Serum protein changes in monkeys infected with Schistosoma mansoni, with special reference to the metabolism of albumin

EXPERIMEh'TAL PARASITOLOGY11, 39-49 (1961)

Serum Protein Changes in Monkeys Infected Schistosoma mansoni, with Special Reference the Metabolism of Albumin S. R. National

Institute

Smithers

and

P. J. Walker

for Medical Research, The Ridgeway,

(Submitted

for publication,

with to

14 November

Mill Hill, London 1960)

1. Studies have been carried out on the serum protein changes in seven rhesus monkeys infected with Schistosoma ntansoni, using the biuret method of protein determination and paper electrophoresis. On three of these monkeys, the blood volume and the distribution and metabolism of albumin were investigated simultaneously, using homologous lslI-labelled albumin. 2. A sudden change in the concentration of the serum proteins occurs 6 to 7 weeks after the initial infection, i.e., about the time when eggs first appear in the faeces. The change consists of an increase in gamma-globulin concentration; usually an increase in total protein concentration; and, at least in heavy infections, a decrease in albumin concentration; in some monkeys there is a rise in the beta globulin concentration. with large numbers of cercariae, similar When resistant monkeys are “challenged” changes occur earlier, i.e., 2 weeks after exposure. 3. The isotope studies show that associated with the serum protein changes there is a fall of total body and intravascular albumin with a subsequent rapid recovery, and a marked increase in the intravascular albumin “catabolic” rate, followed by a slow return to normal. Between the 8th and 12th week of infection there is an increase in the albumin distribution ratio, signifying an increase in the size of the extravascular pool of albumin ; this is followed by a slow return to normal. 4. It is believed that the fall in albumin is due to a sudden increase in albumin catabolism incompletely compensated by an increase in anabolism.

An increase in the concentration of the gamma- and beta-globulin fractions of the serum of mice and hamsters infected with Schistosoma mansoni has been reported by Evans and Stirewalt (1957; 1958). Rabbits infected with S. japonicum show an increase in gammaglobulin and a decrease in serum albumin concentration (Sadun and Walton, 1958). Similar quantitative changes appear to take place in the serum proteins of humans infected with S. mansoni and S. japonicum. (Fiorillo 1954; Sadun and Walton ZOC. cit.). This paper is a report of observations on the behaviour of the serum proteins of rhesus monkeys infected with S. mansoni. Hitherto such information was lacking, although these animals are used extensively for studying certain aspects of the host parasite relationships of the disease.

In order to determine the influence of the schistosome parasite on the total circulating plasma, our investigation included the use of homologous l”lI-labelled albumin. This also enabled us to determine the catabolic rate and distribution of albumin within the body at intervals during the infection. MATERIALS

AND METHODS

Experimental Animals Young rhesus monkeys (Macaca mdatta) of both sexes, weighing between 2.4 and 3.7 kg were used. They were maintained on the stock Institute cube diet (Bruce and Parkes, 1949) with supplements of greenstuffs twice weekly. All monkeys were maintained under these conditions for at least 3 months prior to experimentation. Iodide-chloride water (containing 0.005% NaI and 0.4770 NaCl) was 39

40

SMITHERS

AND

given for drinking to those animals used in the radioactive experiments. The Parasite and Method of Injection An Egyptian strain of S. mansoni, obtained through the courtesy of Dr. 0. D. Standen of the Wellcome Laboratories of Tropical Medicine, was used throughout the work. The parasite had been passaged for several years through Australorbis glabratus and maintained in mice or hamsters. The monkeys were infected under Nembutal anaesthesia by dropping a cercarial suspension of known concentration on to a shaved area of the groin, and allowing 45 minutes for the cercariae to penetrate the skin. Cercariae shed from ten or more snails were used in order to avoid the risk of unisexual infections. The faeces of infected monkeys were examined for the presence of schistosome eggs by the “AEX” method of Loughlin and Stoll ( 1946). Serum Protein Estimations Blood samples were taken from the leg veins ; 1 ml of blood was allowed to clot and the serum was separated by centrifugation. Total serum proteins were estimated by the biuret method of Gornall, Bardawill, and David (1949) ; the biuret solution was first standardised against rhesus serum of known protein content, which had been determined previously by the method of Jacobs (1960). Paper electrophoresis of serum proteins was carried out in a closed vertical tank using Whatman’s 3 MM chromatography paper and a barbiturate buffer at pH 8.6, ionic strength 0.075. The electrophoresis lasted for 16 hours at a constant current of 0.4 mA per cm width of paper (voltage 1SO-180 v) . The separated proteins were fixed by heat and stained with Lissamine Green (I.C.I., SF. 150). The stained strips were scanned in a Joyce-Loebl double-beam reflectance densitometer; the percentages of the various protein fractions were estimated by cutting out the protein peaks drawn on the paper and weighing them. Four paper strips were prepared from each serum sample. The standard errors of the mean of each protein fraction for the four strips were calculated. When these values were expressed as percentages of the mean values they were found to be less than + 7%1

WALKER

for the albumin- and gamma-globulin fractions, and less than & 12% for the alpha-l, alpha-2 and beta-globulin fractions. The total protein estimations obtained by the biuret method were used to convert the percentage values of the protein fractions to absolute values in mg/ml. Blood Values The erythrocyte sedimentation rate (E.S. R.) and packed cell volume (P.C.V.) estimations were made according to Wintrobe’s method. Measurements of plasma volumes were made by estimating the dilution of ‘“‘I-labelled albumin 5 minutes after injection of the radioactive sample. Preparation oj Albumin An albumin sample was prepared chromatographically from normal rhesus monkey serum using a carboxymethylcellulose column according to the method employed by Cohen (1958) for separation of rat albumin. The albumin fraction obtained by this method contained an extra protein which ran in the gamma-l region on paper electrophoretic strips. Accordingly, the albumin fraction was further purified by zone electrophoresis on a column of treated cellulose (Porath, 1954). After this treatment, paper electrophoresis of the sample showed no other fraction than albumin to be present; starch-gel electrophoresis revealed a scarcely perceptible band in the beta-globulin region but no other protein bands. The albumin sample was divided into 10 mg lots, freeze dried in ampoules and stored at 4” C. Radioactive Techniques The albumin was labelled by the method of McFarlane ( 1958). For each 10 mg sample of albumin, 250 pC of carrier-free iodide were used. The efficiency of labelling was between 25-30s giving an activity of between 6 and 7 pC per mg of albumin and not more than one atom of iodine per albumin molecule. Precipitation of the protein with 10% trichloracetic acid showed that in the solutions for injection, less than 5 % of the radioact,ivity was due to non-protein bound 1311. For each radioactive run one ampoule containing 10 mg albumin was used, and each

41

SERUM PROTEIN CHANGES IN SCHISTOSOMA-INFECTED MONKEYS

extravascular activity reaches a maximum value at approximately 1% days after injection, when exchange between the intra- and extravascular pools is assumed to be in dynamic equilibrium. At this point in time, the gradient of a tangent to the intra-vascular curve, gives the true intravascular catabolic rate of albumin, uninfluenced by exit or reentry of albumin from the extravascular compartment. The intravascular and extravascular pool sizes are obtained from the relevant percentage activities of the two pools at equilibrium time. From the pool sizes the distribution ratio (R) is determined:

monkey received 1 mg of the labelled albumin. Paper electrophoretograms of serum from these monkeys when scanned showed the radioactivity to be confined to the albumin zone. 0.5 ml of blood was withdrawn from the monkeys 5 minutes and 1, 2, 3, 4, and 7 days after injection. The serum was measured for radioactivity in a well-type scintillation counter. The low activity for injection was chosen in order to minimise the residual activity at the time of the next run, 4 to 5 weeks later. Measurements of the total body radioactivity were made at the same time using a ring counter as described by Matthews (1957). All counts were corrected for radioactive decay, taking the half life of rRII as 8.14 days. Method of Analysis Estimates of the intra- and extravascular pool sizes of serum albumin and its catabolic rate were obtained by using “the equilibriumtime” method (Matthews, 1957). A brief outline of the method is as follows: using semilogarithmic paper, graphs are constructed of (a) the percentage counts retained in the body (total body counts) and (b) the percentage specific serum activity (intravascular counts). For each day, the intravascular activity is subtracted from the total body activity and from these results a third graph is drawn which represents the extravascular activity (Fig. 1). It will be noticed that the IOOFC

MONKEY I

6

3rd. WEEK

R =

Ti: extravascular counts s intravascular counts

It can be shown that at equilibrium time I = B (1 + R) where I is the intravascular breakdown rate in per cent per day and B is the total body breakdown rate, i.e., the gradient of total body curve (Fig. 1). This equation has been used in all graphs to check the accuracy of the gradient of the tangent to the intravascular curve at equilibrium time. RESULTS

Preliminary Experiment As a preliminary experiment measurements were made on the serum proteins of four infected rhesus monkeys, and from these results ,

1001,

MONKEY I

6

,ol\\e I~cquillbrium

8th WEEK

time

I

\I

intravascular

2c 0

I

2

3

4

5

6

7

days days FIG. 1. “Equilibrium time” method of analysis of albumin distribution and catabolic rate.

I

42

SMITHERS

the outline of the radioactive experiment was decided. The four monkeys weighed between 3.2 and 3.7 kg; two were exposed to 2,000 cercariae, one to 1,000 cercariae and one was initially exposed to 500 cercariae followed by a further 500 four weeks later. Eggs of S. ntansoni were first detected in the faeces of all the monkeys 6 weeks after infection, and during the following weeks the faecal egg count reached a maximum. Six months after infection the passage of eggs had either ceased or reached a very low level. The measurements made on the serum proteins throughout the infection showed the following changes at the 6th or 7th week. i) The concentration of the total serum proteins in three of the monkeys increased by 14-387(. One monkey which had been exposed to 2,000 cercariae showed no change in the total serum proteins. ii) All monkeys showed an increase in the concentration of serum gamma-globulin; the average increase was 2.5 times the original concentration (range 1.6 to 3.3). There was no correlation between the rise in gammaglobulin and the intensity of infection. iii) Both monkeys which had been exposed to 2,000 cercariae showed a fall in the concentration of serum albumin to about 60% of the original value. The monkeys exposed to 1,000 cercariae showed no fall in serum albumin concentration. No significant changes were detected in the alpha-l, alpha-2, or beta-globulin fractions of the serum. Six months after the monkeys were infected, the relative proportions of the serum proteins had almost reverted to their pre-infection values. Radioactive Experiment Outline: As a result of the preliminary experiment, it was decided to repeat the serum protein studies on three further monkeys this time in conjunction with plasma volume and albumin metabolism measurements. In order to be certain of obtaining a fall in serum albumin concentration all monkeys were exposed to between 1,600 and 2,000 cercariae. Blood samples were taken for serum protein measurements at approximately fortnightly intervals during the first 12 weeks of infection. Observations on blood values and albu-

AND

WALKER

min metabolism using ‘“‘I-labelled monkey albumin were made five times in all. Two observations were made before the serum changes were expected to occur (2 weeks before and 3 weeks after infection), and two just after (8 and 12 weeks after infection). The final observation, 27 weeks after infection, was made when the serum proteins were expected to have almost reverted to their normal values. The same measurements were made on a control monkey during the period corresponding to 3 to 12 weeks of infection, Course of the infection: Monkey 2 (male) was exposed to 1,700 cercariae; monkey 6 (male) to 2,000 cercariae; and monkey 7 (female) to 1,600 cercariae. Eggs of S. mansoni were present in the faeces of these monkeys 7 weeks after exposure. No further faecal examinations were made until the 27th week, when at this time eggs could not be detected in the faeces. Between the 8th and 12th week of infection small amounts of blood and. mucus were noticed in the faeces. Monkeys 2 and 7 showed a slight debility during the ‘ith-10th weeks of infection. Monkey 6 appeared to be more seriously ill during this period; it became listless, and its behaviour changed from an aggressive nature to one of complete submission. By the 12th week of infection, the general condition of all the monkeys appeared to be good. Table I shows the weights and various blood values of the infected and control monkeys during the course of the experiment. Serum proteins: The results of the serum protein measurements are shown in Fig. 2. They confirm the results of the preliminary experiment, showing, between the 5th and 8th week of infection, an increase in concentration of serum proteins and gamma globulin, and a decrease in serum albumin concentration. No significant change was noted in the alpha-l and alpha-2 globulin fractions but the beta globulin fraction in monkeys 2 and 7 rose slightly. In all cases there is a trend to the pre-infection values 27 weeks after exposure to cercariae. Albumin metabolism: The measurements of total body albumin, total intravascular albumin, the distribution ratio between the extra- and intravascular compartments, and

SERUM

PROTEIN

CHANGES

IN

SCHISTOSOMA-INFECTED

I

TABLE

Weights and Blood Values of Monkeys Weight Monkey

2

6

7

in Radioactive

E.S.R. (mm)

(kg) Control

2

6

7

1

5

1

43

MONKEYS

Experiment Plasma vol. (ml)

P.C.V. (70,

Control

2

6

7

46

40

43

Contro1

Con2

6

7

11s

151

127

tro1

Week -2 Week 0 Week 3

2.9

35

2.7

3.0 3.0

3.4 3.5

2.8 2.8

2.4

1 1

2 2

1 1

1

45 48

40 41

42 44

42

125

145

138

101

Week Week

5 8

2.8 2.9

3.5 2.9

2.8 2.6

2.3 2.5

1 4

2 17

1 7

1 1

44 40

38 36

39 35

38 40

135

149

146

114

Week Week Week

10 12 27

3.0 3.1 4.2

3.2 3.7 4.5

2.8 2.9 3.7

2.5 2.6

4 2 3

43 17 11

2 2 20

1 1

38 42 43

32 37 39

37 40 40

38 40

140 154

169 185

136 165

119

the intravascular albumin catabolic rate for each infected monkey are expressed in Fig. 3. The graphs for each monkey show consistent changes. The values for the distribution ratio and catabolic rate of the control monkey (Fig. 3 with monkey 7) show only small fluctuations, except for the first measurement of the catabolic rate which is, inexplicably, rather high. The distribution ratio falls slightly at 3 weeks, and then rises distinctly at the 12th week, and possibly beyond, before falling again (2 7th week). The total intravascular albumin in monkeys 2 and 7 remains roughly constant during the first 12 weeks; monkey 6 shows a fall in total intravascular albumin at the 8th week, and a return to its original value by the 12th week. All monkeys show a rise in intravascular albumin 27 weeks after infection. This rise is to be expected when the increase in weight of the monkeys is taken into account. The measurements of total body albumin follow a steadily ascending curve which appears to be associated with growth, except however, at the 8th week, when the total body albumin of all 3 monkeys falls below the expected level. Assuming a passive distribution of albumin between the extravascular and intravascular compartments, these results show a marked rise in the size of the extravascular pool between the 8th and 12th week, and a return to the normal distribution value between the 12th and 27th week. The catabolic rate of albumin within the intravascular pool remains more or less constant 2 weeks before and 3 weeks after infection, but at the 8th week the mean cata-

bolic rate of the three infected monkeys rises from 13.5’5%per day to 20.3% per day. In monkeys 6 and 7 the catabolic rate remains at about this high level at the 12th week, but falls by the 27th week. In monkey 2, the fall is already apparent by the 12th week. Challenge Experiment Two monkeys which had developed an acquired immunity to S. mansoni by a previous infection were used to determine the changes occurring in the serum protein concentrations after a heavy “challenge” infection. Monkey 23 was initially infected with 2,000 cercariae and challenged 65 weeks later with 7,000 cercariae. At the time of the challenge eggs could not be detected in the faeces, and they did not re-appear during the next 8 weeks, at which time the monkey was killed. Monkey 509 was initially exposed to 500 cercariae followed by a further 500 four weeks later. It was first challenged 25 weeks after the initial exposure, with 2,000 cercariae. At this time the passage of eggs in the faeces had reached a low level, but there was no increase in egg output, as a result of the challenge, during the next 12 weeks. Ninety-two weeks after the initial infection the monkey was again challenged, by exposure to 7,000 cercariae. At the time of the second challenge eggs could not be detected in the faeces, nor were eggs seen in weekly examinations for a further 8 weeks. After this time the monkey was killed. The serum protein measurements on monkey 509 were carried out during the 2nd challenge.

44

SMITHERS

AND WALKER

TOTAL CONTROL

GAMMA /m-.-m

-\.

PROTEIN MONKEY

--A ‘1.

GLOB.

I

-----

.

./‘A

f201 I3 -.-.-

---_-.

.%-----A ,-

\lO-S?* -,-.-t-t

5

a

weeks

IO

- - -. -. ---_-

I2

27

of infection

‘00 80

.

e.w*w.-.-.-,==.==.=.==*-

weeks loo

MONKEY

2 2o-JL r***-•

>lO! E

B

IO

of

infection

-----=*

- - - -. - - _____

I2

27

7

,--o(i!~~---+~4~4~4---=--= -2 0 3

l ------.-.% 5

a

-‘---. IO

I2

____+

weeks of infection FIG. 2. Radioactive Exp. Concentration of serum proteins in three men keys before and after infection with S. ntansoni.

SERCM

PROTEIN

CHANGES

IN

,*monkey IO

0’ .

4.5

MONKEYS

monkey 6

2

TOTAL BODY ALBUMIN

SCHISTOSOMA-INFECTED

.-/

1.

/ INTRAVASCULAR

*I.-----~ -23812

27

-2

3

812

27

-2

-2

3

812

27

-23

3

8

27

I2

--7

CATABOLIC

812

27

Al RATE R

\ \ \. --7

-2

3

Radioactive

Exp.

‘4lbumin

27

values

in three monkeys

The results are expressed in Fig. 4. In both monkeys, there is a decrease in albumin, and an increase in gamma-globulin concentration similar to that found in monkeys initially infected. However, the time of the changes differs: whereas in monkeys infected for the first time, the serum protein concentrations alter at the 6th or 7th week, in the two resistant monkeys, the changes occur 2 weeks

----;;7

-2

3

8 12

weeks

weeks

weeks FIG. 3.

8 12

before

and after infection

with

S. mattsoni.

after exposure. Both resistant monkeys also show a slight rise in beta-globulin concentration 2 weeks after challenge, but no changes in the alpha-globulins. DISCUSSION Technique: The “equilibrium-time” method was chosen because it offers certain advantages over the extrapolation te&nique de-

46

SMITHERS

AND

WALKER

l-l.-*, O-+-W

l

TOTAL PROTEIN ,’

60-

-I

0

I

2

3

weeks “r

4

after

5

6

8

challenge

MONKEY 509

TOTAL

\e

PROTEIN

l

,’ 60 5 E 40 /-A

2

-.-. GAMMA

I

-I

A-A

\

ALBUMIN

A/------a-.-~.

‘A--&---A a

GLOB.

//-*-*-+----*---+...~ =z=rz:_, ea&I 0

I

2

weeks

3

4

after

5

6

8

challenge

FIG. 4. Challenge Exp. Concentration of serum proteins monkeys before and after a “challenge” infection.

scribed by Sterling (1951). In both methods of analysis, the pool masses, exchange rates, and catabolic rates are assumed to be constant (Freeman and Matthews, 1958). Owing to a disturbed metabolism due to the infection, it was possible that the catabolic rate changed during the week following administration of the labelled albumin. However, the “equilibrium-time” method is much less sensitive to such a change, because the pool masses and

. :,

---e

in two resistant

catabolic rates are estimated within two days of the start of each series of measurements. Furthermore, the extrapolation technique is subject to an inherent error so far as the intravascular decay curve is concerned; after equilibrium has been reached, albumin re-enters the blood from the extravascular pool and thus no exponential decay is found. Errors due to free iodide counts and any denatured protein due to preparation and labelling, are

SERUM

PROTEIN

CHANGES

IN

SCHISTOSOMA-INFECTED

MONKEYS

47

for by an increase in the distribution ratio very small, owing to their rapid excretion because, in two monkeys at least, the fall in before the equilibrium time is reached (Matthews, 1957). The normal values for the serum albumin occurs before the 8th week, whereas the distribution ratio does not rise albumin catabolic rate of the control monkey until the 12th week. On the other hand, the at the 8th and 12th weeks, when the infected monkeys were showing uniformly high values, rise in the catabolic rate of albumin might indicates that the albumin had neither de- well account for the albumin decrease. For example, the total body albumin of monkey natured nor developed any antigenic prop6 fell by 21p/r, between the 5th and 8th week. erties. If this fall took place over 2 weeks (as hapResults: Our results have shown that in rhesus monkeys infected with S. mansoni a pened in the monkeys of the preliminary exsudden change in the concentration of the periment), then a difference of only 2F between the anabolic and catabolic rates of alserum proteins occurs 6-7 weeks after infection. This change consists of an increase in bumin would be sufficient to account for it. gamma-globulin concentration, usually an in- In monkeys 2 and 7 where the total albumin crease in total protein concentration, and, cer- fall was less, an even smaller difference between anabolic and catabolic rates would eftainly in heavy infections, a decrease in albumin concentration. Six months after the date fect the albumin change. Therefore, the lowerof infection the serum protein pattern almost ing of the serum and total body albumin is reverts to its pre-infection value. When im- probably due to a sudden increase in its mune monkeys are challenged with large num- catabolic rate, which is incompletely combers of cercariae, similar changes occur two pensated by an increase in its anabolic rate. weeks after exposure. The liver has been shown to be the chief, if not the sole, site of albumin synthesis Studies on the plasma volume and albumin (Miller, Bly, and Bale, 1954). The question metabolism of infected monkeys indicate that therefore arises as to whether liver damage, when the concentration of serum albumin which might be expected in schistosome infalls, there is also a fall in the total body albumin, at least below the expected value when fections, causes, to a greater or lesser extent, the lowering of the albumin value. It is ungrowth of the monkey is taken into account. This fall is followed rapidly by an increase, likely however, that liver damage if present, is responsible in any way for the fall in albringing the albumin value back to normal. Furthermore, these serum changes are as- bumin. Even for monkey 6, which at 8 weeks produced the largest fall in total albumin, and sociated with a rapid increase in the catabolic the smallest rise in catabolic rate, it has alrate of albumin. The only investigation comparable to our ready been calculated that the anabolic rate work recorded in the literature is that by must remain within 2% of the catabolic rate. BjGrneboe and Schwartz (1959) who carried This represents a value for the anabolic rate out similar studies on immunized rabbits using of 17% per day, which is a rise of at least 35%. At the 12th week of infection, although Sterling’s method of analysis. Following hyperimmunization, rabbits show an increase in the catabolic rate remains at a high level, the total body albumin has returned to its exgamma-globulin and a fall in serum albumin pected value, and it is obvious that the anaconcentration. The authors conclude that durbolic rate must therefore have exceeded the ing immunization, the fall in concentration of serum albumin is due to an increase in the catabolic rate. In other words at the 8th and 12th weeks of infection, the liver was in fact plasma volume. In our experimental monkeys, the fall in synthesising more albumin than normal. It has been suggested by Bjgrneboe (1943; total body albumin, which occurs at the same time as the fall in the serum albumin concen- 1945) that a fall in albumin is correlated with tration, indicates that the fall in the serum a rise in gamma-globulin as a regulatory albumin is not a passive fall due to an in- mechanism with the function to keep the colloid osmotic pressure (C.O.P.) within cercrease in plasma volume. Moreover, the fall in serum albumin is unlikely to be accounted tain limits. We have calculated the colloid

48

SMITHERS

AND

osmotic pressure of our infected monkeys using Key’s formula (quoted in Documenta Geigy) zGz.: C,. P, (cm H o) =f

(45.2 alb. + 18.9 gamma-glob.)

2

100

where the albumin and gamma-globulin values are in mg/ml and f is a coefficient derived empirically and dependent upon the total serum protein value. Recent confirmation of the necessity of this coefficient has been given by Rowe (1957). Values of f are not quoted above 80 mg/ml total serum protein, and when, in our monkeys, the serum protein values exceed this value, f has been taken at its highest value, and the results expressed as “greater than” ( >). Only the gammaglobulin and albumin values are included in the formula; as the other globulin fractions remain roughly constant throughout the infection, the omission of these components makes no difference to the significance of the changes of the colloid osmotic pressure. Table II shows the calculated colloid osmotic pressures of our infected monkeys, and it will be seen that there is a marked rise in values from the 8th week onwards; the least rise is an increase of 4Or/c (monkey 7). We Calc&ted

TABLE II Colloid Osmotic Pressures (cm H,O) Monkeys in Radioactive Experiment

of

WALKER

1960; Weinbren and Coyle, 1960). These changes are probably manifestations of a common non-specific response by the host to invasion by parasites. In two cases alterations in the turnover rate of plasma proteins have been reported; Smithers and Terry (1959) have shown that the gamma-globulin metabolism increases in monkeys with trypanosomiasis; Cohen (personal communication) has shown an unchanged rate of albumin turnover and high metabolic rate of gamma-globulin in African subjects chronically infected with malaria. The present investigation discloses a third example of an altered plasma protein metabolism in a parasitic infection; this time an increase in albumin catabolism has been demonstrated, during the acute phase of schistosomiasis in monkeys. These animals, which tolerate the schistosome parasite well, show a return to the normal albumin turnover rate as the disease becomes chronic. ACKNOWLEDGMENTS

The authors would like to thank Dr. S. Cohen for his advice throughout this investigation, and for his help in the preparation of the albumin sample. We are also grateful to Dr. F. Hawking, Dr. P. A. Charlwood and Dr. D. R. Bangham for their suggestions, and to Mr. R. C. Holloway for his help in iodinating the albumin. Thanks are also due to Miss P. M. Pritchard, Mr. A. Hills and Mr. M. J. Worms for their excellent technical assistance.

Monkey Week

2

6

-2 0 3

19.5 22.4 21.0

19.6 24.4 23.7

5 8 10

20.3 24.4 >28.3

12 27

>>31.0 26.3

23.8 25.8 25.3 : >31.0 25.6

REFERENCES 7

20.5 21.3 20.7 20.4 24.5 26.6 28.1 23.6

do not consider that such rises are evidence of a regulatory function of serum albumin concentration. Serum protein changes similar to those reported in this paper have been described in many parasitic diseases, including malaria, leishmaniasis, trypanosomiasis, trichinosis, Trichostrongylus and Fasciola infections (Stauber, 1954; Leland, Drudge, and Wyant,

M. 1943. Serum proteins during immunisation. dcta Pathologica et Microbiologica Scandinavica m, 22 1-239. BJ@RNEBOE, M. 1945. Serum albumin and serum globulin after intravenous injection of large amounts of globulin and albumin: A hypothesis about the regulations of the colloid-osmotic pressure of the blood. Acta Pathologica et Microbiologica Scandinavica 22, 323-334. BJ~RNEBOE, M., AND SCHWARTZ, M. 1959. Investigations ccncerning the changes in serum proteins during immunization: The cause of hypoalbuminemia with high gamma-globulin values. Journal of Experimental Medicine 110, 259-270.

BJ~RNEBOE,

BRUCE, H. M., AND PARKES, A. S. 1949.

Feeding

and

breeding of laboratory animals. IX. A complete cubed diet for mice and rats. Journal of Hygiene 47, 202-208. COHEN, S. 1958. Turnover of some chromatographically separated serum protein fractions in

SERUM

PROTEIN

CHANGES

IN

SCHISTOSOMA-INFECTED

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