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Biomedical subjects

K Severin

Publications and source records attributed to K Severin.

25 records · Page 2Linked to original sources
PubMed1994

Formation of 4-hydroxybenzoate in Escherichia coli: characterization of the ubiC gene and its encoded enzyme chorismate pyruvate-lyase.

Chorismate pyruvate-lyase from Escherichia coli converts chorismate to 4-hydroxybenzoate. The enzyme was enriched 3000-fold by overexpression and chromatographic purification. It has an apparent Km value for chorismate of 6.1 microM and an isoelectric point of pH 6.45. The enzyme activity did not require metal cofactors. Promoter sequences in the 5' flanking sequences of the ubiCA operon were localized by transcription and translation of active chorismate pyruvate-lyase in vitro from different PCR fragments. Sequencing of the ubiC gene of the mutant strain AN244 revealed a G-->A transition resulting in a change from glutamic acid to lysine. A feeding experiment with [1,7-13C2]shikimate confirmed the chorismate pyruvate-lyase as the sole enzymic source of 4-hydroxybenzoate in vivo.

Bacterial Proteins↗
PubMed1993

Effect of human and recombinant IFN-alpha and IFN-beta on the sister-chromatid exchange (SCE) frequency in amniotic fluid cells in vitro.

Sister-chromatid exchange (SCE) and rates of proliferation in human amniotic fluid cells from healthy donors exposed to human IFN-alpha and IFN-beta and recombinant IFN-alpha and -beta were investigated. Amniotic fluid cells were obtained from pregnant women undergoing genetic amniocentesis. For 46 h, cells were treated with IFNs at concentrations of 10(3)-10(5) U/l. A dose-depending decrease of SCE rate with IFN-alpha and IFN-beta was observed. Our studies in amniotic fluid cells show that the mean SCE frequencies are reduced after incubation with IFN-alpha as well as with IFN-alpha. In contrast to IFN-gamma, the type I IFNs IFN-alpha and IFN-beta cause a genetic effect on DNA repair or a protection from DNA damage. Previously we had shown that a significant dose-depending increase of SCE rates was found in amniotic fluid cultures after addition of IFN-gamma. Therefore, IFN-alpha and IFN-beta (both human IFNs) and also recombinant IFN-alpha and IFN-beta, also in high doses, are neither genotoxic/clastogenic nor embryotoxic. Amniotic cells are vulnerable human cells, which may be well suited for examining the effects of agents like interferon.

Amniotic Fluid↗
PubMed1992

Ubiquinone biosynthesis. Cloning of the genes coding for chorismate pyruvate-lyase and 4-hydroxybenzoate octaprenyl transferase from Escherichia coli.

Chorismate pyruvate-lyase activity was detected in extracts of Escherichia coli. 4-Hydroxybenzoate was identified as the product of the enzymatic reaction by chemical derivatization and GC-MS analysis. The ubiC gene, coding for the chorismate pyruvate-lyase, was cloned and sequenced. The molecular weight of the gene product was calculated as 18,776 Da and confirmed by expression of the protein in E. coli minicells. The ubiA gene, coding for the 4-hydroxybenzoate octaprenyl transferase, was identified by sequence homology and complementation of a ubiA- strain. It is located directly downstream of ubiC in a typical operon structure.

Alkyl and Aryl Transferases↗
PubMed1990

Heat-inducible hygromycin resistance in transgenic tobacco.

We have constructed a chimaeric gene consisting of the promoter of the soybean heat shock (hs) gene Gmhsp17, 6-L, the coding region of a hygromycin phosphotransferase (hpt) gene, and the termination sequence of the nopaline synthase (nos) gene. This gene fusion was introduced into tobacco by Agrobacterium-mediated gene transfer. Heat-inducible synthesis of mRNA was shown by northern hybridization, and translation of this RNA into a functional protein was indicated by plant growth on hygromycin-containing media in a temperature-dependent fashion. One hour incubation at 40 degrees C per day, applied for several weeks, was sufficient to express the resistant phenotype in transgenic plants containing the chimaeric hs-hpt gene. These data suggest that the hygromycin resistance gene is functional and faithfully controlled by the soybean hs promoter. The suitability of these transgenic plants for selection of mutations that alter the hs response is discussed.

Amino Acid Oxidoreductases↗
PubMed1982

The antenatal use of ambroxol (bromhexine metabolite VIII) to prevent hyaline membrane disease: a controlled double-blind study.

A prospective double-blind clinical trial was carried out to determine whether ambroxol (bromhexine metabolite VIII) treatment (1000 mg/day for a period of 5 days) reduces the risk of hyaline membrane disease (HMD) in potentially premature infants. Amniocentesis was performed before the first and 24 h after the last application of ambroxol or placebo to assess the development of the total phospholipid phosphorus content, the L/S ratio, the P/S ratio, and the properties of the surface tension of the amniotic fluid after ambroxol or placebo. There were 246 infants born to 224 mothers. Of the 116 infants with less than or equal to 36 completed weeks' gestation, 56 were in the ambroxol and 60 in the placebo group. No differences between groups occurred in risk factors for HMD (diabetes, asphyxia, male sex, cesarean section). Statistically significant differences in favor of the infants in the ambroxol group were found in the HMD incidence: 23.2% in the ambroxol group compared with 41.7% in the placebo group (p less than 0.05). There was no reduction of the HMD incidence in the less than or equal to 32-week gestational age category in the ambroxol group compared with the placebo group inspite of the fact that all the examined parameters for determining lung maturity reflected a stimulatory effect of ambroxol compared with the results of the placebo group, particularly before the 33rd week of gestation. Prolonged rupture of the membranes played no protective role against HMD.

Ambroxol↗
PubMedDate not supplied

Dioxin concentration in milk and tissues of cows and sheep related to feed and soil contamination.

If cows or sheep are grazing on areas known for a higher dioxin level of the soil, respectively, dry cows are fed with feedstuffs produced on such areas, the dioxin concentration in food, in this case in cows' milk and livers of sheep could reach or exceed maximum levels. Furthermore large amounts of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzo-p-furans (PCDD/F) can be excreted with the faeces. But there are chances for farmers to prevent or at least to minimize the dioxin load of feed and with it of food (including the harvesting technique and the feeding strategy).

Animal Feed↗