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W Briegleb

Publications and source records attributed to W Briegleb.

At least 37 records · Page 2Linked to original sources
PubMed1989

Light microscopic analysis of the gravireceptor in Xenopus larvae developed in hypogravity.

The paper describes an investigation of the influence of gravity on the early differentiation of gravity receptors in Xenopus embryos and larvae. There is evidence that the expression of crystals in the saccus endolymphaticus was statistically greater when the embryos developed in near weightlessness (hypogravity) than on earth. The function of these crystals is unknown but they may contribute to the functioning of the vestibular apparatus.

Animals↗
PubMed1988

The response of structure and function of the gravireceptor in a vertebrate to near weightlessness.

The paper sums up results of a 7-day space flight experiment (D-l-Mission-BW-STA 00-STATEX) using growing frog embryos and larvae (Xenopus laevis) as a model system. Evaluation of photographs taken from the surface of sectioned deep-frozen objects, and micrographs using TEM and SEM show no aberrations in the shape, size, position, or respective electron density of the otolith membranes in larvae developed for 154 h under near-zero g. The further evaluation of the "weightless larvae" revealed a probably not yet described otolith-like formation below the dorsal wall of the vestibulum. In the weightless larvae this formation outnumbers, also qualitatively, strongly the 1-g control samples. The swimming behavior of the tadpoles which was observed about one hour after landing of the Space Shuttle showed a typical anomaly (loop swimming), which is known from larvae developed on the clinostat or from fish flown aboard Apollo capsules. An extra result is the lack of striking effects of cosmic radiation on the embryonic development of the flown Xenopus eggs.

Animals↗
PubMed1986

Classification of gravity effects on "free" cells.

When cell physiologists detect gravity related reactions of their objects it is often difficult to decide where the receptors for the observed effects are located. Answering this question is necessary for any further analysis of a detected gravity effect on cells. In previous papers we have discussed direct and indirect gravity effects in relation to the smallest functional units where the primary receptor, which interacts with gravity, is positioned inside and outside of such a unit, respectively. So, in a first approximation we can conclude that in a multicellular aquatic organism, which changes its metabolism in weightlessness, the primary receptors of gravity are located inside the cells of that organism. A special approach is necessary when free living cells, the density of which may be higher than the one of the (liquid) medium, or even cells living on a free surface are observed. In these two cases also indirect effects have to be taken into account, which will be demonstrated with the aid of the slime mold Physarum polycephalum. Additionally the environment of the organisms can be changed directly and indirectly by gravity.

Animals↗
PubMed1986

Confirmation of gravisensitivity in the slime mold Physarum polycephalum under near weightlessness.

We have investigated Physarum polycephalum, a unicellular organism with no special gravity receptors, on its ability to react to gravity. The first experiments were 0 g-simulation experiments on the fast-rotating clinostat conducted with plasmodial strands of this acellular slime mold. In these earth-bound experiments the observed parameters were periodicity of the contractions and dilatations of the strand's ectoplasm as well as the periodicity and velocity of the striking cytoplasmic (endoplasmic) shuttle streaming. During 0 g-simulation these parameters showed significant changes indicating the existence of a gravisensitivity of the slime mold. The Space-Shuttle experiment (ESA-Biorack in D 1-Mission) should demonstrate the validity of the 0 g-simulation on the fast-rotating clinostat. The experiment was designed in a way enabling the registration of the same parameters as on the clinostat (using the light microscope in combination with a photo diode and a cinecamera). Only one of the two planned measurement sessions was fully successful and provided us with data confirming the results gained on the fast-rotating clinostat: The slime mold showed under real near weightlessness in the D 1-Space Shuttle Mission a transient frequency increase in tis contraction rhythmicity and a (steady) increase in the streaming velocity of its endoplasm.

Animals↗
PubMed1986

Survey of the vestibulum, and behavior of Xenopus laevis larvae developed during a 7-days space flight.

Aquatic animals have almost no body weight related proprioception for spatial orientation. Xenopus larvae, like fish, maintain their attitude in water by continuous correction with their fin(s). For these reasons a special performance of the equilibrium system compared to terrestrial animals is necessary. Evidently fish therefore have more compact (dense) otoliths; Xenopus larvae have less dense otolith (membranes) similar to land vertebrates; but their sacculus-otoliths are vertically positioned, which also may lead to a higher g-sensitivity. For plausibility reasons gravity should influence the embryonic development of gravity receptors. Yet, evaluations of photographs taken from the surface of cut deep-frozen objects by incident light show no aberration of the shape of the whole vestibulum and of the shape, density, size and position of the otolith membrane in larvae developed under near-zero g (NEXPA-BW-STATEX in D-1-Mission). The further evaluation of the "weightless-larvae" revealed a probably not yet described statolith-like formation in the dorsal wall of the vestibulum. In the weightless larvae this formation outnumbers, also qualitatively, strongly the l-g controls. An extra result is the lack of striking effects of cosmic radiation on the embryonic development of the flown Xenopus eggs. The swimming behavior of the larvae which was observed about one hour after landing of the Space Shuttle showed a typical anomaly (loop swimming), which is known from larvae developed on the clinostat or from fish flown aboard Apollo capsules.

Animals↗
PubMed1986

Gravisensitivity of the acellular slime mold Physarum polycephalum demonstrated on the fast-rotating clinostat.

The acellular slime mold Physarum polycephalum was used to investigate a postulated general gravisensitivity of cells. Physarum was subjected i) to a rotation on the fast-rotating clinostat, which enables the simulation of weightlessness (0 g), and ii) to single horizontal turns of 180 degrees. On the fast-rotating clinostat the response consists of a frequency increase in radial contractile activity, an oscillation of the mean values (frequency regulation phenomena) and an increase in standard deviation. A combination of 0 g and respiration impediment inhibits the response to 0 g, i. e., the frequency increase in radial contractile activity during weightlessness simulation. Turning the specimens horizontally about 180 degrees in a normally positioned light microscope also leads to a frequency increase in radial contractile activity, but the temporal pattern of the frequency increase differs in comparison to the experiments performed on the clinostat during weightlessness simulation. These results demonstrate the occurrence of gravisensitivity in Physarum polvcephalum. Regulation phenomena and the possible role of mitochondria in graviperception are discussed.

Animals↗
PubMed1984

Acceleration reactions of cells and tissues--their genetic-phylogenic implications.

This paper speculates about the interplay between adaptational modifications with mutation and selection. Gravity effects are supposed to be very well suited to prove the role of direct adaptations for phylogenic processes. The speculation is based on strong hints that the cell in general reacts to accelerations (besides other mechanical stimuli) in the order of 1g and near weightlessness. Several-generations experiments in space may contribute to solve this fundamental question of evolution.

Acceleration↗
PubMed1983

Influence of zero gravity simulation on time course of mitosis in microplasmodia of Physarum polycephalum.

Detrimental effects of weigntlessness are no longer expected to hinder successful mitosis. Experiments in space and on the fast clinostat give no hints of this. Nevertheless we are thinking of a g sensitivity during the process of chromosome condensation and distribution. The time course of nuclear division in microplasmodia of the slime mold Physarum polycephalum was investigated under 0 g simulation on the fast rotating clinostat in comparison to 1 g controls. The result of this experiment is: A significant shortening of mitosis under 0 g simulation compared to 1 g controls.

Animals↗
PubMed1982

Cell morphological, ontogenic, and genetic reactions to 0-g simulation and hyper-g.

Organisms use gravity for spatial orientation, and differentiation into species during evolution follows geological processes which are caused by gravity. On the other hand, the task of most organismic functions which have or may have a relation to gravity is to compensate gravity. Furthermore, today it is very obvious that organisms do not disintegrate under the conditions of weightlessness, at least for the currently tested durations. These previous statements indicate a large field of still unknown regulation and adaptation mechanisms. Experiments to simulate weightlessness on the fast clinostat and with hyper-g show a highly developed ability of the genetic chain and of differentiating cells in being autonomous against mechanical stresses caused by outer accelerations. Nevertheless, different strong and slight changes of different tested end points were found. The question remains if the cells react actively or only passively.

Animals↗
PubMed1981

Changes in the microstructure of the vestibular apparatus of tadpoles (Rana temporaria) developed in simulated weightlessness.

The vestibular apparatus of tadpoles (Rana temporaria) exposed to simulated weightlessness was examined by electron microscopy. Extended exposure to simulated weightlessness is followed by significant alterations in the sensory epithelia and also in the otolith membrane. Large vacuoles, filled with necrobiotic mitochondria and fragments of endoplasmic reticulum, were concentrated in the region where an otolith membrane covers the hair cells but were mostly absent in zones of the epithelia with undifferentiated cells. The number of otoconia in the otolith membrane was diminished. The results were compared with data from space flight experiments and some concordance was noted. The possible connection between some unusual behavior of the tadpoles after weightlessness simulation and the structural alterations in the gravitational sensors was discussed.

Animals↗
PubMed1980

Effect of hypogravity on human lymphocyte activation.

Cultures of human lymphocytes were exposed to the mitogen concanavalin A in a low-G environment generated by a fast rotating clinostat. DNA-synthesis was determined by incorporation of 3H-thymidine as the parameter for activation, cell ultrastructure was analyzed by electron microscopy, and cell movements were recorded by a cinecamera. The results were compared with 1-G controls. The cells cultured at low G show: (i) depression of activation by 50%, (ii) appearance of "mitochondria-rich" cells, and (iii) enhanced formation of pseudovilli and uropods. Our investigations in vitro at low and high G and reports on the effect of spaceflights on lymphocytes from cosmonauts and astronauts suggest that hypogravity depresses, whereas hypergravity enhances, lymphocyte activation by mitogens. This study is complementary to an experiment which will study the in vitro activation of lymphocytes in weightlessness during the first Spacelab mission.

Cell Movement↗
PubMed1975

Influence of simulated weightlessness on the rate of anomalies of the flour beetle Tribolium confusum.

Experiments with Tribolium confusum showed that the morphological characteristics of the beetles are modified by simulated weightlessness (fast running clinostat). Because of possible side effects due to differences in fertility of inbred lines, the first experiments were made with a genetically heterogeneous stock. Thereafter experiments were confirmed with inbred beetles. For both stocks a rise of mainly wing anomalies resulted from rotation of whole cultures of beetles within horizontal tubes. The extent to which these anomalies are teratogenetic or genetic has not yet been analysed in detail.

Animals↗
PubMed1974

Histological studies on the vestibular organ of frog embryos and larvae after simulated weightlessness.

The ontology of gravity receptors is discussed. As well as phylogenetic aspects of the question, we may ask whether the different gravity receptors in plants and animals derive from the same source; did they evolve from a general sensitivity of the living cell or do they represent parallel inventions. One may also ask whether during ontogeny of the receptor it receives information from gravity or whether the development of function of the organ is an autonomous process. In many cases ontogeny shows traces of phylogeny. Statoliths, e.g. the differentiating statolith membranes of the frog embryo, look somewhat like sedimentational structures. Furthermore the amphibian embryo in its relatively early stages takes up a special position in relation to the direction of gravity. Which mechanism is involved here? The materials studied were frog embryos and larvae which developed within a fast rotating clinostat. The results may help to answer the question as to whether the differentiation of the frog statolith membrane is an autonomous process.

Animals↗