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At least 523 records · Page 29Linked to original sources
PubMed2004

Gravitational effects on apoptosis of presumptive ectodermal cells of amphibian embryo.

The effects of simulated microgravity (clinostat rotation at 6 rpm) on the presumptive ectodermal cells of amphibian embryos were examined. When morulae of Cynops pyrrhogaster developed under the influence of simulated microgravity, the thickness of the presumptive ectoderm was greater significantly. Embryonic cells isolated from the presumptive ectoderm of morulae were cultured for one day under the influence of simulated microgravity. The number of cells was greater after such clinostat rotation than in the control culture. TUNEL staining and electron microscopy revealed apoptotic cells both in embryos and among cultured cells, but the number of apoptotic cells was smaller in clinostat-treated embryos and cultured cells than in their controls. These results suggest that simulated microgravity suppresses apoptosis in the amphibian embryo, and as a result, affects the thickness of the presumptive ectoderm.

Animals↗
PubMed1994

Anatomical and gravitational influences on cardiac displacement in snakes (Lepidosauria, Serpentes).

Radiographs of live, unanesthetized snakes were used to document the position of the heart in the body cavity during horizontal, head-up, and head-down postures. The extent of cardiac displacement observed during these postural changes differed substantially among the snakes examined, ranging from virtually none in a thin-bodied arboreal snake to as much as three vertebral lengths (= half the length of the heart) in a heavy-bodied terrestrial Crotalus. The basis of this differential cardiac displacement is attributed to the anatomical "packaging" of the pericardial sac. In some snakes the pericardial sac is loosely suspended in the body cavity by the great vessels and connective tissue sheets. In contrast, in other snakes the pericardical sac is buttressed against the body wall, the lung, or the liver. We hypothesize that cardiac displacement during postural change may alter the pattern of blood flow in the aortae of snakes.

Animals↗
PubMed1991

Cytoplasmic streaming in Chara rhizoids: studies in a reduced gravitational field during parabolic flights of rockets.

In-vivo videomicroscopy of Chara rhizoids under 10(-4)g demonstrated that gravity affected the velocities of cytoplasmic streaming. Both, the acropetal and basipetal streaming velocities increased on the change to microgravity. The endogenous difference in the velocities of the oppositely directed cytoplasmic streams was maintained under microgravity, yet the difference was diminished as the basipetal streaming velocity increased more than the acropetal streaming velocity. Direction and structure of microfilaments labeled by rhodamine-phalloidin had not changed after 6 min of microgravity.

Acceleration↗
PubMed1992

Hydrostatic pressure mimics gravitational pressure in characean cells.

Hydrostatic pressure applied to one end of a horizontal Chara cell induces a polarity of cytoplasmic streaming, thus mimicking the effect of gravity. A positive hydrostatic pressure induces a more rapid streaming away from the applied pressure and a slower streaming toward the applied pressure. In contrast, a negative pressure induces a more rapid streaming toward and a slower streaming away from the applied pressure. Both the hydrostatic pressure-induced and gravity-induced polarity of cytoplasmic streaming respond identically to cell ligation, UV microbeam irradiation, external Ca2+ concentrations, osmotic pressure, neutral red, TEA Cl-, and the Ca2+ channel blockers nifedipine and LaCl3. In addition, hydrostatic pressure applied to the bottom of a vertically-oriented cell can abolish and even reverse the gravity-induced polarity of cytoplasmic streaming. These data indicate that both gravity and hydrostatic pressure act at the same point of the signal transduction chain leading to the induction of a polarity of cytoplasmic streaming and support the hypothesis that characean cells respond to gravity by sensing a gravity-induced pressure differential between the cell ends.

Calcium↗
PubMed1997

Gravitational gradients and blood flow patterns in specialized arboreal (Ahaetulla nasuta) and terrestrial (Crotalus adamanteus) snakes.

Blood pressure and blood flow patterns were recorded from the carotid artery and aortae of a thick-bodied terrestrial snake (Crotalus adamanteus) and a thin-bodied arboreal species (Ahaetulla nasuta) anesthetized with ketamine hydrochloride. Hemodynamic stress induced by rotation resulted in pronounced changes in the blood flow patterns and pressure in C. adamanteus: rotation of A. nasuta produced changes of a similar type, but of a much lower magnitude. The markedly different responses of these two species, the baroreceptor reflexes of which were disrupted, suggest that morphological factors--such as differential gross cardiac displacement, or variation in the interaortic foramen--in addition to physiological factors, are important in determining a snake's ability to withstand hemodynamic stress.

Adaptation, Physiological↗