Charge Donation by Calcium into the t1g Band of C60.

Photoemission spectra of compounds prepared by the reaction of C(60) films with calcium show two distinct metallic phases, whereas alkali-doped C(60) films have only one. In the first phase the bulk t(1u) band, derived from the lowest unoccupied molecular orbital of C(60), is partially occupied. This is followed by an insulating phase that has the composition Ca(3)C(60) in which the t(1u) band is filled and has properties analogous to those of K(6)C(60). Continued exposure to calcium produces a second metallic phase in which electrons are donated into the t(1g) band. The superconductivity of Ca(5)C(60) is associated with the t(1g) band.

Photoemission Spectra and Electronic Properties of KxC60.

Photoemission spectra of vacuum deposited layers of C(60), before and after exposure to K vapor, show that the K donates its conduction electron into the band derived from the lowest unoccupied molecular orbital. A compound with composition of K(3)C(60), corresponding to the maximum conductivity, has been prepared. In it the potassium atoms presumably occupy both the octahedral and the two tetrahedral interstitial sites of the face-centered-cubic (fcc) C(60) structure.

Volatile carboxylic acid profiling in physiological fluids: direct injection into a gas chromatograph/mass spectrometer.

We present a procedure for the profiling of the volatile carboxylic acids and neutral compounds in blood or urine using the direct injection of the acidified sample into a gas chromatograph interfaced with a mass spectrometer by a jet separator. The non-volatile components remain at the head of the SP-1000 column while the volatile components move through the column. Up to sixty physiological samples can be analyzed before any degradation in mass spectrometer operating parameters is observed.

Effect of chemically induced propionic acidemia on neurobehavioral development of rats.

High levels of propionic acid (PPA) comparable to those of human propionic acidemia were achieved in blood (1-5 mmol/l) and brain (1 micromol/g) of rats by administering saline-buffered propionate (pH 7.4) subcutaneously twice a day from the 6th to the 28th day of life. PPA doses ranged from 1.44 to 1.92 micromol/g body weight as a function of animal age. Control rats were treated with saline in the same volumes. Growth and development of physical landmarks were assessed by monitoring the following parameters daily: body weight, upper incisor eruption, eye opening, and hair coat. Development of some reflexes was also monitored, and a specific subset of motor skills was evaluated at days 14 and 21 of life by the free-fall righting test and the spontaneous alternation test. Chronic PPA administration had no effect on body weight, cerebral cortex weight, or cerebellum weight, but caused slight but significant delays in the day of appearance of hair coat and eye opening, indicating an effect of PPA on the development of physical parameters. Free-fall righting was impaired in PPA-treated animals. On the other hand, PPA administration had no effect on the performance of the animals in the spontaneous alternation tests. Long-term effects of early PPA administration were investigated by assessing animal performance in an aversive task (two-way shuttle avoidance task) and in a nonaversive (open-field task) behavioral task at 60 days of age. PPA-treated rats did not habituate to the open field, and presented a lack of retention of the shuttle-avoidance task. Our results suggest that early postnatal PPA administration to rats alters normal development and induces long-term behavioral deficits in aversive and nonaversive tasks.

Photodiode array detection for liquid chromatographic profiling of carboxylic acids in physiological fluids: 3-hydroxy-3-methylglutaric aciduria.

3-Hydroxy-3-methylglutaric aciduria was detected in a newborn. The progress of the dietary therapy for the disorder was monitored by dual-column "high-performance" liquid chromatography with a computer-controlled photodiode array spectrophotometric detector. This procedure is a quick way to detect and monitor the progress of 3-hydroxy-3-methylglutaric aciduria.

Early identification of isovaleric aciduria using photodiode array detection for liquid chromatographic profiling of urinary carboxylic acids.

The 190 nm high performance liquid chromatographic photodiode array profiling of the urinary carboxylic acids of the first urine of a newborn affected with isovaleric aciduria afforded an abnormal peak at 27.8 min. This peak was greatly increased in the carboxylic acid profiling of the 14 h urine sample from the same infant. Isolation of this peak by fraction collecting; solvent extraction of the eluent; trimethylsilyl derivatization of the residue and gas chromatographic/mass spectrometric analysis identified the compound as isovalerylglycine. Correlation of the 190 nm absorbance of isovalerylglycine (y) with concentration (x) afforded a least squares curve: y = 476.4x-13.72 (r = 0.99); run-to-run variation 6.92%; day-to-day variation 8.88% with a minimum detectable concentration of 25 micrograms/ml.

Photodiode array ultraviolet spectrophotometric profiling of carboxylic acids in physiological fluids.

In this paper the use of a computer-controlled photodiode array spectrophotometric detector for the high-performance liquid chromatographic (HPLC) profiling of carboxylic acids in physiological fluids is reported. The ultraviolet spectrum of the flowing eluent is obtained at 6-sec intervals and is displayed as the absorbance at 190 nm. A three-dimensional (time versus wavelength versus absorbance) presentation of the HPLC profile facilitates peak identification through ultraviolet spectrum matching and relative retention time comparison with carboxylic acid standards. Several examples of HPLC urinary carboxylic acid profiles from infants with various inborn errors of metabolism are shown.

Paired-ion high-performance liquid chromatographic assay for plasma choline.

Choline was isolated from deproteinized plasma by cation-exchange chromatography. Isolated choline was directly converted to the 3,5-dinitrobenzoate derivative and was analyzed by paired-ion high-performance liquid chromatography with UV detection at 254 nm. An internal standard, 3-hydroxy-N,N,N-trimethylpropanaminium iodide was used for quantitation of plasma choline. Linearity was achieved from 1--500 nmole/ml with a reproducibility of +/- 6%. Plasma choline concentrations below 1 nmole/ml could not be accurately measured while plasma choline concentrations in the micromole/ml range deviated from linearity.

Positive-ion thermospray liquid chromatography-mass spectrometry: detection of organic acidurias.

Positive-ion thermospray liquid chromatography-mass spectrometry (TSP-LC-MS) is used to detect organic acids via the direct injection of untreated urine from newborns and infants. Two methods are reported for the separation of organic acids. The separation of urinary organic acids is effected in either an acidic, pH 2.5 sulfuric acid, or a non-acidic, 0.05 M ammonium acetate, pH 6.8, mobile phase. Use of pH 2.5 sulfuric acid and an HPX-87H organic acid column produces better separation but has less sensitivity than the use of 0.05 M ammonium acetate, pH 6.8 and a C18 column. Positive ion TSP-LC-MS has been used to detect methylmalonic aciduria, 3-hydroxy-3-methylglutaric aciduria, propionic aciduria, isovaleric aciduria and argininosuccinic aciduria.

Metabolic aspects of protection by glycine against hypoxic injury to isolated proximal tubules.

To clarify the roles of butyrate and acylglycine formation in hypoxic proximal tubule cell injury and protection by glycine and to test the contribution of iodoacetate-suppressible metabolism to protection, (1) it was determined whether protection by glycine is fully expressed when glucose, lactate, alanine, and butyrate are replaced by alpha-ketoglutarate as the sole substrate for the tubules, (2) butyrate metabolism and acylglycine formation were directly measured in control and hypoxic preparations, and (3) it was assessed whether injury produced by iodoacetate, a potent inhibitor of glycolytic metabolism, is subject to protection by glycine. Susceptibility to hypoxic injury in medium with alpha-ketoglutarate as the sole substrate was similar to that seen in medium containing glucose, lactate, alanine, and butyrate. Tubules in alpha-ketoglutarate medium showed high degrees of protection by glycine against injury produced by 30-min of hypoxia, by iodoacetate alone, and by iodoacetate combined with hypoxia. Protection did not require preservation of cell ATP or glutathione. In glucose-lactate-alanine-butyrate medium, butyrate, measured by gas chromatography, was rapidly metabolized by oxygenated tubules and fully accounted for basal rates of oxygen consumption. Butyrate utilization stopped during hypoxia. Neither aspect of butyrate metabolism was altered by glycine. Formation of acylglycines was assessed by gas chromatography/mass spectroscopy. In preparations treated with glycine, butyrylglycine was detected under both oxygenated and hypoxic conditions; the quantities, however, were small and no other acylglycines were found. These observations indicate that protective effects of glycine are independent of short-chain acylglycine formation and glycolytic metabolism.

Metabolic studies in a mouse model of hepatorenal tyrosinemia: absence of perinatal abnormalities.

Radiation induced chromosomal deletions at the albino locus in the mouse, lethal when homozygous, cause abnormalities of expression of several unlinked liver specific genes. Recently, the gene encoding FAH was shown to be included in the deletions. Since in humans FAH mutations cause tyrosinemia type I, deletion homozygous mice were suspected of having tyrosinemia. Studies of plasma amino acids did not confirm this suspicion. Also, succinylacetone levels were normal in fetal and newborn livers of deletion homozygotes. The present evidence, therefore, does not support the assumption that the earlier described ultrastructural and enzyme abnormalities in deletion homozygotes are secondary effects of tyrosinemia caused by the deletion of FAH.