Signs of Müller cell gliotic response found in the retina of newts exposed to real and simulated microgravity

The effects of real and simulated microgravity on the eye tissue regeneration of newts were investigated. For the first time changes in Müller glial cells in the retina of eyes regenerating after retinal detachment were detected in newts exposed to clinorotation. The cells divided, were hypertrophied, and their processes were thickened. Such changes suggested reactive gliosis and were more significant in animals exposed to rotation when compared with desk-top controls. Later experiments onboard the Russian biosatellite Bion-11 showed similar changes in the retinas that were regenerating in a two-week spaceflight. In the Bion-11 animals, GFAP, the major structural protein of retinal macroglial cells, was found to be upregulated. In a more recent experiment onboard Foton-M3 (2007), GFAP expression in retinas of space-flown, ground control (kept at 1 g), and basal control (sacrificed on launch day) newts was quantified, using microscopy, immunohistochemistry, and digital image analysis. A low level of immunoreactivity was observed in basal controls. In contrast, retinas of space-flown animals showed greater GFAP immunoreactivity associated with both an increased cell number and a higher thickness of intermediate filaments. This, in turn, was accompanied by up-regulation of stress protein (HSP90) and growth factor (FGF2) expressions. It can be postulated that such a response of Müller cells was to mitigate the retinal stress in newts exposed to microgravity. Taken together, the data suggest that the retinal population of macroglial cells could be sensitive to gravity changes and that in space it can react by enhancing its neuroprotective function.     

A fault-tolerant magnetic spin stabilizing controller for the JC2Sat-FF mission

This paper presents a spin-stabilization algorithm for the Japan Canada Joint Collaboration Satellite-Formation Flying (JC2Sat-FF) mission using magnetic actuation only. It is shown that under a reasonable assumption on the Earth’s magnetic field, the resulting control law is asymptotically stabilizing for an axisymmetric spacecraft, even under the failure of up to two magnetic torque rods and magnetic torque rod saturation. It is also stabilizing under quantization. The satellite motion remains stable under control outages, meaning that the error can be reduced by implementing the control intermittently. The effectiveness of the control law is demonstrated using a high fidelity attitude control system simulator for the JC2Sat-FF satellite.     

Assistant systems for aircraft guidance: cognitive man-machine cooperation

This paper presents the concept of cognitive assistant systems which represents an approach to ensure the highest degree possible of situation awareness of the flight crew as well as a satisfactory workload level. This concept offers the solution to counteract susceptibility to pilot errors typical of lack of attention or other cognitive limitations. It is founded on cognitive system engineering. This technology enables a cockpit design in order to systematically comply with the requirements of ‘Human-Centred Automation (HCA)’. The underlying approach behind the concept has become real with the development of the cockpit assistant system prototype family CASSY/CAMA as described in this paper. CASSY/CAMA has been extensively tested in a flight simulator and successfully field tested with the ATTAS (Advanced Technologies Testing Aircraft System) of the DLR. Some of the test results with CAMA will be presented in this paper.     

Influence of longitudinal whole animal clinorotation on lens, tail, and limb regeneration in urodeles.

Two species of newts (Urodela) and two types of clinostats for fast clinorotation (60 rpm) were used to investigate the influence of simulated weightlessness on regeneration and to compare results obtained with data from spaceflight experiments. Seven or fourteen days of weightlessness in Russian biosatellites caused acceleration of lens and limb regeneration by an increase in cell proliferation, differentiation, and rate of morphogenesis in comparison with ground controls. After a comparable time of clinorotation the results obtained with Triturus vulgaris using a horizontal clinostat were similar to those found in spaceflight. In contrast, in Pleurodeles waltl using both horizontal and radial clinostats the results were contradictory compared to Triturus. We speculate that different levels of gravity or/and species specific thresholds for gravitational sensitivity could be responsible for these contradictory results.     

Microgravity effects on neural retina regeneration in the newt.

Data on forelimb and eye lens regeneration in urodeles under spaceflight conditions (SFC) have been obtained in our previous studies. Today, evidence is available that SFC stimulate regeneration in experimental animals rather than inhibit it. The results of control on-ground experiments with simulated microgravity suggest that the stimulatory effect of SFC is due largely to weightlessness. An original experimental model is proposed, which is convenient for comprehensively analyzing neural regeneration under SFC. The initial results described here concern regeneration of neural retina in Pleurodeles waltl newts exposed to microgravity simulated in radial clinostat. After clinorotation for seven days (until postoperation day 16), a positive effect of altered gravity on structural restoration of detached neural retina was confirmed by a number of criteria. Specifically, an increased number of Mullerian glial cells, an increased relative volume of the plexiform layers, reduced cell death, advanced redifferentiation of retinal pigment epithelium, and extended areas of neural retina reattachment were detected in experimental newts. Moreover, cell proliferation in the inner nuclear layer of neural retina increased as compared with control. Thus, low gravity appears to intensify natural cytological and molecular mechanisms of neural retina regeneration in lower vertebrates.