Influence of chronic acceleration on energy metabolism of chickens and animals, as indicated by maintenance feed requiremen

Besch, E. L.

Burton, R. R.

Kelly, C. F.

Sluka, S. J.

Smith, A. H.

English

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PROGRESS REPORT 
1 September 1966 
National Aeronautics and Space Administration Grant: 05-004-008 
With: The University of California (Davis Campus); 
Entitled: "CHRONIC ACCELERATION STUDIES -- PHYSIOLOGICAL RESPONSES TO 
ARTIFICIAL ALTERATIONS IN WEIGHT. I' 
CC-nvinci-nl r..-..GLpaA T----- s ~ ~ ~ ~ ~ t i g a t c r r s :  C. F. Kelly, Professor of Engineering 
A .  H. Smith, Professor of Physiology 
Principal Collaborators: E. L. Besch, Assistant Research Physiologist 
R. R. Burton, Associate Specialist (Pathology) 
S. J. Sluka, Associate Specialist (Engineering) 
INFLUENCE OF THE AXBIENT ACCELERATIVE FORCE ON FEED INTAKE- 
Comparative studies over the past century have established an 
exponential relationship between body size and metabolism -- as well as 
between body size and many other physiological and anatomic parameters. 
Reviews and historical accounts of these classic concepts are contained in 
the books by Brody (1945) and Kleiber (1961). These relationships between 
size and metabolism generally have been referred to some derivative of body 
weight -- which, by definition, is equivalent to body mass under the condition 
of Earth-gravity. However, weight is not a fundamental property of matter, 
but merely a phenomenon developed in a restrained body exposed to an acceler- 
ative force: 
W = M x Z  g 
Where: "W" and "M" represent weight and mass in equivalent units 
(i-e., lbs., kg., etc.); and, 
a is the ambient accelerative force, in the same units 
as "g", the Earth'? gravitational constant (i.e., 980 
dynes, 32 ft./sec. , etc.). 
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The dynamic properties of an environment are described by the W:M ratio 
(conventionally designated as "G:" see: Dixon and Patterson, 1953; and, 
Human Acceleration Studies, 1961). It also is evident from the above equation 
that a body of a certain mass may exhibit a different weight, when exposed 
to a force other than Earth-gravity. 
With the development of astronautics, prolonged alteration of the W:M 
ratio of man, as well as other organisms, has become a reality. Changes in 
metabolic function (including the maintenance feed requirement) may be anti- 
cipated from such "artificial changes in weight.'' For example, the work 
required for moving a body against an accelerative force is a function of its. 
weight, rather than its mass, as indicated by the equation,for qotential 
energy : 
P . E . = h x M x Z = h x W  g 
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https://ntrs.nasa.gov/search.jsp?R=19660025878 2020-03-16T20:09:30+00:00Z
Where: "h" is the distance of movement; and, other symbols have 
the same significance indicated previously. 
Consequently, in a hyperdynamic (llsuper-gravity'l) environment, a greater 
work requirement may be anticipated for equivalent tonus, locomotion, 
circulation, etc., and this must be met by an increased energy metabolism. 
Over the past fifteen years, several programs have been developed to 
examine various aspects of biological changes resulting from the chronic 
exposure of animals to fields of greater strength than Earth-gravity. 
Others have been reported by: Matthews, 1953; Wunder, et al., 1963; Oyama 
and Platt, 1965; and Lang et al., 1965. One of our interests is the 
influence of chronic-acceleration on energy metabolism, as indicated by the 
maintenancefeed requirement, and the results of these investigations are 
reported herein. 
METHODS 
On Earth, studies of the effectsd prolonged alteration of the dynamic 
property of the environment necessarily deal o n l y  with increases, since 
no way is known to limit the force of gravitation. Also such studies must 
depend upon centrifugal forces, since even moderate linear accelerations 
would place an exposed object in Earth-orbit in a matter of minutes. 
Unfortunately, in addition of producing an accelerative force, centrifugation 
also involves turning -- which has distinct biological effects. This can 
be reduced, but not eliminated, by lengthening the centrifuge's radius of 
rotation. However, the influence of turning upon observed phenomena can 
be tested separately. Since the centrifugal force is proportional to the 
square of the rotation rate (at a particular radius), it is possible to 
expose animals to a fairly rapid turning (e.g., 5-10 rpm) without developing 
a significant increase in the accelerative force. Under such conditions, 
no differences are evident between "rotated" and control animals. Other 
studies (Winget, et al., 1962) have indicated no great change in laby- 
rinthine function as a result of chronic acceleration at much greater 
rates of rotation (e.g., 30 rpm). From such observations, we conclude 
that the predominant factor in the centrifuge environment is the increased 
accelerative force. A l s o ,  from Einstein's "principle of equivalence" it is 
generally considered that the effects of accelerative forces produced by 
motion are the same as those produced by gravitation. 
The contructional details of the instrument used in some earlier 
experiments, as well as the operating characteristics of animal centrifuges 
generally, have been communicated previously (Kelly et al., 1960). The 
experiments reported herein were done on a larger (18' diameter) centrifuge, 
which has only been partially described elsewhere (Smith & Kelly, 1965; 
Wunder, 1965). The acceleration schedule for these experiments is described 
in Figure 1. During an experiment the centrifuges are stopped for a few 
minutes each day to permit feeding and a brief examination of the birds 
(e.g., so that "sick" birds could be eliminated). Weekly, the centrifuges 
are stopped for a longer time (perhaps 1-2 hours), to permit cleaning cages, 
determination of body mass, etc. Thus, the indicated treatment prevailed 
about 98% of the time. 
All experiments were conducted on adult Leghorn (SCWL) chickens, from 
an "acceleration tolerant" strain developed by serially reproducing survivors 
of chronic acceleration experiments (Smith and Kelly, 1961; Burton and Smith, 
1965). These animals differ from unselected strains principally by exhibit- 
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RESULTS 
The - ad l i b i t u m  feed i n t a k e ,  and a s soc ia t ed  changes i n  body m a s s  (both 
as gms/kg body mass/day) f o r  each observa t ion  per iod  of c o n t r o l  and c e n t r i -  
fuging animals are presented  i n  Table 1. An examination of t hese  d a t a  
reveals r a t h e r  s u b s t a n t i a l  v a r i a t i o n s  i n  feed i n t a k e ,  even f o r  t h e  same 
group between observa t ion  per iods .  
r e l a t e d  t o  changes i n  t h e  environment. 
measurements were pooled f o r  s eve ra l  pe r iods ,  where t h e  observa t ions  w e r e  
completed wi th in  30-40 days ,  and t h i s  reduced t h e  v a r i a b i l i t y .  Such d a t a  
are presented  f o r  feed i n t a k e  and m e t a b o l i z a b i l i t y  i n  Table 2 ,  and f o r  mean 
body mass and change i n  body m a s s  i n  Table 3 .  Only d a t a  obta ined  more than  
30 days a f t e r  t h e  last groups ( i .e. ,  5 ,  6 ,  9 and 10, F igure  1 )  w e r e  placed 
on t h e  c e n t r i f u g e  are included.  A t  t h i s  t i m e ,  no marked d i f f e r e n c e s  i n  
r e s u l t s  are evident  between groups t h a t  had been c e n t r i f u g i n g  f o r  30 days,  
and those  cen t r i fug ing  f o r  130 days. 
Some of t h i s  v a r i a b i l i t y  is  t e c h n i c a l  o r  
Consequently t h e  feed  i n t a k e  and o t h e r  
I n  t h e  d a t a  presented i n  T a b l e s  2 and 3,  v a r i a t i o n  i n  feed  i n t a k e  
accompanied by s imilar  changes i n  body m a s s .  Consequently, a l i n e a r  r e g r e s s i o n  
of changes i n  body m a s s  upon feed i n t a k e  w a s  made,using d a t a  from i n d i v i d u a l  
pe r iods  over  t h e  6 months covered by per iods  "i" t o  "r" (Table l), and t h e  
r e s u l t s  of t h i s  a n a l y s i s  are presented i n  Table 4. From t h e s e  i t  is  evident  
t h a t  as t h e  ambient a c c e l e r a t i v e  f o r c e  inc reases  (from normal g r a v i t y  t o  2G), 
t h e  feed  requirement f o r  min tenance  i n c r e a s e s ,  and t h e  change i n  body m a s s  
p e r  gm f eed  ( i . e . ,  t he  s l o p e  of the r eg res s ion )  a l s o  inc reases .  This  lat ter 
r e s u l t  c o r r e l a t e s  with t h e  g r e a t e r  rate of l o s s  of body subs tance  by c e n t r i -  
fug ing  animals during 3 day f a s t s  (which w e r e  i n t e r s p e r s e d  between t h e  feed  
i n t a k e  t r i a l s ) :  
Fas t ing  l o s s  rate Recovery rate 
(d (gm/kp body m s s / d a y )  (gm/kg body mass/day) 
Normal g r a v i t y  1 4  
1 .5  G 18 
2.0 G 20 
26.1 + 1.3* 
33.9 1.2 
38.8 2 1.1 
25.0 + 2.1* 
35.7 z 1.5 
39.1 5 1.0 
* mean and s tandard  e r r o r  
This  g r e a t e r  change i n  body mass, r e l a t i v e  t o  change i n  feed  i n t a k e ,  of 
c e n t r i f u g i n g  b i r d s  i n d i c a t e s  a lesser energy conten t  of t h e i r  t i s s u e s .  This  
a l s o  is  evident  i n  t h e  lesser body f a t  of c e n t r i f u g i n g  b i r d s  (Smith & Kel ly ,  
1963),  which appears  t o  be a genera l  response,  being observed i n  cen t r i fuged  
rats as w e l l  (Casey, 1965). Several  groups (1, 5 and 1 0 )  w e r e  s a c r i f i c e d  
a t  t h e  end of t h e  c e n t i r f u g a t i o n  per iod ,  and t h e  dressed  carcasses analyzed 
f o r  f a t  conten t :  
g r a v i t y  
1.5G 
2.OG 
Composition of ca rcas  s o f t  t i s s u e  
feed equ iva len t  
water (%) p er gm t i s s u e *  f a t  (%) 
8 . 1 7 5 . 0 6  69.23 2 2.03** 5.17 gm 
5 .20+0.63 70.12 5 0.42 4.16 gm 
4.40+0.63 - 72.07 5 0.71 2.08 gm 
* r e c i p r o c a l s  of s lopes  of r eg res s ions ,  Table 4 
** mean and s tandard  e r r o r  


Chronic acceleration studies - Physiological responses to artificial alterations in weight Progress report

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