In addition, centrifugal force can cause the vestibular system to give one the sense that downward is in the direction away from the center of the centrifuge rather than the true downward direction. Dizziness due to spinning
When one spins and stops suddenly, fluid in the inner ear continues to rotate causing a sense of continued spinning while ones visual system no longer detects motion. Virtual reality
Usually, VR programs would detect the motion of the users head and adjust the rotation of vision to avoid dizziness. However, some cases such as system lagging or software crashing could cause lags in the screen updates. In such cases, even some small head motions could trigger the motion sickness by the defense mechanism mentioned below: the inner ear transmits to the brain that it senses motion, but the eyes tell the brain that everything is still. Motion seen but not felt
In these cases, motion is detected by the visual system and hence the motion is seen, but no motion or little motion is sensed by the vestibular system. Motion sickness arising from such situations has been referred to as "visually induced motion sickness" (VIMS). Space motion sickness
Zero gravity interferes with the vestibular systems gravity-dependent operations, so that the two systems, vestibular and visual, no longer provide a unified and coherent sensory representation. This causes unpleasant disorientation sensations often quite distinct from terrestrial motion sickness, but with similar symptoms.
Mechanism
In cell biology, actinomycin D is shown to have the ability to inhibit transcription. Actinomycin D does this by binding DNA at the transcription initiation complex and preventing elongation of RNA chain by RNA polymerase. History
Actinomycin D was the first antibiotic shown to have anti-cancer activity. It was first isolated by Selman Waksman and his co-worker H. Boyd Woodruff in 1940. It was approved by the U.S. Food and Drug Administration (FDA) on December 10, 1964, and launched by Merck Sharp and Dohme under the trade name Cosmegen. Research use
Because actinomycin can bind DNA duplexes, it can also interfere with DNA replication, although other chemicals such as hydroxyurea are better suited for use in the laboratory as inhibitors of DNA synthesis. Actinomycin D and its fluorescent derivative, 7-aminoactinomycin D (7-AAD), are used as stains in microscopy and flow cytometry applications. The affinity of these stains/compounds for GC-rich regions of DNA strands makes them excellent markers for DNA. 7-AAD binds to single stranded DNA; therefore it is a useful tool in determining apoptosis and distinguishing between dead cells and live ones. References
External links
"Dactinomycin". Drug Information Portal. U.S. National Library of Medicine.