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Purine metabolites in the CSF in presenile and senile dementia of Alzheimer type, and in multi infarct dementia
Arch. Gerontol. Geriatr., 7 (1988) 173-178 Elsevier
173
AGG 00215
Purine metabolites in the CSF in presenile and senile dementia of Alzheimer type, and in multi infarct dementia Istvhn Degrell
a
and Frank Niklasson b
a Department of Neurology and Psychiatry, University of Debrecen Medical School, H-4012 Debrecen, Hungary and b Department of Clinical Chemistry, University Hospital, Uppsala, Sweden (Received 12 June 1987; revised version received 12 November 1987; accepted 13 November 1987)
Summary Concentrations of hypoxanthine, xanthine, uric acid and creatinine were measured in CSF of pauents suffering from presenile and senile dementia of Alzheimer type (PDAT, SDAT) and multi infarct dementia (MID) and in a reference group of young neurotic patients. There was no difference in hypoxanthine concentration, but there was a marked elevation of xanthine concentration in each dementia group, independent of the type of dementia. There was a significant elevation of uric acid in SDAT and MID but not in PDAT. The concentration of uric acid was higher in MID than in SDAT. There was a higher level of creatinine in the dementia groups, but no difference was seen among the dementia groups. These results are discussed in order to better interpret the etiology and the differentiated diagnosis of the types of dementia. Purine metabofites; Cerebrospinal fluid; Types of dementia
Introduction T h e r e are n u m e r o u s investigations of the c a r b o h y d r a t e m e t a b o l i s m of the b r a i n in dementia, i.e. m e a s u r i n g c a r b o h y d r a t e m e t a b o l i t e c o n c e n t r a t i o n s in the c e r e b r o s p i n a l fluid. T h e level of energy-rich p h o s p h a t e s ( a d e n o s i n e - t r i p h o s p h a t e , creatine p h o s p h a t e ) is l o w e r e d o n l y in cases o f very m a r k e d energy insufficiency. S o m e years ago it was stated b y Saugstad a n d G l u c k (1982) a n d K a r m a z s i n a n d Balla (1985) that the energy n e e d in h y p o x i c n e o n a t e s is sh o w n m o r e sensitively b y the p l a s m a h y p o x a n t h i n e level t h a n by either l act at e or p H levels. T h e r e is a
All correspondence should be sent to Istvfin Degrell MD, Department of Neurology and Psychiatry, University of Debrecen Medical School, Nagyerdei krt. 98, H-4012 Debrecen, Hungary. 0167-4943/88/$03.50 © 1988 Elsevier Science Publishers B.V. (Biomedical Division)
174
characteristic change in the hypoxanthine and xanthine levels in the CSF of patients suffering from (1) cerebral infarction, (2) global cerebral ischemia due to heart attack, (3) transitory ischemic attack and (4) reversible ischemic neurological disease (Hallgren et al., 1983). In our present work we want to further investigate purine metabolites that show the energy state of the brain in presenile and senile dementia of Alzheimer type (PDAT and SDAT) and in multi infarct dementia (MID). This work is a part of a series of investigations analysing the CSF metabolite concentrations in the different types of dementia (Degrell et al., 1985, 1987).
Methods The patients were divided into three groups on the basis of their clinical data and the ischemic score of Hachinski and there was a fourth reference group: (1) presenile dementia of Alzheimer type (number of patients n = 7, age range 54-63 years, mean age 59.4 years), (2) senile dementia of Alzheimer type (n = 9, 73-82 years, mean age 77.1 years), (3) multi infarct dementia (n = 15, 54-82 years, mean age 69.0 years); (4) the reference group consisted of 16 neurotic patients without any organic neurological disease (16-47 years, mean age 29.0 years). After bedrest overnight and before breakfast, lumbar puncture was performed at 9 o'clock. After collection of 20 ml of CSF in a test tube, the specimen was shaken, dividedinto smaller quantities and immediately frozen in liquid nitrogen of - 180 o C until analysis. Analyses of xanthine, hypoxanthine, uric acid and creatinine were performed with a high performance liquid chromatographic method (Niklasson, 1983). Significant differences in the purine metabolite levels were calculated between the dementia groups using Student's t test. Ethical and practical considerations do not allow the drawing of 20 ml CSF from healthy elderly persons. For this reason, we have no age-matched groups. In order to control the role of age in the values of purine metabolites, we have calculated the correlation between age and level of metabolites. This calculation was carried out in: (1) the reference group, (2) the dementia group cumulating every type of dementia, and (3) each type of dementia.
Results Hypoxanthine concentrations There was no significant difference between the reference and the dementia groups. Xanthine levels Compared to the reference group there was a marked elevation in xanthine concentration in each dementia group (Fig. 1), but there was no difference among the different types of dementia.
175 Hypoxonthim
/tlr~/I
R
POAT
MID
/Jmd/i R
Xonthim PI:IN' 50AT
MID
I0,
". •
~
Uric Qcid /Jmolll R
i
p..:.o~ l
Crtmtinine
P Q A T SI::)AT MID
3 0 o
l
"
*P
blr'no¢II R
60
POAT
$l::~T
MID
"
Fig. 1. Concentrations of hypoxanthine, xanthine, uric acid and creatinine in CSF of patients suffering from presenile dementia of Alzheimer type (PDAT), senile dementia of Alzheimer type (SDAT) and multi infarct dementia (MID). The reference group (R) consisted of neurotic patients.
TABLE I Correlation coefficients (r) between age and level of purine metabolites and creatinine in cerebrospinal fluid Hypoxanthine
Xanthine
Uric acid
Creatinine
Reference group (n =16)
r p
0.119 NS
0.367 NS
0.000 NS
0.534 p < 0.05
Dementia groups together (n = 31)
r
0.085
0.016
0.224
0.150
p
NS
NS
NS
NS
PDAT (n = 7)
r p
0.205 NS
0.441 NS
0.411 NS
0.543 NS
MID (n =15)
r p
0.007 NS
0.079 NS
0.272 NS
0.064 NS
SDAT (n = 9)
r p
0.396 NS
0.211 NS
0.323 NS
0.265 NS
176
Levels of uric acid Compared to the reference group, there was a significant elevation in SDAT and MID but not in PDAT. Comparing the dementia groups themselves, there was a significant difference between the PDAT and MID, with the concentration of uric acid being higher in MID. Creatinine level There was a significant elevation in each dementia group compared to the reference group, but there was no significant difference among the dementia groups.
Correlation between age and CSF level of metabolites (Table I) In the reference group (age between 16-47 years) there was no significant correlation between age and level of hypoxanthine, xanthine, and uric acid, while the creatinine concentration correlated ( p < 0.05) with age. No significant age-related correlation was found in the 'cumulated' dementia group (age between 54-82 years), nor in the separated dementia groups.
Discussion
The origin of the measured substrates It is postulated that hypoxanthine and xanthine in CSF originate in the brain. The possibility cannot be excluded, however, that the hypoxanthine might be due to active uptake from blood plasma, at least in part, in pathological situations, e.g. hypoxia (Hallgren et al., 1983). The brain metabolizes AMP to adenosine ~ inosine hypoxanthine, and xanthine (the last one via GMP, guanosine and guanine). The brain contains the enzymes involved in this pathway (Niklasson, 1983). Furthermore, this opinion is supported by the concentration gradients in CSF for xanthine and hypoxanthine. The level of these metabolites diminishes rostrocaudally, if we compare successive fractions of lumbar samples (Niklasson, Hetta and Degrell, in press). Uric acid originates from the plasma since the brain has no xanthine oxidase enzyme and thus can not produce uric acid (A1-Kahlidi and Chaglassian, 1965). The concentration of uric acid in CSF is about 1/20 of the serum concentration, while the hypoxanthine and xanthine concentrations are much higher (accordingly, 5 times for both substances) in CSF than in plasma (Niklasson, 1983a). There is a linear relationship between the plasma and CSF urate concentrations. The concentration o f urate in the CSF increases in a rostrocaudal direction. This is quite the opposite of hypoxanthine and xanthine concentration distributions. The ratio of CSF urate/plasma urate could be used as a marker of blood-brain barrier function (Niklasson, Hetta and Degrell, in press). The levels of creatinine in plasma and in CSF are similar. It was shown that the CSF creatinine concentration increases with age, but this is not the case with the plasma (Niklasson and .~gren, 1984).
177
Interpretation of our findings In our investigations the elevated xanthine levels in CSF of the demented patients indicate a state of energy need, which is independent of the type of dementia. It is not easy to explain why there is no difference in the hypoxanthine level of CSF between the control group and any of the dementia groups. It could have been hypothesized that, at least in MID, the hypoxanthine concentration is elevated, since the cerebral blood flow and the oxygen utilization are markedly reduced in MID (Hachinski et al., 1975). One explanation would be that hypoxanthine is reutilized for nucleotide synthesis and that the steady-state level was reached again at the time the CSF specimen was obtained in chronic ischemic diseases. As it was experienced in global cerebral ischemia, in the acute state there is first an enhancement of the level of hypoxanthine and xanthine, but some days later the level of hypoxanthine is normal, while the level of xanthine remains high (Hallgren et al., 1983). The level of uric acid was elevated both in SDAT and MID, but not in PDAT. Since PDAT is probably strictly a disease of the brain, there is no cause to hypothesize a heightened production of uric acid in the periphery of these relatively young patients. Moreover, SDAT and MID patients are older, and this could explain the higher values in CSF of uric acid (originating from plasma). It is known that the ratio of C S F / p l a s m a urate increases significantly with age (Niklasson and Agren, 1984), and increased CSF urate levels have been suggested to reflect blood-brain barrier function (Carlsson and Dencker, 1973). The creatinine levels were found to be higher in each type of dementia. It may indicate the poor function of brain energy metabolism, namely the creatine-creatine phosphate shuttle. The concentration of CrP diminishes earlier in energy need situations than that of ATP. The CSF creatinine level increases with age too, but this is not the case in plasma (Niklasson and ,~gren, 1986). The lack of the age-related changes in the CSF metabolite level seems to show that the biochemical changes dependent on the types of dementia have a greater role than the age per se. Naturally, we do not mean to imply that the role of age must be excluded. Summarizing these results, the patterns of the purine levels in the CSF can be characteristic in chronic organic brain diseases, e.g. in different types of dementia. The etiology and the metabolic changes in dementia are far from being understood, but it seems that the knowledge of the levels of hypoxanthine, xanthine, uric acid, and creatinine can be used to help differentiate the dementias.
Acknowledgements This work was supported by the twinning grant of the European Training Programme in Brain and Behaviour Research (Strasbourg) Nr. 83/281 (I. Degrell).
178
References AI-Kahlidi, V.A.S. and Chaglassian, T.H. (1965): Species distribution of xanthine oxidase. Biochem. J., 97, 316-320. Carlsson, C. and Dencker, S.J. (1973): Cerebrospinal uric acid in alcoholics. Acta Neurol. Scand., 49: 39-46. DegreU, I., Prk, G., Nagy, D., Nagy, E. and Hoyer, S. (1985): Dementias, psychological tests, and neurotransmitters. Arch. Gerontol. Geriatr., 4, 365-371. Degrell, I., Nagy, E. and Hoyer, S. (1987): Carbohydrate metabolite concentrations in CSF in different types of dementia. Submitted for publication. Hachinski, V.C., Iliff, L.D., Hilhka, E., Du Boulay, G.H., McAllister, V.L., Marshall, J., Russell, R.W.R. and Symon, L. (1975): Cerebral blood flow in dementia. Arch. Neurol., 32: 632-637. Hiillgren, R., Niklasson, F., Terent, A., Akerblom, ,~. and Widerl/Sv, E. (1983): Oxypurines in cerebrospinal fluid as indices of disturbed brain metabolism. A clinical study of ischemic brain diseases. Stroke, 14: 382-388. Karmazsin, L. and Balla, G. (1985): Plasma hypoxanthine and xanthine levels in the early newborn period in problem-free preterm babies and those with idiopathic respiratory distress syndrome. Acta Paediat. Hung., 26: 1-9. Niklasson, F. (1983a): Experimental and clinical studies on human purine metabolism. Acta Univ. Upps., Abstracts of Uppsala Dissertations from the Faculty of Medicine, 473. Uppsala. Niklasson, F. (1983b): Simultaneous liquid-chromatographic determination of hypoxanthine, xanthine, urate, and creatinine in cerebrospinal fluid with direct injection HPLC. Clin. Chem., 29, 1543-1546. Niklasson, F. and ~,gren, H. (1984): Brain energy metabolism and blood-brain barrier permeability in depressive patients: Analyses of creatine, creatinine, urate and albumin in CSF and blood. Biol. Psychiat., 19, 1183-1206. Nildasson, F., Hetta, J. and Degrell, I. (1987): Hypoxanthine xanthine, urate and creatinine concentration gradients in cerebrospinal fluid. Submitted for publication. Saugstad, O.D. and Gluck, L. (1982): Plasma hypoxanthine levels in newborn infants: a specific indicator of hypoxia. J. Perinat. Med., 10: 266-272.
173
AGG 00215
Purine metabolites in the CSF in presenile and senile dementia of Alzheimer type, and in multi infarct dementia Istvhn Degrell
a
and Frank Niklasson b
a Department of Neurology and Psychiatry, University of Debrecen Medical School, H-4012 Debrecen, Hungary and b Department of Clinical Chemistry, University Hospital, Uppsala, Sweden (Received 12 June 1987; revised version received 12 November 1987; accepted 13 November 1987)
Summary Concentrations of hypoxanthine, xanthine, uric acid and creatinine were measured in CSF of pauents suffering from presenile and senile dementia of Alzheimer type (PDAT, SDAT) and multi infarct dementia (MID) and in a reference group of young neurotic patients. There was no difference in hypoxanthine concentration, but there was a marked elevation of xanthine concentration in each dementia group, independent of the type of dementia. There was a significant elevation of uric acid in SDAT and MID but not in PDAT. The concentration of uric acid was higher in MID than in SDAT. There was a higher level of creatinine in the dementia groups, but no difference was seen among the dementia groups. These results are discussed in order to better interpret the etiology and the differentiated diagnosis of the types of dementia. Purine metabofites; Cerebrospinal fluid; Types of dementia
Introduction T h e r e are n u m e r o u s investigations of the c a r b o h y d r a t e m e t a b o l i s m of the b r a i n in dementia, i.e. m e a s u r i n g c a r b o h y d r a t e m e t a b o l i t e c o n c e n t r a t i o n s in the c e r e b r o s p i n a l fluid. T h e level of energy-rich p h o s p h a t e s ( a d e n o s i n e - t r i p h o s p h a t e , creatine p h o s p h a t e ) is l o w e r e d o n l y in cases o f very m a r k e d energy insufficiency. S o m e years ago it was stated b y Saugstad a n d G l u c k (1982) a n d K a r m a z s i n a n d Balla (1985) that the energy n e e d in h y p o x i c n e o n a t e s is sh o w n m o r e sensitively b y the p l a s m a h y p o x a n t h i n e level t h a n by either l act at e or p H levels. T h e r e is a
All correspondence should be sent to Istvfin Degrell MD, Department of Neurology and Psychiatry, University of Debrecen Medical School, Nagyerdei krt. 98, H-4012 Debrecen, Hungary. 0167-4943/88/$03.50 © 1988 Elsevier Science Publishers B.V. (Biomedical Division)
174
characteristic change in the hypoxanthine and xanthine levels in the CSF of patients suffering from (1) cerebral infarction, (2) global cerebral ischemia due to heart attack, (3) transitory ischemic attack and (4) reversible ischemic neurological disease (Hallgren et al., 1983). In our present work we want to further investigate purine metabolites that show the energy state of the brain in presenile and senile dementia of Alzheimer type (PDAT and SDAT) and in multi infarct dementia (MID). This work is a part of a series of investigations analysing the CSF metabolite concentrations in the different types of dementia (Degrell et al., 1985, 1987).
Methods The patients were divided into three groups on the basis of their clinical data and the ischemic score of Hachinski and there was a fourth reference group: (1) presenile dementia of Alzheimer type (number of patients n = 7, age range 54-63 years, mean age 59.4 years), (2) senile dementia of Alzheimer type (n = 9, 73-82 years, mean age 77.1 years), (3) multi infarct dementia (n = 15, 54-82 years, mean age 69.0 years); (4) the reference group consisted of 16 neurotic patients without any organic neurological disease (16-47 years, mean age 29.0 years). After bedrest overnight and before breakfast, lumbar puncture was performed at 9 o'clock. After collection of 20 ml of CSF in a test tube, the specimen was shaken, dividedinto smaller quantities and immediately frozen in liquid nitrogen of - 180 o C until analysis. Analyses of xanthine, hypoxanthine, uric acid and creatinine were performed with a high performance liquid chromatographic method (Niklasson, 1983). Significant differences in the purine metabolite levels were calculated between the dementia groups using Student's t test. Ethical and practical considerations do not allow the drawing of 20 ml CSF from healthy elderly persons. For this reason, we have no age-matched groups. In order to control the role of age in the values of purine metabolites, we have calculated the correlation between age and level of metabolites. This calculation was carried out in: (1) the reference group, (2) the dementia group cumulating every type of dementia, and (3) each type of dementia.
Results Hypoxanthine concentrations There was no significant difference between the reference and the dementia groups. Xanthine levels Compared to the reference group there was a marked elevation in xanthine concentration in each dementia group (Fig. 1), but there was no difference among the different types of dementia.
175 Hypoxonthim
/tlr~/I
R
POAT
MID
/Jmd/i R
Xonthim PI:IN' 50AT
MID
I0,
". •
~
Uric Qcid /Jmolll R
i
p..:.o~ l
Crtmtinine
P Q A T SI::)AT MID
3 0 o
l
"
*P
blr'no¢II R
60
POAT
$l::~T
MID
"
Fig. 1. Concentrations of hypoxanthine, xanthine, uric acid and creatinine in CSF of patients suffering from presenile dementia of Alzheimer type (PDAT), senile dementia of Alzheimer type (SDAT) and multi infarct dementia (MID). The reference group (R) consisted of neurotic patients.
TABLE I Correlation coefficients (r) between age and level of purine metabolites and creatinine in cerebrospinal fluid Hypoxanthine
Xanthine
Uric acid
Creatinine
Reference group (n =16)
r p
0.119 NS
0.367 NS
0.000 NS
0.534 p < 0.05
Dementia groups together (n = 31)
r
0.085
0.016
0.224
0.150
p
NS
NS
NS
NS
PDAT (n = 7)
r p
0.205 NS
0.441 NS
0.411 NS
0.543 NS
MID (n =15)
r p
0.007 NS
0.079 NS
0.272 NS
0.064 NS
SDAT (n = 9)
r p
0.396 NS
0.211 NS
0.323 NS
0.265 NS
176
Levels of uric acid Compared to the reference group, there was a significant elevation in SDAT and MID but not in PDAT. Comparing the dementia groups themselves, there was a significant difference between the PDAT and MID, with the concentration of uric acid being higher in MID. Creatinine level There was a significant elevation in each dementia group compared to the reference group, but there was no significant difference among the dementia groups.
Correlation between age and CSF level of metabolites (Table I) In the reference group (age between 16-47 years) there was no significant correlation between age and level of hypoxanthine, xanthine, and uric acid, while the creatinine concentration correlated ( p < 0.05) with age. No significant age-related correlation was found in the 'cumulated' dementia group (age between 54-82 years), nor in the separated dementia groups.
Discussion
The origin of the measured substrates It is postulated that hypoxanthine and xanthine in CSF originate in the brain. The possibility cannot be excluded, however, that the hypoxanthine might be due to active uptake from blood plasma, at least in part, in pathological situations, e.g. hypoxia (Hallgren et al., 1983). The brain metabolizes AMP to adenosine ~ inosine hypoxanthine, and xanthine (the last one via GMP, guanosine and guanine). The brain contains the enzymes involved in this pathway (Niklasson, 1983). Furthermore, this opinion is supported by the concentration gradients in CSF for xanthine and hypoxanthine. The level of these metabolites diminishes rostrocaudally, if we compare successive fractions of lumbar samples (Niklasson, Hetta and Degrell, in press). Uric acid originates from the plasma since the brain has no xanthine oxidase enzyme and thus can not produce uric acid (A1-Kahlidi and Chaglassian, 1965). The concentration of uric acid in CSF is about 1/20 of the serum concentration, while the hypoxanthine and xanthine concentrations are much higher (accordingly, 5 times for both substances) in CSF than in plasma (Niklasson, 1983a). There is a linear relationship between the plasma and CSF urate concentrations. The concentration o f urate in the CSF increases in a rostrocaudal direction. This is quite the opposite of hypoxanthine and xanthine concentration distributions. The ratio of CSF urate/plasma urate could be used as a marker of blood-brain barrier function (Niklasson, Hetta and Degrell, in press). The levels of creatinine in plasma and in CSF are similar. It was shown that the CSF creatinine concentration increases with age, but this is not the case with the plasma (Niklasson and .~gren, 1984).
177
Interpretation of our findings In our investigations the elevated xanthine levels in CSF of the demented patients indicate a state of energy need, which is independent of the type of dementia. It is not easy to explain why there is no difference in the hypoxanthine level of CSF between the control group and any of the dementia groups. It could have been hypothesized that, at least in MID, the hypoxanthine concentration is elevated, since the cerebral blood flow and the oxygen utilization are markedly reduced in MID (Hachinski et al., 1975). One explanation would be that hypoxanthine is reutilized for nucleotide synthesis and that the steady-state level was reached again at the time the CSF specimen was obtained in chronic ischemic diseases. As it was experienced in global cerebral ischemia, in the acute state there is first an enhancement of the level of hypoxanthine and xanthine, but some days later the level of hypoxanthine is normal, while the level of xanthine remains high (Hallgren et al., 1983). The level of uric acid was elevated both in SDAT and MID, but not in PDAT. Since PDAT is probably strictly a disease of the brain, there is no cause to hypothesize a heightened production of uric acid in the periphery of these relatively young patients. Moreover, SDAT and MID patients are older, and this could explain the higher values in CSF of uric acid (originating from plasma). It is known that the ratio of C S F / p l a s m a urate increases significantly with age (Niklasson and Agren, 1984), and increased CSF urate levels have been suggested to reflect blood-brain barrier function (Carlsson and Dencker, 1973). The creatinine levels were found to be higher in each type of dementia. It may indicate the poor function of brain energy metabolism, namely the creatine-creatine phosphate shuttle. The concentration of CrP diminishes earlier in energy need situations than that of ATP. The CSF creatinine level increases with age too, but this is not the case in plasma (Niklasson and ,~gren, 1986). The lack of the age-related changes in the CSF metabolite level seems to show that the biochemical changes dependent on the types of dementia have a greater role than the age per se. Naturally, we do not mean to imply that the role of age must be excluded. Summarizing these results, the patterns of the purine levels in the CSF can be characteristic in chronic organic brain diseases, e.g. in different types of dementia. The etiology and the metabolic changes in dementia are far from being understood, but it seems that the knowledge of the levels of hypoxanthine, xanthine, uric acid, and creatinine can be used to help differentiate the dementias.
Acknowledgements This work was supported by the twinning grant of the European Training Programme in Brain and Behaviour Research (Strasbourg) Nr. 83/281 (I. Degrell).
178
References AI-Kahlidi, V.A.S. and Chaglassian, T.H. (1965): Species distribution of xanthine oxidase. Biochem. J., 97, 316-320. Carlsson, C. and Dencker, S.J. (1973): Cerebrospinal uric acid in alcoholics. Acta Neurol. Scand., 49: 39-46. DegreU, I., Prk, G., Nagy, D., Nagy, E. and Hoyer, S. (1985): Dementias, psychological tests, and neurotransmitters. Arch. Gerontol. Geriatr., 4, 365-371. Degrell, I., Nagy, E. and Hoyer, S. (1987): Carbohydrate metabolite concentrations in CSF in different types of dementia. Submitted for publication. Hachinski, V.C., Iliff, L.D., Hilhka, E., Du Boulay, G.H., McAllister, V.L., Marshall, J., Russell, R.W.R. and Symon, L. (1975): Cerebral blood flow in dementia. Arch. Neurol., 32: 632-637. Hiillgren, R., Niklasson, F., Terent, A., Akerblom, ,~. and Widerl/Sv, E. (1983): Oxypurines in cerebrospinal fluid as indices of disturbed brain metabolism. A clinical study of ischemic brain diseases. Stroke, 14: 382-388. Karmazsin, L. and Balla, G. (1985): Plasma hypoxanthine and xanthine levels in the early newborn period in problem-free preterm babies and those with idiopathic respiratory distress syndrome. Acta Paediat. Hung., 26: 1-9. Niklasson, F. (1983a): Experimental and clinical studies on human purine metabolism. Acta Univ. Upps., Abstracts of Uppsala Dissertations from the Faculty of Medicine, 473. Uppsala. Niklasson, F. (1983b): Simultaneous liquid-chromatographic determination of hypoxanthine, xanthine, urate, and creatinine in cerebrospinal fluid with direct injection HPLC. Clin. Chem., 29, 1543-1546. Niklasson, F. and ~,gren, H. (1984): Brain energy metabolism and blood-brain barrier permeability in depressive patients: Analyses of creatine, creatinine, urate and albumin in CSF and blood. Biol. Psychiat., 19, 1183-1206. Nildasson, F., Hetta, J. and Degrell, I. (1987): Hypoxanthine xanthine, urate and creatinine concentration gradients in cerebrospinal fluid. Submitted for publication. Saugstad, O.D. and Gluck, L. (1982): Plasma hypoxanthine levels in newborn infants: a specific indicator of hypoxia. J. Perinat. Med., 10: 266-272.