Biomedical subjects

F Hänel

Publications and source records attributed to F Hänel.

27 records · Page 2Linked to original sources

PubMed1996

[Validity of fiber optic cerebral vein oximetry during extracorporeal circulation].

INTRODUCTION: This study investigates the accuracy of continuous jugular bulb venous oximetry during different conditions of hypothermic cardiopulmonary bypass (CPB) (27 degrees C) for coronary artery bypass graft. METHODS: 38 ASA III patients were studied following Ethical Care Committee approval and informed consent. Patients were anaesthetized with fentanyl, midazolam, continuous infusion of etomidate and pancuronium. Ventilation was performed with oxygen in air. CPB was managed according to alpha-stat conditions under moderate hypothermia (27 degrees C). SjO2 (%) and jugular bulb temperature (degree C) were measured by a fiberoptic thermodilution catheter (Opticath F 5.5, Abbott Critical Care Systems) placed in the jugular bulb via the internal jugular vein. Appropriate catheter position was x-ray controlled prior to the measurements. The fiberoptic data were compared to co-oximetric data of blood samples after induction of anaesthesia, 2 min following start of CPB, during cooling, stable hypothermia and rewarming of CPB. STATISTICS: Assessing of agreement (Bland/Altman and Bartko). RESULTS: Jugular venous oximetry correlated closely with the co-oximeter determinations after induction of anaesthesia. However, following start of CPB accuracy was decreased. During cooling, stable hypothermia and rewarming oximetric data correlated well with co-oximetry, however, over-estimating the SjO2 by 1.4 to 2%. CONCLUSION: The present data show that continuous jugular bulb venous oximetry is accurate and reliable for continuous SjO2 monitoring during hypothermic CPB for cardiac surgery. Induction of CPB and hemodilution affect accuracy slightly, but changes are well detected. Before clinical intervention SjO2 should be confirmed by laboratory co-oximetry.

Adult↗

PubMed1993

Nucleotide sequence analysis of five putative Streptomyces griseus genes, one of which complements an early function in daunorubicin biosynthesis that is linked to a putative gene cluster involved in TDP-daunosamine formation.

Sequence analysis of the lkmB region of the daunorubicin biosynthetic gene cluster of Streptomyces griseus JA3933 revealed two contiguous open reading frames (ORF) in the same orientation, and three ORFs in the opposite orientation together extending over a 4.6 kb region adjacent to a homologue of the S. peucetius dnrJ gene. ORF1 complemented in trans the lkmB mutation, which seems to affect an early step in daunorubicin biosynthesis. Its deduced product showed no similarity to any known enzyme in the databases. The mutation in ORF1 was localised to a C-T transition at position 1172, leading to the change from a glycine to aspartic acid in the deduced protein. The lack of any homology to known polyketide synthesis enzymes indicates a regulatory role for the product of ORF1, despite the ability of lkmB mutants to further metabolise alkanoic acid. The genes of the oppositely oriented cluster seem to be involved in sugar metabolism. The putative ORF3 protein revealed strong homology to eukaryotic acyl CoA dehydrogenases and might encode an enzyme for the oxidoreduction preceding the introduction of the amino group into daunosamine, and the ORF4 protein is homologous to several epimerases, central enzymes in the formation of the L-2,3,6-trideoxy-3-aminohexoses from TDP-D-glucose. ORF5 seems also to be related to enzymes metabolising nucleotide-activated hexoses.

Amino Acid Sequence↗

PubMed1989

Arsenical resistance of growth and phosphate control of antibiotic biosynthesis in Streptomyces.

Twenty-six wild-type Streptomyces strains tested for resistance to arsenate, arsenite and antimony(III) could be divided into four groups: those resistant only to arsenite (3) or to arsenate (2) and those resistant (8) or sensitive (13) to both heavy metals. All strains were sensitive to antimony. The structural genes for the ars operon of Escherichia coli were subcloned into various Streptomyces plasmid vectors. The expression of the whole ars operon in streptomycetes may be strain-specific and occurred only from low-copy-number plasmids. The arsC gene product could be expressed from high-copy plasmids and conferred arsenate resistance to both E. coli and Streptomyces species. The ars operon expressed in S. lividans and the arsC gene expressed in S. noursei did not render the synthesis of undecylprodigiosin and nourseothricin, respectively, phosphate-resistant. In addition in wild-type strains of Streptomyces phosphate sensitivity of antibiotic biosynthesis did not show strong correlation with resistance of growth to arsenicals.

Anti-Bacterial Agents↗

PubMed1985

Influence of inorganic phosphate on the lipid synthesis of a phosphate-deregulated mutant of Streptomyces noursei.

Phosphate-dependent changes of the mycelial lipid composition were studied in the streptothricin-producing parental strain Streptomyces noursei JA 3890 b/2 and its mutant RG 2. In contrast to its ancestor, the mutant was capable of producing the antibiotic nourseothricin even when large quantities of inorganic phosphate were present in the medium. The apparent insensitivity of the secondary metabolism to phosphate inhibition corresponds to a decreased level of phospholipids in the presence of excessive inorganic phosphate and, during phosphate limitation, to a much higher production of the alkaline phosphatases. A model is discussed which proposed the control by a common genetic element of both the phospholipid and antibiotic production.

Alkaline Phosphatase↗

PubMed1985

Occurrence of squalene and dehydrosqualene in streptomycetes.

Squalene, dehydrosqualene and related hydrocarbons were found to constitute an essential part of the neutral lipid fraction extracted from mycelia and membranes of S. hygroscopicus, S. griseus and S. noursei. In comparison with the fraction of the triglycerides, these terpenoid compounds failed to incorporate (U-14C)-acetic acid throughout pulse labelling experiments. This suggested that the pertinent precursors were formed via alternative routes, for instance by catabolising branched-chain amino acids.

Acetates↗

PubMed1985

Freeze-fracture observations of Corynebacterium glutamicum: the occurrence of an outer membrane-like structure and the influence of temperature on the cytoplasmic membrane.

In order to elucidate temperature-dependent morphological changes in the cell envelope of the Gram-positive L-lysine-overproducing Corynebacterium glutamicum 9366 we carried out freeze-fracture investigations of native cells and studied their fatty acid composition. In addition to the cytoplasmic membrane C. glutamicum possesses at the periphery of the cell an additional fracture plane which is unusual in Gram-positive bacteria and is designated here as outer membrane-like structure. The fracture faces of this layer display a distinguishable appearance in several regions of the cell. Bacteria grown at various temperatures showed changes in the relation of the saturated to unsaturated fatty acids. We demonstrated that the cytoplasmic membrane was affected by these changes in the fatty acid composition.

Cell Membrane↗

PubMed1984

ATP levels in phosphate-deregulated and arsenate-resistant mutants of Streptomyces noursei.

Mycelial levels of ATP and glucose-6-phosphate were investigated in mutants of streptothricin-producing S. noursei JA 3880b differing from the wild-type strain in antibiotic formation, in the control by inorganic phosphate of the secondary metabolism, and in the resistance to growth inhibition by toxic arsenate ions. As compared with the ancestral strain, mutants exhibited a lower content of ATP in the mycelium while addition of 0.1 M arsenate to growing cultures provoked only moderate changes in the level of this high-energy metabolite. The results suggest that there exists a correlation between growth resistance to arsenate and insensitivity to phosphate inhibition of the secondary metabolism, on the one hand, and the capacity to produce streptothricin-type antibiotics, on the other.

Adenosine Triphosphate↗

PubMed1983

[Effect of phosphate on the biosynthesis of tentoxin by Alternaria alternata (Fr.) Keissler].

Alternaria alternata (Fr.) Keissler produces a phytotoxic substance tentoxin. The influence of inorganic phosphate on the formation of this secondary metabolite was analyzed. Distinct phases of growth and metabolite formation can be defined. The first phase shows exponential growth, high QO2, protein and nucleic acid values and a rapid uptake of inorganic phosphate from the medium. The second phase shows linear growth and active tentoxin formation takes place. The highest yields of tentoxin are obtained, when inorganic phosphate in the medium was limited. The phosphate level also influences the ATP-pool of the mycelium. The role of ATP as an effector in phosphate mediated control of tentoxin synthesis was discussed.

Adenosine Triphosphate↗

PubMed1983

Cyanide-resistant respiration in Streptomyces citreofluorescens.

The capacity of Streptomycetes to carry out cyanide-resistant respiration was investigated. With the model strain, Streptomyces citreofluorescens, it was shown that deprivation of glucose followed by transition from exponential to stationary growth was coupled with declining sensitivity of cellular respiration to cyanide ions. Cyanide-resistant oxidase is located within the cytoplasmic membrane. The occurrence of the cyanide-resistant oxidase did not correspond to qualitative changes of cytochrome spectrum. Cytochrome d is involved neither in cyanide-sensitive nor in cyanide-resistant respiratory chain.

Carbon Monoxide↗