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Retrograde motion in astronomy is, in general, orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is, the central object (right figure). It may also describe other motions such as precession or nutation of an object's rotational axis .
Retrograde signaling in biology is the process where a signal travels backwards from a target source to its original source. For example, the nucleus of a cell is the original source for creating signaling proteins. During retrograde signaling, instead of signals leaving the nucleus, they are sent to the nucleus. [1]
The retrograde motion of a hypothetical extremely distant (and nearly non-moving) planet would take place during a half-year, with the planet's apparent yearly motion being reduced to a parallax ellipse. The center of the retrograde motion occurs at the planet's opposition which is when the planet is exactly opposite the Sun.
Retrograde motion is an apparent change in the movement of a planet in the sky, but that doesn’t mean the planet is physically moving backward in its orbit. Retrogrades are visual illusions that ...
Each night the planet appeared to lag a little behind the stars, in what is called prograde motion. Near opposition, the planet would appear to reverse and move through the night sky faster than the stars for a time in retrograde motion before reversing again and resuming prograde. Epicyclic theory, in part, sought to explain this behavior.
Retrograde axonal transport is mediated by cytoplasmic dynein, and is used for example to send chemical messages and endocytosis products headed to endolysosomes from the axon back to the cell. [2] Operating at average in vivo speeds of approximately 2 μm/sec, [18] [19] fast retrograde transport can cover 10-20 centimeters per day. [2]
This is the source of traction required for migration; the focal adhesion acts as a molecular clutch when it tethers to the ECM and impedes the retrograde movement of actin, thus generating the pulling (traction) force at the site of the adhesion that is necessary for the cell to move forward.
Animation depicting Eudoxus' model of retrograde planetary motion. The two innermost homocentric spheres of his model are represented as rings here, each turning with the same period but in opposite directions, moving the planet along a figure-eight, or hippopede. Eudoxus of Cnidus was the first astronomer to develop the concept of concentric ...