Factors affecting flavor perception in space: Does the spacecraft environment influence food intake by astronauts?

The intention to send a crewed mission to Mars involves a huge amount of planning to ensure a safe and successful mission. Providing adequate amounts of food for the crew is a major task, but 20 years of feeding astronauts on the International Space Station (ISS) have resulted in a good knowledge base. A crucial observation from the ISS is that astronauts typically consume only 80% of their daily calorie requirements when in space. This is despite daily exercise regimes that keep energy usage at very similar levels to those found on Earth. This calorie deficit seems to have little effect on astronauts who spend up to 12 months on the ISS, but given that a mission to Mars would take 30 to 36 months to complete, there is concern that a calorie deficit over this period may lead to adverse effects in crew members. The key question is why astronauts undereat when they have a supply of food designed to fully deliver their nutritional needs. This review focuses on evidence from astronauts that foods taste different in space, compared to on Earth. The underlying hypothesis is that conditions in space may change the perceived flavor of the food, and this flavor change may, in turn, lead to underconsumption by astronauts. The key areas investigated in this review for their potential impact on food intake are the effects of food shelf life, physiological changes, noise, air and water quality on the perception of food flavor, as well as the link between food flavor and food intake.

A transcriptomic atlas of mammalian olfactory mucosae reveals an evolutionary influence on food odor detection in humans

The mammalian olfactory system displays species-specific adaptations to different ecological niches. To investigate the evolutionary dynamics of olfactory sensory neuron (OSN) subtypes across mammalian evolution, we applied RNA sequencing of whole olfactory mucosa samples from mouse, rat, dog, marmoset, macaque, and human. We find that OSN subtypes, representative of all known mouse chemosensory receptor gene families, are present in all analyzed species. Further, we show that OSN subtypes expressing canonical olfactory receptors are distributed across a large dynamic range and that homologous subtypes can be either highly abundant across all species or species/order specific. Highly abundant mouse and human OSN subtypes detect odorants with similar sensory profiles and sense ecologically relevant odorants, such as mouse semiochemicals or human key food odorants. Together, our results allow for a better understanding of the evolution of mammalian olfaction in mammals and provide insights into the possible functions of highly abundant OSN subtypes.

Parallel replica dynamics simulations of reactions in shock compressed liquid benzene

The study of the long-term evolution of slow chemical reactions is challenging because quantum-based reactive molecular dynamics simulation times are typically limited to hundreds of picoseconds. Here, the extended Lagrangian Born-Oppenheimer molecular dynamics formalism is used in conjunction with parallel replica dynamics to obtain an accurate tool to describe the long-term chemical dynamics of shock-compressed benzene. Langevin dynamics has been employed at different temperatures to calculate the first reaction times in liquid benzene at pressures and temperatures consistent with its unreacted Hugoniot. Our coupled engine runs for times on the order of nanoseconds (one to two orders of magnitude longer than traditional techniques) and is capable of detecting reactions that are characterized by rates significantly slower than we could study before. At lower pressures and temperatures, we mainly observe Diels-Alder metastable reactions, whereas at higher pressures and temperatures we observe stable polymerization reactions.

Engaging stakeholders in research to address water-energy-food (WEF) nexus challenges

The water-energy-food (WEF) nexus has become a popular, and potentially powerful, frame through which to analyse interactions and interdependencies between these three systems. Though the case for transdisciplinary research in this space has been made, the extent of stakeholder engagement in research remains limited with stakeholders most commonly incorporated in research as end-users. Yet, stakeholders interact with nexus issues in a variety of ways, consequently there is much that collaboration might offer to develop nexus research and enhance its application. This paper outlines four aspects of nexus research and considers the value and potential challenges for transdisciplinary research in each. We focus on assessing and visualising nexus systems; understanding governance and capacity building; the importance of scale; and the implications of future change. The paper then proceeds to describe a novel mixed-method study that deeply integrates stakeholder knowledge with insights from multiple disciplines. We argue that mixed-method research designs-in this case orientated around a number of cases studies-are best suited to understanding and addressing real-world nexus challenges, with their inevitable complex, non-linear system characteristics. Moreover, integrating multiple forms of knowledge in the manner described in this paper enables research to assess the potential for, and processes of, scaling-up innovations in the nexus space, to contribute insights to policy and decision making.

Biophysical and functional characterization of the N-terminal domain of the cat T1R1 umami taste receptor expressed in Escherichia coli

Umami taste perception is mediated by the heterodimeric G-protein coupled receptors (GPCRs), formed by the assembly of T1R1 and T1R3 subunits. T1R1 and T1R3 subunits are class C GPCRs whose members share common structural homologies including a long N-terminal domain (NTD) linked to a seven transmembrane domain by a short cysteine-rich region. The NTD of the T1R1 subunit contains the primary binding site for umami stimuli, such as L-glutamate (L-Glu) for humans. Inosine-5’-monophosphate (IMP) binds at a location close to the opening of the T1R1-NTD “flytrap”, thus creating the observed synergistic response between L-Glu and IMP. T1R1/T1R3 binding studies have revealed species-dependent differences. While human T1R1/T1R3 is activated specifically by L-Glu, the T1R1/T1R3 in other species is a broadly tuned receptor, sensitive to a range of L-amino acids. Because domestic cats are obligate carnivores, they display strong preferences for some specific amino acids. To better understand the structural basis of umami stimuli recognition by non-human taste receptors, we measured the binding of selected amino acids to cat T1R1/T1R3 (cT1R1/cT1R3) umami taste receptor. For this purpose, we expressed cT1R1-NTD in bacteria as inclusion bodies. After purification, refolding of the protein was achieved. Circular dichroism spectroscopic studies revealed that cT1R1-NTD was well renatured with evidence of secondary structures. Using size-exclusion chromatography coupled to light scattering, we found that the cT1R1-NTD behaves as a monomer. Ligand binding quantified by intrinsic tryptophan fluorescence showed that cT1R1-NTD is capable of binding L-amino acids with K_d values in the micromolar range. We demonstrated that IMP potentiates L-amino acid binding onto renatured cT1R1-NTD. Interestingly, our results revealed that IMP binds the extracellular domain in the absence of L-amino acids. Thus, this study demonstrates that the feasibility to produce milligram quantities of cT1R1-NTD for functional and structural studies.

Sedation in the intensive care unit

Analgesics and sedatives are commonly prescribed in the ICU environment for patient comfort, however, recent studies have shown that these medications can themselves lead to adverse patient outcomes. Interventions that facilitate a total dose reduction in analgesic and sedative medications e.g. the use of nurse controlled protocol guided sedation, the combination of spontaneous awakening and breathing trials, and the use of short acting medications, are associated with improved outcomes such as decreased time of mechanical ventilation and ICU length of stay. This purpose of this review is to provide an overview of the pharmacology of commonly prescribed analgesics and sedatives, and to discuss the evidence regarding best prescribing practices of these medications, to facilitate early liberation from mechanical ventilation and to promote animation in critically ill patients.

Validation of a pre-anaesthetic screening questionnaire

We developed a screening questionnaire to be used by nurses to decide which patients should see an anaesthetist for further evaluation before the day of surgery. Our objective was to measure the accuracy of responses to the questionnaire. Agreement between questionnaire responses and the anaesthetist's assessment was assessed. For questions with a prevalence of 5 to 95%, the Kappa coefficient was used; percentage agreement was used for all other questions. Criterion validity was excellent/good for all questions with a prevalence between 5 and 95%, except for the question 'Do you have kidney disease?' For questions with prevalence < 5%, all demonstrated adequate criterion validity except the questions 'Has anyone in your family had a problem following an anaesthetic?' and 'If you have been put to sleep for an operation were there any anaesthetic problems?' Therefore, it is reasonable for nurses to use this questionnaire to determine which patients an anaesthetist should see before the day of surgery.