ABSTRACT
It has been shown that the minimum gravity exposure requirements vary greatly among different physiological systems. A preliminary comparison between two extremes, vessels vs. bones, shows that not only the mechanostat at the tissue level differs greatly, but also the bone loss during weightlessness may also involve calcium deposition-resorption changes. It seems that the surprising efficacy of intermittent artificial gravity (IAG) is due to the vascular tissues possessing a strong resilience or "memory" function toward restoring their original pre-stress and tensegrity state at the 1 G environment. It appears that the bone tissue is related to a more complex tensegrity paradigm involving both osteoblasts and osteoclasts, and a longer half time for calcium deposition-absorption. Cell-level models (CellML) for calcium dynamics is currently available. We hope that the Physiome Project can use this modeling framework to help interpret the resistance of bones to IAG and to evaluate whether the "intermittent" or "continuous" AG scheme should be adopted eventually for future exploration-class spaceflight.
Subject(s)
Animals , Rats , Bone and Bones , Calcium , Gravity, Altered , Osteoblasts , Osteoclasts , Weightlessness , Weightlessness SimulationABSTRACT
It has been demonstrated that individuals exposed to actual or simulated microgravity often experience cardiovascular dysfunctions when returning to Earth. The underlying mechanisms of orthostatic intolerance and countermeasure treatment are still poorly understood. In this paper, the progress in the mechanism of cardiovascular deconditioning from the view of vascular remodeling, increased venous compliance in the lower limbs, cellular proliferation and differentiation, and cell signaling pathway was reviewed. Meanwhile, an overview of the countermeasures including exercise, lower body negative pressure, thigh cuffs, traditional Chinese herb medicine and artificial gravity was presented.
Subject(s)
Humans , Cardiovascular Deconditioning , Physiology , Cell Communication , Cell Differentiation , Cell Proliferation , Gravity, Altered , Vascular Remodeling , Weightlessness , Weightlessness SimulationABSTRACT
<p><b>OBJECTIVE</b>To explore the effect of simulated navigation stimulation on the anesthetic sensitivity of sevoflurane in rats, so as to provide basis for rational using sevoflurane during navigation.</p><p><b>METHODS</b>SD rats were stimulated by Crampton model and the conditioned taste aversion (CTA) was regarded as criterion of motion sickness. (1) 60 rats were randomly divided into control (n = 15) and rotation group (n = 45). The changes of behavior and autonomic activity, sevoflurane concentration achieved sleep and anesthesia states, and the revitalization time were observed in two group rats. (2) 32 rats were randomly divided into control (I), rotation (II), anesthesia (III) and rotation plus anesthesia (IV) group (n = 8). The acetylcholine (Ach), norepinephrine (NE), r-aminobutyric acid (GABA), glutamic acid (Glu) of brain cortex, thalamus and hippocampus were determined respectively in the four group rats.</p><p><b>RESULTS</b>In control group, the sevoflurane concentration achieved sleep and anesthesia states were 1.74% +/- 0.05% and 3.54% +/- 0.05% respectively, but, those concentrations were 1.51% +/- 0.06% and 3.14% +/- 0.08% in rotation group. There were lower significantly in rotation group than those in control group (P < 0.01). It was a major characteristic that all of the neurotransmitters were reduced significantly in II group, this was even more in brain cortex and thalamus (P < 0.01). In II group, Ach was upward in brain cortex, NE and GABA were reduced in hippocampus obviously. The change tendency of neurotransmitters in IV group was more close to II group, that was, the effect of rotation stimulation was more obvious.</p><p><b>CONCLUSION</b>The anesthetic sensitivity of sevoflurane could be obvious increased in rats simulated navigation stimulation.</p>
Subject(s)
Animals , Male , Rats , Anesthetics , Pharmacology , Cerebral Cortex , Metabolism , Gravity, Altered , Hippocampus , Metabolism , Methyl Ethers , Pharmacology , Neurotransmitter Agents , Norepinephrine , Physical Conditioning, Animal , Rats, Sprague-Dawley , Rotation , Thalamus , Metabolism , gamma-Aminobutyric AcidABSTRACT
Pacientes afectados con síndrome hemorrágico inducido por contacto con orugas del género lanomia presentan desde el punto de vista clínico: hematomas, equimosis, hematuria, hemoragias digestivas, pulmonares y peritoneales que pueden conducir a la muerte. Los estudios de la hemostasia han demostrado: recuento de plaquetas normal, con alargamiento de las pruebas globales de coagulación (TP. aTPT y TT), disminuyendo del Fg, FV, FXIII, Pg y &2AP, elevación del factor VIII:c, FvW, PDF y diemeros D con un recuento plaquetario normal. La administración de sangre total o plasma fresco congelado induce una disminución severa del número de plaquetas con agravamiento del cuadro clínico. La administración de fibrinógeno humano purificado (grado terapéutico) ó crioprecipitado y antifibrinolíticos producen una recuperación clínica rápida sin modificación del número de plaquetas. Se concluye que en estos pacientes existe una hiperfibrinolisis con una coagulación intravascular diseminada (CID) leve que se manifiesta al administrar sangre total o plasma fresco congelado. Actualmente se recomienda para la terapia el fibrinógeno humano purificado (grado terapéutico) o crioprecipitado, de acuerdo a los valores del fibrinógeno. Se debe administrar también antifibrinolíticos como aprotinina, y en caso de no disponer de este inhibidor, usar EACA o ácido tranexámico, vigilando la evolución de las plaquetas. No debe administrarse sangre total ni plasma fresco congelado. En Brasil se esta usando un suero anti-lonomia obliqua producido en caballos. En Lanomia achelous se han identificado activadores del FII, FV y del Pg; compuestos parecidos a la plasmina, al FXa y a la calicreína, además de una proteasa que degrada al FXIII y un inhibidor del FV. En la lonomia obliqua se han identificado activadores del FII y del FX y un compuesto parecido a la fosfolipasa A2. El extracto crudo de la lonomia achelous y una de las fracciones cromatográficas, al ser administrados subcutáneamente a conejos producen descenso del Fg, Pg y FXIII. La inyección endovenosa de la proteasa que degrada al FXIII induce lisis de trombos preformados en la vena yugular de conejos, e inhibición del crecimiento posterior del trombo remanente, con descenso del Fg, Pg y FXIII. En la lonomia oblicua, el activador de la protrombina administrado por vía endovenosa induce una CID