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Biomedical subjects

B Ebert

Publications and source records attributed to B Ebert.

At least 109 records · Page 6Linked to original sources
PubMed1984

Articular chondrocalcinosis in a hospital population: an Australian experience.

A group of hospital patients aged 55 years or over (53 men, 74 women) were screened for articular chondrocalcinosis (ACC) with high-resolution radiographs of knees, wrists, hand and pelvis. Two men (4%) aged 79 and 86 years had ACC involving knees, wrists and symphysis pubis. Both had clinical joint disease and radiological osteoarthritis (OA). Eighteen women (24%) had ACC with sites affected including the knees (89%), wrists (39%) and symphysis pubis (44%). Metabolic screening did not reveal any predisposing factors in patients with ACC. Symptoms and signs of joint disease were not significantly more common in women with ACC compared to those without ACC, and 44% of those with knee calcification were clinically asymptomatic and had no evidence of OA radiologically. However, the presence of knee ACC significantly increased the risk for OA in the same knee by a factor of three-to-four while knee calcification was associated with the more severe grades of radiographic OA.

Aged↗
PubMed1983

Study of H2O2-supported N-demethylations catalyzed by cytochrome P-450 and horseradish peroxidase.

H2O2-supported oxidative demethylation reactions catalyzed by cytochrome P-450 and horseradish peroxidase have been compared. In contrast to peroxidase catalyzed reactions no free substrate radicals could be detected by EPR stopped flow measurements in demethylation reactions catalyzed by highly purified cytochrome P-450 although the rate of product formation for both enzyme systems was identical. These findings cause doubts in a general peroxide dependent demethylation mechanism valid for all hemoproteins and in the hypothesis that free substrate radicals are principally formed during cytochrome P-450 catalysis.

Aminopyrine↗
PubMed1983

Mechanism studies of enzymatically formed tolidine blue and determination of peroxidatic activities.

In aqueous solution peroxidase catalyzes the conversion of o-tolidine to tolidine blue by hydrogen peroxide. This reaction of practical significance for analytical tests was studied by optical and ESR spectroscopy. For the blue dye formed in aqueous solution a meriquinoidic structure was proposed which is in equilibrium with an instable radical compound. This equilibrium is shifted to higher radical concentrations by ethylene glycol. Naphthene derivatives stabilize the meriquinoidic structure by means of non-covalent interactions resulting in a decrease of the radical concentration. In crosslinked gelatin the dye formation runs analogously, so that this system is suitable for providing evidence for H2O2-forming reactions. Naphthene derivatives substituted by sufficiently long aliphatic groups are diffusion stable in crosslinked gelatin. By interacting with the dye they prevent its rapid chemical decomposition and diffusion into the sample solution. It was shown, furthermore, that by means of such systems with a suitable structure of the layers both substrates and enzymes participating in the reaction may be determined analytically. This does provide a basis for developing new analytical test variants.

Benzidines↗
PubMed1983

Analysis of paramagnetic intermediates at the reaction of hemoglobin with nitrite using EPR.

The autocatalytic oxidation of hemoglobin by nitrite was analysed. It was shown that the obtained paramagnetic species have a strong temperature dependence. The time of annihilation of these species decreases about 4 times in the temperature region between 10 degrees C and 30 degrees C, whereas the time of formation decreases only 1.7 times. These data explain the strange temperature dependence of the formation of methemoglobin by nitrite and support the assumption that the short-lived radical is localized on the hemoglobin molecule.

Adult↗
PubMed1982

Preparation of spin-labeled poly(U) and its activity in assays with eukaryotic ribosomes.

ESR studies on the interaction of spin-labeled polynucleotides with ribosomes require a sufficient label-to-nucleotide ratio. Using three different spin labels (SL) we have elaborated a technique to label poly(U) up to a ratio of 1 SL per 30 uridine residues. This ratio is much higher than maximal values obtained by other authors. The SL-poly(U) was shown to have the same activity as unlabeled poly(U) to direct synthesis of poly(Phe). SL-poly(U) binds to rat liver ribosomes in the presence of Mg2+ as shown by ESR. Titration with EDTA leads to a release of SL-poly(U) from ribosomes.

Animals↗
PubMed1980

Temperature behaviour of human serum albumin.

Structural alterations of albumin, their dependence on concentration and the role of free --SH groups at thermal denaturation, as well as the reversibility of thermally induced structural changes, were studied. Application of various physical methods provides information on a series of structural parameters in a major concentration range. Apart from changes of the helix content, heat treatment gives rise to beta structures which are amplified on cooling and which are correlated with the aggregation of albumin. With rising temperature and concentration the proportion of beta structures and aggregates increases. At degrees of denaturation of up to 20% complete renaturation is possibly in every case. The structure content is concentration-dependent even at room temperature. It may be that intermolecular interactions induce additional alpha-helix structures which are less stable, however, than the ones stabilized by intramolecular interactions. Unfolding of the pocket containing the free --SH group of cysteine-34 enables disulphide bridges to be formed leading to stable aggregates and irreversible structural alterations. Through binding of N-ethymaleimide to free --SH groups, which blocks the formation of disulphide bridges, it is possible to prevent aggregation and irreversible conformational changes. At temperatures below 65--70 degrees C, oligomers are formed mainly via intermolecular beta structures.

Circular Dichroism↗
PubMed1980

[Study of the state of blood plasma by the spin probe method].

To evaluate the potentialities of the spin probe method in examination of the blood plasma state, a study was made into the blood plasma bound nitroxyl radical 2,2,4,4-tetramethyl-1,2,3,4-tetrahydro-5,6-benzo-gamma-carbolin-3-oxyl in healthy rabbits and those with pronounced experimental atherosclerosis. The probe absorption by high molecular plasma components was assayed in order to determine the binding constants and concentration of the binding centers, mobility of adsorbed probes and polarity of their surroundings. In the course of experimental atherosclerosis development these parameters underwent changes correlating with those of blood plasma cholesterol level. The data obtained suggest that the spin probe method may be used for assessement of the plasma state for diagnostic and research purposes.

Animals↗
PubMed1977

[A group-behavior-psychotherapy concept: treatment of psychosomatic disorders].

The paper concerns with group-behavior-therapy with patients having psychosomatic disorders. The therapy was applied to two groups. The therapy has not been fully standardized but individual differences of each client's behavior-analysis was taken into account. The clients were to learn the understanding of the development of their symptoms and the conditions under which the symptoms remained and changed. Clients should help each other as co-therapists. The group-therapy was divided into three parts: (1) communication-training in the group, (2) introduction to the basic principles of learning, (3) application of special therapeutic methods. The therapy procedure as well as the results of the first follow-up are reported. The concept of group-therapy is discussed.

Adaptation, Psychological↗
PubMed1976

[Spectroscopic investigatons on the structural thermal stability of leucine aminopeptidase. ESR, CD and fluorescence studies].

The thermal behaviour of leucine aminopeptidase (LAP, EC: 3.4.11.1) from bovine eye lens has been investigated in the temperature region 20--70 degrees C by spin-labelling of SH-groups (ESR), by CD and by fluorescence of tryptophane residues. Enzymatic activity of LAP was compared with spectroscopic data in this temperature region. From 20-60 degrees C the structural parts (alpha, beta, random coil) estimated from CD spectra remain unchanged. Within 20-55 degrees C no irreversible exposure of tryptophane residues takes place. In both types of spin-labelled LAP the strong immobilizing environment of the label retains its highly ordered structure up to 55 degrees C. Reversible changes of mobility and polarity of the environment of the label induced by temperature within 20-50 degrees C do not reduce the enzymatic activity and are regarded as local loosening of ordered structure. At 65 degrees C strong precipitation occurs. From 55 degrees C to 65 degrees C tryptophane residues are irreversibly exposed. The highly ordered environment of the label is destroyed about 55 degrees C, and a considerable amount of spin label molecules is reduced at the NO group by exposed SH groups. The above mentioned local loosening of structure becomes irreversible at 60 degrees C. The environment of both labels dominating above 60 degrees C is highly mobile and strongly polar and represents an extensively unfolded conformation. Until 60 degrees C no essential disordering of protein structure leading to a decrease of enzymatic activity occurs. Above 60 degrees C a sharp breakdown of ordered structures takes place, which is accompanied by a strong diminution of enzymatic activity.

Animals↗
PubMed1975

Adsorption of small molecules to bovine serum albumin studied by the spin-probe method.

A spin-probe technique is used for quantitative EPR studies of adsorption of small molecules on globular proteins, of the rigidity of their binding to the protein and of the polarity of the environment. In the case of bovine serum albumin it is shown that nitroxyl radical (2, 2, 6, 6-tetramethyl-4-oxy-1-oxyl-piperidine)-stearate (I) has an adsorption behaviour similar to that of the fatty acids, nitroxyl radical (2, 2,4, 4-tetramethyl-1, 2, 3, 4-tetrahydro-5, 6-benzo-gamma-carboline-3-oxyl) (II) to that of the tryptophan molecule. Radical I rotates relative to the protein molecule, while Radical II is rigidly bound to the protein.

Adsorption↗
PubMedDate not supplied

Placental vascular corrosion cast studies: a comparison between ruminants and humans.

The microvasculature of both the ruminant placentomes of cattle, sheep, and goats and the human placenta were compared, using corrosion casts of blood vessels and scanning electron microscopy. The fetal vascular trees of ruminant and human placenta differ in form and size, which correlates with the degree of ramification; however, their architecture of stem, intermediate, and terminal villi is similar. In the human, the system of serially linked capillary convolutions of terminal villi is longer than that in ruminants. Therefore, in guaranteeing blood flow against flow resistance, the human vessels particularly need a straight course, anastomoses, and sinusoidal dilations. Specifically in the ruminants studied, the venous vessels outweigh the arterial ones by volume and by number. They are suggested to be absorptive for substances metabolized in the zone of the capillary complex. The most extreme interspecies difference relates to the maternal vasculature, which, in contrast to the fetal system, is a closed system in the ruminant septas and an open lacunal intervillous space in the human. Converging and differing morphological vascular phenomena of ruminants and human placenta are discussed in terms of maternofetal exchange related to placental efficiency. In summary, the ruminant placenta, concerning the fetal vascular tree, in many aspects is workable as a model for the human.

Animals↗
PubMedDate not supplied

[Study of the conformational changes of serum albumin molecules within a pre-denaturation temperature range by a spin probe technique].

To study conformational changes of protein molecules in a pre-denaturation temperature range, nitroxyl radicals adsorbed by a protein are suggested to be used. A spin probe technique is specially developed to be implied for this aim by using a probe specifically bound to the bovine serum albumin molecule, it was possible to reveal a dependence of the rotation correlation time of the adsorbed radical and the environment polarity on the temperature. The data obtained testify in favour of a change occurring in the intramolecular structure of the protein under study due to a temperature change within the pre-denaturation temperature range.

Animals↗
PubMedDate not supplied

[A study of the Brownian movement of alpha-chymotrypsin molecules by the spin probe method].

The rotation of alpha-chymotripsin in water solution is studied by use of nitroxyl radical, which is adsorbed by the alpha-chymotrypsin. It has been shown that under the conditions used the probe is fixed on the rotating diffusive protein monomer. Theoretical calculations of possible rotation correlation times for alpha-chymotripsin molecule were performed taking into account hydration and non-spherical shape. Experimental data obtained are in good agreement with theoretical values.

Chemical Phenomena↗
PubMedDate not supplied

[Rotatory mobility and intermolecular reactions of serum albumin studied using the spin-probe method].

Dependence of the rotational mobility of bovine serum albumin on the protein concentration in solution has been studied by means of nitroxyl radical tightly bound to the protein. The rotational correlation time of radical, bound with protein for weak solution has been compared with the theoretical values of correlation times for protein monomer, calculated in terms of its hydration and deviation from the spherical shape. A conclusion about radical orientation relatively to the protein molecule has been drawn from this comparison. The concentration dependence of ratational correlation time for radical, bound with protein, was explained by the protein dimerization in solution. A conclusion has been drawn about the stability of intramolecular structure of serum albumin during its dimerization on the basis of the stability of anisotropic hyperfine constants of adsorbed radical.

Electron Spin Resonance Spectroscopy↗