Basolateral membrane Na+/H+ exchange enhances HCO3- absorption in rat medullary thick ascending limb: evidence for functional coupling between basolateral and apical membrane Na+/H+ exchangers.

The role of basolateral membrane Na+/H+ exchange in transepithelial HCO3- absorption (JHCO3) was examined in the isolated, perfused medullary thick ascending limb (MTAL) of the rat. In Na(+)-free solutions, addition of Na+ to the bath resulted in a rapid, amiloride-sensitive increase in intracellular pH. In MTALs perfused and bathed with solutions containing 146 mM Na+ and 25 mM HCO3-, bath addition of amiloride (1 mM) or 5-(N-ethyl-N-isopropyl) amiloride (EIPA, 50 microM) reversibly inhibited JHCO3 by 50%. Evidence that the inhibition of JHCO3 by bath amiloride was the result of inhibition of Na+/H+ exchange included the following: (i) the IC50 for amiloride was 5-10 microM, (ii) EIPA was a 50-fold more potent inhibitor than amiloride, (iii) the inhibition by bath amiloride was Na+ dependent, and (iv) significant inhibition was observed with EIPA as low as 0.1 microM. Fifty micromolar amiloride or 1 microM EIPA inhibited JHCO3 by 35% when added to the bath but had no effect when added to the tubule lumen, indicating that addition of amiloride to the bath did not directly inhibit apical membrane Na+/H+ exchange. In experiments in which apical Na+/H+ exchange was assessed from the initial rate of cell acidification following luminal EIPA addition, bath EIPA secondarily inhibited apical Na+/H+ exchange activity by 46%. These results demonstrate basolateral membrane Na+/H+ exchange enhances transepithelial HCO3- absorption in the MTAL. This effect appears to be the result of cross-talk in which an increase in basolateral membrane Na+/H+ exchange activity secondarily increases apical membrane Na+/H+ exchange activity.

An apical permeability barrier to NH3/NH4+ in isolated, perfused colonic crypts.

Fermentation of nonabsorbed nutrients in the colon generates high concentrations of NH3/NH4+ in the colonic lumen. NH3 is a small, lipophilic neutral weak base that readily permeates almost all cell membranes, whereas its conjugate weak acid NH4+ generally crosses membranes much more slowly. It is not known how colonocytes maintain intracellular pH in the unusual acid-base environment of the colon, where permeant acid-base products of fermentation exist in high concentration. To address this issue, we hand dissected and perfused single, isolated crypts from rabbit proximal colon, adapting techniques from renal-tubule microperfusion. Crypt perfusion permits control of solutions at the apical (luminal) and basolateral (serosal) surfaces of crypt cells. We assessed apical- vs. basolateral-membrane transport of NH3/NH4+ by using fluorescent dyes and digital imaging to monitor intracellular pH of microvacuolated crypt cells as well as luminal pH. We found that, although the basolateral membranes have normal NH3/NH4+ permeability properties, there is no evidence for transport of either NH3 or NH4+ across the apical borders of these crypt cells. Disaggregating luminal mucus did not increase the transport of NH3/NH4+ across the apical border. We conclude that, compared to the basolateral membrane, the apical border of crypt colonocytes has a very low permeability-area product for NH3/NH4+. This barrier may represent an important adaptation for the survival of crypt cells in the environment of the colon.

Calamocrinus diomedæ : a new stalked crinoid, with notes on the apical system and the homologies of echinoderms / by Alexander Agassiz.

v.17:no.2 (1892)

Apical hypertrophic cardiomyopathy : a review

Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2014

Carbon leakage: an overview. CEPS Special Report No. 79, 6 December 2013

Carbon leakage is central to the discussion on climate policy, given the confluence of issues that are currently being debated, including the 2030 Energy and Climate Framework and the review of the EU carbon leakage list by 2014. Carbon leakage is the result of asymmetrical carbon policies, especially carbon pricing, and the resulting carbon cost, which affects the international competitive position of some EU industry and could displace production and/or investment, and the emissions of the activities displaced. This paper identifies the difference between carbon price and carbon cost to leakage exposed industry as one of two fundamental issues to be understood and addressed; lack of visibility on future climate policies and anti-leakage provisions is the other key issue. While this is a global issue, most of the experience has been accumulated in the EU. Carbon leakage is only one of the factors that could affect the competitive position of sectors, but it is difficult to attribute the impact of carbon costs versus other variables such as energy costs, labour, etc. Studies have predicted the risk of a significant amount of production leakage in a number of energy-intensive industries. To address the danger, they were included in the EU ETS carbon leakage list, which gave them access to free allowances. However, a limited number of studies undertaken after the end of the second trading period (2012) show little evidence of production leakage and asks the question whether the issue has not been blown out of proportion. The paper argues that the past may not be a good representation of the future, as it was heavily influenced by a high level of free allocation, the exceptional economic downturn, CO2 prices significantly below what was anticipated, as well as the potential for changes in some fundamental variables such as the shrinking pool of allowances available for free allocation. It emphasises the need for a well-informed debate in the EU on measures to address carbon leakage post-2020, underpinned by a number of options, and objective criteria to evaluate those options. It emphasises that the debate should cover both investment and production leakage, caused by both direct and indirect carbon costs.

Carbon Leakage: Options for the EU. CEPS Special Report, March 2014

This CEPS Special Report builds on the first deliverable of the project entitled “Carbon leakage: Options for the EU”. It identifies carbon costs, and the ability to pass through carbon costs, as the main risk factors that could lead from asymmetrical carbon policies to carbon leakage. It also outlines and evaluates, based on criteria discussed in the paper, options for detecting and mitigating the risk of carbon leakage in three jurisdictions, with special attention to the EU ETS (Emissions Trading Scheme). Based on the analysis of approaches currently used in a number of existing carbon pricing systems, it identifies the balance between the number of sectors identified as being at risk, and the amount of compensation provided as a risk mitigation measure, as the critical element in providing an optimum approach to address carbon leakage risks. It also identifies a risk-based approach to identifying sectors at risk as allowing for a better reflection of reality in a counterfactual argument. Finally, the paper concludes that while, with some exceptions, there has been limited carbon leakage until now, the past may not be a good reflection of the future and that measures need to be put in place for the post-2020 period. While examining a number of approaches, it identifies free allocation as the most likely way forward for mitigating the risk of carbon leakage. While other approaches may provide interesting options, they also present challenges for implementation, from a market functioning, to international trade and relations, points of view. A number of challenges will need to be addressed in the post-2020 period, with many of them part of the EU ETS structural reform package. Some of these challenges include, among others, the need to recognise, and provide for individual sectoral characteristics, as well as for changes in production patterns, due to economic cycles, and other factors. Finally, the paper emphasises the need for an open dialogue regarding the post-2020 provisions for carbon leakage as no overall Energy and Climate Package is likely to be agreed on until this matter is addressed.

Prevention of cement leakage into the hip joint by a standard cement plug during PFN-A cement augmentation: a technical note.

Medial penetration of the helical blade into the hip joint after fixation of trochanteric fractures using the proximal femur nail antirotation (PFN-A) is a potential failure mode. In low demand patients a blade exchange with cement augmentation may be an option if conversion to total hip arthroplasty is unfeasible to salvage the cut-through. This article describes a technique to avoid intraarticular cement leakage using a cement plug to close the defect in the femoral head caused by the cut-through.

Solute losses from various shoot parts of field-grown wheat by leakage in the rain

Leakage from field-grown wheat was investigated during two seasons differing considerably in their rainfall patterns. For all solutes analyzed, these losses were low from non-senescing plant parts, increased after the onset of senescence and became maximal in fully senesced (dry, brown) organs. The cumulative losses of potassium by leakage in the rain were 65% of the content at anthesis for the flag leaf and 95% for the third leaf from the top, while these relative values were lower for magnesium (50 to 80%) and calcium (around 55%) and extremely low for sodium (<10%). The differences between potassium and sodium may be due to a different compartmentation on the tissue level or on the subcellular level. It became evident that for certain nutrients (e.g. potassium or magnesium) leakage in the rain may represent a major loss from senescing leaves and can be a relevant flux in maturing wheat.

(Table 2) Rate of reduction in cell size (apical length) and growth rate for seven Fragilariopsis kerguelensis strains sampled during POLARSTERN cruise ANT-XXI/3

The planktonic diatom Fragilariopsis kerguelensis plays an important role in the biogeochemical cycles of the Southern Ocean, where remains of its frustules form the largest deposit of biogenic silica anywhere in the world. We assessed the genetic identity of 26 strains, from cells collected at various sites in the Southern Ocean, using three molecular markers, LSU and ITS rDNA and rbcL. The LSU sequences were identical among the tested strains, ITS sequences were highly similar, and only one base pair difference was detected among the rbcL sequences. These results, together with a large number of successful mating experiments demonstrated that the strains belong to a single biological species. We investigated the mating system and life cycle traits of F. kerguelensis. Cell size diminished gradually in clonal strains. Gamete formation only occurred when strains of opposite mating type - within a cell size range of 7-36 µm - were mixed together. Two binucleate gametes were formed in each gametangium and gamete conjugation produced a zygote that had four nuclei and was surrounded by thin siliceous scales. Two out of the four nuclei subsequently degenerated and the zygote expanded to form an auxospore surrounded by a transverse and a longitudinal perizonium. Staining with the fluorochrome PDMPO provided for the first time a clear demonstration that the longitudinal perizonium is formed after auxospore expansion is complete. Initial cells produced within the mature auxospores were 78-101 µm in length. Various authors have shown that the average valve size of F. kerguelensis varies in sediment samples collected in regions and seasons with different primary production regimes and this parameter has thus been proposed as a biological proxy for palaeo-productivity. A better understanding of the life cycle of F. kerguelensis should help the design of future investigations aimed at testing the link between cell size distribution in the natural environment and the role that environmental factors might have in the regulation of population cell size.

Leakage in the proximity of microwave diathermy applications used on humans or phantom models /

Mode of access: Internet.

Heavy water reactor plant leakage /

"United States Atomic Energy Commission, Savannah River Operations Office, Contract AT (38-1) 213, supplements 1 & 2."

Investigation of centrifugal pumps : Part II, Experiments with a six inch horizontal centrifugal pump, comparing the efficiency of circular and spiral cases and showing the effect of air leakage

Mode of access: Internet.

Organizational maintenance repair parts and special tool lists for indicator, outlet valve leakage, M4A1 (FSN 6665-738-2128).

"14 February 1964."

Operator and organizational maintenance manual : indicator, outlet valve leakage, M4A1 (end item code 667).

Includes index.