Adenine nucleotide levels in Rhodospirillum rubrum during switch-off of whole-cell nitrogenase activity.

Adenine nucleotide pools were measured in Rhodospirillum rubrum cultures that contained nitrogenase. The average energy charge [([ATP] + 1/2[ADP])/([ATP] + [ADP] + [AMP])] was found to be 0.66 and 0.62 in glutamate-grown and N-limited cultures respectively. Treatment of glutamate-grown cells with darkness, ammonia, glutamine, carbonyl cyanide m-chlorophenylhydrazone, or phenazine methosulphate resulted in perturbations in the adenine nucleotide pools, and led to loss of whole-cell nitrogenase activity and modification in vivo of the Fe protein. Treatment of N-limited cells resulted in similar changes in adenine nucleotide pools but not enzyme modification. No correlations were found between changes in adenine nucleotide pools or ratios of these pools and switch-off of nitrogenase activity by Fe protein modification in vivo. Phenazine methosulphate inhibited whole-cell activity at low concentrations. The effect on nitrogenase activity was apparently independent of Fe protein modification.

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.

Linkage analysis using heterozygote detection in phenylketonuria.

This linkage investigation was undertaken utilizing an improved method for phenylketonuria (PKU) heterozygote detection. This method is based on studies of semi-fasting, noon-time, blood specimens obtained from 85 obligate heterozgotes and 45 controls who were neither pregnant nor on birth control medication. The best separation between heterozygotes and normals was achieved with a discriminant function involving the logarithms of the serum concentrations of phenylalanine, tyrosine and tryptophan. The theoretical overlap area between the distributions of heterozygotes and controls, based on the above function, was between the distributions of heterozygotes and controls, based on the above function, was 3.75%. In 19 obligate heterozygotes and 13 controls who were either pregnant or on birth control medication, the best separation was achieved with a discriminant function involving the logarithms of the serum concentrations of phenylalanine and tyrosine. The theoretical overlap area was 8.23%. These equations identified heterozygotes with sufficient accuracy to permit efficient genetic linkage analysis. We were unable to demonstrate genetic linkage between the PKU locus and 15 common blood, serum, and urinary markers. All but loose linkage (theta greater than 0.3) was excluded for Rh, ABO, Gc, Kidd, and AP. Moderate linkage exclusion (theta less than 0.2) was shown for PGM, Duffy, Hp, MNS, HL--A, and Kell. Close linkage (theta less than 0.1) was excluded for Amy2, 6PGD, P, and ADA. We were unable to find linkage heterogeneity between the Amish and non-Amish populations.

Phenylketonuria heterozygote detection in families with affected children.

Improved approaches to the problem of heterozygote detection for phenylketonuria (PKU) were developed in this study. The discrimination was based on 85 obligate heterozygotes and 45 controls who were neither pregnant nor on birth control medication. The best separation between hetrozygotes and normals was achieved with a linear discriminant function involving the logarithms of the serum concentrations of phenylalanine, tyrosine, and tryptophan. The theoretical overlap area between the distributions of heterozygotes and controls based on the above function, was 3.75%. In the 19 obligate hetrozygotes and 13 controls who were either pregnant or on birth control medication, the best separation was achieved with a linear discriminant function involving the logarithms of the serum concentrations of phenylalanine and tyrosine. The theoretical overlap area was 8.23%. The genetic accuracy of the discriminant function was confirmed by testing the results with parental-child exclusions, segregation analysis, and the frequency of heterozygosity in nonrelated collateral spouses. Finally, there was evidence suggesting that the antihypertensive agent, aldomet, alters serum tyrosine and tryptophan levels.

Evidence for nonlikage of genes for HLA and hereditary angioedema.

Since the genes for several disorders of the complement system have been found to be linked to the HLA loci on chromosome 6, studies of the inhibitor of the activated first component of complement (Cl INH) and HLA in two families with hereditary angioedema (HAE) were undertaken. A total of 17 individuals were found to be affected in these three-generation families. Evidence was provided against close linkage of the genes for HLA and HAE. Other genetic markers studied were generally noninformative, although evidence was obtained against close linkage of the loci for HAE and ABO and HAE and transferrins. The reliable identification of individuals affected with HAE by Cl INH assay provides potential for establishing linkage relationships in the various phenotypes of this dominantly inherited condition.