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Biomedical subjects

D Krebs

Publications and source records attributed to D Krebs.

At least 199 records · Page 11Linked to original sources
PubMed1984

Pleiotropic effects of a butyrolactone-type autoregulator on mutants of Streptomyces griseus blocked in cytodifferentiation.

Mutants of Streptomyces griseus blocked in cytodifferentiation regained their capacity to form differentiated mycelia and/or anthracycline pigments in the presence of butyrolactone-type autoregulatory effectors such as trans-2-(6'-methylheptanol-1'-yl)-3-hydroxymethyl-4-butanolide+ ++. In the pertinent indicator strains, the effect has been correlated with the increase of lipid synthesis, with changes in the composition of lipid fraction and with the restoration of the production of neutral proteinases. The results suggest that autoregulatory butyrolactones from streptomycetes stimulate cytodifferentiation of their producers at an early stage of development.

4-Butyrolactone↗
PubMed1983

Effect of the autoregulator from Streptomyces griseus JA 5142 on surface cultures of blocked mutant ZIMET 43682.

Zero time addition of the autoregulator (L-factor) from S. griseus (Lkm+Amy+) to surface cultures of its bald mutant ZIMET 43 682 (Amy-Lkm-) restored the capacity to form both anthracycline-type antibiotic leukaemomycin and aerial mycelium. The pertinent mycelia displayed the same growth rate and cellular levels of nucleic acids as the asporogeneous phenotype but the composition of fatty acids and phospholipids as well as the ratio of cytochromes b and c were altered. These differences indicate alterations in the cellular architecture of substrate and aerial hyphae. The results suggest that the autoregulator triggers the onset of a complex programme of differentiation at a very early stage.

4-Butyrolactone↗
PubMed1983

[Ovarian stimulation in an in-vitro fertilization programme].

The in-vitro fertilization of human ova and the subsequent transfer of the embryo are a possibility for infertile patients with damaged fallopian tubes to achieve a pregnancy. The results of different methods of ovarian stimulation in an in-vitro fertilization programme are described. The Clomiphen/hCG treatment and the overlapping Clomiphen/hMG/hCG treatment were used. Between July 1982 and March 1983, 130 patients had a laparoscopic aspiration of ovarian follicles at the Department for Obstetrics and Gynaecology in Luebeck. 585 follicles were aspirated and 404 ova retrieved. 210 showed the criteria of a preovulatory ovum. Of these 210, 177 were fertilized. In 95 patients an embryo transfer at the 2-8 cell stage was carried out. Inspite of the good fertilization rate of over 80% and the good embryo transfer rate of over 70%, pregnancy was achieved only in 13 cases. The number of follicles and of the retrieved preovulatory ova as well as the fertilization rate were best in the group which received combined Clomiphen and hMG. The pregnancy rate was not different compared to the other group. The first delivery of a healthy infant following laparoscopic aspiration of a follicle and in-vitro fertilization and embryo transfer in Luebeck occurred in March 1983.

Adult↗
PubMed1983

[Effect of the menstrual cycle on spontaneous and mitogenous lymphocyte transformation].

The spontaneous and the mitogenous lymphocyte transformation by phyt-hemaglutinine P of the peripheral T-cells of healthy women during the menstrual cycle and after the menopause was measured by the 3H thymidine incorporation into DNA. Whereas the transformation of lymphocytes has a uniform pattern after the menopause, the spontaneous transformation in women with menstrual cycles is diminished during the secretory phase of the cycle and periovulatory reduced stimulation by phyt-hemaglutinine P is observed. The formation of spontaneous rosettes was not different.

Adult↗
PubMed1982

Fatty acid composition of lipids of Escherichia coli W 1655 F+ and its stable protoplast type L-form.

The comparative fatty acid analysis of extractable and non-extractable lipids of Escherichia coli W 1655 F+ and its stable protoplast type L-form shows quantitative as well as qualitative differences. From 10 different fatty acids obtained 16:0, 17:0 and 18:0 are present at about the same quantities in the lipid fractions of the bacterial and L-form. The absence of larger amounts of 12:0, 14:0, and 14:beta OH fatty acids in non-extractable L-form lipids reflects the loss of the cell wall in L-form cells. 16:1 fatty acid was found in L-form lipids only. This qualitative difference and the 2-3 times higher content of 18:1 in L-form lipids and the 7 times lower content of cyc 19:0 in extractable lipids of the L-form may be interpreted as alterations characteristic for the changed composition of the cytoplasmic membrane in L-form cells.

Chromatography, Gas↗
PubMed1982

Effect of l-valine and l-isoleucine on fatty acid composition of Streptomyces hygroscopicus and S. griseus.

The effects of L-valine and L-isoleucine on the composition of mycelial fatty acids were investigated during growth of differentiating parent strains of Streptomyces hygroscopicus and Streptomyces griseus as well as their non-differentiating derivatives (Amy-strains) on a synthetic medium. Both in the Amy+ and Amy- strains, in the presence of L-valine, the portion of the isopalmitic acid (iC16:0) increased, but the addition of L-isoleucine led to an elevated level of the 12-methyltetradecanoic acid (aC15:0). The results suggest that the genetically determined alterations in the ratio of both fatty acids in the non-differentiating derivatives may be due to specific changes in the biosynthetic pathways of both amino acid precursors rather than due to changes of their catabolism.

Fatty Acids↗
PubMed1982

A new method of evaluating fetal lung maturity: the enzymatic lecithin determination in amniotic fluid.

The concentration of phospholipids is well suited as indicator for the prognosis of a possibly postnatal respiratory distress syndrome. The method used most frequently up to now has been the determination of the lecithin/sphingomyelin ratio (L/S ratio) by thin layer chromatography. We have developed a specific assay for the quantitative determination of lecithin in amniotic fluid, which yields absolute concentration values and does not require the determination of a concentration ratio. Lecithin is hydrolized by phospholipase C and alkaline phosphatase. Choline is determined afterwards by a highly specific choline kinase from yeast. The total time required is less than 2 h. The usual lecithin concentration present in the 35th to 38th wk of gestation can be determined with a coefficient of variation of 2-3% (n=30). Fetal lung maturity can be expected at a lecithin concentration above 4.7-5.1 mg/100 ml. The method compares well with the L/S ratio. Detailed data about clinical significance will be presented. Good precision accuracy and simple handling make enzymatic lecithin determinations suitable for routine use.

Amniotic Fluid↗
PubMed1982

[In-vitro fertilization of human eggs and embryo transfer].

This is a first report on experience with in-vitro fertilization of human eggs and embryo transfer. The follicle was aspirated to obtain eggs in 24 patients. A successful fertilization of the oocytes with obvious formation of a pronucleus was observed in 3 cases. In 9 more cases cell divisions were obtained and the embryos were transferred at the 4-cell stage. In spite of the unfavourable female patient population a good fertilisation and embryo transfer rate was achieved.

Adult↗
PubMed1982

Biochemical characteristics of non-streptomycin-producing mutants of Streptomyces griseus. II. Lipids and fatty acid composition of vegetative mycelia.

Five non-streptomycin-producing non-aerial-mycelium-forming mutants (Str-Amy-) of Streptomyces griseus obtained either by spontaneous degeneration or during continuous cultivation of the high-producing aerial-mycelium-forming parent strain HP (Str+Amy+) were checked with regard to the composition of mycelial lipid material. All the Str-Amy- derivatives differed from their ancestor strain HP by an increased ration of 12-methyltetradecanoic acid (aC15:0) to isopalmitic acid (iC16:0) during growth on a chemically defined medium lacking branched-chain amino acids. This finding attests alterations in the availability of precursors for the biosynthesis of methyl-branched fatty acids. The qualitative composition of phospholipids and other polar lipids in one mutant group was found to be similar to the progenitor strain but, additionally, both a yellow pigment and a neutral lipid component were produced in excess. A second type of mutant differed by its incapability to form ornithinolipids even under phosphate limitation. Changes of phospholipid composition were demonstrated in the course of fermentation. Formation of ornithinolipid was suppressed by an excess of inorganic phosphate in the medium, while the portions of phosphatidylethanolamine and cardiolipin increased strongly. Furthermore, the formation of ornithinolipids was influenced by nitrogen sources. these results suggest that the composition of membrane of S. griseus varies in dependence upon the composition of the medium and the age of the mycelium.

Cell Membrane↗
PubMed1981

[The antepartum evaluation of pulmonary maturity in high risk pregnancies (author's transl)].

In normal pregnancies the determination of the L/S ratio permits a reliable ante-partum evaluation of fetal maturity. Good correlation between ante-partum determination and the condition of the newborn is obtained. In the 566 L/S ratios obtained from abnormal pregnancies the method was also reliable. There was 217 Rh incompatabilities, 51 pre-eclampsias, 31 diabetic patients, 112 premature labours, 78 placental insufficiencies and 77 premature ruptures of the membranes. In patients with diabetes the ante-partum diagnosis of pulmonary maturity is doubtful. In some patients with diabetes pulmonary maturity appears to be delayed. A difference between the abnormal pregnancies was not recognized. In the different types of high risk pregnancies no acceleration or retardation of pulmonary maturity was detected with statistical significance. However, in some cases of premature rupture of the membranes, premature labour and placental insufficiency, pulmonary maturity appears to be accelerated.

Amniotic Fluid↗