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171.
D.?G.?MilchunasEmail author A.?R.?Mosier J.?A.?Morgan D.?R.?LeCain J.?Y.?King J.?A.?Nelson 《Plant and Soil》2005,268(1):111-122
A modified root ingrowth method was developed to minimize destructive sampling in experiments with limited space, and used to estimate belowground net primary production and root tissue quality in a native semiarid grassland exposed to elevated CO2 for five years. Increases in root production of over 60% were observed with elevated CO2 during years of intermediate levels of precipitation, with smaller effects in a very wet year and no effects in a very dry year. Aboveground to belowground production ratios, and the depth distribution of root production, did not differ between ambient and elevated CO2 treatments. Root soluble concentrations increased an average of 11% and lignin concentrations decreased an average of 6% with elevated CO2, while nitrogen concentrations decreased an average of 21%. However, most tissue quality responses to CO2 varied greatly among years, and C:N ratios were higher in only one year (22 ambient vs. 33 elevated). Among years, root nitrogen concentrations declined with increasing aboveground plant nitrogen yield, and increased over the study period. Estimates of root production by the ingrowth donut method were much lower than previous estimates in the shortgrass steppe based on 14C decay. We discuss reasons why all ingrowth methods will always result in relative rather than absolute estimates of root production. 相似文献
172.
H D Mosier R A Jansons 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1985,178(3):457-461
The pattern of growth hormone (GH) secretion was determined in rats injected with cortisone acetate, 5 mg/rat/day subcutaneously, or with an equivalent volume of saline for 4 days from age 40 days. Cortisone injections resulted in inhibition of growth of body weight and tail length. During recovery the rats resumed a normal rate of growth but failed to show catch-up growth acceleration. From 17 to 27 days of recovery, plasma was sampled at 15-min intervals through the lights-on period, 06:00 to 18:00, via a catheter chronically implanted in the superior vena cava. During sampling each rat was housed singly in an insulated chamber, unrestrained, and with food and water ad lib. Cortisone-treated animals had a normal periodicity of GH plasma concentration, but they showed a reduction in values in the range of 50 to 99 ng/ml (P less than 0.01) and an increase of values in the range of 200 to 499 ng/ml (P less than 0.025) and above 1000 ng/ml (P less than 0.05). The area under the GH concentration curve of the cortisone-treated rats was significantly greater than that of the controls, 100.9 +/- 18.7 (mean +/- SE) units vs 55.3 +/- 7.4 (P less than 0.025). Thus, increased growth hormone secretion during the light phase persisted in spite of failure of catch-up growth acceleration. The findings indicate that the mechanism involved in GH release is linked to the catch-up growth control. 相似文献
173.
This report describes a lysozyme expressed at high levels in the stomach of
the hoatzin, the only known foregut-fermenting bird. Evolutionary
comparison places it among the calcium-binding lysozymes rather than among
the conventional types. Conventional lysozymes were recruited as digestive
enzymes twice in the evolution of mammalian foregut fermenters, and these
independently recruited lysozymes share convergent structural changes
attributed to selective pressures in the stomach. Biochemical convergence
and parallel amino acid replacements are observed in the hoatzin stomach
lysozyme even though it has a different genetic origin from the mammalian
examples and has undergone more than 300 million years of independent
evolution.
相似文献
174.
Astringency of aqueous solutions of phenolic compounds (grape seed tannins,
tannic acid, catechin and gallic acid) increased upon addition of citric
acid, whereas the astringency of alum was reduced. Astringency of alum was
decreased equivalently by addition of equi-sour levels of lactic acid,
citric acid or hydrochloric acid. The difference between alum and the
phenolic compounds is speculated to result from chemical modifications
affecting binding of the astringents with oral proteins rather than
cognitive differences. Chelation of the aluminum ion in alum by acids
reduces its availability for interacting with salivary proteins or
epithelial proteins. In contrast, the increased astringency produced upon
acidification of phenolic compounds is speculated to result from the pH
driven increase in the affinity of the phenols for binding with proteins.
These results suggest that alum cannot be used interchangeably with
phenolic astringents in psychophysical studies.
相似文献
175.
The ontogeny of thymic independent antibody responses in vitro in normal mice and mice with an X-linked B cell defect. 总被引:10,自引:0,他引:10
D E Mosier J J Mond E A Goldings 《Journal of immunology (Baltimore, Md. : 1950)》1977,119(6):1874-1878
The primary in vitro antibody response of neonatal spleen cells to three thymic independent antigens has been examined. The time of onset of responsiveness to TNP-Brucella abortus and TNP-lipopolysaccharide was significantly earlier than the onset of responsiveness to TNP-Ficoll. This ontologic sequence was not affected by T cell depletion or antigen presentation on adult macrophages. In neonatal mice bearing the X-linked CBA/N defect, the response to TNP-Brucella abortus and TNP-lipopolysaccharide was much delayed and no response to TNP-Ficoll developed. We conclude that different thymic independent antigens address different subpopulations of B cells, one of which appears earlier in ontogeny than the other. 相似文献
176.
The X-chromosome-linked B lymphocyte defect of CBA/N mice has been studied in vitro by comparing the ability of (CBA/N X DBA/2)F1 (X-/X- X X+/Y) male (X-/Y) and female (X-/X+) spleen cells to respond to the thymus-independent antigen DNP (or TNP)-AECM-Ficoll. (CBA/N X DBA/2)F1 male spleen cells failed to generate significant in vitro anti-TNP antibody responses to DNP- or TNP-AECM-Ficoll, in contrast to spleen cells from F1 female (X-/X+) mice which responded normally to these T-independent antigens. Spleen cells from male F1 mice responded almost as well as F1 female cells to the thymus-dependent antigen, TNP-sheep red blood cells (TNP-SRBC) in vitro. Adding F1 male cells to F1 female cells failed to reduce the response of the latter to DNP-AECM-Ficoll, suggesting that the inability of F1 male cells to respond was not due to active suppression. The response of F1 male spleen cells to TNP-SRBC was not impaired by adding high concentrations of TNP-AECM-Ficoll indicating that the mechanism of unresponsiveness was not tolerance induction in all TNP-specific precursors. Lymphocytes from F1 male mice were capable of forming anti-TNP antibody after stimulation with lipopolysaccharide (LPS) in high concentrations; DNP-AECM-Ficoll had no effect on this polyclonal response. B lymphocytes from mice bearing only the X-chromosome of the CBA/N strain thus display a profound defect in B cell activation. This functional defect may represent either an inability of the defective B cells to be activated by thymus-independent antigens or the absence of a sub-class of B cells which respond to thymus-independent antigens. 相似文献
177.
Nitrogen (N) availability is a key role in food and fiber production. Providing plant-available N through synthetic fertilizer in the 20th and early 21st century has been a major contributor to the increased production required to feed and clothe the growing human population.To continue to meet the global demands and to minimize environmental problems, significant improvements are needed in the efficiency with which fertilizer N is utilized within production systems. There are still major uncertainties regarding the fate of fertilizer N added to agricultural soils and the potential for reducing losses to the environment. Enhancing the technical and economic efficiency of fertilizer N is seen to promote a favorable situation for both agricultural production and the environment, and this has provided much of the impetus for a new N fertilizer project.To address this important issue, a rapid assessment project on N fertilizer (NFRAP) was conducted by SCOPE (the Scientific Committee on Problems of the Environment) during late 2003 and early 2004. This was the first formal project of the International Nitrogen Initiative (INI). As part of this assessment, a successful international workshop was held in Kampala, Uganda on 12 -16 January, 2004. This workshop brought together scientists from around the world to assess the fate of synthetic fertilizer N in the context of overall N inputs to agricultural systems, with a view to enhancing the efficiency of N use and reducing negative impacts on the environment.Regionalization of the assessment highlighted the problems of too little N for crop production to meet the nutrient requirements of sub-Saharan Africa and the oversupply of N in the major rice-growing areas of China. The results of the assessment are presented in a book (SCOPE 65)which is now available to provide a basis for further discussions on N fertilizer. 相似文献
178.
Microscopic examination of changes of plant cell structure in corn stover due to hot water pretreatment and enzymatic hydrolysis 总被引:3,自引:0,他引:3
Zeng M Mosier NS Huang CP Sherman DM Ladisch MR 《Biotechnology and bioengineering》2007,97(2):265-278
Particle size associated with accessible surface area has a significant impact on the saccharification of plant cell walls by cellulolytic enzymes. Small particle sizes of untreated cellulosic substrate are more readily hydrolyzed than large ones because of higher specific surface area. Pretreatment enlarges accessible and susceptible surface area leading to enhanced cellulose hydrolysis. These hypotheses were tested using ground corn stover in the size ranges of 425-710 and 53-75 microm. Ultrastructural changes in these particles were imaged after treatment with cellulolytic enzymes before and after liquid hot water pretreatment. The smaller 53-75 microm corn stover particles are 1.5x more susceptible to hydrolysis than 425-710 microm corn stover particles. This difference between the two particle size ranges is eliminated when the stover is pretreated with liquid hot water pretreatment at 190 degrees C for 15 min, at pH between 4.3 and 6.2. This pretreatment causes ultrastructural changes and formation of micron-sized pores that make the cellulose more accessible to hydrolytic enzymes. 相似文献
179.
Using nitrification inhibitors to mitigate agricultural N2O emission: a double‐edged sword? 下载免费PDF全文
Nitrification inhibitors show promise in decreasing nitrous oxide (N2O) emission from agricultural systems worldwide, but they may be much less effective than previously thought when both direct and indirect emissions are taken into account. Whilst nitrification inhibitors are effective at decreasing direct N2O emission and nitrate (NO3–) leaching, limited studies suggest that they may increase ammonia (NH3) volatilization and, subsequently, indirect N2O emission. These dual effects are typically not considered when evaluating the inhibitors as a climate change mitigation tool. Here, we collate results from the literature that simultaneously examined the effects of nitrification inhibitors on N2O and NH3 emissions. We found that nitrification inhibitors decreased direct N2O emission by 0.2–4.5 kg N2O‐N ha?1 (8–57%), but generally increased NH3 emission by 0.2–18.7 kg NH3‐N ha?1 (3–65%). Taking into account the estimated indirect N2O emission from deposited NH3, the overall impact of nitrification inhibitors ranged from ?4.5 (reduction) to +0.5 (increase) kg N2O‐N ha?1. Our results suggest that the beneficial effect of nitrification inhibitors in decreasing direct N2O emission can be undermined or even outweighed by an increase in NH3 volatilization. 相似文献
180.
Tânia M. Shiga Weihua Xiao Haibing Yang Ximing Zhang Anna T. Olek Bryon S. Donohoe Jiliang Liu Lee Makowski Tao Hou Maureen C. McCann Nicholas C. Carpita Nathan S. Mosier 《Biotechnology for biofuels》2017,10(1):310