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11.
12.
Sylvain Meloche 《Journal of cellular physiology》1995,163(3):577-588
Mitogen-activated protein (MAP) kinases are serine/threonine kinases that are rapidly activated in response to mitogenic stimuli. Here we examined the enzymatic activity and phosphorylation state of the individual p44mapk and p42mapk isoforms during early G1 and late G1 phase of the mammalian cell cycle. Release of fibroblast cells from early G1 block was accompanied by a rapid rise in the myelin basic protein (MBP) kinase activity of p44mapk and p42mapk, which declined slowly over several hours to reach negligible values as cells enter S phase. When cells were released from late G1 block, the activity of p44mapk and p42mapk increased transiently, and then rapidly declined to baseline values during G1 to S phase transition. Cells released at the G1/S boundary in a medium lacking growth factors entered S phase in the complete absence of MAP kinase activity. Unlike MAP kinases, the histone H1 kinase activity of p33cdk2 was elevated in late G1-arrested cells and continued to increase during S phase entry. The enzymatic activation of p44mapk and p42mapk in both early G1 and late G1 phase was accompanied by an increase in the phosphothreonine and phosphotyrosine content of the proteins. These findings suggest that the sustained activation of MAP kinases during G1 progression and their inactivation at the G1/S transition are two regulatory processes involved in the mitogenic response to growth factors. © 1995 Wiley-Liss, Inc. 相似文献
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The effect of mutual shading on the root/shoot ratio and on the number of nodal roots of maize was studied. Plants of two varieties (Dea and LG2281) were grown in individual pots of 9 L, at three plant densities: 7.5, 11 and 15 plants m–2. A control experiment was carried out in order to study if root growth was affected by the small size of the pots. Maize plants (cv Dea) were grown at a low plant density (7.5 plants m–2) in pots of two different volumes (9 and 25 L respectively). In both experiments plants were watered every two hours with a nutrient solution. Some plants were sampled at five dates in the main experiment and the following data were recorded: foliar stage; root, stem and leaf dry weight; number of root primordia and number of emerged roots per phytomer. The final sampling date occurred at silking.Results of the control experiment showed that the root biomass was lower in small pots but the number of nodal roots per phytomer was not affected.Results of the main experiment showed that the total plant biomass and the root/shoot ratio were lower at high plant density. The number of emerged roots was strongly reduced on the upper phytomer (P8). This reduction was mainly due to a lower percentage of root primordia which elongated. A proposed interpretation is that the number of roots which emerge on upper phytomers is controlled by carbohydrate availability. 相似文献
15.
Sylvain Biquand Véronique Biquand-Guyot Ahmed Boug Jean-Pierre Gautier 《International journal of primatology》1992,13(5):533-543
Papio hamadryas was surveyed throughout its range in Saudi Arabia and was observed at altitudes ranging from 0 to 2300 m.
Wild populations occur along the whole range of altitude, while commensal populations are only found above 850 m altitude.
No variation in group size was found with altitude. Comparison of wild and commensal populations showed the following. (1)
Their composition in terms of age and sex classes, overall adult sex ratios, and group size does not significantly differ.
(2) Groups of both populations include, in similar proportions, three types of parties: one-male units (>70%), two-male units
(>13%), and a few other units of variable composition. (3) The mean size of commensal parties is significantly larger than
in the wild population; specifically one-male units are larger in the commensal population due to a larger number of females
per male. Thus, female distribution in commensal groups is more inequitable than that in wild groups. (4) Finally, the number
of females included in two-male units increases with altitude. These differences are discussed in terms of food availability
and predator pressure and are compared with results obtained on other Arabian and Ethiopian populations. 相似文献
16.
The distribution ofPapio hamadryas in Saudi Arabia: Ecological correlates and human influence 总被引:1,自引:0,他引:1
Sylvain Biquand Véronique Biquand-Guyot Ahmed Boug Jean-Pierre Gautier 《International journal of primatology》1992,13(3):223-243
We describe the distribution ofPapio hamadryas in Saudi Arabia in relation to ecological constraints and recent changes in human activities and land use. Baboons are present
only in the Sarawat and southern Hijaz mountains, which border the Red Sea in the southwestern region of the country. Our
distribution data confirms that their range, described as of 1981, should be extended 200 km northward, from 21°40N (Taif)
to 23°20N (Al Akhal). This new limit of range is not due to recent deployment of the baboons, but instead corrects inaccurate
surveys by previous reporters. Ecological factors that affect baboon distribution include low annual rainfall (less than 100
mm per yr), which limits baboon range in the north and east, and the absence of suitable sleeping cliffs in the coastal plain,
which limits their range in the west. Relative abundance is discussed in relation to vegetation and predator distribution.
Human influence is also significant: commensal troops persist near urban centers, while agricultural development reduces baboon
numbers in some regions. Habitat characteristics are discussed in comparison with similar data on the range of hamadryas in
Ethiopia. 相似文献
17.
Sylvain P. Terver Ronald M. Constine John Csongradi Richard Kleinman Eugene E. Bleck 《The Western journal of medicine》1979,131(2):98-103
A retrospective analysis of 62 patients with 78 congenital dislocations of the hip (CDH) referred to Children''s Hospital at Stanford was done to ascertain whether CDH was being diagnosed as early as had been thought possible and whether various treatments were effective. In this series there were a substantial number of cases of CDH that were not diagnosed within the first 48 hours of life. At Children''s Hospital the Pavlik harness was the most effective form of treatment of congenital dislocations of the hip in the perinatal period. 相似文献
18.
19.
Silvina Dayer Laurent J Lamarque Rgis Burlett Giovanni Bortolami Sylvain Delzon Jos C Herrera Herv Cochard Gregory A Gambetta 《Plant physiology》2022,190(3):1673
Climate change is challenging the resilience of grapevine (Vitis), one of the most important crops worldwide. Adapting viticulture to a hotter and drier future will require a multifaceted approach including the breeding of more drought-tolerant genotypes. In this study, we focused on plant hydraulics as a multi-trait system that allows the plant to maintain hydraulic integrity and gas exchange rates longer under drought. We quantified a broad range of drought-related traits within and across Vitis species, created in silico libraries of trait combinations, and then identified drought tolerant trait syndromes. By modeling the maintenance of hydraulic integrity of current cultivars and the drought tolerant trait syndromes, we identified elite ideotypes that increased the amount of time they could experience drought without leaf hydraulic failure. Generally, elites exhibited a trait syndrome with lower stomatal conductance, earlier stomatal closure, and a larger hydraulic safety margin. We demonstrated that, when compared with current cultivars, elite ideotypes have the potential to decrease the risk of hydraulic failure across wine regions under future climate scenarios. This study reveals the syndrome of traits that can be leveraged to protect grapevine from experiencing hydraulic failure under drought and increase drought tolerance.This article quantifies the diversity of hydraulic traits across grapevine genotypes and reveals the trait combinations that can help increase grapevine drought tolerance. 相似文献
20.
Facilitation in plant communities: the past, the present, and the future 总被引:24,自引:11,他引:24
Rob W. Brooker Fernando T. Maestre Ragan M. Callaway Christopher L. Lortie Lohengrin A. Cavieres Georges Kunstler Pierre Liancourt Katja Tielbörger Justin M. J. Travis Fabien Anthelme Cristina Armas Lluis Coll Emmanuel Corcket Sylvain Delzon Estelle Forey Zaal Kikvidze Johan Olofsson Francisco Pugnaire Constanza L. Quiroz Patrick Saccone Katja Schiffers Merav Seifan Blaize Touzard Richard Michalet 《Journal of Ecology》2008,96(1):18-34