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11.
Piotr H. Ma?eckiWojciech Rypniewski Maciej SzymańskiJan Barciszewski Arne Meyer 《Biochimica et Biophysica Acta - Proteins and Proteomics》2012,1824(2):334-338
The crystal structure of the ribosome inhibiting protein Mistletoe Lectin I (ML-I) derived from the European mistletoe, Viscum album, in complex with kinetin has been refined at 2.7 Å resolution. Suitably large crystals of ML-I were obtained applying the counter diffusion method using the Gel Tube R Crystallization Kit (GT-R) on board the Russian Service Module on the international space station ISS within the GCF mission No. 6, arranged by the Japanese aerospace exploration agency (JAXA). Hexagonal bi-pyramidal crystals were grown during three months under microgravity. Before data collection the crystals were soaked in a saturated solution of kinetin and diffraction data to 2.7 Å were collected using synchrotron radiation and cryogenic techniques. The atomic model was refined and revealed a single kinetin molecule in the ribosome inactivation site of ML-I. The complex demonstrates the feasibility of mistletoe to bind plant hormones out of the host regulation system as part of a self protection mechanism. 相似文献
12.
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
13.
The major purpose of this spaceflight project was to investigate the starch-statolith hypothesis for gravity perception,
and a secondary goal was to study plant growth and development under spaceflight conditions. This research was based on our
ground studies of gravity perception in the wild type and three starch-deficient (one starchless and two reduced starch) mutants
of Arabidopsis thaliana (L.) Heynh. Dark-grown seedlings that developed in microgravity were given one of several (30 min, 60 min, or 90 min) 1-g stimuli by an on-board centrifuge, and additional controls for seedling development also were performed. These latter control
experiments included a morphological study of plants that developed in space in microgravity (F μg), in space on a centrifuge (F 1g), on the ground (G 1g), and on a rotating clinostat on the ground. Since elevated levels of ethylene were reported in the spacecraft atmosphere,
additional controls for morphology and gravitropism with added ethylene also were performed. While exogenous ethylene reduced
the absolute magnitude of the response in all four strains of Arabidopsis, this gas did not appear to change the relative graviresponsiveness among the strains. The relative response of hypocotyls
of microgravity-grown seedlings to the stimuli provided by the in-flight centrifuge was: wild type > starch-deficient mutants.
Although the protoplast pressure model for gravity perception cannot be excluded, these results are consistent with a statolith-based
model for perception in plants.
Received: 12 February 1999 / Accepted: 9 March 1999 相似文献
14.
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
15.
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
16.
Although biofilm formation is widely documented on Earth, it has not been demonstrated in the absence of gravity. To explore this possibility, Pseudomonas aeruginosa, suspended in sterile buffer, was flown in a commercial payload on space shuttle flight STS-95. During earth orbit, biofilm formation was induced by exposing the bacteria to sterile media through a 0.2-microm (pore size) polycarbonate membrane. Examination of these membranes by confocal microscopy revealed biofilms to be present and that these biofilms could persist in spite of vigorous agitation. These results represent the first report of biofilm formation under microgravity conditions. 相似文献
17.
18.
Prolonged exposure to microgravity has shown to have deleterious effects on the human spine, indicated by low back pain during spaceflight and increased incidence of post-spaceflight herniated nucleus pulposus. We examined the effect of microgravity on biomechanical properties of lumbar and caudal discs from mice having been on 15-day shuttle mission STS-131. Sixteen C57BL/C mice (spaceflight group, n=8; ground-based control group, n=8) were sacrificed immediately after spaceflight. Physiological disc height (PDH) was measured in situ, and compressive creep tests were performed to parameterize biomechanical properties into endplate permeability (k), nuclear swelling pressure strain dependence (D), and annular viscoelasticity (G). For caudal discs, the spaceflight group exhibited 32% lower PDH, 70% lower D and crept more compared to the control mice (p=0.03). For lumbar discs, neither PDH nor D was significantly different between murine groups. Initial modulus, osmotic pressure, k and G for lumbar and caudal discs did not appear influenced by microgravity (p>0.05). Decreases in both PDH and D suggest prolonged microgravity effectively diminished biomechanical properties of caudal discs. By contrast, differences were not noted for lumbar discs. This potentially deleterious interaction between prolonged weightlessness and differential ranges of motion along the spine may underlie the increased cervical versus lumbar disc herniation rates observed among astronauts. 相似文献
19.
Abstract Free‐running circadian rhythms of locomotor activity of Tenebrionid beetles Trigonoscelis gigas Reitt., taken from the Turkmenian sand desert, were monitored in DD. The effects of microgravity (μG) ‐11 days in space flight aboard the Russian BION‐10 “COSMOS”; satellite, and of 2G hypergravity ‐ seven days on a centrifuge, were determined. Two kinds of effects were found. In stable 2‐peak records, there was a moderate decrease of τ in μG and an increase of τ in 2G, both of about 0.3 hr. In unstable records, alterations of gravity caused drastic deviations of τ and ?. Remarkably, two peaks of the activity rhythm, which are supposed to be controlled by separate oscillators, responded to gravity transitions in different ways. Gravity effects on the circadian system could be explained from a direct effect on the oscillator(s) itself or from a feed‐back by altered locomotion to the pacemaker. Thus, for the first time the gravity dependence of a free‐running circadian rhythm was proved in a combination of real space flight and centrifuge experiments. 相似文献
20.
Ishihara A Yamashiro J Matsumoto A Higashibata A Ishioka N Shimazu T Ohira Y 《Neurochemical research》2006,31(3):411-415
The cell body sizes and succinate dehydrogenase (SDH) activities of motoneurons in the dorsolateral region of the ventral horn at the cervical and lumbar segments in the rat spinal cord were determined following 9 days of spaceflight with or without 10 days of recovery on Earth. The motoneurons were divided into three types based on their cell body sizes; small-, medium-, and large-sized motoneurons. In control rats, there was no difference in the cell body size or SDH activity of small- and large-sized motoneurons between the cervical and lumbar segments. The SDH activity of medium-sized motoneurons in control rats was higher in the lumbar segment than in the cervical segment, while the cell body sizes of medium-sized motoneurons were identical. The SDH activity of medium-sized motoneurons in the lumbar segment decreased to a level similar to that in the cervical segment of control rats following spaceflight. In addition, the decreased SDH activity of medium-sized motoneurons persisted for at least 10 days of recovery on Earth. It is concluded that spaceflight selectively affects the SDH activity of medium-sized motoneurons in the lumbar segment of the spinal cord, which presumably innervate skeletal muscles having an antigravity function. 相似文献