Net Absorption Research Articles

The Interactions of P-Glycoprotein with Antimalarial Drugs, Including Substrate Affinity, Inhibition and Regulation.

The combination of passive drug permeability, affinity for uptake and efflux transporters as well as gastrointestinal metabolism defines net drug absorption. Efflux mechanisms are often overlooked when examining the absorption phase of drug bioavailability. Knowing the affinity of antimalarials for efflux transporters such as P-glycoprotein (P-gp) may assist in the determination of drug absorption and pharmacokinetic drug interactions during oral absorption in drug combination therapies. Concurrent administration of P-gp inhibitors and P-gp substrate drugs may also result in alterations in the bioavailability of some antimalarials. In-vitro Caco-2 cell monolayers were used here as a model for potential drug absorption related problems and P-gp mediated transport of drugs. Artemisone had the highest permeability at around 50 x 10−6 cm/sec, followed by amodiaquine around 20 x 10−6 cm/sec; both mefloquine and artesunate were around 10 x 10−6 cm/sec. Methylene blue was between 2 and 6 x 10−6 cm/sec depending on the direction of transport. This 3 fold difference was able to be halved by use of P-gp inhibition. MRP inhibition also assisted the consolidation of the methylene blue transport. Mefloquine was shown to be a P-gp inhibitor affecting our P-gp substrate, Rhodamine 123, although none of the other drugs impacted upon rhodamine123 transport rates. In conclusion, mefloquine is a P-gp inhibitor and methylene blue is a partial substrate; methylene blue may have increased absorption if co-administered with such P-gp inhibitors. An upregulation of P-gp was observed when artemisone and dihydroartemisinin were co-incubated with mefloquine and amodiaquine.

Do Compensatory Changes Occur in Intestinal Glucose Transport Following Gastric Bypass in Type 2, Diabetic Rats

Although there is a considerable amount of evidence in the literature showing that Rouen‐en‐Y‐Gastric Bypass (RYGB) in particular, is very effective in resolving Type 2, Diabetes (T2D), a very fundamental question that has not yet been addressed is how transmural glucose transport is modified across the newly configured anatomy of the upper intestinal segments following RYGB? Thus, the objective of the study was to examine potential adaptations in glucose transport across the Roux Limb and distal ileum of ZDF (Zucker Diabetic Fatty) and ZLC (Zucker Lean Control) rats following RYGBUnidirectional glucose fluxes were measured in Ussing chambers under symmetrical, short‐circuited conditions in vitro ~ 10 weeks following the surgical procedure. Segments that were removed included ~ 4 cm of proximal Roux Limb measured from the stomach pouch insertion point; a segment ~ 4 cm at the location measured 35 cm from the ileo‐caecal valve and representing the “predestined” Roux limb in control rats; and a similar size segment immediately proximal to the ileocaecal valve which is the most distal ileum that is not reconfigured in any animal. Using radio‐labeled [14C]‐3‐0‐methylglucose, unidirectional fluxes of glucose were measured across paired adjacent tissues from the mucosal to serosal bath, Jms (absorptive component) and in the opposite direction from serosal to mucosal, Jsm (secretory component) over a 45 min time period. The overall net transport of glucose (Jnet) was determined by subtracting the two unidirectional fluxes. Both the short‐circuit current (Isc) and the transepithelial voltage generated by the tissue is recorded at 15 min intervals and tissue conductance (GT) is calculated from these electrical parameters using Ohm's Law.Major changes in glucose fluxes occurred in obese ZDF/RYGB rats compared to ZDF controls in both of the intestinal segments examined. The unidirectional glucose fluxes are dramatically reduced in RYGB rats and the direction of net glucose transport is reversed across the Roux Limb. It is also notable that tissue conductance of the Roux Limb is reduced by ~ 48% (from GT of 12.0 ± 2.2 mS.cm‐2 in n=8 “predestined” Roux Limb tissues to GT = 6.2 ± 1.3 mS.cm‐2, n=6 Roux Limb tissues) consistent with the lowering (~40% in Jms and ~95% in Jsm) of both unidirectional glucose fluxes indicating an adaptive change in overall tissue permeability. A significant reduction (~82%) occurred in net glucose absorption across the ZDF/RYGB distal ileum (which is not surgically re‐configured) largely via a 64% reduction in Jms. The “predestined” Roux limb of the lean ZLC rats supports a very robust net absorption of glucose that is completely abolished in the reconfigured ZLC/RYGB limb and the unidirectional fluxes were greatly diminished (~90% in Jms and ~70% in Jsm) as was GT from 14.5 ± 2.8 mS.cm‐2 in n=4 “predestined” Roux Limb tissues to GT = 8.0 ± 1.1 mS.cm‐2, n=4 Roux Limb tissues) which is a very similar response to that observed in the obese ZDF rats. There were also major alterations in glucose fluxes across the distal ileum of the lean ZLC/RYGB rats which supported a robust net secretion compared to a net absorption in the lean ZLC controls and no change in GT. To our knowledge, these are the first measurements of intestinal glucose transport in ZDF rats with/without RYGB. In conclusion, we are proposing that altered intestinal handling of glucose may be contributing to the resolution of T2D post RYGB.Support or Funding InformationDK089000

(Invited) Multiple Photosynthetic Reaction Centers of Porphyrinic Polypeptide-Li+@C60 Supramolecular Complexes

Extensive efforts have so far been devoted to mimic light harvesting and charge separation processes in natural photosynthesis.1 Multiporphyrin arrays have been employed as light-harvesting units. Light-harvesting and charge-separation units have been combined by coordination bonds between metalloporphyrins and electron acceptor moieties bearing Lewis base ligands. Thus, metal centres have been required for construction of supramolecular complexes between porphyrins acting as light harvesting units and electron acceptors containing Lewis base ligands for coordination to the metal centers. As such there has been only few report on supramolecular complexes of free base porphyrin arrays and electron acceptors without Lewis base ligands, in which the binding is rather weak. We report herein construction of supramolecular complexes of free base porphyrin polypeptides (P(H2P) n : n = 4, 8) with lithium ion-encapsulated C60 (Li+@C60)2,3 (Figure 1), in which binding is much stronger than the caes of C60 in benzonitirle (PhCN). The photodynaimcs were studied by femtosecond and nanosecond laser-induced transient absorption and fluorescence lifetime measurements.4 Upon mixing a PhCN solution of Li+@C60 with that of P(H2P)8, the intensity of the Soret band decreased with increasing concentration of Li+@C60. A Soret band was slightly red-shifted from 425 to 427 nm by the addition of Li+@C60 to the solution. From the net absorption change at 425 nm in which the absorption due to Li+@C60 was subtracted, a linear Benesi-Hildebrand plot was obtained, indiating that each porphyrin unit of P(H2P)8 forms a 1:1 supramolecular charge-transfer complex with Li+@C60 independently with approximately the same binding constant of the unit of M–1. The binding constant at 298 K was determined to be 2.1 ´ 104 M–1, which is significantly larger than that of C60 (5.3 ´ 103 M–1). The stronger binding of Li+@C60 as compared with C60 may result from the stronger elecron acceptor ability of Li+@C60, which facilitates the charge-transfer interaction as reported for the stronger charge-transfer binding of Li+@C60 with corranulerene. Similary the binding constant of the supramolecular complex of P(H2P)4 was determined from the spectral titration to be 6.2 × 103 M–1. In the case of P(H2P)2 and P(H2P)1, howerver, the spectral change was too small to be able to determine the binding constants accurately. Thus, multiporphyris may facilitate charge-transfer interactions through encapsulation of Li+@C60 by multiple porphyrins.4 Nanosecond laser-induced transient absorption spectra of P(H2P)8 with Li+@C60 (40 mM) at the excitation wavelength of 532 nm showed the transient absorption band at 730 nm due to the triplet excited state of Li+@C60 (3Li+@C60 *) observed together with the absorption band at 1035 nm due to Li+@C60 •–. The decay of the absorption at 730 nm coincides with the appearance of Li+@C60 •–. Thus, electron transfer from P(H2P)8 to 3Li+@C60 * occurs to produce the triplet charge-separate (CS) state of P(H2P)8 •+ and Li+@C60 •–. The transient absorption due to P(H2P)8 •+ is overlapped with that of 3Li+@C60 * in the 600-700nm region. The photoexcitation of 532 nm resulted in the excitation of Li+@C60 leading to the formation of 3Li+@C60 * via intersystem crossing. The decay of the absorbance at 1035 nm due to Li+@C60 •– obeyed first-order kinetics with the lifetime of 210 ms. Thus, back electron transfer from Li+@C60 •– to P(H2P)8 •+ occurs in the supramolecular complex. The lifetime is long because of the spin-forbidden back electron transfer in the triplet CS state.4 References [1] Fukuzumi, S.; Ohkubo, K.; Suenobu, T. Acc. Chem. Res. 2014, 47, 1455. [2] Kawashima, Y.; Ohkubo, K.; Fukuzumi, S. Chem. Asian J. 2015, 10, 44. (Review) [3] (a) N. Solladié , A. Hamel and M. Gross, Tetrahedron Lett., 2000, 41, 6075; (b) F. Aziat, R. Rein, J. Peon, E. Rivera and N. Solladié, J. Porphyrins Phthalocyanines, 2008, 12, 1232 [4] Ohkubo, K.; Hasegawa, T.; Rein, R.; Solladié, N.; Fukuzumi, S. Chem. Commun. 2015, 51. 17517. Figure 1

Design rules for net absorption enhancement in pseudo-disordered photonic crystal for thin film solar cells.

The role of pseudo-disordered photonic crystals on the absorption efficiency of simplified thin film crystalline silicon solar cells is presented and discussed. The expected short circuit current can thus be further increased compared to a fully optimized square lattice of holes, thanks to carefully controlled positions of the nanoholes in the considered realistic simplified solar cell stack. In addition, the pseudo-disordered structures are less sensitive to the angle of incidence, especially in the long wavelength range.

Capillary dynamics and the interstitial fluid–lymphatic system

The capillaries are the ‘business end’ of the circulatory system, where materials exchange between the plasma and tissues. Water-soluble molecules can diffuse through pores in the capillaries, and a Gibbs–Donnan equilibrium exists between the plasma and interstitium. There are several types of capillaries, which vary in their anatomical integrity and permeability. There is also a bulk flow of fluids between the plasma and interstitium, described by the Starling forces. Originally, these forces were thought to cause fluids to leave the capillaries at the arteriolar end and return at the venular end; the role of the lymphatics was to provide an ‘overflow’ mechanism due to protein leakage out of the capillaries. More recent work indicates that this concept needs modification. Lymph flow and interstitial colloidal osmotic pressure are now known to be greater than first thought, and the interstitium has a slightly negative hydrostatic pressure. It is now believed that filtration takes place along most of the capillary, and the lymphatic system plays a more important role in maintaining plasma–interstitium equilibrium and preventing oedema. The system acts as a ‘closed’ one in that the changes in fluid formation (e.g. following haemorrhage or cardiac failure) are self-limiting. However, in some circulations (e.g. those to the kidneys, glands and the gut), net fluid production or absorption is required. This requirement is fulfilled by an independence from the Starling forces, the systems behaving as ‘open’ ones.

Measuring intestinal fluid transport in vitro: Gravimetric method versus non-absorbable marker

The gut sac is a long-standing, widely used in vitro preparation for studying solute and water transport, and calculation of these fluxes requires an accurate assessment of volume. This is commonly determined gravimetrically by measuring the change in mass over time. While convenient this likely under-estimates actual net water flux (Jv) due to tissue edema. We evaluated whether the popular in vivo volume marker [14C]-PEG 4000, offers a more representative measure of Jvin vitro. We directly compared these two methods in five teleost species (toadfish, flounder, rainbow trout, killifish and tilapia). Net fluid absorption by the toadfish intestine based on PEG was significantly higher, by almost 4-fold, compared to gravimetric measurements, compatible with the latter under-estimating Jv. Despite this, PEG proved inconsistent for all of the other species frequently resulting in calculation of net secretion, in contrast to absorption seen gravimetrically. Such poor parallelism could not be explained by the absorption of [14C]-PEG (typically <1%). We identified a number of factors impacting the effectiveness of PEG. One was adsorption to the surface of sample tubes. While it was possible to circumvent this using unlabelled PEG 4000, this had a deleterious effect on PEG-based Jv. We also found sequestration of PEG within the intestinal mucus. In conclusion, the short-comings associated with the accurate representation of Jv by gut sac preparations are not overcome by [14C]-PEG. The gravimetric method therefore remains the most reliable measure of Jv and we urge caution in the use of PEG as a volume marker.

Investigation of graphene assisted tunable terahertz metamaterials absorber

By using the graphene-SiO2-Si-dielectrics-metallic ground plane (GSiO2SiDM) structures, we investigate the tunable properties of graphene metamaterials (MMs) absorbers in the terahertz region, including the effects of operation frequency, Fermi level, and graphene structure patterns. The results manifest that the graphene tunable GSiO2SiDM structure can achieve net absorption by changing structure parameters and the Fermi level of graphene layer. The resonant absorption and reflection curves of the GSiO2SiDM structures can be shifted in a wide range via controlling the applied electric fields. The modulation depth of resonant amplitude and frequency can reach more than 60% and 30%, respectively. The resonant peak (dip) of the absorption (reflection) curves shift to high frequency with the increase of Fermi level of the graphene layer. Due to broad absorption curve, the graphene MMs absorbers structures are suitable for the fabrication of broad absorber. The results are very useful to design novel devices, such as thermal detectors, imager, and biosensors.

Enhanced photoresponse in dye-sensitized solar cells via localized surface plasmon resonance through highly stable nickel nanoparticles.

We demonstrated the localized surface plasmon resonance (LSPR) effect of Ni nanoparticles (NiNPs) on the performance of dye-sensitized solar cells (DSSCs). Our study revealed that NiNPs in a conventional I(-)/I3(-) electrolyte (NiNPs@I(-)/I3(-)) increased the net optical absorption of a N719 dye over a broad wavelength range by LSPR, and concurrently improved the power conversion efficiency (PCE) in DSSCs. At an optimized concentration of the NiNPs@I(-)/I3(-) electrolyte (1 mg mL(-1)), N719-sensitized DSSCs with a photoanode thickness of ca. 2, 5, and 10 μm, exhibited net PCEs of 2.32, 6.02, and 9.83%, respectively. These efficiencies were consistent with a net improvement of 43.2, 20.4, and 12.7%, respectively and were mainly attributed to a significant enhancement of the short circuit current density (Jsc) by the LSPR from the NiNPs. Similar effects were observed for cells sensitized by the N3, Ru505, and Z907 dyes. Furthermore, the NiNPs exhibited excellent resistance to corrosion from a conventional I(-)/I3(-) electrolyte over a period of 60 days.

Cysteamine: a human health dietary additive with potential to improve livestock growth rate and efficiency

Cysteamine is a biological compound produced in the gastrointestinal tract and hypothalamus of all animals that acts on the somatotrophic axis. Cysteamine is finding increasing application in human medicine and also as a natural, in-feed growth promotant for monogastric and ruminant livestock that increases feed conversion efficiency, growth rate and leanness. It improves nutrient digestion and absorption by increasing portal-drained viscera blood flow and net portal absorption, while also reducing gastroenteropancreatic, plasma and hypothalamus concentrations of the inhibitory hormone, somatostatin (SRIF). Dietary inclusion rates required to achieve growth responses are typically about 10 times higher in ruminants than those required for pigs, but it is unclear whether ruminal breakdown of cysteamine is contributing to this difference. While short-term stimulation of growth, milk production and improved feed use efficiency are apparent, studies over longer periods are required, especially in breeding animals, due to the process of SRIF depletion being reversible. This review provides an overview of cysteamine’s mode of action in improving nutrient utilisation and its application in human nutrition and health, as well as its potential use as a growth promotant in the livestock industries.

青藏高原不同生境下湿生扁蕾(Gentianopsis paludosa)个体大小依赖的繁殖分配

PDF HTML阅读 XML下载 导出引用 引用提醒 青藏高原不同生境下湿生扁蕾(Gentianopsis paludosa)个体大小依赖的繁殖分配 DOI: 10.5846/stxb201403130437 作者: 作者单位: 西北师范大学,青海省农林科学院,西北师范大学,西北师范大学,西北师范大学,西北师范大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(31360064) Size-dependent reproductive allocation of Gentianopsis paludosa in different habitats of the Qinghai-Tibetan Plateau Author: Affiliation: Northwest Normal University,Qinghai Academy of Agriculture and Forestry Sciences,Northwest Normal University,Northwest Normal University,Northwest Normal University,Northwest Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:植物对资源的投资和分配是生态学中的重要问题,它反映了植物应对环境变化时的生活史策略。选择青藏高原东缘同一海拔下的嵩草草甸(Kobresia sp. meadow)、金露梅灌丛(Potentilla fruticosa shrub meadow)以及草甸-灌丛交错带3种生境类型,并以3种生境下的湿生扁蕾(Gentianopsis paludosa)为对象,研究了其繁殖分配特征。结果发现:(1)在种群水平上,在生境从草甸经交错带到灌丛的变化中,湿生扁蕾个体大小和繁殖分配比例逐渐增加;3个种群湿生扁蕾的总花数目没有显著差异,但草甸生境湿生扁蕾的蕾期花数目显著高于灌丛生境,而果期花数目则显著低于灌丛生境;(2)在个体水平上,湿生扁蕾的繁殖绝对投入与个体大小显著正相关,且各种群植株都存在繁殖所需的个体大小阈值,而繁殖阈值在生境从草甸经交错带到灌丛的过渡中逐渐减小;湿生扁蕾的繁殖相对投入与个体大小负相关,但相关系数随着生境从草甸经交错带到灌丛的过渡中逐渐减小;各种群花数目与湿生扁蕾植株个体大小显著正相关。研究表明,湿生扁蕾的繁殖投资存在大小依赖效应,但生境差异会对其繁殖投资和生活史策略造成显著影响,而这种影响主要是由不同生境下自然条件的不同造成的。同时,资源分配也与湿生扁蕾的遗传特性和延迟自交的繁育系统特征有关。湿生扁蕾这种不同生境下个体大小依赖的繁殖投资差异是湿生扁蕾与其生境长期适应和进化(生境选择)的结果。 Abstract:Understanding plant resource investment and allocation is an important issue in ecology, since this can reflect the plant life-history strategies as a response to the changing environment. Many studies in the last decades have focused on plant resource allocation at different elevations, and most of them have determined that the plant resource allocation is strongly correlated with the plant size, representing a positive correlation between reproductive investment and plant size but a negative correlation between reproductive allocation and plant size. However, research has also shown that the reproductive allocation had no correlation with plant size. Significant elevation variation in the Qinghai-Tibetan Plateau provides the ecologists an ideal platform to reveal the plant resource allocations, since elevation variation can bring strong environment variances. However, previous studies did not address the variation in plant habitats, which could have directly affected the plant's resource allocation. In this study, we tested the reproductive allocation characters of Gentianopsis paludosa at three habitats located on the same elevation, on the east Qinghai-Tibetan Plateau: Kobresia sp. meadow (CD), Potentilla fruticosa shrub meadow (GC), and their junction area (JC). Centering the study on two levels, population and individual, we aimed to test the resource allocation characters of G. paludosa and reveal the relationship between the plant resource allocation and the plant habitats. Our results revealed the following: (1) The abiotic conditions were different among the three habitats, among which habitat CD displayed relatively better abiotic conditions compared with the others since the soil temperature and humidity, air temperature, and the net carbon absorptions were higher and optimal for plant growth. (2) At the population level, the individual size and reproductive allocation increased following the habitat variation of CD-JC-GC; the total flower numbers of G.paludosa did not differ significantly among the three habitats, whereas the bud numbers in the meadow were greater than those in the shrub meadow, and fruiting flower numbers in the meadow habitat were lower than those in the shrub meadow. (3) At the individual level, the reproductive biomass was positively correlated with individual size; a size threshold existed in G.paludosa and it declined with the habitat variation of CD-JC-GC; the reproductive allocation of G.paludosa had a negative correlation with the individual size, whereas the correlation coefficient declined following the habitat variation of CD-JC-GC; the flower number was positively correlated with individual size in all three habitats. These results suggest that reproductive allocation of G. paludosa is size-dependent, and that habitat variation can influence reproductive allocation and life-history strategies. The plant size and reproductive allocation characters were strongly related with their habitats, and reproductive allocation varied at both the population level and individual level. These variations were caused, primarily, in two ways: (1) the different natural conditions of the three habits could play an important role in determining the reproductive allocation characters; and (2) the genetic characters and the delayed-selfing breeding system were also correlated with the reproductive allocation. Although it was difficult to determine which of the two was dominant, the size-dependent reproductive allocation of G. paludosa in different habitats was undoubtedly a result of co-evolution between a plant and its habitat. 参考文献 相似文献 引证文献

Rhubarb extract partially improves mucosal integrity in chemotherapy-induced intestinal mucositis.

AIMTo investigate the effects of orally gavaged aqueous rhubarb extract (RE) on 5-fluorouracil (5-FU)-induced intestinal mucositis in rats.METHODSFemale Dark Agouti rats (n = 8/group) were gavaged daily (1 mL) with water, high-dose RE (HDR; 200 mg/kg) or low-dose RE (LDR; 20mg/kg) for eight days. Intestinal mucositis was induced (day 5) with 5-FU (150 mg/kg) via intraperitoneal injection. Intestinal tissue samples were collected for myeloperoxidase (MPO) activity and histological examination. Xenopus oocytes expressing aquaporin 4 water channels were prepared to examine the effect of aqueous RE on cell volume, indicating a potential mechanism responsible for modulating net fluid absorption and secretion in the gastrointestinal tract. Statistical significance was assumed at P < 0.05 by one-way ANOVA.RESULTSBodyweight was significantly reduced in rats administered 5-FU compared to healthy controls (P < 0.01). Rats administered 5-FU significantly increased intestinal MPO levels (≥ 307%; P < 0.001), compared to healthy controls. However, LDR attenuated this effect in 5-FU treated rats, significantly decreasing ileal MPO activity (by 45%; P < 0.05), as compared to 5-FU controls. 5-FU significantly reduced intestinal mucosal thickness (by ≥ 29% P < 0.001) as compared to healthy controls. LDR significantly increased ileal mucosal thickness in 5-FU treated rats (19%; P < 0.05) relative to 5-FU controls. In xenopus oocytes expressing AQP4 water channels, RE selectively blocked water influx into the cell, induced by a decrease in external osmotic pressure. As water efflux was unaltered by the presence of extracellular RE, the directional flow of water across the epithelial barrier, in the presence of extracellular RE, indicated that RE may alleviate water loss across the epithelial barrier and promote intestinal health in chemotherapy-induced intestinal mucositis.CONCLUSIONIn summary, low dose RE improves selected parameters of mucosal integrity and reduces ileal inflammation, manifesting from 5-FU-induced intestinal mucositis.

Variations of carbon dioxide exchange in paddy field ecosystem under water-saving irrigation in Southeast China

Based on the results of continuous flux measurements in the Taihu Lake Region of China, the carbon dioxide (CO2) exchange of paddy fields under water-saving irrigation and its influence factors were analyzed. The net ecosystem exchange of CO2 (NEE) were negative during the daytime and positive at night, and the minimum value appeared around noon. The peak CO2 uptake in the flourishing period was approximately 1.5 times the values observed in the tillering and ripening stages. Frequent alternation of wetting and drying in paddy fields with water-saving irrigation resulted in larger NEE for the typical day before soil rewatering than that for the day after soil rewatering in the early growth stage. These alterations had a minimal effect on diurnal variation of NEE in the late rice growth stage. The average NEE for the typical days after soil rewatering in July and August were 2.30 and 1.38 times that before soil rewatering, respectively. CO2 exchange in paddy field ecosystem under water-saving irrigation displayed seasonal variation with the change of rice plant growth. The total ecosystem respiration (Reco), NEE and gross primary productivity (GPP) were 1996.88, −1284.15 and 3281.03gm−2, respectively, throughout the growth stage. These results showed that the paddy field ecosystem under water-saving irrigation was a sink for atmospheric CO2. Frequent alternation of wetting and drying processes increased the ecosystem reparation of paddy fields under water-saving irrigation and produced smaller net CO2 absorption compared to that of flooding irrigation. The net CO2 absorption because of plant photosynthesis during the daytime and the net CO2 release at night measured by static transparent chamber method were larger than those measured by eddy covariance method (P<0.05). The nighttime respiration of paddy field ecosystem under water-saving irrigation increased exponentially with temperature. Additionally, a larger temperature sensitivity coefficient (Q10) was observed for paddy fields under water-saving irrigation compared to that under flooding irrigation. The photosynthetic photon flux density (PPFD) was the most important factor for regulating daytime GPP. And the light saturation point during the heading-flowering and milk stages of paddy field ecosystem with water-saving irrigation (1500μmolm−2s−1) was higher than that of fields with flooding irrigation in previous studies. A significant positive correlation was found between the leaf area index (LAI) and the daily GPP.

Human Adult Retinal Pigment Epithelial Stem Cell–Derived RPE Monolayers Exhibit Key Physiological Characteristics of Native Tissue

We tested what native features have been preserved with a new culture protocol for adult human RPE. We cultured RPE from adult human eyes. Standard protocols for immunohistochemistry, electron microscopy, electrophysiology, fluid transport, and ELISA were used. Confluent monolayers of adult human RPE cultures exhibit characteristics of native RPE. Immunohistochemistry demonstrated polarized expression of RPE markers. Electron microscopy illustrated characteristics of native RPE. The mean transepithelial potential (TEP) was 1.19 ± 0.24 mV (mean ± SEM, n = 31), apical positive, and the mean transepithelial resistance (RT) was 178.7 ± 9.9 Ω·cm2 (mean ± SEM, n = 31). Application of 100 μM adenosine triphosphate (ATP) apically increased net fluid absorption (Jv) by 6.11 ± 0.53 μL·cm2·h-1 (mean ± SEM, n = 6) and TEP by 0.33 ± 0.048 mV (mean ± SEM, n = 25). Gene expression of cultured RPE was comparable to native adult RPE (n = 5); however, native RPE RNA was harvested between 24 and 40 hours after death and, therefore, may not accurately reflect healthy native RPE. Vascular endothelial growth factor secreted preferentially basally 2582 ± 146 pg/mL/d, compared to an apical secretion of 1548 ± 162 pg/mL/d (n = 14, P < 0.01), while PEDF preferentially secreted apically 1487 ± 280 ng/mL/d compared to a basolateral secretion of 864 ± 132 ng/mL/d (n = 14, P < 0.01). The new culture model preserves native RPE morphology, electrophysiology, and gene and protein expression patterns, and may be a useful model to study RPE physiology, disease, and transplantation.

Strong and highly asymmetrical optical absorption in conformal metal-semiconductor-metal grating system for plasmonic hot-electron photodetection application.

We propose an architecture of conformal metal-semiconductor-metal (MSM) device for hot-electron photodetection by asymmetrical alignment of the semiconductor barrier relative to the Fermi level of metals and strong energy localization through plasmonic resonances. Compared with the conventional grating design, the multi-layered grating system under conformal configuration is demonstrated to possess both optical and electrical advantages for high-sensitivity hot-electron photodetection. Finite-element simulation reveals that a strong and highly asymmetrical optical absorption (top metal absorption >99%) can be realized under such a conformal arrangement. An analytical probability-based electrical simulation verifies the strong unidirectional photocurrent, by taking advantage of the extremely high net absorption and a low metal/semiconductor barrier height, and predicts that the corresponding photoresponsivity can be ~3 times of that based on the conventional grating design in metal-insulator-metal (MIM) configuration.

THz behavior of indium-tin-oxide films on p-Si substrates

This paper reports broadband THz free-space transmission measurements and modeling of indium-tin-oxide (ITO) thin films on p-doped Si substrates. Two such samples having ITO thickness of 50 and 100 nm, and DC sheet conductance 260 and 56 Ω/sq, respectively, were characterized between 0.2 and 1.2 THz using a frequency-domain spectrometer. The 50-nm-film sample displayed very flat transmittance over the 1-THz bandwidth, suggesting it is close to the critical THz sheet conductance that suppresses multi-pass interference in the substrate. An accurate transmission-line-based equivalent circuit is developed to explain the effect, and then used to show that the net reflectivity and absorptivity necessarily oscillate with frequency. This has important implications for the use of thin-film metallic coupling layers on THz components and devices, such as detectors and sources. Consistent with previous reported results, the sheet conductance that best fits the THz transmittance data is roughly 50% higher than the DC values for both samples.

The air‐water CO2 exchange of a coastal sea—A sensitivity study on factors that influence the absorption and outgassing of CO2 in the Baltic Sea

AbstractIn this study, the BALTSEM model is used to estimate how air‐water CO2 fluxes in the Baltic Sea respond to parameterizations of organic alkalinity (Aorg), gas transfer, and phytoplankton growth, and further to changes in river loads. The forcing data include the most complete compilation of Baltic river loads for dissolved inorganic and organic carbon (DIC and DOC) and total alkalinity (TA). In addition, we apply the most recent estimates of internal TA generation in the system. Our results clearly demonstrate how air‐water CO2 fluxes of a coastal sea depend on river loads of carbon, TA, and nutrients as well the freshwater import itself. Long‐term changes in DIC loads are shown to be compensated by corresponding changes in air‐water CO2 exchange. By adding Aorg, a discrepancy in the carbonate system calculations was removed, and the simulated net CO2 absorption of the system decreased by 11%. A new parameterization for cyanobacteria growth significantly improved the seasonal development of pCO2 in the central Baltic Sea, although the net effect on CO2 fluxes was below 5%. By applying either a linear, quadratic, or cubic wind speed dependence for gas transfer, the long‐term net CO2 exchange was adjusted by less than 5%. There is no clear indication that any one of these parameterizations provides a more accurate estimate of CO2 fluxes than the other two. Our findings are applicable in other coastal areas that are heavily influenced by river loads of TA, DIC, and DOC.

Chronic metabolic acidosis reduces urinary oxalate excretion and promotes intestinal oxalate secretion in the rat.

Urinary oxalate excretion is reduced in rats during a chronic metabolic acidosis, but how this is achieved is not clear. In this report, we re-examine our prior work on the effects of a metabolic acidosis on urinary oxalate handling [Green et al., Am J Physiol Ren Physiol 289(3):F536-F543, 2005], offering a more detailed analysis and interpretation of the data, together with new, previously unpublished observations revealing a marked impact on intestinal oxalate transport. Sprague-Dawley rats were provided with 0.28 M ammonium chloride in their drinking water for either 4 or 14 days followed by 24 h urine collections, blood-gas and serum ion analysis, and measurements of (14)C-oxalate fluxes across isolated segments of the distal colon. Urinary oxalate excretion was significantly reduced by 75% after just 4 days compared to control rats, and this was similarly sustained at 14 days. Oxalate:creatinine clearance ratios indicated enhanced net re-absorption of oxalate by the kidney during a metabolic acidosis, but this was not associated with any substantive changes to serum oxalate levels. In the distal colon, oxalate transport was dramatically altered from net absorption in controls (6.20 ± 0.63 pmol cm(-2) h(-1)), to net secretion in rats with a metabolic acidosis (-5.19 ± 1.18 and -2.07 ± 1.05 pmol cm(-2) h(-1) at 4 and 14 days, respectively). Although we cannot rule out modifications to bi-directional oxalate movements along the proximal tubule, these findings support a gut-kidney axis in the management of oxalate homeostasis, where this shift in renal handling during a metabolic acidosis is associated with compensatory adaptations by the intestine.

CO2 absorption into aqueous blends of ionic liquid and amine in a membrane contactor

Ionic liquids (ILs), 1-butyl-3-methyl-imidazolium tetrafluoroborate ([bmim][BF4]) and 1-(3-aminopropyl)-3-methyl-imidazolium tetrafluoroborate ([apmim][BF4]), were mixed with an alkanolamine of 2-amino-2-methyl-1-propanol (AMP) to form two IL-based aqueous blends as CO2 absorbents, respectively. A membrane absorption coupling process was used to evaluate the performance of the IL-based aqueous blended absorbents for CO2 capture. Mixed process of the ILs with the AMP was investigated. Characteristics of the coupling process of the membrane contactor with the IL-based blended absorbents were studied by various modes of cyclic and non-cyclic absorption operations, static hot regeneration, and continuous circulation of absorption and regeneration, respectively. Results show that membrane flux and loading capacity of the IL-based blends could be enhanced by an addition of AMP into the ILs. Membrane flux and loading capacity of [apmim][BF4]+AMP reached 1.05×10−3molm−2s−1and 0.65molmol−1, respectively. A regeneration efficiency of almost 100% for the IL-based absorbents could be obtained by the static hot regeneration. The blended absorbents could give higher net and circular absorption capacities comparing with the corresponding single ILs in the coupling process of continuous circulation of absorption and regeneration. Net absorption capacities of [apmim][BF4]+AMP arrived at 0.48molmol−1. AMP mixed into ILs significantly influenced the performance of the IL-based absorbents as well as the coupling process.

Distinct α-intercalated cell morphology and its modification by acidosis define regions of the collecting duct.

During metabolic acidosis, the cortical collecting duct (CCD) of the rabbit reverses the polarity of bicarbonate flux from net secretion to net absorption, and this is accomplished by increasing the proton secretory rate by α-intercalated cells (ICs) and decreasing bicarbonate secretion by β-ICs. To better characterize dynamic changes in H(+)-secreting α-ICs, we examined their morphology in collecting ducts microdissected from kidneys of normal, acidotic, and recovering rabbits. α-ICs in defined axial regions varied in number and basolateral anion exchanger (AE)1 morphology, which likely reflects their relative activity and function along the collecting duct. Upon transition from CCD to outer medullary collecting duct from the outer stripe to the inner stripe, the number of α-ICs increases from 11.0 ± 1.2 to 15.4 ± 1.11 and to 32.0 ± 1.3 cells/200 μm, respectively. In the CCD, the basolateral structure defined by AE1 typically exhibited a pyramidal or conical shape, whereas in the medulla the morphology was elongated and shallow, resulting in a more rectangular shape. Furthermore, acidosis reversibly induced α-ICs in the CCD to acquire a more rectangular morphology concomitant with a transition from diffusely cytoplasmic to increased basolateral surface distribution of AE1 and apical polarization of B1-V-ATPase. The latter results are consistent with the supposition that morphological adaptation from the pyramidal to rectangular shape reflects a transition toward a more "active" configuration. In addition, α-ICs in the outer medullary collecting duct from the outer stripe exhibited cellular morphology strikingly similar to dendritic cells that may reflect a newly defined ancillary function in immune defense of the kidney.

PTH-231 Pathways of epithelial leakage and zinc malabsorption in environmental enteropathy imaged by confocal endomicroscopy

<h3>Introduction</h3> Environmental enteropathy (EE) is associated with growth failure in children in low income countries, malabsorption, and impaired responses to oral vaccines. EE is characterised by morphological changes (villous blunting), increased permeation of macromolecules, microbial translocation, and impaired absorption. We set out to image the leakiness of the enteropathic small intestine using confocal laser endomicroscopy (CLE) of the duodenum following fluorescein injection, and correlate this with other markers of structure, absorption and microbial translocation. <h3>Method</h3> Fifty adults were recruited from a poor community in Lusaka where we have previously established that EE is ubiquitous, and then underwent CLE on the day after permeability (lactulose 5g, rhamnose 1g) and net zinc absorption from a 25mg test dose were measured. Between 35 and 225 CLE images per procedure were quantified for a range of cellular abnormalities and fluorescein leakage. Duodenal biopsies were assessed morphometrically and claudin-4 expression quantified. Of the 50 participants, one had pyloric stenosis and in 8 the image quality was sub-standard, so full data are available from 41 (14 men, mean age 32 y, 11 HIV seropositive). Watson scores were 1 in 4 people, 2 in 6, and 3 in 31, which contrasts markedly with published control data in healthy German adults in which nearly all were grade 1 (<i>P &lt; 0</i>.0001). <h3>Results</h3> Leakage of fluorescein into the duodenal lumen was inevitably present when visible cell defects or microerosions were present, and was inversely associated with net absorption of zinc (r = -0.39; <i>P = 0</i>.04). Direct markers of microbial translocation (LPS and LPS binding protein) were correlated (in HIV seropositives only) with gastric pH (r = 0.72; <i>P = 0</i>.01) and with a serum marker of epithelial damage, fatty acid binding protein (FABP, r = −0.62; <i>P = 0</i>.04). FABP was strongly correlated with leakage, especially in HIV infection (r = −0.69; <i>P = 0</i>.007). Leakage was also inversely correlated with the intensity of expression of claudin-4 along the basolateral surface of the enterocyte (r = −0.49; <i>P = 0</i>.01). In multiple linear regression, LPS was strongly correlated with cell shedding and GLP-2 in serum. <h3>Conclusion</h3> These data indicate that the damaged epithelium of EE leads to leakage of circulating molecules into the gut, and may explain at least one measure of absorptive defect. Pathways of translocation maybe more complex, with some translocation that cannot be explained by cell disruption. Translocation pathways are not well reflected by lactulose permeation. A clearer understanding of mechanisms will be important to reducing translocation in the enteropathic gut. <h3>Disclosure of interest</h3> None Declared.