Volatile and organic compositions of sedimentary rocks in Yellowknife Bay, Gale crater, Mars

H2O, CO2, SO2, O2, H2, H2S, HCl, chlorinated hydrocarbons, NO, and other trace gases were evolved during pyrolysis of two mudstone samples acquired by the Curiosity rover at Yellowknife Bay within Gale crater, Mars. H2O/OH-bearing phases included 2:1 phyllosilicate(s), bassanite, akaganeite, and amorphous materials. Thermal decomposition of carbonates and combustion of organic materials are candidate sources for the CO2. Concurrent evolution of O2 and chlorinated hydrocarbons suggests the presence of oxychlorine phase(s). Sulfides are likely sources for sulfur-bearing species. Higher abundances of chlorinated hydrocarbons in the mudstone compared with Rocknest windblown materials previously analyzed by Curiosity suggest that indigenous martian or meteoritic organic carbon sources may be preserved in the mudstone; however, the carbon source for the chlorinated hydrocarbons is not definitively of martian origin.

Formation of amino acids and nucleotide bases in a Titan atmosphere simulation experiment

The discovery of large (>100 u) molecules in Titan's upper atmosphere has heightened astrobiological interest in this unique satellite. In particular, complex organic aerosols produced in atmospheres containing C, N, O, and H, like that of Titan, could be a source of prebiotic molecules. In this work, aerosols produced in a Titan atmosphere simulation experiment with enhanced CO (N(2)/CH(4)/CO gas mixtures of 96.2%/2.0%/1.8% and 93.2%/5.0%/1.8%) were found to contain 18 molecules with molecular formulae that correspond to biological amino acids and nucleotide bases. Very high-resolution mass spectrometry of isotopically labeled samples confirmed that C(4)H(5)N(3)O, C(4)H(4)N(2)O(2), C(5)H(6)N(2)O(2), C(5)H(5)N(5), and C(6)H(9)N(3)O(2) are produced by chemistry in the simulation chamber. Gas chromatography-mass spectrometry (GC-MS) analyses of the non-isotopic samples confirmed the presence of cytosine (C(4)H(5)N(3)O), uracil (C(5)H(4)N(2)O(2)), thymine (C(5)H(6)N(2)O(2)), guanine (C(5)H(5)N(5)O), glycine (C(2)H(5)NO(2)), and alanine (C(3)H(7)NO(2)). Adenine (C(5)H(5)N(5)) was detected by GC-MS in isotopically labeled samples. The remaining prebiotic molecules were detected in unlabeled samples only and may have been affected by contamination in the chamber. These results demonstrate that prebiotic molecules can be formed by the high-energy chemistry similar to that which occurs in planetary upper atmospheres and therefore identifies a new source of prebiotic material, potentially increasing the range of planets where life could begin.

Chemical characterization of Titan's tholins: solubility, morphology and molecular structure revisited

In this work Titan's atmospheric chemistry is simulated using a capacitively coupled plasma radio frequency discharge in a N(2)-CH(4) stationnary flux. Samples of Titan's tholins are produced in gaseous mixtures containing either 2 or 10% methane before the plasma discharge, covering the methane concentration range measured in Titan's atmosphere. We study their solubility and associated morphology, their infrared spectroscopy signature and the mass distribution of the soluble fraction by mass spectrometry. An important result is to highlight that the previous Titan's tholin solubility studies are inappropriate to fully characterize such a heterogeneous organic matter and we develop a new protocol to evaluate quantitatively tholins solubility. We find that tholins contain up to 35% in mass of molecules soluble in methanol, attached to a hardly insoluble fraction. Methanol is then chosen as a discriminating solvent to characterize the differences between soluble and insoluble species constituting the bulk tholins. No significant morphological change of shape or surface feature is derived from scanning electron microscopy after the extraction of the soluble fraction. This observation suggests a solid structure despite an important porosity of the grains. Infrared spectroscopy is recorded for both fractions. The IR spectra of the bulk, soluble, and insoluble tholins fractions are found to be very similar and reveal identical chemical signatures of nitrogen bearing functions and aliphatic groups. This result confirms that the chemical information collected when analyzing only the soluble fraction provides a valuable insight representative of the bulk material. The soluble fraction is ionized with an atmospheric pressure photoionization source and analyzed by a hybrid mass spectrometer. The congested mass spectra with one peak at every mass unit between 50 and 800 u confirm that the soluble fraction contains a complex mixture of organic molecules. The broad distribution, however, exhibits a regular pattern of mass clusters. Tandem collision induced dissociation analysis is performed in the negative ion mode to retrieve structural information. It reveals that (i) the molecules are ended by methyl, amine and cyanide groups, (ii) a 27 u neutral moiety (most probably HCN) is often released in the fragmentation of tholin anions, and (iii) an ubiquitous ionic fragment at m/z 66 is found in all tandem spectra. A tentative structure is proposed for this negative ion.

In situ analysis of the Martian soil by gas chromatography: Decoding of complex chromatograms of organic molecules of exobiological interest

Gas chromatography-mass spectrometry (GC-MS) will be used in future space exploration missions, in order to seek organic molecules at the surface of Mars, and especially potential chemical indicators of life. Carboxylic acids are among the most expected organic species at the surface of Mars, and they could be numerous in the analysed samples. For this reason, a chemometric method was applied to support the interpretation of chromatograms of carboxylic acid mixtures. The method is based on AutoCovariance Function (ACVF) in order to extract information on the sample--number and chemical structure of the components--and on separation performance. The procedure was applied to standard samples containing targeted compounds which are among the most expected to be present in the Martian soil: n-alkanoic and benzene dicarboxylic acids. ACVF was computed on the obtained chromatograms and plotted versus retention time: peaks of the ACVF plot can be related to specific molecular structures and are diagnostic for chemical identification of compounds.

Comparative pharmacokinetics of equimolar doses of 5-aminosalicylate administered as oral mesalamine (Asacol) and balsalazide: a randomized, single-dose, crossover study in healthy volunteers

BACKGROUND

Existing pharmacokinetic data are insufficient to determine whether a delayed-release formulation of mesalamine (Asacol) results in greater systemic exposure to 5-aminosalicylic acid and its major metabolite N-acetyl-5-aminosalicylic acid than a prodrug (balsalazide).

AIM

To determine the pharmacokinetic parameters of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid from equimolar doses of 5-aminosalicylic acid administered as Asacol and balsalazide.

METHODS

Nineteen healthy volunteers completed an open-label, single-dose, randomized, crossover study comparing the pharmacokinetics of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid from equimolar doses of 5-aminosalicylic acid (800 mg) administered as Asacol (800 mg) and balsalazide (2250 mg). Plasma and urine samples were analysed for 5-aminosalicylic acid, N-acetyl-5-aminosalicylic acid, and balsalazide (urine only) using high-performance liquid chromatography methods with mass spectrometric detection. Pharmacokinetic parameters assessed for 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid included: percentage of dose excreted in urine (A(e)%), area under the plasma concentration-time curve (AUCt(last)); and maximum plasma concentration (C(max)).

RESULTS

The geometric mean total (5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid) urinary excretion values (A(e)%) of Asacol and balsalazide were 19.26 and 19.31% (P = 0.98). The geometric mean A(e)% values of 5-aminosalicylic acid for Asacol and balsalazide were 0.39 and 0.37% (P = 0.78); the geometric mean A(e)% values of N-acetyl-5-aminosalicylic acid for Asacol and balsalazide were 18.78 and 18.83% (P = 0.98). The geometric mean 5-aminosalicylic acid AUC(t(last)) values for Asacol and balsalazide were 3295 and 3449 ng h/mL (P = 0.85); the geometric mean N-acetyl-5-aminosalicylic acid AUC(t(last)) values for Asacol and balsalazide were 15 364 and 16 050 ng h/mL (P = 0.69). The geometric mean 5-5-aminosalicylic acid C(max) values for Asacol and balsalazide were 319 and 348 ng/mL (P = 0.80); the geometric mean N-acetyl-5-aminosalicylic acid C(max) values for Asacol and balsalazide 927 and 1009 ng/mL (P = 0.67).

CONCLUSIONS

The systemic absorption of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid from Asacol and balsalazide are comparable based upon plasma pharmacokinetic parameters and urinary excretion values.

Solvent extraction of organic molecules of exobiological interest for in situ analysis of the Martian soil

A solid-liquid extraction method able to perform in situ extraction of organic compounds on Mars is proposed. The extraction efficiency of various organic solvents was tested and compared to that of water. The selected key compounds are molecules of exobiological interest: glycine, alanine, serine, glutamic acid, oxalic acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid and 1,3,5-benzenetricarboxylic acid. Among the organic solvents, propanol gives the highest yield of extraction for all the targeted compounds except for benzoic acid. A mixture of propanol and ethyl acetate increases significantly the extraction yield of benzoic acid. The extraction time was considerably reduced (140 h to 15 min) by using sonication. The method is discussed for an easy automation with coupling to an in situ GC-MS space instrument.

Steady-state bioavailability of estradiol from two matrix transdermal delivery systems, Alora and Climara

OBJECTIVE

The relative bioavailability of estradiol from two matrix transdermal delivery systems, Alora (0.05 mg/day when applied for 3-4 days) and Climara (0.05 mg/day when applied for 7 days), was evaluated in this two-period, randomized crossover study.

DESIGN

A total of 27 healthy, postmenopausal women completed this study. Each subject received four successive doses of Alora every 84 h (3.5 days) and two doses of Climara every 168 h (7 days) in a randomized sequence without a washout period. Serial serum samples were collected over a 7-day period during the second week of each treatment. Samples were analyzed for estradiol and estrone using a validated radioimmunoassay method. Pharmacokinetic analyses were conducted using baseline-corrected parameters.

RESULTS

Fluctuations in serum estradiol levels were 44% higher for Climara, as indicated by the ratio of Cmax/Cmin. Because the Cmin values for the two regimens were similar, the differences in fluctuation reflected the difference in their Cmax values (49.8 pg/ml for Alora, 67.7 pg/ml for Climara.) The estradiol AUC for Climara was 124% (95% CI 115.6-133.7) of the value for Alora.

CONCLUSIONS

Serum estradiol concentrations were maintained at a more constant level during twice-weekly application of Alora than during once-weekly application of Climara. Both regimens were generally well tolerated and no serious skin or other adverse effects were reported by the subjects. However, Alora exhibited better skin tolerability as indicated by a lower incidence of moderate skin erythema. In addition, there was less adhesive transfer to skin at the application site with Alora.

Site-differential gastrointestinal absorption of benazepril hydrochloride in healthy volunteers

The absorption of benazepril-HCl (BZPH), an orally active angiotensin-converting enzyme (ACE) inhibitor, in various regions of the gastrointestinal (GI) tract was investigated using an intestinal intubation technique. Thirteen subjects completed this single-dose, three-phase sequential crossover study. The drug (20 mg) was administered either as a 4-hr colonic infusion (COLON) or as a small intestinal infusion (SI) in the first two phases and as an oral bolus solution (ORAL) in the third phase, with a 2-week washout between each treatment. Serial plasma and urine samples were collected for up to 4 days after dosing. BZPH and its active metabolite benazeprilat (BZPL) were determined using a gas chromatography/mass spectrometry method. BZPH was absorbed rapidly into the bloodstream (Tmax = 0.5 hr after ORAL). Absorption was also rapid for SI, with a postinfusion half-life (0.57 hr) nearly identical to that for ORAL (0.59 hr). The absorption rate after COLON was much slower (lower Cmax and longer Tmax) compared to that after SI, and the apparent half-life (1.7 hr) was prolonged. SI delivered 90%, whereas COLON delivered 23%, of the drug into the systematic circulation as compared to ORAL. BZPL was rapidly formed upon drug absorption. The metabolite-to-drug AUC ratios were comparable for SI and ORAL (8.9 vs 9.7), indicating that first-pass metabolism of BZPH was neither saturable nor input rate dependent. The metabolite-to-drug AUC ratio was reduced for COLON (5.0), indicating that the mechanism of absorption of BZPH in the colon may be different than that after SI and ORAL. Urinary recovery data were consistent with plasma data.(ABSTRACT TRUNCATED AT 250 WORDS)

Familial CNS tumors

A family with central nervous system tumors in five individuals in two generations is reported. Of five sisters, two had an isolated meningioma and one an ependymoma. Amongst the four children of those affected there was a son with two cerebral meningiomas and a daughter with a spinal meningioma. Signs typical of von Recklinghausen neurofibromatosis (NF1) or bilateral acoustic neurofibromatosis (NF2) were not present. The pattern is consistent with autosomal dominant inheritance with relatively high penetrance.

Animal and plant mitochondria contain specific thioredoxins

Thioredoxins have been purified from pig heart and potato tuber mitochondria which differ in chromatographic behaviour, enzyme activating capacity, and slightly higher molecular mass (Mr = 12,500) from the major thioredoxin(s) present in mitochondria-free fractions of the same tissue. Both mt-thioredoxins can serve as hydrogen donor for E. coli ribonucleotide reductase but only the plant protein activates spinach chloroplast NADP malate dehydrogenase in vitro. Mitochondrial target enzymes specifically activated by thioredoxin have not as yet been identified.

Renal tolerance of fleroxacin in healthy volunteers

In order to evaluate kidney tolerance of fleroxacin, a new fluoroquinolone, we performed a volunteer study with 16 healthy males, 20-27 years old. On three consecutive days 800 mg of fleroxacin was administered orally. Alanine-aminopeptidase and distal- and pan-tubular antigens were determined in 24 h urine collections with specific monoclonal antibodies. Routine haematological and biochemical parameters were determined daily and were in the normal range during the follow-up. No significant changes in excretion of alanine-aminopeptidase and of the urinary antigens were observed during the three days of fleroxacin administration and on the following three days. The results obtained in this volunteer study indicate that fleroxacin has no nephrotoxic side effects.