Folate sufficient subjects do not accumulate additional folates during supplementation.

In a double-blinded placebo-controlled trial of folic acid supplementation in 82 alcoholic subjects, it was found that whole blood folate levels, determined by a mass spectrometric method, do not increase in subjects whose baseline folate levels are above the third quartile (folate sufficiency). Since a state of folate sufficiency can now be identified, a recommended daily allowance (RDA) for folate can be determined using objective means.

Glutathione oxidation in real time by thermospray liquid chromatography-mass spectrometry.

The oxidation and reduction of glutathione and oxidized glutathione were studied in real time by liquid chromatography-mass spectrometry during exposure to hydrogen peroxide and mercaptoethanol. By mass spectrometry mixed disulfides and both reversible and irreversible oxidations of sulfur to higher states (sulfinic and sulfonic acids) were directly observed during exposure to hydrogen peroxide. The irreversible oxidation of glutathione to glutathione sulfonic acid could be detected after 30 min exposure of glutathione to 40 mM H2O2 at 20 degrees C. A peak consistent with glutathione-sulfinic acid was transiently present, suggesting this compound behaved as an oxygen consuming antioxidant. Liquid chromatography-mass spectrometry appears to be an excellent method to study oxidation and reductions of sulfur containing peptides and amino acids.

Unpredictable intra-individual variations in serum homocysteine levels on folic acid supplementation.

OBJECTIVE: To determine if changes in serum homocysteine values during folic acid supplementation can identify objectively healthy subjects with subclinical folate deficiency. DESIGN: Blood drawn and processed in a regimented fashion from fasting subjects. Serum homocysteine values determined by gas chromatography-mass spectrometry twice before and on days 5 and 8 of daily folic acid supplementation. SETTING: Outpatient University Hospital Clinical Research Center, Denver, Colorado. SUBJECTS: Subjectively healthy adults with normal hematologic and biochemical screening tests. INTERVENTION: Folic acid 1 mg daily for eight consecutive days. RESULTS: Homocysteine values of the group fell significantly during folic acid supplementation. Values pre supplementation were 7.8 +/- 1.8 and 7.4 +/- 2.4 mumol/L while values on days 5 and 8 of supplementation were 6.5 +/- 2.2 and 6.3 +/- 2.2 mumol/L. However, the homocysteine values of any given individual varied up to 60% (rises up to 7 mumol/L and falls of 5 mumol/L) during folic acid supplementation despite the controlled circumstances of blood handling, and an assay coefficient of variation of 8%. CONCLUSIONS: Although group values of serum homocysteine fall during folic acid supplementation, intraindividual variation is so great that subjects with subclinical folate deficiency can not be identified using this study design. Furthermore, these data suggest than an individuals homocysteine values vary enough that single values must be interpreted with caution.

Quantitation of homogentisic acid in normal human plasma.

A new stable isotope dilution gas chromatograph-mass spectrometric method of analysis of homogentisic acid is described. Using this method, homogentisic acid is measured for the first time in normal human plasma. The assay of sera from nine normal individuals yielded a range of values from 2.4 to 12 ng/ml. The method appears to be very sensitive and may be useful in the characterization of heterozygotes for alkaptonuria and other disorders of tyrosine degradation.

A noninvasive stable-isotope method to simultaneously assess pancreatic exocrine function and small bowel absorption.

OBJECTIVE: To determine if a single-step noninvasive stable isotope method of assessing digestive function could separate normal subjects from subjects with pancreatic insufficiency (maldigestion) or small bowel dysfunction (malabsorption) and to see if subjects with maldigestion could be simultaneously separated from subjects with malabsorption. METHODS: Forty (40) normal volunteers, 18 adults with cystic fibrosis and four adults with celiac sprue, ingested a liquid test meal along with bentiromide, [13C6]PABA, and xylose (PABAX test). Serum was collected at 1 h and analyzed for PABA, [13C6]PABA, and xylose by stable isotope dilution methods using gas chromatography mass spectrometry. RESULTS: All subjects with cystic fibrosis had abnormal pancreatic function test results, whereas three of four adults with sprue had normal values of pancreatic function. All subjects with sprue had abnormal small bowel absorption tests, whereas all adults with cystic fibrosis had apparently normal intestinal function. CONCLUSION: The one-step, 1-h PABAX test can reliably separate normal subjects from those with either maldigestion or malabsorption and can also separate subjects with maldigestion from those with malabsorption.

Quantitation of red blood cell folates by stable isotope dilution gas chromatography-mass spectrometry utilizing a folate internal standard.

We report a new gas chromatography-mass spectrometry (GC-MS) method of measurement of red blood cell folates utilizing a stable isotope-labeled bacterial synthesized folate internal standard. The GC-MS method exploits the fact that the common feature of all folate molecules is a p-aminobenzoic acid moiety sandwiched between a pteridine ring and a polyglutamate chain of varying length. In this method, red blood cell folates together with a folate internal standard are specifically purified using bovine folate binding protein and the folates are subsequently chemically cleaved to p-aminobenzoic acid, pteridines, and glutamic acids. Since all six carbon atoms of the benzene ring in the p-aminobenzoic acid moiety of the folate internal standard are labeled with [13C], it is possible to use selected ion monitoring and stable isotope dilution GC-MS to quantitate folates. The method appears to be sensitive, specific, and accurate. The method has been applied to generate a reference range of red blood cell folates based on assay of 25 normal individuals.

Serum xylose analysis by gas chromatography/mass spectrometry.

A gas chromatography/mass spectrometric (GC/MS) isotope dilution assay for xylose was developed using tertbutyldimethylsilyl-derivatized xylose and [13C]1xylose, and applied to human serum samples. A calibration curve in serum using this assay showed < 3% variation (< 10 mg/L) for any given point. The correlation coefficient for xylose measurements made on 27 sera between a colorimetric method performed by a national commercial reference laboratory and the GC/MS method developed here was .952. However, xylose determinations of 10 of 27 samples differed by > 10% (up to 150 mg/L) when colorimetric values were compared to GC/MS. Two of these samples had borderline-low xylose values by GC/MS, but were well within the normal range by colorimetric analysis. gas chromatography/mass spectrometric isotope dilution assay appears to be an accurate method to measure xylose in serum. These data also suggest that further prospective studies comparing GC/MS to colorimetric methods are indicated for subjects undergoing oral xylose testing.

Are neuropsychiatric manifestations of folate, cobalamin and pyridoxine deficiency mediated through imbalances in excitatory sulfur amino acids?

Folate, cobalamin and pyridoxine deficiency are associated with psychiatric or neurological symptomatology. Disturbances in sulfur amino acid metabolism leading to accumulation of homocysteine occurs in all three conditions as the metabolism of homocysteine depends on enzymes requiring these vitamins as cofactors. Oxidation products of homocysteine (homocysteine sulfinic acid and homocysteic acid) and cysteine (cysteine sulfinic acid and cysteic acid) are excitatory sulfur amino acids and may act as excitatory neurotransmitters, whereas taurine and hypotaurine (decarboxylation products of cysteic acid and cysteine sulfinic acid) may act as inhibitory transmitters. Homocysteic acid and cysteine sulfinic acid have been considered as endogenous ligands for the N-methyl-D-aspartate (NMDA) type of glutamate receptors. The profile of these sulfur amino acid neurotransmitters could be altered in a similar fashion in states of decreased availability of folate, cobalamin or pyridoxine. It is proposed that the mechanism of neuropsychiatric manifestations in all three conditions result from a combination of two insults to homocysteine catabolism in the brain.

Measurement of excitatory sulfur amino acids, cysteine sulfinic acid, cysteic acid, homocysteine sulfinic acid, and homocysteic acid in serum by stable isotope dilution gas chromatography-mass spectrometry and selected ion monitoring.

Oxidized sulfur-containing amino acids are recognized as agonists of excitatory amino acid receptors in the mammalian nervous system. Homologues of glutamic acid (homocysteine sulfinic acid and homocysteic acid) and aspartic acid (cysteine sulfinic acid and cysteic acid) have been shown to be agonistic to N-methyl-D-aspartate receptors in animal brain and have been demonstrated in brain tissue. Considerable evidence exists for the role of homocysteic acid and cysteine sulfinic acid as endogenous ligands for excitatory amino acid receptors. We report, for the first time, the quantitation of these compounds in normal human serum, by a newly developed gas chromatography-mass spectrometry method that employs stable isotope-dilution selected ion monitoring using internal standards prepared in our laboratory. We also report new methods of synthesis of stable isotope-labeled internal standards used in measuring cysteine sulfinic acid, cysteic acid, homocysteine sulfinic acid, and homocysteic acid.

Thrombocytosis. Etiologic analysis of 663 patients.

Six hundred sixty-three children aged 1 to 16 years with thrombocytosis (defined as a platelet count of more than 500 x 10(9)/L) seen in a university hospital over a 1-year period were studied prospectively for etiology. The causes of thrombocytosis were infection (30.6%), hemolytic anemia (19.3%), tissue damage (15.2%), rebound thrombocytosis (14.8%), chronic inflammation (4.1%), renal disorders (4.1%), and malignancy (2%). Thrombocytosis associated with multiple, simultaneous causative factors was seen in 3.3% of cases. Among all patients with infections, osteomyelitis and septic arthritis were associated with higher platelet counts than other infections (P < .0001). Thrombocytosis secondary to infections was significantly more common in children under 5 years of age, whereas chronic inflammation, malignancy, and renal disorders were more common causes of thrombocytosis in children over 5 years of age. Thrombocytosis of 1 million or more platelets was seen in 13 (2%) children. No thrombocytosis-related complications were seen in any children, and none required any specific treatment. Thrombocytosis is a frequent finding in children. It is due to a variety of etiologic factors and is of little clinical discriminatory value. It is often due to an acute-phase phenomenon in response to infection, tissue damage, blood loss, or anemia, and is rarely due to malignancy.

Ceftazidime and amikacin as empiric treatment of febrile episodes in neutropenic patients in Saudi Arabia.

Sixty-four consecutive febrile episodes in 50 consecutive patients with malignancy and neutropenia were empirically treated with a combination of ceftazidime and amikacin. Of 52 analysable episodes, the response rate was 59.6% overall and 26.3% of episodes with microbiologically documented infections with septicaemia. Infection-related death occurred in 10 patients (19.2% of episodes). The response rates were similar in patients with acute leukaemia or other malignancies. Poor response is attributed to increased frequency of infections with Gram-positive and fungal organisms. A modified empiric regimen including cover for Gram-positive and fungal organisms is suggested in similar patient populations.

Thrombocytosis in adults: analysis of 777 patients.

A total of 777 patients with thrombocytosis, defined as a platelet count of greater than 500 x 10(9)l-1, seen in a University hospital over a 1-year period, were studied prospectively for aetiology. The most frequent causes of thrombocytosis were infection (21.9%), rebound thrombocytosis (19.4%), tissue damage (17.9%), chronic inflammatory disorders (13.1%) and malignancy (5.9%). Thrombocytosis associated with multiple causative factors, occurring simultaneously, was seen in 6.1% of cases. Thrombocytosis of greater than or equal to 1 million x 10(9)l-1 was found most frequently in patients with multiple aetiological factors occurring at the same time, in myeloproliferative disorders, or in postsplenectomy patients.

Spontaneous pneumothorax in metastatic choriocarcinoma.

We report a case of spontaneous bilateral pneumothoraces due to metastatic choriocarcinoma. The patient was successfully treated with tube thoracostomy and chemotherapy. Pneumothorax as a complication of choriocarcinoma has not been reported previously.

Unusual skin tumors in Langerhans' cell histiocytosis.

A case of Langerhans' cell histiocytosis with unusual skin manifestations in the form of multiple large skin tumors is described. The skin lesions responded partially to chemotherapy with etoposide and prednisone, and residual lesions were excised surgically. The patient developed central diabetes insipidus during treatment.