In Vivo Biological Behavior of Polymer Scaffolds of Natural Origin in the Bone Repair Process

Autologous bone grafts, used mainly in extensive bone loss, are considered the gold standard treatment in regenerative medicine, but still have limitations mainly in relation to the amount of bone available, donor area, morbidity and creation of additional surgical area. This fact encourages tissue engineering in relation to the need to develop new biomaterials, from sources other than the individual himself. Therefore, the present study aimed to investigate the effects of an elastin and collagen matrix on the bone repair process in critical size defects in rat calvaria. The animals (Wistar rats, n = 30) were submitted to a surgical procedure to create the bone defect and were divided into three groups: Control Group (CG, n = 10), defects filled with blood clot; E24/37 Group (E24/37, n = 10), defects filled with bovine elastin matrix hydrolyzed for 24 h at 37 °C and C24/25 Group (C24/25, n = 10), defects filled with porcine collagen matrix hydrolyzed for 24 h at 25 °C. Macroscopic and radiographic analyses demonstrated the absence of inflammatory signs and infection. Microtomographical 2D and 3D images showed centripetal bone growth and restricted margins of the bone defect. Histologically, the images confirmed the pattern of bone deposition at the margins of the remaining bone and without complete closure by bone tissue. In the morphometric analysis, the groups E24/37 and C24/25 (13.68 ± 1.44; 53.20 ± 4.47, respectively) showed statistically significant differences in relation to the CG (5.86 ± 2.87). It was concluded that the matrices used as scaffolds are biocompatible and increase the formation of new bone in a critical size defect, with greater formation in the polymer derived from the intestinal serous layer of porcine origin (C24/25).     

Wettability of cellular polyurethane

Cellular polymers constitute an important field of investigation due to their unique properties as shock absorbers and thermal or acoustic insulators. The knowledge of the wetting properties of these materials is important in applications where adhesion or weathering behavior are an issue. In this study, cellular polyurethane polymers were used to investigate the effect of the cellular structure on the wetting properties. The polymeric substrates were analyzed by scanning electron microscopy and the wetting properties were studied by goniometry. The contact angles of water and diiodomethane were measured as a function of time and the surface tension of the expanded polymers was evaluated by the geometric and harmonic mean methods. It was found that the wettability and the surface energy of the cellular polymers increase as the density decreases. © 1997 John Wiley & Sons, Inc.     

Effects of Prenatal Exposure to Aflatoxin B1: A Review

Aflatoxins are mycotoxins produced as secondary fungal metabolites. Among them, aflatoxin B1 (AFB1) stands out due to its genotoxic and mutagenic potential, being a potent initiator of carcinogenesis. In this review, the outcomes from the published literature in the past 10 years on the effects of AFB1 pathophysiological mechanisms on embryological and fetal development are discussed. In several animal species, including humans, AFB1 has a teratogenic effect_, resulting in bone malformations, visceral anomalies, lesions in several organs, and behavioral and reproductive changes, in addition to low birth weight. The mutagenic capacity of AFB1 in prenatal life is greater than in adults, indicating that when exposure occurs in the womb, the risk of the development of neoplasms is higher. Studies conducted in humans indicate that the exposure to this mycotoxin during pregnancy is associated with low birth weight, decreased head circumference, and DNA hypermethylation. However, as the actual impacts on humans are still unclear, the importance of this issue cannot be overemphasized and studies on the matter are essential.     

Non-Toxic Dimeric Peptides Derived from the Bothropstoxin-I Are Potent SARS-CoV-2 and Papain-like Protease Inhibitors

The COVID-19 outbreak has rapidly spread on a global scale, affecting the economy and public health systems throughout the world. In recent years, peptide-based therapeutics have been widely studied and developed to treat infectious diseases, including viral infections. Herein, the antiviral effects of the lysine linked dimer des-Cys¹¹, Lys¹²,Lys¹³-(pBthTX-I)₂K ((pBthTX-I)₂K)) and derivatives against SARS-CoV-2 are reported. The lead peptide (pBthTX-I)₂K and derivatives showed attractive inhibitory activities against SARS-CoV-2 (EC₅₀ = 28–65 µM) and mostly low cytotoxic effect (CC₅₀ > 100 µM). To shed light on the mechanism of action underlying the peptides’ antiviral activity, the Main Protease (M^pro) and Papain-Like protease (PL^pro) inhibitory activities of the peptides were assessed. The synthetic peptides showed PL^pro inhibition potencies (IC₅₀s = 1.0–3.5 µM) and binding affinities (K_d = 0.9–7 µM) at the low micromolar range but poor inhibitory activity against M^pro (IC₅₀ > 10 µM). The modeled binding mode of a representative peptide of the series indicated that the compound blocked the entry of the PL^pro substrate toward the protease catalytic cleft. Our findings indicated that non-toxic dimeric peptides derived from the Bothropstoxin-I have attractive cellular and enzymatic inhibitory activities, thereby suggesting that they are promising prototypes for the discovery and development of new drugs against SARS-CoV-2 infection.     

An Insight into Kiwiberry Leaf Valorization: Phenolic Composition,Bioactivity and Health Benefits

During kiwiberry production, different by-products are generated, including leaves that are removed to increase the fruit’s solar exposure. The aim of this work was to extract bioactive compounds from kiwiberry leaf by employing microwave-assisted extraction (MAE). Compatible food solvents (water and ethanol) were employed. The alcoholic extract contained the highest phenolic and flavonoid contents (629.48 mg of gallic acid equivalents (GAE) per gram of plant material on dry weight (dw) (GAE/g dw) and 136.81 mg of catechin equivalents per gram of plant material on dw (CAE/g dw), respectively). Oppositely, the hydroalcoholic extract achieved the highest antioxidant activity and scavenging activity against reactive oxygen and nitrogen species (IC₅₀ = 29.10 μg/mL for O₂^•−, IC₅₀ = 1.87 μg/mL for HOCl and IC₅₀ = 1.18 μg/mL for ^•NO). The phenolic profile showed the presence of caffeoylquinic acids, proanthocyanidin, and quercetin in all samples. However, caffeoylquinic acids and quercetin were detected in higher amounts in the alcoholic extract, while proanthocyanidins were prevalent in the hydroalcoholic extract. No adverse effects were observed on Caco-2 viability, while the highest concentration (1000 µg/mL) of hydroalcoholic and alcoholic extracts conducted to a decrease of HT29-MTX viability. These results highlight the MAE potentialities to extract bioactive compounds from kiwiberry leaf.     

Preface

Journal of Thermal Analysis and Calorimetry -     

A theoretical study of radical-only and combined radical/carbocationic mechanisms of arachidonic acid cyclooxygenation by prostaglandin H synthase

Prostaglandin H synthase catalyzes the oxygenation of arachidonic acid into the cyclic endoperoxide, prostaglandin G₂ (PGG₂), and the subsequent reduction of PGG₂ to the corresponding alcohol, prostaglandin H₂ (PGH₂), the precursor of all prostaglandins and thromboxanes. Both radical abstraction by a neighboring tyrosyl radical and combined radical/carbocationic models have been proposed to explain the cyclooxygenase part of this reaction. We have used density functional theory calculations to study the mechanism of the formation of the cyclooxygenated product PGG₂. We found an activation free energy for the initial hydrogen abstraction by the tyrosine radical of 15.6 kcal/mol, and of 14.5 kcal/mol for peroxo bridge formation, in remarkable agreement with the experimental value of 15.0 kcal/mol. Subsequent steps of the radical-based mechanism were found to happen with smaller barriers. A combined radical/carbocation mechanism proceeding through a sigmatropic hydrogen shift was ruled out, owing to its much larger activation free energy of 36.5 kcal/mol. Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00214-003-0476-9. Electronic Supplementary MaterialSupplementary material is available in the online version of this article at Electronic Supplementary Material: Supplementary material is available in the online version of this article at     

Mechanistic studies on the formation of glycosidase-substrate and glycosidase-inhibitor covalent intermediates

Glycoside hydrolases catalyze the breaking of the glycosidic bond. This type of bond fashioned between two monosaccharides is very stable, and the polymers created are involved in multiple cellular processes, being crucial to life. In this article, computational methods were used to study the first step of the mechanism of reaction of retaining glycoside hydrolases in atomic detail. The systems modeled included a simplified reaction center and a small substrate/inhibitor. Using DFT calculations we were able to corroborate and provide molecular-level detail to the dissociative mechanism proposed in the literature. The role of the hydrogen bridge between the nucleophile and the C(2)--OH group of the ring was also investigated. Therefore, we concluded that this bridge is responsible for lowering the activation barrier by 5.1 kcal mol(-1) with functional BB1K/6-311+G(2d,2p), and the absence of the bridge explains, at least in part, the inhibitory effect of fluoro-substituted glycosides in the -2 position. The hydrogen bridge could also be involved in favoring the ring distortion verified in the transition state, and the dissociative character of the reaction mechanism. Using the NBO method, point atomic charges were calculated. In the transition state, the positive charge generated in the sugar ring is distributed nearly equally between the anomeric carbon and the ring oxygen, through a partial double bond involving the two atoms.     

Evaluation and application of bismuth as an internal standard for the determination of lead in wines by simultaneous electrothermal atomic absorption spectrometry

A method for the direct determination of Pb in wines by simultaneous multi-element atomic absorption spectrometry (SIMAAS) using a transversely heated graphite atomizer, Zeeman-effect background corrector and internal standardization is proposed. Bismuth was used as an internal standard and Pd(NO3)2 plus Mg(NO3)2 as chemical modifier to stabilize both the analyte and the internal standard. The implementation of two pyrolysis steps avoided any build-up of carbonaceous residues on the graphite platform. All diluted samples (1 + 1 v/v) in 0.2% v/v HNO3 and reference solutions (5.0-50 microg l(-1) Pb in 0.2% v/v HNO3) were spiked with 25 microg l(-1) Bi. For a 20 microl aliquot dispensed into the graphite tube, a good correlation (r = 0.9997) was obtained between the ratio of the analyte signal to the internal standard signal and the analyte concentration of the reference solutions. The electrothermal behaviour of Pb and Bi in red, white and rosé wines were compared. In addition, absorbance variations due to changes in experimental conditions, such as atomizer temperature, integration time, injected sample volume, radiation beam intensity, graphite tube surface, dilution and sample composition, were minimized by using Bi as internal standard. Relative standard deviations of measurements based on integrated absorbance varied from 0.1 to 3.4% and from 0.5 to 7.3% (n = 12) with and without internal standard correction, respectively. Good recoveries (91-104%) for Pb spikes were obtained. The characteristic mass was 45 pg Pb and the limit of detection based on integrated absorbance was 0.9 microg l(-1) Pb. Internal standardization increased the lifetime of the tube by 25%. Direct determinations of Pb in wines with and without internal standardization approaches were in agreement at the 95% confidence level. The repeatability and the tube lifetime were improved when using Bi as internal standard. The improvement in accuracy using an internal standard was only observed when the analytical results were affected by errors.     

Evaluation of polymeric flocculants for oily water systems using a photometric dispersion analyzer

During oil production and treatment, oil-in-water (O/W) emulsions are formed. These dispersions require treatment prior to disposal. In order to improve oil/water separation processes through any physical process (decanting, flotation, centrifuging etc), the particle size of the dispersed phase should be increased. This may be obtained by a flocculation process, which consists in the agglomeration of several particles or drops using as flocculating agent hydrophilic high molecular weight macromolecules. Poly (ethylene-b-propylene oxide) and poly (vinyl alcohol) polymers have been evaluated as flocculating agents for oily water systems. Their performance is related to the particle size increase of the dispersed phase. In this work, a photometric dispersion analyzer (PDA) has been used to accomplish the oil drop agglomeration. Synthetic as well as produced water was used. Data are in good agreement with previous tests. Qualitative information related to aggregates or particle size distribution of the oily water systems can be obtained using PDA.