Do tastants have a smell?

The stimuli used in taste research are usually considered to be odourless. This was tested in two experiments with aqueous solutions of two representative compounds for each of the five taste qualities including umami. In the first experiment elderly and young subjects rated the intensity and pleasantness of three concentrations of the stimuli, while wearing or not wearing a noseclip. Saliva production was also measured. Blocking olfaction only influenced salivation for umami. It reduced taste intensity ratings, but as in an earlier experiment with the same compounds in food products, this effect was stronger in the young, who also liked the stimuli better wearing the noseclip. In the second experiment, another group of young people tried to detect the odours of the tastants dissolved in demineralized, double-distilled or Evian water. A considerable number of subjects could regularly detect seven of the ten tastants by olfaction and the extent to which they did correlated significantly with the reduction in taste intensity ratings for the different tastants found in the first experiment. We suggest that most tastants can be smelled and that this smell contributes to taste intensity ratings.     

Do small animals have a biogeography?

It has been stated that small organisms do not have barriers for distribution and will not show biogeographic discreteness. General models for size-mediated biogeographies establish a transition region between ubiquitous dispersal and restricted biogeography at about 1–10 mm. We tested patterns of distribution versus size with water mites, a group of freshwater organisms with sizes between 300 μm and 10 mm.We compiled a list of all known water mite species for Sierra del Guadarrama (a mountain range in the centre of the Iberian Peninsula) from different authors and our own studies in the area. Recorded habitats include lotic, lentic and interstitial environments. Species body size and world distribution were drawn from our work and published specialized taxonomic literature. The null hypothesis was that distribution is size-independent. The relationship between distribution and size was approached via analysis of variance and between size and habitat via logistic regression. Contrary to expectations, there is no special relationship between water mite size and area size distribution. On the other hand, water mite size is differentially distributed among habitats, although this ecological sorting is very weak. Larger water mites are more common in lentic habitats and smaller water mites in lotic habitats. Size-dependent distribution in which small organisms tend to be cosmopolitan breaks down when the particular biology comes into play. Water mites do not fit a previously proposed size-dependent biogeographical distribution, and are in accordance with similar data published on Tardigrada, Rotifera, Gastrotricha and the like.     

Do facts have a place in science?

The use of the word ‘fact’ in science is discussed. It is suggested that the everyday meaning of the term is assumed when it is used in science and that this can create problems. Some possible ways of overcoming these difficulties are indicated.     

Do miRNAs have a deep evolutionary history?

The recent discovery of microRNAs (miRNAs) in unicellular eukaryotes, including miRNAs known previously only from animals or plants, implies that miRNAs have a deep evolutionary history among eukaryotes. This contrasts with the prevailing view that miRNAs evolved convergently in animals and plants. We re-evaluate the evidence and find that none of the 73 plant and animal miRNAs described from protists meet the required criteria for miRNA annotation and, by implication, animals and plants did not acquire any of their respective miRNA genes from the crown ancestor of eukaryotes. Furthermore, of the 159 novel miRNAs previously identified among the seven species of unicellular protists examined, only 28 from the algae Ectocarpus and Chlamydomonas, meet the criteria for miRNA annotation. Therefore, at present only five groups of eukaryotes are known to possess miRNAs, indicating that miRNAs have evolved independently within eukaryotes through exaptation of their shared inherited RNAi machinery.     

Do spherical tokamaks have a thermonuclear future?

This work has been initiated by the publication of a review by B.V.Kuteev et al., ??Intense Fusion Neutron Sources?? [Plasma Physics Reports 36, 281 (2010)]. It is stated that the key thesis of the above review that a spherical tokamak can be recommended for research neutron sources and for demonstration hybrid systems as an alternative to expensive ??classical?? tokamaks of the JET and ITER type is inconsistent. The analysis of the experimental material obtained during the last 10 years in the course of studies on the existing spherical tokamaks shows that the TIN-ST fusion neutron source spherical tokamak proposed by the authors of the review and intended, according to the authors?? opinion, to replace ??monsters?? in view of its table-top dimensions (2 m³) and laboratory-level energetics cannot be transformed into any noticeable stationary megawatt-power neutron source competing with the existing classical tokamaks (in particular, with JET with its quasi-steady DT fusion power at a level of 5 MW). Namely, the maximum plasma current in the proposed tokamak will be not 3 MA, as the authors suppose erroneously, but, according to the present-day practice of spherical tokamaks, within 0.6?C0.7 MA, which will lead to a reduction on the neutron flux by two to three orders of magnitude from the expected 5 MW. The possibility of the maintenance of the stationary process itself even in such a ??weakened?? spherical tokamak is very doubtful. The experience of the largest existing devices of this type (such as NSTX and MAST) has shown that they are incapable of operating even in a quasi-steady operating mode, because the discharge in them is spontaneously interrupted about 1 s after the beginning of the current pulse, although its expected duration is of up to 5 s. The nature of this phenomenon is the subject of further study of the physics of spherical tokamaks. This work deals with a critical analysis of the available experimental data concerning such tokamaks and a discussion of the potential possibility of their use in thermonuclear research.     

Do eosinophils have a role in the killing of helminth parasites?

Eosinophils have been shown to be potent effector cells for the killing of helminth parasites in in vitro cultures. However, an in vivo role for eosinophils has been more difficult to establish. Early data showed close associations between eosinophils and damaged or dead parasites in histological sections, and significant correlations between resistance to parasites and the capacity to induce eosinophilia after infection. However, more recent studies, using mice that have reduced or increased eosinophil levels through targeting of the eosinophil-specific cytokine interleukin 5, have not unanimously supported an in vivo role for eosinophils in resistance to parasites. Here, Els Meeusen and Adam Balic review these studies and suggest a major role for the innate immune response in unnatural mouse-parasite models to explain some of the findings. They conclude that the data so far are consistent with a role for eosinophils in the killing of infective larval stages, but not adults, of most helminth parasites.     

Do some carriers of hemochromatosis gene mutations have higher than normal rates of disease and death?

Some heterozygote carriers of hemochromatosis HFE gene mutations become iron loaded with ensuing increased risk of disease and premature death. Contributing nutritional, behavioral and genetic factors are beginning to be identified. Carriers of HFE gene mutations should be advised to minimize contributing factors, if possible, and to have their iron values tested periodically. If values begin to rise, a schedule of phlebotomies should be considered.     

Is there a functional link between gene interdigitation and multi‐species conservation of synteny blocks?

It is often overlooked that, in addition to the integrity of protein-coding sequences (PCSs), human health is crucially linked to the normal expression of genes by cis-regulatory sequences (CRSs). These CRSs often lie at some considerable distance from the PCSs whose expression they control and often within other genes. The resulting gene interdigitation can make long-range CRS identification and characterisation difficult. We propose that the need to conserve long-range CRSs in cis with their target PCSs through evolution, in combination with gene interdigitation and co-regulation of many genes by individual CRSs, has contributed to the persistence of conserved synteny blocks between diverse species. We further hypothesise that examination of the varying extents of synteny blocks between multiple species in combination with phylogenetic footprinting to find CRSs might provide important clues to the existence of crucial functional CRS-PCS linkages. Identifying CRS-PCS linkages crucial to human health will lead to a better understanding of how their disruption by CRS mutation or chromosome translocation might contribute to many distressing human diseases.     

Do you have a probiotic in your future?

The possibility of using microbes to maintain health, and to prevent or treat disease is a topic as old as microbiology. However, one factor impeding the introduction of effective probiotics has been our very limited understanding of the composition of the human microbiome, as well as the biological requirements for these organisms. With advances in understanding the microbiome and its metagenome in humans and other mammals, we now can build a more robust scientific basis to develop probiotic strategies. Increasing knowledge of intramicrobial competition and cooperation, as well as host-microbe cross-signaling, will facilitate design of new probiotics and the modeling of their deployment, leading to eventual clinical trials.     

Do bacteria have sex?

Do bacteria have genes for genetic exchange? The idea that the bacterial processes that cause genetic exchange exist because of natural selection for this process is shared by almost all microbiologists and population geneticists. However, this assumption has been perpetuated by generations of biology, microbiology and genetics textbooks without ever being critically examined.     

Do coral-reef fish faunas have a distinctive taxonomic structure?

Do the highly diverse fish faunas that associate with coral reefs have distinguishing taxonomic and ecological characteristics, as proposed by Choat and Bellwood (1991) and Bellwood (1996)? Does a 50?my old (Eocene) fossil fish fauna from Italy represent a coral-reef fish assemblage that provides unique information about the evolution of such assemblages, as claimed by Bellwood (1996)? I compared the structure of the reef fish faunas of adjacent tropical regions rich and poor in coral reefs, in both America and Polynesia, and found that they exhibit no substantive differences in relative species richness among families of typical “coral-reef” fishes. While coral-rich regions have larger reef fish faunas, a variety of factors probably contribute to such differences. Thus coral-reef fish faunas may lack a distinctive taxonomic structure. A similar comparative approach would be useful for assessing whether assemblages of fishes on coral reefs have distinctive ecological characteristics. Based on patterns of habitat use by modern tropical shorefishes, the Italian Eocene fauna includes few definite reef fishes, and may well consist primarily of non-reef fishes preserved in a non-reef habitat. Until we know more about the environment in which those fossils were preserved, that fauna can contribute little to understanding how coral reef fish assemblages have evolved.     

Do delta F508 heterozygotes have a selective advantage?

In this paper the fitness of the delta F508 heterozygote is assessed and the age of the delta F508 mutation in the cystic fibrosis locus is estimated. Data from three microsatellite loci are applied. The analysis is performed conditional on the present-day frequency of the delta F508 mutation and based on assumptions about the demographic history of the European population and the mutation rate in the three microsatellite loci. It is shown that the data gives evidence of positive selection (up to 2-3% per delta F508 heterozygote), but also that data could be explained by negative selection of roughly the same order of magnitude. The age of the delta F508 mutation is subsequently estimated; it is found that the mutation is at least 580 generations old, but could be much older depending on the microsatellite mutation rate and the exact number of substitutions experienced in the history of the three microsatellite loci.     

The regulation of autophagy by calcium signals: Do we have a consensus?

Macroautophagy (hereafter called ‘autophagy’) is a cellular process for degrading and recycling cellular constituents, and for maintenance of cell function. Autophagy initiates via vesicular engulfment of cellular materials and culminates in their degradation via lysosomal hydrolases, with the whole process often being termed ‘autophagic flux’. Autophagy is a multi-step pathway requiring the interplay of numerous scaffolding and signalling molecules. In particular, orthologs of the family of ∼30 autophagy-regulating (Atg) proteins that were first characterised in yeast play essential roles in the initiation and processing of autophagic vesicles in mammalian cells. The serine/threonine kinase mTOR (mechanistic target of rapamycin) is a master regulator of the canonical autophagic response of cells to nutrient starvation. In addition, AMP-activated protein kinase (AMPK), which is a key sensor of cellular energy status, can trigger autophagy by inhibiting mTOR, or by phosphorylating other downstream targets. Calcium (Ca²⁺) has been implicated in autophagic signalling pathways encompassing both mTOR and AMPK, as well as in autophagy seemingly not involving these kinases. Numerous studies have shown that cytosolic Ca²⁺ signals can trigger autophagy. Moreover, introduction of an exogenous chelator to prevent cytosolic Ca²⁺ signals inhibits autophagy in response to many different stimuli, with suggestions that buffering Ca²⁺ affects not only the triggering of autophagy, but also proximal and distal steps during autophagic flux. Observations such as these indicate that Ca²⁺ plays an essential role as a pro-autophagic signal. However, cellular Ca²⁺ signals can exert anti-autophagic actions too. For example, Ca²⁺ channel blockers induce autophagy due to the loss of autophagy-suppressing Ca²⁺ signals. In addition, the sequestration of Ca²⁺ by mitochondria during physiological signalling appears necessary to maintain cellular bio-energetics, thereby suppressing AMPK-dependent autophagy. This article attempts to provide an integrated overview of the evidence for the proposed roles of various Ca²⁺ signals, Ca²⁺ channels and Ca²⁺ sources in controlling autophagic flux.