Perfluorooctanoic acid rigidifies a model lipid membrane.

We report a combined dynamic light scattering and neutron spin-echo (NSE) study on vesicles composed of the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine under the influence of varying amounts of perfluorooctanoic acid. We study local lipid bilayer undulations using NSE on time scales up to 200 ns. Similar to the effect evoked by cholesterol, we attribute the observed lipid bilayer stiffening to a condensing effect of the perfluorinated compound on the membrane.

Influence of charge density on bilayer bending rigidity in lipid vesicles: a combined dynamic light scattering and neutron spin-echo study.

We report a combined dynamic light scattering and neutron spin-echo study on vesicles composed of the uncharged stabilizing lipid 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) and the cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP). Mechanical properties of a model membrane and thus the corresponding bilayer undulation dynamics can be specifically tuned by changing its composition through lipid headgroup or acyl chain properties. We compare the undulation dynamics in lipid vesicles composed of DMPC/DOTAP to vesicles composed of a mixture of the uncharged helper lipid DMPC with the also uncharged reference lipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). We have performed dynamic light scattering on the lipid mixtures to investigate changes in lipid vesicle size and the corresponding center-of-mass diffusion. We study lipid translational diffusion in the membrane plane and local bilayer undulations using neutron spin-echo spectroscopy, on two distinct time scales, namely around 25 ns and around 150 ns. Finally, we calculate the respective bilayer bending rigidities κ for both types of lipid vesicles. We find that on the local length scale inserting lipid headgroup charge into the membrane influences the bilayer undulation dynamics and bilayer bending rigidity κ less than inserting lipid acyl chain unsaturation: We observe a bilayer softening with increasing inhomogenity of the lipid mixture, which could be caused by a hydrophobic mismatch between the acyl chains of the respective lipid components, causing a lateral phase segregation (domain formation) in the membrane plane.

Influence of cholesterol on the collective dynamics of the phospholipid acyl chains in model membranes.

We have studied the packing and collective dynamics of the phospholipid acyl chains in a model membrane composed of 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) and cholesterol in varied phase state. After a structural characterization of this two-component model bilayer using X-ray reflectivity, we have carried out coherent inelastic neutron scattering to investigate the chain dynamics. Both DMPC/cholesterol membranes exhibited much sharper and more pronounced low-energy inelastic excitations than a pure DMPC membrane. In the high-energy regime above 10 meV, the insertion of cholesterol into the membrane was found to shift the position of the inelastic excitation towards values otherwise found in the pure lipids gel phase. Thus, the dissipative collective short-range dynamics of the acyl chains is strongly influenced by the presence of cholesterol.

Biochemical activities of berberine, palmatine and sanguinarine mediating chemical defence against microorganisms and herbivores.

The alkaloids berberine, palmatine and sanguinarine are toxic to insects and vertebrates and inhibit the multiplication of bacteria, fungi and viruses. Biochemical properties which may contribute to these allelochemical activities were analysed. Acetylcholine esterase, butyrylcholinesterase, choline acetyl transferase, alpha 1- and alpha 2-adrenergic, nicotinergic, muscarinergic and serotonin2 receptors were substantially affected. Sanguinarine appears to be the most effective inhibitor of choline acetyl-transferase (IC50 284 nM), while the protoberberines were inactive at this target. Berberine and palmatine were most active at the alpha 2-receptor (binding with IC50 476 and 956 nM, respectively). Furthermore, berberine and sanguinarine intercalate DNA, inhibit DNA synthesis and reverse transcriptase. In addition, sanguinarine (but not berberine) affects membrane permeability and berberine protein biosynthesis. In consequence, these biochemical activities may mediate chemical defence against microorganisms, viruses and herbivores in the plants producing these alkaloids.

Linear analysis applied to the comparative study of the I-D-P phase of chlorophyll fluorescence as induced by actinic PS-II light, PS-I light and changes in CO2-concentration.

The investigation of the kinetics of chlorophyll-fluorescence under continuous background light enables the application of linearizing conditions. This approach, which provides a quantitative evaluation by means of curve-fitting routines, is applied to the investigation of the linear kinetics of the I-D-P phase. Using changes in PS II-light, PS I-light and in CO2-concentration as input signals showed that a pool at the acceptor side of PS I, in addition to the plastoquinone pool, plays an essential role in the generation of the dip. The occurrence of the dip is related to the sign of the faster one of the two components related to the I-D and the D-P phase. This sign can be inverted by the ratio of PS I and PS II light. However, model calculations show that the change of this sign does not allow a decision which one of the two components is related to which one of the two pools. The dependence of the sign of the faster component on light conditions can generate different types of I-D-P transitions, namely nearly monophasic increases, sigmoid responses or dips. As these phenomena are already created by the linear responses, non-linear effects or additional loops between PS II and PS I are not required for the explanation of the basic features.

Standard deviation score charts of skeletal maturity and its velocity in Swedish children assessed by the Tanner-Whitehouse method (TW2-20).

Reference values, means and standard deviations for skeletal maturity of Swedish children, evaluated in terms of the Tanner-Whitehouse method (TW2-20), have been expressed in mathematical functions. Almost 4000 radiograms have been assessed. The radiograms were taken on 212 children aged between one month and 18 years as part of a longitudinal study of growth and development. Up to the age of 10 years, the Swedish children had a more advanced skeletal maturation (about 0.5 SD) than the British children. Means and standard deviations have been used in preference to medians and centiles, since this makes it possible to use the results in the assessment of children with grossly deviating maturation. The selected functions were chosen in order to give a good description of the empirical distributions and no biological implications of the estimated parameters were sought. This method improves the assessment of skeletal maturity in several respects; reference values are given parametrically, which facilitates the computing of the individual standard deviation scores, and reference charts are presented for both attained scores and velocity scores (for boys between one and 13 years and for girls between one and 11 years).

Long-term treatment with corticosteroids/ACTH in asthmatic children. IV. Skeletal maturation.

Skeletal maturation in severe bronchial asthma was studied in 15 children during and after treatment with depot tetracosactrin and in 6 children during treatment with prednisolone. Attained skeletal maturity before treatment was below the reference mean in the majority of children. Skeletal maturation was enhanced during treatment with depot tetracosactrin, which led to more advanced attained skeletal maturity at withdrawal than at start of treatment. There was a tendency towards larger increases of skeletal maturity than of height. The influence of adrenal androgens, released by ACTH-stimulation and good control of the disease are probably relevant factors for the acceleration of skeletal maturation. After withdrawal of depot tetracosactrin the rate of skeletal maturation normalized. During prednisolone treatment there was a delay of skeletal maturation leading to a progressive relative decrease of attained skeletal maturity, and closely related to a delay in linear growth. Treatment with depot tetracosactrin may thus induce enhancement of skeletal maturation, but with the treatment regimen found to be efficacious in bronchial asthma, the effect is not very pronounced and does not perceptibly affect the ultimate outcome of growth.

V. a new method for the assessment of skeletal maturity- the mat- method (mean appearance time of bone stages).

By means of probit analysis of the age at the appearance of the various bone stages according to Tanner-Whitehouse and using a logarithmic time concept (logarithmic conceptional age), a new approach to the evaluation of skeletal maturity has been elaborated. The maturity score of each bone stage corresponds to th4 mean maturity level of the observation of being within each stage. The individual maturity level is calculated by averaging the maturity scores of the stages of the various bones and is then evaluated is standard deviation scores by comparing with teh Gaussian fitted distribution of averages maturity scores of the age of the child examined. Special conditions apply for the scoring of a first and a last bone stage in a sequence, which will introduce less bias in the estimation of individual skeletal maturity with the MAT-method than with the TW-method. Ossification during early infancy can be evaluated and sequence polymorphism be detected by using the bone stage chart of the MAT-method.

IV. skeletal development from birth to 7 years.

The skeletal development of 212 randomly selected Swedish urban children has been investigated as part of a prospective longitudinal study of growth and development. Radiograms of the hand and wrist were taken at specified ages. Up to the age of seven years 2.191 radiograms were assessed. When comparing the timing of the first ossification of the various bones in the present study and an older Swedish investigation a secular trend was found. In contrast to a North-American growth study, there was a striking similarity of the pattern of the first ossification in the two Swedish investigations for both sexes separately. However, the relative sex differences of the ossification were quite similar in the North-American growth study and the present investigation. In comparison with British children the skeletal development of Swedish children was advanced at all ages, the advancement being greater for epiphyseal bones than for carpal bones.