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121.
De novo root formation in thin cell layers of tobacco: changes in free and bound polyamines 总被引:4,自引:0,他引:4
Patrizia Torrigiani Maria Maddalena Altamura Francesca Capitani Donatella Serafini-Fracassini Nello Bagni 《Physiologia plantarum》1989,77(3):294-301
Thin cell layers excised from tobacco ( Nicotiana tabacum L. cv. Samsun) stem internodes, with an appropriate exogenous hormonal balance, were able to form a greater number of roots, and in a larger percentage of the explants (93%) than when they were excised from pedicels (40%). The developmental sequence of root formation and explant growth were followed by histological analysis. Free and bound [trichloroacetic acid (TCA)-soluble and -insoluble] putrescine and spermidine increased in the explants, particularly when root meristemoids appeared. These meristemoids originated in the superficial (day 6 in culture) or deep (days 10–11) layers and inside the newly formed callus (day 25). At those times, TCA-soluble and, to a lesser extent, TCA-insoluble bound putrescine predominated over the other polyamines. Spermine was always present in trace amounts. Polyamines decreased again when root and callus formation was completed (day 30). The involvement of these three classes of polyamines (free, TCA-soluble and -insoluble) in morphogenic processes is discussed. 相似文献
122.
J Chodakowska B Wocial H Ignatowska-Switalska K Knypl E Brym E Czerniewska J Wac?awek-Maczkowska E Jab?ońska-Skwiecińska D Drygieniec W Januszewicz 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1989,44(12-13):297-300
An effect of enalapril maleate on the activity of renin-angiotensin-aldosterone system and sympathetic reactivity, erythrocyte prostaglandin and sodium levels as well as blood beta-endorphin was investigated in 28 patients with the essential arterial blood hypertension. It was found that enalapril maleate significantly increased plasma renin activity, decreased plasma norepinephrine and its 24-hour excretion, and decreased erythrocyte beta-endorphin and sodium levels. Blood epinephrine and aldosterone levels and their daily excretion remained unchanged similarly to prostaglandins. The above results suggest that a decrease in sympathetic system activity and intracellular sodium concentration may play a role in the hypotensive action of enalapril maleate related to the inhibition of angiotensin II formation. 相似文献
123.
Pregnenolone, dehydroepiandrosterone, and their sulfate and fatty acid esters in the rat brain 总被引:6,自引:1,他引:5
The rat brain contains large amounts of pregnenolone (P) and dehydroepiandrosterone (D) arising from local biosynthetic pathways. We have devised a procedure for the measurement of both "neurosteroids" either unconjugated or released from their sulfate (S) or fatty acid (L) esters. The measurements were performed at the acrophase of the circadian variation of neurosteroids, and confirmed the large accumulation of P (25 +/- 8 ng/g, mean +/- SD) and of PS (19 +/- 6 ng/g) and DS (2.1 +/- 0.5 ng/g) in the brain of adult male rats. We found that fatty acid esters constitute the major species of neurosteroids in brain (PL 46 +/- 14, and DL 36 +/- 7 ng/g, in adult males). The levels of P and DS were increased by daily injection of vehicle to intact males, whereas castration, without or with testosterone or estradiol supplementation (2 mg daily for 7 days), did not produce a significant change of neurosteroids concentrations. Measurements of neurosteroids had not been previously reported in cyclic females. The levels of P, PL, and DS were identical in proestrous females and in intact males, whereas PS (26 +/- 6 ng/g) and DL (50 +/- 16 ng/g) were increased in females. Compared to proestrous females, diestrous females had lower levels of PS (19 +/- 6 ng/g), DS (1.7 +/- 0.4 ng/g), and PL (43 +/- 19 ng/g). These differences suggested a modulatory role of ovarian secretions on the metabolism of neurosteroids. 相似文献
124.
125.
Maria C. Nieto Elizabeth S. Song Denise McKinney Minnie McMillan Robert S. Goodenow 《Immunogenetics》1989,30(5):361-369
We have analyzed changes in the antigenicity of major histocompatibility complex class I molecules resulting from the association
of human beta-2 micro-globulin (B2m) with the mouse class I heavy chain. In particular, the H-2Ld molecule exhibited enhanced crossreactivity for the 34-1-2 monoclonal antibody. In order to assess the nature of this structural
alteration induced by human B2m, we utilized H-2 class I hybrid molecules in the mapping of the 34-1-2 determinant to the
helical region of the alpha-1 domain. H-2Ld class I hybrid molecules were then used to establish the importance of the alpha-2 and- 3 domains in the observed increase
of 34-1-2 cross-reactivity following exchange with human B2m. The H-2Ld hybrids suggest that alterations in interdomain contact are responsible for enhanced 34-1-2 cross-reactivity on the H-2Ld molecule. It is likely that this alteration arises through changes in class I conformation at regions of the molecule distant
from points of contact between B2m and the class I molecule. This suggests that perturbations induced by association of human
B2m with H-2Ld can affect the conformation of the alpha-1 and- 2 superdomain. That class I antigenic determinants are altered by the association
of human B2m with mouse class I further suggests that the class I molecule is structurally flexible and may reflect the ability
of the class I molecule to bind and present a vast array of disparate peptides to the T-cell receptor. 相似文献
126.
Hydrolysis of sunflower oil by means of hydrophobic membrane with lipolytic activity 总被引:3,自引:0,他引:3
Magdalena Rucka Bozena Turkiewicz Maria Tomaszewska Nikodem Chlubek 《Biotechnology letters》1989,11(3):167-172
Polytetrafluoroethylene (PTFE) membranes of different porosity were used for lipase from Rhizopus immobilization. The immobilized enzyme applied to sunflower oil hydrolysis achieved the activity of 1228 U/m2 of the membrane area and the half-life time was calculated to be 7 days. 相似文献
127.
L. M. Popescu C. Cernescu I. I. Moraru St. N. Constantinescu F. Baltã M. Manciulea E. Brãiloiu L. Buzilã 《Bioscience reports》1989,9(5):531-539
A monospecific inhibitory antibody directed to phospholipase C (phosphoinositidase C) blocked the antiviral effect of human interferons alpha and beta when tested on human quiescent fibroblasts challenged with the vesicular stomatitis virus. This action was due to specific inhibition of polyphosphoinositide hydrolysis because (a) the F(ab)2 fragment of the antibody molecule was also inhibitory; (b) excess antibodies directed to phospholipase A2 and to a phosphatidylcholine-preferring phospholipase C did not have any inhibitory effect, and (c) the combination of 12-O-tetradecanoylphorbol-acetate and calcium ionophore A23187 had an interferon-like antiviral effect which was not influenced by the inhibitory anti-phospholipase C antibodies. To avoid an interferon-like effect due to induction of interferon by second messengers, Vero cells, which lack interferon biosynthesis, were also used. Liposomes containing inositol 1,4,5-triphosphate and 1-oleoyl-2-acetyl-rac-glycerol protected Vero cells against the infection with the vesicular stomatitis virus. These results taken together show that phosphoinositide-derived second messengers are involved in triggering the antiviral effect of interferons alpha and beta. 相似文献
128.
Giorgio Di Marco Nicola D'Ambrosio Maria T. Giardi Angelo Massacci Domenico Tricoli 《Photosynthesis research》1989,21(2):117-122
We investigated several photosynthetic parameters of a virescent mutant of durum wheat and of its wild-type. Electron transport rate to ferricyanide was the same in the two genotypes when expressed on leaf area basis while O2 evolution of the leaf tissue in saturating light and CO2 was slightly higher in the yellow genotype. RuBPCase was also slightly higher. Quantum yield per absorbed light was similar in the two genotypes. P700 and Cyt f were less concentrated in the mutant while PS II was only marginally lower. The light response curve of CO2 assimilation indicated higher level of photosynthesis of the mutant in high light, which corresponded to a lower non-photochemical quenching compared to the wild-type. It is concluded that the reaction centres, cyt f and chlorophyll are not limiting factors of electron transport in wheat seedlings and that electron transport capacity is in excess with respect to that needed for driving photosynthesis. Since the differences in photosynthesis reflect differences in RuBPCase activity, it is suggested that this enzyme limits photosynthesis in wheat seedlings also at high light intensities.Abbreviations cyt f
cytochrome f
- chl
chlorophyll
- PS II
photosystem II
- Pnmax
maximum photosynthesis
- RuBCase
Ribulose, 1-5,bisphosphate carboxylase 相似文献
129.
Tobacco cells are sensitive to bleomycin and phleomycin. The Tn5 and the Streptoalloteichus hindustanus (Sh) bleomycin resistance (Ble) genes conferring resistance to these antibiotics have each been inserted into two plant expression vectors. They are flanked by the nopaline synthase (nos) or the cauliflower mosaic virus (CaMV) 35S promoters on one side, and by the nos polyadenylation signal on the other. These four chimaeric genes were introduced into the binary transformation vector pGA 492, which were thereafter mobilized into Agrobacterium tumefaciens strain LBA 4404. The resulting strains were used to transform Nicotiana tabacum cv. Xanthi nc using the leaf disc transformation procedure. In all cases, phleomycin- and bleomycin-resistant tobacco plants were regenerated from transformed cells under selective conditions; however the highest frequency of rooted plants was obtained when transformation was carried out with the Sh Ble gene under the control of the 35S promoter. Phleomycin resistance was stably transmitted to sexual offspring as a dominant nuclear trait as confirmed by Southern blotting. 相似文献
130.
Summary
dl-Malic acid grown cells of Candida sphaerica (anamorph of Kluyveromyces marxianus) formed a saturable transport system that mediated accumulative transport of l(-)malic acid with the following kinetic parameters at pH 5.0: V
max, 0.44 nmol l(-)malate·s-1 per milligram dry weight; K
m
,0.1 mM
l(-)malate. Initial uptake of the acid was accompanied by disappearance of extracellular protons, the rates of which followed Michaelis-Menten kinetics as a function of the acid concentration. Variation with extracellular pH of the K
m
values, calculated either as the concentrations of anions or of undissociated acid, pointed to anions as the transported form. Furthermore, accumulated free acid suffered rapid efflux after the addition of the protonophore carbonylcyanide-M-chlorophenyl-hydrazone (CCCP). These results suggested that the transport system was a dicarboxylate-proton symporter. The system was inducible and was subject to glucose repression. Succinic, fumaric, -ketoglutaric, oxaloacetic and d-malic acid, but not maleic, malonic, oxalic nor l(+)-tartaric acid, apparently used the same transport system since they acted as competitive inhibitors of l(-)malic acid transport and induced proton movements that followed Michaelis-Menten kinetics. Experiments with glucose-repressed cells showed that undissociated dicarboxylic acid (measured with labelled succinic acid) entered the cells slowly by simple diffusion. The permeability of the cells for undissociated acid increased exponentially with pH, the diffusion constant increasing 100-fold between pH 3.5 and 6.0. 相似文献