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At least 865 records · Page 48Linked to original sources
PubMed1995

[Gravitational mechanisms of interactions of sensory systems in invertebrates in the evolutionary aspect].

The paper concerns the origin and the interaction of sensory organs in the context of locomotion. The Earth's gravity, light, sound, electrical, mechanical, etc. impacts were the morphogenetic factors of evolution which pushed the gene to elaborate adequate mechanisms for surmounting gravity, i.e. for exercising directed locomotion. Indeed, even some species of bacteria have mobile levers, flagelli. As a rule, the flagellum itself is the carrier of protein sensory molecules perceiving gravity as a mechanic stress, light, chemical ligands, sound, electricity, etc. On the molecular, subcellular, cellular, and organic levels in unicells and most ancient multicellular organisms an attempt has been made to follow the evolution of locomotion substrate and sensory organs and nerve centers interacting with the substrate and each other and, taken together, recognized as the locomotor-sensory system (LMSS).

Animals↗
PubMed1994

Gravitational neuromorphology.

This review shows that morphological studies of the central, peripheral and autonomic nervous system of animals exposed to altered gravity yield data which are extremely significant for our understanding of the mechanisms of adaptation of the nervous system, and of the mammalian organism as a whole, to increased and decreased loading. Neuromorphological studies, correlating structure and function, indicate a decreased activity in weightlessness for spinal ganglia neurons and motoneurons of the spinal cord, as well as the neurons of the hypothalamic nuclei producing arginine vasopressin and growth hormone releasing factor. Structural changes of the somatosensory cortex and spinal ganglia suggest a decreased afferent flow to the somatosensory cortex in microgravity. The results characterize the mechanisms of structural adaptation to a decreased afferent flow in microgravity by the neurons in the hemisphere cortex and brain stem nuclei. There is also morphological evidence for an increased sensitivity of the otolith apparatus and for the development of a hyponoradrenergic syndrome in weightlessness. These studies have shown that both microgravity and the simulation of microgravity effects by tail suspension-induced structural changes in the large neurons of lumbar spinal ganglia and motoneurons of the lumbar spinal cord, which occur under conditions of nerve cell hypoactivity. The structural changes, and consequently the development of neuron hypoactivity, are expressed more extensively after microgravity than after tail suspension for the same length of time. The influence of microgravity and hypergravity on animals is expressed by opposing changes in nervous tissue structure in the spinal ganglia, spinal cord, and nodulus of cerebellar vermis. These changes indicate neuron hypoactivity under microgravity and neuron hyperactivity under 2 G. Morphological assessment of the functional state of other structures of the brain under hypergravity will require further study. Can all structural changes which occur in nerve tissue under microgravity or under hypergravity be explained on the basis of increased or decreased activity of its structural elements? The presently available data regarding the correlation of structure and functional state of cells in brain and spinal cord suggest an affirmative answer. Ultrastructural studies of the nodular cortex of the cerebellum in rats after different duration spaceflights provide what appears to be a convincing example. However, it should be pointed out that the criteria for the morphological assessment of the functional state of single nerve cells will certainly be different from those for groups of neurons connected in a nerve cell network.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

[The effect of pikamilon and fenibut on the blood supply of the brain at rest and under gravitational exposures].

The effects of Picamilonum, 10 mg/kg, and Phenibutum, 50 mg/kg, on the cerebral blood flow, oxygen saturation and vascular reactivity in the cerebral cortex, thalamus, and hypothalamus were studied at rest during antiorthostatic hypokinesia and while rocking in antiorthostasis. Picamilonum was shown to have more steady vasodilatory effect, but it decreased a cerebrovascular response to CO2 and O2 inhalation. The reactivity of cerebral vessels to antiorthostasis under the influence of the drugs inversed, that of cerebrovascular vessels to CO2 inhalation decreased. Picamilonum enhanced vasoconstrictory responses to CO2 inhalation, whereas Phenibutum decreased it. With the combined effects of Phenibutum and Picamilonum, while rocking in antiorthostasis, a phase of vasodilatation was not observed and oxygen saturation and cerebrovascular reactivity were decreased.

Animals↗
PubMedDate not supplied

Early eccentricity in gravitationally oriented quail germs.

Germs in extracted white shelled quail eggs were obliquely or vertically oriented by air-bubble method (Callebaut, 1991) and further incubated. After their bilateral symmetrization we observed a parallelism between the eccentricity of the area pellucida, the aspect of the subgerminal cavity and the subgerminal yolk. Our observations suggest that at that moment the subgerminal yolk has tendency to rotate (symmetrization rotation) under the germ in a topwards direction. The subgerminal cavity extends below the lower germ wall and so the contact of the germ with the underlying yolk is disrupted in its central lower (cranial) part and there numerous free yolk masses (forming the "anti-sickle") were seen. By contrast at the upper (caudal) part of the germ no such tearing occurs. There the original subgerminal cavity ends abruptly against the anlage of Koller sickle. The Koller sickle thus develops where the most central direct contact of the germ with the subgerminal yolk persists for longer periods.

Animals↗
PubMedDate not supplied

[Biomechanical criteria of artificial gravitation].

On the basis of the pertinent literature data and their own findings the authors formulate the basic biophysical criteria that should be taken into consideration while developing an artificial gravity system. These criteria can be used to define the range of variations of the main parameters of artificial gravity systems that should be permissible in terms of normal life activity and performance of consmonauts. The numerical values of the parameters should be considered as theoretical guiding lines for the advanced development of artificial gravity systems.

Acceleration↗
PubMedDate not supplied

[Change in the gravitation level as a stressor].

Animal (rats, mice) experiments have shown that a gravity change within the range of +/- 1 g relative to the Earth gravity field (zero g in space flight, increased gravity in centrifugation experiments) results in the development of similar reactions--growth delay, involution of lymph organs, lymphopenia. These are classic signs of stress reactions. Centrifugation experiments have demonstrated that the stress-effect of increased gravity can be counteracted by intermittent pretraining on the centrifuge. With respect to the literature data and the authors' own experimental findings, the ratio of specific and nonspecific components in animal responses to gravity changes as well as the contribution of animal reactivity and resistance to these responses were discussed.

Adaptation, Physiological↗
PubMedDate not supplied

[Effect of the orientation of the head in the gravitational field on the intensity of caloric nystagmus].

The relationship between the intensity of the vertical and horizontal caloric nystagmus and the head orientation in the gravity field was studied experimentally. The positions in which the nystagmus reached the highest intensity were identified. The experimental results showed that during caloric stimulation the major contribution to the excitation of semi-circular canals was made by the convective flow of the endolymph which was dependent on the head orientation relative to the acceleration vector. The caloric tests can induce stimulation of vertical semi-circular canals which is comparable to that of horizontal canals in its strength.

Adolescent↗
PubMedDate not supplied

[Patterns in the growth and functioning of single-cell organisms under conditions of altered gravitational force].

The results of studies over many years on various types of unicellular free-swimming organisms in conditions of altered gravity (hyper-, hypo-, and microgravity ranging from 10(-5) to 5 g) were reviewed. Laws governing their growth and functioning under these conditions were established. In general, gravisensing of unicellular free-swimming organisms depends on their metabolic activity and mobility, on the one hand, and on the environmental conditions of the population, on the other. A working hypothesis on the priority of ecophysiological properties (environment, metabolic activity, and mobility) over morphological properties (mass, dimensions, and shape) in receiving and processing of gravity stimuli at the cellular level has been formulated.

Amoeba↗
PubMed1977

[Condition of the microcirculatory bed of cat ventricular myocardium following exposure to gravitational stress].

The status of microcirculatory bed in the cat ventricular myocardium was studied after a single (10 units for 3 min) and repeated effect (6 units for 3 min every other day for a month) of overloading in the cranio-caudal direction (+Qz). The material to examine was taken in 20 min, 1, 3, 7 and 30 days after the completion of the experiment. The myocardial vessels were injected with water emulsion of Indian ink and studied by routine histological methods, amino nitrogen silver impregnation and electron microscopy. A single overloading was stated to result in changes of capillary permiability which was evident in the increasing amount of pinocyte vesicles, polysoma and endothelial plasmic processes. The effect of repeated overloadings produces more severe disorders in the walls of different components of the myocardial microcirculatory bed.

Animals↗
PubMedDate not supplied

[The role of gravitational force in the evolution of living systems (the biomechanical and energy aspects)].

Possible pathways of the origin and development of adaptive mechanisms in the living systems of various levels of organization are considered from the positions of biomechanics and bioenergetics. Main attention is paid to the specific feature of functional rearrangements in the living organisms during change of habitat, at the stage of their exit from water to land. The following problems of interaction between the living systems and gravity during evolution are discussed: cellular level of organization and transition to multicellularity, formation and improvement of the skeletal and skeletal-motor systems in plants and animals, and thermal homeostasis of the living organisms in the gravity field. We showed a leading role of gravity in organization of the morphofunctional status of the living organisms during their evolution.

Adaptation, Physiological↗