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1.
Transforming growth factor-beta (TGF-beta) induces a marked decrease in adhesion of MG-63 human osteosarcoma cells to laminin-coated surfaces, but does not significantly alter adhesion to fibronectin- or collagen-coated surfaces. We provide evidence that this effect is due to a switch in the repertoire of cell adhesion receptors in response to TGF-beta. MG-63 cells express high levels of alpha 3 beta 1-integrin, which is a polyspecific laminin/collagen/fibronectin receptor, and low levels of alpha 2 beta 1- and alpha 5 beta 1-integrins, which are collagen and fibronectin receptors, respectively. No other integrins of the beta 1-class could be detected in MG-63 cells. Treatment with TGF-beta 1 induces a marked (approximately 60%) decrease in the level of expression of alpha 3-integrin subunit mRNA and protein and a concomitant 8-fold increase in alpha 2-subunit expression. These responses become maximal 7-12 h after addition of TGF-beta 1 to the cells. Expression of alpha 5- and beta 1-integrin subunits also increases in response to TGF-beta 1, but to a lesser extent than alpha 2-subunit expression. Thus, as a result of TGF-beta action, the alpha 2 beta 1-collagen and alpha 5 beta 1-fibronectin receptors replace the alpha 3 beta 1-laminin/collagen/fibronectin receptor as the predominant integrins of the beta 1-class in MG-63 cells. These results suggest that one of the effects of TGF-beta is to modify the adhesive behavior of certain tumor cells by changing the binding specificity of the complement of integrins that they express. 相似文献
2.
P. Heino G. Sandman V. Lång K. Nordin E. T. Palva 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1990,79(6):801-806
Summary Abscisic acid (ABA) has been implicated as a regulatory factor in plant cold acclimation. In the present work, the cold-acclimation properties of an ABA-deficient mutant (aba) of Arabidopsis thaliana (L.) Heynh. were analyzed. The mutant had apparently lost its capability to cold acclimate: the freezing tolerance of the mutant was not increased by low temperature treatment but stayed at the level of the nonacclimated wild type. The mutational defect could be complemented by the addition of exogenous ABA to the growth medium, restoring freezing tolerance close to the wild-type level. This suggests that ABA might have a central regulatory function in the development of freezing tolerance in plants. Cold acclimation has been previously correlated to the induction of a specific set of proteins that have been suggested to have a role in freezing tolerance. However, these proteins were also induced in the aba mutant by low temperature treatment. 相似文献
3.
The effects of source and caging on the valve movements of the freshwater unionid mussel (Anodonta anatina) were studied in a reciprocal transplant experiment between a lake and its outflow. Caged mussels were moved and compared with those remaining in their natural environment on the lake or river bottom. At both sites, the mussels from the study site and the transplanted mussels from the opposite site were monitored simultaneously. In river the averaged weighted valve openness was higher and the number of valve movements was lower than in the lake. The mussels monitored in the lake exhibited a diurnal rhythm of valve movements which differed between the lake-bottom and the caged animals. Caging was found to increase valve openness. On the other hand, little variation appeared in valve openness between caged and bottom animals in the river, where diurnal rhythms were almost nonexistent. In the river the valve movements were more variable in respect to time than in the lake. 相似文献
4.
5.
M. Heino V. Kaitala E. Ranta J. Lindstr?m 《Proceedings. Biological sciences / The Royal Society》1997,264(1381):481-486
We explore extinction rates using a spatially arranged set of subpopulations obeying Ricker dynamics. The population system is subjected to dispersal of individuals among the subpopulations as well as to local and global disturbances. We observe a tight positive correlation between global extinction rate and the level of synchrony in dynamics among thesubpopulations. Global disturbances and to a lesser extent, migration, are capable of synchronizing the temporal dynamics of the subpopulations over a rather wide span of the population growth rate r. Local noise decreases synchrony, as does increasing distance among the subpopulations. Synchrony also levels off with increasing r: in the chaotic region, subpopulations almost invariably behave asynchronously. We conclude that it is asynchrony that reduces the probability of global extinctions, not chaos as such: chaos is a special case only. The relationship between global extinction rate, synchronous dynamics and population growth rate is robust to changes in dispersal rates and ranges. 相似文献
6.
Smooth-pursuit eye movements were recorded in two rhesus monkeys in order to compare the influence of structured visual backgrounds
on smooth-pursuit initiation, steady-state pursuit and pursuit termination. Different target trajectories were used in order
to study smooth-pursuit initiation and termination. The influence of visual backgrounds on pursuit initiation was characterized
by recording ocular responses elicited by step-ramp target displacements starting from straight ahead. Pursuit termination
was characterized by analysing the transition from steady-state smooth-pursuit to fixation when a centripetally directed target
ramp was terminated by a small target step in the direction of the ramp as soon as the target had come close to the straightahead
position. The quantification of steady-state pursuit was based on ocular responses elicited by either paradigm. In accordance
with previous work, we found that the onset of smooth-pursuit eye movements was delayed and initial eye acceleration reduced
in the presence of a structured visual background. Likewise, mean eye velocity during steady-state pursuit was reduced by
structured visual backgrounds. However, neither the latency nor the time course of smooth-pursuit termination was altered
when the homogeneous background was replaced by a structured visual background. The lack of sensitivity of pursuit termination
to the presence of visual structured backgrounds supports a previous contention that pursuit termination is mediated by a
process which is different from the ones mediating smooth-pursuit initiation and steady-state pursuit. The absence of any
noticeable effect of structured backgrounds on pursuit termination suggests that at least the fast component of the optokinetic
reflex is suppressed during pursuit termination.
Received: 24 October 1994/Accepted in revised form: 16 December 1994 相似文献
7.
A rapid and efficient method to enrich SAF-protein from scrapie brains of hamsters 总被引:20,自引:0,他引:20
Scrapie hamster brains contain at least 5–10 g of scrapie-associated fibrils (SAF) per brain as estimated by the amount of its major constituent, a protein of about 26 000 daltons (SAF-protein). It can be extracted efficiently by a 10% solution of sarkosyl and can be enriched by differentia] centrifugation and buffer extraction. Scrapie infectivity, SAF, and SAF-protein copurify. 相似文献
8.
In fodder yeast production from sulphite spent liquor, sulphur dioxide is well-known as a yeast poison. The present paper deals with the detailed influence of sulphur dioxide. The experimental work was done in a laboratory fermenter under technical conditions. A decrease in biomass yield, and an increase in oxygen consumption, caused by increasing carbon dioxide production, were found. During the fermentation, there is no destruction of the carbonyl-bisulphite adduct to be observed. Sulphur dioxide has no influence on the crude protein content of yeast cells, and there is also no influence on the morphology of cells. 相似文献
9.
Henrik Gislason Jeremy Collie Brian R. MacKenzie Anders Nielsen Maria de Fatima Borges Teresa Bottari Corina Chaves Andrey V. Dolgov Jakov Dul
i Daniel Duplisea Heino O. Fock Didier Gascuel Luís Gil de Sola Jan Geert Hiddink Remment ter Hofstede Igor Isajlovi Jnas Pll Jonasson Ole Jrgensen Kristjn Kristinsson Gudrun Marteinsdottir Hicham Masski Sanja Mati‐Skoko Mark R. Payne Melita Peharda Jakup Reinert Jn Slmundsson Cristina Silva Lilja Stefansdottir Francisco Velasco Nedo Vrgo
《Global Ecology and Biogeography》2020,29(5):842-856
10.
Jun Wang Jiancheng Hu Tao Tang Jani Heino Xiaoming Jiang Zhengfei Li Zhicai Xie 《Ecology and evolution》2020,10(2):692-704
Identifying seasonal shifts in community assembly for multiple biological groups is important to help enhance our understanding of their ecological dynamics. However, such knowledge on lotic assemblages is still limited. In this study, we used biological traits and functional diversity indices in association with null model analyses to detect seasonal shifts in the community assembly mechanisms of lotic macroinvertebrates and diatoms in an unregulated subtropical river in China. We found that functional composition and functional diversity (FRic, FEve, FDis, MNN, and SDNN) showed seasonal variation for macroinvertebrate and diatom assemblages. Null models suggested that environmental filtering, competitive exclusion, and neutral process were all important community assembly mechanisms for both biological groups. However, environmental filtering had a stronger effect on spring macroinvertebrate assemblages than autumn assemblages, but the effect on diatom assemblages was the same in both seasons. Moreover, macroinvertebrate and diatom assemblages were shaped by different environmental factors. Macroinvertebrates were filtered mainly by substrate types, velocity, and CODMn, while diatoms were mainly shaped by altitude, substrate types, and water quality. Therefore, our study showed (a) that different biological assemblages in a river system presented similarities and differences in community assembly mechanisms, (b) that multiple processes play important roles in maintaining benthic community structure, and (c) that these patterns and underlying mechanisms are seasonally variable. Thus, we highlight the importance of exploring the community assembly mechanisms of multiple biological groups, especially in different seasons, as this is crucial to improve the understanding of river community changes and their responses to environmental degradation. 相似文献