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41.
42.
植物同工酶的研究和应用 总被引:30,自引:2,他引:28
同工酶作为生物界存在的一种普遍现象受到了广泛的研究。同工酶学(Isozymology)虽然不是一个确定的学科,但它已渗透到生物学的每一个领域,尤其是对酶学、物理生物化学和比较生物化学、生理学、发育生物学、细胞和分子生物学、遗传学、进化论等学科更加完善起了并将继续起着重大作用。在科学史上,很少有象同工酶的概念及 相似文献
43.
Neurotransmitter-Mediated Regulation of Brain Aromatase: Protein Kinase C- and G-Dependent Induction
Abstract: Aromatase in the diencephalic neurons, the level of which increases transiently during the prenatal to neonatal period, has been suggested to be involved in control of sexual behavior and differentiation of the CNS. Effects of neurotransmitters on levels of aromatase mRNA in cultured neurons were investigated to determine factors regulating the developmental increase that occurs in level of fetal brain aromatase. The expression of aromatase in diencephalic neurons of fetal mice at embryonic day 13, cultured in vitro, was significantly affected by α1 -adrenergic receptor ligands. Aromatase mRNA levels were higher in neurons treated with the α1 -agonist phenylephrine than in control neurons, whereas prazosin, an α1 -antagonist, suppressed this increase, and ligands for α2 - or β-adrenergic receptors did not exert any influence. The profile of α1 -adrenergic receptor subtypes during actual development in vivo suggested that the α1B subtype is in fact responsible for the signal transduction. Substance P, cholecystokinin, neurotensin, and brain natriuretic peptide also increased the level of expression along with phorbol 12-myristate 13-acetate and dibutyryl-cyclic GMP, whereas forskolin and dibutyryl-cyclic AMP caused a decrease. These data indicate that stimulation via α1 (possibly α1B )-adrenergic receptors, as well as receptors of specific neuropeptides, controls the expression of aromatase in embryonic day 13 diencephalic neurons through activation of protein kinase C or G. β-Adrenergic receptors would not appear to participate in the regulation, judging from their developmental profile, although cyclic AMP might be a suppressive second messenger. 相似文献
44.
Christian Tessier Gian-Paolo Rossini Jean-François Pageaux Hélène Cohen Michel Lagarde Christian Laugier Jean-Michel Fayard 《FEBS letters》1996,390(3):311-314
Rat uterine stromal cells (UIII) express pancreatic type PLA2 (PLA2-I) receptor and internalize the enzyme bound to receptors. Here, we investigate the proliferating effect and alterations in binding of PLA2-I. There is a dramatic decline in PLA2-I binding in UIII cells as they progress from a nonconfluent proliferating state (40,000 sites/cell) to a confluent state (1300 sites/cell). Intracellular concentration of PLA2-I changed with the alteration in binding, suggesting that regulation in the PLA2 binding capacity may have important implications in growth control mechanisms. 相似文献
45.
Free Air Temperature Increase (FATI): a new tool to study global warming effects on plants in the field 总被引:4,自引:1,他引:3
I. NIJS F. KOCKELBERGH H. TEUGHELS H. BLUM G. HENDREY I. IMPENS 《Plant, cell & environment》1996,19(4):495-502
A new technique, called Free Air Temperature Increase (FATI), was developed to artificially induce increased canopy temperature in field conditions without the use of enclosures. This acronym was chosen in analogy with FACE (Free Air CO2 Enrichment), a technique which produces elevated CO2 concentrations [CO2] in open field conditions. The FATI system simulates global warming in small ecosystems of limited height, using infrared heaters from which all radiation below 800 nm is removed by selective cut-off filters to avoid undesirable photomorpho-genetic effects. An electronic control circuit tracks the ambient canopy temperature in an unheated reference plot with thermocouples, and modulates the radiant energy from the lamps to produce a 2.5°C increment in the canopy temperature of an associated heated plot (continuously day and night). This pre-set target differential is relatively-constant over time due to the fast response of the lamps and the use of a proportional action controller (the standard deviation of this increment was <1°C in a 3 week field study with 1007 measurements). Furthermore, the increase in leaf temperature does not depend on the vertical position within the canopy or on the height of the stand. Possible applications and alternative designs are discussed. 相似文献
46.
Alexander A. Bulychev Tijmen van Voorthuysen Wim J. Vredenberg 《Physiologia plantarum》1996,98(2):605-611
Electrochemical data obtained with TMPD+ -sensitive electrodes indicate that ammonium-uncoupled chloroplasts retain TMPD (N,N,N',N'-tetramethyl- p -phenylenediamine) mainly in the reduced form during illumination, whereas uncoupled DCMU-treated chloroplasts accumulate TMPD in the oxidized form (TMPD+ ). This observation indicates that the reduced plastoquinol is the preferred electron donor for photosystem I (PSI) and TMPD can only compete efficiently when plastoquinone reduction is blocked. After adding DCMU the formation of a transmembrane gradient for TMPD+ is reflected by a slow-down of the electrogenic electron transport and by the emerging of the overshoot of the membrane current in the light-off response. A light-dependent increase in photoelectric current generated by chloroplasts in the presence of NH4 Cl and TMPD is observed and considered to be caused by a reversible release of current limitation in the interfacial conductance barriers in the lumen. 相似文献
47.
Grain yield, symbiotic N2 fixation and interspecific competition for inorganic N in pea-barley intercrops 总被引:4,自引:0,他引:4
Erik Steen Jensen 《Plant and Soil》1996,182(1):25-38
The effect of mixed intercropping of field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.), compared to monocrop cultivation, on the yield and crop-N dynamics was studied in a 4-yr field experiment using 15N-isotope dilution technique. Crops were grown with or without the supply of 5 g 15N-labeled N m-2. The effect of intercropping on the dry matter and N yields, competition for inorganic N among the intercrop components, symbiotic fixation in pea and N transfer from pea to barley were determined. As an average of four years the grain yields were similar in monocropped pea, monocropped and fertilized barley and the intercrop without N fertilizer supply. Nitrogen fertilization did not influence the intercrop yield, but decreased the proportion of pea in the yield. Relative yield totals (RYT) showed that the environmental sources for plant growth were used from 12 to 31% more efficiently by the intercrop than by the monocrops, and N fertilization decreased RYT-values. Intercrop yields were less stable than monocrop barley yields, but more stable than the yield of monocropped pea. Barley competed strongly for soil and fertilizer N in the intercrop, and was up to 30 times more competitive than pea for inorganic N. Consequently, barley obtained a more than proportionate share of the inorganic N in the intercrop. At maturity the total recovery of fertilizer N was not significantly different between crops, averaging 65% of the supplied N. The fertilizer N recovered in pea constituted only 9% of total fertilizer-N recovery in the intercrop. The amount of symbiotic N2 fixation in the intercrop was less than expected from its composition and the fixation in monocrop. This indicates that the competition from barley had a negative effect on the fixation, perhaps via shading. At maturity, the average amount of N2 fixation was 17.7 g N m-2 in the monocrop and 5.1 g N m-2 in the intercropped pea. A higher proportion of total N in pea was derived from N2 fixation in the intercrop than in the monocrop, on average 82% and 62%, respectively. The 15N enrichment of intercropped barley tended to be slightly lower than of monocropped barley, although not significantly. Consequently, there was no evidence for pea N being transferred to barley. The intercropping advantage in the pea-barley intercrop is mainly due to the complimentary use of soil inorganic and atmospheric N sources by the intercrop components, resulting in reduced competition for inorganic N, rather than a facilitative effect, in which symbiotically fixed N2 is made available to barley.Abbreviations MC
monocrop
- IC
intercrop
- PMC
pea monocrop
- BMC
barley monocrop
- PIC
pea in intercrop
- BIC
barley in intercrop 相似文献
48.
Ronald J. Prokopy Ratana Poramarcom Manon Sutantawong Ranu Dokmaihom Jorge Hendrichs 《Journal of Insect Behavior》1996,9(1):133-142
Oriental fruit flies,Bactrocera dorsalis, cultured in the laboratory for six generations, were released when 12–14 days old in an orchard of nonfruiting host trees that were furnished with either food and water, nonpunctured host fruit, punctured host fruit, or no resources. Nearly all flies of both sexes, all sexual behavior of males, and all mating pairs were observed on trees with fruit. Moreover, on trees with fruit, nearly all flies of both sexes, nearly all sexual behavior of males, and nearly all mating pairs occurred on the fruit itself rather than on the foliage or branches. In a subsequent test, both sexes were found to be strongly attracted to the odor of host fruit. For a polyphagous species of a tropical tephritid, these findings are the first to show a high level of male aggregation and a high amount of male sexual behavior on the fruit of host trees. Findings are discussed in relation to current knowledge of tephritid mating behavior. An additional quality-control test for laboratory cultured males used in the sterile insect technique of fly management is recommended. 相似文献
49.
B. E. Nixdorf-Bergweiler E. Wallhusser-Franke T. J. Devoogd 《Developmental neurobiology》1995,27(2):204-215
We investigated the development of spiny neurons in the lateral magnocellular nucleus of the anterior neostriatum before, during, and after song learning in male zebra finches (Taeniopygia guttata). The frequency of dendritic spines, dendritic field size, and branching characteristics were quantified at different ages in Golgi-stained tissue using a three-dimensional computerized tracing system. During development, overall spine frequencies increase between 3 and 5 weeks and decrease thereafter. In particular, spine frequencies of middle segments decrease significantly by 14% between 5 and 7 weeks posthatching (p = 0.017). A further reduction of 48% occurs between 7 weeks and adulthood (p < 0.001), resulting in a spine reduction of 56% on middle segments between 35 days of age and adulthood. In addition to the reduction of spine frequencies, we find regressive events also on some of the neuronal parameters that we have quantified. In general, dendrites of adult animals terminate closer to the cell body than those of 7-, 5-, or 3-week-old birds. Whereas no changes in segment length of first- and second-order dendrites have been identified, third-order dendrites end 19% closer to the cell body in adults than in younger birds (p < 0.024). Second-order dendrites in adult animals branch less frequently than in 3-week-old animals (35%, p = 0.017). There is also a trend of a smaller number of tertiary branches in adulthood compared with 3-week-old birds (41%, p = 0.060). The morphological changes may be related to the function of this nucleus and the sensitive phase for song acquisition. © 1995 John Wiley & Sons, Inc. 相似文献
50.
再生稻二化螟幼虫的空间布型为负二项分布和聚集分布,其lwao的线性回归方程为m^*=0.0099 2.4753m,属负二项分布。根据聚集均数(λ)测定结果,分析了聚集原因,在分布型研究的基础上,探讨了资料代换模式,Kuno‘s种群序贯抽样模型和最适抽样数模型。 相似文献