The free amino acids of human spinal fluid determined by ion exchange chromatography

Taurine in Cerebrospinal Fluid in Friedreich's Ataxia

In a previous study we reported low values of taurine and aspartic acid in the CSF of patients with Friedreich's ataxia, when the results were compared to the literature. Further studies have revealed that tinforetold difficulties with the advertised methodology of sequential multi-sample amino acid analysis were responsible for low values in the determination of these two amino acids in the small volumes necessary for CSF. A corrected method is presented. With the latter method the differences disappear for CSF taurine and aspartic acid, but they remain valid for the previously reported blood and urine values in Friedreich's ataxia. GABA levels are also normal in Friedreich's ataxia CSF.

Leu1 plays a role in iron metabolism and is required for virulence in Cryptococcus neoformans

Amino acid biosynthetic pathways that are absent in mammals are considered an attractive target for antifungal therapy. Leucine biosynthesis is one such target pathway, consisting of a five-step conversion process starting from the valine precursor 2-keto-isovalerate. Isopropylmalate dehydrogenase (Leu1) is an Fe-S cluster protein that is required for leucine biosynthesis in the model fungus Saccharomyces cerevisiae. The human pathogenic fungus Cryptococcus neoformans possesses an ortholog of S. cerevisiae Leu1, and our previous transcriptome data showed that the expression of LEU1 is regulated by iron availability. In this study, we characterized the role of Leu1 in iron homeostasis and the virulence of C. neoformans. We found that deletion of LEU1 caused leucine auxotrophy and that Leu1 may play a role in the mitochondrial-cytoplasmic Fe-S cluster balance. Whereas cytoplasmic Fe-S protein levels were not affected, mitochondrial Fe-S proteins were up-regulated in the leu1 mutant, suggesting that Leu1 mainly influences mitochondrial iron metabolism. The leu1 mutant also displayed increased sensitivity to oxidative stress and cell wall/membrane disrupting agents, which may have been caused by mitochondrial dysfunction. Furthermore, the leu1 mutant was deficient in capsule formation and showed attenuated virulence in a mouse inhalation model of cryptococcosis. Overall, our results indicate that Leu1 plays a role in iron metabolism and is required for virulence in C. neoformans.

The human arginases and arginase deficiency

Arginase is the final enzyme in the urea cycle. Its deficiency is the least frequently described disorder of this cycle. It results primarily in elevated blood arginine, and less frequently in either persistent or acute elevations in blood ammonia. This appears to be due to a second arginase locus, expressed primarily in the kidney, which can be recruited to compensate, in part, for the deficiency of liver arginase. The liver arginase gene structure permitted study of the molecular pathology of patients with the disorder and the results of these studies and the inferences about the protein structure are presented. The conserved regions among all arginases allowed the cloning of AII, the second arginase isoform. It has been localized to the mitochondrion and is thought to be involved in ornithine biosynthesis. It shares the major conserved protein sequences, and structural features of liver arginase gene are also conserved. When AI and AII from various species are compared, it appears that the two diverged some time prior to the evolution of amphibians. The evidence for the role of AII in nitric oxide and polyamine metabolism is presented and this appears consonant with the data on the tissue distribution.

Kinetic analysis of glutamate transport by the miniswine choroid plexus in vitro

Transport of glutamic acid by the choroid plexus, the blood-cerebrospinal fluid (CSF) barrier, was investigated by using the isolated choroid plexi from the fourth (FVCP) and lateral ventricles (LVCP) of the young adult miniswine in vitro. Glutamic acid uptake was very pronounced, with concentrations 7-fold (LVCP) and 2.4-fold (FVCP) higher in tissue than in medium after only 5 min of incubation with 1 microM glutamic acid. Tissue/medium ratios reached steady state by 15 min at 30-fold (LVCP) and 11-fold (FVCP). Uptake was energy-dependent and inhibited by ouabain and hypothermia. L-Aspartic acid was shown to be inhibitory in a concentration-dependent manner, suggesting that it shares a common transport system, whereas neither octanoic acid nor okadaic acid (transported by a separate fatty acid system) inhibited glutamic acid transport. At the same temperature, the labeled metabolite of glutamate (glutamine) in the tissue was 64.7%, 73.2%, and 72.5% of total radioactivity at 5, 30, and 60 min, respectively. The estimated Km values for glutamate uptake by the choroid plexus are 264 microM (FVCP) and 196 microM (LVCP); Vmax values are 87 (FVCP) and 147 (LVCP) nmol/g/min, respectively. These results indicate that, in addition to the metabolism of glutamate to glutamine, an active uptake mechanism is present in the choroid plexus of miniswine which may serve to regulate glutamic acid concentration in the CSF.

Reference values for amino acids in cerebrospinal fluid of children determined using ion-exchange chromatography with fluorimetric detection

One thousand specimens of CSF were collected from subjects ranging in age from newborn to 18 yr, who were undergoing a diagnostic lumbar puncture. Sixty-two samples were judged retrospectively as being suitable for calculating reference age-related values. The analyses were performed by an amino acid analyser using ion-exchange chromatography with fluorimetric detection giving a tenfold increase in sensitivity, thereby enhancing the diagnostic capabilities. As many as 36 known compounds could be detected, additionally 10 we could not identify. In children older than 3 yr nine of the identified compounds showed age-dependency. We found 22 amino acids to be significantly higher in infants younger than 1 yr, with only gamma-aminobutyric acid being significantly lower in infants. Alpha-aminoadipic acid showed a sex difference, being slightly higher in girls.

Quantitation of free amino acids in biological samples by high-performance liquid chromatography. Application of the method in evaluating amino acid levels in cerebrospinal fluid and plasma of patients with multiple sclerosis

An automatic on-line high-performance liquid chromatographic method based on a precolumn derivatization with o-phthalaldehyde has been developed to quantitate levels of free amino acids in cerebrospinal fluid (CSF) and plasma samples from 12 patients with multiple sclerosis (MS) and 12 controls. The analytical method gave reproducible results with relative standard deviations of 0.5-3% for all amino acids. The separation of 24 amino acids was performed on a reversed-phase C18 column, using two solvents and a multiple-step gradient. Each chromatographic experiment was completed within 40 min. The results showed higher levels of Glu, Gln, Gly and Ala and lower levels of Met, Val, Phe and Lys in plasma of MS patients. In CSF, increased levels of Gln, Arg, Ser and Tyr and decreased levels of Asp, Glu, Met, gamma-aminobutyric acid and Phe were found in MS patients, whereas the levels of other amino acids remained more or the less same in both groups.

Elevated cerebrospinal fluid histidine in alcohol withdrawal

Cerebrospinal fluid (CSF) histidine concentration was significantly elevated in seven patients early in the alcohol withdrawal syndrome (206.3 +/- 74.4 (SEM) nanomols/ml CSF). When these same patients were restudied an average of six days later when alcohol withdrawal was clinically resolved, their mean CSF histidine concentration continued to be significantly elevated (164.7 +/- 24.7) when compared to normal (12.0 +/- 0.5 nanomols/ml CSF). Other amino acids (aspartic acid, serine, alanine, methionine, leucine, tyrosine, phenylalanine, lysine and arginine) showed no definite changes from normal, and no change during the course of alcohol withdrawal. Possible reasons for these high concentrations and the extreme variability (especially early in alcohol withdrawal) are discussed.

Analysis of amino acids in brain and plasma samples by sensitive gas chromatography-mass spectrometry

Gas chromatography-mass spectrometry-selected-ion monitoring provided a simple and sensitive method for analyzing amino acids in plasma and brain samples. Although the sensitivities of chemical ionization and electron-impact ionization were similar chemical ionization produced higher-mass ions, which might increase the selectivity of the assay. Both chemical and electron-impact ionization distinguished the natural amino acids from the 15N-labelled amino acids. The recovery of amino acids from plasma and brain samples was ca. 75%. The amino acid levels determined by gas chromatography-mass spectrometry were comparable with the amino acid levels determined by high-performance liquid chromatography or amino acid analyzer.

Physiological amino acid data management: quantitation, assessment, reporting and storage

A series of routines, written in BASIC, have been developed to aid in the analysis, reporting and storage of physiological amino acid data used in the diagnosis and management of inherited metabolic disorders. The concentrations of 44 compounds are determined for three types of physiological samples: plasma, urine or cerebral spinal fluid. The programs facilitate the editing of numerical data, the creation of a patient and sample information file to be merged with the results, the flagging of abnormal results, the addition of diagnostic or interpretive comments and the generation of hard copy reports. Files containing the foregoing information provide records which may be manipulated using data base programs for further analysis.

Lesch-Nyhan syndrome and its pathogenesis: purine concentrations in plasma and urine with metabolite profiles in CSF

Purine metabolism in the Lesch-Nyhan syndrome has been re-examined in 10 patients. Hypoxanthine and xanthine concentrations in plasma and CSF and urinary excretion have been studied, on and off allopurinol treatment, using high performance liquid chromatographic methods. Accumulation of the substrate, hypoxanthine, of the missing hypoxanthine guanine phosphoribosyltransferase (HPRT) enzyme, is more marked in urine and in CSF than in plasma. The greater increase in CSF is consistent with the most metabolically active tissue, brain, showing the most marked functional changes. The function of HPRT seems to be the recycling of hypoxanthine which is released from tissues in increasing quantities as energy use, ATP 'turnover', in the tissue increases. The existing screening method for HPRT deficiency, the ratio of the urinary concentration of urate to that of creatinine, shows overlap between the values in severe HPRT deficiency and in controls; this overlap is not found with a urinary hypoxanthine/creatinine molar concentration ratio.

Analysis of aspartate and glutamate in human cerebrospinal fluid by high-performance liquid chromatography with automated precolumn derivatization

A method is described for the analysis of the neuroexcitatory amino acids, aspartate and glutamate, in human cerebrospinal fluid (CSF) by reverse-phase, high-performance liquid chromatography. Fluorescent isoindole derivatives of the amino acids were prepared by reacting the amino acids with ortho-phthalaldehyde in an automated, precolumn procedure. Chromatographic conditions were developed that resolve the isoindole derivatives of aspartate and glutamate from those of at least 10 unidentified components of CSF. Amino acids were reliably quantified in 5-microliter samples of CSF, and deproteinization of the specimens was not required. Furthermore, it was found that deproteinization by precipitation with strong acid can lead to artifactually high measurements of glutamate. The concentrations of free aspartate and glutamate in lumbar CSF from 15 neurologically normal children were 0.30 +/- 0.11 and 0.48 +/- 0.26 microM (mean +/- SD), respectively. The value for glutamate is considerably lower than has been reported in any previous study of human CSF.

Difficulties in assessing the effect of strychnine on the outcome of non-ketotic hyperglycinaemia. Observations on sisters with a mild T-protein defect

Sisters with a mild variant of non-ketotic hyperglycinaemia resulting from a defect in the T-protein of the glycine cleavage system had different clinical outcomes. The older sister was ascertained at 6 months of age because of mental retardation. She received only brief treatment with sodium benzoate from 11-15 months and at 15 years of age is profoundly retarded and has epilepsy. The younger sister was diagnosed 36 h after birth, was treated with strychnine, sodium benzoate and arginine from the neonatal period and at 27 months of age is only moderately retarded and free of seizures. The possible role of strychnine in the improved outcome is discussed.

Free and conjugated amino acids in human CSF: influence of age and sex

An extended baseline characterization of amino acids (AAs) and related amino compounds in CSF is reported. Thirty-one amino compounds were measured in deproteinized CSF before and after acid hydrolysis using a triple-column HPLC/fluorometric analyzer. CSF specimens were collected under strictly controlled conditions from neurologically normal myelogram patients and carefully pooled with regard to subject age and sex. Consideration was given to factors which may produce artifactual alterations in AA levels during CSF collection, storage and handling. Conjugated AAs were determined as the difference between levels of free AAs (measured in CSF prior to hydrolysis) and total AAs (measured in hydrolyzed CSF) and are taken as an index of total CSF peptide AAs. Results documented conjugated forms of all non-acid-labile CSF AAs except citrulline and ethanolamine. In general, ratios of conjugated to free AAs were relatively low, however for the neurotransmitter AAs aspartate, glutamate, glycine and GABA as well as for beta-alanine hydrolysis produced marked increases indicating that these compounds are present predominantly in bound form in CSF. Results also revealed the significant influence of both age and sex on levels of a number of CSF free and conjugated AAs. Compared to younger individuals (those less than 40 years of age), older individuals exhibited significantly higher levels of free aspartate, glycine, alpha-aminobutyric acid, valine, isoleucine, leucine, phenylalanine and 3-methylhistidine as well as significantly lower levels of free phosphoethanolamine, serine, GABA, homocarnosine, conjugated GABA and conjugated beta-alanine. Additionally, significantly higher levels of free tyrosine, ethanolamine, arginine and conjugated aspartate were documented in males compared to females.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of glutamine on glutamate release from hippocampal slices induced by high K+ or by electrical stimulation: interaction with different Ca2+ concentrations

To characterize the effect of glutamine on the release of glutamate, aspartate, and gamma-aminobutyric acid (GABA), rat hippocampal slices were superfused with different concentrations of glutamine or Ca2+. Amino acids released and retained were analyzed by HPLC. Glutamine (0.5 mmol/L) increased more than threefold the release of glutamate evoked by 50 mmol/L K+ in the presence of 2.6 mmol/L Ca2+ without a corresponding increase in glutamate content, while the release of aspartate was increased less and that of GABA not at all by glutamine. The evoked release of all three amino acids, including the enhanced release of glutamate in the presence of glutamine, was strongly dependent on Ca2+ concentrations between 0.1 and 2.6 mmol/L. The potentiation of glutamate release by glutamine reached a plateau at 0.25 mmol/L glutamine. Intermittent electrical field stimulation increased the release of only glutamate and this release was nearly doubled by glutamine. The increased release was Ca2+ dependent and tetrodotoxin (TTX) sensitive. Results suggest that extracellular glutamine promotes primarily the formation of releasable glutamate and this enhancement is dependent on extracellular Ca2+.

Cerebrospinal fluid free amino acids in patients with spinal space-occupying lesions. A preliminary report

18 different free amino acids were determined in the cerebrospinal fluid of 28 patients with various spinal space--occupying lesions. The study group included 15 patients with lumbar disc lesions (control group), 8 patients with cervical radiculopathy, 4 patients with cervical myelopathy, and 1 patient with a thoracic spinal angioma. The values from the control group were in general accord with those previously observed in normal adults of 5 studies of the literature. Comparison of the values in the different subgroups showed normal values of all amino acids in patients with cervical myelopathy, and significantly higher levels of glutamic acid in patients with cervical radiculopathy. In the case of a thoracic spinal angioma however most free amino acids were extremely high. The authors conclude that this may be due to alterations of the spinal metabolism and that determination of free amino acids in CSF of patients with intradural spinal lesions may help to improve preoperative diagnosis in addition to neuroradiological methods.

5,10-Methylenetetrahydrofolate reductase deficiency. Clinical and biochemical features of a further case

We report the case of a boy with 5,10-methylenetetrahydrofolate reductase deficiency. The clinical features consisted of severe mental retardation, spasticity and seizures remaining static to 7 years of age followed by a phase of rapid deterioration and death at 7 1/2 years of age. The main biochemical findings were homocystinaemia, homocystinuria, a normal methionine level in plasma and cerebrospinal fluid, an increased excretion of methionine in urine and a very low level of folate in the cerebrospinal fluid. The activity of 5,10-methylenetetrahydrofolate reductase was greatly reduced in the patient's lymphocytes and liver.

Triple-column ion-exchange physiological amino acid analysis with fluorescent detection: baseline characterization of human cerebrospinal fluid

A highly resolving triple-column amino acid analyzer with fluorometric detection is described. The reliability of this technique was evaluated and it was used in a baseline investigation of amino acids and related compounds in human cerebrospinal fluid (CSF). The procedure employs three distinct ion-exchange columns to elute the acidic, neutral, and basic amino acids, respectively. Each column is run isocratically with lithium citrate buffers designed to provide overlapping elution profiles. Studies using CSF collected under strictly controlled conditions documented nanomolar concentrations of aspartate, gamma-aminobutyric acid (GABA), beta-alanine, 1-methylhistidine, and 3-methylhistidine, as well as low levels of glutamate, methyllysine, and ammonia. In addition, other common amino acids were also quantified. Chromatograms of CSF from all three systems (acidic, neutral, and basic) exhibited numerous uncharacterized compounds emphasizing the resolution and sensitivity of the analytical procedure. In vitro stability studies revealed that levels of aspartate, glutamate, GABA, homocarnosine, and ammonia are subject to significant change when CSF is maintained at room temperature for various periods of time up to 24 h. It is concluded that the valid and accurate measurement of CSF amino compounds, especially the neurotransmitter amino acids, requires a highly specific and sensitive assay procedure as well as strict control of CSF manipulation in vitro.

Proline in the cerebrospinal fluid of normal subjects and Alzheimer's-disease patients, as determined with a new double-labeling assay technique

Past studies have implicated proline involvement in the function of memory and learning. A new micromethod has been developed that is suitable for measuring proline accurately in as little as 0.1 ml of CSF. In normal human CSF, the average proline level was found to be consistently about 1.3 microM. In the CSF of patients with Alzheimer's disease and mixed dementias, the levels of proline showed no statistically significant difference from proline levels in the CSF of normal controls. Furthermore, the proline levels in the CSF of the Alzheimer's disease patients did not reflect, consistently, the cognitive deficits or the symptomatic severity of the disease. Proline levels in CSF showed no statistically significant change with the age of individuals tested.

Increased concentrations of aspartic acid in the cerebrospinal fluid of patients with epilepsy and trigeminal neuralgia: an effect of medication?

The concentrations of free amino acids in the cerebrospinal fluid (CSF) were quantitated in 14 patients with epilepsy, 7 patients with trigeminal neuralgia, 10 patients with various neurological diseases and in 30 apparently healthy individuals. In the CSF of patients with epilepsy, the mean concentrations of aspartic acid (Asp), glutamine (Gln), histidine and phosphoserine were significantly higher than in the healthy individuals. The mean concentration of aspartic acid was higher in the patients on antiepileptic drug (AED) therapy than in the patients without AED therapy. The patients with trigeminal neuralgia had significantly increased CSF-concentrations of aspartic acid, glutamine and phosphoserine as compared to healthy individuals. Some patients receiving AED showed increased concentration of gamma-amino-butyric-acid (GABA).

Amino acid metabolism in the brain with convulsive disorders. Part 3: Free amino acid patterns in cerebrospinal fluid in infants and children with convulsive disorders

Free amino acid patterns of cerebrospinal fluid in infants and children with various types of convulsive disorders were compared with those in age-matched normal subjects. The total free amino levels in Lennox syndrome were higher than the normal values, and those in infantile spasms controlled by ACTH were higher than those in uncontrolled infantile spasms. Although the levels of only one or two amino acids in tonic-clonic seizure, focal seizure and febrile seizure were higher or lower than those of the controls, the levels of 8 amino acids in infantile spasms were lower and those of 10 amino acids in Lennox syndrome were generally higher compared to the controls. Among amino acids in CSF of children with tonic-clonic seizure, infantile spasms or Lennox syndrome, only the ornithine level was commonly lower than that of the controls. After the treatment, in tonic-clonic seizure, the levels of taurine, asparagine and glycine were increased, and in infantile spasms, those of asparagine, glutamine, glycine, alanine, phenylalanine, lysine and arginine were increased while that of taurine was decreased. These results suggest that each type of convulsive disorder shows the specific amino acid pattern, and the effects of anticonvulsants may be partially understood through the changes of the free amino acid patterns in the brain.

Normal cerebrospinal fluid and brain glutamate levels in schizophrenia do not support the hypothesis of glutamatergic neuronal dysfunction

A recently proposed hypothesis to explain schizophrenia is based on reports of reduced concentrations of glutamic acid in the cerebrospinal fluid (CFS) of schizophrenic patients. This hypothesis suggests that there may be a dysfunction of glutamatergic neurons in schizophrenia, with either a degeneration of these neurons, or their failure to release glutamate as a neurotransmitter. Direct measurement of glutamate levels in CSF and autopsied brain of schizophrenic patient showed no differences from glutamate levels in suitable adult control subjects. The data presented here do not offer support for the new hypothesis.

Treatment of hyperargininaemia due to arginase deficiency with a chemically defined diet

A brother and sister aged 11 and 17 years have been reported previously to have hyperargininaemia and arginase deficiency: they were treated with a semi-synthetic diet consisting of fat, carbohydrate, minerals, vitamins and essential amino acids in amounts equivalent to 0.55-0.65 g protein kg-1 day-1 for 2 years. Plasma arginine levels fell from 0.50-0.90 mumol/1 to 0.13-0.30 mumol/1 (normal range 0.02-0.15). Increased concentrations of arginine in the cerebrospinal fluid (CSF) fell from 0.069-0.098 mumol/l to 0.040-0.056 mumol/l (normal mean +/- SD = 0.020 +/- 0.006). Dibasic aminoaciduria returned to normal within 1 week. Substitution of the keto-acid analogues of five essential amino acids in the formula lowered arginine concentrations further, but proved to be unpalatable. Urinary concentrations of orotic acid, uridine and uracil fell toward normal but remained increased, even when the plasma ammonia concentration was measured as normal. Both patients showed a stable clinical improvement.

In vitro retina as an experimental model of the central nervous system

Methods are described for isolating adult rabbit retinal and maintaining it in a medium designed to resemble CSF. Morphologic, metabolic, nd electrophysiologic measurements obtained on the in vitro retinas showed that they remained in a nearly physiological state for at least 8 h, and even after 2 days in vitro they still exhibited a high level of metabolic activity and electrical responsiveness to light. Physiological activity was modified by photic stimulation, and data are presented to document changes in metabolism in response to the changes in function. The isolated retina appears to offer a number of unusual advantages for studying relationships between function and metabolism in organized mammalian central nervous tissue.

Plasma and cerebrospinal fluid amino acid concentrations in phenylketonuria during the newborn period

Plasma and cerebrospinal fluid amino acid values were determined in 29 infants 9 to 30 days of age with a confirmed diagnosis of phenylketonuria. Phenylalanine concentrations in plasma and cerebrospinal fluid were markedly elevated; the degree of elevation in the cerebrospinal fluid had a significant relationship to that of the plasma. The only other significant deviations in the plasma were reductions in the threonine and tyrosine values. Cerebrospinal fluid threonine, alanine, and arginine concentrations were reduced, whereas those of serine, isoleucine, and histidine were elevated. This combined deficiency and excess of amino acids in the central nervous system may have a significant effect on protein synthesis at a time in life when this synthesis and turnover is most active.

Cerebral and systemic amino acid metabolism in experimental acute amphetamine poisoning in guinea pigs

Protein catabolism, as measured by plasma amino acids is increased by amphetamine injection (15 mg/kg body wt) administered to 10 adult male guinea pigs. Changes in the cerebrospinal fluid were less marked than those in the plasma. The amphetamine seemed to inhibit the enzymes of the metabolic pathways that use amino acids.

Protein turnover in retina

Rabbit retinas were exposed in vitro to 0.5-h pulses of [3H]leucine or [14C]leucine. Some retinas were harvested promptly after labeling to measure synthesis. These were combined, in double-labeling experiments, with retinas that had been returned to unlabeled medium for a subsequent 1 h or 3.75 h to measure degradation. All of the proteins were solubilized, and separated according to size by gel electrophoresis. The gels were cut into 95 slices, and each slice was differentially counted. The amount of protein in the slice was estimated from the Coomassie blue staining, and its molecular weight from the distribution of molecular weight (MW) standards. Turnover rates of the various sizes of proteins were calculated from these data using certain well-defined assumptions. Retinal protein contained about 32 X 10(3) nmol of polypeptide per g, with a median MW of 27,000. Total synthesis was at the rate of 103 nmol/g of protein/h, with the most rapid synthesis in the 33,000--43,000 MW range, at 2 nmol/g/h for every 1000 increment in MW. Protein renewal averaged 0.52%/h, but varied directly (p < 0.0001) with MW, so that proteins of 10,000 MW were being renewed at about 0.1%/h and proteins of 140,000 MW at about 1.4%/h. Taken together, the measurements of fractional renewal and the measurements of degradation of the newly synthesized proteins demonstrated that each slice contained proteins with markedly different breakdown coefficients, and provided enough information to characterize the proteins in the slice in terms of a fast and slow subgroup. This analysis indicated that: breakdown coefficients varied much more than rates of synthesis and were therefore the prime determinant of the amount of each protein that was present; as MW increased, breakdown coefficients of the long-lived proteins increased (p < 0.0001), accounting in major part for the correlation between size and turnover; most staining bands were due to proteins with peculiarly long lifespans; the proteins with the slowest turnover of all appeared to be histones; there was an unusually rapid synthesis of a 138,000 MW polypeptide with a moderately short half-life (about 3 h).

Enzymatic and immunological evidence for two forms of carnosinase in the mouse

Carnosinase (aminoacyl-L-histidine hydrolase, EC 3.4.13.3) hydrolyzes the dipeptide carnosine (beta-alanyl-L-histidine), which is thought to play a role in cerebral and skeletal muscular function and has been implicated as a neuroaffector in the olfactory bulb. Carnosinase activity is present in many tissues of the mouse including heart, liver and lung, but it is most active in kidney, uterus and nasal olfactory mucosa. Kinetic measurements with 1H-NMR spectroscopy indicate that the enzyme is stereospecific and can hydrolyze L-but not D-carnosine. Anserine is a poorer substrate, while homocarnosine is essentially a non-substrate. However, these two dipeptides are effective inhibitors of the hydrolysis of L-carnosine. Carnosinase activity is unaffected when assayed in 2H2O at 99% isotopic purity. From considerations of the effect of Mn2+ on (1) substrate concentration velocity curves; (2) thermostability, and (3) inhibitor behavior, tissues with carnosinase can be divided into two groups. Kidney, uterus and olfactory mucosa represent one group, while central nervous system, muscle, spleen, etc. represent the second. The validity of this classification is confirmed by immunological evidence. Antiserum prepared against carnosinase purified from kidney cross-reacts with and inhibits the activity of olfactory mucosa, kidney and uterus but not that from central nervous system, heart or liver.

Observed range of assay values for plasma and cerebrospinal fluid amino acid levels in infants and children aged 3 months to 10 years

From data collected at the Children's Hospital, Vancouver, during a two year period, 1976 - 1977, we have determined a range of values for children aged 3 months to 6 years for 24 plasma amino acids and for children aged 3 months to 10 years for 18 cerebrospinal fluid amino acids. A total of 26 plasma and 21 cerebrospinal fluid samples were accepted for our reference population. Six of the children in the plasma group were also in the cerebrospinal fluid group, making a total of 39 children in the study.

The subcellular distribution of carnosine, carnosine synthetase, and carnosinase in mouse olfactory tissues

The dipeptide, carnosine, its synthetic enzyme, carnosine synthetase, and its degradative enzyme, carnosinase, appear to be localized in the cytosol of mouse olfactory bulb and epithelium. Mouse olfactory bulbs and epithelium were prelabeled in vivo with [3H]carnosine following intranasal irrigation with [3H]beta-alanine. [3H]carnosine co-distributed in olfactory bulb with lactate dehydrogenase with only 10% in the crude mitochondrial fraction. Similar results were also seen with endogenous carnosine distribution. Over 70% of the carnosine present in the crude mitochondrial fraction was localized in synaptosomes following sucrose gradient centrifugation. However, further fractionation of vesicle containing fractions from osmotically lysed crude mitochondrial fractions indicated that [3H]carnosine was not associated with vesicles. Nearly 70% of all the [3H]carnosine present in olfactory epithelium was soluble with most of the remainder in the crude nuclear fraction. The enzymes carnosine synthetase and carnosinase were clearly soluble in olfactory epithelium with 98% and 85% of the activity in the cytosol. Less than 2% was found in the crude mitochondrial fraction. In olfactory bulb both enzymes also appeared soluble.

Hyperlysinemia with saccharopinuria due to combined lysine-ketoglutarate reductase and saccharopine dehydrogenase deficiencies presenting as cystinuria

A 7-year-old boy with speech delay, hyperactive behavior, and minor neurologic abnormalities had been found in the past to have "intermittent cystinuria." A more detailed investigation revealed hyperlysinemia and hyperlysinuria, with lesser increases in urinary excretion of arginine and cystine. The plasma and urine abnormalities increased on a diet of 3 gm of protein/kg body weight/day. Saccharopine, a normal metabolite of lysine not found in the body fluids of normal people, was present in plasma, cerebrospinal fluid, and urine of the patient. Lysine-ketoglutarate reductase and saccharopine dehydrogenase activities were not detectable in extracts of cultured skin fibroblasts. Re-examination of the urine of previously studied cases of this double enzyme deficiency suggests that saccharopinuria of variable degree is the rule and not the exception.

Dicarboxylic aminoaciduria: an inborn error of amino acid conservation

A 38-month-old apparently healthy male has been followed for three years because of a massive glutamic and aspartic aminoaciduria detected shortly after birth in a neonatal screening program. Amino acid clearance studies revealed the presence of renal wastage of dicarboxylic amino acids. Intestinal transport and in vitro oxidation of dicarboxylic amino acids were found to be intact. Clinical and metabolic data obtained on a previously described patient and the present case suggest that some patients with dicarboxylic aminoaciduria might have a selective renal conservation defect without clinical abnormalities, whereas others might demonstrate an additional defect in intestinal transport associated with fasting hypoglycemia.

Cerebrospinal fluid glycine in nonketotic hyperglycinemic: effect of treatment with sodium benzoate and a ventricular shunt

In three infants with nonketotic hyperglycinemia, glycine was increased three-to fourfold in plasma, 13- to 28-fold in lumbar spinal fluid, and was higher yet in ventricular fluid. Oral sodium benzoate lowered cerebrospinal fluid (CSF) glycine by greater than 40%, but did not change the abnormal plasma: CSF ratio. An adult control, made hyperglycinemic with oral glycine, had a normal plasma: CSF ratio. Treatment of one patient with sodium benzoate from birth did not prevent mental retardation; the degree of brain stem depression was a function of CSF glycine in another patient. The persistance of glycine elevation in CSF, although therapy maintained normal concentration in plasma, appears to be caused by overproduction in brain and limitation of the high-capacity lumbar spinal reabsorptive mechanism. Treatment through lowering of CNS glycine by use of a ventricular shunt was explored.

Hyperargininemia

A 7 1/2-year-old boy had progressive psychomotor retardation, behavior disturbance, and spasticity, and had growth arrest from age three. Plasma arginine on a self-selected protein-poor diet was increased (4.05 mg/dl; nl 0.4 to 2.6), whereas urinary amino acid excretion was normal. Red blood cell arginase was less than 1% of normal in the patient and was half normal in both parents, in two normal siblings, and in his paternal grandfather. Three hours after a meal providing 2 gm protein/kg body weight, the plasma arginine value rose to 13.2 mg/dl, dibasic aminoaciduria was seen clearly for the only time, but blood ammonia concentration remained normal. We conclude that arginase deficiency in the red blood cells and probably in the liver is inherited in an autosomal recessive manner and is responsible for the clinical syndrome in this patient.

Maturational changes of amino acid concentration in cerebrospinal fluid of the rat

The cisternal spinal fluid (CF), plasma, and brain stem concentrations of 6 amino acids were measured in suckling rats between birth and one months of age. Each of the amino acids studied had its distinctive maturational pattern of CF concentration. Presumably these amino acids have separate mechanisms of transport from CF, which mature at different times.

Protein synthesis in central nervous tissue: studies on retina in vitro

Rabbit retinas were maintained in vitro in medium that resembled CSF but with leucine varied from 2 to 1000 microM. Both leucine and threonine were isotopically labelled. When leucine in the medium was 100-1000 microM, leucine was incorporated into protein at 2.03 +/- 0.04 (S.E.M.) mumol/g dry wt./h, a turnover per h of 0.55% of the leucine in retinal protein. Incorporation was constant for at least 7 h. It was reduced 34% when the other amino acids were omitted from the medium and 24% when they were increased 15 fold above physiological levels. When medium leucine was reduced to 2 microM with other amino acids constant, 14C-leucine incorporation fell 70% without significant change in 3H-threonine incorporation, indicating a fall in intracellular specific activity of leucine. The intracellular/extracellular concentration ratio of labelled leucine was 4:1 with medium leucine 23 microM. It fell markedly when medium leucine was reduced to 2 microM or increased to 1000 microM. The concentration ratio of labelled threonine was 15:1 with medium leucine at physiological levels but fell to 6:1 when medium leucine was increased to 1000 microM. Decarboxylation removed 1.5% of free intracellular leucine per min and, at physiological concentrations, was 7.7% the rate of protein incorporation. The ratio of protein synthesis/breakdown, estimated from changes in leucine and 7 other essential amino acids in the medium, was nearly unity. The potential of this preparation for study of CNS protein metabolism is discussed.

[Free amino acids in human Eocrine sweat (author's transl)]

With the aid of ion exchange column chromatography we determined quantitatively the free amino acids in eccrine, thermal sweat. Sweat was collected (a) from the face of 27 healthy men and 26 healthy women (b) from the face, chest, armpits, shoulders, back, upper part of the abdomen, hypogastrium, forearms and thighs of the same individual and (c) from the face of the same individual at different times. Sweat was deproteinised by adding an equal volume of 5% sulphosalicylic acid. 1. The results showed not only a constant, qualitative amino acid pattern in sweat, but also a relative constancy among the individual amino acids. 2. The concentrations of the free amino acids in sweat showed significant, individual variations. Particularly high excretion rates were observed in the following amino acids: alanine, glycine, citrulline, histidine, ornithine, threonine and serine. 3. As compared to men, women had an increased excretion of all the examined amino acids in sweat from the face, except for cystine. Statistically significant higher excretion was seen within this sex-specific comparison for the following amino acids: alanine, citrulline, glycine, histidine, isoleucine, serine, taurine, threonine, tyrosine and valine. 4. Essential amino acids such as isoleucine, leucine, lysine, methionine, phenylalanine and valine and also cystine were always excreted only in small amounts. 5. Significant differences were also observed in the total amino acid excretion and in the individual amino acid excretions in sweat obtained from different parts of the body of the same person. 6. The amino acid concentrations determined in the sweat from the face of the same individual at different times showed a relative constancy as compared to the large differences of the amino acid concentrations determined in the sweat from the face of different individuals.

Subacute necrotizing encephalomyelopathy. Clinical, ultrastructural, biochemical and therapeutic studies in an infant

Subacute necrotizing encephalomyelopathy (SNE) has been observed in an infant with regressing psychomotor development. The concentrations of alanine, pyruvate and lactate were increased in the serum and blood as well as in the cerebrospinal fluid. Pyruvate carboxylase activity was reduced in the liver tissue. An inhibitor of thiamine-pyrophosphate-ATP-phosphotransferase was present in the urine. Thiamine treatment was followed by a decrease of serum alanine and blood pyruvate and lactate, but there was no clinical improvement during a period of 17 months. Ultrastructural investigations revealed high glycogen levels in liver tissue and skeletal muscle. These findings contrast with decreased gluconeogenesis, which is suggested by the diminished pyruvate carboxylase activity. Therefore it is concluded that reduced hepatic pyruvate carboxylase activity is not the primary cause of SNE.

Free amino acids in serum of patients with epilepsy: significant increase in taurine

More than half the amino acids determined in serum were lower in patients with epilepsy than in control subjects. Taurine was the only amino acid to be increased in epilepsy. The changes could represent a compensatory metabolic reaction to limit the imbalance of amino acids in epileptic brain and to facilitate uptake of taurine, which has an anticonvulsant action.

Placental transfer of glutamate and its metabolites in the primate

When radioactive glutamate was infused into pregnant rhesus monkeys, 69 to 88 per cent of radioactivity in the maternal plasma remained in association with glutamate while 10 to 22 per cent was converted to glucose. In the fetal plasma, glucose and lactate accounted for more than 80 per cent of radioactivity, with less than 2 per cent of the label found in glutamate. Maternal glutamate infusions resulting in a ten- to twenty-fold increase in maternal plasma glutamate levels (60 to 100 mumoles per 100 ml.) had no effect upon fetal glutamate levels. Infusions producing maternal glutamate levels 70 times normal (280 mumoles per 100 ml.) did result in some transfer of glutamate to the fetal circulation. Labeled glutamate administered to the fetus at 1.5 to 2.4 Gm. per kilogram of fetal weight did not result in glutamate transfer to the maternal circulation. Infusion of glutamate to the fetus at 5 Gm. per kilogram of fetal weight increased fetal plasma glutamate levels to 2, 000 mumoles per 100 ml. and resulted in some transfer of glutamate to maternal circulation. Glutamate metabolites (lactate and glucose) were readily transferred across the placenta in either direction. These studies indicate that the primate placenta is virtually impermeable to glutamate unless extreme elevations of plasma glutamate are induced.