Ciguatoxin-like toxicity distribution in flesh of amberjack (Seriola spp.) and dusky grouper (Epinephelus marginatus).

Ciguatoxins (CTXs) are marine neurotoxins that cause ciguatera poisoning (CP), mainly through the consumption of fish. The distribution of CTXs in fish is known to be unequal. Studies have shown that viscera accumulate more toxins than muscle, but little has been conducted on toxicity distribution in the flesh, which is the main edible part of fish, and the caudal muscle is also most commonly targeted for the monitoring of CTXs in the Canary Islands. At present, whether this sample is representative of the toxicity of an individual is undisclosed. This study aims to assess the distribution of CTXs in fish, considering different muscle samples, the liver, and gonads. To this end, tissues from four amberjacks (Seriola spp.) and four dusky groupers (Epinephelus marginatus), over 16.5 kg and captured in the Canary Islands, were analyzed by neuroblastoma-2a cell-based assay. Flesh samples were collected from the extraocular region (EM), head (HM), and different areas from the fillet (A-D). In the amberjack, the EM was the most toxic muscle (1.510 CTX1B Eq·g-1), followed by far for the caudal section of the fillet (D) (0.906 CTX1B Eq·g-1). In the dusky grouper flesh samples, D and EM showed the highest toxicity (0.279 and 0.273 CTX1B Eq·g-1). In both species, HM was one of the least toxic samples (0.421 and 0.166 CTX1B Eq·g-1). The liver stood out for its high CTX concentration (3.643 and 2.718 CTX1B Eq·g-1), as were the gonads (1.620 and 0.992 CTX1B Eq·g-1). According to these results, the caudal muscle next to the tail is a reliable part for use in determining the toxicity of fish flesh to guarantee its safe consumption. Additionally, the analysis of the liver and gonads could provide further information on doubtful specimens, and be used for CTX monitoring in areas with an unknown prevalence of ciguatera.

Alkylation converts riboflavin into an efficient photosensitizer of phospholipid membranes.

A new decyl chain [-(CH2)9CH3] riboflavin conjugate has been synthesized and investigated. A nucleophilic substitution (SN2) reaction was used for coupling the alkyl chain to riboflavin (Rf), a model natural photosensitizer. As expected, the alkylated compound (decyl-Rf) is significantly more lipophilic than its precursor and efficiently intercalates within phospholipid bilayers, increasing its fluorescence quantum yield. The oxidative damage to lipid membranes photoinduced by decyl-Rf was investigated in large and giant unilamellar vesicles (LUVs and GUVs, respectively) composed of different phospholipids. Using a fluorogenic probe, fast radical formation and singlet oxygen generation was demonstrated upon UVA irradiation in vesicles containing decyl-Rf. Photosensitized formation of conjugated dienes and hydroperoxides, and membrane leakage in LUVs rich in poly-unsaturated fatty acids were also investigated. The overall assessment of the results shows that decyl-Rf is a significantly more efficient photosensitizer of lipids than its unsubstituted precursor and that the association to lipid membranes is key to trigger phospholipid oxidation. Alkylation of hydrophilic photosensitizers as a simple and general synthetic tool to obtain efficient photosensitizers of biomembranes, with potential applications, is discussed.

Synthesis, Characterization and Photocleavage of Bis-decyl Pteroic Acid: A Folate Derivative with Affinity to Biomembranes†.

Here, we provide mechanistic insight to the photocleavage of a compound in the folate family, namely pteroic acid. A bis-decyl chain derivative of pteroic acid was synthesized, structurally characterized and photochemically investigated. We showed that, like folic acid, pteroic acid and the decylated derivative undergo a photocleavage reaction in the presence of H2 O, while no reaction was observed in methanol solution. Furthermore, density functional theory calculations were carried out to predict relative stabilities of hypothetical mono-, bis- and tris-decylated pteroic acid derivatives to help rationalize the regioselectivity of the bis-decyl pteroic acid product. Additionally, the lipophilicity of the bis-decyl pteroic acid appears to confer a hydrophobic property enabling an interaction with biomembranes.

Cov-caldas: A new COVID-19 chest X-Ray dataset from state of Caldas-Colombia.

The emergence of COVID-19 as a global pandemic forced researchers worldwide in various disciplines to investigate and propose efficient strategies and/or technologies to prevent COVID-19 from further spreading. One of the main challenges to be overcome is the fast and efficient detection of COVID-19 using deep learning approaches and medical images such as Chest Computed Tomography (CT) and Chest X-ray images. In order to contribute to this challenge, a new dataset was collected in collaboration with "S.E.S Hospital Universitario de Caldas" ( https://hospitaldecaldas.com/ ) from Colombia and organized following the Medical Imaging Data Structure (MIDS) format. The dataset contains 7,307 chest X-ray images divided into 3,077 and 4,230 COVID-19 positive and negative images. Images were subjected to a selection and anonymization process to allow the scientific community to use them freely. Finally, different convolutional neural networks were used to perform technical validation. This dataset contributes to the scientific community by tackling significant limitations regarding data quality and availability for the detection of COVID-19.

Metabolic Hepatic Disorders Caused by Ciguatoxins in Goldfish (Carassius auratus).

Ciguatera poisoning (CP) is a foodborne disease known for centuries; however, little research has been conducted on the effects of ciguatoxins (CTXs) on fish metabolism. The main objective of this study was to assess different hepatic compounds observed in goldfish (Carassius auratus) fed C-CTX1 using nuclear magnetic resonance (NMR)-based metabolomics. Thirteen goldfish were treated with C-CTX1-enriched flesh and sampled on days 1, 8, 15, 29, 36, and 43. On day 43, two individuals, referred to as 'Detox', were isolated until days 102 and 121 to evaluate the possible recovery after returning to a commercial feed. At each sampling, hepatic tissue was weighed to calculate the hepatosomatic index (HSI) and analyzed for the metabolomics study; animals fed toxic flesh showed a higher HSI, even greater in the 'Detox' individuals. Furthermore, altered concentrations of alanine, lactate, taurine, glucose, and glycogen were observed in animals with the toxic diet. These disturbances could be related to an increase in ammonium ion (NH4+) production. An increase in ammonia (NH3) concentration in water was observed in the aquarium where the fish ingested toxic meat compared to the non-toxic aquarium. All these changes may be rationalized by the relationship between CTXs and the glucose-alanine cycle.

Kinetics of the invasion of a non-phagocytic fish cell line, RTG-2 by Yersinia ruckeri serotype O1 biotype 1.

Yersiniosis, caused by the fish pathogen Yersinia ruckeri, is a serious bacterial septicaemia affecting mainly salmonids worldwide. The acute infection may result in high mortality without apparent external disease signs, while the chronic one causes moderate to considerable mortality. Survivors of yersiniosis outbreaks become carriers. Y. ruckeri is able to adhere to, and to invade, phagocytic and non-phagocytic fish cells by using unknown molecular mechanisms. The aim of this study was to describe the kinetics of cell invasion by Y. ruckeri serotype O1 biotype 1 in a fish cell line (RTG-2) originating from rainbow trout gonads. The efficiency of invasion by Y. ruckeri was found to be temperature dependent, having a maximum at 20 °C. The bacterium was able to survive up to 96 h postinfection. The incubation of the cells at 4 °C and the pre-incubation of the bacteria with sugars or heat-inactivated antiserum significantly decreased the efficiency of invasion or even completely prevented the invasion of RTG-2 cells. These findings indicate that Y. ruckeri is capable of adhering to, entering and surviving within non-phagocytic cells, and that the intracellular environment may constitute a suitable niche for this pathogen that can favour the spread of infection and/or the maintenance of a carrier state of fish.

Ciguatoxin Detection in Flesh and Liver of Relevant Fish Species from the Canary Islands.

The Canary Islands are a ciguatoxin (CTX) hotspot with an established official monitoring for the detection of CTX in fish flesh from the authorised points of first sale. Fish caught by recreational fishermen are not officially tested and the consumption of toxic viscera or flesh could lead to ciguatera poisoning (CP). The objectives of this study were to determine the presence of CTX-like toxicity in relevant species from this archipelago, compare CTX levels in liver and flesh and examine possible factors involved in their toxicity. Sixty amberjack (Seriola spp.), 27 dusky grouper (Epinephelus marginatus), 11 black moray eels (Muraena helena) and 11 common two-banded seabream (Diplodus vulgaris) were analysed by cell-based assay (CBA) and Caribbean ciguatoxin-1 (C-CTX1) was detected by liquid chromatography mass spectrometry (LC-MS/MS) in all these species. Most of the liver displayed higher CTX levels than flesh and even individuals without detectable CTX in flesh exhibited hepatic toxicity. Black moray eels stand out for the large difference between CTX concentration in both tissues. None of the specimens with non-toxic liver showed toxicity in flesh. This is the first evidence of the presence of C-CTX1 in the common two-banded seabream and the first report of toxicity comparison between liver and muscle from relevant fish species captured in the Canary Islands.

Screening of New Potential Probiotics Strains against Photobacterium damselae Subsp. piscicida for Marine Aquaculture.

On intensive fish farms, 10% of the population dies exclusively from pathogens, and Photobacterium damselae subsp. Piscicida (Ph. damselae subsp. Piscicida), the bacteria causing pasteurellosis in marine aquaculture, is one of the major pathogens involved. The objective of this study was to obtain new probiotic strains against pasteurellosis in order to limit the use of chemotherapy, avoiding the environmental repercussions generated by the abusive use of these products. In this study, 122 strains were isolated from the gills and intestines of different marine fish species and were later evaluated in vitro to demonstrate the production of antagonistic effects, the production of antibacterial substances, adhesion and growth to mucus, resistance to bile and resistance to pH gradients, as well as its harmlessness and the dynamic of expression of immune-related genes by real-time PCR after administration of the potential probiotic in the fish diet. Only 1/122 strains showed excellent results to be considered as a potential probiotic strain and continue its characterization against Ph. damselae subsp. piscicida to determine its protective effect and elucidating in future studies its use as a possible probiotic strain for marine aquaculture.

Mono- and Bis-Alkylated Lumazine Sensitizers: Synthetic, Molecular Orbital Theory, Nucleophilic Index and Photochemical Studies.

Mono- and bis-decylated lumazines have been synthesized and characterized. Namely, mono-decyl chain [1-decylpteridine-2,4(1,3H)-dione] 6a and bis-decyl chain [1,3-didecylpteridine-2,4(1,3H)-dione] 7a conjugates were synthesized by nucleophilic substitution (SN 2) reactions of lumazine with 1-iododecane in N,N-dimethylformamide (DMF) solvent. Decyl chain coupling occurred at the N1 site and then the N3 site in a sequential manner, without DMF condensation. Molecular orbital (MO) calculations show a p-orbital at N1 but not N3 , which along with a nucleophilicity parameter (N) analysis predict alkylation at N1 in lumazine. Only after the alkylation at N1 in 6a, does a p-orbital on N3 emerge thereby reacting with a second equivalent of 1-iododecane to reach the dialkylated product 7a. Data from NMR (1 H, 13 C, HSQC, HMBC), HPLC, TLC, UV-vis, fluorescence and density functional theory (DFT) provide evidence for the existence of mono-decyl chain 6a and bis-decyl chain 7a. These results differ to pterin O-alkylations (kinetic control), where N-alkylation of lumazine is preferred and then to dialkylation (thermodynamic control), with an avoidance of DMF solvent condensation. These findings add to the list of alkylation strategies for increasing sensitizer lipophilicity for use in photodynamic therapy.

Immobilization of alkyl-pterin photosensitizer on silicon surfaces through in situ SN2 reaction as suitable approach for photodynamic inactivation of Staphylococcus aureus.

The tuning of surface properties through functionalization is an important field of research with a broad spectrum of applications. Self-assembled monolayers (SAMs) allow the surface tailoring through the adsorption of molecular layers having the appropriate functional group or precursor group enabling in situ chemical reactions and thus to the incorporation of new functionalities. The latter approach is particularly advantageous when the incorporation of huge groups is needed. In this study, we report the immobilization of pterin moieties on 11-bromoundecyltrichlorosilane-modified silicon substrates based on the in situ replacement of the bromine groups by pterin (Ptr), the parent derivative of pterins, by means of a nucleophilic substitution reaction. The modified surface was structurally characterized through a multi-technique approach, including high-resolution XPS analysis, contact angle measurements, and AFM. The designed synthesis method leads to the functionalization of the silicon surface with two compounds, O-undecyl-Ptr and N-undecyl-Ptr, with a higher proportion of the N-derivative (1:8 ratio). The alkyl-pterins immobilized via the proposed strategy, retain their photochemical properties, being able to inhibit Staphylococcus aureus growth under irradiation (84.3 ± 15.6 % reduction in viable cells). Our results open the possibility for the modification of several materials, such as glass and metal, through the formation of SAMs having the proper head group, thus allowing the design of photosensitive surfaces with potential microbiological self-cleaning properties.