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931.
Fossil plants of the Chingandzha flora were studied from volcanogenic sediments of the Chingandzha and Rond formations on
the northern coast of the Sea of Okhotsk. It was concluded that all platanaceous leaves earlier described in this flora as
different taxa belong to one highly variable species, Pseudoprotophyllum cordatum Samyl. emend. Shczepetov et Golovneva. 相似文献
932.
In the experiments on redox potential measurement for a series of identical samples of purified and presettled water it was found that the response to ultraviolet irradiation varies appreciably within a few days after treatment, including stepwise changes. In a few hours after exposure, leading to a higher content of reactive oxygen species as compared with the equilibrium values, long-term changes including variations in redox potential and optical system parameters are recorded in water and diluted aqueous media. We propose a heuristic organization model of the water-gas system with an increased content of reactive oxygen species. 相似文献
933.
The combination of alpha interferon and vinblastine has been reported to yield a response rate of 30-40% in previously untreated patients with metastatic renal cell carcinoma. This combination was given to nine patients with advanced metastatic renal carcinoma after they failed or relapsed on alpha-interferon alone, to attempt to evaluate the role of vinblastine in this combination. Neither complete nor partial response was observed. Two patients had disease stabilization for two and seven months. Our preliminary results suggest that vinblastine did not add to the efficacy of interferon in this group of patients. 相似文献
934.
935.
936.
B P Sharonov I V Churilova 《Biochemical and biophysical research communications》1992,189(2):1129-1135
Bovine superoxide dismutase (SOD) was inactivated during incubation with phorbol myristate acetate-stimulated neutrophils. In addition, stimulated neutrophils were able to disrupt the SOD structure. Inactivation and structural damage were dependent on the action of hypochlorous acid, an oxidant generated by the myeloperoxidase-hydrogen peroxide-chloride system of neutrophils. Incubation of SOD with stimulated neutrophils lead to long-wavelength fluorescence (ex, 350 nm; em, 450 nm) and the appearance of new structural forms with other isoelectric points. These additional forms possess catalytic activity. Generation of catalytically active new forms of SOD demonstrates the inaccessibility of the active centre of SOD to hypochlorite and may be a reason for the successful application of SOD during anti-inflammatory therapy. 相似文献
937.
A A Shandra L S Godlevski? A M Mazarati R S Vast'ianov 《Biulleten' eksperimental'no? biologii i meditsiny》1992,113(3):236-239
It is shown that both intracerebral and intraperitoneal neurotropin administration resulted in a decrease of seizure susceptibility of preliminary picrotoxin--kindled rats. On the other hand, neurotropin did not change the course of kindling development. Under conditions of acute picrotoxin--induced seizures it was observed that preliminary cycloheximide (protein-synthesis blocker) administration abolished anticonvulsant properties of neurotropin. It is concluded that anticonvulsant effects of neurotropin are realized via modulation of endogenous peptides synthesis and, in particular, cerulein. 相似文献
938.
G. N. Mishina G. V. Serezhkina T. V. Avetisyan A. S. Ryabchenko L. N. Andreev 《Biology Bulletin》2001,28(4):354-360
A cytophysiological study was carried out of the functional status of a halo as a response of the host plant to contact with a powdery mildew pathogen. Interactions of the powdery mildew causative agents with barley, wheat, wheat–wheat-grass hybrids, wheat-aegilops lines, and aegilops with different genotypic resistance lead to the expression of haloes during pathogens, which are induced by infection pegs of the primary growth tubes, appressoria, and hyphal lobes. Haloes are visualized using cytochemical reactions to proteins and scanning electron microscopy. The observed differences in the size of haloes and intensity of their staining (uniform or zonal) are related, to a great extent, to individual reactions of the plant cell at the penetration site and, to a lesser extent, to the level of genotypic resistance. An analysis of electron microscopy and cytochemistry studies suggests that the halo as a physiologically active zone is localized at the level of the plant cell plasmalemma. Active taxis of the cell organelles to the site of infection during the formation of a halo suggests that some kind of informational signals to changes in the cell metabolism are spread from the halo zone, which lead to compatible or incompatible interactions. 相似文献
939.
Roberta L. Millstein 《Journal of the history of biology》2008,41(2):339-367
Biologists and philosophers have been extremely pessimistic about the possibility of demonstrating random drift in nature,
particularly when it comes to distinguishing random drift from natural selection. However, examination of a historical case
– Maxime Lamotte’s study of natural populations of the land snail, Cepaea nemoralis in the 1950s – shows that while some pessimism is warranted, it has been overstated. Indeed, by describing a unique signature
for drift and showing that this signature obtained in the populations under study, Lamotte was able to make a good case for
a significant role for␣drift. It may be difficult to disentangle the causes of drift and selection acting in a population,
but it is not (always) impossible. 相似文献
940.
Phytochrome A regulates red-light induction of phototropic enhancement in Arabidopsis. 总被引:20,自引:5,他引:15
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Phytochrome A (phyA) and phytochrome B photoreceptors have distinct roles in the regulation of plant growth and development. Studies using specific photomorphogenic mutants and transgenic plants overexpressing phytochrome have supported an evolving picture in which phyA and phytochrome B are responsive to continuous far-red and red light, respectively. Photomorphogenic mutants of Arabidopsis thaliana that had been selected for their inability to respond to continuous irradiance conditions were tested for their ability to carry out red-light-induced enhancement of phototropism, which is an inductive phytochrome response. We conclude that phyA is the primary photoreceptor regulating this response and provide evidence suggesting that a common regulatory domain in the phyA polypeptide functions for both high-irradiance and inductive phytochrome responses. 相似文献