Biomedical subjects

K Rohde

Publications and source records attributed to K Rohde.

At least 109 records · Page 6Linked to original sources

PubMed1980

Some aspects of the ultrastructure of Gotocotyla secunda and Hexostoma euthynni.

The ultrastructure of the spermatozoon, the protonephridia, the intestine and the tegument of Gotocotyla secunda (Monogenea, Gotocotylidae) and of the intestine of Hexostoma euthynni (Monogenea, Hexostomatidae) is described. The "connecting cells" in the intestine of at least some Monogenea show secretory activity and are possibly involved in extracellular digestion. Sloughing of whole haematin cells appears to be common and may be an important component in the digestive process. Flame cells appear to be a very conservative element and their more or less identical structure in all major groups of parasitic platyhelminths indicates that parasitic platyhelminths have originated from one or a few closely related groups of freeliving Turbellaria with the same type of flame cell.

Animals↗

PubMed1980

Theoretical study of an energy metabolizing system satisfying Mitchell's postulates.

An energy metabolizing system was modelled, which carries as characteristic features substrate uptake and product extrusion, respiration and ATP-synthesis, coupled by the protonmotive potential corresponding to Mitchell's chemiosmotic hypothesis of oxidative phosphorylation. The influence of the electric part of the protonmotive potential on the rate laws of the different processes has been taken into account by a phenomenological exponent of the proton concentration, thus fortifying the osmotic concentration part of the protonmotive potential. The steady-state behaviour of the model was investigated. It could be shown that a model of such kind reveals multistationarity, homeostasis and trigger behaviour. Curves of respiration control (respiration velocity over ADP/(ATP + ADP) or ATP/ADP) are in qualitative accordance with experimental facts (state 3 and state 4 of mitochondria) as well as curves describing the effect of uncouplers on the respiratory rate.

Adenosine Triphosphate↗

PubMed1979

Kinetics of elementary steps in the cytochrome P-450 reaction sequence. IV. Mechanism of the NADPH reduction reaction of cytochrome P-450LM.

The aerobic NADPH reduction of the Triton N-101 disintegrated cytochrome P-450LM system has been studied. At this organization level--the components being dispersed in solution--a first-order monophasic reaction is exhibited. Neither the complex formation of cytochrome and reductase, respectively, nor preceding diffusion is rate limiting. The initial rate follows the ratio reductase/P-450 (mole/mole) thus indicating a Michaelis-Menten type enzyme mechanism. A model treatment of the reaction fits the systems behaviour as a whole. A multiparameter equilibrium state and different specified time function equations were developed for the determination of individual step rate constants and other system parameters as well.

Aerobiosis↗

PubMed1979

NADPH reduction of cytochrome P-450 at different integrational levels of the enzyme system.

The complex monooxygenatic enzyme exhibits different functional behaviour at different integrational levels, thus indicating distinct organizational states. The aerobic NADPH reduction of microsomes, solubilized and reconstituted systems follows a biphasic kinetics, the two phases are attributed to associated state (cluster) and random cytochrome P-450 reduction. States of different cytochrome P-450/reductase ratio (associates) could not be differentiated in rate. Detergents (Triton N-101, cholate) are capable of disintegrating the system, at last only monophasic slow reduction is observed. The hydroxylation activity follows the respective reduction behaviour. Sedimentation analysis proves the distinct structural states. Reconstitution of the system can be achieved by means of detergent dilution as well as by combining the constituents. The activity of the reconstituted system depends on the composition of the phospholipids as well as on its organizational state. The reassociation of the solubilized enzyme system at nearly microsomal components stoichiometry (Triton N-101 dilution) proves to be thermodynamically governed leading to self-organization of the system without matrix prerequisite. Individual step rate constants of the reduction reaction and other system parameters are accessible by means of a model treatment of the disintegrated system. Further application to mixed kinetics systems is in progress.

Aerobiosis↗

PubMed1978

Effect of protein-protein interactions on binding of ligands by proteins.

In general, saturation curves for ligand binding by proteins are described by the Adair-equation. The approach to ligand binding with methods of statistical mechanics leads not only to expressions for the Adair-constants, but gives also the possibility of describing the effect of protein-protein interactions on the binding of ligands by proteins. Under the assumption of the superposition-approximation for the potential of mean force between proteins in a solution, which contains also ligand molecules, the variations of the second and third virial coefficient with ligand activity are calculated for several simple model-pontentials. Finally the pair potential of hemoglobin molecules known from X-ray measurements will be approximated by such a simple square-well potential. With that the effect of hemoglobin density on oxygenation will be estimated. One finds for our model system that at relatively high protein density a further increase in density should be accompanied by a decrease in affinity (hindrance of saturation) and an increasing steepness of the slope of the saturation curve.

Calorimetry↗

PubMed1977

The bird schistosome austrobilharzia terrigalensis from the Great Barrier Reef, Australia.

Austrobilharzia terrigalensis from Egretta sacra and Larus novaehollandiae at Heron Island, Great Barrier Reef, is described. The prosobranch snail Planaxis sulcatus is the natural intermediate host of A. terrigalensis at Heron Island. The life-cycle of A. terrigalensis was worked out using naturally and experimentally infected Planaxis sulcatus and experimentally infected chickens. Experiments to produce a dermatitis with cercariae of A. terrigalensis were negative. Austrobilharzia terrigalensis infects a wide range of natural hosts in Canada, continental United States, Hawaii and Australia, and uses different snail genera belonging to different families as intermediate hosts in different areas. The wide distribution is apparently due to the habits of some hosts which migrate between the northern and southern hemispheres.

Animals↗

PubMed1975