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C Bauer

Publications and source records attributed to C Bauer.

At least 361 records · Page 20Linked to original sources
PubMed1980

The problem of negative results for styrene in the in vitro mutagenesis test with metabolic activation (microsomal assay):explanation by gas chromatographic analysis.

Mutagenic experiments in vitro were performed on yeast (S. pombe) with styrene with metabolic activation by adding at fixed times fresh mouse microsomes to the incubation mixture. Preceding studies with a single initial addition of microsomes were negative up to the maximal dose of 100 mM styrene for 60 min (5). The addition of fresh microsomes at the times 12, 24, 36 and 48 min in the presence of EDTA 40 mM resulted in an increased toxicity of styrene in vitro, but not in increased mutagenicity. Gas chromatographic determination of styrene oxide in the incubation mixture with 50 mM styrene revealed a concentration of active metabolite not capable of acting mutagenically.

Ascomycota↗
PubMed1980

2,3-DPG levels in relation to red cell enzyme activities in rat fetuses and hypoxic newborns.

We have measured in red cells from fetal and adult Sprague-Dawley and Wistar rats the activities of phosphofructokinase (PFK), pyruvate kinase (PK) and diphosphoglyceromutase (DPGM) as key enzymes in the regulation of 2,3-diphosphoglycerate (2,3-DPG) levels to gather information on the possible causes of the low concentration of 2,3-DPG in fetal red cells. The most striking differences were seen with regard to PK and DPGM activities. The activity of PK was ten times higher in fetal compared to adult red cells, whereas red cell DPGM activity was absent in fetuses and high in adults. In addition, we studied postnatal changes in red cell PK and DPGm activities as well as in the 2,3-DPG concentration in Sprague-Dawley rats. The concentration of 2,3-DPG and the activity of DPGM in red cells increased to almost the adult value within 2 and 4 weeks after birth, respectively, while the activity of PK decreased concomitantly. The postnatal changes occurred similarly, when newborn rats grew up under conditions of hypoxic hypoxia at 0.46 atm (pO2 = 9.2 kPa). Our studies support the hypothesis that postnatal changes in 2,3-DPG levels are due to changes in the activity of certain glycolytic enzymes and that the switch from fetal-type to adult-type red cells follows a genetically determined time course.

Aging↗
PubMed1980

beta 2-Adrenergic stimulation of erythropoiesis in busulfan treated mice.

The capability of chronic beta 2-adrenoceptor activation to effectively stimulate erythrocyte production in vivo was investigated in mice which had been treated with the hematopoiesis inhibiting agent busulfan. A relatively low dose (5 mg/kg i.p.) of busulfan produced moderate depression of erythropoiesis 10 days after a single injection, as determined by 59Fe-incorporation into erythrocytes. Administration of albuterol (1 mg/kg s.c. twice daily), a selective beta 2-adrenergic agonist, significantly enhanced erythropoiesis for 5--10 days after the injection of busulfan. In a long-term study with albuterol at the same dose a significant increase in hematocrit values as well as in the circulating erythrocyte mass was found in busulfan (5 mg/kg i.p. weekly) treated mice when compared to saline-busulfan treated control mice. Simultaneous injections of the beta-adrenergic blocking agent propanolol (4 mg/kg i.p.) diminished the effect of albuterol on erythropoiesis. Albuterol at a lower dose (0.1 mg/kg) had no significant effect on erythrocyte mass. In view of recent findings, which have shown that the proliferation of the pluripotent hemopoietic stem cell pool is blocked by busulfan, it is concluded that the main site of beta 2-adrenergic action on erythropoiesis is on the erythroid committed stem cell pool. In addition, enhanced release of erythropoietin from the kidney following the application of albuterol may contribute to beta 2-adrenergic stimulation of erythropoiesis.

Albuterol↗
PubMed1979

The interaction of inositol pentaphosphate with the hemoglobins of highland and lowland geese.

We have studied the binding of inositol pentaphosphate (IPP) to the hemoglobins from two species of goose living at low and high altitudes, using the proton absorption method. Measurements were done at 25 and 37 degrees C in a pH range between 6.0 and 8.8. The bird hemoglobins show a high affinity and a binding stoichiometry of 1 IPP molecule/hemoglobin tetramer both in the ligated and unligated state, indicating the same binding site for IPP in oxy- and deoxyhemoglobin. The results indicate that the interaction of IPP with both geese hemoglobins is very similar. For the deoxyhemoglobins of both species the IPP-binding constant shows a strong pH dependence extending over a wide pH range (i.e. +/- 2 x 10(6) M at pH 8.8 and +/- 6 x 10(10) M at pH 6.0). The binding constant of IPP for the oxyhemoglobins shows a much weaker pH dependence (i.e. +/- 4 x 10(4) M at pH 8.8 and +/- 3 x 10(6) M at pH 6.0), indicating that the interaction of IPP with the goose hemoglobin is strongly dependent on the state of ligation of the protein. The IPP binding constants for the oxy- and deoxyhemoglobins are found to be in good agreement with the IPP-induced change in oxygen affinity of both hemoglobins as estimated from oxygen binding curves.

Altitude↗
PubMed1979

Studies on the incubation mixtures for the in vitro mutagenesis test with metabolic activation (microsomal assay). Behaviour of mixed function oxidase and lipid peroxidation in the presence of some xenobiotics.

The effect of some xenobiotics on microsomal mixed function oxidase and lipid peroxidation, in mice, in incubation mixtures for the in vitro mutagenesis test with metabolic activation was studied. Aniline 1 or 2 mM and aminopyrine 0.38 or 8.33 mM completely inhibited the lipid peroxidation with small protection of the monooxygenase. Styrene 50 or 100 mM inhibited to a lesser extent the lipid peroxidation with marked increase in the inactivation of the monooxygenase. By a technique based on successive additions of fresh microsomes it was possible to evaluate the part of the inactivation due to enzyme denaturation and that due to inhibition. EDTA 40 mM was not able to protect from inactivation in the presence of aniline 1mM. Data of this type could be utilized to obtain more reliable results of in vitro mutagenesis tests with metabolic activation by suitably managing the enzyme activity in the incubation mixtures in order to keep it as constant as possible.

Aminopyrine↗
PubMed1979

[Role of NADPH-dependent lipid peroxidation in the oxidase inactivation in mixed hepatic microsomal function].

When mouse liver microsomes were preincubated at 37 degrees with buffer, the monooxygenase activity was nearly constant and lipid peroxidation very low over 15 min. When preincubated with NADPH, there was an increase in lipid peroxidation accompanied by loss in enzyme activity (about 40%). The addition of EDTA 5 or 40 mM depressed lipid peroxidation and protected the monooxygenase activity with a rate increasing with concentration. The addition of FeSO4 0.5 mM had only little effect one enzyme activity whereas stimulated the response of the 2-thiobarbituric acid test.

Animals↗
PubMed1979

[Glycoproteins: their biological and clinical significance. I (author's transl)].

Increasing knowledge on structure, biosynthesis and catabolism of glycoproteins have given new insights on the patho-biochemical and clinical significance of these macromolecules. The most important results and conclusions are summarized in this review. 1. The terminal sugars of glycoproteins--N-acetylneuraminic acid (NANA) and L-fucose--as well as the penultimate galactose molecule have important functions in cell interaction, adhesion and recognition. Moreover, these carbohydrates mediate the migration and distribution of cells and it is believed that they are essential part of the feto-maternal "immunological barrier". 2. Evidence indicating that the composition and pattern of plasma membrane glycoproteins is associated with tumour growth and metastatic formation is accumulating. Moreover, the determination of serum glycosyltransferase activity is gaining increasing interest, because the level of these enzymes is substantially elevated in patients with neoplastic disease. 3. Diseases of the autoimmunosystem are likely linked to a disturbed glycoprotein metabolism. The clinical importance is underlined by studies on immunotherapy of tumours.

Autoimmune Diseases↗
PubMed1978

High pyruvate kinase activity causes low concentration of 2,3-diphosphoglycerate in fetal rabbit red cells.

1. The high oxygen affinity of fetal blood in rabbits is due to a very low concentration of 2,3-diphosphoglycerate (2,3-DPG) in the red cells. In order to gather informations on the factors responsible for this characteristic we have studied synthesis and break-down of 2,3-DPG in fetal and adult rabbit red cells in vitro and examined possible regulative pathways which may lead to the low 2,3-DPG concentration in vivo. 2. Under conditions where 2,3-DPG and 3-phosphoglycerate (3-PGA) accumulate in adult erythrocytes, i.e. in a solution containing inosine, pyruvate and inorganic phosphate, the amount of 2,3-DPG synthetized in fetal red cells was only 40% of the adult value and 3-PGA was not measurable. Upon inhibition of enolase by NaF, however, both 2,3-DPG and 3-PGA increased to a similar extent in fetal and adult red cells. These findings point towards differences in the pyruvate kinase (PK) reaction which is one of the rate limiting steps of glycolysis. Direct measurements revealed an over tenfold higher PK activity in fetal compared to adult red cells. This higher activity of PK will lead to a decreased concentration of 3-PGA with a consecutive fall in 2,3-DPG concentration. 3. Other factors, like a decreased glucose utilization, a decreased activity of 2,3-DPG mutase or an increased 2,3-DPG phosphatase activity could be excluded as a cause for the low 2,3-DPG concentration in fetal red blood cells. The same holds for extraerythrocytic factors like glucose concentration or pH value in fetal blood. 4. During the postnatal development of rabbits the PK activity decreased. 50 days after birth, PK activity was 20% of the fetal value but still somewhat higher than in adult erythrocytes. This change is paralleled by an increase in 2,3-DPG concentration and half saturation oxygen pressure. With respect to the synthesis of 2,3-DPG and ATP, the fetal rabbit red cell is comparable to hereditary high PK activity in human erythrocytes.

Animals↗