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171.
Philip J. McCall Ted C. J. Turlings John Loughrin Adron T. Proveaux James H. Tumlinson 《Journal of chemical ecology》1994,20(12):3039-3050
The effect of herbivory on the composition of the volatile blends released by cotton seedlings was investigated by collecting volatiles from undamaged, freshly damaged (0–2 hr after initiation of feeding), and old damaged (16–19 hr after initiation of feeding) plants on which corn earworm caterpillars (Helicoverpa zea Boddie) were actively feeding. A blend of 22 compounds was consistently observed to be emitted by the old damaged plants with nine occurring either only in, or in significantly greater amounts in old damaged, as compared with freshly damaged plants. These were (Z)-3-hexenyl acetate, hexyl acetate, (E)--ocimene, (3E)-4,8-dimethyl-1,3,7-nonatriene, (Z)-3-hexenyl butyrate, (E)-2-hexenyl butyrate, (Z)-3-hexenyl 2-methylbutyrate, (E)-2-hexenyl 2-methylbutyrate, and indole. The nature of this response is compared with other studies where herbivore-induced volatile responses are also known. The presence of large amounts of terpenes and aldehydes seen at the onset of feeding and the appearance of other compounds hours later suggest that cotton defense mechanisms may consist of a constitutive repertoire that is augmented by an induced mechanism mobilized in response to attack. A number of the induced compounds are common to many plants where, in addition to an immediate defensive function, they are known to be involved in the attraction of natural enemies. 相似文献
172.
Nitric oxide (NO) is a free radical involved in the regulation of several functions of the male genitourinary system. It is produced by neurons and the endothelium and epithelia of reproductive system; it mediates penile erection and regulates sperm motility, viability, and metabolism. Here we show that human spermatozoa exhibit a detectable NO synthase (NOS) activity, measured both as ability of the intact sperm and cell lysate to convert L-[3H]arginine into L-[3H]citrulline and as 24 h accumulation of extracellular nitrite in intact sperm suspensions. NOS activity (identified as an endothelial isoform) was inhibited by L-canavanine and N(G)-monomethyl-L-arginine, and nitrite accumulation was inhibited by the NO scavenger hemoglobin; both enzyme activity and nitrite production were increased by a 24 h incubation of spermatozoa with protein-enriched extracts of human follicular fluid (PFF); a significant increase of citrulline synthesis was observed only after a 4 h incubation with 40% PFF, a time period during which acrosomal reactivity was significantly increased. PFF-induced acrosomal reaction was inhibited by L-canavanine and hemoglobin, and the NO donors sodium nitroprusside (SNP), S-nitroso-N-acetyl-penicillamine (SNAP), and DETA NONOate were able to increase the percentage of reacted spermatozoa. Our results suggest that NO synthesized by human sperm may play a role in follicular fluid-induced acrosomal reaction. 相似文献
173.
GE McCall WC Byrnes SJ Fleck A Dickinson WJ Kraemer 《Canadian Metallurgical Quarterly》1999,24(1):96-107
Acute and chronic hormonal responses to resistance training were evaluated in 11 college men who completed 12 weeks (33 sessions) of high volume resistance training. No differences in resting concentrations of growth hormone (GH), insulin-like growth factor-I, testosterone, or sex hormone-binding globulin occurred from pre- and posttraining in the trained vs. nontrained control group. However, cortisol (c) decreased 17% for both groups (p < 0.05). There were no differences in exercise-induced responses between Sessions 10 and 20, with all hormone concentrations increasing (p < 0.05) from pre- at mid- and post exercise session. However, after correction for plasma volume decreases, only C and GH showed differences, with C increased from mid- to postsession (48% 10th; 49% 20th), and GH increased from pre- at mid- and postsession for both sessions 10 (0.16 +/- 0.42 pre; 4.77 +/- 6.24 mid; 6.26 +/- 5.19 post; microg x L-1) and 20 (0.33 +/- 0.85 pre; 5.42 +/- 9.08 mid; 8.24 +/- 7.61 post; microg x L-1). Significant correlations (p< 0.05) existed only between absolute mean GH increases from presession and the degree of muscle fiber hypertrophy for type I (r = 0.70 mid, 0.74 post) and type II (r = 0.71 post) fibers. In conclusion, resistance training had no effect on resting serum hormone concentrations, whereas similar acute exercise responses occurred between the 10th and 20th training sessions. 相似文献
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175.
The physical, chemical, and thermal changes in fabrics treated with a commercial crease‐resisting compound (CPNS) were investigated. The samples were analyzed by a scanning electron microscope equipped with an energy dispersive X‐ray microanalyzer, elemental analysis, and differential thermogravimetry. X‐ray microanalysis of the treated fabrics revealed that changes in gross integral counts of O, N, Mg, Al, Si, S, Cl, and Ca as a result of the treatments were related to the application rate of the compound. This result was broadly supported by mineral analysis data determined by standard wet chemistry methods. The effects of over‐ and undercuring were also investigated. In addition, the increase in nitrogen content as a result of the higher application rate can also be detected by EA. Differential thermogravimetric analyses of the samples showed distinct changes in the profile of the thermally stable fraction. This could be due to the formation of a crosslinked cellulose complex, which pyrolyzed at the significantly higher decomposition temperature of 481°C in comparison with 473°C for untreated material. The advantages of using instrumental techniques for assessing the efficiency of treatments are briefly discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1209–1219, 1999 相似文献
176.
177.
The molecular ion H3+ is considered the cornerstone of interstellar chemistry because it initiates the reactions responsible for the production of many larger molecules. Recently discovered in dense molecular clouds, H3+ has now been observed in the diffuse interstellar medium toward Cygnus OB2 No. 12. Analysis of H3+ chemistry suggests that the high H3+ column density (3.8 x 10(14) per square centimeter) is due not to a high H3+ concentration but to a long absorption path. This and other work demonstrate the ubiquity of H3+ and its potential as a probe of the physical and chemical conditions in the interstellar medium. 相似文献
178.
Chaudhary A. Day T. Fender K. Fendrick L. McCall J. 《Industry Applications Magazine, IEEE》2003,9(6):34-39
This article describes a novel application of the impedance method to provide complete bank protection by measuring the impedance of each series string of the capacitor bank. 相似文献
179.
Coffman Jennifer L.; Ornstein Peter A.; McCall Laura E.; Curran Patrick J. 《Canadian Metallurgical Quarterly》2008,44(6):1640
This longitudinal study was designed to (a) examine changes in children's deliberate memory across the 1st grade; (b) characterize the memory-relevant aspects of their classrooms; and (c) explore linkages between the children's performance and the language their teachers use in instruction. To explore contextual factors that may facilitate the development of skills for remembering, 107 first graders were assessed 3 times with a broad set of tasks, while extensive observations were made in the 14 classrooms from which these children were sampled. When the participating teachers were classified as high or low in terms of their "mnemonic orientation," in part on the basis of their use of metacognitive information and requests for deliberate remembering during instruction in language arts and mathematics, differences were observed in the use of mnemonic techniques by the children in their classes. By the end of the year, the children drawn from these 2 groups of classrooms differed in their spontaneous use of simple behavioral strategies for remembering and in their response to training in more complex verbally based mnemonic techniques. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
180.