The antioxidant activity of polysaccharides: a structure-function relationship overview

Over the last years, polysaccharides have been linked to antioxidant effects using both in vitro chemical and biological models. The reported structures, claimed to act as antioxidants, comprise chitosan, pectic polysaccharides, glucans, mannoproteins, alginates, fucoidans, and many others of all type of biological sources. The structural features linked to the antioxidant action include the polysaccharide charge, molecular weight, and the occurrence of non-carbohydrate substituents. The establishment of structure/function relationships can be, however, biased by secondary phenomena that tailor polysaccharides behavior in antioxidant systems. In this sense, this review confronts some basic concepts of polysaccharides chemistry with the current claim of carbohydrates as antioxidants. It critically discusses how the fine structure and properties of polysaccharides can define polysaccharides as antioxidants. Polysaccharides antioxidant action is highly dependent on their solubility, sugar ring structure, molecular weight, occurrence of positive or negatively charged groups, protein moieties and covalently linked phenolic compounds. However, the occurrence of phenolic compounds and protein as contaminants leads to misleading results in methodologies often used for screening and characterization purposes, as well as in vivo models. Despite falling in the concept of antioxidants, the role of polysaccharides must be well defined according with the matrices where they are involved.publishe

Production of 9-thioxo-2, 3, 4, 9-tetrahydro-pyrrolo[3, 4-b]quinolin-1-one derivatives from the aminolysis of 3, 3, 9-trichloro-3H-thieno[3, 4-b]quinolin-1-one

Treatment of the title substrate with propylamine yielded 2-propyl-9-propylamino-3-propylimino-2, 3-dihydro-pyrrolo[3, 4-b] quinolin-1-one (15%) and a S-containing product (63%). The latter is inferred (from its spectral and chemical properties) to be a (1:1) complex of 2-propyl-3-propylimino-9-thioxo-2, 3, 4, 9-tetrahydro-pyrrolo[3, 4-b]quinolin-1-one (derived via an unusual S-rearrangement) with propylamine. The propylamine in the complex is removed by acid or thermally to provide the aforementioned 9-thioxo component which structure was substantiated froma X-ray crystal analysis. Aminolysis of the title substrate with ethylamine afforded the analogous ethyl-substituted products. (South African Journal of Chemistry: 2003 56: 30-33

[μ-1,2-Bis(diphenyl­phosphan­yl)-1,2-diethyl­hydrazine-κ2 P:P′]bis­[chlorido­gold(I)] tetra­hydro­furan disolvate

The title compound, [Au2Cl2(C28H30N2P2)]·2C4H8O, was synthesized from a bidentate phosphine ligand complexed to two linear gold(I) chloride moieties. The Au(I) atom is in an almost linear coordination with a P—Au—Cl angle of 179.22 (4)°. The complex molecules reside on a twofold rotation axis

Correlations between corneal biomechanical properties measured with the ocular response analyzer and icare rebound tonometry

Purpose: To investigate the biomechanical properties of the normal cornea, and correlate them with central and peripheral corneal thickness and age. Methods: Seventy-six right eyes of volunteers were measured with Ocular Response Analyzer (ORA), ICare rebound tonometry and an ultrasound pachymeter at corneal center and at 4 mm from corneal center in the nasal and temporal directions. Results: ICare readings were significantly correlated with central and peripheral corneal thickness and corneal biomechanical properties. Corneal resistance factor was the biomechanical parameter with the higher correlation with ICare IOP values. ICare tonometry at center and Goldmann equivalent IOP obtained with ORA were significantly higher for thicker than thinner corneas (p<0.05). IOP compensated for corneal properties with the ORA was lower than the remaining IOP values measured in the study. Higher correlation was found between Goldmann equivalent IOP with ORA and ICare IOP values. Conclusions: Intra-ocular pressure values obtained with the rebound tonometer are higher in thicker corneas and are positively correlated with biomechanical corneal parameters, namely corneal resistance factor. Although corneal thickness plays a significant role in rebound tonometry, elastic and viscous properties of the cornea seem to play a significant role in the interaction of the tonometer probe with the ocular surface. However, the mechanism behind this process is presently unknown

Sistema de sensorização móvel e controlo baseado em ZigBee para bicicletas elétricas

Este artigo apresenta um sistema de monitorização e controlo centrado em dispositivos móveis concebido para aplicação em cenários que permitem tirar partido de uma bicicleta eléctrica. A bicicleta, para além de um meio de transporte, é uma excelente ferramenta para a promoção do exercício físico, podendo contribuir para melhorar a aptidão física de utilizadores de diversas faixas etárias. O sistema proposto, baseado numa rede ZigBee, permite recolher sinais fisiológicos dos utilizadores e controlar o motor elétrico da bicicleta de modo a possibilitar a implementação de diversos modos de utilização. Este trabalho descreve a solução utilizada para implementar a comunicação sem fios entre os sensores ZigBee e um smartphone Android, bem como os sensores para monitorização de sinais fisiológicos que foram desenvolvidos. De modo a ajudar a perceber onde este trabalho pode ser aplicado, são explicados alguns modos de utilização baseados no controlo do esforço físico, bem como as vantagens do sistema em relação às bicicletas convencionais e bicicletas estáticas.Fundação para a Ciência e a Tecnologia (FCT

Accuracy and repeatability of a new portable ultrasound pachymeter

To assess the accuracy and repeatability of central corneal thickness (CCT) measurements taken with a new portable ultrasound (US) pachymeter. Methods: Central thickness measurements were taken with a portable pachymeter (SP-100 Handy;Tomey, Nagoya, Japan) and a conventional US pachymeter (Nidek UP-1000; Nidek Technologies, Gamagori, Japan) from 57 right corneas of 57 young adults (19 males, 38 females) aged 18–44 years (mean ± S.D., 22.95 ± 3.92). Three repeated measures were obtained and then compared to obtain the repeatability of each instrument and the agreement between the pachymeters. The three readings taken with the portable pachymeter were compared against each other in order to evaluate intra-session repeatability and bias of each individual measurement with respect to the mean of three. Results: Mean values of CCT were 537 ± 35 micron for conventional and 534 ± 35 micron for the new portable pachymeter. A high agreement was found between the two instruments mean difference = 2.58 micron; 95% CI 1.41–3.75 micron) with only two eyes presenting differences larger than ± 8.6 micron which represents 95% CI in the Bland-Altman plots which represents 1.6% of the mean CCT. The first reading taken showed the highest agreement with the mean value for the portable pachymeter. Conclusions: The instrument tested in this study is able to take reliable measurements of corneal thickness even if a single reading is considered. Intra-session repeatability was very high, as was also the agreement between the average of three readings taken with the two US pachymeters

Deficit Irrigation in Mediterranean Fruit Trees and Grapevines: Water Stress Indicators and Crop Responses

In regions with Mediterranean climate, water is the major environmental resource that limits growth and production of plants, experiencing a long period of water scarcity during summer. Despite the fact that most plants developed morphological, anatomical, physiological, and biochemical mechanisms that allow to cope with such environments, these harsh summer conditions reduce growth, yield, and fruit quality. Irrigation is implemented to overcome such effects. Conditions of mild water deficit imposed by deficit irrigation strategies, with minimal effects on yield, are particularly suitable for such regions. Efficient irrigation strategies and scheduling techniques require the quantification of crop water requirements but also the identification of pertinent water stress indicators and their threshold. This chapter reviews the scientific information about deficit irrigation recommendations and thresholds concerning water stress indicators on peach trees, olive trees, and grapevines, as case studies

Non contact tonometry synchronized with cardiac rhythm and its relationship with blood pressure

Purpose: The main objectives of this study were to determine the differences between non-synchronized intraocular pressure (IOP_N) and intraocular pressure readings synchronized with cardiac pulse and try to determine if these parameters are related to blood pressure values. Methods: One hundred and sixty-five right eyes from 165 volunteers (107 females, 58 males) aged from 19 to 73 years (mean ± S.D., 29.93 ± 11.17) were examined with the Nidek NT-4000, a new non-contact tonometer that allows the measurement of IOP synchronized with the cardiac rhythm. IOP measurements in the four different modes of synchronization were taken in a randomized order. Three measures of each parameter were taken and then averaged. The blood pressure was determined three times with a portable manometer and mean values of systolic and diastolic pressure and the pulse rate were computed. Mean arterial pressure (MAP) was determined as being 1/3 of systolic plus 2/3 of diastolic blood pressure. Results: The mean ± S.D. values for the standard intraocular pressure (IOP_N: 14.76 ± 2.86), intraocular pressure in the systolic instant or peak (IOP_P: 14.99 ± 2.85), intraocular pressure in the middle instant between heartbeats or middle (IOP_M: 14.68 ± 2.76), and intraocular pressure in the diastolic instant or bottom (IOP_B: 13.86 ± 2.61) were obtained. The IOP_P was higher than the remaining values. A significant difference in mean IOP existed between IOP_B and the remaining modes of measuring (p < 0.05). Differences were statistically significant for all pair comparisons involving IOP_B. Arterial blood pressure values were systolic 125.5 ± 14.22, diastolic 77.7 ± 8.38 and MAP 93.64 ± 9.44 mmHg. The pulse rate was 77.3 ± 12.6 beats per minute. Except for the MAP (p = 0.025) there was no significant correlation between different IOP values and systolic or diastolic blood pressure, or pulse rate. Conclusions: NT-4000 is able to differentiate IOP values when synchronized with the cardiac rhythm and those differences are expected to be within a range of ±2.5 to ± 3.0 mmHg. IOP_B seems to be the parameter whose value differs from the non-synchronized and the remaining synchronized parameters in a significant way. Other than a weak association with MAP, no significant correlation between IOP and BP was found. The measurements of IOP readings for the three modes are consistent with timings during the cardiac cycle and IOP pulse cycle