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Biomedical subjects

D Müller

Publications and source records attributed to D Müller.

At least 469 records · Page 26Linked to original sources
PubMed1978

Relationships between association state and enzymic activity of human erythrocyte phosphofructokinase.

Human erythrocyte phosphofructokinase has been subjected to active band centrifugation and stability measurements over a broad range of conditions. The enzyme behaves differently in-Tris buffer containing ATP and phosphate buffer containing fructose 6-phosphate. In the first buffer, dissociation is favoured and after prolonged storage of the enzyme tetramers represent the highest state of association. At 4 degrees C the enzyme exhibits the phenomenon of reversible cold-inactivation. This property is attributed to slow dissociation of the active associated states of the enzyme to dimers. The cold-inactivated enzyme can be reactivated by fructose 1,6-bisphosphate. Inorganic phosphate and fructose 6-phosphate have been found to protect the enzyme from cold-inactivation. Under these conditions, the sedimentation coefficient and the specific activity depend on the enzyme concentration only. The specific activity does not change on storage of the diluted enzyme at 4 degrees C. At 20 degrees C, however, a slow activation proceeds during incubation of the diluted enzyme. The correlations between the association state and the enzymic activity are discussed.

Enzyme Activation↗
PubMed1977

Ultrastructural findings of peripheral nerve in a preclinical case of adult metachromatic leukodystrophy.

In a 13-year-old neurologically healthy boy from a family with adult-onset of metachromatic leukodystrophy (MLD) showing arylsulfatase A-deficiency in the adult, sural nerve biopsy probably was performed 2-3 decades before clinical manifestation of the disease could be expected. Ultrastructurally 4 basic types of inclusion bodies in Schwann cells could be demonstrated (pleo-morphic "zebra body"-like inclusions, double-lamellated inclusions, "tuff-stone"-like inclusions, granular osmiophilic inclusions). Additionally, endoplasmatic reticulum, mitochondria and lysosomes showed marked alterations. Advanced damage of myelin was only rarely seen, but initial segmental demyelination was a common finding. These early pathological changes in chronic MLD are thought to represent a subcellular metabolic insufficiency of Schwann cells in this disease.

Adolescent↗
PubMed1977

Ethylmorphine-N-demethylation by liver homogenate of newborn and adult rats; Enzyme kinetics and age course of Vmax and Km1.

Optimum incubation conditions for determination of ethylmorphine-N-demethylation with newborn and adult rat liver homogenate have been determined: 1 ml 1:20 liver homogenate in 1.15% KCl, 1 ml 0.1 M phosphate buffer with ethylmorphine, NADP, and glucose-6-P, final concentrations 10, 0.33 and 5 mM, respectively, no nicotinamide, no MgCl2, 1 ml 0.5 M phosphate buffer; 3 ml final volume, 20 min incubation time. With both age groups NADH increases the activity to the same extent. With NADPH, saturation could be achieved only with newborn liver, but not with adult liver homogenate. Postnatally, the activity increases about fivefold, with a break at the 10th day of life. The Lineweaver-Burk plot was linear with newborn liver homogenate, whereas for all other age groups the graphs showed an angle. Statistical analysis pointed out that a two-enzyme model fits the experimental data only insignificantly better than a one-enzyme model. From other experimental evidence and manifold reproduction without any exception of these results, however, it may be concluded that there are different monooxygenases which show different affinities towards one substrate (ethylmorphine) and which show different developmental patterns.

Age Factors↗
PubMed1977

The influence of NADH on the ethylmorphine-N-demethylation in liver microsomes from control and phenobarbital-treated rats or different ages.

The ethylmorphine-N-demethylation by liver microsomes from control and phenobarbital-treated rats of different ages was investigated by means of adding NADPH in combination with NADH to the incubation medium. The rate of ethylmorphine-N-demethylation in the presence of NADPH without NADH is greater in adult than in young rats and greater in induced that in control rats. The higher the activity of ethylmorphine metabolism with NADPH alone the more it is abolsutely enhanced by NADH. The relative increase in ethylmorphine metabolism caused by NADH is equal in all groups of animals. It is concluded that there are no differences in the introduction of the second electron from NADH to the oxygenated cytochrome P-450 but there are differences in the concentration of cytochrome-substrate complex and, consequently, in the oxygenated cytochrome-substrate complex. The enhancing effect of NADH is higher at lower NADPH concentrations. In the presence of NADH, the NADPH concentrations necessary to obtain a msximum metabolic rate are lower than without NADH.

Animals↗
PubMed1977

[Neuropsychological parameters of droperidol-induced psychoses].

To each of twelve normal subjects 140 to 200 mg of droperidol were administered. The psychopathological (temporary hallucinatory syndrome), electroencephalographic (distinct posterior theta groups), electromyographic and electroneurographic (H amplitude depression), as well as electrocardiographic (tachycardia, extrasystoles) results are discussed with reference to possible mechanisms of action.

Adolescent↗
PubMed1976

[Studies on the pH-dependence, inhibition and reactivation of angiotension II-amide splitting enzymes in human erythrocytes (author's transl)].

Aminopeptidase activity of three fractions of human erythrocytes (membranes free of hemoglobin; hemolysate free of membranes; enzyme protein fraction made free of hemoglobin by DEAE-cellulose) was measured by a NADH dependent optical test using asparaginyl1-angiotension II-amide as substrate. 1. From the enzyme protein fraction 6 subfractions were obtained by (NH4)2SO4 precipitation. By measuring enzyme kinetics at three different pH-values (pH 5,0; 7,0; 8,0) with and without addition of the effectors Na2EDTA and Ca++ the existence of 6 different enzymes could be demonstrated. 2. The aminopeptidase activity of the hemolysate made free of membranes could be inhibited by diisopropylfluorphosphate and p-chloromercuribenzoate at three different pH-values (pH 5,0; 6,5; 7,0; 8,0 and 6,5; 7,0; 8,0 respectively). 3. A reduction of enzymatic activity of 20% was found after incubation at 37degreesC for two hours.

Calcium↗
PubMed1976

[Comparative methods for the determination of the activity of serumcholinesterases (acylcholin-acyl-hydrolase E.C. 3.1.1.8) and their diagnostical value (author's transl)].

The activities of serum cholinesterases were determined in parallel with acetyl-, butyryl- and propionyl-thiocholiniodide in healthy persons and patients with acute and chronic hepatitis, cirrhosis of the liver, fatty liver, cholestasis, intoxication and malignant tumors. The following normal values were obtained: See Article. The correlations between the various methods, especially between butyryl- and propionylthiocholiniodide are statistically significant. Compared to healthy persons, the activity of serum-cholinesterases, determined with the three substrates, decreased significantly in patients with acute and chronic hepatitis, cirrhosis of the liver, intoxication and malignant tumors. A change of specificity of serum-cholinesterases towards acetyl-, butyryl- and propionylthiocholiniodide in normal persons and patients with endogenous or exogenous coma of the liver was not observed. In all cases a parallel decrease of activity in sera was determined.

Acetylcholinesterase↗
PubMed1976

[Correlation between reflex behavior and EEG in a brain-stem tumor].

In a female patient with a tumour of the brain stem the e.e.g. showed signs of increasing general functional disorders and additional transient high voltage monographic waves with bilateral frontal and central accentuation, which we regarded as brain stem disturbances. At the same time the authors observed a characteristic inhibition of the amplitude of brain reflexes as well as high phases of a polyphasic stimulation--response potential with stimulation of the tibial nerve. Beside these inhibition phenomena, signs of disinhibition were verified (nociceptive, trigemino-trigeminal reflex, polyphasic disinhibited brain reflex?). The photostimulation was without influence on the sensitivity of motoneurons.

Adolescent↗