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At least 505 records · Page 28Linked to original sources
PubMed1973

Behavioral regulation of gravity: schedule effects under escape-avoidance procedures.

Squirrel monkeys were restrained in a centrifuge capsule and trained to escape and avoid increases in artificial gravity. During escape-avoidance, lever responses reduced centrifugally simulated gravity or postponed scheduled increases. The effect of variation in the interval of postponement (equal to the duration of decrease produced by escape responses) was studied under a multiple schedule of four components. Three components were gravity escape-avoidance with postponement times of 20, 40, and 60 sec. The fourth component was extinction. Each component was associated with a different auditory stimulus. Rate of responding decreased with increasing postponement time and higher mean g-levels occurred at shorter intervals of postponement. Effects of the schedule parameter on response rate and mean g-level were similar to effects of the schedule on free-operant avoidance and on titration behavior maintained by shock.

Acceleration↗
PubMedDate not supplied

Development of a gravity-independent wastewater bioprocessor for advanced life support in space.

Operation of aerobic biological reactors in space is controlled by a number of challenging constraints, mainly stemming from mass transfer limitations and phase separation. Immobilized-cell packed-bed bioreactors, specially designed to function in the absence of gravity, offer a viable solution for the treatment of gray water generated in space stations and spacecrafts. A novel gravity-independent wastewater biological processor, capable of carbon oxidation and nitrification of high-strength aqueous waste streams, is presented. The system, consisting of a fully saturated pressurized packed bed and a membrane oxygenation module attached to an external recirculation loop, operated continuously for over one year. The system attained high carbon oxidation efficiencies often exceeding 90% and ammonia oxidation reaching approximately 60%. The oxygen supply module relies on hydrophobic, nonporous, oxygen selective membranes, in a shell and tube configuration, for transferring oxygen to the packed bed, while keeping the gaseous and liquid phases separated. This reactor configuration and operating mode render the system gravity-independent and suitable for space applications.

Bacteria, Aerobic↗
PubMed2004

[Natural history of flowers and gravity].

Many flowers have coevolved with their pollinator animals. Gravity has been one of selection pressure for the evolution of flowers. Gravity rules morphology and other features of flowers in many aspects. Pair matching between the flower and its specific pollinator is one of factors that determine the fitness of both sides. Evolution of flower morphology and its molecular basis are reviewed briefly. Anemophilous flowers are also under the influence of gravity. Shape and other features of entomophilous flowers have been highly diversed. Gravitropic response and its mechanism are summarized. Recent findings on gravitropism and phototropism of pistils and stamens are presented in this article.

Biological Evolution↗
PubMed1995

Behavioral reactions of the bat Carollia perspicillata to abrupt changes in gravity.

As part of an ongoing survey of the behavioral responses of vertebrates to abrupt changes in gravity, we report here on the reactions of bats (Carollia perspicillata) exposed to altered gravity during parabolic aircraft flight. In microgravity, mammals typically behave as if they were upside-down and exhibit repetitive righting reflexes, which often lead to long axis rolling. Since bats, however, normally rest upside-down, we hypothesized that they would not roll in microgravity. Only one of three specimens attempted to fly during microgravity. None rolled or performed any righting maneuvers. During periods of microgravity the bats partially extended their forearms but kept their wings folded and parallel to the body. Between parabolas and occasionally during microgravity the bats groomed themselves. Both the extended limbs and autogrooming may be stress responses to the novel stimulus of altered gravity. This is the first behavioral record of Chiroptera in microgravity.

Animals↗
PubMed1980

Relationship between the head's and the body's center of gravity during normal standing.

An apparatus for the recording of head movements has been developed and a basic study was performed to determine the normal values of head movement and to estimate the significance of the head movement as a righting reflex. The locus traced by the head closely resembled that of the center of gravity, though shorter in overall length. The head also moves more slowly than the center of gravity. The phase delay of its movement was observed during standing with eyes closed. These results suggest that the head's movement is controlled by the body's center of gravity and that the latter moves in order to keep the head steady, maintaining the eyes in normal position.

Adolescent↗
PubMed2000

Gravity separation of raw bovine milk: fat globule size distribution and fat content of milk fractions.

This project determined effects of time and temperature on changes of fat globule size distribution and fat content in milk fractions during gravity separation. Fresh raw bovine milk was gravity separated at 4 or 15 degrees C. After 2, 6, 12, and 48 h, seven fractions, from bottom fraction (F1) to top fraction (F7), were successively drained from a separation column. Higher temperature resulted in a faster rate of fat separation. Within 2 h, large fat globules had already moved to the top, and the volume mean diameter of F7 increased from 3.13 microm (without separation) to 3.48 and 3.64 microm, respectively, at 4 and 15 degrees C. In F7, there was little change in globule size distribution after 2 h, but fat content continued to increase with separation time. The fat content of F7 reached 26.6% after 48 h at 4 degrees C, achieving a 58.8% creaming capacity. For F1 to F6, longer separation time resulted in smaller fat globule sizes and lower fat contents, especially for F1. After 48 h at 4 degrees C, the volume mean diameter of F1 decreased from 3.23 microm (without separation) to 1.16 microm, and fat content decreased from 3.75% (without separation) to 0.20%. Gravity separation may have unique applications in the dairy industry today. Its simplicity makes it an effective procedure for small-scale dairy product manufacturers to produce milks with a range of fat contents without using a centrifugal cream separator.

Animals↗
PubMed1986

Execution of "ARC" experiment on space shuttle "Discovery" STS 51-C: some results on aggregation of red blood cells under zero gravity.

A project on "Aggregation of Red Cells" has been accepted by NASA in 1977. An automated slit-capillary photo-viscometer has been designed during 1979-1984, and its last version met NASA's space hazards requirements. The 'heart' of instrument is a set of two highly polished glass plates, spaced by a gap of 12.5 micrometers. An original drum-like infusion pump allows utilization of up to eight blood samples. During a sequential process, blood flows through the slit, and then stops to allow formation of aggregates. Micro- and macro-photography is carried out, and 500 photographs are obtained. Blood from normal donors and patients with history of ischaemic heart disease, colon cancer, juvenile-onset diabetes, hyperlipidaemia, etc., is anticoagulated and adjusted to haematocrit of 0.30 using native plasma. Samples are divided, and infused into the 'flight' and 'ground' instruments. Prior to experiment temp. is 5 degrees C; temp. during experiment is 25 degrees C. Experiments took place on 24-25 January 1985, on the middeck of space shuttle 'Discovery'. Subsequent results showed that red blood cells do not change shape under zero gravity; that aggregation of red cells does take place; that aggregates in pathologic blood show morphology of normal rouleaux under zero gravity, while identical blood shows clumps of red cells on the ground. The latter observation suggests that zero gravity might affect cell-to-cell interaction, and perhaps microstructure of the cell membrane. These aspects must remain however tentative till a confirmation by subsequent experiments can be obtained.

Adult↗
PubMed1979

Effects of different short-term dietary phosphorus levels on egg specific gravity and blood phosphorus of hens.

In the first 2 experiments, laying hens were fed a diet containing .30% phosphorus for a preliminary period of 3 days. At the beginning of the experimental period, hens were fed .30, .75, or 1.40% phosphorus with 3.50% calcium. Another group of hens was fed .75% phosphorus and 1.40% calcium. Specific gravity of the eggs and blood serum inorganic phosphorus were determined and compared with those from control hens continuously fed a diet containing .75% phosphorus and 3.50% calcium. Both high phosphorus and/or low calcium decreased the specific gravity of eggs and increased the serum phosphorus level. In experiment 2, hens were fed different levels of phosphorus at different times of the day. Birds receiving 1.40% phosphorus between 0700 and 0930 hr and .30% phosphorus between 0930 and 2000 hr (Treatment 2) laid eggs with higher specific gravity than hens fed .30% phosphorus between 0700 and 0930 hr and 1.40% phosphorus between 0930 and 2000 hr (Treatment 3). there was no further improvement in egg shell quality over that from hens fed .75% phosphorus for both time periods (0700 to 2000 hr). In both experiments it was apparent that the dietary phosphorus level affected egg shell quality.

Animals↗
PubMed1993

[Changes in the utricular otoconia of the chick embryo developed under 2G-gravity].

Whether or not vestibular adaptation occurs upon exposure to altered gravity is an important human problem. Studies have been performed to ascertain whether morphological changes in vestibular organs occur in animal models upon exposure to microgravity. On the other hand, the morphological changes which occur in vestibular organs under hypergravity have not yet been fully elucidated and morphological changes in the otoconia of the chick embryo exposed to hypergravity during the embryonic period remain to be thoroughly examined. The purpose of this paper is to clarify the effects of hypergravity on vestibular organs, especially its effects on otoconial formation in the developing chick embryo. Thus, we designed an apparatus which creates artificial gravity, creating approximately 2G gravity by means of centrifugation. The utricular macula was chosen for study because it can be prepared for examination with a minimum of dissection artifacts. The data presented show that morphological changes were confined to otoconial size alterations according to scanning electron microscopic observations. Giant otoconia were observed along the marginal zones of utricle .

Animals↗
PubMed1999

[The use of microfluorimetric analysis for the studies of the influence of changed gravity on isolated lymphocytes in the spleen of the mouse].

Effects of simulated changed gravity on isolated splenetic lymphocytes of mouse were evaluated with the microfluorimetic technique enabling observation of probe fluorescence in individual cells. It was stated that 5 and 60 min of clinostatting stimulated fluorochrome accumulation in cells whereas centrifugation, particularly for 60-minutes, decreased the ability of cells to accumulate fluorescein. Also, alteration of the gravity force had the opposite effect on the ability of cells to retain fluorescein. The most significant drain of the dye immediately after short hypogravity may be indicative of the functional lability of cells during clinostatting. However, as judged by slight changes in intracellular pH, metabolic and regulatory functions were not affected. Hypergravity for 15 min decreased intracellular pH. The increased period of centrifugation stabilized the parameter. Absence of changes in the proliferative activity in all the test exposures also backs up the conclusion that short-term changes in gravity do not produce any substantial shifts in the morphofunctional state of cells in vitro.

Animals↗
PubMed2000

Regulation of heat shock protein message in Jurkat cells cultured under serum-starved and gravity-altered conditions.

Although our understanding of effects of space flight on human physiology has advanced significantly over the past four decades, the potential contribution of stress at the cellular and gene regulation level is not characterized. The objective of this ground-based study was to evaluate stress gene regulation in cells exposed to altered gravity and environmentally suboptimal conditions. We designed primers to detect message for both the constitutive and inducible forms of the heat shock protein, HSP-70. Applying the reverse transcriptase-polymerase chain reaction (RT-PCR), we probed for HSP-70 message in human acute T-cell leukemia cells, Jurkat, subjected to three types of environmental stressors: (1) altered gravity achieved by centrifugation (hypergravity) and randomization of the gravity vector in rotating bioreactors, (2) serum starvation by culture in medium containing 0.05% serum, and (3) temperature elevation (42 degrees C). Temperature elevation, as the positive control, significantly increased HSP-70 message, while centrifugation and culture in rotating bioreactors did not upregulate heat shock gene expression. We found a fourfold increase in heat shock message in serum-starved cells. Message for the housekeeping genes, actin and cyclophilin, were constant and comparable to unstressed controls for all treatments. We conclude that gravitational perturbations incurred by centrifugal forces, exceeding those characteristic of a Space Shuttle launch (3g), and culture in rotating bioreactors do not upregulate HSP-70 gene expression. In addition, we found RT-PCR useful for evaluating stress in cultured cells.

Aerospace Medicine↗
PubMed1996

Isokinetic trunk flexors and extensors performance with and without gravity correction.

We study the influence of the calculation of the trunk gravity correction, in standing position, on the isokinetic trunk flexors and extensors performance of a healthy population. Thirty men and 30 women are subjected to two tests, one with gravity correction, the other without, at angular speeds of 30 degrees/s and 120 degrees/s. In all cases the results with gravity correction show: a significant decrease of Peak Torque (PT) and Power (P) recorded on the trunk flexors and a significant increase of Peak Torque and Power recorded on the trunk extensors. Thus, the flexors/extensors ratios (50%) of both parameters are quite different from the ratios usually referred to in the literature (70%).

Adult↗
PubMed1989

Gravity-dependent phenomena at the scale of the single cell.

Progress in gravitational cell biology research will depend on the continuing evaluation of a wide variety of physical phenomena affected by gravity and their roles in extracellular, intercellular, and intracellular processes. This paper examines those responses of organisms to gravity which depend on functions at the single cell level. Single cell functions are affected by perturbations in their internal and external environment by a variety of factors, one of which is the effect of gravity. Physical phenomena that could influence cell function include sedimentation, buoyancy-driven convection, streaming potential, hydrostatic pressure, and interactions among physical transport processes. Thermal motion and fluid viscosity play a significant role in all transport processes at the cellular level. The sedimentation of intracellular organelles tends to be counteracted by the cytoskeleton. Intracellular convective transport may be possible in large cells. In a microgravity environment extracellular solutes must be transported by diffusion or active circulatory processes in the absence of density gradient-driven convection, and flocculation and coalescence are reduced by the lack of motion of aggregates.

Animals↗
PubMed1993

The behavioral reactions of a snake and a turtle to abrupt decreases in gravity.

We report here on the behavioral reaction of two reptiles to abrupt decreases in gravity. One striped rat snake, Elaphe quadrivirgata, and three striped-neck pond turtles, Mauremys japonica, were exposed to microgravity on parabolic flight, during the filming of a documentary for the NHK television station in Japan. The video films revealed that the snake reflexively responded to the shift from hyper- to hypogravity by taking up a defensive posture--on the first parabola, the snake struck at itself. The turtles actively extended their limbs and hyper-extended their neck in microgravity, a posture which is identical to the displayed during their contact "righting reflex", when placed upside-down in normal gravity. The aggressive display of the snake was unexpected, although the righting response of the turtles was consistent with that shown by other vertebrates, including fish and mammals, exposed to microgravity. An implication of these observations is that the afferent signal for the righting reflex of vertebrates in normal gravity must be the unloading of ventral receptors in the sensory system, rather than the loading of dorsal receptors. These are the first behavioral records for any reptiles exposed to hypogravity.

Aggression↗
PubMed1998

The influence of short term gravity changes on mouse spleen lymphocytes in vitro (microfluorimetry with probes).

Despite of the great successes achieved in gravitational cell biology, problem of mechanisms underlying cell effects of gravity is far from being solved. Available data are very contradictory, because of the differences in experimental conditions: gravity value, exposition time, type of cells and other factors. Besides, there are no satisfactory methods to avoid additional influence of various biologically active factors on cells during the space experiments. It is absolutely clear, that successful development in this field may be provided only by investigations in controlled experimental conditions, including analysis of cell functional activity and state of cell regulatory systems. One of the most adequate approaches for these scientific tasks is cell microfluorimetry with using of fluorescent probes. The study of influence of short-term pattern changes in gravity (clinostation and centrifugation) on hydrolytic activity of intracellular content of mouse spleen lymphocytes, leakage of accumulated fluoresce in and intracellular pH is the goal of present research.

Animals↗
PubMed1999

Gravity, stress, calcium and gene expression.

Cytoplasmic calcium is a major regulator of plant metabolism and its levels are under strict control, but it increases rapidly and transiently after stress treatments such as cold and touch (Trewavas 1999). Gravity is also thought to affect Ca2+ levels, although one report, using fluorescence microscopy of Ca(2+)-binding dyes, showed no changes (Legue et al. 1997). However, in these studies Ca2+ could not be visualized for at least 1 min after gravistimulation and thus changes could have occurred more rapidly. In order to circumvent problems associated with the delay in taking readings imposed by the fluorescence microscopy techniques, we chose a different method using plants transgenic for the Ca(2+)-binding, light-emitting jellyfish protein aequorin (Knight & Knight 1995). We subjected Arabidopsis and tomato plants to heat-wounding, vibration and gravity stimulation and measured cytoplasmic Ca2+ levels. We also measured the levels of several transcripts after heat-wound and gravity stimulation to determine whether both treatments evoked the same changes.

Aequorin↗
PubMed1999

Diurnal height variations in growth of children: effects of gravity.

Many specialists in various scientific fields are interested in human growth and development of body sizes of children as a physiological phenomenon. However, our knowledge on human growth has not yet reached a solid foundation and consensus, and at present gravity potential is known to be a lasting condition that influences human lives in various ways. Therefore, more basic research is needed by examining detailed processes of human growth on the earth, with the effect of gravity in prospect. Although modern human growth study is constructed mainly on the basis of observations at one-year intervals, whether such long-interval observations can reveal a true statistical model of human growth is questionable. Togo and Togo (1982, 1989) observed growth in five siblings at one-month intervals for more than 15 years and found fluctuations observed from the start to the end of growth observations consisted of trend, regular, and irregular factors. This indicates the importance of examining human growth by short-interval observation. Thus, our study focused on diurnal variations of height, measuring twice daily, and discusses the effects of gravity on growth of children.

Adolescent↗
PubMed1999

Circumnutations without gravity: a two-oscillator model.

Helical growth movements termed circumnutations occur in a number of different plant organs. The underlying mechanism are complicated. They consist of an endogenous as well as an erogenous component. Since circumnutations in sunflower hypocotyls occur also under gravity free conditions in Space, gravity is not necessary for them to arise. However, the changes of period and amplitude of circumnutations with the applied gravitational force indicate that gravity plays a modifying role. Models for circumnutations have to take these features into account. It seems natural to study minimum models with at least two oscillating units. Two-oscillator models for circumnutations have already been discussed. We have studied the interaction between two coupled oscillatory units. With this model we could simulate movements of hypocotyls. The results of simulations were compared with experimentally recorded movements of the Arabidopsis hypocotyl.

Arabidopsis↗