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Offline Andrew K Fletcher

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Micro-gravity and its effects on living subjects
« on: 11/05/2005 13:28:57 »
CHINESE HATCH SPACE-CHICKENS
Sticking with a space-theme, Chinese scientists in Beijing have recently been looking at the effects of space-travel on the development of chickens. Chinese researchers sent a clutch of chickens eggs into space for 7 days, during which they orbited the Earth over 100 times aboard the Shenzhou III space capsule. The eggs were then returned to the laboratory and hatched. The scientists are now looking for any genetic defects caused by the space travel and hope to breed from the chicks that they have reared so that they can study their offspring to see if any side effects are passed on. Naturally, if humans are to sustain themselves on long space journeys to colonise distant planets then an understanding of the impact of space travel on reproduction is critical, which is why this work is extremely important.

http://www.thenakedscientists.com/HTML/Shows/2002.07.07.htm#2

Is this the origin of Egg Flew Young?


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Offline Andrew K Fletcher

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Re: Micro-gravity and its effects on living subjects
« Reply #1 on: 11/05/2005 13:55:35 »
Snakes in Space:

http://spacephysiology.arc.nasa.gov/projects/snakes.html#tolerance
Gravity affects all organisms, particularly terrestrial animals that are large or vertically oriented. Both humans and giraffes, for example, have cardiovascular systems which are specially adapted to circulate body fluids against the force of gravity and to maintain adequate blood flow to the brain. Snakes, however, are unique in their extent and range of cardiovascular adaptations to variable gravity.

More on the Giraffe later.



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Offline Andrew K Fletcher

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Re: Micro-gravity and its effects on living subjects
« Reply #2 on: 11/05/2005 14:08:46 »
Comp Biochem Physiol A 1986;83(2):207-11
Does gravitational pressure of blood hinder flow to the brain of the
giraffe?
Badeer HS
Vascular pressure consists of the sum of two pressures: (a) pressure
developed by the pumping of the ventricles against the resistance of
vessels, designated as viscous flow pressure, and (b) pressure caused by
gravity, traditionally called hydrostatic, better described as gravitational
pressure. In a conduit, both of these pressures must be overcome when a
liquid is discharged to a higher level of gravitational potential energy. If
a liquid is returned to its original level, gravity neither helps nor
hinders flow because of the siphon effect. This circumstance prevails in the
circulatory system. Hence, P1-P2 in the Poiseuille equation excludes
gravitational pressure between those points. The long neck of the giraffe,
therefore, poses no impediment to blood flow in the erect posture. The
giraffe has a high aortic pressure. This is not for driving the blood to its
head but is for minimizing the gravitational drop of intravascular pressure
and collapse of the vessels. The cerebral circulation is protected by the
cerebrospinal fluid which undergoes parallel changes in pressure with
posture. Other vessels in the head are less protected by connective tissue,
surrounding muscles and other structures. The high aortic pressure in the
giraffe is probably caused by the high total peripheral resistance of the
systemic circuit due to vascular adaptations related to the overall height
of the animal.
PMID: 2869860, UI: 86163084


Tierarztl Prax 1989;17(1):97-100
[The immobilization of giraffes].
[Article in German]
Wiesner H, von Hegel G
Munchner Tierpark Hellabrunn.
The anatomical and physiological conditions of blood circulation in the
giraffe are pointed out. 16 immobilizations in the giraffe of either sex are
reported, of which 10 were immobilized according to the following scheme. 1.
Premedication: 30 mg Xylazine 150 mg Hyaluronidase 2. 15 minutes later a
halter with two long ropes is put on to hold up the animals' heads after
they lay down. 3. 20 minutes after premedication the injection of 5.6-6.0 mg
Etorphine (2.5-2.7 ml Immobilon) together with 150 I.U. Hyaluronidase
follows. 4. We think that the most important fact is to hold the animals
head and neck in an upright position during the whole time of
immobilization. 5. Within 3 to 5 minutes after the intravenous application
of 15 mg Diprenorphine (5.0 ml Revivon) the animals raise without any
problems.
PMID: 2718168, UI: 89242651


Am J Physiol 1989 Feb;256(2 Pt 2):R567-71
Siphon mechanism in collapsible tubes: application to circulation of the
giraffe head.
Hicks JW, Badeer HS
Department of Physiology, School of Medicine, Creighton University, Omaha,
Nebraska 68178-0224.
Controversy exists over the principles involved in determining blood flow to
the head of a giraffe, specifically over the role of gravity pressure (pgh)
in the collapsible jugular vein in facilitating uphill flow in arteries.
This study investigated the pressures within vertically oriented models
containing both rigid and collapsible tubes. An inverted U tube was
constructed (height = 103 cm) of thick rubber tubing in the ascending limb
and collapsible dialysis tubing in the descending limb. Water flow was
induced by a variable speed pump maintained at the reservoir level such that
the descending limb was partially collapsed. Pressure ...


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Offline Andrew K Fletcher

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Re: Micro-gravity and its effects on living subjects
« Reply #3 on: 23/07/2005 10:48:51 »
Human Space Adaptation Helps us Understand Aging


Astronauts: Simulating the Aging Process

Life on Earth evolved in the presence of gravity. For this reason, gravity plays a role in all life processes, and exposure to the microgravity environment of space affects living things significantly. Certain physiological changes that occur in space also occur with aging: for example, cardiovascular deconditioning, balance disorders, weakening bones and muscles, disturbed sleep, and depressed immune response. An important difference, however, is that these changes are reversible in astronauts.Research has shown that insufficient exercise- due to aging, paralysis, weakness, injury, or prolonged bedrest, for example- can cause a downward spiral in an individual's health over time, increasing susceptibility to bone fractures and slowing recovery from injuries and other ailments. What researchers learn about the physiological effects of the inactivity that accompanies space flight may yield ways of limiting the deconditioning symptoms of the inactivity that comes with aging.Are these changes inevitable?

http://weboflife.ksc.nasa.gov/curre...hives/aging.htm

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Gravitational biology has the objective of understanding how cells perceive and respond to gravity and how whole organisms use this information. This knowledge is essential for promoting human adaptation to the microgravity of space and to furthering our understanding of how organisms function on Earth.

* Major problems facing astronauts in flight and on return to Earth are neurological disorders of the vestibular system. Similar disorders occur in the general population as a result of infection, intracranial tumors, and head injuries. These lead to significant disabilities because of the profound influence of the vestibular system on posture, balance, and eye and head movements. Ground-based research jointly sponsored by NASA and the National Institute on Deafness and Other Communications Disorders (NIDCD) is making significant headway in understanding the biomechanical and behavioral properties of vestibulospinal postural stabilizing systems. The goal is to discover the neural mechanisms controlling posture and how these processes change in altered gravity environments. This project has generated the first comprehensive model of the head and neck system in which each bone and muscle is modeled as a well-defined element. This multilevel research project illustrates the progress that NASA has made in its cooperation with other agencies in pursuing cutting-edge research that benefits multiple agencies.
http://www.faseb.org/opar/consensus99/nasa.html

***********************************
Neurovestibular Adaptation

The most overt change affecting an astronaut in space flight is the immediate response of the neurovestibular system to changes in gravity. Astronauts experience orientation illusions, posture and locomotion disturbances, vestibulo-occular function and gaze changes, space motion sickness, and possible structural changes affecting sensory-motor behavior and reorganization. Research and technology efforts include ground-based tests of neurological adaptation, operational implications, countermeasures, and impacts on other physiological systems; and instrumentation, models and methods to improve preflight adaptation and better understand individual responses. Countermeasures include artificial gravity, preflight training and adaptation, automated landing systems, inflight exercises, and advanced VR systems.

http://criticalpath.jsc.nasa.gov/Ri...p?DiscMode=D009

***********************************

Cardiovascular Alterations
Cardiovascular adaptation to spaceflight is rapid, with no evidence of functional impairment during spaceflight. Risks include: occurrence of serious cardiac dysrhythmia; impaired cardiovascular response to orthostatic stress; impaired cardiovascular response to exercise stress; manifestation of previously asymptomatic cardiovascular disease; and diminished cardiovascular function. Research and technology focuses on: understanding the mechanisms and processes underlying cardiovascular alterations; risk assessment strategies; models to derive thresholds of operational significance; and potential crew screening and selection criteria. Countermeasures may include pharmacological agents, exercise regimes, artificial gravity, nutritional supplements, mechanical aids, and electro-myostimulation to minimize these risks.
http://criticalpath.jsc.nasa.gov/Ri...p?DiscMode=D003

*************************
Bone Loss
Bones of the legs, pelvis and spine are subject to decreased stress in weightlessness, leading to the release of calcium, leaving the bone more brittle and weak. Risks include: acceleration of age-related osteoporosis; fracture and impaired fracture healing; injury to soft connective tissue and joint cartilage, and intervertebral disc rupture; and renal stone formation. It is unknown whether these changes continue unabated, nor whether they can be totally reversed. Countermeasure research and technology efforts focus on diagnostic tools to monitor and measure critical parameters, including the cellular and molecular mechanisms of bone loss. Prevention and rehabilitation involves pharmacological, exercise and nutritional regimens, artificial gravity options, and crew screening and selection criteria to identify “at risk” individuals.
http://criticalpath.jsc.nasa.gov/Ri...p?DiscMode=D002

**************************************

It's actually astonishing that something as tiny as sperm could be affected by gravity. Physicists, says Tash, "might argue that the size of molecules critical to sperm movement are not big enough to be sensitive to gravity." But, he points out, the head of a sperm is about the same size as statoliths in plants -- small floating granules that help plants tell up from down. Gravity may in fact affect things that are even smaller. Researchers, says Tash, are now beginning to find evidence that even the individual proteins that form the structures of the sperm tail may be sensitive to gravity changes.No one knows exactly how gravity affects cells. It may have to do with the cytoskeleton: the structure that gives a cell its shape. Proteins that send signals are often physically connected with the cytoskeleton, says Tash. Perhaps, he says, there is a mechanism in which the gravitational forces on the sperm head are somehow transmitted into the cytoskeleton, which then affects the signaling pathways that alter movement.
http://weboflife.ksc.nasa.gov/curre...ngFertility.htm


********************


SPACE RESEARCH PROVIDES NEW EVIDENCE ON THE ROLE OF GRAVITY IN FERTILIZATION
Oct. 12, 2001Dwayne Brown
Headquarters, Washington
(Phone: 202/358-1726)RELEASE: 01-196NASA researchers have uncovered evidence that gravity, or the lack thereof, may play an important role in the development and evolution of life. The study suggests fertilization is gravity-sensitive and works differently in the near-weightless environment of space than it does here on Earth.Using sperm from tiny sea urchins, the research team conducted both ground- and space-based experiments to examine the impact gravity has on the reproduction process. According to a paper authored by Dr. Joseph Tash, a NASA researcher and a professor at the University of Kansas Medical Center in Kansas City, scientists found gravitational changes may influence a species' ability to reproduce. His team's findings were published in a recent issue of Biology of Reproduction."The research shows that fertilization is altered in a microgravity environment," said Tash. "Such alterations have implications for reproduction of plant and animal food and for long-term space habitation by humans. This research will be essential for prolonged space exploration."The experiments were conducted under a grant from NASA's Office of Biological and Physical Research in Washington. The research program provides investigators with the opportunity to use microgravity or low-gravity environments to investigate the role this fundamental physical force and other space-flight factors have on biological and ecological systems."All life is influenced by the pull of Earth's gravity. NASA scientists are conducting research to explore the role of gravity at all levels of biological processing," said Dr. Kathie Olsen, Acting Associate Administrator for Biological and Physical Research at NASA Headquarters. "Without the presence of Earth's gravity, we are able to pursue answers to questions of how living organisms develop."
http://spaceresearch.nasa.gov/gener...BPR-01-196.html


**************************

One of the complications of prolonged weightlessness is the development of mild anemia associated with reduced red cell production and low reticulocyte response. Strict bedrest has been used as an earth-bound model of space flight, and a qualitatively similar decrease in red cell mass has been found. There is evidence to indicate that this anemia of space flight and bedrest is due to decreased production of red cells rather than hemolysis. Dr. Krantz and his collaborators hypothesize that the decrease in sympathetic nervous system activity produced by bedrest contributes to this decrease by causing impaired erythropoietin production.
http://www.mc.vanderbilt.edu/gcrc/space/


"The explanation requiring the fewest assumptions is most likely to be correct."
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Re: Micro-gravity and its effects on living subjects
« Reply #3 on: 23/07/2005 10:48:51 »

 

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