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Effect of dietary protein level on mature and aged rats in the presence and absence of trauma
NUTRITION RESEARCH, Vol 4, pp. 123-128, 1984 0271-5317/84 $3.00 + .00 Printed in the USA. Copyright (c) 1984 Pergamon Press Ltd. All rights reserved.
EFFECT OF DIETARY PROTEIN LEVEL ON MATURE ANDIAGED RATS IN THE PRESENCE AND ABSENCE OF TRAUMA Jong-Hee Chyun, Ph.D. and Paul Griminger, Ph.D. Department of Nutrition, Rutgers, The State University, New Brunswick, NJ 08903
ABSTRACT
The effect of dietary protein level on reducing body protein losses following trauma was studied in two age groups. Mature (4month old) and aged (24-month old) Fischer 344 male rats were given a 20% casein diet for 7 days before traumatization by laparotomy under sodium pentobarbital anaesthesia. After surgery, the rats were given 5, I0, 20 or 40% casein diets. Nitrogen balance studies (N intake N output in urine, feces and hair) were carried out during the last 3 days pre-trauma and 5 days post-trauma periods. Traumatization by laparotomy significantly reduced N retention of rats. Aged rats retained significantly less N than mature ones during both pre- and post-trauma periods. As the casein level of the diet increased, N retention of rats increased linearly. Except in non-traumatized mature rats, those given a 20% casein diet retained significantly more N than rats given a 10% casein diet; the difference in N retention between the rats consuming the 20% and 40% casein diets was not significant, except for the non-traumatized mature rats. The results show that a relatively high protein level during the posttrauma period reduces body protein losses and that aging compounds the effect of trauma with respect to N loss. KEY WORDS: Aging, trauma, protein level.
INTRODUCTION
It is well known that trauma causes a series of metabolic and hormonal changes in the body (I-5). Among the responses to trauma, loss of body protein is the most characteristic phenomenon (5). The extent of body protein loss is related to the severity and the type of injury sustained (6), and can be influenced by post-traumatic nutrition and environmental conditions (7-10). In this study, the effect of dietary protein level on nitrogen (N) retention in rats after laparotomy was investigated. Since the elderly are frequently exposed to trauma and generally need more time to overcome their infirmities (11), it was of interest to compare young adult rats with aged rats and observe possible age-related differences in the response to trauma.
I. New Jersey Agricultural Experiment Station Publication No. D-14406-I-83 Supported by state funds and by NIH Grant PHS AG00160 from the National Institute of Aging.
]23
124
CHYUN AND GRIMINGER: PROTEIN MODULATION OF RESPONSETO TRAUMA MATERIALS AND METHODS
Twenty-four mature (4-month old) and the same number of aged (24-month old) male Fisher 344 rats (Charles River Breeding Laboratories) averaging 230 and 390g, respectively, were housed individually in suspended stainless steel metabolism cages and received a stock diet (Purina Rat Chow) and water ad libitum. T h e animal laboratory was maintained on a 12 hour light-dark cycle, and the temperature was kept between 20 and 22~ After an adjustment period of one week, rats of each age group were divided into four dietary groups of six rats each. All rats received a 20% casein diet for seven days. On the seventh day, three rats in each group were traumatized and the remaining three rats served as non-traumatlzed controls. Trauma consisted of a laparotomy, an abdominal incision 5 cm long through the skin and muscle layers under sodium pentobarbital anaesthesia (intraperitoneal injection, 3 mg/lO0 g body weight). The muscle incision was closed with braided silk 000 sutures by continuous stitches and the skin was closed with metal wound clips (9 mm). After the laparotomy, each of the four groups received a different level of protein, provided by 5, I0, 20 and 40% casein (Table i) a_~dlibitum for five days. TABLE I Diet Composition
Ingredients
% of Casein
5%
10%
20%
40%
(z)
(~)
(z)
(z)
5.0
I0.0
20.0
40.0
a Casein L-Methionine Corn Starch
b
Sucrose Fiber
c
Corn Oil
d
Mineral Mix Vitamin Mix
e
f
Choline Bitartrate
a b c d e f
0.08
0.15
0.3
0.6
18.51
17.34
15.0
10.32
61.71
57.81
50.0
34.38
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
3.5
3.5
3.5
3.5
1.0
1.0
1.0
1.0
0.2
0.2
0.2
0.2
Dellwood Food Inc., Yonkers, NY Corn product, CPC International, Englewood Cliffs, NJ Solka-floc, Brown Company, Berlin, NH Bio-Service Inc,, French Town, NJ AIN 76A mineral mixture, Dyers, Bethlehem, PA. For composition see J. Nutrition 107:1340-1348, 1972. AIN 76A vitamin mixture, Dyets, Bethlehem, PA. For composition see J. Nutrition 110:1726, 1980.
CHYUN AND GRIHINGER: PROTEIN HODULATION OF RESPONSE TO TRAUMA
125
Urine, feces and hair were collected for the last three days of pre-trauma and five days of post-trauma periods daily in order to determine the nitrogen (N) balance. Total N content of urine, feces, hair and diet were determined by a modification of the Kjeldahl method (12). When the urine samples could not be analyzed immediately, they were stored frozen at -20~ Results were subjected to analysis of variance according to the p r i n c i p l e s outlined by Zar (13).
RESULTS AND DISCUSSION
Food intake of traumatized animals was sharply reduced on thefirst day after laparotomy and increased gradually until day five post-trauma (Fig. la to Id). However, the amount ot rood consumed did not reach the pre-trauma level (7.6 vs 13.1 g/day, p<0.Ol). Possibly due to the change in feed and the disturbance caused by recovering, removing and returning the traumatized animals, the 20
20 //
o
I~
W
\\
//
,c
);/
z o o o
5
t
U_
I
I
ore1 2 3 4 trauma Ave. POST-TRAUMA
i
5
0
(Days)
I 5 (Days)
20,
20
15 Ld ,c~ lO i-
~J v
FZ
_z
o o o
O
o o. kL
"r" I I I Dra1 2 3 4 trauma Ave. POST-TRAUMA
b - 10% protein
a - 5% protein
o
/ s/
5
0
5
u_
~JI~/ I I ~re1 2 3 4 trauma Ave. POST-TRAUMA
, ~re trauma Ave.
POST-TRAUMA
c
20% protein
-
(Days)
I 5
(Days)
d - 40% protein FIG. I
Food intake of mature (M) and aged tA), traumatized (T) or non-traumatized (N) rats. Post-trauma dietary protein levels indicated (below graphs) O M-N; 9 M-T; /k A-N; 9 A-T
126
CHYUN AND GRIMINGER: PROTEIN MODULATION OF RESPONSE TO TRAUMA
non-traumatlzed rats also reduced their food intake slightly on day one of the trauma period; however, they increased it to the pre-trauma level on the second day. Aged rats consumed slightly less food post-surgically compared to the mature rats, but the difference was not significant. Nor was there a significant difference in pre-trauma food intake between the four dietary groups. After surgery, however, the 40% casein group significantly reduced its food intake Compared to the other three groups (p<0.01). Most N in the body was eliminated in the urine and the amount of urinary N was significantly changed by the dietary manipulation. There were no significant differences in percentage of fecal N of the total N excretion between traumatized and non-traumatized rats (9.6 vs 10.7%) and between mature and aged rats (9.9 vs 9.3%) respectively. However, as the protein level increased the percentage of fecal N tended to decrease (13.3, 10.7, 8.3 and 5.8%). Loss of N by hair was variable depending on animals. On the average, hair N loss was equivalent to 2.4% of total N excretion. During the pre-trauma period, N retention of traumatized animals did not 20C
"~
200
t
100
Z
~
~o
\~
o
Z
F
S--:""
I00
o
Ld
Oz
.J -lOO .r
._l -loo
m
i11
Z
z
-200
-200 i
1 tfou~v~
pre
Ave.
1
i
I
i
2
3
4
5
POST-TRAUMA
(Ooys)
a - 5% protein
re~ ~roumo
.o[
Ave.
2
3
i 4
POST-TRAUMA
5 (Doys)
b - 10% protein
200
,oop
>-. I00 o Z
~
o'
~.~"
W U Z
/ /
i;/
._1 -10c m
7 -200
-2OOI 2 3 4 trour~o Av=. PO 3T-TRAUMA
~re
c -
pre troumo
5
(Days)
20% p r o t e i n
Ave. d -
I
I
I
I
I
|
2
5
4
5
POST-TRAUMA
(Doys)
407o p r o t e i n
FIG. 2 Nitrogen balance of mature (M) and aged (A) traumatized (T) or non-traumatized (N) rats. Post-trauma dietary protein levels indicated (below graphs) O M-N; 9 M-T; /~ A-N; A A'T
CHYUN AND GRIMINGER: PROTEIN MODULATION OF RESPONSE TO TRAUMA
127
differ significantly from that of the non-traumatized control groups (Fig. 2a to 2d). Traumatization significantly reduced N retention of rats on the first and second day (p<0.01). Traumatized rats started to retain body N from the third or fourth day after surgery. Five day post-trauma mean N retention was significantly less in all traumatized rats than in all non-traumatized controls (-38.9 vs 32.5 mg/day, p<0.01). Aged rats retained significantly less N than mature ones during both pre- and post-trauma periods (14.3 vs 75.5 mg/day during pre-trauma, -24.1 vs 17.7 mg/day during post-trauma period, p<0.01, when all dietary groups were averaged). As the casein level of the diet increased during the post-trauma period, rats increased N retention linearly (-60, -29, 21 and 55 mg/day, p<0.05). There was a significant interaction between trauma and age in N retention when averaged over all casein levels; non-traumatlzed mature and aged rats retained more N than traumatlzed mature and aged ones, respectively (62 vs -27 mg/day in mature rats, p<0.01, and 3 vs -51 mg/day in aged rats, p<0.05. As the protein level of the diet was increased, both traumatized and non-traumatlzed animals showed linear increases in N retention, (-75, -63, -36 and 18 mg/day, p<0.01 in the traumatized and -45, 6, 77 and 92 mg/day, p<0.01, in the non-traumatized, respectively), when the two age groups were averaged. The interaction among casein level, trauma and age was significant (p<0.03). The aged rats could not maintain positive N balances with the lower protein levels even in the absence of trauma. On switching the diet from 20% casein in pre-trauma to lower post-trauma levels of casein (5 and 10%), non-traumatlzed mature rats showed negative N balances only on the first day; from the second day on they started to retain N in the body, while non-traumatized aged rats given the 5% casein diet could not recover from their negative N balances until five days after switching the diet; non-traumatlzed aged rats given 10% casein recovered from the negative N balance on the third day. When rats were traumatized, aged rats with 5% and 10% casein diets and mature rats with a 5% casein diet could not maintain positive N balances until the fifth day after surgery, while mature rats with a 10% casein diet showed a positive N balance on day three after surgery. It is apparent, therefore, that aging compounds the effect of trauma with respect to N loss. While a loss of N occurred in both the traumatized mature and aged rats, the aged rats were at a disadvantage because they retained less N in the absence of trauma. Except for the non-traumatized mature rats, the groups fed the 20% casein diet retained significantly more N than those given the 10% casein diet, while the difference in N retention between the 20% and 40% casein diets was not significant. This indicates that a relatively high protein diet during the post-trauma period reduces body N losses.
REFERENCES
i.
Cuthbertson, D.P. Observations on the disturbance of metabolism produced by injury to the limbs. Quart. J. Med. 25: 233-246, 1932.
2.
Cuthbertson, D.P. Further observations on the disturbance of metabolism caused by injury with particular reference to the dietary requirements of fracture cases. Brit. J. Surgery 23: 505-521, 1936.
3.
Johnson, I.D.A. 255-285, 1972.
4.
Albertl, K.G., Johnston, M.M. and Johnston, D.G. Cortisol and catabolism: a new prospective. Clln. Scl. Mol. Med. 52: 333-336, 1977.
The endocrine response to trauma.
Adv. Clin. Chem. 15:
128
CHYUN AND GRIMINGER: PROTEINMODULATION OF RESPONSETO TRAUMA
5.
Cuthbertson, D.P. The disturbance of N and S in urine during conditions of increased catabolism. Biochem. J. 25: 236-244, 1931.
6.
Carrnie, A.B., Campbell, R.M., Pullar, J.D. and Cuthbertson D.P. The heat production consequent on injury. Brit. J. Exp. Path. 38: 504-511, 1957.
7.
Cuthbertson, D.P., Fell, G.S., Smith, C.M. and Tilstone, W.J. Nutrition in the post-traumatlc period. Nutr. Metabolism 14, suppl: 92-109, 1972.
8.
Sitren, H.S. and Fisher, H. Nitrogen retention in rats fed on diets enriched with arginine and glycine. Brit. J. Nutr. 37: 195-208, 1977.
9.
Caldwell, F.T. Metabolic response to thermal trauma: II. Nutritional studies with rats at two environmental temperatures. Ann. Surgery 155: 119-126, 1962.
I0. Cuthbertson, D.P. and Tilstone, W.J. The effect of environmental temperature on the closure of full thickness skin wounds in the rat. Quart. J. Exp. Physiol. 52: 249-257, 1967. II. Walker, W.F., Watt, A., Morgan, H.C. and Parker, J. Metabolism after surgery in the elderly. Proc. Nutr. Soc. 30: 172-179, 1967. 12. Marsh, W.H., Fingerhut, B. and Miller, H. Automated and manual direct methods for the determination of blood urea. Clin. Chem. ii: 624-627, 1965. 13. Zar, J.H.
Biostatistical Analysis, Prentice-Hall, Englewood, N.J., 1974.
Accepted for publication November 10, 1983.
EFFECT OF DIETARY PROTEIN LEVEL ON MATURE ANDIAGED RATS IN THE PRESENCE AND ABSENCE OF TRAUMA Jong-Hee Chyun, Ph.D. and Paul Griminger, Ph.D. Department of Nutrition, Rutgers, The State University, New Brunswick, NJ 08903
ABSTRACT
The effect of dietary protein level on reducing body protein losses following trauma was studied in two age groups. Mature (4month old) and aged (24-month old) Fischer 344 male rats were given a 20% casein diet for 7 days before traumatization by laparotomy under sodium pentobarbital anaesthesia. After surgery, the rats were given 5, I0, 20 or 40% casein diets. Nitrogen balance studies (N intake N output in urine, feces and hair) were carried out during the last 3 days pre-trauma and 5 days post-trauma periods. Traumatization by laparotomy significantly reduced N retention of rats. Aged rats retained significantly less N than mature ones during both pre- and post-trauma periods. As the casein level of the diet increased, N retention of rats increased linearly. Except in non-traumatized mature rats, those given a 20% casein diet retained significantly more N than rats given a 10% casein diet; the difference in N retention between the rats consuming the 20% and 40% casein diets was not significant, except for the non-traumatized mature rats. The results show that a relatively high protein level during the posttrauma period reduces body protein losses and that aging compounds the effect of trauma with respect to N loss. KEY WORDS: Aging, trauma, protein level.
INTRODUCTION
It is well known that trauma causes a series of metabolic and hormonal changes in the body (I-5). Among the responses to trauma, loss of body protein is the most characteristic phenomenon (5). The extent of body protein loss is related to the severity and the type of injury sustained (6), and can be influenced by post-traumatic nutrition and environmental conditions (7-10). In this study, the effect of dietary protein level on nitrogen (N) retention in rats after laparotomy was investigated. Since the elderly are frequently exposed to trauma and generally need more time to overcome their infirmities (11), it was of interest to compare young adult rats with aged rats and observe possible age-related differences in the response to trauma.
I. New Jersey Agricultural Experiment Station Publication No. D-14406-I-83 Supported by state funds and by NIH Grant PHS AG00160 from the National Institute of Aging.
]23
124
CHYUN AND GRIMINGER: PROTEIN MODULATION OF RESPONSETO TRAUMA MATERIALS AND METHODS
Twenty-four mature (4-month old) and the same number of aged (24-month old) male Fisher 344 rats (Charles River Breeding Laboratories) averaging 230 and 390g, respectively, were housed individually in suspended stainless steel metabolism cages and received a stock diet (Purina Rat Chow) and water ad libitum. T h e animal laboratory was maintained on a 12 hour light-dark cycle, and the temperature was kept between 20 and 22~ After an adjustment period of one week, rats of each age group were divided into four dietary groups of six rats each. All rats received a 20% casein diet for seven days. On the seventh day, three rats in each group were traumatized and the remaining three rats served as non-traumatlzed controls. Trauma consisted of a laparotomy, an abdominal incision 5 cm long through the skin and muscle layers under sodium pentobarbital anaesthesia (intraperitoneal injection, 3 mg/lO0 g body weight). The muscle incision was closed with braided silk 000 sutures by continuous stitches and the skin was closed with metal wound clips (9 mm). After the laparotomy, each of the four groups received a different level of protein, provided by 5, I0, 20 and 40% casein (Table i) a_~dlibitum for five days. TABLE I Diet Composition
Ingredients
% of Casein
5%
10%
20%
40%
(z)
(~)
(z)
(z)
5.0
I0.0
20.0
40.0
a Casein L-Methionine Corn Starch
b
Sucrose Fiber
c
Corn Oil
d
Mineral Mix Vitamin Mix
e
f
Choline Bitartrate
a b c d e f
0.08
0.15
0.3
0.6
18.51
17.34
15.0
10.32
61.71
57.81
50.0
34.38
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
3.5
3.5
3.5
3.5
1.0
1.0
1.0
1.0
0.2
0.2
0.2
0.2
Dellwood Food Inc., Yonkers, NY Corn product, CPC International, Englewood Cliffs, NJ Solka-floc, Brown Company, Berlin, NH Bio-Service Inc,, French Town, NJ AIN 76A mineral mixture, Dyers, Bethlehem, PA. For composition see J. Nutrition 107:1340-1348, 1972. AIN 76A vitamin mixture, Dyets, Bethlehem, PA. For composition see J. Nutrition 110:1726, 1980.
CHYUN AND GRIHINGER: PROTEIN HODULATION OF RESPONSE TO TRAUMA
125
Urine, feces and hair were collected for the last three days of pre-trauma and five days of post-trauma periods daily in order to determine the nitrogen (N) balance. Total N content of urine, feces, hair and diet were determined by a modification of the Kjeldahl method (12). When the urine samples could not be analyzed immediately, they were stored frozen at -20~ Results were subjected to analysis of variance according to the p r i n c i p l e s outlined by Zar (13).
RESULTS AND DISCUSSION
Food intake of traumatized animals was sharply reduced on thefirst day after laparotomy and increased gradually until day five post-trauma (Fig. la to Id). However, the amount ot rood consumed did not reach the pre-trauma level (7.6 vs 13.1 g/day, p<0.Ol). Possibly due to the change in feed and the disturbance caused by recovering, removing and returning the traumatized animals, the 20
20 //
o
I~
W
\\
//
,c
);/
z o o o
5
t
U_
I
I
ore1 2 3 4 trauma Ave. POST-TRAUMA
i
5
0
(Days)
I 5 (Days)
20,
20
15 Ld ,c~ lO i-
~J v
FZ
_z
o o o
O
o o. kL
"r" I I I Dra1 2 3 4 trauma Ave. POST-TRAUMA
b - 10% protein
a - 5% protein
o
/ s/
5
0
5
u_
~JI~/ I I ~re1 2 3 4 trauma Ave. POST-TRAUMA
, ~re trauma Ave.
POST-TRAUMA
c
20% protein
-
(Days)
I 5
(Days)
d - 40% protein FIG. I
Food intake of mature (M) and aged tA), traumatized (T) or non-traumatized (N) rats. Post-trauma dietary protein levels indicated (below graphs) O M-N; 9 M-T; /k A-N; 9 A-T
126
CHYUN AND GRIMINGER: PROTEIN MODULATION OF RESPONSE TO TRAUMA
non-traumatlzed rats also reduced their food intake slightly on day one of the trauma period; however, they increased it to the pre-trauma level on the second day. Aged rats consumed slightly less food post-surgically compared to the mature rats, but the difference was not significant. Nor was there a significant difference in pre-trauma food intake between the four dietary groups. After surgery, however, the 40% casein group significantly reduced its food intake Compared to the other three groups (p<0.01). Most N in the body was eliminated in the urine and the amount of urinary N was significantly changed by the dietary manipulation. There were no significant differences in percentage of fecal N of the total N excretion between traumatized and non-traumatized rats (9.6 vs 10.7%) and between mature and aged rats (9.9 vs 9.3%) respectively. However, as the protein level increased the percentage of fecal N tended to decrease (13.3, 10.7, 8.3 and 5.8%). Loss of N by hair was variable depending on animals. On the average, hair N loss was equivalent to 2.4% of total N excretion. During the pre-trauma period, N retention of traumatized animals did not 20C
"~
200
t
100
Z
~
~o
\~
o
Z
F
S--:""
I00
o
Ld
Oz
.J -lOO .r
._l -loo
m
i11
Z
z
-200
-200 i
1 tfou~v~
pre
Ave.
1
i
I
i
2
3
4
5
POST-TRAUMA
(Ooys)
a - 5% protein
re~ ~roumo
.o[
Ave.
2
3
i 4
POST-TRAUMA
5 (Doys)
b - 10% protein
200
,oop
>-. I00 o Z
~
o'
~.~"
W U Z
/ /
i;/
._1 -10c m
7 -200
-2OOI 2 3 4 trour~o Av=. PO 3T-TRAUMA
~re
c -
pre troumo
5
(Days)
20% p r o t e i n
Ave. d -
I
I
I
I
I
|
2
5
4
5
POST-TRAUMA
(Doys)
407o p r o t e i n
FIG. 2 Nitrogen balance of mature (M) and aged (A) traumatized (T) or non-traumatized (N) rats. Post-trauma dietary protein levels indicated (below graphs) O M-N; 9 M-T; /~ A-N; A A'T
CHYUN AND GRIMINGER: PROTEIN MODULATION OF RESPONSE TO TRAUMA
127
differ significantly from that of the non-traumatized control groups (Fig. 2a to 2d). Traumatization significantly reduced N retention of rats on the first and second day (p<0.01). Traumatized rats started to retain body N from the third or fourth day after surgery. Five day post-trauma mean N retention was significantly less in all traumatized rats than in all non-traumatized controls (-38.9 vs 32.5 mg/day, p<0.01). Aged rats retained significantly less N than mature ones during both pre- and post-trauma periods (14.3 vs 75.5 mg/day during pre-trauma, -24.1 vs 17.7 mg/day during post-trauma period, p<0.01, when all dietary groups were averaged). As the casein level of the diet increased during the post-trauma period, rats increased N retention linearly (-60, -29, 21 and 55 mg/day, p<0.05). There was a significant interaction between trauma and age in N retention when averaged over all casein levels; non-traumatlzed mature and aged rats retained more N than traumatlzed mature and aged ones, respectively (62 vs -27 mg/day in mature rats, p<0.01, and 3 vs -51 mg/day in aged rats, p<0.05. As the protein level of the diet was increased, both traumatized and non-traumatlzed animals showed linear increases in N retention, (-75, -63, -36 and 18 mg/day, p<0.01 in the traumatized and -45, 6, 77 and 92 mg/day, p<0.01, in the non-traumatized, respectively), when the two age groups were averaged. The interaction among casein level, trauma and age was significant (p<0.03). The aged rats could not maintain positive N balances with the lower protein levels even in the absence of trauma. On switching the diet from 20% casein in pre-trauma to lower post-trauma levels of casein (5 and 10%), non-traumatlzed mature rats showed negative N balances only on the first day; from the second day on they started to retain N in the body, while non-traumatized aged rats given the 5% casein diet could not recover from their negative N balances until five days after switching the diet; non-traumatlzed aged rats given 10% casein recovered from the negative N balance on the third day. When rats were traumatized, aged rats with 5% and 10% casein diets and mature rats with a 5% casein diet could not maintain positive N balances until the fifth day after surgery, while mature rats with a 10% casein diet showed a positive N balance on day three after surgery. It is apparent, therefore, that aging compounds the effect of trauma with respect to N loss. While a loss of N occurred in both the traumatized mature and aged rats, the aged rats were at a disadvantage because they retained less N in the absence of trauma. Except for the non-traumatized mature rats, the groups fed the 20% casein diet retained significantly more N than those given the 10% casein diet, while the difference in N retention between the 20% and 40% casein diets was not significant. This indicates that a relatively high protein diet during the post-trauma period reduces body N losses.
REFERENCES
i.
Cuthbertson, D.P. Observations on the disturbance of metabolism produced by injury to the limbs. Quart. J. Med. 25: 233-246, 1932.
2.
Cuthbertson, D.P. Further observations on the disturbance of metabolism caused by injury with particular reference to the dietary requirements of fracture cases. Brit. J. Surgery 23: 505-521, 1936.
3.
Johnson, I.D.A. 255-285, 1972.
4.
Albertl, K.G., Johnston, M.M. and Johnston, D.G. Cortisol and catabolism: a new prospective. Clln. Scl. Mol. Med. 52: 333-336, 1977.
The endocrine response to trauma.
Adv. Clin. Chem. 15:
128
CHYUN AND GRIMINGER: PROTEINMODULATION OF RESPONSETO TRAUMA
5.
Cuthbertson, D.P. The disturbance of N and S in urine during conditions of increased catabolism. Biochem. J. 25: 236-244, 1931.
6.
Carrnie, A.B., Campbell, R.M., Pullar, J.D. and Cuthbertson D.P. The heat production consequent on injury. Brit. J. Exp. Path. 38: 504-511, 1957.
7.
Cuthbertson, D.P., Fell, G.S., Smith, C.M. and Tilstone, W.J. Nutrition in the post-traumatlc period. Nutr. Metabolism 14, suppl: 92-109, 1972.
8.
Sitren, H.S. and Fisher, H. Nitrogen retention in rats fed on diets enriched with arginine and glycine. Brit. J. Nutr. 37: 195-208, 1977.
9.
Caldwell, F.T. Metabolic response to thermal trauma: II. Nutritional studies with rats at two environmental temperatures. Ann. Surgery 155: 119-126, 1962.
I0. Cuthbertson, D.P. and Tilstone, W.J. The effect of environmental temperature on the closure of full thickness skin wounds in the rat. Quart. J. Exp. Physiol. 52: 249-257, 1967. II. Walker, W.F., Watt, A., Morgan, H.C. and Parker, J. Metabolism after surgery in the elderly. Proc. Nutr. Soc. 30: 172-179, 1967. 12. Marsh, W.H., Fingerhut, B. and Miller, H. Automated and manual direct methods for the determination of blood urea. Clin. Chem. ii: 624-627, 1965. 13. Zar, J.H.
Biostatistical Analysis, Prentice-Hall, Englewood, N.J., 1974.
Accepted for publication November 10, 1983.