Determination of urinary amino acids by liquid chromatography with "dabsyl chloride"

We describe a "high-performance" liquid-chromatographic procedure for measuring amino acids in 0.5 mL of urine. The procedure includes direct derivatization of amino acids in urine samples with "dabsyl chloride" (4-dimethylaminoazobenzene-4'-sulfonyl chloride). An aliquot of this dabsylated amino acid solution is analyzed on a muBondapak C18 column with ethanol/sodium acetate (20 mmol/L, pH 4.0) 4/6 (by vol.), as mobile phase. Dabsylated amino acids are detected by their absorbance at 425 nm and quantitated by measuring peak heights. The procedure allows for the reliable analysis of amino acids in urine at concentrations near 16 mg/L. The sensitivity of this analysis on column approaches 5 ng/sample. Higher urinary tryptophan concentrations were found in the urines of some cancer patients, whereas we saw no significant difference in urinary glycine between cancer patients and control subjects. The present method was shown to be a straightforward procedure for detecting phenylalanine in phenylketonuric urine. Extension of this procedure to screening for other inborn errors of aminoaciduria is recommended.

Determination of urinary amino acids by liquid chromatography with “dabsyl chloride"

We describe a “high-performance” liquid-chromatographic procedure for measuring amino acids in 0.5 mL of urine. The procedure includes direct derivatization of amino acids in urine samples with “dabsyl chloride" (4-dimethylaminoazobenzene-4’-sulfonyl chloride). An aliquot of this dabsylated amino acid solution is analyzed on a muBondapak C18 column with ethanol/sodium acetate (20 mmol/L, pH 4.0) 4/6 (by vol.), as mobile phase. Dabsylated amino acids are detected by their absorbance at 425 nm and quantitated by measuring peak heights. The procedure allows for the reliable analysis of amino acids in urine at concentrations near 16 mg/L. The sensitivity of this analysis on column approaches 5 ng/sample. Higher urinary tryptophan concentrations were found in the urines of some cancer patients, whereas we saw no significant difference in urinary glycine between cancer patients and control subjects. The present method was shown to be a straightforward procedure for detecting phenylalanine in phenylketonuric urine. Extension of this procedure to screening for other inborn errors of aminoaciduria is recommended.

Determination of urinary amino acids by liquid chromatography with “dabsyl chloride"

We describe a “high-performance” liquid-chromatographic procedure for measuring amino acids in 0.5 mL of urine. The procedure includes direct derivatization of amino acids in urine samples with “dabsyl chloride" (4-dimethylaminoazobenzene-4’-sulfonyl chloride). An aliquot of this dabsylated amino acid solution is analyzed on a muBondapak C18 column with ethanol/sodium acetate (20 mmol/L, pH 4.0) 4/6 (by vol.), as mobile phase. Dabsylated amino acids are detected by their absorbance at 425 nm and quantitated by measuring peak heights. The procedure allows for the reliable analysis of amino acids in urine at concentrations near 16 mg/L. The sensitivity of this analysis on column approaches 5 ng/sample. Higher urinary tryptophan concentrations were found in the urines of some cancer patients, whereas we saw no significant difference in urinary glycine between cancer patients and control subjects. The present method was shown to be a straightforward procedure for detecting phenylalanine in phenylketonuric urine. Extension of this procedure to screening for other inborn errors of aminoaciduria is recommended.

Construction of a new unclipped digital correlator for quasielastic light scattering

An unclipped digital correlator that we have built has been described. Our digital correlator can be easily incorporated (with only a moderate cost) in an established light scattering laboratory equipped with a computer.

Constancy of growth on simple and complex media

An apparatus has been developed in which bacterial growth can be measured very precisely over short intervals of time. Its precision is presented and used to assess the constancy of growth in batch culture. Under certain conditions, i.e., Luria broth or 0.2% glucose-M9 medium at very low cell densities, the specific growth rate of Escherichia coli appeared to be constant within the measurement limits of the method. In succinate minimal medium, the growth rate increased gradually over several days and never became constant. With nutrient broth and with Luria broth, growth slowed progressively at moderate cell densities within the range considered to be in the logarithmic phase of growth. In addition, temporary slowdown in growth rate occurred in these two complex media at characteristic cell densities. These gradual increases in succinate minimal medium and temporary slowdowns in the complex media would be undetectable without precise measurements and may have been a source of variability in many bacteriological studies.

Suppression of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and of incorporation of acetate into cholesterol in homozygous hypercholesterolemic fibroblasts by ferritin-low density lipoprotein conjugates

Conjugates of ferritin with low density lipoproteins (LDL) were prepared and separated by sucrose gradient centrifugation. These conjugates, at cholesterol concentration of 100--132 microgram/ml, caused a greater than 90% suppression of hydroxymethylglutaryl coenzyme A reductase activity and of acetate incorporation into cholesterol in cultured skin fibroblasts from a normal subject as well as from a subject with homozygous familial hypercholesterolemia. The half maximal inhibition concentration was approx. 10 microgram/ml cholesterol for LDL and ferritin . (LDL)2 and 5 microgram/ml for (ferritin)2 . LDL in both cell lines. In contrast, native low density lipoproteins have only a minimal inhibitory effect in homozygous cells. The ability of the conjugates to stimulate the incorporation of oleate into cholesteryl esters was also equal in the two cell lines, although the conjugates were only 10% as active as low density lipoproteins in the normal cells. LDL reduced the ferritin . (LDL)2-mediated suppression of hydroxymethylglutaryl-CoA reductase activity in homozygous cells while ferritin . (LDL)2 reduced the LDL-mediated stimulation of cholesteryl ester formation in normal cells.

Changes in absorption, fluorescence, dichroism, and Birefringence in stained giant axons: : optical measurement of membrane potential

The absorption, fluorescence, dichroism, and birefringence of stained squid axons were measured during action potentials and voltage clamp steps in an effort to find large optical signals that could be used to monitor membrane potential. Changes in all four optical properties were found that were linearly related to membrane potential and, with several new dyes, the signal-to-noise ratios were larger than any obtained previously. The problem of photodynamic damage was greatly diminished; with a merocyaninerhodanine dye, the photodynamic damage associated with intense light and the presence of oxygen was negligible. The absorption change obtained with this dye was relatively large; it could be measured with a signal-to-noise ratio of 100:1 during a single action potential.

An electron microscopic and radioautographic study on experimental kernicterus. II. Bilirubin movement within neurons and release of waste products via astroglia

Response of the neurons to bilirubin in asphyxiated newborn rabbits was studied in vivo with the use of the electron microscope and radioautographic technics. A morphologic basis for the mode of intraneuronal bilirubin movement in kernicterus has been established. The absorbed bilirubin had ready access to the Golgi complex from the dendrite through the neurotubules by a mechanism of centripetal dendroplasmic flow. The endoplasmic reticulum provided a subcellular canalicular system for the directed passage from the Golgi complex to the nuclear membrane. Proximodistal flow of bilirubin in the axoplasm caused spotty destruction of axons. The release of waste products from the affected neurons toward the capillaries is very likely an effect of reverse transastroglial transport.

An electron microscopic and radioautographic study on experimental kernicterus. I. Bilirubin transport via astroglia

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The biogenesis of ethylene in penicillium digitatum

The origin of the ethylene carbon skeleton in Penicillium digitatum appears to be intimately associated with the Krebs cycle acids, particularly the middle carbon atoms of dicarboxylic acids. Among the other compounds studied, certain carbon atoms of beta-alanine, propionic acid, and methionine can be incorporated into the ethylene carbon skeleton presumably by way of an indirect route via the Krebs cycle acids. Carbon atoms of acrylic acid, particularly C-2, were also found to be incorporated into the ethylene skeleton. Inhibition of ethylene but not respiratory CO(2) formation in the mold by cis-3-chloroacrylic acid at 1 x 10(-3)m pointed to the possibility that acrylic acid may be related to the precursor for ethylene.

Utilization of fructose and glutamate by Rhodospirillum rubrum

Fructose served as sole carbon source for the growth of Rhodospirillum rubrum anaerobically under light or aerobically in the dark while glucose did not. Glucose was not utilized by the organism at all. Radiorespirometric studies, using 14C specifically labelled fructose as substrate, revealed that fructose is catabolized exclusively via the Embden–Meyerhof–Parnas (EMP) glycolytic pathway. Both L-glutamic and D-glutamic acids can be utilized by this organism, via the tricarboxylic acid cycle (TCA) pathway, under either aerobic-dark or anaerobic-light conditions.

Comparative glucose catabolism of Xanthomonas species

Glucose catabolism in eight Xanthomonas species has been comparatively examined by means of the radiorespirometric method. The basic mechanisms for the respective xanthomonads closely resembled each other. The Entner-Doudoroff pathway, in conjunction with the tricarboxylic acid cycle pathway, was the predominant mechanism for glucose catabolism. A small portion (8 to 16%) of substrate glucose was routed into the pentose phosphate pathway. The hexose cycle pathway did not appear to play any significant role in glucose catabolism of these xanthomonads. The results are also consistent with the well-recognized close phylogenic relationship between xanthomonads and pseudomonads.