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Biomedical subjects

R Naumann

Publications and source records attributed to R Naumann.

45 records · Page 3Linked to original sources
PubMed1986

Protein crystal growth. Growth kinetics for tetragonal lysozyme crystals.

A method for immobilizing protein crystals has been devised for determining face growth rates, and used to investigate the growth kinetics of hen egg white lysozyme crystals. Growth rates were determined at 22 degrees C in 0.1 M sodium acetate, 5% NaCl, pH 4.0, on the visually identified (110) face of tetragonal lysozyme crystals. Protein concentrations ranged from 13 to 57 mg/ml (saturation concentration = 1.7 mg/ml). Growth rate data were fit to the equation R = kappa sigma ri, where R = rate in cm/s; kappa = constant; sigma i = solute growth interface supersaturation; and r = rate dependence upon super-saturation, with the result that kappa = 0.146 X 10(-8) cm/s and r = 2.0. A model of the growth process was developed and the experimental data were used to determine the relative roles of transport and interfacial kinetics in the growth of this crystal. Values for the width of the boundary layer delta, the interfacial concentration Ci, and growth rate R were determined. The model may be used to extrapolate to other growth conditions. The relative role of transport and interfacial kinetics can be expressed by the coefficient gamma = (CB - Ci)/(CB - Cs), when CB is the bulk concentration and Cs the saturation. Values for gamma were found to range from much less than 0.1 for submicron-size crystals to approximately 0.15 for cm sizes. The results indicate that attachment or surface effects are rate-limiting in lysozyme crystal growth in Earth's gravity because solutal convection always provides more transport of solute than can be accommodated by the interface. In order to grow such crystals under transport limiting conditions, it would be necessary to suppress this solutal convection.

Animals↗
PubMed1985

Investigation of the carbohydrate metabolism of normal and neoplastic hepatocytes using 2,6-dichlorophenolindophenol as a probe for NAD(P)H production measured by voltammetry.

An electrochemical technique is described for measurement of intracellular NAD(P)H production. This technique involves an auxiliary redox system taken up by the cells which is then measured voltammetrically after reduction by NAD(P)H. The redox system used was 2, 6-dichlorophenolindophenol (DCPIP). It was shown to undergo a quasi-reversible two-electron transfer at the rotating gold disc electrode serving as an indicator electrode. The anodic wave of the reduced form of DCPIP was taken to indicate the amount of NAD(P)H produced by metabolic processes with glucose as substrate for a given number of cells. The following types of cell were investigated in suspension: Morris hepatoma 3924, a hepatocyte-derived cell line, and normal hepatocytes. Marked differences between normal and transformed cells were found under aerobic compared to anaerobic conditions. These were explained in terms of alterations in carbohydrate metabolism, e.g., Pasteur effect occurring on cell transformation.

2,6-Dichloroindophenol↗
PubMed1985

Voltammetric measurements of the kinetics of enzymatic reduction of 2, 6-dichlorophenolindophenol in normal and neoplastic hepatocytes using glucose as substrate.

Amperometric methods were used to study reaction kinetics of 2, 6-dichlorophenolindophenol (DCPIP) with NADH in the homogeneous phase. The second-order rate constant of the reaction was calculated to be 2.4 M-1 . s-1 at 37 degrees C. The reoxidation of the reduced form of DCPIP in air-saturated phosphate-buffered saline was found to follow pseudo-first-order reaction kinetics with rate constant of 5.9 X 10(-4) s-1. These data were compared to the reduction of DCPIP in suspensions of normal and neoplastic hepatocytes, in the absence and presence of oxygen. The reduction of DCPIP by intracellular NAD(P)H was shown to follow mixed-type reaction kinetics different from those of the homogeneous phase. From this, the conclusion was drawn that complexes of enzymes transferring electrons to and from NAD(P)H are involved in intracellular reduction of DCPIP.

Animals↗
PubMed1985

[Clinical relevance of protease inhibitors in nasal secretions].

The normal human nasal mucous membrane is protected against negative effects of proteases by special inhibitors. This inhibitor pool consists of both secretory-specific and humoral inhibitors. A method is presented to determine the function of protease inhibitors in nasal secretion. Investigations have been carried out on secretions of healthy subjects, as well as patients suffering from sinusitis. The differences are illustrated. The results enable an evaluation of the degree of infection; the course of the disease can be documented. A possibility of producing synthetic inhibitors for therapy is discussed.

Blood Proteins↗
PubMed1979

Rat liver alterations after chronic treatment with hexachlorobenzene.

Groups of female rats were treated orally with 0.5, 2.0, 8.0, and 32 mg/kg hexachlorobenzene twice a week for 203 days. The liver content of hexachlorobenzene was found to be dose-dependent. In the animals treated with the highest dose the concentration was 273 mug/g hexachlorobenzene. In the fresh and fixed hepatic tissue of the treated animals pink fluorescence was observed. Electron microscopy revealed a dose dependent enlargement of all hepatocytes due to proliferation of the SER in the centrolobular area or to increased glycogen deposits (beta- or alpha-particles) and SER in the intermediary and periportal area. Numerous porphyrin deposits and siderosomes, intimate disorganisation and moderate dislocation of the RER and a moderate enlargement of bizarre-sharped mitochondria were recognized. The relationship between porphyrin crystals and mitochondria on the one hand and between SER and glycogen deposits on the other is discussed.

Animals↗
PubMedDate not supplied

Transverse leukonychia following chemotherapy in a patient with Hodgkin's disease.

Nail changes often represent diagnostic hallmarks for a variety of systemic diseases. The awareness of drug-induced nail injuries is important in order to avoid unnecessary diagnostic activities. We observed a 21-year-old female patient with Hodgkin's lymphoma, who developed transverse leukonychia of all fingernails associated with polychemotherapy.

Adult↗