Preparation of supported-deep eutectic solvent membranes: Effects of bath medium composition on the structure and performance of supported-deep eutectic solvent membrane for CO2/N2 gas separation

Polyvinylidene fluoride-co-polytetrafluoroethylene, PVDF-co-PTFE polymer was used as a membrane support. The asymmetric membranes were formed by immersion of casted membrane film into the coagulation bath. This work manipulated the coagulant bath medium by mixing ethanol with distilled water at different weight percentages (0, 25 and 50 wt. % of ethanol). The structures of fabricated membranes were observed to have different morphologies. Higher ethanol content altered the membrane structure from finger-like to sponge-like structure, and hence differed in membrane porosity. Vacuum-based technique was chosen to impregnate the deep eutectic solvent (DES) into the pores of membrane support. DES was prepared by mixing choline chloride (ChCl) and ethylene glycol at a ratio of 1:3. Scanning electron microscopy (SEM) was used to study the membrane morphology changes while in order to determine the immobilization of DES, energy dispersive X-ray (EDX) analysis was used. The porosity of fabricated PVDF-co-PTFE membrane was determined by means of gravimetric method. Lastly, the membrane separation performance using CO2 and N2 gasses were used to determine the capability of the supported-DES-membrane. The results demonstrated the highest immobilization of DES in supported membrane pores was achieved when combination of 25 wt. % of ethanol and 75 wt. % distilled water was used as a coagulant bath medium. The respective membrane has 74.5% porosity with the most excellent performance of CO2 separation at 25.5 x 103 GPU with CO2/N2 selectivity of 2.89.

Production of Bioactive Lichen Compounds by Alginate-Immobilized Bionts Isolated from Cladonia verticillaris: An in Vitro Study

Bionts isolated from thalli of Cladonia verticillaris, immobilized in calcium alginate, produce two depsidones, fumarprotocetraric and protocetraric acids, and the depside atranorin, that exhibit antimicrobial activity against Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae. Organic lichen extract (acetone/ether/chloroform) shows the highest antimicrobial activity due to a possible synergism between these substances. Antioxidant capacity of soluble metabolites secreted from the immobilisates to the bath medium of incubation during the first 12 days of immobilization has been found (˃80% oxidation inhibition). The concentration of soluble phenolic substances depends on the immobilization time (during 32 days), exogenous supply of acetate (1.0m mM sodium or calcium acetate) and on the type of isolated biont (phycobionts, mycobionts, whole thallus or immobilized phycobionts co-incubated with the mycobionts ones). The role of phycobionts in phenol production has been interpreted as a possible modification of the polymalonyl pathway; for example, atranorin is actively produced and secreted during immobilization while it is not detected in thallus in natura. Co-incubated bionts secrete higher amounts of atranorin to the media during the first 12 days of immobilization. Immobilization of isolated bionts could be used as a biotechnological technique to obtain a potential source of biological active compounds. On the other hand, the physiological state detected of C. verticillaris in the Cerrado is much better for experimentation than that of the specimens collected in Caatinga since, in this case, the thalli showed the fragility that the extreme environmental conditions of the semi-arid region of NE Brazil impose on this lichen species. To date, no priority has been defined for lichen conservation in Brazilian ecosystems. It is therefore suggested that it imust important to include lichen ecophysiology studies in public conservation policies.

Temperature-independent Inhibition of L-Type Calcium Currents by Halothane and Sevoflurane in Human Atrial Cardiomyocytes

Background Cardiac L-type calcium currents (ICa,L) are affected by volatile anesthetics, possibly contributing to their side effects. Actions of anesthetics on ion channels are usually studied in vitro at room temperature. However, the solubility of anesthetic gases as well as ICa,L are markedly sensitive to the study temperature. Therefore, temperature-dependent effects of halothane and sevoflurane on cardiac ICa,L were analyzed. Methods ICa,L were studied at 21 degrees C and 36 degrees C with the patch clamp technique in isolated human atrial cardiomyocytes. Concentrations of anesthetics brought into solution by gassing at both temperatures were determined with gas chromatography. Results The aqueous concentrations of halothane and sevoflurane were linearly related to their concentration in the gas phase (1 to 3 minimum alveolar concentration [MAC]). At 21 degrees C, the slope of this relation was 0.52 and 0.12 mm/vol % for halothane and sevoflurane, respectively, and decreased at 36 degrees C to 0.29 and 0.09 mm/vol %, respectively. ICa,L displayed significantly higher current amplitudes at 36 degrees C than at 21 degrees C and significantly accelerated time-dependent inactivation. Halothane (1-2 MAC) and sevoflurane (1-3 MAC) evoked stronger inhibitions of ICa,L at 21 degrees C than at 36 degrees C. In spite of different temperature-dependent current amplitudes, the fractional (percent) inhibition of ICa,L showed the same linear relationship to the concentrations of halothane and sevoflurane in the bath medium at both temperatures, as revealed from present and previous experiments. Conclusions Inhibition of ICa,L by halothane and sevoflurane is determined by the aqueous concentration of the anesthetics, independently of the temperature. Increased solubility may explain the stronger effects of the anesthetics at lower temperatures.

Extracellular adenosine modulates a volume-sensitive-like chloride conductance in immortalized rabbit DC1 cells

Cl−currents induced by cell swelling were characterized in an immortalized cell line (DC1) derived from rabbit distal bright convoluted tubule by the whole cell patch-clamp techniques and by125I− efflux experiments. Exposure of cells to a hypotonic shock induced outwardly rectifying Cl−currents that could be blocked by 0.1 mM 5-nitro-2-(3-phenylpropyl-amino)benzoic acid, 1 mM DIDS, and by 1 mM diphenylamine-2-carboxylate. 125I− efflux experiments showed that exposure of the monolayer to a hypotonic medium increased 125I− loss. Preincubation of cells with LaCl3 or GdCl3 prevented the development of the response. The addition of 10 μM adenosine to the bath medium activated outwardly rectifying whole cell currents similar to those recorded after hypotonic shock. This conductance was inhibited by the A1-receptor antagonist 8-cyclopentyl-1,3-diproxylxanthine (DPCPX), LaCl3, or GdCl3 and was activated by GTPγS. The selective A1-receptor agonist N 6-cyclopentyladenosine (CPA) mimicked the effect of hypotonicity on 125I− efflux. The CPA-induced increase of 125I− efflux was inhibited by DPCPX and external application of LaCl3 or GdCl3. Adenosine also enhanced Mn2+ influx across the apical membrane. Overall, the data show that DC1 cells possess swelling- and adenosine-activated Cl− conductances that share identical characteristics. The activation of both conductances involved Ca2+ entry into the cell, probably via mechanosensitive Ca2+ channels. The effects of adenosine are mediated via A1 receptors that could mediate the purinergic regulation of the volume-sensitive Cl−conductance.

Effect of luminal perfusion on glucose production by isolated proximal tubules

The effects of luminal perfusion on glucose production by the proximal tubule were examined by use of the technique of in vitro microperfusion with an ultramicroassay for glucose to measure the net glucose production rates in isolated mouse midproximal tubule segments. Tubules bathed in Krebs-Ringer bicarbonate (KRB) buffer containing L-glutamine and acetate and perfused with KRB buffer at a high flow rate produced glucose at a lower rate (0.12 +/- 0.02 pmol.min-1.mm-1) than unperfused segments (0.40 +/- 0.03) or segments perfused at a lower flow rate (0.24 +/- 0.03). In contrast, the estimated rates of glucose utilization were not affected by luminal perfusion. The inhibition of net fluid reabsorption by perfusion with a modified KRB buffer containing amiloride or by addition of ouabain to the bath medium raised glucose production rates to levels equaling or exceeding those observed in unperfused tubules. The inhibition of glucose production by luminal perfusion occurred in the presence of multiple substrates (i.e., glutamine, acetate, lactate, pyruvate, alanine, and valerate) or nonammoniagenic substrates (i.e., lactate and pyruvate) in the bath medium. Thus net glucose production is inhibited by luminal perfusion and the inhibitory effect is dependent on intact fluid reabsorption. The reduction in net glucose production observed with perfusion does not result from increased glucose utilization and is not dependent on the presence of specific substrates.

Suppression of snake-venom cardiotoxin-induced cardiomyocyte degeneration by blockage of Ca2+ influx or inhibition of non-lysosomal proteinases

The incubation of 10(5) single neonatal rat cardiomyocytes with 1 microM-cardiotoxin in a bath medium, Tyrode solution in the presence of 1 mM-Ca2+, at 37 degrees C evoked the following chain of events. Firstly, there appeared a latent period of about 10 min during which the cells behaved normally. Neither lactate dehydrogenase nor ATP leaked from the cells. Cytosolic free Ca2+ increased considerably, as measured by the fluorescence intensity of fura-2-Ca2+ complex. At the same time a large portion of endogenous ATP was depleted. Secondly, after the latent period, the cell beating became irregular and eventually stopped. Thirdly, blebs appeared on the cell surface, leading to cell degeneration. If, before the appearance of blebs, the cells were washed with the bath medium exhaustively or incubated in the presence of the toxin antibody, cytosolic free Ca2+ and endogenous ATP returned to normal levels and cells resumed regular beating. Preincubation of the cells with 3.75 microM-flunarizine or 3.75 microM-diltiazem (both are Ca2+ antagonists), or 1.5 microM-fura-2 acetoxymethyl ester (a chelate for Ca2+), or 200 microM-leupeptin or 50 microM-antipain (both are proteinase inhibitors) considerably suppressed the toxin's ability to degenerate the cells. On the other hand, lysosomal proteinase inhibitor, autophage inhibitor, serine proteinase inhibitor, phospholipase inhibitor and calmodulin antagonist did not inhibit the toxin's activity. The results suggest that the toxin may act on the extracellular surface of intact cardiomyocytes to increase cytosolic free Ca2+. The subsequent cell degeneration may result from the activation of a Ca2+-dependent non-lysosomal proteolytic system.

Contribution of adenosine to arteriolar autoregulation in striated muscle

The contribution of adenosine to blood flow autoregulation in striated muscle was evaluated by direct in vivo visualization of arterioles in the rat cremaster muscle. Male Sprague-Dawley rats were anesthetized with pentobarbital sodium, and the cremaster muscle was surgically exposed and maintained in a controlled tissue bath environment with pH 7.40, CO2 tension (PCO2) congruent to 40 mmHg, and O2 tension (PO2) at either a high (congruent to 70 mmHg) or a low (congruent to 10 mmHg) value. Local adenosine activity was blocked in some animals by the addition of theophylline (3 X 10(-5) M) to the bath medium. Individual second (2A)- and third (3A)-order arterioles were observed via closed-circuit television microscopy, and blood flow in each arteriole was calculated from simultaneous measurements of arteriolar diameter and red blood cell velocity. Perfusion pressure to the animal's hindquarters was altered by varying the degree of occlusion of the sacral aorta; arteriolar diameter, velocity, and blood flow responses were plotted as a function of the varying pressure. Both 2A and 3A arterioles exhibited vasodilation and substantial superregulation of blood flow (increased blood flow with decreased perfusion pressure) when bath PO2 was low and adenosine activity was not blocked. Addition of theophylline to the cremaster bath medium significantly reduced the dilation and abolished superregulation, although substantial autoregulation remained. When bath PO2 was high, the degree of arteriolar dilation and autoregulation was reduced compared with the low bath PO2 responses, and blocking adenosine activity had no effect on the responses. These results support the concept that changes in local adenosine levels are involved in the autoregulatory responses observed in the rat cremaster muscle and that the magnitude of adenosine's contribution is directly related to the degree of tissue hypoxia. However, blocking adenosine activity did not totally abolish autoregulation, suggesting that other metabolic and/or myogenic factors may also be contributing to blood flow regulation in this tissue.