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31.
In vivo effect of abscisic acid (ABA) on photosynthetic oxygen evolution was investigated in barley chloroplasts. The most important kinetic parameters of O2-producing reactions were changed. The results show inhibition of the O2-flash yields at ABA concentrations of 10 mol/l and 100 mol/l and an increase in the degree of damping of the oscillations. ABA has a marked effect on the distribution of the oxygenevolving centers in S0 and S1 states and on sum of the centers (S0+S1) estimated according to the Kok model. In addition, the amplitude and the shape of the initial oxygen burst under continuous illumination are also significantly altered. At a concentration of 100 mol/l, ABA strongly inhibits Hill reaction activity measured by DCPIP reduction. The results cannot be explained by the hypothesis of socalled stomata effect. On the other hand, no effects were observed on the investigated parameters in experiments involving ABA applied in vitro to isolated chloroplasts. It is hypothesized that ABA disrupts the granal chloroplasts structure and raises the degree of participation of the cooperative mechanism of O2-evolution connected with the functioning of PS II centers in the stroma situated thylakoids.Abbreviations DCPIP
2,6-Dichlorophenolindophenol
- DCMU
3-(3,4-dichlorophenil)-1,1-dimethylurea
- HEPES
N-2-Hydroxyethylpiperazine-N-2-ethane sulfonic acid
- PSII
photosystem II
- RubisCO
Ribulose-1,5-bis-phosphate carboxylase-oxygenase 相似文献
32.
M D Sabet S R Gordon 《Biology of the cell / under the auspices of the European Cell Biology Organization》1989,65(2):171-179
The distribution of the extracellular matrix (ECM) protein, fibronectin (FN), has been examined ultrastructurally in noninjured and injured rat corneal endothelium in vivo and in vitro by immunoperoxidase cytochemistry. In noninjured endothelia, FN was observed within the rough endoplasmic reticulum (RER) cisternae but not along the cell-Descemet's membrane (DM) interface. Twenty-four and 48 h after a circular freeze injury, immunoperoxidase reaction product was detected at the cell-DM interface as well as within cytoplasmic vesicles and intercellular spaces. By 1 and 2 wk post-injury, a line of reaction product could still be demonstrated at the cell-DM interface and evidence for newly deposited basement membrane material was observed in this region. In order to understand whether fibronectin deposition during wound repair was dependent on cytoskeletal influences, organ culture experiments were performed in which the media was supplemented with either 10(-8) M colchicine or 2.5 X 10(-3) M cytochalasin B. Without inhibitors, injured corneas cultured for 24 h had FN deposition at the cell-DM interface similar to the in vivo results. Corneas cultured in the presence of cytochalasin B also showed FN deposition at the cell-DM interface. However, when injured endothelia were cultured in the presence of colchicine, no reaction product was observed at the cell-DM interface, although it could be detected intracellularly within RER. Incubating the tissues in the presence of puromycin abolished all extracellular and intracellular staining. These results indicate that during wound repair, corneal endothelial cells produce fibronectin and deposit it upon Descemet's membrane by a mechanism that may be mediated by microtubules. 相似文献
33.
J. B. T. M. Roerdink 《Journal of mathematical biology》1989,27(3):309-319
In a previous paper (J. Math. Biol. 26, 199–215 (1988)) we calculated the mean and variance of the long-run geometric growth rate of a discrete-time population model with two age classes in a random environment. The formula which was used in that paper as the starting point for the computation of the variance represents only the contribution of the one-period variances. Here we supplement these results by a calculation of the exact variance. All qualitative conclusions reached before are unaffected. 相似文献
34.
Realized heritabilities were estimated for the character of phenthoate resistance in two local strains of the diamond-back moth, Plutella xylostella L. (Lepidoptera: Yponomeutidae), by performing artificial laboratory selection for resistance and susceptibility to phenthoate. Heritability estimates indicated that such traits are moderately heritable (
2=0.42 and 0.41 in the resistant selection and
2=0.31 and 0.21 in the susceptible selection), and give an experimental basis accounting for rapid evolutionary changes of phenthoate resistance observed in field populations of this insect.The observed changes in variances of phenthoate susceptibility are discussed in relation to the additive genetic variance eliminated by directional selection. The explanation stresses the importance on the underlying genetic system.
Résumé L'héritabilité de la résistance au phenthoate obtenue chez deux souches locales de P. xylostella L. (Lep.; Yponomeutidae) a été calculée en procédant au laboratoire à des sélections artificielles pour la résistance et pour la sensibilité à cet insecticide. Les calculs de l'héritabilité ont montré que de tels caractères sont moyennement héritables ( 2=0,42 et 0,41 lors de la sélection pour la résistance, et 2=0,31 et 0,21 lors de la sélection pour la sensibilité), et ont fourni la base expérimentale rendant compte des changements évolutifs rapides observés pour la résistance au phenthoate chez des populations naturelles de cet insecte.Les changements observés de la variance de la sensibilité au phenthoate sont discutés en fonction de la variance génétique additive éliminée par la sélection orientée. L'explication insiste sur l'importance du système génétique souligné.相似文献
35.
Kunio Yonemasu Takako Sasaki Yoshiko Dohi Charles M. Lapière Betty Nusgens 《生物化学与生物物理学报:疾病的分子基础》1990,1096(1):47-51
C1q, a collagen-like complement protein, was purified from the serum of a ddermatosparactic calf which lacks procollagen N-terminal proteinase (pN-proteinase). The specific hemolytic activity of the serum Clq from the dermatosparactic animal was identical to that of C1q from a normal calf. Gel-filtration of serum from dermatosparactic calf, on Sepharose 6B, showed the presence of C1q-antigenic material at only one position which was identical to the elution position of normal bovine C1q. No differdence, under dissociating conditions, could be seen in the size of the chains of C1q in specific immunoprecipitates isolated from the sera of dermatosparactic and normal animals, as judged by polyacrylamidegel electrophoresis (PAGE) in the presence of sodium dodecyl sulfate (SDS). The C1q from the dermatosparactic animal showed the same N-terminal amino acid and typtic-digest peptide pattern on HPLC as C1q from the normal calf. These results strongly suggest that pN-proteinase is not involved in the extracellular processing of C1q. 相似文献
36.
37.
电刺激猫小脑顶核对动脉血压和肾交感神经放电的影响 总被引:1,自引:0,他引:1
在38只麻醉及人工呼吸的猫,观察到电刺激小脑顶核嘴侧部能引起动脉血压显著升高;肾交感神经放电于刺激期间显著增加。去缓冲神经对刺激顶核所引起的血压反应的幅度和肾交感神经放电均无明显影响,但可明显延长血压反应升高相以及血压恢复期的时间。静脉注射氯庄定引起血压降低、心率减慢及肾交感神经放电的抑制,并能减弱刺激顶核引起的血压反应,但增强了刺激顶核引起的肾神经放电的变化。电解损毁延髓腹外侧面引起血压降低及肾交感神经放电的抑制,然而无论单侧还是双侧损毁延髓腹外侧面都不能阻断刺激顶核所引起的血压和肾交感神经放电的反应。以上结果表明,电刺激顶核能引起明显的心血管反应,其反应的下行性通路可能不通过延髓腹外侧面。 相似文献
38.
Chromium is an essential trace element and is associated with some biological pathways, especially with glucose tolerance.
For these reasons, we decided to determine the concentration of chromium in two sets of Brazilian medicinal plants. The first
group consisted of plants that are considered as antidiabetic, whereas the second included plants that do not have this therapeutic
property. The concentration of chromium was determined by flameless atomic absorption. All the plants analyzed contain chromium
in the normal range for this element, but the hypoglycemic plants contain more chromium than the others (1–4 μg/g compared
to 0.5–1.5 μg/g). 相似文献
39.
Organisation and expression of a wound/ripening-related small multigene family from tomato 总被引:3,自引:0,他引:3
cDNA clones derived from a ripe tomato fruit cDNA library were used to investigate changes in the abundance of specific mRNAs in ripening fruit and wounded leaves. mRNAs related to one cDNA clone (pTOM 13) were expressed in both situations. This clone was used to identify homologous sequences in a tomato genomic library. Three groups of related clones that hybridised to the pTOM 13 cDNA insert were identified and subcloned into plasmid vectors. Genomic Southern analysis of tomato DNA using gene-specific DNA fragments isolated from the subcloned DNAs indicated that all pTOM 13 closely related genes had been isolated. RNA dot blot analysis with these DNA fragments as probes indicated differential expression of this small multigene family in leaves and fruit. 相似文献
40.