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排序方式: 共有348条查询结果,搜索用时 15 毫秒
1.
Kazimierz S. Kasprzak Michael P. Waalkes Lionel A. Poirier 《Biological trace element research》1987,13(1):253-273
Interactions between the physiologically essential metals calcium, magnesium, and zinc and the carcinogenic metals nickel
and cadmium were investigated to help elucidate the mechanisms of action of the carcinogenic metals. Bioassay studies revealed
several significant findings, including: (1) the ability of magnesium and calcium to inhibit nickel-induced elevation of pulmonary
adenoma incidence in strain A mice; (2) the ability of magnesium, but not of calcium, to prevent cadmium-induced subcutaneous
sarcoma formation; and (3) the ability of magnesium, but not of calcium, to inhibit nickel-induced muscle tumor formation.
Biochemical studies indicated a direct relationship between the antitumorigenic potential of magnesium and the capacity of
this metal to: (1) inhibit nickel and cadmium uptake by the target tissues in vivo; (2) inhibit nickel-induced disturbances
in DNA synthesis in vivo; (3) inhibit nuclear and cytosolic uptake of nickel by the target tissue cells in vivo; and (4) inhibit
nickel and cadmium binding to DNA in vitro. Calcium, which in most cases did not prevent carcinogenesis, had no consistent
influence on the uptake of carcinogenic metals or their biochemical effects in the target tissues. Magnesium and zinc, but
not calcium, were also found to attenuate the acute toxic effects of nickel, indicating a possible correlation between prevention
of acute effects and reduction in tumorigenicity. Zinc, which antagonizes cadmium tumorigenicity in the rat testis, was found
to reduce markedly cadmium uptake into isolated testicular interstitial cells. Also, zinc was found to inhibit strongly cadmium
binding to DNA in vitro. 相似文献
2.
Kazimierz Browicz 《Plant Systematics and Evolution》1989,162(1-4):305-314
The Euxinian and the Hyrcanian floristic province are analysed in respect to their trees and shrubs. These provinces mark the southern limit of the Euro-Siberian Region in SW. Asia. Mesophyllic forests dominate; they are deciduous, but there is a substantial component of evergreen shrubs in the understorey. Characteristics species frequently have a relic nature. Species lists and some exemplary distribution maps are presented for the Euxinian and the Hyrcanian element, both with endemic and more wide-spread species, including the characteristic Euxine-Hyrcanian group. 相似文献
3.
Kazimierz Szczepanek 《Aerobiologia》1994,10(1):65-70
Summary During 1982 – 1991 pollen deposition in the centre of Cracow (southern Poland) was investigated using the gravimetric method. 32 taxa of the 84 identified were taken into consideration, and nearly all of them can be allergenic. The beginning of mass pollen fall was observed in the second decade of March, and the third decade of September saw the completion of the yearly cycle of abundant appearance of pollen in the aeroplankton. Tree pollen dominates quantitatively. 相似文献
4.
Edward Bańkowski Wiktor Rzeczycki Henry K. F. Nowak Kazimierz J. Jodczyk 《Molecular and cellular biochemistry》1978,20(2):77-83
Summary Rat kidney fibroblasts transformed with SV-40 produce in vitro a significantly lower amount of hydroxyproline-containing material which is collagenase sensitive as compared to normal cells. In contrast to normal fibroblast cultures, no collagenous material was found by histochemical methods in intercellular spaces of transformed cultures. 相似文献
5.
6.
Mateusz Koselski Piotr Wasko Kamila Kupisz Kazimierz Trebacz 《Physiologia plantarum》2019,167(3):433-446
Microelectrode measurements carried out on leaf cells from Physcomitrella patens revealed that a sudden temperature drop and application of menthol evoked two types of different‐shaped membrane potential changes. Cold stimulation evoked spike‐type responses. Menthol depolarized the cell membrane with different rates. When it reached above 1 mV s?1, the full response was recorded. Characteristic for the full responses was also a few‐minute plateau of the membrane potential recorded after depolarization. The influence of inhibitors of calcium channels (5 mM Gd3+), potassium channels (5 mM Ba2+), chloride channels (200 μM Zn2+, 50 μM niflumic acid) and proton pumps (10 μM DES), an activator of calcium release from intracellular stores (Sr2+), calcium chelation (by 400 μM EGTA) and phytohormones (50 μM auxin, 50 μM abscisic acid (ABA), 500 μM salicylic acid) on cold‐ and menthol‐evoked responses was tested. Both responses are different in respect to the ion mechanism: cold‐evoked depolarizations were influenced by Ba2+ and DES; in turn, menthol‐evoked potential changes were most effectively blocked by Zn2+. Moreover, the effectiveness of menthol in generation of full responses was reduced after administration of auxin or ABA, i.e. phytohormones known for their participation in responses to cold and regulation of proton pumps. The effects of DES indicated that one of the main conditions for generation of menthol‐evoked responses is inhibition of the proton pump activity. Our results indicate that perception of cold and menthol by plants proceeds in different ways due to the differences in ionic mechanism and hormone dependence of cold‐ and menthol‐evoked responses. 相似文献
7.
Michal Lorenz Brygida Bisikirska Beata Hanus-Lorenz Kazimierz Strzalka Aleksander F. Sikorski 《Cell biology international》1995,19(7):625-632
It was found either in Western-blot analysis or in indirect immunofluorescence microscopy that cells of the alga Chlamydomonas reinhardtii contain polypeptides cross-reacting with antibodies directed against red blood cell spectrin. The protein could also be detected by immunoprecipitation with anti-spectrin antibodies. C. reinhardtii cells contain distinct polypeptide chains reacting with antibodies directed against either α- or β-spectrin subunits. This protein was extracted from the cells with low ionic strength solution but was not with nonionic detergent. 相似文献
8.
Kruk Jerzy Burda Kveta Schmid Georg H. Radunz Alfons Strzałka Kazimierz 《Photosynthesis research》1998,58(2):203-209
We have found that in petroleum-ether extracted tobacco thylakoids, plastoquinone A (PQ-A) and plastoquinone C (PQ-C) had similar efficiency in restoration of oxygen-evolving activity, while plastoquinone B (PQ-B), which is a fatty acid ester of PQ-C, was about 50% less effective. This indicates that apart from PQ-A, PQ-C and to a smaller extent PQ-B may function as electron acceptors of Photosystem II (PS II). The DCMU inhibition curves for PQ-C and PQ-B were biphasic and an initial slow decline was followed by a sharp decrease in oxygen evolution yield with a 50% inhibition (I50) at 0.25 M DCMU. In the case of PQ-A (I50 = 0.20 M DCMU), the activity decreased gradually without the sharp transition. The corresponding inhibition curve for unextracted thylakoids, where all the native prenylquinones are present, shows an intermediate shape between PQ-A and PQ-C but with a higher I50, equal to 0.32 M, suggesting that the contribution of PQ-C as an electron acceptor of Photosystem II might be significant in thylakoid membranes with natural prenyllipid composition. -Tocopherol quinone showed no activity in the restoration of oxygen evolution in extracted thylakoids, indicating that it cannot accept electrons from PS II. The fatty acid composition of PQ-B isolated from maple leaves showed a high degree of saturated fatty acids like myristic and palmitic acid, and its unique composition indicates that it is a natural component of the thylakoid membrane. 相似文献
9.
Characteristics of action potentials in Helianthus annuus 总被引:1,自引:0,他引:1
Tadeusz Zawadzki Eric Davies Halina Dziubinska Kazimierz Trebacz 《Physiologia plantarum》1991,83(4):601-604
The action potentials induced by nondamaging electrical stimuli in 16- to 22-day-old plants of Helianthus annuus were examined. Typical recordings are presented. Mean values of their amplitudes and conduction velocities in the stem, the strength-duration relation, the 'all-or-none' law and the refractory periods have been determined. The amplitude and velocity of propagation were essentially identical in the upward and downward direction, but greater in the upper than in the lower half. In 'electrically active' plants, the rheobase value is 2 V, the minimum period for stimulation is 1.8 s. and the chronaxie 2.3 s. It is noted that the excitability level between similar plants on the same day and in the same plant on different days is highly variable and undergoes periodic changes. 相似文献
10.
Mysliwa-Kurdziel Beata; Barthelemy Xavier; Strzalka Kazimierz; Franck Fabrice 《Plant & cell physiology》1997,38(11):1187-1196
The relationship between functional and structural aspects ofPSII formation during greening of etiolated barley leaves hasbeen investigated using fluorescence lifetime measurements,fluorescence kinetics analysis and analysis of chlorophyll-proteincomplexes by IEF-PAGE. Two phases of different character couldbe distinguished in the course of the greening process in dark-grownplants. An early phase covering the first 34 h afterthe onset of illumination and a late phase covering the subsequentgreening. During the first phase the formation of PSII reactioncenters and their minor antenna components was observed as manifestedby the IEF-PAGE polypeptide pattern. This was accompanied byshortening of the slow and middle components of the fluorescencelifetime, as well as by the rapid drop in the amplitude of theslow component. A room temperature emission band at 676 nm wasassociated with uncoupled chlorophyll and with the slow fluorescencelifetime component during the first hours of greening. Duringthe late greening phase peripheral light-harvesting complexesof PSII were formed concomitantly to an increase in lifetimeand amplitude of the fast component and to a further decreasein the lifetime of the middle component. The gradual increasein PSII complexity during both phases of greening was also manifestedby changes in proportion and kinetic properties of PSII 相似文献