Protein crystallography under xenon and nitrous oxide pressure: comparison with in vivo pharmacology studies and implications for the mechanism of inhaled anesthetic action

In contrast with most inhalational anesthetics, the anesthetic gases xenon (Xe) and nitrous oxide (N(2)O) act by blocking the N-methyl-d-aspartate (NMDA) receptor. Using x-ray crystallography, we examined the binding characteristics of these two gases on two soluble proteins as structural models: urate oxidase, which is a prototype of a variety of intracellular globular proteins, and annexin V, which has structural and functional characteristics that allow it to be considered as a prototype for the NMDA receptor. The structure of these proteins complexed with Xe and N(2)O were determined. One N(2)O molecule or one Xe atom binds to the same main site in both proteins. A second subsite is observed for N(2)O in each case. The gas-binding sites are always hydrophobic flexible cavities buried within the monomer. Comparison of the effects of Xe and N(2)O on urate oxidase and annexin V reveals an interesting relationship with the in vivo pharmacological effects of these gases, the ratio of the gas-binding sites' volume expansion and the ratio of the narcotic potency being similar. Given these data, we propose that alterations of cytosolic globular protein functions by general anesthetics would be responsible for the early stages of anesthesia such as amnesia and hypnosis and that additional alterations of ion-channel membrane receptor functions are required for deeper effects that progress to "surgical" anesthesia.     

Pharmacological evidence for beta2-adrenoceptor in right atria from stressed female rats.

The purpose of the present study was to demonstrate a physiological response to TA2005, a potent m-adrenoceptor (beta2-AR) selective agonist, in right atria isolated from stressed female rats under the influence of the estrous cycle. We obtained concentration-response curves to the agonist in the presence and in the absence of selective antagonists in right atria isolated from female rats submitted to three daily foot-shock sessions (30 min duration, 120 pulses of 1.0 mA, 1.0 s, applied at random intervals of 5-25 s) and sacrificed at estrus or diestrus. Our results showed that the pD2 values of TA2005 were not influenced by estrous cycle phase or foot-shock stress. However, in right atria from stressed rats sacrificed during diestrus, the concentration-response curve to TA2005 was biphasic, with a response being obtained at concentrations of 0.1 nM, whereas during estrus no response was observed at doses lower than 3 nM. ICI 1118,551, a beta2-AR antagonist, abolished the response to nanomolar concentrations of TA2005 in right atria from stressed rats at diestrus, with no changes in agonist pD2 values in right atria from control rats (7.47 +/- 0.09, p > 0.05) but a 3-fold decrease in pD2 values of TA2005 in right atria from foot shock stressed rats (7.90 +/- 0.07, p < or = 0.05). Concentration-response curves to TA2005 in the presence of ICI118,551 were best fitted by a one-site model equation. The beta1-AR antagonist, CGP20712A, shifted to the right only the second part of the concentration-response curves to the agonist, unmasking the putative beta2-AR-mediated response to the agonist in tissues isolated from stressed rats at diestrus. Under this condition, concentration-response curves to the agonist were best fitted by a two-site model equation. pD2 and maximum response of TA2005 interaction with beta1- and putative beta2-adrenoceptor components were calculated. Schild analyses gave a pK(B) value for CGP20712A that was typical for the interaction with beta1-AR in each experimental group. pK(B) values for ICI118,551 could not be obtained in stressed rats sacrificed at diestrus since Schild plot slopes were lower than 1.0. In right atria from control rats, ICI118,551 pK(B) values were similar to reported values for the interaction of the antagonist with beta1-AR. These results confirm that a heterogenous beta-AR population mediating the chronotropic response to catecholamines can be demonstrated in right atria from foot shock stressed female rats sacrificed at diestrus. The stress-induced response seems to be mediated by the beta2-AR subtype. Right atria from rats sacrificed during estrus are protected against stress-induced alterations on the homogeneity of beta-AR population.     

Modelling of a continuous pilot photobioreactor for microalgae production

In this study, a model of a continuous pilot photobioreactor for microalgae production is proposed. Three aspects have been studied: the modelling of kinetic growth, the gas-liquid transfer and the hydrodynamics in the photobioreactor. The modelling of each aspect has been developed with the dynamic simulation software SpeedUp, after experimental studies, then validated step-by-step. The connection of these three aspects aims to predict and optimise biomass production of the pilot plant.     

Combined effect of the growth temperature and salinity of the medium on the accumulation of compatible solutes by Rhodothermus marinus and Rhodothermus obamensis

In this study we propose revised structures for the two major compatible solutes of Rhodothermus marinus. We have also examined the accumulation of compatible solutes by the type strains of the slightly halophilic and thermophilic species Rhodothermus marinus and Rhodothermus obamensis at several growth temperatures and salinities. The major solutes of R. marinus were identified as α-mannosylglycerate (α-MG) and α-mannosylglyceramide (α-MGA), whereas R. obamensis accumulated only α-mannosylglycerate. The total osmolyte content was higher during the early exponential phase and decreased abruptly as growth continued into the stationary phase. At low growth temperatures, R. marinus responded to water stress by accumulation of α-mannosylglycerate and its amide, in addition to low levels of trehalose, glutamate, and glucose. At the highest growth temperature, α-mannosylglycerate was the major compatible solute and α-mannosylglyceramide was not detected. When both compounds were present, an increase in the salinity of the growth medium favored the accumulation of α-mannosylglyceramide over α-mannosylglycerate. The absence of α-mannosylglyceramide in R. obamensis at all growth temperatures and salinities constituted the most pronounced difference in the profiles of compatible solute accumulation by the two strains. Trehalose was also a prominent solute in this organism. Both organisms accumulated higher levels of α-mannosylglycerate as the temperature was raised. The importance of the two compounds in the mechanisms of thermoadaptation and osmoadaptation is discussed. Received: February 10, 1998 / Accepted: January 11, 1999     

Recent Male-Mediated Gene Flow over a Linguistic Barrier in Iberia, Suggested by Analysis of a Y-Chromosomal DNA Polymorphism

We have examined the worldwide distribution of a Y-chromosomal base-substitution polymorphism, the T/C transition at SRY-2627, where the T allele defines haplogroup 22; sequencing of primate homologues shows that the ancestral state cannot be determined unambiguously but is probably the C allele. Of 1,191 human Y chromosomes analyzed, 33 belong to haplogroup 22. Twenty-nine come from Iberia, and the highest frequencies are in Basques (11%; n=117) and Catalans (22%; n=32). Microsatellite and minisatellite (MSY1) diversity analysis shows that non-Iberian haplogroup-22 chromosomes are not significantly different from Iberian ones. The simplest interpretation of these data is that haplogroup 22 arose in Iberia and that non-Iberian cases reflect Iberian emigrants. Several different methods were used to date the origin of the polymorphism: microsatellite data gave ages of 1,650, 2,700, 3,100, or 3,450 years, and MSY1 gave ages of 1,000, 2,300, or 2,650 years, although 95% confidence intervals on all of these figures are wide. The age of the split between Basque and Catalan haplogroup-22 chromosomes was calculated as only 20% of the age of the lineage as a whole. This study thus provides evidence for direct or indirect gene flow over the substantial linguistic barrier between the Indo-European and non-Indo-European-speaking populations of the Catalans and the Basques, during the past few thousand years.     

Divergent Human Y-Chromosome Microsatellite Evolution Rates

In this work, we analyze several characteristics influencing the low variability of the microsatellite DYS19 in the major founder Amerindian Y chromosome lineage containing the point mutation DYS199-T. Variation of DYS19 was compared with that of five other Y-linked tetranucleotide repeat loci (DYS389A, DYS389B, DYS390, DYS391, and DYS393) in the DYS199-T lineage. All the other microsatellites showed significantly higher levels of variability than DYS19 as measured by gene diversity and repeat number variance. Moreover, we had previously shown that DYS19 had high diversity in Brazilians and in several other populations worldwide. Thus, the slow DYS19 evolution in the DYS199-T lineage seems to be both locus and allele specific. To understand the slow DYS19 evolutionary rate, the microsatellite loci were compared according to their mapping on the Y chromosome and also on the basis of structural aspects such as the base composition of the repeat motif and flanking regions and the degree of perfection and size (repeat number) of the variable blocks. The only observed difference that might be related to the low DYS19 variability is its small average number of repeats, a value expected to be closer to the founder DYS19 allele in the DYS199-T lineage. These data were also compared to other derived Y lineages. The Tat-C lineage displayed a lower DYS19 variability correlated to a small average repeat number, while in the DYS234-G lineage, a high DYS19 variability was found associated to a larger average repeat number. This approach reveals that evolution of Y microsatellites in lineages defined by slowly evolving markers, such as point mutations, can be greatly influenced by the size (number of repeats of the variable block) of the founder allele in each microsatellite locus. Thus lineage-dating methods using microsatellite variation should be practiced with great care. Received: 7 November 1998 / Accepted: 9 April 1999     

NDUFV1 mutations in complex I deficiency: Case reports and review of symptoms

Mitochondrial complex I (CI) deficiency is the most common oxidative phosphorylation disorder described. It shows a wide range of phenotypes with poor correlation within genotypes. Herein we expand the clinics and genetics of CI deficiency in the brazilian population by reporting three patients with pathogenic (c.640G>A, c.1268C>T, c.1207dupG) and likely pathogenic (c.766C>T) variants in the NDUFV1 gene. We show the mutation c.766C>T associated with a childhood onset phenotype of hypotonia, muscle weakness, psychomotor regression, lethargy, dysphagia, and strabismus. Additionally, this mutation was found to be associated with headaches and exercise intolerance in adulthood. We also review reported pathogenic variants in NDUFV1 highlighting the wide phenotypic heterogeneity in CI deficiency.     

Structural characterization (shape and dimensions) and stability of polysaccharide/lipid nanoparticles

The structure of a new supramolecular drug carrier (named Biovectors—BV) was studied using light scattering and scanning electronic microscopy techniques. This system consists of a polysaccharide core of chemically cross-linked maltodextrins to which phospholipids (and, in some cases, cholesterol) are added. Both polysaccharide cores and BV cross-linked with phosphate (negatively charged) and epichlorhydrin (no net charge) are spherical particles. The increase in the ionic strength of the medium increases the density of the charged polysaccharide cores. The lipid strongly interacts with neutral and negatively charged cores, decreasing both intra- and interparticle interactions. The results (mainly, ρ = R_g/R_h < 0.775 in some cases) suggest that BV are gel-like particles of variable density, referred to as microgels or soft spheres. Neutral polysaccharides have a strong tendency to self-aggregate. This self-aggregation of polysaccharide neutral cores is prevented by the addition of lipid or dimethylsulfoxide. © 1997 John Wiley & Sons, Inc. Biopoly 41: 511–520, 1997