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Biomedical subjects

H Ruf

Publications and source records attributed to H Ruf.

At least 19 recordsLinked to original sources
PubMed1999

Size distributions of chylomicrons from human lymph from dynamic light scattering measurements.

Chylomicrons, the vehicles for the transport of exogeneous triglycerides and cholesterol in the lymph and the blood, were characterized by their size from dynamic light scattering measurements. To achieve an appropriate resolution, correlation data were collected over several hours. Analysis was performed with an extended version of the regularization method CONTIN, and special attention was given to errors in the experimental baseline and to randomness of the residuals. The solutions selected by means of Fisher's F-test by CONTIN agreed with those obtained with the stability plot of Schnablegger and Glatter, when in the case of data of lower statistical accuracy the solution was taken from the lower part of the confidence interval of the F-test. The intensity-weighted size distributions indicated two classes of particle, their mean diameters being 100-140 nm and 330-350 nm. The ability to resolve two peaks of such a size ratio is demonstrated. The numbers of particles associated with the two peaks were estimated by means of the scattering properties of the particles, which showed that the overwhelming majority were small ones. This estimation also suggested that the mean size of the first peak of the number distribution is significantly smaller than the typical size of chylomicrons. This was consistent with the finding that the sample contained not only apolipoprotein B-48 but also a similar amount of apolipoprotein B-100, which is associated with lipoproteins of smaller size. The larger particles of the second peak are probably dietary triglyceride-rich chylomicrons.

Algorithms↗
PubMed1994

Influence of vesicle curvature on fluorescence relaxation kinetics of fluorophores.

The effect of membrane curvature on the fluorescence decay of 2-p-toluidinyl-naphthalene-6-sulfonic acid (TNS), 2-(9-anthroyloxy) stearic acid (2-AS) and 12-(9-anthroyloxy)-stearic acid (12-AS) was investigated for egg lecithin vesicles of average diameter dm = 22 nm and 250 nm. The biexponential fluorescence decay of TNS at the red edge of the emission spectrum was analysed according to the model of Gonzalo and Montoro [1]. Over the entire temperature range (1-40 degrees C) the small TNS labelled vesicles showed significantly shorter solvent relaxation times tau(r) than their larger counterparts (e.g. 1.3 ns compared with 2.1 ns at 5 degrees C), indicating a higher mobility of the hydrated headgroups in the highly curved, small vesicles. The fluorescence decay of both AS derivatives is also biexponential. While the shorter decay times (1-3 ns) are practically identical for small and large vesicles, the longer decay times (5-14 ns) are identical only for 12-AS but not for 2-AS. This indicates that the microenvironment is similar in small and large vesicles deep in the membrane in spite of the differences in curvature.

Journal Article↗
PubMed1992

[Contribution of Doppler in fetal prognosis].

Uteroplacental and cerebral artery velocimetry is a predictive factor in the outcome of many high-risk pregnancies. Positive predictive value is good for intrauterine growth retardation (complications due to preeclampsia, diabetes or twin pregnancy). Velocimetry is also a predictor of adverse outcome in small for gestational age fetuses and for oligohydramnios but not for anemic fetuses of isoimmune pregnancies or post-term pregnancies.

Cerebral Arteries↗
PubMed1992

Ionics and conformational transitions of Na,K-ATPase.

Equilibrium binding studies have been carried out by spectrofluorometric precision titrations on FITC-Na,K-ATPase and employing the styryl dye RH-421 to obtain equilibrium constants and stoichiometric coefficients together with information related to competition between different binding equilibria. A new interpretation concerning the assignment of spectral properties and cation complex formation equilibria, as well as the involvement of conformational transitions, is suggested, based on a differentiation between selective and unselective alkali ion binding. The kinetics of K+ binding to the FITC-enzyme have been studied by employing a new microvolume technique consisting of flash photolysis of caged-K+.

Animals↗
PubMed1989

Effects of normalization errors on size distributions obtained from dynamic light scattering data.

This paper presents a study of the influence of normalization errors on size distributions obtained from the analysis of intensity fluctuations by photon correlation spectroscopy. The effects of these errors are demonstrated by means of computer-generated autocorrelation functions simulating light scattered from a monomodal Schulz distribution of small, spherical, unilamellar lipid vesicles. The calculations show that even small errors in the baseline, modifying the data upon normalization systematically, will cause serious errors in the estimated size distribution. As it turns out this is due to the peculiar characteristics of normalization errors in data of the first order autocorrelation function. The errors introduced there are described in parts by functions of the delay time having positive exponents. Such components are not considered in the integral equations commonly used to analyze the measured data. The error's property to be a function of delay time in turn enables us to obtain the relative baseline error from the inversion of the data. The new method for its determination is described in some detail. Here, it has been realized with a modified version of the size distribution algorithm CONTIN.

Light↗
PubMed1989

Caged-Ca2+: a new agent allowing liberation of free Ca2+ in biological systems by photolysis.

The alkaline earth cation complexes of DM-nitrophen [1-(2-nitro-4,5-dimethoxyphenyl)-N,N,N',N'-tetrakis-[(oxycarbonyl) methyl]- 1,2-ethanediamine)] release the bound cation in the millisecond time range upon irradiation by a short UV-light pulse. This technique allows to generate cation (eg. Ca2+) concentration jumps or pulses in solution or in cellular systems. The physico-chemical properties of DM-nitrophen and its Mg2+, Ca2+ and Ba2+ complexes are investigated by employing spectrophotometric and potentiometric techniques. In case of Ca2+ a stability constant of the complex up to nearly 10(11) M-1 is found. The magnitude of representative Mg2+ and Ca2+ concentration jumps which can be generated under realistic experimental conditions are calculated on the basis of the thermodynamic parameters reported here.

Acetates↗
PubMed1988

[Psychotropic drugs and pregnancy].

The multiplicity of psychotropic medications and their widespread prescription, justifies a review of the possible effect of psycholeptics and psycho-analeptics on the fetus in-utero, and on lactation. The authors attempt to differentiate between diverging if not conflicting opinions in most cases. They conclude that it is necessary to prescribe these products only with precise indications and after careful consideration.

Abnormalities, Drug-Induced↗
PubMed1987

The kinetics of binding of o-methyl red to the outer surface of unilamellar spherical phospholipid vesicles.

The kinetics of adsorption of the proton carrier o-methyl red to the surface of unilamellar spherical phospholipid vesicles have been investigated by means of the temperature-jump relaxation technique with absorbance detection. Single-exponential relaxation curves were observed with time constants in the range 30-130 microseconds. o-Methyl red binds in both its anionic form A- and protonated form AH. Adsorption-desorption of the two species is coupled by two fast protolytic reactions, occurring in the aqueous bulk phase and in the surface region of the membrane. The rate constants for adsorption and desorption of the two species were obtained from the dependences of the relaxation time on lipid concentration at different pH values. The analysis yielded apparent adsorption rate constants of kasAH = 9.8 X 10(6) M-1 s-1 and kasA = 1.3 X 10(6) M-1 s-1 (expressed in terms of monomeric lipid), and kasAH = 1.2 X 10(11) M-1 s-1 and kasA = 1.6 X 10(10) M-1 s-1 (expressed in terms of vesicle concentration). From the order of these rate constants it is concluded that adsorption of both species is actually diffusion-controlled. The peculiar pH dependence of the relaxation time is a consequence of the protolytic reaction in the surface region of the membrane. Its implication for the kinetics of adsorption-desorption processes are discussed.

Azo Compounds↗
PubMed1987

[AIDS and pregnancy. Management of the seropositive pregnant female].

The population of women, HIV positive, and susceptible to become pregnant, increases with time. Pregnancy must be contra-indicated in seropositive women. A termination of pregnancy must be performed in the first trimester and a therapeutic abortion may be offered but left to the mother's decision. Delivery must be carried out via natural passages in the absence of obstetrical dystocia. Nursing is contra-indicated. A number of precautions must be taken by the medical and para-medical personnel during obstetrical procedures.

Abortion, Therapeutic↗
PubMed1987

Reconstitution of the erythrocyte anion transport system: recent progress.

The anion transport system of the human erythrocyte membrane was reconstituted in phosphatidylcholine vesicles by a new procedure. The reconstituted system shows all major properties of the sulfate transport system found in the erythrocyte membrane (Scheuring, U., K. Kollewe, W. Haase, and D. Schubert: J. Membrane Biol. 90, 123-135 (1986)). Modifications of the reconstitution method have now led to increased values of the internal volumes of the protein-lipid vesicles and of the average turnover number of the transport protein (which is now larger than in the erythrocyte membrane). Gel filtration on Sephacryl S-1000 has allowed the isolation of vesicles of a narrow size distribution.

Anions↗