The Impact of Ca2+ on Intracellular Distribution of Hemoglobin in Human Erythrocytes

The membrane-bound hemoglobin (Hb) fraction impacts red blood cell (RBC) rheology and metabolism. Therefore, Hb-RBC membrane interactions are precisely controlled. For instance, the signaling function of membrane-bound deoxy-Hb and the structure of the docking sites in the cytosolic domain of the anion exchanger 1 (AE-1) protein are well documented; however, much less is known about the interaction of Hb variants with the erythrocyte's membrane. Here, we identified factors other than O2 availability that control Hb abundance in the membrane-bound fraction and the possible variant-specific binding selectivity of Hb to the membrane. We show that depletion of extracellular Ca2+ by chelators, or its omission from the extracellular medium, leads to membrane-bound Hb release into the cytosol. The removal of extracellular Ca2+ further triggers the redistribution of HbA0 and HbA2 variants between the membrane and the cytosol in favor of membrane-bound HbA2. Both effects are reversible and are no longer observed upon reintroduction of Ca2+ into the extracellular medium. Fluctuations of cytosolic Ca2+ also impact the pre-membrane Hb pool, resulting in the massive transfer of Hb to the cellular cytosol. We hypothesize that AE-1 is the specific membrane target and discuss the physiological outcomes and possible clinical implications of the Ca2+ regulation of the intracellular Hb distribution.

Response of cells and tissues to shear stress

Shear stress is essential for normal physiology and malignancy. Common physiological processes - such as blood flow, particle flow in the gut, or contact between migratory cell clusters and their substrate - produce shear stress that can have an impact on the behavior of different tissues. In addition, shear stress has roles in processes of biomedical interest, such as wound healing, cancer and fibrosis induced by soft implants. Thus, understanding how cells react and adapt to shear stress is important. In this Review, we discuss in vivo and in vitro data obtained from vascular and epithelial models; highlight the insights these have afforded regarding the general mechanisms through which cells sense, transduce and respond to shear stress at the cellular levels; and outline how the changes cells experience in response to shear stress impact tissue organization. Finally, we discuss the role of shear stress in collective cell migration, which is only starting to be appreciated. We review our current understanding of the effects of shear stress in the context of embryo development, cancer and fibrosis, and invite the scientific community to further investigate the role of shear stress in these scenarios.

Alginate Gel-Based Carriers for Encapsulation of Carotenoids: On Challenges and Applications

Sodium alginate is one of the most interesting and the most investigated and applied biopolymers due to its advantageous properties. Among them, easy, simple, mild, rapid, non-toxic gelation by divalent cations is the most important. In addition, it is abundant, low-cost, eco-friendly, bio-compatible, bio-adhesive, biodegradable, stable, etc. All those properties were systematically considered within this review. Carotenoids are functional components in the human diet with plenty of health benefits. However, their sensitivity to environmental and process stresses, chemical instability, easy oxidation, low water solubility, and bioavailability limit their food and pharmaceutical applications. Encapsulation may help in overcoming these limitations and within this review, the role of alginate-based encapsulation systems in improving the stability and bioavailability of carotenoids is explored. It may be concluded that all alginate-based systems increase carotenoid stability, but only those of micro- and nano-size, as well as emulsion-based, may improve their low bioaccessibility. In addition, the incorporation of other biopolymers may further improve encapsulation system properties. Furthermore, the main techniques for evaluating the encapsulation are briefly considered. This review critically and profoundly explains the role of alginates in improving the encapsulation process of carotenoids, suggesting the best alternatives for those systems. Moreover, it provides a comprehensive cover of recent advances in this field.

Alginate/soy protein system for essential oil encapsulation with intestinal delivery

Preparation of alginate-soy protein isolate (AL/SPI) complex beads containing essential oil of thyme was carried out by emulsification of thyme oil in aqueous sodium alginate solution blended with SPI solution, followed by atomization via electrostatic extrusion and gelification with calcium ions. The process parameters were optimized by variation of the alginate (1-2.5 wt.%) and SPI (0-1.5 wt.%) concentrations. Dry alginate-SPI particles exhibited wrinkle surface while shape distortion of hydrogel beads occurred with ≥1.5 wt.% alginate concentration, whereas SPI induced reduction of the particle size. Encapsulation efficiency of 72-80 % based on total polyphenols was achieved. In SGF the samples exhibited oil release of 42-55 % (due to matrix shrinkage and proteins degradation by pepsin activity), while the rest was delivered in SIF within 2.5 h simultaneously with swelling and degradation of the matrix.

Essential Oils as Feed Additives-Future Perspectives

The inconsistency of phytogenic feed additives' (PFA) effects on the livestock industry poses a risk for their use as a replacement for antibiotic growth promoters. The livestock market is being encouraged to use natural growth promotors, but information is limited about the PFA mode of action. The aim of this paper is to present the complexity of compounds present in essential oils (EOs) and factors that influence biological effects of PFA. In this paper, we highlight various controls and optimization parameters that influence the processes for the standardization of these products. The chemical composition of EOs depends on plant genetics, growth conditions, development stage at harvest, and processes of extracting active compounds. Their biological effects are further influenced by the interaction of phytochemicals and their bioavailability in the gastrointestinal tract of animals. PFA effects on animal health and production are also complex due to various EO antibiotic, antioxidant, anti-quorum sensing, anti-inflammatory, and digestive fluids stimulating activities. Research must focus on reliable methods to identify and control the quality and effects of EOs. In this study, we focused on available microencapsulation techniques of EOs to increase the bioavailability of active compounds, as well as their application in the animal feed additive industry.

Development of low calorie jams with increased content of natural dietary fibre made from tomato pomace

In this study, four jam formulations were developed, starting with the basic formulation (Jam 1) containing sucrose and without added pectin. Sucrose was partially (50%) replaced by stevioside in formulations of Jam 2 and 3, while in Jam 4 sucrose was completely replaced by fructose and stevioside, making this formulation suitable for diabetic patients. Jam formulations 1 and 2, prepared without added pectin, were thermally stable in the temperature range of 25-90°C, which indicate their potential use as fruit fillings. Jam formulations 3 and 4 were assessed by the sensory panel as more spreadable since tomato pomace particles are incorporated in pectin network which acts as a lubricant. Jam formulations were characterized by a lower total carbohydrate content (17.23-43.81%) and lower energy value (87.1-193.7kcal/100g) when compared to commercial products. Tomato pomace jams contained 15-20 times more dietary fibre than commercial apricot jam.

Ca-alginate hydrogel mechanical transformations—The influence on yeast cell growth dynamics

A mathematical model was formulated to describe yeast cell growth within the Ca-alginate microbead during air-lift bioreactor cultivation. Model development was based on experimentally obtained data for the intra-bead cell concentration profile, after reached the equilibrium state, as well as, total yeast cell concentration per microbed and microbead volume as function of time. Relatively uniform cell concentration in the carrier matrix indicated that no internal nutrient diffusion limitations, but microenvironmental restriction, affected dominantly the dynamics of cell growth. Also interesting phenomenon of very different rates of cell number growth during cultivation is observed. After some critical time, the growth rate of cell colonies decreased drastically, but than suddenly increased again under all other experimental condition been the same. It is interpreted as disintegration of gel network and opening new free space for growth of cell clusters. These complex phenomena are modeled using the thermodynamical, free energy formalism. The particular form of free energy functional is proposed to describe various kinds of interactions, which affected the dynamics of cell growth and cause pseudo-phase transition of hydrogel. The good agreement of experimentally obtained data and model predictions are obtained. In that way the model provides both, the quantitative tools for further technological optimization of the process and deeper insight into dynamics of cell growth mechanism.