929 resultados para Microcomplement Fixation


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"May 1960."

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In v. 37 of a series of botanical tracts collected and bound together by Rev. Julius A. Nieuwland, University of Notre Dame.

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"Based on Public Health Monograph No. 74, Standardized Diagnostic Complement Fixation Method and Adaptation to Micro Test."

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Mode of access: Internet.

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"Issued December 1981"--2d prelim. page.

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"April 7, 1911."

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Trichodesmium sp. isolated from the Great Barrier Reef lagoon was cultured in artificial seawater media containing a range of salinities. Trichodesmium sp. actively grew over a wide range of salinities (22 to 43 psu) and hence can be classed as euryhaline. Maximum growth occurred with salinities in the range 33 to 37 psu. Chl a content and alkaline phosphatase activity were found to increase with salinity over the range 22 to 43 psu, but the N-2 fixation rate was reduced at salinities below and above the range for maximum growth. Growth in media exhibiting maximum growth was characterised by well-dispersed cultures of filaments, while significant aggregations of filaments formed in other media. It is proposed that the tendency for Trichodesmium filaments to aggregate in media with salinities outside the range for maximum growth is an opportunistic response to a deficiency of cellular nitrogen, which results from the reduced N-2 fixation rates, and the aggregation occurs in order to enhance the uptake of combined N released within the aggregates and/or the N-2 fixation within the aggregates.

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Various factors affecting N-2 fixation of a cultured strain of Trichodesmium sp. (GBRTRLI101) from the Great Barrier Reef Lagoon were investigated. The diurnal pattern of N2 fixation demonstrated that it was primarily light-induced although fixation continued to occur for at least 1 h in the dark in samples that had been actively fixing N-2. N-2 fixation was dependent on the light intensity and stimulated more by white light when compared with blue, green, yellow and red light whereas rates of N-2 fixation decreased most under red light. Inorganic phosphorous concentrations in the lower range of treatments up to 1.2 muM significantly stimulated N-2 fixation and further additions promoted little or no increase in N-2 fixation. Organic phosphorous (Na-glycerophosphate) also stimulated N-2 fixation rates. Added combined nitrogen (NH4+, NO3-, urea) of 10 muM did not inhibit N-2 fixation in short-term studies (first generation), however it was depressed in the long-term studies (fifth generation). (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

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Simultaneous fixation was investigated for a marine organism: the monogenean flatworm ectoparasite Merizocotyle icopae. Four protocols for primary fixation were compared: 3% glutaraldehyde alone in OAM cacodylate buffer for a minimum of 2 hours; 1% glutaraldehyde in combination with 1% osmium tetroxide, both in 0.1M cacodylate buffer, until tissues darkened (5-20 minutes); 1% glutaraldehyde in OAM cacodylate buffer in combination with 0.5% potassium ferricyanide-reduced osmium until tissues darkened (5-20 minutes); 1% glutaraldehyde in combination with 1% osmium tetroxide, both in 0.1M cacodylate buffer, for 30 minutes. The study confirms that the standard method for transmission electron microscopic fixation (first listed protocol) routinely applied to platyhelminths is optimal for ultrastructural preservation, but some simultaneous fixation methods (second and third listed protocols) are acceptable when rapid immobilization is needed. Scanning electron microscopic preparations may be improved using simultaneous primary fixation. (C) 2004 Wilcy-Liss, Inc.

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Significant acetylene reduction and therefore N-2 fixation was observed for Lyngbya majuscula only during dark periods, which suggests that oxygenic photosynthesis and N-2 fixation are incompatible processes for this species. Results from a series of batch and continuous-flow-culture reactor studies showed that the specific growth rate and N-2 fixation rate of L, majuscula increased with phosphate (P-PO4) concentration up to a maximum value and thereafter remained constant. The P-PO4 concentrations corresponding to the maximum N-2 fixation and maximum growth rates were -0.27 and -0.18 muM respectively and these values are denoted as the saturation values for N-2 fixation and growth respectively. Regular monitoring studies in Moreton Bay, Queensland, show that concentrations Of P-PO4 generally exceed these saturation values over a large portion of the Bay and therefore, the growth of the bloom-forming L, majuscula is potentially maximised throughout much of the Bay by the elevated P-PO4 concentrations. Results from other studies suggest that the elevated P-PO4 concentrations in the Bay can be largely attributed to discharges from waste-water treatment plants (WWTPs), and thus it is proposed that the control of the growth of L. majuscula in Moreton Bay will require a significant reduction in the P load from the WWTP discharges. If the current strategy of N load reduction for these discharges is maintained in the absence of substantial P load reduction, it is hypothesised that the growth of L, majuscula and other diazotrophs in Moreton Bay will increase in the future.