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Biomedical subjects

R Guthrie

Publications and source records attributed to R Guthrie.

At least 73 records · Page 4Linked to original sources
PubMed1982

A neonatal screening test for argininosuccinic acid lyase deficiency and other urea cycle disorders.

A simple enzyme-multiple auxotroph assay has been developed for the identification of newborn infants with several of the inherited metabolic defects in the Krebs cycle for the detoxification of ammonia and in the ornithine metabolic pathway. This mass screening test is used with dried filter paper blood specimens and can easily be added to existing multiple testing programs presently used in screening for phenylketonuria or congenital hypothyroidism. This assay can be used to detect patients with citrullinemia, argininosuccinic acid lyase deficiency, and argininemia. In addition to these urea cycle disorders, the several types of ornithinemia, which can result in gyrate atrophy of the retina or mental retardation, should be detectable with this assay. The strengths and weaknesses of this assay are discussed and a large-scale pilot screening trial is proposed.

Amino Acid Metabolism, Inborn Errors↗
PubMed1980

Urine screening for metabolic disease in newborn infants.

A new method for urine screening for metabolic disease in newborn infants is described. A battery of bacterial inhibition assays to test urine-impregnated filter paper from 3- to 4-week-old infants for amino acids, purines, and pyrimidines was used. We were able to establish the accuracy and efficiency of the method by examining 289 unknown specimens from other laboratories and by collecting and testing 18,400 newborn infants' urine specimens. The major advantages over existing chromatography methods are that: (1) the technology to perform the test already exists in most laboratories screening for metabolic disorders; (2) it is relatively inexpensive; (3) collection of the sample is easy and cooperation of the parents is good; (4) the false positive rate is low (0.9%); and (5) tests can be targeted to detect clinically significant disorders. In this screening program, we detected two cases of persistent neonatal tyrosinemia, two cases of cystinuria, and one case of citrullinemia. These results suggest that urine screening is a good adjunct to blood screening of newborn infants.

Humans↗
PubMed1980

Fluorometric micromethod for determination of arginase activity in dried blood spots on filter paper.

We describe a microfluorometric method for determination of arginase activity in dried blood spots on filter paper. The arginase in discs punched from such dried blood specimens is activated by preincubation with Mn2+ at 37 degrees C. After incubation with substrate at the same temperature, urea is determined fluorometrically by oxidation of NADH to NAD+ in a coupled kinetic reaction. We compare the results of this method with those of a colorimetric method involving liquid blood samples, and assess the stability of the enzyme in dried blood on filter paper. The presence of serum has no effect on the activity. This method may be useful in the early detection of arginase deficiency and certain hematological disorders.

Adult↗
PubMed1980

beta-Lipoprotein quantitation in cord blood spotted on filter paper: a screening test.

We describe an electroimmunodiffusion technique for measuring beta-lipoprotein in cord blood spotted on filter paper. A series of cord-blood samples, taken from 916 consecutive live-birth infants, was spotted directly onto filter paper and assayed for beta-lipoprotein. Eleven had above-normal beta-lipoprotein. Of these 11, seven were tested two to six months later, along with their parents, for total cholesterol and triglyceride concentrations. Five infants had increased cholesterol values, and four parents of these infants had either increased cholesterol or triglyceride values. We also measured beta-lipoprotein concentrations in 63 paired samples of dried cord-blood and three-day post-delivery blood specimens, routinely collected for phenylketonuria screening. We saw a significant correlation between results for the specimens, but detected no cases of increased beta-lipoprotein. beta-Lipoprotein assay in dried specimens of cord blood is simple, inexpensive, and potentially is useful in mass screening of newborns for familial type II and combined hyperlipidemia.

Blood Specimen Collection↗
PubMed1979

Measurement of urinary pyrimidine bases and nucleosides by high-performance liquid chromatography.

A rapid procedure for the isolation, separation, identification and measurement of urinary pyrimidine bases and nucleosides by high-performance liquid chromatography (HPLC) is presented. The initial isolation of these compounds from urine was accomplished with small disposable ion-exchange columns. HPLC was performed on a silica gel column with a mobile phase composed of methylene chloride, methanol and 1 M aqueous ammonium formate buffer. Peaks were recorded at both 254 nm and 280 nm and the response ratio was used in combination with the elution volume for compound identification. The minimum detectable amount (signal-to-noise ratio = 2) ranged from 0.2 ng for uracil to 2.2 ng for cytidine. Linearity and recovery for thymine, uracil, uridine, pseudouridine, orotic acid and orotidine added to urine was demonstrated over almost a 10(3) concentration range. The potential application of this method for the study of inborn errors in the urea cycle is discussed.

Chromatography, High Pressure Liquid↗
PubMed1978

Phenylalanine depletion for the management of phenylketonuria: use of enzyme reactors with immobilized enzymes.

Multitubular enzyme reactors with immobilized phenylalanine ammonia lyase were tested in vitro and in vivo for depletion of phenylalanine in circulating blood. Sustained reduction of phenylalanine was achieved in less than 30 minutes. A 50% decrease of phenylalanine was obtained with a 2-hour application of enzyme reactors and was maintained for more than 2 days. Similar enzyme reactors have therapeutic potential for temporary management of phenylketonuric patients when their circulating phenylalanine becomes exceedingly high because of infection, fever, or pregnancy.

Ammonia-Lyases↗
PubMed1978

Erythropoietic protoporphyria, heterozygous cystinuria, and reduced peptidase A activity in a patient with 46,XX/46,XX,18q--mosaicism.

An interesting patient with a deletion of the long arm of chromosome 18 is presented. Her symptoms are severe in comparison with some other 18q--patients, yet she was found to have a mosaicism with a normal 46,XX karyotype in about 20% of her cultured lymphocytes. In addition, she had erythropoietic protoporphyria, was heterozygous for type II or III cystinuria, and had reduced levels of peptidase A activity. Detailed studied on the patient, her family, and two additional 18q--patients suggest that the association with erythropoietic protoporphyria is coincidental and that the cystinuria gene was inherited from the patient's father. The reduced peptidase A activity, however, supports earlier observations that the peptidase A locus maps in the q22 to terminus region of chromosome 18.

Child↗
PubMed1978

Newborn screening for maple syrup urine disease (branched-chain ketoaciduria).

Routine newborn screening for maple syrup urine disease (MSUD) has been conducted since 1964, and more than 9 1/2 million newborns throughout the world have been tested with use of a bacterial inhibition assay (BIA) for leucine on dried filter paper blood specimens. Forty-three confirmed cases of the "classical" and the "intermediate" variant forms have been detected. The frequency of MSUD, based on these data, is approximately one in 224,000 newborns. The sensitivity and the specificity of the leucine BIA are demonstrated. There are several problems in routine screening for MSUD, including the fact that the "intermittent" variant form will be missed. A brief summary of the clinical course of the 13 cases detected by our collaborative laboratories is presented.

Bacillus subtilis↗
PubMed1978

Micromethod for estimating adenosine deaminase activity in dried blood spots on filter paper.

We describe a fluorometric micromethod for measuring adenosine deaminase activity in dried blood spots on filter paper. Earlier methods require venipuncture and preparation of washed erythrocytes; in the present method, whole capillary blood, spotted on filter paper and mailed (dried) to a central laboratory, is used. The stability of the enzyme in dried blood on filter paper was assessed. The results were compared with those of a spectrophotometric method. The presence of serum appears not to affect the estimation of the activity and the method may be useful in early detection of severe combined immunodeficiency disease and hereditary hemolytic anemia.

Adenosine Deaminase↗