Structure of the novel membrane-coating material in proton-secreting epithelial cells and identification as an H+ATPase.

Specialized proton-secreting cells known collectively as mitochondria-rich cells are found in a variety of transporting epithelia, including the kidney collecting duct (intercalated cells) and toad and turtle urinary bladders. These cells contain a population of characteristic tubulovesicles that are believed to be involved in the shuttling of proton pumps (H+ATPase) to and from the plasma membrane. These transporting vesicles have a dense, studlike material coating the cytoplasmic face of their limiting membranes and similar studs are also found beneath parts of the plasma membrane. We have recently shown that this membrane coat does not contain clathrin. The present study was performed to determine the structure of this coat in rapidly frozen and freeze-dried tissue, and to determine whether the coat contains a major membrane protein transported by these vesicles, a proton pumping H+ATPase. The structure of the coat was examined in proton-secreting, mitochondria-rich cells from toad urinary bladder epithelium by rapidly freezing portions of apical membrane and associated cytoplasm that were sheared away from the remainder of the cell using polylysine-coated coverslips. Regions of the underside of these apical membranes as large as 0.2 micron2 were decorated by studlike projections that were arranged into regular hexagonal arrays. Individual studs had a diameter of 9.5 nm and appeared to be composed of multiple subunits arranged around a central depression, possibly representing a channel. The studs had a density of approximately 16,800 per micron2 of membrane. Similar arrays of studs were also found on vesicles trapped in the residual band of cytoplasm that remained attached to the underside of the plasma membrane, but none were seen in adjacent granular cells. To determine whether these arrays of studs contained H+ATPase molecules, we examined a preparation of affinity-purified bovine medullary H+ATPase, using the same technique, after incorporation of the protein eluted from a monoclonal antibody affinity column into phospholipid liposomes. The affinity-purified protein was shown to be capable of ATP-dependent acidification. In such preparations, large paracrystalline arrays of studs identical in appearance to those seen in situ were found. The dimensions of the studs as well as the number per square micrometer of membrane were identical to those of toad bladder mitochondria-rich cells: 9.5 nm in diameter, 16,770 per micron2 of membrane.(ABSTRACT TRUNCATED AT 400 WORDS

Narrow-band optical filter through phase conjugation by nondegenerate four-wave mixing in sodium vapor

An ultrahigh-Q tunable optical filter with a FWHM bandwidth of 41 MHz is demonstrated. The filtering is produced by nondegenerate phase conjugation through four-wave mixing in atomic-sodium vapor. The filter is observed to have a maximum quantum efficiency of 4 x 10^-3. However, degenerate phase-conjugation experiments in sodium suggest that a quantum efficiency of greater than unity can be attained on a cw basis

Sustainability and the Canadian Forest Sector

This paper was presented as a keynote address at the conference on Forest Sustainability - Beyond 2000 held in May 2000 in Thunder Bay, Canada. The conference brought together forest sector leaders and professionals from across Canada. This paper is an extension of earlier work on the sustainability North American wood supplies (Nilsson et al., 2000). The present paper examines the efficiency of the current established criteria and indicators for sustainable development of the forest sector. The current system of criteria and indicators concentrates on the management aspects instead of the objectives setting. The current system is too complicated to be implemented and neglects the fact that sustainability cannot be achieved by a top-down approach but only by the people working on the ground at the local level. This paper presents a number of guidelines on the necessary steps to be taken in order to move towards A Forest Sector for Sustainable Development

Uncertainties of the CJK 5 Flavour LO Parton Distributions in the Real Photon

Radiatively generated, LO quark (u,d,s,c,b) and gluon densities in the real, unpolarized photon, calculated in the CJK model being an improved realization of the CJKL approach, have been recently presented. The results were obtained through a global fit to the experimental F2^gamma data. In this paper we present, obtained for the very first time in the photon case, an estimate of the uncertainties of the CJK parton distributions due to the experimental errors. The analysis is based on the Hessian method which was recently applied in the proton parton structure analysis. Sets of test parametrizations are given for the CJK model. They allow for calculation of its best fit parton distributions along with F2^gamma and for computation of uncertainties of any physical value depending on the real photon parton densities. We test the applicability of the approach by comparing uncertainties of example cross-sections calculated in the Hessian and Lagrange methods. Moreover, we present a detailed analysis of the chi^2 of the CJK fit and its relation to the data. We show that large chi^2/DOF of the fit is due to only a few of the experimental measurements. By excluding them chi^2/DOF approx 1 can be obtained.Comment: 28 pages, 8 eps figures, 2 Latex figures; FORTRAN programs available at http://www.fuw.edu.pl/~pjank/param.html; table 10, figure 10 and section 6 correcte

Apical endosomes isolated from kidney collecting duct principal cells lack subunits of the proton pumping ATPase.

Endocytic vesicles that are involved in the vasopressin-stimulated recycling of water channels to and from the apical membrane of kidney collecting duct principal cells were isolated from rat renal papilla by differential and Percoll density gradient centrifugation. Fluorescence quenching measurements showed that the isolated vesicles maintained a high, HgCl2-sensitive water permeability, consistent with the presence of vasopressin-sensitive water channels. They did not, however, exhibit ATP-dependent luminal acidification, nor any N-ethylmaleimide-sensitive ATPase activity, properties that are characteristic of most acidic endosomal compartments. Western blotting with specific antibodies showed that the 31- and 70-kD cytoplasmically oriented subunits of the vacuolar proton pump were not detectable in these apical endosomes from the papilla, whereas they were present in endosomes prepared in parallel from the cortex. In contrast, the 56-kD subunit of the proton pump was abundant in papillary endosomes, and was localized at the apical pole of principal cells by immunocytochemistry. Finally, an antibody that recognizes the 16-kD transmembrane subunit of oat tonoplast ATPase cross-reacted with a distinct 16-kD band in cortical endosomes, but no 16-kD band was detectable in endosomes from the papilla. This antibody also recognized a 16-kD band in affinity-purified H+ ATPase preparations from bovine kidney medulla. Therefore, early endosomes derived from the apical plasma membrane of collecting duct principal cells fail to acidify because they lack functionally important subunits of a vacuolar-type proton pumping ATPase, including the 16-kD transmembrane domain that serves as the proton-conducting channel, and the 70-kD cytoplasmic subunit that contains the ATPase catalytic site. This specialized, non-acidic early endosomal compartment appears to be involved primarily in the hormonally induced recycling of water channels to and from the apical plasma membrane of vasopressin-sensitive cells in the kidney collecting duct

Full Carbon Account for Russia.

The Forestry Project (FOR) at IIASA has produced a full carbon account (FCA) for Russia for 1990, together with scenarios for 2010. Currently, there are rather big question marks regarding the existing carbon accounts for Russia, and Russia is critical to the global carbon balance due to its size. IIASA is in a position to perform solid analysis of Russia because of the databases that the Institute has built over the years. FOR based this work on a comprehensive geographic information system comprising georeferenced descriptions of the environment and land of Russia, which in turn are based on a number of thematic, digitized maps and databases. For the Russian energy sector and other industrial sectors (except the forest industry), the project used emissions estimates from the recent IIASA study "Global Energy Perspectives" (1998). The project carried out a separate substudy for the Russian forest industry sector. According to FOR's estimate, the total fluxes (including energy and industry sectors) in Russia were a net source of 527 teragrams of carbon (Tg C) in 1990. To illustrate the possible development of the carbon pools and fluxes over the next 10 years, FOR developed three different scenarios for the period 1990-2010, reflecting different assumptions regarding Russia's GDP growth. According to these scenarios, Russia will continue to be a net source of carbon to the atmosphere with 156-385 Tg C in 2010, including the emissions from energy and other industrial sectors. However, analysis of the FCA also shows considerable uncertainties involved in the carbon accounting. These uncertainties exceed the calculated changes in the full flux balance for the period 1990-2010. At present, this raises grave questions regarding the reliability of any accounting system used to measure terrestrial ecosystems for compliance with the Kyoto Protocol.

Agriculture's contribution to national emissions

This info note offers an overview of the distribution of agricultural emissions among countries and the relative contribution of agriculture to national emissions. It is based on three data sources: the FAOSTAT database of greenhouse gas emissions from agriculture, United States Environmental Protection Agency (EPA) global emission estimates for 2010 and national reports to the United Nations Framework Convention on Climate Change (UNFCCC).

Testing Color Evaporation in Photon-Photon Production of J/Psi at CERN LEP II

The DELPHI Collaboration has recently reported the measurement of J/Psi production in photon-photon collisions at LEP II. These newly available data provide an additional proof of the importance of colored c bar{c} pairs for the production of charmonium because these data can only be explained by considering resolved photon processes. We show here that the inclusion of color octet contributions to the J/Psi production in the framework of the color evaporation model is able to reproduce this data. In particular, the transverse-momentum distribution of the J/Psi mesons is well described by this model.Comment: 10 pages, 5 Figures, Revtex

Design of a real-time wind turbine simulator using a custom parallel architecture

The design of a new parallel-processing digital simulator is described. The new simulator has been developed specifically for analysis of wind energy systems in real time. The new processor has been named: the Wind Energy System Time-domain simulator, version 3 (WEST-3). Like previous WEST versions, WEST-3 performs many computations in parallel. The modules in WEST-3 are pure digital processors, however. These digital processors can be programmed individually and operated in concert to achieve real-time simulation of wind turbine systems. Because of this programmability, WEST-3 is very much more flexible and general than its two predecessors. The design features of WEST-3 are described to show how the system produces high-speed solutions of nonlinear time-domain equations. WEST-3 has two very fast Computational Units (CU's) that use minicomputer technology plus special architectural features that make them many times faster than a microcomputer. These CU's are needed to perform the complex computations associated with the wind turbine rotor system in real time. The parallel architecture of the CU causes several tasks to be done in each cycle, including an IO operation and the combination of a multiply, add, and store. The WEST-3 simulator can be expanded at any time for additional computational power. This is possible because the CU's interfaced to each other and to other portions of the simulation using special serial buses. These buses can be 'patched' together in essentially any configuration (in a manner very similar to the programming methods used in analog computation) to balance the input/ output requirements. CU's can be added in any number to share a given computational load. This flexible bus feature is very different from many other parallel processors which usually have a throughput limit because of rigid bus architecture