Acta biologica et medica Germanica最新文献

Adult rats were exposed to 5 degrees C for 5 and 24 h and thereafter the adenylate cyclase and phosphodiesterase (EC were studied in heart and liver. The cold exposure caused a significant increase in the myocardial adenylate cyclase with a simultaneous decrease of the phosphodiesterase activity. Long term cold exposure exhibited a decrease in the adenylate cyclase activity and an increase in the phosphodiesterase activity in rat liver.

We describe an enzyme-immunoassay for the determination of factor VIII related antigen. The principle of the method is the following: Test plasma is mixed with rabbit antibodies against human factor VIII in excess and incubated at 37 degrees C. The incubation mixture is added to polystyrene tubes coated with human factor VIII. The rabbit antibody is available to adhere to factor VIII coating the tube and can be detected with an enzyme-labeled wether antibody to rabbit IgG. This method is sensitive to 7.8 x 10(-3) U/ml factor VIII antigen.

The interaction of cytochrome P-450 LM2 with cytochrome b5 is accompanied by a high spin shift in P-450 LM2 and the improvement of a second derivative spectra in the near ultraviolet region. After incorporation into phospholipid vesicles the interaction between P-450 LM2 and b5 is increased according to a decrease of the apparent binding constant. The involvement of a tryptophanyl residue in the interaction will be discussed. Contrary the tryptic fragment of cytochrome b5 which lacks the membrane binding tail does not show an interaction with P-450 LM2 either in the absence or presence of phospholipids.

In ten chloralose narcotized, relaxed and constantly oxygenated cats the stomachs were dilated with two different pressures in acute experiments. Photically evoked potentials (PEP) were derived from the visual cortex of the animals. The aim of the work was to find out in which respect the processing of an exteroreceptive stimulus (light stimulus of only 200 ms) in the visual analyzer can be influenced by an interoceptive stimulation. Besides, it had to be established to which extent the visceral stimulation leads to a change of other vegetative parameters. Qualitative alterations of different PEP-parameters, blood pressure and heart rate of the experimental animals were examined at different stomach pressures. Changes of the positive and negative amplitudes and the time of the negative component of the primary complex of the evoked potential have been observed. Moreover, there could be registered an increase in blood pressure depending on the height of stomach pressure. The heart rate was not influenced. Further studies will have to clarify whether the changes of the PEP are produced by the interoreceptive stimulus or by the changes of blood pressure or respiration.

The interaction of highly purified cytochrome P-450 from bovine adrenal cortex mitochondria (cytochrome P-450scc) with N,N-dimethylaniline (DMA), aniline, N-dimethylcyclohexylamine and cumene hydroperoxide (CHP) has been investigated. The formation of complexes between cytochrome P-450scc and the above listed compounds could be demonstrated. The reaction of oxidative demethylation of DMA by cumene hydroperoxide involving cytochrome P-450scc has been carried out at 37 degrees C; the mechanism of this process is discussed. Incubation of cytochrome P-450scc with negatively charged phospholipids, phosphatidylglycerol (PG), and phosphatidylinosite (PI) exerts an inhibiting effect on the reaction of oxidative demethylation. The interaction of cytochrome P-450scc with CHP is accompanied by hemoprotein destruction in a complex biphasic way. The process of oxidative demethylation of DMA in the system of cytochrome P-450scc-CHP has been concluded to have a predominantly radical character.

The interactions between cytochrome P-450 LM2, NADPH-dependent P-450 reductase and different phospholipids have been analysed in reconstituted systems utilizing spin equilibrium and the reduction reaction as sensitive probes. The results have been correlated with structural data derived from second derivative spectroscopic measurements. The data obtained indicate that phospholipids with acidic groups are of special importance in shifting the spin equilibrium to the high spin state. The detergent substitution of phospholipids, on the other hand, in the reduction reaction provides evidence that the capability to shift the spin state is not strictly correlated with the functional integrity of the system. The results imply that the phospholipids exert a linker function orienting the proteins within the bilayer into a proper interaction state. This function can be substituted by detergents. The phospholipid effect is specified by their head groups and increases with negative charges.

This study has been carried out by measuring the cholinesterase (ChE) activity in blood serum and in some organs (brain, liver, spleen, kidney, small intestine, lung, and cardiac muscle) of rats before and at different time intervals after infusion of 65 dextran 70, and 5% gelatin 40 solutions (1 ml/100 g body weight). The controls received infusions of the diluent of the gelatin preparation. The data obtained showed that the infusion of the diluent in rats has no effect on ChE activity neither in blood serum nor in other organs at any time intervals after infusion. In case of dextran and gelatin, a significant increase in ChE activity in blood serum and the tested organs was observed at different time intervals after infusion. The increase in case of dextran was more marked than in case of gelatin. These measurements returned to base-line values during 72 h after infusion. Furthermore, the study failed to disclose any untoward reactions, either immediate or delayed, which could be attributed to the infusion solutions.

Well preserved pancreatic islet cell suspensions were isolated by trypsin treatment from islets of Langerhans of newborn rats. (Pro)insulin biosynthesis of freshly isolated islet cells can be stimulated by increasing glucose concentrations. In contrast insulin secretion on glucose as the only stimulus is drastically reduced but can be potentiated by 3-isobutyl-1-methylxanthine (IBMX). Within a period of 4-6 days in tissue culture pancreatic islet cells of newborn rats show the tendency to aggregate and form pseudo-islets of different size.