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Concentration is one factor that is known to determine how metabolic gases influence the growth and secondary metabolism of plant tissues in culture. How actual gas bioavailability influences these processes has not been studied despite its potential importance in specialized applications. A simple model system, soybean [Glycine max (L.) Merr. cv. Acme] callus culture, was selected for experiments because exogenous cytokinin (6-benzylaminopurine; BAP) elicits two types of responses: (1) enhanced callus proliferation, and (2) rapid induction of the isoflavonoid daidzein (7,4′-dihydroxyisoflavone). Synthetic atmospheres supplying metabolic gases with higher or lower bioavailability than in air were created by replacing the nitrogen moiety in standard air with either helium or argon, respectively. Callus was cultured on agar or in liquid shake cultures according to standard procedures. At an optimal cytokinin concentration for stimulation of callus proliferation, 4.4 × 10−7 M BAP, increased diffusion rates for the metabolic gases resulted in greater weight gain in agar cultures. Weight gain was 11% higher for He-treated and 39% lower for Ar-treated cultures than for the nitrogen control. In contrast, there was no significant effect of metabolic gas diffusion rate on daidzein production in either agar or liquid cultures. Apart from the potential application of these synthetic atmospheres for enhancing plant tissue culture growth, they may have unique value for the space program as an effective way of replicating the gas exchange limitations posed for plants by microgravity (Ar atmosphere), and as a countermeasure for this limitation (He atmosphere). 相似文献
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血管内皮作为血管壁的衬里,参与调节组织器官的局部血流和机体其它生理进程,在维持血管完整性和内环境稳定中发挥关键作用。内皮细胞对包括重力在内的机械应力刺激极为敏感,重力变化可对其形态和功能构成不同程度的影响。研究发现,失重/模拟失重通过诱导内皮细胞细胞骨架重塑、质膜caveolae重布,使其合成分泌血管活性物质、炎性介质的能力以及细胞表面粘附分子表达发生改变,这些分子变化又对内皮细胞的生长、增殖、凋亡、迁移和血管生成等具有精细调控作用。本文综合评述了失重/模拟失重对内皮细胞功能的影响,同时围绕文献报道中一些尚存争议的观点进行了适当讨论。 相似文献
4.
Gravity and light effects on the circadian clock of a desert beetle,Trigonoscelis gigas 总被引:1,自引:0,他引:1
Hoban-Higgins TM Alpatov AM Wassmer GT Rietveld WJ Fuller CA 《Journal of insect physiology》2003,49(7):671-675
Circadian function is affected by exposure to altered ambient force environments. Under non-earth gravitational fields, both basic features of circadian rhythms and the expression of the clock responsible for these rhythms are altered. We examined the activity rhythm of the tenebrionid beetle, Trigonoscelis gigas, in conditions of microgravity (microG; spaceflight), earth's gravity (1 G) and 2 G (centrifugation). Data were recorded under a light-dark cycle (LD), constant light (LL), and constant darkness (DD). Free-running period (tau) was significantly affected by both the gravitational field and ambient light intensity. In DD, tau was longer under 2 G than under either 1 G or microG. In addition, tauLL was significantly different from tauDD under microG and 1 G, but not under 2 G. 相似文献
5.
Lentil root statoliths reach a stable state in microgravity 总被引:3,自引:0,他引:3
The kinetics of the movement of statoliths in gravity-perceiving root cap cells of Lens culinaris L. and the force responsible for it have been analysed under 1 g and under microgravity conditions (S/MM-03 mission of Spacehab 1996). At the beginning of the experiment in space, the amyloplasts
were grouped at the distal pole of the statocytes by a root-tip-directed 1-g centrifugal acceleration. The seedlings were then placed in microgravity for increasing periods of time (13, 29, 46 or 122 min)
and chemically fixed. During the first 29 min of microgravity there were local displacements (mean velocity: 0.154 μm min−1) of some amyloplasts (first at the front of the group and then at the rear). Nevertheless, the group of amyloplasts tended
to reconstitute. After 122 min in microgravity the bulk of amyloplasts had almost reached the proximal pole where further
movement was blocked by the nucleus. After a longer period in microgravity (4 h; experiment carried out 1994 during the IML
2 mission) the statoliths reached a stable position due to the fact that they were stopped by the nucleus. The position was
similar to that observed in roots grown continuously in microgravity. Treatment with cytochalasin D (CD) did not stop the
movement of the amyloplasts but slowed down the velocity of their displacement (0.019 μm min−1). Initial movement patterns were the same as in control roots in water. Comparisons of mean velocities of amyloplast movements
in roots in space and in inverted roots on earth showed that the force responsible for the movement in microgravity (Fc) was about 86% less (Fc = 0.016 pN) than the gravity force (Fg = 0.11 pN). Treatment with CD reduced Fc by two-thirds. The apparent viscosity of the statocyte cytoplasm was found to be 1 Pa s or 3.3 Pa s for control roots or
CD treated roots, respectively. Brownian motion or elastic forces due to endoplasmic reticulum membranes do not cause the
movement of the amyloplasts in microgravity. It is concluded that the force transporting the statoliths is caused by the actomyosin
system.
Received: 22 March 1999 / Accepted: 18 December 1999 相似文献
6.
Gravity independence of seed-to-seed cycling in Brassica rapa 总被引:2,自引:0,他引:2
Musgrave ME Kuang A Xiao Y Stout SC Bingham GE Briarty LG Levenskikh MA Sychev VN Podolski IG 《Planta》2000,210(3):400-406
Growth of higher plants in the microgravity environment of orbital platforms has been problematic. Plants typically developed
more slowly in space and often failed at the reproductive phase. Short-duration experiments on the Space Shuttle showed that
early stages in the reproductive process could occur normally in microgravity, so we sought a long-duration opportunity to
test gravity's role throughout the complete life cycle. During a 122-d opportunity on the Mir space station, full life cycles
were completed in microgravity with Brassica rapa L. in a series of three experiments in the Svet greenhouse. Plant material was preserved in space by chemical fixation, freezing,
and drying, and then compared to material preserved in the same way during a high-fidelity ground control. At sampling times
13 d after planting, plants on Mir were the same size and had the same number of flower buds as ground control plants. Following
hand-pollination of the flowers by the astronaut, siliques formed. In microgravity, siliques ripened basipetally and contained
smaller seeds with less than 20% of the cotyledon cells found in the seeds harvested from the ground control. Cytochemical
localization of storage reserves in the mature embryos showed that starch was retained in the spaceflight material, whereas
protein and lipid were the primary storage reserves in the ground control seeds. While these successful seed-to-seed cycles
show that gravity is not absolutely required for any step in the plant life cycle, seed quality in Brassica is compromised by development in microgravity.
Received: 3 August 1999 / Accepted: 27 August 1999 相似文献
7.
P. Ritz K. J. Acheson P. Gachon L. Vico J. J. Bernard C. Alexandre B. Beaufrère 《European journal of applied physiology and occupational physiology》1998,78(4):308-314
Microgravity-induced changes in body composition (decrease in muscle mass and increase in fat mass) and energy metabolism
were studied in seven healthy male subjects during a 42-day bed-rest in a head-down tilt (HDT) position. Resting energy expenditure
(REE), fat and glucose oxidation were estimated by indirect calorimetry on days 0, +8 and +40 of the HDT period. Assessments
were performed both in post-absorptive conditions and following two identical test meals given at 3-h intervals. Body composition
(dual x-ray absorptiometry) was measured on days 0, +27, +42. Mean post-absorptive lipid oxidation decreased from 53 (SEM
8) mg · min−1 (day 0) to 32 (SEM 10) mg · min−1 (day 8, P=0.04) and 36 (SEM 8) mg · min−1 (day 40, P=0.06). Mean post-absorptive glucose oxidation rose from 126 (SEM 15) mg · min−1 (day 0) to 164 (SEM 14) mg · min−1 (day 8, P=0.04) and 160 (SEM 20) mg · min−1 (day 40, P=0.07). Mean fat-free mass (FFM) decreased between days 0 and 42 [58.0 (SEM 1.8) kg and 55.3 (SEM 1.7) kg, P<0.01] while fat mass increased without reaching statistical significance. The mean REE decreased from 1688 (SEM 50) kcal · day−1 to 1589 (SEM 42) kcal · day−1 (P=0.056). Changes in REE were accounted for by changes in FFM. Mean energy intake decreased from 2532 (SEM 43) kcal · day−1 to 2237 (SEM 50) kcal · day−1 (day 40, P<0.01) with only a minor decrease in the proportion of fat. We concluded that changes in fat oxidation at the whole body level
can be found during HDT experiments. These changes were related to the decrease in FFM and could have promoted positive fat
balance hence an increase in fat mass.
Accepted: 26 March 1998 相似文献
8.
Cucumis sativus L. cv Burpee Hybrid II) grown under conditions of normal gravity, microgravity, and simulated microgravity (clinostat rotation).
Seeds were germinated on the ground, in clinostats and on board the space shuttle (STS-95) for 1–2 days, frozen and subsequently
examined for their stage of development, degree of hook formation, number of pegs formed, and peg morphology. The frequency
of peg formation in space-grown seedlings was found to be nearly identical to that of clinostat-grown seedlings and to differ
from that of seedlings germinated under normal gravity only in a minority of cases; ˜6% of the seedlings formed two pegs and
nearly 2% of the seedlings lacked pegs, whereas such abnormalities did not occur in ground controls. The degree of hook formation
was found to be less pronounced for space-grown seedlings, compared to clinostat-grown seedlings, indicating a greater degree
of decoupling between peg formation and hook formation in space. Nonetheless, in all seedlings having single pegs and a hook,
the peg was found to be positioned correctly on the inside of the hook, showing that there is coordinate development even
in microgravity environments. Peg morphologies were altered in space-grown samples, with the pegs having a blunt appearance
and many pegs showing alterations in expansion, with the peg extending out over the edges of the seed coat and downwards.
These phenotypes were not observed in clinostat or ground-grown seedlings.
Received 12 October 1999/ Accepted in revised form 18 October 1999 相似文献
9.
Hideyuki Takahashi Hidetoshi Mizuno Motoshi Kamada Nobuharu Fujii Atsushi Higashitani Shigeki Kamigaichi Sachiko Aizawa Chiaki Mukai Toru Shimazu Keiji Fukui Masamichi Yamashita 《Journal of plant research》1999,112(4):497-505
peg , on the transition zone between hypocotyl and root. Our spaceflight experiment verified that the lateral positioning of a
peg in cucumber seedlings is modified by gravity. It has been suggested that auxin plays an important role in the gravity-controlled
positioning of a peg on the ground. Furthermore, cucumber seedlings grown in microgravity developed a number of the lateral
roots that grew towards the water-containing substrate in the culture vessel, whereas on the ground they oriented perpendicular
to the primary root growing down. The response of the lateral roots in microgravity was successfully mimicked by clinorotation
of cucumber seedlings on the three dimensional clinostat. However, this bending response of the lateral roots was observed
only in an aeroponic culture of the seedlings but not in solid medium. We considered the response of the lateral roots in
microgravity and on clinostat as positive hydrotropism that could easily be interfered by gravitropism on the ground. This
system with cucumber seedlings is thus a useful model of spaceflight experiment for the study of the gravimorphogenesis, root
hydrotropism and their interaction.
Received 13 September 1999/ Accepted in revised form 12 October 1999 相似文献
10.
We previously reported that the space environment consisting of microgravity and space radiation induced an increased level of p53 protein, a tumor suppressor gene product, in rat skin. Here, we report the increase of p53 protein in the muscles of rats that traveled into space. Rats were divided into three groups. The first group remained on earth (VC), and did not show any change in p53 protein level. The second group made a 14-day flight into space on the Second Spacelab Life Science (SLS-2) Mission (F). The third group was experimentally subjected to the same kinds of stress as those in the second group without making a space flight (SC). F and SC rats were sacrificed on day zero (F-0, SC-0) and day nine (F-9, SC-9) after return from space. F-0 rats showed a 1.5-fold increase in p53 protein level compared with that of SC-0 rats, whereas, F-9 rats showed a 1.35-fold increase in p53 protein compared with that of SC-9 rats. These results suggest that the accumulation of cellular p53 protein induced by space environments occurs not only in rat skin cells, but also in rat muscle cells. 相似文献