To develop three-dimensional (3D) cytotoxicity models further, microcystin-induced cytoskeletal disruption was tested in two different models of multicellular hepatocyte aggregate formation ...(hepatospheroids). Rat hepatocyte suspensions were seeded either onto poly(2-hydroxyethylmethacrylate)-treated culture wells (poly-HEMA) or in a rotating wall vessel (RWV) device which provides minimal shear forces and enhances differentiated 3D growth. Ninety percent of spheroids forming on poly-HEMA tended to fuse and form nonhomogeneous multilobular structures by day 4 of incubation. In contrast, spheroids cultured in the low-shear environment formed homogeneous aggregates that averaged 126 + 10 microm diameter in size at day 7. Microcystin-LR (10(-6) mol/L) was put into contact (90 min in serum-free medium) with hepatocyte suspensions and spheroids formed in both systems for 1, 4 or 7 days. As already described, microcystin-LR (after 90 min), induced cytoskeletal disruptions (blebs) in 98% of the isolated primary hepatocytes maintained in suspension. In 3D cultures, blebs were detected only on poly-HEMA nonhomogeneous early prespheroids. All other mature spheroids (poly-HEMA or RWV) exposed to the toxin did not exhibit obvious morphological signs of toxicity. Moreover, microcystin-LR pre-incubation with hepatocyte suspension prevented the formation of conventional spheroids. In conclusion, the low-shear, simulated-microgravity environment generated high yields of regularly engineered spheroids. In both models, progressive resistance of mature spheroids to microcystin-LR-induced cell deformation developed with time in culture. Microcystin-LR inhibition of the formation of rat hepatospheroids in isolated hepatocyte suspension could be used as a complementary biological assay for detection of the presence of biologically active microcystin-LR in water samples.
Adrenergic vascular control Mano, T
Medicine and science in sports and exercise,
10/1996, Letnik:
28, Številka:
10 Suppl
Journal Article
Recenzirano
Odprti dostop
The gravity-dependency and age-dependency of noradrenergic vasoconstrictor outflow to skeletal muscle (muscle sympathetic nerve activity; MSNA) in humans was analyzed by applying microneurography ...technique. The basal level of MSNA in the horizontally supine position increased with aging without significant changes in arterial baroreflex sensitivity. MSNA responded to +Gz load by head-up tilt and to simulated microgravity by thermoneutral head-out immersion with increasing and decreasing the activity, respectively. These gravity related responses of MSNA were age-dependent, being reduced by aging. Simultaneously monitored hemodynamic responses to +Gz load and to simulated microgravity were also age-dependent, being reduced by aging. The gravity-dependent and also age-dependent changes in the noradrenergic vasoconstrictor outflow to muscle seem to be related to the mechanisms controlling the gravity-dependent fluid shift in the human body.
Simulated microgravity within the NASA High Aspect Rotating-Wall Vessel (HARV) provides a quiescent environment to culture fragile insect cells. In this vessel, the duration of stationary and death ...phase for cultures of
Spodoptera frugiperda cells was greatly extended over that achieved in shaker-flask controls. For both HARV and control cultures,
S. frugiperda cells grew to concentrations in excess of 1 × 10
7 viable cell ml
−1 with viabilities greater than 90%. In the HARV, stationary phase was maintained 9–15 days in contrast to 4–5 days in the shaker flask. Furthermore, the rate of cell death was reduced in the HARV by a factor of 20–90 relative to the control culture and was characterized with a death rate constant of 0.01–0.02 day
−1. Beginning in the stationary phase and continuing in the death phase, there was a significant decrease in population size in the HARV versus an increase in the shaker flask. This phenomenon could represent cell adaptation to simulated microgravity and/or a change in the ratio of apoptotic to necrotic cells. Differences observed in this research between the HARV and its control were attributed to a reduction in hydrodynamic forces in the microgravity vessel.
The effects of simulated microgravity conditions produced by a horizontal clinostat on the entire life cycle of Arabidopsis thaliana ecotype Columbia and Landsberg erecta were studied. Horizontal ...clinorotation affected little germination of seeds, growth and development of rosette leaves and roots during early vegetative growth stage, and the onset of the bolting of inflorescence axis and flower formation in reproductive growth stage, although it suppressed elongation of inflorescence axes. The clinorotation substantially reduced the numbers of siliques and seeds in Landsberg erecta, and completely inhibited seed production in Columbia. Seeds produced in Landsberg erecta on the clinostat were capable of germinating and developing rosette leaves normally on the ground. On the other hand, growth of pinformed mutant (pin/pin) of Arabidopsis ecotype Enkheim, which has a unique structure of inflorescence axis with no flower and extremely low levels of auxin polar transport activity, was inhibited and the seedlings frequently died during vegetative stage on the clinostat. Seed formation and inflorescence growth of the seedlings with normal shape (pin/+ or +/+) were also suppressed on the clinostat. These results suggest that the growth and development of Arabidopsis, especially in reproductive growth stage, is suppressed under simulated microgravity conditions on a clinostat. To complete the life cycle probably seems to be quite difficult, although it is possible in some ecotype
If a cardiac arrest occurs in microgravity, current emergency protocols aim to treat patients via a medical restraint system within 2-4 min. It is vital that crewmembers have the ability to perform ...single-person cardiopulmonary resuscitation (CPR) during this period, allowing time for advanced life support to be deployed. The efficacy of the Evetts-Russomano (ER) method has been tested in 22 s of microgravity in a parabolic flight and has shown that external chest compressions (ECC) and mouth-to-mouth ventilation are possible.
There were 21 male subjects who performed both the ER method in simulated microgravity via full body suspension and at +1 Gz. The CPR mannequin was modified to provide accurate readings for ECC depth and a metronome to set the rate at 100 bpm. Heart rate, rate of perceived exertion, and angle of arm flexion were measured with an ECG, elbow electrogoniometers, and Borg scale, respectively.
The mean (+/- SD) depth of ECC in simulated microgravity was lower in each of the 3 min compared to +1 G2. The ECC depth (45.7 +/- 2.7 mm, 42.3 +/- 5.5 mm, and 41.4 +/- 5.9 mm) and rate (104.5 +/- 5.2, 105.2 +/- 4.5, and 102.4 +/- 6.6 compressions/min), however, remained within CPR guidelines during simulated microgravity over the 3-min period. Heart rate, perceived exertion, and elbow flexion of both arms increased using the ER method.
The ER method can provide adequate depth and rate of ECC in simulated microgravity for 3 min to allow time to deploy a medical restraint system. There is, however, a physiological cost associated with it and a need to use the flexion of the arms to compensate for the lack of weight.
We review the graviresponse under true and simulated microgravity conditions on a clinostat in higher plants, and its regulation in molecular bases, especially on the aspect of auxin polar transport ...in etiolated pea (Pisum sativum L. cv. Alaska) seedlings which were the plant materials subjected to STS-95 space experiments. True and simulated microgravity conditions substantially affected growth and development in etiolated pea seedlings, especially the direction of growth of stems and roots, resulting in automophosis. In etiolated pea seedlings grown in space, epicotyls were the most oriented toward the direction far from the cotyledons, and roots grew toward the aerial space of Plant Growth Chamber. Automorphosis observed in space were well simulated by a clinorotation on a 3-dimensional clinostat and also phenocopied by the application of auxin polar transport inhibitors of 2,3,5-triiodobenzoic acid, N-(1-naphtyl)phthalamic acid and 9-hydroxyfluorene-9-carboxylic acid. Judging from the results described above together with the fact that activities of auxin polar transport in epicotyls of etiolated pea seedlings grown in space substantially were reduced, auxin polar transport seems to be closely related to automorphosis. Strenuous efforts to learn in molecular levels how gravity contributes to the auxin polar transport in etiolated pea epicotyls resulted in successful identification of PsPIN2 and PsAUX1 genes located in plasma membrane which products are considered to be putative efflux and influx carriers of auxin, respectively. Based on the results of expression of PsPIN2 and PsAUX1 genes under various gravistimulations, a possible role of PsPIN2 and PsAUX1 genes for auxin polar transport in etiolated pea seedlings will be discussed.
Plant seedlings show exaggerated growth responses on a three-dimensional clinostat. Such an automorphogenesis appears to be one of major factors which govern the life cycle of higher plants under a ...microgravity environment. On the three-dimensional clinostat, maize roots exhibited curvatures in three different portions; 1) the basal region just protruding from the coleorhiza, 2) the region between the mature and the elongation zone, and 3) the elongation zone, several mm from the tip. Even non-clinostatted control roots showed some degree of curvature. The curvature occurred at random without any dorsiventrality. There was no difference in the osmotic concentration of the cell sap between the convex and the concave halves of any region. However, the convex, rapidly expanding side exhibited a higher extensibility of the cell wall in some regions, which appears to be a cause of the curvature. In order to understand the role of gravity in regulation of plant growth and development, we should clarify a series of events by which an automorphogenesis is induced under simulated microgravity conditions.
The photosynthetic rate, the leaf characteristics related to photosynthesis, such as the chlorophyll content, chlorophyll a⁄b ratio and density of the stomata, the leaf area and the dry weight in ...seedlings of Japanese flowering cherry grown under normal gravity and simulated microgravity conditions were examined. No significant differences were found in the photosynthetic rates between the two conditions. Moreover, leaf characteristics such as the chlorophyll content, chlorophyll a⁄b ratio and density of the stomata in the seedlings grown under the simulated microgravity condition were not affected. However, the photosynthetic product of the whole seedling under the simulated microgravity condition increased compared with the control due to its leaf area increase. The results suggest that dynamic gravitational stimulus controls the partitioning of the products of photosynthesis.
Scopolamine/dextroamphetamine has been used to combat motion sickness generated aboard research aircraft for decades. While it has shown to be effective, previous studies differ as to the presence of ...visual side effects secondary to scopolamine's anticholinergic properties. This study sought to quantify any such effects in order to determine if they are operationally significant.
Fliers in NASA's Reduced Gravity Program received a weight-based dose of scopolamine/ dextroamphetamine prior to boarding the aircraft. Measurements of pupil size, visual acuity, and accommodation were taken in identical conditions using subjects' dominant eyes prior to medication administration and again after landing. We enrolled 131 subjects ages 18-48. Pre- and postflight measurements of pupil size and acuity were available for 125 subjects.
Average pupil size increased by 1.1 mm (95% CI 0.9-1.2). Only 1.6% of subjects experienced a change in visual acuity of greater than 10 ft. The average near-point accommodation changed from 8.61 to 7.84 diopters, a difference of -0.77 (-1.01 to -0.53) diopters or 1.34 cm (0.87-1.81). Increasing age also correlated significantly with worsening change in accommodation.
This study found statistically significant changes in pupil size and near point accommodation that do not appear to be clinically important. No significant decrement in acuity was noted. While direct effects on in-flight performance could not be assessed, the use of scopolamine/dextroamphetamine among fliers aboard research aircraft does not appear to yield visual side effects sufficient to compromise later ground operations.
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