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H Oehring

Publications and source records attributed to H Oehring.

At least 19 recordsLinked to original sources
PubMed2001

Towards versatile metal associating substrates for the determination of peroxidatic activity/hydrogen peroxide by chemical designing of Schiff base derivatives.

Novel chromogenic N-arylmethyl-aniline-substrates of the general formula R-NH-CH2C6H5-n-Xn (X = OH, NHR) for the localization of peroxidatic activity/hydrogen peroxide were synthesized in two steps from starting amines and aromatic aldehydes. When using 1,2-dinucleophiles (e.g. diaminobenzidine) as starting material there may be limitations resulting from dominant altemative reaction courses (amino-imines vs bis-imines) or tautomerism (amino-imines vs benzimidazolines). This has been investigated in a model study on 1,2-phenylendiamine. All substrates were evaluated for application in histochemistry, electrophoresis, colorimetry and electron microscopy. Thus, 1/ endogenous peroxidatic activity in native cryotome sections of Wistar rats was stained. One selected reagent was used for immuno-histochemical demonstration of vimentine and applied for laser microscopy at 543 nm as well. 2/ Electro-blotted dilution series of horseradish peroxidase were stained and reagents ranked according to their sensitivity. 3/ In test tube experiments precipitation behavior, color and solubility of precipitates was investigated. 4/The chromogens are capable of forming electron opaque final reaction products by way of increased osmiophilicity of the specific reaction product or/and by complexation of electron dense metals as demonstrated by electron microscopical investigations. As a result, two novel reagents derived from 1,2-phenylendiamine and 2-aminophenol are recommended especially for electron microscopy: The discrimination between internum and extemum of specific granules after osmium tetroxide treatment is resolved clearly as compared with results obtained with the standard Kamovsky protocol.

Animals↗
PubMed2000

Novel chromogenic substrates with metal chelating properties for the histochemical detection of peroxidasic activity, derived from 3-amino-9-ethylcarbazole (AEC) and 3,6-diamino-9-ethylcarbazole.

For staining of peroxidase activity routinely employed 3-amino-9-ethylcarbazole 1 (AEC) was chemically modified in order to obtain chromogenic enzyme substrates with improved staining properties. In conclusion of systematically structure/staining considerations of a series of novel substrates, it can be generalized that the performance of traditional chromogenic peroxidase amine-substrates is accessible an considerably improvement in terms of sensitivity and adaptibility for various application purposes (solubility and color of the reaction product, electron dense and osmiophilic properties, ...) by attachment of chelating N-benzyl-moieties making available highly efficient the well known metal catalytic effect in a proposed intramolecular way. Thus, the model compounds 3(arylmethyl)amino-9-ethyl-carbazole 4 and 3,6-bis-(arylmethyl)amino-9-ethyl-carbazole 7 were synthesized by condensation of 3-amino-9-ethylcarbazole 1 (AEC) or the corresponding 3,6-diamine 5 with aromatic aldehydes 2. The resulting Schiff bases 3 and 6 were subsequently reduced with sodium borohydride. The obtained benzylamines 4 and 7 were examined as chromogenic substrates: 1) qualitatively in test tube experiments concerning color, precipitation behavior and solubility of the precipitates, 2) quantitatively by means of electroblotted dilution series of horseradish peroxidase, and finally in a biological environment for the localization of endogenous peroxidasic activity 3) in native cryotome tissues of Wistar rats. 4) The usefulness of the new approach for electron microscopy was revealed, too. Thus the discrimination between internum and externum of specific granules after osmium tetroxide contrastate was higher if compared with results obtained by the Karnovsky protocol. The wide spread variation of substitution patterns of the novel reagents gave reason for structure-reactivity considerations and ongoing leading structures. The stereochemical and electronic factors as well as competing reaction pathways governing the reaction course are briefly discussed. In addition, the metal associating reagents are highly effective in oxidative side-coupling reactions with aromatic amine or phenol-additives exemplified here by means of 4-amino-N,N-diphenylamine. The reagents 4 and 7 are obtainable in a simple in situ synthesis, too, offering in principle a 'chemical construction unit'. The demonstrated approach is of general interest for bioanalytical applications offering an access to potentially novel chromogens and electron opaque markers for the detection of peroxidasic activity/hydroperoxides or related redox enzyme systems.

Animals↗
PubMed1996

Quantitative assessment of primary cerium reaction product formed by glucose-6-phosphatase activity in a male rat liver: an image analysis study.

Glucose-6-phosphatase (G6Pase) activity has been determined in periportal and pericentral areas of the liver of normal male rats. Measurements were performed on unfixed cryostat sections mounted on semipermeable membranes. In the present study, the oxidized primary reaction product of a cerium-based histochemical method [Ce(IV)perhydroxyphosphate] instead of the final reaction product after a second-step incubation was measured. For quantification of the amount of Ce(IV)perhydroxyphosphate formed the digital image analyzing system Quantimet 500+ was used. Estimated values of optical densities of Ce(IV)perhydroxyphosphate over test areas were employed for calculation of kinetic parameters of (G6Pase). Highest activities of G6Pase (higher Km and Vmax levels) were found in periportal areas of the rat liver, indicating a higher amount of active enzyme molecules and a lower affinity for the substrate. Differences in values for both Km and Vmax between periportal and pericentral zones were highly significant and closely comparable to those for male fed rats. Correlations between Km and Vmax were significant for periportal as well for pericentral liver areas. The results of the present study thus allow the same biological implications as histochemical methods employing a final reaction for quantification of enzyme activities. The present method avoids the drawbacks of enhancement reactions and demonstrates the feasibility of in situ analysis of enzyme kinetic parameters by quantification of oxidized primary cerium reaction products.

Animals↗
PubMed1994

Dysmorphic erythrocytes in glomerulonephritis. 1. Electron microscopical and histochemical investigation.

Dysmorphic erythrocyte malformation in urine is characteristic of glomerulonephritis. The mechanisms leading to this phenomenon are still unknown. To obtain evidence of the site as well as of the process of erythrocyte damage, electron microscopical and histochemical investigations of renal biopsy materials from 19 patients with histologically defined glomerulonephritis were performed. The results suggest that the initial damage of erythrocytes in the glomerular area is reasoned by enzymatic glycocalyx destruction. On passage through the tubular system the osmotically sensitized surface altered cells undergo rapid hemolysis and losses of membrane skeletal proteins leading to dysmorphic shape transformations.

Adult↗
PubMed1994

Dysmorphic red cell formation in glomerulonephritis. 2. In vitro generation of dysmorphic erythrocytes.

In the present study influences leading to in vitro formation of dysmorphic erythrocytes were studied. Fresh and surface altered erythrocytes pretreated with several proteases were passed through different solutions representing distinct nephronís fluids. After passage of intact erythrocytes only 12-15% dysmorphic cells were observed. In case of protease treated cells the number of dysmorphic cells rose to 35-80%. The hemoglobin content was decreased. PAGE and electron microscopical findings demonstrated substantial losses of transmembrane and membrane skeleton proteins. It is assumed that surface protein degradation, loss of membrane skeleton proteins and hemolysis seem to be closely associated with dysmorphic malformation of urinary erythrocytes characteristical for glomerulonephritis.

Anisotropy↗
PubMed1992

[Microbiological studies of self-disinfecting alginate impression materials].

Using microbiologically experimental methods and observations corresponding to praxis the efficiency of the addition of antiseptics to alginate is evaluated. The addition of chlorhexidine to the alginate leads to a considerable reduction of the amounts of germs, but an one hundred percent disinfection of the alginates is not always performed. An influence of the alginate materials and the water quality on the antimicrobial efficacy of chlorhexidine has been proved. The always occurring contamination of the impression tray rules out a complete stopping of infection between the patient and the laboratory staff.

Alginates↗
PubMed1992

[The effect of biomaterials and other industrial materials on the growth of several aerobic bacterial species in vitro].

The article deals with interactions between bio-vitro-materials and bacteria species in vitro. The growth of S. aureus, Sc. salivarius, E. coli and Ps. aeruginosa in a salt solution with and without addition of biomaterials was examined until the day 60 in a static culture. By counting the cfu/ml and determination the relative change of germ capacity the results were compared. The data of such series obtained with working materials of similar chemical composition were collected and evaluated. We found, that Ps. aeruginosa was promoted in growth by all materials, especially those, which contained carbon. The same can be said about the last materials and E. coli. In contrast as well Ca- and P-containing as--free biomaterials reduced the numbers of germs. Changes of multiplying of S. aureus and Sc. salivarius seldom were observed. It ist apparent, that the biomaterials tested are not indifferent against a few germs, which may cause infections, but they promote the growth of a few species in vitro. This may favour an infection, if such materials should be implanted. It is proposed to test biomaterials microbiologically before clinical application. Materials with indifferent behavior or low anti-microbiological effect have to be favoured.

Bacteria, Aerobic↗
PubMed1991

Employment of merocyanine 540 fluorescence to form diaminobenzidine (DAB) oxidation product: a photoconversion method for the visualization of erythrocyte membrane fluidity for light and electron microscopy.

Intact native red blood cells (RBC) and treated RBC preparations were labelled with MC 540 and irradiated in the presence of diaminobenzidine (DAB). The polymerized diaminobenzidine reaction product is permanently stable in comparison with the labile fluorescence labelling. The brownish stained DAB polymerization product (DAB brown) and osmium black (after conversion of DAB brown with OsO4) allow the densitometrical determination with the light microscope. The latter product can be directly observed in the electron microscope. A direct correlation exists between the fluorescence intensity and the polymerized diaminobenzidine staining. It can be deduced that the enhancement of the DAB mediated contrast is reflecting an increased fluidity of the red cell membrane. The reaction was successful with all red cell preparations tested. This method is also suitable for the determination of fluidity changes in other cell membranes.

Diamide↗
PubMed1990

Polarization-optical investigation (topo-optical analysis) of the structure of the human erythrocyte glycocalyx. Influence of pH, ionic strength and diamide-induced spectrin cross linking.

The value of membrane anisotropy after fixation and topo-optical analysis of erythrocytes stained with toluidine blue is a measure for the degree of spatial order of the dyestuff-binding acidic residues of the glycocalyx and thus a parameter for the characterization of the glycocalyx structure. Lowering the pH value and/or the ionic strength of the staining medium results in a decrease of membrane anisotropy indicating a lower order of the anionic residues. In agreement with the findings of other authors this phenomenon seems to be connected with an expansion of the glycocalyx. Diamide-induced oxidative crosslinking of spectrin before fixation and staining with toluidine blue at physiological pH and ionic strength also results in a decreased anisotropy. This indirect influence on the glycocalyx structure may be caused by an increase of the charge density within the glycocalyx due to a diamide-induced rearrangement of the membrane skeleton and of the transmembrane proteins bound to it.

Diamide↗
PubMed1990

[Antibacterial efficiency and toxicity of hydrogen peroxide and other antiseptics].

The results suggest a relatively favourable relation between minimum bactericidal concentration (enterococci) and toxic agent concentration (chicken embryos) of hydrogen peroxide in comparison with chlorhexidin-digluconate, sodium-tosylchloramide and peracetic acid. For chlorhexidin-digluconate a somewhat more favourable relation between minimum bacteriostatic and toxic concentration of the agent was established.

Animals↗
PubMed1990

[Experimental microbiological research on instrument and denture disinfection with a disinfectant spray for dental practice and the use of patients. 2. Virological studies; the evaluation summary].

Carrier experiments using Echo- and Influenza-viruses on denture basis resins and fragments of orthodontic appliances resulted in good and even very good virucidal effects of disinfectant sprays Desident and Fesia-sept. The application of the disinfectant as spray seem to be advantageous, but is not recommendable. The diverse causes of this conclusion are discussed and an alternative way is proposed.

Aerosols↗
PubMed1990

[Experimental microbiological research on instrument and denture disinfection with a disinfectant spray for dental practice and the use of patients. 1. The formulation of the problem and bacteriological studies].

Three disinfectant sprays (Arugeen, Desident and Fesia-sept) proved to be very efficient against pure cultures of aero bacteria species, Cand. albicans, saliva flora and entero- and influenza viruses. The methods included carrier experiments using denture basis resins, fragments of orthodontic appliances and screws (instead of instruments).

Aerosols↗
PubMed1989

[Model studies of erythrophagocytosis in vitro].

Macrophages of the RHS are important for the elimination of aged and altered erythrocytes. An increase in the membrane bound autologous IgG generates a recognition signal in the plasmalemma, which triggers the RBC-phagocytosis. The IgG-receptors are buried in the band 3 proteins of the membrane. Enzymatic degradations or conformational changes of the glycocalyx are accompanied by an expression of these receptors. Similar effects were obtained after alteration of the membrane skeleton (crosslinking of the spectrin). A clustering of IgG-receptors due to interaction of the denatured hemoglobin (Heinz-bodies) with the membrane seems to be unlikely. Exovesiculation represents a process of formation of an intact membrane structure. Prolonged stay of RBC in the spleen can induce membrane altering continued by increased IgG loading.

Animals↗
PubMed1989

[Escape of hydrogen peroxide and oxygen from the root canal].

In vitro investigations demonstrate that hydrogen peroxide, like the oxygen emitted from the root canal, escapes into the area around the root. The amount measurable was dependent on the concentration, the amount of time that the hydrogen peroxide was left in the root canal and the patency of the foramen apicale. The growth of the Staphylococcus aureus (SG 511) was restricted in the area around those roots whose root canal contained a 5% solution of hydrogen peroxide.

Dental Pulp Cavity↗