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Biomedical subjects

H Appel

Publications and source records attributed to H Appel.

At least 37 records · Page 2Linked to original sources
PubMed1992

Influence of protein dynamics on the metal-sites of ovotransferrin.

Using the perturbed angular correlations (PAC) technique, the formation of hafnium-ovotransferrin complexes has been studied. Two binding configurations at each of the two specific binding-sites of the protein have been observed. They are characterized by well-defined electric quadrupole frequencies. Information about the dynamics of the protein was derived from temperature dependent measurements of the relaxation constant. The well-resolved spectra taken with fast BaF2-detectors allow a precise determination of the relaxation behaviour of the protein. The results are compared with the predictions from a hydrodynamic model for the reorientation of macromolecules. Thus the hydrodynamic volume of ovotransferrin and its N-terminal half-molecule were determined. The ovotransferrin volume is in agreement with a value derived for human serum transferrin from small angle neutron scattering. From experiments with immobilized protein material there is evidence for internal protein dynamics which is probed by the Hf-ion bound to the specific metal-sites.

Animals↗
PubMed1987

TDPAC studies of the metal-binding sites in serum transferrin: comparison between 181Hf-labeled human- and rat-serum transferrin.

The binding of hafnium to human serum transferrin was studied using the time differential perturbed angular correlation (TDPAC-) technique. The samples were prepared in vitro by adding 181Hf-NTA solution to human serum. Two specific electric quadrupole interactions were observed, which correspond to two well-defined binding configurations. Their relative intensities depend on the pH, salt- and hafnium-concentrations, and on the incubation time. The present data may be compared with the results of a previous rat serum study, where the hafnium binding to transferrin behaved rather similarly. Small but significant differences, however, can be deduced from the TDPAC-parameters for these human and rat transferrin species. For either binding configuration, the electric field gradient (EFG) is slightly higher in the case of rat transferrin. The most characteristic difference, however, concerns the asymmetry parameter eta 2 of the second binding configuration, which is about 10% smaller for rat serum transferrin. The TDPAC-technique might be used as a sensitive and reliable analytical method to study the metal-binding sites of different transferrin species.

Animals↗
PubMed1986

A hydrogen bond study in tobacco mosaic virus using Moessbauer spectroscopy.

The Moessbauer method was applied to obtain information on a suggested hydrogen bond in tobacco mosaic virus (TMV), between the hydroxyl group of Tyr 139 and a carboxyl oxygen of Glu 22 in a neighbouring subunit. Spectra of 129I were taken of 3,5-di-iodo-L-tyrosine as a free amino acid and in situ in TMV. The increase of the pK value of 3,5-di-iodo-L-tyrosine by 0.8 units at position 139 in TMV compared to the free value is a strong argument in favour of the existence of a hydrogen bond via the relevant hydroxyl group. The reported study demonstrates the surprising sensitivity of the observable Moessbauer parameters to details of the electronic configuration in the neighbourhood of the probe nucleus.

Biophysical Phenomena↗
PubMed1986

In vivo and in vitro studies of hafnium-binding to rat serum transferrin.

The binding of hafnium to rat serum transferrin was studied using the time differential perturbed angular correlation (TDPAC) technique. Hafnium is interesting as a toxic metal binding to transferrin because it behaves metabolically similarly to plutonium. The isotope 181Hf offers favorable access to the TDPAC-method. Samples were prepared in vivo by intravenous injection of Hf-NTA, Hf-citrate, and Hf-oxalate solutions, respectively, into Sprague-Dawley rats and in vitro by adding Hf-NTA solution to fresh rat serum. In both cases two specific electric quadrupole interactions were observed, which correspond to two well-defined binding configurations. They may be attributed to the N-terminal and the C-terminal binding site in the transferrin molecule. The 181Hf-distribution between these two binding states depends on pH, salt and hafnium concentrations, temperature, and incubation time. With a fast TDPAC-setup of four BaF2-detectors a time resolution of about 600 ps could be achieved. The specific binding configurations of 181Hf and the comparatively slow relaxation times lead to spectra of considerable accuracy.

Animals↗
PubMed1984

Diverse deoxyribonucleotide profiles in cultured human cells with differential sensitivity to thymidine.

Intracellular deoxyribonucleotide pools were examined before and after thymidine treatment in highly sensitive T-lymphoid cells, relatively resistant B-lymphoid cells and moderately sensitive melanoma cells. Among the 4 cell lines studied, proportions of the 4 deoxyribonucleotide pools varied appreciably while ribonucleotide profiles were similar. The ratio of dGTP to dCTP increased with sensitivity to thymidine. Increase in dTTP levels with increasing thymidine concentration was dependent on sensitivity of cells to thymidine and was accompanied by reduction in the dCTP pool. dGTP levels increased as did dTTP levels in all cells, while dATP pool expansion correlated with thymidine sensitivity. The results indicate an additional aspect of purine deoxyribonucleotide involvement in the growth inhibitory effects of thymidine.

B-Lymphocytes↗
PubMed1982

Purine modulation of thymidine activity in L1210 leukemia cells in vitro.

Alteration of purine metabolism using adenine was studied in mouse L1210 leukemia cells for its effect on dThd-mediated inhibition of growth and deoxyribonucleotide pool perturbations. Inhibition of cell growth caused by 10 to 50 microM dThd was enhanced more than additively by 100 microM adenine which was only slightly inhibitory when administered alone. Adenine at 100 microM affected ribonucleotide levels by expanding the ATP pool and causing slight decreases in the GTP, UTP and CTP pools, while dThd alone or in combination with adenine had no effect on ribonucleotide pools. dThd at 10 microM caused a more than 2-fold increase in the dTTP pool and a marked but transient decrease in the dCTP pool with lesser effects on purine deoxyribonucleotide levels. Adenine at 100 microM produced only slight, transient increase in the dATP pool. Exposure of cells to dThd plus adenine compared with individual agents produced more than additive increases in dTTP and dATP pools. The decrease in the dCTP level was more with combined agents than with dThd alone. The results showed that an alteration in adenine nucleotide pools modifies the activity of dThd through greater enhancement of dTTP levels leading to a greater suppression of the dCTP pool.

Adenine↗
PubMed1981

Inhibition of cell growth by N-(phosphonacetyl)-L-aspartate in human and murine cells in vitro.

Two murine cell lines, L1210 leukemia (T-cell) and B16 melanoma, and 3 human cell lines, CCRF-CEM leukemia (T-cell), NC37 lymphoblasts (B-cell) and IPC-48 melanoma were compared with respect to sensitivity to N-(phosphonacetyl)-L-aspartate (PALA), growth rate and aspartate transcarbamylase activity. No correlation between drug sensitivity and growth rate was found. The melanoma cell lines were more sensitive to PALA than were the lymphocytic cell lines. The 2 T-cell leukemia lines had similar sensitivities to PALA while the B-lymphoblasts were more resistant at 10(-3) M PALA and less resistant at 10(-4) M PALA than were L1210 and CCRF-CEM cells. Aspartate transcarbamylase activity was similar among the 2 melanoma cell lines and among the 3 lymphocytic cell lines and was 2-fold higher in the latter.

Animals↗
PubMed1981

[Experimental neurotraumatology--rotation (author's transl)].

Experimental simulations of motion of the brain at impact were carried out. Rotational accelerations from 2,000 up to 8,000 rad/s2 with durations of 8 to 32 ms were applied to preparations of human skull and brain. The tests were filmed with a high-speed camera with up to 3,000 frames/s. Due to inertia there were relative motion and displacement of the upper part of the brain relative to the skull-cap. Marked displacements (maximum: 2cm) were observed on atrophied brains. Test results are discussed and compared with other investigations.

Acceleration↗
PubMed1980

[Actinomycotic cerebral abscess. Apropos of a case].

A case of an actinomycotic brain abscess in an adult patient apparently free of systemic infection is presented. The rarity of this etiology of brain abscess is underlined. The patient was treated by complete surgical excision and prolonged antibiotic therapy with penicillin. The authors stress the importance of taking into account this infrequent cause of brain abscess, the necessity of radical surgical treatment followed by intensive, prolonged and adequate antibiotic therapy, as the only means of reducing the high mortality rate.

Actinomycosis↗
PubMed1978

[Patterns of injuries of restrained car passengers (author's transl)].

A detailed analysis of actual traffic accidents involving car passengers wearing seat belts was carried out by an interdisciplinary team. The passengers were examined for the severity of their injuries, the combination of their injuries, and the practicality of their seat belt system. The type of injury to the car, the speed, and the line of impact were related to the injuries. Incorrect use of the belt system, malfunction due to external causes, and construction defects in the seat belt system were described and evaluated according to their specific importance.

Accidents, Traffic↗