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Biomedical subjects

E Knobloch

Publications and source records attributed to E Knobloch.

At least 37 records · Page 2Linked to original sources
PubMed1989

Metabolism of bilirubin and riboflavin in the course of phototherapy for hyperbilirubinaemia in the newborns.

The study of bilirubin photochemical degradation in the presence of riboflavin has shown that, in this case, the primary process is photooxidation during which riboflavin acts as a receptor and bilirubin as a donor of electrons. The reaction proceeds under anaerobic conditions in an equilibrated manner, under aerobic ones as a catalytic process during which the catalyst, i. e., riboflavin is regenerated. The primary intermediate product is biliverdin in vitro, later this is further broken down. For the purpose of studying the mechanism of this process liquid chromatography and computerized technique based on solving nonlinear differential equations have been used. It appears that during phototherapy in the newborn infant there develops a decrease of the blood level of riboflavin reaching up to hypovitaminotic values and a transient biliverdin level elevation. Oral riboflavin administration may maintain this level within physiological range and at the same time shorten the necessary duration of phototherapy. In severe cases of hyperbilirubinaemia a shift of the ratio between flavin-adenin-dinucleotide and free riboflavin, as compared to the physiological state, has been recorded. The results of this work are discussed in the light of our current knowledge concerning the mechanisms of bilirubin breakdown during prototherapy.

Bilirubin↗
PubMed1988

Study of the mechanism of the photochemical oxidation of bilirubin by high-performance liquid chromatography.

The photochemical degradation of bilirubin was studied in vitro using high-performance liquid chromatography and spectrophotometry. Attention was centered on the formation of biliverdin, which is produced as an intermediate in the photooxidation catalysed by riboflavin. approximate values of the overall and partial relative rate constants were calculated using the physiochemical criteria for a pseudo-monomolecular reaction. A more precise evaluation was made by non-linear regression programmes on a Hewlett-Packard 9835 A computer. In addition to the formation of biliverdin, attention was also paid to accompanying processes affecting the reaction mechanism, which were explained as aggregation and dimerization of bilirubin and biliverdin. It was also found that during phototherapy of newborn babies suffering from hyperbilirubinaemia the level of biliverdin in the plasma increased. The results are discussed from the point of view of phototherapy.

Bilirubin↗
PubMed1986

Kinetics of the formation of biliverdin during the photochemical oxidation of bilirubin monitored by column liquid chromatography.

In the photochemical oxidation of bilirubin, biliverdin is formed as the primary product and is further degraded. This photooxidation is especially significant in the presence of riboflavin. Column liquid chromatography was used to monitor the kinetics of this reaction. The biliverdin concentration amounts to a maximum of ca. 38% of the total loss of bilirubin in experiments in vitro. It is probable that this mechanism is also operative during phototherapy. The formation of a product of the photooxidation of biliverdin that has not yet been identified has been observed; the product behaves as a dimer. A method for the determination of biliverdin in the blood of newborn infants has been developed. It has been found that the biliverdin content increases during hyperbilirubinaemia.

Bilirubin↗
PubMed1986

Interaction of bilirubin with human lymphocytes and granulocytes--the effect on bilirubin metabolism.

An in vitro degradation of bilirubin by isolated human granulocytes and lymphocytes is described. Changes in the bilirubin concentration during interaction with these cells were determined spectrophotometrically. The dependence of the reaction velocity on the original bilirubin concentration followed an adsorption isotherm, typical of enzyme processes with a Km of 79 microM at a cell concentration of 500/microL. The primary event is the adsorption of bilirubin to the cell surface and, in addition, its detoxication. Cyanide and sonic treatment of cells inhibit the reaction, salicylic acid enhances the cell activity. The bilirubin-detoxicating effect is discussed with respect to the therapy of hyperbilirubinaemia in neonates.

Bilirubin↗