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At least 379 records · Page 21Linked to original sources
PubMed1978

[Effect of single gravitational overloading on various parts of the brain (experimental electron and light microscopic study)].

After application of single gravitational overloadings on the cat brain, perivascular edema, peripheral chromatolysis and cytoplasmic edema in neurons, dendrites and astrocytes have been observed. Some shifts in ultrafine composition of presynaptic buds and vascular walls have been described. Structures of myelin and amyelin fibers are preserved. Ultrastructural reconstructions are expressed differently in different brain structures in connection with their functional differentiation. The reconstructions revealed are of reversible character.

Animals↗
PubMedDate not supplied

[Formation of complex behavior habits in white rats after exposure to artificial gravitation aboard the Cosmos-936 biosatellite].

A study was made of the behaviour of albino rats solving complex tasks in the Lachman maze and in a maze of original design, on the 18th to 24th days after exposure on board the "Kosmos-936" biosatellite. In conditions of artificial gravitation the animals solved such tasks significantly worse than those which were not subjected to centrifugation on board. Control trials on Earth and some features of the experimental technique suggest that this fact is due to negative influence of angular velocities during centrifugation on the animal's central nervous system.

Animals↗
PubMed1981

Contact of migrating L5222 leukemia cells with the substrate as studied under the action of gravitational force.

The interaction of actively migrating L5222 cells with the serum-coated glass surface was studied under the influence of an external force. In order to generate such force, the plane on which the cells were migrating, was inclined at different angles. The analysis of the L5222 cell migration pattern reveals that the modification of the cell movement direction relative to the surface appears when the plane is inclined at 1 degree. The increase of the slope to 2 degrees makes this effect more evident. When the slope is equal to 3 degrees the active motion of L5222 cells seems to disappear. The component of the gravitational force parallel to the plane on which the cells migrate ranges from 6.3 X 10(-15) N to 1.9 X 10(-14) N for the slopes from 1 degree to 3 degrees, respectively. The results of the study indicate that the force of interaction of migrating L5222 cells with the substrate is very small in comparison with the force of adhesion (not accompanied by locomotion) and seems to be comparable to that which operates in the near-substrate region of non-locomotive cells (e. g. L1210). Thus, the cell-substrate contact related to active movement and the non-locomotory adhesion of L5222 cells are probably different phenomena. As only L5222 cells were studied in this work, the above conclusions should be restricted to this cell type only.

Animals↗
PubMed1981

[Effect of gravitational pulmonary atelectasis on expiratory airway closure].

The effect of gravitation +Gz (2-8 Gz, 5 min) combined with air or pure oxygen breathing on the lung volume and expiratory airway closure was studied in 9 subjects. It was demonstrated that lung atelectasis induced by oxygen breathing causes restriction of lung ventilation and obstruction of the peripheral airways. The authors discuss the effect of restrictive and obstructive disorders of lung ventilation on gas exchange and development of circulatory hypoxia during acceleration.

Adolescent↗
PubMed1993

[Prognostic significance of baseline state of platelet aggregation and blood viscosity during gravitational plasmapheresis in patients with angina pectoris].

The study was undertaken to examine 56 patients (mean age 54.9 +/- 1.1 years) who had functional class III (n = 12), IV (n = 32), and unstable (n = 12) angina pectoris. Due to inefficacy of conservative therapy, all the patients underwent gravitation plasmapheresis (GPA). The parameters of induced platelet aggregation were examined by the Born-O'Brien method and blood viscosity on a rotor viscometer before, immediately and on days 1 and 3 after GPA. It was found that the baseline blood viscosity and platelet aggregation should be known to predict the natural history of angina in the following 1-3 days after GPA. There was a pronounced positive clinical effect in higher blood viscosity and platelet aggregation. An improvement in the clinical course of the disease and its stabilization were not observed in the baseline lower blood viscosity and platelet in patients with progressive angina.

Adult↗
PubMed1977

[Post-traumatic regeneration of rat skin with stimulation under conditions of gravitational stress].

Albino rats were subjected to multiple gravitation stress (11units) before infliction wounds. A marked vascular reaction was noted in the wound contents at the early observation period. The appearance and differentiation of granulation and epidermis proliferation periods were delayed. Healing the wound occurred on the 30th day (on the 15th--18th day in controls). Administration of the skin tissue extract (prepared by Filatory's method) under these conditions, simultaneously with the wound infliction and up to their healing sharply reduced the vascular reaction, accelerated the granulation differentiation and the epithelialization of the wound; in respect to the character and the periods of tissue differentiation development the restoration process thus approached the course of the post-traumatic skin regeneration under usual conditions.

Animals↗
PubMedDate not supplied

[Response of regional vascular tone to orthostatic and gravitational effects].

The effect of active orthostasis and +Gz acceleration on regional vessels was investigated with the participation of 6 test subjects. Using photoplethysmography, the arterial pulse and venous blood filling of vessels of the finger at the level of the right atrium and at 41 cm above and below it were measured. This corresponded to variations of the intravascular hydrostatic pressure within the range +/- 30 mm Hg. This test was performed before and after exposure to acceleration of 5, 7, 8 and 9 G for 30 s at an onset rate of 1.0 G/s in the horizontal and vertical position. Arterial and venous responses were determined by comparing the results obtained at extreme levels of hydrostatic pressure. In all cases, increase in hydrostatic pressure led to enhancement of arterial tone and venous blood filling. After exposure to acceleration arterial tone and venous blood filling grew to a greater extent, particularly in the horizontal position. It is believed that the above method of measuring responses of regional vessels may prove useful to assess the vascular function after orthostatic, gravitational and other effects.

Acceleration↗
PubMed1977

[Effect of gravitational loads (+Gx) of the training schedule on the structure of the main arteries of dogs].

In dogs subjected to gravitational overloadings (+Gx) according to a special training schedule the wall structure of the main arteries (carotid, humeral, femoral and aorta) was studied by histological methods. The amount of catecholamines (adrenaline and noradrenaline) in the venous blood plasma and in the adrenal tissue was the index of the sympathoadrenal system condition. It was demonstrated that in trained animals the tolerance threshold to continuously increasing overloadings (+Gx) rose. It was accompanied by an elevated amount of catecholamines in blood and the adrenals In the walls of the main arteries studied a moderate hyperelastosis and a slight collagenization of the adventitia was noted. All parts of the microcirculatory bed were moderately dilated, which favoured a better blood outflow. The data obtained demonstrate adaptational changes, which can be interpreted as indices of training and reliability of the organism.

Adaptation, Physiological↗
PubMed2002

Gravitational smoothing as a global optimization strategy.

An optimization scheme for atomic cluster structures, based on exaggerating the importance of the gravitational force, is introduced. Results are presented for calculations on Lennard-Jones clusters of 13, 38, and 55 atoms, and the 13-atom Morse cluster.

Journal Article↗
PubMed2005

Size fractionation of marine sediments by pinched inlet gravitational split-flow thin fractionation and the study of size dependent PCDD/Fs concentrations from different bay areas.

Pinched inlet gravitational split-flow thin fractionation (PI-GSF) has been applied to the continuous size fractionation of marine sediments in order to study the difference in sediment size distribution and the concentration of PCDD/Fs contained in different particle sizes. A PI-GSF channel, known to improve the separation efficiency by reducing the sample inlet thickness, was utilized to fractionate sediments collected from three different bay areas (Geoje, Ulsan, and Pohang) in Korea into 5 different sub-populations (<2.0, 2.0-5.0, 5.0-10, 10-20, 20-63 microm in diameter). The sorted sediment fractions from PI-GSF were examined using electron microscopy to obtain size distribution and the results showed a variation in particle size distribution between bay areas. When the collected particle fractions were examined for size dependent levels of PCDD/Fs, the concentrations of total PCDD/Fs were shown to be much greater for samples collected close to heavy industry complexes than sediments from bay areas without major industry.

Journal Article↗
PubMed2005

Pinched inlet gravitational split-flow thin fractionation of airborne particles and analysis of size dependent level of PCDD/Fs.

Fine particles in air have a direct influence on human health because they carry toxic chemicals that can be deposited in the human lung when inhaled. Thus, particle size distribution and size dependent level of contamination of the airborne particles are important parameters for the study and assessment of environmental pollution. In this study, gravitational split-flow thin (SPLITT) fractionation (or GSF), a semi-preparative scale separation technique for particles, was applied for the continuous size sorting of airborne particles collected in urban area. About 2.0 g of airborne particles was fractionated into four different size intervals (<1.5, 1.5-2.5, 2.5-5.0, and >5.0 microm), and the collected fractions were examined by electron microscopy for particle size distribution and analyzed for the size dependent levels of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs). It was found that more than 60% of particles including dissolved matters in weight were smaller than 5.0 microm and they contained more than 86% of the total PCDD/Fs amount in airborne particles.

Benzofurans↗
PubMed1996

Gravitational loading of a simulated launch alters mRNA expression in osteoblasts.

Serum-deprived mouse osteoblastic cells (MC3T3-E1a) were centrifuged under a regime designed to simulate a space shuttle launch (maximum of 3g). Messenger RNA levels for eight genes involved in bone growth and maintenance were determined using RT-PCR. Following 30 min of centrifugation, mRNA level for early response gene c-fos was significantly increased 89% (P < 0.05). The c-fos induction was transient and returned to control levels after 3 h. The mRNA level for the mineralization marker gene osteocalcin was significantly decreased to 44% of control level (P < 0.005) 3 h after centrifugation. No changes in mRNA levels were detected for c-myc, TGFbeta1, TGFbeta2, cyclophilin A, or actin. No basal mRNA level for TGFbeta3 was detected. In addition, no change in the steady-state synthesis of prostaglandin E2 was detected, possibly due to lack of lipid substrates in serum-deprived cells, suggesting that the increase in c-fos mRNA in response to gravitational loading is a result of mechanical stimulation. These results indicate that a small magnitude mechanical loading, such as that experienced during a shuttle launch, can alter mRNA levels in quiescent osteoblastic cells.

Actins↗
PubMed1997

The Gravitational Stability of the Interface between Two Electrorheological Fluids

The propagation of gravitational waves between two semi-infinite superposed electrorheological fluids is investigated. Criteria for stability in the presence of a vertical or a horizontal electric field are examined. A modified Chandrasekhar transcendental dispersion relation is obtained. Stability analysis is discussed throughout the case of a small dimensionless phase velocity. The influence of the nondimensional parameters on the growth rate of the Rayleigh-Taylor instability is discussed. The behavior of the growth rate with respect to the stratified viscosity, as well as the stratified retardation time in the presence or absence of an electric field, is investigated. It is shown that a vertical electric field retards the stabilizing influence of both the retardation time and the viscosity, while the presence of a tangential field suppresses the destabilizing influence of the stratified density. A mechanism that shields against the destabilizing influence of the vertical electric field is observed. This shielding mechanism is due to viscous and elastic effects.

Journal Article↗
PubMed1989

Gravitational representation of simultaneously recorded brainstem respiratory neuron spike trains.

Experiments designed to study concurrent processes in neural networks have been hampered by limitations of available analytical methods. A recently described gravitational representation of spike train data was used to evaluate groups of simultaneously monitored medullary respiratory related neurons in anesthetized, vagotomized cats. The results establish that the method can detect and define functional associations among elements of such groups after as few as 20 respiratory cycles.

Action Potentials↗
PubMed1994

Metabolic adaptation of skeletal muscles to gravitational unloading.

Responses of high-energy phosphates and metabolic properties to hindlimb suspension were studied in adult rats. The relative content of phosphocreatine (PCr) in the calf muscles was significantly higher in rats suspended for 10 days than in age-matched cage controls. The Pi/PCr ratio, where Pi is inorganic phosphate, in suspended muscles was less than controls. The absolute weights of soleus and medial gastrocnemius (MG) were approximately 40% less than controls. Although the % fiber distribution in MG was unchanged, the % slow fibers decreased and the % fibers which were classified as both slow and fast was increased in soleus. The activities (per unit weight or protein) of succinate dehydrogenase and lactate dehydrogenase in soleus were unchanged but those of cytochrome oxidase, beta-hydroxyacyl CoA dehydrogenase, and citrate synthase were decreased following unloading. None of these enzyme activities in MG changed. However, the total levels of all enzymes in whole muscles decreased by suspension. It is suggested that shift of slow muscle toward fast type by unloading is associated with a decrease in mitochondrial biogenesis. Further, gravitational unloading affected the levels of muscle proteins differently even in the same mitochondrial enzymes.

Animals↗
PubMed1994

Size- and density-dependent elution of normal and pathological red blood cells by gravitational field-flow fractionation.

Elution of normal and pathological human red blood cells (RBCs) was performed by gravitational field-flow fractionation (GFFF). The reproducibility of the retention factor was lower than 10% and elution at high and low flow-rates confirmed the existence of "lifting forces". No direct correlation between size and retention was observed for normal RBCs in the absence of density information. Elution of pathological human RBCs, known to be modified in shape, density and rigidity, was performed. The elution parameters confirmed that the retention mechanism of RBCs is at least density dependent but that other factors can be involved, such as shape or deformity. Moreover, peak profile description parameters (standard deviation and asymmetry) can be qualitatively related to some biophysical parameters. Numerous elution characteristics can be linked to cell properties described in the literature and although GFFF appeared to have limited capabilities in terms of size analysis it appeared to be a versatile tool for studying cell biophysical characteristics.

Anemia, Sickle Cell↗
PubMed1995

Selective elution and purification of living Trichomonas vaginalis using gravitational field-flow fractionation.

Gravitational field-flow fractionation is one of the simplest separation methods for biological materials. Its potential in parasitology is demonstrated for Trichomonas vaginalis, a parasite responsible for one of the most widespread sexually transmitted diseases. It was observed that this unicellular parasite can be purified in a culture medium with a recovery of 85% for the living trophozoites. The parasite retention characteristics were different when motile living and non-motile dead cells were eluted, motile cells being less retained than the non-motile cells.

Adult↗