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N Krüger

Publications and source records attributed to N Krüger.

At least 37 records · Page 2Linked to original sources
PubMed1991

Identification and molecular characterization of the Alcaligenes eutrophus H16 aco operon genes involved in acetoin catabolism.

Acetoin:dichlorophenolindophenol oxidoreductase (Ao:DCPIP OR) and the fast-migrating protein (FMP) were purified to homogeneity from crude extracts of acetoin-grown cells of Alcaligenes eutrophus. Ao:DCPIP OR consisted of alpha and beta subunits (Mrs, 35,500 and 36,000, respectively), and a tetrameric alpha 2 beta 2 structure was most likely for the native protein. The molecular weight of FMP subunits was 39,000. The N-terminal amino acid sequences of the three proteins were determined, and oligonucleotides were synthesized on the basis of the codon usage of A. eutrophus. With these, the structural genes for the alpha and beta subunits of Ao:DCPIP OR and FMP, which were referred to as acoA, acoB, and acoC, respectively, were localized on one single EcoRI restriction fragment which has been cloned recently (C. Fründ, H. Priefert, A. Steinbüchel, and H. G. Schlegel, J. Bacteriol. 171:6539-6548, 1989). The nucleotide sequences of a 5.3-kbp region of this fragment and one adjacent fragment were determined, and the structural genes for acoA (1,002 bp), acoB (1,017 bp), and acoC (1,125 bp) were identified. Together with the gene acoX, whose function is still unknown and which is represented by a 1,080-bp open reading frame, these genes are probably organized in one single operon (acoXABC). The transcription start site was identified 27 bp upstream of acoX; this site was preceded by a region which exhibited complete homology to the enterobacterial sigma 54-dependent promoter consensus sequence. The amino acid sequences deduced from acoA and acoB for the alpha subunit (Mr, 35,243) and the beta subunit (Mr, 35,788) exhibited significant homologies to the primary structures of the dehydrogenase components of various 2-oxo acid dehydrogenase complexes, whereas those deduced from acoC for FMP (Mr, 38,941) revealed homology to the dihydrolipoamide acetyltransferase of Escherichia coli. The occurrence of a new enzyme type for the degradation of acetoin is discussed.

Acetoin↗
PubMed1991

Identification and characterization of two Alcaligenes eutrophus gene loci relevant to the poly(beta-hydroxybutyric acid)-leaky phenotype which exhibit homology to ptsH and ptsI of Escherichia coli.

From genomic libraries of Alcaligenes eutrophus H16 in lambda L47 and in pVK100, we cloned DNA fragments which restored the wild-type phenotype to poly(beta-hydroxybutyric acid) (PHB)-leaky mutants derived from strains H16 and JMP222. The nucleotide sequence analysis of a 4.5-kb region of one of these fragments revealed two adjacent open reading frames (ORF) which are relevant for the expression of the PHB-leaky phenotype. The 1,799-bp ORF1 represented a gene which was referred to as phbI. The amino acid sequence of the putative protein I (Mr, 65,167), which was deduced from phbI, exhibited 38.9% identity with the primary structure of enzyme I of the Escherichia coli phosphoenolpyruvate:carbohydrate phosphotransferase system (PEP-PTS). The upstream 579-bp ORF2 was separated by 50 bp from ORF1. It included the 270-bp phbH gene which encoded protein H (Mr, 9,469). This protein exhibited 34.9% identity to the HPr protein of the E. coli PEP-PTS. Insertions of Tn5 in different PHB-leaky mutants were mapped at eight different positions in phbI and at one position in phbH. Mutants defective in phbH or phbI exhibited no pleiotropic effects and were not altered with respect to the utilization of fructose. However, PHB was degraded at a higher rate in the stationary growth phase. The functions of these HPr- and enzyme I-like proteins in the metabolism of PHB are still unknown. Evidence for the involvement of these proteins in regulation of the metabolism of intracellular PHB was obtained, and a hypothetical model is proposed.

Alcaligenes↗
PubMed1991

CO2 breath tests using 14C-caffeine, 14C-methacetin and 14C-phenacetin for assessing postnatal development of monooxygenase activities in rats and marmosets.

The time course in which the activities of cytochrome P450-dependent drug-metabolizing enzymes develop during the perinatal period differs for various types of monooxygenases as well as for various animal species. Using [3-methyl14C]-, [7-methyl14C]-caffeine, [14CH3]-methacetin and [14C2H5]-phenacetin as substrates in breath tests, the developmental changes in the rates of 14CO2 formation, due to changes in the activity of monooxygenases, were studied in rats and marmoset monkeys (Callithrix jacchus). In rats a rate of 0.006% of the dose administered/min was found to be exhaled as 14CO2 in the caffeine breath tests on the 1st day of life. This value increased gradually reaching adult rates of 14CO2 exhalation after 21 days for [3-methyl14C]-caffeine and after 25 days for [7-methyl14C]-caffeine. In marmosets the rate of 14CO2 exhalation for [3-methyl14C]- and [7-methyl14C]-caffeine was also low at birth and developed gradually reaching adult values of 14CO2 exhalation within 120-200 days. In rats the capacity for dealkylation of methacetin and phenacetin developed much faster compared with caffeine: 9 days postnatally, the exhalation of 14CO2 reached adult values. Offspring of marmosets reached adult values of 14CO2 exhalation at 8 days postnatally when using [14CO2]-methacetin as substrate and at 30 days postnatally using [14C2H5]-phenacetin in the breath test. The results suggest that the monooxygenases for the N-demethylation of caffeine, the O-demethylation of methacetin and the O-deethylation are rather substrate specific in the two species studied. The breath tests used are sensitive methods for assessing the development of different monooxygenases in vivo in rats and marmosets, and they may well (using 13C-labelled substrates) be applicable for studies in children to monitor effects of certain environmental pollutants.

Acetamides↗
PubMed1991

[The significance of PCDD's/PCDF's (dioxins) in pediatrics].

No epidemiological data are available up to now which reveal adverse effects induced by dioxins during an exposure through breast milk. Furthermore, very few data on the concentration of PCDDs/PCDFs in the newborn and during the first year of life have been published. Of all PCDDs/PCDFs, the substance with the highest toxicity is 2,3,7,8-tetrachlorodibenzo-p-dioxin. However, in the environment this congener is often only a minor component. A sensitive biological effect triggered by TCDD is the enzyme induction of hepatic monooxygenases. Using a 14CO2-breath-test the apparent enzyme induction by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) of the metabolic conversion of [3-methyl14C]-caffeine was studied during the perinatal period in Wistar rats and in a non-human-primate (marmoset, Callithrix jacchus). It could be shown that the apparent induction of monooxygenase activity by TCDD in rat offspring as measured with the breath-test, is dose-dependent and mainly achieved by postnatal exposure via mothers' milk. Our data indicate that caffeine is a convenient substrate for studying monooxygenase activities (probably P450 IA-dependent) to be induced by TCDD, and very likely also by other congeners. These results, therefore, may provide the rationale for applying a [13C]-caffeine breath-test in human newborn and infants to analyse possible biological effects induced by TCDD and similar pollutants in breast-fed children. Since PCDDs/PCDFs are pollutants without any benefit, strong efforts should be continued to further reduce the output of dioxins, the human exposure, and thereby also concentrations in human milk.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Low fractions of mono- and diconjugated bilirubin in patients with beta-thalassemia: an approach to characterize hepatic conjugation capacity.

Unconjugated and mono- and diconjugated bilirubin was determined by alkaline methanolysis and thin-layer chromatography in serum from 16 pediatric patients with homozygous beta-thalassemia (aged 1-23 years), in 14 age-matched controls, and in 26 healthy adults. Total bilirubin amounted to 21 +/- 20 mumol/L in patients with thalassemia compared with 7 +/- 4 mumol/L in healthy children and 11 +/- 3 mumol/L in healthy adults. The fractions of bilirubin conjugates in the various groups were 8 +/- 4% (patients with thalassemia), 18 +/- 5% (age-matched controls; p less than 0.001), and 16 +/- 5% (healthy adults; p less than 0.001). The low fraction of bilirubin conjugates in patients with thalassemia showed no correlation to any other physical or laboratory finding. It is concluded that subnormal values of bilirubin conjugates in thalassemia indicate defective bilirubin conjugation.

Adolescent↗
PubMed1990

Characterization of alcohol dehydrogenase genes of derepressible wild-type Alcaligenes eutrophus H16 and constitutive mutants.

The nucleotide sequence of the gene that encodes the fermentative, derepressible alcohol dehydrogenase (ADH) in Alcaligenes eutrophus H16 and of adjacent regions was recently determined. Two potential -10 regions resembling the Escherichia coli sigma 70 consensus sequence were identified 77 and 93 nucleotides upstream of the structural gene. By determination of the 5' mRNA terminus of the wild-type adh gene, the proximal -10 region was identified as responsible for adh expression under derepressive conditions. Transcription started seven nucleotides downstream of this region, at position 388. Sequence analysis of seven mutants expressing the adh gene under aerobic conditions revealed mutations in one or the other potential -10 region. In all seven strains, the mutations restored the invariant T of the E. coli promoter consensus sequence. Mutants altered in the proximal -10 region transcribed the adh gene under aerobic conditions with the same 5' mRNA terminus as in the wild type; gene expression was impaired very little under aerobic conditions. Mutants altered in the distal -10 region also transcribed the adh gene aerobically but were still partially derepressible. The 5' mRNA terminus was seven nucleotides downstream of the distal -10 region, at position 372. When these mutants were cultivated under conditions of restricted oxygen supply, the adh gene was transcribed from both -10 regions, resulting in the synthesis of two mRNA species with different 5' termini.

Alcaligenes↗
PubMed1990

[Multi-parity in Saudi Arabia].

The relation between birthweight and parity of the mother was examined in Saudi patients from Tabuk and Najran. 4,664 newborns were taken into consideration from 1985-1988. 30.7% (1,430) of these newborns were born to mothers with more than 5 deliveries. A positive correlation between the increasing number of the parity and the birthweight can be demonstrated in our patients from parity 9. From parity 9 to parity 11 there is an increasing birth-weight of the male newborns, whereas the weight of the female newborns shows different tendencies. The average age of a Saudi primipara is 20.5 years and increases by 1.05-1.99 years until parity 11. From parity 11 to parity 13 it increases by 0.7 years.

Adult↗
PubMed1986

[Continuous subcutaneous deferoxamine infusions in thalassemia major. Improvement in glucose tolerance].

Exocrine and endocrine pancreatic functions were studied in 30 patients with homozygotic beta-thalassaemia. All were treated with continuous subcutaneous deferoxamine infusions for a mean period of 30 months. Three patients (aged 18-22 years) had insulin-dependent diabetes, two before and one shortly after the onset of deferoxamine administration. There was no improvement during the treatment. An abnormal glucose tolerance test was demonstrated in 14 patients (47%) before and in seven (23%) during deferoxamine infusion. Enzyme activity of alpha-amylase and lipase as an expression of exocrine pancreatic function was normal in all during the observation period. Improvement in endocrine pancreatic function was apparently age-dependent: the younger the patient at the onset of treatment the more likely is normalization of the oral glucose tolerance test.

Adolescent↗
PubMed1986

[Longitudinal growth of patients with homozygote beta-thalassemia during continuous subcutaneous infusion of deferoxamine].

Subcutaneous continuous infusions of deferoxamine were administered to 28 children with thalassaemia major. Longitudinal growth beyond the eleventh year was favourably influenced. The normal growth spurt during puberty was not demonstrable in six patients (three boys and three girls) during their puberty. Taking into account standard height allowing for parents' height, prospective final height and ethnic origin, the treatment favourably influenced longitudinal growth in 26 of the 28 children.

Age Determination by Skeleton↗
PubMed1985

[Continuous subcutaneous deferoxamine treatment in thalassemia major. Decrease of hemosiderosis and improvement of liver function].

Liver function during continuous subcutaneous deferoxamine therapy was investigated in 29 patients with homozygotic beta-thalassaemia. Average duration of treatment was 26 months (range 8-51 months). A decrease in haemosiderosis and an improvement in liver function was observed in 27 patients: Mean liver density, determined by computed tomography, decreased from 98 to 84 HU, mean serum ferritin concentration fell from 8028 to 3661 ng/ml, mean serum GOT activity from 44 to 13 U/l and GPT from 51 to 16 U/l. Mean cholinesterase activity, reflecting the improved synthetic activity of the liver, increased from 4063 to 4530 U/l.

Adolescent↗
PubMed1985

[Frequent occurrence of Yersinia infection in hemosiderosis].

Antibodies against Yersinia were found in 12 of 50 patients with hemosiderosis, in 11 of 47 patients with thalassemia major and in one of three patients with Blackfan-Diamond anemia. All patients were treated with subcutaneous continuous deferoxamin-infusions. A systemic yersiniosis occurred in seven patients, all with homozygous beta-thalassemia, in five during and in two before treatment with deferoxamin. Hemosiderosis and infusions with deferoxamin seem to increase the risk of yersinia septicemia.

Adolescent↗
PubMed1984

[Deferoxamine in hemosiderosis. Fecal iron excretion during continuous subcutaneous infusion].

Faecal iron excretion during continuous subcutaneous deferoxamine infusion was measured by flameless atom-absorption spectral photometry in 21 patients with homozygous ss-thalassaemia and one patient with Blackfan-Diamond anaemia. Taking into account faecal and urinary iron excretion, more iron was eliminated than was taken up during transfusion and by intestinal absorption. Urine contained 37.9%, faeces 62.1% of the amount of iron eliminated.

Adolescent↗