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101.
H. L. Xu J. Lopez F. Rachii N. Tremblay L. Gauthier Y. Desjardins A. Gosselin 《Physiologia plantarum》1996,96(4):722-726
Sulphate accumulates in the rhizosphere of plants grown in hydroponic systems. To avoid such sulphate accumulation and promote the use of environmentally sound hydroponic systems, we examined the effects of four sulphate concentrations (0.1, 5,2, 10.4 and 20.8 m M ) on photosynthesis, ribulose-l,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) activities and related physiological processes in greenhouse–grown tomato plants ( Lycopersicon esculentum Mill. cv. Trust). The lowest sulphate concentration (0.1 m M ) significantly decreased photosynthetic capacity (Pc ) and Rubisco activities on a leaf area basis. This result was supported by our data for dry matter per plant, which was low for plants in the 0.1 m M treatment. The photosynthesis-related variables such as leaf conductance, chlorophyll and soluble protein were lowest for the 0.1 m M treatment. Both total Rubisco activity and the activated ratio were reduced with this treatment. However, Rubisco activities expressed per g of protein or per g of chlorophyll were not significantly affected. These results suggest that sulphur deficiency depressed Pc – by reducing the amount of both Rubisco and chlorophyll and by causing an inactivation of Rubisco. The ratio of organic sulphur vs organic nitrogen (S/N) in plants of the 0.1 m M treatment was far below the normal values. This low S/N ratio might be accountable for the negative effect of low sulphate on Pc and plant growth. Pc and dry matter were not affected until sulphate concentration in the nutrient solution reached a high level of 20.8 m M . 相似文献
102.
F. J. Castillo 《Oecologia》1996,107(4):469-477
The antioxidative protection during the C3-CAM shift induced by water stress was investigated in the temperate succulent Sedum album L. The C3-CAM shift was characterized in terms of CO2 exchange, titratable acidity and phosphoenolpyruvate carboxylase activity. Well-watered plants displayed C3-like patterns of gas exchange and exhibited a mild day-night acid fluctuation indicating that those plants were performing CAM-cycling metabolism. Imposed drought highly stimulated CAM cycling, decreasing the net CO2 uptake during the day, eliminating net CO2 efflux at night and stimulating tissue acid fluctuations. As water deficit developed, chlorophyll fluorescence measurements showed a decrease in the Fv/Fm ratio, indicating that photoinhibition could follow after severe drought. Protection might be performed by the increased activity of enzymes involved in the destruction of free radicals and oxidants, but their response depended on the water status of the plant. Ascorbate peroxidase and superoxide dismutase activities increased in plants subjected to mild stress but declined during severe water stress. Catalase activity, however, was quite stable under mild water stress and was clearly inhibited under severe water stress. At this stage, glutathione reductase and monodehydroascorbate reductase seemed to be very important in the protection against oxidants, both increasing considerably their activities under severe water stress. Even if recycling has been shown to alleviate photoinhibition, our results clearly demonstrate that antioxidative enzymes play an important role in the protection of plants from oxidants during the C3-CAM shift induced by water stress. 相似文献
103.
104.
Characterization of Monoclonal Antibodies Specific for Erwinia carotovora subsp. atroseptica and Comparison of Serological Methods for Its Sensitive Detection on Potato Tubers 总被引:1,自引:0,他引:1 下载免费PDF全文
María Teresa Gorris Benito Alarcon María M. Lopez Mariano Cambra 《Applied microbiology》1994,60(6):2076-2085
Seven monoclonal antibodies (MAbs) to Erwinia carotovora subsp. atroseptica have been produced. One, called 4G4, reacted with high specificity for serogroup I of E. carotovora subsp. atroseptica, the most common serogroup on potato tubers in different serological assays. Eighty-six strains belonging to different E. carotovora subsp. atroseptica serogroups were assayed. Some strains of serogroup XXII also reacted positively. No cross-reactions were observed against other species of plant pathogenic bacteria or 162 saprophytic bacteria from potato tubers. Only one strain of E. chrysanthemi from potato cross-reacted. A comparison of several serological techniques to detect E. carotovora subsp. atroseptica on potato tubers was performed with MAb 4G4 or polyclonal antibodies. The organism was extracted directly from potato peels of artificially inoculated tubers by soaking or selective enrichment under anaerobiosis in a medium with polypectate. MAb 4G4 was able to detect specifically 240 E. carotovora subsp. atroseptica cells per ml by indirect immunofluorescence and immunofluorescence colony staining and after soaking by ELISA-DAS (double-antibody sandwich enzyme-linked immunosorbent assay) after enrichment. The same amount of cells was detected by using immunolectrotransfer with polyclonal antibodies, and E. carotovora subsp. atroseptica and subsp. carotovora were distinguished by the latter technique. ELISA-DAS using MAb 4G4 with an enrichment step also efficiently detected E. carotovora subsp. atroseptica in naturally infected tubers and plants. 相似文献
105.
Studies were undertaken on interactions between panicle size, insect density, host plant, and the environment for sorghum
head bug,Calocoris angustatus Lethiery on five sorghum genotypes in terms of bug population increase, grain damage and loss in grain mass across four panicle
sizes (5, 10 or 20 branches/panicle and whole panicle), and three infestation levels (5, 10 and 15 pairs of bugs/panicle).
Head bug numbers increased and grain damage decreased with an increase in panicle size in the head bug susceptible cultivars,
CSH 1 and CSH 5. However, the increase in bug numbers or decrease in grain damage was not significant in head bug resistant
genotypes, IS 17610 and IS 17645. Head bug numbers increased with an increase in infestation level in CSH 1 and CSH 5, however,
such an increase was not substantial in IS 17610 and IS 17645. Grain damage was significantly lower in IS 17610 and IS 17645
compared with CSH 1 and CSH 5 across infestation levels. Head bug population increased at a greater rate during the rainy
season compared with the dry season. Panicle size and infestation levels accounted for greater variation in grain damage and
percentage loss in grain mass during the rainy season than in the dry season. To identify reliable sources of resistance to
insects, it is important to study insect host plant-interactions across panicle sizes (levels of food availability), infestation
levels and seasons. 相似文献
106.
107.
Richard J. Castillo 《Culture, medicine and psychiatry》1994,18(2):141-162
Psychoanalytic theory appears flawed in the way it has been traditionally applied in anthropological studies of spirit possession in South Asia. It is suggested that pathological spirit possession in South Asia has a similar etiology to multiple personality disorder in North America, which is caused by spontaneous trance reactions to extreme situations in the environment, particularly child abuse. Reanalyses of previously published case histories of spirit possession illnesses in South Asia are presented from the perspective of dissociation theory, highlighting possible etiology not considered relevant in earlier psychoanalytic theories. 相似文献
108.
Nucleocapsid-glycoprotein interactions required for assembly of alphaviruses. 总被引:30,自引:19,他引:11 下载免费PDF全文
We have studied interactions between nucleocapsids and glycoproteins required for budding of alphaviruses, using Ross River virus-Sindbis virus chimeras in which the nucleocapsid protein is derived from one virus and the envelope glycoproteins are derived from the second virus. A virus containing the Ross River virus genome in which the capsid protein had been replaced with that from Sindbis virus was almost nonviable. Nucleocapsids formed in normal numbers in the infected cell, but very little virus was released from the cell. There are 11 amino acid differences between Ross River virus and Sindbis virus in their 33-residue E2 cytoplasmic domains. Site-specific mutagenesis was used to change 9 of these 11 amino acids in the chimera from the Ross River virus to the Sindbis virus sequence in an attempt to adapt the E2 of the chimera to the nucleocapsid. The resulting mutant chimera grew 4 orders of magnitude better than the parental chimeric virus. This finding provides direct evidence for a sequence-specific interaction between the nucleocapsid and the E2 cytoplasmic domain during virus budding. The mutated chimeric virus readily gave rise to large-plaque variants that grew almost as well as Ross River virus, suggesting that additional single amino acid substitutions in the structural proteins can further enhance the interactions between the disparate capsid and the glycoproteins. Unexpectedly, change of E2 residue 394 from lysine (Ross River virus) to glutamic acid (Sindbis virus) was deleterious for the chimera, suggesting that in addition to its role in nucleocapsid-E2 interactions, the N-terminal part of the E2 cytoplasmic domain may be involved in glycoprotein-glycoprotein interactions required to assemble the glycoprotein spikes. The reciprocal chimera, Sindbis virus containing the Ross River virus capsid, also grew poorly. Suppressor mutations arose readily in this chimera, producing a virus that grew moderately well and that formed larger plaques. 相似文献
109.
Dr. Stephen K. Fisher Diana M. Slowiejko Edward L. McEwen 《Neurochemical research》1994,19(5):549-554
Agonist occupancy of muscarinic cholinergic receptors in human SH-SY-5Y neuroblastoma cells elicited two kinetically distinct phases of phosphoinositide hydrolysis when monitored by either an increased mass of inositol 1,4,5-trisphosphate, or the accumulation of a total inositol phosphate fraction. Within 5s of the addition of the muscarinic agonist, oxotremorine-M, the phosphoinositide pool was hydrolyzed at a maximal rate of 9.5%/min. This initial phase of phosphoinositide hydrolysis was short-lived (t1/2=14s) and after 60s of agonist exposure, the rate of inositol lipid breakdown had declined to a steady state level of 3.4%/min which was then maintained for at least 5–10 min. This rapid, but partial, attenuation of muscarinic receptor stimulated phosphoinositide hydrolysis occurred prior to the agonist-induced internalization of muscarinic receptors.Abbreviations I(1,4,5)P3
inositol 1,4,5-trisphosphate
- IP
total inositol phosphate fraction
- IPL
total inositol lipid fraction
- mAChR
muscarinic acetylcholine receptor
- NMS
N-methylscopolamine
- Oxo-M
oxotremorine-M
- PI
phosphatidylinositol
- PIP
phosphatidylinositol 4-phosphate
- PIP2
phosphatidylinositol 4,5-bisphosphate
- PPI
phosphoinositide
- QNB
quinuclidinyl benzilate
Special issue dedicated to Dr. Bernard W. Agranoff 相似文献
110.
Eduardo Lissi Carlos Pascual Maria D. Del Castillo 《Free radical biology & medicine》1994,16(6):833-837
Addition of horseradish peroxidase to a luminol solution (pH = 9.4) produces a burst of light followed by a steady luminescence that lasts for several minutes. This steady-state luminescence is readily quenched by SOD, with a
concentration (the additive concentration needed to decrease by one-half the emitted luminescence intensity) of c.a. 4 ng/ml (14 mU/ml). The luminescence intensity decrease can then be employed to evaluate SOD activity in SOD-containing samples. However, the light intensity can also be quenched by additives, such as Trolox, that are able to trap luminol-derived intermediates. It is proposed that double quenching experiments must be performed in order to be able to relate the observed effect of an additive to its SOD-like activity. 相似文献