(2) and electrical potential difference of + 0.9 +/- 0.17 mV (CSF side positive). Active P-i absorption from CSF was inhibited by 10 mM arsenate, 0.2 mM ouabain, Na+ -free medium, and increasing the K+ concentration from 5 to 100 mM. Li+ stimulated transport twofold compared with Na+-free medium. Phosphonoformic acid (1 mM) had no effect on active Pi transport. RT-PCR revealed both P-i transporter (PiT) 1 and PiT2 (SLC20 family) gene expression, but no Na+ -P-i cotransporter II (SLC34 family) expression, in the shark CP. PiT2 immunoreactivity was shown by immunoblot analysis and localized by immunohistochemistry in (or near) the CP apical microvillar membranes of both the shark and rat. PiT1 appeared to be localized primarily to vascular endothelial cells. Taken together, these data indicate that the CP actively removes P-i from CSF. This process has transport properties consistent with a PiT2, Na+-dependent transporter that is located in the apical region of the CP epithelium.National Science Foundation [0843253]; Fundacao para a Ciencia e a Tecnologia, Portuga

Evaluation of an acute osmotic stress in European sea bass via skin mucus biomarkers

European sea bass is a marine teleost which can inhabit a broad range of environmental salinities. So far, no research has studied the physiological response of this fish to salinity challenges using modifications in skin mucus as a potential biological matrix. Here, we used a skin mucus sampling technique to evaluate the response of sea bass to several acute osmotic challenges (for 3 h) from seawater (35¿) to two hypoosmotic environments, diluted brackish water (3¿) and estuarine waters (12¿), and to one hyperosmotic condition (50¿). For this, we recorded the volume of mucus exuded and compared the main stress-related biomarkers and osmosis-related parameters in skin mucus and plasma. Sea bass exuded the greatest volume of skin mucus with the highest total contents of cortisol, glucose, and protein under hypersalinity. This indicates an exacerbated acute stress response with possible energy losses if the condition is sustained over time. Under hyposalinity, the response depended on the magnitude of the osmotic change: shifting to 3¿ was an extreme salinity change, which affected fish aerobic metabolism by acutely modifying lactate exudation. All these data enhance the current scarce knowledge of skin mucus as a target through which to study environmental changes and fish status