Oxygenation-deoxygenation cycle of erythrocytes modulates submicron cell membrane fluctuations

Low frequency submicron fluctuations of the cell membrane were recently shown to be characteristic for different cell types, nevertheless their physiological role is yet unknown. Point dark-field microscopy based recordings of these local displacements of cell membrane in human erythrocytes, subjected to cyclic oxygenation and deoxygenation, reveals a reversible decrease of displacement amplitudes from 290 +/- 49 to 160 +/- 32 nm, respectively. A higher rate of RBC adhesion to a glass substratum is observed upon deoxygenation, probably due to a low level of fluctuation amplitudes. The variation in the amplitude of these displacements were reconstituted in open RBC ghosts by perfusing them with composite solutions of 2,3 diphosphoglycerate, Mg+2, and MgATP, which mimic the intracellular metabolite concentrations in oxygenated and deoxygenated erythrocytes. The mere change in intracellular Mg+2 during oxygenation-deoxygenation cycle is sufficient to explain these findings. The results imply that the magnitude of fluctuations amplitude is directly connected with cell deformability. This study suggests that the physiological cycle of oxygenation-deoxygenation provides a dynamic control of the bending deformability and adhesiveness characteristics of the RBC via a Mg+2-dependent reversible assembly of membrane-skeleton proteins. The existing coupling between oxygenation-deoxygenation of the RBC and its mechanical properties is expected to play a key role in blood microcirculation and may constitute an example of a general situation for other circulating blood cells, where the metabolic control of cytoskeleton dynamics may modulate their dynamic mechanical properties

Effect of 1-methylcyclopropene on the antioxidant capacity and postharvest quality of tomato fruit

Tomato fruits ‘1402’ were harvested at mature green (MG), light pink (LP) and light red (LR) stages and treated with 0.3 μL L-1 of 1-methylcyclopropene (1-MCP) at 20°C for 24 h to investigate the ability to retard tomato fruit ripening. The treated and control fruit were stored at 5°C and 12 oC for 14 days and a further 4 days at 20oC for a shelf life period. The results show that the effects of 1-MCP on fruit ripening were related to the stage of maturity and storage temperature. The MG stage was the optimal stage for 1-MCP treatment when fruit storage was at 12°C. 1-MCP treatment reduced the lipophilic antioxidant activity (LAA) of the tomato fruit, but the hydrophilic antioxidant activity (HAA) remained similar to that observed at harvest. 1-MCP is a potential tool for extending shelf life, delaying tomato fruit ripening (slowing color development and firmness loss) and enhancing quality of tomatoes.Keywords: Tomato, 1-MCP, storage, stage of maturity, temperatureAfrican Journal of Biotechnology Vol. 12(6), pp. 547-55

Photoselective shade nets reducing postharvest decay development in pepper fruits

During two-year studies, we evaluated the influence of photoselective coloured shade nets on the quality of fresh harvested pepper fruits (Capsicum annuum) after prolonged storage and shelf life simulation. Pepper cultivar ‘Romans’ grown in a semi arid region under 35% pearl and yellow shade nets significantly maintained better pepper fruit quality after 16 days at 7°C plus three days at 20°C, mainly by reducing decay incidence during two consecutive years (2008 and 2009), compared to commercial black and red nets. No significant differences were observed in percentage of weight loss, firmness and total soluble solids in fruit harvested under the different coloured shade nets. The skin colour of fruit harvested under Pearl net was significantly lighter than that of fruit harvested under red and black shade nets and this fact can be associated with inhibition of fruit ripening during growth. After storability and shelf life simulation however skin colour was red to dark red under all shade nets. Pearl and yellow shade nets significantly reduced Alternaria spp. population in the field, which was evaluated with Alternaria-selective growing medium. The highest Alternaria population was found under red shade net. The significant low decay incidence in fruit harvested under pearl and yellow shade nets can be explained by the low inoculum level of Alternaria spp. in the field, and inhibition of fungal sporulation, and/or by a slowing of fruit ripening during its growth, reducing fruit susceptibility to fungal infection in the field due to the scattered light, its quality and the ratio between the light spectrum under the two shade nets

New medical therapies on the horizon: oral octreotide

Somatostatin analog treatment is first line medical treatment in patients with acromegaly. This drug is currently mainly administered by monthly depot preparations of octreotide and lanreotide. With the innovative transient permeability enhancer, a technology enabling the absorption of drug molecules via transient opening of the tight junctions of the gut epithelium, it is possible to achieve therapeutic octreotide levels after oral ingestion. The present review summarized the preclinical work and the recently reported phase I and III study on oral octreotide capsules in patients with acromegaly. Maintenance of control in 155 participating patients was achieved in 65% at the end of core period. Once controlled on oral octreotide, the response was maintained to the end of the extension phase in 85%. Side effects were comparable to currently available preparations. There was a profound suppression of growth hormone levels, and significant symptom reduction. Currently available parental somatostatin analogs are generally well tolerated and are able to achieve longstanding biochemical control in patients with somatostatin sensitive tumors. Potential advantages of an oral alternative is the lack injection-related side effects, but there will be an ongoing need for a very strict compliance with the 2 daily dose regimen and fasting around drug administrations. A second phase III study is currently being conducted. The potential place in the treatment of acromegaly is discussed

Two-Component Fluid Membranes Near Repulsive Walls: Linearized Hydrodynamics of Equilibrium and Non-equilibrium States

We study the linearized hydrodynamics of a two-component fluid membrane near a repulsive wall, via a model which incorporates curvature- concentration coupling as well as hydrodynamic interactions. This model is a simplified version of a recently proposed one [J.-B. Manneville et al. Phys. Rev. E, 64, 021908 (2001)] for non-equilibrium force-centres embedded in fluid membranes, such as light-activated bacteriorhodopsin pumps incorporated in phospholipid (EPC) bilayers. The pump/membrane system is modeled as an impermeable, two-component bilayer fluid membrane in the presence of an ambient solvent, in which one component, representing active pumps, is described in terms of force dipoles displaced with respect to the bilayer midpoint. We first discuss the case in which such pumps are rendered inactive, computing the mode structure in the bulk as well as the modification of hydrodynamic properties by the presence of a nearby wall. We then discuss the fluctuations and mode structure in steady state of active two-component membranes near a repulsive wall. We find that proximity to the wall smoothens membrane height fluctuations in the stable regime, resulting in a logarithmic scaling of the roughness even for initially tensionless membranes. This explicitly non-equilibrium result, a consequence of the incorporation of curvature-concentration coupling in our treatment, also indicates that earlier scaling arguments which obtained an increase in the roughness of active membranes near repulsive walls may need to be reevaluated.Comment: 39 page Latex file, 3 encapsulated Postscript figure

Nonequilibrium Fluctuations, Travelling Waves, and Instabilities in Active Membranes

The stability of a flexible fluid membrane containing a distribution of mobile, active proteins (e.g. proton pumps) is shown to depend on the structure and functional asymmetry of the proteins. A stable active membrane is in a nonequilibrium steady state with height fluctuations whose statistical properties are governed by the protein activity. Disturbances are predicted to travel as waves at sufficiently long wavelength, with speed set by the normal velocity of the pumps. The unstable case involves a spontaneous, pump-driven undulation of the membrane, with clumping of the proteins in regions of high activity.Comment: 4 two-column pages, two .eps figures included, revtex, uses eps

Intracoronary Injection of In Situ Forming Alginate Hydrogel Reverses Left Ventricular Remodeling After Myocardial Infarction in Swine

ObjectivesThis study sought to determine whether alginate biomaterial can be delivered effectively into the infarcted myocardium by intracoronary injection to prevent left ventricular (LV) remodeling early after myocardial infarction (MI).BackgroundAlthough injectable biomaterials can improve infarct healing and repair, the feasibility and effectiveness of intracoronary injection have not been studied.MethodsWe prepared a calcium cross-linked alginate solution that undergoes liquid to gel phase transition after deposition in infarcted myocardium. Anterior MI was induced in swine by transient balloon occlusion of left anterior descending coronary artery. At 4 days after MI, either alginate solution (2 or 4 ml) or saline was injected selectively into the infarct-related coronary artery. An additional group (n = 19) was treated with incremental volumes of biomaterial (1, 2, and 4 ml) or 2 ml saline and underwent serial echocardiography studies.ResultsExamination of hearts harvested after injection showed that the alginate crossed the infarcted leaky vessels and was deposited as hydrogel in the infarcted tissue. At 60 days, control swine experienced an increase in left ventricular (LV) diastolic area by 44%, LV systolic area by 45%, and LV mass by 35%. In contrast, intracoronary injection of alginate (2 and 4 ml) prevented and even reversed LV enlargement (p < 0.01). Post-mortem analysis showed that the biomaterial (2 ml) increased scar thickness by 53% compared with control (2.9 ± 0.1 mm vs. 1.9 ± 0.3 mm; p < 0.01) and was replaced by myofibroblasts and collagen.ConclusionsIntracoronary injection of alginate biomaterial is feasible, safe, and effective. Our findings suggest a new percutaneous intervention to improve infarct repair and prevent adverse remodeling after reperfused MI

Quantification of neonicotinoid pesticides in six cultivable fish species from the River Owena in Nigeria and a template for food safety assessment

The Owena River Basin in Nigeria is an area of agricultural importance for the production of cocoa. To optimise crop yield, the cocoa trees require spraying with neonicotinoid insecticides (Imidacloprid, Thiacloprid Acetamiprid and Thiamethoxam). It is proposed that rainwater runoff from the treated area may pollute the Owena River and that these pesticides may thereby enter the human food chain via six species of fish (Clarias gariepinus, Clarias anguillaris, Sarotherodon galilaeus, Parachanna obscura, Oreochromis niloticus and Gymnarchus niloticus) which are cultured in the river mostly for local consumption. This work aims to establish a working method to quantify the likely levels of the insecticides in the six species of fish, firstly by undertaking a laboratory-based study employing the QuEChERS method to extract the four neonicotinoids from fish purchased in marketplace in the UK, spiked with known quantities of the pesticide and using liquid chromatography coupled with tandem mass spectrometry (LC-MS-MS) as the detection method; secondly, by using these samples to optimise the detection method for very low levels of pesticides, then applying the optimised techniques to the analysis of three of each six species of fish taken from the Owena River. A significant benefit of this combined technique is that only small samples of fish are required. Success with this part of the study showed that very low concentrations of the insecticides could be detected in fish muscle. The third aim is to apply a simple quantitative risk assessment model using the data sets obtained, together with information about daily diet, human body weight and recommended safety limits of pesticides in food to illustrate how human health may be affected by the consumption of these fish. The multiple determinations of neonicotinoids in edible fishes in Nigeria are pioneer research and fill a gap in addressing the relationship between waterborne pesticides and food quality in the country. Fundamentally, this work is an exercise to demonstrate the applicability of the aforementioned instrumental method of analysis to fish muscle, which requires only a small sample size of fish; a large number of fish is not required for a proof of concept, in this case. Although not a monitoring programme for the whole Owena River Basin ecosystem per se, this work successfully demonstrates the technical feasibility of a system of chemical analysis and establishes the foundation for ecological surveys in the immediate future. Parameters involving exposures to xenobiotics in ecotoxicological modelling can now be expressed in terms of both mass and molar concentrations of a chemical in animal tissues if so desired

Regulation of STIM1 and SOCE by the Ubiquitin-Proteasome System (UPS)

The ubiquitin proteasome system (UPS) mediates the majority of protein degradation in eukaryotic cells. The UPS has recently emerged as a key degradation pathway involved in synapse development and function. In order to better understand the function of the UPS at synapses we utilized a genetic and proteomic approach to isolate and identify novel candidate UPS substrates from biochemically purified synaptic membrane preparations. Using these methods, we have identified Stromal interacting molecule 1 (STIM1). STIM1 is as an endoplasmic reticulum (ER) calcium sensor that has been shown to regulate store-operated Ca2+ entry (SOCE). We have characterized STIM1 in neurons, finding STIM1 is expressed throughout development with stable, high expression in mature neurons. As in non-excitable cells, STIM1 is distributed in a membranous and punctate fashion in hippocampal neurons. In addition, a population of STIM1 was found to exist at synapses. Furthermore, using surface biotinylation and live-cell labeling methods, we detect a subpopulation of STIM1 on the surface of hippocampal neurons. The role of STIM1 as a regulator of SOCE has typically been examined in non-excitable cell types. Therefore, we examined the role of the UPS in STIM1 and SOCE function in HEK293 cells. While we find that STIM1 is ubiquitinated, its stability is not altered by proteasome inhibitors in cells under basal conditions or conditions that activate SOCE. However, we find that surface STIM1 levels and thapsigargin (TG)-induced SOCE are significantly increased in cells treated with proteasome inhibitors. Additionally, we find that the overexpression of POSH (Plenty of SH3′s), an E3 ubiquitin ligase recently shown to be involved in the regulation of Ca2+ homeostasis, leads to decreased STIM1 surface levels. Together, these results provide evidence for previously undescribed roles of the UPS in the regulation of STIM1 and SOCE function