Phorbol Ester Activation of an NHE-Like Electroneutral Na+ /H+ Antiporter in Isolated E-Cells of Lobster (Homarus Americanus) Hepatopancreas

The basolateral membrane of Atlantic lobster (Homarus americanus) epithelium possesses an electroneutral Na+ /H+ antiporter that functionally resembles members of the vertebrate NHE family. Regulatory mechanisms of this antiporter in purified hepatopancreatic E-cell suspensions, produced with a centrifugal elutriation technique, were investigated. Suspensions routinely consisted of greater than 95% E-cells displaying greater than 90% viability. Intracellular pH (pHi) was monitored by loading cells with the fluorescent dye 2´,7´-bis(carboxyethyl)-5,6- carboxyfluorescein (BCECF), and placing suspensions in a spectrofluorometer. Recovery from induced acid-loading was mediated by a Na+ -dependent, dimethylamiloride-sensitive proton efflux. Antiport activation was a sigmoidal function of pHi at values below 7.0. Addition of 20 nM phorbol 12-myristate 13-acetate (PMA) to cells suspended in a lobster physiological saline (pHo = 7.4) increased pHi from 7.2 to 7.5 over a 10-min interval. Phorbol ester-induced activation of the Na+ / H+ antiporter was due to an increased affinity for internal H+ (apparent pK was shifted toward more alkaline values) at the level of an internal H+ -binding allosteric modifier site. No effect was observed when cells were exposed to 2 µM 8-Br-cAMP. Phorbol ester activation of the lobster NHE-like Na+ /H+ antiporter was inhibited by 10 nM bisindoylmaleimide I, a potent protein kinase C inhibitor. These results taken together suggest a remarkable conservation of Na+ /H+ antiport across phyla

Characterization of a Basolateral Electroneutral Na+/H+ Antiporter in Atlantic Lobster (Homarus Americanus) Hepatopancreatic Epithelial Vesicles

Purified basolateral membrane vesicles (BLMVs) were prepared from Atlantic lobster (Homarus americanus) hepatopancreas using a Percoll density gradient technique. Enrichments of the Na+/K+-ATPase and alkaline phosphatase activities of these vesicles were 15.4- and 1.2- fold, respectively. The presence of amiloride-sensitive Na+/H+ exchange was demonstrated. Contrary to electrogenic 2Na+/1H+ exchange on apical membranes from the same tissue, kinetic studies of Na+ transport by these basolateral membranes indicate an electroneutral antiport with a Km of 28±1.7 mmol l21 and a Jmax of 1.74±0.13 mmol mg21 min21. Amiloride interacted at a single binding site (Ki=39mmol l21) and external Li+ was shown to be an effective competitive inhibitor of the exchange process (Ki=493mmol l21). The presence of a membrane-potential-sensitive, Na+-accepting ion channel was also demonstrated. The basolateral Na+/H+ exchanger physiologically resembles members of the NHE family of Na+/H+ antiporters described in vertebrates and departs from the apical electrogenic system previously described in lobster. Whether or not the basolateral Na+/H+ antiporter is an NHE isoform remains to be determined

Ca2+ and Zn2+ are Transported by the Electrogenic 2Na+/1H+ Antiporter in Echinoderm Gastrointestinal Epithelium

45Ca2+ uptake by purified brush-border membrane vesicles of starfish (Pycnopodia helianthoides) pyloric ceca was stimulated by an outwardly directed H+ gradient and this stimulation was enhanced by the simultaneous presence of an induced membrane potential (inside negative; K+/valinomycin). External amiloride (competitive inhibitor; Ki=660mmol l21) and a monoclonal antibody raised against proteins associated with the lobster (Homarus americanus) electrogenic 2Na+/1H+ antiporter both inhibited approximately half of the proton-gradient stimulated 45Ca2+ uptake. These results suggested that Ca2+ might be transported by the electrogenic antiporter and that the crustacean antibody was inhibitory to the exchange function in echinoderms, as was recently shown in crustacean epithelial brush-border membrane vesicles. Carrier-mediated 45Ca2+ influx by amiloride-sensitive and amiloride-insensitive systems displayed the following kinetic constants: (amiloride-sensitive) Kt=66±2 mmol l21; Jmax=0.173±0.002 pmol mg21 protein 8 s21; (amiloride-insensitive) Kt=18±0.3 mmol l21; Jmax=0.100±0.001 pmol mg21 protein 8 s21. Zn2+ was a mixed inhibitor of 45Ca2+ influx by carrier-mediated transport, displaying a Ki of 920mmol l21. Mn2+, Cu2+, Fe2+ and Mg2+ also inhibited 45Ca2+ uptake, but the mechanism(s) of inhibition by these other cations was not disclosed. An equilibrium shift experiment showed that both Na+ and Zn2+ were able to exchange with equilibrated 45Ca2+ in these vesicles, suggesting that both monovalent and divalent cations were able to enter pyloric cecal cells through a common carrier-mediated transport system. In addition, the echinoderm electrogenic system appeared to exhibit a molecular component recognized by the crustacean antibody that may imply a similar epitope in the two animals

Role of the Invertebrate Electrogenic 2Na+/H+ Antiporter in Monovalent and Divalent Cation Transport

In recent years, an electrogenic 2Na+/1H+ antiporter has been identified in a variety of invertebrate epithelial brush-border membranes of gut, kidney and gill tissues. The antiporter differs significantly in its physiological properties from the electroneutral 1Na+/1H+ antiporter proposed for vertebrate cells. In all invertebrate cells examined, the antiporter displayed a 2:1 transport stoichiometry, responded to an induced transmembrane potential and exhibited a high binding affinity for the divalent cation Ca2+, which acted as a competitive inhibitor of Na+ transport. A monoclonal antibody specific for the crustacean electrogenic antiporter inhibited 2Na+/1H+ exchange, but was without effect on Na+-dependent D-glucose transport. Immunoreactivity was localized at hepatopancreatic brush-border and vacuolar membranes, antennal gland coelomosac podocytes and posterior gill epithelial cells – all locations where published reports described unique cation exchange kinetics. Significant fractions of Ca2+ transport into invertebrate cells across brush-border membranes occurred by an electrogenic, amiloride-sensitive exchange process, probably by the 2Na+/1H+ antiporter, and this transport was markedly inhibited by exogenous zinc and cadmium. A recently identified electroneutral, amiloride-sensitive, hepatopancreatic epithelial basolateral Na+/H+ antiporter was uninfluenced by the brush-border monoclonal antibody, exhibited an apparent 1:1 transport stoichiometry and possessed a minimal divalent cation specificity. Calcium transport at this epithelial pole occurred by the combination of a Ca2+/Na+ antiporter, an ATP-dependent Ca2+-ATPase and a verapamil-sensitive calcium channel. These crustacean brush-border and basolateral transporters may play significant roles in calcification and heavy metal detoxification

Herd It in the Gobi: Deserting pastoralism?

Global drylands host more than USD 1 trillion in resource extraction investments, which serve to reconfigure communities and landscapes. In Mongolia’s Gobi Desert mega-mining brings social challenges and environmental changes that question if nomadic herding and mining can coexist. Whilst company and community conflict are common, nascent frameworks and mediation models suggest alternate ways to resolve the mining–community conundrum. Here we investigate environmental transformations that herders encounter in the presence of the Oyu Tolgoi mega-mine in Mongolia’s Khanbogd soum (district). Using socio-economic and physical data collected through interviews, field studies and climate records, we assessed local engagement and adaptation to largescale mining. Combining qualitative and quantitative methods enabled us to examine the implications of mining for herder lives and lands in an integrated way. This study presents a holistic assessment of the roles of herders, governments and mines in reshaping pastoralism. In our chosen case study, we find that—contrary to common narratives—mining and herding can, and do, coexist in Khanbogd soum, though ongoing challenges exist which deserve critical attention.info:eu-repo/semantics/publishedVersio

Electrostatic colloid-membrane complexation

We investigate numerically and on the scaling level the adsorption of a charged colloid on an oppositely charged flexible membrane. We show that the long ranged character of the electrostatic interaction leads to a wrapping reentrance of the complex as the salt concentration is varied. The membrane wrapping depends on the size of the colloid and on the salt concentration and only for intermediate salt concentration and colloid sizes we find full wrapping. From the scaling model we derive simple relations for the phase boundaries between the different states of the complex, which agree well with the numerical minimization of the free energy.Comment: 7 page, 11 figure

The 13 November 1984 occultation of BD +08 deg 0471 by (1) Ceres

The 13 November 1984 occultation of BD +08 deg 0471 was discovered during a photographic search carried out with the 0.5 meter Carnegie Double Astrograph at Lick Observatory and the Lowell Observatory PDS microdensitometer. Such a search was stimulated by the curious fact that few favorably located occultations of AGK3 or SAO catalog starts by Ceres will occur during the 1980s. The occultation on 13 November, however, is a particularly good event. The star is 1000 cubic M in V, yielding a predicted drop at occultation of about 10%. Such a drop can be detected by small telescopes equipped with photoelectric photometers, but is too small to be seen visually. The track was predicted to cross the Caribbean, Florida, southern Texas, and Mexico. Based on this prediction, preparations were made to observe the event in Mexico using four portable occultation data systems

The Passions and Self-Esteem in Mary Astell\u27s Early Feminist Prose

This dissertation examines the influence of Cambridge Platonism and materialist philosophy on Mary Astell\u27s early feminism. More specifically, I argue that Astell co-opts Descartes\u27s theory of regulating the passions in his final publication, The Passions of the Soul, to articulate a comprehensive, Enlightenment and body friendly theory of feminine self-esteem that renders her feminism modern. My analysis of Astell\u27s theory of feminine self-esteem follows both textual and contextual cues, thus allowing for a reorientation of her early feminism vis-a-vis contemporary feminist theory. An entire chapter in the dissertation is devoted to Astell\u27s use of Descartes\u27s theory of regulating the passions to render women more substantial and inherently worthy. This rendering becomes more concrete in Astell\u27s feminist framework as she employs the language of the social contract in her fourth publication, Reflections Upon Marriage, to depict wives as contractual slaves. I argue that her assertion concerning women\u27s slavery is theoretically consistent when read in light of her theory of feminine self-esteem, since this theory is based on the Enlightenment principles of self-mastery, independence and self-preservation. Further, I align Astell\u27s early feminism in a dialogic sense with the Continental querelle des femmes, especially as presented in writings by Christine de Pizan and Agrippa. Astell, I argue, contributes to the querelle by framing the feminist problem she wishes to solve concerning women\u27s equality (despite bodily inferiority ) in a robust , philosophical manner that uncannily prefigures Wollstonecraft\u27s call for the universalization of human virtues and the reform of of women\u27s education

Brainstem volume mediates seasonal variation in depressive symptoms : A cross sectional study in the UK Biobank cohort

This research has been conducted using the UK Biobank resource. UK Biobank was established by the Wellcome Trust medical charity, Medical Research Council, Department of Health, Scottish Government and the Northwest Regional Development Agency. This work was supported by the Aberdeen Biomedical Imaging Centre with financial support from the Roland Sutton Academic Trust (RSAT-0039/R/16) and the Saudi Cultural Bureau in contact with Jazan University (PhD scholarship for NAM). Data Availability: The datasets processed and analysed during the current study are available from the online open access UK Biobank repository (https://www.ukbiobank.ac.uk/). This research was conducted under the UK Biobank Resource under Application Number 24089 (PI Waiter).Peer reviewedPublisher PD