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11.
The cellular mechanism of action of 3,5,3-triiodo-L-thyronine (T3) in enhancing SG-G100 gonadotropin-induced ovarian secretion of 17-estradiol (E2) was studiedin vitro using oocyte follicular preparations of rainbow trout. The dependence of the T3 stimulatory action on the level of intracellular 3,5-cyclic adenosine monophosphate (cAMP) was shown in experiments in which forskolin or dibutyryl cAMP enhanced E2 secretion. In the presence of partially purified salmon gonadotropin (SG-G100), T3 stimulation of E2 secretion was prevented by theophylline, suggesting that T3 may exert part of its stimulatory action by inhibiting phosphodiesterase. 相似文献
12.
Triton X-100-solubilized Mycoplasma gallisepticum and M. synoviae ELISA antigens were found to be more specific and sensitive than six other antigens at a concentration of 250 ng protein/0.1 ml per microtiter plate well. 相似文献
13.
The effects of drought on the free amino acid pools in 21- to 23-week-old seedlings of black spruce (Picea mariana (Mill.) Britt.), white spruce (Picea glauca (Moench.) Voss) and jack pine (Pinus banksiana Lamb.) were followed during soil drying. Although water and pressure potentials were sensitive to water deficits, large changes in osmotic potential were not recorded until after the development of severe drought. Total soluble amino nitrogen in the shoots and roots of the three species rose as turgor declined, with peak concentrations attained late in the drought period when the pressure potentials of the shoots approached zero. All white spruce seedlings were alive at zero turgor and showed large decrements in osmotic potential, but concentrations of free amino nitrogen in the roots and shoots showed only modest increases, reaching 125 to 150% of their control values. In contrast, large numbers of black spruce and jack pine were dead or severely damaged at zero turgor, and only small changes in osmotic potential were detected during soil drying. Nevertheless, concentrations of soluble amino nitrogen in both species reached 150 to 200% of control values a few days before the seedlings died. Alanine, arginine, aspartic acid/asparagine, glutamic acid/glutamine, glycine, hydroxyproline and proline were the major components of the free amino acid pools under both water-stressed and non-stressed conditions, with the largest and most consistent increases observed in the roots of all three conifers. Although proline was an important and dynamic component of the free pools, absolute concentrations were commony equalled or exceeded by other free amino acids in the roots and shoots and nearly always exceeded by the concentration of aspartic acid/asparagine in both tissues. Differences in drought resistance among the three conifers were not reflected by unique patterns of amino acid accumulation or by large differences in absolute concentrations of the free amino acid pools. 相似文献
14.
Chest tube drainage circuitry in mammals 总被引：2，自引：0，他引：2
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16.
The acute and chronic effects of excess iodide (KI or NaI) were studied on thyroid function of rainbow trout at 11±1°C. No
Wolff-Chaikoff effect, characteristic of mammals, was observed and instead plasma L-thyroxine (T4) levels increased 6 hr after a single iodide injection. Plasma 3,5,3′-triiodo-L-thyronine (T3) did not change and by 24 hr plasma T4 returned to normal. This iodide-induced elevation in plasma T4 was probably not due to toxic effects demonstrated at higher NaI or KI doses. A single iodide injection also decreased the
plasma iodide distribution space, decreased the fractional rate of plasma iodide loss and completely blocked thyroidal uptake
of radioiodide. Injections of iodide over a 22-day period elevated plasma iodide 200X with no mortality and no influence on
plasma T4 or T3. It is concluded that: (i) apart from the transient 6h increase in plasma T4, trout thyroid function, as judged by plasma hormone levels, is insensitive to considerable iodide excess, (ii) non-invasive
iodide suppression of thyroidal radioiodide recycling may be useful in kinetic studies of125I-labeled thyroid hormones, and (iii) fundamental differences in intrathyroidal iodine metabolism appear to exist between
mammals and fish. 相似文献
17.
T D Cyr R C Lawrence E G Lovering 《Journal of the Association of Official Analytical Chemists》1987,70(6):976-978
A titrimetric method, suitable for use at a limit of 5 mEq/L, has been developed for the determination of total nonesterified fatty acids in intravenous fat emulsion preparations. The method differentiates titrant consumed by the nonesterified fatty acids from that consumed by egg yolk phospholipids, usually present as an emulsifying agent. The total nonesterified fatty acids in 8 products from 4 manufacturers were in the range from 0.4 to 3.8 mEq/L. The mean standard deviation of the method is 0.09 mEq/L. 相似文献
18.
Yan Boulanger Anthony R. Taylor David T. Price Dominic Cyr Elizabeth McGarrigle Werner Rammer Guillaume Sainte-Marie André Beaudoin Luc Guindon Nicolas Mansuy 《Landscape Ecology》2017,32(7):1415-1431
Context
Forest landscapes at the southern boreal forest transition zone are likely to undergo great alterations due to projected changes in regional climate.Objectives
We projected changes in forest landscapes resulting from four climate scenarios (baseline, RCP 2.6, RCP 4.5 and RCP 8.5), by simulating changes in tree growth and disturbances at the southern edge of Canada’s boreal zone.Methods
Projections were performed for four regions located on an east–west gradient using a forest landscape model (LANDIS-II) parameterized using a forest patch model (PICUS).Results
Climate-induced changes in the competitiveness of dominant tree species due to changes in potential growth, and substantial intensification of the fire regime, appear likely to combine in driving major changes in boreal forest landscapes. Resulting cumulative impacts on forest ecosystems would be manifold but key changes would include (i) a strong decrease in the biomass of the dominant boreal species, especially mid- to late-successional conifers; (ii) increases in abundance of some temperate species able to colonize disturbed areas in a warmer climate; (iii) increases in the proportions of pioneer and fire-adapted species in these landscapes and (iv) an overall decrease in productivity and total biomass. The greatest changes would occur under the RCP 8.5 radiative forcing scenario, but some impacts can be expected even with RCP 2.6.Conclusions
Western boreal forests, i.e., those bordering the prairies, are the most vulnerable because of a lack of species adapted to warmer climates and major increases in areas burned. Conservation and forest management planning within the southern boreal transition zone should consider both disturbance- and climate-induced changes in forest communities.19.
Hooshang Pakdel Pierre-Louis Cyr Bernard Riedl James Deng 《Wood Science and Technology》2008,42(2):133-148
The potential merits of X-ray photoelectron spectroscopy (XPS) technique for the quantification of nitrogen on the wood fiber
surface before and after resination with UF resin was investigated and the resin content was calculated. The bulk nitrogen
content of the fibers obtained by XPS after grinding was compared with those obtained by combustion and Kjeldahl methods.
Four different fluorescence staining agents were tested by UV spectroscopy. Their λmax shifted to longer wavelengths when reacted with UF resin. Appropriate analysis conditions were tested for a satisfactory analysis
of wood fibers by the confocal laser scanning microscopy (CLSM). The result obtained by CLSM was compared with that obtained
by XPS. 相似文献
20.
Nathalie R. Le François Sarah Tremblay-Bourgeois Bernard-Antonin Dupont Cyr Arianne Savoie Robert L. Roy Albert K. Imsland 《Journal Of Applied Aquaculture》2013,25(3):248-264
The purpose of this study was to determine the cortisol response of spotted wolffish (Anarhichas minor) after exposure to air immersion and netting (acute stress) under a range of increasing densities (chronic stressor). In addition, the presence of a cumulative negative impact from chronic stress was assessed by the application of an additional acute stressor following rearing at various densities, and proxies of behavior were evaluated (feeding and aggression data). The stress response to air immersion and netting led to increasing plasma cortisol values at 0.5, 13, and 37 h post-stress, with the highest value achieved after 13 h. At 168 h, cortisol concentrations returned to similar pre-stress value. Changes in cortisol concentrations were relatively low after acute stress (five to six fold increases) and recovery time long lasting (>37 h). Prolonged rearing at 20, 30, and 40 kg m?2 showed a non-significant trend of increasing cortisol values with increasing density, and the cortisol response after the application of an additional acute stressor was significantly altered, i.e., higher cortisol levels were measured in unstressed (chronic stress only) compared to stressed fish (chronic stress + acute stress). Our results suggest that (1) spotted wolffish is a low responder that additionally displays a long-lasting cortisol elevation following an acute stressor; (2) fixed densities did not lead to significant differences of plasma cortisol concentration or aggression levels, although involved marked changes in daily feed intake and food conversion efficiency were observed; and (3) cortisol levels reached acute stress values after prolonged chronic stress. Although this species displays indications of being relatively resistant to handling disturbances during aquaculture practices, it is nevertheless responsive to chronic stress factors that could alter the physiological response to subsequent acute stressor. 相似文献