Dimethylformamide dimethyl acetal reagent for in situ chiral analyses of organic molecules on Titan with the Dragonfly mass spectrometer space instrument (Dragonfly mission)

Thanks to the Cassini-Huygens space mission between 2004 and 2017, a lot was learned about Titan, the biggest satellite of Saturn, and its intriguing atmosphere, surface, and organic chemistry complexity. However, key questions about the potential for the atmosphere and surface chemistry to produce organic molecules of direct interest for prebiotic chemistry and life did not find an answer. Due to Titan potential as a habitable world, NASA selected the Dragonfly space mission to be launched in 2027 to Titan's surface and explore the Shangri-La surface region for minimum 3 years. One of the main goals of this mission will be to understand the past and actual abundant prebiotic chemistry on Titan, especially using the Dragonfly Mass Spectrometer (DraMS). Two recently used sample pre-treatments for Gas Chromatography - Mass Spectrometry (GC-MS mode of DraMS) analyses are planned prior analysis to extract refractory organic molecules of interest for prebiotic chemistry and astrobiology. The dimethylformamide dimethylacetal (DMF-DMA) derivatization reaction offers undoubtedly an opportunity to detect biosignatures by volatilizing refractory biological or prebiotic molecules and conserving the chiral carbons' conformation while an enantiomeric excess indicates a chemical feature induced primarily by life (and may be aided on the primitive systems by light polarization). The goal of this study is to investigate the ageing of DMF-DMA in DraMS (and likely MOMA) capsules prior to in situ analysis on Titan (or Mars). The main results highlighted by our work on DMF-DMA are first its satisfactory stability for space requirements through time (no significant degradation over a year of storage and less than 30 % of lost under thermal stress) to a wide range of temperature (0 °C to 250 °C), or the presence of water and oxidants during the derivatization reaction (between 0 and 10 % of DMF-DMA degradation). Moreover, this reagent derivatized very well amines and carboxylic acids in high or trace amounts (ppt to hundreds of ppm), conserving their molecular conformation during the heat at 145 °C for 3 min (0 to 4% in the enantiomeric form change).

Evaluation of the interference of Tenax®TA adsorbent with dimethylformamide dimethyl acetal reagent for gas chromatography-Dragonfly mass spectrometry and future gas chromatography-mass spectrometry in situ analysis

Among future space missions, national aeronautics and space administration (NASA) selected two of them to analyze the diversity in organic content within Martian and Titan soil samples using a gas chromatograph - mass spectrometer (GC-MS) instrument. The Dragonfly space mission is planned to be launched in 2027 to Titan's surface and explore the Shangri-La surface region for years. One of the main goals of this mission is to understand the past and actual abundant prebiotic chemistry on Titan, which is not well characterized yet. The ExoMars space mission is planned to be launched in 2028 to Mars' surface and explore the Oxia Planum and Mawrth Vallis region for years. The main objectives focus on the exploration of the subsurface soil samples, potentially richer in organics, that might be relevant for the search of past life traces on Mars where irradiation does not impact the matrices and organics. One recently used sample pre-treatment for gas chromatography - mass spectrometry analysis is planned on both space missions to detect refractory organic molecules of interest for astrobiology. This pre-treatment is called derivatization and uses a chemical reagent - called dimethylformamide dimethyl acetal (DMF-DMA) - to sublimate organic compounds keeping them safe from thermal degradation and conserving the chirality of the molecules extracted from Titan or Mars' matrices. Indeed, the detection of building blocks of life or enantiomeric excess of some organics (e.g. amino acids) after DMF-DMA pre-treatment and GC-MS analyses would be both bioindicators. The main results highlighted by our work on DMF-DMA and Tenax®TA interaction and efficiency to detect organic compounds at ppb levels in a fast and single preparation are first that Tenax®TA did not show the onset of degradation until after 150 experiments - a 120 h at 300 °C experiment - which greatly exceeds the experimental lifetimes for the DraMS and GC-space in situ investigations. Tenax®TA polymer and DMF-DMA produce many by-products (about 70 and 46, respectively, depending on the activation temperature). Further, the interaction between the two leads to the production of 22 additional by-products from DMF-DMA degradation, but these listed by-products do not prevent the detection of trace-level organic molecules after their efficient derivatization and volatilization by DMF-DMA in the oven ahead the GC-MS trap and column.

Influence of pH and salts on DMF-DMA derivatization for future Space Applications

For gas chromatography - mass spectrometry (GC-MS) analyses performed in situ, pH and salts (e.g., chlorides, sulfates) may enhance or inhibit the detection of targeted molecules of interest for astrobiology (e.g. amino acids, fatty acids, nucleobases). Obviously, salts influence the ionic strength of the solutions, the pH value, and the salting effect. But the presence of salts may also produce complexes or mask ions in the sample (masking effect on hydroxide ion, ammonia, etc.). For future space missions, wet chemistry will be conducted before GC-MS analyses to detect the full organic content of a sample. The defined organic targets for space GC-MS instrument requirements are generally strongly polar or refractory organic compounds, such as amino acids playing a role in the protein production and metabolism regulations for life on Earth, nucleobases essential for DNA and RNA formation and mutation, and fatty acids that composed most of the eukaryote and prokaryote membranes on Earth and resist to environmental stress long enough to still be observed on Mars or ocean worlds in geological well-preserved records. The wet-chemistry chemical treatment consists of reacting an organic reagent with the sample to extract and volatilize polar or refractory organic molecules (i.e. dimethylformamide dimethyl acetal (DMF-DMA) in this study). DMF-DMA derivatizes functional groups with labile H in organics, without modifying their chiral conformation. The influence of pH and salt concentration of extraterrestrial materials on the DMF-DMA derivatization remains understudied. In this research, we studied the influence of different salts and pHs on the derivatization of organic molecules of astrobiological interest with DMF-DMA, such as amino acids, carboxylic acids, and nucleobases. Results show that salts and pH influence the derivatization yield, and that their effect depend on the nature of the organics and the salts studied. Second, monovalent salts lead to a higher or similar organic recovery compared to divalent salts regardless of pH below 8. However, a pH above 8 inhibits the DMF-DMA derivatization influencing the carboxylic acid function to become an anionic group without labile H. Overall, considering the negative effect of the salts on the detection of organic molecules, future space missions may have to consider a desalting step prior to derivatization and GC-MS analyses.

Comparison of tetramethylammonium hydroxide (TMAH), trimethylsulfonium hydroxide (TMSH), and trimethylphenylammonium hydroxide (TMPAH) thermochemolysis for in situ space analysis of organic molecules in planetary environments

One of the main objectives of present and future space exploration missions dedicated to astrobiology is the detection of organic molecules of interest for life (e.g. amino and fatty acids). With this aim, a sample preparation and a gas chromatograph (connected to a mass spectrometer) are generally used. To date, tetramethylammonium hydroxide (TMAH) has been the first and only thermochemolysis reagent to be used for in situ sample preparation and chemical analysis of planetary environments. Although TMAH is widely used in terrestrial laboratories, numerous applications also leverage other thermochemolysis reagents that may be more relevant than TMAH to meet both scientific and technical objectives of space instrumentation. The present study compares the performance of tetramethylammonium hydroxide (TMAH), trimethylsulfonium hydroxide (TMSH), and trimethylphenylammonium hydroxide (TMPAH) reagents on molecules of interest to astrobiology. The study focuses on the analyses of 13 carboxylic acids (C₇-C₃₀), 17 proteinic amino acids, and the 5 nucleobases. Here we report the derivatization yield without stirring or adding solvents, the detection sensitivity with mass spectrometry, and the nature of the degradation products from the reagents produced during pyrolysis. We conclude that TMSH and TMAH are the best reagents for analyzing carboxylic acids and nucleobases. Amino acids are not relevant targets for a thermochemolysis over 300 °C as they are degraded and showed high limits of detection. As TMAH, and probably TMSH, meet the space instrumentation requirements, this study informs sample treatment approaches prior to GC-MS analysis in in situ space studies. The thermochemolysis reaction using TMAH or TMSH is also recommended for space return missions to extract organics from a macromolecular matrix, derivatize polar or refractory organic targets, and volatilize with the fewest organic degradations.

Thermal stability of adsorbents used for gas chromatography in space exploration

For analytical purpose, thermal desorption is now used in gas chromatographs developed to analyse the chemical composition of planetary environments. Due to technical constraints, the thermal desorption cannot be as finely controlled as in the laboratory resulting in possible thermal alteration of the adsorbents used. For these reasons, the influence of heat on physical and chemical properties of various adsorbents, either used or that could be used in gas chromatographs for space exploration, is studied. If the adsorbents made of carbon molecular sieves and graphitised carbon black that were tested show a very high thermal stability up to 800°C, the porous polymers tested are highly degraded from a minimum temperature that depends on the nature of the polymer. Poly-2,6-diphenylphenylene oxide is shown to be the more thermally robust as it is degraded at higher temperatures, confirming it is currently the best choice for analysing organic molecules with a space instrument. Finally, the products of degradation of the porous polymers tested were analysed after heating the porous polymers at 400 °C and 800 °C. They were identified and listed as potential contaminants of analyses performed with this type of adsorbent. If the exposure to the higher temperature produces numerous organic compounds, mainly aromatic ones, a few ones are also detected at the lower temperature tested, meaning they should be considered as potential contaminants. Again poly-2,6-diphenylphenylene oxide should be preferred because it releases less organic compounds, the structure of which is completely specific to the adsorbent composition.

Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars

The Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory Curiosity rover is designed to conduct inorganic and organic chemical analyses of the atmosphere and the surface regolith and rocks to help evaluate the past and present habitability potential of Mars at Gale Crater. Central to this task is the development of an inventory of any organic molecules present to elucidate processes associated with their origin, diagenesis, concentration, and long-term preservation. This will guide the future search for biosignatures. Here we report the definitive identification of chlorobenzene (150-300 parts per billion by weight (ppbw)) and C₂ to C₄ dichloroalkanes (up to 70 ppbw) with the SAM gas chromatograph mass spectrometer (GCMS) and detection of chlorobenzene in the direct evolved gas analysis (EGA) mode, in multiple portions of the fines from the Cumberland drill hole in the Sheepbed mudstone at Yellowknife Bay. When combined with GCMS and EGA data from multiple scooped and drilled samples, blank runs, and supporting laboratory analog studies, the elevated levels of chlorobenzene and the dichloroalkanes cannot be solely explained by instrument background sources known to be present in SAM. We conclude that these chlorinated hydrocarbons are the reaction products of Martian chlorine and organic carbon derived from Martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources such as meteorites, comets, or interplanetary dust particles.

KEY POINTS

First in situ evidence of nonterrestrial organics in Martian surface sediments Chlorinated hydrocarbons identified in the Sheepbed mudstone by SAM Organics preserved in sample exposed to ionizing radiation and oxidative condition.

Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars

The Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory Curiosity rover is designed to conduct inorganic and organic chemical analyses of the atmosphere and the surface regolith and rocks to help evaluate the past and present habitability potential of Mars at Gale Crater. Central to this task is the development of an inventory of any organic molecules present to elucidate processes associated with their origin, diagenesis, concentration, and long-term preservation. This will guide the future search for biosignatures. Here we report the definitive identification of chlorobenzene (150-300 parts per billion by weight (ppbw)) and C₂ to C₄ dichloroalkanes (up to 70 ppbw) with the SAM gas chromatograph mass spectrometer (GCMS) and detection of chlorobenzene in the direct evolved gas analysis (EGA) mode, in multiple portions of the fines from the Cumberland drill hole in the Sheepbed mudstone at Yellowknife Bay. When combined with GCMS and EGA data from multiple scooped and drilled samples, blank runs, and supporting laboratory analog studies, the elevated levels of chlorobenzene and the dichloroalkanes cannot be solely explained by instrument background sources known to be present in SAM. We conclude that these chlorinated hydrocarbons are the reaction products of Martian chlorine and organic carbon derived from Martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources such as meteorites, comets, or interplanetary dust particles.

KEY POINTS

First in situ evidence of nonterrestrial organics in Martian surface sediments Chlorinated hydrocarbons identified in the Sheepbed mudstone by SAM Organics preserved in sample exposed to ionizing radiation and oxidative condition.

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.

[Diskography--myelography]

One hundred patients were submitted to a prospective, comparative study of metrizamide myelography and discography. In the 32 patients with cervical myelopathy discography yielded no additional information and was thus abandoned. The 68 patients with radiculopathy disease the following results were obtained: In view of the agreement between clinical and myelographic monosegmental findings, discography was considered unnecessary. However, in seven cases with negative myelograms it was possible to show a disc prolapse by discography. When the myelogram was pathological over several segments discography furnished additional information for the differential diagnosis between osteochondrotic or discogenic space-occupying lesions.

Sustained effect of zinc-protamin-glucagon in hyperlipidaemic patients

Is is well known from laboratory investigations and acute intervention studies that glucagon is involved in lipid metabolism. The present study was undertaken in order to evaluate a possible sustained effect of zinc-protamin-glucagon in moderately hyperlipidaemic patients. 4 patients were investigated after an acute bolus dose of glucagon 5 mg intravenously and 16 patients were given zinc-protamin-glucagon 5 mg subcutaneously, b.i.d. for 5 days. A similar degree of decrease of plasma cholesterol and triglycerides was obtained in the acute and chronic study, while the increase in fasting blood sugar and plasma insulin seen in the acute study was not present after 5 days treatment. The effect on plasma triglycerides was much more variable than the effect on plasma cholesterol. Five days after treatment the lipid concentrations had returned to the pretreatment values. The effect could not be predicted from the pretreatment lipid concentrations, neither by the type of hyperlipidaemia present. The decrease in plasma cholesterol and triglycerides were not correlated. The drug might prove useful in the long term research of lipid metabolism and the various complex hormonal interactions.

Cervical disk syndromes: value of metrizamide myelography and diskography

This paper reports on the respective diagnostic values of myelography with water-soluble contrast media and diskography in a study of 100 patients examined between 1979 and 1981 and operated on because of cervical disk disease. The results of the study led to a change of the diagnostic procedures formerly applied in radicular syndromes (i.e., diskography, and then perhaps myelography) and in cervical myelopathy (myelography, rarely followed by diskography). Now cervical metrizamide myelography is always performed first. Diskography is only indicated in radicular syndromes to determine the segment causing clinical symptoms when there is a polysegmental space-occupying lesion on the myelogram in combination with a mono- or oligoradicular neurologic symptomatology; or in the case of a normal myelogram with complaints resistant to conservative treatment.

Treatment of vaginal candidosis with natamycin and effect of treating the partner at the same time

Thirty-three patients with vaginal candidosis were treated with natamycin vaginal tablets for 10 days and their partners were treated double-blind with natamycin cream/placebo cream. Follow-up examinations were carried out one week after the treatment was discontinued and again about one month later. The cure rate in patients having actively treated partners was 94%, not differing significantly from the cure rate of 88% in patients whose partners had been treated with placebo. One month after the treatment there was a high recurrence/re-infection rate, about 30% in both groups. Thus, treating the partners of patients with vaginal candidosis has no influence upon the therapeutic outcome or recurrence rate. The recurrence is presumably due to re-infection from the patient herself.