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At least 649 records · Page 36Linked to original sources
PubMed2001

[Gravitational osmotic pressure effect for a series of flat polymer membranes positioned horizontally].

In this paper the results of study pressure graviosmotic effect for a double-membrane osmotic-diffusive cell, in which series of two (Ml and M(r)), microporous and symmetrical flat polymeric membranes (Nephrophane and Cellulose IMP-1) separate three compartments (l, m, r) containing the heterogeneous and binary (aqueous glucose or ethanol solutions) or ternary (glucose solutions in 0.75 mole.l-1 aqueous ethanol solution or ethanol solutions in 0.1 mole.l-1 aqueous glucose solution) non-ionic solutions. In this system the solution concentrations fulfill the condition Ckl > Ckm > Ckr. The inter-membrane compartment (m) consists of the infinitesimal layer of solution. The volume of compartment m and external compartment (l and r) fulfill the conditions Vm-->0 and Vl = Vr-->infinity respectively. The calculations of pressure graviosmotic effect for configurations A and B of the double-membrane osmotic-diffusive cell were elaborated. In configuration A solution was placed in compartment below membrane M(r) and water above membrane Ml. In configuration B solution was placed in compartment above membrane Ml and water below membrane Ml. These calculated results are interpreted in terms of the convective instability that increases the diffusive permeability coefficients of complexes: concentration boundary layers (membrane Ml or M(r)) concentration boundary layer.

Diffusion↗
PubMed1975

[Morphologic and cytophotometric indices of the state of the neurons of the spinal cord and spinal cord ganglia following exposure to gravitational stress].

The work presents data on the state of the neurons of the spinal ganglia and the spinal cord of the lumbosacral part in 96 cats subjected to single stresses (10g) and repeated ones (6g). The material was stained with thionin after Nissl. RNA was detected after Einarson. Photometry of the sections was made in MUP.5. Morphological changes were shown to be more pronounced in sensory cells. The method of cytophotometry established the increase by 25% amount of RNA in their cytoplasm after single stresses. Repeated stresses resulted in depletion of RNA. The amount of RNA returned to the initial level within 2 days after single stresses and within 3 days after repeated rotations. The shifts were much less pronounced in motoneurons.

Animals↗
PubMed1976

[The effect of gravitational stress in the pelvis--head direction on the blood vessels of the sympathetic trunk].

The experiment was carried out in 15 rabbits. Three of them were control. The stress of the pelvis--head direction was obtained in a centrifuge of 1 m radius. Six animals were rotated for 1 min., the other six--til death, which came within 3--4,5 min. of the experiment. By methods of injection, clearing and measuring it was found that in the vessels of the sympathetic trunk congestion phenomena were first and foremost under effects of stresses of the caudo-cranial direction. Their intensity is in direct dependence on the duration of stress. In the 1st series (1 min.) a considerable congestion of venous blood in the cranial sympathetic ganglion was observed in 1 case, while in the 2nd series (3--4,5 min.) very drastic congestion phenomena, with an enlarged diameter, vein deformity and so on, were constantly noted. A support is given to literature data that such "negative" stresses are less endurable for animals, death comes soon, since the phase of relative compensation under given conditions is promptly changed for the phase of decompensation.

Animals↗
PubMed1976

[Changes in the microcirculatory bed of the compact substance of bones following local mechanical pressure, gravitational stress and hypokinesia].

Effects of different stimuli upon the structure of the microcirculatory bed of the compact substance of long tubular bones were studied in 89 animals (rabbits and cats). Prolonged local pressure on the bone resulted in transformations characterized by lacunar resorption of the compact substance in the site of application of the force and endosteal bone-formation on the opposite side of the same part of the bone. Hypergravitation caused a considerable transformation of the microcirculatory bed and the histoarchitectonics of the bone compact substance. Smooth and linear perivascular resorption took place around dilated vessels in osteon canals. It resulted information of resorption cavities. In addition, processes of bone formation took place. Due to effects of hypokinesia the transformation of the compact substance is of a regressive character. The fibrous structures of the bony tissue and blood vessels lose their regular orientation and acquire chaotic direction.

Animals↗
PubMedDate not supplied

[The ecological-morphological characteristics of the growth and distribution of cultures of single-cell organisms in a gravitational field].

The paper analyses and summarizes the experimental results obtained by the authors and data accumulated in the literature during recent years in order to reveal the general regularities of the growth, distribution and behavioral parameters of the cells under conditions of reduced gravity ranged from 10(-5) to 5 g. It is indicated that an intensity of gravity effect on these parameters of unicellular organisms depends greatly on the environments, types of cells and their metabolic levels. The effects of changed gravity at the cellular level are the result of shifting the primary physiological characteristics and physicochemical parameters of the culture and cell environments as an integrated biological system.

Animals↗
PubMedDate not supplied

[A physical model of gravitational erythrocyte sedimentation].

A model of erythrocyte sedimentation under gravity is proposed. The model is based on two-phase description of the blood and it involves a kinetic equation of erythrocyte aggregation. A method of characteristics is employed for analysing the physical pattern of sedimentation for different hematocrit. An approximate decision for trajectory of the interface between pure plasma and low-located region of the erythrocyte suspension is obtained. By utilizing this decision the simple coefficient of the erythrocyte aggregation ability calculated in terms of hematocrit and erythrocyte sedimentation rate is possible.

Blood Sedimentation↗