An experimental biomimetic platform for artificial olfaction

Artificial olfactory systems have been studied for the last two decades mainly from the point of view of the features of olfactory neuron receptor fields. Other fundamental olfaction properties have only been episodically considered in artificial systems. As a result, current artificial olfactory systems are mostly intended as instruments and are of poor benefit for biologists who may need tools to model and test olfactory models. Herewith, we show how a simple experimental approach can be used to account for several phenomena observed in olfaction. An artificial epithelium is formed as a disordered distributed layer of broadly selective color indicators dispersed in a transparent polymer layer. The whole epithelium is probed with colored light, imaged with a digital camera and the olfactory response upon exposure to an odor is the change of the multispectral image. The pixels are treated as olfactory receptor neurons, whose optical properties are used to build a convergence classifier into a number of mathematically defined artificial glomeruli. A non-homogenous exposure of the test structure to the odours gives rise to a time and spatial dependence of the response of the different glomeruli strikingly similar to patterns observed in the olfactory bulb. The model seems to mimic both the formation of glomeruli, the zonal nature of olfactory epithelium, and the spatio-temporal signal patterns at the glomeruli level. This platform is able to provide a readily available test vehicle for chemists developing optical indicators for chemical sensing purposes and for biologists to test models of olfactory system organization.     

Sex differences in control of blood pressure: role of oxidative stress in hypertension in females

In general, blood pressure is higher in normotensive men than in age-matched women, and the prevalence of hypertension in men is also higher until after menopause, when the prevalence of hypertension increases for women. It is likely then that the mechanisms by which blood pressure increases in men and women with aging may be different. Although clinical trials to reduce blood pressure with antioxidants have typically not been successful in human cohorts, studies in male rats suggest that oxidative stress plays an important role in mediating hypertension. The exact mechanisms by which oxidative stress increases blood pressure have not been completely elucidated. There may be several reasons for the discrepancies between clinical and animal studies. In this review, the data obtained in selected clinical and animal studies are discussed, and the hypothesis is put forward that oxidative stress may not be as important in mediating hypertension in females as has been shown previously in male rats. Furthermore, it is likely that differences in genetics, age, length of time with hypertension, endothelial dysfunction, and sex are all factored in to modulate the responses to antioxidants in humans. As such, future clinical trials should be designed and powered to evaluate the effects of oxidative stress on blood pressure separately in men and women.     

Indole alkaloids as systematic markers of the Apocynaceae

Indole alkaloids can be characterized by skeletal specialization (S), determined upon consideration of their relative position on a biogenetic map and the number of their naturally occurring substitutional derivatives, as well as by oxidation level (O). The mean (S) and (O) for contained alkaloids of a given plant taxon are taken to represent evolutionary advancement parameters, respectively EA_s and EA_o.A correlation of these EA_s/EA_o values for tribes of the Apocynaceae-Plumerioideae reveals a chemical gradient, given by gradually increasing EA_s and EA_o values, to link Carisseae-Alstonieae-Rauvolfieae-Tabernaemontaneae.     

Self-assembly and structural characterization of Echinococcus granulosus antigen B recombinant subunit oligomers

Echinococcus granulosus antigen B is an oligomeric protein of 120-160 kDa composed by 8-kDa (AgB8) subunits. Here, we demonstrated that the AgB8 recombinant subunits AgB8/1, AgB8/2 and AgB8/3 are able to self-associate into high order homo-oligomers, showing similar properties to that of parasite-produced AgB, making them valuable tools to study AgB structure. Dynamic light scattering, size exclusion chromatography and cross-linking assays revealed approximately 120- to 160-kDa recombinant oligomers, with a tendency to form populations with different aggregation states. Recombinant oligomers showed helical circular dichroism spectra and thermostability similar to those of purified AgB. Cross-linking and limited proteolysis experiments indicated different degrees of stability and compactness between the recombinant oligomers, with the AgB8/3 one showing a more stable and compact structure. We have also built AgB8 subunit structural models in order to predict the surfaces possibly involved in electrostatic and hydrophobic interactions during oligomerization.     

The F-Box Domain-Dependent Activity of EMI1 Regulates PARPi Sensitivity in Triple-Negative Breast Cancers

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Identification of all FK506-binding proteins from Neurospora crassa

Immunophilins are intracellular receptors of immunosuppressive drugs, carrying peptidyl-prolyl cis-trans isomerase activity, with a general role in protein folding but also involved in specific regulatory mechanisms. Four immunophilins of the FKBP-type (FK506-binding proteins) were identified in the genome of Neurospora crassa. Previously, FKBP22 has been located in the endoplasmic reticulum as part of chaperone/folding complexes and FKBP13 has been found to have a dual location in the cytoplasm and mitochondria. FKBP11 is apparently located exclusively in the cytoplasm. It is not expressed during vegetative development of the fungus although its expression can be induced with calcium and during sexual development. Overexpression of the respective gene appears to confer a growth advantage to the fungus in media containing some divalent ions. FKBP50 is a nuclear protein and its genetic inactivation leads to a temperature-sensitive phenotype. None of these proteins is, alone or in combination, essential for N. crassa, as demonstrated by the isolation of a mutant strain lacking all four FKBPs.     

Alvarez waves in pregnancy: a comprehensive review

Alvarez waves are local rhythmic contractions of the myometrium with high frequency and low intensity. They can be detected using internal or external tocography and electrohysterography. Some researchers correlate these small contractions with the initiation of labor, since they have been described as a pattern representing the uterine response to prostaglandin production. Other authors either do not validate a causality relation between Alvarez waves and labor or suggest that they have low predictive value for preterm labor. Alvarez waves’ research has become a multidisciplinary subject with inputs ranging from medical science, biomedical engineering, and related areas. A comprehensive review is herein conducted to summarize the state of the art regarding Alvarez waves and their role in the initiation of labor, namely in preterm birth. The results show that a large number of studies have analyzed and characterized Alvarez waves without necessarily digging into their relationship with labor. Publications were categorized in three groups: (A) reports about morphology and characterization of Alvarez waves; (B) publications reporting a positive causality relation between Alvarez waves and labor; and (C) publications reporting an absence of causality regarding the previous hypothesis. Studies in group B outnumbered those in group C. A critical analysis is presented.     

Genetic structure of natural populations ofDryas iulia (Lepidoptera: Nymphalidae) revealed by enzyme polymorphism and mitochondrial DNA (mtDNA) restriction fragment length polymorphism (RFLP)

Dryas iulia appears to have undergone a mode of evolution different from that of other members of its subfamily (Heliconiinae). While other species constitute highly subdivided and inbred populations, those ofD. iulia are thought to be large and uniform. Analyzing six samples from Southern Brazil (state of Rio Grande do Sul) in relation to three enzyme systems (EST, LAP, and PGM) and their mtDNA RFLP patterns, we found that they are very similar at the molecular level. TheF statistics for enzyme polymorphism data revealed that inbreeding makes a great contribution to the population homozygosity, sinceF _IS equals 0.1322 andF _ST equals 0.0023. Since the chi-square test showed thatF _ST is not significant, we conclude that all localities belong to the same population. The mtDNA differentiation was about 12 times greater than for nuclear genes;F _ST was equivalent to 0.0265. We suggest that this difference is due to a higher dispersal of males, in relation to females.     

Immunomicroscopical localization of human preformed natural antibodies against pig tissues in xenogeneic transplantation

Summary The targets of preformed natural antibodies need to be identified whenever the use of pig organs is considered for human transplantation. In this study we used extracorporeal perfusion of pig organs with human blood, immunocytological techniques and immuno-electron microscopy to identify the targets and the nature of human preformed natural antibodies against pig antigens. The antibodies were found to be mainly of the IgG and IgM type and directed not only against endothelial cells, but also against mesenchymal and epithelial structures. To reproduce an in vivo situation, a Bio-pump was used to xenoperfuse pig kidneys and livers with human fresh oxygenated blood at 37°C, drawn from polycythaemic patients. Biopsies showed a deposition of human IgG and IgM on tubuli and glomeruli of pig kidneys and on endothelial cells of pig livers. Preperfusion of pig liver with human blood for 45 minutes before perfusion of kidneys significantly reduced the deposition of the natural antibodies.