Gravity is the most fundamental biomechanical stimulus for posture change.Pressure of blood flow is one of primary indicators to evaluate cardiovascular performance.Up to now, the underlying mechanism of effects of posture change on cardiovascular system is still unclear.A 3D FSI mathematical model with posture change was presented.By applying the body force terms to the fluid equation and the vessel wall equation, the model could be used to study posture change and the effects of gravity on the pressure of blood flow quantitively.Under different inlet-outlet pressure difference(IODP) and different postures such as horizontal, upright and upside-down one, the effects of gravity were simulated.In horizontal position, the pressure distributions of blood flow transformed from 2D(two-dimensional) axis-symmetry without gravity to 3D asymmetry with gravity under small IODP.With IODP increasing, gravity had less effects on pressure distribution and extreme value.As IODP reached 10 665.6 Pa(80 mmHg) and 2 666.4 Pa(20 mmHg) respectively, this effect was observed to be constant.Similar results were obtained from 3D fluid-only model.In either upright or upside-down position, 2D axis-symmetric pressure distribution was observed with and without gravity, yet the position, in which extreme pressure appeared, was different in upright position from that in upside-down one.Finally, the effect intensity of gravity in upright or upside-down position was more than twice as much as that in horizontal one.The results indicate that introducing body force term into the fluid and solid equations to present a novel model, which was based on hemodynamics, will provide a new way to study posture change.Effects of gravity on pressure distribution and extreme value changed with different postures and IODP.If IODP is small, ignoring effect of gravity and postures so as to simplify the hemodynamics model to 2D axis-symmetric one, the conclusion should be drawn with caution.

Returning astronauts had experienced decreased immune function and increased vulnerability to infection during spaceflights.In immune system,cell adhesion molecules(CAMs) play an important role in regulating immune response in normal physiological conditions.Studying changes of CAMs under microgravity could not only understand the effects of microgravity and its molecular mechanism on immune function,but also help to study the relative mechanism about cell sensation of microgravity.In this review,we will introduce some downstream signal pathways,gene expression and the effects on cell functions under microgravity.All of them are regulated by cell adhesion molecules related with the immune system.

Rotating wall vessels (RWVS), an ingenious apparatus for three-dimensional suspension culture, is widely used to build a simulated microgravity-effect on cell. Independent researchers have proposed hypotheses to illustrate why RWVS can simulate certain aspects of microgravity. Many of the hypotheses stated that the culture condition in RWVS is determined by the cellular mechanical environment which is a result of low fluid shear and microcarrier's motion. The microcarrier's motions consist of primary and secondary motions. In the light of the analysis of forces loaded by the microcarriers, some conclusions are drawn from the data on microcarriers' primary and secondary motions about which many simulations and observations have already been conducted.
Cell Culture Techniques ; instrumentation ; methods ; Gravitation ; Models, Theoretical ; Motion ; Rotation ; Stress, Mechanical ; Weightlessness Simulation

Although it is clear that changes of gravity can alter dramatically the functions and structures of cells, little is known about how living cells sense these signals and convert them into a biochemical response. Recent studies estimated that the changes of gravity might influence the single cell directly and indirectly. So far, the molecular mechanism of gravisensing remains unknown, however, according to a great deal of researches focusing on this point, several pathways could be considered: (1) Pre-stress perception pathway; (2) Cytoskeleton-perception pathway; (3) Stress-sensitive ion channel pathway; (4) Indirect effects of gravitational change.
Cell Physiological Phenomena ; Cytoskeleton ; physiology ; Gravitation ; Gravity Sensing ; physiology ; Signal Transduction ; Space Flight ; Weightlessness

The molecular mechanism underlying muscular atrophy and gravisensing during spaceflight is still unknown. The major effects of spaceflight on body-wall muscles of Caenorhabditis elegans (C. elegans) in the structures and functions wore examined, and five important muscle-related genes and three proteins were studied after nearly 15-day spaceflight. The changes for the wall-muscles were observed in situ. Decreased muscle fiber size was observed with myosin immunofluorescence and duller dense-body staining in flight samples, which suggested that muscular atrophy had happened during spaceflight. However, F-actin staining showed no differences between the spaceflight group and ground control group. Otherwise, after returning to the earth the C eleganu displayed reduced rate of movement with a lower ratio (height/width) in crawl trace wave, which indicated a functional defect. These results demonstrated that C. elegans muscular development was changed in response to microgravity, and changes also occurred at the level of gene transcription and protein translation. Expression of dys-I increased significantly in body-wall muscles, while hlh-1, myo-3, uric-54 and eg1-19 RNA levels decreased after spaceflight. Dystrophin (encoded by dys-1) is one of important components in dystrophin-glycoprotein complex (DGC). Increased dys-I expression after flight implied that the muscular cell would accept more gravity signals by DGC in mierogravity in order to keep mechanical balance within the cells. It is concluded that DGC was involved into the mechanical transduction in body-wall muscles of C. elegans when gravity varied, which potentially played a vital role in gravisensing. The changes ofhlh-l, myo-3, tmc-54 and egl-19 suggested that they had the effects of promoting microgravity-induced muscular atrophy in strcture and function aspects. Result of Western blotting showed that the level of myosin A in spaceflight group decreased, further confirmed that atrophy happened during flight.

Bioseperation, cell cultivation and cell electrofusion are three main biological processes in space laboratories. Microgravity is free from the influences of convection and sedimentation. Therefore, it is an ideal realm for cell electrofusion and hence it can be used in the research of monoclonal antibody, cross breeding and microgravity biology. This paper reviews the research of cell electrofusion under microgravity, including the changes of cytoskeleton and the mechanism of cell electrofusion.
Animals ; Cell Culture Techniques ; Cell Fusion ; methods ; Electric Stimulation ; Electroporation ; methods ; Mice ; Microelectrodes ; Weightlessness ; Weightlessness Simulation

CHO cells expressing human GPIb/IX and rabbit red blood cells coated with human von Willebrand factor (VWF) were adapted to our study on the binding probability and the detachment force of GPIb/IX and VWF. With the micropipette system, the two cells were impinged under a constant force for controlled time. When the cells were pulled apart, the deformation of RBC was recorded, and the binding score and detachment force of the proteins were determined. After the two cells were impinged into 0.5 microm for 30 s, the binding probability of the two cells carrying GPIb/IX and VWF was 15.0%. Via analyzing the deformation of red blood cells, we found out the distribution of rupture forces of cells with GPIb/IX and VWF. Therefore, we infer that the continuous distribution of the detachment force is due to the stochastic effect. The most probable value of the detachment force was 10 pN.
Animals ; Binding Sites ; Blood Platelets ; metabolism ; CHO Cells ; Cell Adhesion ; Cricetinae ; Cricetulus ; Humans ; Platelet Activation ; physiology ; Platelet Glycoprotein GPIb-IX Complex ; chemistry ; metabolism ; Rabbits ; von Willebrand Factor ; chemistry ; metabolism

This study sought to detect the pathological changes of anterior cruciate ligament (ACL) and medial collateral ligament (MCL) under injury stretch. Bone-ACL-Bone (B-ACL-B) and B-MCL-B complexes were isolated from 20 male Wister rats, and were immersed in phosphate buffered saline. The complexes were stretched with 10% or 20% strain for 10 min or 30 min. After being stretched, the specimens were fixed in 10% buffered formalin, then mounted in paraffin. Sections were stained with Alcian blue-PAS and HE. The following results were found: In the control group, the matrix in ACL contained much more GAGs, as compared with that in MCL. When stretched with 10%, most of the fibroblasts in ACL were elongated like spindles in shape, and some pyknotic nuclei were found increased with stretching time. With 20% strain, ACL showed disruption in parts of collagen fibrils and lysis. But MCL was often torn at its tibia end. The injury can be detected in pathological slices under microscope, even this injury can not be found with naked eye. This injury first starts with the disturbance of the nucleus in the ligament, but following further stretching, it will extend to the rupture of collagen fibrils, and the serious injury of the fibroblasts is especially bad to the repair of the ligament.
Animals ; Anterior Cruciate Ligament ; pathology ; Anterior Cruciate Ligament Injuries ; Male ; Medial Collateral Ligament, Knee ; injuries ; pathology ; Rats ; Rats, Wistar ; Stress, Mechanical