Reverse metabolomics for the discovery of chemical structures from humans.

Determining the structure and phenotypic context of molecules detected in untargeted metabolomics experiments remains challenging. Here we present reverse metabolomics as a discovery strategy, whereby tandem mass spectrometry spectra acquired from newly synthesized compounds are searched for in public metabolomics datasets to uncover phenotypic associations. To demonstrate the concept, we broadly synthesized and explored multiple classes of metabolites in humans, including N-acyl amides, fatty acid esters of hydroxy fatty acids, bile acid esters and conjugated bile acids. Using repository-scale analysis1,2, we discovered that some conjugated bile acids are associated with inflammatory bowel disease (IBD). Validation using four distinct human IBD cohorts showed that cholic acids conjugated to Glu, Ile/Leu, Phe, Thr, Trp or Tyr are increased in Crohn's disease. Several of these compounds and related structures affected pathways associated with IBD, such as interferon-γ production in CD4+ T cells3 and agonism of the pregnane X receptor4. Culture of bacteria belonging to the Bifidobacterium, Clostridium and Enterococcus genera produced these bile amidates. Because searching repositories with tandem mass spectrometry spectra has only recently become possible, this reverse metabolomics approach can now be used as a general strategy to discover other molecules from human and animal ecosystems.

Bile salt hydrolase catalyses formation of amine-conjugated bile acids.

Bacteria in the gastrointestinal tract produce amino acid bile acid amidates that can affect host-mediated metabolic processes1-6; however, the bacterial gene(s) responsible for their production remain unknown. Herein, we report that bile salt hydrolase (BSH) possesses dual functions in bile acid metabolism. Specifically, we identified a previously unknown role for BSH as an amine N-acyltransferase that conjugates amines to bile acids, thus forming bacterial bile acid amidates (BBAAs). To characterize this amine N-acyltransferase BSH activity, we used pharmacological inhibition of BSH, heterologous expression of bsh and mutants in Escherichia coli and bsh knockout and complementation in Bacteroides fragilis to demonstrate that BSH generates BBAAs. We further show in a human infant cohort that BBAA production is positively correlated with the colonization of bsh-expressing bacteria. Lastly, we report that in cell culture models, BBAAs activate host ligand-activated transcription factors including the pregnane X receptor and the aryl hydrocarbon receptor. These findings enhance our understanding of how gut bacteria, through the promiscuous actions of BSH, have a significant role in regulating the bile acid metabolic network.

Caloric restriction disrupts the microbiota and colonization resistance.

Diet is a major factor that shapes the gut microbiome1, but the consequences of diet-induced changes in the microbiome for host pathophysiology remain poorly understood. We conducted a randomized human intervention study using a very-low-calorie diet (NCT01105143). Although metabolic health was improved, severe calorie restriction led to a decrease in bacterial abundance and restructuring of the gut microbiome. Transplantation of post-diet microbiota to mice decreased their body weight and adiposity relative to mice that received pre-diet microbiota. Weight loss was associated with impaired nutrient absorption and enrichment in Clostridioides difficile, which was consistent with a decrease in bile acids and was sufficient to replicate metabolic phenotypes in mice in a toxin-dependent manner. These results emphasize the importance of diet-microbiome interactions in modulating host energy balance and the need to understand the role of diet in the interplay between pathogenic and beneficial symbionts.

Legislative Intent and Agency: A Rational Unity Account.

Realist theories of legislative intent can be divided between aggregative theories (on which legislative intent is what some proportion of legislators intend) and common intent theories (on which legislative intent is a unanimous intent among legislators). In this article, we advance and defend an alternative realist conception of legislative intent: the rational unity account. On this account, the legislature is an agent with a distinctive 'rational point of view'-a concept we adopt from social ontology. The legislature's rational point of view is shaped by its procedures and structures, in ways not determined by either a common intention held by legislators or an aggregation of the intentions of legislators. We explain how our view improves on existing accounts. We then apply it to three cases to demonstrate its implications for legal interpretation. Importantly, on the proposed account, legislative intent can depart from what individual legislators think or know.

Synthetically Tunable White-, Green-, and Yellow-Green-Light Emission in Dual-Luminescent Gold(I) Complexes Bearing a Diphenylamino-2,7-fluorenyl Moiety.

The syntheses and photophysical characterization of five new gold(I) complexes bearing diphenylamine-substituted fluorenyl moieties are reported; four are characterized by X-ray diffraction crystallography. Ancillary ligation on gold(I) is provided by organophosphine and N-heterocyclic carbene ligands. Two complexes, Au-DPA0 and Au-DPA1, are σ-aryls, two, Au-ADPA0 and Au-ADPA1, are σ-alkynyls, and one, Au-TDPA1, is a σ-triazolyl bound through carbon. All complexes show vibronically structured absorption and luminescence bands that are assignable to π-π* transitions localized on the diphenylamine-substituted fluorenyl π system. The excited-state dynamics of all five chromophores are governed by selection of the ancillary ligand and σ attachment of the diphenylamine-substituted fluorenyl moiety. All of these chromophores are dual luminescent in a toluene solution at 298 K. The luminescence from the aryl derivatives, Au-ADPA0 and Au-DPA1, appears green. The alkynyl derivative containing a phosphine ancillary ligand, Au-ADPA0, is a white-light emitter, while the alkynyl derivative containing an N-heterocyclic carbene ancillary ligand, Au-ADPA1, is a yellow-light emitter. The luminescence from the triazolyl-linked chromophore, Au-TDPA1, appears as yellow-green. Spin-restricted density functional theory calculations support the assignments of ligand-centric optical transitions but with contributions of ligand-to-metal charge transfer involving the vacant Au 6p orbital.

Pharmacy utilization of electronic patient-reported outcomes in oncology populations.

Telehealth applications are demonstrated to be useful tools for patients with cancer to facilitate improvements in quality of care. The use of electronic patient-reported outcomes is one way to leverage telehealth to better understand outcomes important to patients. However, use of electronic patient-reported outcomes and direct involvement of pharmacists is not yet a standard practice across cancer centers. The use of pharmacist-led telehealth services offers a unique opportunity for pharmacists to provide cost-effective and convenient patient care interventions. This survey work describes the current practices of pharmacy utilization of electronic patient-reported outcomes in oncology populations at National Comprehensive Cancer Network member institutions. Of survey respondents, only 33% of the institutions reported current engagement with electronic patient-reported outcomes. These initiatives largely focused on symptom management. Limitations in staff, resources, and competing priorities limit many institutions from introducing or expanding upon direct pharmacist involvement in electronic patient-reported outcomes. Further work developing the involvement of pharmacists in electronic patient-reported outcomes will be an important way to leverage the growing landscape of telehealth within oncology and highlight the value of the pharmacist.

[Ageing and memory loss: opinions of Haitian migrants living in Quebec.] / Vieillissement et perte de mémoire : avis de migrants haïtiens résidant au Québec.

INTRODUCTION: ‘Dementia’ is usually presented as a syndrome characterized by the decline of one or more cognitive abilities such as memory loss. However, memory loss does not necessarily mean dementia. The most common type of dementia is Alzheimer’s disease. Its incidence increases with age. In medical anthropology, diseases represent socio-cultural constructs that are not recognized and interpreted in the same way by everyone. Moreover, the migratory context is a source of difficulties in the field of dementia. In this article, we discuss the links between old age, dementia and seeking help in this context. METHOD: This is an exploratory qualitative study. Ten semi-structured interviews were conducted with women and men born in Haiti who then immigrated to Quebec. These interviews allowed us to discuss seniors’ status issues, the meaning of memory loss and seeking help. RESULTS: Interview data reveal a plurality of representations about memory loss and Alzheimer’s disease. They highlight a diversity of beliefs, attitudes and values that reflect cultural and social changes within the same community. Taking into account the context makes it possible to consider the transformation or continuity of representations and behaviors vis-à-vis loss of memory. CONCLUSION: Dementia does not seem to be a phenomenon that is easily approached in the Haitian community in Quebec. Our study reveals a lack of information in this regard.

Microbiota-Mediated Modulation of Organophosphate Insecticide Toxicity by Species-Dependent Interactions with Lactobacilli in a Drosophila melanogaster Insect Model.

Despite the benefits to the global food supply and agricultural economies, pesticides are believed to pose a threat to the health of both humans and wildlife. Chlorpyrifos (CP), a commonly used organophosphate insecticide, has poor target specificity and causes acute neurotoxicity in a wide range of species via the suppression of acetylcholinesterase. This effect is exacerbated 10- to 100-fold by chlorpyrifos oxon (CPO), a principal metabolite of CP. Since many animal-associated symbiont microorganisms are known to hydrolyze CP into CPO, we used a Drosophila melanogaster insect model to investigate the hypothesis that indigenous and probiotic bacteria could affect CP metabolism and toxicity. Antibiotic-treated and germfree D. melanogaster insects lived significantly longer than their conventionally reared counterparts when exposed to 10 µM CP. Drosophila melanogaster gut-derived Lactobacillus plantarum, but not Acetobacterindonesiensis, was shown to metabolize CP. Liquid chromatography tandem-mass spectrometry confirmed that the L. plantarum isolate preferentially metabolized CP into CPO when grown in CP-spiked culture medium. Further experiments showed that monoassociating germfree D. melanogaster with the L. plantarum isolate could reestablish a conventional-like sensitivity to CP. Interestingly, supplementation with the human probiotic Lactobacillus rhamnosus GG (a strain that binds but does not metabolize CP) significantly increased the survival of the CP-exposed germfree D. melanogaster This suggests strain-specific differences in CP metabolism may exist among lactobacilli and emphasizes the need for further investigation. In summary, these results suggest that (i) CPO formation by the gut microbiota can have biologically relevant consequences for the host, and (ii) probiotic lactobacilli may be beneficial in reducing in vivo CP toxicity.IMPORTANCE An understudied area of research is how the microbiota (microorganisms living in/on an animal) affects the metabolism and toxic outcomes of environmental pollutants such as pesticides. This study focused specifically on how the microbial biotransformation of chlorpyrifos (CP; a common organophosphate insecticide) affected host exposure and toxicity parameters in a Drosophila melanogaster insect model. Our results demonstrate that the biotransformation of CP by the gut microbiota had biologically relevant and toxic consequences on host health and that certain probiotic lactobacilli may be beneficial in reducing CP toxicity. Since inadvertent pesticide exposure is suspected to negatively impact the health of off-target species, these findings may provide useful information for wildlife conservation and environmental sustainability planning. Furthermore, the results highlight the need to consider microbiota composition differences between beneficial and pest insects in future insecticide designs. More broadly, this study supports the use of beneficial microorganisms to modulate the microbiota-mediated biotransformation of xenobiotics.

Promising Prebiotic Candidate Established by Evaluation of Lactitol, Lactulose, Raffinose, and Oligofructose for Maintenance of a Lactobacillus-Dominated Vaginal Microbiota.

Perturbations to the vaginal microbiota can lead to dysbiosis, including bacterial vaginosis (BV), which affects a large portion of the female population. In a healthy state, the vaginal microbiota is characterized by low diversity and colonization by Lactobacillus spp., whereas in BV, these species are displaced by a highly diverse population of bacteria associated with adverse vaginal health outcomes. Since prebiotic ingestion has been a highly effective approach to invigorate lactobacilli for improved intestinal health, we hypothesized that these compounds could stimulate lactobacilli at the expense of BV organisms to maintain vaginal health. Monocultures of commensal Lactobacillus crispatus, Lactobacillus vaginalis, Lactobacillus gasseri, Lactobacillus johnsonii, Lactobacillus jensenii, and Lactobacillus iners, in addition to BV-associated organisms and Candida albicans, were tested for their ability to utilize a representative group of prebiotics consisting of lactitol, lactulose, raffinose, and oligofructose. The disaccharide lactulose was found to most broadly and specifically stimulate vaginal lactobacilli, including the strongly health-associated species L. crispatus, and importantly, not to stimulate BV organisms or C. albicans Using freshly collected vaginal samples, we showed that exposure to lactulose promoted commensal Lactobacillus growth and dominance and resulted in healthy acidity partially through lactic acid production. This provides support for further testing of lactulose to prevent dysbiosis and potentially to reduce the need for antimicrobial agents in managing vaginal health.IMPORTANCE Bacterial vaginosis (BV) and other dysbioses of the vaginal microbiota significantly affect the quality of life of millions of women. Antimicrobial therapy is often poorly effective, causes side effects, and does not prevent recurrences. We report one of very few studies that have evaluated how prebiotics-compounds that are selectively fermented by beneficial bacteria such as Lactobacillus spp.-can modulate the vaginal microbiota. We also report use of a novel in vitro polymicrobial model to study the impact of prebiotics on the vaginal microbiota. The identification of prebiotic lactulose as enhancing Lactobacillus growth but not that of BV organisms or Candida albicans has direct application for retention of homeostasis and prevention of vaginal dysbiosis and infection.

Notch cooperates with Lozenge/Runx to lock haemocytes into a differentiation programme.

The diverse functions of Notch signalling imply that it must elicit context-specific programmes of gene expression. With the aim of investigating how Notch drives cells to differentiate, we have used a genome-wide approach to identify direct Notch targets in Drosophila haemocytes (blood cells), where Notch promotes crystal cell differentiation. Many of the identified Notch-regulated enhancers contain Runx and GATA motifs, and we demonstrate that binding of the Runx protein Lozenge (Lz) is required for enhancers to be competent to respond to Notch. Functional studies of targets, such as klumpfuss (ERG/WT1 family) and pebbled/hindsight (RREB1 homologue), show that Notch acts both to prevent the cells adopting alternate cell fates and to promote morphological characteristics associated with crystal cell differentiation. Inappropriate activity of Klumpfuss perturbs the differentiation programme, resulting in melanotic tumours. Thus, by acting as a master regulator, Lz directs Notch to activate selectively a combination of target genes that correctly locks cells into the differentiation programme.

Long Duration Energy Storage Using Hydrogen in Metal-Organic Frameworks: Opportunities and Challenges.

Materials-based H2 storage plays a critical role in facilitating H2 as a low-carbon energy carrier, but there remains limited guidance on the technical performance necessary for specific applications. Metal-organic framework (MOF) adsorbents have shown potential in power applications, but need to demonstrate economic promises against incumbent compressed H2 storage. Herein, we evaluate the potential impact of material properties, charge/discharge patterns, and propose targets for MOFs' deployment in long-duration energy storage applications including backup, load optimization, and hybrid power. We find that state-of-the-art MOF could outperform cryogenic storage and 350 bar compressed storage in applications requiring ≤8 cycles per year, but need ≥5 g/L increase in uptake to be cost-competitive for applications that require ≥30 cycles per year. Existing challenges include manufacturing at scale and quantifying the economic value of lower-pressure storage. Lastly, future research needs are identified including integrating thermodynamic effects and degradation mechanisms.

Postoperative Hydration in Children Using Intermittent Boluses of Balanced Salt Solution: Results of a Randomized Control Trial.

BACKGROUND: Postoperative maintenance fluids are traditionally provided via hypotonic dextrose containing fluids administered intravenously by continuous infusion. We hypothesized that scheduled weight-based boluses of balanced salt solution would be more physiologic, reduce fluid volumes, and improve patient comfort. METHODS: As part of an IRB-approved randomized controlled trial (Boluses of Ringer's in Surgical Kids, BRiSK), we randomized patients aged 1-21 years undergoing elective abdominal or thoracic surgery to post-operatively receive weight-based D50.45NS+20mEq/L KCl at a continuous rate or intermittent boluses of Lactated Ringer's solution until oral liquid toleration. Patients with nephropathy, diabetes, or receiving parenteral nutrition were excluded. We analyzed electrolytes, urine output, fluid volume, and adverse events. RESULTS: We enrolled and randomized 60 patients: 29 to continuous fluids and 31 to bolus fluids. One patient from the bolus group dropped out. No patients crossed over due to difficulties with application of the bolus protocol. There were no baseline differences between groups with a mean age of 12.6 ± 1.4yr and weight of 50.9 ± 7.2 kg. There were no serious adverse events or electrolyte disturbances in either group. Patients in the bolus group received significantly less total fluid than those in the continuous group (0.43 mL/kg/h vs 1.1 mL/kg/h, p < 0.001) with no difference in urine output [1.4 ± 0.2 mL/kg/h vs 1.6 ± 0.3 mL/kg/h, p = 0.211]. There were two episodes of mild hypoglycemia in the bolus group compared to seven episodes of mild hyperglycemia in the continuous group. CONCLUSIONS: Administration of post-operative intravenous fluids as boluses of balanced salt solution is feasible, safe, and results in significantly less fluid administered compared to a traditional continuous protocol. LEVEL OF EVIDENCE: II.

Positive clinical outcome using a modified dosing regimen of benznidazole in dogs at high risk for infection or acutely infected with Trypanosoma cruzi.

Trypanosoma cruzi infection in dogs can cause heart failure and sudden death with few treatment options available. A litter of 4 dogs living in a T cruzi endemic area were randomized to prophylaxis and nonprophylaxis groups as part of a study evaluating a modified benznidazole dosing regimen administered twice weekly to prevent T cruzi infection during a vector transmission season. The 2 dogs that received prophylaxis remained healthy without T cruzi infection or cardiac disease for >2 years. One dog that did not receive prophylaxis died unexpectedly with acute T cruzi-induced pancarditis, and the second dog tested positive for T cruzi and developed complex arrhythmias with markedly increased cardiac troponin I and improved with a higher benznidazole treatment dose. Although the small sample size precludes definitive conclusions, we describe the potential clinical benefit of prophylactic and early treatment with modified benznidazole dosing regimens for dogs with T cruzi infection.

Electrocardiographic abnormalities are associated with seropositive Trypanosoma cruzi infection status using a simplified cardiac diagnostic evaluation in dogs.

OBJECTIVE: To describe associations between cardiac abnormalities and Trypanosoma cruzi serostatus by use of a simplified diagnostic evaluation in dogs at risk for T cruzi infection. METHODS: A prospective, cross-sectional study was performed using a simplified diagnostic evaluation including high-sensitivity cardiac troponin I, 30-second ECG, and echocardiogram with 7 variables in 46 client-owned dogs from high-risk environments. Dogs were categorized as serologically positive (SP), negative (SN), or discordant (SD) by use of 2 antibody tests. Functional evaluation of cardiac health scores and blood PCR were obtained. RESULTS: Dogs were SP (n = 19), SN (17), and SD (10), with 9 PCR positive (7 SP, 1 SN, 1 SD). Troponin was above reference range in 6 of 46 (4 SP, 1 SN, 1 SD), and functional evaluation of cardiac health scores were 0 in all dogs. Conduction system abnormalities (prolonged interval durations, second-degree atrioventricular block, splintered QRS complex) and ventricular arrhythmias were documented in 8 (7 SP, 0 SN, 1 SD). Twenty-six (12 SP, 8 SN, 6 SD) had echocardiographic abnormalities, most often myxomatous mitral valve disease (MMVD) and left ventricular enlargement. Seropositive dogs were significantly older and had a higher likelihood of MMVD. Conduction system abnormalities were associated with positive serostatus. CONCLUSIONS: Echocardiographic abnormalities were complicated by MMVD and did not distinguish between serostatus. An ECG with assessment and detailed measurement of complexes and cardiac troponin I are simple tests to perform with abnormalities detected in seroreactive dogs. CLINICAL RELEVANCE: Electrocardiographic abnormalities in high-risk or seroreactive dogs should prompt further evaluation and monitoring of T cruzi infection.

Bile acids and the gut microbiota: metabolic interactions and impacts on disease.

Despite decades of bile acid research, diverse biological roles for bile acids have been discovered recently due to developments in understanding the human microbiota. As additional bacterial enzymes are characterized, and the tools used for identifying new bile acids become increasingly more sensitive, the repertoire of bile acids metabolized and/or synthesized by bacteria continues to grow. Additionally, bile acids impact microbiome community structure and function. In this Review, we highlight how the bile acid pool is manipulated by the gut microbiota, how it is dependent on the metabolic capacity of the bacterial community and how external factors, such as antibiotics and diet, shape bile acid composition. It is increasingly important to understand how bile acid signalling networks are affected in distinct organs where the bile acid composition differs, and how these networks impact infectious, metabolic and neoplastic diseases. These advances have enabled the development of therapeutics that target imbalances in microbiota-associated bile acid profiles.

Effect of Concurrent Proton Pump Inhibitors With Palbociclib Tablets for Metastatic Breast Cancer.

BACKGROUND: Palbociclib is indicated for the treatment of hormone receptor positive (HR+) human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer (MBC) in combination with an aromatase inhibitor or fulvestrant. Two retrospective studies found that concurrent proton pump inhibitor (PPI) use with palbociclib capsules significantly reduced progression free survival (PFS) versus patients without a PPI. Palbociclib tablets were released in 2020 without restriction on PPI use. No study to date has evaluated the combination of palbociclib tablets with concurrent PPI use. METHODS: Patients were retrospectively evaluated after they received palbociclib tablets for the treatment of HR+ HER2- MBC in the first line setting with or without a PPI. Patients were assigned to the no PPI use arm if they never used a PPI and the PPI use arm if they used a PPI for >50% of the duration of palbocicib therapy. The primary endpoint was PFS. The secondary endpoints included overall survival (OS) and adverse events. RESULTS: Eighty-two patients were identified; 50 in the no PPI use group and 32 in the PPI use group. The median PFS was 20.6 months (95% confidence interval [CI], 16.07 to not estimable) in the no PPI use arm versus 21.0 months (95% CI, 15.15 to not estimable) in the PPI use arm (P = 0.95). Median OS was not reached in either arm. Adverse effects did not differ between arms. CONCLUSION: Use of a concurrent PPI with palbociclib tablets does not significantly reduce PFS in patients treated for HR+ HER2- MBC.

Impact of Dose Intensity on Pathologic Complete Response Rate in HER2-Positive Breast Cancer Patients Receiving Neoadjuvant Docetaxel, Carboplatin, Trastuzumab and Pertuzumab (TCHP).

BACKGROUND: Neoadjuvant chemotherapy is the cornerstone treatment for locally advanced breast cancer. Balancing toxicity and efficacy are a common concern of patients treated with chemotherapy. OBJECTIVE: The objective of this study was to determine the impact of dose intensity on pathologic complete response (pCR) at the time of surgery in patients with human epidermal growth factor receptor 2-positive (HER2+) breast cancer. PATIENTS AND METHODS: A retrospective, single-center review was conducted on patients with HER2+ breast cancer who received neoadjuvant docetaxel, carboplatin, trastuzumab and pertuzumab (TCHP) followed by definitive surgery. RESULTS: A total of 159 patients were included in the analysis; pCR was obtained in 66 patients (42%). There was no statistically significant difference between the mean dose intensity of each of the individual agents in TCHP and pCR rates. The mean overall dose intensity of docetaxel, carboplatin, trastuzumab and pertuzumab was 90.5%, 90.9%, 97.5%, and 93.9%, respectively. Although higher chemotherapy dose intensity (> 85%) was associated with higher pCR rates, no statistically significant difference was found compared with chemotherapy dose intensity < 85%. The TCHP regimen was difficult to tolerate; 104 patients (65%) required a dose reduction or dose delay during treatment due to toxicity. CONCLUSION: The TCHP regimen, which combines chemotherapy and HER2-directed therapy is effective at obtaining pCR in patients with locally advanced HER2+ breast cancer. These results suggest that the dose intensity of the individual agents did not have a significant impact on pCR rates. Given these findings, providers may be more comfortable allowing dose reductions for greater patient tolerability without sacrificing efficacy.

Prophylactic low-dose, bi-weekly benznidazole treatment fails to prevent Trypanosoma cruzi infection in dogs under intense transmission pressure.

Trypanosoma cruzi naturally infects a wide variety of wild and domesticated mammals, in addition to humans. Depending on the infection dose and other factors, the acute infection can be life-threatening, and in all cases, the risk of chagasic heart disease is high in persistently infected hosts. Domestic, working, and semi-feral dogs in the Americas are at significant risk of T. cruzi infection and in certain settings in the southern United States, the risk of new infections can exceed 30% per year, even with the use of vector control protocols. In this study, we explored whether intermittent low-dose treatment with the trypanocidal compound benznidazole (BNZ) during the transmission season, could alter the number of new infections in dogs in an area of known, intense transmission pressure. Preliminary studies in mice suggested that twice-weekly administration of BNZ could prevent or truncate infections when parasites were delivered at the mid-point between BNZ doses. Pre-transmission season screening of 126 dogs identified 53 dogs (42.1%) as T. cruzi infection positive, based upon blood PCR and Luminex-based serology. Serial monitoring of the 67 uninfected dogs during the high transmission season (May to October) revealed 15 (22.4%) new infections, 6 in the untreated control group and 9 in the group receiving BNZ prophylaxis, indicating no impact of this prophylaxis regimen on the incidence of new infections. Although these studies suggest that rigorously timed and more potent dosing regimen may be needed to achieve an immediate benefit of prophylaxis, additional studies would be needed to determine if drug prophylaxis reduced disease severity despite this failure to prevent new infections.

Current Challenges and Recent Developments in Mass Spectrometry-Based Metabolomics.

High-resolution mass spectrometry (MS) has advanced the study of metabolism in living systems by allowing many metabolites to be measured in a single experiment. Although improvements in mass detector sensitivity have facilitated the detection of greater numbers of analytes, compound identification strategies, feature reduction software, and data sharing have not kept up with the influx of MS data. Here, we discuss the ongoing challenges with MS-based metabolomics, including de novo metabolite identification from mass spectra, differentiation of metabolites from environmental contamination, chromatographic separation of isomers, and incomplete MS databases. Because of their popularity and sensitive detection of small molecules, this review focuses on the challenges of liquid chromatography-mass spectrometry-based methods. We then highlight important instrumentational, experimental, and computational tools that have been created to address these challenges and how they have enabled the advancement of metabolomics research.

Quantification of arterial, venous, and cerebrospinal fluid flow dynamics by magnetic resonance imaging under simulated micro-gravity conditions: a prospective cohort study.

BACKGROUND: Astronauts undergoing long-duration spaceflight are exposed to numerous health risks, including Spaceflight-Associated Neuro-Ocular Syndrome (SANS), a spectrum of ophthalmic changes that can result in permanent loss of visual acuity. The etiology of SANS is not well understood but is thought to involve changes in cerebrovascular flow dynamics in response to microgravity. There is a paucity of knowledge in this area; in particular, cerebrospinal fluid (CSF) flow dynamics have not been well characterized under microgravity conditions. Our study was designed to determine the effect of simulated microgravity (head-down tilt [HDT]) on cerebrovascular flow dynamics. We hypothesized that microgravity conditions simulated by acute HDT would result in increases in CSF pulsatile flow. METHODS: In a prospective cohort study, we measured flow in major cerebral arteries, veins, and CSF spaces in fifteen healthy volunteers using phase contrast magnetic resonance (PCMR) before and during 15° HDT. RESULTS: We found a decrease in all CSF flow variables [systolic peak flow (p = 0.009), and peak-to-peak pulse amplitude (p = 0.001)]. Cerebral arterial average flow (p = 0.04), systolic peak flow (p = 0.04), and peak-to-peak pulse amplitude (p = 0.02) all also significantly decreased. We additionally found a decrease in average cerebral arterial flow (p = 0.040). Finally, a significant increase in cerebral venous cross-sectional area under HDT (p = 0.005) was also observed. CONCLUSIONS: These results collectively demonstrate that acute application of -15° HDT caused a reduction in CSF flow variables (systolic peak flow and peak-to-peak pulse amplitude) which, when coupled with a decrease in average cerebral arterial flow, systolic peak flow, and peak-to-peak pulse amplitude, is consistent with a decrease in cardiac-related pulsatile CSF flow. These results suggest that decreases in cerebral arterial inflow were the principal drivers of decreases in CSF pulsatile flow.