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C Hagemann

Publications and source records attributed to C Hagemann.

5 recordsLinked to original sources
PubMed1992

Characterization of the transport of tri- and dicarboxylates by pig intestinal brush-border membrane vesicles.

1. Transport of citrate and fumarate across the pig intestinal brush-border membrane (BBM) was investigated using isolated BBM vesicles. 2. Citrate and fumarate uptake was stimulated by an inwardly directed Na+ gradient consistent with Na+/citrate (fumarate) co-transport. Cis-inhibition and trans-stimulation experiments strongly suggest the existence of a common transport site for tri- and dicarboxylates. 3. The protonated forms of citrate (citrate-1, citrate-2) seem to be much better transported than citrate-3, indicated by the strong stimulation of citrate uptake at an extravesicular pH of 5.6 compared to pH 7.8. 4. Uptake of tri- and dicarboxylates seems to be potential-sensitive since citrate and in particular fumarate transport was enhanced by an inside negative potential difference. 5. Kinetics of succinate transport revealed a single carrier-mediated component with apparent kinetic constants of 0.43 nmol/mg protein-3 s (Vmax) and 0.14 mmol/l (Km).

Animals↗
PubMed1991

Regression of high-affinity carrier-mediated intestinal transport of taurine in adult cats.

The sulfur-containing beta-amino acid taurine is an essential nutrient for cats. Owing to some metabolic peculiarities, cats are more dependent on dietary sources of taurine than other mammals. We therefore studied taurine uptake by intestinal brush-border membrane vesicles (BBMV) isolated from cat small intestine. Taurine uptake by feline BBMV was not influenced by a transmembrane Na+ gradient compared with Na(+)-free conditions. Kinetic analysis of initial taurine uptake yielded no evidence for a carrier-mediated transport process. These findings cannot be attributed to an overall inability of cumulative substrate uptake in our vesicle preparations because D-glucose uptake was strongly Na+ dependent, showing the overshoot phenomenon typically associated with active transport in vesicle experiments. Furthermore, L-leucine transport was mediated by a single Na(+)-dependent carrier mechanism (maximal transport velocity 1.2 nmol.mg protein-1.s-1, Km = 2.1 mM). In contrast to taurine uptake by feline BBMV, transport of taurine by pig intestinal BBMV was markedly enhanced by an inwardly directed Na+ gradient. Thus, differing from other mammalian species, taurine uptake across the intestinal brush-border membrane of the adult cat seems not to be mediated by a specific transport mechanism. Therefore taurine absorption from the gastrointestinal tract will possibly become a limiting factor for maintenance of taurine homeostasis in the cat under conditions of decreased dietary taurine intake.

Alkaline Phosphatase↗
PubMed1985

[Recall system].

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Appointments and Schedules↗
PubMed1975

[Conformational changes before and after DNA synthesis increase cytogenetically lethal radiation damage].

Chinese hamster ovary fibroblasts were synchronized by mitotic selection and showed cytogenetic lethally acting radiation damages, which depended on age at irradiation time. The development of cell cultures was followed by counting of the killed cells in the 3rd daughter generation of the irradiated ones and by evaluation of the colony size spectra 73.5 h after innoculation. At a dose of 300 rads two narrow but high peaks of radiation sensitivity were induced, which appeared at the beginning and at the end of the S-phase of the cell cycle and therefore are reduced to conformation changes of the DNA. Consequently the DNA-super-structures linking pieces of the nucleoprotein-fibre during fastening to, and detaching from, the nuclear membrane are assumed to be the loci of the increased radiation sensitivity.

Cell Division↗