Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Weightlessness Simulation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,423 records · Page 79Linked to original sources
PubMed2000

[Effects of IAA and stimulated microgravity on formation of adventitious roots of Chinese cabbage].

Under the induction of indole-3-acetic acid (IAA), adventitious roots were differentiated on hypocotyl segments derived from seedlings of Chinese cabbage (Brassica campestris spp. pekinensis). IAA at concentration of 0.4-1.0 mg/L in solid MS medium incited many adventitious roots on hypocotyl segments. The earliest anatomic changes were observed on cut surface of hypocotyl segments under optical microscope 24 hours after IAA treatment: cytoplasmic and nuclear density became higher in a few of parenchytmatous cells adjacent to phloem in tissue of pericycle, followed by cell divisions. Lately, the dividing cells expanded and developed into root primordium from which root cap was differentiated. After five days, most roots protruded through hypocotyl cortex and appeared just below the cut surface. The rooting capacity of the segments derived from three regions of each hypocotyl was different. High level of IAA modified the polarity of root formation on segment inserted upside down and sucrose increased the function of IAA. Additionally, microgravity did not significantly change the rooting polarity under the condition of stimulated microgravity, but it increased the competence of explants to IAA treatment. The results presented here provided an experimental system for further investigation of molecular events associated with adventitious root initiation.

Brassica↗
PubMed1977

Nutations of sunflower seedlings on tilted clinostats.

The kinetics of hypocotyl nutations in Helianthus annuus L. were measured on plants which were rotated on clinostats with axes of rotation inclined at various angles, alpha, away from the vertical. The g-force component acting in the direction of the plant axis was taken as g cos alpha. The average period and average amplitude of nutation were constant for all such axially directed g-forces between 1.0 and 0.2 g (vertical to about 80 degrees inclination). On the horizontal clinostat (90 degrees inclination) nutation was neither initiated nor sustained. The g-force just sufficient fully to activate nutational oscillations should be sought in the range of the g-force parameter, 0 < g < 0.2.

Gravitation↗
PubMed2001

Tissue engineering in space.

The purpose of this paper is to present the status of that part of the [Microgravity Application Program] project related to the study of cartilage formation from pig chondrocytes. The work carried out so far followed two lines: (i) chondrocytes were incubated for up to three weeks in the RPM; (ii) a module developed for in-vitro cartilage formation will be tested in a sounding rocket flight (MASER 9, November 2001).

Animals↗
PubMed2001

The ultrastructure of Chlorella mitochondria and their energetic state under altered gravity.

This study looks at the predominance of the participation of the mitochondria in the energy supply of Chlorella cells. The localization of the Mg(2+)-activated ATPases were studied during the culture development under the geterotrophic conditions, and with an investigation of the mitochndria ultrastructure at the various stages of the culture development under clinorotation. It was found that the activity level of this enzyme is one main indice of the energy state of these organelles.

Ca(2+) Mg(2+)-ATPase↗
PubMed2001

Clinorotation [correction of Clinoratation] effects on the structural-functional response in potato minitubers.

It is established that high plant growth and development in microgravity occurred normal. However, the change of plant growth rate is accompanied by the change of carbohydrate metabolism in photosynthesized cells (Kordyum, 1997). The decrease of starch grain size in chloroplasts and the decrease of content cellulose in cell wall were revealed (Sytnik et al., 1984; Nedukha, 1996). The change carbohydrate metabolism in photosynthesized organs could influence on the growth of underground organs and content of storage carbohydrates in these organs. Therefore, the aim of our study was to investigate the long-term clinorotation influence on the formation, structure of potato minitubers and content of starch and sugars in minitubers.

Acceleration↗
PubMed2001

Adenilate pool and thylakoid ATP-synthase content in pea leaves under clinorotation.

It is known that plant resistance to stress factors is connected with energy metabolism. The energy stored in the process of photophosphorylation in the form of ATP is used then to support respiration, transpiration, organic compound synthesis, growth and development as well as to restore cell structure after its damage under extremal environmental factors. Transformation of light energy into chemical energy of ATP is catalyzed by thylakoid membrane enzymatic complex of ATPsynthase-CF1CF0. Its activity and amount in the thylakoid membrane depends on plant growth conditions. The aim of this work was investigation of clinorotation effect on light-induced dynamics of adenyl nucleotides (AMP, ADP and ATP) and estimation of CF1CF0 content in thylakoids of pea leaves grown under slow clinorotation and vertical control.

Adenine Nucleotides↗
PubMed2001

Nucleolar structure and function under clinorotation.

A nucleolus is the dynamic part of a cell nucleus where rDNA transcription, rRNA precursor processing and transport are proceeding. Investigations of the influence of microgravity and clinorotation on the structure and function of nucleolus began more than thirty years ago but, unfortunately, now there are only some articles concerning the nucleolar peculiarities in altered gravity. Available data about alterations of nucleolar morphology and function under the influence of high and low temperature, hypoxia and UV-microbeam irradiation allow us to put intent attention to the study of the nucleolus reactions on clinorotation. Therefore, the aim of our work was to investigate the ultrastructural organization and functional activity of nucleoli in Lepidium sativum root meristematic cells under clinorotation in order to understand whether a nucleolus can react to gravity.

Cell Nucleolus↗
PubMed2001

Influence of clinorotation on some parameters of photosynthetic apparatus.

This study aimed to examine the electron transport rates in the thylakoids, isolated from leaves of pea plants grown under clinorotation and in vertical control, to measure the chlorophyll a/b (Chl a/b) ratio in such thylakoids and in photosystem I (PSI) particles isolated from them, to elucidate if there are any differences in changes of PS II activity in thylakoids and Chl a/b ratio in PS I particles under phosphorylation of polypeptides of thylakoid pigment-protein complexes.

Chlorophyll↗
PubMed2001

Effect of clinorotation on growth and pigment biosynthesis in etiolated barley plants.

Altered gravity conditions (hyper- or hypogravity) leads to changes in metabolic processes in living organisms (Kordyum, 1997). One important subject of plant space biology is the investigation of the effects of microgravity conditions on the development of the photosynthetic apparatus. The impact of microgravity on the photosynthetic apparatus of plants has been studied in a number of space-flight experiments. Particularly, the Chl (a+b) content and Chl a/b ratio were determined in several experiments, however the results did not allow understanding how microgravity affects pigment apparatus of the plants since presented contradictory results [Laurinavichius et al. 1984; Volovik et al, 1999]. To elucidate how clinorotation affects pigment apparatus formation in etiolated plants, we studied morphological characteristics and pigment (chlorophyll and carotenoids) biosynthesis in the first period of greening of barley plants.

Carotenoids↗
PubMed2001

Is there resetting of central venous pressure in microgravity?

In the early phase of the Space Shuttle program, NASA flight surgeons implemented a fluid-loading countermeasure in which astronauts were instructed to ingest eight 1-g salt tablets with 960 ml of water approximately 2 hours prior to reentry from space. This fluid loading regimen was intended to enhance orthostatic tolerance by replacing circulating plasma volume reduced during the space mission. Unfortunately, fluid loading failed to replace plasma volume in groundbased experiments and has proven minimally effective as a countermeasure against post-spaceflight orthostatic intolerance. In addition to the reduction of plasma volume, central venous pressure (CVP) is reduced during exposure to actual and groundbased analogs of microgravity. In the present study, we hypothesized that the reduction in CVP due to exposure to microgravity represents a resetting of the CVP operating point to a lower threshold. A lower CVP 'setpoint' might explain the failure of fluid loading to restore plasma volume. In order to test this hypothesis, we conducted an investigation in which we administered an acute volume load (stimulus) and measured responses in CVP, plasma volume and renal functions. If our hypothesis is true, we would expect the elevation in CVP induced by saline infusion to return to its pre-infusion levels in both HDT and upright control conditions despite lower vascular volume during HDT. In contrast to previous experiments, our approach is novel in that it provides information on alterations in CVP and vascular volume during HDT that are necessary for interpretation of the proposed CVP operating point resetting hypothesis.

Aerospace Medicine↗
PubMed2001

Average magnitude of heartbeat fluctuations in healthy subjects after exposure to 4 hours head down bed rest.

Orthostatic intolerance, induced by microgravity exposure, has been hypothesized to be related to a disorder of the autonomic control of the cardiovascular system. Non-invasive measurement of Heart Rate Variability (HRV) have been used as a valuable tool to characterize the ability of the autonomic system to modulate the cardiovascular function by analyzing the spontaneous fluctuations of arterial pressure and heart period on a beat-to-beat basis. Concerning this, conflicting results have been reported on the heart rate and blood pressure variability responses during exposure to microG. These differences seem to be due to different experimental designes used. Moreover, the different behavior of normal subjects in response to orthostatic stress after HD, i.e. Symptomatic (S) or Non Symptomatic (NS), could play some role in producing these discrepancies [correction of dicrepancies]. In this study we suggest the analysis of "magnitude" or "volatility" as a new method to study HRV variability. The volatility is a measure of the beat-to-beat excursion capability of the heart, regardless to its direction (positive or negative): the higher the volatility, the greater the excursion. The aim of the present study was to examine R-R volatility before and after 4 hours of HD -6 degrees in normal subjects.

Adult↗