An ideal stimuli-responsive magnetic system possibilities the monitoring of the medication in the organism followed by the treatment using local drug delivery or hyperthermia.
In recent years, ...magnetic nanoparticles have been studied due to their potential applications as magnetic carriers in biomedical area. These materials have been increasingly exploited as efficient delivery vectors, leading to opportunities of use as magnetic resonance imaging (MRI) agents, mediators of hyperthermia cancer treatment and in targeted therapies. Much attention has been also focused on “smart” polymers, which are able to respond to environmental changes, such as changes in the temperature and pH. In this context, this article reviews the state-of-the art in stimuli-responsive magnetic systems for biomedical applications. The paper describes different types of stimuli-sensitive systems, mainly temperature- and pH sensitive polymers, the combination of this characteristic with magnetic properties and, finally, it gives an account of their preparation methods. The article also discusses the main in vivo biomedical applications of such materials. A survey of the recent literature on various stimuli-responsive magnetic gels in biomedical applications is also included.
Chondroitin sulfate (CS) is a type of glycosaminoglycan described as an antioxidant molecule that has been found in animal species such as fish. Tilapia (Oreochromis niloticus) represents an ...eco-friendly source of this compound, since its economical processing generates usable waste, reducing the negative environmental impact. This waste was used for CS extraction, purification, characterization by enzymatic degradation, and evaluation of its antioxidant effect. CS obtained from tilapia presented sulfation mainly at carbon 4 of galactosamine, and it was not cytotoxic at concentrations up to 200 microg/mL. Furthermore, 100 microg/mL of CS from tilapia reduced the levels of reactive oxygen species to 47% of the total intracellular reactive oxygen species level. The ability of CS to chelate metal ions in vitro also suggested an ability to react with other pathways that generate oxidative radicals, such as the Haber-Weiss reaction, acting intracellularly in more than one way. Although the role of CS from tilapia remains unclear, the pharmacological effects described herein indicate that CS is a potential molecule for further study of the relationship between the structures and functions of chondroitin sulfates as antioxidants. Key words: Glycosaminoglycans; Chondroitin sulfate; Oreochromis niloticus; Antioxidant; Reactive oxygen species
•An unsupervised method to detect blood vessels in fundus images is proposed.•The algorithm effectively tackles image distortions such as central vessel reflex.•The two expert vessel identification ...images present significant differences.•The average observer plays an important role in defining a neutral standard.•Balanced accuracy is an alternative for performance evaluation of segmentation.
Algorithms for retinal vessel segmentation are powerful tools in automatic tracking systems for early detection of ophthalmological and cardiovascular diseases, and for biometric identification. In order to create more robust and reliable systems, the algorithms need to be accurately evaluated to certify their ability to emulate specific human expertise. The main contribution of this paper is an unsupervised method to detect blood vessels in fundus images using a coarse-to-fine approach. Our methodology combines Gaussian smoothing, a morphological top-hat operator, and vessel contrast enhancement for background homogenization and noise reduction. Here, statistics of spatial dependency and probability are used to coarsely approximate the vessel map with an adaptive local thresholding scheme. The coarse segmentation is then refined through curvature analysis and morphological reconstruction to reduce pixel mislabeling and better estimate the retinal vessel tree. The method was evaluated in terms of its sensitivity, specificity and balanced accuracy. Extensive experiments have been conducted on DRIVE and STARE public retinal images databases. Comparisons with state-of-the-art methods revealed that our method outperformed most recent methods in terms of sensitivity and balanced accuracy with an average of 0.7819 and 0.8702, respectively. Also, the proposed method outperformed state-of-the-art methods when evaluating only pathological images that is a more challenging task. The method achieved for this set of images an average of 0.7842 and 0.8662 for sensitivity and balanced accuracy, respectively. Visual inspection also revealed that the proposed approach effectively addressed main image distortions by reducing mislabeling of central vessel reflex regions and false-positive detection of pathological patterns. These improvements indicate the ability of the method to accurately approximate the vessel tree with reduced visual interference of pathological patterns and vessel-like structures. Therefore, our method has the potential for supporting expert systems in screening, diagnosis and treatment of ophthalmological diseases, and furthermore for personal recognition based on retinal profile matching.
•The SBSp was proven to be a suitable technique to produce antimicrobial coatings.•Deposition of AgNPs on partially crosslinked PDMS favored their deposition near the surface of the ...coating.•Flexibility of SBSp favored the superficial deposition of nanoparticles on coating.•AgNPs sprayed over PDMS coating changed its topography and hydrophobicity.•Silver mapping of coating surface (SEM/EDS) showed that AgNPs were well dispersed.
Antimicrobial coatings of poly(dimethyl siloxane) with silver nanoparticles (PDMS/AgNPs) were produced by solution blow spraying (SBSp), an adaptation of the solution blow spinning technique (SBS). Firstly, AgNPs were synthesized by the Turkevich method and characterized by dynamic light scattering (DLS), ultraviolet-visible spectroscopy (UV–vis), agar disk diffusion tests against Escherichia coli and Staphylococcus aureus, and toxicity to Artemia salina. Further, the PDMS/AgNPs coating was prepared in two steps by deposition of PDMS solution in hexane (2:1) over the substrate, and then, five depositions, in intervals of 7.5 min each, of the colloidal dispersion of AgNPs onto partially cured PDMS surface. The neat PDMS and PDMS/AgNPs coatings were characterized by inductively coupled plasma atomic emission spectrometry (ICP-AES), atomic force microscopy (AFM), contact angle and scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM/EDS). Furthermore, the antimicrobial activity against S. aureus and E. coli biofilm formation was evaluated by fluorescence. The results indicate that AgNPs were adhered near the PDMS coating surface, assuring antimicrobial activity against the studied microorganisms at a concentration of about 0.04 μg cm−2 and average particle size of 170.5 nm. Therefore, the SBSp technique, used to produce PDMS/AgNPs coating in two steps, proved to be a suitable method to produce antimicrobial coatings with potential applications in active packaging and self-disinfecting surfaces.
SAR Image Segmentation Using the Roughness Information Avila Rodrigues, F. A.; Rocha Neto, J. F. S.; Pinheiro Marques, R. C. ...
IEEE geoscience and remote sensing letters,
2016-Feb., 2016-2-00, 20160201, Letnik:
13, Številka:
2
Journal Article
Recenzirano
Image segmentation can be applied to a broad class of different problems. However, it is not usually a simple task for synthetic aperture radar (SAR) images due to the presence of speckle. Given the ...importance of SAR images in remote sensing problems, this letter introduces a simplified and general methodology to achieve SAR image segmentation by using the estimated roughness parameters of SAR data modeled by G I 0 and G A 0 distributions, instead of directly processing the speckled images. In this letter, we adopted the log-cumulants method for the roughness parameter estimation. The performance evaluation of the results was attained in terms of the error of segmentation and cross-region fitting measures for synthetic and real SAR images, respectively. With regard to synthetic images, we performed Monte Carlo experiments which confirmed the suitability of SAR image segmentation by means of roughness parameters. The results showed that the methodology provides a feasible input to SAR image segmentation algorithms which also include thresholding-based methods. The proposed approach accomplished satisfactory results for the most interesting and critical study case, i.e., the single-look images, which are markedly affected by speckle.
Docosahexaenoic acid (DHA) is an n-3 polyunsaturated fatty acid that is highly enriched in the brain, and the oxidation products of DHA are present or increased during neurodegenerative disease ...progression. The characterization of the oxidation products of DHA is critical to understanding the roles that these products play in the development of such diseases. In this study, we developed a sensitive and specific analytical tool for the detection and quantification of twelve major DHA hydroperoxide (HpDoHE) and hydroxide (HDoHE) isomers (isomers at positions 4, 5, 7, 8, 10, 11, 13, 14, 16, 17, 19 and 20) in biological systems. In this study, HpDoHE were synthesized by photooxidation, and the corresponding hydroxides were obtained by reduction with NaBH4. The isolated isomers were characterized by LC-MS/MS, and unique and specific fragment ions were chosen to construct a selected reaction monitoring (SRM) method for the targeted quantitative analysis of each HpDoHE and HDoHE isomer. The detection limits for the LC-MS/MS-SRM assay were 1-670 pg for HpDoHE and 0.5-8.5 pg for HDoHE injected onto a column. Using this method, it was possible to detect the basal levels of HDoHE isomers in both rat plasma and brain samples. Therefore, the developed LC-MS/MS-SRM can be used as an important tool to identify and quantify the hydro(pero)xy derivatives of DHA in biological system and may be helpful for the oxidative lipidomic studies.
The article delves into the intricate phenomenon of deposition in heat exchangers and how a piece of equipment known as the benchtop heat exchanger test instrument (BHETI) has been developed to ...expedite the examination of this phenomenon. The BHETI subjects samples to substantial stress, facilitating the assessment of an oil’s tendency to generate deposits. Tests were conducted on two crude oil blends referred to as blend A and blend B using a BHETI unit. This equipment permits testing under various controlled conditions, including temperature, pressure, and volumetric flow rate. The results indicated that blend A exhibited a higher susceptibility to deposition compared to blend B due to its elevated concentration of light hydrocarbons. The wall temperature exerted a significant influence on the deposition rate, with higher temperatures leading to elevated deposition rates. Conversely, lower oil flow rates resulted in increased deposition rates. Furthermore, extended-term tests unveiled fluctuations in deposition rates over time when blending the two oil samples, suggesting intermittent fouling processes, possibly attributable to thermodynamic imbalances induced by mixing, rendering the oil’s asphaltenes less stable. The outcomes were subjected to analysis employing the Colloidal Instability Index (CII), which indicated that the majority of samples exhibited values exceeding 0.9, signifying asphaltene instability. Additionally, the examination of saturated, aromatic, and NSO (nitrogen, sulfur, oxygen) fractions revealed decreased saturation and increased aromatics after the deposition tests.
Bet‐hedging is an ecological risk‐aversion strategy in which a population does not commit all its effort toward a single reproductive event or specific environmental condition, and instead spreads ...the risk to include multiple reproductive events or conditions. For aquatic invertebrates in dry wetlands, this often takes the form of some propagules hatching in the first available flood, while remaining propagules hatch in subsequent floods (the “hedge”); this better ensures that a subset of propagules will hatch in a flood of sufficient duration to successfully complete development. Harsh environmental conditions are believed to promote an increased reliance on bet‐hedging. Bet‐hedging studies have typically been restricted to single sites or single populations. Community‐level assessments may provide more robust support for the range of hatching strategies that exist in nature. Here, we tested whether freshwater zooplankton assemblages inhabiting ephemeral and unpredictable wetlands of a semiarid zone of tropical Brazil employ hatching strategies suggestive of bet‐hedging; few efforts have addressed bet‐hedging in the tropics where the unique conditions may influence the strategy. We collected dry sediments from six ephemeral wetlands, and flooded them across a sequence of three hydrations under similar laboratory conditions to assess whether hatching patterns conform to some of the predictions of the bet‐hedging theory. We found that taxa showing hatching patterns akin to bet‐hedging associated with delayed hatching numerically dominated the assemblages that emerged from dry sediments, although there was large heterogeneity in the hatching rate among sites and across taxa. While some populations distributed their hatching across all three floods and committed most of their hatching fraction to the first hydration, others committed as much or more effort to the second hydration (the “hedge”) or the third hydration (another substantial “hedge”). Thus, in the harsh study wetlands, hatching patterns akin to bet‐hedging associated with delayed hatching were common and occurred at multiple temporal scales. Our community assessment found that a commitment to the “hedge” was greater than the current theory would predict. Our findings have broader implications; bet‐hedger taxa seem especially well equipped to tolerate stress if conditions become harsher as environments change.
Caloric restriction (CR) promotes lifespan extension and protects against many pathological conditions, including ischemia/reperfusion injury to the brain, heart and kidney. In the liver, ...ischemia/reperfusion damage is related to excessive mitochondrial Ca2+ accumulation, leading to the mitochondrial permeability transition. Indeed, liver mitochondria isolated from animals maintained on CR for 4 months were protected against permeability transition and capable of taking up Ca2+ at faster rates and in larger quantities. These changes were not related to modifications in mitochondrial respiratory activity, but rather to a higher proportion of ATP relative to ADP in CR liver mitochondria. Accordingly, both depletion of mitochondrial adenine nucleotides and loading mitochondria with exogenous ATP abolished the differences between CR and ad libitum (AL) fed groups. The prevention against permeability transition promoted by CR strongly protected against in vivo liver damage induced by ischemia/reperfusion. Overall, our results show that CR strongly protects the liver against ischemia/reperfusion and uncover a mechanism for this protection, through a yet undescribed diet-induced change in liver mitochondrial Ca2+ handling related to elevated intramitochondrial ATP.
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•Caloric restriction protects liver mitochondria against Ca2+ induced permeability transition.•Mitochondrial Ca2+ uptake rates are also increased by the intervention.•Both of these effects seems to be mediated by elevated ATP/ADP ratios.•Decreased susceptibility to permeability transition induced by CR protects mouse livers against ischemia/reperfusion injury.
•Administration of Passiflora edulis induces antidepressant-like effects in mice.•Flavonoids seem to be mediating the antidepressant effects of Passiflora edulis.•5-HT and dopamine transmission are ...needed for the antidepressant action of P. edulis.
The genus Passiflora is popularly used to treat anxiety. Recent studies showed antidepressant-like effects of two varieties of P. edulis (edulis and flavicarpa) in mice. However, the mechanisms of antidepressant actions are still unknown. Here, the effects of P. edulis fo. edulis aqueous extract (AE, 100–300mg/kg, po), and ethyl acetate (AcOEt, 25–50mg/kg, po), butanol (BuOH, 25–50mg/kg, po) and residual aqueous (25–100mg/kg, po) fractions were investigated in the mouse forced swimming test. In addition, the involvement of monoamines in the P. edulis fractions-induced antidepressant actions was approached. HPLC analyses showed that AcOEt and BuOH, but not residual, fractions shared with AE the main peaks between 25 and 70min (UV 340nm), which are suggestive of flavonoids. Nortriptyline and fluoxetine reduced the immobility time and similar results were observed for AE, AcOEt and BuOH but not residual fractions. PCPA (inhibitor of 5-HT synthesis), AMPT (inhibitor of catecholamine synthesis) and sulpiride (selective D2 receptor antagonist), but not DSP-4 (noradrenergic neurotoxin), blocked the antidepressant actions of AcOEt and BuOH. In conclusion, AcOEt and BuOH fractions shared with AE similar phytochemical composition and antidepressant actions. Preserved 5-HT and dopamine transmissions were required for the antidepressant effects of P. edulis fractions.
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