Habitability on Mars from a Microbial Point of View

International audienceExtraterrestrial habitability is a complex notion. We briefly review what is known about the origin of life on Earth, that is, life based on carbon chemistry and water. We then discuss habitable conditions (past and present) for established life and for the survival of microorganisms. Based on these elements, we propose to use the term habitable only for conditions necessary for the origin of life, the proliferation of life, and the survival of life. Not covered by this term would be conditions necessary for prebiotic chemistry and conditions that would allow the recognition of extinct or hibernating life. Finally, we apply this concept to the potential emergence of life on Mars where suitable conditions for life to start, proliferate, and survive have been heterogeneous throughout its history. These considerations have a profound impact on the nature and distribution of eventual traces of martian life, or any precursor, and must therefore inform our search-for-life strategies. Key Words: Mars-- Microbial life--Punctuated habitabilit

Thiahelicene-grafted halloysite nanotubes: Characterization, biological studies and pH triggered release

A novel drug delivery nanosystem was here designed, linking thiahelicenes to halloysite nanotubes. Tetrathia[7]helicenes are very promising DNA intercalators, whose usage in biomedical field has been so far limited by their poor bioavailability. The study of appropriate drug delivery systems is needed to exploit helicenes as therapeutics. In this work, imine chemistry was adopted to covalently attach the bioactive compound and release it in acidic environments such as those surrounding tumour cells. To this aim, halloysite nanotubes were functionalized with (3-aminopropyl)triethoxysilane. The latter acted as linker providing NH2 groups to react with the formyl moiety of the thiahelicene derivative. The nanoconstruct preparation was studied in depth by surface-sensitive spectroscopies and angle-resolved X-ray absorption, to investigate the attachment mode, surface coverage and molecular orientation of the thiahelicene units. Release tests were carried out also in vitro on two tumour cell lines with different extracellular pH values. Mildly acidic pH conditions catalyzed the hydrolysis of the imine bond and promoted the cytotoxic compound release, which proved selective to slight pH differences, confirming the potential of this novel nanoconstruct

May Strenuous Endurance Sports Activity Damage the Cardiovascular System of Healthy Athletes? A Narrative Review

The positive effects of physical activity are countless, not only on the cardiovascular system but on health in general. However, some studies suggest a U-shape relationship between exercise volume and effects on the cardiovascular system. On the basis of this perspective, moderate-dose exercise would be beneficial compared to a sedentary lifestyle, while very high-dose physical activity would paradoxically be detrimental. We reviewed the available evidence on the potential adverse effects of very intense, prolonged exercise on the cardiovascular system, both acute and chronic, in healthy athletes without pre-existing cardiovascular conditions. We found that endurance sports activities may cause reversible electrocardiographic changes, ventricular dysfunction, and troponin elevation with complete recovery within a few days. The theory that repeated bouts of acute stress on the heart may lead to chronic myocardial damage remains to be demonstrated. However, male veteran athletes with a long sports career show an increased prevalence of cardiovascular abnormalities such as electrical conduction delay, atrial fibrillation, myocardial fibrosis, and coronary calcifications compared to non-athletes. It must be underlined that the cause–effect relationship between such abnormalities and the exercise and, most importantly, the prognostic relevance of such findings remains to be established

Characterizing Rock Abundance At ExoMars Landing Site Candidates

We present preliminary work to characterize surface rock abundance at ExoMars Rover landing site candidates. A challenge in quantifying the abundance of surface rocks is using the population of large (≳1 m) rocks that are resolved in orbital images to infer the size of the smaller, unresolved rock population. This is particularly relevant for the ExoMars Rover mission, where the Landing Module’s clearance of 35 cm makes it necessary to know the probability of encountering rocks where 0.35 < D < 1 m. ‘Float rocks’ are individual fragments of rock not associated with a continuous outcrop or body of rock —e.g. transported rocks or impact debris. These can be identified in Mars Reconnaissence Orbiter HiRISE images, where the mid-afternoon local solar time, dictated by MROs’ orbit, causes float rocks to appear as bright sunlit features adjacent to strong shadows. However, the smallest features resolvable in HiRISE images occupy around 3-4 pixels, corresponding to ~1-m sized rocks. This inherently limits the ability to directly identify from orbit the small, but potentially hazardous rock population. ‘Outcrop’ is defined as continuous expanses of bedrock or surficial deposits exposed at the surface. Both float rocks and outcrop can contribute to slopes that may constitute a hazard for landed missions. We present rock counts at ExoMars Rover landing site candidates and assess approaches to constrain the morphological characteristics of Mars’ surface that are relevant to rover and lander safety

Direct comparison of B-Type Natriuretic Peptide (BNP) and amino-terminal proBNP in a large population of patients with chronic and symptomatic heart failure: the Valsartan Heart Failure (Val-HeFT) data

Background: The B-type or brain natriuretic peptides (BNP) and the amino-terminal probrain natriuretic peptide (NT-proBNP) are good markers of prognosis and diagnosis in chronic heart failure (HF). It is unclear, however, whether differences in their biological characteristics modify their clinical correlates and prognostic performance in HF. This work aimed to provide a direct comparison of the prognostic value of BNP and NTproBNP in patients with chronic and stable HF. Methods: We measured BNP and NT-proBNP at baseline in 3916 patients enrolled in the Valsartan Heart Failure Trial. To identify the variables associated with both peptides, we conducted simple and multivariable linear regression analyses. We used Cox multivariable regression models to evaluate the independent prognostic value for all-cause mortality, mortality and morbidity, and hospitalization for HF. Prognostic performance was assessed by pairwise comparisons of the area under the curve of receiver-operator characteristic curves. Results: NT-proBNP and BNP had similar relationships with age, left ventrical ejection fraction, and internal diameter and creatinine clearance. Either peptide ranked as the first independent predictor of outcome after adjustment for major confounding clinical characteristics. ROC curves were almost superimposable for all-cause mortality (area under the curve (SE): BNP 0.665 (0.011) vs NT-proBNP 0.679 (0.011); P 0.0734), but NT-proBNP was superior to BNP for predicting mortality and morbidity (P 0.032) or hospitalization for HF (P 0.0143). Overall sensitivity and specificity ranged from 0.590 to 0.696. Conclusions: The natriuretic peptides BNP and NTproBNP showed subtle differences in their relation to clinical characteristics and prognostic performance in a large population of patients with chronic and stable HF. They were the most powerful independent markers of outcome in HF

2018 MAX-C/ExoMars Mission: The Orleans Mars-Analogue Rock Collection for Instrument Testing

International audienceIn order to reply to the exobiological goals of the 2018 MAX-C/ExoMars mission, the Orléans-OSUC analogue rock collection and database contains well characterised Mars analogue rocks and minerals for use in instrument testing and in situ missions