Dos episodios de secuestro esplénico en un lactante con drepanocitosis homozigota / Two splenic sequestrations in an infant with homozygous sickle cell anemia

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Evaluation of the effects of East Indian sandalwood oil and alpha-santalol on humans after transdermal absorption.

The aim of the study was to investigate the effects of East Indian sandalwood oil ( Santalum album, Santalaceae) and alpha-santalol on physiological parameters as well as on mental and emotional conditions in healthy human subjects after transdermal absorption. In order to exclude any olfactory stimulation, the inhalation of the fragrances was prevented by breathing masks. Eight physiological parameters, i. e., blood oxygen saturation, blood pressure, breathing rate, eye-blink rate, pulse rate, skin conductance, skin temperature, and surface electromyogram were recorded. Subjective mental and emotional condition was assessed by means of rating scales. While alpha-santalol caused significant physiological changes which are interpreted in terms of a relaxing/sedative effect, sandalwood oil provoked physiological deactivation but behavioral activation. These findings are likely to represent an uncoupling of physiological and behavioral arousal processes by sandalwood oil.

Functional magnetic resonance imaging of human olfaction.

Olfaction is our basic sense phylogenetically and embryologically. Little is known, however, about how the human brain encodes the quality of odors, odor-associated memories, and emotions. Olfactory information is projected from the olfactory bulb to the primary olfactory cortex, which is composed of the anterior olfactory nucleus, the olfactory tubercle, the piriform cortex, the amygdala, the periamygdaloid region, and the entorhinal cortex. From there, the primary olfactory cortex projects to secondary olfactory regions including the hippocampus, ventral striatum and pallidum, hypothalamus, thalamus, orbitofrontal cortex, agranular insular cortex, and cingulate gyrus. Functional MR studies using olfactory stimuli as paradigms show activation of many of these areas and can advance our understanding of odor perception in humans.

The lactose transport protein is a cooperative dimer with two sugar translocation pathways.

The Major Facilitator Superfamily lactose transport protein (LacS) undergoes reversible self-association in the detergent-solubilized state, and is present in the membrane as a dimer. We determined the functional unit for proton motive force (Deltap)-driven lactose uptake and lactose/methyl-beta-D-galactopyranoside equilibrium exchange in a proteoliposomal system in which a single cysteine mutant, LacS-C67, defective in Deltap-driven uptake, was co-reconstituted with fully functional cysteine-less protein, LacS-cl. From the quadratic relationship between the uptake activity and the ratio of LacS-C67/LacS-cl, we conclude that the dimeric state of LacS is required for Deltap-driven uptake. N-ethylmaleimide (NEM) treatment of proteoliposomes abolished the LacS-C67 exchange activity but left the LacS-cl unaffected. After NEM treatment, the exchange activity decreased linearly with increasing ratios of LacS-C67/LacS-cl, suggesting that the monomeric state of LacS is sufficient for this mode of transport. We propose that the two subunits of LacS are functionally coupled in the step associated with conformational reorientation of the empty binding site, a step unique for Deltap-driven uptake.

Xyloside transport by XylP, a member of the galactoside-pentoside-hexuronide family.

This paper describes the functional characterization of the xyloside transporter, XylP, of Lactobacillus pentosus with the aid of a spectroscopy-based assay system. In order to monitor the transport reaction, the natural xyloside isoprimeverose, a building block of hemicellulose, and the analogue methyl-isoprimeverose were chemically synthesized by a new and efficient procedure. The XylP protein was purified by metal affinity chromatography, following high level expression in Lactococcus lactis from the nisin-inducible promoter. The purified XylP protein was incorporated into liposomes, in which the glucose dehydrogenase from Acinetobacter calcoaceticus (sGDH) was entrapped. sGDH can oxidize aldose sugars in the presence of dichlorophenol-indophenol as electron acceptor. The coupled assay thus involves XylP-mediated isoprimeverose uptake followed by internal oxidation of the sugar by sGDH, which can be monitored from the reduction of 2,6-dichlorophenol-indophenol at 600 nm. The uptake of isoprimeverose was stimulated by the presence of the non-oxidizable methyl-isoprimeverose on the trans-side of the membrane, indicating that exchange transport is faster than unidirectional downhill uptake. Unlike other members of the galactoside-pentoside-hexuronide family, XylP does not transport monosaccharides (xylose) but requires a glycosidic linkage at the anomeric carbon position. Consistent with a proton motive force-driven mechanism, the uptake was stimulated by a membrane potential (inside negative relative to outside) and inhibited by a pH gradient (inside acidic relative to outside). The advantages of the here-described transport assay for studies of carbohydrate transport are discussed.

Hierarchical control versus autoregulation of carbohydrate utilization in bacteria.

The involvement of phosphoeno/pyruvate:sugar phosphotransferase (PTS) proteins, like HPr and IIA(Glc), in the regulation of carbohydrate utilization has been well established in Gram-negative and Gram-positive bacteria. The majority of the studies of PTS-mediated regulation have been concerned with the hierarchical control of carbohydrate utilization, which results in the preferential utilization of a particular carbohydrate from a mixture of substrates. The underlying mechanisms of PTS-mediated hierarchical control involve the inhibition of expression of other catabolic enzymes and transporters and/or the allosteric regulation of their activity, which prevents the transcriptional inducer to be formed or taken up into the cell. More recently, it has become clear that PTS components allow also the cell to tune the uptake rate(s) to the carbohydrate availability in the medium and the metabolic capacity of the cell. The different phosphorylated species of HPr play a central role in this autoregulatory control circuit, both at the gene and at the protein level. Our knowledge of hierarchical control and autoregulation of carbohydrate utilization in bacteria is discussed.

The influence of essential oils on human attention. I: alertness.

Scientific research on the effects of essential oils on human behavior lags behind the promises made by popular aromatherapy. Nearly all aspects of human behavior are closely linked to processes of attention, the basic level being that of alertness, which ranges from sleep to wakefulness. In our study we measured the influence of essential oils and components of essential oils [peppermint, jasmine, ylang-ylang, 1,8-cineole (in two different dosages) and menthol] on this core attentional function, which can be experimentally defined as speed of information processing. Substances were administered by inhalation; levels of alertness were assessed by measuring motor and reaction times in a reaction time paradigm. The performances of the six experimental groups receiving substances (n = 20 in four groups, n = 30 in two groups) were compared with those of corresponding control groups receiving water. Between-group analysis, i.e. comparisons between experimental groups and their respective control groups, mainly did not reach statistical significance. However, within-group analysis showed complex correlations between subjective evaluations of substances and objective performance, indicating that effects of essentials oils or their components on basic forms of attentional behavior are mainly psychological.

Effects of chiral fragrances on human autonomic nervous system parameters and self-evaluation.

The effects of chiral fragrances (enantiomers of limonene and carvone) on the human autonomic nervous system (ANS) and on self-evaluation were studied in 20 healthy volunteers. Each fragrance was administered to each subject by inhalation using an A-A-B design. Individuals were tested in four separate sessions; in one session one fragrance was administered. ANS parameters recorded were skin temperature, skin conductance, breathing rate, pulse rate, blood oxygen saturation and systolic as well as diastolic blood pressure. Subjective experience was assessed in terms of mood, calmness and alertness on visual analog scales. In addition, fragrances were rated in terms of pleasantness, intensity and stimulating property. Inhalation of (+)-limonene led to increased systolic blood pressure, subjective alertness and restlessness. Inhalation of (-)-limonene caused an increase in systolic blood pressure but had no effects on psychological parameters. Inhalation of (-)-carvone caused increases in pulse rate, diastolic blood pressure and subjective restlessness. After inhalation of (+)-carvone increased levels of systolic as well as diastolic blood pressure were observed. Correlational analyses revealed that changes in both ANS parameters and self-evaluation were in part related to subjective evaluation of the odor and suggest that both pharmacological and psychological mechanisms are involved in the observed effects. In conclusion, the present study indicates that: (i) prolonged inhalation of fragrances influences ANS parameters as well as mental and emotional conditions; (ii) effects of fragrances are in part based on subjective evaluation of odor; (iii) chirality of odor molecules seems to be a central factor with respect to the biological activity of fragrances.

A spectroscopic assay for the analysis of carbohydrate transport reactions.

A carbohydrate-transport assay was developed that does not require isotopically labelled substrates, but allows transport reactions to be followed spectrophotometrically. It makes use of a membrane system (hybrid membranes or proteoliposomes) bearing the transport system of interest, and a pyrroloquinoline quinone-dependent aldose dehydrogenase [soluble glucose dehydrogenase (sGDH)] and the electron acceptor 2,6-dichloroindophenol (Cl2Ind) enclosed in the vesicle lumen. After transport across the vesicular membrane, the sugar is oxidized by sGDH. The accompanying reduction of Cl2Ind results in a decrease in A600. The assay was developed and optimized for the lactose carrier (LacS) of Streptococcus thermophilus, and both solute/H+ symport and exchange types of transport could be measured with high sensitivity in crude membranes as well as in proteoliposomes. To observe exchange transport, the membranes were preloaded with a nonoxidizable substrate analogue and diluted in assay buffer containing an oxidizable sugar. Transport rates measured with this assay are comparable with those obtained with the conventional assay using isotopically labelled substrates. The method is particularly suited for determining transport reactions that are not coupled to any form of metabolic energy such as uniport reactions, or for characterizing mutant proteins with a defective energy-coupling mechanism or systems with high-affinity constants for sugars.

Azide reduces the hydrophobic barrier of the bacteriorhodopsin proton channel.

The sensitivity of a nitroxide spin label to the polarity of its environment has been used to estimate the hydrophobic barrier of the proton channel of the transmembrane proton pump bacteriorhodopsin. By means of site-specific mutagenesis, single cysteine residues were introduced at 10 positions located at the protein surface, in the protein interior, and along the proton pathway. After reaction with a methanethiosulfonate spin label, the principle values of the hyperfine tensor A and the g-tensor were determined from electron paramagnetic resonance spectra measured at 170 K. The shape of the hydrophobic barrier of the proton channel is characterized in terms of a polarity index, DeltaA, determined from the variation of the hyperfine coupling constant Azz. The maximum of the hydrophobic barrier is found to be close to the retinal chromophore in the proton uptake pathway. The effect of the asymmetric distribution of charged and polar residues in the proton release and uptake pathways is clearly reflected in the behavior of the hydrophobic barrier. The presence of azide reduces the barrier height of both the cytoplasmic and extracellular channels. This finding supports the view of azide and other weakly acidic anions as catalysts for the formation of hydrogen-bonded networks in proton pathways of proteins.

Mechanism of osmotic activation of the quaternary ammonium compound transporter (QacT) of Lactobacillus plantarum.

The accumulation of quaternary ammonium compounds in Lactobacillus plantarum is mediated via a single transport system with a high affinity for glycine betaine (apparent Km of 18 microM) and carnitine and a low affinity for proline (apparent Km of 950 microM) and other analogues. Mutants defective in the uptake of glycine betaine were generated by UV irradiation and selected on the basis of resistance to dehydroproline (DHP), a toxic proline analogue. Three independent DHP-resistant mutants showed reduced glycine betaine uptake rates and accumulation levels but behaved similarly to the wild type in terms of direct activation of uptake by high-osmolality conditions. Kinetic analysis of glycine betaine uptake and efflux in the wild-type and mutant cells is consistent with one uptake system for quaternary ammonium compounds in L. plantarum and a separate system(s) for their excretion. The mechanism of osmotic activation of the quaternary ammonium compound transport system (QacT) was studied. It was observed that the uptake rates were inhibited by the presence of internal substrate. Upon raising of the medium osmolality, the QacT system was rapidly activated (increase in maximal velocity) through a diminished inhibition by trans substrate as well as an effect that is independent of intracellular substrate. We also studied the effects of the cationic amphipath chlorpromazine, which inserts into the cytoplasmic membrane and thereby influences the uptake and efflux of glycine betaine. The results provide further evidence for the notion that the rapid efflux of glycine betaine upon osmotic downshock is mediated by a channel protein that is responding to membrane stretch or tension. The activation of QacT upon osmotic upshock seems to be brought about by a turgor-related parameter other than membrane stretch or tension.